Processing method of workpiece

Abstract

The present invention provides a method for processing a workpiece that can suppress contamination of the workpiece due to film peeling. [Solution] A method for processing a workpiece in which a first workpiece (100) is fixed to the surface of a second workpiece (200), comprising: a modified layer formation step (S11) in which a laser beam (LB) is irradiated at a predetermined distance inward from the outer edge (109) of the first workpiece (100) to form a first modified layer (11) along an annular region (10) inside the first workpiece (100); a removal step (S13) in which at least a part of the outer peripheral portion of the first workpiece (100) outside the first modified layer (11) is removed; a thinning step (S12) in which the first workpiece (100) is thinned to a predetermined thickness; and a film removal step (S14) in which a film (203) formed on the surface of the second workpiece (200) is laminated with the outer peripheral portion.

Description

Technical Field

[0001] The present invention relates to a method for processing a workpiece.

Background Art

[0002] With the recent trend towards lower profile and higher integration of device chips, the development of three-dimensionally stacked semiconductor wafers (hereinafter referred to as workpieces) has been progressing. For example, a TSV (Through-Silicon Via) workpiece enables the connection of electrodes of two chips by bonding the two chips together with through electrodes.

[0003] Such a workpiece (first workpiece) is ground and thinned while being bonded to a workpiece serving as a base (second workpiece). Usually, since the outer edge of the workpiece is chamfered, when it is ground to an extremely thin thickness, the outer edge of the first workpiece becomes a so-called knife edge, cracks are likely to occur during grinding, and chipping of the edge is likely to occur. As a result, cracks may extend to the device, leading to damage to the device.

[0004] As a countermeasure against the knife edge, a so-called edge trimming technique for cutting the outer peripheral portion of the first workpiece in a ring shape has been developed (see, for example, Patent Document 1). In addition, a method has been proposed in which a laser beam is irradiated along the boundary of the outer peripheral portion of the first workpiece to form an annular modified layer, and then the first workpiece is ground and thinned (see, for example, Patent Document 2).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the methods described in Patent Documents 1 and 2, if a film is formed on the upper surface of the second workpiece (the surface that contacts the first workpiece) during the edge trimming or thinning process, the film may be damaged. As a result, there was a problem that if the film peeled off in a later process, it would adhere to the workpiece and contaminate it.

[0007] The present invention has been made in view of the above, and aims to provide a processing method that can suppress contamination of the workpiece due to film peeling. [Means for solving the problem]

[0008] A method for processing a workpiece according to one aspect of the present invention is a method for processing a workpiece in which a first workpiece is fixed to the surface of a second workpiece, comprising: a modified layer formation step of irradiating a laser beam from a predetermined distance inward from the outer edge of the first workpiece to form a first modified layer along an annular region inside the first workpiece; a removal step of removing at least a portion of the outer peripheral portion of the first workpiece that is outside the first modified layer; a thinning step of thinning the first workpiece to a predetermined thickness; and a film removal step of removing a region of a film formed on the surface of the second workpiece that is laminated with the outer peripheral portion. [Effects of the Invention]

[0009] According to the present invention, contamination of the workpiece due to film peeling can be suppressed. [Brief explanation of the drawing]

[0010] [Figure 1] This is a diagram illustrating the workpiece (wafer) according to the first embodiment. [Figure 2] This is a perspective view of the first workpiece according to the first embodiment. [Figure 3] This is a flowchart illustrating the procedure for processing a workpiece according to the first embodiment. [Figure 4] This figure illustrates the modified layer formation step according to the first embodiment. [Figure 5]It is a cross-sectional view showing a state of the modified layer formation step according to the first embodiment in partial cross-section. [Figure 6] It is a cross-sectional view showing a state of the modified layer formation step according to the first embodiment in partial cross-section. [Figure 7] It is a plan view explaining the position of the modified layer formed in the modified layer formation step according to the first embodiment. [Figure 8] It is a view explaining the thinning step according to the first embodiment. [Figure 9] It is a cross-sectional view showing a state of the thinning step according to the first embodiment in partial cross-section. [Figure 10] It is a view explaining the removal step according to the first embodiment. [Figure 11] It is a cross-sectional view showing a state of the thinning step according to the first embodiment in partial cross-section. [Figure 12] It is a view explaining the film removal step according to the first embodiment. [Figure 13] It is a cross-sectional view showing a state of the film removal step according to the first embodiment in partial cross-section. [Figure 14] It is a flowchart explaining the procedure of the workpiece processing method according to the modified example of the first embodiment. [Figure 15] It is a flowchart explaining the procedure of the workpiece processing method according to the first embodiment. [Figure 16] It is a cross-sectional view showing a state of the modified layer formation step according to the second embodiment in partial cross-section. [Figure 17] It is a cross-sectional view showing a state of the modified layer formation step according to the second embodiment in partial cross-section. [Figure 18] It is a cross-sectional view showing a state of the thinning step according to the second embodiment in partial cross-section. [Figure 19] It is a flowchart explaining the procedure of the workpiece processing method according to the modified example of the second embodiment. [Figure 20] It is a flowchart explaining the procedure of the workpiece processing method according to the third embodiment. [Figure 21]A cross-sectional view showing a state of the thinning step according to the third embodiment in partial cross-section. [Figure 22] A cross-sectional view showing a state of the thinning step according to the third embodiment in partial cross-section.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments will be described with reference to the drawings. (First Embodiment)

