Critical dimension control in synchrotron radiation lithography using a negative-tone chemical amplification resist

Total critical dimension (CD) controllability for 0.14 mu m line-and-space in SR lithography was evaluated for all wafer levels. The evaluation was carried out for the CD accuracy between the wafers, in the wafer and in the exposure field. The influence of the exposure process instability to the CD accuracy was also evaluated. The instability of the 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 found that the CD accuracy between the wafers was degraded by the inaccurate exposure dosage caused by the daily change of the SR beam distribution in the vertical direction. In the exposure field, the CD instability due to SR beam nonuniformity was 4.1 nm and that due to the X-ray mask was 15 nm. Consequently, the total CD controllability is presently 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 achieve the CD accuracy of less than 11nm.