JP3272163B2 - Method for forming transparent conductive film and method for manufacturing photovoltaic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates, SnO ₂ doped with SnO ₂ film or its fluorine example utilized in a transparent electrode of a photovoltaic device: a method of forming a F film.

[0002]

2. Description of the Related Art Among photovoltaic devices typified by solar cells, a photovoltaic device using a thin-film semiconductor, which has attracted attention as being easy to increase the area and reduce the cost, is another commercial product. Since competition with electricity is relatively advantageous in terms of cost, its development is progressing rapidly. A typical configuration of a photovoltaic device using such a thin film semiconductor as a photoelectric conversion layer is a configuration in which a transparent electrode, a pin-junction amorphous silicon (a-Si) film, and a back electrode are sequentially laminated on a glass substrate. is there.

[0003] Then, as the transparent electrode, the cost, in terms of both properties have been used well SnO ₂ film formed by normal pressure CVD method, also the fluorine SnO ₂ in order to reduce the specific resistance of the SnO ₂ Doped SnO ₂ : F films have also been used. By doping with fluorine, a crystal grain size is grown to about 300 nm to form a SnO ₂ transparent electrode having a so-called textured structure on the surface, thereby improving the characteristics as a photovoltaic device.

[0004] Such a transparent conductive film made of a SnO ₂ : F film has been conventionally formed as follows. 500 ℃
The glass substrate is carried into a normal pressure CVD apparatus whose temperature has been raised to about the same, and SnCl ₄ , H ₂ O, O _2, and F dopant gases (CF ₃ CH ₂ F, CHF ₃ , CH ₃ CH) are used as material gases.
F _2, etc.) are introduced into the atmospheric pressure CVD apparatus, and a SnO ₂ : F film is formed on a glass substrate by thermal decomposition. Here, H ₂ O acts as an oxygen source of SnO ₂ ,
O ₂ acts to promote the release of fluorine from the F dopant gas.

There is also known a method of forming a SnO ₂ : F film by using a combination of material gases different from the above-mentioned method. This method uses Sn (CH ₃ ) as a material gas.
₄ , O ₂ and F dopant gas (CF ₃ CH ₂ F, CH
With F _3, CH ₃ CHF _2, etc.), and forms at atmospheric thermal CVD method similar to the method described above. In this case, O ₂ has a function of serving as an oxygen source of SnO ₂ and a function of releasing fluorine from the F dopant gas.

[0006]

However, with any of the above-described forming methods, it is difficult to grow all the SnO ₂ crystals to a uniform grain size of about 300 nm, and some of them do not grow. Sufficient and often small defects may be seen. Such a minute defect causes a bulk leak in a-Si and is a major cause of deterioration of photoelectric conversion characteristics.

[0007] Further, as in the above-described forming method, S is formed by releasing fluorine from the F dopant gas with O _2.
The specific resistance of the nO ₂ : F film is limited to about 1 × 10 ⁻³ Ω · cm, and SnO ₂ : used for a transparent electrode for a photovoltaic device is:
This value cannot be said to be a sufficient value for the F film.

[0008] The present invention has been made in view of such circumstances.
And SnCl_FourH as an oxygen source for_TwoD in addition to O_Two
By using O (heavy water), SnO_TwoCrystal growth
Good surface shape with improved uniformity and fewer defects (texture
(Char shape) _TwoFilm can be formed
Method for forming a transparent conductive film, and using the method
Light with higher conversion efficiency
An object of the present invention is to provide a method for manufacturing an electromotive device.

Another object of the present invention is to provide an F dopant gas.
O as a gas that releases fluorine from _TwoO instead of
_ThreeBy using (ozone), SnO having lower resistance can be used.
_Two: Method of forming transparent conductive film capable of forming F film
And the conversion efficiency by using this forming method
Of manufacturing a photovoltaic device capable of increasing power compared to conventional
The purpose is to provide.

