Abstract: A modulated reflectance measurement system includes three monochromatic diode-based lasers. Each laser can operate as a probe beam or as a pump beam source. The laser outputs are redirected using a series of mirrors and beam splitters to reach an objective lens. The objective lens focuses the laser outputs on a sample. Reflected energy returns through objective and is redirected by a beam splitter to a detector. A lock-in amplifier converts the output of the detector to produce quadrature (Q) and in-phase (I) signals for analysis. A Processor uses the Q and/or I signals to analyze the sample. By changing the number of lasers used as pump or probe beam sources, the measurement system can be optimized to measure a range of different samples types.

Abstract: A method for modeling diffraction includes constructing a theoretical model of the subject. A numerical method is then used to predict the output field that is created when an incident field is diffracted by the subject. The numerical method begins by computing the output field at the upper boundary of the substrate and then iterates upward through each of the subject's layers. Structurally simple layers are evaluated directly. More complex layers are discretized into slices. A finite difference scheme is performed for these layers using a recursive expansion of the field-current ratio that starts (or has a base case) at the lowermost slice. The combined evaluation, through all layers, creates a scattering matrix that is evaluated to determine the output field for the subject.

Abstract: A method is disclosed for measuring the dose and energy level of ion implants forming a shallow junction in a semiconductor sample. In the method, two independent measurements of the sample are made. The first measurement monitors the response of the sample to periodic excitation. In the illustrated embodiment, the modulated optical reflectivity of a reflected probe beam is monitored to provide information related to the generation of thermal and/or plasma waves in the sample. A second spectroscopic measurement is also performed. This measurement could be either a spectroscopic reflectometry measurement or a spectroscopic ellipsometry measurement. The data from the two measurements are combined in a manner to yield information about both the dose (concentration) of the dopants as well as the energy used to inject the dopants in the semiconductor lattice. The method will useful in controlling the formation of shallow junctions.

Abstract: An aperture for reducing tilt sensitivity in normal incidence optical metrology is formed to include one or more holes. The aperture is positioned to partially occlude one-half of the pupil of a normal incidence objective. A probe beam is projected to fill the pupil of the objective. The portion of the incident probe beam that passes through the aperture is reduced in cross-sectional profile. As a result, after reflection by the sample, that portion of the probe beam underfills the non-occluded portion of the pupil. The portion of the incident probe beam that passes through the non-occluded portion of the pupil overfills the occluded pupil upon reflect by the sample. The combination of underfilling and overfilling reduces the sensitivity of the objective to tilting of the sample.

Abstract: A modulated reflectance measurement system includes two diode-based lasers for generating a probe beam and an intensity modulated pump beam. The pump and probe beams are joined into a collinear beam using a laser diode power combiner. One or more optical fibers are used to transport the beams either before and/or after they are combined. The collinear beam is focused through one or more lenses or other optical components for collimation. The collinear beam is then focused by an objective lens onto a sample. Reflected energy returns through an objective and is redirected by a beam splitter to a detector. A lock-in amplifier converts the output of the detector to produce quadrature (Q) and in-phase (I) signals for analysis. A processor uses the Q and/or I signals to analyze the sample.

Abstract: A method for improving the measurement of semiconductor wafers is disclosed. In the past, the repeatability of measurements was adversely affected due to the unpredictable growth of a layer of contamination over the intentionally deposited dielectric layers. Repeatability can be enhanced by removing this contamination layer prior to measurement. This contamination layer can be effectively removed in a non-destructive fashion by subjecting the wafer to a cleaning step. In one embodiment, the cleaning is performed by exposing the wafer to microwave radiation. Alternatively, the wafer can be cleaned with a radiant heat source. These two cleaning modalities can be used alone or in combination with each other or in combination with other cleaning modalities. The cleaning step may be carried out in air, an inert atmosphere or a vacuum. Once the cleaning has been performed, the wafer can be measured using any number of known optical measurement systems.

Abstract: A method for rapidly analyzing data gathered during scatterometry and related methods uses a combination of database lookup, database interpolation and theoretical model evaluation. Database lookup is used to provide an initial mapping between a measured optical response and a set of associated measurement parameters. Interpolation is then used to refine the optical response and parameters. A theoretical model is then repeatedly evaluated to refine the optical response and parameters previously refined by the interpolation. In this way, the present invention avoids the inaccuracies associated with traditional interpolation-based analysis and without incurring the computational complexity associated with real-time database supplementation.

Abstract: The subject invention relates to a broadband optical metrology system that segregates the broadband radiation into multiple sub-bands to improve overall performance. Each sub-band includes only a fraction of the original bandwidth. The optical path—the light path that connects the illuminator, the sample and the detector—of each sub-band includes a unique sub-band optical system designed to optimize the performance over the spectral range spanned by the sub-band radiation. All of the sub-band optical systems are arranged to provide small-spot illumination at the same measurement position. Optional purging of the individual sub-band optical paths further improves performance.

Abstract: A method for analyzing asymmetric structures (including isolated and periodic structures) includes a split detector for use in a broadband spectrometer. The split has detector has separate right and left halves. By independently measuring and comparing the right and left scattered rays, information about asymmetries can be determined.

