INFICON SQM-160 Thin Film Deposition Monitor - Manual (Page 99)

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SQM-160 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 SQM-160's knowledge of
the density of this added material (specified in the density parameter in material
grid) 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 material grid.
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 7-2 .
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
(1000-5000 Å).
5 After deposition, remove the test substrate and measure the film thickness with
either a multiple beam interferometer or a stylus-type profilometer.
6 Determine the new density value with equation [1] :
[1]
Density g cm
3
   D
1
T
x
T
m
-------
 
 
 
=