Chip manufacturing method

Abstract

To provide a manufacturing method of a chip, capable of being divided even in a workpiece that does not have a crystalline without meander.SOLUTION: A manufacturing method of a chip, comprises: a modified layer formation step 102 of forming a modified layer for a division origin to a region corresponded to a scheduled division line of a workpiece by positioning a focal point of a laser beam with a wavelength having a transmissivity to the workpiece into the inner part of the workpiece, setting the laser beam to a first output, and irradiating the laser beam in a burst mode; a division step 103 of applying an external force to the workpiece, and being divided along the scheduled division line; and a crack induction layer format step 101 of irradiating the plurality of focal points of the laser beam which is formed so as to be arranged along to a processing feeding direction prior to the modified layer formation step 102 into the inner part of the workpiece by an output that is smaller than the first output, and forming a crack induction layer for inducting an extension direction of a crack to a laser beam incident surface side from the modified layer for the division origine.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a chip.

Background Art

[0002] As a method for manufacturing a chip by dividing a plate-like object such as a semiconductor wafer, after irradiating a laser beam having a wavelength that is transmissive to the plate-like object to form a modified layer inside the plate-like object, an external force is applied to divide it into individual chips starting from the modified layer (for example, see Patent Document 1).

[0003] In the above method, a modified layer is formed along the planned division line of the wafer to extend cracks in the thickness direction, and the cracks are exposed on the front or back surface of the wafer. Then, by pressing the wafer on the extending side of the crack, the wafer is divided.

[0004] However, in the method disclosed in Patent Document 1, especially in the case of a non-crystalline wafer such as glass, cracks do not extend linearly from the modified layer, and the cracks exposed on the front or back surface side of the wafer may meander.

[0005] In order to solve this type of problem, prior to forming the modified layer for the division starting point, a technique has been proposed to perform laser processing with a lower output than the modified layer for the division starting point to form a crack induction layer that induces the crack extension direction (for example, see Patent Document 2).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] While the method described in Patent Document 2 allows for the crack propagation direction to be guided by the crack induction layer, thereby suppressing meandering, there was a need for further improvement in processing quality.

[0008] The present invention has been made in view of the above facts, and its purpose is to provide a method for manufacturing chips that can divide even workpieces that do not have crystalline properties without meandering. [Means for solving the problem]

[0009] To solve the above-mentioned problems and achieve the objective, the present invention provides a chip manufacturing method for a workpiece, which involves irradiating the workpiece with a laser beam along a plurality of planned division lines set on the workpiece to divide the workpiece and manufacture a chip, comprising: a modified layer formation step in which a laser beam with a wavelength that is transparent to the workpiece is focused at a point inside the workpiece from one side of the workpiece, and the laser beam is set to a first output and irradiated in burst mode to form a modified layer for division starting points in the region of the workpiece corresponding to the planned division lines; and a division step in which, after performing the modified layer formation step, an external force is applied to the workpiece to divide it along the planned division lines, wherein prior to the modified layer formation step, In the crack induction layer formation step, Multiple laser beams, aligned along the processing feed direction, are focused at an output lower than the first output, irradiating the inside of the workpiece with these focal points. This forms a crack-inducing layer on one side of the modified layer for splitting, guiding the crack's extension direction. As a result, cracks are extended from the modified layer for splitting toward the crack-inducing layer, forming cracks that appear on the one side of the workpiece. Furthermore, the workpiece is composed of an amorphous material. It is characterized by the following: In the chip manufacturing method described above, the output of the laser beam in the crack induction layer formation step may be less than the first output. In the chip manufacturing method described above, in the modified layer formation step, the laser beam oscillated by the laser oscillator may be thinned out at a repetition frequency specified in the processing conditions, and multiple laser beams may be irradiated at each repetition frequency. [Effects of the Invention]

[0010] This invention has the effect of enabling the division of workpieces that do not have crystalline properties without meandering. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a perspective view showing an example of the configuration of a laser processing apparatus that implements a part of the chip manufacturing method according to Embodiment 1. [Figure 2] Figure 2 is a schematic diagram showing the configuration of the laser beam irradiation unit of the laser processing apparatus shown in Figure 1. [Figure 3] Figure 3 shows the laser beam oscillated by the seeder of the oscillator of the laser beam irradiation unit shown in Figure 2. [Figure 4] Figure 4 is a flowchart showing the flow of the chip manufacturing method according to Embodiment 1. [Figure 5] Figure 5 shows the laser beam generated by the AOM of the laser oscillator during the crack induction layer formation step of the chip manufacturing method shown in Figure 4. [Figure 6] Figure 6 is a schematic cross-sectional view of a workpiece showing the crack induction layer formation step of the chip manufacturing method shown in Figure 4. [Figure 7] Figure 7 is a schematic plan view of the workpiece showing the crack induction layer formation step of the chip manufacturing method shown in Figure 4. [Figure 8] Figure 8 shows the laser beam generated by the AOM of the laser oscillator during the modified layer formation step of the chip manufacturing method shown in Figure 4. [Figure 9] Figure 9 is a schematic cross-sectional view of a workpiece illustrating the modified layer formation step in the chip manufacturing method shown in Figure 4. [Figure 10] Figure 10 is a schematic side view showing a partial cross-section of the state in which the splitting device holds the workpiece during the splitting step of the chip manufacturing method shown in Figure 4. [Figure 11] Figure 11 is a schematic side view showing a partial cross-section of the state in which the splitting device has divided the workpiece into chips during the splitting step of the chip manufacturing method shown in Figure 4. [Modes for carrying out the invention]

[0012] Embodiments for implementing the present invention will be described in detail with reference to the drawings. The present invention is not limited by the content described in the following embodiments. Also, the constituent elements described below include those that can be easily assumed by those skilled in the art and substantially identical ones. Furthermore, the configurations described below can be combined as appropriate. Also, various omissions, substitutions, or changes in the configuration can be made without departing from the gist of the present invention.

[0013] [Embodiment 1] A method for manufacturing a chip according to Embodiment 1 of the present invention will be described based on the drawings. FIG. 1 is a perspective view showing a configuration example of a laser processing apparatus for implementing a part of the method for manufacturing a chip according to Embodiment 1. The method for manufacturing a chip according to Embodiment 1 is partially implemented by the laser processing apparatus 1 shown in FIG. 1. The laser processing apparatus 1 shown in FIG. 1 is a processing apparatus that irradiates a workpiece 200 with a laser beam 21.

[0014] (Workpiece) The workpiece 200 to be processed by the laser processing apparatus 1 shown in FIG. 1 is a wafer such as a disk-shaped semiconductor wafer or an optical device wafer having a substrate 201 made of a non-crystalline material. As shown in FIG. 1, the workpiece 200 has a plurality of division planned lines 203 intersecting each other on a surface 202 corresponding to one surface, and a device 204 is formed in a region partitioned by the division planned lines 203.

[0015] The device 204 is, for example, an integrated circuit such as an IC (Integrated Circuit) or LSI (Large Scale Integration), an image sensor such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), or a memory (semiconductor memory device).

[0016] In Embodiment 1, the workpiece 200 has a substrate 201 made of glass as an amorphous material. However, in the present invention, the workpiece 200 is not limited to glass as long as it is an amorphous material; the substrate 201 may be made of quartz or silica, etc. Thus, in Embodiment 1, the workpiece 200 has a substrate 201 made of an amorphous material and does not have crystalline properties. Also, in Embodiment 1, the thickness of the substrate 201 of the workpiece 200 is 200 μm.

[0017] In Embodiment 1, as shown in Figure 1, the workpiece 200 is supported within the opening of the annular frame 207 by attaching a tape 206, which is disc-shaped with a diameter larger than the outer diameter of the workpiece 200 and has an annular frame 207 attached to its outer edge, to the back surface 205, which corresponds to the other side of the back surface 202. The workpiece 200 is divided into individual chips 210 by irradiating a planned division line 203 with a laser beam 21, for example. Each chip 210 includes a substrate 201 and a device 204.

[0018] (Laser processing equipment) The laser processing apparatus 1 shown in Figure 1 is a processing apparatus that performs laser processing on a workpiece 200 by setting a focal point 211 inside the substrate 201 of a pulsed laser beam 21 with a wavelength that is transparent from the surface 202 of the workpiece 200 to the substrate 201 that makes up the workpiece 200, and irradiating the workpiece 200 along the division line 203 with the laser beam 21.

[0019] As shown in Figure 1, the laser processing apparatus 1 includes a holding table 10 for holding the workpiece 200, a laser beam irradiation unit 20, a moving unit 30, an imaging unit 40, and a control unit 60.

[0020] The holding table 10 holds the workpiece 200 on a holding surface 11 parallel to the horizontal direction. The holding surface 11 is a disc shape formed from porous ceramic or the like, and is connected to a vacuum suction source (not shown) via a suction path (not shown). The holding table 10 holds the workpiece 200 placed on the holding surface 11 by suction from the vacuum suction source. Multiple clamping parts 12 are arranged around the holding table 10 to hold an annular frame 207 that supports the workpiece 200 within the opening.

