130 nm and 150 nm line-and-space critical-dimension control evaluation using XS-1 x-ray stepper

Critical-dimension (CD) control for 130 and 150 nm line-and-space (L/S) patterns printed with the XS-1 x-ray stepper was evaluated using two kinds of resists: SAL606 and TDUR-N908. The largest factor in the CD variation was the nonuniformity of the x-ray dose, which was +/-4.4% in a 20 mm x 20 mm field. In replicated resist patterns, the CD variation due to mask-CD variation dropped to less than half the mask-CD variation because of Fresnel diffraction. For 130 nm L/S patterns, the CD variation for an 8-in.-diam wafer was 7.9 nm (3 sigma) for SAL606, and 12.0 nm (3 sigma) for TDUR-N908. For 150 nm L/S patterns, the values were 10.5 nm (3 sigma) and 14.6 nm (3 sigma), respectively. Although the major factors causing CD variation are dose nonuniformity and mask-CD variation, different resist materials reflect the effects of these factors to different degrees. The CD variation of 150 nm L/S patterns among seven wafers exposed on the same day was +/-2.8 nm for SAL606 and +/-3.7 nm for TDUR-N908, which is most likely due to fluctuations in the exposure dose of +/-2.7%. The total CD variation for SAL606 was roughly estimated to be 9.0 nm (3 sigma) for 130 nm L/S patterns and 11.9 nm (3 sigma) for 150 nm L/S patterns. These values are within +/-10% of the design rule. (C) 1998 American Vacuum Society. [S0734-211X(98)10206-8].