Split-gate Flash Research Articles

Simulation of enhanced injection split gate flash EEPROM device programming

The recent trend of mixed technology processes for versatile chip design has prompted the need for 5 V only CMOS compatible non-volatile memory devices. However, for high-speed applications flash EEPROM devices are generally used but often require external power supplies for the writing cycles. The High Injection MOS (HIMOS) cell can be programmed at high speed with a 5 V power supply and so is promising for low-density high-speed applications where only a single power supply is available. To aid in the design and optimisation of the HIMOS device a 2-D numerical device simulator HFIELDS has been adapted to simulate the hot-electron injection currents. This is the first time that numerical simulations of a split gate type flash EEPROM device have been reported and comparisons with measured data show good agreement.

A 512-kb flash EEPROM embedded in a 32-b microcontroller

A 512-kb flash EEPROM developed for microcontroller applications is reported. Many process and performance constraints associated with the conventional flash EEPROM have been eliminated through the development of a new flash EEPROM cell and new circuit techniques. Design of the 512-kb flash EEPROM, which is programmable for different array sizes, has been evaluated from 256- and 384-kb arrays embedded in new 32-b microcontrollers. The 512-kb flash EEPROM has incorporated the newly developed source-coupled split-gate (SCSG) flash EEPROM cell, Zener-diode controlled programming voltages, internally generated erase voltage, and a new differential sense amplifier. It has eliminated overerase and program disturb problems without relying on tight process controls and on critical operational sequences and timings, such as intelligent erase, intelligent program, and preprogram before erase. A modular approach was used for chip design to minimize development time and for processing technology to achieve high manufacturability and flexibility.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>