TWI850507B - Wafer processing method and wafer processing device - Google Patents

Abstract

Provided is a wafer processing method and a wafer processing device that can efficiently process a wafer into individual chips regardless of the type of wafer or the type of processing.

According to the present invention, a wafer processing method and a wafer processing device can be provided. The aforementioned wafer processing method is composed of the following steps: a holding step, holding the wafer in a holding mechanism; a damage layer forming step, positioning the focal point of the shock wave on the wafer held in the holding mechanism and forming a damage layer in the area to be divided; and a dividing step, dividing the wafer into individual chips starting from the damage layer. The aforementioned wafer processing device is composed of the following steps: a holding mechanism, holding the wafer; and a damage layer forming mechanism, positioning the focal point of the shock wave on the wafer held in the holding mechanism and forming a damage layer in the area to be divided.

Description

Wafer processing method and wafer processing device

The present invention relates to a wafer processing method for dividing a wafer into individual chips, and a wafer processing device for dividing a wafer into individual chips.

The wafer on the front side is divided into multiple devices such as IC, LSI, LED by predetermined dividing lines, and is divided into individual device chips by laser processing equipment, and can be used in electronic devices such as mobile phones and personal computers.

The laser processing device may include the following: a holding mechanism for holding a workpiece (wafer), a laser light irradiation mechanism for irradiating a laser light of a wavelength that is absorbent to the workpiece held by the holding mechanism, an X-axis feeding mechanism for feeding the holding mechanism and the laser light irradiation mechanism in the X-axis direction relative to each other, and a Y-axis feeding mechanism for feeding the holding mechanism and the laser light irradiation mechanism in the Y-axis direction orthogonal to the X-axis direction relative to each other, and the laser processing device positions the focal point on the predetermined division line of the wafer to irradiate and perform ablation processing, and forms a division groove on the predetermined division line to divide the wafer into individual device wafers (see, for example, Patent Document 1).

Furthermore, the laser processing device may include the following: a holding mechanism for holding a workpiece (wafer), a laser light irradiation mechanism for irradiating a laser light of a wavelength penetrating the workpiece held by the holding mechanism, and a Y-axis feeding mechanism for feeding the holding mechanism and the laser light irradiation mechanism relative to each other in a Y-axis direction orthogonal to the X-axis direction, and the laser processing device positions the focal point of the laser light inside the predetermined division line of the wafer for irradiation, and forms a modified layer that serves as a starting point for division along the inside of the predetermined division line and divides the wafer into individual device wafers (see, for example, Patent Document 2).

Prior art literature Patent Literature

Patent document 1: Japanese Patent Publication No. 10-305420

Patent document 2: Japanese Patent Publication No. 2012-2604

However, in the technologies described in the above-mentioned patent documents 1 and 2, the wavelength of the laser light irradiated on the wafer must be absorbent or penetrable according to the type of wafer or the type of processing, so a laser processing device corresponding to the type of wafer or the type of processing must be prepared. From these circumstances, there will be problems of not meeting economic benefits.

This invention is made in view of the above facts. Its main technical subject is to provide a wafer processing method and a wafer processing device that can efficiently process wafers into individual chips regardless of the type of wafer or the type of processing.

In order to solve the above-mentioned main technical problems, according to the present invention, a wafer processing method can be provided, wherein the aforementioned wafer processing method is to divide the wafer into individual chips, and is composed of the following steps: a holding step, in which the wafer is held in a holding mechanism; a damage layer forming step, in which the focus of the shock wave is positioned on the wafer held in the holding mechanism and a damage layer is formed in the area to be divided; and a dividing step, in which the wafer is divided into individual chips with the damage layer as the starting point.

Furthermore, according to the present invention, a wafer processing device for dividing a wafer into individual chips can be provided. The aforementioned wafer processing device is composed of: a holding mechanism for holding the wafer; and a damage layer forming mechanism for positioning the focal point of the shock wave on the wafer held in the holding mechanism and forming a damage layer in the area to be divided.

The structure may be such that: the destruction layer forming mechanism is a first laser light irradiation mechanism for irradiating pulsed laser light, and the first laser light irradiation mechanism forms each pulse of laser light into a ring shape having a time difference for each wavelength, and the pulsed laser light formed into the ring shape is irradiated toward the wafer to generate a shock wave and form a focal point in the area to be divided, and the position of the focal point of the shock wave can be set by adjusting the time difference with the first laser light irradiation mechanism.

Furthermore, the destruction layer forming mechanism may also be configured as follows: a liquid layer forming mechanism to form a liquid layer on the upper surface of the wafer; and a second laser light irradiation mechanism to condense the pulsed laser light. The point is positioned on the layer of the liquid for irradiation; and the elliptical dome chamber is immersed in the layer of liquid and is set to: position the focusing point of the pulsed laser light on the first focal point of the elliptical dome chamber for irradiation. , a shock wave is generated in the liquid layer, and the second focus of the elliptical dome chamber will be positioned from the upper surface of the wafer to the area to be divided, so that the second focus becomes the focus point of the shock wave.

In addition, the damage layer forming mechanism may be composed of: a liquid layer forming mechanism, which forms a liquid layer on the upper surface of the wafer; a third laser light irradiation mechanism, which irradiates a pulse laser light; and a shock wave generating mechanism, which is immersed in the liquid layer and generates a shock wave in the liquid layer by irradiating the pulse laser light and forms a focal point of the shock wave, and the focal point formed by the shock wave generating mechanism is positioned at the area of the wafer to be divided.

The wafer processing method of the present invention comprises the following steps: a holding step, holding the wafer in a holding mechanism; a damage layer forming step, positioning the focal point of the shock wave on the wafer held in the holding mechanism and forming a damage layer in the area to be divided; and a dividing step, dividing the wafer into individual chips starting from the damage layer. Therefore, it is not necessary to select laser light with absorption or penetration corresponding to the material of the wafer. Therefore, the wafer can be divided into individual chips efficiently without preparing a laser processing device corresponding to the type of wafer or the type of processing.

Furthermore, the wafer processing device of the present invention comprises the following: a holding mechanism for holding the wafer; and a damage layer forming mechanism for positioning the focal point of the shock wave on the wafer held by the holding mechanism and forming a damage layer in the area to be divided, so there is no need to select a laser beam with an absorption or penetration corresponding to the material of the wafer, and thus the wafer can be efficiently divided into individual chips without preparing a laser processing device corresponding to the type of wafer or the type of processing.

