Title: Gas gate for isolating regions of differing gaseous pressure
Abstract: Disclosed herein is an improved gas gate for interconnecting regions of differing gaseous composition and/or pressure, more particularly between atmosphere and a vacuum. The gas gate includes a cylinder within a housing situated between the regions of differing gaseous pressure, wherein the gas gate provides for choke mode transonic flow of air leaks between the regions. A web of substrate material is adapted to move between the regions with at least one roller in a first region and at least one roller in a second region. The rollers are positioned to create sufficient tension as the web advances over the top peripheral portion of the cylinder between the two regions or under the bottom peripheral portion of the cylinder between the two regions.
Patent Number: 6,878,207 Issued on 04/12/2005 to Doehler, et al.
| Inventors:
|
Doehler; Joachim (Santa Barbara, CA);
Cannella; Vincent (Beverly Hills, MI)
|
| Assignee:
|
Energy Conversion Devices, Inc. (Rochester Hills, MI)
|
| Appl. No.:
|
368835 |
| Filed:
|
February 19, 2003 |
| Current U.S. Class: |
118/718; 156/345.31; 204/298.24; 118/719; 118/733 |
| Intern'l Class: |
C23C 016//00; C23C 014//00; C23F 001//00 |
| Field of Search: |
118/718,733
204/298.24
414/217
|
References Cited [Referenced By]
U.S. Patent Documents
| 2952569 | Sep., 1960 | Baer et al. | 427/295.
|
| 2972330 | Feb., 1961 | Bugbee | 118/718.
|
| 2989026 | Jun., 1961 | Gardner et al. | 118/718.
|
| 3660146 | May., 1972 | Chadsey et al. | 427/172.
|
| 3868106 | Feb., 1975 | Donckel et al. | 277/345.
|
| 4551310 | Nov., 1985 | Imada et al. | 422/186.
|
| 5088908 | Feb., 1992 | Ezaki et al. | 425/73.
|
| 6334751 | Jan., 2002 | Vanden Brande et al. | 414/217.
|
| 2003/0079837 | May., 2003 | Hirai et al. | 156/345.
|
Primary Examiner: Hassanzadeh; Parviz
Assistant Examiner: Moore; Karla
Attorney, Agent or Firm: Serventi; Anthony J., Siskind; Martin S., Schumaker; David W.
Claims
We claim:
1. An apparatus for the interconnecting a first region having a gaseous
pressure and a second region having a gaseous pressure, wherein the
gaseous pressure of said first region is different from the gaseous
pressure of said second region, said apparatus comprising:
a gas gate interconnecting said first region and said second region, said
gas gate comprising, a cylinder, having a top peripheral portion and a
bottom peripheral portion, set in a housing through which a web of
substrate material is adapted to move between said first region and said
second region, said web maintaining contact with the top peripheral
portion of said cylinder to create a top gap between said web and said
housing, said gas gate providing for choke mode transonic flow of air
leaks between said first region and said second region;
at least one roller positioned in said first region, said at least one
first region roller adapted to guide said web into said top gap;
at least one roller positioned in said second region, said at least one
second region roller adapted to guide said web out of said top gap; and
at least one means for evacuating at least one of said first region and
said second region.
2. The apparatus of claim 1, said housing having a top plate and a bottom
plate, wherein said cylinder is set between said top plate and said bottom
plate.
3. The apparatus of claim 2, said top plate having a contour, wherein said
top plate contour is fashioned to approximately equal the arc of the top
peripheral portion of said cylinder.
4. The apparatus of claim 2, said bottom plate having a contour, wherein
said bottom plate contour is fashioned to approximately equal the arc of
the bottom peripheral portion of said cylinder.
5. The apparatus of claim 2, said housing having a first side wall between
said top plate and said bottom plate and second side wall between said top
plate and said bottom plate, wherein said cylinder is set between said
first side wall and said second side wall to rotate about an axis between
said first side wall and said second side wall.
6. The apparatus of claim 1, wherein the circumferential surface of said
cylinder, which contacts the web the substrate material is fabricated from
a low friction, low thermal conductivity material.
7. The apparatus of claim 1, wherein the circumferential surface of said
cylinder is formed from a material selected from the group consisting of
aluminum, stainless steel, plated steel and borosilicate glass.
8. The apparatus of claim 1, wherein the substrate material is selected
from the group consisting of polycarbonate, poly methyl methacrylate,
polyolefin, polyester, poly vinyl chloride, polysulfone and cellulosic
substances.
9. The apparatus of claim 1, wherein one of said first region and said
second region is evacuated to a pressure of about 0.001 Torr to about 0.01
Torr.
10. The apparatus of claim 1, wherein said at least one means for
evacuating is at least one diffusion pump.
11. The apparatus of claim 3, said top plate being at all points
equidistant from said web, wherein said top gap maintains a uniform
distance between said web and said top plate.
12. The apparatus of claim 2, said at least one first region roller
comprising one first region roller, wherein said one first region guides
said web into said gap at an angle sufficient to avoid web contact with
said top plate.
13. The apparatus of claim 2, said at least one second region roller
comprising one second region roller, wherein said one second region roller
guides said web out of said gap at an angle sufficient to avoid web
contact with said top plate.
14. The apparatus of claim 2, said at least one first region roller
comprising a first set rollers and a second set of rollers,
wherein said web is adapted to move between each roller of said first set
and each roller of said second set,
wherein each roller of said first and second sets maintains contact with
said web sufficient to move said web into said gap,
wherein a reduction in web tension between said first set and said second
set produces an angle in said web sufficient to avoid web contact with
said top plate.
15. The apparatus of claim 14, said at least one second region roller
comprising a third set rollers and a forth set of rollers,
wherein said web is adapted to move between each roller of said third set
and each roller of said forth set,
wherein each roller of said third and forth sets maintains contact with
said web sufficient to move said web out of said gap,
wherein a reduction in web tension between said third set and said forth
set produces an angle in said web sufficient to avoid web contact with
said top plate.
