Minimizing the impact of image icquisition on CD-SEM LER/LWR measurements

As gate linewidth control values approach the dimensions of resist polymer units, the accurate measurement of resist line edge (width) roughness (LER/LWR) takes on increased importance, not only as a guide to quantifying lithographic pattern quality, but also in its influence on device performance. It is therefore critical to be able to measure LWR in a manner that minimizes any image acquisition artifacts that may occlude the true nature of the roughness. In this paper, we study the effects on LWR that can result from the image acquisition process on a CD-SEM, with emphasis on the observations noted in 193 nm resist LWR, and in the use of sub-200 eV Ultra-Low Voltage (ULV) measurement energies, that have been explored as a means of minimizing the impact on 193 nm resist LWR.