JP3408805B2 - Cutting origin region forming method and workpiece cutting method - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for forming a starting point region for cutting and a method for cutting an object to be processed used for cutting an object to be processed such as a semiconductor material substrate, a piezoelectric material substrate or a glass substrate.

[0003]

2. Description of the Related Art Cutting is one of laser applications, and general cutting by laser is as follows. For example, a laser beam having a wavelength absorbed by the object to be processed is irradiated to a point where the object to be processed such as a semiconductor wafer or a glass substrate is cut, and the surface of the object to be processed is directed from the front surface to the back surface at the position to be cut by absorbing the laser light. The heating and melting are advanced to cut the object to be processed. However, according to this method, the periphery of the area to be cut on the surface of the workpiece is also melted. Therefore, when the object to be processed is a semiconductor wafer, among the semiconductor elements formed on the surface of the semiconductor wafer, the semiconductor elements located in the vicinity of the above region may melt.

[0004]

As a method of preventing melting of the surface of an object to be processed, for example, Japanese Patent Application Laid-Open No. 2000-21.
There are laser cutting methods disclosed in Japanese Patent No. 9528 and Japanese Patent Laid-Open No. 2000-15467. In the cutting methods of these publications, the cutting point of the workpiece is heated by laser light, and the workpiece is cooled,
The object to be processed is cut by causing a thermal shock at the place where the object to be processed is cut.

However, in the cutting methods disclosed in these publications, when the thermal shock generated on the object to be machined is large, the surface of the object to be machined is cracked off the planned cutting line or to a point before laser irradiation. Unnecessary cracks may occur. Therefore, precision cutting cannot be performed by these cutting methods. In particular, the object to be processed is a semiconductor wafer,
In the case of a glass substrate on which a liquid crystal display device is formed or a glass substrate on which an electrode pattern is formed, unnecessary cracks may damage the semiconductor chip, the liquid crystal display device and the electrode pattern. Further, since the average input energy is large in these cutting methods, thermal damage to the semiconductor chip or the like is also large.

An object of the present invention is to provide a method for forming a starting point region for cutting and a method for cutting an object to be processed which do not cause unnecessary cracks on the surface of the object to be processed and the surface is not melted.

[0007]

According to the method for forming a starting point region for cutting according to the present invention, a laser beam is irradiated to a wafer-shaped object to be processed so that a converging point is aligned, and multi-photon absorption is performed inside the object. The modified region is formed by
The method is characterized by including a step of forming a region serving as a starting point of cutting along a predetermined cutting line of the processing object and inside a predetermined distance from the laser light incident surface of the processing object.

According to the method of forming a starting point region for cutting according to the present invention, by utilizing the phenomenon of multi-photon absorption by irradiating a laser beam with a converging point inside the object to be processed,
A modified region is formed inside the object to be processed. If there is some starting point at the point where the object to be machined is cut, the object to be machined can be cut with a relatively small force. According to the cutting starting point region forming method of the present invention, the processing target object can be cut by cracking the processing target object along the planned cutting line starting from the modified region. Therefore, since the object to be processed can be cut with a comparatively small force, the object to be processed can be cut without causing unnecessary cracks on the surface of the object to be cut that deviate from the planned cutting line.

Further, according to the method of forming the starting point region for cutting according to the present invention, the modified region is formed by locally causing multiphoton absorption inside the object to be processed. Therefore, the laser beam is hardly absorbed on the surface of the object to be processed, so that the surface of the object to be processed is not melted. The converging point is a place where the laser light is condensed. The line to be cut may be a line actually drawn on the surface or inside of the object to be processed, or a virtual line.

In the method for forming a starting point region for cutting according to the present invention, a converging point is set inside a wafer-shaped object to be processed, and the peak power density at the converging point is 1 × 10 ⁸ (W / cm ² ) or more. And, the laser beam is radiated under the condition that the pulse width is 1 μs or less, and a modified region including a crack region is formed inside the object to be processed, and by this modified region, the object to be processed along the planned cutting line of the object to be processed. The method is characterized by including a step of forming a region serving as a starting point of cutting inside a predetermined distance from the laser light incident surface of the object.

According to the method for forming the starting point region for cutting according to the present invention, the focusing point is aligned inside the object to be processed, and the peak power density at the focusing point is 1 × 10 ⁸ (W / cm ² ) or more and Laser light is emitted under the condition that the pulse width is 1 μs or less. Therefore, a phenomenon called optical damage occurs due to multiphoton absorption inside the object to be processed. This optical damage induces thermal strain inside the object to be processed, thereby forming a crack region inside the object to be processed. Since this crack region is an example of the modified region, according to the cutting start region forming method of the present invention, without causing unnecessary cracks off the melting or planned cutting line on the surface of the workpiece , Laser processing becomes possible. The processing target is, for example, a member containing glass. The peak power density means the electric field strength at the condensing point of the pulsed laser light.

According to the method of forming a starting point region for cutting according to the present invention, a focusing point is set inside a wafer-shaped object to be processed, and a peak power density at the focusing point is 1 × 10 ⁸ (W / cm ² ) or more. And, the laser beam is irradiated under the condition that the pulse width is 1 μs or less to form a modified region including the melt processing region inside the object to be processed, and by this modified region, the object to be processed is processed along the planned cutting line. The method is characterized by including a step of forming a region serving as a starting point of cutting inside a predetermined distance from the laser light incident surface of the object.

According to the method for forming a starting point region for cutting according to the present invention, the focusing point is aligned inside the object to be processed, and the peak power density at the focusing point is 1 × 10 ⁸ (W / cm ² ) or more and Laser light is emitted under the condition that the pulse width is 1 μs or less. Therefore, the inside of the object to be processed is locally heated by multiphoton absorption. By this heating, a melt processing region is formed inside the object to be processed. Since this melting treatment area is an example of the above-mentioned modified area, according to the cutting start area forming method of the present invention, it is possible to generate unnecessary cracks on the surface of the object to be melted or out of the planned cutting line. Without
Laser processing becomes possible. The object to be processed is, for example, a member containing a semiconductor material.

In the method for forming a starting point region for cutting according to the present invention, a converging point is set inside a wafer-like object to be processed, and the peak power density at the converging point is 1 × 10 ⁸ (W / cm ² ) or more. Further, the laser beam is radiated under the condition that the pulse width is 1 ns or less, and a modified region including a refractive index changing region, which is a region where the refractive index is changed, is formed inside the object to be processed. The method is characterized by including a step of forming a region serving as a starting point of cutting along a predetermined cutting line inside a predetermined distance from a laser light incident surface of the processing object.

According to the method for forming a starting point region for cutting according to the present invention, the focusing point is set inside the object to be processed, and the peak power density at the focusing point is 1 × 10 ⁸ (W / cm ² ) or more and Laser light is emitted under the condition that the pulse width is 1 ns or less. When the pulse width is made extremely short as in the present invention and multiphoton absorption is caused inside the object to be processed, the energy due to the multiphoton absorption is not converted into thermal energy, and the ion value inside the object to be processed is increased. A permanent structural change such as a number change, crystallization, or polarization orientation is induced to form a refractive index change region. Since this refractive index change region is an example of the modified region, according to the cutting start region forming method of the present invention,
Laser processing can be performed without causing melting or unnecessary cracks off the planned cutting line on the surface of the object to be processed. The object to be processed is, for example, a member containing glass.

A mode applicable to the method for forming a starting point region for cutting according to the present invention is as follows. The laser light emitted from the laser light source may include pulsed laser light. Since pulsed laser light can concentrate the laser energy spatially and temporally,
Even if there is only one laser light source, the electric field strength (peak power density) at the condensing point of the laser light can be made large enough to cause multiphoton absorption.

To irradiate a laser beam with the converging point inside the object to be processed means to condense the laser light emitted from one laser light source and to bring the converging point into the inside of the object to be processed. Illuminating with light can be exemplified. According to this, since the laser light is condensed, even if there is only one laser light source, the electric field strength at the condensing point of the laser light can be made large enough to cause multiphoton absorption.

Irradiating a laser beam with a focused point inside the object to be processed means irradiating each laser beam emitted from a plurality of laser light sources from different directions with the focused point inside the object to be processed. Can be illustrated. According to this, since a plurality of laser light sources are used, it is possible to make the electric field strength at the condensing point of the laser light large enough to cause multiphoton absorption. Therefore, the modified region can be formed even with continuous wave laser light whose instantaneous power is smaller than that of pulsed laser light. Each laser beam emitted from the plurality of laser light sources may be incident from the surface of the object to be processed. Also,
The plurality of laser light sources may include a laser light source that emits laser light that enters from the front surface of the processing target and a laser light source that emits laser light that enters from the back surface of the processing target. The plurality of laser light sources may include a light source unit in which the laser light sources are arranged in an array along the planned cutting line. According to this, it is possible to simultaneously form a plurality of converging points along the planned cutting line,
The processing speed can be improved.

The modified region is formed by relatively moving the object to be processed with respect to the converging point of the laser beam which is fitted inside the object to be processed. According to this, the relative movement forms a modified region inside the object to be processed along the planned cutting line on the surface of the object to be processed.

After the step of forming the region to be the starting point of cutting,
You may make it provide the cutting process of cutting a to-be-processed object along a cutting line. If the object to be processed cannot be cut in the step of forming the region to be the starting point of cutting, the object to be processed is cut by this cutting step. In the cutting step, since the object to be processed is divided from the modified region as a starting point, the object to be processed can be cut with a relatively small force. This allows
It is possible to cut the object to be processed without causing unnecessary cracks on the surface of the object to be cut, which deviate from the planned cutting line.

As the object to be processed, a member containing glass, a piezoelectric material and a semiconductor material is exemplified. Further, as the object to be processed, there is a member that is transparent to the irradiated laser light. Further, this cutting starting point region forming method can be applied to a processing object having an electronic device or an electrode pattern formed on its surface. The electronic device means a semiconductor element, a display device such as a liquid crystal, a piezoelectric element and the like.

