INFICON SQC-310 Thin Film Deposition Controller - Manual (Page 88)

Appendix
Formula Density Z-Ratio Material Name
VO
2
4.340 *1.000 Vanadium Dioxide
W 19.300 0.163 Tungsten
WB
2
10.770 *1.000 Tungsten Boride
WC 15.600 0.151 Tungsten Carbide
WO
3
7.160 *1.000 Tungsten Trioxide
WS
2
7.500 *1.000 Tungsten Disulphide
WSi
2
9.400 *1.000 Tungsten Suicide
Y 4.340 0.835 Yttrium
Y
2
O
3
5.010 *1.000 Yttrium Oxide
Yb 6.980 1.130 Ytterbium
Yb
2
O
3
9.170 *1.000 Ytterbium Oxide
Zn 7.040 0.514 Zinc
Zn
3
Sb
2
6.300 *1.000 Zinc Antimonide
ZnF
2
4.950 *1.000 Zinc Fluoride
ZnO 5.610 0.556 Zinc Oxide
ZnS 4.090 0.775 Zinc Sulfide
ZnSe 5.260 0.722 Zinc Selenide
ZnTe 6.340 0.770 Zinc Telluride
Zr 6.490 0.600 Zirconium
ZrB
2
6.080 *1.000 Zirconium Boride
ZrC 6.730 0.264 Zirconium Carbide
ZrN 7.090 *1.000 Zirconium Nitride
ZrO
2
5.600 *1.000 Zirconium Oxide
Z-Factor is used to match the acoustic properties of the material being deposited to the
acoustic properties of the base quartz material of the sensor crystal.
Z-Factor = Z
q
/ Z
m
For example, the acoustic impedance of gold is Z=23.18, so:
Gold Z-Factor = 8.83 / 23.18 = .381
Unfortunately, Z Factor is not readily available for many materials. Z Factor can be
calculated empirically using this method:
1. Deposit the material until Crystal Life is near 50%, or near the end of life,
whichever is sooner.
2. Place a new substrate adjacent to the used quartz sensor.
3. Set QCM Density to the calibrated value; Tooling to 100%. Zero thickness.
4. Deposit approximately 1000 to 5000 Å of material on the substrate.
5. Use a profilometer or iterferometer to measure the actual substrate film thickness.
6. Adjust the Z Factor of the instrument until the correct thickness reading is shown.
Another alternative is to change crystals frequently. For a crystal with 90% life, the error
is negligible for even large errors in the programmed versus actual Z Factor.