JP2906794B2 - Method of manufacturing wafer with insulating film and wafer with insulating film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a compound semiconductor crystal wafer with an insulating film and a compound semiconductor crystal wafer with an insulating film.

[0002]

2. Description of the Related Art Compound semiconductors have been used in the fabrication of Schottky gate field effect transistors (MESFETs), high mobility transistors (HEMTs), heterojunction bipolar transistors (HBTs), and various light receiving and emitting devices. A semiconductor surface / interface, that is, a free surface, a semiconductor-semiconductor interface, a metal-semiconductor interface, and an insulator-semiconductor interface are basic components of any semiconductor device.
In particular, surfaces with a large number of unbound species are intrinsically active and tend to adsorb external atoms, molecules, and ions, thereby changing the electronic state of the surface. Therefore, the surface is covered with an insulating film or the like to terminate dangling bonds, and the surface is made inactive. Since semiconductor devices use a semiconductor surface, this surface passivation technique is a very important technique.

[0003] The surface of a GaAs crystal is oxidized to form high-density surface states. This causes a device having a MIS structure to hinder fabrication of GaAs. As a method for stabilizing the surface, photochemical oxidation, sulfide treatment, selenization treatment and the like have been proposed, but a method for sufficiently stabilizing the surface has not yet been found. Recently, as a method of improving the surface stabilization by developing sulfide treatment, As ₂ S ₃ film is made of GaAs.
A method of depositing on s-crystal surfaces was reported by E. Yablonovitch et al. This method comprises the following five steps, which are performed in order from to.

H ₂ SO ₄ : H ₂ O ₂ : H ₂ O = 1:
Etching with 8: 500 solution, washing with water Dipping in (NH ₄ ) ₂ S solution, washing with water Dipping in a solution of 0.16 M As ₂ S ₃ dissolved in ammonia solution: CH ₃ OH = 2: 1 Spin drying 290- Heat treatment at 300 ° C (air atmosphere)

[0005]

By the way, the aforementioned E.
When As ₂ S ₃ is deposited by a wet process such as Yablonovitch to produce a MIS diode, the CV curve is shifted (several volts) from the ideal curve, and hysteresis also appears. This is because the interface state between the GaAs substrate and the insulating film As ₂ S ₃ is not sufficiently reduced,
Also, there is a problem with the purity of the film quality. As described above, a method for depositing an insulating film having a sufficiently low interface state density that a MIS structure device can be formed on a GaAs substrate has not yet been found, and a wafer with an insulating film has not been developed.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide an insulating film capable of lowering the interface state density at the insulating film-substrate interface sufficiently for the MIS structure device to operate completely. An object of the present invention is to provide a method for manufacturing a wafer with a film and a wafer with an insulating film.

[0007]

The present invention SUMMARY OF THE INVENTION In order to achieve the above object, is to deposit the As ₂ S ₃ insulating film by the CVD method on the III-V compound semiconductor crystal wafer surface such as GaAs. Further, As is deposited on the surface of the crystal wafer, and the As is reacted with a hydrogen sulfide gas or a sulfur fluoride gas to form an As ₂ S ₃ film. Furthermore, Langmuir-Blodgett film of Chiofuin derivative and thiophenol derivatives crystal wafer surface (hereinafter referred to as "LB film".) By adhering a protective film, by heat-treating it at the time of actually create the element As ₂ S ₃ It forms a film. Furthermore, an As ₂ S ₃ film is formed on the surface of a crystal wafer, and a SiO ₂ film or a SiN film is formed thereon by a CVD method or the like.

In the present invention, examples of the III-V compound semiconductor crystal wafer include GaAs, InP and GaP.

As the CVD method, high frequency plasma CVD is used.
, Plasma CVD such as electron synchrotron resonance plasma CVD, thermal decomposition CVD, infrared excitation CVD,
There is a light excitation CVD method such as an ultraviolet excitation CVD method.

