JP3326442B2 - Polishing method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for polishing a semiconductor substrate such as an SOI (Silicon-on-Insulator) substrate or a Si substrate to a uniform thickness.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, while flowing a colloidal silica liquid over the surface of a workpiece 1 such as a substrate,
A polyurethane pad attached to the lower end of a polishing rod 29 disposed above the workpiece 1 is brought into contact with the workpiece 1 and the polishing rod 29 is rotated around a center line while relatively rotating on the workpiece 1. Polishing is performed by sequentially moving in the lateral direction while reciprocating. The amount of polishing is measured in advance by measuring the thickness of each part of the workpiece 1, and the rotation speed of the polishing rod 29, the pressing force on the workpiece 1, and the stagnation time are adjusted to correspond to the amount of polishing of each part. It is done by doing. The low processing efficiency due to the small polishing area of one polishing rod 29 at a time is compensated for by arranging a plurality of polishing rods 29.

In this polishing method, the polishing rod 29 is disposed so as to be perpendicular to the polishing surface of the workpiece 1, and the polishing rod 29
Is formed in a plane parallel to the polishing surface, and the workpiece 1 does not rotate, and the polishing rod 29 rotates. Therefore, the relative speed of the polishing rod 29 to the workpiece 1 is at the outermost peripheral portion. It becomes maximum and becomes zero at the center. Therefore, at a certain polishing position, only the periphery of the polishing rod 29 is polished, and a region immediately below the center of the polishing rod 29 remains as a mountain. Extremely speaking, the surface of the workpiece 1 has irregularities such as hills and valleys in a hill, but when polishing the hills, this tendency becomes remarkable and polishing cannot be performed as desired.

When the polishing rod 29 is inclined with respect to the polished surface of the workpiece 1, the polished surface is processed asymmetrically.
In a so-called planetary motion type apparatus in which the polishing rod 29 revolves while rotating the polishing rod 29, it is possible to solve the problem that the processing is extremely advanced only in the outermost peripheral portion of the polishing rod 29 described above. However, in this apparatus, the driving mechanism of the polishing rod 29 is complicated and large, so that the plurality of polishing rods 29 cannot be densely arranged above the workpiece 1, and a product with high processing efficiency cannot be obtained. . The problem that asymmetric processing occurs when the polishing rod 29 is inclined with respect to the polishing surface of the workpiece 1 cannot be solved.

In such a polishing rod rotating type polishing apparatus, the processing speed is determined by the linear velocity at the outermost peripheral portion of the polishing rod 29. However, when the contact pressure at the outermost peripheral portion is reduced, the processing efficiency is reduced. It is necessary to apply a necessary and sufficient load to the outer peripheral portion. For this reason, a strong shear stress acts on the surface layer of the workpiece 1 between the periphery of the polishing rod 29 pressed against the workpiece 1 and the outer periphery thereof, and in some cases, the crystal structure such as single crystal silicon has a defect. There was also a problem that caused.

The inventor of the present invention has solved the above-mentioned problems of the conventional apparatus, and has been able to polish a workpiece to a uniform thickness more efficiently than in the prior art, without causing defects in the crystal structure. The device was proposed in Japanese Patent Application No. 4-350977.

