Processing methods

Abstract

To provide a processing method that can suppress defects in the division of a workpiece. [Solution] The processing method is a method for processing a workpiece on which a division line has been formed, comprising: a division starting point formation step 103 on which a modified layer that is the starting point of division is formed on the workpiece along the division line; a division step 104 on which an external force is applied to the workpiece to divide it along the modified layer; and a lamination step 102 on which, at least before performing the division step 104, the adhesive of a first sheet consisting of adhesive and a base material is attached to the workpiece and a second sheet is laminated on the base material of the first sheet, wherein in the division step 104 an external force is applied to the workpiece by expanding the second sheet to divide the workpiece.

Description

Technical Field

[0001] The present invention relates to a method for processing a workpiece in which a planned division line is formed.

Background Art

[0002] For example, after irradiating a semiconductor device wafer with a laser beam to form division starting points such as a modified layer and a laser processing groove, an expanding device is used to apply an external force to the semiconductor device wafer by expanding a tape to which the semiconductor wafer having the division starting points is attached, thereby dividing it into a plurality of chips (see, for example, Patent Document 1 and Patent Document 2).

[0003] The above-mentioned tape is required to be able to hold the chip during division and to be peeled off from the tape without breaking the chip after division, and is selected according to the size and thickness of the chip.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a planned division line with little metal such as a circuit layer or a TEG (Test Element Group) in a region overlapping the planned division line, when an external force is applied to the workpiece, it is likely to be divided along the planned division line.

[0006] On the other hand, in a planned division line with a large amount of metal in a region overlapping the planned division line, division is difficult, and when the sheet is expanded to apply an external force to the workpiece, a planned division line that is divided and a planned division line that is not divided occur.

[0007] If the sheet continues to expand while divided and undivided division lines are mixed, the sheet in the divided areas will stretch while the sheet in the undivided areas will not, leading to problems such as the sheet tearing.

[0008] In recent years, semiconductor wafers with thicker device layers compared to conventional semiconductor device wafers, such as high-bandwidth memory device wafers, have emerged. Processing these types of wafers is particularly difficult, and improvements are urgently needed.

[0009] The object of the present invention is to provide a processing method that can suppress defects in the division of a workpiece. [Means for solving the problem]

[0010] To solve the above-mentioned problems and achieve the objective, the present invention provides a processing method for a workpiece on which a division line is formed, comprising: a division starting point formation step of forming a division starting point on the workpiece along the division line; a division step of applying an external force to the workpiece to divide it along the division starting point; and a lamination step of attaching the adhesive of a first sheet, which consists of adhesive and a base material, to the workpiece and laminating a second sheet onto the base material of the first sheet, at least before performing the division step, wherein in the division step, an external force is applied to the workpiece by expanding the second sheet to divide the workpiece.

[0011] In the processing method described above, the second sheet may have a greater tensile elongation than the first sheet.

[0012] In the processing method described above, the second sheet may be thinner than the first sheet.

[0013] In the processing method described above, in the lamination step, the outer periphery of the laminated sheets may be fixed to the ring frame so that the opening of the ring frame is covered by the first sheet and the second sheet, and the workpiece may be housed within the opening.

[0014] In the above processing method, in the splitting starting point formation step, an opening is formed on the back surface of the workpiece to which the first sheet is attached, and in the splitting step, the second sheet side of the laminated sheet exposed between the outer circumference of the workpiece and the inner circumference of the ring frame may be pressed with a pressing unit.

[0015] In the processing method described above, the lamination step may be performed before the splitting starting point formation step.

[0016] The processing method further includes a cleaning step of cleaning the workpiece with a cleaning solution before performing the splitting point formation step, the lamination step is performed before the cleaning step, the cleaning step is performed with the workpiece fixed to the laminated sheet, and the first sheet may be resistant to the cleaning solution. [Effects of the Invention]

[0017] This invention has the effect of suppressing defects in the division of the workpiece. [Brief explanation of the drawing]

