ES364975A1 - A SEMICONDUCTOR DEVICE. - Google Patents

Abstract

A region of a semi-conductor device having a junction intersecting a surface where it is covered with an insulating layer is contacted by means of a layer of crystalline semi-conductor material disposed in an opening in the insulating layer and having a thickness greater than that of the insulating layer and a layer of metal on the crystalline layer. As shown, Fig. 1, in an overlay transistor having an N type collector region 6 and a P type base region 10 provided with heavily doped collector and annular base contact regions 2 and 8 respectively, a plurality of emitter regions 14 are provided by depositing phosphorus from the vapour phase to form a compound layer (e.g. P 2 O 5 ) over the surface of an apertured SiO 2 mask 20, and heating to diffuse-in the phosphorus. The phospho-silicate glass layer which forms over the mask is removed by etching. The wafer is then subjected to an epitaxial deposition process to provide N type emitter contacts 16 in the windows the process being continued until these regions have grown to a thickness greater than that of the oxide layer 20 and have started to spread out on its surface. Windows are then formed over the base contact regions and aluminium is deposited, masked, etched and sintered to produce emitter contacts 18 and interconnections (not shown) and base contacts 12. The insulating layer may also be silicon nitride. In an alternative embodiment, Figs. 2 to 4 (not shown), emitter windows are formed in the insulating layer (20) a shallow phosphorus diffusion is performed, N+ type contacts (22) heavily doped with phosphorus are epitaxially grown in the windows, the surface impurity concentration of the epitaxial contacts is increased by a phosphorus diffusion, and the device is then heated to diffuse phosphorus from the epitaxial contacts (22) into the P type base region (10) to form the emitter regions (24). Ohmic contacts are then applied. The crystalline contact material may also be a polycrystalline semi-conductor material and the overlying metal may also be indium or tungsten. The semi-conductor wafer may also be of germanium or of a III-V compound.