Wafer processing method

Abstract

A wafer processing method is provided that can fully remove grinding debris attached to a wafer held on a chuck table during grinding. The wafer processing method includes the following steps: a thermocompression bonding sheet placement step, in which a thermocompression bonding sheet of a size sufficient to cover the wafer is placed on the front surface of the wafer; an integration step, in which the thermocompression bonding sheet is heated and pressed with a flat member to flatten the thermocompression bonding sheet and integrate it with the wafer; a grinding step, in which the thermocompression bonding sheet is held on the chuck table of a grinding device and grinding is performed to a predetermined thickness while supplying grinding water to the back surface of the wafer; and a thermocompression bonding sheet cleaning step, in which the integrated wafer is removed from the chuck table and the thermocompression bonding sheet is cleaned.

Description

Technical Field

[0001] The present invention relates to a wafer processing method for grinding the back surface of a wafer divided by a plurality of intersecting planned dividing lines and having a plurality of devices formed on the front surface. Background Art

[0002] A wafer having a plurality of devices such as ICs and LSIs formed on the front side thereof divided by a plurality of intersecting predetermined dividing lines is protected by affixing adhesive tape to the front side, and then the protective tape side is held on a chuck table of a grinding device, and the back side is ground to a desired thickness (for example, refer to patent document 1).

[0003] The wafer formed to a desired thickness as described above is divided into individual device chips by a dicing device or a laser processing device. The divided device chips are used in electronic devices such as mobile phones and personal computers.

[0004] The grinding device is generally composed of the following components: a chuck table that holds the wafer; a grinding unit that has a rotatable grinding tool that grinds the wafer held by the chuck table; a grinding water supply component that supplies grinding water to the wafer and the grinding tool; and a cleaning unit that cleans the wafer after grinding. The grinding device can grind the wafer to a desired thickness.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-246491

[0006] When the back of a wafer is ground using a grinding device, the grinding chips generated by the grinding are almost all carried to the outside of the chuck table by the grinding water. However, since negative pressure is applied to the upper surface (holding surface) of the chuck table to attract and hold the wafer, a portion of the grinding chips enters through the gap between the chuck table and the protective tape and adheres to the lower surface of the protective tape affixed to the wafer held by the chuck table. In particular, when a protective tape is affixed to the front of the wafer using an adhesive or the like, undulations are formed on the front side of the wafer. These undulations reduce the adhesion between the chuck table and the protective tape, which may be the main reason for the grinding chips to enter the gap between the chuck table and the protective tape. In addition, in the wafer that has been ground in this way, although the grinding surface is cleaned by the cleaning unit provided in the grinding device, since the protective tape side of the wafer held by the chuck table is not cleaned sufficiently, there is a problem of becoming a source of contamination when it is transported to the next process. Summary of the Invention

[0007] Therefore, an object of the present invention is to provide a wafer processing method capable of sufficiently removing grinding chips adhering to a wafer held by a chuck table during grinding.

[0008] According to the present invention, a method for processing a wafer is provided, wherein the back side of a wafer divided by a plurality of intersecting predetermined dividing lines and having a plurality of devices formed on the front side is ground, wherein the method for processing the wafer comprises the following steps: a thermocompression bonding sheet arrangement step, wherein a thermocompression bonding sheet of a size covering the wafer is arranged on the front side of the wafer; an integration step, wherein the thermocompression bonding sheet is heated and pressed with a flat component to flatten the thermocompression bonding sheet and integrate the thermocompression bonding sheet and the wafer; a grinding step, wherein after the integration step is performed, the thermocompression bonding sheet side is held on a chuck worktable of a grinding device, and the wafer is ground to a desired thickness while supplying grinding water to the back side of the wafer; and a thermocompression bonding sheet cleaning step, wherein after the grinding step is performed, the integrated wafer and the thermocompression bonding sheet are removed from the chuck worktable and the thermocompression bonding sheet is cleaned.

[0009] Preferably, the wafer processing method further comprises a peeling step of peeling the thermocompression bonding sheet from the front surface of the wafer by locally heating or cooling the thermocompression bonding sheet to generate a temperature difference after the thermocompression bonding sheet cleaning step.

[0010] The heat-compression bonding sheet is preferably a polyolefin sheet or a polyester sheet. When the heat-compression bonding sheet is a polyolefin sheet, it is preferably selected from a polyethylene sheet, a polypropylene sheet, and a polystyrene sheet. The temperature at which the heat-compression bonding sheet is heated during the integration step is preferably 120°C to 140°C for the polyethylene sheet, 160°C to 180°C for the polypropylene sheet, and 220°C to 240°C for the polystyrene sheet.

