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Dear ALL

Hoe measure the thin film thickness by refelction and transmitted light using monochoromator.

I need basic information for this methode

It is easy and tricky at the same time...

1. It works only for transparent in the given light wavelength range film materials.
2. The intensity of reflected or transmitted light varies with film thickness as sinusoid. Light intensity minimums or maximums take place when the film optical thickness nd (n - film material refraction index for the given monitoring wavelength L, mcm, d - physical film thickness, mcm) = kL/4, where k = 1, 2, 3,.... For instance, for TiO2 film with n = 2.3 deposited on glass substrate and monitoring wavelength 600 nm reflected light intensity first maximum will be at film thickness (550/4)/2.3 = 59.8 nm, then minimum at 119.6 nm, then second maximum at 179.4 nm, second minimum at 239.2 nm , and so on. In general, you can select wavelength to obtain required thickness when reflected or transmitted light gets extremum, on practice it is not so easy.

Don't forget, that the film thickness deposited on unmoving monitor sample is not equal to film thickness deposited on rotating parts. Do not forget about film thickness non-uniform distribution over substrate holder. And there are some extra tricks. You need to use correction coefficients obtained for your machine in experiment.

There are a few softwares allowing to calculate optical monitoring, TFCalc, for instance. As a device, it is not very hard to make it yourself, but better to use a professional one. There are not a lot of them on the market from about 10K (simpliest) to 40K (the best).

Regards,

Vladimir

zafar0126 wrote: