Snapshot ellipsometer

Abstract

A snapshot ellipsometer or polarimeter does not require a time-modulating element to measure a sample, but instead uses one or more spatially varying compensators (e.g., microretarder arrays and compound prisms) to vary the polarization state within a measurement beam of electromagnetic radiation. Analysis of the intensity profile of the beam after interaction with the spatially varying compensator and the sample allows for characterization of sample parameters without any moving optics.

Description

Technical Field

[0001] The present invention relates to systems such as ellipsometers for measuring the optical properties and physical parameters of samples. More particularly, the present invention relates to a spectroscopic ellipsometer that characterizes a sample by spatially varying the polarization state of a measurement beam.

Background Art

[0002] In traditional polarization analysis methods (ellipsometry), the polarization state of an electromagnetic radiation beam is modulated and / or analyzed by changing at least one polarization state parameter as a function of time. A rotating optical ellipsometer linearly changes the azimuthal position of at least one optical element by rotating the element. Each rotating element induces a time modulation in the signal intensity at a frequency related to the rotation rate of the optical system. In the initial development, a rotating analyzer or polarizer was used that could not measure the sign of the phase change (Δ) caused by the sample. In subsequent improvements, a rotating compensator was utilized to provide sensitivity to this parameter. Another type of ellipsometer uses a photoelastic modulator that changes the retardance of the optical system as a function of time, typically sinusoidally, by applying a voltage to a piezoelectric transducer that induces stress in a photoelastic crystal. This stress results in a change in birefringence within the crystal, which results in a retardation (phase shift) in the measurement beam. In each of the above types of ellipsometers, the time modulation in the signal intensity is analyzed to determine the optical properties of the sample.

[0003] Generally, elements such as rotary compensators and photoelastic modulators have several drawbacks. Since polarization modulation is a function of time, multiple measurement frames must be captured to fully describe the polarization state of the beam. For this reason, the measurement speed of time-modulated ellipsometers is, in principle, limited by its hardware. As in the coating process, it is advantageous to complete the measurement using a stationary optical system in order to move or rapidly change the sample. Also, a stationary-element ellipsometer can potentially be more stable, simpler, and more compact than a time-modulated system.

[0004] To overcome the limitations of prior art ellipsometers, several designs for systems that eliminate the use of time modulation of the detected beam have been proposed. Channelized ellipsometers and polarimeters encode information regarding the polarization state of the beam onto the same dimension of a detector where spectral or spatial information is utilized. In spectral channelized ellipsometry, this is achieved using multiple retarders. Retarders have a strong wavelength-dependent polarization effect, thereby generating strong modulation patterns at higher frequencies within the spectral intensity profile. Similarly, a spatially channelized system modulates the intensity along one or both dimensions of the image plane by imaging a spatially varying optical system such as a wedged retarder. Systems that utilize this approach have the potential to simultaneously capture a lot of information about the spectral, polarization, and spatial components of the beam, as described in Patent Document 1 by Oka et al. The main drawback of channelized systems is that the information associated with each variable must be separated. In many prior arts, this is achieved by Fourier transforming the obtained intensity information to extract the characteristic frequencies of the individual causes of the modulation. Some drawbacks of this technique include more complex signal processing, increased noise, and reduced resolution.

[0005] The snapshot ellipsometer and polarimeter can provide the advantages of a stationary optical system without the drawbacks of a channelized system. In a snapshot system, spatial modulation of the signal is induced by imaging spatially varying optical elements onto the dedicated dimension of a multi-element detector. When a two-dimensional detector is used, the other dimension can be used to capture information related to the spectral, angular, or spatial characteristics of the sample or beam. In the case of snapshot spectroscopic ellipsometry, additional elements spectrally separate the electromagnetic radiation along the dimension of the orthogonal detector and enable complete characterization of the polarization state and spectral profile of the beam in a single-frame capture of the detector. Since the spectral separation and polarization modulation directions are independent, signal processing is simple and similar to traditional polarization analysis techniques. In the case of a two-dimensional detector, the other dimension can be used to capture information related to the spectral, angular, or spatial characteristics of the sample or beam. In snapshot spectroscopic ellipsometry, additional elements spectrally separate the electromagnetic radiation along the dimension of the orthogonal detector and enable complete characterization of the polarization state and spectral profile of the beam in a single-frame capture of the detector. Since the spectral separation and polarization modulation directions are independent, signal processing is simple and similar to traditional polarization analysis techniques.

[0006] Mueller-Stokes calculations are used to represent the polarization changes produced by each element within the optical train of the ellipsometer. The polarization state of electromagnetic radiation is represented by a Stokes vector, and each element is described by a Mueller matrix that describes the polarization effect of the optical system.

[0007] The Mueller-Stokes descriptions for some common polarization elements are given as follows.

[0008] Unpolarized light is characterized by an intensity I and is described by the following Stokes vector:

[0009]

Number

[0010] The following matrix converts the Stokes vector representing a polarized beam into a scalar representation of the intensity on the detector.

[0011]

Number

[0012] A polarizer is an element having a characteristic axis through which only electromagnetic radiation having polarization oriented along the axis passes.

[0013]

Number

[0014] An analyzer is a polarizer that exists after the sample in an ellipsometry system. The Mueller matrix describing the analyzer is identical to that of the polarizer.

[0015]

Number

[0016] A compensator acts by retarding one component of a transverse electromagnetic wave with respect to its orthogonal component. This effect is described by the following equation when the retardance (d) is a function of the extraordinary and ordinary refractive indices (n e , n0) of a birefringent crystal and the thickness (T) of the material through which electromagnetic radiation of wavelength (λ) propagates.

[0017]

Number

[0018] [[ID=4*]]The Mueller matrix describing a general compensator is as follows:

[0019]

Number

[0020] For any element having a characteristic polarization axis, such as a polarizer or a compensator, a rotation matrix is used to describe the azimuthal position (θ) of the element with respect to the plane of incidence.

[0021] [Number]

[0022] The most common mathematical description of a sample is a Mueller matrix consisting of 16 elements that can completely describe any change in the polarization state of the beam caused by the sample.

[0023] [Number]

[0024] In conventional ellipsometry, the polarization change caused by a sample was described by two parameters ψ and Δ, but this notation is insufficient to describe a partially polarized beam or a depolarizing sample.

[0025] [Number]

[0026] An alternative notation can be used to completely describe an isotropic sample and a partially polarized beam. The isotropic quantities are related and can be substituted into the previous matrix as follows:

[0027] [Number]

[0028] [Number]

[0029] The notations for N, C, and S are advantageous as they provide a simple relationship for depolarization. Depolarization is defined as the conversion of completely polarized electromagnetic radiation to partially polarized electromagnetic radiation and can be expressed for an isotropic sample as follows:

[0030]

Number

[0031] Polarization cancellation can be caused by various factors, including surface electromagnetic radiation scattering, sample inhomogeneity, spectrometer bandwidth resolution, angular spread from non-parallel input beams, and incoherent addition of electromagnetic radiation reflected from the back surface of the substrate. Polarization cancellation measurements can help identify non-idealities in the sample or system.

[0032] One of the most common elements used in prior art snapshot ellipsometers is a wedge of a birefringent crystal. Since the retardance of the compensator is proportional to its thickness, a birefringent optical system with spatially varying thickness has different values of retardance at different positions. Since different parts of the measurement beam interact with different parts of the optical system, the polarization state of the measurement beam is spatially modulated.

[0033] The simplest example of such an optical system is a linear wedge made of a birefringent crystal. The thickness T of such a wedge can be described as a function of the spatial position x along the direction of variation, where the rate of change is defined by the slope w of the wedge.

