Reflectometry system and method for determining reflectivity

Abstract

A reflectometer system (1, 10) for analyzing a sample (2) comprising: a measurement radiation system comprising a measurement radiation source (3) for generating a measurement beam (30); a reflectivity sensor (4) for detecting an intensity of the measurement beam (30) after reflection off the sample (2) in the presence of the sample (2); an alignment radiation source (5) for generating an alignment beam (50); an optical element (61, 62) configured for directing the measurement beam (30) and / or the alignment beam (5) towards the sample (2) in the presence of the sample (2); and a position sensor (7) for measuring a position of the alignment beam (50) after reflection off the sample (2) on the position sensor (7), wherein the reflectometer system (1, 10) is adapted to determine an alignment of the system (1, 10) relative to the sample (2) based on the measured position of the alignment beam (50), wherein a beam width of the alignment beam (50) is smaller than a beam width of the measurement beam (30), wherein the reflectometer system (1, 10) is configured such that at least a part of a propagation path of the measurement beam (30) is substantially parallel to at least a part of a propagation path of the alignment beam (50) when the alignment of the reflectometer system (1, 10) is optimized.

Description

Technical Field

[0001] This invention relates to a reflectometer system and a method for determining the reflectivity of a sample. Background Technology

[0002] Reflectance measurement is a widely used technique for analyzing the properties of a sample by measuring the intensity of light reflected from it. This method is crucial for various industries, including semiconductor manufacturing, materials science, and optics, where accurate measurements of reflectance can provide valuable information about the composition, structure, and quality of materials.

[0003] In the field of reflectance measurement, accurate alignment of the sample with respect to the measurement beam is crucial for obtaining reliable and reproducible results. Misalignment can lead to significant errors in reflectance measurements because the angle of incidence and the position of the beam illuminating the sample surface greatly affect the general or spectral intensity of the reflected light.

[0004] One challenge in this field is the difficulty in achieving and maintaining precise alignment, especially when measuring a range of samples and dealing with a variety of sample sizes, shapes, and types. The alignment process can be time-consuming and complex, particularly when high precision is required.

[0005] Despite advancements in reflectance measurement techniques, these challenges highlight the need for further improvement in the field. The need persists for more efficient, accurate, and user-friendly systems that can provide reliable reflectance measurements while minimizing the possibility of errors due to sample misalignment. Therefore, further development in this field is still required to address these challenges. Summary of the Invention

[0006] The purpose of embodiments of the present invention is to provide a good system and method for reflectance measurement, which can provide accurate alignment of the sample for reflectance measurement by utilizing a narrow alignment beam combined with a position sensor.

[0007] This objective is achieved through a reflectometer system and a method for determining the reflectivity of a sample.

[0008] An advantage of embodiments of the present invention is that a precise and accurate determination of the alignment of the sample relative to the reflectometer system can be achieved, and in turn a precise and accurate alignment. The precise and accurate determination of the alignment can be achieved by using a narrow alignment beam which allows to accurately determine the position of the sample relative to the measurement beam. Since the diameter of the alignment beam can be significantly smaller than the diameter of the measurement beam, a highly accurate determination of the position of the alignment beam on the position sensor can be achieved. Thus, embodiments of the present invention can facilitate to accurately determine whether the reflectometer system is well aligned (e.g. whether the system is aligned within predetermined specifications). Furthermore, this can in turn lead to a more precise alignment procedure which is advantageous for precise reflectance measurements.

[0009] In a first aspect, the present invention relates to a reflectometer system for analyzing a sample. The reflectometer system comprises a measurement radiation system comprising a measurement radiation source for generating a measurement beam. The reflectometer system comprises a reflectance sensor for detecting the intensity of the measurement beam upon reflection off the sample when present, an alignment radiation source for generating an alignment beam, a position sensor for measuring the position of the alignment beam upon reflection off the sample on said position sensor, and an optical element configured for directing said measurement beam and / or said alignment beam towards the sample when present or for directing said alignment beam towards the position sensor. The reflectometer system is adapted to determine the alignment of the system relative to the sample based on the measured position of the alignment beam. The beam width of the alignment beam is smaller than the beam width of the measurement beam. Said beam width can be determined at the sample and / or at the position sensor.

[0010] The reflectometer system for analyzing a sample can be used to determine the reflectance of the sample, or to determine a property of the sample (e.g. the composition or a surface property) based on the determined reflectance of the sample, or to determine a property of a coating present on the surface of the sample.

[0011] The reflectometer system is configured such that at least a part of the propagation path of the measurement beam is substantially parallel to at least a part of the propagation path of the alignment beam when the alignment of the reflectometer system is optimized. Preferably, the propagation path of the measurement beam and the propagation path of the alignment beam are at least substantially parallel at the sample when the alignment of the reflectometer system is optimized. For example, both beams can be substantially parallel upon incidence on the sample and upon reflection off the sample, or the alignment beam upon incidence on the sample can be substantially parallel to the measurement beam upon reflection off the sample. This configuration facilitates a correct and simple alignment or determination of the alignment of the reflectometer system as it can ensure that both beams interact with the sample in a similar manner.

[0012] In embodiments, when the alignment is optimized, the propagation paths of the alignment beam and the measurement beam can substantially overlap on at least a portion of their propagation paths toward the sample. This overlap of optical paths can further improve the accuracy of the alignment or the precision of the alignment determination by ensuring that the beams follow a common path on a portion of their propagation paths toward the sample. These embodiments can also further ensure that the two beams interact with the sample in a similar manner, thereby further improving the reliability of the determined alignment and the alignment process.

[0013] In embodiments, when the alignment is optimized, the measuring beam and the alignment beam can be guided at an angle of up to 16°, preferably up to 12°, and typically close to 8°, relative to the perpendicular incidence to the sample when it is present. In a preferred embodiment, when the alignment is optimized, the measuring beam and the alignment beam can be guided at a substantially perpendicular incidence to the sample when it is present. This configuration can further facilitate determining the alignment of the reflectometer system because it ensures that the two beams interact with the sample in a similar manner. Furthermore, in this configuration, the alignment or precise position of the sample along the beam propagation direction may not be critical for the measured reflectance.

[0014] In embodiments, the alignment radiation source can be positioned near the reflectivity sensor such that the alignment beam is guided in a direction substantially opposite to that of the measurement beam, which, when reflected by the sample in the presence of the sample, is incident on the reflectivity sensor. For example, in these embodiments, the alignment radiation source (such as a laser) can be positioned adjacent to the reflectivity sensor (e.g., a CCD detector). For example, in these embodiments, the optical fiber of the alignment radiation source for providing the alignment beam can be positioned adjacent to the optical fiber of the reflectivity sensor for receiving the measurement beam. This arrangement improves the reliability of reflectivity measurements by preventing the alignment beam from interfering with the measurement beam, thus preventing the alignment beam from being detected by the reflectivity sensor.

