Characterization and modeling of bipolar transistors fabricated with combined oxide and diffused isolation structures

This paper presents a theoretical and experimental study on the isolation junction characteristics of bipolar transistors fabricated with combined oxide and diffused isolation structures. Using a quasi two-dimensional approach, the junction capacitance and junction breakdown voltage are computed as functions of device design parameters such as impurity concentration profiles and spacing between the diffusion window edges. Threshold voltage of surface inversion is also computed by taking into account the non-uniformity of the boron profiles and the boron depletion effect. Advantages and disadvantages of forming an N channel stop by reach-up and reach-down boron diffusions are compared. Experimental results are included to substantiate the theoretical results.