Proton Inserted SiO2 Dielectrics for Nonvolatile Memory-Thin Film Transistor

Abstract

We demonstrated the nonvolatile memory functionality of both nano-crystalline silicon (nc-Si) and amorphous indium gallium zinc oxide (a-IGZO) field effect transistors (FETs) using mobile protons that are generated by very short time (within 5 minutes) hydrogen neutral beam (H-NB) treatment at room temperature (25 °C). Some researches try to hydrogen insertion process via long time (40 minutes) high-pressure hydrogen annealing (HPHA) at high temperature (400 °C) that also need several steps such as poly silicon deposition, HPHA process, and poly silicon etching process. However our hydrogen insertion process does not need any other additional process but only H-NB process during normal thin film transistor fabrication. Also the whole memory fabrication process kept under 50 °C (except SiO2 deposition process; 300 °C). These NVM-TFT(nc-Si and a-IGZO) and devices exhibited reproducible hysteresis, reversible switching, and nonvolatile memory behaviors in comparison with those of the conventional FET devices. We also investigated neutral beam energy effect on non-volatile memory functionality with IGZO NVM-TFTs. The hysteresis widths of the IGZO NVM-TFTs exhibited strong linear dependency on the H-NB treatment energy. We expected this result from the energy dependent hydrogen surface density profile. The sandwiched hydrogen between insulators becomes mobile proton without annealing process. This H-NB dependent mobile proton density variation is meaningful because until now the only way to increase proton density was increasing ambient temperature or annealing time. The hydrogen neutral beam process between insulators to generate mobile proton is easily controlled by reflector bias. Our study will further provide a useful route of creating memory functionality and incorporating proton-based storage elements onto a probability of next generation flexible memorable electronics such as low power consumption flexible display panel. Figure 1