Method of making semiconductor film

A method of making a semiconductor film on a substrate having a non-flat surface, by placing the substrate in a reaction chamber including at least a pair of discharge electrodes, an inlet of a reaction gas for producing a desired semiconductor film, and an outlet for reduced pressure, and performing a discharge in the presence of said reacrion gas for producing said semiconductor film, while arranging said non-flat surface of said substrate outside a plasma region formed between said discharge electrodes and further locating said non-flat surface substantially in a vertical direction with respect to electrode surfaces of said discharge electrodes, thereby semiconductor film being directly and uniformly deposited on said non-flat surface of said substrate, which is of worth in the production of, e.g., roofing tile-shaped photovoltaic devices.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a method of making a semiconductor film, and more 
particularly to a method of making a semiconductor film and a photovoltaic 
device for depositing a semiconductor film by plasma decomposition of a 
reaction gas on a non-flat surface combined with a curved or flat surface 
of a substrate. 
2. Description of the Prior Art 
A semiconductor film of an amorphous silicon system obtained by the plasma 
decomposition of the reaction gas has been used as photovoltaic devices, 
so called solar cells for directly converting solar energy to electrical 
energy, photoconductive drums for electronic photography or copiers, and 
the like. Since photovoltaic devices employ inexhaustible solar energy as 
an energy source, they have attracted the attention as a solution to the 
problem associated with exhaustion of energy resources. The sun renders 
the energy of about 1 kW/m.sup.2 to the ground during fine weather. When 
the photovoltaic device for converting such solar energy to electrical 
enerry is used in a home as a power source, it is generally installed on 
the rooftop or roof of the house. 
Roofing tiles provided with solar cells, that is, tile-shaped photovoltaic 
devices, as disclosed in Japanese published unexamined patent application 
No. 57-68454 or Japanese published unexamined utility model application 
No. 58-11261, are suitable for home power sources. 
One object of the present invention is to provide a method of making a 
semiconductor film for depositing a good semiconductor film on a curved 
surface of a substrate such as a photoconductive drum or roofing tile with 
solar cells suitable for the home power source. 
It has been known that an amorphous silicon film is produced by a glow 
discharge in a silicon compound atmosphere as disclosed in Japanese 
published examined patent application No. 53-37718 (U.S. Pat. No. 
4,064,521). The formation of the amorphous semiconductor film by using 
known glow discharge has such a disadvantage that since a glass or 
stainless steel substrate to deposit the semiconductor film is located 
between opposing parallel electrodes for exciting the glow discharge, the 
substrate is intersected with the moving direction of high speed charged 
particles of plasma in the moving range with the result that the high 
speed charged particles in the plasma impinge upon the substrate surface, 
thereby deteriorating characteristics of a transparent conductive film 
previously deposited on the substrate or the amorphous semiconductor film 
gradually deposited on the substrate. In addition, although the surface of 
the substrate to deposit the amorphous semiconductor film is flat, the 
substrate according to the present invention is of curved surface. 
Therefore, when the substrate with the curved surface is arranged between 
parallel flat electrodes as in the conventional technique, the distance 
between the curved surface and one of parallel flat electrodes becomes 
unequal, so that the deposited amorphous semiconductor film may not become 
uniform. 
Accordingly, it was difficult to directly deposit uniform semiconductor 
film on the substrate having the non-flat surface. 
SUMMARY OF THE INVENTION 
According to the present invention, there is provided a method of making a 
semiconductor film which comprises the steps of: placing a substrate 
having a non-flat surface in a reaction chamber including at least a pair 
of discharge electrodes, an inlet of a reaction gas for producing a 
desired semiconductor film and an outlet for reduced pressure; and 
performing a discharge in the presence of the reaction gas of producing 
the semiconductor film, while arranging the non-flat surface of the 
substrate outside a plasma region formed between the discharge electrodes 
and further locating the non-flat surface substantially in a perpendicular 
direction with respect to the electrode surfaces of discharge electrodes, 
thereby depositing a semiconductor film on the non-flat surface of the 
substrate. 
Further, according to the present invention, a method of making a 
photovoltaic device using the method described above is provided.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
One of the most characteristic points of the present invention is to 
arrange a substrate for depositing a semiconductor film outside a plasma 
region. Another of the most characteristic points is to substantially 
locate the substrate in a perpendicular direction with respect to 
electrode surfaces of discharge electrodes, thereby arranging a non-flat 
surface of the substrate in opposition to the plasma region. 
Substrates having at least a non-flat surface may be employed. Cylindrical 
substrates, substrates with corrugated curved surfaces, and the like may 
be typically given. Further, its material may depend on the use, and 
usually it may be preferable to utilize insulating materials although 
insulating materials such as glass, ceramics, plastics, etc, and 
conductive materials such as aluminum die casting can be used. 
