JP2004111428A - Chip manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chip manufacturing method which uses a laser dicing device that irradiates the surface of a wafer with a laser beam so as to form modified regions inside the wafer, is capable of dividing the thick wafer well even when the layers of the modified regions formed inside the wafer are small in number, and high in efficiency. <P>SOLUTION: The chip manufacturing method using the laser dicing device 10 to manufacture chips of optional shapes comprises a process of irradiating the front surface of the wafer W with a laser beam L as it conforms to the shape of the chip so as to form the modified regions inside the wafer W and furthermore an additional process of grinding the rear surface of the wafer W or vibrating the wafer W or extruding chips from the wafer W. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a chip manufacturing method for dividing a semiconductor device, an electronic component, and other wafers into individual chips, and particularly to a chip manufacturing method using laser light.
[0002]
[Prior art]
Conventionally, in order to divide a wafer having a semiconductor device, electronic components, and the like formed on its surface into individual chips, a dicing apparatus that cuts the wafer by cutting the wafer with a grinding groove using a thin grindstone called a dicing blade has been used. . The dicing blade is obtained by electrodepositing fine diamond abrasive grains with Ni, and has a very thin thickness of about 30 μm.
[0003]
The dicing blade was rotated at a high speed of 30,000 to 60,000 rpm to cut into the wafer, and the wafer was completely cut (full cut) or incompletely cut (half cut or semi-full cut). Half cut is a method of cutting about half the thickness of the wafer, and semi-full cut is the case where a ground groove is formed while leaving a thickness of about 10 μm.
[0004]
However, in the case of grinding using a dicing blade, the wafer is a brittle mode because the wafer is a highly brittle material, and chipping occurs on the front and back surfaces of the wafer, and this chipping is a factor that degrades the performance of the divided chips. Was. In particular, chipping on the back surface is a troublesome problem because cracks gradually progress inside. Further, in the case of grinding with this dicing blade, straight machining is possible, but machining of an arbitrary shape such as curve machining is impossible.
[0005]
As a means to solve this chipping problem in the dicing process, instead of cutting with a conventional dicing blade, a laser beam with a focused point is incident on the inside of the wafer, and the modified region due to multiphoton absorption is inside the wafer. Techniques related to a laser processing method of forming and dividing into individual chips have been proposed (for example, see Patent Documents 1 to 6).
[0006]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 2002-192667
[Patent Document 2]
Japanese Patent Application Laid-Open No. 2002-192368
[Patent Document 3]
JP-A-2002-192369
[Patent Document 4]
Japanese Patent Application Laid-Open No. 2002-192370
[Patent Document 5]
JP 2002-192371 A
[Patent Document 6]
JP-A-2002-205180
[Problems to be solved by the invention]
However, the technique proposed in the above-mentioned patent document is based on a cutting technique using laser light, and the modified area is formed by irradiating laser light from the surface of the wafer and forming a modified area inside the wafer. From the starting point, the wafer is cut.
[0013]
For this reason, when the thickness of the wafer is large, it is not possible to cut the wafer well. In the case of a thick wafer, the modified region is formed by forming a plurality of layers in the thickness direction of the wafer. Therefore, dicing time is required in proportion to the number of formation layers in the modified region, and the processing capability of the apparatus is reduced.
[0014]
The present invention has been made in view of such circumstances, and uses a laser dicing apparatus that irradiates a laser beam from the surface of a wafer to form a modified region inside the wafer, and forms the inside of the wafer for a thick wafer. It is an object of the present invention to provide an efficient chip manufacturing method capable of cutting a wafer satisfactorily even if the number of layers in a modified region to be formed is small.
[0015]
[Means for Solving the Problems]
According to an aspect of the present invention, there is provided a laser dicing method for dicing the wafer by irradiating a laser beam from a surface of the wafer and forming a modified region inside the wafer. In a chip manufacturing method for manufacturing a chip of an arbitrary shape from the wafer using an apparatus, the wafer surface is scanned with the laser light according to the shape of the chip, and the inside of the wafer is modified according to the shape of the chip. The method is characterized in that the wafer is divided into chips of an arbitrary shape by a step of forming a region layer and a step of grinding the back surface of the wafer to a predetermined thickness.
[0016]
According to the first aspect of the present invention, a step of grinding the back surface of the wafer to a predetermined thickness is added to the step of forming the modified region layer inside the wafer. However, it can be easily cut into chips of any shape.
[0017]
The invention according to claim 2 uses a laser dicing apparatus that dices the wafer by irradiating a laser beam from the surface of the wafer and forming a modified region inside the wafer, and forms an arbitrary shape from the wafer. In a chip manufacturing method for manufacturing a chip, a step of scanning the wafer surface with the laser light according to the shape of the chip, forming a modified region layer inside the wafer according to the shape of the chip, Vibrating the wafer to cut the wafer into chips of an arbitrary shape.
[0018]
According to the invention of claim 2, since the step of vibrating the wafer is added to the step of forming the modified region layer inside the wafer, the number of layers in the modified region is small in a thick wafer. In addition, the wafer can be satisfactorily cleaved into chips of an arbitrary shape, and the processing ability can be improved.
[0019]
The invention according to claim 3 uses a laser dicing apparatus that dices the wafer by irradiating a laser beam from the surface of the wafer and forming a modified region inside the wafer, and a chip having an arbitrary shape from the wafer. In the method of manufacturing a chip, a step of scanning the surface of the wafer with the laser light according to the shape of the chip, forming a modified region layer inside the wafer according to the shape of the chip, Extruding the chips from the front surface or the back surface to cut the wafer into chips of an arbitrary shape.
[0020]
According to the third aspect of the present invention, since the step of pushing out chips is added to the step of forming the modified region layer inside the wafer, even if the number of layers in the modified region is small in a thick wafer. The wafer can be satisfactorily cleaved into chips of an arbitrary shape, and the processing ability can be improved.
[0021]
The invention according to claim 4 uses a laser dicing apparatus that dices the wafer by irradiating a laser beam from the surface of the wafer and forming a modified region inside the wafer, wherein a plane from the wafer has an arbitrary shape. In the chip manufacturing method for manufacturing a chip having a trapezoidal cross section, the wafer surface is scanned with the laser light in accordance with the planar shape of the chip, and a multi-layer modified region along the slope of the trapezoidal cross section inside the wafer Forming a layer and extruding the chip having the trapezoidal cross section from the upper bottom side toward the lower bottom side, whereby the wafer is cut into chips having a trapezoidal cross section with an arbitrary flat surface. .
[0022]
According to the fourth aspect of the present invention, in the chip manufacturing method for manufacturing a chip having a trapezoidal cross section with an arbitrary flat surface, the step of forming a multilayer modified region layer along the slope of the trapezoidal cross section inside the wafer includes a trapezoid. Since the process of extruding from the upper bottom side to the lower bottom side of the chip having the cross section is added, even if the number of layers in the modified region is small with a thick wafer, adjacent chips interfere with each other The wafer can be satisfactorily cut into chips of an arbitrary shape without any problems, and the processing ability can be improved.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a chip manufacturing method according to the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same members are given the same numbers or symbols.
[0024]
FIG. 1 is a schematic configuration diagram of a laser dicing apparatus used in the chip manufacturing method according to the present invention. As shown in FIG. 1, the laser dicing apparatus 10 includes a wafer moving unit 11, a laser optical unit 20, an observation optical unit 30, a control unit 50, and the like.
[0025]
The wafer moving unit 11 includes an XYZθ table 12 provided on a main body base 16 of the laser dicing apparatus 10, a suction stage 13 mounted on the XYZθ table 12 for sucking and holding the wafer W via the dicing tape T, and held on the XYZθ table 12. Frame holder 14 and the like. The wafer W is precisely moved in the XYZθ directions in the figure by the wafer moving unit 11.
[0026]
The laser optical section 20 includes a laser head 21, a collimating lens 22, a half mirror 23, a condensing lens 24, and the like. The observation optical unit 30 includes an observation light source 31, a collimating lens 32, a half mirror 33, a condensing lens 34, a CCD camera 35 as an observation unit, a television monitor 36, and the like.
[0027]
In the laser optical section 20, the laser light oscillated from the laser head 21 is condensed inside the wafer W via an optical system such as a collimator lens 22, a half mirror 23, and a condensing lens 24. Here, a laser beam that is transparent to the dicing tape is used under the condition that the peak power density at the focal point is 1 × 10 ⁸ (W / cm ² ) or more and the pulse width is 1 μs or less. The Z-direction position of the focal point is adjusted by the Z-direction fine movement of the XYZθ table 12.
[0028]
In the observation optical unit 30, the illumination light emitted from the observation light source 31 irradiates the surface of the wafer W via optical systems such as a collimator lens 32, a half mirror 33, and a condensing lens 24. Light reflected from the surface of the wafer W is incident on a CCD camera 35 as observation means via a condensing lens 24, half mirrors 23 and 33, and a condensing lens 34, and a surface image of the wafer W is captured. The image data is displayed on the television monitor 36 via the control unit 50.
[0029]
The control unit 50 includes a CPU, a memory, an input / output circuit unit, and controls the operation of each unit of the laser dicing apparatus 10.
[0030]
Next, dicing of the wafer W by the chip manufacturing method of the present invention using the laser dicing apparatus 10 will be described. When the wafer W is diced, as shown in FIG. 2, the wafer W is mounted on a ring-shaped dicing frame F via a dicing tape T having an adhesive on one surface, and is conveyed in this state during the dicing process. Is done. Since the dicing tape T is stuck on the back surface of the wafer W in this way, even if the wafer W is divided into individual chips, it does not fall apart one by one.
[0031]
The wafer W is held by suction on the suction stage 13 in this state. First, a circuit pattern formed on the surface of the wafer W is imaged by the CCD camera 35, and alignment in the θ direction and positioning in the XY directions are performed by image processing means and alignment means (not shown).
[0032]
When the alignment is completed, the XYZθ table 12 moves to XY, and the laser light L is incident along the chip shape of the wafer W. Since the focal point of the laser light incident from the surface of the wafer W is set inside the thickness direction of the wafer W, the energy of the laser light L transmitted through the surface of the wafer W is concentrated at the focal point inside the wafer. Then, modified regions such as a crack region, a melting region, and a refractive index change region due to multiphoton absorption are formed near the converging point inside the wafer W.
[0033]
As a result, the balance of the intermolecular force of the wafer W is lost, and if the wafer W is thin, the wafer W is cleaved spontaneously with the modified region as a starting point or is applied by applying a slight external force.
[0034]
FIG. 3 is a conceptual diagram illustrating a modified region formed in the vicinity of a focal point inside the wafer. FIG. 3A shows a state in which the laser light L incident on the inside of the wafer W has formed the modified region P at the converging point, and FIG. 3B shows the state under the intermittent pulsed laser light L. Indicate that the wafer W is moved in the horizontal direction and discontinuous modified regions P, P,... Are formed side by side. In this state, if the wafer W is thin, the wafer W is cleaved spontaneously starting from the modified region P or by applying a slight external force. In this case, the wafer W is easily divided into chips without chipping on the front surface or the back surface.
[0035]
In the case of a thick wafer W, since the layer of the modified region P cannot be cut by one layer, the focal point of the laser beam L is moved in the thickness direction of the wafer W to form the modified region P in multiple layers. Let it. When only the modified region P is formed, it is not possible to satisfactorily cut unless the number of modified region layers is increased, and there is a problem in the processing ability.
[0036]
FIG. 4 is a conceptual diagram of an embodiment for explaining a chip manufacturing method of the present invention. In the present invention, in the case of a thick wafer W, as shown in FIG. 4A, the focal point of the laser beam L is set to a portion close to the lower surface (surface) of the wafer W, and a modified region P is formed near the surface. Let it. Next, as shown in FIG. 4B, the back surface of the wafer W is ground with a grinding wheel 81 and processed to a predetermined thickness. Next, the back surface of the wafer W is polished with a polishing cloth (not shown) to remove a damaged layer generated during the grinding. Accordingly, the wafer W is thinned and easily split, and is also easily split by the processing pressure of the grinding wheel 81 and the polishing cloth, and divided into individual chips.
[0037]
FIG. 5 is a view for explaining another embodiment of the invention of the chip manufacturing method. The vibration used in the step of applying vibration to the wafer W following the step of forming the modified region layer on the wafer W is described. The device 60 is shown.
[0038]
The vibration device 60 has a frame base 62 fixed on a base 61, and a suction base 63 for holding the wafer W by suction is supported by compression springs 65, 65 and pressed against the frame base 62. Electromagnets 64 at appropriate intervals are arranged below the attraction table 63, and the attraction table 63 is drawn downward by energization of the electromagnet 64.
[0039]
When applying vibration to the wafer W, the frame F on which the wafer W is mounted is mounted on the frame table 62 via the dicing tape T, and the wafer W is mounted on the suction table 63 via the dicing tape T. , Vacuum suction. In this state, ON / OFF of the electromagnet 64 is repeated at high speed. As a result, the suction table 63 repeats minute vibrations in the vertical direction, and the wafer W is easily cut into chips starting from the modified region layer formed inside.
[0040]
As described above, by adding the step of applying vibration to the wafer W following the step of forming the modified region layer, even if the thickness of the wafer W is large, the number of modified region layers can be easily reduced. Since the cutting can be performed, the processing capacity is further improved.
[0041]
FIG. 6 is a view for explaining an embodiment of a chip manufacturing method according to still another invention, and conceptually shows a step of extruding chips from the wafer W following a step of forming a modified region layer on the wafer W. ing. The example of FIG. 6 shows a case where a chip having a trapezoidal cross section is manufactured. In the step of forming a modified region layer on the wafer W, multiple modified region layers are formed along the trapezoidal slope of the chip.
[0042]
After the modified region layer forming step, the frame F on which the wafer W is mounted is fixed to a table (not shown), and the trapezoidal cross-section chip is moved from the upper bottom side (lower side in FIG. 6) to the lower bottom side (upper side in FIG. 6). ), The chips are pushed up by a pusher 71 attached to a driving means such as an air cylinder (not shown), and the chips are extracted from the wafer W.
[0043]
FIG. 7 is a perspective view showing a chip having a trapezoidal cross section manufactured in this manner. FIG. 7A illustrates a truncated pyramid-shaped chip, and FIG. 7B illustrates a truncated cone-shaped chip.
[0044]
As described above, by adding the step of extruding the chips subsequent to the step of forming the modified region layer, even if the thickness of the wafer W is large, the wafer W can be easily cut with a small number of modified region layers. Processing capacity is further improved. Also, in the case of a chip having a trapezoidal cross section, the chip is extracted from the upper bottom side to the lower bottom side, so that cracks and chips are not generated at the periphery of the chip.
[0045]
In the drawings describing the above-described embodiment, the conceptual diagram of forming the layer having the discontinuous modified region P using the intermittent wave of the laser light L is used. A continuous modified region P may be formed. In the case where the discontinuous modified region P is formed, the laser light L is hard to be cut as compared with the case where the continuous modified region P is formed. Whether a wave or an intermittent wave is used is appropriately selected.
[0046]
【The invention's effect】
As described above, the chip manufacturing method of the present invention for manufacturing a chip having an arbitrary shape using a laser dicing apparatus includes the step of irradiating a laser beam from the surface of a wafer according to the shape of the chip to form a modified region inside the wafer. In addition to the forming step, a step of grinding the back surface of the wafer, a step of vibrating the wafer, or a step of extruding chips from the wafer is added. Therefore, even if the wafer is a thick wafer having chips of an arbitrary shape, even if the number of layers in which the modified regions are formed is smaller than in the process of forming the modified regions only, the wafer can be cut well and chips of an arbitrary shape can be cut. Since it can be easily obtained, the operation rate of the laser dicing apparatus is improved, and the processing capability of the entire chip manufacturing process is significantly improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a laser dicing apparatus used in a chip manufacturing method according to an embodiment of the present invention. FIG. 2 is a perspective view showing a wafer mounted on a frame. FIG. 3 is a modification formed inside the wafer. FIG. 4 is a conceptual diagram illustrating an embodiment of the present invention. FIG. 5 is a mechanical diagram illustrating an embodiment of the present invention. FIG. 6 is a conceptual diagram illustrating an embodiment of the present invention. FIG. 7 is a perspective view showing a chip having a trapezoidal cross section.
DESCRIPTION OF SYMBOLS 10 ... Laser dicing apparatus, 11 ... Wafer moving part, 12 ... XYZ (theta) table, 13 ... Suction stage, 20 ... Laser optical part, 21 ... Laser head, 22, 32 ... Collimate lens, 23, 33 ... Half mirror, 24, 34 ... Condensed lens, 30 ... Observation optical unit, 31 ... Observation light source, 35 ... CCD camera, 36 ... TV monitor, 50 ... Control unit, 60 ... Vibration device, 71 ... Pusher, 81 ... Grinding stone, F ... Frame L: laser beam, P: modified area, T: dicing tape, W: wafer

Claims (7)

In a chip manufacturing method for manufacturing a chip of an arbitrary shape from the wafer, using a laser dicing apparatus for irradiating laser light from the surface of the wafer and dicing the wafer by forming a modified region inside the wafer,
Scanning the wafer surface with the laser light according to the shape of the chip, forming a modified region layer inside the wafer according to the shape of the chip,
Grinding the back surface of the wafer to a predetermined thickness,
Wherein the wafer is divided into chips of an arbitrary shape. In a chip manufacturing method for manufacturing a chip of an arbitrary shape from the wafer, using a laser dicing apparatus for irradiating laser light from the surface of the wafer and dicing the wafer by forming a modified region inside the wafer,
Scanning the wafer surface with the laser light according to the shape of the chip, forming a modified region layer inside the wafer according to the shape of the chip,
Vibrating the wafer;
Cutting the wafer into chips having an arbitrary shape. In a chip manufacturing method for manufacturing a chip of an arbitrary shape from the wafer, using a laser dicing apparatus for irradiating laser light from the surface of the wafer and dicing the wafer by forming a modified region inside the wafer,
Scanning the wafer surface with the laser light according to the shape of the chip, forming a modified region layer inside the wafer according to the shape of the chip,
Extruding the chips from the front or back surface of the wafer,
Cutting the wafer into chips having an arbitrary shape. Laser light is incident from the surface of the wafer, and a laser dicing apparatus that dices the wafer by forming a modified region inside the wafer is used to manufacture chips having a trapezoidal cross section with an arbitrary flat surface from the wafer. In the chip manufacturing method,
Scanning the wafer surface with the laser light according to the planar shape of the chip, forming a multi-layer modified region layer along the slope of the trapezoidal cross section inside the wafer,
Extruding the chip having the trapezoidal cross section from the upper bottom side to the lower bottom side,
Cutting the wafer into chips having a trapezoidal cross section with an arbitrary flat surface. 5. The method according to claim 1, wherein the step of forming the modified region layer is a step of forming a layer having a continuous modified region using a continuous wave of laser light. The chip manufacturing method according to any one of the preceding claims. 5. The method according to claim 1, wherein the step of forming the modified region layer is a step of forming a layer having a discontinuous modified region using a discontinuous wave of laser light. 6. The chip manufacturing method according to any one of the preceding claims. The method according to claim 1, wherein the arbitrary shape is one of a circle, an ellipse, and a polygon.

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