Tantalum Nitride as Promising Gate Electrode for MOS Technology

Abstract

Tantalum nitride (TaN) films have been obtained by DC sputtering deposition, using different nitrogen flow and discharge power on Si substrates. The N2/Ar ratio and sputtering power effects on structural and electrical properties of TaN films were investigated by scan profiler (film thickness and deposition rate), atomic force microscopy (rms roughness and grain size) and four-probe technique (electrical resistivity). The deposition rates, between 4 and 78 nm/min, decreased with an increase of N2/Ar ratio, and electrical resistivities, between 150 and 7500 μΩ.cm, increased. For the best condition for N2/Ar of 0.33 and discharge power of 1000W, low electrical resistivity of 350 μΩ.cm, the rms roughness of 0.8 nm and grain size of 380 nm2 were obtained. This best film has been used as gate electrodes in MOS capacitors, which were fabricated with SiNxOy as gate dielectric. These capacitors were used to obtain capacitance-voltage (C-V) measurements. The flat-band voltage of -1.34 V and effective charge densities of about 1011 cm-2 were extracted from all C-V curves, indicating that the TaN/SiNxOy/Si structures present similar behavior when are compared to those presented in literature. Therefore, our TaN gate electrode can be considered as promising gate electrode for CMOS technology.