Abstract: An optical metrology includes a library, a metrology tool and a library evolution tool. The library is generated to include a series of predicted measurements. Each predicted measurement is intended to match the measurements that a metrology device would record when analyzing a corresponding physical structure. The metrology tool compares its empirical measurements to the predicted measurements in the library. If a match is found, the metrology tool extracts a description of the corresponding physical structure from the library. The library evolution tool operates to improve the efficiency of the library. To make these improvements, the library evolution tool statistically analyzes the usage pattern of the library. Based on this analysis, the library evolution tool increases the resolution of commonly used portions of the library. The library evolution tool may also optionally reduce the resolution of less used portions of the library.

Abstract: A method and apparatus are disclosed for accurately and repeatably determining the thickness of a thin film on a substrate. A rotating compensator ellipsometer is used which generates both 2? and 4? output signals. The 4? omega signal is used to provide an indication of the temperature of the sample. This information is used to correct the analysis of the thin film based on the 2? signal. These two different signals generated by a single device provide independent measurements of temperature and thickness and can be used to accurately analyze a sample whose temperature is unknown.

Abstract: An apparatus for scatterometry measurements is disclosed. The apparatus includes a modulated pump source for exciting the sample. A separate probe beam is directed to interact with the sample and the modulated optical response is measured. The measured data is subjected to a scatterometry analysis in order to evaluate geometrical sample features that induce light scattering.

Abstract: Systems and methods for operating an optical measurement system are disclosed which permit measurements to be made more uniformly in regions close the edge of a sample, such as a wafer. An optical measurement system can include a probe beam that is focused to an elliptically shaped spot on the surface of the sample. Improved measurements near the edge of the sample can be obtained by rotating the wafer with respect to the measurement spot to ensure that the short axis of the ellipse is perpendicular to the wafer edge.

Abstract: An apparatus for characterizing multilayer samples is disclosed. An intensity modulated pump beam is focused onto the sample surface to periodically excite the sample. A probe beam is focused onto the sample surface within the periodically excited area. The power of the reflected probe beam is measured by a photodetector. The output of the photodetector is filtered and processed to derive the modulated optical reflectivity of the sample. Measurements are taken at a plurality of pump beam modulation frequencies. In addition, measurements are taken as the lateral separation between the pump and probe beam spots on the sample surface is varied. The measurements at multiple modulation frequencies and at different lateral beam spot spacings are used to help characterize complex multilayer samples. In the preferred embodiment, a spectrometer is also included to provide additional data for characterizing the sample.

Abstract: Systems and methods are disclosed for evaluating nitrogen levels in thin gate dielectric layers formed on semiconductor samples. In one embodiment, a tool is disclosed which includes both a narrow band ellipsometer and a broadband spectrometer for measuring the sample. The narrowband ellipsometer provides very accurate information about the thickness of the thin film layer while the broadband spectrometer contains information about the nitrogen levels. In another aspect of the subject invention, a thermal and/or plasma wave detection system is used to provide information about the nitrogen levels and nitration processes.

Abstract: An ellipsometric apparatus provides a rotating focused probe beam directed to impinge a sample in any direction. A rotating stage rotates the wafer into a linear travel range defined by a single linear axis of a single linear stage. As a result, an entire wafer is accessed for measurement with the single linear stage having a travel range of only half the wafer diameter. The reduced single linear travel results in a small travel envelope occupied by the wafer and consequently in a small footprint of the apparatus. The use of a rotating probe beam permits measurement of periodic structures along a preferred direction while permitting the use of a single reduced motion stage.

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, multi-wavelength, DUV-IR (185<?<900 nm) all-refractive optical systems. The designs have net focusing power and this is achieved by combining at least one positively powered optical element with one negatively powered optical element. The designs have small spot-size over the wavelength range spanning 185-900 nm with substantially reduced spherical aberration, axial color, sphero-chromatism and zonal spherical aberration. The refractive optical systems are broadly applicable to a large class of broadband optical wafer metrology tools including spectrophotometers, spectroscopic reflectometers, spectroscopic ellipsometers and spectroscopic scatterometers.

Abstract: An ellipsometer capable of generating a small beam spot is disclosed. The ellipsometer includes a light source for generating a narrow bandwidth probe beam. An analyzer is provided for determining the change in polarization state of the probe beam after interaction with the sample. A lens is provided having a numerical aperture and focal length sufficient to focus the beam to a diameter of less than 20 microns on the sample surface. The lens is formed from a graded index glass wherein the index of refraction varies along its optical axis. The lens is held in a relatively stress free mount to reduce stress birefringence created in the lens due to changes in ambient temperature. The ellipsometer is capable of measuring features on semiconductors having a dimensions as small as 50×50 microns.

