WO2012042022A1

WO2012042022A1 - Ellipsometer

Info

Publication number: WO2012042022A1
Application number: PCT/EP2011/067116
Authority: WO
Inventors: Michael Totzeck; Nico Correns; Frank Widulle; Christian Koos
Original assignee: Carl Zeiss Ag
Priority date: 2010-09-30
Filing date: 2011-09-30
Publication date: 2012-04-05
Also published as: DE102010041814A1; DE102010041814B4

Abstract

The invention relates to an ellipsometer for examining a sample (2, 3), comprising an illumination beam path (4), which is designed to illuminate the sample (2, 3) with illuminating radiation (10) of certain polarization and divergence (w) at a certain angle (a), a measurement beam path (5), which is designed to collect, as a diverging reflection beam (11), illuminating radiation (10) reflected at the sample (2, 3) in a reflection angle range (u) or reflection location range and to analyze said reflected illuminating radiation in regard to spectral composition and polarization state, wherein the measurement beam path (5) has: a spectrometer (13), into which the reflection beam (11) is coupled and which spectrally divides the reflection beam (11), a 2-D detector (15) arranged in the spectrometer (13), and a polarization device, which is arranged in front of the detector (15) and which spatially filters the reflection beam (11) according to the polarization state before the spectral decomposition, wherein the spectrometer (13) has a longitudinally extended inlet gap (17), the measurement beam path (5) has a collecting device (12), which collects the reflection beam (11) and guides the reflection beam to the inlet gap (17) of the spectrometer (13), and the spectrometer (13) directs the reflection beam (11), which is spectrally decomposed, at the detector (15) transversely to the propagation direction of the reflection beam (11) and transversely to the longitudinal extension of the inlet gap (17), wherein the polarization device comprises a plurality of groups (G1-Gn), which each have a plurality of different polarizers (18-21), which each filter the reflection beam (11) in regard to different polarization states, wherein the groups (G1-Gn) and the polarizers (18-21) in the groups (G1-Gn) are arranged next to each other on the inlet gap (17) or in the inlet gap (17) of the spectrometer (15), the collecting device (12) distributes the reflection beam (11) among the groups (G1-Gn) according to the reflection angle or reflection location and guides the reflection beam to the inlet gap (17) in such a way that the reflection angle or reflection location varies along the longitudinal extension of the inlet gap (17).

Description

ellipsometer

The invention relates to an ellipsometer for examining a sample, having an illumination beam path, which is designed to illuminate the sample with illumination radiation of certain polarization and divergence at a certain angle, a Meßstrahlengang which is formed on the sample in a reflex angle range or Reflexortsbereich reflected illumination radiation as a divergent reflection beam bundle and to analyze the spectral composition and polarization state, the Meßstrahlengang comprising: a spectrometer into which the reflected radiation beam is coupled and which spectrally splits the reflected radiation beam, a spectrometer arranged in the 2D detector and a polarizer means, the detector is upstream, and which spatially filters the reflected radiation beam before the spectral decomposition depending on the polarization state, wherein the spectrometer has an elongated entrance slit comprises, the Meßstrahlengang comprises means for collecting, which collects the reflection beam and passes to the entrance slit of the spectrometer, and the spectrometer spectrally disperses the reflected radiation beam transversely to the propagation direction of the reflected radiation beam and transversely to the longitudinal extent of the entrance slit on the detector. The invention further relates to an ellipsometer for examining a sample, having a sample illumination beam path, which is designed to illuminate the sample with illumination radiation of particular polarization and divergence at a certain angle, a Meßstrahlengang which is formed on the sample in a reflex angle range or Reflexionsbereich reflected illumination radiation as a divergent reflection beam bundle and analyze the spectral composition and polarization state, the Meßstrahlengang comprising: a spectrometer into which the reflected radiation beam is coupled and which spectrally splits the reflected radiation beam, arranged in a spectrometer 2D detector and a polarizer device, the Detector is arranged upstream, and spatially filters the reflected radiation beam before the spectral decomposition depending on the polarization state, wherein the Meßstrahlengang a Comprises means for collecting, which couples the reflected radiation beam in an optical fiber bundle, the optical fiber bundle Einzellichtleitfasern, which end along a longitudinal extension adjacent to an input of the spectrometer, and the spectrometer supplied to the input reflex beam bundles spectrally split across the longitudinal direction to the detector, wherein the Polarization device is realized by a polarization-filtering property of the individual optical fibers or by the Einzelellichtleitfasern upstream or downstream polarizers, the polarization-filtering properties of the Einzelellichtleitfasern or the polarizers in each case the reflection radiation (1 1) filter with respect to different polarization states.

