Development of 3.3V flash ZE(2)PROM cel and array.

摘要

Most of the conventional flash E2PROM cells have major limitations for low voltage applications and suffer from slow programming speeds. This thesis describes a Zener based MOS flash memory cell (ZE 2PROM), programmed by hot electrons generated by a heavily doped reverse biased p+n+ junction attached to the drain. The Zener based programming method provides a practical solution to some of the limitations of conventional channel hot electron programming method. This cell operates with a single supply of 3.3V and achieves an order of magnitude reduction of programming time compared to conventional flash memory cells. The reduced Zener breakdown current also enables many bits to be programmed simultaneously. The cell can be implemented in a NOR type memory array. It uses an orthogonal write technique to achieve fast programming with low power dissipation and reduced drain disturbance. The modeling of the charge transfer behavior of the ZE2PROM cell is investigated using 2-D device simulations to specify the charging and discharging of the floating gate during programming and erasing.; Experimental ZE2PROM arrays were implemented in a 0.8 m m lithography CMOS process flow in which the n-LDD step was replaced with a one sided p+ boron implant with a doping level of ∼ 1019cm-3. This minor change to a standard CMOS process, makes the concept highly attractive for embedded memory applications. A programming time of 850ns at 3.3V supply was achieved on fabricated test devices.