Non-destructive and reliable determination of sample parameter values

Abstract

The invention relates to a photoelectron spectrometer (100) with a sample value determination module (50) and a method for determining a value of at least one of n sample parameters at a measurement point (22) of a sample (20) based on a photoemission measurement without destroying the sample (20) during the photoemission measurement, in which a value for at least one and up to n-1 sample parameters from a set of n sample parameters at the measurement point (22) of the sample (20) and a plurality of photoemission spectra recorded with different excitation energies from the measurement point (22) of the sample (20) are obtained. Based on the values ​​of up to n-1 sample parameters and the photoemission spectra, the value of the at least one sample parameter at the measurement point (22) of the sample (20) is determined.

Description

[Technical field]

[0001] The invention relates to a measurement method for determining a value of at least one sample parameter out of n sample parameters at a measurement point of a sample based on a photoemission measurement without destroying the sample during the photoemission measurement. Furthermore the invention relates to a sample parameter value determination module, a photoelectron spectrometer comprising the sample parameter value determination module, a corresponding computer program product and a computer readable medium comprising the computer program product.

[0002] Prior Art From the publication "Non-destructive depth profile evaluation of multi-layer thin film stack using simultaneous analysis of data from multiple X-ray photoelectron spectroscopy instruments" by Y. Hoschina et al., 2022 Jpn. J. Appl. Phys. 61 046501, a measurement method is known in which photoemission measurements are carried out on a sample in various photoelectron spectrometers at various excitation energies and under different emission angles in order to characterize the sample, in particular to determine the depth profile of the sample without destroying it.

[0003] From EP 2 542 035 a photoelectron spectrometer is known in which the sample can be illuminated at the measuring point with two different excitation energies.

[0004] Description of the invention It is an object of the present invention to provide a measurement method, a sample parameter value determination module, a photoelectron spectrometer, a computer program product, and a computer-readable medium that allow an improved or more reliable non-destructive determination of values ​​for sample parameters.

[0005] According to a first aspect of the invention, a measurement method is envisaged for determining a value of at least one of n sample parameters at a measurement point of a sample based on a photoemission measurement without destroying the sample during the photoemission measurement, the method comprising the following steps: - obtaining a value for at least one and up to n-1 sample parameters from a set of n sample parameters at a measurement point on the sample; - obtaining a number of photoemission spectra recorded using different excitation energies from a measurement point on the sample; - determining a value of at least one sample parameter at a measurement point of the sample based on the values ​​of up to n-1 sample parameters and on the photoemission spectrum.

[0006] The inventors have realized that based on the photoemission spectrum it is not possible to fully characterize the sample, in particular to reliably create a depth profile of the sample with information on the chemical composition as well as the layer structure, including layer thicknesses, especially for depth profile analysis, depending on the number of unknown sample parameters. In particular, more complex layer structures with multiple layers of different layer thicknesses with various depth profiles may have similar photoemission spectra.

[0007] The method according to the invention makes it possible to reliably determine the value of one or more sample parameters, such as the layer thickness, the chemical composition of the layer, the homogeneity of the layer and the chemical state of the material in the layer, such as the oxidation state, based on multiple photoemission measurements.

[0008] Preferably, the sample is a solid sample having one or more layers. The sample may for example be a silicon (Si) wafer with a layer sequence stacked thereon. The sample may also include a layer structure with solid, liquid and / or gas layers. The sample may also have another sample structure. For example, in the sample structure, different materials may be arranged in different areas on the same horizontal surface. Additional layers may be arranged on the sample, for example contamination layers or layers that do not affect the function of the sample. Instead of a complete layer, additional areas may be arranged on the surface of the sample that do not form a complete layer, for example impurity areas. These additional layers do not form part of the sample in the sense of the present invention. For example, a contamination layer may occur on the surface of the sample due to the deposition of dust or dirt. Such a contamination layer does not essentially form part of the sample. However, a contamination layer on the sample may be part of the sample if it should form part of the sample from the user's point of view, for example based on the possible influence of the contamination layer on the property to be measured of the sample. A contamination layer may for example be formed by oxidation or deposition of dust or dirt on the surface. The method may be adapted for this purpose to take into account contamination layers, for example with carbon layers or carbon-containing layers.

[0009] Alternatively, the method can envisage cleaning of the surface of the sample and / or preparation of the surface in a negative pressure system, so that the surface of the sample has a reduced layer thickness of the contamination layer or is free from the contamination layer. For cleaning the surface of the sample, for example irradiation of the contamination layer or sputtering of the sample can be envisaged.

