JPH11266030A - Semiconductor element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the strain for increasing the photoelectric conversion efficiency, by providing a region mixed with fine crystal grains different particle diameter in a semiconductor element. SOLUTION: A reflection layer 110 made of metals such as Al, Cu, Ag2 etc., a reflection augmented layer 109 made of metallic oxides such as zinc oxide, indium oxide, tin oxide, etc., are formed on a conductive substrate made of metals such as stainless steel or an insulating substrate made of glass, etc. Next, i type semiconductor layer (a layer having a second electrical characteristics) 107, p type or n type semiconductor layer (a layer having a third electrical characteristics) 106 are formed on n type or p type semiconductor layer (a layer having a first electrical characteristics) 108 of a bottom photoelectromotive element 112. Next, an n type or p type semiconductor layer 105, an i type semiconductor layer 104 of a top photoelectromotive element 113 are deposited. Finally, a transparent electrode 102 such as ITO, etc., and a grid (collector electrode) 101 are deposited on a p type or n type semiconductor layer 103. Besides, the fine crystal is preferably in slender columnar shape in the charge shifting direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device and a method for manufacturing the same, and more particularly, to a functional semiconductor device such as a photovoltaic device and a thin film transistor and a method for manufacturing the same.

[0002]

2. Description of the Related Art A microcrystalline silicon semiconductor was announced in 1979 (S. USUI and M. KIKU).
CHI "PROPERTIES OF HEAVIL
Y DOED GD-Si WITH LOW RE
SISTIVITY "Journal of Non
e-Crystalline Solids 34 (1
979) 1-11). This paper describes that a low-resistance microcrystalline silicon semiconductor doped with phosphorus was deposited by a glow discharge method.

[0003] The same applies to A. MATSUDA, S.M.
YAMASAKI et al. , "Electric
al and Structural Property
is of Phosphorous-Doped
Glow-Discharge Si: F: H and
Si: H Films "Japan Jou
rnal of Applied Physics V
ol. 19, no. 6, JUNE, 1980 pp. L
305-L308.

The characteristics of a mixed system of boron-doped amorphous and microcrystalline silicon are described in MATSU
DA, M .; MATSUMURA et al. , “Bo
ron Doping of Hydrogenen
ated SiliconThin Films ”J
aperture Journal of Applier
d Physics Vol. 20, no. 3, MAR
CH, 1981 pp. L183-L186.

[0005] Further, regarding the structure of a system in which amorphous and microcrystals are mixed, A.A. MATSUDA, T .; YOSH
IDA et al. , “Structural Stu
dyon Amorphous-Microcryst
alline Mixed-Phase Si: HF
ilms "Japane Journalof
Applied Physics Vol. 20, N
o. 6, JUNE, 1981 pp. L439-L44
2.

However, although the possibility of applying such a mixed layer of amorphous and microcrystalline silicon to a semiconductor device such as a solar cell has been suggested so far, it has not been practically applied.

A solar cell using a microcrystalline silicon semiconductor is disclosed in US Pat. No. 4,600,801 “FULUORIN.
ATED P-DOPED MICROCRYSTAL
LINE SILICON SEMICONDUCTO
R ALLOY MATERIAL ", USP4609
771 "TANDEM JUNCTION SOLA
R CELL DEVICES INCORPORATE
ING IMPROVED MICROCRYSTAL
LINE P-DOPED SEMICONDUC
TO ALLOY MATERIAL ", USP4
775425 "P AND N-TYPE MICRO
CRYSTALLINE SEMICONDUCTOR
ALLOY MATERIAL INCLUDING
BAND GAP WIDENING ELEMENT
TS, DEVICES UTILIZING SAM
E "etc. However, the microcrystalline silicon semiconductors described therein are amorphous i
It is used for a p-type semiconductor layer or an n-type semiconductor layer of a solar cell having a pin structure using a type semiconductor layer.

On the other hand, in recent years, papers on solar cells using microcrystalline silicon for the i-type semiconductor layer have been published. For example, "ON THE WAY TOWARDS HI
GHEFFICIENCY THIN FILM SI
LICON SOLARCELLS BY THE M
ICROMORPH CONCEPT "J. Meie
r, p. Torres et. al. Mat. Re
s. Soc. Symp. Proc. Vol. 420
(1996) p. No. 3 etc. However, as the authors of the paper also recognize, a single-structure solar cell using microcrystalline silicon for the i-type semiconductor layer has an initial photoelectric conversion efficiency of 7.7%, and amorphous silicon having the same configuration. It was lower than the solar cell using.

[0009]

SUMMARY OF THE INVENTION The present inventor has determined that the conversion efficiency of a solar cell using the microcrystalline silicon semiconductor for the i-type semiconductor layer is lower than the conversion efficiency of an amorphous silicon solar cell having a similar structure. We studied diligently. In particular, transmission electron microscope and X-ray diffraction data were analyzed. as a result,
It became clear that structural strain tends to concentrate between relatively large microcrystal grains, and that many defects exist. These defects reduce the traveling property (mobility) of the photoexcited free charge and shorten the lifetime, thereby deteriorating the characteristics of the semiconductor element. Further, it has been clarified that there is a cause at the interface between the n-type semiconductor layer or the p-type semiconductor layer and the i-type semiconductor layer. That is, the present inventor has found that there are many defect levels near the interface between the n-type semiconductor layer and the i-type semiconductor layer and near the interface between the p-type semiconductor layer and the i-type semiconductor layer, and these work as recombination centers. Found. The presence of the recombination center causes a decrease in the number of photoexcited free charges in the i-type semiconductor layer and a decrease in running properties. As a result, the open-circuit voltage (Voc) and short-circuit current (Js) of the solar cell
c) The shape factor (fill factor: FF) decreases. In addition, this causes an increase in the series resistance of the solar cell and a decrease in the shunt resistance. For these reasons, the conversion efficiency of the solar cell decreases.

Further, the cause of the increase in defect levels near the interface was examined by combining a transmission electron microscope and a secondary ion mass spectrometer. As a result, an n-type semiconductor layer and an i-type semiconductor layer or a p-type semiconductor layer were examined. The present inventors have found that the layer and the i-type semiconductor layer are stacked discontinuously. That is, it is presumed that the cause of the increase in the number of defect levels near the interface is that the n-type semiconductor layer and the i-type semiconductor layer or the p-type semiconductor layer and the i-type semiconductor layer are stacked discontinuously. You.

When a normal semiconductor device is left in an air environment, molecules (water, oxygen, nitrogen, nitrogen oxides, sulfur compounds, etc.) in the air and elements contained therein diffuse into the semiconductor device. As a result, the characteristics of the semiconductor element may be degraded. Similarly, when a semiconductor element such as a solar cell is sealed with another substance (encapsulating material), the chemical substance (acetic acid or the like) contained in the encapsulating material diffuses into the semiconductor element, so that the semiconductor element is sealed. Of the device may deteriorate. In particular, when each layer is discontinuously stacked at a semiconductor junction (junction between an n-type semiconductor layer and an i-type semiconductor layer, junction between a p-type semiconductor layer and an i-type semiconductor layer, etc.), the above-described interface defect may be caused. The diffusion material is trapped and the semiconductor characteristics deteriorate.

An object of the present invention is to solve the above problems and improve the photoelectric conversion efficiency of a photoelectric conversion element represented by a solar cell.

Another object of the present invention is to provide a semiconductor device having excellent semiconductor characteristics by reducing defects between microcrystalline grains and eliminating discontinuities at a semiconductor junction.

[0014] In addition, the present invention provides heat resistance of a semiconductor device,
The purpose is to improve durability.

