JP2000246623A - Polishing device - Google Patents

Abstract

(57) [Problem] To provide a substantially uniform polishing rate even when a plurality of polished objects to be polished at once have different thicknesses or a thickness deviation exists in the surface of the polished objects. Provided is a polishing apparatus that can be polished by a polishing method. SOLUTION: A silicon rubber sheet 2 and a polishing pad 3 are fixed on an upper surface of a polishing table 1 in this order, and the polishing table 1 is driven to rotate by a driving device (not shown). The thickness of this silicone rubber sheet 2 is 4
mm to 20 mm, and the hardness (JIS K6301) of the silicone rubber sheet 2 is 15 or less. The thickness of the polishing pad 3 is 3 mm or less, and the hardness (JISK6301) of the polishing pad 3 is 90 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a VLSI or UL
The present invention relates to a polishing apparatus mainly used for manufacturing semiconductor devices such as SI.

[0002]

2. Description of the Related Art FIG. 3 is a schematic side sectional view showing a chemical mechanical polishing apparatus disclosed in Japanese Patent Application Laid-Open No. 9-321001. In the figure, reference numeral 21 denotes a ceramic formed into a short cylindrical shape. This is a polishing table. On the upper surface of the polishing table 21, a silicon rubber sheet 22 and a polishing pad 23 are fixed in this order,
The polishing table 21 is driven to rotate by a driving device (not shown). The thickness of the silicone rubber sheet 22 is 0.5 mm to 3.0 mm.
Has a hardness of 20 to 90, preferably 30 to 60 (JISK).
6301).

[0003] Above the polishing table 21, a columnar supporting table 25 is arranged in parallel with the polishing table 21 to hold the wafer W. The supporting table 25 is rotated at the center of the upper surface of the supporting table 25. And an ascending and descending shaft 26 are connected. A circular concave portion is provided in the center of the lower surface of the support 25, and a ceramic plate 27 having a thickness substantially the same as the depth of the concave portion is firmly fitted in the concave portion. A backing pad 28 made of non-woven fabric is fixed to the lower surface of the ceramics plate 27 with an adhesive or a double-sided adhesive tape, and has an inner diameter substantially equal to the diameter of the wafer W. An annular retainer 29 having a thickness substantially equal to the thickness is fixedly attached.

In such an apparatus, after a wafer W is fitted and held in a retainer 29, the polishing table 21 and the support table 25 are rotated, and a slurry in which abrasive grains are suspended in an alkaline solution such as KOH is used. To the surface of the wafer W,
The surface of the wafer W is chemically and mechanically polished by lowering the support 25 and bringing the wafer W into sliding contact with the polishing pad 23.

[0005]

When a wafer having a relatively small diameter of less than 8 inches is polished by such a polishing apparatus, a plurality of supports are arranged opposite to the polishing table, and a plurality of wafers are made identical. The polishing conditions are as follows. When a wafer having a diameter of 8 inches or more is polished, a support having a corresponding diameter is arranged to face the polishing table. However, in the conventional polishing apparatus, when the thicknesses of a plurality of wafers to be polished at one time are different, there is a large variation in the polishing rate of each wafer, and the rate of defective polishing is high. In addition, when there is a thickness deviation in the plane of one wafer, the polishing rate varies greatly at a plurality of positions in the plane of the wafer, and the defective polishing area is large.

The present invention has been made in view of such circumstances, and it is an object of the present invention to provide a polishing table having a hardness (JISK6301) of 15 or less and a thickness of 4 mm.
By stacking an elastic sheet and a polishing pad of not less than 20 mm in this order, when the thickness of a plurality of polished objects to be polished at once is different, or when there is a thickness deviation in the surface of the polished object. However, an object of the present invention is to provide a polishing apparatus capable of polishing at a substantially uniform polishing rate.

[0007]

According to a first aspect of the present invention, there is provided a polishing apparatus having an elastic sheet and a polishing pad stacked on a polishing table in this order. In a polishing apparatus for polishing an object to be polished, the hardness (JISK
6301) is 15 or less, and the thickness is 4 mm or more and 20 m.
m or less elastic sheets are provided.

