P‐137: High Performance Coplanar IGZO TFT Image Sensor with Partial Passivation‐less Structure for Digital X‐ray Detector

• Published in: SID International Symposium Digest of technical papers 2022-06, Vol.53 (1), p.1160-1163
• Main Authors: Yoon, Jaeho, Kim, Soyoung, Kang, Moon-Soo, Shin, Chul-Sang, Jeong, Hoon, Park, Kwon-Shik, Park, Jeong-Ki, Choi, Hyung-Seok
• Format: Article
• Language: English
• Subjects: Backplanes; Coplanar IGZO TFT; Damage prevention; Deposition; Digital imaging; Digital X-ray detector (DXD); Flat panels; Indium gallium zinc oxide; Insulating layers; Leakage current; Partial passivation-less structure (PPLS); Passivity; Photodiode (PIN diode); Photodiodes; PIN diodes; Semiconductor devices; Sensors; Thin film transistors; Threshold voltage
• ISSN: 0097-966X; 2168-0159
• DOI: 10.1002/sdtp.15708

Recently, digital X‐ray detector (DXD) technology is needed to implement high‐resolution and high‐definition images, and low‐dose exposure of X‐ray imaging systems. This technology requires the IGZO TFT structure with better mobility and lower leakage current than the a‐Si backplane. In order to supplement stability and improve PIN diode (photodiode) performance, when SiNx‐based insulating layers and thick photodiodes are applied, continuous damage due to high concentration impurities occurs in the plasma environment, and thus the threshold voltage (Vth) shift problem of the IGZO TFT transistor occurs. To solve this problem, a high performance partial passivation‐less structure (PPLS) was applied to prevent damage using 43×43 centimeter flat panel X‐ray detector, and we investigated the improvement of the IGZO TFT characteristics. Before PIN diode deposition, Vth was +0.24V and after PIN diode & SiNx deposition, it moved slightly to Vth ‐0.17V, but the same characteristics as initial performance were guaranteed after TFT was completed.