| US 7,538,004 B2 | ||
| Method of fabrication for SiGe heterojunction bipolar transistor (HBT) | ||
| Peter J. Geiss, Underhill, Vt. (US); Alvin J. Joseph, Williston, Vt. (US); Rajendran Krishnasamy, Essex Junction, Vt. (US); and Xuefeng Liu, South Burlington, Vt. (US) | ||
| Assigned to International Business Machines Corporation, Armonk, N.Y. (US) | ||
| Filed on Nov. 09, 2007, as Appl. No. 11/937,534. | ||
| Application 11/937534 is a division of application No. 10/711482, filed on Sep. 21, 2004, granted, now 7,317,215. | ||
| Prior Publication US 2008/0124882 A1, May 29, 2008 | ||
| Int. Cl. H01L 21/331 (2006.01) | ||
| U.S. Cl. 438—368 [438/342; 257/E21.372; 257/E21.608] | 9 Claims |
| 1. A method of fabricating a heterojunction bipolar transistor comprising:
providing a semiconductor substrate of a first conductivity type comprising a collector region;
forming a base region on said substrate, said base region comprising a first base region doped with a non-dopant having a
first concentration and a second base region doped with said non-dopant having a second concentration; and
forming an emitter region over said base region, said emitter region comprising a first polysilicon layer in-situ doped with
a dopant having a first concentration and a second polysilicon layer in-situ doped with said dopant having a second concentration.
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