A defect printability analysis study using virtual stepper system in a production environment

In this paper, the simulation of wafer images for Attenuated Phase Shift Masks (ATTPSM) and repaired binary masks are performed by Virtual Stepper(R) System in a real production environment. In addition, the Automatic Defect Severity Scoring (ADSS) module in Virtual Stepper is also used to calculate the defect severity score for each defect. ADSS provides an overall score that quantifies the impact of a given defect on the surrounding features. For the binary masks, the quality of repaired defects is studied. For the ATTPSM, three types of programmed defects (protrusion, intrusion, and pin-dot) on both line/space and contact hole patterns are assessed. Wafer exposures are performed using 248 nm imaging technology and inspection images generated on a KLA-Tencor's SLF27 system. These images are used by the Virtual Stepper System to simulate wafer images under the specific stepper parameters. The results are compared to SEM images of resist patterns and Aerial Image Measurement System (AIMS(TM)) simulated results.