Electron energy spectrum device and method

Abstract

A method of determining a chemical composition of a sample using electron spectroscopy is described, the method comprising: ablating material from a region on a surface of the sample by irradiating the region with one or more pulses of laser light; irradiating at least a portion of the area with an excitation beam of electron or electromagnetic radiation; measuring the intensity and energy of electrons emitted from at least a portion of the region of the sample due to the excitation beam; and repeating the steps of ablating the material, irradiating with the excitation beam, and measuring the intensity and energy to determine a quantitative surface depth profile of the chemical composition of at least a portion of the sample. An electron spectroscopy apparatus for determining a chemical composition of a sample is also described.

Description

Technical Field

[0001] The present invention relates to an apparatus and method for electron spectroscopy with depth profiling. In particular, the apparatus and method provide improved compositional accuracy, increased depth profiling speed and greater detection depth. Background Art

[0002] Surfaces and interfaces of materials represent the boundary between a solid and its environment or between two contacting surfaces. Surfaces and interfaces are thus the sites of fundamentally important chemical, physical, electrical and mechanical processes that enable and influence the operation and performance of structures, machines, devices and organisms.

[0003] In engineering applications, important physicochemical processes (such as corrosion, oxidation, wear and adhesion) occur at surfaces and interfaces. Understanding such phenomena allows material scientists and engineers to optimize their benefits and mitigate their harmful effects. Such mitigation measures include surface engineering processes, such as the deposition of protective coatings or enhancing the mechanical properties of the surface by hardening or toughening processes. On the other hand, stronger adhesives have been developed by optimizing their chemical formulations, enabling a stronger bond to be formed between the adhesive and the material surface.

[0004] Surfaces and interfaces are crucial for the operation of functional devices. The performance of optoelectronic and electrochemical devices, sensors, actuators, etc. depends on the properties of the host material and the efficiency of surface / interface chemical and electrical processes. In order to achieve the desired multifunctional properties of the device, multilayer structures of different materials are usually fabricated, where the thickness of the layers can vary from many micrometers to a single atomic layer.

[0005] Accurate and reliable chemical analysis of solids in bulk, at their surfaces, and at their interfaces with other solids is key to understanding the fabrication and properties of technologically important materials and devices, the development of new multifunctional materials, and understanding material failure.

[0006] Two of the most widely used and highly developed methods for surface chemical analysis are the electron spectroscopy techniques, namely X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). XPS is a photoemission spectroscopy method in which electronic core level and valence band spectra from atoms in a solid are obtained by irradiating the material with an X-ray beam. Chemical state information is extracted from the spectrum in the form of shifts in the electron binding energies of the electrons due to changes in the local chemical environment. AES is similar to XPS, but is based on the analysis of Auger electrons emitted as part of the relaxation process following excitation of the core levels. For AES, the excitation occurs by incident radiation as an X-ray or electron beam.

[0007] Both XPS and AES can provide quantitative surface chemical composition, with a sensitivity of 0.1at.% to 1at.% for all elements except hydrogen and helium, and a depth of about 5nm. Both methods also provide information about the chemical state of the elements, but for most elements, XPS is superior to AES in this respect.

[0008] Often it is important to determine the chemical composition at depths greater than the depth of the XPS / AES analysis. For example, the chemical composition of a sub-micron multilayer filter or a 1μm to 5μm multi-process surface treatment is examined for conservation purposes. To achieve this, material must be removed from the surface and the XPS / AES analysis repeated at the new surface revealed by the material removal. This cycle of material removal and XPS / AES analysis continues until the chemical composition at the depth of interest has been recorded. The elemental composition at each level is calculated and plotted as a function of the number of cycles, called a depth profile. If the depth is measured, assuming the material removal rate is constant, a depth profile can be plotted based on the chemical composition as a function of the actual depth. For example, if the depth is measured, the material removal rate is constant. Figure 1A As shown, thin films with a thickness of 50 nm to 500 nm can be analyzed using existing XPS depth profiling techniques. Thicker films up to about 5 μm can also be analyzed, but this would take many hours to perform using conventional techniques.

[0009] In the XPS / AES depth profiling process, material removal is usually achieved using ion beam bombardment from an ion gun mounted in the spectrometer. The ion beam is aligned with an X-ray spot (for XPS) or electron beam (for AES) on the sample surface, allowing a cyclic depth profiling process to be performed. The ion gun accelerates the ions to high energies that, after impacting the surface, have enough energy to remove surface atoms in a process called sputtering. Figure 1B Schematic diagram of a conventional XPS apparatus with an ion beam. The apparatus comprises a vacuum chamber, such as a UHV chamber 10, into which a sample 20 for analysis is inserted. An X-ray source 30 is provided, which directs the X-ray beam to a target area on the surface of the sample. The surface material emits electrons, which are collected by a detector 50 and the electron energy is measured by an electron analyzer 40. The apparatus also comprises an ion gun 60. The ion gun can generate a beam of monatomic ions or (polyatomic) cluster ions, which are directed to the sample surface to remove a layer from the surface by sputtering. Argon is typically used to generate ions, but other ion sources may also be used.

[0010] AES and XPS commercial spectrometers have been available as scientific tools since around 1970. To date, sputtering has been used as the only practical method for generating XPS / AES depth profiles. However, despite the fact that sputtering depth profiling has been used for 50 years and is the only current method for generating XPS / AES depth profiles, sputtering depth profiling has the following problems:

[0011] (i) Sample damage and preferential sputtering

[0012] Many materials are ion beam sensitive. This means that the sputtering process damages the underlying surface, resulting in changes in the chemical composition recorded by XPS / AES across the depth profile. In chemical compounds, this can take the form of sputtering one element more than others, known as preferential sputtering, and this is particularly observed for inorganic materials. For polymeric materials, in addition to preferentially sputtering elements such as oxygen from polymers, the ion beam also damages the molecular structure. Therefore, for ion beam sensitive materials, the ability of XPS / AES to provide accurate quantitative composition information may be compromised, and incorrect chemical composition may be recorded throughout the XPS / AES sputtering depth profile. In addition, the extent of preferential sputtering varies depending on the ion beam conditions and material composition. For any new material or ion beam condition, the extent of preferential sputtering cannot be reliably predicted. Therefore, when performing depth profiling on potential ion beam sensitive materials, the analyst cannot know whether preferential sputtering is changing the apparent composition of the collected depth profile. For technologies that are considered to be able to provide accurate chemical composition, incorrect composition recorded during depth profile measurements and the inability to know whether this occurs in the material being studied are significant problems.

[0013] The above-mentioned argon cluster ion beam or gas cluster ion beam (GCIB) enables drastically reduced damage to most hot polymers during depth profiling. GCIB has also been shown to reduce but not eliminate preferential sputtering in metal oxides. However, this also leads to new problems arising from the thermal spikes associated with GCIB strikes.

[0014] (ii) Low material removal rate

[0015] Another problem with sputtering is that the sputtering rate for many materials, especially inorganic materials, is relatively low. The sputtering rate can be improved by using higher ion beam energy and current, but the increased energy generally introduces more surface damage. Sputtering rates of tens to hundreds of nanometers per hour are achieved using ion beam energies of 0.5 keV to 3 keV and typical currents delivered by ion guns used on modern XPS / AES instruments. For analysis of materials that require removal of greater than 1 micron to 2 microns, XPS / AES depth profiling is typically performed overnight given the total time for sputtering and analysis of thick layers that require a lot of material removal or multilayer structures that require multiple cycles of sputtering and measurement. XPS / AES depth profiling by ion beam induced sputtering to a depth of more than about 5 microns is generally considered impractical. Therefore, it is desirable to seek a solution to the problem of performing XPS / AES depth profiling through thicker layers. For example, for analyzing Figure 1A The host material, interlayer or buried interface shown in .

[0016] The paper by Graham et al., "Integrated experimental setup for angle resolved photoemission spectroscopy of transuranic materials," Review of Scientific Instruments, 84, 093902, September 2013, describes work on developing angle resolved photoemission spectroscopy (ARPES) for transuranic materials. A technical report by Joyce et al., "Combining X-Ray Photoelectron Spectroscopy with Laser Ablation for Nuclear Forensics of Pu and U" (Report No. LA-UR-14-23989) from Los Alamos National Laboratory describes methods for cleaning oxides from Pu- and U-based materials and analyzing Pu- and U-based materials. Summary of the invention

[0017] The present invention is directed to solving problems associated with (a) incorrect chemical composition of determined materials and / or (b) limited material removal rates during XPS / AES depth profiling. The present invention is particularly advantageous in being able to provide improved accuracy of chemical composition and chemical state information during depth profiling of polymers, metal oxides, other inorganics, semiconductors, alloys and other materials. The ability to access increased depths for analysis allows access to subsurface regions of different chemical compositions, buried interfaces and subsurface discrete layers compared to ion beam depth profiling.

[0018] The present invention is achieved by using laser pulses for material ablation in combination with electron spectroscopy techniques such as XPS and AES.

[0019] The present invention provides a method for determining the chemical composition of a sample using electron spectroscopy, the method comprising: ablating material from an area on the surface of the sample by irradiating the area with one or more laser pulses; irradiating at least a portion of the area with an excitation beam of electrons or electromagnetic radiation; measuring the intensity and energy of electrons emitted from at least a portion of the area of ​​the sample due to the excitation beam; and repeating the steps of ablating material, irradiating with an excitation beam, and measuring the intensity and energy to determine a quantitative surface depth profile, producing a chemical composition of at least a portion of the sample. In a preferred embodiment, the method further comprises irradiating at least a portion of the unablated area with an excitation beam of electrons or electromagnetic radiation, and measuring the intensity and energy of electrons emitted from at least a portion of the unablated area of ​​the sample due to the excitation beam, before ablating material from the area for the first time.

[0020] The method may also include determining the elemental composition of at least a portion of the ablated region based on the intensity and energy of the emitted electrons, and optionally determining the chemical state of the elements based on the energy of the emitted electrons. The method may also include determining the depth or relative depth of one or more ablated regions, for example relative to an unablated surface adjacent to the ablated region or relative to the sample surface before ablation. In order to determine the depth or relative depth of one or more ablated regions, the method may also include determining the ablation rate per pulse for the material present in the surface depth profile. Additionally, the method may also include converting the number of pulses into depth. Alternatively, the depth may be determined independently, for example by measuring the final pit depth using a profilometer type method, microscopy, white light interferometry, or other method.

[0021] One or more pulses of the laser beam may be femtosecond pulses.

[0022] The method may further include repeating the steps of ablating material, irradiating with the excitation beam, and measuring the intensity and energy of the emitted electrons to determine a depth profile, for example down to greater than 5 μm, greater than 10 μm, greater than 100 μm, or greater than 200 μm.

[0023] Each step of ablating material may include removing a layer from about one nanometer to several hundred nanometers or even from about one atomic layer, such as 0.3 nm to 10 μm (e.g., 0.3 nm to 1000 nm or 1 nm to 10 μm, 1 nm to 1000 nm or 10 nm to 500 nm).

[0024] The excitation beam may be an X-ray beam, and the energy spectrum may be XPS or AES. Alternatively, the excitation beam may be an electron beam, and the energy spectrum may be AES.

[0025] The method may also include tilting the sample relative to the ablation laser beam. Tilting the sample relative to the laser beam can reduce the roughness of the bottom of the pit and / or enable a deeper depth profile. The method may include rotating or partially rotating the sample between ablation layers or steps (e.g., rotating less than 90°, such as between 15° and 85°, or between 25° and 75°, or between 35° and 75°, or between 45° and 65°, or between 50° and 60°, for example rotating 45°, 55° or 65°). Compared with simple laser ablation, this again can reduce the roughness of the bottom of the pit and / or enable a deeper depth profile and greater measurement depth resolution. The method may include incremental rotation of the sample surface between ablation layers or steps or laser pulses, or may include continuously rotating the sample surface during the method. Sample surface rotation (which is a rotational motion in the plane of the surface) has the effect of changing or randomizing the laser direction relative to the surface in multiple ablation steps. Otherwise, if there are multiple laser pulses using the same direction on the surface, undesirable laser induced periodic surface structures (LIPSS) may be established. In this way, the sample surface rotation should preferably avoid rotation steps that are multiples of 90 degrees (e.g., 90 degrees or 180 degrees), and this is why, for example, a rotation of 55 degrees works well over many pulses. The laser beam can be a linearly polarized laser beam. The method may include rotating the angle of the linearly polarized laser beam incrementally or continuously during ablation or between ablation steps. In other words, the orientation of the polarization plane of the laser beam can be rotated during ablation or between ablation steps or laser pulses, for example, incrementally or continuously. As with the sample surface rotation, the rotation of the polarization of the laser beam has the effect of changing or randomizing the laser direction relative to the surface in multiple ablation steps. Similarly, in order to avoid potential undesirable LIPSS, the laser polarization rotation should preferably avoid rotation steps that are multiples of 90 degrees (e.g., 90 degrees or 180 degrees), and this is why, for example, a rotation of 55 degrees works well over many pulses. The method may include rotating the laser polarization by less than 90° between ablation layers or steps, such as between 15° and 85°, or between 25° and 75°, or between 35° and 75°, or between 45° and 65°, or between 50° and 60°, for example by 45°, 55° or 65°. Alternatively, the method may include converting a linearly polarized beam into a beam having circular polarization or elliptically polarized. The use of a laser beam having circular polarization or elliptically polarized may optionally be used together with rotation and / or polarization of the sample.

