U.S. patent number 3,664,948 [Application Number 04/878,062] was granted by the patent office on 1972-05-23 for sputtering system.
This patent grant is currently assigned to Texas Instruments Incorporated. Invention is credited to Joseph Victor Graffeo, Jr., Bertran W. Mason, Jr., Wells, Wallace Ogden.
United States Patent |
3,664,948 |
Graffeo, Jr. , et
al. |
May 23, 1972 |
SPUTTERING SYSTEM
Abstract
A sputtering system includes a pair of spaced electrodes, one
formed from titanium and the other formed from platinum. Substrates
are rotated over both electrodes by a turntable that is actuated by
a reversible drive mechanism. A mask alternately blocks each
electrode. The mask is coupled to the turntable drive mechanism by
a slip clutch and is moved between the two blocking positions when
the direction of rotation of the turntable is reversed. In the use
of the system, the electrodes are actuated in sequence. The mask is
positioned to block each electrode during the initial portion of
its operation. This deposits the material of the electrodes on the
mask until the electrodes are clean.
Inventors: |
Graffeo, Jr.; Joseph Victor
(Dallas, TX), Mason, Jr.; Bertran W. (Sherman, TX),
Wells, Wallace Ogden (Garland, TX) |
Assignee: |
Texas Instruments Incorporated
(Dallas, TX)
|
Family
ID: |
25371297 |
Appl.
No.: |
04/878,062 |
Filed: |
November 19, 1969 |
Current U.S.
Class: |
204/298.11;
204/298.26 |
Current CPC
Class: |
C23C
14/35 (20130101) |
Current International
Class: |
C23C
14/35 (20060101); C23c 015/00 () |
Field of
Search: |
;204/298,192 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Tung; T.
Assistant Examiner: Kanter; Sidney S.
Claims
What is claimed is:
1. A deposition system including:
a deposition chamber including at least two sputtering electrodes
positioned at spaced points in the chamber;
means for transporting workpieces through the chamber;
means extending into the chamber for driving the transporting
means;
wherein the workpiece transporting means includes a turntable and
wherein the driving means alternately rotates the turntable in
opposite directions;
a mask mounted in the chamber;
means coupling the mask to the driving means for moving the mask
through the chamber;
means for limiting the movement of the mask in the chamber, and
wherein the coupling means includes a slip clutch that couples the
mask to the driving means for movement in opposite directions with
the turntable and wherein the movement limiting means includes a
pair of stops each for limiting the movement of the mask in a
different direction and wherein the mask moving means and the
movement limiting means cooperate to alternately position the mask
in a blocking relationship with first one and then the other of the
electrodes.
2. The deposition system according to claim 1 further including
means for receiving material sputtered from the first electrode
while the mask is positioned in alignment therewith and for
producing an output indicative of the cleanliness of the first
electrode.
3. The deposition system according to claim 1 wherein the workpiece
moving means alternately moves workpieces through the chamber in
two directions and wherein the mask moving means is coupled to the
workpieces moving means and moves the mask to one of its positions
whenever the workpieces moving means moves workpieces in one
direction and moves the mask to the other of its positions whenever
the workpiece moving means moves workpieces in the other
direction.
4. The deposition system according to claim 1 further including
means for operating the electrodes in sequence and for coordinating
the operation of the mask moving means with the operation of the
electrodes so that the mask blocks each electrode during the
initial portion of the operation thereof.
5. The deposition system according to claim 1 wherein the mask
moving means includes a pair of stops each corresponding to one of
the positions of the mask and means for alternately moving the mask
between the stops.
6. The deposition system according to claim 1 wherein the workpiece
moving means includes a workpiece supporting turntable and a
mechanism for rotating the turntable through the chamber and
wherein the mask positioning means includes a mechanism for
rotating the mask through the chamber and a clutch for coupling the
mask rotating mechanism to the turntable rotating mechanism.
