Influence of metallization process on solution-processed InGaZnO thin film transistors

Byeongwan Kim; Hyunkyung Lee; Seungyeon Hong; Hyo Jung Kim; Kanghyun Kim; Haeyong Kang

doi:10.1088/1361-6528/ac0eaf

Influence of metallization process on solution-processed InGaZnO thin film transistors

Nanotechnology. 2021 Jul 13;32(40). doi: 10.1088/1361-6528/ac0eaf.

Authors

Byeongwan Kim¹, Hyunkyung Lee¹, Seungyeon Hong^{2

3}, Hyo Jung Kim^{2

3}, Kanghyun Kim⁴, Haeyong Kang¹

Affiliations

¹ Department of Physics, Pusan National University, Busan 46241, Republic of Korea.
² Department of Organic Material Sceience and Engineering, Pusan National University, Busan 46241, Republic of Korea.
³ School of Chemical Engineering, Pusan National University, Busan 46241, Republic of Korea.
⁴ Samsung Display, Chungcheongnam-Do 31454, Republic of Korea.

PMID: 34171856
DOI: 10.1088/1361-6528/ac0eaf

Abstract

Low-temperature solution-processed InGaZnO (IGZO) thin film transistors (TFTs) have recently attracted significant attention as the next-generation flexible display TFTs, owing to their high transparency, high electrical performance, low-cost fabrication, and large-area scalability. However, solution-processed amorphous IGZO TFTs have several drawbacks, such as poor film quality or low stability, and have been studied with view to improving the device performance. One of the critical components determining device characteristics is the metallization process, which we systematically studied using aluminum (Al) source and drain electrodes. The electrical properties were measured for different channel lengths and evaluated using the threshold voltage (V_th) and subthreshold swing (SS). Al electrodes directly affect the channel region, enhancing the electron density because of the doping effect from Al and oxygen vacancy-related oxidation of Al and causing an abnormal negative shift ofV_th, which is confirmed by the component analysis via various spectroscopies. To understand and improve the TFT characteristics, we conducted a low-temperature post-annealing process and polymer passivation and succeeded in movingV_thfrom over 150 V to near 0 V and remarkably improved SS. This study discovered that the influence of source-drain metallization on the channel region determines the device characteristics through the close relation between metal oxidation and the number of oxygen vacancies.

Keywords: InGaZnO; annealing; poly(methyl methacrylate) passivation; solution-processed; thin film transistor; time-of-flight secondary ion mass spectrometer; x-ray photoelectron spectroscopy.