In the method of forming a starting point region for cutting according to the present invention, a focusing point is set inside a wafer-shaped object to be processed made of a semiconductor material, and the peak power density at the focusing point is 1 × 1.
Laser light is irradiated under the condition that the pulse width is 0 ⁸ (W / cm ² ) or more and the pulse width is 1 μs or less to form a modified region inside the object to be processed, and the modified region is to cut the object to be processed. The method is characterized in that a step of forming a region serving as a starting point of cutting is provided inside a predetermined distance from the laser light incident surface of the processing object along the line. Further, according to the method of forming a starting point region for cutting according to the present invention, the peak power density at the converging point is 1 × 10 ⁸ (W / cm ²⁾ by aligning the converging point inside the wafer-shaped object to be processed made of the piezoelectric material. ) Above and pulse width is 1
Laser light is irradiated under the condition of μs or less to form a modified region inside the object to be processed, and the modified region causes a predetermined distance from the laser light incident surface of the object to be processed along the line to cut the object to be processed. The method is characterized by including a step of forming a region serving as a starting point of cutting inside the distance. According to these cutting starting point region forming methods, due to the same reason as the cutting starting point region forming method according to the present invention, without causing unnecessary melting or deviation from the planned cutting line on the surface of the workpiece. Laser cutting processing is possible. In the cutting starting point region forming method according to the present invention, the object to be processed has a plurality of circuit parts formed on its surface, and the object to be processed faces a gap formed between adjacent circuit parts among the plurality of circuit parts. The converging point of the laser light can be adjusted inside the object. According to this, it is possible to reliably cut the object to be processed at the position of the gap formed between the adjacent circuit portions.

In the method for forming the starting point region for cutting according to the present invention, the laser light can be condensed at an angle at which the plurality of circuit portions are not irradiated with the laser light. According to this, the laser light can be prevented from entering the circuit portion, and the circuit portion can be protected from the laser light.

In the method for forming a starting point region for cutting according to the present invention, a laser beam is irradiated to a wafer-shaped object to be processed which is made of a semiconductor material so that a focal point is aligned with the laser beam to form a melt-processed area inside the object to be processed. Then, the step of forming the region serving as the starting point of the cutting is formed by the melting processing region along the line to cut the processing target, inside the laser light incident surface of the processing target by a predetermined distance. According to the cutting starting point region forming method of the present invention, it is possible to perform laser processing without causing unnecessary cracks on the surface of the object to be processed and melting the surface for the same reason as above. The formation of the melt-processed region may be due to multiphoton absorption or may be due to other causes.

[0025]

DETAILED DESCRIPTION OF THE INVENTION

A preferred embodiment of the present invention will be described below with reference to the drawings. In the laser processing method according to this embodiment, the modified region is formed by multiphoton absorption. Multiphoton absorption is a phenomenon that occurs when the intensity of laser light is made extremely high. First, the multiphoton absorption will be briefly described.

When the photon energy hν is smaller than the absorption band gap E _G of the material, it becomes optically transparent. Therefore, the condition under which absorption occurs in the material is hν> E _G. However, even if it is optically transparent, if the intensity of the laser light is made extremely large, the condition of nhν> E _G (n = 2, 3, 4, ...
The absorption occurs in the material. This phenomenon is called multiphoton absorption. In the case of a pulse wave, the intensity of the laser light is determined by the peak power density (W / cm ² ) at the condensing point of the laser light. For example, the multiphoton is generated under the condition that the peak power density is 1 × 10 ⁸ (W / cm ² ) or more. Absorption occurs. The peak power density is (energy per pulse of laser light at the converging point)
÷ (Laser beam beam spot cross-sectional area x pulse width). Further, in the case of a continuous wave, the intensity of the laser light is determined by the electric field intensity (W / cm ² ) at the condensing point of the laser light.

The principle of laser processing according to this embodiment using such multiphoton absorption will be described with reference to FIGS. FIG. 1 is a plan view of a processing object 1 during laser processing, FIG. 2 is a cross-sectional view of the processing object 1 shown in FIG. 1 along line II-II, and FIG. 3 is a processing object after laser processing. 4 is a plan view of the object 1, FIG. 4 is a sectional view taken along line IV-IV of the object 1 shown in FIG. 3, and FIG. 5 is a view taken along line VV of the object 1 shown in FIG. 6 is a sectional view, and FIG. 6 is a plan view of the cut object 1.

As shown in FIG. 1 and FIG.
The surface 3 has a planned cutting line 5. The planned cutting line 5 is an imaginary line extending linearly. In the laser processing according to the present embodiment, the modified region 7 is formed by irradiating the processing object 1 with the laser light L by aligning the converging point P inside the processing object 1 under the condition that multiphoton absorption occurs. The converging point is a place where the laser light L is condensed.

By moving the laser beam L relatively along the planned cutting line 5 (that is, along the direction of arrow A), the focal point P is moved along the planned cutting line 5. As a result, as shown in FIG. 3 to FIG.
Are formed only inside the object 1 along the planned cutting line 5. In the laser processing method according to the present embodiment, the object to be processed 1 absorbs the laser light L to cause the object to be processed 1 to generate heat and the modified region 7 is not formed. The modified region 7 is formed by transmitting the laser light L to the processing target 1 and causing multiphoton absorption inside the processing target 1. Therefore, since the laser beam L is hardly absorbed on the surface 3 of the processing object 1, the surface 3 of the processing object 1 is not melted.

In the cutting of the object 1 to be processed, if the starting point is at the cutting point, the object 1 will be broken from the starting point, so that the object 1 can be cut with a relatively small force as shown in FIG. it can. Therefore, the surface 3 of the workpiece 1
The workpiece 1 can be cut without causing unnecessary cracks.

There are two possible ways of cutting the object to be processed starting from the modified region. One is a case where an artificial force is applied to the object to be processed after forming the modified region, so that the object to be processed is cracked and the object to be processed is cut from the modified region as a starting point. This is, for example, cutting when the thickness of the object to be processed is large. The application of artificial force means that thermal stress is generated by, for example, applying bending stress or shear stress to the workpiece along the planned cutting line of the workpiece or by giving a temperature difference to the workpiece. It is to let. The other is when the modified region is formed, so that the modified region is the starting point and is naturally cracked in the cross-sectional direction (thickness direction) of the workpiece, resulting in cutting of the workpiece. Is. This is possible even with one modified region, for example, when the thickness of the workpiece is small,
When the thickness of the object to be processed is large, it becomes possible by forming a plurality of modified regions in the thickness direction. Even in the case of spontaneous cracking, cracks do not precede on the surface where the modified region is formed on the surface of the cut portion,
Since only the portion where the modified portion is formed can be cleaved, the cleaving can be well controlled. In recent years, the thickness of semiconductor wafers such as silicon wafers has tended to be thin, and such a cleaving method with good controllability is very effective.

The modified regions formed by multiphoton absorption in this embodiment include the following (1) to (3). (1) In the case where the modified region is a crack region including one or a plurality of cracks, laser light is applied to an object to be processed (for example, glass or L
The electric field strength at the condensing point is 1 × 10 ⁸ (W / cm ² ) by fitting the condensing point inside the piezoelectric material (iTaO ₃ ).
Irradiation is performed under the above conditions and a pulse width of 1 μs or less. The magnitude of this pulse width is a condition that a crack region can be formed only inside the object to be processed without causing extra damage to the surface of the object to be processed while causing multiphoton absorption. As a result, a phenomenon called optical damage due to multiphoton absorption occurs inside the object to be processed. This optical damage induces thermal strain inside the object to be processed, thereby forming a crack region inside the object to be processed. The upper limit of the electric field strength is, for example, 1 × 10 ¹² (W / cm ² ). The pulse width is preferably 1 ns to 200 ns, for example.
The formation of crack regions by multiphoton absorption is described in, for example, the 45th Laser Thermal Processing Research Group Proceedings (1998.
Dec., pp. 23-28, "Internal marking of glass substrates by solid-state laser harmonics".

The inventor of the present invention experimentally determined the relationship between the electric field strength and the crack size. The experimental conditions are as follows. (A) Object to be processed: Pyrex (registered trademark) glass (thickness 700 μm) (B) Laser light source: Semiconductor laser excitation Nd: YAG laser Wavelength: 1064 nm Laser light spot cross-sectional area: 3.14 × 10 ⁻⁸ cm ² oscillation Form: Q switch pulse repetition frequency: 100 kHz Pulse width: 30 ns Output: Output <1 mJ / pulse Laser light quality: TEM ₀₀ Polarization characteristics: Linearly polarized light (C) Condensing lens Laser transmittance wavelength: 60% (D) Moving speed of the mounting table on which the processing target is mounted: 10
0 mm / sec The laser beam quality of TEM ₀₀ means that the laser beam has a high light focusing property and can be focused up to the wavelength of the laser beam.

FIG. 7 is a graph showing the results of the above experiment. The horizontal axis represents the peak power density. Since the laser light is pulsed laser light, the electric field strength is represented by the peak power density. The vertical axis represents the size of a crack portion (crack spot) formed inside the object to be processed by one pulse of laser light. The crack spots gather to form a crack area. The size of the crack spot is the size of the portion having the maximum length in the shape of the crack spot. The data indicated by the black circles in the graph is the condenser lens (C)
Is 100 times and the numerical aperture (NA) is 0.80. On the other hand, the data indicated by white circles in the graph are for the case where the condenser lens (C) has a magnification of 50 and a numerical aperture (NA) of 0.55. Peak power density is 10 ¹¹ (W / cm ² )
It can be seen from the degree that a crack spot occurs inside the object to be processed, and the crack spot also increases as the peak power density increases.

Next, in the laser processing according to this embodiment, the mechanism of cutting the object to be processed by forming the crack area will be described with reference to FIGS. As shown in FIG. 8, a laser beam L is irradiated to the processing object 1 by aligning the converging point P inside the processing object 1 under the condition that multiphoton absorption occurs, and a crack region is formed inside along the planned cutting line. 9 is formed. The crack region 9 is a region including one or a plurality of cracks. As shown in FIG. 9, the crack further grows from the crack region 9 as a starting point, and as shown in FIG. 10, the crack reaches the front surface 3 and the back surface 21 of the workpiece 1,
As shown in FIG. 11, the processing object 1 is cut by breaking the processing object 1. The crack reaching the front surface and the back surface of the object to be processed may grow naturally, or may be grown by applying a force to the object to be processed.

