Protective sheet sticking method

Abstract

To provide a protective sheet sticking method capable of reliably sticking a protective sheet onto a wafer.SOLUTION: A method includes: a step of preparing a frame 8 with an opening for receiving a wafer 2 in a center of the frame; a step of preparing a protective sheet sticking machine 10; a protective sheet sticking step of sticking the protective sheet 30 onto the frame 8; a wafer supporting step of supporting a rear surface 2b of the wafer 2 by a wafer support part 12; a step of supporting the frame 8 by a frame support part 14 while placing the protective sheet 30 stuck on the frame 8 to face a front surface 2a of the wafer 2: and a frame unit formation step of bringing an upper chamber 16 and a lower chamber 18 of the protective sheet sticking machine 10 into vacuum while holding the frame 8 by the upper chamber 16 and the lower chamber 18 and opening only the upper chamber 16 to atmospheric air, and then sticking the protective sheet 30 onto the front surface 2a of the wafer 2 to form a frame unit 34 comprising the wafer 2 and the frame 8 integrated by the protective sheet 30.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a method for attaching a protective sheet to the surface of a wafer having a plurality of devices formed on its surface by dividing lines. [Background technology]

[0002] A wafer has a plurality of devices such as ICs and LSIs formed on its surface along planned dividing lines, and the back surface is ground to the desired thickness. The wafer is then divided into individual device chips using a cutting device, laser processing device or the like, and each of the divided device chips is used in electrical equipment such as mobile phones and personal computers.

[0003] A grinding device for grinding the back surface of a wafer includes at least a chuck table for holding the wafer, and a grinding means for rotatably supporting a grinding wheel having grinding stones arranged in a ring shape for grinding the back surface of the wafer held on the chuck table, and can grind the wafer to a desired thickness (for example, see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-164837 A Summary of the Invention [Problem to be solved by the invention]

[0005] When the back surface of the wafer is ground by a grinding device, the front surface of the wafer comes into contact with the chuck table, and therefore a protective sheet is attached to the front surface of the wafer to prevent the front surface from being scratched. However, if the protective sheet is relatively hard and curved, there is a problem that it is difficult to attach the protective sheet to the front surface of the wafer.

[0006] An object of the present invention is to provide a method for attaching a protective sheet that can reliably attach a protective sheet to a wafer. [Means for solving the problem]

[0007] According to the present invention, there is provided the following protective sheet attachment method that solves the above problems. "A method for attaching a protective sheet to a surface of a wafer on which a plurality of devices are formed by dividing the surface of the wafer along planned dividing lines, comprising the steps of: a frame preparation step of preparing a frame having an opening in the center for accommodating a wafer; a protective sheet application machine preparation step of preparing a protective sheet application machine which includes a wafer support part for supporting a wafer, a frame support part for supporting a frame, and an upper chamber and a lower chamber which sandwich the frame from above and below, and which applies a protective sheet to a wafer by evacuating the upper chamber and the lower chamber and opening only the upper chamber to the atmosphere; a protective sheet attachment step of attaching a protective sheet to the frame; a wafer supporting step of supporting a back surface of the wafer on the wafer supporting portion; a frame supporting step of supporting the frame on the frame supporting portion in such a manner that the protective sheet attached to the frame faces the front surface of the wafer; and a frame unit forming step of clamping a frame between the upper chamber and the lower chamber of the protective sheet application machine, evacuating the upper chamber and the lower chamber while opening only the upper chamber to the atmosphere, and applying a protective sheet to the surface of a wafer to form a frame unit in which the wafer and the frame are integrated by the protective sheet.

[0008] a frame unit holding step of holding the frame unit on a table including a frame holding table for holding a frame, a wafer holding table for holding a wafer, and a ring-shaped space formed between the frame holding table and the wafer holding table; It is preferable that the method includes a cutting step of positioning a cutter blade in the ring-shaped space and cutting the protective sheet along the outer periphery of the wafer while applying ultrasonic waves to the cutter blade to produce a form in which the protective sheet is attached to the surface of the wafer.

