Performance monitoring circuitry for integrated circuits

Process monitoring circuitry according to the invention incorporates test structures placed across an integrated circuit die to monitor the performance of the fabrication process across the die. The integrity of the semiconductor fabrication process used to manufacture a particular integrated circuit is ascertained by comparing data extracted the test structures by automated test equipment (ATE) to simulation values. In one embodiment in the invention, the process monitoring circuitry comprises inverters arranged in a generally linear fashion. The inverters may be composed of simple CMOS inverters or other logic gates configured as inverters. The logic gates are arranged in horizontal and/or vertical test paths in which the gates are disposed across various sections of the integrated circuit die. An input test pad and an output test pad for each test path are provided at opposing sides of the integrated circuit die. In one alternate embodiment of the invention, multiplexing circuitry is utilized at the input and output test pads in order to minimize the impact of the process monitoring circuitry. The various test paths may incorporate comparatively lengthy metal routing lines, allowing accurate measurement of metal interconnect delays.