Method for operating a polarimetric measuring device and polarimetric measuring device

Abstract

The invention relates to a method for operating a polarization measuring device (10), wherein light (14) having a preset input polarization state is guided to a sample (16) for the purpose of a potentially polarization-altering interaction with the sample, and from the sample is guided through an analyzer (28) which performs a polarization screening and is guided at least in component fashion to an intensity detector (20), wherein - in the range of a polarization modulation, the relative angle between the output polarization state of the light (14) leaving the sample (14) and the analyzer (28) is changed, and - in the range of a spectral modulation, the wavelength of the light (14) reaching the intensity detector (20) is changed, and wherein by means of the intensity detector (20) a plurality of intensity measurements is carried out in succession, on the one hand in differently adjusted polarization modulation states and on the other hand in differently adjusted spectral modulation states, and the respective intensity values are stored together with polarization values which represent the corresponding polarization modulation states and spectral values which represent the corresponding spectral modulation states. The invention is characterized in that the polarization modulation and the spectral modulation are carried out simultaneously and continuously, wherein during a single monotonic change of the polarization modulation states the spectral modulation states are changed periodically a plurality of times, and during each spectral modulation period (T) a plurality of intensity measurements is carried out in succession. The invention also relates to a polarization measuring device (10) which is set up for carrying out the method according to the invention.

Description

Technical Field

[0001] This invention relates to a method for operating a polarization measurement device, wherein light having a preset input polarization state is guided to the sample for the purpose of potentially altering the polarization of the light, and guided from the sample through a polarization-screening analyzer and at least in a component manner to an intensity detector, wherein... - Within the range of polarization modulation, the relative angle between the output polarization state of the light leaving the sample and the analyzer is changed, and - Within the range of spectral modulation, the wavelength of the light component arriving at the detector is changed. Furthermore, with the aid of a detector, multiple intensity measurements are sequentially performed in different constellations (Konstellations) composed of polarization modulation states and spectral modulation states, and the corresponding intensity values ​​are stored together with the polarization and spectral values ​​representing the corresponding constellations.

[0002] The present invention also relates to a polarization measurement device, comprising: - A light source used to generate light that interacts with the sample; - Sample holder, used to position the sample in the beam path of light. - Intensity detector, used to detect the intensity of light after it has interacted with a sample. - A polarization state generator, which is positioned between the light source and the sample, and is suitable for providing a preset input polarization state for the light; - A polarization-sensitive analyzer, positioned between the sample and an intensity detector, is suitable for filtering out light components with a preset polarization state. This allows specific light components to pass through depending on their polarization state, while suppressing other light components, for example, through absorption, reflection, or diffraction. - A spectral modulator, which is used to change the wavelength of the light arriving at the detector. - A polarization modulator, which is used to change the relative angle between the output polarization state of light leaving the sample and the analyzer, and - Control unit, which is suitable for operating the intensity detector, polarization modulator and spectral modulator according to a preset operating method. Background Technology

[0003] This type of polarization measurement device is commonly referred to as a polarimeter or ellipsometer. The same principle applies to its operating method.

[0004] The purpose of this polarization measurement is to determine specific characteristics of a sample by analyzing the changes in the polarization state of the measurement beam caused by the interaction between the sample and the defined beam (i.e., the measurement beam). Here, the interaction between the measurement beam and the sample can occur in either transmission or reflection. In the case of transmission, the polarization method or polarimeter is mentioned; in the case of reflection, the ellipsometric method or ellipsometer is mentioned. Both of these variations should be referred to together as polarization measurement or polarization measurement equipment.

[0005] Since the polarization of light is not known to be a directly measurable parameter, measurement is performed indirectly through an intensity detector, upstream of which is a polarization-sensitive analyzer. This polarization-sensitive analyzer is characterized in that it allows only light components with a polarization state preset according to their angular position to pass through, while suppressing others. The intensity of the light passing through the analyzer and reaching the detector varies depending on the relative position of the polarization state of the light falling on the analyzer and the analyzer's orientation.

