U.S. patent application number 13/567361 was filed with the patent office on 2014-02-06 for process of manufacturing crystalline silicon solar cell.
This patent application is currently assigned to Atomic Energy Council-Institute of Nuclear Energy Research. The applicant listed for this patent is Tsun-Neng Yang. Invention is credited to Tsun-Neng Yang.
Application Number | 20140038339 13/567361 |
Document ID | / |
Family ID | 50025889 |
Filed Date | 2014-02-06 |
United States Patent
Application |
20140038339 |
Kind Code |
A1 |
Yang; Tsun-Neng |
February 6, 2014 |
PROCESS OF MANUFACTURING CRYSTALLINE SILICON SOLAR CELL
Abstract
A process of manufacturing a crystalline silicon solar cell
includes forming a rough surface on a surface of the crystalline
silicon wafer and an Al.sub.2O.sub.3 film is coated on a non-rough
surface thereof. A single-sided n diffusion layer and
phosphosilicate glass film are formed. An anti-reflection layer
SiNx film is formed on a top surface of the phosphosilicate glass
film. An Al metallic film is formed as a back ohmic electrode on
the Al.sub.2O.sub.3 film. The local area of the anti-reflection
layer SiNx film and the phosphosilicate glass film is melted and
removed to form a local area of n+-Si layer. Then, an Al--Si back
ohmic contact electrode is formed between the Al metallic film and
the crystalline silicon wafer. A front ohmic contact electrode is
formed on the molten and removed area of the antireflection layer
SiNx film and the phosphosilicate film by light-induced
plating.
Inventors: |
Yang; Tsun-Neng; (Taipei
City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Yang; Tsun-Neng |
Taipei City |
|
TW |
|
|
Assignee: |
Atomic Energy Council-Institute of
Nuclear Energy Research
Taoyuan County
TW
|
Family ID: |
50025889 |
Appl. No.: |
13/567361 |
Filed: |
August 6, 2012 |
Current U.S.
Class: |
438/71 ;
257/E31.13 |
Current CPC
Class: |
Y02P 70/521 20151101;
H01L 31/022425 20130101; Y02P 70/50 20151101; H01L 31/068 20130101;
Y02E 10/547 20130101; H01L 31/1804 20130101; H01L 31/02363
20130101 |
Class at
Publication: |
438/71 ;
257/E31.13 |
International
Class: |
H01L 31/18 20060101
H01L031/18 |
Claims
1. A process of manufacturing a crystalline silicon solar cell,
comprising at least the following steps: Step 1: taking a
crystalline silicon wafer, in which a wet-chemical process is used
to remove any mechanical damages on a surface of the crystalline
silicon wafer, and then the wafer is subject to clean; Step 2:
forming a rough surface on the surface of the crystalline silicon
wafer by using a plasma device; Step 3: coating an Al.sub.2O.sub.3
film on a non-rough surface of the crystalline silicon wafer, and
then placing the wafer into a high-temperature phosphorus diffusion
furnace for phosphorus diffusion. Step 4: forming a single-sided n
diffusion layer on the rough surface of the crystalline silicon
wafer by using the phosphorus diffusion process; and forming a
phosphosilicate glass (PSG) film on a top surface of the
single-sided n diffusion layer; Step 5: coating an anti-reflection
layer SiNx film directly on a top surface of the PSG film; Step 6:
coating an Al metallic film as a back ohmic electrode on one side
of the Al.sub.2O.sub.3 film; Step 7: irradiating a laser beam
directly onto the anti-reflection layer SiNx film and the PSG film
for the melting and removal of a local area, diffusing phosphorus
atoms of the PSG film into the n diffusion layer to form a local
area of n+-Si layer, and then directly irradiating the
Al.sub.2O.sub.3 film and the Al metallic film with a laser beam for
local area melting and removal so that an Al--Si back ohmic contact
electrode is formed between the Al metallic film and the
crystalline silicon wafer; Step 8: forming a Ni film on the molten
and removed area of the antireflection layer SiNx film and the PSG
film by light-induced plating, and then electroplating a front
ohmic contact electrode of copper material on the Ni film to form a
solar cell component; and Step 9: form spacers, as peripheral
electrical isolation, on the anti-reflection layer SiNx film, the
PSG film, the n diffusion layer and the crystalline silicon wafer
of the solar cell component by irradiating the laser beam.
2. The process of manufacturing a crystalline silicon solar cell of
claim 1, wherein the crystalline silicon wafer is a p-type
crystalline silicon wafer.