[0026] Thus, embodiments of the method may include (i) rotating the sample in the plane of the sample's surface between ablation steps and / or between laser pulses, and / or (ii) rotating the polarization plane of the laser pulses between ablation steps and / or between laser pulses, or (iii) converting the polarization of the laser pulses to circular polarization or elliptical polarization. Sample rotation, polarization rotation, and / or polarization conversion may reduce pit bottom roughness and / or enable deeper depth profiles to be achieved.

[0027] The one or more pulses may ablate the material by Coulomb explosion and / or thermal processes. The method may include adjusting one or more of the pulse energy, pulse length and other parameters, and depending on the material, to produce the most appropriate ablation process for analytical purposes.

[0028] The step of determining the chemical composition may include determining the concentration of the chemical elements. The concentration of the chemical elements may be expressed as atomic percent (at.%) or stoichiometric, or in another manner. The chemical concentration of the elements may be quantitatively determined based on the relative measured intensities. The chemical elements and the chemical states of the elements may be determined based on the measured energies.

[0029] The step of ablating the material may form a pit in the surface of the sample, and at least a portion of the area irradiated with the excitation beam of X-rays / electrons may include an area at the bottom of the pit.

[0030] The pit preferably has a substantially flat bottom, and the excitation beam preferably illuminates at least a portion of the substantially flat bottom. The excitation beam preferably illuminates at least a portion of the substantially flat bottom, and preferably does not illuminate the edges or sidewalls of the pit. The ratio of the pit width (across the pit bottom) to the excitation beam spot size may be at least 3:1, or at least 4:1, or at least 5:1. A ratio of at least 5:1 is preferred.

[0031] The width of the substantially flat bottom of the pit may be greater than the width of the excitation beam. The width of the excitation beam may be determined as the full width at half maximum (FWHM) of the beam intensity, 1 / e 2 The diameter or other measure of the width of the beam that contains most of the energy of the beam.

[0032] The step of ablating material from the region of the sample may include moving the relative position of the laser pulses to scan the pulses over the region on the surface of the sample to ablate pits in the surface.

[0033] The relative position of the laser pulses may be moved by scanning the laser or by scanning the position of the sample. Scanning may include irradiating the sample with one or more pulses at a plurality of partially overlapping pixel positions.

[0034] The method may include passing the laser pulse through an optical device that converts a typical Gaussian intensity laser pulse into a substantially flat-top or top-hat intensity profile across its diameter incident on the sample surface. The laser pulse may produce a pit having a width corresponding to the width of the flat-top or top-hat intensity profile. The beam shaping element may include a diffractive optical element. Alternatively, the beam shaping element may be a refractive optical element or other optical element.

[0035] Combinations of scanning and flat or top-hat beam profiles may also be used.

[0036] The laser pulses may each have a duration of less than 1 nanosecond (ns), less than 1 picosecond (ps), less than 500 femtoseconds (fs), less than 100 fs, less than 10 fs, or less than 1 fs. As an example of a range, the laser pulse may have a duration in the range of 1 fs to 1 ns, or 1 fs to 1 ps, or 1 fs to 500 fs, or 1 fs to 200 fs, or 1 fs to 100 fs. The lower limit of the range may be lower than 1 fs, such as, for example, 0.1 fs.

[0037] The laser pulse energy in one or more repetitions (pulses), preferably one pulse, should be sufficient to ablate the material. In some embodiments, the energy of each laser pulse may be in the range of 10 nJ to 1000 μJ, or 1 μJ to 1000 μJ, or 10 μJ to 1000 μJ, such as between 50 μJ and 500 μJ. Alternatively, the repetition may be a pulse train or a pulse sequence, wherein the train or sequence has these energies.

[0038] The diameter of the laser pulses on the sample surface may be in the range of 1 μm to 1000 μm, such as 10 μm to 300 μm, or 50 μm to 150 μm.

[0039] The method may also include: setting or adjusting, by a controller, one or more parameters of a pulse of the laser based on composition information about the sample; and performing the step of ablating the material, wherein the parameters of the laser pulse are set or adjusted by the controller. The controller may be a computing device having a memory and a processor.

[0040] The one or more parameters of the laser pulses that may be set or adjusted by the controller include one or more of: pulse duration, pulse energy, repetition rate, wavelength, and spot size.

[0041] The setting or adjusting step may also include: receiving input from a user indicating compositional information about the sample; and the controller adjusting one or more laser parameters based on the compositional information.

[0042] The method may also include performing a survey scan or a survey profiling to determine an approximate measure of elemental composition in the sample; and generating one or more parameters of the laser pulses based on the approximate measure.

[0043] The method may also include performing mechanical profilometry or microscopy (eg, atomic force microscopy) or white light interferometry (WLI) on the sample surface; and generating or adjusting one or more parameters of the laser pulses based on the profilometry, microscopy, or interferometry.

[0044] The controller may use a reference database or an algorithm to determine laser parameters based on information about the sample.

[0045] The method may include, after the steps of ablating material, irradiating with an excitation beam, and measuring electron intensity and energy, adjusting one or more parameters of the laser based on measured or predicted compositional information about the sample at a depth after ablation, and repeating the steps of ablating material, irradiating with an excitation beam, and measuring electron intensity and energy using the adjusted one or more parameters of the laser.

[0046] The method may further include repeating the steps of adjusting, ablating material, irradiating with the excitation beam, and measuring electron intensity and energy until the sample has been analyzed to a target depth.

[0047] The method may include placing the sample on a sample stage in a vacuum chamber and then performing the steps of ablating the material, irradiating with an excitation beam, and measuring the intensity and energy of the emitted electrons. Between the ablation step and the irradiation with an excitation beam, the sample may not be moved by an amount greater than the laser spot or scan size.

[0048] The laser pulse and the excitation beam may overlap spatially at the sample surface. In this context, the term overlap does not mean that the laser pulse and the excitation beam must have exactly the same spatial extent and position at the sample surface, but that there is at least an overlap. Preferably, the excitation beam spot size is smaller than the laser pulse spot size. The excitation pulse may be centered on the laser pulse.

[0049] The ablating step may include raster scanning ablative laser pulses relative to the sample surface, and wherein the excitation beam coincides with at least a portion of the sample surface area that is ablated.

[0050] The present invention provides further methods which will now be described. These methods may be combined in any combination.

[0051] A method of electron spectroscopy, the method comprising: ablating material from a surface of a sample by irradiating the region with one or more pulses of laser light, wherein the ablation forms a pit in the surface of the sample; irradiating at least a portion of the ablated region at the bottom of the pit with an excitation beam of electrons or electromagnetic radiation (such as X-rays); measuring the intensity and energy of electrons emitted from at least a portion of the region of the sample due to the excitation beam; and determining the chemical composition of the surface of the pit based on the measured intensity and energy of the emitted electrons. The ablation step can be repeated to form a pit of greater depth.

[0052] A method of electron spectroscopy, the method comprising: ablating material from a surface of a sample by irradiating the region with one or more pulses of a laser, wherein the laser pulse has a duration of less than 1 ns, less than 1 ps, less than 500 fs, less than 100 fs, less than 10 fs, or less than 1 fs; irradiating at least a portion of the ablated region with an excitation beam of electrons or electromagnetic radiation (such as X-rays). The method may also include: measuring the intensity and energy of electrons emitted from at least a portion of the region of the sample due to the excitation beam; and determining the chemical composition of the surface based on the measured intensity and energy of the emitted electrons.

[0053] A method of electron energy spectroscopy, the method comprising: setting one or more parameters of a pulse of a laser by a controller based on compositional information about a sample; ablating material from a region on the surface of the sample by irradiating the region with one or more pulses of the laser, wherein the parameters of the pulses have been set by the controller; irradiating at least a portion of the region with an excitation beam of electrons or electromagnetic radiation (such as X-rays); measuring the intensity and energy of electrons emitted from at least a portion of the region of the sample due to the excitation beam; and determining the chemical composition of the surface based on the measured intensity and energy of the emitted electrons.

[0054] A method of electron energy spectroscopy, the method comprising: placing a sample on a sample stage in a vacuum chamber; ablating material from the area on the surface of the sample by irradiating the area with one or more pulses of laser light; irradiating at least a portion of the area with an excitation beam of electrons or electromagnetic radiation (such as X-rays); measuring the intensity and energy of electrons emitted from at least a portion of the area of ​​the sample due to the excitation beam; determining the chemical composition of the surface based on the measured intensity and energy of the emitted electrons; wherein, between the ablation step and the irradiation step with the excitation beam, the sample is not moved by an amount greater than the size of the laser spot or scanning area.

[0055] A method of electron spectroscopy, the method comprising: placing a sample on a sample stage in a vacuum chamber; ablating material from a surface of the sample by irradiating the area with one or more pulses of a laser, the laser being configured to direct the pulses at the sample surface; irradiating at least a portion of the area with an excitation beam of electrons or electromagnetic radiation (such as X-rays); measuring the intensity and energy of electrons emitted from at least a portion of the area of ​​the sample due to the excitation beam; determining the chemical composition of the surface based on the measured intensity and energy of the emitted electrons; wherein the laser pulses and the excitation beam spatially coincide at the sample surface.

[0056] The present invention provides an electron energy spectroscopy device for determining the chemical composition of a sample, the device comprising: a vacuum chamber; a sample stage installed in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed; a laser being configured to generate laser pulses and guide the laser pulses to a target area of ​​the sample to ablate the surface of the sample; an excitation beam source being configured to generate an excitation beam of electrons or electromagnetic radiation and guide the excitation beam to the target area of ​​the sample; and an electron detector and analyzer being configured to measure the intensity and energy of electrons emitted from the sample surface in response to the excitation beam and determine a quantitative surface depth profile of the chemical composition of the sample.

[0057] The electronic analyzer and detector can also be configured to determine the elemental composition of the target area according to the intensity and energy of the emitted electrons, and optionally determine the chemical state of the elements in the elemental composition according to the intensity and energy of the emitted electrons. The electronic analyzer can include an analyzer of an electrostatic ring capacitor type, such as an electrostatic concentric hemispherical analyzer. Other types of electronic analyzers can be used, such as a cylindrical mirror analyzer. One or more electron multipliers can be used to detect electrons. The electron multiplier can include a single channel multiplier, or a channel multiplier array, or a microchannel plate. The detector (also referred to as an electronic counter) can include one or more channel electron multipliers (Channeltron) detectors. Alternatively, a channel plate multiplier used in combination with a position sensitive element (such as a delay line detector (DLD) or a resistor divider) can be used to simultaneously detect the number of electrons and the landing position of each electron.

[0058] The laser is preferably configured to generate nanosecond or picosecond or more preferably femtosecond pulses.

[0059] The excitation beam source may be configured to generate an X-ray beam or an electron beam.

[0060] The excitation beam source can be configured to generate an X-ray beam, and the electron detector and analyzer are configured to measure photoelectrons and Auger electrons. Alternatively, the excitation beam source is configured to generate an electron beam, and the electron analyzer is configured to measure Auger electrons. If the excitation beam is an X-ray beam, the electrons are photoelectrons and the energy spectrum is XPS. If the excitation beam is an electron beam, the electrons are Auger electrons and the energy spectrum is AES.

[0061] The sample stage may be configured to be tilted relative to the ablation laser beam.

[0062] The sample stage may include a positioning device to move the sample in orthogonal directions in the plane of the sample, for example, to raster scan the sample relative to the incident position of the ablating laser pulses.

[0063] The laser may include a mirror to adjust the incident position of the laser pulse on the sample, thereby raster scanning the laser pulse across the sample.

[0064] The laser may include a beam shaping element to convert the laser pulse to have a substantially flat or top-hat intensity profile across its diameter at which it is incident on the sample surface.

[0065] The laser beam shaping element may be configured to convert the laser pulse to have a substantially flat or top-hat intensity profile across its diameter incident on the sample surface.The diameter at the surface of the sample is preferably larger than the diameter of the excitation beam at the surface of the sample.

[0066] The beam shaping element may include a diffractive optical element, a refractive optical element, or other optical elements.

[0067] The laser may be configured to generate pulses, each pulse having a duration of less than 1 ns, less than 1 ps, less than 500 fs, less than 100 fs, less than 10 fs, or less than 1 fs.

