14-nm photomask simulation sensitivity

Abstract

This study quantifies the impact of systematic mask errors on OPC model accuracy and proposes a methodology to reconcile the largest errors via calibration to the mask error signature in wafer data. First, we examine through simulation, the impact of uncertainties in the representation of photomask properties including CD bias, corner rounding, refractive index, thickness, and sidewall angle. The factors that are most critical to be accurately represented in the model are cataloged. CD bias values are based on state of the art mask manufacturing data while other variable values are speculated, highlighting the need for improved metrology and communication between mask and OPC model experts. It is shown that the wafer simulations are highly dependent upon the 1D/2D representation of the mask, in addition to the mask sidewall for 3D mask models.In addition, this paper demonstrates substantial accuracy improvements in the 3D mask model using physical perturbations of the input mask geometry when using Domain Decomposition Method (DDM) techniques. Results from four test cases demonstrate that small, direct modifications in the input mask stack slope and edge location can result in model calibration and verification accuracy benefit of up to 30%. We highlight the benefits of a more accurate description of the 3D EMF near field with crosstalk in model calibration and impact as a function of mask dimensions. The result is a useful technique to align DDM mask model accuracy with physical mask dimensions and scattering via model calibration.

Mitigating the Impact of Mask Absorber Error on Lithographic Performance by Lithography System Holistic Optimization

“…In addition, the MAT error and tapered SWA deformation of the absorber are increased by repeated mask cleaning process [12,13]. Recently, Sturtevant et al and Rudolph et al studied the impact of photomask uncertainties on computational lithography [4,14,15]. The results revealed that the variations of MAT and SWA cause significant CD errors (CDEs) that cannot be ignored.…”