Comparative study of calixarene and HSQ resist systems for the fabrication of sub-20 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.