[0068] The laser is configured to generate pulses having an energy per pulse in the range of 10 nJ to 1000 μJ or 1 μJ to 100 μJ or 10 μJ to 1000 μJ, such as between 50 μJ and 500 μJ.

[0069] The laser may be configured to generate pulses having a spot size at the sample surface in the range of 1 μm to 1000 μm, such as 10 μm to 300 μm, or 50 μm to 150 μm.

[0070] The controller may be configured to adjust one or more parameters of the pulses of the laser based on compositional information about the sample.

[0071] The one or more parameters of the laser pulses set by the controller may include one or more of: pulse duration, pulse energy, repetition rate, wavelength, and spot size.

[0072] The controller may be configured to: receive input from a user indicating compositional information about the sample; and adjust one or more laser parameters based on the compositional information.

[0073] The controller may be configured to reference a reference database or algorithm to determine laser parameters based on information about the sample.

[0074] The laser and excitation beam sources may be configured to direct the laser pulses and the excitation beam, respectively, to spatially coincide at the sample surface.

[0075] The invention provides further means which will now be described. These means may be combined in any combination.

[0076] An electron energy spectrometer apparatus comprises: a vacuum chamber; a sample stage installed in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed; a laser being configured to generate laser pulses and direct the laser pulses to a target area of ​​the sample to ablate the surface of the sample, wherein the laser is configured to ablate material to form pits in the surface of the sample; an excitation beam source being configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to the target area of ​​the sample; and an electronic analyzer and a detector being configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a surface depth profile of the chemical composition of the sample.

[0077] An electron energy spectrometer apparatus comprises: a vacuum chamber; a sample stage installed in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed; a laser configured to generate laser pulses and direct the laser pulses to a target area of ​​the sample to ablate the surface of the sample, wherein the laser is configured to generate pulses having a duration of less than 1ns, less than 1ps, less than 500fs, less than 100fs, less than 10fs, or less than 1fs; an excitation beam source configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to a target area of ​​the sample; and an electronic analyzer and a detector configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a surface depth profile of the chemical composition of the sample.

[0078] An electron energy spectrometer apparatus comprises: a vacuum chamber; a sample stage installed in the vacuum chamber and configured to receive a sample to be analyzed; a laser configured to generate laser pulses and direct the laser pulses to a target area of ​​the sample to ablate the surface of the sample; a controller configured to adjust or set one or more parameters of the laser pulses based on information about the sample; an excitation beam source configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to a target area of ​​the sample; and an electronic analyzer and a detector configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a surface depth profile of the chemical composition of the sample.

[0079] An electron energy spectrometer apparatus comprises: a vacuum chamber; a sample stage installed in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed; a laser being configured to generate laser pulses and direct the laser pulses to a target area of ​​the sample to ablate the surface of the sample; an excitation beam source being configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to the target area of ​​the sample; and an electronic analyzer and a detector being configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a surface depth profile of the chemical composition of the sample, wherein the sample stage is configured for a maximum movement amount corresponding to the size of the sample.

[0080] An electron energy spectrometer apparatus comprises: a vacuum chamber; a sample stage installed in the vacuum chamber and configured to receive a sample to be analyzed; a laser configured to generate laser pulses and guide the laser pulses to a target area of ​​the sample to ablate the surface of the sample; an excitation beam source configured to generate an excitation beam of electrons or electromagnetic radiation and guide the excitation beam to the target area of ​​the sample; and an electronic analyzer and a detector configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a surface depth profile of the chemical composition of the sample, wherein the laser and the excitation beam source are respectively configured to guide the laser pulses and the excitation beam to spatially coincide at the sample surface.

[0081] In each of the above methods and apparatuses, the excitation beam may be an electron beam or an electromagnetic radiation beam, such as X-rays. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Embodiments of the present invention and aspects of the prior art will now be described with reference to the accompanying drawings, in which:

[0083] Figure 1Ais a schematic diagram showing the analytical depth that can be achieved using conventional XPS;

[0084] Figure 1B is a schematic diagram of an XPS apparatus having an ion source for sputtering away a material layer;

[0085] Figure 2 is a schematic diagram of an XPS apparatus with an ablation laser according to the present invention;

[0086] Figure 3A is a schematic diagram of an optical setup for an ablation laser according to the present invention;

[0087] Figure 3B is a schematic diagram showing sample surface rotation and / or laser polarization rotation or translation during an ablation step;

[0088] Figure 4A is a process flow diagram of steps for performing an electron spectroscopy method for generating composition depth profiles using laser ablation;

[0089] Figure 4B Shown are the different depth resolutions achieved when depth profiling through a nickel / chromium multilayer structure with the laser polarization rotated between pulses (left) and not (right);

[0090] Figure 5A and Figure 5B are peak-fitted XPS spectra showing the background signal of the Ag 3d XPS spectrum and the C1s XPS spectrum showing the various peaks of carbon in different chemical states, respectively;

[0091] Figure 6 a and Figure 6 b shows an example of a quantitative laser ablation XPS depth profile plotted as a function of ablation level and depth, respectively;

[0092] Figure 7 a is a schematic diagram of the beam scanning method of laser ablation, and Figure 7 b is a schematic cross-sectional view through the ablated region with the excitation beam incident thereon;

[0093] Figure 8 is a schematic representation of Gaussian beam overlap that enables uniform intensity across pixels used for ablation;

[0094] Fig. 9 is a schematic representation of an optical arrangement for generating a top-hat or flat-top beam intensity profile;

[0095] Fig.10 is a graph of the top-hat intensity profile of a laser pulse, showing the intensity in plan and cross-sectional views;

[0096] Fig.11 It is shown that according to Fig.10 a graph of a mechanical profilometry trace over a pit in a sample surface formed by a raster scan pulse of

[0097] 12a-12c are chemical composition depth profiles of TiO2 samples obtained using laser ablation, conventional sputtering, and cluster ion beam sputtering, and FIGS. 12d-12f are corresponding photoelectron spectroscopy spectra;

[0098] Fig.13 a and Fig.13 b is the surface depth profile of InP obtained using laser ablation and sputtering, respectively;

[0099] Fig.14 a to Fig.14 c relates to the surface depth profile of the iron oxide layer on iron obtained using laser ablation, where Fig.14 a shows the Fig.14 b and Fig.14 Three different stratified regions in the surface profile of c (Fe 2+ / 3+ , Fe 2+ and Fe 0 )’s XPS spectrum; and

[0100] Fig.15 a is the surface depth profile of PET on steel obtained using laser ablation, and Fig.15 b and Fig.15 c shows the corresponding XPS spectrum from the PET layer. DETAILED DESCRIPTION

[0101] Figure 2 is a schematic diagram of an X-ray photoelectron spectroscopy (XPS) apparatus 100 according to an embodiment of the present invention. The apparatus includes a vacuum chamber 110, which may be similar to Figure 1B The apparatus further comprises a sample stage on which a sample 120 may be received. An X-ray source 130 is provided for generating an excitation beam of X-rays. Alternatively, for Auger electron spectroscopy (AES), an electron source may be provided for generating an excitation beam of electrons. An electron analyzer 140 is provided for analyzing the photoelectrons and Auger electrons generated by the incidence of the excitation beam on the sample surface before the detector 150 detects the photoelectrons and Auger electrons. A laser 160, such as a femtosecond laser, is provided for irradiating the sample surface to ablate the sample surface so that XPS or AES may be performed at a certain depth. The laser replaces Figure 1B The device may also include a controller 180, for example, for controlling the parameters of the laser. Figure 2As shown, the sample stage receives a sample 120 in a vacuum chamber 110. The sample stage 120 may be a movable sample stage that includes a positioning mechanism to adjust the position of the sample in two orthogonal directions in the sample plane (e.g., the x-direction and the y-direction). The positioning mechanism may also have a z-direction (height) adjustment. The sample stage may also include a positioning mechanism for in-plane rotational motion (such as rotation in the xy plane). The in-plane rotational motion is further shown in Figure 3B The sample stage may further include a tilting mechanism for tilting the sample relative to the ablation laser beam.

[0102] The electron analyzer 140 may include an electrostatic toroidal capacitor type analyzer, such as an electrostatic concentric hemispherical analyzer. Other types of electron analyzers may be used, such as a cylindrical mirror analyzer. The electron analyzer measures the energy of the emitted electrons.

[0103] The detector 150 (also referred to as an electron counter) may include one or more channel electron multiplier (Channeltron) detectors. Alternatively, a channel plate multiplier used in conjunction with a position sensitive element (such as a delay line detector (DLD) or a resistor divider) may be used to simultaneously detect the number of electrons and the landing position of each electron. The detector measures the intensity of the emitted electrons.

[0104] The X-ray source or electron source 130 is configured to generate electrons or X-rays and direct them to the sample surface. The X-rays may be monochromatic X-rays and may be generated from a high energy electron gun arranged to accelerate electrons toward a target anode. The target anode may be aluminum so that the generated X-rays are generated with appropriate energy. The X-rays may be directed to the chamber via a monochromator crystal and focused toward the sample surface. The X-rays pass through an opening or hole to pass to the sample surface. Upon incident on the sample surface, the X-rays cause the emission of photoelectrons or Auger electrons.

[0105] The apparatus may also include an immersion electron gun 131 to provide charge neutralization at the sample surface during analysis, since the emission of electrons may result in the accumulation of positive charge on the sample. This is most serious in the case where the sample surface is insulating, since the charge accumulation remains at the surface and is not dissipated by charge transport through the sample. Positive charge may affect the XPS spectrum by causing the peak to shift to higher binding energies and become distorted. The immersion electron gun may be of any suitable type, such as the type disclosed in GB2411763 A. The immersion electron gun neutralizes the charge on the sample surface by replenishing the emitted electrons. The neutralization action stabilizes and controls the charging of the sample surface.

[0106] The apparatus may also include one or more cameras 132, 133. These may be mounted outside the vacuum chamber and configured to provide an image of the sample stage. The cameras may be mounted to collect images of the sample on the sample stage through an optical window in the vacuum chamber. Figure 2 Two cameras are shown in FIG. 1 . A lamp 134 is shown illuminating the sample from above, for example in the same direction that the electrons are ejected from the sample. The light from the lamp 134 may be directed to the sample via a pair of mirrors 135, 136. Mirror 136 may be a toroidal mirror arranged so that the electrons emitted from the sample pass through a central hole in the mirror. This pair of mirrors provides a periscope arrangement that allows the lamp to be conveniently positioned. Camera 132 is arranged to observe the sample from above using toroidal mirror 136. Mirror 135 is a one-way or half-silvered mirror that reflects the light from the lamp toward the sample but allows at least some of the light from the sample to be incident on camera 132. Camera 132 has the advantage that by observing the sample from directly above, a good view of the surface of the emitted electrons is provided. A second camera 133 may observe the sample more directly but at a more acute angle and may therefore not provide such a good view of the surface, but no image is lost compared to camera 132 observing via toroidal mirror 136. An auxiliary lamp 137 may be provided. Although not apparent from the schematic, the auxiliary light 137 may illuminate the sample from a direction similar to that from which the camera 133 views the sample. The laser 160 may also be mounted outside the vacuum chamber, and the ablation pulses directed through a window into the vacuum chamber to reach the sample 120. Figure 3A 1 shows more details of an embodiment of the laser 160. The laser may include a femtosecond (fs) laser source 210. In other embodiments, the laser may be a picosecond laser or a nanosecond laser. The fs laser source 210 may be based on a diode-pumped Yb medium that can provide a range of pulse lengths, pulse wavelengths, and pulse energies. Figure 3A As shown, the pulses output from the laser source pass through a series of optical components that tune the pulses and direct them to the target area on the sample surface. The role of the beam expander 215 is to appropriately adjust the size of the beam and collimate the beam for the flat top shaper 220, which converts the Gaussian beam into a beam with a flat top intensity profile. Mirror 225 guides the beam or pulses toward the variable attenuator 230 and polarization adjustment optical device 235. If necessary, the variable attenuator 230 can be used to reduce the beam power / energy. The polarization adjustment optical device 235 can include a zero-order half-wave plate or a zero-order quarter-wave plate and can be rotatable. In this way, the polarization of the laser beam can be rotated (for linearly polarized lasers) or converted to circular polarization or elliptical polarization, both of which are Figure 3BAs shown in . In some embodiments, more than one of the above wave plates in series may be used, and / or wave plates operating at different (non-zero) orders may be used. Other birefringent materials may be used, for example in the form of prisms. In general, control of the polarization state of the incident laser provides a method for suppressing the formation of laser-induced periodic surface structures (LIPSS). In practice, there are different ways in which such polarization control can be achieved, wherein the key requirement is to control the phase difference between the orthogonal polarization components of the incident laser beam at its operating wavelength. In this way, the polarization of the laser beam can be rotated (for linearly polarized lasers) or converted into circular or elliptical polarization. This can be achieved by using a single or multiple zero-order or multi-order wave plates or by using other types of single-layer or multi-layer birefringent optical materials, waveguides and components. The second beam expander 240 may be placed before the mirror 245 to adjust the spot size of the beam at the focus. Although the laser is described in terms of the beam, since the continuous wave beam is not generated by a femtosecond laser source, it is generally referred to as a pulse or a pulse train. Mirror 245 guides the pulse through focusing lens 250, which focuses the pulse to the desired spot size on the sample surface. The pulse passes through window 255 (such as a glass window) into the vacuum chamber of the XPS or AES spectrometer so that the pulse is incident on the target area of ​​the surface of the sample 260. Controller 280 can control fs laser source 210, variable attenuator 230 and polarization adjustment optical device 235 to set laser parameters as needed. As needed, the controller can also control one or two beam expanders in beam expander 215 and beam expander 240. Embodiments of laser optical devices can achieve smooth, flat-bottomed pits and thus achieve good profiling performance. Due to the laser-induced periodic surface structure (LIPSS) that may develop on the surface during profiling, the change in the linear polarization direction achieved by using polarization adjustment optical devices between pulses can minimize possible ripple morphology. The method may include rotating the angle of the linearly polarized laser beam incrementally or continuously during ablation or between ablation shots. Alternatively, the method may include converting a linearly polarized beam into a beam having circular polarization or elliptical polarization. Sample rotation, polarization rotation, and / or polarization conversion may reduce pit bottom roughness and / or enable deeper depth profiles.

[0107] In some embodiments, the femtosecond laser has a wavelength of 1030nm and a pulse length of 160fs. Alternatively, the laser wavelength can be 515nm. Shorter or longer pulses can also be used, such as in the range of 10fs to 10ps, or 10fs to 1ps, or even in the range of less than 1fs and 1ns. The spot size of the laser pulse at the sample surface can vary. In some embodiments, the spot size is in the range of about 50μm to 150μm. The energy of each pulse can vary according to the desired material and ablation volume, such as between 10nJ and 1000μJ, or more preferably between 50μJ and 500μJ. In one embodiment, the energy of each pulse can be about 600μJ. The pulse repetition rate can vary. In some embodiments, a pulse repetition rate of up to about 10kHz can be used. By combining laser beam scanning and stage rasterization, a depth of hundreds of microns can be achieved.

[0108] The controller 180 may be configured to receive input from a user to set laser parameters suitable for the sample under investigation. For example, the pulse energy, spot size, and / or pulse duration may be adjusted to provide energy at the sample surface that is higher than the ablation threshold of the material but lower than the energy or duration sufficient to cause damage to the remaining surface chemicals. The controller 180 receives input from a user interface or from another computer. The input may include settings for adjusting one or more of the spot size, pulse energy, pulse duration, pulse repetition frequency, and wavelength. Alternatively, the input may provide an indication of the expected material or material type. The controller may include an algorithm, a lookup table, a library, or a database, such as when a computer program is executed on a processor of the controller, to provide laser parameters that are optimized to ablate the surface while avoiding or minimizing damage to the underlying chemical composition of the expected material or material type. The parameters may be further optimized to provide rapid ablation while minimizing damage to the underlying chemical composition.

[0109] Another method to determine how to adjust the parameters of the laser for different sample materials is to perform a survey scan of the sample surface to be ablated. This can include performing an electron energy spectrum as described herein, such as XPS or AES. Other sample survey scanning techniques can also be used. In one example, for a single-layer sample, a survey scan can determine the elemental composition in the surface layer. A library of similar materials can then be used to optimize settings, such as one or more of the fluence, frequency, pulse duration, wavelength, to achieve the desired ablation rate (i.e., nm per level or pulse), thereby retaining the chemical information in the surface layer. The number of pulses can then also be set for the desired depth or level of the profile. The pit morphology, such as size, shape and / or surface roughness or variation, can also be considered. For multi-layer samples, the method for a single layer can be repeated for each layer. Alternatively, for multi-layer samples, existing knowledge of the layer-by-layer composition or survey analysis can be used to determine the laser parameters to be used. For example, the survey analysis can include an approximate assessment of the composition, followed by the use of a library of similar materials to optimize the settings for the single layer. When the library is insufficient or inaccurate for the sample, the ablation rate can be determined by ex situ analysis (eg, mechanical profilometry, microscopy, or white light interferometry) of pits formed using different flow rates and pulse / level numbers.

[0110] The ablation rate (ie, nm per level or pulse) is material dependent and can be determined by ex situ analysis (eg, mechanical profilometry, microscopy, or white light interferometry) of pits formed using different flow rates and numbers of pulses / level.

[0111] return Figure 2 , the laser 160 and the X-ray source or electron source 130 are configured so that they direct the laser pulses and the X-rays or electrons, respectively, to the same target area on the sample surface, i.e. the laser pulses and the X-rays or electrons coincide on the sample surface. By alternately operating the laser to remove layers from the sample surface and the X-ray source or electron source to irradiate the sample surface causing electrons to be emitted from the sample, a compositional depth profile of the sample can be established. The use of a femtosecond laser is particularly advantageous because it avoids or reduces damage to the composition of the sample surface compared to ion beam sputtering.

[0112] Now describe in more detail Figure 2 The method of operating the device. Figure 4A Yes Operation Figure 2A process flow chart of a method 300 of an apparatus of the invention. The process begins at step 310, where a sample is positioned in a vacuum chamber of the apparatus. This may include placing the sample on a sample stage in the chamber and moving the sample stage to position the sample so that the ablation beam and the excitation beam will be incident on a target area of ​​the sample. The sample may be introduced into the chamber by breaking the vacuum to place the sample on the sample stage and then evacuating the chamber, or the sample may be introduced via a vacuum load lock. The method may additionally or alternatively include adjusting the laser and X-ray or electron sources so that their beams are incident on the correct position on the sample. In one arrangement, a coarse alignment may be performed using a positioner of the sample stage, and a fine alignment may be achieved by adjusting the position of the laser and X-ray or electron source beams. Preferably, at step 315 before ablation, an excitation beam of X-rays or electrons is generated and directed to the native surface of the sample. The X-rays or electrons may be directed to the native surface within the area to be ablated. Alternatively, in this step, X-rays or electrons can be directed to any area of ​​the surface of the sample, such as outside the area to be ablated, for example, if the sample has a uniform composition, as is usually the case with thin films. At step 320, the intensity and energy of the emitted electrons are measured using a detector and an electronic analyzer. The emitted electrons of interest are photoelectrons and / or Auger electrons. Optionally, at step 325, the laser can be adjusted by controller 280 to tune the pulse parameters of the material used for the sample. For example, the pulse can be adjusted to quickly ablate more material or reduce damage to the surface composition. Different materials may require lower pulse energies for ablation and / or may be more easily damaged for longer pulses. Although step 325 is shown in the figure as after initial irradiation and measurement steps 315 and 320, this optional step can be performed at one or more different points in the method at any time before the ablation step, such as before or after optional steps 315, 320. At step 330, the laser generates a pulse for ablating the sample surface. After ablation, as shown at step 340, an excitation beam of X-rays or electrons is generated and directed onto the new surface generated by ablation. Because the excitation beam and the ablation pulses are substantially spatially coincident, this step can be performed without moving the sample. At step 350, the intensity and energy of the emitted electrons are measured using a detector and an electronic analyzer. The emitted electrons of interest are photoelectrons and Auger electrons. As shown at step 360, the steps of laser ablation, irradiation with an excitation beam, and measurement of electron intensity and energy can be repeated to establish composition information on the sample layer. Between each step of laser ablation 330, or between each laser pulse used in each step of laser ablation 330, the polarization plane of the sample surface and / or the laser beam is rotated stepwise, for example 55 degrees.The degree of rotation between each laser pulse may be selected so that LIPSS formation becomes effectively suppressed, which may be a rotation between 10 and 80 degrees, such as between 40 and 70 degrees, for example 55 degrees. Alternatively, the laser pulses may be converted to elliptically polarized or circularly polarized in order to suppress LIPSS formation. At step 370, a composition depth profile is generated or calculated.

[0113] The physics and advantages of using femtosecond laser ablation over other material removal techniques are now described in more detail.

[0114] For laser ablation, the material removal process depends on the laser pulse length, but involves two competing mechanisms: thermal and electrostatic processes, also known as Coulomb explosions. In both cases, the laser photon energy is mainly absorbed by electrons. In the thermal process, the excited electrons relax through electron-phonon interactions and the lattice equilibrates after a few picoseconds by local heating. The material is ejected due to mechanisms including evaporation and hydrodynamic expansion of the heated material, the actual mechanism involved depends on the laser pulse length and energy. In the Coulomb explosion mechanism, the strong electric field associated with the high-intensity short pulse of light enables strong-field ionization and processes such as multiphoton and tunnel ionization to occur, resulting in a high concentration of ions in the surface region. When the electrostatic attraction between the ejected electrons or the electrostatic repulsion between the positively charged ions exceeds the local bond strength, the ions are ejected from the material surface in a Coulomb explosion. When the laser pulse is shortened in length to the ultrashort femtosecond range, there is a greater decoupling of the electron and solid relaxation processes because there is not enough time for them to occur. Therefore, for ultrashort pulse-induced ablation, the Coulomb explosion dominates over the thermal mechanism.

[0115] The conventional techniques of monatomic and cluster ion sputtering have disadvantages compared with ultrafast laser ablation. In monatomic ion sputtering, the incident ions penetrate the surface layer, resulting in momentum cascades with atoms in the local area. When enough energy is transferred to the surface atoms so that the bonds with adjacent atoms can be destroyed, the surface atoms are ejected (sputtered) into the vacuum. In cluster ion sputtering, the low average energy of the ions and the collisions between the ions in the cluster when colliding with the surface cause much less penetration or no penetration of the incident ions, but still cause multiple collisions between the surface atoms, causing the surface atoms to be ejected into the vacuum again. The high average energy of each atom in monatomic sputtering causes chemical damage to the surface to be analyzed by XPS or AES. In polymers, this results in effects such as preferential removal of functional groups and changes in bonding, resulting in disordered graphite-type carbonaceous structures. In inorganic materials, chemical damage usually takes the form of preferential sputtering, wherein one element is preferentially sputtered compared to another element in the compound. The much lower average energy per atom in cluster ion sputtering results in much less or minimal damage in polymers, but still results in preferential sputtering effects in inorganic materials.

[0116] The preferential sputtering of one element relative to another in a compound is generally considered to be caused by two effects: the mass difference effect and the surface binding energy. The mass difference effect takes into account the change in energy transfer to elements of different masses when the incident ions enter the surface of the compound and the effect of this change on the sputtering yield of each element. The surface binding energy is the energy required to remove an atom from the outer surface atomic layer. The surface binding energy takes into account the change in the binding energy of different atoms in the compound and usually adopts the sublimation enthalpy of the surface composition. Generally, for inorganic compounds, the mass difference effect is the main mechanism leading to preferential sputtering.

[0117] With femtosecond laser ablation, the high-energy ultrashort pulses of the laser beam lead to multiphoton ionization, which promotes electrons from the valence band into the conduction band. Further absorption of energy through inverse bremsstrahlung leads to avalanche ionization and space charge effects. The electrons are ejected into the vacuum. The electrostatic repulsion between the ions retained in the surface region and the attraction to the ejected electrons leads to a Coulomb explosion, in which the ions are "pushed" or "pulled" out of the surface, resulting in ablation. For femtosecond laser ablation, the absorption of the pulse energy occurs on such a short time scale that the energy is transferred to the electrons, but not directly to the phonons, causing minimal heating.

[0118] In the Coulomb explosion mechanism of laser ablation, the bonds between the leaving ions and the atoms below are broken, but there is likely to be no atom-to-atom momentum transfer as in the sputtering process. Therefore, there is no mass difference effect. In addition, it is not necessarily the surface layer of atoms that is ablated, so the surface binding energy is not important in this process. Therefore, in laser ablation, neither of the two effects that lead to preferential sputtering in sputtering depth profiling occurs. Therefore, using optimized laser parameters, analysis of the material surface after laser ablation can cause minimal or much less damage to the surface of the ablated pits compared to ion beam sputtering, and more accurately determine the surface composition by XPS / AES.

[0119] Femtosecond laser ablation is a very fast process (10 -15 Seconds to 10 -12Seconds), and the volume of removed material depends on the energy and spot size of the laser pulse and the operating mode of the laser. The operating mode of a pulsed laser can vary from a single pulse to repeated pulses of different frequencies. As the energy increases, the amount of material removed by a single pulse can range from a few nm to >500 nm. Therefore, the use of laser ablation as a material removal process enables the removal of tens to hundreds of microns of material in a practical time scale. Therefore, XPS / AES depth profiles can be recorded at much greater depths, and laser ablation depth profiling is used to expose deeply buried layers and interfaces, in contrast to sputtering depth profiling, where it is impractical to approach such depths.

