U.S. patent number 3,921,572 [Application Number 05/445,199] was granted by the patent office on 1975-11-25 for vacuum coating apparatus.
This patent grant is currently assigned to International Business Machines Corporation. Invention is credited to Rolf H. Brunner, Quiedo J. Carbone, William C. Lester.
United States Patent |
3,921,572 |
Brunner , et al. |
November 25, 1975 |
Vacuum coating apparatus
Abstract
Vacuum coating apparatus having isolatable coating and vacuum
chambers whose volumes are correlated to each other to minimize
contamination and pump-down time, with the coating chamber having a
closure means mounting a substrate holder for positioning
substrates in an evaporant stream from a vapor source contained in
the vacuum chamber.
Inventors: |
Brunner; Rolf H. (Poughkeepsie,
NY), Carbone; Quiedo J. (Newburgh, NY), Lester; William
C. (Hopewell Junction, NY) |
Assignee: |
International Business Machines
Corporation (Armonk, NY)
|
Family
ID: |
23767966 |
Appl.
No.: |
05/445,199 |
Filed: |
February 25, 1974 |
Current U.S.
Class: |
118/730 |
Current CPC
Class: |
C23C
14/56 (20130101) |
Current International
Class: |
C23C
14/56 (20060101); C23C 013/08 () |
Field of
Search: |
;118/48-49.5
;117/106-107.2,201 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Kaplan; Morris
Attorney, Agent or Firm: Powers; Henry
Claims
What is claimed is:
1. A vacuum coating apparatus comprising:
A. an evaporation chamber;
B. a coating chamber in communication with said evaporation
chamber;
C. gate means reciprocally movable between an open and closed
position intermediate said coating and evaporation chambers for
selectively isolating each from the other;
D. a vapor source means in said evaporation chamber for generating
an evaporant stream of coating material into said coating
chamber;
E. a port in a wall of said coating chamber for access thereto and
wherein the ratio of the area of said port to the volume of said
coating chamber is in the range from about 1:20 to about 1:30;
F. door means pivotally mounted on said wall for movement into open
and closed positions relative to said port with said closed
position securing said door means in sealing relation with said
coating chamber;
G. substrate holder means mounted on an inner surface of said door
means for supporting substrates in a coating position within said
evaporant stream in said coating chamber;
H. means for rotating said substrates on said holder means;
I. means for maintaining said evaporation chamber under a
continuous vacuum;
J. a second vacuum means for roughing a vacuum in said coating
chamber when isolated from said evaporation chamber by said gate
means;
K. means for isolating said second vacuum means from said coating
chamber when said gate means is to be moved to the open
position;
L. gas means for controllably introducing an inert gas flow in said
coating chamber when isolated from said evaporation chamber, when
said gate means is in the closed position, to minimize ingress of
ambients into said coating chamber when said door means is in the
open position; and
M. valve means for shutting off the flow of said inert gas to said
coating chamber; wherein the ratio of the volumes of said
evaporation chamber to said coating chamber is in the range from
about 10:1 to about 30:1.
2. A vacuum coating apparatus comprising:
A. an evaporation chamber;
B. a coating chamber in communciation with said evaporation
chamber;
C. gate means reciprocally movable between an open and closed
position intermediate said coating and evaporation chambers for
selectively isolating each from the other;
D. a vapor source means in said evaporation chamber for generating
an evaporant stream of coating material into said coating
chamber;
E. a port in a wall of said coating chamber for access thereto and
wherein the ratio of the area of said port to the volume of said
coating chamber is in the range from about 1:20 to about 1:30;
F. door means pivotally mounted on said wall for movement into open
and closed positions relative to said port with said closed
position securing said door means in sealing relation with said
coating chamber;
G. substrate holder means mounted on an inner surface of said door
means for supporting substrates in a coating position within said
evaporant stream in said coating chamber;
H. means for rotating said substrates on said holder means;
I. means for maintaining said evaporation chamber under a
continuous vacuum; wherein said holder means supports said
substrates within and at an angle to said evaporant stream;
J. a second vacuum means for roughing a vacuum in said coating
chamber when isolated from said evaporation chamber by said gate
means;
K. means for isolating said second vacuum means from said coating
chamber when said gate means is to be moved to the open
position;
L. gas means for controllably introducing an inert gas flow in said
coating chamber when isolated from said evaporation chamber, when
said gate means is in the closed position, to minimize ingress of
ambients into said coating chamber when said door means is in the
open position; and
M. valve means for shutting off the flow of said inert gas to said
coating chamber; wherein the ratio of the volumes of said
evaporation chamber to said coating chamber is in the range from
about 10:1 to about 30:1.
