JPH069300A - Method for carrying out pre-treatment of substrate for crystal growth - Google Patents

Abstract

PURPOSE:To obtain a pre-treating substrate which does not induce the surface injury by bonding a substrate to a substrate holder, then placing the substrate in an inert gas atmosphere, feeding an etching solution while rotating the substrate, feeding a cleaning liquid thereto and then drying the substrate. CONSTITUTION:A substrate 1 is bonded to a substrate holder 2 using a low melting metal 3 and attached to a spinner 4 in an etching device and the interior of the device is kept in an inert gas atmosphere. Then an etching solution 5 such as methanol solution of bromine is dropped from a nozzle 6 to the center of the substrate 1 for a prescribed time while rotating the substrate holder 2 provided with the substrate 1 to remove fine particles and impurities attached to the surface of substrate. A volatile solvent for cleaning such as methanol is successively dropped to the substrate to remove the etching solution 5 and then the surface of the substrate is dried by increasing number of revolutions of the substrate to provide the substrate for crystal growth free from adhesion of impurities and fine particles to the substrate surface and hardly inducing damage of the surface. Then the substrate is quickly introduced into a growth device without exposing in the air.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pretreatment method for a crystal growth substrate.

[0002]

2. Description of the Related Art Conventionally, when a substrate surface film such as a natural oxide film cannot be removed in a growth chamber, the surface film is removed by etching the substrate immediately before introducing it into the growth chamber (Journal of Crystals).・ Growth (J. Crystal Growth 54 (198
1) 577)). In order to improve heat conduction between the substrate and the substrate holder, the substrate is usually bonded to the substrate holder using a low melting point metal such as indium or gallium. In order to shorten the time from the etching to the introduction as much as possible and prevent the formation of an oxide film, the etching treatment is performed after the substrate and the substrate holder are bonded. Drying after the etching process is usually performed by nitrogen blowing.

When the substrate surface film can be removed in the growth chamber, substrate heating (J. Electroche Society (J. Electroche)
m. Soc. 133 (1986) 666)), etching with an etching gas (J. Appl. Phys. 61 (1.
987) 4889)), ion sputtering (Journal of Vacuum Science and Technology (J.Vac.Sci.Technol.A6.
(1988) 2813)) and the like to remove the surface film.

[0004]

When the substrate and the substrate holder are simultaneously etched, the etching liquid enters between the substrate and the substrate holder and / or a gap in the details of the substrate holder,
Even if cleaning is performed, it is difficult to sufficiently remove the etching solution. The etching solution that cannot be removed enters the growth film as an impurity and deteriorates the crystal characteristics. Further, the substrate and the metal for adhesion are attacked by the residual etching solution to become impurities or deteriorate the surface of the substrate.

Further, when performing the drying after the etching treatment,
It is difficult to completely remove the solvent that has entered the gap, and the residual solvent is taken into the growth film as an impurity or contaminates the growth chamber. When the growth chamber is evacuated, the ultimate vacuum is deteriorated.

[0006] Nitrogen blow during drying entrains the surrounding fine particles and causes them to adhere to the surface of the substrate, which causes macroscopic crystal defects.

When the surface film is removed in the growth chamber, the substrate is atomically disturbed (substrate heating), the apparatus is complicated, the growth chamber is contaminated (etching gas), and the substrate surface is damaged (ion sputtering). ), Etc. may be induced.

The present invention has been made in view of such conventional circumstances, and does not cause impurities and fine particles to adhere to the surface of the substrate without causing contamination or complication of the growth chamber, and does not induce surface damage. It is an object to provide a pretreatment method for a crystal growth substrate.

[0009]

In order to achieve the above object, in the pretreatment method for a substrate for crystal growth according to the present invention, the substrate and the substrate holder are bonded after the substrate is bonded to the substrate holder by using a low melting point metal or the like. Is placed in an inert gas atmosphere, and the etching solution is dropped on the substrate surface for a certain period of time while rotating about the normal vector at the center of the substrate surface as an axis.
Furthermore, after dropping the volatile solvent for cleaning, the substrate and the substrate holder are dried while being rotated as it is.