[0015] In embodiments, the alignment radiation source can be positioned adjacent to or incorporated into the measurement radiation source, such that the alignment beam and the measurement beam follow similar paths. In these embodiments, the alignment and measurement radiation sources can have similar interactions with all optical elements and with the sample. This arrangement allows for equivalent optical paths for the alignment and measurement beams, and the position sensor can measure the position of the alignment beam on the position sensor, for example, by filtering or removing the signal of the measurement beam based on the different radiation characteristics of the alignment and measurement beams (by the alignment beam having a higher intensity and / or a different spectral composition than the measurement beam and / or by alternately emitting pulses...).

[0016] In embodiments, when the alignment is optimized, the measurement beam and the alignment beam can be guided with non-perpendicular incidence relative to the sample (when the sample is present). In embodiments, when the alignment is optimized, the measurement beam and the alignment beam can be guided at an angle greater than zero relative to the perpendicular incidence to the sample (when the sample is present), preferably from 1° to 20°, more preferably from 3° to 10°. In these embodiments, the optical paths of the measurement beam and the alignment beam can be V-shaped, and the optical path of the beam toward the sample generally does not overlap with the optical path of the same beam reflected from the sample. An advantage of these embodiments is that the number of beam splitters can be limited, thereby limiting the measurement time. The inventors have found that the reproducibility and accuracy of measurements can be particularly good in such reflectometer systems. Preferably, the optical paths are parallel, or substantially overlap at least a portion of their propagation paths. For example, the optical path of the alignment beam toward the sample can be substantially parallel to, or substantially overlap with, the optical path of the measurement beam reflected from the sample; or in other words, the alignment beam and the measurement beam can propagate in opposite directions along substantially the same path at least a portion of their propagation paths. In these embodiments, a beam splitter can be used to guide the aligned beam toward the position sensor.

[0017] In an embodiment, when a sample is present, the diameter of the alignment beam on the sample can be less than half the diameter of the measuring beam on the sample. A smaller diameter of the alignment beam can result in a more precise determination of the alignment of the sample. In an embodiment, when a sample is present, the diameter or width of the alignment beam on the sample can be less than 20%, preferably less than 10%, of the diameter or width of the measuring beam on the sample. This further reduction in the diameter of the alignment beam can provide even greater accuracy in determining the alignment.

[0018] In an embodiment, when the alignment is optimized, the alignment beam and / or measurement beam can be substantially collimated at least at the sample. In an embodiment, when the alignment is optimized, the alignment beam and / or measurement beam can have a beam divergence angle at least at the sample, having a magnitude of up to 16°, preferably up to 12°, more preferably up to 8°, i.e., an absolute value. In an embodiment, when the alignment is optimized, the alignment beam and / or measurement beam can have a beam convergence angle at least at the sample, having a magnitude of up to 16°, preferably up to 12°, more preferably up to 8°, i.e., an absolute value.

[0019] The alignment source can be any type of light source, such as a light-emitting diode or a laser. In a preferred embodiment, the alignment radiation source can be a laser. Using a laser can provide an alignment beam with a narrow width, which is beneficial for achieving precise alignment.

[0020] In this embodiment, the measuring radiation source can be a diffuse light source. A diffuse light source can provide uniform illumination of the sample, which can be important for accurate reflectance measurements. For example, when using a diffuse light source, the intensity of the measuring beam can be substantially uniform along the beam width. This type of light source is commonly used in reflectometer systems to provide uniform illumination over a large area of ​​the sample. Examples of diffuse light sources include frosted bulbs, fluorescent lamps, and light-emitting diodes with diffuse optics, including both continuous and patterned lens and mirror systems. In this embodiment, the measuring radiation source can include a Ulbricht sphere. A Ulbricht sphere helps create a highly diffuse and uniform light source, which can further improve the quality of reflectance measurements. Also known as an integrating sphere, a Ulbricht sphere is typically used in conjunction with a light source to produce diffuse illumination for reflectance measurements in a reflectometer system.

[0021] Using a laser as the alignment radiation source is beneficial for precise alignment, while using a diffused light source (such as an Ulricht sphere) as the measurement radiation source is beneficial for producing uniform illumination across the entire sample surface, which is desirable for accurate reflectivity measurements.

[0022] In one embodiment, the position sensor may include at least two pixels. In another embodiment, the position sensor may include a two-dimensional photodetector, such as a photodetector comprising a two-dimensional pixel array. The use of a two-dimensional photodetector allows for the capture of more detailed spatial information about the position of the alignment beam, which is advantageous for fine-tuning alignment. In another embodiment, the photodetector may be selected from charge-coupled devices (CCDs) and complementary metal-oxide-semiconductor (CMOS) sensors. Using a two-dimensional photodetector (such as a CCD or CMOS sensor) as a position sensor is advantageous because it enables the detection of the position of the alignment beam on the position sensor with generally high accuracy and resolution. In another embodiment, the photodetector may be selected from position-sensitive devices (PSDs) or optical position sensors (OPS), thereby allowing the measurement of the position of a spot on the sensor surface in one or two dimensions. Such a device may require only a limited number of connection pins (e.g., only five) while still being able to determine the (one-dimensional or two-dimensional) position of the spot.

[0023] In an embodiment, the diameter of the alignment beam on the position sensor can be less than half the diameter of the measuring beam on the position sensor. A smaller diameter of the alignment beam can result in a more accurate determination of the sample alignment. In an embodiment, the diameter or width of the alignment beam on the position sensor can be less than 20%, preferably less than 10%, of the diameter or width of the measuring beam on the position sensor. This further reduction in the diameter of the alignment beam can provide even greater accuracy in determining alignment.

[0024] In some embodiments, the photodetector may have a photosensitive area larger than the beam width of the alignment beam at the photodetector. These embodiments ensure that the entire alignment beam is captured by the photodetector, which is important for accurate position measurement. Furthermore, this allows for the detection of larger deviations or sample misalignment.

[0025] In one embodiment, the width of the pixels of the photodetector can be smaller than the beam width of the alignment beam at the photodetector. This pixel size configuration ensures that the photodetector can resolve small spot sizes of the alignment beam, which is preferred for accurate alignment detection.

[0026] In one embodiment, the position sensor is adapted to distinguish the alignment beam from the measurement beam.

[0027] In an embodiment, the wavelength of the measurement beam may differ from the wavelength of the alignment beam. This difference in wavelength helps distinguish the two beams, reduces the possibility of crosstalk, and improves measurement accuracy. In an embodiment, the reflectivity sensor is adapted to separate or filter out the wavelength of the alignment beam. For example, the reflectivity sensor may include a spectral filter for filtering out the wavelength of the alignment beam. For example, the reflectivity sensor may have higher sensitivity for the wavelength of the measurement beam than for the wavelength of the alignment beam. In an embodiment, the wavelength of the measurement beam may be separated by a position sensor. Preferably, the measurement beam may be refracted by a grating, and the refracted measurement beam may be projected onto a one-dimensional or two-dimensional CCD, such that the measurement beam is spectrally separated from the alignment beam, thereby allowing the measurement beam to be detected separately. For example, the position sensor may be adapted to sense light having the wavelength of the alignment beam and not sense light having the wavelength of the measurement beam, for example by using a bandpass filter adapted to allow the alignment beam to pass through and block the measurement beam. Furthermore, a laser or light-emitting diode with a narrow wavelength bandwidth may be selected, which can be easily separated from the spectral composition of the measurement radiation source, or has spectral components outside the sensing wavelength range of the reflectivity sensor.

