JP2022075072A - Processing method for wafer - Google Patents

Abstract

To provide a processing method for a wafer, using a grinding device that does not uselessly consume loose abrasive grains and does not deteriorate productivity.SOLUTION: A processing method for a wafer comprises: a pseudo-grinding step of bringing a grinding surface 35a of an abrasive pad 35 into contact with a holding surface 53 of a chuck table 52, and performing pseudo-grinding the holding surface of the chuck table as if grinding a wafer, while supplying water L instead of loose abrasive grains; and a wafer holding step of, after the pseudo-grinding step, holding the wafer on the holding surface of the chuck table; and a grinding step of grinding the wafer while supplying the loose abrasive grains to the wafer held on the chuck table.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method for processing a wafer by a polishing device.

A wafer in which a plurality of devices such as ICs and LSIs are partitioned by a planned division line and formed on the front surface is formed by grinding the back surface with a grinding device to form a predetermined thickness, and then the back surface of the wafer is polished by a polishing device. By removing the grinding marks, the anti-folding strength after being divided into individual device chips by the dicing device is enhanced, and it is used for electric devices such as mobile phones and personal computers.

The polishing device for polishing the back surface of the wafer is a polishing device that polishes the back surface of the polishing pad while supplying a chuck table having a holding surface for holding the wafer and a slurry containing free abrasive grains to the wafer held on the chuck table. With at least means, the grinding marks can be efficiently removed from the back surface of the wafer (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 08-09265

By the way, the polishing pad of the polishing device is made of a material that causes elastic deformation such as urethane foam or felt (non-woven) sheet, and the shape of the polishing pad was initially changed when the polishing pad was pressed against the wafer to carry out the polishing process. Since it is not stable, there is a problem that it is difficult to obtain the desired polishing quality until the shape of the polishing pad becomes stable. Therefore, conventionally, a dummy wafer on which a device or the like is not formed on the surface is prepared and held in the holding means of the polishing apparatus, and a plurality of wafers (for example, 2 to 2) are supplied while supplying the free abrasive grains used in the actual polishing process. The dummy wafers (3 sheets) are actually polished, and after the elastic deformation of the polishing pad is stabilized, the wafer on which the device, which is the actual workpiece, is formed is polished.

However, in the above-mentioned conventional technique, it is necessary to polish a plurality of dummy wafers before performing the polishing process on the wafer, and there is a problem that the productivity is deteriorated. Further, when using the polishing device, it is necessary to always prepare a dummy wafer, and there is a problem that it is uneconomical because free abrasive grains are wasted.

The present invention has been made in view of the above facts, and its main technical problem is to provide a method for processing a wafer by a polishing apparatus without deteriorating productivity and wastefully consuming free abrasive grains. To do.

In order to solve the above-mentioned main technical problem, according to the present invention, a chuck table having a holding surface for holding a wafer and polishing on the polished surface of a polishing pad while supplying free abrasive grains to the wafer held on the chuck table. It is a method of processing a wafer by a polishing device equipped with at least a polishing means for polishing, in which the polishing surface of the polishing pad is brought into contact with the holding surface of the chuck table, and the chuck is supplied with water in place of free abrasive grains. A quasi-polishing step of quasi-polishing the holding surface of the table so as to polish the waha, a waha holding step of holding the waha on the holding surface of the chuck table after the pseudo-polishing step, and a waha holding step of holding the waha on the chuck table. Provided is a polishing step of polishing the waha while supplying free abrasive grains to the waha, and a method for processing the waha including the process of polishing the waha.

The method for processing a waha of the present invention includes a chuck table having a holding surface for holding the waha, and a polishing means for polishing on the polishing surface of the polishing pad while supplying free abrasive grains to the waha held on the chuck table. It is a method of processing a wafer by at least a polishing device provided, in which the polishing surface of the polishing pad is brought into contact with the holding surface of the chuck table, and the holding surface of the chuck table is pressed while supplying water instead of free abrasive grains. A pseudo-polishing step of pseudo-polishing the waha, a waha holding step of holding the waha on the holding surface of the chuck table after the quasi-polishing step, and a waha holding step of holding the waha on the holding surface of the chuck table, and free abrasive grains are applied to the waha held on the chuck table. Since it includes a polishing process of polishing the waha while supplying it, the polishing pad can be elastically deformed to a stable state without using a dummy waha, and free abrasive grains are wasted. Since there is no such thing, productivity is improved and the problem of uneconomical is solved.

