JP3133136B2 - Manufacturing method of ternary compound semiconductor thin 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 producing an I-III-VI group compound semiconductor thin film as a photovoltaic element or an optical element such as a solar cell.

[0002]

2. Description of the Related Art Conventionally, the following methods have been known as methods for producing semiconductor thin films. That is, a vacuum evaporation method such as simultaneous evaporation of component elements and evaporation of an intermetallic compound (Japanese Patent Laid-Open No.
7-502196), a method of sequentially depositing copper, indium, and selenium and performing a heat treatment in a hydrogen-containing gas or an atmosphere containing selenium or sulfur in a hydrogen-containing gas (Japanese Patent Application Laid-Open No. 1-231313), and copper and indium. By electroplating, sequentially or simultaneously, electrodepositing on the substrate and heat-treating in the presence of selenium or sulfur-containing gas, or heat-treating in an inert atmosphere by depositing elemental selenium on copper or indium layer Method (Japanese Patent Laid-Open No. 61-2374)
76, and a method of forming by a spray pyrolysis method (Japanese Patent Application Laid-Open No. 2-73674) are known.

However, when performing simultaneous deposition of component elements in the above-mentioned prior art, it is general to heat the substrate to a temperature of 300 to 450 ° C. in order to achieve composition control and crystallinity improvement at one time. Had to use expensive equipment for this purpose,
Even if very complicated operations were performed, the reproducibility was poor. In this case, when each element is deposited without heating the substrate and then heat-treated for the purpose of improving the crystallinity, the compound thin film tends to peel off from the substrate in the heat treatment furnace.

[0004] In the solid-phase selenization (or solid-state sulfurization) method in which copper, indium, and selenium (or sulfur) are laminated and then heat-treated, the copper, indium is alloyed, selenized, and crystallized. Heat treatment was performed in two or three steps, but the reaction between copper and selenium or sulfur proceeds very quickly even at low temperatures, making it difficult to perform alloying and selenization separately. Met. Therefore, the intermediate product Cu _x Se or Cu _x
generation of _x S can not be avoided, even after crystallization not only can not be obtained only heterophasic mixed state in the presence of these intermediate layers, the crystallinity of the film by this method was very poor.

After laminating only copper and indium,
In the gas-phase selenization method in which heat treatment is performed in an atmosphere containing selenium and sulfur, it is possible to carry out the alloying of copper-indium and the selenization reaction separately, and improvement in crystallinity was also expected. Since the selenization was generally heated to 400 ° C. or higher, the reaction between the substrate and selenium and sulfur was unavoidable under such conditions, resulting in a structure in which different phases were mixed and at the same time, the crystallinity of the film. Is almost determined by the selenization temperature, and even if the crystallization temperature is set to a high temperature, there is practically no effect, and it is customary to carry out selenization and crystallization at the same temperature.

All of these methods have the following drawbacks because the selection range of manufacturing conditions is extremely limited. (1) In order to improve the characteristics, it is desirable that the film has good crystallinity and a dense film. For this purpose, a heat treatment at a high temperature is effective. A reaction product is formed between the two. As a result, not only the characteristic deterioration but also the reproducibility of the production of the compound semiconductor becomes extremely poor, and mass production is difficult. (2) Under conditions of good reproducibility, it is difficult to improve performance due to poor crystallinity. (3) In order to avoid these problems, the selection range of the manufacturing conditions is narrow and very limited. (4) The film formed by the selenization or sulfidation method was porous and had poor denseness.

[0007]

As described above, in the conventional method, the production conditions could be adjusted only in an extremely narrow range. However, in the present invention, there was no reaction between the substrate and selenium or sulfur, and at the same time, the film was not formed. It is an object of the present invention to provide a novel method for producing a high-quality group I-III-VI-based compound semiconductor thin film which improves the crystallinity.

[0008]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems. As a result of performing the heat treatment step in two stages, there is no reaction with the substrate, and the dense and extremely crystalline structure is obtained. It has been found that a ternary semiconductor thin film having good properties can be obtained, and the method of the present invention has been provided.

