JPH10309657A - Grinding device for wafer and method for grinding wafer by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grinding device for a wafer, by which the throughput of grinding can be improved, and a method for grinding the wafer, using it. SOLUTION: A laminated base plate 11 is loaded, sucked and fixed in a chuck 15 of a chuck table 12. At this time, the upper side of a wafer 11A for an active layer projects from the chuck 15 by the grinding allowance. Next, a traverse base table 16A is moved, a grinding head 13 is arranged on the table 12, and the grinding head 13 is lowered at the speed in the range of 0.05 to 1.0 μm/sec while rotating a grinding fixed part 18 by a rotary motor 17. As a result, the front surface of the wafer 11A is ground by a cup-shaped grinding wheel 19 in rotating. Since twenty seven partial grinding wheels of the cup-shaped grinding wheel 19 are arranged into a complete round shape with respect to the rotational axis of the grinding wheel fixed part 18, the grinding time can be shortened in comparison with the conventional grinding wheel, and the grinding throughput is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a wafer grinding apparatus capable of increasing a grinding throughput and a wafer grinding method using the apparatus.

[0002]

2. Description of the Related Art Today, silicon wafers are manufactured by various methods. For example, there is a method of slicing and chamfering a wafer cut out of a single crystal ingot, and then grinding the wafer surface one by one through a lapping process. 2. Description of the Related Art Conventionally, as a single-side grinding apparatus, there is known a single-side grinding apparatus including, for example, a chuck table for mounting and fixing a wafer, and a grinding head for grinding a surface of the wafer fixed by the chuck table using a grindstone. In addition,
The grindstone here is a cup-shaped grindstone in which a number of partial grindstones are annularly arranged on the outer peripheral portion of the lower surface of the grinding head. Conventional cup-shaped grindstones are arranged in a triangular tapered shape or an elliptical shape when each partial grindstone is viewed from the bottom. During wafer grinding, the wafer after the lapping process is mounted and fixed on the chuck table, and the cup-shaped grindstone of the rotating grinding head is lowered.
First, the surface of the wafer is ground. Thereafter, the wafer is turned over and re-fixed, and then the grinding head is lowered to grind the back surface of the wafer.

[0003]

However, the above-described conventional wafer grinding apparatus has the following problems. That is, since the shape of the cup-shaped grindstone provided in the grinding head was a triangular conical or elliptical shape,
A unique undulation, that is, a grinding mark was generated on the ground surface. As a result, in order to prevent the occurrence of this grinding mark, it is necessary to set the processing speed lower, and because spark-out is required for a long time to remove it,
There is a problem that it takes a long time to perform the grinding and the throughput of the grinding is reduced.

In a bonded substrate in which an active layer wafer is bonded on a supporting substrate wafer, the active layer wafer is 500 to 600 μm after bonding heat treatment.
A small amount is removed by grinding and polishing. In particular,
A bonded substrate with the support substrate wafer side facing down is mounted and fixed on the chuck table of the single-side grinding apparatus, and the surface of the active layer wafer is ground by a rotating grinding head in the same manner. Also in this case, the shape of the cup-shaped grindstone mounted on the grinding head is a triangular conical shape, and as a result, there is a similar problem.

[0005]

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a wafer grinding apparatus capable of increasing the grinding throughput and a wafer grinding method using the apparatus. Another object of the present invention is to provide a wafer grinding apparatus capable of preventing burn-in of a grindstone during grinding.

[0006]

According to the first aspect of the present invention, a wafer cut out of a single crystal ingot is mounted and fixed on a chuck table, and a rotating grinding head is lowered and abutted, and a lower peripheral portion of the grinding head is provided. In a wafer grinding apparatus that grinds the wafer surface by a cup-shaped grindstone composed of a number of partial grindstones arranged annularly in the portion, the cup-shaped grindstone applies the respective partial grindstones around a rotation axis of the grinding head. This is a wafer grinding device arranged in a perfect circle.

The wafer to be ground is premised on two-stage grinding for any kind of wafer such as a silicon wafer, a wafer having a SiO ₂ film formed on its surface, and a wafer having a polysilicon film formed on its surface. If it is possible. Further, the wafer may be ground only on one side or on both sides. Alternatively, a bonded substrate in which an active layer wafer is bonded to a support substrate wafer may be used. The bonded substrate referred to here is not limited to the type of the substrate as long as it is a substrate for bonding wafers. For example, a Si / Si substrate, SOI (Silicon on)
(Insulator) substrate or SiO ₂ / SiO ₂ substrate.