The method of making the semiconductor film according to the present 
invention is preferable as a method of fabricating a photovoltaic device 
for directly forming a photoelectric conversion region on a substrate 
particularly having a non-flat surface. That is, using a substrate on 
which a film electrode has been provided, the photoelectric conversion 
region can be made by depositing a semiconductor film according to the 
method described above and further depositing an electrode on the 
semiconductor film, whereby the photovoltaic device directly provided with 
the photoelectric conversion region on the surface will be obtained. In 
this case, it may be preferable to use transparent materials as 
substrates, and it may also be preferable to employ transparent conductive 
oxide layers such as indium tin oxide as film electrodes. 
The photoelectric conversion region may be generally divided into sections. 
The division may be performed by patterning the film electrode, the 
semiconductor film and the upper electrode, respectively, using masks and 
energy beam. 
A method of making a semiconductor film on a substrate according to the 
present invention will now be described by embodiments applied to a method 
of producing a roofing tile-shaped photovoltaic device. 
FIGS. 1 and 2 show a photovoltaic device produced by the method of the 
present invention, wherein FIG. 1 is a perspective view and FIG. 2 is a 
sectional view taken along I--I line in FIG. 1. (1) is a substrate which 
is obtained by molding a transparent and insulating material such as 
reinforced glass, transparent ceramics, etc into a tile and which includes 
a corrugated insulated surface. (2a) to (2e) are a plurality of 
photoelectric conversion regions which are arranged on the insulated 
surface of the substrate (1) at desired distances. Each photoelectric 
conversion region (2a) to (2e) presents a film-shaped structure of micron 
order which is provided by successively depositing a transparent 
conductive film (3) such as tin oxide, indium tin oxide, etc, an amorphous 
silicon system semiconductor film (4) having a semiconductor junction, and 
a back electrode film (5) making an ohmic contact with the semiconductor 
film on the substrate (1). 
The amorphous semiconductor film (4) includes P-type layer with a thickness 
of the order of 50 to 250 .ANG., an I-type (intrinsic) layer with a 
thickness of the order of 4000 to 7000 .ANG., and N-type layer with a 
thickness of the order of 300 to 600 .ANG. from the light receiving 
surface so as to form PIN junction parallel to the film surface in the 
interior thereof, which are successively deposited on the substrate. 
accordingly, when the solar rays are applied to the amorphous 
semiconductor film through the substrate (1) and the transparent 
conductive film (3), free electrons and holes are mainly generated in the 
I-type layer. The resulting electrons and holes are attracted by the 
electric potential of the PIN junction provided by the respective layers 
and collected to each transparent conductive film (3) and each back 
electrode film (5), so that added electric power will be obtained by 
electrically connecting the transparent conductive film (3) of the 
photoelectric conversion region (2a) to (2e) to the back electrode film 
(5) in series. 
FIGS. 3 to 11 are partially enlarged sectional views and schematic 
perspective views for explaining a method of making the photovoltaic 
device shown in FIG. 1. 
An indium oxide layer and a tin oxide layer are successively deposited by 
electron beam evaporation techniques on entire curved surface of the 
substrate which includes a plurality of photoelectric conversion regions 
(2a) to (2e), while covering the circumference of the substrate (1) with a 
mask, thereby providing the transparent conductive film (3) with a 
thickness of 500 to 4000 .ANG. having a laminated structure thereon. FIG. 
3 shows a condition such that the transparent conductive film (3) is 
divided into respective photoelectric conversion regions (2a) to (2e) by 
applying an energy beam such as laser beams thereto. Nd:YAG laser having 
the wavelength of 1.06 .mu.m, the energy density of 7.times.10.sup.7 
W/cm.sup.2, and the pulse frequency of 3 KHz is preferably used as the 
laser. The transparent conductive film (3) is patterned at the scanning 
speed of 50 mm/sec by using an objective with the focus of 50 mm. The 
distance (L1) between transparent conductive films (3), which is obtained 
by removing conductive film by laser patterning process, is given by about 
50 .mu.m. 
The point to be remarked in the laser patterning process is that the 
distance between transparent conductive films (3) of the workpiece must 
not be greatly changed. That is, with respect to the laser beam applied to 
the objective, the energy density and the processing width are controlled 
by the convergence action due to the lens. Therefore, when the distance 
between workpieces is greatly changed as described above, the energy 
density and the processing width are also changed so that desired 
processing can not be performed. 
Accordingly, when the transparent conductive film (3) directly deposited on 
the curved insulated surface is intended to be divided into respective 
photoelectric conversion regions (2a) to (2e), the substrate (1) is 
disposed on XYZ stage (6) which is movable in directions of X, Y and Z 
axes as shown in FIG. 4, and the direction of X axis on XYZ stage (6) is 
aligned with the direction of edge line of the surface of an the substrate 
(1). The laser beam (8) is then applied to the workpiece in the process 
for moving the stage in the direction of X axis while keeping the distance 
between the objective (9) and the workpiece at a constant state. 