[0006] However, within the scope of polarization or ellipsometric measurements, the polarization state of the light emitted from the sample and falling onto the analyzer is precisely unknown; what is known is only the typical, clearly adjustable input polarization state of the light when it strikes the sample. The term "polarization state generator" (PSG) is commonly used in this paper. P olarisation S tate G The enerator is understood purely functionally. The corresponding instrument can be designed entirely differently, and in extreme cases (if the light source itself already provides the desired input polarization state), it can be completely omitted.

[0007] To determine the effect of the interaction with the sample on the polarization of the measurement beam, it is necessary to perform multiple intensity measurements with different relative settings for the analyzer and polarization state generator. The corresponding changes in the relative settings are here referred to purely functionally as "polarization modulation." The corresponding device for implementing this function is also here referred to purely functionally as a "polarization modulator." Depending on the specific experimental setup, polarization modulation can be performed, for example, by changing the PSG settings and / or analyzer settings, which, in addition to their primary functions, also perform the function of a polarization modulator.

[0008] According to various methods known to those skilled in the art, mathematical target parameters, such as ellipticity parameters Delta and Psi, the so-called Mueller matrix, and / or the so-called Jones matrix, can be calculated from these obtained intensity measurements (and an understanding of the corresponding polarization modulation states). Based on a properly parameterized model of the sample, specific sample characteristics can be inferred from these mathematical target parameters using error minimization methods known to those skilled in the art.

[0009] It is known that the effect of interaction with the sample on the polarization state of the measurement beam can be largely related to its wavelength. Therefore, for a comprehensive examination of the sample, it is common practice to perform the above-described methods at different wavelengths and to evaluate them based on a correspondingly complex sample model. In this document, the term "wavelength" is used here in a simplified manner commonly used in technical terms, referring to a spectral band that is appropriately narrowly selected in specific individual cases. To tune to the desired wavelength, for example, the desired spectral band can be selected from the broadband spectrum of the light source using a monochromator or variable filter, for example, before impacting the sample and preferably even before the PSG implemented by the instrument if necessary, or after the sample and preferably also after the analyzer, but in each case before entering the detector. Alternatively, a tunable light source can also be used. Regardless of the specific technical implementation, this change in wavelength is hereby referred to purely functionally as "spectral modulation." The corresponding device for implementing this function is hereby (also purely functionally) referred to as a "spectral modulator."

[0010] The polarization measurement according to the present invention includes performing multiple intensity measurements in different polarization modulation states on the one hand and in different spectral modulation states on the other hand, i.e., performing multiple intensity measurements in different constellations of polarization modulation states and spectral modulation states.

[0011] Intensity detectors can be implemented in various ways. For example, substantially point-like photodiodes, one-dimensional line cameras, or two-dimensional image detectors can be used within the scope of this invention. In particular, two-dimensional image detectors are particularly advantageous for ellipsometric imaging, which is especially beneficial in the context of this invention and may play a major role, for example, in quality control in the semiconductor industry (provided sufficient operating speed is achieved), where it is necessary to precisely measure or inspect the thickness and / or refractive index of very thin layers or coatings or similar small structures over a relatively large area. In such applications, imaging optics are typically also provided to image the sample onto the image detector.

[0012] The commonly used ellipsometric apparatus corresponds to the so-called PCSA concept: the measurement beam generated by the light source passes through a PSG constructed from a polarizer configured as a linear polarizing filter and a subsequent compensator (typically a λ quarter-wave plate), is reflected at the sample upon which the measurement beam strikes at an angle of incidence, and then passes through an analyzer also configured as a linear polarizing filter before reaching the detector. Here, polarization modulation is typically performed according to the so-called RC principle, where the compensator rotates about the optical axis (… R otating C (Ompensator, i.e., rotary compensator). This is electrically implemented in automated methods used in industrial quality assurance.

