Measurement system for measuring a thickness of a layer on a substrate, deposition apparatus, method of measuring a thickness of a layer on a substrate, and method of controlling a thickness of a layer on a substrate

Abstract

A substrate (100) configured for measuring a thickness of a layer on the substrate (10) is described. The substrate (10) includes an optical coupling element (14) provided on a frontside (10F) of the substrate (10), wherein a metal film (11) is provided on the optical coupling element (14). Additionally, a measurement system configured to measure a thickness of a layer on a substrate, a deposition apparatus and a method of measuring a thickness of a layer on a substrate are described.

Description

MEASUREMENT SYSTEM FOR MEASURING A THICKNESS OF A LAYER ON A SUBSTRATE, DEPOSITION APPARATUS, METHOD OF MEASURING A THICKNESS OF A LAYER ON A SUBSTRATE, AND METHOD OF CONTROLLING A THICKNESS OF A LAYER ON A SUBSTRATETECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to measurement systems for measuring a layer thickness on a substrate. Further embodiments of the present disclosure relate to deposition apparatuses having a layer thickness measurement system. Yet further embodiments relate to methods of measuring layer thickness and methods of controlling layer thickness.BACKGROUND

[0002] For devices comprising thin film layers, such as OLED devices, meticulous control of film thickness is imperative to meet stringent performance specifications and uphold overall quality standards. Particularly in the realm of OLED devices, a thickness repeatability of ±2% between substrates is the established norm, with an escalating demand for even tighter tolerances to achieve superior device performance and elevate overall quality.

[0003] In pursuit of highly accurate thickness control, the ongoing development involves the implementation of in-situ thickness measurement techniques. However, it is essential to acknowledge that existing solutions, such as spectroscopic reflectometry and spectroscopic ellipsometry, exhibit certain limitations.

[0004] Spectroscopic reflectometry encounters limitations in providing the required sensitivity when dealing with ultra-thin layers, specifically those with thicknesses of 20nm or less. This method faces difficulties in accurately discerning the thickness of each individual layer within a multi-layered structure,demanding dedicated measurement spots for precise characterization.

[0005] Spectroscopic ellipsometry offers the capability to measure extremely thin layers, even as thin as 10nm or less, with the necessary sensitivity. However, it comes with the trade-off of requiring a larger system footprint and a more extended measurement duration. While it provides the potential to measure the thickness of individual layers in a multi-layered structure, the process necessitates a larger system size and incurs a time overhead.

[0006] Accordingly, there is a demand for improved approaches for measuring layer thickness on a substrate which at least partially overcome one or more of the disadvantages of the state of the art.SUMMARY

[0007] In light of the above, a substrate configured for measuring a thickness of a layer the substrate, a measurement system configured to measure a thickness of a layer on a substrate, a deposition apparatus for depositing material on a substrate, a method of measuring a thickness of a layer on a substrate, and a method of controlling a thickness of a layer on a substrate according to the independent claims are provided. Further aspects, benefits, and features of the present disclosure are apparent from the claims, the description, and the accompanying drawings.

[0008] According to an aspect of the present disclosure, a substrate configured for measuring a thickness of a layer on the substrate. The substrate includes an optical coupling element provided on a frontside of the substrate and a metal film on the optical coupling element.

[0009] According to another aspect of the present disclosure, a method of manufacturing a substrate configured for measuring a thickness of a layer on the substrate is provided. The method includes providing an optical coupling element on a frontside of the substrate by using lithography. Further, the method includes providing a metal film on at least a part of the optical coupling element.In particular, the substrate is a substrate according to any embodiments describe herein.

[0010] According to a further aspect of the present disclosure, a measurement system configured to measure a thickness of a layer on a substrate according to any embodiments described herein is provided. The measurement system includes a light source to provide light to the optical coupling element from a backside of the substrate. Additionally, the measurement system includes a detector for detecting reflected light from the metal film.

[0011] According to another aspect of the present disclosure, a deposition apparatus for depositing material on a substrate is provided. The deposition apparatus, includes a vacuum deposition chamber, a deposition source provided inside the vacuum deposition chamber, and a measurement system according to any embodiments described herein.

[0012] According to a further aspect of the present disclosure, a method of measuring a thickness of a layer on a substrate is provided. The method includes providing light to an optical coupling element from a backside of the substrate. The optical coupling element is provided on a frontside of the substrate. A metal film is provided on the optical coupling element. Additionally, the method includes exciting surface plasmon polaritons on a surface of the metal film. Further, the method includes detecting light reflected from the metal film.

[0013] According to yet another aspect of the present disclosure, a method of controlling a thickness of a layer on a substrate is provided. The method includes depositing a first layer on the substrate. Further, the method includes measuring a first thickness of the first layer by employing the method of measuring a thickness of a layer on a substrate according to any embodiments described herein. Additionally, the method includes conducting a first analysis of the measured first thickness of the first layer, with respect to a deviation from a target layer thickness of the first layer, based on an optical model for the firstlayer. Further, the method includes feeding the analysis result back to a deposition rate controller for adjusting the deposition rate for a subsequent first layer deposition on a further substrate. Moreover, the method includes updating the optical model based on the analysis result. The updated optical model is used for conducting a second analysis of a measured second thickness of a second layer, with respect to a deviation from a second target layer thickness of the second layer.

[0014] Embodiments are also directed at apparatuses for carrying out the disclosed methods and include apparatus parts for performing each described method aspect. These method aspects may be performed by way of hardware components, a computer programmed by appropriate software, by any combination of the two or in any other manner. Furthermore, embodiments according to the disclosure are also directed at methods for operating the described apparatus. The methods for operating the described apparatus include method aspects for carrying out every function of the apparatus.BRIEF DESCRIPTION OF THE DRAWINGS

[0015] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described in the following:

[0016] FIG. 1A shows a schematic sectional view of a substrate according to embodiments of the present disclosure;

[0017] FIGS. 1 B to 8 show schematic sectional views of a substrate according to embodiments of the present disclosure together with a measurement system according to embodiments describe herein;

[0018] FIG. 9 shows a top view of the exemplary embodiment of FIG.8;

[0019] FIG. 10 shows a schematic sectional view of a measurement system according to a further embodiment of the present disclosure;

[0020] FIGS. 11A-11 C show schematic sectional views of a deposition apparatus for depositing material on a substrate according to embodiments of the present disclosure;

[0021] FIG. 12 shows a block diagram for illustrating a method of measuring a thickness of a layer on a substrate according to embodiments of the present disclosure; and

[0022] FIG. 13 shows a block diagram for illustrating a method of controlling a thickness of a layer on a substrate according to embodiments of the present disclosure.DETAILED DESCRIPTION OF EMBODIMENTS

[0023] Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in each figure. Each example is provided by way of explanation and is not meant as a limitation. For example, features illustrated or described as part of one embodiment can be used on, or in conjunction with, any other embodiment to yield yet a further embodiment. It is intended that the present disclosure includes such modifications and variations.

[0024] Within the following description of the drawings, the same reference numbers refer to the same or to similar components. Generally, only the differences with respect to the individual embodiments are described. Unless specified otherwise, the description of a part or aspect in one embodiment can apply to a corresponding part or aspect in another embodiment as well.

[0025] With exemplary reference to FIG. 1A, a substrate 10 configured for measuring a thickness of a layer on the substrate 10 according to embodiments of the present disclosure is described. According to embodiments, which can be combined with other embodiments described herein, the substrate 100 includesan optical coupling element 14 provided on a frontside 10F of the substrate 10. In particular, the optical coupling element 14 is in contact with the frontside 10F of the substrate 10. The substrate 10 further includes a metal film 11 provided on the optical coupling element 14. In particular, the metal film 11 is a coating provided on the optical coupling element 14.

[0026] FIG. 1 B shows a measurement system 100 configured to measure a thickness of a layer on a substrate 10 according to embodiments of the present disclosure. According to embodiments, which can be combined with other embodiments described herein, the measurement system 100 includes a light source 120. The light source is configured to provide light to the optical coupling element 14 from a backside 10B of the substrate 10. Further, the measurement system 100 includes a detector 130. The detector is configured to detect reflected light from the metal film 11 . An exemplary light path 122 from the light source 120 to the detector 130 is indicated in FIG.1 .

[0027] Accordingly, the substrate according to embodiments described herein is beneficially configured for measuring and monitoring layer thickness on the substrate by surface plasmon resonance. Further, the substrate has the advantage that a thickness of a layer on the substrate can be measured and monitored in real-time during material deposition on the substrate. Further, by integrating an optical coupling element directly onto the substrate, the need for external optical components, such as prisms, is eliminated, thereby simplifying the overall design and fabrication process. Moreover, the integration of the optical coupling element directly onto the substrate enhances system robustness by reducing reliance on external alignments and minimizing mechanical or environmental vulnerabilities. Additionally, the elimination of external components, such as separate prisms, lowers material costs and assembly complexity, resulting in a more cost-effective solution. Moreover, the integrated optical coupling element ensures precise and consistent light delivery to the metal film, optimizing the conditions for efficient surface plasmon resonance (SPR) and improving system performance.

[0028] Surface plasmon resonance (SPR) is a phenomenon that occurs when surface plasmons oscillate in response to the interaction with electromagnetic waves at the interface between a dielectric (e.g. glass) and a metal film, particularly a thin metal film. When light strikes a metal-dielectric interface at a specific angle (known as the resonance angle), it can excite surface plasmon polaritons on the metal surface. When electromagnetic waves internally reflect at any interface, they create an evanescent wave that extends into the adjacent medium. An evanescent wave does not propagate as an electromagnetic wave and decays exponentially with distance from the interface. FIG. 1 schematically indicates the surface plasmon 12 and the evanescent wave 13. The evanescent wave penetrates a short distance into the medium adjacent to the metal surface and propagates to the interface plane for a short distance. Therefore, the evanescent wave can be coupled with surface plasmons resulting in excitation of surface plasmon polaritons under specific conditions. The coupling condition is highly sensitive to changes in the refractive indices and the thickness in the medium where the evanescent wave exists. When molecules attach to the metal surface, the refractive indices and the thickness change, leading to alterations in the characteristics of the surface plasmon resonance. By monitoring the changes in the characteristics of surface plasmon resonance, such as changes in intensity at certain angle(s) and wavelength(s), it is possible to detect and quantify interactions at the metaldielectric interface. The changes in the characteristics of the surface plasmon resonance can be detected by analyzing the light reflected from the metal film.

[0029] In the present disclosure, a "substrate configured for measuring a thickness of a layer on the substrate" can be understood as a substrate specifically configured to facilitate to measure and determine a thickness of a layer deposited on the substrate surface. In particular, the substrate as described herein is configured to facilitate the measurement and monitoring of a thickness of a layer in real-time during layer deposition, particularly by using SPR. In other words, the substrate is configured to exploit the SPR phenomenon for the determination of a film thickness on the substrate.

[0030] In the present disclosure, a "substrate" can be understood as a material or object onto which some form of processing, treatment, or material deposition is applied. In particular, the substrate can be a large area substrate as described herein. Typically, the substrate is of transparent material, e.g. transparent glass or transparent plastic. A “frontside of the substrate”, as used herein, refers to the surface of the substrate designated for material deposition. In other words, the frontside of the substrate is the functional side where deposition processes are intended to occur. Accordingly, a “backside of the substrate”, as used herein, refers to the surface of the substrate opposite to the frontside.

[0031] According to embodiments, which can be combined with other embodiments described herein, the substrate thickness T can be selected from a range 0.1 mm < T < 1.8 mm, particularly 0.1 mm < T < 0.9 mm, such as 0.5 mm. The term “substrate” as used herein may particularly embrace substantially inflexible substrates, e.g., a glass plate, a plastic plate or other suitable substrates. However, the present disclosure is not limited thereto and the term “substrate” may also embrace flexible substrates such as a web or a foil. The term “substantially inflexible” is understood to distinguish over “flexible”. Specifically, a substantially inflexible substrate can have a certain degree of flexibility, e.g. a glass plate having a thickness of 0.9 mm or below, such as 0.5 mm or below, wherein the flexibility of the substantially inflexible substrate is small in comparison to the flexible substrates. Typically, the substrate is made of a material being transparent for light with a wavelength A of 380 nm < A < 3000 nm.

[0032] Embodiments described herein particularly relate to deposition of materials, e.g. for display manufacturing on large area substrates. According to some embodiments, large area substrates or holders supporting one or more substrates may have a size of 0.5 m2or larger, particularly of 1 m2or larger. For instance, the deposition system may be adapted for processing large area substrates, such as substrates of GEN 4.5, which corresponds to about 0.67 m2of substrate (0.73 x 0.92m), GEN 5, which corresponds to about 1.4 m2substrates (1.1 m x 1.3 m), GEN 6, which corresponds to about 2.7 m2(1 .5 m x about 1.8 m), GEN 7.5, which corresponds to about 4.29 m2substrates (1.95 m x 2.2 m), GEN 8.5, which corresponds to about 5.7 m2substrates (2.2 m x 2.5 m), or even GEN 10, which corresponds to about 8.7 m2substrates (2.85 m x 3.05 m). Even larger generations such as GEN 11 and GEN 12, and corresponding substrate areas can similarly be implemented. According to yet further implementations, half sizes of the above-mentioned substrate generations can be processed.

[0033] In the present disclosure, an “optical coupling element” can be understood as an optical component or structure that is used to facilitate the coupling of light into the metal film, leading to the excitation of surface plasmon polaritons. Further, the optical coupling element is typically configured to direct light emitted from the light source via one or more reflections from the metal film to the detector. For instance, the optical coupling element can be a triangulated structure, particularly a triangular prism. Alternatively, the optical coupling element can be a trapezoidal polyhedron, particularly a trapezoidal prism. According to another example, the optical coupling element may be a triangular prism, a quadrilateral prism (e.g. a cuboid or cube), a pentagonal prism, a hexagonal prism or any other suitable prism.

[0034] Typically, the optical coupling element is produced by lithography, typically including etching, particularly wet etching or dry etching. In particular, the optical coupling element is made of one or more silicon-based materials. More specifically, the one or more silicon-based materials may be selected from the group consisting of: silicon oxide (SiO2), silicon nitride (Si3N4), silicon oxynitride (SiON), silicon carbide (SiC), amorphous silicon (a-Si), silicon dioxide hydride (SiO2H), silicon germanium (SiGe), silicon boron nitride (SiBN), silicon aluminum oxynitride (SiAION), silicon phosphide (SiP), and silicon oxycarbide (SiOC).

[0035] In the present disclosure, a “metal film” on the optical coupling element can be understood as a coating or layer provided on the optical coupling element. In particular, the metal film is configured for SPR. Typically, the metalfilm is a thin metal film with a film thickness T of T < 80 nm, particularly 5 nm < T < 50 nm. For instance, the metal film can be of gold, silver, aluminum, or other metals suitable for SPR.

[0036] In the present disclosure, a “light source” can be understood as a device that generates and emits light. For instance, the light source can be a VIS-NIR light source. In particular, the VIS-NIR light source is configured for providing light in the visible wavelength spectrum and the near infrared wavelength spectrum. For instance, the VIS-NIR light source can be configured for providing light with a wavelength A of 380 nm < A < 3000 nm.

[0037] In the present disclosure, a "detector for detecting reflected light" can be understood as a device configured for detecting light. In particular, the detector may be a VIS-NIR spectrometer configured for detecting light in the visible wavelength spectrum and the near infrared wavelength spectrum. For instance, the VIS-NIR spectrometer can be configured for detecting light with a wavelength A of 380 nm < A < 3000 nm. Typically, the detector is configured for capturing and analyzing changes of specific wavelength(s) and / or incident angle(s) and / or intensity of light, particularly light reflected from the metal film 11 as described herein. It is to be understood that after interacting with the metal film, the reflected light carries information about the SPR phenomenon. The detector captures reflected light, transforming the captured light into an electrical signal. Typically, the parameters monitored are the intensity of the reflected light at specific wavelength(s) and / or incident angle(s). Changes in these parameters correspond to variations in the refractive indices and the thickness of the layers coated on the metal surface of the metal film.

[0038] According to embodiments, which can be combined with other embodiments described herein, the optical coupling element 14 includes a first interfacial plane 141 between a material of the optical coupling element 14 and the metal film 11. The first interfacial plane 141 is inclined by an angle a with respect to the frontside 10F of the substrate 10. Typically, the inclination angle a of the first interfacial plane 141 with respect to the frontside 10F of the substrate10 is selected from a range 30° < a < 75°, particularly 35° < a < 65°, more particularly 40° < a < 60°.

[0039] In the present disclosure, an angle measured counterclockwise from a defined reference line is considered positive, following standard conventions in mathematics and physics where counterclockwise rotations are positive and clockwise rotations are negative.

[0040] Typically, as exemplarily illustrated in FIGS. 1 to 4, the first interfacial plane 141 interacts primarily with light that either directly emanates from the light source 120 or has undergone refraction through an adjacent medium. This means that the light striking the first interfacial plane 141 is not influenced by any prior reflection within the system. Consequently, no reflected light is present at the first interfacial plane 141 , as the incident light originates directly from the light source or as refracted rays, rather than being a product of reflective interactions.

[0041] According to embodiments, which can be combined with other embodiments described herein, the optical coupling element 14 includes a second interfacial plane 142 between the material of the optical coupling element 14 and the metal film 11. The second interfacial plane 142 is inclined by an angle [3 with respect to the frontside 10F of the substrate 10. Typically, the inclination angle [3 of the second interfacial plane 142 with respect to the frontside 10F of the substrate 10 is selected from a range 120° < [3 < 165°, particularly 125° < [3 < 155°, more particularly 130° < [3 < 150°. As exemplary shown in Figs. 1 to 4, typically, the second interfacial plane 142 receives light reflected from the metal film 11 at the first interfacial plane 141 .

