Method of fabricating an ultra-thin active region for high speed

Details Method of fabricating an ultra-thin active region for high speed Method of fabricating an ultra-thin active region for high speed

1992-01-24

1993-01-05

Quach, T. N.

Fishing, trapping, and vermin destroying

437 95, 437131, 148DIG41, H01L 21328

Patent

active

051770253

ABSTRACT:
A method of fabricating a semiconductor device to retard diffusion of a dopant from a center active region into adjacent regions. The center active region is epitaxially formed by selectively increasing and decreasing an introduction of diffusion-suppressing material, preferably germanium, into a semiconductor material, preferably silicon, so that a vertical profile of the content of the diffusion-suppressing material is such that outdiffusion of a dopant is minimized. One embodiment of the tailoring is to increase the concentration of the diffusion-suppressing material at both of the opposed sides of a base region of a bipolar transistor, thereby providing concentration peaks at the interfaces of the base region with collector and emitter regions. The concentration of germanium in a Si.sub.1-x Ge.sub.x layer is such that the value x is within the range 0.08 to 0.35 and optimally within the range 0.15 to 0.31. The dopant, preferably boron, also has a tailored concentration profile to minimize outdiffusion. A thinner, more highly doped active region is thereby achieved.

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