[0015]

According to the present invention, there is provided a semiconductor device having a microcrystalline semiconductor, wherein the semiconductor device has a region in which microcrystal grains having different grain sizes are mixed.

Further, the present invention provides a semiconductor device in which a semiconductor layer having first electrical characteristics, a semiconductor layer having second electrical characteristics, and a semiconductor layer having third electrical characteristics are sequentially stacked. At least one of the semiconductor layers is a semiconductor element in which microcrystal grains having different particle diameters are mixed.

Further, the present invention relates to a method for manufacturing a semiconductor device, comprising the step of forming a semiconductor layer made of microcrystals on a substrate by generating plasma in a gas phase to decompose a raw material gas. A method for manufacturing a semiconductor element, characterized in that a semiconductor layer in which microcrystal grains having different sizes are mixed is formed by periodically changing electric power supplied to plasma.

In addition, the present invention relates to a method for manufacturing a semiconductor device, comprising the step of forming a semiconductor layer containing microcrystals on a substrate by generating plasma in a gas phase to decompose a raw material gas. A method of manufacturing a semiconductor device, characterized in that a semiconductor layer composed of fine crystal grains having different sizes is formed by periodically adding a halogen-containing gas to the source gas.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present inventors have conducted intensive studies in order to solve the above problems. As a result, in a semiconductor element having a microcrystalline semiconductor, mixing microcrystal grains of different crystal grain sizes in a semiconductor layer and having a semiconductor junction in the microcrystal grains are effective in solving the above problems. Was found. The “semiconductor layer in which microcrystal grains having different particle diameters are mixed” in the present invention refers to a semiconductor layer in which microcrystal grains having different particle diameters do not have regularity and are distributed almost randomly. In addition, the fact that fine crystal grains having different particle diameters are mixed is caused by the fact that the average crystal grain diameter calculated from the half value width of the (220) peak of the X-ray diffraction and the average crystal grain calculated from the dark field image of the transmission electron microscope. It is confirmed from the fact that the diameter differs by 50 ° or more. In the semiconductor device,
By mixing fine crystal grains with different crystal grain sizes,
Distortion can be reduced as compared with the case where a three-dimensional space (semiconductor layer) is filled with fine crystal grains having the same crystal grain size. As a result, the traveling property (mobility) of the photoexcited free charge in the microcrystalline semiconductor layer can be increased and the life of the charge can be extended. Further, in the semiconductor element, at least a part of two semiconductor layers having different electric characteristics from each other (for example, a part of an n-type semiconductor layer and a part of an i-type semiconductor layer, or a part of a p-type semiconductor layer and an i-type semiconductor layer). (A part of the type semiconductor layer) is formed in the same microcrystal grain near the interface between the respective layers. In other words, in the semiconductor element, microcrystal grains exist over two semiconductor layers. By forming a semiconductor junction such as p / i or n / i in a microcrystal grain in this manner, the defect level near the interface can be extremely reduced. As a result, the open-circuit voltage (Vo) of the solar cell
c) It is possible to prevent the short circuit current (Jsc) and the form factor (FF) from decreasing. Further, it is possible to prevent the series resistance of the solar cell from increasing and the shunt resistance from decreasing. As a result, the conversion efficiency of the solar cell can be improved.

Further, the heat resistance of the semiconductor element can be improved by forming the semiconductor junction in the microcrystal grains.

In addition, by forming a semiconductor junction in microcrystal grains, discontinuity of a layer interface at a semiconductor junction can be eliminated, and characteristics of a semiconductor element can be improved.

For example, by forming a semiconductor junction in microcrystal grains, the depletion layer of the semiconductor junction is wider than that of a conventional semiconductor element having a semiconductor junction. As a result, the rectification characteristics are improved as compared with the conventional semiconductor junction, and the dark current when a reverse bias is applied can be suppressed.

Hereinafter, a photovoltaic element will be described as an example of the semiconductor element of the present invention with reference to the drawings.

FIG. 1 shows an example of the layer structure of a photovoltaic element which is an example of the semiconductor element of the present invention. This photovoltaic element is formed by depositing Al, C on a substrate (a conductive substrate made of metal such as stainless steel or an insulating substrate made of glass or the like) 111.
a reflective layer 110 made of a metal such as u, Ag, etc., zinc oxide,
The reflection enhancement layer 109 made of a metal oxide such as indium oxide or tin oxide, and the n-type or p-type of the bottom photovoltaic element 112
A semiconductor layer (a layer having first electric characteristics) 108, an i-type semiconductor layer (a layer having second electric characteristics) 107, a p-type or n-type semiconductor layer (a layer having third electric characteristics) 106,
N-type or p-type semiconductor layer 10 of top photovoltaic element 113
5, i-type semiconductor layer 104, p-type or n-type semiconductor layer 10
3 and a transparent electrode 102 such as ITO and a grid (collecting electrode) 101. In this photovoltaic device, the i-type semiconductor layer of the bottom photovoltaic device is composed of a microcrystalline silicon semiconductor.

FIGS. 3 to 5 are enlarged views of the reflection increasing layer 109, the layer 108 having the first electric characteristic, and the layer 107 having the second electric characteristic in FIG.

FIG. 3 shows an example in which microcrystalline semiconductor layers 302 and 305 are grown almost immediately above the reflection enhancement layer 301.
The semiconductor layer having the first electrical characteristic is a portion 305 below the straight line 303. The semiconductor layer having the second electric characteristic is a portion 302 above the straight line 303. FIG. 4 shows the reflection increasing layer 4.
01, for example, several hundreds of
(5) In this example, microcrystalline semiconductor layers 402 and 405 are deposited and grown thereon. The semiconductor layer having the first electric characteristic is a portion 405 below the straight line 403. The semiconductor layer having the second electric characteristic is a portion 402 above the straight line 403. FIG. 5 shows that the microcrystalline semiconductor layer 50 is formed on the reflection enhancement layer 501.
4 is, for example, deposited several hundred degrees or less, on which microcrystalline semiconductor layers 502 and 505 are grown. The semiconductor layer having the first electric property is a portion 505 below the straight line 503.
It is. The semiconductor layer having the second electric characteristic is a straight line 503.
Is a part 502 above. In each case, a semiconductor junction exists in the microcrystal grains. The shape of the microcrystal having a semiconductor junction in the microcrystal grain is preferably a columnar shape when observed with a transmission electron microscope. The content of the additive that changes the electrical characteristics in the microcrystal having the semiconductor junction in the microcrystal grains is, for example, one of the preferable modes that is changed in the thickness direction in the semiconductor layer having the first electrical characteristics. It is.

FIG. 6 is a schematic partial sectional view showing the difference between the microcrystalline semiconductor layer of the conventional semiconductor device and the microcrystalline semiconductor layer of the semiconductor device of the present invention. In a microcrystalline semiconductor layer of a conventional semiconductor element, since the microcrystal grains have a uniform particle size, there is an amorphous layer having many defects which are not filled with microcrystal grains in the microcrystal semiconductor layer. On the other hand, since the microcrystalline semiconductor layer of the semiconductor element of the present invention is composed of microcrystal grains of different crystal grain systems, there is substantially no space in which microcrystal grains are not filled. As a result, the mobility and lifetime of charges in the microcrystalline semiconductor layer of the semiconductor element of the present invention are larger than those in the related art.

