Correlation between Electrical and Optical Properties of Tantalum Anodic Oxide and Electron Cyclotron Resonance Etching Studies of E-beam Deposited Ta2O5 Films

Abstract

The anodicTa2O5 films were grown in 5ml/98%H2SO4 electrolyte. Discharge currents were collected immediately after growth. The optical properties were studied with a Spectroscopic Ellipsometer, over a wide range of frequencies from the UV to the IR. It was established that films for which the discharge current followed the known "~ -1" power dependence (characteristic of films that can sustain electric fields of MV/cm) have different optical properties as compared to films for which the discharge current is not represented by that function. Etching studies of the e-beam deposited Ta2O5 films, combined with reflectance measurements after each etch step, resulted in a shift in the reflectance spectrum as a function of film thickness, d. This empirical f versus d dependence (where f is the frequency corresponding to the reflectance minimum for each d) was used to calculate the energies of the 4d doublet of Ta+5 in Ta2O5.