Post coat delay effects on chemically amplified resists and storage condition impacts

摘要

Critical dimension (CD) requirements are continually tightening for mask manufacturing for mean to target and uniformity control as advanced technology nodes are introduced. In addition, the CD repeatability of structures relevant to optical proximity correction is also becoming more critical with each advancing node. Chemically amplified resists commonly in use in the mask industry are sensitive to post coat delay (PCD), storage and handling conditions, and environmental contaminants. In this paper, the CD sensitivity of a commonly used photoresist is characterized as a function of post coat delay. The impact to average CD, uniformity, linearity, thru pitch, clear to dark, and e-beam proximity effect are all examined. An analysis of post develop resist thickness loss is presented to supplement the understanding of CD uniformity behavior. In addition, the impact of several storage scenarios is evaluated including storage in a sealed foil bag, an unsealed dry nitrogen environment, and storage boxes made from two different materials. The impact of storage conditions on CD uniformity is critical and is shown to be strongly influenced by the choice of material for the containers and the storage environment.