Patent ID: 7687887
Filing Date: 2010-03-30
Classification: H01L

Abstract:
1. A method of forming a bipolar transistor structure in a semiconductor substrate having a first conductivity type, the bipolar transistor structure including a collector region having a second conductivity type that is opposite the first conductivity type and that is formed in a substrate active device region defined by isolation dielectric material formed in an upper surface of the semiconductor substrate, the bipolar transistor structure further including an epitaxial layer having a monocrystalline portion formed over the collector region and a polycrystalline portion formed over the isolation dielectric material, the method comprising: forming a dielectric layer over the epitaxial layer; forming a patterned mask over the dielectric layer, the patterned mask having a mask opening formed therein to expose an upper surface area of the dielectric layer, the upper surface area having a first width; performing an etch step utilizing the mask opening to define a sloped emitter window in the dielectric layer to expose an emitter surface area of the monocrystalline portion of the epitaxial layer such that the emitter surface area has a second width that is less than the first width; forming in-situ doped emitter material having the second conductivity type in the sloped emitter window; exposing the emitter material; forming dielectric spacer material on sidewalls of the emitter material to provide an emitter structure; and utilizing the emitter structure to introduce dopant having the first conductivity type into portions of the epitaxial layer.