Patent Description:
As demand for ever-shrinking semiconductor devices continues to increase, so too will the demand for improved semiconductor wafer metrology systems. The fabrication of semiconductor devices, such as logic and memory devices, typically includes processing a semiconductor wafer using a large number of semiconductor fabrication processes to form various features and multiple levels of the semiconductor devices. Multiple semiconductor devices may be fabricated in an arrangement on a single semiconductor wafer and then separated into individual semiconductor devices.

Metrology processes are used at various steps during a semiconductor manufacturing process to monitor and control one or more semiconductor layer processes. For example, metrology processes are used to measure one or more characteristics of a wafer such as dimension (e.g., line width, thickness, angle, etc.) of features formed on the wafer during a process step, wherein the quality of the process step can be determined by measuring the one or more characteristics. In this scenario, a given semiconductor sample may include a set of metrology targets, with film stacks or two-dimensional and three-dimensional patterned structures surrounded by one or more materials of various geometries and properties.

Spectroscopic ellipsometry (SE) metrology measurements sample the light reflected off metrology targets at different optical parameters. The SE data of metrology targets is used to determine wafer characteristics. There is a continuing need for improved SE metrology tools, for example, so that SE data for different target characteristics can be readily decoupled.

<CIT> discloses a dynamically adjustable semiconductor metrology system.

<CIT> describes a system and method for apodization in a semiconductor device inspection system.

<CIT> discloses optical metrology using targets with field enhancement elements.

The following presents a simplified summary of the disclosure in order to provide a basic understanding of certain embodiments of the invention. This summary is not an extensive overview of the disclosure and it does not identify key/critical elements of the invention or delineate the scope of the invention. Its sole purpose is to present some concepts disclosed herein in a simplified form as a prelude to the more detailed description that is presented later.

The present invention provides an ellipsometer apparatus for performing metrology of a semiconductor sample as recited in claim <NUM>. Further advantageous features are recited in the dependent claims.

These and other aspects of the invention are described further below with reference to the figures.

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, limited only by the scope of the appended claims. In other instances, well known component or process operations have not been described in detail to not unnecessarily obscure the present invention. While the invention will be described in conjunction with the specific embodiments, it will be understood that it is not intended to limit the invention to the embodiments. The invention is limited only by the scope of the appended claims. In the following, the terms "embodiment" and/or "implementation" do not necessarily mean an embodiment/implementation of the invention.

One problem with using a spectroscopic ellipsometer (SE) system pertains to the coupling of detected data. The measured ellipsometric parameters from a particular sample, such as a semiconductor wafer or reticle, depends on a number of metrology parameters, such as wavelength (λ) and x and y target position. In general, the ellipsometric data at different tool settings (e.g., λ, target position, etc.) is collected independently and input to a model for deducing target characteristics, such as CD or overlay. As the target becomes more complex, the collected data for changes in target characteristics become highly correlated or insufficient so that the model cannot accurately determine target characteristics.

Although an SE system that can be configured to generate different specific narrow ranges of AOI's may break correlations between target parameters, such a system may be unable to provide small spot sizes for each narrow range of AOI's and resulting NA. For example, SE systems with AOI selection may not include a mechanism for achieving a small enough spot size, which may be useful for measuring certain small dimension features (e.g., equal to or less than <NUM> microns x <NUM> microns). Additionally, such SE systems may have a limited range of AOI's and not achieve near-Brewster angles for providing high sensitivity for certain metrology applications.

For brevity, the term "AOI" is used herein as a shorthand for the phrase "discrete, narrow range of AOI's. " Similarly, the term "discrete AOI's" is used interchangeably with the term "discrete ranges of AOI's. " Some SE systems may be configured and set up with a single or discrete AOI. However, the SE system generally may not actually generate only a single or discrete AOI, but instead generates a small range of AOI's that are centered around the "selected" single or discrete AOI or includes the "selected" single AOI. In other SE systems, a small narrow range of AOI's may be input as a setup or recipe parameter, as opposed to inputting a single or discrete AOI.

Certain ellipsometry systems provide an ellipsometer for obtaining measurements at simultaneous or sequential multiple angles of incidence (AOI's) and azimuth angles (AZ's), which tends to break these correlations between target characteristics. The ellipsometer tool may also include polarization state generating and polarization state analyzing optical components that are configurable to determine all or a subset of the Mueller matrix elements of the target. The tool may also include a bright light source that is configurable to a wide range of wavelength ranges, including VUV (vacuum ultra violet), visible, near infrared (NIR) and infrared (IR). In certain embodiments, an SE system provides different selectable AOI configurations, including AOI and multiple AOIs, simultaneous and sequential AOI's, configurable polarization states for Mueller matrix ellipsometry, and selectable VUV through NIR wavelength ranges. The illumination side of this system embodiment (as well as other embodiments described herein) may include reflective optics to work with VUV to UV and be broadly color corrected across the entire VUV-IR range.

In certain embodiments, multiple AOI and AZ in a spectroscopic ellipsometry (SE) can be provided to allow improved measurement repeatability and stability by using fixed illumination and collection pupils and fixed illumination and collection field stops. <FIG> is a diagrammatic representation of a spectroscopic ellipsometry (SE) tool <NUM> for collecting light at specific angles of incidence (AOI's). In general, the metrology tool may include illumination optics <NUM> for providing bright illumination light at configurable wavelengths and collection optics <NUM> for detecting light from a target on the sample (sample) <NUM> at discrete, spatially separated, ranges of AOI's (or discrete ranges of AZ's) one at a time or simultaneously. The illumination optics <NUM> and collection optics <NUM> may also be configurable to produce and collect light with various polarization states, including the polarization states for determining the complete or partial Mueller matrix of the target.

As shown, the illumination optics <NUM> includes one or more light sources, e.g., <NUM> for producing an illumination beam. In the illustrated implementation, the one or more illumination sources <NUM> may include one or more broadband sources covering the wavelength range of vacuum UV to near infrared (e.g., about <NUM> to about <NUM>). In one example, the illumination source is a laser sustained (LSP) source for producing high brightness light. One example LSP is an EQ-<NUM> that is commercially available from Energetiq Technology, Inc. , Woburn, Mass. Several LSP embodiments are described in U. Patent Applications: Publication No. <CIT>, and Publication No. <CIT>, which applications are incorporated herein by reference. Other light sources may include solid-state lasers or other types of lasers.

In one example, the one or more light sources also provide at least a peak brightness of <NUM> W/(nm cm<NUM> Sr) for generating simultaneous AOI's in the range of <NUM>-<NUM> degrees. In another aspect, the one or more light sources may provide at least a peak brightness of <NUM> W/(nm cm<NUM> Sr) for wavelengths around <NUM>.

