With the evolution of exposure tools for optical lithography towards larger numerical apertures, the semiconductor industry expects continued demand for improved wafer flatness at the exposure site. The Allowable site flatness for 300 mm wafers is expected to be less than 45 nm by 2010 and it may be as low as 25 nm by 2015 according to the International Technology Roadmap for Semiconductors (ITRS 2006). This presents a challenge for both wafer polishing and metrology tools, which must be capable of meeting the specifications. We report the results of fabricating ultra-flat 300 mm silicon wafers with a deterministic subaperture finishing process. The finishing process used for this project was magnetorheological finishing (MRF). The wafer thickness metrology, which guided the finishing process, was provided by an infrared interferometer developed at the National Institute of Standards and Technology (NIST). The finishing method in combination with the lnterferometric wafer metrology enabled the fabrication of 300 mm silicon wafers with a total hickness variation (TTV) of about 40 nm.
Proceedings Title: Characterization and Metrology for Nanoelectronics: 2007 International conference on Frontiers of Characterization and Metrology
Conference Dates: March 27-29, 2007
Conference Location: Washington, DC
Conference Title: 2007 International Conference of Characterization and Metrology
Pub Type: Conferences
300 mm wafers, wafer thickness variations