Efficient use of spare gates for post-silicon debug and enhancements

Abstract

A spare gate cell on a integrated circuit contains both a configurable logic gate and one or more inverters. Inputs of these circuits have an appearance, accessible by the automatic place-and-route tool, at the topmost metal layer on the integrated circuit, which is metal,or higher. The outputs of the circuit preferably are accessible up to the same metal layer. The combination of the configurable gate circuit and one or more inverters enables any one such cell to selectively implement a wide range of logic functions by making appropriate connections during fib-mill processing of the integrated circuit device. The use of interconnections at the topmost layer facilitates reconfiguring a circuit to implement desired logic and interconnection thereof into the pre-defined logic on the integrated circuit. The inventive spare gate cells provide a high degree of design flexibility, both for circuit debug operations and for implementation of enhanced logic functions.