The metrology system may also include a fast feedback to the light source for stabilizing its power and wavelength. Several mechanisms for controlling such LSPs and other broad band light sources are described further in <CIT>, which application is incorporated herein by reference. The light sources may also comprise a Xenon lamp and/or a deuterium lamp.

In another implementation, the light sources are comprised of a plurality of laser diodes formed into different sets of laser diodes that are selectable to cover different ranges of wavelengths, as needed in the particular metrology application. For instance, the laser diode arrays provide wavelength widths that are selectively obtained from the Deep-UV (ultra-violet), UV, VIS (visible), and NIR (near-infrared) range. Several embodiments of laser diode arrays are further described in <CIT>, which application is incorporated herein by reference in its entirety.

The illumination optics <NUM> may also include ellipsometer illumination optics <NUM> for conditioning the illumination beam, including setting aperture and field stop locations and sizes,, and conditioning the illumination beam for a polarizer <NUM>. The ellipsometer illumination optics <NUM> may generally be configured to perform any suitable beam shaping functions, such as manipulating the beam profile, collimating, converging, expanding, reducing, etc..

Polarizer <NUM> may be configurable to rotate for rotating polarizer ellipsometry (RPE) or to be fixed for other types of ellipsometry. The illumination optics may also include an illumination compensator <NUM> in the illumination path in the form of a waveplate (or alternately a photoelastic modulator, acousto-optic modulator, liquid-crystal modulator, or other polarization-sensitive phase modulation device). The illumination compensator <NUM> may be configurable as fixed or rotating, for example, for a rotating compensator ellipsometry (RCE) mode. Rotating this illumination path's compensator <NUM> and/or rotating the polarizer <NUM> allows the polarization state of the illumination beam to be varied. These polarization states can include S and P polarization states, as well as more general polarization states. The polarization states may be selected to perform Mueller matrix based ellipsometry as further described herein.

The polarizer <NUM> and compensator <NUM> may be designed to work with broadband light in the range from VUV to NIR. For example, suitable polarizers include MgF<NUM> Rochon prisms and suitable waveplates include MgF<NUM> and quartz waveplates, as well as other materials depending on wavelength range.

The illumination optics may also include either fixed or movable apertures and/or shutters for discrete AOI or AZ selection. In the illustrated example, mirrors <NUM> and <NUM> are configured to focus the illumination beam on the sample <NUM>, and the apertures <NUM> define one or more ranges of AOI's and/or AZ's that are focused onto the sample <NUM>. For instance, a non-reflective material can be patterned onto a mirror to provide particular reflective type apertures where the non-reflective material is absent.

The aperture element <NUM> contains a set of fixed apertures for providing spatially discrete sets of AOI's or AZ's onto the sample. Alternatively, the aperture element <NUM> may also include a shutter for each aperture so that each set of discrete AOI's or AZ's may be selected independently to illuminate the sample. In another embodiment, the aperture element <NUM> may include one or more movable apertures for selecting different spatially discrete ranges of AOI or AZ. Several configurable apertures are described further in PCT International Application No. <CIT>, which application is incorporated herein by reference in its entirety.

The aperture device can also be in the form of a transmissive aperture element that is arranged so that the illumination light passes through holes of an opaque material or a transmissive type material that is patterned with an opaque material. The illumination beam's rays may then be focused onto the wafer at discrete AOI and AZ, for example, by a transmissive type focusing element. However, a transmissive type aperture element may not work well in VUV to UV.

In either aperture example, the aperture element is arranged at or near the pupil plane and is configured to transmit or reflect illumination rays at particular spatial portions of this pupil plane to result in selected discrete ranges of AOI or AZ. Said in another way, the metrology system may provide discrete selection of ranges of AOI and AZ for the illumination beam simultaneously (e.g., without shutters or movable apertures) or one at a time (e.g., via shutters or movable apertures). For instance, discrete sets of AOI's that each have an AOI range of about equal or less than <NUM>° with at least about <NUM>° of separation between sets, where all of the sets together cover a range between about about <NUM>° and <NUM>°. In one embodiment, at least one of the selectable ranges of AOI includes an AOI that is greater than about <NUM>°. Likewise, discrete ranges of AZ may each have an AZ range of about equal or less than <NUM>° with at least about <NUM>° of separation between sets, where all of the sets cover a range between <NUM>° and <NUM>°.

The detection optics <NUM> may be configurable to collect light from the sample <NUM> at discrete AOI's and AZ's. That is, the detection optics <NUM> are sized so as to collect detected light having a plurality of different AOI's and AZ's from the sample <NUM>. In the illustrated embodiment, mirrors <NUM> and <NUM> collect the illumination beam reflecting off the sample <NUM> and direct the beam towards the detector module <NUM>. Aperture element <NUM> is configured to select different AOI's and AZ's. For instance, one of three different collection apertures may be used to select one of three different AOI sets one at a time, centered on three different AOI's.

Optical elements may then be arranged to analyze the polarization state of light reflected by the sample <NUM>. For instance, a second compensator <NUM> and analyzer <NUM> may be rotated or fixed to different configurations to collect different polarization states. The second compensator may take the form of a waveplate (or alternately a photoelastic modulator, acousto-optic modulator, liquid-crystal modulator, or other polarization-sensitive phase modulation device).

In a rotating polarizer ellipsometry (RPE) mode, only the polarizer is rotating, while other rotatable ellipsometry components (such as an illumination compensator in the illumination path, an analyzer, and a collection compensator in the collection path) remained fixed. Other modes may include RPRC (rotating polarizer, rotating illumination compensator or rotating collection compensator, and a fixed analyzer) mode and RCRC (fixed polarizer, rotating illumination compensator, rotating collection compensator, and fixed analyzer) mode. Other modes may include RCE (fixed polarizer, rotating illumination compensator, and fixed analyzer), RCRC (fixed polarizer, rotating illumination and collection compensators, and fixed analyzer), or a fixed polarizer and rotating analyzer combination. The system may include either an illumination or collection compensator, or the system may exclude both compensators.

Any system embodiments described herein may be configurable for Mueller ellipsometry, where the sample is described by a <NUM>-by-<NUM> matrix, where each of the elements in the matrix is a set of spectra. Any combination of the polarizer <NUM>, the analyzer <NUM>, the first compensator <NUM>, the second compensator <NUM>, and sample <NUM> can rotate during a measurement. Each polarization generating or analyzing optical element may also be rotated at selectable angular frequencies. Different configurations produce different numbers of harmonic spectra, where some produce a sufficient number of harmonic spectra to completely determine the Mueller matrix of the target. Various techniques for performing Mueller Matrix ellipsometry are described further in <CIT>, which patent is incorporated herein by reference in its entirety.