[0028] In embodiments, the pulses of the measurement beam and / or the alignment beam on one side, and / or the pulses on the reflectivity sensor and / or the position sensor on the other side, can be alternating. In embodiments, the measurement radiation source can be configured to generate pulses of the measurement beam and / or the alignment radiation source can be configured to generate pulses of the alignment beam, and, simultaneously or synchronously with the source, the reflectivity sensor and / or the position sensor can be configured to pulse-like detect the measurement beam and / or the alignment beam. Preferably, the measurement beam is continuous (i.e., not pulsed) to prevent variations in the spectral composition of the measurement beam that may occur due to pulsed emission. The reflectivity sensor can be adapted to pulse-like measure (e.g., continuous) of the measurement beam, wherein the alignment beam is emitted in pulse form during the intervals between pulses or time periods in which the reflectivity sensor measures the measurement beam. In embodiments, the alignment radiation source can be adapted to provide a pulsed alignment beam, and the reflectivity sensor can be adapted to separate or filter out the alignment beam. The alternation of pulses allows for temporal separation of the measurement beam and the alignment beam, enabling the position sensor and / or the reflectivity sensor to distinguish between the measurement beam and the alignment beam. This can reduce potential interference and improve the overall accuracy of the system.

[0029] In this embodiment, the reflectivity sensor is adapted to detect the intensity of a measurement beam after it has been reflected by a sample. The signal from the reflectivity sensor can be used to quantify the amount of light reflected, which is related to the reflectivity of the sample. Examples of reflectivity sensors include photodiodes, photomultiplier tubes, and spectrophotometers.

[0030] In an embodiment, the reflectometer system may further include a beam splitter for separating a portion of the measurement beam before it is reflected by the sample in the presence of a sample, and a reference sensor for detecting the intensity of the separated measurement beam. Typically, the beam splitter is an optical element with a finite absorptivity, such that a portion of the incident radiation is transmitted and a portion is reflected. This portion can be any value typically between 5% and 95%. If the absorptivity is low, the sum of the transmittance and reflectance portions will be close to 100%. The reference sensor can be, for example, a photodiode, a photomultiplier tube, or a spectrophotometer. This feature provides a reference signal for measuring the intensity of the beam, and can therefore be used to calibrate the system and ensure accurate reflectance measurements.

[0031] In one embodiment, the reflectometer system includes a controller for receiving a determined position from a position sensor. The controller may be adapted to compare the determined position with a predetermined area or range, and alignment may be considered optimized when the determined position falls within the predetermined area or range.

[0032] In one embodiment, the reflectometer system may include a sample holder for holding the sample, wherein the sample holder is adapted to displace (e.g., rotate) the sample to optimize the alignment based on the measured position of the alignment beam on a position sensor. This capability can allow for mechanical adjustment of the sample's orientation to achieve optimal alignment, which can be crucial for accurate reflectivity measurements.

[0033] In an embodiment, the reflectometer system may further include a steering mechanism for altering the configuration of the optical elements to improve the alignment of the reflectometer system based on the measured position of the alignment beam on the position sensor. This feature enables dynamic adjustment of the optical path to correct misalignment, thereby enhancing the system's flexibility and accuracy. The optical components whose configuration can be adapted to improve alignment typically include any optical components, and when alignment is optimized, the alignment beam, propagating in its propagation path from the alignment radiation source toward the position sensor, is reflected on the optical component, as is the measurement beam, propagating in its propagation path from the measurement radiation source toward the reflectivity sensor.

[0034] In one embodiment, the reflectometer system may further include a controller for automating the steering mechanism based on a measured position of the alignment beam on a position sensor. Automating the alignment process can increase the system's efficiency and repeatability, reducing the need for manual intervention.

[0035] In embodiments, at least three, more preferably each, selected from a radiation measurement system, an alignment radiation source, a reflectivity sensor, and a position sensor may be located within the same housing, wherein the reflectometer system is configured to analyze samples located outside the housing. In embodiments, the reflectometer system may be configured to analyze samples located at a distance from the housing greater than the beam width of the measurement beam (e.g., at least 5 times the beam width, or even greater than 10 times the beam width). These embodiments can promote flexibility and compatibility between the reflectometer system and different types of samples that can be analyzed.

[0036] The same housing can refer to a single solid housing or chassis containing the at least three components of the reflectometer system. Having the components in the same housing indicates that at least three of the following—the radiation measurement system, the alignment radiation source, the reflectivity sensor, and the position sensor—are all integrated into the same structural unit, which can enhance the stability and portability of the reflectometer system.

[0037] In a second aspect, the present invention relates to an apparatus comprising a reflectometer system according to the embodiment of the first aspect and a vacuum system (e.g., a vacuum sputtering system), the vacuum system comprising a vacuum chamber including an optical window. The optical window may be disposed in an interface flange. The reflectometer system is located outside the vacuum chamber and arranged such that a measurement beam and a alignment beam pass through the optical window for analysis of a sample in the vacuum chamber when a sample is present.

[0038] In a third aspect, the present invention relates to a method for determining the reflectivity of a sample in a reflectometer system, comprising: guiding an alignment beam toward the sample to reflect the alignment beam; measuring the position of the reflected alignment beam on a position sensor; determining the alignment of the reflectometer system based on the measured position; guiding a measurement beam having a beam width greater than that of the alignment beam toward the sample to reflect the measurement beam; and measuring the intensity of the reflected measurement beam to determine the reflectivity. The reflectometer system is configured such that when the alignment of the reflectometer system is optimized, at least a portion of the propagation path of the measurement beam is substantially parallel to at least a portion of the propagation path of the alignment beam.

[0039] After determining the alignment of the reflectometer system, the alignment can be optimized based on the determined alignment. This optimized alignment can be performed before measuring the intensity of the reflected measurement beam to determine the reflectivity. Alternatively, the alignment beam and the measurement beam can be directed to the sample simultaneously, and the determined alignment and optionally optimized alignment can be performed during the measurement of the intensity of the reflected measurement beam to determine the reflectivity. Again, alternatively, alignment optimization may not be performed. For example, the determined position can be compared to a predetermined area or range, and if the determined position falls within the predetermined area or range, the measured reflectivity can be assumed to be accurate, while if the determined alignment falls outside the predetermined area or range, the measured reflectivity can be assumed to be inaccurate.

[0040] Specific and preferred aspects of the invention are set forth in the appended independent and dependent claims. Features from the dependent claims may be suitably combined with features from the independent and other dependent claims, and not merely as expressly stated in the claims.

