Abstract: Characteristics of a standard logic cell, e.g., a random logic cell, are determined using an effective cell approximation. The effective cell approximation is smaller than the standard logic cell and represents the density of lines and spaces of the standard logic cell. The effective cell approximation may be produced based on a selected area from the standard logic cell and include the same non-periodic patterns as the selected area. The effective cell approximation, alternatively, may represent non-periodic patterns in the standard logic cell using periodic patterns having a same density of lines and spaces as found in the standard logic cell. A structure on the sample, such as a logic cell or a metrology target produced based on the effective cell approximation is measured to acquire data, which is compared to the data for the effective cell approximation to determine a characteristic of the standard logic cell.

Abstract: Overlay is determined for a device using signals measured from the device and a signal response to overlay determined from a plurality of calibration targets. Each calibration target has the same design as the device, but includes a known overlay shift. The calibration targets may be located in a scribe line, within a product area on the wafer, or on a separate calibration wafer. Each calibration target may have a different overlay shift, including zero overlay shift. The device may serve as a calibration target with zero overlay shift. The overlay shift may be in two orthogonal directions. The signal response to overlay may be determined based on a set of signals obtained from the calibration targets. A second set of signals may then be obtained from the device and the overlay determined based on the second set of signals and the determined signal response to overlay.

Abstract: An interferometric metrology device characterizes a surface topography of a sample at different length scales by combining the interferometric data into blocks of different length scales or by filtering the interferometric data at different length scales and then determining statistical moments or surface properties of the surface topography at the different length scales. The interferometric metrology device determines a best focus position for a processing tool based on different length scales and/or based on weighting functions that are based on the structure-dependent focus budget and a variable local topography. Additionally, the topography data may be used by itself or combined with design data, design simulation depth-of-focus data and lithography scanner focus data to define regions of interest for additional characterization with a different metrology device.

Abstract: An interferometric metrology device characterizes a surface topography of a sample at different length scales by combining the interferometric data into blocks of different length scales or by filtering the interferometric data at different length scales and then determining statistical moments or surface properties of the surface topography at the different length scales. The interferometric metrology device determines a best focus position for a processing tool based on different length scales and/or based on weighting functions that are based on the structure-dependent focus budget and a variable local topography. Additionally, the topography data may be used by itself or combined with design data, design simulation depth-of-focus data and lithography scanner focus data to define regions of interest for additional characterization with a different metrology device.