[0120] An important process that occurs during repeated laser ablation of a surface is the formation of laser-induced periodic surface structures (LIPSS), which exhibit a corrugated morphology. The formation of LIPSS is a complex process, and different theories have been proposed to explain this phenomenon [J. Bonse, S. Laser Photonics Reviews 14(2020)2000215]. The formation of LIPSS on surfaces is problematic for electron spectroscopy depth profiling because the corrugated morphology makes the surface rough and potentially worsens the depth resolution of the depth profile, resulting in layers in the profile that are not clearly resolved and / or diffuse rather than sharp interfaces. One of the most accepted theories for LIPSS formation is that the incident light is scattered by the surface roughness [Bonse and Ibid.]. Other surface waves, such as surface plasmons, can also be excited. The incident radiation interferes with the primary scattered radiation and the surface plasmon polaritons, resulting in spatial variations in the incident beam energy distribution and a wave morphology that develops at the material surface as the number of ablation pulses increases. Many factors influence the different LIPSS structures that are formed, including sample roughness, polarization direction, incident angle, and material dielectric constant [Bonse and Ibid.]. Since sample roughness and polarization orientation are important factors in LIPSS formation, various experimental and optical strategies can be employed to delay and limit LIPSS formation, thereby promoting the generation of smoother pit bottoms during depth profiling. To achieve this goal, one or more of the following operations are performed:

[0121] (i) In an optical setup, the polarization plane of the linearly polarized laser beam is:

[0122] (a) Continuous rotation;

[0123] (b) is converted into a circularly or elliptically polarized beam before being incident on the sample; and /

[0124] or

[0125] (c) Rotate stepwise by an angle between 0 and 360 degrees between each laser pulse,

[0126] and / or

[0127] (ii) The sample is rotated continuously or between each laser pulse by an angle between 0 and 360 degrees.

[0128] Figure 4B Shown are the different depth resolutions achieved when depth profiling through a nickel / chromium multilayer structure with the laser polarization rotated between pulses (left) and not (right).

[0129] Quantification

[0130] Electron spectroscopy instruments count the number (intensity) and energy of electrons emitted from the surface of a material after being excited by an energy source (e.g., by X-rays, UV, or electron radiation). The total electron intensity is plotted as a function of the energy of the electron (binding energy or kinetic energy). Quantification in electron spectroscopy is based on the direct relationship between the intensity of the photoelectron and / or Auger electron peaks and the mole fraction concentration of the element within the analysis depth. This relationship is described in equation (1), where I is the peak intensity, J is the photon flux, p is the concentration of atoms or ions, σ is the cross section for electron emission, K is the spectrometer factor, and L is the electron decay length:

[0131] I=JρσKL (1)

[0132] The cross section σ for emission is the probability that a photoelectron or Auger electron is emitted by exposure to an energy source. The cross section will vary with elements, electron orbits, and total angular momentum. The spectrometer factor K explains the variation in detector performance between instruments and incorporates both the transmission function (i.e., the ratio of electrons transmitted through the detector as a function of kinetic energy) and the detector efficiency (i.e., the ratio of transmitted electrons contributing to the detected signal). The inelastic mean free path describes the distance that the emitted electrons travel before being inelastically scattered. However, in equation (1), a more accurate term, the attenuation length L, is used, which corrects the inelastic mean free path of elastic scattering and allows determination of the intensity emitted from a given depth in a given direction. Inelastic scattering causes electrons to have no contribution to the peak intensity of photoelectrons and / or Auger electrons.

[0133] The contribution of each of the above factors (σ, K, L) to the photoelectron / Auger electron peak intensity for any particular peak in the spectrum is combined into a single term, called the sensitivity factor F, which allows the relative proportion of that element in the analytical depth to be determined (see equation (2) below). The sensitivity factor may be taken from a library of theoretically determined values, experimentally determined values, or user determined values. Where a library value has been determined on / for an electronic spectrometer with a different transmission function, then a correction will need to be made for that different transmission function.

[0134] Peak intensities are typically measured graphically as the integrated area of ​​the photoelectron and / or Auger electron peaks, and the background signal is then subtracted using a suitable method. Figure 5A The Ag 3d photoelectron peak is shown. Background C is calculated using different methods, including linear, Shirley or Tougaard. There are other methods for determining peak intensity, such as using peak height instead of peak area and measuring the peak-to-peak differential spectrum encountered in electronic excitation Auger spectroscopy.

[0135] Assuming a homogeneous mixture of elements within the analysis depth, using equation (1) and given a constant photon flux, the normalized peak intensity can be used to calculate the element concentration as an atomic percentage. Based on this assumption, the concentration of element A in a multi-element material is given by equation (2):

[0136] [A]at%=[(I A / F A ) / Σ(I / F)]×100(2)

[0137] I and F represent the peak intensity and sensitivity factor (I A is the peak intensity of element A, F A is the sensitivity factor for element A). However, in the case where an electron source is used to generate Auger electrons, corrections due to matrix effects will be needed. The sample is assumed to comprise a homogeneous mixture of elements within the analytical depth for quantification of photoelectron and Auger electron spectroscopy, but other methods that give a more accurate description of the elemental distribution within the analytical depth may be used if such an elemental distribution is known or expected to occur within the analytical depth.

[0138] Convolution of peaks can occur due to overlapping energy peaks or the presence of multiple chemical states. Figure 5B In order to quantify the different chemical states in such cases, peak fitting must be performed to separate the peak intensity contributions from the various components present and then quantify these peak intensity contributions separately, as described in the previous paragraph. The binding energies / kinetic energies of the different chemical states of the element are determined by recording standard spectra of such materials with known composition or by available spectral libraries. Figure 5BAn example of the C1s region from an XPS spectrum is shown, which contains contributions from carbon in different chemical states CC, CO, and C=O. Peak fitting has been used to determine the relative peak intensities corresponding to each chemical state, allowing quantification of the various chemical states. The relative atomic concentrations of CC, C=O, and CO are 77.73%, 12.74%, and 9.53%, respectively.

[0139] To construct the depth profile, electron spectroscopy spectra are recorded from the surface and after each laser ablation cycle. The spectra are quantified and the chemical composition is determined based on equation (2). For the surface and each cycle / depth for which the electron spectrum has been recorded, the fractional composition of each element or elemental chemical state is plotted as a function of the number of laser ablation cycles or depth. The conversion of cycle number to depth can be performed by measuring the depth or by a priori knowledge of the layer thickness. Figure 6 a and Figure 6 b shows an example of a quantitative laser ablation XPS depth profile plotted as a function of ablation level and depth, respectively.

[0140] Pit formation

[0141] It has been described above how the ablation beam and the excitation beam spatially coincide at the sample surface. If the excitation beam is larger than or close to the size of the area of ​​the sample surface area to be ablated in terms of its area of ​​incidence on the area, the excitation beam may be incident on the edge or sidewall of the ablated area. This may result in the emission and analysis of electrons originating from the edge or sidewall in addition to the electrons emitted from the surface desired to be studied. These electrons from the edge or sidewall may come from a different chemical composition than the pit surface desired to be studied, and may therefore result in inaccuracies in the measurement. Therefore, the area of ​​the desired ablation area is larger than the area of ​​the excitation beam when it is incident on the sample surface.

[0142] One way to increase the surface area of ​​the ablated region is to scan the ablation beam over the sample surface. Another way is to use a wider beam to ablate a larger area. These options will now be described.

[0143] Figure 7 a is a schematic diagram of a beam scanning method that produces a large ablation area at the sample surface. Focused laser pulses 141 from laser 130 are raster scanned in a box-like pattern. The scan consists of overlapping pixels. Each pixel can be ablated by one or more pulses, and then the pulse position is moved to the next pixel. The number of pixels required is determined by the size of the area to be ablated and the spacing between pixels. Figure 7In , the area to be ablated has a width of Xμm and a length of Yμm. The pixel spacing is xμm in the width direction and yμm in the length direction, respectively. At each pixel, the laser delivers a single pulse or multiple pulses at a given repetition rate. The process can be repeated, and the pit depth is increased by setting a given number of passes to complete the box pattern. The sample can also be rotated by a given angle around the center point of the raster area between passes in order to reduce the roughness of the pit bottom. For example, in the first scan, the pulse position is first moved in the x direction, and after completing a set of x pixels, the position is stepped in the y direction, and these steps are repeated to establish a raster scan of the area XY. For the next layer, the scanning process can be rotated 90° so that the first scan of the pixel is in the y direction, and then the position is stepped in the x direction. Other scanning patterns are also possible.

[0144] This can be accomplished by including a movable mirror in the optical device (e.g. Figure 3A In one embodiment, the maximum area desired is 2 mm 2 , but in other embodiments this can be larger. Larger areas are useful for accessing deeper layers by overcoming aspect ratio issues that smaller areas may have. However, larger areas will take longer to ablate.

[0145] Figure 8 is a schematic representation of Gaussian beam overlap, which is used to achieve uniform radiation density on the sample surface for ablation. The figure shows possible beam overlap conditions, which are based on full width at half maximum (FWHM) to achieve uniform radiation intensity across the rasterized area and thus achieve flat bottomed pits. As shown in the figure, the beams at two adjacent pixel positions overlap so that the position of the FWHM for one pixel position just touches the FWHM for the adjacent position.

[0146] Figure 7 b is a schematic cross-sectional view of the pit depth, showing a flat bottom profile. For comparison, an excitation beam of narrower width, such as an X-ray beam, is shown at 151.

[0147] For an X-ray spot size range of 10 μm to 400 μm, it is preferred to use the largest possible spot size while maintaining the recommended ratio of pit width to X-ray spot size of 5: 1. The center of the X-ray spot for XPS analysis is positioned at the center of the pit.

[0148] Instead of scanning the beam while keeping the sample position fixed as described above, an alternative approach is to move the sample and keep the beam position fixed. The pulse of the laser is focused to a fixed point in xyz that coincides with the X-ray beam focus. The sample stage is raster scanned at each pixel with a laser ablation step in a similar manner to that described above. After each pass, the stage is moved back to the center point of the raster area in order to perform the XPS analysis. Again, the sample can be rotated a given angle around the center point of the raster area between passes in order to reduce the pit bottom roughness.

[0149] For AES analysis, the electron beam focus position is also centered on the center of the pit, and similar recommended spot size ratios as set forth above apply.

[0150] As mentioned above, another alternative is to use a wider beam to ablate the area. Fig. 9 is a schematic diagram of an optical arrangement for producing a top-hat shaped beam or pulse intensity. A top-hat (or flat-top) beam profile is formed using a diffractive optical element (DOE) beam shaping element as part of the optical arrangement. As shown, the top-hat intensity profile is formed near but not at the minimum focus spot location. The laser pulse first passes through a beam expander to increase the cross-sectional area of ​​the beam. This may correspond to Figure 3A The variable beam expander is used to expand the incident Gaussian beam (TEM 00 ) sized and aligned to the nominal 1 / e required for the selected DOE component 2 diameter. A top hat or flat top beam shaping element may correspond to Figure 3A The flat top shaper 220 in FIG. At a given working distance from the objective focusing lens, the Gaussian intensity profile is converted into a uniform intensity spot in the shape of a circle, square or rectangle. The spot size is determined by the incident beam size, the incident beam wavelength and the effective focal length (EFL) of the focusing lens.

[0151] Using this method, the maximum uniform top hat area is likely to be about 500 μm x 500 μm. Without combining this method with one of the scanning processes described above, the maximum ablation area will therefore also be about 500 μm x 500 μm. Using an ideal pit width to X-ray spot size ratio of 5:1, this will allow X-ray spot sizes up to 100 μm, such as in the range of 10 μm to 100 μm.

[0152] Fig.10 The top hat profile achieved to generate an elliptical pit is shown, which is caused by the laser being at a 45 degree angle to the sample surface. In general, the laser can be angled to the sample surface at any angle of incidence between 0 and 90 degrees, such as between 30 and 60 degrees. In this figure, the top hat is achieved at a position after the focal plane rather than before the focal plane, as shown in FIG. Fig. 9 As shown. Fig.10 In the upper figure, the solid ellipse line indicates the FWHM. In the lower figure, the intensity profile is obtained along the X direction and the Y direction of the upper figure. The FWHM in the X direction is about 404 μm, and the FWHM in the Y direction is about 544 μm.

