JPH06101431B2 - Semiconductor thin film manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention includes zinc, which is a component of a short-wavelength visible light emitting diode, a semiconductor laser, a thin film EL element, and the like.
The present invention relates to a method for manufacturing a II-VI group compound semiconductor and a mixed crystal thin film thereof.

<Outline of the Invention> The present invention is a metal-organic vapor phase thermal decomposition using an adduct of a dialkylzinc and a dialkylsulfur represented by the general formula R ₂ Zn-SR ₂ (R represents CnH ₂ n ₊₁ ) as a zinc source. The purpose of the present invention is to obtain a high quality thin film with good reproducibility by forming a II-VI group compound semiconductor thin film by the method.

<Prior Art> Conventionally, in the production of a II-VI group compound semiconductor containing zinc as a constituent element and its mixed crystal thin film by a MOCVD method, dimethylzinc: (CH ₃ ) ₂ Zn, diethylzinc as a source of zinc was used as a raw material. It is customary to use a dialkylzinc such as (C ₂ H ₅ ) ₂ Zn and react with a group VI hydride such as hydrogen sulfide: H ₂ S and hydrogen selenide: H ₂ Se. The chemical reaction when these raw materials are used is represented by the following formula.

R ₂ Zn + H ₂ S → ZnS + RR ……… R ₂ Zn + H ₂ S → ZnSe + RR ……… However, since R ₂ Zn is active, these reactions are mixed with Group VI hydrides and at room temperature near room temperature. The reaction progresses in the phase, and a fine-particle reaction product is formed before the raw material reaches the substrate surface. Since the fine particles adhere to the surface of the substrate and adversely affect the thin film growth process that proceeds on the surface of the substrate, the quality of the obtained crystal is not very good, and it cannot be used for manufacturing a semiconductor device.

Conventionally, the following measures have been taken as a method for solving these problems.

1) Mix the source gases in the immediate vicinity of the substrate. (For example, refer to J. Crystal Gvowth 59 (1982) P.1) 2) Reduce the pressure to increase the linear velocity of gas. (For example
Japan JAP 22 (1983) L583) However, good quality crystals have not been obtained even with the above-mentioned means. For example, Extended Abstracts of the
15th Conference on Solid State Devices and
As described in Materials, Tokyo, 1983, PP.349-352, ZnS is applied as an application of the above-mentioned countermeasures to semiconductor device fabrication.
A trial production of an element using the single crystal thin film as a light emitting layer is under study. In the above cited example, a ZnS single crystal film with Al added is formed on an n-type Gap substrate, and the ZnS: Al ′ thin film has a high specific resistance of 10 KΩ · cm. Therefore, current injection cannot be performed, and blue light emission has not been obtained yet. The high resistance of the ZnS: Al thin film is considered to be due to the low crystal quality of the obtained ZnS: Al thin film because dimethylzinc is used as the Zn source in MOCVD.

As a method for improving the above-mentioned drawbacks of the MOCVD method using R ₂ Zn as a zinc source to obtain a high quality single crystal thin film, it is described in the 45th JSAP Proceedings of the Applied Physics Society PP.633 lecture code 12P-S-4. As described above, a method has been proposed in which an adduct obtained by mixing equimolar amounts of R ₂ Zn and R ₂ S is used as a Zn source.
This aims to reduce the reactivity of R ₂ Zn with respect to Group VI hydrides by forming an adduct with R ₂ Zn and R ₂ S. Since the bond between R ₂ Zn and R ₂ S is not so strong, the adduct is easily dissociated in the heating zone near the substrate, and the resulting R ₂ Zn reacts with the Group VI hydride to grow a thin film on the substrate. Happens. Since R ₂ S does not easily decompose thermally, it does not participate in thin film growth and is merely used as a reaction inhibitor for R ₂ Zn.

In the MOCVD method using an adduct as a Zn source, a low resistance ZnS: Al single crystal thin film exhibiting a specific resistance of several Ω · cm or less in as-grown has been obtained by doping Al.
Furthermore, an insulating film and an electrode are laminated on this low resistance ZnS: Al to form a MIS.
By forming the mold structure, blue light emission having an emission spectrum peak of 470 nm was confirmed when forward biased. Low resistance such as an adduct in the MOCVD method in as-grown and R ₂ Zn who has failed obtained by the MOCVD method to Zn source by a Zn source ZnS: Preparation and light-emitting layer its Al single crystal film The realization of the production of a semiconductor device is that the use of the adduct can suppress the reaction between R ₂ Zn and the Group VI hydrogen compound in the gas phase at room temperature, and the crystal quality of the obtained single crystal thin film can be suppressed. It is considered that this is due to the remarkable improvement.

<Problems and Objectives to be Solved by the Invention> However, in the above-mentioned prior art, since only equimolar amounts of R ₂ Zn and R ₂ S are mixed, the adduct formation reaction must be completed. However, the following problems occurred.

1. R ₂ Zn, which remains mixed as an unreacted product, reacts when mixed with Group VI hydride to produce fine particles of the reaction product.
It reduces the crystallinity of the grown film.

2. The controllability of the doping amount is poor because the mixed R ₂ S as an end reaction forms a stable adduct with the organometallic compound introduced as a dopant.

3. Since the degree of formation of the adduct varies from lot to lot, the growth rate and crystal quality of the thin film will differ even if growth is performed under the same conditions if the growth is performed using the adduct having different lots as the source.

Therefore, the present invention solves such problems,
It is an object of the invention to provide a method for producing a semiconductor thin film, which has less variation in characteristics and is excellent in reproducibility.

<Means for Solving Problems> The method for producing a semiconductor thin film according to the present invention is carried out according to the general formula R ₂ Zn—SR ₂
(R represents CnH ₂ n ₊₁ ) A II-VI group compound semiconductor thin film is formed by a metalorganic vapor phase thermal decomposition method using an adduct of dialkylzinc and dialkylsulfur represented by the formula (Z) as a zinc source. And

Further, as the adduct, dialkylzinc and dialkylsulfur are excessively mixed in an amount of a low boiling point component of both,
The reaction product is characterized by using an adduct of dialkylzinc and dialkylsulfur which is obtained by distilling off the excessively mixed components after the reaction and aging.

Further, the reaction and aging are characterized by being a reaction and aging by heat treatment including a step of holding at 0 ° C to 40 ° C, a step of gradually raising the temperature, and then a step of holding at 30 ° C to 80 ° C. To do.

<Example> A method for producing an organozinc compound comprising an adduct used in the present invention will be described.

The reaction of adduct formation between R ₂ Zn and R ₂ S depends on R ₂ as an electron acceptor.
₂ Zn and R ₂ S as an electron donor form an R ₂ Zn-SR ₂ type adduct. The following steps are required to manufacture the adduct.

R ₂ Zn and R ₂ S are mixed with each other, and the low-boiling components of both are almost in excess.
Preferably, the ratio of low boiling point component to high boiling point component is 1.1 to 1.2.
Mix as an equivalence ratio, and both are below the boiling point of the low boiling point component,
The reaction is sufficiently performed at about 0 ° C to 40 ° C for 10 minutes to 3 hours, preferably at 10 to 35 ° C for 1 to 2 hours.

After that, to complete the reaction, gradually raise the temperature to 30-80 ° C.
The temperature is raised for 10 minutes to 2 hours, preferably 10 to 15 ° C./hour, and aged at 30 to 70 ° C. for 30 minutes to 1 hour.

Finally, excess components are removed by distillation.

The formation of the adduct can be confirmed by the following facts.

(1) Heat is generated by mixing the two.

(2) The vapor pressure-temperature curve of the produced adduct is different from that of R ₂ Zn and R ₂ S as starting materials.

(3) the remaining amount obtained by subtracting the distillate excess component from the charged amounts of the raw materials is R ₂ Zn and R ₂ S 1: match the weight was assumed to form the adduct with 1.

As a specific production example, an adduct (CH ₃ ) ₂ Zn-S (C ₂ H ₅ ) ₂ composed of (CH ₃ ) ₂ Zn and (C ₂ H ₅ ) ₂ S will be described.

S (C ₂ H ₅ ) ₂ 109.5 g (1.2166 mol) in a 300 ml round bottom flask
Was charged, and 122.0 g (1.279 mol) of (CH ₃ ) ₂ Zn was added dropwise with a dropping funnel and reacted with stirring. The reaction was exothermic and the amount of heat generated was large.

The reaction temperature was controlled at 10 to 15 ° C and the reaction was carried out for 1 hour. Thereafter, the temperature was gradually raised at a rate of 10 ° C./hour and aged at 38 ° C. for 30 minutes. After that, unnecessary excess was distilled off by distillation. The product weighed 227 g.

