JPH1094958A - Substrate polishing method and polishing device used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To polish the surface of a substrate uniformly by a front surface standard by polishing the front surface of the substrate while pressurizing the back surface of the substrate by a gas and also supplying a polish liquid to the front surface of the substrate through a polishing pad. SOLUTION: When a substrate 1 is arranged between a surface plate 2 and a substrate holder 3 and the back surface of the substrate 1 is pressurized by a gas supplied from the substrate holder 3 side and also the surface plate 2 and the substrate holder 3 are rotated together and the front surface of the substrate 1 is polished while supplying a polish liquid 6 from the surface plate 2 side to the front surface of the substrate 1 through a polishing pad 4, the back surface of the substrate 1 is positioned in a state separated from the substrate holder 3 through a gas space 24 except the outer periphery part and the front surface of the substrate 1 is polished.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of polishing a substrate, and more particularly to a method of polishing a substrate on a surface basis and a polishing apparatus used in the method.

[0002]

2. Description of the Related Art A semiconductor wafer (hereinafter simply referred to as a wafer) is used as a starting material when manufacturing a semiconductor device such as an IC or an LSI. In each manufacturing process of the semiconductor device, since various process processes for forming circuit elements are performed on the surface of the wafer, the surface of the wafer needs to be polished so as to be flat beforehand. Alternatively, this polishing may be performed in the middle of each manufacturing process as necessary. Such polishing is performed using a dedicated polishing apparatus.

FIG. 4 is a sectional view showing a conventional polishing apparatus. In FIG. 1, reference numeral 1 denotes a wafer to be polished, and the wafer 1 is disposed between a surface plate 2 and a wafer holder (substrate holder) 3. Reference numeral 4 denotes a polishing pad attached to the surface of the surface plate 2, and reference numeral 5 denotes a nozzle for supplying a polishing liquid 6 to the polishing pad 4.

[0004] The wafer holder 3 is composed of the following components. Reference numeral 7 denotes a reference plate, which is disposed so as to face the back surface of the wafer 1, has small holes 8 for pressure reduction and pressurization for supplying a gas such as air, and is fixed to the support plate 10 by a reference plate set screw 9. ing. 11 is a universal joint provided between the pair of upper plates 18 above the support plate 10,
Reference numeral 12 denotes a large pressure reducing and pressurizing hole provided at the center of the support plate 10 and the upper plates 18. 13 is a small hole 8 for decompression and pressurization of the reference plate 7 and a large hole 1 for decompression and pressurization of the support plate 10.
2, a depressurizing and pressurizing groove communicating with 2, a seal ring provided around the depressurizing and pressurizing groove 13, and a backing pad 15 attached to the surface of the reference plate 7.
A retainer ring 16 is provided around the reference plate 7 to prevent the wafer 1 from jumping out. The retainer ring 16 is fixed to the support plate 10 by a retainer set screw 17.

[0005] In such a polishing apparatus, when polishing the wafer 1, the wafer 1 is placed below the backing pad 15 constituting the wafer holder 3.
Through a small hole 8 for decompression and pressurization, a groove 13 for decompression and pressurization, and a large hole 12 for decompression and pressurization, vacuum suction is performed from the outside,
The back surface of the wafer 1 is attracted to the backing pad 15 surface.
Next, the wafer holder 3 is placed above the platen 2 while the wafer 1 is being sucked, the surface of the backing pad 15 is held under reduced pressure or normal pressure, and the surface of the wafer 1 is placed on the polishing pad 4 of the platen 2. Press Subsequently, while the polishing liquid 6 is supplied to the polishing pad 4 from the nozzle 5, the surface of the wafer 1 is polished by rotating the platen 2 and the wafer holder 3 together.

[0006]

By the way, in a polishing method using a conventional polishing apparatus, a backing pad 1 is used.
5 has a problem that the polishing surface of the wafer 1 is not uniformly polished because the thickness unevenness directly causes the polishing pressure to be uneven.

[0007] That is, the backing pad 1 does not have the required surface-based polishing for the polished surface of the wafer 1.
The back-side polishing depends on the thickness unevenness of No. 5. Therefore, in-plane uniformity becomes insufficient particularly for flattening polishing of a wafer having a step on the surface,
There is a need for a polishing method capable of surface-based polishing.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem. The present invention is directed to pressurizing the back surface of a substrate with a gas and supplying a polishing liquid to the surface of the substrate via a polishing pad. It is an object of the present invention to polish a substrate with good in-plane uniformity on a surface basis.