It is an overall perspective view of the polishing apparatus suitable for this invention. It is an enlarged perspective view which shows a part of the polishing means and the holding means arranged in the polishing apparatus shown in FIG. 1. It is a perspective view which shows the embodiment of the pseudo-polishing process. It is a perspective view which shows the embodiment of the wafer holding process. It is a perspective view which shows the embodiment of a polishing process.

Hereinafter, embodiments relating to a wafer processing method configured based on the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a perspective view of a polishing apparatus 1 suitable for carrying out the wafer processing method of the present invention. The polishing device 1 includes a substantially rectangular device housing 2, a polishing unit 3 arranged on the device housing 2 as a polishing means for polishing a workpiece (wafer W), and a holding means for holding the wafer W. 5 and the first cassette 6 arranged on the front side in the drawing accommodating the wafer W before polishing, and the first cassette 6 arranged on the other side in the Y-axis direction in the drawing and polishing. A second cassette 7 for accommodating the later wafer W, a temporary placing means 8 for centering the wafer W arranged adjacent to the first cassette 6 in the X-axis direction in the figure, and a second cassette. The cleaning means 9 disposed adjacent to the 7 in the X-axis direction and the wafer W stored in the first cassette 6 are carried out to the temporary storage means 8, and the wafer W cleaned by the cleaning means 9 is carried out. The chuck of the holding means 5 in which the first conveying means 10 to be conveyed to the second cassette 7 and the wafer W placed on the temporary placing means 8 and centered are positioned at the carrying-in / out position (front side in the figure). A second transport means 11 for transporting onto the table 52 and a third transport means 12 for transporting the polished wafer W from the chuck table 52 located at the carry-in / out position to the cleaning means 9. There is. The wafer W housed in the first cassette 6 has a back surface ground in a grinding process performed before being carried into the polishing device 1, and a grinding mark is formed. The method for processing a wafer is carried out in order to remove the grinding marks from the wafer W.

The polishing unit 3 is movably mounted on a pair of guide rails 22 and 22 extending in the vertical direction on the inner surface of the support wall 21 erected on the rear end side of the device housing 2. The polishing unit 3 has a unit housing 31, a wheel mount 33 rotatably supported by the unit housing 31 at the lower end of a rotating shaft 32, and a polishing pad 35 attached to the wheel mount 33 and attached to the lower surface thereof. The polishing wheel 34 is provided with an electric motor 36 mounted on the upper end of the unit housing 31 to rotate the wheel mount 33, and a moving base 38 for supporting the unit housing 31 via a support member 37. The moving base 38 is provided with guided grooves that are slidably fitted to the guide rails 22 and 22 provided on the support wall 21 described above, and the polishing unit 3 is supported so as to be movable in the vertical direction. Ru. Further, as shown in an enlarged manner on the left side of FIG. 1, the polishing surface 35a on the lower surface side of the polishing pad 35 arranged on the polishing wheel 34 has a groove 35b formed in a grid pattern and an opening in the center. The opening 35c is formed, and during the polishing step described later, the slurry S containing the free abrasive grains supplied through the internal passage 32b of the rotating shaft 32 is ejected from the opening 35c, and the groove 35b is formed. The slurry S is supplied over the entire polished surface 35a of the polishing pad 35. The slurry S of the present embodiment is supplied in a liquid form in which water and free abrasive grains are mixed. The material of the polishing pad 35 is not particularly limited, but can be formed of an elastically deformable material such as urethane foam or a felt (nonwoven fabric) sheet.

