JP2001144056A - Method of polishing semiconductor crystal wafer and wafer obtained thereby - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of polishing a semiconductor crystal wafer for stably obtaining a wafer having a low haze level, as well as a wafer obtained by the method. SOLUTION: Since a polishing solution having a strong oxidizing power is used for polishing a semiconductor wafer, the oxidizing power of the polishing solution must be stopped instantly upon completion of polishing. A traditional method wherein the oxidizing power is reduced by means of dilution is not successful in instantly stopping the oxidation reaction. To instantly stop the oxidation power, an acidic solution can be used for neutralization. If an acidic solution having a low pH is used, the interior of a polishing machine is corroded. Further, the pH ranging from 5 to 7 reduces the neutralizing power of the acidic solution, preventing the instant stoppage of the oxidizing power of the polishing solution. Therefore, an optimal pH level is between 3 and 5. Thus, by cleaning the semiconductor crystal wafer with an acidic solution whose pH ranges from 3 to 5 immediately after the completion of the polishing, a semiconductor crystal wafer having a low haze level can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for polishing a semiconductor crystal wafer and a wafer obtained by the method.

[0002]

2. Description of the Related Art Compound semiconductors are used for manufacturing various light emitting and receiving devices such as a Schottky gate field effect transistor (MESFET), a high electron mobility transistor (HEMT), and a heterojunction bipolar transistor (HBT). The active layer of these devices is formed on a mirror-finished wafer surface by a molecular beam epitaxial growth (MBE) method, an organic metal layer epitaxial growth (MOVPE) method, or the like.

[0003] A mirror wafer is manufactured as follows.

[0004] A crystal ingot is sliced and a wafer is cut out. This sliced wafer is lapped with alumina abrasive grains of # 800 to # 3000 to improve flatness. After attaching this wafer to an alumina ceramic plate, a hypochlorite-based aqueous solution of pH 8 to pH 10 is used as a polishing liquid, and a polishing cloth having a porous layer on the surface is polished by a single-side polishing machine to finish the mirror surface. . After the polishing, the wafer is rinsed together with the plate and dried by nitrogen blow. Next, the wafer is removed from the plate, degreased and washed, washed with a cleaning solution having a very slight etching action and washed with ultrapure water, and dried by isopropyl alcohol vapor drying or spin drying.

[0005]

However, in the above-mentioned conventional method for polishing a semiconductor crystal wafer, a polishing liquid having a strong oxidizing property is used. To stop the oxidation reaction. If the polishing liquid cannot be instantaneously diluted, the wafer surface is oxidized by the polishing liquid and haze, so-called "cloudiness", is generated on the surface. When an epitaxial crystal is grown on a wafer on which haze has occurred, there has been a problem that the surface of the epitaxial crystal becomes rough and deteriorates the crystal quality.

An object of the present invention is to solve the above-mentioned problems and to provide a method of polishing a semiconductor crystal wafer for stably obtaining a wafer having a low haze level and a wafer obtained by the method.

[0007]

In order to achieve the above object, a method for polishing a semiconductor crystal wafer according to the present invention is to polish the semiconductor crystal wafer, and immediately after the polishing is completed, the semiconductor crystal wafer is washed with an aqueous acid solution of pH 3 to 5. Is what you do.

The semiconductor crystal wafer of the present invention has been washed with an aqueous acid solution having a pH of 3 to 5 immediately after polishing is completed.

The semiconductor crystal wafer of the present invention has been washed with an aqueous acid solution of pH 3 to 5 immediately after polishing of a semiconductor wafer made of a III-V compound semiconductor or a II-VI compound semiconductor.

In addition to the above structure, in the semiconductor crystal wafer of the present invention, the III-V compound semiconductor is preferably GaAs or semi-insulating GaAs.

In addition to the above-mentioned constitution, in the semiconductor crystal wafer of the present invention, it is preferable that the II-VI compound semiconductor is one of an aqueous solution of carbonic acid, an aqueous solution of acetic acid, or an aqueous solution of hydrogen cyanide.