7. The deposition system according to claim 1 further including
means for operating a first of the electrodes for a first period of
time and for subsequently operating the second electrode for a
second period of time and including a mask positioning means which
positions the mask between the first electrode and the path during
the initial portion of the first period, then positions the mask
between the second electrode and the path during the terminal
portion of the first period and during the initial portion of the
second period, then positions the mask between the first electrode
and the path during the terminal portion of the second period.
8. The deposition system according to claim 1 further including
means for causing each electrode to sputter first onto the mask and
then onto workpieces carried by the transporting means.
9. The deposition system according to claim 1 wherein the
deposition chamber comprises housing means formed from a material
having high thermal and electrical conductivity.
Description
BACKGROUND OF THE INVENTION
In the manufacture of various electronic components it is necessary
to deposit thin metal films on substrates formed from silicon and
other materials. One method of forming thin films is known as
vacuum sputtering. Typically, vacuum sputtering systems include a
vacuum chamber that houses a sputtering electrode and a substrate
supporting target. The electrode is energized to direct the
material of the electrode toward the target and onto substrates
supported on the target.
To date, most vacuum sputtering systems have been comprised of
laboratory type equipment. Such systems are incapable of large
volume production and are, therefore, unsuitable for most
commercial applications. Conversely, the few high volume vacuum
sputtering systems that have been designed heretofore have been so
expensive as to prevent their widespread commercial use.
This invention relates to a high volume vacuum sputtering system
that is relatively inexpensive to manufacture and operate. The
system includes a large turntable that transports substrates over
electrodes formed from different materials. This permits the
deposition of two thin films in one operation. The chamber of the
system is relatively small in volume so that the cycle time of the
system is minimized and has a small number of mechanical and
electrical inputs to prevent leaks. Fully automatic control is
provided to reduce human errors and yet permit adjustments in the
operation of the system.
SUMMARY OF THE INVENTION
In accordance with the preferred embodiment, this invention
comprises a vacuum sputtering system that includes a pair of
electrodes and a mask that is alternately moved into alignment with
each electrode. Preferably, workpieces are transported along a path
that extends over both electrodes by a drive system that also moves
the mask.
DESCRIPTION OF THE DRAWINGS
A more complete understanding of the invention may be had by
referring to the following detailed description when taken in
conjunction with the drawings wherein:
FIG. 1 is a top view of a sputtering system employing the invention
in which certain parts have been broken away more clearly to
illustrate certain features of the invention;
FIG. 2 is a sectional view taken generally along the line 2--2 in
FIG. 1;
FIG. 3 is an enlargement of a portion of FIG. 2;
FIG. 4 is an enlargement of another portion of FIG. 2;
FIG. 5 is a partial sectional view taken generally along the line
5--5 in FIG. 3, and
FIG. 6 is a schematic illustration of a control circuit employed in
the operation of the system shown in FIGS. 1 and 2.
DETAILED DESCRIPTION
Referring now to the drawings, there is shown a sputtering system
10 employing the invention. Referring particularly to FIG. 2, the
system 10 is mounted on a cylinder 12 having a flange 14 extending
from it. The cylinder 12 and the flange 14 preferably comprise
portions of a commercially available vacuum pump. It should be
understood that the cylinder and the flange are representative only
and that the system 10 can be adapted for use with any of the many
commonly employed vacuum pumping systems.
The system 10 includes a main housing 16 that rests upon the flange
14 and a cover 18 that rests upon the housing 16. The housing and
the cover are both formed from a material having high thermal and
electrical conductivity, such as aluminum. A pair of O-rings 20 and
22 are positioned between the housing 16 and the flange 14 and
between the cover 18 and the housing 16, respectively, to effect
seals therebetween. A pair of cooling coils 24 and 26 are mounted
in the housing 16 and the cover 18, respectively, for use in
controlling the temperature of the system 10.
As is best shown in FIG. 1, the housing 16 includes a central hub
portion 28 and a large outer portion 30. A plurality of holes 32
and 34 are formed through the housing 16 between the hub portion 28
and the outer portion 30 to permit a vacuum to be more easily
established within the housing 16. The outer portion 30 of the
housing 16 is divided into two half-moon shaped sections 36 and 38
by a pair of radially extending partitions 40, a circular inner
wall 42 and the outer wall of the housing. As is best shown in FIG.
