As tolerance requirements for the lithography process continue to shrink with each new technology node, the
contributions of all process sequence steps to the critical dimension error budgets are being closely examined, including
wafer exposure, resist processing, pattern etch, as well as the photomask process employed during the wafer exposure.
Along with efforts to improve the mask manufacturing processes, the elimination of residual mask errors via pattern
correction has gained renewed attention. The portfolio of correction tools for mask process effects is derived from well
established techniques commonly used in optical proximity correction and in electron beam proximity effect
compensation. The process component that is not well captured in the correction methods deployed in mask
manufacturing today is etch. A mask process model to describe the process behavior and to capture the physical effects
leading to deviation of the critical dimension from the target value represents the key component of model-based
correction and verification. This paper presents the flow for generating mask process models that describe both shortrange
and long-range mask process effects, including proximity loading effects from etching, pattern density loading
effects, and across-mask process non-uniformity. The flow is illustrated with measurement data from real test masks.
Application of models for both mask process correction and verification is discussed.