[0012] First, the configuration of the workpiece W, which is the object to be processed, will be described. FIG. 1 is a diagram for explaining the workpiece (work) according to the first embodiment. The workpiece W is a so-called bonded workpiece formed by bonding one surface 101 of the first workpiece 100 and one surface 201 of the second workpiece 200. In the following description, in each of the first workpiece 100 and the second workpiece 200, the bonding surface is shown as the front surface, and the surface opposite to the bonding surface is shown as the back surface. That is, one surface 101 of the first workpiece 100 is shown as the front surface 101, and the other surface 102 is shown as the back surface 102. Also, one surface of the second workpiece 200 is shown as the front surface 201, and the other surface 202 is shown as the back surface 202.

[0013] The first workpiece 100 is a disc-shaped semiconductor workpiece, optical device workpiece, etc., with a substrate 104 made of silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), or silicon carbide (SiC). The outer edge 109 of the first workpiece 100 is chamfered so that the center in the thickness direction protrudes most outward, and the cross-section is arc-shaped from the surface 101 to the back surface 102 of the substrate 104. The first workpiece 100 has a device layer 103 on the surface 101 side of the substrate 104. Figure 2 is a perspective view of the first workpiece according to the first embodiment. As shown in Figure 2, the device layer 103 has a central region 105 and an outer peripheral excess region 106 surrounding the central region 105. Devices 108 are formed in each region of the central region 105, which is partitioned by a plurality of intersecting division lines 107. Device 108 is an integrated circuit such as an IC (Integrated Circuit) or LSI (Large Scale Integration). The outer peripheral surplus region 106 is the region surrounding the central region 105 of the device layer 103 where device 108 is not formed.

[0014] The second workpiece 200 is, for example, a disc-shaped semiconductor workpiece, optical device workpiece, etc., with a substrate 104 made of silicon (Si), sapphire (Al2O3), gallium arsenide (GaAs), or silicon carbide (SiC). The second workpiece 200 has its outer edge 209 beveled so that the center in the thickness direction protrudes most outward, and the cross-section is arc-shaped from the surface 201 to the back surface 202 of the substrate 204. The second workpiece 200 has a film 203 formed on the surface 201 side of the substrate 204. The film 203 is, for example, an oxide film (SiO2), a nitride film (SiN), an oxynitride film (SiON), or a metal film (e.g., Cu). The second workpiece 200 may have a device layer between the substrate 204 and the film 203.

[0015] The first workpiece 100 and the second workpiece 200 are, for example, formed by bonding the surface 101 of the first workpiece 100 and the surface 201 of the second workpiece 200 together via siloxane bonding to form workpiece W.

[0016] The first workpiece 100 and the second workpiece 200 are joined, for example, as follows: First, plasma treatment is applied to at least one of the joining surfaces (surfaces 101 and 201) of the first workpiece 100 and the second workpiece 200. Plasma treatment removes surface impurities such as organic matter adsorbed on surfaces 101 and 201, exposing clean surfaces. Furthermore, hydroxyl groups (OH groups) are bonded to the unbonded Si species on the exposed clean surfaces 101 and 201. In other words, OH groups are formed on surfaces 101 and 201 that have been activated by plasma treatment.

[0017] Next, the surface 101 of the first workpiece 100 and the surface 201 of the second workpiece 200 are bonded together. At this time, the hydrogen atoms (H) of the OH groups formed on the surface 101 of the first workpiece 100 form hydrogen bonds with the oxygen atoms (O) of the OH groups formed on the surface 201 of the second workpiece 200. Also, the hydrogen atoms (H) of the OH groups formed on the surface 201 of the second workpiece 200 form hydrogen bonds with the oxygen atoms (O) of the OH groups formed on the surface 101 of the first workpiece 100. As a result, the first workpiece 100 and the second workpiece 200 are attracted to each other by hydrogen bonds and are temporarily joined. The bonding strength at the time of temporary joining by hydrogen bonding is, for example, 10 to 200 J / m 2 It is to that extent.

[0018] Finally, the temporarily joined workpiece W is subjected to annealing using a method such as RTA (Rapid Thermal Annealing). In the heated workpiece W, a dehydration condensation reaction occurs at the joint surface between the first workpiece 100 and the second workpiece 200. That is, water (H2O) is lost from the OH groups formed on surfaces 101 and 201, resulting in covalent bonds via oxygen atoms (O), thus improving the bond strength between surface 101 of the first workpiece 100 and surface 201 of the second workpiece 200. The bond strength due to siloxane bonding is, for example, 1000 to 20000 J / m 2 It is to that extent.

[0019] Thus, the siloxane bond is a Si-O-Si bond in which silicon (Si) and oxygen (O) are alternately bonded, and since the first workpiece 100 and the second workpiece 200 are joined by heat treatment, a strong bond state is maintained even at high temperatures.