2, a trough 43 extends along the outer edge of each of the sections
36 and 38.
The sections 36 and 38 of the housing 16 each enclose a half-moon
shaped sputtering electrode 44. In the preferred embodiment, the
section 36 houses an electrode 44T formed from titanium while the
section 38 houses an electrode 44P formed from platinum. It should
be understood, however, that the electrodes 44 may be formed from
other materials and that the system 10 may be used in conjunction
with deposition systems other than sputtering systems, if
desired.
Referring now to FIGS. 2 and 4, electrical energy is supplied to
each electrode 44 by an electrical feed through assembly 46. Each
assembly 46 includes a conventional high voltage connector 48 that
is coupled to the cylinder 12 and that is sealed to prevent leaks
between the interior of the system 10 and the outside atmosphere.
The connector 48 includes an insulator 49 that extends into a glass
elbow 50. The elbow 50 in turn leads to a ceramic insulator 52. The
insulator 52 is secured to the elbow 50 by a spring clip 54 and is
secured to the housing 16 by a pair of fasteners 56.
A copper lead 58 extends through the elbow 50 to a titanium
conductor 60 positioned within the insulator 52. The electrode 44
is secured to the conductor 60 by a fastener 62 formed from the
same material as the electrode. Each electrode 44 is supported
within the housing 16 by its respective ceramic insulator 52 and by
a plurality of spacers 66 mounted at spaced points in the housing.
The spacers 66 are formed from aluminum oxide and serve to conduct
heat from the electrodes 44 to the housing 16.
As is best shown in FIGS. 2 and 3, a vertically extending shaft 70
is rotably supported in the central hub portion 28 of the housing
16. The upper end of the shaft 70 comprises a frustro-concical
drive member 72. A substrate transporting turntable 74 is supported
on and driven by the drive member 72. The turntable 74 includes a
hub 76 and a substrate supporting plate 78 which extends radially
outwardly from the hub 76. The plate 78 is formed from a material
having a low coefficient of thermal expansion, such as
molybdenum.
The hub 76 of the turntable 74 has a frustro-concical cavity 80
formed in it. The walls of the cavity 80 are adapted for driving
engagement with the drive member 72 of the shaft 70. The substrate
supporting plate 78 of the turntable 74 has a plurality of
substrate receiving holes 82 formed in it. As is best shown in FIG.
1, each substrate receiving hole 82 has a substrate retaining lip
84 formed along its lower edge. In a typical use of the turntable
74, a substrate is mounted in each hole 82 in engagement with the
lip 84 thereof and a ballast or heat sink member 86 of the type
shown in FIG. 2 is mounted in the hole 82 on the top of the
substrate.
The shaft 70 is supported in the hub portion 28 by a pair of
bearings 90 and 92. From the drive member 72, the shaft 70 extends
through the bearings 90 and 92 to a bevel gear 94. The gear 94 is
mounted in mesh with a bevel gear 96 that is secured to a shaft 98.
The shaft 98 is rotably supported in a pair of bearings 100 and 102
that are in turn secured to a vertically extending tubular member
104. The member 104 is secured in the hub portion 28 of the housing
16 by a plurality of fasteners 106.
The shaft 98 is connected to a conventional coupler 108 that is in
turn connected to a commercially available rotary feed through 110.
The feed through 110 is of the greaseless variety and operates to
seal the interior of the system 10 against contamination from the
outside atmosphere. The rotary feed through 110 is driven by a
conventional gear motor 112 through a belt 114. The gear motor 112
is reversible so that the shaft 70 and the turntable 74 may be
rotated in either direction, as desired.
