JPH03281165A - Polishing method utilizing chemical action - Google Patents

Abstract

PURPOSE:To provide a clean machined surface through removal of a residue, e.g. a reactant, abrasive grains, on a material surface by feeding the abrasive grains in a state that the abrasive grains are suspended in an acid or alkaline solution. CONSTITUTION:A reactant is produced at a contact point between a material and abrasive grains by using the abrasive grains having hardness lower than that of the material. In this case, the abrasive grains are fed in a state to be suspended in an acid or alkaline solution to effect polishing. This method prevents residence of a reactant on a material surface.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for polishing hard and brittle materials.

[Prior Art] Generally, polishing of hard and brittle materials is carried out using abrasive grains (mainly diamond) that are harder than the material and utilize mechanical effects such as micro-fractures caused by the abrasive grains. In this case, although a certain degree of processing efficiency can be obtained, scratches often remain on the processed surface and processing distortion occurs, and in the case of electronic and optical materials, the electrical and optical properties of the material deteriorate and the structure (1) For building materials, the mechanical strength decreases, leading to breakage and other damage to the properties of the material. Furthermore, although an alkaline solution is sometimes used as the machining liquid in this method, the purpose of this is to soften the surface of the material, making it more likely that scratches will occur on the machined surface.

On the other hand, mechanochemical materials dryly supply abrasive grains with a lower hardness than the material, generate reactants under high temperature and high pressure conditions at the point of contact between the material and the abrasive grains, and remove the reactants using frictional force. There is a ging method (Electronic Technology Research Institute Research Report No. 776). This processing method uses abrasive grains with a lower hardness than the material, so the abrasive grains are not pushed into the material, the material surface is not destroyed, and no scratches remain or processing distortion occurs. Furthermore, by selecting appropriate abrasive grains for the material to be processed, processing efficiency comparable to or higher than that of a general polishing method using abrasive grains harder than the material can be obtained.

However, in this mechanochemical boriding method, (2) reactants generated on the material surface are removed only by frictional force, so there is a possibility that the reactants are not completely removed and remain on the surface as a residue. In addition, since it is a dry process that does not use processing fluid, it is difficult to supply it evenly to the material surface.
Machining becomes uneven, making it difficult to polish accurately. Furthermore, the scattering of abrasive grains causes a deterioration of the working environment.

[Problems to be Solved by the Invention] The present invention provides a polishing method for hard brittle materials in which abrasive grains having a lower hardness than the material are used to generate reactants at the contact point between the material and the abrasive grains. This paper proposes a polishing method that solves the problems of material removal, uneven processing, and deterioration of the working environment, and also improves processing efficiency.

[Means for Solving the Problems] The present invention is a method for polishing hard and brittle materials, which is a mechano-based method that uses abrasive grains with lower hardness than the material and generates reactants at the contact point between the material and the abrasive grains. (3) The chemical bollizing method is characterized in that the abrasive grains are suspended in an acidic or alkaline solution and then supplied for bolishing.

[Function] In the conventional mechanochemical boring method, the reactants generated at the contact point between the material and the abrasive grains are removed only by frictional force, but in the present invention, not only the frictional force but also the etching of the reactants is removed. It can also be removed by etching with active acidic or alkaline solutions. Therefore, unlike the conventional mechanochemical boriding method, there is no possibility that reactants remain on the material surface. Furthermore, by superimposing the etching action, generated reactants can be efficiently removed, resulting in significantly higher processing efficiency than in the past. Furthermore, by supplying the abrasive grains together with the liquid, the abrasive grains can be evenly supplied to the material, which prevents uneven machining and enables highly accurate machining. Furthermore, since it is a wet process, scattering of abrasive grains can be prevented, improving the working environment.

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

In the case of Si, silicate (4) is formed as a reactant with BaCO3 or CaCO3 abrasive grains. This silicate is KOH
, dissolves in strong alkalis such as NaOH and hydrofluoric acid,
These are used as processing fluids. In this case, pH 9 to 12 is desirable for alkalinity, and pH 3 to 5 is desirable for acidity. The reason for limiting the pH of the solution here is that in a pH range of more than 5 and less than 9, where the degree of acidity and alkalinity is low, no chemical action occurs on the reactants between the abrasive grains and the material;
This is because if the degree of acidity/alkalinity is too high, such as less than 3 or more than 12, the characteristics of the abrasive grains will deteriorate.