Abstract: 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.

Abstract: A detector network for an optical metrology system includes an analog to digital converter for each photodetector or detector array. Each analog to digital converter is connected to provide digitally encoded output from its associated detector. Each analog to digital converter is also connected to a hub. The hub receives commands from a processor and distributes them to the analog to digital converters. The converters sample the output of their associated detectors and return the digitized results to the hub. In turn, the hub passes the digitized results to the processor for analysis.

Abstract: A method for modeling optical scattering includes an initial step of defining a zero-th order structure (an idealized representation) for a subject including a perturbation domain and a background material. A Green's function and a zero-th order wave function are obtained for the zero-th order structure using rigorous coupled wave analysis (RCWA). A Lippmann-Schwinger equation is constructed including the Green's function, zero-th order wave function and a perturbation function. The Lippmann-Schwinger equation is then evaluated over a selected set of mesh points within the perturbation domain. The resulting linear equations are solved to compute one or more reflection coefficients for the subject.

Abstract: A wafer-cleaning module can remove contaminants from a semiconductor wafer prior to measurement in a metrology tool. A heating chamber and heater plate of the cleaning module can be used to heat the wafer by conduction, while a separate cooling chamber can be used to cool the wafer. The system is controlled by a processor so the heating cycle, cooling cycle and the time periods between these cycles and the measurement cycle are uniform for all wafers.

Abstract: A method and apparatus for combining the spectral outputs of multiple light sources to provide a high-efficiency broad-band illuminator for optical metrology is disclosed. The illuminator combines the output radiation from a plurality of broad-band lamps in a novel optical arrangement that creates a virtual source and avoids the use of beam-splitters. Consequently, the illuminator offers increased performance at reduced cost. The illuminator can be optimized and configured for application in a broad class of optical metrology instruments.

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: This invention relates to optical metrology tools that are used to evaluate small measurement areas on a semiconductor wafer, where the measurement area is surrounded by a material different from the measurement area. In one embodiment, a probe beam is scanned over the measurement area and the surrounding material as data is taken at multiple locations. A processor determines the characteristics of the measurement area by identifying an extremum value of the measurements which represents the center of the measurement area. In another embodiment, the processor determines the characteristics of the sample using a combination of light measured from within and without the measurement area. The measured data is treated as a combination of light from both regions and mathematically modeled to account for both the contribution of the light reflected from the measurement area and the light reflected from the surrounding material.

Abstract: A metrology instrument for measuring grating-like microstructures on a sample for parameters of interest is characterized by an illumination spot that is elongated. The elongated illumination spot is produced by providing the designing the illumination optics to have a limiting aperture that is also elongated. The limiting aperture and corresponding illumination spot will have respective long directions that are perpendicular to each other. The sample is supported in a measurement relation to the instrument wherein the illumination spot is oriented generally transverse to linear elements of a microstructure. The microstructure can be also be a two-dimensional bigrating, with the illumination spot on a row or column of the bigrating.

Abstract: A method is disclosed for evaluating isolated and aperiodic structure on a semiconductor sample. A probe beam from a coherent laser source is focused onto the structure in a manner to create a spread of angles incidence. The reflected light is monitored with an array detector. The intensity or polarization state of the reflected beam as a function of radial position within the beam is measured. Each measurement includes both specularly reflected light as well as light that has been scattered from the aperiodic structure into that detection position. The resulting output is evaluated using an aperiodic analysis to determine the geometry of the structure.

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: An apparatus for characterizing multilayer samples is disclosed. An intensity modulated pump beam is focused onto the sample surface to periodically excite the sample. A probe beam is focused onto the sample surface within the periodically excited area. The power of the reflected probe beam is measured by a photodetector. The output of the photodetector is filtered and processed to derive the modulated optical reflectivity of the sample. Measurements are taken at a plurality of pump beam modulation frequencies. In addition, measurements are taken as the lateral separation between the pump and probe beam spots on the sample surface is varied. The measurements at multiple modulation frequencies and at different lateral beam spot spacings are used to help characterize complex multilayer samples. In the preferred embodiment, a spectrometer is also included to provide additional data for characterizing the sample.