Processing method and laser processing program

Abstract

To enable a suppression of a division defect.SOLUTION: A processing method is a processing method of a workpiece having a base material and a device layer laminated on the base material, in which a plurality of division lines are set. The device layer includes a specific layer in a region overlapping at least the division lines, and includes a specific layer alteration step 1001 of altering the specific layer constituting the device layer by irradiating the specific layer with a laser beam along the division lines of a workpiece through the base material; and a modification step 1002 of irradiating the laser beam along the division lines to form a modified layer along the division lines on the base material and forming a crack extending from the modified layer to divide the device layer after the specific layer alteration step 1001 is performed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for processing a workpiece having a substrate and a device layer, and a laser processing program. [Background technology]

[0002] For example, a processing method has been proposed in which a laser beam is used to divide a semiconductor wafer in which device layers constituting devices are stacked on a semiconductor substrate (see, for example, Patent Document 1).

[0003] The processing method disclosed in Patent Document 1 forms a modified layer inside the semiconductor substrate by focusing a laser beam inside the semiconductor wafer and irradiating it along the streets, and then causes cracks to extend from the modified layer toward the surface of the semiconductor wafer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-86161 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the processing method disclosed in Patent Document 1, depending on the thickness and material of the device layer, cracks may not extend straight from the modified layer but may extend diagonally, or may extend in two directions from the modified layer. Such poor dividing results in variations in the outer diameter size of the chips formed by dividing the semiconductor wafer, and therefore improvement is urgently needed.

[0006] An object of the present invention is to provide a processing method and a laser processing program that can suppress division defects. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems and achieve the object, the processing method of the present invention is a method for processing a workpiece having a substrate and a device layer laminated on the substrate, and having a plurality of planned division lines set thereon, wherein the device layer is composed of a plurality of layers laminated on top of each other, and is characterized by comprising: a specific layer modification step in which a laser beam is irradiated through the substrate along the planned division lines of the workpiece to modify a specific layer that constitutes the device layer; and a modification step in which, after the specific layer modification step, a laser beam is irradiated along the planned division lines to form a modified layer on the substrate along the planned division lines and to form cracks that extend from the modified layer and divide the device layer.

[0008] In the processing method, in the specific layer modifying step, the laser beam may be irradiated onto an area of ​​the specific layer having a predetermined width in a direction perpendicular to the extension direction of the planned dividing lines.

[0009] In the above processing method, in the specific layer modifying step, the laser beam may be irradiated with a focal point of the laser beam positioned at a position different from the specific layer.

[0010] In the processing method, in the specific layer altering step, a pulsed laser beam may be irradiated along the planned division line so that a pulsed laser beam spot formed by irradiating the specific layer with one pulsed laser beam and a pulsed laser beam spot formed by irradiating the specific layer with the next pulsed laser beam overlap each other.

[0011] The processing method may further include a grinding step of grinding the substrate to thin it after the modifying step is performed.

[0012] The laser processing program of the present invention is a laser processing program for processing a workpiece having a substrate and a device layer laminated on the substrate, and having a plurality of planned division lines set thereon, wherein the device layer is composed of a plurality of layers laminated on top of each other, and is characterized in that the program has a computer execute a specific layer modification step in which a laser beam is irradiated through the substrate along the planned division lines of the workpiece to modify a specific layer that constitutes the device layer, and a modification step in which, after the specific layer modification step, a laser beam is irradiated along the planned division lines to form a modified layer on the substrate along the planned division lines and to form cracks that extend from the modified layer and divide the device layer. [Effects of the Invention]

