Scalable approach for external collector resistance calculation

For device modelling purposes, the geometry dependence of the external collector resistance has been investigated. Firstly, the collector resistance is split into a perfectly 1D vertical resistance and a 2D horizontal contribution. Using specific test structures and DC measurements, geometry independent parameters are then extracted. An analytical scalable formula based on Fourier techniques finally computes both components for a given geometry by taking into account the current distribution in the horizontal layer. This new method is applied to a double poly BiCMOS technology and results are discussed.