(2) When the modified region is a melt-processed region A laser beam is focused on the inside of an object to be processed (semiconductor material such as silicon), and the electric field strength at the focused point is 1 × 10. ⁸ (W / cm ² ) or more and pulse width is 1
Irradiate under conditions of μs or less. As a result, the inside of the object to be processed is locally heated by multiphoton absorption. By this heating, a melt processing region is formed inside the object to be processed.
The melt processing region means at least one of a region once melted and then resolidified, a region in a molten state, and a region in a state of being solidified again from melting. Further, the melt-processed region can also be referred to as a region having a phase change or a region having a changed crystal structure. The melt-processed region can also be referred to as a region in which one structure is changed to another structure in a single crystal structure, an amorphous structure, or a polycrystalline structure. That is, for example, a region in which a single crystal structure is changed to an amorphous structure, a region in which a single crystal structure is changed to a polycrystalline structure, or a region in which a single crystal structure is changed to a structure including an amorphous structure and a polycrystalline structure is meant. To do. When the object to be processed has a silicon single crystal structure, the melt-processed region has, for example, an amorphous silicon structure. The upper limit value of the electric field strength is, for example, 1 × 10 ¹² (W / cm ² ). The pulse width is preferably 1 ns to 200 ns, for example.

The present inventor has confirmed by experiments that a melt-processed region is formed inside a silicon wafer. The experimental conditions are as follows. (A) Object to be processed: silicon wafer (thickness 350 μm,
4 inch outer diameter) (B) Laser light source: Semiconductor laser pumped Nd: YAG laser wavelength: 1064 nm Laser light spot cross-sectional area: 3.14 × 10 ⁻⁸ cm ² Oscillation form: Q switch pulse repetition frequency: 100 kHz Pulse width: 30 ns Output: 20 μJ / pulse Laser light quality: TEM ₀₀ Polarization characteristic: Linearly polarized light (C) Condensing lens Magnification: 50 times NA: 0.55 Transmittance for laser light wavelength: 60% (D) Workpiece is placed Moving speed of the mounting table: 10
0 mm / sec

FIG. 12 is a view showing a photograph of a cross section of a part of a silicon wafer cut by laser processing under the above conditions. A melt processing region 13 is formed inside the silicon wafer 11. The size of the melt-processed region formed under the above conditions in the thickness direction is about 100 μm.

It will be described that the melt-processed region 13 is formed by multiphoton absorption. FIG. 13 is a graph showing the relationship between the wavelength of laser light and the transmittance inside the silicon substrate. However, the reflection components on the front surface side and the back surface side of the silicon substrate are removed, and the transmittance of only the inside is shown. Silicon substrate thickness t is 50 μm, 100 μm, 200 μm
The above relationship was shown for each of m, 500 μm, and 1000 μm.

For example, when the wavelength of the Nd: YAG laser is 1064 nm, the thickness of the silicon substrate is 500 μm.
If it is less than m, the laser light will be 80 inside the silicon substrate.
It can be seen that more than% is transmitted. Since the thickness of the silicon wafer 11 shown in FIG. 12 is 350 μm, the melt-processed region by multiphoton absorption is formed near the center of the silicon wafer, that is, at a portion 175 μm from the surface. The transmittance in this case is 90% or more when a silicon wafer having a thickness of 200 μm is referred to.
There is little absorption inside and most of it penetrates. This does not mean that the laser light is absorbed inside the silicon wafer 11 and the melting treatment area is formed inside the silicon wafer 11 (that is, the melting treatment area is formed by normal heating with the laser light). It means that the treated region was formed by multiphoton absorption. The formation of the melt-processed region by multiphoton absorption is described, for example, in pages 72 to 7 of the 66th Annual Meeting of the Welding Society National Conference (April 2000).
It is described in “Evaluation of processing characteristics of silicon by picosecond pulse laser” on page 3.

The silicon wafer is cracked in the cross-sectional direction starting from the melt-processed region and reaches the front and back surfaces of the silicon wafer, resulting in the cutting. The crack reaching the front surface and the back surface of the silicon wafer may grow naturally, or may grow when a force is applied to the object to be processed. It should be noted that cracks naturally grow on the front and back surfaces of the silicon wafer from the melt processing area when the crack grows from the area that has once been melted and then resolidified, or when the crack grows from the molten area. And at least one of the cases where a crack grows from a region in a state of being re-solidified from melting. In each case, the cut surface after cutting is shown in Figure 1.
As shown in FIG. 2, the melt-processed region is formed only inside.
When forming the melt-processed region inside the object to be processed, it is difficult to cause unnecessary cracks that deviate from the planned cutting line at the time of cutting, so that the cutting control becomes easy.

(3) When the modified region is a refractive index changing region The laser beam is focused on the inside of the object to be processed (eg glass), and the electric field strength at the focused point is 1 × 10 ⁸ (W).
/ Cm ² ) or more and the pulse width is 1 ns or less. When the pulse width is made extremely short and multiphoton absorption is caused inside the object to be processed, the energy due to multiphoton absorption is not converted into thermal energy, and the ion valence change and crystallization occur inside the object to be processed. Alternatively, a permanent structural change such as polarization orientation is induced to form a refractive index change region. The upper limit of the electric field strength is, for example, 1 × 10 ¹² (W / c
m ² ). The pulse width is, for example, preferably 1 ns or less, more preferably 1 ps or less. The formation of the refractive index change region by multiphoton absorption is described, for example, in the 42nd Laser Thermal Processing Research Group Proceedings (November 1997), pp. 105-111, "Inside glass by femtosecond laser irradiation. Light-induced structure formation ”.

Next, a specific example of this embodiment will be described. [First Example] A laser processing method according to a first example of the present embodiment will be described. FIG. 14 is a schematic configuration diagram of a laser processing apparatus 100 that can be used in this method. Laser processing device 1
Reference numeral 00 has a laser light source 101 that generates a laser light L, a laser light source control unit 102 that controls the laser light source 101 to adjust the output and pulse width of the laser light L, and a reflection function of the laser light L. And the direction of the optical axis of the laser light L is set to 9
Dichroic mirror 10 arranged to change 0 °
3, a condenser lens 105 for condensing the laser light L reflected by the dichroic mirror 103, and a condenser lens 1
Workpiece 1 irradiated with the laser beam L focused in 05
A mounting table 107 on which the table is mounted, an X-axis stage 109 for moving the mounting table 107 in the X-axis direction, and a mounting table 10.
Y for moving 7 in the Y-axis direction orthogonal to the X-axis direction
The Z-axis stage 1 for moving the axis stage 111 and the mounting table 107 in the Z-axis direction orthogonal to the X-axis and Y-axis directions.
13 and these three stages 109, 111, 113
And a stage control unit 115 that controls the movement of the.

Since the Z-axis direction is the direction orthogonal to the surface 3 of the object 1 to be processed, it is the direction of the depth of focus of the laser light L incident on the object 1 to be processed. Therefore, set the Z-axis stage 113 to Z
By moving the laser beam L in the axial direction, the focus point P of the laser light L can be aligned inside the object 1. Also,
The movement of the condensing point P in the X (Y) axis direction is caused by the processing target 1
X (Y) by the X (Y) axis stage 109 (111)
This is done by moving in the axial direction. The X (Y) axis stage 109 (111) is an example of a moving unit.

The laser light source 101 is an Nd: YAG laser which emits pulsed laser light. Other lasers that can be used for the laser light source 101 include Nd: YVO
_{There are 4} lasers, Nd: YLF lasers and titanium sapphire lasers. Nd: YAG laser, Nd: YVO ₄ laser, N
It is preferable to use a d: YLF laser. When forming the refractive index changing region, it is preferable to use a titanium sapphire laser.

In the first example, pulsed laser light is used for processing the object 1, but continuous wave laser light may be used as long as it can cause multiphoton absorption. In addition, in the present invention, the laser light is meant to include a laser beam. The condenser lens 105 is an example of a condenser. Z-axis stage 1
Reference numeral 13 is an example of means for aligning the focal point of the laser light with the inside of the object to be processed. By moving the condensing lens 105 in the Z-axis direction, the condensing point of the laser light can be adjusted to the inside of the object to be processed.

The laser processing apparatus 100 further includes a mounting table 1
For observing light source 117 for generating visible light for illuminating the object 1 placed on 07 with visible light, and for dichroic mirror 103 and condensing lens 105 arranged on the same optical axis Beam splitter 119
And The dichroic mirror 103 is arranged between the beam splitter 119 and the condenser lens 105. The beam splitter 119 has a function of reflecting approximately half of visible light and transmitting the other half, and is arranged so as to change the direction of the optical axis of visible light by 90 °. About half of the visible light emitted from the observation light source 117 is reflected by the beam splitter 119, and the reflected visible light is reflected by the dichroic mirror 103 and the condenser lens 105.
And illuminates the surface 3 of the object 1 including the planned cutting line 5 and the like.

The laser processing apparatus 100 further includes the image pickup device 12 arranged on the same optical axis as the beam splitter 119, the dichroic mirror 103 and the condenser lens 105.
1 and the imaging lens 123. The image sensor 121 is, for example, a CCD (charge-coupled d).
device) There is a camera. The reflected light of visible light that illuminates the surface 3 including the planned cutting line 5 and the like is collected by the condenser lens 1.
05, the dichroic mirror 103, and the beam splitter 119, and is imaged by the imaging lens 123 and imaged by the imaging element 121, and becomes imaging data.

The laser processing apparatus 100 further includes an imaging data processing section 125 to which the imaging data output from the image sensor 121 is input, an overall control section 127 for controlling the entire laser processing apparatus 100, and a monitor 129. . The imaging data processing unit 125 calculates focus data for focusing the visible light generated by the observation light source 117 on the surface 3 based on the imaging data. The stage control unit 115 controls the movement of the Z-axis stage 113 based on this focus data, so that the visible light is focused on the surface 3. Therefore, the imaging data processing unit 125 functions as an autofocus unit. Further, the imaging data processing unit 125 calculates image data such as an enlarged image of the surface 3 based on the imaging data. This image data is sent to the overall control unit 127, various processing is performed in the overall control unit 127, and sent to the monitor 129. As a result, an enlarged image or the like is displayed on the monitor 129.

