U.S. patent application number 12/612967 was filed with the patent office on 2010-05-06 for light-induced plating.
Invention is credited to Bernd Bitnar, Andreas Krause, Claudia Lengsfeld, Holger Neuhaus.
Application Number | 20100108525 12/612967 |
Document ID | / |
Family ID | 42130107 |
Filed Date | 2010-05-06 |
United States Patent
Application |
20100108525 |
Kind Code |
A1 |
Krause; Andreas ; et
al. |
May 6, 2010 |
LIGHT-INDUCED PLATING
Abstract
An apparatus for the light-supported precipitation of an
electrolyte on a semiconductor component comprises a plating bath
with an electrolyte, a first electrode arranged in the plating bath
and a second electrode arranged outside the plating bath, a holding
device for the semiconductor component and an irradiation device
for irradiating the semiconductor component with electromagnetic
radiation, the irradiation device being arranged outside the
plating bath.
Inventors: |
Krause; Andreas; (Dresden,
DE) ; Bitnar; Bernd; (Freiberg, DE) ;
Lengsfeld; Claudia; (Freiberg, DE) ; Neuhaus;
Holger; (Freiberg, DE) |
Correspondence
Address: |
MCGLEW & TUTTLE, PC
P.O. BOX 9227, SCARBOROUGH STATION
SCARBOROUGH
NY
10510-9227
US
|
Family ID: |
42130107 |
Appl. No.: |
12/612967 |
Filed: |
November 5, 2009 |
Current U.S.
Class: |
205/50 ; 204/227;
205/91 |
Current CPC
Class: |
C25D 17/001 20130101;
C25D 5/006 20130101; C25D 7/123 20130101 |
Class at
Publication: |
205/50 ; 204/227;
205/91 |
International
Class: |
C25D 7/12 20060101
C25D007/12; C25D 17/08 20060101 C25D017/08; C25D 5/00 20060101
C25D005/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 6, 2008 |
DE |
10 2008 056 093.6 |
Claims
1. An apparatus for the light-supported precipitation of a metal
from an electrolyte on a semiconductor component (1) comprising a.
a plating bath (2) with i. an electrolyte (3), ii. a first
electrode (4) arranged in the plating bath (2) and iii. a second
electrode (5) arranged outside the plating bath (2), b. a holding
device (9) for the semiconductor component (1) and c. an
irradiation device (15) for irradiating the semiconductor component
(1) with electromagnetic radiation, d. the irradiation device (15)
being arranged outside the plating bath (2) and e. the electrolyte
forming a layer with a layer thickness of a maximum of 10 mm
between the semiconductor component (1) and the irradiation device
(15).
2. An apparatus according to claim 1, wherein the irradiation
device (15) comprises at least one light-emitting diode (LED).
3. An apparatus according to claim 1, wherein the irradiation
device (15) comprises a plurality of LEDs.
4. An apparatus according to claim 1, wherein the irradiation
device (15) comprises at least one halogen lamp.
5. An apparatus according to claim 1, wherein the electromagnetic
radiation generatable by means of the irradiation device exhibits
at least a portion in the red to near-infrared wavelength
range.
6. An apparatus according to claim 1, wherein the portion in the
red to near-infrared wavelength range, exhibited by the
electromagnetic radiation generatable by means of the irradiation
device, is an intensity maximum.
7. An apparatus according to claim 1, wherein the electromagnetic
radiation generatable by means of the irradiation device exhibits
at least an intensity maximum in the read to near-infrared
wavelength range in the range of 650 nm to 1200 nm.
8. An apparatus according to claim 1, wherein the electromagnetic
radiation generatable by means of the irradiation device exhibits
at least an intensity maximum in the read to near-infrared
wavelength range in the range of 840 nm to 1050 nm.
9. An apparatus according to claim 1, wherein the electromagnetic
radiation generatable by means of the irradiation device exhibits
at least an intensity maximum in the read to near-infrared
wavelength range in the range of 940 nm to 970 nm.
