Reliable non-destructive determination of sample parameter values

Abstract

The invention relates to a photoelectron spectrometer (100) comprising a sample value determining module (50) and to a method for determining the value of at least one of n sample parameters at a measuring point (22) of a sample (20) on the basis of photoemission measurements without having to destroy the sample (20) during the photoemission measurements. Values for at least one and up to n-1 sample parameters are obtained from the quantity of n sample parameters at the measuring point (22) of the sample (20) and multiple photoemission spectra from the measuring point (22) of the sample (20), said photoemission spectra being captured using different levels of excitation energy. The value of the at least one sample parameter at the measuring point (22) of the sample (20) is determined on the basis of the values of the up to n-1 sample parameters and the photoemission spectra.

Description

[0001] Non-destructive reliable determination of sample parameter values

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a measurement method for determining a value of at least one of n sample parameters at a measurement point of a sample based on photoemission measurements without destroying the sample during the photoemission measurements. Furthermore, the invention relates to a sample parameter value determination module, a photoelectron spectrometer with the sample parameter value determination module, a corresponding computer program product, and a computer-readable medium with the computer program product.

[0004] STATE OF THE ART

[0005] A measurement method is known from Y. Hoshina et al. “Non-destructive depth profile evaluation of multi-layer thin film stack using simultaneous analysis of data from multiple X-ray photoelectron spectroscopy instruments”, 2022 Jpn. J. Appl. Phys. 61 046501 in which photoemission measurements with different excitation energies and at different emission angles are carried out on a sample using different photoelectron spectrometers in order to characterise the sample and in particular to determine a depth profile of the sample without destroying the sample.

[0006] EP 2 542 035 B1 discloses a photoelectron spectrometer which can irradiate a sample at one measuring point with two different excitation energies.

[0007] DESCRIPTION OF THE INVENTION

[0008] It can be seen as an object of the invention to provide a measuring method, a sample parameter value determination module, a photoelectron spectrometer, a computer program product and a computer-readable medium that enable an improved or more reliable non-destructive determination of values ​​for sample parameters.

[0009] According to a first aspect of the invention, a measurement method is provided for determining a value of at least one of n sample parameters at a measurement point of a sample based on photoemission measurements without destroying the sample during the photoemission measurements. The method comprises the steps:

[0010] Obtaining values ​​for at least one and up to n-1 sample parameters from the set of n sample parameters at the measuring point of the sample,

[0011] Obtaining several photoemission spectra recorded with different excitation energies from the measuring point of the sample,

[0012] Determining the value of the at least one sample parameter at the measuring point of the sample based on the up to n-1 sample parameters and the photoemission spectra.

[0013] The inventors have recognized that a complete characterization of a sample based on a photoemission spectrum, in particular the creation of a depth profile of the sample with information about the layer structure containing the chemical composition and layer thicknesses, is not reliably possible, especially for depth profile analysis, depending on the number of unknown sample parameters. In particular, more complex layer structures with multiple layers of different thicknesses, which have different depth profiles, can have similar photoemission spectra.

[0014] The method according to the invention makes it possible to reliably determine the value of one or more sample parameters, such as layer thicknesses, chemical compositions of layers, homogeneity of the layers and chemical states of materials in the layers, such as oxidation states, or the like, based on several photoemission measurements.

[0015] The sample is preferably a solid sample with one or more layers. The sample can, for example, be a silicon (Si) wafer with a layer sequence deposited thereon. The sample can also contain a layer structure with solid, liquid and / or gaseous layers. The sample can also have a different sample structure. For example, different materials can be arranged in different regions on an identical horizontal plane in the sample structure. Additional layers, for example contamination layers or layers that do not influence the function of the sample, can be arranged on the sample. Instead of a complete layer, an additional region, for example a contamination region, can be arranged on the surface of the sample that does not form a complete layer. The additional layers do not form part of the sample within the meaning of the invention.For example, a contamination layer can arise from the deposition of dust or dirt on a sample surface. Such a contamination layer does not, in principle, form part of the sample. However, a contamination layer on the sample can be part of the sample if, from the user's perspective, it should form part of the sample, e.g., due to a possible influence of the contamination layer on the sample properties to be measured. The contamination layer can, for example, be formed by oxidation or the deposition of dust or dirt on the surface. The method can be designed to take the contamination layer, for example, a carbon layer or carbon-containing layer, into account.

[0016] Alternatively, the method may involve cleaning the surface of the sample and / or preparing the surface in a vacuum system so that the surface of the sample has a reduced layer thickness of a contamination layer or is free of the contamination layer. For example, irradiating the contamination layer or sputtering the sample may be used to clean the surface of the sample.

[0017] The sample is not destroyed within the meaning of the patent if it remains unchanged from its state prior to a photoemission measurement, except for changes caused by the photoemission measurement. The photoemission measurement consists of irradiating the sample with radiation of a specific wavelength and receiving photoelectrons emitted by the sample with a detector, resolved according to kinetic energies. The sample is destroyed within the meaning of the patent, for example, if layers of the sample become contaminated by foreign atoms or if layers are removed. Removing the contamination layer, for example, during cleaning during sample preparation, is not understood as destroying the sample. The sample is not destroyed within the meaning of the patent by cleaning the sample, since the contamination layer is not part of the sample to be measured.To avoid damaging the sample during cleaning by sputtering with ions, for example, it can be ensured that the ions do not penetrate the sample being measured. The contamination layer can also be considered as part of the sample, for example, using sample parameters.

[0018] Photoemission spectra can be provided by a photoelectron spectrometer with multiple wavelengths. For example, the photoelectron spectrometer can have a monochromator for different wavelengths. The different wavelengths correspond to different excitation energies. This makes it possible to generate radiation with different excitation energies in a photoelectron spectrometer.

[0019] The sample parameters can include sample structure parameters and sample material parameters. The sample structure parameters can include, for example, the sample structure, the layer structure, chemical compositions of layers of the sample, chemical compositions of regions of the sample, materials present in the respective layers of the sample, layer thicknesses t, or the like. The layer structure of the sample can, for example, contain information on the chemical composition of layers contained in the sample and their layer thicknesses. The materials contained in the sample can, for example, be described by a molecular formula. Alternatively, the concentrations of the materials can be specified as a function of a position in the sample. For example, the concentration can be specified as a function of a horizontal and a vertical position of the material in the sample depending on a reference point.For the vertical position, for example, a surface oriented in the direction of the incident radiation can be used as a reference surface and a depth as a relative distance to the reference surface can be used to determine the vertical position.

[0020] The sample material parameters can be, for example, the total photoionization cross section c, the asymmetry parameter ß, the extinction length E which depends on the kinetic energy of photoelectrons kin ), binding energies E b , mass densities, particle number densities, band gaps, atomic numbers, or the like.

[0021] The at least one sample parameter whose value is to be determined can describe a part of a sample structure, in particular a layer structure, at the measuring point of the sample. This enables reliable depth profiling of the sample at a measuring point. The sample structure of the sample can indicate a concentration of the chemical elements as a function of depth. The at least one sample parameter can, for example, be a concentration of a chemical element as a function of depth or a layer thickness of a layer of the sample. For example, several sample parameters can also represent a layer structure of the sample; for example, the sample parameters can represent the chemical compositions of the layers of the sample. The chemical compositions of the layers of the sample can, for example, represent mixtures of chemical elements in the various layers and their arrangement in the sample.

[0022] Determining the value of the at least one sample parameter may comprise at least one of the steps:

[0023] Determining peak areas in each of the photoemission spectra, determining a background in each of the photoemission spectra, and one of the steps:

[0024] Determining the value of the at least one sample parameter based on the peak areas of the photoemission spectra,

[0025] Determining the value of the at least one sample parameter based on the backgrounds of the photoemission spectra, and

[0026] Determining the value of the at least one sample parameter based on the peak areas and backgrounds of the photoemission spectra.

[0027] A peak corresponds to a peak in a photoemission spectrum. The peak area is the area under the peak curve, reduced by a background. The background can be determined based on various background models, for example, based on various inelastic scattering models for the photoelectrons.

[0028] The background is caused by non-primarily emitted photoelectrons, for example, inelastically scattered photoelectrons in the sample, and can be determined using background models. The background can be determined using the same or a different background model than the one used to determine peak areas.

[0029] Determining the value of at least one sample parameter based on the backgrounds or the peak areas and backgrounds allows for a more reliable determination of the value since additional information can be obtained from the spectra.

[0030] The sample surface oriented in the direction of the incident radiation, through which radiation is irradiated to generate photoelectrons during the photoemission measurement, can be smooth, rough, or structured. Furthermore, surfaces between adjacent layers of the sample can also be smooth, rough, or structured. The method for determining the value of the at least one sample parameter can take into account the type of sample surface oriented in the direction of the incident radiation and the type of surfaces between adjacent layers of the sample. For example, for a rough or structured surface or area, the structure or roughness can also be taken into account.

[0031] Obtaining the values ​​for the at least one and up to n-1 sample parameters may include one or more of the following steps:

[0032] Entering a respective value for one or more of the sample parameters by a user,

[0033] Measuring a respective value for one or more of the sample parameters using another measuring method,

[0034] Reading out a respective value for one or more of the sample parameters from a sample parameter database with predetermined values ​​for the sample parameters.

[0035] The additional measurement methods can, for example, include optical methods such as ellipsometry. Depending on the additional measurement method, values ​​for different sample parameters can be obtained. The different method steps for obtaining the values ​​for up to n-1 sample parameters can also be combined to obtain a value for each type of sample parameter. For example, the user can enter the value for one or more of the sample parameters and, based on this value or these sample parameter values, values ​​for additional sample parameters can be read from the sample parameter database. For example, the user can enter the chemical composition of the sample structure, and the material parameters of the materials contained in the sample structure, in particular for their chemical elements, can be read from the sample parameter database.In the sample parameter database, sample parameter values ​​can be assigned to other sample parameter values, such as chemical elements' binding energies of the various orbitals of the chemical element. By obtaining the sample parameter values, the value of at least one sample parameter can be determined more reliably. The larger the number of obtained values ​​for the n-1 sample parameters, the more reliably the value of at least one sample parameter can be determined.