The optical elements positioned between the polarizer <NUM> and analyzer <NUM> may be reflective elements for reflecting the illumination light towards the sample and collecting the output light from the sample. Several different arrangements of reflective optical elements in a spectroscopic ellipsometry tool are further described in <CIT>, which patent is incorporated herein by reference for the purpose of providing further embodiments of various spectroscopic ellipsometry features, such as light sources, optical components for reflectively focusing an illumination beam onto a sample, autofocusing components, polarizer/compensator/analyzer composition and arrangements, reference channel components for generating and detecting a reference illumination beam, control and processor mechanisms, spectrometer/detector arrangements, spectrophotometer system components, etc., which may be utilized with the system embodiments described herein.

The collected light can then be received by detector module <NUM>. In one embodiment, the detector is a spectrometer having sufficiently high quantum efficiency for a wide range of wavelengths. The detector module may include a spectrometer slit, one or more reflecting mirrors for reflecting the output beam through a prism, which is configured to refract different wavelengths in different directions so as to fall along different linear portions of a detector or sensor. Other detector module arrangements are also contemplated. In specific embodiments, the detector can comprise one or more of the following UV-enhanced components: a charged coupled device (CCD) detector with sufficiently high quantum efficiency over wavelength range of about <NUM> to about <NUM>, a photo diode array with sufficiently high quantum efficiency over a wavelength range of about <NUM> to about <NUM>, a photo diode array with sufficiently high quantum efficiency over wavelength range of about <NUM> to about <NUM>. Suitable detectors include charge coupled devices (CCD), CCD arrays, time delay integration (TDI) sensors, TDI sensor arrays, photomultiplier tubes (PMT), and other sensors.

The system <NUM> may also include a controller <NUM>, which comprises any suitable combination of software and hardware and is generally configured to control various components of the metrology system <NUM>. For instance, the controller may control selective activation of the illumination sources <NUM>, illumination polarizer and compensator settings, the detection compensator and analyzer settings, illumination aperture/shutter settings, etc. The controller <NUM> may also receive signal or image data generated by the detector <NUM> and be configured to analyze the resulting signal or image to characterize the target or sample by determining sample parameters or determine whether defects are present on the sample, or characterize defects present on the sample.

The system <NUM> may also include a positioning mechanism <NUM> for rotation, tilt, and/or translation movement of various movable components, such as sample stage, fixed apertures/masks, shutters, polarizer, analyzer, compensator, etc., to different positions. By way of examples, the positioning mechanism <NUM> may include one or more motor mechanisms, such as a screw drive and stepper motor, linear drive with feedback position, band actuator and stepper motor, etc..

The system <NUM>, as well as any system described herein, also preferably includes a purge system for filling a vacuum chamber with nitrogen or any other gas that is suitable for working in vacuum UV. For <NUM> operation, for example, the entire optical path is enclosed with a chamber and such chamber is filled with dry nitrogen gas. Example purge systems and techniques are further described in (i) <CIT> and (ii) <CIT>, which application and patent are incorporated herein by reference for such features.

Each controller described herein may be configured (e.g., with programming instructions) to provide a user interface (e.g., on a computer screen) for displaying resultant test images and other metrology characteristics. The controller may also include one or more input devices (e.g., a keyboard, mouse, joystick) for providing user recipe input, such as selecting wavelength ranges, AOI/AZ, and polarization states of incident light or collected light, as well as detection parameters. The controller typically has one or more processors coupled to input/output ports and one or more memories via appropriate buses or other communication mechanisms.

Because such information and program instructions may be implemented on a specially configured computer system, such a system includes program instructions / computer code for performing various operations described herein that can be stored on a computer readable media. Examples of computer readable media include, but are not limited to, magnetic media such as hard disks, floppy disks, and magnetic tape; optical media such as CD-ROM disks; magneto-optical media such as optical disks; and hardware devices that are specially configured to store and perform program instructions, such as read-only memory devices (ROM) and random access memory (RAM).

It should be noted that the above diagrams and description are not to be construed as a limitation on the specific components of the system and that the system may be embodied in many other forms, limited only by the scope of the appended claims. For example, it is contemplated that the metrology tool may include any number and type of suitable components arranged for determining target features and properties on the sample, limited only by the scope of the appended claims. By way of example, a metrology tool may include one or more components for VUV to NIR, spectroscopic, ellipsometry, reflectometry or scatterometry.

In another example SE tool embodiment, simultaneous wavelength and AOI or AZ resolution is provided to the tool's detector system. <FIG> is a diagrammatic representation of a configurable SE tool <NUM> for simultaneous detection of multiple AOI's. In this example, light at different AOI's or AZ's off the sample <NUM> is collected by the collection optics <NUM> and sent to a detector module <NUM>. In the illustrated embodiment, collection optics <NUM> contains collection mirrors <NUM> and <NUM> for focusing collected light onto dispersion optics and detector module <NUM>. In an alternative embodiment, the detected light is not spatially resolved into discrete AOI's or AZ's.

Any suitable collection side mechanism for mapping wavelength and AOI/AZ onto two different directions, such as orthogonal x and y directions, in a plane may be incorporated into the SE tool. In general, the system <NUM> may include collection optics with different optical power (e.g., cylinder power, toroidal power, etc.) in two different directions, such as x and y directions, for mapping wavelength and AOI (or AZ) across two different directions on a 2D detector. As shown, dispersion optics and detector module <NUM> provide a 2D spectrometer function (expanded and shown as <NUM>) having one axis for AOI/AZ and another axis for wavelength. The dispersion optics may be configured to have power in the wavelength direction that causes the detector to be at or near a plane conjugate to the field stop and have power in the AOI direction to make the detector plane to be at or near conjugate to the pupil plane. Alternatively, AZ may be substituted for AOI in this example.

In the illustrated example, the dispersion optics and detector module <NUM> includes a dispersive element for receiving the detected beam at the spectrometer entrance and conditioning the beam to be received by a detector that maps light as a function of wavelength to a first axis (e.g., in an X direction) and maps the detected light as a function of AOI/AZ to a second axis (e.g., in a Y direction). That is, the dispersive element disperses the detected light's wavelength components onto a first detector axis and disperses the detected light's AOI/AZ components onto a second detector axis, for example, which is orthogonal to the first axis. In a specific implementation, the dispersive element includes a cylinder that is configured to turn a point focus into a line, which is proportional in length to the numerical aperture (NA), and a dispersive element that disperses light into a spectrum. The NA is related to the collected AOI/AZ.

The detector may include any suitable detection mechanisms for detecting light dispersed in two directions, such as a CCD for sensing light at varying wavelength, AOI, and AZ ranges as described herein. The detector may include any suitable number of shift registers for data from selected pixels. For instance, the detector may include two shift registers for parallel processing of light emitted off the sample from two different AOIs. In another example, the detector has more than two shift registers for parallel processing of light emitted off the samples from more than two different AOIs. In yet another example, the detector has as few as one row of pixels per shift register for the AOI direction for a faster readout.

The system <NUM> may also include controller <NUM> that is configured to control any of the components of system <NUM>. For example, controller <NUM> is configured to select wavelengths of one or more illumination sources <NUM>, angular frequency and/or azimuth angles and timing of polarizer <NUM>, illumination compensator <NUM>, analyzer <NUM>, and collection compensator <NUM>, etc. The controller <NUM> may also receive the signal or image generated by the detector and be configured to analyze the resulting signal or image to characterize the sample by determining sample parameters or determine whether defects are present on the sample, or characterize defects present on the sample. The system <NUM> may also include positioning mechanism <NUM> for rotation, tilt, and/or translation movement of various movable components, such as a sample stage, fixed apertures/masks, shutters, polarizer, analyzer, compensator, etc., to different positions.

In certain embodiments, detected light can be converted into digital data corresponding to different AOI's, AZ's, and wavelengths, and this data can be independently analyzed as a function of AOI, AZ, and wavelength (as well as polarization state). The data corresponding to the detected light may be divided so as to correspond to separate regions of the detector corresponding to different AOI's/AZ's and/or wavelengths, and such separated data can then be analyzed as a function of AOI, AZ, and wavelength (as well as polarization state). Certain embodiments allow improved measurement throughput by simultaneously acquiring and processing light signals from different AOIs. An increased illumination NA will allow the target size to be reduced by decreasing the diffraction limited spot size on the target region of the sample. Alternately for a target whose size has not been reduced, this increased NA increases the ratio of detected light coming from within the target area to detected light coming from the surrounding area, reducing signal contamination.

<FIG> is a simplified diagrammatic example of a SE tool <NUM> for simultaneously collecting multiple AOI regions at multiple detectors in accordance with a specific implementation of the present invention. As shown, the tool <NUM> includes light source <NUM> for providing light at a plurality of wavelengths and ellipsometer illumination optics <NUM> for providing different polarization states for the illumination beam directed at sample <NUM>. The ellipsometer illumination optics <NUM> may also be configured to direct the illumination beam at multiple AOI's and may also be configured to direct light at multiple AZ's. The tool <NUM> may also include ellipsometer collection optics <NUM> for collecting light at multiple AOI's (and AZ's) and multiple polarization states. The light source <NUM>, ellipsometer illumination optics <NUM>, and ellipsometer collection optics <NUM> may correspond to any of the various illumination and collection components described herein.

The collection side of the tool <NUM> may also include wavelength and AOI dispersing optics <NUM> for dispersing the collected light in two orthogonal directions according to wavelength and AOI. As shown, the dispersion results <NUM> at plane <NUM> (<NUM>) are illustrated as comprising three different AOI regions <NUM>, <NUM>, and <NUM> on a first vertical axis and wavelength dispersion across all AOI regions on a second horizontal axis. Of course, any suitable number of AOI regions may be defined by dispersing optics <NUM>. The dispersing optics <NUM> may be configured to have different optical power (e.g., cylinder power, toroidal power, etc.) for AOI (and/or AZ) and wavelength dispersion in two different directions as described herein.

The tool <NUM> may also include AOI sub-dividing optics <NUM> for dividing the beam that was dispersed in AOI (or AZ) into different AOI regions by dispersing optics <NUM>. The AOI sub-dividing optics also may be configured to direct each AOI region onto an individual detector (e.g., 314a, 314b, 314c) that resolves wavelength, integrating over one AOI (or AZ) range. If the planes of AOI (or AZ) and wavelength resolution are not sufficiently separated in space, re-imaging optics <NUM> may be placed between those planes to re-image the wavelength resolved plane onto each detector. Each detector may be configured to detect over a wavelength of <NUM> to about <NUM>, and all detectors may be configured to be read simultaneously. Optic <NUM>, <NUM>, and <NUM> and detectors <NUM> may also be configured to collect and/or detect wavelengths in the range <NUM>-<NUM>. For example, Si based detectors may be used for wavelengths less than about <NUM>, while InGaAs based detectors may be used for wavelengths greater than about <NUM>. This SE embodiment allows simultaneous acquisition and processing of light signals from different AOI/AZ's.

The system <NUM> may also include a controller <NUM> that is configured to control various components and analyze detected data. The controller <NUM> may, for example, be similar to the controller <NUM> of <FIG>. Additionally, the controller <NUM> may be configured to control multiple detectors and analyze images and signals obtained by such detectors. The system <NUM> may also include a positioning mechanism <NUM> for translation, rotational, or tilt movement of any of movable components, similar to the positioning mechanism of <FIG> with additional selective positioning of multiple detectors.

An alternative multiple AOI system may comprise apertures for selected AOI at a single detector. <FIG> is a simplified diagrammatic second example of a SE tool <NUM> having a configurable AOI mask <NUM> for selecting an AOI range from among multiple AOI's in accordance with another specific implementation of the present invention. As shown, the wavelength and AOI (and/or AZ) dispersing optics <NUM> are still configured to disperse AOI (or AZ) and wavelength into two different directions (e.g., orthogonal), but wavelengths are dispersed at a plane that is positioned before the plane of AOI/AZ dispersion. That is, the AOI dispersing optics <NUM> of <FIG> may operate similarly to the AOI dispersing optics described with respect to <FIG>, but not disperse wavelength in a same plane as the AOI/AZ dispersal.

An AOI mask <NUM> may be positioned at the plane onto which AOI is dispersed by the dispersing optics <NUM>, and this AOI mask may be configurable to selectively transmit different AOI regions to detector <NUM>. For example, AOI mask <NUM> provides a mechanism for selecting AOI/AZ regions off the sample one AOI/AZ region at a time. View <NUM> shows an example of AOI region selection. In this view <NUM>, AOI region <NUM> is selectively transmitted to detector <NUM> through an aperture of AOI mask <NUM>, while AOI regions <NUM> and <NUM> are blocked by mask portions of AOI mask <NUM> that are opaque to light transmission.

The AOI mask <NUM> may take any suitable form for selecting a specific AOI region. For example, the AOI mask or aperture <NUM> may include a plurality of fixed apertures that each include a shutter to select a different AOI region or may include a single movable aperture (as shown). In the multiple fixed aperture example, each aperture is spatially separated so as to resolve different AOI regions of the sample as described further herein.

