Definition of new quality criteria and assessment means for masks at 150-nm design rules and beyond

Low-k₁ lithography requires enhancement techniques like phase shift and OPC. These techniques impose new and challenging specifications on photomasks. A development to establish means and methods to verify corner rounding, line end shortening, defect printability and the size of jogs, serifs and assist lines in a production worthy manner is based on the assessment of mask production data through a new cluster software tool which combines the output data of a mask defect inspection system, a CD metrology system, an AIMS based mask review station and printing simulation results. Possible definitions of new type photomask quality criteria are discussed and measurement procedures are proposed. As a key application the review of critical features on reticles (OPC, classical defects, contact printability, etc.) at changing stepper conditions ((lambda) , N.A., (sigma) ) is discussed. The concept and the development status of a Photomask Qualification Cluster is presented and early performance results are examined against the target values which are a defect detection sensitivity of 125 nm, optical resolution of 200 nm lines for assist line assessment, CD measurement on lines, contacts and OPC structures with 5 nm repeatability and mask pattern fidelity assessment at printing conditions down to 500 nm lines at reticle level.