[0010] A sample is not destroyed in the sense of the patent if it does not change from its state before the photoemission measurement, in addition to the changes produced by the photoemission measurement. Photoelectron measurement here consists of irradiating the sample with radiation having a wavelength and receiving, resolved according to the kinetic energy of the photoelectrons emitted from the sample by means of a detector. For example, a sample is destroyed in the sense of the patent if a layer of the sample is contaminated by foreign atoms or if a layer is removed. Removal of a contaminating layer, for example cleaning during sample preparation, is not understood here as destruction of the sample. A sample is not destroyed by cleaning of the sample in the sense of the patent, since the contaminating layer is not part of the sample to be measured. For example, during cleaning by sputtering with ions, it may be assumed that in order not to destroy the sample, it is ensured that the ions are implanted into the sample to be measured. Contaminating layers can also be taken into account as part of the sample, for example using sample parameters.

[0011] The photoemission spectrum can be provided by a photoelectron spectrometer with multiple wavelengths. For example, the photoelectron spectrometer can have monochromators for different wavelengths. Different wavelengths correspond to different excitation energies. This allows the generation of radiation with different excitation energies in the photoelectron spectrometer.

[0012] 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, the chemical composition of the layers of the sample, the chemical composition of the regions of the sample, the materials present in the respective layers of the sample, the layer thickness t, etc. The layer structure of the sample can include, for example, information on the chemical composition of the layers contained in the sample and their layer thicknesses. The materials contained in the sample can be described, for example, by a composition formula. Alternatively, for example, the concentration of the material can be presented depending on the position in the sample. For example, the concentration can be presented depending on the horizontal and 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 plane, and the depth can be used as the relative distance to the reference plane for the determination of the vertical position.

[0013] The sample material parameters include, for example, the total photoionization cross section σ, the asymmetry parameter β, and the extinction length λ (E kin ), bond energy E b , mass density, particle number density, band gap, atomic number, etc.

[0014] The at least one sample parameter, the value of which is to be determined, can describe a part of the sample structure, in particular a part of the layer structure, at the measurement point of the sample. This allows a reliable depth profiling of the sample at the measurement point. The sample structure of the sample can describe a concentration of a chemical element in dependence on depth. The at least one sample parameter can be, for example, a concentration of a chemical element in dependence on depth or on a layer thickness of a layer of the sample. For example, a number of sample parameters can be mapped to the layer structure of the sample, for example the sample parameters can indicate a chemical composition of a layer of the sample. The chemical composition of a layer of the sample can, for example, indicate a mixture of chemical elements in the various layers and their arrangement in the sample.

[0015] The step of determining the value of the at least one sample parameter comprises the steps of: - determining the peak areas in each of the photoemission spectra; - determining the background in each of the photoemission spectra, and - determining a value of at least one sample parameter based on a peak area of ​​the photoemission spectrum; - determining a value of at least one sample parameter based on a background photoemission spectrum; - determining a value of at least one sample parameter based on the peak area and background of the photoemission spectrum.

[0016] A peak corresponds to the apex of the photoemission spectrum. A peak area is the area under the peak curve, reduced by the background. The background can be determined, for example, based on various background models, for example, based on various inelastic scattering models for photoelectrons.

[0017] The background arises from photoelectrons that are not primarily emitted, e.g., photoelectrons that are inelastically scattered in the sample, and can be determined using a background model, which can be the same as or different from the background model used to determine the peak area.

[0018] Determining the value of at least one sample parameter based on background, or based on peak area and background, allows for a more reliable determination of the value, since additional information can be obtained from the spectrum.

[0019] The surface of the sample oriented in the direction of the incident radiation, through which radiation is applied to generate photoelectrons during photoelectron measurements, may be smooth, rough or structured. Furthermore, the surface between adjacent layers of the sample may also be smooth, rough or structured. The method for determining the value of at least one sample parameter may take into account the type of surface of the sample oriented in the direction of the incident radiation and the type of surface between adjacent layers of the sample. For example, for roughened or structured surfaces or surfaces, the structure or roughness may additionally be taken into account.

[0020] Obtaining values ​​for at least one and up to n-1 sample parameters may include the steps of: - inputting, by a user, respective values ​​for one or more of the sample parameters; - measuring a respective value for one or more of the sample parameters using a further measurement method; - retrieving a respective value for one or more of the sample parameters from a sample parameter database having predetermined values ​​for the sample parameters.

[0021] The further measurement method may include, for example, optical methods such as ellipsometric measurements. Depending on the further measurement method, values ​​for different sample parameters can be obtained. Different method steps for obtaining values ​​for up to n-1 sample parameters can also be combined to obtain values ​​for any type of sample parameter. For example, a user can input values ​​for one or more sample parameters and, based on this value or these values ​​of the sample parameters, values ​​for further sample parameters can be retrieved from a sample parameter database. For example, a user can input a chemical composition of a sample structure and retrieve material parameters of the material, in particular the chemical elements contained in the sample structure, from a sample parameter database. In this sample parameter database, the value of the sample parameter may be assigned to other values ​​of the sample parameter, such as, for example, binding energies that determine the chemical elements of various orbitals of the chemical elements. By obtaining values ​​for the sample parameters, the value of at least one sample parameter can be determined with higher confidence. The more values ​​obtained for the n-1 sample parameters, the more confident the value of at least one sample parameter can be determined.

[0022] In the sample parameter database, predefined values ​​of sample parameters may be assigned, for example, to a given photoemission spectrum and / or to values ​​of parameters derived from the photoemission spectra recorded with a plurality of different excitation energies acquired, e.g., energy position of a peak, relative depth, etc. The sample parameter database may be generated, for example, by a collection and corresponding assignment of known values ​​of sample parameters to photoemission spectra and / or by a collection and corresponding assignment of values ​​of parameters derived from the photoemission spectra. Retrieving a respective value for one or more sample parameters from the sample parameter database may include the following steps: - comparing the photoemission spectra and / or values ​​of parameters derived from the plurality of acquired photoemission spectra recorded using different excitation energies contained in the sample parameters database with the plurality of acquired photoemission spectra and / or values ​​of parameters derived from the plurality of acquired photoemission spectra recorded using different excitation energies; - retrieving from the derived parameters of the sample parameter database the best matching photoemission spectrum or respective values ​​for the one or more sample parameters assigned to the best matching values.

[0023] The method can also envisage obtaining values ​​of one or more sample parameters before comparing the values ​​of the photoemission spectrum and / or derived parameters contained in the sample parameter database with the values ​​of a plurality of acquired photoemission spectra and / or derived parameters recorded with different excitation energies. This allows a limiting of the search space of possible photoemission spectra. This can allow a faster and more reliable search for the best suitable values ​​of the best suitable photoemission spectrum and / or derived parameters, since values ​​for fewer photoemission spectra and / or derived parameters need to be compared. This improves the reading out of the respective values ​​of one or more sample parameters from the sample parameter database. For example, as sample parameters, chemical elements present in the sample, such as silicon (Si), hafnium (Hf), oxygen (O), nickel (Ni), etc., can be entered by the user before further sample parameters are read out from the sample parameter database in a subsequent method step.

[0024] The sample parameter database may contain values ​​for various sample parameters, including, for example, the known layer structure of the sample, binding energy, mass density, particle number density, total photoionization cross section, asymmetry parameter, band gap, atomic number, etc. This may allow an unknown sample to be assigned a layer structure or a value of a derived parameter based on multiple acquired photoemission spectra recorded with different excitation energies.

[0025] The method may envisage the suggestion of a layer structure. The user may confirm the proposed layer structure as correct or reject it. If the user rejects the proposed layer structure, the next best layer structure may be suggested based on the photoemission spectrum. Alternatively, for multiple layer structures, the value of at least one sample parameter may be determined based on up to n-1 sample parameters and the photoemission spectrum. Thus, the best suited layer structure, for example having the smallest chi-square, may be suggested as the layer structure. These layer structures may be arranged in a priority order depending on how well suited they are.

[0026] The photoemission spectra recorded with different excitation energies can include photoemission spectra recorded with different emission angles from a measurement point of the sample. The photoemission spectra can include photoemission spectra with the same excitation energy and different emission angles and / or can include photoemission spectra with the same emission angle and different excitation energies. This allows more information to be obtained from the sample. The photoemission spectra with different emission angles can be recorded by an angularly resolved photoelectron spectrometer. This allows fast and accurate photoemission measurements without the need to change the sample gradient. An angularly resolved photoelectron spectrometer is known, for example, from US Pat. No. 6,104,029. To measure different sample emission angles, for example, different electron trajectories can be selected using an angularly resolved photoelectron spectrometer. Alternatively, the sample gradient can be changed to measure different emission angles.

[0027] The emission angles can be spread out over 60° intervals. Photoemission spectra can be recorded, for example, in a 5° pattern, for example, using -30°, -25°, -20°, -15°, -10°, -5°, 0°, 5°, 10°, 15°, 20°, 25°, and 30°. For example, photoemission spectra for 13 different angles between -30° and +30° relative to the optical axis of the lens arrangement of the photoelectron spectrometer can be recorded. Alternatively, photoemission spectra with other irregular angle step widths or irregular angle intervals can also be recorded.

[0028] The measuring points of the sample can have an elongation of 100 μm or less, preferably 10 μm or less. This allows the determination of a local value of at least one sample parameter at the measuring point of the sample. A measuring point is not to be understood here as a point in the mathematical sense, but as a point of elongation that can have different shapes and sizes, for example depending on the focusing of the beam for exciting photoelectrons from the sample. If the sample has different values ​​of the sample parameter in the horizontal direction, then by shifting the measuring point, different local values ​​of the sample can be recorded. For example, the sample can also be scanned. This allows the value of at least one sample parameter to be displayed almost continuously depending on the vertical position on the sample. This can, for example, allow a concentration gradient to be determined in the horizontal direction.