The polishing device 1 in the illustrated embodiment includes a polishing feed mechanism 39 that raises and lowers the moving base 38 of the polishing unit 3 along the guide rails 22 and 22. The polishing feed mechanism 39 includes a male screw rod 39a rotatably supported on the support wall 21 in the vertical direction parallel to the guide rails 22 and 22, and a pulse motor 39b for rotationally driving the male screw rod 39a. It is equipped with a female screw block (not shown) that is mounted on the moving base 38 and screwed with the male screw rod 39a. By driving the male screw rod 39a in the forward and reverse directions by the pulse motor 39b, the polishing unit 3 is driven in the Z-axis direction (vertical direction). ).

On the front side of the device housing 2 in which the first transport means 10 is arranged, an operation panel 13 for instructing a control means (not shown) to perform polishing processing and designating polishing processing conditions is provided. Further, a display monitor (not shown) configured to display the processing status of the polishing apparatus 1 and to be provided with a touch panel function so that work instructions can be appropriately performed is arranged.

In the present embodiment, the water supply means 100 that supplies water L when the pseudo-polishing step described later is carried out to the internal passage 32b opened at the rotary shaft end 32a above the rotary shaft 32 described above, and the polishing described later. When the process is carried out, the free abrasive grain supply means 120 for supplying the slurry S is connected via a common path 134.

The water supply means 100 includes a water tank 102 having a built-in pressure feed pump (not shown) and a water supply passage 106 provided with an on-off valve 104, and a common path for water L pumped from the water tank 102. It is supplied to the rotary shaft end 32a via 134 and ejected from the central opening 35c of the polished surface 35a of the polishing pad 35 through the internal passage 32b of the rotary shaft 32. Further, the free abrasive grain supply means 120 includes a free abrasive grain tank 122 having a built-in pressure feed pump (not shown) and a free abrasive grain supply path 126 provided with an opening / closing valve 124, and the free abrasive grain tank 122. The slurry S pumped from is supplied to the rotary shaft end 32a via the common path 134, and is ejected from the opening 35c of the polishing surface 35a of the polishing pad 35 through the internal passage 32b of the rotary shaft 32. In FIG. 1, for convenience of explanation, both the water supply means 100 and the free abrasive grain supply means 120 are shown outside the device housing 2, but may be housed inside the device housing 2. ..

The holding means 5 includes a cover table 51 and a chuck table 52 arranged so as to project upward in the center of the cover table 51. The chuck table 52 is formed, for example, with a diameter of 200 mm. The chuck table 52 includes a holding surface 53 on which the wafer W is held and a support member 54 that surrounds and supports the holding surface 53, and the holding surface 53 is made of a breathable member, for example, porous ceramics. ing. The chuck table 52 is rotatably supported and rotated by a rotary drive source (not shown). Further, the chuck table 52 is configured to be movable in the X-axis direction indicated by the arrow X by a moving means (not shown) arranged in the apparatus housing 2, and the loading / unloading position on the front side in the X-axis direction and the loading / unloading position on the front side in the X-axis direction. It is moved to and from the polishing position directly below the polishing unit 3.

As shown in FIG. 2, the chuck table 52 is connected to the water supply means 140 and the suction means 150. The water supply means 140 includes a water tank 142 having a built-in pressure pump (not shown), a water supply path 146 provided with an on-off valve 144, and a common path for water L pumped from the water tank 142. It is supplied to the internal passage 54a via 158 and ejected from the holding surface 53 of the chuck table 52. Further, the suction means 150 includes a suction pump 152 and a suction path 156 provided with an opening / closing valve 154, and a support member that supports the holding surface 53 of the chuck table 52 by operating the suction pump 152 to suck. A suction negative pressure V is supplied onto the holding surface 53 via the internal passage 54a of the 54 and the common path 158. Since the water supply means 140 described above has the same configuration as the water supply means 100 described above, the water supply means 110 is used in combination without installing the water supply means 140. You may.

The polishing apparatus 1 applied to the wafer processing method of the present embodiment generally shows the configuration as described above, and the wafer processing method by the polishing apparatus 1 described above will be described more specifically.