The detector <NUM> (and <NUM>) may take any suitable form that detects along at least one direction (for wavelength), such as the 2D detectors described above, or a 1D linear photodiode array. The detector <NUM> (and <NUM>) is preferably located in the wavelength resolving plane. The detector <NUM> may include mask <NUM> defined by the width of the photosensitive area or by a mask integrated into the detector device. In this case, dispersing optics <NUM> disperse wavelength in a same plane as the AOI/AZ dispersal. Also in this case, the detector <NUM> would be moved similarly to mask <NUM> for AOI region selection.

The system <NUM> may also include a controller <NUM> and positioning mechanism <NUM>, which is configured with functions that are similar to any of the controllers and/or positioning mechanisms described herein, with the addition of controlling or moving AOI mask <NUM> and/or detector <NUM>.

An SE metrology tool that provides multiple AOI illumination onto the sample and selective collection of AOI regions one at a time or onto separate detectors without moving the illumination and collection optical paths, such as the systems of <FIG>, <FIG>, and <FIG>, can provide better measurement repeatability and stability due to fixed illumination and collection pupils and fixed illumination and collection field stop, as compared to systems in which the pupils and field stops change for each AOI measurement. System embodiments having a movable field stop, such as the system of <FIG>, can provide a smaller distance of the movement of the apertures near the detector to achieve faster throughput, as compared with systems having moving apertures that are near the collection mirrors, and an associated cost of instability, as compared to a system with no moving apertures. All embodiments with fixed imaging path optics have a throughput advantage over systems that achieve AOI resolution by moving imaging optics.

In another example, a single 2D detector can also be used to simultaneously collect multiple AOI regions. <FIG> illustrates simultaneous collection of multiple AOI/AZ regions on a single detector <NUM> in accordance with an alternative embodiment. In this example, the detector is divided into a plurality of AOI regions, e.g., 372a, 372b, and 372c, which correspond to spatially separated AOI regions that may be simultaneously detected and then analyzed separately. The detector AOI regions can be spatially separated by optically inactive regions, e.g., 374a and 374b, which correspond to optically inactive pixels or signal portions that are not analyzed.

In any of the dispersion embodiments, both AOI and AZ dispersion may occur simultaneously by using a beam splitter to send beams to two 2D detectors, one configured for wavelength and AOI dispersion and the other configured for wavelength and AZ dispersion. <FIG> is a diagrammatic representation of collection side optics <NUM> for simultaneously collecting dispersed AOI and AZ in accordance with one embodiment. As shown, ellipsometer collection optics <NUM> may collect light at multiple AOI and AZ from the sample and direct such output to splitter <NUM>. The splitter directs the output light to wavelength and AOI dispersing optics <NUM> and wavelength and AZ optics <NUM>.

The AOI dispersing optics <NUM> are configured to disperse wavelength and AOI along two directions in the same or a different plane. The dispersed wavelength and AOI are received by wavelength and AOI detector module <NUM>, which may be configured for simultaneously or sequentially detecting spatially separated AOI regions that each have dispersed wavelength as described above. Similarly, dispersed wavelength and AZ may be received by a wavelength and AZ detector module <NUM>, which is configured for simultaneously or sequentially detecting spatially separated AZ regions that each have dispersed wavelength.

<FIG> is a diagrammatic representation of configurable SE tool <NUM> with a single or a plurality of apodizers <NUM> and/or <NUM> in accordance with another embodiment of the present invention. In one arrangement, a single, non-moving apodizer <NUM> is placed at or near the illumination pupil configured for shaping the illumination beam and controlling the point spread function of the focus at the sample <NUM> for all selected AOI's (or AZ's). In another arrangement, one or more movable apodizers <NUM> may be moved in and out of the illumination pupil and generally configured for shaping the illumination beam and controlling the point spread function of the focus at the sample <NUM> for different selected AOI's (or AZ's). For instance, each selected apodizer may be configured to control the spot size for a specific set of AOI's (or AZ's). In a specific example, each apodizer is configured to shape the illumination light for a particular AOI such that the irradiance level for a spot position farther than <NUM> microns from the center of the spot is less than <NUM>-<NUM> of the peak irradiance at the center of the spot. For instance, each selected apodizer may be configured to suppress side lobes and improve measurement box size in the sample wafer plane to reduce contamination in the measured signals at the particular selected AOI's (or AZ's).

In another embodiment, one or more collection apodizers <NUM> may be located or movable to a position at or near a plane that is conjugate to a collection pupil. Such collection side apodizers may provide predefined collection profiles corresponding to all of the discrete ranges of AOI and/or AZ. A collection side apodizer may control diffraction side lobes from the hard-edged collection apertures. For example, such collection apodizer may be configured to shape the intensity distribution incident on the spectrometer slit in a similar way that the illumination apodizer shapes the intensity distribution at the wafer sample. Such collection apodizer could also be configured to reduce contamination from outside the measurement box and provide fine grained control of the spot at the spectrometer.

In the illustrated example, different collection apertures are used for different AOI collection so that the spot at the slit will be different for the different AOIs, while the slit is the same for each AOI range. In this arrangement, a collection apodizer that is configured for the particular AOI that is being used may be helpful for adjusting the spot for the particular AOI. This collection apodizer preferably is placed at or near the plane of the collection aperture, but it is conceivable that the apodizer could be placed downstream as well. In a specific implementation, the number of apodizers corresponds to the number of collection apertures, and a selected apodizers can be moved into the collection path, for example, in direction <NUM>. Alternatively, a dynamically configurable single apodizer may be used and located in the collection path.

Apodization can be generally defined as altering the light distribution in the entrance pupil of an optical system (e.g., using a mask to alter the amplitude and/or phase of the illumination beam) thereby changing the intensity profile of the illumination beam. In the present case, each apodizer may be configured to reduce irradiance in the "tails" of the illumination spot (e.g., portions of the illumination spot greater than <NUM> microns from the center of the illumination spot) to less than <NUM>-<NUM> of the peak irradiance) thereby reducing signal contamination. Including such an apodizer in any of the metrology systems described herein is one of the features that may enable metrology using relatively small spot sizes on relatively small targets.

Transmissive type apodizers, such as fused silica, may work for wavelengths down to about <NUM>. In general, an apodizer may be manufactured using standard lithography reticle/mask blanks, which are optimized for <NUM>. Reflective apodizers are also contemplated.

In general, each apodizer design may be tailored to each particular set of selectable illumination-side AOI's (or AZ's) and is movable into the illumination beam path so as to control a spot size for each particular set of AOI's (or AZ's). That is, these apodizer embodiments may each possess an optical function that cannot be reconfigured. In addition, the set of apodizers <NUM> may include apodizers that are also configured for specific targets under test. For example, different illumination amplitude profiles may be achieved, even with the same AOI's. Besides the system of <FIG>, any of the system embodiments described herein, may also include configurable apodizers.

