Skjerven, Morrill, MacPherson, Franklin & Friel LLP
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, that forms a PN junction with adjoining semiconductor material and abuts a slanted sidewall of a field insulating region. The doped region 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, 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
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Y10S Y10S H01L
additional additional inventional
Hung-Sheng Chih Sieh
Chen Teng