JP2021048288A - Wafer processing method - Google Patents

Abstract

To provide a wafer manufacturing method that can prevent device chips from scattering when a wafer is divided into individual device chips and can prevent deterioration in quality of the device chips.SOLUTION: A wafer processing method includes at least a divisional groove forming step of forming divisional grooves 18 having a depth corresponding to a finished thickness of device chips 42 on planned division lines 4, a wettability enhancing step of radiating ultraviolet rays onto a front surface 2a of the wafer 2 on which the divisional grooves 18 have been formed, thereby enhancing the wettability of the front surface 2a of the wafer 2, a thermocompression bonding step of placing and heating a thermocompression bonding sheet 22 on the front surface 2a of the wettability-enhanced wafer 2, and pressing the thermocompression bonding sheet 22 to crimp the thermocompression bonding sheet 22 onto the front surface 2a of the wafer 2, and a grinding step of holding a thermocompression bonding sheet 22 side by a chuck table 28 of a grinding device 26, and grinding a back surface 2b of the wafer 2 to expose the divisional grooves 18 to the back surface 2b of the wafer 2, thereby dividing the wafer into individual device chips 42.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method for processing a wafer in which a plurality of devices are partitioned by a scheduled division line and a wafer formed on the surface is divided into individual device chips.

A wafer in which a plurality of devices such as ICs and LSIs are divided by a scheduled division line and formed on the surface is divided into individual device chips by a dicing device, and each divided device chip is used for an electric device such as a mobile phone or a personal computer. It will be used.

Further, a dividing groove having a depth corresponding to the thickness of the device chip is formed on the planned division line, and then a protective tape is arranged on the surface of the wafer to grind the back surface of the wafer to expose the dividing groove on the back surface of the wafer. A technique called so-called pre-dicing, in which the wafer is divided into individual device chips, has been proposed (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 11-405250

However, although it is possible to reduce the thickness of the device chip by pre-dicing, when a wafer having a device chip size of 1 mm square or less (for example, 30 μm square, thickness 20 μm) is divided into individual device chips, There is a problem that swelling occurs between the device chips and the device chips are chipped, resulting in deterioration of quality.

Further, as a method for solving the above-mentioned problems, a protective tape having an ultraviolet curable adhesive layer is attached to the surface of the wafer, and then a slight amount of ultraviolet rays is irradiated from the protective tape side to cure the adhesive layer. Although the swell between the device chip and the device chip on the adhesive layer of the protective tape can be reduced, there is a problem that the device chip is peeled off from the adhesive layer of the protective tape and scattered due to the decrease in adhesive strength.

The problem of the present invention made in view of the above facts is that it is possible to prevent the device chips from scattering when the wafer is divided into individual device chips, and it is possible to prevent the quality of the device chips from deteriorating. To provide a processing method for wafers.

The present invention provides the following wafer processing method in order to solve the above problems. That is, it is a method of processing a wafer in which a plurality of devices are partitioned by a scheduled division line and the wafer formed on the surface is divided into individual device chips, and a dividing groove having a depth corresponding to the finished thickness of the device chip is divided. A step of forming a split groove formed on a planned line, a step of improving the wettability of the surface of the wafer by irradiating the surface of the wafer on which the split groove is formed with ultraviolet rays, and a step of improving the wettability of the surface of the wafer, and the surface of the wafer having improved wettability. A thermocompression bonding sheet is placed on the wafer, heated and pressed to press the thermocompression bonding sheet onto the surface of the wafer, and the surface of the wafer is held by the chuck table of the grinding device to grind the back surface of the wafer. The present invention provides a method for processing a wafer, which comprises at least a grinding step in which the dividing groove is exposed on the back surface of the wafer and divided into individual device chips.