[0041] The above and other features, characteristics, and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, which illustrate the principles of the invention by way of example only. This description is given for illustrative purposes only and does not limit the scope of the invention. The reference numerals used below refer to the accompanying drawings. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of a reflectometer system according to an embodiment of the present invention.

[0043] Figure 2 This is a schematic diagram of a reflectometer system with optimized sample alignment according to an embodiment of the present invention.

[0044] Figure 3 This is a schematic diagram of a reflectometer system with components integrated within a housing, according to an embodiment of the present invention.

[0045] Figure 4 This is a schematic diagram of a position sensor used in a reflectometer system according to an embodiment of the present invention.

[0046] Figure 5 This is a schematic diagram of a reflectometer system according to an embodiment of the present invention, wherein a light beam is incident on a sample in a non-perpendicular direction.

[0047] Figure 6A This is a schematic diagram of a reflectometer system according to an embodiment of the present invention, which includes a sample, a reference sample, and a light-shielding plate, wherein the reflectometer system is aligned with the sample.

[0048] Figure 6B This is a schematic representation of a cross-sectional view of a branched optical fiber, which includes six fiber filaments for emitting aligned beams and for receiving... Figure 6B The measurement beam of the reflectometer system is a single central fiber filament.

[0049] Figure 7 This is a schematic diagram of a reflectometer system according to claim 6A of an embodiment of the present invention, which includes a sample, a reference sample and a light shield, wherein the reflectometer system is aligned with the reference sample.

[0050] Figure 8 This is a schematic diagram of a reflectometer system according to claims 6A and 7 of the present invention, which includes a sample, a reference sample and a light shield, wherein the reflectometer beam is blocked by the light shield.

[0051] In different accompanying drawings, the same reference numerals refer to the same or similar elements. Detailed Implementation

[0052] The invention will be described with reference to specific embodiments and certain accompanying drawings, but is not limited thereto, but is limited only by the claims. The drawings are illustrative only and are not restrictive. In the drawings, the dimensions of some elements may be exaggerated and not drawn to scale for illustrative purposes. Dimensions and relative dimensions do not correspond to the actual scale-down of the invention.

[0053] Furthermore, the use of terms such as first, second, third, etc., in the specification and claims is to distinguish similar elements and not necessarily to describe sequences, whether temporally, spatially, sequentially, or in any other way. It is to be understood that such terms are interchangeable where appropriate, and the embodiments of the invention described herein can operate in sequences other than those described or illustrated herein.

[0054] Furthermore, the terms top, bottom, above, below, etc., used in the specification and claims are for descriptive purposes and not necessarily for describing relative positions. It is to be understood that such terms are interchangeable where appropriate, and the embodiments of the invention described herein can operate in orientations other than those described or illustrated herein.

[0055] It is important to note that the term "comprising" as used in the claims should not be construed as limiting oneself to the means subsequently listed; it does not exclude other elements or steps. Therefore, it should be interpreted as specifying the presence of the mentioned features, integers, steps, or components, but not excluding the presence or addition of one or more other features, integers, steps, or components, or groups thereof. The term "comprising" thus covers both the presence of only the stated features and the presence of these features along with one or more other features. The term "comprising" according to the invention therefore also includes the absence of further components as a single embodiment. Therefore, the scope of the expression "a device comprising means A and B" should not be construed as limiting oneself to a device consisting only of components A and B. This means that for the present invention, the only relevant components of the device are A and B.

[0056] Similarly, it should be noted that the term "coupling" should not be interpreted as limited to direct connections. The terms "coupling" and "connection," as well as their derivatives, can be used. It should be understood that these terms are not synonyms for each other. Therefore, the scope of the expression "device A is coupled to device B" should not be limited to devices or systems in which the output of device A is directly connected to the input of device B. This implies the existence of a path between the output of A and the input of B, which can be a path that includes other devices or means. "Coupling" can mean two or more elements in direct physical or electrical contact, or two or more elements that are not in direct contact with each other but still cooperate or interact with each other.

[0057] Throughout this specification, references to "an embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in association with that embodiment is included in at least one embodiment of the invention. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing throughout this specification do not necessarily refer to the same embodiment, but may. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments, as will be apparent to those skilled in the art from this disclosure.

[0058] Similarly, it should be understood that in the description of exemplary embodiments of the invention, various features of the invention are sometimes combined in a single embodiment, drawing, or description thereof in order to simplify the disclosure and facilitate understanding of one or more various aspects of the invention. However, this method of disclosure should not be construed as reflecting an intent that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the following claims, inventive aspects lie in fewer than all features of a single foregoing disclosed embodiment. Therefore, the claims immediately following the detailed description are hereby expressly incorporated into that detailed description, wherein each claim exists independently as a separate embodiment of the invention.

[0059] Furthermore, while some embodiments described herein include features not included in other embodiments, combinations of features from different embodiments are intended to be within the scope of the invention and form different embodiments, as will be understood by those skilled in the art. For example, any claimed embodiment may be used in any combination within the following claims.

[0060] Furthermore, some embodiments described herein are described as methods or combinations of methods that can be implemented by a processor of a computer system or other means of performing such functions. Therefore, a processor having the necessary instructions for performing such methods or elements constitutes a means for performing the method or elements of the method. Furthermore, the elements of the device embodiments described herein are examples of means for performing functions performed by those elements for carrying out the invention.

[0061] Numerous specific details are set forth in the specification provided herein. However, it should be understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0062] The following terms are provided only to aid in understanding the invention.

[0063] As used herein and unless otherwise stated, the term "beam width" refers to the diameter or dimension of a beam or other electromagnetic radiation at a specified location along the beam's propagation path, such as on the surface of a sample or at a position sensor. The width can be full width at half height (FWHM) or half-power beam width, or alternatively, 1 / e 2 Beam width is a parameter known in the art for determining beam width. In the case of asymmetric (e.g., non-circular) beam profiles, the width can be the minimum width along the beam propagation path at a given location. Beam width is an important parameter for determining the resolution and accuracy of a reflectometer system. "Smaller beam width" indicates a narrower beam, which is typically used for alignment purposes, while "greater beam width" indicates a wider beam, which is typically used for measurement purposes.

[0064] As used herein and unless otherwise stated, the term "beam divergence angle" refers to the angle at which a beam of light or other electromagnetic radiation propagates from its source or spreads after passing through an optical system. As used herein and unless otherwise stated, the term "beam convergence angle" refers to the angle at which a beam of light or other electromagnetic radiation propagating toward a focal point narrows or converges. The beam convergence angle or divergence angle can be calculated, for example, by the magnitude or absolute value of 2×arctan((w1-w2) / (2×l)), where w1 and w2 are the beam widths at two different locations along the beam propagation path, and l is the distance along the beam propagation path between said two different locations.

[0065] As used herein and unless otherwise stated, a collimated beam refers to a beam or other electromagnetic radiation that has parallel rays or therefore does not diverge or converge over a certain distance. When, for example, it is said that the collimated beam is “substantially collimated” at least at the sample, this can indicate that the collimated beam maintains a substantially consistent beam width as it propagates toward and illuminates the sample.

