FORMATION OF A HIGH ASPECT RATIO TRENCH IN A SEMICONDUCTOR SUBSTRATE AND A BIPOLAR SEMICONDUCTOR DEVICE HAVING A HIGH ASPECT RATIO TRENCH ISOLATION REGION

摘要

Disclosed is a trench formation technique wherein a first etch process forms an opening through a semiconductor layer into a semiconductor substrate and then a second etch process expands the portion of the opening within the substrate to form a trench. However, prior to the second etch, a doped region is formed in the substrate at the bottom surface of the opening. Then, the second etch is performed such that an undoped region of the substrate at the sidewalls of the opening is etched at a faster etch rate than the doped region, thereby ensuring that the trench has a relatively high aspect ratio. Also disclosed is a bipolar semiconductor device formation method. This method incorporates the trench formation technique so that a trench isolation region formed around a collector pedestal has a high aspect ratio and, thereby so that collector-to-base capacitance Ccb and collector resistance Rc are both minimized.

主权项

1. A method comprising:
providing a semiconductor substrate; depositing a semiconductor layer on a top surface of said semiconductor substrate; performing a first etch process to form an opening extending vertically through said semiconductor layer into said semiconductor substrate such that said opening has sidewalls and a bottom surface within said semiconductor substrate, said semiconductor substrate comprising a first semiconductor material and said semiconductor layer comprising a second semiconductor material different from said first semiconductor material; implanting a dopant into said semiconductor substrate to form a doped region immediately adjacent to said bottom surface of said opening; and performing a second etch process such that an undoped region of said semiconductor substrate immediately adjacent to said sidewalls is etched at a faster etch rate than said semiconductor layer and said doped region in order to form a trench within said semiconductor substrate below said semiconductor layer.