When carrying out the wafer processing method of the present embodiment, the polishing surface of the polishing pad 35 is brought into contact with the holding surface 53 of the chuck table 52, and the holding surface 53 of the chuck table 52 is pressed while supplying water L instead of the slurry S. , A pseudo-polishing step of performing pseudo-polishing so as to polish the wafer W is carried out. More specifically, as shown in FIG. 2, first, the chuck table 52 is positioned at the polishing position directly under the polishing unit 3 in a state where the wafer W is not placed on the holding surface 53.

Next, as shown in FIG. 3, the open / close valve 124 is closed with the free abrasive grain supply means 120 stopped, and the water supply means 100 is operated to open the open / close valve 104, and the common path 134 and the rotary shaft 32 are opened. Water L is supplied through the internal passage 32b of the above and is ejected from the opening 35c (see FIG. 1) of the polishing surface 35a of the polishing pad 35 of the polishing unit 3. At the same time, the on-off valve 154 is closed with the suction means 150 on the chuck table 52 side stopped, and the water supply means 140 is operated to open the on-off valve 144 to open the common path 158 and the inside of the support member 54. Water L is ejected onto the holding surface 53 through the passage 54a. Further, a rotation drive member (not shown) is operated to rotate the chuck table 52 in the direction indicated by the arrow R1, and the electric motor 36 described above is operated to rotate the rotary shaft 32 of the polishing unit 3 in the direction indicated by the arrow R2. The above-mentioned polishing feed mechanism 39 is operated to lower the polishing unit 3 in the direction indicated by the arrow R3, so that the polishing surface 35a of the polishing pad 35 is pressed against the holding surface 53 of the chuck table 52 with a predetermined pressing load. Push. As a result, the holding surface 53 of the chuck table 52 is pseudo-polished (pseudo-polishing step) as if the wafer W is polished.

The implementation conditions of the pseudo-polishing step described above are set as follows, for example.
Polishing pad pressing load: 900N
Rotational speed: 700 rpm
Chuck table rotation speed: 700 rpm
Water L supply amount: 10 L / min Pseudo-polishing time: 3 to 5 minutes

By carrying out the pseudo-polishing step in this way, the polishing pad 35 is pressed against the holding surface 53 of the chuck table 52 and is gradually elastically deformed, and can be deformed to a desired state to be in a stable state. After the above-mentioned pseudo-polishing time has elapsed, the water supply means 100 is stopped to close the on-off valve 104, and the water supply means 140 is stopped to close the on-off valve 144. In the pseudo-polishing step described above, the polishing pad 35 was pressed against the holding surface 53 of the chuck table 52 to perform pseudo-polishing. However, the holding surface 53 of the chuck table 52 is made of hard porous ceramics. Further, since the water L containing no free abrasive grains is supplied (10 L / min) to the polishing pad 35, the holding surface 53 of the chuck table 52 is not polished and deformed. Further, in the pseudo-polishing step of the above-described embodiment, the water supply means 100 and the water supply means 140 are operated to supply the water L on the holding surface 53 of the chuck table 52, but it is not always necessary to operate both of them. It is also possible to supply water L from only one of them. However, by operating the water supply means 100 and the water supply means 140 to supply water L from both the polishing pad 35 and the holding surface 53 of the chuck table 52, the stitches of the holding surface 53 of the chuck table 52 are supplied. It is possible to more reliably prevent clogging and deterioration of the polishing pad 35.

After carrying out the pseudo-polishing step, the wafer holding step of holding the wafer W on the holding surface 53 of the chuck table 52 is carried out. A wafer W is, for example, a device in which a plurality of devices are partitioned by a planned division line and formed on a surface Wa (not shown), and as shown in FIG. 4, the wafer W is protected toward the surface Wa side facing downward. Tape T is attached. In the wafer holding step, the wafer W is placed on the holding surface 53 of the chuck table 52 moved to the loading / unloading position with the front surface Wa side to which the protective tape T is attached facing downward and the back surface Wb side facing upward. The wafer is placed, the suction means 150 is operated to open the opening / closing valve 154, a suction negative pressure V is generated on the holding surface 53 of the chuck table 52, and the wafer W is sucked and held (wafer holding step).

