Using Constraint Satisfaction Approach to Solve the Capacity Allocation Problem for Photolithography Area

This paper addresses the capacity allocation problem for photo- lithography area (CAPPA) under an advanced technology environment. The CAPPA problem has two characteristics: process window and machine dedication. Process window means that a wafer needs to be processed on machines that can satisfy its process capability (process specification). Machine dedication means that after the first critical layer of a wafer lot is being processed on a certain machine, subsequent critical layers of this lot must be processed on the same machine to ensure good quality of final products. A production plan, constructed without considering the above two characteristics, is difficult to execute and to achieve its production targets. Thus, we model the CAPPA problem as a constraint satisfaction problem (CSP), which uses an efficient search algorithm to obtain a feasible solution. Additionally, we propose an upper bound of load unbalance estimation to reduce the search space of CSP for searching an optimal solution. Experimental results show that the proposed model is useful in solving the CAPPA problem in an efficient way.