(1) A polishing cloth is placed in contact with the polished surface of the workpiece, and a polishing rod is used to polish the polished surface of the workpiece with a pressure bar in an area smaller than the area of the polished surface of the workpiece. The cloth is pressed against the polishing cloth while adjusting the contact pressure.
A polishing method characterized in that polishing is performed while making a revolving motion of a radius smaller than the crossing length of the above-mentioned area without rotating along the polishing surface. (2) The polishing method according to the above (1), wherein the surface of the pressure bar facing the polishing cloth is formed as a convex spherical surface. (3) The polishing method according to any one of the above (1) and (2), wherein a plate-shaped elastic body is disposed on the pressing rod side of the polishing cloth. (4) A plurality of pressure rods are arranged above the polishing surface of the workpiece, and the polishing surface of the workpiece is simultaneously polished at a plurality of locations.
(1) The polishing method according to any one of (2) and (3). (5) A workpiece support device that supports the workpiece and makes a zigzag movement that moves along the polishing surface while moving around the polishing surface of the workpiece and further moves in a direction opposite to one direction, and A polishing cloth support device that supports the polishing cloth at the periphery thereof in parallel with the polishing surface relative to the polishing surface of the workpiece and moves the polishing cloth so as to be able to move toward and away from the polishing surface of the workpiece, and is opposite to the workpiece of the polishing cloth. A pressure rod supporting device disposed on the side of the polishing pad so as to movably hold the plurality of pressure rods toward the polishing cloth, wherein the tip of the pressure rod facing the polishing cloth has a convex spherical surface. (6) On the pressing rod side of the polishing cloth, a plate-like elastic body is disposed in contact with the polishing cloth, or the convex spherical surface at the tip of the pressing rod is covered with an elastic body along the convex spherical surface. The polishing apparatus according to the above (5). It is in.

According to the present invention, the polishing cloth is brought into pressure contact with the polishing surface of the workpiece by adjusting the contact pressure with the pressing rod to the area having an area smaller than the area of the polishing surface of the workpiece. Therefore, the polishing amount can be finely adjusted at a local portion of the surface of the workpiece by one pressure rod to polish the portion. By doing so, the local processing accuracy can be increased.

If the workpiece is polished while rotating around the polishing cloth without rotating along the polishing surface, any portion of the polishing surface is uniformly circulated. In addition, the relative movement speed of the polishing surface with respect to the polishing cloth becomes uniform in any portion.

As shown in FIG. 2, the radius R of the orbital motion E is made smaller than the length of the region F on the polishing surface to which the polishing cloth is pressed, so that the periphery of the region G processed by the orbital motion is reduced. The portion is only intermittently pressed by the polishing cloth, while its central portion is continuously pressed by the polishing cloth and continues to be polished. Therefore, the total processing time is maximum at the central portion and gradually shortens at the peripheral portion.
As a result, the region G to be processed does not have a hollow annular shape but is superimposed on the inner peripheral portion, and the processing amount becomes maximum at the central portion, and gradually decreases toward the peripheral portion.

The reason why the radius of the orbital motion is smaller than the crossover length of the above-mentioned region is that if the radius of the orbital motion is larger than the crossover length of the above-mentioned region, the region processed by the orbital motion becomes a hollow annular shape, This is because there is a disadvantage that the projection cannot be effectively flattened.

By making the tip of the pressure rod a convex spherical surface,
When the workpiece comes into contact with the workpiece through the polishing cloth, the contact pressure is highest at the top surface, and gradually decreases as the distance from the top surface increases. Since the polishing pressure gradually decreases in the vicinity, no shear stress is applied to the substrate as in the related art, and there is no possibility that a defect occurs in the crystal structure of the substrate. The problem of asymmetric processing caused by the inclination of the pressure rod with respect to the polishing surface can also be solved.

In addition, since the tip of the pressure rod presses the polishing cloth via the elastic body, the pressing force of the pressure rod is:
The elastic body is deformed to the outer periphery of the contact area between the pressing rod and the elastic body, and the polishing cloth is pressed against the workpiece in a state where the pressing force is gradually reduced on the outer periphery of the pressing rod. When polishing a mountain portion, the contact pressure at the top of the mountain is large and the contact pressure gradually decreases as it goes to the foot of the mountain, so the distribution of the contact pressure further spreads while gradually decreasing from the center to the periphery. It will be. By this operation, the polishing can be efficiently performed to a uniform thickness as compared with the related art.

[0014] Even with one pressing rod, the polishing surface of the workpiece is circulated while moving the polishing surface parallel to the polishing surface of the workpiece.
Move in one direction from one end to the other with respect to the pressure rod, then move at a right angle in one direction, then move with a slight overlap in the opposite direction from one direction Sweep from one side to the other while moving in zigzag By polishing the workpiece, the entire surface of the workpiece can be polished.

In order to improve the processing efficiency, it is possible to solve the problem by simultaneously polishing the polishing surface with a plurality of pressing rods, for example, by arranging six pressing rods in one row and six rows. In this case, the area in which one pressing rod is in charge of polishing becomes small, and the range in which the zigzag movement is performed is narrow and constant. Therefore, the rectangular area may be polished by moving it from the outside or from the inside in a spiral shape along the square outline.

In the above-mentioned apparatus, the polishing cloth support device is provided so as to be able to contact and separate from the workpiece, but is not provided so as to translate or rotate with respect to the workpiece. Was.

A generally used polishing cloth is a non-woven fabric made of polyurethane, or a hardened cloth impregnated with a polyurethane resin. It was found that the surface had irregularities, and that there was uneven hardness due to uneven density of the coarse structure, and that a random pressure distribution was given when a load for polishing was applied.

In the above-mentioned polishing apparatus, since the narrow area is polished by the pressure bar, the polishing cloth does not rotate or move with respect to the workpiece, but always comes into contact with the workpiece at the same position. Uneven hardness and irregularities tend to be transferred to the surface of the workpiece, and irregularities occur in the distribution of the processing amount. As a result, the undulation that occurs is the degree of the roughness of the structure of the polishing pad (0.1).
(Approximately 0.5 mm), which indicates that the surface roughness of the workpiece surface is deteriorated.

[0019]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polishing apparatus which can prevent the surface roughness from being deteriorated by a polishing cloth in the above-mentioned apparatus.

[0020]

According to the present invention, there is provided the above-mentioned apparatus, wherein the polishing pad supporting device rotatably holds the polishing pad supporting device at the same position, and the frictional force generated between the polishing pad and the workpiece. The above problem is solved by performing polishing while rotating the polishing cloth at the same position by the orbital movement of the workpiece.

[0021]

According to the present invention, since the polishing cloth makes a rotational movement with respect to the workpiece along a plane parallel to the processing surface of the workpiece,
The unevenness of the polishing cloth surface, which is the cause of the irregular distribution of the processing amount, is averaged over a wide area, so that the problem of the irregular distribution of the processing amount does not occur, and the intended processing amount can be given every moment.

[0022]

FIG. 1 shows an embodiment in which a plate-like elastic body is arranged in contact with a polishing cloth on the pressing rod side of the polishing cloth.
The apparatus of the present invention includes a workpiece support device 3 and a polishing cloth support device 4.
And a pressure rod support device 5, and the workpiece support device 3
Is a ring-shaped fixed frame 6, a processing table 7 having a peripheral edge joined to the fixed frame 6 by a rubber bellows 8 inside the fixed frame 6, and a support frame 9.
And a shaft 10 supported by a support frame 9 and rotated by a motor (not shown). The processing table 7 is constrained by a rubber bellows 8 by an eccentric portion 11 formed at one end of the shaft 10, and has an eccentric portion at the same position. A revolving motion corresponding to the eccentric amount of 11 is performed. In order to eliminate the vibration caused by this eccentric movement, the shaft 1
A weight 24 is attached to the shaft 10 outside the zero.

The workpiece 1 such as a substrate can be fixed on the processing table 7 in the fixed frame 6 by suction.
The workpiece support device 3 including the fixed frame 6, the support frame 9, and the like,
By means of a device (not shown), the workpiece 1 moves in one direction on a plane parallel to the polishing surface 12, then slightly moves in a lateral direction perpendicular to one direction, moves in the opposite direction, and moves in the same direction as before. The zigzag movement of slight movement in the horizontal direction is performed in a certain area.

This feeder is a normal XY table provided with a feed mechanism using ball screws in two perpendicular directions.
The amount of feed in each direction is adjusted by the amount of rotation of a motor that rotationally drives the ball screw. The zigzag motion is performed by performing the feed at a constant speed in the right angle direction while periodically increasing and decreasing the feed amount in one direction.
The fixed frame 6 is provided with a supply and discharge port for the colloidal silica solution so that the colloidal silica solution passes from one side to the other so that the workpiece 1 is immersed.

