The Effect of Active-Layer Thickness and Back-Channel Conductivity on the Subthreshold Transfer Characteristics of Hf-In-Zn-O TFTs

• Published in: IEEE electron device letters 2011-08, Vol.32 (8), p.1077-1079
• Main Authors: Maeng, W. J., Joon Seok Park, Hyun-Suk Kim, Eok Soo Kim, Kyoung Seok Son, Tae Sang Kim, Myungkwan Ryu, Sangyoon Lee
• Format: Article
• Language: English
• Subjects: Active-layer thickness; Applied sciences; back channel; Channels; Conductivity; Devices; Electronics; Exact sciences and technology; Gates; Hafnium; hump; Logic gates; Mathematical analysis; Pixel; Plasmas; Screening; Semiconductor devices; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Thin film transistors; thin-film transistors (TFTs); Threshold voltage; Transistors
• ISSN: 0741-3106; 1558-0563
• DOI: 10.1109/LED.2011.2156756

The effect of active-layer thickness and back-channel conductivity on the subthreshold transfer characteristics of hafnium-indium-zinc-oxide (HIZO) thin-film transistors was studied. Experiments show that subthreshold humps in the transfer curves become more pronounced as the active-layer thickness increases, in the presence of a highly conductive back channel. With a highly conductive thin back channel, subthreshold humps were observed as the total active-layer thickness exceeded 80 nm. The above results can be interpreted as a consequence of a reduction in the effective gate field as the active thickness exceeds the "screening length". The screening length of the HIZO layer is calculated to be approximately 78 nm, and accordingly, as the active thickness exceeds this value, subthreshold humps that are anticipated to originate from the back-channel conduction appear.