JPH09309065A - Grinding device and grinding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an increase in clogging of a grinding pad to stabilize the speed of grinding a wafer for a long time. SOLUTION: The device is a wafer grinding device having a retainer on its outer peripheral part, plural projected parts 17 of high hardness are provided on the retainer surface facing a grinding pad, and recessed parts between the projected parts 17 of high hardness are filled with material 18 of lower hardness than that of the projected parts. The wafer is ground by using this grinding device under the condition where the upper face of the retainer is higher than the upper surface of the wafer by a range 0mm or more to 0.1mm or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polishing apparatus and a polishing method for a wafer (plate-like object) such as a silicon wafer, and more particularly to a polishing apparatus and a polishing method suitable for polishing a wafer used in a semiconductor device manufacturing process. .

[0002]

2. Description of the Related Art A wafer is polished in a semiconductor device manufacturing process by pressing a polishing pad against a wafer held on a sample table and supplying a polishing slurry (abrasive grain liquid) between the wafer and the sample table. It is performed by rotating either or both of the polishing pad and the polishing pad.

A large force is applied to the outer edge of the wafer by this rotational movement during polishing, and the slurry exuded from between the wafer and the polishing pad stays near the outer edge of the wafer, so that the peripheral portion of the wafer is excessive. It is often abraded, causing surface sagging. As a countermeasure against this, a polishing apparatus has been proposed in which a retainer having a predetermined thickness is provided around the wafer to polish the wafer.

FIG. 1 is a schematic vertical sectional view showing a wafer polishing apparatus. Polishing surface plate 2 to which polishing pad 21 is attached
2 rotates (revolves) around the polishing platen rotation axis AA '. The sample table 10 provided with the wafer mounting part 11 rotates (revolves) around the sample table rotation axis BB ′. The polishing platen rotation axis AA ′ and the sample stage rotation axis BB ′ may be the same or different. Wafer mount 1 having retainer 15
1 rotates about the wafer mounting portion rotation axis CC ′.

FIG. 2 is a schematic plan view showing a sample stage of a wafer polishing apparatus. The sample table 10 has a wafer mounting portion 1
Five 1s are provided. In FIG. 2, each wafer mounting part 11, sample stage 10, and polishing surface plate (not shown)
Are all rotating in the same direction.

FIG. 3 is a schematic vertical sectional view showing a wafer mounting portion of a wafer polishing apparatus.

The wafer mounting portion 11 is made of acrylic resin or the like, and the wafer mounting surface 12 is formed with wafer holding grooves 13 concentrically and radially in a range smaller than the portion on which the wafer is mounted. . Exhaust through holes 14 are formed in the wafer holding groove 13 at several positions, and the exhaust through holes 14 communicate with a vacuum exhaust device (not shown).
By evacuating the wafer holding groove 13 to a vacuum via the exhaust through hole 14, the wafer S is vacuum-sucked on the wafer mounting surface 12.

The retainer 15 described above is arranged around the wafer mounting surface 12. The upper surface of the retainer 15 is made flat, and the height of the upper surface of the retainer 15 is
When the wafer S is mounted on the wafer mounting surface 12, the wafer S
The height is adjusted to be almost the same as the upper surface of the. As a result, the polishing pad 21 during polishing of the wafer S rotates on a stable plane, and the occurrence of surface sagging at the peripheral edge of the wafer S is prevented.

[0009]

However, in the polishing apparatus using the polishing pad as described above, the polishing pad is clogged and the polishing rate of the wafer decreases as the polishing time elapses. .

The present invention has been made to solve the above problems, and a polishing apparatus and a polishing method capable of suppressing the progress of clogging of a polishing pad and stabilizing a wafer polishing rate for a long period of time. Is intended to provide.

[0011]

A polishing apparatus according to the present invention presses a polishing pad against a wafer held on a sample table, supplies a polishing slurry between the wafer and the polishing pad, and removes the sample table and / or the polishing pad. Is a polishing device for polishing a wafer by rotating, and a retainer is provided on the outer peripheral portion of the portion of the sample stage on which the wafer is mounted, and the surface of the retainer facing the polishing pad has a higher hardness than the polishing pad. A plurality of convex portions are provided, and the concave portions between the convex portions having high hardness are filled with a material having a hardness lower than that of the convex portions.

According to the polishing apparatus of the present invention, during the polishing step of the wafer, the high hardness protrusions provided on the upper surface of the retainer come into contact with the polishing pad, and the surface of the polishing pad is scraped, so that the polishing pad Seasoning can be performed. As a result, the progress of clogging of the polishing pad can be suppressed.

On the other hand, when seasoning is performed with a retainer provided with a convex portion having a high hardness, the seasoning effect of the polishing pad may be great, and the polishing pad may be worn heavily.