[0034]

Number

[0035] Substituting the thickness of the wedge into the general retardance equation, the retardance across the wedge can be described as a function of spatial position.

[0036]

Number

[0037] The new term D is defined to represent the rate of change of retardance.

[0038]

Number

[0039] The Mueller matrix description of a wedge-shaped birefringent crystal is the same as that of a standard compensator, and the spatial retardance is defined by d(x).

[0040]

Number

[0041] Any optical system having birefringence and variable thickness spatially modulates the polarization state of the beam incident thereon, and the term "wedge" is used herein to describe any optical system having such thickness variations, without specifically defining that the thickness varies linearly or continuously as in the above example. An optical system showing a discrete stepped thickness profile, or an optically non-linearly varying system, can be readily replaced by one skilled in the art.

[0042] A common variant of the linear wedge retarder as described above is the Babinet compensator. The Babinet compensator is an assembly of two equal wedge-shaped crystals of uniaxial anisotropic material. The wedges are oriented such that, as illustrated in Fig. 3(B), the two wedge faces are in contact or have a small gap therebetween, are parallel to each other and perpendicular to the incident beam. The optical axes of the two wedges are perpendicular to each other and to the beam.

[0043] The Mueller matrix describing the Babinet compensator can be defined by the matrix multiplication of two-component wedges with optical axes W1 and W2:

[0044]

Number

[0045] Since the gradients of the two wedges are equal and opposite, the retardance rates are defined as B for the first wedge and -B for the second wedge.

[0046]

Number

[0047] This matrix is clearly equivalent to a single wedge matrix having a retardance change rate twice that of the constituent wedges. Thus, it will be apparent to those skilled in the art that if it is recognized that the Babinet compensator produces the same polarization modulation as a single wedge having a different tilt, the birefringent wedges can be replaced by a combination of wedges to produce a spatial modulation of the polarization state within the beam. The advantage of the Babinet compensator is that the retardance near the center of the optical system is of the zero order, and when the beam passes through it, it is less susceptible to polarization and separation. Therefore, the term "wedge" is further understood to refer to both the individual wedges used to affect the spatially varying retardance for a beam along one azimuth angle, and combinations of wedges or optical systems such as the Babinet compensator.

[0048] Patent Document 2 by Fluckiger et al. describes an ellipsometer that uses a single wedge to impart a spatially varying retardance to a beam. The ellipsometer system described by Fluckiger was novel in its implementation, but it could not detect all the sample parameters for describing isotropic samples and was severely limited in the measurement of anisotropic samples. For the above reasons, Fluckiger specified that the Babinet compensator was preferred over a single wedge.

[0049] Using the matrix defined above, the spatially varying signal intensity of a single wedge system can be represented by the following matrix multiplication:

[0050]

Number

[0051] The polarizer and the analyzer need to be arranged in the wedge's non - eigen - polarization state for each measurement. Assuming an isotropic sample and setting the azimuth angles of the polarizer and the analyzer to 45°, the spatial variation of the beam intensity can be expressed as follows:

[0052]

Number

[0053] The Fourier transform of the signal along the axis of variation on the detector decomposes the equation into components that occur at different spatial frequencies into.

[0054]

Number

[0055] The real part (α k ) and the imaginary part (β k ) of the Fourier coefficients are non - zero at a specific frequency k related to the spatial variation of the compensator. The Fourier transform of the theoretical intensity equation identifies a single - harmonic frequency (k = 2D) and a DC (k = 0) term. The theoretical Fourier coefficients are related to the sample parameters as follows:

[0056]

Number

[0057] Solving for the sample parameters using the theoretical formula for the Fourier coefficients, it is clear that a snapshot ellipsometer using a single wedge can measure only two sample parameters in any single measurement, as shown in the following Mueller matrix description of the sample (X indicates insensitivity to the parameter).

[0058]

Number

[0059] Therefore, a single wedge system can only measure two out of the three sample parameters simultaneously, and thus cannot fully characterize an isotropic sample. When measuring a sample with psi (ψ) near 45° as arranged, the systematic error and noise in the measurement data are amplified. For a single wedge system, all arrangements of the polarization optical system result in amplified errors in ψ (Psi) and Δ (Delta) for a specific sample type.

[0060] In addition to the U.S. patents by Oka et al. (Patent Document 1) and Fluckiger et al. (Patent Document 2) already mentioned, they are disclosed and additional patents have been identified. For convenience, all known prior art patents are presented and directly and briefly explained.

[0061] Patent Document 2 by Fluckiger et al. describes an ellipsometer that uses a single wedge to impart a spatially varying retardance to the beam. Fluckige The ellipsometer system described by r was novel in its implementation, but could not detect all the sample parameters that describe an isotropic sample and was severely limited in the measurement of anisotropic samples. Fluckiger specified a Babinet compensator, which is more preferable than a single wedge.

[0062] Some inventions in the related field of polarimetry (polarimetry) have sought to solve the same problems faced in ellipsometry. A polarimeter is a device used to measure the polarization state of an electromagnetic radiation beam and, sometimes, its spectral characteristics. Similarly, in ellipsometry, the optical properties and physical structure of a sample can be determined by knowing the state of the beam before and after interacting with the sample. To determine more information about the sample, it is advantageous to be able to fully characterize the polarization state of the electromagnetic radiation beam after interacting with the sample. However, a polarimeter is not an ellipsometer in that it does not have the ability to directly extract sample parameters from an electromagnetic radiation source, a polarization state generator, or the measured polarization information. Polarimeters have traditionally used time-varying elements to analyze the beam, but some recent inventors have sought to create polarimeters with static elements.

[0063] Patent Document 3 by Thoma et al. patents a single wedge polarimeter that is identical to that used by Fluckiger in his ellipsometer but does not have the ability to measure spectroscopically. He also claims to use two wedges with different tilt directions to determine more information about the polarization state of the beam. By orienting the wedges in different directions, variable retardance is applied independently to two axes, enabling simplified data analysis but requiring two dimensions on the detector for analysis.

[0064] Patent Document 1 by Oka et al. patents an advanced imaging version described by Thoma, where the two wedges are similarly oriented in different tilt directions to separate each retardance modulation on different axes of the detector. The retardance fluctuation rate is high enough that many orders of modulation are captured and the data can be determined independently at many points across both dimensions of the beam.

[0065] Patent Document 4 by Sparks et al. also patents the polarimeter described by Fluckiger in the form of a point-and-shoot spectroscopic polarimeter with an entrance slit. This patent also describes the possibility of using two sets of wedges to fully characterize the measurement beam using the requirement that "the gradient of the retardance of the second optical system is at a different angle and intensity than the first optical system". The claims specify that the second wedge is "either parallel or antiparallel to the first birefringent wedge and has twice the birefringence of the first wedge", i.e., the difference in the intensity of the gradient is due to the different birefringences of the wedges. As described above, the Sparks system is a spectroscopic polarimeter that requires an entrance slit immediately adjacent to the wedge pair.

[0066] Patent Document 5 by Ansley et al. describes a polarimeter having an input slit that is focused onto a detector with three overlapping polarizing filters. Using only polarizing filters, like the initial polarizing filter, means that the device cannot characterize the direction of rotation with respect to circular polarization.

[0067] Patent Document 6 by Abraham et al. patents a polarimeter that utilizes a specific type of spatially varying retarder array consisting of a deposited dielectric grid structure having a spacing smaller than the wavelength of the electromagnetic radiation being used. This optical system generates retardance through the interaction of the grid structure of the element with the beam, rather than due to the birefringence of the material. This modulation is used in the polarimeter to determine the polarization state of the beam. Abraham also describes two specific applications of his polarimeter. First, as an imaging ellipsometer in a reflection-type electromagnetic radiation microscope. In this application, the optical system and the polarizing film are superimposed on the detector. Second, a more traditional ellipsometer with a laser light source.

