Skjerven, Morrill, MacPherson, Franklin & Friel, LLP
Use of oblique implantation in forming base of bipolar transistor
 In fabricating a bipolar transistor, semiconductor dopant is introduced into a semiconductor body during a base doping operation to define a doped region, part of which constitutes a base region for the transistor. The base doping operation entails ion implanting the dopant into the body at a tilt angle of at least 15.degree. relative to the vertical. The minimum lateral base thickness and, when the base region abuts a slanted sidewall of a field insulating region, the minimum sidewall base thickness increase relative to the minimum vertical base thickness. As a result, the magnitude of the collector-to-emitter breakdown voltage typically increases. The minimum lateral, sidewall, and vertical base thicknesses vary with the tilt angle and base-implant energy in such a manner that the minimum lateral base thickness and the minimum sidewall base thickness are separately controllable from the minimum vertical base thickness. 
National Semiconductor Corporation
Y H Y
Y10S H01L Y10S
additional inventional additional
Chih S. Hung-Sheng
Teng Chen