Study of time dependent 193 nm reticle haze

Abstract

While significant progress has been made in reducing the occurrence rate of progressive defect growth on photomasks used at 193nm, the issue continues to be a problem for many semiconductor fabs. Increasing evidence from multiple sources indicates that further reduction in haze risk involves closely controlling the storage and exposure environment of the photomask. Further controlled testing is necessary to characterize the impact of environment and individual components on growth. In this way, photomask users, equipment and material providers may be better prepared to ensure the proper storage and use of photomasks in order to reduce the risk of haze growth. In continuation of work previously reported by Toppan Photomasks, advanced test apparatus, recently designed and built, now enables researchers to generate and maintain stable and controlled levels of multiple impurities which potentially effect haze growth. Supported by on-line and off-line analytical methods and instrumentation, new experimental set-up enables accuracy in the testing and validation of the impacts of environmental variables. Different classes of pollutants in multiple combinations have been studied to more precisely characterize environmental sensitivity of varying types of 193 nm reticles. Authors report further on the study of the effect of environmental conditions on severity and rate of haze formation to provide insight into the requirements for reducing or even preventing such conditions.