Proposal for the Coma Aberration Dependent Overlay Error Compensation Technology

概要

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A new method for overlay accuracy improvement which compensates for the positional shifts of patterns due to coma aberrations, using the pattern placement error-corrected mask is proposed. Various types of resolution enhancement technologies such as modified illumination and phase shifting techniques significantly improve the resolution. The effects of residual aberrations in the lens system cannot be ignored because such resolution enhancement technologies emphasize the effects of the aberrations in the projected images. One of the key issues is the deterioration of the positional accuracy due to coma aberrations. As the positional shifts of patterns heavily depend on the spatial frequency of the pattern and the illumination conditions. 2.0-µm isolated line patterns and 0.3-µm line-and-space patterns are selected and their pattern shift examined. Two types of correction methods were investigated in this work using the pattern placement error-corrected mask, the absolute correction and the relative correction method. By the use of these correction methods, the overlay errors due to coma aberrations can be reduced to half of the error obtained without application of these correction methods.
1998-12-30