[0013] The present invention has an effect of suppressing division defects. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view showing an example of the structure of a workpiece to be processed by the processing method according to the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically showing a main part of the workpiece shown in FIG. [Figure 3] FIG. 3 is a flowchart showing the flow of the processing method according to the first embodiment. [Figure 4] FIG. 4 is a perspective view showing an example of the configuration of a laser processing device that performs the specific layer altering step and the modifying step of the processing method shown in FIG. [Figure 5] FIG. 5 is a diagram showing the configuration of the laser beam irradiation unit of the laser processing apparatus shown in FIG. [Figure 6] FIG. 6 is a cross-sectional view schematically showing a main part of a workpiece having a tape attached to its surface in the specific layer modifying step of the processing method shown in FIG. [Figure 7] FIG. 7 is a cross-sectional view of a workpiece, schematically illustrating a state in which the workpiece is irradiated with a laser beam in the specific layer modifying step of the processing method shown in FIG. [Figure 8]FIG. 8 is a plan view of a workpiece, schematically showing a pulsed laser beam spot irradiated on a specific layer of the laser beam shown in FIG. [Figure 9] FIG. 9 is a cross-sectional view schematically showing a main part of the workpiece during the modification step of the processing method shown in FIG. [Figure 10] FIG. 10 is a cross-sectional view schematically showing a main part of the workpiece after the modification step of the processing method shown in FIG. [Figure 11] FIG. 11 is a perspective view schematically showing the grinding step of the processing method shown in FIG. [Figure 12] FIG. 12 is a cross-sectional view schematically showing a main part of the workpiece after the grinding step of the processing method shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the configuration can be made within the scope of the gist of the present invention.

[0016] [Embodiment 1] A processing method according to a first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a perspective view showing an example of the structure of a workpiece to be processed by the processing method according to the first embodiment. Fig. 2 is a cross-sectional view schematically showing a main part of the workpiece shown in Fig. 1. Fig. 3 is a flowchart showing the flow of the processing method according to the first embodiment.

[0017] (Workpiece) The processing method according to the first embodiment is a method for processing a workpiece 200 shown in FIG. 1. The workpiece 200, which is the target of processing by the processing method according to the first embodiment, is, as shown in FIG. 1, a wafer such as a disk-shaped semiconductor wafer or an optical device wafer, with a substrate 201 made of, for example, silicon, sapphire, gallium, or SiC. As shown in FIG. 1, the workpiece 200 has a surface 202 partitioned into a grid-like pattern by a plurality of planned division lines 203 that intersect with each other, and devices 204 are formed in each of the regions. The devices 204 are, for example, integrated circuits such as ICs (Integrated Circuits) or LSIs (Large Scale Integrations), or memories (semiconductor memory devices). In this way, a plurality of planned division lines 203 are set on the workpiece 200.

[0018] 1 and 2, the workpiece 200 has a substrate 201 and a device layer 205 laminated on the substrate 201. The device layer 205 includes a specific layer 206 laminated on the substrate 201 and a functional layer 207 laminated on the specific layer 206. In the first embodiment, the specific layer 206 is a metal layer made of a metal that is a ductile material. The functional layer 207 includes a low-k insulating film (hereinafter referred to as a low-k film) made of an inorganic film such as SiOF or BSG (SiOB), an organic film such as a polymer film of a polyimide or parylene, or carbon-containing silicon dioxide (SiOCH), and a circuit layer including a conductive metal pattern or metal film.

[0019] The low-k film is laminated with a circuit layer to form the device 204. The circuit layer constitutes the circuit of the device 204. For this purpose, the device 204 is composed of low-k films laminated on each other, such as functional layers 207 laminated on specific layers 206 on the substrate 201, and a circuit layer laminated between the low-k films. At the planned dividing line 203, the device layer 205 is composed of the specific layer 206 and the low-k film laminated on the specific layer 206, excluding the TEG (Test Elementary Group). In this way, the device layer 205 includes the specific layer 206 at least in the area overlapping the planned dividing line 203, and is composed of multiple laminated layers.

