Multi-incident angle semiconductor metrology systems and methods

Abstract

To solve the problem in which improvement in a SE measurement tool is continuously demanded and even if a target feature is different, these SE data can be readily separated.SOLUTION: An ellipsometer device includes: a high-luminance light source 106 that provides an irradiation beam of selectable multiple wavelengths within a range from a far ultraviolet wavelength to an infrared wavelength; an irradiation optical system 102 that, in order to provide a spectroscopic ellipsometry, guides the irradiation beam toward a sample at selectable each set of an angle of incidence (AOI) or azimuth angle (AZ) and a polarization state, and includes an apodizer for controlling a spot diameter of the illumination beam hitting the sample at each selectable set of the angle of incidence or the azimuth angle; a collection optical system 104 that, in each selectable set of the angle of incidence or azimuth angle and polarization state, guides an output beam from the sample responding to the irradiation beam toward a detector generating an output signal or output image on the basis of the output beam; and a control unit that characterizes a feature of the sample on the basis of the output signal or output image.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims priority to (i) U.S. Provisional Patent Application No. 61 / 752,202, entitled Multi - Incidence Angle Semiconductor Measurement System, filed on January 14, 2013 by David Y. Wang et al., and (ii) U.S. Provisional Patent Application No. 61 / 878,561, entitled Multi - Incidence Angle Semiconductor Measurement System and Method, filed on September 16, 2013 by David Y. Wang et al., and incorporates by reference in its entirety the contents of these applications for all purposes as part of this specification.

[0002] The present invention relates generally to the field of semiconductor measurement systems. More particularly, the present invention relates to ellipsometry systems, reflection measurement systems, and scatterometry systems.

Background Art

[0003] The demand for miniaturization of semiconductor devices has been on the rise, thereby also demanding improvement of semiconductor wafer measurement systems. When manufacturing semiconductor devices (such as logic devices and memory devices), it is usually necessary to process semiconductor wafers using a number of semiconductor manufacturing processes to produce semiconductor devices with various shapes and multiple layers. It is also possible to fabricate a plurality of semiconductor devices side by side on a single semiconductor wafer and then separate them into individual semiconductor devices.

[0004] By using a measurement process in various steps during a semiconductor manufacturing process, the process of one or more semiconductor layers is monitored and controlled. For example, the measurement process is used to measure one or more characteristics regarding a wafer. Such characteristics include, for example, dimensions of a shape formed on the wafer during a process step (e.g., line width, thickness, angle, etc.), and the quality of the process step can be determined by measuring one or more characteristics. In the above-described configuration, a given semiconductor sample may include a set of measurement targets, and in such a sample, a stacked film or a two-dimensional and three-dimensional pattern structure is surrounded by one or more materials having various outer shapes and properties.

[0005] In a measurement using spectroscopic ellipsometry (SE), light reflected at locations with different optical constants in the measurement target is extracted. The SE data of the measurement target is used to determine the characteristics of the wafer.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] There is a continuous demand for improvement of SE measurement tools, whereby, for example, even if the target characteristics are different, their SE data can be easily separated.

Means for Solving the Problems

[0008] The following presents a simplified overview of the present disclosure in order to provide a basic understanding of certain embodiments of the present invention. This "Summary of the Invention" is neither an extensive overview of the present disclosure, nor does it identify important / critical components of the present invention, nor does it describe the scope of the present invention. Its sole purpose is to present some concepts in a simplified form as a preparation for the more detailed description presented later.

[0009] In one embodiment, an ellipsometer apparatus for measuring a semiconductor sample is disclosed. The apparatus provides an irradiation beam at a plurality of wavelengths selectable within a range from vacuum ultraviolet (VUV) wavelengths to infrared (IR) wavelengths, and directs the irradiation beam towards the sample at a plurality of angles of incidence (AOI) and / or azimuth angles (AZ). It includes an irradiation optical system module for guiding, and a collection optical system module that collects the output beam exiting from the sample at angles of incidence and / or azimuth angles in a plurality of discrete ranges and guides this output beam to a detector module. The discrete ranges are collected one by one, and the output beam responds to the irradiation beam applied to the sample. The irradiation optical system module includes a polarization generation optical element that generates a plurality of polarization states for the irradiation beam, and the collection optical system module includes a polarization analysis optical element that analyzes the polarization state of the output beam. The irradiation optical system module and the collection optical system module include a reflection optical element between the polarization generation optical element and the polarization analysis optical element. The apparatus further includes a detection module that receives and detects the output beam from the sample at angles of incidence and / or azimuth angles and polarization states in a discrete range, and generates a plurality of signals based on the output beam at angles of incidence and / or azimuth angles and polarization states in the discrete range. The apparatus further includes one or more control units configured to control one or more of selecting the wavelength range, selecting one or more discrete ranges of angles of incidence and / or azimuth angles for collecting the output beam, selecting the polarization state, and analyzing the signals at angles of incidence and / or azimuth angles and polarization states in the discrete range to determine the characteristics of the sample. In one example, the sample is one or more targets on a semiconductor wafer.

[0010] In a specific embodiment, the discrete ranges of the incident angle and / or the azimuth angle are spatially separated from each other. In another aspect, the wavelength range is in the range of about 150 nm to about 2000 nm. In another aspect, the illumination optical system module includes a high-intensity laser sustained plasma (LSP) source that generates an illumination beam. In one aspect, the LSP source generates an illumination beam with a peak luminance of about 0.1 W / nm / cm 2 / sr or more. In one aspect, the discrete portions of the incident angle or the azimuth angle are each separated by at least 0.1°. In another aspect, the discrete ranges of the incident angle and / or the azimuth angle include an incident angle greater than about 60°. In a specific aspect, the discrete ranges of the incident angle and / or the azimuth angle include azimuth angles from 0° to 360° of a plurality of discrete ranges. In the present embodiment, the apparatus may include a positioning mechanism that rotates the sample to obtain azimuth angles from 0° to 360° of the discrete range. In another aspect, the discrete ranges of the incident angle and / or the azimuth angle include azimuth angles from 0° to 90° of a plurality of discrete ranges.

[0011] In one embodiment, the illumination optical system module includes a plurality of fixed apertures or one movable aperture for providing an illumination beam at each discrete range of the incident angle and / or the azimuth angle that is substantially the same as that collected and detected by the collection optical system module. In one aspect, the illumination optical system module includes a plurality of fixed apertures for providing one illumination beam at each discrete range of the incident angle and / or the azimuth angle, respectively, and shutters that cover each of the fixed apertures. In another aspect, the illumination optical system module is further configured to simultaneously provide an illumination beam with a range of incident angles and / or azimuth angles that substantially includes the discrete ranges of the incident angle and / or the azimuth angle when the collection optical system module collects and detects one by one. In another embodiment, the collection optical system module includes a plurality of fixed apertures for collecting one output beam at each discrete range of the incident angle and / or the azimuth angle, respectively, and shutters that cover each of the fixed apertures. In another embodiment, the collection optical system module includes either a movable aperture for collecting one output beam at each discrete range of the incident angle and / or the azimuth angle, respectively, or a plurality of fixed apertures each provided with a shutter.

[0012] In a specific embodiment, the polarization generation optical element includes a polarizer and a first compensator within the illumination optical system module, and the polarization analysis optical element includes a second compensator and an analyzer within the collection optical system module. Selecting a polarization state includes rotating any one or more of the polarizer, the first compensator, the second compensator, and the analyzer, or leaving them stationary. In another embodiment, the polarization generation optical element includes a polarizer and an analyzer, and selecting a polarization state includes rotating the polarizer and leaving the analyzer stationary. In a further aspect, the polarization analysis optical element further includes a collection compensator, and selecting a polarization state further includes rotating the collection compensator. In a further aspect, the illumination optical system module includes an apodizer for minimizing the point spread function of the focus on the object in the sample for each discrete range of the incident angle and / or azimuth angle. Illumination (or collection) apodization can generally be defined as the transformation of the light distribution at the entrance pupil of an optical system (e.g., changing the amplitude and / or phase of the illumination beam or the collection beam using a mask), thereby changing the intensity profile of the illumination (or collection) beam. In yet another aspect, the polarization generation optical element further includes an illumination compensator, and selecting a polarization state further includes rotating the illumination compensator.

[0013] In another example, the polarization generation optical element includes a polarizer and an illumination compensator, and the polarization analysis optical element includes an analyzer. Selecting a polarization state includes rotating the illumination compensator and leaving the polarizer and the analyzer stationary. In a further aspect, the polarization analysis optical element further includes a collection compensator, and selecting a polarization state further includes rotating the collection compensator. In another embodiment, the polarization generation optical element includes a polarizer, and the polarization analysis optical element includes an analyzer. Selecting a polarization state includes leaving the polarizer stationary and rotating the analyzer.

[0014] In a specific embodiment, the illumination optical system module includes one or more beam shaping optical elements for shaping the illumination beam and controlling the point spread function of the focus coupled to the object on the sample for the incident angle and / or azimuth angle of each discrete range. For example, the one or more beam shaping elements are configured to reduce the illumination at a predetermined distance from the center of the illumination spot generated by the illumination beam applied to the sample to less than a predetermined value of the peak illumination at the center of the illumination spot.

[0015] In an exemplary embodiment, the one or more beam shaping elements are apodizers, and each apodizer has a non-reconfigurable optical function respectively. The apparatus further includes a positioning mechanism for moving the selected apodizer to a plane conjugate to the pupil of the illumination beam or near it, and the control unit is further configured to cause the positioning mechanism to move the selected apodizer. The apodizer provides a predetermined illumination profile corresponding to all of the incident angles and / or azimuth angles of the discrete ranges.

