JPS61166969A - 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 in a vapor phase as a zinc 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 dimethyl zinc is sealed in a bubbler 13 and the dimethyl selenium 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 tube 1. The dimethyl zinc and the dimethyl selenium join first and the addition product is formed in the vapor phase. The addition product is thereafter uniformly mixed with H2S. The formation of ZnS in the vapor phase is suppressed by using the above-mentioned addition product. 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 manufacturing zinc sulfide (ZnS) thin films. More specifically, the present invention relates to a method for producing a zinc sulfide thin film using a metal organic vapor phase pyrolysis method (MOCVD method).

[Conventional technology]

The MOCVD method is a technology that is attracting much 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 IVI OCV D method to produce a ZnS thin film, which is promising as a short wavelength light emitting element material, 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 used in the zinc source. That is, as soon as gaseous dialkylzinc is mixed with hydrogen sulfide (H2S), it reacts rapidly even at room temperature to produce ZnS. ZnS generated in gas phase
The particles form clumps and accumulate 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/H2S 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 Gr, owth 66 (19
84)26-34)2, Dialkylzinc and general 2R3
An adduct obtained by equimolar mixing with a thioether represented by R' (R% R' is an alkyl group) (reactivity with H2S is lower than that of dialkyl zinc) is used as a zinc source. (■Patent application: Sorotaka) By taking these measures, the generation of ZnS in the gas phase, which was a problem with the dialkylzinc/HZS system, can be significantly reduced, and the crystal quality of the resulting single conjunctiva has been improved. .

[Problem that the invention seeks to solve]

However, the above-mentioned conventional technology 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.

If the growth temperature is high, inclusions of lattice defects and impurities are penetrated.・In B, dialkylzinc and H2S are generated by the dissociation of the adduct introduced into the heating zone containing the substrate.
The growth temperature is the same as that of the dialkylzinc/HzS system, but there is a problem with the thermal stability of the adduct used. For example, diethylzinc (D
The adduct DEZ-DES obtained by equimolar mixing of EZ) and diethyl sulfur (DES) does not produce ZnS at around room temperature even when mixed with H2S in a gaseous state.
Since the dissociation of the adduct and the production of ZnS proceed simultaneously upon entering the heating zone, the production of ZnS fine particles can be confirmed with the naked eye in the heating zone even when the growth temperature is relatively low at 300°C. As mentioned above, the ZnS thin film obtained using the DEZ-DBS adduct is affected by the ZnS fine particles generated in the gas phase inside the first heating zone, so the half-value width of the rocking curve of the K(400) diffraction X-ray peak is Only about α25' was obtained.

Further, when the adduct DMZ-DES obtained by mixing dimethylzinc (DMZ) and DES is distilled under reduced pressure at 50°C, the boiling point changes slightly over time. This suggests that part of the adduct is dissociated at 50°C, and the DM generated by dissociation
Considering that Z reacts with HtS, this is not preferable.

Therefore, the present invention solves the above-mentioned problems.
Using an adduct that is more difficult to dissociate than an adduct consisting of dialkyl zinc and dialkyl sulfur, Zn has a higher crystal quality.
There is a company that manufactures S film.

[Failure to solve the problem]

In the method for producing a zinc sulfide thin film according to the present invention, an MO using dialkyl zinc as a Zn source and a HzSf:S source is used.
When manufacturing a ZnS thin film by the CVD method, dialkyl zinc and dimethyl selenium are mixed in a gas phase to form an adduct, and the Zn source is supplied in the form of the adduct to a heating region including the substrate. At this time, H2 of dialkyl zinc
Since the reactivity towards S can be made extremely poor by forming an adduct with dimethylselenium, dialkylzinc is mixed with H2S after forming an adduct with dimethylselenium. Here, since dimethylselenium is a chemically stable compound, Z due to the decomposition of dimethylselenium
The contamination of Se into n5Il may not be a problem.