FIG. 1 shows the vapor pressure-temperature characteristics of the obtained adduct. The horizontal axis is temperature and the vertical axis is vapor pressure.

The solid lines are the adducts, and the solid lines are the raw materials S, respectively.
₂ shows vapor pressure characteristics of (C ₂ H ₅ ) ₂ and (CH ₃ ) ₂ Zn.

R ₂ Zn and R ₂ S as shown in Table I were prepared in the same manner as in the above Production Example.
It is possible to manufacture an adduct for the combination of.

Table 2 exemplifies the vapor pressures of organozinc compounds consisting of an adduct of R ₂ Zn and R ₂ S with respect to typical temperatures.

It is apparent that the adducts formed by the above-mentioned production method are not limited to those shown in Table 1 but can be produced by using other combinations of R ₂ Zn and R ₂ S.

<Example 1> The adduct obtained in the above example is used as a zinc source.
ZnS as an example of manufacturing a semiconductor thin film by the MOCVD method.
Now, the contents of the present invention will be described in detail.

FIG. 2 is a schematic diagram of the MOCVD apparatus used in the present invention.

Inside a horizontal quartz glass reaction tube, a SiC coated grafitite susceptor is placed, and on top of that a substrate is placed.

The substrate is heated from the side of the reaction furnace by using a high-frequency heating furnace, an infrared furnace, a resistance heating furnace, or the like.

The substrate temperature is monitored by a thermocouple embedded in the Graphite susceptor. The reaction tube consists of an exhaust system, a waste gas treatment system, and a valve. Connected through. The Zn source adduct is enclosed in a bubbler. In addition, triethylaluminum (TE
Al) is enclosed in a bubbler. Carrier gas and hydrogen sulfide are cylinders. Is filled in.
The carrier gas and hydrogen sulfide purified by the purifier are flow-controlled by a mass flow controller. Bubbler. The additional body and TEAl sealed in are kept at a predetermined temperature in a constant temperature bath. By introducing an appropriate amount of carrier gas into the bubbler and performing bubbling, a desired amount of the adduct and TEAl can be supplied. Bubbler. And the adduct supplied from the cylinder, TEA
The hydrogen sulfide and the hydrogen sulfide are diluted with the carrier gas, respectively, and then combined and introduced into the reaction tube through the three-way valve. The three-way valve switches between introduction of raw material gas into the reaction tube and disposal to the waste gas treatment system. Although a horizontal reactor is shown in FIG. 2, the basic structure is the same in a vertical reactor. However, it is necessary to ensure the uniformity of the film obtained by providing the rotation mechanism of the substrate.

As the substrate, low resistance n-type gallium arsenide (Ga) is sliced on the (100) plane and a plane having a deviation of 5 ° or 2 ° from the (100) plane to the (110) plane and polished.
As), gallium phosphide (GaP) and silicon (Si) were used after ultrasonic cleaning with trichloroethylene, acetone and methanol and then etching. The etching conditions are as follows.

GaAs substrate, H ₂ SO ₄ : H ₂ O ₂ : H ₂ O = 3: 1: 1 (volume ratio) 2min at room temperature GaP substrate Hcl: HNO ₃ = 3: 1 (volume ratio) 30sec at room temperature Si substrate HF: H ₂ O = 1: 1 (volume ratio) At room temperature, the etching was stopped with pure water for 2 min, washed with pure water and methanol, and then stored in Daiflon. The substrate is taken out of the diflon immediately before the reaction tube is set, and the diflon is dried and removed by dry nitrogen blowing. After the substrate is set, the inside of the reaction furnace is evacuated to about 10 ^-5 Torr to remove the gas remaining in the system. After introducing the carrier gas and returning the system to normal pressure, the temperature rise is started while flowing the carrier gas at about 1 to 2 / min. An infrared heating furnace was used for heating. As carrier gas, He with a purity of 99.9999% or H ₂ passed through a purifier was used. After the substrate temperature reaches a predetermined temperature and becomes stable, the supply of the raw material gas is started and the low resistance ZnS film is grown. However, in the case of a Si substrate, it is necessary to clean the substrate surface by heat treatment in a hydrogen stream at 900 ° C for about 10 minutes. The adduct used is an adduct (CH ₃ ) ₂ Zn- formed by dimethylzinc and diethylsulfur.
S (C ₂ H ₅ ) ₂ . Approximately 3μ under the growth conditions shown below
A ZnS: Al single crystal film of m is formed.

