Non-destructive reliable determination of sample parameter values

Abstract

The invention relates to a photoelectron spectrometer (100) comprising a sample parameter value determination module (50) and to 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 damaging the sample (20) during the photoemission measurement. Values for at least one and up to n-1 sample parameters of the set of n sample parameters at the measurement point (22) of the sample (20) are obtained and a plurality of photoemission spectra of the measurement point (22) of the sample (20) recorded with different excitation energies are obtained. A value of the at least one sample parameter at a measurement point (22) of the sample (20) is determined based on the values of the up to n-1 sample parameters and the photoemission spectrum.

Description

Technical Field

[0001] The invention relates to a measuring method for determining the value of at least one of n sample parameters at a measuring 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 said sample parameter value determination module, a corresponding computer program product and a computer-readable medium comprising said computer program product.

[0002] Background technology

[0003] The following measurement method is known from Y. Hoshina et al. in "Non-destructive depth profile evaluation of multi-layer thin film Stack using simultaneous analysis of data from multiple X-ray photoelectron spectroscopy instruments" in "Jpn. J. Appl. Phys.", Vol. 61, 2022, 046501, in which photoemission measurements are performed on the sample on different photoelectron spectrometers with different excitation energies and at different emission angles, so as to characterize the sample without destroying the sample and, in particular, determine the depth profile of the sample.

[0004] EP 2 542 035 B1 discloses a photoelectron spectrometer which can irradiate a sample at a measuring point using two different excitation energies. Summary of the invention

[0005] It may be seen as an object of the present invention to provide a measuring method, a sample parameter value determination module, a photoelectron spectrometer, a computer program product and a computer-readable medium which enable an improved or more reliable non-destructive determination of the value of a sample parameter.

[0006] According to a first aspect of the present invention, there is provided a measurement method for determining the 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. The method comprises the following steps:

[0007] - obtaining values ​​for at least one and up to n-1 sample parameters of the set of n sample parameters at a measurement point of the sample;

[0008] - obtaining a plurality of photoemission spectra of a measurement point of the sample recorded at different excitation energies;

[0009] - determining a value of said at least one sample parameter at a measuring point of the sample based on said up to n-1 sample parameters and said photoemission spectrum.

[0010] The inventors have found that, due to the number of unknown sample parameters, in particular for depth profile analysis, it is not possible to reliably fully characterize a sample, in particular to create a depth profile of the sample including information about the layer structure (including chemical composition and layer thickness), based on one photoemission spectrum. In particular, more complex layer structures including multiple layers of different layer thicknesses with different depth profiles can have similar photoemission spectra.

[0011] The method according to the invention enables reliable determination of values ​​of one or more sample parameters such as, for example, layer thickness, chemical composition of the layers, homogeneity of the layers and chemical state of the material in the layers (such as, for example, oxidation level or the like) based on a plurality of photoemission measurements.

[0012] Preferably, the sample is a solid sample with one or more layers. The sample can be, for example, a silicon (Si) wafer including a layer sequence deposited thereon. The sample can also be a layer structure including a solid layer, a liquid layer and / or a gas layer. The sample can also have another sample structure. For example, in the sample structure, different materials can be arranged in different areas on the same horizontal plane. Additional layers, such as contamination layers or layers that do not affect the function of the sample can be arranged on the sample. Instead of a complete layer, additional areas, such as contamination areas, that do not form a complete layer can also be arranged on the surface of the sample. The additional layer does not constitute a part of the sample in the sense of the present invention. For example, a contamination layer can be produced by dust or dirt being deposited on the surface of the sample. Such a contamination layer does not constitute a part of the sample in principle. However, the contamination layer on the sample can be a part of the sample, as long as the contamination layer should constitute a part of the sample from the user's point of view, for example, because the contamination layer may affect the characteristics of the sample to be measured. The contamination layer can be formed, for example, by oxidation or dust or dirt being deposited on the surface. The method can be constructed to take into account a contamination layer, such as a contamination layer formed by a carbon layer or a layer containing carbon.

[0013] Alternatively, the method can provide for pre-treating the surface and / or cleaning the surface of the sample in a negative pressure system so that the surface of the sample has a reduced layer thickness of the contamination layer or is free of the contamination layer. For example, irradiating the contamination layer or spraying the sample can be provided to clean the surface of the sample.

