Comparative study of calixarene and HSQ resist systems for the fabrication of sub-20Â nm MOSFET device demonstrators

For the fabrication of future MOSFET device demonstrators with electron beam lithography negative resists with target resolutions smaller than 20 nm are needed. Calixarenes and hydrogen-silesquioxane are commonly used resists at present for this critical dimension (CD). We have compared two organic calixarene derivatives, 4-methyl-acetoxy-calix-6-arene and chloro-methyl-tetrakis-methoxy-calix-4-arene and the inorganic low-k material hydrogen-silesquioxane in terms of their compatibility to standard CMOS processes. Resist thicknesses of 50-150 nm have been produced with both types of resist with different dilutions. Contrasts are 1.8 for both calixarenes, with a clearing dose of 1200 μC/cm2 for calix-6-arene and 330 μC/cm2 for calix-4-arene. The contrast of 2.3 at 67 μC/cm2 for HSQ could be increased to 3.3 by use of Choline developer instead of TMAH. Dose dependence on linewidth has been studied in detail. Etching selectivities of 4:1 for calixarene to TEOS in a fluorine gas mixture and 14:1 of densified HSQ to Si in an HBr/O2 plasma have been achieved.