Wafer processing method

Abstract

To provide a wafer processing method which can easily peel a resist film from the surface of a wafer having a bump processed to a predetermined height.SOLUTION: A wafer processing method includes: a preparation step of preparing a processor including holding means and byte means; a water-soluble resin film formation step of coating a wafer 2 with a water-soluble resin, and forming a water-soluble resin film 18' between bumps 8; a resist film formation step of coating the water-soluble resin film 18' with a resist so as to excess the heights of the bumps 8 processed to a predetermined height, and forming a resist film 20'; a holding step of exposing a surface where the water-soluble resin film 18' and the resist film 20' are coated, and making the holding means hold the wafer 2; a bump processing step of rotating a byte, machining the tips of the bumps 8, and processing the bumps 8 to the predetermined height; and a resist film peeling step of supplying water to the wafer 2 where the bumps 8 are processed to the predetermined height, dissolving the water-soluble resin film 18' from the wafer 2, and peeling the resist film 20'.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for processing a wafer having a surface on which a plurality of devices having bumps formed thereon are formed by being divided by dividing lines. [Background technology]

[0002] A wafer has multiple devices such as ICs and LSIs formed on its surface, separated by planned dividing lines. The back surface is ground to the desired thickness, and then the wafer is divided into individual device chips using a dicing machine and laser processing machine. Each of these device chips is then used in electrical equipment such as personal computers and mobile phones.

[0003] A device may be provided with a plurality of protruding electrodes called bumps. In this case, the present applicant has proposed a processing device that turns a cutting tool parallel to the surface of the wafer to align the top ends of the bumps (see, for example, Patent Document 1). However, turning the tips of the bumps with a cutting tool creates burrs, which reduces the quality of the device. To address this issue, a technology has been proposed that suppresses the generation of burrs by coating the surface of the wafer with a resist film and then turning the resist film along with the tips of the bumps with a cutting tool (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-047651 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-173954 Summary of the Invention [Problem to be solved by the invention]

[0005] However, to remove the resist film, it is necessary to wash it with acetone, which takes a considerable amount of time, and this is a problem that is unbearable.

[0006] An object of the present invention is to provide a wafer processing method that can easily strip a resist film from the surface of a wafer on which bumps have been processed to a predetermined height. [Means for solving the problem]

[0007] According to the present invention, there is provided the following wafer processing method that solves the above-mentioned problems. "A method for processing a wafer having a surface on which a plurality of devices having bumps formed thereon are formed by being divided by planned dividing lines, a preparation step of preparing a processing device including holding means for holding a wafer and bit means having a bit that rotates parallel to the surface of the wafer held by the holding means and turns the tips of the bumps to a predetermined height; a water-soluble resin film forming step of applying a water-soluble resin to the surface of the wafer to form a water-soluble resin film between the bumps; a resist film forming step of applying a resist to the water-soluble resin film so as to exceed the height of the bumps to be processed to the predetermined height, thereby forming a resist film; a holding step of holding the back surface of the wafer on the holding means while exposing the surface coated with the water-soluble resin film and the resist film; a bump processing step in which the cutting tool is rotated to turn the tips of the bumps formed on the surface of the wafer held by the holding means to a predetermined height; a resist film stripping step of supplying water to the wafer on which the bumps have been processed to the predetermined height to dissolve the water-soluble resin film from the surface of the wafer and strip the resist film; A wafer processing method including the steps of:

[0008] Preferably, in the resist film stripping step, ultrasonic waves are applied via water. [Effects of the Invention]

[0009] The wafer processing method of the present invention includes: A method for processing a wafer having a surface on which a plurality of devices each having bumps formed thereon are formed by being partitioned by planned division lines, the method comprising the steps of: a preparation step of preparing a processing device including holding means for holding a wafer and bit means having a bit that rotates parallel to the surface of the wafer held by the holding means and turns the tips of the bumps to a predetermined height; a water-soluble resin film forming step of applying a water-soluble resin to the surface of the wafer to form a water-soluble resin film between the bumps; a resist film forming step of applying a resist to the water-soluble resin film so as to exceed the height of the bumps to be processed to the predetermined height, thereby forming a resist film; a holding step of holding the back surface of the wafer on the holding means while exposing the surface coated with the water-soluble resin film and the resist film; a bump processing step in which the cutting tool is rotated to turn the tips of the bumps formed on the surface of the wafer held by the holding means to a predetermined height; a resist film stripping step of supplying water to the wafer on which the bumps have been processed to the predetermined height to dissolve the water-soluble resin film from the surface of the wafer and strip the resist film; Since the resist film can be easily peeled off from the surface of the wafer on which the bumps have been processed to a predetermined height. [Brief explanation of the drawings]