A method for depositing As on the surface of a crystal wafer;
The surface of the wafer with AsH_ThreeHeat treatment in a gas atmosphere
There is a method of depositing As on the wafer surface by
sH _ThreeIn addition to AsCl_Three, As (C_TwoH_Five), As (C
H_Three), As (OC_TwoH_Five), C_TwoH₉AsH_TwoUsing
You may. In addition, As is deposited on the wafer surface in vacuum
Is also good.

As the sulfur fluoride gas, S ₂ F ₄ , SF
_4, there is a SF _6.

The number of layers of the LB film is preferably two or more.

[0013]

According to the above-mentioned structure, an insulating film is favorably formed on the surface of the III-V compound semiconductor crystal wafer, and the wafer surface is sufficiently stabilized. In addition, As
By forming a ₂ S ₃ film and forming a SiO ₂ film or a SiN film thereon, E. Yablonovit described in the section of the prior art can be used.
even ch a factor that interface is not formed between the insulation and the wafer of film at the time of forming the As ₂ S ₃ film by a method such as Ga is contained in the film, Ga of the As ₂ S ₃ film Si
It is piled up in the O ₂ , SiN film.

Therefore, the interface state density at the interface between the insulating film and the wafer is sufficiently low for the MIS structure device to operate completely.

[0015]

Embodiments of the present invention will be described below.

(Example 1) After etching an n-type (100) GaAs substrate with a sulfuric acid system, the surface thereof was coated with AsH ₃ , H
Electron synchrotron resonance (ECR) using ₂ S as source gas
An As ₂ S ₃ film serving as an insulating film was deposited at 1000 A by a CVD method. Then, an Au electrode is formed on the substrate by mask evaporation, and an In-G
(a) Solder was applied to produce a MIS diode.

Example 2 After an n-type (100) GaAs substrate was subjected to sulfuric acid etching, the substrate was placed in a heating furnace and heated at 300 ° C. in an AsH ₃ atmosphere. Next, H ₂ S gas is introduced into the furnace, and is reacted with As deposited on the substrate.
_{A 2} S ₃ film was deposited at 1000A. Then, an MIS diode was manufactured in substantially the same process as in the first embodiment.

(Example 3) An n-type (100) GaAs wafer was subjected to sulfuric acid etching and washed with running pure water. During this time, several drops of a solution of a thiophene derivative and a thiophenol derivative using ether as a solvent were dropped into another container containing pure water to form a monomolecular film on the water surface. The wafer under running water washing was taken out, and the wafer was vertically moved up and down across the water surface covered with the monomolecular film to form an LB film composed of several molecular layers. Next, the wafer with the LB film is heat-treated at 300 to 400 ° C. in a hydrogen, nitrogen or argon atmosphere. Thus, the uppermost layer of the LB film is evaporated with impurities adhering to the surface, the lower layer is As and the chemical reaction of the thermal decomposed wafer surface to form a As ₂ S ₃ film on the wafer surface. Then, an MIS diode was manufactured in substantially the same process as in the first embodiment.

(Example 4) After an n-type (100) GaAs substrate is subjected to sulfuric acid etching, a 50 A As ₂ S ₃ film is first deposited on the surface of the substrate by a plasma CVD method or a wet processing method such as E. Yablonovitch. And then plasma C
A 700 A SiO ₂ film was deposited by the VD method. Then, an MIS diode was manufactured in substantially the same process as in the first embodiment.

(Comparative Example) 750 A of an As ₂ S ₃ film was deposited by a wet process performed by E. Yablonovitch et al. By a vacuum evaporation method using As ₂ S ₃ as a source (raw material). An MIS diode was manufactured by the process.

The MIS diode fabricated as described above was evaluated for CV characteristics and insulating film quality.
The CV characteristics were measured at a frequency of 1 MHz.

As a result, the diodes of Examples 1 to 4
In each case, the CV characteristics were in good agreement with the ideal curve, no hysteresis appeared, the interface state density at the interface between the insulating film and the substrate was sufficiently low, and the film quality of As ₂ S ₃ was good.

On the other hand, in the comparative example, the CV characteristics were shifted from the ideal curve by several volts (V), and hysteresis also appeared.

