The invention relates to a method for determining a registration error of a structure on a mask for semiconductor lithography, comprising the following method steps: generating an image of at least one region of the mask, determining at least one measuring contour in the image, and matching the forms of a design contour and a measuring contour to one another while at the same time matching the registration of the two contours.

Methods and systems for determining one or more characteristics of light in an optical system are provided. One system includes first detector(s) configured to detect light having one or more wavelengths shorter than 190 nm emitted from a light source at one or more first angles mutually exclusive of one or more second angles at which the light is collected from the light source by an optical system for illumination of a specimen and to generate first output responsive to the light detected by the first detector(s). In addition, the system includes a control subsystem configured for determining one or more characteristics of the light at one or more planes in the optical system based on the first output.

Methods and systems for determining one or more characteristics of light in an optical system are provided. One system includes first detector(s) configured to detect light having one or more wavelengths shorter than 190 nm emitted from a light source at one or more first angles mutually exclusive of one or more second angles at which the light is collected from the light source by an optical system for illumination of a specimen and to generate first output responsive to the light detected by the first detector(s). In addition, the system includes a control subsystem configured for determining one or more characteristics of the light at one or more planes in the optical system based on the first output.

A mask characterization method comprises measuring an interference signal of a reflection or transmission mask for use in lithography; and determining a quality metric for the reflection or transmission mask based on the interference signal. A mask characterization apparatus comprises a light source arranged to illuminate a reflective or transmissive mask with light whereby mask-reflected or mask-transmitted light is generated; an optical grating arranged to convert the mask-reflected or mask-transmitted light into an interference pattern; and an optical detector array arranged to generate an interference signal by measuring the interference pattern.

Metrology methods and targets are provided for reducing or eliminating a difference between a device pattern position and a target pattern position while maintaining target printability, process compatibility and optical contrast—in both imaging and scatterometry metrology. Pattern placement discrepancies may be reduced by using sub-resolved assist features in the mask design which have a same periodicity (fine pitch) as the periodic structure and/or by calibrating the measurement results using PPE (pattern placement error) correction factors derived by applying learning procedures to specific calibration terms, in measurements and/or simulations. Metrology targets are disclosed with multiple periodic structures at the same layer (in addition to regular target structures), e.g., in one or two layers, which are used to calibrate and remove PPE, especially when related to asymmetric effects such as scanner aberrations, off-axis illumination and other error sources.

Metrology methods and targets are provided for reducing or eliminating a difference between a device pattern position and a target pattern position while maintaining target printability, process compatibility and optical contrast—in both imaging and scatterometry metrology. Pattern placement discrepancies may be reduced by using sub-resolved assist features in the mask design which have a same periodicity (fine pitch) as the periodic structure and/or by calibrating the measurement results using PPE (pattern placement error) correction factors derived by applying learning procedures to specific calibration terms, in measurements and/or simulations. Metrology targets are disclosed with multiple periodic structures at the same layer (in addition to regular target structures), e.g., in one or two layers, which are used to calibrate and remove PPE, especially when related to asymmetric effects such as scanner aberrations, off-axis illumination and other error sources.

Methods and systems for detecting defects on a mask are provided. One method includes generating a database reference image for a multi-die mask by simulation and detecting first defects on the mask by comparing the database reference image to images of the mask generated by an imaging subsystem for a first of the multiple dies. The method also includes generating a die reference image for the first of the multiple dies by applying one or more parameters of the imaging subsystem learned by generating the database reference image to the images generated by the imaging subsystem of one or more of the multiple dies other than the first multiple die. In addition, the method includes detecting second defects on the mask by comparing the die reference image to the images of the mask generated by the imaging subsystem for the first of the multiple dies.

Methods and systems for detecting defects on a mask are provided. One method includes generating a database reference image for a multi-die mask by simulation and detecting first defects on the mask by comparing the database reference image to images of the mask generated by an imaging subsystem for a first of the multiple dies. The method also includes generating a die reference image for the first of the multiple dies by applying one or more parameters of the imaging subsystem learned by generating the database reference image to the images generated by the imaging subsystem of one or more of the multiple dies other than the first multiple die. In addition, the method includes detecting second defects on the mask by comparing the die reference image to the images of the mask generated by the imaging subsystem for the first of the multiple dies.

Disclosed is a blank mask including a transparent substrate and a light shielding film disposed on the transparent substrate, wherein the light shielding film includes a transition metal and at least one selected from the group consisting of oxygen and nitrogen, wherein when a surface of the light shielding film includes nine sectors formed by trisecting the surface of the light shielding film vertically and horizontally, each of the nine sectors has a Rsk value, respectively, and an average value of the Rsk values of the nine sectors is equal to −0.64 or more and less than or equal to 0, where Rsk value is a height symmetry of the surface of the light shielding film measured in accordance with ISO_4287, and wherein an average value of Rku values, which are kurtosis of the surface of the light shielding film measured in accordance with ISO_4287, of the nine sectors is 3 or less.

A microscope system for flexibly, efficiently and quickly inspecting patterns and defects on extreme ultraviolet (EUV) lithography photomasks. The system includes a stand-alone plasma-based EUV radiation source with an emission spectrum with a freestanding line emission in the spectral range from 12.5 nm to 14.5 nm has a relative bandwidth of λ/Δλ>1000, means for the broadband spectral filtering λ/Δλ<50 for selecting the dominant freestanding emission line, means for suppressing radiation with wavelengths outside of the EUV spectral region, zone plate optics for magnified imaging of the object with a resolution which corresponds to the width of an outermost zone of the zone plate, a numerical aperture corresponding to more than 1000 zones, and a EUV detector array for capturing the patterned object.