JP2001274435A - Forming method for p-type noncrystalline semiconductor film and producing method for photoelectric converting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forming method for p-type noncrystalline semiconductor film, with which lowering in the light transmittance of a translucent conductive film can be suppressed. SOLUTION: While using a chlorine-containing gas (SiH2Cl2 gas) as a raw material gas, a p-type noncrystalline semiconductor film 3 is formed on a glass substrate 1/transmissive conductive film 2 (SnO2 film) by a plasma CVD method (b). An i-type noncrystalline semiconductor film 4 and an n-type noncrystalline semiconductor film 5 are successively formed on the p-type noncrystalline semiconductor film 3 (c). In the case of forming the p-type noncrystalline semiconductor film 3, there are the conditions of substrate temperature <=210 deg.C and reaction pressure >=100 mTorr, more preferably, substrate temperature <=180 deg.C and reaction pressure >=200 mTorr.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for forming a p-type amorphous semiconductor film on a light-transmitting conductive film, and a method for manufacturing a photoelectric conversion element using the method.

[0002]

2. Description of the Related Art A photoelectric conversion element such as a solar cell or an optical sensor using an amorphous semiconductor film such as amorphous silicon or microcrystalline silicon is formed on a transparent substrate made of glass, plastic, or the like by using SnO _2. , ITO, etc., and p-type, i
It is manufactured by forming each of the amorphous semiconductor film of n-type and n-type and a highly reflective conductive film of Ag, Al or the like in this order.

As a method for forming each of these p-type, i-type and n-type amorphous semiconductor films, a vapor phase growth method typified by a plasma CVD method is usually used. -type amorphous semiconductor film gas mixture obtained by mixing the p-type doping gas such as B ₂ H ₆ in SiH ₄ gas to the formation of, i-type amorphous semiconductor film SiH ₄ gas to form the, n-type amorphous semiconductor film Is formed by adding n such as PH _{3 to} SiH ₄ gas.
It is common to use a mixed gas into which a mold doping gas is mixed.

[0004]

When forming a p-type amorphous semiconductor film on a light-transmitting conductive film, if the forming temperature is increased or the applied high-frequency power is increased, the light-transmitting property is reduced. A phenomenon occurs in which the light transmittance of the conductive film decreases. This is considered to be because hydrogen contained in the source gas acts on the light-transmitting conductive film to reduce the light-transmitting conductive film. When such a decrease in light transmittance occurs, the amount of light incident on the i-type amorphous semiconductor film decreases, which causes a decrease in photoelectric conversion characteristics. Therefore, attempts have been made to form a p-type amorphous semiconductor film under relaxed conditions so that the light transmittance of the light-transmitting conductive film is less reduced. However, a sufficient effect has not been obtained, and further improvement of the formation method is desired.

[0005] The present invention has been made in view of such circumstances, and by using a gas containing chlorine as a raw material gas, it is possible to suppress a decrease in the light transmittance of the light-transmitting conductive film as described above. Forming method of type amorphous semiconductor film, and
An object is to provide a method for manufacturing a photoelectric conversion element using the same.

[0006]

According to a first aspect of the present invention, there is provided a method of forming a p-type amorphous semiconductor film on a light-transmitting conductive film by using a vapor phase growth method. ,
A gas containing chlorine as a constituent element is used as a source gas.

In the first invention, a p-type amorphous semiconductor film is formed on a translucent conductive film using a source gas containing chlorine as a constituent element. Accordingly, the film formation surface is covered with chlorine instead of hydrogen, and a decrease in light transmittance of the light-transmitting conductive film can be suppressed.

According to a second aspect of the present invention, in the method for forming a p-type amorphous semiconductor film according to the first aspect, the source gas is SiH ₂
It is a Cl ₂ gas.

In the second invention, SiH ₂ Cl ₂ gas is used as a source gas. The SiH ₂ Cl ₂ gas has a low cost among gases containing chlorine, and can reduce the cost.

The method of forming a p-type amorphous semiconductor film according to a third aspect of the present invention is the method according to the second aspect, wherein the formation temperature is set to 210 ° C. or lower and the reaction pressure is set to 100 mTorr or higher. Is formed.

In the third invention, the conditions for the vapor phase growth method are that the formation temperature is 210 ° C. or less and the reaction pressure is 100 mT
orr or more. Therefore, the effect of suppressing a decrease in light transmittance of the light-transmitting conductive film can be increased.

A method for forming a p-type amorphous semiconductor film according to a fourth aspect of the present invention is the method according to the second aspect, wherein the formation temperature is set to 180 ° C. or less and the reaction pressure is set to 200 mTorr or more. Is formed.