[0011] When the thermocompression bonding sheet is a polyester sheet, it is preferably selected from either a polyethylene terephthalate sheet or a polyethylene naphthalate sheet. The temperature at which the thermocompression bonding sheet is heated during the integration step is preferably 250°C to 270°C for the polyethylene terephthalate sheet and 160°C to 180°C for the polyethylene naphthalate sheet.

[0012] According to the wafer processing method of the present invention, even when the wafer is held on a chuck table during the grinding process, grinding debris can be prevented from entering through the gap between the thermocompression sheet and the holding surface of the chuck table, thereby preventing the grinding debris from adhering to the thermocompression sheet. Furthermore, even if grinding debris adheres to the thermocompression sheet during the grinding process, the thermocompression sheet cleaning process can reliably remove the grinding debris from the front surface of the thermocompression sheet, thereby eliminating the problem of the grinding debris becoming a source of contamination in the next process during transport. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1(a) and (b) are perspective views showing an embodiment of a thermocompression bonding sheet arranging step.

[0014] Figure 2 It is a perspective view showing an embodiment of the integration process.

[0015] Figure 3 It is a perspective view showing an embodiment of a cutting step.

[0016] Figure 4 It is an overall perspective view of a grinding device preferably used in this embodiment.

[0017] Figure 5 The chip is kept in Figure 4 A perspective view of the grinding device shown in the chuck table manner.

[0018] Figure 6 Is shown by Figure 4 A perspective view of the grinding device shown in FIG. 1 showing the manner in which the grinding process is performed.

[0019] Figure 7 (a) is a perspective view showing an embodiment of a thermal compression bonding sheet cleaning process. Figure 7 (b) is its side view.

[0020] Figure 8 This is a perspective view showing a manner in which a wafer is placed on a chuck table for peeling in which a peeling step is performed.

[0021] Figure 9 It is a perspective view showing an embodiment of the peeling step.

[0022] Description of labels

[0023] 1: Grinding device; 2: Device housing; 3: Rough grinding unit; 4: Fine grinding unit; 5: Rotary worktable; 6: Chuck worktable; 7: First box; 8: Second box; 9: Temporary storage area; 10: Thermocompression bonding sheet cleaning unit; 10a: Roller brush; 10b: Cleaning water supply pipe; 11: Grinding surface cleaning unit; 12: First transfer mechanism; 13: Second transfer mechanism; 14: Third transfer mechanism; 21: Stationary support substrate; 22, 23: Guide rails; 31: Unit housing; 31a: Rotating shaft; 33: Rough grinding wheel; 33a: Grinding tool; 34: Electric motor; 35: Moving base; 36: Grinding feed mechanism; 41: Unit housing; 41a: Rotating shaft; 43: Grinding wheel; 43a: Grinding tool; 44: Electric motor; 45: Moving base; 46: Grinding feed mechanism; 100: Chuck worktable; 110: Thermocompression bonding sheet; 120: Integrated component; 122: Pressing member; 124: Lower surface; A: Workpiece loading / unloading area; B: Rough grinding area; C: Fine grinding area; W: Wafer; Wa: Front side; Wb: Back side; D: Device; L1: Grinding water; L2: Cleaning water. Detailed implementation mode

[0024] Hereinafter, an implementation mode of a method for processing a wafer according to an implementation mode of the present invention will be described in detail with reference to the accompanying drawings.

[0025] The method for processing a wafer according to this implementation mode includes the following steps: a thermocompression bonding sheet arranging step of arranging a thermocompression bonding sheet having a size covering the wafer on the front side of the wafer; an integration step of flattening the thermocompression bonding sheet and integrating the thermocompression bonding sheet with the wafer; a grinding step of holding the thermocompression bonding sheet side on a chuck worktable of a grinding device and grinding to a desired thickness while supplying grinding water to the back side of the wafer; and a thermocompression bonding sheet cleaning step of taking out the wafer integrated with the thermocompression bonding sheet from the chuck worktable and cleaning the thermocompression bonding sheet. Hereinafter, each step will be described in sequence.

