Method and apparatus for monitoring a coating process

Abstract

The invention relates to a method for monitoring a coating process, wherein, when a substrate having a substrate plane is subjected to a coating process in which a first side of the substrate extending parallel to the substrate plane and / or a second side opposite the first side and extending parallel to the substrate plane is in each case applied with at least one coating layer, a light beam is emitted onto the substrate and at least partially transmitted through the substrate, a sub-beam is coupled out of the transmitted light beam, the coupled-out sub-beam impinges onto a sensor, after the coupled-out sub-beam the transmitted light beam is redirected onto the substrate and at least partially transmitted through the substrate again, the transmitted light beam impinges onto a last sensor, the light beam impinging onto the last sensor and the sub-beams impinging onto the sensors preceding this are each associated, a spectrum is determined, and at least one of the determined spectra is used to determine at least one property of the at least one coating layer currently being applied to the substrate and / or at least one property of the at least one coating layer currently being applied to at least one further substrate subjected to the same coating process as the substrate and / or at least one property of the coating process being carried out. The invention also relates to a device for monitoring a coating process using the method according to the invention.

Description

Technical Field

[0001] This invention relates to a method for monitoring a coating process, wherein, when a substrate having a substrate plane undergoes a coating process—in which at least one coating is applied to a first side of the substrate extending parallel to the substrate plane and / or a second side of the substrate opposite the first side and extending parallel to the substrate plane—a light beam is emitted onto the substrate and at least partially transmitted through the substrate; a portion of the transmitted beam is separated from the transmitted beam; the separated portion of the beam illuminates a sensor; and after the portion of the beam is separated, the transmitted beam is guided back onto the substrate and again at least partially transmitted through the substrate; the transmitted beam illuminates a final sensor; a spectrum is determined based on the beam illuminating the final sensor and based on the portions of the beams from the sensors preceding the final sensor; and, by means of at least one of the determined spectra, at least one characteristic of at least one coating currently being applied to the substrate, and / or at least one characteristic of at least one coating of at least one other substrate currently being applied and undergoing the same coating process as the substrate, and / or at least one characteristic of the currently implemented coating process. Furthermore, this invention also relates to an apparatus for monitoring a coating process using the method of this invention. Background Technology

[0002] Optical coatings are layers of material applied to the surface of optical elements to alter their optical properties. An interference filter is an optical coating consisting of several layers of material applied in such a way that they transmit light of a specific wavelength while reflecting or absorbing light of other wavelengths (if the material itself is absorbent). Interference filters are commonly used in applications requiring very narrow spectral wavelengths of light, such as spectrometers or color photography.

[0003] Interference filters are made by coating an optical substrate with several layers of material having different refractive indices. The thickness of each layer can be calculated such that it corresponds to an integer number of wavelengths for a given wavelength. When light passes through these layers, the waves passing through each layer are delayed, causing them to either reinforce or attenuate each other depending on whether they are in phase. This results in an interference effect, i.e., transmitting light of a specific wavelength while absorbing other light. Alternatively, the layer thicknesses can be chosen such that they do not correspond to an integer number of wavelengths. Here, the interference effect is still superimposed in such a way that a specific filtering function is ultimately achieved. In the latter case, it is called a non-periodic design.

[0004] Interference filters offer several advantages over other types of optical coatings. They are highly precise, transmitting a narrow spectrum of light wavelengths. They are also very robust and durable, capable of being used repeatedly without performance degradation. They are commonly used in applications requiring high precision and reliability, such as medical diagnostics or industrial process control.

[0005] Optical components are typically coated. This coating is often a broadband anti-reflective coating. The substrate material is usually glass or plastic, with a variety of materials used in various applications. For glass, these include, for example, quartz, borosilicate glass, SF6, etc. For plastics, for example, CR39, polycarbonate, PMMA, or other materials may also be used.

[0006] The percentage of light reflected by the substrate material depends on the refractive index of the optical element. The reflectivity R relative to air is calculated using the following formula:

[0007]

[0008] Where n is the refractive index of the optical element. Light is reflected or transmitted to varying degrees at the transition between the two layers. At the transition from the first layer with a refractive index of n1 to the second layer with a refractive index of n2, the reflectivity is:

[0009] Almost any coating function can be achieved by stacking multiple thin films. This is possible as long as the coherence condition is met. For visible light, the coherence length can be very long (>100 μm).

[0010] Anti-reflective coatings are frequently used. In the case of anti-reflective coatings, it is usually necessary to coat both sides of the optical element. Typically, a wider or narrower spectral range is used. For simple broadband anti-reflective coatings, anti-reflection is often achieved in the 420-680 nm range, where reflectivity is required to be less than 0.5%. If the substrate is planar, for example, the following type of coating is sufficient:

[0011] SiO2 is a low refractive index material with a refractive index of about 1.45; TiO2 is a high refractive index material with a refractive index of 2.4 to 2.7.

[0012] In addition to anti-reflective coatings, various other filters can be displayed. For example, the function of a periodic dielectric mirror is achieved through the following layer structure:

[0013] In this case, S represents the substrate. H or L corresponds to a high-refractive-index or low-refractive-index layer with a thickness of λ / 4. N is the number of cycles in the double shift sequence (HL, i.e., "high-low"). The geometric layer thickness is defined as:

[0014] With a refractive index n = 2.0 (for layer H) and a wavelength of 550 nm, the λ / 4 layer can therefore be 62.5 nm thick. Periodic layer stacking is a relatively simple form of optical filter. The function of the layers can also be achieved using aperiodic layer structures, or a combination of periodic and aperiodic layers. The more layers used in a stack, the more complex the requirements the coating can meet. This means that it can block or transmit one or more specific spectral ranges.