In a polishing apparatus according to a second aspect of the present invention, an elastic sheet and a polishing pad are stacked on a polishing table in this order, and the object to be polished is vacuum-adsorbed to a support table disposed opposite to the polishing pad. In a polishing apparatus for polishing an object to be polished in sliding contact with a pad, an elastic sheet having a hardness (JIS K6301) of 15 or less and a thickness of 4 mm to 20 mm is provided.

In these inventions, since the elastic sheet having the optimized hardness and thickness is interposed between the polishing table and the polishing pad, the thickness of a plurality of objects to be polished at once can be increased. The difference in thickness or the thickness deviation existing in the surface of the object to be polished is absorbed by the elastic sheet, and the applied pressure is made uniform between the objects to be polished or over the entire surface of the object to be polished. Thereby, even when the thickness of a plurality of objects to be polished at one time is different, or even when there is a thickness deviation in the surface of the object to be polished, polishing can be performed at a substantially uniform polishing rate. .

The hardness of the elastic sheet is determined according to Japanese Industrial Standard (JI).
1 when measured by K6301 specified in S)
When it exceeds 5, the thickness deviation of the object to be polished cannot be sufficiently absorbed, and the variation in the polishing rate exceeds 10%. The smaller the hardness of the elastic sheet, the smaller the variation in polishing rate, but from the viewpoint of handling characteristics, the hardness of the elastic sheet is preferably 3 or more. That is, when the hardness of the elastic sheet is less than 3, when the elastic sheet is fixed to the polishing table, wrinkles are easily generated in the elastic sheet.

On the other hand, when the thickness of the elastic sheet is less than 4 mm, the thickness deviation of the object to be polished cannot be sufficiently absorbed, and the variation in polishing rate exceeds 10%. On the other hand, if the thickness of the elastic sheet exceeds 20 mm, the elastic sheet is greatly deformed and the polishing pad is easily wrinkled, so that the variation in the polishing rate exceeds 10%. Further, as the polishing rate decreases, the flatness of the polished portion of the object to be polished also decreases.

A polishing apparatus according to a third aspect of the present invention provides the polishing apparatus according to the first or second aspect.
In the invention, the elastic sheet is made of silicone rubber.

[0013] In the case of silicone rubber, the hardness can be easily adjusted by adjusting the amount of silicone oil mixed with the base material. An elastic sheet having a thickness can be easily obtained. Also, silicone rubber has a long life due to its high drug resistance.

The polishing apparatus according to the fourth aspect of the present invention comprises the first to third polishing apparatuses.
In any of the inventions, the hardness (JIS K6301) is 9
A polishing pad having a value of 0 or more is provided.

Since the hardness of the polishing pad is 90 or more,
Even when the polishing pad is mounted on a relatively soft elastic sheet, the surface of the polishing pad is flat during the polishing operation, and the object to be polished is uniformly polished on the entire surface.

[0016]

Embodiments of the present invention will be specifically described below with reference to the drawings. (Embodiment 1) FIG. 1 is a schematic side sectional view showing a main part of a polishing apparatus according to the present invention. In the figure, reference numeral 1 denotes a polishing table formed by molding ceramics into a short cylindrical shape. Polishing table 1
The silicon rubber sheet 2 and the polishing pad 3
However, the polishing table 1 is fixed in this order, and the polishing table 1 is rotationally driven by a driving device (not shown).

The thickness of the silicone rubber sheet 2 is 4 mm
２０20 mm, and the hardness of the silicone rubber sheet 2 (JI
SK6301) is 15 or less. Note that the hardness of the silicone rubber sheet 2 is preferably 3 or more because handling when the silicone rubber sheet is fixed to the polishing table 1 is easy.