[0029] The excitation energy may be in the range of 1 keV to 10 keV. This allows the achievement of different depths in the sample, for example between 5 nm and 30 nm. The use of different excitation energies allows, on the one hand, the acquisition of information from different depths and, on the other hand, the consideration of different information from the same depth. In the case of higher excitation energies, deeper depths in the sample can be achieved. In addition, however, information from shallower depths is also obtained, which, in combination with information of less excitation energy for shallower depths, allows, for example, more reliable information on the layer structure at shallower depths.

[0030] The various excitation energies can be generated, for example, by irradiation of various anode materials with electrons from an electron gun. The excitation energies can include, for example, AlKα: 1.49 keV, AgLα: 2.98 keV, AgLβ: 3.15 keV, TiKα: 4.51 keV, CrKα: 5.41 keV, Cu: 8.05 keV, and Au: 9.71 keV. The excitation energies used to generate photoemission spectra using different excitation energies can be selected at similar energy distances from each other. For example, excitation energies of 1.49 keV, 2.98 keV, 4.51 keV, and 5.41 keV can be selected at distances between 0.9 keV and 1.53 keV. This allows for improved information yield while taking into account the space constraints of a photoelectron spectrometer with multiple wavelengths.

[0031] The method comprises the steps of: - providing a calibration sample having known values ​​of sample structure and chemical composition; - determining values ​​for the measurement method parameters using the calibration samples to determine the value of at least one sample parameter.

[0032] A calibration sample or reference sample may be, for example, a sample whose sample structure and chemical composition are known, but on which an additional layer, such as, for example, an impurity layer, may be arranged. This impurity layer may, for example, be taken into account when determining the value of the measurement method parameter or may be removed by cleaning. For a calibration sample, values ​​for a sufficient number of sample parameters are known, which allow the values ​​for the measurement method parameters to be determined with sufficient precision or tolerance. The use of a calibration sample allows the measurement method parameters to be determined. This allows the calculation of more reliable absolute and relative values ​​for samples in which the value of at least one sample parameter is unknown. These method steps allow a calibration, for example a calibration of the absolute angle scale for the angularly resolved photoemission spectrum. These measurement method parameters may, for example, include the transmission function between the sample and the detector arrangement of the photoelectron spectrometer, the angular calibration of the absolute angle of the photoelectron spectrometer, the measurement geometry, the imaging properties of the analyzer, the transmission properties of the analyzer, the ratio of the photon currents of the radiation source for different excitation energies or another measurement method parameter. The measurement geometry may depend, for example, on the orientation of the sample relative to the input aperture of the lens arrangement of the photoelectron spectrometer and on the distance of the sample relative to the input aperture of the lens arrangement of the photoelectron spectrometer. The imaging properties of the analyzer may include, for example, a functional relationship between the raw data generated thereby and a measured quantity, such as, for example, electron energy and direction, in the coordinate system of the analyzer. The transmission properties of the analyzer may include, for example, a measured photoelectron current relative to an emitted photoelectron current, depending on the energy and direction of the photoelectrons. The ratio of the photon current of a radiation source, such as an X-ray source, for different excitation energies may, for example, be at least partially due to the transmission properties of the photoelectron spectrometer. The measurement method parameters may, for example, be determined for the peak areas and background of the photoemission spectrum such that the expected peak areas and expected backgrounds match the measured peak areas and measured backgrounds, respectively.

[0033] The method comprises the steps of: Additionally, the method may include determining a value for at least one sample parameter based on a measurement method parameter determined using a calibration sample.

[0034] This allows for a reliable determination of the value of at least one sample parameter.

[0035] According to a further aspect of the invention, a specimen parameter value determination module is envisaged for determining a value of at least one of n specimen parameters at a measurement point of the specimen based on a photoemission measurement without destroying the specimen during the photoemission measurement, the specimen parameter value determination module comprising: - an interface for obtaining a value for at least one and up to n-1 sample parameters from a set of n sample parameters at a measurement point on the sample and for obtaining a plurality of photoemission spectra recorded with different excitation energies from the measurement point on the sample; a processor for determining a value of at least one sample parameter at a measurement point of the sample based on the values ​​of up to n-1 sample parameters and on the photoemission spectrum.

[0036] This allows a reliable determination of the value of one or more sample parameters at a measurement point on the sample.

[0037] According to a further aspect of the invention, a photoelectron spectrometer is envisaged comprising a sample parameter value determination module according to claim 11 or an embodiment of said sample parameter value determination module for determining a value of at least one of n sample parameters at a measurement point of said sample on the basis of a photoelectron emission measurement without destroying the sample during the photoelectron emission measurement. - an illumination device for illuminating the sample at the measuring point with radiation of different wavelengths; a detector arrangement for capturing photoelectrons emitted from the sample, wherein the photoelectron spectrometer is configured to record a plurality of photoemission spectra from a measurement point on the sample using different excitation energies and provide the spectra to the sample parameter value determination module; Here, the sample parameter value determination module is configured to determine a value of at least one sample parameter at a measurement point of the sample based on up to n-1 sample parameters from a set of n sample parameters and the photoelectron emission spectrum acquired by the detector device.

[0038] The detector arrangement may be configured to capture photoelectrons emitted from the sample in an angularly resolved manner. The photoelectron spectrometer may be an angularly resolved photoelectron spectrometer. This allows for the provision of a compact photoelectron spectrometer for reliably determining a value of at least one of the n sample parameters at a measurement point of the sample based on photoemission measurements.

[0039] The photoelectron spectrometer may have a hermetically sealable hollow space, in particular a vacuum chamber, in which the illumination device and the detector device may be arranged. A negative pressure, in particular an ultra-high vacuum, may be generated in the hollow space. The photoelectron spectrometer may have or be connected to an ultra-high vacuum pump in order to generate an ultra-high vacuum in the hollow space, in particular in the vacuum chamber. Additionally or alternatively, the photoelectron spectrometer may have or be connected to a negative pressure pump in order to generate a negative pressure in the hollow space. The negative pressure pump may be configured to generate a negative pressure in the hollow space. The negative pressure pump may be configured to generate an absolute pressure, for example, 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 allows the generation of various pressures close to the ambient pressure, in particular close to atmospheric pressure. The negative pressure pump may be, for example, a diaphragm pump.

[0040] The illumination device may comprise a radiation source, for example a radiation source for electromagnetic radiation, such as X-rays, synchrotron radiation or deep UV radiation (English title: deep ultra-violet or DUV). The illumination device may additionally comprise a monochromator for spectrally separating or monochromatizing certain wavelengths from the radiation incident from the radiation source. This allows the provision of radiation that can be used to illuminate the sample.

[0041] The illumination device may be movable and / or tiltable so that it can be moved towards the sample to irradiate the sample with radiation. Alternatively or additionally, the detector device may be movable and / or tiltable so that it can be moved towards the sample to receive photoelectrons emitted from the sample. Alternatively or additionally, the sample may also be movable and / or tiltable, for example using a manipulator.

[0042] The detector arrangement may have a front cap electrode, one or more electron lenses, one or more deflectors, an analyzer, and / or a detector. The detector arrangement may be formed, for example, by a front cap electrode, an electron lens, an analyzer, and a detector. The detector arrangement may have one or more interconnected hollow spaces forming an interior space of the detector arrangement, in which photoelectrons emitted from the sample can be guided from the front cap electrode to the detector. Additionally, the detector arrangement may also have one or more deflectors for arranging the photoelectrons to the input side of the analyzer.

[0043] The front cap electrode can have a conical shape and an input opening with a conical extension, so that gas molecules entering the input opening can quickly disperse behind the input opening in the hollow space surrounded by the front cap electrode. This allows for a quick decompression. This allows for a long free path length for electrons behind the input opening. This is useful, for example, when photoemission measurements are performed at close to atmospheric pressure to ensure a sufficiently high intensity.

[0044] Different negative pressures can be present in the interconnected hollow spaces. These negative pressures can be further reduced in the direction from the input opening to the detector. For this purpose, various pressure reduction stages can be provided, and the pressure can be reduced with different intensities, for example by means of pumps pumping with different intensities in the hollow spaces arranged one after the other. This allows a lower pressure to be maintained in the detector arrangement, for example an absolute pressure of 0.1 mbar to 100 mbar, for example 25 mbar, upstream of the front cap electrode, and a pressure of 10 mbar in the hollow space surrounded by the front cap electrode. -4 mbar~10 -2 mbar, e.g. 10 -3 Absolute pressure in the range of mbar, 10 in the downstream hollow space -6 mbar~10 -4 mbar, e.g. 10 -5 mbar absolute pressure, 10 in the hollow space upstream of the detector -8 mbar~10 -5 mbar, e.g. 10 -6 Absolute pressures in the mbar range can be maintained.

[0045] The analyzer may be, for example, a hemispherical energy analyzer or may have such a hemispherical energy analyzer. The detector may be, for example, an electron multiplier, a fluorescent screen device, a video camera, a CCD sensor (English: charge-coupled device) and / or a CMOS sensor (English: complementary metal-oxide-semiconductor). The detector may be configured as a DLD (English: delay line detector).

[0046] According to a further aspect of the invention, the use of the method or an embodiment of this method according to at least one of claims 1 to 10 for: - determining whether the layer of the sample has a predetermined layer thickness at a measurement point on the sample, and / or - determining the degree of diffusivity of layer boundaries between adjacent layers, and / or - determining the degree of stretching of layer boundaries between adjacent layers, and / or - determining the reproducibility of the manufacturing process of the samples, and / or - examining the influence of the value of at least one specimen parameter on the functional form of the specimen, and / or -Compare different samples, and / or -It is envisaged to be used to find recipes for manufacturing samples.

[0047] Determining whether a layer of a sample has a predetermined layer thickness at a measurement point on the sample allows for improved quality control.

[0048] Determining the degree of diffusion of the layer boundaries between adjacent layers makes it possible, for example, to determine whether diffusion between layers has occurred. The layer boundaries may, for example, be sharp or completely diffuse. At sharp layer boundaries, the material of one layer abuts the material of the other layer at the layer boundary without the material of said layer extending across the layer boundary into the respective other layer. At diffuse layer boundaries, the material of one layer is also present in the other layer across the layer boundary and vice versa. The degree of diffusion depends on what proportion of the material extends across the layer boundary. In the case of a diffusion rate of 0%, the materials of the different layers do not extend across the layer boundary. At a diffusion rate F of 100%, adjacent layers form a mixture with a mixture of the materials of the adjacent layers of 50% by volume each at the layer boundary.

[0049] Determining the degree of stretching of the layer boundaries between adjacent layers makes it possible to examine whether interlayer diffusion is occurring and how much material is diffusing from one layer to the other.

[0050] Determining the reproducibility of the manufacturing process of the samples allows for improved quality control.

[0051] Examining the influence of the value of at least one sample parameter on the functional form of the sample makes it possible to optimize the sample structure for the functional form of the sample. Here, samples with various values ​​of at least one sample parameter can be produced, and by comparison it can be determined how the change in value affects the functional form of the sample. The measuring method can check whether the production of the sample actually leads to the desired value of the sample parameter. This can, for example, make it possible to find and optimize a recipe for the production of the sample.

[0052] According to a further aspect of the invention, a computer program product is envisaged, comprising instructions which, when executed by a processor, cause the processor to perform at least one of the methods or embodiments of the methods according to claims 1 to 10.

[0053] According to a further aspect, a computer readable medium having the computer program product stored thereon is contemplated.

[0054] 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 defined in particular in the dependent claims.

[0055] Furthermore, preferred embodiments of the invention may also be any combination of the features of the dependent claims or the above-mentioned embodiments in conjunction with the corresponding independent claim.

[0056] In the following, this and further aspects of the invention will be explained in more detail with reference to examples shown in the drawings. [Brief description of the drawings]

[0057] [Figure 1] FIG. 13 shows a schematic and exemplary embodiment of a photoelectron spectrometer having a sample parameter value determination module for determining a value of at least one sample parameter out of n sample parameters at a measurement point of the sample based on photoelectron emission measurement without destroying the sample during photoelectron emission measurement. [Diagram 2] 1 is a flow chart illustrating an embodiment of a method for determining a value of at least one of n specimen parameters at a measurement point on a specimen based on a photoemission measurement without destroying the specimen during the photoemission measurement.

[0058] Description of the embodiment 1 shows, in a schematic and exemplary manner, an embodiment of a photoelectron spectrometer 100 with a sample parameter value determination module 50 for determining the value of at least one of n sample parameters at a measurement point 22 of a sample 20 based on photoelectron emission measurements without destroying the sample 20 during the photoelectron emission measurements, for example by sputtering with an ion gun. This photoelectron spectrometer 100 can be used to implement the method for determining the value of at least one of n sample parameters at a measurement point 22 of a sample based on photoelectron emission measurements without destroying the sample during the photoelectron emission measurements shown in FIG.

[0059] The photoelectron spectrometer 100 is in this embodiment an angular resolved photoelectron spectrometer. It comprises an illumination device 10 for illuminating a sample 20 at a measurement point 22 with beams in the form of X-rays X of different wavelengths, a detector device 30 for capturing photoelectrons p emitted from the sample 20, an ultra-high vacuum pump 40, a sample parameter value determination module 50 and a hollow space in the form of a vacuum chamber 60. Additionally, in this embodiment a measurement device 70 for further measurements at the measurement point 22 of the sample 20 is arranged. This measurement device 70 can for example carry out ellipsometric measurements, for example to determine the value of a sample parameter.

[0060] The illumination device 10 includes, in this embodiment, an X-ray source 12 and a monochromator 14. In the X-ray source 12, X-rays X having different wavelengths are generated by irradiating different anode materials with electrons from an electron gun. These X-rays X are then monochromatized in the monochromator 14 and focused at a measurement point 22 on the sample. The monochromator 14 is configured to monochromatize X-rays X having different wavelengths and focus them at the same measurement point 22. To this end, the monochromator 14 can, for example, have a plurality of reflective elements suitable for the corresponding wavelengths in a corresponding arrangement.

[0061] The sample 20 is placed on a sample holder (not shown) in this embodiment. The sample holder is movable and tiltable. This allows scanning of the sample 20. Additionally, the sample 20 can be scanned via scanning over the anode material with the electron gun of the X-ray source 12.

[0062] The detector arrangement 30 includes a front cap electrode 32, a lens element assembly 34, an analyzer 36 in the form of a hemispherical analyzer, and a detector 38 in the form of a CMOS detector. In alternative embodiments, for example, other analyzers and / or other detectors may be used.