10. An apparatus according to claim 1, wherein the holding device
(9) comprises at least three supports (10) which are arranged in
the plating bath (2).
11. An apparatus according to claim 1, wherein the holding device
(9) comprises a plurality of supports (10) which are arranged in
the plating bath (2).
12. An apparatus according to claim 10, wherein the supports (10)
are adjustable.
13. An apparatus according to claim 10, wherein the supports (10)
are at least one of height-adjustable and adjustable sideways.
14. An apparatus according to claim 10, wherein there are envisaged
contact elements (13) for electrically contacting the semiconductor
component (1), which are each arranged in an extension of one of
the supports (10) outside the plating bath (2).
15. A method for producing a semiconductor component (1) comprising
the following steps: Providing a plating bath (2) with an
electrolyte (3), a first electrode (4) arranged in the plating bath
(2) and a second electrode (5) arranged outside the plating bath
(2), providing an irradiation device (15) for generating
electromagnetic radiation, providing a semiconductor substrate (6)
of a planar design with a first side (7) and a second side (8)
lying opposite thereto, immersing at least the second side (8) of
the semiconductor substrate (6) into the electrolyte (3), producing
an electrical contact between the first side (7) of the
semiconductor substrate (6) and the second electrode (5),
irradiating at least the first side (7) of the semiconductor
substrate (6) by means of the irradiation device (15).
16. A method according to claim 15, wherein the semiconductor
substrate (6) is immersed on partly into the electrolyte (3).
17. A method according to claim 15, wherein the semiconductor
substrate (6) is immersed on into the electrolyte (3) only so far
that the first side (7) remains dry.
18. A method according to claim 15, wherein the semiconductor
substrate (6), after immersion into electrolyte (3), is lifted back
out of the electrolyte so far that a surface meniscus (17) forms
between the second side (8) of the semiconductor substrate (6) and
the electrolyte (3).
19. A method according to claim 15, wherein the semiconductor
substrate (6) is immersed fully into the electrolyte (3), however,
only so far that the first side (7) is covered by a layer of a
depth of a maximum 10 mm.
20. A method according to claim 15, wherein the semiconductor
substrate (6) is immersed fully into the electrolyte (3), however,
only so far that the first side (7) is covered by a layer of a
depth of a maximum 5 mm.
21. A method according to claim 15, wherein the semiconductor
substrate (6) is immersed fully into the electrolyte (3), however,
only so far that the first side (7) is covered by a layer of a
depth of a maximum 2 mm.
22. A method according to claim 15, wherein the first side (7) of
the semiconductor substrate (6) is its rear side.
23. A method according to claim 15, wherein the first side (7) of
the semiconductor substrate (6) is its front side.
24. A semiconductor component (1) comprising a. a semiconductor
substrate (6) with i. a first side (7), ii. a second side (8) lying
opposite thereto and iii. a thickness (D) in a direction vertically
to the sides (7, 8), b. with at least the first side (7) being
designed such that it is, at least in some areas, at least 50%
permeable for the electromagnetic radiation with a wavelength in
the range of 650 nm to 1200 nm.
25. A semiconductor component (1) according to claim 24, wherein
the semiconductor substrate (6) is designed such that it is at
least 50% permeable, at least in some areas, in at least one
direction for electro-magnetic radiation with a wavelength in the
range of 650 nm to 1200 nm up to a penetration depth of at least
50% of the thickness (D).
26. A semiconductor component (1) according to claim 24, wherein
the semiconductor substrate (6) is designed such that it is at
least 50% permeable, at least in some areas, in at least one
direction for electromagnetic radiation with a wavelength in the
range of 650 nm to 1200 nm up to a penetration depth of at least
75% of the thickness (D).
27. A semiconductor component (1) according to claim 24, wherein
the semiconductor substrate (6) is designed such that it is at
least 50% permeable, at least in some areas, in at least one
direction for electromagnetic radiation with a wavelength in the
range of 650 nm to 1200 nm up to a penetration depth of at least
90% of the thickness (D).