The thickness of the polishing pad 3 is 3 mm or less,
The polishing pad 3 preferably has a hardness (JIS K6301) of 90 or more, preferably 92 to 1 mm.
00. As a material satisfying such conditions, for example, IC1000 or IC1 manufactured by Rodale Nitta Co., Ltd.
400 or the like can be applied to the polishing pad 3. When the thickness of the polishing pad 3 exceeds 3 mm, the effect of the silicon rubber sheet 2 having a low hardness is reduced as described below, and a problem occurs that the polishing rate varies widely.
Further, the hardness (JIS K6301) of the polishing pad 3 is 90.
If it is less than the above, during the polishing operation, the flatness of the polishing pad 3 and the flatness of the polished portion of the wafer W decrease.

Above the polishing table 1, a columnar supporting table 5 is arranged in parallel with the polishing table 1 to hold the wafer W, and the supporting table 5 is rotated at the center of the upper surface of the supporting table 5. And a supporting shaft 6 that moves up and down. A circular concave portion is provided in the central portion of the lower surface of the support base 5, and a ceramic plate 7 having a thickness substantially the same as the depth of the concave portion is firmly fitted into the concave portion. A backing pad 8 made of non-woven fabric is fixed to the lower surface of the ceramic plate 7 with an adhesive or a double-sided adhesive tape.
An annular retainer 9 having an inner diameter substantially equal to the diameter of the wafer W and having a thickness substantially equal to the thickness of the wafer W is fixed thereto.

In such an apparatus, an interlayer insulating film such as SiO ₂ , an element isolation film (STI), Si, W, C
metal film such as u or Al, or TiN or TaN
After the wafer W on which a barrier metal or the like is formed is fitted and held in the retainer 9, the polishing table 1 and the support table 5 are
While rotating at a rotation speed of rpm, a slurry in which abrasive grains are suspended in an acidic solution, a neutral solution or an alkaline solution is supplied to the surface of the wafer W, and the support 5 is lowered to 100 to 7
The surface of the wafer W is chemically and mechanically polished by sliding the wafer W against the polishing pad 3 while applying a polishing pressure of 50 g / cm ² to the wafer W.

At this time, since the silicon rubber sheet 2 having a hardness (JISK6301) of 15 or less and a thickness of 4 mm to 20 mm is interposed between the polishing table 1 and the polishing pad 3, the wafer W , A substantially uniform pressure is applied to the entire surface of the wafer W, and the polishing rate is substantially uniform over the entire surface of the wafer W. Also,
As described above, the hardness of the polishing pad 3 (JISK630)
Since 1) is 90 or more, even when the polishing pad 3 is stacked on the relatively soft silicon rubber sheet 2, the surface of the polishing pad 3 is flat during the polishing operation, and the wafer W Polished uniformly.

(Embodiment 2) FIG. 2 is a schematic side sectional view showing Embodiment 2 of the present invention.
Is fixed. In the figure, parts corresponding to the parts shown in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. A cylindrical concave portion 12 is provided at the center of the upper surface of the stainless steel support base 11, and the concave portion 12 has a chuck made of an acrylic resin (Young's modulus: about 330 kgf / mm ² ).
13 is inset. A retainer 17 is provided around the concave portion 12 of the support base 11, and the chuck 13 is
Inserted in 17.

On the upper surface of the chuck 13, a plurality of grooves 14, 14,.
Are provided in parallel at appropriate intervals. Each of the grooves 14, 14,... Is provided with an opening of a through path 15, 15,... Which penetrates the chuck 13, and each of the through paths 15, 15,. Further, the lower surface of the polishing table 1 has a hardness (JIS K6301) of 15 or less and a thickness of 4 m.
A silicon rubber sheet 2 having a thickness of m to 20 mm is fixed, and a polishing pad 3 having a thickness of 3 mm or less and a hardness (JISK6301) of 90 or more is fixed to the lower surface of the silicon rubber sheet 2.

In such an apparatus, after the wafer W is fitted into the retainer 17, the through-holes 15, 15,.
14, the wafer W is chucked by evacuating the inside.
The polishing table 1 is rotated and the polishing table 1 and the support table 11 are rotated, and a slurry is supplied to the surface of the wafer W. The polishing table 1 is lowered to bring the wafer W into sliding contact with the polishing pad 3. Is chemically and mechanically polished.

