Wafer transfer system

Details Wafer transfer system Wafer transfer system

1999-03-09

2001-05-01

Mills, Gregory (Department: 1763)

Coating apparatus

Gas or vapor deposition

Multizone chamber

C118S728000, C156S345420

Reexamination Certificate

active

06224680

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The field of this invention relates generally to semiconductor manufacturing, and more particularly to an apparatus and method for stripping resist from a substrate in a transfer chamber, while at substantially the same time, another substrate is being transferred between a load lock chamber and the transfer chamber of the system. Therefore, throughput is increased because processing and transferring of the substrate occurs in parallel instead of as two separate events.
2. Description of Related Art
During the process of semiconductor fabrication, photoresist, a light sensitive film, is often deposited on a wafer surface and then “exposed” using high intensity light through a mask. The exposed photoresist is then dissolved off the wafer with developers. The pattern of photoresist remaining after development will prevent subsequent etch or implant operations in some areas while allowing etching or implant in other areas. Once the etch or implant operation is completed, the remaining photoresist is removed or stripped from the wafer surface.
A prior art chemical vapor deposition system
100
that can be adapted to remove photoresist from a wafer is illustrated in FIG.
1
. The prior art system comprises a load lock chamber
125
and a transfer chamber
105
. A complicated robot
130
with one platen
135
, a first cassette
140
for holding wafers and a second cassette
150
are disposed within the load lock chamber
125
. The transfer chamber
105
includes six fins (
110
a
-
110
f
) mounted to a common center
120
on one end of each fin. The other end of each of the fins
110
a.
The robot
130
would then extend the platen
135
toward the fin
110
A. The fin
110
a
(including the fin assembly) would move up to receive the new wafer. The robot
130
would retract after the wafer was transferred to the fin
110
a.
The fin
110
a
would then rotate towards processing stage
115
b
and then move down so that fin
110
a
is now located where fin
110
b
was located. In other words, all six fins (
110
a
-
110
f
) have moved in a counterclockwise direction since all six fins (
110
a
-
1100
are attached to a common center
120
. Thus, fin
110
a
will then move down so that the wafer is now on processing stage
115
b.
The entire sequence of events typically takes about 27 seconds to unload a processed wafer from the transfer chamber to the load lock chamber and then back into a cassette (
140
or
150
) and to load a new wafer into the transfer chamber. During this transfer sequence, all processing stops.
Once a new wafer is introduced into the transfer chamber
105
, processing of the wafer resumes. The processing time usually takes about 15 seconds. While a wafer is being processed in the transfer chamber
105
, the robot
130
is inactive and no wafers are being loaded or unloaded between the load lock chamber
125
and the transfer chamber
105
.
When a second wafer is introduced into the transfer chamber
105
, the first wafer which was on processing stage
115
b
will be moved to processing stage
115
c
so that the new wafer may be placed on processing stage
115
b.
However, during the loading and unloading sequence, the processing of the wafers inside the transfer chamber
105
must cease. Thus, throughput is greatly reduced because the wafers cannot be processed in parallel with the wafers being loaded and unloaded between the load lock chamber
125
and the transfer chamber
105
.
It was a common belief that if one sacrificed one of the process stages in the transfer chamber to act solely as a loading and unloading station, then a loss in throughput would occur. Therefore, all the previous continued to utilize all six wafer stages as processing stages and to separate the processing of wafers from the transferring of wafers into two events. It was also believed that if one introduced a complicated mechanism inside a process environment, it would create a contamination problem for the wafers. Thus, most of the complicated robotic mechanisms used were in the load lock chamber and not in the transfer chamber where the processing occurred.
Thus, what is needed is a wafer transfer mechanism inside the transfer chamber that will allow the wafer loading time to substantially parallel the wafer processing time in order to increase throughput at a reduced cost and without introducing contamination concerns into the process environment.
SUMMARY
The present invention describes an apparatus and method for processing a wafer in a transfer chamber, while at substantially the same time, another wafer is being transferred between a load lock chamber and the transfer chamber of a wafer transfer system.
According to a preferred embodiment, the wafer transfer system comprises a transfer chamber having a wafer transfer blade disposed within the transfer chamber, a load lock chamber coupled to the transfer chamber, and a slider which moves the wafer transfer blade between the transfer chamber and the load lock chamber while processing continues in parallel in the transfer chamber. The wafer transfer blade is capable of transferring a wafer between the transfer chamber and the load lock chamber.
According to another embodiment of the present invention a method of processing and transferring a wafer in a system comprising a load lock chamber and a transfer chamber having at least a stage (preferably six stages). The method comprises the following steps: providing radio-frequency (RF) power of a predetermined amount; providing a gas flow combined with RF power that will become a plasma with the desired ionic and/or neutral species; and determining a tact time, wherein the tact time is the sum of the processing time and the fin index time. The processing time is defined as the processing time that a wafer undergoes while on a processing stage. The fin index time is defined as the time that it takes for a first fin to transfer a wafer from one processing stage to another processing stage or between the wafer transfer blade and a processing stage. The loading time for the wafer substantially parallels the processing time and covers the following steps. First, the wafer transfer blade extends toward the load lock chamber to deposit the processed wafer into a shelf of the wafer holder. Second, the wafer transfer blade retracts. Third, the wafer holder indexes to the next wafer slot. Fourth, the wafer transfer blade extends and then the wafer holder indexes so that a new wafer is deposited on the wafer transfer blade. Finally, the wafer transfer blade retracts so that the new wafer is being processed in the transfer chamber. Thus, wafers are processed in the transfer chamber while new and processed wafers are transferred between the load lock chamber and the transfer chamber. The result is higher throughput, lower manufacturing costs, smaller space occupancy for the system and higher reliability.


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