Laminated sheet, method for manufacturing a laminated sheet, method for processing a workpiece, and method for manufacturing a device chip

Abstract

To provide a laminated sheet that can reduce thickness variations while adequately protecting the wafer surface during wafer grinding, a method for manufacturing a laminated sheet, a method for processing a workpiece, and a method for manufacturing a device chip. [Solution] The laminated sheet 1 has a first layer 10 in which the storage modulus of elasticity in the tensile direction is 1.0E+9 Pa or more and 1.0E+10 Pa or less when a frequency of 1 Hz is applied in an environment of 50°C, and a second layer 20 laminated on the first layer 10 in which the storage modulus of elasticity in the tensile direction is 1.0E+6 Pa or more and 1.0E+8 Pa or less when a frequency of 1 Hz is applied in an environment of 50°C. The difference in solubility parameters between the first layer 10 and the second layer 20 is 3.0 or less, and they are laminated without an adhesive layer in between.

Description

Technical Field

[0001] The present invention relates to a laminated sheet, a method for manufacturing the laminated sheet, a method for processing a workpiece, and a method for manufacturing a device chip.

Background Art

[0002] In the manufacturing process of a device chip, the back surface of a wafer on which a device is formed on the front surface is ground and thinned, and then diced along streets to be divided into individual device chips. When grinding the back surface of the wafer, the front surface of the wafer is protected with a sheet for surface protection, and the back surface side is ground while holding this sheet side on the holding surface of a holding table (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the wafer surface has irregularities such as bumps and the surface protection sheet is a single layer, irregularities are formed following the irregularities such as bumps, and there are problems that the front surface side of the wafer cannot be sufficiently protected or that it causes thickness variations during grinding. Even when the surface protection sheet is a laminated sheet in which two or more sheets are laminated, if the sheets are joined by an adhesive, there is a problem that the thickness variation of the adhesive layer directly leads to the thickness variation during grinding.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide a laminated sheet, a method for manufacturing the laminated sheet, a method for processing a workpiece, and a method for manufacturing a device chip that can sufficiently protect the surface of a wafer and reduce thickness variations when grinding the wafer. [Means for solving the problem]

[0006] To solve the above-mentioned problems and achieve the objective, the laminated sheet of the present invention comprises a first layer having a tensile storage modulus of 1.0E+9Pa or more and 1.0E+10Pa or less when a frequency of 1Hz is applied in an environment of 50°C, and a second layer laminated on the first layer having a tensile storage modulus of 1.0E+6Pa or more and 1.0E+8Pa or less when a frequency of 1Hz is applied in an environment of 50°C, wherein the difference in solubility parameters between the first layer and the second layer is 3.0 or less, and the layers are laminated without an adhesive layer.

[0007] Furthermore, in the laminated sheet of the present invention, it is preferable that the thickness of the first layer is smaller than the thickness of the second layer.

[0008] Furthermore, the present invention provides a method for manufacturing a laminated sheet, comprising: a preparation step of preparing a first sheet having a tensile storage modulus of 1.0E+9Pa or more and 1.0E+10Pa or less when a frequency of 1Hz is applied in a 50°C environment; and a second sheet having a tensile storage modulus of 1.0E+6Pa or more and 1.0E+8Pa or less when a frequency of 1Hz is applied in a 50°C environment, and having a difference of solubility parameter of 3.0 or less from the first sheet; and a heating and pressing step of laminating the first sheet and the second sheet without an adhesive and pressing them together while melting the interface by heating.

[0009] Furthermore, the present invention relates to a method for processing a workpiece having irregularities on its surface, and is characterized by comprising: a sheet fixing step of fixing the second layer side of the laminated sheet to the surface side of the workpiece; and a grinding step of grinding the back side of the workpiece after performing the sheet fixing step.

[0010] Furthermore, the present invention relates to a method for manufacturing a device chip, comprising: a sheet fixing step of fixing the second layer side of a laminated sheet manufactured by the method for manufacturing a laminated sheet described in claim 1 or 2, or by the method for manufacturing a laminated sheet described in claim 3, to the front or back surface of the workpiece; and a dividing step of performing processing on the workpiece from the side opposite to the side on which the laminated sheet is fixed, thereby dividing it along the planned division line.

[0011] Furthermore, in the method for manufacturing a device chip of the present invention, it is preferable to fix the second layer side of the laminated sheet to the surface of the workpiece in the sheet fixing step.

[0012] Furthermore, in the method for manufacturing a device chip of the present invention, a film may be formed on the back surface of the workpiece.

[0013] Furthermore, the method for manufacturing a device chip of the present invention further includes an imaging step of imaging a division line set on the surface of a workpiece via the laminated sheet fixed to the surface side of the workpiece, wherein in the division step, it is preferable to perform processing along the division line from the back side of the workpiece based on the position of the division line imaged in the imaging step. [Effects of the Invention]

[0014] This invention makes it possible to reduce thickness variations while adequately protecting the wafer surface during wafer grinding. [Brief explanation of the drawing]

[0015] [Figure 1] Figure 1 is a cross-sectional view showing the schematic configuration of the laminated sheet according to the embodiment. [Figure 2] Figure 2 is a flowchart showing the flow of the manufacturing method for the laminated sheet according to the embodiment. [Figure 3]FIG. 3 is a schematic diagram for explaining an example of a method for manufacturing a laminated sheet. [Figure 4] FIG. 4 is a schematic diagram for explaining an example of a method for manufacturing a laminated sheet. [Figure 5] FIG. 5 is a perspective view showing a schematic configuration of a workpiece which is a processing target of a processing method for a workpiece according to an embodiment. [Figure 6] FIG. 6 is a flowchart showing the flow of a processing method for a workpiece according to an embodiment. [Figure 7] FIG. 7 is a side view showing a state of a sheet fixing step shown in FIG. 6 in partial cross section. [Figure 8] FIG. 8 is a side view showing a state after FIG. 7 in partial cross section. [Figure 9] FIG. 9 is a side view showing a state of a grinding step shown in FIG. 6 in partial cross section. [Figure 10] FIG. 10 is a side view showing a state of a grinding step shown in FIG. 6 in partial cross section. [Figure 11] FIG. 11 is a flowchart showing the flow of a method for manufacturing a device chip according to an embodiment. [Figure 12] FIG. 12 is a side view showing a state of a sheet fixing step shown in FIG. 11 in partial cross section. [Figure 13] FIG. 13 is a side view showing a state of an imaging step shown in FIG. 11 in partial cross section. [Figure 14] FIG. 14 is a side view showing an example of a dividing step shown in FIG. 11 in partial cross section. [Figure 15] FIG. 15 is a side view showing another example of a dividing step shown in FIG. 11 in partial cross section.

