Emitter-collector shorts in bipolar devices

A number of processing defects may produce emitter-to-collector shorts in double-diffused bipolar transistors. Photolithography errors may cause lateral shorting of adjacent emitter and collector regions; or a localized masking during base diffusion can result in the absence of a base region between emitter and collector (in a vertical direction). Surface inversion of the base region may also give rise to an electrical path between emitter and collector, although this would certainly be a rare phenomenon with the relatively high surface concentration of dopants in bipolar devices and with modern processing methods to control surface charge. Particulate contamination, especially if it contains phosphorus, can also result in localized emitter-collector shorts by overdoping the p-type base region (1). However, by far the most interesting, and the most troublesome, incidence of emitter-collector shorts is that due to "pipes."