〔Example〕

FIG. 1 shows a schematic diagram of an MOCVD apparatus used in the present invention. A graphite susceptor 〇 coated with SiC coating 5 is set inside the transparent quartz reaction tube 〇, and a substrate 〇 is set on top of the susceptor 〇. The tip of a thermocouple (■) is embedded inside the susceptor (○) to monitor the substrate temperature. Around the reaction tube, there is a heating furnace that uses resistance heating, high frequency, infrared, etc.
is installed to heat the substrate. The reaction tube (2) is connected to a waste gas treatment system (stock) and an exhaust system (2) via a valve, (2) or (2), respectively. [Co., Ltd.], (2), a carrier gas purified by a purification device is flowing through the tank with its flow rate controlled by a mask low controller. The carrier gas may be either Hz or H6. Po/Be is filled with H 2 S diluted by about 2% with a carrier gas, and the supply amount can be directly controlled by a mask low controller OK. Bubbler O contains dimethyl zinc (DMZ)
Dimethyl selenium (DMSe) is used in the bubbler [phase].
is included. DMZ and DMSe are supplied by being vaporized 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 the piping and reaches the reactor (2). At this time, DMZ and DMSe first merge to form an adduct.

Thereafter, it is combined with H2S, and the adduct and Hz S are uniformly mixed. At this time, ZnS is present inside the pipe downstream of the confluence point of the adduct and H2S and near the inlet to the reaction tube.
generation was not confirmed. However, when the supply of DMSe was interrupted, fine particles of ZnS were observed to flow in the form of mist from the gas inlet to the reaction tube. By supplying DMSe, an adduct of DMZ and DMSe is formed, and DMZ and H
It can be seen that the 2S reaction is suppressed.

When growing at normal pressure, open the valve ■■ and guide the reaction gas to the waste gas treatment system ■. When carrying out the process under reduced pressure, the valve (2) is closed, and the growth is performed while adjusting the degree of vacuum in the reactor by adjusting the displacement of the valve (2), the rotary pump (2), and the flow rate of the reaction gas. The reaction gas leaving the rotary pump is led to the waste gas treatment system (■).

[Example 1] Below is a description of the ZnS single crystal film.
The process of growing onto a PsSl substrate will be described.

1. Surface cleaning of the substrate by thermal etching The surface was previously treated by chemical etching. GaAstG
The aPnSi substrate was set in the reaction tube (2), and the system was evacuated. Next, carrier gas is introduced and vacuum is drawn again.

This operation removes residual oxygen and moisture in the system.

GaAs is
In the case of a GaP substrate, it is heated to 500 to 600°C, and in the case of a Si substrate, it is heated to 900 to 1000°C. This thermal etching can remove the oxide film remaining on the substrate surface.

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

2 H2S from Crystal Growth Pombe [Co., Ltd.] and DM from Bubbler ■
The supply of Se, followed by DMZ from bubbler 0 to reaction tube 2 is started in this order. As a result, ZnS grows on the substrate. Typical growth conditions are shown below.

Carrier gas (He): Total flow rate 4.5 Jl/min
, DMse bubbling gas flow rate at -20°C: 65 m/min s (At this time, DMSe and D
MZ supply ratio is approximately 10:1) H2 or He pace 2% HzS supply rate: 100p/min, growth temperature: 300-550°C or higher, depending on the growth temperature and type of growth substrate. sSe was almost constant at 0.8 to 1.0 μm/he, and no sSe was detected in the analysis of the grown film using an IM,A (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 α15 to α20°. D
By using MZ-DMSeO, an improvement in crystallinity was observed compared to when DEz-DBS was used as the zinc source.

During the above-mentioned 0ZnS growth, ZnS in the gas phase inside the heating zone, such as when using the DEZ-DES adduct,
No generation of fine particles was observed.