[0016] In another example, the one or more beam shaping elements are dynamically adjustable apodizers arranged in a plane conjugate to the pupil of the illumination beam or near it, and the dynamically adjustable apodizer is configured to provide a predetermined illumination profile corresponding to all of the incident angles and / or azimuth angles of the discrete ranges. The control unit is further configured to adjust the dynamically adjustable apodizer.

[0017] In another embodiment, the collection optical system module includes one or more apodizers arranged at or near the position of the plane conjugate to the collection pupil or movable to that location, and the apodizer provides a predetermined collection profile corresponding to all of the incident angles and / or azimuth angles of the discrete ranges.

[0018] In another embodiment, the illumination optical system module includes: (i) a first off-axis parabolic (OAP) mirror; and (ii) a first translation mirror that is movable to receive the illumination beam at a plurality of positions and direct the illumination beam to a plurality of positions on the first OAP mirror so that the first OAP reflects the illumination beam to the sample at discrete ranges of incident angles and / or azimuth angles one by one. In this embodiment, the collection optical system module includes: (i) a detector; (ii) a second OAP; and (iii) a second translation mirror that is movable to receive the output beam at a plurality of positions and direct the output beam to a plurality of positions on the second OAP mirror so that the second OAP reflects the output beam to the detector at discrete ranges of incident angles and / or azimuth angles one by one.

[0019] In another embodiment, the illumination optical system module includes a beam splitter, an off-axis parabolic (OAP) mirror, and a translation mirror. The translation mirror is movable to receive the illumination beam at a plurality of translation positions of the translation mirror via the beam splitter and direct the illumination beam to a plurality of corresponding positions on the OAP mirror so that the OAP reflects the illumination beam to the sample at discrete ranges of incident angles and / or azimuth angles one by one. The collection optical system module includes: (i) a beam splitter; (ii) an OAP; (iii) a translation mirror; and (iv) a spherical mirror that outputs the second output beam from the sample by returning and reflecting the output beam to the sample, reflects it from the corresponding position on the OAP, and then reflects it from the translation mirror to the beam splitter and then to the detector at a plurality of translation positions to collect the second output beam at discrete ranges of incident angles and / or azimuth angles one by one.

[0020] In another aspect, the collection optical system module is further configured to collect the zero-order light from the output beam for bright-field measurement and the non-zero-order light from the output beam for dark-field measurement by irradiating at one or more incident angles and collecting over one or more different incident angles. In one embodiment, the collection optical system module collects the same incident angle (azimuth angle) as the incident angle (azimuth angle) of the irradiation reflected by the sample. In another example, the collection optical system module collects an incident angle (azimuth angle) different from the incident angle (azimuth angle) of the irradiation reflected by the sample. In yet another example, the collection optical system module includes a dispersive element that disperses light into a spectrum. In another embodiment, the illumination pupil and the collection pupil of the apparatus are arranged to set the numerical aperture of illumination and the numerical aperture of collection, and the illumination field stop and the collection field stop of the apparatus are arranged to set the size of the light source and the size of the image.

[0021] In an alternative embodiment, the apparatus comprises: (i) an illumination optical system module that provides an illumination beam at a plurality of wavelengths selectable within a range from vacuum ultraviolet (VUV) wavelengths to infrared (IR) wavelengths, and directs the illumination beam towards the sample at a plurality of angles of incidence (AOI) and / or azimuth angles (AZ); and (ii) a collection optical system module that collects substantially all of the output beam exiting the sample at all angles of incidence or azimuth angles, and directs this output beam substantially simultaneously to one or more detectors, wherein the output beam is responsive to the illumination beam incident on the sample. The illumination optical system module includes a polarization generation optical element that generates a plurality of polarization states for the illumination beam, the collection optical system module includes a polarization analysis optical element that analyzes the polarization state of the output beam, and the illumination optical system module and the collection optical system module include a reflective optical element between the optical element that generates a plurality of polarization states and the optical element that analyzes the polarization state. The apparatus also includes one or more detectors that receive and detect the output beam from the sample at the angle of incidence and / or azimuth angle and polarization state, and generate a plurality of signals or images based on the output beam at the angle of incidence and / or azimuth angle and polarization state, and one or more control units each configured to control one or more of selecting the wavelength range, selecting the polarization state, and analyzing the signals or images at the wavelength, angle of incidence and / or azimuth angle, and selected polarization state to determine characteristics of the sample.

[0022] In one embodiment, the collection optical system includes one or more dispersive elements that disperse the wavelength in the wavelength direction and the incident angle and / or azimuth angle in the incident angle / azimuth angle direction, and the wavelength as well as the incident angle and / or azimuth angle are dispersed along two different detection directions. In a further embodiment, the two different directions are orthogonal to each other. In another embodiment, the one or more dispersive elements have two different optical refractive powers for two different directions. In yet another embodiment, the one or more detectors consist of a plurality of detectors, and each detector is configured to determine the dispersed wavelength and perform integration over one of the separate incident angle regions. In a further embodiment, the collection optical system module further includes a partial splitting optical system that splits the output beam from the one or more dispersive elements into separate incident angle regions each of which is output to one of the detectors. In another example, the collection optical system further includes a re-imaging optical system located between the wavelength plane and the incident angle and / or azimuth angle plane, and the re-imaging optical system is configured to re-image the wavelength plane onto each detector.

[0023] In another embodiment, the collection optical system module includes an incident angle / azimuth angle mask in a plane conjugate to the pupil for selectively sending a specific incident angle / azimuth angle region from a plurality of spatially separated incident angle / azimuth angle regions in the output beam, and a detector that receives the specific incident angle / azimuth angle region, determines the dispersed wavelength, and integrates the determined wavelength over the specific incident angle / azimuth angle region, and the control unit is further configured to select one specific incident angle / azimuth angle region at a time. In a further embodiment, the wavelength plane is located in front of the incident angle / azimuth angle plane. In another embodiment, the incident angle / azimuth angle mask is composed of a plurality of fixed apertures each having a shutter. In yet another example, the incident angle / azimuth angle mask is composed of a fixed movable aperture.

[0024] In another embodiment, the collection optical system module includes a single detector that determines the dispersed wavelengths and integrates over separate angle-of-incidence regions, with a non-pixel region that does not perform angle-of-incidence decomposition and analysis included between adjacent ones of the separate angle-of-incidence regions. In another aspect, the collection optical system includes a beam splitter that splits the output beam into a first output beam and a second output beam, a first dispersive element that receives the first output beam and disperses the wavelength and angle of incidence of the output beam along two different detection directions of a first detector, and a second dispersive element that receives the second output beam and disperses the wavelength and azimuth angle of the output beam along two different detection directions of a second detector. In another example, the wavelength plane is located in the same plane as the angle-of-incidence / azimuth plane. In another aspect, the collection optical system module includes a detector with at least two registers that process parallel data from two different angle-of-incidence regions. In other embodiments, the illumination optical system and the collection optical system include the above features.

[0025] In another embodiment, the apparatus comprises: (i) one or more high-intensity light sources that provide an illumination beam at a plurality of wavelengths selectable within a range from vacuum ultraviolet (VUV) wavelengths to infrared (IR) wavelengths; (ii) an illumination optical system that directs the illumination beam towards a sample at a plurality of selectable sets of angles of incidence (AOI) and / or azimuth angles (AZ) and in a plurality of polarization states, the illumination optical system including at least one apodizer that controls the spot diameter of the illumination beam incident on the sample for each respective set of selectable angles of incidence and / or azimuth angles; (iii) a collection optical system that directs the output beam exiting the sample in response to the illumination beam towards a detector for each respective set of selectable angles of incidence or azimuth angles and modification states; (iv) a detector that generates an output signal or an output image based on the output beam; and (v) a control unit that characterizes the characteristics of the sample based on the output signal or the output image as a function of wavelength, angle of incidence and / or azimuth angle, and / or polarization state, or a combination thereof.

[0026] In one embodiment, the one or more light sources include a laser sustained plasma (LSP) source. In a specific embodiment, at least one apodizer consists of a set of apodizers each having a non-reconfigurable optical function and each movable inside and outside the illumination pupil plane, and each fixed apodizer is configured to control the spot diameter for each respective selectable set of incident angles or azimuth angles. In another aspect, at least one apodizer is disposed in a plane conjugate to the illumination pupil plane or in the vicinity thereof to control the spot diameter for all of the respective selectable sets of incident angles and / or azimuth angles. In another aspect, at least one apodizer is a dynamically adjustable apodizer and can be configured to control the spot diameter by reducing the illumination at a predetermined distance from the center of the illumination spot to less than a predetermined value of the peak illumination at the center of the illumination spot. In another embodiment, at least one apodizer is configured to control the spot diameter by suppressing side lobes within the illumination beam. In yet another example, at least one apodizer can further be configured for a plurality of various targets on the sample.

[0027] In another aspect, the illumination optical system includes a scanning mirror that scans the illumination beam applied to the sample at each respective selectable set of incident angles or azimuth angles, and the collection optical system includes an incident angle / azimuth angle selector for determining each selected set of incident angles or azimuth angles one by one. In a further aspect, the incident angle / azimuth angle selector includes a plurality of fixed apertures each having a shutter or at least one movable aperture. In another aspect, at least one apodizer is a dynamically adjustable apodizer. In one example, the dynamically adjustable apodizer is a spatial light modulator (SLM). In another embodiment, at least one apodizer can be configured to form a plurality of binary amplitude patterns for each respective selectable set of incident angles or azimuth angles. In another example, at least one apodizer is configured to form a plurality of amplitude patterns for each respective selectable set of incident angles or azimuth angles, and at least one of the amplitude patterns is continuously variable.