16. An apparatus for continuously moving of a web of substrate material
into a vacuum chamber from an atmospheric region, said apparatus
comprising:
an evacuable vacuum chamber;
means for evacuating said vacuum chamber to sub-atmospheric pressure;
a gas gate interconnecting said atmospheric region and said vacuum chamber,
said gas gate comprising, a cylinder having a top peripheral portion set
in a housing through which a web of substrate material is adapted to move
between said atmospheric region and said vacuum chamber, said web
maintaining contact with the top peripheral portion of said cylinder to
create a gap between said web and said housing, said gas sate providing
for choke mode transonic flow of air leaks between said atmospheric region
and said vacuum chamber;
a first roller positioned in said atmospheric region, said first roller is
adapted to guide said web into said gap; and
a second roller positioned inside said vacuum chamber, said second roller
adapted to guide said web out of said gap.
17. The apparatus of claim 16, said housing having a top plate and a bottom
plate, wherein said cylinder is set between said top plate and said bottom
plate.
18. The apparatus of claim 17, said top plate having a contour, wherein
said top plate contour is fashioned to approximately equal the arc of the
top peripheral portion of said cylinder.
19. The apparatus of claim 17, said bottom plate having a contour, wherein
said bottom plate contour is fashioned to approximately equal the arc of
the bottom peripheral portion of said cylinder.
20. The apparatus of claim 17, said housing having a first side wall
between said top plate and said bottom plate and second side wall between
said top plate and said bottom plate, wherein said cylinder is set between
said first side wall and said second side wall to rotate about an axis
between said first side wall and said second side wall.
21. The apparatus of claim 16, wherein the circumferential surface of said
cylinder, which contacts the web the substrate material is fabricated from
a low friction, low thermal conductivity material.
22. The apparatus of claim 16, wherein the circumferential surface of said
cylinder is formed from a material selected from the group consisting of
aluminum, stainless steel, plated steel and borosilicate glass.
23. The apparatus of claim 22, wherein the substrate material is selected
from he group consisting of polycarbonate, poly methyl methacrylate,
polyolefin, polyester, poly vinyl chloride, polysulfone and cellulosic
substances.
24. The apparatus of claim 16, wherein said means for evacuating evacuates
said vacuum chamber to a pressure of about 0.001 Torr to about 0.01 Torr.
25. The apparatus of claim 16, wherein said means for evacuating evacuates
said vacuum chamber is a diffusion pump.
26. The apparatus of claim 18, said top plate being at all points
equidistant from said web, wherein said gap maintains a uniform distance
between said web and said top plate.
27. The apparatus of claim 16, wherein said first roller guides said web
into said gap at an angle sufficient to avoid web contact with said top
plate.
28. The apparatus of claim 16, wherein said second roller guides said web
out of said gap at an angle sufficient to avoid web contact with said top
plate.
29. An apparatus for continuously moving of a web of substrate material
into a vacuum chamber from an atmospheric region, said apparatus
comprising:
an evacuable vacuum chamber;
means for evacuating said vacuum chamber to sub-atmospheric pressure; a gas
gate interconnecting said atmospheric region and said vacuum chamber, said
gas gate comprising, a cylinder having a top peripheral portion set in a
housing through which a web of substrate material is adapted to move
between said atmospheric region and said vacuum chamber, said web
maintaining contact with the top peripheral portion of said cylinder to
create a gap between said web and said housing, said gas gate providing
for choke mode transonic flow of air leaks between said atmospheric region
and said vacuum chamber;
a first set rollers and a second set of rollers,
wherein said web is adapted to move between each roller of said first set
and each roller of said second set,
wherein each roller of said first and second sets maintains contact with
said web sufficient to move said web into said gap,
wherein a reduction in web tension between said first set and said second
set produces an introductory angle in said web sufficient to avoid web
contact with said housing; and
a third set rollers and a forth set of rollers,
wherein said web is adapted to move between each roller of said third set
and each roller of said forth set,
wherein each roller of said third and forth sets maintains contact with
said web sufficient to move said web out of said gap,
wherein a reduction in web tension between said third set and said forth
set produces an exit angle in said web sufficient to avoid web contact
with said housing.
30. The apparatus of claim 29, said housing having a top plate and a bottom
plate, wherein said cylinder is set between said top plate and said bottom
plate.
31. The apparatus of claim 30, said top plate having a contour, wherein
said top plate contour is fashioned to approximately equal the arc of the
top peripheral portion of said cylinder.
32. The apparatus of claim 30, said bottom plate having a contour, wherein
said bottom plate contour is fashioned to approximately equal the arc of
the bottom peripheral portion of said cylinder.
33. The apparatus of claim 30, said housing having a first side wall
between said top plate and said bottom plate and second side wall between
said top plate and said bottom plate, wherein said cylinder is set between
said first side wall and said second side wall to rotate about an axis
between said first side wall and said second side wall.
34. The apparatus of claim 29, wherein the circumferential surface of said
cylinder, which contacts the web the substrate material is fabricated from
a low friction, low thermal conductivity material.
35. The apparatus of claim 29, wherein the circumferential surface of said
cylinder is formed from a material selected from the group consisting of
aluminum, stainless steel, plated steel and borosilicate glass.
36. The apparatus of claim 29, wherein the substrate material is selected
from the group consisting of polycarbonate, poly methyl methacrylate,
polyolefin, polyester, poly vinyl chloride, polysulfone and cellulosic
substances.
37. The apparatus of claim 29, wherein said means for evacuating evacuates
said vacuum chamber to a pressure of about 0.001 Torr to about 0.01 Torr.
38. The apparatus of claim 29, wherein said means for evacuating evacuates
said vacuum chamber is a diffusion pump.
39. The apparatus of claim 30, said top plate being at all points
equidistant from said web, wherein said gap maintains a uniform distance
between said web and said top plate.