[0068] Patent Document 7 by Alonso et al. describes a focused beam scattering apparatus that provides a focused beam onto a sample to be investigated from a light source disposed vertically above the sample. This system includes a beam splitter and a focusing lens in front of the sample to be investigated, and the focused beam exhibits a spatially varying polarization state, but there is no element on the detector side that imparts such a spatially varying polarization state. The beam is incident on the sample along a trajectory perpendicular to the sample and reflects back along the incident beam path.

[0069] Patent Document 8 by Lee describes an improvement to the ellipsometer described by Fluckiger and Abraham. That is, Lee uses a retroreflective path design with a polarization beam splitter and a concave mirror to make the unit more compact.

Prior Art Documents

Patent Documents

[0070]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Summary of the Invention

Problems to be Solved by the Invention

[0071] Even considering the known prior art, there is still a need for progress in the fields of ellipsometry and polarimetry (polarimetry).

Means for Solving the Problem

[0072] The present invention is partially a) an electromagnetic radiation beam source (2), b) a polarization state generator (4), c) a facility for interacting an electromagnetic radiation beam (3), whether parallelized or not, with a sample (5) at a known angle of incidence, d) a polarization state analyzer (6), and e) a multi-element detector (8) for electromagnetic radiation is an ellipsometer.

[0073] In use, an electromagnetic radiation beam (3) is generated by the electromagnetic radiation beam source (2) and interacted with the polarization state generator (4), the sample (5), the polarization state analyzer (6), and the multi-element detector (8). The polarization state generator (4) and / or the polarization state analyzer (6) further includes at least one of the following spatially varying compensators (10): a combination of two or more birefringent optical systems (16) having mutually oblique crystal axes and a spatial variation in thickness, and an array (13) of retardation elements (14) that are not structured on the order of the measured wavelength (13).

[0074] The spatially varying compensator (10) functions to impart a plurality of spatially separated polarization states, such that the spatial distribution of intensity across the cross-sectional area of the beam, after interacting with the polarization state analyzer (6), is detected by a corresponding plurality of spatially distributed elements within the detector (8) at corresponding plurality of positions, and this is analyzed to determine sample characteristics.

[0075] The ellipsometer can further include at least one imaging element existing between the spatially varying compensator (10) and the multi-element detector (8) in order to improve the resolution regarding the correspondence between a specific point on the spatially varying compensator (10) and a specific point on the detector (8).

[0076] The ellipsometer can be configured such that the beam provided by the electromagnetic radiation beam source (2) includes a plurality of wavelengths, the detector (8) is two-dimensional, the ellipsometer further includes at least one wavelength separation element (7) in front of the detector (8), and in use, the polarization effect of the sample can be determined for a plurality of wavelengths at each position of the sample being investigated. The at least one wavelength separation element (7) can be selected from the group consisting of: A planar or curved diffraction grating; A dispersive prism; and An attenuation or reflection filter element that transmits, blocks, or reflects different wavelengths at different positions thereof.

[0077] Furthermore, the ellipsometer can be configured such that at least one additional imaging optical system (12) decomposes the spectral variations caused by the wavelength separation element (7) onto one dimension of the detector (8).

[0078] The ellipsometer can be configured such that the electromagnetic radiation beam source (2) is selected from the group consisting of: A broadband or monochromatic laser; A broadband or narrowband LED; A monochromator; A broadband source; An FTIR source; A Globar source; An incandescent light source; and An arc lamp.

[0079] The ellipsometer can use a combination of a plurality of light sources (2) of the electromagnetic radiation beam to provide a wider or more preferred spectrum.

[0080] The ellipsometer can further include a beam splitting element, and the intensity profiles of both of the obtained beams are detected in order to improve data quality or to provide an image of the beam profile or the sample surface.

[0081] The ellipsometer can have a spatially varying compensator (10) present in both the polarization state generator (4) and the polarization state analyzer (6), and the spatial modulations of the two elements can be optically superposed in a known relationship using imaging optics and / or low-divergence illumination.

[0082] The ellipsometer can be such that the spatially varying compensator (10) gives different effective modulation frequencies to the detector via the magnifying optics, the change in the spatially varying compensator characteristics, and / or convergent or divergent illumination.

[0083] The ellipsometer can be such that the effective spatial modulation frequencies of the polarization state generator (4) and the polarization state analyzer (6) are in a ratio of 1:3, 3:1, 1:5, 5:1, 3:5, or 5:3.

[0084] The ellipsometer can be such that the angle of incidence of the electromagnetic radiation beam on the surface of the sample (5) is adjustable via a mechanism that moves part or all of the optical system of the ellipsometer relative to the sample.

[0085] The ellipsometer can be such that the electromagnetic radiation beam source (2) is the output from a monochromator, an optical fiber, or a pinhole, and the beam has preferred spectral or spatial characteristics.

[0086] The ellipsometer can be such that the electromagnetic radiation beam provided by the electromagnetic radiation beam source (2) approaches the sample surface along a trajectory that is perpendicular or substantially perpendicular to the sample surface.

[0087] The ellipsometer can be characterized by at least one selection from the group consisting of: The light source does not comprise one or more lasers, and There is no series combination of a slit and a wedge-shaped compensating element between the light source and the sample.

[0088] A method of characterizing a sample includes the following steps: a) Providing an ellipsometer as described above; b) Accessing data provided by the detector (8) in response to a beam of electromagnetic radiation input to the detector (8), c) Analyzing the data to characterize the sample (5).

[0089] The present invention alternatively a) An electromagnetic radiation beam source (2); b) A polarization state generator (4); c) Equipment for interacting the sample with the beam at a known angle of incidence; d) A polarization state analyzer (6); and e) A multi-element detector (8) of electromagnetic radiation is listed as an ellipsometer including:.

[0090] The ellipsometer includes at least one element in which both the polarization state generator (4) and the polarization state analyzer (6) have a plurality of positions (13)(14), or a plurality of elements each having at least one position (16), or a combination thereof, and each of the element positions acts to provide beam polarization characteristics that depend on how a part of the beam cross-section interacts with at least one of the positions therein.

[0091] In use, the electromagnetic radiation beam generated by the electromagnetic radiation beam source (2) is made to interact with the polarization state generator (4), the sample (5), and the polarization state analyzer (6), as a result of which the spatial intensity distribution across the cross-section of the beam and the corresponding plurality of positions in the beam cross-section are detected substantially simultaneously by the multi-element detector (8). From that the intensity profile can be analyzed using knowledge of the characteristics of the polarization state generator (4) and the polarization state analyzer (6) in order to characterize the properties of the sample (5).

[0092] A method of characterizing a sample includes the following steps: a) providing an ellipsometer as described above; b) accessing data provided by the detector (8) in response to a beam of electromagnetic radiation input to the detector (8), c) analyzing the data to characterize the sample (5).

[0093] The invention also relates to a spectroscopic polarimeter:[[]]END]] a) equipment for capturing a beam of electromagnetic radiation; b) a polarization state analyzer (4); c) a wavelength separating element (7); and c) a multi-element detector (8) for electromagnetic radiation comprising.[[]]END]]

[0094] In use, the captured beam of electromagnetic radiation enters the spectroscopic polarimeter and is made to interact with the polarization state analyzer (6), the wavelength separating element, and the multi-element detector (8).