In the analysis of thin layers, as they occur in photovoltaics, semiconductor manufacturing and architectural glass production, layer thickness, refractive index and refractive index profiles must be determined. The coarse layer structure is generally known, but there are - especially in the process development - large fluctuation ranges in the values. One of the most accurate methods for layer measurement is spectroscopic ellipsometry.

In an ellipsometer, a layer system is illuminated at a defined angle - usually near 45 ° - with radiation of a well-defined polarization state. The polarization state of the reflected light is analyzed with a polarimeter. The name Ellipsometrie comes from the fact that this is often converted linearly polarized light.

The measured polarization state is compared with a polarization state calculated from a layer model. For simple interfaces, Fresnel's equations are most often used, for layer systems the so-called "Thin Film Matrix Theory." The parameters of the simulated layer system (thicknesses and indices of refraction) are varied until the measurement and simulation are in line, since ellipsometry provides only two output magnitudes - Ellipticity and Azimuth - naturally only two parameters can be reconstructed, which is why layer thicknesses with a known refractive index of the solid material are often determined.

In order to investigate more parameters of a layer structure, the spectroscopic ellipsometry was developed, in which the above process is performed for a whole wavelength spectrum. This results in a set of parameters that allows to reconstruct multilayer layer systems.

With regard to the ellipsometer, different variants are known. In ellipsometry using a rotating polarizer either the polarizer in the illumination beam path or the Polarizer rotates in the measuring beam path. Depending on the angle of rotation, the transmitted power is measured. If, in addition to or instead of the polarizer, a lambda-quarter plate is rotated in the illumination or measuring beam path, the so-called Jones matrix can additionally be completely determined. Since quarter-wave plates show a strongly wavelength-dependent behavior, this variant is not suitable for spectroscopic ellipsometry without further ado.

Another variant of ellipsometry is the so-called null-ellipsometry. Here, the polarization state of the illumination radiation is adjusted so that after reflection on the sample linearly polarized light is present. Then set the analyzer, d. H. the polarizer device in the measuring beam path perpendicular to this polarization direction, the intensity of the detected reflected radiation beam at the detector is almost zero. From polarization angles of the illumination radiation and the polarizer device serving as an analyzer in front of the detector, refractive index and visible thickness of the sample can be determined. Since this method works in the dark field, so to speak, it is also well suited to find minimal variations around a preset setpoint, so z. B. layer fluctuations to make a target surface resolved visible.

Spectroscopic ellipsometers are widely known in the art, such. B. in the form of successive illumination of the sample with narrow-band illumination radiation of different wavelengths, as described in US 5076696 or EP 1574842 A1. DE 1 0146945 A1 proposes for a spectrally analyzing ellipsometer to guide the spectrally fanned-out radiation through a micropolarization filter, which is arranged after the spectral fanning in front of the detector and has filter pixels, wherein each filter pixel is associated with one pixel of the detector. The filter pixels have different transmission or major axis directions for polarized radiation. With this approach, the effort required for the polarization device in the measuring beam path increases noticeably with increasing resolution of conventional 2D detectors. In US 6320657 a spectroscopic ellipsometer is disclosed which analyzes all wavelengths in parallel via a monochromator. The polarization device is designed as a rotating compensator. US 5,329,357 also describes a spectroscopic ellipsometer in which the polarizer, i. H. Polarization of illumination radiation, and analyzer, d. H. rotate the detector upstream polarizer. Furthermore, it is disclosed here to provide the illumination radiation via the optical fiber and also to collect the reflection radiation via an optical fiber and to supply it to the spectrometer.

In addition to mechanical adjustment of the polarization components of course, electronic settings in the prior art are known, for example in the US 7265835 and US 6753961. US Pat. No. 7,492,455 discloses a spectrally analyzing ellipsometer which contains a multiplicity of illumination sources, including a polarization setting for the illumination radiation, which are successively switched into the beam path. In this case, only discrete states of polarization are used and no continuously varying states in that several broadband sources are each combined with discrete polarization states to provide the illumination radiation and activated sequentially for the measurement.