The overall controller 127 includes the stage controller 1
Data from the image pickup device 15, image data from the image pickup data processing unit 125, and the like are input, and the laser light source control unit 102, the observation light source 117, and the stage control unit 115 are controlled based on these data, thereby the laser processing apparatus. Control 100 as a whole. Therefore, the overall control unit 127 functions as a computer unit.

Next, the laser processing method according to the first example of the present embodiment will be described with reference to FIGS. 14 and 15. Figure 15
FIG. 6 is a flowchart for explaining this laser processing method. The processing object 1 is a silicon wafer.

First, the light absorption characteristics of the object 1 to be processed are measured by a spectrophotometer (not shown) or the like. Based on this measurement result, the laser light source 101 that emits the laser light L having a wavelength transparent to the object 1 or a wavelength with little absorption is selected (S101). Next, the thickness of the processing object 1 is measured. Based on the thickness measurement result and the refractive index of the processing object 1, the amount of movement of the processing object 1 in the Z-axis direction is determined (S1).
03). This is because the condensing point P of the laser light L is the object 1 to be processed.
Is the amount of movement of the object 1 to be processed in the Z-axis direction with respect to the condensing point of the laser light L located on the surface 3 of the object 1 to be positioned inside. This movement amount is controlled by the overall control unit 12
Input to 7.

The object 1 to be processed is mounted on the mounting table 107 of the laser processing apparatus 100. Then, visible light is generated from the observation light source 117 to illuminate the processing object 1 (S10).
5). Workpiece 1 including illuminated cutting line 5
The surface 3 of the image is imaged by the image sensor 121. The image pickup data is sent to the image pickup data processing unit 125. Based on this imaged data, the imaged data processing unit 125 determines that the observation light source 1
The focus data is calculated such that the focus of visible light 17 is located on the surface 3 (S107).

This focus data is sent to the stage controller 115. The stage control unit 115 moves the Z-axis stage 113 in the Z-axis direction based on this focus data (S109). As a result, the focus of visible light of the observation light source 117 is located on the surface 3. The imaging data processing unit 1
25 calculates enlarged image data of the surface 3 of the object 1 including the planned cutting line 5 based on the imaged data. This enlarged image data is sent to the monitor 1 via the overall control unit 127.
Then, the monitor 129 displays an enlarged image near the planned cutting line 5 on the monitor 129.

In step S10, the overall control unit 127 is set in advance.
The movement amount data determined in 3 is input, and the movement amount data is sent to the stage control unit 115. Based on this movement amount data, the stage control unit 115 sets Z at the position where the condensing point P of the laser light L is inside the processing target 1.
The workpiece 1 is moved in the Z-axis direction by the shaft stage 113 (S111).

Next, laser light L is generated from the laser light source 101, and the laser light L is applied to the planned cutting line 5 on the surface 3 of the object 1. Since the condensing point P of the laser light L is located inside the object to be processed 1, the melting processing region is formed only inside the object to be processed 1. Then, the X-axis stage 109 and the Y-axis stage 111 are moved along the planned cutting line 5 to form a melting processing region inside the processing object 1 along the planned cutting line 5 (S11).
3). Then, the object 1 is cut by bending the object 1 along the planned cutting line 5 (S11).
5). As a result, the processing target 1 is divided into silicon chips.

The effect of the first example will be described. According to this
The pulsed laser light L is applied to the planned cutting line 5 under the condition of causing multiphoton absorption and with the converging point P aligned with the inside of the workpiece 1. Then, by moving the X-axis stage 109 and the Y-axis stage 111, the condensing point P
Is moved along the planned cutting line 5. As a result, a modified region (for example, a crack region, a melting treatment region, a refractive index change region) is formed inside the object 1 to be processed along the planned cutting line 5. If there is some starting point at the point where the object to be machined is cut, the object to be machined can be cut with a relatively small force. Therefore, the workpiece 1 can be cut with a comparatively small force by breaking the workpiece 1 along the planned cutting line 5 starting from the modified region. As a result, the processing target 1 can be cut without causing unnecessary cracks on the surface 3 of the processing target 1 that deviate from the planned cutting line 5.

Further, according to the first example, the pulse laser light L is to be cut line 5 under the condition that multi-photon absorption is caused in the object 1 to be processed and the focusing point P is set inside the object 1 to be cut. Is irradiating. Therefore, the pulsed laser light L is transmitted through the object 1 to be processed, and the pulsed laser light L is hardly absorbed on the surface 3 of the object 1 to be processed, so that the surface 3 is damaged by melting or the like due to the formation of the modified region. There is no.

As described above, according to the first example, it is possible to cut the object 1 without causing unnecessary cracks or melting off the planned cutting line 5 on the surface 3 of the object 1. it can. Therefore, when the processing target 1 is, for example, a semiconductor wafer, the semiconductor chip can be cut out from the semiconductor wafer without causing unnecessary cracking or melting off the planned cutting line. The same applies to a processed object having an electrode pattern formed on the surface and a processed object having an electronic device formed on the surface such as a glass substrate on which a display device such as a piezoelectric element wafer or liquid crystal is formed. Therefore, according to the first example, the yield of a product (for example, a display device such as a semiconductor chip, a piezoelectric device chip, or a liquid crystal) manufactured by cutting a processing target can be improved.

Further, according to the first example, the planned cutting line 5 on the surface 3 of the object 1 is not melted, and therefore the width of the planned cutting line 5 (this width becomes a semiconductor chip in the case of a semiconductor wafer, for example). It is possible to reduce the distance between regions.). As a result, the number of products manufactured from one processing object 1 is increased, and the productivity of the products can be improved.

Further, according to the first example, since the laser light is used for cutting the object 1 to be processed, more complicated processing than dicing using a diamond cutter is possible. For example, even if the planned cutting line 5 has a complicated shape as shown in FIG. 16, according to the first example, cutting can be performed. These effects are the same in the example described later.

The laser light source is not limited to one and may be plural. For example, FIG. 17 is a schematic diagram for explaining the laser processing method according to the first example of the present embodiment in which there are a plurality of laser light sources. This irradiates three laser beams emitted from the three laser light sources 15, 17, and 19 from different directions with the focus point P aligned inside the object 1. Each laser beam from the laser light sources 15 and 17 enters from the surface 3 of the processing object 1. Laser light from the laser light source 19 enters from the back surface 3 of the processing object 1. According to this, since a plurality of laser light sources are used, even if the laser light is a continuous wave laser light having a power lower than that of the pulsed laser light, the electric field strength at the condensing point is set to a magnitude at which multiphoton absorption occurs. It becomes possible. For the same reason, it becomes possible to cause multiphoton absorption without a condenser lens. In this example, the condensing point P is formed by the three laser light sources 15, 17, and 19, but the present invention is not limited to this, and any number of laser light sources may be used.

FIG. 18 is a schematic diagram for explaining another laser processing method according to the first example of the present embodiment in which a plurality of laser light sources are used. In this example, a plurality of laser light sources 23 are provided with three array light source units 25, 27, and 29 arranged in a line along the planned cutting line 5. Array light source unit 25, 2
The laser light emitted from the laser light sources 23 arranged in the same row in each of 7 and 29 forms one converging point (for example, converging point P ₁ ). According to this example, since a plurality of converging points P ₁ , P ₂ , ... Can be formed simultaneously along the planned cutting line 5, the processing speed can be improved. Further, in this example, it is possible to simultaneously form a plurality of modified regions by performing laser scanning on the surface 3 in a direction orthogonal to the planned cutting line 5.

[Second Example] Next, a second example of the present embodiment will be described. This example is a method and apparatus for cutting a light transmissive material. The light transmissive material is an example of an object to be processed. In this example, a piezoelectric element wafer (substrate) made of LiTaO ₃ and having a thickness of about 400 μm is used as the light transmissive material.

The cutting device according to the second example comprises the laser processing device 100 shown in FIG. 14 and the devices shown in FIGS. 19 and 20. The device shown in FIGS. 19 and 20 will be described. The piezoelectric element wafer 31 is held by a wafer sheet (film) 33 as a holding means. The surface of the wafer sheet 33 on the side for holding the piezoelectric element wafer 31 is made of an adhesive resin tape or the like and has elasticity. The wafer sheet 33 is sandwiched by the sample holders 35 and set on the mounting table 107. The piezoelectric element wafer 31 includes a large number of piezoelectric device chips 37 that are cut and separated later, as shown in FIG. Each piezoelectric device chip 37 has a circuit section 39. The circuit portion 39 is formed on the surface of the piezoelectric element wafer 31 for each piezoelectric device chip 37, and a predetermined gap α (about 80 μm) is formed between the adjacent circuit portions 39. Note that FIG. 20 shows a state in which a minute crack region 9 as a modified portion is formed only inside the piezoelectric element wafer 31.

Next, based on FIG. 21, the light according to the second example will be described.
A method of cutting the transparent material will be described. First, the cutting pair
Light-transmissive material serving as an elephant material (in the second example, LiT
aO ₃Of the light absorption characteristics of the piezoelectric element wafer 31) consisting of
(S201). For light absorption characteristics, use a spectrophotometer, etc.
It can be measured by The light absorption characteristics are measured
Then, based on the measurement result, for the material to be cut
Emits laser light L having a wavelength that is transparent or has little absorption
The laser light source 101 is selected (S203). In the second example
Then, the pulse wave (P
A W) type YAG laser has been selected. This YAG
The laser has a pulse repetition frequency of 20 Hz,
The pulse width is 6 μns and the pulse energy is 300 μJ.
is there. In addition, the laser light L emitted from the YAG laser
The spot diameter is about 20 μm.

Next, the thickness of the material to be cut is measured (S
205). When the thickness of the material to be cut is measured, based on the measurement result, the material to be cut in the optical axis direction of the laser light L is positioned so that the focal point of the laser light L is located inside the material to be cut. The displacement amount (movement amount) of the condensing point of the laser light L from the surface (incident surface of the laser light L) is determined (S2).
07). The displacement amount (movement amount) of the condensing point of the laser light L is set in accordance with the thickness and the refractive index of the material to be cut, for example, to half the thickness of the material to be cut.