The system <NUM> of <FIG> includes a scanning mirror arrangement, such as scanning mirror <NUM>, for scanning an illumination beam through different AOI's onto the sample <NUM>. The scanning mirror is preferably in or near a plane conjugate to the sample <NUM>. The scanning mirror <NUM> may replace the polarizer slit or may be conjugate to the polarizer slit. If the scanning mirror replaces the polarizer slit, it may contain a mask to define the illumination field stop. If the scanning mirror is conjugate to the polarizer slit, additional imaging optics may be present between the polarizer slit and the scanning mirror. Scanning mirror <NUM> can replace a movable, fixed aperture (e.g., as described above) to selectively scan the illumination beam at different AOI's (or AZ's). The scanning mirror <NUM> may be configurably moved (e.g., translated, tilted, or rotated) by any suitable positioning mechanism so as to select a particular AOI (or AZs) one at a time. In the illustrated example, scanning mirror <NUM> tilts in direction <NUM> so that the illumination beam is scanned through a particular range of AOI's (or AZ's). That is, scanning mirror <NUM> causes the illumination to walk along different AOI positions in the pupil plane without moving the illumination spot at the sample <NUM>.

Scanning mirror <NUM> is reflective so as to work with a wide range of wavelengths. A reflective scanning mirror <NUM> allows the illumination beam to have a broad range of wavelengths, including VUV light that requires reflective optical elements.

A fixed mirror <NUM> may be used to direct the scanned illumination beam that is reflected from scanning mirror <NUM>. Alternatively, multiple mirrors may be used to direct different AOI's towards the sample <NUM>.

Illumination optics <NUM> may be configured for optimally directing the illumination light at different AOI's (or AZ's) on the sample <NUM>. For instance, mirrors <NUM> and <NUM> direct and focus illumination beams from a particular set of AOI's (or AZ's) onto the sample <NUM>. In one example, the mirrors <NUM> and <NUM> are sized to direct all of the light from <NUM>° to <NUM>° onto the sample <NUM>.

Similar to other embodiments, an arrangement of fixed or movable apertures <NUM> and/or shutters may be used to selectively collect light at different AOI's (or AZ's). Apertures/Shutters <NUM> may be configurable to select an AOI one at a time if needed.

The illumination optics <NUM> and collection optics <NUM> may include components for generating and/or collecting different polarization states (e.g., polarizer <NUM>, compensators <NUM> and <NUM>, and analyzer <NUM>).

The controller <NUM> and/or positioning mechanism <NUM> may be configured to control any of the components of system <NUM>. For example, controller <NUM> and/or positioning mechanism <NUM> are configured to select wavelengths of one or more illumination sources <NUM>, tilt position of tilt mirror <NUM>, angular frequency and/or azimuth angles and timing of polarizer <NUM>, illumination compensator <NUM>, collection compensator <NUM>, and analyzer <NUM>, position of each apodizer <NUM>, settings for illumination and/or collection shutters, position of movable apertures, etc..

In most of the embodiments and examples described herein, an amplitude apodizer may be used in the illumination path to suppress side lobes and improve measurement box size in the wafer plane and reduce contamination in the measured signals. Although a single configurable apodizer or a set of movable apodizers can provide suitable amplitude apodization for a particular set of AOI's (or AZ's), such an apodizer system may not be easily altered to change the apodizer pattern. Additionally, this arrangement may be associated with slow switching and hardware repeatability issues. 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, for example, based on MEMS SLM technology, can be switched very quickly without affecting the alignment of the system.

<FIG> is a diagrammatic representation of configurable SE tool <NUM> with dynamically adjustable apodizers in accordance with an alternative embodiment of the present invention. This system includes a reflective dynamically configurable apodizer element <NUM> in the illumination path on which an apodizing pattern is dynamically formed for each particular selected AOI, AZ and NA of the illumination and collection optics. This dynamically configurable apodizer <NUM> is preferably reflective so as to work with a broadband range, including VUV to UV. As shown, the reflective optical element <NUM> may be arranged to receive illumination light <NUM> from rotating compensator <NUM> via illumination slit <NUM>.

As described above, various illumination mechanisms may be used to select particular AOI's (and AZ's) and various collection mechanisms may be used to collect particular AOI's (and AZ's). The dynamically adjustable apodizer element <NUM> is configured to dynamically adjust the amplitude and/or phase of the illumination light based on the selected AOI (and AZ) of the illumination and collection optics. In certain embodiments, the illumination beam may be passed through a scanning mirror and/or one or more fixed or movable apertures and/or shutters, which are configured to select one or more spatially separated AOI's (AZ's), prior to reaching the apodizer element <NUM>. Alternatively, the dynamic apodizer element <NUM> is positioned before such AOI (or AZ) selection mechanisms. The dynamic apodizer element <NUM> is preferably placed at or near a pupil plane. Alternatively, the dynamic apodizer element <NUM> can be located at or near the collection pupil. Alternatively, the dynamic apodizer elements <NUM> can be located at or near both illumination and collection pupils. A collection side apodizer configuration can control the spot shape at the detector slit, for example. This type of apodization may reduce outside-of-the-box contamination that is received by the detector and may also have improved resolution (or PSF) of the detector. Additionally or alternatively, different AOI's (or AZ's) may be collected by fixed or movable apertures and/or shutters and the like.

In a specific implementation the variable apodizer <NUM> is formed from a spatial light modulator (SLM) that is configurable to control amplitude reflectance distribution across the area of the apodizer <NUM>. One suitable SLM is a micro-electro-mechanical systems (MEMS) SLM. Example SLM type devices include DLP (digital light processing) devices available from Texas Instruments of Dallas, TX and SLM devices from Fraunhofer Institute of Munich, Germany.

As in the case of a DLP device, the apodization pattern may be a binary amplitude pattern, where the effective (continuous) reflectance pattern is obtained by integrating over a number of pixels. The proportion of pixels in the local region reflecting light into the illumination optics gives the desired local apodization level. A spatial filtering aperture may be used downstream from the DLP SLM to block light reflected away from the illumination optics and filter out diffraction from the periodic structure of the DLP SLM. This aperture may be incorporated into the aperture of the focusing optics themselves.

In another SLM implementation, the apodizing pattern may be continuously variable. However, a continuously variable amplitude distribution may be achieved by encoding the pattern in a phase distribution produced by the SLM. To get the resulting desired amplitude pattern the light must be Fourier filtered using an aperture, which may be incorporated in the focusing optics of the system.

The system <NUM> may also include a controller and/or positioning mechanism (not shown), similar to the any of the above described controllers and/or positioning mechanisms with the addition of controlling dynamic apodizer <NUM>.

