Abstract:
A read-mostly memory cell is disclosed comprising a floating gate avalanche injection field effect transistor storage device equipped with an erasing electrode. The memory portion of the erasable storage devices comprises a P channel FET having a floating polycrystalline silicon gate separated from an N-doped substrate by a layer of silicon dioxide. The erasing portion of the device comprises an erasing electrode separated from the polycrystalline silicon floating gate by a thermally grown layer of silicon dioxide having a leakage characteristic which is low in the presence of low electrical fields and high in the presence of high electrical fields. The floating gate is heavily doped with boron which also partially dopes the thermally grown silicon dioxide layer. The floating gate is charged negatively by avalanche breakdown of the FET drain while the erase gate is grounded to the substrate. The floating gate is discharged (erased) upon the application of a positive pulse to the erase electrode with respect to the semiconductor substrate causing electrodes on the charged floating gate to leak through the thermal oxide to the erasing electrode.
Abstract:
An electronically rewritable read-only memory comprising an integrated semiconductor array of P-N junctions formed in a semiconductor substrate. A dielectric film is formed on the surface of the substrate on top of which a thin metallic film is deposited. The dielectric is thinner above an active region of each of the junctions than it is above the other regions of the substrate. When a suitable voltage is applied across the metallic film and dielectric, the metallic film diffuses through the dielectric film at the thinner areas, thereby forming ohmic via connections with the active junction regions. At the same time, the dielectric ''''self-heals'''' i.e., the via connections are disconnected from the metallic film around the periphery of the thin areas of the dielectric. A second layer of metallization over the metallic film establishes conductive contact between the layer and the active junction region. The contacts can be broken at selected junctions by passing a current through the diffused metallization. The contacts can be reestablished at selected junctions by applying a suitable healing voltage across the metallic film and the dielectric.