[0014] If the sample does not change relative to its state before the photoelectric emission measurement except for the changes produced by the photoelectric emission measurement, then the sample is not destroyed in the sense of this patent. The photoelectric emission measurement includes: radiation with a wavelength is incident on the sample and photoelectrons emitted from the sample are received by a detector according to kinetic energy resolution. For example, if a layer of the sample is contaminated by foreign atoms or a layer is removed, then the sample is destroyed in the sense of this patent. For example, the removal of the contamination layer during cleaning during pretreatment of the sample should not be understood as destruction of the sample. In the sense of this patent, the sample will not be destroyed by cleaning the sample because the contamination layer is not part of the sample to be measured. In order not to destroy the sample, for example, when cleaning by ion injection, it can be provided to ensure that ions do not enter the sample to be measured. The contamination layer can also be considered as part of the sample by means of sample parameters.

[0015] 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 enables the generation of radiation with different excitation energies in the photoelectron spectrometer.

[0016] The sample parameters may include sample structure parameters and sample material parameters. The sample structure parameters may include, for example, the sample structure, the layer structure, the chemical composition of each layer of the sample, the chemical composition of each region of the sample, the materials present in the corresponding layer of the sample, the layer thickness t or the like. The layer structure of the sample may, for example, include information about the chemical composition of each layer contained in the sample and its layer thickness. The materials contained in the sample may, for example, be described by a general formula. Alternatively, for example, the concentration of the material may be given according to the position in the sample. For example, the concentration may be given according to the horizontal and vertical position of the material in the sample relative to a reference point. For the vertical position, for example, a surface oriented in the direction of the incident radiation may be used as a reference plane and the depth may be used as a relative spacing from the reference plane to determine the vertical position.

[0017] The sample material parameters may include, for example, the total photoionization cross section σ, the asymmetry parameter β, the extinction length λ (E kin ), binding energy E b , mass density, particle number density, band gap, atomic number, or something like that.

[0018] The at least one sample parameter whose value is to be determined can describe a part of the sample structure at the measuring point of the sample, in particular a part of the layer structure. This enables a reliable depth profile of the sample at the measuring point. The sample structure of the sample can give a depth-dependent concentration of a chemical element. The at least one sample parameter can be, for example, a depth-dependent concentration of a chemical element or a layer thickness of a layer of the sample. For example, a plurality of sample parameters can also describe the layer structure of the sample, for example, a sample parameter can represent the chemical composition of the layers of the sample. The chemical composition of the layers of the sample can, for example, represent the mixing of chemical elements in different layers and their arrangement in the sample.

[0019] Determining the value of the at least one sample parameter may comprise at least one of the following steps:

[0020] - determining the peak area in each photoemission spectrum in said photoemission spectrum;

[0021] - determining the background in each of the photoemission spectra, and comprising one of the following steps:

[0022] - determining the value of the at least one sample parameter based on the peak area of ​​each photoemission spectrum;

[0023] - determining a value of said at least one sample parameter based on the background of each photoemission spectrum; and

[0024] - determining the value of the at least one sample parameter based on the peak area and the background of each photoemission spectrum.

[0025] The peak corresponds to the top in the photoemission spectrum. The peak area is the area under the curve of the peak minus the background. The background can be determined, for example, based on different background models, for example based on different inelastic scattering models for photoelectrons.

[0026] The background is generated by photoelectrons not originally emitted, for example photoelectrons scattered inelastically in the sample, and can be determined with the aid of a background model. The background can be determined using the same or a different background model than that used to determine the peak areas.

[0027] Determining the value of the at least one sample parameter based on the background or based on the peak area and the background enables a more reliable determination of the value, since additional information can be obtained from the respective spectrum.

[0028] The surface of the sample oriented in the direction of the incident radiation, through which the radiation is incident for generating photoelectrons during the photoemission measurement, can be smooth, rough or structured. In addition, the 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 surface of the sample oriented in the direction of the incident radiation and the type of surface between adjacent layers of the sample. For rough or structured surfaces or surfaces, for example, the structure or roughness can be additionally taken into account.

[0029] Obtaining values ​​for the at least one and up to n-1 sample parameters may comprise one or more of the following steps:

[0030] - input by the user of respective values ​​for one or more of said sample parameters;

[0031] - measuring a corresponding value for one or more of said sample parameters using a further measurement method;

[0032] - reading the corresponding value for one or more of said sample parameters from a sample parameter database having predetermined values ​​for said sample parameters.

[0033] The other measurement method may, for example, include an optical method, such as an ellipsometry measurement method. According to the other measurement method, values ​​for different sample parameters can be obtained. Different method steps for obtaining values ​​for the up to n-1 sample parameters can also be combined to obtain values ​​for each type of sample parameter. For example, a user can enter values ​​for one or more sample parameters in the sample parameters, and values ​​for other sample parameters can be read from a sample parameter database based on the values ​​or these values ​​of the sample parameters. For example, a user can enter the chemical composition of a sample structure, and material parameters of a material, especially chemical elements contained in the sample structure, can be read from a sample parameter database. In the sample parameter database, the values ​​of the sample parameters can correspond to other values ​​of the sample parameters, such as, for example, chemical elements can correspond to specific binding energies of different orbits of chemical elements. By obtaining values ​​for the sample parameters, the value of the at least one sample parameter can be determined more reliably. The larger the number of values ​​obtained for the n-1 sample parameters, the more reliably the value of the at least one sample parameter can be determined.