[0063] An ultra-high vacuum pump 40 is used for this purpose to create an ultra-high vacuum inside the vacuum chamber 60 .

[0064] The sample parameter value determination module 50 includes 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 can include or be any other type of interface, such as a cable interface or a keyboard for user input. The processor 54 is configured to execute a computer program product including instructions for the method illustrated in FIG. 2. The computer program product is stored on the computer readable medium 56. Additionally, in this embodiment, a sample parameter database is also stored in which predefined values ​​of sample parameters are assigned to specific photoemission spectra. In another embodiment, the values ​​of the sample parameters may be assigned to values ​​of parameters derived from the photoemission spectra.

[0065] During operation of the photoelectron spectrometer 100, monochromated X-rays X having different wavelengths are focused on the measurement point 22 having an elongation of 10 μm. In another embodiment, the measurement point may have an elongation of, for example, 100 μm or less, preferably 10 μm or less, or may have a size between 10 μm and 100 μm. Different wavelengths correspond to different excitation energies. These excitation energies may be in the range between 1 keV and 10 keV, for example. The X-rays X having different wavelengths generate photoelectrons p at different depths of the sample 20. These photoelectrons p are emitted from the surface of the sample 20 and are received by the front cap electrode 32 of the detector device 30. The lens element assembly 34 guides the photoelectrons p to the analyzer 36, where they are resolved according to their kinetic energy. In the detector 38, the photoelectrons p are detected. A photoemission spectrum is then generated from the data measured by the detector 38. In this embodiment, photoemission spectra using different excitation energies and different emission angles are recorded.

[0066] These photoemission spectra are obtained from the detector device via the interface 52 for their further processing. Additionally, the interface 52 obtains values ​​of the sample parameters obtained from further measurement methods, for example from the measurement device 70. In another embodiment, a parameter database may be stored externally for the sample parameter value determination module 50, and values ​​for the sample parameters are further obtainable via the interface 52. In this embodiment, the values ​​of the sample parameters are provided to the sample parameter value determination module 50 from the sample parameter database via the computer-readable medium 56. In this embodiment, the sample parameter value determination module 50 obtains values ​​for at least one and up to n-1 sample parameters from a set of n sample parameters at the measurement points 22 of the sample 20, and obtains a number of photoemission spectra recorded with different excitation energies and emission angles from the measurement points 22 of the sample 20. The processor 54 determines the value of at least one sample parameter at the measurement points 22 of the sample 20 based on the values ​​of up to n-1 sample parameters and the photoemission spectrum.

[0067] 2 shows a flow chart of an embodiment of a method 200 for determining the value of at least one of n sample parameters at a measurement point of a sample based on a photoemission measurement without destroying the sample during the photoemission measurement. In this embodiment, the at least one sample parameter whose value is to be determined describes a part of the sample structure, in particular a part of a layer structure, at the measurement point of the sample. The method is particularly suitable for producing a depth profile for the sample, without destroying the sample in the process.

[0068] In an optional step 202, a calibration sample can be provided, with known values ​​of sample structure and chemical composition, which can be used to calibrate the measurement method parameters, in particular the instrumental parameters for the measurement.

[0069] In optional step 204, values ​​for the measurement method parameters may be determined using calibration samples.

[0070] In step 206, values ​​for at least one and up to n-1 sample parameters at the measurement points of the sample are obtained. The number n of sample parameters of a sample is a positive integer and is sample dependent. The values ​​for the sample parameters can be obtained in various types. In this embodiment, the values ​​for the sample parameters are obtained in three types of steps: - inputting respective values ​​for one or more sample parameters by a user; - measuring a respective value for one or more sample parameters using a further measurement method; - retrieving respective values ​​for one or more sample parameters from a sample parameter database using predetermined values ​​for the sample parameters; is obtained from a combination of

[0071] In another embodiment, the values ​​may be obtained by only one or two of these types.

[0072] In step 208, a plurality of photoemission spectra recorded using different excitation energies are obtained from the measurement points on the sample. Additionally, photoemission spectra recorded using different emission angles can also be obtained from the measurement points on the sample. The emission angles can be elongated, for example, at intervals of 60°. The measurement points can have an elongation of, for example, 100 μm or less, preferably 10 μm or less. The excitation energies can range between 1 keV and 10 keV.

[0073] In step 210, a value of at least one sample parameter at a measurement point of the sample is determined based on the values ​​of up to n-1 sample parameters and the photoemission spectrum. To determine the value of the at least one sample parameter at a measurement point of the sample, a peak area in each of the photoemission spectra and / or a background in each of the photoemission spectra can be determined. The value of the at least one sample parameter at the measurement point of the sample can then be determined based on the peak area, the background, or both. If optional steps 202 and 204 have been performed, the value of the at least one sample parameter can additionally be determined based on measurement method parameters determined using a calibration sample.

