Study of Novel Floating-Gate Oxide Semiconductor Memory Using Indium--Gallium--Zinc Oxide for Low-Power System-on-Panel Applications

A novel floating-gate oxide semiconductor (FLOTOS) memory using a wide-band-gap indium--gallium--zinc oxide (IGZO) is presented for low-power system-on-panel applications. An IGZO thin-film-transistor (TFT) is used as a memory transistor for controlling read current as well as a switching transistor for storing charges in a storage capacitor ($C_{\text{s}}$). The FLOTOS memory is fabricated using a standard IGZO TFT process without any additional process or mask steps. The proposed precharge-assisted threshold voltage compensation technique makes it possible to realize an infinite number of write cycles and a low-power write operation with a bit-line voltage of 5 V. Furthermore, excellent data retention longer than 10 h is obtained at 60 °C even under the worst bias-stress condition of read operation with the ultra low off-state leakage ($2.8\times 10^{-20}$ A/μm) of the IGZO TFTs, which is estimated to be smaller by more than 7 orders of magnitude than that of polycrystalline silicon TFTs.