Effects of O sub(2) rapid thermal annealing on the microstructural properties and reliability of RF-sputtered Ta sub(2)O sub(5) films

• Published in: IEEE transactions on dielectrics and electrical insulation Vol. 7; no. 3; pp. 316 - 321
• Main Authors: Wang, Ching-Wu, Lin, Ren-De, Chen, Shih-Fang, Lin, Wen-Kuan
• Format: Journal Article
• Language: English
• Published: 01.01.2000
• ISSN: 1070-9878

The microstructural properties and reliability of sputtered Ta sub(2)O sub(5) films treated by various temperatures of rapid thermal annealing (RTA) in O sub(2) atmosphere have been systematically investigated. Analytical results revealed that whenever the RTA temperature was > 650 degree C, the non-crystallinity of as-grown Ta sub(2)O sub(5) film would be effectively improved from an amorphous phase to the beta -Ta sub(2)O sub(5) phase. Leakage current measurement indicated that leakage current decreases with increasing annealing temperature in a low RTA temperature range ( greater than or equal to 650 degree C) and, contrarily, increases with increasing annealing temperature in a high RTA temperature range (650 to 950 degree C). The former result was asserted that reducing pinholes and oxygen vacancies played key factors. However, the latter result was suggested to arise due to significant Si diffusion into the Ta sub(2)O sub(5) film, causing a leaky transition layer and/or being distributed along the grain boundary to form the leakage path. Finally, the time-dependent dielectric-breakdown experiments revealed that 950 degree C O sub(2) RTA treated Ta sub(2)O sub(5) film possessed the superior crystallinity, creating less interfacial hole trap states at the junction of Ta sub(2)O sub(5)/Si and exhibiting the best long-term reliability.