[0021] Furthermore, the holding table 10 is rotated by the rotational movement unit 33 of the moving unit 30 around an axis that is perpendicular to the holding surface 11 and parallel to the Z-axis direction which is also parallel to the vertical direction. Together with the rotational movement unit 33, the holding table 10 is moved in the X-axis direction (corresponding to the machining direction) parallel to the horizontal direction by the X-axis movement unit 31 of the moving unit 30, and moved in the Y-axis direction which is parallel to the horizontal direction and perpendicular to the X-axis direction by the Y-axis movement unit 32. The holding table 10 is moved by the moving unit 30 between the machining area below the laser beam irradiation unit 20 and the loading / unloading area away from below the laser beam irradiation unit 20 where the workpiece 200 is loaded and unloaded.

[0022] The moving unit 30 moves the holding table 10 and the focal point 211 of the laser beam 21 irradiated by the laser beam irradiation unit 20 relative to each other in the X-axis direction, Y-axis direction, Z-axis direction, and around an axis parallel to the Z-axis direction. The X-axis direction and Y-axis direction are mutually orthogonal and parallel to the holding surface 11 (i.e., the horizontal direction). The Z-axis direction is perpendicular to both the X-axis direction and the Y-axis direction.

[0023] The moving unit 30 includes an X-axis moving unit 31, which is a machining feed unit that moves the holding table 10 in the X-axis direction; a Y-axis moving unit 32, which is an indexing feed unit that moves the holding table 10 in the Y-axis direction; a rotational moving unit 33 that rotates the holding table 10 around an axis parallel to the Z-axis direction; and a Z-axis moving unit 34 that moves the focal point 211 of the laser beam 21 of the laser beam irradiation unit 20 in the Z-axis direction.

[0024] The Y-axis movement unit 32 is an indexing feed unit that moves the holding table 10 and the focusing point 211 of the laser beam 21 of the laser beam irradiation unit 20 relative to each other in the Y-axis direction. In Embodiment 1, the Y-axis movement unit 32 is installed on the main body 2 of the laser processing apparatus 1. The Y-axis movement unit 32 supports the movable plate 5 that supports the X-axis movement unit 31 so as to be movable in the Y-axis direction.

[0025] The X-axis movement unit 31 is a machining feed unit that moves the holding table 10 and the focusing point 211 of the laser beam 21 of the laser beam irradiation unit 20 relative to each other in the X-axis direction. The X-axis movement unit 31 is installed on a movement plate 5. The X-axis movement unit 31 supports a second movement plate 6 that is movable in the X-axis direction, and the second movement plate 6 supports a rotational movement unit 33 that rotates the holding table 10 around an axis parallel to the Z-axis direction. The second movement plate 6 supports the rotational movement unit 33 and the holding table 10. The rotational movement unit 33 supports the holding table 10.

[0026] The Z-axis movement unit 34 is a feed unit that moves the holding table 10 and the focusing point 211 of the laser beam 21 of the laser beam irradiation unit 20 relative to each other in the Z-axis direction. The Z-axis movement unit 34 is installed on an upright wall 3 that is erected from the main body of the device 2. The Z-axis movement unit 34 supports a support column 4, which has a part of the laser beam irradiation unit 20, including the focusing lens 26 (described later), positioned at its tip, so as to be movable in the Z-axis direction.

[0027] The X-axis movement unit 31 includes a well-known ball screw that is rotatable around its axis and moves the second movement plate 6 in the X-axis direction when rotated around its axis, a well-known pulse motor that rotates the ball screw around its axis, and a well-known guide rail that supports the second movement plate 6 so as to be movable in the X-axis direction. The Y-axis movement unit 32 includes a well-known ball screw that is rotatable around its axis and moves the movement plate 5 in the Y-axis direction when rotated around its axis, a well-known pulse motor that rotates the ball screw around its axis, and a well-known guide rail that supports the movement plate 5 so as to be movable in the Y-axis direction. The Z-axis movement unit 34 includes a well-known ball screw that is rotatable around its axis and moves the support column 4 in the Z-axis direction when rotated around its axis, a well-known pulse motor that rotates the ball screw around its axis, and a well-known guide rail that supports the support column 4 so as to be movable in the Z-axis direction. The rotational movement unit 33 includes a motor that rotates the holding table 10 around its axis, etc.

[0028] Furthermore, the laser processing apparatus 1 includes an X-axis position detection unit (not shown) for detecting the position of the holding table 10 in the X-axis direction, a Y-axis position detection unit (not shown) for detecting the position of the holding table 10 in the Y-axis direction, and a Z-axis position detection unit (not shown) for detecting the position (corresponding to the height position) of the focusing lens 26 (shown in Figure 2) of the laser beam irradiation unit 20 in the Z-axis direction. Each position detection unit outputs the detection result to the control unit 60. In this embodiment 1, the X-axis and Y-axis positions of the holding table 10 of the laser processing apparatus 1 and the Z-axis position of the focusing lens 26 of the laser beam irradiation unit 20 are determined by the distances in the X-axis, Y-axis, and Z-axis directions from a predetermined reference position (not shown).

