Method of manufacturing increased conductivity base contact/feeders with self-aligned structures
AssigneeSGS-Thomson Microelectronics S.A.
InventorWilliam P. Imhauser
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Abstract
A very deep P.sup.+ diffusion step is performed prior to the definition of a self-aligning emitter/P.sup.+ region. Furthermore, the initial P.sup.+ region is formed with dimensions sufficiently narrow to allow the subsequent emitter/P.sup.+ formation step to overlap the deeper P.sup.+ step by enough distance for the P.sup.+ step to completely cover the deep P.sup.+ region with its significant lateral diffusion. In this manner, a low sheet resistance in combination with proper alignment of the P.sup.+ heavy region with the emitter region is obtained.
Claims6
A method for forming a self-aligned semiconductor device, comprising the steps of:
- a) forming a deep P.sup.+ region in an epitaxial layer at a top surface of a semiconductor device, wherein the deep P.sup.+ region is formed using a high concentration diffusion step at high temperature;
- b) forming a base region by ion implantation after formation of said deep P.sup.+ region, at the top surface of the semiconductor device and over the deep P.sup.+ region;
- and
- c) forming a shallow P.sup.+ region, with doping concentration and depth less than said deep P.sup.+ region, by implantation which overlaps said deep P.sup.+ region, which simultaneously isolates the emitter region from said deep P.sup.+ region, wherein the emitter region is formed at the top surface of the semiconductor device and is separated from the shallow P.sup.+ region by a spacer,
- wherein said shallow P.sup.+ region overlaps the deep P.sup.+ region so that alignment between said deep P.sup.+ region and said emitter region is maintained, and wherein said shallow P.sup.+ region has a depth which is less than the depth of said deep P.sup.+ region.
Dependencies are inferred from the claim text.