In addition to driving the turntable 74, the shaft 70 drives a slip
clutch 118. The clutch 118 includes a collar 120 that is formed
from one of the various low friction plastic materials and that is
secured to the shaft 70 at a point just above the point of
attachment of the gear 94. A two pitch helical spring 122 is
positioned around the collar 120 and within an annularly shaped
member 124 that is also formed from a low friction plastic
material. The spring 122 forms a two directional slip clutch
between the members 120 and 124. That is, because of its double
helical construction, the spring 122 slips relative to the collar
120 when a torque in excess of a predetermined level is developed
between the members 120 and 124 in one direction and slips relative
to the annularly shaped member 124 when an excess torque is
developed in the reverse direction.
The annularly shaped member 124 is connected to a drive sleeve 126
that is rotatably supported in the member 104 by a pair of bearings
128 and 130. The drive sleeve 126 is in turn connected to a mask
132 comprised of a hub 134 and a semicircularly shaped shutter 136
that extends radially outwardly from the hub 134. As is best shown
in FIG. 5, the drive sleeve 126 has a slot 138 formed in it which
extends to a pair of spring clips 140 and 142. The clips 140 and
142 are mounted for engagement with a pair of pins 144 and 146,
respectively. The pins 144 and 146 are supported in a member 104 by
a pair of insulators 148.
Whenever the motor 112 is operated to rotate the turntable 74 in a
counterclockwise direction, the mask 132 is driven through the slip
clutch 118 in a counterclockwise direction until the clip 142 on
the sleeve 126 engages the pin 146. Thereafter, the slip clutch 118
permits the turntable 74 to continue to rotate in the
counterclockwise direction while the mask remains in its most
counterclockwise position. Similarly, whenever the motor 112 is
actuated to rotate the turntable 74 in a clockwise direction, the
mask 132 is driven in a clockwise direction through the slip clutch
118 until the clip 140 engages the pin 144. Thereafter, the mask
remains in its most clockwise position while the turntable 74
continues to rotate.
The pins 144 and 146 and the clips 140 and 142 are so positioned in
the member 104 and in the sleeve 126 respectively, that the mask
132 is aligned with the electrode 44T positioned in the section 36
whenever the clip 142 is engaged with the pin 146. Similarly, the
mask 132 is aligned with the electrode 44P positioned in the cavity
38 whenever the clip 140 is engaged with the pin 144. Thus, the
shutter 136 of the mask 132 alternately blocks each of the
electrodes 44 as the direction of rotation of the turntable 74 is
reversed.
In addition to enclosing the titanium electrode 44T, the half-moon
shaped section 36 encloses a resistance monitor 150. The resistance
monitor 150 includes a glass plate 152 that is secured between a
pair of connectors 154 and 156. The connector 154 is secured to the
housing 16 by an insulating member 158 and is connected to suitable
resistance monitoring circuitry by a lead 160. The connector 156 is
grounded through a lead 162 that is connected to one of the
fasteners 106.
It should be noted that in the system 10, the housing 16 and the
cover 18 comprise a combined vacuum enclosure and grounded target
for the electrodes 44. This feature results in increased substrate
capacity and reduced system volume. These results combine to
greatly increase the number of slices that can be processed in a
given period of time relative to prior sputtering systems. It
should be further noted that the cover 18 and the turntable 74 are
secured to the respective mating parts by the force of gravity
alone. This greatly facilitates the loading and unloading of
substrates into and out of the system 10.
In the use of the system 10, the substrates supporting plate 78 of
the turntable 74 is loaded by positioning substrates on the lips 84
of the holes 82 therein and then positioning a ballast 86 on top of
each substrate. When the entire turntable has been loaded with
substrates and ballasts, the cover 18 of the system 10 is removed
and the turntable 74 is positioned in engagement with the drive
members 72 of the shaft 70. A suitable handle (not shown) is
provided for mounting the turntable 74 in the system 10 so that the
interior of the housing 16 is not contaminated during the loading
operation.
When the loaded turntable 74 is in place in the housing 16, the
cover 18 is replaced and the vacuum pump of which the cylinder 12
and the flange 14 form a part is actuated to establish a vacuum in
the housing 16. When the housing has been evacuated sufficiently,
argon is fed into the housing 16. As is well known in the
sputtering art, the presence of argon in a sputtering chamber aids
in the establishment of a sputtering plasma therein.