3. A vacuum coating apparatus comprising:
A. an evaporation chamber;
B. a coating chamber in communication with said evaporation
chamber;
C. gate means reciprocally movable between an open and closed
position intermediate said coating and evaporation chambers for
selectively isolating each from the other;
D. a vapor source means in said evaporation chamber for generating
an evaporant stream of coating material into said coating
chamber;
E. a port in a wall of said coating chamber for access thereto and
wherein the ratio of the area of said port to the volume of said
coating chamber is in the range from about 1:20 to about 1:30;
F. door means pivotally mounted on said wall for movement into open
and closed positions relative to said port with said closed
position securing said door means in sealing relation with said
coating chamber;
G. substrate holder means mounted on an inner surface of said door
means for supporting substrates in a coating position within said
evaporant stream in said coating chamber;
H. means for rotating said substrates on said holder means;
I. means for maintaining said evaporation chamber under a
continuous vacuum; wherein said holder means supports said
substrates within and at an angle to said evaporant stream; wherein
said holder means supports said substrates within and at an angle
to said evaporant stream;
J. heater means in said coating chamber within said evaporant
stream for heating said subtrates to deposition means;
K. an evaporant shield for said heater means in said coating
chamber;
L. a second vacuum means for roughing a vacuum in said coating
chamber when isolated from said vacuum chamber by said gate
means;
M. means for isolating said second vacuum means from said coating
chamber when said gate means is to be moved to the open
position;
N. gas means for controllably introducing an inert gas flow in said
coating chamber when isolated from said evaporation chamber, when
said gate means is in the closed position, to minimize ingress of
ambients into said coating chamber when said door means is in the
open position; and
O. valve means for shutting off the flow of said inert gas to said
coating chamber; wherein the ratio of the volumes of said
evaporation chamber to said coating chamber is in the range from
about 10:1 to about 30:1.
4. A vacuum coating apparatus comprising:
A. an evaporation chamber;
B. a coating chamber in communication with said evaporation
chamber;
C. gate means reciprocally movable between an open and closed
position intermediate said coating and evaporation chambers for
selectively isolating each from the other;
D. a vapor source means in said evaporation chamber for generating
an evaporant stream of coating material into said coating
chamber;
E. a port in a wall of said coating chamber for access thereto and
wherein the ratio of the area of said port to the volume of said
coating chamber is in the range from about 1:20 to about 1:30;
F. door means pivotally mounted on said wall for movement into open
and closed positions relative to said port with said closed
position securing said door means in sealing relation with said
coating chamber;
G. substrate holder means mounted on an inner surface of said door
means for supporting substrates in a coating position within said
evaporant stream in said coating chamber;
H. means for rotating said substrates on said holder means;
I. mans for maintaining said evaporation chamber under a continuous
vacuum;
J. a valve means in said evaporation chamber reciprocally movable
between an open and closed position relative to the first said
vacuum means for selectively placing said evaporation chamber and
the first said vacuum means in communicating and isolating
relationship with each other;
K. a second vacuum means for roughing a vacuum in said coating
chamber when isolated from said evaporation chamber by said gate
means;
L. means for isolating said second vacuum means from sad coating
chamber when said gate means is to be moved to the open
position;
M. gas means for controllably introducing an inert gas flow in said
coating chamber when isolated from said evaporation chamber, when
said gate means is in the closed position, to minimize ingress of
ambients into said coating chamber when said door means is in the
open position; and
N. valve means for shutting off the flow of said inert gas to said
coating chamber; wherein the ratio of the volumes of said
evaporation chamber to said coating chamber is in the range from
about 10:1 to about 30:1.
