Semiconductor device manufacturing: process – Formation of semiconductive active region on any substrate
Reexamination Certificate
2001-09-28
2003-04-22
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Formation of semiconductive active region on any substrate
C438S479000, C438S492000, C117S054000
Reexamination Certificate
active
06551908
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid phase growth method and a liquid phase growth apparatus, specifically to a liquid phase growth method and a liquid phase growth apparatus for forming substrates which can be used for producing semiconductor devices, in particular, such as solar cells and optical sensors.
2. Related Background Art
As the global warming is becoming more serious, there has arisen a movement to limit CO
2
emissions worldwide. And attention is now being directed to the solar cell power generation which emits no CO
2
at the time of power generation.
Crystal silicon-based solar cells utilizing single-crystalline or polycrystalline silicon are high in photoelectric conversion efficiency and low in degradation, as compared with amorphous Si-based solar cells, but have the disadvantage of high production costs. In order to reduce such costs, in recent years attempts have been carried out to make thin a crystalline portion of silicon which is to be a power generating layer.
The crystalline Si-based solar cell made in a thin film state can withstand a certain bend; therefore, the shape of the solar cell as a product can be freely selected to some extent, and in some cases, the solar cell can be adhered to a curved surface.
One of the methods for forming single- or poly-crystalline Si which is to be a power generating layer of solar cells is the liquid phase growth method. The liquid phase growth method does not waste raw materials and allows obtaining a thin film having a necessary thickness as a power generating layer inexpensively, as compared with a vapor phase growth. Therefore, in order to improve the mass production of the thin films, there have been demands for a liquid phase growth method and an apparatus therefore which make it possible to treat a plurality of substrates together.
As a concrete example of the methods for treating a plurality of substrates together, Japanese Patent Application Laid-Open No. 1-72988 discloses a liquid phase growth method for treating a plurality of substrates together. A state in which this liquid phase growth method is carried out is shown in
FIGS. 1A and 1B
. In
FIGS. 1A and 1B
, reference numeral
101
denotes a substrate holder, numeral
102
a graphite container, numeral
103
a solution, and numeral
104
substrates.
FIG. 1A
shows a state in which the substrates
104
are arranged horizontally to the solution surface and
FIG. 1B
a state in which the substrates
104
are arranged perpendicularly to the solution surface. In this treatment apparatus, a semiconductor layer is formed on each of the substrate
104
by dipping the substrate in the solution
103
stored in the graphite container
102
.
Similarly, Japanese Patent Application Laid-Open No. 5-330984 discloses a liquid phase growth method, in which a plurality of substrates are arranged horizontally to the solution surface and a dipping process is adopted, and a holder used in the method.
The configuration of the liquid phase growth apparatus is shown in
FIGS. 2 and 3
. In
FIG. 2
, reference numeral
201
denotes a vertical barrel type reactor core, numeral
203
a crucible, numeral
204
a heater, numeral
103
a solution, numeral
104
growing substrates, numeral
209
a substrate holder, and numeral
220
a holding rod.
FIG. 3
shows a substrate holder, in which reference numeral
210
denotes an attaching frame, numeral
215
a holding frame, numeral
216
side-legs, numeral
216
a
slotted holes, numeral
218
b
engaging pins, numeral
217
a bottom plate, and numeral
218
spacers.
A plurality of substrates
104
for growth which are held by each spacer can be housed in the holder. And as seen from
FIG. 2
, the substrates
104
for growth are held horizontally to the surface of the solution
103
.
Japanese Patent Application Laid-Open No. 5-330979 discloses a liquid phase growth method, in which a plurality of substrates are arranged perpendicularly to the solution surface and a dipping process is adopted, and a holder used in the method. The configuration of the liquid phase growth apparatus is shown in FIG.
4
. In
FIG. 4
, reference numeral
310
denotes an electric furnace, numeral
203
a crucible, numeral
103
a solution, numeral
312
substrates for growth which can be attached to a holding rod, numeral
315
a holding rod, numeral
317
a driving means, numeral
318
a holder, and numeral
319
a lifter.
The substrates
312
are held perpendicularly to the solution surface, and at the time of lowering the holding rod
315
, the substrates are dipped in the solution
103
to start crystal growth.
In the liquid phase growth methods disclosed in Japanese Patent Application Laid-Open No. 1-72988 and Japanese Patent Application Laid-Open No. 5-330984, at the time of holding the substrates horizontally to the solution surface, since the solution depths of the dipped substrates are different from each other, the growth conditions of the substrates vary from each other, thereby giving rise to a problem of non-uniformness in crystal film thickness among the substrates.
On the other hand, like the liquid phase growth method disclosed in Japanese Patent Application Laid-Open No. 5-330979, when holding the substrates perpendicularly to the solution surface and rotating the substrate in the plane thereof, fluctuations in film thickness are decreased; however, since the substrates themselves are fixed to the holding rod in such a manner that the rod penetrates through the substrate, they are required to have a hole drilled therein, which means the drilled portions cannot be used for crystal growth. Further, since each substrate rotates on its center in a predetermined position, there arises a problem of limiting the supply of the solution to the substrate surface, thereby not making it possible to speed up the film deposition. And furthermore, the substrate arrangement of the prior art makes it difficult to treat many substrates together.
SUMMARY OF THE INVENTION
The present invention has been achieved under such circumstances as described above. Accordingly, a primary object of the present invention is to provide a method and an apparatus for producing semiconductor thin films which can ensure improvement in mass production by treating a plurality of substrates together while making full use of the characteristics of the liquid phase growth method and which can also ensure crystal films having uniform thickness and high quality.
In order to attain the above object, the present invention provides a method for producing semiconductor thin films, which comprises dipping a plurality of substrates into a solution filled in a crucible, the solution containing a semiconductor as a solute, and growing the semiconductor thin films on the plurality of substrates while moving the plurality of substrates in the solution, wherein an angle between the direction of a normal line on the central portion of a growing surface of each of the above substrates and the direction of the movement of the above substrates is set to be in a range of 5 degrees to 87 degrees, and wherein the movement of the above substrates generates the flow of the above solution.
Further, the present invention provides a method for producing semiconductor thin films, which comprises dipping a plurality of substrates into a solution filled in a crucible, the solution containing a semiconductor as a solute, and growing the semiconductor thin films on the plurality of substrates while moving the plurality of substrates in the solution, wherein an angle between the direction of a normal line on the central portion of a growing surface of each of the above substrates and the direction of the movement of the above substrate is set to be in a range of 93 degrees to 175 degrees, and wherein the movement of the above substrates generates the flow of the above solution without generating a substantial vortical flow in the vicinity of the above growing surface.
Further, the present invention provides an apparatus for producing semiconductor thin film
Iwakami Makoto
Iwane Masaaki
Mizutani Masaki
Nishida Shoji
Saito Tetsuro
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Niebling John F.
Roman Angel
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