40. The apparatus of claim 1, wherein the ends of said cylinder are
leak-proofed by an annularly-shaped end seal.
41. The apparatus of claim 40, wherein each of the end seals include a pair
of spaced O-rings.
42. The apparatus of claim 41, wherein a pump is provided to evacuate the
space between each of the O-rings.
43. An apparatus for the interconnecting an first region having a gaseous
pressure and a second region having a gaseous pressure, wherein the
gaseous pressure of said first region is different from the gaseous
pressure of said second region, said apparatus comprising:
a gas gate interconnecting said first region and said second region, said
gas gate comprising, a cylinder, having a top peripheral portion and a
bottom peripheral portion, set in a housing through which a web of
substrate material is adapted to move between said first region and said
second region, said web maintaining contact with the bottom peripheral
portion of said cylinder to create a bottom gap between said web and said
housing, said housing having a top plate and a bottom plate, wherein said
cylinder is set between said top plate and said bottom plate, said housing
having a first side wall between said top plate and said bottom plate and
second side wall between said top plate and said bottom plate, wherein
said cylinder is set between said first side wall and said second side
wall to rotate about an axis between said first side wall and said second
side wall;
a first O-ring set between the first side wall and the cylinder, said first
O-ring adapted to reduce an influx of air from a space between the first
side wall and the cylinder and further comprising a second O-ring set
between the second side wall and the cylinder, said second O-ring adapted
to reduce an influx of air from a space between the second side wall and
the cylinder;
at least one roller positioned in said first, said at least one first
region roller adapted to guide said web into said bottom gap;
at least one roller positioned in said second region, said at least one
second region roller adapted to guide said web out of said bottom gap; and
at least one means for evacuating at least one of said first region and
said second region.
44. The apparatus of claim 43, said top plate having a contour, wherein
said top plate contour is fashioned to approximately equal the arc of the
top peripheral portion of said cylinder.
45. The apparatus of claim 43, said bottom plate having a contour, wherein
said bottom plate contour is fashioned to approximately equal the arc of
the bottom peripheral portion of said cylinder.
46. The apparatus of claim 43, wherein the circumferential surface of said
cylinder, which contacts the web the substrate material is fabricated from
a low friction, low thermal conductivity material.
47. The apparatus of claim 43, wherein the circumferential surface of said
cylinder is formed from a material selected from the group consisting of
aluminum, stainless steel, plated steel and borosilicate glass.
48. The apparatus of claim 43, wherein the substrate material is selected
from the group consisting of polycarbonate, poly methyl methacrylate,
polyolefin, polyester, poly vinyl chloride, polysulfone and cellulosic
substances.
49. The apparatus of claim 43, wherein said at least one means for
evacuating evacuates said transition chamber to a pressure of about 0.001
Torr to about 0.01 Torr.
50. The apparatus of claim 43, wherein said at least one means for
evacuating said transition chamber is a diffusion pump.
51. The apparatus of claim 44, said bottom plate being at all points
equidistant from said web, wherein said top gap maintains a uniform
distance between said web and said top plate.
52. The apparatus of claim 43, said at least one first region roller
comprising one first region roller, wherein said one first region roller
guides said web into said gap at an angle sufficient to avoid web contact
with said bottom plate.
53. The apparatus of claim 43, said at least one second region roller
comprising one second region roller, wherein said one second region roller
guides said web out of said gap at an angle sufficient to avoid web
contact with said bottom plate.
54. The apparatus of claim 43, said at least one first region roller
comprising a first set rollers and a second set of rollers,
wherein said web is adapted to move between each roller of said first set
and each roller of said second set,
wherein each roller of said first and second sets maintains contact with
said web sufficient to move said web into said bottom gap,
wherein a reduction in web tension between said first set and said second
set produces an angle in said web sufficient to avoid web contact with
said bottom plate.
55. The apparatus of claim 43, said at least one second region roller
comprising a third set rollers and a forth set of rollers,
wherein said web is adapted to move between each roller of said third set
and each roller of said forth set,
wherein each roller of said third and forth sets maintains contact with
said web sufficient to move said web out of said bottom gap,
wherein a reduction in web tension between said third set and said forth
set produces an angle in said web sufficient to avoid web contact with
said bottom plate.
56. The apparatus of claim 43, said first O-ring comprising a first
C-shaped O-ring adapted to receive a first pressure, said first pressure
pressing said first C-shaped O-ring against the cylinder, said second
O-ring comprising a second C-shaped O-ring adapted to receive a second
pressure, said second pressure pressing said second C-shaped O-ring
against the cylinder.
57. The apparatus of claim 56, said first pressure comprising at least one
first spring set between the first side wall and the first O-ring, said
second pressure comprising at least one second spring set between the
second side wall and the second O-ring.
58. The apparatus of claim 5, further comprising a first O-ring set between
the first side wall and the cylinder, said first O-ring adapted to reduce
an influx of air from a space between the first side wall and the cylinder
and further comprising a second O-ring set between the second side wall
and the cylinder, said second O-ring adapted to reduce an influx of air
from a space between the second side wall and the cylinder.
59. The apparatus of claim 58, said first O-ring comprising a first
C-shaped O-ring adapted to receive a first pressure, said first pressure
pressing said first C-shaped O-ring against the cylinder, said second
O-ring comprising a second C-shaped O-ring adapted to receive a second
pressure, said second pressure pressing said second C-shaped O-ring
against the cylinder.
60. The apparatus of claim 59, said first pressure comprising at least one
first spring set between the first side wall and the first O-ring, said
second pressure comprising at least one second spring set between the
second side wall and the second O-ring.