[0020] In the present invention, the material of the substrate 201 of the workpiece 200 and the type of the device 204 are not limited to those described in embodiment 1. In the present invention, the specific layer 206 is not limited to a metal layer made of metal, but may be a resin layer made of a ductile resin. When the specific layer 206 is a resin layer, it is desirable that the specific layer 206 be an insulator layer made of a polymer-based insulator that is a resin. Furthermore, the specific layer 206 is not limited to being interposed between the substrate 201 and the functional layer 207, but may be a layer within the functional layer 207.

[0021] (Processing method) Next, a processing method according to embodiment 1 will be described. As shown in Fig. 3, the processing method according to embodiment 1 includes a specific layer altering step 1001, a modification step 1002, and a grinding step 1003. The specific layer altering step 1001 and the modification step 1002 are performed by a laser processing apparatus 1 shown in Fig. 4.

[0022] (Laser processing equipment) Next, the laser processing apparatus 1 shown in Fig. 4 will be described. Fig. 4 is a perspective view showing an example of the configuration of a laser processing apparatus that performs the specific layer alteration step and the modification step of the processing method shown in Fig. 3. Fig. 5 is a diagram showing the configuration of the laser beam irradiation unit of the laser processing apparatus shown in Fig. 4. As shown in Fig. 4, the laser processing apparatus 1 includes a holding unit 10, a moving unit 30, a laser beam irradiation unit 20, an imaging unit (not shown), a cleaning unit 40, a transport unit 50, and a control unit 100.

[0023] The holding unit 10 is disk-shaped, and has a flat holding surface 11 formed of porous ceramic or the like along the horizontal direction for holding the workpiece 200. The holding unit 10 is also provided so as to be movable by a moving unit 30 between a processing area below the laser beam irradiation unit 20 and a carry-in / out area spaced from below the laser beam irradiation unit 20 where the workpiece 200 is carried in and out.

[0024] The holding unit 10 is connected to a vacuum suction source (not shown), and is sucked by the vacuum suction source to suck and hold the workpiece 200 placed on the holding surface 11. In the first embodiment, the holding unit 10 sucks and holds the front surface 202 side of the workpiece 200 via a tape 209 attached to the front surface 202 of the workpiece 200.

[0025] The moving unit 30 moves the holding unit 10 and the laser beam irradiation unit 20 relatively. The moving unit 30 includes at least a Y-axis moving unit 31, which is an indexing feed unit that moves the holding unit 10 in the Y-axis direction parallel to the horizontal direction, an X-axis moving unit 32, which is a processing feed unit that moves the holding unit 10 in the X-axis direction that is parallel to the horizontal direction and perpendicular to the Y-axis direction, and a rotational moving unit 33 that rotates the holding unit 10 around an axis parallel to the Z-axis direction that is parallel to the vertical direction.

[0026] The Y-axis movement unit 31 is installed on the apparatus main body 2, and moves the moving plate 3 on which the X-axis movement unit 32 is installed in the Y-axis direction, thereby moving the holding unit 10 in the Y-axis direction. The X-axis movement unit 32 is installed on the moving plate 3, and moves the second moving plate 4 on which the rotational movement unit 33 is installed in the X-axis direction, thereby moving the holding unit 10 in the X-axis direction. The rotational movement unit 33 is installed on the second moving plate 4, and supports the holding unit 10, thereby rotating the holding unit 10 around its axis.

[0027] The Y-axis moving unit 31 moves each moving plate 3, the X-axis moving unit 32, the second moving plate 4, the rotational moving unit 33, and the holding unit 10 in the Y-axis direction. The X-axis moving unit 32 moves each second moving plate 4, the rotational moving unit 33, and the holding unit 10 in the X-axis direction.

[0028] The Y-axis moving unit 31 and the X-axis moving unit 32 each include a well-known ball screw rotatably mounted around its axis, a well-known motor for rotating the ball screw around its axis, and a well-known guide rail for supporting the moving plates 3 and 4 so that they can move in the X-axis or Y-axis direction. The rotational moving unit 33 includes a well-known motor for rotating the holding unit 10 around its axis.