[0036] In the sample parameter database, predetermined values ​​of the sample parameters can be assigned, for example, to specific photoemission spectra and / or values ​​of parameters derived from the obtained multiple photoemission spectra recorded with different excitation energies, such as energy positions of peaks, relative depths, or the like. The sample parameter database can be generated, for example, by collecting and correspondingly assigning known values ​​of sample parameters to photoemission spectra and / or values ​​of parameters derived from photoemission spectra. Reading a respective value for the one or more sample parameters from the sample parameter database can comprise a step:

[0037] Comparing the photoemission spectra contained in the sample parameter database and / or the values ​​of the parameters derived from the obtained plurality of photoemission spectra recorded with different excitation energies with the obtained plurality of photoemission spectra recorded with different excitation energies and / or values ​​of derived parameters and reading out the respective value for the one or more sample parameters associated with the best matching photoemission spectra or the best matching values ​​from the derived parameters of the sample parameter database.

[0038] The method can also provide for obtaining the value of one or more sample parameters before comparing the photoemission spectra contained in the sample parameter database and / or the values ​​of the derived parameters with the obtained multiple photoemission spectra recorded with different excitation energies and / or the values ​​of the derived parameters. This makes it possible to restrict the search space of the possible photoemission spectra. This can enable faster and more reliable finding of the best-fitting photoemission spectra and / or the best-fitting values ​​of the derived parameters, since fewer photoemission spectra and / or values ​​for derived parameters have to be compared. This improves the reading of the respective value for the one or more sample parameters from the sample parameter database. For example, chemical elements present in the sample, e.g.Silicon (Si), hafnium (Hf), oxygen (O), nickel (Ni), etc. are entered by a user before further sample parameters are read from the sample parameter database in a subsequent process step.

[0039] The sample parameter database can contain values ​​for various sample parameters, such as known layered sample structures, binding energies, mass densities, particle number densities, total photoionization cross sections, asymmetry parameters, band gaps, atomic numbers, or the like. This can make it possible to assign a layered structure to an unknown sample based on the obtained multiple photoemission spectra recorded with different excitation energies or the values ​​of the derived parameters.

[0040] The method may provide for proposing a layer structure. The user can confirm the proposed layer structure as correct or reject it. If the user rejects the proposed layer structure, a layer structure that matches the second best based on the photoemission spectra can be proposed. Alternatively, for multiple layer structures, the value of at least one sample parameter can be determined based on up to n-1 sample parameters and the photoemission spectra. The best-fitting layer structure, e.g., with the lowest chi-square, can then be proposed as the layer structure. The layer structures can be ranked depending on how well they fit.

[0041] The multiple photoemission spectra recorded with different excitation energies can include photoemission spectra recorded from the sample measurement point at different emission angles. The photoemission spectra can include photoemission spectra with the same excitation energy and different emission angles, and / or photoemission spectra with the same emission angle and different excitation energies. This allows for more information to be obtained from the sample. The photoemission spectra with different emission angles can be recorded by an angle-resolving photoelectron spectrometer. This enables fast and precise photoemission measurements without having to vary the sample inclination. An angle-resolving photoelectron spectrometer is known, for example, from US6104029A.To measure different sample emission angles, for example, different electron trajectories can be selected using the angle-resolving photoelectron spectrometer. Alternatively, the sample inclination can be changed to measure a different emission angle.

[0042] The emission angles can span an interval of 60°. The photoemission spectra can be recorded, for example, in a 5° grid, with -30°, -25°, -20°, -15°, -10°, -5°, 0°, 5°, 10°, 15°, 20°, 25°, and 30°. For example, photoemission spectra can be recorded for 13 different angles between -30° and +30° to the optical axis of a lens device of the photoelectron spectrometer. Alternatively, photoemission spectra can also be recorded with other, even irregular, angular step sizes or with irregular angular spacings.

[0043] The measuring point of the sample can have an extension of 100 pm or less, preferably 10 pm or less. This makes it possible to determine a local value of the at least one sample parameter at the measuring point of the sample. The measuring point is not to be understood here as a point in the mathematical sense, but as a point with an extension that can have different shapes and sizes, for example, depending on the focusing of a beam for exciting photoelectrons from the sample. If the sample has different values ​​of the sample parameter in the horizontal direction, different local values ​​of the sample can be recorded by shifting the measuring point. For example, a sample can also be rasterized. This makes it possible to display the value of the at least one sample parameter quasi-continuously as a function of the vertical position in the sample. This can, for example, make it possible to determine concentration gradients in the horizontal direction.