Here, since a highly oxidizing polishing liquid is used for polishing the semiconductor wafer, it is necessary to stop the oxidizing power of the polishing liquid immediately after the polishing is completed. It is difficult to instantaneously stop the oxidation reaction by the conventional method of diluting to reduce the oxidizing power. In order to stop the oxidizing power instantaneously, it is sufficient to neutralize with an acidic aqueous solution. However, when an acidic aqueous solution having a low pH is used, the inside of the polishing machine is corroded. PH 5
In Nos. 7 to 7, the oxidizing power of the polishing liquid cannot be instantaneously reduced because the neutralizing ability is reduced. Therefore, the optimal pH is 3-5.

For this reason, the semiconductor crystal wafer having a low haze level can be obtained by washing the semiconductor crystal wafer with an aqueous acid solution having a pH of 3 to 5 immediately after the completion of polishing.

[0014]

Embodiments of the present invention will be described below.

The method for polishing a semiconductor crystal wafer according to the present invention comprises:
The semiconductor crystal wafer is polished, and pH 3-5 immediately after the polishing is completed.
The semiconductor crystal wafer is cleaned with an aqueous acid solution.
In addition, the semiconductor crystal wafer of the present invention has p
It was washed with an aqueous acid solution of H3 to H5.

The semiconductor crystal wafer having a low haze level can be obtained by washing the semiconductor crystal wafer with an aqueous acid solution having a pH of 3 to 5 immediately after the polishing is completed.

[0017]

EXAMPLE 1 4 inch (10.16 cm) GaAs wrapped with # 1500 alumina abrasive grains
The wafer was stuck to a φ360 alumina ceramic plate and roughly polished with alumina having a particle size of 0.5 μm. Then, a hypochlorite-based aqueous solution was used as a polishing liquid, and a polishing cloth having a porous layer on the surface was used. Mechanochemical polishing was performed with a polishing machine. Immediately after the polishing, the wafer surface was washed with a carbonated aqueous solution adjusted to pH 3 to 6 for 1 minute. Next, the substrate was washed with ultrapure water for 5 minutes, and finally, nitrogen blow drying was performed. The haze level of the mirror-polished wafer was examined using a mirror inspection apparatus (Surfscan 6200 manufactured by Tencor Corporation).

For comparison, a similar experiment was performed on a wafer that was polished and washed with only ultrapure water.

FIG. 1 is a graph showing the relationship between pH and haze level in one embodiment of a wafer to which the method of polishing a semiconductor crystal wafer according to the present invention is applied. The horizontal axis indicates pH, and the vertical axis indicates haze level. Show.

The haze level of the wafers washed with carbonated water of pH 3, 4, 5 was as low as 0.1 to 0.5 ppm.
However, the haze level of a wafer washed with an aqueous carbonate solution having a pH of 5.5 or more and washed only with ultrapure water has a haze level of 3.0 ppm.
The above values were high.

(Example 2) A 4-inch GaAs wafer wrapped with # 1500 alumina abrasive grains was subjected to φ360
Alumina ceramic plate with a particle size of 0.5
After coarse polishing with alumina of μm, a hypochlorite-based aqueous solution was used as a polishing solution, and a polishing cloth having a porous layer on the surface was used.
Mechanochemical polishing was performed with a 6B single-side polishing machine. Immediately after the polishing was completed, the wafer surface was washed with an aqueous acetic acid solution adjusted to pH 3 to 6 for 1 minute. Next, the substrate was washed with ultrapure water for 5 minutes, and finally, nitrogen blow drying was performed. The haze level of the mirror-polished wafer was examined using a mirror inspection apparatus (Surfscan 6200 manufactured by Tencor Corporation).

For comparison, a similar experiment was performed on a wafer that was polished and washed only with ultrapure water.

