A HIGH CAPACITIVE COUPLING RATIO (HICR) CELL FOR SINGLE 3V POWER-SUPPLY FLASH MEMORIES

A contactless cell with High Capacitive Coupling Ratio (HiCR) of 0.8, which is programmed and erased by Fowler-Nordheim (F-N) tunneling, has been developed for single 3 V power supply 64 Mbit and future flash m emories. A 1.43 mu m(2) cell area is obtained by using 0.4 mu m techno logy. The HiCR cell structure is realized by (1) self-aligned definiti on of small tunnel-regions underneath the floating-gate sidewall and ( 2) an advanced rapid thermal process for 7.5 nm-thick tunnel-oxynitrid e. The internal voltages used for PROGRAM and ERASE operations are +8 V and +12 V, respectively. The use of low positive internal voltages r esults in reducing total process step numbers compared with reported m emory cells. The HiCR cell also realizes low-power and fast random acc ess with a single 3 V power supply.