Substrate temperature 300-350 ℃, distance from raw material inlet to substrate 20
cm, bubbling amount of adduct 30 ml / min at -15 ℃, TEAl
Bubbling amount-20 ml / min at -10 ℃, diluted with He 2
% H ₂ S supply rate 200 ml / min, total gas flow rate including carrier gas 4.5 / min, growth time 190 min.

The ZnS: Al single crystal thin film produced by the above process showed a reproducibility of about 0.1 to 10 Ω · cm at room temperature with good reproducibility.

The obtained low resistance ZnS film was applied to He-Cd laser (oscillation wavelength 3250
When it was excited by Å), it showed strong blue emission at room temperature (emission wavelength 460-470 nm).

An example of the photoluminescence spectrum of the low resistance ZnS film at room temperature is shown in FIG. 460-470 nm even when the excitation wavelength is changed from 250 nm to 400 nm using a xenon lamp
Nothing was observed except for the light emission in the vicinity. The above facts show that the ZnS: Al produced in the present invention has an extremely high quality.

The following effects were obtained by using the zinc source as the adduct produced through the steps as shown in the above-mentioned examples.

1. Specific resistance of ZnS: Al obtained under the same production conditions when thin film production is continued using the adduct enclosed in the same bubbler,
The peak wavelength and intensity of photoluminescence, the crystal quality, and the growth rate of the thin film showed the same characteristics without change depending on the number of productions, and the reproducibility was extremely good. At this time, variations in specific resistance, photoluminescence intensity, and growth rate were less than a fraction of those of the prior art.

2. When ZnS: Al was manufactured using adducts with different lots as sources, there was no variation in properties.

As can be easily inferred from the above description, similarly to the addition of Al to ZnS, the addition of Ga and In also corresponds to the corresponding organometallic compounds such as triethylgallium (boiling point = 143 ° C.) and triethylindium (boiling point = 184 ° C.). C.) is possible. The ZnS: Ga, ZnS: In obtained when the supply amount calculated from the vapor pressure at the bubbling temperature and the flow rate of the bubbling gas was equal to that of triethylaluminum.
Showed similar electrical characteristics to ZnS: Al.

Hereinafter, as a device application example of the low resistance ZnS manufactured by the present invention, manufacturing of a blue light emitting element will be described.

1. An Al-doped low-resistance ZnS layer is grown to a thickness of about 3 μm on the (100) -plane sliced n-type GaAs substrate according to the MOCVD process described above.

2. After depositing Au-Ge (Ge = 12wt-%) for about 2000Å on the back surface of the substrate, heat treatment is performed at 350 ° C for 5-10 min in an inert atmosphere to form an ohmic contact with the GaAs substrate.

3. Lay about 100Å SiO ₂ on ZnS with a sputter.

4. A semi-transparent Au electrode having a thickness of about 300 to 500 Å is laminated on SiO ₂ .

Surface A of the device having the MIS structure manufactured as described above
When a forward bias voltage was applied between the u electrode and the ohmic contact provided on the GaAs substrate, light emission was observed from around 1 to 2V. The emission spectrum had a peak at around 460-470 nm at room temperature, and the emission intensity increased in proportion to the current flowing through the device. The quantum efficiency was about 10 ^-3 .

Similar to the effect on the characteristics of the thin film, by using the zinc oxide source as the adduct described in <Example 1>, it is possible to greatly reduce the variations in characteristics such as the threshold voltage, the current and the quantum efficiency of the light emitting device. It is less than a fraction of the above.

By introducing an organic compound containing chlorine, hydrogen chloride or a halogen element in place of the organometallic compound of the m-group element during the ZnS growth in the above-mentioned embodiment, ZnS: X exhibiting the same electrical characteristics as ZnS: Al. A single crystal thin film of (X = Cl, Br, I) can be manufactured. A MIS type blue light emitting device using this as a light emitting layer could be manufactured. The characteristics of the obtained device were similar to those of the device using ZnS: Al as the light emitting layer.

In this example, an adduct obtained from (CH ₃ ) ₂ Zn and (C ₂ H ₅ ) ₂ S was used. However, the adducts shown in Table 2 and other adducts formed in the same manner as Zn were used. As the source, if the supply amount and manufacturing conditions are the same as in this example, (CH ₃ ) ₂ Zn-S (C
_A thin film having the same characteristics as the thin film obtained by using ₂ H ₅ ) ₂ was obtained. The characteristics of the device manufactured using the above-mentioned thin film were similar to those of the device composed of the thin film manufactured using DMZ-DES.