2A, 2B: Wafer processing equipment

21: X-axis movable plate

21a,3a:Guide track

22: Movable plate in Y-axis direction

23: Pillar

25: Workbench

25a: Keep the face

26: Cover plate

27: Clamps

3: Base

30: Mobile mechanism

31: X-axis feed mechanism

32: Y-axis feed mechanism

33,35: Pulse motor

34,36: Ball screw

37:Frame

37a: Vertical wall

37b: horizontal wall

4: Maintaining mechanism

6: First laser irradiation mechanism

61: Oscillator

62: Delay mechanism by wavelength

621: Optical fiber on the output side

63: Collimating lens

64: Ring-generating mechanism

641,642: Conical lens

643:Diffraction grating

66,83:Reflector

67: First concentrator

671: Focusing lens

7: Filming agency

70: Splitting device

71: Frame retaining member

72: Clamp

73: Expansion Cylinder

74: Support mechanism

74a: Cylinder

74b: Piston rod

8A: Second laser irradiation mechanism

81: Oscillator

82: Collimating lens

84a: Second concentrator

841a,841b: Focusing lens

842a,842b: Glass plate

843a: Laser beam introduction unit

844a,844b,844c: Liquid inlet

845a: Opening

85a: Oval Dome Room

851a,851b,851c: Liquid layer

86a,86b,86c: lower end

87: Open Department

8B: The third laser irradiation mechanism

84b: Third concentrator

85b: Dome chamber components

852: Lower space

8C: Laser irradiation mechanism (variation of the third laser irradiation mechanism)

84c: Fourth concentrator

85c: Hemisphere

85d: spherical surface

85e: Flat surface

88: Wall

89: Passageway

90: Liquid supply mechanism

92: Piping

10: Wafer

10a: Front

10b: Back

12: Devices

12’: Device chip

14: Split the predetermined line

a1~a4: Radius

C: Center

F:Framework

H: Opening hole

H1~H4: Distance

P1,P1’,P4,P5: Position

P2: First focus

P3: Second focus

Pz,Pz’: Depth

PL0,PL1,PL2: Pulsed laser light

PL1a: Red light

PL1b: Yellow light

PL1c: Green light

PL1d: blue light

PL2a,PL2b,PL2c,PL2d: Ring light

PL3,PL3’,PL3a,PL3b,PL3c: shock wave

S1~S5: Destruction layer

T: Protective tape

X,Y,Z: Arrow (direction)

Figure 1 is an overall three-dimensional diagram of the wafer processing device of the first embodiment.

FIG2 is a block diagram showing an optical system of the first laser light irradiation mechanism provided in the wafer processing device shown in FIG1.

FIG3 is a conceptual diagram showing how a damage layer is formed inside a wafer by generating shock waves based on multiple annular lights irradiating the wafer.

FIG4 is a side view showing the implementation of the segmentation step.

Figure 5 is an overall three-dimensional diagram of the wafer processing device of the second and third embodiments.

FIG6 is a block diagram showing an optical system of a second laser beam irradiation mechanism provided in the wafer processing device shown in FIG5.

Figure 7 (a) is a partially enlarged cross-sectional view showing the third condenser of the third laser light irradiation mechanism, and (b) is a partially enlarged cross-sectional view showing the fourth condenser provided in a modified example of the third laser light irradiation mechanism.

The form used to implement the invention

The following describes in detail the wafer processing method according to the present invention and the implementation form of the wafer processing device suitable for implementing the wafer processing method while referring to the attached drawings.

FIG. 1 shows an overall three-dimensional diagram of a wafer processing device 2A of the first embodiment.

The wafer processing device 2A has a base 3, a holding mechanism 4 for holding the workpiece, a first laser beam irradiation mechanism 6 provided as a destruction layer generation mechanism, a photographing mechanism 7, a moving mechanism 30 for moving the holding mechanism 4, and a control mechanism (not shown).

The holding mechanism 4 includes a rectangular X-axis movable plate 21 mounted on the base 3 so as to be movable in the X-axis direction indicated by an arrow X in the figure, a rectangular Y-axis movable plate 22 mounted on the X-axis movable plate 21 so as to be movable in the Y-axis direction indicated by an arrow Y in the figure, a cylindrical support 23 fixed to the upper surface of the Y-axis movable plate 22, and a rectangular cover plate 26 fixed to the upper end of the support 23. A circular work clamp 25 extending upward through a long hole is provided on the cover plate 26, and the work clamp 25 is rotatably configured by a rotation drive mechanism not shown. The holding surface 25a defined by the X-axis coordinate and the Y-axis coordinate constituting the upper surface of the work clamp 25 is formed of a porous material and has air permeability, and is connected to a suction mechanism (not shown) through a flow path passing through the inside of the support 23. The work clamp 25 is also provided with a clamp 27 for fixing the annular frame F, and the annular frame F supports the workpiece through a protective tape T. Furthermore, the workpiece in this embodiment is, for example, a wafer 10 as shown in FIG. 1, and the wafer 10 is formed on the front side 10a by dividing the device 12 on the silicon substrate by the predetermined dividing line 14. The wafer 10 is attached to the protective tape T with the front surface 10a facing upward and the back surface 10b facing downward, and is held by the annular frame F through the protective tape T.

The moving mechanism 30 includes an X-axis direction feeding mechanism 31 disposed on the base 3 and feeding the holding mechanism 4 in the X-axis direction, and a Y-axis direction feeding mechanism 32 for indexing the Y-axis direction movable plate 22 in the Y-axis direction. The X-axis feeding mechanism 31 converts the rotational motion of the pulse motor 33 into a linear motion through a ball screw 34 and transmits it to the X-axis direction movable plate 21, so that the X-axis direction movable plate 21 moves forward and backward in the X-axis direction along the guide rails 3a, 3a on the base 3. The Y-axis direction feed mechanism 32 converts the rotational motion of the pulse motor 35 into linear motion through the ball screw 36 and transmits it to the Y-axis direction movable plate 22, so that the Y-axis direction movable plate 22 moves forward and backward in the Y-axis direction along the guide rails 21a, 21a on the X-axis direction movable plate 21. Furthermore, although not shown in the figure, a position detection mechanism is provided on the X-axis direction feed mechanism 31, the Y-axis direction feed mechanism 32 and the work clamp 25, and the X-axis coordinate, the Y-axis coordinate, and the circumferential rotation position of the work clamp 25 can be accurately detected, and the position information is transmitted to the control mechanism not shown in the figure. Furthermore, the X-axis direction feed mechanism 31, the Y-axis direction feed mechanism 32, and the rotation drive mechanism of the work clamp 25 (not shown) can be driven by the indication signal indicated by the control mechanism according to the position information, so as to position the work clamp 25 to the desired position on the base 3.