[0015] Physical vapor deposition (PVD) processes are commonly used to deposit optical coatings. This is a technique that deposits layers through a physical process that utilizes the vaporization of the material. One of the most common PVD processes for depositing optical interference coatings is sputtering (including magnetron sputtering or ion beam sputtering). ALD (atomic layer deposition), particularly dynamic ALD, is also utilized. Existing techniques also include using an electron beam to vaporize the source material.

[0016] To ensure high-quality coatings, precise control of layer thickness and refractive index is essential. Therefore, optical monitoring is commonly used today to inspect coatings. Transmission or reflection measurements can be employed. Optical monitoring during the coating process is used to monitor the progress of the coating process and evaluate the quality of the resulting coating. This is particularly important in the production of optical coatings, as these coatings must be very thin and uniform to achieve good performance.

[0017] One of the most common methods for optical monitoring of the coating process is in-situ reflectance measurement. It measures the reflective behavior of the coating during deposition. To this end, a light beam is directed onto the substrate surface, and the proportion of reflected light is measured. Based on the wavelength of the light and the layer characteristics, the layer thickness and uniformity can be determined. This method is also commonly used in transmission measurements, where the transmitted light beam is measured. The coating thickness is determined in such a way that the theoretical transmittance or reflectance is fitted to the measured value, with the coating thickness used as the fitting parameter. The advantage of in-situ measurement is that it can be repeated frequently, thus requiring only the layer currently being grown to be measured.

[0018] A distinction was made between direct and indirect measurements. Direct measurements involve measuring directly on the coating material, while indirect measurements involve measuring on a traveling reference substrate, which ideally has the same coating as the coating material.

[0019] Transmission or reflection measurements can be performed at a single wavelength or over a broadband range within a selected spectral range.

[0020] There are many other methods for optical monitoring of the coating process, which can be selected based on requirements and available resources.

[0021] Previous known monitoring methods were used to detect coatings on only one side. The coating being grown was measured only on one side. However, coating systems exist that apply the coating to both sides. Here, not only is one side of the substrate coated, but both sides of the substrate are coated simultaneously. Advantages of such coating systems include, for example, higher production efficiency, since the coating often must be applied to both sides.

[0022] Another advantage of coating both sides simultaneously is that thin coatings often cause substrate warping because compressive stress is frequently generated within the layer to achieve good coating performance. For example, this warping causes variations in coating coverage across different areas of the substrate. This can be avoided by coating both sides simultaneously.

[0023] However, the problem here is that it is unclear how coating detection can be performed if the coating is applied to both the front and back sides simultaneously. In principle, in reflectance measurements, light from the back side can be optically blocked from entering the receiver, separating the two sides. This can be achieved by using a light-absorbing reference substrate. However, this is difficult to implement for transmission measurements. Summary of the Invention

[0024] Therefore, the object of the present invention is to provide a method for monitoring the coating process, thereby enabling better monitoring of the coating on the substrate. Furthermore, the object of the present invention is to provide an apparatus for implementing this method.

[0025] This problem is solved by relating a method for monitoring a coating process having the features of claim 1, and an apparatus for monitoring a coating process having the features of claim 11. The corresponding dependent claims describe preferred improvements.

[0026] According to the present invention, a method for monitoring a coating process is provided, wherein, when a substrate having a substrate plane undergoes a coating process, a first side of the substrate extending parallel to the substrate plane and / or a second side of the substrate opposite to the first side and extending parallel to the substrate plane are each applied with at least one coating. a) A light beam is emitted onto the substrate and at least partially transmitted through the substrate. b) Separate a portion of the transmitted beam from the transmitted beam, irradiate (preferably guide) at least one sensor, and after the portion of the beam is separated, guide the transmitted beam back onto the substrate and transmit it through the substrate again at least partially, (wherein step b) may optionally be repeated once or several times. c) The beam of light transmitted in step b) illuminates (preferably guided upwards) the final sensor. d) Determine the spectrum by illuminating (or guiding) the final sensor from step c) and by illuminating (or guiding) the various portions of the sensor from step b). e) Determine, by means of at least one of the determined spectra (preferably by means of several of the determined spectra, particularly preferably by means of the determined spectra), that: At least one characteristic of at least one coating currently being applied to the substrate, and / or At least one characteristic of at least one coating currently being applied to at least one other substrate, said at least one other substrate undergoing the same coating process as said substrate, and / or At least one characteristic of the coating process currently being implemented.

[0027] Therefore, the method of the present invention is a method for monitoring a coating process performed on a substrate during a coating process. In this coating process, a first side of the substrate extending parallel to the substrate plane and / or a second side of the substrate opposite the first side and extending parallel to the substrate plane are each coated with at least one coating. Therefore, the coating process can involve single-sided or double-sided coating. Thus, the method according to the present invention can be used to monitor single-sided and double-sided coating of a substrate.

[0028] During the coating process, multiple substrates (or additional substrates) may be coated, each substrate having a substrate plane, wherein a first side of each substrate extending parallel to the substrate plane and / or a second side of each substrate opposite to the first side and extending parallel to the substrate plane are each coated with at least one coating. The method steps for monitoring the coating process may then be preferably implemented on one of the other substrates, or alternatively on several or all of the substrates.

[0029] The method for monitoring the coating process according to the present invention includes steps a) to e).

[0030] In step a), a light beam is first emitted onto a substrate, wherein the emitted light beam is at least partially transmitted through the substrate. The light beam may be emitted onto a first side or a second side of the substrate. Preferably, the light beam is emitted onto the substrate in such a manner that it illuminates the substrate (or the first or second side of the substrate) in a generally perpendicular manner.

