Effect of fluorination and hydrogenation by ion implantation on reliability of poly-Si TFTs under gamma irradiation

• Published in: Journal of physics. D, Applied physics Applied physics, 2011-01, Vol.44 (1), p.015101-015101
• Main Authors: Jelenković, Emil V, Ristić, G S, Pejović, M M, Jevtić, Milan M, Jha, Shrawan K, Videnović-Mišić, Mirjana, Pejović, M, Tong, K Y
• Format: Article
• Language: English
• Subjects: Applied sciences; Density; Electronics; Exact sciences and technology; Fluorination; Gamma irradiation; Gamma rays; Grain boundaries; Semiconductor devices; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Stability; Thin film transistors; Transistors
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/44/1/015101

Sputtered thin film transistors (TFTs), which were hydrogenated and fluorinated by ion implantation, were exposed to gamma irradiation up to 2500 Gy. Long term post-irradiation stability of TFTs was studied after eight months of storage and under positive bias test at 150 °C in time intervals of 1–10 h. The effects induced by irradiation and during relaxation period were monitored by current–voltage ( I – V ) measurements. I – V data were used to determine post-irradiation changes in different TFT parameters, such as threshold voltage, interface states density and grain boundaries trap density. The behaviour of these parameters was compared for four types of TFTs: non-fluorinated-hydrogenated, fluorinated, hydrogenated and fluorinated-hydrogenated, and it was found that hydrogenated TFTs showed greater instability. A mechanism for grain boundary traps generation is proposed.