[0020] Next, the processing method for the workpiece W in this embodiment will be described. Figure 3 is a flowchart illustrating the procedure for processing the workpiece according to the first embodiment. As shown in Figure 3, the processing method for the workpiece according to the first embodiment includes four steps: a modified layer formation step (S11), a thinning step (S12), a removal step (S13), and a film removal step (S14). Each step will be described in detail below.

[0021] First, in the modified layer formation step, a modified layer is formed on the substrate 104 of the first workpiece 100 (S11). The modified layer refers to a region in which the density, refractive index, mechanical strength, or other physical properties differ from those of the surrounding area due to irradiation with laser light LB. The modified layer may be a melted region, a cracked region, a dielectric breakdown region, a refractive index change region, or a region where these regions are mixed. The modified layer has lower mechanical strength, etc., than other parts of the first workpiece 100. In the modified layer formation step (S11) of the first embodiment, two modified layers (first modified layer 11, second modified layer 21) are formed within the first workpiece 100.

[0022] Figure 4 is a diagram illustrating the modified layer formation step according to the first embodiment. The formation of the first modified layer 11 and the second modified layer 21 is performed using a laser processing apparatus 50 (only a portion is shown) as shown in Figure 4. The laser processing apparatus 50 comprises a holding table 52 and a laser beam irradiation unit 54. The holding table 52 holds the workpiece W on its holding surface and is rotatable around a vertical axis. The laser beam irradiation unit 54 irradiates the workpiece W held on the holding table 52 with laser light LB. The laser light LB is a laser beam with a wavelength that is penetrating to the first workpiece 100, for example, infrared rays (IR). The laser beam irradiation unit 54 includes a focuser 56 that positions the focal point of the laser light LB at a desired position. The laser processing apparatus 50 further comprises a moving unit (not shown) for moving the holding table 52 and the laser beam irradiation unit 54 relative to each other, and an imaging unit (not shown) for imaging the workpiece W held on the holding table 52.

[0023] The first modified layer 11 is formed using the laser processing apparatus 50 described above. First, the back surface 202 side of the second workpiece 200 is held by suction to the holding surface (upper surface) of the holding table 52. Next, the first workpiece 100 and the focuser 56 of the laser beam irradiation unit 54 are aligned. Specifically, the holding table 52 is moved to the irradiation area below the laser beam irradiation unit 54 by a moving unit (not shown). Next, the first workpiece 100 is photographed and aligned with an imaging unit (not shown) to position the irradiation part of the laser beam irradiation unit 54 vertically opposite to the first workpiece 100 at a predetermined distance inward from the outer edge 109, and then the focusing point of the laser beam LB is set inside the first workpiece 100.

[0024] Next, while rotating the holding table 52 around a vertical axis, pulsed laser light LB is irradiated from the laser beam irradiation unit 54 onto the back surface 102 of the first workpiece 100. That is, the laser light LB is irradiated in an annular shape along a position a predetermined distance inward from the outer edge 109 of the first workpiece 100. As a result, the first modified layer 11 is formed in the annular region 10 set at a predetermined distance inward from the outer edge 109 of the first workpiece 100. Cracks 12 extend from the first modified layer 11, and the connection between the first modified layer 11 and the cracks 12 forms a splitting starting point at a predetermined distance inward from the outer edge 109 of the first workpiece 100. The annular region 10 at a predetermined distance inward from the outer edge 109 is located, for example, at the boundary between the central region 105 and the outer peripheral excess region 106.

[0025] Figure 5 is a cross-sectional view showing a state of the modified layer formation step according to the first embodiment. Figure 5 shows a partial cross-section of the workpiece W during the formation of the first modified layer 11. As shown in Figure 5, in the modified layer formation step, it is preferable to form the first modified layer 11 such that cracks 12 extending from the first modified layer 11 are exposed on the surface 101 side of the first workpiece 100.

[0026] In forming the first modified layer 11, it is preferable to change the height of the focal point of the laser beam LB and irradiate the workpiece 100 with the laser beam LB multiple times to form multiple layers of annular first modified layer 11 in the thickness direction of the first workpiece 100. In this case, the annular first modified layer 11 is formed sequentially from the surface 101 side toward the back surface 102 side. For example, when forming four layers of annular first modified layer 11, the focal point of the laser beam LB is positioned close to the surface 101 (for example, at a depth of 700 μm from the back surface 102) and irradiated, while the holding table 52 is rotated to form the first layer of annular first modified layer 11. Then, while rotating the holding table 52, the focal point is moved toward the back surface 102 side (upwards) three times, for example, increasing the depth from the back surface 102 to a depth of 500 μm → 300 μm → 150 μm, thereby forming a total of four layers of annular first modified layer 11. Furthermore, if cracks extending from the modified layer connect adjacent first modified layers 11, the gap between adjacent modified layers may be formed with an opening in at least one of the depth direction or the surface direction. If it is difficult to connect adjacent first modified layers 11 with cracks, the modified layers may be formed overlapping in at least one of the depth direction or the surface direction.

[0027] Furthermore, the annular first modified layer 11 is not limited to four layers; it may be five or more layers, or three or fewer layers. Also, the position (depth) at which each layer is formed in the thickness direction is not limited to the depths described above, but may be set to an appropriate depth depending on the thickness of the first workpiece 100, etc.