[0009] After the protective sheet attachment step and before the frame unit holding step, it is desirable to lay a flowable resin that flattens the unevenness of the wafer transferred to the protective sheet side to which the wafer is attached, and then to place a further sheet. Effect of the Invention

[0010] The protective sheet attachment method of the present invention comprises the steps of: A protective sheet attachment method for attaching a protective sheet to a surface of a wafer having a plurality of devices formed on the surface by dividing lines, the method comprising the steps of: a frame preparation step of preparing a frame having an opening in the center for accommodating a wafer; a protective sheet application machine preparation step of preparing a protective sheet application machine which includes a wafer support part for supporting a wafer, a frame support part for supporting a frame, and an upper chamber and a lower chamber which sandwich the frame from above and below, and which applies a protective sheet to a wafer by evacuating the upper chamber and the lower chamber and opening only the upper chamber to the atmosphere; a protective sheet attachment step of attaching a protective sheet to the frame; a wafer supporting step of supporting a back surface of the wafer on the wafer supporting portion; a frame supporting step of supporting the frame on the frame supporting portion in such a manner that the protective sheet attached to the frame faces the front surface of the wafer; The method includes a frame unit forming step of sandwiching a frame between the upper and lower chambers of the protective sheet application machine, evacuating the upper and lower chambers while opening only the upper chamber to the atmosphere, and applying a protective sheet to the surface of a wafer to form a frame unit in which the wafer and frame are integrated by the protective sheet, thereby enabling the protective sheet to be reliably applied to the wafer. [Brief description of the drawings]

[0011] [Figure 1] FIG. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] 5A to 5C are schematic diagrams showing a wafer supporting step and a frame supporting step. [Diagram 5] FIG. [Figure 6] FIG. [Figure 7] 13 is a schematic diagram showing a state in which a fluid resin is laid on a protective sheet of a frame unit and then a sheet is placed thereon. FIG. [Figure 8] FIG. [Figure 9] (a) Schematic diagram showing the cutting process, (b) Cross-sectional view of the wafer. [Figure 10] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] BEST MODE FOR CARRYING OUT THE DISCLOSURE Hereinafter, preferred embodiments of the protective sheet attachment method according to the present invention will be described with reference to the drawings.

[0013] (Wafer 2) 1 shows a disk-shaped wafer 2 to which a protective sheet can be attached by the protective sheet attachment method according to the present invention. The wafer 2 can be made of an appropriate semiconductor material such as silicon. A surface 2a of the wafer 2 is partitioned into a plurality of rectangular regions by lattice-shaped division lines 4. Devices 6 such as ICs and LSIs are formed in the rectangular regions.

[0014] (Frame preparation process) In this embodiment, first, a frame preparation step is performed to prepare a frame having an opening in the center for accommodating the wafer 2. In this step, for example, a frame 8 as shown in Fig. 2 is prepared. The frame 8 is ring-shaped, and a circular opening 8a capable of accommodating the wafer 2 is provided in the center of the frame 8.

[0015] (Protection sheet application machine preparation process) In addition, a protective sheet application machine preparation step is performed to apply a protective sheet to the wafer 2. The protective sheet application machine preparation step may be performed before or after the frame preparation step. In the protective sheet application machine preparation step, for example, a protective sheet application machine 10 shown in FIG. 4 can be prepared.

[0016] The protective sheet application machine 10 includes a wafer support 12 that supports the wafer 2, a frame support 14 that supports the frame 8, and an upper chamber 16 and a lower chamber 18 that sandwich the frame 8 from above and below. The wafer support 12 may be formed by the upper surface of a circular member. The frame support 14 may be formed by the upper surface of a ring-shaped member arranged on the outer periphery of the wafer support 12. The upper chamber 16 includes a top plate 20 and a side wall 22 that extends downward from the periphery of the top plate 20. The side wall 22 is provided with a suction port 24 connected to a suction means (not shown). The lower chamber 18 includes a circular bottom plate (not shown) and a cylindrical side wall 26 that extends upward from the periphery of the bottom plate. Similar to the side wall 22 of the upper chamber 16, the side wall 26 of the lower chamber 18 is also provided with a suction port 28 connected to a suction means. In this embodiment, the frame support 14 is formed by the upper surface of the side wall 26 of the lower chamber 18. It is preferable to provide a packing such as rubber in the areas corresponding to the frame support portion 14 and the upper chamber 16 to improve adhesion.

[0017] In the protective sheet application machine 10, the upper chamber 16 and the lower chamber 18 are evacuated, and only the upper chamber 16 is opened to the atmosphere, so that the protective sheet can be applied to the wafer 2. This will be described in detail in the frame unit formation process below.