Thereafter. when the removal of the transparent conductive film (3) 
located at one space portion is finished by moving the substrate (1) in 
the direction of X axis, the substrate (1) is moved in the direction of Y 
axis so as to oppose the objective (9) to the transparent conductive film 
(3) located at the portion to be next removed. Under the condition, the 
distance between the objective (9) and the workpiece is different from 
such a case that the laser beam has been applied to the transparent 
conductive film, because the curved insulated surface of the substrate (1) 
is varied in direction of Y axis. Accordingly, XYZ stage (6) is vertically 
moved in the direction of 7, axis and corrected to obtain predetermined 
distance. After the correction, XYZ stage (6) is again moved in the 
direction of X axis with the result that unwanted transparent conductive 
film (3) located at a space portion is removed by application of the laser 
beam. Such operations are repeatedly carried out to pattern the 
transparent conductive film (3) in parallel with the curved edge line (7) 
as shown in FIG. 3. 
After patterning of the transparent conductive film (3), the process turns 
on the deposition process of the amorphous semiconductor film (4). FIG. 5 
shows schematically a process for depositing an amorphous silicon system 
amorphous semiconductor film (4), such as amorphous silicon (a-Si:H), 
amorphous silicon carbide (a-Si.sub.x C.sub.1-x :H), amorphous silicon 
stannate (a-Si.sub.y Sn.sub.1-y :H), and the like, on the substrate (1) by 
exciting a glow discharge in a silicon compound atmosphere such as 
monosilane (SiH.sub.4), disilane (Si.sub.2 H.sub.6), and the like and 
plasma decomposing the reaction gas. 
The substrate (1) with the curved insulated surface used for the present 
invention are not disposed between parallel flat electrodes (discharge 
electrodes) opposed to each other. The deposition surfaces of the 
substrates (1) are arranged outside the parallel flat electrodes and 
substantially located in a perpendicular direction with respect to 
opposite surfaces of the electrodes. In such a condition, the amorphous 
semiconductor film (4) is produced while moving the substrates (1) in the 
direction of the curved surface as shown in the drawing, that is, in the 
perpendicular direction with respect to the edge line (7). In the 
embodiment of FIG. 5, the parallel flat electrodes constitute a 
multielectrode structure in which earth electrodes (10),(10),(10) and 
radio frequency electrodes (12)(12) are alternately opposed and arranged 
in parallel, and the substrates (1) are transferred in the parallel 
direction of these electrodes (10) and (12). 
On the multielectrode structure, however, the glow discharge is basically 
excited between one earth electrode (10) and one radio frequency electrode 
(12) that are opposed to each other, thereby generating the plasma between 
both electrodes, and silicon atoms, for example, obtained by decomposing 
the reaction gas are deposited on the curved surfaces of the substrates 
(1) near located outside both electrodes to form gradually the amorphous 
semiconductor film (4) on the substrate surfaces. Accordingly, it is not 
always necessary to adopt the multielectrode structure. 
By arranging the substrates (1) outside alternately opposed earth 
electrodes (10)(10)(10) and radio frequency electrodes (12)(12), as 
described above, the deposition surfaces of the substrates (1) are 
separated from the moving region of the high speed charged particles in 
the plasma, and the collision of charged particles is remarkably reduced 
with the result that unwanted damage to the amorphous semiconductor film 
(4) is decreased. Next, for forming (depositing) the amorphous 
semiconductor film (4), the substrates (1) are moved in the curved 
direction of each surface (the parallel direction of electrodes), thereby 
providing the amorphous semiconductor film (4) having high uniformity as 
shown in FIG. 6. 
In addition, it is also possible to increase the deposition rate of the 
film since the high frequency output, which has been suppressed so as to 
reduce the damage caused by the high speed charged particles during the 
deposition of the amorphous semiconductor film, can be increased. 
In the embodiment shown in FIG. 5, two substrates (1) are provided so as to 
put alternately disposed earth electrodes (10)(10)(10) and radio frequency 
electrodes (12)(12) therebetween. Accordingly, the formation of the 
amorphous semiconductor film (4) is performed against two substrates 
(1)(1) at the same time. At this time, a heater to heat the substrates 
(1)(1) is buried in a recessed portion of a reaction chamber not shown, 
thereby uniformly heating respective substrates (1)(1) from back surfaces. 
