JPH0822503B2 - Polishing method using chemical action - Google Patents

Description

The present invention relates to a method for polishing hard and brittle materials.

[Prior Art] In general, polishing of a hard and brittle material is performed by using abrasive grains (mainly diamond) having a hardness higher than that of the material and utilizing mechanical action such as minute fracture due to the abrasive grains. In this case, although some processing efficiency can be obtained, scratches and processing strain often occur on the processed surface, and in the case of electronic materials and optical materials, the electrical characteristics and optical characteristics of the material deteriorate and the structure In the case of materials and the like, the mechanical strength is lowered, leading to damage and impairing the characteristics of the materials. In this method, an alkaline solution may be used as the working liquid, but this is intended to make the material surface soft, and scratches are more likely to occur on the working surface.

On the other hand, mechanochemical polishing in which abrasive grains with hardness lower than that of the material are supplied in a dry manner, a reaction product is generated at a contact point between the material and the abrasive grain due to high temperature and high pressure, and the reaction product is removed by friction force. There is a law (Research Report No. 776, Institute of Electronics, Technology). In this processing method, since the abrasive grains having hardness lower than that of the material are used, the abrasive grains are not pushed into the material, the material surface is not broken, and the scratches are not left and the processing strain is not generated. Further, by selecting an appropriate abrasive grain for the material to be processed, it is possible to obtain a processing efficiency equal to or higher than that of a polishing method using an abrasive grain having a hardness higher than that of a general polishing material.

However, in this mechanochemical polishing method, since the reaction product generated on the material surface is removed only by the frictional force,
The reactant may not be completely removed and may remain on the surface as a residue. Further, since it is a dry method that does not use a working liquid, it is difficult to uniformly supply it to the surface of the material, and the working becomes non-uniform, and it is difficult to polish it accurately. In addition, the scattering of abrasive grains causes the work environment to deteriorate.

[Problems to be Solved by the Invention] The present invention is directed to a reaction of a material surface in a polishing method for a hard and brittle material in which a reaction product is generated at a contact point between the material and the abrasive grain by using an abrasive grain having hardness lower than that of the material. In addition to solving problems such as removal of objects, uneven processing, and deterioration of work environment,
Furthermore, the present invention proposes a polishing method that improves the processing efficiency.

[Means for Solving the Problems] The present invention is a mechanical method for producing a reaction product at a contact point between a material and an abrasive grain by using an abrasive grain having a hardness lower than that of the material which is one of polishing methods for hard and brittle materials. In the chemical polishing method, a polishing method utilizing chemical action is characterized in that the reaction product is etched by the working liquid by suspending and supplying abrasive grains to the working liquid.

[Operation] In the conventional mechanochemical polishing method, the reaction product generated at the contact point between the material and the abrasive grain is removed only by the frictional force. However, in the present invention, not only the frictional force but also the etching action on the reaction product is removed. It is also removed by the etching action of an acidic or alkaline processing liquid having. Therefore, unlike the conventional mechanochemical polishing method, there is no possibility that the reactant remains on the surface of the material. Furthermore, since the reaction product generated by superimposing the etching action can be efficiently removed, a much higher processing efficiency can be obtained as compared with the conventional case.
Further, by supplying the abrasive grains together with the liquid, the abrasive grains can be uniformly supplied to the material, and the machining can be performed with high accuracy without uneven machining. Furthermore, since it is a wet type, scattering of abrasive grains can be prevented and the working environment can be improved.

Table 1 shows examples of combinations of hard and brittle materials, abrasive grains, types of working fluids, and PH values.

In the case of Si, silicate is formed as a reaction product with the abrasive grains of BaCO ₃ or CaCO ₃ . Since this silicate dissolves in strong alkali such as KOH and NaOH, and hydrofluoric acid, these are used as a working fluid. In this case, PH9 to 12 is desirable for alkaline, and PH3 to 5 is desirable for acidic. PH of solution in Table 1
Is limited to PH5 with low acidity and alkalinity
This is because in the range of more than 9 and less than 9, the chemical action on the reaction product of the abrasive grains and the material does not occur, while when it is less than PH3 and more than 12 and the degree of acidity and alkalinity is too high, the characteristics of the abrasive grains deteriorate.