[0028] Furthermore, it is preferable to form each layer such that the distance between the first modified layer 11 and the outer edge 109 increases with increasing distance for layers closer to the back surface 102, which is the incident surface of the laser beam and opposite to the bonding interface. That is, it is preferable that the cracks 12 connecting the first modified layers 11 stacked in the thickness direction are formed inclined outward from the center of the first workpiece 100 in a cross-sectional view with the laser incident surface facing upward, as shown in Figure 5. However, the cracks 12 only need to intersect with the surface 101, which is the surface opposite to the incident surface of the laser, and may be perpendicular to the surface 101 or inclined in the opposite direction to that shown in Figure 5 (towards the center of the first workpiece 100 from the outside).

[0029] Next, the second modified layer 21 is formed. Figure 6 is a cross-sectional view showing one state of the modified layer formation step according to the first embodiment. Figure 6 shows a partial cross-section of the workpiece W during the formation of the second modified layer 21. While maintaining the height of the focal point of the laser beam LB at a substantially constant height, the laser beam LB is irradiated at predetermined intervals to the area outside the annular region 10 of the first workpiece 100 while moving the position of the irradiation part of the laser beam irradiation unit 54 or the holding table 52 in the horizontal direction. That is, the second modified layer 21 is formed along the planar direction of the workpiece W over the entire area outside the annular region 10 where the first modified layer 11 is formed. If cracks connect adjacent second modified layers 21, the gaps between adjacent modified layers may be left open in the planar direction of the workpiece W, and if it is difficult to connect adjacent second modified layers 21 with cracks, adjacent second modified layers 21 may be formed overlapping in the planar direction of the workpiece W.

[0030] The second modified layer 21 only needs to be formed on a surface that is substantially in the same direction as the surface direction of the first workpiece 100 (or the second workpiece 200), and may be formed in a direction that is slightly offset rather than perfectly parallel to the surface direction. Furthermore, it is preferable that the second modified layer 21 be formed near the surface 101. Cracks 22 extend from the second modified layer 21, and the connection between the second modified layer 21 and the cracks 22 forms the starting point for peeling in the thickness direction in the excess outer region 106 of the first workpiece 100.

[0031] Furthermore, when a laser beam is irradiated from the surface 101, the first modified layer scatters the light below the first modified layer 11, making it impossible to accurately irradiate the laser beam LB. For this reason, if the first modified layer 11 is formed such that the cracks 12 connecting the first modified layers 11 stacked in the thickness direction are inclined in the opposite direction to the direction shown in Figure 5 (the direction from the outside toward the center of the first workpiece 100 in a cross-sectional view of the workpiece with the laser incident surface facing upwards), then when attempting to irradiate a laser beam from the surface 101, the first modified layer 11 obstructs the irradiation of the laser beam, making it impossible to form the outer edge of the first modified layer 11 (and crack 12) and the central edge of the second modified layer 21 (and crack 22) in close proximity.

[0032] In contrast, if the cracks 12 connecting the first modified layers 11, which are stacked in the thickness direction, are formed at an inclination outward from the center of the first workpiece 100, then even when a laser beam is incident from the surface 101, scattering of the laser beam by the first modified layers 11 is less likely to occur. As a result, as shown in Figure 6, the second modified layer 21 can be formed up to the vicinity of the first modified layers 11 and the cracks 12. By forming the starting point of the planar separation due to the connection of the first modified layer 11 and the cracks 12, and the starting point of the peeling in the thickness direction due to the connection of the second modified layer 21 and the cracks 22 in close proximity, the removal of the outer periphery of the first workpiece 100 becomes easier in the subsequent removal step. Therefore, when forming an annular first modified layer 11 in layers, it is preferable to form each layer such that the distance between the first modified layer 11 and the outer edge 109 increases with increasing distance for layers closer to the back surface 102.

[0033] In the modified layer formation step described above, for example, as shown in Figure 7, a radial fourth modified layer 41 may be formed extending from the annular region 10 on which the annular first modified layer 11 is formed, in the direction of the outer edge 109. Figure 7 is a plan view illustrating the position of the modified layer formed in the modified layer formation step according to the first embodiment. The fourth modified layer 41 is a modified layer that, in the subsequent removal step, performs the function of further dividing the chamfered portion 110 into smaller parts when removing the annular region (hereinafter referred to as the chamfered portion) 110, which is part of the outer periphery of the first workpiece 100. For example, the fourth modified layer 41 is formed by irradiating the back surface 102 of the first workpiece 100 with laser light LB under the same laser processing conditions as when forming the first modified layer 11. The fourth modified layer 41 is formed at multiple locations (eight locations in Figure 7) at equal intervals on the outer periphery of the first workpiece 100. By forming this fourth modified layer 41, the chamfered portion 110 is finely divided in the removal process described later, making it easier to remove the chamfered portion 110 from the first workpiece 100. The fourth modified layer 41 is not limited to being formed in the radial direction, but may be formed in a grid or annular shape, continuously or discontinuously.

