Linearity and Lateral Isolation in a BiCMOS Process Through Counter-Doping Of Epitaxial Silicon Region

A method comprising:

• growing an epitaxial layer over a semiconductor substrate, wherein the semiconductor substrate has a first conductivity type and the epitaxial layer has a second conductivity type, opposite the first conductivity type;
• forming a mask over the epitaxial layer, wherein the mask covers a first region of the epitaxial layer and exposes a second region of the epitaxial layer;
• implanting a dopant having the first conductivity type through the mask into the second region of the epitaxial layer, whereby the second region of the epitaxial layer becomes counter-doped to the first conductivity type;
• forming one or more shallow trench isolation regions in the counter-doped second region of the epitaxial layer, wherein portions of the counter-doped second region of the epitaxial layer are exposed through the one or more shallow trench isolation regions, and wherein the one or more shallow trench isolation regions and the counter-doped second region of the epitaxial layer form an isolation region.

A method comprising:

• growing an epitaxial layer over a semiconductor substrate, wherein the semiconductor substrate has a first conductivity type and the epitaxial layer has a second conductivity type, opposite the first conductivity type;
• forming a mask over the epitaxial layer, wherein the mask includes openings that define locations of shallow trench isolation regions to be formed;
• etching into the epitaxial layer through the openings in the mask, thereby creating a plurality of shallow trenches, wherein thinned portions of the epitaxial layer remain below the shallow trenches;
• implanting a dopant having the first conductivity type through the mask into the thinned portions of the epitaxial layer, whereby the thinned portions of the epitaxial layer are counter-doped to the first conductivity type;
• and
• filling the shallow trenches with a dielectric material, thereby forming shallow trench isolation regions.