JPH08148453A - Wafer holder - Google Patents

Abstract

PURPOSE: To provide a wafer retainer with which the consumption of a guide member and the slowing of polishing speed are mitigated and retentive polishing material can be removed. CONSTITUTION: A number of microscopic diamond grains 7 are embedded in the surface of a retainer 6 by the metal bond such as cast iron and the like. When a wafer 8 is mounted on an attracting part 3, the difference between the upper surface of the wafer 8 and the upper surface of the retainer 6 becomes 0.2mm or smaller. Simultaneously with the polishing of the wafer by a polishing pad 10, the polishing pad 10 is seasoned (setting) by diamond grains 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer holder for holding a wafer when polishing the wafer.

[0002]

2. Description of the Related Art Wafer polishing in a semiconductor device manufacturing process is performed by bringing a rotating polishing pad into contact with the wafer surface. At this time, a large impact is applied to the edge of the wafer due to the rotational movement of the polishing pad. Further, the slurry (abrasive material) protruding between the wafer and the polishing pad stays near the edge of the wafer. In many cases, the peripheral portion of the wafer is excessively polished by these. As a countermeasure against this, there has been proposed a wafer holder in which a retainer having a predetermined thickness is provided around the wafer for polishing.

FIG. 8 is a schematic vertical sectional view showing a conventional wafer holder disclosed in Japanese Patent Laid-Open No. 56-33835. A ring-shaped groove 32 is formed on the surface of the flat holding body 31, and a retainer 33 is planted in the groove 32. An inner portion of the groove 32 is formed as a pedestal portion 35 for mounting the wafer 8, and the pedestal portion 35 is provided with a thin vacuum suction hole 35. The height of the upper surface of the retainer 33 is lower than the height of the upper surface of the wafer 8.

In this conventional apparatus, since the wafer 8 is polished in the state where the retainer 33 exists around the wafer 8, it is possible to prevent the polishing deformation in the outer peripheral portion of the wafer 8 and perform the polishing process with high accuracy.

FIG. 9 is a schematic vertical sectional view showing a conventional wafer holder disclosed in Japanese Patent Laid-Open No. 4-206946. An air hole communicating with the air passage 42 is formed in the lower surface of the ceramic plate 43 of the wafer holder 41 having a plurality of air passages 42.
A water-containing adsorption pad 45 comprising 44 is attached. Furthermore, a ring-shaped holding template (retainer) 46 is attached to the peripheral portion of the lower surface of the water-containing adsorption pad 45 in order to maintain the peripheral shape of the wafer 8.

The wafer 8 is brought into contact with the lower surface of the water-containing adsorption pad 45, and the wafer 8 is evacuated through the air passage 42 and the air hole 44 by the vacuum pump.
Is adsorbed on. At this time, since the holding template 46 is present and the water-containing adsorption pad 45 is elastically deformed, the wafer 8 can be polished with high accuracy.

[0007]

The retainer (33, 46) is generally made of the same material as the material to be polished such as a wafer. For example, quartz is used when polishing the insulating film,
A metal is used when polishing tungsten. In this case, there is a problem in that the retainer itself is polished similarly to the wafer, and the retainer is heavily consumed. On the contrary, when the retainer is attached, the polishing area becomes large, so that the clogging of the polishing pad progresses rapidly and the polishing rate is lowered.

Furthermore, since there is a slight gap between the wafer 8 and the retainer (33, 46), polishing abrasive grains are deposited on this portion, deteriorating the positioning accuracy of the wafer and loosening the surface of the outer periphery of the wafer ( Excessive polishing) may be promoted.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a wafer holder that reduces the wear of the retainer and the reduction of the polishing rate by providing a regenerating unit on the surface of the retainer. To aim. Another object of the present invention is to provide a wafer holder that is capable of removing stagnant abrasives by providing a suction groove inside the retainer and outside the wafer.

