JPS5922329A - Polisher for polishing of semiconductor wafer - Google Patents

Abstract

PURPOSE:To obtain the semiconductor wafer having favorable precision of the shape and having the mirror surface of no distortion by a method wherein the polisher is consisting of two layer structure of a polishing layer and an elastic body layer. CONSTITUTION:The semiconductor wafers 1 adhered to an adhesive surface plate 2 are sticked to a polishing surface plate 6 consisting of a rotary disk, and polishing is performed rotating in the directions shown with arrow marks. The polisher has the concave parts enabled to hold an abrasive, and has two layer strcture consisting of the polishing layer 4 of the soft quality of material of 70 or less at a rubber hardness meter and the elastic body layer 5 of the hard quality of material of 80 or more at the rubber hardness meter. The lubricous layers 3 of the abrasive are generated between the semiconductor wafers 1 and the polishing layer 4 of the polisher, and uncontactingly polish the semiconductor wafers 1. Even when the semiconductor wafers 1 come in contact with the polishing layer 4 of the polisher during the process of polishing, no scratch is generated on the surfaces of the wafers because the polishing layer 4 is soft. Moreover because the elastic body layer 5 is hard, and no sinking of the wafers 1 in the polisher is generated, deterioration of flatness of the wafers 1 is not generated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polishing polisher used for finishing the surface of a semiconductor wafer with high precision and a distortion-free mirror surface. Polishing is the final process of polishing silicon wafers for LSI, and is performed with the aim of finishing Ueno to a distortion-free mirror surface. It is a polishing process in which fine particles of about 100 to 2001 are suspended in an alkaline aqueous solution with a pH of about 9 to 12. The semiconductor wafer is polished using a polisher made of polyurethane or the like, which is mounted on a rotating disk.

Conventionally, in order to achieve high precision flatness of semiconductor wafers, a hard polisher with a small tab that causes less sinking of the wafer into the polisher is appropriate, and to obtain a distortion-free mirror surface, a soft polisher is appropriate. It has been thought that Improving the shape accuracy of the pick-up semiconductor wafer and making it a distortion-free mirror surface are contradictory demands.

Therefore, in order to obtain a wafer with good shape accuracy and a distortion-free mirror surface, polishing is divided into two steps, and in order to obtain a wafer with good shape precision in the first polishing, a hard polisher that does not sink into the polisher is used. Currently, secondary polishing is performed using a soft polisher to obtain a distortion-free mirror surface. However, since deterioration in shape accuracy due to the use of a soft polisher in the secondary borising cannot be avoided, there is a limit to the shape accuracy in this two-step boring.

The present invention eliminates the above-mentioned drawbacks and provides a polisher that provides a mirror surface with good shape accuracy and no distortion.

According to the present invention, the rubber #! On the back side of a thin abrasive layer that is soft and has a uniform thickness of 70 or less, an elastic layer made of a material that is considerably harder than the abrasive layer (80 or more on a rubber hardness meter) is laminated, and the abrasive layer and the elastic layer are laminated. By polishing a semiconductor wafer with a polisher characterized by having a two-layer structure, it is possible to obtain a semiconductor wafer with good shape accuracy and a non-distorted mirror surface.

Clarifying the polishing mechanism using the polisher of the present invention, when carefully observing the polisher that has concave portions uniformly over the entire surface that can hold an abrasive agent, it is possible to see that the polisher is Bolishing is performed by forming a lubricating layer of a few micrometers with abrasive between the semiconductor wafer and the polisher without making direct contact with the polisher. It was experimentally found that this is a unique property.

Furthermore, by using a soft material with a rubber hardness of 70 or less (with a hardness of 80 or more, processing distortion was detected on the wafer processing surface), even if the wafer collides with the polisher,
A wafer with a distortion-free mirror surface without any scratches on the wafer surface can be obtained.

Furthermore, in order to improve the shape of the wafer, it has been experimentally required that a polisher that sinks into the wafer polisher with a small amount is suitable.

