JP3311873B2 - Manufacturing method of semiconductor thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a compound semiconductor thin film. More specifically, the present invention relates to a method for manufacturing a semiconductor thin film useful for a light absorption layer of a solar cell having high energy conversion efficiency.

[0002]

2. Description of the Related Art Compound semiconductor thin films (chalcopyrite-structured semiconductor thin films) composed of group Ib, IIIa and VIa elements
It has been reported that a thin-film solar cell using CuInSe ₂ as a light absorbing layer has high energy conversion efficiency and has the advantage that the efficiency is not deteriorated by light irradiation or the like. These CuInSe ₂ thin-film solar cells generally use soda-lime glass as a substrate. Group Ia element Na in this soda lime glass is CuInSe ₂
There is a report that it affects the film quality and carrier concentration of the film. For example, April 1, 1994 in Amsterdam
12th EC Photovoltaic SolarEnergy Confer on 12th to 15th
M. Bodegard et al., "The Influence of Sodium on the Grain Structure of CuInS."
e ₂ Films Fore photo voltaic dichroic app Kei Schons (THE INFLUENCE OF SODIUM ON THE G
RAIN STRUCTURE OF CuInSe ₂ FILMS FOR PHOTOVOLTAIC
APPLICATIONS) "reported that Na of soda lime glass diffused into the CuInSe ₂ film and grains grew.
The result shows that the solar cell using the Se ₂ film has higher energy conversion efficiency. At the same meeting,
Holtz et al., “THE EFFECT OF SUBSTRATE IMPURITIES ON THIS EFFECTS OF SUBSTRATE IMPURITYS ON THE ELECTRONIC CONDUCTIVITY IN CIS SIN FILMS”
E ELRCTRONIC CONDUCTIVITY IN CIS THIN FILMS) " When ion implantation of Na in CuInSe ₂ film on the sapphire substrate titled conductivities are reported to increase 3 orders of magnitude. As can be seen from the above report, CuInSe ₂ film The diffusion of Na is effective for promoting the growth of Al and controlling the electrical conductivity, but when used for solar cells, the natural diffusion of Na in soda-lime glass is conventionally used, and CuIn is used.
There has been no report on a method of actively controlling the incorporation of Na in the process of producing the Se ₂ film.

[0003]

It is considered that the diffusion of Na from soda lime glass can be controlled by the film formation temperature of CuInSe ₂ . However, there is a problem of a controllable temperature range. In order to produce CuInSe ₂ having good crystallinity, a film formation temperature of 500 ° C. or more is required. On the other hand, the softening temperature of soda lime glass is 570 ° C,
If the temperature is higher than 600 ° C., cracks may occur. Therefore, since the controllable temperature range is in the range of 500 to 600 ° C., it is difficult to precisely control the diffusion amount of Na depending on the film formation temperature. Further, when used for a solar cell, it is necessary to form an electrode (mainly a Mo film) on glass. This electrode film becomes an obstacle, and reduces the diffusion amount of Na. Further, since the diffusion amount of Na varies depending on the thickness of the electrode film, reproducibility and non-uniformity in the film surface become problems. From the above, the method of natural diffusion of Na in soda-lime glass during the CuInSe ₂ film formation, poor controllability, CuInSe ₂ film with good reproducibility uniformly produced having a conductivity suitable for a solar cell with high quality It is difficult.

Further, in order to form a chalcopyrite thin film having excellent crystallinity at a high temperature of 600 ° C. or higher and to produce a solar cell having higher conversion efficiency, it is necessary to use alumina or a metal film as a substrate. Further, in order to manufacture a flexible solar cell having a wide range of use, it is necessary to use an organic film such as polyimide as a substrate.
Ia was added to chalcopyrite thin film prepared on these substrates.
Injecting the group element is effective for improving the efficiency of the solar cell. When a substrate other than soda-lime glass is used, there has been no report on a method of adding a group Ia element such as Na to a chalcopyrite thin film other than the above-described ion implantation of Na such as Holtz. The ion implantation method has problems such as the distribution of implanted elements in the film surface and damage to the film due to ions. Therefore, a method of adding the group Ia element effectively and with good control is required.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention relates to a compound semiconductor thin film comprising a group Ib group, a group IIIa and a group VIa element, and a compound thin film comprising a group Ia group and a group VIa element. A manufacturing method is provided.