A spectral detection of a sample by means of ellipsometer also describes the US 2010/0004773 A1. Here, a reflection on a sample in a flat sample area is detected and imaged onto a 2D detector. Prior to imaging on the detector, in one of the embodiments described in US 2010/0004773 A1, a spatial modulation of the recorded reflection radiation with respect to the polarization state takes place by means of a so-called hypercube. However, the computational reconstruction effort for sample analysis is considerable.

US 7372568 B1 describes a polarimeter for the evaluation of four polarization states. In this case, a polarizer block is used whose entrance surface is divided into four sections, which cause different polarizations.

DE 19621512 A1 describes a polarimeter for evaluating the wavelength-dependent polarization state of radiation. For this purpose, a polarization grating with lithographically produced microstructures and a spectral deflection grating is used. US 5440390 A discloses a polarimeter comprising an optical fiber bundle whose individual beams have different polarization effects. The radiation to be analyzed is coupled into the optical fiber bundle and then passed to a 2D detector so that the radiation from the end faces of the individual fibers is spatially resolvable. From the intensity distribution on the 2D detector then a statement about the polarization state of the coupled radiation is derived.

US 2007/0229852 A1 discloses an ellipsometer which has conventional prisms as a polarizer in the illumination beam path and as an analyzer in the detection beam path. DE 19547552 C1 relates to the field of air surveillance and discloses a device for determining the polarization state of radiation received from a half-space at different picture elements. Each picture element consists of at least three different polarization filters arranged side by side. By a polarization filter passed and polarized radiation is then passed through an optical waveguide. There are three optical fibers for each pixel. All optical fibers are then arranged side by side in an entrance slit of a spectrometer along the gap.

US 6052188 discloses a spectroscopically operating ellipsometer of the type mentioned, wherein optical fibers can be used in the beam path to the entrance slit of the spectrometer. The DE 1 0021378 A1 also describes an ellipsometer of the type mentioned. The radiation reflected at the sample is passed through a polarizing Wollaston prism for filtering, so that after the prism two output light beams are present, of which one polarized s and the other p is polarized. These two beams are then coupled by means of collimators in two optical fibers and passed from there to a spectrometer.

The latter two publications disclose an ellipsometer having a sample illumination beam path which illuminates the sample with illumination radiation of certain polarizations and divergence and at a certain angle, a measurement beam path which collects illumination radiation reflected from the sample as a reflection beam and analyzes for spectral composition and polarization state and a spectrometer with 2D detector and a polarization device, which spatially filters the reflected radiation beam before the spectral decomposition depending on the polarization state includes. In both devices, a collimator device is provided in the measurement beam path, which couples the reflected radiation beam into an optical fiber bundle, which has individual light fibers and directs the reflected radiation beam to the spectrometer input. However, these ellipsometers are not suitable for recording areal samples.

The invention has the object of developing an ellipsometer of the type mentioned in such a way that a rapid analysis of area even complex layer systems is possible. In particular, the spectrometer should be able to be used directly in production processes, so have so-called in-line capability.

