Active solid-state devices (e.g. – transistors – solid-state diode – Non-single crystal – or recrystallized – semiconductor... – Amorphous semiconductor material
Reexamination Certificate
2002-06-26
2003-12-16
Jackson, Jerome (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Non-single crystal, or recrystallized, semiconductor...
Amorphous semiconductor material
C257S431000, C257S449000, C257S634000, C136S250000
Reexamination Certificate
active
06664567
ABSTRACT:
This application is based on applications Nos. 2001-195878, 2001-224634, and 2001-257608 filed in Japan, the content of which is incorporated hereinto by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photoelectric device using numerous crystalline semiconductor particles. This photoelectric conversion device is utilized suitably in solar cells.
The present invention also relates to a glass composition for coating silicon that is used for protecting a part of or the entire surface of silicon or for insulation between electrodes.
The present invention also relates to an insulating coating that is formed in a silicon semiconductor device and in contact with the silicon.
2. Description of the Related Art
(A) Advent of a next-generation, low-cost solar cell that allows the amount of the raw material, silicon, to be small has been eagerly awaited.
Conventional photoelectric devices in which crystalline semiconductor particles are used are shown in
FIGS. 4
to
6
.
FIG. 4
illustrates a structure disclosed in Japanese Unexamined Patent Publication (Kokai) No. Showa 61-124179. There is disclosed a photoelectric conversion device in which a first aluminum foil
10
is formed with apertures into which silicon balls
2
each having a n-type surface layer
9
formed on the surface of a p-type ball are inserted. The portions of the n-type surface layers
9
that have penetrated the back surface of the first aluminum foil
10
are removed, and an oxide layer
3
is formed on the back surface of the first aluminum foil
10
. Portions of the oxide layer
3
that cover the silicon balls are removed, and then a second aluminum foil
8
is formed so as to join to the silicon balls
2
.
FIG. 5
illustrates a structure disclosed in Japanese Patent Publication No. 2641800. There is disclosed a photoelectric conversion device in which a low melting-point metal layer
11
such as a tin layer is formed on a substrate
1
. Crystalline semiconductor particles
2
of first conductivity-type are deposited on the low melting-point metal layer
11
, and an amorphous semiconductor layer
7
of second conductivity-type is formed on the crystalline semiconductor particles
2
with an insulating layer
3
interposed between the low melting-point metal layer
11
and the amorphous semiconductor layer
7
.
FIG. 6
illustrates a structure disclosed in Japanese Examined Patent Publication No. H08-34177. There is disclosed a method in which a high melting-point metal layer
12
, a low melting-point layer
11
and fine crystalline semiconductor grains
13
are successively deposited on a substrate
1
, and the fine crystalline semiconductor grains
13
are melted, saturated, and gradually cooled so that the semiconductor is grown by liquid-phase epitaxial growth, thereby forming the fine crystalline semiconductor grains
13
into a polycrystalline thin film. Incidentally, in
FIG. 6
, the numeral
14
denotes a polycrystalline or amorphous semiconductor layer of the opposite conductivity type, and the numeral
6
denotes a transparent conductive film.
In the photoelectric conversion device shown in
FIG. 4
, however, since the first aluminum foil
10
is formed with apertures into which the silicon balls
2
are pressed and inserted so as to join the n-type layers
9
of the silicon balls
2
and the aluminum foil together, the silicon balls
2
are required to have a uniform diameter. The manufacturing cost is therefore high. Also, since the temperature used for joining is lower than 577° C., which is the eutectic temperature of aluminum and silicon, the joining tends to be unstable.
In the photoelectric conversion device shown in
FIG. 5
, since the insulator
3
is formed after the crystalline semiconductor particles have been fixed on the low melting-point metal layer
11
, the insulator
3
is formed not only on the low melting-point metal layer
11
but also on the crystalline semiconductor particles
2
. Therefore, the insulator
3
on the crystalline semiconductor particles
2
needs to be removed before the amorphous semiconductor layer
7
is formed, which causes the number of processes to increase. Since the thickness of the amorphous semiconductor layer
7
needs to be small taking the great light absorption thereof into account. When the thickness of the amorphous semiconductor layer
7
is small, the tolerance to defects also becomes small necessitating stricter management of the cleaning process and the production environment. As a result, the manufacturing cost is high.
In the photoelectric conversion device shown in
FIG. 6
, since the low melting-point metal layer
11
is mixed into the first conductivity-type liquid-phase epitaxial polycrystalline layer
13
, the performance of the solar cell is degraded. And due to the absence of insulator, current leakage occurs between the upper electrode
6
and the lower electrode
12
.
In addition, it has been known that when conventional glass compositions are employed for the insulator in conventional photoelectric conversion devices, bubbling occurs due to its reaction to the crystalline semiconductor particles, and microcracks are generated during reliability tests.
It is a primary object of the present invention to provide a photoelectric conversion device with high conversion efficiency that can be manufactured at low cost.
(B) In today's age of intense information, information and communications technologies have rapidly been developing. Along with this trend, the demand for silicon semiconductor devices for use in MPUs and memories has been sharply on the rise. In addition, with the increasing consciousness for the environment, applications of silicon semiconductor devices other than information and communications equipment, such as solar cells, have been increasing fast.
In order to prevent errors and secure long-time reliability, the silicon is covered with an insulating coating in such semiconductor devices. By covering the silicon with an insulating coating, the silicon is protected from water and dust and insulation is provided between the electrodes.
For insulating coatings used for protecting silicon in optical semiconductor devices such as optical sensors and solar cells or insulating coatings for insulation between the electrodes in such optical semiconductor devices, transparency is required in addition to the insulation property and sealing property.
For the purpose of silicon protection, organic resin is employed for protection and sealing in applications in which the demand for reliability is relatively low. In applications for which high reliability is required, the insulating coating needs to be formed by using glass.
Generally, the insulating coatings made from glass are formed by covering silicon with glass paste, which is obtained by mixing particulate glass, organic binder, and solvent together, by a known printing method, a dispensing process, dipping or spin-coating, and thereafter performing a heat treatment to soften and fluidize the glass. The glass which has been conventionally used for forming insulating coatings to cover silicon is low softening-point glass composed mainly of PbO so that influence on the semiconductor device by heat is minimized.
However, since the PbO content needs to be large in order to lower the softening point and glass transition point, PbO-based low softening-point glass has a thermal expansion coefficient as high as 80×10
−7
/° C. at temperatures 40 to 400° C. When PbO-based low softening-point glass with such a high thermal expansion coefficient is employed for protection and insulation in silicon semiconductor devices with thermal expansion coefficients as low as 30×10
−7
/° C. to 45×10
−7
/° C., especially in large scale silicon semiconductor devices or solar cells with greater areas, due to thermal stress accompanying the ON/OFF switching of the semiconductor device and changes in the environment of use, cracks are generated in the glass and silicon and peeling occurs at the interfaces.
In order to lo
Arimune Hisao
Fukuda Jun
Kawai Shinya
Kyoda Takeshi
Hogan & Hartson
Jackson Jerome
Kyocera Corporation
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