Inficon SQC-310

7 - 3
PN 074-550-P1C
SQC-310 Operating Manual
7.4 Laboratory Determination of Z-Ratio
A list of Z-Ratios for materials commonly used are available in Table A-1. 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/cm
2
) 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-Ratios of materials in thin-film form are very close
to the bulk values. However, for high stress producing materials, Z-Ratios 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 section 7.2 on page 7-1.
2 Install a new crystal and record its starting frequency, F
co
. The starting
frequency will be displayed on the SQC-310 Main screen.
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
.
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
---
=