Description
FIELD OF THE INVENTION
[0001] The invention relates to an apparatus and a method for the
light-supported precipitation of a metal from an electrolyte on a
semiconductor component. The invention also relates to a
semiconductor component.
BACKGROUND OF THE INVENTION
[0002] Light-induced and light-supported galvanic processes are
suitable for the production of highly efficient solar cells.
Generally, the light source for such methods is located opposite
the front side of the solar cell, the electrolyte being arranged
between the solar cell and the light source. What is
disadvantageous here is that the electrolyte absorbs more or less
of the light of the light source. Moreover, a light source arranged
directly in front of the surface to be coated adversely affects, on
the one hand, convection directly in front of the electrode and, on
the other hand, stream line distribution, which can have a very
adverse effect on the galvanic process. Finally, if the light
source is arranged in the galvanic bath, the constructional and
safety effort is considerable.
SUMMARY OF THE INVENTION
[0003] The invention is therefore based on the object of improving
an apparatus and a method for the light-supported precipitation of
a metal from an electrolyte on a semiconductor component. The
invention is also based on the object of creating an improved
semiconductor component.
[0004] Said objects are achieved by an apparatus for the
light-supported precipitation of a metal from an electrolyte on a
semiconductor component comprising a plating bath with an
electrolyte, a first electrode arranged in the plating bath and a
second electrode arranged outside the plating bath, a holding
device for the semiconductor component and an irradiation device
for irradiating the semiconductor component with electromagnetic
radiation, the irradiation device being arranged outside the
plating bath and the electrolyte forming a layer with a layer
thickness of a maximum 10 mm between the semiconductor component
and the irradiation device. Furthermore, said objects are achieved
by a method for producing a semiconductor component comprising the
steps of providing a plating bath with an electrolyte, a first
electrode arranged in the plating bath and a second electrode
arranged outside the plating bath, providing an irradiation device
for generating electromagnetic radiation, providing a semiconductor
substrate of a planar design with a first side and a second side
lying opposite thereto, immersing at least the second side of the
semiconductor substrate into the electrolyte, producing an
electrical contact between the first side of the semiconductor
substrate and the second electrode, and irradiating at least the
first side of the semiconductor substrate by means of the
irradiation device. Said objects are further achieved by a method
according to the invention, wherein the first side of the
semiconductor substrate is its front side. The core of the
invention consists in arranging the irradiation device for the
irradiation of the semiconductor component outside the plating
bath.
[0005] The irradiation device is preferably arranged on the
semiconductor component side not to be coated, i.e. the
semiconductor component is illuminated from the side not to be
coated.
[0006] As a light source there is advantageously considered an
arrangement of light-emitting diodes and/or one or a plurality of
halogen lamps. The electromagnetic radiation generated by the
irradiation device preferably exhibits an intensity maximum in the
red to near-infrared range.
[0007] The method according to the invention is characterised in
that the semiconductor substrate is immersed into the electrolyte
with at least one first side, while it is irradiated by the
irradiation device on the second side lying opposite to the first
side.
[0008] The semiconductor substrate is preferably immersed into the
electrolyte only so far that the second side remains dry.
[0009] Alternatively, full immersion of the semiconductor substrate
in the electrolyte is possible such that the second side is covered
with only a few milli-metres of electrolyte.
[0010] Features and details of the invention result from the
description of several embodiments based on the drawing.
BRIEF DESCRIPTION OF THE DRAWING
[0011] FIG. 1 a schematic representation of the apparatus for the
light-supported precipitation of an electrolyte on a semiconductor
component according to a first embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] In the following, a first embodiment of the invention is
described with reference to FIG. 1. An apparatus for the
light-supported precipitation of an electrolyte on a semiconductor
component 1 comprises a plating bath 2 with an electrolyte 3, a
first electrode 4 arranged in the plating bath 2 and a second
electrode 5 arranged outside the plating bath 2. The electrolyte 3
contains at least some cobalt and/or nickel and/or silver and/or
copper and/or tin and/or a compound of said metals. The electrodes
4, 5 are electrically conductively connected to a voltage source
14. Instead of the voltage source 14 there can also be envisaged
only an electrical contact with the electrically conductive
connection of the electrodes 4 and 5.
