US PATENT SUBCLASS 257 / 543
.~.~.~.~ Lightly doped junction isolated resistor (e.g., ion implanted resistor)

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}
528  DF  .~ Passive components in ICs {4}
536  DF  .~.~ Including resistive element {2}
539  DF  .~.~.~ Combined with bipolar transistor {4}
543.~.~.~.~ Lightly doped junction isolated resistor (e.g., ion implanted resistor)

DEFINITION

Classification: 257/543

Lightly doped junction isolated resistor (e.g., ion implanted resistor):

(under subclass 539) Subject matter wherein the resistive element is of the form of a lightly doped layer of one conductivity type located in a region of opposite conductivity type, such that the pn junction between the resistor region and its containing opposite conductivity type region serves to isolate the resistor.

(1) Note. A resistor region is considered to be lightly doped if it is substantially less heavily doped than the base region of the bipolar transistors in the same integrated circuit, or if it is has a doping density not greater than 100 times that of the opposite conductivity type region in which it is contained.

(2) Note. Such lightly doped resistors are typically formed by the process of ion implantation, wherein desired dopant atoms are placed in the semiconductor body by ionizing the dopant material and accelerating the resulting ions through a carefully controlled voltage to impinge on the surface of the semiconductor material, so that the depth of the resulting dopant atoms is determined by the accelerating voltage and the doping density is determined by the flux of the ion beam.