[0009]

According to the present invention, there is provided a substrate polishing method comprising:
Place the substrate between the surface plate and the substrate holder, pressurize the back surface of the substrate with gas supplied from the substrate holder side, while supplying the polishing liquid from the surface plate side to the surface of the substrate via a polishing pad, A substrate polishing method for polishing the surface of a substrate by rotating both a platen and a substrate holder, wherein the substrate holder positions the back surface of the substrate apart from the substrate holder via a gas space except for an outer peripheral portion. And polishing the surface of the substrate.

Therefore, according to the substrate polishing method of the present invention, the substrate is polished by positioning the rear surface of the substrate with the substrate holder floating except the outer peripheral portion from the substrate holder. Therefore, since the conventional backing pad is not required, the substrate can be polished with good in-plane uniformity on the basis of the surface.

The polishing apparatus of the present invention comprises: a platen provided with a polishing pad on a contact surface with a substrate to be polished; a reference plate having a gas supply hole disposed opposite to the back surface of the substrate; A sealing cushion that is arranged to be shrunk in the height direction around the periphery of the sealing cushion and that holds the outer periphery of the back surface of the substrate, and that is arranged so as to be movable in the height direction around the sealing cushion and surrounds the side surface of the substrate A retainer ring, and a substrate holder fixed at least on the surface plate provided with at least a retainer cushion that is disposed in contact with the retainer ring so as to be contractable in the height direction and moves the retainer ring as described above, A gas is supplied from a hole in a reference plate of the substrate holder, and the substrate is positioned while being separated from the reference plate via a gas space.

Therefore, according to the polishing apparatus of the present invention, the reference plate having a hole for supplying gas, which is disposed so as to face the back surface of the substrate, is disposed around the reference plate so as to be contractable in the height direction. A sealing cushion for holding an outer peripheral portion of the back surface of the substrate, a retainer ring disposed movably in a height direction around the sealing cushion and surrounding the side surface of the substrate, and a height direction in contact with the retainer ring. Since the substrate holder is configured by providing at least a retainer cushion that is arranged to be retractable and moves the retainer ring as described above, gas is supplied from a hole in the reference plate, and the substrate is moved from the reference plate through the gas space. Can be positioned in a separated state. Therefore, since the conventional backing pad is not required, the substrate can be polished with good in-plane uniformity on the basis of the surface.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 is a sectional view showing a polishing apparatus used for carrying out the substrate polishing method of the present invention, FIG. 2 is a sectional view showing a wafer holder 3 which is a main part of the polishing apparatus, and FIG. 3 is a bottom view showing the wafer holder 3. .

1 to 3, reference numeral 1 denotes a wafer to be polished, 2 denotes a surface plate, 3 denotes a wafer holder, and wafer 1 is disposed between the surface plate 2 and the wafer holder 3. Reference numeral 4 denotes a polishing pad attached to the surface of the surface plate 2, and reference numeral 5 denotes a nozzle for supplying a polishing liquid 6 to the polishing pad 4.

The wafer holder 3 is composed of the following components. A reference plate 7 is made of a rigid material such as ceramic or glass, and is disposed so as to face the back surface of the wafer 1 and has a small hole 8 for pressure reduction and pressurization for supplying a gas such as air. The reference plate 7 is a support plate made of a material such as metal or ceramic and fixed by the reference plate set screw 9.

Reference numeral 11 denotes a pair of upper plates 18 above the support plate 10.
The universal joint 12 provided between the support plate 10 and the upper plate 1
8, a large hole for pressure reduction and pressurization provided at the center of 8, a groove 13 for pressure reduction and pressurization for communicating the small hole 8 for pressure reduction and pressurization of the reference plate 7 with the large hole 12 for pressure reduction and pressurization of the support plate 10, 14
Is a seal ring provided around the depressurizing and pressurizing groove 13. A sealing cushion 19 made of a highly elastic material such as soft silicon rubber is arranged around the reference plate 7 so as to be contractable in the height direction. The sealing cushion 19 is in contact with the support plate 10. The sealing cushion 19 functions to hold the outer peripheral portion of the back surface of the wafer 1.