[0026] (Thermocompression bonding sheet arranging step)

[0027] In Figure 1 a perspective view showing an implementation mode of the thermocompression bonding sheet arranging step is sequentially shown. The thermocompression bonding sheet arranging step is implemented before the grinding step described later. When implementing the thermocompression bonding sheet arranging step, first, as Figure 1As shown in (a), a wafer W to be processed and a chuck table 100 for the thermal compression bonding step are prepared. The wafer W is made of silicon (Si), for example, and is divided by a plurality of intersecting predetermined dividing lines, with a plurality of devices D formed on the front surface Wa. The chuck table 100 is composed of a disc-shaped adsorption chuck 100a and a circular frame portion 100b. The adsorption chuck 100a is made of porous ceramic with air permeability, and the circular frame portion 100b surrounds the outer periphery of the adsorption chuck 100a. The chuck table 100 is connected to a suction member (not shown) and can attract and hold the wafer W placed on the upper surface (holding surface) of the adsorption chuck 100a.

[0028] After the wafer W and the chuck table 100 are prepared, Figure 1 As shown in (a), the back side Wb of the wafer W is placed downward and the wafer W is placed on the center of the adsorption chuck 100a of the chuck table 100. After the wafer W is placed on the adsorption chuck 100a, as shown in FIG. Figure 1 As shown in (b), a circular heat-compression bonding sheet 110 having a thickness of 20 μm to 100 μm is placed on the front surface Wa of the wafer W. As the heat-compression bonding sheet 110, a polyolefin sheet or a polyester sheet can be selected. In the case of a polyolefin sheet, for example, a polyethylene (PE) sheet can be selected. Figure 1 As can be seen from (b), the diameter of the adsorption chuck 100a is set to be slightly larger than the diameter of the wafer W. By placing the wafer W on the center of the adsorption chuck 100a, the adsorption chuck 100a is exposed so as to surround the outer periphery of the wafer W. In addition, the thermocompression bonding sheet 110 is at least large enough to cover the wafer W. Preferably, it is formed with a diameter larger than the diameter of the adsorption chuck 100a and with a diameter slightly smaller than the circular frame portion 100b of the chuck table 100. As a result, the entire surface of the adsorption chuck 100a and the wafer W are covered by the thermocompression bonding sheet 110. In addition, no adhesive layer such as paste is formed on the side of the thermocompression bonding sheet 110 that is placed on the wafer W.

[0029] The thermocompression bonding sheet 110 is a sheet that develops adhesive strength by heating and is not limited to the polyethylene sheet. When a polyolefin sheet is used as the thermocompression bonding sheet 110, in addition to the polyethylene sheet, for example, a polypropylene (PP) sheet or a polystyrene (PS) sheet can also be used. Furthermore, when a polyester sheet is used as the thermocompression bonding sheet 110, for example, a polyethylene terephthalate (PET) sheet or a polyethylene naphthalate (PEN) sheet can be used.

[0030] After the wafer W and the thermocompression bonding sheet 110 are placed on the chuck table 100, a suction member (not shown) including a suction pump is operated. Figure 1As shown in (b), the suction force Vm is applied to the adsorption chuck 100a to attract the wafer W and the thermocompression sheet 110. As described above, the entire upper surface (holding surface) of the adsorption chuck 100a and the wafer W are covered by the thermocompression sheet 110. Therefore, the suction force Vm acts on the wafer W and the thermocompression sheet 110 as a whole, attracting and retaining the wafer W and the thermocompression sheet 110 on the adsorption chuck 100a, and also attracting the air remaining between the wafer W and the thermocompression sheet 110 to form a close contact between the two. The front surface Wa of the wafer W has tiny bumps and depressions formed by the plurality of devices D. By using the chuck table 100 for suction and retention, the thermocompression sheet 110 is brought into close contact with the bumpy surface of the front surface Wa of the wafer W. Thus, the thermocompression sheet placement process is completed.

[0031] (Integrated process)

[0032] After the above-mentioned heat-compression bonding sheet placement step is performed, the integration step is then performed. Figure 2 and Figure 3 The integration process is described.

[0033] When implementing an integrated process, Figure 2 As shown, an integration member 120 (only a portion is shown) is positioned above the chuck table 100, which is holding the wafer W and the thermocompression sheet 110 by suction. The integration member 120 is used to heat and flatten the thermocompression sheet 110, thereby integrating the thermocompression sheet 110 and the wafer W. The integration member 120 includes a disc-shaped flat member 122 with a built-in heater and temperature sensor (not shown). The lower surface 124 is a flat surface coated with fluororesin. The diameter of the flat member 122 is set to be at least equal to or greater than the diameter of the wafer W.