In the present invention, there are four methods for mixing a compound comprising a group Ia element and a group VIa element. First
The present invention is a method for simultaneously depositing a compound comprising a group Ia and a group VIa element when depositing a compound semiconductor thin film comprising a group Ib group, a group IIIa and a group VIa element on a substrate.

The second invention is a method of depositing a compound semiconductor thin film comprising a group Ib, IIIa and VIa element on a substrate, and then depositing a compound thin film comprising a group Ia and a VIa element on the thin film. is there.

A third invention is a method of depositing a compound thin film comprising a group Ia and a group VIa on a substrate and then depositing a compound semiconductor thin film comprising a group Ib, a group IIIa and a group VIa on the thin film. .

A fourth invention is a method of alternately depositing at least two or more compound semiconductor thin films comprising a group Ib, IIIa and VIa element and a compound thin film comprising a Ia group and a VIa group element.

It is preferable to perform heat treatment after forming a film by the first to fourth invention methods, and it is more preferable to perform heat treatment in an atmosphere containing a group VIa element. And Ia
Compounds composed of VIa group elements include Li ₂ S, Li ₂
It is preferable to be composed of at least one of the group consisting of Se, Na ₂ S, and Na ₂ Se.

Further, the present invention provides a solar cell using the above semiconductor thin film for a light absorbing layer.

[0012]

[Action] An alkali metal consisting only of a Group Ia element such as Li, Na, K and the like violently reacts with moisture and oxygen, and thus requires careful handling. Therefore, when a group Ia element is added to a chalcopyrite structure semiconductor thin film, it is effective to use a group Ia-VIa compound (hereinafter referred to as an Ia-VIa compound) which is relatively easy to handle. Where the compound VI
Since the group a element is one of the constituent elements of the chalcopyrite-structured semiconductor thin film, there is no problem that lattice defects or impurity defects occur even if mixed in the film.

First, when depositing a chalcopyrite-structure semiconductor thin film as in the first invention, at the same time, Ia-VIa
In the method of depositing the compound, it is possible to uniformly distribute the group Ia element in the film. At this time, the amount of the Ia group in the film can be controlled by the evaporation amount or the evaporation rate of the Ia-VIa compound.

Next, the second to fourth inventions are methods for arbitrarily distributing the group Ia element in the cross-sectional direction of the chalcopyrite structure semiconductor thin film. When a distribution in which the carrier concentration increases as the distance from the pn junction surface is increased in the light absorbing layer of the solar cell, an internal electric field is generated due to the carrier concentration difference. The photoexcited minority carriers move due to the internal electric field, are collected at the pn junction surface, and are extracted to the outside. In the carrier movement by such an electric field, a large photocurrent can be obtained because the recombination probability in the light absorption layer is greatly reduced as compared with the movement by diffusion. The distribution of the carrier concentration substantially corresponds to the distribution of the impurities. Therefore, by distributing the group Ia element which is an impurity in the chalcopyrite thin film, it becomes possible to induce an internal electric field due to the carrier concentration distribution.

The second and third inventions are effective as methods for providing a carrier concentration distribution after forming a pn junction and before forming the pn junction, respectively. Specifically, the second method is effective for a super-late type solar cell formed by forming a p-type chalcopyrite structure semiconductor thin film on an n-type window layer on a transparent electrode, The present invention is effective for a substrate type solar cell formed by forming a p-type chalcopyrite structure semiconductor thin film on a metal electrode on a substrate and then forming an n-type window layer. Further, in the fourth invention, it is possible to form an arbitrary carrier concentration distribution in the chalcopyrite structure semiconductor thin film irrespective of the superstrate type and the substrate type.

Further, in the first to fourth inventions, Ia
By performing a heat treatment after depositing the chalcopyrite structure semiconductor thin film containing the -VIa compound, the Ia group element is buried in the deficient portion of the Ib group element in the chalcopyrite structure semiconductor thin film, thereby reducing carrier capture by lattice defects. Become. Therefore, the carrier concentration increases. Further, in the second and third inventions, a heat treatment is required to cause the diffusion of the Ia-VIa compound film into the chalcopyrite structure semiconductor thin film. In order to prevent the detachment of the group VIa element from the chalcopyrite structure semiconductor thin film in the above heat treatment, it is effective to carry out the method in an atmosphere containing the group VIa element.