[0034] As shown in Figure 7, the first modified layer 11 is formed in an annular shape on the first workpiece 100 by the modified layer formation step described above. In addition, a second modified layer 21 is formed along the surface direction of the workpiece W in the entire region outward from the first modified layer 11. Furthermore, a radial fourth modified layer 41 is formed extending from the first modified layer 11 toward the outer edge 109.

[0035] Next, in the thinning step, the first workpiece 100 constituting the workpiece W is ground from the exposed surface (back surface 102) side to thin it to the finished thickness (S12). In this embodiment, the removal step (S13) is performed simultaneously with the thinning step (S12). The removal step is a process of separating and removing the chamfered portion 110, which is partitioned by the first modified layer 11 and the second modified layer 21, from the workpiece W.

[0036] The thinning of the first workpiece 100 is performed using a grinding device 60 (only a portion is shown) as shown in Figure 8. Figure 8 is a diagram illustrating the thinning step according to the first embodiment. The grinding device 60 includes a grinding means 62 for grinding and thinning a workpiece W held by suction on a holding table 61. The grinding means 62 includes a rotating spindle 621 that is rotated by a rotational drive mechanism (not shown), a wheel mount 622 attached to the lower end of the rotating spindle 621, and a grinding wheel 623 attached to the lower surface of the wheel mount 622. A plurality of grinding wheels 624 are arranged in an annular pattern on the lower surface of the grinding wheel 623.

[0037] As shown in Figure 8, the workpiece W is placed on the holding table 61 with the back surface 202 of the second workpiece 200 facing downwards, and is held in place by suction by activating a suction means (not shown). Next, the rotating spindle 621 of the grinding means 62 is rotated at, for example, 6000 rpm in the direction indicated by arrow R2 in Figure 8, while the holding table 61 is rotated at, for example, 300 rpm in the direction indicated by arrow R3. Then, grinding water is supplied onto the back surface 102 of the first workpiece 100 by a grinding water supply means (not shown), and the grinding feed means (not shown) is activated to bring the grinding wheel 624 into contact with the back surface 102 of the first workpiece 100. Then, by bringing the grinding wheel 623 closer downwards as indicated by arrow R4 at, for example, a grinding feed speed of 0.1 μm / second, the back surface 102 of the first workpiece 100 is ground with the grinding wheel 624, and thinned to a predetermined finish thickness.

[0038] Figure 9 is a cross-sectional view showing one state of the thinning step according to the first embodiment. As the first workpiece 100 is thinned by grinding, a crack 12 is exposed from the top surface, as shown in Figure 9. If grinding is further carried out with the grinding wheel 624 in this state, as shown in Figure 10, a grinding force is applied as an external force from the back surface 102 side of the first workpiece 100, and the chamfered portion 110 is removed from the workpiece W, with the first modified layer 11 and the second modified layer 21 as the starting point for separation. Figure 10 is a diagram illustrating the removal step according to the first embodiment. At this time, if the fourth modified layer 41 has been formed, the annular chamfered portion 110 is separated with the fourth modified layer 41 as the starting point, and can be easily removed as scrap material 110'.

[0039] Figure 11 is a cross-sectional view showing a partial cross-section of one state of the thinning step according to the first embodiment. Figure 11 shows a partial cross-section at the end of the thinning step. When the thinning step (and removal step) is completed, the thickness of the region of the first workpiece 100 on the central side of the first modified layer 11 (crack 12) is thinned to a predetermined thickness. Also, the chamfered portion 110 is removed from the region on the outer edge side of the first modified layer 11 (crack 12) (hereinafter referred to as the trimming region TR), and the substrate 104 of the first workpiece 100 is exposed. That is, when the thinning step (and removal step) is completed, a portion of the outer periphery of the first workpiece 100 remains on the joint surface between the first workpiece 100 and the second workpiece 200 in the trimming region TR.

[0040] Therefore, a final film removal step is performed to remove the remaining portion of the outer periphery of the first workpiece 100 and the film 203 from the trimming region TR (S14). Figure 12 is a diagram illustrating the film removal step according to the first embodiment. The removal of the film 203 and the like is performed using the polishing apparatus 70 shown in Figure 12 (only a part of it is shown).

[0041] The polishing apparatus 70 comprises a base 71 that is rotatable around a vertical axis by a rotational drive means (not shown), and a polishing pad 72 attached to the lower surface of the base 71. The workpiece W is held by suction on a holding table (not shown). While supplying slurry (not shown), the polishing pad 72 is brought into contact with the exposed surface (upper surface) of the trimming region TR. Then, by rotating the polishing pad 72 around its axis and pressing it downward, the exposed surface (upper surface) of the trimming region TR is polished. Polishing removes the layers laminated on the trimming region TR (the remaining portion of the outer periphery of the first workpiece 100 and the film 203). In order to prevent the removal of remaining film 203, it is preferable to continue polishing after the removal of film 203 to also remove a portion of the area on the substrate 204 of the second workpiece 200 that is laminated with film 203.

