Wafer processing method

Abstract

To provide a processing method of a wafer that can resolve the problem in which a protective sheet closely attached on a surface of the wafer by atmospheric pressure using a vacuum chamber breaks due to a step of the surface.SOLUTION: A processing method of a wafer comprises: a wafer accommodation step that accommodates a wafer in a vacuum chamber; a protective sheet arrangement step that arranges a protective sheet on a surface of the wafer before or after the wafer accommodation step; a decompression step that decompresses the inside of the vacuum chamber after the wafer accommodation step and the protective sheet arrangement step; a crimping step that presses the protective sheet on an outer periphery excessive region of the wafer in the vacuum chamber to crimp after the decompression step; and a carrying out step that closely attaches the protective sheet on the surface of the wafer by atmospheric pressure by opening the inside of the vacuum chamber to atmospheric air to carry out the wafer after the crimping step. The protective sheet arrangement step fills a concave division schedule line with water, and suppresses the protective sheet arranged in the wafer carried out in the carrying out step from being embedded in the concave division schedule line by the atmospheric pressure.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] Wafers have device regions on their front surface, with IC, LSI, MEMS or other devices defined by planned division lines. The back surface is ground to thin the wafer to a specified thickness, and the wafer is then divided into individual device chips using a dicing machine and laser processing machine. These chips are then used in electrical devices such as mobile phones and personal computers. [Background technology]

[0002] When the back surface of the wafer is ground to thin it, the front surface of the wafer is held on a chuck table, and a protective sheet is placed on the front surface of the wafer in advance to prevent the devices from being damaged (see, for example, Patent Document 1).

[0003] In a wafer having multiple MEMS formed in the device region, the MEMS protrude upward by about 100 μm, and the electrode pads and planned division lines of the MEMS are formed in the recessed region between adjacent MEMS. Since it is difficult to properly position a protective sheet under atmospheric pressure due to the steps formed between the MEMS, electrode pads, and planned division lines, a protective sheet is pressed against the peripheral excess region surrounding the device region of the wafer in a vacuum chamber, and then the vacuum chamber is opened to the atmosphere to allow the atmospheric pressure to adhere the protective sheet to the surface of the wafer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-246098 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the protective sheet is attached to the surface of the wafer by atmospheric pressure using a vacuum chamber as described above, the protective sheet penetrates deeply into the recessed area of ​​the wafer, and a strong pressure is applied by the atmospheric pressure, which causes a problem that the protective sheet breaks into fibers at the above-mentioned step-formed portion. This problem is not limited to MEMS, but can occur in any wafer having steps on its surface, even if the wafer has IC, LSI, or other devices formed thereon.

[0006] In addition, when grinding the back surface of the wafer, a flattening sheet is placed on the upper surface of the protective sheet via a flexible sheet. However, after grinding the back surface of the wafer, when the flexible sheet and flattening sheet are peeled off from the front surface of the wafer together with the protective sheet, a problem occurs in that the electrode pads formed in the recessed areas are deformed due to breakage of the protective sheet.

[0007] The present invention has been made in consideration of the above-mentioned facts, and its main technical object is to provide a wafer processing method that can solve the problem of a protective sheet that is adhered to the front surface of a wafer by atmospheric pressure using a vacuum chamber being broken due to steps on the front surface, and can also solve the problem of the electrode pad being deformed when the protective sheet is peeled off after the back surface of the wafer is ground. [Means for solving the problem]

[0008] In order to solve the above-mentioned main technical problem, according to the present invention, there is provided a method for processing a wafer having a device region and a peripheral surplus region surrounding the device region, in which the device region is partitioned into a plurality of convex devices by concave division lines, and having a surface with a step between the devices and the division lines, the method comprising: a wafer storing step of storing the wafer in a vacuum chamber; a protective sheet providing step of providing a protective sheet on the surface of the wafer before or after the wafer storing step; and a step of removing the wafer from the vacuum chamber after the wafer storing step and the protective sheet providing step. a pressure-reducing step of reducing the pressure inside the vacuum chamber, a pressure-bonding step of pressing and bonding a protective sheet against the peripheral excess region of the wafer inside the vacuum chamber after the pressure-reducing step, and a carrying-out step of opening the vacuum chamber to the atmosphere after the pressure-bonding step, bringing the protective sheet into close contact with the surface of the wafer by atmospheric pressure, and carrying out the wafer, wherein in the protective sheet providing step, water is filled into the recessed intended dividing line, and the protective sheet provided on the wafer carried out in the carrying-out step is prevented from being buried in the recessed intended dividing line by atmospheric pressure.

