Patent ID: 8203695

Claim:
A method for characterizing focus errors in a photolithography system, the method comprising: placing a microelectronic substrate onto a substrate support of the photolithography system, the microelectronic substrate being divided into a plurality of fields individually partitioned into a plurality of regions; developing a raw focus error map for the microelectronic substrate on the substrate support, the raw focus error map having a focus error corresponding to the individual regions of the plurality of fields; deriving at least one of an inter-field focus error map and an intra-field focus error map based on the raw focus error map, the inter-field focus error map having an inter-field focus error corresponding to the individual fields and the intra-field focus error map having an intra-field focus error corresponding to the individual regions; determining a scanning direction of the individual fields; and wherein deriving at least one of an inter-field focus error map and an intra-field focus error map includes: deriving the inter-field focus error map by calculating a first inter-field arithmetic mean of the focus errors of the plurality of regions in a first field; calculating a second inter-field arithmetic mean of the focus errors of the plurality of regions in a second field; and developing an inter-field polynomial describing a relationship between the first and second inter-field arithmetic means; and deriving the intra-field focus error map by calculating a first intra-field arithmetic mean of the focus errors corresponding to a first subset of the fields for a first region, the first subset being scanned in a first direction; calculating a second intra-field arithmetic mean of the focus errors corresponding to the first subset of the fields for a second region; developing a first intra-field polynomial describing a relationship between the first and second intra-field arithmetic means; calculating a third intra-field arithmetic mean of the focus errors corresponding to a second subset of the fields for the first region, the second subset being scanned in a second direction opposite the first direction; calculating a fourth intra-field arithmetic mean of the focus errors corresponding to the second subset of the fields for the second region; and developing a second intra-field polynomial describing a relationship between the third and fourth intra-field arithmetic means.