Mask write time reduction: deployment of advanced approaches and their impact on established work models

Abstract

The extension of 193nm exposure wavelength to smaller nodes continues the trend of increased data complexity and subsequently longer mask writing times. In particular inverse lithography methods create complex mask shapes. We introduce a variety of techniques to mitigate the impact -data simplification post-optical proximity correction (OPC), LShots, multi-resolution writing (MRW) and optimization based fracture. Their potential for shot count reduction is assessed. All of these techniques require changes to the mask making work flow at some level -the data preparation and verification flow, the mask writing equipment, the mask inspection and the mask qualification in the wafer manufacturing line. The paper will discuss these factors and conduct a benefit -effort assessment for the deployment. Some of the techniques do not reproduce the originally targeted mask shape. The impact of the deviations will be studied at wafer level with simulations of the exposure process and quantified as to their impact on the exposure process window. Based on the results of the assessment a deployment strategy will be discussed.