[0018] (Protective sheet attachment process) After the frame preparation step is performed, a protective sheet attachment step is performed in which a protective sheet 30 is attached to the frame 8. The protective sheet attachment step may be performed before the protective sheet attachment machine preparation step, or may be performed after the protective sheet attachment machine preparation step. In the protective sheet attachment step, a circular protective sheet 30 is attached to the frame 8 so as to close the opening 8a of the frame 8. The protective sheet 30 is made of an appropriate synthetic resin such as polyethylene terephthalate (PET). As the protective sheet 30, for example, any one of three types of protective sheets 30a, 30b, and 30c shown in FIG. 3 can be attached to the frame 8.

[0019] One side of the type 1 protective sheet 30a is provided with two ring-shaped adhesive layers 32 of different sizes. The outer adhesive layer 32 is attached to the frame 8, and the inner adhesive layer 32 is attached to the wafer 2. The inner adhesive layer 32 is sized so that it is attached to the peripheral excess area on the front surface 2a of the wafer 2 where the devices 6 are not formed, and is not attached to the device area where the devices 6 are formed. Therefore, when the protective sheet 30a is later peeled off from the front surface 2a of the wafer 2, the adhesive material of the protective sheet 30a does not remain in the device area.

[0020] One surface of the type 2 protective sheet 30b is provided on the outer periphery of the protective sheet 30b with one adhesive layer 32. The frame 8 and the wafer 2 are attached to the adhesive layer 32 of the protective sheet 30b. The size of the adhesive layer 32 is such that the adhesive layer 32 is attached to the outer periphery excess region of the wafer 2, but the adhesive layer 32 is not attached to the device region of the wafer 2.

[0021] In the type 3 protective sheet 30c, an adhesive layer 32 is provided over one entire surface.

[0022] (Wafer support process / Frame support process) After the protective sheet application machine preparation process and the protective sheet application process are performed, a wafer supporting process is performed in which the back surface 2b of the wafer 2 is supported by the wafer support part 12, and then a frame supporting process is performed in which the protective sheet 30 attached to the frame 8 is faced to the front surface 2a of the wafer 2 and the frame 8 is supported by the frame support part 14 (see Figure 4).

[0023] (Frame unit forming process) After the wafer supporting process and the frame supporting process are performed, a frame unit forming process is performed in which the frame 8 is clamped between the upper chamber 16 and the lower chamber 18 of the protective sheet application machine 10, the upper chamber 16 and the lower chamber 18 are evacuated, and only the upper chamber 16 is opened to the atmosphere, and the protective sheet 30 is applied to the surface 2a of the wafer 2 to form a frame unit in which the wafer 2 and the frame 8 are integrated by the protective sheet 30.

[0024] 5, in the frame unit formation process, first, the upper chamber 16 is placed on the lower chamber 18, and the frame 8 is sandwiched between the upper chamber 16 and the lower chamber 18. At this time, it is preferable to sandwich the protective sheet 30 between the upper chamber 16 and the lower chamber 18 together with the frame 8. Next, the suction means connected to the suction port 24 of the upper chamber 16 and the suction port 28 of the lower chamber 18 are operated to evacuate the inside of the upper chamber 16 and the inside of the lower chamber 18.

[0025] After the upper chamber 16 and the lower chamber 18 are evacuated, only the upper chamber 16 is opened to the atmosphere while the lower chamber 18 is kept in a vacuum state. Then, the pressure in the upper chamber 16 becomes greater than the pressure in the lower chamber 18, and the pressure difference between the upper chamber 16 and the lower chamber 18 presses the adhesive layer 32 of the protective sheet 30 against the surface 2a of the wafer 2. This allows the adhesive layer 32 of the protective sheet 30 to be in close contact with the surface 2a of the wafer 2 even if the protective sheet 30 is relatively hard and curved. In this way, a frame unit 34 is formed in which the wafer 2 and the frame 8 are integrated by the protective sheet 30, as shown in FIG. 6.

[0026] After the frame unit 34 is formed, as shown in FIG. 7, it is preferable to lay a fluid resin 36 for flattening the irregularities of the wafer 2 transferred to the protective sheet 30 to which the wafer 2 is attached, and then to place a sheet 38. As a result, the irregularities of the front surface 2a of the wafer 2 are absorbed by the fluid resin 36, so that the irregularities of the front surface 2a do not affect the sheet 38. That is, the exposed surface of the sheet 38 becomes flat, and the back surface 2b of the wafer 2 and the exposed surface of the sheet 38 become parallel with high accuracy. The sheet 38 is circular and made of an appropriate synthetic resin. The diameter of the sheet 38 is the same as the diameter of the wafer 2, and the thickness of the sheet 38 may be about 10 to 50 μm.

[0027] (Frame unit holding process) After the frame unit forming process is performed, a frame unit holding process is performed in which the frame unit 34 is held on a table having a frame holding table for holding the frame 8, a wafer holding table for holding the wafer 2, and a ring-shaped space formed between the frame holding table and the wafer holding table.

[0028] In the frame unit holding step, for example, a table 40 shown in Fig. 8 can be used. The table 40 includes a ring-shaped frame holding table 42, a circular wafer holding table 44, and a ring-shaped space 46. A plurality of suction holes 42a are formed at intervals on the upper surface of the frame holding table 42, and the plurality of suction holes 42a are connected to a suction means (not shown). A circular suction chuck 48 made of a porous member such as porous ceramics is disposed on the upper end of the wafer holding table 44. The suction chuck 48 is connected to the suction means.

[0029] 7 is inverted, the frame 8 of the frame unit 34 is placed on the frame holding table 42, and the wafer 2 of the frame unit 34 is placed on the wafer holding table 44. At this time, the back surface 2b of the wafer 2 is faced upward, and the sheet 38 is brought into contact with the upper surface of the wafer holding table 44. The center of the wafer 2 is also aligned with the center of the wafer holding table 44.

[0030] Next, the suction means is operated to generate a suction force in the suction holes 42a of the frame holding table 42 and the suction chuck 48 of the wafer holding table 44. This causes the frame 8 to be suction-held by the frame holding table 42, and also causes the wafer 2 to be suction-held by the wafer holding table 44 via the sheet 38. In this manner, the frame unit 34 is held on the table 40.

[0031] (cutting process) After carrying out the frame unit holding process, a cutting process is carried out in which a cutter blade is positioned in the ring-shaped space portion 46 and ultrasonic waves are applied to the cutter blade while cutting the protective sheet 30 along the outer periphery of the wafer 2 to produce a form in which the protective sheet 30 is attached to the surface 2a of the wafer 2.

[0032] The cutting step can be performed, for example, by using a cutting device 50 shown in Fig. 9. The cutting device 50 includes an arm 52 supported by an appropriate bracket (not shown) so as to be movable up and down and rotatable, a motor 54 for rotating the arm 52, a cutter blade 56 attached to the tip of the arm 52, and an ultrasonic unit 58 for applying ultrasonic waves to the cutter blade 56. The base end (center of rotation) of the arm 52 is positioned at the center of the wafer holding table 44. The rotation radius of the arm 52 corresponds to the radius of the wafer 2.

[0033] In the cutting step, first, the arm 52 is lowered, the cutter blade 56 is positioned in the ring-shaped space 46, and the cutter blade 56 is caused to cut into the protective sheet 30 located on the outer periphery of the wafer 2. Then, the arm 52 is rotated by the motor 54, so that the protective sheet 30 is cut along the outer periphery of the wafer 2 by the cutter blade 56. At this time, it is preferable to apply ultrasonic waves from the ultrasonic unit 58 to the cutter blade 56. This prevents a gap from being formed between the front surface 2a of the wafer 2 and the protective sheet 30 when the protective sheet 30 is cut. In this way, a form in which the protective sheet 30 is attached to the front surface 2a of the wafer 2 is generated.

[0034] (Grinding process) After the cutting step, a grinding step is performed in which the back surface 2b of the wafer 2 is ground to thin the wafer 2 to a desired thickness.

[0035] The grinding step can be performed, for example, by using a grinding device 60 shown in Fig. 10. The grinding device 60 includes a chuck table 62 that holds the wafer 2 by suction, and a grinding means 64 that grinds the wafer 2 held by suction on the chuck table 62. The grinding means 64 includes a spindle 66 extending in the vertical direction, and a disk-shaped wheel mount 68 fixed to the lower end of the spindle 66. An annular grinding wheel 72 is fastened to the lower surface of the wheel mount 68 by a bolt 70. A plurality of grinding stones 74 are fixed to the outer periphery of the lower surface of the grinding wheel 72, and are arranged in a ring shape at intervals in the circumferential direction.

