Quasi-dielectrically isolated bipolar junction transistor with subcollector fabricated using silicon selective epitaxy

A novel quasi-dielectrically isolated bipolar junction transistor (QDI-BJT) was developed for intelligent power ICs. Using a combination of junction and dielectric isolation, the QDI-BJT was achieved by selective epitaxial growth (SEG) of single-crystal silicon in an oxide-lined trench. Buried collectors formed by ion implantation and in situ doped SEG silicon drastically reduce collector resistance with no detrimental effects on transistor performance. The emitter-base and collector-base ideality factors at 1.10 and 1.09, respectively, were very close to those of similar devices fabricated in the substrate in the same die, indicating excellent crystal quality of the SEG silicon. Due to the use of a trench structure to facilitate isolation and control the SEG thickness, the QDI process can be used for any application where the thickness and resistivity of the control and power areas are independently optimized