[0010] [Figure 1] (a) A perspective view of the wafer, (b) A partial cross-sectional view of the wafer shown in (a). [Figure 2] FIG. 2 is a schematic diagram showing a state in which a wafer is held by a holding table. [Figure 3] FIG. 2(a) is a schematic diagram showing a water-soluble resin film forming step, and FIG. 2(b) is a partial cross-sectional view of a wafer on which a water-soluble resin film has been formed. [Figure 4] FIG. 2(a) is a schematic diagram showing a resist film forming step, and FIG. 2(b) is a partial cross-sectional view of a wafer on which a resist film has been formed. [Figure 5] FIG. [Figure 6] FIG. [Figure 7] (a) A schematic diagram showing a bump processing step, and (b) A perspective view of a wafer that has been subjected to the bump processing step. [Figure 8] (a) A schematic diagram showing a resist film stripping step, (b) A perspective view of a wafer from which the resist film has been stripped, and (c) A partial cross-sectional view of the wafer shown in (b). DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, preferred embodiments of the wafer processing method according to the present invention will be described with reference to the drawings.

[0012] (Wafer 2) FIG. 1(a) shows a disk-shaped wafer 2 to be processed by the wafer processing method according to the present invention. The wafer 2 can be made of an appropriate semiconductor material such as silicon. The thickness of the wafer 2 is, for example, 700 μm. The surface 2a of the wafer 2 is partitioned into a plurality of rectangular regions by grid-like division lines 4. A device 6 such as an IC or LSI is formed in each of the rectangular regions. As shown in FIGS. 1(a) and 1(b), a plurality of protruding bumps 8 are formed as electrodes on each device 6. The height of the bumps 8 (the amount of protrusion of the bumps 8 on the device 6) is, for example, 50 μm.

[0013] (Water-soluble resin film formation process) In this embodiment, first, a water-soluble resin film forming step is carried out in which a water-soluble resin is applied to the front surface 2a of the wafer 2 to form a water-soluble resin film between the bumps 8.

[0014] The water-soluble resin film forming process can be carried out using, for example, a holding device 10 shown in Fig. 2. The holding device 10 includes a circular holding table 12 that holds the wafer 2, and a motor 14 that rotates the holding table 12. A porous suction chuck 16 connected to suction means (not shown) is disposed on the upper end of the holding table 12.

[0015] In the water-soluble resin film forming process, first, the wafer 2 is placed on the upper surface of the holding table 12 with the front surface 2a of the wafer 2 facing upward. Next, the suction means is activated to generate a suction force on the upper surface of the suction chuck 16, and the back surface 2b of the wafer 2 is suction-held on the upper surface of the holding table 12. Next, as shown in FIG. 3(a), the holding table 12 holding the wafer 2 is rotated in the direction indicated by arrow R1 at a predetermined rotational speed (e.g., 2000 rpm). Next, a liquid water-soluble resin 18 is dropped onto the center of the wafer 2. The liquid water-soluble resin 18 may be, for example, polyvinyl alcohol (PVA). After the liquid water-soluble resin 18 has been dropped onto the wafer 2, the holding table 12 continues to rotate for an appropriate time (e.g., approximately 90 seconds), causing the liquid water-soluble resin 18 to flow by centrifugal force. 3(b), the water-soluble resin 18 can be applied to the front surface 2a of the wafer 2 to form a water-soluble resin film 18' between the bumps 8. The thickness of the water-soluble resin film 18' (for example, 5 μm) is smaller than the height of the bumps 8 after processing (for example, 30 μm).

[0016] (Resist film formation process) After the water-soluble resin film forming step is performed, a resist film forming step is performed in which a resist is applied to the water-soluble resin film 18′ so as to overlap the height of the bumps 8 to be processed to a predetermined height (the height of the bumps 8 after processing), thereby forming a resist film. The resist film forming step can also be performed using the holding device 10.

[0017] In the resist film formation process, as shown in FIG. 4(a), the holding table 12 holding the wafer 2 on which the water-soluble resin film 18' has been formed is rotated in the direction indicated by arrow R1. Next, liquid resist 20 is dispensed onto the center of the wafer 2. The liquid resist 20 may be, for example, an acrylic resin (PMMA). After the liquid resist 20 has been dispensed onto the wafer 2, the holding table 12 continues to rotate for an appropriate time depending on the rotation speed of the holding table 12 (for example, approximately 15 seconds at 100 rpm, approximately 10 seconds at 500 rpm, and approximately 7 seconds at 1000 rpm), causing the liquid resist 20 to flow by centrifugal force. As a result, a resist film 20' can be formed on top of the water-soluble resin film 18', as shown in FIG. 4(b).

[0018] In this embodiment, the sum of the thickness of the water-soluble resin film 18' and the thickness of the resist film 20' immediately after the resist film formation step is smaller than the height of the bump 8 before processing, but larger than the height of the bump 8 after processing. For example, if the height of the bump 8 before processing is 50 μm and the height of the bump 8 after processing is 30 μm, the sum of the thickness of the water-soluble resin film 18' and the thickness of the resist film 20' immediately after the resist film formation step may be 45 μm. Note that the sum of the thickness of the water-soluble resin film 18' and the thickness of the resist film 20' immediately after the resist film formation step may be larger than the height of the bump 8 before processing.

[0019] (preparation process) After the resist film forming step is performed, a preparation step is performed to prepare a processing device including a holding means for holding the wafer 2 and a bit means having a bit that rotates parallel to the front surface 2a of the wafer 2 held by the holding means and turns the tips of the bumps 8 to a predetermined height. However, the preparation step may be performed before the water-soluble resin film forming step or the resist film forming step.

[0020] (Processing equipment 22) In the preparation step, for example, a processing device 22 shown in Fig. 5 may be prepared. The processing device 22 includes a holding means 24 for holding the wafer 2, a cutting tool 26 equipped with a cutting tool that rotates parallel to the front surface 2a of the wafer 2 held by the holding means 24 and turns the tips of the bumps 8 to a predetermined height, and an elevating means 28 for raising and lowering the cutting tool 26.

[0021] (Holding means 24) The holding means 24 has a chuck table 30 that is provided so as to be movable in the direction indicated by the arrow X in Fig. 5. The chuck table 30 is moved in the X-axis direction by a ball screw type X-axis feed means (not shown) between a wafer loading / unloading position (position shown in Fig. 5) and a turning position below the cutting tool 26.

[0022] A circular suction chuck 32 is disposed on the upper end of the chuck table 30. The suction chuck 32 is formed from a porous material such as porous ceramics. The suction chuck 32 is connected to a suction means (not shown). In the holding means 24, the suction means generates a suction force on the upper surface of the suction chuck 32, thereby suction-holding the wafer 2 placed on the upper surface of the suction chuck 32.

[0023] (Part-time job method 26) The cutting tool 26 includes a lift plate 36 supported on a support wall 34 at an end (the rear end in FIG. 5) of the processing device 22 so as to be able to move up and down, a protruding member 38 protruding from the lift plate 36, a spindle 40 supported on the protruding member 38 so as to be rotatable about an axis extending in the vertical direction, and a spindle motor 42 that rotates the spindle 40. A disk-shaped mount 44 is fixed to the lower end of the spindle 40. A rod-shaped cutting tool 46 is fixed to the outer periphery of the mount 44 via a tightening bolt 48. A cutting blade 46a, which may be made of diamond or the like, is provided at the lower end of the cutting tool 46 (see FIG. 7(a)).

[0024] (Lifting means 28) 5, the lifting means 28 has a ball screw 50 extending in the vertical direction along one surface of the support wall 34, and a motor 52 that rotates the ball screw 50. A nut portion (not shown) of the ball screw 50 is connected to the lifting plate 36. The lifting means 28 converts the rotational motion of the motor 52 into linear motion using the ball screw 50 and transmits it to the lifting plate 36, thereby lifting and lowering the tool tool 26 along a pair of guide rails 34a attached to one surface of the support wall 34.

[0025] (holding process) After the resist film forming step and the preparation step are performed, a holding step is performed in which the back surface 2b of the wafer 2 is held by a holding means 24 while exposing the front surface 2a coated with the water-soluble resin film 18' and the resist film 20'.

[0026] In the holding step, first, the X-axis feed means is operated to position the chuck table 30 at the wafer loading / unloading position shown in Fig. 5. Next, as shown in Fig. 6, the wafer 2 is placed on the upper surface of the chuck table 30 with the front surface 2a coated with the water-soluble resin film 18' and the resist film 20' facing upward (with the back surface 2b of the wafer 2 facing downward). Then, the suction means is operated to generate a suction force on the upper surface of the suction chuck 32, causing the back surface 2b of the wafer 2 to be suction-held by the holding means 24.

[0027] (Bump processing process) After the holding step is performed, a bump processing step is performed in which the cutting tool 46 is rotated to turn the tips of the bumps 8 formed on the surface 2a of the wafer 2 held by the holding means 24 to a predetermined height.

