Highly stable fluorine-passivated In–Ga–Zn–O thin-film transistors under positive gate bias and temperature stress

Abstract

A highly stable fluorine-passivated In-Ga-Zn-O (IGZO) thin-film transistor (TFT) was demonstrated under positive gate bias and temperature stress (PBTS). The defects in the IGZO TFT were passivated by fluorine, which was introduced into a SiO x etching stopper during the deposition of fluorinated silicon nitride for passivation and diffused during post-fabrication annealing. From the results of secondary ion mass spectrometry analysis, the reliability of the IGZO TFT under PBTS was observed to be markedly improved even at a stress temperature of 100 °C when fluorine diffusion was detected in the IGZO channel. The fluorine-passivated IGZO TFT has improved operation temperature and is advantageous for achieving high-performance and high-reliability oxide TFTs for next-generation displays.

Suppression of Negative Gate Bias and Illumination Stress Degradation by Fluorine-Passivated In-Ga-Zn-O Thin-Film Transistors

“…We have reported in Ref. 19 that, for the TFT with SiN X :F passivation, F was incorporated into the SiOx-ESL during the SiN X :F passivation deposition, and the F in SiOx-ESL diffused into the IGZO channel when the post-annealing time was increased. The results indicated that appropriate amount of F passivated effectively the electron traps in the IGZO bulk or at a GI/IGZO interface; however, excess F in the IGZO increased carrier concentration since F also acted as a shallow donor in IGZO.…”

“…19), and the initial properties of the TFTs with either SiO X or SiN X :F passivation after 1 h and 3 h annealing, respectively, were summarized in Table I. Both subthreshold swing (S) and hysteresis ( V H ) were improved for the TFT with SiN X :F-Pa when the post-annealing time was increased from 1 to 3 h. When the annealing time further increased to 5h, electrical properties of the TFT with SiO X -Pa did not change significantly, whereas that of the TFT with SiN X :F-Pa became conductive and did not exhibit switching properties.…”

“…We demonstrated that the fluorine-passivated IGZO TFT is advantageous for achieving highly reliable oxide TFTs under conditions of both NBIS and PBTS. 19 …”

“…1, and detail fabrication process of the IGZO TFTs was reported in Ref. 19. The SiO X passivation was deposited at 170…”

“…19 It was found that fluorine (F) effectively passivated electron traps and weakly bonded oxygen in an IGZO channel and at a gate insulator (GI)/channel interface when F diffused into an IGZO channel. However, both the F passivation effect of the near-VBM state and its influence on the NBIS stability of the IGZO TFT have not been investigated.…”