Influence of Sputtering Parameters on the Structural and Electrical Properties of Sputtered Deposited Ta2O5 Thin Films for Microelectronic Applications

Abstract

Tantalum oxide (Ta2O5) thin film is considered as an alternative dielectric layer in complementary metal oxide semiconductor (CMOS) devices due to its high dielectric constant, high breakdown field and low leakage current density. In this research, radio-frequency magnetron sputtering was used to deposit Ta2O5 thin films on p-type Si (100) substrates. During the film deposition, the RF power and Ar/O2 gas flow ratio were kept constant while the sputtering pressure and substrate temperature were varied. The films were annealed in air ambient for an hour at 900 °C after the deposition. Orthorhombic β – phase structure of Ta2O5 films is observed from XRD investigation. The crystallinity of the films was found to be improved with the increase in the sputtering pressure and substrate temperature. The films, deposited at higher working pressure, became rough, whereas the films deposited at higher temperature became smooth. The capacitance-voltage and current-voltage techniques were used to study the electrical properties of the thin films. Low oxide charge density is calculated from the shift in flat-band voltage of C-V curve and found to be 6.5 × 1011 cm-2 and 3.1 × 1012 cm-2 at sputtering pressure of 8.0 ⨯ 10-3 mbar and substrate temperature of 300 °C, respectively. A lower leakage current is found for the film deposited at 8.0 ⨯ 10-3 mbar of sputtering pressure and substrate temperature of 300 °C.