JP2021048287A - Wafer processing method - Google Patents

Abstract

To provide a wafer processing method that, in dividing a wafer into individual device chips, is capable of preventing the device chips from being dispersed and capable of preventing quality of the device chips from being reduced.SOLUTION: A wafer processing method is constituted by at least: a division groove forming step of forming a division groove 18 having a depth corresponding to a finish thickness of a device chip 42, on a division scheduled line 4; a wettability improving step of radiating ultraviolet light to a surface 2a of a wafer 2 on which the division groove 18 is formed to improve wettability of the surface 2a of the wafer 2; a protective tape sticking step of sticking a protective tape 22 having an ultraviolet curing adhesive layer on the surface 2a of the wafer 2 having improved wettability; an adhesive layer curing step of slightly radiating ultraviolet light from the protective tape 22 side to slightly cure the adhesive layer; and a grinding step of holding the protective tape 22 side using a chuck table 28 of a grinding device 26, grinding a rear surface 2b of the wafer 2 to expose the division groove 18 on the rear surface 2b of the wafer 2, and 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. A protective tape affixing step of attaching a protective tape having an ultraviolet curable adhesive layer to the wafer, an adhesive layer curing step of slightly irradiating the adhesive layer with ultraviolet rays from the protective tape side to slightly cure the adhesive layer, and a protective tape side. Is held by the chuck table of the grinding device, the back surface of the wafer is ground, the dividing groove is exposed on the back surface of the wafer, and the wafer is divided into individual device chips. The invention provides.

The method for processing a wafer 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 a scheduled split line, and irradiating the surface of the wafer on which the split groove is formed with ultraviolet rays. The wettability improving step of improving the wettability of the surface of the wafer, the protective tape sticking step of sticking a protective tape having an ultraviolet curable adhesive layer on the surface of the wafer with improved wettability, and the protective tape side. The adhesive layer curing step of slightly irradiating the adhesive layer with ultraviolet rays to slightly cure the adhesive layer, and the protective tape side is held by the chuck table of the grinding device to grind the back surface of the wafer and the dividing groove is displayed on the back surface of the wafer. Since it is composed of at least a grinding process in which the wafer is taken out and divided into individual device chips, even if the protective tape is slightly irradiated with ultraviolet rays in the adhesive layer curing process, the required adhesion between the wafer and the protective tape is required. Since the force is maintained, it is possible to prevent the device chip from scattering from the protective tape in the grinding process. Further, in the processing method of the wafer of the present invention, it is possible to suppress the swell between the device chips on the protective tape so that the device chips are not chipped when the wafer is divided into individual device chips. Since the adhesive layer of the protective tape is slightly cured to the extent possible, deterioration of the quality of the device chip can be prevented.

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 the protective tape attaching process is being carried out, and (b) a perspective view showing a state in which the protective tape is brought into close contact with the wafer by a roller. The perspective view which shows the state which carries out the adhesive layer hardening process. (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, as shown in FIG. 4, a protective tape sticking step of sticking the protective tape 22 having the ultraviolet curable adhesive layer on the surface 2a of the wafer 2 having the improved wettability is carried out. The protective tape 22 for protecting the device 6 has a circular shape having the same diameter as the diameter of the wafer 2. In the protective tape attaching step, after the protective tape 22 is attached to the surface 2a of the wafer 2, as shown in FIG. 4B, the roller 24 is rolled while pressing the protective tape 22 against the wafer 2 with an appropriate roller 24. , The protective tape 22 is brought into close contact with the surface 2a of the wafer 2.

Since the protective tape sticking step is carried out in a state where the wettability of the surface 2a of the wafer 2 is improved, between the surface 2a of the wafer 2 and the adhesive layer of the protective tape 22 after the protective tape sticking step is carried out. The adhesive strength is stronger than the adhesive strength when the protective tape 22 is attached 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 carrying out the protective tape sticking step, the adhesive layer curing step of slightly irradiating the protective tape 22 side with ultraviolet rays to slightly cure the adhesive layer is carried out.

In the adhesive layer curing step, as shown in FIG. 5, the wafer 2 is first positioned below the ultraviolet irradiation device 20 with the wafer 2 facing downward and the protective tape 22 facing upward. Next, the device chip is not chipped when the wafer 2 is divided into individual device chips in the grinding step described later by slightly irradiating the ultraviolet irradiation device 20 with ultraviolet rays (for example, irradiating with an output of 100 W for about 2 seconds). As described above, the adhesive layer of the protective tape 22 is slightly cured to such an extent that the swell between the device chips on the protective tape 22 can be suppressed.

The adhesive force between the wafer 2 and the protective tape 22 after the adhesive layer curing step is performed will be described. As described above, in the protective tape attaching step, the protective tape 22 is attached to the surface 2a of the wafer 2 in a state where the wettability of the surface 2a of the wafer 2 is improved, and the wettability of the surface 2a of the wafer 2 is improved. The adhesive strength between the wafer 2 and the protective tape 22 is stronger than when the protective tape 22 is attached to the surface 2a of the wafer 2 in the unfinished state. Further, in the adhesive layer curing step, if the adhesive layer of the protective tape 22 is slightly cured by irradiation with ultraviolet rays, the adhesive force between the wafer 2 and the protective tape 22 is slightly reduced. At this time, the adhesive force between the wafer 2 and the protective tape 22 after performing the adhesive layer curing step is such that the wettability of the surface 2a of the wafer 2 is not improved, and the protective tape 22 is applied to the surface 2a of the wafer 2. The adhesive layer of the protective tape 22 is slightly cured by irradiation with ultraviolet rays so that the adhesive strength between the wafer 2 and the protective tape 22 when the wafer is attached is about the same. As a result, the required adhesive force is maintained between the wafer 2 and the protective tape 22, so that it is possible to prevent the device chip from scattering from the protective tape 22 in the grinding process described later.

After performing the adhesive layer curing step, the protective tape 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. 6, 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. 6B, 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. 7, 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. The protective tape 22 is then removed from the device chip 42.

As described above, in the wafer processing method of the illustrated embodiment, the protective tape 22 having an ultraviolet curable adhesive layer is attached to the surface 2a of the wafer 2 whose wettability is improved by irradiation with ultraviolet rays, so that it is adherent. In the layer curing step, even if the protective tape 22 is slightly irradiated with ultraviolet rays to slightly cure the adhesive layer of the protective tape 22, the required adhesion between the surface 2a of the wafer 2 and the adhesive layer of the protective tape 22 is required. Power is maintained. Therefore, in the wafer processing method of the illustrated embodiment, it is possible to prevent the device chip 42 from scattering from the protective tape 22 when the wafer 2 is divided into individual device chips 42 in the grinding process.

Further, in the wafer processing method of the illustrated embodiment, the device chip 42 and the device chip 42 on the protective tape 22 are provided so that the device chip 42 is not chipped when the wafer 2 is divided into individual device chips 42. Since the adhesive layer of the protective tape 22 is slightly cured to the extent that swelling between them can be suppressed, deterioration of the quality of the device chip 42 can be prevented.

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

Claims (1)

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 protective tape application process in which a protective tape having an ultraviolet curable adhesive layer is attached to the surface of a wafer with improved wettability.
An adhesive layer curing step in which the adhesive layer is slightly cured by slightly irradiating ultraviolet rays from the protective tape side, and
A grinding process in which the protective tape side is held by the chuck table of the grinding device, the back surface of the wafer is ground, the dividing groove is exposed on the back surface of the wafer, and the wafer is divided into individual device chips.
Wafer processing method consisting of at least.

Images