[0013] Process speed plays a crucial role precisely in industrial environments, particularly in quality control. To date, the common practice for performing spectrally resolved polarization measurements involves first progressively adjusting a number of different polarization modulation states within a pre-tuned wavelength to obtain the target polarization or ellipsoidal parameters needed in individual cases, recording the corresponding intensity measurements, and then repeating the same polarization measurements with the same pre-tuned polarization modulation states in subsequent sequentially pre-tuned wavelengths. This method is time-consuming. The acceleration resulting from the faster sequence of steps involving polarization modulation, especially the rotation of the compensator, requires more powerful and expensive motors, and introduces vibration risks due to the stronger acceleration during the start-up and shutdown of the compensator. Vibration can have adverse effects, especially in imaging methods. Therefore, despite its significant potential in principle, polarization measurement, particularly ellipsoidal measurement for imaging, has not yet been fully established in industrial quality control.

[0014] A method and instrument for identifying specific components in a sample are known from US 5,920,393 A. Essentially, this involves polarization-extended spectral analysis, in which a targeted search is conducted for a specific “pattern” characteristic of a suspected component in the sample. The starting point is the understanding that specific substances possess unique optical properties, particularly absorption, reflection, and optical activity—that is, the ability to alter the polarization characteristics of incident light—which are known in relation to the concentration of the substance in the sample and the wavelength of the incident light. The sample, in which such a substance is suspected as a component, is illuminated with light, the characteristics of which, particularly wavelength, amplitude, and polarization, change uniquely over time; correspondingly, the characteristics of the detector for the light emitted from the sample also change. The illumination and detection “pattern” is specifically tailored to the suspected substance in the sample, thereby identifying its specific effect on the incident light and thus enabling the identification of the relevant substance as a component of the sample. The literature mentioned does not describe a specific “style” for this type, but only points out an unlimited number of conceivable “styles” in principle, and the unique necessity of tailoring them to substances that are suspected to be components in the sample. Summary of the Invention

[0015] Purpose of the invention

[0016] The objective of this invention is to provide a polarization measurement method and a corresponding apparatus, by means of which shorter measurement times can be achieved with little or no significant loss of mass.

[0017] Invention Summary

[0018] This task is solved according to the present invention by providing a method for operating a polarization measurement device, wherein light having a preset input polarization state is guided to the sample for the purpose of potentially altering the polarization of the sample, and guided from the sample through an analyzer performing polarization screening and at least in a component manner to an intensity detector, wherein... - Within the range of polarization modulation, the relative angle between the output polarization state of the light leaving the sample and the analyzer is changed, and - Within the range of spectral modulation, change the wavelength of the light reaching the intensity detector. Furthermore, by using an intensity detector, multiple intensity measurements are sequentially performed under different polarization modulation states and different spectral modulation states. The corresponding intensity values, along with the polarization values ​​representing the corresponding polarization modulation states and the spectral values ​​representing the corresponding spectral modulation states, are stored together. The polarization modulation and spectral modulation are performed simultaneously and continuously, wherein the spectral modulation state is periodically changed multiple times during a single monotonic change in the polarization modulation state, and multiple intensity measurements are performed sequentially during each spectral modulation cycle.

[0019] This task is further solved according to the present invention in the following manner: a polarization measurement device is proposed, comprising: - A light source used to generate light that interacts with the sample; - Sample holder, used to position the sample in the beam path of light. - Intensity detector, used to detect the intensity of light after it has interacted with a sample. - Polarization state generator, which is arranged between the light source and the sample and is suitable for providing a preset input polarization state to the light; - A polarization-sensitive analyzer, positioned between the sample and the intensity detector, suitable for filtering out light components with a preset polarization state. - Spectral modulator, a spectral modulator is used to change the wavelength of light arriving at an intensity detector. - Polarization modulators are used to change the relative angle between the output polarization state of light leaving the sample and the analyzer. - Control unit, which is suitable for operating the intensity detector, polarization modulator, and spectral modulator according to a preset operating method. The control unit is configured to operate the intensity detector, polarization modulator, and spectral modulator according to the method of the present invention.

[0020] Preferred embodiments will be further described below.

