Wafer processing method

Abstract

A method for processing a wafer is provided, wherein the quality of the device is not reduced even if the back side of the wafer is processed by supporting the wafer through a substrate. According to the present invention, a method for processing a wafer is provided, wherein the method for processing a wafer comprises at least the following steps: a wafer arrangement step, wherein a peeling layer (16) having a diameter smaller than that of the wafer is arranged on the upper surface of a substrate (18) having a diameter greater than or equal to that of the wafer (10), and any sheet (14) of a polyolefin sheet or a polyester sheet having a diameter greater than or equal to that of the wafer is laid on the upper surface of the substrate (18) via the peeling layer (16), and the front side (10a) of the wafer is positioned on the upper surface of the sheet (14) for arrangement; a sheet thermal compression step, wherein the wafer arranged on the substrate via the sheet is decompressed and the sheet is heated in a closed environment, and the wafer is pressed to thermally compress the wafer onto the substrate via the sheet (14); a processing step, wherein the back side (10b) of the wafer is processed; and a peeling step, wherein the wafer is peeled off from the sheet (14).

Description

Technical Field

[0001] The invention relates to a method for processing a wafer, which processes the back side of the wafer. Background Art

[0002] A wafer having multiple devices such as IC and LSI formed on the front side divided by predetermined dividing lines is ground on the back side by a grinding device to a specified thickness, and then divided into individual device chips by a dicing device for use in electronic devices such as mobile phones and personal computers.

[0003] In recent years, in order to achieve miniaturization and lightness of electronic devices, there is a trend that wafers are processed to be thinner, such as 50 μm and 30 μm. In order to prevent the wafers ground to be thinner from being damaged when being transported to the next process, the applicant of this case proposed a technology of grinding the back of the wafer by supporting the wafer with a substrate, wherein the substrate is made of polyethylene terephthalate (PET), glass, etc. and has a thickness that can obtain rigidity (for example, refer to Patent Document 1).

[0004] Patent Document 1: Japanese Patent Application Publication No. 2004-296839

[0005] When the wafer is supported by the substrate, a method is adopted in which liquid resin, wax, etc. are applied to the bonding surface of the wafer and the substrate, or double-sided tape is used for bonding. However, there is the following problem: when the wafer is supported by the substrate by liquid resin, wax, double-sided tape, etc., the holding force based on the substrate cannot be said to be sufficient, and when the back of the wafer is ground, the wafer moves on the substrate, thereby damaging the wafer during grinding. In particular, when a plurality of protruding electrodes called bumps are formed on the front of the device, there is a problem that stress during grinding is concentrated on the protruding electrodes and damage occurs.

[0006] In addition, when the substrate is peeled off from the front surface of the wafer after grinding, part of the liquid resin, wax, double-sided tape paste, etc. adheres to the electrode and remains, which deteriorates the quality of device chips obtained by dividing the wafer one by one. Summary of the invention

[0007] The present invention has been accomplished in view of the above circumstances, and a main technical object of the present invention is to provide a method for processing a wafer without degrading the quality of a device even when the back side of the wafer is processed while the wafer is supported by a substrate.

[0008] In order to solve the above-mentioned main technical problems, according to the present invention, a method for processing a chip is provided, which processes the back side of a chip divided by a predetermined dividing line and having a plurality of devices formed on the front side, wherein the method for processing the chip includes at least the following steps: a chip arrangement step, in which a peeling layer having a diameter smaller than the chip is arranged on the upper surface of a substrate having a diameter greater than the diameter of the chip, and any sheet of a polyolefin sheet or a polyester sheet having a diameter greater than the diameter of the chip is laid on the upper surface of the substrate via the peeling layer, and the front side of the chip is positioned on the upper surface of the sheet for arrangement; a sheet hot pressing step, in which the chip arranged on the substrate via the sheet is decompressed and heated in a closed environment, and the chip is pressed and hot-pressed onto the substrate via the sheet; a processing step, in which the back side of the chip is processed; and a peeling step, in which the chip is peeled off from the sheet.

[0009] The peeling layer may include at least one of paper, cloth, rice paper, and a polyimide sheet. In addition, in the processing step, a grinding process may be performed to grind the back side of the wafer.

[0010] The polyolefin sheet is preferably composed of any sheet selected from polyethylene sheet, polypropylene sheet, and polystyrene sheet. In the sheet heat pressing step, the heating temperature is preferably 120°C to 140°C when the polyethylene sheet is selected, 160°C to 180°C when the polypropylene sheet is selected, and 220°C to 240°C when the polystyrene sheet is selected.

[0011] The polyester sheet is preferably made of any sheet selected from polyethylene terephthalate sheets and polyethylene naphthalate sheets. In the sheet heat pressing step, the heating temperature is preferably 250°C to 270°C when the polyethylene terephthalate sheet is selected, and the heating temperature is preferably 160°C to 180°C when the polyethylene naphthalate sheet is selected.

[0012] Preferably, in the sheet thermocompression bonding step, the wafer is pressed so that the sheet bulges around the wafer.

[0013] The wafer processing method of the present invention processes the back side of a wafer divided by a predetermined dividing line and having a plurality of devices formed on the front side, wherein the wafer processing method includes at least the following steps: a wafer placement step, in which a peeling layer having a smaller diameter than the wafer is placed on the upper surface of a substrate having a diameter greater than the diameter of the wafer, and any sheet of a polyolefin-based sheet or a polyester-based sheet having a diameter greater than the diameter of the wafer is laid on the upper surface of the substrate via the peeling layer, and the front side of the wafer is positioned on the upper surface of the sheet for placement; a sheet thermal compression step, in which the wafer placed on the substrate via the sheet is decompressed and heated in a closed environment, and the wafer is pressed and thermally compressed onto the substrate via the sheet; a processing step, in which the back side of the wafer is processed; and a peeling step, in which the wafer is peeled off from the sheet. Thus, the wafer is supported on the substrate with sufficient holding force, and the wafer will not be damaged even if the back side of the wafer is ground. In addition, even if a plurality of protruding electrodes (bumps) are formed on the front of the device, the protruding electrodes are reliably held by the sheet, and the stress during grinding is dispersed, thereby solving the problem of breakage. In addition, since liquid resin, wax, double-sided tape, etc. are not used, but the chip is supported on the substrate via the sheet by thermal compression, the liquid resin, wax, double-sided tape paste, etc. will not adhere to the device and remain, thereby not causing the problem of reduced device quality. In addition, a peeling layer with a diameter smaller than that of the chip is arranged between the sheet and the substrate, so that the sheet can be easily peeled off from the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 (a) and (b) are perspective views showing an embodiment of a wafer placement process.

[0015] Figure 2 (a) is a side view of a heat pressing device for performing a sheet heat pressing process. Figure 2 (b) is a cross-sectional view of an integrated chip formed by the sheet thermal compression bonding process.

[0016] Figure 3 This is a perspective view showing a manner in which an integrated wafer is placed on a chuck table of a grinding device for performing a processing step.

[0017] Figure 4 It is a perspective view showing an embodiment of grinding processing using a grinding device.

[0018] Figure 5 (a) is a perspective view showing a method of placing an integrated wafer on a holding unit for peeling. Figure 5 (b) is a perspective view showing an embodiment of a peeling step of peeling a substrate from a wafer.

[0019] Description of symbols

[0020] 10: wafer; 11: device; 12: predetermined dividing line; 14: sheet; 16: peeling layer; 18: substrate; 20: heater workbench; 30: hot pressing device; 32: supporting base; 34: suction hole; 36: sealing cover part; 38: pressing part; 38b: pressing plate; 50: grinding device; 52: chuck workbench; 60: grinding unit; 66: grinding wheel; 68: grinding tool; 70: holding unit. DETAILED DESCRIPTION

[0021] Hereinafter, embodiments of a wafer processing method according to the present invention will be described in detail with reference to the accompanying drawings.

[0022] exist Figure 1 (a) shows a wafer 10 divided by planned dividing lines 12 and having a plurality of devices 11 formed on a front surface 10a. In this embodiment, a back surface 10b of the wafer 10 is processed.

