Multi-valued charge trapping memory based on amorphous-indium-gallium-zinc oxide thin film transistor with designed Ga ₂ O ₃ /Al ₂ O ₃ stack insulator

Abstract

Multi-valued charge trapping memory is demonstrated based on an amorphous-indium-gallium-zinc oxide thin-film transistor (a-IGZO-TFT) with a Ga 2 O 3 /Al 2 O 3 stack gate insulator. The memory device shows a positive shift of threshold voltage as large as 12.6 V after +20 V/1 s programming. The erasing process can be divided into two stages. Vertical electrical field erases the trapped electrons partially, resulting in negative threshold voltage shift with hump current in sub-threshold region. It is defined as a first erasing stage. Furthermore, the memory can be erased by UV-light effectively due to the generated electron-hole pairs in a-IGZO channel. It is defined as second erasing stage. The good retention characteristics are confirmed for various storage states. The storage mechanism is analyzed according to the energy band alignment obtained by XPS narrow scans and valence band spectra.

High-performance amorphous indium-gallium-zinc-oxide thin-film-transistor and its applications

“…This structure refers to a sandwich-like stack of blocking layer (BL) interfacing with gate electrode to reduce leakage current, chargetrapping layer (CTL) providing abundant trap sites to capture/release carriers when the program/erase signal is applied, and tunneling layer (TL) interfacing with IGZO to prevent trapped carriers diffusing back to IGZO. [152]- [154] The commonly used materials for CTL include SiNx [155] , HfO2 [156] , defect-engineered AlOx [157], [158] , Sm2O3 [159] , etc. P. Ma designed and demonstrated a charge-trapping-flash (CTF) memory with IGZO channel in combination with an Alumina-based gate stack (Fig.…”