[0018] [Figure 1] Figure 1 is a schematic perspective view showing the workpiece to be processed by the processing method according to Embodiment 1. [Figure 2] Figure 2 is a flowchart showing the flow of the processing method according to Embodiment 1. [Figure 3] Figure 3 is a schematic cross-sectional view showing the workpiece after the lamination step of the processing method shown in Figure 2. [Figure 4] Figure 4 is a schematic cross-sectional view showing a partial cross-section of the division starting point formation step of the processing method shown in Figure 2. [Figure 5]FIG. 5 is a side view schematically showing in a partial cross-section a state in which a dividing device holds a workpiece in a dividing step of the processing method shown in FIG. 2. [Figure 6] FIG. 6 is a side view schematically showing in a partial cross-section a state in which a dividing device divides a workpiece into individual device chips in a dividing step of the processing method shown in FIG. 2. [Figure 7] FIG. 7 is an enlarged cross-sectional view schematically showing a main part of a workpiece in a state where the adhesive of the first sheet is divided in the processing method of the comparative example. [Figure 8] FIG. 8 is an enlarged cross-sectional view schematically showing a main part of a workpiece after expansion of the first sheet in the processing method of the comparative example. [Figure 9] FIG. 12 is an enlarged cross-sectional view schematically showing a main part of a workpiece in a state where the adhesive of the first sheet is divided in a dividing step of the processing method according to Embodiment 1. [Figure 10] FIG. 10 is an enlarged cross-sectional view schematically showing a main part of a workpiece in a state where the laminated sheet shown in FIG. 9 is expanded. [Figure 11] FIG. 11 is an enlarged cross-sectional view schematically showing a main part of a workpiece after expansion of the laminated sheet in a dividing step of the processing method according to Embodiment 1. [Figure 12] FIG. 12 is a perspective view schematically showing a laminating step of the processing method according to Embodiment 2. [Figure 13] FIG. 13 is a perspective view schematically showing a dividing step of the processing method according to Embodiment 2. [Figure 14] FIG. 14 is a flowchart showing the flow of the processing method according to Embodiment 3. [Figure 15] FIG. 15 is a cross-sectional view schematically showing a state in which a carrier substrate is fixed to the surface of a workpiece in a grinding step of the processing method shown in FIG. 14. [Figure 16] FIG. 16 is a cross-sectional view schematically showing a state in which the back surface of a workpiece is being ground in a grinding step of the processing method shown in FIG. 14. [Figure 17]Figure 17 is a schematic cross-sectional view showing the state in which the adhesive of the first sheet of the laminated sheet is attached to the back surface of the workpiece during the lamination step of the processing method shown in Figure 14. [Figure 18] Figure 18 is a schematic cross-sectional view showing the state after the carrier substrate has been peeled off from the surface of the workpiece during the lamination step of the processing method shown in Figure 14. [Figure 19] Figure 19 is a schematic side view showing a partial cross-section of the cleaning step of the processing method shown in Figure 14. [Figure 20] Figure 20 is a schematic cross-sectional view showing a partial cross-section of the division starting point formation step of the processing method shown in Figure 14. [Figure 21] Figure 21 is a schematic side view showing a partial cross-section of the splitting device holding the workpiece during the splitting step of the processing method shown in Figure 14. [Figure 22] Figure 22 is a schematic side view showing a partial cross-section of the state in which the dividing device divides the workpiece into individual device chips during the dividing step of the processing method shown in Figure 14. [Modes for carrying out the invention]

[0019] 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 those skilled in the art, and those that are substantially the same. In addition, the components described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the present invention.

[0020] [Embodiment 1] The processing method according to Embodiment 1 of the present invention will be described based on the drawings. Figure 1 is a schematic perspective view showing the workpiece to be processed by the processing method according to Embodiment 1. Figure 2 is a flowchart showing the flow of the processing method according to Embodiment 1.

[0021] (Workpiece) The processing method according to Embodiment 1 is a method for processing the workpiece 1 shown in Figure 1. The workpiece 1 to be processed by the processing method according to Embodiment 1 is, for example, a disc-shaped semiconductor wafer or an optical device wafer with a substrate 2 made of silicon, sapphire, gallium, or SiC. As shown in Figure 1, the workpiece 1 has a plurality of intersecting division lines 4 formed on its surface 3, and devices 5 are formed in each region partitioned in a grid pattern by the division lines 4 on the surface 3.

[0022] Device 5 is, for example, an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), or a memory (semiconductor memory device). The workpiece 1 is divided into individual device chips 10 along the division line 4. The device chip 10 comprises a part of the substrate 2 and a device 5 formed on the surface 3 of the substrate 2.

[0023] The device 5 is composed of a device layer consisting of an organic film such as an inorganic film like SiOF or BSG (SiOB), or a polymer film such as a polyimide or parylene film, or a low-dielectric constant insulating film (hereinafter referred to as a Low-k film) made of carbon-containing silicon oxide (SiOCH) laminated on the substrate 2, and a circuit layer containing a conductive metal pattern or metal film laminated between the Low-k films.

[0024] Furthermore, in Embodiment 1, the workpiece 1 has a TEG (Test Element Group) (not shown) formed on the division line 4. The TEG is made of metal and is an evaluation element for finding design and manufacturing problems that occur in the device 5, and is provided on the center of a portion of the division line 4 in the width direction. In this invention, the workpiece 1 may have metal provided on the surface of the division line 4 instead of the TEG. Also, in this invention, the workpiece 1 does not need to have metal such as a TEG formed on the surface 3 of the division line 4. In Embodiment 1, the workpiece 1 is composed of a low-k film in the division line 4, excluding metal such as a TEG.

[0025] Furthermore, in this invention, the workpiece 1 does not necessarily have a device 5 formed on its surface 3, is not limited to a disc shape, and is not limited to a specific material. Also, the workpiece 1 may not have division lines 4 formed on it, and may only have individual division sizes set (i.e., division lines are set as imaginary lines).

[0026] (Processing method) The processing method according to Embodiment 1 is a method for manufacturing multiple device chips 10 by dividing the workpiece 1 described above along the division line 4. As shown in Figure 2, the processing method according to Embodiment 1 comprises a grinding step 101, a lamination step 102, a division starting point formation step 103, and a division step 104.

[0027] (Grinding step) The grinding step 101 is a step in which the workpiece 1 is thinned to a predetermined finish thickness. In Embodiment 1, in the grinding step 101, a well-known grinding device grinds the back surface 6 of the back surface 3 of the workpiece 1 to thin the workpiece 1 to a predetermined finish thickness.

[0028] (Lamination step) Figure 3 is a schematic cross-sectional view showing the workpiece after the lamination step of the processing method shown in Figure 2. The lamination step 102 is a step in which the adhesive 211 of the first sheet 21, which consists of adhesive 211 and a base material 212, is attached to the workpiece 1 and the second sheet 22 is laminated onto the base material 212 of the first sheet 21, at least before the division step 104 is performed. In Embodiment 1, the lamination step 102 is performed before the division starting point formation step 103.

[0029] In Embodiment 1, in the lamination step 102, the surface 3 of the workpiece 1 is attached to the center of the adhesive 211 of the first sheet 21 of the laminated sheet 20, which comprises a first sheet 21 and a second sheet 22 laminated on the base material 212 of the first sheet 21. As shown in Figure 3, the first sheet 21 comprises an adhesive 211 made of a flexible and adhesive resin, and a base material 212 laminated on the adhesive 211 and made of a flexible and non-adhesive resin.

[0030] The adhesive 211 and base material 212 of the first sheet 21 are made of a resin that is resistant to corrosive liquids such as ammonia water, hydrogen peroxide, hydrofluoric acid, or liquids to which acidic or alkaline substances have been added, or dioxolane. In Embodiment 1, the base material 212 of the first sheet 21 is made of polyolefin, for example. Also in Embodiment 1, the combined thickness of the adhesive 211 and base material 212 of the first sheet 21 is 100 μm or more and 150 μm.

[0031] As shown in Figures 9, 10, and 11, the second sheet 22 comprises an adhesive 221 made of a flexible and adhesive resin, and a base material 222 laminated to the adhesive 221 and made of a flexible and non-adhesive resin. Note that Figures 9, 10, and 11 show the adhesive 221 and base material 222, but the other figures omit the adhesive 221 and base material 222.

[0032] The adhesive 221 and base material 222 of the second sheet 22 are made of a resin with a greater tensile elongation than the first sheet 21. The combined thickness of the adhesive 221 and base material 222 of the second sheet 22 is thinner than that of the first sheet 21. For this reason, in Embodiment 1, the second sheet 22 has a greater tensile elongation than the first sheet 21 and is thinner than the first sheet 21.

[0033] In Embodiment 1, the base material 222 of the second sheet 22 is made of, for example, polyvinyl chloride. Also in Embodiment 1, the combined thickness of the adhesive 221 and the base material 222 of the second sheet 22 is 50 μm or more and 90 μm. In this invention, the second sheet 22 may have the same thickness as the first sheet 21, or it may be thicker than the first sheet 21.

[0034] The laminated sheet 20 is formed when the adhesive 221 of the second sheet 22 adheres to the base material 212 of the first sheet 21.

