Formation of an asymmetric trench in a semiconductor substrate and a bipolar semiconductor device having an asymmetric trench isolation region

摘要

Disclosed is a trench formation technique wherein an opening having a first sidewall with planar contour and a second sidewall with a saw-tooth contour is etched through a semiconductor layer and into a semiconductor substrate. Then, a crystallographic wet etch process expands the portion of the opening within the semiconductor substrate to form a trench. Due to the different contours of the sidewalls and, thereby the different crystal orientations, one sidewall etches faster than the other, resulting in an asymmetric trench. Also disclosed is a bipolar semiconductor device formation method that incorporates the above-mentioned trench formation technique when forming a trench isolation region that undercuts an extrinsic base region and surrounds a collector pedestal. The asymmetry of the trench ensures that the trench isolation region has a relatively narrow width and, thereby ensures that both collector-to-base capacitance Ccb and collector resistance Rc are minimized within the resulting bipolar semiconductor device.

主权项

1. A bipolar semiconductor device comprising:
a first terminal region in a semiconductor substrate, said semiconductor substrate having a top surface; a second terminal region in a first semiconductor layer on said top surface of said semiconductor substrate, said second terminal region being aligned above said first terminal region; a third terminal region in a second semiconductor layer on said first semiconductor layer, said third terminal region being aligned above said second terminal region; an opening extending vertically through said first semiconductor layer and positioned laterally adjacent to said second terminal region; an asymmetric trench in said semiconductor substrate aligned below said opening, said asymmetric trench having a first side adjacent to said first terminal region and a second side opposite said first side, said first side having a first angle relative to said top surface and said second side having a second angle relative to said top surface, said second angle being larger than said first angle; and, at least one isolation material filling said trench so as to form an asymmetric trench isolation region, said at least one isolation material also filling said opening.