[0029] 4, the laser beam irradiation unit 20 is provided at a portion on the tip of a support column 6 whose base end is supported on an erect wall 5 erected from the end of the device body 2 in the Y-axis direction. The laser beam irradiation unit 20 irradiates a laser beam 21 (shown in FIG. 5) onto a workpiece 200 held by the holding unit 10 to perform laser processing.

[0030] 5, the laser beam irradiation unit 20 includes an oscillator 22, an attenuator 23 which is an output adjustment unit, and a focusing unit 24. The oscillator 22 is a device that generates and oscillates a pulsed laser beam 21 having a wavelength that is transparent to the workpiece 200.

[0031] The attenuator 23 adjusts the output of the laser beam 21 oscillated by the oscillator 22. The focusing unit 24 includes a focusing lens 241 that focuses the laser beam 21 generated and oscillated by the oscillator 22 on the workpiece 200 held by the holding unit 10, and a focusing lens elevating unit 242 that moves the focusing lens 241 up and down along the Z-axis direction to move the focal point 211 of the laser beam 21 up and down along the Z-axis direction.

[0032] The imaging unit includes an imaging element that images an area to be divided of the workpiece 200 held in the holding unit 10 before laser processing. The imaging element is, for example, a CCD (Charge-Coupled Device) imaging element or a CMOS (Complementary MOS) imaging element. The imaging unit images the workpiece 200 held in the holding unit 10 to obtain an image for performing alignment between the workpiece 200 and the laser beam irradiation unit 20, and outputs the obtained image to the control unit 100.

[0033] Cleaning unit 40 cleans workpiece 200 after laser processing. Cleaning unit 40 is disc-shaped and includes spinner table 41, which has a flat holding surface formed of porous ceramic or the like along the horizontal direction for holding workpiece 200, and cleaning nozzle 42. Spinner table 41 is rotated around an axis parallel to the Z-axis direction by a rotary drive source (not shown).

[0034] The holding surface of spinner table 41 is connected to a vacuum suction source (not shown), and is sucked by the vacuum suction source to suck and hold workpiece 200 placed on the holding surface. In the first embodiment, spinner table 41 sucks and holds front surface 202 of workpiece 200 via tape 209.

[0035] The cleaning nozzle 42 supplies cleaning water (pure water in the first embodiment) to the front surface 202 of the workpiece 200 held by the spinner table 41 to clean the back surface 208 behind the front surface 202 of the workpiece 200.

[0036] The transport unit 50 transports the workpiece 200 between the holding unit 10 and the cleaning unit 40. The transport unit 50 includes a transport arm 51 that transports the workpiece 200 between the holding unit 10 and the cleaning unit 40.

[0037] The control unit 100 controls each component of the laser processing apparatus 1 to cause the laser processing apparatus 1 to perform processing operations on the workpiece 200. The control unit 100 is a computer having an arithmetic processing device with a microprocessor such as a CPU (central processing unit), a storage device with memory such as a ROM (read only memory) or RAM (random access memory), and an input / output interface device. The arithmetic processing device of the control unit 100 performs arithmetic processing in accordance with a computer program stored in the storage device, and outputs control signals for controlling the laser processing apparatus 1 to each component of the laser processing apparatus 1 via the input / output interface device.

[0038] The control unit 100 is connected to a display unit (not shown) that is configured with a liquid crystal display device or the like that displays the status of the machining operation, images, etc., and an input unit (not shown) that the operator uses to register machining content information, etc. The input unit is configured with at least one of a touch panel provided on the display unit and an external input device such as a keyboard.

[0039] 1, the control unit 100 includes a processing control unit 101 and a storage unit 102. The processing control unit 101 controls each component of the laser processing device 1 to cause the laser processing device 1 to perform a processing operation on the workpiece 200.

[0040] The storage unit 102 stores a laser processing program 103. The laser processing program 103 is a computer program that causes the control unit 100, which is a computer, i.e., the laser processing apparatus 1, to execute a specific layer altering step 1001 and a modification step 1002, thereby laser processing the workpiece 200.

