Flexible packed stencil design with multiple shaping apertures for e-beam lithography

Electron-beam direct write (EBDW) lithography is a promising solution for chip production in the sub-22nm regime. To improve the throughput of EBDW lithography, character projection method is commonly employed and a critical problem is to pack as many characters as possible onto the stencil. In this paper, we consider two enhancements in packed stencil design over previous works. First, the use of multiple shaping apertures with different sizes is explored. Second, the fact that the pattern of a character can be located anywhere within its enclosing projection region is exploited to facilitate flexible blank space sharing. For this packed stencil design problem with multiple shaping apertures and flexible blank space sharing, a dynamic programming based algorithm is proposed. Experimental results show that the proposed enhancement and the associated algorithm can significantly reduce the total shot count and hence improve the throughput of EBDW lithography.