Improving the electrical performance of vertical thin-film transistor by engineering its back-channel interface

• Published in: Microelectronic engineering Vol. 253; p. 111676
• Main Authors: Lee, Kwang-Heum, Lee, Seung Hee, Cho, Sang-Joon, Hwang, Chi-Sun, Park, Sang-Hee Ko
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 15.01.2022; Elsevier BV
• Subjects: Back-channel; Electric resistance; Mechanical properties; Mobility; Oxide semiconductor; Photolithography; Semiconductor devices; Silicon dioxide; Surface morphology; Thin film transistors; Thin films; Transistors; Vertical thin-film transistor; Back-channel; Oxide semiconductor; Vertical thin-film transistor; Surface morphology
• ISSN: 0167-9317; 1873-5568
• DOI: 10.1016/j.mee.2021.111676

This paper reports the effect of the properties of a back-channel region of a vertical thin-film transistor (VTFT) on its electrical performance. The deposition of a thin layer of SiO2 on a damaged back-channel region was found to improve the subthreshold swing (SS) from 0.25 to 0.12 V/dec, while maintaining the field-effect mobility. Detailed analysis of the surface morphology of the back-channel region revealed that the application of advanced photolithography resulted in a significantly smoother back-channel interface, yielding higher-performing VTFTs. The VTFT fabricated using a high-resolution, stepper photolithography system exhibited a linear mobility (μlin) of 14.60 cm2/Vs, a saturation mobility (μsat) of 23.69 cm2/Vs, and an SS value of 0.13 V/dec. Meanwhile, the VTFT fabricated using a standard projection aligner displayed μlin, μsat, and SS values of 5.74 cm2/V·s, 13.87 cm2/V·s, and 0.27 V/dec, respectively. These results revealed the electrical performance of the VTFT to be strongly influenced by the properties of the back-channel region. [Display omitted] •Back-channel interface of a VTFT was engineered.•Back-channel interface properties strongly affected the electrical performance of VTFTs.•BCP process was effective for the improvement of sub-threshold swing, while field-effect mobility was maintained the same.•Overall performance enhancement was obtained from advanced photolithography for dry-etch patterning.•The patterning process – back channel roughness relationship was confirmed by SEM/TEM and 3D-AFM analyses.