Wafer processing method

Abstract

Provided is a wafer processing method capable of sufficiently removing grinding chips attached to a wafer held by a chuck table when performing grinding processing. The wafer processing method includes the following steps: a dicing tape attaching step of attaching a dicing tape to a front surface of a wafer; a heat staking piece arranging step of arranging a heat staking piece on the dicing tape attached to the front surface of the wafer; an integration step of integrating the heat staking piece to the dicing tape by heating the heat staking piece and pressing the heat staking piece with a flat member; a grinding step of holding the heat staking piece side to a chuck table of a grinding device, and grinding to a desired thickness while supplying grinding water to a back surface of the wafer; and a peeling step of moving out the integrated wafer from the chuck table, and peeling the heat staking piece from the dicing tape.

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 a protective tape affixed to the front side, and then the adhesive 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, although the grinding surface of the wafer that has been ground in this manner is cleaned by a 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 the wafer 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 that prevents grinding chips from adhering to an adhesive tape attached to a holding surface of a wafer held by a chuck table during grinding.

[0008] According to the present invention, a method for processing a wafer is provided, which grinds 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 method for processing the wafer has the following steps: an adhesive tape pasting step of pasting an adhesive tape on the front side of the wafer; a hot pressing sheet arrangement step of arranging a hot pressing sheet on the adhesive tape pasted on the front side of the wafer; an integration step of heating the hot pressing sheet and pressing it with a flat component to press the hot pressing sheet onto the adhesive tape for integration; a grinding step of, after the integration step is implemented, holding the hot pressing sheet side on the chuck worktable of a grinding device, and grinding the wafer to a desired thickness while supplying grinding water to the back side of the wafer; and a peeling step of removing the wafer integrated with the hot pressing sheet from the chuck worktable and peeling the hot pressing sheet from the adhesive tape.

[0009] Preferably, in the peeling step, the thermocompression bonding sheet is locally heated or cooled to generate a temperature difference, thereby peeling the thermocompression bonding sheet from the adhesive tape.

[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 the group consisting of 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 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 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, grinding chips are not allowed to directly adhere to the adhesive tape, thereby solving the problem of grinding chips becoming a contamination source in the next step when the wafer is transported to the next step. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a perspective view showing an embodiment of the adhesive tape applying process.

[0014] Figure 2 It is a perspective view showing an embodiment of a thermocompression bonding sheet arranging step.

[0015] Figure 3 It is a perspective view showing an embodiment of a thermocompression bonding sheet arranging step.

[0016] Figure 4 It is a perspective view showing an embodiment of a cutting step.

[0017] Figure 5 It is an overall perspective view of a grinding device preferably used in this embodiment.

[0018] Figure 6 The chip is kept in Figure 5 A perspective view of the grinding device shown in the chuck table manner.

[0019] Figure 7 Is shown by Figure 5 A perspective view of the grinding device shown in FIG. 1 showing the manner in which the grinding process is performed.

[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] Label Description

[0023] 1: Grinding device; 2: Device housing; 3: Rough grinding unit; 4: Fine grinding unit; 5: Rotating table; 6: Chuck table; 7: First cassette; 8: Second cassette; 9: Temporary storage area; 11: Cleaning unit; 12: First conveying mechanism; 13: Second conveying mechanism; 14: Third conveying mechanism; 21: Stationary support base; 22, 23: Guide rails; 31: Unit housing; 31a: Rotating axis; 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: movable base; 46: grinding feed mechanism; 100: chuck table; 110: hot pressing plate; 120: integrated component; 122: pressing component; 124: lower surface; A: workpiece moving in / out area; B: rough grinding processing area; C: fine grinding processing area; D: device; L1: grinding water; L2: cleaning water; T: adhesive tape; W: chip; Wa: front side; Wb: back side. DETAILED DESCRIPTION

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

[0025] The wafer processing method of this embodiment includes the following steps: an adhesive tape applying step of applying adhesive tape to the front surface of the wafer; a thermocompression bonding sheet placement step of placing a thermocompression bonding sheet on the adhesive tape applied to the front surface of the wafer; an integration step of heating the thermocompression bonding sheet and pressing it with a flat member to press the thermocompression bonding sheet onto the adhesive tape for integration; a grinding step of holding the thermocompression bonding sheet on a chuck table of a grinding device and grinding the wafer to a desired thickness while supplying grinding water to the back surface of the wafer; and a peeling step of removing the wafer, integrated with the thermocompression bonding sheet, from the chuck table and peeling the thermocompression bonding sheet from the adhesive tape. Each step is described below in order.

