Effective Radiation Damage to Floating Gate of Flash Memory

Abstract

Non-volatile memory (NVM) devices, based on floating gate (FG) technology, including EEPROM, NAND and OR Flash memories, are increasingly used today in both consumer products and high-end applications. Quality of 3D NAND Flash in solid-state drive (SSD) storage used in data center, automotive and space science is critical. While NOR Flash used in TWS earbuds for smartphones and IoT/5G products offers a quality of live option. To ensure reliability of the high-end products, e.g. for space application where ionizing radiation can produce potential damage to FGs, single event effects (SEEs) and total ionizing dose (TID) are typical assessments to evaluate product quality of Flash memory, subject to ionizing radiation particles of different energy and hence linear energy transfer (LET) in interactions with CMOS materials, Si and SiO2. Reported studies of SEE and TID using energy; stopping power (SP or S) or LET on various Flash memories are numerous. However, the quantitative results at various energy, S or LET can be misleading, as neither energy nor LET is an ideal quality factor in interpreting radiation hazards. Based on previous analysis of various radiation particles in CMOS silicon gate, the current study is extended to using the characteristics of range (R) of particle trajectory and specific ionization (Is) to analyze mean free path (Δ, distance between two ionization events) of electron, proton and several heavy ions in FG of Flash memory and the impact of electric charges generated by ionizing radiations. In the past decades the silicon process (of the gate length) has progressed from 100 nm down to 10 nm, our work further aims to explore effective radiation damage of SEE and TID by different types of particles, with respect to gate sizes of NVM cells.