Negative-Tone Molecular Resists Based on Cationic Polymerization

There is increasing demand for higher performance resists with superior resolution, sensitivity, and line edge roughness for both electron beam and extreme ultraviolet lithography applications. A new class of negative tone chemically amplified molecular resists has been developed based on epoxide cross-linking that combines high sensitivity with low line edge roughness and excellent resolution. Three different resists from this class have been made that all show superior performance compared to SU-8 in high resolution dense patterns. The functionality and size of the resist molecules were systematically changed to investigate these effects on imaging performance under e-beam lithography. The di-functional epoxy resist, 2-Ep, had < 25 nm half-pitch resolution in dense 1:1 line-space patterns, sensitivity of 38 mu C/cm(2), and low 3 sigma LER of 2.9 nm for 30 nm half-pitch. The tri-functional epoxy resist, 3-Ep, showed 30 nm resolution in dense features, 3 sigma LER of 2.3 nm, and a sensitivity of 20 mu C/cm(2). The tetra-functional epoxy resist, 4-Ep, likewise showed good resolution of 35 nm half-pitch in dense features, sensitivity of 22 mu C/cm(2), and a low 3 sigma LER of 2.3 nm. This class of negative tone resist compounds are able to obtain an excellent combination of resolution, LER, and sensitivity, and show promise as high performance resists for next generation lithography.