[0026] (Adhesive tape attaching process)

[0027] exist Figure 1 In the embodiment of the adhesive tape pasting process, a three-dimensional diagram showing the embodiment of the adhesive tape pasting process is shown. When the adhesive tape pasting process is implemented, first, a Figure 1 The wafer W to be processed is shown, along with an adhesive tape T attached to the wafer W, and a chuck table 100 for carrying out the adhesive tape attachment step and the later-described heat-compression sheet placement step. The wafer W is made of, for example, silicon (Si), and is divided by predetermined dividing lines, with a plurality of devices D formed on its front surface Wa. The adhesive tape T is made of, for example, a circular polyvinyl chloride sheet having a shape roughly the same as that of the wafer W, and an adhesive (for example, an acrylic resin) applied to the front surface of the polyvinyl chloride sheet. The chuck table 100 is composed of a disc-shaped suction chuck 100a and a circular frame 100b. The suction chuck 100a is made of porous ceramic with air permeability. The circular frame 100b surrounds the outer periphery of the suction chuck 100a and can attract and hold the wafer W placed on the upper surface (holding surface) of the suction chuck 100a by operating a suction member (not shown).

[0028] As described above, after the wafer W, adhesive tape T, and chuck table 100 are prepared, the adhesive tape T is attached with the side coated with the adhesive facing the front surface Wa of the wafer W where the device D is formed. When the adhesive tape T is attached to the front surface Wa of the wafer W, the adhesive tape T can be attached to the front surface Wa of the wafer W. Figure 1 Although the chuck table 100 is shown, the tape can also be attached using a previously known tape attaching machine (not shown) or the like.

[0029] (Thermocompression bonding sheet placement process)

[0030] After the adhesive tape T is attached as described above, Figure 2 As shown, the hot pressing sheet arrangement process is implemented. First, prepare the wafer W with the adhesive tape T attached to the front Wa through the above-mentioned adhesive tape arrangement process, as shown in FIG. Figure 2As shown, the wafer W is placed on the center of the adsorption chuck 100a of the chuck table 100 with the front side Wa of the wafer W having the adhesive tape T facing upward and the back side Wb facing downward. After the wafer W is placed on the adsorption chuck 100a, a circular heat-compression sheet 110 having a thickness of 20 μm to 100 μm is placed on the adhesive tape T attached to the wafer W. As the heat-compression 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 2 As can be seen, the diameter of the suction chuck 100a is set slightly larger than the diameter of the wafer W. By placing the wafer W on the center of the suction chuck 100a, the suction chuck 100a is exposed, surrounding the outer periphery of the wafer W. The thermocompression 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 suction chuck 100a and slightly smaller than the diameter of the circular frame portion 100b of the chuck table 100. Thus, the entire surface of the suction chuck 100a and the wafer W are covered by the thermocompression sheet 110. Furthermore, no adhesive layer, such as paste, is formed on the thermocompression sheet 110 placed on the adhesive tape T.

[0031] The thermocompression bonding sheet 110 is a sheet that develops adhesive strength by heating, but 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.

[0032] After the wafer W with the adhesive tape T attached and the thermocompression sheet 110 are placed on the chuck table 100, a suction unit (not shown) including a suction pump is activated to apply a suction force Vm to the suction chuck 100a, thereby sucking the wafer W and the thermocompression sheet 110. As described above, the entire upper surface (holding surface) of the suction chuck 100a and the wafer W are covered by the thermocompression sheet 110. Therefore, the suction force Vm is applied to the entire wafer W and the thermocompression sheet 110, thereby sucking and holding the wafer W and the thermocompression sheet 110 on the suction chuck 100a. Furthermore, the suction force Vm is sucked away from the space between the adhesive tape T on the wafer W and the thermocompression sheet 110, thereby ensuring close contact between the two. The front surface of the adhesive tape T has minute irregularities caused by the influence of the multiple devices D and the adhesive applied to the adhesive surface of the adhesive tape T. However, the chuck table 100 suctions and holds the tape T, sucking away any remaining air from the minute irregularities, allowing the thermocompression sheet 110 to adhere closely to the tape T. This completes the thermocompression sheet placement process.

[0033] (Integrated process)

[0034] After the above-mentioned heat-compression bonding sheet placement step is performed, the integration step is then performed. Figure 3 and Figure 4 The integration process is explained.

[0035] When implementing an integrated process, Figure 3 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 press 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.

