JPS61166968A - Production of thin zinc sulfide film - Google Patents

Abstract

PURPOSE:To obtain a thin zinc sulfide film having a high crystal grade by using an addition product obtd. by mixing dialkyl zinc and dimethyl selenium at an equal molar ratio as a zinc source and hydrogen sulfide as a sulfur source. CONSTITUTION:A substrate 3 is set on a susceptor 2 provided in a reaction tube 1. H2S diluted by a carrier gas is packed in a cylinder 16. The addition product formed by mixing the dialkyl zinc and dimethyl selenium at an equal ratio is sealed into a bubbler 13 and dimethyl selenium (DMSe) is sealed into a bubbler 14. The respective gaseous raw materials are diluted by the carrier gas flowing in a piping 18 and flow to the reaction furnace 1. The formation of ZnS in a vapor phase occurring heretofore in the deficiency of the thermal stability of the addition product is suppressed by using the above-mentioned addition product as the zinc source. The crystallinity of the thin ZnS film obtd. by a thermal vapor cracking method of org. metal is thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing zinc sulfide (Zns) thin films. For more details, please refer to the organic metal vapor phase decomposition method (MOCVD method)
This invention relates to a method for producing a zinc sulfide thin film using.

[Conventional technology]

The MOCVD method is a technology that is attracting attention in the field of optoelectronic materials and device manufacturing because it allows the production of high-quality compound dry conductor thin films and is highly suitable for mass production. Although attempts have been made to use this MOCVD method to create a ZnS thin film, which is a promising material for short-wavelength light emitting devices, formation of a thin film at a level that can be used for device production has not yet been achieved. This is due to the extremely high reactivity of the dialkylzinc contained in the zinc source.

That is, as soon as gaseous dialkylzinc is mixed with hydrogen sulfide (H2S), it reacts rapidly even at room temperature.
ZnS generated in the gas phase that generates Zns becomes particles and accumulates on the growth substrate like snow. Since the ZnS grains deposited on the substrate surface have a negative effect on the crystal growth process proceeding on the substrate surface, the crystal quality of the ZnS thin film obtained with the dialkyl zinc/HZ S system was not very high.

Recently, Zn in the gas phase has been improved by replacing at least one of dialkyl zinc or hydrogen sulfide with a less reactive one.
Attempts have been made to suppress S generation. This will be discussed below.

1. A cyclic sulfur compound whose reactivity with dialkylzinc is lower than that of H2S is used as a sulfur source.

(J, Crystal Growth 66 (198
4) 26-34)2) Dialkylzinc and general formula R
An adduct (having lower reactivity with H2S than dialkylzinc) obtained by equimolar mixing with a thioether represented by 8R' (R% R' is an alkyl group) is used as a zinc source. (■Patent Application Arrangement A 20476) By taking these measures, cydialkylzinc/HZ
The generation of ZnS in the gas phase, which was a problem with the S system, can be significantly reduced, and the crystal quality of the resulting single conjunctiva has been improved. It has the following problems. 1
．． Since cyclic sulfur compounds are difficult to decompose, it is necessary to raise the growth temperature to obtain a sufficient growth rate.

When the growth temperature is high, the inclusion of lattice defects and the incorporation of impurities are accelerated. 2. In , the adduct introduced into the heating zone containing the substrate dissociates and forms dialkylzinc and Hz.
Since ZnS reacts with S to produce ZnS, the growth temperature is the same as the dialkylzinc/Hz S system, but there is a problem with the thermal stability of the adduct used. For example, diethylzinc (
The adduct DEZ-DES obtained by equimolar mixing of DEZ) and diethyl sulfur (DES) is
Although ZnS will not be produced near room temperature even when mixed with The generation of ZnS fine particles can be confirmed with the naked eye. As mentioned above, the ZnS thin film obtained using the DEZ-DES adduct exhibits anomalous (aOO) diffraction
The rocking curve average width of the line peak was only about 0.25°.

Further, when the adduct DMZ-DES obtained from dimethylzinc (DMZ) and DES is distilled under reduced pressure at 30°C, the boiling point changes slightly over time. This suggests that a part of the adduct is dissociated at 30°C, and the DMZ produced by the dissociation is H
Considering that it reacts with 2S, it is not preferable. Therefore, the present invention solves the above-mentioned problems by using an adduct that is more difficult to dissociate than an adduct consisting of dialkyl zinc and dialkyl sulfur, and producing a ZnS film with even higher crystal quality.

[Means for solving problems]

The method for producing a zinc sulfide thin film according to the present invention is characterized in that an adduct obtained by equimolar mixing of dialkylzinc and dimethylselenium is used as the zinc source, and H2S is used as the sulfur source.