[0028] In an alternative embodiment, the present invention relates to a method for performing spectroscopic polarization analysis in a measurement system. The method includes: (i) generating irradiation light of multiple wavelengths; (ii) selecting multiple different polarization states for the irradiation light; (iii) selecting multiple angles of incidence (AOI) or azimuth angles (AZ) for the irradiation light; (iv) shaping and guiding the irradiation light to form spots on an object at multiple wavelengths, different polarization states, and angles of incidence or azimuth angles; (v) collecting and detecting output light emitted from a sample in response to the irradiation light, and generating a signal or an image based on the detected output light as a function of each wavelength, different polarization states, and angles of incidence or azimuth angles; and (vi) analyzing the signal or the image to determine characteristics of the sample.

[0029] These or other aspects of the present invention will be further described below with reference to the respective figures.

Brief Description of the Drawings

[0030]

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Mode for Carrying Out the Invention

[0031] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be practiced without some or all of these specific details. In other instances, well-known components or process steps have not been described in detail in order not to obscure the present invention needlessly. The present invention will be described in connection with specific embodiments, but it is understood that the present invention is not intended to be limited to these embodiments.

[0032] One problem in the use of a spectroscopic ellipsometry (SE) system relates to the combination of detected data. Measured ellipsometry parameters derived from a particular sample (such as a semiconductor wafer or reticle) depend on a plurality of measurement parameters such as wavelength (λ) and the x, y positions of interest. Generally, ellipsometry data (e.g., λ, position of interest, etc.) for different tool settings are collected separately and input into a model (e.g., CD, overlay) for inferring target characteristics. As the target becomes more complex, the collected data for changing target characteristics becomes closely related or insufficient. As a result, the target characteristics cannot be accurately determined by the above model.

[0033] By using an SE system configurable to form different specific narrow ranges of incident angles, the target parameters can be uncorrelated. However, in such a system, it may not be possible to reduce the spot diameter for each of the narrow range of incident angles and the resulting NA. For example, an SE system for selecting an incident angle may not include a mechanism for obtaining a sufficiently small spot diameter that can be useful for measuring a constant small dimensional shape (e.g., 40 microns × 40 microns or less). Further, in such an SE system, since the range of incident angles can be limited, it may not be possible to be near the Brewster angle, and it may not be possible to perform measurements for certain applications with high sensitivity.

[0034] For simplicity, the term "angle of incidence" shall be taken to mean, in this specification, the expression "discrete narrow range of angles of incidence" with the words omitted. Similarly, the term "discrete angle of incidence" is used synonymously with the term "discrete range of angles of incidence". Some SE systems can be configured and set using a single angle of incidence or a discrete angle of incidence. However, in SE systems, generally, it may not actually be possible to use only a single angle of incidence or only a discrete angle of incidence. Instead, a narrow range of angles of incidence centered on a "selected" single angle of incidence or discrete angle of incidence can be used, or a "selected" single angle of incidence can be included. In other SE systems, it is also possible to input a narrow range of angles of incidence as a setting parameter or a recipe parameter instead of a single angle of incidence or a discrete angle of incidence. Note that the angle of incidence is the angle formed with the normal to the sample. Also, the azimuth angle is an angle based on one of the axial directions such as the x and y directions that are orthogonal to each other and define the two-dimensional plane of the sample surface.

[0035] Certain embodiments of the polarization analysis in the present invention provide an ellipsometer that obtains measurement values at multiple angles of incidence (AOI) and multiple azimuth angles (AZ) simultaneously or sequentially, thereby making it easier to eliminate the correlation between target characteristics. This ellipsometer tool may also include an optical component for generating a polarization state and an optical component for analyzing the polarization state. These components can be configured to determine all or some of the Mueller matrix elements of the object. This tool may also include a high-brightness light source that can be configured in a wide wavelength range including vacuum ultraviolet (VUV), visible light, near infrared (NIR), and infrared (IR). In certain embodiments, the SE system provides various selectable angle-of-incidence configurations (including angles of incidence and multiple angles of incidence), simultaneous and sequential angles of incidence, a configurable polarization state for analyzing the Mueller matrix, and a selectable wavelength range from VUV to NIR. The irradiation side of the embodiments of this system (as well as other embodiments described herein) can function from VUV to UV and may include a reflective optical system for performing broad color correction over the entire range from VUV to IR.

[0036] In certain embodiments, spectroscopic ellipsometry (SE) can be performed at multiple angles of incidence and multiple azimuthal angles. Thereby, the repeatability and stability of the measurement can be improved by using fixed illumination and collection pupil, and fixed illumination and collection field stop. FIG. 1 illustrates a spectroscopic ellipsometry (SE) tool 100 that collects light at a specific angle of incidence (AOI) according to one embodiment of the present invention. Typically, this measurement tool can include an illumination optical system 102 that provides high-intensity illumination light at configurable wavelengths, and a collection optical system 104 that detects light from an object on a sample (sample) 132 one by one or simultaneously at spatially separated discrete ranges of angles of incidence (or discrete ranges of azimuthal angles). The illumination optical system 102 and the collection optical system 104 may also be configured to generate and collect light in various polarization states (including polarization states for determining all or part of the Mueller matrix of the object).

[0037] As shown, the illumination optical system 102 includes one or more light sources (e.g., light source 106) that generate an illumination beam. In the illustrated embodiment, the one or more illumination sources 102 may include one or more broadband light sources that cover wavelengths in the range from vacuum UV to near infrared (e.g., from about 150 nm to about 2000 nm). In one example, the illumination source is a laser sustained plasma (LSP) source that generates high-intensity light. One example of an LSP is the EQ-1000 commercially available from Energetiq Technology, Inc. (Woburn, Massachusetts). Some embodiments of the LSP are described in U.S. Patent Application Publication No. 2011 / 0204265, entitled "Laser-Driven Light Source," filed May 3, 2011, and U.S. Patent Application Publication No. 2009 / 0032740, entitled "Laser-Driven Light Source," filed Jul. 2, 2008, by Donald K. Smith et al., which are hereby incorporated by reference in their entirety as part of this specification. Other light sources may include solid-state lasers or other types of lasers.

[0038] In one example, the one or more light sources are also at least 0.1 W / (nm cm to form a simultaneous angle of incidence in the range of 57° to 73° 2It also has the peak luminance of Sr). In another aspect, one or more light sources have a peak luminance of at least 0.1 W / (nm cm near a wavelength of 190 nm 2 and may have the peak luminance of Sr).

[0039] Also, in order to stabilize the output and wavelength of the light source, high-speed feedback may be applied to the light source of the measurement system. Some mechanisms for controlling such LSPs and other broadband light sources are further described in U.S. Patent Application No. 2011 / 0069312, titled "Measurement System and Method," filed on August 31, 2010, by Daniel Kandel et al., and this application is incorporated herein by reference as part of this specification. The light source may also be composed of a xenon lamp and / or a deuterium lamp.

[0040] In another embodiment, the light source is composed of a plurality of laser diodes in the form of different sets of laser diodes. These laser diodes can be selected to cover various ranges of wavelengths required for specific measurement applications. For example, these laser diode arrays provide wavelength widths selectively obtained from the ranges of far ultraviolet (UV), UV, visible light (VIS), and near infrared (NIR). Some embodiments of the laser diode array are further described in U.S. Application No. 13 / 924,216, titled "Broadband Light Source for Wafer Inspection Tool Using Diode Lasers," filed on June 21, 2013, by Anant Chimmalgi et al., and the entire application is incorporated herein by reference as part of this specification.

[0041] The illumination optical system 102 may also include an ellipsometer illumination optical system 108 for adjusting the illumination beam. Such adjustments include setting the position and size of the aperture and field stop, and adjusting the illumination beam with respect to the polarizer 110. The ellipsometer illumination optical system 108 may generally be configured to perform functions of shaping the beam into any suitable form (such as operations on the beam shape such as parallelization, focusing, beam diameter expansion, and beam diameter reduction).

[0042] The polarizer 110 may be configured to rotate to perform rotating polarizer ellipsometry (RPE), or may be configured to be fixed to perform other types of ellipsometry. The illumination optical system may also include an illumination compensator 112 (or a photoelastic modulator, an acousto-optic modulator, a liquid crystal light modulator, or other polarization-sensitive phase modulation device) in the form of a wave plate in the illumination path. The illumination compensator 112 may be configured as a fixed type or a rotating type (for example, in the case of the rotating compensator ellipsometry (RCE) mode). By rotating the compensator 112 and / or the polarizer 110 in this illumination path, it becomes possible to change the polarization state of the illumination beam. These polarization states can include more general polarization states together with the S polarization state and the P polarization state. These polarization states may be further selected to perform polarization analysis based on the Mueller matrix as described herein.

[0043] The polarizer 110 and the compensator 112 may be designed to act on broadband light in the range from VUV to NIR. For example, in addition to other materials according to the wavelength range, for example, suitable polarizers include MgF 2 Rochon prism, and suitable wave plates include MgF 2 and quartz wave plates.

[0044] The illumination optical system may also include a fixed aperture or a movable aperture and / or a shutter so that a discrete incident angle or a discrete azimuth angle can be selected. In the illustrated embodiment, the mirrors 115, 116 are configured to focus the illumination beam onto the sample 132, and the aperture 114 defines one or more ranges of incident angles and / or azimuth angles for focusing onto the sample 132. For example, by patterning a non-reflective material on the mirror, a specific reflection-type aperture can be provided at a location without the non-reflective material.

[0045] In the illustrated embodiment, the aperture element 114 includes a set of fixed apertures so as to provide the sample with each set of spatially discrete angles of incidence or azimuth angles. Alternatively, the aperture element 114 may also include a shutter for each aperture so that each set of discrete angles of incidence or discrete azimuth angles can be independently selected to irradiate the sample. In another embodiment, the aperture element 114 may include one or more movable apertures for selecting various ranges of spatially discrete angles of incidence or azimuth angles. Some configurable apertures are further described in PCT International Application No. PCT / US2013 / 028650 filed on March 1, 2013 by KLA-Tencor, and the entire application is incorporated herein by reference as part of this specification.

