Protonic nonvolatile field effect transistor memories in Si/SiO2/Si structures

A low-voltage, radiation-tolerant, nonvolatile field effect transistor (NVFET) memory involving proton motion in SiO₂ is illustrated in both bulk Si and silicon-on-insulator devices. We discuss a mechanism by which the protons are created in the oxide layer by a forming gas anneal. At low temperature (T<250°C), the H⁺ is largely “imprisoned” in the buried SiO₂ layer; i.e., the ions are sandwiched between the two encapsulating Si layers. The Si layers can be either c-Si or poly-Si, thus the technology is compatible with standard Si processing. The protons can be reliably and controllably drifted from one interface to another without any noticeable degradation in the signal past 10⁶ cycles. Under an unbiased condition, the net proton density is not significantly affected by radiation up to at least 100 krad (SiO₂). Last, we compare many of the properties of the NVFET to commercial flash nonvolatile memories