Critical challenges for EUV resist materials

Abstract

Although Extreme ultraviolet lithography (EUVL) is now well into the commercialization phase, critical challenges remain in the development of EUV resist materials. The major issue for the 22-nm half-pitch node remains simultaneously meeting resolution, line-edge roughness (LER), and sensitivity requirements. Although several materials have met the resolution requirements, LER and sensitivity remain a challenge. As we move beyond the 22-nm node, however, even resolution remains a significant challenge. Chemically amplified resists have yet to demonstrate the required resolution at any speed or LER for 16-nm half pitch and below. Going to non-chemically amplified resists, however, 16-nm resolution has been achieved with a LER of 2 nm but a sensitivity of only 70 mJ/cm 2 .

EUV Resist Materials for 16 nm And below Half Pitch Applications

“…According to this hypothesis, we have developed a new EUV additive that reform only properties of film surface from hydrophobic to hydrophilic (Scheme 1), and defectivity data of the resist with this new EUV additive is summarized in Figure 9. This clearly shows that adding the new EUV additive to the hydrophobic resist reduced density of blob defect from 100 counts/cm 2 Figure 9. Density of blob type defect for resist (a) without a EUV additive and (b) with a EUV additive.…”

“…We have investigated that resist blur of CAR is comparable with that of non CAR if we utilize PAG with controlled design, especially polymer bound PAG (PBP) [7,8]. Recent studies have been also revealed that CAR enables resolution capability down to 18 nm by decreasing thickness of resist film even though sensitivity is still high, 40 mJ/cm 2 , for satisfying manufacturing requirement.…”

“…The main issue for developing EUV resist is to satisfy the ITRS target of resolution, line-width roughness (LWR), and sensitivity simultaneously [1][2][3][4]. Although 15 nm hp resolution has been recently demonstrated using non CAR on micro-field exposure tool (MET) at SEMATECH Berkeley, its sensitivity of 70 mJ/cm 2 was still far from target of 15 mJ/cm 2 [5].…”

Negative-tone Imaging with EUV Exposure toward 13 nm hp

“…A 21 nm block mask resolution was not affected by exposure dose and explored toward low dose down to 18 mJ/cm 2 by reducing quencher loading. In addition, there was a negligible amount of increase in LCDU for isolated dot pattern when decreasing exposure dose from 66 mJ/cm 2 to 24 mJ/cm 2 . On the other hand, there appeared tradeoff relationship between LCDU and dose for dense dot pattern, indicating photon-shot noise restriction, but strong dependency on patterning features.…”

“…Dark mask limitation due mainly to mask defectivity issue makes NTI with EUV favorable approach for printing block mask to produce logic circuit. A good resolution of CD-X 21 nm/CD-Y 32 nm was obtained for block mask pattern using NTI with usable process window and dose of 49 mJ/cm 2 . Minimum resolution now reaches CD-X 17 nm / CD-Y 23 nm for the block.…”