3. The process of manufacturing a crystalline silicon solar cell of
claim 1, wherein the solar cell component comprises, from top to
bottom, the anti-reflection layer SiNx film, the PSG film, the n
diffusion layer, the crystalline silicon wafer, the Al.sub.2O.sub.3
film and the back ohmic contact electrode, and the front ohmic
electrode is located between the anti-reflection layer SiNx film
and the PSG film.
4. The process of manufacturing a crystalline silicon solar cell of
claim 1, wherein at Step 7, according to computerized patterns, the
laser beam is directly irradiated on the anti-reflection layer SiNx
film and the PSG film for melting the local area, while diffusing
phosphorus atoms of the PSG film into the n diffusion layer to form
a local area of n+-Si layer, and then eradicating the local area of
the anti-reflection layer SiNx film and the PSG film by using the
laser, completely retaining the area where is not exposed to the
laser beam.
5. The process of manufacturing a crystalline silicon solar cell of
claim 1, wherein at Step 7, according to the computerized patterns,
the laser beam is irradiated on the Al.sub.2O.sub.3 film and the Al
metallic film for local area melting and removal so that an Al--Si
back ohmic contact electrode is formed with the irradiated area of
the Al.sub.2O.sub.3 film being eradicated by the laser beam while
the non-irradiated area being completely retained.
6. The process of manufacturing a crystalline silicon solar cell of
claim 1, wherein the laser beam used at Step 7 and Step 9 is
ultraviolet laser, green laser, or infrared light laser.
7. The process of manufacturing a crystalline silicon solar cell of
claim 1, wherein at Step 8, according to the computerized patterns,
a mask pattern is formed between the local area of the
anti-reflection layer SiNx film and the PSG film and the
non-irradiated area of the antireflection layer SiNx film and the
PSG film.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a process of manufacturing
a crystalline silicon solar cell, and more particularly, to a
process which not only offers the simplified chemical process with
minimal problems about dealing with follow-up chemical solutions,
but also achieves the improvement on the photoelectric conversion
efficiency of the crystalline silicon solar cell, without adding
any extra processing steps to the existing standard process of
manufacturing the crystalline silicon solar cell.
[0003] 2. Description of Related Art
[0004] The sun is the source of all energy on Earth. Most of
currently known energies such as oil, coal, natural gas, water
power, solar energy, wind power, photosynthesis energy, and ocean
energy are directly or indirectly from the sun. The energy
(.about.5.times.1020 J) generated by irradiating the sunlight over
the entire Earth's surface for one hour is enough for the whole
human being to use about 1 year. It is estimated the sun continues
emitting sunlight at least five billion years or more, so that the
solar energy is regarded as unexhausted, free clean energy.
[0005] After the Industrial Revolution, the rapid growth of the
global population, the development of the civilization, the
improvement of relative technology, and demand for high living
quality result in increasingly high demand for and dependence on
the energy. Large-scale use of fossil fuels leads to significant
decrease in global storage capacity and rise in prices. Large
amount of pollutant emission causes global warming and climate
anomalies, and other issues about posing threats to human living
environment as well. Soaring in the prices of fossil fuels
including oil and gas has drawn attention to the global emphasis on
alternative energy. It greatly effluences the countries such as
Taiwan which heavily relies on imported energy, up to 98% of what
is needed. The average CO.sub.2 emission for traditional energy
generation is about 530 t/GWh. Even though the solar energy is
comparatively environmentally friendly, it still generates CO.sub.2
emission of 5 t/GWh.
[0006] The currently standard process of manufacturing a
crystalline silicon solar cell includes the following nine steps:
[0007] (1) wafer inspecting, surface defect etching, and cleaning;
[0008] (2) textured; [0009] (3) phosphorus diffusing; [0010] (4)
phosphosilicate glass etching; [0011] (5) laser isolation; [0012]
(6) anti-reflection film coating; [0013] (7) screen printing
(silver and aluminum glum); [0014] (8) connector sintering; [0015]
(9) solar cell testing and detecting.
[0016] Among the above steps, step (1), (2), (3) and (4) are
wet-chemical processes which need to use organic acidic and alkali
chemicals such as hydrochloric acid (HCl), nitric acid (HNO.sub.3),
hydrofluoric acid (HF) and isopropyl alcohol (IPA). Those chemicals
produce large amount of organic acidic and alkali gas and liquid
waste, resulting in the burden on the environment. Therefore, the
currently available solar cells cannot be regarded as green
products.
[0017] The inventors have made long-term efforts in solving such a
problem, and successfully got an approach to achieve a process of
manufacturing a crystalline silicon solar cell, which can overcome
the problem encountered in the prior art.
