Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
2002-11-01
2004-08-03
Larkin, Daniel S. (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
C073S040000, C073S049200, C073S049300
Reexamination Certificate
active
06769288
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to the field of plasma processes and, more particularly, to detecting leaks in systems utilized to perform such plasma processes.
BACKGROUND OF THE INVENTION
Plasma is used in various types of industrial-type processes in the semiconductor and printed wiring board industries, as well as in various other industries such as in the medical equipment and automotive industries. One common use of plasma is for etching away materials in an isolated or controlled environment. Various types of materials may be etched by one or more plasmas, including glasses, silicon or other substrate materials, organics such as photoresist, waxes, plastics, rubbers, biological agents, and vegetable matter, and metals such as copper, aluminum, titanium, tungsten, and gold. Plasma is also utilized for depositing materials such as organics and metals onto an appropriate surface by various techniques, such as via chemical vapor deposition. Sputtering operations may also utilize plasmas to generate ions which sputter away material from a source (e.g., metals, organics) and deposit these materials onto a target such as a substrate. Surface modification operations also use plasmas, including operations such as surface cleaning, surface activation, surface passivation, surface roughening, surface smoothing, micromachining, hardening, and patterning.
Plasma processes are typically conducted in a highly controlled environment, such as a sealed processing chamber. It is thereby desirable to avoid an introduction of impurities (e.g., air and/or water vapor) into the plasma processing system since any such impurity may have an adverse effect on one or more aspects of the plasma process. By way of example, impurities may enter a plasma processing system through one or more leaky seals. One conventional way in which at least the potential for leaks is detected is by monitoring pressure within the processing chamber. In the event that the system will not hold a vacuum or pressure at a desired level, an assumption may be made that this is due to an existence of one or more leaks. How the location(s) of these leaks is identified is typically quite cumbersome. Upon discovering that the system will not hold a vacuum or pressure at a desired level, a chamber of the plasma processing system is shut down (i.e., taken off line). The plasma processing system is subsequently “opened” to allow leak detection equipment (e.g., mass spectrometer) to be incorporated in an appropriate flow path. Thereafter, the system is once again sealed and helium is applied on one or more seals on the exterior of the system to detect a presence of helium within the corresponding chamber of the plasma processing system via the installed leak detection equipment. While such a leak detection protocol may enable leak detection, shut down of the system (sometimes accompanied by evacuation of the plasma from the system) typically results in fiscal and/or temporal inefficiency. It would thus be desirable to provide a leak detection system that increases the potential for minimizing and/or alleviating one or more of the above-mentioned drawbacks associated with conventional leak detection systems.
SUMMARY OF THE INVENTION
Accordingly, the present invention is generally directed to detection of leaks in a plasma system. Moreover, the present invention allows for accomplishing such leak detection while maintaining a plasma within the plasma system and optionally while a product (e.g., a wafer) is positioned within the corresponding plasma chamber. Herein, “maintaining” a plasma in the plasma system refers to avoiding intentional removal of the plasma from the plasma system. In other words, the plasma is generally not removed from the plasma system prior to leak detection. As another potential benefit, the present invention may be a portable (i.e., handheld) assembly for conducting such leak detection. Accordingly, when analysis of the plasma is desired to check for the presence of a leak, this portable device may simply be pointed at and looking through a window of the plasma system. Herein, “portable,” “portability,” and the like generally refer to a characteristic of the associated leak detection assembly which enables the same to be freely moved and/or carried about by a potential user. In other words, a potential user (e.g., engineer, operator, technician, or the like) may be able to carry a leak detection assembly of the invention with him/her in a tool box or on his/her clothing (e.g., on a tool belt or supported by a shirt/pant pocket).
A first aspect of the invention is generally embodied in a method of detecting a leak in a plasma system. This method of the first aspect generally includes maintaining a plasma in the plasma system and obtaining optical emissions spectral data of the plasma within the plasma system at least at a plurality of times while maintaining the plasma in the plasma system. The method also includes monitoring for an existence of air in the plasma while both maintaining the plasma in the plasma system and obtaining optical emissions spectral data of the same. If air is identified in the plasma, a first external surface of the plasma system is exposed to a test gas while maintaining the plasma in the plasma system. Optical emissions spectral data of the plasma can then be analyzed for the presence of the test gas (e.g., helium, neon, and/or argon) to determine if the first external surface to which the test gas was exposed is the location of the leak.
Various refinements exist of the features noted in relation to the subject first aspect of the present invention as well. Further features may also be incorporated in the subject first aspect of the present invention as well. These refinements and additional features may exist individually or in any combination. For example, monitoring the plasma for the existence of air may include comparing the optical emissions spectral data of the plasma with predetermined optical emissions spectral data of air. Moreover, the optical emissions spectral data indicative of air may be acquired and stored on a computer-readable storage medium (e.g., E-PROM, a floppy disk, compact disk, hard disk) to be utilized during monitoring the plasma for the existence of air.
Some embodiments in the case of the first aspect may include exposing a second external surface (i.e., different from the first external surface) of the plasma system to the test gas upon failing to identify a presence of the test gas in the plasma after the first external surface was exposed to the test gas. In other words, if the test gas is not detected within the plasma system within a reasonable time after exposing the first external surface to the test gas, the first aspect may include exposing the second external surface of the plasma system to the test gas. Upon exposure of the second external surface of the plasma system to the test gas, the plasma is once again analyzed to determine if the test gas is present therein. This may be repeated until the leak has been located or until all external surfaces have been tested in this general manner. In some embodiments, any product (e.g., a wafer or chip precursor) originally disposed within the plasma system may be removed prior to exposing any external surfaces of the plasma system to the test gas. However, other embodiments provide for any product originally disposed within the plasma system to remain there while the external surface(s) is exposed to the test gas. In other words, in these other embodiments, a product may be located within the plasma system, and a plasma process may be running while the external surface(s) is exposed to the test gas for leak detection purposes.
In the case of the first aspect, a leak detector may be utilized for comparing the optical emissions spectral data of the plasma with spectral data of air stored on the leak detector and/or for comparing the optical emissions spectral data of the plasma with spectral data of the test gas stored on the leak detector. So, the leak detector may oper
Smith, Jr. Michael Lane
Stevenson Joel O'Don
Ward Pamela Peardon Denise
Larkin Daniel S.
Marsh & Fischmann & Breyfogle LLP
Peak Sensor Systems LLC
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