Description
FIELD OF THE INVENTION
This invention relates generally to isolating mechanisms for operatively
interconnecting regions of differing gaseous pressure. More specifically
the instant invention relates to a gas gate that separates a first region
having an atmospheric pressure from an evacuable second region having a
pressure from about 0.01 Torr and below. Further, the gas gate of the
present invention uses a cylinder to simultaneously achieve
atmospheric-to-vacuum or vacuum-to-atmospheric capability and non-contact
on the film deposition side of a moving web of material.
BACKGROUND OF THE INVENTION
A variety of products may be fabricated by thin film processes. Examples of
the products that may be fabricated by the deposition of thin film
materials include interferometer stacks for optical control and solar
control, semiconductor based solar cells, aluminized coffee pouches and
organic semiconductor devices such as OLED displays, organic FETs, smart
tags, organic PV devices and sensors, organic semiconductors, etc. These
products may be mass produced using roll-to-roll processes. Some
roll-to-roll processors use a pay-off roll and a take-up roll kept in
vacuum chambers. Once the pay-off roll is empty, or the take-up roll is
full, the respective roll must be changed to a fresh roll. During the
changing process, the pay-off and take-up chambers must be vented, opened,
loaded/unloaded, closed and pumped out. During this cycle, the production
process is typically interrupted. Alternatively, the roll to roll
production of some types of devices requires the integration of many
processes in-line without intermediate roll-up and unrolling of the
product substrates, because any contact with the product surface during
rolling completion would destroy the device performance. In such cases it
is critical for a product substrate to be able to pass continuously from
processes at atmospheric pressure to processes in vacuum, and back to
atmospheric pressure.
Typically, gas gates are incorporated between discreet regions for
deposition to maintain the chemical integrity of the regions. As disclosed
in U.S. Pat. No. 4,462,332 to Nath et al., assigned to the assignee of the
instant application and the disclosure of which is hereby incorporated
herein by reference, it has been determined that despite the relatively
small size of the gas gate passageway, dopant process gases introduced
into one deposition chamber back diffuse into the adjacent chamber,
thereby contaminating the process gases introduced thereinto and the
semiconductor layer deposited in the adjacent chamber. The '332 patent
discloses an apparatus (namely ceramic magnets positioned above the gas
gate passageway for urging the magnetic substrate upwardly) by which the
height dimension of the passageway could be reduced. The reduction in the
height dimension of the passageway provided for a corresponding reduction
of the back diffusion of dopant gases for a given flow rate, thereby
decreasing the contamination of the process gases introduced into the
intrinsic deposition chamber.
However, because the magnets urge the substrate into sliding contact with
the upper passageway wall, frictional abrasion between the wall and the
bare side of the substrate causes problems with the deposition apparatus
such as, for example, wear of the upper passageway wall of the gas gate.
Also, abraded particles of substrate and passageway wall material collect
in the passageway and deposition chambers causing scratching of the
layered side of the substrate and co-depositing with the semiconductor
material, which in turn, causes short circuiting due to the protruding
particles which cannot be fully covered by a one micron thick
semiconductor alloy layer. The abrasion, in addition to being detrimental
to the semiconductor layer and the equipment, limits the minimum thickness
of the web of substrate material which can be realistically used due to
possible tearing. In some product applications the substrate the substrate
material is non magnetic, for example, a polymer substrate.
Additionally, as was disclosed in U.S. Pat. Nos. 4,438,724 and 4,450,786
each to Doehler et al., both assigned to the assignee of the instant
application and the disclosures of which are hereby incorporated herein by
reference, when the web of substrate material is urged against the upper
wall of the passageway, the passageway is divided by the web of substrate
into a relatively narrow upper portion, between the substrate and the
upper passageway wall, and a relatively wide lower portion, between the
substrate and the lower passageway wall. Also, irregular spacing between
the substrate and the upper passageway wall occurred because waffling
(warping) of the web of substrate material could not be entirely
eliminated by the attractive force of the magnets. Much of the warping of
the substrate is caused by temperature gradients in the substrate. The
process gases, being inherently viscous (and especially viscous at the
elevated deposition temperatures employed with glow discharge deposition
processes), are unable to travel through the narrow upper portion with
sufficient velocity to prevent cross-contamination of process gases from
one deposition chamber to the other. It was to the end of decreasing the
amount of cross-contamination of process gases through the narrow upper
portion between the bare side of the substrate and the upper passage wall
that the '724 and '786 patents were directed.
In the past, considerable efforts have been made to develop processes for
depositing layers of amorphous semiconductor alloy material, each of which
can encompass relatively large areas, and which can be doped to form
p-type and n-type materials for the fabrication of p-i-n-type photovoltaic
devices which are, in operation, substantially equivalent to their
crystalline counterparts. For many years such work with amorphous silicon
or germanium films was substantially unproductive because of the presence
therein of microvoids and dangling bonds which produce a high density of
localized states in the energy gap. Initially, the reduction of the
localized states was accomplished by glow discharge deposition of
amorphous silicon films using silane (SiH.sub.4) gas and hydrogen gas as
precursors. The material so deposited is an intrinsic amorphous material
consisting of silicon and hydrogen. To produce a doped amorphous material,
phosphine gas (PH.sub.3) for n-type or a Boron-containing gas, such as
diborane (B.sub.2 H.sub.6) for p-type conduction, is premixed with the
silane gas. The material so deposited includes supposedly substitutional
phosphorus or boron dopants and is shown to be extrinsic and of n or p
conduction type, respectively.
It is now possible to prepare greatly improved amorphous silicon alloy
materials, that have significantly reduced concentrations of localized
states in the energy gap thereof, while providing high quality electronic
properties by glow discharge as is fully described in U.S. Pat. No.
4,226,898 to Ovshinsky et al., and by vapor deposition as described in
U.S. Pat. No. 4,217,374 to Ovshinsky et al., both assigned to the assignee
of the instant application and the disclosures of which are hereby
incorporated by reference. As disclosed in these patents, fluorine
introduced into the amorphous silicon semiconductor operates to
substantially reduce the density of localized states therein and
facilitates the addition of other alloying materials, such as germanium.