[0036] In the grinding process, first, the back surface 2b of the wafer 2 is faced up (the exposed surface of the sheet 38 is faced down), and the wafer 2 is suction-held on the upper surface of the chuck table 62. As described above, in this embodiment, the exposed surface of the sheet 38 is flat, so that when the wafer 2 is suction-held on the chuck table 62, the exposed surface of the sheet 38 comes into close contact with the upper surface of the chuck table 62.

[0037] After the wafer 2 is held by the chuck table 62, the chuck table 62 is rotated at a predetermined rotation speed (e.g., 300 rpm) in the direction indicated by the arrow R1 in FIG. 10. The spindle 66 is also rotated at a predetermined rotation speed (e.g., 6000 rpm) in the direction indicated by the arrow R2 in FIG. 10. Next, the spindle 66 is lowered to bring the grinding wheel 74 into contact with the back surface 2b of the wafer 2, and grinding water is supplied to the portion where the grinding wheel 74 is in contact with the back surface 2b. Thereafter, the spindle 66 is lowered at a predetermined grinding feed rate (e.g., 1.0 μm / s). This allows the back surface 2b of the wafer 2 to be ground to thin the wafer 2 to a desired thickness.

[0038] As described above, in this embodiment, the frame 8 is clamped between the upper chamber 16 and the lower chamber 18 of the protective sheet application machine 10, the upper chamber 16 and the lower chamber 18 are evacuated, and only the upper chamber 16 is opened to the atmosphere, and the protective sheet 30 is applied to the surface 2a of the wafer 2 to form a frame unit in which the wafer 2 and the frame 8 are integrated by the protective sheet 30. Therefore, even if the protective sheet 30 is relatively hard and curved, the adhesive layer 32 of the protective sheet 30 can be adhered to the surface 2a of the wafer 2.

[0039] Furthermore, in this embodiment, the back surface 2b of the wafer 2 and the exposed surface of the sheet 38 are parallel to each other with high accuracy, so that the thickness of the wafer 2 after thinning is uniform. [Explanation of symbols]

[0040] 2: Wafer 2a: Surface of the wafer 2b: Back side of wafer 4: Planned division line 6: Device 8: Frame 8a: opening 10: Protective sheet application machine 12: Wafer support 14: Frame support part 16: Upper chamber 18: Lower chamber 30: Protective sheet 30a: Type 1 protective sheet 30b: Type 2 protective sheet 30c: Type 3 protective sheet 34: Frame unit 36: Fluid resin 38: Sheet 40: Table 42: Frame holding table 44: Wafer holding table 46: Spatial part 56: Cutter blade

Claims

1. A protective sheet attachment method for attaching a protective sheet to a surface of a wafer having a plurality of devices formed on the surface by dividing lines, the method comprising the steps of: a frame preparation step of preparing a frame having an opening in the center for accommodating a wafer; a protective sheet application machine preparation step of preparing a protective sheet application machine which includes a wafer support part for supporting a wafer, a frame support part for supporting a frame, and an upper chamber and a lower chamber which sandwich the frame from above and below, and which applies a protective sheet to a wafer by evacuating the upper chamber and the lower chamber and opening only the upper chamber to the atmosphere; a protective sheet attachment step of attaching a protective sheet to the frame; a wafer supporting step of supporting a back surface of the wafer on the wafer supporting portion; a frame supporting step of supporting the frame on the frame supporting portion in such a manner that the protective sheet attached to the frame faces the front surface of the wafer; a frame unit forming step of clamping a frame between the upper chamber and the lower chamber of the protective sheet application machine, evacuating the upper chamber and the lower chamber while opening only the upper chamber to the atmosphere, and applying a protective sheet to the surface of a wafer to form a frame unit in which the wafer and the frame are integrated by the protective sheet.

2. a frame unit holding step of holding the frame unit on a table including a frame holding table for holding a frame, a wafer holding table for holding a wafer, and a ring-shaped space formed between the frame holding table and the wafer holding table; A method for applying a protective sheet as described in claim 1, further comprising a cutting step of cutting the protective sheet along the outer periphery of the wafer while positioning a cutter blade in the ring-shaped space and applying ultrasonic waves to the cutter blade to generate a form in which the protective sheet is applied to the surface of the wafer.

3. A method for attaching a protective sheet as described in claim 2, further comprising the steps of: after the protective sheet attaching step and before the frame unit holding step, laying a fluid resin for flattening the unevenness of the wafer transferred to the protective sheet side to which the wafer is attached; and then placing a further sheet.

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