Matching of MOS transistors with different layout styles

A test chip with NMOS transistor pairs with different layout styles to study its influence on matching is presented. Common centroid structures are found to have much better matching performance than finger style structures. They show no systematic mismatch, and have a matching dependence on the channel area which is in agreement with measurement results on simple rectangle structures. Under die stress induced by packaging, finger style transistor pairs show a spread on transistor matching up to 5 times higher than the value predicted by only considering random fluctuation of the channel area.