Bipolar transistors having emitter-base junctions of varying depths and/or doping concentrations

摘要

A bipolar transistor comprises at least first and second connected emitter-base (EB) junctions having, respectively, different first and second EB junction depths, and a buried layer (BL) collector having a greater third depth. The emitters and bases corresponding to the different EB junctions are provided during a chain implant. An isolation region overlies the second EB junction location thereby providing its shallower EB junction depth. The BL collector does not underlie the first EB junction and is laterally spaced therefrom by a variable amount to facilitate adjusting the transistor's properties. In other embodiments, the BL collector can underlie at least a portion of the second EB junction. Regions of opposite conductivity type over-lie and under-lie the BL collector, which is relatively lightly doped, thereby preserving the breakdown voltage. The transistor can be readily “tuned” by mask adjustments alone to meet various device requirements.

主权项

1. A bipolar transistor, comprising:
a semiconductor substrate having a first surface; a first emitter region of a first conductivity type in the semiconductor substrate having a first emitter region doping concentration; a first base region of a second, opposite, conductivity type in the semiconductor substrate underlying the first emitter region and having a first base region doping concentration, the first base region forming a first PN or NP junction with the first emitter region at a first depth from the first surface; a second emitter region of the first conductivity type in the semiconductor substrate having a second emitter region doping concentration and Ohmically coupled to the first emitter region; a second base region of the second conductivity type in the semiconductor substrate underlying the second emitter region and having a second base region doping concentration greater than the first base doping concentration, the second base region forming a second PN or NP junction with the second emitter region at a second depth from the first surface less than the first depth; and a buried layer collector region of the first conductivity type in the substrate underlying the first surface and laterally spaced a third distance from the first emitter region.