Film thickness measurement The laser-acoustic technique can also be used for measuring the film thickness. This requires that Young’s modulus and density of the film material are known.
Figure 1 presents an example for a thin titanium film of 7.8 nm deposited on silicon. The data for the film thickness scattered with a standard deviation of 0.4 nm.
Comparing test with ellipsometry yielded a thickness of 7.2 nm for this film. Another example for measuring the film thickness is shown Figure 2. A gold film had been deposited on fused silicon. The heavy gold causes a distinct decrease of the velocity with frequency. This enables the film thickness of 82 nm to be measured with the low standard deviation of 1 nm.
The ellipsometric test yielded a thickness of 78 nm for this film. |
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