As the group Ia element to be added to the chalcopyrite structure semiconductor thin film, Li or Na having a small ionic radius and a high diffusion rate is particularly effective. Therefore, in the present invention, Li ₂ S, Li ₂ Se, Na ₂ S and Na ₂ Se which are sulfides or selenides of Li and Na are suitable. In particular, Li ₂ S and Na ₂ S have no toxicity and are easy to handle.

According to the present invention, since the carrier concentration and distribution can be controlled by mixing the group Ia element, the photoexcited carriers can be efficiently taken out and the conversion efficiency of the solar cell can be improved.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a schematic view of an apparatus used for manufacturing a chalcopyrite structure semiconductor thin film according to an embodiment of the present invention. Here, C is used as a chalcopyrite structure semiconductor thin film.
A uInSe ₂ film was produced. Cu, In, and Se, which are constituent elements of CuInSe ₂ , were put into the evaporation sources 2, 3, and 4 in the vacuum vessel 1, respectively, and were evaporated at the same time. Typical temperatures for each deposition source are 1200 ° C., 870 ° C., and 180 ° C. for Cu, In, and Se, respectively. Further, Na ₂ Se, which is an Ia-VIa compound, was put into the evaporation source 5 and evaporated. An alumina plate was used as the substrate 6. The substrate was kept at 750 ° C. by the heater 7 during the vapor deposition. this time,
Five types of films were prepared by changing the temperature of the Na ₂ Se deposition source. The higher the temperature of the evaporation source, the faster the evaporation rate of Na ₂ Se, and the greater the amount of Na contained in the film.
FIG. 2 shows the change in conductivity with respect to the temperature of the Na ₂ Se deposition source. The white circle on the left end of the figure indicates the conductivity of a film formed under the same conditions without depositing Na ₂ Se. Figure 2 from Na ₂
It can be seen that the conductivity increases as the temperature of the Se deposition source increases. That is, it can be seen that the resistance is lowered by increasing the amount of Na in the film. The conductivity of the film formed at the temperature of the evaporation source of 1000 ° C. is about two orders of magnitude higher than that of the film in which Na is not mixed. The distribution of Na in this film was measured by secondary ion mass spectrometry (SIMS). The results are shown in FIG. Here, the solid line represents the distribution of Na in the film manufactured in this example. The dotted line, broken line, and dashed line will be described later. The distribution of In is also shown for reference. A comparison between the result of Na shown by the solid line and the distribution of In indicates that Na is uniformly distributed in the film.

From the above, when the method of this embodiment is used, N
a is uniformly distributed in the film, and the conductivity of the CuInSe ₂ film can be controlled by the temperature (evaporation rate) of the Na ₂ Se vapor deposition source.

Here, as a method of forming CuInSe ₂ which is a chalcopyrite structure semiconductor thin film,
Although the ternary co-evaporation of the constituent elements Cu, In, and Se was used, the same result can be obtained by using the co-evaporation of the _binary compounds Cu ₂ Se and In ₂ Se _{3 or} the vapor deposition of the CuInSe ₂ compound. Have been.

(Embodiment 2) FIG. 4 is a schematic sectional view showing a part of a manufacturing process of a chalcopyrite structure semiconductor thin film according to another embodiment of the present invention. Here, glass containing no alkali metal was used as the substrate 6. After depositing a CdS film to be the n-type window layer 8 of the solar cell on this glass, a CuInSe ₂ film as a chalcopyrite structure semiconductor thin film 9 was formed. On top of this, Na ₂ which is an Ia-VIa compound film 10
S was deposited. Thereafter, a heat treatment was performed in air at 300 ° C. for 1 hour to diffuse Na ₂ S into the CuInSe ₂ film. The thicknesses of the CdS and CuInSe ₂ films are 0.05 and 2.0 μm, respectively. Here, a sample was prepared in which the thickness of Na ₂ S was changed from 0.01 to 0.10 μm.
FIG. 5 shows a change in the conductivity of the CuInSe ₂ film with respect to the film thickness of Na ₂ S. In FIG. 5, the electric conductivity of the film on which the Na ₂ S film is not deposited is indicated by white circles. It can be seen that the conductivity increases as the film thickness of Na ₂ S increases. Na ₂ S
The dotted line in FIG. 3 shows the SIMS distribution of Na of the sample having a thickness of 0.05 μm. Na is present at a high concentration on the film surface, and sharply decreases from 0.5 μm in film thickness. This suggests that the conductivity of the film surface is higher than in the film. Since the carrier concentration substantially corresponds to the change in the conductivity, it is considered that an internal electric field is generated due to the difference in the carrier concentration between the vicinity of the film surface and the inside of the film.