[0034] In the sample parameter database, the predetermined values ​​of the sample parameters can, for example, correspond to the values ​​of the parameters derived from a specific photoemission spectrum and / or a plurality of photoemission spectra obtained with different excitation energies recorded, such as, for example, the energy position of the peak, the relative depth or the like. The sample parameter database can, for example, be generated by collecting the known values ​​of the sample parameters and making them correspond to the photoemission spectrum and / or the values ​​of the parameters derived from the photoemission spectrum accordingly. Reading the corresponding values ​​of one or more sample parameters for the sample parameters from the sample parameter database can have the following steps:

[0035] - Compare the values ​​of the photoemission spectra and / or the parameters derived from the multiple photoemission spectra obtained and recorded with different excitation energies contained in the sample parameter database with the values ​​of the multiple photoemission spectra obtained and recorded with different excitation energies and / or the derived parameters, and read the corresponding values ​​for the one or more sample parameters, which correspond to the most consistent photoemission spectrum in the sample parameter database or the most consistent value in the derived parameters in the sample parameter database.

[0036] The method can also provide that before comparing the photoemission spectrum contained in the sample parameter database and / or the value of the derived parameter with the obtained photoemission spectrum recorded with different excitation energies and / or the value of the derived parameter, the value of one or more sample parameters is obtained. This can achieve a search space that limits possible photoemission spectra. This can achieve faster and more reliable finding of the most suitable photoemission spectrum and / or the most suitable value of the derived parameter, because fewer photoemission spectra and / or the values ​​for the derived parameters must be compared. Thus improving the reading of the corresponding values ​​for the one or more sample parameters from the sample parameter database. Before reading other sample parameters from the sample parameter database in subsequent method steps, for example, chemical elements present in the sample, such as silicon (Si), hafnium (Hf), oxygen (O), nickel (Ni), etc. can be input by a user as sample parameters.

[0037] The sample parameter database may contain values ​​for different sample parameters, such as, for example, known layer structures, binding energies, mass density, particle number density, total photoionization cross section, asymmetry parameters, band gap, atomic number or the like of the sample. This makes it possible to configure a layer structure for an unknown sample based on a plurality of photoemission spectra obtained and recorded at different excitation energies or the values ​​of the derived parameters.

[0038] The method may provide for proposing a layer structure. The user may confirm the proposed layer structure as correct or reject it. If the user rejects the proposed layer structure, a suboptimal layer structure may be proposed based on the photoemission spectrum. Alternatively, the value of the at least one sample parameter may also be determined for a variety of layer structures based on the up to n-1 sample parameters and the photoemission spectrum. The most suitable layer structure (e.g., with the smallest chi-square) may then be proposed as the layer structure. The various layer structures may be sorted according to their degree of adaptation.

[0039] The multiple photoemission spectra recorded with different excitation energies may include photoemission spectra recorded at different emission angles from the measurement point of the sample. The photoemission spectrum may 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 can achieve more information from the sample. Photoemission spectra with different emission angles can be recorded by an angle-resolved photoelectron spectrometer. This can achieve fast and accurate photoemission measurements without changing the sample inclination. The angle-resolved photoelectron spectrometer is known, for example, from document US6104029A. In order to measure different sample emission angles, for example, different electron trajectories can be selected by means of an angle-resolved photoelectron spectrometer. Alternatively, the sample inclination can be changed to measure other emission angles.

[0040] The emission angle can be spread over an interval of 60°. The photoemission spectrum can be recorded, for example, with a 5° grid (Raster), for example, at -30°, -25°, -20°, -15°, -10°, -5°, 0°, 5°, 10°, 15°, 20°, 25° and 30°. For example, the photoemission spectrum for 13 different angles between -30° and +30° with the optical axis of the lens device of the photoelectron spectrometer can be recorded. Alternatively, the photoemission spectrum can also be recorded with other uneven angular step widths or with uneven angular spacings.

[0041] The measuring point of the sample can have an extension of 100 μm or less, preferably 10 μm or less. This makes it possible to determine the local value of at least one sample parameter at the measuring point of the sample. The measuring point should not be understood here as a point in the mathematical sense, but as a point with an extension, which can have different shapes and sizes, for example, depending on the focusing of the radiation used to excite 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 moving the measuring point. For example, the sample can also be scanned. This makes it possible to quasi-continuously represent the value of the at least one sample parameter depending on the vertical position in the sample. This makes it possible, for example, to determine a concentration gradient in the horizontal direction.

