Characterization of 45 nm Attenuated Phase Shift Mask Lithography with a Hyper Numerical Aperture ArF Tool

Abstract

In the 45 nm half pitch node, a mask induced polarization effect appears. Because of this effect, intensity of diffracted light depends on a pattern size and a diffraction order. This is pronounced in an attenuated phase shift mask (attPSM). A mask topography effect has to be considered for rigorous simulation. A small window attributable to diffraction efficiency is generated, because of an insufficient ratio of 1st order and 0th order diffracted light from the attPSM. Two approaches to produce a sufficient ratio, namely, a low transmittance layer attPSM and a biased pattern attPSM, were investigated by simulation. A mask bias of more than 10 nm on both sides is required to generate an optimal diffraction efficiency ratio for the 0th and 1st orders. The low transmittance (around 1%) attPSM had higher contrast at 45 nm half pitch in the resist image than the biased attPSM. It was also shown that a phase difference between diffraction orders caused lower contrast imaging.

Diffraction Originated Local Heating of Nanometer Scale Device Patterns in Lamp-Based Rapid Thermal Annealing

“…In lithography, it has long been recognized that, as the feature size of patterns approach the wavelength of the illuminating light source, optical resolution is compromised and diffraction effects must be considered in creating the masks to generate the desired patterns on wafers. (6)(7)(8) Lithography has recognized that the light sources are photon radiation sources and the wave characteristics of light must be considered. This insight has been ignored by the RTP community.…”

Diffraction Originated Local Heating of Nanometer Scale Device Patterns in Lamp-Based Rapid Thermal Annealing

“…In lithography, it has long been recognized that, as the feature size of patterns approach the wavelength of the illuminating light source, optical resolution is compromised and diffraction effects must be considered in creating the mask to generate the desired pattern on wafers. [6][7][8] Lithography has recognized that the light sources are photon radiation sources and the wave characteristics of light must be considered. This insight has been ignored by the RTP community.…”