In the fourth invention, the conditions for the vapor phase growth method are that the formation temperature is 180 ° C. or less, and the reaction pressure is 200 mT
orr or more. Therefore, a p-type amorphous semiconductor film having a large optical band gap can be formed.

According to a fifth aspect of the invention, there is provided a method of manufacturing a photoelectric conversion element, comprising: forming a p-type amorphous semiconductor film on a light-transmitting conductive film by using any one of the first to fourth aspects; Sequentially forming an i-type amorphous semiconductor film and an n-type amorphous semiconductor film on the p-type amorphous semiconductor film.

In the fifth aspect, a light-transmitting conductive film in which a decrease in light transmittance is suppressed can be formed, so that a photoelectric conversion element having good photoelectric conversion characteristics can be obtained.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described with reference to its embodiments.
This will be specifically described with reference to the drawings shown. As raw material gas
SiH_TwoCl_TwoPlasma CVD method using gas
Plate temperature 180-250 ° C, reaction pressure 30-300m
Torr, high frequency power 3-5W, hydrogen dilution rate 0-
Glass / SnO under various conditions by changing 10 times
_TwoA non-doped amorphous semiconductor film is formed on a substrate
Glass / SnO as invention example_Two/ Non-doped amorphous semi
A conductor laminate was produced. In addition, SiH is used as a source gas.
_FourBy the plasma CVD method using gas,
Under various similar conditions, a non-doped amorphous semiconductor film
Glass / SnO_TwoFormed on a substrate and used as a comparative example
Las / SnO_Two/ Creates a stacked body of non-doped amorphous semiconductor
Made.

The light transmittance of these laminates was measured. In this case, the light transmittance is defined based on the following equation (1) by compensating for the influence of reflection. Light transmittance = T / (1-R) (1) where T: measured value of light transmittance R: light reflectance

The relative value (normalized light transmittance) of the light transmittance measured for each of the laminates to the light transmittance of the glass / SnO ₂ laminate was calculated. A specific calculation method of the normalized light transmittance will be described. FIG.
Is a graph (horizontal axis: wavelength, vertical axis: light transmittance) showing the wavelength dependence of the light transmittance of each laminate as described above. In the figure, a represents the characteristics of the glass / SnO ₂ laminate, b represents the characteristics of the laminated body of glass / SnO ₂ / non-doped amorphous semiconductor. The normalized light transmittance is specifically defined based on the following equation (2). Normalized light transmittance = B / A (2) where A: glass / integral value of light transmittance of glass / SnO ₂ laminate in wavelength range of 1000 to 2500 nm B: glass / glass in wavelength range of 1000 to 2500 nm
Integral Value of Light Transmittance of Stack of SnO ₂ / Non-doped Amorphous Semiconductor In the above equation (2), the ratio is determined by the integral value in order to eliminate the influence of interference. In addition, the reason why the integrated value in the long wavelength region is adopted is that in the short wavelength region (1000 nm or less), the influence of light absorption is large, and the light transmittance characteristics of SnO ₂ cannot be evaluated correctly.

FIG. 2 shows the results of the normalized light transmittance of each of the laminates calculated as described above. Within the above-mentioned condition range, it was found that the variation in the high-frequency power and the dilution ratio of hydrogen had little effect on the light transmittance, and the light transmittance was greatly affected by the type of the source gas, the substrate temperature and the reaction pressure. Accordingly, FIG. 2 shows the types of these source gases ( _two types of SiH ₂ Cl ₂ gas and SiH ₄ gas), the substrate temperature (three types of 180 ° C., 210 ° C., and 250 ° C.), and the reaction pressure (30 mTorr). , 100mTorr, 200m
(4 types of Torr and 300 mTorr).

From the results shown in FIG. 2, SiH ₂ was used as a source gas.
When Cl ₂ gas is used, a higher normalized light transmittance is obtained than when SiH ₄ gas is used, and light of SnO ₂ (translucent conductive film) accompanying the formation of the semiconductor film is obtained. It can be seen that a decrease in transmittance can be suppressed. Such improvement can be attributed to the fact that the film formation surface was covered with chlorine instead of hydrogen.

Further, from the results of FIG. 2, S
When using iH ₂ Cl ₂ gas at a substrate temperature of 210 ° C. or less and a reaction pressure of 100 mTorr or more, 0.7
It can be seen that a high normalized light transmittance of 5 or more is obtained.

In the above example, the case where a non-doped amorphous silicon film is formed has been described.
The same measurement was performed for a case where a p-type amorphous silicon film was formed using a raw material gas obtained by adding B ₂ H ₆ gas to H ₂ Cl ₂ gas, and the normalized light transmittance was calculated. FIG. 3 shows the calculation results. In FIG. 3, the substrate temperature: 180
C. and a reaction pressure of 30 mTorr, and a case where the substrate temperature was 180 ° C. and the reaction pressure was 300 mTorr, in each of the cases where 1000 ppm of B ₂ H ₆ gas was added.