When the relative movement distance of the grindstone is 3000 to 4000 m / min, the descending speed of the grinding head is 0.05 to 1.0 μm / sec, especially 0.5 to 1.0 μm / sec.
0.8 μm / sec is preferred. 0.05 μm / sec
If it is less than 1, grinding marks on the ground surface of the wafer are not generated, but the grinding time is too long. On the other hand, 1.0 μm /
When the time exceeds sec, the grinding time is shortened, but the grinding marks increase, and the polishing amount on the wafer surface in the polishing step after the grinding increases. The depth of cut on the wafer surface is
The maximum value is preferably about 1/3 of the average grain size of the abrasive grains. That is, for example, with a grinding wheel of # 2000, the average particle size is 4 to 6
μm, the maximum depth of cut is 1.33 to 2
μm. The cutting depth here is determined by the descending speed of the grinding head and the rotation speed of the chuck table. Note that the chuck table normally vacuum-adsorbs the wafer to the mounting surface, but is not necessarily limited to this. These matters also apply to claim 3.

The invention according to claim 2 is the wafer grinding apparatus according to claim 1, wherein the roughness of the cup-type grindstone is # 1500 to # 3000. The preferred roughness of each of the partial whetstones constituting the cup-type whetstone is # 1500 to # 2500. If it is less than # 1500, cracks occur in the wafer, and the damaged layer due to grinding becomes deep. On the other hand, # 300
If it exceeds 0, the grinding wheel will seize due to frictional heat during grinding.

[0010] The invention according to claim 3 is a step of mounting and fixing a wafer cut out of a single crystal ingot on a chuck table, and then lowering and abutting a rotating grinding head so that the outer periphery of a lower surface of the grinding head is completely fixed. A step of grinding a wafer surface of a wafer with a cup-shaped grindstone composed of a large number of partial grindstones arranged in a circle.

[0011]

According to the wafer grinding apparatus and the wafer grinding method using the apparatus, the wafer is mounted and fixed on the chuck table, and the rotating grinding head is lowered and abutted. The surface of the wafer is ground by a cup-shaped grindstone arranged annularly on the outer periphery of the lower surface of the grinding head. In this case, since the cup-type grindstone has a large number of partial grindstones arranged in a perfect circle around the rotation axis of the grinding head, instantaneous fluctuations in the grinding state are small, and thus undulation is unlikely to occur. Therefore, it is possible to maintain the processing speed and reduce spark-out, and the grinding time is relatively shortened, thereby increasing the grinding throughput.

[0012] In particular, according to the wafer grinding apparatus of the second aspect, the roughness of the cup-shaped grindstone is set to a range of # 1500 to # 30.
Since it is set to 00, it is possible to prevent cracks from being generated in the wafer during the grinding, to make the deteriorated layer of the wafer by the grinding process shallow, and to prevent the grindstone from burning due to the frictional heat generated during the grinding.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. Here, the grinding of the active layer wafer of the bonded substrate will be described as an example. FIG. 1 is an overall perspective view of a wafer grinding apparatus according to one embodiment of the present invention.
FIG. 3 is an enlarged perspective view of the grinding head, FIG. 3 is an enlarged bottom view of the grinding head, and FIG. 4 is an explanatory view showing a wafer grinding process using a partial grindstone. In FIG. 1, reference numeral 10 denotes a wafer grinding device. The wafer grinding device 10 includes a chuck table 12 on which a bonded substrate 11 which is an example of a wafer is mounted and fixed, and a fixed bonded substrate 11
And a grinding head 13 for grinding the surface of the active layer wafer 11A.

The bonded substrate 11 is formed on a support substrate wafer 11 B having a SiO ₂ film formed on its surface, and an active layer wafer 11 cut out of a single crystal ingot.
A is bonded at room temperature and then heat-bonded. As a matter of course, as described above, instead of the bonded substrate 11, ordinary single wafers may be used. The chuck table 12 has a rotary table 14 having a circular shape in a plan view that incorporates a drive motor (not shown).
On the rotary table 14, a ring-shaped chuck 15 for fixing the wafer by suction is provided. The rotation direction of the turntable 14 is clockwise in FIG. 1, and the rotation speed is 10 to 50 rpm.

The grinding head 13 is provided so as to be able to move up and down on the traversing base 16A via an elevation motor (not shown) and a vertically extending LM guide 16a. This traversing base 1
6A is a transverse motor (not shown) and an LM extending in the horizontal direction.
It approaches or separates from the chuck table 12 via the guide 16b. A grinding wheel fixing portion 18 of a thick disk is fixed to the downward output shaft of the rotary motor 17. A cup-shaped grindstone 19 having a diameter of 200 mm is mounted on the outer periphery of the lower surface of the grindstone fixing portion 18.

As shown in FIGS. 2 and 3, the cup-shaped grindstone 1
9, 27 partial grinding wheels 20 each having an arc shape,
This is an annular grindstone arranged in a perfect circle around the rotation axis a of the grinding head 13. Each partial grindstone 20 has a roughness of # 2000, and the average grain size of the abrasive grains is 4 to 6 μm. Since the cup-type grindstone has a roughness of # 2000, cracking of the active layer wafer 11A during grinding can be prevented, and the altered layer of the wafer due to grinding can be made shallow. And # 20
At about 00, so high frictional heat is not generated at the time of grinding that the burning of the cup-type grindstone 19 can be prevented.
In addition, in order to increase the holding power of the abrasive grains, an artificial diamond plated with nickel may be employed. The dimensions of the partial grindstone 20 are 20 mm in length and 2 to 4 mm in thickness. Also,
The gap between the respective partial grinding wheels 20 is 1 mm. The rotation direction of the grindstone fixing unit 18 by the rotation motor 17 is counterclockwise in FIG.
The rotation speed is 5500 rpm. The relative movement distance of the cup-type grindstone 19 is 3000 to 4000 m / min.

