Refilled oxide groove isolation technique (ROGI) - A combined isolation and metallization process

A new isolation and metallization process for the fabrication of integrated circuits has been developed. This process utilizes oxide groove to eliminate isolation and collector reach-through diffusion. By refilling the oxide groove with aluminium or polysilicon, a recessed interconnection layer is provided and subcollector can be directly contacted to this second layer. For device fabrication no high temperature cycles are needed either for isolation, collector diffusion or for local oxidation. The outdiffusion of the buried layer is minimized and the thickness of the epitaxial layer can be reduced, maintaining the optimized transistor characteristics. With oxide walled base and direct contact to subcollector, this scheme provides a minimal transistor size. For the circuits of functional devices, such as I²L, the oxide groove enables most effective isolation of logic blocks. The built-in double layer metallization offers a high degree of flexibility to a circuit designer. The relized compact size of a circuit as well as of a single transistor will be discussed with an example of an I²L frequency divider.