[0042] FIG. 1 shows an exemplary embodiment in which the inclination angle a is 45° and the inclination angle [3 is 135°. FIG. 2 shows an exemplary embodiment in which the inclination angle a is larger than 45° and the inclination angle [3 is larger than 135°. FIG.3 shows an exemplary embodiment in which the optical coupling element 14 comprises a first part 14A and a second part 14B. The second part 14B can be spaced apart from the first part by adistance D. The distance D may be selected from a range of 1 mm < D < 20 mm, particularly 2 mm < D < 10 mm. Typically, the first part 14A includes the first interfacial plane 141 according to embodiments described herein. The second part 14B may include the second interfacial plane according to embodiments described herein. The space between the first part 14A and the second part 14B may be a free space as, exemplary shown in FIG. 3. Alternatively, the space between the first part 14A and the second part 14B may be filled with material of the optical coupling element 14 to form a trapezoidal structure, as exemplarily shown in FIG. 4A.

[0043] With exemplary reference, to FIGS. 4 to 7, according to embodiments, which can be combined with other embodiments described herein, the optical coupling element 14 comprises a third interfacial plane 143 between the material of the optical coupling element 14 and the metal film 11 . Typically, the third interfacial plane 143 is parallel to the frontside 10F of the substrate 10. It is to be understood that the third interfacial plane 143 may be provided in combination with the first interfacial plane 141 and the second interfacial plane 142, as exemplarily shown in FIGS. 4B, 5, 6 and 7. However, it is to be noted that the third interfacial plane 143 may be provided alone, as exemplarily shown in FIGS. 4B, 6 and 7, i.e. not in combination with the first interfacial plane 141 and the second interfacial plane 142. Providing a third interfacial plane 143, as described herein, can be beneficial to increase signal strength.

[0044] According to embodiments in which SPR is generated at the third interfacial plane 143, the inclination angle a of the first interfacial plane 141 with respect to the frontside 10F of the substrate 10 is selected from a range 50° < a < 75°, particularly 60° < a < 70°. The inclination angle [3 of the second interfacial plane 142 with respect to the frontside 10F of the substrate 10 is selected from a range 105° < [3 < 130°, particularly 110° < [3 < 120°. As exemplarily indicated in FIG. 4B, the first interfacial plane 141 and the second interfacial plane 142 can be interfacial planes between the material of the optical coupling element 14 and the environment, i.e. without any metal film 11.

[0045] FIGS. 4 and 5 show exemplary embodiments in which the optical coupling element 14 has a trapezoidal structure, e.g. trapezoidal polyhedron, particularly a trapezoidal prism. FIG. 6 shows an exemplary embodiment in which the optical coupling element 14 has an inversed tapered structure. An inversed tapered structure refers to a geometric structure where the lateral extension of the structure gradually increases as the structure extends away from its base. As apparent from the embodiment of FIG. 6, the base of the optical coupling element 14 is the surface of the optical coupling element 14 which is in contact with the substrate front surface 10F.

[0046] With exemplary reference to FIG. 7, according to embodiments, which can be combined with other embodiments described herein, the optical coupling element 14 includes a first structure 144 and a second structure 145. Typically, the second structure 145 covers the first structure 144. The first structure 144 may be embedded in the second structure 145. The first structure 144 can be a sloped structure. The sloped structure can be a triangulated structure, particularly a triangular prism.

[0047] Typically, the first structure 144 is made of a different material than the second structure 145. In particular, the first structure 144 is made of a first material having a first refractive index n-i and the second structure 145 is made of a second material having a second refractive index n2different from the first refractive index n1. In particular, the second refractive index n2is smaller than the first refractive index n-i (n2< n-i). For instance, the second refractive index n2can be selected from a range 1 .3 < n2< 1 .7, particularly 1 .4 < n2< 1 .6. The first refractive index n-i may be selected from a range 1.7 < n-i < 2.3, particularly 1.8 < ni < 2.1.

[0048] According to another aspect of the present disclosure, a method of manufacturing a substrate 10 configured for measuring a thickness of a layer on the substrate is provided. The method includes providing an optical coupling element 14 on a frontside 10F of the substrate 10 by using lithography. In other words, typically a lithographic technique is used for the fabrication of the optical coupling element 14, which is typically a microstructure. The lithographictechnique typically includes creating the optical coupling element 14 on the front surface 14F of the substrate through the use of a resist, particularly a photosensitive material, and exposure to light, electron beams, or other forms of radiation. The exposed areas of the resist undergo chemical changes, allowing selective removal or development of the material to reveal the structure of the optical coupling element 14. For instance, the selective removal may include etching, particularly wet etching or dry etching. Additionally, the method of manufacturing the substrate includes providing a metal film 11 on at least a part of the optical coupling element 14, for instance on at least one of the interfacial plane 141 , the second interfacial plane 142, and the third interfacial plane 143, as described herein. It is to be understood, that the substrate 10, the optical coupling element 14 and the metal film 11 can be configured according to any embodiments described in the present disclosure.

[0049] According to embodiments, which can be combined with other embodiments described herein, the light source 120 of the measurement system 100 is arranged and configured to provide light to the optical coupling element 14 at an angle of incidencewith respect to the backside 10B of the substrate. The angle of incidenceis selected from the range 0°<< 90°.FIGS. 1 to 5 show exemplary embodiments in which the angle of incidencewith respect to the backside 10B of the substrate is £-1=90°. FIGS. 6 and 7 show exemplary embodiments in which the angle of incidencewith respect to the backside 10B of the substrate is within a range of 0° < Ei < 90°.

[0050] According to embodiments, which can be combined with other embodiments described herein, the detector 130 of the measurement system 100 is arranged and configured to detect reflected light from the metal film 11 at an angle of reflection E2with respect to the backside 10B of the substrate. The angle of reflection E2is selected from the range 90°< E2<180°. FIGS. 1 to 5 show exemplary embodiments in which angle of reflection E2with respect to the backside 10B of the substrate is E2= 90°. FIGS. 6 and 7 show exemplary embodiments in which the angle of reflection E2with respect to the backside 10B of the substrate is within a range of 90° < E2< 180°.