[0042] The excitation energy can be in the 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. The use of different excitation energies makes it possible on the one hand to obtain information from different depths and on the other hand to take into account different information from the same depth. In the case of higher excitation energies, greater depths can be reached in the sample. In addition, however, information is also obtained from smaller depths, which, in combination with the information from the smaller excitation energy for the smaller depth, makes it possible, for example, to make more reliable conclusions about the layer structure at the smaller depth.

[0043] Different excitation energies can be generated, for example, by irradiating different anode materials with electrons from an electron gun. The excitation energy can, for example, include aluminum Kα with 1.49 keV, silver Lα with 2.98 keV, silver Lβ with 3.15 keV, titanium Kα with 4.51 keV, chromium Kα with 5.41 keV, copper with 8.05 keV, and gold with 9.71 keV. The excitation energies for generating photoemission spectra with different excitation energies can be selected with energy intervals similar to each other. For example, excitation energies spaced between 0.9 and 1.53 keV can be selected: 1.49 keV, 2.98 keV, 4.51 keV, and 5.41 keV. This can achieve: improving the amount of information while taking into account the spatial limitations in a photoelectron spectrometer with multiple wavelengths.

[0044] The method may include the following steps:

[0045] - providing calibration samples for which the values ​​of the sample structure and chemical composition are known; and

[0046] - Determining the value of a measurement method parameter for determining the value of the at least one sample parameter with the aid of the calibration sample.

[0047] The calibration sample or reference sample can be, for example, a sample whose sample structure and chemical composition are known, but on which additional layers, such as, for example, a contamination layer, can be arranged. The contamination layer can be taken into account, for example, when determining the value of the measurement method parameter or can be removed by cleaning. For the calibration sample, the value of a sufficient number of sample parameters is known, which can be used to determine the value of the measurement method parameter with sufficient accuracy or acceptable error. The determination of the measurement method parameters can be achieved using the calibration sample. This can be achieved by obtaining more reliable absolute and relative values ​​for the sample, wherein the value of at least one sample parameter is unknown. Calibration can be achieved by the method steps, for example, for the absolute angular scale of the angularly resolved photoemission spectrum. The measurement method parameters can, for example, be included in the transmission function between the sample and the detector device of the photoelectron spectrometer, the angular calibration of the absolute angle of the photoelectron spectrometer, the geometric structure of the measurement, the imaging characteristics of the analyzer, the transmission characteristics of the analyzer, the ratio of the photon flow of the radiation source for different excitation energies or other measurement method parameters. The geometry of the measurement can, for example, be related to the orientation of the sample relative to the input opening of the lens arrangement of the photoelectron spectrometer and the spacing of the sample from the input opening of the lens arrangement of the photoelectron spectrometer. The imaging characteristics of the analyzer can, for example, consist in the functional relationship between the raw data generated by it and the measurement variables, such as, for example, the electron energy and the direction in the coordinate system of the analyzer. The transmission characteristics of the analyzer can, for example, consist in the ratio of the measured photoelectron current to the emitted photoelectron current, which is related to the energy and the direction of the photoelectrons. The ratio of the photon currents of radiation sources, such as X-ray sources, for different excitation energies can, for example, be at least partially included in the transmission characteristics of the photoelectron spectrometer. For example, for the peak area and the background of the photoemission spectrum, the measurement method parameters can be determined so that the expected peak area and the expected background are consistent with the corresponding measured peak area and the measured background.

[0048] The method may include the following steps:

[0049] - additionally determining the value of the at least one sample parameter based on the measuring method parameters determined with the aid of the calibration sample.

[0050] This enables a more reliable determination of the value of the at least one sample parameter.

[0051] According to another aspect of the present invention, there is provided a sample parameter value determination module for determining the value of at least one sample parameter among n sample parameters at a measurement point of a sample based on photoemission measurement without destroying the sample during the photoemission measurement. The sample parameter value determination module has:

[0052] - an interface for obtaining values ​​of at least one and up to n-1 sample parameters of the set of n sample parameters at a measurement point of the sample and for obtaining a plurality of photoemission spectra recorded at different excitation energies of the measurement point of the sample; and

[0053] - a processor for determining a value of said at least one sample parameter at a measurement point of the sample based on the values ​​of said at most n-1 sample parameters and said photoemission spectrum.