The polishing cloth support device 4 closes the other end of the cylindrical part 27 of the polishing cloth mounting frame 13 with the polishing cloth mounting frame 13 having a shape in which a flange is formed at one end of the cylindrical part 27 having an open center. There is a polishing cloth 14 fixed to the other end of the cylindrical portion 27 at the peripheral edge, and the polishing cloth 14 is
Contacting the polishing surface 12 in parallel with the polishing surface 12
2 is supported by an up-down device (not shown) so as to be able to be separated from the device 2. On the opposite side of the workpiece 1 of the polishing cloth 14, a plate-like elastic body 15 made of silicon rubber is provided.
4 is adhered.

The pressure rod support device 5 includes a support plate 16 parallel to the polishing pad 14, and a plurality of support members 16 which are movably moved in the axial direction through the support plate 16 at right angles to the support plate 16. A pressure rod 2, a cylinder block 17 disposed above a support plate 16, a linear actuator 18 of the same number as the pressure rods 2 mounted on the upper surface of the cylinder block 17 in opposition to the pressure rod 2, A spring 19 provided in the cylinder block 17 for transmitting the pressing force of the actuator 18 to the pressure rod 2 side, and a connection cylinder 21 connected to the upper end of each pressure rod 2
, A pressure sensor 22 disposed in the connection cylinder 21, and an intermediate shaft 20 that transmits the pressure of the spring 19 to the pressure rod 2 via the pressure sensor 22.

The tip 23 of the pressure rod 2 protruding toward the elastic body 15 is formed as a convex spherical surface. A linear actuator 26 is attached to the support plate 16 and the support plate 16
The polishing cloth guide 25 disposed below the lower side can be moved up and down by a linear actuator 26. The center of the polishing cloth guide 25 is formed in a cylindrical portion 28, and is held above the polishing cloth guide 25 by a linear actuator 26 before and after polishing, and when the polishing cloth 14 is in a processing state in which the polishing cloth 14 contacts the workpiece 1. The polishing cloth guide 25 is lowered by the linear actuator 26 so that the outer periphery of the cylindrical portion 28 is fitted to the inner periphery of the cylindrical portion 27 of the polishing cloth mounting frame 13 so that the polishing cloth mounting frame 13 can be rotated at the same position. Hold.

In the above embodiment, the polishing cloth guide 2
5 is supported by the support plate 16, but may be arranged around the polishing cloth mounting frame.

The polishing of the polishing surface 12 of the workpiece 1 is performed as follows. First, the workpiece 1 whose thickness of each part was measured
Is mounted on the processing table 7, and the colloidal silica liquid is flowed into the fixed frame 6 so that the polishing surface 12 is immersed. Polishing cloth mounting frame 13
To bring the polishing pad 14 into contact with the polishing surface 12. The polishing cloth guide 25 is lowered by the linear actuator 26, and the cylindrical section 28 is inserted into the cylindrical section 27 of the polishing cloth mounting frame 13. By operating the linear actuator 18, the pressure rod 2 is lowered to bring the tip 23 into pressure contact with the elastic body 15.
The rotation of the shaft 10 causes the workpiece 1 to orbit at that position, and starts moving in one direction from one end of the polishing surface to the other end.

At this time, the linear actuator 1 is polished so that polishing corresponding to the polishing amount determined by the measurement result of each portion of the polishing surface 12 pressed by the pressure rod 2 is obtained.
8 is operated, and this operation is returned to the linear actuator 18 by the pressure sensor 22 so that polishing corresponding to the polishing amount of each portion is performed. The polishing surface moved to the other end side is slightly moved at a right angle to one direction, then moved in the opposite direction to one direction and sequentially moved sideways so that the entire polishing surface is swept by a plurality of pressure rods. Grind. When the work piece 1 is given a revolving motion, the polishing cloth 14 is brought into contact with the work piece 1 and the polishing cloth 14.
Due to the friction with the circumferential direction, the self-rotation is performed very slowly in the circulating direction at that position as compared with the circulating speed.