FIG. 7 shows schematically another deposition (formation) process of the 
amorphous semiconductor film (4), which is different from the embodiment 
described above, that is, the first embodiment in the concrete structure 
including the opposed condition relating to earth electrodes (10)(10) and 
radio frequency electrodes (12)(12) and the substrate (1), and a gas 
supply member (13) for discharging the reaction gas. That is, opposite 
surfaces (10a)(12a) of respective earth electrodes (10)(10) and radio 
frequency electrodes (12)(12) opposed to the substrate (1) present curved 
surfaces with similar configuration so as to be opposed to the curved 
surface of the substrate in parallel. Accordingly, by rendering the curved 
surfaces with similar configuration to opposite suriaces (10a)(12a) of 
respective electrodes (10)(12), the opposing distance between opposite 
surfaces (10a)(12a) and the substrate (1) becomes enual so that uniform 
amorphous semiconductor film (4) can be obtained in the stopped condition 
of the substrate. However, if more uniform amorphous semiconductor film 
(4) is desired, it may be preferable that the deposition process is 
performed in the same manner as the first embodiment, while moving the 
substrate (1) in the direction of earth electrodes (10)(10) and radio 
frequency electrodes (12) (12) located in parallel [the direction of edge 
line of the substrate (1)] as shown by an arrow in the drawing. 
Further, the gas supply member (13) includes a gas discharge surface (15) 
having a great number of discharge apertures (14)(14). The gas discharge 
surface (15) is arranged so as to be opposed to the curved surface of the 
substrate (1) through earth electrodes (10)(10) and radio frequency 
electrodes (12)(12), and also presents similar configuration to the 
surface of the substrate (1) so as to make the opposing distance between 
the gas discharge surface and the curved surface of the substrate equal. 
The reaction gas to be discharged depends on the amorphous semiconductor 
to be formed. However, in the case of amorphous silicon, for example, 
diborane (B.sub.2 H.sub.6) containing P-type impurity or phosphine 
containing N-type impurity is preferably added to a base of monosilane 
(SiH.sub.4) or disilane (Si.sub.2 H.sub.6). Another substrate (1) may be 
employed instead of the gas supply member (13). 
According to first and second embodiments, the amorphous semiconductor film 
(4) can be produced by approximately same reaction conditions. 
The following shows basic reaction conditions for producing PIN junction 
type amorphous silicon. 
______________________________________ 
Substrate temperature 
250 to 300.degree. C. 
Radio frequency power source 
13.56 MHz 
Radio frequency output 
100 W 
Reaction gas (composition ratio) 
P--type layer B.sub.2 H.sub.6 /SiH.sub.4 = 0.1% 
I--type layer (non-doped layer) 
SiH.sub.4 = 100% 
N--type layer PH.sub.3 /SiH.sub.4 = 1% 
Gas pressure 0.3 to 1 Torr 
Gas flow rate 10 to 40 cc/min 
______________________________________ 
Further, a concrete reaction apparatus is shown in FIG. 11. FIG. 11 is a 
schematic perspective view of the reaction apparatus corresponding to the 
second embodiment, which includes a reaction chamber (50) comprising 
discharge electrodes (10)(12), the gas supply member (13) having discharge 
apertures for a desired reaction gas, and a reduced pressure and exhaust 
valve (501). In the drawing, (51) is a charging chamber for the substrate, 
(52) is a taking out chamber for the substrate, (511) and (521) are valves 
for reduced pressure, (512) is an inlet shutter, (522) is an outlet 
shutter, (513) is an isolation shutter, (53) is a gas mixer, and (502) is 
a gas supply valve, respectively. (A) to (D) show reaction gas bombs. (A) 
is an SiH.sub.4 bomb, (B) is a B.sub.2 H.sub.6 bomb, (C) is a PH.sub.3 
bomb, and (D) is a CH.sub.4 bomb. In the drawing, a substrate transfer 
arrangement for passing the substrate through the charging chamber (51), 
the reaction chamber (50) and the taking out chamber (52) is omitted. 
SiH.sub.4 used as the silicon supply gas can be substituted for gases 
expressed by Si.sub.n H.sub.2n+2 (n is integer of above 2). Si.sub.2 
H.sub.6, Si.sub.3 H.sub.8, Si.sub.4 H.sub.10 and the like is concretely 
given. SiF.sub.4 may be employed under certain circumstances. 
Gases containing Group III element such as [(CH.sub.3)].sub.3 Ga, (C.sub.2 
H.sub.5).sub.3 Al, and the like can be used instead of B.sub.2 H.sub.6 for 
P-type doping gas. 
PH.sub.3 used as N-type doping gas can be substituted for gases containing 
Group V element such as AsH.sub.3, NH.sub.3, and the like. 
Of course, additional gases for producing the semiconductor film known in 
the field may be added to these gases. 
