Leakage‐Current Increase in Amorphous Ta2 O 5 Films Due to Pinhole Growth during Annealing Below 600°C

Effects of high temperature annealing over the range 400/sup 0/-1000/sup 0/C on the leakage current of tantalum pentoxide (Ta/sub 2/O/sub 5/) films deposited by reactive sputtering are investigated. Leakage current of polycrystalline Ta/sub 2/O/sub 5/ film (annealed above 700/sup 0/C) is about 10/sup 7/-10/sup 8/ times larger than that of as-deposited amorphous film. However, i is found that leakage current in Ta/sub 2/O/sub 5/ film annealed at 600/sup 0/C increases drastically as well, even though the films have no yet recrystallized. TEM observation reveals that pinholes ranging from 5 nm to 15 nm in diameter are formed near the bottom of the depressions in Ta/sub 2/O/sub 5/ film annealed even at 600/sup 0/C. Electrical properties of the Ta/sub 2/O/sub 5/ films are discussed in terms of crystallographic properties such as pinhole growth and grain boundaries.