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

[0055] According to another aspect of the present invention, a photoelectron spectrometer is provided, the photoelectron spectrometer comprising a sample parameter value determination module according to claim 11 or an embodiment of a sample parameter value determination module for determining the value of at least one sample parameter of n sample parameters at a measurement point of the sample based on photoemission measurement without destroying the sample during the photoemission measurement. The photoelectron spectrometer has:

[0056] - an illumination device for illuminating the sample at the measuring point with radiation of a respectively different wavelength;

[0057] - a detector device for detecting photoelectrons emitted from the sample; wherein the photoelectron spectrometer is configured to record a plurality of photoemission spectra from a measurement point of the sample at different excitation energies and to provide them to a sample parameter value determination module; and

[0058] The sample parameter value determination module is configured to determine a value of the at least one sample parameter at a measurement point of the sample based on the up to n-1 sample parameters from the set of n sample parameters and the photoemission spectrum acquired by the detector arrangement.

[0059] The detector arrangement can be designed to detect photoelectrons emitted by the sample in an angle-resolved manner. The photoelectron spectrometer can be an angle-resolved 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 a measurement point of the sample based on a photoemission measurement.

[0060] The photoelectron spectrometer can have a cavity that can be sealed and closed, especially a vacuum cavity, in which the lighting device and the detector device can be arranged. Negative pressure, especially 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, especially the vacuum cavity. Additionally or alternatively, the photoelectron spectrometer can have a negative pressure pump or be connected to a negative pressure pump to generate negative pressure in the cavity. The negative pressure pump can be configured to generate negative pressure in the cavity. The negative pressure pump can be configured, for example, to generate an absolute pressure between 0.1 mbar and 600 mbar, between 0.1 mbar and 400 mbar, or between 0.1 mbar and 100 mbar, for example 20 mbar. This can be achieved by generating different pressures close to the ambient pressure, especially close to atmospheric pressure. The negative pressure pump can be, for example, a diaphragm pump.

[0061] The illumination device can have a radiation source, for example a radiation source for electromagnetic radiation, such as X-ray radiation, synchrotron radiation or deep ultraviolet radiation (English: deep ultra-violet or DUV). The illumination device can additionally have a monochromator for spectrally separating specific wavelengths from the radiation incident by the radiation source or for monochromatization. This makes it possible to provide radiation that can be used to irradiate the sample.

[0062] The illumination device may be movable and / or tiltable so as to be moved close to the sample in order to illuminate the sample with radiation. Alternatively or additionally, the detector device may be movable and / or tiltable so as to be moved close to the sample in order to receive photoelectrons emitted from the sample. Alternatively or additionally, the sample may also be movable and / or tiltable, for example by means of a manipulator.

[0063] The detector device can have a front cover electrode, one or more electron lenses, one or more deflectors, an analyzer and / or a detector. The detector device can be formed, for example, by a front cover electrode, an electron lens, an analyzer and a detector. The detector device can have one or more interconnected cavities, which form an inner space of the detector device, through which photoelectrons emitted from the sample can be guided from the front cover electrode to the detector. Additionally, the detector device can also have one or more deflectors so as to orient the photoelectrons toward the entrance of the analyzer.

[0064] The front cover electrode can have a conical shape and an input opening with a conical direction, so that the gas molecules entering the input opening can be quickly distributed in the cavity downstream of the input opening, which is surrounded by the front cover electrode. This can achieve a rapid pressure reduction. As a result, the free path length for electrons downstream of the input opening can be increased. This is helpful, for example, if photoemission measurements are carried out at near atmospheric pressure in order to ensure a sufficiently high intensity.

[0065] In a plurality of interconnected cavities, different negative pressures can exist, which can decrease further from the inlet opening in the direction of the detector. For this purpose, different pressure reduction stages can be provided, and the pressure can be reduced to different degrees in the cavities arranged one after the other, for example by means of pumps that pump with different degrees of suction. This makes it possible to maintain a relatively low pressure in the detector arrangement, for example, to maintain an absolute pressure of 10 mbar upstream of the front cover electrode at a pressure between 0.1 mbar and 100 mbar, for example 25 mbar, in the cavity surrounded by the front cover electrode. -4 mbar to 10 -2 In the range between mbar, for example 10 -3 The absolute pressure of mbar is maintained at 10 -6 mbar to 10 -4 Between millibars, for example 10 -5 mbar absolute pressure and a pressure of 10 -8 mbar to 10 -5 In the range between mbar, for example 10 -6 Absolute pressure in millibars.

[0066] The analyzer can be, for example, a hemispherical energy analyzer or the analyzer can have such a hemispherical energy analyzer. The detector can, for example, have an electron multiplier, a fluorescent screen, a video camera, a CCD sensor (English: charge-coupled device) and / or a CMOS sensor (English: complementary metal-oxide-semiconductor). The detector can also be implemented as a DLD (English: delayline detector).

