Feasibility study of a positive tone organometal chemically amplified resist for high-resolution EUV single patterning

EUV lithography has been realize to use the mass production for 5nm logic device manufacture and beyond and semiconductor manufacturing plants that introduce EUV exposure system are being built or planned around the world. Therefore, the greatest interest of the EUV lithography is sub 10nm resolution patterning capability using high NA optics system. However, EUV chemically amplified resists (CARs) have had big problems about pattern defects due to stochastic effects from photon shot noise and acid diffusion blur less than 13nm HP. There is a trade-off relationship between resolution, line width roughness (LWR), and sensitivity (RLS trade-off). The RLS trade-off problems have come to a head with the progress of pattern miniaturization. The improvement of LWR and sensitivity without degrading the resolution is technically difficult because of acid diffusion and stochastic effect. Moreover, etching durability of CARs are also gradually surfaced as an issue due to reducing film thickness to prevent pattern collapse. The development of a novel platform for high resolution patterning becomes important. Currently, some of the new resist platform have been investigated and metal oxide resist and dry film resist were particularly achieved good patterning performance and etching durability as negative type resist by using metal component in the systems. On the contrary, performances of metal containing positive type resist by treating metal infiltration have not been sufficient to compare with the negative type resists. Sensitivity of non-CAR resists have a limitation by lack of the reaction probability because of only one reaction per photon at maximum. Therefore, including high concentration of EUV absorbing metal component, using chemically amplified reaction or other sensitivity enhancement techniques are necessary to meet the sensitivity requirement for high NA EUV resist. Previously, we proposed a positive tone organometal chemically amplified resist by making dissolution contrast though chain scission and polarity change to develop for butyl acetate. However, sensitivity and resolution were not sufficient as a photoresist for high NA EUV lithography. Although performance can be improved by modification of some structures, at first, we explored a way to significantly improve sensitivity by using PS-CAR process and new acid generator which can change the structure to UV sensitive one by EUV exposure only exposed area because of an aiming to reduce massive power consumption of EUV lithography.