[0035] In Embodiment 1, in the lamination step 102, as shown in Figure 3, the surface 3 of the workpiece 1 is attached to the center of the adhesive 211 of the first sheet 21 of the laminated sheet 20, which is a disc-shaped laminated sheet 20 with a larger diameter than the workpiece 1, and an annular ring frame 11 with an inner diameter larger than the workpiece 1 is attached to the outer circumference of the adhesive 211 of the first sheet 21. Thus, in Embodiment 1, in the lamination step 102, as shown in Figure 3, the outer circumference of the laminated sheet 20 is fixed to the ring frame 11, so that the opening 12 of the ring frame 11 is covered by the first sheet 21 and the second sheet 22, and the workpiece 1 is housed within the opening 12.

[0036] (Division starting point formation step) Figure 4 is a schematic cross-sectional view showing a partial cross-section of the splitting starting point formation step of the processing method shown in Figure 2. The splitting starting point formation step 103 is a step of forming a modified layer 7, which is the splitting starting point, on the workpiece 1 along the planned splitting line 4. The modified layer 7 refers to a region in which the density, refractive index, mechanical strength, and other physical properties are different from those of the surrounding area, and examples include a melted treatment region, a cracked region, a dielectric breakdown region, a refractive index change region, and a region in which these regions are mixed. Furthermore, the modified layer 7 has lower mechanical strength, etc., than other parts of the workpiece 1.

[0037] In Embodiment 1, in the division starting point formation step 103, the laser processing apparatus 30 shown in Figure 4 uses a second sheet 22 to hold the surface 3 of the workpiece 1 to which the first sheet 21 is attached, to the holding surface of a holding table (not shown) by suction, and clamps the ring frame 11 with clamps on the outer circumference of the holding surface. In Embodiment 1, in the division starting point formation step 103, as shown in Figure 4, the laser processing apparatus 30 moves the laser beam irradiation unit 31 and the workpiece 1 relative to each other along the planned division line 4, sets the focusing point 341 inside the workpiece 1 with the focusing lens 32, the laser oscillator 33 oscillates and irradiates the workpiece 1 with a laser beam 34 of a wavelength that is penetrating, from the laser beam irradiation unit 31, and laser processes the workpiece 1.

[0038] In this embodiment, in the division starting point formation step 103, since the laser beam 34 has a wavelength that is absorbed by the workpiece 1, the laser processing apparatus 30 forms a modified layer 7 inside the substrate 2 of the workpiece 1 along all the planned division lines 4 of the workpiece 1, and forms cracks 8 (corresponding to openings) extending from the modified layer 7 toward the back surface 6 of the back surface 3. Thus, in Embodiment 1, in the division starting point formation step 103, cracks 8 that open on the back surface 6, which is the back surface of the surface 3 to which the first sheet 21 of the workpiece 1 is attached, are formed along all the planned division lines 4.

[0039] (Division step) Figure 5 is a schematic side view in partial cross-section showing the state in which the splitting device holds the workpiece during the splitting step of the processing method shown in Figure 2. Figure 6 is a schematic side view in partial cross-section showing the state in which the splitting device has divided the workpiece into individual device chips during the splitting step of the processing method shown in Figure 2. Note that Figures 5 and 6 omit the structure of the laminated sheet 20 and the cracks 8.

[0040] The splitting step 104 is a step in which an external force is applied to the workpiece 1 to split the workpiece 1 into individual device chips 10 along the modified layer 7 as the starting point. In Embodiment 1, in the splitting step 104, the splitting device 40 clamps the ring frame 11, which is placed on the upper surface of the raised frame mounting plate 41, with the clamping mechanism 42, as shown in Figure 5. At this time, the roller 44 provided at the upper end of the expansion drum 43, which is a pressing unit, is in contact with the second sheet 22 of the laminated sheet 20 that is exposed between the outer edge (corresponding to the outer circumference) of the workpiece 1 and the inner edge (corresponding to the inner circumference) of the ring frame 11.

[0041] In Embodiment 1, in the splitting step 104, the splitting device 40 lowers the frame mounting plate 41 as shown in Figure 6. As a result, the roller 44 provided at the upper end of the expansion drum 43 comes into contact with the outer edge of the workpiece 1 of the laminated sheet 20 and the inner edge of the ring frame 11, and the roller 44 presses the space between the outer edge of the workpiece 1 of the laminated sheet 20 and the inner edge of the ring frame 11 from below upward, causing the laminated sheet 20, i.e., the first sheet 21 and the second sheet 22, to expand in the planar direction. In Embodiment 1, as a result of the expansion of the laminated sheet 20 in the splitting step 104, tensile forces act radially on the laminated sheet 20, i.e., the first sheet 21 and the second sheet 22.

[0042] When a radial tensile force is applied to the laminated sheet 20 attached to the surface 3 of the workpiece 1 in this manner, the workpiece 1 is divided into individual device chips 10 along the division line 4, with the modified layer 7 forming along the division line 4, using the modified layer 7 as a starting point. Thus, in Embodiment 1, in the division step 104, the second sheet 22 side of the laminated sheet 20 exposed between the outer edge of the workpiece 1 and the inner edge of the ring frame 11 is pressed by the expansion drum 43, thereby expanding the laminated sheet 20, i.e., the first sheet 21 and the second sheet 22, and applying a radial tensile force, which is an external force, to the workpiece 1, dividing the workpiece 1 into individual device chips 10.

[0043] As shown in Figure 7, in the conventional comparative example processing method in which only the first sheet 21 is attached to the workpiece 1 and the first sheet 21 is expanded, when the first sheet 21 is expanded, as shown in Figure 8, the workpiece 1 is divided starting from the modified layer 7, and a portion of the adhesive 211 is also divided along the crack 8 extending from the modified layer 7. Figure 7 is a schematic cross-sectional view showing an enlarged view of the main part of the workpiece in the comparative example processing method in which the adhesive of the first sheet has been divided. Figure 8 is a schematic cross-sectional view showing an enlarged view of the main part of the workpiece after the expansion of the first sheet in the comparative example processing method. In Figures 7 and 8, the same reference numerals are used for parts that are the same as in Embodiment 1, and their descriptions are omitted.

[0044] In the comparative example's processing method, as shown in Figures 7 and 8, only the first sheet 21 is attached to the workpiece 1, and the adhesive 211 of the first sheet 21 in the portion attached to the division line 4, which is divided starting from the modified layer 7, is divided along the crack 8 extending from the modified layer 7, but the base material 212 is not divided. For this reason, in the comparative example's processing method, the tensile strength of the portion of the first sheet 21 attached to the division line 4, which is divided starting from the modified layer 7, is lower than the tensile strength of the portion attached to the division line 4 that is not divided starting from the modified layer 7.

[0045] For this reason, in the comparative example's processing method, as shown in Figures 7 and 8, only the portion of the base material 212 attached to the division line 4 that was divided starting from the modified layer 7 of the first sheet 21 expands. As a result, in the comparative example's processing method, as shown in Figures 7 and 8, the portion of the base material 212 of the first sheet 21 that was attached to the division line 4 that was not divided starting from the modified layer 7 does not expand, and the division line 4 that was not divided is not divided starting from the modified layer 7.

[0046] In contrast to such comparative examples, in the processing method according to Embodiment 1, since the second sheet 22 is laminated onto the base material 212 of the first sheet 21, the laminated sheet 20 expands, and as shown in Figures 9, 10, and 11, even if the adhesive 211 of the first sheet 21 in the portion attached to the planned division line 4, which is divided starting from the modified layer 7, is divided along the crack 8 extending from the modified layer 7, the second sheet 22 remains laminated onto the base material 212 of the first sheet 21.

[0047] Figure 9 is a schematic, enlarged cross-sectional view showing the main part of the workpiece in the state where the adhesive of the first sheet has been divided in the dividing step of the processing method according to Embodiment 1. Figure 10 is a schematic, enlarged cross-sectional view showing the main part of the workpiece in the state where the laminated sheet shown in Figure 9 has been expanded. Figure 11 is a schematic, enlarged cross-sectional view showing the main part of the workpiece after the laminated sheet has been expanded in the dividing step of the processing method according to Embodiment 1.

[0048] In the processing method according to Embodiment 1, as shown in Figures 9, 10, and 11, even if the adhesive 211 of the portion of the first sheet 21 attached to the division line 4 which was divided starting from the modified layer 7 is divided along the crack 8 extending from the modified layer 7, the second sheet 22 is laminated on the base material 212 of the first sheet 21. Therefore, the tensile force applied by expanding the laminated sheet 20 is applied to the second sheet 22, and the tensile force applied to the second sheet 22 is also applied to the portion of the first sheet 21 attached to the division line 4 which was not divided starting from the modified layer 7. For this reason, in the processing method according to Embodiment 1, immediately after expanding the laminated sheet 20 in the division step 104, tensile force is also applied to the portion of the first sheet 21 attached to the division line 4 which was not divided starting from the modified layer 7. As shown in Figure 11, immediately after expanding the laminated sheet 20 in the division step 104, the division line 4 which was not divided starting from the modified layer 7 is also divided starting from the modified layer 7.

