Abstract: Method and apparatus for reducing overlay measurements and predicting overlay in unmeasured regions of a wafer are provided. Embodiments include providing a wafer having sets of four fields sharing a common vertex; measuring overlay values near each corner of each field, except for a corner near the common vertex of a first field and a corner near the common vertex of a second field of each set; decomposing the measured overlay values into measured interfield and intrafield correctable and non-correctable errors; forming a virtual stack of all fields; determining an average intrafield correctable error and intrafield non-correctable error for each corner of the virtual stack based on the measured intrafield correctable and non-correctable errors, respectively; and predicting the overlay values for the unmeasured corners of each set based on combinations of the measured interfield correctable and non-correctable errors and the average intrafield correctable and non-correctable errors.

Abstract: Method and apparatus for reducing overlay measurements and predicting overlay in unmeasured regions of a wafer are provided. Embodiments include providing a wafer having sets of four fields sharing a common vertex; measuring overlay values near each corner of each field, except for a corner near the common vertex of a first field and a corner near the common vertex of a second field of each set; decomposing the measured overlay values into measured interfield and intrafield correctable and non-correctable errors; forming a virtual stack of all fields; determining an average intrafield correctable error and intrafield non-correctable error for each corner of the virtual stack based on the measured intrafield correctable and non-correctable errors, respectively; and predicting the overlay values for the unmeasured corners of each set based on combinations of the measured interfield correctable and non-correctable errors and the average intrafield correctable and non-correctable errors.

Abstract: Asymmetric heating and/or thermal expansion of a reticle or an image field is reduced. Embodiments include exposing a wafer with an actual image field (including a pattern for a chip layer) on a multilayer reticle, and performing a dummy exposure with another image field of the reticle. Other embodiments include exposing a wafer with a reticle area including both the actual and one or more other image fields of a multilayer reticle, sacrificing any die on the wafer that is exposed with substantial illumination with an image field other than the actual image field. Further embodiments include dummy exposures or enlargement of the illuminated reticle area of a single layer reticle with variation in pattern density between regions of the image field. Further embodiments include changing the image field geometry of a multilayer or single layer reticle.

Abstract: Asymmetric heating and/or thermal expansion of a reticle or an image field is reduced. Embodiments include exposing a wafer with an actual image field (including a pattern for a chip layer) on a multilayer reticle, and performing a dummy exposure with another image field of the reticle. Other embodiments include exposing a wafer with a reticle area including both the actual and one or more other image fields of a multilayer reticle, sacrificing any die on the wafer that is exposed with substantial illumination with an image field other than the actual image field. Further embodiments include dummy exposures or enlargement of the illuminated reticle area of a single layer reticle with variation in pattern density between regions of the image field. Further embodiments include changing the image field geometry of a multilayer or single layer reticle.

Abstract: A method for the reproducible determination of the positions of structures (3) on a mask (2) is disclosed. A pellicle frame (30) is firmly attached to the mask (2). A theoretical model of the bending of the mask (2) with the firmly attached pellicle frame (30) is calculated, wherein material properties of the mask (2), of the pellicle frame (30), and of the attaching means between the pellicle frame (30) and the mask (2) are taken into account in the calculation of the bending of the mask (2). For the calculation of the bending of the mask (2) its contact with three support points is considered. The positions of the structures (3) on the mask (2) are measured with a metrology tool (1). The measured positions of each structure are corrected with the theoretical model of the bending of the mask at the position of the respectively measured structure.

Abstract: A method for the reproducible determination of the positions of structures (3) on a mask (2) is disclosed. A pellicle frame (30) is firmly attached to the mask (2). A theoretical model of the bending of the mask (2) with the firmly attached pellicle frame (30) is calculated, wherein material properties of the mask (2), of the pellicle frame (30), and of the attaching means between the pellicle frame (30) and the mask (2) are taken into account in the calculation of the bending of the mask (2). For the calculation of the bending of the mask (2) its contact with three support points is considered. The positions of the structures (3) on the mask (2) are measured with a metrology tool (1). The measured positions of each structure are corrected with the theoretical model of the bending of the mask at the position of the respectively measured structure.