[0021] This invention is based on the understanding that, in order to obtain the target parameter of polarization or ellipsoidal deviation, it is only important to perform a minimum number of intensity measurements predetermined according to the target parameter of interest in different polarization modulation states, which are distributed as widely as possible within the available intervals of non-redundant polarization modulation states. Conversely, the specific selection of the polarization modulation states adjusted in individual cases is not important. In the case of a rotatable compensator as a polarization modulator, the available state intervals are equivalent to a 180° rotation. If, for example, six measurements should be performed within this interval, then whether the individual intensity measurements are performed, for example, in 30°, 62°, 87°, 122°, 149°, and 178°, in 2°, 29°, 58°, 92°, 121°, and 151°, or in a similar sequence of polarization modulation states, is not important for calculating the target parameter of polarization or ellipsoidal deviation. The determining factor for obtaining the target parameter is only reaching the predetermined minimum number and knowing the relationship between the various polarization modulation states.

[0022] The inventors have fully utilized this understanding to obtain the target parameters calculated for different wavelengths based on different sets of polarization modulation states. Here, the polarization modulator operates continuously only once for a single state interval. However, during this period, the wavelength of the measurement beam (at least the portion reaching the detector) changes periodically multiple times, more precisely, at least (preferably precisely) corresponding to the minimum number of measurement points used to calculate the desired target parameters. Temporally, intensity measurements are performed for the remaining desired wavelengths between various intensity measurements performed for a particular wavelength. For example, calculating the target parameters in the cases of "red," "yellow," "green," and "blue" is based on intensity measurements performed under different, staggered sets of polarization modulation states. In other words, the time required for the polarization modulator to transition from one measurement state setting to the next for a particular wavelength is used to perform one intensity measurement for each other wavelength of interest. This assumes, typically, that the integration time of the intensity detector is very short compared to the time required for the polarization modulator to tune, and also very short compared to the period of spectral modulation. In other words, the spectral or polarization state during intensity measurement, due to the continuous tuning of the spectrum and the polarization modulator, does not actually affect the measurement quality. Those skilled in the art can adapt the spectral or polarization "blurring" to the requirements of individual cases by appropriately selecting the modulation rate and detector integration time, or can experimentally discover the spectral or polarization "blurring" without much effort.

[0023] The overall result of the solution according to the invention is a significant acceleration of the measurement process and a reduction in vibration due to the continuous rather than stepwise movement of the polarization modulator. This is particularly beneficial to the quality of imaging ellipsometric measurements, as mentioned above, which is of particular interest in the semiconductor industry, where general measurement acceleration is also especially important for quality assurance.

[0024] Preferably, the intensity measurements performed during each spectral modulation cycle are performed immediately after each other. In this document, "immediately after" means at the instrument's preset maximum speed. Therefore, advantageously, there should be no delay between the various intensity measurements, for example, due to waiting for a trigger signal. Instead, an intensity measurement should follow the previous measurement as quickly as possible, as long as the instrument allows; that is, the intensity detector should "operate without interruption," thus allowing the maximum number of intensity measurements to be performed within a given time.

[0025] Here, the integration time for each intensity measurement can be controlled by adjusting the wavelength accordingly. This can compensate for dispersion effects. For example, the output intensity of the spectral modulator may be wavelength-dependent. Similarly, the sensitivity of the intensity detector may also be wavelength-dependent. Even the analyzer may exhibit wavelength-dependent passband attenuation. If this effect is known, then good compensation can be provided by corresponding wavelength-dependent manipulation of the detector integration time. Alternatively, however, it may be possible that the integration time for each intensity measurement is constant, i.e., the integration time is the same in all measurements.

[0026] The wavelength variation within each spectral modulation cycle is preferably monotonically, and especially linearly. In a particularly preferred, and lastly mentioned, case, a sawtooth wavelength profile is produced within the range of spectral modulation. Thus, the temporal sequence of the various intensity measurements always results in the same spectral distance for each subsequent intensity measurement.

[0027] It has proven particularly advantageous that the time span of the monotonic change in polarization state corresponds to an integer multiple of the spectral modulation period. Therefore, the "first" wavelength traversed within the range of spectral modulation falls on the initial setting of the polarization modulator, while the ending position of the polarization modulator falls on the "last" wavelength traversed within the range of spectral modulation. Between these wavelengths, the wavelength is periodically tuned multiple times, preferably precisely the number of times corresponding to the minimum number of polarization modulation states required to obtain the target parameter.

