Find end point of CLF3 clean by pressure change

Details Find end point of CLF3 clean by pressure change Find end point of CLF3 clean by pressure change

1998-12-07

2001-02-13

Mills, Gregory (Department: 1763)

Cleaning and liquid contact with solids

Processes

Including application of electrical radiant or wave energy...

C134S021000, C134S022100, C438S005000, C216S059000, C216S079000

Reexamination Certificate

active

06186154

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to semiconductor manufacturing, and more specifically to end-point detection for the cleaning process of cleaning Chemical Vapor Deposition chambers.
DESCRIPTION OF THE PRIOR ART
The semiconductor industry is continually striving to increase the performance of semiconductor chips while maintaining or striving to decrease the cost of semiconductor chips. These objectives have been successfully addressed by the trend to micro-miniaturization and of the ability to produce chips with sub-micron features.
The attainment of micro-miniaturization has been aided by the advances in specific semiconductor fabrication disciplines, basically photolithography and dry etching. The use of more sophisticated exposure cameras, as well as the use of more sensitive photo-resist materials, have allowed sub-micron features to be routinely achieved in photo-resist layers. In addition, the development of dry etching tools and procedures have allowed the successful transfer of the sub-micron images, in an overlying photo-resist layer, to an underlying material that is used in the fabrication of semiconductors. The tools and procedures used during Reactive Ion Etching (RIE) now allow single wafer etching to be performed. This allows each single wafer to be etched individually, with end point detection used for only this single wafer. Thus wafer to wafer uniformity variations, of the layer being patterned using single layer RIE etching, is not as great a problem as encountered with batch RIE etching. Thus large volumes of wafers can be confidently processed using single wafer RIE procedures, with a decreased risk of under or over-etching due to thickness variations of the material being etched.
A major limitation of dry etching procedures is the ability to maintain a strong end point detection signal from wafer to wafer. With the use of single wafer RIE tools, the wafer being etched is moved to the etch chamber of the single wafer RIE tool, which also contains a window, which allows the monitoring of the etching sequence. Laser endpoint detection apparatus monitors the chemistry of the reactants and by-products, through this window. At the conclusion of the etching cycle the chemistry of the by-products will change, and the end-point detection process will monitor this change. If however the window through which the endpoint monitoring takes place becomes layered with adhering RIE products, the endpoint detection signal will decrease in intensity which can at times result in erroneous end-point signals.
The present invention will describe a process for finding the endpoint for a Chemical Vapor Deposition tool cleaning procedure by monitoring the change in the pressure within the cleaning chamber. The present invention is therefore directed towards the cleaning of sensors or endpoint detection windows.
U.S. Pat. No. 5,584,963 (Takahashi) shows a method to clean a CVD reactor.
U.S. Pat. No. 5,604,134 (Chang et al.) teaches a particle monitor method for reactors.
U.S. Pat. No. 5,753,137 (Ye et al.) shows a CVD chamber cleaning process.
U.S. Pat. No. 5,679,214 (Kuo) discloses an endpoint detection for a dry clean process for a RIE tool.
U.S. Pat. No. 5,387,777 (Bennett et al.) teaches a process for cleaning plasma tools.
U.S. Pat. No. 5,643,364 (Zhao et al.) shows a plasma chamber with a endpoint etch detector.
SUMMARY OF THE INVENTION
In accordance with the present invention, it is an objective of the present invention to provide a method for end-point detection for cleaning CVD chambers.
Another objective of the present invention is to reduce the usage of cleaning gas during the cleaning of CVD chambers.
Yet another objective of the present invention is to prolong the lifetime of CVD processing kits.
In accordance with the objective of the present invention, the invention teaches a method to identify the end-point for the CVD cleaning operation by monitoring the pressure within the cleaning chamber. Experiments have shown that the degree of cleaning of a CVD chamber can be predicted by monitoring the pressure within the chamber.
If the cleaning cycle is started with a clean CVD chamber, the pressure within the chamber remains constant during a repeat cleaning cycle. If the cleaning cycle is started with a CVD chamber into which first a light coating of the cleaning gas has been deposited, the pressure increases during the cleaning cycle. If the cleaning cycle is started with a CVD chamber into which first a heavier coating of the cleaning gas has been deposited, the pressure again increases during the cleaning cycle but this time at a slower rate than in conditions of a light initial coating. The conclusion from these experiments is that as soon as there are no more impurities within the CVD chamber, the pressure within the chamber takes on a constant value. Inversely than, by monitoring the pressure within the chamber and by detecting the point in time where the pressure is stable, it can be concluded that the chamber cleaning process has been completed.


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