[0031] In step b), a portion of the transmitted beam is separated from the transmitted beam, wherein the separated portion illuminates the sensor, preferably directed onto the sensor, and after the portion of the beam is separated, the transmitted beam is directed back onto the substrate, wherein the beam thus directed back onto the substrate is again at least partially transmitted through the substrate. Here, the beam may be directed onto a first side or a second side of the substrate. Preferably, the beam is directed onto the substrate side that was not emitted in step a). In other words, if the beam was emitted onto the first side of the substrate in step a), then in step b), the beam is preferably directed onto the second side of the substrate; or, if the beam was emitted onto the second side of the substrate in step a), then in step b), the beam is preferably directed onto the first side of the substrate. Preferably, the beam is directed onto the substrate in such a way that it illuminates the substrate (or the first or second side of the substrate) in a generally perpendicular manner. Step b) may be repeated once or several times, such that the beam transmitted in step a), after the portion of the beam is separated, is transmitted through the substrate several times, and after each transmission, a portion of the beam is separated and illuminates a corresponding separate sensor, preferably directed onto the corresponding separate sensor. Alternatively, step b) may be performed only once.

[0032] In step c), the light beam transmitted (once or several times) in step b) illuminates the final sensor. Preferably, the light beam transmitted (once or several times) in step b) is guided to the final sensor.

[0033] In step d), the spectrum is determined based on the beam of light illuminating (or guiding) the final sensor in step c) and the beams of light illuminating (or guiding) the various parts of the sensor in step b).

[0034] In step e), using the determined spectrum, Determine at least one characteristic of at least one coating currently being applied to (or prepared) (through the coating process) on the substrate, and / or At least one characteristic of at least one coating being applied (or prepared) (by a coating process) to at least one other substrate, wherein the at least one other substrate undergoes the same coating process as the substrate, and / or At least one characteristic of the coating process currently being implemented (or currently in progress) (of the substrate and optionally at least one other substrate).

[0035] In the method according to the invention, a portion of the light beam that initially passes through the substrate, i.e., in step a), is separated, and the remaining light beam passes through the substrate again. Then, various sensors can be used to measure the light that has passed through the substrate once and the light that has passed through the substrate two or more times. Step b) can be repeated several times, so that eventually different sensors can be used to measure the light passing through two, three, four, or more times. This means that several measurement results, i.e., the determined spectra, can be used for evaluation.

[0036] A method for measuring low absorbance values ​​involves passing a measurement beam through the medium multiple times before measurement. This method is based on the principle that the absorption of a substance (if weak) follows the Lambert-Beer law. ,and

[0037] Where T = transmittance, T0 is the initial transmittance (output transmission), K is the absorption coefficient, k is the absorption index, λ is the wavelength, and d is the optical path or the thickness of the absorption layer.

[0038] By extending the optical path length d, the decrease in transmittance can be measured more effectively.

[0039] Even without absorbing materials, transmittance can vary. These variations are caused by constructive or destructive interference of partially reflected light beams at the interfaces within the stacked layers. Interfaces arise at the transition points between two layers with different refractive indices. The resulting structure is wavelength-dependent, leading to regions of low or high transmittance depending on the wavelength. These values ​​can also be extremely low, for example, less than 1% transmittance or more than 99% transmittance.

[0040] Compared to known methods, the method according to the invention now employs one or more measurements, or simultaneous one and / or multiple measurements, of a light beam transmitted through the substrate at different times. Therefore, the invention aims to achieve the use of different measurement beams (or beams measured by different sensors). The characteristics of the coating currently being prepared or applied (e.g., coating thickness) and / or the characteristics of the coating process currently being implemented (e.g., coating rate) can then be determined using the spectra obtained from the multiple measurements (during the coating process). For example, differences or variations between different spectra can also be utilized here. For example, the range of spectra with the highest sensitivity for determining desired properties (e.g., coating thickness, or the current coating rate derived therefrom over time) can also be utilized. For example, unlike absorptivity, coating rate is a differential parameter corresponding to the time derivative of thickness with respect to time. Therefore, with the measurement method of the invention, edge steepness is more important than the magnitude of the absorptivity itself.

[0041] Contributing to this objective is, for example, the sensor's particularly excellent spectral resolution or slit width, such as a maximum spectral resolution of 2 nm, preferably a maximum of 1 nm, particularly preferably a maximum of 0.5 nm, and extremely preferably a maximum of 0.2 nm. In contrast, spectral sensors used in previously known methods only have spectral resolutions or slit widths exceeding 1 nm to 5 nm. Furthermore, a high dynamic range is also beneficial, for example, in the method according to the invention. For instance, depending on the current layer, specific properties can be determined using the spectra of two-pass or three-pass beams. If the transmittance is 10% for a single pass, it drops to 1% for two passes and to 0.1% for three passes. Therefore, a high dynamic range contributes to obtaining clear measurement results. Simultaneous analysis of several beams is also feasible. Different spectral ranges can also be used to determine one or more of the beams for different beams.

[0042] Alternatively, a portion of the beam can be polarized. The concept here is to install a polarizer in the optical path to produce, for example, p-polarization or s-polarization. In this case, a portion of the beam will be guided through the coating at a specific angle of incidence, allowing for measurement using polarized light. This has the particular advantage of allowing direct monitoring of the filter's specifications in certain situations. These are sometimes specified for oblique incidence and specific polarization states.

[0043] Therefore, the method according to the invention can be used to monitor the coating process, thereby determining and monitoring certain parameters of the coating being formed and / or certain parameters of the coating process during the coating process. For example, during the coating process, it can be determined whether or when the coating process is completed by measuring the coating thickness, and / or by determining the coating rate to check whether the coating is applied at the expected rate.