[0046] In another embodiment, the aperture device can also take the form of a transmissive aperture element. This element is arranged such that the irradiation light passes through a hole opened in an opaque material or a transmissive material patterned using an opaque material. Then, the light rays of the irradiation beam can be focused on the wafer at discrete angles of incidence and discrete azimuth angles, for example, by a transmissive focusing element. However, the transmissive aperture element may not function well enough from VUV to UV.

[0047] In any aperture embodiment, the aperture element is disposed in or near the pupil plane and is configured to transmit or reflect the irradiation light beam at a specific spatial position of this pupil plane, thereby enabling the selection of a discrete range of incident angles or azimuth angles. In other words, this measurement system can discretely select a plurality of ranges of incident angles and azimuth angles for the irradiation beam, either simultaneously (e.g., without using a shutter or a movable aperture) or one by one (via a shutter or a movable aperture). For example, a discrete set of incident angles each having an incident angle range of about 8° or less is separated by at least about 0.1° between each set, and when all these sets are combined, they cover a range of about 50° to about 80°. In one embodiment, at least one of the selectable ranges of incident angles forms an incident angle of more than about 60°. Similarly, the discrete ranges of azimuth angles may each have an azimuth angle range equal to or less than 20°, but are separated by at least about 0.1° between each set, and when all these sets are combined, they cover a range from 0° to 360°.

[0048] The collection optical system 104 may be configured to collect light from the sample 132 at discrete incident angles and discrete azimuth angles. That is, the collection optical system 104 is sized such that it can collect the detected light (having a plurality of different incident angles and azimuth angles) from the sample 132. In the illustrated embodiment, the mirrors 117, 118 collect the irradiation beam reflected by the sample 132 and direct that beam towards the detector 124. The aperture element 126 is configured to select various incident angles and azimuth angles. For example, one of three different collection apertures may be used to select one by one one of three different sets of incident angles (collected at three different incident angles).

[0049] Subsequently, optical elements may be arranged to analyze the polarization state of the light reflected by the sample 132. For example, depending on various configurations, the second compensator 120 and the analyzer 122 may be made rotatable or fixed to collect various polarization states. The second compensator may take the form of a wave plate (or a photoelastic modulator, an acousto-optic modulator, a liquid crystal light modulator, or other polarization-sensitive phase modulation devices).

[0050] In the rotating polarizer polarization analysis (RPE) mode, only the polarizer rotates while other rotatable polarization analysis components (such as the irradiation compensator in the irradiation path, the analyzer, and the collection compensator in the collection path) remain fixed. Other modes include the RPRC (rotating polarizer, rotating irradiation compensator or rotating collection compensator, and fixed analyzer) mode and the RCRC (fixed polarizer, rotating irradiation compensator, rotating collection compensator, and fixed analyzer) mode. Other modes can include combinations of RCE (fixed polarizer, rotating irradiation compensator, and fixed analyzer), RCRC (fixed polarizer, rotating irradiation compensator, and rotating collection compensator, and fixed analyzer), or a fixed polarizer and a rotating analyzer. The system may include either the irradiation compensator or the collection compensator, or may exclude both compensators.

[0051] Embodiments of the systems described herein may all be configured for Mueller polarization analysis. In this analysis, the sample is described by a 4×4 matrix, where each element within the matrix is a set of spectra. Any combination of the polarizer 110, analyzer 122, first compensator 112, second compensator 120, and sample 132 can be rotated during measurement. The polarization generation optical element and the polarization analysis optical element may each be rotated at selectable angular frequencies. Various configurations are used to generate various numbers of harmonic spectra. In some cases, a sufficient number of harmonic spectra are generated to fully determine the Mueller matrix of interest. Various techniques for performing polarization analysis using the Mueller matrix are further described in U.S. Patent No. 8,446,584, entitled “Reconfigurable Spectroscopic Ellipsometer,” by Shankar Krishnan, issued on May 21, 2013, which is hereby incorporated by reference in its entirety as part of this specification.

[0052] The optical element positioned between the polarizer 110 and the analyzer 122 may be a reflective element for reflecting the irradiation light toward the sample and collecting the output light from the sample. Some different arrangement configurations of the reflective optical element in the spectroscopic polarization analysis tool are further described in U.S. Patent No. 5,608,526 by Piwonka-Corle et al., issued on March 4, 1997, and this patent is incorporated herein by reference as part of this specification for the purpose of providing further embodiments regarding various spectroscopic polarization analysis features. Such features include a light source, optical components for reflecting and focusing the irradiation beam onto the sample, components for automatic focus detection, the configuration and arrangement of the polarizer / compensator / analyzer, components for the reference channel for generating and detecting the reference irradiation beam, a control / processing mechanism, the arrangement of the spectrometer / detector, components of the spectrometer system, etc., and these can be utilized in the embodiments of the system described in this specification.

[0053] Next, the collected light can be received by the detector 124. In one embodiment, the detector is a spectrometer having a sufficiently high quantum efficiency over a wide range of wavelengths. The detector module may include a spectrometer slit and one or more reflective mirrors that reflect the output beam passing through the prism, and this prism is configured such that light hits along different linear portions of the detector or sensor by refracting different wavelengths in different directions. Other arrangements of the detector module are also conceivable. In a specific embodiment, the detector can comprise one or more of the following UV-enhanced components. That is, a detector using a charged coupled device (CCD) having a sufficiently high quantum efficiency over a wavelength range from about 190 nm to about 900 nm, a photodiode array having a sufficiently high quantum efficiency over a wavelength range from about 700 nm to about 2000 nm, a photodiode array having a sufficiently high quantum efficiency over a wavelength range from about 150 nm to about 400 nm, etc. Suitable detectors include a charged coupled device (CCD), a CCD array, a time delay integration (TDI) sensor, a TDI sensor array, a photomultiplier tube (PMT), and other sensors.

[0054] System 100 may also include a control unit 130. This control unit includes any suitable combination of software and hardware and is typically configured to control various components of the measurement system 100. For example, this control unit may control the selective activation of the light source 106, the setting of the irradiation polarizer and the irradiation compensator, the setting of the detection compensator and the detection analyzer, the setting of the irradiation aperture / shutter, etc. The control unit 130 may also receive the signal or image data generated by the detector 124, analyze the obtained signal or image, characterize the object or sample by obtaining sample parameters, or determine whether a defect exists in the sample, or may be configured to characterize the defect existing in the sample.

[0055] System 100 may also include a positioning mechanism 131 that rotates, tilts, and / or translates various movable components (such as a sample stage, a fixed aperture / mask, a shutter, a polarizer, an analyzer, a compensator, etc.) to various positions. As an example, the positioning mechanism 131 may include one or more motor mechanisms (such as a screw drive and a stepper motor, a linear drive with position feedback, a band actuator and a stepper motor, etc.).

[0056] Similar to any of the systems described herein, system 100 also preferably includes a purge system for filling the vacuum chamber with nitrogen gas or other gas suitable for operation in vacuum UV. When operating at 150 nm, for example, the entire optical path is sealed in the chamber, and this chamber is filled with dry nitrogen gas. Exemplary purge systems and purge techniques are described in (i) U.S. Patent Application Publication No. 2004 / 0150820, filed on November 19, 2003 by Nikoonahad et al., and (ii) U.S. Patent No. 7,755,764, filed on January 24, 2008, and the present application and this patent are incorporated herein by reference in their entirety for such features.

[0057] Each control unit described in this specification may be configured (e.g., using program instructions) to provide a user interface (e.g., on a computer screen) for displaying the obtained test images and other measurement characteristics. The control unit may also include one or more input devices (e.g., keyboard, mouse, joystick) for providing recipe input to the user. Such recipe input may include, in addition to detection parameters, selecting a wavelength range, an incident angle / azimuth angle, and the polarization state of the incident light or the collected light. The control unit typically comprises one or more processors. The processor is connected to an input / output port and one or more memories via a suitable bus or other communication mechanism.

[0058] Such information and program instructions may be implemented in a specially configured computer system. Such a system includes program instructions / computer code for performing the various operations described herein, which can be stored on a computer-readable medium. Examples of computer-readable media include magnetic media such as hard disks, floppy (registered trademark) disks, and magnetic tapes; optical media such as CD-ROM disks; magneto-optical media such as optical disks; and hardware devices specially configured to store and execute program instructions such as read-only memory (ROM) devices and random access memory (RAM), but are not limited thereto. Exemplary program instructions include both machine code (such as code generated by a compiler) and files containing high-level code that can be executed on a computer using an interpreter.

[0059] It should be noted that the above-described figures and explanations are not to be construed as being limited to specific components of the system, and that the system can be embodied in many other forms. For example, the measurement tool can be considered to include any number and any type of appropriate components arranged to determine the characteristics and properties of the target sample. As an example, the measurement tool may include one or more components for performing polarization analysis, reflected light measurement, or scattered light measurement by spectroscopy from VUV to NIR.

[0060] In another exemplary embodiment of the SE tool, the detector system of the tool simultaneously decomposes the wavelength and the angle of incidence or azimuth angle. FIG. 2 illustrates an SE tool 200 configured to simultaneously detect multiple angles of incidence according to a second embodiment of the present invention. In this example, light of various angles of incidence or azimuth angles reflected by the sample 132 is collected by the collection optical system 204 and sent to the detector module 224. In the illustrated embodiment, the collection optical system 204 includes collection mirrors 226, 118 that focus the collected light on the dispersion optical system and the detector module 224. In an alternative embodiment, the detected light is not spatially decomposed into discrete angles of incidence or discrete azimuth angles.

