Effect of the metal gate on the breakdown characteristics and leakage current of Ta2O5 stack capacitors

摘要

The effect of metal gates (Al, W, TiN) deposited by evaporation (AI) and sputtering (W, TiN) on the breakdown characteristics and leakage currents of 15 nm Ta2O5 stack capacitors has been investigated. Leakage currents, breakdown fields and mechanisms of conductivity are discussed in the terms of possible reactions between the Ta2O5 and the electrode material, as well as electrode-deposition-introduced defects acting as electrically active centers. The top electrode affects the electrical characteristics of the capacitors and sputtered W is found to be the best. During the deposition of TiN and Al, reactions that degrade the properties of the Ta2O5 occur. The high leakage current is attributed to radiation defects generated in the Ta2O5 during sputtering of the TiN, and a damaged interface due to a reaction between the Al and Ta2O5, respectively. W deposition is not accompanied by the introduction of detectable damage leading to a change of the properties of the initial as-grown Ta2O5, (the leakage current is 5 to 8 orders of magnitude lower, as compared to Al and TiN-gate capacitors).