Next, a transparent conductive ITO / ZnO laminated film serving as an electrode was inserted between the glass and the CdS film, and a 0.05 μm-thick Na ₂ S film was added to the structure of the sample shown in FIG. A super-straight solar cell having a configuration in which an Au film serving as an electrode was formed after being diffused under the same conditions as above was manufactured. For comparison, a solar cell having no similar structure and having no Na ₂ S film deposited thereon was also manufactured. As a result of measuring the voltage-current characteristics by irradiating 100 mW / cm ² light of AM 1.5, the short-circuit photocurrent was 32.2 mA / cm for a solar cell in which Na ₂ S was not deposited.
cm ² , whereas 38.7 in the device of this example.
mA / cm ² . It can be seen that the current increased by about 20% due to the diffusion of the Na ₂ S film. This is because the internal electric field generated by the distribution of the carrier concentration considered from the SIMS results indicates the vicinity of the Au electrode (CuInSe in the SIMS distribution).
_It is considered that the photocarriers excited near the _two surfaces can be effectively extracted.

As described above, in the present embodiment, the conductivity of the chalcopyrite-structured semiconductor thin film can be controlled by the film thickness of the Ia-VIa compound, and a distribution in which the group Ia element decreases from the film surface to the film can be formed. It is. Such a change in the carrier concentration due to the distribution of the group Ia element is effective in improving the efficiency of the super-straight solar cell.

(Embodiment 3) FIG. 6 is a schematic sectional view showing a part of a manufacturing process of a solar cell according to another embodiment of the present invention. Alumina was used as the substrate 6. Ia-VIa on alumina
Li ₂ Se is deposited as a compound film 10, and a chalcopyrite structure semiconductor thin film 9 Cu (In _0.8 G
a _0.2 ) Se ₂ was deposited. Here, Cu (In _0.8 G
a _0.2 ) The deposition temperature of Se ₂ is 550 ° C. Note that C
In the u (In _0.8 Ga _0.2 ) Se ₂ compound, the composition ratio of In and Ga is In _x Ga _1-x (where 0 ≦ x ≦ 1).
Therefore, it is represented as Cu (In, Ga) Se ₂ hereinafter.

As described above, Cu (In, Ga) S
A sample was prepared in which the thickness of e ₂ was fixed at 3 μm and the thickness of Li ₂ Se was changed. FIG. 7 shows a change in the conductivity of the Cu (In, Ga) Se ₂ film with respect to the thickness of the Li ₂ Se film.
FIG. 7 shows Cu (In, Ga) Se ₂ without a Li ₂ Se film.
The conductivity of the film is indicated by white circles. It can be seen that the conductivity increases with the film thickness of Li ₂ Se. The broken line in FIG.
₂ Se of a thickness of 0.1μm Cu (In, Ga) shows the distribution in the film of Se ₂ of Li. It can be seen that the Li concentration increases from the film surface into the film. In this case, it is conceivable that an internal electric field is generated from the substrate to the film surface, contrary to the above embodiment.

Next, a Mo film serving as a metal electrode was formed on alumina, and Li ₂ Se was deposited thereon to a thickness of 0.1 μm.
Under the same conditions as above, Cu (In, G) was formed on the Li ₂ Se film.
a) After depositing the Se ₂ film, the CdS film is
m, ZnO and ZnO: Al films were 0.1 μm and 1.
Substrate type solar cells were fabricated by sequentially forming 0 μm. For comparison, a solar cell having no Li ₂ Se film and having the same configuration was also manufactured. Light under the same conditions as in Example 2 was irradiated, and the voltage-current characteristics were measured. The short-circuit current of the device without the Li ₂ Se film was 30.3 mA / cm ² , whereas the device with the Li ₂ Se film deposited was 37.4 mA.
/ Cm ² . The short-circuit photocurrent increased by 20% or more by depositing the Li ₂ Se film. This is considered to be because, similarly to the second embodiment, the photocarriers excited near the Mo film away from the pn junction surface by the internal electric field generated by the Li distribution can be efficiently extracted.

