JPH07331413A - Transparent electrically conductive film, transparent insulating film and production of photoelectric converting semiconductor device using the same - Google Patents

Abstract

PURPOSE:To obtain a transparent insulating film or a transparent electrically conductive film excellent in controllability of electric conductivity by doping a ZnO film with oxide of a group IIIA element in an atmosphere of O2 or H2 when the ZnO film is formed on a substrate by an Ar ion beam sputtering method. CONSTITUTION:A ZnO sintered target and an Al2O3 sintered target are sputtered in vacuum with Ar ion beams to generate ion beams of ZnO and Al2O3. Gaseous O2 is fed to a substrate held by a substrate holder in the vacuum by ISCCM feed and a transparent insulating film made of a ZnO:Al2O3 film is formed in the gaseous O2 atmosphere. A transparent electrically conductive film is formed by using gaseous H2 atmosphere in place of the O2 atmosphere. The objective transparent insulating film having increased resistance or the objective transparent electrically conductive film having reduced resistance is obtd. Both the films are excellent in controllability of electric conductivity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transparent conductive film / transparent insulating film which is used in a high efficiency solar cell or a display device and which has an excellent controllability of the electric conductivity.

[0002]

2. Description of the Related Art Conventionally, a Nesa film (SnO2) or an ITO film has been used as a transparent conductive film, but a ZnO film is cheaper than a Nesa film or an ITO film, and is used as a transparent conductive film. Has become.

Conventionally, a ZnO film is formed by the rf sputtering method, has a non-stoichiometric composition and exhibits an n-type conductivity with an excess of Zn, and the substrate temperature is not higher than 300 ° C.
It had a conductivity of about / Ωcm and had a property of showing high resistance.

Therefore, Ar or Ar and H are used as the sputtering gas, or IIB is used as a host in the ZnO crystal.
The electric resistance was controlled by replacing the group Zn atom with the group IIIA atom or replacing the parent O atom in the ZnO crystal with the F atom.

[0005]

However, when the ZnO film is formed by the rf sputtering method, the ZnO film on the ZnO target and the substrate is alternately etched and deposited repeatedly by the number of times corresponding to the frequency, resulting in many crystal defects. A film is generated. Therefore, the electrical conductivity of the ZnO thin film produced by this rf sputtering method is based on crystal defects which are influenced by the conditions of the sputtering gas composition and the substrate temperature during the production of the thin film, and the controllability is very poor. Met.

Therefore, the present invention provides a method for manufacturing a ZnO film having few crystal defects in order to improve the controllability of the electrical conductivity of the ZnO film. It is an object of the present invention to provide a low resistance transparent conductive film and a high resistance transparent insulating film by controlling electrical conductivity by performing the above, and to provide a method for manufacturing a semiconductor device using the same.

[0007]

In order to solve the above-mentioned problems, the present invention does not use a conventional rf sputtering film formation method in which a large number of crystal defects are generated in a ZnO film, but a high temperature at room temperature. Zn by Ar ion beam sputtering in vacuum
An ion beam of O and an ion beam of Zn or O are produced, and this ion beam is used to produce a ZnO film.

At this time, it is kept under an atmosphere of H or O, and an ion beam of an oxide of any atom of Group IIIA (B, Al, Ga, In) is used in combination to make impurities at arbitrary positions in the ZnO film. A method of controlling conductivity by doping is adopted.

[0009]

A ZnO ion beam, an ion beam of ZnO and Zn or O, or an ion beam of Zn or O produced by sputtering a target with an Ar ion beam of low acceleration energy in a high vacuum is used. When the film is formed, unlike the case where the film is formed by the conventional rf sputtering method, high-speed charged particles do not exist, and since the ion beam has energy of about the heat of coagulation, a ZnO film with extremely few crystal defects can be formed.

Further, in a low temperature process in which the energy for forming a more complete Zn-O bond network can be supplied by the potential of the ions and the substrate temperature is room temperature, ZnO
A film can be produced.

By introducing a slight amount of O 2 gas and performing it in an atmosphere of O in the step of forming a ZnO film having few crystal defects, holes are injected into the Zn-Os-p sigma antibonding orbital, and the excess Zn Oxidized to increase resistance Z
An nO film can be produced.

Further, a slight amount of H is generated in the process of forming the ZnO film.
By introducing 2 in an atmosphere of H, electrons are injected into the Zn-Os-p sigma antibonding orbital forming the conduction band, and O-H groups are generated by O atoms and H atoms in the film. By doing so, electron doping can be realized, and the resistance of the film can be reduced.

Further, by using an ion beam of any atom of Group IIIA (B, Al, Ga, In) in combination, impurity atoms can be doped at an arbitrary position in the ZnO film with good controllability, and a smaller doping amount can be obtained. Thus, the electric resistance can be reduced more effectively.

[0014]

EXAMPLES Examples of the present invention are shown below.

(Embodiment 1) The method of manufacturing a conductive film of this embodiment comprises the following steps (1) to (5). (1) A ZnO sintered target and an Al2O3 sintered target are sputtered using an Ar ion beam in a vacuum of about 1 × 10 -6 Torr to produce an ion beam of ZnO and Al2O3. (2) First, 1 SCCM of O2 gas is supplied to the semiconductor film / metal electrode / glass substrate held by the substrate holder of 300K in the same vacuum through the O2 gas supply line. (3) A shutter facing the semiconductor film / metal electrode / glass substrate is opened, and a ZnO: Al2O3 film is deposited on the semiconductor film / metal electrode / glass substrate in an O2 gas atmosphere. (4) Desired Zn under O2 gas atmosphere by film thickness monitor
After the film thickness of O: Al2O3 film is obtained, the O2 gas is switched to the H2 gas, and the H2 gas is supplied to the 1S for 1S through the H2 gas supply line.
CCM is supplied and a ZnO: Al2O3 film is formed in an H2 gas atmosphere. (5) Desired Zn under H2 gas atmosphere by film thickness monitor
When the film thickness of O: Al2O3 film is obtained, the ion beam is stopped.

Here, the intensity ratio of the ion beams of ZnO and Al2O3 is the intensity ratio required to obtain the desired conductivity, and the temperature of the substrate holder may be room temperature. The high-resistivity ZnO: Al2O3 film formed in the O2 gas atmosphere is a ZnO: Al2O3 film transparent conductive film and semiconductor film formed in the H2 gas atmosphere.
The film thickness is set to prevent a short circuit between metal electrodes.

Tables 1 and 2 show examples of conditions for Ar ion beam sputtering in the O2 gas atmosphere and the H2 gas atmosphere of the ZnO sintered target and the Al2O3 sintered target of the above method.

It can be seen from Tables 1 and 2 that the conductivity can be controlled by sputtering in an O 2 and H 2 gas atmosphere.

[0019]

[Table 1]

[0020]

[Table 2]

When a film is formed using an ion beam,
Z made as understood from the point of view of its deposition mechanism
The crystal defects in the nO film are reduced, the contribution of the crystal defects to the electrical conduction is reduced, and the doping controls the electrical conduction. In the oxygen-doped film, the resistance becomes high, and in the hydrogen-doped film, the effect of impurities is maximized and the effect is low. It becomes resistance.

In practice, the ion energy is 750e.
Under the condition of V, the generation of crystal defects in the ZnO film of high-energy particles is reduced as much as possible, and the reduction of the heat energy to be given by the substrate holder due to the temperature of the substrate holder being compensated by the potential energy of the ions, The optimum result was obtained.

By this ion beam sputtering method, a ZnO film can be formed at room temperature, which facilitates application to solar cells, display devices and the like.

(Example 2) Conventionally, in a solar cell, a chalcopyrite structure compound semiconductor C is used as a semiconductor film in a light absorption layer.
A uInSe2 thin film was used, and a wurtzite structure compound semiconductor CdS thin film was further formed thereon to form a pn heterojunction, and a ZnO film was laminated as a transparent electrode on the semiconductor film.

This structure uses Cd, which is a harmful substance, from the viewpoint of the environment, and also from the viewpoint of energy due to lattice mismatch at the heterojunction interface and the characteristic restriction due to the recombination center. Not the preferred structure.

Therefore, in order to solve the above-mentioned problem in this embodiment, a homojunction CuInSe2 semiconductor layer is formed and Zn is formed by the method of preparing the ZnO transparent insulating / conductive film shown in the first embodiment.
The O transparent electrode is produced at the same time.

The steps of manufacturing the solar cell of this example are shown below. (1) A ZnO sintered target and an Al2O3 sintered target are sputtered using an Ar ion beam in a vacuum of about 1 × 10 -6 Torr to produce an ion beam of ZnO and Al2O3. (2) ZnO in an O2 gas atmosphere while first supplying 1 SCCM of O2 gas through the O2 gas supply line on the chalcopyrite structure compound semiconductor CuInSe2 thin film showing p-type conductivity held in a 300K substrate holder. : Deposit Al2O3 transparent insulating film. (3) Desired O2 gas atmosphere ZnO:
When the thickness of the Al2O3 transparent insulating film is obtained, O2 gas is added to H2
Switch to gas. (4) 1 SCCM of H2 gas through the H2 gas supply line
Then, in the H2 gas atmosphere, a ZnO: Al2O3 transparent conductive film is formed on the ZnO: Al2O3 transparent insulating film. (5) Desired H2 gas atmosphere ZnO:
When the Al2O3 transparent conductive film is obtained, the ion beam is stopped.

