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PN 074-550-P1C
SQC-310 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 density of this added
material 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 factor. The tooling factor can
be experimentally established by following the guidelines in section 7.3 on page
7-2.
If the Z-Ratio is not known, it could be estimated from the procedures outlined in
section 7.4 on page 7-3.
7.2 Determining Density
NOTE: The bulk density values retrieved from Table A-1 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 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 to 5000 Å).
5 After deposition, remove the test substrate and measure the film thickness with
either a multiple beam interferometer or a stylus-type profilometer.
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