[0042] Figure 13 is a cross-sectional view showing a state of the film removal step according to the first embodiment. Figure 13 shows a partial cross-section at the end of the film removal step. As shown in Figure 13, when the film removal step is completed, the region of the film 203 formed on the surface 201 of the second workpiece 200 that is laminated with the outer peripheral portion of the first workpiece is removed. In other words, the region of the film 203 formed on the surface 201 of the second workpiece 200 that is exposed after the remaining portion of the outer peripheral portion of the first workpiece 100 is removed is removed. In addition, the region of the second workpiece 200 that is laminated with the removed film 203 is also removed by a predetermined thickness.

[0043] As described above, according to this embodiment, when thinning a workpiece W in which a first workpiece 100 and a second workpiece are joined, and a film 203 is formed on the joining surface of the first workpiece 100 and the second workpiece 200, the chamfered portion 110 partitioned by the first modified layer 11 and the second modified layer 21 is removed in the removal step, and then the film removal step is performed. In the film removal step, the remaining outer peripheral portion of the first workpiece 100 and the region of the film 203 that is laminated with the outer peripheral portion are removed. In other words, according to this embodiment, when thinning the workpiece W, by removing the region of the film 203 that is exposed on the workpiece W, contamination of the workpiece due to film peeling in subsequent processes can be suppressed.

[0044] In the thinning step described above, the first workpiece 100 is thinned by grinding using the grinding device 60, but the thinning method is not limited to this. For example, other methods such as polishing with a polishing pad or cutting with a cutting tool may be used. Also, in the film removal step described above, the film 203 is removed by polishing using the polishing device 70, but the removal method is not limited to this. For example, other methods such as peeling with a cutting blade, grinding with a grinding wheel, dry etching by plasma etching, wet etching with a chemical solution, or laser removal by irradiation with laser light may be used.

[0045] Furthermore, although the thinning step and the removal step are performed simultaneously using the grinding device 60 described above, they may be performed at different times. Figure 14 is a flowchart illustrating the procedure for processing a workpiece according to a modified example of the first embodiment. As shown in Figure 14, after thinning the first workpiece 100 to a predetermined thickness in the thinning step (S12), the removal step (S13) may be performed using the same grinding device 60 as in the thinning step. Alternatively, the removal step (S13) may be performed following the modified layer formation step (S11), and the thinning step (S12) may be performed after the chamfered portion 110 has been removed from the first workpiece 100. In other words, the thinning step (S12) and the removal step (S13) may be performed either first or simultaneously.

[0046] Furthermore, as shown in the modified example in Figure 14, when the removal step is performed independently, the removal of the chamfered portion 110 in the removal step is not limited to the method of utilizing the external force from the grinding device 60 described above. For example, external force generated by other methods may be used, such as using a cutting device and utilizing the stress load from the cutting blade as the external force, or inserting a peeling member such as a wedge or fluid into the interface of the second modified layer 21 to separate it. (Second embodiment)

[0047] The workpiece processing method according to this embodiment differs from the first embodiment in that the modified layer formed in the modified layer formation step is located at a different position. It also differs from the first embodiment in that the film removal step is performed simultaneously with the removal step, and that the surface treatment step is performed after the film removal step. The differences from the first embodiment will be described below.

[0048] Figure 15 is a flowchart illustrating the procedure for processing a workpiece according to the second embodiment. As shown in Figure 15, the workpiece processing method according to the second embodiment includes five steps: a modified layer formation step (S21), a thinning step (S22), a removal step (S23), a film removal step (S24), and a surface treatment step (S25).

[0049] In the modified layer formation step (S21), two modified layers (first modified layer 11 and third modified layer 31) are formed. The first modified layer 11 is formed within the first workpiece 100, similar to the first embodiment. Figure 16 is a cross-sectional view showing a state of the modified layer formation step according to the second embodiment. Figure 16 shows a partial cross-section of the workpiece W during the formation of the first modified layer 11. The method for forming the first modified layer 11 in this embodiment is the same as in the first embodiment, using a laser processing apparatus 50. The formation position of the first modified layer 11 in the first workpiece 100 is also the same as in the first embodiment. However, as shown in Figure 16, in this embodiment, it is preferable that the crack 12 extending from the first modified layer 11 protrudes from the interface between the first workpiece 100 and the second workpiece 200 and extends into the interior of the second workpiece 200. However, the crack 12 may be exposed only to the extent of the surface 101 of the first workpiece 100, similar to the first embodiment.

[0050] Figure 17 is a cross-sectional view showing a partial cross-section of one state of the modified layer formation step according to the second embodiment. Figure 17 shows a partial cross-section of the workpiece W during the formation of the third modified layer 31. The third modified layer 31 is formed inside the second workpiece 200, similar to the second modified layer 21, along the surface direction of the workpiece W, covering the entire region outside the annular region 10 where the first modified layer 11 is formed. The method for forming the third modified layer 31 in this embodiment is the same as the method for forming the second modified layer 21 in the first embodiment, except for the height of the focal point of the laser beam LB. The third modified layer 31 only needs to be formed on a surface that is substantially in the same direction as the surface direction of the second workpiece 200 (or the first workpiece 100), and does not need to be perfectly parallel to the surface direction, but may be formed in a direction slightly deviated from the surface direction. Furthermore, it is preferable that the third modified layer 31 is formed near the surface 201, which is close to the bonding interface between the two workpieces, on the opposite side of the laser incident surface. In addition, during the modified layer formation step, a fourth modified layer 41 may be formed in the same manner as in the first embodiment.

