摘要:
The invention is a method and apparatus for determining characteristics of a sample. The system and method provide for detecting a monitor beam reflected off a mirror, where the monitor beam corresponds to the intensity of light incident upon the sample. The system and method also provide for detecting a measurement beam, where the measurement beam has been reflected off the sample being characterized. Both the monitor beam and the measurement beam are transmitted through the same transmission path, and detected by the same detector. Thus, potential sources of variations between the monitor beam and the measurement beam which are not due to the characteristics of the sample are minimized. Reflectivity information for the sample can be determined by comparing data corresponding to the measurement beam relative to data corresponding the monitor beam.
摘要:
Alignment accuracy between two or more patterned layers is measured using a metrology target comprising substantially overlapping diffraction gratings formed in a test area of the layers being tested. An optical instrument illuminates all or part of the target area and measures the optical response. The instrument can measure transmission, reflectance, and/or ellipsometric parameters as a function of wavelength, polar angle of incidence, azimuthal angle of incidence, and/or polarization of the illumination and detected light. Overlay error or offset between those layers containing the test gratings is determined by a processor programmed to calculate an optical response for a set of parameters that include overlay error, using a model that accounts for diffraction by the gratings and interaction of the gratings with each others' diffracted field. The model parameters might also take account of manufactured asymmetries. The calculation may involve interpolation of pre-computed entries from a database accessible to the processor. The calculated and measured responses are iteratively compared and the model parameters changed to minimize the difference.
摘要:
A method of measuring at least one parameter associated with a portion of a sample having formed thereon one or more structures with at least two zones each having an associated zone reflectance property. The method includes the steps of illuminating the zones with broadband light, and measuring at least one reflectance property of light reflected from the at least two zones. The measurement includes a substantial portion of non-specularly scattered light, thereby increasing the quality of the measurement. The method further includes the step of fitting a parameterized model to the measured reflectance property. The parameterized model mixes the zone reflectance properties of the zones to account for partially coherent light interactions between the two zones.
摘要:
An optical measurement system for evaluating a sample has a azimuthally rotatable measurement head. A motor-driven rotating mechanism is coupled to the measurement head to allow the optics to rotate with respect to the sample. In particular, a preferred embodiment is a polarimetric scatterometer (FIG. 1) for measuring optical properties of a periodic structure on a wafer sample (12). This scatterometer has optics (30) directing a polarized illumination beam at non-normal incidence onto the periodic structure. In addition to a polarizer (8), the illumination path can also be provided with an E-O modulator for modulating the polarization. The measurement head optics also collect light reflected from the periodic structure and feed that light to a spectrometer (17) for measurement. A polarization beamsplitter (18) is provided in the collection path so that both S and P polarization from the sample can be separately measured. The entire measurement head can be mounted for rotation of the plane of incidence to different azimuthal directions relative to the periodic structures on the wafer. The instrument can be integrated within a wafer process tool in which wafers may be provided at arbitrary orientation.
摘要:
A small-spot imaging, spectrometry instrument for measuring properties of a sample has a polarization-scrambling element, such as a Lyot depolarizer, incorporated between the polarization-introducing components of the system, such as the beamsplitter, and the microscope objective of the system. The Lyot depolarizer varies polarization with wavelength. Sinusoidal perturbation in the resulting measured spectrum can be removed by data processing techniques or, if the depolarizer is thick or highly birefringent, may be narrower than the wavelength resolution of the instrument.
摘要:
A method of measuring at least one parameter associated with a portion of a sample having formed thereon one or more structures with at least two zones each having an associated zone reflectance property. The method includes the steps of illuminating the zones with broadband light, and measuring at least one reflectance property of light reflected from the at least two zones. The measurement includes a substantial portion of non-specularly scattered light, thereby increasing the quality of the measurement. The method further includes the step of fitting a parameterized model to the measured reflectance property. The parameterized model mixes the zone reflectance properties of the zones to account for partially coherent light interactions between the two zones.
摘要:
An apparatus and method are disclosed for characterizing semiconductor wafers or other test objects that can support acoustic waves. Source and receiving transducers are configured in various arrangements to respectively excite and detect acoustic waves (e.g., Lamb waves) in a wafer to be characterized. Signals representing the detected waves are digitally processed and used to compute a measurement set correlated with the waves' velocity in the wafer. A characterization sensitivity is provided that describes how different wafer characteristics of interest vary with changes in the propagation of the acoustic waves. Using the characterization sensitivity and measurement sets computed at a setup time when all wafer characteristics are known and one or more process times when at least one of the characteristics is not known the perturbation in wafer characteristics between the setup and the process times can be determined. Characterization accuracy is improved by a wafer calibration procedure wherein measurement offsets from known conditions are determined for each wafer being characterized. An apparatus and technique are disclosed for correcting for anisotropy of acoustic wave velocity due to the direction of wave propagation with respect to a preferred crystallographic axis of the wafer. An apparatus and technique are also described for measuring wafer temperature using a single transducer whose temperature is related to the temperature of the wafer and, optionally, resonator structures. For characterization steps that occur when the wafer is chucked, a chuck structure is described that reduces the likelihood of the chuck interfering with the waves in the wafer.
摘要:
A method of analyzing a spatial series of waveforms, each waveform of which contains components arising from at least two substantially uncorrelated features, includes the steps of sorting the waveforms into groups or bins according to values of one or more of the features, determining a mean waveform for each group or bin, subtracting the mean waveform from each waveform in the group or bin, returning the waveforms to the original order of the series and determining a remaining feature. Binning, the process of sorting waveforms into groups based on values of features, can be performed for one feature determined from the waveform or for several features. All that is required is that the binning criteria are substantially uncorrelated with the feature of interest. An example of a binning criterion can be frequency or period of a component of the waveform. Also a value of a physical parameter calculated from the waveform can be used as a binning criterion.