As shown in FIG. 22, the actual position of the condensing point P of the laser beam L is determined by the difference between the refractive index of the material to be cut (for example, air) and the refractive index of the material to be cut. The material to be cut (piezoelectric element wafer 3 is larger than the position of the condensing point Q of the laser light L condensed by the condensing lens 105).
It will be located deeper than the surface of 1). That is, in the air, the relationship of “movement amount of the Z-axis stage 113 in the optical axis direction of the laser light L × refractive index of the material to be cut = actual movement amount of the focusing point of the laser light L” is established. Become. The displacement amount (movement amount) of the condensing point of the laser light L is
It is set in consideration of the relationship (thickness and refractive index of the material to be cut) described above. After that, the wafer sheet 33 is placed on the wafer table 33 with respect to the mounting table 107 arranged on the XYZ axis stage (in the present embodiment, the X axis stage 109, the Y axis stage 111, and the Z axis stage 113). The held material to be cut is placed (S209). When the placement of the material to be cut is completed, light is emitted from the observation light source 117, and the emitted light is applied to the material to be cut. Then, based on the image pickup result by the image pickup device 121, Z is set so that the converging point of the laser light L is located on the surface of the material to be cut.
The axis stage 113 is moved to perform focus adjustment (S211). Here, the surface observation image of the piezoelectric element wafer 31 obtained by the observation light source 117 is used as an image pickup element 12.
1, and the imaging data processing unit 125 causes the light emitted from the observation light source 117 to focus on the surface of the material to be cut based on the imaging result.
The moving position of No. 3 is determined and output to the stage control unit 115. The stage control unit 115 includes an imaging data processing unit 125.
Based on the output signal from the Z axis stage 113, the moving position of the Z-axis stage 113 causes the light emitted from the observation light source 117 to focus on the surface of the material to be cut, that is, the condensing point of the laser light L is the material to be cut. The Z-axis stage 113 is controlled so as to be positioned on the surface of the.

When the focus adjustment of the light emitted from the observation light source 117 is completed, the focal point of the laser light L is moved to the focal point corresponding to the thickness and refractive index of the material to be cut (S213). Here, the entire Z-axis stage 113 is moved in the optical axis direction of the laser beam L by the amount of displacement of the condensing point of the laser beam L determined in accordance with the thickness and the refractive index of the material to be cut. The control unit 127 is the stage control unit 11
5, the stage control unit 115 that receives the output signal controls the moving position of the Z-axis stage 113. As described above, by moving the Z-axis stage 113 in the optical axis direction of the laser light L by the amount of displacement of the focal point of the laser light L determined corresponding to the thickness and the refractive index of the material to be cut. The placement of the condensing point of the laser light L inside the material to be cut is completed (S215).

When the arrangement of the condensing point of the laser light L inside the material to be cut is completed, the material to be cut is irradiated with the laser light L and the X-axis stage 109 and the Y-axis stage 111 according to the desired cutting pattern. Move (S
217). Laser light L emitted from the laser light source 101
22 is a predetermined gap α formed between the adjacent circuit portions 39 by the condenser lens 105 as shown in FIG.
Piezoelectric element wafer 3 facing 80 μm (as described above)
The light is condensed so that the light condensing point P is located inside 1. The above-described desired cutting pattern is set so that the gap formed between the adjacent circuit portions 39 is irradiated with the laser light L in order to separate the plurality of piezoelectric device chips 37 from the piezoelectric element wafer 31. Therefore, the laser light L is emitted while confirming the irradiation state of the laser light L on the monitor 129.

Here, the laser light L applied to the material to be cut is formed by the condenser lens 105 on the surface (the surface on which the laser light L is incident) of the piezoelectric element wafer 31, as shown in FIG. The laser light L is condensed on the formed circuit portion 39 at an angle at which it is not irradiated. In this way, by collecting the laser light L at an angle at which the laser light L is not emitted to the circuit portion 39, it is possible to prevent the laser light L from entering the circuit portion 39, and the laser light L is transmitted to the circuit portion 39. Can be protected from.

The laser light L emitted from the laser light source 101 is condensed so that the condensing point P is located inside the piezoelectric element wafer 31, and the energy density of the laser light L at this condensing point P is the cutting target. When the threshold value of the optical damage or the optical breakdown of the material is exceeded, a minute crack region 9 is formed only at the condensing point P inside the piezoelectric element wafer 31 as the material to be cut and its vicinity. At this time, the front and back surfaces of the material to be cut (piezoelectric element wafer 31) are not damaged.

Next, with reference to FIGS. 23 to 27, the point of moving the focal point of the laser beam L to form a crack will be described. With respect to the substantially rectangular parallelepiped cut target material 32 (light transmissive material) shown in FIG.
By irradiating the laser beam L so that the focal point of the laser beam L is located inside the object, as shown in FIGS. 24 and 25, only the focal point inside the material 32 to be cut and the vicinity thereof. A minute crack area 9 is formed. Further, the scanning of the laser light L or the movement of the cutting target material 32 is controlled so that the focus point of the laser light L moves in the longitudinal direction D of the cutting target material 32 intersecting the optical axis of the laser light L. .

Since the laser light L is emitted in a pulse form from the laser light source 101, when the laser light L is scanned or the material 32 to be cut is moved, the crack region 9 is generated.
25, a plurality of crack regions 9 are formed at intervals corresponding to the scanning speed of the laser light L or the moving speed of the cutting target material 32 along the longitudinal direction D of the cutting target material 32, as shown in FIG. Will be done. By decreasing the scanning speed of the laser light L or the moving speed of the material 32 to be cut, the interval between the crack regions 9 is shortened and the number of crack regions 9 formed is increased as shown in FIG. Is also possible. Further, by further slowing down the scanning speed of the laser light L or the moving speed of the material to be cut, as shown in FIG.
It is formed continuously along the scanning direction of the laser light L or the moving direction of the material 32 to be cut, that is, the moving direction of the focal point of the laser light L. The spacing between the crack regions 9 (the number of formed crack regions 9) can be adjusted by changing the relationship between the repetition frequency of the laser light L and the moving speed of the material 32 to be cut (X-axis stage or Y-axis stage). It is feasible. Further, the throughput can be improved by increasing the repetition frequency of the laser light L and the moving speed of the material 32 to be cut.

When the crack region 9 is formed along the desired cutting pattern described above (S219), stress is applied to the material to be cut, particularly the portion where the crack region 9 is formed, due to physical external force application or environmental change. The crack region 9 is generated to grow only inside the material to be cut (focus point and its vicinity), and the material to be cut is cut at the position where the crack region 9 is formed (S221).

Next, with reference to FIGS. 28 to 32, the cutting of the material to be cut by applying a physical external force will be described.
First, the material to be cut (piezoelectric element wafer 31) in which the crack region 9 is formed along the desired cutting pattern is placed in the cutting device while being held by the wafer sheet 33 held by the sample holder 35. The cutting device includes a suction chuck 34, a suction pump (not shown) to which the suction chuck 34 is connected, and a pressure needle 36, which will be described later.
(Pressing member), a pressing needle driving means (not shown) for moving the pressing needle 36, and the like. An actuator such as an electric or hydraulic actuator can be used as the pressurizing needle drive means. 28 to 32, the circuit section 39 is not shown.

When the piezoelectric element wafer 31 is placed in the cutting device, as shown in FIG. 28, the suction chuck 34 is brought closer to the position corresponding to the piezoelectric device chip 37 to be separated. As shown in FIG. 29, by operating the suction pump device in the state where the suction chuck 34 is close to or in contact with the piezoelectric device chip 37 for separating, as shown in FIG. 29, the piezoelectric device chip 37 for separating the suction chuck 34 (piezoelectric element wafer 31) is adsorbed. The piezoelectric device chip 37 (the piezoelectric element wafer 3
When 1) is adsorbed, as shown in FIG. 30, the pressing needle 36 is placed at a position corresponding to the piezoelectric device chip 37 separated from the back surface of the wafer sheet 33 (the back surface on which the piezoelectric element wafer 31 is held). To move.

When the pressing needle 36 is moved further after contacting the back surface of the wafer sheet 33, the wafer sheet 33 is deformed and the pressing needle 3 is moved.
External stress is applied to the piezoelectric element wafer 31 by 6, and stress is generated in the wafer portion where the crack region 9 is formed, and the crack region 9 grows. As the crack region 9 grows up to the front surface and the back surface of the piezoelectric element wafer 31, the piezoelectric element wafer 31 is cut at the end portion of the piezoelectric device chip 37 to be separated, as shown in FIG. Is the piezoelectric element wafer 3
Will be separated from 1. The wafer sheet 33
Since has adhesiveness as described above, it is possible to prevent the cut and separated piezoelectric device chips 37 from scattering.

When the piezoelectric device chip 37 is separated from the piezoelectric element wafer 31, the suction chuck 34 and the pressure needle 36 are moved in a direction away from the wafer sheet 33. When the suction chuck 34 and the pressing needle 36 move, the separated piezoelectric device chip 37 is adsorbed to the suction chuck 34, and thus is separated from the wafer sheet 33 as shown in FIG. At this time, an ion air blower (not shown) is used to send ion air in the direction of arrow B in FIG. 32, and the piezoelectric device chip 37 separated and attached to the suction chuck 34 and held on the wafer sheet 33. The piezoelectric element wafer 31 (front surface) is cleaned with ion air. Instead of the ion air cleaning, a suction device may be provided to clean the piezoelectric device chip 37 and the piezoelectric element wafer 31 which are cut and separated by sucking dust or the like. As a method of cutting the material to be cut by the environmental change, there is a method of changing the temperature of the material to be cut having the crack region 9 formed only inside. In this way, by applying a temperature change to the material to be cut, thermal stress is generated in the material portion where the crack region 9 is formed, and the crack region 9 is grown to cut the material to be cut. it can.