[0051] The subsequent thinning step is similar to that of the first embodiment, in which the first workpiece 100 is thinned to the finished thickness by grinding from the exposed surface (back surface 102) side using, for example, a grinding device 60 (S22). During the thinning step (S22), the removal step (S23) is performed simultaneously. The removal step is a process of separating and removing the chamfered portion 110, which is partitioned by the first modified layer 11 and the third modified layer 31, from the workpiece W. In this embodiment, the removal step (S23) also serves as the film removal step (S24). This is because the region of the film 203 to be removed in the film removal step (S24) is the region of the film 203 formed on the surface 201 of the second workpiece 200 that is included in the chamfered portion 110 (the region laminated with the outer peripheral portion of the first workpiece). Therefore, when the chamfered portion 110 is removed by performing the removal step, the film removal step is also performed simultaneously.

[0052] Figure 18 is a cross-sectional view showing one state of the thinning step according to the second embodiment. As the first workpiece 100 is thinned by grinding, cracks 12 are exposed from the top surface, as shown in Figure 18. If grinding is further carried out with the grinding wheel 624 in this state, grinding force is applied as an external force from the back surface 102 side of the first workpiece 100, and the chamfered portion 110 is removed from the workpiece W, with the first modified layer 11 and the third modified layer 31 as the starting point for separation. If grinding is continued even after the chamfered portion 110 is removed, and the first workpiece 100 is thinned to a predetermined finish thickness, the workpiece W is processed to the same shape as at the end of the film removal step in the first embodiment, as shown in Figure 13.

[0053] In this embodiment, if the surface roughness of the substrate 204 of the second workpiece 200, which is exposed when the chamfered portion 110 is removed, is large, fragments may fall off and become particles, potentially leading to contamination of the workpiece W. Therefore, in this embodiment, it is preferable to perform the surface treatment step after the thinning step is completed.

[0054] The surface treatment step involves polishing the substrate 204 of the second workpiece 200, specifically the area exposed on the upper surface of the workpiece W, using, for example, polishing with an abrasive pad, to reduce surface roughness (S25). The method used in the surface treatment step is not limited to the polishing described above, and other methods may be used, such as grinding with a grinding wheel having a smaller abrasive particle size than that used in the removal step, cutting with a cutting blade, etching with a chemical solution, etching with plasma, or flattening the surface by irradiating it with laser light LB.

[0055] As described above, in this embodiment, by forming the third modified layer 31 along the surface direction of the workpiece W in a region inside the second workpiece 200 that is close to the surface 201, the region to be removed from the film 203 can be included in the chamfered portion 110. Therefore, by performing the thinning step, the film removal step is performed in addition to the removal step. Consequently, the region of the film 203 exposed on the workpiece W can be removed more easily than in the first embodiment. Thus, similar to the first embodiment, contamination of the workpiece due to film peeling can be suppressed in subsequent processes.

[0056] In the above description, the thinning step and the removal step (and film removal step) are performed simultaneously using the grinding device 60 described above, but they may be performed at different times. Figure 19 is a flowchart illustrating the procedure for processing a workpiece according to a modified example of the second embodiment. As shown in Figure 19, after thinning the first workpiece 100 to a predetermined thickness in the thinning step (S22), the removal step (S23) (and film removal step (S24)) may be performed using the same grinding device 60 as in the thinning step. Alternatively, the removal step (S23) (and film removal step (S24)) may be performed following the modified layer formation step (S21), and the thinning step (S22) may be performed after the chamfered portion 110 has been removed from the workpiece W. In other words, the thinning step (S22) and the removal step (S23) (and film removal step (S24)) may be performed either first or simultaneously.

[0057] Furthermore, as shown in the modified example in Figure 19, when the removal step is performed independently, the removal of the chamfered portion 110 in the removal step is not limited to the method of utilizing the external force from the grinding device 60 described above. For example, external force generated by other methods may be used, such as using a cutting device and utilizing the stress load from the cutting blade as the external force, or inserting a peeling member such as a wedge or fluid into the interface of the third modified layer 31 to separate it. (Third embodiment)

[0058] The processing method for the workpiece according to this embodiment differs from the first embodiment in that only the first modified layer 11 is formed in the modified layer formation step. The differences from the first embodiment will be described below.

[0059] Figure 20 is a flowchart illustrating the procedure for processing a workpiece according to the third embodiment. As shown in Figure 20, the workpiece processing method according to the third embodiment includes four steps: a modified layer formation step (S31), a thinning step (S32), a removal step (S33), and a film removal step (S34).

[0060] In the modified layer formation step (S31), the first modified layer 11 is formed in the same manner as in the first embodiment. The first modified layer 11 is formed within the first workpiece 100, in the same manner as in the first embodiment (see Figure 5). At this time, it is preferable that the cracks 12 extending from the first modified layer 11 appear on the surface 101 side of the first workpiece 100.