[0044] Alternatively, the endpoint of a sublayer can be determined more precisely than a single measurement by measuring the minimum or maximum transmittance. Monitoring the minimum or maximum transmittance at a specific wavelength is particularly useful for so-called periodic λ / 4 layer designs, where λ / 4 layers are always stacked on top of each other. A λ / 4 layer is a coating with a thickness of: thickness = λ / 4n, where λ is the wavelength and n is the refractive index of the layer.

[0045] A particular advantage of the method according to the invention is that the different spectra obtained from measurements of light beams passing through the substrate at different times can be used to determine the characteristics of the coating and / or coating process currently being applied or prepared, and is even more preferably applicable to cases where there are coatings on both sides. This can be achieved, for example, by using different wavelength ranges of the spectrum in step e), wherein, for example, one wavelength range is used to determine the characteristics of the coating on the first side of the substrate, while another different wavelength range is used to determine the characteristics of the coating on the second side of the substrate. For example, the differences between different spectra and / or specific regions in different spectra can also be used to determine specific characteristics of the coating on the first side of the substrate or specific characteristics of the coating on the second side of the substrate.

[0046] The method according to the invention can be implemented as a direct measurement method or an indirect measurement method. In the direct measurement method, the measurement is performed directly on one or more substrates to be coated, i.e., directly on the coating material. On the other hand, in the indirect measurement method, the measurement is performed on a reference substrate (or monitoring substrate), which (ideally) has the same coating as the material to be coated. For example, the reference substrate (or monitoring substrate) can be a test tube, etc. The measurement performed on the reference substrate can then be used not only to determine the characteristics of the coating on the reference substrate, but also indirectly to determine the characteristics of the coating on other substrates, i.e., the characteristics of the coating material.

[0047] Therefore, the substrate may preferably be a reference substrate (or a monitoring substrate), wherein, in addition, at least one other substrate undergoes the same coating process as the reference substrate, and in step e), at least one characteristic of at least one coating on at least one other substrate being applied is determined, and / or at least one characteristic of the coating process being performed is determined.

[0048] According to a preferred variant of the method of the invention, step b) is repeated at least once, preferably one to five times, particularly preferably once, twice, or three times, prior to step c), wherein in each repetition, a portion of the beam transmitted in the previous pass of step b) is separated, the separated portion illuminating a sensor that does not correspond to any of the other sensors used in step b), and after the separation of the portion of the beam, the transmitted beam is again guided back onto the substrate and again at least partially transmitted through the substrate. The beam may be guided to a first side or a second side of the substrate, respectively. Preferably, the beam is guided to the side of the substrate that was not illuminated in the previous pass of step b). This means that the beam is preferably always guided alternately to the first and second sides of the substrate. If the light beam has already illuminated, for example, a first side of the substrate during one pass in step b), then in subsequent passes in step b), the light beam is preferably guided to a second side of the substrate; or, if the light beam has been emitted to, for example, a second side of the substrate during one pass in step b), then in subsequent passes in step b), the light beam is preferably guided to a first side of the substrate. Preferably, the light beam (in each case) is guided onto the substrate in such a way that it illuminates the substrate (or the first or second side of the substrate) in a substantially perpendicular manner. The number of repetitions of step b) is preferably adjustable according to the transmittance of the light beam through the substrate. This means that the higher the transmittance of the light beam through the substrate, the more repetitions of step b) are preferably possible.

[0049] In another preferred variant of the method according to the invention, wherein, Between step a) and step b), and / or Between step b) and step c), and / or Between the two crossings (or two repetitions) in step b), The light beam is guided back onto the substrate without separating any portion of the beam, and the beam is again at least partially transmitted through the substrate. This may preferably be repeated once or several times. The light beam may be guided to a first side or a second side of the substrate, respectively. Preferably, the light beam is guided to the side of the substrate that was not guided or emitted when the light previously transmitted through the substrate. In other words, the light beam is preferably always guided alternately to the first side and the second side of the substrate. If the light beam is emitted to, for example, the first side of the substrate during one pass in step b), then in the pass of step b) after that one pass, the light beam is preferably guided to the second side of the substrate; or, if the light beam is emitted to, for example, the second side of the substrate during one pass in step b), then in the pass of step b) after that one pass, the light beam is preferably guided to the first side of the substrate. Preferably, the light beam (in each case) is guided onto the substrate in such a way that it illuminates the substrate (or the first or second side of the substrate) in a generally perpendicular manner.

[0050] In another preferred variant of the method according to the invention, wherein, The at least one characteristic of the at least one coating of the substrate and / or the at least one characteristic of the at least one coating of the at least one other substrate are selected from the group consisting of layer thickness, layer thickness gradient, uniformity, refractive index and its spectral dispersion, wavefront, phase and its dispersion, polarization, surface roughness, color value and combinations thereof, and / or The at least one characteristic of the coating process is selected from the group consisting of coating rate, temperature, particles, particle flow, and combinations thereof.

[0051] In another preferred variant of the method according to the invention, in step e) Based on at least one defined characteristic of the at least one coating of the substrate, and / or Based on the at least one determined characteristic of the at least one other substrate, and / or Based on at least one determined characteristic of the coating process, Used to estimate when the coating process is completed.

[0052] In another preferred variant of the method according to the invention, the light beam emitted onto the substrate in step a) illuminates a first or second side of the substrate in a manner substantially perpendicular to the plane of the substrate and transmits through the substrate.

[0053] In another preferred variant of the method of the invention, the beam illuminating (or guiding) the final sensor in step c) and the portions of the beam illuminating (or guiding) the sensor in step b) each have substantially the same intensity. This achieves better comparability of the determined spectra. To ensure substantially equal beam intensities, a corresponding proportion of the beam can always be separated from the transmitted beam, depending on the number of sensors used.

