NOVEL EPROM DEVICE FABRICATED USING FOCUSED BORON ION-BEAM IMPLANTATION.

A novel floating-gate avalanche injection (FAMOS) type erasable programmable read-only memory (EPROM) device is demonstrated, with a heavily focused ion-beam implanted region of about 0. 2- mu m width at the drain edge of the channel. This heavily B** plus -doped region permits a higher electric field near the drain edge, resulting in a remarkable increase of the hot-carrier generation rate, and reduces both the programming voltage and programming time. A three-dimensional device simulator, CADDETH, predicted that the electric field at the drain edge would increase by about six times, which would lead to hot-carrier generation efficiency three orders of magnitude higher. The programming voltage of a fabricated device is reduced by about one half, in obtaining the same programming characteristics as the conventional device. The programming time of a fabricated device with an effective channel width of 3. 1 mu m is 50 ms, which is 1/50 of that of a conventional device.