The amorphous semiconductor film (4) such as amorphous silicon, uniformly 
deposited on the curved surface of the substrate (1) according to the 
method of the present invention, is placed on XYZ stage (6) shown in FIG. 
4. As shown in FIG. 8, space portions of the amorphous semiconductor film 
(4) are removed by application of a laser beam (8) to provide separated 
photoelectric conversion regions (2a) to (2e), and a part of each 
transparent conductive film (3), covered with the removed amorphous 
semiconductor film (4), is exposed over whole length in the scanned 
direction of the laser beam (8). Nd:YAG laser having the wavelength of 
1.06 .mu.m, the energy density of 5.times.10.sup.7 W/cm.sup.2 and the 
pulse frequency of 3 KHz is used as the laser to be employed. The distance 
(L2) between removed amorphous semiconductor films (4) is set to about 200 
.mu.m. 
For keeping the distance between the objective (9) and the workpiece at a 
constant state in the same manner as the transparent conductive film (3), 
the scanning direction of the laser beam (8) is the direction of edge line 
(7) in the curved surface of the substrate (1) that is aligned with X axis 
of XYZ stage (6). The laser beam (8) is scanned at a rate of 50 mm/sec by 
moving XYZ stage in the direction of X axis. When one of space portions 
has been scanned by the laser beam (8), XYZ stage (6) is transferred in 
the direction of Y axis to oppose the amorphous semiconductor film (4) to 
be next removed to the objective (9). Thereafter, XYZ stage (6) is moved 
in the direction of Z axis so as to correct the opposing distance between 
the amorphous semiconductor film and the objective to predetermined value. 
The scanning operation of the laser beam (8) is repeated by again moving 
the stage in the direction of X axis, thereby patterning the amorphous 
semiconductor film (4)(4) in parallel with the edge line (7) of the 
substrate surface under the exposed condition of a part of the transparent 
conductive films (3)(3). 
Next, as shown in FIG. 9, a back electrode film (5) is continuously 
deposited on all of photoelectric conversion regions (2a) to (2e) which 
include exposed surfaces of amorphous semiconductor films (4)(4) and 
transparent conductive films (3)(3). 
As shown in FIG. 10, the spaoe portions of the back electrode film (5) are 
removed by application of the laser beam (8) in order that an extended 
portion (5a) of the back electrode film (5) extending from one of 
photoelectric conversion regions (2a) to (2e) is connected to an exposed 
portion (3a) of the transparent conductive film (3) of adjacent 
photoelectric conversion region. The length (L3) is set to 50 .mu.m. The 
laser to be employed is Nd:YAG laser in the same manner as the transparent 
conductive film (3) and the amorphous semiconductor film (4). It is 
scanned at a rate of 50 mm/sec by transferring XYZ stage (6) in the 
direction of X axis. 
On the operation after scanning the back electrode film in the direction of 
X axis, that is, on correcting the distance between the objective (9) and 
the workpiece, the description is omitted because it is the same process 
as the laser patterning (removal) process described above. These 
patternings may be performed using a mask. 
When the removing processes of films are carried out by application of the 
laser beam (8), one must note that if another film is present under the 
film portion to be removed, it is not damaged. The density of threshold 
value for processing the amorphous silicon system amorphous semiconductor 
film (4) by the laser beam (8) is about 4.times.10.sup.7 W/cm.sup.2 that 
is lower than 7.times.10.sup.7 W/cm.sup.2 for the transparent conductive 
film (3). Therefore, if the laser beam (8) is directly applied to the 
transparent conductive film (3) in removing process of the amorphous 
semiconductor film (4), unwanted damage is not rendered thereto. 
However, it is general that materials capable of forming the back electrode 
film, that is, metals making an ohmic contact with the amorphous 
semiconductor film (4) are high in the energy density of processing 
threshold value as compared with that of the transparent conductive film 
(3). Since aluminum, for example, is low in the absorption rate of the 
laser beam and is good in the thermal conductivity, the applied heat of 
the laser beam is dissipated. Accordingly, the energy density of 
processing threshold value shows slightly higher value given by about 
8.times.10.sup.7 W/cm.sup.2 at 5000 .ANG. in thick than that of the 
transparent conductive film although it depends upon the film thickness. 
It is then preferable to reduce the energy density of processing threshold 
value to 2.times.10.sup.7 W/cm.sup.2. This is achieved without 
constituting the back electrode film (5) by only aluminum by making the 
film thickness of aluminum thin such as about several hundreds A and 
putting a material having a high absorption rate and a thickness of the 
order of 5000 .ANG., such as titanium or titanium-silver alloys, on the 
aluminum surface to form a laminate. The back electrode film (5) may be 
constituted by only titanium or titanium--silver alloys. 
