CRITICAL DIMENSION CONTROL IN SYNCHROTRON-RADIATION LITHOGRAPHY USINGA NEGATIVE-TONE CHEMICAL AMPLIFICATION RESIST

Total critical dimension (CD) controllability for 0.14 mu m line-and-s pace in SR lithography was evaluated for all wafer levels. The evaluat ion was carried out for the CD accuracy between the wafers, in the waf er and in the exposure field. The influence of the exposure process in stability to the CD accuracy was also evaluated. The instability of th e post exposure baking (FEB) temperature and the post exposure delay ( FED) time affects the CD accuracy, and they were estimated to be less than 5nm, respectively. The CD accuracy at the same point on the X-ray mask was 5.4 nm in the wafer and 10.5 nm between the wafers. It was f ound that the CD accuracy between the wafers was degraded by the inacc urate exposure dosage caused by the daily change of the SR beam distri bution in the vertical direction. In the exposure field, the CD instab ility due to SR beam nonuniformity was 4.1 nm and that due to the X-ra y mask was 15 nm. Consequently, the total CD controllability is presen tly estimated to be 19.5nm for all wafer levels and the improvement of the dose repeatability and X-ray mask CD control is required to achie ve the CD accuracy of less than 11nm.