[0034] After positioning the integrated component 120 above the chuck table 100, the heater built into the integrated component 120 is activated, lowering the flat member 122 to press the thermocompression sheet 110 positioned on the wafer W. The operation of the heater and temperature sensor in the flat member 122 controls the temperature of the lower surface 124 of the flat member 122 to 120°C to 140°C. As described above, the thermocompression sheet 110 of this embodiment is a polyethylene sheet. By heating the sheet to 120°C to 140°C, the polyethylene sheet approaches a melting point, exerting its adhesive strength and softening. Furthermore, since the thermocompression sheet 110 is in close contact with the microscopic uneven surfaces formed by the device D on the front surface Wa of the wafer W, the softened thermocompression sheet 110, heated and softened, increases its close contact with the front surface Wa of the wafer W, allowing the adhesive force of the thermocompression sheet 110 to adhere the wafer W. Furthermore, since the lower surface 124 of the flat member 122 is flat, the front surface of the thermocompression bonding sheet 110 attached to the front surface Wa of the wafer W is flattened. This completes the integration process of the wafer W and the thermocompression bonding sheet 110. Furthermore, as described above, since the lower surface 124 of the flat member 122 is coated with fluororesin, even when the thermocompression bonding sheet 110 is heated and exerts its adhesive force, the flat member 122 can be easily separated from the thermocompression bonding sheet 110.

[0035] In the above-mentioned integration process, as a method of heating and flattening the thermal compression sheet 110 to integrate the wafer W and the thermal compression sheet 110, a method of using Figure 2 The example shown is a flat member 122 with a built-in heater, but the present invention is not limited to this. For example, a heating element may be provided separately from the flat member 122, and the heating element may be used to heat the thermocompression sheet 110 to a predetermined temperature. The thermocompression sheet 110 may then be flattened by pressing against the flat member 122 of the above-described shape. Alternatively, the front surface of the thermocompression sheet 110 may be flattened by heating it with infrared radiation and then pressing against it with a roller, or by heating and pressing against it with a roller equipped with a heater and a temperature sensor.

[0036] In this embodiment, following the above-mentioned integration process, a cutting process is performed to cut the thermal compression bonding sheet 110 along the shape of the wafer W in consideration of the grinding process to be performed in the subsequent process. Although this cutting process is not necessarily required, if this cutting process is performed, it is easy to handle the wafer W integrated with the thermal compression bonding sheet 110, which is advantageous for the grinding process to be described later. Figure 3 The cutting process will be described.

[0037] (Cutting process)

[0038] like Figure 3As shown, the cutting member 70 (only a portion is shown) is positioned on the chuck table 100 that attracts and holds the wafer W and the thermocompression bonding sheet 110. More specifically, the cutting member 70 includes a disc-shaped cutting tool 72 for cutting the thermocompression bonding sheet 110 and a motor 74 for driving the cutting tool 72 to rotate in the direction indicated by arrow R1. The cutting member 70 positions the tip of the cutting tool 72 at the periphery of the wafer W. After the cutting tool 72 is positioned at the periphery of the wafer W, the cutting tool 72 is fed in by an amount equivalent to the thickness of the thermocompression bonding sheet 110, and the chuck table 100 is rotated in the direction indicated by arrow R2. As a result, the thermocompression bonding sheet 110 is cut along the periphery of the wafer W, so that the remaining portion of the thermocompression bonding sheet 110 exposed from the periphery of the wafer W can be cut and separated. Thus, the cutting process is completed.

[0039] (Grinding process / thermocompression bonding sheet cleaning process)

[0040] As described above, after the wafer W and the thermocompression bonding sheet 110 are integrated through the integration process, a grinding process for grinding the back surface Wb of the wafer W and a thermocompression bonding sheet cleaning process for cleaning the thermocompression bonding sheet 110 side are performed. Figure 4 A grinding device 1 suitable for carrying out the grinding step and the thermal compression bonded sheet cleaning step will be described.

[0041] The grinding device 1 has a device housing 2 that is substantially in the shape of a rectangular parallelepiped. Figure 4 In the embodiment, a stationary support plate 21 is erected at the upper right end of the device housing 2. Two pairs of guide rails 22, 22 and 23, 23 extending in the vertical direction are provided on the inner wall surface of the stationary support plate 21. A rough grinding unit 3, serving as a rough grinding unit, is mounted vertically movably on one of the guide rails 22, 22, and a fine grinding unit 4, serving as a fine grinding unit, is mounted vertically movably on the other guide rails 23, 23.