Therefore, the present invention combines the above two properties, and by forming an abrasive layer made of a soft material with recesses capable of holding an abrasive on the surface of the polisher, a semiconductor wafer can be made into a mirror-like surface without distortion. In addition, the main body of the polisher is constructed with a hard elastic layer (80 or higher on a rubber hardness meter), which has the advantage of improving the flatness of the wafer and simultaneously satisfying the wafer's distortion-free mirror surface and shape accuracy. .

This will be explained in detail below using examples.

The figure shows the cross-sectional shape in the boring state. Boring of a semiconductor wafer will be explained according to the figures.

Semiconductor wafer 1 bonded to adhesive plate 2 is polished with abrasive 3 on a polisher consisting of a two-layer structure consisting of an abrasive layer 4 and an elastic layer 5, which is pasted on a borizing plate 6, which is a rotating disk. Boring is performed while rotating in the direction of the arrow.

It has a recess that can hold abrasive and has a rubber hardness of 70 or more.
Abrasive layer 4 made of soft material and rubber hardness meter 80
When the semiconductor wafer 1 is polished with a polisher having a two-layer structure consisting of the elastic layer 5 made of the hard material described above, a lubricant layer of the abrasive 3 is generated between the semiconductor wafer 1 and the polisher's polishing layer 4. Non-contact boring of semiconductor wafers. Even if the semiconductor wafer 1 comes into contact with the abrasive layer 4 of the polisher during the polisher, since the abrasive layer 4 of the polisher is made of a soft material, no scratches will occur on the semiconductor wafer surface, and the polisher can be borated to a mirror-like surface without distortion. can do.

In addition, since the elastic layer 5 of the polisher is hard, the semiconductor wafer 1 does not sink into the polisher.
There is no deterioration in the flatness of the semiconductor wafer 1, and it is possible to obtain a semiconductor wafer 1 with good shape accuracy and a distortion-free mirror surface.

Next, the results of implementing the present invention will be explained.

It has a concave part with a diameter of about 60 μm, a thickness of 41 m, and a polishing layer made of a material mainly composed of polyurethane and synthetic rubber. When the thickness is 80 or more, the thickness is 1. O
A polisher consisting of two layers of an elastic body layer made of a hard material of ff, and has a particle size of 100 to 2ooX as an abrasive.
Osto, using colloidal silica suspended in 1 pH + 1 nory alkali solution, under the condition of pressure 100 g/-, diameter 1
ooIIIWI NosI wafer was polished to 10 μm,
When evaluating the wafer shape and distortion-free specularity, the flatness was 3 μm, and the distortion-free property was O8F as evaluated by OS check using wet oxidation and 5irtl etching.
(oxidation induced stacking
No occurrence of faults was observed, indicating that there was no distortion. Further, when the mirror surface was polished using a commercially available polisher which has been known to produce a distortion-free mirror surface, the flatness was 8 μm although there was no distortion.

Therefore, when using the polisher of the present invention, it is possible to obtain wafers of much higher quality than with conventional polishers, and it is possible to obtain shape accuracy and distortion-free specularity at the same time. It has the advantage of being a one-step process and having excellent productivity.

Furthermore, since the polishing according to the present invention is non-contact polishing, it also has the advantage that it can be applied to polishing other semiconductor wafers by appropriately selecting an abrasive.

[Brief explanation of drawings]

The figure is a diagram showing a cross-sectional shape in a boring state using the polisher of the present invention. In the figure, 1 is a semiconductor wafer, 2 is an adhesive plate for the semiconductor wafer,
3 is an abrasive, 4 is a polishing layer of the polisher, 5 is an elastic layer of the polisher, and 6 is a polishing plate. 119

Claims (1)

[Claims] A thin abrasive layer, which is soft and has a uniform thickness of 70 or less on a rubber hardness meter, and has many concave portions uniformly on its abrasive surface to hold an abrasive, is coated on the back side of the abrasive layer. For polishing a semiconductor wafer, characterized in that it has a two-layer structure of the abrasive layer and the elastic layer, in which elastic layers made of particles are laminated and each layer is hard (80 or more on a rubber hardness test). Polisha.