A system for improving substrate critical dimension uniformity is described. The system includes an exposing means for exposing a plurality of mask patterns on a first plurality of substrates at predetermined locations with common splits of focus ({Fj}) and exposure dose ({Ek}) for each of the first plurality of substrates to form a plurality of perturbed wafers. A measuring means is provided for measuring a critical dimension of the plurality of mask patterns at each of the predetermined locations for each of the plurality of perturbed wafers. An averaging means is provided for averaging the critical dimension measured at each of the predetermined locations over the plurality of perturbed wafers to form a perturbed critical dimension map. A second measuring means is provided for measuring a sidewall angle of the plurality of mask patterns at each of the predetermined locations for each of the plurality of perturbed wafers. A second averaging means is provided for averaging the sidewall angle measured at each of the predetermined locations over the plurality of perturbed wafers to form a perturbed sidewall angle map. The perturbed critical dimension map and the perturbed sidewall angle map can then be provided to an exposure tool.