In the first embodiment, the thermal decomposition CV
D method, high frequency plasma CVD method, ultraviolet excitation CVD method,
The same experiment was performed for the laser excitation CVD method, and the CV characteristics of the diode were good in these CVD methods as in the case of the ECRCVD method.
Further, in Example 3, if the case where SiN is deposited in place of SiO ₂ in SiO ₂ and similar results were obtained.

Further, in Example 4, even after the LB film was deposited, the wafer surface was not oxidized even if the wafer was left in the air. After heat-treating the wafer with the LB film left in the air and forming an As ₂ S ₃ film thereon, a MIS diode is manufactured in substantially the same process as in the first embodiment, and its CV characteristics are measured. did. As a result, it coincided well with the ideal curve, and no hysteresis appeared. Thus, the LB film becomes a good wafer surface protective film, and a good As ₂ S ₃ film can be obtained in the process stage. This is particularly effective when, for example, a time is opened between the epitaxial growth and the process. This is because, in the case of a compound semiconductor crystal wafer grown epitaxially, a method of removing an oxide film by wet etching performed by E. Yablonovitch or the like cannot be used in many cases because multi-layer growth according to the element structure is performed. . Therefore, in order to prevent oxidation of the wafer surface, the above-described processing must be performed immediately after the epitaxial growth. If time is required between the epitaxial growth and the device preparation, contamination occurs on the surface of the As ₂ S ₃ film. In a device such as a laser diode or a hetero-bipolar transistor for the purpose of treating only the end face, there is no problem even if contamination occurs on the surface of the As ₂ S ₃ film. However, an electrode formed on an As ₂ S ₃ film or the like, such as the MIS structure, causes a problem because the contamination deteriorates the characteristics of the interface between the insulating film and the electrode.

Therefore, according to the present invention, a good insulating film is formed on the surface of the group III-V compound semiconductor crystal wafer, and the insulating film having the sufficiently low interface state density at the insulating film-wafer interface is provided. A wafer is obtained. Therefore, by using the wafer with the insulating film, a good MIS structure element and MESFET, HEMT, H
BT, LD and LED can be manufactured,
These device characteristics and yield can be greatly improved.

[0027]

In summary, according to the present invention, III-V
Since a good insulating film is formed on the surface of the group III compound semiconductor crystal wafer, the interface state density at the insulating film-wafer interface is set to MIS.
A wafer with an insulating film that is sufficiently low for the complete operation of the structural device is obtained.

Continuation of the front page (72) Inventor Takeshi Meguro 3550 Kida Yomachi, Tsuchiura City, Ibaraki Prefecture Advanced Research Center, Hitachi Cable, Ltd. (56) References JP-A-4-112520 (JP, A) JP-A-58- 141576 (JP, A) JP-A-5-102128 (JP, A) JP-A-62-240908 (JP, A) JP-A-3-257972 (JP, A) (58) Fields investigated (Int. ⁶ , DB name) H01L 21/314 JICST file (JOIS)

Claims (5)

(57) [Claims] 1. A method of manufacturing a wafer with an insulating film, comprising depositing As ₂ S ₃ as an insulating film on a surface of a III-V group compound semiconductor crystal wafer such as GaAs by a CVD method. 2. As is deposited on the surface of a III-V compound semiconductor crystal wafer such as GaAs, and the deposited As is reacted with a hydrogen sulfide gas or a sulfur fluoride gas to produce As ₂ S.
_A method for producing a compound semiconductor crystal wafer with an insulating film, comprising forming _three films. 3. A method of depositing a Langmuir-Blodgett film of a thioin derivative or a thiophenol derivative on the surface of a III-V compound semiconductor crystal wafer of GaAs or the like, followed by heat treatment to form an As ₂ S ₃ film. A method for manufacturing a wafer with an insulating film, comprising: 4. An As ₂ S ₃ film is formed on the surface of a III-V group compound semiconductor crystal wafer such as GaAs, and Si is formed on the surface.
A wafer with an insulating film, wherein an O ₂ film is formed. 5. An As ₂ S ₃ film is formed on the surface of a III-V group compound semiconductor crystal wafer such as GaAs, and Si
A wafer with an insulating film, wherein an N film is formed.