INFICON SQM-242 Thin Film Deposition Controller Card Operating Manual - Manual (Page 61)

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SQM-242 Operating Manual
4. Crystal oscillates in
vacuum but stops oscillation
after open to air. a. Crystal was near the end
of its life; opening to air
causes film oxidation which
increases film stress. a. Replace crystal.
b. Excessive moisture
accumulates on the crystal. b. Turn off cooling water to
sensor prior to venting, flow
warm water through sensor
while chamber is open.
5. Thermal instability: large
changes in thickness reading
during source warm-up
(usually causes thickness
reading to decrease) and
after the termination of
deposition (usually causes
thickness reading to
increase.) a. Inadequate cooling
water/cooling water
temperature too high. a. Check cooling water flow
rate, be certain that cooling
water temperature is less
than 30°C; refer to
appropriate sensor manual.
b. Excessive heat input to the
crystal. b. If heat is due to radiation
from the evaporation source,
move sensor further away
from source and use silver
crystals for better thermal
stability; install radiation
shield.
c. Crystal not seated properly
in holder. c. Clean or polish the crystal
seating surface on the crystal
holder.
d. Crystal heating caused by
high energy electron flux
(often found in RF
sputtering.) d. Use a sputtering sensor
head.
e. Poor thermal transfer
(Bakeable.) f. Use Al or Au foil washer
between crystal holder and
sensor body.
Table 7-2 Troubleshooting Sensors
SYMPTOM CAUSE REMEDY