As shown in FIG1 , a frame 37 is vertically arranged on the side of the moving mechanism 30. The frame 37 has a vertical wall portion 37a arranged on the base 3, and a horizontal wall portion 37b extending horizontally from the upper end of the vertical wall portion 37a. The optical system of the first laser beam irradiation mechanism 6 is accommodated inside the horizontal wall portion 37b of the frame 37, and the first condenser 67 constituting a part of the optical system is arranged on the lower surface of the front end of the horizontal wall portion 37b.

The photographing mechanism 7 is disposed on the lower surface of the front end of the horizontal wall portion 37b and is spaced apart from the first condenser 67 of the first laser beam irradiation mechanism 6 in the X-axis direction. The photographing mechanism 7 may include a general photographing element (CCD) for photographing with visible light, an infrared irradiation mechanism for irradiating infrared light to the workpiece, an optical system for capturing infrared light irradiated by the infrared irradiation mechanism, and a photographing element (infrared CCD) for outputting an electrical signal corresponding to the infrared light captured by the optical system, etc. The image photographed by the photographing mechanism 7 will be transmitted to the control mechanism (omitted in the figure) and can be appropriately displayed on the display mechanism (omitted in the figure).

The control mechanism is composed of a computer and includes a central processing unit (CPU) that performs calculations according to a control program, a read-only memory (ROM) that stores the control program, and a readable and writable random access memory (RAM) that stores calculation results. In addition, the control mechanism is electrically connected to the first laser light irradiation mechanism 6, the shooting mechanism 7, the moving mechanism 30, etc., to control the operation of each mechanism.

While referring to FIG. 2(a), the optical system of the first laser beam irradiation mechanism 6 built into the horizontal wall portion 37b of the wafer processing device 2A is described.

The first laser light irradiation mechanism 6 shown in FIG2(a) comprises: an oscillator 61, which oscillates to generate a pulse laser light PL0 of a wideband wavelength (e.g., 355nm~1064nm); a wavelength delay mechanism 62, which makes the pulse laser light PL0 of each pulse oscillated by the oscillator 61 have a time difference according to each wavelength and outputs it as a pulse laser light PL1; a collimating lens 63, which sets the pulse laser light PL1 to parallel light; and a ring generating mechanism 64, which makes the pulse The pulse laser beam PL1 generates an annular light and is split into a small annular light to a large annular light according to each wavelength to generate a pulse laser beam PL2; the reflector 66 changes the optical path of the pulse laser beam PL2; and the first condenser 67 includes a condenser lens 671, and the condenser lens 671 condenses the pulse laser beam PL2 to the position specified by the X-axis coordinate and the Y-axis coordinate of the front surface 10a of the wafer 10 that has been held on the work fixture 25 and becomes the upper surface.

The wavelength-delay mechanism 62 for guiding the pulsed laser beam PL0 can be realized by using, for example, an optical fiber that generates wavelength dispersion. More specifically, it is realized by setting a structure as follows: in the optical fiber (not shown) included in the wavelength-delay mechanism 62, a diffraction grating is formed in a manner that the reflection position is different for each wavelength, so that, for example, the reflection distance of light with a longer wavelength becomes shorter, and the reflection distance of light with a shorter wavelength becomes longer. Thus, through the optical fiber 621 set at the output side of the wavelength delay mechanism 62 shown in FIG2(a), each pulse can have a predetermined time difference in the order of wavelength lengthening, and for example, a pulse laser light PL1 can be generated, and the aforementioned pulse laser light PL1 includes red light PL1a, yellow light PL1b, green light PL1c and blue light PL1d with time differences. Furthermore, in this embodiment, although for the sake of convenience, the pulse laser light PL0 is split into red light PL1a, yellow light PL1b, green light PL1c and blue light PL1d corresponding to 4 wavelength regions, it can actually be split corresponding to 10 to 20 wavelength regions.

The ring generating mechanism 64 is realized by, for example, an axis lens body, and the axis lens body has a pair of axis lenses 641, 642 and an annular grating 643 formed symmetrically in the radial direction. The pulsed laser beam PL1 is formed into an annular light by passing through the pair of axis lenses 641, 642, and further passes through the annular grating 643 to generate a pulsed laser beam PL2 which is split into small annular light to large annular light according to each wavelength. The size of the annular light constituting the pulsed laser beam PL2 can be adjusted by adjusting the interval between the pair of axis lenses 641, 642. Furthermore, in this embodiment, although the above-mentioned conical lens is used as an example of a mechanism for splitting the pulsed laser light PL1 into small ring light and large ring light according to each wavelength, the present invention is not limited to this, and a diffraction optical element (DEO) may also be used.

The pulsed laser beam PL2 generated by the annular generating mechanism 64 will be redirected by the reflector 66 to the first focusing device 67 including the focusing lens 671 and irradiated onto the wafer 10. Furthermore, in the description of FIG2(a), the protective tape T and the frame F holding the wafer 10 are omitted.

FIG3 shows a conceptual diagram, which shows the following: the shock wave PL3 is generated by the annular light PL2a~PL2d constituting the pulse laser light PL2, and is focused on a predetermined focal point (position P1) inside the wafer 10. As shown in the figure, the annular light PL2a~PL2d reaches the front surface 10a of the wafer 10, and the shock wave PL3 propagates from each arrival point in the wafer 10. By appropriately setting the time difference t1~t3 when each annular light PL2a~PL2d reaches the front surface 10a of the wafer 10, the shock wave PL3 can be focused as a focal point at a desired position P1 in the thickness direction of the wafer 10 at the center C of each annular light PL2a~PL2d irradiated on the front surface 10a of the wafer 10. In this embodiment, the position P1 is set at a depth of Pz in the Z-axis direction based on the front surface 10a of the wafer 10. When the position P1 is set as the focal point, the procedure for appropriately setting the above-mentioned time difference t1~t3 is as follows.