[0010]

A wafer holder according to a first aspect of the present invention is a wafer holder for holding a wafer in a state of being fitted in a retainer in order to bring the wafer into contact with a polishing pad to polish the wafer. The retainer is composed of a brush, and is provided with a polishing pad regenerating unit on a surface facing the polishing pad, and the regenerating unit is a diamond grain or Si.
It is characterized in that it is composed of ceramic particles such as C and SiN spread.

In the wafer holder according to the second aspect of the present invention, in the first aspect of the present invention, a suction groove is provided at a position inside the retainer and outside the wafer to suck and remove unnecessary substances such as abrasives and polishing debris. It is characterized by being provided.

[0012]

According to the first aspect of the present invention, since the regenerating means contacts the polishing pad during the polishing step, the surface of the polishing pad is scraped by the regenerating means, and the polishing pad is regenerated simultaneously with the polishing of the wafer. In particular, you can perform seasoning. Further, the existence of the regenerating means can significantly reduce the consumption speed of the retainer. Further, since the retainer is formed of a brush-like material, it is possible to remove unnecessary substances such as abrasives that have entered the polishing pad by this brushing action.

According to the second aspect of the invention, since the suction groove is provided at a position inside the retainer and outside the wafer,
It is possible to suck and remove unnecessary substances such as abrasives that have accumulated in the gap between the wafer and the retainer.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings showing the embodiments. Example 1. 1 is a schematic view showing a first embodiment of a wafer holder according to the present invention. 1 (a) is a schematic plan view, and FIG. 1 (b) is a diagram showing both the wafer and the polishing pad.
It is a schematic sectional drawing in the II line of (a). 1 in the figure
Is a circular holder (diameter 200 to 250 mm) made of ceramics such as alumina or metal such as stainless steel.
The peripheral portion of the upper surface of the holding table 1 is omitted, and Al ₂ O
_A ring-shaped retainer 6 made of a material such as ₃ (alumina), SiO ₂ (quartz), or SiC is fitted. Retainer 6
Has its surface lapped or ground, and is attached by vacuum suction, screw fixing, stopper fixing, or the like.

A resin such as Teflon (manufactured by DuPont, polyfluorinated ethylene fiber) having a large number of concentric and radial grooves 5 is formed in the central portion of the surface of the holding base 1 inside the retainer 6. The adsorbing part 3 is attached with an adhesive 2. FIG. 2 is an enlarged view showing a portion A of FIG. 1 (b). The grooves 5 are provided with a width of 0.2 to 0.5 mm and an interval of 0.5 to 2 mm, and are provided in a portion corresponding to the inside of the orientation flat. As a result, the wafer 8
The vacuum does not leak when the (diameter 150 mm) is vacuum-adsorbed, and the wafer 8 is stably held.

A plurality of holes 4 are provided at the center of the suction portion 3 and the bottom of the groove 5 around the suction portion 3. The holes 4 communicate with the vacuum line 14 provided in the holding table 1. The vacuum line 14 is connected to a pressure reducer (not shown).

FIG. 3 is an enlarged view showing part B of FIG. 1 (b). On the surface of the retainer 6, fine diamond grains 7
However, many are embedded with metal bonds such as cast iron.
When the wafer 8 is placed on the suction portion 3, the difference between the upper surface of the wafer 8 and the upper surface of the retainer 6 is 0.2 mm or less. The inner diameter of the retainer 6 is larger than the outer diameter of the wafer 8 by 0.5 to 3 mm.