[0028] In the optimal design for measurement speed, the start of each spectral modulation cycle coincides with the start of the intensity detector's integration time, and the end of each spectral modulation cycle coincides with the end of the intensity detector's integration time. Within each spectral modulation cycle, the exact same number of intensity measurements are performed at different wavelengths corresponding to the target parameter that should be known. In other words, in this configuration, only the minimum number of mandatory measurements are recorded without any time delay during this period. Especially when only a very short integration time is required due to sufficient light intensity, more intensity measurements than mandatory are possible during the spectral modulation cycle. These "redundant" measurements can be discarded or used for other purposes.

[0029] The longer the integration time is compared to the spectral modulation period, the more important some form of synchronization becomes. In one embodiment of the invention, polarization modulation, spectral modulation, and intensity measurement are performed electromechanically and synchronously. Preferably, the order of intensity measurements is pre-set with a basic clock. Spectral modulation is manipulated such that its period is an integer multiple of the integration clock. Polarization modulation itself is manipulated such that the time required to tune the polarization interval is an integer multiple of the spectral modulation period. It should be noted, according to this embodiment, that the basic clock pre-set by the integration time can vary with wavelength. With such synchronized operation of all components, the constellation formed by the respective spectral modulation and polarization modulation states can be determined by simple counting.

[0030] In an alternative implementation, only coarse control synchronization is performed by roughly pre-adjusting each component (intensity detector, polarization modulator, spectral modulator) in the manner described above, but then allowing them to operate "freely." Here, it can be configured that polarization adjustment values ​​representing the respective adjusted polarization modulation states and / or spectral adjustment values ​​representing the respective adjusted spectral modulation states are continuously measured and converted into polarization or spectral values ​​respectively associated with the intensity measurement and to be stored with it. In other words, there is no fully synchronized control of the components; instead, for each intensity measurement, the current settings of the polarization or spectral modulator are measured, and thereby the polarization / spectral constellation associated with each intensity measurement is known and stored.

[0031] In the first scenario described above, very precise and technically complex manipulation of the components is required. Conversely, in the second scenario, the current settings also require separate, technically complex, and very precise measurements. In practice, a hybrid system may prove optimal, where good, but suboptimal, synchronized manipulation is accompanied by good, but suboptimal, state measurements of the components, which are then recalibrated separately.

[0032] Preferably, polarization modulation is performed using a polarization modulator positioned in the beam path before or after the sample and adjustable by a first adjustment motor. Specifically, the polarization modulator can be configured as a pair of polarizers and compensators rotatable by the first adjustment motor, positioned in the beam path between the light source and the sample. In any case, this configuration can be fully utilized such that the polarization adjustment value is a positioning value representing the position of the first adjustment motor. In other words, it is not necessary to directly measure the position of the polarization modulator. Measuring the respective positions of the adjustment motors used to set it is sufficient. Adjustment motors with corresponding outputs capable of reading the current position are known to those skilled in the art and are commercially available.

[0033] Similarly, spectral modulation can be performed using a spectral modulator positioned in the beam path before or after the sample and adjustable by a second adjustment motor. This can be fully utilized in such a way that the spectral adjustment value is a positioning value representing the position of the second adjustment motor. Further explanation is similarly provided above.

[0034] Further details and advantages of the invention will become apparent from the following specific description and drawings. Attached Figure Description

[0035] in:

[0036] Figure 1 : A schematic diagram showing a preferred embodiment of an ellipsometer for imaging, by means of which the method according to the invention can be performed;

[0037] Figure 2 : A schematic diagram illustrating the method flow according to the present invention; and

[0038] Figure 3 : This shows another schematic diagram of the method flow according to the present invention. Detailed Implementation

[0039] The same reference numerals in the accompanying drawings denote the same or similar elements.

