In-line wavefront aberration adjustment of a projection lens for a lithographic tool using the dominant mode method.
Aberration adjustment is of great importance in the lithographic process of integrated circuit manufacturing due to the pressure variance, lens thermal effects, overlay correction, and 3D mask effects. With the objective of removing the crosstalk effect, as well as reducing computational complexity during in-line application, a dominant mode method is proposed to adjust the aberrations of the projection lens for a lithographic tool. Theoretical definitions and corresponding calculations of dominant modes are proposed to select the compensators of the projection lens and to build the control matrix for compensator settings. The proposed method is successfully applied in a practical aberration adjustment of the projection lens in a lithographic tool, and the results demonstrate its feasibility and performance.