Abstract: A method and apparatus for evaluating a semiconductor wafer. A combination of a photothermal modulated reflectance method and system with a photothermal IR radiometry system and method is utilized to provide information which can be used to determine properties of semiconductor wafers being evaluated. The system and method can provide for utilizing a common probe source and a common intensity modulated energy source. The system and method further provide an infrared detector for monitoring changes in infrared radiation emitted from a sample, and photodetector for monitoring changes in beam reflected from the sample.

Abstract: A real-time calibration method for beam profile ellipsometry systems includes projecting an electromagnetic probe beam having a known polarization state though an objective lens onto the surface of a subject and collecting the reflected probe beam using the same objective. The reflected probe beam is then passed through a rotating compensator and analyzer before being received by a detector. A processor performs a harmonic analysis on the detector output to determine normalized Fourier coefficients. The processor uses Fourier coefficients to measure the retardation ?B and the azimuth angle QB of the objective lens; and uses the retardation ?B and the azimuth angle QB to identify the ellipsometric effects of the objective lens.

Abstract: The subject invention relates to broadband optical metrology tools for performing measurements of patterned thin films on semiconductor integrated circuits. Particularly a family of optical designs for broadband optical systems wherein the ratio of illumination system to collection system numerical apertures is less than 1. System performance is enhanced through selection and control of the optical system partial coherence; this is accomplished through installation of beam-control apertures within the illumination and collection optical systems. The invention is broadly applicable to a large class of broadband optical wafer metrology techniques including spectrophotometry, spectroscopic reflectometry, spectroscopic ellipsometry and spectroscopic scatterometry.

Abstract: An optical measuring device generates a plurality of measured optical data from inspection of a thin film stack. The measured optical data group naturally into several domains. In turn the thin film parameters associated with the data fall into two categories: local and global. Local “genes” represent parameters that are associated with only one domain, while global genes represent parameters that are associated with multiple domains. A processor evolves models for the data associated with each domain, which models are compared to the measured data, and a “best fit” solution is provided as the result. Each model of theoretical data is represented by an underlying “genotype” which is an ordered set of the genes. For each domain a “population” of genotypes is evolved through the use of a genetic algorithm. The global genes are allowed to “migrate” among multiple domains during the evolution process.

Abstract: An optical metrology system is disclosed which is configured to minimize the measurement of specularly reflected light and measure primarily scattered light. The system is similar to prior art beam profile measurements but includes a movable baffle to selectively block specularly reflected light. In addition, certain non-periodic, isolated targets are disclosed suitable for evaluating overlay registration.

Abstract: A system for characterizing geometric structures formed on a sample on a real time basis is disclosed. A multi-parameter measurement module generates output signals as a function of either wavelength or angle of incidence. The output signals are supplied to a parallel processor. The processor creates an initial theoretical model and then calculates the theoretical optical response of that sample. The calculated optical response is compared to measured values. Based on the comparison, the model configuration is modified to be closer to the actual measured structure. The processor recalculates the optical response of the modified model and compares the result to the measured data. This process is repeated in an iterative manner until a best fit is achieved. The steps of calculating the optical response of the model is distributed to the processors as a function of wavelength or angle of incidence so these calculations can be performed in parallel.

Abstract: A fast wafer positioning method for optical metrology includes three main steps. In the first step, an initial measurement recipe is constructed for the host system and target wafer. In the next step, the host system performs a test run using the initial measurement and the target wafer. In this step, the initial measurement recipe is refined to eliminate positioning errors produced by the host system. In the final step, the refined measurement recipe is used by the host system to process production wafers (e.g., as part of a production environment). This is performed using the information included in the refined measurement recipe without reference to optical images of the wafers being processed.

Abstract: A combiner for optical beams includes a substrate overlaid by a multi-layer dielectric film stack. The substrate is a clear material and the dielectric film stack is a series of alternating layer of high and low refractive index. This gives the combiner relatively high reflectivity across UV wavelengths and relatively high transmissivity in the visible and longer wavelengths and allows visible light to pass through the combiner while UV light is reflected. At the same time dielectric film stack has minimal absorption and scatter. This means that the intensity of visible light maintains at least 90% of its intensity as it passes through combiner and UV light retains at least 90% of its intensity as it is reflected by combiner.

Abstract: A method for simultaneously monitoring ion implantation dose, damage and/or dopant depth profiles in ion-implanted semiconductors includes a calibration step where the photo-modulated reflectance of a known damage profile is identified in I-Q space. In a following measurement step, the photo-modulated reflectance of a subject is empirically measured to obtain in-phase and quadrature values. The in-phase and quadrature values are then compared, in I-Q space, to the known damage profile to characterize the damage profile of the subject.

Abstract: An apparatus is disclosed for obtaining ellipsometric measurements from a sample. A probe beam is focused onto the sample to create a spread of angles of incidence. The beam is passed through a quarter waveplate retarder and a polarizer. The reflected beam is measured by a detector. In one preferred embodiment, the detector includes eight radially arranged segments, each segment generating an output which represents an integration of multiple angle of incidence. A processor manipulates the output from the various segments to derive ellipsometric information.

Abstract: A method for simultaneously monitoring ion implantation dose, damage and/or dopant depth profiles in ion-implanted semiconductors includes a calibration step where the photo-modulated reflectance of a known damage profile is identified in I-Q space. In a following measurement step, the photo-modulated reflectance of a subject is empirically measured to obtain in-phase and quadrature values. The in-phase and quadrature values are then compared, in I-Q space, to the known damage profile to characterize the damage profile of the subject.