When the proper atmosphere has been established in the housing 16,
the motor 112 is actuated to rotate the turntable 74 in a
counterclockwise direction. This positions the mask 132 in blocking
alignment with the electrode 44T in the section 36 of the housing
16. At this time, high voltage electric current is applied to the
titanium electrode 44T through its respective feed through 46. This
causes titanium from the electrode to initially sputter onto the
shutter 136 of the mask 132.
The mask 132 is positioned in blocking alignment with the electrode
44T during the initial portion of its operation in order to prevent
the material of the electrode from being sputtered onto the
substrates until the electrode is clean. The state of cleanliess of
the electrode 44T is determined with the aid of resistance monitor
150. The glass plate 152 of the resistance monitor 150 is
positioned to receive material sputtered from the electrode 44T.
The resistance across the glass plate 152 is directly proportional
to the cleanliness of the material being sputtered. Thus, when the
resistance across the plate 152 drops to a predetermined level, it
is known that the sputtering of the titanium onto the substrates in
the turntable 74 can begin.
The sputtering of titanium onto the substrates is initiated by
reversing the direction of rotation of the motor 112. This causes
the clutch 118 to drive the mask 132 clockwise until the clip 140
on the sleeve 126 engages the pin 144 on the member 104. At this
time, the mask 132 is positioned in blocking alignment with the
platinum electrode 44P and the titanium electrode 44T is clear.
After the mask has been rotated out of alignment with the titanium
electrode, the operation of that electrode is continued for a
predetermined period of time to deposit a layer of titanium on the
substrates. After a sufficient layer of titanium has been deposited
on each substrate, the operation of the titanium electrode is
terminated and high voltage electric current is directed to the
platinum electrode 44P through its associated feed through 46.
Like the titanium electrode 44T, the platinum electrode 44P is
initially operated with the mask 132 positioned between it and the
substrates in the turntable so that the material of the platinum
electrode is not deposited onto the substrates until the electrode
is clean. When the platinum electrode has been operated for
sufficient period of time to assure its cleanliness, the direction
of rotation of the motor 112 is again reversed. This causes the
clutch 118 to rotate the mask 132 in a counterclockwise direction
until the clip 142 on the sleeve engages the pin 146 on the member
104. At that time, the mask is positioned in alignment with the
titanium electrode 44T and out of alignment with the platinum
electrode 44P. The operation of the platinum electrode is
thereafter continued until a sufficient quantity of platinum has
been deposited on each substrate mounted in the turntable 74.
When the sputtering of platinum has been completed, the interior of
the housing 16 is allowed to cool. Then, the housing 16 is vented
to the atmosphere, the cover 18 is lifted from the housing 16 and
the turntable 74 is removed. Preferably, a second turntable 74 has
meanwhile been loaded with substrates and ballasts. If such be the
case, the second turntable 74 is immediately installed in housing
16, and the operation of the system 10 is re-started.
It will be understood that as the system 10 is repeatedly operated,
layers of titanium and platinum build up on the interior portions
of the housing 16 and the cover 18. As the thickness of these
layers increases they tend to break into pieces and fall toward the
electrodes. Also, the substrates operated upon by the system 10
occasionally shatter during sputtering.
In the event any foreign material, whether it be a dislodged piece
of sputtered metal or a piece of broken substrate, becomes lodged
between an electrode 44 and 16, the electrode is shorted. This
disables the system 10 and necessitates stopping the operation of
the system 10 so that the foreign material can be removed. It has
been found that the trough 43 formed in the housing 16 forms a
reservoir which minimizes electrode shorting in the system 10. That
is, most foreign materials that are generated during the operation
of the system are received by the trough 43 and do not engage
either electrode.
A more complete understanding of the operation of the system 10 may
be had by referring to FIG. 6 wherein a control circuit for the
system is schematically illustrated. Conventional 208 volt, 60
Hertz line current is supplied to the primary of a transformer T.
The secondary of the transformer T has a grounded center tap, and
accordingly, operates to provide equal and opposite output
signals.