The thermocompression bonding sheet is preferably a polyolefin-based sheet or a polyester-based sheet. It is convenient that the thermocompression bonding sheet is either a polyethylene sheet, a polypropylene sheet or a polystyrene sheet among the polyolefin-based sheets. The heating temperature of the thermocompression bonding sheet in the thermocompression bonding step is 120 ° C. to 140 ° C. when the thermocompression bonding sheet is a polyethylene sheet, and 160 ° C. to 180 ° C. when the thermocompression bonding sheet is a polypropylene sheet. The temperature is preferably 220 ° C. to 240 ° C. when the thermocompression bonding sheet is the polystyrene sheet. The thermocompression bonding sheet is preferably either a polyethylene terephthalate sheet or a polyethylene naphthalate sheet among the polyester-based sheets. The heating temperature of the thermocompression bonding sheet in the thermocompression bonding step is 250 ° C. to 270 ° C. when the thermocompression bonding sheet is the polyethylene terephthalate sheet, and 160 when the thermocompression bonding sheet is the polyethylene naphthalate sheet. It is convenient that the temperature is between ° C. and 180 ° C.

The wafer processing method of the present invention includes a split groove forming step of forming a split groove having a depth corresponding to the finished thickness of the device chip on the planned split line, and irradiating the surface of the wafer on which the split groove is formed with ultraviolet rays. A thermocompression bonding sheet is placed on the surface of the wafer with improved wettability, and the surface of the wafer is heated and pressed to press the thermocompression bonding sheet against the surface of the wafer. At least from the thermocompression bonding process, the thermocompression bonding sheet side is held by the chuck table of the grinding device, the back surface of the wafer is ground, and the dividing groove is exposed on the back surface of the wafer and divided into individual device chips. Since it is configured, it is possible to prevent the device chip from scattering from the thermocompression bonding sheet when the wafer is divided into individual device chips in the grinding process, and the device chip and the device chip are placed on the thermocompression bonding sheet. It is possible to suppress swelling between the device chips and the device chips without chipping, and it is possible to prevent deterioration of the quality of the device chips.

Perspective view of the wafer. (A) A perspective view showing a state in which the dividing groove forming step is performed, and (b) a perspective view of a wafer in which the dividing groove is formed. The perspective view which shows the state which carries out the wettability improvement process. (A) A perspective view showing a state in which a thermocompression bonding sheet is arranged on the surface of a wafer, and (b) a perspective view showing a state in which the thermocompression bonding sheet is heated. (A) A perspective view showing a state in which the grinding process is performed, and (b) a perspective view of a wafer divided into individual device chips. The perspective view which shows the state which carried out the wafer transfer process.

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

FIG. 1 shows a disc-shaped wafer 2 processed by the wafer processing method of the present invention. The wafer 2 of the illustrated embodiment is formed of silicon (Si). The surface 2a of the wafer 2 is divided into a plurality of rectangular regions by a grid-like division schedule line 4, and devices 6 such as ICs and LSIs are formed in each of the plurality of rectangular regions.

In the wafer processing method of the illustrated embodiment, first, a dividing groove forming step of forming a dividing groove having a depth corresponding to the finished thickness of the device chip on the planned division line 4 is performed. The dividing groove forming step can be carried out, for example, by using the dicing device 8 shown in part in FIG.

The dicing device 8 includes a chuck table 10 that sucks and holds the wafer 2 and a cutting means 12 that cuts the wafer 2 that is sucked and held by the chuck table 10. The chuck table 10 is configured to be rotatable around an axis extending in the vertical direction, and is configured to be movable in the X-axis direction indicated by the arrow X in FIG. The cutting means 12 includes a spindle 14 rotatably configured around the Y-axis direction (direction indicated by the arrow Y in FIG. 2) orthogonal to the X-axis direction, and an annular cutting blade fixed to the tip of the spindle 14. 16 and are included. The plane defined by the X-axis direction and the Y-axis direction is substantially horizontal.

