INFICON XTC/C Thin Film Deposition Controller - Manual (Page 63)

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XTC/C - XTC/2 Operating Manual
second to 4% per second over 4 seconds and then held at a constant 4% per
second. This feature is designed to allow fine adjustment of the control voltage
when needed, while also allowing rapid control voltage adjustment if desired.
2.8.4 Time Power State Overview
The time power state will only be entered while the instrument is in the
DEPOSIT or RATE RAMP state and the film program has been set to complete
on time-power in the event of a failed crystal. If a crystal fail is detected during
the pre-deposit states the instrument will not sequence further, causing an
instrument STOP even if the complete on TIME-PWR (Y) option is selected.
Once in the TIME-POWER state, the source power will remain at the 5 seconds
average power value of the source control output computed 2.5 seconds prior
to the failure. (These times are appropriately modified for PID control.)
Thickness is accumulated at the programmed DEP RATE value. The
time-power state will terminate when the FINAL THK value has been exceeded.
Any post-deposit states will be executed exactly as if a normal deposition had
occurred. The TIME-PWR annunciator will remain on the display. When the
post-deposit states are complete, the instrument will enter the STOP state. A
RATE RAMP cannot be executed in TIME-POWER and that state is
consequently skipped.
Figure 2-21 State Processing for a Film
2.8.5 Controlling the Source Overview
Stable rate control during the DEPOSIT state requires the proper setting of the
following control loop algorithm adjusting parameters: CTL GAIN, CTL TC, and
CTL DT. By properly adjusting these parameters it is possible to control sources
of nearly any physical characteristic by employing either a PID or integrating
algorithm. The proper adjustment technique and a detailed algorithm
description is covered in
4.5, Tuning the Control Loop .