[0029] Next, the laser beam irradiation unit 20 will be described. Figure 2 is a schematic diagram showing the configuration of the laser beam irradiation unit of the laser processing apparatus shown in Figure 1. Figure 3 is a diagram showing the laser beam oscillated by the seeder of the oscillator of the laser beam irradiation unit shown in Figure 2.

[0030] The laser beam irradiation unit 20 is a laser beam irradiation means that focuses and irradiates a workpiece 200 held on the holding surface 11 of the holding table 10 with a pulsed laser beam 21. In Embodiment 1, a part of the laser beam irradiation unit 20 is positioned at the tip of a support column 4, which is supported by a Z-axis moving unit 34 installed on an upright wall 3 erected from the main body of the apparatus 2, as shown in Figure 1.

[0031] The laser beam irradiation unit 20 irradiates the substrate 201 of the workpiece 200 held on the holding table 10 with a laser beam 21 of a penetrating wavelength. As shown in Figure 2, the laser beam irradiation unit 20 includes a laser oscillator 22 that emits a pulsed laser beam 21, an output adjustment unit 23 that adjusts the output of the laser beam 21 emitted by the laser oscillator 22, a branching unit 24 that changes whether the laser beam 21 whose output has been adjusted by the output adjustment unit 23 is branched or not, a mirror 25 that reflects the branched or unbranched laser beam 21 by the branching unit 24, and a focusing lens 26 which is a light concentrator that focuses the laser beam 21 reflected by the mirror 25 and irradiates the workpiece 200. Note that the clamp section 12 is omitted in Figure 2. Note that in this invention, the output adjustment unit 23 may be provided inside the laser oscillator 22.

[0032] The laser oscillator 22 includes, for example, a seeder that oscillates a low-power, high-frequency pulsed laser beam 212 (shown in Figure 3) that serves as a seed light, an acoust-optical modulator (AOM) that thins out the high-frequency pulsed laser beam 212 oscillated by the seeder at a predetermined repetition frequency to generate any number of high-frequency pulsed laser beams 212, and a damper that absorbs the pulsed laser beams 212 thinned out by the AOM. The pulsed laser beams 212 generated by the AOM are emitted as the laser beam 21 to the output adjustment unit 23.

[0033] In Figure 3, the horizontal axis represents time, and the vertical axis represents the output of the laser beam 212 oscillated by the seeder. The repetition frequency of the laser beam 212 oscillated by the seeder is very high, for example, several tens of megahertz (MHz), and the laser beam 212 oscillated by the seeder has a very high repetition frequency.

[0034] The AOM comprises an acousto-optic medium, for example, made of tellurite-based glass, to which a piezoelectric element (not shown) is bonded. When ultrasonic vibrations are transmitted to the acousto-optic medium by the piezoelectric element, it exhibits the action of a diffraction grating due to the photoelastic effect. An AOM control means is connected to the piezoelectric element of the AOM to generate arbitrary ultrasonic vibrations. The AOM control means, through control, makes it possible to set the number of pulses in the pulsed laser beam 212 generated by the AOM to any desired number. These seeder and AOM control means are appropriately controlled by a control unit 60 provided in the laser processing apparatus 1.

[0035] In Embodiment 1, the branching unit 24 is a spatial light modulator that changes the number of branches or non-branching of the laser beam 21 by changing the displayed phase pattern. As the spatial light modulator, well-known SLM devices such as reflective liquid crystal LCOS (Liquid-Crystal on Silicon), transmissive liquid crystal LCP (Liquid Crystal Panel), deformable mirror, and DMD (Digital Micro-mirror Device) can be used. In Embodiment 1, the spatial light modulator which is the branching unit 24 is an LCOS, but in the present invention, a diffractive optical element may also be used.

[0036] The focusing lens 26 is positioned opposite the holding surface 11 of the holding table 10 in the Z-axis direction. The focusing lens 26 is a focusing optical element that focuses and irradiates a pulsed laser beam 21 onto a workpiece 200 held on the holding table 10. The focusing lens 26 passes through the laser beam 21 emitted from the laser oscillator 22 and reflected by the mirror 25, and focuses the laser beam 21 to a focal point 211. In Embodiment 1, the focusing lens 26 focuses the focal point 211 of the laser beam 21 into the interior of the workpiece 200 held on the holding surface 11 of the holding table 10.

