Method of making shallow junction complementary vertical bipolar transistor pair

摘要

Disclosed is a complementary vertical NPN and PNP pair having matched performance. The PNP collector is located deep in an epitaxial layer overlying a semiconductor substrate. The junction depths and surface concentrations of both emitters are quite similar; the junction depths and surface concentrations of bases of the complementary devices are also similar to each other. The PNP and NPN emitters are provided with self-aligned conductive contacts. A high dopant concentration equal to that in the emitters is provided in all contacts of the transistor elements to reduce the contact resistances. Disclosed too is a process of forming the above structure. Starting with a semiconductor substrate having a blanket N+ NPN subcollector and an epitaxial layer thereon having first and second active regions, an NPN base precursor and PNP collector reach-through precursor are simultaneously implanted in the first and second active regions, respectively. PNP collector is then formed in the second active region by implanting P type species to lodge them at the bottom the epitaxial layer. PNP base precursor is then implanted in the surface region of the epitaxial layer in the second active region. By annealing, the NPN and PNP bases and PNP collector reach-through are obtained from their respective precursors. A high-dopant concentration and shallow NPN emitter and low-resistance contact region for PNP base are simultaneously implanted. PNP emitter and contact regions for PNP collector reach-through and NPN base having a concentration and junction depth similar to those of the NPN emitter are simultaneously implanted. Self-aligned conductive contacts are established with both emitters and all other transistor elements.