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JUNE 26 MONDAY MORNING
MoM-Pl.1 QUALITY VACUUM MEASUREMENTS FOR PROCESS APPLICATIONS.
Charles R. Tilford, Independent Consultant, Gaithersburg, MD USA, CharlesTilford@Verizon.net
Vacuum technology is a rapidly maturing field with many industrial applications. This does not
mean an end to vacuum science investigations and technical development. However, it does mean
an increasing focus on the needs of large-scale processes, whether they are producing energetic particles
or consumer products. In addition, more of a focus on quality—fitness for purpose—whether
the vacuum contribution is hardware, measurements, or techniques. This process is already underway—witness
the change in vacuum equipment to meet the particular needs of the semiconductor
processing industry. But much more needs to be done and the vacuum community will be increasingly
called upon to apply their expertise outside of their own field of interest. There are many ways
of doing this, training courses and documentary standards for example. But there are times when it
is most useful for the vacuum specialist to directly collaborate with equipment manufacturers and
users of vacuum-technology. Because of the large variety of applications, and different backgrounds
of the users, this process can be difficult. But the benefits of such collaborations can be very great,
and such collaborations are already quite common in the vacuum equipment area. With the growing
complexity of vacuum processes and the importance of measurements for process control, it is probable
that there will more instances where the specialized knowledge and experience of vacuum
measurement specialists will be a welcome addition.
Direct participation in problem solving outside of their own field will be a new experience for some
vacuum measurement experts. But this is just the latest step in the evolution of vacuum measurements
and standards. This field started with the need to measure ever-lower pressures. Accuracy, to
the extent that it was ever considered, generally was with respect to a local reference—the “magic”
reading that produced an acceptable product, or agreement with a “standard” gauge. With the
growth of global trade and manufacturing this is no longer acceptable and vacuum measurements
must now be established with respect to the internationally accepted measurement system (the SI).
A great deal of progress has been made in establishing primary vacuum standards and calibration
systems, and ensuring international compatibility. But while proper calibration of an instrument with
respect to the SI is necessary, it is not sufficient to ensure that quality measurements are available for
the end use. It is also necessary that the calibrated instrument be stable, environmental influences
are understood and properly accounted for, the end user is able to properly operate the instrument,
and the entire process is affordable. Vacuum measurements are also especially susceptible to application
effects; where the vacuum instrument is located within the process can be critical, as can the
mix of gases present. The vacuum specialist cannot resolve all of these issues, but in many cases
their participation will be essential if effective solutions are to be devised.
This talk will include a broader discussion of these issues, some examples of past efforts of this type,
and a discussion of vacuum instrumentation characteristics that should be considered in resolving
real world problems. This will include discussion of reference leaks, Spinning Rotor Gages and Residual
Gas Analyzers.
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