[0061] The subsequent thinning step is similar to that of the first embodiment, in which the first workpiece 100 is thinned to the finished thickness by grinding from the exposed surface (back surface 102) side using, for example, a grinding device 60 (S32). During the thinning step (S32), the removal step (S33) is performed simultaneously. The removal step is a process of separating and removing the chamfered portion 110, which is demarcated by the first modified layer 11 and the bonding interface between the first workpiece 100 and the second workpiece 200, from the workpiece W.

[0062] Figure 21 is a cross-sectional view showing one state of the thinning step according to the third embodiment. As the first workpiece 100 is thinned by grinding, a crack 12 is exposed from the top surface, as shown in Figure 21. If grinding is further carried out with the grinding wheel 624 in this state, as shown in Figure 22, a grinding force is applied as an external force from the back surface 102 side of the first workpiece 100, and the chamfered portion 110 is removed from the workpiece W, with the first modified layer 11 and the joint interface between the first workpiece 100 and the second workpiece 200 as the starting points for separation. Figure 22 is a cross-sectional view showing one state of the thinning step according to the third embodiment. Figure 22 shows a partial cross-section at the end of the thinning step. Once the thinning step (and removal step) is complete, the trimming region TR on the outer edge side of the first modified layer 11 (crack 12) has its chamfered portion 110 removed, exposing the film 203 formed on the surface 201 of the second workpiece 200.

[0063] Therefore, a final film removal step is performed to remove the portion of the film 203 that is exposed in the trimming region TR (S34). The film removal step is performed in the same manner as the film removal step (S14) in the first embodiment. When the film removal step (S34) is completed, the workpiece W is processed to the same shape as at the end of the film removal step in the first embodiment, as shown in Figure 13.

[0064] As described above, even when only the first modified layer 11 is formed, the chamfered portion 110 can be demarcated using the first modified layer 11 and the bonding interface between the first workpiece 100 and the second workpiece 200 as the starting points for division. Therefore, the modified layer formation step is simplified, leading to a reduction in processing costs.

[0065] In this embodiment as well, the thinning step and the removal step may be performed independently in a time series, similar to the first embodiment. In this case, either the thinning step or the removal step may be performed first. When the removal step is performed independently, the removal of the chamfered portion 110 in the removal step is not limited to the method of utilizing the external force from the grinding device 60 described above. For example, an external force generated by other methods may be used, such as using a cutting device and utilizing the stress load from the cutting blade as the external force, or inserting a separation member such as a wedge or fluid into the joint interface between the first workpiece 100 and the second workpiece 200 to separate them.

[0066] Furthermore, the bonding interface between the first workpiece 100 and the second workpiece 200 is joined by Si-O-Si siloxane bonds. By supplying a fluid such as water, water vapor, mist, or ammonia to the bonding interface of workpiece W from the outside, the Si-O-Si bonds can be changed to Si-OH-OH-Si bonds, thereby weakening the bonding force on the outer circumference of workpiece W. Therefore, by supplying the fluid to the bonding interface of workpiece W to weaken the bonding force during the removal step, the removal of the chamfered portion 110 in the removal step can be reliably performed.

[0067] While several embodiments of the present invention have been described, these embodiments are provided as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents. [Industrial applicability]

[0068] As described above, the workpiece processing method of the present invention is useful when thinning a workpiece in which the first workpiece is fixed to the surface of the second workpiece, and in particular, when using a second workpiece on which a film has been formed on its surface, it has the effect of suppressing contamination of the workpiece due to film peeling. [Explanation of symbols]

[0069] 10: Ring region 11: First Modified Layer 12, 22: Crack 21: Second Modified Layer 31: Third Modified Layer 41: Fourth Modified Layer 50: Laser processing equipment 52, 61: Holding Table 54: Laser beam irradiation unit 56: Light concentrator 60: Grinding equipment 62: Grinding means 70: Polishing equipment 71: Base 72: Polishing pad 100: First Work 101, 201: Surface 102, 202: Back side 103: Device Layer 104, 204: Circuit board 105: Central area 106: Peripheral surplus area 107: Planned division line 108: Device 109, 209: Outer edge 110: Chamfered part 110': Scrap material 200: Second Work 203: Membrane 621: Rotating spindle 622: Wheel Mount 623: Grinding Wheel 624: Grinding wheel LB: Laser light TR: Trimming area W: Work

Claims

1. The first workpiece is fixed to the surface of the second workpiece. A method for processing a workpiece, A laser beam is irradiated from the outer edge of the first workpiece at a predetermined distance inward. A first modified layer is formed inside the first workpiece along an annular region. Modified layer formation step, The outer peripheral portion of the first workpiece that is outside the first modified layer A removal step to remove at least a portion, A thinning step in which the first workpiece is thinned to a predetermined thickness, The film formed on the surface of the second workpiece, A film removal step to remove the outer peripheral portion and the layered region, A method for processing a workpiece, comprising the following components.

2. The modified layer formation step is, Inside the first workpiece Outside the first modified layer, toward the outer edge of the first workpiece, A second modified layer is further formed, extending along the surface direction of the first workpiece. The method for processing a workpiece as described in claim 1.

3. The modified layer formation step is, Inside the second workpiece Outside the first modified layer, toward the outer edge of the second workpiece, A third modified layer is further formed along the planar direction of the second workpiece. The method for processing a workpiece as described in claim 1.

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