Abstract:
A read only memory having the capability of being written into once after manufacture. The cells of the memory are capable of being fused or permanently altered by directing a fusing current to the selected cells. The cell is a monolithic semiconductor device comprising a diode to be biased in a forward direction and a diode to be biased in the reverse direction structured so as to form back-to-back diodes. The reverse diode has a lower reverse breakdown voltage than the forward diode, and a metal connection, unconnected to any remaining circuit elements contacts the semiconductor device between diode junctions. The fusing current causes a metal-semiconductor alloy to form and short out the reverse diode.
Abstract:
NPN/PNP FABRICATION PROCESS WITH IMPROVED ALIGNMENT A double diffused, lateral PNP structure is disclosed which may be formed simultaneously with the vertical NPN structure. The novel feature of the structure is the vertical projection of the N-type base region for the PNP, down through the surrounding diffused P-type collector?and into an N-type epitaxial layer between the collector diffusion and a buried sub-base, an N-type "sub-base", to electrically contact the base. The N-type epitaxial layer serves as the extrinsic base region permitting contact with the surface. The double diffused base and emitter structure permits a precise intrinsic base width to be formed for the lateral PNP. Thus, a high performance PNP can be constructed with compatible high performance NPNs on the same substrate.