[0066] The invention will now be described in detail through several embodiments thereof. It will be apparent that other embodiments of the invention can be configured based on the knowledge of those skilled in the art without departing from the technical teachings of the invention, which is limited only by the terms of the appended claims.

[0067] In a first aspect, the present invention relates to a reflectometer system for analyzing samples. The reflectometer system includes a measuring radiation system comprising a measuring radiation source for generating a measuring beam. The reflectometer system includes a reflectivity sensor for detecting the intensity of the measuring beam reflected from the sample in the presence of the sample; an alignment radiation source for generating an alignment beam; a position sensor for measuring the position of the alignment beam reflected from the sample on the position sensor; and optical elements configured to guide the measuring beam and / or the alignment beam toward the sample or to guide the alignment beam toward the position sensor in the presence of the sample. The reflectometer system is adapted to determine the alignment of the system relative to the sample based on the measuring position of the alignment beam. The beam width of the alignment beam is smaller than the beam width of the measuring beam. The beam width may be determined at the sample and / or at the position sensor. The reflectometer system is configured such that when the alignment of the reflectometer system is optimized, at least a portion of the propagation path of the measuring beam is substantially parallel to at least a portion of the propagation path of the alignment beam.

[0068] In a second aspect, the present invention relates to an apparatus comprising a reflectometer system and a vacuum system according to the embodiments of the first aspect, the vacuum system comprising a vacuum chamber including an optical window. The reflectometer system is located outside the vacuum chamber and is arranged such that a measuring beam and an alignment beam propagate through the optical window for analysis of a sample in the vacuum chamber when a sample is present.

[0069] In a third aspect, the present invention relates to a method for determining the reflectivity of a sample in a reflectometer system, comprising guiding an alignment beam toward the sample to reflect the alignment beam, measuring the position of the reflected alignment beam on a position sensor, determining the alignment of the reflectometer system based on the measured position, guiding a measurement beam having a beam width greater than that of the alignment beam toward the sample to reflect the measurement beam, and measuring the intensity of the reflected measurement beam to determine the reflectivity. The reflectometer system is configured such that when the alignment of the reflectometer system is optimized, at least a portion of the propagation path of the measurement beam is substantially parallel to at least a portion of the propagation path of the alignment beam.

[0070] refer to Figure 1 , Figure 1 This is a schematic representation of a reflectometer system (1) according to an embodiment of the present invention, used for analyzing the reflectivity of a sample (2) with high precision. Figure 1 In the middle, sample (2) was not properly aligned with reflectometer system (1).

[0071] The system (1) is designed to optimize the alignment of the sample (2) to ensure accurate measurements. For example... Figure 1As shown, the reflectometer system (1) includes a measuring radiation system having a measuring radiation source (3) that generates a measuring beam (30). The measuring beam (30) propagates toward the sample (2) through an optical element that may include two beam splitters (61, 62). The reflectometer system (1) may include other optical elements, such as mirrors or lenses, for guiding the measuring beam (30) toward the sample (2).

[0072] When alignment is optimized, the measurement beam (30) reflected from the sample (2) is reflected by the first beam splitter (61) toward the reflectivity sensor (4). The reflectivity sensor (4) is used to detect the intensity of the measurement beam (30) after reflection from the sample (2). As can be observed, in Figure 1 In the middle, the measurement beam (30) did not hit the reflectivity sensor (4) because the sample (2) was not aligned with the reflectometer system (1).

[0073] In the example shown, the second beam splitter (62) partially separates the measurement beam (30) toward the reference sensor (33) before it is reflected from the sample (2), as... Figure 1 As shown. Alternatively, the system (1) may use a first beam splitter (61), or may include yet another different beam splitter for partially splitting the measurement beam (30) toward the reference sensor (33) before it is reflected from the sample (2). The reference sensor (33) detects the intensity of the split measurement beam (32), thereby providing a reference signal for calibration of the intensity of the measurement beam (30) detected by the reflectivity sensor (4). In the example shown, the controller (8) may receive signals from the reference sensor (33) and from the reflectivity sensor (4), and may determine the reflectivity of the sample (2) based on these signals.

[0074] The system (1) also includes an alignment radiation source (5) that generates an alignment beam (50) having a smaller beam width than the measurement beam (30). The alignment radiation source (5) can be any kind of radiation source (5), such as a laser diode or an LED. In the example shown, the alignment beam (50) is reflected by a first beam splitter (61) to orient the alignment beam (50) toward the sample (2). The first beam splitter (61) is arranged such that the alignment beam (50) incident on the sample (2) and the measurement beam (30) incident on the sample (2) are substantially parallel. In the example shown, after the alignment beam (50) is reflected back by the sample (2), it passes through the first beam splitter (61) and is reflected by a second beam splitter (62) to a position sensor (7), which measures the position of the alignment beam (50) on the position sensor (7) after the alignment beam is reflected by the second beam splitter (62). Since the alignment beam (50) incident on the sample (2) and the measurement beam (30) incident on the sample (2) are basically parallel, the beams (30, 50) are also basically parallel after being reflected by the sample (2).

[0075] The reflectometer system (1) uses information about the position of the alignment beam (50) on the position sensor (7) to determine the alignment of the sample (2). The position sensor (7) may include any type of position-sensitive device. The position sensor (7) may include, for example, a one-dimensional or two-dimensional array having at least two pixels, any type of camera, or any type of position-sensitive device. The position sensor (7) may include a two-dimensional photodetector (7), such as a charge-coupled device or a complementary metal-oxide-semiconductor sensor, preferably having a pixel width smaller than the beam width of the alignment beam (50). In addition, the position sensor (7) may include, for example, a position-sensitive device (PSD) or an optical position sensor (OPS), allowing the position of the light spot on the sensor surface to be measured in one or two dimensions.

[0076] This ensures that the photodetector (7) can resolve the small spot size of the alignment beam (50) for accurate alignment detection.

[0077] The smaller diameter of the alignment beam (50) allows for more precise determination of the alignment of the sample (2).

[0078] The controller (8) can receive information about the position of the alignment beam (50) on the position sensor (7). The alignment beam (50) can be distinguished from the measurement beam (30) in several ways. In the example shown, the alignment beam (50) and the measurement beam (30) are parallel to each other but spatially separated, such that the position sensor (7) can detect the alignment beam (50) separately from the measurement beam (30). Alternatively, the alignment beam (50) can have a different spectral composition or wavelength than the measurement beam (30). The position sensor (7) can be adapted to distinguish the wavelength of the alignment beam (50) from the wavelength of the measurement beam (30), or the system (1) can include a spectral filter to allow the alignment beam (50) to propagate toward the position sensor (7) but block the measurement beam (30) from propagating toward the position sensor (7). Alternatively, pulses from the measuring beam (30) can be alternated with pulses from the alignment beam (50), so that the position sensor (7) can distinguish the beams (30, 50) because of the different times the beams (30, 50) are incident on the position sensor (7).