FIG. 2 shows an example of a deposited film forming apparatus for producing a photovoltaic element as an example of the semiconductor element of the present invention. The deposition film forming apparatus includes a load chamber 201, a microcrystalline silicon i-type semiconductor layer deposition chamber 202, a silicon semiconductor layer (i-type semiconductor layer, p-type semiconductor layer, and n-type semiconductor layer) deposition RF chamber 203, microcrystal It comprises a silicon germanium i-type semiconductor layer deposition chamber 204 and an unload chamber 220.
The load chamber is provided with a laser annealing heater (not shown) and a window 222 for irradiating the semiconductor layer with a laser from a laser (not shown).

The respective chambers are separated by gate valves 206, 207, 208, 209 so that the respective source gases do not mix. The microcrystalline silicon i-type semiconductor layer deposition chamber 202 includes a substrate heating heater 211.
And a plasma CVD chamber 210. RF
The chamber 203 is provided with an n-type semiconductor layer deposition heater 21.
2 and a deposition chamber 215 for n-type semiconductor layer deposition, an i-type semiconductor layer deposition heater 213 and a deposition chamber 2 for i-type semiconductor layer deposition
16, a heater 214 for p-type semiconductor layer deposition and a deposition chamber 217 for p-type semiconductor layer deposition. The microcrystalline silicon germanium i-type semiconductor layer deposition chamber 204 has a heater 218 and a plasma CVD chamber 219.
The substrate is mounted on the substrate holder 221 and the rail 220
It is moved above by rollers driven from the outside. In the plasma CVD chambers 210 and 219, microcrystals are deposited.
To deposit a microcrystalline semiconductor, microwave plasma CV
The D method or the VHF plasma CVD method is preferably used, but the RF plasma CVD method can also be used.

A photovoltaic element as an example of the semiconductor element of the present invention is formed, for example, as follows.

First, the SUS substrate 111 on which the reflection layer 110 and the reflection enhancement layer 109 are formed is set on the substrate holder 221, and is set on the rail 220 in the load chamber 201. The load chamber 201 is moved to several mTorr.
(1 Torr = 133 Pa) or less is evacuated.
The gate valves 206 and 207 are opened, and the substrate holder is moved to the n-type semiconductor layer deposition chamber 215 of the chamber 203.
Each gate valve is closed, and the n-type semiconductor layer 108 is deposited with a desired source gas to a desired thickness. After exhausting sufficiently, the substrate holder is moved to the load chamber 201. The substrate is heated by a heater (not shown) so that the substrate temperature becomes 400 ° C., and after the substrate temperature becomes constant, the n-type semiconductor layer 108 is crystallized by a XeCl laser (not shown).
The internal pressure in the load chamber during laser irradiation is 10-3
The degree of vacuum is maintained at or below Torr. The substrate holder is moved to the microcrystalline silicon i-type semiconductor layer deposition chamber 202, and the gate valves 206 and 207 are closed. Heater 2
In step 11, the substrate is heated to a desired substrate temperature, a required amount of a desired source gas is introduced, a desired degree of vacuum is applied, a predetermined microwave energy or VHF energy is introduced into the deposition chamber 210, and plasma is generated to generate n. A microcrystalline silicon i-type semiconductor layer 107 is deposited on the type semiconductor layer 108 to a desired layer thickness. At this time, after the n-type semiconductor layer 108 is subjected to hydrogen plasma treatment, the i-type semiconductor layer 107 is continuously deposited so that the i-type semiconductor layer 107 is epitaxially grown on the n-type semiconductor layer 108. It is a preferable method to make the substrate temperature during deposition higher than the substrate temperature during deposition of the n-type semiconductor layer 108.

Subsequently, the chamber 202 is sufficiently evacuated, the gate valve 207 is opened, and the substrate holder 221 is moved from the chamber 202 to the chamber 203. The substrate holder 221 is moved to the p-type semiconductor layer deposition chamber 217 of the chamber 203, and the substrate is heated to a desired temperature by the heater 214. A source gas for depositing a p-type semiconductor layer is supplied to the deposition chamber 217 at a desired flow rate, and RF energy is introduced into the deposition chamber 217 while maintaining the deposition chamber 217 at a desired degree of vacuum. Then, the p-type semiconductor layer 106 is deposited to have a desired thickness. After the p-type semiconductor layer 106 is deposited, the deposition chamber 217 is sufficiently evacuated, and the substrate holder 227 is moved to the n-type semiconductor layer deposition chamber 215 in the same chamber 203. An n-type semiconductor layer 105 is deposited on the p-type semiconductor layer 106 in the same manner as the n-type semiconductor layer 108. The deposition chamber 215 is sufficiently evacuated, and the substrate holder 221 is moved to the i-type semiconductor layer deposition chamber 216. The substrate is heated to a predetermined temperature by the heater 213. A source gas for depositing an i-type semiconductor layer is supplied to the deposition chamber 216 at a desired flow rate, and
Maintain the pressure in the six chambers at the desired pressure to introduce the desired RF energy. Thus, the i-type semiconductor layer 104 is deposited on the n-type semiconductor layer 105 so as to have a desired thickness. Next, the deposition chamber 216 is sufficiently evacuated, the substrate holder 221 is moved from the deposition chamber 216 to the deposition chamber 217, and the i-type semiconductor layer 1 is removed in the same manner as the p-type semiconductor layer 106.
On the substrate 04, a p-type semiconductor layer 103 is deposited. After sufficiently exhausting the deposition chamber 217 as described above, the gate valve 2
08 and 209 are opened, and the substrate holder 221 on which the substrate on which the semiconductor layer is deposited is set is moved to the unload chamber 205. Close all gate valves and unload chamber 2
At 05, a nitrogen gas is introduced to cool the substrate to a desired temperature. Thereafter, the take-out valve of the unload chamber 205 is opened, and the substrate holder 221 is taken out. Using a not-shown evaporator for depositing a transparent electrode, the p-type semiconductor layer 10
A transparent electrode 102 is deposited on 3 so as to have a desired layer thickness. Similarly, a current collecting electrode 101 is deposited on the transparent electrode 102 using an evaporator (not shown).

When the microcrystalline i-type semiconductor layer 107 is formed using silicon germanium instead of silicon, the chamber 204 may be used instead of the chamber 202.

A semiconductor element having a semiconductor junction in microcrystal grains can also be formed as follows.

(1) Forming a semiconductor layer (doping semiconductor layer) having a crystalline first electric characteristic, followed by a microcrystalline semiconductor layer having a second electric characteristic (a microcrystalline semiconductor without any doping) Layer or a microcrystalline semiconductor layer having electrical properties different from those of the first doped semiconductor layer)
Is deposited by changing the source gas or the like under the condition that the microcrystals grow continuously, thereby forming a semiconductor junction within the microcrystal grains.

(2) A crystalline semiconductor layer having a first electrical property is formed, and a microcrystalline or amorphous semiconductor layer having a second electrical property is formed on the semiconductor layer. Annealing is performed at the following temperature to form a semiconductor junction in the microcrystal grains.

(3) A crystalline semiconductor layer having first electrical characteristics is formed, and hydrogen plasma treatment is performed on the semiconductor layer to clean the surface of the microcrystalline semiconductor layer having the first electrical characteristics. Then, a semiconductor junction is formed in the microcrystalline grains by epitaxially growing a microcrystalline semiconductor layer having the second electric characteristic on the microcrystalline semiconductor layer having the first electric characteristic.

(4) An amorphous or crystalline semiconductor layer having a first electric property is formed, and an amorphous or microcrystalline semiconductor layer having a second electric property is deposited on the semiconductor layer. (Laser annealing) to form a semiconductor junction in the microcrystal grains.

