The reduction of emitter-collector shorts in a high-speed all-implanted bipolar technology

Abstract

One of the main yield limiting mechanisms in the fabrication of shallow-junction bipolar integrated circuits is emitter-to-collector ( <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E-C</tex> ) leakage. This paper describes the progress made in reducing the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E-C</tex> leakage defect density in an all-implanted integrated circuit technology, which features emitters approximately 0.5 µm deep and bases approximately 0.3 µm wide. Tile median <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E-C</tex> short density was reduced from approximately 2 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> to approximately 200/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> of active emitter area in the course of this study. The processing changes that were adopted to reduce or eliminate the fatal defects include the use of both very low and very high temperature oxidation conditions to eliminate oxidation induced stacking faults (OSF's). A new epitaxial growth technique has reduced the slip dislocation density by more than an order of magnitude. The extended misfit dislocation arrays have been eliminated in both the collector contact and isolation diffusions by reducing the dopant concentrations in each region. Further, dislocation networks arising from buried layer and emitter regions, have been eliminated by limiting the oxygen concentration in their respective drive-in steps.