INFICON XTC/C Thin Film Deposition Controller - Manual (Page 61)

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XTC/C - XTC/2 Operating Manual
2.7.4.4 Measurement of Liquids
The measurement of the mass of a liquid on the face of a crystal is a technique
that is subject to very large errors. The two primary problems with liquids are
that they are not infinitely rigid structures and do not necessarily form in uniform
layers. Because liquids do not oscillate as a rigid solid, not all of the mass
participates in the resonance. Consequently, not all of the liquid is detected. In
some ways, the crystal is more appropriately called a viscosity sensor. The
second problem is that liquids tend to form spheres on the face of the crystal
after only very modest accumulations of a few monolayers. This aggravates the
problem caused by non-infinite rigidity. Another aspect of the problem is that the
liquid spheres form at random locations across the crystal. Because monitor
crystals have differential radial mass sensitivity an uncontrollable measurement
problem exists. Spheres formed at the center of the crystal contribute more than
spheres formed near the edge of the sensor’s aperture.
2.8 Operation as a One Layer Controller
This instrument is designed to provide automatic deposition rate control with
thickness termination as well as pre and post deposition source conditioning.
Fully automatic operation requires that the instrument be interfaced with the
deposition source power supply controller and the source shutter. In addition,
the instrument interfaces to many other deposition system components through
the SYSTEM I/O and AUX I/O connectors.
To operate the instrument as a single layer controller it is necessary to program
the film sequence parameters. A film sequence begins with a START command
and ends when the same film reaches the "IDLE" state.
NOTE: A START command may be provided by pressing START or by
activating the START input on the system I/O connector.
All instrumental action that occurs between these events is determined by the
values programmed into the appropriate film specific parameters. Programming
the instrument is easily accomplished once you have made the determination
to monitor or control the process, chosen the type of material to deposit and its
required rate and thickness and have become familiar with the instrument
programming procedure. If you are familiar with the terminology of depositions,
it is only required that the desired values of each parameter be entered for the
designated FILM #.
A film is composed of many possible states, with a state being defined as one
process event. These states sequence in order and are defined and diagramed
in this manual in
Chapter 4, Programming System Operation Details . The
values used in the various parameters tell the instrument how to specifically
execute the deposition process, see
section 4.2 on page 4-6 for a description
of which parameters affect a given process state. Figure 2-21 on page 2-35 is
a generalized overview of the normal processing of a film and its source control.