In the dividing groove forming step, first, the wafer 2 is sucked and held on the upper surface of the chuck table 10 with the surface 2a of the wafer 2 facing upward. Next, the wafer 2 is imaged from above by the imaging means (not shown) of the dicing apparatus 8, and the scheduled division line 4 is aligned in the X-axis direction based on the image of the wafer 2 captured by the imaging means. The planned division line 4 aligned in the X-axis direction is positioned below the cutting blade 16.

Next, the cutting edge of the cutting blade 16 rotated at high speed in the direction indicated by the arrow A in FIG. 2 is cut into the planned division line 4 from the surface 2a side of the wafer 2 to a depth corresponding to the finished thickness of the device chip. A split groove forming process is performed in which the chuck table 10 is processed and fed relative to the cutting means 12 in the X-axis direction. As a result, the dividing groove 18 having a depth corresponding to the thickness of the device chip can be formed in the wafer 2 along the scheduled division line 4.

Next, the division groove forming process is repeated while indexing and feeding the cutting blade 16 relative to the chuck table 10 in the Y-axis direction by the distance in the Y-axis direction of the planned division line 4, and aligning the cutting blade 16 in the X-axis direction. A dividing groove 18 is formed along all of the planned division lines 4. Further, after rotating the chuck table 10 by 90 degrees, the division groove forming process is repeated while indexing and feeding, and as shown in FIG. 2B, the division orthogonal to the planned division line 4 in which the division groove 18 is formed earlier is formed. Dividing grooves 18 are formed along all of the planned lines 4. In this way, the dividing groove 18 having a depth corresponding to the finished thickness of the device chip is formed in the grid-like division scheduled line 4.

After carrying out the dividing groove forming step, the wettability improving step of irradiating the surface 2a of the wafer 2 on which the dividing groove 18 is formed with ultraviolet rays to improve the wettability of the surface 2a of the wafer 2 is carried out.

In the wettability improving step, as shown in FIG. 3, first, the wafer 2 is positioned below the ultraviolet irradiation device 20 with the front surface 2a of the wafer 2 facing upward and the back surface 2b facing downward. Next, the surface 2a of the wafer 2 is irradiated with ultraviolet rays from the ultraviolet irradiation device 20 (for example, irradiation with an output of 100 W for about 1 to 2 minutes). As a result, organic substances and the like existing on the surface 2a of the wafer 2 can be removed, and the wettability of the surface 2a can be improved.

After carrying out the wettability improving step, a thermocompression bonding step is performed in which a thermocompression bonding sheet is arranged on the surface 2a of the wafer 2 having improved wettability, heated and pressed to press the thermocompression bonding sheet onto the surface 2a of the wafer 2. carry out.

In the thermocompression bonding step, first, as shown in FIG. 4A, a circular thermocompression bonding sheet 22 having the same diameter as the wafer 2 is arranged on the surface 2a of the wafer 2. The thermocompression bonding sheet 22 is a sheet that exhibits adhesive strength and softens when heated to an appropriate temperature, and the thickness of the thermocompression bonding sheet 22 may be about 20 to 100 μm.

As the thermocompression bonding sheet 22, a polyolefin-based sheet or a polyester-based sheet can be used. Examples of the polyolefin-based sheet that can be used as the thermocompression bonding sheet 22 include a polyethylene (PE) sheet, a polypropylene (PP) sheet, and a polystyrene (PS) sheet. Further, examples of the polyester-based sheet that can be used as the thermocompression bonding sheet 22 include a polyethylene terephthalate sheet (PET) and a polyethylene naphthalate (PEN) sheet. The thermocompression bonding sheet 22 does not have an adhesive layer (glue layer).

After arranging the thermocompression bonding sheet 22 on the surface 2a of the wafer 2, as shown in FIG. 4B, the thermocompression bonding sheet 22 is subjected to a heating roller 24 adjusted to a temperature at which the thermocompression bonding sheet 22 exhibits adhesive strength and softens. By rolling the heating roller 24 while pressing downward, the thermocompression bonding sheet 22 is heated and softened, and the thermocompression bonding sheet 22 exerts an adhesive force. The thermocompression bonding sheet 22 softened by this is brought into close contact with the surface 2a of the wafer 2, and the thermocompression bonding sheet 22 is pressure-bonded to the surface 2a of the wafer 2 by the adhesive force of the thermocompression bonding sheet 22.