With this arrangement, the chucking member such as the backing pad 8 shown in FIG.
Even when the wafer W is directly fixed to 13, as before,
A substantially uniform pressure can be applied to the entire surface of the wafer W,
The entire surface of the wafer W can be polished at a substantially uniform polishing rate.

[0026]

Next, the results of a comparative test will be described. A silicon rubber sheet of various thicknesses and hardness is provided on a support base, and an 8 inch wafer having a 1 μm oxide film formed on a surface thereof is coated with 12.5 wt% of a famed silica slurry (pH
10.8) at 1000 ml / min.
A polishing pressure of 50 g / cm ² was applied, and the support table and the polishing table were rotated at a rotation speed of 40 rpm to perform polishing for 2 minutes.
In addition, as a polishing pad, an IC manufactured by Rodale Nitta is used.
1000 was used. After the polishing, the thickness of the polished film was measured at 92 points on the wafer, and the variation in the polishing rate was calculated. The results are shown in Table 1 below.

[0027]

[Table 1]

As is clear from Table 1, in any of the comparative examples, the variation in the polishing rate exceeded 10%, and the wafer could not be uniformly polished. In contrast, in the example of the present invention, the variation in the polishing rate was 10%.
, And the wafer could be polished uniformly.

[0029]

In the polishing apparatus according to the first and second aspects of the present invention, the elastic sheet having the optimized hardness and thickness is interposed between the polishing table and the polishing pad. The difference in thickness of the plurality of polished objects to be polished, or the thickness deviation existing in the plane of the polished object is absorbed by the elastic sheet and applied between the respective polished objects or on the entire surface of the polished object. Pressure is equalized. Thereby, even when the thickness of a plurality of objects to be polished at one time is different, or even when there is a thickness deviation in the surface of the object to be polished, polishing can be performed at a substantially uniform polishing rate. .

In the polishing apparatus according to the third invention, the hardness can be easily adjusted, and the elastic sheet having a required thickness can be easily obtained. Furthermore, the life span is long due to high drug resistance.

In the polishing apparatus according to the fourth aspect of the present invention, a relatively hard polishing pad is used. Therefore, even if the polishing pad is mounted on a relatively soft elastic sheet, the polishing pad is not damaged during the polishing operation. The present invention has excellent effects such that the surface is flat and the object to be polished is uniformly polished on the entire surface.

[Brief description of the drawings]

FIG. 1 is a schematic side sectional view showing a configuration of a main part of a polishing apparatus according to the present invention.

FIG. 2 is a schematic side sectional view showing a second embodiment.

FIG. 3 is a schematic side sectional view showing a chemical mechanical polishing apparatus disclosed in Japanese Patent Application Laid-Open No. 9-321001.

[Explanation of symbols]

 Reference Signs List 1 polishing table 2 silicon rubber sheet 3 polishing pad 5 support table 8 backing pad 9 retainer W wafer

Claims (4)

[Claims] An elastic sheet and a polishing pad are stacked in this order on a polishing table, and a polishing apparatus for polishing an object to be polished by sliding the object to be polished on the polishing pad has a hardness (JISK6301). ) Is 15 or less and the thickness is 4
A polishing apparatus, comprising an elastic sheet having a thickness of not less than 20 mm and not more than 20 mm. 2. An elastic sheet and a polishing pad are stacked on a polishing table in this order, and an object to be polished, which is vacuum-adsorbed to a support table disposed opposite to the polishing pad, is brought into sliding contact with the polishing pad. A polishing apparatus for polishing an object to be polished has a hardness (JIS K6301) of 15 or less and a thickness of 4 or less.
A polishing apparatus, comprising an elastic sheet having a thickness of not less than 20 mm and not more than 20 mm. 3. The polishing apparatus according to claim 1, wherein said elastic sheet is made of silicone rubber. 4. The polishing apparatus according to claim 1, further comprising a polishing pad having a hardness (JIS K6301) of 90 or more.