A method of correcting physically conditioned errors in the measurement of an object detects an image of the object to be measured, measures the imaged object, determines a measurement error caused by structural surroundings of the object, and corrects the measurement result in dependence on the measurement error.

A method, and a system for employing the method, for providing a modified optical proximity correction (OPC) for correcting distortions of pattern lines on a semiconductor circuit wafer. The method comprises producing a mask having one or more pattern regions, and producing the semiconductor circuit wafer from the mask. The pattern regions include one or more non-edge pattern regions located adjacent to other of the non-edge pattern regions on the mask. The pattern regions further include one or more edge pattern regions located at or near an area on the mask not having the other non-edge pattern regions. The edge pattern regions have widths calculated to minimize the variance in dimensions between one or more pattern lines on the semiconductor circuit wafer formed from them and one or more pattern lines on the semiconductor circuit wafer formed from the non-edge pattern regions. The distances between any two of the pattern regions are calculated to minimize the variance in dimensions between the one or more pattern lines formed from the edge pattern regions and the one or more pattern lines formed from the non-edge pattern regions. The above producing step includes producing the semiconductor circuit wafer from the mask having the pattern lines formed from the non-edge pattern regions and having the pattern lines formed from the edge pattern regions, where the pattern lines formed from the non-edge regions are permitted to differ in distances between them.

A measurement tool connects to an automatic inspection machine for measuring microscopic characteristics of features on a photographic mask. Widths of densely packed lines are measured for features having sizes of less than about the wavelength of the examining radiation. A simulated intensity profile is subtracted from the actual measured intensity profile to obtain an error profile. The error profile provides edge position corrections which adjust the originally estimated edge positions. A new, simulated intensity profile is created and the process is repeated until the error profile is deemed acceptable. The line width is measured by measuring between the estimated edge positions. The opacity of a feature is determined and used for correcting dimension measurements. A formula determines the opacity based upon the contrast, the measured dimension and the single data point. Width or height of an irregular feature is calculated accurately. Dimension of the feature is determined using the peak width data and the peak width standard deviation.

A method of controlling imaging and process parameters in a lithographic process comprises providing a control pattern having an isolated feature with a pitch greater than twice a width of an individual feature, and exposing and developing a calibration resist layer with the control pattern design at a plurality of dose and focus settings. Width of the printed calibration control pattern feature is measured near the top and bottom of the resist layer thickness, and optimum dose and focus settings are then determined. Control patterns are printed at fixed exposure dose and focus settings on a production substrate, and width is measured near the top and bottom of the resist layer thickness. The widths of the production control pattern features are compared with the control pattern model parameters, and the imaging and process parameter settings in the production process are adjusted based on the comparison of the widths.

An OPC feature measurement technique accurately measures serif area of OPC features, feature separation and line symmetry, and is especially useful for measuring dimensions which are less than about the wavelength of the examining radiation. The relative area of serifs present on a line end is measured by first defining a region of interest around the line end and then an intensity profile is created. The differences between data points on the profile and a constant value are summed in order to calculate a flux value. The flux value is divided by the intensity range to determine an area. The separation distance between a line end and another feature is determined by first defining a region of interest that spans the separation distance between the two features. Next, an intensity profile is created. The differences between data points on the profile and a constant value are summed to calculate a flux value. The separation distance between the features is calculated from the flux value. The asymmetry of serifs of a line present on a photomask is determined by first defining two regions of interest: a shank region of interest that includes the shank of the line and an end region of interest that includes the end of the line. Intensity profiles are created for both regions of interest. The profiles are created by summing values in a longitudinal direction with respect to the line. Finally, an asymmetry area value for the serifs is calculated using the end intensity profile and a centroid of the shank region of interest. The effective diameter, the separation distance and the asymmetry area are useful for evaluating the quality of the photomask.