Stress-Induced Hump Effects of p-Channel Polycrystalline Silicon Thin-Film Transistors

• Published in: IEEE electron device letters Vol. 29; no. 12; pp. 1332 - 1335
• Main Authors: HUANG, Ching-Fang, PENG, Cheng-Yi, YANG, Ying-Jhe, SUN, Hung-Chang, CHANG, Hung-Chih, KUO, Ping-Sheng, CHANG, Huan-Lin, LIU, Chee-Zxaing, CHEE WEE LIU
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.12.2008; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Active matrix liquid crystal displays; Applied sciences; Channels; Corners; Electric potential; Electron traps; Electronics; Exact sciences and technology; Gates; Hump; Insulators; Intrusion detection; MOSFETs; Plasma displays; Plasma temperature; poly-Si; positive bias temperature instability (PBTI); Semiconductor devices; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Silicon compounds; Stress; Thin film transistors; Thin films; thin-film transistor (TFT); Transistors; Voltage; Thermal stress; thin-film transistor (TFT); Dielectric materials; Electric stress; Polycrystal; Charge carrier trapping; p channel; Hump; Electric field; Flux density; p type semiconductor; Transistor channel; Stress effects; Trapped electron; Thin film transistor; poly-Si; positive bias temperature instability (PBTI); Fowler Nordheim tunneling; Damaging
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2008.2007306

Positive bias temperature instability in p-channel polycrystalline silicon thin-film transistors is investigated. The stress-induced hump in the subthreshold region is observed and is attributed to the edge transistor along the channel width direction. The electric field at the corner is higher than that at the channel due to thinner gate insulator and larger electric flux density at the corner. The current of edge transistor is independent of the channel width. The electron trapping in the gate insulator via the Fowler-Nordheim tunneling yields the positive voltage shift. As compared to the channel transistor, more trapped electrons at the edge lead to more positive voltage shift and create the hump. The hump is less significant at high temperature due to the thermal excitation of trapped elections via the Frenkel-Poole emission.