[0051] According to embodiments, which can be combined with other embodiments described herein, the light source 120 and the detector 130 are arranged such that the light provided from the light source and the reflected light detected by the detector are parallel to each other. In particular, the angle of incidence with respect to the backside 10B of the substrate 10 can= 90° and the angle of reflection s2with respect to the backside 10B of the substrate can be s2= 90°.

[0052] With exemplary reference to FIG. 8, according to embodiments, which can be combined with other embodiments described herein, the measurement system 100 further includes a holder 110 for holding the substrate 10. Typically, the substrate 10 is provided on a front side 110F of the holder 110. In particular, a backside 10B of the substrate 10 is at least partially in contact with the front side 11 OF of the holder 110. As exemplarily shown in FIG. 8, typically, the holder 110 has a measurement opening 111 for providing optical access to the optical coupling element 14 provided on the frontside 10F of the substrate 10 from a backside 110B of the holder 110.

[0053] In the present disclosure, a "holder for holding the substrate” can be understood as a tool, fixture, or platform configured to securely support a substrate during substrate processing. Typically, the holder ensures stability, protection, and proper positioning of the substrate during processing, e.g. layer deposition. It is to be understood that the holder can be configured for holding a large area substrate as described herein. The holder may also be referred to as a substrate holder. The substrate holder can include an electrostatic chuck (E- chuck) providing an electrostatic force for holding the substrate, particularly at a substrate support surface of the holder, e.g. the front side 110F of the holder 110 shown in FIG. 8. For example, the substrate holder may include an electrode arrangement configured to provide an attracting force acting on the substrate. Typically, the holder 110 is configured for holding the substrate 10 during material deposition in a substantially vertical orientation. A “substantially vertical orientation” of the substrate can be understood in that the orientation of the substrate is vertical within a tolerance T of T < ±15°, particularly T < ±10°, fromthe perfect vertical orientation. Alternatively, the holder can be configured holding the substrate during material deposition in a substantially horizontal orientation. A “substantially horizontal orientation” of the substrate or the mask can be understood in that the orientation of the substrate or the mask is horizontal within a tolerance T of T < ±15°, particularly ? < ±10°, from the perfect horizontal orientation. According to an example, the holder can be a carrier. A carrier is typically configured for transporting an object, e.g. the substrate. A holder does typically not travel within a processing system. Accordingly, a substrate holder stays in the process chamber (at least for a certain period), whereas a substrate carrier travels with the substrate within the processing system.

[0054] In the present disclosure, a "measurement opening of the holder " can be understood as a specific aperture (intentionally) provided and positioned within the holder, to allow optical access to the optical coupling element provided on the frontside of the substrate. The term "optical access" indicates that the measurement opening allows light to reach the optical coupling element. Typically, a size of the measurement opening is less than 10%, particularly less than 5%, more particularly less than 2.5%, of a total size of the holder. FIG. 9 shows a non-limiting example in which the measurement opening 111 is provided at an edge portion of the holder 110. An edge portion of the holder can be understood as the outer 20%, particularly outer 15%, more particularly the outer 10%, of the holder 110. As exemplarily shown in FIG. 9, the measurement opening 111 may have an open lateral side towards the edge of the holder 110. However, also not explicitly shown, it is to be understood that the measurement opening 111 can have a closed opening edge.

[0055] As exemplarily shown in FIGS. 2 to 7, according to embodiments, which can be combined with other embodiments described herein, the measurement system 100 includes a polarizer 121 , provided in the light path 122 between the light source 120 and the optical coupling element 14. In particular, the polarizer 121 is a linear polarizer. A “polarizer” can be understood as an optical device that selectively transmits light waves oscillating in a specificdirection while absorbing or blocking light waves oscillating in other directions. A “linear polarizer” is a type of polarizer that selectively transmits light waves oscillating in a specific linear direction. In the context of SPR, a polarizer, particularly a linear polarizer, may be used to control the polarization state of incident light. In particular, the polarizer is used to gain p-polarized light (parallel to the incident plane). The p component fulfills the condition to excite surface plasmon polaritons.

[0056] With exemplary reference to FIG. 10, according to embodiments, which can be combined with other embodiments described herein, the light source 120 and the detector 130 can be arranged within an atmospheric box 150. In the present disclosure, an “atmospheric box” can be understood as an enclosed volume or space in which atmospheric conditions, particularly atmospheric pressure conditions, are provided and / or can be controlled. Typically, the atmospheric box 150 has a first transparent portion 151 for allowing light emitted from the light source 120 to exit the atmospheric box 150. Further, the atmospheric box 150 typically has a second transparent portion 152 for allowing light reflected from the metal film 11 to enter the atmospheric box 150 towards the detector 130. Alternatively, the atmospheric box 150 may have a first fiber optic vacuum feedthrough in which a first optical fiber is provided for allowing light emitted from the light source 120 to exit the atmospheric box 150. Further, the atmospheric box 150 can have a second fiber optic vacuum feedthrough in which a second optical fiber is provided for allowing light reflected from the metal film 11 to enter the atmospheric box 150 towards the detector 130.

[0057] According to embodiments, which can be combined with other embodiments described herein, the atmospheric box 150 is attached or connected to the holder 110, particularly to the backside 110B of the holder 110, as exemplarily shown in FIG. 10. Alternatively, the atmospheric box 150 can be attached or connected to a wall of a vacuum deposition chamber 210 as exemplarily shown in FIGS. 11 B and 11 C. According to another alternative configuration (not shown), the atmospheric box 150 can be attached to astructure inside the vacuum deposition chamber 210, which may have some advantages with respect to adjustment and positioning. FIG. 11 B shows an example in which the atmospheric box 150 is attached or connected to an interior side of a wall of a vacuum deposition chamber 210. FIG. 11 C shows an example in which the atmospheric box 150 is attached or connected to an exterior side of a wall of a vacuum deposition chamber 210.

[0058] With exemplary reference to FIGS. 11A to 110, a deposition apparatus 200 for depositing material on a substrate 10 according to embodiments of the present disclosure is described. According to embodiments, which can be combined with other embodiments described herein, the deposition apparatus 200 includes a vacuum deposition chamber 210, a deposition source 220 provided inside the vacuum deposition chamber 210, and a measurement system 100 according to any embodiments described herein.