[0042] The rough grinding unit 3 comprises a unit housing 31; a rough grinding wheel 33 mounted on a wheel mount 32 having a plurality of grinding tools 33a arranged in an annular pattern on its lower surface. The wheel mount 32 is mounted on the lower end of a rotating shaft 31a rotatably supported by the unit housing 31; an electric motor 34 mounted on the upper end of the unit housing 31 to rotate the wheel mount 32 in the direction indicated by arrow R3; and a movable base 35 to which the unit housing 31 is mounted. The movable base 35 is supported by guide rails 22, 22 provided on the stationary support plate 21 and moves the rough grinding unit 3 in the vertical direction. The grinding device 1 of this embodiment includes a grinding feed mechanism 36 for vertically feeding the movable base 35 of the rough grinding unit 3. The grinding feed mechanism 36 includes: an externally threaded rod 361, which is arranged on the stationary support plate 21 in the vertical direction parallel to the guide rails 22, 22 and is supported so as to be rotatable; a pulse motor 362, which is used to rotationally drive the externally threaded rod 361; and an internally threaded block (not shown), which is mounted on the movable base 35 and is screwed into the externally threaded rod 361. By using the pulse motor 362 to drive the externally threaded rod 361 in the forward and reverse directions, the rough grinding unit 3 is moved in the vertical direction.

[0043] The fine grinding unit 4 is constructed similarly to the rough grinding unit 3 described above. It includes a unit housing 41; a fine grinding wheel 43 mounted on a wheel mount 42 with a plurality of grinding tools 43a arranged in an annular pattern on its lower surface. The wheel mount 42 is mounted on the lower end of a rotating shaft 41a rotatably supported by the unit housing 41; an electric motor 44 mounted on the upper end of the unit housing 41 to rotate the wheel mount 42 in the direction indicated by arrow R4; and a movable base 45 to which the unit housing 41 is mounted. The movable base 45 is supported by guide rails 23, 23 provided on the stationary support plate 21, allowing the fine grinding unit 4 to move vertically. The grinding tools 43a of the fine grinding unit 4 are composed of finer abrasive grains than the grinding tools 33a of the rough grinding unit 3. The grinding device 1 of this embodiment includes a grinding feed mechanism 46 for moving a movable base 45 of the fine grinding unit 4 along the guide rails 23, 23. The grinding feed mechanism 46 includes an externally threaded rod 461, which is arranged in the vertical direction parallel to the guide rails 23, 23 on the stationary support plate 21 and is supported for rotation; a pulse motor 462 for rotationally driving the externally threaded rod 461; and an internally threaded block (not shown), which is mounted on the movable base 45 and threadedly engaged with the externally threaded rod 461. The pulse motor 462 drives the externally threaded rod 461 in the forward and reverse directions, thereby moving the fine grinding unit 4 in the vertical direction.

[0044] A grinding water supply unit (not shown) is connected to the rotating shaft ends 31b and 41b of the rotating shafts 31a and 41a, which are rotated by the electric motors 34 and 44. The grinding water supply unit includes a grinding water tank with a built-in pressure pump. Grinding water L1, which is pressurized from the grinding water tank, is introduced into the rotating shafts 31a and 41a and supplied through through-holes formed in the rotating shafts 31a and 41a. The water is then sprayed from the lower end surfaces of the rough grinding wheel 33 and the fine grinding wheel 43.

[0045] The grinding device 1 of this embodiment has a rotating table 5 located in front of the stationary support plate 21. This rotating table 5 is arranged approximately coplanar with the upper surface of the device housing 2. The rotating table 5 is formed into a relatively large-diameter disk and is rotated appropriately in the direction indicated by arrow R5 by a rotational drive mechanism (not shown). In this embodiment, three chuck tables 6 are evenly spaced on the rotating table 5. The chuck tables 6 consist of a disk-shaped frame 61 and a suction chuck 62 made of a porous ceramic material. The workpiece placed on the suction chuck 62 is attracted and held by the operation of a suction member (not shown). The frame 61 supports the suction chuck 62 and forms an outer edge surrounding the suction chuck 62. The upper surface of the suction chuck 62 and the outer edge of the frame 61 are coplanar in height. The chuck tables 6 thus configured are rotated in the direction indicated by arrow R6 by a rotational drive mechanism (not shown). The three chuck tables 6 arranged on the rotating table 5 move sequentially to the workpiece loading / unloading area A → the rough grinding area B → the fine grinding area C → the workpiece loading / unloading area A each time the rotating table 5 rotates 120 degrees in the direction indicated by the arrow R5.