[0036] After the integrated component 120 is positioned above the chuck table 100, the heater built into the integrated component 120 is activated, causing the flat member 122 to descend, pressing the thermocompression bonding 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 bonding sheet 110 of this embodiment is a polyethylene sheet. When heated to 120°C to 140°C, the polyethylene sheet approaches a melting point, exhibiting adhesive strength and softening. Furthermore, as described above, the thermocompression bonding sheet 110 is in close contact with the microscopic irregularities formed on the adhesive tape T affixed to the front surface Wa of the wafer W. Therefore, the softened thermocompression bonding sheet 110, heated by heat, increases the contact between the thermocompression bonding sheet 110 and the adhesive tape T on the wafer W, and the heat-generated adhesive force of the thermocompression bonding sheet 110 creates a pressure bond. Furthermore, since the lower surface 124 of the flat member 122 is flat, the front surface of the thermocompression bonding sheet 110 affixed to the adhesive tape T on the wafer W is flattened. This completes the integration process of the thermocompression bonding sheet 110 to the adhesive tape T and the wafer W. Furthermore, since the lower surface 124 of the flat member 122 is coated with fluororesin as described above, 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.

[0037] In the above-mentioned integration process, as a method of heating the thermocompression bonding sheet 110 and pressing the thermocompression bonding sheet 110 onto the adhesive tape T on the wafer W to integrate the thermocompression bonding sheet 110 and the wafer W, a method of using Figure 2The 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, and then the flat member 122 of the above-described shape may be used to press and bond the sheet. Alternatively, the thermocompression sheet 110 may be pressed and bonded to the adhesive tape T by irradiating the front surface of the thermocompression sheet 110 with infrared light to heat it, or by pressing and bonding it to the adhesive tape T using a roller-shaped flat member, heated to a predetermined temperature using a roller equipped with a heater and temperature sensor.

[0038] 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 4 The cutting process will be described.

[0039] (Cutting process)

[0040] like Figure 4 As shown, the cutting unit 70 (only a portion is shown) is positioned on the chuck table 100 that attracts and holds the wafer W to which the thermocompression bonding sheet 110 is crimped. More specifically, the cutting unit 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 unit 70 positions the tip of the cutting tool 72 at the outer periphery of the wafer W. After the cutting tool 72 is positioned at the outer 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 outer periphery of the wafer W, so that the remaining portion of the thermocompression bonding sheet 110 exposed from the outer periphery of the wafer W can be cut and separated. Thus, the cutting process is completed.

[0041] (Grinding process / thermocompression bonding sheet cleaning process)

[0042] As described above, after the wafer W, the adhesive tape T, and the thermocompression bonding sheet 110 are integrated through the integration process, a grinding process is performed to grind the back surface Wb of the wafer W. Figure 5 A grinding device 1 suitable for performing this grinding process will be described.

[0043] The grinding device 1 has a device housing 2 that is substantially in the shape of a rectangular parallelepiped. Figure 5In 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.

[0044] 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.

[0045] 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.

[0046] 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. The grinding water L1 is then supplied through through-holes formed in the rotating shafts 31a and 41a, and sprayed from the lower end surfaces of the rough grinding wheel 33 and the fine grinding wheel 43.

[0047] 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.

[0048] The grinding device 1 includes: a first cassette 7, which is arranged on one side relative to the workpiece carry-in / out area A and stores wafers W as workpieces before grinding; a second cassette 8, which is arranged on the other side relative to the workpiece carry-in / out area A and stores wafers W as workpieces after grinding; a temporary storage area 9, which is arranged between the first cassette 7 and the workpiece carry-in / out area A and performs center alignment of the workpiece; and a cleaning unit 11. In addition, the grinding device 1 has: a first conveying mechanism 12, which conveys the wafer W as the workpiece stored in the first box 7 to the temporary storage area 9, and conveys the wafer W cleaned by the cleaning unit 11 to the second box 8; a second conveying mechanism 13, which conveys the wafer W placed on the temporary storage area 9 and centered to the chuck worktable 6 positioned in the workpiece carry-in / out area A; and a third conveying mechanism 14, which conveys the wafer W after grinding, which is placed on the chuck worktable 6 positioned in the workpiece carry-in / out area A, to the cleaning unit 11.

[0049] 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 allows the operator to instruct the grinding process or specify processing conditions, while the display monitor 16 displays the grinding process status and has a touch panel function. In addition to the aforementioned components, the grinding device 1 of this embodiment is also equipped with control means 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.

[0050] The grinding device 1 of this embodiment has the structure as described above. Figures 5 to 7 A grinding process performed using the grinding device 1 will be 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 thereto, and the grinding process may also consist of only one grinding process.

[0051] When performing the grinding process, Figure 6 As shown, the wafer W, which is integrated with the adhesive tape T and the thermocompression bonding sheet 110 by pressure bonding, is turned over with the back surface Wb facing upward and the thermocompression bonding sheet 110 facing downward, and the wafer W is placed 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.

