Line width roughness remains a critical issue when moving towards smaller feature sizes in EUV lithography. We
present a stochastic resist modeling approach to accurately predict LWR and CD simultaneously. The stochastic model
simulates the roughness effects due to the shot noise and secondary electron effects during exposure, and the interaction
amongst the finite number of chemical molecules (inhibitor, PAG, quencher) during PEB. The model calibration used
the imec baseline EUV resist (Shinetsu SEVR140) with over 250 measured CDs and corresponding line width roughness
data. The validation was performed with 1D and 2D patterns. Especially for contact holes the predictability regarding
local CD uniformity is discussed. The good match between the simulations and wafer results for SRAM patterns further
exhibits the predictive power of the model. The model has been applied to simulate the new ASML NXE: 3100 EUV
conditions for both thin and thick absorber EUV masks. The comparison between the simulation results and wafer data
We analyzed the lithographic performance of a double patterning technology (DPT) with resist freeze
(LFLE) process for printing dense contact holes (CH). For the first time, we quantified the contribution
of the substrate - frozen resist and topography effects. The impact on image contrast, and NILS was
In comparing to the case of a uniform L/S, the image through-pitch performance is degraded in LFLE
CH. This is resulted from diffraction by the underlying topography and materials. The process steps
(between first-and-second Litho) cause additional challenges in the fabrication of CHs using DPT.
Current inspection of the process effects only observes the reflected signal for position alignment. We
have introduced simulations of a phase change in polarized signal (ellipsometry) after first and second
lithography steps for suggesting a new methodology for detection and validation of topography changes
in DPT flow. In DPT the first Litho result is fabricated in substrate, so the analysis of ellipsometry signal
can be applied to sensitively detect correlations between two steps.
The spectroscopic ellipsometry simulation results were shown; α and β parameters demonstrate the
sensitivity w.r.t. substrate topography, by changing the incident optical direction from x-z to y-z plane.
This represents the correlation between parameters observed by respective Litho steps of perpendicular
Furthermore, ellipsometry signal was used to optimize the "frozen" resist n and k values w.r.t aerial
image performance, which can be fed back to DPT design.
Concluding, the information obtained by ellipsometry is useful to characterize substrate topography in