In the retainer of the polishing apparatus of the present invention, a material having a hardness lower than that of the convex portion is embedded to a proper position in the concave portion between the convex portions having high hardness. This allows
It is possible to prevent the high-hardness convex portion from biting into the polishing pad, prevent excessive seasoning of the polishing pad, and stably obtain an appropriate seasoning effect. as a result,
The polishing rate of the wafer can be stabilized over a long period of time.

Further, according to the polishing apparatus of the present invention, since the convex portion of high hardness is present on the surface of the retainer facing the polishing pad, it is possible to reduce the wear rate of the retainer.

The high-hardness convex portion is formed by electrodepositing diamond grains or the like on a stainless steel plate or the like, and
It can be formed by adding groove processing to a ceramic plate such as iC or SiN.

A resin such as Teflon or acryl can be used as a material to be embedded in the concave portions between the high hardness convex portions.

The amount of the low hardness material embedded in the concave portion between the high hardness convex portions depends on the material of this material, the material of the polishing pad, the material of the convex portion on the upper surface of the retainer and the upper surface of the retainer. It may be determined from the positional relationship of the height of the upper surface of the wafer.

Further, in the polishing method of the present invention, the wafer is held on the sample stage of the above-mentioned polishing apparatus, and the wafer is polished under the condition that the upper surface of the retainer is higher than the upper surface of the wafer within the range of 0 mm to 0.1 mm. It is characterized by that.

By making the upper surface of the retainer higher than the upper surface of the wafer, it is possible to effectively scrape the surface of the polishing pad and season the polishing pad. Further, when the wafer is polished under the condition that the upper surface of the retainer is much higher than the upper surface of the wafer, the polishing rate at the peripheral portion of the wafer decreases, and the uniformity of the polishing rate within the wafer deteriorates. By polishing the wafer within a range in which the upper surface of the retainer is within a height of 0.1 mm from the upper surface of the wafer, it is possible to suppress a decrease in the polishing rate at the peripheral portion of the wafer and uniformly polish the wafer.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a polishing apparatus according to the present invention will be described. An example of the polishing apparatus of the present invention is an apparatus having the same structure as the polishing apparatus shown in FIGS. 1, 2 and 3, but only the retainer is different. Therefore, the description of the parts other than the retainer is omitted.

FIG. 4 shows a retainer 1 of the polishing apparatus of the present invention.
It is a schematic plan view of an example. A convex portion 17 is formed on the upper surface of the retainer by electrodepositing diamond grains. The grain size of diamond grains is preferably about 0.1 to 1.0 mm.

FIG. 5 is a schematic vertical sectional view of a part of this retainer. Diamond particles (protrusions 17) are electrodeposited on a retainer 15 made of stainless steel or the like, and an electroplating process is performed between the diamond particles 17 with a high hardness metal such as nickel to form an electrodeposition layer 16. In order to prevent the diamond grains 17 from falling off, the embedding rate of the diamond grains 17 in the electrodeposition layer 16 is preferably 50% or more. The electrodeposited layer 16 is coated with a low-hardness material 18 such as a resin such as Teflon or acrylic, and diamond grains 17
Fill in the gaps. The electrodeposited layer 16 of diamond grains 17
The final embedding rate in the low hardness material 18 may be determined from the seasoning effect of the polishing pad, but is usually 60.
~ 99% is preferred. The low hardness material 18 has a thickness of 20 to
It is preferably 500 μm.

FIG. 6 is a schematic plan view showing another example of the retainer of the polishing apparatus of the present invention. It is an example of a sintered ceramics plate such as SiC or SiN in which the pattern of the convex portions 19 is formed. The seasoning effect of the polishing pad can be changed by changing the size, shape and interval of the convex portions.

FIG. 7 is a schematic vertical sectional view of a part of this retainer. A structure in which a resin such as Teflon or acryl as a low-hardness material 18 is coated and embedded in a concave portion between the convex portions 19 of the ceramics.

An example of the polishing method of the present invention will be described with reference to FIG.

When the wafer S is mounted on the wafer mounting surface 12, the surface of the retainer is almost at the same height as the surface of the wafer S, and the tips of the high hardness protrusions are slightly higher than the surface of the wafer S. The retainer 15 is attached in advance.

A wafer S such as a silicon wafer is mounted on the wafer mounting surface 12.

The wafer holding groove 13 is evacuated to a vacuum through the exhaust through hole 14 and the wafer S is vacuum-sucked to the wafer mounting surface 12.

While rotating the polishing pad 21, the wafer mounting portion 11, and the sample stage on which the wafer mounting portion 11 is provided, the polishing slurry is supplied from a polishing slurry supply hole (not shown) in the central portion of the polishing platen. Are supplied to the polishing pad 21.

The polishing pad 21 is lowered, and the polishing pad 21 is pressed against the wafer S while applying a predetermined polishing load to polish the upper surface of the wafer S.