[0079] Based on the determined position of the alignment beam (50) on the position sensor (7), for example by comparing the determined position with a predetermined position, or by determining whether the determined position falls within a predetermined area or range, the alignment of the reflectometer system (1) can be optimized. Specifically, in the example shown, the sample (2) can be moved (e.g., rotated). For example, the sample (2) can be positioned in a sample holder (not shown), and the controller (8) can cause the sample holder to move, for example, rotate the sample (2).

[0080] exist Figure 2 In the example shown, the reflectometer system (1) is shown after the sample (2) has been rotated, such that the alignment is optimized, for example, such that the alignment beam (50) is incident on the position sensor (7) within a predetermined area. In the example shown, when the alignment is optimized, the measurement beam (30) and the alignment beam (50) are incident on the sample (2) at perpendicular incidence.

[0081] The high precision of the alignment can be achieved, especially when the position sensor (7) is farther from the sample (2) than the reflectivity sensor (4) used to measure the source signal of the reflection. Indeed, the length of the propagation path of the alignment beam (50) from the sample (2) to the position sensor (7) is preferably greater than the length of the propagation path of the measurement beam (30) from the sample (2) to the reflectivity sensor (4) (when the alignment of the system (1) is optimized).

[0082] In the example shown, the alignment radiation source (5) is positioned near the reflectivity sensor (4) to prevent interference between the alignment beam (50) and the measurement beam (30). Indeed, when alignment is optimized, the alignment beam (50) propagates in substantially opposite directions relative to the measurement beam (30), and the alignment beam (50) is unlikely to incident on the reflectivity sensor (4). Furthermore, the beams (30, 50) are parallel to each other at least at the sample (2), which facilitates proper alignment of the reflectometer system (1) based on the detection of the alignment beam (50) by the position sensor (7). More specifically, in the example shown, when alignment is optimized (such as... Figure 2 As shown in the diagram, the alignment beam (50) from the alignment radiation source (5) via the first beam splitter (61) to the sample (2) and the measurement beam (30) from the sample (2) via the first beam splitter (61) to the reflectivity sensor (4) propagate along substantially parallel paths.

[0083] In the example shown, the method for determining the reflectivity of the sample (2) involves guiding an alignment beam (50) toward the sample (2), measuring the position of the reflected alignment beam (50), determining the alignment of the system (1) based on this measurement, and guiding a measurement beam (30) toward the sample (2) to measure the intensity of the reflected measurement beam (30). The guiding of the alignment beam (50) and the measurement beam (30) toward the sample (2) can overlap in time. While the alignment of the system (1) can be optimized based on the determined alignment, this is not necessary. For example, alternatively, the determined alignment can be used to calibrate the measured reflectivity. Alternatively, the measured reflectivity can be considered acceptable or sufficiently accurate when the determined position of the alignment beam (50) on the position sensor (7) falls within a predetermined range.

[0084] Figure 3 A variation of the reflectometer system (1) is described, in which the measuring radiation source (3), the aligning radiation source (5), the reflectivity sensor (4), and the position sensor (7) are all located within the same housing (9). In the example shown, the controller (8) is adapted to control the position of the first beam splitter (61). The orientation of the first optical element (61) can be adjusted by a combination of rotation and translation of the beam splitter (61). The system (1) is aligned when the aligning beam (50) hits a predetermined position on the position sensor (7), thereby ensuring that the measuring beam (30) is incident on the reflectivity sensor (4). The reflectometer system (1) is configured such that when the position of the aligning beam (50) is incident on the predetermined position of the position sensor (7), the reflectometer system (1) is aligned such that the measuring beam (30) is incident on the reflectivity sensor (4). In the example shown, when the alignment is optimized (e.g. Figure 3When the alignment is optimized (as shown), the beams (30, 50) are substantially parallel at sample (2). In the example shown, when the alignment is optimized (as shown), the beams (30, 50) are substantially parallel at sample (2). Figure 3 As shown, beams (30, 50) can be incident on the sample (2) at an angle different from that of perpendicular incidence. This may be to optimize the alignment by aligning different optical components instead of aligning the sample (2), specifically, in the example shown, the different optical component is the first beam splitter (61). Indeed, since the alignment beam (50) is reflected in its propagation path from the alignment radiation source (5) toward the position sensor (7), and the measurement beam (30) is reflected in its propagation path from the measurement radiation source (3) toward the reflectivity sensor (4), the realignment of the first beam splitter (61) realigns the propagation paths of the alignment beam (50) toward the position sensor (7) and the measurement beam (30) toward the reflectivity sensor (4). Therefore, the alignment optimization of the alignment beam (50) can be carried out together with the alignment optimization of the measurement beam (30), or in other words, the propagation directions of the two beams (30, 50) can be adjusted simultaneously, so that when the position of the alignment beam (50) on the position sensor (7) is optimized, the alignment of the measurement beam (30) relative to the reflectivity sensor (4) is also optimized.

[0085] In the example shown, the sample (2) is located outside the housing (9). A light beam (30, 50) can exit the housing (9) towards the sample (2) through an opening, and after being reflected by the sample (2), the light beam (30, 50) can re-enter the housing (9) through the same opening (90). Therefore, in the example shown, it may be difficult to align the sample (2) by, for example, rotating it. However, the advantage of this configuration is that the housing (9) and portions of the system (1) located therein can be easily installed, while the alignment of the system (1) can still be optimized regardless of the specific orientation of the housing (9) relative to the sample (2).

[0086] Figure 4 An exemplary position sensor (7) is shown, comprising a two-dimensional array (70) of pixels (71), for example, 12x12 pixels (71) in the example shown. In contrast to the large spot (31) used to measure the beam, the narrow spot (51) used to align the beam provides high precision for determining the alignment of the reflectometer system (1). Different spot sizes are caused by different beam widths. Determining the location of the center of the broadband spot (31) on the position sensor (7) can lead to a large error in the determined location. Furthermore, in practice, the size of the larger spot (31) used to measure the beam may be larger than the photosensitive area (70) of the position sensor (7).

[0087] In the example shown, the alignment of the sample or system is considered optimized when the narrow spot (51) used for alignment beam is incident on the center of the position sensor (7). Therefore, in the example shown, the alignment is considered optimized.

[0088] Conversely, when alignment is not optimized, the position sensor (7) can detect the spot (51) of the alignment beam at a location far from the center of the position sensor (7). For example, as Figure 1 As in the example, sample (2) can be slightly tilted or misaligned. In this case, the alignment of the system can be optimized, wherein the alignment is considered optimized when the narrow spot (51) used for the alignment beam is incident on the center of the position sensor (7). Alternatively, a signal from the reflectivity sensor can be received when the deviation of the narrow spot (51) on the position sensor (7) is within a given boundary, and the signal from the reflectivity sensor can be corrected based on the signal read from the position sensor (7), or the signal from the reflectivity sensor can be ignored when the alignment is considered not optimized.

