Browse Prior Art Database

Direct Cooling Technique for Quartz Deposition Monitors

IP.com Disclosure Number: IPCOM000122635D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 67K

Publishing Venue

IBM

Related People

Kanazawa, KK: AUTHOR [+2]

Abstract

The quartz resonator is ubiquitously used as the transducer for monitoring deposit thickness and deposition of stripping rates in a variety of materials preparation environments. Its frequency is monitored as the measured variable. Unfortunately, the frequency is also sensitive to the temperature of the resonator and inadvertent heating of the crystal can give rise to significant errors in measurement. Disclosed is a method of directly cooling the quartz resonator to minimize heating of the crystal by nearby thermal sources such as evaporation boats.

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Direct Cooling Technique for Quartz Deposition Monitors

      The quartz resonator is ubiquitously used as the
transducer for monitoring deposit thickness and deposition of
stripping rates in a variety of materials preparation environments.
Its frequency is monitored as the measured variable. Unfortunately,
the frequency is also sensitive to the temperature of the resonator
and inadvertent heating of the crystal can give rise to significant
errors in measurement. Disclosed is a method of directly cooling the
quartz resonator to minimize heating of the crystal by nearby thermal
sources such as evaporation boats.

      The heating problem is sufficiently important that cooled
crystal mounts for the quartz crystals are commercially available.
The mount for the quartz crystal must be made such that the active
surfaces of the disc-shaped resonator remain free to move.  That is,
no mechanical contact to these surfaces can be made without impairing
the motion of the crystal.  The crystals are frequently mounted in
metallic cans with the active surfaces free.  The metal can is cooled
using a heat exchanger to a moving fluid.  The cooling of the quartz
is inefficient, relying primarily on indirect radiative cooling.

      Contrary to popular belief, the quartz resonator can be
operated even when interfaced to a liquid (1).  While the quality
factor, or Q, of the resonator is degraded typically from values of
100,000 down to a few thousand, the sensitivity to mass...