This object is achieved with an ellipsometer for examining a sample, with an illumination beam path, which is designed to illuminate the sample with illumination radiation of certain polarization and divergence at a certain angle, a Meßstrahlengang which is formed on the sample in a reflex angle range or Reflex area reflected illumination radiation as collecting and analyzing spectral composition and polarization state, wherein the measuring beam path comprises: a spectrometer into which the reflected radiation beam is coupled and which spectrally splits the reflection radiation beam, a 2D detector arranged in the spectrometer and a polarizer device which is arranged upstream of the detector, and spatially filtering the reflected radiation beam prior to spectral decomposition depending on the state of polarization, the spectrometer having an elongated entrance slit, the measuring beam path having means for collecting, in particular a collimator, collecting the reflected beam and directing it to the entrance slit of the spectrometer, and the spectrometer the reflection beam bundles spectrally dissected transversely to the propagation direction of the reflected radiation beam and transverse to the longitudinal extent of the entrance slit on the detector, wherein the di e polarizer device comprises a plurality of groups, each with a plurality of different polarizers, which each filter the reflected radiation beam with respect to different polarization states, the groups as well as the polarizers in the groups next to each other on the entrance slit or in the entrance slit of the spectrometer are arranged, the means for collecting, the Reflective radiation beam depending on the angle of reflection or reflex location distributed to the groups and so on the entrance slit that varies along the longitudinal extent of the entrance slit, the angle of reflection or reflex locations. The object is further achieved by an ellipsometer for examining a sample, with a sample illumination beam path, which is designed to illuminate the sample with illumination radiation of particular polarization and divergence at a certain angle, a measuring beam path, which is formed on the sample in a reflex angle range or Reflexionsbereich reflected illumination radiation as a divergent reflection beam bundle and analyze the spectral composition and polarization state, the Meßstrahlengang comprising: a spectrometer into which the reflected radiation beam is coupled and which spectrally splits the reflected radiation beam, arranged in a spectrometer 2D detector and a polarizer device, the Precedent detector, and spatially filters the reflected radiation beam before the spectral decomposition depending on the polarization state, wherein the Meßstrahlengang a means for S ammeln, in particular a collimator, which couples the reflected radiation beam in a Lichtleitfaserbündel, the Lichtleitfaserbündel Einzelellichtleitfasern having along a longitudinal extension adjacent to one another at an input of the spectrometer, and the spectrometer deflects the input at the input reflex beam bundled spectrally dissected to the longitudinal extent of the detector in which the polarization device is realized by a polarization-filtering property of the single-fiber fibers or by polarizers disposed upstream or downstream from the single-optical fibers, the polarization-filtering properties of the Einzellichtleitfasern or the polarizers each filter the reflection radiation with respect to different polarization states, wherein the optical fiber bundle comprises a plurality of groups of at least four Einzellichtleitfasern and distributes the means for collecting the radiation of the reflected radiation beam depending on the angle of reflection or reflex location on the groups.

The invention thus provides, in a first and a second variant, for spectrally filtering the reflection radiation and for distributing it at reflex locations or angles at the input of the spectrometer. When the spectrometer operates with a conventional entrance slit, the polarizers are arranged side by side in the entrance slit, so that the spatial separation of the reflected beam with respect to the different polarization states in the entrance slit takes place.

The same happens if the spectrometer has no conventional entrance slit, but optical fibers whose end faces act as an entrance slit. Then, after the coupling out of the optical fibers or before the coupling into the optical fibers or even during coupling / decoupling the polarization filtering is performed.

The placement at this point, d. H. at the entrance slit or at the spectrometer input has the advantage that in the interior of the spectrometer filter no longer need to be arranged. Stray light or back reflections of such filters are thus avoided. Further, the geometric association between the entrance slit or spectrometer entrance and the structured polarizer means comprising the plurality of polarizers and the spectrum on the 2D detector is ideal. A possible adjustment of the polarizers with respect to the detector pixels is omitted, since the spectral breakdown takes place only after the spatial separation of the different polarization states.

Also eliminates the great expense incurred in the so-called Hypercube system of US 2010/0004773 A1, which makes the spatial breakdown significantly before the spectrometer entrance or entrance slit.

In the case of the variant of the invention in which optical fiber ends take over the function of the entrance slit at the spectrometer input, several groups of at least four individual optical fibers are provided in the optical fiber bundle and the means for collecting (eg a collimator device) is designed such that it depends on the reflected radiation Reflection angle or reflex location distributed among the groups. Each group then corresponds to a spectrometer channel, and the spectrometer spectrally fans the radiation coming from a group into a spatial direction. The other spatial direction is then the individual Associated optical fiber groups and thus encodes the reflex location or the angle of reflection, depending on the design of the collimator. This approach is analogous to the ellipsometer, which is not limited to optical fiber optics. The invention achieves a particular suitability of the Eilipsometer for scanning flat samples by a plurality of groups of at least optical fibers or more groups, each with different polarizers, is distributed to the reflecting radiation by the means for collecting depending on the angle of reflection or Reflexort. Such a device for collecting is in no way addressed in the prior art, but allows the rapid detection of a flat sample with the ellipsometer.

The polarizers can be realized in a particularly simple manner by being applied to the entry or exit-side end faces of the individual optical fibers, which are then of course preferably polarization-preserving, in particular if larger fiber light paths are present. With short fibers, polarization maintenance can sometimes be dispensed with.

In addition to the differently polarized elements of the reflected radiation beam, it is expedient to provide a non-polarization filtered dark and / or a white light channel in the entrance slit or at the spectrometer input, z. B. in each group a dark and / or white light channel. This allows a permanent dark measurement and / or a white reference and thus a better evaluation of the radiation by a better normalization of the intensity. If the polarization directions 0 °, 45 °, 90 ° and circular are used for the polarizers, the entire Stokes vector of the radiation can be spectrally decomposed.

In the sense of the description, "reflex" is also understood to mean scattering, ie, the term is not restricted to a specular reflection. <br/> <br/> Basically sufficient information about the layer can also be derived from illumination with unpolarized radiation to understand also unpolarized radiation.

In order to make the ellipsometer particularly suitable for use in a production process for layers, it is advantageous to ensure that the reflection intensity which is detected is as independent of adjustment as possible. It should not change as much as possible if the position of the layer varies. This can be achieved in a first variant particularly simply by illuminating a lighting spot which is much larger than the detected measuring spot in which the reflection radiation is collected. The same can apply alternatively or additionally for the aperture. The difference in size ensures that even when the layer varies within certain tolerances, in particular when the layer is shifted or tilted, the measuring spot / measuring angle range always detects an area which is within the illumination spot / illumination angle range. Of course, an inverted approach is also possible, that is, the measurement spot / measurement angle range is much larger than the illumination spot / illumination angle range. It is therefore essential for this advantage that there is a size and / or aperture difference between the illumination spot and the measuring spot, which is chosen so that even with a certain, predetermined variation of the position of the layer, the smaller spot / the larger aperture is completely within the larger one Stain / the smaller aperture remains. In a second variant, a tracking is provided. By means of a suitable measuring device, the position of the ellipsometer in the space and / or the layer to be measured is determined and regulated in a desired position relative to the layer tracked.

In a third variant, in the determination of layer parameters, a correction can be made that takes into account the position of the ellipsometer in the space and / or the layer and compensates for any deviations from a desired position to the layer, for example by previously determined correction values in a control device are stored. Of course, a measurement of the situation is also provided here. It is understood that the features mentioned above and those yet to be explained below can be used not only in the specified combinations but also in other combinations or alone, without departing from the scope of the present invention. The invention will be explained in more detail for example with reference to the accompanying drawings, which also disclose characteristics essential to the invention. Show it:

1 is a schematic representation of an ellipsometer according to a first embodiment of the invention,

2 is a schematic representation of a spectrometer gap of the ellipsometer of FIG. 1,

3 is a schematic representation of the splitting of the polarization directions for different angles of reflection or reflex locations in an ellipsometer similar to that of FIG. 1, FIG. Fig. 4 is a plan view of a sample with a schematic representation of lighting and

Deflektionsfleck,

Fig. 5 is an ellipsometer another construction and

Fig. 6 is a schematic representation of the input of the ellipsometer of Fig. 5 with the generation of different polarization channels and

Fig. 7-9 representations similar to Fig. 6 of differently shaped ellipsometer inputs.

FIG. 1 schematically shows an ellipsometer 1 a, which is designed to measure a layer 2 on the surface of a sample 3. The ellipsometer 1 a has an illumination beam path 4 and a measuring beam 5. The illumination beam path 4 includes a broadband source 3, the z. B. light, that emits radiation in the visible spectral range. Downstream of the source 6 is a collimator 7, which parallelizes the radiation and passes it on to a polarizer 8, which, as known in ellipsometry, polarizes the radiation. An illuminating optics 9 generates a bundle of convergent illumination radiation 10 with which the layer 2 of the sample 3 is illuminated. The opening angle w of the illumination radiation 10 can preferably be adjusted so that the size of the illuminated spot on the layer 2 of the sample 3 can be varied. Since the illumination beam path 4, as can be seen from the drawing, is tilted onto the layer 2 by an angle a relative to the normal N, the illumination radiation, after an interaction with the sample (for example diffraction on a periodic structure, etc.), becomes a divergent reflection beam 1 1 reflected on the sample 3 and in particular its layer 2. The reflection beam 1 1 is collected by a collimator 12, wherein the opening angle at which the collimator collects the reflection beam is denoted by u. In the illustration of Figure 1, the measuring beam 5 is arranged so that it receives a reflected beam 1 1, which corresponds to a beam, which would be generated in purely specular reflection (ie substantially diffraction zero order). Then, the opening angle u corresponds to the opening angle w. A variation of these parameters is possible, depending on the setting of the collimator 7 in the illumination beam path 4, the collimator 12 in the measuring beam path 5 and properties of the sample (scattering on the surface).

The collimator 12 directs the collected reflection beam to a spectrometer 13. This spectrometer 13 has a fan-out element 14, which spectrally fanned the detected radiation, as will be explained. The radiation is then detected on a two-dimensional detector 15. The spectrometer 13 has an entrance slit 16, which is shown schematically in FIG. The entrance slit 16 extends along a longitudinal direction L and defines an entrance slit commonly known to spectrometers. On the entrance slit, ie on the entrance slit diaphragm 6, two groups G1, G2 with four polarizers 18 to 21 are now arranged along the direction L, which filter the supplied radiation differently with respect to the polarization, namely in the polarization directions 0 ° (polarizer 1 8), 45 ° (polarizer 19), 90 ° (polarizer 20) and circular (polarizer 21). Each polarizer can thus only pass the corresponding polarization direction. The entrance slit is thus divided by the polarizer 17, which is realized by the arranged at the entrance slit 21 polarizers, along the direction L spatially divided into two groups each having four polarization types. Then the fanning-out element 14 is set up in such a way that on the one hand it carries out the usual spectral fanning. This is schematically symbolized by the fan-out direction "lambda" in Figure 3. Transverse to this direction, the polarizer 17 effects such a division that groups defined by the polarizers 18 to 21 are repeated ensures that a larger area of the layer 2 of the sample 2 is scanned with respect to reflections The radiation which is present along the direction L at the entrance slit 16 in the form of the reflection beam 1 1 is thus along the direction L either with respect to the reflex locations or A breakdown according to the reflex locations is achieved when the region detected on the layer 2 extends along a direction perpendicular to the plane of the drawing in Figure 1. A breakdown by reflection angles is obtained when the detected region is around 90 ° turned to it, so that i n of the sectional plane of Figure 1 and perpendicular to the normal N runs.

The spatial or angular resolution is given by the dimension of one of the groups along the direction L. Although FIG. 2 merely shows two groups G1 and G2 by way of example, a larger number of groups can and will be used in most embodiments.

This is illustrated in Figure 3 by groups G1, G2, G3 and Gn, wherein the reference Gn is to illustrate that the number of repetitions is not limited to four, but quite any higher or lower can be selected. Due to the design of the collimator 12 and the polarization device 17, the groups G1 to Gn are assigned to different reflection angles, ie originate from different regions within the opening angle u. Alternatively, the groups G1 to Gn may also be assigned to different locations on the sample 2. This assignment is achieved by suitable design of the collimator 12.

In order to adapt the ellipsometer particularly to the measurement of layers which are produced in a manufacturing process, it is expedient to ensure that the reflection intensity is as independent of adjustment as possible, that is, if possible, does not change if the position of the layer 2 varies along the normal N. , This can be achieved particularly simply by illuminating a lighting spot 32, which is much larger than the measuring spot 33 detected by the collimator 12, as illustrated in FIG. 4. FIG. 4 schematically shows a plan view of the layer 2. For the measuring spot 33, the division into the individual spots is shown schematically, which are assigned to the polarizers at the entrance slit diaphragm. Due to the fact that the illumination spot 32 has a spatial extent which is greater than that of the measuring spot 33, it is possible to ensure that the measuring spot even when the position of the layer varies within certain tolerances, in particular when the layer 2 is displaced along the normal N 33 always detects an area that lies within the illumination spot 32.

Of course, an inverted approach is possible, d. H. that the measuring spot 33 is much larger than the illumination spot 32, so that the illumination intensity within the measuring spot 33 remains constant, even if the layer 2 varies in their position. Essential for this advantage is therefore that between illumination spot 32 and measuring spot 33 there is a difference in size, which is chosen so that even with a variation of the position of the layer 2 within predetermined limits, the smaller spot is completely within the larger spot.

FIG. 5 shows an alternative embodiment of an ellipsometer 1b, which does not differ with respect to the illuminating beam path from the ellipsometer 1a. The differences are due to the collection of the reflection beam 1 1 and the design of the spectrometer.