[0009] The protective sheet is preferably provided with an adhesive layer in an area corresponding to the peripheral excess area of ​​the wafer. In addition, after the carrying-out step, a flattening step is preferably included in which a flattening sheet is disposed on the upper surface of the protective sheet via a flexible sheet. Furthermore, after the carrying-out step, a grinding step is preferably included in which the protective sheet side is held on a chuck table and the back surface of the wafer is ground to thin it. Effect of the Invention

[0010] The method for processing a wafer of the present invention is a method for processing a wafer having a device region and a peripheral excess region surrounding the device region, the device region being partitioned into a plurality of convex devices by concave division lines, the surface having a step between the devices and the division lines, the method comprising the steps of: a wafer storing step of storing a wafer in a vacuum chamber; a protective sheet providing step of providing a protective sheet on the surface of the wafer before or after the wafer storing step; a depressurizing step of depressurizing the inside of the vacuum chamber after the wafer storing step and the protective sheet providing step; and a vacuum chamber having a vacuum chamber having a vacuum chamber and ... The method includes a bonding step in which a protective sheet is pressed against the peripheral excess area of ​​the wafer in an empty chamber to bond the protective sheet to the wafer, and a carrying-out step in which, after the bonding step, the vacuum chamber is opened to the atmosphere, the protective sheet is brought into close contact with the wafer surface by atmospheric pressure, and the wafer is carried out. In the protective sheet providing step, the recessed division lines are filled with water, and the protective sheet provided on the wafer carried out in the carrying-out step is prevented from being embedded in the recessed division lines by atmospheric pressure, thereby eliminating the problem that the protective sheet enters the recessed area, cannot withstand the atmospheric pressure, and breaks into fibers. Also, the problem of the electrode pad being deformed when the protective sheet is peeled off after the back surface of the wafer is ground is also eliminated. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2A is a wafer processed in this embodiment, and FIG. 2B is a cross-sectional view taken along line AA of the wafer shown in FIG. [Diagram 2] 2 is a perspective view showing an embodiment in which water is filled into the dividing lines of the wafer shown in FIG. 1. FIG. [Diagram 3] FIG. 11 is a perspective view showing an embodiment of a protective sheet disposing step. [Figure 4] FIG. 13 is a perspective view showing an embodiment of a wafer accommodation step. [Diagram 5] FIG. 1A is a side view (partially shown in cross section) of a vacuum chamber in which the decompression process and the bonding process are carried out; FIG. 1B is a perspective view of the wafer and protective sheet after the bonding process has been carried out; and FIG. 1C is a BB cross-sectional view of (b). [Figure 6] FIG. 1 is a perspective view illustrating an embodiment of a planarization step. [Figure 7] FIG. 2A is a perspective view showing a mode in which a wafer is placed on a chuck table of a grinding device, and FIG. 2B is a perspective view showing an embodiment of a grinding step. [Figure 8] FIG. 2 is a perspective view showing a manner in which a protective sheet, a flexible sheet, and a flattening sheet are peeled off from a wafer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of a wafer processing method according to the present invention will be described in detail with reference to the accompanying drawings.

[0013] When carrying out the wafer processing method of this embodiment, first, a wafer 10 as shown in Fig. 1(a) is prepared as a workpiece. The wafer 10 has a device region 12A in which a plurality of devices 14 are formed on a surface 10a partitioned by a division line 16, and a peripheral surplus region 12B surrounding the device region 12A (the broken line L1 partitioning the device region 12A and the peripheral surplus region 12B is an imaginary line added for convenience of explanation). As can be understood from the AA cross section of Fig. 1(a) shown in Fig. 1(b), the plurality of devices 14 formed in the device region 12A are convex and partitioned by a concave division line 16, and a step is formed between the devices 14 and the division line 16.

[0014] In the wafer processing method of this embodiment, a protective sheet providing step is carried out, which will be described below. In this protective sheet providing step, water is filled into the recessed dividing lines 16 on the front surface 10a of the wafer 10. More specifically, a water supplying means 20 as shown in FIG. 2 is prepared, and the outlet 22a of the water supply nozzle 22 is positioned above the center of the front surface 10a of the wafer 10. Next, mist water W is sprayed from the outlet 22a of the water supply nozzle 22 and supplied onto the front surface 10a. The amount of water W is at least an amount sufficient to fill the dividing lines 16 forming recesses on the front surface 10a of the wafer 10, and is an amount sufficient to be held on the front surface 10a by surface tension.

