Double patterning will challenge litho, metrology, computation

摘要

While 193nmimmersionlithographyhas taken the industry to 45nm, it will get progressively tougher to move below that. Lithographers will struggle with shrinking margins, more metrology and process control, along with extensive computation, plus double exposure for critical layers, which multiplies their problems. The SPIE Advanced Lithography Conference in San Jose, CA (Feb. 24-29) explored this road ahead. Below 40nm, lithography becomes much more sensitive to stepper variation, and computational optimization will be required, according to Martin van den Brink, EVP, ASML, in a plenary talk. Lithography uniformity becomes critical, and metrology will be very difficult, especially with double exposure. "Stepper controls are not well used today," he said. It is possible to adjust dose point-by-point across the wafer, he suggested, but only with a tremendous amount of computation. Angle-resolved scatterometry feedback loops in production with a DoseMapper recipe might provide optimization. There also must be increased feedback from manufacturing to design, van den Brink added.