JPS6047908B2 - How to polish gallium arsenide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is for finishing or high-speed processing the surface of gallium arsenide (GaAs), which is used for substrates of semiconductor devices and optical devices, into a mirror surface without scratches or defects. The present invention relates to a polishing method mainly based on chemical action.

Conventionally, there have been methods for polishing GaAs single crystal wafers as outlined below.

Generally, an abrasive cloth is attached to a rotating circular surface plate, and while the abrasive liquid is dripped onto the surface of the abrasive cloth, the Ga bonded to the adhesive plate is
This is a method of polishing an As wafer by chemical and mechanical action by pressing the As wafer against the polishing cloth and causing the polishing cloth to rotate and revolve.

. Conventional abrasives include the following: (
1) A solution containing 62 m9 of available chlorine per lmι of solution was used as a standard Na0c1 solution, and this was diluted with water to 13.5 m9 of available chlorine.
It is used after being diluted to ~26 times (Japanese Patent Publication No. 25817/1983).

(2) Na0c1+Na.

CO, (U.S. Pat. No. 3,342,654). (3) Water 300
mι, KA] (SO.) 2. River. Dissolve 142.39% of O, adjust the pH to 7.5 with NaOH, and add bleach solution (1 l
11 (containing 180y of NaOc1) is added, and water is added to make a total of 21 (Japanese Patent Publication No. 53-38595).
, 4) water glass (30 wt% SiO.

) 51 and Cacl.・9 to 2.5 of 6H2O, 4 of water
01 and adjusted to pH 7 with HCl. On the other hand, 3 tumor volume%H. O. Water 301 was purified with NH and OH water.
Adjust to H7. The two solutions are fed separately to the sander by pumps. i.e. mixing just before the outflow (
Special Publication No. 54-10824). (5) 1771, ιNH
4OH water + 700mι30%H by weight.

O. Water [Journal of the Electrochemical
Society (J, Electrochem, Soc,
) 11 & p 1346 (1971)] Among the abrasives mentioned above, those shown in (1) to (3) have a high machining speed when the Na0c1 concentration is high, but they have the disadvantage that the surface is oxidized.

In addition, (4) and (5) are expensive and highly dangerous H. 02
Since the amount of is relatively large, there were disadvantages such as lack of economy, operability, and safety.

The present invention provides a method for polishing gallium arsenide using a new and unprecedented liquid in order to eliminate the above-mentioned drawbacks.

That is, to summarize the present invention, the present invention uses a solution in which Ξ cyanuric chloride is dissolved in an alkaline aqueous solution, and GaA
Gallium arsenide (GaA
The present invention relates to the polishing method of s).

Cyanuric trichloride has the structural formula: i.e. molecular formula C3N3
It is a compound represented by Cl3. It is hardly soluble in water, and its saturated aqueous solution exhibits acid l/1. On the other hand, in the present invention, among the alkalis used in the form of an aqueous solution, preferred ones include sodium hydroxide, potassium hydroxide, and sodium carbonate.

For example, when cyanuric trichloride is dissolved in an aqueous sodium hydroxide solution, the following reaction equation: 2C3N3c13+6N
a0H+ side, O-3Na0c1+3Nac1+3N2↑
It is estimated that the reaction occurs according to +6C02↑+12H2↑, and NaOcl is produced.

NaOcl is stable in alkaline aqueous solutions. Similarly, dissolving cyanuric trichloride in aqueous potassium hydroxide produces KOCl.

As described above, according to the method of the present invention, an arbitrary concentration can be adjusted by dissolving inexpensive cyanuric trichloride powder in an aqueous alkaline solution.

Hereinafter, the present invention will be illustrated by examples, but the present invention is not limited thereto.

In each Example, a powder containing 9% by weight of the active ingredient as cyanuric trichloride was used as a standard.

The polishing method uses a regular rotating disk type polisher, with a diameter of 1
A polyurethane-polyester two-layer nonwoven fabric (product name Polytex
Supreme) was crucified. While dropping the polishing liquid having the composition of each example onto the surface of the polisher, the gallium arsenide single crystal surface (100) adhered to the adhesive plate was pressed against the rotating polisher with a pressure of 58 to 105 ykI1, and by the frictional force. Rotated. Example 1 This example shows an example in which cyanuric trichloride is used after being dissolved in an aqueous sodium hydroxide solution.

The relationship between the concentration, PH and the state of the polished surface in that case is shown in FIG. That is, FIG. 1 is a diagram showing the relationship between the concentration, PH, and the state of the polished surface in the case of creating an aqueous solution of cyanuric trichloride and sodium hydroxide. The horizontal axis shows Fle or molar concentration 5 of sodium hydroxide, and the vertical axis shows the PH value. The numbers in the figure indicate the dissolved amount (Yle) of cyanuric trichloride (90%). For example, 8y cyanuric trichloride in 1e shows a tendency to be neutralized with about 4V0NaOH. The polished surface changes depending on the concentration of cyanuric trichloride and the ratio of O cyanuric trichloride to sodium hydroxide. It is roughly divided into three regions: a region where the film is formed on the surface (■) and a region where a film is formed on the surface (■). 5 When the NaOH concentration is relatively low and the pH is low, a film of reaction products adheres to the polished surface in the region (2).

