Thickness determination of thin films based onx-ray signal decay law

✍ Scribed by Kaltsas, G.; Glezos, N.; Valamontes, E.; Nassiopoulou, A. G.

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 157 KB
• Volume: 26
• Category: Article
• ISSN: 0142-2421
• DOI: 10.1002/(sici)1096-9918(199811)26:12<876::aid-sia429>3.0.co;2-h

✦ Synopsis

A non-destructive method for evaluation of the thickness of Ðlms over bulk substrates is presented. This method is based on evaluation of the parameters of the decay part of the x-ray signal ratio. For a selected energy range of each Ðlm thickness it is demonstrated that the decay part follows an exponential law. The physical parameters involved in this law are the energy exponent and a constant that depends mainly upon the Ðlm thickness. The values found for the energy exponent are in the range 2.0-3.0. This is conÐrmed in a variety of cases (Al/Si, Ti/Si, Cu/Si, Pt/Si, Cu/Ni, Ti/Au and Pt/Au) for Ðlm thicknesses larger than a critical value.

The experimental results are compared to those obtained by two theoretical methods and a Monte-Carlo approach. The Ðrst method is based on solution of the Boltzmann transport equation for the electron beam, an approach developed by one of the authors for e-beam lithography. The second is based on a previously developed semi-empirical formula for the x-ray depth distribution function. The energy dependence of the signal ratio is also discussed using this approach.