[0040] Figure 1 A very schematic illustration shows a basically known ellipsometer for imaging, which operates based on the principle of a rotating compensator (RC principle). The measurement beam 14 originates from the light source 12 at an angle of incidence. The light beam 14 is emitted onto sample 16 and reflected from the sample by imaging optics 18 onto detector 20 for imaging. In its path from light source 12 to sample 16, the measurement beam 14 passes through a (linear) polarizer 22, which together function as a polarization state generator (PSG), and a downstream compensator 24. Here, polarizer 22 can be configured as a linear polarization filter. Compensator 24 can be designed as a λ-quarter-wave plate, by which the light components polarized perpendicular to and parallel to the incident plane are phase-shifted relative to each other. This results in the generally ellipsometric polarization of the measurement beam 14. By rotating compensator 24 about the optical axis (i.e., the beam direction of the measurement beam 14), the ellipticity and axial orientation (angular position) of the polarization of the measurement beam 14 can be changed, thereby altering its polarization state, especially the input polarization state of the measurement beam 14 when it reaches sample 16. This is achieved through… Figure 1 The rotating arrow 26 in the image indicates this.

[0041] The portion of the sample 16 illuminated by the measured beam 14 is imaged onto the intensity detector 20 using imaging optics 18. Here, the light passes through an analyzer 28, which can be configured as a (linear) polarization filter. The analyzer 28, depending on its orientation, allows only specific polarization components of the measured beam 14 to pass through, while other polarization components are suppressed. Furthermore, in the illustrated embodiment, the measured beam passes through an adjustable filter 30 between the sample 16 and the intensity detector 20. This filter (depending on its setting) allows only selected wavelengths of light to pass through, while other light components are suppressed or deflected far enough not to fall onto the intensity detector 20. Instead of positioning the filter 30 in the detection portion of the beam path, the filter or an equivalent spectral converter, such as a monochromator, can be arranged in the illumination portion of the beam path. A preferred practical embodiment includes a monochromator arranged between the light source 12 and the PSGs 22 / 24. Figure 1 The illustration of filter 30 in the probe beam path is for better overview only.

[0042] Within the scope of the method according to the invention, the compensator 24 rotates continuously from an initial position to a final position. This correspondingly changes the input polarization state of the measurement beam 14 when it falls on the sample 16. It also correspondingly changes the output polarization state of the measurement beam 14 when it leaves the sample 16 and interacts with the analyzer 28. Therefore, the intensity of the light component striking the detector, detected by the detector 20, varies with the angular position of the compensator 24, more specifically, periodically with respect to the angular position of the compensator 24 in 180° intervals. This means that during the implementation of the method according to the invention, the adjustment of the compensator 24 is limited to a maximum of 180°, which is indeed the case, for example, in the preferred embodiment.

[0043] During this relatively slow polarization modulation, according to the invention, the wavelength of the light component to strike the detector 20 is modulated multiple times, for example by corresponding multiple variations of the filter 30 or an equivalent spectral modulator.

[0044] The time flow of the method according to the present invention is Figure 2 The illustration is shown schematically and exemplarily. For one cycle, the compensator 24 rotates 180°. Simultaneously, the wavelength λ is tuned multiple times, starting at the initial wavelength λ in the illustrated embodiment. s With the final wavelength λ e The tuning was performed six times. In the preferred embodiment shown, the tuning was performed in a sawtooth pattern, i.e., during the spectral modulation period. During this period, the wavelength adjusted at the spectral modulator changes linearly so as to jump back to the initial state as instantaneously as possible at the end of the cycle. Corresponding adjustment devices, such as the electrically operated grating of a monochromator, are known to those skilled in the art. Simultaneously with polarization modulation and spectral modulation, timed intensity measurements are performed using detector 20. In the illustrated embodiment, the intensity measurement is performed with a constant integration time. conduct.

[0045] In an integral interval During this period, the angular position of the compensator 24 changes by an angle amount δ. RC The wavelength changes by a wavelength amount δ λ The corresponding intensity measurements can be assigned to a constellation composed of polarization and spectral states, which can be considered, for example, as polarization intervals δ each with a corresponding bandwidth. RC or spectral interval δ λ The average value (“fuzzy”).