The radius of the annular light PL2a~PL2d irradiated on the front surface 10a of the wafer 10 is a value set by the diffraction grating 643 included in the annular generating mechanism 64, and can be set to a1~a4 as shown in FIG3, for example. Furthermore, if the Z-axis coordinate (depth) of the position P1 where the operator wants to focus the shock wave PL3 generated by each annular light PL2a~PL2d from the center C of the annular light PL2a~PL2d in the thickness direction of the wafer 10 is set to Pz, the distance H1~H4 from the point where each annular light PL2a~PL2d reaches in the front surface 10a of the wafer 10 to the position P1 can be calculated by the following formula.

H1=(a1 ² +Pz ² ) ^1/2

H2=(a2 ² +Pz ² ) ^1/2

H3=(a3 ² +Pz ² ) ^1/2

H4=(a4 ² +Pz ² ) ^1/2

Here, as described above, when the annular light PL2a~PL2d reaches the front surface 10a of the wafer 10 with a time difference t1~t3 and generates a shock wave PL3 propagating inside the wafer 10, in order to focus the shock wave PL3 at the position P1, it is sufficient to set the time difference t1~t3 that satisfies the following formula. Furthermore, V is the speed (m/s) when the shock wave PL3 propagates inside the wafer 10, and is a speed determined by the material of the wafer 10.

(H1-H2)/V=t1

(H2-H3)/V=t2

(H3-H4)/V=t3

The above-mentioned time difference t1~t3 can be set by the above-mentioned wavelength-delay mechanism 62, and in the above-mentioned wavelength-delay mechanism 62, the position of the diffraction grating (not shown) arranged in accordance with the wavelength in the optical fiber constituting the wavelength-delay mechanism 62 is set to produce the above-mentioned time difference t1~t3.

By irradiating the front surface 10a of the wafer 10 with the annular light PL2a-PL2d with the time difference t1-t3 satisfying the above conditions, the shock wave PL3 generated by the annular light PL2a-PL2d and propagating in the wafer 10 can be focused at the position P1 to produce a stronger shock.

Furthermore, the laser irradiation conditions when the first laser beam irradiation mechanism 6 is activated are, for example, as follows. By appropriately adjusting the average output of the pulse laser beam PL0 irradiated from the oscillator 61, the position P1 inside the wafer 10 can be used as the focal point to focus the shock wave PL3 and cause damage at the position P1.

Wavelength: 355nm~1064nm

Repetition frequency: 50kHz

Average output: 10W~100W

Pulse width: less than 100ps

The wafer processing device 2A of the first embodiment has a configuration roughly as described above. The wafer processing method implemented by the wafer processing device 2A and the first laser beam irradiation mechanism 6 of the wafer processing device 2A functioning as a destruction layer forming mechanism are described below with reference to FIGS. 1 to 3.

When a damage layer is to be generated at a predetermined depth (Pz) position P1 from the front side 10a of the area to be divided (predetermined dividing line 14) of the wafer 10, the protective tape T side attached to the wafer 10 is first placed on the holding surface 25a of the work clamp 25 of the holding mechanism 4, and the suction mechanism (not shown) is activated to suck and hold, and the frame F holding the wafer 10 is fixed by the clamp 27 (holding step). After the holding step is performed, the damage layer forming step is then performed.

When performing the destruction layer formation step, the first step is to actuate the moving mechanism 30 to position the wafer 10 below the photographing mechanism 7. Then, the photographing mechanism 7 photographs the front side 10a of the wafer 10 to detect the position of the area to be divided (i.e., the predetermined dividing line 14) (calibration step).

After the calibration step has been performed, the wafer 10 is moved to the bottom of the first condenser 67, and the predetermined splitting line 14 obtained by the calibration step is set in the direction along the X-axis direction, and the position for starting processing in the predetermined splitting line 14 is positioned directly below the first condenser 67.

As shown in FIG3 , the wafer processing device 2A of this embodiment generates a shock wave PL3 inside the wafer 10 by focusing the annular light PL2a~PL2d of each wavelength by the first focusing device 67 including the focusing lens 671. The shock wave PL3 propagating inside the wafer 10 is focused at the position P1 at a predetermined depth Pz from the front surface 10a of the wafer 10 when viewed in the Z-axis direction by appropriately setting the time difference t1~t3 as described above. At the same time, the actuating moving mechanism 30 is used to feed the worktable 25 in the X-axis direction, and the shock wave PL3 is sequentially focused at the positions of the predetermined depth Pz, and as shown in FIG2(a), a damaged layer S1 is formed inside the wafer 10. As a result, the damage layer S1 can be formed along the predetermined dividing line 14 inside the predetermined dividing line 14. After the damage layer S1 has been formed inside the predetermined dividing line 14, the Y-axis direction feeding mechanism of the moving mechanism 30 is actuated to index the wafer 10, and the adjacent unprocessed predetermined dividing line 14 is positioned directly below the first condenser 67, and the above-mentioned annular light PL2a~PL2d is positioned to the predetermined dividing line 14 for irradiation, and the X-axis direction feeding mechanism 31 is actuated to form the damage layer S1 inside the predetermined dividing line 14. After the destruction layer S1 is formed inside all the predetermined splitting lines 14 along the predetermined direction, the unillustrated rotation drive mechanism that rotates the work clamp 25 can be controlled to rotate the work clamp 25 90 degrees, and the destruction layer S1 is formed inside all the predetermined splitting lines 14 formed in the direction orthogonal to the predetermined splitting lines 14 on which the destruction layer S1 has been formed. By the above, the destruction layer S1 that serves as the starting point for splitting the wafer 10 into individual chips is formed along the predetermined splitting lines 14, and the destruction layer formation step is completed.

After the destruction layer formation step is completed as described above, the segmentation step can be implemented. The aforementioned segmentation step is a step of using the destruction layer S1 as a starting point to segment the wafer 10 into individual device chips 12'. Although the segmentation step can adopt a known mechanism, it can be implemented using a segmentation device 70 such as shown in FIG. 4.