As described above, in the second example, the condensing lens 105 causes the condensing point of the laser light L emitted from the laser light source 101 to be inside the light transmissive material (piezoelectric element wafer 31). By converging light so that it is positioned, the energy density of the laser light L at the converging point exceeds the threshold value of optical damage or optical breakdown of the light transmissive material, and the light is condensed inside the light transmissive material. Minute crack regions 9 are formed only at the points and the vicinity thereof. Since the light-transmissive material is cut at the position of the formed crack region 9, the amount of dust generated is extremely low, and the possibility of dicing scratches, chipping, cracks on the material surface, etc. is also extremely low. Further, since the light transmissive material is cut along the crack region 9 formed by the optical damage or the optical insulation breakdown of the light transmissive material, the directional stability of the cutting is improved and the control of the cutting direction is performed. It can be done easily. Further, the dicing width can be reduced as compared with dicing with a diamond cutter, and the number of light transmissive materials cut from one light transmissive material can be increased. As a result, according to the second example, the light transmissive material can be cut very easily and appropriately.

Further, since a stress is generated in the material to be cut by applying a physical external force or an environmental change, the formed crack region 9 is grown and the light transmissive material (piezoelectric element wafer 31) is cut. The light transmissive material can be reliably cut at the position of the formed crack region 9.

Further, by applying a stress to the light transmissive material (piezoelectric element wafer 31) using the pressure needle 36, the crack region 9 is grown and the light transmissive material is cut, so that it is formed. The light transmissive material can be more reliably cut at the position of the crack region 9.

When the piezoelectric element wafer 31 (light transmissive material) on which a plurality of circuit parts 39 are formed is cut and separated for each piezoelectric device chip 37, the condensing lens 105 is used to separate adjacent circuit parts 39. Since the laser light L is condensed so that the condensing point is located inside the wafer portion facing the gap formed between them and the crack region 9 is formed, the gap formed between the adjacent circuit portions 39 is The piezoelectric element wafer 31 can be reliably cut at the position.

Further, a light-transmitting material (piezoelectric element wafer 3
The crack area 9 is moved along the moving direction of the focus point by moving 1) or scanning the laser light L and moving the focus point in a direction intersecting the optical axis of the laser light L, for example, in a direction orthogonal thereto. Since it is formed continuously, the stability of the cutting direction is further improved, and the cutting direction can be controlled more easily.

Further, in the second example, since there is almost no dusting powder, lubricating cleaning water for preventing scattering of dusting powder is not required, and a dry process in the cutting process can be realized.

Further, in the second example, since the modified portion (crack region 9) is formed by non-contact processing with the laser beam L, the durability of the blade in the dicing with the diamond cutter, the replacement frequency, etc. There is no problem. Also, in the second example, as described above,
Since the formation of the modified portion (crack region 9) is realized by non-contact processing with the laser light L, the light-transmissive material is not completely cut, and the light-transmissive material is cut along a cutting pattern. It is possible to cut the permeable material.
The present invention is not limited to the above-mentioned second example,
For example, the light transmissive material is not limited to the piezoelectric element wafer 31, but may be a semiconductor wafer, a glass substrate, or the like. The laser light source 101 can also be appropriately selected according to the light absorption characteristics of the light transmissive material to be cut. Further, in the second example, as the modified portion, the minute crack region 9 is formed by irradiating the laser beam L, but the present invention is not limited to this. For example, by using an ultra-short pulse laser light source (for example, a femtosecond (fs) laser) as the laser light source 101, a modified portion due to a change in refractive index (high refractive index) can be formed, and such a mechanical portion can be formed. It is possible to cut the light transmissive material by utilizing the change in the characteristics without generating the crack region 9.

In the laser processing apparatus 100, Z
Although the focus adjustment of the laser light L is performed by moving the axis stage 113, the focus adjustment is not limited to this, and the focus adjustment is performed by moving the focusing lens 105 in the optical axis direction of the laser light L. It may be performed.

Further, in the laser processing apparatus 100, the X-axis stage 109 and the Y-axis stage 111 are moved according to a desired cutting pattern, but the invention is not limited to this, and the laser beam L is cut into a desired cutting pattern. You may make it scan according to.

Further, after the piezoelectric element wafer 31 is attracted to the suction chuck 34, the piezoelectric element wafer 31 is cut by the pressure needle 36, but the invention is not limited to this. After cutting the element wafer 31, the cut and separated piezoelectric device chips 37 may be adsorbed to the suction chuck 34. It should be noted that the surface of the piezoelectric device chip 37 that has been cut and separated is covered by the suction chuck 34 by cutting the piezoelectric element wafer 31 with the pressing needle 36 after the piezoelectric element wafer 31 is attracted to the suction chuck 34. Therefore, it is possible to prevent dust and the like from adhering to the surface of the piezoelectric device chip 37.

Further, by using an infrared sensor as the image pickup device 121, the focus adjustment can be performed by utilizing the reflected light of the laser light L. In this case, it is necessary to use a half mirror instead of using the dichroic mirror 103 and to dispose an optical element between the half mirror and the laser light source 101 to suppress the returning light to the laser light source 101. At this time, the output of the laser light L emitted from the laser light source 101 at the time of focus adjustment is higher than the output for crack formation so that the laser light L for focus adjustment does not damage the material to be cut. It is preferable to set a low energy value.

The features of the present invention will be described below from the viewpoint of the second example.

The method of cutting the light transmissive material according to the present invention is
The laser light emitted from the laser light source is condensed so that the condensing point is located inside the light transmissive material, and the modified portion is formed only at the condensing point inside the light transmissive material and in the vicinity thereof. It is characterized by including a modified portion forming step and a cutting step of cutting the light transmissive material at the position of the formed modified portion. In the method for cutting a light transmissive material according to the present invention, in the modified portion forming step, by converging the laser light so that the light condensing point of the laser light is located inside the light transmissive material, The modified portion is formed only at the condensing point inside the material and in the vicinity thereof. In the cutting process, the light-transmissive material is cut at the position of the formed modified portion, the amount of dust generated is extremely low, and dicing scratches, chipping, or cracks on the material surface may occur. It will be extremely low. Further, since the light transmissive material is cut at the position of the formed modified portion, the stability of the cutting direction is improved and the cutting direction can be easily controlled. Also,
The dicing width can be reduced as compared to dicing with a diamond cutter, and the number of light transmissive materials cut from one light transmissive material can be increased. As a result, according to the present invention, the light transmissive material can be cut extremely easily and appropriately.

Further, in the method of cutting a light-transmitting material according to the present invention, since there is almost no dusting powder, lubricating cleaning water for preventing scattering of dusting powder is not required, and the dry process in the cutting process is not required. Process can be realized.

Further, in the method for cutting a light-transmitting material according to the present invention, since the modified portion is formed by non-contact processing with laser light, the blade in dicing with a diamond cutter as in the prior art. Durability,
Problems such as replacement frequency do not occur. Further, in the method of cutting a light-transmitting material according to the present invention, since the formation of the modified portion is realized by non-contact processing with laser light as described above, the light-transmitting material is not completely cut. It is possible to cut the light transmissive material along a cutting pattern that cuts out the transmissive material.

A plurality of circuit portions are formed in the light transmissive material, and the light transmissive material portion facing the gap formed between the adjacent circuit portions in the modified portion forming step is inside the light transmissive material portion. It is preferable to collect the laser light so that the light collection point is located to form the modified portion. With this structure, the light transmissive material can be reliably cut at the position of the gap formed between the adjacent circuit portions.

Further, in the modified portion forming step, when the light transmissive material is irradiated with the laser light, it is preferable to collect the laser light at an angle at which the circuit portion is not irradiated with the laser light. As described above, in the modified portion forming step, when the light transmissive material is irradiated with the laser light, the laser light is incident on the circuit portion by condensing the laser light at an angle at which the laser light is not emitted to the circuit portion. Can be prevented, and the circuit portion can be protected from the laser light.

Further, in the modified portion forming step, the modified portion is continuously formed along the moving direction of the focused point by moving the focused point in the direction intersecting the optical axis of the laser beam. Is preferred. As described above, in the modified portion forming step, by moving the converging point in the direction intersecting the optical axis of the laser light, the modified portion is continuously formed along the moving direction of the converging point. The stability of the cutting direction is further improved, and the cutting direction can be controlled more easily.

The method of cutting a light-transmitting material according to the present invention is
Crack formation that condenses the laser light emitted from the laser light source so that the condensing point is located inside the light transmissive material and forms cracks only at the condensing point inside the light transmissive material and in the vicinity thereof. The method is characterized by including a step and a cutting step of cutting the light transmissive material at the position of the formed crack.

In the method of cutting a light transmissive material according to the present invention, in the crack forming step, the laser light is condensed so that the light condensing point of the laser light is located inside the light transmissive material. The energy density of the laser light at the point exceeds the threshold value of optical damage or optical breakdown of the light transmissive material, and cracks are formed only at the condensing point inside the light transmissive material and in the vicinity thereof. In the cutting process, the light-transmissive material will be cut at the position of the formed crack, the amount of dust generated is extremely low, and the possibility of dicing scratches, chipping or cracks on the material surface is also extremely low. Become. Further, the light transmissive material is cut along the crack formed by the optical damage or the optical insulation breakdown of the light transmissive material, so that the stability of the cutting direction is improved and the control of the cutting direction is facilitated. It can be carried out. Further, the dicing width can be reduced as compared with dicing with a diamond cutter, and the number of light transmissive materials cut from one light transmissive material can be increased. As a result, according to the present invention, the light transmissive material can be cut extremely easily and appropriately.

Further, in the method of cutting a light-transmitting material according to the present invention, since there is almost no dust-generating powder, lubricating cleaning water for preventing scattering of dust-generating powder is unnecessary, and dry cutting in the cutting process is not required. Process can be realized.

Further, in the method of cutting a light-transmitting material according to the present invention, since the formation of cracks is realized by non-contact processing with a laser beam, durability of the blade in dicing with a diamond cutter as in the prior art is achieved. There will be no problems such as sex and replacement frequency. Further, in the method for cutting a light-transmitting material according to the present invention, since the formation of cracks is realized by non-contact processing with a laser beam as described above, the light-transmitting material is not completely cut, It is possible to cut the light transmissive material along a cutting pattern that cuts out the material.

In the cutting step, it is preferable to cut the light transmissive material by growing the formed cracks. As described above, in the cutting step, by cutting the light-transmitting material by growing the formed crack, the light-transmitting material can be surely cut at the position of the formed crack.

