Correlation of trap states with negative bias thermal illumination stress stabilities in amorphous In-Ga-Zn-O thin-film transistors studied by photoinduced transient spectroscopy

• Published in: Japanese Journal of Applied Physics 2017-03, Vol.56 (3S), p.3-03BB02
• Main Authors: Hayashi, Kazushi, Ochi, Mototaka, Hino, Aya, Tao, Hiroaki, Goto, Hiroshi, Kugimiya, Toshihiro
• Format: Article
• Language: English
• Subjects: Channels; Degradation; Deposition; Flow rate; Illumination; Pits; Semiconductor devices; Thin film transistors
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAP.56.03BB02

Negative bias thermal illumination stress (NBTIS) stabilities in amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) were studied by photoinduced transient spectroscopy (PITS). The degradation of TFT performance correlated with trap states in the channel region of a-IGZO TFTs with an etch stop layer (ESL). A prominent peak at approximately 100 K was observed in a-IGZO formed under a partial pressure (p/p) of 4% O2. With increasing O2 p/p, an apparent shoulder of around 230 K appeared in PITS spectra. A higher flow rate of SiH4/N2O for the ESL deposition induced trap states associated with the 230 K peak. The peak at approximately 100 K could originate from the depletion of Zn by preannealing, while the peak at approximately 230 K should be attributed to the oxygen-deficient and/or Zn-rich defects due to the formation of OH in a-IGZO. The trap states in a-IGZO TFTs gave rise to degradation in terms of NBTIS. The threshold voltage shift (ΔVth) was 2.5 V, but it increased with the O2 p/p as well as the flow rate of SiH4/N2O for ESL deposition. The time dependence of ΔVth suggested that hydrogen from the ESL and/or in the a-IGZO thin films was incorporated and modified the trap states in the channel region of the a-IGZO TFTs.