Requirements for control of mask registration errors and wafer overlay errors become more demanding as the integrated circuit (IC) feature size specifications become tighter and tighter. Registration control, also known as RegC, is a well-known laser-based process in the IC industry that has proven to be robust, repeatable, and efficient in adjusting mask registration and wafer overlay. Using an ultrashort pulsed laser, microscopic deformation elements, strain centers, which are also known as pixels, are generated deep inside the fused silica mask substrate causing strain. The induced strain moves the mask pattern in predicted calculated directions to reduce the measured image placement error (IPE). RegC corrections can be applied in two different ways: as a periphery-mask correction, which places the strain centers in the mask frame area outside the exposure field, or as a full-mask correction, that places the strain centers across the entire mask, including the exposure field. Relative pattern displacements up to 1 nm can be achieved between sites located at a distance of 1 mm, reducing the magnitude of the residual IPE by an average of 20% (10% to 25% range) for a periphery correction or 40% (20% to 50% range) for a full-mask correction. The input data for the RegC process are typically taken from mask registration information, which is measured by registration metrology tools or measured from wafer overlay (the latter is not within the scope of this paper). This paper reviews the RegC process flow for improving mask registration in mask shops.