Optimization of a source-side-injection FAMOS cell for flash EPROM applications

A 0.6- mu m FAMOS cell structure, which features a lightly doped source region to achieve enhanced source-side-injection for channel hot electron programming, is presented. The use of the source-side-injection mechanism for EPROM programming has been previously proposed, but this work is the first time that a source-side-injection cell with a lightly doped source region has been fabricated and evaluated. The impact of the source dopant concentration and the depth of this non-overlapped LDD (lightly doped drain) region on cell programming performance has been characterized and optimized. The optimized cells exhibit excellent programmability for drain voltage down to 3.3 V. Studies of reliability issues and write/erase endurance results indicate that this cell is a viable candidate for 5-V, or 3.3-V, high-density flash EPROM applications.<>