[0009] That is, the present invention relates to MI / MII / MIII ₂
(However, MI is one or more metals selected from the group consisting of Cu and Ag, MII is one or more metals selected from the group consisting of In and Ga, and MIII is Se and S
A method for producing a semiconductor thin film comprising a compound of the I-III-VI group represented by one or more metals selected from the group consisting of: MI and MII elements, individually or simultaneously, Oite in the annealing step, not
Previous by heating in an active or reducing atmosphere
Serial to promote alloying of MI and MII, then to form a MI · MII · MIII ₂ compound of low crystalline by supplying <br/> gaseous wherein MIII elemental or compound at the same temperature, subsequently ,
While maintaining the same temperature, the gaseous MIII element or
The supply of the compound is stopped and excess gas is removed from the reaction system.
After removal of the scan-like MIII elements or compounds, three, characterized in that forming a thin film having a second phase Oite the annealing step, further heated by raising the temperature to promote crystallization chalcopyrite type crystal structure The production method of the original compound semiconductor thin film
Further, the heating temperature in the first stage annealing step is 25
0 to 350 ° C. , further comprising a method of producing a ternary compound semiconductor thin film in the second step annealing step.
Ternary heating characterized by a heating temperature of 400 to 650 ° C
Some provide a method for producing a compound semiconductor thin film.

[0010]

In the method of the present invention, a Ti or Mo material is used as a substrate, and Cu and In are laminated on the substrate so as to have a stoichiometric composition. Either method such as electrodeposition may be used, or a method of forming a film as an alloy or a simple lamination may be used.

Next, the Cu-I film thus formed is formed.
The n film is formed under an inert atmosphere or a reducing atmosphere.
Heat to 50-350 ° C and hold for 30-60 minutes;
After promoting the alloying of u-In, selenium or sulfur is reacted by introducing selenium or sulfur in a gaseous state.
In this case, at a temperature of 250 ° C. or less, a chalcopyrite single layer structure is not formed, and an intermediate product is formed. Therefore, the reaction temperature must be higher than this. On the other hand, when the temperature is heated to 350 ° C. or more, a reaction between the substrate and selenium or sulfur occurs, and it becomes inevitable that different phases coexist, and the effect in the subsequent crystallization process cannot be expected. The reaction time of 30 to 240 minutes is sufficient.

After completion of the reaction, the supply of selenium or sulfur is stopped, and the temperature is kept at the same temperature as the reaction temperature for 30 to 60 minutes to remove excess selenium or sulfur from the reaction system.

Finally, 400 to 650 as they are
Temperature to increase the crystallinity.
At a temperature of 00 ° C or less, there is no difference from selenization or sulfidation temperature and no improvement in crystallinity is observed. Conversely, when the temperature is increased to 650 ° C or more, the formed chalcopyrite phase starts to decompose. The above heating must be avoided.

The reason that the crystallization is improved by suppressing the selenization or sulfurization temperature to a low temperature as described above is as follows.
It is considered as follows. That is, since the individual particles of the chalcopyrite phase formed when the reaction is performed at a high temperature exist as perfect crystals, the subsequent crystallization depends on the sinterability of the individual particles. Therefore, unless the temperature is raised to near the melting point, grain growth or the like cannot be expected. On the other hand, particles of a film formed at a temperature low enough to form a chalcopyrite phase have low individual crystallinity and are close to an amorphous state. It is thought to proceed.

Further, by performing the crystallization step in an inert or reducing atmosphere in which no excess selenium or sulfur is present, it is possible to eliminate the reaction with the substrate at a high temperature. In this case, a crystallization time of 30 to 120 minutes is sufficient. There is no particular problem if the operation is performed for a longer time than this, but it is only useless in view of the manufacturing cost.

By manufacturing under the above-mentioned conditions, not only can a chalcopyrite single phase free of an intermediate product or a heterogeneous phase be formed, but also a crystal having good crystallinity and a dense film can be formed. Becomes possible. The reason why the film becomes dense is that the expansion of the film is eased by completely separating the crystallization step from the selenization or sulfurization reaction.

An embodiment will be described in detail below.

