Optimal Order Polynomial Transformation for Calibrating Systematic Errors in Multisite Testing

Multisite (parallel) testing is becoming more widely used in analog and mixed-signal testing to increase throughput and meet high customer demand. However, site-to-site variations are inevitable due to the complexities involved in massive multisite test board design. Sites with pronounced systematic errors (issue sites) lead to measurements not reflecting the true performance of the device under test (DUT), causing potential yield loss and test escapes. Traditional mechanical repair of such sites is expensive, time-consuming, and labor-intensive. Polynomial transformation methods have been successfully explored to calibrate measurements at issue test sites. However, its rigid application could lead to overfitting or underfitting without foreknowledge of the nature and level of induced errors. This paper presents an optimal order polynomial transformation method that is flexible and self-adaptive. It uses a predefined error metric to find the optimal-order of the transformation polynomial and provides optimal calibration coefficients. Simulations and real test data are used to evaluate the effectiveness of the proposed method. Further validation is also provided by comparing the die measurements of issue sites after calibration against a more accurate reference.