U-Groove Isolation Technology for High Density Bipolar LSI's

A new isolation technology for high packing density bipolar LSI's has been developed. This technology is composed of two main processes, U-groove formation and U-groove filling. The U-grooves are formed by anisotropic etching and reactive sputter etching of silicon. The grooves, covered with a composite Si 3 N 4 /SiO 2 layer, are filled with polysilicon. Surface planarity is achieved by selective etching of the polysilicon. An ECL integrated circuit fabricated using the U-groove isolation (U-Iso) technology exibits a minimum isolation distance of 3 µm, an isolation voltage of 50 V, an isolation capacitance of 0.2 pF, and a propagation delay time, measured by ringoscillator, of 0.3 ns/gate.