5. A vacuum coating apparatus comprising:
A. an evaporation chamber;
B. a coating chamber in communication with said evaporation
chamber;
C. gate means reciprocally movable between an open and closed
position intermediate said coating and evaporation chambers for
selectively isolating each from the other;
D. a vapor source means in said evaporation chamber for generating
and evaporant stream of coating material into said coating
chamber:
E. a port in a wall of said coating chamber for access thereto and
wherein the ratio of the area of said port to the volume of said
coating chamber is in the range from about 1:20 to about 1:30;
F. door means pivotally mounted on said wall for movement into open
and closed positions relative to said port with said closed
position securing said door means in sealing relation with said
coating chamber;
G. substrate holder means mounted on an inner surface of said door
means for supporting substrates in a coating position within said
evaporant stream in said coating chamber;
H. means for rotating said substrates on said holder means;
I. means for maintaining said evaporation chamber under a
continuous vacuum; wherein said holder means supports said
substrates within and at an angle to said evaporant stream;
J. a valve means in said evaporation chamber reciprocally movable
between an open and closed position relative to the first said
vacuum means for selectively placing said evaporator section and
the first said vacuum means in communicating and isolating
relationship with each other;
K. a second vacuum means for roughing a vacuum in said coating
chamber when isolated from said evaporation chamber by said gate
means;
L. means for isolating said second vacuum means from said coating
chamber when said gate means is to be moved to the open
position;
M. gas means for controllably introducing an inert gas flow in said
coating chamber when isolated from said evaporation chamber, when
said gate means is in the closed position, to minimize ingress of
ambients into said coating chamber when said door means is in the
open position; and
N. valve means for shutting off the flow of said inert gas to said
coating chamber; wherein the ratio of the volumes of said
evaporation chamber to said coating chamber is in the range from
about 10:1 to about 30:1.
6. A vacuum coating apparatus comprising:
A an evaporation chamber;
B. a coating chamber in communication with said evaporation
chamber;
C. gate means reciprocally movable between an open and closed
position intermediate said coating and evaporation chambers for
selectively isolating each from the other;
D. a vapor source means in said evaporation chamber for generating
an evaporant stream of coating material into said coating
chamber;
E. a port in a wall of said coating chamber for access thereto and
wherein the ratio of the area of said port to the volume of said
coating chamber is in the range from about 1:20 to about 1:30;
F. door means pivotally mounted on said wall for movement into open
and closed positions relative to said port with said closed
position securing said door means in sealing relation with said
coating chamber;
G. substrate holder means mounted on an inner surface of said door
means for supporting substrates in a coating position within said
evaporant stream in said coating chamber;
H. means for rotating said substrates on said holder means;
I. means for maintaining said evaporation chamber under a
continuous vacuum;
wherein said holder means supports said substrates within and at an
angle to said evaporant stream;
J. heater means in said coating chamber within said evaporant
stream for heating said substrates to deposition means;
K. an evaporant shield for said heater means in said coating
chamber;
L. a valve means in said vacuum chamber reciprocally movable
between an open and closed position between said evaporation
chamber and the first said vacuum means for selectively isolating
each from the other;
M. a second vacuum means for roughing a vacuum in said coating
chamber when isolated from said evaporation chamber by said gate
means;
N. means for isolating said second vacuum means from said coating
chamber when said gate means is to be moved to the open
position;
O. gas means for controllably introducing an inert gas flow in said
coating chamber when isolated from said evaporation chamber, when
said gate means is in the closed position, to minimize ingress of
ambients into said coating chamber when said door means is in the
open position; and
P. valve means for shutting off the flow of said inert gas to said
coating chamber;
wherein the ratio of the volumes of said evaporation chamber to
said coating chamber is in the range from about 10:1 to about 30:1.
Description
FIELD OF THE INVENTION
This invention relates to coating apparatus, and more particularly,
to an improved apparatus for coating substrates with an evaporant
stream from a suitable source material in a vacuum system.
BACKGROUND OF THE INVENTION
Vacuum coating of substrates from a suitable source material is
extensively used for various applications. Typically, such
applications involve, among others, the deposition of non-metallic
coatings on optical lenses, coatings on paper, and in particular,
the coating of electrically conductive metal and dielectric films
on semiconductor substrates for enabling subsequent delineation of
conductor patterns in the fabrication of semiconductor devices.
