JPH04343427A - Method and device for mirror surface finish machining of wafer - Google Patents

Abstract

PURPOSE:To improve a grinding speed and a surface average roughness when performing mirror-surface finish by grinding a machining surface of a wafer using a grinding wheel. CONSTITUTION:Mechanical grinding of a machining surface of a wafer 1 is performed by using a grinding wheel 4 and at the same chemical corrosion is induced by dripping an acid or alkali liquid through a nozzle 8, thus obtaining an improved mirror surface of machined surface with a taster grinding speed as compared with a case of the grinding wheel grinding only.

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 mirror finishing a wafer.

0002

2. Description of the Related Art Generally, when grinding a wafer to give it a mirror finish, means are taken to reduce the particle size of the diamond grains in the grinding wheel. At this time, if the grain size of the diamond grains is made too fine, grinding debris from the machined surface will adhere between the diamond grains and cause clogging. Once clogging occurs, the grinding ability of the grindstone decreases, causing grinding burns and grinding cracks on the machined surface.

In order to prevent such a phenomenon, a good mirror surface can be obtained by applying a voltage to a conductive grindstone and dressing the conductive grindstone with electrolysis, as disclosed in, for example, Japanese Unexamined Patent Publication No. 1-188266. Also, a method for obtaining a smooth plane with high efficiency and high speed, and Japanese Patent Application Laid-Open No. 2-1535
A method of preventing clogging and improving the uniformity of the ground surface by providing rough grinding, medium grinding, and finish grinding, as disclosed in Publication No. 28, has been proposed.

0004

[Problems to be Solved by the Invention] However, in the former method of JP-A-1-188266, the bond of the grinding wheel is harder than when using a non-conductive grinding wheel, so it becomes clear when comparing grinding wheels of the same grain size. The surface roughness becomes rough. Therefore, in order to obtain a predetermined mirror-finished surface, it is necessary to use a grindstone with a much finer grain size than when using a non-conductive grindstone, resulting in a problem of reduced grinding efficiency.

[0005] Also, even in the latter method, as in JP-A-2-153528, in which grinding is divided into rough, medium, and finishing stages, it is necessary to use a grindstone with extremely fine diamond grains in order to obtain a desired mirror-finished surface. Although clogging can be reduced to some extent, it cannot be completely eliminated. An object of the present invention is to provide a wafer mirror finishing method and apparatus that solve the above-mentioned problems.

[0006]

[Means for Solving the Problems] A first aspect of the present invention is
A second aspect of the present invention is a wafer mirror finishing method characterized by grinding the processed surface of the wafer while chemically etching it, and a second aspect of the present invention is a grinding wheel for grinding the processed surface of the wafer, and a grinding wheel for grinding the processed surface of the wafer; A wafer mirror finishing apparatus is characterized in that it includes a chemical etchant supply means for supplying a chemical etchant.

[0007]

[Function] Normally, in grinding wafers, it is said that a grindstone of about #2000, for example, is suitable as the finest grindstone that can perform continuous grinding without clogging. The average roughness of the processed surface obtained in this case is several tens of nanometers. On the other hand, the surface roughness obtained by polishing is only a few nanometers, and ordinary grinding methods cannot replace polishing. In the above-mentioned Japanese Patent Application Publication No. 1-188266, the average roughness is several tens of nanometers.
In order to obtain this, it is necessary to use a grindstone of approximately #6000, and the grinding speed must be reduced to a fraction of that when using a non-conductive grindstone.

[0008] In order to solve these problems, the present invention focuses on the mechanism of polishing, which has conventionally been commonly performed to obtain a mirror surface. That is, polishing is a processing method in which a polishing liquid infiltrates between the processed surface and the polishing cloth, and the workpiece is polished. In this case, the polishing is not only performed mechanically by particles in the polishing solution, but the polishing solution is usually an alkaline solution, the surface is polished to a mirror finish by chemical corrosion, and the polishing speed is also different from that of mechanical polishing. Dramatic improvement due to synergy. The present invention makes use of such a polishing mechanism and simultaneously performs chemical corrosion in addition to mechanical grinding with a grindstone, thereby making it possible to obtain a good mirror-finished surface and at the same time improve the grinding speed. be.