[0041] The functions of the storage unit 102 are realized by the above-mentioned storage device, and the functions of the machining control unit 101 are realized by the above-mentioned arithmetic processing device performing arithmetic processing in accordance with the computer program stored in the storage device.

[0042] (Specific layer alteration step) Next, the specific layer modifying step 1001 will be described. Fig. 6 is a cross-sectional view schematically showing a main part of a workpiece having tape attached to its surface in the specific layer modifying step of the processing method shown in Fig. 3. Fig. 7 is a cross-sectional view of the workpiece schematically showing a state in which a laser beam is irradiated onto the workpiece in the specific layer modifying step of the processing method shown in Fig. 3. Fig. 8 is a plan view of the workpiece schematically showing a pulsed laser beam spot irradiated onto the specific layer of the laser beam shown in Fig. 7.

[0043] The specific layer altering step 1001 is a step in which the laser beam 21 is irradiated through the base material 201 along the planned dividing line 203 of the workpiece 200 to alter the specific layer 206. First, in the first embodiment, in the specific layer altering step 1001, as shown in FIG. 6 , a disk-shaped tape 209 having the same diameter as the workpiece 200 is attached to the surface 202 of the workpiece 200. In the first embodiment, in the specific layer altering step 1001, the laser processing apparatus 1 starts the processing operation, i.e., starts execution of the laser processing program 103, when the processing conditions are registered in the control unit 100 by an operator or the like, the surface 202 side of the workpiece 200 is placed on the holding surface 11 of the holding unit 10 via the tape 209, and the control unit 100 receives an instruction to start the processing operation from the operator or the like.

[0044] The processing conditions include the repetition frequency of the pulsed laser beam 21 in the specific layer alteration step 1001 and the modification step 1002, the output of the laser beam 21, the relative movement speed in the X-axis direction of the laser beam irradiation unit 20 and the holding unit 10 (referred to as the processing feed speed), and the position of the focal point 211 of the laser beam 21 (shown in Figure 5, etc.) in the thickness direction of the workpiece 200.

[0045] In the specific layer altering step 1001 of the laser processing apparatus 1 according to the first embodiment, the processing control unit 101 of the control unit 100 suction-holds the front surface 202 side of the workpiece 200 on the holding surface 11 of the holding unit 10 via the tape 209. In the specific layer altering step 1001 of the first embodiment, the processing control unit 101 of the control unit 100 controls the moving unit 30 to move the holding unit 10 toward the processing area, photographs the workpiece 200 with the imaging unit, and performs alignment based on the image captured by the imaging unit. Note that in the present invention, the imaging unit may be, for example, an infrared camera, and alignment may be performed based on an image captured from the back surface 208 side of the workpiece 200 with the infrared camera as the imaging unit. Alternatively, at least a portion of the holding surface 11 of the holding unit 10 may be made of a transparent member, and alignment may be performed by photographing the front surface 202 side of the workpiece 200 through the transparent member.

[0046] 7 , in the specific layer altering step 1001, the laser processing apparatus 1 causes the processing control section 101 of the control unit 100 to control the laser beam application unit 20, the moving unit 30, etc. to relatively move the focusing unit 24 of the laser beam application unit 20 and the holding unit 10 in the X-axis direction along the planned division line 203 while setting the focusing point 211 of the laser beam 21 inside the tape 209, and irradiates the center of the planned division line 203 in the width direction of the workpiece 200 with the laser beam 21 from the back surface 208 side. Thus, in the specific layer altering step 1001 in the embodiment 1, the laser processing apparatus 1 irradiates the laser beam 21 while positioning the focusing point 211 of the laser beam 21 at a position different from the specific layer 206.

