Exposure latitude and CD control study for additively patterned x-ray mask with GBit DRAM complexity.

Abstract

40 kV electron beam lithography has been used to pattern gold plated x-ray masks containing GBit DRAM complexity layouts. The two commercial e-beam resists used, namely PMMA and SAL 601, both showed 0.12 mu m resolution capability in dense and large layouts patterning and also, under optimised exposure and development conditions, exhibited good exposure latitudes which were also evaluated for two different beam spot sizes. Furthermore, a study of development technique and effect of e-beam spot size indicated a marked dependence of ultimate resolution and exposure latitude on such parameters. A statistical analysis of 0.12 mu m resolution SAL patterning on large chip dies (30 x 30 mm(2)) resulted in a dimensional control of 10 nm (3 sigma value).