4 laboratory determination of z-ratio – INFICON IC6 Thin Film Deposition Controller User Manual
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IC6 Operating Manual
12.4 Laboratory Determination of Z-Ratio
NOTE: On the IC6, the Auto-Z function is available to automatically calculate the
Z-Ratio. Especially when precise Z-Ratio values are significant, Auto-Z is
recommended. See
for a description of Auto-Z
theory.
A list of Z-values for materials commonly used is available in the Material Library.
For other materials, Z can be calculated from the following formula:
[3]
[4]
where:
d
f
= density (g/cm
3
) of deposited film
µ
f
= shear modulus (dynes/cm2) of deposited film
d
q
= density of quartz (crystal) (2.649 g/cm
3
)
µ
q
= shear modulus of quartz (crystal) (3.32 x 10
11
dynes/cm
2
)
The densities and shear moduli of many materials can be found in a number of
handbooks.
Laboratory results indicate that Z-values of materials in thin-film form are very close
to the bulk values. However, for high stress producing materials, Z-values of thin
films are slightly smaller than those of the bulk materials. For applications that
require more precise calibration, the following direct method is suggested:
1
Establish the correct density value as described in
2
Install a new crystal and record its starting frequency F
co
. It will be necessary
to send the SS 4 n command to get this information (refer to
).
3
Make a deposition on a test substrate such that the percent crystal life display
will read approximately 50%, or near the end of crystal life for the particular
material, whichever is smaller.
4
Stop the deposition and record the ending crystal frequency F
c
using the
SS 4 n command.
5
Remove the test substrate and measure the film thickness with either a multiple
beam interferometer or a stylus-type profilometer.
Z
d
q
q
d
f
f
------------
1
2
---
=
Z
9.378 10
5
d
f
f
-
1
2
---
=