Degradation Model of Self-Heating Effects in Silicon-on-Glass TFTs

• Published in: IEEE transactions on electron devices Vol. 58; no. 8; pp. 2440 - 2447
• Main Authors: Mativenga, M., Min Hyuk Choi, Jin Jang, Mruthyunjaya, R., Tredwell, T. J., Mozdy, E., Kosik-Williams, C.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.08.2011; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Channels; Charge carrier processes; Devices; Edge effects; Electronics; Exact sciences and technology; Glass; hump effect; Logic gates; self-heating (SH); Semiconductor devices; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Silicon; Silicon dioxide; silicon-on-glass (SiOG); Stress; Stresses; Substrates; Thin film transistors; thin-film transistor (TFT); Transistors; Trapping; thin-film transistor (TFT); Edge effects; silicon-on-glass (SiOG); Thermal behavior; Glass; Transfer characteristic; Active layer; Thermal dissipation; self-heating (SH); IV-VI compound; Single crystal; hump effect; Time dependence; Charge carrier trapping; p channel; Edge effect; Silicon oxides; Self heating; Silicon; Thin film transistor; Damaging
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/TED.2011.2155068

This paper investigates the origin and reduction of self-heating effects in single-crystal silicon-on-glass (SiOG) thin-film transistors (TFTs). A hump forms in the transfer characteristics of p-channel SiOG TFTs when the temperature of the devices is increased either by direct heating or electrical biasing. The size of the hump proportionally scales with the channel width W , indicating that it is related to the bulk active-layer properties such as conduction through a backchannel. While the hump increases in the positive direction, the main transistor shifts in the negative direction with increasing self-heating stress time, supporting the exclusion of edge effects. The time dependence of the hump shift is well described by the stretched-exponential behavior, indicating that the backchannel is a result of electron trapping into the silica layer that is between the glass and silicon active layer. To mitigate this hump effect, we demonstrate in this paper that TFTs with an active layer divided into smaller parts along the W direction (in order to increase heat dissipation) show better stability to self-heating stress (i.e., no hump formation) than TFTs with full active layers. Split devices have more channel edges, compared with those with a full active layer, supporting the idea that the hump is indeed not due to edge effects.