[0023] When executing the wafer processing method of the present embodiment, first prepare the above-mentioned wafer 10, sheet 14, peeling layer 16 and substrate 18. Sheet 14 is a sheet having a diameter greater than or equal to that of wafer 10, and is selected from any sheet of polyolefin-based sheets or polyester-based sheets. In the present embodiment, a polyethylene (PE) sheet is selected. Peeling layer 16 is a circular sheet having a diameter smaller than that of wafer 10, and a non-adhesive film material such as paper is selected. Substrate 18 is formed into a circular shape with a diameter greater than or equal to that of wafer 10, and a glass plate is selected, for example. In addition, peeling layer 16 is not limited to paper, and can be selected from cloth, rice paper, and polyimide sheet. In addition, substrate 18 is not limited to glass, and can be formed of a synthetic resin that is not affected by heat and does not soften even in the heat pressing process described later, such as polyethylene terephthalate (PET).

[0024] (Whip placement process)

[0025] When the wafer placement process is performed, the substrate 18 is first placed on the table surface 22 of the heater table 20, and the heater table 20 is a thermocompression bonding device 30 (see FIG. 1 ) for performing the thermocompression bonding process described later. Figure 2 ) holding unit. The workbench surface 22 is a flat surface, and an electric heater and a temperature sensor (not shown) are built into the heater workbench 20. A peeling layer 16 is arranged on the substrate 18 placed on the front surface 22 of the heater workbench 20. When the peeling layer 16 is arranged, it is preferable to make the center of the substrate 18 coincide with the center of the peeling layer 16. As described above, the substrate 18 is formed to have a diameter greater than the diameter of the wafer 10, and the peeling layer 16 is formed to have a diameter smaller than the wafer 10, so that the substrate 18 is exposed on the outside of the peeling layer 16.

[0026] After the peeling layer 16 is arranged on the substrate 18, the sheet 14 (polyethylene sheet) is further laid on the substrate 18. When the sheet 14 is laid on the substrate 18, the centers of both sides are also aligned. As described above, the peeling layer 16 is formed to have a smaller diameter than the wafer 10, and the sheet 14 is formed to have a circular shape with a diameter greater than the diameter of the wafer 10. Therefore, when the sheet 14 is laid on the substrate 18, the peeling layer 16 is sandwiched between the central areas thereof and the outer periphery of the sheet 14 is in direct contact with the outer periphery of the substrate 18. Then, the front surface 10a of the wafer 10 is positioned on the upper surface of the sheet 14 and arranged in such a manner that the back surface 10b is exposed upward. The above completes the wafer arrangement process.

[0027] (Thermocompression bonding process)

[0028] After the wafer placement process is completed, a thermal compression bonding process is performed. The thermal compression bonding process is a process in which the wafer 10 placed on the substrate 18 via the sheet 14 is depressurized in a closed environment, the sheet 14 is heated, and the wafer 10 is pressed to thermally compress the wafer 10 onto the substrate 18 via the sheet 14. Figure 2 , the functions and effects of the heat pressing device 30 for implementing the sheet heat pressing step will be described.

[0029] The heat pressing device 30 includes: a heater table 20, which has the above-mentioned electric heater and temperature sensor (both are omitted in the figure); a support base 32, which carries and fixes the heater table 20; a suction hole 34, which is formed in the support base 32; and a sealing cover member 36, which is used to make the space S on the support base 32 including the heater table 20 a closed space. The sealing cover member 36 is a box-shaped member that covers the entire upper surface of the support base 32, but in the side view of the heat pressing device 30, the sealing cover member 36 is not shown. Figure 2 In (a), in order to facilitate the description of the internal structure, only the cross section of the sealing cover part 36 is shown.

[0030] An opening 36b is formed in the center of the upper wall 36a of the sealed cover 36, and the opening 36b is used for the support shaft 38a of the pressing part 38 to pass through and move forward and backward in the up and down directions indicated by the arrow Z. In order to make the space S of the sealed cover part 36 isolated from the outside and form a closed environment while making the support shaft 38a move forward and backward up and down, a sealing structure 36c is formed around the opening 36b. A pressing plate 38b is arranged at the lower end of the supporting shaft 38a. The pressing plate 38b is formed in a disk shape with a diameter at least larger than the wafer 10, and is preferably set to a size with a diameter of the same degree as that of the heater workbench 20. An elastic sealing component (not shown in the figure) can be appropriately arranged on the lower end surface of the sealed cover part 36 along the entire circumference. In addition, a driving unit (not shown in the figure) for making the pressing part 38 move forward and backward in the up and down directions is arranged above the pressing part 38.

