INFICON Cygnus Thin Film Deposition Controller - Manual (Page 159)

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Cygnus Operating Manual
Chapter 7
Calibration Procedures
7.1 Importance of Density, Tooling and Z-Ratio
The quartz crystal microbalance is capable of precisely measuring the mass added
to the face of the oscillating quartz crystal sensor. The instrument's knowledge of
the density of this added material (specified in the density parameter in the Channel
Parameters set up) allows conversion of the mass information into thickness. In
some instances, where highest accuracy is required, it is necessary to make a
density calibration as outlined in
section 7.2 .
Because the flow of material from a deposition is not uniform, it is necessary to
account for the different amount of material flow onto the sensor compared to the
substrates. This factor is accounted for in the tooling parameter in Channel
Parameters set up. The tooling factor can be experimentally established by
following the guidelines in
section 7.3 .
In the Cygnus if the Z-ratio is not known, it could be estimated from the procedures
outlined in
section 7.4 , or, typically, the Auto Z function can be used to determine
the Z-ratio.
7.2 Determining Density
NOTE: The bulk density values retrieved from the Material Library are sufficiently
accurate for most applications.
Follow the steps below to determine density value:
1 Place a substrate (with proper masking for film thickness measurement)
adjacent to the sensor, so that the same thickness will be accumulated on the
crystal and this substrate.
2 Set density to the bulk value of the film material or to an approximate value.
3 Set Z-ratio to 1.000 and tooling to 100%.
4 Place a new crystal in the sensor and make a short deposition
(1000-5000 Å), using manual control.
5 After deposition, remove the test substrate and measure the film thickness with
either a multiple beam interferometer or a stylus-type profilometer.
6 Determine the new density value with the following equation: