IMPROVED DOSE METROLOGY IN OPTICAL LITHOGRAPHY

Maintaining critical dimensions (CDs) in optical lithography requires careful control over the UV/DUV dose applied to a photoresist, especia lly as CDs become smaller. To meet the growing need for a UV-measureme nt infrastructure in the semiconductor industry, the National Institut e of Standards and Technology (NIST) is improving its primary radiomet ric standards by an order of magnitude, reducing the absolute uncertai nty in irradiance measurements to about 0.5% in the 100-400-nm range. Parallel improvements in transfer standards and source calibrations wi ll allow the dissemination of highly accurate radiometric scales direc tly to industry.