One output of the transformer T is connected through a fuse F to a
pair of on and off pushbuttons PB1 and PB2. Whenever the on
pushbutton PB1 is actuated, a current path is established between
the one output of the transformer T and ground through an "ON" lamp
L1 and a control relay CR1. Once actuated, the relay CR1 locks
operated through a normally open contact CR1A.
The control circuit further includes a pair of two position
switches S1 and S2. The switch S1 is activated to direct argon into
the housing 16 of the system 10 and to direct cooling water through
the tubes 24 and 26. The switch S2 is selectively actuated to cause
the system 10 to sputter both titanium and platinum on the
substrates or to cause the system to sputter platinum only.
Regardless of the position of the switch S2, a pushbutton PB3 must
be depressed to initiate the operation of the system 10. Assuming
that the curcuit has previously been started by depression of the
pushbutton PB1 and assuming that the switch S2 is in a position
shown, this action initiates the operation of a timer TR1. As soon
as it is started, the timer TR1 closes a pair of normally open
contacts TR1A. This forms a path through a pair of normally closed
contacts TR1B and a control relay CR2. Operation of the relay CR2
closes a normally open contact pair CR2A.
Whenever the clip 142 on the drive sleeve 126 is engaged with the
pin 146 on the member 104, a circuit is established through a
control relay CR3. Assuming this to be the case at the start of the
operation of the system 10, operation of the relay CR3 closes a
normally open contact pair CR3A. When both the contact pair CR2A
and the contact pair CR3A are closed, two circuit paths are
established between the outputs of a low voltage power supply
circuit. One path extends through a signal lamp L2 while the other
extends through a control relay CR4.
Operation of the relay CR4 closes a normally open contact pair CR4A
to establish a circuit path through a control relay CR5. Operation
of the control relay CR5 closes two normally open contact pairs CR5
and CR5B to connect the secondary of the transformer T to an
electrode power supply circuit. The electrode power supply turn
directs operating power to the titanium electrode 44T of the system
10.
When the timer TR1 times out, it momentarily closes a normally open
contact pair TR1C. This initiates the operation of a timer TR2. As
the timer TR2 begins to operate it establishes a current path
through a signal lamp L3 and closes a normally open contact pair
TR2A.
As the timer TR1 times out, its normally closed contact pair TR1B
is opened at the same time the contact TR1C is closed. This breaks
the current path through the control relay CR2 which permits the
contact pair CR2A to open. However, a hold circuit for the control
relay CR4 is maintained by a closure of the contact pair CR2A.
Thus, the secondary of the transformer T remains connected to the
electrode power supply circuit through the contacts CR5A and
CR5B.
The closure of the contact pair TR2A also establishes an operating
path for a control relay CR6. The operation of the relay CR6 closes
two sets of normally open contact pairs CR6A and CR6B and opens two
sets of normally closed contact pairs CR6C and CR6D. This
immediately reverses the direction of operation of the motor
112.
When the motor 112 reverses its direction of operation, the clutch
118 drives the mask 132 clockwise until the clip 140 on the drive
sleeve 126 engages the pin 144 on the member 104. This action
breaks the operating path for the relay CR3 and establishes an
operating path for a relay CR7. Operation of the relay CR7 closes a
normally open contact pair CR7A.
When the timer TR2 times out, it momentarily closes a normally open
contact pair TR2B to establish a starting path for a timer TR3. The
timer TR3 is constructed identically to the timer TR1 and,
accordingly, when the operation of the timer TR3 is initiated, the
timer TR3 immediately closes a normally open contact pair TR3A.
This action establishes a circuit path through a control relay CR8
which immediately operates to close a normally open contact pair
CR8A. Since the contact pair CR7A was closed upon rotation of the
mask 132 to its counterclockwise position, this establishes a hold
path for the relay CR4. By this means, the secondary of the
transformer T is maintained connected to the electrode power supply
circuit even though the contact pair TR2A opens the timing out of
the timer TR2. Similarly, a hold path for the relay CR6 is
maintained through the contacts CR8A.
