RU2545295C1 - Method for chemical-mechanical polishing of gallium arsenide plates - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method includes treating plates with a rotating polisher and a polishing composition, which additionally contains tartaric acid as a complexing agent and ethylene glycol as a lubricant, with the following content of components, vol %: hydrogen peroxide - 7.0-70.0, 30% aqueous tartaric acid solution - 7.0-60.0, ethylene glycol - 5.0-15.0, deionised water - the balance.

EFFECT: single-step treatment using a polishing composition which is abrasive free, high quality of the treated material by reducing surface defects thereof.

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Description

The invention relates to the field of processing of semiconductor materials, and in particular to a chemical-mechanical method (CMP) for polishing gallium arsenide plates. The invention provides high surface quality and can be used in the technology of manufacturing devices, including large-format matrix ones based on gallium arsenide.

Known methods of chemical-mechanical polishing of gallium arsenide [RU 2007784], which use the following compositions:

first composition: after diamond polishing, the plates are treated in a solution containing sulfamic acid and zeolite NaA. The matte surface is removed by superfinishing CMP;

second composition: after diamond polishing, a composition containing an aqueous solution of ammonium carbonate, potassium iron-hydrogen sulfide, silica sol, 30% silicon dioxide is used. Polishing pad is lint-free lavsan fabric.

A known method of chemical-mechanical polishing of semiconductor materials [RU 2457574], containing particles of abrasive - zeolite NaX with a grain size of 15.0-20.0 microns or particles of silicon dioxide, the average size of which is 10.0-1000.0 nm, iodine in an alcohol solution is 0.1-1.0 wt. %, while the content of alcohol iodine in the composition is 1.0-5.0 wt.%.

The disadvantages of these methods are multi-stage polishing processes using abrasive materials, which leads to a complication of processing technology and the creation of defects on the surface.

A known method of chemical-mechanical polishing of gallium arsenide [RU 1715133], containing as an abrasive sodium zeolite in the first stage, silica sol in the second stage, in the following ratio of components, wt.%: Abrasive 10.0-20.0, sulfamic acid 1.3-2.8, peroxide hydrogen 15.0-28.0, sulfanol 0.01-0.8, water the rest.

Closest to the proposed technical solution is a method of chemical-mechanical polishing of gallium arsenide [RU 1715133], in which polishing is carried out in two stages to obtain a high flatness of the surface, moreover, hydrogen peroxide is used as an oxidizing agent, sulfazole is used as a surfactant, with the following ratio of components, wt.%: abrasive 10.0-20.0, sulfamic acid 1.30-2.80, hydrogen peroxide (30%) 15.0-28.0, sulfazole 0.01-0.80, water the rest. At the first stage, sodium zeolite is used as an abrasive, then silicasol, and at the first stage 80-95% of the allowance is removed, at the second - 5-20% of the allowance.

The invention has a drawback, since it involves processing in two stages on the same polishing pad, and during the second stage, thoroughly washing the polishing pad, faceplate and plates to remove the sodium zeolite contained in the composition of the first stage is a laborious process and it is difficult to determine the time of a complete transition from one abrasive to another under conditions of continuous interaction of the polishing pad with two polishing compounds. Another disadvantage of abrasive compositions for chemical-mechanical polishing is that they lead to the creation of impurity-defect complexes in the processed material, which are effective centers of cluster nucleation. In addition, in processing with abrasive materials, even particles of small size can create zones with plastic deformation in materials with low microhardness, which reduce the parameters of the devices.

The purpose of the invention is the elimination of processing in two stages using a polishing composition that does not contain abrasive, and reducing the surface imperfection of the processed material.

This goal is achieved by the fact that they carry out the processing of the plates with a rotating polisher and a polishing composition containing hydrogen peroxide, tartaric acid, ethylene glycol and deionized water. In order to eliminate the processing in two stages and simplify the polishing process while maintaining the surface quality, polishing is carried out with a polishing composition that does not contain abrasive, and tartaric acid is used as a complexing agent, ethylene glycol is used as a lubricant, with the following components in the polishing composition, vol.% :

Hydrogen peroxide 7.0-70.0 30% aqueous solution of tartaric acid 7.0-60.0 Ethylene glycol 5.0-15.0 Deionized water rest

The essence of the claimed invention lies in the fact that in the method of chemical-mechanical polishing of gallium arsenide plates, including exposure to polishing pad and polishing composition, hydrogen peroxide is used as an oxidizing agent, tartaric acid is used as a complexing agent, ethylene glycol is used as a lubricating additive. Chemical-mechanical polishing is carried out on the same polishing pad in one step at a plate pressure of 4.3-7.5 kPa, the polishing pad rotation speed of 20 rpm. The material removal rate is 0.4-1.2 μm / min in the polishing composition with the following ratio of components, vol%: hydrogen peroxide 7.0-70.0, tartaric acid (30%) 7.0-60.0, ethylene glycol 5.0-15.0, deionized water - the rest. In the proposed polishing method, the effect is achieved by using a polishing composition on the surface of gallium arsenide a passive film is formed, consisting of the interaction products of the polishing composition and gallium arsenide, which is easily removed by the fabric surface of soft polishers in the absence of abrasive materials.