[0089] refer to Figure 5 This is a schematic representation of another reflectometer system (10) according to an embodiment of the present invention for analyzing the reflectivity of a sample (2) with high precision.

[0090] The reflectometer system (10) includes a measuring radiation source (3) for generating a measuring beam (30) and an alignment radiation source (5) for generating an alignment beam (50). Here, the diameter of the alignment beam (50) is smaller than the diameter of the measuring beam (30), for example, at least at the sample. In the example shown, when the reflectometer system (10) is aligned, the measuring beam (30) and the alignment beam (50) are incident on the sample (2) with non-perpendicular incidence. As a result, the optical paths of the beams (30, 50) are V-shaped. In the example shown, the measuring beam (30) and the alignment beam (50) follow substantially parallel optical paths (but in opposite directions) for at least a portion of their propagation paths—in the example shown, for most of them. As a result, the orientation of the sample (2) has a similar effect on the two beams (30, 50), which facilitates alignment. However, parallel optical paths are not essential, and alternatively, the optical paths can be non-parallel, which can limit crosstalk.

[0091] In the example shown, the reflectometer system (10) includes a position sensor (7). The position sensor (7) measures the position of the alignment beam (50) reflected from the sample (2) on the position sensor (7), which can be used to determine whether the reflectometer system (10) is correctly aligned. In addition, the reflectometer system (10) includes a sensor (33) for detecting the intensity of the separated measurement beam (32). The reflectometer system (10) also includes a reflectivity sensor (4) for detecting the intensity of the measurement beam (30) reflected from the sample (2).

[0092] The advantage of the reflectometer system (10) shown is that, since the beams (30, 50) are incident non-perpendicularly, the number of beam splitters (62) can be limited. In the example shown, a single beam splitter (62) is used to direct the alignment beam (50) toward the position sensor (7) and to direct a portion of the measurement beam (30) toward a sensor (33) for detecting the intensity of the separated measurement beam (32). Alternatively, in other examples above, additional beam splitters are used to deflect the measurement beam (30) after reflection from the sample (2) from the path of the measurement beam (30) before reflection, and to deflect the alignment beam (50) toward the sample (2) perpendicularly. The fewer beam splitters (62) used, the higher the signal at the sensors (4, 7), and the shorter the measurement time required to achieve accurate and repeatable measurements. In the current embodiment, it is preferred that the transmission level of the beam splitter (62) is greater than its reflection level.

[0093] refer to Figure 6A This is a schematic representation of another exemplary reflectometer system (10) according to an embodiment of the present invention, which can switch between a test sample (2), a reference sample (21), and a light shield (22).

[0094] exist Figure 6AIn this system, a reflectometer system (10) is aligned on a sample (2) for analyzing the sample (2), for example, for determining the reflectivity or reflectivity of the sample (2). The reflectometer system (10) includes a measuring radiation source (3) for generating a measuring beam (30) and an alignment radiation source (5) for generating an alignment beam (50), the measuring radiation source being, for example, an Ulbricht sphere or an integrating sphere. A beam splitter (62) is configured to direct the alignment beam (50) reflected from the sample (2) toward a position sensor (7). The beam splitter (62) is also configured to direct a portion of the measuring beam (30) toward a sensor (33) for detecting the intensity of the separated measuring beam (32). The reflectometer system (10) includes a sensor (33) for detecting the intensity of the separated measuring beam (32). The reflectometer system (10) also includes a reflectivity sensor (4) for detecting the intensity of the measuring beam (30) reflected from the sample (2).

[0095] The position sensor (7) measures the position of the alignment beam (50) reflected by the sample (2) on the position sensor (7), which can be used to determine whether the reflectometer system (10) is correctly aligned. In the example shown, the reflectometer system (10) includes a lens (72) for focusing the reflected alignment beam (50) onto the position sensor (7), which can result in improved sensitivity and accuracy of alignment.

[0096] In the reflectometer system (10) of this example, the reflectivity sensor (4) and the alignment radiation source (5) include optical fiber filaments contained in a branched fiber, for receiving the measurement beam (30) and providing the alignment beam (50), respectively. Figure 6B This is a schematic cross-sectional representation of a branched optical fiber, in the example shown, which includes six fiber filaments (5) for emitting an alignment beam (50) surrounding a single central fiber filament (4) for receiving a measurement beam. However, alternatively, a single fiber filament may be used to provide the alignment beam (50), or more than six fiber filaments (5) may be provided, and the fiber filaments (5) may be provided in a different configuration than the fiber filament (4) surrounding the central measurement beam; the invention is not limited thereto.

[0097] In this example, a lens (54) is provided or arranged for coupling the measurement beam to the optical fiber filament of the reflectivity sensor (4). The lens (54) is also arranged to provide a substantially parallel or substantially collimated alignment beam (50). The measurement beam fiber filament (4) can be optically coupled to a detector for sensing the measurement beam signal. The alignment beam fiber filament (5) can be optically coupled to any source, such as a laser or LED configured to generate the alignment beam (50). The sample (2) can be analyzed, for example, a signal of reflectivity or reflectivity of the sample (2) can be detected. The sensor (33) can detect the intensity of the separated measurement beam (32), which can be used to calibrate the signal. The reflectometer system (10) can include a lens (34) for focusing the separated measurement beam (32) onto the sensor (33). Alternatively, the sensor (33) can include an optical fiber, and the lens (34) can be used to couple the separated measurement beam (32) into the optical fiber. The optical fiber can be coupled to a detector of the sensor (33) for detecting the separated measurement beam (32).

[0098] exist Figure 7 In this example, sample (2) has been removed from the propagation path of beam (30, 50) to expose reference sample (21) onto which beam (30, 50) is now incident. In the example shown, reflectometer system (10) is now aligned on reference sample (21) for detecting reflection from reference sample (21). Due to the different positions of reference sample (21) and sample (2), and Figure 6A In contrast, the realignment of the reflectometer system (10) may have been performed, which can be based on the signal measured by the position sensor (7), as in other examples. Preferably, the realignment is minimized. Furthermore, for accuracy and consistency, considering the angular dependence of reflectivity on the surface, it is preferable that the angle of incidence of the measurement beam (30) on the reference sample (21) when analyzing the reference sample (21) is substantially the same as the angle of incidence of the measurement beam (30) on the sample (2) when analyzing the sample (2) (e.g., Figure 6A (as in the example). A reference sample (21) can be analyzed; for example, a signal for the reflectivity or reflectance of the reference sample (21) can be detected. This reference measurement can be used to correct the signal detected for the sample (2).

