We have studied the contributions of reticle line width ( CD) errors to systematic intrafield CD variations for 0.35 µ m i-line lithography by measuring electrical resistance of lines patterned in polysilicon films. Reticle errors were determined by independent measurements, and their effects on final printed dimensions were analyzed. Both reticles and steppers contribute to the systematic intrafield variation. In some cases, the total variance exceeds the sum of the variances individually associated with steppers and reticles. Because aberrations and reticle errors are not random, analysis of variance must take their correlation into consideration. We have observed cases in which this correlation and nonlinear imaging contribute significantly to total line width variance.