[0010]

The method for forming a transparent conductive film according to claim 1 present in SUMMARY OF THE INVENTION, in a method of forming a transparent conductive film made of SnO ₂ film, SnCl ₄ as a material gas,
The transparent conductive film is formed using H ₂ O and D ₂ O.

According to a second aspect of the present invention, in the method for forming a transparent conductive film according to the first aspect, the ratio of D ₂ O to H ₂ O is increased as the formation of the transparent conductive film proceeds. It is characterized by the following.

A method of manufacturing a photovoltaic device according to claim 3 of the present application is a method of manufacturing a photovoltaic device having a transparent electrode made of a SnO ₂ film on a substrate. The transparent electrode is formed on the substrate by carrying in, and introducing SnCl ₄ , H ₂ O, and D ₂ O as material gases into the atmospheric pressure CVD apparatus.

According to a fourth aspect of the present invention, there is provided a method for forming a transparent conductive film composed of a SnO ₂ : F film, wherein a tin compound, ozone and F
The transparent conductive film is formed using a dopant gas.

According to a fifth aspect of the present invention, there is provided a method of manufacturing a photovoltaic device having a transparent electrode made of a SnO ₂ : F film on the substrate, wherein the substrate is formed by a normal pressure CVD apparatus. The transparent electrode is formed on the substrate by introducing a tin compound, ozone and an F dopant gas as material gases into the atmospheric pressure CVD apparatus.

[0015]

In the first invention, H ₂ O and D ₂ O are used as an oxygen source when forming the SnO ₂ film. Since not only H ₂ O alone but also D ₂ O is added, SnO ₂ to be crystal-grown has high uniformity and a good surface shape with few defects can be obtained. In the first invention, the ratio of D ₂ O to H ₂ O used is increased as the crystal growth of the SnO ₂ film progresses. When H ₂ O is used as the oxygen source, a SnO ₂ film having low adhesion of SnO ₂ crystal but high adhesion to the underlying substrate can be formed as compared with the case where D ₂ O is used as the oxygen source. . In the initial stage of film formation, the ratio of H ₂ O is increased to grow a SnO ₂ film serving as a nucleus that easily adheres to the underlying substrate, and the ratio of D ₂ O is gradually increased as the film formation proceeds. To grow a high quality SnO ₂ film. Therefore, in the photovoltaic device using the SnO ₂ film formed in the first invention as a transparent electrode, the conversion efficiency can be improved.

In the second invention, O ₃ is used instead of O ₂ to release fluorine from the F dopant gas.
Therefore, as compared with the case of using O _2, F dopant decomposition efficiency is improved in gas, a greater amount of fluorine further with SnO ₂ is captured SnO _2: attained the resistance of the F layer. Therefore, in the photovoltaic device using the SnO ₂ : F film formed in the second invention as a transparent electrode, improvement in conversion efficiency can be realized.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described with reference to the drawings showing the embodiments.

Embodiment 1 FIG. FIG. 1 is a block diagram of the first embodiment of the present invention.
nO _2: is a schematic diagram showing a preferred state of the method for forming the F layer. In the drawing, reference numeral 1 denotes a normal pressure CVD furnace, and 10 denotes a glass substrate on which an SnO ₂ : F film is to be formed. The glass substrate 10 carried into the normal pressure CVD furnace 1 is conveyed in the arrow direction. It has become so. Above the transfer area of the glass substrate 10 in the atmospheric pressure CVD furnace 1, from the upstream side to the downstream side in the transfer direction, n film-forming heads 2-1, 2-2, 2-3, ..., 2 -n are arranged in columns in this order. n film forming heads
2-1, 2-2, 2-3, ..., 2-n are SnCl ₄ gas sources 3-1, 3-2, 3-3, ..., 3-n provided outside the atmospheric pressure CVD furnace 1. H ₂ O / D
₂ O gas source 4-1, 4-2, 4-3, ..., 4-n, O ₂ gas source 5-1, 5-
2, 5-3, ..., 5-n, F dopant gas source 6-1, 6-2, 6-3,
..., 6-n.