[0052] After the wafer W is held by suction on the chuck table 6 positioned in the workpiece loading / unloading area A, the rotary table 5 of the grinding apparatus 1 is rotated 120 degrees in the direction indicated by R5, and the chuck table 6 holding the wafer W by suction is positioned directly below the rough grinding unit 3. Figure 7 As shown, the rotation shaft 31a of the rough grinding unit 3 is rotated in the direction indicated by arrow R7 at a speed of, for example, 6000 rpm, and the chuck table 6 is rotated in the direction indicated by arrow R8 at a speed of, for example, 300 rpm. Then, the grinding tool 33a is 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 bottom surface of the rough grinding wheel 32 via the rotation shaft 31a to the grinding surface, i.e., the back surface Wb, of the wafer W. Simultaneously, the thickness of the wafer W can be measured using a contact-type measuring instrument (not shown) while the rough grinding is performed. The back surface Wb of the wafer W is rough-ground to the desired thickness during the rough grinding process, thereby completing the rough grinding process.

[0053] After the rough grinding process is completed as described above, the rotating table 5 is turned to Figure 5The chuck table 6 is further rotated 120 degrees in the direction indicated by R5, 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. The grinding tool 43a is then 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.

[0054] After the grinding step is completed as described above, the rotary table 5 is further rotated 120 degrees in the direction indicated by R5, and the chuck table 6 is positioned in the workpiece loading / unloading area A. In the cleaning step, the wafer W positioned in the workpiece loading / unloading area A is sucked onto its back surface Wb by the operation of the third transport mechanism 14 and transported to the cleaning unit 11. The ground surface of the wafer W, i.e., the back surface Wb of the wafer W, is cleaned by the cleaning unit 11. The wafer W, cleaned and dehydrated in this cleaning step, is then sucked by the first transport mechanism 12, transported, and stored in a predetermined position in the second cassette 8.

[0055] (Peeling process)

[0056] After the grinding and cleaning steps are completed, a peeling step is performed to peel off the thermal compression sheet 110 that was compressed and integrated in the integration step from the adhesive tape T side of the wafer W stored in the second cassette 8. Figure 8 and Figure 9 The peeling step will be described.

[0057] 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, with the side with the thermocompression bonding sheet 110 facing upward, and the back side Wb is placed on the adsorption chuck 92 and held by suction. 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 attracted and 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 thermocompression bonding sheet 110 is peeled off from the adhesive tape T starting from the outer peripheral portion subjected to the cooling or heating treatment.

[0058] According to the present embodiment described above, since the thermocompression bonding sheet 110 pressed against the adhesive tape T attached to the front surface Wa of the wafer W is flattened, even when the wafer W is held on the chuck table 6 of the grinding apparatus 1 and the grinding process is performed, grinding debris is less likely to enter through the gap between the thermocompression bonding sheet 110 and the holding surface of the chuck table 6. Furthermore, even if grinding debris adheres to the thermocompression bonding sheet 110, the flattened thermocompression bonding sheet has a weak adhesion force, thereby suppressing the adhesion of grinding debris to the thermocompression bonding sheet 110. Furthermore, even if minute grinding debris adheres to the thermocompression bonding sheet 110, the thermocompression bonding sheet 110 can be peeled from the adhesive tape T by performing the above-described peeling step before being transported to the next process. This prevents grinding debris from adhering to the adhesive tape T from the outset, thus completely resolving the problem of grinding debris adhering to the thermocompression bonding sheet 110 becoming a source of contamination in the next process. Therefore, in the next step, the adhesive tape T can be made to function as a protective member as it is.

[0059] 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.

[0060] 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.

[0061] 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: an adhesive tape pasting step of pasting the adhesive-coated side of the adhesive tape on the front surface of the wafer; a step of disposing a thermocompression bonding sheet, disposing a thermocompression bonding sheet without forming an adhesive layer on the other side of the adhesive tape attached to the front surface of the wafer, on which the adhesive is not applied; An integration step of heating the heat-compression bonding sheet and pressing it with a flat member to press the heat-compression bonding sheet onto the adhesive tape for integration; 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 peeling step, after the grinding step, the wafer integrated with the thermocompression bonding sheet is unloaded from the chuck table, and the thermocompression bonding sheet is peeled off from the other side of the adhesive tape on which the adhesive is not applied.

2. The wafer processing method according to claim 1, wherein: In the peeling step, the thermocompression bonding sheet is locally heated or cooled to generate a temperature difference, thereby peeling the thermocompression bonding sheet from the adhesive tape.

3. The wafer processing method according to claim 1 or 2, wherein: The heat-compression bonding sheet is 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 can be selected from 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.

Images