C. Lombardi

Two-dimensional numerical analysis of floating-gate EEPROM devices

The importance of transient analysis in the design of floating-gate EEPROMs is demonstrated. Anomalous behavior, which was identified during transient measurements, has been simulated using HFIELDS, a general-purpose two-dimensional (2D) numerical device simulator. The corrective action that was taken at the time to eliminate the problem has been analyzed and explained using the simulation results. In addition, the simulator has been used to investigate 2D effects in the device due to process nonidealities. >

Process Analysis using RSM and Simulation

In this paper a statistical analysis of an advanced CMOS process performed using the Response Surface Method (RSM) applied to process/device simulation is presented. The statistical distribution of the most important electrical parameters (threshold voltages, saturation currents, ...) of the active devices have been predicted starting from the distributions of the input parameters (implant doses, furnace temperatures, ..). The simulated results are compared with data collected in a fabrication line and discussed.

Complete transient simulation of flash EEPROM devices

It has been demonstrated that the Fowler-Nordheim tunneling, hot electron injection, and band-to-band tunneling current models incorporated into the 2D device simulator HFIELDS have allowed an accurate simulation and analysis of the flash EEPROM cell during the transient writing cycles. These represent all the important physical mechanisms which occur during the writing of flash EEPROM devices. The physical models have been verified by comparison with flash EEPROM devices fabricated using a 1.0 mu m technology.<<ETX>>

The numerical simulation of substrate and gate currents in MOS and EPROMs

The gate current that flows during programming in the flash EEPROM device is a result of hot electron injection from the channel. The channel doping is high and the drain junction is abrupt and optimised to enhance the hot carrier avalanche generation in the silicon near the drain junction. As in the case with conventional MOS, this has the further impact of creating a high substrate current. In this work, a new model for both substrate and gate current using the same hot carrier energy distribution function in both models is presented. These models predict gate and substrate currents over a wide range of gate voltages and have been validated for both electron and hole hot carrier avalanche generation in n- and p-channel transistors. These models have been used to simulate flash EEPROM programming so that reliability issues, particularly with respect to the effect of the gate current due to hot hole injection, could be investigated.

Simulation of EPROM Device Programming Using the Hydrodynamic Model

Short channel EPROM devices were modeled using two simulator programs. The first is a classical drift-diffusion simulator and the second is a hydrodynamic one. The hydrodynamic simulator is then used to investigate more deeply the operation of short channel EPROM devices pointing out some possible scaling problems.

A model for hot-electron and hot-hole injection in flash EEPROM programming

Abstract A new model for hot-electron and hot-hole injection is presented. The model has been integrated into a two-dimensional device simulator for the purpose of flash EEPROM programming simulation. The model is demonstrated to be accurate over a range of floating gate voltages, by comparison with measured data from flash EEPROM devices of different gate lengths under different programming conditions.

Analysis of Transient Behaviour of Floating Gate EEPROMs

Charge transport and storage are essentially the mechanisms that describe the operation of non-volatile memory. In this paper, the importance of transient analysis in the design of floating gate EEPROMs is demonstated. Anomalous behaviour, which was identified during transient measurements, has been simulated using HFIELDS, a general purpose device simulator. The corrective action that was taken at the time has been analysed and explained using the simulation results. In addition the simulator has been used to investigate two dimensional effects in the device due to process non-idealities.