Single wafer load lock chamber for pre-processing and...

Details Single wafer load lock chamber for pre-processing and... Single wafer load lock chamber for pre-processing and...

1997-12-15

2001-08-07

Cole, Elizabeth M. (Department: 1771)

Coating apparatus

Gas or vapor deposition

Multizone chamber

C414S217000, C414S935000, C414S936000, C414S937000, C414S939000

Reexamination Certificate

active

06270582

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to the storage and transfer of wafers typically used in the fabrication of integrated circuits and flat panel displays. Specifically, the invention relates to a load lock chamber used to transition wafers from an ambient environment to a vacuum environment in a processing system and methods and apparatuses for pre-processing and post-processing the wafers before or after a primary process is performed on the wafer.
BACKGROUND OF THE INVENTION
Vacuum processing systems for processing 100 mm, 200 mm, 300 mm or other diameter wafers are generally known. An example of a typical vacuum processing system
10
is shown in
FIG. 1
a
. The system
10
typically has a centralized transfer chamber
12
mounted on a monolith platform (not shown). The transfer chamber
12
is the center of activity for the movement of wafers being processed in the system. One or more process chambers
14
attach to the transfer chamber
12
at valves through which the wafers are passed by a robot
16
in the transfer chamber
12
. The valves are selectively opened and closed to isolate the process chambers
14
from the transfer chamber
12
while wafers are being processed in the process chamber
14
. Physically, the process chambers
14
are either supported by the transfer chamber
12
and its platform or are supported on their own platform. Inside the system
10
, the transfer chamber
12
is typically held at a constant vacuum; whereas, the process chambers
14
may be pumped to a greater vacuum for performing their respective processes. Afterward, the chamber pressure must be returned to the level in the transfer chamber
12
before opening the valve to permit access between the chambers.
Access to the transfer chamber for wafers from the exterior of the system, or from the manufacturing facility, is typically through one or more load lock chambers. The load lock chambers cycle between the pressure level of the ambient environment and the pressure level in the transfer chamber in order for the wafers to be passed therebetween, so the load lock chambers transition the wafers between the atmospheric pressure of a very clean environment to the vacuum of the transfer chamber. Load lock chambers typically have a large volume holding several wafers, from about thirteen to about twenty five wafers. The wafers are stacked vertically in a wafer cassette with a space between each wafer permitting a robot blade to reach under a wafer to remove the wafer. Thus, a fairly large volume is being transitioned between the atmospheric pressure and the vacuum pressure, which takes about four minutes. During the time to perform this transition, no process is being performed on the wafers.
The load lock chambers may open to the ambient environment for an operator to load a wafer cassette, or pod, thereinto or the load lock chambers may attach to a mini-environment which transfers wafers in a very clean environment at atmospheric pressure from wafer pods to the load lock chambers. The mini-environment also has a wafer orienter or aligner for aligning the wafer so that the wafer is properly oriented in the load lock chamber.
Some common transfer chambers have four to six facets to mount process chambers and load lock chambers. For a six-faceted transfer chamber, typically two of the facets are designated for load lock chambers, and the other four facets are designated for process chambers. The process chambers include rapid thermal processing (RTP) chambers, physical vapor deposition (PVD) chambers, chemical vapor deposition (CVD) chambers, etch chambers, etc. The productivity of a vacuum processing system is increased when more process chambers are mounted to the transfer chamber because more wafers can be processed at a given time. Additionally, less space is required in the manufacturing facility to process a certain number of wafers if the productivity of the system is maximized.
Some of the processes performed by the process chambers require that the wafers processed therein be pre-processed or post-processed before or after performing the primary process in a process chamber. For example, a process may require that a wafer be pre-heated before performance of the primary process, thus preparing the wafer for the primary process, so that the primary process proceeds more quickly or efficiently. In a second example, a process may require that a wafer be heated after performance of the process, such as a spin-on-glass process that coats the wafer with a liquid glass material that must be cured following deposition by heat-treating the wafer at elevated temperatures. In yet another example, a process may require that a wafer be cooled after performance of the process, so that the wafer is not too hot to handle or so that the wafer is not so hot that dopants or other material in or on the wafer diffuse through the wafer thereby compromising the integrity of the devices formed in or on the wafer.
For such processes, the vacuum processing system typically provides a processing element, such as a wafer heater or wafer cooler, in a location separate from the process chamber to perform the pre-processing or post-processing process on the wafer, so that the wafer spends as little time as possible inside the process chamber, and so that the process chamber does not have to incorporate the extra equipment required to perform these extra processing steps. For example, in the vacuum processing system
100
shown in
FIG. 1
, and described more fully in the detailed description of a preferred embodiment below, the transfer chamber
102
has four facets
106
for mounting process chambers
104
and two facets
112
for mounting load lock chambers
108
. One or more of the facets
106
of the system, however, mount a pre-processing or post-processing chamber such as a cool-down chamber to cool a wafer after a process and/or a heating chamber to heat the wafer before or after a process. This separation of functions permits the system to perform tasks in parallel, so while a wafer is undergoing the pre-processing or post-processing step, another wafer is undergoing the primary processing step. However, the total throughput of the system
100
is reduced since the system
100
has fewer process chambers
104
for performing the primary processing of the wafers.
In order to perform the pre-processing or post-processing processes, the vacuum system
100
maneuvers a wafer through a series of steps prior to transferring the wafer to a process chamber
104
for performance of the primary process. Typically, these steps are performed by the transfer chamber
102
and an attached pre-processing or post-processing chamber. For example, after a load lock chamber
108
transitions a cassette of wafers to the vacuum level of the transfer chamber
102
, a robot in the transfer chamber
102
moves the wafers, one at a time, to a process chamber
104
or a pre-processing chamber. After a wafer has been pre-processed, such as heated to an appropriate temperature, the robot moves the wafer to one of the process chambers
104
for primary processing. After the process chamber
104
completes its process on the wafer, the robot moves the wafer back to a load lock chamber
108
or to a post-processing chamber, such as a cool-down chamber. After the wafer has been post-processed, the robot moves the wafer to the load lock chamber
108
. After all of the wafers in the cassette have been processed, the load lock chamber
108
transitions the wafers back to the ambient environment pressure level. The steps to move the wafers to and from the pre-processing and post-processing chambers add to the overall time required for processing a wafer through the vacuum processing system. The cost to manufacture an integrated circuit is typically directly related to the amount of time required to process the wafer; therefore, since a certain amount of time is required to perform the pre- and post-processing steps and to transition the load lock chamber, as discussed above, it is desirable to compress this time

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