LEAKAGE CURRENT MECHANISM OF AMORPHOUS AND POLYCRYSTALLINE TA2O5 FILMS GROWN BY CHEMICAL-VAPOR-DEPOSITION

The leakage current mechanism of the chemical vapor deposition Ta2O5 f ilm has been investigated. In the case of an as-deposited amorphous fi lm, the presence of impurities such as carbon and hydrogen remaining i n the film leads to the Poole-Frenkel type leakage current. The oxidat ion 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 r educe the leakage current of the Ta2O5 film crystallized at 700 degree s C. This leakage current is not due to C and H, but rather to Si pene traed into the Ta2O5 film from the underlying poly-Si electrode. There fore, the amorphous Ta2O5 film treated by O-2 plasma is most suitable for DRAM use.