[0054] According to another preferred variant of the method of the invention, in step b), when the portion of the beam is separated, only at least one specific intensity range and / or at least one specific wavelength range of the transmitted beam is separated from the transmitted beam. For example, specific intensity ranges and / or specific wavelength ranges in the transmitted beam that require the determination of specific properties or are particularly suitable for this purpose can be separated. Thus, for example, only those regions (at the corresponding moment) where the corresponding desired characteristics need to be determined can be separated. For example, only those regions expected to have sufficient signal or signal variation can be separated.

[0055] In another preferred variant of the method according to the invention, wherein, in step e), the determination is made by means of at least one specific wavelength range of the determined spectrum. The at least one characteristic of the at least one coating currently being applied to the substrate, and / or the at least one characteristic of the at least one coating currently being applied to the at least one other substrate, and / or At least one characteristic of the coating process currently being implemented, Preferably, the at least one specific wavelength range is determined by simulating the determined spectrum before and / or during the coating process. For example, a specific wavelength range of the transmitted beam can be analyzed that is necessary or particularly suitable for determining a specific characteristic. Thus, for example, only those regions (at the corresponding time points) necessary to determine the corresponding desired characteristics can be analyzed. For example, only those regions expected to have sufficient signal or signal variation can be analyzed. By simulating the spectrum, a suitable wavelength range can be determined quickly and easily.

[0056] In another preferred variant of the method according to the invention, wherein, during the coating process, at least one coating is simultaneously and at least partially applied to the first and second sides of the substrate, wherein in step e), the determination is made by means of at least one specific first wavelength range of the determined spectrum. The at least one characteristic of the at least one coating currently being applied to the first side of the substrate, and / or the at least one characteristic of the at least one coating currently being applied to the first side of the at least one other substrate, and / or The at least one characteristic of the coating process currently being performed on the first side of the substrate, and / or the at least one characteristic of the coating process currently being performed on the first side of the at least one other substrate, and Using at least one specific second wavelength range that differs from the first wavelength range of the determined spectrum, determine At least one characteristic of at least one coating currently being applied to the second side of the substrate and / or at least one characteristic of at least one coating on the second side of the at least one other substrate, and / or At least one characteristic of the coating process currently being performed on the second side of the substrate, and / or at least one characteristic of the coating process currently being performed on the second side of the at least one other substrate. Preferably, the at least one specific first wavelength range and / or the at least one specific second wavelength range are determined by simulation of the determined spectrum before and / or during the coating process.

[0057] In this way, in the case of double-sided coating, the characteristics of the two coatings and / or coating processes currently being applied or prepared can be determined. Here, in step e), different wavelength ranges of the spectrum are utilized, wherein, for example, one wavelength range is used to determine the characteristics of the coating on the first side of the substrate, while another different wavelength range is used to determine the characteristics of the coating on the second side of the substrate. Preferably, the specific characteristics of the coating on the first side of the substrate and / or the specific characteristics of the coating on the second side of the substrate can be determined by utilizing the differences between different spectra or specific regions within different spectra. By simulating the spectrum, a suitable wavelength range can be determined quickly and easily.

[0058] The present invention also relates to an apparatus for monitoring a coating process using the method described herein, comprising: A light source for emitting a light beam onto the substrate, the substrate having a substrate plane, a first side of the substrate extending parallel to the substrate plane, and a second side opposite to the first side and extending parallel to the substrate plane. A beam splitter is used to separate a portion of the light beam emitted by the light source and at least partially transmitted through the substrate. A sensor for receiving light is arranged such that a portion of the light beam from the beam splitter illuminates the sensor. The final sensor for receiving light is arranged such that a beam of light transmitted through the substrate several times illuminates the final sensor, and A device for determining the spectrum of the light beam received by the sensor, wherein, The device includes a light guiding device for guiding a transmitted beam from the beam splitter, which has already had a portion of its beam separated, onto the substrate, or The beam splitter is configured such that the transmitted beam, from which a portion of the beam has been separated, is guided onto the substrate (using the beam splitter) and transmitted through the substrate.

[0059] According to a preferred embodiment of the device of the present invention, the device includes a light guiding device for guiding a transmitted light beam from the beam splitter onto the substrate, wherein the device additionally... Includes at least one additional beam splitter for separating a portion of the beam, wherein the at least one additional beam splitter is arranged such that, in each case, a plurality of beams transmitted through the substrate illuminate the at least one additional beam splitter. Includes at least one additional light guiding device for guiding a plurality of transmitted light beams from the at least one additional beam splitter onto the substrate, wherein the at least one additional light guiding device is preferably arranged such that the guided light beams irradiate a first or second side of the substrate in a manner substantially perpendicular to the plane of the substrate, and at least partially transmit through the substrate, and This includes another sensor for receiving light, said other sensor being arranged such that a portion of the light beam from said at least one other beam splitter illuminates said other sensor. Preferably, the beam splitter for coupling out a portion of the light beam, the at least one other beam splitter for coupling out a portion of the light beam, the light guiding device for guiding the transmitted light beam from the beam splitter to the substrate, and the at least one other light guiding device for guiding multiple transmitted light beams from the at least one other beam splitter to the substrate are all arranged outside the coating chamber for coating the first side and / or the second side of the substrate.