[0099] Figure 8This is a schematic representation of a reflectometer system (10), in which a light-shielding plate (22) has been positioned in the propagation path of the beams (30, 50). The light-shielding plate (22) is generally adapted to prevent the measurement beam (30) from being detected by the reflectivity sensor (4). The light-shielding plate (22) may also be adapted to prevent the alignment beam (50) from being detected by the position sensor (7). The light-shielding plate (22) is preferably optically absorptive towards the measurement beam (30). The light-shielding plate (22) is preferably optically absorptive towards the alignment beam (50). When the measurement beam (30) is blocked by the light-shielding plate, a dark measurement can be performed by the reflectivity sensor (4). This dark measurement can be used to correct the background signal of the signal detected for the sample (2) and the reference sample (21). For example, the dark measurement signal can be subtracted from the reflectivity signal of the measured sample (2). For example, the dark measurement signal can be subtracted from the reflectivity signal of the measured reference sample (21).

[0100] Although in the above examples the measuring beam and the alignment beam are generally guided in substantially opposite directions along at least a portion of their propagation paths, the invention is not limited thereto. For example, alternatively, the measuring beam and the alignment beam may be guided in substantially the same direction along at least a portion of their propagation paths.

[0101] It should be understood that although preferred embodiments, specific constructions and configurations, and materials of the device according to the invention have been discussed, various changes or modifications in form and detail may be made without departing from the scope of the invention. Steps may be added to or removed from the methods described within the scope of the invention.

Claims

1. A reflectometer system (1, 10) for analyzing a sample (2), comprising: The measurement radiation system includes a measurement radiation source (3) for generating a measurement beam (30). A reflectivity sensor (4) is used to detect the intensity of the measurement beam (30) after reflection from the sample when the sample (2) is present. Alignment radiation source (5) for generating alignment beam (50), and A position sensor (7) is used to measure the position of the beam (50) reflected from the sample (2) on the position sensor (7), and The reflectometer system (1, 10) is adapted to determine the alignment of the system (1, 10) relative to the sample (2) based on the measurement position of the alignment beam (50). The beam width of the alignment beam (50) is smaller than the beam width of the measurement beam (30), wherein the reflectometer system (1, 10) is configured such that when the alignment of the reflectometer system (1, 10) is optimized, at least a portion of the propagation path of the measurement beam (30) is substantially parallel to at least a portion of the propagation path of the alignment beam (50).

2. The reflectometer system (1, 10) according to claim 1, wherein, When the alignment is optimized, the propagation path of the alignment beam (50) and the propagation path of the measurement beam (30) substantially overlap in at least a portion of their propagation paths toward the sample (2).

3. The reflectometer system (1) according to claim 1 or 2, wherein, When the alignment is optimized, the measurement beam (30) and the alignment beam (50) are guided at an angle of up to 16°, preferably up to 12°, for example typically 8°, relative to the vertical incidence to the sample (2) when the sample is present.

4. The reflectometer system (1, 10) according to any one of claims 1 to 3, wherein, The alignment radiation source (5) is positioned near the reflectivity sensor (4) such that the alignment beam (50) is guided in a direction substantially opposite to that of the measurement beam (30) that is incident on the reflectivity sensor (4) after being reflected by the sample (2) in the presence of the sample (2).

5. The reflectometer system (1, 10) according to any of the preceding claims, wherein, When the sample (2) is present, the diameter of the alignment beam (50) on the sample (2) is less than half the diameter of the measurement beam (30) on the sample (2).

6. The reflectometer system (1, 10) according to any of the preceding claims, wherein, The position sensor (7) includes a two-dimensional photodetector.

7. The reflectometer system (1, 10) according to any of the preceding claims, wherein, The wavelength of the measuring beam (30) is different from the wavelength of the aligning beam (50).

8. The reflectometer system (1, 10) according to claim 7, wherein, The reflectivity sensor (4) is adapted to separate or filter the wavelength of the aligned beam (50).

9. The reflectometer system (1, 10) according to any of the preceding claims, wherein, The pulses of the measuring beam (30) and / or the alignment beam (50) on one side, and / or the pulses on the reflectivity sensor (4) and / or the position sensor (7) on the other side, are alternated.

10. The reflectometer system (1, 10) according to any of the preceding claims, wherein, The alignment radiation source (5) is adapted to provide an alignment beam (50) for pulsed emission, and the reflectivity sensor (4) is adapted to separate or filter out the alignment beam (50).

11. The reflectometer system (1, 10) according to any of the preceding claims further includes a beam splitter (62) for separating a portion of the measurement beam (30) before the measurement beam is reflected by the sample (2) in the presence of the sample (2), and a sensor (33) for detecting the intensity of the separated measurement beam (32).

12. The reflectometer system (1, 10) according to any of the preceding claims, comprising a sample holder for holding the sample (2), wherein, The sample holder is adapted to displace the sample (2) based on the measurement position of the alignment beam (50) to optimize the alignment.

13. The reflectometer system (1, 10) according to any of the preceding claims further includes optical elements (61, 62) configured to direct the measurement beam (30) and / or the alignment beam (5) toward the sample (2) and / or direct the alignment beam (5) toward the position sensor (7) in the presence of the sample (2).

14. The reflectometer system (1, 10) according to claim 13 further includes a steering device for changing the configuration of optical elements (61, 62) to improve the alignment of the reflectometer system (1, 10) based on the measured position of the alignment beam (50) on the position sensor (7).

15. The reflectometer system (1, 10) according to claim 14 further includes a controller (8) for automatically controlling the steering device based on the measured position of the alignment beam (50) on the position sensor (7).

16. The reflectometer system (1, 10) according to any of the preceding claims, wherein at least three selected from the radiation measurement system (1, 10), the alignment radiation source (5), the reflectivity sensor (4) and the position sensor (7) are located in the same housing (9), wherein the reflectometer system (1, 10) is configured to analyze a sample (2) located outside the housing (9).

17. The reflectometer system (1, 10) according to claim 16, wherein, The reflectometer system (1, 10) is configured to analyze a sample (2) located at a distance from the housing (9) greater than the beam width of the measuring beam (30), for example, the distance is greater than at least 5 times the beam width, or even greater than 10 times the beam width.

18. An apparatus comprising a reflectometer system (1, 10) according to any one of the preceding claims and a vacuum system, the vacuum system comprising a vacuum chamber including an optical window, The reflectometer system (1, 10) is located outside the vacuum chamber and is arranged such that the measurement beam and the alignment beam propagate through the optical window for analysis of the sample (2) in the vacuum chamber when the sample is present.

19. A method for determining the reflectance of a sample (2) in a reflectometer system (1, 10), comprising: The alignment beam (50) is directed toward the sample (2) to reflect the alignment beam (50). The position of the reflected aligned beam (50) on the position sensor (7) is measured. The alignment of the reflectometer system (1, 10) is determined based on the measurement position. A measurement beam (30) with a beam width greater than that of the alignment beam (50) is directed toward the sample (2) to reflect the measurement beam (30), and The intensity of the reflected measurement beam (30) is measured to determine the reflectivity. The reflectometer system (1, 10) is configured such that when the alignment of the reflectometer system (1, 10) is optimized, at least a portion of the propagation path of the measurement beam (30) is substantially parallel to at least a portion of the propagation path of the alignment beam (50).

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