Magnetic field detection

Abstract

A solid state triode employs the Hall effect to asymmetrically proportion flow of current through different branches of a number of cascaded bifurcated N- charge carrier channels (10,18,20), thereby providing an indication of strength and direction of an applied magnetic field by measuring magnitude and sense of the difference between currents flowing in the two channel branches (14,16,24,26,30,32). The solid state triode is formed on an silicon-on-insulator (SOI) substrate (47,48,49) in which an N+ source region (54) and at least two end N+ drain regions (56,58) are interconnected by an N- charge carrier channel (60) that is defined by a plurality of P+ regions (64a,64b,64c,64d) in a thin single crystal silicon substrate (49) between the source and drain regions (54,56,58). A polysilicon gate (52) overlies the N- channel and acts as a self-aligning mask during manufacture of the triode to precisely align the N+ and P+ doping to the polysilicon gate configuration. The SOI has a very thin N- doped layer to which the N+ and P+ doping is applied in steps of successively different energy levels so that the doping extends completely through the N- layer and is uniform throughout the thickness of the layer. The N- channel is narrow and has a width at least twice the thickness of the crystal silicon uppermost layer of the SOI substrate.

Dependencies are inferred from the claim text.