[0061] Any suitable collection-side mechanism for mapping the wavelength and the angle of incidence / azimuth angle in two different directions in a plane (such as the x and y directions orthogonal to each other) may be incorporated into the SE tool. Usually, the system 200 may include an optical collection system having different optical refractive powers (such as cylindrical refractive power, annular refractive power, etc.) in two different directions (such as the x and y directions) so that the wavelength and the angle of incidence (or azimuth angle) can be mapped in two different directions of the two-dimensional detector. As shown, the dispersion optical system and the detector module 224 provide the function of a two-dimensional spectrometer (an enlarged one is illustrated at 227) having one axis for the angle of incidence / azimuth angle and another axis for the wavelength. The dispersion optical system may be configured to have a refractive index such that the detector is arranged on or near a plane conjugate to the field stop in the wavelength direction, and to have a refractive index such that the detector plane is arranged at or near a position conjugate to the pupil plane in the angle-of-incidence direction. Alternatively, the angle of incidence in this example may be replaced with the azimuth angle.

[0062] In the illustrated embodiment, the dispersive optical system and detector module 224 receive the beam to be detected at the spectrometer entrance and include a dispersive element for conditioning the beam for receipt by the detector. The detector maps light as a function of wavelength along a first axis (e.g., in the X direction) and maps the light to be detected as a function of angle of incidence / azimuth angle along a second axis (e.g., in the Y direction). That is, the dispersive element disperses the wavelength components of the light to be detected along the first detector axis and disperses the angle of incidence / azimuth angle components of the light to be detected along a second detector axis (e.g., this axis is orthogonal to the first axis). In a specific embodiment, the dispersive element includes a cylinder having a length proportional to the numerical aperture (NA) and configured to align a point focus to a line, and a dispersive element for dispersing light into a spectrum. This NA is related to the collected angle of incidence / azimuth angle.

[0063] The detector may include any suitable detection mechanism for detecting light dispersed in two directions. Such detection mechanisms include, for example, a CCD for detecting light having wavelengths, angles of incidence, and azimuth angles that vary within the ranges described herein. The detector may include any suitable number of shift registers for shifting data from selected pixels. For example, the detector may include two shift registers for processing in parallel light emitted from a sample and incident at two different angles of incidence. In another example, the detector includes more than two shift registers so that light incident on and reflected from the sample at more than two different angles of incidence can be processed in parallel. In yet another example, the detector includes only one row of pixels per shift register for detecting the angle of incidence so that readout can be performed at high speed.

[0064] System 200 may also include a control unit 230 configured to control any component of system 200. For example, the control unit 230 is configured to select the wavelength of one or more light sources 106, the angular frequency and / or azimuth angle and timing of the polarizer 110, the irradiation compensator 112, the analyzer 122, and the collection compensator. The control unit 230 may also be configured to receive a signal or image data generated by a detector and analyze the obtained signal or image. Thereby, the sample is characterized by obtaining sample parameters, or it is determined whether a defect exists in the sample, or the defect existing in the sample is characterized. System 200 may also include a positioning mechanism 231 that rotates, tilts, and / or translates various movable components (such as a sample stage, a fixed aperture / mask, a shutter, a polarizer, an analyzer, a compensator, etc.) to various positions.

[0065] In certain embodiments, it is possible to convert the detected light into digital data according to various incident angles, azimuth angles, and wavelengths, and this data can be independently analyzed as a function of the incident angle, azimuth angle, and wavelength (in addition to the polarization state). The above data corresponding to the detected light may be divided so as to correspond to separate regions of the detector according to various incident angles / azimuth angles and / or wavelengths. Then, the data thus divided can be analyzed as a function of the incident angle, azimuth angle, and wavelength (in addition to the polarization state). In certain embodiments, the measurement processing ability can be improved by simultaneously acquiring and processing optical signals from various incident angles. As the irradiation NA increases, the diffraction-limited spot diameter in the target region of the sample becomes smaller, so that the target size can be reduced. Alternatively, even if the target size is not reduced, increasing the NA in this way increases the ratio of the detected light arriving from within the target region to the detected light arriving from the surrounding region, making the signal less likely to be contaminated.

[0066] FIG. 3A schematically illustrates an example of an SE tool 300 that simultaneously collects multiple angle-of-incidence regions with multiple detectors according to a particular embodiment of the present invention. As shown, the tool 300 includes a light source 106 that provides light of multiple wavelengths, and an ellipsometer illumination optical system 302 that gives various polarization states to the illumination beam directed at the sample 132. The ellipsometer illumination optical system 302 may also be configured to direct the illumination beam at multiple angles of incidence and may be configured to direct light at multiple azimuthal angles. The tool 300 may also include an ellipsometer collection optical system 304 that collects light at multiple angles of incidence (and azimuthal angles) and multiple polarization states. The light source 106, the ellipsometer illumination optical system 302, and the ellipsometer collection optical system 304 may correspond to any of the various illumination components and collection components described herein.

[0067] The collection side of the tool 300 may also include a wavelength·angle-of-incidence dispersion optical system 306 that disperses the collected light in two directions orthogonal to each other according to the wavelength and the angle of incidence. As shown, the dispersion result 309 at the plane 1 (308) is illustrated. In this figure, three different angle-of-incidence regions 1, 2, 3 are included with respect to the first vertical axis, and the wavelength is dispersed over the entire angle-of-incidence region with respect to the second horizontal axis. Of course, any suitable number of angle-of-incidence regions may be defined by the dispersion optical system 306. The dispersion optical system 306 may be configured to have different light refractive powers (e.g., cylindrical refractive power, annular refractive power, etc.) to disperse the angle of incidence (and / or azimuthal angle) and the wavelength in two different directions, as described herein.

[0068] Tool 300 may also include a partial splitting optical system 310 that splits the beam dispersed in the incident angle (or azimuth angle) by the dispersive optical system 306 into various incident angle regions. The incident angle partial splitting optical system may also be configured to determine the wavelength and direct each incident angle region to individual detectors (e.g., 314a, 314b, 314c) that integrate over a range of one incident angle (or azimuth angle). If the planes resolved for the incident angle (or azimuth angle) and wavelength are not spatially well separated, an imaging optical system 312 is arranged between these planes to re-image the plane resolved for the wavelength onto each detector. Each detector may be configured to detect over a wavelength range from 190 nm to about 900 nm. Also, all detectors may be configured to be read out simultaneously. The optical systems 306, 310, 312 and the detectors 314 may also be configured to collect and / or detect wavelengths in the range from 150 nm to 2000 nm. For example, Si-based detectors may be used for wavelengths less than about 1000 nm, and InGaAs-based detectors may be used for wavelengths greater than about 800 nm. With such an SE embodiment, optical signals from various incident angles / azimuth angles can be acquired and processed simultaneously.

[0069] System 300 may also include a control unit 330 configured to control various components and analyze the detected data. The control unit 330 may be, for example, similar to the control unit 230 of FIG. 2. Further, the control unit 330 may be configured to control a number of detectors and analyze the images and signals obtained by such each detector. System 300 may also include a positioning mechanism 331 that translates, rotates or tilts any movable component. This positioning mechanism is similar to the positioning mechanism of FIG. 2, but is further capable of selecting the positions of a number of detectors.

[0070] An alternative multi-incidence angle system may include an aperture for a selected incidence angle in a single detector. FIG. 3B schematically illustrates a second example of an SE tool 350 with an incidence angle mask 351 configured to be able to select an incidence angle range from among multiple incidence angles according to another specific embodiment of the present invention. As shown, the wavelength-incidence angle (and / or azimuth angle) dispersion optical system 348 is still configured to disperse the incidence angle (or azimuth angle) and the wavelength in two different directions (e.g., orthogonal directions), but disperses the wavelength in a plane disposed in front of the dispersion plane of the incidence angle / azimuth angle. That is, although the incidence angle dispersion optical system 348 in FIG. 3B can operate in the same manner as the incidence angle dispersion optical system described with reference to FIG. 3A, it does not disperse the wavelength in the same plane as the dispersion plane of the incidence angle / azimuth angle.

[0071] The incidence angle mask 351 may be placed in a plane and configured to disperse the incidence angle by the dispersion optical system 348 thereon. Using this incidence angle mask, it may be configured to selectively send different incidence angle regions to the detector 352. For example, the incidence angle mask 351 provides a mechanism for selecting one incidence angle / azimuth angle region at a time in the incidence angle / azimuth angle region of the sample. View 354 shows an example of selecting an incidence angle region. In this view 354, through the aperture of the incidence angle mask 351, incidence angle region 2 is selected and sent to the detector 352, while incidence angle regions 1 and 3 are blocked by the mask portion of the incidence angle mask 351 (this mask portion is opaque and does not allow light to pass through).

[0072] The incidence angle mask 351 may take any suitable form so as to be able to select a specific incidence angle region. For example, the incidence angle mask 351 (or aperture) may include a plurality of fixed apertures each having a shutter for selecting different incidence angle regions, or may include a single movable aperture (as shown). In an example using a number of fixed apertures, as further described herein, by spatially separating each aperture, various incidence angle regions of the sample can be resolved.

[0073] Detector 352 (and 314) may take any suitable form for detecting (in the case of wavelength) along at least one direction. For example, there are the two-dimensional detector or one-dimensional linear photodiode array described above. Detector 352 (and 314) is preferably positioned within the wavelength resolution plane. Detector 352 may include a mask 351 defined by the width of the photosensitive region or by a mask incorporated within the detector device. In this case, the dispersive optical system 348 disperses the wavelength in the same plane as the incidence angle / azimuth dispersion plane. Also, in this case, the detector 352 is moved in the same way as the mask 351 for selecting the incidence angle region.

[0074] System 350 may also include a control unit 360 and a positioning mechanism 361. This system is configured by functions similar to any control unit and / or positioning mechanism described herein, but further can control or move the incidence angle mask 351 and / or the detector 352.

