Optical Analysis and Reliability Testing of Dual gate Thin-Film Transistor of Amorphous Indium-Gallium-Zinc-Oxide
Date Issued
2012
Date
2012
Author(s)
Huang, Kuan-Chang
Abstract
Recently, there has been increasing interest in amorphous indium – gallium - zinc oxide (α-IGZO) thin-film transistors (TFTs) for Active Matrix Organic Light Emitting Display (AMOLED). The α-IGZO TFTs have higher on/off current ratio and higher carrier mobility as compared to amorphous Si (α-Si) TFTs, and is suitable for the high performance applications.
The defects within the bandgap especially tail states and shallow states affect the electrical characteristic of α-IGZO TFTs. The absorption coefficient measurement is used to measure the width of tail states (Urbach energy) and inspect the quality of α-IGZO films in early stage of fabrication. α-IGZO films with different process conditions were analyzed.
In convenience to control the threshold voltage of α-IGZO TFT, dual gate TFT is consider to be one of the solutions. We can get larger negative threshold voltage by applying positive bias at top gate and larger positive threshold voltage by applying negative bias at top gate. Thus the instability test for dual gate α-IGZO TFT has become an important issue. The characteristics of α-IGZO TFT such as SS, mobility, Ion, and on/off ratio could be affected during instability test.
The bottom channel has a higher mobility than the top channel due to the process difference. Either to store negative charges in the top gate insulator or to apply negative bias at the top gate, the electrons in the channel can be pushed toward the bottom SiOX/α-IGZO interface by coulomb repulsion force, and the mobility enhancement is observed. The storage of negative charge in the top insulator can be obtained by applying positive voltage at the top gate for controllable time.
Subjects
α-IGZO
TFT
absorption
PBTI
Mobility enhancement
Type
thesis
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