SUMMARY OF THE INVENTION
[0018] A main purpose of this invention is to provide a process of
manufacturing a crystalline silicon solar cell, which not only
offers the simplified chemical process with minimal problems about
dealing with follow-up chemical solutions, but also achieves the
improvement on the photoelectric conversion efficiency of the
crystalline silicon solar cell, without adding any extra processing
steps to the existing standard process of manufacturing the
crystalline silicon solar cell.
[0019] In order to achieve the above and other objectives, the
process of manufacturing a crystalline silicon solar cell according
to the invention includes at least the following steps:
[0020] Step 1: taking a crystalline silicon wafer, in which a
wet-chemical process is used to remove any mechanical damages on a
surface of the crystalline silicon wafer, and then the wafer is
subject to clean;
[0021] Step 2: forming a rough surface on the surface of the
crystalline silicon wafer by using a plasma device;
[0022] Step 3: coating an Al.sub.2O.sub.3 film on a non-rough
surface of the crystalline silicon wafer, and then placing the
wafer into a high-temperature phosphorus diffusion furnace for
phosphorus diffusion.
[0023] Step 4: forming a single-sided n diffusion layer on the
rough surface of the crystalline silicon wafer by using the
phosphorus diffusion process; and forming a phosphosilicate glass
(PSG) film on a top surface of the single-sided n diffusion
layer;
[0024] Step 5: coating an anti-reflection layer SiNx film directly
on a top surface of the PSG film;
[0025] Step 6: coating an Al metallic film as a back ohmic
electrode on one side of the Al.sub.2O.sub.3 film;
[0026] Step 7: irradiating a laser beam directly onto the
anti-reflection layer SiNx film and the PSG film for the melting
and removal of a local area, diffusing phosphorus atoms of the PSG
film into the n diffusion layer to form a local area of n+-Si
layer, and then directly irradiating the Al.sub.2O.sub.3 film and
the Al metallic film with a laser beam for local area melting and
removal so that an Al--Si back ohmic contact electrode is formed
between the Al metallic film and the crystalline silicon wafer;
[0027] Step 8: forming a Ni film on the molten and removed area of
the antireflection layer SiNx film and the PSG film by
light-induced plating, and then electroplating a front ohmic
contact electrode of copper material on the Ni film to form a solar
cell component; and
[0028] Step 9: form spacers, as peripheral electrical isolation, on
the anti-reflection layer SiNx film, the PSG film, the n diffusion
layer and the crystalline silicon wafer of the solar cell component
by irradiating the laser beam.
[0029] In one embodiment of the invention, the crystalline silicon
wafer is a p-type or n-type crystalline silicon wafer.
[0030] In one embodiment of the invention, the solar cell component
includes, from top to bottom, the anti-reflection layer SiNx film,
the PSG film, the n diffusion layer, the crystalline silicon wafer,
the Al.sub.2O.sub.3 film and the back ohmic contact electrode. The
front ohmic electrode is located between the anti-reflection layer
SiNx film and the PSG film.
[0031] In one embodiment of the invention, at Step 7, according to
computerized patterns, the laser beam is directly irradiated on the
anti-reflection layer SiNx film and the PSG film for melting the
local area, while diffusing phosphorus atoms of the PSG film into
the n diffusion layer to form a local area of n+-Si layer, and then
eradicating the local area of the anti-reflection layer SiNx film
and the PSG film by using the laser, completely retaining the area
where is not exposed to the laser beam.
[0032] In one embodiment of the invention, at Step 7, according to
the computerized patterns, the laser beam is irradiated on the
Al.sub.2O.sub.3 film and the Al metallic film for local area
melting and removal so that an Al--Si back ohmic contact electrode
is formed with the irradiated area of the Al.sub.2O.sub.3 film
being eradicated by the laser beam while the non-irradiated area
being completely retained.
[0033] In one embodiment of the invention, the laser beam used at
Step 7 and Step 9 is ultraviolet laser, green laser, or infrared
light laser.
[0034] In one embodiment of the invention, at Step 8, according to
the computerized patterns, a mask pattern is formed between the
local area of the anti-reflection layer SiNx film and the PSG film
and the non-irradiated area of the antireflection layer SiNx film
and the PSG film.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 is a schematic view of Step 1 of a process of
manufacturing a crystalline silicon solar cell according to the
invention.
[0036] FIG. 2 is a schematic view of Step 2 of a process of
manufacturing a crystalline silicon solar cell according to the
invention.
[0037] FIG. 3 is a schematic view of Step 3 of a process of
manufacturing a crystalline silicon solar cell according to the
invention.
[0038] FIG. 4 is a schematic view of Step 4 of a process of
manufacturing a crystalline silicon solar cell according to the
invention.
[0039] FIG. 5 is a schematic view of Step 5 of a process of
manufacturing a crystalline silicon solar cell according to the
invention.
[0040] FIG. 6 is a schematic view of Step 6 of a process of
manufacturing a crystalline silicon solar cell according to the
invention.
[0041] FIG. 7 is a schematic view of Step 7 of a process of
manufacturing a crystalline silicon solar cell according to the
invention.
[0042] FIG. 8 is a schematic view of Step 8 of a process of
manufacturing a crystalline silicon solar cell according to the
invention.
[0043] FIG. 9 is a schematic view of Step 9 of a process of
manufacturing a crystalline silicon solar cell according to the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0044] The aforementioned illustrations and following detailed
descriptions are exemplary for the purpose of further explaining
the scope of the present invention. Other objectives and advantages
related to the present invention will be illustrated in the
subsequent descriptions and appended tables.
[0045] FIG. 1 is a schematic view of Step 1 of a process of
manufacturing a crystalline silicon solar cell according to the
invention. FIG. 2 is a schematic view of Step 2 of a process of
manufacturing a crystalline silicon solar cell according to the
invention. FIG. 3 is a schematic view of Step 3 of a process of
manufacturing a crystalline silicon solar cell according to the
invention. FIG. 4 is a schematic view of Step 4 of a process of
manufacturing a crystalline silicon solar cell according to the
invention. FIG. 5 is a schematic view of Step 5 of a process of
manufacturing a crystalline silicon solar cell according to the
invention. FIG. 6 is a schematic view of Step 6 of a process of
manufacturing a crystalline silicon solar cell according to the
invention. FIG. 7 is a schematic view of Step 7 of a process of
manufacturing a crystalline silicon solar cell according to the
invention. FIG. 8 is a schematic view of Step 8 of a process of
manufacturing a crystalline silicon solar cell according to the
invention. FIG. 9 is a schematic view of Step 9 of a process of
manufacturing a crystalline silicon solar cell according to the
invention. As shown, this invention provides a process of
manufacturing a crystalline silicon solar cell including at least
the following steps:
[0046] Step 1: Take a crystalline silicon wafer 10 (a p-type
crystalline silicon wafer is exemplified for illustration in
embodiments of the present invention). A wet-chemical method is
used to remove any mechanical damages on a surface of the
crystalline silicon wafer 10, and then the wafer is subject to
clean (as shown in FIG. 1).
[0047] Step 2: Form a rough surface 11 on the surface of the
crystalline silicon wafer 10 by using a plasma device (as shown in
FIG. 2).
[0048] Step 3: On a non-rough surface of the crystalline silicon
wafer 10 coat an Al.sub.2O.sub.3 film 12 (as shown in FIG. 3). Then
place the wafer 10 into a high-temperature phosphorus diffusion
furnace for phosphorus diffusion. The Al.sub.2O.sub.3 film 12 can
be used as an incident light internal reflective layer during the
back surface chemical and electric field passivation to prevent the
formation of any non-back surface phosphorus diffusion layers in
phosphorus diffusion.
[0049] Step 4: Form a single-sided n diffusion layer 13 on the
rough surface of the crystalline silicon wafer 10 by using the
phosphorus diffusion process. A phosphosilicate glass (PSG) film 14
is formed on a top surface of the single-sided n diffusion layer 13
(as shown in FIG. 4).
[0050] Step 5: Coat an anti-reflection layer SiNx film 15 directly
on a top surface of the PSG film 14 (as shown in FIG. 5).
[0051] Step 6: Coat an Al metallic film 16 as a back ohmic
electrode on one side of the Al.sub.2O.sub.3 film 12 (shown in FIG.
6).
[0052] Step 7: Based on the computerized patterns, irradiate a
laser beam 3 of ultraviolet laser, green laser, or infrared light
laser directly onto the anti-reflection layer SiNx film 15 and the
PSG film 14 for the melting and removal of a local area. On the one
hand, phosphorus atoms in the PSG film 14 are diffused into the n
diffusion layer 13 to form a local area n+-Si layer, while the
local area of the anti-reflection layer SiNx film 15 and the PSG
film 14 is eradicated by using the laser, completely retaining the
area where is not exposed to the laser. In accordance with the
computerized patterns, the laser beam 3 is directly irradiated on
the Al.sub.2O.sub.3 film 12 and the Al metallic film 16 for local
area melting and removal so that an Al--Si back ohmic contact
electrode 17 is formed between the Al metallic film 16 and the
crystalline silicon wafer 10. The laser beam eradicates the
irradiated area of the Al.sub.2O.sub.3 film 12, while completely
retaining the area where is not irradiated by the laser (as shown
in FIG. 7).
[0053] Step 8: Form a mask pattern between the local area of the
anti-reflection layer SiNx film 15 and the PSG film 14 at Step 7
and the non-irradiated area of the antireflection layer SiNx film
15 and the PSG film 14. A Ni film 18 is formed on the molten area
and removed area of the antireflection layer SiNx film 15 and the
PSG film 14 by light-induced plating. Then a front ohmic contact
electrode 19 of copper material is electroplated on the Ni film 18
to form a solar cell component 1. The solar cell component 1
includes, from top to bottom, respectively, the anti-reflection
layer SiNx film 15, the PSG film 14, the n diffusion layer 13, the
crystalline silicon wafer 10, the Al.sub.2O.sub.3 film 12 and the
back ohmic contact electrode 17. The front ohmic electrode 19 is
located between the anti-reflection layer SiNx film 15 and the PSG
film 14 (as shown in FIG. 8). The Ni thin film 18 at this Step has
another important function of acting as a Cu atom diffusion
barrier. It is proved that Cu atoms will damage the photoelectric
conversion efficiency of crystalline silicon solar cells.
Therefore, the copper film is thickened by electroplating and then
used as the front ohmic contact electrode 19 so as to reduce
material costs and lower the impedance of the front ohmic contact
electrode 19 and the resistance of the solar cells in series.
[0054] Step 9: Form spacers 4, as peripheral electrical isolation,
on the anti-reflection layer SiNx film 15, the PSG film 14, the n
diffusion layer 13 and the crystalline silicon wafer 10 of the
solar component 1 by irradiating the UV laser, green laser, or
infrared light laser. The spacers 4 prevent the back ohmic contact
electrode 17 from mutually electrical contact with the front ohmic
contact electrode 19.
[0055] Therefore, no wet chemical process is used in the above
steps of the present invention, except the Step 1 in which the
crystalline silicon wafer 10 is subject to mechanical damage
removal and cleansing. The use of a number of advanced processing
technologies makes the process of manufacturing the crystalline
silicon solar cell provided by the present invention more
environmentally friendly and progressive with enhanced efficiency
for the solar cells. Additionally, this invention can reach at
least the following advantages:
[0056] 1. No need of any chemical or plasma removal process on the
back surface phosphorus diffusion thin layer, which usually
requires in a conventional phosphorus diffusion process. Therefore,
the process of manufacturing the crystalline silicon solar cells
becomes easier.
[0057] Make full use of the phosphosilicate glass thin layer which
the conventional process must remove as a phosphorus atom source
for an n.sup.+-emitter in secondary phosphorus diffusion so that
the chemical removal process of the phosphosilicate glass thin
layer and the provision of phosphorus atom source for an
n.sup.+-emitter in secondary phosphorus diffusion are not required
any more. Therefore, this novel process of manufacturing p-type
crystalline silicon solar cell is an environmentally friendly and
gains more benefits due to enhanced photoelectric conversion
efficiency of the crystalline silicon solar cells.
[0058] In addition, this invention can be applied not only to the
p-type crystalline silicon wafer but also to a boron diffusion
process in the process of manufacturing n-type crystalline silicon
solar cells. Similarly, the use of other high-dielectric thin-film
materials, such as SiNx film, prevents the back surface boron atom
diffusion layer from being formed, without the need of any chemical
etching remove process that requires in to remove borosilicate
glass films produced in the conventional boron diffusion
process.
[0059] In summary, the process of manufacturing the crystalline
silicon solar cell can effectively improve the shortcomings in the
prior art, without adding processing steps to the existing standard
process of manufacturing the crystalline silicon solar cell. This
invention not only offers the simplified chemical process with
minimal problems about dealing with follow-up chemical solutions,
but also achieves the improvement on the photoelectric conversion
efficiency of the crystalline silicon solar cells. This makes the
invention more progressive and more practical in use which complies
with the patent law.
[0060] The descriptions illustrated supra set forth simply the
preferred embodiments of the present invention; however, the
characteristics of the present invention are by no means restricted
thereto. All changes, alternations, or modifications conveniently
considered by those skilled in the art are deemed to be encompassed
within the scope of the present invention delineated by the
following claims.
* * * * *