[0075] An SE measurement tool (such as each system in FIGS. 1, 2, 3A) that irradiates a sample at multiple incidence angles and selectively collects the incidence angle regions one by one (i.e., collects them to an individual detector) without moving the irradiation optical path and the collection optical path can improve the repeatability and stability of the measurement more by fixed irradiation and collection pupil, and fixed irradiation and collection field stop compared to a system where the pupil and field stop change for each incidence angle measurement. An embodiment of a system with a movable field stop (such as the system in FIG. 3B) can achieve a higher processing speed with a shorter movement distance of the aperture compared to a system with a movable aperture near the collection mirror, but at the cost of being less stable compared to a system without a movable aperture. All embodiments with an optical system having a fixed imaging path have advantages in processing capacity over a system that decomposes the incidence angle by moving the imaging optical system.

[0076] In another embodiment, a single two-dimensional detector can be used to simultaneously collect multiple incident angle regions. FIG. 3C is a diagram showing the simultaneous collection of multiple incident angle / azimuth angle regions on a single detector 370 according to an alternative embodiment. In this embodiment, the detector is divided into a plurality of incident angle regions (e.g., 372a, 372b, 372c), which correspond to spatially separated incident angle regions. These regions are detected simultaneously and can then be analyzed separately. The incident angle regions of the detector can be spatially separated by optically inactive regions (e.g., 374a, 374b). These inactive regions correspond to optically inactive pixel portions or signal portions where no analysis is performed.

[0077] In any of the embodiments using dispersion, it is possible to simultaneously disperse both the incident angle and the azimuth angle by sending the beam to two two-dimensional detectors using a beam splitter. At this time, on the one hand, it is configured to disperse the wavelength and the incident angle, and on the other hand, it is configured to disperse the wavelength and the azimuth angle. FIG. 3D illustrates a collection-side optical system 380 that simultaneously collects the dispersed incident angle and azimuth angle according to an embodiment. As shown, the ellipsometer collection optical system 382 can collect light with multiple incident angles and multiple azimuth angles from the sample and guide its output to the splitter 384. This splitter guides the above output light to the wavelength-incident angle dispersion system 386 and the wavelength-azimuth angle optical system 380.

[0078] The incident angle dispersion optical system 386 is configured to disperse the wavelength and the incident angle along two directions in the same or different planes. The dispersed wavelength and incident angle are received by the wavelength-incident angle detector module 388. This module may be configured to detect spatially separated incident angle regions (each having a dispersed wavelength as described above) simultaneously or sequentially. Similarly, the wavelength-azimuth angle detector module 390 may receive the dispersed wavelength and azimuth angle, and this module may be configured to detect spatially separated azimuth angle regions (each having a dispersed wavelength) simultaneously or sequentially.

[0079] FIG. 4A illustrates a configurable SE tool 400 with one or more apodizers 409 and / or 405 according to another embodiment of the present invention. In one arrangement, a stationary single apodizer 409 is placed at or near the illumination pupil. This apodizer is configured to shape the illumination beam and control the point spread function of the focus coupled to the sample 132 for all selected angles of incidence (or azimuth angles). In another arrangement, one or more movable apodizers 409 may be moved inside (e.g., within direction 410) or outside the illumination pupil. This apodizer is typically configured to shape the illumination beam and control the point spread function of the focus coupled to the sample 132 for various selected angles of incidence (or azimuth angles). For example, each selected apodizer may be configured to control the spot diameter for a specific set of angles of incidence (or azimuth angles). In a specific embodiment, each apodizer is configured to shape the illumination light at a specific angle of incidence such that the illumination level at a spot position more than 25 microns away from the spot center is -3 less than 10% of the peak illumination at the spot center. For example, each selected apodizer may be configured to reduce the contamination of the signal being measured at a selected specific angle of incidence (or azimuth angle) by suppressing sidelobes and improving the measurement box size in the plane of the wafer being sampled.

[0080] In another embodiment, one or more collection apodizers 405 may be placed at or near the position of the plane conjugate to the collection pupil or made movable in place. By using such collection-side apodizers, a predefined collection profile can be provided for all discrete ranges of angles of incidence and / or azimuth angles. The collection-side apodizer can control the diffraction sidelobes generated by the sharp collection aperture. For example, this collection apodizer may be configured to shape the intensity distribution incident on the spectrometer slit in the same manner as the illumination apodizer shapes the intensity distribution on the wafer being sampled. This collection apodizer may also be configured to reduce contamination from outside the measurement box and finely control the spot at the spectrometer.

[0081] In the illustrated embodiment, by using separate collection apertures when collecting different incident angles, while making the slits the same for each incident angle range, the spots at the slits are made different according to the incident angle. In this configuration, a collection apodizer configured for a specific incident angle to be used can be useful for adjusting the spot of the specific incident angle. This collection apodizer is preferably disposed in or near the plane of the collection aperture, but it is also considered possible to dispose this apodizer at a later stage. In a specific embodiment, the number of apodizers corresponds to the number of collection apertures, and the selected apodizer can be moved into the collection path (e.g., in direction 411). Alternatively, a single dynamically configurable apodizer may be used and disposed in the collection path.

[0082] Apodization can generally be defined as the conversion of the light distribution in the entrance pupil of an optical system (e.g., changing the amplitude and / or phase of an irradiation beam using a mask), thereby changing the intensity profile of the irradiation beam. In the present case, each apodizer reduces the irradiation in the "tail" of the irradiation spot (e.g., the part of the irradiation spot wider than 25 microns from the center of the irradiation spot) to less than 10 -3 % of the peak irradiation, thereby being configured to reduce signal contamination. Including such an apodizer in any measurement system described herein is one feature, which can thereby make it possible to measure a relatively small object using a relatively small spot diameter.

[0083] A transmissive apodizer (such as fused silica) can act on wavelengths up to about 170 nm. Generally, apodizers may be manufactured using standard lithography reticle blanks / mask blanks, and these blanks are optimized for 193 nm. The same is considered true for reflective apodizers.

[0084] Generally, when designing each apodizer, it may be adjusted according to each specific set of selectable irradiation side incident angles (or azimuth angles), and each apodizer is movable in the irradiation beam path to control the spot diameter for each specific set of incident angles (or azimuth angles). That is, the embodiments using these apodizers each have a non-reconfigurable optical function. In addition, a set of apodizers 409 may include each apodizer configured for a specific object under test. For example, even at the same incident angle, it is possible to obtain different irradiation amplitude profiles. In addition to the system of FIG. 4A, any of the system embodiments described herein may similarly include configurable apodizers.

[0085] The system 400 of FIG. 4A may be arranged to include a scanning mirror (e.g., scanning mirror 407) so as to be able to scan the irradiation beam that irradiates the sample 132 at various incident angles. This scanning mirror is preferably in or near the plane conjugate to the sample 132. The scanning mirror 407 may be replaced with a polarizer slit, or the scanning mirror 407 may be made conjugate to the polarizer slit. When the scanning mirror replaces the polarizer slit, this scanning mirror may include a mask that defines an irradiation field stop. When the scanning mirror is conjugate to the polarizer slit, another imaging optical system may exist between the polarizer slit and the scanning mirror. The scanning mirror 407 can replace a movable fixed aperture (e.g., the one described above) to selectively scan irradiation beams at various incident angles (or azimuth angles). The scanning mirror 407 may be configured to be movable by any suitable positioning mechanism to select one specific incident angle (or azimuth angle) at a time. In the illustrated embodiment, by tilting the scanning mirror 407 in the direction 408, the irradiation beam is scanned through a specific range of incident angles (or azimuth angles). That is, with the scanning mirror 407, the irradiation is moved along various incident angle positions in the pupil plane without moving the irradiation spot on the sample 132.

[0086] The scanning mirror 407 is reflective and is adapted to operate over a wide range of wavelengths. By using the reflective scanning mirror 407, a wide range of wavelengths can be included in the irradiation beam (including VUV light that requires a reflective optical element).

[0087] The fixed mirror 406 may be used to direct the scanned irradiation beam reflected from the scanning mirror 407. Alternatively, a number of mirrors may be used to direct the sample 132 at various angles of incidence.

[0088] The irradiation optical system 402 may be configured to optimally direct irradiation light at various angles of incidence (or azimuth angles) onto the sample 132. For example, the mirrors 414, 416 direct an irradiation beam from a specific set of angles of incidence (or azimuth angles) and focus it onto the sample 132. In one embodiment, the mirrors 414, 416 are sized to direct all light from 50° to 80° onto the sample 132.

[0089] Similar to other embodiments, the arrangement of the fixed or movable aperture 126 and / or shutter may be used to selectively collect light at various angles of incidence (or azimuth angles). The aperture / shutter 126 may be configured to select one angle of incidence at a time, as needed.

[0090] The irradiation optical system 402 and the collection optical system 404 may include components (e.g., polarizer 110, compensators 112, 120, and analyzer 122) for generating and / or collecting various polarization states.

[0091] The control unit 430 and / or the positioning mechanism 461 may be configured to control any component of the system 400. For example, the control unit 430 and / or the positioning mechanism 461 are configured to select the wavelength of one or more light sources 106, the tilt position of the scanning mirror 407 in the direction 408, the angular frequency and / or azimuth angle and timing of the polarizer 110, the irradiation compensator 112, the collection compensator 120, and the analyzer 122, the position of each apodizer 409, the settings of the irradiation and / or collection shutters, the position of the movable aperture, etc.

[0092] In most of the embodiments described herein, by using an amplitude apodizer in the irradiation path, it is possible to suppress side lobes, improve the measurement box size in the wafer plane, and reduce the contamination of the signal to be measured. Although a single configurable apodizer or a set of movable apodizers can obtain appropriate amplitude apodization for a specific set of incident angles (or azimuth angles), in such an apodizer system, it may be difficult to change the apodizer pattern. Furthermore, this arrangement may be related to the problems of slow switching speed and hardware repetitive accuracy. In an alternative apodization embodiment, a dynamically configurable spatial light modulator (SLM) may be used to dynamically form an apodizer pattern as needed. A variable apodizer (e.g., by MEMS SLM technology) can switch very quickly without affecting the position adjustment of the system.