[0095] The polarization state analyzer (6) is characterized by including at least one of the following spatially varying compensators (10): a combination of two or more birefringent optical systems having crystal axes oblique to each other and a spatial thickness variation; and, an array of retardation elements not structured on the order of the wavelength being measured; Its function is to impart a plurality of polarization states that result in a spatial distribution of intensity across the cross-section of the beam by interaction with a polarization state analyzer (6).

[0096] In use, the intensity is detected at a plurality of positions within that distribution by corresponding ones of the plurality of elements of the detector (8) and analyzed to determine the polarization state of the beam for a range of wavelengths.

[0097] Next, a method of characterizing the polarization state of a beam of electromagnetic radiation is a) providing a system as described above; b) accessing a beam of electromagnetic radiation such that data is generated by the detector (8); c) accessing the data provided by the detector (8) in response to the input of the accessed beam of electromagnetic radiation to the detector, and d) analyzing the data to characterize the beam steps.

[0098] The present invention will be better understood by reference to the detailed description herein in conjunction with the drawings.

[0099] An object of the present invention is to provide a snapshot ellipsometer capable of characterizing a sample in a single frame capture with complete sensitivity of sample parameters ψ and Δ at any range of values. To achieve this object, a novel arrangement of spatially varying polarization elements has been developed. Conventional ellipsometers have used wedge birefringent crystals and Babinet compensators to spatially modulate the polarization state of the measurement beam. This method enables snapshot measurements but cannot fully characterize the sample. The novel feature of the present invention is the use of two such wedges with obliquely oriented crystal axes to spatially modulate the polarization state of the measurement beam. crystal axes.

[0100] Another novel feature of the present invention is to use an array of liquid crystal retardation elements having a plurality of crystal orientations that exist to provide the required spatial modulation.

[0101] Another novel feature of the present invention is that a measurement beam that interacts with a polarization element that spatially varies both before and after interacting with the sample provides additional information about the sample. Some combinations of spatially varying polarization elements, such as an array of variable azimuth retarders on each side of the sample, even make it possible to measure the complete Mueller matrix that characterizes the sample.

Brief Description of the Drawings

[0102]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Best Mode for Carrying Out the Invention

[0103] Referring to the drawings, a preferred embodiment of the ellipsometer (1) of the present invention is shown in FIG. 1. The preferred embodiment includes a light source (2) that generates an electromagnetic radiation beam (3). The electromagnetic radiation beam (3) interacts with a polarization state generator (4) that includes at least a single polarizer (9) to create a known polarization state before interacting with the sample (5). The beam then interacts with a polarization state analyzer (6) consisting of a spatially varying compensator (10) and an analyzer (11) such that the beam has a spatial distribution of intensity along a single dimension (note that the analyzer and the polarizer are elements of the same type, and in an ellipsometer, they are on the Detector side and Light source side of the sample, respectively, and are distinguished by this). A wavelength separation element (7), such as a dispersive prism or a diffraction grating, serves to separate the individual wavelengths along an orthogonal dimension. A multi-element detector (8) captures a portion of the wavelength-dependent intensity profile within a single frame. Knowledge of the polarization effects of the polarization state generator (4) and the polarization state analyzer (6) enables the calculation of wavelength-dependent sample parameters based on the intensity profile of the electromagnetic radiation beam. There is an additional imaging optical system (12) that manipulates the beam and provides the resolution in the required dimensions. The linear variation of the spatially varying compensator (10) is imaged onto one dimension of the detector (8), while the spectral separation caused by the wavelength separation element (7) is imaged onto an orthogonal dimension. The spectral resolution is governed by the divergence of the beam and does not require an additional slit on the detector side.

[0104] This patent discloses the application of two types of spatially varying compensators (10) for use in a snapshot ellipsometer. Both provide appropriate modulation of the polarization state of the beam in order to fully characterize an isotropic sample. The spatially varying compensator (10) is as follows: a) A combination of two or more wedge-shaped birefringent optical systems (16) having crystal axes oblique to one another, and; b) An array of retardation elements (13)(14) that are unstructured on the order of the wavelengths present in the measurement beam.

[0105] Referring to Figure 2, a diagram of the microretarder array (13) is shown along with an enlarged view of the individual compensator elements (14). The azimuth angle of the fast axis of each retarder element is shown to vary linearly along the horizontal dimension θ = Caz[x], while there is no variation in the vertical direction. This pattern enables simplified data extraction along the horizontal dimension and wavelength separation in the vertical dimension.

[0106] The Mueller-Stokes formalism can be used to mathematically describe the disclosed retarder array (13):

[0107]

Number

[0108] Using the Mueller-Stokes formalism, the theoretical signal intensity at the detector (8) of the ellipsometer (1) can be expressed as a function of the spatial position x.

[0109]

Number

[0110] Assuming a quarter-wave retarder array with a variable azimuth angle, a polarizer azimuth angle set to 45°, and an analyzer azimuth angle set to 0°, the following intensity formula is given for an isotropic sample:

[0111]

Equation

[0112] It is clear that the spatially varying intensity for the above-mentioned retarder array is similar to the time variation of a rotating compensator system. The Fourier transform of the signal decomposes the equation into components occurring at different spatial frequencies.

[0113]

Equation

[0114] The Fourier coefficients (α k , β k ) are non-zero at a certain frequency k, which is related to the geometric shape of the optical system. By Fourier transforming the theoretical intensity formula, harmonic frequencies were identified at twice and four times the spatial frequency of the compensator variation.

[0115] The harmonics at 2ω and 4ω provide information on three sample parameters (N, C, and S) in a single measurement. The variable ω here has units of rad / mm rather than rad / s. The theoretical Fourier coefficients are related to the sample parameters as follows:

[0116]

Equation

[0117]

Equation

[0118] Therefore, the theoretical relationship between the Fourier coefficients and the sample parameters is the same as that of the rotation compensator device. This applies to the general case where the polarizer or analyzer position is used. The main requirement for this to hold is that the retardance of the retarder array is constant across all pixels.

[0119] Referring to FIGS. 3(A) to 3(F), several birefringent wedges and composite prisms that can be used as spatially varying compensators are shown. The elements are shown separated in an exploded view but can be attached to each other for ideal performance. FIG. 3(A) shows a single birefringent wedge (15), which provides a spatial variation of retardance. The phase axis of the element is shown as a line on the plane of the optical system. FIG. 3(B) shows a Babinet compensator ( It is shown in Fig. 3(C). It consists of two birefringent wedges mounted such that the compensators are shown on the in-phase axes perpendicular to each other. This combination provides low-order retardance and reduced beam shift. Fig. 3(C) shows a combination of two Babinet compensators (16) with different crystal orientations. Since the directions of the wedges are aligned, the retardance varies only along the vertical direction. The combination of multiple in-phase axes provides additional information about the sample, but it is actually difficult to align four separate wedges. The wedge tilts for the two Babinet compensators can be made the same, enabling data extraction at a single spatial frequency, or can be made different, enabling the modulation of each wedge to be extracted at different spatial frequencies. Fig. 3(D) shows a pair of birefringent wedges (17) with oblique (neither perpendicular nor parallel) crystal axes. This optical system provides the beam modulation necessary for characterizing a completely isotropic sample. This combination of optical systems is novel for use in ellipsometry but exhibits multiple retardances. Fig. 3(E) is a diagram showing a novel improvement to the aforementioned optical system in which additional parallel retardance plates (18) are attached to each side of the wedge pair (17). Since each of the plate retarders has an optical axis perpendicular to one of the wedges and a similar retardance, the effective retardance for each wedge-plate pair is of low order. In addition, the use of only one pair of wedges results in a reduction in beam deviation and simplifies alignment. It is possible to conceptualize many composite wedges that generate the required modulation and serve the same purpose as described. Using at least two birefringent crystals with oblique in-phase axes and thickness variations along one dimension is a novel aspect that enables complete sample characterization.