[0059] The deposition apparatus 200 may also be referred to as a vacuum deposition apparatus. The vacuum deposition apparatus can be understood as an apparatus configured for vacuum deposition of organic or inorganic materials including metallic materials, particularly for display manufacturing, e.g. for OLED display manufacturing.

[0060] In the present disclosure, a "vacuum deposition chamber" can be understood as a chamber configured for vacuum deposition. The term "vacuum", as used herein, can be understood in the sense of a technical vacuum having a vacuum pressure of less than, for example, 10 mbar. Typically, the pressure in a vacuum chamber as described herein may be between 10’5mbar and about 10’8mbar, particularly between 10’5mbar and 10’7mbar.

[0061] In the present disclosure, a “deposition source” can be understood as an arrangement or an assembly configured for material deposition on a substrate as described herein. In other words, the deposition source is configured for providing a source of material to be deposited on the substrate. For instance, the deposition source may have one or more crucibles configured to evaporate the source material to be deposited. A "crucible" can be understoodas a device having a reservoir for the material to be evaporated by heating the crucible. Accordingly, a "crucible" can be understood as a source material reservoir, which can be heated to evaporate the source material into a gas by at least one of evaporation and sublimation of the source material. The crucible can include a heater to evaporate the source material in the crucible into a gaseous source material. For instance, initially the material to be evaporated can be in the form of a powder or a grain. The reservoir can have an inner volume for receiving the source material to be evaporated, e.g. organic or inorganic materials, e.g. metallic materials.

[0062] Further, the deposition source can have one or more distribution assemblies or distribution pipes configured for providing the evaporated material towards the substrate. For instance, a distribution tube or distribution pipe as described herein may provide a line source with a plurality of openings and / or nozzles which are arranged in lines along the length of the distribution tube. Accordingly, the distribution assembly can include a linear distribution showerhead, for example, having a plurality of openings, particularly nozzles (or an elongated slit) disposed therein. A showerhead as understood herein can have an enclosure, hollow space, or tube, in which the evaporated material can be provided or guided, for example from the evaporation crucible to the substrate. According to embodiments which can be combined with any other embodiments described herein, the length of the distribution pipe may correspond at least to the height of the substrate to be deposited. In particular, the length of the distribution pipe may be longer than the height of the substrate to be deposited, at least by 10% or even 20%. Accordingly, a uniform deposition at the upper end of the substrate and / or the lower end of the substrate can be provided. For instance, the source material to be deposited may be an organic or inorganic material, e.g. a metallic material, for use as electrode materials or electron transport layer materials in organic light emitting diode (OLED) production.

[0063] According to embodiments which can be combined with any other embodiments described herein, the deposition apparatus is configured formaterial deposition in a substantially vertical orientation of the substrate. Accordingly, typically the vacuum deposition chamber 210 and the deposition source 220 are configured for material deposition on a substantially vertically arranged substrate 10. Accordingly, it is to be understood that the holder 110 holding the substrate 10 is typically also configured for holding the substrate in a substantially vertical orientation.

[0064] With exemplary reference to FIG. 110, according to embodiments, which can be combined with other embodiments described herein, the vacuum deposition chamber 210 may include a window 211. The light source 120 and the detector 130 can be arranged outside of the vacuum deposition chamber 210. In particular, the light source 120 is arranged to provide light through the window 211 to the optical coupling element 14 provided on the frontside 10F of the substrate 10. The detector 130 is arranged to detect reflected light from the metal film 11 through the window 211. Alternatively, instead of a window, the vacuum deposition chamber 210 may be provided with fiber optic vacuum feedthroughs (not shown) in which optical fibers are provided for sending light from the light source 120 to the optical coupling element 14, and receiving reflected light from the metal film 11 by the detector 130, respectively. When the light source 120 and the detector 130 are arranged outside of the vacuum deposition chamber 210, it is to be understood that the atmospheric box 150 may be omitted (indicated by the dotted line in FIG. 4C), particularly when there are atmospheric conditions outside of the vacuum deposition chamber 210.

[0065] With exemplary reference to the block diagram shown in FIG. 12, a method 300 of measuring a thickness of a layer on a substrate 10 according to embodiments of the present disclosure is described. According to embodiments, which can be combined with other embodiments described herein, the method 300 includes providing light (represented by block 310 in FIG. 12) to an optical coupling element 14 from a backside 10B of the substrate. The optical coupling element 14 is provided on a frontside 10F of the substrate 10. Further, a metal film 11 is provided on the optical coupling element 14. Additionally, themethod 300 includes exciting (represented by block 320 in FIG. 12) surface plasmon polaritons on a surface of the metal film 11 . Moreover, the method 300 includes detecting light (represented by block 330 in FIG. 12) reflected from the metal film 11.

[0066] Typically, the method 300 includes analyzing the detected light (represented by block 340 in FIG. 12) by using an optical model to determine the thickness of the layer. The analysis of the detected light based on the optical model is typically conducted by a computer 160, as schematically indicated in FIG. 10.

[0067] With exemplary reference to the block diagram shown in FIG. 13, a method 400 of controlling a thickness of a layer on a substrate 10 according to embodiments of the present disclosure is described. According to embodiments, which can be combined with other embodiments described herein, the method 400 includes depositing (represented by block 410 in FIG. 13) a first layer on the substrate 10. Further, the method 400 includes measuring (represented by block 420 in FIG. 13) a first thickness of the first layer by employing the method 300 of measuring a thickness of a layer on a substrate 10 according to any embodiments described herein. Additionally, the method 400 includes conducting a first analysis (represented by block 430 in FIG. 13) of the measured first thickness of the first layer with respect to a deviation from a target layer thickness of the first layer, based on an optical model 415 for the first layer. Further, the method 400 includes feeding (represented by block 440 in FIG. 13) the analysis result back to a deposition rate controller for adjusting the deposition rate for a subsequent first layer deposition (represented by block 460 in FIG.13) on a further substrate. Moreover, the method 400 includes updating (represented by block 450 in FIG. 13) the optical model based on the analysis result. The updated optical model 415’ can be used for conducting a second analysis (represented by block 431 in FIG. 13) of a measured second thickness of a second layer with respect to a deviation from a second target layer thickness of the second layer.