As described above, the wafer 10 having the destruction layer S1 formed inside the predetermined separation line 14 by the destruction layer forming step is transported to the separation device 70 shown in FIG. 4. The separation device 70 has: a ring-shaped frame holding member 71 formed in a liftable manner, a clamp 72 for holding the frame F by placing the frame F on its upper surface, an expansion cylinder 73 formed of a cylindrical shape with at least an upper opening for expanding the interval between the devices 12 of the wafer 10 mounted on the frame F held by the clamp 72, and a support mechanism 74 composed of a cylinder 74a and a piston rod 74b, wherein the cylinder 74a is arranged to surround the expansion cylinder 73, and the piston rod 74b extends from the cylinder 74a.

The expansion cylinder 73 is set to be smaller than the inner diameter of the frame F and larger than the outer diameter of the wafer 10 attached to the protective tape T installed on the frame F. Here, as shown in FIG. 4, the splitting device 70 can raise and lower the frame holding member 71 to set the upper surface of the expansion cylinder 73 to a position at which the upper surface portion is approximately the same height (indicated by a dotted line) and the upper end portion of the expansion cylinder 73 is relatively higher than the upper end portion of the frame holding member 71 (indicated by a solid line).

When the frame holding member 71 is lowered as described above, and the upper end of the expansion cylinder 73 is changed from the position indicated by the dotted line to a relatively higher position indicated by the solid line, the protective tape T installed on the frame F is expanded by the upper edge of the expansion cylinder 73. Here, the wafer 10 is formed with a damage layer S1 as a starting point for separation along the predetermined separation line 14 by performing the above-mentioned damage layer forming step, and the tensile force (external force) is radially applied to the wafer 10 by expanding the protective tape T, and the wafer 10 is divided into device chips 12' as shown in Figure 4. After the wafer 10 is divided into individual device chips 12' in this way, it can be picked up by a suitable pickup device not shown in the figure.

According to the above-mentioned implementation form, the pulsed laser beam PL2 formed into a ring can be irradiated to the predetermined dividing line 14 of the front surface 10a of the wafer 10 to generate a shock wave PL3, and it is focused at a predetermined position P1 to generate a destruction layer S1 inside the predetermined dividing line 14. For the laser beam irradiated at this time, it is not necessary to select a wavelength with absorption or penetration corresponding to the material of the wafer 10, but a wide-band wavelength laser beam set in an arbitrary range can be used, so it is not necessary to prepare a laser processing device corresponding to the type of wafer or the type of processing.

Furthermore, the present invention is not limited to the first embodiment described above. For example, as shown in FIG. 2(b), the focus of the shock wave PL3' generated by irradiating the pulsed laser beam PL2 composed of the annular light PL2a~PL2d of each wavelength can be set at the position P1' defined by the depth Pz' near the front surface 10a of the wafer 10. By doing so, it is also possible to form a damaged layer S2 that serves as the starting point of the splitting by ablation processing such as irradiating the front surface 10a of the wafer 10 along the predetermined splitting line 14 with laser beams having an absorptive wavelength.

The present invention is not limited to the first embodiment described above. The second and third embodiments of the wafer processing device that can implement the wafer processing method of the present invention are described with reference to FIGS. 5 to 7.

FIG. 5 shows an overall perspective view of a wafer processing device 2B of the second and third embodiments. The wafer processing device 2B is different from the wafer processing device 2A described with reference to FIG. 1 and FIG. 2 in that the first laser beam irradiation mechanism 6 provided as a damage layer forming mechanism is replaced, and other laser beam irradiation mechanisms 8A to 8C that function as a damage layer forming mechanism are provided. Furthermore, in the following description, detailed descriptions of the same structures with the same numbers as those of the first embodiment shown in FIG. 1 and FIG. 2 will be omitted as appropriate.

In the wafer processing device 2B shown in FIG. 5 , a liquid supply mechanism 90 for supplying liquid L (e.g., water) to the workpiece, i.e., the wafer 10, is provided inside or near the wafer processing device 2B. The liquid supply mechanism 90 has a liquid tank for storing the liquid L, and a pressure pump for discharging the liquid L from the liquid tank to the outside (both are omitted in the figure). The liquid L discharged from the liquid supply mechanism 90 is supplied to the condensers 84a to 84c of other laser light irradiation mechanisms 8A to 8C constituting the destruction layer forming mechanism of the present embodiment through a pipe 92. The optical systems of the other laser light irradiation mechanisms 8A to 8C are accommodated inside the horizontal wall portion 37b of the frame 37 disposed on the base 3. The optical system of the second laser beam irradiation mechanism 8A provided in the second embodiment will be described with reference to FIG. 6.

As shown in FIG6 , the second laser beam irradiation mechanism 8A includes: an oscillator 81 that oscillates to generate a pulsed laser beam PL0 with a wideband wavelength, a collimating lens 82 that sets the pulsed laser beam PL0 as a parallel light, a reflector 83 that changes the optical path of the pulsed laser beam PL0 that has been set as a parallel light by the collimating lens 82 as needed, and a second condenser 84a that introduces the pulsed laser beam PL0 that has been reflected by the reflector 83. Furthermore, although not shown in the figure, the optical system may also include an attenuator, etc., which is used to adjust the output of the pulsed laser beam PL0 oscillated from the oscillator 81.

As shown in FIG6 , when viewed from the side where the pulsed laser beam PL0 is introduced (the upper side in the figure), a focusing lens 841a, a glass plate 842a, a laser beam introduction part 843a, and an elliptical dome chamber 85a are arranged inside the second condenser 84a. The elliptical dome chamber 85a is formed by a part of an elliptical body whose longitudinal section is formed by an ellipse, and the elliptical dome chamber 85a and the laser beam introduction part 843a are connected through the opening 845a. A liquid introduction port 844a that constitutes a liquid layer forming mechanism together with a liquid supply mechanism 90 is connected to the laser beam introduction part 843a from the side. The glass plate 842a allows the pulsed laser light PL0 to pass through and separates the interior of the second concentrator 84a into upper and lower parts.

The elliptical dome chamber 85a formed in the second concentrator 84a is formed by a part of the elliptical body as described above. The ellipse forming the elliptical body is defined by the first focus P2 and the second focus P3 which are the base of the ellipse. The first focus P2 is located on the side of the laser beam introduction part 843a in the elliptical dome chamber 85a. In addition, the second focus P3 is located on the lower side than the lower end 86a of the second concentrator 84a and on the outer side of the elliptical dome chamber 85a.