Since dimethylselenium is a chemically quite stable compound, the incorporation of Se into the ZnS film due to the decomposition of dimethylselenium is not a problem. [Example] Figure 1 shows the MOCVD apparatus used in the present invention. A schematic diagram is shown. A graphite segmenter (2) coated with SiC is set inside the transparent quartz reaction tube (2), and a substrate (2) is set on top of the susceptor (2). The tip of a thermocouple (■) is embedded inside the susceptor (■) to monitor the substrate temperature. A heating furnace 0 consisting of resistance heating, high frequency, infrared, etc. is installed around the reaction tube ■, and the reaction tube ■ which heats the substrate is connected to a waste gas treatment system 0 and an exhaust system ■ through valves ■■ and ■, respectively. connected to. (2) In 0, carrier gas purified by the purification device flows under flow rate control by a mask low controller. Carrier gas is Hz, He
Either is fine.

For bo/besa, H diluted to about 2q6 with carrier gas.
2 S is filled and mask low controller @
The supply amount can be directly controlled by Bubbler O contains an adduct formed by equimolar mixture of dialkylzinc and dimethyl selenium, and Bubbler 0 contains dimethyl selenium (DM
Se) is enclosed. The adduct, DMSe, is supplied by vaporizing it by bubbling with a carrier gas.

Therefore, the supply amount can be controlled by the bubbling gas flow rate and bubbling temperature. Each raw material gas is diluted by the carrier gas flowing through pipe 0 and reaches the reactor.

When performing growth at normal pressure, open the valve ■■ and guide the reaction gas to the waste gas treatment system ■. When performing growth under reduced pressure, close the valve ■ and control the reaction by adjusting the displacement of the valve ■ and rotary pump ■, and the flow rate of the reaction gas. Growth is performed while adjusting the degree of vacuum in the furnace. The reaction gas that exits the rotary pump is passed through the waste gas treatment system (■
be led to.

[Example 1] Below, a process for growing a ZnS single crystal film on a GaAS, GaP, or Si substrate will be described.

As the adduct, DMZ DMSe obtained by equimolar mixing of dimethylzinc and dimethylselenium was used.

Since DMZ-DMSe is a liquid exhibiting a boiling point of 67.2°C at normal pressure, it is considered to be a more thermally stable adduct than DMZ-DES.

1. For thermal etching of the substrate: surface cleaning GaAstG which has been surface treated by chemical etching in advance
Place the aP+Si substrate inside the tube (2) and evacuate the system. Next, carrier gas is introduced and vacuum is drawn again.

Does this operation result in residual oxygen or residual moisture in the system? Remove.

GaA,
The oxide film remaining on the substrate surface can be removed by thermal etching (heating to 500 to 600°C for a 5tGaP substrate and 900 to 1000°C for a Si substrate).

After thermal etching for 5 to 10 minutes, the substrate temperature is set to the growth temperature.

Hz S is supplied from a λ crystal growth cylinder [Co., Ltd.], and the adduct is supplied to the reactor (2) when bubbler 0 starts bubbling. As a result, ZnS grows on the substrate. Typical growth conditions are shown below.

Carrier gas (He): Total flow rate 4.51/mi
Bubbling gas flow rate of adduct at n, -zO℃: 2
5m1% H2 or) (e base 2%, HzS supply amount:
11] Oml/min.

Growth temperature: When the conditions were 500 to 550° C. or higher, the growth rate was approximately constant at 0.8 to 1.0 μm/he regardless of the growth temperature or the type of growth substrate.

Se was not detected in the analysis of the grown film using an IMA (ion microanalyzer). The half width of the (400) diffraction X-ray rocking curve of ZnS with a thickness of 2 μm grown at 450° C. was 0.15 to (120′).

By using DMZ-DMSe, the crystallinity was improved compared to when DEZ-DES was used as the zinc source.

During the ZnS growth described above, ZnS in the gas phase inside the heating zone, such as when the DEZ-DBS addition agent was present.
No generation of fine particles was observed.

The DMZ-DMSe adduct is shown to be more stable than the DEZ-DES adduct.

[Example 2] When the growth is performed according to the above process, the growth temperature is 5
When the temperature reached around 00°C, the morphology of the surface of the grown film became slightly worse. Further, during the growth, Zn5e particles were observed to be generated in the gas phase inside the heating zone, albeit slightly. This is because as the growth temperature increases, the output of the heating furnace (2) increases in FIG. 1, so the reaction gas introduced into the reactor (2) is heated before it reaches the vicinity of the substrate. For this reason, as mentioned above, ZnS is generated in the gas phase, and the generated fine particles are incorporated into the grown film, resulting in deterioration of the surface morphology.