[0068] According to embodiments, which can be combined with other embodiments described herein, the method 400 may include depositing (represented by block 411 in FIG. 13) a second layer on the substrate 10. Further, the method 400 may include measuring (represented by block 421 in FIG. 13) a second thickness of the second layer by employing the method 300 of measuring a thickness of a layer on a substrate 10 according to any embodiments described herein. Additionally, the method 400 can include conducting a second analysis (represented by block 431 in FIG. 13) of the measured second thickness of the second layer with respect to a deviation from a target layer thickness of the second layer, based on the updated optical model 415’ for the second layer. Further, the method 400 includes feeding (represented by block 441 in FIG. 13) the analysis result of the second layer back to the deposition rate controller for adjusting the deposition rate for a subsequent second layer deposition (represented by block 461 in FIG.13) on the further substrate. Moreover, the method 400 includes updating (represented by block 451 in FIG. 13) the optical model used for the second layer based on the analysis result of the second layer. The updated optical model 415” can be used for conducting a third analysis (represented by block 432 in FIG. 13) of a measured third thickness of a third layer with respect to a deviation from a third target layer thickness of the third layer.

[0069] It is to be understood, depending on the number of layers to be provided on the substrate, that the method steps as outlined above for the first layer and the second layer, can be repeated for each further layer. For instance, in the case of three layers, the method 400 may include depositing (represented by block 412 in FIG. 13) a third layer on the substrate 10. Further, the method 400 may include measuring (represented by block 422 in FIG. 13) a third thickness of the third layer by employing the method 300 of measuring a thickness of a layer on a substrate 10 according to any embodiments described herein. Additionally, the method 400 can include conducting a third analysis (represented by block 432 in FIG. 13) of the measured third thickness of the third layer with respect to a deviation from a target layer thickness of the third layer, based on the updated optical model 415” for the third layer. Further, themethod 400 includes feeding (represented by block 442 in FIG. 13) the analysis result of the third layer back to the deposition rate controller for adjusting the deposition rate for a subsequent third layer deposition (represented by block 462 in FIG.13) on the further substrate. In the case of a fourth layer, the method may further include updating the optical model used for the third layer based on the analysis result of the third layer. Said updated optical model can be used for conducting a fourth analysis of a measured fourth thickness of a fourth layer with respect to a deviation from a fourth target layer thickness of the fourth layer.

[0070] Accordingly, in view of the embodiments describe herein, it is to be understood that compared to the state of the art, an improved substrate, an improved measurement system, an improved deposition apparatus, an improved method of measuring a thickness of a layer on a substrate, and an improved method of controlling a thickness of a layer are provided. In particular, embodiments disclosed herein offer distinct advantages, specifically by measuring the surface plasmon resonance (SPR) effect on one or more dedicated spot(s) on the substrate, to assess the thickness of the deposited layer through optical modeling. Further, the measurement can be conducted from the backside of the substrate. It is to be understood that through the use of an appropriate combination and / or range of wavelengths and incident angles in the measurement system, it becomes feasible to detect deviations with a control precision of ±1 %, even for layers as thin as 10nm. Further embodiments described herein provide for the capability to measure layer deposition on the molecular level, such that extremely thin layers can be measured, and the measurement is not limited to layers with sufficient thickness. A further advantage is that it is possible to use one measurement area, particularly one measurement point or location, for layers of a layer stack subsequently deposited. Further, the measurement requires no additional time, since the measurement can be carried out during deposition and / or during deposition source rotation / change and / or substrate transportation. Moreover, by integrating an optical coupling element directly onto the substrate, the need for external optical components, such as prisms, is eliminated. The integration of the optical coupling element on the front side of the substrate simplifies theoverall measurement while enhancing system robustness by reducing dependence on external alignments or positioning of external optical components, such as prisms. Furthermore, eliminating separate components like prisms lowers material costs and assembly complexity, resulting in a more cost-effective solution. The integrated optical coupling element also ensures precise and consistent light delivery to the metal film, optimizing conditions for efficient surface plasmon resonance (SPR) and enhancing overall system performance.

[0071] While the foregoing is directed to embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

[0072] In particular, this written description uses examples to disclose the disclosure, including the best mode, and also to enable any person skilled in the art to practice the described subject-matter, including making and using any devices or systems and performing any incorporated methods. While various specific embodiments have been disclosed in the foregoing, mutually nonexclusive features of the embodiments described above may be combined with each other. The patentable scope is defined by the claims, and other examples are intended to be within the scope of the claims if the claims have structural elements that do not differ from the literal language of the claims, or if the claims include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

WHAT IS CLAIMED:

1. A substrate (10) configured for measuring a thickness of a layer on the substrate (10), comprising:- an optical coupling element (14) provided on a frontside (10F) of the substrate (10), and- a metal film (11 ) on the optical coupling element (14).

2. The substrate (10) of claim 1 , wherein the optical coupling element (14) comprises a first interfacial plane (141 ) between a material of the optical coupling element (14) and the metal film (11 ), wherein the first interfacial plane (141 ) is inclined by an angle a with respect to the frontside (10F) of the substrate (10).

3. The substrate (10) of claim 2, wherein the optical coupling element (14) comprises a second interfacial plane (142) between the material of the optical coupling element (14) and the metal film (11 ), wherein the second interfacial plane (141 ) is inclined by an angle p with respect to the frontside (1 OF) of the substrate (10).

4. The substrate (10) of any of claims 1 to 3, wherein the optical coupling element (14) comprises a third interfacial plane (143) between the material of the optical coupling element (14) and the metal film (11 ), wherein the third interfacial plane (143) is parallel to the frontside (10F) of the substrate.

5. The substrate (10) of any of claims 1 to 4, wherein the optical coupling element (14) comprises a first structure (144), particularly a sloped structure, and a second structure (145) covering the first structure (144), particularly embedding the first structure (144), wherein the first structure (144) is made of a different material than the second structure.

6. The substrate (100) of any of claims 1 to 5, wherein the first structure (144) is made of a first material having a first refractive index n-i and the secondstructure (145) being made of a second material having a second refractive index n2being smaller than the first refractive index n-|.

