US PATENT SUBCLASS 257 / 548
.~.~ At least three regions of alternating conductivity types with dopant concentration gradients decreasing from surface of semiconductor (e.g., "triple-diffused" integrated circuit)

Current as of: June, 1999
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257 /   HD   ACTIVE SOLID-STATE DEVICES (E.G., TRANSISTORS, SOLID-STATE DIODES)

499  DF  INTEGRATED CIRCUIT STRUCTURE WITH ELECTRICALLY ISOLATED COMPONENTS {9}
544  DF  .~ With pn junction isolation {8}
548.~.~ At least three regions of alternating conductivity types with dopant concentration gradients decreasing from surface of semiconductor (e.g., "triple-diffused" integrated circuit)

DEFINITION

Classification: 257/548

At least three regions of alternating conductivity types with dopant concentration gradients decreasing from surface of semiconductor (e.g., "triple-diffused" integrated circuit):

(under subclass 544) Subject matter including at least three regions of alternating conductivity type (p or n), with each successive region contained within the previous region, and each of the regions having a doping concentration which decreases with distance from the same external surface of the semiconductor body.

(1) Note. Junction isolated integrated circuits of this type are typically manufactured by starting with an uniformly doped p-type semiconductor body to serve as the substrate,

then diffusing spaced n-type regions into the P substrate to form collectors of npn transistors, and then successively diffusing p-type base and n-type emitters into the spaced n-type regions. Junction isolated integrated circuits of this type are simple to manufacture, due to the reduced number of processing steps involved, but suffer from non-optimum doping concentration profiles, particularly in the collector regions.