[0010]

In the method of the present invention equipped with such means, the etching liquid contacts only the surface of the substrate and the upper surface of the substrate holder during the etching process. Therefore, the etching solution does not enter into the gaps of details. Therefore, the etching solution is almost completely removed in the next cleaning step. Further, since the volatile solvent for cleaning itself does not enter the unnecessary portion, it is almost completely removed in the drying step, and it does not cause impurities or contaminate the growth chamber.

Since the etching liquid flows from the center of the substrate toward the peripheral portion, fine particles and impurities attached to the substrate surface are removed as the surface film is etched. In addition, since the solvent is shaken off by the centrifugal force in the drying step, there is no possibility that the surrounding fine particles are caught and adhered to the substrate surface.

Since the surface film has already been removed from the introduced substrate, growth can be performed without heating to a high temperature as in the case of removing an oxide film. The heating of the substrate before growth may be performed at a temperature at which degassing from the substrate or the substrate holder is possible. Further, the method of the present invention does not require any change in the growth apparatus specifications.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

In this embodiment, HgCd using a CdTe substrate is used.
This is in the molecular beam epitaxy growth of Te.

FIG. 1 shows the structure of a substrate etching apparatus used in the present invention. A substrate 1 is attached to a substrate holder 2 with a low melting point metal 3 interposed therebetween. The substrate holder is attached to the spinner 4 and can rotate at an arbitrary speed. The etching liquid 5 or the cleaning volatile solvent is dropped on the rotation center of the substrate through the nozzle 6. The entire device is placed in a glove box that has been purged with dry nitrogen.

In this embodiment, gallium is used as the low melting point metal,
Bromine methanol having a bromine concentration of 0.5% was used as an etching solution, and methanol was used as a volatile solvent for cleaning. Rotate the substrate holder at 500 rpm to remove the etching solution
It dripped for second. Subsequently, methanol was dropped for 2 minutes to remove the etching solution. Move the nozzle 6 from above the substrate,
The rotation speed was increased to 1000 rpm and drying was performed. Then, it was immediately introduced into the growth apparatus without being exposed to the atmosphere.
Introduced substrate vacuum degree of 10 ^- A preliminary heating of 200 ° C. in the front chamber which is evacuated to ^{1 0} torr, was introduced to the growth chamber.

After the introduction into the growth chamber, the state of the surface was examined by the reflection high-energy electron diffraction method. As a result, it was found that the oxide film was completely removed and a single crystal surface without damage appeared. HgCdT using molecular beam of Hg, CdTe, Te
When e was grown, a good single crystal epilayer was obtained. The density of the macroscopic defects by particles adhering to the pretreatment time is 10 ³ cm ^- and ² below, was reduced from an order of magnitude two orders as compared with the drying process according to the conventional nitrogen blow.

[0018]

According to the method of the present invention, the pretreatment of the crystal growth substrate is performed without causing the growth chamber to be contaminated or complicated so that impurities and fine particles are hardly attached to the substrate surface and the surface damage is not induced. be able to.

[Brief description of drawings]

FIG. 1 shows the configuration of a substrate etching apparatus used in the present invention.

[Explanation of symbols]

 1 substrate 2 substrate holder 3 low melting point metal 4 spinner 5 etching liquid 6 nozzle

Claims (1)

[Claims] 1. A pretreatment method for a substrate crystal for growing a crystal, which comprises: adhering a substrate to a substrate holder; then placing the substrate and the substrate holder in an inert gas atmosphere; A method for pretreating a substrate for crystal growth, comprising: supplying the substrate surface for a predetermined time, further supplying a cleaning agent, and then drying the substrate while rotating the substrate.