Valves and valve actuation – Fluid actuated or retarded – Pilot or servo type motor
Reexamination Certificate
1998-09-22
2001-01-16
Recla, Henry J. (Department: 3751)
Valves and valve actuation
Fluid actuated or retarded
Pilot or servo type motor
C251S035000, C251S048000, C091S408000
Reexamination Certificate
active
06173938
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to valves commonly used in the fabrication of integrated circuits and flat panel displays. Specifically, the present invention relates to placement and use of pneumatic cylinders in a vacuum processing system to operate a slit valve door.
BACKGROUND OF THE INVENTION
Vacuum processing systems for processing 100 mm, 200 mm, 300 mm or other diameter wafers are generally known. Examples include the CENTURA® and ENDURA® platforms available from Applied Materials, Inc. in Santa Clara, Calif. An example of a typical vacuum processing system
100
is shown in FIG.
1
. The system
100
typically has a centralized transfer chamber
102
(shown in detail in
FIG. 2
) mounted on a monolith platform (not shown). The transfer chamber
102
is the center of activity for the movement of wafers being processed in the system. One or more process chambers
104
and one or more load locks
108
attach to the transfer chamber
102
at its various facets
106
,
112
. Elongated apertures commonly known as slit valve apertures
14
(shown in
FIG. 2
) provide a transfer plane between the process chambers
104
and the load lock chambers
108
through which the wafers are passed. The wafers are transferred by a robot
120
disposed in the transfer chamber
102
. The apertures
14
are selectively opened and closed to isolate the process chambers
104
from the transfer chamber
102
while wafers are being processed in the process chambers
104
. The process chambers
104
are either supported by the transfer chamber
102
and its platform or by their own platform.
Referring briefly to
FIG. 2
, a perspective view is shown of the transfer chamber
102
with the lid and the robot
120
removed so that the interior of the transfer chamber
102
is visible. A centrally located orifice
66
formed in a floor
62
provides a means for mounting the robot
120
therein. Openings
38
formed in the floor
62
are adapted to receive slit valve apparatuses (discussed in detail below) therethrough. As discussed above, the slit valve apertures
14
formed in the facets
106
provide a transfer plane between the transfer chamber
102
and the process chambers
104
(shown in FIG.
1
).
While the transfer chamber
102
is typically held at a constant vacuum, the process chambers
104
may be pumped to a greater vacuum or backfilled with gases to increase the pressure therein in preparation for performing their respective processes. The process chambers
104
may perform various processes such as rapid thermal processing, physical vapor deposition, chemical vapor deposition, etching, etc. After processing, the relative pressures of the process chambers
104
and the transfer chamber
102
are equalized before opening the valve to permit fluid communication between the chambers.
Referring again to
FIG. 1
, a mini-environment, or wafer handling chamber
114
, which attaches to the load lock chambers
108
is shown. A wafer aligner
119
is disposed within the mini-environment
114
so that it is substantially in or near the pathway of a wafer being moved from a pod loader
115
-
118
to a load lock chamber
108
. The wafer aligner
119
centers the wafers and orients the direction of the wafers according to the requirements of a process that the wafers are to undergo in the process chambers
104
. An example of a wafer aligner
119
is the PRE 200 Series Wafer Pre-Aligner available from Equipe Technologies of Sunnyvale, Calif. One or more robots
124
,
125
are disposed within the mini-environment
114
for transferring the wafers between pod loaders
115
-
118
, the wafer aligner
119
, and the load lock chambers
108
. An example of this type of robot
124
,
125
is the ATM-105 available from Equipe Technologies of Sunnyvale, Calif.
As mentioned above, access between the load locks
108
, the transfer chamber
102
, and the process chambers
104
is provided through slit valve apertures
14
which are selectively sealed by a slit valve apparatus.
FIG. 3
shows a typical slit valve apparatus
32
disposed in the transfer chamber
102
. The slit valve apparatus
32
is shown disposed through the opening
38
and mounted to the transfer chamber floor
62
by a mounting bracket
52
. The slit valve apparatus
32
generally includes a piston rod
36
having a first end disposed through a pneumatic cylinder
40
and a second end coupled to a door
28
by an adjustment mechanism
56
. In order to maintain the extreme vacuum within the various environments of the system
100
(shown in FIG.
1
), the slit valve door
28
, having an O-ring
34
disposed thereon, must be hermetically sealed over the aperture
14
. A seat
22
includes a seating surface
24
defining a sealing plane
26
which is angularly disposed with respect to the transfer plane
20
and perpendicular to the axis of actuation
54
. In the closed position, the door
28
abuts the seating surface
24
.
The slit valve apparatus
32
is activated by the injection of compressed air into an inlet/exhaust port
50
of the pneumatic cylinder
40
. A constant psi of compressed air is supplied to the pneumatic cylinder
40
so that a terminal stroke velocity is reached prior to the sealing of the slit valve aperture
14
. At the end of its stroke, the slit valve door
28
impacts the aperture
14
and halts the slit valve apparatus' stroke. Thus, the speed of the door
28
relative to the aperture
14
is abruptly terminated and the processing system
100
(shown in
FIG. 1
) as a whole absorbs the door's kinetic energy.
In an effort to increase throughput, the wafers being processed have become increasingly larger. The trend today is to use 300 mm wafers to form multiple devices thereon. Larger wafers, of course, require larger processing systems which include larger slit valve doors and apertures. Larger doors, in turn, require larger components such as the pneumatic cylinder, mounting bracket and adjustment mechanism. It has been discovered in the scale-up process for 300 mm substrates that increasing the slit valve components creates additional concerns. Since the door's kinetic energy and momentum is a function of it velocity and mass, an increase in mass results in increased kinetic energy and momentum for a given velocity. In general, total system vibration effects reach a critical level creating pervasive adverse conditions. For example, particle generation, metal to metal contact, hermetic sealing, door alignment, and pneumatic cylinder and door damage are significantly more problematic. Further, with larger slit valve doors the vibration is not localized to the immediate chamber area surrounding a particular slit valve. Rather, the force of impact affects remote parts of the chamber, thereby damaging delicate instrumentation and interfering with ongoing processes in other chambers. These undesirable conditions are caused primarily by the sealing impact of more massive slit valves.
There remains a need, therefore, for a slit valve apparatus and method which minimizes the total vacuum system trauma caused by impact of the slit valve door upon closing, thereby reducing the generation of particle debris, vibration, and damage to the vacuum system's components, including the pneumatic air cylinder.
SUMMARY OF THE INVENTION
The invention generally provides a multi-stage, slit valve door assembly which reduces semiconductor processing system trauma caused by the extension, sealing, and retraction of the slit valve door. In one aspect of the invention, the apparatus comprises a multi-speed, pneumatic cylinder preferably including a cylinder body and a bore therein enclosed by end caps. A longitudinally reciprocating piston is disposed within the bore to define a front and back volume. Primary inlet/exhaust ports and auxiliary inlet/exhaust ports are located at both ends of the cylinder with channels connected thereto for providing fluid communication between the bore and the cylinder's external environment. A compressed gas source, supplying a gas such as air, is connecte
Applied Materials Inc.
Maust Timothy L.
Recla Henry J.
Thomason Moser & Patterson
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