Study Of Spectroscopic Ellipsometry Models In Thin Films Grown By Atomic Layer Deposition

As the length scale of devices and materials keeps shrinking, there is a high demand for thin film fabrication methods with precise thickness and components control. Atomic layer deposition(ALD) has emerged as an important method for its precise control of the thickness and components. And the development of an accurate characterization technique for ALD thin films is of great importance. In this work, Spectroscopic Ellipsometry(SE) was chosen to study thin film grown by ALD.For transparent thin films like Al2O3, Cauchy and EMA(Effective Medium Approximation) model were chosen to study their growth. Both models showed the linear growth of Al2O3. But Cauchy model had limitations in predicting the ultrathin film at few cycles, and the fitting results depended on wavelengths range greatly. EMA model was capable of predicting ultrathin film’s physical properties.For semiconductor thin films like CoOx, Cauchy model and General Oscillator(GO) model were used. Cauchy model was applied in the non-absorbing energy region to derive the thickness of the film thickness, then followed the GO with the fixed thickness to get the optical constant of ALD CoOx. The results showed the linear growth of CoOx, and the fitted bandgap was in accordance with the literature.For absorbing films like Palladium(Pd), GO model and EMA model were used. The GO model was firstly applied to fix the optical constants of Pd, then a MG-EMA/GO was developed. For Pd grown on Si substrates, the Pd coverages were consistent with the simulation results of MG-EMA/GO model at more than 300 cycles. Moreover, Pd grown on Self Assembled Monolayers(SAMs) was studied and the Pd coverages were in accordance with the fitted results. These results revealed that MG-EMA/GO is a promising method in simulating absorbing noble thin films.