[0153] Fig.11 Shows the use of Fig.10 An exemplary mechanical profilometry trace of the beam profile in FIG. 1 over the central region of a pit formed on a GaAs single crystal sample. In this example, the beam profile is scanned across the sample surface. Fig.11 In the present invention, a 3x 3 pixel-level raster with 200μm x / y spacing is used. A single shot is applied per pixel with 15 ablation levels and 90° rotation between levels. The pulse energy is about 200μJ per pulse. The pixel positions have about 50% overlap, resulting in a smooth pit bottom surface. Larger pit depths can be achieved with less overlap, as this will result in more material removal, but this will be at the expense of increased pit surface roughness.

[0154] A benefit of using a scanning approach (i.e., scanning beam or stage) is an increase in the maximum achievable pit size compared to a fixed beam approach (i.e., Gaussian or top hat). The maximum depth of profiling can therefore also be increased, since the resulting pit aspect ratio allows the X-ray and immersion electron gun beams to approach the pit bottom at a greater depth. This can allow depths in the range of hundreds of microns. In contrast, a disadvantage of the scanning approach is that the ablation time increases with the number of pixels. Additionally, the pixel spacing may need to be carefully determined to avoid rough pit bottoms from overlapping pulses, which may also result in reduced depth resolution. A combination of a scanning approach and a fixed approach may be preferred, wherein access to the pit bottom surface by the X-ray and immersion electron gun beams is provided by milling channels around the fixed beam pits using the scanning approach. Using a scanning approach can reduce the typical beam size and therefore the pulse energy compared to the fixed beam approach. For example, for a scanning approach, the beam diameter may be in the range of 10um to 100um with a pulse energy in the range of 0.01μJ to 10μJ, while for a fixed beam approach, the beam diameter may be in the range of 100μm to 500μm with a pulse energy in the range of 10μJ to 1000μJ. The lower pulse energies in the range may require multiple pulse trains using a repetition rate in the range of 0.001kHz to 200kHz at each pixel and / or level.

[0155] result

[0156] Figure 12 to Fig.15 Shows the use of Figure 3AResults of femtosecond laser ablation XPS depth profiling using the laser setup shown. The laser pulse duration used in each case was 160 fs and the wavelength was 1030 nm. A comparison with sputtering depth profiling is also provided. Figures 12 and Fig.13 It is shown how the use of femtosecond laser ablation can avoid preferential sputtering effects of two technologically important inorganic materials, TiO2 and InP.

[0157] Figure 12 shows the XPS depth profiles obtained for the bulk TiO2 sample. Figure 12a shows the composition depth profiles obtained using femtosecond laser ablation for nine ablation levels (120 μJ per pulse energy). Figure 12b shows the composition depth profiles obtained using conventional sputtering of a 500 eV argon ion beam. The composition data were recorded after ten seconds of etching, and the etch-measure cycle lasted for a total time of up to 90 seconds in the ten second etching period. Figure 12c shows the composition depth profiles obtained using conventional sputtering of GCIB with 8 keV 300 argon atoms. The composition data were recorded after 30 seconds of etching, and the etch-measure cycle lasted for a total time of up to 270 seconds in the 30 second etching period. XPS was used to determine the elements and their chemical states in the sample based on the intensity and energy of the emitted electrons.

[0158] As shown in Figure 12(d), for the Ti 2p peak, the chemical state of Ti in TiO2 is Ti 4+ , which has a binding energy of 459.0 eV. Figures 12(e) and 12(f) show the lower oxidation state of Ti, i.e., Ti 3+ and Ti 2+ , which have binding energies of 457.7 eV and 456.5 eV, respectively, as will be explained below.

[0159] The sample composition at the surface (initial time period) is different from the sample composition after the first ablation / ion etching due to the presence of surface hydrocarbon contamination. The hydrocarbon XPS C 1s contamination signal has been removed from the profile as it is not relevant to the determination of the TiO2 stoichiometry. The measurements after the initial time period are related to the bulk TiO2. In Figure 12a, it can be seen that the O concentration is 67 at.% and the Ti concentration is 33 at.%, resulting in a TiO2 for the femtosecond laser ablation method. 2.0 In Figures 12b and 12c, the concentration of O is about 62 at.%, and the concentration of Ti is about 38 at.%. Therefore, for 500 eV Ar + Ion sputtering, the stoichiometry was determined to be TiO 1.65 , while for 8keV Ar 300 + Cluster sputtering, the stoichiometry was determined to be TiO 1.70, both of which are incorrect. The Ti 2p spectra (Fig. 12d to Fig. 12f) show that for the femtosecond laser profile (Fig. 12d) only Ti 4+ , as expected for TiO2, but for 500eV Ar + Ion sputtering (Figure 12e) and 8keV Ar 300 + Cluster sputtering (FIG. 12f) and Ti can be clearly observed due to the preferential sputtering of O as a result of ion beam bombardment. 3+ and Ti 2+ The existence of state.

[0160] Fig.13 InP 1.0 A similar composition depth profile. Fig.13 a shows the profile produced using femtosecond laser ablation with pulses of approximately 120 μJ in 18 iterations. Fig.13 b shows a profile produced by 500 eV argon ion sputtering in 390 seconds. For femtosecond laser ablation, the concentrations of In and P are very similar, 50 at.%, while for sputtering, the concentration of In is significantly higher than that of P. As a result, for the femtosecond laser depth profile, the recorded stoichiometry is InP 1.0 , while for sputtering, it is InP 0.7 This is due to the preferential sputtering of P from the sample.

[0161] To demonstrate the rapid depth profiling capability and the ability to extend femtosecond laser ablation XPS techniques to depths of many micrometers, Fig.14 An analysis of an iron oxide layer is presented in . Femtosecond laser ablation XPS depth profiling was performed on an approximately 7 μm iron oxide layer grown on iron. The sample received approximately 100 ablations (each iteration level was 4) at an energy of approximately 300 μJ per pulse (with a 1 second pause between laser shots). After this, the iron substrate was reached. Each laser ablation shot removed approximately 70 nm of material and the profiling was performed in approximately 1.5 minutes, excluding the XPS analysis time. Fig.14 As shown in (b), the metal oxide exhibits two distinct layers, with the outer layer showing a higher O concentration and the inner layer having a lower O content. Fig.14 a shows the Fe 2p spectra from three different regions (outer layer, inner layer and substrate). 0 The spectrum is that from the iron metal substrate. The other two spectra exhibit spectral features (peak shifts and shaking satellites) that indicate different chemical forms of iron oxide in the layer, namely, Fe 2+ (FeO) and Fe 2+ / Fe 3 +(Fe3O4). For the first four ablation iterations, Fe3O4 is evident, and then from about ablation iterations 8 to 18, it transforms to FeO. From iteration 18 onwards, the oxide signal decreases rapidly as the underlying Fe is approached. Thus, it can be seen from the figure that important chemical information is preserved. Principal component analysis identifies "fingerprint spectra" associated with different chemical states of Fe, and can be used to extract regions within the profile where those individual spectra exist. Thus, in Fig.14 c, the chemical composition of each layer can be plotted, and the Fe3O4 / FeO layered structure of the oxide becomes apparent. For comparison, a high current, fast etch rate using a 500 eV argon ion beam would etch at a rate of approximately 10 nm / min, giving a total etch time of 700 min (11.7 hr) for a similar depth. In addition, the iron oxide undergoes preferential sputtering of O, with Fe 3+ The material is reduced to Fe under ion beam bombardment 2+ And even metallic Fe, so important chemical information of the different oxides formed is not preserved in sputtering depth profiling.

[0162] Another example of the advantages of femtosecond laser ablation XPS technology is Fig.15 , which concerns a polymer sample, namely PET. The sample is a 12 μm layer on steel. Fig.15 a shows 24 iterations of femtosecond laser ablation with a single shot pulse energy of 300 μJ for each iteration. The total time for this ablation and measurement sequence is approximately 10 minutes. As the number of iterations increases, and therefore the depth into the PET layer increases, the carbon:oxygen ratio remains constant, indicating no chemical changes at increasing depth. The presence of iron in the steel appears rapidly after 7 to 8 pulses. Fig.15 b and Fig.15 c shows the C1s and O1s spectra, respectively, for the first 7 to 8 iterations of ablation. Good uniformity is seen between the traces in each figure, which shows the correct chemical state and relative intensity of the PET, with no indication of chemical damage. 7 to 8 iterations of ablation and measurement were achieved after about 2.5 minutes. In contrast, to preserve the PET chemical information, as seen in the C1s and O1s XPS spectra for femtosecond laser ablation, argon ion cluster sputtering is required, and after three hours of sputtering excluding the XPS measurement time, the etch depth achieved would only be about 5 μm.

[0163] Those skilled in the art will readily appreciate that various modifications and variations may be made to the above methods and apparatus. Modifications may be made without departing from the scope of the appended claims. For example, the pulse parameters of the ablation laser or the size and shape of the ablation area may be changed. Steps from methods of different embodiments may be combined, and alternative components may be used in the ablation laser.

[0164] Embodiments of the present invention are described in the following clauses:

[0165] A1. A method for determining the chemical composition of a sample using electron spectroscopy, the method comprising:

[0166] ablating material from the area on the surface of the sample by irradiating the area with one or more pulses of laser light;

[0167] irradiating at least a portion of the region with an excitation beam of electrons or electromagnetic radiation;

[0168] measuring the intensity and energy of electrons emitted from at least a portion of the region of the sample as a result of the excitation beam; and

[0169] The steps of ablating material, irradiating with an excitation beam, and measuring intensity and energy are repeated to determine a quantitative surface depth profile of the chemical composition of at least a portion of the sample.

[0170] A2. The method of clause A1, further comprising: irradiating at least a portion of the unablated area with an excitation beam of electrons or electromagnetic radiation before a first ablation of material from the area, and measuring the intensity and energy of electrons emitted from at least a portion of the unablated area of ​​the sample due to the excitation beam.

[0171] A3. The method of clause A1 or clause A2, further comprising determining the chemical state of elements in the chemical composition based on the intensity and energy of the emitted electrons.

[0172] A4. A method according to any of the preceding clauses, further comprising determining the depth or relative depth of one or more ablated regions.

[0173] A5. A method according to any preceding clause, wherein one or more pulses of the laser beam each have a duration of less than 1 ns or less than 1 ps.

[0174] A6. A method according to any preceding clause, further comprising repeating the steps of ablating material, irradiating with an excitation beam, and measuring the energy and intensity of the emitted electrons to determine a depth profile down to a depth greater than 5 μm.

[0175] A7. A method according to any preceding clause, wherein each step of ablating material comprises removing a layer having a thickness in the range of 0.3 nm to 1 μm.

[0176] A8. A method according to any preceding clause, wherein the excitation beam is an X-ray beam.

[0177] A9. A method according to any preceding clause, wherein the excitation beam is an X-ray beam and the energy spectrum is XPS.

[0178] A10. The method according to any preceding clause, further comprising tilting the sample relative to the ablating laser beam.

[0179] A11. A method according to any of the preceding clauses, the method also includes: (i) rotating the sample in the plane of the surface of the sample between ablation steps and / or between laser pulses, and / or (ii) rotating the polarization plane of the laser pulses between ablation steps and / or between laser pulses, or (iii) converting the polarization of the laser pulses into circular polarization or elliptical polarization.

[0180] A12. A method according to any preceding clause, wherein one or more pulses ablate material by Coulomb explosion.

[0181] A13. A method according to any preceding clause, wherein the step of ablating material forms a pit in the surface of the sample, and wherein at least a portion of the area irradiated with the excitation beam of electrons includes an area at the bottom of the pit.

[0182] A14. A method according to clause A13, wherein the pit has a substantially flat bottom and the excitation beam illuminates at least a portion of the substantially flat bottom.

[0183] A15. A method according to clause A14, wherein the excitation beam illuminates at least a portion of the substantially flat bottom and does not illuminate the edges or sidewalls of the pit.

[0184] A16. A method according to any of clauses A13 to A15, wherein the width of the substantially flat bottom of the pit is greater than the width of the excitation beam.

[0185] A17. A method according to any of clauses A13 to A16, wherein the step of ablating material from an area of ​​the sample comprises moving the relative position of the laser pulses to scan the pulses over an area on the surface of the sample to ablate pits in the surface.

[0186] A18. A method according to clause A17, wherein the relative position of the laser pulses is moved by scanning the laser or by scanning the position of the sample.

[0187] A19. A method according to clause A17 or A18, wherein scanning includes irradiating the sample with one or more pulses at multiple partially overlapping pixel locations.

[0188] A20. A method according to any preceding clause, wherein the laser is incident on the surface to be ablated at a non-normal angle, such as between 30 degrees and 60 degrees.

[0189] A21. A method according to any of clauses A13 to A20, further comprising passing the laser pulse through a beam shaping element to convert the laser pulse to have a substantially flat-top or top-hat intensity profile across its diameter at which it is incident on the sample surface.

[0190] A22. A method according to any one of clauses A13 to A21, further comprising passing the laser pulse through a polarization adjustment optical device to change the direction of the linear polarization of the laser beam or convert the linear polarization of the laser beam into a circular or elliptical polarization of the laser beam.

