Transit times in the high-density interconnections on GaAs-based VHSIC

An algorithm for the determination of transit times in the high-density interconnections on GaAs-based very high speed integrated circuits is presented. The interconnection capacitances used in the model include fringing fields as well as the effects of shielding by the neighbouring interconnections. These were determined by the method of moments in conjunction with a Green function appropriate for the geometry of the interconnections. The model also incorporates the effects of the capacitive couplings with the first and second neighbours on both sides of the interconnection. The interconnection was treated as a distributed transmission line terminated by a capacitive load and driven by a unit step-voltage source having impedance equal to the impedance of a typical GaAs MESFET. The model has been used to study the dependences of the delay time and the risetime on the length and the width of the interconnection, and the resistivity of the interconnection material. Furthermore, the dependence of the propagation time on the method of driving an interconnection such as using minimum size inverters, optimum size inverters and cascaded drivers has been examined for the GaAsbased integrated circuits.