[0015] As described above, once the water W has been supplied to the front surface 10a of the wafer 10, a protective sheet T1 is placed on the front surface 10a of the wafer 10 holding the water W, as shown in Fig. 3 (protective sheet placement step). For example, a general resin backgrind tape can be used as the protective sheet T1. On the attachment surface (lower surface) of the protective sheet T1, an adhesive layer is formed in the peripheral region 18 (the outer region separated by the dashed line L2) corresponding to the peripheral excess region 12B of the wafer 10, and no adhesive layer is formed in the inner region corresponding to the device region 12A surrounded by the peripheral region 18.

[0016] As shown in Fig. 3, after the protective sheet T1 is provided on the front surface 10a of the wafer 10 holding the water W, the wafer 10 is transported to a vacuum chamber 30 (only a portion of which is shown) shown in Fig. 4 and accommodated in the vacuum chamber 30 (wafer accommodation step). When accommodating the wafer 10 in the vacuum chamber 30, the wafer 10 is positioned on the pressure bonding table 32 of the vacuum chamber 30 with the protective sheet T1 facing upward and the back surface 10b side of the wafer 10 facing downward, and is placed so that the center of the pressure bonding table 32 and the center of the wafer 10 coincide with each other. In the above embodiment, the protective sheet provision step is performed before the wafer accommodation step is performed, but the present invention is not limited to this, and the protective sheet provision step may be performed in the vacuum chamber 30 after the wafer accommodation step is performed.

[0017] The vacuum chamber 30 will be described in more detail with reference to FIG. 5(a). The vacuum chamber 30 includes a chamber case 31 (shown in cross section for convenience of explanation) in which the above-mentioned pressure bonding table 32 is arranged, and a suction port 33, an opening 34, and a pressing means 35 are arranged in the upper part of the chamber case 31. The suction port 33 is connected to a vacuum pump P, and the opening 34 is open to the atmosphere via an opening / closing valve V. When the air in the vacuum chamber 30 is reduced in pressure to create a vacuum state in the vacuum chamber 30, the opening / closing valve V is closed and the vacuum pump P is operated. When the vacuum state in the vacuum chamber 30 is released, the opening / closing valve V is gradually opened to introduce the atmosphere. The pressing means 35 is arranged in the upper center of the vacuum chamber 30, and includes a drive shaft 35a that penetrates the chamber case 31 and extends in the vertical direction, and a pressing part 35b that is arranged at the lower end of the drive shaft 35a and has an annular opening edge part 35c that is open downward. An elevating means (not shown) for vertically elevating the pressing portion 35b is provided on the upper portion of the drive shaft 35a. The drive shaft 35a is supported by a bearing 36 provided in the chamber case 31. The bearing 36 is a bearing that allows the drive shaft 35a to move vertically while sealing the space between the inside and outside of the chamber case 31.

[0018] The pressing means 35 is arranged so that the center of the annular opening edge portion 35c constituting the pressing portion 35b coincides with the center of the pressure bonding table 32 when viewed in a plane, and the opening edge portion 35c is formed with a shape and dimensions corresponding to the peripheral excess region 12B of the wafer 10 described above.

[0019] As described above, after the protective sheet providing step and the wafer accommodation step have been performed, the vacuum pump P is operated with the on-off valve V closed to reduce the pressure inside the vacuum chamber 30 (pressure reduction step).