[0044] The excitation energies can range between 1 keV and 10 keV. This makes it possible to reach different depths in the sample, for example, between 5 nm and 30 nm. Using different excitation energies makes it possible, on the one hand, to obtain information from different depths and, on the other hand, to consider different information from the same depth. At higher excitation energies, a greater depth in the sample can be reached. In addition, information from shallower depths can also be obtained, which, combined with the information from the lower excitation energies for shallower depths, allows, for example, more reliable information about the layer structure at shallower depths.

[0045] The different excitation energies can be generated, for example, by irradiating different anode materials with electrons from an electron gun. The excitation energies can include, for example, AlKa at 1.49 keV, AgLa at 2.98 keV, AgLß at 3.15 keV, TiKa at 4.51 keV, CrKa at 5.41 keV, Cu at 8.05 keV, and Au at 9.71 keV. The excitation energies used to generate the photoemission spectra with different excitation energies can be selected with a similar energy spacing from each other. For example, the excitation energies 1.49 keV, 2.98 keV, 4.51 keV, and 5.41 keV can be selected with spacings between 0.9 keV and 1.53 keV. This makes it possible to improve the information yield while taking into account the space limitations in a multi-wavelength photoelectron spectrometer.

[0046] The procedure may include the steps:

[0047] Providing a calibration sample for which values ​​of a sample structure and chemical composition are known and

[0048] Determining values ​​for measurement method parameters for determining the value of the at least one sample parameter using the calibration sample.

[0049] A calibration sample or reference sample can, for example, be a sample whose sample structure and chemical composition are known, but on which additional layers may be arranged, such as a contamination layer. The contamination layer can, for example, be taken into account when determining the values ​​of the measurement process parameters, or it can be removed by cleaning. For the calibration sample, values ​​for a sufficient number of sample parameters are known, which allows the values ​​for the measurement process parameters to be determined with sufficient accuracy or an acceptable error. Using a calibration sample enables the determination of measurement process parameters. This makes it possible to determine more reliable absolute and relative values ​​for samples for which the value of at least one sample parameter is unknown.The process steps can be used to calibrate, for example, an absolute angle scale for angle-resolved photoemission spectra. The measurement process parameters can include, for example, transmission functions between the sample and a detector device of the photoelectron spectrometer, an angle calibration of an absolute angle of the photoelectron spectrometer, the geometry of the measurement, imaging properties of an analyzer, transmission properties of the analyzer, a ratio of photon fluxes of a radiation source for different excitation energies, or another measurement process parameter. The geometry of the measurement can depend, for example, on the sample orientation to the entrance aperture of a lens device of the photoelectron spectrometer and the distance of the sample to the entrance aperture of the lens device of the photoelectron spectrometer.The imaging properties of the analyzer can, for example, contain a functional relationship between the raw data it generates and measured variables, such as electron energy and direction in the analyzer's coordinate system. The transmission properties of the analyzer can, for example, contain a measured photoelectron current in relation to an emitted photoelectron current as a function of the energy and direction of the photoelectrons. The ratio of the photon fluxes of the radiation source, e.g., an X-ray source, for the different excitation energies can, for example, be at least partially attributed to the transmission properties of the photoelectron spectrometer.The measurement method parameters can, for example, be determined for the peak areas and backgrounds of the photoemission spectra in such a way that the expected peak areas and backgrounds agree with the measured peak areas and backgrounds.

[0050] The method may include the step:

[0051] Determining the value of the at least one sample parameter additionally based on the measurement method parameters determined with the aid of the calibration sample.

[0052] This allows a more reliable determination of the value of at least one sample parameter.

[0053] According to a further aspect of the invention, a sample parameter value determination module is provided for determining a value of at least one of n sample parameters at a measurement point of a sample based on photoemission measurements, without destroying the sample during the photoemission measurements. The sample parameter value determination module comprises: an interface for obtaining values ​​for at least one and up to n-1 sample parameters from the set of n sample parameters at the measurement point of the sample and several photoemission spectra recorded with different excitation energies from the measurement point of the sample; and a processor for determining the value of the at least one sample parameter at the measurement point of the sample based on the values ​​of the up to n-1 sample parameters and the photoemission spectra.

[0054] This enables a reliable determination of the value of one or more sample parameters at the measuring point of the sample.

[0055] According to a further aspect of the invention, a photoelectron spectrometer is provided with a sample parameter value determination module according to claim 11 or an embodiment of the sample parameter value determination module for determining the value of at least one of the n sample parameters at the measuring point of the sample based on the photoemission measurements without destroying the sample during the photoemission measurements.The photoelectron spectrometer comprises: an illumination device for illuminating the sample at the measuring point with radiation of different wavelengths, a detector device for detecting photoelectrons emitted by the sample, wherein the photoelectron spectrometer is designed to record a plurality of photoemission spectra with different excitation energies from the measuring point of the sample and to provide them to the sample parameter value determination module, and wherein the sample parameter value determination module is designed to determine the value of the at least one sample parameter at the measuring point of the sample based on the up to n-1 sample parameters from the set of n sample parameters and the photoemission spectra obtained from the detector device.