The collimator 12 of the ellipsometer 1 a is replaced by a fiber coupler 22, which couples the reflection beam 1 1 in an optical fiber bundle 23 having at least one group of four Einzelellichtleitfasern. The optical fiber bundle 23 carries the collected reflection beam 1 1 to the spectrometer 24. This now has no conventional entrance slit, but an input in which the Einzellichtleitfasern the optical fiber bundle are adjacent. FIG. 6 shows a plan view of the entrance 31. The Einzelellichtleitfasern are grouped together, each consisting of four Einzelellichtleitfasern in the present embodiment. The ends of these Einzelellichtleitfasern are provided with polarizers 27 to 30. The groups G1 to Gn are juxtaposed, and the fan-out element 25 of the spectrometer 24 fans out like this supplied spectrally on, so that in the result again the field shown in Figure 3 is achieved on the two-dimensional detector.

The assignment of the groups G1 to Gn at different points of incidence or angles is now performed not by the collimator, but by the fiber coupler 22, which ensures that the reflection radiation from different angles of reflection within the angle range u or the reflection radiation from different locations on the different groups is distributed by Einzelellichtleitfasern in the optical fiber bundle 23. Otherwise, the previously said to Eilipsometer 1 a mutatis mutandis.

Of course, providing the polarizers on the exit end faces of the single-fiber fibers is just one of several possibilities. In principle, the polarizers can also be provided on the entry surfaces of the individual optical fibers, or the individual optical fibers themselves can have corresponding polarization-filtering properties.

The use of an optical fiber bundle 23 also makes it possible to combine the groups in such a way that the optical fibers of one polarization type are combined into four groups G1 to G4. This is shown schematically in FIG. The Einzelellichtleitfasern 27 to 30 of the group G1 thus carry all the reflection radiation, which is filtered at a polarization angle of 0 °. They differ from each other by the reflex location or the angle of reflection to which they are assigned. The same applies to the optical fibers G2 to G4. This approach has the advantage that less interference by crosstalk between the individual channels occur. Also leads to less crosstalk, the construction of Figure 8, in which an additional gap 34 is provided between two groups G1 to Gn, which differ with respect to the reflex location or angle of reflection.

FIG. 9 shows diagrammatically that the distribution of the radiation from the individual optical fibers is not restricted solely to the fact that the radiation of a single optical fiber is filtered with respect to exactly one polarization state. FIG. 9 shows by way of example an optical fiber bundle 23 which consists of four individual optical fibers 35 whose radiation is filtered by four individual polarizers 27, 28, 29, 30. The radiation from a single optical fiber 35 thus corresponds to a group G1 to Gn and carries radiation which was recorded with respect to a reflex location or an angle of reflection. FIGS. 1 to 8 thus show construction methods in which four individual optical fibers are used within one spatial resolution cell or one angular resolution cell. In Figure 9, a Einzelellichtleitfaser is used. Other breakdowns are equally possible.

The signals of the detector as information about the corresponding angular settings of the spectrometer 1 a and 1 b are supplied to a not further explained control unit, which performs the above-mentioned simulation for layer analysis. The described ellipsometer 1 a or 1 b thereby allows a variety of operations. Thus, for example, the illumination radiation can be carried out along a line with a small numerical apparatus. The detection then detects the specular reflex as a function of location, i. H. the mentioned groups G1 to Gn represent the location dependency of the recorded spectra.

In a conoscopic spectral ellipsometry is illuminated broadband, with high numerical apparatus at one point. The reflections are then detected as a function of the angle and, of course, of the wavelength, so that the said groups G1 to Gn represent the angular dependence of the spectrally resolved reflection radiation. This system is particularly suitable for the analysis of complex multilayers, whereas the aforesaid mode of operation is particularly suitable for the inspection of produced thin films in the production process. If one does not detect the specular reflex in conoscopic spectral ellipsometry but scattered light, an analysis of microstructured layer systems can be carried out with this variant.