Typical of such apparatuses to which this invention is directed are
those described in U.S. Pat. No. 3,524,426 and 3,641,973. Such
systems comprise a main vacuum or evaporation chamber containing a
source of coating material to be evaporated in a stream to a
substrate supported in a coating chamber which is controllably
placed in communication and isolation with respect to the
evaporation chamber. A vacuum gate valve is included intermediate
the chambers to either, in the open position, place them in
communication with each other or, in the closed position, to
isolate each from the other. In any event, a vacuum source, such as
a diffusion pump, is normally connected to the evaporation chamber
to maintain a continuous vacuum therein.
For loading of the system, the gate valve is moved in the closed
position to isolate the evaporation and coating chambers, the
latter of which is provided with means of access for insertion of
substrate holders in an evaporant stream. On insertion of the
substrate holders and resealing and rough evacuation of the coating
chamber, the gate valve is moved to the open position to place the
chambers in communication with each other. On development of a
common vacuum atmosphere in the chambers, an evaporant stream, of a
source material from an E-beam source, is directed from evaporation
chamber into the coating chamber and onto the substrates, generally
by removal of a shutter placed in the evaporant stream.
SUMMARY OF THE INVENTION
It has been found that the foregoing vacuum systems can be improved
to minimize pump-down time and ambient contamination and conversely
increase through-put of substrate coatings. Briefly, this can be
effected by correlating the volumes of the coating and evaporating
chambers to each other wherein the former comprises a substantially
smaller volume of the latter, generally in the range of about 3
percent to 10 percent. In view of the reduced size of the coating
chamber relative to the evaporation chamber, pump-down time of the
apparatus is substantially reduced. In addition, the resulting
pressure rise of the evaporation chamber is reduced to minimize
defocusing of the E-beam and backstreaming of diffusion pump.
In addition, the coating chamber is also provided with an access
port whose cross-sectional opening is also substantially reduced to
minimize ingress of ambients during loading of substrates.
Generally, the ratio of area of the port to the volume of the
coating chamber will be in the range of about 1:20 to about
1:30.
Also, to minimize ambient contamination, the coating chamber is
provided with means to introduce an inert gas flow (eg. nitrogen,
argon, and the like) to flow through the chamber and out of the
port during removal and loading of substrates.
Also, to minimize pump-down time of the coating apparatus, the
coating chamber is connected through valving to a roughing pump to
generate a vacuum therein prior to placing it in communication with
the evaporation chamber.
Another feature of the invention includes a door or closure member
for the access port and having mounted thereon a holder for
substrates which are positioned within the evaporant stream in the
coating chamber. This feature provides the capability for automatic
loading/unloading of the substrates.
A further feature of the invention includes an additional gating
means (such as a poppet valve) in the evaporation chamber for
sealing with an access port to the vacuum pump to obtain isolation
therebetween, and access to the chamber without need to shut down
the vacuum pump.
Other features, objects and advantages will become more apparent
from the following more detailed description of the invention in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic drawing in cross-section, of one embodiment
of a vacuum coating apparatus in accordance with this
invention.
FIG. 2 is a diagrammatic view of a substrate holder for use in the
embodiment of FIG. 1.
FIG. 3 is a partial schematic drawing, in cross-section, of a
coating chamber in accordance with another embodiment of this
invention.
DESCRIPTION OF PREFERRED EMBODIMENTS
Although the vacuum coating apparatus of this invention has a wide
variety of applications, they will be described below in
conjunction with the coating of electrically conductive metal films
on semiconductor substrates for subsequent photolithographic
delineation of conductor patterns in device fabrication.
Referring to the drawings, the vacuum coating apparatus comprises a
coating chamber 1 and an evaporation chamber 2 operatively in
communication with each other under a common vacuum environment
generated by a vacuum pump 3 (eg. a diffusion pump) through a
vacuum access duct 4 in the lower wall of the chamber enclosure
5.
