Correlation between Electrical and Optical Properties of Tantalum Anodic Oxide and Electron Cyclotron Resonance Etching Studies of E-beam Deposited Ta_2O_5 Films

摘要

The anodicTa_2O_5 films were grown in 5ml/98%H_2SO_4 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 Ta_2O_5 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 Ta_2O_5.