DETAILED DESCRIPTION OF THE INVENTION

[0016] 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. Moreover, 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.

[0017] [Embodiment] <Laminated Sheet 1> First, a laminated sheet 1 according to an embodiment of the present invention will be described with reference to Figure 1. Figure 1 is a cross-sectional view showing the schematic configuration of the laminated sheet according to the embodiment.

[0018] The laminated sheet 1 is a surface protection sheet that is attached to the surface side when processing the back side of a workpiece, such as a semiconductor wafer (for example, the workpiece 200 shown in Figure 5 below), in order to protect the surface side of the workpiece. The laminated sheet 1 is particularly useful when protecting the surface side of a workpiece that has irregularities on its surface, but this does not exclude the possibility of it being attached to a flat surface.

[0019] As shown in Figure 1, the laminated sheet 1 has a multilayer structure in which a first layer 10 and a second layer 20 are laminated without an adhesive layer in between. The second layer 20 is laminated on top of the first layer 10. The laminated sheet 1 is attached to the surface side of the workpiece with the second layer 20 side facing it.

[0020] Preferably, the difference in solubility parameter (SP value) between the first layer 10 and the second layer 20 is 3.0 or less, more preferably 2.0 or less, and even more preferably 1.5 or less. By setting the difference in SP value between the first layer 10 and the second layer 20 to 3.0 or less, the bond between the first layer 10 and the second layer 20 becomes strong, and peeling can be suppressed.

[0021] Preferably, the first layer 10 has a tensile storage modulus of 1.0E+9 Pa or more and 1.0E+10 Pa or less when a frequency of 1 Hz is applied in an environment of 50°C. If the storage modulus of the first layer 10 is less than 1.0E+9 Pa, it is too soft, and when the laminated sheet 1 is attached to the workpiece, it may warp together with the second layer 20, following the surface irregularities of the workpiece. By setting the storage modulus of the first layer 10 to 1.0E+9 Pa or more, warping on the first layer 10 side of the laminated sheet 1 can be suppressed. If the storage modulus of the first layer 10 exceeds 1.0E+10 Pa, it is difficult to select a material because there are few resins that exceed this storage modulus.

[0022] The constituent material of the first layer 10 is not particularly limited, as long as the difference in SP value and storage modulus between it and the second layer 20 are within the above range. The first layer 10 may be formed from resins such as methacrylic resin (SP value: 9.1), polyethylene terephthalate (SP value: 10.7), polybutylene terephthalate (SP value: 10), polycarbonate, polylactic acid (SP value: 12.1), epoxy resin (SP value: 9.7-10.9), and vinyl chloride resin (SP value: 9.4-10.8).

[0023] The second layer 20 preferably has a tensile storage modulus of 1.0E+6 Pa or more and 1.0E+8 Pa or less when a frequency of 1 Hz is applied in an environment of 50°C, and more preferably 1.0E+7 Pa or more and 1.0E+8 Pa or less. The upper and lower limits of the storage modulus of the second layer 20 can be combined as appropriate. If the storage modulus of the second layer 20 is less than 1.0E+6 Pa, it is too soft, making it difficult to peel the laminated sheet 1 from the workpiece, and there is a possibility that a part of the second layer 20 will remain on the workpiece. By setting the storage modulus of the second layer 20 to 1.0E+6 Pa or more, it is possible to deform it in a way that sufficiently absorbs surface irregularities of the workpiece while making it easy to peel from the workpiece. Furthermore, by setting the storage modulus of the second layer 20 to 1.0E+7 Pa or more, it is possible to make it even easier to peel from the workpiece. If the storage modulus of the second layer 20 exceeds 1.0E+8Pa, it becomes difficult to adhere to the workpiece, requiring a higher temperature during adhesion, which could lead to damage to the device. By setting the storage modulus of the second layer 20 to 1.0E+8Pa or less, adhesion to the workpiece is facilitated, and the layer can be deformed to adequately absorb surface irregularities of the workpiece.

[0024] The material of the second layer 20 is not particularly limited as long as the difference in SP value and storage modulus from the first layer 10 are within the above range, but may be formed from synthetic resins including, for example, polyethylene (SP value: 8.0), polypropylene (SP value: 8.0), polybutadiene (SP value: 8.3), vinyl acetate resin (SP value: 9.2), methacrylic resin (SP value: 9.1), vinyl chloride resin (SP value: 9.4~10.8), α-olefin, SEPS, SIS, SBS, etc.

[0025] In this embodiment, the storage moduli of the first layer 10 and the second layer 20 are measured using a dynamic viscoelasticity measuring device (Hitachi High-Tech Science Corporation's "DMA-7100") on the following strip samples. The measurement conditions are as follows. • Sample width: 10mm • Sample length: 20mm • Sample thickness: 0.1 mm • Measurement mode: Tensile mode • Test temperature: 20℃ → 120℃ (increase of 2℃ per minute) • Frequency: 1Hz

[0026] Furthermore, the thickness 12 of the first layer 10 is preferably 5 μm or more and 50 μm or less, and more preferably 10 μm or more and 20 μm or less. The upper and lower limits of the thickness 12 of the first layer 10 can be combined as appropriate. The thickness 12 of the first layer 10 is preferably less than the thickness 22 of the second layer 20. The thickness 22 of the second layer 20 is preferably 50 μm or more and 300 μm or less, and more preferably 100 μm or more and 200 μm or less. The upper and lower limits of the thickness 22 of the second layer 20 can be combined as appropriate. Furthermore, the thickness 22 of the second layer 20 is preferably 125% or more and 200% or less of the height of the irregularities (such as the electrode bumps 205 shown in Figure 5 below) formed on the surface to which the laminated sheet 1 is to be attached.