7. The substrate (10) of any of claims 1 to 6 in combination with claim 2, wherein the angle a of the first interfacial plane (141 ) with respect to the frontside (10F) of the substrate (10) is selected from a range 30° < a < 75°, particularly 35° < a < 65°, more particularly 40° < a < 60°.

8. The substrate (10) of any of claims 1 to 7 in combination with claim 3, wherein the angle [3 of the second interfacial plane (142) with respect to the frontside (10F) of the substrate (10) is selected from a range 120° < [3 < 165°, particularly 125° < [3 < 155°, more particularly 130° < [3 < 150°.

9. The substrate (10) of any of claims 1 to 8 in combination with claim 4, wherein the angle a of the first interfacial plane (141 ) with respect to the frontside (10F) of the substrate (10) is selected from a range 50° < a < 75°, particularly 60° < a < 70°, and wherein the inclination angle [3 of the second interfacial plane 142 with respect to the frontside (10F) of the substrate (10) is selected from a range 105° < [3 < 130°, particularly 110° < [3 < 120°.

10. The substrate (100) of any of claims 1 to 9, wherein the optical coupling element (14) is made of a one or more silicon-based materials, particularly selected from the group consisting of silicon oxide (SiO2), silicon nitride (Si3N4), silicon oxynitride (SiON), silicon carbide (SiC), amorphous silicon (a-Si), silicon dioxide hydride (SiO2H), silicon germanium (SiGe), silicon boron nitride (SiBN), silicon aluminum oxynitride (SiAION), silicon phosphide (SiP), and silicon oxycarbide (SiOC).11 . The substrate (10) of any of claims 1 to 10, wherein the substrate is a planar substrate, particularly having a substrate thickness T selected from a range 0.1 mm < T < 1 .8 mm, more particularly 0.1 mm < T < 0.9 mm.

12. The substrate (10) of any of claims 1 to 11 , wherein the substrate is made of a material being transparent for light with a wavelength A of 380 nm < A < 3000 nm.

13. A method of manufacturing a substrate (10) configured for measuring a thickness of a layer on the substrate, the method comprising:- providing an optical coupling element (14) on a frontside (10F) of the substrate (10) by using lithography, and- providing a metal film (11 ) on at least a part of the optical coupling element (14), particularly wherein the substrate is a substrate according to any of claims 1 to 12.

14. A measurement system (100) configured to measure a thickness of a layer on a substrate (10) according to any of claims 1 to 13, the measurement system (100) comprising:- a light source (120) to provide light to the optical coupling element (14) from a backside (10B) of the substrate; and- a detector (130) for detecting reflected light from the metal film (11 ).

15. The measurement system (100) of claim 14, wherein the light source (120) is arranged and configured to provide light to the optical coupling element (14) at an angle of incidencewith respect to the backside (10B) of the substrate, whereinis selected from the range 0°<< 90°, and wherein the detector (130) is arranged and configured to detect reflected light from the metal film (11 ) at an angle of reflection s2with respect to the backside (10B) of the substrate, wherein s2is selected from the range 90°< s2<180°.

16. The measurement system (100) of claim 14 or 15, wherein the light source (120) and the detector (130) are arranged such that the light provided from the light source and the reflected light detected by the detector are parallel to each other.

17. The measurement system (100) of claim 16, wherein the angle of incidence with respect to the backside (1 OB) of the substrate is= 90°, and wherein the angle of reflection s2with respect to the backside (10B) of the substrate is s2= 90°.

18. The measurement system (100) of any of claims 14 to 17, wherein the light source (120) and the detector (130) are arranged within an atmospheric box (150), particularly wherein the atmospheric box (150) has a first transparent portion (151 ) for allowing light emitted from the light source (120) to exit the atmospheric box (150), and particularly wherein the atmospheric box (150) has a second transparent portion (152) for allowing light reflected from the metal film (11 ) to enter the atmospheric box (150) towards the detector (130).

19. The measurement system (100) of claim 18, wherein the atmospheric box (150) is attached to a holder (110) holding the substrate, wherein the holder has a measurement opening (111 ) for providing optical access to the optical coupling element (14) from a backside (110B) of the holder (110).

20. A deposition apparatus (200) for depositing material on a substrate (10), comprising:- a vacuum deposition chamber (210)- a deposition source (220) provided inside the vacuum deposition chamber (210); and- a measurement system (100) according to any of claims 14 to 19.21 . The deposition apparatus (200) of claim 20, wherein the vacuum deposition chamber (210) comprises a window (211 ), and wherein the light source (120) and the detector (130) are arranged outside of the vacuum deposition chamber (210), wherein the light source (120) is arranged to provide light through the window (211 ) to the optical coupling element (14), and wherein the detector (130) is arranged to detect reflected light from the metal film (10M) through the window (211 ).

22. A method (300) of measuring a thickness of a layer on a substrate (10), comprising:- providing (310) light to an optical coupling element (14) from a backside (10B) of the substrate, wherein the optical coupling element (14) is provided on a frontside (10F) of the substrate (10), and wherein a metal film (11 ) is provided on the optical coupling element (14);- exciting (320) surface plasmon polaritons on a surface of the metal film (11 ), and- detecting (330) light reflected from the metal film (11 ).

23. The method (300) of claim 22, further comprising using at least one of a substrate (10) according to any of claims 1 to 12 and a measurement system (100) according to any of claims 14 to 19.

24. A method (400) of controlling a thickness of a layer on a substrate, comprising:- depositing (410) a first layer on the substrate (10);- measuring (420) a first thickness of the first layer by employing the method according to claim 22 or 23;- conducting a first analysis (430) of the measured first thickness of the first layer with respect to a deviation from a target layer thickness of the first layer based on an optical model for the first layer;- feeding (440) the analysis result back to a deposition rate controller for adjusting the deposition rate for a subsequent first layer deposition (460) on a further substrate; and- updating (450) the optical model based on the analysis result, the updated optical model being used for conducting a second analysis (431 ) of a measured second thickness of a second layer with respect to a deviation from a second target layer thickness of the second layer.

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