Printability study with polarization based AIMS fab 193i to investigate mask polarization effects

Abstract

Immersion lithography offers the semiconductor industry the chance to extend the current ArF processes to smaller nodes before switching to a shorter wavelength. The move to immersion will require increased attention to the photomask along with new effects influencing the aerial image formation as the numerical apertures (NA) of scanners move up to at least 0.93 and even higher. Feature sizes on the photomask become comparable or even smaller than the wavelength and hence act more like wire grid polaris ers which lead to polarisation effects. As of today AIMS™ fab tools are in operation worldwide. The novel AIMS™ fab 193i tool with a maximum NA of 0.93 is the latest aerial image measurement system for ArF-lithography emulation down to the 65nm node. Common adjustments are numerical aperture, illumination type and partial illumination coherence to match the conditions in 193nm scanners . In addition to non-polarized illu mination, the AIMS™ fab 193i allows the user to select linear x and y polaris ed light for different settings and types , e.g. off-axis annular, quadrupole or dipole illumination. In this paper the polaris ation effects of different photomask features are explored by comparing measurement results using linear polarised illumination parallel and perpendicular to line and space patterns and non-polaris ed illumination. Different MoSiON embedded phase shift masks have been investigated at the highest possible NA=0.93 and for different half-pitches from 500nm to 260nm, the latter corresponding to the 65nm node at the wafer level.