[0191] A23. A method according to clause A21 or A22, wherein the beam shaping element comprises a diffractive optical element or a refractive optical element.

[0192] A24. A method according to any preceding clause, wherein the laser pulses each have a duration of less than 1 ns, less than 1 ps, less than 500 fs, less than 100 fs, less than 10 fs or less than 1 fs.

[0193] A25. A method according to any preceding clause, wherein the energy of each laser pulse is in the range of 10 nJ to 1000 μJ, such as between 50 μJ and 500 μJ.

[0194] A26. A method according to any preceding clause, wherein the spot size of the laser pulses at the sample surface is in the range of 1 μm to 1000 μm.

[0195] A27. A method according to any of the preceding clauses, further comprising:

[0196] setting, by the controller, one or more parameters of the pulses of the laser based on compositional information about the sample; and

[0197] The step of ablating material is performed, wherein parameters of the laser pulses are set by a controller. A28. The method of clause A27, wherein the one or more parameters of the laser pulses set by the controller include one or more of: pulse duration, pulse energy, repetition rate, wavelength, and spot size.

[0198] A29. The method according to clause A27 or A28, wherein the setting step further comprises:

[0199] receiving input from a user indicating compositional information about the sample; and

[0200] The controller adjusts one or more laser parameters based on the composition information.

[0201] A30. A method according to clause A27 or A28, further comprising:

[0202] Performing survey scans or survey profiling to determine approximate measurements of elemental composition in the sample; and

[0203] and generating one or more parameters of the laser pulse based on the approximate metric.

[0204] A31. A method according to any one of clauses A27 to A30, which also includes performing mechanical profilometry, microscopy or white light interferometry on the sample surface; and generating or adjusting one or more parameters of the laser pulse based on the profilometry, microscopy or white light interferometry.

[0205] A32. A method according to any of clauses A27 to A31, further comprising the controller using a reference database or algorithm to determine laser parameters based on information about the sample.

[0206] A33. A method according to any one of clauses A27 to A32, the method further comprising: after the steps of ablating material, irradiating with an excitation beam, and measuring electron intensity and energy, adjusting one or more parameters of the laser based on measured or predicted composition information about the sample at a depth after ablation, and repeating the steps of ablating material, irradiating with an excitation beam, and measuring electron intensity and energy using the adjusted one or more parameters of the laser.

[0207] A34. A method according to clause A33, further comprising repeating the steps of adjusting, ablating material, irradiating with an excitation beam, and measuring electron intensity and energy until the sample has been analyzed to a target depth.

[0208] A35. A method according to any preceding clause, further comprising placing the sample on a sample stage in a vacuum chamber and subsequently performing the steps of ablating the material, irradiating with an excitation beam, and measuring the intensity and energy of the emitted electrons,

[0209] Therein, between the ablation step and the irradiation step with the excitation beam, the sample is not moved by an amount greater than the size of the sample.

[0210] A36. A method according to any preceding clause, wherein the laser pulses and the excitation beam spatially coincide at the sample surface.

[0211] A37. A method according to clause 35, wherein the ablating step comprises raster scanning ablating laser pulses relative to the sample surface, and wherein the excitation beam coincides with the ablated sample surface.

[0212] B38. A method of electronic energy spectroscopy, the method comprising:

[0213] ablating material from the area on the surface of the sample by irradiating the area with one or more pulses of laser light, wherein the ablation forms a pit in the surface of the sample;

[0214] irradiating at least a portion of the ablated area at the bottom of the pit with an excitation beam of electrons or electromagnetic radiation;

[0215] measuring the intensity and energy of electrons emitted from at least a portion of the region of the sample as a result of the excitation beam; and

[0216] The chemical composition of the surface of the pit is determined based on the measured intensity and energy of the emitted electrons.

[0217] C39. A method of electronic energy spectroscopy, the method comprising:

[0218] ablating material from a region on a surface of a sample by irradiating the region with one or more pulses of laser light, wherein the laser pulses have a duration of less than 1 ns, less than 1 ps, less than 500 fs, less than 100 fs, less than 10 fs, or less than 1 fs;

[0219] irradiating at least a portion of the ablated region with an excitation beam of electrons or electromagnetic radiation;

[0220] measuring the intensity and energy of electrons emitted from at least a portion of the region of the sample as a result of the excitation beam; and

[0221] The chemical composition of the surface is determined based on the measured intensity and energy of the emitted electrons.

[0222] D40. A method of electronic energy spectroscopy, the method comprising:

[0223] setting, by the controller, one or more parameters of the pulses of the laser based on compositional information about the sample;

[0224] ablating material from the area on the surface of the sample by irradiating the area with one or more pulses of laser light, wherein parameters of the pulses have been set by a controller;

[0225] irradiating at least a portion of the region with an excitation beam of electrons or electromagnetic radiation;

[0226] measuring the intensity and energy of electrons emitted from at least a portion of the region of the sample as a result of the excitation beam; and

[0227] The chemical composition of the surface is determined based on the measured intensity and energy of the emitted electrons.

[0228] E41. A method of electronic energy spectroscopy, the method comprising:

[0229] placing a sample on a sample stage in a vacuum chamber;

[0230] ablating material from the area on the surface of the sample by irradiating the area with one or more pulses of laser light;

[0231] irradiating at least a portion of the region with an excitation beam of electrons or electromagnetic radiation;

[0232] measuring the intensity and energy of electrons emitted from at least a portion of the region of the sample as a result of the excitation beam;

[0233] determining the chemical composition of the surface based on the measured intensity and energy of the emitted electrons;

[0234] Therein, between the ablation step and the irradiation step with the excitation beam, the sample is not moved by an amount greater than the size of the sample.

[0235] F42. A method of electronic energy spectroscopy, the method comprising:

[0236] placing a sample on a sample stage in a vacuum chamber;

[0237] ablating material from the region on the surface of the sample by irradiating the region with one or more pulses of a laser configured to direct the pulses at the surface of the sample;

[0238] irradiating at least a portion of the region with an excitation beam of electrons or electromagnetic radiation;

[0239] measuring the intensity and energy of electrons emitted from at least a portion of the region of the sample as a result of the excitation beam; and

[0240] The chemical composition of the surface is determined based on the measured intensity and energy of the emitted electrons,

[0241] Therein, the laser pulse and the excitation beam coincide spatially at the sample surface.

[0242] G43. An electron spectroscopy apparatus for determining the chemical composition of a sample, the apparatus comprising:

[0243] Vacuum chamber;

[0244] a sample stage mounted in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed;

[0245] a laser configured to generate laser pulses and direct the laser pulses to a target area of ​​the sample to ablate a surface of the sample;

[0246] an excitation beam source configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to a target area of ​​the sample; and

[0247] An electron analyzer and detector configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a quantitative surface depth profile of the chemical composition of the sample.

[0248] G44. An apparatus according to clause G43, wherein the electron analyzer is also configured to determine the chemical state of elements in the chemical composition based on the intensity and energy of the emitted electrons.

[0249] G45. An apparatus as described in clause G43 or G44, wherein the laser is configured to generate pulses having a duration of less than 1 ns, less than 1 ps, less than 500 fs, less than 100 fs, less than 10 fs or less than 1 fs.

[0250] G46. An apparatus according to any one of clauses G43 to G45, wherein the excitation beam source is configured to generate an X-ray beam.

[0251] G47. An apparatus according to any one of clauses G43 to G45, wherein the excitation beam source is configured to generate an X-ray beam and the electron analyzer is configured to measure photoelectrons.

[0252] G48. An apparatus according to any one of clauses G43 to G47, wherein the sample stage is configured to be tilted relative to the ablation laser beam.

[0253] G49. A method according to any one of clauses G43 to G48, wherein: (i) the sample stage is configured to rotate the sample in a plane of the surface of the sample, and the controller is configured to control the rotation of the sample stage between ablation steps and / or between laser pulses, and / or the laser includes a polarization controller configured to (ii) rotate the polarization plane of the laser pulse between ablation steps and / or between laser pulses, or (iii) convert the polarization of the laser pulse into circular polarization or elliptical polarization.

[0254] G50. An apparatus according to any one of clauses G43 to G49, wherein the sample stage includes a positioning device to move the sample in an orthogonal direction in the sample plane so as to raster scan the sample relative to the incident position of the ablation laser pulses.

[0255] G51. An apparatus according to any one of clauses G43 to G50, wherein the laser includes a mirror to adjust the incident position of the laser pulse on the sample so as to raster scan the laser pulse across the sample.

[0256] G52. An apparatus according to any one of clauses G43 to G51, wherein the laser includes a beam shaping element for converting the laser pulses into an intensity profile having a substantially flat top or top hat across its diameter at which it is incident on the sample surface.

[0257] G53. An apparatus as described in clause G52, wherein the laser beam shaping element is configured to convert the laser pulse into an intensity profile having a substantially flat top or top hat across its diameter at the surface of the sample, and the diameter at the surface of the sample is larger than the diameter of the excitation beam at the surface of the sample.

[0258] G54. An apparatus according to clause G52 or G53, wherein the beam shaping element comprises a diffractive optical element or a refractive optical element.

[0259] G55. An apparatus according to any one of clauses G43 to G54, wherein the laser is configured to generate pulses having an energy per pulse in the range of 10 nJ to 1000 μJ.

[0260] G56. An apparatus according to any of clauses G43 to G55, wherein the laser is configured to generate pulses having a spot size at the sample surface in the range of 1 μm to 1000 μm.

[0261] G57. An apparatus according to any one of clauses G43 to G56, further comprising a controller configured to adjust one or more parameters of a pulse of the laser based on compositional information about the sample.

[0262] G58. An apparatus as described in any of clauses G43 to G57, wherein one or more parameters of the laser pulse set by the controller include one or more of the following: pulse duration, pulse energy, repetition rate, wavelength, and spot size.

[0263] G59. An apparatus according to any one of clauses G43 to G58, wherein the controller is configured to:

[0264] receiving input from a user indicating compositional information about the sample; and

[0265] One or more laser parameters are adjusted based on the composition information.

[0266] G60. An apparatus as described in any of clauses G43 to G59, wherein the controller is configured to determine laser parameters based on information about the sample with reference to a reference database or algorithm.

[0267] G61. An apparatus according to any one of clauses G43 to G60, wherein the laser and the excitation beam source are respectively configured to direct the laser pulses and the excitation beam to spatially coincide at the sample surface.

[0268] H62. An electronic energy spectrum device, the electronic energy spectrum device comprising:

[0269] Vacuum chamber;

[0270] a sample stage mounted in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed;

[0271] a laser configured to generate laser pulses and direct the laser pulses at a target area of ​​the sample to ablate a surface of the sample, wherein the laser is configured to ablate material to form a pit in the surface of the sample;

[0272] an excitation beam source configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to a target area of ​​the sample; and

[0273] An electron analyzer and detector configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a surface depth profile of the chemical composition of the sample.

[0274] I63. An electronic energy spectrum device, the electronic energy spectrum device comprising:

[0275] Vacuum chamber;

[0276] a sample stage mounted in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed;

[0277] a laser configured to generate laser pulses and direct the laser pulses to a target area of ​​the sample to ablate a surface of the sample, wherein the laser is configured to generate pulses having a duration of less than 1 ns, less than 1 ps, less than 500 fs, less than 100 fs, less than 10 fs, or less than 1 fs;

[0278] an excitation beam source configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to a target area of ​​the sample; and

[0279] An electron analyzer and detector configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a surface depth profile of the chemical composition of the sample.

[0280] J64. An electronic energy spectrum device, the electronic energy spectrum device comprising:

[0281] Vacuum chamber;

[0282] a sample stage mounted in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed;

[0283] a laser configured to generate laser pulses and direct the laser pulses to a target area of ​​the sample to ablate a surface of the sample;

[0284] a controller configured to adjust or set one or more parameters of the pulses of the laser based on information about the sample;

[0285] an excitation beam source configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to a target area of ​​the sample; and

[0286] An electron analyzer and detector configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a surface depth profile of the chemical composition of the sample.

[0287] K65. An electronic energy spectrum device, the electronic energy spectrum device comprising:

[0288] Vacuum chamber;

[0289] a sample stage mounted in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed;

[0290] a laser configured to generate laser pulses and direct the laser pulses to a target area of ​​the sample to ablate a surface of the sample;

[0291] an excitation beam source configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to a target area of ​​the sample; and

[0292] an electron analyzer and detector configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a surface depth profile of the chemical composition of the sample,

[0293] Wherein, the sample stage is configured for a maximum movement amount corresponding to the size of the sample. L66. An electron energy spectrum device, the electron energy spectrum device comprising:

[0294] Vacuum chamber;

[0295] a sample stage mounted in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed;

[0296] a laser configured to generate laser pulses and direct the laser pulses to a target area of ​​the sample to ablate a surface of the sample;

[0297] an excitation beam source configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to a target area of ​​the sample; and

[0298] an electron analyzer and detector configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a surface depth profile of the chemical composition of the sample,

[0299] The laser and the excitation beam source are respectively configured to guide the laser pulse and the excitation beam to spatially coincide at the sample surface.