[0120] For the optical systems described in Figs. 3(C), (D), and (E), the theoretical signal intensity of the ellipsometer (1) having the crystal axis orientations of each wedge (W1, W2) can be represented by the following matrix multiplication:

[0121]

Equation

[0122] The polarizer and analyzer are not oriented to the wedge's eigenpolarization state for each measurement. Assuming an isotropic sample, a polarizer azimuth angle of 45°, a phase axis of 0° for the first wedge, a phase axis of 90° for the second wedge, an analyzer azimuth angle of 0°, and equal magnitudes and opposite retardance fluctuation rates for both wedges, the theoretical signal intensity takes the following form.

[0123] [Number]

[0124] The Fourier transform of the signal decomposes the expression into components that occur at different spatial frequencies.

[0125] [Number]

[0126] The Fourier coefficients (α k , β k ) are non-zero at a certain spatial frequency k related to the orientation and spatial variation of the compensator. By Fourier-transforming the theoretical intensity expression, the harmonic frequencies related to the retardance fluctuation rate and DC term of the wedge are identified. Each frequency component consists of a real part and an imaginary part. The theoretical Fourier coefficients are related to the sample parameters as follows:

[0127] [Number]

[0128] Using the theoretical expressions for the Fourier coefficients to solve for the sample parameters, it is clear that a snapshot ellipsometer consisting of two spatially varying elements can measure three sample parameters in any single measurement, as shown in the following Mueller matrix description of the sample. X indicates non-sensitivity to that parameter.

[0129] [Number]

[0130] Thus, the described spatially varying retarder array or double wedge compensator snapshot ellipsometer is sensitive to at least three sample parameters and can measure ψ and Δ at any range of values.

[0131] In addition to the general layout described above, several modifications of the preferred embodiments are possible to improve the functionality of the system. Many of these are shown in FIGS. 4(A) and 4(B).

[0132] The electromagnetic radiation beam incident on the sample can be focused with additional imaging optics so that the beam has a smaller cross-sectional area at the sample. This modification reduces the impact of sample misalignment and non-uniformity on data quality.

[0133] By using spatially varying compensators (10) in both the polarization state generator (4) and the polarization state analyzer (6), the full Mueller matrix describing the sample can be measured. If each spatially varying compensator (10) provides different spatial frequencies to the detector (8), the parameters can be extracted at each of the component frequencies as well as the sum and difference of these frequencies. This can be achieved by using two SVCs with different spatial frequencies or by magnifying each so that they are different on the detector.

[0134] The intensity profile that occurs on the detector (8) is affected by the spatial variation of the spatially varying compensator (10), so it is important to achieve an appropriate resolution between the two components. Referring to FIGS. 4(A) and 4(B), an additional imaging optical system (12) is shown and used to ensure that the image planes of the spatially varying compensator (10) overlap each other and enter the detector (8). In FIGS. 4(A) and 4(B), an additional imaging optical system (12) near the sample (5) is used to focus the beam onto the sample (5) and image the spatially varying compensator (10) after it interacts with the sample (5). If the spatially varying compensator (10) has only one-dimensional variations, it is only necessary to image the axis of variation onto the detector (8), which can be achieved by using a cylindrical optical system. A slit can be utilized, but this is done instead of using a slit at the entrance of the detector. The cylindrical optical system after the polarization state analyzer (6) and the spherical optical system after the wavelength separation element (7) serve to image the variations of the spatially varying compensator (10) onto one dimension of the detector (8) and image the wavelength separation onto an orthogonal dimension.

[0135] In a system including two spatially varying compensators (10), the easiest way to ensure appropriate resolution and appropriate magnification is shown in FIG. 5. The beam used in this example acts as a point source such as the output of an optical fiber or a pinhole. The fiber can serve to homogenize the beam and provide flexibility in the layout. The point source of the electromagnetic radiation beam (2) guarantees that both spatially varying compensation elements (10) are properly resolved onto the detector (8) without the use of additional optical systems, similar to the function of a pinhole camera. The expanding nature of the beam serves to expand the spatially varying compensators (10) relative to each other, resulting in modulation of each spatially varying compensator (10) having different spatial frequencies on the detector (8) and enabling separation of the signals.

[0136] The system layout of FIG. 6 is the same as that of FIG. 1, except that the sample is measured here by transmission instead of reflection. This can be advantageous for certain samples.

[0137] The layouts shown in FIGS. 7(A) and 7(B) represent a spectroscopic polarimeter that can be used to measure an electromagnetic radiation beam and consists of a polarization state analyzer (6), a wavelength separation element (7), and a detector (8), as described above. The polarization state analyzer (6) includes a spatially varying compensator (10) and an analyzer (11) that fully characterizes the polarization information of the beam. The wavelength separation element (7) enables the full polarization state to be characterized for multiple optical wavelengths. An additional imaging optical system ensures the resolution between the axis of variation of the spatially varying compensator (10) and the detector (8). The wavelength separation element (7) is shown as a curved diffraction grating and does not require additional optics for decomposing the spectral information of the beam. The beam is filtered or homogenized using a pinhole, slit, and optical fiber and can guarantee data accuracy, similar to a standard polarimeter. The electromagnetic radiation beam source (2) can be selected from the group consisting of the following, provided that it is not excluded by the language of the claims:

[0138] Laser; LED; Broadband source; FTIR source; Globar source; Incandescent light source; and Arc lamp.

[0139] Furthermore, multiple electromagnetic radiation sources can be used and their optical signals combined to function as a single source of electromagnetic radiation beam (2) with more favorable spectral characteristics. For example, the electromagnetic radiation from several LEDs and lasers can be collimated using a hot / cold mirror, beam splitter, branched optical fiber, or other methods to generate a broadband beam.

[0140] ​The electromagnetic radiation beam source (2) may be the output of a monochromator that supplies only one optical wavelength. The electromagnetic radiation beam source (2) acts as a point source and can also be provided as the output of an optical fiber or a pinhole through which the electromagnetic radiation is transmitted in order to homogenize the beam.

[0141] If not excluded by the wording of the claims, the spatially varying compensator (10) can be selected from the group consisting of: A combination of an array (13) of retarder elements (14) that are not structured on the scale of the optical wavelengths present, and At least two birefringent wedges (16) having crystal axes oriented obliquely to each other.

[0142] In a preferred embodiment, the modulation generated by the spatially varying compensator (10) is only one-dimensional, and the light source (2) used further generates a beam having a plurality of optical wavelengths present. A wavelength separation element (e.g., (7)) such as a dispersive prism or a diffraction grating is used to separate the individual wavelengths along the other dimension of the two-dimensional detector (8). This makes it possible to determine the sample parameters independently for each wavelength.

[0143] If not excluded by the wording of the claims, the wavelength separation element (7) can be any element or any combination of elements that enables the separation or selection of different wavelengths present in the beam. The wavelength separation element is A flat or curved diffraction grating; A dispersive prism; and A filter element that transmits, attenuates, or reflects different wavelengths at different positions is included.

[0144] The retarder array can be designed to vary the retardance and / or the fast axis orientation spatially either sequentially or non-sequentially. This preferred embodiment describes a retarder array in which the azimuthal orientation of each compensator element is varied sequentially, either through optical design or data manipulation. This approach is mathematically similar to a rotating compensator ellipsometer but The azimuth rotation matrix has spatial dependence rather than time dependence. In the case of an array of retardation elements, as long as there is an appropriate azimuth or retardance to characterize the sample, the individual elements or zones can be in any pattern. If the elements vary linearly in azimuth and are constant in retardance, the above Fourier analysis can be used for data extraction. For other patterns or values of the elements, alternative analysis methods can be used.

