JP3468484B2 - Method for producing chalcopyrite semiconductor thin film solar cell - 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 manufacturing a chalcopyrite semiconductor thin film solar cell and a semiconductor thin film processing apparatus used therein.

[0002]

_2. Description of the Related Art In manufacturing a solar cell using CuInSe ₂ or CuInS ₂ thin film (hereinafter referred to as a CIS solar cell), as shown in FIG. 5, excess CuInSe formed on a substrate 1 on which an electrode 2 is formed is used. ₂ or CuInS ₂ thin film 3,
After processing with the KCN (potassium cyanide) solution 55 in the processing container 54, it is possible to obtain a conversion efficiency of 10% or more by forming a bond. Reported by Sheer et al. (Proc. Of 12th ECPVSEC, Amsterdam, (1994) P175
1 ~). This is CuInSe ₂ and CuInS with excess Cu.
_{2 The} thin film contains CuSe and CuS heterogeneous phase, but K
This is because the heterogeneous phase can be removed by the CN solution treatment, and a thin film having relatively high crystallinity and a high hole concentration can be obtained. The authors point out that any cell using a heterojunction with CdS still has room for improvement compared to the open circuit voltage (Voc: open circuit voltage) expected from the band gap of CuInSe ₂ or CuInS ₂ . There is. To do so, 1) adjust the band offset of the junction to CdZn.
It is stated that it should be made smaller by using S or the like, and 2) it is necessary to devise to shift the junction to the absorption layer side.

[0003]

However, since the conventional manufacturing method uses a liquid containing a large amount of KCN solution, it requires a waste liquid treatment facility for the harmful liquid, which is a factor of increasing the manufacturing cost. The original purpose of the KCN solution treatment is to selectively remove the different phases of CuSe and CuS existing in the Cu-excessive CuInSe ₂ and CuInS ₂ thin films. Therefore, a solar cell manufacturing process that has the same effect as this treatment and that can establish a dry process is desired.

In order to solve the above-mentioned conventional problems, it is an object of the present invention to provide a chalcopyrite semiconductor thin film solar cell safely and at low cost without using a KCN solution.

[0005]

In order to achieve the above object, a method of manufacturing a solar cell according to the present invention comprises a lower electrode formed on an insulating substrate, and a group I element in excess I-III-VI ₂
-Type chalcopyrite semiconductor thin film is formed, and the thin film is formed by exposing the thin film to a gas containing a halogen element.
The step of removing the heterogeneous phase therein , forming a window layer for forming a junction on the chalcopyrite semiconductor thin film, and forming a translucent upper electrode, the gas containing a halogen element is a gas.
It is a plasma or radicalized gas. Excessive group I element means a stoichiometrically ideal composition ratio I
Group element: Group III element: Group VI element = 25:25:50
On the other hand, it means a state in which only the group I element exceeds the ideal value, for example, the group I element occupies 30 atom%.

In the above structure, the gas containing the halogen element is Cl ₂ , Br ₂ , HCl, HBr, HI, and BC.
It is preferably at least one selected from l ₃ . Further, in the above structure, it is preferable to heat the substrate to 150 to 200 ° C. when exposing the thin film to a gas containing a halogen element.

[0007]

In the above structure, the group I element is Cu.
Is preferred. In the above configuration, II
The Group I element is preferably at least one of In and Ga.

Further, in the above structure, the group VI element is preferably at least one of S, Se and Te. Next, the chalcopyrite semiconductor thin film processing apparatus of the present invention has a gas exhaust port, and a processing container having a gas outlet and a substrate holder for holding a substrate therein,
A gas supply unit for supplying gas into the container and a gas flow rate control unit for controlling the gas supply amount are provided.

In the above structure, it is preferable to have a heating means for heating the substrate holder. Further, in the above configuration, it is preferable that a plate provided opposite to the substrate holder and a high frequency power source electrically connected to the plate are provided.

Further, in the above structure, it is preferable that an ultraviolet irradiation device is provided so as to face the substrate holder.