[0046] The grinding device 1 includes: a first box 7, which is arranged on one side relative to the workpiece carry-in / out area A and stores wafers that are workpieces before grinding; a second box 8, which is arranged on the other side relative to the workpiece carry-in / out area A and stores wafers that are workpieces after grinding; a temporary storage area 9, which is arranged between the first box 7 and the workpiece carry-in / out area A and performs center alignment of the workpiece; and a hot pressing sheet cleaning unit 10 and a grinding surface cleaning unit 11, which are arranged between the workpiece carry-in / out area A and the second box 8. The grinding apparatus 1 also includes a first transport mechanism 12 for transporting wafers, serving as workpieces, stored in the first cassette 7 to the temporary storage area 9 and transporting wafers cleaned by the grinding surface cleaning unit 11 to the second cassette 8; a second transport mechanism 13 for transporting wafers, placed on the temporary storage area 9 and centered, to the chuck table 6 positioned in the workpiece loading / unloading area A; and a third transport mechanism 14 for transporting the ground wafers, placed on the chuck table 6 positioned in the workpiece loading / unloading area A, to the thermal compression sheet cleaning unit 10 and the grinding surface cleaning unit 11. The thermal compression sheet cleaning unit 10 is disposed between the workpiece loading / unloading area A and the grinding surface cleaning unit 11 and includes a roller brush 10a and a pair of cleaning water supply pipes 10b positioned so as to oppose each other with the roller brush 10a interposed therebetween.

[0047] An operation panel 15 and a display monitor 16 are provided on the front side of the device housing 2, near the location of the first transport mechanism 12. The operation panel 15 is used to instruct grinding operations or specify processing conditions, while the display monitor 16 displays the status of the grinding process and, by having a touch panel function, enables appropriate operation instructions. In addition to the aforementioned configuration, the grinding device 1 of this embodiment is also equipped with a control unit for controlling the various operating units, and thickness gauges (not shown) located adjacent to the rough grinding area B and the finish grinding area C, respectively, for measuring the thickness of the wafer.

[0048] The grinding device 1 of this embodiment has the structure as described above. Figures 4 to 7 The grinding process and the thermally bonded sheet cleaning process performed using the grinding device 1 are described. The grinding process described below is based on an example consisting of a rough grinding process performed by the rough grinding unit 3 and a fine grinding process performed by the fine grinding unit 4. However, the present invention is not limited to this, and the process may also consist of only one grinding process.

[0049] like Figure 5As shown, the wafer W integrated with the thermocompression sheet 110 is placed with its back surface Wb facing upward and the thermocompression sheet 110 facing downward on the suction chuck 62 of the chuck table 6 positioned in the workpiece loading / unloading area A of the grinding apparatus 1. The suction chuck 62 of the chuck table 6 is connected to a suction member (not shown), and by operating the suction member to exert suction, the wafer W is attracted and held on the chuck table 6.

[0050] After the wafer W is held by suction on the chuck table 6 positioned at the workpiece loading / unloading area A, the rotary table 5 is rotated in the direction indicated by R5 to position the chuck table 6 holding the wafer W by suction right below the rough grinding unit 3. Figure 6 As shown, the rotating shaft 31a of the rough grinding unit 3 is rotated in the direction indicated by the arrow R7 at a speed of, for example, 6000 rpm, and the chuck table 6 is rotated in the direction indicated by the arrow R7. Figure 6 The wafer W is rotated in the direction indicated by the arrow R8 at a speed of, for example, 300 rpm. The grinding tool 33a is then brought into contact with the back surface Wb of the wafer W, and the grinding wheel 32 is fed downward, i.e., perpendicularly to the chuck table 6, at a grinding feed speed of, for example, 1 μm / second. At this time, grinding water L1 is supplied from the lower surface of the rough grinding wheel 32 via the rotating shaft 31a to the grinding surface, i.e., the back surface Wb, of the wafer W. Furthermore, while the thickness of the wafer W is measured using a contact measuring instrument (not shown), the rough grinding process can be completed while the back surface Wb of the wafer W is rough ground to the desired thickness during rough grinding.