[0067] According to a further aspect of the invention, a use of the method or an embodiment of the method according to at least one of claims 1 to 10 is proposed:

[0068] - determining whether a layer of the sample has a predetermined layer thickness at the measuring point of the sample; and / or

[0069] - determining the degree of diffusivity of layer boundaries between adjacent layers; and / or

[0070] - determining the extent of layer boundaries between adjacent layers; and / or

[0071] - determine the reproducibility of the manufacturing process of the sample; and / or

[0072] - checking the influence of the value of said at least one sample parameter on the way the sample functions; and / or

[0073] - compare different samples; and / or

[0074] - Find a solution to manufacture samples.

[0075] Determining whether a layer of the sample has a predetermined layer thickness at a measuring point of the sample enables improved quality control.

[0076] Determining the degree of diffusivity of layer boundaries between adjacent layers makes it possible, for example, to determine whether diffusion has occurred between the layers. Layer boundaries can be, for example, sharp or completely diffuse. In the case of sharp layer boundaries, the material of one layer meets the material of another layer at the layer boundary, and the material of the individual layers does not extend across the layer boundary into the respective other layer. In the case of diffuse layer boundaries, the material of one layer is also in the other layer on the other side of 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 diffusivity F of 0%, no material of different layers extends beyond the layer boundary. In the case of a diffusivity F of 100%, adjacent layers form a mixture, wherein 50% by volume of the material of the adjacent layers are mixed at the layer boundary.

[0077] Determining the extent of layer boundaries between adjacent layers makes it possible to check whether diffusion between the layers occurs and how far material diffuses from one layer into another.

[0078] Determining the reproducible performance of the manufacturing process of a sample enables improved quality control.

[0079] Checking the influence of the value of the at least one sample parameter on the functional mode of the sample makes it possible to optimize the sample structure for the functional mode of the sample. Samples with different values ​​of the at least one sample parameter can be produced, and by comparison it can be determined how the change in value affects the functional mode of the sample. The measuring method makes it possible to check whether the production of the sample has actually achieved the desired value of the sample parameter. This can, for example, make it possible to find and optimize a recipe for producing the sample.

[0080] According to a further aspect of the invention, a computer program product is provided which comprises commands which, when the computer program product is executed by a processor, cause the processor to carry out the method or an embodiment of the method according to at least one of claims 1 to 10 .

[0081] According to a further aspect, a computer-readable medium is provided, on which the computer program product is stored.

[0082] 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 can have similar and / or identical preferred embodiments, as defined in particular in the dependent claims.

[0083] Furthermore, preferred embodiments of the invention may also be any combination of the features of the dependent claims or of the above-described embodiments in conjunction with the respective independent claim.

[0084] This and further aspects of the invention are explained in more detail below with reference to the exemplary embodiments shown in the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] In the following figure:

[0086] Figure 1 Schematically and exemplarily, an embodiment of a photoelectron spectrometer is shown, the photoelectron spectrometer comprising a sample parameter value determination module for determining the value of at least one sample parameter of n sample parameters at a measurement point of the sample based on a photoemission measurement without destroying the sample during the photoemission measurement;

[0087] Figure 2 A flow chart showing an embodiment of 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. DETAILED DESCRIPTION

[0088] Figure 1 An embodiment of a photoelectron spectrometer 100 is schematically and exemplarily shown, the photoelectron spectrometer comprising a sample parameter value determination module 50 for determining the 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 (e.g. by using an ion cannon ejection). The photoelectron spectrometer 100 may be used to implement Figure 2 The method is shown in the for determining the value of at least one sample parameter of n sample parameters at a measuring point of a sample based on a photoemission measurement without destroying the sample during the photoemission measurement.

[0089] The photoelectron spectrometer 100 is an angle-resolved photoelectron spectrometer in the embodiment. The photoelectron spectrometer 100 comprises: an illumination device 10 for illuminating a sample 20 at a measuring point 22 with radiation in the form of X-rays X of correspondingly different wavelengths; a detector device 30 for detecting photoelectrons p emitted from the sample 20; an ultra-high vacuum pump 40; a sample parameter value determination module 50 and a cavity in the form of a vacuum chamber 60. In addition, a measuring device 70 for performing further measurements at the measuring point 22 of the sample 20 is provided in the embodiment. The measuring device 70 can implement, for example, ellipsometry in order to determine the value of a sample parameter.

[0090] The illumination device 10 comprises an X-ray source 12 and a monochromator 14 in the described embodiment. X-rays X with different wavelengths are generated in the X-ray source 12 by firing electrons with an electron gun onto different anode materials. The X-rays X are then monochromatized in the monochromator 14 and focused onto a measurement point 22 of the sample. The monochromator 14 is configured to monochromatize the X-rays X with different wavelengths and focus them onto the same measurement point 22. For this purpose, the monochromator 14 can have, for example, a plurality of reflective elements suitable for the corresponding wavelengths in a corresponding arrangement.