[0060] According to another preferred embodiment of the device of the invention, the beam splitter is arranged such that a transmitted beam from which a portion of the beam is coupled is guided (by means of the beam splitter) onto the substrate and transmitted through the substrate, wherein the device additionally The system includes at least one additional beam splitter for coupling out a portion of the beam, preferably one or two additional beam splitters, wherein the at least one additional beam splitter is arranged such that, in each case, a beam of light transmitted through the substrate illuminates the at least one additional beam splitter a plurality of times, and is configured such that a beam of light coupling out from it is guided onto the substrate and at least partially transmitted through the substrate. Includes at least one additional sensor for receiving light, said at least one additional sensor being arranged such that a portion of the light beam from said at least one additional beam splitter illuminates said at least one additional sensor. Preferably, the beam splitter for coupling out a portion of the light beam and the at least one other beam splitter for coupling out a portion of the light beam are arranged in a coating chamber for coating the first side and / or the second side of the substrate.

[0061] According to another preferred embodiment of the device of the invention, the device includes exactly two additional beam splitters for coupling out portions of the light beam, wherein the two additional beam splitters are arranged and configured such that a light beam transmitted through the substrate is reflected back and forth between the two additional beam splitters a number of times, wherein the light beam is transmitted through the substrate after each reflection by one of the two additional beam splitters and before the light beam illuminates the other of the two additional beam splitters (8c), and wherein the two additional beam splitters are configured such that they couple out portions of the light beam from the light beam illuminating (preferably guided above) the at least one other sensor only in some cases where the light beam illuminates one of the two additional beam splitters.

[0062] In another preferred embodiment of the device according to the present invention, wherein, The sensor has a spectral slit width of up to 5 nm, preferably up to 1 nm, particularly preferably up to 0.5 nm, extremely preferably up to 0.2 nm, and / or The sensor is a broadband sensor, preferably with a measurement range of 190 to 2500 nm, and / or The sensor is arranged outside the coating chamber for coating the first and / or second sides of the substrate, and / or The light source is broadband, among which, The preferred light source is a broadband laser, a halogen lamp, or a laser-driven arc lamp, and / or The light source has a wavelength range from 190 nm to 2500 nm, and / or The light source is arranged such that the light beam illuminates a first or second side of the substrate in a manner substantially perpendicular to the plane of the substrate, and is at least partially transmitted through the substrate, and / or The light source is disposed outside the coating chamber for coating the first and / or second sides of the substrate, and / or The light guiding device and / or another light guiding device are each a mirror, and / or The light guiding device and / or another light guiding device are each arranged such that a light beam guided onto the substrate illuminates a first side or a second side of the substrate in a manner substantially perpendicular to the plane of the substrate, and at least partially transmits through the substrate, and / or A beam splitter and / or another beam splitter for separating a portion of the transmitted beam are arranged outside or inside the coating chamber for coating the first and / or second sides of the substrate. Detailed Implementation

[0063] The present invention is illustrated by the following figures and examples, but is not intended to limit the invention to the parameters specifically shown.

[0064] Exemplary Example 1 Figure 1 A miniaturized embodiment of the invention is illustrated. Light from a light source 7, such as a lamp, is guided through a window 3 of the coating system or coating chamber. This window 3 may also be referred to as a vacuum window or separation window. The coating system has chamber walls 2. Substrate 4 is the coating substrate. Substrate 5 is a monitoring substrate, such as test glass. The coating process here is dynamic, i.e., substrates 4 and 5 move linearly or circularly between a measuring station and one or more coating areas, and possibly one or more plasma areas.

[0065] A beam splitter 8, such as a partially transparent mirror, is used to separate a portion of the transmitted beam that illuminates the sensor 1. This can be a broadband sensor, measuring, for example, the entire spectrum or a portion thereof in the ultraviolet-visible-near-infrared (UV-VIS-NIR) range. A typical measurement range is 200 to 1700 nm. After the partial beam is separated, the transmitted beam is guided back onto the substrate 5 and transmitted through it again using a light guiding device 6, such as a mirror. Polarization compensation can be performed here. The beam splitter 8 is positioned between the window 3 and the sensor 1.

[0066] The beam of light guided back onto the substrate is transmitted through the substrate 5 again. Another beam splitter 8a, for example a partially transparent mirror, is used to separate another portion of the beam from the re-transmitted light, which illuminates sensor 1a. After this second portion of the beam is separated, it is guided back onto the substrate 5 by means of a polarizing device 6a, for example a mirror, and transmitted through the substrate 5 again before illuminating the final sensor 1b. Sensors 1a and 1b can also be broadband sensors, measuring, for example, the entire spectrum or a portion thereof in the ultraviolet-visible-near-infrared (UV-VIS-NIR) range, with a typical measurement range of 200 to 1700 nm.

[0067] To ensure that the three sensors 1, 1a, and 1b receive the same light intensity, it is wise to coat a beam splitter 8 so that 1 / 3 of the light is coupled out and illuminates sensor 1, while 2 / 3 of the light is reflected back onto the substrate by the light guide device 6. Then, the beam splitter 8a should couple out 50% of the light, so that the three sensors 1, 1a, and 1b ultimately receive the same light intensity.

[0068] The light beam spectra received by sensors 1, 1a, and 1b can be determined by device 9 for determining the spectra. With the aid of one or more of these spectra, at least one characteristic of the coating currently applied to substrates 4 and / or 5 can be determined, and / or at least one characteristic of the coating process currently being performed or in progress can be determined.

[0069] Exemplary Example 2 Figure 2 Another exemplary embodiment of the present invention is shown. The meanings of the reference numerals correspond to those in Exemplary Embodiment 1. For clarity, Figure 2 Some components, such as light sources and devices used to determine the spectrum, are not shown.

