Title :
Effects of O2 rapid thermal annealing on the microstructural properties and reliability of RF-sputtered Ta2O5 films
Author :
Wang, Ching-Wu ; Lin, Ren-De ; Chen, Shih-Fang ; Lin, Wen-Kuan
Author_Institution :
Dept. of Electron. Eng., I-Shou Univ., Taiwah, Taiwan
fDate :
6/1/2000 12:00:00 AM
Abstract :
The microstructural properties and reliability of sputtered Ta2O5 films treated by various temperatures of rapid thermal annealing (RTA) in O2 atmosphere have been systematically investigated. Analytical results revealed that whenever the RTA temperature was >650°C, the noncrystallinity of as-grown Ta2O5 film would be effectively improved from an amorphous phase to the β-Ta2O5 phase. Leakage current measurement indicated that leakage current decreases with increasing annealing temperature in a low RTA temperature range (⩽650°C) and, contrarily, increases with increasing annealing temperature in a high RTA temperature range (650 to 950°C). The former result was asserted in that reducing pinholes and oxygen vacancies played key factors. However, the latter result arose due to significant Si diffusion into the Ta2O5 film, causing a leaky transition layer distributed along the grain boundary to form the leakage path. Finally, the time-dependent dielectric-breakdown experiments revealed that 950°C O2 RTA treated Ta2 O5 film possessed the superior crystallinity, creating less interfacial hole trap states at the junction of Ta2O5/Si and exhibiting the best long-term reliability
Keywords :
grain boundaries; hole traps; insulating thin films; integrated circuit reliability; leakage currents; permittivity; rapid thermal annealing; sputtered coatings; tantalum compounds; 650 to 950 degC; RF-sputtered films; Ta2O5; annealing temperature; grain boundary; interfacial hole trap states; leakage current measurement; leaky transition layer; microstructural properties; noncrystallinity; pinholes; rapid thermal annealing; reliability; time-dependent dielectric-breakdown experiments; vacancies; Amorphous materials; Atmosphere; Crystallization; Current measurement; Dielectrics; Grain boundaries; Leakage current; Rapid thermal annealing; Semiconductor films; Temperature distribution;
Journal_Title :
Dielectrics and Electrical Insulation, IEEE Transactions on