[0093] FIG. 4B illustrates a configurable SE tool 450 with a dynamically adjustable apodizer according to an alternative embodiment of the present invention. This system includes a dynamically configurable reflective apodizer 456 in the irradiation path. In this irradiation path, an apodizing pattern is dynamically formed for each of the specific incident angles, azimuth angles, and NAs selected in the irradiation optics and the collection optics. This apodizer 456 is preferably reflective so as to act over a wide range including VUV to UV. As shown, the apodizer 456 may be arranged to receive the irradiation light 452 from the rotary compensator 454 via the irradiation slit 458.

[0094] As described above, various irradiation mechanisms may be used to select a specific incident angle (and azimuth angle), and various collection mechanisms may be used to collect a specific incident angle (and azimuth angle). The apodizer 456 is configured to dynamically adjust the amplitude and / or phase of the irradiation light based on the incident angle (and azimuth angle) selected in the irradiation optical system and the collection optical system. In certain embodiments, the irradiation beam may pass through a scanning mirror, or one or more fixed or movable apertures, or shutters, or combinations thereof. These are configured to select one or more spatially separated incident angles (azimuth angles) before reaching the apodizer 456. Alternatively, the apodizer 456 is disposed before such an incident angle (or azimuth angle) selection mechanism. The apodizer 456 is preferably disposed at or near the pupil plane. Alternatively, the apodizer 456 can also be disposed at or near the collection pupil. Alternatively, the apodizer 456 can also be disposed at or near both the irradiation pupil and the collection pupil. With a configuration using a collection-side apodizer, for example, the spot shape at the detector slit can be controlled. Such a type of apodization can reduce contamination from outside the box when received by the detector and can also improve the resolution (or PSF) of the detector. Additionally or alternatively, various incident angles (or azimuth angles) may be collected by fixed or movable apertures and / or shutters, etc.

[0095] In a specific embodiment, the apodizer 456 consists of a spatial light modulator (SLM). This spatial light modulator can be configured to control the amplitude reflection distribution over the entire range of the apodizer 456. A suitable SLM is an SLM based on a micro-electro-mechanical system (MEMS). Exemplary SLM type devices include DLP (Digital Light Processing, registered trademark) devices available from Texas Instruments (Dallas), as well as TX devices and SLM devices from the Fraunhofer Society (Munich, Germany).

[0096] As in the case of a DLP device, the apodization pattern may be a binary amplitude pattern, and by integrating over a plurality of pixels, an effective (continuous) reflection pattern can be obtained. Local apodization at a desired level can be obtained by the ratio of the pixels within the local area that reflects light in the illumination optical system. A spatial filtering aperture may be used downstream of the DLP SLM to block the light reflected away from the illumination optical system and filter out and remove the diffraction resulting from the periodic structure of the DLP SLM. This aperture may be incorporated into the aperture of the focusing optical system itself.

[0097] In another embodiment of the SLM, the apodizing pattern may be made continuously variable. However, continuous variability of the amplitude distribution may be achieved by encoding the pattern within the phase distribution generated by the SLM. In order to obtain the desired amplitude pattern result, it is necessary to apply a Fourier filter to the light using an aperture, but such an aperture may be incorporated into the focusing optical system of the system.

[0098] System 450 may also include a control unit and / or a positioning mechanism (not shown). These are the same as any of the above control units and / or positioning mechanisms, but further include control of the apodizer 456.

[0099] In certain embodiments described herein, a fixed or movable aperture may be used to select a particular incident angle (or azimuth angle) in an illumination beam directed towards a sample or a collected beam collected from the sample. FIG. 5A is a side view of an exemplary aperture system 500 according to one embodiment. As shown, the aperture system 500 may include a reflective substrate 502 on which a mask is formed. The mask consists of absorption or non-reflective regions (e.g., 504a, 504b, 504c) in which holes / vias (e.g., 506a, 506b, 506c) are formed. Exemplary absorption or non-reflective materials include metal sheet materials or metal foil materials (such as stainless steel and aluminum) and black anodized materials. These holes may be filled with a transparent material or left unfilled. Shutters (e.g., 508a, 508b, 508c) may be disposed or attached to cover each mask aperture (e.g., 506a, 506b, 506c). The entire aperture system 500 may also be movable (e.g., in direction 514), thereby positioning the aperture within the illumination path or collection path as further described herein.

[0100] These shutters may be opened or closed to reflect incident light at a particular incident angle (or azimuth angle). As shown, for the light beam 510b, the shutter 508b is closed while the shutters 508a, 508c are open. In this way, the light ray 510a is reflected from the reflective substrate 502 as the light ray 512a at the first selected incident angle (or azimuth angle), and the light ray 510c is reflected as the light ray 512c at the next selected incident angle (or azimuth angle).

[0101] FIG. 5B is a side view of an exemplary aperture system 550 according to the second embodiment. As shown, the aperture system 550 may include a reflective substrate 552. The aperture system 550 does not include a shutter and is movable along direction 564 so as to position fixed apertures (e.g., 554a, 554b, 554c). These apertures are formed in an absorption or antireflection mask material (e.g., 556a, 556b, 556c). These apertures can be positioned at a specific incident angle (or azimuth angle) within the irradiation path or collection path. As shown, the light ray 560a is reflected as the light ray 562a at the first selected incident angle, the light ray 560b is reflected as the light ray 562b at the second selected incident angle, and the light ray 560c is reflected as the light ray 562c at the third selected incident angle.

[0102] Any embodiment of the system may include a transmissive illumination selector that selectively applies an aperture to each of a plurality of pupil positions, thereby enabling selection of a specific set of incident angles (or azimuth angles) as described herein. However, this illumination selector is applicable only to transmissible wavelengths and not for reflection. Generally, the illumination selector is configured to obtain an individual range of incident angles / azimuth angles by allowing the light beam to pass through each position of the pupil individually. FIG. 6A is a perspective view of an illumination selector according to an embodiment of the present invention. In this example, the illumination selector is composed of three aperture disks 602, 604, 606. Each aperture disk includes a plurality of different aperture configurations (e.g., aperture configurations 608a, 608b for disk 602, aperture configuration 610a for disk 604, and aperture configurations 612a, 612b, 612c for disk 606). A specific aperture configuration for receiving the incident beam (or light beam) 614 can be selected for each disk, and then the three aperture configurations selected from the three disks can then be superimposed. This results in various numbers of aperture settings and, as a result, various numbers of illumination pupil profiles.

[0103] Generally, the aperture configuration of each disk includes at least one transparent portion and may also include one or more opaque regions. For example, the transparent portion can be formed from any suitable transparent material (such as glass, crystal, fused quartz, etc.). Alternatively, each transparent region can simply be a material-deficient area such that light passes through each transparent portion of the aperture configuration. In contrast, each opaque portion blocks the corresponding spatial portion of the incident beam in the pupil plane. Each opaque portion is typically formed from an opaque material, and examples of such opaque materials include chromium, molybdenum silicide (MoSi), tantalum silicide, tungsten silicide, OMOG (opaque MoSi on glass), etc. A polysilicon film may be added between the opaque layer and the transparent substrate to improve adhesion. A low-reflection film may be formed on the opaque material. Examples of such low-reflection films include molybdenum oxide (MoO 2 ), tungsten oxide (WO 2 ), titanium oxide (TiO 2 ) or chromium oxide (CrO 2 ), etc. The shape of the transparent portion of each aperture can be any suitable shape. For example, it can be rectangular, circular, elliptical, LHC screen (lhcscreen) (superposition of a circle and a rectangle), marguerite (two LHC screens with one rotated by 90°), rectellipse (superposition of an ellipse and a rectangle), racetrack-shaped, etc.

[0104] Typically, by using one aperture configuration, a specific incident beam profile or a specific set of incident angles and azimuth angles is created. In a specific embodiment, SMO (Source Mask Optimization) or any pixelated irradiation technique may be implemented. In the illustrated embodiment, each aperture configuration covers the entire irradiation pupil region and is disposed at the center of the optical axis. However, as another option, the aperture configuration may be disposed in a part of the pupil region or at another point (not the pupil plane) along the optical path of the incident beam.

[0105] FIG. 6B is a diagram showing how a second embodiment of the aperture configuration is obtained by combining three aperture configurations. For simplicity, the size of the transparent portion is exaggerated. In this embodiment, the first aperture configuration 610a is completely transparent across the entire pupil region. The second aperture configuration 608b has a transmissive vertical transparent strip 652 surrounded by opaque portions 654, 656. The third aperture configuration 612b has a horizontal transparent strip 622 surrounded by opaque portions 624, 620. As a result, the aperture configuration 630 has a square transparent portion 634 surrounded by an opaque portion 632, and can thus be configured to select a specific set of incident angles.

[0106] FIG. 7A illustrates a configurable measurement tool 700 including an off-axis parabolic (OAP) mirror according to another embodiment of the present invention. This system 700 includes an off-axis parabolic (OAP) mirror 710a on the illumination side 702 used with a translatable mirror 712, and selects multiple incident angles (e.g., from an illumination beam received from a reflective mirror 722a), and as an example, moves the mirror 712 from position 712a to position 712b. Typically, for example, it is possible to shift the movable illumination mirror 712 along a certain direction (e.g., 714a), thereby reflecting the illumination beam from the illumination OAP 710a, and obtaining a specific set of incident angles based on the position on the curve of the OAP where the illumination beam is reflected. In the illustrated embodiment, the positions 712a, 712b of two different illumination translation mirrors are shown, and two spatially separated different incident angles are sequentially obtained one by one on the sample 132, but more mirror positions (configured to reflect the illumination beam from various regions in the curve of the OAP) may be used to obtain more incident angles.