Table 1 Also, for Si3N4, Cr2O3, Fe2O3, S
For iC, if Cr2O is used as the abrasive grain, both become Sin.

(5) Form. Since SiO□ is soluble in hydrofluoric acid, hydrofluoric acid is used as the processing fluid. In this case as well, for the same reason, PH
3-5 is desirable.

[Example] Example I A Si wafer was prepared using BaC0 as an abrasive grain, 1-■dry process, 1-■suspended in a KOH aqueous solution of PH9, 1-■PH1
Suspended in KOH aqueous solution of 0.5, 1-■KOH of PH12
It was suspended in an aqueous solution and fed in a wet manner for boring. The processing pressure was 200 g/cm'', the average abrasive grain diameter was 1.2 μm, and the abrasive grain concentration was 25 wt% in 1-■ to 1-■.

As a result, each machining efficiency is as shown in Table 2.
1-■5. Jzm/hr, 1-■9.0 p m/hr
, 1-■12゜Ott m/hr, 1-■14.0 μ
m/hr. In addition, 1-■.

As a result of analyzing the Si surface processed under the conditions of 1-0 by ESCA, no abrasive grains or processed products of abrasive grains and Si were detected, and a clean surface without any residue was obtained. In addition, TTV (Total Th1ckness), which represents the flatness of the wafer,
Variation) is 2.2pm for 1-■, and ■-
In case (2), it was 1.0 μm, which was a great improvement.

(6) Example 2 An Sj wafer was polished using BaCO3 as an abrasive by supplying it in a 2-■ dry process and 2-■ suspending it in an HF aqueous solution of PH3 and supplying it in a wet process. Processing pressure is 200g/Qm"
The average abrasive grain diameter was 1.2 μm, and in 2-■, the abrasive grain concentration was 25 wt%. As a result, the respective machining efficiency was 2-5.0 μm/hr as shown in Table 2.

2-■ 10.0 μm/hr. As a result of analyzing the Si surface processed under the conditions of 2-2 by ESCA, no abrasive grains or processed products of abrasive grains and Si were detected, and a clean surface without any residue was obtained. Also, T represents the flatness of the wafer.
T V (Total Th1ckness Vari
ation) is 2.2 μm for 2-■, 1 for 2-■
．． It was 5 μm, which was an improvement.

Example 3 Si, N4 with Cr203 (average particle size 3 μm), 3-
Polishing was carried out by (1) dry method and (3) wet method (suspended in HF aqueous solution of pH 5: abrasive grain concentration 10 wt%). As a result, the respective machining efficiency is as shown in Table 2, dry type = 3μm/
hr.

Wet type = 8 μm/hr. In addition, when the surface of the wet-boring sample7) was analyzed by ESCA, no SiO□ was detected.

SiC with Cr203 (average particle size 3 μm), 4-■ dry method, 4-■ wet method (suspended in HF aqueous solution with pH 4: abrasive grain concentration 1)
0 wt%). As a result, the processing efficiency of each method is as shown in Table 2. Dry method = 2 μm/hr
, wet type = 5 μm/hr. Furthermore, when the surface of the wet-polished sample was analyzed by ESCA, 5i02 was not detected.

[Effects of the Invention] (8) According to the present invention, in a polishing method for a hard brittle material in which a reactant is generated at a contact point between the material and the abrasive grain using abrasive grains having a lower hardness than the material, a) Residues such as reactants and abrasive grains can be removed, resulting in a clean machined surface. b) Non-uniformity in machining is eliminated and highly accurate machining can be performed. C) There is no scattering of abrasive grains and the working environment is improved. d) Effects such as improved processing efficiency can be obtained.

Claims (1)

[Claims] A polishing method for hard and brittle materials that uses abrasive grains with lower hardness than the material to generate reactants at the point of contact between the material and the abrasive grains, characterized by supplying the abrasive grains suspended in an acidic or alkaline solution. Policing method.