Patent ID: 9111986
Filing Date: 2015-08-18
Classification: H01L

Abstract:
1. A method of forming a device structure for a bipolar junction transistor, the method comprising: forming an intrinsic base layer on a semiconductor substrate; forming an etch stop layer on the intrinsic base layer; forming an extrinsic base layer on the etch stop layer; forming a first trench penetrating through the extrinsic base layer to the etch stop layer by etching the extrinsic base layer selective to the etch stop layer; forming a second trench penetrating through the extrinsic base layer to the etch stop layer; extending the first trench through the etch stop layer to the intrinsic base layer by etching the etch stop layer selective to the intrinsic base layer; extending the second trench through the etch stop layer to the intrinsic base layer; and after the first trench is extended through the etch stop layer, forming an emitter using the first trench, wherein the second trench is concurrently formed with the first trench, and the second trench is concurrently extended through the etch stop layer with the first trench.