INFICON IQM-233 Thin Film Deposition Controller PCI-Express Card Operating Manual - Manual (Page 87)

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IQM-233 Operating Manual
Chapter 6
Calibration Procedures
6.1 Importance of Density, Tooling and Z-Ratio
The quartz crystal microbalance precisely measures the mass added to the face of
the oscillating quartz crystal sensor. The IQM-233’s knowledge of 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 6.2 .
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 is accounted for by the Tooling parameter. Tooling can be
experimentally established by following the guidelines in
section 6.3 on page 6-2 .
The Z-Ratio compensates for the elasticity of the deposited material to the quartz
crystal. If the Z-Ratio is not known, it can be estimated from the procedures outlined
in
section 6.4 on page 6-3 .
6.2 Determining Density
NOTE: The bulk density values retrieved from Appendix A, Material Table 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 100.00%.
4 Place a new crystal in the sensor and make a short deposition
(1000-5000 Å).
5 After deposition, remove the test substrate and measure the film thickness with
a multiple beam interferometer or a stylus-type profilometer.