JP2002025957A - Cleaning method for removing organic material of semiconductor wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method of removing an organic material of a semiconductor wafer for removing an organic material and cleaning completely without using an expensive specific etchant and realizing drastic improvement in yield and in manufacturing cost. SOLUTION: After the semiconductor wafer with a specularly ground surface is dipped in ultra-pure water, the organic material stuck on the surface of the semiconductor wafer is removed while an ultrasonic wave is applied to the ultra-pure water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for cleaning and removing organic substances from a semiconductor wafer.

[0002]

2. Description of the Related Art Compound semiconductor wafers are widely used as base wafer materials for semiconductor devices such as Schottky gate field-effect transistors (MESFETs), high mobility transistors (HEMTs), heterojunction bipolar transistors (HBTs), and various light emitting and receiving devices. Have been.

The active layers of these semiconductor devices are formed on the surface of a mirror-polished compound semiconductor wafer by molecular beam epitaxy (MBE), metal organic vapor phase epitaxy (MOVPE), ion implantation, or the like.

[0004] Generally, the procedure for manufacturing a mirror-polished compound semiconductor wafer is as follows. Production of Compound Semiconductor Single Crystal Ingot First, a compound semiconductor single crystal ingot is produced.

Slicing work of compound semiconductor single crystal ingot Next, the compound semiconductor single crystal ingot obtained above is mounted on a slicing apparatus and sliced to obtain a slice compound semiconductor wafer.

Rough polishing of sliced compound semiconductor wafer Next, the sliced compound semiconductor wafer obtained above is mounted on a rough polishing apparatus, and then coarsely polished by using alumina abrasives of # 800 to # 3000. This is a compound semiconductor wafer. This rough polishing is from # 800 to # 30
Lapping is carried out so as to remove the saw mark with 00 abrasive grains.

[0007] The roughly polished compound semiconductor wafer obtained here has improved flatness.

Mirror Polishing of Roughly Polished Compound Semiconductor Wafer Next, an attaching blade whose surface flatness is finished with high precision is prepared, and it is mounted on a mirror polishing machine.

Next, the roughly polished compound semiconductor wafer obtained above is attached to the attaching blade using wax or the like.

[0010] Next, the rough polishing compound semiconductor wafer stuck on the sticking blade is subjected to mechanochemical polishing to obtain a mirror-polished compound semiconductor wafer.

Here, the following is used for the mechanochemical polishing.

A. Polishing solution: hypochlorous acid aqueous solution, bromine ~
Methanol solution, colloidal silica b. Polishing cloth: polishing cloth having a porous layer on the surface Degreasing and cleaning of the mirror-polished compound semiconductor wafer Next, the mirror-polished compound semiconductor wafer obtained above is subjected to degreasing treatment, cleaning treatment, and ultrapure water cleaning with ultrapure water. Perform sequentially.

Drying of Ultrapure Water Cleaning Compound Semiconductor Wafer Next, the ultrapure water cleaning compound semiconductor wafer obtained above is mounted in an isopropyl alcohol vapor dryer or a spin dryer.

Then, the wafer is dried for a predetermined period of time by using these drying apparatuses to obtain a finished product of a mirror-polished compound semiconductor wafer.

[0015]

[0005] Now, when an epitaxial growth operation is performed on the mirror surface of a dried and finished product of a mirror-polished compound semiconductor wafer obtained by performing the above-described highly precise polishing operation, cleaning operation, drying operation, and the like. And haze defects occur.
The semiconductor device having the haze defect has extremely poor performance and cannot be put to practical use.

It is known that the cause of the haze defect is a trace amount of organic substances remaining on the mirror surface.

Therefore, in an actual epitaxial growth operation, a pre-etching operation is performed on a dried and finished product of a mirror-polished compound semiconductor wafer on which the epitaxial growth operation is performed.

The etching operation before the epitaxial growth operation of the dried and finished product of the mirror-polished compound semiconductor wafer is as follows:
The surface is etched to a depth of 1 to 2 μm with an etchant such as a sulfuric acid-based etchant or an ammonia-based etchant. By this etching operation of 1 to 2 μm, even trace amounts of organic substances adhering to the surface of the dried and finished product of the mirror-polished compound semiconductor wafer can be completely removed.

However, once the mirror-polished compound semiconductor wafer is dried and completed, the etching operation is performed again, thereby lowering the productivity and increasing the manufacturing cost.

In addition, when the dried and finished product of the mirror-polished compound semiconductor wafer is etched, the etching may cause abnormal mirror surface defects,
As a result, there was a problem that the yield was reduced.

The present invention has been made in view of such a point, and an object of the present invention is to solve the above-mentioned disadvantages of the prior art and to completely remove and clean organic substances without using an expensive special etchant. It is therefore an object of the present invention to provide a method of removing and cleaning an organic substance on a semiconductor wafer, whereby the productivity can be significantly improved and the manufacturing cost can be significantly reduced.

[0022]

The gist of the present invention is to immerse a semiconductor wafer whose surface has been mirror-polished into an ultrapure water tank, and then apply the ultrasonic wave to the ultrapure water while polishing the mirror-polished semiconductor wafer. An organic substance removing and cleaning method for a semiconductor wafer, comprising removing and cleaning an organic substance attached to a surface of a semiconductor wafer.

In the present invention, the ultrasonic wave is 900 kHz.
Preferably, the frequency is equal to or higher than z.

This is because the efficiency of removing and cleaning organic substances sharply increases when ultrasonic waves having a frequency of 900 kHz or more are applied in ultrapure water.