Included between coating chamber 1 and evaporation chamber 2 is a
valve housing 6 for a conventional vacuum gate valve 7 which is
movable in the housing 6 by means of a pneumatic or hydraulic
cylinder 8 mounted at one end of housing 6 and having a
reciprocable extending rod 9 attached to valve plate 7. The gate
valve is shown in the closed position in FIG. 1 to isolate or seal
the coating and evaporation chambers 1 and 2, respectively, from
each other to allow access to the coating chamber 1 while
maintaining a continuous vacuum in the evaporation chamber 2. The
mounting of this valve is such that its sealing surface faces
upward, thereby inherently shielding said surface from evaporant
deposits.
Activation of cylinder 8 to retract rod 9, will move the valve
plate 7 to the open position to place coating chamber 1 and
evaporation chamber 2 in communication with each other for
development of a common vacuum environment.
The evaporation chamber 2 includes a conventional vapor or ion
source 10 of the type shown in U.S. letters Pat. No. 3,710,072
which may be referred to for details of construction. Source 10
will normally comprise a water cooled crucible 11 having coolant
passages 12 through which a coolant may be circulated by suitable
means, not shown. Crucible 11 contains a molten pool 14 of
evaporant material from which vapor of the coating is produced, as
for example aluminum or copper aluminum alloy for coating of an
electrically conductive film of semiconductor substrates 13 (see
FIG. 2) in device fabrication. The molten pool 14 is heated by an
electron beam 15, deflected in an arcuate path by suitable magnetic
field, from an electron beam gun 16.
Mounted in evaporation chamber 2, about vacuum source 10, is an
enclosing evaporant shield 17 having an opening 18 in top wall 19
thereof, for shaping the evaporant stream 20 of the coating
material from source 10.
In order to prevent the coating of valve plate 7 in the closed
position, a shutter 21 is provided between the source material 10,
at the shaping port 18, and the coating chamber 1. The shutter 21
is mounted on a pivot shaft 22 extending through shield 17, the
bottom wall 23 (of evaporation chamber 2) and in a vacuum tight
bushing 24 secured thereto.
Also included in evaporation chamber 2 is a poppet valve 25 having
a sealing plate 26 disposed opposite vacuum access duct 4, for
sealing engagement therewith when ram 27 is extended by actuation
of a pneumatic or hydraulic cylinder 28.
Coating chamber 1 includes an access port 29 which serves to load
and unload substrates 13 into and out of the chamber. A second
access flange is provided opposite the access port for maintenance
purposes. The access port 29 is adapted to be opened and closed by
a door or cover member 30 pivotally mounted to a bracket 31 and
having an annular groove 32 for mounting of an O-ring 33 or other
suitable sealing means.
Mounted on the exterior of closure member 30 is a bracket 34 to
which is secured a motor 35 having a drive shaft 36 extending
through closure member 30 into the coating chamber 1. Secured to
the free end of drive shaft 36 is a substrate holder 37 for
supporting substrates in a coating position with respect to the
evaporant stream in coating chamber 1. Motor 35 is used to rotate
the holder 37 and secure substrates 13 in the evaporant stream in
order to provide an more uniform coating on the substrates.
Holder 37 comprises a support base 38 having a plurality of finger
grips 39 having pivoted clamping lips 40 positioned over the
support face of base 38 by means of compression springs 41 which
are secured between annular seats 42, secured to the back side of
support base 38, and like registered annular seats 43 secured to
lateral extensions 44, of grips 39, pivotally mounted to brackets
45, also secured to the back side of support base 38. As will be
noted, the lips 40 are formed with an angular configuration 46 to
facilitate camming of grips 39 open if a tool is desired to be
employed for positioning substrate 13 on holder 37.
Also provided in communication relationship with coating chamber 1
is a roughing line 50 extending through valve 51 to a vacuum
roughing pump (not shown) in order to evacuate coating chamber 1
down to a safe level for opening valve plate 7 to place the chamber
into communication with evaporation chamber 2 without drastic
equilization therebetween.
Also provided in communicating relationship with coating chamber 1
is an inert gas line 52 extending through valve 53 to an inert gas
source, not shown, of nitrogen, argon and the like, for purposes of
establishing a flowing atmosphere of the inert gas through the
chamber 1 and out of the access port 29 when the closure member 30
is in the open position. The flow of inert gas out of access port
29 will minimize ingress of ambients into the chamber and thus
conversely minimize contamination thereof.
