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Remarkable Improvement in Foldability of Poly‐Si Thin‐Film Transistor on Polyimide Substrate Using Blue Laser Crystallization of Amorphous Si and Comparison with Conventional Poly‐Si Thin‐Film Transistor Used for Foldable Displays
Author(s) -
Do Youngbin,
Jeong Duk Young,
Lee Suhui,
Kang Seongbok,
Jang Seonhyang,
Jang Jin
Publication year - 2020
Publication title -
advanced engineering materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.938
H-Index - 114
eISSN - 1527-2648
pISSN - 1438-1656
DOI - 10.1002/adem.201901430
Subject(s) - materials science , thin film transistor , amorphous solid , polyimide , optoelectronics , annealing (glass) , amorphous silicon , crystallization , substrate (aquarium) , transistor , silicon , layer (electronics) , crystallography , composite material , crystalline silicon , voltage , electrical engineering , chemical engineering , chemistry , oceanography , engineering , geology
Highly robust poly‐Si thin‐film transistor (TFT) on polyimide (PI) substrate using blue laser annealing (BLA) of amorphous silicon (a‐Si) for lateral crystallization is demonstrated. Its foldability is compared with the conventional excimer laser annealing (ELA) poly‐Si TFT on PI used for foldable displays exhibiting field‐effect mobility of 85 cm 2 (V s) −1 . The BLA poly‐Si TFT on PI exhibits the field‐effect mobility, threshold voltage ( V TH ), and subthreshold swing of 153 cm 2 (V s) −1 , −2.7 V, and 0.2 V dec −1 , respectively. Most important finding is the excellent foldability of BLA TFT compared with the ELA poly‐Si TFTs on PI substrates. The V TH shift of BLA poly‐Si TFT is ≈0.1 V, which is much smaller than that (≈2 V) of ELA TFT on PI upon 30 000 cycle folding. The defects are generated at the grain boundary region of ELA poly‐Si during folding. However, BLA poly‐Si has no protrusion in the poly‐Si channel and thus no defect generation during folding. This leads to excellent foldability of BLA poly‐Si on PI substrate.