Cell Library Development Methodology for Throughput Enhancement of Electron Beam Direct-Write Lithography Systems

We propose a cell library development methodology for throughput enhancement of electron beam direct-write (EBDW) systems. First, an ILP (integer linear programming)-based cell selection is proposed for EBDW systems in which both of the character projection (CP) and the variable shaped beam (VSB) methods are available, in order to minimize the number of electron beam (EB) shots, that is, time to fabricate chips. Secondly, the influence of cell directions on area and delay time of chips is examined. The examination helps to reduce the number of EB shots with a little deterioration of area and delay time because unnecessary directions of cells can be removed to increase the number of cells on a CP aperture mask. Finally, a case study is shown in which the numbers of EB shots are examined under several cases.