In this apparatus, a polyurethane fiber non-woven fabric impregnated with a polyurethane resin was used as the polishing cloth 14. The diameter of the tip 23 of the pressure rod 2 was 20 mm, and the radius of curvature of the lower surface was 25 mm. Elastic body 1 made of plate-like silicon rubber
The thickness of 5 was 5 mm, and the diameter of the contact portion of the elastic body 15 at the tip 23 was 15 mm. Polishing was performed with the workpiece 1 having a circumference diameter of 2 mm, a rotation speed of 1000 times / minute, an amplitude of 25 mm during reciprocating movement of the workpiece 1 and a reciprocating overlap width of 0.2 mm. The average surface roughness was 20 ° in terms of Ra value. On the other hand, the average surface roughness of the finished surface in the conventional polishing cloth fixed type polishing apparatus was 100 ° in terms of Ra value.

[0032]

According to the present invention, the workpiece can be polished to a uniform thickness, the surface can be polished to a better surface roughness than in the past, and there is no risk of defects occurring in the single crystal of the silicon substrate. A polishing method and apparatus can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of the device of the present invention.

FIG. 2 is an explanatory diagram of a relationship between a revolving motion of a workpiece and a processing area by one pressure rod in the method of the present invention.

FIG. 3 is an explanatory view of a conventional polishing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Workpiece 2 Pressing rod 3 Workpiece support device 4 Polishing cloth support device 5 Pressing rod support device 6 Fixed frame 7 Processing table 8 Rubber bellows 9 Supporting frame 10 Axis 11 Eccentric part 12 Polishing surface 13 Polishing cloth mounting frame 14 Polishing cloth 15 Elastic body 16 Support plate 17 Cylinder block 18 Linear actuator 19 Spring 20 Intermediate shaft 21 Connecting cylinder 22 Pressure sensor 23 Tip 24 Weight 25 Polishing cloth guide 26 Linear actuator 27 Cylindrical part 28 Cylindrical part

Claims (6)

(57) [Claims] 1. A polishing cloth is arranged in contact with a polishing surface of a workpiece, and a polishing cloth is applied to a polishing surface of the processing object with a pressure rod in a region having an area smaller than an area of the polishing surface of the workpiece. Is pressed while adjusting the contact pressure, and the workpiece is made to circulate along the polishing surface with a radius smaller than the crossing length of the region without rotating along the polishing surface, and A polishing method wherein the polishing is performed while rotating the polishing cloth at the same position by a frictional force generated between the polishing cloth and the workpiece and the orbital movement of the workpiece. 2. The polishing method according to claim 1, wherein a surface of the pressure bar facing the polishing cloth is formed as a convex spherical surface. 3. The polishing method according to claim 1, wherein a plate-shaped elastic body is arranged on the pressing rod side of the polishing cloth. 4. The polishing method according to claim 1, wherein a plurality of pressure rods are arranged above the polishing surface of the workpiece, and the polishing surface of the workpiece is simultaneously polished at a plurality of locations. Polishing method. 5. A workpiece support device for supporting a workpiece and moving along the polishing surface while moving around the polishing surface of the workpiece, and a polishing surface opposed to the polishing surface of the workpiece. A polishing cloth supporting device that supports the polishing cloth at the peripheral edge thereof in parallel with and moves the polishing cloth so as to be able to approach and separate from the polishing surface of the workpiece, and is rotatably held at the same position, and a workpiece of the polishing cloth. A polishing rod supporting device which is disposed on the opposite side and movably holds the plurality of pressure rods toward the polishing cloth, wherein a tip of the pressure rod facing the polishing cloth has a convex spherical surface. 6. A plate-shaped elastic body is arranged on the pressing rod side of the polishing cloth in contact with the polishing cloth, or the convex spherical surface at the tip of the pressing rod is
The polishing apparatus according to claim 5, wherein the polishing apparatus is covered with an elastic body having a shape along the convex spherical surface.