[0049] The processing method according to Embodiment 1 described above expands a laminated sheet 20, which is constructed by laminating a second sheet 22 onto a first sheet 21 attached to the workpiece 1. Therefore, the tensile force applied to the second sheet 22 of the laminated sheet 20 can also be applied to the base material 212 of the first sheet 21 in the portion attached to the division line 4 that was not divided immediately after expansion.

[0050] As a result, the processing method according to Embodiment 1 can also expand the base material 212 of the first sheet 21 that is attached to the division line 4 that was not divided immediately after expansion, thereby suppressing division defects of the workpiece 1.

[0051] [Embodiment 2] Next, the processing method according to Embodiment 2 will be described based on the drawings. Figure 12 is a schematic perspective view showing the lamination step of the processing method according to Embodiment 2. Figure 13 is a schematic perspective view showing the division step of the processing method according to Embodiment 2. In Figures 12 and 13, the same reference numerals are used for parts that are the same as in Embodiment 1, and their descriptions are omitted. Also, in Figures 12 and 13, the adhesive 221 and base material 222 of the second sheet 22 are omitted, and in Figure 13, the crack 8 is omitted.

[0052] The processing method according to Embodiment 2 is the same as Embodiment 1, except that the laminated sheet 20 used in the lamination step 102 and the dividing step 104 are different. As shown in Figure 12, the laminated sheet 20 used in the lamination step 102 of the processing method according to Embodiment 2 has a rectangular planar shape for both the second sheet 22 and the first sheet 21, with the planar shape of the first sheet 21 being smaller than that of the second sheet 22, and the base material 212 of the first sheet 21 laminated in the center of the second sheet 22.

[0053] In Embodiment 2, during the lamination step 102, the surface 3 of the workpiece 1 is attached to the center of the adhesive 211 of the first sheet 21 of the laminated sheet 20. In this way, four edges are formed on the outer edge of the second sheet 22.

[0054] In Embodiment 2, in the splitting step 104, as shown in Figure 13, the splitting device 50 clamps only each side of the outer edge of the second sheet 22 of the first sheet 21 with a linear clamper 51. In Embodiment 2, in the splitting step 104, as shown in Figure 13, the splitting device 40 moves the clampers 51 that position the workpiece 1 between them in a direction away from each other, expanding the second sheet 22, and by expanding the second sheet 22, it applies an external force, which is a tensile force, to the first sheet 21 via the second sheet 22, thereby splitting the workpiece 1 into individual device chips 10.

[0055] The processing method according to Embodiment 1 described above expands only the second sheet 22 of the laminated sheet 20, which is constructed by laminating a second sheet 22 onto a first sheet 21 attached to the workpiece 1. Therefore, the tensile force applied to the second sheet 22 can also be applied to the base material 212 of the first sheet 21 in the portion attached to the division line 4 that was not divided immediately after expansion. This has the effect of suppressing division defects in the workpiece 1, similar to Embodiment 1.

[0056] [Embodiment 3] Next, the processing method according to Embodiment 3 will be described based on the drawings. Figure 14 is a flowchart showing the flow of the processing method according to Embodiment 3. Figure 15 is a schematic cross-sectional view showing the state in which the carrier substrate is fixed to the surface of the workpiece during the grinding step of the processing method shown in Figure 14. Figure 16 is a schematic cross-sectional view showing the state in which the back surface of the workpiece is ground during the grinding step of the processing method shown in Figure 14. Figure 17 is a schematic cross-sectional view showing the state in which the adhesive of the first sheet of the laminated sheet is attached to the back surface of the workpiece during the lamination step of the processing method shown in Figure 14. Figure 18 is a schematic cross-sectional view showing the state in which the carrier substrate is peeled off from the surface of the workpiece during the lamination step of the processing method shown in Figure 14. Figure 19 is a schematic side view showing a partial cross-section of the cleaning step of the processing method shown in Figure 14. Figure 20 is a schematic cross-sectional view showing a partial cross-section of the division starting point formation step of the processing method shown in Figure 14. Figure 21 is a schematic side view in partial cross-section showing the state in which the splitting device holds the workpiece during the splitting step of the processing method shown in Figure 14. Figure 22 is a schematic side view in partial cross-section showing the state in which the splitting device has divided the workpiece into individual device chips during the splitting step of the processing method shown in Figure 14.