Claims

claims

1 . Eilipsometer for the examination of a sample (2, 3), with

- an illumination beam path (4), which is designed to illuminate the sample (2, 3) with illumination radiation (10) of specific polarization and divergence (w) at a certain angle (a),

a Meßstrahlengang (5), which is formed on the sample (2, 3) in a reflex angle range (u) or Reflexortsbereich reflected illumination radiation (10) as divergent reflected radiation beam (1 1) to collect and analyze with respect to spectral composition and polarization state, the Measuring beam path (5) has:

a spectrometer (13), in which the reflected radiation beam (1 1) is coupled and which spectrally splits the reflected radiation beam (1 1),

- In the spectrometer (13) arranged 2D detector (15) and

a polarizer device which is arranged upstream of the detector (15) and which spatially filters the reflected radiation beam (1 1) before the spectral decomposition depending on the polarization state, wherein

the spectrometer (13) has an elongate entrance slit (17),

- The Meßstrahlengang (5) comprises a means for collecting (12), which collects the reflection beam (1 1) and leads to the entrance slit (17) of the spectrometer (13), and

the spectrometer (13) deflects the reflected radiation beam (1 1) across the propagation direction of the reflected radiation beam (1 1) and across the longitudinal extent of the entrance slit (1 7) spectrally dissected onto the detector (15),

characterized in that

the polarizer device comprises a plurality of groups (G1 -Gn), each with a plurality of different polarizers (18-21), each of which filter the reflected radiation beam (1 1) with respect to different polarization states, wherein the groups (G1 -Gn) as Also, the polarizers (18-21) in the groups (G1 -Gn) are arranged side by side on the entrance slit (17) or in the entrance slit (17) of the spectrometer (15)

the means for collecting (12) the reflected radiation beam (1 1) depending on the angle of reflection or reflection on the groups (G1 -Gn) distributed and so on the entrance slit (17) directs that along the longitudinal extent of the entrance slit (17) of the angle of reflection or reflex locations varied.

2. Eilipsometer to examine a sample (2, 3), with

a sample illumination beam path (4) which is designed to illuminate the sample (2, 3) with illumination radiation (10) of specific polarization and divergence (w) at a specific angle (a),

a spectrometer (24), in which the reflected radiation beam (1 1) is coupled and which spectrally splits the reflected radiation beam (1 1),

a in the spectrometer (24) arranged 2D detector (26) and

a polarizer device which is arranged upstream of the detector (26) and which spatially filters the reflection radiation beam (1 1) before the spectral decomposition depending on the polarization state,

in which

the measuring beam path (5) has a device for collecting (22) which couples the reflected radiation beam (1 1) into an optical fiber bundle (23),

the optical fiber bundle (23) comprises Einzelellichtleitfasern which end along a longitudinal extent adjacent to one another at an input (31) of the spectrometer (24), and

the spectrometer (24) guides the reflected radiation bundle (1 1), which is supplied spectrally disassembled transversely to the longitudinal extent, at the input (31) to the detector (15),

wherein the polarization device by a polarization-filtering property of the individual optical fibers or by the Einzelellichtleitfasern upstream or downstream polarizers (27-30) is realized, wherein the polarization-filtering properties of the Einzelellichtleitfasern or the polarizers (27-30) respectively the reflection radiation (1 1) with respect to different Filter polarization states,

characterized in that

the optical fiber bundle (23) has a plurality of groups (G1 -Gn) of at least four Einzelellichtleitfasern and the means for collecting (22) the radiation of the reflected radiation beam (1 1) depending on the angle of reflection or reflex location on the groups (G1 -Gn) distributed.

3. Eilipsometer according to claim 2, characterized in that the individual fibers are optical fibers, on whose end face a polarizer is applied, wherein the

Optical fibers are preferably polarization maintaining.

4. Eilipsometer according to one of the above claims, characterized in that in addition at least one non-polarization filtered dark and a white light channel in the entrance slit (17) or at the Spektrometereingang (31) is provided.

5. Eilipsometer according to one of the above claims, characterized in that the polarizers (1 8-21; 27-30) or polarization-filtering individual light fibers a first linear polarization state, a second orthogonal to linear polarization state, a third, at an angle of 45 ° to filter the first polarization state linear polarization state and a circular polarization state.

6. Eilipsometer according to claim 2 or one of the above claims in conjunction with claim 2, characterized in that each Einzellichtleitfaser a multipolarization filter is arranged downstream, which has along the longitudinal extent adjacent different polarization states filtering Einzelpolarisatoren.

7. Eilipsometer according to claim 2 or one of the above claims in conjunction with claim 2, characterized in that between the plurality of groups (G1 -Gn) each have an additional gap is provided.

8. Eilipsometer according to one of the above claims, characterized in that the illumination radiation (4) illuminates a location or angular range which is greater or smaller than the reflex angle range (u) or the Reflexortsbereich, of which the Meßstrahlengang (5) the reflected radiation beam ( 1 1) receives.