Single-crystal – oriented-crystal – and epitaxy growth processes; – Processes of growth from liquid or supercritical state – Liquid phase epitaxial growth
Reexamination Certificate
1998-11-27
2001-05-15
Kunemund, Robert (Department: 1765)
Single-crystal, oriented-crystal, and epitaxy growth processes;
Processes of growth from liquid or supercritical state
Liquid phase epitaxial growth
C117S060000, C117S934000, C118S412000
Reexamination Certificate
active
06231667
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid phase growth method an a liquid phase growth apparatus and, more particularly, to a liquid phase growth method or a liquid phase growth apparatus that can be applied to production of such devices as solar cells or photosensors.
2. Related Background Art
Emission of greenhouse-effect gases such as carbon dioxide and nitrogen oxides, resulting from combustion of petroleum in thermal power generation, combustion of gasoline in engines of cars, and so on, is responsible for deterioration of the global environments. There are also worries that crude oil will have been exhausted in the future, and attention thus has been focused on power generation using the solar cells.
Since thin film crystalline Si solar cells have a thin electricity-generating layer and use a small amount the raw material of Si, they can be produced at lower cost. Since the electricity-generating layer is crystalline Si, higher conversion efficiency and less deterioration can be expected, as compared with the solar cells amorphous Si or the like. Further, the thin film crystalline Si solar cells can be bent to some extent, and they can thus be used as being bonded to a curved surface, e.g. a body of a car, a household electrical appliance, a rood file, and so on.
For implementing the thin film crystalline Si solar cells, Japanese Patent Application Laid-Open No. 8-213645 discloses that thin-film single-crystal Si epitaxially grown is separated through a porous Si layer.
FIG. 20
is a sectional view to show a method for forming a solar cell of thin film Si described in Japanese Patent Application Laid-Open No. 8-213645. In the figure, reference numeral
101
designates a Si wafer,
102
a porous Si layer,
103
a p
+
Si layer,
104
a p
−
Si layer,
105
a n
+
Si layer,
106
a protective film,
109
,
111
an adhesive, and
110
,
112
a jig. In the production method of solar cell of
FIG. 20
, the porous Si layer
102
is formed in the surface of Si wafer
101
by anodization. After that, the p
−
Si layer
103
is epitaxially grown on the porous Si layer
102
and then the p
−
Si layer
104
and n
−
Si layer
105
are further grown thereon. Then the protective layer
106
is formed. After that, the adhesive
111
,
109
is applied onto the protective layer
106
and onto the Si wafer
101
, which are bonded to the jig
112
,
110
. After that, tensile force is exerted on the jig
112
,
110
so as to separate the Si wafer
101
from the epitaxial Si layers
103
,
104
,
105
through the porous Si layer
102
. Then the solar cell is formed in the epitaxial Si layers
103
,
104
,
105
and the Si wafer
101
is again used in like steps, thereby achieving cost reduction.
There are liquid phase growth methods as methods for forming single-crystal Si or polycrystal Si. The liquid phase growth methods permit the thick Si layers necessary for the electricity-generating layer of a solar cell to be produced at lower cost than such methods as CVD (Chemical Vapor Deposition). A specific example of the liquid phase growth method is disclosed in U.S. Pat. No. 4,778,478.
FIG. 21
is a sectional view of a liquid phase growth apparatus of a sliding method disclosed in U.S. Pat. No. 4,778,478. In the figure, reference numeral
50
denotes a sliding boat of a fire-resistive material such as graphite,
54
,
56
liquid baths,
58
a movable slide comprised of a metal substrate,
60
a recessed part in the bottom surface of the boat,
63
a barrier layer,
68
,
70
solvents,
72
a section for adhering a transparent conductive electrode,
75
a nozzle for forming an antireflection film,
74
a chamber thereof,
76
a wheel, and
78
a nozzle for forming the barrier layer. First, the movable slide
58
rolled up around the wheel
76
is unrolled and the barrier layer
63
is formed thereon by the nozzle
78
. Then semiconductor layers to become the electricity-generating layer are formed by liquid phase growth from the solvents
68
,
70
in the baths
54
,
56
. Thereafter, the transparent electrode is formed at the section
72
for adhering the transparent conductive electrode, and the antireflection film is formed by the nozzle
75
, thereby completing the solar cell. This liquid phase growth method of the sliding method has high efficiency of liquid phase growth and is thus advantageous in mass production of solar cells.
U.S. Pat. No. 5,544,616 discloses another liquid phase growth apparatus of a dipping system. A sectional view of this liquid phase growth apparatus is illustrated in FIG.
22
. In the figure, numeral
201
represents an exit,
202
a quartz crucible,
203
a graphite boat,
204
a heater,
205
an inlet of argon gas,
206
a thermocouple,
208
a lid,
209
an insulating region, and
210
a support base of graphite. The apparatus of U.S. Pat. No. 5,544,616 forms a semiconductor layer on a growth substrate by dipping the growth substrate in the solvent stored in the quartz crucible
202
.
In the case wherein the semiconductor layer is intended to be formed by liquid phase growth on a wafer as a substrate as it is, the sliding boat larger than the size of the wafer has to be prepared in the sliding method, e.g., in U.S. Pat. No. 4,778,478. It is, however, not easy to fabricate the sliding boat in a large scale, because it is made of the heat-resistant material such as graphite. In this aspect, the liquid phase growth apparatus of the sliding method is disadvantageous in producing large-area devices such as the solar cells or the photosensors. Therefore, the larger the size of the wafer, the more disadvantageous the use of the liquid phase growth apparatus of the sliding method.
Further, since the liquid phase growth apparatus using the dipping system as disclosed in U.S. Pat. No. 5,544,616 etc. excels in the liquid phase growth of large areas, it is advantageous in the case of the wafer being used as a substrate as it is, but is disadvantageous in continuous formation of the semiconductor layers such as the p-layer and n-layer.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a liquid phase growth apparatus using the dipping system suitably applicable to mass production using large-area devices such as the solar cells. Further, another object of the present invention is to provide a liquid phase growth method using the dipping system suitably applicable to mass production using large-area devices such as using solar cells.
Thus, present invention provides a liquid phase growth method using a dipping system comprising growing a semiconductor on a plurality using substrates, wherein the semiconductor is liquid-phase grown on the plurality of substrates using a plurality of liquid phase growth chambers.
The growth of the semiconductor on these plural substrates are preferably carried out simultaneously.
Incidentally, the term “simultaneously” as used in the specification and claims means that execution times of the plural operations overlap with each other even a little. In that case, it is preferable that during a period of execution of a certain operation, another operation be started and completed; more preferably, either start times or end times of plural operations or the both are coincident with each other.
Further, the present invention also provides a liquid phase growth method using a dipping system comprising growing a semiconductor on a plurality of substrates, wherein simultaneously with liquid phase growth of the semiconductor on one of the plurality of substrates, another of the plurality of substrates is subjected to annealing.
In addition, the present invention further provides a liquid phase growth method using a dipping system comprising growing a semiconductor on a plurality of substrates, wherein using a liquid phase growth apparatus having a liquid phase growth chamber and an annealing chamber, the semiconductor is liquid-phase grown on one of the plurality of substrates and another of the plurality of substrates is subj
Iwane Masaaki
Nakagawa Katsumi
Nishida Shoji
Shoji Tatsumi
Tanikawa Isao
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Kunemund Robert
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