[0047] Thus, in the specific layer altering step 1001 in the first embodiment, the laser processing apparatus 1 irradiates the specific layer 206 with the laser beam 21 in a so-called defocused manner, and causes the pulsed laser beam spot 212 on the specific layer 206 to have a larger diameter than the focal point 211, as shown in Fig. 8. Also, in the first embodiment, in the specific layer altering step 1001, the laser processing apparatus 1 causes the pulsed laser beam spot 212 on the specific layer 206 to have a larger diameter than the focal point 211, and causes the laser beam 21 to irradiate an area of ​​the specific layer 206 that has a predetermined width 213 in a direction 203-2 orthogonal to the extension direction 203-1 of the intended division line 203, on which the laser beam 21 is irradiated, as shown in Fig. 8.

[0048] Also, in the specific layer altering step 1001 in the embodiment 1, the laser processing apparatus 1 is set to a processing feed rate and a repetition frequency at which pulsed laser beam spots 212 on the specific layer 206 overlap each other. Thus, in the specific layer altering step 1001 in the embodiment 1, the pulsed laser beam 21 is irradiated along the planned division line 203, so that the pulsed laser beam spot 212 formed by irradiating the specific layer 206 with one pulsed laser beam 21 and the pulsed laser beam spot 212 formed by irradiating the specific layer 206 with the next pulsed laser beam 21 overlap each other. Also, in the specific layer altering step 1001 in the embodiment 1, the laser processing apparatus 1 sets the output of the laser beam 21 to a value that does not exceed the processing threshold of the base material 201 (in the embodiment 1, a value that is about 1 / 10 of the output in the modifying step 1002) with the focal point 211 set at the above-mentioned position, so that the base material 201 is not processed.

[0049] In the first embodiment, in the specific layer altering step 1001, the laser beam 21 is so-called defocused onto the specific layer 206 by the condenser lens 241, but in the present invention, in addition to defocusing, the pulsed laser beam spot 212 of the laser beam 21 generated by the oscillator 22 may be expanded in diameter onto the specific layer 206 by a beam expander or a spatial light modulator. Also, in the present invention, in the specific layer altering step 1001, the pulsed laser beam spots 212 onto the specific layer 206 do not need to overlap each other, and in addition to the pulsed laser beam 21, a CW (Continuous Wave) laser beam may be irradiated.

[0050] In the first embodiment, in the specific layer altering step 1001, the laser processing apparatus 1 irradiates the specific layer 206 along all of the planned dividing lines 203 with a defocused laser beam 21 to heat and alter the specific layer 206 along the planned dividing lines 203, thereby forming an altered portion 210 in the specific layer 206. Note that the altered portion 210 has lower mechanical strength than the other specific layers 206, and is easier to divide by external force than the other specific layers 206. In the first embodiment, in the specific layer altering step 1001, the laser processing apparatus 1 forms an altered portion 210 in the specific layer 206 along all of the planned dividing lines 203.

[0051] (Modification step) Next, the modification step 1002 will be described. Fig. 9 is a cross-sectional view schematically showing a main part of the workpiece during the modification step of the processing method shown in Fig. 3. Fig. 10 is a cross-sectional view schematically showing a main part of the workpiece after the modification step of the processing method shown in Fig. 3. The modification step 1002 is a step in which, after the specific layer modification step 1001 has been performed, a laser beam 21 is irradiated along the planned division lines 203 to form modified layers 220 along the planned division lines 203 in the substrate 201, and cracks 221 extending from the modified layer 220 and dividing the device layer 205 are formed.

[0052] The modified layer 220 refers to a region where the density, refractive index, mechanical strength, or other physical properties are different from those of the surrounding area, and examples thereof include a melting treatment region, a crack region, a dielectric breakdown region, a refractive index change region, and a region where these regions are mixed. The modified layer 220 also has lower mechanical strength, etc. than other parts of the base material 201 of the workpiece 200.