[0074] 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 a photoemission measurement without destroying the sample during the photoemission measurement. Values ​​for at least one, and up to n-1 sample parameters at the measurement point of the sample and a number of photoemission spectra recorded with different excitation energies are obtained 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

1. A method for determining a value of at least one of n sample parameters at a measurement point (22) of a sample (20) based on a photoemission measurement without destroying the sample (20) during the photoemission measurement, comprising the steps of: obtaining a value for at least one and up to n-1 sample parameters from a set of n sample parameters at said measurement point (22) of said sample (20); obtaining a plurality of photoemission spectra recorded using different excitation energies from the measurement point (22) of the sample (20); determining a value of the at least one sample parameter at the measurement point (22) of the sample (20) based on the values ​​of the up to n-1 sample parameters and the photoemission spectrum.

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

3. Determining the value of the at least one sample parameter comprises the steps of: determining a peak area in each of said photoemission spectra; determining a background in each of said photoemission spectra; and determining a value of the at least one sample parameter based on the peak area of ​​the photoemission spectrum; determining a value of the at least one specimen parameter based on the background of the photoemission spectrum; and determining a value of the at least one sample parameter based on the peak area and the background of the photoemission spectrum.

4. The step of obtaining values ​​for at least one and up to n-1 sample parameters comprises the steps of: inputting, by a user, respective values ​​for one or more of said sample parameters; measuring a respective value for one or more of said sample parameters using a further measurement method; 4. The method according to claim 1 , further comprising one or more steps of: and retrieving respective values ​​for one or more of the sample parameters from a sample parameter database having predetermined values ​​for the sample parameters.

5. 5. The method according to claim 1, wherein the plurality of photoemission spectra recorded using different excitation energies comprises photoemission spectra recorded using different emission angles from the measurement point (22) of the sample (20).

6. The method of claim 5 , wherein the emission angles are spread out in intervals of 60°.

7. 7. The method according to claim 1, wherein the measuring point (22) of the sample (20) has an elongation of less than 100 μm, preferably less than 10 μm.

8. The method according to at least one of the preceding claims, wherein the excitation energy is in the range between 1 keV and 10 keV.

9. The method comprises the steps of: Providing a calibration sample having known values ​​of sample structure and chemical composition; 9. The method according to claim 1 , further comprising the step of: determining a value for a measurement method parameter using said calibration sample to determine the value of said at least one sample parameter.

10. The method comprises the steps of:

10. The method of claim 9, additionally comprising determining a value of the at least one sample parameter based on the method parameters determined using the calibration samples.

11. A sample parameter value determination module (50) for determining a value of at least one sample parameter of n sample parameters at a measurement point (22) of a sample (20) based on a photoemission measurement without destroying the sample (20) during the photoemission measurement, said sample parameter value determination module (50) comprising: an interface (52) for obtaining a value for at least one and up to n-1 sample parameters from a set of n sample parameters at the measurement point (22) of the sample (20) and for obtaining a plurality of photoemission spectra recorded with different excitation energies from the measurement point (22) of the sample (20); and a processor (54) for determining a value of the at least one sample parameter at the measurement point (22) of the sample (20) based on values ​​of the at most n-1 sample parameters and the photoelectron emission spectrum.

12. 12. A photoelectron spectrometer (100) comprising a sample parameter value determination module (50) according to claim 11 for determining a value of at least one of n sample parameters at a measurement point (22) of a sample (20) based on a photoelectron emission measurement without destroying the sample (20) during the photoelectron emission measurement, comprising: The photoelectron spectrometer (100) comprises: an illumination device (10) for illuminating the sample (20) at the measurement points (22) with radiation (X) of different wavelengths; a detector device (30) for capturing photoelectrons (p) emitted from the sample (20); the photoelectron spectrometer (100) is configured to record a plurality of photoelectron emission spectra from the measurement point (22) of the sample (20) using different excitation energies and provide them to the sample parameter value determination module (50); The sample parameter value determination module (50) is configured to determine a value of the at least one sample parameter at the measurement point (22) of the sample (20) based on up to n-1 sample parameters from a set of n sample parameters and a photoelectron emission spectrum acquired by the detector device (30).

13. Use of the method according to at least one of claims 1 to 10 for: Determining whether the layer of the sample has a predetermined layer thickness at a measurement point on the sample, and / or Determining the degree of diffusivity of layer boundaries between adjacent layers; and / or Determining the degree of stretching of layer boundaries between adjacent layers, and / or determining the reproducibility of the manufacturing process of said samples; and / or Investigating the influence of the value of at least one specimen parameter on the functional behavior of the specimen, and / or Compare different samples, and / or Use to find a recipe for manufacturing a sample.

14. A computer program product comprising instructions that, when the computer program product is executed by a processor (54), cause the processor (54) to perform a method according to at least one of claims 1 to 10.

15. A computer readable medium (56) having stored thereon the computer program product according to claim 14.

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