Each SnCl_FourGas source 3-1, 3-2, 3-3,…, 3-
From n, the connected film forming heads 2-1, 2-2, 2-3, ...,
SnCl identical to 2-n_FourGas is supplied and each O_Two
From the gas sources 5-1, 5-2, 5-3,…, 5-n,
Same O for membrane heads 2-1, 2-2, 2-3, ..., 2-n_TwoGas supply
, 6-2, 6-3,..., 6-n
From the connected deposition heads 2-1, 2-2, 2-3, ..., 2-
n is supplied with the same F dopant gas
I have. The F dopant gas is CF _ThreeCH_Two
F, CHF_Three, CH_ThreeCHF_TwoUse etc.

However, each H_TwoO / D_TwoO gas source 4-1, 4-2,
From 4-3, ..., 4-n, H_TwoO
/ D_TwoO-containing gas is connected to each of the connected deposition heads 2-1 and 2-
2, 2-3, ..., 2-n. Each H
_TwoO / D_TwoO gas sources 4-1, 4-2, 4-3, ..., 4-n
, 2-2, 2-3, ..., 2-n
The flow ratio of the combined gas is as shown in FIG. In FIG.
In the figure, the horizontal axis is from the upstream side in the transport direction of the glass substrate 10.
N film-forming heads 2-1, 2-2, 2 arranged over the downstream side
-3,..., 2-n, and the vertical axis indicates D with respect to the total amount_Two
O gas ratio (D _TwoO flow rate / (H_TwoO flow rate + D_TwoO flow
Amount)). Deposition head 2- located at the most upstream side
1 contains D_TwoA gas (H_TwoO alone
Gas) is H _TwoO / D_TwoIt is supplied from the O gas source 4-1.
Further, the film deposition head 2-n arranged at the most downstream side has D_TwoO
A gas having a gas ratio of 1 (D_TwoO alone gas) is H_Two
O / D _TwoIt is supplied from an O gas source 4-n. Between the two
The other film formation heads 2-2, 2-3,…
D as you go_TwoH with increasing proportion of O gas_TwoO
/ D_TwoO mixed gas corresponds to H_TwoO / D_TwoO gas source 4-2,
 4-3, ... respectively.

While the glass substrate 10 is transported in the atmospheric pressure CVD furnace 1 from directly below the film-forming head 2-1 on the most upstream side to directly below the film-forming head 2-n on the most downstream side, each film is formed. Head 2-1,
From 2-2, 2-3, ..., 2-n, SnCl ₄ , H
₂ O / D ₂ O, O ₂ , F dopant gas is injected,
SnO ₂ : F is sequentially grown on the glass substrate 10.

Next, the operation will be described. First, the glass substrate 10 on which a film is to be formed is loaded into the atmospheric pressure CVD furnace 1 and transported therein. Each film deposition head 2-1, 2-2, 2-3,…, 2-
n to SnCl ₄ gas, H ₂ O / D ₂ O mixed gas, O ₂
The gas and the F dopant gas are sprayed onto the glass substrate 10 to be conveyed, and a SnO ₂ : F film is formed thereon. Here, a mixed gas having a high H ₂ O content is introduced at the start of film formation, and a mixed gas having a gradually increased D ₂ O content is introduced as the film formation proceeds. Accordingly, a SnO ₂ : F film having high adhesiveness is formed on the glass substrate 10 side,
As the distance from the glass substrate 10 increases, a SnO ₂ : F film having excellent crystal growth uniformity is formed.

In Example 1, H ₂ was used as the oxygen source of SnO _2.
Since D ₂ O is used in addition to ₂ O, the growing SnO ₂
The uniformity of the crystal is improved, and a high-quality SnO ₂ : F film with few defects and no unevenness on the surface can be obtained. Then, an a-Si photovoltaic device using the SnO ₂ : F film formed in Example 1 as a transparent electrode was manufactured.
Conventional SnO ₂ formed using only H ₂ O:
As a result of comparing the conversion efficiency with the conventional a-Si photovoltaic device using the F film as the transparent electrode, an improvement of 5% was confirmed.

In the first embodiment, SnO ₂ :
Although the case where the F film is formed has been described, it goes without saying that the same can be applied to the case where a SnO ₂ film not doped with fluorine is formed. In this case, it is not necessary to introduce O ₂ and F dopant gases.

Embodiment 2 FIG. FIG. 3 is a diagram showing S in Embodiment 2 of the present invention.
FIG. 3 is a schematic view showing an embodiment of a method of forming an nO ₂ : F film, in which 11 is a normal pressure CVD furnace, and 10 is a glass substrate on which an SnO ₂ : F film is to be formed. A film forming head 12 for injecting a material gas onto the glass substrate 10 is provided in an upper part of the normal pressure CVD furnace 11. The film forming head 12 is a normal pressure CVD furnace
N ₂ gas source 13 11 provided outside, SnCl ₄ gas source 14, H ₂
They are connected to an O gas source 15 and an F dopant gas source 16, respectively. The film forming head 12 is also connected to an O ₂ gas source 18 via an ozonizer 17 that converts oxygen into ozone.

N_TwoCarry from the gas source 13 to the deposition head 12
N as Agus_TwoGas is supplied and SnCl_FourMoth
Source 14, H_TwoO gas source 15 and F dopant gas source 16
SnCl is used as a material gas in the film forming head 12._FourGas, H_TwoO
Gas and F dopant gas are supplied.
You. Also, O_TwoO from gas source 18_TwoGas is ozonizer 17
O changed by_ThreeGas is also supplied to the deposition head 12.
It is supposed to be. In addition, as F dopant gas
Is the same as in the first embodiment._ThreeCH_TwoF, CHF _Three, C
H_ThreeCHF_TwoEtc. can be used.

Then, the gas carried into the atmospheric pressure CVD furnace 11 is
From the film forming head 12 on the glass substrate 10, N _TwoGas, SnCl_Four
Gas, H_TwoO gas, F dopant gas (the following theory of this example)
Ming is CF_ThreeCH_TwoF gas), O_ThreeGas injected
And SnO on the glass substrate 10_Two: As F grows
Has become.

Next, the operation will be described. First, a glass substrate 10 on which a film is to be formed is carried into a normal-pressure CVD furnace 11. Then, the substrate temperature was set to 500 ° C., and the flow rates of the respective material gases were respectively SnCl ₄ : 0.8 g / min, H ₂ O: 2.9 g / min, CF ₃ CH ₂ F: 2.8 l / min, O ₃ : 2
Each gas is sprayed onto the glass substrate 10 by the film forming head 12 at a setting of about 10 liters / minute, and a SnO ₂ : F film is formed thereon.

In the second embodiment, since O ₃ is used to release fluorine from the F dopant gas, the thermal decomposition of the F dopant becomes easier and a larger amount of fluorine is used as compared with the conventional example using O _2. Is taken into SnO ₂ to lower the specific resistance. SnO ₂ : F in Example 2 and Conventional Example
A comparison of the specific resistance of the films is shown in FIG. In FIG.
Δ indicates the case of the second embodiment, and ─ indicates the case of the conventional example. In FIG. 4, the horizontal axis indicates the flow rate (liter / minute) of O ₂ (conventional example) and O ₃ (present embodiment 2), and the vertical axis indicates the specific resistance [× 10 ⁻⁴ Ω · cm]. Is shown. As can be seen from the results of FIG. 4, the specific resistance of the SnO ₂ : F film can be reduced to about half in the _second embodiment as compared with the conventional example.

In the second embodiment, SnO ₂ : F having a low specific resistance is used.
Since a film can be formed, the Sn formed in Example 2 can be formed.
In a photovoltaic device using an O ₂ : F film as a transparent electrode, it can be expected that photoelectric characteristics such as conversion efficiency will be greatly improved.

In the second embodiment, the SnO_Two:
SnCl as tin source for F film_FourBut with a tin source
And Sn (CH_Three)_FourIs used, the conventional O
_TwoO_Three The same effect can be obtained by replacing with. What
In this case, O _Three Is SnO_TwoThe oxygen source
H, as shown in the above-described second embodiment._Two
No introduction of O gas is required.

[0032]

As described in detail above, in the first invention, S
Since D ₂ O is used in addition to H ₂ O as an oxygen source of nO ₂ , the uniformity of crystal growth of SnO ₂ can be improved and a SnO ₂ film having a good surface shape with few defects can be formed. In the photovoltaic device using the transparent conductive film formed as described above as the back electrode, the photoelectric characteristics including the conversion efficiency can be significantly improved.

Also, in the second invention, since O ₃ is used instead of O ₂ as a decomposer for the F dopant gas, a SnO ₂ : F film having a low specific resistance can be formed. In a photovoltaic device using the formed transparent conductive film as a back electrode, photoelectric characteristics including conversion efficiency can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an embodiment of a method for forming a SnO ₂ : F film according to a first embodiment of the present invention.

FIG. 2 is a graph showing a ratio of D ₂ O in a D ₂ O / H ₂ O mixed gas introduced from each film forming head in Example 1.

FIG. 3 is a schematic view showing an embodiment of a method for forming a SnO ₂ : F film according to a _second embodiment of the present invention.

FIG. 4 is a graph showing a comparison of the specific resistance of a SnO ₂ : F film between Example 2 and a conventional example.

[Explanation of symbols]

1 Atmospheric pressure CVD furnace 2-1, 2-2, 2-3, ..., 2-n Film formation head 3-1, 3-2, 3-3, ..., 3-n SnCl ₄ gas source 4-1, 4-2, 4-3, ..., 4- n H 2 O / D 2 O gas source 5-1, 5-2, 5-3, ..., 5-n O 2 gas source 6-1, 6-2 , 6-3,..., 6-n F dopant gas source 10 glass substrate 11 atmospheric pressure CVD furnace 12 film formation head 13 N ₂ gas source 14 SnCl ₄ gas source 15 H ₂ O gas source 16 F dopant gas source 17 ozonizer 18 O ₂ gas source

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-210715 (JP, A) JP-A-2-168507 (JP, A) JP-A-63-61959 (JP, A) JP-A-5-210 339732 (JP, A) JP-A-5-239635 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 31/04-31/078 H01B 5/00-5/16 H01B 13/00-13/34 C01G 19/02 C23C 16/00-16/56

Claims (5)

(57) [Claims] 1. A method for forming a transparent conductive film comprising a SnO ₂ film, wherein the transparent conductive film is formed using SnCl ₄ , H ₂ O and D ₂ O as material gases. Formation method. 2. The method for forming a transparent conductive film according to claim 1, wherein the ratio of D ₂ O to H ₂ O is increased as the formation of the transparent conductive film proceeds. 3. A method for manufacturing a photovoltaic device having a transparent electrode made of a SnO ₂ film on a substrate, wherein the substrate is loaded into an atmospheric pressure CVD apparatus, and SnCl is supplied as a material gas into the atmospheric pressure CVD apparatus. _{4. A} method for manufacturing a photovoltaic device, comprising forming the transparent electrode on the substrate by introducing H ₂ O and D ₂ O. 4. A method for forming a transparent conductive film comprising a SnO ₂ : F film, wherein the transparent conductive film is formed using a tin compound, ozone and an F dopant gas as a material gas. Formation method. 5. A method for manufacturing a photovoltaic device having a transparent electrode made of a SnO ₂ : F film on a substrate, wherein the substrate is carried into an atmospheric pressure CVD apparatus, and a material gas is introduced into the atmospheric pressure CVD apparatus. Forming a transparent electrode on the substrate by introducing a tin compound, ozone and an F dopant gas.