[0091] In the exemplary 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. In addition, the sample 20 can be scanned by scanning the electron gun of the X-ray source 12 over the anode material.

[0092] The detector arrangement 30 comprises a front cover 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 other embodiments, for example, additional analyzers and / or additional detectors may also be used.

[0093] The ultra-high vacuum pump 40 is used to form an ultra-high vacuum inside the vacuum chamber 60 .

[0094] The sample parameter value determination module 50 comprises an interface 52 in the form of a transmitter-receiver, a processor 54 and a computer-readable medium 56 in the form of a memory 56. Alternatively or additionally, the interface may also comprise 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, which comprises a computer program for executing a computer program in a manner Figure 2 The computer program product is stored on a computer readable medium 56. In addition, in the embodiment described, a sample parameter database is also stored, in which predetermined values ​​of sample parameters correspond to specific photoemission spectra. In other embodiments, the values ​​of sample parameters may also correspond to the values ​​of parameters derived from the photoemission spectra.

[0095] In the operation of the photoelectron spectrometer 100, monochromatized X-rays X with different wavelengths are focused on a measurement point 22 with an extension range of 10 μm. In other embodiments, the measurement point may also have an extension range of 100 μm or less, preferably 10 μm or less, or the size of the measurement point may be between 10 μm and 100 μm. Different wavelengths correspond to different excitation energies. The excitation energy may be, for example, in the range between 1 keV and 10 keV. Photoelectrons p are generated at different depths of the sample 20 by X-rays X with different wavelengths. The photoelectrons p escape from the surface of the sample 20 and are received by the front cover electrode 32 of the detector device 30. The lens element assembly 34 introduces the photoelectrons p into the analyzer 36, where the photoelectrons are resolved according to kinetic energy. The photoelectrons p are detected in the detector 38. Then a photoemission spectrum is generated from the data measured by the detector 38. In the embodiment, a photoemission spectrum with different excitation energies and different emission angles is recorded.

[0096] The photoemission spectrum is obtained by the detector device via the interface 52 so that it can be further processed. In addition, the interface 52 obtains the value of the sample parameter that has been obtained by another measurement method, for example, by the measuring device 70. In other embodiments, the parameter database can also be stored outside the sample parameter value determination module 50 and the value for the sample parameter can be obtained via the interface 52. In the embodiment, the value of the sample parameter from the sample parameter database can be used by the sample parameter value determination module 50 via a computer-readable medium 56. The sample parameter value determination module 50 obtains the value of at least one of the set of n sample parameters at the measurement point 22 of the sample 20 and up to n-1 sample parameters and a plurality of photoemission spectra recorded at different excitation energies and emission angles at the measurement point 22 of the sample 20 in the embodiment. The processor 54 determines the value of the at least one sample parameter at the measurement point 22 of the sample 20 based on the value of the up to n-1 sample parameters and the photoemission spectrum.

[0097] Figure 2 A flow chart of an exemplary embodiment of a method 200 for determining the value of at least one of n sample parameters at a measuring point of a sample based on a photoemission measurement without destroying the sample during the photoemission measurement. In the exemplary 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 the layer structure, at the measuring point of the sample. The method is particularly suitable for creating a depth profile for the sample without destroying the sample.

[0098] In an optional step 202, a calibration sample may be provided for which the values ​​of the sample structure and chemical composition are known. This may be used to calibrate measurement method parameters, in particular instrument parameters for the measurement.

[0099] In optional step 204 , values ​​for measurement method parameters can be determined with the aid of calibration samples.

[0100] 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 the sample is a positive integer and is related to the sample. The values ​​for the sample parameters can be obtained in different ways. In the embodiment, the values ​​for the sample parameters are obtained by a combination of the following three ways:

[0101] - input by the user of respective values ​​for one or more of said sample parameters;

[0102] - measuring a corresponding value for one or more of said sample parameters using a further measurement method; and

[0103] - reading the corresponding value for one or more of said sample parameters from a sample parameter database having predetermined values ​​for said sample parameters.

[0104] In other embodiments, the value may also be obtained by only one of the above methods or two of the above methods.

[0105] In step 208, a plurality of photoemission spectra recorded at different excitation energies of the measurement point of the sample are obtained. Additionally, photoemission spectra recorded at different emission angles of the measurement point of the sample can also be obtained. The emission angle can, for example, span an interval of 60°. The measurement point can, for example, have an extension range of 100 μm or less, preferably 10 μm or less. The excitation energy can be in the range between 1 keV and 10 keV.