[0057] Note that in Figures 14, 15, 16, 17, 18, 19, 20, 21, and 22, the same reference numerals are used for parts identical to those in Embodiment 1, and their descriptions are omitted. In Figures 17, 18, 19, and 20, the adhesive 221 and base material 222 of the second sheet 22 are omitted, in Figures 20, 21, and 22, the crack 8 is omitted, and in Figures 21 and 22, the structure of the laminated sheet 20 is omitted.

[0058] The processing method according to Embodiment 3 is characterized in that the device 5 of the workpiece 1 is made of HBM (High Bandwidth Memory), and as shown in Figure 14, it includes a grinding step 101, a stacking step 102, a splitting starting point formation step 103, a splitting step 104, and a cleaning step 105. The device layer constituting the device 5 of the workpiece 1 to be processed in the processing method according to Embodiment 3 is thicker than the device layer constituting a typical integrated circuit (IC), LSI (Large Scale Integration), or memory (semiconductor memory device). For this reason, the workpiece 1 to be processed in the processing method according to Embodiment 3 is more difficult to divide into individual device chips 10 than if the device 5 were a typical integrated circuit (IC), LSI (Large Scale Integration), or memory (semiconductor memory device).

[0059] In Embodiment 3, in the grinding step 101, as shown in Figure 15, the carrier substrate 14 is fixed to the surface 3 of the workpiece 1 before grinding via adhesive 13. In Embodiment 3, the carrier substrate 14 is made of translucent glass and is formed in the shape of a disc with the same diameter as the workpiece 1 and thicker than the workpiece 1 before grinding.

[0060] In Embodiment 3, in the grinding step 101, the grinding device 60 shown in Figure 16 holds the carrier substrate 14 by suction to the holding surface 62 of the holding table 61. In Embodiment 3, in the grinding step 101, as shown in Figure 16, the grinding device 60 rotates the grinding wheel 64 around its axis using the spindle 63 and rotates the holding table 61 around its axis while supplying grinding water, and brings the grinding wheel 65 into contact with the back surface 6 of the workpiece 1 and brings it closer to the holding table 61 at a predetermined feed rate, thereby grinding the back surface 6 of the workpiece 1 with the grinding wheel 65 and thinning the workpiece 1 to the finished thickness.

[0061] In Embodiment 3, the lamination step 102 is performed before the cleaning step 105, as shown in Figure 14. In Embodiment 3, in the lamination step 102, as shown in Figure 17, the central part of the adhesive 211 of the first sheet 21 of the laminated sheet 20 is attached to the back surface 6 of the workpiece 1 that was ground in the grinding step 101, and the ring frame 11 is attached to the outer circumference of the adhesive 211. In Embodiment 3, in the lamination step 102, as shown in Figure 18, the carrier substrate 14 is peeled off from the surface 3 of the workpiece 1, adhesive 13 at a time. Thus, in Embodiment 3, the back surface 6 is the surface to which the adhesive is attached, and the surface 3 is the back surface to which the adhesive is attached.

[0062] In Embodiment 3, the cleaning step 105 is a step in which the workpiece 1 is cleaned with a cleaning solution 72 before carrying out the splitting point formation step 103. The cleaning solution 72 used in the cleaning step 105 is, for example, ammonia water, hydrogen peroxide, hydrofluoric acid, or a liquid to which acidic or alkaline substances have been added, or a corrosive liquid such as dioxolane. For this reason, the adhesive 211 and base material 212 of the first sheet 21 are resistant to the cleaning solution 72.

[0063] In Embodiment 3, during the cleaning step 105, the cleaning device 70 shown in Figure 19 holds the second sheet 22 of the laminated sheet 20 by suction to the holding surface of a spinner table (not shown), rotates the spinner table around its axis, and supplies cleaning liquid 72 from the cleaning nozzle 71 to the center of the surface 3 of the workpiece 1. The supplied cleaning liquid 72 flows from the center to the outer circumference of the surface 3 of the workpiece 1 due to the centrifugal force generated by the rotation of the spinner table, cleaning the surface 3 of the workpiece 1. Thus, in Embodiment 3, the cleaning step 105 is performed with the workpiece 1 fixed to the laminated sheet 20.