The energy density of the laser for recrystallization with an excimer laser is 200 mJ / cm ^2-
800 mJ / cm ² is preferred. At the time of laser annealing, the total thickness of the first semiconductor layer and the second semiconductor layer is preferably 100 ° to 700 °. After recrystallization,
The thickness of the semiconductor layer having the second electric property can be increased by epitaxially growing a semiconductor layer having the same electric property as the semiconductor layer on the semiconductor having the second electric property. In the case of laser annealing, it is desirable to increase the ambient temperature, specifically, to 100 to 800 ° C. In particular, when a support having low heat resistance such as a stainless thin film or glass is used as the support (substrate), the ambient temperature is set to 100 to 60.
Preferably, the temperature is 0 ° C. Lasers suitable for laser annealing include ArF (wavelength: 193 nm),
KrF (wavelength: 248 nm), XeCl (wavelength: 308)
nm) and XeF (wavelength: 351 nm). When annealing the silicon-based semiconductor layer, XeC
1 (wavelength: 308 nm) is particularly preferred.

(5) A semiconductor junction can be formed in the same semiconductor by forming a crystalline semiconductor having the first electric characteristic and ion-implanting an impurity (dopant) into the semiconductor.

In this case, it is preferable to perform thermal annealing at a temperature in the range of 100 to 800 ° C. after the ion implantation.

The present invention is applicable not only to a semiconductor junction in which one layer is not doped, such as a p / i or n / i junction, but also to a semiconductor junction having opposite electric characteristics, such as an n / p junction, or an n / n junction. , P / p, etc., can be similarly applied to semiconductor junctions having the same kind but strictly different electrical properties.

A microcrystalline semiconductor layer composed of microcrystalline grains having different particle sizes can be formed, for example, as follows.

(1) In the process of depositing a microcrystalline semiconductor layer while diluting a source gas with hydrogen in large amounts, the power supplied to the plasma is changed periodically.

In this way, active hydrogen promotes crystal growth where crystals on the growth surface of the semiconductor layer are difficult to grow. As a result, the semiconductor layer is filled with microcrystal grains having different grain sizes.

It is preferable that the input power is changed with a maximum value of 1.1 times or more and 2 times or less before the change. 2
If it is changed more than twice, the influence on the growth surface of the semiconductor increases, and the defect level may increase.

(2) The microcrystalline semiconductor layer is deposited while periodically adding a halogen-containing gas to the source gas.

By doing so, it is possible to activate the growth surface of the semiconductor layer where crystal growth is difficult.
Crystal growth is promoted. As a result, the semiconductor layer is filled with microcrystal grains having different grain sizes.

When the halogen-containing gas is added, it is preferable to add the halogen-containing gas at a ratio (volume concentration) of 0.2 to 0.9 times the halogen-free source gas. If the amount of the halogen-containing gas exceeds this range, the plasma becomes unstable, and a desired semiconductor film may not be obtained.

The semiconductor layers (the semiconductor layer having the first electric property and the semiconductor layer having the second electric property) adjacent to the semiconductor junction in the microcrystal grains are deposited when they are crystallized by post-processing. Sometimes it may be amorphous or crystalline. In the case where crystallization by post-processing is not performed, it is necessary to be crystalline at the time of deposition. In the case where the semiconductor is made crystalline at the time of deposition, a microcrystalline semiconductor is preferably used.

It is preferable that the average crystal grain size of the fine crystal grains is 100 ° to 1000 ° calculated from the half width of the (220) peak of X-ray diffraction using the Scherrer equation. Further, it is preferable that the thickness be 100 ° to 10 μm as determined from a dark field image of a transmission electron microscope. In addition, when calculating | requiring the average crystal grain size of a columnar microcrystal using a transmission microscope, it is preferable that the geometric mean of a major axis and a minor axis exists in the said range.

The ratio of amorphous contained in the microcrystalline semiconductor is preferably such that the ratio of the peak relating to the amorphous to the peak relating to the crystal is not more than 70% as seen from the Raman spectrum. If the average crystal grain size is smaller than 100 °, a large amount of amorphous material will be present at the crystal grain boundaries, and light deterioration is likely to occur. In addition, when the crystal grain size is small, the mobility and lifetime of electrons and holes are reduced, and the characteristics as a semiconductor may be reduced. On the other hand, when the average crystal grain size calculated by using the Scherrer's formula is larger than 1000 °, the relaxation of the crystal grain boundaries does not sufficiently proceed, and defects such as unbonded hands are generated in the crystal grain boundaries, and the defects become electrons or It acts as a recombination center for holes, and as a result, the properties of the microcrystalline semiconductor may be reduced. Further, the shape of the microcrystal is preferably long and narrow (columnar) along the moving direction of the electric charge. In addition, the proportion of hydrogen atoms or halogen atoms contained in the microcrystalline semiconductor layer of the present invention is desirably 30% or less.

As the semiconductor layer in the semiconductor device of the present invention, a doping layer such as a p-type semiconductor layer and an n-type semiconductor layer, i.
Semiconductor layer, and the like.

When applied to a photovoltaic device, the doping layer is an important layer that affects the characteristics of the device, and the i-type semiconductor layer is an important layer that generates and transports carriers by light incidence. .

Examples of the amorphous semiconductor material, microcrystalline semiconductor material, and polycrystalline semiconductor material that can be suitably applied to the semiconductor device of the present invention include, for example, a-Si: H, a-Si: H
X, a-SiC: H, a-SiC: HX, a-SiG
e: H, a-SiGeC: H, a-SiO: H, a-S
iN: H, a-SiON: HX, a-SiOCN: H
X, μc-Si: H, μc-SiC: H, μc-Si:
HX, μc-SiC: HX, μc-SiGe: H, μc
—SiO: H, μc-SiGeC: H, μc-SiN:
H, μc-SiON: HX, μc-SiOCN: HX,
poly-Si: H, poly-Si: HX, poly
-SiC: H, poly-SiC: HX, poly-S
iGe: H, poly-Si, poly-SiC, po
ly-SiGe or the like is preferably used. X is a halogen.

When these materials are applied to the doping layer, a p-type valence electron controlling agent (Group III atom of the periodic table: B, Al, Ga, In, Tl) or an n-type valence electron control agent It is preferable to add an agent (Group V atom of the periodic table: P, As, Sb, Bi) at a high concentration. The addition amount of Group III atoms to the p-type semiconductor layer and the addition amount of Group V atoms to the n-type semiconductor layer are preferably 0.1 to 50 atm%.

Further, hydrogen atoms (H, D) and / or halogen atoms (F, Cl, etc.) contained in the p-type semiconductor layer or the n-type semiconductor layer are not bonded to the p-type semiconductor layer or the n-type semiconductor layer. It functions to compensate for the hand, and improves the doping efficiency of the p-type semiconductor layer or the n-type semiconductor layer. The amount of hydrogen atoms and / or halogen atoms added to the p-type semiconductor layer or the n-type semiconductor layer is preferably 0.1 to 40 atm%. In particular, when the p-type semiconductor layer or the n-type semiconductor layer is crystalline, the addition amount of hydrogen atoms and / or halogen atoms is preferably 0.1 to 8 atm%.

Further, the semiconductor layer of the semiconductor device of the present invention comprises:
The content of hydrogen atoms (H, D) and / or halogen atoms (F, Cl, etc.) is increased near each interface between the p-type semiconductor layer / i-type semiconductor layer and the n-type semiconductor layer / i-type semiconductor layer. Are preferred. The content of hydrogen atoms and / or halogen atoms in the vicinity of the interface is preferably in the range of 1.1 to 2 times the content in the bulk of the p-type semiconductor layer or the n-type semiconductor layer,
In the i-type semiconductor layer, a preferable range is 1.1 to 2 times the content in the bulk region. Thus p
By increasing the content of hydrogen atoms or halogen atoms near each interface between the n-type semiconductor layer / i-type semiconductor layer and the n-type semiconductor layer / i-type semiconductor layer, the defect level and mechanical strain near the interface are reduced. And the characteristics of the semiconductor device of the present invention can be improved. In particular, when applied to a photovoltaic element, photovoltaic power and photocurrent can be increased.