Therefore, according to the present invention, in addition to mechanical grinding using a conventional grindstone, chemical etching is simultaneously applied to the machined surface so that etching is performed at the same time as grinding of the machined surface. The speed is improved and a good mirror surface can be obtained. Further, when there is no need to increase the grinding speed, the grindstone grain size can be increased, so that the same level of surface roughness as in the conventional example can be obtained without clogging. Note that even if the grindstone grain size is reduced without changing the grinding speed, stable grinding can be performed without clogging.

Furthermore, when the grinding speed and grindstone grain size are the same as in the conventional example, better surface roughness can be obtained than in the conventional example. Furthermore, even if the grinding speed is increased, if the grindstone grain size remains the same as before, surface roughness comparable to that of the conventional example can be ensured. In this case, the workpiece in the grinding wheel is less likely to become clogged due to chemical corrosion, and even if clogging occurs, the clogged part tends to peel off, so it is possible to increase the grinding speed without clogging. Can be done.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing the configuration of a grinding device showing an embodiment of the present invention. In the figure, 1 is a wafer,
2 is a wafer chuck that grips the wafer 1, and 3 is a wafer chuck spindle that rotates the wafer chuck 2. 4 is a grindstone for grinding the processed surface of wafer 1, 5
is a grindstone spindle that rotates the grindstone 4. 6 is a chemical etchant tank, 7 is a chemical etchant pipe, and 8 is a nozzle for supplying the chemical etchant to the processing surface of the wafer 1. As the chemical corrosive liquid, it is preferable to use, for example, a mixed liquid of nitric acid, hydrofluoric acid, and acetic acid, or an alkaline liquid such as potassium hydroxide.

When processing the wafer 1 using the grinding apparatus configured as described above, the wafer chuck 2 holding the wafer 1 is rotated in the direction of the arrow by the wafer chuck spindle 3, and the grinding wheel spindle 5 is rotated in the direction of the arrow. The surface of the abrasive grains 4a of the rotating whetstone 4 is brought into contact with the processing surface of the wafer 1 to mechanically grind it. At the same time nozzle 8
The chemical etchant in the chemical etchant tank 6 is dripped onto the processed surface of the wafer 1 through the chemical etchant tank 6 to chemically etch the processed surface of the wafer 1.

FIG. 2 shows that the grindstone grain size is # on the silicon wafer.
The surface roughness when applying the present invention example in which grinding was performed using a #2000 grinding wheel and a chemical etching solution of a mixed acid consisting of nitric acid, hydrofluoric acid, and acetic acid was compared to that of the conventional example using only a grinding wheel with a grinding wheel grain size of #2000. A comparison of the surface roughness is shown, and it can be seen that the surface roughness obtained by the example of the present invention is about 1/2 that of the conventional example. Further, FIG. 3 shows the effect of the grinding speed at that time, and it can be seen that the grinding speed of the example of the present invention is increased by about 30% compared to the conventional example.

[0014]

[Effects of the Invention] As explained above, according to the present invention, since chemical corrosion is applied at the same time as grinding with a whetstone, it is possible to obtain a mirror-like machined surface with better quality than with conventional grinding with a whetstone alone. Furthermore, the grinding speed can be increased, thereby improving wafer quality and processing efficiency.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the configuration of a grinding device showing an embodiment of the present invention.

FIG. 2 is a graph comparing the surface roughness of an example of the present invention and a conventional example.

FIG. 3 is a graph comparing the grinding speeds of an example of the present invention and a conventional example.

[Explanation of symbols]

1 Wafer 2 Wafer chuck 3 Wafer chuck spindle 4 Whetstone 5 Grinding wheel spindle 6 Chemical corrosive liquid tank 7 Chemical corrosive liquid piping 8 Nozzle

Claims (2)

[Claims] 1. A method for polishing a wafer to a mirror finish, which comprises grinding the processed surface of the wafer while chemically etching it. 2. A wafer mirror finishing apparatus comprising: a grinding wheel for grinding a processed surface of a wafer; and a chemical etchant supply means for supplying a chemical etchant to the processed surface.