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This article relates generally to integrated circuit fabrication and, more particularly, to ion implantation of base dopant in high performance transistors.
English (United States)
This text was extracted from a PDF file.
This is the abbreviated version, containing approximately
87% of the total text.
Page 1 of 1
Fabrication of Bipolar Transistor
This article relates generally to integrated circuit fabrication and, more
particularly, to ion implantation of base dopant in high performance transistors.
The distribution profile of an ion-implanted base can be made steeper in
single crystal silicon by first bombarding the silicon crystal to make it amorphous,
then implanting a dopant, such as boron, for the base. The amorphousness
should extend just into the subcollector. Thereafter, the amorphous region is
recrystallized by annealing at temperatures above 600OEC. There is no
significant redistribution of the boron, but defects remain in the crystal lattice
immediately beneath the recrystallized region. The defects may move toward the
surface during subsequent heat treatment and cause junction leakage or "pipes."
Defect motion can be constrained by implanting oxygen, which can be done
at the time the boron is implanted. The oxygen-implanted layer pins the crystal
dislocations in a dense network of defects and the layer should be located below
the depletion region of the collector junction.
Emitter formation may be accomplished by either implanting arsenic or
depositing polysilicon. If polysilicon is used, recrystallization of the amorphous
region occurs during the deposition but subsequent heat treatment at higher
temperature is required to drive the polysilicon slightly into the crystal. If
redistribution of arsenic is desired, a heat treatment at a higher temperature is