| 摘要 |
A method for forming an epitaxial base layer in a bipolar device. The method comprises the steps of: providing a structure having a field isolation oxide region ( 12 ) adjacent to an active silicon region ( 10 ); forming a silicon nitride/silicon stack ( 14, 16 ) above the field isolation oxide region (12), wherein the silicon nitride/silicon stack ( 14, 16 ) includes a top layer of silicon ( 14 ) and a bottom layer of silicon nitride (16); performing an etch to the silicon nitride/silicon stack ( 14, 16 ) to form a stepped seed layer, wherein the top layer of silicon is etched laterally at the same time the bottom layer of silicon nitride is etched; and growing an Si/SiGe/Si stack ( 20 ) over the stepped seed layer and active region ( 10 ).
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