In the cutting step, it is preferable that a pressure member is used to apply stress to the light-transmissive material to grow cracks and cut the light-transmissive material.
As described above, in the cutting step, the pressing member is used to apply stress to the light-transmissive material to grow cracks and cut the light-transmissive material. It can be cut more reliably.

The cutting device for a light-transmitting material according to the present invention comprises:
A laser light source, a holding means for holding the light transmissive material, an optical element for condensing the laser light emitted from the laser light source so that its condensing point is located inside the light transmissive material, and a light transmissive material. A cutting means for cutting the light transmissive material at the position of the modified portion formed only in the condensing point of the laser light inside the transparent material and in the vicinity thereof.

In the light-transmissive material cutting device according to the present invention, the laser light is condensed by the optical element so that the condensing point of the laser light is located inside the light-transmissive material.
The modified portion is formed only in the light condensing point inside the light transmissive material and in the vicinity thereof. Then, the cutting means cuts the light-transmitting material at the position of the modified portion formed only inside the light-condensing point of the laser light inside the light-transmitting material and in the vicinity thereof, so that the light-transmitting material is formed. Further, it is surely cut along the modified portion, the amount of dust generated is extremely low, and the possibility of dicing scratches, chipping, cracks on the material surface, etc. is extremely low. Further, since the light transmissive material is cut along the modified portion, the stability of the cutting direction is improved, and the cutting direction can be easily controlled.
Also, compared to dicing with a diamond cutter,
The dicing width can be reduced, and the number of light transmissive materials cut from one light transmissive material can be increased. As a result, according to the present invention, the light transmissive material can be cut extremely easily and appropriately.

Further, in the cutting device for the light-transmitting material according to the present invention, since there is almost no dusting powder, lubricating cleaning water for preventing scattering of dusting powder is not required, and dry cutting in the cutting process is not required. Process can be realized.

Further, in the light-transmissive material cutting device according to the present invention, since the modified portion is formed by non-contact processing with laser light, the durability of the blade in dicing with a diamond cutter as in the conventional technique is improved. There will be no problems such as sex and replacement frequency. Further, in the light-transmissive material cutting device according to the present invention, since the modified portion is formed by the non-contact processing by the laser light as described above, the light-transmissive material is not completely cut. It is possible to cut the light transmissive material along a cutting pattern that cuts out the material.

The light-transmitting material cutting device according to the present invention is
A laser light source, a holding means for holding the light transmissive material, an optical element for condensing the laser light emitted from the laser light source so that its condensing point is located inside the light transmissive material, and a light transmissive material. Cutting means for cutting the light transmissive material by growing a crack formed only in the condensing point of the laser light inside the transparent material and in the vicinity thereof.

In the light-transmissive material cutting apparatus according to the present invention, the laser light is condensed by the optical element so that the condensing point of the laser light is located inside the light-transmissive material.
The energy density of the laser light at the condensing point exceeds the threshold value of optical damage or optical breakdown of the light transmissive material, and a crack is formed only at the condensing point inside the light transmissive material and in the vicinity thereof. . Then, the cutting means cuts the light transmissive material by growing cracks formed only at and near the condensing point of the laser light inside the light transmissive material. The material will be reliably cut along the cracks formed by optical damage or optical breakdown of the material, the amount of dust generated will be extremely low, and dicing scratches, chipping or cracks on the material surface may occur. Is also extremely low. Also,
Since the light transmissive material is cut along the cracks, the stability of the cutting direction is improved and the cutting direction can be easily controlled. Also, compared to dicing with a diamond cutter, the dicing width can be reduced,
It is possible to increase the number of light transmissive materials cut from one light transmissive material. As a result, according to the present invention, the light transmissive material can be cut extremely easily and appropriately.

Further, in the cutting device for the light-transmitting material according to the present invention, since there is almost no dusting powder, lubricating cleaning water for preventing scattering of dusting powder is not required, and dry cutting in the cutting process is not required. Process can be realized.

Further, in the light-transmissive material cutting device according to the present invention, since the cracks are formed by the non-contact processing by the laser light, the durability of the blade in the dicing by the diamond cutter as in the conventional technique, Problems such as replacement frequency do not occur. Further, in the light-transmissive material cutting device according to the present invention, since the cracks are formed by the non-contact processing by the laser light as described above, the light-transmissive material is not completely cut, It is possible to cut the light transmissive material along a cutting pattern such as cutting out.

Further, it is preferable that the cutting means has a pressing member for applying stress to the light transmissive material.
As described above, since the cutting means has the pressing member for applying the stress to the light-transmissive material, it becomes possible to apply the stress to the light-transmissive material by the pressing member to grow the cracks. It is possible to more reliably cut the light transmissive material at the position of the crack.

The light transmissive material is a light transmissive material having a plurality of circuit parts formed on the surface thereof, and the optical element has a light transmissive property facing a gap formed between adjacent circuit parts. It is preferable to focus the laser light so that the focusing point is located inside the material portion. With this structure, the light transmissive material can be reliably cut at the position of the gap formed between the adjacent circuit portions.

Further, it is preferable that the optical element collects the laser light at an angle at which the circuit portion is not irradiated with the laser light.
In this way, the optical element can prevent the laser light from entering the circuit portion by condensing the laser light at an angle at which the circuit portion is not irradiated with the laser light, and protect the circuit portion from the laser light. You can

Further, it is preferable to further include a condensing point moving means for moving the condensing point in a direction intersecting the optical axis of the laser beam. As described above, by further including the focal point moving means for moving the focal point in the direction intersecting the optical axis of the laser light, cracks are continuously formed along the focal point moving direction. Therefore, the stability of the cutting direction is further improved, and the cutting direction can be controlled more easily.

[0117]

【The invention's effect】

According to the method for forming a starting point region for cutting and the method for cutting an object to be processed according to the present invention, the object to be processed can be cut without melting or cracking off the planned cutting line on the surface of the object to be processed. it can. Therefore, the yield and productivity of products (for example, display devices such as semiconductor chips, piezoelectric device chips, and liquid crystals) manufactured by cutting the object to be processed can be improved.

[Brief description of drawings]

FIG. 1 is a plan view of an object to be processed during laser processing by a laser processing method according to this embodiment.

FIG. 2 is a sectional view taken along line II-II of the object to be processed shown in FIG.

FIG. 3 is a plan view of an object to be processed after laser processing by the laser processing method according to the present embodiment.

FIG. 4 is a sectional view taken along line IV-IV of the processing object shown in FIG.

5 is a sectional view taken along line VV of the object to be processed shown in FIG.

FIG. 6 is a plan view of an object to be processed cut by the laser processing method according to the present embodiment.

FIG. 7 is a graph showing the relationship between the electric field strength and the crack size in the laser processing method according to the present embodiment.

FIG. 8 is a sectional view of an object to be processed in the first step of the laser processing method according to the present embodiment.

FIG. 9 is a sectional view of an object to be processed in a second step of the laser processing method according to the present embodiment.

FIG. 10 is a sectional view of an object to be processed in a third step of the laser processing method according to the present embodiment.

FIG. 11 is a sectional view of an object to be processed in a fourth step of the laser processing method according to the present embodiment.

FIG. 12 is a view showing a photograph of a cross section of a part of a silicon wafer cut by the laser processing method according to the present embodiment.

FIG. 13 is a graph showing the relationship between the wavelength of laser light and the transmittance inside the silicon substrate in the laser processing method according to the present embodiment.

FIG. 14 is a schematic configuration diagram of a laser processing apparatus that can be used in the laser processing method according to the first example of the present embodiment.

FIG. 15 is a flowchart for explaining a laser processing method according to a first example of the present embodiment.

FIG. 16 is a plan view of a processing object for explaining a pattern that can be cut by the laser processing method according to the first example of the present embodiment.

FIG. 17 is a first embodiment of the present embodiment relating to a plurality of laser light sources.
It is a schematic diagram explaining the laser processing method which concerns on an example.

FIG. 18 is a first embodiment of the present embodiment relating to a plurality of laser light sources.
It is a schematic diagram explaining the other laser processing method which concerns on an example.

FIG. 19 is a schematic plan view showing a piezoelectric element wafer held on a wafer sheet in a second example of the present embodiment.

FIG. 20 is a schematic cross-sectional view showing a piezoelectric element wafer held on a wafer sheet in a second example of the present embodiment.

FIG. 21 is a flowchart for explaining a cutting method according to a second example of the present embodiment.

FIG. 22 is a cross-sectional view of a light transmissive material irradiated with laser light by the cutting method according to the second example of the present embodiment.

FIG. 23 is a plan view of a light transmissive material irradiated with laser light by a cutting method according to a second example of the present embodiment.

24 is a cross-sectional view of the light transmissive material XXIV-XX shown in FIG. 23;
It is sectional drawing which followed the IV line.

FIG. 25 is a XXV-XXV of the light transmissive material shown in FIG. 23.
It is sectional drawing which followed the line.

FIG. 26 is a cross-sectional view taken along line XXV-XXV of the light transmissive material shown in FIG. 23 when the moving speed of the focusing point is slowed.

27 is a sectional view taken along line XXV-XXV of the light transmissive material shown in FIG. 23 when the moving speed of the condensing point is further reduced.

FIG. 28 is a cross-sectional view of the piezoelectric element wafer or the like showing the first step of the cutting method according to the second example of the present embodiment.

FIG. 29 is a sectional view of a piezoelectric element wafer or the like showing a second step of the cutting method according to the second example of the present embodiment.

FIG. 30 is a sectional view of a piezoelectric element wafer or the like showing a third step of the cutting method according to the second example of the present embodiment.

FIG. 31 is a cross-sectional view of a piezoelectric element wafer or the like showing a fourth step of the cutting method according to the second example of the present embodiment.

FIG. 32 is a cross-sectional view of a piezoelectric element wafer or the like showing a fifth step of the cutting method according to the second example of the present embodiment.