[0145] The prior art discloses using a single wedge system and a patterned dielectric grid retarder to analyze an electromagnetic radiation beam after interaction with a sample. However, for any type of spatially varying polarization element in the polarization state generator (4), probing the sample with a beam of electromagnetic radiation having a plurality of polarization states at some spatial positions therein is a novel approach in ellipsometry.

[0146] Also, in order to be able to fully characterize an anisotropic sample, while analyzing the polarization states present in the spatially varying polarization element in the polarization state generator (6), and at the same time, due to any type of spatially varying polarization element in the polarization state generator (4), for probing the sample with a beam of electromagnetic radiation having a plurality of polarization states at some spatial positions therein, it is also novel to use spatially varying polarization elements in both the polarization state generator (4) and the polarization state analyzer (6).

[0147] For clarity and conciseness, the exemplary system has generally been shown and described as using refractive optics. However, those skilled in the art should recognize that refractive optics, reflective optics, and diffractive optics can all be used to achieve the same function as the described elements. Further, although the measurement beam is shown to interact with the sample in a reflection mode, electromagnetic radiation passing through the sample can also enable the characterization of the sample.

[0148] Also, it should be noted that Fourier transform is described as one signal processing technique for extracting sample parameters. Those skilled in the art will recognize other signal processing techniques that enable the extraction of sample parameters from the measured intensity profile.

[0149] It should be noted that the beam propagation direction can be defined for any beam and may be collimated, or focused, or otherwise. While it is not important for the present invention how this is actually done in a particular case, it should be understood that for the purposes of this disclosure, the term "beam" is to be understood as being characterized by the propagation direction of electromagnetic radiation having a finite cross-sectional area. The cross-section of the beam enables the identification of different positions within it, each of which is the same as a separate beam and refers to any convenient two-dimensional measurement of the beam. That is, the present invention is considered to be an effective combination of many individual "separate" beams that can be affected differently, substantially independently of how other similar "independent" beams are effectively affected by the electromagnetic radiation beam.

[0150] It should be noted that the terms "cylindrical" and "spherical" are sometimes used to refer to imaging elements such as curved mirrors and lenses. These terms are not used to describe the exact shape of the optical element surface, but are only used to identify whether the optical element has curvature in only one dimension as part of a cylinder, or in both dimensions as part of a sphere. It is understood that other portions of parabolic, elliptical, and aspherical geometric shapes are also included.

[0151] The recited negative limitations can be incorporated into the claims to avoid reference to the prior art, but if the negative limitations are not included in the claims, the absence of said elements does not indicate the absence of elements in the present invention system at at least one of its positions, rather, the claims are premised on "comprising".

[0152] ​Also, it should be noted that although not relied upon to provide novelty, the various elements referred to in this application are not specifically presented in the drawings. Examples include wavelength filters, beam splitters, slits and optical fibers as part of a beam source of electromagnetic radiation, cylindrical optical systems, spherical optical systems applied in beam resolution at detectors, planar gratings, and various light source types such as lasers, LEDs, broadband, FTIR, globars, incandescent arc lamps, etc. Such elements are well known in the art and can be found and described, for example, in patents granted to J.A. Woollm Co., Inc., which are identified and available on the PTO website. Currently, there are approximately 195 such patents, all of which are incorporated herein by reference. Applicants reserve the right to incorporate content from the identified patents.

[0153] While the subject matter of the present invention has been disclosed herein, it will be apparent that many modifications, substitutions, and variations of the present invention are possible in light of the teachings. Accordingly, it is to be understood that the invention may be practiced otherwise than as specifically described and that the breadth and scope of the invention should be limited only by the claims.

Claims

1. a) an electromagnetic radiation beam source (2), b) a polarization state generator (4), c) a facility for interacting an electromagnetic radiation beam (3), which may or may not be collimated, with a sample (5) at a known angle of incidence, d) a polarization state analyzer (6), and e) a multi-element detector (8) for electromagnetic radiation comprising, in use, an electromagnetic radiation beam (3) is generated by said electromagnetic radiation beam source (2) and interacted with said polarization state generator (4), said sample (5), said polarization state analyzer (6), and said multi-element detector (8), wherein said polarization state generator (4) and / or said polarization state analyzer (6) further comprises a spatially varying compensator (10) which is a combination of two birefringent optical systems (16) having crystal axes oblique to each other and a spatial thickness variation, wherein at least one of said spatially varying compensators (10) imparts a plurality of spatially separated polarization states to produce an intensity distribution across the cross-section of said beam, and after interacting with said polarization state analyzer (6), is detected at a corresponding plurality of positions by a corresponding plurality of spatially distributed elements within said detector (8), and is analyzed to determine sample properties an ellipsometer.

2. further comprising at least one imaging element existing between said spatially varying compensator (10) and said multi-element detector (8) for improving resolution with respect to the coincidence between a specific point on said spatially varying compensator (10) and said detector (8) The ellipsometer according to claim 1.

3. wherein the beam provided by said electromagnetic radiation beam source (2) comprises a plurality of wavelengths, said detector (8) is two-dimensional, and said ellipsometer further comprises at least one wavelength separation element (7) in front of said detector (8), and in use, the polarization effect of the sample is determined for a plurality of wavelengths at each position of the sample being investigated The ellipsometer according to claim 1.

4. wherein at least one wavelength separation element (7) is selected from the group consisting of The ellipsometer according to claim 3: a planar or curved diffraction grating, a dispersive prism, and an attenuation or reflection filter element which transmits, blocks, or reflects different wavelengths at different positions.

5. At least one additional focusing optical system decomposes the spectral fluctuations caused by the wavelength separation element (7) onto one dimension of the detector (8), and the at least one focusing optical system is present between the analyzer (11) and the multi-element detector (8). The ellipsometer according to claim 3.

6. The electromagnetic radiation beam source (2) is selected from the group consisting of The ellipsometer according to claim 1: Broadband or monochromatic laser; Broadband or narrowband LED; Monochromator; Broadband light source; FTIR light source; Globar light source; Incandescent light source; and Arc lamp.

7. A plurality of light sources of the electromagnetic radiation beam (2) are used in combination to extend the wavelength range or to provide a more uniform intensity profile across the measured electromagnetic spectrum The ellipsometer according to claim 1.

8. Further comprising a beam splitting element, and the intensity profiles of both resulting beams are detected to improve data quality or to provide an image of the beam profile or the sample surface The ellipsometer according to claim 1.

9. Spatially varying compensators (10) are present in both the polarization state generator (4) and the polarization state analyzer (6), and the spatial modulations of the two compensators are optically superposed in a known relationship using imaging optics and / or low-divergence illumination The ellipsometer according to claim 1.

10. The spatially varying compensator imparts different effective modulation frequencies to the detector via an enlarging optical system, a change in the spatially varying compensator characteristics, and / or convergent or divergent illumination The ellipsometer according to claim 9.

11. The effective spatial modulation frequencies of the polarization state analyzer and the polarization state generator are imaged onto the detector (8) in a ratio of 1:3, 3:1, 1:5, 5:1, 3:5, or 5:3 The ellipsometer according to claim 10.

12. The incident angle of the electromagnetic radiation beam on the surface of the sample is adjustable The ellipsometer according to claim 1.

13. The electromagnetic radiation beam source (2) is the output from a monochromator, an optical fiber, or a pinhole, such that the beam has favorable spectral or spatial characteristics The ellipsometer according to claim 1.