When a multi-component (alloy-based) semiconductor layer such as SiC or SiGe is used, the content of hydrogen atoms and / or halogen atoms must be changed in accordance with the change in content of silicon atoms. Is preferred. The semiconductor layer has a reduced content of hydrogen atoms and / or halogen atoms in a narrow band gap corresponding to the band gap. The content of hydrogen atoms and / or halogen atoms where the content of silicon atoms is minimum is preferably in a range of 1 to 10 atm%,
Or 0.3 to the region where the content of halogen atoms is the maximum
It is preferably 0.8 times.

Although the details of the mechanism are unknown, when depositing an alloy semiconductor containing silicon atoms and germanium atoms, the electromagnetic energy obtained by each of the atoms depends on the difference in ionization rate between the silicon atoms and germanium atoms. It is considered that a difference occurs, and as a result, even if the hydrogen content and / or the halogen content in the alloy-based semiconductor is small, the relaxation is sufficiently advanced and a high-quality alloy-based semiconductor can be obtained.

When the semiconductor element of the present invention is applied to a photovoltaic element, the p-type semiconductor layer and the n-type semiconductor layer preferably have an activation energy of 0.2 eV or less, and preferably 0.1 eV or less. Is best. The specific resistance is preferably 100 Ωcm or less, and most preferably 1 Ωcm or less. Further, the thickness of the p-type semiconductor layer and the n-type semiconductor layer is preferably 1 to 50 nm, and most preferably 3 to 10 nm.

As the p-type semiconductor layer or the n-type semiconductor layer on the light incident side, a crystalline semiconductor layer with little light absorption or an amorphous semiconductor layer with a wide band gap is suitable.

In the semiconductor device of the present invention, a slightly p-type or n-type semiconductor layer (substantially i-type semiconductor layer) can be used as the i-type semiconductor layer (p-type semiconductor layer). It depends on the distribution of intrinsic defects such as tail state).

When the semiconductor device of the present invention is applied to a photovoltaic device, the i-type semiconductor layer contains a silicon atom and a germanium atom in addition to a semiconductor having a uniform band gap. Also suitable are those in which the band gap changes smoothly in the layer thickness direction, and the local minimum value of the band gap deviates from the center of the i-type semiconductor layer toward the interface between the p-type semiconductor layer and the i-type semiconductor layer. Also suitable are those in which a valence electron controlling agent serving as a donor and a valence electron controlling agent serving as an acceptor are simultaneously doped in the i-type semiconductor layer.

The band gap of the i-type semiconductor layer is p
It is preferable to design so as to be wide in each interface direction of the n-type semiconductor layer / i-type semiconductor layer and the n-type semiconductor layer / i-type semiconductor layer. With such a design, the photovoltaic power and the photocurrent of the photovoltaic element can be increased, and furthermore, it is possible to prevent light deterioration or the like when used for a long time.

The preferable thickness of the i-type semiconductor layer largely depends on the structure (for example, single cell, tandem cell, triple cell) of the photovoltaic element and the band gap of the i-type semiconductor layer. ３30.0 μm is mentioned as a suitable layer thickness.

Next, as a preferable method for depositing the semiconductor layer of the semiconductor device of the present invention, RF plasma CVD, V
An HF plasma CVD method and a microwave plasma CVD method are mentioned. The frequency of RF and VHF is 1 MH
z to 300 MHz is a preferable range. In the case of RF, a frequency near 13.56 MHz is optimal, and in the case of VHF, a frequency near 105 MHz is optimal. The preferred range of the microwave frequency is 0.5 GHz to 10 GHz.

In particular, when depositing microcrystalline silicon,
The deposition rate depends on the electromagnetic wave to be used, and the higher the frequency, the higher the deposition rate with the same input energy. Therefore, it is preferable to use a high-frequency electromagnetic wave.

As the source gas suitable for depositing the semiconductor layer of the semiconductor element of the present invention, a gas composed of a gasizable compound containing a silicon atom, a gas composed of a gasizable compound containing a germanium atom, and a carbon atom are used. Examples thereof include a gas containing a compound that can be gasified and a mixed gas of these compounds.

Specific examples of the gasizable compounds containing silicon atoms include SiH ₄ , Si ₂ H ₆ , Si ₃ H ₈ ,
SiF ₄ , SiHF ₃ , SiH ₂ F ₂ , SiH ₃ F, SiH ₃
Cl, SiH ₂ Cl ₂ , SiHCl ₃ , SiCl ₄ , SiD
₄ , SiHD ₃ , SiH ₂ D ₂ , SiH ₃ D, SiD ₃ F, S
Suitable compounds include silane compounds such as iD ₂ F ₂ , SiHD ₃ and Si ₂ H ₃ D ₂ .

Specific examples of the gasifiable compound containing a germanium atom include GeH ₄ , GeF ₄ , G
eHF ₃ , GeH ₂ F ₂ , GeH ₃ F, GeHCl ₃ , Ge
H ₂ Cl ₂ , GeH ₃ Cl, GeHD ₃ , GeH ₂ D ₂ , Ge
Germanic compounds such as H ₃ D, GeD ₄ , Ge ₂ H ₆ , and Ge ₂ D ₆ are preferred.

[0072] Further, as the gasifiable compounds containing specific carbon _{atoms, C n H 2n + 2 (} n is an integer) a compound represented by such as CH _4, C _n H such C ₂ H ₂ Compounds represented by _2n (n is an integer), CD ₄ , C ₆ H ₆ , CO ₂ , CO and the like are preferred.

Further, the source gas may contain a gas containing a nitrogen atom or a gas containing an oxygen atom.

As the gas containing a nitrogen atom, N ₂ ,
NH ₃ , ND ₃ , NO, NO ₂ , N ₂ O are mentioned.

As the gas containing oxygen, O ₂ , C
O, CO ₂ , NO, NO ₂ , N ₂ O, CH ₃ CH ₂ OH, C
H ₃ OH and the like.

The compounds capable of being gasified are H ₂ , H
It may be appropriately diluted with a gas such as e, Ne, Ar, Xe, or Kr and introduced into the deposition chamber.

In particular, when depositing the microcrystalline semiconductor layer of the present invention, it is preferable to dilute these source gases with hydrogen gas, helium gas or the like in order to form a favorable microcrystalline semiconductor. The dilution ratio with hydrogen gas is preferably 10 times or more. A particularly preferred range of the dilution ratio is 10 to 100 times. When the dilution ratio is small, microcrystals are not easily formed, and amorphous is easily formed. On the other hand, if the dilution ratio is too high, the deposition rate of the microcrystals becomes too low, and there is a problem in practical use.

In particular, when depositing a semiconductor layer having a small light absorption or a wide band gap such as a microcrystalline semiconductor or a-SiC: H, the source gas is diluted 2 to 100 times with a hydrogen gas or the like and introduced. Preferably, the RF power, VHF power, or microwave power is relatively high.