Claims

1. A method for determining the chemical composition of a sample using electron spectroscopy, the method comprising: ablating material from a region on a surface of a sample by irradiating the region with one or more pulses of laser light; irradiating at least a portion of the region with an excitation beam of electrons or electromagnetic radiation; measuring intensity and energy of electrons emitted from the at least a portion of the region of the sample as a result of the excitation beam; as well as The steps of ablating material, irradiating with an excitation beam, and measuring intensity and energy are repeated to determine a quantitative surface depth profile of the chemical composition of at least a portion of the sample.

2. The method according to claim 1, further comprising: Prior to a first ablation of material from the area, at least a portion of the unablated area is irradiated with an excitation beam of electrons or electromagnetic radiation and intensity and energy of electrons emitted from the at least a portion of the unablated area of ​​the sample due to the excitation beam are measured.

3. The method of claim 1 or claim 2, further comprising determining the chemical state of elements in the chemical composition based on the intensity and energy of the emitted electrons.

4. A method according to any preceding claim, further comprising determining the depth or relative depth of one or more ablated regions.

5. A method according to any preceding claim, wherein: The one or more pulses of the laser beam each have a duration of less than 1 ps.

6. A method according to any preceding claim, further comprising repeating the steps of ablating material, irradiating with the excitation beam, and measuring the energy and intensity of the emitted electrons to determine a depth profile down to a depth greater than 5 μm.

7. A method according to any preceding claim, wherein: Each step of ablating material involves removing a layer with a thickness ranging from 0.3 nm to 1 μm.

8. A method according to any preceding claim, wherein: The excitation beam is an X-ray beam.

9. A method according to any preceding claim, wherein: The excitation beam is an X-ray beam and the energy spectrum is XPS.

10. A method according to any preceding claim, further comprising tilting the sample relative to the ablating laser beam.

11. The method according to any preceding claim, further comprising: (i) rotating the sample in the plane of the surface of the sample between the ablation steps and / or between the laser pulses, and / or (ii) rotating the polarization plane of the laser pulses between the ablation steps and / or between the laser pulses, or (iii) converting the polarization of the laser pulses into circular polarization or elliptical polarization.

12. A method according to any preceding claim, wherein: The one or more pulses ablate material via a Coulomb explosion.

13. A method according to any preceding claim, wherein: The step of ablating material forms a pit in the surface of the sample, and wherein the at least a portion of the area irradiated with an excitation beam of electrons comprises an area at a bottom of the pit.

14. The method according to claim 13, wherein: The pit has a substantially flat bottom, and the excitation beam illuminates at least a portion of the substantially flat bottom.

15. The method according to claim 14, wherein: The excitation beam illuminates the at least a portion of the substantially planar bottom and does not illuminate an edge or a sidewall of the pit.

16. The method according to any one of claims 13 to 15, wherein: The substantially flat bottom of the pit has a width greater than a width of the excitation beam.

17. The method according to any one of claims 13 to 16, wherein: The step of ablating material from the region of the sample includes moving the relative position of the laser pulses to scan the pulses over the region on the surface of the sample to ablate the pits in the surface.

18. The method according to claim 17, wherein: The relative position of the laser pulses is moved by scanning the laser or by scanning the position of the sample.

19. The method according to claim 17 or 18, wherein: The scanning includes illuminating the sample with one or more pulses at a plurality of partially overlapping pixel locations.

20. A method according to any preceding claim, wherein: The laser is incident on the surface to be ablated at a non-normal angle, such as between 30 and 60 degrees.

21. The method of any one of claims 13 to 20, further comprising passing the laser pulse through a beam shaping element to convert the laser pulse to have a substantially flat-top or top-hat intensity profile across its diameter at which it is incident on the sample surface.

22. The method of any one of claims 13 to 21, further comprising passing the laser pulse through a polarization adjustment optical device to change the direction of the linear polarization of the laser beam or convert the linear polarization of the laser beam into a circular polarization or an elliptical polarization of the laser beam.

23. The method according to claim 21 or 22, wherein: The beam shaping element comprises a diffractive optical element or a refractive optical element.

24. A method according to any preceding claim, wherein: The laser pulses each have a duration of less than 1 ns, less than 1 ps, less than 500 fs, less than 100 fs, less than 10 fs, or less than 1 fs.

25. A method according to any preceding claim, wherein: The energy of each laser pulse is in the range of 10 nJ to 1000 μJ, such as between 50 μJ and 500 μJ.

26. A method according to any preceding claim, wherein: The spot size of the laser pulse at the sample surface is in the range of 1 μm to 1000 μm.

27. A method according to any preceding claim, further comprising: setting, by a controller, one or more parameters of the pulses of the laser based on compositional information about the sample; as well as The step of ablating material is performed wherein the parameters of the laser pulses are set by the controller.

28. The method according to claim 27, wherein: The one or more parameters of the laser pulses set by the controller include one or more of: pulse duration, pulse energy, repetition rate, wavelength, and spot size.

29. The method according to claim 27 or 28, wherein: The setting step also includes: receiving input from a user indicating the composition information about the sample; and The controller adjusts the one or more laser parameters based on the composition information.

30. The method according to claim 27 or 28, further comprising: performing a survey scan or survey profiling to determine an approximate measure of elemental composition in the sample; as well as The one or more parameters of the laser pulse are generated based on the approximation metric.

31. The method of any one of claims 27 to 30, further comprising performing mechanical profilometry, microscopy, or white light interferometry on the sample surface; and generating or adjusting the one or more parameters of the laser pulses based on the profilometry, microscopy, or white light interferometry.

32. The method of any one of claims 27 to 31 , further comprising the controller using a reference database or algorithm to determine the laser parameters based on the information about the sample.

33. The method according to any one of claims 27 to 32, further comprising: After the steps of ablating material, irradiating with an excitation beam, and measuring electron intensity and energy, adjusting the one or more parameters of the laser based on measured or predicted compositional information about the sample at the depth after the ablation, and repeating the steps of ablating material, irradiating with an excitation beam, and measuring electron intensity and energy using the adjusted one or more parameters of the laser.

34. The method of claim 33, further comprising repeating the steps of adjusting, ablating material, irradiating with an excitation beam, and measuring electron intensity and energy until the sample has been analyzed to a target depth.

35. A method according to any preceding claim, further comprising placing the sample on a sample stage in a vacuum chamber and subsequently performing the steps of ablating material, irradiating with an excitation beam, and measuring the intensity and energy of the emitted electrons, in, Between the ablating step and the irradiating with the excitation beam step, the sample is not moved by an amount greater than a dimension of the sample.

36. A method according to any preceding claim, wherein: The laser pulses and the excitation beam spatially coincide at the sample surface.

37. The method of claim 35, wherein: The ablating step includes raster scanning the ablating laser pulses relative to the sample surface, and wherein the excitation beam coincides with the ablated sample surface.

38. A method for electronic spectroscopy, the method comprising: ablating material from a region on a surface of a sample by irradiating the region with one or more pulses of laser light, wherein the ablation forms a pit in the surface of the sample; irradiating at least a portion of the ablated area at the bottom of the pit with an excitation beam of electrons or electromagnetic radiation; measuring the intensity and energy of electrons emitted from the at least a portion of the region of the sample as a result of the excitation beam; and The chemical composition of the surface of the pit is determined based on the measured intensity and energy of the emitted electrons.

39. A method for electronic spectroscopy, the method comprising: ablating material from a region on a surface of a sample by irradiating the region with one or more pulses of laser light, wherein the laser pulses have a duration of less than 1 ns, less than 1 ps, less than 500 fs, less than 100 fs, less than 10 fs, or less than 1 fs; irradiating at least a portion of the ablated region with an excitation beam of electrons or electromagnetic radiation; measuring the intensity and energy of electrons emitted from the at least a portion of the region of the sample as a result of the excitation beam; and The chemical composition of the surface is determined based on the measured intensity and energy of the emitted electrons.

40. A method for electronic energy spectroscopy, the method comprising: setting, by the controller, one or more parameters of the pulses of the laser based on compositional information about the sample; ablating material from a region on a surface of the sample by irradiating the region with one or more pulses of the laser, wherein the parameters of the pulses have been set by the controller; irradiating at least a portion of the region with an excitation beam of electrons or electromagnetic radiation; measuring the intensity and energy of electrons emitted from the at least a portion of the region of the sample as a result of the excitation beam; and The chemical composition of the surface is determined based on the measured intensity and energy of the emitted electrons.

41. A method for electronic energy spectroscopy, the method comprising: placing a sample on a sample stage in a vacuum chamber; ablating material from a region on a surface of the sample by irradiating the region with one or more pulses of laser light; irradiating at least a portion of the region with an excitation beam of electrons or electromagnetic radiation; measuring intensity and energy of electrons emitted from the at least a portion of the region of the sample as a result of the excitation beam; determining a chemical composition of the surface based on the measured intensity and energy of the emitted electrons; Wherein, between the ablating step and the irradiating step with the excitation beam, the sample is not moved by an amount greater than a size of the sample.

42. A method for electronic spectroscopy, the method comprising: placing a sample on a sample stage in a vacuum chamber; ablating material from a region on a surface of the sample by irradiating the region with one or more pulses of a laser configured to direct pulses at the sample surface; irradiating at least a portion of the region with an excitation beam of electrons or electromagnetic radiation; measuring intensity and energy of electrons emitted from the at least a portion of the region of the sample as a result of the excitation beam; as well as determining the chemical composition of the surface based on the measured intensity and energy of the emitted electrons, The laser pulse and the excitation beam are spatially overlapped at the sample surface.

43. An electron spectroscopy apparatus for determining the chemical composition of a sample, the apparatus comprising: Vacuum chamber; a sample stage, the sample stage being installed in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed; a laser configured to generate laser pulses and direct the laser pulses to a target area of ​​the sample to ablate a surface of the sample; an excitation beam source configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to the target area of ​​the sample; as well as An electron analyzer and detector configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a quantitative surface depth profile of the chemical composition of the sample.

44. An electronic energy spectrum device, comprising: Vacuum chamber; a sample stage, the sample stage being installed in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed; a laser configured to generate laser pulses and direct the laser pulses at a target area of ​​the sample to ablate a surface of the sample, wherein the laser is configured to ablate material to form pits in the surface of the sample; an excitation beam source configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to the target area of ​​the sample; as well as An electron analyzer and detector configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a surface depth profile of the chemical composition of the sample.

45. An electronic energy spectrum device, comprising: Vacuum chamber; a sample stage, the sample stage being installed in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed; a laser configured to generate laser pulses and direct the laser pulses to a target area of ​​the sample to ablate a surface of the sample, wherein the laser is configured to generate pulses having a duration of less than 1 ns, less than 1 ps, less than 500 fs, less than 100 fs, less than 10 fs, or less than 1 fs; an excitation beam source configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to the target area of ​​the sample; and An electron analyzer and detector configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a surface depth profile of the chemical composition of the sample.

46. ​​An electronic energy spectrum device, comprising: Vacuum chamber; a sample stage, the sample stage being installed in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed; a laser configured to generate laser pulses and direct the laser pulses to a target area of ​​the sample to ablate a surface of the sample; a controller configured to adjust or set one or more parameters of pulses of the laser based on information about the sample; an excitation beam source configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to the target area of ​​the sample; as well as An electron analyzer and detector configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a surface depth profile of the chemical composition of the sample.

47. An electronic energy spectrum device, comprising: Vacuum chamber; a sample stage, the sample stage being installed in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed; a laser configured to generate laser pulses and direct the laser pulses to a target area of ​​the sample to ablate a surface of the sample; an excitation beam source configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to the target area of ​​the sample; as well as an electron analyzer and detector configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a surface depth profile of the chemical composition of the sample, The sample stage is configured for a maximum movement amount corresponding to the size of the sample.

48. An electronic energy spectrum device, comprising: Vacuum chamber; a sample stage, the sample stage being installed in the vacuum chamber, the sample stage being configured to receive a sample to be analyzed; a laser configured to generate laser pulses and direct the laser pulses to a target area of ​​the sample to ablate a surface of the sample; an excitation beam source configured to generate an excitation beam of electrons or electromagnetic radiation and direct the excitation beam to the target area of ​​the sample; as well as an electron analyzer and detector configured to measure the energy and intensity of electrons emitted from the sample surface in response to the excitation beam and determine a surface depth profile of the chemical composition of the sample, The laser and the excitation beam source are respectively configured to guide the laser pulse and the excitation beam to overlap spatially at the sample surface.

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