Patent ID: 7325225

Claim:
A method of accessing model error in an optical proximity correction (OPC) model, comprising: a. obtaining a preliminary mask using an OPC model; b. creating an etched wafer from the preliminary mask using lithography; c. measuring a first Critical Dimension (CD) on the wafer and a second CD on the wafer; d. determining a first edge placement error (EPE) that corresponds to a difference between a measured value of the second CD on the wafer and a desired value of the second CD on the wafer; e. repeating steps a-d for a plurality of different values of the first CD to obtain an EPE for each of the different values of the first CD; f. for each of the plurality of values of the first CD, correlating a measured value of the second CD on the wafer with a corresponding value of the second CD on the mask; g. for each of the plurality of values of the first CD, correlating the measured value of the second CD on the wafer with its corresponding value of the second CD on the mask as predicted by the OPC model; h. for each correlation obtained in step (g) and at a selected measured value of the second CD on the wafer, obtaining a difference ΔCD between the measured second CD on the mask and the corresponding value of the second CD on the mask as predicted by the OPC model; i. transforming each value of ΔCD into an OPC model error that each correspond to a particular value of the first CD; j. obtaining a total residual error for each value of the first CD by summing the EPE corresponding to each particular value of the first CD with the OPC model error corresponding to each of the particular values of the first CD; k. comparing each value of the total residual error to a predetermined acceptable value of the total residual error; and l. revising the OPC model based on the OPC model error when the value of the total residual error is greater than the predetermined acceptable value of the total residual error.