Cleaning and liquid contact with solids – Processes – Using solid work treating agents
Reexamination Certificate
2000-12-21
2004-05-11
Kornakov, Mikhail (Department: 1746)
Cleaning and liquid contact with solids
Processes
Using solid work treating agents
C134S019000, C134S026000, C134S030000, C134S034000, C134S902000, C216S067000, C438S906000, C438S928000, C015S021100
Reexamination Certificate
active
06733594
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to apparatus and methods for processing substrates such as semiconductor substrates for use in IC fabrication or glass panels for use in flat panel display applications. More particularly, the present invention relates to improved techniques for reducing He backside faults during wafer processing.
FIG. 1A
illustrates a typical processing module
100
for processing a wafer
112
. The processing module
100
generally includes a chamber
114
within which processing takes place, and a chuck
116
for holding the wafer
112
during processing. The processing module
100
also includes a gas inlet port
118
for releasing gaseous source materials, i.e., etchants, into the chamber
114
, and a gas exhaust port
120
for exhausting by-product gases formed during processing. The exhaust port
120
is typically coupled to a pump (not shown) that maintains the appropriate pressure inside chamber
114
.
The chuck
116
also includes a heat transfer system
122
for controlling the temperature (e.g., cooling) of the wafer
112
during processing. As shown, the heat transfer system
122
is generally configured for distributing He gas to a backside
113
of the wafer
112
. In most cases, the heat transfer system
122
includes a mass flow controller
124
, a main channel
126
, and a plurality of outlet channels
128
. The mass flow controller
124
delivers He gas (under pressure) to the main channel
126
and the main channel
126
distributes the He gas to the plurality of outlet channels
128
, which then distributes the He gas to the backside
113
of the wafer
112
. The He gas then exits out the side of the chuck
116
(as shown by arrow
129
) where it is exhausted through exhaust port
120
. As should be appreciated, the He gas acts as a heat transfer medium for accurately controlling the temperature of the wafer
112
during processing so as to ensure uniform and repeatable processing results.
A pressure sensor
132
and a controller
134
is also provided to continuously monitor the pressure of the He gas, and adjust the mass flow controller
124
accordingly. For example, the controller
134
, via a measurement signal from the pressure sensor
132
, generally sends a command signal to the mass flow controller
124
to adjust the He flow so as to maintain a set point pressure at the backside of the wafer
112
. In most cases, the set point pressure is maintained throughout a processing task, however, in some cases an He backside fault may be formed when the pressure is too low and/or the flow rate is too high (e.g., base on predetermined limits). By way of example, an He backside fault may occur when an excessive amount of He gas flows out the side of the chuck
116
. The He backside fault is typically formed to stop processing so as to prevent undesirable and/or unpredictable gas pressures and gas chemistries from forming in the chamber
114
. As should be appreciated, undesirable and/or unpredictable gas pressures and gas chemistries may lead to process drift and/or process failure.
He backside faults, which are caused by excessive He flow, generally occur when the backside of the wafer does not seat properly on the top surface of the chuck, i.e., the backside of the wafer is offset or de-chucked relative to the top surface of the chuck. By way of example, a gap may be formed between the wafer backside and the chuck top surface allowing a greater amount of He gas to escape. As should be appreciated, the escaping gas tends to cause the pressure to decrease and thus the mass flow controller (via the pressure sensor and controller) increases the flow rate of the outputted He gas. It has generally been found that gaps are formed when the wafer is warped or when particles are trapped between the chuck and the wafer. With regards to trapped particles, the particles may be dust, polymer deposits and/or excess photo-resist that has accumulated or collected on the backside of the wafer and/or top surface of the chuck during prior processing steps and/or transfers.
To facilitate discussion,
FIG. 1B
illustrates the processing module
100
with a gap
136
formed between the bottom side
113
of the wafer
112
and the top surface
117
of the chuck
116
. By way of example, the gap
136
may be formed when a particle
138
is trapped between the bottom side
113
of the wafer
112
and the top surface
117
of the chuck
116
. As shown, the particle
138
does not allow the wafer
112
to sit flat. In most cases, the gap
136
tends to cause the He gas to escape more readily thus creating excessive He flow (shown by the larger arrow
139
). As should be appreciated, the excessive He flow tends to trigger He backside faults.
Conventional methods for overcoming the He backside faults have included clearing the alarm and resuming processing, removing the wafer from the processing module and reprocessing it in the same module at a later time, removing the wafer from the processing module and reprocessing it in a different module at a later time, and/or removing the wafer from the processing module and determining what is causing the error, i.e., polymer deposits, warp, dust, etc. In the later method, if it is determined that dust was the culprit, then the wafer may be cleaned in a water based solution and reprocessed in the same or a different module. If it is determined that photo-resist or polymer deposits are the culprit, then the entire wafer may be stripped in a solvent solution and re-patterned before reprocessing it in the same or a different module.
Unfortunately, however, He backside faults, as well as the aforementioned methods, stop the processing module from continuously running and thus a significant amount of tool downtime may be created. As should be appreciated, downtime leads to a loss in productivity and thus increased costs. For example, the He backside faults may prevent an entire wafer lot from completing that particular processing step and steps that may occur thereafter. By way of example, it may take an operator about 0.25 hours to about 1 hour to clear an He backside fault alarm. In addition, it may take an operator about 0.25 hours to about 2 hours to resume processing or to remove the wafer from the processing module. Further, it may take about 0.5 hours to about 48 hours to make a determination of the problem, clean the wafer, re-pattern the wafer and/or reprocess the wafer.
In view of the foregoing, there are desired improved techniques for reducing He backside faults during wafer processing.
SUMMARY OF THE INVENTION
The invention relates, in one embodiment, to a method of processing a wafer. The method includes receiving a wafer having a process side and a backside. The method further includes removing un-wanted particles from the backside of the wafer. The method also includes performing a specific processing task on the process side of the wafer after cleaning the backside of the wafer. In most embodiments, the unwanted particles are removed from the backside of the wafer to prevent gaps from forming between the backside of the wafer and a chucking surface.
The invention relates, in another embodiment, to a method of processing a wafer having a process side and a backside opposite the process side. The method includes providing a cleaning module for cleaning the backside of the wafer and a processing module for performing a processing task on the process side of the wafer. The method further includes receiving a wafer for processing. The method additionally includes loading the wafer into the cleaning module and cleaning the backside of the wafer to remove particles therefrom. The method also includes transferring the wafer to the processing module. The method further includes loading the wafer into the processing module and performing the processing task on the process side of the wafer.
The invention relates, in another embodiment, to a system for reducing He backside faults when processing a wafer having a process side and a backside opposite the process side. The system includes a cleaning mo
Beyer Weaver & Thomas LLP
Kornakov Mikhail
Lam Research Corporation
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