INFICON IC6 Thin Film Deposition Controller - Manual (Page 127)

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IC6 Operating Manual
RateWatcher™ Sample and Hold Feature
Two parameters, Ratewatcher Time and Ratewatcher Accuracy, define the Sample
and Hold feature. When enabled by selecting RateWatcher Option = Yes, this
feature periodically samples the deposition rate by automatically opening the
sensor shutter and exposing the sensor to the deposition source. The power is
adjusted so the actual rate is set to the desired rate. The sensor shutter is then
automatically closed and power is held constant at the adjusted level. A five second
time delay for thermal stabilization occurs between opening the shutter and taking
measurements. During this time, DELAY is displayed in the IC6 message area.
The RateWatcher Sample phase uses the measured deposition rate to control the
source power. When the deposition rate meets the requirements of the
RateWatcher Accuracy parameter, the RateWatcher Acceptance Window Time is
started. If the rate falls out of the RateWatcher Accuracy requirement, the
RateWatcher Acceptance Time Interval is reset to zero.
If the deposition rate meets the RateWatcher Accuracy requirement for the duration
of the Acceptance Window Time, the sensor shutter is closed and RateWatcher
enters Hold phase for the RateWatcher Time duration.
Finally, after the Hold Time has elapsed, RateWatcher will enter a 5 second Delay
phase. During the Delay phase, the crystal is exposed to the deposition, but the
accumulated rate and sustained power are that from the previous Hold phase. This
Delay phase allows the crystal to thermally stabilize to the deposition before
re-entering the RateWatcher Sample phase.
The RateWatcher Sample Acceptance Window Time (that is, the length of time that
the rate must be within the accuracy range before going into hold) will be calculated
as follows:
Time
Power Avg
Time
Rate Filter
Time
RateWatcher
Sample
Acceptance
Window Time
Rate and Power Averages Used
0 min < 10 s 5 s 2.5 minus 0.5 second averages
0 min 10 s 10 s 2.5 minus 0.5 second averages
1 min anything 60 s 2.5 minus 0.5 second averages
> 1 min anything Average Time
* 60 seconds
Average of minute averages (as with Time Power)
of Average Time - 1 minute