[0051] As mentioned above, after the rough grinding process is completed, the rotary table 5 is moved to the Figure 4 The chuck table 6 is rotated in the direction indicated by R5 in the figure, and is moved to directly below the fine grinding unit 4. After the chuck table 6 is moved to directly below the fine grinding unit 4, the rotational spindle 41a of the fine grinding unit 4 is rotated at a speed of, for example, 6000 rpm, and the chuck table 6 is rotated at a speed of, for example, 300 rpm. Then, the grinding tool 43a is brought into contact with the back surface Wb of the wafer W, and the grinding wheel 42 is fed downward, i.e., perpendicularly to the chuck table 6, at a grinding feed speed of, for example, 0.1 μm / second. At this time, grinding water L1 is supplied from the lower surface of the fine grinding wheel 42 to the grinding surface, i.e., the back surface Wb, of the wafer W via the rotational spindle 41a. In addition, at the same time, the thickness of the chip W can be measured using a contact measuring instrument not shown in the figure while grinding, so that the back side Wb of the chip W is ground to the desired thickness in the fine grinding, thereby completing the fine grinding process and completing the grinding process consisting of the above-mentioned rough grinding process and the fine grinding process.

[0052] As described above, after the grinding process is completed, the rotary table 5 is rotated in the direction indicated by R5 to position the chuck table 6 in the workpiece carrying in / out area A. Figure 7 As shown in (a), the third conveying mechanism 14 is operated to suck the back side Wb of the wafer W so that the hot pressing sheet 110 side passes from the chuck table 6 positioned at the workpiece loading / unloading area A to the hot pressing sheet cleaning unit 10 disposed between the workpiece loading / unloading area A and the grinding surface cleaning unit 11. As described above, the hot pressing sheet cleaning unit 10 has a roller brush 10a and a pair of cleaning water supply pipes 10b disposed opposite to each other with the roller brush 10a therebetween. When the wafer W passes over the hot pressing sheet cleaning unit 10, the unillustrated rotation drive mechanism is operated to rotate the roller brush 10a in the direction indicated by the arrow R10, and cleaning water L2 is sprayed from the spray holes 10c formed in the cleaning water supply pipes 10b, 10b. As shown Figure 7 As shown in (b), as the wafer W passes through the thermocompression bonding sheet cleaning unit 10, cleaning water L2 is sprayed from the cleaning water supply pipe 10b toward the thermocompression bonding sheet 110. The roller brush 10a rotates while contacting the entire area of ​​the thermocompression bonding sheet 110, thereby removing grinding debris adhered to the front surface of the thermocompression bonding sheet 110. In this way, by passing the wafer W through the thermocompression bonding sheet cleaning unit 10, grinding debris is removed from the entire area of ​​the thermocompression bonding sheet 110 adhered to the front surface Wa of the wafer W, completing the thermocompression bonding sheet cleaning process.

[0053] After the above-mentioned thermal compression sheet cleaning step is completed, the wafer W sucked by the third transport mechanism 14 is directly transported to the ground surface cleaning unit 11, and the ground surface cleaning unit 11 cleans the ground surface of the wafer W, that is, the back surface Wb of the wafer W (ground surface cleaning step). The wafer W cleaned in this ground surface cleaning step is sucked by the first transport mechanism 12 and transported to a predetermined position in the second cassette 8 for storage.

[0054] (Peeling process)

[0055] After the grinding process, the hot pressing sheet cleaning process and the grinding surface cleaning process are completed, a peeling process is performed to peel off the hot pressing sheet 110 integrated with the wafer W in the above-mentioned integration process from the front surface Wa side of the wafer W stored in the second cassette 8. Figure 8 and Figure 9 The peeling step will be described.

[0056] When performing the peeling process, prepare Figure 8The peeling chuck workbench 90 shown. The peeling chuck workbench 90 has a disk-shaped adsorption chuck 92 made of porous ceramic with air permeability in the center. The adsorption chuck 92 is connected to a suction member not shown in the figure. The chip W that has been ground is taken out from the second box 8, and the front Wa side with the thermocompression bonding sheet 110 pasted thereon is directed upward, and the back Wb side is placed and held by adsorption chuck 92 by adsorption. Next, the cooling member or heating member not shown is operated to locally cool or heat the peripheral portion of the thermocompression bonding sheet 110 of the chip W held by the adsorption chuck 92, thereby generating a temperature difference between the peripheral portion and other portions, so that the thermocompression bonding sheet 110 is in a state that is easy to peel off from its peripheral portion. Then, as shown in the figure Figure 9 As shown, while the wafer W is held by suction on the suction chuck 92 , the thermal compression sheet 110 is peeled off from the peripheral portion subjected to the cooling or heating treatment.