<Example 2> In <Example 1>, by introducing hydrogen selenide or dialkyl tellurium (hereinafter abbreviated as R ₂ Te) in place of hydrogen sulfide, a ZnSe, ZnTe single crystal thin film is formed of GaAs, Ge or the like. It can be formed on a crystal substrate.

Further, by simultaneously supplying a plurality of VI group element sources, ZnSxSe1-x, ZnSxTe1-x, ZnSexTe1-x (0 <
It is also possible to grow a mixed crystal single crystal thin film such as x <1).

The undoped insulating property on the light emitting layer obtained by doping these single crystal thin films with group III elements or halogen elements
By stacking ZnS and electrode layers to form an MIS structure, it is possible to manufacture an MIS type LED that emits light determined by the band gap of the light emitting layer.

In addition, n-type ZnSe or n-type ZnSxSe1 formed on GaAs
By stacking P-type ZnSe or P-type ZnSxSe1-x on -x, application to a Pn junction type light emitting diode is also possible.

Furthermore, by stacking the above mixed crystal thin films, GaAs, G
It is also applicable to a light emitting device having a double hetero structure or a superlattice structure made of the following material systems on a single crystal substrate such as e or InAs.

Zn (STe) / Zn (SSeTe) / GaAs, Ge. ZnS0.6Te0.4 / ZnSe / GaAs ZnSeTe / Zn (SSeTe) / GaAs, Ge, InAs As is apparent from the above description, the semiconductor thin film according to the present invention The manufacturing method of (1) exhibits the same effects as those shown in the above-described embodiments for manufacturing II-VI group compound semiconductors having Zn as a constituent element and mixed crystal thin films thereof. As can be easily analogized, the present invention can be applied to a polycrystalline thin film by selecting a growth substrate.

<Effects of the Invention> As described above, an organometallic gas containing an adduct of a dialkylzinc and a dialkylsulfur represented by the general formula R ₂ Zn-SR ₂ (R represents CnH ₂ n ₊₁ ) as a zinc source is used. II by the phase pyrolysis method
By forming a group VI compound semiconductor thin film, a high quality thin film can be manufactured with extremely excellent reproducibility.

We believe that the present invention makes a great contribution to the production of visible light emitting diodes, semiconductor lasers, thin film EL devices and the like.

[Brief description of drawings]

Figure 1 is _{(CH 3) 2 Zn-S} (C 2 H 5) 2 vapor pressure - temperature characteristic diagram. 1 ... Temperature, 2 ... Vapor pressure, 3 ... Additional body, 4 ... (C ₂
H ₅ ) ₂ S, 5 ... (CH ₃ ) ₂ Zn FIG. 2 is a schematic view of the MOCVD apparatus used in the present invention. 6 ... Quartz glass reaction tube, 7 ... SiC coated graphite susceptor, 8 ... Substrate, 9 ...
High frequency heating furnace or infrared furnace or resistance heating furnace, 10 …… thermocouple, 11 …… exhaust system, 12 …… waste gas treatment system, 13,14 …… valve, 15 …… bubbler with additional body, 16… … Bubblers containing organometallic compounds of Group III elements such as triethylaluminum, 17… Cylinders containing carrier gas,
18 …… Cylinder containing hydrogen sulfide, 19 …… Gas purifier,
20 ... Mass controller, 21 ... Constant temperature bath, 22 ... Three-way valve, 23 ... Valve FIG. 3 is a photoluminescence spectrum of low resistance ZnS: Al produced in the present invention.

Claims (3)

[Claims] 1. A metal-organic vapor phase pyrolysis method using a zinc source of an adduct of a dialkylzinc represented by the general formula R ₂ Zn-SR ₂ (R represents CnH ₂ n ₊₁ ) as a zinc source. A method for producing a semiconductor thin film, which comprises forming a II-VI group compound semiconductor thin film. 2. As the adduct, dialkylzinc and dialkylsulfur are mixed in excess with an amount of a low boiling point component of both, and after reaction and aging, the excess mixed component is distilled off. The method for producing a semiconductor thin film according to claim 1, wherein the resulting adduct of dialkylzinc and dialkylsulfur is used. 3. The reaction and aging are the reaction and aging by heat treatment including a step of holding at 0 ° C. to 40 ° C., a step of gradually raising the temperature, and then a step of holding at 30 ° C. to 80 ° C. The method for producing a semiconductor thin film according to claim 2, wherein: