Protonic nonvolatile field effect transistor memories in Si/SiO/sub 2//Si structures

Abstract

A low-voltage, radiation-tolerant, nonvolatile field effect transistor (NVFET) memory involving proton motion in SiO/sub 2/ 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/spl deg/C), the H/sup +/ is largely imprisoned in the buried SiO/sub 2/ 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 10/sup 6/ cycles. Under an unbiased condition, the net proton density is not significantly affected by radiation up to at least 100 krad (SiO/sub 2/). Last, we compare many of the properties of the NVFET to commercial flash nonvolatile memories.