Atomic Layer Deposition- and Chemical Vapor Deposition-TiN Top Electrode Optimization for the Reliability of Ta2O5 and Al2O3 Metal Insulator Silicon Capacitor for 0.13 µm Technology and Beyond

Abstract

TiCl4-based atomic layer deposition (ALD)- and chemical vapor deposition (CVD)-TiN films are applied as the metal top electrode for Ta2O5 and Al2O3 metal insulator silicon (MIS) capacitor. The effects of factors such as Cl content, step coverage, deposition temperature of the TiN top electrode processes and pre-NH3 flushing on the electrical properties and reliability of the Ta2O5 and Al2O3 MIS capacitor are studied. Among these factors, poor step coverage shows distinctly degraded electrical properties of MIS capacitor, and high deposition temperature of TiN processes also degraded electrical properties, particularly those of Ta2O5. Although similar capacitance and leakage characteristics are measured with high chlorine content and pre-NH3 flushing TiN processes, a difference in the orders of magnitude is observed in time dependent dielectric breakdown (TDDB) measurements. Regarding the deposition temperature and pre-NH3 flushing effect, the electrical and TDDB characteristics of Ta2O5 degrade even more severely than those of Al2O3. Degradation of TDDB in TiN films with NH3 flushing prior to deposition is attributed to the reduction effect of the dielectric material by NH3 gas. Based on the X-ray photoelectron spectroscopy (XPS) analysis results, Al2O3 is chemically more inert than Ta2O5. In addition, the degradation of TDDB characteristics is directly correlated to the early generation of Vp-dependent solid “0” fail bit counts. Due to the relatively low deposition temperature as well as to the excellent step coverage and low resistivity, the ALD-TiN process is ideal for enhancing the reliability of a MIS capacitor.