System and method for ac performance tuning by thereshold voltage shifting in tubbed semiconductor technology

Abstract

A system and method are described for separating the bulk connections for FETs on a semiconductor wafer from the supply rails, testing the wafer to determine if a shift in the threshold voltage, V , of certain devices within the wafer, as defined by the bulk-wells, can remove an AC defect in the IC circuit, and tailoring the voltage or voltages applied to the bulk nodes, post-manufacture, such that the integrated circuit meets its performance targets or is sorted to a more valuable performance level. The method requires generating a gate level netlist of the IC's circuitry and performing timing calculations on these circuit netlists using static timing analyses, functional delay simulations, circuit activity analyses, and functional performance testing. The failures are then correlated to respective IC circuits, worst case slack circuits are investigated, and proposed changes to the threshold voltages are employed in the hardware.