At the periphery of the sealing cushion 19, a retainer ring 16 made of, for example, Delrin, epoxy resin or the like is disposed so as to be movable in the height direction. It is fixed to the support plate 10. The retainer cushion 21 is made of a highly elastic material such as soft silicone rubber, for example, and is arranged so as to be contractable in the height direction. The retainer ring 16 is moved in the height direction by the elastic force of the retainer cushion 21 and functions to prevent the wafer 1 from jumping out to the side.

A free screw clamp 22 is provided around the upper plate 18. The free screw clamp 22 has its protruding end 22 a arranged so as to be able to move up and down in the insertion hole 23 of the retainer free screw 20. , The retainer free screw 20 can be pressed.

Next, a description will be given of a substrate polishing method using such a substrate polishing apparatus.

First, as shown in FIG.
The wafer 1 to be polished is placed on the orientation flat 1a with respect to the sealing cushion 19 constituting
Are set to have a predetermined positional relationship. As shown in FIG. 2, the outer periphery of the back surface of the wafer 1 is reduced by vacuum suction from the outside through the small holes 8 for pressure reduction and pressurization, the grooves 13 for pressure reduction and pressurization, and the large holes 12 for pressure reduction and pressurization. The part is adsorbed on the surface of the reference plate 7 in a state where the sealing cushion 19 is compressed. At this time, as shown by the arrow in FIG. 2, the free screw clamp 22 is lowered and the retainer free screw 20 is pushed down to keep the retainer ring 16 at the lowermost end. In this state, the bottom of the retainer ring 16 is 50
It protrudes downward by ５００500 μm (preferably 100-200 μm).

Next, as shown in FIG. 1, the wafer holder 3 holding the wafer 1 is placed on the platen 2 and fixed at a position where the retainer ring 16 contacts the polishing pad 4. Subsequently, when a gas such as air is supplied from the outside via the small holes 8 for pressure reduction and pressurization, the grooves 13 for pressure reduction and pressurization, and the large holes 12 for pressure reduction and pressurization, the back surface of the wafer 1 is added by the gas. Since it is pressed, it is separated from the surface of the reference plate 7 and pressed against the polishing pad 4. Reference numeral 24 denotes a gas space formed between the reference plate 7 and the wafer 1. As a result, the wafer 1 is pressed by the gas space 24 without using a backing pad as in the related art.

Next, as shown in FIG. 1, when the free screw clamp 22 is raised as shown by the arrow, the retainer free screw 20 is no longer pressed, so that the retainer ring 16 compresses the retainer cushion 21 to compress the wafer. 1 so as to be at the same height as the surface 1. Thereby, the retainer fly screw 20 is also raised by the amount corresponding to the compression. Subsequently, while the polishing liquid 6 is supplied to the polishing pad 4 from the nozzle 5, the surface of the wafer 1 is polished by rotating the platen 2 and the wafer holder 3 together. In such a polished state, the compression amount of the sealing cushion 19 changes while responding to the fluctuation of the surface pressure during the polishing. The sealing effect against gas is always maintained. As described above, the followability of the vertical movement is good, but the frictional force is large with respect to the lateral force,
There is no rotation or displacement of the wafer 1 with respect to the sealing cushion 19. Therefore, the wafer 1 rotates in synchronization with the rotation of the wafer holder 3.

Also, even if the wafer 1 is misaligned during polishing, the wafer 1 is prevented from jumping out to the side by the retainer ring 16 in contact with the surface of the polishing pad 4. Further, even if the wafer 1 has undulation or warpage, the polishing surface of the wafer 1 is pressed against the surface of the polishing pad 4 by the back pressure, so that the polishing can be performed substantially on the basis of the surface. Therefore, for example, when flattening and polishing a wafer having an interlayer film step in the middle of the process of manufacturing a MOSIC, the pattern step can be removed with good in-plane uniformity.

As described above, according to the substrate polishing method of the present invention,
The wafer 1 is positioned while the back surface of the wafer 1 is separated from the wafer holder 3 via the gas space except for the outer peripheral portion.
Since the surface is polished, the following effects can be obtained.