The wafer 8 is mounted on the holding table 1 constructed as described above.
And the vacuum line 14 is evacuated, the wafer 8 is vacuum-sucked by the suction unit 3. Then, the wafer 8 is polished by the rotating polishing pad 10. Then, the polishing pad 10 contacts the wafer 8 and the retainer 6 in which the diamond grains 7 are embedded. Therefore, at the same time when the polishing pad 10 polishes the wafer 8, the polishing pad 10 is seasoned with the diamond grains 7. As a result, the surface of the polishing pad 10 is constantly regenerated during polishing, so that the progress of clogging of the polishing pad 10 can be significantly delayed. Further, since the diamond grains 7 are embedded in the surface of the retainer 6, it is possible to prevent the retainer 6 from being polished and consumed by the polishing pad 10. The retainer 6 is replaced regularly. Also, instead of diamond grains 7, Si
The same effect can be obtained by using ceramic grains such as C and SiN.

FIG. 4 is a graph showing changes with time in polishing rate in the wafer holder of the present invention and the conventional wafer holder shown in FIG. The vertical axis shows the polishing rate at the start of polishing as 1
And the polishing time is plotted on the horizontal axis. As is apparent from FIG. 4, the polishing rate is gradually decreased in the conventional wafer holder, whereas in the wafer holder of the present invention, the polishing rate is almost decreased even after about 5 hours have elapsed from the start of polishing. I haven't.

Further, as shown in Table 1, the retainer loss in the conventional wafer holder shown in FIG. 1 was 2 μm / h, whereas in the wafer holder of the present invention it was 0.2 μm / h, which was 1 μm / h.
It is / 10. Further, the life of the retainer is about 100 hours with the conventional wafer holder and about 1000 hours with the wafer holder of the present invention. As described above, the life of the retainer of the present invention is about 10 times longer, and the number of times of replacement of the retainer 6 can be reduced.

[0021]

[Table 1]

Example 2. FIG. 5 is a schematic vertical cross-sectional view showing a wafer holder in Example 2 of the present invention together with a wafer and a polishing pad. In this embodiment, the retainer 6 is replaced with a hard resin such as Teflon, acrylic, urethane, etc., and hairs (or needles) having a length of 1 to 10 mm and a thickness of 0.3 to 5 mm are densely spread at equal intervals. Brush retainer
I'm using 11. The retainer 11 is attached to the above-mentioned lacking portion of the peripheral edge of the holding table 1 via an elastic body 12. FIG. 6 is an enlarged view showing part C of FIG. The tips of the retainers 11 may be spherical or pointed. Further, the retainer 11 is preferably made of a material that does not swell with a slurry (abrasive material). Other configurations are the same as those shown in FIG. 1, and the same reference numerals are given and description thereof is omitted.

In this embodiment, the slurry and polishing debris that have entered the polishing pad 10 can be removed by the brushing action of the retainer 11. As a result, the polishing pad 10 is regenerated. Due to the appropriate deformation of the brush-shaped retainer 11 and the elastic action of the elastic body 12, the upper surface of the wafer 8 and the upper surface of the retainer 11 are substantially flush with each other, wear of the retainer 11 is reduced, and polishing of the wafer 8 is performed. Can be done with high precision.

Further, since the retainer 11 has a brush shape, the liquid slurry (polishing liquid) supplied to the periphery of the retainer 11 permeates into the retainer 11 due to the capillary phenomenon between a large number of bristles. Therefore, when the tip of the retainer 11 sweeps the surface of the polishing pad 10, it serves to apply and supply the liquid slurry evenly to the surface of the polishing pad 10. Therefore, the reproducibility of polishing is improved.

Example 3. FIG. 7 is a schematic vertical cross-sectional view showing a wafer holder in Example 3 of the present invention, which is intended to remove the slurry accumulated in the gap between the retainer and the wafer. In this embodiment, the retainer 6
Suction grooves 13a of about 0.5 to 2 mm are provided at a plurality of positions inside the suction line 13a, and the suction grooves 13a communicate with a vacuum line 13 different from the vacuum line 14. The vacuum line 13 can be evacuated separately from the vacuum line 14.