[0037] The laser beam irradiation unit 20 irradiates the workpiece 200, which is held on the holding table 10, with a laser beam 21 of a wavelength that the substrate 201 of the workpiece 200 can penetrate, thereby performing laser processing on the workpiece 200. In Embodiment 1, the wavelength of the laser beam 21 is in the infrared region (for example, 1064 nm).

[0038] The imaging unit 40 images the workpiece 200 held on the holding table 10. The imaging unit 40 is equipped with an image sensor such as a CCD (Charge Coupled Device) image sensor or a CMOS (Complementary MOS) image sensor whose objective lens is opposite in the Z-axis direction. In Embodiment 1, as shown in Figure 1, the imaging unit 40 is positioned at the tip of the support column 4, with the objective lens aligned with the condensing lens 26 along the X-axis direction.

[0039] The imaging unit 40 acquires the image captured by the image sensor and outputs the acquired image to the control unit 60. The imaging unit 40 also images the workpiece 200 held on the holding surface 11 of the holding table 10 and acquires an image for performing alignment, which involves positioning the workpiece 200 with the laser beam irradiation unit 20.

[0040] The control unit 60 controls each of the above-mentioned components of the laser processing apparatus 1 to cause the laser processing apparatus 1 to perform processing operations on the workpiece 200. The control unit 60 is a computer having an arithmetic processing unit with a microprocessor such as a CPU (central processing unit), a storage device with memory such as ROM (read-only memory) or RAM (random access memory), and an input / output interface device. The arithmetic processing unit of the control unit 60 performs calculations according to the computer program stored in the storage device and outputs control signals for controlling the laser processing apparatus 1 to the above-mentioned components of the laser processing apparatus 1 via the input / output interface device, thereby realizing the function of the control unit 60.

[0041] Furthermore, the laser processing apparatus 1 includes a display unit 61, which is a display means consisting of a liquid crystal display device that displays the status of processing operations and images, and an input unit 62, which is an input means used by the operator to input processing conditions and the like. The display unit 61 and the input unit 62 are connected to the control unit 60. In Embodiment 1, the input unit 62 is made up of a touch panel provided on the display unit 61.

[0042] (Method of manufacturing chips) The chip manufacturing method according to Embodiment 1 is a method for manufacturing a chip 210 by irradiating a laser beam 21 along a plurality of division lines 203 set on the surface 202 of a workpiece 200 to divide the workpiece 200. Figure 4 is a flowchart showing the flow of the chip manufacturing method according to Embodiment 1. As shown in Figure 4, the chip manufacturing method comprises a crack induction layer formation step 101, a modified layer formation step 102, and a division step 103.

[0043] (Crack induction layer formation step) Figure 5 shows the laser beam generated by the AOM of the laser oscillator during the crack induction layer formation step of the chip manufacturing method shown in Figure 4. Figure 6 is a schematic cross-sectional view of the workpiece showing the crack induction layer formation step of the chip manufacturing method shown in Figure 4. Figure 7 is a schematic plan view of the workpiece showing the crack induction layer formation step of the chip manufacturing method shown in Figure 4.

[0044] The crack induction layer formation step 101 is a step that precedes the modification layer formation step 102, in which the focal points 211 of multiple laser beams 21, which are arranged along the processing feed direction, are irradiated into the workpiece 200 at an output less than or equal to (preferably less than) the first output of the modification layer formation step 102, thereby forming a crack induction layer 302 (shown in Figure 6) that guides the extension direction of the crack 306 (shown in Figure 9) on the surface 202 side (corresponding to one side) of the modification layer 301 (shown in Figure 9) for splitting initiation. The modification layer 301 for splitting initiation consists of multiple modification regions 303 arranged along the planned splitting line 203, and the crack induction layer 302 consists of multiple crack induction regions 304 arranged along the planned splitting line 203.

[0045] The modified region 303 and the crack induction region 304 refer to areas within the substrate 201 where the density, refractive index, mechanical strength, and other physical properties differ from those of the surrounding area. Examples include melted areas, cracked areas, dielectric breakdown areas, refractive index change areas, and areas where these areas are mixed. The modified region 303 and the crack induction region 304 have lower mechanical strength than other parts of the substrate 201.

[0046] In Embodiment 1, during the crack induction layer formation step 101, the control unit 60 of the laser processing apparatus 1 receives and registers the processing conditions for the crack induction layer formation step 101 and the modified layer formation step 102 input by the operator, and the workpiece 200 is placed on the holding surface 11 of the holding table 10 located in the loading / unloading area. In Embodiment 1, during the crack induction layer formation step 101, when the control unit 60 receives a processing start instruction from the operator, the laser processing apparatus 1 uses suction to hold the workpiece 200 on the holding surface 11 of the holding table 10, and clamps the annular frame 207 with the clamping section 12.