[0056] The detector device can be configured to detect the photoelectrons emitted by the sample in an angle-resolved manner. The photoelectron spectrometer can be an angle-resolving photoelectron spectrometer. This makes it possible to provide a compact photoelectron spectrometer for reliably determining the value of at least one of the n sample parameters at the measurement point of the sample based on the photoemission measurements.

[0057] The photoelectron spectrometer can have a hermetically sealable cavity, in particular a vacuum chamber, in which the illumination device and the detector device can be arranged. A negative pressure, in particular an ultra-high vacuum, can be generated in the cavity. The photoelectron spectrometer can have an ultra-high vacuum pump or be connected to an ultra-high vacuum pump to generate an ultra-high vacuum in the cavity, in particular the vacuum chamber. Additionally or alternatively, the photoelectron spectrometer can have a vacuum pump or be connected to a vacuum pump to generate a negative pressure in the cavity. The vacuum pump can be designed to generate a negative pressure in the cavity. The vacuum pump can, for example, be designed to generate an absolute pressure between 0.1 mbar and 600 mbar, between 0.1 mbar and 400 mbar, or between 1 mbar and 100 mbar, for example 20 mbar.This makes it possible to generate various pressures close to ambient pressure, especially close to atmospheric pressure. The vacuum pump can be a diaphragm pump, for example.

[0058] The illumination device may comprise a radiation source, for example, a radiation source for electromagnetic radiation such as X-rays, synchrotron radiation, or deep ultraviolet (DUV) radiation. The illumination device may additionally comprise a monochromator for spectrally isolating a specific wavelength from a beam incident from the radiation source, or for monochromatizing it. This makes it possible to provide radiation that can be used to irradiate the sample.

[0059] The illumination device can be movable and / or tiltable, allowing it to be moved toward the sample to irradiate the sample with radiation. Alternatively, or additionally, the detector device can be movable and / or tiltable, allowing it to be moved toward the sample to receive photoelectrons emitted from the sample. Alternatively, or additionally, the sample can also be movable and / or tiltable, for example, with the aid of a manipulator.

[0060] The detector device may comprise a front cap electrode, one or more electronic lenses, one or more deflectors, an analyzer, and / or a detector. The detector device may, for example, be formed by the front cap electrode, the electronic lenses, the analyzer, and the detector. The detector device may comprise one or more interconnected cavities forming an interior of the detector device through which photoelectrons emitted from the sample can be guided from the front cap electrode to the detector. Additionally, the detector device may also comprise one or more deflectors to direct the photoelectrons toward an input of the analyzer.

[0061] The front cap electrode can be conical in shape and have a tapered entrance opening, allowing gas molecules entering the entrance opening to quickly disperse behind the entrance opening into the cavity enclosed by the front cap electrode. This allows for rapid pressure reduction. This can increase the free path for electrons behind the entrance opening. This is useful, for example, when performing photoemission measurements at pressures close to atmospheric pressure to ensure sufficiently high intensity.

[0062] Different negative pressures can prevail in the several interconnected cavities, which can further decrease from the inlet opening towards the detector. For this purpose, different pressure reduction stages can be provided, and the pressure can be reduced to different degrees, for example, by means of pumps with different pumping powers in the successively arranged cavities. This can make it possible to maintain a lower pressure in the detector device. For example, in the case of an absolute pressure between 0.1 mbar and 100 mbar, e.g., 25 mbar, an absolute pressure in the range of 10 -4 mbar to 10 -2 mbar, e.g. 10 -3 mbar in the cavity enclosed by the front cap electrode, an absolute pressure of 10 -6 mbar to 10 -4 mbar, e.g. 10 -5 mbar in a subsequent cavity and an absolute pressure in the range of 10 -8 mbar to 10 -5mbar, e.g. 10 -6 mbar, in the cavity in front of the detector.

[0063] The analyzer can be, for example, a hemispherical energy analyzer or the analyzer can comprise one. The detector can comprise, for example, an electron multiplier, a phosphor screen, a video camera, a CCD (charge-coupled device) sensor, and / or a CMOS (complementary metal-oxide-semiconductor) sensor. The detector can also be designed as a DLD (delay line detector).

[0064] According to a further aspect of the invention, a use of the method according to at least one of claims 1 to 10 or an embodiment of the method is provided for:

[0065] Determining whether a layer of the sample has a predetermined layer thickness at the measuring point of the sample, and / or

[0066] Determining a degree of diffusivity of a layer boundary between adjacent layers, and / or

[0067] Determining an extent of a layer boundary between adjacent layers, and / or

[0068] Determining a reproducibility of a manufacturing process of the sample, and / or testing an influence of the value of the at least one sample parameter on a functioning of the sample, and / or

[0069] Comparing different samples and / or finding recipes for preparing samples. Determining whether a layer of the sample has a predetermined thickness at the sample measurement point enables improved quality control.

[0070] Determining the degree of diffusion of a layer boundary between adjacent layers makes it possible to determine, for example, whether diffusion has occurred between the layers. Layer boundaries can, for example, be sharp or completely diffuse. At a sharp layer boundary, materials from one layer meet materials from the other layer at the layer boundary without the materials of the layers extending across the layer boundary into the other layer. At a diffuse layer boundary, materials from one layer are also found beyond the layer boundary in the other layer and vice versa. The degree of diffusion depends on the proportion of materials that extend across the layer boundary. With a diffusion of 0%, none of the materials from the different layers extend across the layer boundary.At a diffusivity F of 100%, the adjacent layers form a mixture with 50 vol% mixing of the materials of the adjacent layers at the layer boundary.

[0071] Determining the extent of a layer boundary between adjacent layers makes it possible to check whether diffusion has occurred between the layers and how far material from one layer has diffused into the other layer.

[0072] Determining the reproducibility of a sample manufacturing process enables improved quality control. Testing the influence of the value of at least one sample parameter on the functionality of the sample makes it possible to optimize sample structures for the functionality of a sample. Samples can be produced with different values ​​of at least one sample parameter, and by comparing them, it can be determined how the change in the value affects the functionality of the sample. The measurement method makes it possible to check whether the sample manufacturing process actually led to the desired value of the sample parameter. This can, for example, make it possible to find and optimize recipes for sample manufacturing.

[0073] According to a further aspect of the invention, a computer program product comprising instructions which, when the computer program product is executed by a processor, cause the processor to carry out the method according to at least one of claims 1 to 10 or an embodiment of the method, is provided.

[0074] According to a further aspect, a computer-readable medium is provided on which the computer program product is stored.

[0075] The method according to claim 1, the sample parameter value determination module according to claim 11, the photoelectron spectrometer according to claim 12, the use according to claim 13, the computer program product according to claim 14 and the computer-readable medium according to claim 15 may have similar and / or identical preferred embodiments, as particularly defined in the dependent claims.

[0076] Furthermore, a preferred embodiment of the invention may also be any combination of the features of the dependent claims or the aforementioned embodiments in conjunction with the corresponding independent claim.

[0077] These and other aspects of the invention are explained in more detail below with reference to embodiments shown in the figures.

[0078] SHORT DESCRIPTION OF THE CHARACTERS

[0079] In the following figures shows:

[0080] FIG 1 shows schematically and by way of example an embodiment of a photoelectron spectrometer with a sample parameter value determination module for determining a value of at least one of n sample parameters at a measuring point of a sample based on photoemission measurements, without destroying the sample during the photoemission measurements;

[0081] FIG 2 shows a flowchart of an embodiment of a method for determining a value of at least one of n sample parameters at a measuring point of a sample based on photoemission measurements without destroying the sample during the photoemission measurements.

[0082] DESCRIPTION OF THE EMBODIMENTS

[0083] FIG. 1 schematically and exemplarily shows an embodiment of a photoelectron spectrometer 100 with a sample parameter value determination module 50 for determining a value of at least one of n sample parameters at a measurement point 22 of a sample 20 based on photoemission measurements, without destroying the sample 20 during the photoemission measurements, for example, by sputtering with an ion gun. The photoelectron spectrometer 100 can be used to perform the method shown in FIG. 2 for determining a value of at least one of n sample parameters at a measurement point of a sample based on photoemission measurements, without destroying the sample during the photoemission measurements.

[0084] In this embodiment, the photoelectron spectrometer 100 is an angle-resolving photoelectron spectrometer. The photoelectron spectrometer 100 includes an illumination device 10 for illuminating the sample 20 at the measurement point 22 with radiation in the form of X-rays X of different wavelengths, a detector device 30 for detecting photoelectrons p emitted by the sample 20, an ultra-high vacuum pump 40, the sample parameter value determination module 50, and a cavity in the form of a vacuum chamber 60. Additionally, in this embodiment, a measuring device 70 for further measurements is arranged at the measurement point 22 of the sample 20. The measuring device 70 can, for example, perform ellipsometry measurements to determine values ​​of sample parameters.

[0085] In this embodiment, the illumination device 10 contains an X-ray source 12 and a monochromator 14. In the X-ray source 12, X-rays X with different wavelengths are generated by firing electrons from an electron gun onto different anode materials. The X-rays X are then monochromatized in the monochromator 14 and focused onto the measurement point 22 of the sample. The monochromator 14 is designed to monochromatize X-rays X with different wavelengths and focus them onto the same measurement point 22. For this purpose, the monochromator 14 can, for example, have a plurality of reflective elements suitable for the corresponding wavelengths in a corresponding arrangement.

[0086] In this embodiment, the sample 20 is arranged on a sample holder (not shown). The sample holder is movable and tiltable. This enables scanning of the sample 20. Additionally, the sample 20 can be scanned by scanning the anode material using the electron gun of the X-ray source 12. The detector device 30 includes a front cap electrode 32, a lens element arrangement 34, an analyzer 36 in the form of a hemispherical analyzer, and a detector 38 in the form of a CMOS detector. In other embodiments, a different analyzer and / or a different detector can also be used.

[0087] The ultra-high vacuum pump 40 serves to create an ultra-high vacuum within the vacuum chamber 60.