As can be seen by comparing FIG. 3 and FIG.
The case of p-type amorphous silicon also exhibits substantially the same normalized light transmittance characteristics as non-doped amorphous silicon. This is because the amount of B ₂ H _{6 to be} added is as small as about 1000 ppm, so that the influence on the light transmittance is extremely small.

Next, the substrate temperature, the reaction pressure, the high-frequency power, and the hydrogen dilution rate were varied on the glass substrate by plasma CVD using SiH ₂ Cl ₂ as the raw material gas in the same manner as described above. An amorphous silicon film was formed under various conditions. Then, the optical band gap of the formed amorphous silicon film was measured. FIG. 4 shows the measurement results. As for the optical band gap, similarly to the above-described normalized light transmittance, the influence of the high-frequency power and the dilution rate of hydrogen was small, and the influence of the substrate temperature and the reaction pressure was large. Therefore, FIG.
℃, 210 ℃, 250 ℃) and the reaction pressure (3
0mTorr, 100mTorr, 200mTorr,
(4 types of 300 mTorr).

From the results shown in FIG. 4, a higher optical band gap was obtained as the substrate temperature was lower. In particular, the substrate temperature was set to 180 ° C. by using SiH ₂ Cl ₂ gas as a source gas.
Hereinafter, it is understood that a large optical band gap of 2.0 eV or more is obtained when the reaction pressure is 200 mTorr or more.

[0026] Incidentally, similarly to the light transmittance, for the optical band gap, the amount of B ₂ H ₆ gas 1000pp
When it is about m, even in the case of p-type amorphous silicon, substantially the same characteristics as in the case of non-doped amorphous silicon are exhibited. FIG. 5 shows the measurement results of the optical band gap of this p-type amorphous silicon film. The film forming conditions are the same as those for the light transmittance.

Next, a method for manufacturing the photoelectric conversion element of the present invention will be described. FIG. 6 is a schematic sectional view showing the process. First, SnO was formed on the glass substrate 1 by sputtering.
_Two films are formed to form the light-transmitting conductive film 2 (FIG. 6).
(A)). Next, a p-type amorphous semiconductor film 3 is formed on the translucent conductive film 2 by a plasma CVD method (FIG. 6).
(B)). The forming conditions at this time are shown in Table 1 below. next,
I is formed on the p-type amorphous semiconductor film 3 by the plasma CVD method.
The amorphous semiconductor film 4 and the n-type amorphous semiconductor film 5 are sequentially formed (FIG. 6C). The forming conditions at this time are shown in Table 1 below. Finally, an Ag film is formed on the n-type amorphous semiconductor film 5 by a sputtering method to form a light-reflective conductive film 6, thereby manufacturing a photoelectric conversion element as an example of the present invention (FIG. 6D )).

[0028]

[Table 1]

Further, SiH_TwoCl_TwoSiH, not gas
_FourExcept for using a gas to form a p-type amorphous semiconductor film,
Under the same conditions as those described above, a photovoltaic element as a comparative example
The child was manufactured. In the example of the present invention, as described above, the substrate temperature
Temperature to low temperature_TwoCl _TwoP formed using gas
-Type amorphous semiconductor film tends to widen the optical band gap
There is. Therefore, the primary occurrence of light absorption in the p-type amorphous semiconductor film
In order to remove the difference between the clear example and the comparative example,
CH during the formation of the p-type amorphous semiconductor film_FourMix appropriate amount of gas
Then, the optical band gap is set to that of the example of the present invention.
I tried to make them almost equal.

The substrate temperature (180 ° C., 200 ° C., 230
Table 4 below shows the short-circuit current (Isc) of the photoelectric conversion element of the present invention example in which the p-type amorphous semiconductor film 3 was formed by changing the four types (C and 250 ° C.). The values shown in Table 2 are values normalized by the short-circuit current of the photoelectric conversion element of the comparative example. By changing the substrate temperature during formation, the p-type amorphous semiconductor film 3 can be formed.
Optical band gap changes, substrate temperature is 180 ° C
, The largest short-circuit current is obtained.

[0031]

[Table 2]

As described above, according to the present invention, the p-type amorphous semiconductor film 3 can be formed on the light-transmitting conductive film 2 without greatly reducing the light transmittance unlike the conventional case. Therefore, by sequentially forming the i-type amorphous semiconductor film 4 and the n-type amorphous semiconductor film 5 on the p-type amorphous semiconductor film 3, a photoelectric conversion element having a pin structure excellent in photoelectric conversion characteristics Can be manufactured.

In the example described above, the source gas is S
has been described the case of using iH ₂ Cl ₂ gas, may be Ore contain chlorine as a constituent element, SiHCl ₃ gas,
SiH ₃ Cl gas, SiCl ₄ gas or the like may be used.

Further, the case where the amorphous silicon film is formed on the light-transmitting conductive film has been described. However, the present invention is not limited to this. Even when the microcrystalline silicon film is formed on the light-transmitting conductive film. In addition, since the film formation surface is covered with chlorine instead of hydrogen, a decrease in the light transmittance of the light-transmitting conductive film can be suppressed.

Although the p-type semiconductor film is formed by the plasma CVD method, other vapor phase growth methods such as a thermal CVD method or an optical CVD method can be used.

Although SnO ₂ is used as the light-transmitting conductive film, other materials such as ITO and ZnO may be used. Further, a tandem photoelectric conversion element having a plurality of pin structures may be used.

[0037]

As described above, according to the present invention, a p-type amorphous semiconductor film is formed on a light-transmitting conductive film by using a gas containing chlorine as a constituent element as a source gas. Is coated with chlorine instead of hydrogen, so that a decrease in light transmittance of the light-transmitting conductive film can be suppressed.

Further, since the SiH ₂ Cl ₂ gas is used as the source gas, the cost can be reduced.

The conditions for forming the p-type amorphous semiconductor film are as follows:
Forming temperature: 210 ° C. or less, reaction pressure: 100 mTorr
With the above configuration, the effect of suppressing a decrease in light transmittance of the light-transmitting conductive film can be increased.

The conditions for forming the p-type amorphous semiconductor film are as follows:
Forming temperature: 180 ° C. or less, reaction pressure: 200 mTorr
With the above, a p-type amorphous semiconductor film having a large optical band gap can be formed.

Further, since a light-transmitting conductive film in which a decrease in light transmittance is suppressed can be formed, a photoelectric conversion element having good photoelectric conversion characteristics can be manufactured.

[Brief description of the drawings]

FIG. 1 shows a laminate (glass / SnO ₂ , glass / SnO ₂₎
4 is a graph showing the wavelength dependence of the light transmittance of the (/ non-doped amorphous semiconductor).

FIG. 2 is a view showing normalized light transmittance of a laminate (glass / SnO ₂ / non-doped amorphous semiconductor).

FIG. 3 is a diagram showing normalized light transmittance of a laminate (glass / SnO ₂ / p-type amorphous semiconductor).

FIG. 4 is a diagram showing an optical band gap of a non-doped amorphous semiconductor film.

FIG. 5 is a diagram showing an optical band gap of a p-type amorphous semiconductor film.

FIG. 6 is a schematic cross-sectional view showing steps of a method for manufacturing a photoelectric conversion element of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 glass substrate 2 light-transmitting conductive film 3 p-type amorphous semiconductor film 4 i-type amorphous semiconductor film 5 n-type amorphous semiconductor film 6 light-reflective conductive film

Continued on the front page (71) Applicant 500132649 Michio Kondo 1-4-1 Umezono, Tsukuba, Ibaraki Pref. Electronic Technology Research Institute (74) The above three agents 100078868 Patent Attorney Tono Kono (72) Invention Takeshi Nakajima 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Inventor Akihisa Matsuda 1-4-1 Umezono, Tsukuba-city, Ibaraki Pref. ) Inventor Michio Kondo 1-4-1 Umezono, Tsukuba, Ibaraki Pref. AF07 BB08 BB16 CA13 DA65 DA68 5F051 AA04 AA05 CA07 CA08 CA16 DA04 FA03 FA06 FA23 GA03

Claims (5)

[Claims] 1. A method of forming a p-type layer on a light-transmitting conductive film using a vapor phase epitaxy method.
A method for forming a p-type amorphous semiconductor film, wherein a gas containing chlorine as a constituent element is used as a source gas. 2. The method for forming a p-type amorphous semiconductor film according to claim 1, wherein the source gas is a SiH ₂ Cl ₂ gas. 3. The method for forming a p-type amorphous semiconductor film according to claim 2, wherein the formation temperature is set to 210 ° C. or lower and the reaction pressure is set to 100 mTorr or higher to form the amorphous p-type amorphous semiconductor film in an amorphous state. 4. The method for forming a p-type amorphous semiconductor film according to claim 2, wherein the formation temperature is set to 180 ° C. or lower and the reaction pressure is set to 200 mTorr or higher to form the amorphous p-type amorphous semiconductor film. 5. A step of forming a p-type amorphous semiconductor film on a light-transmitting conductive film by using the method according to claim 1, and forming i-type amorphous semiconductor film on the formed p-type amorphous semiconductor film. Forming a n-type amorphous semiconductor film and an n-type amorphous semiconductor film sequentially.