According to this polishing method, when the wafer S is polished, the polishing pad 21 rotates on a stable plane, the occurrence of surface sagging at the peripheral portion of the wafer S is prevented, and the seasoning of the polishing pad 21 is stable. Will be done. As a result, the progress of clogging of the polishing pad is suppressed, and the polishing rate of the wafer can be stabilized for a long period of time.
Further, since the convex portion having the high hardness exists, the consumption speed of the retainer itself can be reduced.

Generally, by attaching the retainer so that the tip of the high-hardness convex portion of the retainer is about 0 to 0.1 mm higher than the upper surface of the wafer, the surface of the polishing pad is effectively scraped and polished. The pad can be appropriately seasoned, and the uniformity of the polishing rate in the wafer surface can be kept good.

[0034]

EXAMPLES Examples of the present invention will be described. The polishing apparatus used in this example is the polishing apparatus shown in FIGS. 1, 2 and 3, and the retainer used is the retainer electrodeposited with the diamond grains shown in FIGS. 2 and 3.

The retainer was manufactured as follows. Diamond grains 17 were electrodeposited on the upper surface of the retainer 15 body made of stainless steel, and electroplating treatment was performed between the diamond grains 17 with nickel to form an electrodeposition layer 16. Then, the electrodeposition layer 16 was coated with Teflon (resin 18), and the diamond grains 17 were embedded so that only the tip was visible from the surface. The grain size of diamond grains is 0.5 mm. The embedding rate of the diamond grains 17 in the electrodeposition layer 16 is 60%. The coating amount of Teflon (low hardness material 18) was 100 μm in thickness.

Using this retainer, the thermal oxide film formed on the 8-inch silicon wafer was polished. The polishing pad is made of foamed polyurethane, and the polishing slurry is
It is a suspension of silica in an aqueous KOH solution.

When the retainer of this embodiment is used, the polishing rate is about 200 even when processing 5000 wafers.
nm / min, and the variation of the polishing rate was 5% or less. On the other hand, when the conventional flat retainer made of quartz is used and the processing of about 200 to 300 wafers is performed, the polishing rate is about 1 nm from the initial value of about 200 nm / min.
It decreased by 0% or more.

In the retainer of this embodiment, the tip of the high hardness convex portion of the retainer is 0.02 mm with respect to the upper surface of the wafer.
It was attached so that it was slightly higher. Further, the conventional flat retainer made of quartz was attached so that the upper surface thereof was at the same height as the upper surface of the wafer.

From these results, it was confirmed that the polishing apparatus using the retainer of this example can stabilize the polishing rate of the wafer. Further, there was no occurrence of surface sagging at the peripheral portion of the wafer.

Further, in the conventional case, when about 200 wafers were processed, it was necessary to replace the retainer. On the other hand, when the retainer of this embodiment was used, replacement was not necessary until about 10,000 wafers were processed.

[0041]

As described in detail above, according to the polishing apparatus and the polishing method of the present invention, the progress of clogging of the polishing pad can be suppressed and the polishing rate of the wafer can be stabilized for a long period of time.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing a wafer polishing apparatus.

FIG. 2 is a schematic plan view showing a sample stage of a wafer polishing apparatus.

FIG. 3 is a schematic vertical sectional view showing a wafer mounting portion of a wafer polishing apparatus.

FIG. 4 is a schematic plan view of an example of a retainer of the polishing apparatus of the present invention.

5 is a schematic vertical cross-sectional view of the retainer shown in FIG.

FIG. 6 is a schematic plan view of another example of the retainer of the polishing apparatus of the present invention.

FIG. 7 is a schematic vertical sectional view of the retainer shown in FIG.

[Explanation of symbols]

 10 Sample Table 11 Wafer Placement Part 12 Wafer Placement Surface 13 Wafer Holding Groove 14 Exhaust Through Hole 15 Retainer 16 Electrodeposition Layer 17 Convex Part (Diamond Grain) 18 Low Hardness Material 19 Convex Part 21 Polishing Pad 22 Polishing Constant Board S wafer

Claims (2)

[Claims] 1. A polishing apparatus for polishing a wafer by pressing a polishing pad against a wafer held on a sample stage, supplying a polishing slurry between the wafer and the polishing pad, and rotating the sample stage and / or the polishing pad. It is provided with a retainer on the outer peripheral portion of the portion of the sample table on which the wafer is placed, the surface of the retainer facing the polishing pad is provided with a plurality of convex portions having a hardness higher than that of the material of the polishing pad, A wafer polishing apparatus, characterized in that a convex portion having a high hardness and a concave portion between the convex portions are filled with a material having a hardness lower than that of the convex portion. 2. The wafer is held on a sample stage of the polishing apparatus according to claim 1, and the wafer is polished under the condition that the upper surface of the retainer is higher than the upper surface of the wafer within a range of 0 mm or more and 0.1 mm or less. Method for polishing wafer.