[0088] The sample parameter value determination module 50 contains an interface 52 in the form of a transceiver, a processor 54, and a computer-readable medium 56 in the form of a memory 56. Alternatively or additionally, the interface may also contain or be any other type of interface, for example, a cable interface or a keyboard for input from a user. The processor 54 is designed to execute a computer program product comprising instructions for the method shown in FIG. 2. The computer program product is stored on the computer-readable medium 56. Furthermore, in this exemplary embodiment, a sample parameter database is also stored, in which predetermined values ​​of the sample parameters are assigned to specific photoemission spectra. In other exemplary embodiments, the values ​​of the sample parameters may also be assigned to values ​​of parameters derived from photoemission spectra.

[0089] During operation of the photoelectron spectrometer 100, monochromatized X-rays X with different wavelengths are focused onto the measurement point 22 with an extension of 10 pm. In other embodiments, the measurement point can also have an extension of 100 pm or less, preferably 10 pm or less, or be between 10 pm and 100 pm. The different wavelengths correspond to different excitation energies. The excitation energies can, for example, be in a range between 1 keV and 10 keV. The X-rays X with different wavelengths generate photoelectrons p at different depths of the sample 20. The photoelectrons p emerge from the surface of the sample 20 and are received by the front cap electrode 32 of the detector device 30. The lens element arrangement 34 guides the photoelectrons p into the analyzer 36, where they are resolved according to their kinetic energies.The photoelectrons p are detected in detector 38. Photoemission spectra are then generated from the data measured by detector 38. In this embodiment, photoemission spectra are recorded with different excitation energies and different emission angles.

[0090] The photoemission spectra are received from the detector device via interface 52 for further processing. Additionally, interface 52 receives values ​​of sample parameters obtained from further measurement methods, for example, from measurement device 70. In other embodiments, the parameter database can also be stored externally to sample parameter value determination module 50, and values ​​for sample parameters can be obtained via interface 52. In this embodiment, the values ​​of the sample parameters from the sample parameter database are available to sample parameter value determination module 50 via computer-readable medium 56.In this embodiment, the sample parameter value determination module 50 receives values ​​for at least one and up to n-1 sample parameters from the set of n sample parameters at the measuring point 22 of the sample 20 and several photoemission spectra recorded with different excitation energies and emission angles from the measuring point 22 of the sample 20. The processor 54 determines the value of at least one sample parameter at the measuring point 22 of the sample 20 based on the values ​​of the up to n-1 sample parameters and the photoemission spectra.

[0091] FIG. 2 shows a flowchart of an embodiment of a method 200 for determining a value of at least one of n sample parameters at a measurement point of a sample based on photoemission measurements, without destroying the sample during the photoemission measurements. In this embodiment, the at least one sample parameter whose value is to be determined describes a part of a sample structure, in particular a layer structure, at the measurement point of the sample. The method is particularly suitable for creating a depth profile for the sample without destroying the sample.

[0092] In optional step 202, a calibration sample can be provided for which values ​​of a sample structure and chemical composition are known. This can be used to calibrate measurement process parameters, in particular instrumental parameters for the measurement.

[0093] In the optional step 204, values ​​for the measurement method parameters can be determined using the calibration sample.

[0094] In step 206, values ​​for at least one and up to n-1 sample parameters are obtained at the sample measurement point. The number of sample parameters n of the sample is a positive integer and depends on the sample. The values ​​for the sample parameters can be obtained in various ways. In this embodiment, the values ​​for the sample parameters are obtained from a combination of the following three ways:

[0095] Entering a respective value for one or more of the sample parameters by a user,

[0096] Measuring a respective value for one or more of the sample parameters using another measuring method, and

[0097] Reading a respective value for one or more of the sample parameters from a sample parameter database with predetermined values ​​for the sample parameters. In other embodiments, the values ​​can also be obtained by only one of the methods or by two of the methods.

[0098] In step 208, several photoemission spectra recorded with different excitation energies are obtained from the sample's measurement point. Additionally, photoemission spectra recorded with different emission angles can also be obtained from the sample's measurement point. The emission angles can, for example, span an interval of 60°. The measurement point can, for example, have an extension of 100 pm or less, preferably 10 pm or less. The excitation energies can range between 1 keV and 10 keV.

[0099] In step 210, the value of the at least one sample parameter at the sample measurement point is determined based on the values ​​of up to n-1 sample parameters and the photoemission spectra. To determine the value of the at least one sample parameter at the sample measurement point, peak areas in each of the photoemission spectra and / or the background in each of the photoemission spectra can be determined. The value of the at least one sample parameter at the sample measurement point can then be determined based on the peak areas, the backgrounds, or both. If the optional steps 202 and 204 have been performed, the value of the at least one sample parameter can additionally be determined based on the measurement method parameters determined using the calibration sample.

[0100] The invention relates to a photoelectron spectrometer with a sample value determination module and a method for determining a value of at least one of n sample parameters at a measurement point of a sample based on photoemission measurements, without destroying the sample during the photoemission measurements. Values ​​are obtained for at least one and up to n-1 sample parameters at the measurement point of the sample and several photoemission spectra recorded with different excitation energies from the measurement point of the sample. Based on the values ​​of the up to n-1 sample parameters and the photoemission spectra, the value of the at least one sample parameter at the measurement point of the sample is determined.