(1) Since surface-based polishing of the wafer 1 can be performed, in-plane uniformity is improved.

(2) As the in-plane uniformity is improved,
Since the polishing pad 4 made of a hard material can be used, it is easy to flatten the step.

(3) Since the back surface of the wafer 1 can be polished in a non-contact manner, the back surface is not damaged.

(4) Since the outer peripheral portion of the back surface of the wafer 1 is always sealed by the sealing cushion 19 made of a highly elastic material, gas leakage due to pressurization can be prevented.
The applied pressure stabilizes.

(5) Warpage, undulation,
Polishing can be performed almost without being affected by uneven thickness or the like.

In the description of the present invention, the case where a semiconductor wafer is polished has been described as an example. However, the present invention is not limited to this, and the same can be applied to a case where a wafer-like substrate is polished. Further, the polishing has been described by taking an example in which one wafer is polished, but the present invention can also be applied to a case in which a plurality of wafers are polished simultaneously. Further, the specific material of each component constituting the wafer holder is not limited to those exemplified in the text, and any material having an equivalent function can be similarly used.

[0032]

As described above, according to the present invention, the surface of the substrate is polished by positioning the rear surface of the substrate apart from the substrate holder via the gas space except for the outer peripheral portion. The substrate can be polished with good in-plane uniformity on a surface basis.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a polishing apparatus used for carrying out a substrate polishing method of the present invention.

FIG. 2 is a sectional view showing a substrate holder which is a main part of a polishing apparatus used for carrying out the substrate polishing method of the present invention.

FIG. 3 is a bottom view showing a substrate holder which is a main part of a polishing apparatus used for carrying out the substrate polishing method of the present invention.

FIG. 4 is a sectional view showing a conventional polishing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Wafer (substrate), 2 ... Surface plate, 3 ... Wafer holder (substrate holder), 4 ... Polishing pad, 5 ... Nozzle, 6 ... Polishing liquid, 7 ... Reference plate, 10 ... Support plate, 14 ... Seal ring,
16 ... retainer ring, 19 ... cushion for sealing,
20: Retainer free screw, 21: Retainer cushion, 22: Free screw clamp, 24: Gas space.

Claims (6)

[Claims] 1. A substrate is disposed between a surface plate and a substrate holder, the back surface of the substrate is pressurized by gas supplied from the substrate holder side, and the surface of the substrate is polished from the surface plate side via a polishing pad. A substrate polishing method for polishing a surface of a substrate by rotating the surface plate and the substrate holder together while supplying a polishing liquid, wherein the substrate holder removes gas from the substrate holder except for an outer peripheral portion of the substrate. And polishing the surface of the substrate by positioning the substrate in a separated state. 2. The substrate polishing method according to claim 1, wherein the surface of the substrate is polished by a substrate holder while surrounding the side surface of the substrate. 3. The substrate polishing method according to claim 1, wherein a sealing cushion is provided on the substrate holder, and the outer peripheral portion of the back surface of the substrate is held by the sealing cushion to prevent leakage of gas for pressurizing the back surface. Method. 4. A retainer ring is provided on a substrate holder,
3. The method for polishing a substrate according to claim 2, wherein the side surface of the substrate is surrounded by the retainer ring. 5. The height of the substrate holder is fixed at a position where the retainer ring of the substrate holder contacts the polishing pad of the surface plate, and the distance of the back surface of the substrate from the substrate holder in the height direction is determined. The substrate polishing method according to claim 4, wherein: 6. A reference plate provided with a polishing pad on a contact surface with a substrate to be polished, a reference plate arranged to face a back surface of the substrate and having a hole for supplying gas, and a peripheral portion of the reference plate. A sealing cushion arranged so as to be contractable in the height direction and holding an outer peripheral portion of the back surface of the substrate, a retainer ring arranged movably in the height direction around the sealing cushion and surrounding the side surface of the substrate; A substrate holder which is provided at least with a retainer cushion which is arranged in contact with the retainer ring so as to be contractable in the height direction and which moves the retainer ring as described above, and which is fixed on the platen; A polishing apparatus, characterized in that a gas is supplied from a hole in a plate to position the substrate while keeping the substrate away from a reference plate.