EDGE ROUGHNESS OF A 200-NM PITCH RESIST PATTERN FABRICATED BY ION PROJECTION LITHOGRAPHY

The edge roughness of test patterns fabricated by ion projection litho graphy has been investigated to indicate the optimum experimental cond itions for sub-100-nm resolution. Direct observation in a scanning ele ctron microscope, electron metrology, and atomic force microscopy has been employed for the evaluation of widths in the resist structures. I mperfections in the open stencil mask give rise to the main part of ed ge roughness, especially if electrostatic charging occurs. Lines and s paces in PMMA resist developed with high contrast show a roughness of 10 nm per edge if the mask has no defects and the projection system an d resist performance have been adjusted satisfactorily. Statistical fl uctuations of the ion current have no influence if a medium sensitive resist like PMMA is used resulting in exposure times of 100 ms.