Claims

REQUIREMENTS:

1. Method for determining a value of at least one of n sample parameters at a measuring point (22) of a sample (20) based on photoemission measurements, without destroying the sample (20) during the photoemission measurements, comprising: Obtaining values ​​for at least one and up to n-1 sample parameter from the set of n sample parameters at the measuring point (22) of the sample (20), Several photoemission spectra recorded with different excitation energies from the measuring point (22) of the sample (20), Determining the value of at least one sample parameter at the measuring point (22) of the sample (20) based on the values ​​of up to n-1 sample parameters and the photoemission spectra.

2. Method according to claim 1, wherein the at least one sample parameter whose value is to be determined describes a part of a sample structure, in particular a layer structure, at the measuring point (22) of the sample (20).

3. Method according to claim 1 or 2, wherein determining the value of the at least one sample parameter comprises at least one of the following steps: Determining peak areas in each of the photoemission spectra, Determine a background in each of the photoemission spectra, and perform one of the following steps: Determining the value of at least one sample parameter based on the Peak areas of the photoemission spectra, Determining the value of at least one sample parameter based on the backgrounds of the photoemission spectra, and Determining the value of at least one sample parameter based on the peak areas and backgrounds of the photoemission spectra is included.

4. Method according to at least one of claims 1 to 3, wherein obtaining the values ​​for the at least one and up to n-1 sample parameters comprises one or more of the following steps: Entering a respective value for one or more of the sample parameters by a user Measuring a specific value for one or more of the sample parameters using a further measurement method, Reading out a specific value for one or more of the sample parameters from a sample parameter database with predetermined values ​​for the sample parameters.

5. Method according to at least one of claims 1 to 4, wherein the multiple photoemission spectra recorded with different excitation energies include photoemission spectra recorded from the measuring point (22) of the sample (20) with different emission angles.

6. Method according to claim 5, wherein the emission angles span an interval of 60°.

7. Method according to at least one of claims 1 to 6, wherein the measuring point (22) of the sample (20) has an extent of 100 pm or less, preferably 10 pm or less.

8. Method according to at least one of claims 1 to 7, wherein the excitation energies are in the range between 1 keV and 10 keV.

9. A method according to at least one of claims 1 to 8, comprising the steps of: providing a calibration sample for which values ​​of a sample structure and a chemical composition are known and Determining values ​​for measurement procedure parameters to determine the value of at least one sample parameter using the calibration sample.

10. The method according to claim 9, comprising the step of: Determining the value of at least one sample parameter additionally based on the measurement procedure parameters determined using the calibration sample.

11. Sample parameter value determination module (50) for determining a value of at least one of n sample parameters at a measurement point (22) of a sample (20) based on photoemission measurements, without destroying the sample (20) during the photoemission measurements, wherein the sample parameter value determination module (50) comprises: an interface (52) for obtaining values ​​for at least one and up to n-1 Sample parameters from the set of n sample parameters at the measuring point (22) of the sample (20) and several photoemission spectra recorded with different excitation energies from the measuring point (22) of the sample (20) and a processor (54) for determining the value of at least one sample parameter at the measuring point (22) of the sample (20) based on the values ​​of the up to n-1 sample parameters and the photoemission spectra.

12. Photoelectron spectrometer (100) with a sample parameter determination module (50) according to claim 11 for determining the value of at least one of the n sample parameters at the measurement point (22) of the sample (20) based on the photoemission measurements, without destroying the sample (20) during the photoemission measurements, wherein the photoelectron spectrometer (100) comprises: an illumination device (10) for illuminating the sample (20) at the measurement point (22) with radiation (X) of different wavelengths, a detector device (30) for detecting photoelectrons (p) emitted by the sample (20), wherein the photoelectron spectrometer (100) is configured to record several photoemission spectra with different excitation energies from the measurement point (22) of the sample (20) and to provide them to the sample parameter determination module (50), and wherein the sample parameter determination module (50) is configuredto determine the value of at least one sample parameter at the measuring point (22) of the sample (20) based on the up to n-1 sample parameters from the set of n sample parameters and the photoemission spectra obtained from the detector device (30).

13. Use of the method according to at least one of claims 1 to 10 for determining whether a layer of the sample has a predetermined layer thickness at the measuring point of the sample, and / or Determining the degree of diffusion of a layer boundary between adjacent layers, and / or Determining the extent of a layer boundary between adjacent layers, and / or Determining the reproducibility of a sample manufacturing process, and / or testing the influence of the value of at least one sample parameter on a Function of the sample, and / or Comparing different samples, and / or Finding recipes for making samples.

14. Computer program product, comprising instructions that are used in the execution of the computer program product by means of a processor (54) cause it to execute the method according to at least one of claims 1 to 10.

15. Computer-readable medium (56) on which the computer program product according to claim 14 is stored.

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