A pure water nozzle 16 for supplying pure water to the surface of the holding table 1 and a scrubber for scrubbing the surface of the holding table 1
17 are provided. These pure water nozzle 16 and scrubber
The acting portion 17 is configured to rotate, and the holding table 1
It faces the holding table 1 only when cleaning the surface, and can be removed from the holding table 1 at other times. The working portion of the scrubber 17 comprises a horizontally rotatable pad 17a. Other configurations are the same as those shown in FIG. 1, and the same reference numerals are given and description thereof is omitted.

A method of cleaning the holding table 1 in this embodiment will be described. First, the pure water nozzle 16 is rotated to rotate the holder 1.
Face up and spray pure water from the pure water nozzle 16 onto the holding table 1 at high pressure. Then, the scrubber 17 scrubs the upper surface of the holding table 1 including the suction portion 3 and the retainer 6. At this time, if the vacuum lines 13 and 14 are kept in vacuum, the slurry accumulated in the suction groove 13a is sucked through the vacuum line 13, and the slurry on the adsorption unit 3 is sucked through the hole 4 and the vacuum line 14. It By removing the slurry that has accumulated between the wafer 8 and the retainer 6 in this way, excessive polishing of the peripheral portion of the wafer 8 is prevented. Further, when the next wafer is held, it is possible to prevent the outer peripheral portion of the wafer 8 from being raised and held due to the residual slurry. As a result, the wafer 8 is stably held every time, and the polishing accuracy is improved.

At the time of polishing, the vacuum line 13 is controlled so as not to perform vacuuming so that the slurry supplied between the wafer 8 and the polishing pad 10 is not sucked. As a result, it is possible to prevent the smooth supply of the slurry from being hindered, and thus to prevent the polishing rate from decreasing. Scrubber
17 is not provided, pure water is supplied from the pure water nozzle 16 and suction groove 13a
The configuration may be such that only suction is performed from the. Further, the deionized water nozzle 16 may not be provided and only the suction groove 13a may be used for suction.

[0029]

As described above, the wafer holder according to the present invention is provided with the regenerating means on the surface of the retainer to prevent the polishing pad from polishing the retainer,
On the contrary, since the regenerating means grinds the surface of the polishing pad, it is possible to reduce wear of the retainer and a decrease in polishing rate. Further, since the suction groove is provided at a position inside the retainer and outside the wafer, it is possible to reduce the polishing rate by sucking and removing the polishing material accumulated in the gap between the wafer and the retainer. As described above, the present invention has excellent effects.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a first embodiment of a wafer holder according to the present invention.

FIG. 2 is an enlarged view showing a portion A of FIG.

FIG. 3 is an enlarged view showing a portion B of FIG.

FIG. 4 is a graph showing changes over time in the polishing rate in the wafer holder of the present invention and the conventional wafer holder.

FIG. 5 is a schematic vertical sectional view showing a wafer holder in Example 2 of the present invention together with a wafer and a polishing pad.

FIG. 6 is an enlarged view showing a C portion of FIG.

FIG. 7 is a schematic vertical sectional view showing a wafer holder in Example 3 of the present invention.

FIG. 8 is a schematic vertical sectional view showing a conventional wafer holder.

FIG. 9 is a schematic vertical sectional view showing a conventional wafer holder.

[Explanation of symbols]

 1 Holding table 6, 11 Retainer 7 Diamond grain 8 Wafer 10 Polishing pad 13, 14 Vacuum line 13a Suction groove

Claims (2)

[Claims] 1. A wafer holder for holding a wafer in a state of being fitted in a retainer for polishing the wafer by bringing the wafer into contact with the polishing pad, wherein the retainer is composed of a brush, and the polishing pad A wafer holder characterized in that a polishing pad regenerating unit is provided on the opposite surface, and the regenerating unit is constituted by spreading diamond grains or ceramic grains such as SiC and SiN. 2. A suction groove for sucking and removing unnecessary substances such as abrasives and polishing debris is provided at a position inside the retainer and outside the wafer.
Wafer holder described.