[0107] The collection optical system 704 of the system 700 may include, for example, a corresponding collection OAP mirror 710b arranged to collect the output beam from the sample 132 at a selected incident angle, and a similar collection translation mirror 713 configured to move to a plurality of positions (e.g., 713a, 713b) within the direction 714b, so as to receive these output beams one by one from the collection OAP 710b at the selected incident angle. The collection optical system 704 may also include any suitable optical elements (e.g., a convex mirror 720 and a reflecting mirror 722b) for guiding the output beam (e.g., the collimated beam 716) to the detector 124.

[0108] In another aspect, the translation mirrors (712 and 713) and the OAP mirrors (710a and 710b) may be configured to correspond to a wide range of incident angles (up to near grazing incidence). That is, the translation mirrors and the OAP mirrors may be configured to select the incident angle over a continuous range.

[0109] The control unit 730 and / or the positioning mechanism 761 may be configured to control any component of the system 700. For example, the control unit 730 and / or the positioning mechanism 761 are configured to select the wavelength of one or more light sources 106, the angular frequency and / or azimuth angle and timing of the polarizer 110, the irradiation compensator 112, the analyzer 122, and the collection compensator 120, the translation of each translation mirror 712, 713, the rotation of the OAP mirror, etc.

[0110] FIG. 7B illustrates, in another embodiment, a dual-path measurement tool 750 according to an alternative embodiment of the present invention, comprising an off-axis parabolic (OAP) mirror. This system 750 includes an off-axis parabolic (OAP) mirror 760 used with a translationally movable mirror 762, and selects multiple angles of incidence (e.g., from the illumination beam received from the beam splitter 752) by moving the mirror 762 from position 762a to 762b. Typically, for example, it is possible to shift the movable illumination mirror 762 along a certain direction (e.g., 764), thereby reflecting the illumination beam from the illumination OAP 760 and obtaining a specific set of angles of incidence based on the position on the curve of the OAP where the illumination beam is reflected. Due to this movement, the output beam emitted from the sample 132 will return to the extraction position after being reflected by the spherical mirror 754, although the position on the spherical mirror 754 changes. The second output beam is emitted from the sample 132 in response to the beam returned from the spherical mirror 754 as described above and the target characteristics after scanning the sample. Then, the second output beam is collected by the OAP mirror 760, the translationally movable mirror at position 762a or position 762b, and the beam splitter 752, and is directed to a detector (not shown).

[0111] In another embodiment shown in FIG. 7B, a positioning mechanism 791 may be used together with the control unit 780 to configure the sample 132 or the test target surface around the measurement point 756 to be tipped / chipped. For example, continuously or sequentially scanning the incident angle and azimuth angle can be achieved by tipping / chipping the sample via the positioning mechanism 791. With this movement, although the position of the output beam emitted from the sample 132 changes at the spherical mirror 754, it is reflected by this spherical surface 754 and then returns to the extraction position. The second output beam is emitted from the sample 132 in response to the beam returned from the spherical mirror 754 as described above and the target characteristics after scanning the sample. Then, the second output beam is collected by the OAP mirror 760, the mirror 762 (this mirror is fixed in this embodiment), and the beam splitter 752 and guided to a detector (not shown). In this embodiment, the wafer is tilted while keeping the position of the translation mirror 762 fixed.

[0112] Embodiments of the multi-incident angle and multi-azimuth angle systems described herein may also be configured such that the collection side extracts the zero-order light reflected by the sample for bright-field operation, or the collection arm extracts the non-zero-order light reflected by the sample for dark-field operation. In one arrangement, spatially separated sets of irradiation apertures and another spatially separated set of collection apertures are arranged so that bright-field operation and dark-field operation can be selected. In bright-field operation, the collection side extracts the same incident angle (azimuth angle) of the irradiation light reflected by the sample. In dark-field operation, the collection side extracts an incident angle (azimuth angle) different from that of the irradiation light reflected by the sample.

[0113] In any of these multi-incident angle (or azimuth angle) systems, the irradiation optical system can be configured to generate a number of irradiation beams separated in the azimuth direction of the wafer (e.g., covering 0° to 90° simultaneously). This system may include a spatially separated set of detectors. These detectors can receive separate light beams, and the irradiation optical system and the collection optical system correspond to multi-incident angles and multi-azimuth angles for each beam.

[0114] Any suitable measurement process may be implemented along with the system described in this specification. FIG. 8 is a flowchart showing an SE measurement procedure 800 according to an embodiment of the present invention. First, irradiation light of multiple wavelengths (e.g., from VUV to IR) may be generated in step 802. In step 804, one or more polarization states may be selected for this irradiation light. In step 806, one or more ranges of incident angles and / or azimuth angles may also be selected for the irradiation light. In step 808, as an example, the irradiation light may be further shaped and guided to form a small spot on the target of the wafer.

[0115] In step 810, then, an output beam exiting the wafer in response to the irradiation beam may be collected. In step 812, one or more incident angles or azimuth angles may be further selected for collecting the output beam. In step 814, one or more polarization states may also be selected. In step 816, then, the output beam may be detected and used to generate a signal or an image. In step 818, then, the generated signal or image may be analyzed to determine the characteristics of the target on the wafer. For example, for various target characteristics, the corresponding target characteristics may be determined by comparing the signal / image output from the model after simulation with the generated signal / image for various irradiation characteristics (e.g., polarization state, wavelength, incident angle, and azimuth angle).

[0116] Exemplary sample parameters that can be determined based on one or more detected signals or detected images include critical dimension (CD), film thickness, metal gate recess, High-k recess, sidewall angle, step, pitch walking, trench profile, and contact profile, overlay, material properties, parameters for semiconductor manufacturing processes (e.g., scanner focus and exposure dose, etch rate of an etching tool), and the like. Note that examples of the above material properties include, for example, material composition, refractive index, stress on critical films (including ultrathin diffusion layers, ultrathin gate oxide films, advanced photoresists, 193 nm ARC layers, ultrathin multilayer stacks, CVD layers, and advanced high-k metal gates (HKMG)), stress on ultrathin DPN (decoupled plasma nitridation) process layers, stress on non-critical films (including intermediate insulators, photoresists, bottom anti-reflection films, thick oxides and nitrides, and back end of line (BEOL) layers), and the like.

[0117] Although the above invention has been described in some detail for ease of understanding, it will be apparent that certain changes and modifications can be made within the scope of the appended claims. It should be noted that there are many alternative ways for the processes, systems, and apparatuses of the present invention. For example, although embodiments of a system applicable to the measurement of semiconductor devices are described herein, it is contemplated that such a system may also be used for other types of applications (such as the measurement or defect inspection of other types of samples). Therefore, this embodiment should be considered as illustrative and not restrictive, and the present invention should not be limited to the details described herein.

Claims

1. An ellipsometer apparatus for measuring a semiconductor sample, comprising: one or more high intensity light sources providing radiation beams at a plurality of selectable wavelengths ranging from vacuum ultraviolet (VUV) to infrared (IR) wavelengths; an illumination optics system for directing the illumination beam toward a semiconductor sample at a plurality of selectable ranges of angles of incidence (AOI) and / or azimuth angles (AZ) and a plurality of polarization states to provide spectroscopic ellipsometry metrology, the illumination optics including at least one illumination-side apodizer for controlling a spot diameter of an illumination spot of the illumination beam on the semiconductor sample at each of the selectable sets of angles of incidence and / or azimuth angles; a collection optics system for directing an output beam emerging from the semiconductor sample in response to the illumination beam toward a detector at each of the selectable sets of angles of incidence and / or azimuth angles and polarization states, the collection optics including a collection apodizer for controlling a spot diameter at the detector; a detector that generates an output signal or an output image based on the output beam; and a control unit for characterizing features or detecting defects in the semiconductor specimen based on the output signal or image as a function of wavelength, or angle of incidence, or azimuth angle, or polarization state, or a combination thereof; the at least one illumination-side apodizer comprises a set of apodizers each movable in and out of an illumination pupil plane, each apodizer configured to control the spot diameter for each of the selectable sets of incidence angles and / or azimuth angles; The illumination optics has an illumination selector for selecting a particular set of angles of incidence, the illumination selector including a first aperture disk having a first aperture configuration, a second aperture disk having a second aperture configuration, and a third aperture disk having a third aperture configuration, the first aperture configuration being transparent over an entire pupil area, the second aperture configuration having transmissive vertical transparent strips surrounded by opaque portions, and the third aperture configuration having horizontal transparent strips surrounded by opaque portions. Ellipsometer instrument.

2. 2. The apparatus of claim 1, wherein the at least one illumination-side apodizer is a dynamically adjustable apodizer and is configurable to control the spot diameter for all of the selectable sets of incidence angles and / or azimuth angles by reducing irradiance at a predetermined distance from the center of the illumination spot to less than a predetermined value of peak irradiance at the center of the illumination spot.

3. The apparatus of claim 1 , wherein the at least one illumination-side apodizer is configured to control the spot diameter by suppressing side lobes in the illumination beam.

4. 10. The apparatus of claim 1, wherein the at least one illumination-side apodizer is further configurable for a plurality of different targets on the semiconductor specimen.

5. The apparatus of claim 1 , wherein the incidence angle / azimuth angle selector includes a plurality of fixed apertures or at least one movable aperture, each aperture having a shutter.

6. The apparatus of claim 1 , wherein the at least one illumination-side apodizer is a dynamically adjustable apodizer.

7. The apparatus of claim 6 , wherein the dynamically adjustable apodizer is a spatial light modulator (SLM).

8. The apparatus of claim 1 , wherein the at least one illumination-side apodizer is configurable to form a plurality of binary amplitude patterns for each of the selectable sets of incidence or azimuth angles.

9. 10. The apparatus of claim 1, wherein the at least one illumination-side apodizer is configured to produce a plurality of amplitude patterns for each of the selectable sets of incidence or azimuth angles, and at least one amplitude pattern is continuously variable.

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