Sensitivity analysis of line-edge roughness measured by means of scatterometry: a simulation-based investigation

Various reports state that LER/LWR has a significant impact on lithography-fabricated ICs, rendering it desirable to be able to determine the LER in-line so that it never exceeds certain specified limits. In our simulation work we deal with the challenge of measuring LER on CD-50nm resist gratings using plane-mount scatterometry. We show that there is a difference between LER and no-LER scatter signatures which first: depends on the polarization and second: is proportional to the amount of LER. Moreover - we show that the said difference can be best-fit to the difference between scatter signatures of two rigorously determined, specific no-LER CDs, which allows us to predict the sensitivity of ITRS' "manufacturable solution" for scatterometric LER measurement just by using computationally cheap 1D RCWA simulations. As it can be shown the sensitivity is not uniform for all realizations of the same CD (e.g. for different resist heights), so not in all gratings LER is equally easy to determine.