Abstract: A method for correcting misalignment between a reticle and a stage in a MICRASCAN step-and-repeat exposure system. In such a system, the reticle and the stage lie in parallel X-Y planes and there are at least two temperature sensors associated with the reticle, sensor 1 and sensor 2, sensor 1 having a sensor 1 temperature output and sensor 2 having a sensor 2 temperature output. The method comprises the steps of estimating an X shift and a Y shift of the reticle relative to the stage using the sensor 1 temperature output and sensor 2 temperature output and correcting misalignment between the reticle and the stage using the estimated X and Y shifts.