When a p-type semiconductor layer or an n-type semiconductor layer is deposited, a valence electron controlling agent (a group III atom or a group V atom in the periodic table) is added to each source gas to control valence electrons.
It is preferred to add a compound containing

Compounds that can be effectively used as compounds for introducing Group III atoms include those for introducing boron atoms.
_{B 2 H 6, B 4 H} 10, B 5 H 9, B 5 H 11, B 6 H 10, B
₆ H _12, B ₆ H _14, etc. borohydride, may be mentioned BF _3, BCl ₃ or the like boron halide or the like. In addition,
As a compound for introducing a Group III atom other than boron, Al
Cl ₃ , GaCl ₃ , InCl ₃ , TlCl _{3 and the} like can also be mentioned. Among these compounds, in particular, B ₂ H ₆ , B
F ₃ is suitable.

Compounds that are effectively used as a compound for introducing a group V atom include PH3,
Phosphorus hydride such as P2H4, PH ₄ I, PF ₃ , PF ₅ , PC
and phosphorus halides such as l ₃ , PCl ₅ , PBr ₃ , PBr ₅ and PI ₃ . In addition, as a compound for introducing a group V atom other than phosphorus, AsH ₃ , AsF ₃ , AsCl ₃ , As
_{Br 3, AsF 5, SbH 3} , SbF 3, SbF 5, SbC
l ₃ , SbCl ₅ , BiH ₃ , BiCl ₃ , BiBr _{3 and the} like can also be mentioned. Among these compounds, in particular, P
H ₃ and PF ₃ are suitable.

When a semiconductor layer is deposited by the RF plasma CVD method, the substrate temperature in the deposition chamber is 100 to 350.
° C, internal pressure is 0.1-10 Torr, RF power is
0.01 to 5.0 W / cm ² , the deposition rate is 0.1 to 3
0 ° / sec is a suitable condition. Also, R
When a semiconductor layer is deposited by an F plasma CVD method, a capacitively coupled RF plasma CVD method is suitable.

When a semiconductor layer is deposited by the microwave plasma CVD method, the substrate temperature in the deposition chamber is 100 to 400.
C., the internal pressure is preferably 0.5 to ³⁰ mTorr, and the microwave power is preferably 0.01 to 1 W / cm ³ . As a microwave plasma CVD apparatus used when a semiconductor layer is deposited by a microwave plasma CVD method,
A method in which microwaves are introduced into a deposition chamber through a waveguide through a dielectric window (alumina ceramics or the like) is suitable.

The substrate temperature for depositing a microcrystalline semiconductor layer suitable for the present invention is 100 to 500 ° C. In particular, when increasing the deposition rate, it is desirable to set the substrate temperature to a relatively high temperature. The degree of vacuum in the chamber when depositing the microcrystalline semiconductor layer of the present invention is 1 mT
orr to 1 Torr is mentioned as a suitable range. In particular, when the microcrystalline semiconductor layer is deposited by a microwave plasma CVD method, the degree of vacuum is preferably 1 mTorr to 10 mTorr.

The input power to the chamber when depositing the microcrystalline semiconductor layer of the present invention is 0.01 to 10 W /
The range of cm ³ is mentioned as a suitable range. In terms of the relationship between the flow rate of the source gas and the input power, a power-limited region where the deposition rate depends on the input power is suitable.

Further, in depositing the microcrystalline semiconductor layer of the present invention, the distance between the substrate and the electrode for power supply is an important factor. In order to obtain a microcrystalline layer suitable for the present invention, the distance between electrodes must be 1
It is preferable to set it to 0 mm to 50 mm.

The i-type semiconductor layer containing silicon atoms or germanium atoms formed by the above-described method for forming a deposited film has less tail state on the valence band side even when the deposition rate is increased to 5 nm / sec or more. , The tilt of the tail state is 60 meV or less, and the density of dangling bonds by electron spin resonance (esr) is 10 ¹⁷ / cm.
³ or less.

Hereinafter, the present invention will be described in detail with reference to examples. Of course, the present invention is not limited to the following examples.

[0089]

<Example 1> In this example, a photovoltaic element was manufactured using the deposited film forming apparatus shown in FIG. Table 1 shows the deposition conditions for each semiconductor layer. In all of the examples and comparative examples including this example, the method of forming members such as electrodes was performed according to a standard method. When depositing the bottom photovoltaic element, the input power was changed between the value shown in Table 1 and a value 1.5 times the value in a cycle of 6 seconds. The microcrystalline semiconductor having a semiconductor junction in the same microcrystalline semiconductor of the present invention was applied between the n-type semiconductor layer n1 and the i-type semiconductor layer i1 of the bottom photovoltaic element. After deposition of the n-type semiconductor layer n1, the n-type semiconductor layer n1 is irradiated with an excimer laser in the load chamber under the conditions shown in Table 2 to obtain n
The type semiconductor layer n1 was crystallized. Then VHF plasma C
An i-type semiconductor layer i1 was continuously deposited on the n-type semiconductor layer n1 by the VD method.

<Comparative Example 1> As a photovoltaic element for comparison with Example 1, except that the applied power is constant at the values shown in Table 1 and that the n-type semiconductor layer n1 is not treated with an excimer laser. In the same manner as in Example 1, a photovoltaic element was prepared.

<Comparison between Example 1 and Comparative Example 1> The characteristics of the photovoltaic element formed in this way were measured by WACOM Corporation.
The measurement and evaluation were performed using WXS-130S-20T manufactured as a light source. The spectrum of the light source was AM 1.5 and the light intensity was 1 sun. The results are shown in Table 3 as relative values with Comparative Example 1 as 1. The photovoltaic device of Example 1 exhibited better photovoltaic characteristics than the device of Comparative Example 1. Further, the photovoltaic element of Example 1 had a lower series resistance and a higher shunt resistance than the element of Comparative Example 1.

Under the same conditions as in Example 1 and Comparative Example 1, 100 photovoltaic elements were produced. These photovoltaic elements were left in an atmosphere containing acetic acid at a temperature of 85 ° C. and a humidity of 85% for 2000 hours. Thereafter, the photovoltaic characteristics were measured. In the photovoltaic device of Example 1, the variation in the characteristics of the 100 photovoltaic devices was very small as compared with the device of Comparative Example 1. That is, the photovoltaic element of the present invention had extremely high environmental resistance (durability).

Observation of the cross sections of these photovoltaic elements with a transmission electron microscope showed that the region considered to be the boundary between the n-type semiconductor layer and the i-type semiconductor layer had a layer thickness of the photovoltaic element of Example 1. It was confirmed that it was composed of fine crystal grains having a length in the direction of 2000 to 4000 °. Further, secondary ion mass spectrometry confirmed that impurities (dopants) were localized in the substrate of the fine crystal grains.

Further, from the dark-field image obtained by the electron microscope, it was confirmed that microcrystal grains having different sizes were distributed in the semiconductor layer of the bottom photovoltaic element of Example 1. On the other hand, it was confirmed that microcrystal grains having a uniform size were distributed in the semiconductor layer of the bottom photovoltaic element of Comparative Example 1.

<Example 2> A photovoltaic element was produced using the deposition film forming apparatus shown in FIG. The n-type semiconductor layer n1 was crystallized in the same manner as in Example 1 by irradiating an excimer laser under the conditions shown in Table 5. A bottom i-type semiconductor layer i1 was deposited thereon by a so-called HRCVD method in which a hydrogen gas was activated by microwave plasma and reacted with SiF4 to deposit a semiconductor layer. When depositing the i-type semiconductor layer i1 of the bottom photovoltaic element, the microwave energy
The value was changed every 6 seconds between the described value and 1.3 times the value.

<Comparative Example 2> The same procedure as in Example 2 was carried out except that the microwave energy was constant at the values shown in Table 4 when depositing the i-type semiconductor layer i1 and that the n-type semiconductor layer n1 was not subjected to laser treatment. A photovoltaic element was produced in the same manner.

