Leakage current mechanism of amorphous and polycrystalline Ta2O5 films grown by chemical vapor deposition

The leakage current mechanism of the chemical vapor deposition Ta2O5 film has been investigated. In the case of an as-deposited amorphous film, the presence of impurities such as carbon and hydrogen remaining in the film leads to the Poole-Frenkel type leakage current. The oxidation of these impurities results in a reduction in leakage current. O-2 plasma is especially effective for oxidizing impurities, leading to a drastic reduction of the leakage current. However O-2 plasma cannot reduce the leakage current of the Ta2O5 film crystallized at 700 degrees C. This leakage current is not due to C and H, but rather to Si penetraed into the Ta2O5 film from the underlying poly-Si electrode. Therefore, the amorphous Ta2O5 film treated by O-2 plasma is most suitable for DRAM use.