[0031] The sealed cover member 36 is lowered onto the support base 32 including the heater stage 20 on which the wafer 10 is placed in the wafer placement step, so that the space S becomes a sealed environment. Figure 2 As shown in FIG. 1 (a), the pressing plate 38 b is lifted to an upper position where it does not contact the upper surface of the wafer 10 .

[0032] After the space S formed inside the sealed cover part 36 becomes a closed environment, the suction unit (not shown) is operated to suck the air in the space S through the suction hole 34, and the area containing the chip 10 is depressurized to a state close to vacuum. At the same time, the electric heater and temperature sensor (not shown) built into the heater workbench 20 are operated to control the temperature of the upper surface 22 of the heater workbench 20. Specifically, the polyethylene sheet constituting the sheet 14 is heated to 120°C to 140°C near the melting temperature. In addition, the driving unit (not shown) is operated to lower the pressing plate 38b in the direction indicated by the arrow Z, so that the entire upper surface of the chip 10 is pressed with uniform force. The space S containing the chip 10 is depressurized to a state close to vacuum, and air is appropriately sucked and removed from each bonding surface of the chip 10, the sheet 14, the peeling layer 16 and the substrate 18. Then, the sheet 14 is heated to a temperature near the melting point of the sheet 14 (120°C to 140°C) to soften and exert adhesiveness, and the wafer 10, the sheet 14, the peeling layer 16 and the substrate 18 are placed on the substrate 18. Figure 2 The peeling layer 16 is made of a material (paper) that does not exhibit adhesiveness even when heated, and the peeling layer 16 is arranged in a substantially vacuum state, and the sheet 14 and the substrate 18 are thermally pressed in the peripheral region. In addition, at this time, the wafer 10 is pressed by the pressing plate 38b, so that Figure 2 As shown in (b), the outer periphery of the softened sheet 14 disposed directly below the wafer 10 bulges to form a bulging portion 14a surrounding the outer periphery of the wafer 10, thereby more firmly fixing the wafer 10. In this way, the thermal compression bonding process is completed to form an integrated wafer W in which the wafer 10, the sheet 14, the peeling layer 16, and the substrate 18 are integrated.

[0033] (Processing steps)

[0034] After the above-mentioned thermal compression bonding process is completed to form an integrated wafer W, a processing step of processing the back side of the wafer 10 is performed. The processing step of this embodiment is to grind the back side 10b. Figure 3 , Figure 4 A more specific description will be given.

[0035] exist Figure 31 shows a chuck table 52 of a grinding device 50 (only a part is shown), and the upper surface of the chuck table 52 is composed of a suction chuck 54, which is composed of porous ceramics with air permeability. The integrated wafer W is placed on the suction chuck 54 with the substrate 18 side facing downward. After the integrated wafer W is placed on the suction chuck 54, a suction unit (not shown) connected to the chuck table 52 is operated to suck and hold the integrated wafer W.

[0036] like Figure 4 As shown, the grinding device 50 has a grinding unit 60 for grinding and thinning the back surface 10b of the wafer 10 held by suction on the chuck table 52. The grinding unit 60 has a rotating spindle 62 that is rotated by a rotation drive mechanism (not shown); a mounting seat 64 that is mounted on the lower end of the rotating spindle 62; and a grinding wheel 66 that is mounted on the lower surface of the mounting seat 64. A plurality of grinding tools 68 are provided in an annular shape on the lower surface of the grinding wheel 66.

[0037] After the integrated wafer W is sucked and held on the chuck table 52, the rotating spindle 62 of the grinding unit 60 is moved in a Figure 4 The chuck table 52 is rotated in the direction indicated by the arrow R1 at, for example, 6000 rpm, while Figure 4The wafer 10 is rotated in the direction indicated by the arrow R2 at, for example, 300 rpm. Furthermore, while grinding water is supplied to the wafer 10 exposed on the upper surface of the integrated wafer W by a grinding water supply unit (not shown), the grinding tool 68 is brought into contact with the back side 10b of the wafer 10, and the grinding wheel 66 supporting the grinding tool 68 is ground and fed downward at a grinding feed speed of, for example, 1 μm / second. At this time, the wafer 10 can be ground while measuring its thickness by a thickness detection device (not shown), and the back side 10b of the wafer 10 is ground by a predetermined amount so that the wafer 10 becomes a predetermined thickness (for example, 50 μm), and then the grinding unit 60 is stopped. In this way, the processing step of grinding the back side 10b of the wafer 10 is completed. As described above, in the present embodiment, the wafer 10 is supported on the substrate 18 via the sheet 14 composed of a polyethylene sheet by thermal compression. Thus, sufficient holding force can be exerted, and even if grinding is performed on the back side 10b of the wafer 10, the wafer 10 will not move, thereby preventing damage. In particular, in the present embodiment, when the wafer 10 is thermally pressed to the substrate 18 via the sheet 14, a bulging portion 14a surrounding the wafer 10 is formed on the periphery of the sheet 14, thereby further improving the holding force for holding the wafer 10. In addition, since the wafer 10 is supported on the substrate 18 via the sheet 14, even if a plurality of protruding electrodes are formed on the front side of the device 11, the protruding electrodes are reliably held by the sheet 14, and the stress during grinding is dispersed, thereby solving the problem of protruding electrode damage.

