JPS6056867A - Grinding device - Google Patents

Abstract

PURPOSE:To provide a wafer with strain-less mirror surfaces by supporting a support plate or polishing plate to make a gap between the support plate and polishing plate adjustable and immerse both plates together with a workpiece in polishing liquid. CONSTITUTION:When a polishing plate 7 is rotated in the direction of arrow 9 in an apparatus for polishing the surface of a workpiece into a strain-less mirror surface, the workpiece 1 and the plate 7 have relative speed to produce flow of polishing liquid 10 through a gap 8. The more the relative speed is increased, the lesser the pressure of liquid 10 in the gap 8 is reduced to reduce the gap 8 so that grains included in the liquid 10 rub the surface of the workpiece 1 to permit working in the order of atom. When the rotation of the plate 7, is stopped the relative speed of the workpiece 1 and the plate 7 is lost so that the gap 8 is returned to the condition prior to the polishing. Thus, since the surface of the workpiece 1 does not contact the plate 7, a wafer having a strain-less mirror surface can be provided which has never been conventionally produced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polishing apparatus for polishing the surface of a workpiece to a distortion-free mirror surface. Taking a semiconductor wafer as an example of a workpiece, as the yellow density of IJI increases, crystal defects in the surface layer of the semiconductor wafer greatly affect the yield of devices, so polishing that polishes the surface layer without strain is required. Demand for equipment is increasing.

Conventionally used polishing equipment presses the workpiece held on a support plate onto the polishing plate under a pressure of several hundred f/i through a polishing liquid in which abrasive grains are suspended in a chemical liquid. This is a device that polishes the workpiece through relative movement between the workpiece and the polishing plate. However, when this device is used, the workpiece is pressed against the polishing plate through the abrasive grains and polished, so the abrasive grains on the polishing plate are pushed into the workpiece, causing distortion in the workpiece. There was a drawback to it. The object of the present invention is to eliminate this drawback and provide an apparatus for polishing a workpiece to a distortion-free mirror surface.

In the apparatus of the present invention, the workpiece held on the support plate and the polishing plate have a relative velocity of a preset value or more.
In a polishing device that moves relative to each other, magnets are arranged in a circumferential manner (the center of rotation is aligned with the support plate, and the magnets are arranged in a circumferential manner so as to face the magnets provided on the support plate and whose lines of magnetic force are opposite to each other). The polishing plate is provided with an abrasive plate, the support plate or the abrasive plate is supported such that the gap between the support plate and the abrasive plate is made freely, and the support plate and the abrasive plate including the workpiece are immersed in a polishing liquid. A polishing device characterized by:

The effects and processing principle when using the apparatus of the present invention will be explained. This device holds the workpiece, and the center of rotation coincides with a support plate provided with magnets in a circumferential shape, and magnets are provided in a circumferential manner, facing the magnets on the support plate and having magnetic lines of force in opposite directions. The support plate and the abrasive plate are supported such that the gap between the support plate and the abrasive plate is freely adjusted. When the object and the abrasive plate are moved relative to each other at a relative speed greater than a preset value, a flow occurs between the support plate containing the workpiece and the abrasive plate, and as the relative speed increases, a flow occurs between the support plate containing the workpiece and the abrasive plate. The pressure decreases, the support plate containing the workpiece is attracted toward the polishing plate, and the gap between the workpiece and the polishing plate created using the repulsive force of the magnet becomes minute. Therefore, the abrasive grains contained in the polishing liquid rub against the surface of the workpiece, processing on the atomic order is performed, and as a result, the workpiece is polished. Further, when the relative movement between the workpiece and the polishing plate is stopped, the pressure between the workpiece and the polishing plate returns to the value before polishing, and the gap between the workpiece and the polishing plate is restored to the state before polishing. Therefore, when the apparatus of the present invention is used, the workpiece does not come into contact with the abrasive plate, so the abrasive grains are not pressed onto the workpiece, so there is an advantage that no distortion is introduced to the surface of the workpiece. ing.

This will be explained in more detail in Examples below.

