Journal of the Korean Institute of Electrical and Electronic Material Engineers (한국전기전자재료학회논문지)

The Korean Institute of Electrical and Electronic Material Engineers (한국전기전자재료학회)
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Analysis of An Anomalous Hump Phenomenon in Low-temperature Poly-Si Thin Film Transistors

저온 다결정 실리콘 박막 트랜지스터의 비정상적인 Hump 현상 분석

  • Kim, Yu-Mi (Department of Electronics Engineering, Chungnam National University) ;
  • Jeong, Kwang-Seok (Department of Electronics Engineering, Chungnam National University) ;
  • Yun, Ho-Jin (Department of Electronics Engineering, Chungnam National University) ;
  • Yang, Seung-Dong (Department of Electronics Engineering, Chungnam National University) ;
  • Lee, Sang-Youl (Department of Electronics Engineering, Chungnam National University) ;
  • Lee, Hi-Deok (Department of Electronics Engineering, Chungnam National University) ;
  • Lee, Ga-Won (Department of Electronics Engineering, Chungnam National University)
  • Received : 2011.08.30
  • Accepted : 2011.09.26
  • Published : 2011.11.01

Abstract

In this paper, we investigated an anomalous hump phenomenon under the positive bias stress in p-type LTPS TFTs. The devices with inferior electrical performance also show larger hump phenomenon. which can be explained by the sub-channel induced from trapped electrons under thinner gate oxide region. We can confirm that the devices with larger hump have larger interface trap density ($D_{it}$) and grain boundary trap density ($N_{trap}$) extracted by low-high frequency capacitance method and Levinson-Proano method, respectively. From the C-V with I-V transfer characteristics, the trapped electrons causing hump seem to be generated particularly from the S/D and gate overlapped region. Based on these analysis, the major cause of an anomalous hump phenomenon under the positive bias stress in p-type poly-Si TFTs is explained by the GIDL occurring in the S/D and gate overlapped region and the traps existing in the channel edge region where the gate oxide becomes thinner, which can be inferred by the fact that the magnitude of the hump is dependent on the average trap densities.

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Acknowledgement

Supported by : 한국과학재단

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