SU1701759A1 - Compound for chemical-mechanical polishing of semiconductor crystal surface - Google Patents

Abstract

The invention relates to compositions for chemical-mechanical polishing (CMP) of semiconductor materials and can be used in semiconductor technology, in particular when preparing the surface of CdSb crystals used for IR-optical elements. The aim of the invention is to improve the quality of the polished surface of CdSb crystals. The composition for chemical-mechanical polishing contains the following components, may%: aerosil 2-25; monoethanolamine 3-5; sodium hydroxide 5-8; hydrogen peroxide

Description

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The invention relates to compositions for chemical-mechanical polishing of semiconductor materials and can be used in semiconductor technology, in particular, in preparing the surface of single crystals for IR-optical elements.

In connection with the use of laser radiation with an A of 10.6 µm in the IR technique, it becomes necessary to use optical elements made of CdSb single crystals in such equipment. However, due to the high power and radiation energy, such preparation of the surface of single crystals is required, which would ensure the minimum thickness of the broken layer. This is due to the fact. that layer near the surface being disturbed by mechanical

it has a God-induced concentration of current carriers and it heats up more under irradiation, which, in turn, leads to a further increase in the concentration of current carriers. Such a self-acceleration. This process leads to an increase in the absorption thickness and, as a result, at high energies, to a decrease in the transmission and destruction of the material.

For a variety of semiconductor materials used in the manufacture of optical elements, the required quality of the treated surface is achieved by using a variety of compositions for chemical and mechanical polishing.

A known composition for polishing PbTe, PbSe, PbSn crystals and Ge PbSnSe, including (CH) b, NaOH (

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However, the CdSb surface treated with the indicated composition becomes oxidized and contains traces of the used reagents and their reaction products with the CdSb material.

Closest to the present invention is a composition for polishing the surface of semiconductor materials containing glycerin, ethylenediamine, hydrogen peroxide, aerosil, and water. The composition of the herbalist following wt.%:

Glycerol-3

Ethylenediamine 5-73

Н2025-13

Aerosil 4-45

Water47-80

However, the well-known etchant composition poorly polishes CdSb single crystals. Passivating oxide films are formed on the surface of single crystals, selective etching is often observed, pickles and scratches are observed on the polished surface. The purpose of the invention is to improve the quality of the polished surface of CdSb crystals used for IR-optical elements.

The goal is achieved by the fact that the composition for chemical-mechanical cross-cutting, including aerosil, glycerin, hydrogen peroxide, water and amine-containing compounds, additionally contains gmdroxid sodium, and as an amine-containing compound - monoethanolamine in the following ratio of ingredients, wt. .%:

Aerosil2-25

Monoethanolamine 3-5

Sodium hydroxide 5-8

Peroxide

hydrogen (30%) 15-20

Glycerin 10-12

Water 30-65

The proposed composition differs from that known by introducing new components, sodium hydroxide and monosanolamine.

Example. In order to determine the optimal composition of the etchant, a series of experiments were carried out, including the cutting of single crystals into washers, mechanical grinding, mechanical polishing and chemical-mechanical polishing. In each of these experiments, a single CdSb single crystal was cut into washers 3 mm thick with a tungsten wire (d 200 μm) with an M 5 abrasive () parallel to the crystallographic plane.

Mechanical grinding was carried out on a glass with free abrasives and subsequently M 10, M 5, M 3. In this case, a layer of 50 µm was removed. Mechanical polishing was done on faux suede with diamond grit powders in series.

1/0, 3/0 and 0.1 / 0. The thickness of the removed layer was 8 μm. After grinding and polishing, the sample was thoroughly washed with deionized water and ethyl alcohol. Then there was a chemical-mechanical

0 polishing on artificial suede with colloidal silica compositions, the compositions of which are given in Table. 1. As a solid phase, ultradispersed powders of un-modified NECA cream of size 20-380A with a surface containing groups of SI OH were used. Chemically active ingredient - monoethylenediamine.

The hydrophilic character of aminoethoxy-erosyl (AEA) makes it very easy to introduce it into aqueous media and to obtain stable aqueous dispersions of Z SI - O - —CH 2 —CH 2 —NH 2.

Products formed during polishing are removed from the surface due to good absorption capacity, due to the highly developed surface of AEA, as well as due to complex formation due to the presence of amino groups, which allows avoiding smearing of surface defects and ensuring high efficiency throughout the entire process. .