14. The electromagnetic radiation beam provided by the electromagnetic radiation beam source (2) does not approach the sample surface along a trajectory that is perpendicular or substantially perpendicular to the sample surface. The ellipsometer according to claim 1.

15. Characterized by at least one selection from the group consisting of the following: The ellipsometer according to claim 1: The light source does not include one or more lasers, and There is no series combination of a slit and a wedge-shaped compensating element between the light source and the sample.

16. a) An electromagnetic radiation beam source (2), b) A polarization state generator (4), c) Equipment for interacting the sample with the beam at a known angle of incidence, d) A polarization state analyzer (6), and e) A multi-element detector (8) for electromagnetic radiation comprising: Both the polarization state generator (4) and the polarization state analyzer (6) are provided with two elements of a birefringent optical system (16) having crystal axes oblique to each other and a spatial thickness variation, and each of said elements acts to provide beam polarization characteristics depending on the manner of interaction of a part of the beam cross-section with at least one of said element positions; In use, the electromagnetic radiation beam generated by the electromagnetic radiation beam source (2) is interacted with the polarization state generator (4), the sample (5), and the polarization state analyzer (6), thereby generating a spatial intensity distribution across the cross-section of the beam, and corresponding multiple positions in the beam cross-section are detected substantially simultaneously by the multi-element detector (8); In order to characterize the properties of the sample (5), in use, the spatial intensity distribution is analyzed using the properties of the polarization state generator (4) and the polarization state analyzer (6). Ellipsometer.

17. a) Equipment for capturing the beam, b) A polarization state analyzer (4), c) A wavelength separation element (7), and d) A multi-element detector (8) for electromagnetic radiation A spectroscopic polarimeter comprising: The polarization state analyzer (6) is provided with at least one of the following spatially varying compensators (10), The polarization state generator (4) and / or the polarization state analyzer (6) further includes a spatially varying compensator (10) which is a combination of two birefringent optical systems (16) having crystal axes oblique to each other and a spatial thickness variation. When the spectral polarimeter is in use, the intensity is detected at a plurality of positions of its distribution by a corresponding plurality of elements of the detector (8), and analyzed to determine the polarization state of the beam for a certain range of wavelengths. Spectral polarimeter.

18. a) a') An electromagnetic radiation beam source (2), b') A polarization state generator (4), c') Equipment for interacting the parallelized or converged electromagnetic radiation beam (3) with the sample (5) at a known incident angle, d') A polarization state analyzer (6), and e') A multi-element detector (8) of electromagnetic radiation comprising, In use, the electromagnetic radiation beam (3) is generated by the electromagnetic radiation beam source (2) and interacted with the polarization state generator (4), the sample (5), the polarization state analyzer (6), and the multi-element detector (8); The polarization state generator (4) and / or the polarization state analyzer (6) further includes the following spatially varying compensator (10) which is a combination of two birefringent optical systems (16) having crystal axes oblique to each other and a spatial thickness variation, The spatially varying compensator (10) imparts a plurality of spatially separated polarization states to produce an intensity distribution across the cross-section of the beam, and after interacting with the polarization state analyzer (6), is detected at corresponding positions by a corresponding plurality of spatially distributed elements in the detector (8) and analyzed to determine sample characteristics. Providing an ellipsometer; b) Interact the electromagnetic radiation beam source (2) with the polarization state generator (4), and interact with the sample (5) accessed through equipment for interacting the parallelized or non-parallelized beam (3) of electromagnetic radiation with the sample at a known incident angle, interact with the polarization state analyzer (6), and supply an electromagnetic radiation beam (3) directed to be incident on the multi-element detector (8) of electromagnetic radiation; c) Access the data provided by the detector (8) in response to the electromagnetic radiation input thereto; d) Analyze the data to characterize the sample (5); A method for characterizing a sample.

19. a) a') Equipment for capturing a beam, b') A polarization state analyzer (4), c') A wavelength separation element (7), and d') A multi-element detector (8) of electromagnetic radiation A spectral polarimeter comprising In use, the beam of electromagnetic radiation enters the spectral polarimeter and interacts with the polarization state analyzer (6), the wavelength separating element, and the multi-element detector (8), The polarization state analyzer (6) includes a spatially varying compensator (10) that is a combination of two birefringent optical systems with mutually oblique crystal axes and a spatial thickness variation, The spatially varying compensator (10) is a combination of two birefringent optical systems with mutually oblique crystal axes and a spatial thickness variation, The polarization state analyzer (6) functions to provide a plurality of polarization states that result in a spatial distribution of intensity across the cross-section of the beam upon interaction with the beam, The spectral polarimeter, in use, has an intensity that is detected by a corresponding plurality of elements of the detector (8) at a plurality of positions of the intensity distribution and is analyzed to determine the polarization state of the beam for a range of wavelengths, Providing a spectral polarimeter, b) accessing an electromagnetic radiation beam, c) accessing data provided by the detector (8) in response to the electromagnetic radiation beam input thereto, d) analyzing the data to characterize the beam (5), A method for determining the polarization state of an electromagnetic radiation beam in a wavelength range.

20. The ellipsometer further includes at least one imaging element existing between the spatially varying compensator (10) and the multi-element detector (8) to improve the resolution regarding the correspondence between a specific point on the spatially varying compensator (10) and a specific point on the detector (8), The ellipsometer according to claim 1.

21. The beam source provided by the electromagnetic radiation beam source (2) includes a plurality of wavelengths, the detector (8) is two-dimensional, the ellipsometer further includes at least one wavelength separating element (7) in front of the detector (8), and in use, the polarization effect of the sample can be determined for a plurality of wavelengths at each position of the sample to be investigated, At least one additional focusing optical system decomposes the spectral fluctuations caused by the wavelength separating element (7) onto one dimension of the detector (8), and the at least one focusing optical system exists between the analyzer (11) and the multi-element detector (8), The ellipsometer according to claim 1 or 20.

22. Combining and using a plurality of electromagnetic radiation beam sources (2) to provide a broader or more preferred spectrum, The ellipsometer according to any one of claims 1, 20, and 21.

23. The ellipsometer further includes a beam splitting element, and in order to improve data quality or to provide an image of the beam profile or the sample surface, the intensity profiles of both resulting beams are detected. The ellipsometer according to any one of claims 1, 20 to 22.

24. In the ellipsometer, spatially varying compensators (10) are present in both the polarization state generator (4) and the polarization state analyzer (6), and the spatial modulations of the two compensators are optically superposed in a known relationship using imaging optics and / or low-divergence illumination. The ellipsometer according to any one of claims 1, 20 to 23.

25. Each of the polarization state generator (4) and the polarization state analyzer (6) includes at least one element having a plurality of positions (22) (13), or a plurality of elements each having at least one position (16), or a combination thereof. The spatial modulations of the elements included in the polarization state generator (4) and the elements included in the polarization state analyzer (6) are optically superposed in a known relationship using imaging optics and / or low-divergence illumination. The ellipsometer according to any one of claims 1, 20 to 24.

26. Each of the polarization state generator (4) and the polarization state analyzer (6) includes at least one element having a plurality of positions (13) (14), or a plurality of elements each having at least one position (16), or a combination thereof. The spatial modulations of the elements included in the polarization state generator (4) and the elements included in the polarization state analyzer (6) are optically superposed in a known relationship using imaging optics and / or low-divergence illumination, and the effective spatial modulation frequencies of the polarization state analyzer and the polarization state generator are in a ratio of 1:3, 3:1, 1:5, 5:1, 3:5, or 5:

3. The ellipsometer according to any one of claims 1, 20 to 25.

27. The electromagnetic radiation beam source (2) is an output from a monochromator, an optical fiber, or a pinhole, so that the beam has preferred spectral characteristics or spatial characteristics. The ellipsometer according to any one of claims 1, 20 to 26.