[0064] In Embodiment 3, in the division starting point formation step 103, the laser processing apparatus 30 shown in Figure 20 holds the surface 3 of the workpiece 1 by suction to the holding surface 36 of the holding table 35, and clamps the ring frame 11 with the clamp 37 on the outer circumference of the holding surface 36. In Embodiment 3, in the division starting point formation step 103, as shown in Figure 20, the laser processing apparatus 30 moves the laser beam irradiation unit 31 and the workpiece 1 relative to each other along the planned division line 4, setting the focal point 341 inside the substrate 2 of the workpiece 1, and irradiates the back surface 6 of the workpiece 1 with a laser beam 34 of a wavelength that is transparent to the workpiece 1 through the laminated sheet 20 from the laser beam irradiation unit 31.

[0065] In Embodiment 3, in the division starting point formation step 103, the laser processing apparatus 30, as shown in Figure 20, forms a modified layer 7 inside the workpiece 1 along all the planned division lines 4 of the workpiece 1, similar to Embodiment 1, and also forms cracks 8 (corresponding to openings, which are omitted in Figure 20) extending from the modified layer 7 toward the surface 3 on the back surface 6, which is the surface to which the modified layer 7 is attached.

[0066] In Embodiment 3, in the splitting step 104, the splitting device 40 holds the workpiece 1, as shown in Figure 21, similar to Embodiment 1. In Embodiment 3, in the splitting step 104, the splitting device 40 expands the laminated sheet 20, i.e., the first sheet 21 and the second sheet 22, as shown in Figure 22, similar to Embodiment 1, to split the workpiece 1 into individual device chips 10.

[0067] The processing method according to Embodiment 3 described above expands the laminated sheet 20, which is constructed by laminating a second sheet 22 onto a first sheet 21 attached to the workpiece 1. As a result, the tensile force applied to the second sheet 22 can also be applied to the base material 212 of the first sheet 21 in the portion attached to the division line 4 that was not divided immediately after expansion. This has the effect of suppressing division defects in the workpiece 1, similar to Embodiment 1.

[0068] 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 of the present invention. For example, in the present invention, in the division starting point formation step 103, a laser beam of an absorbing wavelength may be irradiated onto the workpiece 1 from the back surface 6 side of the workpiece 1, or a cutting blade may be used to cut into the back surface 6 side to form a recess from the back surface 6, i.e., a processing groove that opens to the back surface 6, as a division starting point. [Explanation of Symbols]

[0069] 1 Workpiece 3. Surface (the side to which it is attached, the back of the side to which it is attached) 4 planned division lines 6. Back side (back of the attached surface, the attached surface) 7. Modified layer (starting point of splitting) 8. Cracks (openings) 11 Ring Frame 12 aperture 20 Laminated Sheets 21 First sheet 22 Second seat 43. Expansion Drum (Pressing Unit) 72 Cleaning solution 102 Lamination Step 103 Dividing starting point formation step 104 division steps 105 Washing Step 211 Glue 212 Base material

Claims

1. A method for processing a workpiece in which division lines have been formed, A division starting point formation step in which a division starting point is formed on the workpiece along the planned division line, A splitting step in which an external force is applied to the workpiece to split the workpiece along the splitting starting point, The process includes, at least before performing the dividing step, a lamination step in which the adhesive of a first sheet, consisting of adhesive and a base material, is attached to the workpiece, and a second sheet is laminated onto the base material of the first sheet, A processing method comprising the division step of applying an external force to the workpiece by expanding the second sheet to divide the workpiece.

2. The processing method according to claim 1, wherein the second sheet has a greater tensile elongation than the first sheet.

3. The processing method according to claim 1, wherein the second sheet is thinner than the first sheet.

4. The processing method according to any one of claims 1 to 3, wherein in the lamination step, the outer periphery of the laminated sheets is fixed to the ring frame so that the opening of the ring frame is covered by the first sheet and the second sheet, and the workpiece is housed within the opening.

5. In the division starting point formation step, an opening is formed on the back surface of the workpiece to which the first sheet is attached. The processing method according to claim 4, wherein in the dividing step, the second sheet side of the laminated sheet exposed between the outer circumference of the workpiece and the inner circumference of the ring frame is pressed with a pressing unit.

6. The processing method according to any one of claims 1 to 3, wherein the lamination step is performed before the splitting starting point formation step.

7. The process further includes a cleaning step in which the workpiece is cleaned with a cleaning solution before performing the division starting point formation step, The lamination step is performed before the cleaning step, The cleaning step is performed with the workpiece fixed to the laminated sheet. The processing method according to any one of claims 1 to 3, wherein the first sheet is resistant to the cleaning solution.

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