[0053] 9, in the laser processing apparatus 1, the processing control unit 101 of the control unit 100 controls the laser beam application unit 20, the moving unit 30, etc. to relatively move the focusing unit 24 of the laser beam application unit 20 and the holding unit 10 in the X-axis direction along the planned division line 203, while setting the focusing point 211 of the laser beam 21 inside the base material 201, and irradiates the laser beam 21 from the back surface 208 side to the center in the width direction of the planned division line 203 of the workpiece 200. In the embodiment, in the modifying step 1002, since the laser beam 21 has a wavelength that is transparent to the base material 201 of the workpiece 200, a modified layer 220 is formed inside the base material 201 along the planned division line 203, and cracks 221 are formed extending from the modified layer 220 toward the altered portion 210 and from the altered portion 210 toward the surface 202, as shown in FIG.

[0054] Thus, in the modifying step 1002, cracks 221 are formed that divide the device layer 205. Also, in the first embodiment, in the modifying step 1002, the laser processing apparatus 1 sets the output of the laser beam 21 to a value exceeding the processing threshold of the base material 201 (in the first embodiment, a value about 10 times the output of the specific layer modifying step 1001) with the focal point 211 set to the position described above, and forms a modified layer 220 inside the base material 201.

[0055] In the first embodiment, the specific layer altering step 1001 and the modification step 1002 use the laser beam 21 generated by the same oscillator 22, but the present invention is not limited to this, and the specific layer altering step 1001 and the modification step 1002 may use laser beams 21 generated by different oscillators 22. In the modification step 1002 in the first embodiment, the laser processing apparatus 1 forms modified layers 220 and cracks 221 inside the workpiece 200 along all of the planned dividing lines 203.

[0056] Also, in embodiment 1, in the modification step 1002, after forming modified layers 220 and cracks 221 inside the workpiece 200 along all of the planned dividing lines 203, the laser processing apparatus 1 causes the processing control unit 101 of the control unit 100 to control the moving unit 30, etc., to move the holding unit 10 to the loading / unloading area, and stops suction holding of the holding surface 11 of the holding unit 10 in the loading / unloading area.

[0057] In the modification step 1002 of the first embodiment, the laser processing apparatus 1 has the processing control section 101 of the control unit 100 control the transport unit 50 to place the workpiece 200 from the holding unit 10 on the holding surface of the spinner table 41 of the cleaning unit 40. In the modification step 1002 of the first embodiment, the laser processing apparatus 1 has the processing control section 101 of the control unit 100 suction-hold the front surface 202 side of the workpiece 200 on the holding surface of the spinner table 41 via the tape 209, rotate the spinner table 41 around its axis, and drop liquid cleaning water from the cleaning nozzle 42 onto the center of the front surface 202 side of the workpiece 200.

[0058] The dropped cleaning water flows from the center toward the outer periphery on the front surface 202 of the workpiece 200 due to centrifugal force generated by the rotation of the spinner table 41, cleaning the back surface 208 of the workpiece 200. In the first embodiment, in the modifying step 1002, the laser processing apparatus 1 supplies cleaning water for a predetermined time while rotating the spinner table 41 about its axis, thereby cleaning the back surface 208 of the workpiece 200. Note that in the present invention, the workpiece 200 does not necessarily need to be cleaned in the modifying step 1002.

[0059] (Grinding step) Next, the grinding step 1003 will be described. Fig. 11 is a perspective view that schematically shows the grinding step of the processing method shown in Fig. 3. Fig. 12 is a cross-sectional view that schematically shows a main part of the workpiece after the grinding step of the processing method shown in Fig. 3. The grinding step 1003 is a step in which the base material 201 of the workpiece 200 is ground to thin it.

[0060] 11 suction-holds the front surface 202 of the workpiece 200 on the holding surface 62 of the holding table 61 via the tape 209. In the grinding step 1003 of the first embodiment, as shown in FIG. 11 , the grinding device 60 rotates the grinding wheel 64 about its axis by the spindle 63 and rotates the holding table 61 about its axis while supplying grinding water, and grinding stone 65 is brought into contact with the back surface 208 of the workpiece 200 and moved toward the holding table 61 at a predetermined feed rate, thereby grinding the back surface 208 of the workpiece 200 with the grinding stone 65.

