INFICON Sputtering Sensor - Manual (Page 41)

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Sputtering Crystal Sensor Operating Manual
Chapter 4
Maintenance
4.1 General Precautions
4.1.1 Handle the Crystal with Care
Always use clean nylon lab gloves and clean plastic tweezers when handling the
crystal. Handle the crystals only by their edges. Anything that comes in contact with
the crystal surfaces may leave contamination, which may lead to poor film
adhesion. Poor film adhesion will result in high rate noise and premature crystal
failure.
CAUTION
Do not use metal tweezers to handle crystals. Metal
tweezers may chip the edge of the crystal.
4.1.2 Maintain the Temperature of the Crystal
Periodically measure the water flow rate through the crystal sensor to verify that it
meets or exceeds the value specified on
see page 1-1 . Depending upon the
condition of the cooling water used, the addition of an in-line water filtering
cartridge system may be necessary to prevent flow obstructions. Many system
coaters use parallel water supply taps that provide high total flows. An obstruction
or closed valve in the pipe that supplies water to the sensor head would not result
in a noticeable reduction of total flow. The best test is to directly monitor the flow
leaving the sensor.
The crystal requires sufficient water cooling to sustain proper operational and
temperature stability. Ideally, a constant heat load is balanced by a constant flow of
water at a constant temperature. INFICON’s quartz crystals are designed to
provide the best possible stability under normal operating conditions. No crystal
can completely eliminate the effects of varying heat loads. Sources of heat
variation include radiated energy emanating from the evaporant source and from
substrate heaters.
4.1.3 Use the Optimum Crystal Type
Silver crystals are recommended for sputtering applications. Certain materials,
especially dielectrics, may not adhere strongly to the crystal surface and may
cause erratic readings. For many dielectrics, adhesion is improved by using
crystals with silver coated electrodes. Gold is preferred for other applications.