Activated fluorine readily diffuses into, and bonds to, amorphous silicon
in a matrix body to substantially decrease the density of localized states
therein. This is because the small size of the fluorine atoms enable them
to be readily introduced into an amorphous silicon matrix. The fluorine is
believed to bond to the dangling bonds of the silicon and form a partially
ionic stable bond with flexible bonding angles, which results in a more
stable and more efficient compensation or alteration than could be formed
by hydrogen, or other compensating or altering agents which were
previously employed.
The concept of utilizing multiple cells, to enhance photovoltaic device
efficiency, was discussed at least as early as 1955 by E. D. Jackson, U.S.
Pat. No. 2,949,498. The multiple cell structures therein discussed
utilized p-n junction crystalline semiconductor devices. Essentially the
concept is directed to utilizing different band gap devices to more
efficiently collect various portions of the solar spectrum and to increase
open circuit voltage (V.sub.oc). The tandem cell device has two or more
cells with the light directed serially through each cell, with a large
band gap material followed by a smaller band gap material to absorb the
light passed through the first cell or layer. By substantially matching
the generated currents from each cell, the overall open circuit voltage is
the sum of the open circuit voltages of each cell while the short circuit
current remains substantially constant.
Due to the beneficial properties attained by the introduction of fluorine,
amorphous alloys used to produce cascade type multiple cells may now
incorporate fluorine to reduce the density of localized states without
impairing the electronic properties of the material. Further band gap
adjusting element(s), such as germanium and carbon, can be activated and
are added in vapor deposition, sputtering or glow discharge processes. The
band gap is adjusted as required for specific device applications by
introducing the necessary amounts of one or more of the adjusting elements
into the deposited alloy cells in at least the photocurrent generation
region thereof. Since the band gap adjusting element(s) has been tailored
into the cells without adding substantial deleterious states, the cell
material maintains high electronic qualities and photoconductivity when
the adjusting element(s) are added to tailor the device wavelength
characteristics for a specific photoresponse application.
It is of obvious commercial importance to be able to mass produce
photovoltaic devices. Unlike crystalline silicon which is limited to batch
processing for the manufacture of solar cells, amorphous silicon
semiconductor alloys can be deposited in multiple layers over large area
substrates to form solar cells in a high volume, continuous processing
system. Continuous processing systems of this kind are disclosed, for
example, in U.S. Pat. Nos. 4,440,409; 4,542,711; 4,410,558; 4,438,723; and
4,492,181 each of which is assigned to the assignee of the instant
application and the disclosures of which are hereby incorporated by
reference. As disclosed in these patents, a substrate may be continuously
advanced through a succession of deposition chambers, wherein each chamber
is dedicated to the deposition of a specific semiconductor layer. In
making a solar cell of p-i-n-type configuration, the first chamber is
dedicated for depositing a p-type amorphous silicon semiconductor alloy
material, the second chamber is dedicated for depositing an intrinsic
amorphous silicon semiconductor alloy material, and the third chamber is
dedicated for depositing an n-type amorphous silicon semiconductor alloy
material. Since each deposited semiconductor alloy material, and
especially the intrinsic semiconductor alloy material must be of high
purity, the deposition environment in the deposition chamber is isolated
from the doping constituents within the other chambers to prevent
cross-contamination of doping constituents into the intrinsic process
gases in the intrinsic chamber. In the previously mentioned patents,
wherein the systems are primarily concerned with the production of
photovoltaic cells, chemical isolation between the chambers is
accomplished by gas gates through which (1) a unidirectional flow of
process gases between deposition chambers is established, and (2) an inert
gas may be "swept" along the web of substrate material. The gas gate
disclosed in previously mentioned U.S. Pat. No. 4,462,332 contemplated the
creation of a plurality of magnetic fields adapted to urge the magnetic
web of substrate material against a wall of the gas gate passageway
opening so that the height dimension of the passageway opening could be
reduced. The reduced height of the opening, in the described pressure and
flow regimes, correspondingly decreased the quantity of process gas, which
would otherwise diffuse from the dopant deposition chambers to the
intrinsic deposition chamber, without correspondingly increasing the risk
that the amorphous semiconductor layers deposited on the substrate would
contact and be damaged by a wall of the gas gate passageway opening.
While the magnetic gas gate disclosed in U.S. Pat. No. 4,462,332 reduced
the height dimension of the passageway opening, this gas gate design
caused two additional problems, (1) the aforementioned problems of
friction, and (2) it divided the passageway into wide and narrow portions,
as discussed hereinabove. Regarding the latter of these problems, the
velocity of the inert sweep gas and residual process gases traveling
through the wide lower portion is sufficiently great to substantially
prevent cross-contamination of dopant gases into the intrinsic chamber.
However, due to the viscosity of the process gases, the drag on the sweep
gases along (1) the upper passageway wall and (2) the uncoated surface of
the substrate (which define the relatively narrow upper portion of the
passageway) results in a relatively low velocity flow therethrough.
Accordingly, an undesirably high amount of dopant process gas is able to
diffuse into the intrinsic chamber through the narrow upper portion.
The problem of cross-contamination was reduced in U.S. Pat. Nos. 4,438,724
and 4,450,786 by providing a plurality of elongated grooves (extending the
entire length of the gas gate passageway opening) from the dopant
deposition chamber to the adjacent intrinsic deposition chamber in the
wall of the passageway opening above the web of substrate material. In
this manner, a plurality of spaced, relatively high velocity flow channels
were provided in the space between the uncoated surface of the web of
substrate material and the upper wall of the passageway opening. Because
the sweep gases were forced into the channels by independent means, they
flowed unidirectionally therethrough at substantial velocities despite the
drag incurred as said gases contacted the passageway wall and the
substrate surface. While the gas gate of the '724 and '786 patents reduced
the problem of cross-contamination through the aforementioned narrow upper
section, it failed to reduce the problem of frictional abrasion between
the uncoated side of the substrate and the upper passageway wall.