[0070] and Figure 1 The arrangement comparison shown Figure 1 The optical elements used for beam splitting and guiding, namely beam splitters 8 and 8a and light guiding devices 6 and 6a, are arranged outside the coated chamber, while... Figure 2 In the arrangement shown, optical elements for beam splitting and guiding, namely beam splitters 8b and 8c, are arranged inside the coated cavity. Beam splitter 8b is a beam splitter configured such that a portion of the transmitted beam separated from it is guided onto and transmitted through the substrate. Beam splitter 8c consists of two mirrored walls that together form a waveguide structure. Here, the beam guided onto the substrate by beam splitter 8b and transmitted through the substrate again passes through the waveguide structure formed by the two mirrored walls, allowing it to be transmitted through the substrate multiple times and achieving higher measurement resolution. Due to the more compact structure, it is preferable to use a beam that can be well focused and maintain good collimation over a long distance. This is feasible for, for example, broadband lasers.

[0071] Exemplary Example 3 – Example of Single-Layer Measurement In this exemplary embodiment, the measurement results of a single Ta2O5 layer on the glass were examined as part of an exemplary variant of the method according to the invention. Figure 3 The graph shows the transmittance of a 65 nm thick layer as a function of wavelength when light passes through the substrate one, two, and three times. If the layer thickness is changed to 66 nm, the signal change is so small that it cannot be observed in the graph. Therefore, Figure 4The graphs shown illustrate the differences between the measured signals (transmittance at a thickness of 66 nm - transmittance at a thickness of 65 nm). Line #1 shows the difference in transmission spectra measured during a single pass, line 2 shows the difference in transmission spectra measured during two passes, and line 3 shows the difference in transmission spectra measured during three passes. Each measurement is superimposed with a typical noise level, which is typically in the range of a few thousandths (0.1%) of the actual measured signal.

[0072] Exemplary Example 4 - Filter In this embodiment, the manufacturing process for an ultrasonic narrowband filter is simulated. The transmission range of this filter is typically from a few nanometers to less than 1 nanometer. Figure 5 The transmission spectrum of this filter is shown. Typically, such filters are made of periodic λ / 4 layers.

[0073] The filter shown here is made up of 53 layers using the following formula:

[0074] The following section will provide a detailed analysis of layer 12H (layer 45), which is marked with an underline. Here, H represents a high-refractive-index λ / 4 layer, and N represents a low-refractive-index λ / 4 layer, both at a wavelength of 550 nm. 12H indicates a layer with a thickness 12 times that of λ / 4. The symbol "^4" indicates that this layer is repeated 4 times.

[0075] Figure 6 The diagram shows the signal changes as light passes through layer 45 once, twice, and three times. Layer 45 is a cavity layer with a thickness of 12 times λ / 4. It shows that the signal deviation is much steeper when light passes through the layer three times than when it passes through it once or twice. Since setting the correct thickness at the end of the layer is important when manufacturing the cavity layer, a steeper slope means a larger signal change when light passes through the layer two to three times. This allows the layer thickness to be set more precisely, such as... Figure 7 The view is shown again.

[0076] Exemplary Example 5 - Coating on both sides As illustrated in this example, the method and apparatus according to the invention are also particularly applicable to double-sided coatings.

[0077] Transmission measurements of the coating on both sides are shown as part of an exemplary variant of the method of the present invention. Both sides have a form of... The layer stack has a λ / 4 wavelength of 550 nm on the front side and a λ / 4 wavelength of 700 nm on the back side.

[0078] Layer 1: Front and side views ,or On the dorsal side .

[0079] Figure 8 The graphs in the image show two spectra. One spectrum has the exact thickness obtained according to formula (layer 1), while the second spectrum was calculated by increasing both the upper and lower layer thicknesses by 1 nm, i.e.: Layer 2: (HL)^550nm + 1nm L on the positive side, or (HL)^(700nm) + 1nm L on the dorsal side.

[0080] The two spectra differ by only a tiny amount, so they may be almost indistinguishable by measurement.

[0081] exist Figure 9 The differential signal was analyzed in the graph shown. The transmittance difference between the two layers at each wavelength was calculated: Differential signal = Transmittance (layer 1) - Transmittance (layer 2).

[0082] In addition, calculations were performed for multiple crossings:

[0083]

[0084] It is now shown that the most favorable signal variation depends on the wavelength. While the differential signal is highest in the 450–700 nm wavelength range for a single pass, it is highest starting at 1000 nm for two or even better six passes. In six passes, the differential signal at 450–700 nm is too small to be measured. Therefore, it is reasonable to pre-select the correct wavelength range to obtain optimal results.

Claims

1. A method for monitoring a coating process, wherein, When a substrate (4, 5) having a substrate plane undergoes a coating process, during the coating process, at least one coating is applied to a first side of the substrate (4, 5) extending parallel to the substrate plane and / or a second side of the substrate (4, 5) extending parallel to the substrate plane and opposite to the first side. a) The light beam is emitted onto the substrates (4, 5) and is at least partially transmitted through the substrates (4, 5). b) Separate a portion of the transmitted beam from the transmitted beam, illuminate the sensor (1, 1a) with the separated portion of the beam, and after the separated portion of the beam is separated, guide the transmitted beam back onto the substrate (4, 5) and transmit it through the substrate (4, 5) again at least partially. c) The beam transmitted in step b) illuminates the final sensor (1b). d) Determine the spectrum of the light beams illuminating the final sensor (1b) from step c) and the partial light beams illuminating the sensors (1, 1a) from step b). e) Using at least one of the determined spectra, determine: At least one characteristic of at least one coating currently being applied to the substrate (4, 5), and / or At least one characteristic of at least one coating currently being applied to at least one other substrate (4), the at least one other substrate (4) undergoing the same coating process as the substrate, and / or At least one characteristic of the coating process currently being implemented.