[0047] In Embodiment 1, during the crack induction layer formation step 101, the control unit 60 of the laser processing apparatus 1 controls the movement unit 30 to move the holding table 10 to the processing area, and the imaging unit 40 images the workpiece 200 held on the holding table 10 to perform alignment. In Embodiment 1, during the crack induction layer formation step, the laser processing apparatus 1 thins out the laser beam 212 oscillated by the seeder of the laser oscillator 22 using an AOM at a repetition frequency 213 (shown in Figure 5) specified in the processing conditions, generating one laser beam 212 (i.e., a single pulse) for every repetition frequency 213 as shown in Figure 5, and outputs it as a laser beam 21 to the output adjustment unit 23. In Embodiment 1, the repetition frequency 213 of the laser beam 212 generated by the AOM is several MHz to 10 MHz. The horizontal axis in Figure 5 represents time, and the vertical axis in Figure 5 represents the output of the laser beam 212.

[0048] In Embodiment 1, in the crack induction layer formation step 101, the laser processing apparatus 1 adjusts the output of the laser beam 21 emitted by the AOM to the output specified in the processing conditions using the output adjustment unit 23, and branches it into multiple (two in Embodiment 1) beams in the X-axis direction, which is the processing feed direction, using the branching unit 24. In Embodiment 1, in the crack induction layer formation step 101, the laser processing apparatus 1 sets the focal point 211 of the laser beam 21 inside the substrate 201 based on the processing conditions, and as shown in Figures 6 and 7, moves the holding table 10 in the X-axis direction using the moving unit 30, and irradiates the planned division line 203 of the workpiece 200 with a pulsed laser beam 21 from the surface 202 side of the substrate 201, thereby forming a crack induction region 304 inside the substrate 201 of the workpiece 200.

[0049] In Embodiment 1, in the crack induction layer formation step 101, the laser beam 212 is split into multiple (two in Embodiment 1) beams and each beam is focused into the interior of the substrate 201 using a focusing lens 26, thereby simultaneously forming multiple crack induction regions 304 inside the substrate 201. As a result, the changes within the substrate 201 as adjacent crack induction regions 304 are formed cause the crack induction regions 304 to connect with each other by cracks 305. Thus, in Embodiment 1, in the crack induction layer formation step 101, a crack induction layer 302 consisting of multiple crack induction regions 304 is formed along all of the planned division lines 203 of the workpiece 200.

[0050] In Embodiment 1, the processing conditions for the crack induction layer formation step 101 are as follows: the distance in the X-axis direction of the focal point 211 of the branched laser beam 21 is 12 μm, the output of the laser beam 21 adjusted by the output adjustment unit 23 is 0.8 W, the defocus is 0.57 mm, and the feed rate of the holding table 10 is 1200 mm / second.

[0051] (Modified layer formation step) Figure 8 shows the laser beam generated by the AOM of the laser oscillator in the modified layer formation step of the chip manufacturing method shown in Figure 4. Figure 9 is a schematic cross-sectional view of the workpiece showing the modified layer formation step of the chip manufacturing method shown in Figure 4. The modified layer formation step 102 is a step in which a laser beam 21 with a wavelength that is transparent to the workpiece 200 is focused at a focal point 211 from the surface 202 side of the workpiece 200 into the interior of the workpiece 200, and the laser beam 21 is set to first output and irradiated in burst mode to form a modified layer 301 for the division starting point in the region corresponding to the planned division line 203 of the workpiece 200.

[0052] In Embodiment 1, during the modified layer formation step 102, the laser processing apparatus 1 thins out the laser beam 21 oscillated by the seeder of the laser oscillator 22 using an AOM at a repetition frequency 214 (shown in Figure 8) specified in the processing conditions. As shown in Figure 8, multiple (5 in this embodiment) laser beams 212 are generated for every repetition frequency 214, and these are emitted as laser beam 21 to the output adjustment unit 23. In Embodiment 1, the repetition frequency 214 of the laser beams 212 generated by the AOM is several MHz to 10 MHz. The horizontal axis in Figure 8 represents time, and the vertical axis in Figure 8 represents the output of the laser beams 212.

[0053] In Embodiment 1, in the modified layer formation step 102, the laser processing apparatus 1 adjusts the output of the laser beam 21 emitted by the AOM to a first output specified in the processing conditions using the output adjustment unit 23, and sets the focal point 211 of the laser beam 21 inside the substrate 201 based on the processing conditions. In Embodiment 1, in the modified layer formation step 102, the laser processing apparatus 1 does not branch the laser beam 21 with the branching unit 24, but as shown in Figure 9, moves the holding table 10 in the X-axis direction with the moving unit 30, and irradiates the planned division line 203 of the workpiece 200 with a pulsed laser beam 21 from the surface 202 side of the substrate 201, thereby forming a modified region 303 on the back surface 205 side, which is the other side of the crack induction region 304 inside the substrate 201 of the workpiece 200.

