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 64Mbit and future flash memories. A 1.43 μm 2 cell area is obtained by using 0.4 μm technology. The HiCR cell structure is realized by (1) self-aligned definition of small tunnel-regions underneath the floating-gate sidewall and (2)an advanced rapid thermal process for 7.5 nm-thick tunnel-oxynitride. The internal voltages used for PROGRAM and ERASE operations are +8 V and +12 V, respectively. The use of low positive internal voltages results in reducing total process step numbers compared with reported memory cells. The HiCR cell also realizes low-power and fast random access with a single 3 V power supply.