On-wafer method and apparatus for pre-processing measurements of process and environment-dependent circuit performance variables for statistical analysis

Abstract

An on-wafer method and apparatus for pre-processing measurements of process and environment-dependent circuit performance variables improves yield/performance test and analysis throughput. An on-wafer circuit calculates the sums of multiple exponentiations of outputs of one or more measurement circuits, thereby reducing the amount of data that must be transferred from the wafer without losing information valuable to the analysis. An integer scaling of the input data is arranged between zero and unity so that the exponentiations all similarly lie between zero and unity. The circuit can use look-up tables and adder/accumulators to accumulate the contributions of each measurement to each exponentiation, or use a multiplier arrangement to determine the contributions. The multipliers can be implemented in the adder/accumulators by clocking the adder/accumulators by corresponding counts determined from the measurement data and lower-order exponentiations. Ranges of the measurement values are determined by capturing maximum and minimum values using comparators as the measurements are input.

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