[0027] If the thickness 12 of the first layer 10 is less than 5 μm, the second moment of area is too small, and when the laminated sheet 1 is attached to the workpiece, it may warp together with the second layer 20, following the surface irregularities of the workpiece. If the thickness 12 of the first layer 10 exceeds 50 μm, when the laminated sheet 1 is rolled, the total length of the laminated sheet 1 wound on one roll will be shorter, which may increase the frequency of replacement and downtime. If the thickness 22 of the second layer 20 is less than 50 μm, it may not be able to fully absorb the surface irregularities of the workpiece. If the thickness 22 of the second layer 20 exceeds 300 μm, when the laminated sheet 1 is rolled, the total length of the laminated sheet 1 wound on one roll will be shorter, which may increase the frequency of replacement and downtime.

[0028] The thickness 12 of the first layer 10 is 5 μm or more and 50 μm or less, and the thickness 22 of the second layer 20 is 50 μm or more and 300 μm or less. This allows the second layer 20 to sufficiently absorb surface irregularities of the workpiece while suppressing the effect of deformation of the second layer 20 on the first layer 10. Furthermore, if the thickness 22 of the second layer 20 is 100 μm or more and 200 μm or less, peeling from the workpiece can be made easier.

[0029] <Method for manufacturing laminated sheet 1> Next, a method for manufacturing the laminated sheet 1 according to an embodiment of the present invention will be described using Figures 2 to 4. Figure 2 is a flowchart showing the flow of the manufacturing method of the laminated sheet 1 according to an embodiment. Figures 3 and 4 are schematic diagrams illustrating an example of the manufacturing method of the laminated sheet 1.

[0030] As shown in Figure 2, the manufacturing method of the laminated sheet 1 includes a preparation step 101 and a heat-pressing step 102. The preparation step 101 is the step of preparing the first sheet 14 and the second sheet 24. The heat-pressing step 102 is the step of laminating the first sheet 14 and the second sheet 24 without using an adhesive and pressing them together while melting the interface by heating.

[0031] The first sheet 14, when formed on the laminated sheet 1, corresponds to the first layer 10 described above. That is, the first sheet 14 preferably has a storage modulus in the tensile direction of 1.0E+9 Pa or more and 1.0E+10 Pa or less when a frequency of 1 Hz is applied in an environment of 50°C.

[0032] Furthermore, the second sheet 24 corresponds to the second layer 20 described above when formed on the laminated sheet 1. That is, the second sheet 24 preferably has a storage modulus in the tensile direction of 1.0E+6Pa or more and 1.0E+8Pa or less when a frequency of 1Hz is applied in an environment of 50°C, and more preferably 1.0E+7Pa or more and 1.0E+8Pa or less. The difference in SP value between the first sheet 14 and the second sheet 24 is preferably 3.0 or less, more preferably 2.0 or less, and even more preferably 1.5 or less.

[0033] In the example shown in Figure 3, a laminated sheet 1 is manufactured using a lamination device 40. The lamination device 40 includes a first feed roller 42, a second feed roller 44, a pair of heating rollers 46-1 and 46-2, and support rollers 48-1 and 48-2. In the following description, unless otherwise distinguished, heating rollers 46-1 and 46-2 will simply be referred to as heating roller 46. Similarly, unless otherwise distinguished, support rollers 48-1 and 48-2 will simply be referred to as support roller 48.

[0034] The first feed roller 42 is cylindrical, with its axis extending in one horizontal direction, and is rotatably supported around its axis. The first feed roller 42 is inserted into the core of the first sheet roll 14-1, which is a roll-shaped first sheet 14, and supports the first sheet roll 14-1 around its axis. The first feed roller 42 fixes the inner surface of the core of the first sheet roll 14-1 to its outer surface and, by rotating around its axis, feeds the first sheet 14 sequentially from one end toward the heating roller 46-1 side between the heating rollers 46-1 and 46-2.

[0035] The second feed roller 44 is cylindrical, with its axis extending parallel to the axis of the first feed roller 42, and is rotatably supported around its axis. The second feed roller 44 is inserted into the core of the second sheet roll 24-1, which is a roll-shaped second sheet 24, and supports the second sheet roll 24-1 around its axis. The second feed roller 44 fixes the inner circumferential surface of the core of the second sheet roll 24-1 to its outer circumferential surface, and by rotating around its axis, it feeds the second sheet 24 sequentially from one end toward the heating roller 46-2 side between the heating rollers 46-1 and 46-2.

[0036] The heating roller 46 is equipped with a heat source inside. The heating roller 46 is cylindrical, with its axis extending in a direction parallel to the axis of the first feed roller 42, and is supported so as to be rotatable around its axis. The pair of heating rollers 46-1 and 46-2 are positioned at a predetermined distance apart from each other. Between the pair of heating rollers 46-1 and 46-2, the first sheet 14 fed from the first feed roller 42 and the second sheet 24 fed from the second feed roller 44 merge and stack. The pair of heating rollers 46-1 and 46-2 rotate in opposite directions to each other, joining the first sheet 14 and the second sheet 24 by sandwiching and heat-pressing them together.

[0037] The heating roller 46-1 has its outer surface in contact with one side of the first sheet 14, heating it from the first sheet 14 side and pressing it towards the heating roller 46-2 side. The heating roller 46-2 has its outer surface in contact with one side of the second sheet 24, heating it from the second sheet 24 side and pressing it towards the heating roller 46-2 side. The laminated sheet 1 is manufactured by being heated and pressed between the pair of heating rollers 46-1 and 46-2, causing the other side of the first sheet 14 and the other side of the second sheet 24 to melt and join together. The heating roller 46 may have its surface coated with fluororesin.

[0038] The support roller 48 is cylindrical, with its axis extending in a direction parallel to the axis of the first feed roller 42, and is rotatably supported around its axis. The multiple support rollers 48-1 and 48-2 transport the laminated sheet 1 from the heating roller 46 to a winding roller (not shown) that winds the manufactured laminated sheet 1 into a roll, and apply tension to the laminated sheet 1 to suppress slack. In this embodiment, the support roller 48-1 is downstream of the heating roller 46-2, in contact with the second sheet 24 (second layer 20) side of the laminated sheet 1, and presses against the first sheet 14 (first layer 10) side. In this embodiment, the support roller 48-2 is downstream of the heating roller 46-1 and the support roller 48-1, in contact with the first sheet 14 (first layer 10) side of the laminated sheet 1, and presses against the second sheet 24 (second layer 20) side. The laminated sheet 1, heated by the heating roller 46, is cooled in a room temperature environment while being conveyed, for example, by the support roller 48. The support roller 48 may be equipped with a cooling source for cooling the laminated sheet 1.

[0039] When manufacturing the laminated sheet 1 using the bonding apparatus 40 shown in Figure 3, the preparation step 101 corresponds to, for example, preparing the first sheet roll 14-1 and the second sheet roll 24-1, or feeding out the first sheet 14 and the second sheet 24 from them. The heating and pressing step 102 corresponds to heating and pressing using a pair of heating rollers 46-1 and 46-2.

[0040] In the example shown in Figure 4, a laminated sheet 1 is manufactured using an extruder 60. The extruder 60 comprises a first material supply source 62, a second material supply source 64, a T-die 66, and support rollers 68-1, 68-2, 68-3, and 68-4. In the following description, unless otherwise specified, the support rollers 68-1, 68-2, 68-3, and 68-4 will simply be referred to as support rollers 68.

[0041] The first material source 62 supplies the first material 16, which is a component of the first layer 10, to the T-die 66. The first material 16 may be supplied in pellet, granular, or powder form. The second material source 64 supplies the second material 26, which is a component of the second layer 20, to the T-die 66. The second material 26 may be supplied in pellet, granular, or powder form.

[0042] In this embodiment, the T-die 66 is divided into two layers internally upstream, with a first material 16 and a second material 26 supplied to each layer. The T-die 66 heats and melts the first material 16 supplied from the first material supply source 62, and then presses it into a sheet to form the first sheet 14. The T-die 66 also heats and melts the second material 26 supplied from the second material supply source 64, and then presses it into a sheet to form the second sheet 24. The two layers merge inside the T-die 66. The merged first sheet 14 and second sheet 24 are in a laminated state. The laminated first sheet 14 and second sheet 24 are heated inside the T-die 66 and co-extruded, thereby being heat-pressed together. This joins the molten interfaces, and a laminated sheet 1 is manufactured. The laminated sheet 1 is discharged from the extrusion port (slit at the lower end) of the T-die 66.

[0043] The support roller 68 is cylindrical, with its axis horizontal and extending in a direction parallel to the surface of the laminated sheet 1 discharged from the T-die 66, and is rotatably supported around its axis. The multiple support rollers 68-1, 68-2, 68-3, and 68-4 transport the laminated sheet 1 from the T-die 66 to a winding roller (not shown) that winds the manufactured laminated sheet 1 into a roll, and apply tension to the laminated sheet 1 to suppress sagging. In this embodiment, support roller 68-1 is located downstream of the T-die 66, in contact with the first sheet 14 (first layer 10) side of the laminated sheet 1 and pressing against the second sheet 24 (second layer 20) side. In this embodiment, support roller 68-2 is located opposite support roller 68-1, in contact with the second sheet 24 (second layer 20) side of the laminated sheet 1 and pressing against the first sheet 14 (first layer 10) side. In this embodiment, support roller 68-3 is located downstream of support rollers 68-1 and 68-2, contacting the second sheet 24 (second layer 20) side of the laminated sheet 1 and pressing it towards the first sheet 14 (first layer 10) side. Support roller 68-4 is located downstream of support roller 68-3, contacting the first sheet 14 (first layer 10) side of the laminated sheet 1 and pressing it towards the second sheet 24 (second layer 20) side. The laminated sheet 1, heated by the T-die 66, is cooled, for example, by pressing the water-cooled support rollers 68-1 and 68-2 against the laminated sheet 1. The support rollers 68 are made of, for example, SUS.

[0044] When manufacturing the laminated sheet 1 using the extrusion apparatus 60 shown in Figure 4, the preparation step 101 corresponds to, for example, forming the first sheet 14 and the second sheet 24 from the first material 16 and the second material 26 inside the T-die 66. The heating and pressing step 102 corresponds to laminating and co-extruding the first sheet 14 and the second sheet 24 inside the T-die 66.

[0045] <Workpiece 200> Next, the workpiece 200, which is the target of processing in the processing method for the workpiece 200 according to an embodiment of the present invention, will be described with reference to Figure 5. Figure 5 is a perspective view showing the schematic configuration of the workpiece 200, which is the target of processing in the processing method for the workpiece 200 according to an embodiment.

[0046] As shown in Figure 5, the workpiece 200 is a wafer such as a semiconductor wafer or optical device wafer formed from materials such as silicon (Si), silicon carbide (SiC), gallium nitride (GaN), gallium arsenide (GaAs), or other semiconductors, or a substantially disc-shaped substrate made of materials such as sapphire (Al2O3), lithium tantalate (LiTaO3), glass, or quartz. The glass includes, for example, alkali glass, alkali-free glass, soda-lime glass, lead glass, borosilicate glass, and quartz glass. In the embodiment, the thickness of the substrate 201 from the front surface 202 to the back surface 206 of the workpiece 200 is 775 μm.

[0047] As shown in Figure 5, the workpiece 200 has a plurality of division lines 203 arranged in a grid pattern, and a device 204 formed on the surface 202 side of the region partitioned by the intersecting division lines 203. The device 204 is, for example, an integrated circuit such as an IC (Integrated Circuit) or LSI (Large Scale Integration), an image sensor such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), a MEMS (Micro Electro Mechanical Systems), or a memory (semiconductor memory device).