[0038] (Peeling process)

[0039] After the above-mentioned processing step of processing the back side 10b of the wafer 10 is completed, the integrated wafer W is taken out of the grinding device 50 and transported to a grinding machine for performing grinding. Figure 5 The holding unit 70 in the peeling step shown in (a) of FIG. The upper surface of the holding unit 70 is formed of an air-permeable adsorption chuck 72 similarly to the above-mentioned chuck table 52, and is connected to a suction unit (not shown).

[0040] The integrated wafer W transferred to the holding unit 70 is placed on the suction chuck 72 with the back side 10b of the wafer 10 facing downward (i.e., with the substrate 18 facing upward). After the integrated wafer W is placed on the suction chuck 72, the suction unit (not shown) is operated to suck and hold the integrated wafer W.

[0041] After the integrated wafer W is attracted and held in the holding unit 70, as shown in FIG. Figure 5As shown in (b), the substrate 18, the peeling layer 16, and the sheet 14 are peeled off while the chip 10 in the integrated chip W remains on the suction unit 70. At this time, it is preferable to heat or cool the integrated chip W. Since the sheet 14 is softened by heating as described above, it is easy to peel off from the chip 10 even if it has adhesive force. In addition, since the sheet 14 is hardened by cooling and the adhesive force is reduced, it can also be easily peeled off by cooling. When performing the peeling process, whether to perform heating or cooling can be selected in consideration of the material constituting the sheet 14 or the adhesive force of the sheet 14. In addition, in Figure 5 In (b), the substrate 18, the peeling layer 16, and the sheet 14 in the integrated wafer W are shown as being peeled off in a state where they are integrated, but the peeling is not necessarily limited to being integrated, and only the substrate 18 may be peeled off first, and then the peeling layer 16 and the sheet 14 may be peeled off together from the front side 10a of the wafer 10. The peeling process is completed as above.

[0042] In the present embodiment, liquid resin, wax, double-sided tape, etc. are not used, but the chip 10 is supported on the substrate 18 via the sheet 14 that exerts adhesive force by heating. Therefore, even if the sheet 14 is peeled off from the chip 10, there is no problem that the liquid resin, wax, double-sided tape paste, etc. adheres to and remains around the bumps constituting the protruding electrodes, and the quality of the device will not be reduced. In addition, since a peeling layer 16 having a diameter smaller than that of the chip 10 is sandwiched between the sheet 14 and the substrate 18 in a vacuum state and is only thermally pressed at the periphery, air enters the area of ​​the peeling layer 16 during the process of peeling the sheet 14 from the substrate 18, and the sheet 14 after thermal pressing can be easily peeled off, thereby improving workability.

[0043] In addition, in the above-mentioned embodiment, the sheet 14 is composed of a polyethylene sheet, but the present invention is not limited to this. As a sheet 14 that can support the chip 10 on the substrate 18 without using liquid resin, double-sided tape, wax, etc., it can be appropriately selected from polyolefin-based sheets and polyester-based sheets. As a polyolefin-based sheet, in addition to the above-mentioned polyethylene sheet, for example, a polypropylene (PP) sheet and a polystyrene (PS) sheet can be selected. In addition, as a polyester-based sheet, for example, a polyethylene terephthalate (PET) sheet and a polyethylene naphthalate (PEN) sheet can be selected.

[0044] In the above-mentioned embodiment, the temperature at which the sheet 14 is heated in the sheet heat-pressing step is set to a temperature near the melting point of the polyethylene sheet (120°C to 140°C), but when other sheets are selected to constitute the sheet 14 as described above, it is preferable to heat to a temperature near the melting point of the material of the selected sheet. For example, when the sheet 14 is composed of a polypropylene sheet, it is preferable to set the temperature at the time of heating to 160°C to 180°C, and when the sheet 14 is composed of a polystyrene sheet, it is preferable to set the temperature at the time of heating to 220°C to 240°C. In addition, when the sheet 14 is composed of a polyethylene terephthalate sheet, it is preferable to set the temperature at the time of heating to 250°C to 270°C, and when the sheet 14 is composed of a polyethylene naphthalate sheet, it is preferable to set the temperature at the time of heating to 160°C to 180°C. In addition, when the substrate 18 is composed of a synthetic resin as described above, it is required not to be affected by heat during heat-pressing. Therefore, when the sheet 14 is made of a polyethylene terephthalate sheet, the substrate 18 is preferably made of glass.

[0045] In the above embodiment, the release layer 16 is formed into a circular shape, but it does not necessarily need to be circular, and its shape is not particularly limited as long as it has a smaller diameter than the wafer 10 and can bond the sheet 14 and the substrate 18 at the peripheral region.

[0046] In the above-mentioned embodiment, the case where a grinding process is performed on the back side 10b of the chip 10 as a processing step for processing the back side 10b of the chip 10 is described, but the present invention is not limited to this, and can also be applied to the case of a grinding process for grinding the back side 10b of the chip 10, the case of performing a cutting process from the back side 10b of the chip 10 by a cutting tool, and the case of performing laser processing by irradiating a laser beam from the back side 10b of the chip 10.

[0047] In addition, in the above-mentioned embodiment, by Figure 2 The device shown in (a) implements hot pressing, but the present invention is not limited to this. The following sheet hot pressing process can also be implemented: while pressing the entire surface of the chip 10 side using a roller with a heating unit (not shown) to heat the sheet 14 to the desired temperature, the chip 10 and the substrate 18 are hot pressed through the sheet 14.

Claims

1. A method for processing a wafer, wherein the back side of the wafer is processed by a predetermined dividing line and a plurality of devices are formed on the front side, wherein: The wafer processing method comprises at least the following steps: A wafer placement step of placing a peeling layer having a smaller diameter than the wafer and made of a material that does not exhibit adhesiveness even when heated, on the upper surface of a substrate having a larger diameter than the wafer, and placing a polyolefin-based sheet or a polyester-based sheet having a diameter greater than the diameter of the wafer on the upper surface of the substrate via the peeling layer, and placing the wafer with the front side of the wafer positioned on the upper surface of the sheet; a sheet thermal compression bonding step of decompressing the wafer disposed on the substrate via the sheet in a closed environment, heating the sheet to allow the sheet to exhibit adhesiveness, and pressing the wafer to thermally compress the wafer onto the substrate via the sheet; A processing step is performed on the back side of the wafer; as well as The peeling step is to peel the wafer from the sheet. In the sheet thermal compression bonding process, the wafer is pressed so that the sheet bulges around the wafer. The release layer is released from the substrate in the release step after the processing step.

2. The wafer processing method according to claim 1, wherein: The release layer includes at least one of paper, cloth, rice paper, and a polyimide sheet.

3. The wafer processing method according to claim 1 or 2, wherein: In this processing step, a grinding process is performed to grind the back surface of the wafer.

4. The wafer processing method according to claim 1 or 2, wherein: The polyolefin-based sheet is composed of any sheet of a polyethylene sheet, a polypropylene sheet, or a polystyrene sheet.

5. The wafer processing method according to claim 4, wherein: In the sheet thermal compression bonding step, the polyethylene sheet is heated to a temperature of 120°C to 140°C, the polypropylene sheet is heated to a temperature of 160°C to 180°C, and the polystyrene sheet is heated to a temperature of 220°C to 240°C.

6. The wafer processing method according to claim 1 or 2, wherein: The polyester-based sheet is composed of any sheet of a polyethylene terephthalate sheet or a polyethylene naphthalate sheet.

7. The wafer processing method according to claim 6, wherein: In the sheet thermal compression bonding step, the heating temperature of the polyethylene terephthalate sheet is 250°C to 270°C, and the heating temperature of the polyethylene naphthalate sheet is 160°C to 180°C.

Images