The magnetic roller gas gate of commonly owned and assigned our U.S. Pat.
No. 5,374,313 and hereby incorporated herein by reference, substantially
reduced the frictional abrasion between the unlayered side of the
substrate and the passageway wall without substantially increasing in the
cross-contamination of process gases between deposition chambers. While
the magnetic roller gas gate of the '313 Patent reduced the frictional
abrasion problem and did not increase the cross contamination problem, the
gas gates of the prior art cannot be used to operatively interconnect
regions having a pressure differential between the chambers of greater
than about 10%. However in many instances, it is desirable, if not
essential, to interconnect two processing chambers having pressure
differentials of greater than an order of magnitude (i.e., such as
pressures of 10.sup.-1 and 10.sup.-3 Torr respectively).
Although the foregoing discussion dealt with a single dopant deposition
chamber and an adjacent transition chamber, it should be apparent that
other deposition chambers may be operatively connected to the
air-to-vacuum gas gate of the present invention for any apparatus or
process that uses roll to roll deposition. For example, a p-type
deposition chamber may be connected on one side of the intrinsic
deposition chamber and an n-type deposition chamber may be connected to
the other side of the intrinsic deposition chamber so as to produce a
p-i-n type semiconductor device. Alternatively, a plurality of these
triads of deposition chambers could be interconnected to produce a
plurality or p-i-n-type cells. For that matter, the improved gas gate of
the instant invention is applicable to any continuous production apparatus
or process that requires the chemical isolation of regions having
different gaseous pressure.
SUMMARY OF THE INVENTION
The present invention relates to a gate that allows a web of substrate to
be introduced continuously from a first region having a pressure into a
second region having a pressure different from the first region. More
particularly, the present invention relates to an air-to-vacuum gas gate
that allows a web to be introduced continuously into a vacuum chamber from
an atmospheric region or into an atmospheric region from a vacuum chamber.
Additionally, the present invention discloses an apparatus for
continuously fabricating devices on a web of substrate material by
depositing thereon at least one layer in at least one vacuumized
deposition chamber, wherein the web may be introduced continuously into
the deposition chamber(s) from the atmosphere via a first transition
chamber then exit the deposition chamber(s) into the atmosphere via a
second transition chamber. The gas gate of the present invention may be
used with any web material, including but not limited to thermoplastic
polymer, such as polycarbonate, poly methyl methacrylate, polyolefin,
polyester, poly vinyl chloride, polysulfone, cellulosic substances, etc.
The composition of each layer is dependent upon the particular gases
introduced into and isolated from each of the deposition chambers.
In a preferred embodiment, the web is fed from the atmosphere into a
pressurized transition chamber having a gas gate of the present invention
between the atmosphere and the transition chamber that leads to one or
more deposition chambers then from the deposition chambers into a second
pressurized transition chamber having a gas gate of the present invention
and back into the atmosphere. More particularly, the transition chamber
and ambient air are separated by a gas gate which includes a relatively
narrow passageway created by a cylinder (1) through which the web of
substrate material passes; and (2) adapted to substantially isolate the
ambient air from the transition chamber to permit the exchange of a web
without upsetting the pressure of the deposition chambers.
The gas gate of the present invention includes a cylinder within a housing
situated between the regions of differing gaseous pressure. A web of
substrate material is adapted to move between the regions over the
cylinder through a small gap between the top peripheral surface of the
cylinder and the housing. The gap is sufficiently wide to allow the web of
substrate to maintain contact with the cylinder without coming in contact
with the housing. Rollers are positioned in the atmospheric region and the
transition chamber to guide the web of substrate material into and out of
the top peripheral gap. In a preferred embodiment, two sets of rollers
guide the web into the gap and two sets of rollers guide the web out of
the gap, which minimizes the contact between the rollers and the web. The
sets of rollers are positioned to create an angle of entry into and an
angle of exit out of the cylinder, because the web assumes the arced shape
of the top peripheral portion of the cylinder. Further, the angles are
necessary to prevent contact by the web with the housing, contact that may
contaminate or damage the substrate. In another embodiment, rollers are
positioned so that the bottom peripheral surface of each roller is below
the top peripheral surface of the cylinder, which creates tension as the
web advances below the first roller, over the cylinder and below the
second roller.
In another embodiment, the position of the web relative to the cylinder is
reversed from the top peripheral portion of the cylinder to the bottom
peripheral portion of the cylinder. In this embodiment, a web of substrate
material is adapted to move between the regions under the cylinder through
a small gap between the bottom peripheral surface of the cylinder and the
housing. The bottom peripheral gap is sufficiently wide to allow the web
of substrate to maintain contact with the cylinder without coming in
contact with the housing. Rollers are positioned in the first region and
the second region to guide the web of substrate material into and out of
the bottom peripheral gap. In a preferred embodiment, two sets of rollers
guide the web into the gap and two sets of rollers guide the web out of
the gap, which minimizes the contact between the rollers and the web. The
sets of rollers are positioned to create an angle of entry into and an
angle of exit out of the cylinder, because the web assumes the arced shape
of the bottom peripheral portion of the cylinder. Further, the angles are
necessary to prevent contact by the web with the housing, contact that may
contaminate or damage the substrate. In another embodiment, rollers are
positioned so that the top peripheral surface of each roller is below the
bottom peripheral surface of the cylinder, which creates tension as the
web advances over the first roller, under the cylinder and over the second
roller.
Preferably, the first region and the second region have differing gaseous
pressure and at least one of the first and second chambers is evacuable.
In a preferred embodiment, a gas gate of the present invention may take a
web of substrate from an atmospheric region having an atmospheric pressure
to a transition chamber having a pressure lower than the atmospheric
pressure. Additionally, a gas gate of the present invention may take a web
of substrate from a transition chamber having a pressure lower than
atmospheric pressure to an atmospheric region having an atmospheric
pressure.
