Epitaxial regrowth in double-diffused polysilicon emitters

A study is made of epitaxial regrowth of polysilicon in double-diffused polysilicon emitter bipolar transistors. TEM and RBS are used to assess the extent of the epitaxial regrowth, and a simple sheet resistance measurement is used to give a sensitive measure of the amount of regrowth. The temperature of the RTA used for the second diffusion is varied between 950 and 1150°C, with epitaxial regrowth occurring for temperatures at and above 1050°C. Polysilicon emitter bipolar transistors are fabricated to demonstrate the electrical effects of the epitaxial regrowth.