Geometrical instruments – Gauge – Collocating
Reexamination Certificate
2001-06-13
2003-09-30
Gutierrez, Diego (Department: 2859)
Geometrical instruments
Gauge
Collocating
C033S613000
Reexamination Certificate
active
06625898
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to automated workpiece handling systems, and more particularly, to methods and devices for aligning a cassette for workpieces in an automated workpiece handling system.
BACKGROUND OF THE INVENTION
In order to decrease contamination and to enhance throughput, semiconductor processing systems often utilize one or more robots to transfer semiconductor wafers, substrates and other workpieces between a number of different vacuum chambers which perform a variety of tasks. An article entitled “Dry Etching Systems: Gearing Up for Larger Wafers”, in the October, 1985 issue of Semiconductor International magazine, pages 48-60, describes a four-chamber dry etching system in which a robot housed in a pentagonal-shaped mainframe serves four plasma etching chambers and a loadlock chamber mounted on the robot housing. In order to increase throughput, it has been proposed to utilize two loadlock chambers as described in U.S. Pat. No. 5,186,718. In such a two-loadlock chamber system, both loadlock chambers are loaded with full cassettes of unprocessed wafers.
FIG. 1
of the present application illustrates two typical loadlock chambers LLA and LLB, each having a cassette
190
therein for holding unprocessed wafers
192
to be unloaded by a robot
194
in a transfer chamber
195
and transferred to various processing chambers
196
attached to a mainframe
198
.
The loadlock chamber LLA, for example, is a pressure-tight enclosure which is coupled to the periphery of the mainframe
198
by interlocking seals which permit the loadlock chamber to be removed and reattached to the mainframe as needed. The cassette
190
is loaded into the loadlock chamber LLA through a rear door, which is closed in a pressure-tight seal. The wafers are transferred between the mainframe
198
and the loadlock chamber LLA through a passageway
199
which may be closed by a slit valve to isolate the loadlock chamber volume from the mainframe volume.
As shown in
FIG. 2
, a typical cassette
190
is supported by a platform
200
of a cassette handler system
208
, which includes an elevator
210
, which elevates the platform
200
and the cassette
190
. The platform
200
has a top surface, which defines a base plane
220
on which the cassette
190
rests. As the cassette includes a plurality of “slots”
204
or wafer support locations, the elevator moves the cassette to sequentially position each of the slots with the slit valves to allow a robot blade to pass from the mainframe, through the slit valve, and to a location to “pick” or deposit a wafer in a wafer slot.
The slots
204
of the cassette may be initially loaded with unprocessed wafers or other workpieces before the cassette is loaded into the loadlock chamber LLA. The number of unprocessed wafers initially loaded into the cassette may depend upon the design of the cassette. For example, some cassettes may have slots for 25 or more wafers.
After the loadlock access door is closed and sealed, the loadlock chamber is then pumped by a pump system down to the vacuum level of the mainframe
198
before the slit valve is opened. The robot
194
which is mounted in the mainframe
198
then unloads the wafers from the cassette one at a time, transferring each wafer in turn to the first processing chamber. The robot
194
includes a robot hand or blade
206
, which is moved underneath the wafer to be unloaded. The robot
194
then “lifts” the wafer from the wafer slot supports supporting the wafers in the cassette
190
. By “lifting,” it is meant that either the robot blade
206
is elevated or the cassette
190
is lowered by the handler mechanism
208
such that the wafer is lifted off the cassette wafer supports. The wafer may then be withdrawn from the cassette
190
through the passageway and transferred to the first processing chamber.
Once a wafer has completed its processing in the first processing chamber, that wafer is transferred to the next processing chamber (or back to a cassette) and the robot
194
unloads another wafer from the cassette
190
and transfers it to the first processing chamber. When a wafer has completed all the processing steps of the wafer processing system, the robot
194
returns the processed wafer back to the cassette
190
from which it came. Once all the wafers have been processed and returned to the cassette
190
, the cassette in the loadlock chamber is removed and another full cassette of unprocessed wafers is reloaded. Alternatively, a loaded cassette may be placed in one loadlock, and an empty one in the other loadlock. Wafers are thus moved from the full cassette, processed, and then loaded into the (initially) empty cassette in the other loadlock. Once the initially empty cassette is full, the initially full cassette will be empty. The full “processed” cassette is exchanged for a full cassette of unprocessed wafers, and these are then picked from the cassette, processed, and returned to the other cassette. The movements of the robot
194
and the cassette handler
208
are controlled by an operator system controller
222
(FIG.
1
), which is often implemented with a programmed workstation.
As shown in
FIGS. 2 and 3
, the wafers are typically very closely spaced in many wafer cassettes. For example, the spacing between adjacent wafers
230
and
232
in the cassette may be as small as 0.050 inches. Thus, the wafer blade
206
is often very thin, to fit between wafers as cassettes are loaded or unloaded. As a consequence, it is often preferred in many processing systems for the cassette and the cassette handler
208
to be precisely aligned with respect to the robot blade and wafer to avoid accidental contact between either the robot blade or the wafer carried by the blade and the walls of the cassette or with other wafers held within the cassette.
A metrology tool system which facilitates alignment of a cassette and a cassette handler is indicated generally at
400
in FIG.
4
and is described in copending application Ser. No. 09/294,301, filed Apr. 19, 1999 and entitled “METHOD AND APPARATUS FOR ALIGNING A CASSETTE” and assigned to the assignee of the present application. As described therein, the cassette alignment tool system
400
comprises a metrology tool or “cassette”
410
which emulates an actual cassette to be aligned. A cassette controller
412
is coupled by communication cables
414
to the metrology cassette
410
, and a computer
416
is coupled by a communication cable
418
to the cassette controller
412
. The metrology cassette
410
is secured to the cassette handler platform
200
in the same manner as an actual wafer cassette such as the cassette
190
of FIG.
2
and thus emulates the wafer cassette
190
.
For example, the metrology cassette
410
preferably approximates the size and weight of a production wafer cassette full of wafers. In addition, the metrology cassette has alignment and registration surfaces similar to those of an actual cassette. The top surface of the top plate
612
and the bottom surface of the base plate
630
are both machined to imitate the bottom alignment and registration features of common wafer cassettes. This allows it to be inserted into most systems with measurement sensors directed upward or downward as needed.
Thus, the metrology cassette
410
has on the bottom of its frame a leading edge surface
422
and a trailing edge surface
424
of an H-bar
430
(
FIGS. 5
a
-
5
c
), and interior edge surfaces
562
of a pair of support runner or side rails
570
(
FIG. 5
b
) which are received by corresponding alignment and registration surfaces of the cassette handler to align the cassette with respect to the handler. Similarly, the metrology cassette
410
has on the top of its frame an H-bar
430
(
FIGS. 5
c
-
5
d
), and side rails
570
(
FIG. 5
d
) which are likewise received by corresponding alignment and registration surfaces of the cassette handler to align the cassette with respect to the handler in the inverted position. Still further, the metrology cassette
410
has rear edge surfaces
572
and side fac
Applied Materials Inc
Konrad Raynes & Victor & Mann LLP
Reis Travis
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