The housing has a top plate and a bottom plate and the cylinder is set
between the top plate and the bottom plate. Preferably, the top plate has
a contour fashioned to approximately equal the arc of the top peripheral
portion of the cylinder. Similarly, the bottom plate preferably has a
contour fashioned to approximately equal the arc of the bottom peripheral
portion of the cylinder. Further, the housing has a first side wall
between the top plate and the bottom plate and a second side wall between
the top plate and the bottom plate. The cylinder is positioned between the
first side wall and the second side wall to rotate about an axis between
the side walls. A first O-ring may be set between the first side wall and
the cylinder. The first O-ring adapted to reduce the influx of air from
the space between the first side wall and the cylinder. A second O-ring
may be set between the second side wall and the cylinder. The second
O-ring adapted to reduce the influx of air from the space between the
second side wall and the cylinder. Preferably, the O-ring are C-shaped
O-rings adapted to receive pressure to press the respective O-ring against
the cylinder. The pressure may be supplied by at least one first spring
set between the first side wall and the first O-ring, and at least one
second spring set between the second side wall and the second O-ring.
The gas gate is characterized in that the height of the passageway between
the top plate of the housing and the top peripheral portion of the
cylinder or the passageway between the bottom plate of the housing and the
bottom peripheral portion of the cylinder, depending on the embodiment.
The flow rate of the gas therethrough provides for transonic flow of the
gas between the cylinder inlet and at least one of the two interconnected
regions, thereby effectively isolating one region, characterized by one
composition and pressure, from another region, having a differing
composition and/or pressure, by decreasing the mean-free-path length
between collisions of diffusing species within the transonic flow region.
An embodiment of the present invention is to provide a gas gate that
separates two regions of different gaseous pressure.
Another embodiment of the present invention is to provide an air-to-vacuum
gas gate which separates an atmospheric region from a evacuable transition
chamber that leads to a deposition chamber, which allows a web roll to be
changed without venting the deposition chamber.
Another embodiment of the present invention is to provide roll to roll
apparatus for continuously fabricating devices on a web of substrate
material with a transition chamber that enables a pay-off roll or a
take-up roll to be changed without disrupting the vacuum of the deposition
chamber.
When the gas gate of the instant invention is used in an apparatus for the
production of amorphous semiconductor solar cell devices, a transition
chamber is set after the pay-off roll and before the take-up roll.
Deposition chambers adapted to deposit amorphous silicon semiconductor
alloys are set between the transition chambers. For example, a web of
substrate may pass from an atmospheric region through a gas gate of the
present invention into a first transition chamber and proceed into a first
deposition chamber in which a first layer may be deposited onto one
surface of the substrate in the first deposition chamber, the substrate
can then pass through a second deposition chamber wherein a second layer
is deposited atop the first layer, the substrate can then pass through a
second transition chamber, then proceed through a gas gate of the present
invention and into the atmospheric region.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary, cross-sectional view of a tandem or cascade
photovoltaic device comprising a plurality of p-i-n-type cells, each layer
of the cells formed from an amorphous silicon alloy material;
FIG. 2 is a diagrammatic representation of a multiple glow discharge
chamber deposition system adapted for the continuous production of the
photovoltaic devices shown in FIG. 1, which system includes a preferred
embodiment of the air-to-vacuum gas gates for isolating the pay-off roll
and take-up roll;
FIG. 3 is a side view of a preferred embodiment of the gas gate of the
present invention which details the tension created by two rollers and the
main cylinder as the web of substrate material advances from atmospheric
pressure to vacuum pressure;
FIG. 4 is a side view of an embodiment of the gas gate of the present
invention which details the tension created by a four sets of rollers, two
sets in the atmospheric region and two sets in the vacuum region, and the
main cylinder as the web of substrate material advances from atmospheric
pressure to vacuum pressure;
FIG. 5 is a partial cross-sectional view taken along line 5--5 of FIG. 4
and illustrating the operative disposition of a vacuum-tight end seal for
preventing leakage between the interior of the gas gate of the subject
invention and the atmospheric region; and
FIG. 6 is a graphical representation of the relationship between the
pressure in the transition chamber, plotted on the ordinate, and the flow
of air in the transonic flow channel, plotted on the abscissa.
FIG. 7 is a magnified illustration of 7 from FIG. 5 which illustrates a
U-shaped O-ring receiving pressure from a spring.
DETAILED DESCRIPTION OF THE INVENTION
The current invention relates to an apparatus that allows a moving web of
substrate to be introduced continuously into a vacuum chamber from an
atmospheric region. A similar device at the other end of the production
machine allows the web to be returned to atmospheric pressure from a
vacuum chamber. The gas gate of the present invention is described as the
invention relates to the production of a tandem or cascade-type
photovoltaic cells, however, this is for illustrative purposes only and
should not be considered limiting. It is understood that the embodiments
of the gas gate described herein may be effectively incorporated into any
system that requires a web of material to be advanced through regions of
varying gaseous pressure. Additionally, the gas gate of the present
invention allows various layers of deposition materials to be deposited
onto the web of substrate without having the deposition areas of the web
touch any solid object as the web enters and exits the deposition
chambers.
I. The Photovoltaic Cell
Referring to the drawings and particularly to FIG. 1, a tandem or
cascade-type photovoltaic cell, formed of successive p-i-n layers each
including an amorphous silicon alloy material, is shown generally by
numeral 10. It is for the production of this type of photovoltaic device,
wherein layers of amorphous silicon alloy material are continuously
deposited onto a moving web of substrate material in isolated deposition
chambers, that the gas gates of the present invention were developed.
