INFICON Sputtering Sensor - Manual (Page 29)

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Sputtering Crystal Sensor Operating Manual
Figure 2-3 Suggested Sensor Locations in Sputtering System
Because of geometric factors, variations in surface temperature, and differences in
electrical potential, the crystals and substrates often do not receive the same
amount of material. If you want the thickness indication on the unit to represent the
thickness on the substrates, calibration is required to determine the tooling. Refer
to the instrument manual for calibration procedures. The following precautions
must be observed when installing the sputtering sensor.
1 Use water cooling during the sputtering process. Approximately 0.2 gpm (750
cc/min) at 30 °C maximum temperature water flow should be sufficient for most
applications. Always check the water flow before starting the glow discharge.
2 In sputtering systems which use a substrate shutter, the sensor should be
mounted in a location where it is always exposed to glow discharge. If it is not,
and the shutter is covering the sensor, there will be a small thickness jump
when the shutter is opened, caused by thermal stress in the crystal.