Improvement of poly emitter n-p-n transistor matching in a 0.6 micron mixed signal technology

Standard high frequency n-p-n poly emitter transistor pairs show a significant parameter offset during the matching characterization depending on the position on the wafer. Special octagon matching transistors on the other hand have a good matching behavior. The main reason for the offset of the high frequency transistors is a dimensional difference in the emitter cut due to a non-uniform development process of the resist mask for the emitter cut etch and/or proximity effects. By the use of a modified photoresist and development process, the matching characteristics for all used transistor types could be significantly improved.