28. ​ A spatially varying compensator (10) is present in both the polarization state generator (4) and the polarization state analyzer (6), and the spatial modulations of the two compensators are optically superposed in a known relationship using an imaging optical system and / or low-divergence illumination. An ellipsometer according to any one of claims 1, 20 to 27.

29. The spatially varying compensator imparts different effective modulation frequencies to the detector via a magnifying optical system, a change in the spatially varying compensator characteristics, and / or convergent or divergent illumination. An ellipsometer according to claim 28.

30. The effective spatial modulation frequencies of the polarization state analyzer and the polarization state generator are imaged on the detector (8) in a ratio of 1:3, 3:1, 1:5, 5:1, 3:5, or 5:

3. An ellipsometer according to claim 29.

31. The beam source provided by the electromagnetic radiation beam source (2) includes a plurality of wavelengths, the detector (8) is two-dimensional, and the ellipsometer further includes at least one wavelength separation element (7) in front of the detector (8), and in use, it is possible to determine the polarization effect of the sample for a plurality of wavelengths at each position of the sample to be investigated. A method according to claim 18.

32. The beam source provided by the electromagnetic radiation beam source (2) includes a plurality of wavelengths, the detector (8) is two-dimensional, and the ellipsometer further includes at least one wavelength separation element (7) in front of the detector (8), and in use, it is possible to determine the polarization effect of the sample for a plurality of wavelengths at each position of the sample to be investigated. At least one wavelength separation element (7) is selected from the group consisting of A method according to any one of claims 18 and 31: A planar or curved diffraction grating; A dispersive prism, and An attenuation or reflection filter element that transmits, blocks, or reflects different wavelengths at different positions.

33. The electromagnetic radiation beam source (2) is selected from the group consisting of A method according to any one of claims 18, 31, and 32: A broadband or monochromatic laser; A broadband or narrowband LED; A monochromator; A broadband light source; An FTIR light source; A Globar light source; An incandescent light source; and An arc lamp.

34. The incident angle of the electromagnetic radiation beam on the surface of the sample is adjustable. A method according to any one of claims 18, 31 to 33.

35. The electromagnetic radiation beam provided by the electromagnetic radiation beam source (2) does not approach the sample surface along a trajectory that is perpendicular or substantially perpendicular to the sample surface The method according to any one of claims 18, 31 to 34 **Claim 36** The ellipsometer is characterized by at least one selection from the group consisting of The method according to any one of claims 18, 31 to 35 The light source does not include one or more lasers, and There is no series combination of a slit and a wedge-shaped compensating element between the light source and the sample **Claim 37** The ellipsometer further comprises at least one imaging element existing between the spatially varying compensator (10) and the multi-element detector (8) in order to improve the resolution regarding the correspondence between a specific point on the spatially varying compensator (10) and a specific point on the detector (8) The method according to claim 18 **Claim 38** The beam source provided by the electromagnetic radiation beam source (2) includes a plurality of wavelengths The detector (8) is two-dimensional, the ellipsometer further includes at least one wavelength separation element (7) in front of the detector (8), and in use, the polarization effect of the sample can be determined for a plurality of wavelengths at each position of the sample to be investigated. At least one additional focusing optical system decomposes the spectral fluctuations caused by the wavelength separation element (7) onto one dimension of the detector (8), and the at least one focusing optical system exists between the analyzer (11) and the multi-element detector (8) The method according to any one of claims 18 and 37 **Claim 39** Combining and using a plurality of electromagnetic radiation beam sources (2) to provide a broader or more preferred spectrum The method according to any one of claims 18, 37 and 38 **Claim 40** The ellipsometer further includes a beam splitting element, and in order to improve the data quality, or to provide a beam profile or an image of the sample surface, the intensity profiles of both resulting beams are detected The method according to any one of claims 18, 37 to 39 **Claim 41** The ellipsometer has spatially varying compensators (10) present in both the polarization state generator (4) and the polarization state analyzer (6), and the spatial modulations of the two compensators are optically superposed in a known relationship using an imaging optical system and / or low-divergence illumination. The method according to any one of claims 18, 37 to 40.

42. Each of the polarization state generator (4) and the polarization state analyzer (6) includes at least one element having a plurality of positions (22)(13), or a plurality of elements each having at least one position (16), or a combination thereof. The spatial modulations of the elements included in the polarization state generator (4) and the elements included in the polarization state analyzer (6) are optically superposed in a known relationship using an imaging optical system and / or low-divergence illumination. The method according to any one of claims 18, 37 to 41.

43. Each of the polarization state generator (4) and the polarization state analyzer (6) includes at least one element having a plurality of positions (13)(14), or a plurality of elements each having at least one position (16), or a combination thereof. The spatial modulations of the elements included in the polarization state generator (4) and the elements included in the polarization state analyzer (6) are optically superposed in a known relationship using an imaging optical system and / or low-divergence illumination. The effective spatial modulation frequencies of the polarization state analyzer and the polarization state generator are in a ratio of 1:3, 3:1, 1:5, 5:1, 3:5, or 5:

3. The method according to any one of claims 18, 37 to 42.

44. The electromagnetic radiation beam source (2) is an output from a monochromator, an optical fiber, or a pinhole, such that the beam has favorable spectral or spatial characteristics. The method according to any one of claims 18, 37 to 43.

45. Spatially varying compensators (10) are present in both the polarization state generator (4) and the polarization state analyzer (6), and the spatial modulations of the two compensators are optically superposed in a known relationship using an imaging optical system and / or low-divergence illumination. The method according to any one of claims 18, 37 to 44.

46. The spatially varying compensator imparts different effective modulation frequencies to the detector via a magnifying optical system, a change in the spatially varying compensator characteristics, and / or convergent or divergent illumination. The method according to claim 45.

47. The effective spatial modulation frequencies of the polarization state analyzer and the polarization state generator are imaged onto the detector (8) in a ratio of 1:3, 3:1, 1:5, 5:1, 3:5, or 5:

3. The method according to claim 46. **Claim 48** a) an electromagnetic radiation beam source (2), b) a polarization state generator (4), c) a facility for interacting an electromagnetic radiation beam (3), which may or may not be collimated, with a sample (5) at a known angle of incidence, d) a polarization state analyzer (6), and e) a multi-element detector (8) for electromagnetic radiation comprising, in use, an electromagnetic radiation beam (3) is generated by the electromagnetic radiation beam source (2) and interacted with the polarization state generator (4), the sample (5), the polarization state analyzer (6), and the multi-element detector (8), the polarization state generator (4) and / or the polarization state analyzer (6) further comprises a spatially varying compensator (10) which is a combination of two birefringent optical systems (16) having crystal axes oblique to each other and a spatial thickness variation, at least one of the spatially varying compensators (10) imparts a plurality of spatially separated polarization states to produce an intensity distribution across the cross-section of the beam, and after interacting with the polarization state analyzer (6), is detected at a corresponding plurality of positions by a corresponding plurality of spatially distributed elements in the detector (8), analyzed to determine sample characteristics, spatially varying compensators (10) are present in both the polarization state generator (4) and the polarization state analyzer (6), and the spatial modulations of the two compensators are optically superposed in a known relationship using imaging optics and / or low-divergence illumination, An ellipsometer. **Claim 49** The spatially varying compensator imparts different effective modulation frequencies to the detector via an enlarging optical system, a change in the characteristics of the spatially varying compensator, and / or convergent or divergent illumination. The ellipsometer according to claim 48.

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