Flare in extreme ultraviolet lithography: metrology, out-of-band radiation, fractal point-spread function, and flare map calibration

Abstract

The critical role of flare in extreme ultraviolet ͑EUV͒ lithography is well known. In this work, the implementation of a robust flare metrology is discussed, and the proposed approach is qualified both in terms of precision and accuracy. The flare measurements are compared to full-chip simulations using a simplified single fractal point-spread function ͑PSF͒, and the parameters of the analytical PSF are optimized by comparing the simulation output to the experimental results. After flare map calibration, the matching of simulation and experiment in the flare range from 4 to 12% is quite good, clearly indicating an offset of about 3%. The origin of this offset is attributed to the presence of DUV light. An experimental estimate of the DUV component is found in good agreement with the predicted value.

Review of resist-based flare measurement methods for extreme ultraviolet lithography

“…The contrast method was one of the nonvisual inspection methods for determining dose-toclear and has been shown to work well in some cases. 26 However, because image contrast is affected by differences in the photoresist, under-layer coating material, postexposure baking conditions, and SEM settings, other experimental conditions may not yield the same results. LaFontaine et al determined the dose-to-clear by the appearance of peaks of grating structures with scatterometry.…”

“…2 in Ref. 26. The contrast method was one of the nonvisual inspection methods for determining dose-toclear and has been shown to work well in some cases.…”

“…Unfortunately, the value for the dose-to-clear determined by the visual inspection method is inevitably affected by person-to-person differences and a new method, independent of operator influence, is needed. Lorusso et al 26 in 2009 proposed an automated algorithm to calculate E B and E D . The contrast of the pad images was plotted as a function of dose.…”

“…(11) is determined, PSF and TIS can also be calculated. The OoB is usually measured with metal blades 26 or with a metal-coated mask. 27 From Table 1 in Ref.…”

Challenges for patterning process models applied to large scale

“…57,58 These models are already in a mature stage of development. It is important to highlight that "OPC" will indeed be required for EUV, despite the fact that the lower wavelength will deliver a substantially higher k1 factor than 193 nm lithography.…”