FIG. 1 shows a p-i-n type photovoltaic device such as a solar cell made up
of individual p-i-n type cells 12a, 12b and 12c. Below the lowermost cell
12a is a substrate 11 which may be transparent or formed from a metallic
surfaced foil. Although certain applications may require a thin oxide
layer and/or a series of base contacts prior to application of the
amorphous semiconductor material, for purposes of this application, the
term "substrate" shall include not only a flexible film, but also any
elements added thereto by preliminary processing. The substrate material
11 may be stainless steel, aluminum, tantalum, molybdenum or chrome, as
well as substrates formed of synthetic polymers, glass or glass-like
material on which an electrically conductive electrode is applied.
Each of the cells 12a, 12b and 12c include an amorphous semiconductor body
containing at least a silicon alloy. Each of the semiconductor bodies
include an n-type conductivity region or layer 20a, 20b and 20c; an
intrinsic region or layer 18a, 18b and 18c; and a p-type conductivity
region or layer 16a, 16b and 16c. The term "amorphous" as used herein
includes all materials exhibiting long-range disorder, regardless of their
short or intermediate range order and regardless of whether those
materials are otherwise labeled polycrystalline or crystalline. As
illustrated, cell 12b is an intermediate cell and, as indicated in FIG. 1,
additional intermediate cells may be stacked atop the illustrated cells
without departing from the spirit or scope of the present invention. Also,
although tandem p-i-n cells are illustrated, the gas gates of this
invention are equally adapted for use in any multiple chamber apparatus.
The novel air-to-vacuum gas gate described herein is illustrated as the
invention is incorporated into a deposition for producing p-i-n cells.
However, it should be readily apparent that the novel gas gate of the
current invention is also applicable to any system requiring the isolation
of regions of different gaseous pressure, such as deposition systems for
producing n-i-p cells, chemical vapor deposition systems, or other organic
semiconductors or organic light emitting diode (OLED) materials.
For each of the cells 12a, 12b and 12c, the p-type and n-type layers of
semiconductor material are characteristically light transmissive and
highly conductive. The intrinsic layers of semiconductor material are
characterized by an adjusted wavelength threshold for solar photoresponse,
high light absorption, low dark conductivity and high photoconductivity,
including sufficient amounts of a band gap adjusting element or elements
to optimize the band gap for the particular cell application. Preferably,
the intrinsic layers of semiconductor material are band gap adjusted to
provide cell 12a with the lowest band gap, cell 12c with the highest band
gap and cell 12b with a band gap between the other two, as light enters
the semiconductor material from the top. However, the intrinsic layers of
semiconductor material are band gap adjusted to provide cell 12a with the
highest band gap, cell 12c with the lowest band gap and cell 12b with a
band gap between the other two, if light enters the semiconductor material
from the bottom. The n-type layers of semiconductor material are
characterized by low light absorption and high conductivity. The thickness
of the band gap adjusted layers of intrinsic material may be in the range
of 800 to 5,000 angstroms. The thickness of the n-type and p-type layers
may be in the range of 25 to 400 angstroms.
II. The Multiple Glow Discharge Deposition Chambers
Turning now to FIG. 2, a diagrammatic representation of a multiple glow
discharge chamber deposition apparatus for the continuous production of
the tandem photovoltaic cells, previously described, is generally
illustrated by the reference numeral 100. The multiple glow discharge
chamber deposition apparatus 100 includes transition chambers 200a and
200b, interconnected to the atmosphere by air-to-vacuum gas gates in
accordance with the principles of the present invention. A first
transition chamber 200a takes the web from a pay-off roll 202 in the
atmospheric region having atmospheric pressure and leads the web to the
deposition chambers. A second transition chamber 200b takes the web from
the deposition chambers and leads the web back to atmospheric region and
take-up roll 203. The apparatus 100 includes a plurality of dedicated
deposition chambers, adjacent chambers of which being operatively
interconnected. The term "isolated" as used herein will mean that the
reaction gas mixture introduced into one of the adjacent deposition
chambers is substantially prevented from cross-contaminating the mixtures
introduced into the adjacent chamber. Note that the word "substantially"
was used to modify "prevented"; this is because no isolation mechanism is
100% effective.
The apparatus 100 is adapted to deposit a high volume of large area,
amorphous photovoltaic cells having a p-i-n configuration onto the surface
of a substrate 11, which is continually fed therethrough. To deposit the
layers of amorphous semiconductor material required for producing a tandem
cell of the p-i-n configuration, the apparatus 100 includes at least one
triad of deposition chambers, each triad comprising: a first deposition
chamber 28 in which a p-type conductivity layer of amorphous silicon alloy
material is deposited onto the surface of the substrate 11 as the
substrate 11 passes therethrough; a second deposition chamber 30 in which
an intrinsic layer of amorphous silicon alloy material is deposited atop
the p-type layer on the surface of the substrate 11 as the substrate 11
passes therethrough; and a third deposition chamber 32 in which an n-type
conductivity layer of silicon alloy material is deposited atop the
intrinsic layer on the surface of the substrate 11 as the substrate 11
passes therethrough.
It should be apparent that: (1) although one triad of deposition chambers
has been described, additional triads or additional individual chambers
may be added to the apparatus to provide the apparatus with the capability
of producing photovoltaic cells having any number of layers; (2) the
air-to-vacuum gas gate of the present invention is applicable in any
environment in which a substrate must be taken from atmospheric pressure
to a vacuumized region or taken from a vacuumized region to atmospheric
pressure; (3) although the substrate material is shown and described as a
continuous web of material, the concept of the present invention may be
adapted for depositing successive layers atop discrete substrate plates
which can be continuously fed through the plurality of deposition
chambers; (4) although not shown, other chambers (such as a chamber for
adding a TCO layerer atop the uppermost dopant layer of the photovoltaic
device) may be operatively connected to the glow discharge apparatus 100;
and (5) the substrate pay-off roll 202 and the substrate take-up roll 203
are not shown in separate chambers. However, the respective rolls may be
in any area of atmospheric pressure, such as a vacuumized chamber, or any
area with a pressure highe
