INFICON STC-2000A Thin Film Deposition Controller Operating Manual - Manual (Page 23)

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STC-2000A DEPOSITION CONTROLLER
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SIMPLE QUICK GENERALIZED OVERVIEW
SECTION 2.0
The STC-2000A addresses the needs of thin film deposition within the vacuum coating industry.
The main function of the STC-2000A is to provide the means for a controlled and repeatable process,
which is the deposition of material on a target surface.
[ process in which material is deposited on a target
surface.
Without such control, the power [supplies] used to start (or stop) the generation of deposits could be
switched on (or off) at human reaction speeds. Once on, the power [supply] outputs could be altered to vary
the deposit rate, again at human reaction speeds. From the human perspective, the relatively brief time
intervals typically required would be unwieldy at best for accurate control of even a slow process. This
kind of direct human control also assumes that a time versus deposition rate and final thickness is known
for the various deposited materials. Factor in the many physical elements that effect deposition and the
system user, with only time based control, would find it extremely difficult at best for even slowly
accumulating thick depositions, and, for thin depositions, impossible to obtain the desired results, much
less the consistent desired results. The first need is to at least monitor the deposition and know the
thickness (and rate) at any point in time. The next is to be able to control the process based on the
monitored information in real time such that the reaction time between monitor and control is at the needed
speeds. Fortunately, the needed monitor/calculation/control speed is easily within the range of a
moderately priced microprocessor.
The STC-2000A has a microprocessor: on the sensor card and on the communications/control/database
/user interface board (includes interconnected displays, keys, touchscreens, etc.). This multiprocessor
approach provides greater bandwidth and dedication to specialized functions with obvious benefits: speed,
control, etc. The microprocessors used are actually microcontrollers, which can include A/D, D/A,
communications, etc. thus providing cost savings and greater reliability because of the higher degree of
integration.
Along with an oscillator and crystal sensor(s), the STC-2000A instrument is the basis of process control
and repeatability within a material deposition system. The STC-2000A can be used to monitor and control
the process manually, or to monitor and control the process automatically.
Utilizing the inherent flexibility of the STC-2000A, there are many possible levels of manual control
(requiring human intervention at user determined points in the process). This is also true of the automatic
process mode. During an automated process, for example, an input state or some other condition can be
made to pause the process for user inspection. If satisfactory, the automated process can be resumed by
another preprogrammed user input. In addition, reactions between monitor and control (response time,
overshoot control, etching vs. depositing, etc.) can be tailored to meet various requirements by user
programmable parameters (discussed in PID control section).
The material deposited on the target may be from a single element or a compound (alloy) to create single or
multilayered metal deposits, lens coatings, the creation of an alloy combination that has special properties,
metalized plastic, etc. The products range from sunglasses, jewelry, automotive decoration, CDs at the low
end to optical lenses, mirrors, filters, semiconductors, superconductors, metallurgical research, etc. at the
high end.
SECTION 2.XX page 23 of 292