When preparing polishing compositions, the following order of mixing is recommended. Azron is suspended in deionized water with constant stirring. After a homogeneous solution of aerosil in water is obtained, monoethylenamine and glycerin are added with constant stirring. Sodium hydroxide is dissolved in deionized water, and the filtrate is added to a four-component solution. The solution is thoroughly mixed and 30% peroxide is added.

5 hydrogen. After 5 minutes of stirring, the solution is ready for use. Polishing is carried out with constant stirring of the solution. The polishing properties of the composition are determined by the pH, the optimum

0 whose value is 12.0.

Analysis of the data given in table. 1, suggests that the best results are obtained when using solutions of the proposed device.

5 The polishing composition of such a composition makes it possible to obtain a defect-free, chemically pure, most perfect CdSb surface in crystal structure and relief. When using compounds with extreme levels of content of components on the polished surface, a weak oxide deposit is observed, and pickling and scratching are often formed. The thickness of the surface oxide layer and the half width of the swing curves also exceed the values obtained by polishing with the proposed composition.

The optimal layer removal rate is 0.2-0.5 µm / min, loads in the order of 100-200 g / cm, the rotation speed of the polishing pad 80-100 rpm.

The rate of polishing depends on the concentration of alkali and peroxide in the solution and practically does not change with increasing concentration of glycerol. Experiments carried out on washers cut parallel to the (100), (010) and (001) planes showed that the polishing rate for the (100) plane was always somewhat higher.

The surface composition of CdSb samples after chemical-mechanical polishing was studied by Auger electron spectroscopy on a Jamp-U instrument with a computer. The spectra are taken in the range of 15–550 eV. In addition to the main components: Cd (381 EV) and Sb (454 eV), traces of only CuO were found in the spectra. The thickness of the surface oxide layer after chemical-mechanical polishing is 65 A.

The crystallographic perfection of the CdSb surface after chemical-mechanical polishing was investigated by the Berg-Barrett rectifier topography for reflection and the magnitude of the half-width of the swing curve. Swing curve half width for samples with dislocation density

An ND of 10 cm is in the range of 8-13, which corresponds to theoretical values for a perfect single crystal.

The results of polishing CdSb single crystals by known and proposed minerals are presented in Table. 2

Claims (1)

Thus, chemical and mechanical polishing of CdSb with colloidal silica compositions allows one to obtain the most perfect samples in structure, composition, and topography with a minimum thickness of the surface oxide layer. Chemical-mechanical polishing allows you to increase the energy of the transmitted laser radiation I 10.6 microns by 3-5 times compared to mechanical polishing. Claims An inventive composition for chemical-mechanical polishing of the surface of semiconductor crystals, including aerosil, glycerin, hydrogen peroxide, water and a flame-containing compound, characterized in that, in order to improve the quality of the polished surface of CdSb crystals used for PC-optical elements, the composition additionally contains sodium hydroxide, and as an amine-containing compound, monoethanol amine in the following ratio, wt.%: Aerosil2-25 Monoethanolamine 3-5 Sodium hydroxide 5-8 Hydrogen peroxide (30%) 15-20 Glycerin 10-12 WaterEverything comp.% Polishing speed V, m / min Aerosil 1 Monoethanolamine NaOH k V) 11 C3H80E 9 HZO 70 Aerosil 1 Monoethanolamine NaOH5 Н20г 5 C3H803 ngo 10 65 Aerosil 15 NaOH7 monoethanol Н20г18 C3H803 h2o eleven five Aerosil 25 Monoethanol NaOH 8 H 2 O 2 C 3 H 80 12 H20 30 Aeros 26 Monoethanol NaOH9 Glycerin13 NgO25 Surface condition The composition of the polished surface On the surface there is a weak oxide buildup. 130-260 26 Cd, Sb, C, O Mirror surface. no defects, tsirapin and mox etching 65 1 (0 ten Cd, Sb Also 65 kQ eight Cd, Sb -j ate to -И65 kQ 13 Cd, Sb On the polished surface, we see pickles, scratches 35 Cd, Sb, C, O Roughness of a relief Swing curve half width The composition of the polished surface This is a selective etching effect. 200-300 ACO A 8-13 Cd, Sb, K, Fe, Cd, Sb, C, 0, Cd, Sb C, 0, ClS, Cl Table 2 This is a selective etching effect.