Abstract:
A method for a metrology process, the method includes obtaining first measurement data relating to a first set of measurement conditions and determining a first measurement recipe based on the first measurement data. At least one performance indicator is determined from one or more components of the first measurement data obtained from a component analysis or statistical decomposition. Alternatively, at least one performance indicator is determined from a comparison of one or more first measurement values relating to the first measurement recipe and one or more second measurement values relating to a second measurement recipe, where second measurement recipe is different to the first measurement data and relates a second set of measurement conditions, the second set of measurement conditions being different to the first set of measurement conditions.
Abstract:
A method of inferring a value for at least one local uniformity metric relating to a product structure, the method including: obtaining intensity data including an intensity image relating to at least one diffraction order obtained from a measurement on a target; obtaining at least one intensity distribution from the intensity image; determining, from the at least one intensity distribution, an intensity indicator expressing a variation of either intensity over the at least one diffraction order, or a difference in intensity between two complimentary diffraction orders over the intensity image; and inferring the value for the at least one local uniformity metric from the intensity indicator.
Abstract:
Disclosed is a metrology device (1600) configured to produce measurement illumination comprising a plurality of illumination beams, each of said illumination beams being spatially incoherent or pseudo-spatially incoherent and comprising multiple pupil points in an illumination pupil of the metrology device. Each pupil point in each one of said plurality of illumination beams has a corresponding pupil point in at least one of the other illumination beams of said plurality of illumination beams thereby defining multiple sets of corresponding pupil points, and the pupil points of each set of corresponding pupil points are spatially coherent with respect to each other.
Abstract:
Target structures such as overlay gratings (Ta and Tb) are formed on a substrate (W) by a lithographic process. The first target is illuminated with a spot of first radiation (456a, Sa) and simultaneously the second target is illuminated with a spot of second radiation (456b, Sb). A sensor (418) detects at different locations, portions (460x−, 460x+) of said first radiation that have been diffracted in a first direction by features of the first target and portions (460y−, 460y+) of said second radiation that have been diffracted in a second direction by features of the second target. Asymmetry in X and Y directions can be detected simultaneously, reducing the time required for overlay measurements in X and Y. The two spots of radiation at soft x-ray wavelength can be generated simply by exciting two locations (710a, 710b) in a higher harmonic generation (HHG) radiation source or inverse Compton scattering source.
Abstract:
Apparatus, systems, and methods are used for detecting the alignment of a feature on a substrate using a polarization independent interferometer. The apparatus, system, and methods include optical elements that receive light that has diffracted or scattered from a mark on a substrate. The optical elements may split the diffracted light into multiple subbeams of light which are detected by one or more detectors. The diffracted light may be combined optically or during processing after detection. The system may determine alignment and/or overlay based on the received diffracted light having any polarization angle or state.
Abstract:
Metrology targets are formed on a substrate (W) by a lithographic process. A target (T) comprising one or more grating structures is illuminated with spatially coherent radiation under different conditions. Radiation (650) diffracted by from said target area interferes with reference radiation (652) interferes with to form an interference pattern at an image detector (623). One or more images of said interference pattern are captured. From the captured image(s) and from knowledge of the reference radiation a complex field of the collected scattered radiation at the detector. A synthetic radiometric image (814) of radiation diffracted by each grating is calculated from the complex field. From the synthetic radiometric images (814, 814′) of opposite portions of a diffractions spectrum of the grating, a measure of asymmetry in the grating is obtained. Using suitable targets, overlay and other performance parameters of the lithographic process can be calculated from the measured asymmetry.
Abstract:
Disclosed is a method of improving a measurement of a parameter of interest. The method comprises obtaining metrology data comprising a plurality of measured values of the parameter of interest, relating to one or more targets on a substrate, each measured value relating to a different measurement combination of a target of said one or more targets and a measurement condition used to measure that target and asymmetry metric data relating to asymmetry for said one or more targets. A respective relationship is determined for each of said measurement combinations relating a true value for the parameter of interest to the asymmetry metric data, based on an assumption that there is a common true value for the parameter of interest over said measurement combinations. These relationships are used to improve a measurement of the parameter of interest.
Abstract:
A metrology apparatus (302) includes a higher harmonic generation (HHG) radiation source for generating (310) EUV radiation. Operation of the HHG source is monitored using a wavefront sensor (420) which comprises an aperture array (424, 702) and an image sensor (426). A grating (706) disperses the radiation passing through each aperture so that the image detector captures positions and intensities of higher diffraction orders for different spectral components and different locations across the beam. In this way, the wavefront sensor can be arranged to measure a wavefront tilt for multiple harmonics at each location in said array. In one embodiment, the apertures are divided into two subsets (A) and (B), the gratings (706) of each subset having a different direction of dispersion. The spectrally resolved wavefront information (430) is used in feedback control (432) to stabilize operation of the HGG source, and/or to improve accuracy of metrology results.
Abstract:
Disclosed is a metrology sensor apparatus and associated method. The metrology sensor apparatus comprises an illumination system operable to illuminate a metrology mark on a substrate with illumination radiation having a first polarization state and an optical collection system configured to collect scattered radiation, following scattering of the illumination radiation by the metrology mark. The metrology mark comprises a main structure and changes, relative to the first polarization state, at least one of a polarization state of a first portion of the scattered radiation predominately resultant from scattering by the main structure and a polarization state of a second portion of radiation predominately resultant from scattering by one or more features other than the main structure, such that the polarization state of the first portion of the scattered radiation is different to the polarization state of the second portion of the scattered radiation. The metrology sensor apparatus further comprises an optical filtering system which filters out the second portion of the scattered radiation based on its polarization state.
Abstract:
An alignment sensor for a lithographic apparatus has an optical system configured to deliver, collect and process radiation selectively in a first waveband (e.g. 500-900 nm) and/or in a second waveband (e.g. 1500-2500 nm). The radiation of the first and second wavebands share a common optical path in at least some portion of the optical system, while the radiation of the first waveband is processed by a first processing sub-system and the radiation of the second waveband is processed by a second processing sub-system. The processing subsystems in one example include self-referencing interferometers. The radiation of the second waveband allows marks to be measured through an opaque layer. Optical coatings and other components of each processing sub-system can be tailored to the respective waveband, without completely duplicating the optical system.