| US 7,544,577 B2 | ||
| Mobility enhancement in SiGe heterojunction bipolar transistors | ||
| Thomas N. Adam, Poughkeepsie, N.Y. (US); and Dureseti Chidambarrao, Weston, Conn. (US) | ||
| Assigned to International Business Machines Corporation, Armonk, N.Y. (US) | ||
| Filed on Aug. 26, 2005, as Appl. No. 11/212,187. | ||
| Prior Publication US 2007/0045775 A1, Mar. 01, 2007 | ||
| Int. Cl. H01L 21/331 (2006.01) | ||
| U.S. Cl. 438—344 [438/345] | 17 Claims |
| 1. A method for enhancing carrier mobility in a heterojunction bipolar transistor that has a SiGe-containing base layer of
not more than about 100 nm in thickness, while without changing quasi-static drift field of said base layer, comprising:
measuring the thickness of said SiGe-containing base layer;
calculating a critical germanium content based on the thickness of the SiGe-containing base layer, wherein the calculated
critical germanium content of the SiGe-containing base layer is not less than about 10 atomic %;
measuring germanium content in said SiGe-containing base layer to determine germanium content profile of said SiGe-containing
base layer; and
changing the germanium content profile of the SiGe-containing base layer, by uniformly increasing the germanium content in
the SiGe-containing base layer by a sufficient amount so that the changed germanium content profile has an average germanium
content of not less than about 80% of the calculated critical germanium content.
|