Transient Simulation to Analyze Flash Memory Erase Improvements Due to Germanium Content in the Substrate

We present a detailed and accurate physics-based transient simulation for modeling Flash memory erase characteristics when the substrate contains different percentages of germanium (Ge). Typical cells are erased by moving electrons from the floating gate to the drain, source, or substrate. This paper addresses substrate erase modeling using a simulation based on the solution to Poisson's equation with Ge percentage as an independent variable. The goal of this paper is to demonstrate the derivation of an accurate erase simulation and show the improvements that can be achieved by using silicon-germanium (SiGe) substrate material versus silicon (Si) only. Several papers have been published on MOSFETs with SiGe substrates, but none has been published on the use of SiGe substrates in Flash memory.