In addition, Cr ₂ O ₃ and Fe ₂ O ₃ for Si ₃ N ₄ , and Cr for SiC.
_{When 2} O ₃ is used as abrasive grains, both form SiO ₂ . S
Since iO ₂ is soluble in hydrofluoric acid, hydrofluoric acid is used as a working fluid. In this case as well, PH3 to 5 are desirable for the same reason.

[Examples] Example 1 A Si wafer using BaCO ₃ as abrasive grains, 1-dry type,
Suspended in 1-PH9 KOH aqueous solution, 1-PH10.5 KOH aqueous solution, 1-PH12 KOH aqueous solution, wet-supplied and polished. The processing pressure is 200 g / cm ² , the average grain size is 1.2 μm, and the grain concentration is 25 w for 1- to 1-.
t%. As a result, the respective processing efficiencies are 1-5.0 μm / hr, 1-9.0 μm / hr, 1-5.0 μm / hr, as shown in Table 2.
The values were 12.0 μm / hr and 1-14.0 μm / hr. In addition, 1-
As a result of ESCA analysis of the Si surface processed under the conditions of 1 and 1, no abrasive grains and the processed product of the abrasive grains and Si were detected, and a clean surface without residue was obtained. Also, TTV (Total Thickness Variation), which represents the flatness of the wafer, is 1-
2.2 μm, 1-1.0 μm, which is a great improvement.

Example 2 A Si wafer was supplied by 2-dry method using BaCO ₃ as abrasive grains, suspended in an HF aqueous solution of 2-PH 3 and supplied by wet method for polishing. The working pressure was 200 g / cm ² , the average abrasive grain size was 1.2 μm, and in 2-, the abrasive grain concentration was 25 wt%. As a result, the respective processing efficiencies were 2-5.0 μm / hr and 2-10.0 μm / hr, as shown in Table 2. As a result of ESCA analysis of the Si surface processed under the condition of 2, the abrasive grains and the processed product of the abrasive grains and Si were not detected, and a clean surface without residue was obtained. Also, TTV (Total Thickness Variation), which represents the flatness of the wafer, is 2.
2 μm, and in 2-, it was 1.5 μm, which was an improvement.

Example 3 Si ₃ N ₄ was mixed with Cr ₂ O ₃ (average particle size 3 μm) by 3-dry method, 3
Polishing was performed by wet method (suspended in PH5 HF aqueous solution: abrasive grain concentration 10 wt%). As a result, the respective processing efficiencies were, as shown in Table 2, dry type: 3 μm / hr and wet type: 8 μm / hr. The surface of the wet-polished sample was analyzed by ESCA, but SiO ₂ was not detected.

Example 4 SiC with Cr ₂ O ₃ (average particle size 3 μm), 4-dry type, 4-
Polishing was performed by a wet method (suspended in HF aqueous solution of PH4: abrasive grain concentration 10 wt%). As a result, each processing efficiency is the second
As shown in the table, the dry type was 2 μm / hr and the wet type was 5 μm / hr. The surface of the wet-polished sample was analyzed by ESCA, but SiO ₂ was not detected.

[Advantages of the Invention] According to the present invention, in a polishing method for a hard and brittle material in which an abrasive grain having a hardness lower than that of the material is used to generate a reactant at a contact point between the material and the abrasive grain, Residues such as abrasive grains can be removed and a clean machined surface can be obtained. b) Non-uniformity of processing is eliminated, and high-precision processing can be performed. c)
Abrasive particles are not scattered and the working environment is improved. d) Effects such as improvement in processing efficiency can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-49-64994 (JP, A) JP-A-48-90081 (JP, A) JP-A-60-263666 (JP, A) JP-B-59- 53317 (JP, B2)

Claims (1)

[Claims] 1. In a polishing method for a hard and brittle material in which an abrasive having a hardness lower than that of the material is used to generate a reaction product at a contact point between the material and the abrasive, the abrasive is suspended in a working liquid and supplied. The chemical-based polishing method is characterized in that the reaction product is etched with a processing liquid.