Next, a method of grinding a wafer for an active layer of a bonded substrate using the wafer grinding apparatus 10 according to one embodiment of the present invention will be described. As shown in FIG. 1, when grinding the active layer wafer 11A, first, the chuck table 1
The bonded substrate 11 is mounted in the second chuck 15 with the supporting substrate wafer 11B facing downward. Next, the chuck 15 is operated to fix the bonded substrate 11 by vacuum suction.

Next, the traversing base 16A is moved to the chuck table 12 via the LM guide 16b, and the grinding head 13 is placed on the table 12. Then, while rotating the grinding wheel fixing unit 18 by the rotation motor 17,
0.5 to 1.0 μm / sec through the M guide 16a
Descend at the speed of. Thus, the surface of the active layer wafer 11A is ground by the rotating cup-shaped grindstone 19 (FIG. 4).
reference). The cutting depth of each partial grindstone 20 from the surface of the active layer wafer 11A is determined by the average grain size of the abrasive grains (4 to
6 μm) (1.33 to 2 μm) or less.

At this time, since the cup-type grindstone 19 is formed by arranging a large number of partial grindstones 20 in a perfect circle with the rotation axis a of the grinding head 13 as a center, the instantaneous change in the grinding state is small. Swell is unlikely to occur. Therefore, it is possible to maintain the processing speed and reduce spark-out, and the grinding time is shorter than that of the conventional grindstone, so that the grinding throughput is increased. A comparative experiment was conducted by actually arranging the partial whetstones 20 in a triangular conical shape or an elliptical shape. As a result, when the wafer grinding apparatus 10 of the example was used, the grinding time was shortened, and the throughput was 1.5 times. The present invention is not limited to this embodiment, and includes any change in design without departing from the scope of the present invention.

[0020]

As described above, according to the wafer grinding apparatus and the wafer grinding method according to the first to third aspects, the surface of the wafer mounted and fixed on the chuck table is provided. The rotating grinding head is pressed against the wafer surface to grind the wafer surface with a cup-shaped grindstone arranged in a perfect circle, so that the instantaneous change in the grinding state is small and undulation is unlikely to occur. Therefore, the processing speed can be maintained and spark-out can be reduced, so that the grinding time of the wafer is relatively shortened and the grinding throughput is increased.

In particular, according to the wafer grinding apparatus of the second aspect, the roughness of the cup-type grindstone is set to # 150 to # 30.
Since it is set to 00, cracks can be prevented from being formed in the wafer during grinding, the deteriorated layer of the wafer due to grinding can be made shallow, and burn-in of the grindstone due to frictional heat during grinding can be prevented.

[Brief description of the drawings]

FIG. 1 is an overall perspective view of a wafer grinding apparatus according to one embodiment of the present invention.

FIG. 2 is an enlarged perspective view of a grinding head.

FIG. 3 is an enlarged bottom view of the grinding head.

FIG. 4 is an explanatory view showing a wafer grinding process using a partial grinding wheel.

[Explanation of symbols]

 Reference Signs List 10 Wafer grinding device, 11 Laminated substrate, 11A Active layer wafer, 11B Support substrate wafer, 12 Chuck table, 13 Grinding head, 19 Cup-type grindstone, 20 Partial grindstone, a rotating shaft.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Akihiro Terasawa 1-5-1, Otemachi, Chiyoda-ku, Tokyo Mitsubishi Materials Silicon Corporation

Claims (3)

[Claims] 1. A wafer cut out of a single crystal ingot is mounted and fixed on a chuck table, a rotating grinding head is lowered and abutted, and a plurality of partial grinding wheels are annularly arranged on the outer periphery of a lower surface of the grinding head. In a wafer grinding apparatus for grinding a wafer surface by a cup-shaped grindstone comprising: the above-described cup-shaped grindstone, wherein each of the partial grindstones is arranged in a perfect circle around a rotation axis of the grinding head. apparatus. 2. The cup-shaped grindstone has a roughness of # 1500 to # 1500.
The wafer grinding apparatus according to claim 1, which is # 2500. 3. A step of mounting and fixing a wafer cut out of a single crystal ingot on a chuck table, and then lowering and abutting a rotating grinding head so as to be arranged in a perfect circle on an outer peripheral portion of a lower surface of the grinding head. A step of grinding the surface of a wafer with a cup-shaped grindstone composed of a number of partial grindstones.