In the present invention, the ultrasonic wave may be 4
It is preferably at least 00W.

This is because when ultrasonic waves of 400 W or more are applied in ultrapure water, the efficiency of removing and cleaning organic substances is drastically improved.

Further, in the present invention, it is preferable that the ultrasonic cleaning be performed with an ultrasonic wave having a frequency of 900 kHz or more and an intensity of 400 W or more for 5 minutes or more.

This is because the cleaning efficiency sharply increases when ultrasonic cleaning is performed for 5 minutes or more.

In the present invention, the semiconductor wafer for removing and cleaning organic substances is a compound semiconductor wafer, for example, GaAs.
Preferably, it is a wafer or semi-insulating GaAs.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a method for removing and cleaning organic substances from a semiconductor wafer according to the present invention will be described.

(Comparative Example 1) First, a dried and finished mirror-polished semi-insulating GaAs wafer was immersed in a sulfuric acid-based etchant to etch the surface to a depth of 2 μm.

Next, the etched semi-insulating GaAs
The s wafer was washed with ultrapure water and then dried by a spin drying method to obtain a mirror-polished semi-insulating GaAs wafer.

Next, undoped A1 _x Ga ₁ -x As (X = 0.5) is grown to a thickness of 500 nm on the surface of the dried and finished mirror-polished semi-insulating GaAs wafer by MOVPE epitaxial growth. Thus, a semiconductor device was obtained.

Next, the surface of the semiconductor device obtained here was irradiated with light by a condensing lamp to observe the surface in detail, but no haze defect was found at all.

Comparative Example 2 First, ultra-pure water cleaning was performed by immersing a mirror-polished semi-insulating GaAs wafer in an ultra-pure water bath for 15 minutes.

Next, the semi-insulating G having been subjected to the ultrapure water cleaning is used.
The aAs wafer was dried by a spin drying method to obtain a mirror-polished semi-insulating GaAs wafer.

Next, undoped A1 _x Ga ₁ -x As (X = 0.5) is grown to a thickness of 500 nm on the surface of the dried and finished mirror-polished semi-insulating GaAs wafer by MOVPE epitaxial growth. Thus, a semiconductor device was obtained.

Next, the surface of the obtained semiconductor device was observed in detail by irradiating light with a condensing lamp on the surface thereof.
Bad haze was found.

(Example 1) First, a mirror-polished semi-insulating GaAs wafer was immersed in an ultrapure water tank to which ultrasonic waves of 1 MHz and 550 W were applied for 15 minutes to perform ultrapure water cleaning. .

Next, the semi-insulating G having been subjected to the ultrapure water cleaning is used.
The aAs wafer was dried by a spin drying method to obtain a mirror-polished semi-insulating GaAs wafer.

Next, undoped A1 _x Ga ₁ -x As (X = 0.5) is grown to a thickness of 500 nm on the surface of the dried mirror-polished semi-insulating GaAs wafer by MOVPE epitaxial growth. Thus, a semiconductor device was obtained.

Next, the surface of the semiconductor device obtained here was irradiated with light by a condensing lamp to observe the surface in detail, but no haze defect was found.

(Test Results) In the method of cleaning and removing organic substances from a semiconductor wafer of Comparative Example 1, a finished mirror-polished semi-insulating GaAs wafer is etched so that productivity is reduced and production costs are increased. Was.

Further, in the method of cleaning and removing organic substances from a semiconductor wafer of Comparative Example 2, it was not possible to completely remove and clean the organic substances of the semiconductor wafer, and as a result, a haze defect was found.

On the other hand, in the method of removing and cleaning an organic substance on a semiconductor wafer according to the first embodiment of the present invention, the organic substance can be completely removed and cleaned without using an expensive special etchant, thereby greatly improving the productivity. And a significant reduction in manufacturing cost.

[0046]

According to the method of removing and cleaning an organic substance of a semiconductor wafer according to the present invention, an organic substance can be completely removed and cleaned without using an expensive special etchant, thereby greatly improving productivity and reducing manufacturing costs. It is possible to achieve a significant reduction and is industrially useful.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaya Onishi 5-1-1 Hidaka-cho, Hitachi City, Ibaraki Prefecture Inside the Hidaka Factory, Hitachi Cable Co., Ltd. (72) Inventor Shinfumi Komata Hidaka, Hitachi City, Ibaraki Prefecture 5-1-1, Hachimachi, Hidaka Factory, Hitachi Cable, Ltd.

Claims (6)

[Claims] 1. A semiconductor wafer whose surface has been mirror-polished is immersed in an ultrapure water bath, and an organic substance adhering to the surface of the mirror-polished semiconductor wafer is removed and washed while applying ultrasonic waves to the ultrapure water. A method for removing organic substances from a semiconductor wafer. 2. The method according to claim 1, wherein the ultrasonic wave has a frequency of 900 kHz or more. 3. The method according to claim 1, wherein the ultrasonic wave has an intensity of 400 W or more. 4. The ultrasonic cleaning is performed at a frequency of 900 kHz or more.
2. The method for removing organic matter from a semiconductor wafer according to claim 1, wherein the cleaning is performed with an ultrasonic wave having an intensity of 400 W or more for 5 minutes or more. 5. The method according to claim 1, wherein the semiconductor wafer is a compound semiconductor wafer. 6. The method according to claim 5, wherein the compound semiconductor wafer is a GaAs wafer or semi-insulating GaAs.