Abstract: An apparatus and method of compensating for lens imperfections in a projection lithography tool, includes extracting from a diffraction image created by the projection lithography tool a lens transmittance function, and then using the extracted lens transmittance function as a compensator in the lithography projection tool. Another preferred apparatus and method of synthesizing a photomask pattern includes obtaining a phase and an amplitude of a transmittance function of an imaging system; forming a computational model of patterning that includes the transmittance function of the imaging system; and then synthesizing a mask pattern from a given target pattern, by minimizing differences between the target pattern and another pattern that the computational model predicts the synthesized mask pattern will form on a wafer.

Abstract: A system and method for characterizing an imaging system causes a diffraction image indicative of a test structure having a generalized line-grating to be formed and then extracts from a measurement of the diffraction image a lens transmittance function, a photoresist property or a defocus distance.

Abstract: A method for measuring overlay in a sample includes obtaining an image of an overlay target that includes a series of grating stacks each having an upper and lower grating, each grating stack having a unique offset between its upper and lower grating. The image is obtained with a set of illumination and collection optics where the numerical aperture of the collection optics is larger than the numerical aperture of the illumination optics and with the numerical apertures of the illumination and collection optics are selected so that the unit cells of gratings are not resolved, the grating stacks are resolved and they appear to have a uniform color within the image of the overlay target.

Abstract: A method for measuring overlay in semiconductor wafers includes a calibration phase in which a series of calibration samples are analyzed. Each calibration sample has an overlay that is known to be less than a predetermined limit. A difference spectrum for a pair of reflectively symmetric overlay targets is obtained for each calibration sample. The difference spectra are then combined to define a gross overlay indicator. In subsequent measurements of actual wafers, difference spectra are compared to the overlay indicator to detect cases of gross overlay.

Abstract: A method for measuring overlay in semiconductor wafers includes obtaining diffraction based and imaging based measurements of the same target. The two separate measurements are then combined in a way that is consistent to both measurements to obtain an overlay measurement that has high precision and large range.

Abstract: A system and method for characterizing an imaging system causes a diffraction image indicative of a test structure having a generalized line-grating to be formed and then extracts from a measurement of the diffraction image a lens transmittance function, a photoresist property or a defocus distance.

Abstract: An apparatus and method for modifying a mask data set includes calculating a derivative of a figure-of-merit, indicative of a data set defined by a plurality of polygon edges and then segmenting polygon edges in response to said step of calculating.

Abstract: An apparatus and method of synthesizing a photolithographic data set includes using a first computational model to calculate a first figure-of-merit for the photolithographic data set; changing a first part of the photolithographic data set to increase the first figure-of-merit; and then using a second computational model to calculate a second figure-of-merit of the photolithographic data set; and changing a second part of the photolithographic data set to increase the second figure-of-merit. The second computational model enables figure-of-merit calculations to be executed at a significantly faster execution rate that the first computational model.

Abstract: An apparatus and method of compensating for lens imperfections in a projection lithography tool, includes extracting from a diffraction image created by the projection lithography tool a lens transmittance function, and then using the extracted lens transmittance function as a compensator in the lithography projection tool. Another preferred apparatus and method of synthesizing a photomask pattern includes obtaining a phase and an amplitude of a transmittance function of an imaging system; forming a computational model of patterning that includes the transmittance function of the imaging system; and then synthesizing a mask pattern from a given target pattern, by minimizing differences between the target pattern and another pattern that the computational model predicts the synthesized mask pattern will form on a wafer.

Abstract: A method for measuring overlay in a sample includes obtaining an image of an overlay target that includes a series of grating stacks each having an upper and lower grating, each grating stack having a unique offset between its upper and lower grating. The image is obtained with a set of illumination and collection optics where the numerical aperture of the collection optics is larger than the numerical aperture of the illumination optics and with the numerical apertures of the illumination and collection optics are selected so that the unit cells of gratings are not resolved, the grating stacks are resolved and they appear to have a uniform color within the image of the overlay target.

Abstract: A method for measuring overlay in semiconductor wafers includes a calibration phase in which a series of calibration samples are analyzed. Each calibration sample has an overlay that is known to be less than a predetermined limit. A difference spectrum for a pair of reflectively symmetric overlay targets is obtained for each calibration sample. The difference spectra are then combined to define a gross overlay indicator. In subsequent measurements of actual wafers, difference spectra are compared to the overlay indicator to detect cases of gross overlay.

Abstract: A method for measuring overlay in semiconductor wafers includes obtaining diffraction based and imaging based measurements of the same target. The two separate measurements are then combined in a way that is consistent to both measurements to obtain an overlay measurement that has high precision and large range.

Abstract: A method for optically inspecting and evaluating a semiconductor wafer includes projecting a probe beam at two overlay targets. Each overlay target includes an upper grating and a lower grating. At each target, the combined intensity of the 1st diffracted orders generated by the upper and lower gratings are measured. The combined intensity of the −1st diffracted orders generated by the upper and lower gratings are also measured for each target. The method then calculates an overlay offset between an upper layer and a lower layer as a function of the measured intensity information.