Design for e-beam: design insights for direct-write maskless lithography

摘要

Designers always want maximum freedom in design, but they understand that chips have to yield and at a reasonable cost. The strong ecosystem support of restricted design rules to make 193i workable for sub-30nm nodes is evidence of this. In direct write e-beam, there are design insights that lead to a tangible improvement in throughout while minimizing the restrictions on the designer. It turns out that a smaller number of primitive cells in a standard cell methodology can enable data compression for multi-beam systems, and enable faster write times for character projection in VSB-based multiple column machines. This requires a co-design of the standard cell library with the stencil mask (either virtual or real) that goes into the machine. This co-design step is required only once per library and not on a design-by-design basis, thus minimizing the impact on designers. 10-20X speedups in e-beam throughput depending on layer are seen in typical layout examples for character projection machines.