<Comparison between Example 2 and Comparative Example 2> The characteristics of these photovoltaic elements were measured in the same manner as in Example 1 and Comparative Example 1. The results are shown in Table 6 as relative values with Comparative Example 2 as 1. The photovoltaic device of Example 2 exhibited excellent photovoltaic characteristics as compared with the device of Comparative Example 2.

The cross sections of these photovoltaic elements were observed with an electron microscope, and the amount of impurities was measured by secondary ion mass spectrometry. As a result, in the photovoltaic device of Example 2, it was confirmed that part of the n-type semiconductor layer and the i-type semiconductor layer were formed in the same microcrystalline grains. The shape of the fine crystal grains is columnar, and the length in the layer thickness direction is 30.
There was 00 ° and the length in the direction perpendicular to the layer thickness was 300 °.

Further, when a dark field image of these photovoltaic elements was observed with a transmission electron microscope, the photovoltaic element of Comparative Example 2 was observed to have a space not filled with fine crystal grains. In No. 2, the space was filled with microcrystals having different particle sizes.

<Embodiment 3> Instead of the method of Embodiment 1 in which the n-type semiconductor layer n1 is crystallized with a laser and the i-type semiconductor layer i1 is laminated thereon, the i-type semiconductor layer n1 is deposited after the n-type semiconductor layer n1 is deposited. In the semiconductor layer deposition chamber 202, a hydrogen plasma treatment shown in Table 7 was performed, and a raw material gas for forming an i-type semiconductor layer was added without cutting off the discharge.
1 was deposited. Otherwise, a photovoltaic element was formed in the same manner as in Example 1.

<Comparison between Example 3 and Comparative Example 1> Example 3
Was evaluated in the same manner as in Example 1. The results are shown in Table 8 as relative values with Comparative Example 1 as 1.

As is evident from Table 8, the photovoltaic device of Example 3 exhibited excellent photovoltaic characteristics.

Example 4 A photovoltaic element was formed under the deposition film forming conditions shown in Table 9 using the deposition film forming apparatus shown in FIG. After depositing a microcrystalline i-type semiconductor layer (i0 layer), an ion implantation apparatus (not shown)
Phosphorus atoms were implanted into the i0 layer under the conditions shown in FIG. 0, and the phosphorus atoms were activated in the semiconductor by annealing. During the deposition of the i0 layer, a 50% SiF ₄ gas of silane gas was added at a rate of 10 times / min for 1 second per time.

<Comparison between Example 4 and Comparative Example 1> Example 4
Was evaluated in the same manner as in Example 1. The results are shown in Table 11 as relative values with Comparative Example 1 as 1.

As is clear from Table 11, the photovoltaic device of Example 4 exhibited excellent photovoltaic characteristics.

Observation of a cross section of the photovoltaic element of Example 4 with an electron microscope confirmed that single microcrystal grains were formed in the i0 layer over the entire thickness direction of 3000 °. Further, it was confirmed by secondary ion mass spectrometry that the phosphorus atoms implanted were distributed only on the substrate side, that is, that a semiconductor junction was formed within a single microcrystal grain.

Further, a dark-field image of a transmission electron microscope was observed, and X-ray diffraction was measured. The average crystal grain size of the photovoltaic device of Comparative Example 1 calculated from the half-width of the (220) peak of X-ray diffraction was about 200 °. Further, when the average crystal grain size of the photovoltaic element of Comparative Example 1 was calculated from the dark-field image of the transmission electron microscope, about 20
It was 0 °. On the other hand, when the average crystal grain size of the photovoltaic device of Example 4 was calculated from the half width of the (220) peak of X-ray diffraction, it was about 250 °. The photovoltaic device of Example 4 had an average particle size of about 750 ° measured from a dark field image of a transmission electron microscope. The difference between the average particle size calculated from the X-ray diffraction and the average particle size of the transmission electron microscope indicates that microcrystals having different particle sizes exist in the microcrystalline semiconductor layer of Example 4.

<Example 5> A photovoltaic element was formed under the deposition film forming conditions shown in Table 12 using the deposition film forming apparatus shown in FIG. A microcrystalline semiconductor having a semiconductor junction in the same microcrystalline grain is formed of an n-type semiconductor layer n1 of a bottom photovoltaic element.
And between the i-type semiconductor layer i1. n-type semiconductor layer n
After one deposition, the n-type semiconductor layer n1 was irradiated with an excimer laser in the load chamber under the conditions shown in Table 2 to crystallize the n-type semiconductor layer n1. After that, VHF plasma CVD
The i-type semiconductor i1 layer was continuously deposited on the n-type semiconductor layer n0 by the method. At the time of depositing the i-type semiconductor layer i1, the input power of VHF was changed between the value shown in Table 12 and a value twice as high as that of Table 12 at a period of 3 seconds.

<Comparative Example 3> As a photovoltaic element for comparison with Example 5, the point that the n-type semiconductor layer was not treated with an excimer laser and the point that the VHF power was constant at the numerical values shown in Table 12 were used. Except for the above, a photovoltaic element was prepared in the same manner as in Example 5.

<Comparison between Example 5 and Comparative Example 3> Photovoltaic element characteristics of these photovoltaic elements were measured in the same manner as in Example 1 and Comparative Example 1. The results are shown in Table 13 as relative values when Comparative Example 3 is set to 1. The photovoltaic device of Example 5 showed excellent photovoltaic characteristics as compared with the device of Comparative Example 3. The photovoltaic element of Example 5 had a lower series resistance and a higher shunt resistance than the element of Comparative Example 3.

Further, under the same conditions as in Example 5 and Comparative Example 3, 100 photovoltaic elements were produced, respectively. These photovoltaic elements were left in an atmosphere at a temperature of 85 ° C. and a humidity of 85% for 2000 hours. Thereafter, the photovoltaic characteristics were measured. The variation of the characteristics of the 100 photovoltaic elements of Example 5 was very small as compared with the element of Comparative Example 3. That is, the photovoltaic element of the present invention had extremely high environmental resistance (durability).

The cross sections of these photovoltaic elements were observed with a transmission electron microscope. As a result, in the photovoltaic element of Example 5, the region considered to be the boundary between the n-type semiconductor layer and the i-type semiconductor layer was a film. It was confirmed that it was composed of fine crystal grains having a length in the thickness direction of 2000 to 5000 °. Further, secondary ion mass spectrometry confirmed that impurities (dopants) were localized in the substrate of the fine crystal grains.

<Embodiment 6> After stacking p-type semiconductor layers,
A photovoltaic element was prepared in the same manner as in Example 1, except that the p-type semiconductor layer was irradiated with excimer laser light under the same laser irradiation conditions as those for the crystallization of the n-type semiconductor layer, that is, under the conditions shown in Table 2. By the irradiation, a microcrystalline layer having a semiconductor junction in microcrystalline grains was also formed between the i-type semiconductor layer and the p-type semiconductor layer.

<Comparison of Example 6 with Example 1 and Comparative Example 1> The photovoltaic element of Example 6 was evaluated in the same manner as in Example 1. The results are shown in Table 14 as relative values when Comparative Example 1 is set to 1. The photovoltaic device of this example exhibited better characteristics than the device of Comparative Example 1 and the device of Example 1.

For the photovoltaic device of this example, it was confirmed by using a transmission electron microscope and a secondary ion mass spectrometer whether a semiconductor junction was formed in the same microcrystal grain.
As a result, it was confirmed that the n-type semiconductor layer and the i-type semiconductor layer were in the same microcrystal grain, and the i-type semiconductor layer and the p-type semiconductor layer were in the same microcrystal grain.

