Improved Conformality of CVD Titanium Nitride Films

Abstract

AbstractWe demonstrate a novel approach to improving the step coverage of thin films made by chemical vapor deposition (CVD). Titanium nitride (TiN) films were deposited by atmospheric pressure CVD using tetrakis(diethylamido)titanium vapor (TDEAT) and ammonia gas (NH3) carried in nitrogen gas. Trimethylamine (NMe3) gas was added during some of the depositions. The substrates were patterned silicon wafers having holes with aspect ratio of 3.5 through a silicon dioxide layer. We discovered that the step coverage was significantly increased for TiN films made with NMe3. At 320 °C, the step coverage was increased from 70% to nearly 100%. Within the range of deposition temperatures used in our study, 320 °C to 370 °C, the amount of improvement increased as the deposition temperature decreased. The trimethylamine did not increase the resistivity or the impurity levels in the films, but it did reduce the growth rate slightly. We suggest that the trimethylamine adsorbs onto the surface, temporarily blocking some of the sites on which growth could take place. Thus the effective sticking coefficients for the precursors are decreased, and the step coverage is increased.