The Effect of Various Sputtering Parameters on Ta Phase Formation Using an I-Optimal Experimental Design

Abstract

Five process factors are varied to find conditions necessary for α and β phase formation in tantalum thin films deposited on SiC. These are: sputtering time, input power, pre-sputter etch time, preheat time at 250 C and sputtering temperature. An empirical model is developed which predicts the maximum or minimum amount of β phase possible over a large range of film thickness (∼25 to ∼2,000 nm). The maximum predicted (average) % β phase at the maximum sputtering temperature is only 8%, with 95% confidence bounds of [5%, 12%]. The other factors place a much lower restriction on β phase formation. Pure α phase is easily produced over a wide range of operating conditions. Only a weak relationship is found between film thickness and phase composition. The Ta film resistivity increases with the amount of b phase, in agreement with the literature.