[0106] In step 210, the value of at least one sample parameter at the measurement point of the sample is determined based on the values ​​of the up to n-1 sample parameters and the photoemission spectrum. In order to determine the value of the at least one sample parameter at the measurement point of the sample, the peak area in each photoemission spectrum in the photoemission spectrum and / or the background in each photoemission spectrum in the photoemission spectrum 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 are performed, the value of the at least one sample parameter can be additionally determined based on the measurement method parameters determined with the aid of a calibration sample.

[0107] The invention relates to a photoelectron spectrometer comprising a sample parameter value determination module and a method 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. Values ​​for at least one and up to n-1 sample parameters at the measurement point of the sample are obtained and a plurality of photoemission spectra recorded at different excitation energies for the measurement point of the sample are obtained. The value of the at least one sample parameter at the measurement point of the sample is determined based on the values ​​of the up to n-1 sample parameters and the photoemission spectra.

Claims

1. A method for determining the 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, the method comprising: - obtaining values ​​for at least one and up to n-1 sample parameters of the set of n sample parameters at a measurement point (22) of the sample (20); - obtaining a plurality of photoemission spectra of a measurement point (22) of the sample (20) recorded at different excitation energies; - determining the value of the at least one sample parameter at a measurement point (22) of the sample (20) based on the values ​​of the at most n-1 sample parameters and the photoemission spectrum.

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 the layer structure, at a measuring point (22) of the sample (20).

3. The 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 the peak area in each photoemission spectrum in said photoemission spectrum; - determining the background in each of said photoemission spectra, and comprising one of the following steps: - determining the value of the at least one sample parameter based on the peak area of ​​each photoemission spectrum; - determining the value of the at least one sample parameter based on the background of each photoemission spectrum; and - determining the value of the at least one sample parameter based on the peak area and the background of each photoemission spectrum.

4. The method according to at least one of claims 1 to 3, wherein: Obtaining values ​​for the at least one and up to n-1 sample parameters comprises one or more of the following steps: - input by the user of respective values ​​for one or more of said sample parameters; - measuring a corresponding value for one or more of said sample parameters using a further measurement method; - reading the corresponding value for one or more of said sample parameters from a sample parameter database having predetermined values ​​for said sample parameters.

5. The method according to at least one of claims 1 to 4, wherein: The plurality of photoemission spectra recorded at different excitation energies at the measurement points (22) of the sample (20) include photoemission spectra recorded at different emission angles.

6. The method according to claim 5, wherein: The emission angle spans an interval of 60°.

7. The method according to at least one of claims 1 to 6, wherein: The measuring point (22) of the sample (20) has an extension of 100 μm or less, preferably 10 μm or less.

8. The method according to at least one of claims 1 to 7, wherein: The excitation energy is in the range of 1 keV to 10 keV.

9. The method according to at least one of claims 1 to 8, comprising the steps of: - providing calibration samples for which the values ​​of the sample structure and chemical composition are known; and - Determining the value of a measurement method parameter for determining the value of the at least one sample parameter with the aid of the calibration sample.

10. The method according to claim 9, comprising the steps of: - additionally determining the value of the at least one sample parameter based on the measuring method parameters determined with the aid of the calibration sample.

11. A sample parameter value determination module (50) for determining the 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, wherein: The sample parameter value determination module (50) comprises: - an interface (52) for obtaining the values ​​of at least one and up to n-1 sample parameters of the set of n sample parameters at a measurement point (22) of the sample (20) and for obtaining a plurality of photoemission spectra recorded at different excitation energies at the measurement point (22) of the sample (20); and - a processor (54) for determining a value of said at least one sample parameter at a measurement point (22) of said sample (20) based on the values ​​of said at most n-1 sample parameters and said photoemission spectrum.

12. A photoelectron spectrometer (100), comprising 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 a photoemission measurement without destroying the sample (20) during the photoemission measurement according to claim 11, the photoelectron spectrometer (100) having: - an illumination device (10) for illuminating the sample (20) at the measuring point (22) with radiation (X) of respectively different wavelengths; - detector means (30) for detecting photoelectrons (p) emitted from said sample (20); in, The photoelectron spectrometer (100) is configured to record a plurality of photoemission spectra from a measurement point (22) of a sample (20) at different excitation energies and provide the spectra to the sample parameter value determination module (50); and The sample parameter value determination module (50) is configured to determine the value of at least one sample parameter at a measurement point (22) of the sample (20) based on the maximum n-1 sample parameters in the set of n sample parameters and the photoemission spectrum obtained by the detector device (30).

13. Use of the method according to at least one of claims 1 to 10: - 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 diffusivity of layer boundaries between adjacent layers; and / or - determining the extent of layer boundaries between adjacent layers; and / or - determine the reproducibility of the manufacturing process of the sample; and / or - checking the influence of the value of said at least one sample parameter on the way the sample functions; and / or - compare different samples; and / or - Find a solution to manufacture samples.

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

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

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