The heating roller 24 shown in FIG. 4B includes an electric heater and a temperature sensor (neither of which is shown), and the temperature of the outer peripheral surface of the heating roller 24 is adjusted by an appropriate control device. .. The outer peripheral surface of the heating roller 24 is coated with fluororesin so that the thermocompression bonding sheet 22 does not stick to the heating roller 24 even if the thermocompression bonding sheet 22 exerts its adhesive strength.

The heating temperature of the thermocompression bonding sheet 22 (polyolefin sheet) in the thermocompression bonding step is 120 ° C. to 140 ° C. when the thermocompression bonding sheet 22 is a polyethylene sheet, and 160 ° C. when the thermocompression bonding sheet 22 is a polypropylene sheet. The temperature is about 180 ° C., and when the thermocompression bonding sheet 22 is a polystyrene sheet, the temperature is preferably 220 ° C. to 240 ° C.

The heating temperature of the thermocompression bonding sheet 22 (polyester-based sheet) in the thermocompression bonding step is 250 ° C. to 270 ° C. when the thermocompression bonding sheet 22 is a polyethylene terephthalate sheet, and when the thermocompression bonding sheet 22 is a polyethylene naphthalate sheet. Is preferably 160 ° C to 180 ° C.

In the thermocompression bonding step, the thermocompression bonding sheet 22 is bonded to the surface 2a of the wafer 2 in a state where the wettability of the surface 2a of the wafer 2 is improved, so that the bonding force between the surface 2a of the wafer 2 and the thermocompression bonding sheet 22 is applied. Is stronger than the bonding force when the thermocompression bonding sheet 22 is pressure-bonded to the surface 2a of the wafer 2 in a state where the wettability of the surface 2a of the wafer 2 is not improved.

After performing the thermocompression bonding step, the thermocompression bonding sheet 22 side is held by the chuck table of the grinding device, the back surface 2b of the wafer 2 is ground, and the dividing groove 18 is exposed on the back surface 2b of the wafer 2 to form individual device chips. Carry out a grinding process to divide. The grinding step can be carried out, for example, by using the grinding device 26 shown in part in FIG.

The grinding device 26 includes a chuck table 28 that sucks and holds the wafer 2 and a grinding means 30 that grinds the wafer 2 that is sucked and held by the chuck table 28. The chuck table 28 that sucks and holds the wafer 2 on the upper surface is rotatably configured around an axis extending in the vertical direction. The grinding means 30 includes a spindle 32 rotatably configured about the vertical direction as an axis, and a disc-shaped wheel mount 34 fixed to the lower end of the spindle 32. An annular grinding wheel 38 is fixed to the lower surface of the wheel mount 34 by bolts 36. A plurality of grinding wheels 40 arranged in an annular shape at intervals in the circumferential direction are fixed to the outer peripheral edge of the lower surface of the grinding wheel 38.

Continuing the description with reference to FIG. 5, in the grinding process, first, the back surface 2b of the wafer 2 is turned upward, and the wafer 2 is sucked and held from the protective member 22 side on the upper surface of the chuck table 28. Next, the chuck table 28 is rotated at a predetermined rotation speed (for example, 300 rpm) counterclockwise when viewed from above. Further, the spindle 32 is rotated at a predetermined rotation speed (for example, 6000 rpm) counterclockwise when viewed from above.

Next, the spindle 32 is lowered by an elevating means (not shown) of the grinding device 26, and the grinding wheel 40 is brought into contact with the back surface 2b of the wafer 2. Then, the spindle 32 is lowered at a predetermined grinding feed rate (for example, 1.0 μm / s). As a result, as shown in FIG. 5B, the back surface 2b of the wafer 2 can be ground to expose the dividing groove 18 on the back surface 2b of the wafer 2, and the wafer 2 can be divided into individual device chips 42.

