System, method and computer program product for instructing allocation of a plurality of exposure units

A method for instructing allocation of a plurality of exposure units, comprising:

• selecting first and second exposure units to be employed in processes of forming first and second exposure patterns on an objective substrate, respectively, among the exposure units;
• computing overlay correction values for canceling differences in stage and lens characteristics between the first and second exposure units;
• and
• instructing to allocate the first exposure unit for the objective substrate prior to another substrate scheduled for the first exposure unit.

A computer program product for instructing allocation of a plurality of exposure units, comprising:

• instructions configured to select a first exposure unit to be employed in a process of forming a first exposure pattern on an objective substrate among the exposure units;
• instructions configured to compute overlay correction values for canceling differences in stage and lens characteristics between the first exposure unit and a second exposure unit-that is employed in a process of forming a second exposure pattern on the objective substrate;
• and
• instructions configured to instruct to allocate the first exposure unit for the objective substrate prior to another substrate scheduled for the first exposure unit.