The figure is a sectional view showing the device of the invention. The present invention will be explained in detail according to the drawings. A support plate 3 that holds the workpiece 1 and has magnets 2 arranged around its circumference is fixed to a flange 51C supported by a fixed bearing 4, and has a magnet 6 that faces the magnet 2 and has opposite magnetic lines of force. The polishing plate 7 is provided in a circumferential manner, and a gap 8 is provided between the workpiece 1 and the polishing plate 6 due to the repulsive force between the magnets 2 and 6. Here, polishing plate 7
When rotates in the direction of arrow 9, the workpiece 1 and the polishing plate 7 have a relative velocity, and a flow of polishing liquid io flows through the gap 8.
The pressure decreases, the gap 8 becomes minute, and the abrasive grains contained in the polishing liquid 10 rub against the surface of the workpiece 1, resulting in atomic-order processing. Then, when the rotation of the polishing plate 7 is stopped, the relative speed between the workpiece 1 and the polishing plate 7 disappears, and the pressure of the polishing liquid 1O in the gap 8 returns to the value before polishing.
The gap 8 is restored to its state before polishing.

Therefore, since the surface of the workpiece 10 does not come into contact with the polishing plate 7, there is an advantage that the workpiece 1' is not subjected to VC strain.

Next, one implementation result of the present invention will be explained.

For example, a silicon wafer is used as the workpiece, a ferrite magnet is used as the magnet, and a particle size of 0 is used as the polishing liquid.
．． When the polishing plate was rotated at 30 rpm in a solution using 0.1 μm silicon dioxide as abrasive grains, the silicon dioxide
:/The gap between the polishing plate and the polishing plate is about several tens of μm,
A silicon polishing speed of 8 people/min was obtained. Also,
One method to investigate defects in silicon wafers is to
An OS check using wet oxidation and 8irtl etching revealed that no silicon wafer defects were observed and the silicon wafer was free of distortion.

Therefore, in the apparatus of the present invention, a workpiece is immersed in an abrasive liquid, and a gap is created between the workpiece and the polishing plate by using the repulsive force between the support plate holding the workpiece and the magnet that is placed on the polishing plate. Therefore, the workpiece can be polished without causing distortion to the workpiece.

In the above embodiments, semiconductor material was used as an example of the workpiece, but it goes without saying that other materials may also be used effectively. In the embodiment, the polishing plate was rotated, but the same effect can be obtained by rotating the support plate holding the workpiece. Alternatively, a heater for heating the liquid may be used. When using a chemical liquid, the surface of the polishing plate may be covered with a sheet made of a material such as resin in order to protect the magnets on the polishing plate.

Although ferrite magnets are provided in a circumferential manner on the support plate and the polishing plate in this embodiment, the magnets are not limited to ferrite magnets, but other rare earth magnets may be used.

Further, in order to improve the flow of the liquid during polishing, holes may be provided in the center of the support plate or polishing plate to allow the liquid to pass through.

From the above results, by using the apparatus of the present invention, it is possible to obtain a wafer with an unprecedented distortion-free mirror surface, and for example, for semiconductor wafers, it is possible to obtain a wafer that is fully compatible with miniaturization in the element process. , the yield of device formation is dramatically improved.

[Brief explanation of the drawing]

The figure is a cross-sectional view of the polishing apparatus of the present invention, in which 1... Workpiece, 2... Magnet, 3... Support plate, 4... Bearing. 5...Flange, 6...Magnet, 7...Abrasive plate, 8
···gap. 9... rotation direction, 10... polishing liquid, 11... tank. Susumu Uchihara

Claims (1)

[Claims] In a polishing device in which a workpiece held on a support plate and a polishing plate move relative to each other at a relative speed greater than a preset value, the center of rotation coincides with the support plate provided with a circumferential magnet, and the The button support plate or the abrasive plate is provided with an abrasive plate having a circumference of magnets arranged opposite to the magnets provided on the support plate and whose lines of magnetic force are opposite in direction, and in which the gap between the support plate and the abrasive plate is freely adjusted. A polishing apparatus characterized in that a support plate and a polishing plate including the workpiece are immersed in a polishing liquid.