When the wafer processing method of this embodiment is implemented using the second laser irradiation mechanism 8A, the wafer 10 is first held on the work clamp 25 by performing the above-mentioned holding step. Then, the wafer 10 held on the work clamp 25 is moved to the bottom of the photographing mechanism 7, and the photographing mechanism 7 photographs the wafer 10 to perform the calibration step. After the calibration step is performed, the worktable 25 is rotated and moved by the moving mechanism 30 according to the position and direction of the predetermined splitting line 14 grasped from the image of the wafer 10 by the control mechanism (not shown), and the predetermined splitting line 14 of the wafer 10 is adjusted to the direction along the X-axis direction, and the position where the processing should start is positioned on the predetermined splitting line 14 directly below the second condenser 84a of the second laser light irradiation mechanism 8A.

Once the wafer 10 has been positioned directly below the second condenser 84a of the second laser beam irradiation mechanism 8A, the height adjustment mechanism (not shown) can be actuated to adjust the height of the second laser beam irradiation mechanism 8A, and the second focus P3 of the elliptical dome chamber 85a is positioned inside the predetermined splitting line 14 of the wafer 10 and at a predetermined depth position (Pz) for generating the damage layer S3 from the front surface 10a of the wafer 10.

Next, the liquid supply mechanism 90 is actuated to introduce liquid L from the liquid inlet 844a through the pipe 92. The liquid L introduced from the liquid inlet 844a is introduced into the elliptical dome chamber 85a through the laser light introduction part 843a, and is discharged to the outside from the gap between the lower end 86a of the second condenser 84a and the front surface 10a of the wafer 10. In this way, the liquid L introduced into the second condenser 84a can be used to form the following state: a liquid layer 851a is formed on the wafer 10, and the elliptical dome chamber 85a is immersed in the liquid layer 851a.

As described above, the second focus P3 of the ellipse forming the elliptical dome chamber 85a is positioned below Pz from the front surface 10a of the wafer 10, and the moving mechanism 30 is actuated, and while the wafer 10 is moved along the predetermined dividing line 14 arranged in the X-axis direction, the second laser light irradiation mechanism 8A is actuated to irradiate the pulsed laser light PL0. Here, as shown in FIG. 6, the focusing lens 841a is set to focus the pulsed laser light PL0 on the first focus P2 located in the liquid layer 851a. And, when the laser light PL0 is focused on the first focus P2, a shock wave PL3a is generated at the first focus P2. The shock wave PL3a generated at the first focus point P2 propagates in the liquid L constituting the liquid layer 851a and is reflected at various locations on the inner wall of the elliptical dome chamber 85a. The shock wave PL3a reflected at various locations on the inner wall of the elliptical dome chamber 85a reaches the front surface 10a of the wafer 10 and further propagates within the wafer 10, focusing the second focus point P3 located at a depth Pz in the Z-axis direction from the front surface 10a of the wafer 10 as a focal point, and forming a damage layer S3 along the inside of the predetermined splitting line 14 located in the X-axis direction.

As described above, after the damage layer S3 has been formed in the X-axis direction at the predetermined depth (Pz), the moving mechanism 30 is actuated, and the work clamp 25 is appropriately indexed and fed in the Y-axis direction, and the second focus P3 is positioned inside the predetermined separation line 14 adjacent to the previously generated predetermined separation line 14 of the damage layer S3, and the work clamp 25 is further moved along the X-axis direction to form the damage layer S3. By repeating such processing, the damage layer S3 is formed inside all the predetermined separation lines 14 formed in the predetermined direction of the wafer 10. After the destruction layer S3 is formed inside all the predetermined splitting lines 14 along the predetermined direction, the unillustrated rotation drive mechanism can be controlled to rotate the work clamp 25 90 degrees, and the destruction layer S3 is formed inside all the predetermined splitting lines 14 in the direction orthogonal to the predetermined splitting lines 14 on which the destruction layer S3 has been formed. By the above, the destruction layer S3 that serves as the starting point for splitting the wafer 10 into individual chips is formed along the predetermined splitting lines 14, and the destruction layer forming step is completed (destruction layer forming step). After the destruction layer forming step has been implemented, the above-mentioned splitting device 70 can be used to implement the splitting step to split the wafer 10 into individual device chips 12'.

Furthermore, in the destruction layer forming step in this embodiment, the laser irradiation conditions implemented by the second laser light irradiation mechanism 8A are set as follows, for example.

Wavelength: 355nm~1064nm

Repetition frequency: 50kHz

Average output: 10W~100W

Pulse width: less than 100ps

Since even according to the above-mentioned implementation form, the impact wave PL3a can still be generated on the wafer 10 and propagated inside the wafer 10, and the damage layer S3 is generated by focusing at the second focus P3 set at the predetermined depth Pz along the predetermined dividing line 14 of the wafer 10, and the laser light irradiated at this time does not need to select a wavelength with absorption or penetration corresponding to the material of the wafer 10, but a wide-band wavelength laser light set in an arbitrary range can be used, so there is no need to prepare a laser processing device corresponding to the type of wafer or the type of processing.

According to the present invention, it is not further limited to the above-mentioned implementation form, and various variations can be provided. The third implementation form and the variation of the third implementation form are described while referring to FIG. 7.

The third laser irradiation mechanism 8B used in the third embodiment shown in FIG. 7(a) replaces the second condenser 84a of the second laser irradiation mechanism 8A of the wafer processing device 2B of the second embodiment described in FIG. 5 and FIG. 6, and is different in the following point: a third condenser 84b is provided. Accordingly, in FIG. 7(a), only the structure of the third condenser 84b of the third laser irradiation mechanism 8B is shown, and other structures are omitted.

As shown in FIG. 7( a ), the third concentrator 84b, viewed from above, has a concentrating lens 841b and a glass plate 842b inside, and a dome chamber member 85b composed of a hollow hemispherical surface that functions as the shock wave generating mechanism of the present invention is arranged in the lower space 852 separated by the glass plate 842b. A liquid introduction port 844b that forms a liquid layer forming mechanism together with a liquid supply mechanism 90 is formed on the side of the lower space 852, and a pipe 92 that can guide the liquid L from the above-mentioned liquid supply mechanism 90 is connected to the liquid introduction port 844b. An opening hole H is formed at the top of the above-mentioned dome chamber member 85b, and the upper side of the dome chamber member 85b and the hollow interior are connected. Furthermore, the dome chamber component 85b is formed of a hard component that does not allow the pulsed laser light PL0 to penetrate, and can be formed of metal, glass, etc. The following describes the function of the third concentrator 84b formed in this way.

