JPH04324647A - Manufacture of cuinse2 thin film - Google Patents

Abstract

PURPOSE:To obtain a manufacturing method of a CuInSe2 thin film wherein a forming method of CuInSe2 which is called as a selenide method is improved, the use or the generation of highly poisonous H2Se is avoided, and the formation of In2O3, which is liable to be formed in an inert gas atmosphere, can be prevented. CONSTITUTION:A Cu/In/Se lamination film or a Cu/In lamination film is heat- treated in the atmosphere of inert gas wherein oxygen partial pressure is adjusted to be 10<-10>atm or lower or in the atmosphere wherein Se gas is contained in above inert gas. A CuInSe2 thin film is formed by reaction and mutual diffusion between the above layers, and the oxygen partial pressure is adjusted in the manner in which inert gas composed of N2 or Ar is made to pass in heated metal deoxidizer, e.g. Mg or Al heated at 300-650 deg.C.

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 a CuInSe2 thin film as a semiconductor material forming a heterojunction for converting optical energy into electrical energy.

0002

BACKGROUND OF THE INVENTION Conventionally known methods for producing CuInSe2 thin films involve depositing layers of copper and indium either sequentially or simultaneously on a substrate, followed by a selenium-containing gas, preferably H2.
A method of heat-treating in the presence of Se to obtain CuInSe2, or a method of electroplating elemental selenium on an indium layer laminated on a copper layer and heat-treating it in an inert atmosphere (Japanese Patent Application Laid-open No. 61-237476),
A method in which copper, indium, and selenium are sequentially vapor-deposited and heat-treated in a hydrogen-containing gas or an atmosphere containing selenium or sulfur in the hydrogen-containing gas (Japanese Unexamined Patent Publication No. 1-231313), and further, copper and indium are sequentially deposited by DC magnetron sputtering. After lamination, heat treatment is performed in the presence of a selenium-containing gas to obtain a CuInSe2 thin film (Japanese Unexamined Patent Publication No. 20381/1983).

[0003] Among these conventional techniques, there is a vapor phase selenization method in which copper and indium are heat-treated in the presence of a selenium-containing gas, or a solid-phase selenization method in which selenium is also formed as a solid phase and then heat-treated. It has been accepted by many researchers.

0004

[Problems to be Solved by the Invention] However, among these methods, when H2 Se is used as a selenium source, extreme caution is required in storage and handling since H2 Se is extremely toxic. Furthermore, even if H2 Se is not used, if H2 is used in the reaction atmosphere, H2 Se
occurred, and there was a similar risk. In order to solve these problems, a method using an inert gas as a reaction atmosphere has been adopted, but N2, which is used as an inert gas,
Usually 0.1 to 10 ppm in gas or Ar gas
of O2 (oxygen partial pressure 10-7 to 10-5 atm) is present.

Therefore, the conventional techniques are summarized as follows: (1) When H2 Se or H2 gas containing Se is used as a selenium source, extremely toxic H2 Se
A lot of cost and attention had to be paid to countermeasures. (2) When the selenium source is Se gas or solid phase elemental selenium and the reaction atmosphere is an inert gas atmosphere, In is oxidized during the heat treatment process by a trace amount of oxygen that is normally contained as an impurity in the inert gas. and could not prevent the formation of undesired In2O3 in the final product.

Therefore, an object of the present invention is to avoid the use or production of H2Se, which is highly toxic, and at the same time avoid the use or formation of H2Se, which is highly toxic.
An object of the present invention is to provide an improved method for producing a CuInSe2 thin film that can prevent the formation of CuInSe2.

[0007]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present inventors have developed a system that uses O2 in an inert gas atmosphere during heat treatment.
As a result of research into the problem of the formation of In2O3 in products by reacting with In, it was found that O
2. We found that oxidation of In can be substantially prevented by adjusting the concentration and performing heat treatment, and that it is easy to achieve such an oxygen concentration by using, for example, heated Mg or Al as an oxygen scavenger. We have arrived at the present invention.

Therefore, the present invention firstly provides Cu/In/
In the method of manufacturing a CuInSe2 thin film by selenization heat treatment of a Se laminated film or a Cu/In laminated film, a metal oxygen scavenger heated with an inert gas consisting of N2 or Ar,
Preferably, the inert gas is passed through Mg or Al heated to 300 to 650 °C, and heat treated in an inert gas atmosphere in which the oxygen concentration of the inert gas is adjusted so that the oxygen partial pressure is 10-10 atm or less. The above Cu, In
CuIn and Se due to reaction and interdiffusion between each layer.
CuInSe characterized by forming a Se2 thin film
2. It provides a method for manufacturing thin films.

The above manufacturing method of the present invention replaces part or all of the In of the laminated film with Ga, which belongs to the same group IIIB in the periodic table, or replaces part or all of the Se with S, which belongs to the same group VIB in the periodic table. It was confirmed that it is also effective when replacing with , and manufacturing corresponding semiconductor thin films.

0010

[Operation] Normally, N2 or Ar gas supplied from a gas cylinder or in a liquefied state contains impurities of 10-5 to 1
It contains 0-7 atm of oxygen, but when this gas is passed through a heated metal oxygen absorber, the following chemical formula:
Oxygen can be removed until the reaction shown in Chemical Formula 1 reaches equilibrium. M in the formula represents a metal.

