Combining Negative Binomial and Weibull Distributions for Yield and Reliability Prediction

A key productivity metric in semiconductor manufacturing is wafer test yield - the fraction of dies deemed functional following wafer probe testing. Wafer test yield is directly related to semiconductor manufacturing profitability: The higher the yield, the lower the cost of producing a functional chip, and therefore the greater the potential profit. Because wafer test yield is such a critical variable in a products profit potential, accurate yield projection models are essential to semiconductor manufacturers economic success. It is important to understand the correlation between defects causing yield loss and defects causing reliability failures. This article presents a modeling methodology and supporting data, demonstrating that yield and reliability defects can be directly linked in a unified model.