Collector diffusion isolated integrated circuits

A new, simplified, bipolar integrated circuit structure is described. This structure eliminates the need for the conventional isolation diffusion. Isolation is accomplished with the collector diffusion. This results in fewer fabrication steps than are required in fabrication of the standard buried collector structure. In addition, the new structure has greater circuit packing density because of the smaller area required for isolation. Transistor-transistor logic circuits have been fabricated using the new structure. Using 5 µm masking tolerances and line widths, propagation delays of 5-7 ns have been obtained at a power dissipation of 4 mW while achieving circuit packing densities 2.5 times higher than obtainable using the standard buried collector structure with the same masking tolerances. Circuits formed using 2-3 µm tolerances and line widths resulted in propagation delays of 20 ns at 0.4 mW power dissipation.