INFICON STC-2000A Thin Film Deposition Controller Operating Manual - Manual (Page 24)

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STC-2000A DEPOSITION CONTROLLER
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SECTION 2.1
how is it used ?
First, a few terms and their definitions are needed.
The material to be deposited shall be alternately and henceforth referred to in this manual as an evaporant
source.
The target surface shall be alternately and henceforth referred to as a substrate.
The material is known as an evaporant when it has reached sufficient temperature/excitation to leave the
surface of the source material supply prior to deposition. The STC-2000A automatically, as it monitors
material deposition rate and thickness, controls the power that generates the evaporant within the bounds of
the user-defined parameters and other programming. The STC-2000A is programmed through an LCD
screen with a touch panel overlay. All choices are made within groups of predetermined menu selection
alternatives or, as in the case of some data entries, bounded by a screen specified range with software
enforcing the range of entry acceptance.
With the crystal sensor[s] in the same space as, but not necessarily in relative close proximity to, the
substrate, the crystal sensor[s] should accumulate the same amount (or a ratio) of deposited material as the
substrate. As the crystal frequency is proportionally related to a deposited mass (within specific bounds),
thickness on a substrate can be inferred and deposition rate can be calculated based on thickness values
through the progression of time.
[For additional information, search the web using "quartz crystal microbalances".]
Other dependent factors such as the type of material deposited (as reflected in material density and z factor)
and the physical positioning of the crystal sensor[s] (see tooling factor discussion) are also part of the
deposition calculations and are included among the user programmable parameters of the STC-2000A.
In a typical case of evaporant stream generation, a high current (or high voltage) power supply is used to
heat the material in a boat, crucible or coiled filament. This power supply is controlled by the control
output voltage of the STC-2000A sensor card. This power supply can thus be controlled through the STC-
2000A either manually or automatically. Manual mode can be used to setup the system before the auto
mode is employed. The power supply, in this case, is manually controlled while the deposition is
monitored. In non-sequencing mode (defined shortly), the final thickness parameter can be set to terminate
the process when reached (evaporant source shutter closure). The power could be switched off via an
output relay (a poor man's controller). In the auto mode (sequencing mode), a user programmable PID loop
can be used for process monitor/power supply control with a relatively high degree of precision based on
needed system speed elements. All methods of evaporant stream generation need power supply control. A
power supply that is controlled by the STC-2000A typically provides thermal excitation of the target
material by laser, electron beam (accurate control), resistance heating (low cost/complexity) or sputter
(large area) deposition, each process type having favorable attributes for specific process goals.
Regarding higher level system control, the STC-2000A can be programmed to function in this capacity
(keeping in mind failsafe measures). [On a higher level of system control].
Using one of the four user programmable fixed front panel keys and output relays, gates/valves could be
closed and pumps could be activated as a prelude to the previously described automated process. A
pressure monitoring device would signal the STC-2000A through an opto-input when the pressure was
correct and the automated deposition would begin. One of the user programmable front panel indicators
could be used to show this and that of other points during the process had been reached.
SECTION 2.XX page 24 of 292