Example No. 1. Chemical-mechanical polishing of gallium arsenide plates is carried out. To prepare one liter of polishing composition, 630 ml of hydrogen peroxide, 200 ml of a 30% aqueous solution of tartaric acid, 100 ml of ethylene glycol are poured into the container, the rest is deionized. The removal rate is 0.8 μm / min at a plate pressure of 4.3-7.5 kPa.

Example No. 2. Chemical-mechanical polishing of gallium arsenide plates is carried out. To prepare one liter of polishing composition, 430 ml of hydrogen peroxide, 400 ml of a 30% aqueous solution of tartaric acid, 100 ml of ethylene glycol are poured into a container, the rest is deionized. The removal rate is 1.2 μm / min with a plate pressure of 4.3 kPa.

Example No. 3. Chemical-mechanical polishing of gallium arsenide plates is carried out. To prepare one liter of polishing composition, 700 ml of hydrogen peroxide, 130 ml of a 30% aqueous solution of tartaric acid, 100 ml of ethylene glycol are poured into a container, the rest is deionized. The removal rate is 0.4 μm / min at a plate pressure of 7.5 kPa.

Example No. 1 shows that the removal rate does not depend on the pressure on the plate in the specified range. The examples also show that with an increase in the ratio of the concentration of hydrogen peroxide to the concentration of tartaric acid in solution, the removal rate decreases.

The remaining compositions of polishing solutions used in chemical-mechanical polishing are shown in the table.

Compositions of solutions for chemical-mechanical polishing Hydrogen peroxide, vol.% 30% aqueous solution of tartaric acid, vol.% Ethylene glycol, vol.% Water, vol.% The removal rate, microns / min 50.0 20.0 10.0 20.0 0.9 50.0 40.0 10.0 0.0 0.9 25.0 20.0 10.0 45.0 0.1 25.0 55.0 10.0 10.0 1.7 35.0 20.0 10.0 35.0 1.0 15.0 45.0 7.0 33.0 1.5 40.0 20.0 5.0 35.0 1.7 45.0 20.0 15.0 20.0 1.5 15.0 45.0 15.0 25.0 1.0 7.0 50.0 15.0 28.0 1.0 7.0 55.0 8.0 30.0 0.7 7.0 60.0 8.0 25.0 0.7 8.0 55.0 15.0 22.0 1.5 55.0 7.0 13.0 25.0 1.5

In all examples, a machine with a working table with a diameter of 220 mm, on which a cambric was fixed, was used for chemical-mechanical polishing. The cambric before the chemical-mechanical polishing was wetted with a working solution for 1-2 minutes. Polishing pad rotation speed 20 rpm. The gallium arsenide plate is placed in the device, which is installed on the desktop of the polishing pad. The feed rate of the solution into the polishing zone is 15.0-20.0 ml / min. After polishing, the plate is washed in running deionized water for 5 minutes and dried in a centrifuge.

All the plates after processing had a mirror surface of grade 14 according to GOST 11141-84, without risks and oxide film. Figure 1 presents the surface profile of the plate of gallium arsenide after grinding, before processing CMP. The average deviation of the profile is 2 μm. Figure 2 - profile of the surface treated by the CMP method, after removing the layer of 200 μm. The average deviation of the profile is 0.02 μm, which corresponds to class 14. The flatness of the plates at a diameter of 50 mm was 2-3 microns. The relief and flatness were monitored on a Dektak XT profilograph (Bruker).

X-ray studies showed the absence of a disturbed layer after treatment.

Claims (1)

A method of chemical-mechanical polishing of gallium arsenide plates, comprising treating the plates with a rotating polisher and a polishing composition, characterized in that the polishing composition additionally contains tartaric acid as a complexing agent, ethylene glycol as a lubricant in the following components in the polishing composition, vol. %:
hydrogen peroxide 7.0-70.0 30% aqueous solution of tartaric acid 7.0-60.0 ethylene glycol 5.0-15.0 deionized water rest.

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