Coating apparatus – Gas or vapor deposition
Reexamination Certificate
2000-11-14
2002-09-17
Dang, Thi (Department: 1763)
Coating apparatus
Gas or vapor deposition
C156S345420, C204S298250, C204S298350
Reexamination Certificate
active
06451118
ABSTRACT:
TECHNICAL FIELD
The present invention is directed to cluster tools for processing wafers and the like, and, more particularly, to a cluster tool architecture to be used, inter alia in sulfur trioxide processing of such wafers.
BACKGROUND ART
Cluster tools have been available for many years. Such tools are used for automated processing of semiconductor wafers, for example.
FIGS. 1-4
are schematic drawings of prior art cluster tools, and are shown here as an aid to differentiate the present invention from the prior art cluster tools.
FIG. 1
depicts an example of prior art cluster tool architecture,
110
, which is similar to a sputtering tool produced by Varian Associates. In this architecture, silicon wafers (not shown) are handled alternately from cassettes
112
and
114
. First, the entire cassette assembly is pumped down to vacuum and the substrates are unloaded, one at a time, by means of a vacuum transfer arm
116
to an alignment station
117
. The substrates are then loaded with a second arm
118
into one of several process stations
120
,
122
,
124
, or
126
, and then out to a de-gas and cool-down station
128
and finally back into the original cassette. This architecture primarily provides a method for integrating several vacuum processes, which can be performed in a random order. The sputtering tool
110
is a vacuum-only processing apparatus.
FIG. 2
depicts a second type of cluster tool architecture
210
, similar to the cluster tool manufactured by Applied Materials, which integrates several vacuum processes that must be isolated and performed at different vacuum levels. In this architecture, cassettes
212
and
214
are pumped down from atmosphere, and the wafers are unloaded one at a time, aligned and then reloaded into the process chambers
232
,
234
,
236
, and
238
by means of the vacuum transfer arm
216
. In the cluster tool architecture
210
, the process chambers are specifically limited to vacuum processes such as chemical vapor deposition (CVD). After CVD, the wafer is loaded into the buffer station
240
, where it is purged and further pumped down for lower vacuum processing in sputtering stations
220
,
222
,
224
, and
226
, employing vacuum transfer arm
218
. After sputtering, the wafer is loaded into a second buffer station
242
, where pressure is changed to match the pressure in the area
216
(different vacuum level). The wafer is then cooled down and moved from the buffer station to any of the CVD process chambers
232
,
234
,
236
, or
238
or out of the apparatus into one of the cassettes
213
,
214
. Cluster tool architecture
210
is a random order processing with two isolated sections. However, it is still a vacuum-processing tool.
FIG. 3
depicts a third architecture
310
, which is similar to the tools manufactured by Brooks Automation, PRI, and others. This architecture is based on the concept of staging two or more cassettes
312
a,
312
b,
314
a,
and
314
b,
to unload wafers, one at a time, in atmosphere, using an atmosphere transfer arm
316
. The wafers are aligned, if required, at flat-finding station
317
before being loaded into the buffer station
340
, which is then pumped down to vacuum. Once the buffer station
340
is at vacuum, a second vacuum robot
318
unloads the buffer station and loads the wafer, in random order, to the first available vacuum process chamber
320
,
322
,
324
, or
326
. After processing, the wafers are removed and loaded into the second buffer station
342
to be vented back to atmosphere and loaded to its original cassette or any available cassette
312
a,
312
b,
314
a,
or
314
b.
FIG. 4
depicts an example of a forth prior art architecture
410
which combines vacuum and atmospheric processing in a linear architecture, similar to the architecture employed in the Lam Research metal-etch tool. Here, the wafer is unloaded from the cassette
412
, aligned at an aligner
417
, and loaded into a buffer station
440
, which is pumped down to vacuum. Subsequently, the wafer is loaded into a plasma etch chamber
420
(in vacuum) for processing, and is moved into a separate buffer station
442
for venting to atmosphere. After venting, the wafer is loaded to a clean station
444
where the wafer is rinsed or scrubbed with water, at atmosphere, and then dried and loaded into an exit cassette
446
. The prior art architecture
410
provides a linear processing sequence that is inflexible to accommodate variations in the processing steps.
The disadvantages of prior art approaches are:
1. cluster tool processing is done only in a vacuum environment;
2. the atmospheric section of the cluster tool does not integrate atmospheric processing in a cluster format; and
3. tool architectures that have integrated vacuum and atmospheric processing have done so in a linear work flow format. This linear architecture does not allow wafers to return to an original slot in the cassette. Neither does it allow a plurality of processing chambers for parallel processing, in order to achieve a higher throughput.
Processing of wafers using sulfur trioxide is the subject of U.S. Pat. No. 5,037,506, issued Aug. 6, 1991, and U.S. Pat. No. 5,763,016, issued Jun. 9, 1998. Automated processing of wafers with sulfur trioxide requires controlled atmospheres prior to, during, and subsequent to the exposure to sulfur trioxide, due to the various processing steps involved.
However, the prior art architectures are unable to perform sulfur trioxide processing. All known prior art tools, with the exception of Brooks/PRI tool (FIG.
3
), transfer wafers under pumped down conditions and all of the processing takes place in vacuum or a reduced atmosphere environment. In the Brooks/PRI tools, while wafer cassettes are unloaded in atmosphere, no atmospheric processing is performed. The Brooks/PRI architecture's intent is to load substrates to a vacuum processing cluster tool from a number a multiple of wafer cassettes staged in atmosphere.
Thus, there is a need for a cluster tool architecture to process wafers in the presence of sulfur trioxide, or other reactive gases such that it permits: (1) loading the wafers in an atmospheric-cluster environment, (2) performing one or more atmospheric processes, (3) exchanging wafers between atmospheric and vacuum environments, (4) random order processing using a multiple of vacuum-compatible processing stages, (5) returning the waters to the atmospheric-cluster environment for additional atmospheric processing, and (6) finally returning the wafers to an exit cassette or the original cassette slot.
DISCLOSURE OF INVENTION
In accordance with the present invention, a cluster tool architecture and method are provided for processing substrates by exposure to sulfur trioxide and other process environments, as well as prior and subsequent treatments thereto. The cluster tool architecture comprises:
(a) an atmospheric processing area, maintained at atmospheric pressure;
(b) cassette means for introducing a plurality of the substrates into the atmospheric processing area;
(c) at least one process station in the atmospheric processing area for exposing the substrates to a first process environment;
(d) an enclosed vacuum processing area, maintained at a vacuum pressure;
(e) a first buffer station between the atmospheric processing area and the enclosed vacuum processing area to pump and vent from atmospheric to vacuum pressures and transition the substrates from the atmospheric processing area to the enclosed vacuum processing area;
(f) at least one process station in the enclosed vacuum processing area for exposing the substrates to a second process environment;
(g) a second buffer station between the enclosed processing area and the atmospheric processing area to re-pressurize from vacuum to atmospheric pressures and transition the substrates from the enclosed vacuum processing area to the atmospheric processing area;
(h) an atmospheric transfer arm in the atmospheric processing area for transferring the substrates from the cassette means between one of the buffer stations and at least on
Anon, Inc.
Collins David W.
Dang Thi
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