Simulation of applications of high-transmittance embedded layer in transmittance control mask and optimization of attenuated phase-shifting mask by design of experiment

Abstract

The applications of a high-transmittance embedded layer (HTEL) (T = 15-35%) in an attenuated phase-shifting mask were studied by simulation with the aid of Taguchi design of experiment. A modified transmittance control mask with HTEL was proven to be useful in preventing photoresist bridging between two adjacent contact holes on a wafer. The optimal trnasmittance (T) was determined to be 30-35%. With optimization, the optimized results of the fabrication of a 45 nm isolated line using a 193 nm wavelength light source in the immersion mode indicated that the exposure latitude (FL) increases from 1.20 to 1.31 mJ/cm(2) with the following settings: HTEL T of 35%, annular off-axis illumination (OAI) sigma(outer) of 0.7, sigma(inner) of 0.4, and numerical aperture (NA) of 1.152. For the optimization of the fabrication of 70 nm iso-dense lines, the simulation results showed that EL increases from 2.21 to 2.30 mJ/cm(2) with the following settings: HTEL T of 25%, dipole OAI sigma(center) of 0.6, sigma(radius) of 0.2, and NA of 1.224.