In certain embodiments described herein, fixed or movable apertures may be used to select particular AOI's (or AZ's) in the illumination beam directed towards the sample or the collected beam collected from the sample. <FIG> is a diagrammatic side view of an example aperture system <NUM> in accordance with one implementation. As shown, the aperture system <NUM> may include a reflective substrate <NUM> upon which a mask is formed. The mask is formed from absorptive or nonreflecting regions (e.g., 504a, 504b, and 504c) with holes/vias formed therein (e.g., 506a, 506b, and 506c). Example absorptive or non-reflective materials may include metal sheet or foil materials, such as stainless steel or aluminum, and black anodized materials. These holes may be filled with transparent material or left unfilled. Shutters (e.g., 508a, 508b, and 508c) may be placed or affixed over each mask aperture <NUM>. The entire aperture system <NUM> may also be movable, for example, in direction <NUM> so as to position apertures in the illumination or collection path as described further herein.

The shutters may be opened or closed so as to allow incident light to be reflected at particular AOI's (or AZ's). As shown, shutter 508b is closed to block ray 510b, while shutters 508a and 508c are open so as to allow ray 510a to be reflected as ray 512a at a first selected AOI (or AZ) and ray 510c to be reflected as ray 512c at a second selected AOI (or AZ), respectively from the reflected substrate <NUM>.

<FIG> is a diagrammatic side view of an example aperture system <NUM> in accordance with second implementation. This aperture system <NUM> does not include shutters and is movable along direction <NUM> for positioning fixed apertures (e.g., 554a, 554b, and 554c), which are formed in absorptive or nonreflecting mask material (e.g., 556a, 556b, and 556c). The apertures can be positioned in the illumination or collection path at particular AOI (or AZ) positions. As shown, ray 560a is reflected as a ray 562a at a first selected AOI; ray 560b is reflected as a ray 562b at a second selected AOI; and ray 560c is reflected as a ray 562c at a third selected AOI.

Any of the system embodiments may include a transmissive illumination selector for selectively applying an aperture to each of a plurality of pupil positions so as to select particular sets of AOI's (or AZ's) as described herein. However, this illumination selector may be applied only to wavelengths that can be transmitted, as opposed to reflected. In general, the illumination selector is configured to allow a ray bundle to individually pass through each position of the pupil and result in individual ranges of AOI/AZ. <FIG> is diagrammatic perspective view of an illumination selector in accordance with one embodiment of the present invention. In this example, the illumination selector comprises three apertures disks <NUM>, <NUM>, and <NUM>. Each aperture disk includes a plurality of different aperture configurations (e.g., aperture configurations 608a and 608b for disk <NUM>, aperture configuration 610a for disk <NUM>, and aperture configurations 612a, 612b, and 612c for disk <NUM>). A particular aperture configuration for receiving the incident beam (or ray bundles) <NUM> can be selected for each disk and then the three selected aperture configurations from the three disks can then be overlaid to result in a diverse number of aperture settings and resulting illumination pupil profiles.

In general, each aperture configuration of each disk includes at least one transparent portion and may also include one or more opaque regions. For example, the transparent portions can be formed from any suitable transparent materials, such as glass, quartz, fused silica, etc., or each transparent region can merely be devoid of material so 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 at the pupil plane, and each opaque portion is generally formed from an opaque material, such as chrome, molybdenum silicide (MoSi), tantalum silicide, tungsten silicide, opaque MoSi on glass (OMOG), etc. A polysilicon film may also be added between the opaque layer and transparent substrate to improve adhesion. A low reflective film, such as molybdenum oxide (MoO<NUM>), tungsten oxide (WO<NUM>), titanium oxide (TiO<NUM>), or chromium oxide (CrO<NUM>) may be formed over the opaque material. The shape of each aperture's transparent portion may be any suitable shape, such as rectangular, circular, elliptical, an lhcscreen (superposition of a circle and rectangle), marguerite (two lhcscreens, one rotated by <NUM>°), rectellipse (superposition of an ellipse and rectangle), racetrack, etc..

In general, an aperture configuration produces a particular incident beam profile or set of AOI's and AZ's. In a specific example, Source Mask Optimization (SMO) or any pixelated illumination technique may be implemented. In the illustrated embodiment, each aperture configuration covers the entire illumination pupil area and is centered on the optical axis. However, an aperture configuration may alternatively be placed in a portion of the pupil area or at some other point (not pupil plane) along the optical path of the incident beam.

<FIG> illustrates combining three aperture configurations to achieve a second example of an aperture configuration. The size of the transparent portions are exaggerated for simplicity. In this example, the first aperture configuration 610a is totally transparent over the entire pupil area. The second aperture configuration 608b has a transparent vertical transparent strip <NUM> surrounded by opaque portions <NUM> and <NUM>. The third aperture configuration 612b has a horizontal transparent strip <NUM> surrounded by opaque portions <NUM> and <NUM>. The resulting aperture configuration <NUM> has a square transparent portion <NUM> surrounded by opaque portion <NUM>, which can be configured to select a particular set of AOI's.

<FIG> is a diagrammatic representation of configurable metrology tool <NUM> having off-axis parabolic (OAP) mirrors. This system <NUM> includes an off-axis parabolic mirror (OAP) 710a in the illumination side <NUM> used in conjunction with a movable translation mirror <NUM> to select multiple AOI's (e.g., from the illumination beam received from reflecting mirror 722a) to move from positions 712a and 712b, by way of example. In general, the movable illumination mirror <NUM> can be displaced, for example, along direction (e.g., 714a) to cause the illumination beam to be reflected off the illumination OAP 710a so as to achieve a particular set of AOI's based on the position on the curve of the OAP from which the illumination beam is reflected. In the illustrated embodiment, two different illumination translation mirror positions 712a and 712b are shown for sequentially achieving two different spatially separated AOI's one at a time on the sample <NUM>, although more mirror positions (configured to cause the illumination beam to reflect from different areas of the OAP's curve) may be used to achieve more AOI's.

The collection optics <NUM> of the system <NUM> may include corresponding collection OAP mirror 710b that is arranged to collect the output beams at the selected AOI's from the sample <NUM> and corresponding collection translating mirror <NUM> that is configurable to move to a plurality of positions (e.g., 713a and 713b) in direction 714b, for example, to receive these output beams at the selected AOI's one at a time from the collection OAP 710b. The collection optics <NUM> may also include any suitable optic elements (e.g., convex mirror <NUM> and reflecting mirrors 722b) for directing the output beams (e.g., collimated beam <NUM>) to detector <NUM>.

In another aspect, the translation mirrors (<NUM> and <NUM>) and the OAP mirrors (710a and 710b) may be configured for supporting a large range of AOI's (up to near grazing incidence). That is, the translation and OAP mirrors may be configured for selecting AOI's over a continuous range.