[0020] Next, the lifting means is operated to lower the pressing portion 35b in the direction indicated by the arrow R1 relative to the wafer 10 placed on the pressure table 32 in the vacuum chamber 30, and the opening edge 35c of the pressing portion 35b is pressed against the outer peripheral region 18 of the protective sheet T1 disposed on the wafer 10. As described above, the opening edge 35c of the pressing portion 35b is formed with a shape and dimensions corresponding to the outer peripheral excess region 12B of the wafer 10, and as shown in FIG. 5(b), the outer peripheral region 18 of the protective sheet T1 is pressure-bonded to the outer peripheral excess region 12B of the wafer 10 (pressure-bonding process). An adhesive layer is formed on the lower surface side of the outer peripheral region 18 of the protective sheet T1, and the outer peripheral excess region 12B of the wafer 10 and the outer peripheral region 18 of the protective sheet T1 are firmly attached to each other. As a result, as shown in Fig. 5(c), the water W filled in the division line 16 between the adjacent devices 14 formed on the front surface 10a of the wafer 10 is confined by the protective sheet T1. In the above embodiment, the protective sheet T1 is pressed from above onto the adhesive layer formed on the lower surface of the outer peripheral region 18 of the protective sheet T1 to be pressure-bonded to the front surface 10a of the wafer 10, but the present invention is not limited thereto. For example, the protective sheet T1 may be formed of a thermocompression sheet that exerts adhesive force when heated, and a heating means may be provided in the pressing portion 35b of the pressing means 35 to thermocompress the outer peripheral region 18 of the protective sheet T1 from above, thereby carrying out the pressure-bonding step.

[0021] After the above-mentioned pressure bonding step, the operation of the vacuum pump P is stopped, the opening / closing valve V connected to the opening 34 shown in Fig. 5(a) is gradually opened, and the above-mentioned lifting means is operated to raise the pressing part 35b. As a result, air is introduced into the vacuum chamber 30, and the protective sheet T1 is brought into close contact with the front surface 10a of the wafer 10 by the atmospheric pressure, and the wafer 10 is carried out of the vacuum chamber 30 (carrying out step).

[0022] In this embodiment, the wafer 10 removed from the vacuum chamber 30 as described above is placed on an appropriate work table 40 as shown in FIG. 6, and a flexible sheet T2 that absorbs the irregularities of the front surface 10a of the wafer 10 and a flattening sheet T3 are disposed on the protective sheet T1 that is in close contact with the wafer 10. When the flexible sheet T2 and the flattening sheet T3 are disposed on the protective sheet T1, for example, a member having fluidity and adhesiveness can be used as the flexible sheet T2, and for example, a hard resin sheet can be used as the flattening sheet T3. The flexible sheet T2 is not limited to being in a sheet shape from the beginning, and may be formed into a sheet shape by applying a liquid resin onto the protective sheet T1.

[0023] In this embodiment, after the above-mentioned flattening step is performed, a grinding step is performed in which the back surface 10b of the wafer 10 is ground to thin it. More specifically, the wafer 10 to which the protective sheet T1, the flexible sheet T2, and the flattening sheet T3 are attached is transported to a grinding device 50 (only a part of which is shown) shown in FIG. 7(a). The grinding device 50 is provided with a chuck table 51 having a holding surface 52. The chuck table 51 is provided with a rotation drive means (not shown). The holding surface 52 of the chuck table 51 is formed of a breathable member, and is connected to a suction means (not shown). By operating the suction means, a negative pressure is generated on the holding surface 52. The wafer 10 transported to the grinding device 50 is inverted as shown in the figure, and placed on the chuck table 51 with the flattening sheet T3 side facing downward and the back surface 10b side of the wafer 10 facing upward, and is held by suction.

[0024] 7(b), the grinding device 50 is provided with a grinding means 53. The grinding means 53 includes a rotating spindle 54 rotated by a rotation drive mechanism (not shown), a wheel mount 55 attached to the lower end of the rotating spindle 54, and a grinding wheel 56 attached to the lower surface of the wheel mount 55. A plurality of grinding stones 57 are arranged in an annular shape on the lower surface of the grinding wheel 56.

[0025] After the wafer 10 is suction-held on the chuck table 51, the rotating spindle 54 of the grinding means 53 is rotated in the direction indicated by the arrow R2 in FIG. 7(b) at, for example, 6000 rpm, and the chuck table 51 is rotated in the direction indicated by the arrow R3 at, for example, 300 rpm. Then, while supplying grinding water onto the back surface 10b of the wafer 10 by a grinding water supplying means (not shown), the grinding wheel 57 is brought into contact with the back surface 10b of the wafer 10, and the grinding wheel 56 is fed for grinding in the direction indicated by the arrow R4 (downward) at, for example, a speed of 1.0 μm / sec. At this time, the grinding can be advanced while measuring the amount of grinding of the wafer 10 by a contact-type measuring gauge (not shown). When the back surface 10b of the wafer 10 is ground by a predetermined amount to thin the wafer 10 to a predetermined thickness, the grinding means 53 is stopped, and the grinding process is completed through cleaning, drying, etc.

