A cost benefit analysis of photolithography and metrology dedication in a metrology constrained multipart number fabricator

Abstract

Dedication in photolithography provides better process control and accurate data collection while driving reductions in both rework and process defects. The trade-off, however, is the limitation it places on the manufacturing system by restricting the number of servers where a given lot can be directed. Relaxing dedication and deployment allows for a lower cycle time through the process step, but this same relaxation may also drive the need for additional processing and measurement processing in the photolithography sector, thus encouraging longer overall cycle time for the sector. This paper analyzes the costs and benefits of dedication on the basis of overall photosector cycle time. The variables controlled by the decisions to dedicate include send-aheads, number of measurements, sample size, and skip-plan levels. Strict photolithography dedication drives fewer send-aheads, measurements, a smaller sample size and larger skip plans; a level is reached where the dedication is offset by additional waiting time for dedicated lots at specific photolithography tools. The same level of rework and process defects can be achieved at a lower overall sector cycle time by determining the minimum cycle time while maintaining the same operating procedures and quality controls. The solution, in this instance, depends on the number of technologies and part numbers being run through the photolithography sector, an effect that must be detailed and analyzed.