After the wafer holding step is carried out, a polishing step of polishing the wafer W while supplying the slurry S to the wafer W sucked and held on the holding surface 53 of the chuck table 52 is carried out. More specifically, it is carried out by the following procedure described with reference to FIG.

First, the chuck table 52 is rotated in the direction indicated by the arrow R1 by a rotation driving means (not shown), and the electric motor 36 described above is operated to rotate the rotating shaft 32 of the polishing unit 3 in the direction indicated by the arrow R2. The above-mentioned polishing feed mechanism 39 is operated to lower the polishing unit 3 in the direction indicated by the arrow R3. At the same time, with the water supply means 100 stopped, the free abrasive grain supply means 120 is operated to open the opening / closing valve 124, and the slurry S is supplied from the free abrasive grain tank 122 described above to provide free polishing. The slurry S is ejected onto the polishing surface 35a of the polishing pad 35 via the grain supply path 126, the common path 134, and the internal passage 32b of the rotating shaft 32. The polishing surface 35a is brought into contact with the back surface Wb of the wafer W, pressed by a predetermined pressing load while supplying the slurry S, and the polishing process is performed for a predetermined polishing time, and the polishing process is performed in advance from the back surface Wb of the wafer W. Removes grinding marks caused by the grinding process.

The above-mentioned polishing processing implementation conditions are set as follows, for example.
Polishing pad pressing load: 900N
Rotational speed: 700 rpm
Chuck table rotation speed: 700 rpm
Slurry supply amount: 5 L / min Pseudo-polishing time: 1-2 minutes

Even when the polishing pad 35 is elastically deformed by the above-mentioned pseudo-polishing step, the shape of the polishing pad 35 returns to its original shape as time elapses after the pseudo-polishing step is completed. The above-mentioned polishing step is preferably carried out within 5 minutes after the pseudo-polishing step is completed.

According to the above-described embodiment, before the polishing step is performed, the holding surface 53 of the chuck table 52 is regarded as the polishing surface of the wafer, and the polishing surface 35a of the polishing pad 35 is pressed against the holding surface 53 of the chuck table 52. And carry out a pseudo-polishing process. As a result, the polishing pad 35 can be elastically deformed to a stable state without polishing the dummy wafer, productivity is improved, and the slurry containing free abrasive grains is not wasted. Therefore, the problem of uneconomical is solved.

1: Polishing device 2: Device housing 21: Support wall 22: Guide rail 3: Polishing unit 31: Unit housing 32: Rotating shaft 32a: Rotating shaft end 32b: Internal passage 33: Wheel mount 34: Polishing wheel 35: Polishing pad 35a : Polished surface 35c:
36: Electric motor 37: Support member 38: Moving base 39: Polishing feed mechanism 5: Holding means 51: Cover table 52: Chuck table 53: Holding surface 54: Support member 54a: Internal passage 6: First cassette 7: Second cassette 8: Temporary storage means 9: Cleaning means 10: First transport means 11: Second transport means 12: Third transport means 100: Water supply means 102: Water tank 104: Open / close valve 106: Water Supply path 120: Free abrasive grain supply means 122: Free abrasive grain tank 124: Open / close valve 126: Free abrasive grain supply path 134: Common path 140: Water supply means 142: Water tank 144: Open / close valve 146: Water supply path 150: Suction means 152: Suction pump 154: Open / close valve 156: Suction path 158: Common path L: Water S: Slurry T: Protective tape V: Suction negative pressure W: Waha

Claims (1)

Mafer processing by a polishing device equipped with at least a chuck table having a holding surface for holding a wafer and a polishing means for polishing on the polishing surface of a polishing pad while supplying free abrasive grains to the wafer held on the chuck table. It ’s a method,
A pseudo-polishing step in which the polishing surface of the polishing pad is brought into contact with the holding surface of the chuck table, and the holding surface of the chuck table is quasi-polished so as to polish a wafer while supplying water instead of free abrasive grains.
After the pseudo-polishing step, a wafer holding step of holding the wafer on the holding surface of the chuck table and a wafer holding step.
A polishing step of polishing the wafer while supplying free abrasive grains to the wafer held on the chuck table.
Wafer processing method composed of.

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