FIG. 2 is a graph showing the relationship between the pH and the haze level in another embodiment of the wafer to which the method of polishing a semiconductor crystal wafer according to the present invention is applied. The horizontal axis indicates the pH, and the vertical axis indicates the haze level. Is shown.

The haze level of the wafer washed with the acetic acid aqueous solution having a pH of 3, 4, or 5 was as low as 0.1 to 0.5 ppm. However, the haze level of a wafer washed with an acetic acid aqueous solution having a pH of 5.5 or more and washed only with ultrapure water has a haze level of 3.0 p.
pm or more.

(Example 3) A 4-inch GaAs wafer wrapped with # 1500 alumina abrasive grains was subjected to φ360
Alumina ceramic plate with a particle size of 0.5
After coarse polishing with alumina of μm, a hypochlorite-based aqueous solution was used as a polishing solution, and a polishing cloth having a porous layer on the surface was used.
Mechanochemical polishing was performed with a 6B single-side polishing machine. Immediately after the polishing was completed, the wafer surface was washed with an aqueous hydrogen cyanide solution adjusted to pH 3 to 6 for 1 minute. Next, the substrate was washed with ultrapure water for 5 minutes, and finally, nitrogen blow drying was performed. The haze level of the mirror-polished wafer was examined using a mirror inspection apparatus (Surfscan 6200 manufactured by Tencor Corporation).

For comparison, a similar experiment was performed on a wafer which was polished and washed only with ultrapure water.

FIG. 3 is a graph showing the relationship between the pH and the haze level in another embodiment of the wafer to which the method for polishing a semiconductor crystal wafer according to the present invention is applied. The horizontal axis indicates the pH, and the vertical axis indicates the haze level. Is shown.

The haze level of a wafer washed with an aqueous solution of hydrogen cyanide having a pH of 3, 4, or 5 is 0.1 to 0.5 ppm.
Was low. However, the haze level of a wafer washed with an aqueous hydrogen cyanide solution having a pH of 5.5 or more and washed with ultrapure water was as high as 3.0 ppm or more.

As described above, according to the method for polishing a semiconductor crystal wafer of the present invention, a wafer having a low haze level can be obtained stably. By using this wafer, a high-quality epitaxial layer can be obtained, Can be raised.

[0030]

In summary, according to the present invention, the following excellent effects are exhibited.

A method of polishing a semiconductor crystal wafer for stably obtaining a wafer having a low haze level and a wafer obtained by the method can be provided.

[Brief description of the drawings]

FIG. 1 is a view showing the relationship between pH and haze level in one embodiment of a wafer to which a method for polishing a semiconductor crystal wafer according to the present invention is applied.

FIG. 2 is a view showing a relationship between a pH and a haze level in another example of a wafer to which the method for polishing a semiconductor crystal wafer of the present invention is applied.

FIG. 3 is a diagram showing a relationship between a pH and a haze level in another example of a wafer to which the semiconductor crystal wafer polishing method of the present invention is applied.

Claims (5)

[Claims] 1. A method for polishing a semiconductor crystal wafer, comprising: polishing the semiconductor crystal wafer; and washing the semiconductor crystal wafer with an acid aqueous solution having a pH of 3 to 5 immediately after the polishing is completed. 2. A semiconductor crystal wafer washed with an aqueous acid solution having a pH of 3 to 5 immediately after polishing is completed. 3. A compound semiconductor of group III-V or II-V
A semiconductor crystal wafer characterized by being washed with an aqueous acid solution having a pH of 3 to 5 immediately after polishing of a semiconductor wafer made of a Group VI compound semiconductor. 4. The method according to claim 1, wherein the III-V compound semiconductor is GaAs.
4. The semiconductor crystal wafer according to claim 3, wherein the semiconductor crystal wafer is made of semi-insulating GaAs. 5. The semiconductor crystal wafer according to claim 3, wherein said II-VI group compound semiconductor is one of an aqueous solution of carbonic acid, an aqueous solution of acetic acid, and an aqueous solution of hydrogen cyanide.