INFICON IC/5 Thin Film Deposition Controller - Manual (Page 89)

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IC/5 Operating Manual
4 Unable to detect anharmonic frequency.
As mass is deposited onto the crystal, the oscillation is damped. This damping
may be severe enough that the resonance can no longer be determined. If the
instrument loses the ability to measure the first anharmonic frequency, but is
still able to determine the fundamental frequency, the “unable to Auto Z”
message is displayed. The instrument will then continue to use the fundamental
frequency to monitor the deposition.
If the instrument loses the ability to measure the fundamental frequency, the
“XTAL fail” message is displayed.
Unable to Auto Z
An “unable to Auto Z” condition occurs whenever:
 The anharmonic frequency cannot be measured.
 The fundamental and anharmonic frequencies of the monitor crystal have
not been continuously measured from the uncoated to the coated state.
3.6.4 Auto Tune - Optimizing the Control Loop
The control loop parameters can often be calculated automatically by the IC/5. This
is done by using the AutoTune feature. For a detailed description of AutoTune, see
section 12.6 on page 12-11 .
3.6.5 Rate Watcher
The IC/5 includes a sample and hold function which enables periodic sampling of
the deposition rate by opening and closing the sensor shutter. If you are controlling
inherently stable deposition sources, this function is useful in maximizing crystal
life. When RateWatcher is enabled, during deposit, rate control will be established.
Then the sensor shutter will close for a designated amount of time. The shutter will
once again be opened to validate and adjust the power level. This procedure is
repeated throughout the deposition. Two process parameters - RateWatch time
and RateWatch accuracy - control this function. See
section 5.3 on page 5-4 for
details on programming these parameters.