DMZ-D formed by mixing DMZ and DMSe
MSe adduct 2>f, indicating that it is 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, ZnS fine particles were observed to be generated in the gas phase inside the heating zone, although only 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 dimethyl selenium in even greater excess. 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 large excess, the thermal equilibrium can be shifted in the direction of adduct formation. Thereby, dissociation of the adduct can be suppressed. When the growth temperature was 500°C under the growth conditions of [Example 1], 15% of DMSe sealed in the bubbler
℃, 65m/! It was supplied by bubbling at /min. The amount of DMSe supplied corresponds to about 20 times the amount of adduct. By introducing a large excess of DMSe, ZnS in the gas phase
It was possible to suppress the formation of and improve the deterioration of surface morphology. A similar effect was obtained by further increasing the amount of DMSe supplied when the growth temperature was higher. According to IMA, it was found that there was no incorporation of Se into the ZnS film.

[Example 5] Similar to the process shown in [Example 1.2], an amorphous substrate such as glass, quartz, or a transparent electrode such as ITO, Ta+zOs, 5H)2, Si3N4%Alz
It is possible to form a ZnS film on an insulating film such as Os, , a SmxOs. After brush washing with a weak alkaline cleaning solution, ultrasonic cleaning in pure water, alcohol, and die 7 was performed sequentially on an amorphous substrate [Example 1]
A ZnS film was grown according to the process and growth conditions shown in ]. The thickness of the ZnS film obtained by growing 90 lines was about 7000^, and the growth rate was CL 5 μm/hr.

The reason why the growth rate is lower than that of QaAs%GaP substrate is because
This is thought to be due to the use of an infrared furnace as a heating source. In other words, since the infrared absorption coefficient of transparent quartz is small, even if the temperature set by the thermocouple monitor is the same, the actual temperature of the substrate surface will be GaAl1. This is probably because it is lower than the GaP substrate. The electron beam diffraction pattern of the obtained ZnS film exhibits concentric circles with shading, indicating that it is a polycrystalline film.

The above examples have shown the formation of adducts by mixing DMZ and DMSe, but even in the formation of adducts by mixing DEZ and DMSe, if the growth conditions are the same, DMZ-
Results similar to those of the DMSe system were obtained, and the crystallinity of the formed ZnS thin film was also at the same level.

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

〔Effect of the invention〕

As described above, according to the present invention, an adduct formed by mixing dialkylzinc and dimethylselenium in a gas phase is used as a zinc source. The formation of ZnS in the gas phase, which was caused by this, 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 drawings]

FIG. 1 shows a schematic diagram of the MOCVD system used in the present invention. 1. Transparent quartz reaction tube 2.8 Graphite susceptor with IC coating 5. Substrate 4. Thermocouple 50. Pulp to adjust the degree of vacuum inside the reaction tube 6. 1 Pulp & rotary pump 9. Waste gas treatment system 1.CL high vacuum evacuation system 11. Heating furnace using resistance heating, infrared rays, high frequency, etc. 12. i% accuracy needle valve Bubbler containing 15 dialkyl zinc 14. Bubbler containing dimethyl selenium 15. Piping system 16. Cylinder containing hydrogen sulfide 1
Z mass flow controller 1a piping system 19.2
α pulp or higher

Claims (3)

[Claims] (1) When producing a zinc sulfide thin film by the gas phase pyrolysis method (MOCVD method) using dialkylzinc as the zinc source and hydrogen sulfide as the sulfur source, dialkylzinc and dimethylselenium are mixed in the gas phase to form an adduct of both. 1. A method for producing a zinc sulfide thin film, the method comprising forming a zinc sulfide thin film and using the adduct as a zinc source. (2) The method for producing a zinc sulfide thin film according to claim 1, characterized in that dimethylselenium is supplied in an amount equal to or in excess of the amount of dialkylzinc during adduct formation. Method for manufacturing zinc sulfide thin film. (3) In claim 1, dialkylzinc and dimethyl selenium are first mixed to form an adduct, then the adduct and hydrogen sulfide are mixed, and then introduced into the heating region containing the substrate. A method for producing a zinc sulfide thin film characterized by: