The impact of flare, polarized light and aberration on CD uniformity of butting pattern and CD control

The variation of the image quality and critical dimension (CD) uniformity due to the flare, geometrical aberrations and polarized light is studied in order to understand the implication on CD errors control. Some of the surprising phenomena, which occurring at high numerical aperture (NA), are studied with 2-dimension (2D) mask by calculating the latent images of 65 nm butting pattern. When the flare is 5%, the variation of gap-width will reach 27%. The flare's impact on the gap-width is higher than that on the line-width. By introducing a fixed amount of aberration for each Zernike coefficient with all other aberrations being zero, the image quality and CD uniformity are calculated with different flare and polarized light when each Zernike coefficient is 0.02λ. The 3rd order astigmatism (0.02λ) causes the gap-width to reduce 27%, and the 3rd order spherical (0.02λ) causes the gap-width to reduce 5%; the 3rd order coma (0.02λ) has little effect on the gap-width. The horizontal linear polarized light and azimuthally polarized light can enhance the image contrast. The polarized light causes the line-widths to vary a little, while it causes the gap-widths to vary greatly. So adjusting polarization state to compensate the gap-width errors caused by the flare and geometrical aberrations is feasible. By making use of the characteristics of polarized light's imaging can lead to substantial gains in exposure latitude and CD uniformity. We illustrate the feasibility of adjusting polarization state to compensate the CD errors caused by the flare and geometrical aberrations.