[0018]

EXAMPLE 1 A Ti plate was used as a substrate, and Cu
And In were laminated by an electrodeposition method so that the molar ratio of Cu / In became 1. This film thickness was about 1 μm. This was placed in a reactor, and a N ₂ + H ₂ mixed gas was supplied at 500 cc / mi.
While introducing at n, the temperature was raised to 300 ° C. at a rate of 5 ° C./min. After maintaining at this temperature for 30 minutes, Se gas was newly introduced, and further maintained for 2 hours. Thereafter, the introduction of the Se gas was stopped, and the temperature was maintained at the same temperature for one hour in order to remove Se remaining in the reaction tube or Se adhering excessively. Then, while maintaining this state, 5 ° C up to 500 ° C.
The temperature was raised at a rate of / minute, and the temperature was maintained for 1 hour, followed by cooling.

When the structure of the obtained film was analyzed by XRD, it was found to be a single phase of CuInSe ₂ . When the state of the surface was observed by SEM, it was found to be a dense film of triangular plate-like crystals having a particle size of several μm. Its composition is Cu / In
/ Se = 24/26/50 (at%), almost the stoichiometric ratio.

[0020]

Example 2 The procedure of Example 1 was repeated except that the selenization temperature was set at 200 ° C. The composition of the obtained film was Cu / In / S
The stoichiometric ratio was obtained when e = 24/27/49.
It contained Cu _x Se crystals in addition to uInSe ₂ , and was in a state where different phases were mixed.

[0021]

Example 3 The procedure of Example 1 was repeated except that the selenization temperature was set to 400 ° C. The composition of the obtained film was Cu / In / S
Although the stoichiometric ratio was obtained when e = 23/27/50,
UInSe TiSe ₂ is formed is the reaction product of Ti and Se is ₂ substrate in addition, heterogeneous phases were mixed.

[0022]

As described above, in the method of the present invention, in order to completely separate the selenization or sulfidation reaction and the crystallization,
After reacting at a temperature low enough to obtain a chalcopyrite single phase, a two-step heat treatment is carried out to improve the crystallinity at a high temperature. The formation of a single compound without the formation of a foreign phase without the formation of a product was enabled. Further, since the compound formed at a low temperature is relatively rich in sinterability, the crystallinity is improved by a subsequent temperature rise, and the denseness is improved by relaxing the film expansion during the reaction, It has become possible to obtain a high quality film.

Continuation of the front page (72) Inventor Hiroshi Mitone 1-8-2 Marunouchi, Chiyoda-ku, Tokyo Dowa Mining Co., Ltd. (56) References JP-A-2-94669 (JP, A) JP-A-5-13795 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 31/04-31/078 C01B 19/00-19/04 H01L 21/20-21/205

Claims (3)

(57) [Claims] (1) MI / MII / MIII ₂ (where MI is C
one or more metals selected from the group consisting of u and Ag, MII is one or more metals selected from the group consisting of In and Ga, and MIII is one or more metals selected from the group consisting of Se and S). In the method for producing a semiconductor thin film comprising a group I-III-VI-based compound shown in FIG.
And MII elements individually or simultaneously,
Oite the first stage annealing process, an inert atmosphere or in place
By heating in an elemental atmosphere, the combination of MI and MII
Promotes metallization and then at the same temperature the gaseous MIII
Low crystalline MI, MII, M by supplying element or compound
III Form _two compounds and continue to maintain the same temperature.
Further, the supply of the gaseous MIII or the compound is stopped to stop the reaction.
Removing excess gaseous MIII element or compound from the reaction system
After removal, in the second annealing step ,
A method for producing a ternary compound semiconductor thin film, comprising heating and heating to promote crystallization to form a thin film having a chalcopyrite-type crystal structure. 2. A heating temperature in a first stage annealing step .
2. The method for producing a ternary compound semiconductor thin film according to claim 1, wherein the temperature is 250 to 350 ° C. 3. The heating temperature in the second-stage annealing step
3. The method for producing a ternary compound semiconductor thin film according to claim 1, wherein the temperature is 400 to 650 ° C.