[0013] The semiconductor component 1 is especially a solar cell.
The semiconductor component 1 comprises a semiconductor substrate 6
of a planar design with a first side 7, a second side 8 lying
opposite thereto and a thickness D in a direction vertically to the
sides 7, 8. According to the first embodiment, the first side 7 of
the semiconductor substrate 6 is its rear side. The semiconductor
substrate 6 consists at least partly of silicon. Other
semiconductor materials are, however, also conceivable.
[0014] The apparatus also comprises a holding device 9 for holding
the semiconductor component 1. The holding device 9 comprises at
least three, especially a plurality of supports 10, by means of
which the position of the semiconductor component 1 is fixable in
the apparatus. The supports 10 are arranged in the plating bath 2.
They are especially attached to a floor 11 of the plating bath 2.
The supports 10 are preferably adjustable sideways, i.e. in the
direction parallel to the floor 11 and thus parallel to the sides
7, 8 of the semiconductor substrate 6. This way it is possible to
ensure that they are positioned, with respect to the semiconductor
component 1, at predeterminable points, e.g. in the area of a
busbar and/or lying opposite thereto. Advantageously, the supports
10 are designed to be height-adjustable. For height adjustment,
there is preferably envisaged an adjustment device 12 indicated
only schematically in FIG. 1.
[0015] Furthermore, the apparatus comprises contact elements 13 for
electrically contacting the semiconductor component 1. The contact
elements 13 are preferably designed as spring load mounted contact
pins. They are electrically conductively connected to the second
electrode 5. They are also electrically conductively connectable to
the first side 7 of the semiconductor substrate 6. The contact
elements 13 can be designed to be part of the holding device 9.
Advantageously, the contact elements 13 are each arranged in
extension of one of the supports 10. Hence, they each stand
opposite one of the supports 10 with respect to the semiconductor
substrate 6. This prevents bending of the semiconductor substrate
6. The contact elements 13, especially their electrical connection
to the second electrode 5, are preferably arranged outside the
plating bath 2.
[0016] Finally, the apparatus comprises an irradiation device 15
for irradiating the semiconductor component 1 with electromagnetic
radiation. The irradiation device 15 is advantageously arranged
outside the plating bath 2. It is thus arranged on the side 7 of
the semiconductor component 1 facing away from the side 8 to be
immersed into the plating bath 2. The irradiation device 15
comprises at least one light source 16 designed as a light-emitting
diode (LED). The light source 16 comprises especially a plurality
of LEDs. The LEDs are arranged in a raster of planar design.
[0017] The electromagnetic radiation generatable by means of the
irradiation device 15 exhibits at least a portion, especially an
intensity maximum, in the wavelength range of 650 nm to 1200 nm,
especially in the range of 840 nm to 1050 nm, especially in the
range of 940 nm to 970 nm. It is thus electromagnetic radiation
with a portion in the red to near-infrared range. The output
radiatable by the irradiation device 15 is at least 100 mW,
especially at least 1 W. The irradiation device 15 is controllable
by means of a control device 18 illustrated only schematically in
FIG. 1.
[0018] According to the first embodiment, the first side 7 of the
semiconductor substrate 6 is its rear side. Decisive for the method
according to the invention is that the first side 7 facing the
irradiation device 15 is designed such that it is, at least in some
areas, at least partly, especially at least 50% permeable for the
electromagnetic radiation from the irradiation device 15.
[0019] The semiconductor substrate 6 is thus designed such that it
is at least 50% permeable, at least in some areas, in at least one
direction for electromagnetic radiation from the irradiation device
15 up to a penetration depth of at least 50%, especially at least
75%, especially at least 90% of the thickness D.
[0020] To this end it exhibits a metalisation 19 on the first side
7 of the semiconductor substrate 6, which is designed to be at
least partly transparent. The metalisation 19 is preferably
designed as a grid. Alternatively, the metalisation 19 can also be
designed as a transparent semiconductor or as a metal layer that is
only a few nanometres thin and thus transparent. Finally, the
semiconductor component 1 can also exhibit on the first side 7 of
the semiconductor substrate 6 a metalisation of planar design with
laser-fired contacts, at which the metalisation 19 is selectively
opened and thus permeable for the electromagnetic radiation
generated by the irradiation device 15.
[0021] The second side 8 of the semiconductor substrate 6, which
side is to be immersed into the electrolyte 3 and faces away from
the irradiation device 15, exhibits predetermined precipitation
areas 20, on which the galvanic precipitation of the electrolyte 3
occurs. The precipitation areas 20 are preferably designed as a
seed layer applied onto the semiconductor substrate 6 by means of
fine line printing. Alternatively, the precipitation areas 20 may
be designed as apertures in an anti-reflection layer on the second
side 8 of the semiconductor substrate 6.
[0022] The following describes the function of the apparatus on the
basis of a method, according to the present invention, for
producing a semiconductor component 1. According to the method
according to the present invention, there is first provided the
plating bath 2 with the electrolyte 3 and the electrodes 4, 5 as
well as the irradiation device 15. Next, the semiconductor
substrate 6 is arranged in the holding device 9 with the second
side 8 of the semiconductor substrate 6 facing the electrolyte 3.
Then, the semiconductor substrate 6 is immersed, with its second
side 8, into the electrolyte 3 by adjusting the supports 10 by
means of the adjustment device 12. The semiconductor substrate 6 is
preferably immersed into the electrolyte 3 only in part, especially
only so far that the first side 7 remains dry. To this end, the
semiconductor substrate 6, after immersion in the electrolyte 3, is
lifted back out of the electrolyte 3 by pushing out the supports 10
so far that a surface meniscus 17 forms between the second side 8
of the semiconductor substrate 6 and the electrolyte 3. The second
side 8 is thus at least largely, especially fully in direct contact
with the electrolyte 3. The first side 7 of the semiconductor
substrate 6, however, is above the electrolyte 3 in the plating
bath 2.
[0023] Alternatively, the semiconductor substrate 6 is immersed
fully into the electrolyte 3, however, only so far that the first
side 7 is covered by the electrolyte 3 by a layer with a depth of a
maximum 10 mm, especially a maximum 5 mm, especially a maximum 2
mm. The electrolyte 3 thus forms between the semiconductor
component 1 and the irradiation device 15 a layer with a layer
thickness of a maximum 10 mm, especially a maximum 5 mm, especially
a maximum 2 mm. The layer thickness is preferably 0 mm, i.e. there
is no electrolyte 3 between the semiconductor component 1 and the
irradiation device 15.
[0024] The first side 7 of the semiconductor substrate 6 is
electrically conductively connected to the second electrode 5
arranged outside the plating bath 2. For the light-induced or
light-supported galvanic precipitation of a metal from the
electrolyte 3 on the second side 8, the first side 7 of the
semiconductor substrate 6, which side 7 lies opposite the second
side 8 to be coated, is irradiated by means of the irradiation
device 15. Owing to the appropriately selected spectral range of
the irradiation device 15, especially in the red to near-infrared
range, the electromagnetic radiation generated by means of the
irradiation device 15 exhibits a depth penetration into the
semiconductor substrate 6 of at least 100 .mu.m, especially at
least 150 .mu.m, especially at least 180 .mu.m. Thus, free charge
carriers are generated in the semiconductor substrate 6 near the PN
junction of the semiconductor substrate 6 by the electromagnetic
radiation produced by means of the irradiation device 15. Said free
charge carriers lead to a current flow in the circuit formed by the
electrodes 4, 5 and the semiconductor component 1 and thus to a
galvanic precipitation of the electrolyte 3 in predeterminable
areas on the second side 8 of the semiconductor substrate 6.
[0025] In a second embodiment the irradiation device 15 comprises,
instead of the LEDs, at least one halogen lamp as a light source
16. Said lamp has a broad spectrum with a large portion in the
long-wave range. This way it is ensured that a sufficient portion
of the electromagnetic radiation emitted by the irradiation device
15 exhibits a penetration depth of at least 50%, especially at
least 75%, especially at least 90% of the thickness D of the
semiconductor substrate 6, and that in this way the free charge
carriers produced by the irradiation device 15 in the semiconductor
substrate 6 reach the PN junction of the semiconductor substrate
6.
[0026] According to a third embodiment of the invention, the second
side 8 of the semiconductor substrate 6 is the rear side of a solar
cell. The first side 7 thus forms the light incidence side of the
solar cell. On this embodiment, the second side 8 is preferably
designed as an opened anti-reflection layer, but it may also be
coated across its entire surface. On this embodiment, the contact
elements 13 are preferably arranged on the conductor paths formed
by the metalisation 19 designed as a grid and/or the busbars of the
semiconductor component 1.
[0027] According to a fourth embodiment of the invention, the
supports 10 serve to produce an electrical contact between the
second side 8 and the second electrode 5. To this end, the supports
10 are electrically conductively connected to the second electrode
5. They are designed to be insulated from the electrolyte 3. This
embodiment is particularly suited for galvanic thickening of the
contacts on the rear side of an emitter-wrap-through solar
cell.
[0028] According to a fifth embodiment of the invention, the
galvanic bath 2 is designed as a so-called cup plater for the
application of fountain plating. Such a cup plater is e.g. known
from DE 10 2007 020 449 A1. Here, the plating bath 2 comprises a
preferably hollow cylinder-shaped insert, which, in the area of the
floor 11, exhibits an aperture from which electrolyte 3
continuously flows into its interior space. To this end, the
electrolyte 3 is pumped through the aperture on the floor 11 into
the interior space of the insert by means of a pump. The
electrolyte 3 pumped into the interior space flows over an upper
rim of said insert. The insert protrudes clearly from the surface
of the electrolyte 3 in the plating bath 2. The insert has,
especially in the area of its upper rim, a cross-section that is
adapted to the size and shape of the semiconductor substrate 6.
During operation of the apparatus, the semiconductor substrate 6 is
arranged such on the rim of the insert, which serves as supports
10, that the second side 8 faces the interior space of the insert.
The electrolyte 3 flowing through the aperture into interior space
of the insert thus flows past the second side 8 of the
semiconductor substrate 6. As a result of the continuous flow of
the electrolyte 3 generated by the pump, there is ensured on the
one hand good convection in the immediate electrode vicinity, and
on the other hand the semiconductor substrate 6 is pushed against
the rim serving as supports 10 and is, as a result, fixed to
prevent displacement. With this arrangement, especially the first
side 7 of semiconductor substrate 6 is kept dry.
[0029] The apparatus can, of course, also be designed as an in-line
plant, with the semiconductor component 1 being transportable
parallel to the sides 7, 8 of the semiconductor substrate 6 through
the apparatus by means of a transportation device not shown in FIG.
1, and the supports 10 being designed as rollers on which the
semiconductor substrate 6 is movable through the plant, and
especially the contact elements 13 also being designed as
rollers.
[0030] In a vertical design the semiconductor substrate 6 is
attached to a steel strap, by which it is at the same time
contacted and guided vertically through the plating bath 2. During
this, the semiconductor substrate 6 side 7, 8 to be irradiated is
guided as closely as possible past a transparently designed wall of
the plating bath 2, on the rear side of which, i.e. opposite,
relative to the wall, of the side 7, 8 to be irradiated, the
irradiation device 15 is arranged. The side 7, 8 to be irradiated
is preferably the rear side of the semiconductor component 1.
* * * * *