[0048] In this embodiment, the workpiece 200 has a plurality of electrode bumps 205 mounted on the surface 202 side of the substrate 201, which are protrusions that extend from the surface of the device 204. The workpiece 200 has irregularities on its surface 202 due to the mounting of the electrode bumps 205. Each of the electrode bumps 205 is electrically connected to the device 204, and when the workpiece 200 is divided to form the device chip 210, they function as electrodes for inputting and outputting electrical signals to and from the device 204. The electrode bumps 205 are made of a metallic material such as gold, silver, copper, or aluminum. The electrode bumps 205 have a height of 100 μm to 300 μm and protrude from the surface of the device 204. In this embodiment, the height of the electrode bumps 205 is 200 μm.

[0049] The workpiece 200 is divided into individual devices 204 along a planned division line 203, and then fragmented into device chips 210. The device chip 210 includes a portion of the substrate 201 and the devices 204. In this embodiment, the workpiece 200 is divided into device chips 210, which are mounted on a mounting substrate by a mounting technique called flip-chip bonding, with the devices 204 having electrode bumps 205.

[0050] In Figure 5, the device chip 210 is square in shape, but it may also be rectangular. Furthermore, in this embodiment, the workpiece 200 has an uneven surface 202 formed by mounting electrode bumps 205 protruding from the surface of the device 204. However, the processing method for the workpiece 200 of the present invention is not limited to electrode bumps 205 and is useful for workpieces 200 that have uneven surfaces 202.

[0051] <Processing method for workpiece 200> Next, a method for processing the workpiece 200 according to an embodiment of the present invention will be described using Figures 6 to 10. Figure 6 is a flowchart showing the flow of the processing method for the workpiece 200 according to an embodiment. As shown in Figure 6, the processing method for the workpiece 200 includes a sheet fixing step 301 and a grinding step 302.

[0052] Figure 7 is a side view showing a partial cross-section of one state of the sheet fixing step 301 shown in Figure 6. Figure 8 is a side view showing a partial cross-section of the state after Figure 7. The sheet fixing step 301 is a step of fixing the second layer 20 side of the laminated sheet 1 to the surface 202 side of the workpiece 200.

[0053] As shown in Figures 7 and 8, in the sheet fixing step 301, the second layer 20 side of the laminated sheet 1 is placed opposite the surface 202 side of the workpiece 200, and then the second layer 20 side of the laminated sheet 1 is attached to the surface 202 side of the workpiece 200. At this time, in the sheet fixing step 301, the second layer 20 side of the laminated sheet 1 is attached to the surface 202 side of the workpiece 200 while the laminated sheet 1 is heated.

[0054] The sheet fixing step 301 may be performed, for example, with the back surface 206 of the workpiece 200 placed on the holding surface of a holding table (not shown). The holding table may be a heat table equipped with a heating source capable of heating the holding surface. In the sheet fixing step 301, first, the back surface 206 of the workpiece 200 is held by the holding table, and the second layer 20 of the laminated sheet 1 is placed facing the front surface 202 of the workpiece 200.

[0055] In the sheet fixing step 301, the laminated sheet 1 is then placed on the surface 202 side of the workpiece 200 and pressed down. One method for pressing the laminated sheet 1 on the surface 202 side of the workpiece 200 is to use a pressing roller (not shown) that rolls from one end to the other end of the workpiece 200. The pressing roller may be a heat roller equipped with a heating source inside. The sheet fixing step 301 may also be performed with the first layer 10 side of the laminated sheet 1 placed on the holding surface of the holding table.

[0056] In the sheet fixing step 301, the laminated sheet 1 is heated and pressed against the workpiece 200 while heating at least one of the laminated sheet 1 and the workpiece 200, thereby performing heat-pressing on the laminated sheet 1 against the workpiece 200. As a result, the second layer 20 side of the laminated sheet 1 and the surface 202 side of the workpiece 200 are pressed together, and the second layer 20 side of the laminated sheet 1 is fixed to the surface 202 side of the workpiece 200.

[0057] Furthermore, the method is not limited to heat rollers; for example, the heat pressing of the laminated sheet 1 onto the workpiece 200 may be performed by a pressing unit (not shown) having a flat and horizontal pressing surface on its lower surface facing the holding surface of the heat table, and being able to move up and down relative to the heat table. The pressing unit may be equipped with a heating source capable of heating the pressing surface. In addition, when the laminated sheet 1 is heated and pressed by the heat table, heat rollers, or pressing unit, it is preferable that it be heated to a temperature above the softening point and below the melting point.

[0058] Figures 9 and 10 are side views showing a partial cross-section of one state of the grinding step 302 shown in Figure 6. The grinding step 302 is performed after the sheet fixing step 301 is completed. The grinding step 302 is a step in which the back surface 206 side of the workpiece 200 is ground.

[0059] As shown in Figures 9 and 10, the grinding step 302 of the embodiment is carried out by a grinding device 80. The grinding device 80 comprises a holding table 82, a grinding unit 84, and a grinding fluid supply unit (not shown). The grinding unit 84 has a spindle 86 which is a rotating shaft member, a grinding wheel 88 attached to the lower end of the spindle 86, and a grinding wheel 90 mounted on the lower surface of the grinding wheel 88. The spindle 86 rotates on a rotation axis parallel to the axis of the holding table 82.

[0060] As shown in Figure 9, in the grinding step 302, first, the laminated sheet 1 side of the workpiece 200, to which the laminated sheet 1 is fixed, is held by suction on the holding surface of the holding table 82. That is, the first layer 10 side of the laminated sheet 1 is held by suction. Next, with the holding table 82 rotating around its axis, the spindle 86 and grinding wheel 88 are rotated around their axes. Grinding fluid is supplied to the processing point by a grinding fluid supply unit (not shown), and the grinding wheel 90 of the grinding wheel 88 is brought closer to the holding table 82 at a predetermined feed rate, thereby grinding the back surface 206 side of the workpiece 200 with the grinding wheel 90 and thinning it to a predetermined finish thickness.

[0061] After performing the grinding step 302, the workpiece 200 is divided into individual device chips 210 (see Figure 5) by, for example, dicing along the planned division line 203 (see Figure 5). At this time, the cutting blade is made to cut from the grinding surface 207 side of the workpiece 200, so as not to divide the laminated sheet 1, thereby suppressing the device chips 210 from falling apart during the cutting process. The individualized device chips 210 are then peeled off from the laminated sheet 1 one by one or in groups by, for example, a pickup device.

[0062] The grinding step 302 may be performed on a workpiece 200 in which a division starting point is formed along the planned division line 203. The division starting point includes, for example, a modified layer formed inside the workpiece 200 by laser processing, or a machined groove formed on the surface 202 side of the workpiece 200 by cutting. If a machined groove is formed on the surface 202 side of the workpiece 200, the division starting point is formed before the sheet fixing step 301.

[0063] In this way, by performing the grinding step 302 on the workpiece 200, which has a division starting point formed along the division planned line 203, the external force exerted by the grinding wheel 90 pressing against the grinding surface 207 of the workpiece 200 causes the workpiece 200 to be divided along the division planned line 203, starting from the division starting point, and is broken down into individual device chips 210.

[0064] <Method for manufacturing device chips> Next, a method for manufacturing the device chip 210-1 according to an embodiment of the present invention will be described using Figures 11 to 15. Figure 11 is a flowchart showing the flow of the method for manufacturing the device chip according to the embodiment. As shown in Figure 11, the method for manufacturing the device chip 210-1 includes a sheet fixing step 401, an imaging step 402, and a division step 403.

[0065] Figure 12 is a side view showing a partial cross-section of one state of the sheet fixing step shown in Figure 11. The sheet fixing step 401 is a step of fixing the second layer 20 side of the laminated sheet 1 to the surface 202 or back surface 206 of the workpiece 200-1. In the sheet fixing step 401 of this embodiment, the second layer 20 side of the laminated sheet 1 is fixed to the surface 202 of the workpiece 200-1.

[0066] Here, the workpiece 200-1, which is the object to be processed in the manufacturing method of the device chip 210-1 of the embodiment, will be described. The basic structure of the workpiece 200-1 is the same as that of the workpiece 200 described above, but the workpiece 200-1 does not have electrode bumps 205 mounted on it, and instead a film 208 is formed on the back surface 206 side opposite to the surface 202 on which the device 204 is formed. In the embodiment, the entire back surface 206 of the workpiece 200-1 is covered with a film 208 of substantially constant thickness. The film 208 is, for example, a layer of metal, or it may be an oxide film.

[0067] The method for manufacturing the device chip 210-1 involves dividing a workpiece 200-1, which has division lines 203 set on its surface 202, along the division lines 203 to manufacture the device chip 210-1. The workpiece to be processed in the method for manufacturing the device chip 210-1 is not limited to a workpiece 200-1 without electrode bumps 205, but may also be a workpiece 200 with electrode bumps 205. Furthermore, the workpiece to be processed is not limited to a workpiece 200-1 with a film 208 formed on its back surface 206, but may also be a workpiece 200 without a film 208 formed on its back surface 206.

[0068] The sheet fixing step 401 of the manufacturing method for the device chip 210-1 is carried out in the same manner and procedure as the sheet fixing step 301 of the processing method for the workpiece 200 described above. That is, as shown in Figure 12, in the sheet fixing step 401, the second layer 20 side of the laminated sheet 1 is placed opposite the surface 202 side of the workpiece 200-1, and then the second layer 20 side of the laminated sheet 1 is attached to the surface 202 side of the workpiece 200-1. At this time, in the sheet fixing step 401, the second layer 20 side of the laminated sheet 1 is attached to the surface 202 side of the workpiece 200-1 while the laminated sheet 1 is heated.

[0069] In the sheet fixing step 401, simultaneously or sequentially, the outer periphery of the laminated sheet 1, which is to be attached to the workpiece 200-1, is attached to the annular frame 220 (see Figure 14 or 15 described later). The frame 220 is an annular plate member made of metal or resin and has an opening larger than the outer diameter of the workpiece 200-1. In this way, the frame 220 supports the workpiece 200-1 via the laminated sheet 1.

[0070] Figure 13 is a side view showing a partial cross-section of one state of the imaging step shown in Figure 11. The imaging step 402 is performed after the sheet fixing step 401 and before the division step 403. The imaging step 402 is a step in which the division line 203 set on the surface 202 of the workpiece 200-1 is imaged via the laminated sheet 1 fixed to the surface 202 side of the workpiece 200-1.

[0071] In the imaging step 402, first, the surface 202 side of the workpiece 200-1 is held on the holding surface 422 of the holding table 420 via the laminated sheet 1. At this time, the first layer 10 side of the laminated sheet 1 is held on the holding surface 422 of the holding table 420. Since the first layer 10 is harder than the second layer 20, adhesion to the holding surface 422 can be reduced. The holding table 420 is formed so that at least a portion of the holding surface 422 includes a transparent member 424 which is transparent. The holding table 420 has, for example, a disc-shaped transparent member 424 and an annular frame 426 that holds the outer edge of the transparent member 424.

[0072] The transparent member 424 is made of a transparent material such as quartz glass, borosilicate glass, sapphire, calcium fluoride, lithium fluoride, or magnesium fluoride, and is formed in a disc shape with a constant thickness. The outer diameter of the transparent member 424 is larger than the outer diameter of the workpiece 200-1 and smaller than the inner diameter of the opening of the frame 220 (see Figure 14 or Figure 15 described later). The outer edge of the transparent member 424 is supported by the frame 426 and is exposed above and below the holding table 420.

[0073] The frame 426 is made of a metal such as stainless steel. The frame 426 is formed with an inner diameter equal to the outer diameter of the transparent member 424 and is attached to the outer edge of the transparent member 424. The upper surface of the frame 426 is formed flat along the horizontal direction and is located on the same plane as the holding surface 422. The frame 426 is provided with a suction groove 428 that is concave from the upper surface and has an annular planar shape on the inner edge of the upper surface. The suction groove 428 is connected to a suction source (not shown) via a suction passage (not shown) that penetrates the interior of the frame 426. The holding table 420 holds the workpiece 200 and the frame 220 by suction on the holding surface 422 (the upper surface of the frame 426) via the laminated sheet 1, by the suction source (not shown) drawing suction through the suction groove 428 via the suction passage.

[0074] Furthermore, the holding table 420 may have clamp members 430 (see Figure 14 or Figure 15, described later) arranged around the holding surface 422. The clamp members 430 clamp the frame 220.

[0075] In imaging step 402, an imaging device 440 is positioned below the holding table 420. The imaging device 440 includes an image sensor that images the surface 202 side of the workpiece 200-1 through the transparent member 424 and the laminated sheet 1. The image sensor is, for example, a CCD image sensor or a CMOS image sensor. The imaging device 440 images the surface 202 of the workpiece 200-1 through the transparent member 424 and the laminated sheet 1. Then, in imaging step 402, the planned division line 203 can be detected by imaging the surface 202 of the workpiece 200-1 with the imaging device 440.

[0076] The imaging step 402 is particularly useful when a film 208 such as metal is formed on the back surface 206, as in the embodiment, and alignment from the back surface 206 side is difficult. It is preferable that the holding table 420 supporting the workpiece 200-1 in the imaging step 402 is the same as the holding table 420 of the processing device (cutting device 450 shown in Figure 14 or laser processing device 460 shown in Figure 15) that performs the next division step 403.

[0077] Figure 14 is a side view showing a partial cross-section of an example of the splitting step shown in Figure 11. The splitting step 403 is performed after the sheet fixing step 401 is carried out. The splitting step 403 is a step in which the workpiece 200-1 is processed from the side opposite to the side on which the laminated sheet 1 is fixed (the front surface 202 in the embodiment) (the back surface 206 in the embodiment) and split along the planned splitting line 203.

[0078] In the example shown in Figure 14, a cutting device 450 is used to perform a cutting operation on a workpiece 200-1 along a planned division line 203. The cutting device 450 comprises a holding table 420 and a cutting unit 452. The cutting device 450 also further comprises a cutting fluid supply unit that supplies cutting fluid to the machining point, a moving unit and a rotating unit (not shown) that move the holding table 420 and the cutting unit 452 relative to each other, and a control unit that controls each component.

[0079] In this embodiment, the holding table 420 is the same as the holding table 420 in the imaging step 402. The holding table 420 is movable relative to the cutting unit 452 in the machining feed direction (X-axis direction), indexing feed direction (Y-axis direction), and depth of cut feed direction (Z-axis direction) by a moving unit (not shown). The holding table 420 is also rotatable around an axis parallel to the Z-axis direction by a rotating unit (not shown).

[0080] The cutting unit 452 is a unit that cuts the workpiece 200-1 held on the holding table 420. The cutting unit 452 has a spindle 454 and a cutting blade 456. The spindle 454 is rotatable around an axis parallel to the Y-axis direction, and the cutting blade 456 is mounted at its tip so as to be coaxial. The cutting blade 456 is a cutting tool for forming cutting grooves in the workpiece 200-1, and has a cutting edge made of diamond abrasive grains or CBN (Cubic Boron Nitride) abrasive grains bonded with a bonding material such as metal or resin, and is an extremely thin disc-shaped and annular cutting wheel.

[0081] In the cutting division step 403 shown in Figure 14, the surface 202 side of the workpiece 200-1 is held on the holding surface 422 of the holding table 420 via the laminated sheet 1, continuing from the imaging step 402. In the division step 403, first, the division line 203 is detected based on the image of the surface 202 of the workpiece 200-1 captured in the imaging step 402, and alignment is performed by a moving unit (not shown) to align the holding table 420 and the cutting blade 456. Specifically, the machining point of the cutting blade 456 is positioned above the division line 203 of the workpiece 200-1.

[0082] In the splitting step 403, the cutting fluid is then supplied to the machining point of the cutting blade 456, and the spindle 454 is started to rotate. Next, while the holding table 420 is fed in the X-axis direction, the cutting edge of the cutting blade 456 is made to cut into the laminated sheet 1 attached to the surface 202 side of the workpiece 200-1. As a result, the workpiece 200-1 is split along the planned splitting line 203 and divided into individual pieces into device chips 210-1. Thus, in the splitting step 403 of this embodiment, machining is performed along the planned splitting line 203 from the back surface 206 side of the workpiece 200-1 based on the position of the planned splitting line 203 captured in the imaging step 402.

[0083] Figure 15 is a side view showing a partial cross-section of another example of the division step shown in Figure 11. In the example shown in Figure 15, a laser processing device 460 is used to perform laser processing to cut the workpiece 200-1 along the division line 203. The laser processing device 460 comprises a holding table 420 and a laser beam irradiation unit 462. The laser processing device 460 also further comprises a moving unit and a rotating unit (not shown) for relatively moving the holding table 420 and at least the concentrator of the laser beam irradiation unit 462, a control unit for controlling each component, and so on.

[0084] In this embodiment, the holding table 420 is the same as the holding table 420 in the imaging step 402. The holding table 420 is movable relative to the laser beam irradiation unit 462 in the processing feed direction (X-axis direction), the indexing feed direction (Y-axis direction), and the focusing point position adjustment direction (Z-axis direction) by a moving unit (not shown). The holding table 420 is also rotatable around an axis parallel to the Z-axis direction by a rotating unit (not shown).

[0085] The laser beam irradiation unit 462 is a unit that irradiates a workpiece 200-1 held on a holding table 420 with a laser beam 464. The laser beam irradiation unit 462 includes an oscillator that emits the laser beam 464, a concentrator that focuses the laser beam 464 toward the holding table 420, and various optical elements arranged in the optical path between the oscillator and the concentrator. The laser beam 464 is a laser beam having a wavelength that is absorbed by the workpiece 200-1, for example, ultraviolet (UV).

[0086] In the laser processing division step 403 shown in Figure 15, the surface 202 side of the workpiece 200-1 is held on the holding surface 422 of the holding table 420 via the laminated sheet 1, continuing from the imaging step 402. In the division step 403, first, the division line 203 is detected based on the image of the surface 202 of the workpiece 200-1 captured in the imaging step 402, and alignment is performed by a moving unit (not shown) to align the holding table 420 with the focuser of the laser beam irradiation unit 462. Specifically, the position where the laser beam 464 is irradiated (focus point) is positioned on the back surface 206 of the workpiece 200-1, and the horizontal direction is positioned on the division line 203. The focus point of the laser beam 464 may also be positioned at a predetermined distance in the height direction from the back surface 206 of the workpiece 200-1 (defocusing is also possible).

[0087] In the division step 403, a moving unit (not shown) is used to move the workpiece 200-1 from the back surface 206 side while relatively feeding the workpiece 200-1 from the division line 203 and the focal point of the laser beam 464 along the X-axis. As a result, the workpiece 200-1 is divided along the division line 203 and fragmented into device chips 210-1. Thus, in the division step 403 of this embodiment, processing is performed along the division line 203 from the back surface 206 side of the workpiece 200-1 based on the position of the division line 203 captured in the imaging step 402.

[0088] As described above, the laminated sheet 1 according to this embodiment does not have an adhesive layer, so thickness variations during grinding or polishing caused by variations in the thickness of the adhesive layer do not occur, thus reducing overall thickness variations. In addition, the workpiece 200 is not contaminated by seepage of the adhesive layer, which suppresses product defects and reduces the environmental burden. Furthermore, when imaging is performed through the sheet (laminated sheet 1) supporting the workpiece 200-1, as in the manufacturing method of the device chip 210-1 according to the embodiment described above, the absence of an adhesive layer makes imaging easier.

[0089] It should be noted that the present invention is not limited to the embodiments described above. That is, it can be implemented with various modifications without departing from the core principles of the present invention.

[0090] For example, in the manufacturing method of the device chip 210-1 of the embodiment, the workpiece 200-1 having a film 208 on the back surface 206 side was processed from the back surface 206 side, but the target may also be a workpiece without a film 208, and processing may be done from the front surface 202 side. Also, in the imaging step 402, the laminated sheet 1 may be held by the holding table 420 so that it is exposed, and imaging may be taken from above. In this case, the holding table 420 does not have to have a part of its holding surface 422 that is a transparent member 424. [Explanation of symbols]

[0091] 1 Laminated sheet 10. The First Layer 12, 22 Thickness 14 First sheet 16. The first material 20 Second Layer 24 Second seat 26 Second material 40 Bonding device 46 Heating roller 60 Extrusion device 66 T-die 80 Grinding equipment 200 Workpiece 202 Surface 205 Electrode Bump 206 Back side 208 Membrane 210, 210-1 Device Chips 440 Imaging device 450 Cutting equipment 460 Laser Processing Machine 464 laser beams

Claims

1. It is a laminated sheet, A first layer having a storage modulus in the tensile direction of 1.0E+9 Pa or more and 1.0E+10 Pa or less when a frequency of 1 Hz is applied in an environment of 50°C, The first layer is laminated with a second layer having a tensile storage modulus of 1.0E+6Pa or more and 1.0E+8Pa or less when a frequency of 1 Hz is applied in an environment of 50°C, The first layer and the second layer are, The difference in solubility parameters is 3.0 or less, and the layers are laminated without an adhesive layer. A laminated sheet characterized by the following features.

2. The thickness of the first layer is less than the thickness of the second layer. The laminated sheet according to claim 1, characterized in that

3. A preparation step of preparing a first sheet having a tensile storage modulus of 1.0E+9 Pa or more and 1.0E+10 Pa or less when a frequency of 1 Hz is applied in a 50°C environment, and a second sheet having a tensile storage modulus of 1.0E+6 Pa or more and 1.0E+8 Pa or less when a frequency of 1 Hz is applied in a 50°C environment, and the difference in solubility parameters between the first sheet and the second sheet is 3.0 or less. A heating and pressing step involves laminating the first sheet and the second sheet without using an adhesive, and then heating them to melt the interface and press them together. including A method for manufacturing a laminated sheet, characterized by the following:

4. A method for processing a workpiece having irregularities on its surface, A sheet fixing step of fixing the second layer side of the laminated sheet manufactured by the laminated sheet manufacturing method described in claim 1 or 2, or the laminated sheet manufactured by the laminated sheet manufacturing method described in claim 3, to the surface side of the workpiece, After performing the sheet fixing step, a grinding step is performed to grind the back side of the workpiece, including A method for processing a workpiece, characterized by the features described above.

5. A method for manufacturing a device chip, which involves dividing a workpiece on which division lines are set on the surface along the division lines to produce a device chip, A sheet fixing step of fixing the second layer side of a laminated sheet manufactured by the method for manufacturing a laminated sheet according to claim 1 or 2, or by the method for manufacturing a laminated sheet according to claim 3, to the surface or back surface of the workpiece, After performing the sheet fixing step, a dividing step is performed on the workpiece from the side opposite to the side on which the laminated sheet is fixed, and the workpiece is divided along the planned dividing line. including A method for manufacturing a device chip, characterized by the following features.

6. In the seat fixing step, The second layer side of the laminated sheet is fixed to the surface of the workpiece. A method for manufacturing a device chip according to claim 5, characterized in that

7. The workpiece has a film formed on its back surface. A method for manufacturing a device chip according to claim 6, characterized in that

8. The method further includes an imaging step of imaging the planned division lines set on the surface of the workpiece via the laminated sheet fixed to the surface side of the workpiece, In the division step, Based on the position of the planned division line captured in the imaging step, processing is performed along the planned division line from the back side of the workpiece. A method for manufacturing a device chip according to claim 6, characterized in that

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