An Investigation on the High-k (Ta2O5)0.92-(TiO2)0.08Thin Films as Gate Dielectric of nm-scaled MISFETs

• Main Authors: Liang-Tsai Su, 蘇良財
• Other Authors: Shih-Chih Chen
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/27906086327393565932

碩士 === 國立雲林科技大學 === 電子與資訊工程研究所碩士班 === 92 === (Ta2O5)0.92-(TiO2)0.08 thin films with a thickness of 250 Å were deposited on p-Si (100) substrate by RF sputtering at 400℃. Before deposited (Ta2O5)0.92-(TiO2)0.08 thin films, the native oxide on Si substrate removed by Ar plasma treatment. Si3N4 and SiNO very thin layers will be grown by using N2-plasma to bombard heated Si-substrate or sputtering system with Si3N4 target. The Si3N4 and SINO layers might be as barrier to forbid out-diffusion of oxygen and silicon atoms to promote the MIS performance. To compare among these samples, the dielectric for a film after Ar plasma treatment 5 minutes , N2 plasma treatment 3 minutes and furnace annealed at 700℃ increased to 27 and its leakage current density lowered to 1.18 × 10-8 A/cm2 at 1.5V. (Ta2O5)0.92-(TiO2)0.08 films were exposed under oxygen plasma with different duration . Compared to pure Ta2O5 (ε=25) thin film, significant enhancement in dielectric constant(ε=39) is obtained by 3 minutes of oxygen plasma duration furnace annealed at 700℃. It was also found that the leakage current density, 1.05 ×10-8 A/cm2 at an applied voltage of -1.5 V, of the (Ta2O5)0.92-(TiO2)0.08 capacitor can be improved by one order of magnitude as compared to that of non-plasma-treated samples. It was also found that the leakage current density, 1.24 ×10-9 A/cm2 at an applied voltage of 1.5 V .The same result was also found in the alternative sputtering samples. The improvement was suggested to be due to the elimination of oxygen vacancies by oxygen plasma surface treatment or multistage deposition method. Furthermore, the dielectric properties of (Ta2O5)0.92-(TiO2)0.08 films were found to be remarkably sensitive to the post-annealing duration. The dominant leakage mechanisms are the Schottky Emission at low electric field and the Poole-Frenkel at high electric field.