[0026] After the grinding process is completed, as shown in FIG. 8, the back surface 10b of the wafer 10 is placed in an opening Fa of an annular frame F that can accommodate the wafer 10, with the back surface 10b facing downward, and the wafer 10 is attached to an adhesive tape T4 and held by the frame F via the adhesive tape T4. After that, the protective sheet T1, the flexible sheet T2, and the flattening sheet T3 are peeled off from the front surface 10a of the wafer 10 to expose the front surface 10a. After the front surface 10a is exposed, the water W filled in the front surface 10a is appropriately removed, and the wafer 10 held by the frame F is transported to a dicing device or a laser processing device to perform a division process in which the wafer 10 is divided into individual device chips.

[0027] According to the above-described embodiment, when performing the protective sheet disposing step of disposing the protective sheet T1 on the front surface 10a of the wafer 10, the water W is filled into the recessed division line 16 formed between adjacent devices 14. Then, the protective sheet T1 is disposed thereon and is brought into close contact with the front surface 10a of the wafer 10 by atmospheric pressure, so that the protective sheet T1 is prevented from being embedded in the recessed division line by atmospheric pressure, and the problem that the protective sheet T1 enters the recessed area and cannot withstand the atmospheric pressure and breaks into fibers is solved.

[0028] In addition, in the above-mentioned embodiment, a flattening process is carried out in which protective sheet T1 is placed on the front surface 10a of the wafer 10 and flattening sheet T3 is placed on the upper surface of the protective sheet T1 via flexible sheet T2. As a result, unevenness on the front surface 10a of the wafer 10 is absorbed by the flexible sheet T2 and the front surface 10a side is supported flatly, allowing the back surface 10b of the wafer 10 to be uniformly ground. In addition, since the protective sheet T1 is not broken into fibers as described above, even if an electrode pad is present on the intended division line 16, the problem of the electrode pad being deformed when the protective sheet T1 is peeled off from the front surface 10a of the wafer 10 is eliminated. [Explanation of symbols]

[0029] 10: Wafer 10a: surface 10b: Back side 12A: Device area 12B: Surplus outer area 14: Device 16: Planned division line 18: Outer area 20:Water supply means 22: Water supply nozzle 22a: Nozzle 30: Vacuum chamber 31: Chamber case 32: Crimping table 33: Suction port 34: Open mouth 35: Pressing means 35a: Drive shaft 35b: Pressing part 35c: Opening edge 36: Bearings 50: Grinding equipment 51: Chuck table 52: Holding surface 53: Grinding means 54: Rotating spindle 55: Wheel mount 56: Grinding wheel 57: Grinding wheel T1: Protective sheet T2: Flexible sheet T3: Flattening sheet T4: Adhesive tape F: Frame P: Vacuum pump W:Water

Claims

1. A method for processing a wafer having a device region and a peripheral excess region surrounding the device region, the device region being partitioned into a plurality of convex devices by concave division lines, the wafer having a surface having a step between the devices and the division lines, the method comprising the steps of: a wafer accommodation step of accommodating a wafer in a vacuum chamber; a protective sheet providing step of providing a protective sheet on the front surface of the wafer before or after the wafer accommodation step; a depressurizing step of depressurizing the inside of the vacuum chamber after the wafer accommodation step and the protective sheet arrangement step; a pressure-bonding step of pressing and bonding a protective sheet to the peripheral excess region of the wafer in the vacuum chamber after the pressure-reducing step; and a carrying-out step of opening the vacuum chamber to the atmosphere after the pressure bonding step, bringing the protective sheet into close contact with the surface of the wafer by atmospheric pressure, and carrying out the wafer, In the protective sheet disposing step, the recessed dividing line is filled with water, thereby preventing the protective sheet disposed on the wafer unloaded in the unloading step from being buried in the recessed dividing line due to atmospheric pressure.

2. 2. The method for treating a wafer according to claim 1, wherein the protective sheet has an adhesive layer in an area corresponding to the peripheral excess area of ​​the wafer.

3. 3. The method for treating a wafer according to claim 1, further comprising a planarizing step of disposing a planarizing sheet on the upper surface of the protective sheet via a flexible sheet after the unloading step.

4. 4. The method for treating a wafer according to claim 1, further comprising a grinding step of grinding a back surface of the wafer to thin it, while holding the protective sheet side on a chuck table after the carrying-out step.

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