[0046] Figure 3 The location of each intensity measurement is shown in the polarization / wavelength plane, where solid arrows indicate the temporal sequence of the intensity measurements. It should be noted that, for clarity, Figure 3 The illustration shows only intensity measurements at four different polarization intervals and three different spectral intervals (according to...). Figure 2 The method employed will result in intensity measurements at six different polarization intervals and four different spectral intervals.

[0047] from Figure 3As can be seen from the simplified diagram, due to the method according to the invention, the spectral and polarization states change from one intensity measurement to another, but as a result, four intensity measurements are recorded for three specified wavelengths under different, substantially equidistant polarization states. For each wavelength, predetermined polarization or ellipsoidal target parameters (ellipticity parameters Δ and Ψ in the illustrated example) can be determined with the same precision. As is known to those skilled in the art, the number of measurement points required for each wavelength is related to the respective target parameters of interest and the specific instrumentation. However, as from... Figure 2 As can be seen, there is no "dead time" during data recording. Instead, the intensity detector operates at its instrumentally preset maximum speed, allowing measurements to be performed with maximum efficiency at the theoretically highest possible speed. Here, because the compensator 28 makes only one slow and continuous change, no vibrations that would interfere with the image recording quality of the detector 22 are introduced. Therefore, compared to what is possible with prior art to date, the resulting imaging ellipsometric measurements are not only faster but also of higher quality and accuracy.

[0048] exist Figure 2 In the embodiment shown, spectral modulation, polarization modulation, and intensity measurement are coordinated sequentially in time in such a way that the spectral period is... Equivalent to the integration time of detector 20 Integer multiples of, while polarization period Equivalent to spectral period The synchronization can be achieved by controlling the corresponding synchronization of the components of each instrument. Alternatively, the operating speed of each component can be pre-adjusted, and their respective settings can be monitored and measured so that the positioning of each intensity measurement in the polarization / wavelength plane can be subsequently determined (see...). Figure 3 In practice, combinations of these approaches may be accepted, where a rough electromechanical synchronization is achieved, i.e., synchronous control, and corrected for by positioning measurements recorded in parallel during method execution.

[0049] Of course, the embodiments discussed in the detailed description and shown in the accompanying drawings are merely illustrative examples of the invention. Given this disclosure, a wide range of possibilities for variation are provided to those skilled in the art. In particular, the method according to the invention can be used in both polarization and ellipsometric contexts. The selection of target parameters for polarization or ellipsometrics, respectively, for determination, does not imply a limitation on the method. The number of intensity measurements to be recorded is derived, in a manner recognizable to those skilled in the art, from the selection of the target parameters being searched and the specific instrumentation, particularly the instrument characteristics of the polarization modulator. Regarding the specific instrument design of the modulator, those skilled in the art are certainly not limited to the embodiment with motor-driven mechanical adjustment elements preferably described herein. Electro-optic, magneto-optic, acousto-optic, and other devices that can be used as functional polarization modulators or spectral modulators are now known to those skilled in the art. Future devices may also be used within the scope of this invention. Specific detection techniques are also applicable here.

