JPS6294257A - Polishing device - Google Patents

Abstract

PURPOSE:To make possible to control the space between a workpiece and a polishing head to keep a constant value, in the captioned device for a Si wafer and the like, by providing the optical means for detecting said space and a feedback circuit therefor. CONSTITUTION:The spindle of a sample holding plate 4, to which a workpiece 3 such as a Si wafer is sticked, is supported by a bearing while said spindle is supported, a part from a polishing and 5, by a magnetic means composed of a electromagnet 6A and permanent magnet 6B. And, the space <d> between the workpiece 3 and the polishing pud 5 is detected by a light source 7A and light receiving device 7B comprising a optical means 7 so that the detected value is converted, in response to the detected signal, to a driving current outputting to the electromagnet 6A by a feedback circuit 8 so as to control the resiliency between the magnets. Therefore, the static pressure of polishing liquid independently to the rotating speed of a polishing machine, thereby it is possible to keep the space between the workpiece 3 and the polishing and 5 to the predetermined value.

Description

[Detailed Description of the Invention] [(Important)] In a floating non-contact polishing device, the distance between the sample to be polished and the polishing pad is detected by an optical sensor, and the distance is returned to the electromagnet that supports the sample holding plate that holds the sample to be polished. The present invention proposes an apparatus in which the static pressure of the polishing liquid is controlled to maintain the distance at a predetermined value, thereby obtaining optimal polishing conditions.

[Industrial application field]

The present invention relates to a static pressure controlled floating type non-contact polishing apparatus that can maintain a constant distance between a sample to be polished and a polishing pad.

This device is used for mirror polishing of semiconductor substrates, etc., and polishes a sample holding plate to which a silicon (Si) wafer or the like is attached as a sample to be polished by performing planetary motion in a polishing solution. An important polishing condition is the distance between the wafer and the polishing pad that faces each other via the polishing liquid.

However, when the polishing disk rotates, the polishing liquid moves outward due to centrifugal force, and the sample holding plate is subjected to static pressure (pressure acting perpendicular to the streamlines of the polishing liquid) that attracts it toward the polishing pad. Therefore, measures are desired to control this and maintain optimal polishing conditions.

[Conventional technology]

FIG. 2 is a sectional view of a conventional floating type non-contact polishing device.

In the figure, reference numeral 1 denotes a polishing disk, which is a dish-shaped disk that rotates around its center line by an external drive.A polishing pad 5 is placed on the bottom of the disk, and a polishing liquid 2 is filled.

3 is a sample to be polished, which is attached to a sample holding plate 4;

The spindle of the sample holding plate 4 is supported by a bearing 9, and the sample holding plate 4 is structured to rotate as the polishing plate 1 rotates.

10 schematically shows a ring to a ball of the bearing 9.

Permanent magnets 11 and 12 support the sample holding plate 4 while maintaining the distance d between the sample to be polished 3 and the polishing pad 5 by mutual repulsion.

In such an apparatus, in order to change the distance d between the sample 3 to be polished and the polishing pad 5, the rotation speed of the polishing disk is changed, the static pressure of the polishing liquid is changed, and the sample 3 to be polished is moved up and down. Therefore, there was a drawback that the degree of freedom in selecting polishing conditions was small and optimum polishing could not be performed.

[Problem that the invention seeks to solve]

In conventional floating non-contact polishing equipment, the distance between the sample to be polished and the polishing blade/nod cannot be freely controlled, making it impossible to select optimal polishing conditions.

[Means for solving problems]

The solution to the above problem is to remove the sample to be polished (3) in the polishing liquid (2).
magnetic means (6) for supporting the sample holding plate (4) holding the sample (3) away from the polishing pad (5);
) and the polishing pad (5); and an optical means (7) for detecting the distance (d) between the polishing pad (5) and the magnetic means (
a feedback circuit (8) that feeds back to the feedback circuit (6);
8) returns the interval detection signal of the optical means (7) to the magnetic means (6), thereby detecting the interval (d).
This is achieved by the polishing apparatus according to the present invention, which is capable of keeping the constant value.

[Effect]

The present invention uses an electromagnet instead of a conventional permanent magnet to support the sample holding plate, detects the distance between the sample to be polished and the polishing pad using an optical sensor, and feeds this signal back to the electromagnet to rotate the polishing disk. The distance between the sample to be polished and the polishing band can be freely selected and maintained independently of the speed.

〔Example〕

FIG. 1 is a sectional view of a static pressure controlled floating non-contact polishing apparatus according to the present invention.

In the figure, reference numeral 1 denotes a polishing disk, which is a dish-shaped disk that rotates around its center line by an external drive.A polishing pad 5 is placed on the bottom of the disk, and a polishing liquid 2 is filled.

The polishing liquid 2 includes, for example, sodium (Na), potassium, (
Silica (SiOz) suspended in an alkaline solution such as K) is used.

As the polishing pad 5, for example, a huff made of polyurethane foam is used.

Reference numeral 3 denotes a sample to be polished, for example a Si wafer, which is attached to a sample holding plate 4.

The spindle of the sample holding plate 4 is supported by a bearing 9, and the sample holding plate +Ii, 4 has a structure that can rotate as the polishing plate 1 rotates.

10 schematically shows a ball bearing of the bearing 9.

The above is the same as the conventional device.

6 is a magnetic means for supporting the sample holding plate 4 away from the polishing pad 5, 68 is an electromagnet, and 6B is a permanent magnet.

The sample holding plate 4 is supported by the mutual repulsive force between the electromagnet 68 and the permanent magnet 6B.

7 is an optical means for detecting the distance d between the sample to be polished 3 and the polishing pad 5, 7A is a light source, and 7B is a light receiver.

Reference numeral 8 denotes a feedback circuit that returns from the optical means 7 to the magnetic means 6, which changes the drive current output to the electromagnet 68 in accordance with the interval detection signal input from the light receiver 7B, thereby increasing the distance between the two magnets. By controlling the repulsive force, the distance d between the sample to be polished 3 and the polishing pad 5 can be maintained at a predetermined gap.

〔Effect of the invention〕

As explained above, in the apparatus of the present invention, the static pressure of the polishing liquid can be controlled independently of the rotation speed of the polishing disk, the distance between the sample to be polished and the polishing pad can be maintained at a predetermined gap, and the polishing conditions can be selected. It has the advantage of having a large degree of freedom and being able to perform optimal polishing.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a static pressure controlled floating non-contact polishing device according to the present invention, and FIG. 2 is a sectional view of a conventional floating non-contact polishing device. In the figure, 1 is a polishing disk, 2 is a polishing liquid, 3 is a sample to be polished, 4 is a sample holding plate, 5 is a polishing pad, 6 is a magnetic means for supporting the sample holding plate, 6A is an electromagnet, and 6B is a permanent magnet , 7 is an optical means for detecting the distance between the sample to be polished and the polishing pad, 7A is a light source, 711 is a light receiver, Blood 7 Magnetic tip vJ Senyakue, Katsuu 4 Yodan Kitani Hitanosho 1'' attached illustration 1 country

Claims (1)

[Scope of Claims] Magnetic means (6) for supporting a sample holding plate (4) that holds a sample to be polished (3) in a polishing liquid (2) at a distance from a polishing pad (5); Distance (d) between sample (3) and the polishing pad (5)
an optical means (7) for detecting; a feedback circuit (8) for feeding back from the optical means (7) to the magnetic means (6); A polishing apparatus characterized in that the distance (d) can be kept constant by feeding back the distance detection signal of (7) to the magnetic means (6).