When the wafer processing method of this embodiment is implemented using the third laser beam irradiation mechanism 8B, after the above-mentioned holding step and calibration step are implemented, the work clamp 25 is rotated by the moving mechanism 30 to adjust the direction of the predetermined splitting line 14 of the wafer 10 to the direction along the X-axis direction, and the processing start position of the predetermined splitting line 14 is positioned directly below the third condenser 84b of the third laser beam irradiation mechanism 8B. When the processing start position of the predetermined splitting line 14 is positioned directly below the third condenser 84b of the third laser beam irradiation mechanism 8B, the height adjustment mechanism not shown in the figure is activated to adjust the height of the third laser beam irradiation mechanism 8B to a predetermined height. The predetermined height will be described later.

As described above, when the predetermined dividing line 14 of the wafer 10 is positioned directly below the third condenser 84b and the third laser beam irradiation mechanism 8B is positioned at a predetermined height, the liquid supply mechanism 90 is activated to introduce the liquid L into the lower space 852 through the piping 92 and the liquid inlet 844b.

The liquid L introduced from the liquid inlet 844b will fill the lower space 852 in the third concentrator 84b, and will be introduced into the hollow area inside the dome chamber component 85b through the opening hole H formed at the top of the dome chamber component 85b to form a liquid layer 851b. The liquid L with the liquid layer 851b formed will be discharged to the outside from the gap between the lower end 86b of the third concentrator 84b and the front surface 10a of the wafer 10. In this way, the following state is achieved: the liquid layer 851b is formed on the wafer 10 by the liquid L introduced into the lower space 852 of the third concentrator 84b, and the dome chamber component 85b is immersed in the liquid layer 851b.

If the third laser irradiation mechanism 8B including the third condenser 84b provided with the above-mentioned dome chamber component 85b is positioned at a predetermined height relative to the predetermined dividing line 14 of the wafer 10, the third laser irradiation mechanism 8B can be operated while the wafer 10 is moved in the X-axis direction by the moving mechanism 30, and the pulsed laser beam PL0 can be irradiated under the same laser irradiation conditions as the above-mentioned second embodiment. As shown in FIG. 7(a), the pulsed laser beam PL0 can be guided to the focusing lens 841b of the third condenser 84b to be focused, and then irradiated to the dome chamber component 85b through the glass plate 842b. As described above, the dome chamber component 85b is formed of a hard component (metal, glass, etc.) that does not allow the pulsed laser beam PL0 to penetrate but transmits vibration, and the pulsed laser beam PL0 can be irradiated to the upper surface of the dome chamber component 85b to generate a shock wave PL3b in the liquid layer 851b. The shock wave PL3b propagates in the liquid layer 851b formed inside the dome chamber component 85b and reaches the front surface 10a of the wafer 10, and further propagates inside the wafer 10. In this embodiment, as described above, the height of the third laser beam irradiation mechanism 8B is adjusted to a predetermined height, and this predetermined height refers to the predetermined height at which the position P4 of the damage layer S4 formed by focusing the shock wave PL3b generated by the dome chamber component 85b inside the wafer 10 becomes the desired depth Pz.

As described above, even by the third laser beam irradiation mechanism 8B shown in FIG. 7(a), it is still possible to generate the damage layer S4 by focusing along the predetermined dividing line 14 of the wafer 10 at the position P4 set at the predetermined depth Pz, without selecting the laser beam having the absorption or penetration corresponding to the material of the wafer 10, and without preparing the laser processing device corresponding to the type of wafer or the type of processing.

In addition, with reference to FIG. 7(b), the laser light irradiation mechanism 8C shown as a variation of the third laser light irradiation mechanism 8B provided in the third embodiment is described. The laser light irradiation mechanism 8C replaces the third condenser 84b of the third laser light irradiation mechanism 8B described in FIG. 7(a), and is different in the following point: a fourth condenser 84c is provided. Accordingly, in FIG. 7(b), only the fourth condenser 84c is shown, and other structures are omitted.

As shown in FIG. 7( b ), the fourth concentrator 84c, viewed from above, is provided with a concentrating lens 841c and a solid hemisphere 85c that functions as the shock wave generating mechanism of the present invention. A liquid introduction port 844c that constitutes a liquid layer forming mechanism together with the aforementioned liquid supply mechanism 90 is formed in the wall portion 88 constituting the fourth concentrator 84c, and a passage 89 that guides the liquid L guided from the liquid introduction port 844c to the lower end 86c side of the fourth concentrator 84c is formed in the wall portion 88. A pipe 92 that guides the liquid L from the liquid supply mechanism 90 is connected to the liquid introduction port 844c. The hemispherical body 85c is disposed on the lower side of the fourth concentrator 84c, and is configured such that the spherical surface 85d of the hemispherical body 85c faces the upper side where the focusing lens 841c is disposed, and the flat surface 85e forms a flush plane with the lower end 86c of the fourth concentrator 84c. The hemispherical body 85c is formed of a hard component that does not allow the pulsed laser light PL0 to penetrate, and is formed of, for example, metal, glass, etc. The lower end 86c side of the fourth concentrator 84c is blocked by the hemispherical body 85c. The following is an explanation of the function of the fourth concentrator 84c formed in this way.

When the wafer processing method of this embodiment is implemented using the fourth condenser 84c, the above-mentioned holding step and calibration step are implemented, and the work clamp 25 is rotated by the moving mechanism 30 to adjust the direction of the predetermined splitting line 14 of the wafer 10 to the direction along the X-axis direction, and the processing start position of the predetermined splitting line 14 of the wafer 10 is positioned directly below the fourth condenser 84c. Similar to the third embodiment, when the predetermined splitting line 14 is positioned directly below the fourth condenser 84c, the height adjustment mechanism not shown is actuated to adjust the height of the laser light irradiation mechanism 8C to a predetermined height.