[0061] 12, the workpiece 200 has a modified layer 220 and cracks 221 formed therein, and is therefore divided into individual devices 204 along the intended division lines 203 starting from the modified layer 220 and cracks 221 by grinding stress applied from the grinding wheel 64. In the grinding step 1003, the grinding device 60 grinds the back surface 208 of the workpiece 200 until the workpiece 200 reaches a predetermined thickness.

[0062] As described above, in the processing method and laser processing program 103 according to the first embodiment, before forming the modified layer 220 on the substrate 201 in the modifying step 1002, the specific layer 206 included in the device layer 205 is irradiated with the laser beam 21 in the specific layer modifying step 1001 to form the modified portion 210 by modifying a part of the specific layer 206. After forming the modified portion 210 by modifying a part of the specific layer 206 in the specific layer modifying step 1001, the processing method and laser processing program 103 according to the first embodiment form the modified layer 110 on the substrate 201 in the modifying step 1002, and also form the crack 221 that extends from the modified layer 220 and divides the device layer 205.

[0063] As a result, the processing method and laser processing program 103 according to embodiment 1 have the effect that, by forming an altered portion 210 in the specific layer 206, the crack 221 from the modified layer 220 extends straight in the thickness direction, thereby dividing the device layer 205, thereby suppressing the division failure of the workpiece 200.

[0064] The present invention is not limited to the above-described embodiment, and can be implemented in various modifications without departing from the gist of the present invention. [Explanation of symbols]

[0065] 21 Laser beam 100 Control unit (computer) 103 Laser Processing Program 200 Workpiece 201 Base material 203 Planned division line 203-1 Extension direction 203-2 Orthogonal Direction 205 Device Layer 206 Specific layer 211 Focus point 212 Pulse laser beam spot 213 width 220 Modified layer 221 Crack 1001 Specific layer alteration step 1002 Modification step 1003 Grinding Step

Claims

1. A method for processing a workpiece having a substrate and a device layer laminated on the substrate, the workpiece having a plurality of planned division lines set thereon, the method comprising: The device layer is configured by stacking a plurality of layers, a specific layer modifying step of modifying a specific layer constituting the device layer by irradiating a laser beam along the intended dividing line of the workpiece through the substrate; and a modification step in which, after the specific layer modification step is performed, a laser beam is irradiated along the planned division line to form a modified layer on the substrate along the planned division line, and a crack extending from the modified layer to separate the device layer is formed.

2. 2. The processing method according to claim 1, wherein in the specific layer modifying step, the laser beam is irradiated onto an area of ​​the specific layer having a predetermined width in a direction perpendicular to the extension direction of the planned dividing lines.

3. 3. The processing method according to claim 2, wherein in the specific layer modifying step, the laser beam is irradiated with a focal point of the laser beam positioned at a position different from the specific layer.

4. In the specific layer modifying step, a pulse laser beam is irradiated along the intended dividing line; 4. The processing method according to claim 2, wherein the pulse laser beam spot formed by irradiating the specific layer with one pulse laser beam and the pulse laser beam spot formed by irradiating the specific layer with the next pulse laser beam are overlapped with each other.

5. The processing method according to claim 1 , further comprising a grinding step of grinding the substrate to thin it after the modifying step is performed.

6. A laser processing program for processing a workpiece having a substrate and a device layer laminated on the substrate, the workpiece having a plurality of planned division lines set thereon, The device layer is configured by stacking a plurality of layers, a specific layer modifying step of modifying a specific layer constituting the device layer by irradiating a laser beam along the intended dividing line of the workpiece through the substrate; a modification step of irradiating a laser beam along the planned division line to form a modified layer along the planned division line on the substrate after carrying out the specific layer modification step, and forming cracks extending from the modified layer to divide the device layer.

Images