Mechanical movement of the closure member or lid 30 can be effected
by pivotally connecting mounting bracket 34 to a clevis member 60
on the end of a piston rod 61 of a pneumatic or hydraulic cylinder
62 suitably mounted (not shown) in any convenient manner to the
vacuum coating apparatus.
As indicated previously, in order to minimize pump-down time, the
volume of coating chamber 1 is substantially smaller than the
volume of the evaporating chamber. Generally, the practical ratios
of the volume of the coating chamber 1 to the volume of the
evaporating chamber 2 will be in the range of from about 1:10 to
about 1:30. In one unit fabricated in accordance with this
invention, the volume of coating chamber 1 was 5 liters while the
volume of the evaporation chamber 2 was 150 liters.
Also as indicated previously, to minimize ingress of contaminating
ambients when closure member 30 is open, the cross-sectional area
of acess port 29 is also correlated to the volume of coating
chamber 1. Generally, the practical ratios of the cross-sectional
area of access port 29 to the volume of coating chamber 1 will be
in the range of from about 1:20 to about 1:30. Such a restricted
access port 29 also serves to throttle the flow of inert gas out of
coating chamber 1 and retain temperature control of internal
tooling surfaces. In the above indicated fabricated unit having a
coating chamber 1 volume of about 5 liters (310 in.sup.3), the
access port 29 had a cross-sectional area of about .apprxeq.10
in.sup.2.
FIG. 3 shows a variation of the coating chamber 1 of the apparatus
of this invention. In this embodiment an access port 29A to the
coating chamber 1A is provided in an enclosure wall 71 formed on an
angle to the evaporant stream form the source 10 in evaporation
chamber 2. Pivotally mounted to a bracket 72 on the enclosure wall
is the closure member or lid 30A provided on its outer surface with
a motor 35A with a drive shaft 36 extending through a vacuum seal
into the coating chamber 1A, and having secured to its free end a
rotatable substrate holder 37 to support a substrate at an angle
within the evaporant stream in the coating chamber 1A. Also
contained in coating chamber 1A are heating elements 70 for heating
substrates to deposition temperatures. The heater elements are
protected from the evaporant stream by a shield 75.
In operation, for loading of substrates, the valve plate 7 (FIG. 1)
is moved to the closed position to isolate coating chamber 1 from
evaporation chamber 2 in which a vacuum (eg. of about 3 to 9
.times. 10.sup.-.sup.7 TORR) is continued to be maintained by
virtue of its communication through vacuum port 4 to the vacuum
pump 3. Prior to opening of closure member 30, valve 53 is opened
in inert gas line 52 to connect coating chamber 1 to an inert gas
source, whereupon closure member 30 is opened. At this point, any
substrate on holder 37 may be removed and a new substrate 13 (e.g.
a semiconductor wafer) mounted thereon followed by closure of lid
30. The inert gas flow is stopped by closure of valve 53, and the
coating chamber connected to a roughing pump by opening of valve 51
is roughing line 50. When the coating chamber 1 is evacuated to a
suitable level (eg. about 50 microns), the roughing line valve 51
is closed, followed by moving valve plate 7 to the open position.
After statilization of the unit, the shutter 21 will be rotated out
of in front of the shaping port 18, to permit the evaporant stream
from vacuum source 10 in the evaporation chamber 2, to flow into
the coating chamber 1 onto the substrate 13 mounted on holder 37.
Substrate rotation, heating, and source rise and soak can be
started after communication is established between the coating and
evaporation chambers. For photolithographic delineation of
conductor patterns on semiconductor devices, the vacuum source can
comprise a molten pool of 70 aluminum/30 copper alloy to coat the
electrically conductive metal film on the wafer (eg.
substrate).
For servicing of the evaporation chamber 2, without shutting down
vacuum pump 3, the poppet valve 28 is extended into a closed
position with vacuum port 4, and both coating and evaporation
chambers vented to the atmosphere when suitable servicing access
can be obtained to both chambers.
It is to be understood that while the invention has been
particularly shown and described with reference to the preferred
embodiments thereof, it will be understood by those skilled in the
art that the foregoing and other changes in form and detail may be
made therein without departing from the spirit and scope of the
invention.
* * * * *