[0054] In Embodiment 1, in the modified layer formation step 102, the laser beam 21 is irradiated in a so-called burst mode, in which multiple (5 in this embodiment) laser beams 21 are irradiated at every repetition frequency 214. Thus, burst mode refers to irradiating multiple consecutive laser beams 21 from the laser beam 212 oscillated by the seeder at every repetition frequency 214.

[0055] In Embodiment 1, during the modified layer formation step 102, the laser processing apparatus 1 irradiates the laser beam 21 in burst mode, making it easier for cracks 306 to spread outwards compared to when the modified region 303 is formed by a single-pulse laser beam 21. Furthermore, in Embodiment 1, prior to the modified layer formation step 102, the crack induction layer 302 is formed on the surface 202 side of the modified region 303 during the crack induction layer formation step 101. As a result, changes within the substrate 201 during the formation of the modified region 303 cause cracks 306 to extend from the modified region 303 to the crack induction region 304 of the crack induction layer 302, and further, the cracks 306 extend from the crack induction region 304 of the crack induction layer 302 to the surface 202 of the workpiece 200, becoming visible on the surface 202.

[0056] Thus, in Embodiment 1, in the modified layer formation step 102, a modified layer 301 for splitting initiation is formed, consisting of a plurality of modified regions 303 that are along all of the planned splitting lines 203 of the workpiece 200 and connected by the crack induction layer 302 and cracks 306. In this way, the chip manufacturing method according to Embodiment 1 forms the crack induction layer 302 on the surface 202 side of the modified region 303 in the crack induction layer formation step 101 prior to the modified layer formation step 102, thereby causing cracks 306 to extend from the modified layer 301 for splitting initiation toward the crack induction layer 302, and then extend from the crack induction layer 302 toward the surface 202, forming cracks 306 that are exposed on the surface 202 side.

[0057] In Embodiment 1, the number of laser beams 21 in burst mode of the processing conditions for the modified layer formation step 102 is 5, the output of the laser beams 21 adjusted by the output adjustment unit 23 is 2.3W, the defocus is 0.65mm, and the feed rate of the holding table 10 is 1200mm / s.

[0058] Furthermore, in the present invention, in the modified layer formation step 102, the laser beam 21 may be irradiated multiple times along the entire length of each planned division line 203 while moving the holding table 10 in the X-axis direction to form a modified layer 301 for the division starting point. In this case, the position of the focusing point 211 in the height direction may or may not be changed. Note that in Embodiment 1, in the crack induction layer formation step 101 and the modified layer formation step 102, the laser beam 21 is incident from the surface 202 side of the workpiece 200, but in the present invention, in the crack induction layer formation step 101 and the modified layer formation step 102, the laser beam 21 may be incident from the back surface 205 side of the workpiece 200.

[0059] (Division step) Figure 10 is a schematic side view showing a partial cross-section of the state in which the splitting device holds the workpiece during the splitting step of the chip manufacturing method shown in Figure 4. Figure 11 is a schematic side view showing a partial cross-section of the state in which the splitting device has split the workpiece into chips during the splitting step of the chip manufacturing method shown in Figure 4.

[0060] The splitting step 103 is a step in which, after performing the modified layer formation step 102, an external force is applied to the workpiece 200 to split the workpiece 200 into individual chips 210 along the planned splitting line 203. In the splitting step 103, as shown in Figure 10, the splitting device 70 holds the workpiece 200 by clamping the annular frame 207 that supports the workpiece 200 on the inside and the outer edge of the tape 206 in the frame clamping portion 71, and also brings a roller member 73 provided at the upper end of the cylindrical expansion drum 72 into contact with the tape 206.

[0061] Thus, in the splitting step 103, as shown in Figure 10, the splitting device 70 holds the annular frame 14 supporting the workpiece 200 with the frame clamping portion 71, with the tape 13 flat across its outer edge and central portion. In the splitting step 103, the splitting device 70 moves the annular frame 207 and the workpiece 200 relatively along a direction that intersects (orthogonal in Embodiment 1) with respect to the surface 202 of the workpiece 200. In Embodiment 1, in the splitting step 103, the splitting device 70 raises the expansion drum 72 to move the annular frame 207 and the workpiece 200 relatively along a direction that intersects (orthogonal in Embodiment 1) with respect to the surface 202 of the workpiece 200, as shown in Figure 11.