[Chemical formula 1]

For example, when Mg and Al are used as metals,
Oxygen in the gas can be removed by the reaction of these into MgO and Al2 O3, and theoretically the oxygen partial pressure is 10-6.
Although it is possible to deoxidize up to about 0 atm, deoxidation that is actually possible is limited to an oxygen partial pressure of up to 10-20 atm.

In equilibrium theory, oxygen partial pressure = 10-15 ~ 1
Even at 0-20 atm, In is oxidized and becomes In2 O3
However, the above M generated by deoxidation
Since gO or Al2O3 is thermodynamically more stable than In2O3, 10-15 to 10-20
It is considered that the oxidation of In does not substantially proceed if the oxygen concentration is atm.

[0013] Furthermore, the reason why the deoxidation temperature is set at 300°C or higher is that below this temperature, the ability to remove oxygen is poor and the reaction rate is slow. On the other hand, the maximum is 650
The melting point of Mg and Al is 65°C, respectively.
This is because the temperatures are 0°C and 660°C, so it is desirable to operate at a temperature lower than these temperatures.

[0014]

[Example 1] Corning #7059, which is barium borosilicate glass, was used as a substrate, and Cu, In, and S
The films were formed by vacuum evaporation in the order of 2000 Å (angstroms), 4500 angstroms, and 1.3 μm in thickness. This substrate was placed in a reaction tube, and N2 gas was introduced. N2 gas was vaporized from a liquefaction tank and had an oxygen partial pressure of 2 x 10-6 atm, and before entering the reaction tube, it was heated to 600°C filled with a magnesium agent.
The oxygen was removed by passing through a cylindrical furnace heated to . The oxygen concentration in the N2 gas after deoxygenation is 3 x 10-17 atm
Met.

After the inside of the reaction tube was replaced with deoxygenated N2 gas, the temperature was raised to 400°C at a rate of 5°C/min, maintained at this temperature for 1 hour, and then lowered.

When the formed film was examined by X-ray diffraction, it was found that
Only the peak of CuInSe2 was observed, and no formation of In2O3 was observed.

[0017]

[Comparative Example 1] A CuInSe2 film was produced in the same manner as in Example 1 except that the deoxidation temperature was 250°C. The oxygen concentration in the N2 gas after deoxygenation is as follows: oxygen partial pressure is 7×1
It was 0-9 atm.

As a result of X-ray diffraction, most of the formed film was CuInSe2, but some In2O3 peaks were observed.

[0019]

[Example 2] Cu on the substrate (Corning #7059)
, In to film thicknesses of 2000 Å and 4500 Å, respectively, and heat treated in a mixed atmosphere of Se gas and Ar gas. The Ar gas used had an oxygen partial pressure of 6 x 10-7 atm, which was deoxidized with an aluminum agent heated to 600°C to give an oxygen partial pressure of 4 x 10-15 atm.

In the heat treatment, the inside of the reaction tube was sufficiently replaced with deoxygenated Ar gas, the temperature was raised to 400°C at a rate of 5°C/min, and after being held at this temperature for 30 minutes, Se
The grains were placed in a reaction tube at a position exhibiting a temperature of 300°C or higher. At this time, care was taken to prevent outside air from entering. In this state, Se was volatilized, turned into a gas, and reacted with Cu and In. After 1 hour, the Se was transferred to a place in the reaction tube at a temperature below 100°C, and then heated at 400°C for an additional 30 minutes and then cooled.

According to the results of X-ray diffraction, the formed film was only of CuInSe2, and no peak of In2O3 was observed.

[0022]

[Comparative Example 2] A CuInSe2 film was formed in the same manner as in Example 2. However, the Ar gas was not deoxidized and the oxygen partial pressure of 6×10 −7 atm was used as it was.

According to the results of X-ray diffraction of the formed film, a fairly large peak for In2O3 was observed, indicating that a considerable amount of In2O3 was produced.

[0024]

Effects of the Invention As explained above, according to the production method of the present invention, CuInSe2
In the formation method, the use or generation of highly toxic H2Se is eliminated, improving operational safety, and
N2 whose oxygen partial pressure was adjusted to 10-10 atm or less using a heated metal deoxidizer made of Mg or Al.
Alternatively, since the heat treatment is performed under an inert gas atmosphere consisting of Ar gas, it is possible to prevent In from oxidizing.

Claims (3)

[Claims] [Claim 1] Cu/In/Se laminated film or Cu/
When producing a CuInSe2 thin film by heat treatment for selenization of an In laminated film, an inert gas consisting of N2 or Ar is passed through a heated metal deoxidizing agent to adjust the oxygen partial pressure to 10-10 atm or less, By performing heat treatment in this inert gas atmosphere or an atmosphere in which Se gas is added, a CuInSe2 thin film is formed by reaction and interdiffusion between the Cu, In, and Se layers. Manufacturing method. 2. The metal oxygen scavenger is Mg or Al, and the heating temperature of these oxygen scavengers is 300 to 650.
2. The method according to claim 1, wherein the temperature is .degree. 3. The Cu/In/Se laminated film or C
In the u/In laminated film, part or all of In is replaced by Ga.
2. The manufacturing method according to claim 1, wherein a corresponding semiconductor thin film is formed by replacing Se with S, or by replacing part or all of Se with S.