As described above, when the predetermined dividing line 14 of the wafer 10 is positioned directly below the fourth concentrator 84c and the fourth concentrator 84c is positioned at a predetermined height, the liquid supply mechanism 90 is activated and the liquid L is introduced from the liquid introduction port 844c through the pipe 92. The liquid L introduced from the liquid introduction port 844c passes through the passage 89 in the wall portion 88 constituting the fourth concentrator 84c and the liquid L is supplied to the lower end 86c side of the fourth concentrator 84c. The liquid L supplied to the lower end 86c side of the fourth concentrator 84c can fill the space formed by the front surface 10a of the wafer 10 and the flat surface 85e of the hemispherical body 85c and form a liquid layer 851c. In this way, the flat surface 85e of the hemispherical body 85c is immersed in the liquid layer 851c.

If the fourth condenser 84c including the above-mentioned hemispherical body 85c is positioned at a predetermined height relative to the front surface 10a of the wafer 10 and a liquid layer 851c is formed, the wafer 10 can be moved in the X-axis direction by the moving mechanism 30 while the laser light irradiation mechanism 8C is operated to irradiate the pulsed laser light PL0 under the same laser irradiation conditions as the above-mentioned third embodiment. As shown in FIG. 7(b), the pulsed laser light PL0 can be guided to the focusing lens 841c of the fourth condenser 84c to be focused and irradiated on the spherical surface 85d of the hemispherical body 85c. As mentioned above, the hemispherical body 85c is formed of a hard component (metal, glass, etc.) that does not allow the pulsed laser beam PL0 to penetrate but transmits vibrations, and the shock wave PL3c can be generated by irradiating the pulsed laser beam PL0 on the spherical surface 85d of the hemispherical body 85c.

The shock wave PL3c generated by the hemispherical body 85c propagates in the hemispherical body 85c and reaches the flat surface 85e, and generates the shock wave PL3c in the liquid layer 851c. In addition, the shock wave PL3c reaches the front surface 10a of the wafer 10, and further generates the shock wave PL3c propagating in the wafer 10. At this time, the shock wave PL3c propagating in the wafer 10 is focused at the position P5 of the predetermined depth Pz inside the predetermined dividing line 14 of the wafer 10 by the action of the spherical surface 85d forming the upper surface of the hemispherical body 85c, and forms the damage layer S5. In this embodiment, as described above, when the predetermined splitting line 14 of the wafer 10 is positioned directly below the fourth condenser 84c of the laser light irradiation mechanism 8C, the height of the laser light irradiation mechanism 8C is adjusted to a predetermined height, and this predetermined height refers to the height at which the position P5 at which the shock wave PL3c generated by the hemisphere 85c is focused inside the wafer 10 to form the damage layer S5 becomes the desired depth Pz. In addition, by operating the moving mechanism 30 according to the above procedure, the damage layer S5 that becomes the starting point when splitting the wafer 10 can be formed inside all the predetermined splitting lines 14 of the wafer 10.

Even with the modified example of the third laser irradiation mechanism shown in FIG. 7(b) above, the damage layer S5 can still be generated by focusing along the predetermined dividing line 14 of the wafer 10 at the position P5 set at the predetermined depth Pz, without selecting a laser beam having an absorptivity or a penetrability corresponding to the material of the wafer 10, and without preparing a laser processing device corresponding to the type of wafer or the type of processing.

Furthermore, in the above description, the dome chamber component 85b and the hemisphere 85c that function as the shock wave generating mechanism are referred to as "spherical surface" and "sphere" for convenience with respect to the shape of the portion irradiated with the pulsed laser light. However, in order to focus the shock wave generated by the pulsed laser light at the desired position, the curvature of the surface can be appropriately adjusted and is not limited to a perfect spherical surface or sphere. Furthermore, in the above-mentioned embodiments, although in any embodiment, the front surface 10a of the wafer 10 is used as the upper surface to irradiate the laser beam, or the shock wave generated by the irradiation of the laser beam is propagated, the present invention is not limited to this, and the back surface 10b of the wafer 10 can also be set as the upper surface to be attracted and held on the work clamp 25, and the processing is performed from the back surface 10b side of the wafer 10. In addition, even in the above-mentioned second embodiment and third embodiment, the focus of the shock wave PL3a~PL3c can be positioned near the upper surface of the predetermined division line 14 of the wafer 10, and the upper surface of the wafer 10 can be processed such as ablation.

10: Wafer

10a: Front

25: Workbench

6: First laser irradiation mechanism

61: Oscillator

62: Delay mechanism by wavelength

621: Optical fiber on the output side

63: Collimating lens

64: Ring-generating mechanism

641,642: Conical lens

643:Diffraction grating

66: Reflector

67: First concentrator

671: Focusing lens

P1,P1’: Position

Pz,Pz’: Depth

PL0,PL1,PL2: Pulsed laser light

PL1a: Red light

PL1b: Yellow light

PL1c: Green light

PL1d: blue light

PL3,PL3’: shock wave

S1, S2: Destruction layer

X,Y: Arrow (direction)

Claims (2)

A wafer processing method is to divide a wafer into individual chips. The wafer processing method comprises the following steps: a holding step, holding the wafer in a holding mechanism; a damage layer forming step, positioning the focus of the shock wave on the wafer held in the holding mechanism and forming a damage layer in the area to be divided; and a dividing step, dividing the wafer into individual chips with the damage layer as the starting point. The bad layer forming step is to form each pulse of laser light into a ring with a time difference for each wavelength by using a first laser light irradiation mechanism for irradiating pulsed laser light, and irradiate the pulsed laser light formed into the ring toward the wafer to generate a shock wave and form a focal point in the area to be divided, and the position of the focal point of the shock wave can be set by adjusting the time difference with the first laser light irradiation mechanism. A wafer processing device is used to divide a wafer into individual chips. The wafer processing device includes the following: a holding mechanism that holds the wafer; and a damage layer forming mechanism that positions the focal point of the shock wave on the wafer held by the holding mechanism and forms a damage layer in the area to be divided. The damage layer forming mechanism is a first laser light irradiation mechanism that irradiates pulsed laser light, and the first laser light irradiation mechanism forms each pulse of laser light into a ring with a time difference according to each wavelength, and irradiates the pulsed laser light formed into the ring toward the wafer to generate a shock wave and form a focal point in the area to be divided, and the position of the focal point of the shock wave can be set by adjusting the time difference with the first laser light irradiation mechanism.

Images