Determination of proximity effect parameters by means of CD-linearity in sub 100nm electron beam lithography
Along with the introduction of the 32nm technology node in the next years, the methods for correcting the proximity effect face certain limitations of measurement performance and the underlying point spread function based models themselves. To extend these methods to future technology nodes, they have to rely on more generalized coherences between nominal and measured feature sizes than just the absolute measurement values. In this work, a method is introduced to determine the forward scattering range and backward scattering ratio by printing isolated lines with various line widths and pre-assigned variable exposure doses. The line widths are then measured using standard inline scanning electron microscopy and correlated to their nominal values. This is done in terms of linearity to find the best match between the input parameters of the methodology and the intrinsic values of the resist-substrate system. A comparison between simulated and experimental results conclude that significant line width nonlinearities will occur, when relying on conventional methodologies especially for feature sizes below 40nm.
e-beam lithography proximity effect correction parameter determination