An improved arrangement for transmission image sensing Disclosed anonymously

摘要

Two gratings at reticle level each give rise to an aerial image at substrate-level. While the known approach sets substrate-level gratings in the middle of these aerial images and shifts the substrate stage to move the gratings and achieve a phase shift, the present invention instead proposes a grating arrangement which gives rise to an inherent relative phase bias. The two gratings at substrate level are thus arranged with a positive and a negative shift relative to the aerial image (i.e. shift relative to the reticle-level), respectively. Biases can be applied at substrate- or at reticle-level, or both. Biases may preferably be, but are not limited to, -. Depending on the combination of biased gratings, stage shifting and focus dependency (cross-talk) may be eliminated, thus resulting in a more efficient and more accurate alignment process. In an aspect therefore, a transmission image sensing device for sensing an aerial image is proposed that comprises: an object mark at reticle level, configured to receive and transmit radiation to form an aerial image, a detector at substrate level comprising a detection mark configured to receive Ihe radiation transmitted from the object mark and to detect the intensity of said radiation as a function of aerial image position, wherein at least one of the object mark and/or the detection mark comprises a pair of gratings, one of said gratings arranged with a positive phase shift relative to the aerial image and the other of said gratings arranged with a negative phase shift relative to the aerial image.