Patterning Fidelity on Low-Energy Multiple-Electron-Beam DirectWrite Lithography

摘要

The Multiple E-beam Direct Write (MEBDW) technology has been considered a promising solution for the nextgeneration lithography to delineate 32-nm half-pitch and beyond. A low-energy, say 5 keV, e-beam direct writing systemhas advantages in lower exposure dosage, less heating effect on resist, and less damage to devices underneath, comparingwith a high energy one, such as 50 keV or 100 keV. However, the low-energy electron-beam is easily blurred due toforward scattering in the substrate due to its shallow penetration and hence loses resolution. In this paper, variablesaffecting patterning fidelity of a raster-scan MEBDW system are investigated. In order to realize a MEBDW system with acceptable throughput, a relatively large beam size is chosen for sufficientbeam current to sustain throughput while maintaining enough resolution. The imaging resolution loss and the proximityeffect, due to beam blurring through the resist, have been observed. The in-house software MOSES, incorporating theMonte Carlo simulation and the Double Gaussian model was used to evaluate 1-D and 2-D pattern fidelity with variousexposure conditions. The line width roughness, which represents 1-D fidelity, was evaluated on 32-nm dense lines.Pattern fidelity of 2-D features such as the zigzag poly line and dense metal patterns was also examined. The impact toLWR of using the edge dithering method, instead of dosage modulation, to control the line width accuracy beyond thepixel size was studied.