[0028] In the bump processing step, first, the cutting tool 46 is rotated and positioned at a predetermined height. Specifically, the cutting tool 46 is rotated at a predetermined rotation speed in the direction indicated by arrow R2 in FIG. 7(a). The elevating means 28 also lowers the cutting tool 26, and the lower end of the cutting blade 46a of the cutting tool 46 is positioned at a predetermined height. That is, the cutting blade 46a is used to turn the tips of the bumps 8 formed on the front surface 2a of the wafer 2, and the lower end of the cutting blade 46a is positioned at a position where the bumps 8 can be processed to the predetermined height.

[0029] The cutting tool 46 is rotated and positioned at a predetermined height. The chuck table 30 is then moved at a predetermined feed rate by the X-axis feed mechanism in the direction indicated by the arrow X1 in FIG. 7(a). In this manner, the cutting edge 46a of the cutting tool 46 turns the resist film 20' along with the tips of the bumps 8 formed on the front surface 2a of the wafer 2, thereby reducing the height of the bumps 8 to a predetermined value. This turning is performed dry, without supplying any machining fluid. In this embodiment, the front surface 2a of the wafer 2 is covered with the resist film 20', thereby suppressing the generation of burrs caused by turning the tips of the bumps 8 with the cutting edge 46a of the cutting tool 46. FIG. 7(b) shows the wafer 2 after the bump processing step. Numerous arc-shaped turning marks 54 caused by the cutting edge 46a of the cutting tool 46 are formed on the front surface 2a of the wafer 2.

[0030] (Resist film removal process) After the bump processing step is performed, a resist film removal step is performed in which water is supplied to the wafer 2 on which the bumps 8 have been processed to a predetermined height to dissolve the water-soluble resin film 18' from the surface 2a of the wafer 2 and remove the resist film 20'.

[0031] The resist film stripping step can be performed using, for example, a stripping apparatus 56 shown in Fig. 8(a) . The stripping apparatus 56 includes a water tank 58, a table 60 installed at the bottom of the water tank 58, and an ultrasonic wave generating means 62 movably installed above the water tank 58.

[0032] In the resist film peeling step, first, the wafer 2 is placed on the upper surface of a table 60 in a water tank 58 with the surface 2a coated with the water-soluble resin film 18' and the resist film 20' facing upward. Then, water 64 (e.g., pure water) is supplied into the water tank 58, and the wafer 2 is immersed in the water 64. This dissolves the water-soluble resin film 18', and the resist film 20' can be peeled off from the surface 2a of the wafer 2 (see FIGS. 8(b) and 8(c)).

[0033] In the resist film stripping step, it is preferable to immerse the wafer 2 in water 64, and then operate the ultrasonic wave generating means 62 to apply ultrasonic waves to the wafer 2 via the water 64 in the water tank 58. This makes it possible to efficiently dissolve the water-soluble resin film 18' and strip the resist film 20' from the front surface 2a of the wafer 2. When applying ultrasonic waves, it is preferable to apply ultrasonic waves to the entire front surface 2a of the wafer 2 while appropriately moving the ultrasonic wave generating means 62 horizontally above the wafer 2.

[0034] As described above, in this embodiment, the resist film 20' can be easily peeled off from the front surface 2a of the wafer 2 on which the bumps 8 have been processed to a predetermined height. [Explanation of symbols]

[0035] 2: Wafer 2a: Surface of wafer 2b: Backside of wafer 4: Planned division line 6: Device 8: Bump 18: Water-soluble resin 18': Water-soluble resin film 20: Resist 20': Resist film 22: Processing equipment 24: Holding means 26: Part-time job means 46: Byte

Claims

1. A method for processing a wafer having a surface on which a plurality of devices each having bumps formed thereon are formed by being partitioned by planned division lines, the method comprising the steps of: a preparation step of preparing a processing device including holding means for holding a wafer and bit means having a bit that rotates parallel to the surface of the wafer held by the holding means and turns the tips of the bumps to a predetermined height; a water-soluble resin film forming step of applying a water-soluble resin to the surface of the wafer to form a water-soluble resin film between the bumps; a resist film forming step of applying a resist to the water-soluble resin film so as to exceed the height of the bumps to be processed to the predetermined height, thereby forming a resist film; a holding step of holding the back surface of the wafer on the holding means while exposing the surface coated with the water-soluble resin film and the resist film; a bump processing step in which the cutting tool is rotated to turn the tips of the bumps formed on the surface of the wafer held by the holding means to a predetermined height; a resist film stripping step of supplying water to the wafer on which the bumps have been processed to the predetermined height to dissolve the water-soluble resin film from the surface of the wafer and strip the resist film; A wafer processing method comprising:

2. 2. The wafer processing method according to claim 1, wherein ultrasonic waves are applied via water in the resist film stripping step.

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