[0062] Then, the roller member 73 presses from below upward between the outer edge of the workpiece 200 on the tape 206 and the inner edge of the annular frame 207, causing the tape 206 to expand in the planar direction. As a result of the expansion of the tape 206, a radial tensile force acts on the tape 206. When a radial tensile force acts on the tape 206 attached to the back surface 205 side of the workpiece 200, the workpiece 200 is divided along the planned division line 203, starting from the modified layer 301 and the crack induction layer 302, and is divided into individual chips 210 along the planned division line 203. The individually divided chips 210 are picked up from the tape 206.

[0063] The chip manufacturing method according to Embodiment 1 described above involves branching a single-pulse laser beam 21 in the X-axis direction, which is the processing feed direction, and irradiating the workpiece 200 with it to form a crack induction layer 302, and then irradiating the workpiece 200 with the laser beam 21 in burst mode to form a splitting initiation point modification layer 301.

[0064] In the chip manufacturing method according to Embodiment 1, the crack induction layer 302 is formed by a laser beam 21 that is branched in the X-axis direction, making it easier for crack induction regions 304 aligned in the X-axis direction of the crack induction layer 302 to connect with each other via cracks 305. For this reason, the chip manufacturing method according to Embodiment 1 can suppress the extension of cracks 305 in a direction different from the planned division line 203, and can reduce the meandering of the crack induction layer 302.

[0065] Furthermore, in the chip manufacturing method according to Embodiment 1, by irradiating the laser beam 21 in burst mode, a modified region 303 of the splitting initiation modified layer 301 is formed. As a result, the modified region 303 of the splitting initiation modified layer 301 is connected to the crack induction layer 302 by a crack 306, and the crack 306 extends from the crack induction layer 302 toward the surface 202, causing the crack 306 to be exposed on the surface 202. For this reason, in the splitting step 103, the chip manufacturing method according to Embodiment 1 can promote the propagation of cracks from the modified region 303 along the crack 306, suppress the meandering of the splitting initiation modified layer 301, and suppress splitting defects such as unsplit workpiece 200.

[0066] As a result, the chip manufacturing method according to Embodiment 1 has the effect of enabling division without meandering even when the workpiece 200 does not have crystalline properties.

[0067] It should be noted that the present invention is not limited to the embodiments described above. That is, it can be implemented with various modifications without departing from the core principles of the present invention. For example, Figure 9 shows an example in which the modified regions 303 of the splitting initiation modified layer 301 and the crack induction regions 304 of the crack induction layer 302 are arranged in the same position and in the same number in the thickness direction. However, in practice, the modified regions 303 of the splitting initiation modified layer 301 and the crack induction regions 304 of the crack induction layer 302 do not have to be arranged in the same position and in the same number in the thickness direction. The number of modified regions 303 of the splitting initiation modified layer 301 may be smaller, and their positions in the thickness direction do not have to be aligned. [Explanation of Symbols]

[0068] 21 Laser beam 101 Crack Induction Layer Formation Step 102 Modified layer formation step 103 division steps 200 Workpiece 202 Surface (one side) 203 planned division lines 210 chips 211 Focusing point 301 Modified layer for splitting starting point 302 Crack Induction Layer 306 Crack

Claims

1. A method for manufacturing chips, which involves irradiating a workpiece with a laser beam along multiple predetermined division lines to divide the workpiece and thereby manufacturing chips, A modified layer formation step involves positioning the focal point of a laser beam with a wavelength that is transparent to the workpiece from one side of the workpiece into the interior of the workpiece, and irradiating the workpiece in burst mode with the laser beam set to first output to form a modified layer for the division starting point in the region corresponding to the planned division line of the workpiece. The process includes, after performing the modified layer formation step, a dividing step in which an external force is applied to the workpiece to divide it along the planned dividing line, Prior to the modification layer formation step, in the crack induction layer formation step, multiple laser beams, aligned along the processing feed direction, are focused into the workpiece at an output lower than the first output to form a crack induction layer that guides the crack extension direction on one side of the modification layer for splitting initiation, thereby causing the crack to extend from the modification layer for splitting initiation toward the crack induction layer, forming a crack that appears on the one side of the workpiece, A method for manufacturing a chip, characterized in that the workpiece is composed of an amorphous material.

2. The method for manufacturing a chip according to claim 1, characterized in that the output of the laser beam in the crack induction layer formation step is less than the first output.

3. The method for manufacturing a chip according to Claim 2, characterized in that, in the modified layer formation step, the laser beam oscillated by the laser oscillator is thinned out at a repetition frequency determined by the processing conditions, and a plurality of laser beams are irradiated at each repetition frequency.

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