The controller <NUM> and/or positioning mechanism <NUM> may be configured to control any of the components of system <NUM>. For example, controller <NUM> and/or positioning mechanism <NUM> are configured to select wavelengths of one or more illumination sources <NUM>, angular frequency and/or azimuth angles and timing of polarizer <NUM>, illumination compensator <NUM>, analyzer <NUM>, and collection compensator <NUM>, translation movement of each translating mirror <NUM> and <NUM>, rotation of OAP mirrors, etc..

<FIG> illustrates a dual-pass metrology tool <NUM> having off-axis parabolic (OAP) mirrors. This system <NUM> includes an off-axis parabolic mirror (OAP) <NUM> used in conjunction with a movable translation mirror <NUM> to select multiple AOI's (e.g., from the illumination beam received from beam splitter <NUM>) to move from positions 762a and 762b, by way of example. In general, the movable illumination mirror <NUM> can be displaced, for example, along direction (e.g., <NUM>) to cause the illumination beam to be reflected off the illumination OAP <NUM> so as to achieve a particular set of AOI's based on the position on the curve of the OAP from which the illumination beam is reflected. This movement will cause the output beam emanating from the sample <NUM> to change its position on a spherical mirror <NUM>, but be returned to the sampling point after its reflection on this spherical surface <NUM>. A second output beam emanates from the sample <NUM> in response to this returned beam from the spherical mirror <NUM> and sample's scanned target characteristics. The second output beam may then be collected by OAP mirror <NUM>, translating mirror at position 762a or position 762b, and beam splitter <NUM> and directed to a detector (not shown).

As shown in <FIG>, positioning mechanism <NUM>, in conjunction with a controller <NUM> may be configured to provide tip/tilt the sample <NUM> or the surface that needs to be tested around the measurement point <NUM>. For instance, a continuous or sequential scanning of the AOI and AZ can be realized by tipping/tilting of the sample via the positioning mechanism <NUM>. This movement will cause the output beam emanating from the sample <NUM> to change its position on a spherical mirror <NUM>, but be returned to the sampling point after its reflection on this spherical surface <NUM>. A second output beam emanates from the sample <NUM> in response to this returned beam from the spherical mirror <NUM> and sample's scanned target characteristics. The second output beam may then be collected by OAP mirror <NUM>, mirror <NUM>, which in this embodiment is fixed, and beam splitter <NUM> and directed to a detector (not shown). In this embodiment, the translation mirror <NUM> remains in a fixed position while the wafer is tilted.

The multiple AOI and AZ system embodiments described herein may also be configured for bright field operation where the collection side samples the 0th order light off the sample, dark field operation where the collection arm samples non-0th order light off the sample. In one arrangement, a set of spatially separated illumination apertures and another set of spatially separated collection apertures are arranged for selecting between bright field and dark field operations. In the brightfield operation the collection side samples the same AOI's (AZ's) of illumination light off the sample. In the dark field operation, the collection side samples different AOI's (AZ's) than the illumination light off the sample.

In any of these multiple AOI (or AZ) systems, the illumination optics can be configured for producing multiple illuminations beams that are separated in the Azimuth direction on the wafer, such as zero to <NUM> degrees are covered simultaneously. This system may have a set of spatially separated detectors capable of receiving separate optical beams, and illumination and collection optics supporting multiple AOIs and multiple AZs for each beam.

Any suitable metrology processes may be implemented with the systems described herein. <FIG> is a flow chart illustrating a SE metrology procedure <NUM>. Initially, illumination light at multiple wavelengths (e.g., VUV to IR) may be generated in operation <NUM>. One or more polarization states for this illumination light may be selected in operation <NUM>. One or more ranges of AOI and/or AZ for the illumination light may also be selected in operation <NUM>. The illumination light may also be shaped and directed to form a small spot on a target of a wafer, by way of example, in operation <NUM>.

An output beam emanating from the wafer in response to the illumination beam may then be collected in operation <NUM>. One or more AOI's or AZ's for collecting the output beam may also be selected in operation <NUM>. One or more polarization states may also be selected in operation <NUM>. The output beam may then be detected and used to generate a signal or image in operation <NUM>. The generated signal or image may then be analyzed to determine a characteristic of the target on the wafer in operation <NUM>. For instance, the simulated output signal/image from a model for different target characteristics and different illumination characteristics (e.g., polarization state, wavelength, AOI, and AZ) may be compared to the generated signal/image to determine the corresponding target characteristic.

Example sample parameters that can be determined based on one or more detected signals or images include critical dimension (CD) , film thickness, metal gate recess, high k recess, side wall angle, step height, pitch walking, trench and contact profile, overlay, material properties (e.g., material composition, refractive index, stress on critical films, including ultra-thin diffusion layers, ultra-thin gate oxides, advanced photoresists, <NUM> ARC layers, ultra-thin multi-layer stacks, CVD layers, and advance high-k metal gate (HKMG), ultra-thin decoupled plasma nitridation (DPN) process layers, stress on noncritical films, including inter-dielectrics, photoresists, bottom anti-reflective coatings, thick oxides and nitrides, and back end of line layers), semiconductor manufacturing process parameters (e.g. focus and dose for scanners, etch rate for etching tools), etc..

Claim 1:
An ellipsometer apparatus (<NUM>) for performing metrology of a semiconductor sample (<NUM>), comprising:
one or more bright light sources (<NUM>) for providing an illumination beam at a plurality of wavelengths that are selectable within a range from a vacuum ultraviolet (VUV) wavelength to an infrared (IR) wavelength;
illumination optics (<NUM>) for directing the illumination beam towards a sample at a plurality of selectable ranges of angles of incidence (AOI) and/or azimuth angle (AZ) and a plurality of polarization states to provide spectroscopic ellipsometry metrology, wherein the illumination optics comprise at least one apodizer (<NUM>) for controlling a spot size of an illumination spot of the illumination beam on the sample at each of the selectable sets of AOI's and/or AZ's ;
collection optics (<NUM>) for directing an output beam, which is emanating from the sample in response to the illumination beam, at each of the selectable sets of AOI's and/or AZ's and polarization states towards a detector (<NUM>);
the detector (<NUM>) for generating an output signal or image based on the output beam; and
a controller (<NUM>) for characterizing a feature of the sample or detecting defects based on the output signal or image as a function of wavelength, AOI and/or AZ, and/or polarization state;
characterized in that
the illumination optics comprises a scanning mirror (<NUM>) for scanning the illumination beam on the sample at each of the selectable sets of AOI's or AZ's and the collection optics comprises an AOI/AZ selector for resolving the selected sets of AOI's or AZ's one at a time.