Chemically amplified resist materials with a different sensitivity were prepared to investigate impact of sensitivity on resolution at 15 nm half-pitch (hp) using a EUV microfield exposure tool (MET) at SEMATECH Berkeley. Sensitivity at least slower than 30 mJ/cm 2 was required to resolve 15 nm hp patterns using current EUV resists. It is noteworthy that resolution of 15 nm hp was limited by not only pattern collapse but also pinching of patterns. The same tendency is observed in E-beam patterning at 20 nm hp. A strong relationship between pinching and sensitivity in E-beam exposure indicates contribution of photon-shot noise on the pinching. Clear correlation between diffusion length and pinching using the E-beam exposure indicates that acid diffusion is another contributor on the pinching. Bound PAG into polymer and molecular PAG with a big anchor group showed almost same character on pinching. Key conclusion here is even in a molecular PAG, we can control acid diffusion to achieve 15 nm hp resolution capability. Strategy to improve sensitivity is to utilize resist with high deprotection efficiency. Polymer with a low thermal activation energy on deprotection (low Ea polymer) was demonstrated as a key technology to achieve 15 nm hp resolution with a faster sensitivity below 26 mJ/cm 2. Special rinse material was effective for reducing LWR by ~ 20%. Sensitivity dependency of outgassing have been systematically discussed at first. A good linear correlation between a cleanable outgassing amount and exposure energy strongly indicates tradeoff relationship between outgassing and sensitivity. Applying a new EUV topcoat to resist demonstrated reduction of outgassing from 7.39 nm to below 0.1 nm with maintaining resolution.

Blurs, swelling properties and lithographic performance for polymer bound PAG and polymer PAG blended type resists were studied. A Blur strongly depends on PAG size and the polymer bound PAG type resist reduces the Blur. The Blur for the polymer bound PAG type resist is smaller than that for ZEP (non CAR). The fact indicates that polymer bound PAG should reduce secondary electron diffusion. The polymer bound PAG type resist acquires very small Blur with higher sensitivity and suppresses swelling very well, therefore polymer bound PAG is one of the promising technologies that improve resolution, LWR and sensitivity (RLS) property. RLS property on EUV exposure tool is significantly improved by using the polymer bound PAG type resist. Resolution reaches 24 nmhp and is limited by pattern collapse and line breaking. Further lithographic experiments on EB exposure tool which has higher NILS than EUV exposure tool are carried out in order to make clear relation between Blur and resolution. The resolution of the polymer bound PAG type resist reaches 17.5 nmhp with 35 nm thickness and there is possibility that the resolution of an optimized polymer bound PAG type resist reaches under 15 nmhp. The resolution of the resist with lower capillary force (C.F.) given and lower swelling and on higher NILS exposure tool strongly depends on the Blur.

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A series of polymer with different hydrophobicity have been synthesized to investigate effects of contact angle on ultimate resolution. Contact angle of these polymers was widely changed by utilizing polymers having a different chemical structure and protection ratio. It is revealed that resolution of 20 nm half-pitch (hp) was limited by pattern collapse and improved by increasing contact angle of polymer under E-beam exposure. It is noteworthy that resolution of 20 nm hp and below for current EUV resists with exposures on a NXE:3100 and a micro-field exposure tool (MET) at SEMATECH Berkeley was also limited by pattern collapse. Low diffusion character of current EUV resists with controlled PAG design, especially polymer bound PAG (PBP), suppressed degradation of resolution by chemical blur. Combination of high contact angle polymer with low diffusivity PAG showed resolution of 18 nm hp using a MET at SEMATECH Berkeley with a LWR of 2.6 nm, sensitivity of 20 mJ/cm 2 , and Z-factor of 3.9 × 10 -9 mJnm 3 . Unfortunately density of blob defect for the hydrophobic polymer was above 100 counts/cm 2 . Hydrophobicity of film surface was found to be a main cause of its poor defectivity. Adding the new EUV additive to the hydrophobic resist reduced density of blob defect from 100 counts/cm 2 to below 0.1 counts/cm 2 .

Polymers with a different Tg and activation energy were prepared to clarify influences of acid diffusion on resolution at 15 nm half-pitch (hp) and 14 nm hp using a EUV micro-field exposure tool (MET) at LBNL. Resolution on such a narrow pattern was limited by collapse and pinching. Clear relationship between pinching numbers and polymer Tg indicates that acid diffusion is one of major contributors on the pinching. In addition, polymers with a low thermal activation energy (Ea) on deprotection were effective for reducing pinching. This is probably originated from its high chemically amplification character even in low post-exposure bake (PEB) temperature to obtain both large chemical contrast and short acid diffusion. On the other hand, a good correlation between a cleanable outgassing amount and Ea indicates trade-off relationship between outgassing and resolution. Advantages of n-butyl acetate (nBA) developer have been investigated in viewpoint of dissolution uniformity. Surface roughness of a non-patterned resist film at half-exposed area, which was well correlated with LWR, was measured by AFM as indicator of uniformity in development process. To avoid any differences in resist chemistry other than development process, cross linking negative tone resist was applied for this study. The surface roughness obtained by nBA, which is conventional negative-tone imaging (NTI) developer, was 32 % lower than that obtained by 2.38 % TMAH solution. NTI resist system with a nBA developer and optimized resist reduced LWR from 4.8 nm to 3.0 nm in comparison with conventional positive tone resist with a 2.38 % TMAH developer. In addition, advantage on semi-dense trench patterning was well defined. New EUV sensitizer with 1.15 times higher EUV absorption resulted in 1.15 times higher acid yield by EUV exposure. Lithography performance of the new EUV sensitizer has been investigated by MET at SEMATECH Albany. Sensitivity was indeed improved from 20 mJ/cm 2 to 17 mJ/cm 2 according to the acid yield increase, but resolution was significantly degraded.