| 摘要 |
A method and apparatus to eliminate bias between dense and sparse patterns of photoresist images is presented. By placing an attenuator along the optical axis of a photolithography mask and its projected image, the intensity of radiation passing through a sparse pattern of the photolithography mask is attenuated so that the intensity of the projected sparse pattern falls within the same range as the intensity of radiation that passes the dense pattern of the photolithography mask. In this way, the bias between dense patterns and sparse patterns caused by differing radiation intensities during exposure is eliminated. The attenuator has both a transparent region and an attenuating region. The attenuating region is designed to attenuate only the sparse patterns projected from the photolithography mask. The attenuator is covered by materials that can attenuate the density of passed radiation to make the intensity of both low spatial frequency and high spatial frequency images fall within the same intensity range.
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