When the growth temperature is high, the above-mentioned problem can be solved by supplying dimethylselenium in addition to the adduct. In other words, the dissociation equilibrium of the adduct is expressed by the following equation.

For example, in the case of DMZ-DMSe, DMZ - DMSe: DMZ +
This is because in DMSe, by supplying DMSe in excess, the thermal equilibrium can be shifted in the direction of adduct formation. Thereby, dissociation of the adduct can be suppressed. Growth temperature 5 under the growth conditions of [Example 1]
When the temperature is 0°C, DMSe sealed in the bubbler ■ is heated to 0°C.
It was supplied by bubbling at 25 m/min. DMS
The amount of e supplied corresponds to approximately four times the amount of adduct. D
By introducing MSe, the generation of ZnS in the gas phase could be suppressed, and the deterioration of surface morphology could also be improved. When the growth temperature was higher, a similar effect was obtained by increasing the amount of DMSe supplied. According to IMA, Se in the ZnS film
It was found that there was no uptake.

[Example 3] Similar to the process shown in [Example 1.2], an amorphous substrate such as glass, quartz, or a transparent electrode such as ITO, TazOs, SiO2, 5f3N4, Alzo
It is possible to form a ZnS film on an insulating film such as x, Sm 20 s, etc. A ZnS film was formed on an amorphous substrate that had been brush-washed with a weak alkaline cleaning solution and then sequentially ultrasonically cleaned in pure water, alcohol, and Guiflon according to the process and growth conditions shown in Example 1. I grew up.

The thickness of the ZnS film obtained by the growth of 90 yen is approximately 70 yen.
00^: The growth rate was 15 μ'm/hr.

The reason why the growth rate is lower than that of the GaAS%GaP, s i substrate is thought to be because an infrared furnace was used as a heating source. In other words, it is thought that because the infrared absorption coefficient of transparent quartz is small, the actual temperature of the substrate surface is lower than that of GaAS and GaP substrates even if the temperature set by the thermocouple monitor is the same. The electron beam diffraction pattern of the obtained ZrtS film exhibits concentric circles with shading, indicating that it is a polycrystalline film.

Although the above examples were shown for DMZ-DMSe adducts, when the growth conditions are the same, results similar to those of DMZ-DMSe can be obtained for DEZ-DMSe adducts, and the crystallinity of the formed ZnS thin film is also at the same level. Met.

Although the embodiments have described growth of heteroepitaxylol and growth on an amorphous substrate, the present invention is not limited to such scope, and may be applied to, for example, homoepitaxial growth of ZnS on ZNS or other ZnS thin films. It can be applied to the growth of

〔Effect of the invention〕

As described above, according to the present invention, by using an adduct obtained by equimolar mixing of dialkylzinc and dimethylselenium as a zinc source, the adduct has conventionally been caused by poor thermal stability. The generation of ZnS in the gas phase could be suppressed. This improved the crystallinity of the ZnS thin film obtained.

We believe that the present invention will greatly contribute to the production of high-quality thin films of ZnS, which are promising as materials for short-wavelength light-emitting devices.

[Brief explanation of the drawing]

FIG. 1 shows a schematic diagram of the MOCVD system used in the present invention. 1. Transparent quartz reaction tube 2. Graphite susceptor with 8IC coating 5. Substrate 4. Thermocouple 50. Valve to adjust the degree of vacuum inside the reaction tube 6. Z pulp a. Rotary pump 9. Waste gas treatment system 1.alpha. High vacuum exhaust system 11. Heating furnace using resistance heating, infrared rays, high frequency, etc.
12. High precision needle valve Bubbler with 1 pentaadduct 14. Bubbler containing dimethyl selenium 15
．． Piping system 16. Honbe containing hydrogen sulfide 1Z mass flow controller 1a piping system 19.2L1. More than a valve

Claims (3)

[Claims] (1) When producing a zinc sulfide thin film by the metal organic vapor phase pyrolysis method (MOCVD method), the adduct obtained by equimolar mixing of dialkylzinc and dimethyl selenium (DMSe) is used as the zinc source, and hydrogen sulfide is A method for producing a zinc sulfide thin film characterized by its use as a sulfur source. (2) A method for producing a zinc sulfide thin film according to claim 1, characterized in that the adduct and hydrogen sulfide are uniformly mixed in a gas phase and then supplied to a heating region including a substrate. Method for producing zinc thin film. (3) In the method for producing a zinc sulfide thin film according to claim 1, the adduct and dimethyl selenium are thoroughly mixed in a gas phase, and then both adducts are uniformly mixed with hydrogen sulfide. , a method for producing a zinc sulfide thin film, characterized in that the zinc sulfide thin film is supplied to a heated region including a substrate.