A new approach for eliminating unwanted patterns in attenuated phase shift masks

Abstract

A new approach is identified to eliminate unwanted patterns in high transmission phase shift masks to achieve useful patterning across pitch. A sub-resolution structure is added to the reticle where the propensity of unwanted pattern is found to be maximum. This sub-resolution feature is fully transmitting and has a phase opposite to that of the background. Simulations prove that the light from this feature is successful in nullifying the background intensity responsible for producing the unwanted patterns, while the radiation coming out of the added feature itself gets cancelled and there is no resulting aerial image intensity at the location of the main feature. This technique will help patterning at dense (side lobe prone) pitches even for high transmission masks. Also, the mask-making process will be lot simpler than that of a ternary mask. © 2003 Elsevier Ltd. All rights reserved.