INFICON STC-2002 Thin Film Deposition Controller Operating Manual - Manual (Page 33)

p STC-2002 DEPOSITION CONTROLLER y
SECTION 2.XX e page 31 of 276 ^
sensor should be covered to prevent deposition on its surface. Typically a metal shutter (that can be
controlled by an STC-2002 output card and solenoid) is moved remotely to cover or expose the crystal
surface and/or the evaporant source. The STC-2002 also has a user programmable shutter delay. Tapped
holes are provided on the sensor body for mounting the shutter assembly and/or a mounting bracket to
secure the sensor from movement. The sensor body can be opened so that the crystal can be replaced. A
"solenoid assembly" is used to provide the compressed air to the shutter and can be electrically controlled
by one of the STC-2002 output relays. There are available manual shutters activated through a
feedthrough.
The sensor head has a minimum distance to the evaporant source of 10 inches to preclude being struck by
larger droplets that which in turn results in incorrect or no readings. These droplets are not part of the
evaporant stream and are therefore meaningless to the deposition process measurement. The maximum
distance is that which keeps [maintains] the crystal sensor within the evaporant stream. The crystal sensor's
deposition surface should be perpendicular to the evaporation source. The sensor mounting must not be
free to move or vibrate. If the rigidity of the pipes is not sufficient, secure the sensor with a mounting
bracket and screws into the sensor's mounting holes. The evaporant stream needs a clear path (line of sight)
to the crystal sensor's deposition surface otherwise intervening physical elements could cast a shadow in the
evaporant stream.
Water Coolin
Microdot Coaxial Connec
#4-40 Tap -- 4 holes
Equally Spaced
on o0.731 B.C.
The crystal sensor has a pipe bent around most of its circumference for the purpose of transferring heat
away from the crystal. Water is sent through the pipe at a specified minimum flow rate to ensure proper
cooling. The water lines are typically cut and bent to suit the needs of the chamber interior. The pipes, as
previously noted, also provide mechanical support for the sensor. Sensor pipes can be TIG welded or silver
soldered to feedthrough pipes. Swagelok compression fittings are an alternative to welding or soldering that
allow the easy connect/disconnect of pipes (the long pipes attached to the crystal sensor pass through the
Swagelok equipped feedthrough pipes). Covering the pipes and sensor cable as a group with fresh clean
aluminum (or other metal) foil helps dissipate heat from the cable thus allowing higher temperature usage
while minimizing cable movement. This also keeps deposition materials off the pipes and cable for a
cleaner environment when the foil is changed frequently.
Caution
CAUTION Ensure that the water lines are clear of obstructions and restricting bends before
operating the sensor above room temperature. (water flow rate details are in section X?.)
Crystal Sensor Variations: The so called "right angle" crystal sensor has the microdot connector
emerging from the bottom flat surface along with the water cooling pipes (there are no shutter mounting
holes on this unit). The so-called "Bakeable" crystal sensor has fixed length water pipes between the
sensor body and a thick metal disc, which fits into a flange. Also between the sensor body and the thick
metal disc, is a rigid fixed length tubing that houses the electrical connection to the crystal (this allows