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Easy Rate Sensor
PN 074-677-P1A
Installation
Install the sensor as far as possible from the evaporation source (a minimum of 25.4 cm
(10 in.)) while still being in a position to accumulate thickness at a rate proportional to
accumulation on the substrate.
shows proper and improper methods of
installing sensors.
Figure 2 Proper and improper methods of installing sensors
NOTE:
For best process reproducibility, rigidly support the sensor by the #4-40 screw
mounting holes on the back of the sensor so it cannot move during maintenance
and crystal replacement.
To guard against spattering, use a source shutter to shield the sensor during initial soak
periods. If the crystal is hit with even a minute particle of molten material, it may be
damaged and stop oscillating. Even in cases when it does not completely stop
oscillating, it may immediately become unstable or, shortly after deposition begins,
instability may occur.
Plan the installation to ensure there are no obstructions blocking a direct path between
the sensor and the source. Install sensors in such a manner that the crystal face is aimed
directly at the source to be monitored. Verify that the angle of the sensor location (with
reference to the source) is well within the evaporant stream. If the sensor is not
perpendicular to the source, the coating on the crystal will be tapered and shortened
crystal life can result.