After performing the grinding step, as shown in FIG. 6, a wafer transfer step of transferring a plurality of device chips 42 to the adhesive tape 46 arranged in the opening 44a of the annular frame 44 while maintaining the form of the wafer 2. To carry out. In the wafer transfer step, first, the plurality of device chips 42 are attached to the adhesive tape 46 with the surface 2a side (device 6 side) of the wafer 2 facing upward. Next, the thermocompression bonding sheet 22 is removed from the device chip 42.

As described above, in the wafer processing method of the illustrated embodiment, the thermocompression bonding sheet 22 is thermocompression bonded to the surface 2a of the wafer 2 having improved wettability, and the wettability of the surface 2a of the wafer 2 is improved. Since the surface 2a of the wafer 2 and the thermocompression bonding sheet 22 are more strongly bonded than when the thermocompression bonding sheet 22 is pressure-bonded to the surface 2a of the wafer 2 in the non-exposed state, the wafer 2 is attached to the individual device chips 42 in the grinding process. It is possible to prevent the device chip 42 from scattering from the thermocompression bonding sheet 22 when the wafer is divided into two. Further, since the thermocompression bonding sheet 22 does not have an adhesive layer, it is possible to suppress swelling between the device chip 42 and the device chip 42 on the thermocompression bonding sheet 22, and the device chip 42 is not chipped. It is possible to prevent deterioration of the quality of the device chip 42.

2: Wafer 2a: Wafer front surface 2b: Wafer back surface 4: Scheduled division line 6: Device 18: Division groove 22: Thermocompression bonding sheet 26: Grinding device 28: Chuck table 42: Device chip

Claims (6)

It is a processing method of a wafer in which a plurality of devices are partitioned by a scheduled division line and the wafer formed on the surface is divided into individual device chips.
A dividing groove forming step of forming a dividing groove having a depth corresponding to the finished thickness of the device chip on the planned division line, and
A wettability improving step of irradiating the surface of the wafer on which the dividing groove is formed with ultraviolet rays to improve the wettability of the surface of the wafer.
A thermocompression bonding process in which a thermocompression bonding sheet is placed on the surface of the wafer with improved wettability, heated and pressed to press the thermocompression bonding sheet onto the surface of the wafer.
A grinding process in which the thermocompression bonding sheet side is held by a chuck table of a grinding device, the back surface of the wafer is ground, and the dividing groove is exposed on the back surface of the wafer to be divided into individual device chips.
Wafer processing method consisting of at least. The method for processing a wafer according to claim 1, wherein the thermocompression bonding sheet is a polyolefin-based sheet or a polyester-based sheet. The method for processing a wafer according to claim 2, wherein the thermocompression bonding sheet is any one of a polyethylene sheet, a polypropylene sheet, and a polystyrene sheet among the polyolefin-based sheets. The heating temperature of the thermocompression bonding sheet in the thermocompression bonding step is 120 ° C. to 140 ° C. when the thermocompression bonding sheet is a polyethylene sheet, and 160 ° C. to 180 ° C. when the thermocompression bonding sheet is a polypropylene sheet. The method for processing a wafer according to claim 3, wherein the temperature is 220 ° C to 240 ° C when the thermocompression bonding sheet is a polystyrene sheet. The method for processing a wafer according to claim 2, wherein the thermocompression bonding sheet is either a polyethylene terephthalate sheet or a polyethylene naphthalate sheet among the polyester-based sheets. The heating temperature of the thermocompression bonding sheet in the thermocompression bonding step is 250 ° C. to 270 ° C. when the thermocompression bonding sheet is the polyethylene terephthalate sheet, and 160 when the thermocompression bonding sheet is the polyethylene naphthalate sheet. The method for processing a wafer according to claim 5, wherein the temperature is between ° C. and 180 ° C.

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