[Explanation of symbols]

1 ... Object to be processed, 3 ... Surface, 5 ... Planned cutting line, 7 ... Modified area, 9 ... Crack area, 1
1 ... Silicon wafer, 13 ... Melt processing area, 1
5, 17, 19, 23 ... Laser light source, 25, 27,
29 ... Array light source unit, 31 ... Piezoelectric element wafer,
37 ... Piezoelectric device chip, 100 ... Laser processing device, 101 ... Laser light source, 105 ... Focusing lens, 109 ... X-axis stage, 111 ... Y-axis stage, 113 ... ..Z-axis stage, P ... Focus point

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI // B23K 101: 40 H01L 21/78 B (72) Inventor Toshimitsu Wakuda 1126 1 Nonomachi, Hamamatsu City, Shizuoka Prefecture Hamamatsu Photonics Co., Ltd. (56) References JP-A-4-111800 (JP, A) JP-A-10-163780 (JP, A) JP-A-10-305420 (JP, A) Hideoka Takaoka, for dicing ultra-thin semiconductor wafers Principles and characteristics of optimal stealth dicing technology, electronic materials, Japan, Japan Industrial Co., Ltd., September 1, 2002, Volume 41, No. 9, P. 17-21 (58) Fields surveyed (Int.Cl. ⁷ , DB name) B23K 26/00-26/42 B28D 5/00 C03B 33/09 H01L 21/301

Claims (37)

(57) [Claims] 1. A wafer-shaped object to be processed is irradiated with a laser beam with a converging point aligned to form a modified region by multiphoton absorption inside the object to be processed. A method for forming a cutting starting point region, comprising a step of forming a region serving as a starting point of cutting along a predetermined cutting line of the processing target object and inside a predetermined distance from a laser light incident surface of the processing target object. 2. A focusing point is set inside a wafer-shaped object, and the peak power density at the focusing point is 1 × 10.
Laser light is radiated under the condition that the pulse width is ⁸ (W / cm ² ) or more and the pulse width is 1 μs or less, and a modified region including a crack region is formed inside the object to be processed.
A method for forming a cutting starting point region, comprising a step of forming a region serving as a starting point of cutting along a predetermined cutting line of the processing target object and inside a predetermined distance from a laser light incident surface of the processing target object. 3. A converging point is set inside a wafer-shaped object, and the peak power density at the converging point is 1 × 10.
^A laser beam is irradiated under the condition of ⁸ (W / cm ² ) or more and a pulse width of 1 μs or less to form a modified region including a melt-processed region inside the object to be processed.
A method for forming a cutting starting point region, comprising a step of forming a region serving as a starting point of cutting along a predetermined cutting line of the processing target object and inside a predetermined distance from a laser light incident surface of the processing target object. 4. A peak power density at the converging point is 1 × 10 when the converging point is aligned inside a wafer-shaped object to be processed.
Laser light is irradiated under the condition that the pulse width is ⁸ (W / cm ² ) or more and the pulse width is 1 ns or less, and a modified region including a refractive index changing region, which is a region where the refractive index has changed, is formed inside the object to be processed. Then, the modified starting region includes a step of forming a region serving as a starting point of cutting, at a predetermined distance inside from a laser light incident surface of the processing target along a planned cutting line of the processing target, a cutting starting point region Forming method. 5. The cutting origin region forming method according to claim 1, wherein the laser light emitted from the laser light source includes pulsed laser light. 6. A laser beam emitted from one laser light source is converged by irradiating a laser beam with a converging point inside the object to be processed and condensing the laser beam inside the object. 6. The method for forming a starting point region according to claim 1, further comprising irradiating with laser light. 7. The irradiation of the laser light with the converging point inside the object to be processed means that each laser beam emitted from a plurality of laser light sources is brought into the inside of the object to be converged. The cutting origin region forming method according to claim 1, wherein irradiation is performed from different directions. 8. The cutting start region forming method according to claim 7, wherein each of the laser beams emitted from the plurality of laser light sources enters from the surface of the object to be processed. 9. The plurality of laser light sources include a laser light source that emits laser light that enters from the front surface of the processing target object and a laser light source that emits laser light that enters from the back surface of the processing target object. The method for forming a starting area for cutting according to claim 7. 10. The cutting origin region forming method according to claim 7, wherein the plurality of laser light sources include a light source unit in which the laser light sources are arranged in an array along the planned cutting line. 11. The modified region is formed by moving the object to be processed relative to a converging point of a laser beam fitted inside the object to be processed. 10. The method for forming a starting point region for cutting according to any one of 10. 12. The method of forming a starting point region for cutting according to claim 1, wherein the object to be processed includes glass. 13. The method for forming a starting point region according to claim 1, wherein the object to be processed contains a piezoelectric material. 14. The processing object includes a semiconductor material.
The cutting origin region forming method according to claim 1. 15. The cutting origin region forming method according to claim 1, wherein the object to be processed is a material having a property of transmitting an irradiated laser beam. 16. The method for forming a starting point region for cutting according to claim 1, wherein an electronic device or an electrode pattern is formed on the surface of the object to be processed. 17. A cutting step of cutting the object to be processed along the planned cutting line after forming an area serving as a starting point of cutting by the method for forming a starting point area according to any one of claims 1 to 16. A method for cutting an object to be processed. 18. A focusing point is set inside a wafer-shaped object made of a semiconductor material, and a peak power density at the focusing point is 1 × 10 ⁸ (W / cm ² ) or more and a pulse width is 1 μs. Laser light is irradiated under the following conditions to form a modified region inside the object to be processed, and the modified region causes the laser light incident surface of the object to be processed along a line to cut the object to be processed. A method for forming a cutting starting point region, which comprises a step of forming a region serving as a cutting starting point inside a predetermined distance from. 19. A focusing point is set inside a wafer-shaped workpiece made of a piezoelectric material, and the peak power density at the focusing point is 1 × 10 ⁸ (W / cm ² ) or more and the pulse width is 1 μs. Irradiate laser light under the following conditions, to form a modified region inside the object to be processed, by this modified region,
A method for forming a cutting starting point region, comprising a step of forming a region serving as a starting point of cutting along a predetermined cutting line of the processing target object and inside a predetermined distance from a laser light incident surface of the processing target object. 20. The processing target has a plurality of circuit parts formed on its surface, and the inside of the processing target faces a gap formed between adjacent circuit parts of the plurality of circuit parts. The converging point of the laser light is adjusted to the.
The method for forming a cutting start region according to any one of 1. 21. The method of forming a starting point region according to claim 20, wherein the laser light is focused at an angle such that the laser light is not applied to the plurality of circuit portions. 22. A wafer-shaped object to be processed made of a semiconductor material is irradiated with a laser beam with a focus point aligned to form a melt-processed area inside the object to be processed. A method for forming a cutting starting point region, comprising a step of forming a region serving as a starting point of cutting along a predetermined cutting line of the processing target object and inside a predetermined distance from a laser light incident surface of the processing target object. 23. A laser beam is irradiated onto a wafer-shaped object to be processed so that a focusing point is aligned, and a laser beam of the object to be processed is formed inside the object to be processed along a cutting line of the object to be processed. A method for cutting an object to be processed, which comprises cutting the object to be processed by forming a modified region by multiphoton absorption in a direction along a light incident surface. 24. The method of cutting a processed object according to claim 23, wherein the modified region is formed inside a predetermined distance from the laser light incident surface. 25. A focusing point is set inside a wafer-shaped object, and the peak power density at the focusing point is 1 × 1.
Laser light is irradiated under the condition that the pulse width is 0 ⁸ (W / cm ² ) or more and the pulse width is 1 μs or less. A method for cutting an object to be processed, which comprises cutting the object to be processed by forming a modified region including a crack region in a direction along the incident surface. 26. The method of cutting a workpiece according to claim 25, wherein the modified region is formed inside a predetermined distance from the laser light incident surface. 27. A converging point is set inside a wafer-shaped object to be processed, and a peak power density at the converging point is 1 × 1.
Laser light is irradiated under the condition that the pulse width is 0 ⁸ (W / cm ² ) or more and the pulse width is 1 μs or less. A method for cutting an object to be processed, which comprises cutting the object to be processed by forming a modified region including a melt-processed region in a direction along an incident surface. 28. The method of cutting a processed object according to claim 27, wherein the modified region is formed inside a predetermined distance from the laser light incident surface. 29. A converging point is set inside a wafer-shaped object, and the peak power density at the converging point is 1 × 1.
Laser light is irradiated under the condition that the pulse width is 0 ⁸ (W / cm ² ) or more and the pulse width is 1 ns or less, and the laser light of the processing object is generated inside the processing object along the line to cut the processing object. A method for cutting an object to be processed, which comprises cutting the object to be processed by forming a modified region including a region where the refractive index is changed in a direction along the incident surface. 30. The method of cutting a processed object according to claim 29, wherein the modified region is formed inside a predetermined distance from the laser light incident surface. 31. A focusing point is set inside a wafer-shaped object made of a semiconductor material, and a peak power density at the focusing point is 1 × 10 ⁸ (W / cm ² ) or more and a pulse width is 1 μs. By irradiating a laser beam under the following conditions, by forming a modified region in the direction along the laser light incident surface of the processing object inside the processing object along the planned cutting line of the processing object A method of cutting an object to be processed, which comprises cutting the object to be processed. 32. The method of cutting a processing object according to claim 31, wherein the modified region is formed inside a predetermined distance from the laser light incident surface. 33. A focusing point is set inside a wafer-shaped workpiece made of a piezoelectric material, and a peak power density at the focusing point is 1 × 10 ⁸ (W / cm ² ) or more and a pulse width is 1 μs. By irradiating a laser beam under the following conditions, by forming a modified region in the direction along the laser light incident surface of the processing object inside the processing object along the planned cutting line of the processing object A method of cutting an object to be processed, which comprises cutting the object to be processed. 34. The method of cutting a processing object according to claim 33, wherein the modified region is formed inside a predetermined distance from the laser light incident surface. 35. A wafer-shaped object to be processed made of a semiconductor material is irradiated with a laser beam so that a converging point is aligned, and the processing is performed inside the object to be processed along a cutting line of the object to be processed. A method of cutting an object to be processed, which comprises cutting the object to be processed by forming a melt-processed region in a direction along a laser light incident surface of the object. 36. The method for cutting an object to be processed according to claim 35, wherein the melting processed region is formed inside a predetermined distance from the laser light incident surface. 37. A processing object cutting method comprising a cutting step of cutting the processing object along the planned cutting line after forming an area serving as a cutting starting point by the cutting starting point area forming method according to claim 22. .