[0050] List of reference numerals

[0051] 10. Ellipsometry for imaging

[0052] 12 Light Sources

[0053] 14 Measuring the beam

[0054] 16 samples

[0055] 18 Imaging Optics

[0056] 20 intensity detector

[0057] 22 Polarizer

[0058] 24 Compensators

[0059] 26 Rotating Arrows

[0060] 28 Analyzer

[0061] 30 filter

[0062] Points Time

[0063] Polarization modulation period

[0064] δ RC polarization interval

[0065] Spectral modulation period

[0066] δ λ spectral interval

Claims

1. A method for operating a polarization measurement device (10), wherein, Light (14) having a preset input polarization state is guided to the sample (16) for the purpose of potentially altering the polarization of the light, and is guided from the sample through a polarization-screening analyzer (28) and at least in a component manner to an intensity detector (20), wherein, - Within the range of polarization modulation, the relative angle between the output polarization state of the light (14) leaving the sample (16) and the analyzer (28) is changed, and - Within the range of spectral modulation, the wavelength of the light (14) reaching the intensity detector (20) is changed. Furthermore, using the intensity detector (20), multiple intensity measurements are sequentially performed in different polarization modulation states and in different spectral modulation states, and the corresponding intensity values ​​are stored together with the polarization values ​​representing the corresponding polarization modulation states and the spectral values ​​representing the corresponding spectral modulation states. The feature is that the polarization modulation and the spectral modulation are performed simultaneously and continuously, wherein the spectral modulation state is periodically changed multiple times during a single monotonic change in the polarization modulation state, and multiple intensity measurements are sequentially performed during each spectral modulation cycle.

2. The method according to claim 1, characterized in that, Intensity measurements performed during each spectral modulation cycle are performed one after another.

3. The method according to claim 1, characterized in that, The integration time for each intensity measurement depends on the individually adjusted wavelength.

4. The method according to claim 1, characterized in that, The integration time used for each intensity measurement is constant.

5. The method according to claim 1, characterized in that, The wavelength changes monotonically within each spectral modulation cycle.

6. The method according to claim 1, characterized in that, The time span of the monotonic change in the polarization modulation state is equivalent to an integer multiple of the spectral modulation period.

7. The method according to claim 1, characterized in that, The polarization modulation, the spectral modulation, and the intensity measurement are performed synchronously and electromechanically.

8. The method according to claim 1, characterized in that, The polarization adjustment value representing the respective adjusted polarization modulation state and / or the spectral adjustment value representing the respective adjusted spectral modulation state are continuously measured and converted into polarization or spectral values ​​respectively associated with the intensity measurement and to be stored together.

9. The method according to claim 1, characterized in that, The polarization modulation is performed by means of a polarization modulator, which is arranged in the beam path before or after the sample (16) and can be adjusted by a first adjustment motor.

10. The method according to claim 9, characterized in that, The polarization modulator is configured as a pair consisting of a polarizer (22) and a compensator (24) that can be rotated by the first regulating motor, positioned in the beam path between the light source and the sample.

11. The method according to claim 9, characterized in that, The polarization adjustment values, representing the respective adjusted polarization modulation states, are continuously measured and converted into polarization values ​​that are respectively associated with the intensity measurement and stored together, wherein the polarization adjustment value is a positioning value representing the position of the first adjustment motor.

12. The method according to claim 1, characterized in that, Spectral modulation is performed using a spectral modulator, which is arranged in the beam path before or after the sample and can be adjusted by a second regulating motor.

13. The method according to claim 12, characterized in that, The spectral adjustment values ​​representing the respective adjusted spectral modulation states are continuously measured and converted into spectral values ​​that are respectively associated with the intensity measurement and are to be stored together, wherein the spectral adjustment values ​​are positioning values ​​representing the position of the second adjustment motor.

14. The method according to claim 5, characterized in that, The wavelength change occurs linearly within each spectral modulation cycle.

15. A polarization measurement device (10), comprising: - Light source (12) for generating light (14) to interact with the sample (16); - A sample holder for positioning the sample (16) in the beam path of the light (14), - An intensity detector (20) is used to detect the intensity of light after the light (14) interacts with the sample (16). - A polarization state generator, which is arranged between the light source (12) and the sample (16) and is adapted to provide a preset input polarization state to the light (14); - A polarization-sensitive analyzer (28), the analyzer being arranged between the sample (16) and the intensity detector (20), and suitable for filtering out light components with a preset polarization state. - A spectral modulator (30) adapted to change the wavelength of light (14) arriving at the intensity detector (20), - Polarization modulator (24), the polarization modulator being adapted to change the relative angle between the output polarization state of the light (14) leaving the sample (16) and the analyzer (28), and - Control unit, which is adapted to operate the intensity detector (20), the polarization modulator (24) and the spectral modulator (30) according to a preset operating method. The control unit is characterized in that it is configured to operate the intensity detector (20), the polarization modulator (24) and the spectral modulator (30) according to any one of claims 1 to 14.

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