That is, according to the above method, p-type CInSe 2 is irradiated with Al ion beams to form p-type C near the interface with ZnO.
CuInSe2 with n-type conductivity by doping Al into uInSe2
A layer is formed to provide a pn homojunction, and subsequently, a transparent insulating film for preventing a short circuit between the semiconductor light absorption layer and the transparent conductive film is formed, and a transparent conductive film is formed thereon to provide a transparent electrode. It is a thing.

In the present invention, the ZnO: Al2O3 film is formed at the same time as or immediately after the CuInSe2 homojunction is formed. At the same time when the ZnO: Al2O3 film is formed, oxygen doping and then hydrogen doping are performed to make the ZnO thin film intrinsic. High resistance, n-type, and low resistance are achieved.

As a result, it is not necessary to use Cd, which is a harmful substance, and further, the lattice mismatch at the bonding interface and the restriction on the characteristics due to the recombination center can be reduced. Can be configured.

Although Al 2 O 3 is used as an example in this embodiment, Ga, In, B oxides may be used. Alternatively, a transparent electrode may be produced by supplying an oxidizing or reducing gas other than oxygen or hydrogen as an atmospheric gas.

Further, in the method for manufacturing a photoelectric conversion semiconductor device of the present invention, since the homojunction is formed after the basic structure of the photoelectric conversion semiconductor device is manufactured, the manufacturing process can be simplified. Further, since it can be applied as a means for finely adjusting the conversion efficiency of the photoelectric conversion semiconductor device, it also has an effect of improving the yield.

[0033]

The method of the present invention increases the electric resistance,
It is possible to dope H or O that causes reduction, or dope impurity atoms such as Al with good controllability from the viewpoint of conductivity and its spatial distribution. The application in the manufacture of a semiconductor device having a complicated device configuration is larger than that of the conventional method of mixing.

Further, in the production of the photoelectric conversion semiconductor device, not only the electric resistance of the ZnO transparent conductive / insulating film is reduced / increased, but also the speed of accelerated H and O or the speed of the ion beam such as Al is controlled. Thus, the surface of the semiconductor film as the base can be cleaned and the charge carriers can be doped to an arbitrary depth, and a favorable homojunction can be formed, and the manufacturing process of the photoelectric conversion semiconductor device can be simplified.

Further, by using the technique of the present invention for forming a good homojunction having a clean joint surface in the chalcopyrite structure thin film, the conventionally used lattice mismatch due to the formation of a heterojunction, and the accompanying re-alignment. Solves the problem of characteristic deterioration due to the bonding center, and further, Cd of harmful substances
It can realize pollution-free solar cells that do not use, and contribute to solving energy and environmental problems.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location H01L 31/04 H (72) Inventor Takashi Hirao 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. Within

Claims (4)

[Claims] 1. A ZnO ion beam, a ZnO ion beam and a Zn and O ion beam, or a Zn and O ion beam, and a group IIIA ion beam by an Ar ion beam sputtering method in an atmosphere containing an oxidizing gas. Ion beam of oxides containing any or all of the atoms, or II or any of the atoms of group IIIA
A transparent insulating film obtained by sputtering with an ion beam of group IA atoms and an ion beam of O to form a ZnO film in which the group IIIA atoms are dispersed on a substrate. 2. An ion beam of ZnO, an ion beam of ZnO and an ion beam of Zn and O, or an ion beam of Zn and O, and an ion beam of ZnA and a group IIIA by an Ar ion beam sputtering method in an atmosphere containing a reducing gas. Ion beam of oxides containing any or all of the atoms, or II or any of the atoms of group IIIA
A transparent conductive film obtained by sputtering a group IA atom ion beam and an O ion beam to form a ZnO film having the group IIIA atoms dispersed therein on a substrate. 3. A method of manufacturing a photoelectric conversion semiconductor device comprising the following steps (1) and (2). (1) A semiconductor film forming a heterojunction or a homojunction is used as a base, and ZnO is formed on the base in an atmosphere containing oxygen.
Forming a film and laminating a high-resistivity transparent insulating film on the substrate. (2) forming a ZnO film in an atmosphere containing hydrogen,
A step of causing the group IIIA atom to exist in the nO film and laminating a transparent conductive film having a low resistivity on the transparent insulating film. 4. A method of manufacturing a photoelectric conversion semiconductor device, which comprises the following steps (1) to (3). (1) A step of forming a ZnO film on a transparent substrate in an atmosphere containing hydrogen and laminating a low resistance transparent conductive film on the substrate. (2) forming a ZnO film in an atmosphere containing oxygen,
A step of stacking a high-resistance transparent insulating film on the low-resistance transparent conductive film by allowing the group IIIA atoms to exist in the nO film. (3) A step of forming a semiconductor film forming a heterojunction or a homojunction on the ZnO film.