As described above, the photovoltaic element having the n-type semiconductor layer and the i-type semiconductor layer in the same microcrystal grain and having the i-type semiconductor layer and the p-type semiconductor layer in the same microcrystal grain is most preferable. It was confirmed that it had excellent characteristics.

100 photovoltaic elements of Example 6 and 100 photovoltaic elements of Comparative Example 1 were prepared, each having a temperature of 85 ° C., a humidity of 95% and an AM of 1.5 and 100 m in a nitrogen oxide atmosphere.
It was left for 3000 hours while irradiating light of W / cm ² .
The photovoltaic device of this example had a smaller rate of change in characteristics than the photovoltaic device of Comparative Example 1.

The photovoltaic device of Example 6 and Comparative Example 1
The current values were measured and compared when a reverse bias of 2 V was applied to the device. As a result, the current value of the photovoltaic element of Example 6 was lower by about one digit than that of the element of Comparative Example 1.

[0119]

[Table 1]

[0120]

[Table 2]

[0121]

[Table 3]

[0122]

[Table 4]

[0123]

[Table 5]

[0124]

[Table 6]

[0125]

[Table 7]

[0126]

[Table 8]

[0127]

[Table 9]

[0128]

[Table 10]

[0129]

[Table 11]

[0130]

[Table 12]

[0131]

[Table 13]

[0132]

[Table 14]

[0133]

According to the present invention, by mixing fine crystal grains having different crystal grain sizes, the distortion can be reduced as compared with the case where the three-dimensional space (semiconductor layer) is filled with the fine crystal grains having the same crystal grain size. As a result, the traveling property (mobility) of the photoexcited free charge in the microcrystalline semiconductor layer can be increased and the life of the charge can be extended.

By forming a semiconductor junction such as p / i or n / i in the same microcrystal grain, the defect level near the interface can be extremely reduced. As a result, it is possible to prevent the open-circuit voltage (Voc), short-circuit current (Jsc), and form factor (FF) of the photovoltaic element from decreasing. Further, it is possible to prevent the series resistance of the photovoltaic element from increasing and the shunt resistance from decreasing. As a result, the photoelectric conversion efficiency of the photovoltaic element can be improved.

Further, since the semiconductor junction is formed in the microcrystal grains, the heat resistance of the semiconductor element is improved.

Further, since the semiconductor junction is formed in the microcrystal grains, it is possible to prevent the deterioration of the characteristics due to the atmosphere and the sealing material.

In addition, since the semiconductor junction is formed in the microcrystal grains, the depletion layer of the semiconductor junction is wider than that of a conventional semiconductor element having a semiconductor junction. As a result, the rectification characteristics are improved as compared with the conventional semiconductor junction, and the dark current when a reverse bias is applied can be suppressed.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a layer configuration of a photovoltaic element which is an example of a semiconductor element of the present invention.

FIG. 2 is a schematic view showing an example of a deposited film forming apparatus for producing a photovoltaic element which is an example of a semiconductor element of the present invention.

FIG. 3 is a schematic cross-sectional view schematically showing an example in which a microcrystalline semiconductor layer is grown almost immediately above a reflection enhancement layer.

FIG. 4 is a schematic cross-sectional view schematically showing an example in which an amorphous layer is deposited on a reflection enhancement layer, and a microcrystalline semiconductor layer is grown thereon.

FIG. 5 is a schematic cross-sectional view schematically showing an example in which a microcrystalline semiconductor layer is deposited on a reflection enhancement layer, and a microcrystalline semiconductor layer is further grown thereon.

FIG. 6 is a schematic partial sectional view showing a difference between a microcrystalline semiconductor layer of a conventional semiconductor element and a microcrystalline semiconductor layer of a semiconductor element of the present invention.

[Explanation of symbols]

Reference Signs List 101 grid (collecting electrode) 102 transparent electrode 103 p-type or n-type semiconductor layer 104 i-type semiconductor layer 105 n-type or p-type semiconductor layer 106 p-type or n-type semiconductor layer 107 i-type semiconductor layer 108 n-type or p-type Semiconductor layer 109 Reflection increasing layer 110 Reflective layer 111 Substrate 112 Bottom photovoltaic element 113 Top photovoltaic element 201 Load chamber 202 Microcrystalline silicon i-type semiconductor layer deposition chamber 203 Silicon deposition RF chamber 204 Microcrystalline silicon germanium i-type Semiconductor layer deposition chamber 205 Unload chamber 206, 207, 208, 209 Gate valve 210, 219 Plasma CVD chamber 211, 218 heater 212 n-type semiconductor layer deposition heater 213 i-type semiconductor layer deposition heater 214 p-type semiconductor layer deposition Heater 215 Deposition chamber for depositing n-type semiconductor layer 216 Deposition chamber for depositing i-type semiconductor layer 217 Deposition chamber for depositing p-type semiconductor layer 220 Rail 221 Substrate holder 222 Laser irradiation window 301, 401, 501 Reflection increasing layer 302, 402 , 502 of the microcrystalline semiconductor layer
Line portions 303, 403, 503 of the layer having the electric characteristics of 305, 405, 505 indicating the boundary at which the electric characteristics change.
404 Amorphous semiconductor layer 504 Microcrystalline semiconductor layer

Claims (12)

[Claims] 1. A semiconductor element including a microcrystalline semiconductor, which has a region in which microcrystalline grains having different particle diameters are mixed. 2. The semiconductor device according to claim 1, wherein the microcrystalline semiconductor contains silicon atoms. 3. The semiconductor device according to claim 1, wherein the microcrystalline semiconductor contains a germanium atom. 4. The semiconductor device according to claim 1, wherein said microcrystalline semiconductor contains a hydrogen atom. 5. The semiconductor device according to claim 1, wherein said microcrystalline semiconductor contains a halogen atom. 6. The semiconductor device according to claim 1, wherein said fine crystal grains have a columnar shape. 7. The semiconductor device according to claim 1, wherein a semiconductor junction is provided in the microcrystal grains. 8. A semiconductor layer having a first electrical characteristic and a second
A semiconductor element in which a semiconductor layer having electric characteristics of and a semiconductor layer having third electric characteristics are sequentially stacked,
At least one of the semiconductor layers is a semiconductor layer in which microcrystal grains having different particle diameters are mixed. 9. The semiconductor device according to claim 1, wherein microcrystal grains are present over at least a part of the semiconductor layer having the first electric characteristic and at least a part of the semiconductor layer having the second electric characteristic. Item 9. A semiconductor element according to item 8. 10. One of the semiconductor layer having the first electric characteristic and the semiconductor layer having the third electric characteristic is a p-type semiconductor layer, and the other is an n-type semiconductor layer. The semiconductor device according to claim 8, wherein the semiconductor layer has an i-type semiconductor layer. 11. A method for manufacturing a semiconductor device, comprising a step of generating a plasma in a gas phase to decompose a raw material gas to form a semiconductor layer made of microcrystals on a substrate, wherein the method is applied to the plasma. A method for manufacturing a semiconductor element, wherein a semiconductor layer in which microcrystal grains having different sizes are mixed is formed by periodically changing electric power. 12. A method for manufacturing a semiconductor device, comprising a step of forming a semiconductor layer made of microcrystals on a substrate by generating plasma in a gas phase to decompose a source gas, wherein the source gas contains A method for manufacturing a semiconductor element, wherein a semiconductor layer in which microcrystal grains having different sizes are mixed is formed by periodically adding a halogen-containing gas.