The epitaxy-over-oxide diode

The fabrication of a diode in a one-step epitaxial deposition-diffusion is described. The simple, low cost manufacture yields a self-passivated device of high performance. A low resistivity substrate wsfer is overlaid with a relatively thin epitaxial layer of the same impurity type and the proper resistivity. Oxide is grown or deposited over this and circular windows are cut. When the wafer + oxide sandwich is subjected to an epitaxial deposition of silicon containing a high density of impurities of the opposite type, single crystalline silicon forms over the oxide window and polycrystalline silicon forms elsewhere. In addition, since the deposited material has many more impurities per volume element than the original epitaxy, diffusion occurs during the deposition process. Finally, the deposited polycrystalline material is etched into a mesa down to the oxide layer and a large metallic button formed. Diodes are separated by conventional scribe and break, or by etch separation.