In the intermediate NaOH concentration range, gallium arsenide is dissolved during polishing through a suitable product diffusion layer, resulting in region I where a mirror surface is obtained. When NaOH is in excess and the pH is high, the dissolution rate of the reaction product is high;
As the reaction rate-determining process approaches, selective etching occurs, resulting in a region (3) with large surface roughness. As described above, when the cyanuric trichloride concentration is high, the rate of production of reaction products is high, so in order to obtain a mirror surface, it is necessary to increase the NaOH concentration.

Example 2 This example shows an example in which cyanuric trichloride is used after being dissolved in an aqueous potassium hydroxide solution.

FIG. 2 shows the relationship between the concentration at the time of polishing, the PH, and the state of the polished surface. That is, FIG. 2 is a diagram showing the relationship between the concentration, PH, and the state of the polished surface in the case of preparing an aqueous solution of cyanuric trichloride and potassium hydroxide. The horizontal axis shows the molar concentration of potassium hydroxide, and the vertical axis shows the PH value. The numbers in the figure indicate the dissolved amount (Yle) of cyanuric trichloride (90%). As in Example 1, the KOH concentration is relatively high;
When the pH is large, a selectively etched region (■) is obtained, and when the ratio of cyanuric trichloride and KOH is appropriate, a mirror-like region (1) is obtained.

Example 3 This example shows an example in which cyanuric trichloride is used after being dissolved in an aqueous sodium carbonate solution.

FIG. 3 shows the relationship between the concentration, PH, and the state of the polished surface in that case. In other words, in Figure 3, 1N●
FIG. 2 is a diagram showing the relationship between the amount of cyanuric trichloride (90%) dissolved in an aqueous sodium carbonate solution (ql'), the pH, and the condition of a polished surface. The horizontal axis is cyanuric trichloride (9
0%), and the vertical axis shows the pH value.
As in Example 1, when the Na2cO3 concentration is relatively low, a film adheres to the surface (■), and when the ratio of cyanuric trichloride and Na2cO3 is appropriate, a mirror-like region (1 ) is obtained.

Example 4 This example shows the results when cyanuric trichloride is dissolved in aqueous solutions of sodium hydroxide, potassium hydroxide, or sodium carbonate at various concentrations, and when the polishing pressure is varied. , the polishing speed will be exemplified.

The obtained results are shown in FIG. In other words, Figure 4 is
Cyanuric trichloride (90%) in aqueous solutions of sodium hydroxide, potassium hydroxide, or sodium carbonate at various concentrations.
The drawings show the changes in polishing speed when the concentration of the particles is changed and the polishing pressure is changed. The horizontal axis is the amount of cyanuric trichloride (90%) dissolved (q
l'), and the vertical axis shows the polishing speed (μm/hour).
The numbers in the figure are NaOH. KOH or Na2c
The normal concentration of O3 is shown. In the figure, the "●" mark indicates the polishing pressure of 105 gIcT11 "○" with NaOH aqueous solution.
” mark means polishing pressure 58VId1 “Δ” with NaOH aqueous solution
The mark indicates a polishing pressure of 105 VIcT11 using a KOH aqueous solution.
This represents the case of L. The polishing speed is approximately proportional to the concentration of cyanuric trichloride, and for the same cyanuric trichloride concentration, the higher the alkali concentration, the faster the polishing speed.

At a concentration of 1% cyanuric trichloride, 100PTn. A high polishing speed of more than /hour was obtained. In addition, in the above chemical treatment liquid,
Particle size 0.01-0.05pm. It has been found that mixing in SlO2 powder of 20% is effective in removing reaction products and improves the stability of the polishing speed.

As explained above, according to the method of the present invention, the price of the abrasive is low, the polishing speed is high, and the polishing is based on chemical action, so that essentially no processing distortion occurs and a mirror surface is created. It has the advantage of being obtainable.

Furthermore, the method of the present invention is particularly suitable for rough polishing of gallium arsenide substrates by taking advantage of its high polishing speed, and is suitable not only for single-sided polishing but also for double-sided mirror polishing using a double-sided simultaneous polishing machine. It can also be applied to

[Brief explanation of drawings]

FIG. 1 is a drawing showing the relationship between the concentration, PH, and the state of the polished surface in the case of preparing an aqueous solution of cyanuric trichloride and sodium hydroxide.

Claims (1)

[Claims] 1. A method for polishing gallium arsenide, which comprises polishing gallium arsenide using a solution prepared by dissolving cyanuric trichloride in an alkaline aqueous solution. 2. The method for polishing gallium arsenide according to claim 1, wherein the alkali is sodium hydroxide, potassium hydroxide, or sodium carbonate.