[0012]

According to the above-described manufacturing method of the present invention, the lower electrode is formed on the insulating substrate, and the I-III-V group I element is excessive.
An I ₂ -type chalcopyrite semiconductor thin film is formed and a gas containing a halogen element, particularly Cl ₂ , Br ₂ , HCl, HBr,
By exposing the thin film to at least one selected from HI and BCl ₃ , forming a window layer for forming a junction on the chalcopyrite semiconductor thin film, and forming a translucent upper electrode, harmful CuSe and Cu without using a solution
Heterogeneous phases such as S can be efficiently removed, and a chalcopyrite semiconductor thin film solar cell can be efficiently and rationally manufactured. Further, according to the preferable example of the present invention in which the substrate is heated to 150 to 200 ° C. when the thin film is exposed to the gas containing the halogen element, excellent solar cell characteristics can be obtained. Further, according to the preferable example of the present invention in which the gas containing the halogen element is gas plasma or is radicalized, the reactivity of the halogen element is enhanced. Further, the group I element is Cu, the group III element is at least one of In and Ga, or the group VI element is S, Se and T.
According to the preferable example of the present invention, which is at least one of e, a solar cell having excellent crystallinity can be manufactured.

Next, according to the chalcopyrite semiconductor thin film processing apparatus of the present invention, a processing container having a gas exhaust port, having a gas ejection port and a substrate holder for holding a substrate therein, and the above processing are provided. By providing the gas supply unit for supplying the gas into the container and the gas flow rate control unit for controlling the supply amount of the gas, it is possible to realize the processing apparatus suitable for the manufacturing method of the present invention. Further, according to a preferred example of the present invention in which a heating means for heating the substrate holder is provided, the substrate can be processed while being heated to 150 to 200 ° C. Further, according to the preferable example of the present invention in which the plate provided opposite to the substrate holder and the high frequency power source electrically connected to the plate are provided, halogen gas can be turned into plasma. Further, according to a preferred example of the present invention in which an ultraviolet irradiation device is provided opposite to the substrate holder, the halogen gas can be radicalized by ultraviolet rays.

[0014]

【Example】

(Embodiment 1) FIG. 1 shows an apparatus of this embodiment. The size of this device varies depending on the size of the substrate, but it is 10 x 10
When processing a substrate of about cm, the diameter is usually 200 mm
× The size is about 200 mm high with each control system attached to the container. In this process, as shown in FIG. 4A, Mo is formed as the lower electrode 2 on the glass substrate 1 by sputtering, and Cu-excessive CuInS ₂ thin film 3 (Cu:
30 at%, In: 23 at%, S: 47 at%) is used after being formed by the multi-source vapor deposition method. Figure 4
The thickness of each layer is: glass substrate 1: about 1 mm, lower electrode 2: about 1 μm, CuInS ₂ thin film 3: about 2.5 μm. The preferable range of the thickness of each layer is as follows: Substrate 1: 0.5-2
mm, lower electrode 2: 1 μm, semiconductor thin film 3: 2
It is about 3 μm. As mentioned above, Cu-rich C
The uInS ₂ thin film is a film (10 to 100 Ω ⁻¹ cm ⁻¹ ) having a low electrical resistance due to the presence of a different phase such as CuS. A substrate on which such a Cu-excessive CuInS ₂ thin film is formed is installed in the substrate holder 7 shown in FIG. 1, and the gas flow source 11 and the gas flow controller 10 and the gas ejection port 9
Was exposed to the gas by introducing BCl ₃ gas into the vessel 6 via At this time, the inside of the container is 100 to 700 To
It is maintained at a slightly reduced pressure of rr and the gas flow rate is about 50 s.
It is ccm. When the CuInS ₂ thin film is treated for 30 minutes in this state, the film has a slightly high electrical resistance (0.01-0.
001 Ω ⁻¹ cm ⁻¹ ) is obtained. This phenomenon is caused by CuIn
It shows that CuS mixed with the S ₂ thin film was removed by this treatment. The processing time was 30 to 60 minutes. Furthermore, when the substrate holder 7 was kept at 150 to 200 ° C. by the substrate heater 8 and the same treatment was performed, the treatment time was shortened to about 5 minutes. However, 200
If the treatment is performed at a temperature higher than ° C, the composition of the CuInS ₂ thin film itself changes, which is not preferable. After the process described above, as in the conventional case, as shown in FIG.
The window layer 4 of S was formed by vapor deposition to a thickness of about 0.1 μm, and ITO was formed as the transparent conductive film 5 by sputtering to a thickness of about 0.5 μm to complete the solar cell.
Preferable thickness ranges of the window layer 4 and the transparent conductive film 5 are about 0.05 to 0.1 μm and 0.2 to 1 μm, respectively.
The CuInS ₂ thin-film solar cell of this example exhibited a conversion efficiency of 10%, which was comparable to the KCN treatment of the conventional process.

According to this embodiment, CuInS containing excess Cu is used.
e ₂ , CuInTe ₂ and Cu (In, Ga) (S, Se,
It was also effective in the production of a mixed crystal thin film solar cell of Te). Also, as the halogen gas used, Cl ₂ , Br ₂ , HCl, HBr, and HI were effective because they had the same action in addition to BCl ₃ .

(Embodiment 2) FIG. 2 shows an apparatus of this embodiment.
You This process is based on the glass-based method as shown in Fig. 4 (a).
Mo is sputtered on the plate 1 as the lower electrode 2.
Formed with Cu excess CuInS₂Thin film (Cu: 30 original)
%, In: 23 atomic%, S: 47 atomic%)
This is the process used after forming by the method. Already mentioned
As shown in Cu₂CuS, etc. for the thin film
Electrically low resistance film (10-
100Ω^-1cm^-1). Such Cu excess Cu
InS ₂The substrate on which the thin film is formed is shown in FIG.
Installed on the dar 7, gas flow controller from the gas supply source 11
BCl through 10 and gas outlet 9₃Gas in container 6
Exposed to gas by introduction. At this time, in the container
The vacuum degree is about 1 Torr. The high frequency power supply 13 is
It is electrically connected to rate 15. The gas is 13.
Plasma discharge of about 10W by high frequency of 56MHz
Is in a state. The gas flow rate is about 50 sccm. this
CuInS for 5 minutes₂Electrically when processing thin films
Highly resistant film (0.01-0.001Ω^-1cm^-1)But
can get. This phenomenon is caused by CuInS₂Mixed with thin film
Showing that CuS was removed by this process
There is. After the process described above, as shown in FIG.
As shown in (b), the CdS window layer 4 is formed by vapor deposition.
Then, ITO is formed by sputtering as the transparent conductive film 5.
Then the solar cell was completed. CuInS of this embodiment₂Thin film
The solar cell shows a conversion efficiency of 10%,
It was as good as KCN treatment of Su.

According to this embodiment, CuInS containing excess Cu is used.
e ₂ , CuInTe ₂ and Cu (In, Ga) (S, Se,
It was also effective for a mixed crystal thin film solar cell of Te). In addition to BCl ₃ , the halogen gas used is C
l ₂ , Br ₂ , HCl, HBr, and HI had similar effects and were effective.

(Embodiment 3) FIG. 3 shows an apparatus of this embodiment.
You This process is based on the glass-based method as shown in Fig. 4 (a).
Mo is sputtered on the plate 1 as the lower electrode 2.
Formed with Cu excess CuInS₂Thin film (Cu: 30 original)
%, In: 23 atomic%, S: 47 atomic%)
This is the process used after forming by the method. Already mentioned
As shown in Cu₂CuS, etc. for the thin film
Electrically low resistance film (10-
100Ω^-1cm^-1). Such Cu excess Cu
InS ₂The substrate on which the thin film is formed is shown in FIG.
Installed on Dar 7, BCl₃Gas is supplied from the gas supply source 11.
Through the flow rate control device 10 and the gas ejection port 9 into the container 6
Exposed by introducing. At this time, the vacuum in the container
The pressure is maintained at a slightly reduced pressure of 100 to 700 Torr.
Halogen gas is emitted from an ultraviolet lamp (heavy
It is in a radical state by the hydrogen lamp) 14. Of gas
The flow rate is about 50 sccm. CuI for 5 minutes in this state
nS₂A film with slightly higher electrical resistance when processed with a thin film
(0.01-0.001Ω^-1cm^-1) Is obtained. this
The phenomenon is CuInS ₂CuS mixed with thin film is
It has been removed by the process. Described above
After the solid process, it is shown in Fig. 4 (b) as before.
Window layer 4 of CdS is formed by a vapor deposition method to form a transparent conductive film 5.
Then, ITO is formed by sputtering to complete the solar cell.
did. CuInS of this embodiment₂Thin-film solar cells have a conversion effect
The rate is 10%, which is comparable to conventional KCN treatment.
There was no color.

According to this embodiment, Cu-rich CuInS
e ₂ , CuInTe ₂ and Cu (In, Ga) (S, Se,
It was also effective for a mixed crystal thin film solar cell of Te). Further, as a gas containing a halogen element to be used, BCl
_In addition to ₃ , Cl ₂ , Br ₂ , HCl, HBr, and HI had similar effects and were effective.

[0020]

As described above, according to the manufacturing method of the present invention, the lower electrode is formed on the insulating substrate to form the I-III-VI ₂ type chalcopyrite semiconductor thin film having an excessive amount of the group I element. , A gas containing a halogen element, especially Cl ₂ , B
At least one selected from r ₂ , HCl, HBr, HI, and BCl ₃ is exposed to the thin film, a window layer for forming a junction is formed on the chalcopyrite semiconductor thin film, and a transparent upper electrode is formed. By forming, a hetero phase such as CuSe or CuS can be efficiently removed without using a harmful solution, and a chalcopyrite semiconductor thin film solar cell can be efficiently and rationally manufactured.

Next, according to the chalcopyrite semiconductor thin film processing apparatus of the present invention, a processing container having a gas exhaust port, having a gas ejection port and a substrate holder for holding a substrate therein, and the above processing are provided. By providing the gas supply means for supplying the gas into the container and the gas flow rate control means for controlling the supply amount of the gas, it is possible to provide the processing apparatus suitable for the manufacturing method of the present invention.

Therefore, according to the present invention, the chalcogenide compound of the group I element existing on the surface of the I-III-VI ₂ type chalcopyrite semiconductor thin film and the crystal grain boundary in which the group I element is excessive is exposed to a gas containing a halogen element. By doing so, it becomes possible to remove it, and a dry process can be realized.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of a chalcopyrite thin film processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing the configuration of a chalcopyrite thin film processing apparatus according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram showing a configuration of a chalcopyrite thin film processing apparatus according to a third embodiment of the present invention.

4A is a cross-sectional view of a semiconductor thin film before processing according to an embodiment of the present invention, and FIG. 4B is a cross-sectional view of a semiconductor thin film after processing.

FIG. 5 is a schematic cross-sectional view showing a conventional method for treating a I-III-VI ₂ type chalcopyrite thin film.

[Explanation of symbols]

1 Insulating Substrate 2 Lower Electrode 3 I-III-VI ₂ Type Chalcopyrite Semiconductor Thin Film 4 Window Layer 5 Translucent Upper Electrode 6 Semiconductor Thin Film Processing Container 7 Substrate Holder 8 Substrate Heater 9 Gas Jet 10 Gas Flow Control Device 11 Gas supply device 12 Gas outlet 13 High frequency power supply 14 Ultraviolet lamp 15 Plate 54 Container 55 KCN solution

Claims (6)

(57) [Claims] 1. A lower electrode is formed on an insulative substrate, a I-III-VI ₂ type chalcopyrite semiconductor thin film having an excess of a group I element is formed, and the thin film is exposed to a gas containing a halogen element . Removing the foreign phase in the thin film ,
A step of forming a window layer for forming a junction on the chalcopyrite semiconductor thin film and forming a translucent upper electrode is included.
If the gas containing halogen element is gas plasma or
A method for producing a chalcopyrite semiconductor thin film solar cell which is a gas that has been calcified. 2. The gas containing a halogen element is Cl ₂ or Br.
_The method for producing a chalcopyrite semiconductor thin film solar cell according to claim 1, wherein the method is at least one selected from ₂ , HCl, HBr, HI, and BCl ₃ . 3. The method for producing a chalcopyrite semiconductor thin film solar cell according to claim 1, wherein the substrate is heated to 150 to 200 ° C. when the thin film is exposed to a gas containing a halogen element. 4. The method for producing a chalcopyrite semiconductor thin film solar cell according to claim 1, wherein the Group I element is Cu. 5. The method for producing a chalcopyrite semiconductor thin film solar cell according to claim 1, wherein the Group III element is at least one of In and Ga. 6. The method for producing a chalcopyrite semiconductor thin film solar cell according to claim 1, wherein the Group VI element is at least one of S, Se and Te.