[0057] According to the present embodiment described above, since the thermocompression bonding sheet 110 disposed on the front surface of the wafer W is flattened, even when the wafer W is held on the chuck table 6 of the grinding apparatus 1 to perform the grinding process, grinding chips are less likely to enter through the gap between the thermocompression bonding sheet 110 and the holding surface of the chuck table 6, thereby suppressing the adhesion of grinding chips to the thermocompression bonding sheet 110. Furthermore, even if grinding chips adhere to the thermocompression bonding sheet 110 during the grinding process, the adhesion of the grinding chips is weak due to the flattening of the thermocompression bonding sheet, and the grinding chips can be reliably removed from the front surface of the thermocompression bonding sheet 110 by the thermocompression bonding sheet cleaning unit 10, thereby solving the problem of the grinding chips becoming a source of contamination in the next process during the wafer transfer to the next process.

[0058] In the above embodiment, a polyethylene sheet is used as the thermal compression bonding sheet 110 , but the present invention is not limited thereto, and a sheet may be appropriately selected from a polyolefin-based sheet or a polyester-based sheet.

[0059] When thermocompression bonding sheet 110 is selected from polyolefin-based sheets, it can be selected from polypropylene sheets or polystyrene sheets in addition to polyethylene sheets. When a polypropylene sheet is selected as thermocompression bonding sheet 110, the temperature during the integration process is preferably set to 160°C to 180°C. When a polystyrene sheet is selected as thermocompression bonding sheet 110, the temperature during the integration process is preferably set to 220°C to 240°C.

[0060] When thermocompression bonding sheet 110 is a polyester sheet, it can be selected from polyethylene terephthalate sheets or polyethylene naphthalate sheets. When polyethylene terephthalate sheets are selected as thermocompression bonding sheet 110, the temperature during the integration process is preferably set to 250°C to 270°C. When polyethylene naphthalate sheets are selected as thermocompression bonding sheet 110, the temperature during the integration process is preferably set to 160°C to 180°C.

Claims

1. A method for processing a wafer, comprising grinding the back side of a wafer divided by a plurality of intersecting predetermined dividing lines and having a plurality of devices formed on the front side, wherein: The wafer processing method has the following steps: a step of placing a thermocompression bonding sheet on the front surface of the wafer, wherein the thermocompression bonding sheet is large enough to cover the wafer and is made of a material that does not have an adhesive layer but exerts adhesive force by being softened by heat; An integration step of heating the thermocompression bonding sheet and pressing it with a flat member to flatten the thermocompression bonding sheet and integrating the thermocompression bonding sheet and the wafer using an adhesive force generated by heating; a grinding step of holding the thermal compression bonding sheet side on a chuck table of a grinding device after the integration step, and grinding the wafer to a desired thickness while supplying grinding water to the back side of the wafer; and In the hot pressing sheet cleaning process, after the grinding process is carried out, the grinding surface side of the chip is sucked by the conveying unit to move the chip integrated with the hot pressing sheet out of the chuck worktable. Before being conveyed to the cleaning unit for cleaning the grinding surface of the chip, the hot pressing sheet that is softened by heating and exerts adhesive force is directly cleaned while the chip is sucked by the conveying unit.

2. The wafer processing method according to claim 1, wherein: The wafer processing method further comprises a peeling step of peeling the thermocompression bonding sheet from the front surface of the wafer by locally heating or cooling the thermocompression bonding sheet to generate a temperature difference after the thermocompression bonding sheet cleaning step.

3. The wafer processing method according to claim 1 or 2, wherein: The heat-compression bonding sheet is composed of a polyolefin-based sheet or a polyester-based sheet.

4. The wafer processing method according to claim 3, wherein: When the thermocompression bonding sheet is the polyolefin-based sheet, it is selected from the group consisting of a polyethylene sheet, a polypropylene sheet, and a polystyrene sheet.

5. The wafer processing method according to claim 4, wherein: The temperature at which the thermocompression-bonded sheet is heated in the integration step is 120° C. to 140° C. for the polyethylene sheet, 160° C. to 180° C. for the polypropylene sheet, and 220° C. to 240° C. for the polystyrene sheet.

6. The wafer processing method according to claim 3, wherein: When the thermocompression bonding sheet is a polyester sheet, it is selected from the group consisting of polyethylene terephthalate sheets and polyethylene naphthalate sheets.

7. The wafer processing method according to claim 6, wherein: The temperature at which the thermocompression bonding sheet is heated in the integration step is 250° C. to 270° C. in the case of the polyethylene terephthalate sheet, and is 160° C. to 180° C. in the case of the polyethylene naphthalate sheet.

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