Threshold voltage instability and polyimide charging effects of LTPS TFTs for flexible displays

• Published in: Scientific reports Vol. 11; no. 1; p. 8387
• Main Authors: Kim, Hyojung, Park, Jongwoo, Khim, Taeyoung, Bak, Sora, Song, Jangkun, Choi, Byoungdeog
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 16-04-2021; Nature Publishing Group; Nature Portfolio
• Subjects: 639/166/987; 639/766/1130; 639/925; 639/925/927; 639/925/930; Glass substrates; Humanities and Social Sciences; multidisciplinary; Science; Science (multidisciplinary); Silicon dioxide
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/s41598-021-87950-0

In this paper, we investigate the V
th
shift of p-type LTPS TFTs fabricated on a polyimide (PI) and glass substrate considering charging phenomena. The V
th
of the LTPS TFTs with a PI substrate positively shift after a bias temperature stress test. However, the V
th
with a glass substrate rarely changed even with increasing stress. Such a positive V
th
shift results from the negative charging of fluorine stemmed from the PI under the gate bias. In fact, the C–V characterization on the metal–insulator-metal capacitor reveals that charging at the SiO
2
/PI interface depends on the applied gate bias and the PI material, which agrees well with the TCAD simulation and SIMS analyses. As a result, the charging at the SiO
2
/PI interface contributes to the V
th
shift of the LTPS TFTs leading to image sticking.