When both contact pair CR7A and the contact pair CR8A are closed,
an operating circuit for a relay CR9 is established. Operation of
the relay CR9 opens a normally closed contact pair CR9A and closes
a normally opened contact pair CR9B. This action reverses the
operation of the electrode power supply circuit so that the circuit
discontinues supplying power to the titanium electrode 44T and
begins supplying platinum to the platinum electrode 44P.
When the timer TR3 times out it momentarily closes a normally open
contact pair TR3C to complete a circuit path to a timer TR4.
Operation of the timer TR4 immediately establishes a circuit path
through a signal lamp L4 and closes a normally open contact pair
TR3A. This establishes hold paths for both the relay CR4 and the
relay CR9 so that the electrode power supply circuit continues to
supply operating power to the platinum electrode 44P of the system
10.
As the timer TR3 times out, it breaks the circuit path including
the relay CR8 and thereby opens the contact pair CR8A. Since the
contact pair TR2A was opened upon the timing out of the relay TR2,
no path is available to maintain the relay CR6 operated. When the
relay CR6 is de-energized, the contact pairs CR6A and CR6B are
re-closed and the contact pairs CR6C and CR6D are re-opened. This
reverses the direction of operation of the motor 112 so that the
mask 132 is rotated counterclockwise into alignment with the
titanium electrode 44T of the system 10.
When the timer TR4 times out, it momentarily closes a contact pair
TR4B. This action initiates the operation of a timer TR5. The
timing out of the timer TR4 also opens the contact pair TR4A. This
breaks the last hold path for the control relay CR4 and thereby
causes the relay CR4 to de-energize. De-energization of the relay
CR4 opens the contact pair CR4A which causes the relay CR5 to
de-energize. This action disconnects the secondary of the
transformer T from the electrode power supply circuit and thereby
discontinues the operation of both of the electrodes 44 of the
system 10.
During the operation of the timer TR5 the interior of the housing
16 gradually cools. When the timer TR5 times out, it closes a
normally open contact pair TR5A. This actuates an alarm A1 which
produces a signal indicative of the end of the operating cycle of
the system 10. The alarm A1 is reset by actuation of a pushbutton
PB4.
In addition to the various instrumentalities which control the
normal functions of the system 10 the control circuit shown in FIG.
6 includes a temperature monitoring circuit TC which operates to
discontinue the operation of the system 10 should the temperature
of the cooling water in the tubes 24 and 26 exceed a predetermined
level. The temperature monitoring circuit TC includes a temperature
sensitive element and a relay (not shown) which operates under the
control of the temperature sensitive element to open a normally
closed contact pair TC1 should the temperature in the housing
become too high. This action interrupts the operation of any of the
timers TR1 through TR5 which may be operating and also discontinues
the operation of the electrode power supply circuit which is
connected to the contact pair TR1 through mated connector pairs
C1-C2. In the event the operation of the system 10 is discontinued
by the temperature monitoring circuit TC, it may be restarted by
depressing the pushbutton PB4.
In some cases it is desirable to sputter substrates with platinum
only rather than with both titanium and platinum. In such a case
the switch S2 is actuated to break the connection from the
pushbutton PB3 to the timer TR1 and to establish the connection
with the pushbutton PB3 to the timer TR3. In such a case the
operating cycle of the control circuit shown in FIG. 6 is the same
as the complete operating cycle except that it begins with the
initiation of the operation of the timer TR3 rather than with the
initiation with the operation of the timer TR1.
From the foregoing it will be understood that the control circuit
shown in FIG. 6 provides completely automatic control over the
operation of the system 10. This eliminates any possibility of
human error in the operation of the system. Nevertheless, since
each stage of the operation of the system 10 is controlled by a
separate timer, the circuit shown in FIG. 6 allows complete control
over every phase of the operation of the system.
Although only embodiment of the invention is illustrated in the
drawing and described herein, it will be understood that the
invention is not limited to the embodiment disclosed but is capable
of rearrangement, modification and substitution of parts and
elements without departing from the spirit of the invention.
* * * * *