As described above, in this embodiment, the conductivity of the chalcopyrite structure semiconductor thin film can be controlled by the thickness of the Ia-VIa compound film, and the concentration of the Ia group element can be reduced from the substrate to the film surface. Such a change in the carrier concentration due to the distribution of the group Ia element is effective for improving the efficiency of the substrate type solar cell.

In this embodiment, the group Ib, the group IIIa and the group VI
A chalcopyrite-structured semiconductor thin film in which a group Ia element is diffused is produced while maintaining a substrate temperature at 550 ° C. when depositing a compound semiconductor film composed of a group a element. After deposition on the Ia-VIa compound film, the same Ia is obtained even when a heat treatment at 500 ° C. or more is performed in an atmosphere in which Se as a VIa group element is evaporated.
A chalcopyrite structure semiconductor thin film in which the group III element is diffused is obtained.

(Embodiment 4) FIG. 8 is a schematic sectional view of a part of a manufacturing process of a solar cell showing another embodiment of the present invention. As the substrate 6, polyimide as a transparent polymer material was used. On this, an ITO / ZnO film serving as the transparent conductive film layer 11 and a CdS film serving as the n-type window layer 8 were formed. On the CdS film, chalcopyrite structure semiconductor 8 CuInSe ₂ and Ia−
Na ₂ S films of Group VIa compound 9 are alternately laminated. At this time, the thickness of one CuInSe ₂ film was fixed at 0.2 μm, and the thickness of the Na ₂ S film was 2 nm for the first layer.
The film thickness was gradually increased by nm, and the final 10th layer was formed to have a thickness of 20 nm to form a CuInSe ₂ film. Na
The total thickness of ₂ S was 0.11 μm (110 nm).
The deposition temperature of the laminated film was kept at 350 ° C. An Au film was deposited on this laminated film to produce a solar cell.

The dashed line in FIG. 3 shows CuInSe ₂ and Na
_It shows the distribution of Na in the 2Se laminated film. Na of CuInSe ₂ film produced by the method of Example 2 shown by the dotted line
It can be seen that the distribution decreases almost linearly from the film surface into the film. Therefore, it is considered that an internal electric field is generated in the entire film. The distribution can be controlled by changing the cycle of the laminated film and the thickness of each layer.

The solar cell was irradiated with light under the same conditions as in the above-described embodiment, and the voltage-current characteristics were measured. As a result, a short-circuit photocurrent of 39.1 mA / cm ² was obtained. The substrate is different,
A value higher than that of the device of Example 2 was obtained. This is considered to be due to the internal electric field distribution spread in the film due to the linear distribution of Na.

In this embodiment, Na ₂ S is used as the thin film of the group Ia-VIa compound. However, in order to precisely control the distribution of the group Ia element, an element having a small diffusion rate and a large atomic weight is more effective. It is. Therefore, K ₂ S, K ₂ Se, Cs ₂ S, Cs ₂ Se and the like are effective as the Ia-VIa group compounds.

(Embodiment 5) In this embodiment, it will be described that the present invention is also effective when a chalcopyrite structure semiconductor thin film is formed by a reaction between a metal film and a gas. A Mo sheet plate was used as a substrate. After depositing about 0.05 μm of a Li ₂ S film, which is an Ia-VIa compound, on Mo,
A Cu film as a metal b and an In film as a Group IIIa metal were sequentially deposited so as to have a thickness of 0.25 μm and 0.58 μm, respectively. This film was prepared at 10 vol. A containing% H ₂ S
and heat-treated for 1 minute at 650 ℃ in r atmosphere CuInS ₂
A film was prepared. On the CuInS ₂ film, an n-type semiconductor CdS serving as a window layer and a ZnO: Al film serving as a transparent electrode were deposited to produce a solar cell. Also, for comparison, L
A solar cell without i ₂ S deposition was also fabricated. The capacitance was measured by changing the voltage applied to the solar cell, and the hole concentration as a carrier of the p-type semiconductor was measured. As a result, L
The hole concentration of the device without i ₂ S was about 10 ¹⁴ / cm ^3, whereas that of the device with Li ₂ S deposited increased to about 10 ¹⁶ / cm ³ . From this, it is understood that the hole concentration (carrier concentration) is increased by mixing Li ₂ S. As a result of measuring the voltage-current characteristics of the two solar cells by irradiating the same light as in the above embodiment, the conversion efficiency was 6% in the element not using Li ₂ S, whereas Li ₂ S was deposited. In the device thus manufactured, the ratio was about 10%. From the above results, L
It is considered that the increase in the hole concentration due to the mixing of i ₂ S contributes to the improvement of the conversion efficiency.

[0035]

According to the present invention, the carrier concentration of a chalcopyrite structure semiconductor thin film can be controlled, and a carrier concentration distribution suitable for a solar cell and capable of efficiently extracting a photocurrent can be formed. In addition, it is possible to increase the efficiency of a solar cell formed on many substrates not containing a Group Ia element.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus for manufacturing a semiconductor thin film used in one embodiment of the present invention.

FIG. 2 shows CuInSe versus Na ₂ Se deposition source temperature.
_The figure which shows the change of the electric conductivity of _two films.

FIG. 3 is a diagram showing a distribution of a group Ia element in a compound semiconductor film including a group Ib, a group IIIa, and a group VIa.

FIG. 4 is a view showing a part of a manufacturing process of a chalcopyrite structure semiconductor thin film according to one embodiment of the present invention.

FIG. 5 is a diagram showing a change in the electrical conductivity of the CuInSe ₂ film with respect to the thickness of the Na ₂ S film.

FIG. 6 is a view showing a part of a manufacturing process of a chalcopyrite structure semiconductor thin film according to one embodiment of the present invention.

FIG. 7 shows the relationship between the thickness of a Li ₂ Se film and Cu (In,
a) A diagram showing a change in conductivity of the Se ₂ film.

FIG. 8 is a diagram showing a part of a manufacturing process of a solar cell according to one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Vacuum container 2 Deposition source of Cu which is an Ib group element 3 Deposition source of In which is a IIIa group element 4 Deposition source of Se which is a VIa group element 5 Deposition source of Na ₂ Se which is an Ia-VIa compound 6 Substrate Reference Signs List 7 Substrate heater 8 N-type window layer (CdS) 9 Compound semiconductor thin film composed of group Ib, IIIa and VIa elements (chalcopyrite structure semiconductor thin film) 10 Compound thin film composed of Ia group and group VIa element 11 Transparent Conductive film

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-320381 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 31/04-31/078 H01L 21 / 363

Claims (8)

(57) [Claims] 1. A method of manufacturing a semiconductor thin film, comprising: simultaneously depositing a compound comprising a group Ia and a group VIa element when depositing a compound semiconductor thin film comprising a group Ib group, a group IIIa and a group VIa element. 2. A method of manufacturing a semiconductor thin film, comprising: depositing a compound semiconductor thin film comprising a group Ib, IIIa, and VIa element on a substrate, and depositing a compound thin film comprising a group Ia and a VIa element on the thin film. 3. After depositing a compound thin film comprising a group Ia and a group VIa on a substrate, a group Ib, a group IIIa and a group VIa are deposited on the thin film.
A method for producing a semiconductor thin film, wherein a compound semiconductor thin film comprising a group a element is deposited. 4. A method for manufacturing a semiconductor thin film, comprising alternately depositing at least two or more compound semiconductor thin films composed of Group Ib, Group IIIa, and Group VIa elements and compound thin films composed of Group Ia and Group VIa elements. 5. The method of manufacturing a semiconductor thin film according to claim 1, further comprising a step of performing a heat treatment after manufacturing the semiconductor thin film. 6. The method of manufacturing a semiconductor thin film according to claim 5, further comprising a step of performing a heat treatment in an atmosphere containing a group VIa element. 7. The compound comprising Group Ia and Group VIa elements is L
The method for producing a semiconductor thin film according to claim 1, wherein the method comprises at least one of a group consisting of i ₂ S, Li ₂ Se, Na ₂ S, and Na ₂ Se. 8. The method according to claim 1, wherein the semiconductor thin film is a light absorbing layer of a solar cell.