Further, when the amorphous silicon system amorphous semiconductor film on 
a surface of a photoconductor drum by the plasma decomposition of the 
reaction gas such as SiH.sub.4 and the like described above, a 
photoconductive layer composed of an amorphous semiconductor film for 
making uniform electrostatic latent images with good quality can be 
obtained if the deposition process is carried out while rotating and 
transferring the photoconductor drum. 
FIGS. 12 and 13 are another example of a photovoltaic device manufactured 
by the method according to the present invention. 
The characteristic of this embodiment is that a plurality of photoelectric 
conversion regions (2)(2) are arranged so as to intersect with the edge 
line (7) of the curved surface of the substrate (1). That is, in the 
embodiment strip-shaped photoelectric conversion regions (2)(2) are 
arranged in parallel so that long sides of regions are vertically 
intersected with the edge line (7) of the corrugated curved surface. FIG. 
13 corresponds to the sectional view taken along such edge line (7). 
The photovoltaic device shown in FIG. 12 is more preferable as compared 
with the device shown in FIG. 1. The reason for this will be described as 
follows. 
FIG. 14 shows schematically a relation between solar rays S.sub.1, S.sub.2 
and S.sub.3 and incident angles with respect to the photoelectric 
conversion regions when the photovoltaic device of the embodiment is 
installed on a roof facing the south. This is an example in the case where 
the sun with an angle of .theta. is inclined to the east or west with the 
southing as the center. That is, when the solar rays S.sub.1 irradiate the 
photoelectric conversion region (2)(2) from the position that is inclined 
in the direction of the south by an angle of .theta., they are vertically 
applied to the light receiving portion A, and the photoelectric conversion 
operation of the light receiving portion A becomes maximum. However, as 
the solar rays S.sub.1 are not vertically applied to light receiving 
portions B and C, the incident light energy become hv sin .alpha..sub.1 
and hv sin .alpha..sub.2, respectively. when the light energy of the solar 
rays S.sub.1 are given by hv and respective incidence angles are rendered 
by .alpha..sub.1 and .alpha..sub.2. Accordingly, the light energy applied 
to the light receiving portion C having low incidence angle becomes 
minimum. 
But, the incident light energy is given by only the solar rays S.sub.1 as 
the incidence light. The incidence of light from another direction, the 
reduction of incidence light due to reflection, and the like are not 
considered. 
Accordingly, respective light receiving portions A, B and C are operated as 
photoelectric conversion portions in proportion to the incident light 
energies hv, hv sin .alpha..sub.1 and hv sin .alpha..sub.2. The quantity 
of power generation of the light receiving portion A becomes maximum, 
while the quantity of power generation of the light receiving portion C 
becomes minimum. That is, the quantities of power generation in respective 
light receiving portions are different from one another. 
In the case of the southing where the solar rays S.sub.2 are vertically 
applied to the light receiving portion B, the quantity of power generation 
of the light receiving portion B becomes maximum, and the quantity of the 
light receiving portion A equal to sin component of the incidence angle 
and the quantity of the light receiving portion C are lower than that of 
the light receiving portion B. 
Further, when the solar rays S.sub.3 irradiate the photoelectric conversion 
regions (2)(2) from a position where the sun is inclined in the west at an 
angle of .theta., the relative relation among respective quantities of 
light receiving portions A, B and C are reversed; the light receiving 
portion C becomes maximum conversely when the photoelectric conversion 
regions are irradiated from a position where the sun is inclined in the 
east at an angle of .theta.. 
As described above, the quantity of power generation in each light 
receiving portion is varied with the movement of the sun. 
On the contrary, in the photovoltaic device (the area of the photoelectric 
conversion regions is equal to one another) shown in FIG. 1, the first 
photoelectric conversion region (2a) renders maximum photoelectric 
conversion operation with respect to the solar rays S.sub.1 inclined in 
the west at an angle of .theta., thereby generating a photocurrent of 
about 15 mA/cm.sup.2. But, the respective photocurrents of second and 
third photoelectric conversion regions (2b) and (2c) become 15 mA/cm.sup.2 
.times.sin 60.degree..apprxeq.13 mA/cm.sup.2 and 15 mA/cm.sup.2 .times.sin 
30.degree.=7.5 mA/cm.sup.2 when incidence angles .alpha..sub.1 and 
.alpha..sub.2 are given by 60.degree. and 30.degree.. Since whole output 
current of the photovoltaic device is regulated by the minimum output as 
known in the prior art, it becomes 7.5 mA/cm.sup.2 of the third 
photoelectric conversion region (2c). That is, in the photovoltaic device 
that includes photoelectric conversion regions (2a)(2b) and (2c) arranged 
in parallel with the edge line (7) of the tile-shaped substrate (1) as 
shown in FIG. 1, if a certain photoelectric conversion region generates 
maximum photocurrent with the movement of the sun, whole output power of 
the photovoltaic device is regulated by the low photocurrent when the 
photocurrent of another photoelectric conversion region becomes low. 
However, when respective photoelectric conversion regions (2)(2) are 
aligned and arranged so as to intersect with the edge line (7) as shown in 
FIG. 12, one of photoelectric conversion regions (2)(2) includes all of 
light receiving portions A, B and C at the same time. Accordingly, if the 
sun is moved, photocurrents generated by respective photoelectric 
conversion regions (2)(2) are always equal to one another with the result 
that whole output current of the photovoltaic device is increased. As 
compared with the device of FIG. 1 having the output current of 7.5 
mA/cm.sup.2, for example, the output of the device shown in FIG. 12 is 
given by (15+13+7.5)/3=11.8 mA/cm.sup.2 whose value is rendered by the 
arithmetic mean of photocurrents generated in the light receiving portions 
A, B and C. Accordingly, the output power is increased to about 60% in the 
photovoltaic device which is provided with both the substrate (1) having 
the same configuration and the equal total light receiving area. 
One suitable structure in the photovoltaic device shown in FIG. 12 is 
practically constituted by using a reinforced glass substrate having a 
height difference of curved surface of about 30 mm and about 300 mm square 
(thickness:about 10 mm) and providing about 11 photoelectric conversion 
regions (2)(2) on the glass substrate at equal distances of several mm. 
This photovoltaic device can generate the electric power of about 2 W 
every one sheet or unit. Therefore, the electric power can be sufficiently 
supplied to general homes during daytime by using about 500 sheets, for 
example, as roofing tiles. 
The photovoltaic device shown in FIG. 12 can be produced in the same manner 
as the device shown in FIG. 1. However, if the laser beam is converged in 
the patterning process of the amorphous semiconductor film so as to obtain 
the photoelectric conversion regions (2)(2) by merely using one projected 
tye objective, there is provided such a problem that the opposing distance 
between the objective and the workpiece is changed. This is a critical 
problem as compared with case for patterning the amorphous semiconductor 
film or transparent conductive film in parallel with the edge line as 
shown in FIG. 1. As shown in FIGS. 15 and 16, a convergence arrangement 
(70) for a laser beam (60) comprises a convex lens (80) with a focal 
length f1 located at a side of laser source (not shown), and a concave 
lens (90) with a short focal length f2 coaxially located in a side of the 
workpiece so as to align the focus (F) of the convex lens (80) with the 
virtual focus. That is, the laser beam (60) emitted from the laser source 
and being in parallel with an optical axis (100) is applied to the convex 
lens (80), refracted and gradually converged towards the focus (F). The 
laser beam (60), which is adapted to be entered in the concave lens (90) 
disposed in the convergent way, is applied to the concave lens (90) since 
the virtual focus of the concave lens (90) is aligned with the focus (F) 
of the convex lens (80). After refraction, the laser beam is transmitted 
in parallel with the optical axis (100). 
As described above, after the beam diameter w1 of the laser beam (60) is 
once converged by the convex lens (80), the laser beam (60) is transmitted 
through the concave lens (90) and converted to a parallel beam with a beam 
diameter w2 to perform desired processing. Consequently, even if the 
opposing distance between the concave lens (90) and the workpiece was 
varied along the curved surface of the substrate (1) by moving (scanning) 
XY stage (6') in a direction of X axis, the beam diameter w2 of the laser 
beam (60) applied to the workpiece, that is, the energy density and the 
processing width will not be changed as shown in FIG. 17, thereby carrying 
out desired processing. 
In the explanation described above, there has been described the example in 
detail wherein the converged diameter w2 of the laser beam (60) is kept 
constant by combination of the convex lens (80) and the concave lens (90) 
without variation of the opposing distance between the workpiece and the 
concave lens. However, if the scanning direction of the laser beam (60), 
for example, was given by the direction of X axis as shown in FIG. 5, it 
can be possible to use a lens array or short focus lens array as 
convergence arrangements. The lens array is that the focal length is 
momentarily changed in the direction of X axis corresponding to the 
variation of the opposing distance between the workpiece and the cancave 
lens. The short focus lens array is that rod-shaped short focus lenses, 
whose lens length is momentarily changed, are aligned and arranged in the 
direction of X axis. 
The tile-shaped (corrugated) photovoltaic device (1') produced by the 
method of the present invention described above is usually employed by 
combining a plurality of devices together with outside connected 
reverse-current protective diodes (20) and reverse withstand voltage 
diodes (30) as shown in FIG. 18. 
Under certain circumstances, these reverse-current protective diodes and 
reverse withstand voltage diodes are directly provided on the substrates. 
FIG. 19 shows this embodiment. Photovoltaic devices (1') (1') with the 
film-shaped photovoltaic elements, the reverse-current protective diodes 
and reverse withstand voltage diodes are contiguously arranged in such a 
manner that a part of them is overlapped at four sides as usual tile array 
when a house is covered with tiles. Such example is adapted to tile 
arrangements of roofs and directed to power modules utilizing solar light 
irradiated to the roof. 
FIGS. 20 to 23 show details of the device (1'). Referring to FIGS. 20 and 
21 illustrating main and back surfaces of the device (1'), a film-shaped 
photoelectric conversion region (41) is deposited on the center of the 
back surface (1a) of the substrate. A film-shaped reverse current 
protective diode (42) and a film-shaped reverse withstand voltage diode 
(43), which are electrically connected to the region (41), are provided at 
upper and left sides of the back surface. First and second conductive 
films (44) and (45), electrically connected to the region (41), are 
further provided at right and lower sides of the back surface. Third and 
fourth conductive films (46) and (47), electrically connected to the 
reverse-current protective diode (42) and the reverse withstand voltage 
diode (43). are deposited at upper and right sides of the main surface 
(1b) of the substrate. 
First to fourth conductive films (44) to (47) are located at overlapped 
portions of adjacent substrates when devices (1') are arranged in the form 
of the tile as shown in FIG. 19. The electrical connection among 
respective substrates is achieved by connecting each conductive film (44) 
to (47) to the fourth conductive film (47), the third conductive film 
(46), the second conductive film (45) and the first conductive film (44) 
of adjacent substrates. The reverse-current protective diode (42) and the 
reverse withstand voltage diode (43) are also located at the overlapped 
portions, so that any influence is not rendered to the occupying area of 
the device (1'). 
FIGS. 22 and 23 show details of the device and respective diodes (42)(43). 
The device (1') comprises a plurality of parallel regions (11a) to (11e) 
each of which includes the transparent electrode film (3) deposited on the 
back surface (1a) of the substrate, the amorphous semiconductor film (4) 
with PIN junction deposited on the electrode film (3), and the back 
electrode film (5) of aluminum. Light entered in the substrate (1) from 
the main surface (1b) reaches the amorphous semiconductor film (4) through 
the transparent conductive film (3) to perform the power generation. 
Respective regions (11a) to (11e) are arranged in the form of series 
connection, so that voltages generated in respective regions are mutually 
added and appear between the transparent conductive film (3) of one end 
region (11a) and the back electrode film (5) of the other region (11e). 
The reverse-current protective diode (42) includes an amorphous 
semiconductor film (33) with a PN junction deposited on the extended 
portion (3a) of the transparent electrode film (3) constituting one end 
region (11a), and a cathode electrode film (34) of aluminum. A first 
conductive coating film (35) coated on the side surface of the substrate 
(1) is overlapped on the cathode electrode film (34) and extends to the 
substrate surface (1b) to provide the third conductive film (46). 
The reverse withstand voltage diode (43) comprises an anode electrode film 
(26) formed on the back surface (1a) of the substrate, an amorphous 
semiconductor film (27) with a PN junction deposited on the anode 
electrode film (26), and a cathode electrode film (28) of aluminum. Any 
materials may be used as materials of anode electrode film (26) if making 
an ohmic contact with the amorphous semiconductor film (27), but it may be 
preferable to employ the same material as that of the transparent 
electrode film (3) for the purpose of the manufacture of the device. A 
second conductive coating film (29) coated on the side surface of the 
substrate (1) is overlapped on the anode electrode film (26) and extends 
to the substrate surface (1b) to provide the fourth conductive film (47). 
Respective cathode electrode films (34) and (28) of reverse-current 
protective diode (42) and reverse withstand voltage diode (43) are 
composed of the same material and electrically connected through a wiring 
layer (300) (FIG. 21) formed on the back surface (1a) of the substrate. An 
extended portion (310) extending from the anode electrode film (26) of the 
reverse withstand voltage diode (43) and an extended portion (320) 
extending from the back electrode film (5) of another region (11c) are 
overlapped at respective end portions on the back surface (1a) of the 
substrate, thereby electrically connecting the anode electrode film (26) 
to the back electrode film (5). 
As respective diodes (42) and (43), Schottky barrier may be used instead of 
PN junction. Further, either diode can be omitted under certain 
circumstances. 
First and second conductive films (44) and (45) are provided by extending 
the back electrode film (5) that constitutes another region (11e). 
According to the device described above, the electrical connection among 
photovoltaic elements of substrates will be performed only by continuously 
arranging substrates having photoelectric conversion regions under 
partially overlapped condition. Further, it is not necessary to perform 
the external connection for the reverse-current protective diode and the 
reverse withstand voltage diode by using lead wires. Consequently, the 
connection for many devices can be easily carried out.