INFICON IQM-233 Thin Film Deposition Controller PCI-Express Card Codeposition Software Operating Manual User Manual
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IQS-233 Operating Manual
3
Make a deposition on a test substrate such that the percent crystal Life readout
in the Readings window displays approximately 50%, or near the end of crystal
life for the particular material, whichever is smaller (the accuracy of the Z-Ratio
determination will improve with increased material thickness).
4
Stop the deposition and record the ending crystal frequency F
c
from the
Frequency (MHz) readout of the Readings window.
5
Remove the test substrate and measure the film thickness with either a multiple
beam interferometer or a stylus-type profilometer.
6
Using the density value from step 1 and the recorded values for
F
co
and
F
c
,
adjust the Z-Ratio value in thickness
to bring the calculated
thickness value into agreement with the actual thickness. If the calculated value
of thickness is greater than the actual thickness, increase the Z-Ratio value. If
the calculated value of thickness is less than the actual thickness, decrease the
Z-Ratio value.
[5]
where:
T
f
= Thickness of deposited film (kÅ)
F
co
= Starting frequency of the sensor crystal (Hz)
F
c
= Final frequency of the sensor crystal (Hz)
F
q
= Nominal blank frequency = 6045000 (Hz)
z
= Z-Ratio of deposited film material
Z
q
= Specific acoustic impedance of quartz = 8765000 (kg/(m
2
x s))
p
= Density of deposited film (g/cm
3
)
For multiple layer deposition (for example, two layers), the Z-Ratio used for the
second layer is determined by the relative thickness of the two layers. For most
applications the following three rules will provide reasonable accuracies:
If the thickness of layer 1 is large compared to layer 2, use the Z-Ratio of
material 1 for both layers.
If the thickness of layer 1 is thin compared to layer 2, use the Z-Ratio of material
2 for both layers.
If the thickness of both layers is similar, use a value for Z-Ratio which is the
weighted average of the two Z-Ratios for deposition of layer 2 and subsequent
layers.
T
f
Z
q
10
4
2
zp
--------------------
1
F
co
--------
ATan zTan
F
co
F
q
-----------
1
F
c
-----
ATan zTan
F
c
F
q
---------
–
=