2. The method according to the preceding claim, characterized in that: Before step c), step b) is repeated at least once, preferably one to five times, particularly preferably once, twice or three times, wherein in each repetition, a portion of the beam transmitted in the previous pass of step b) is separated, the separated portion of the beam illuminating a sensor (1a) which does not correspond to any of the other sensors used in step b), and after the portion of the beam is separated, the transmitted beam is guided back onto the substrate (4, 5) and again at least partially transmitted through the substrate (4, 5).

3. The method according to any one of the preceding claims, characterized in that, Between step a) and step b), and / or Between step b) and step c), and / or Between the two crossings in step b), The beam is guided back onto the substrate (4, 5) without separating a portion of the beam, and the beam is again at least partially transmitted through the substrate (4, 5).

4. The method according to any one of the preceding claims, characterized in that, The at least one characteristic of the at least one coating of the substrate (4, 5) and / or the at least one characteristic of the at least one coating of the other substrate (4) are selected from the group consisting of layer thickness, layer thickness gradient, uniformity, refractive index and its spectral dispersion, wavefront, phase and its dispersion, polarization, surface roughness, color value and combinations thereof, and / or The at least one characteristic of the coating process is selected from the group consisting of coating rate, temperature, particle type, particle material, particle size, particle shape, particle flow, and combinations thereof.

5. The method according to any one of the preceding claims, characterized in that, In step e), the completion time of the coating process is inferred based on at least one determined characteristic of the at least one coating of the substrate (4, 5), and / or based on at least one determined characteristic of the at least one coating of the at least one other substrate (4), and / or based on at least one determined characteristic of the coating process.

6. The method according to any one of the preceding claims, characterized in that, In step a), the light beam emitted onto the substrate (4, 5) illuminates the first or second side of the substrate (4, 5) in a manner substantially perpendicular to the plane of the substrate and passes through the substrate (4, 5).

7. The method according to any one of the preceding claims, characterized in that, The beam that illuminates the final sensor (1b) in step c) and the beams that illuminate the sensors (1, 1a) in step b) each have approximately the same intensity.

8. The method according to any one of the preceding claims, characterized in that, In step b), when the portion of the beam is separated, a portion of the transmitted beam is separated from the transmitted beam that has only at least one specific intensity range and / or at least one specific wavelength range.

9. The method according to any one of the preceding claims, characterized in that, In step e), at least one characteristic of the at least one coating currently being applied to the substrate (4, 5), and / or at least one characteristic of the at least one coating currently being applied to the at least one other substrate (4), and / or at least one characteristic of the coating process currently being performed, is determined by means of at least one specific wavelength range of the determined spectrum, wherein, preferably, the at least one specific wavelength range is determined by simulation of the determined spectrum performed before and / or during the coating process.

10. The method according to any one of the preceding claims, characterized in that, During the coating process, at least one coating is simultaneously and at least partially applied to the first and second sides of the substrates (4, 5), respectively. In step e), at least one characteristic of the at least one coating currently being applied to the first side of the at least one other substrate (4) and / or the first side of the substrates (4, 5), and / or at least one characteristic of the coating process currently being performed on the first side of the at least one other substrate (4) and / or the first side of the substrates (4, 5), is determined by means of at least one specific first wavelength range of the determined spectrum. By using at least one specific second wavelength range of the determined spectrum that differs from the first wavelength range, at least one characteristic of at least one coating currently being applied to the second side of the at least one other substrate (4) and / or the substrate (4, 5), and / or at least one characteristic of the coating process currently being performed on the second side of the at least one other substrate (4) and / or the substrate (4, 5), are determined. Preferably, the at least one specific first wavelength range and / or the at least one specific second wavelength range are determined by simulation of the determined spectrum before and / or during the coating process.

11. An apparatus for monitoring a coating process using the method according to any one of the preceding claims, comprising: A light source (7) is used to emit a light beam onto the substrates (4, 5), the substrates (4, 5) having a substrate plane, a first side extending parallel to the substrate plane, and a second side opposite to the first side and extending parallel to the substrate plane. Beam splitters (8, 8b) are used to separate a portion of the light beam from the light beam emitted by the light source (7) and at least partially transmitted through the substrate (4, 5). A sensor (1) for receiving light is arranged such that a portion of the light beam from the beam splitter (8, 8b) illuminates the sensor (1). The final sensor (1b) for receiving light is arranged such that a beam of light transmitted through the substrates (4, 5) several times illuminates the final sensor (1b), and A device (9) for determining the spectrum of the light beam received by the sensors (1, 1a, 1b), wherein, The device includes a light guiding device (6) for guiding a transmitted beam from the beam splitter (8) that has been partially separated onto the substrate (4, 5), or The beam splitter (8b) is configured such that the transmitted beam, from which a portion of the beam has been separated, is guided onto the substrate (4, 5) and transmitted through the substrate (4, 5).

12. The apparatus according to claim 11, characterized in that, The device includes a light guiding device (6) for guiding a transmitted light beam from the beam splitter (8) onto the substrate (4, 5), wherein the device additionally... Includes at least one additional beam splitter (8a) for separating a portion of the beam, wherein the at least one additional beam splitter (8a) is arranged such that a plurality of beams transmitted through the substrates (4, 5) are respectively irradiated onto the at least one additional beam splitter (8a). The system includes at least one additional light guiding device (6a) for guiding a plurality of transmitted light beams from the at least one additional beam splitter (8a) onto the substrate (4, 5), wherein the at least one additional light guiding device (6a) is preferably arranged such that the guided light beams irradiate a first or second side of the substrate (4, 5) in a manner substantially perpendicular to the plane of the substrate, and at least partially transmit through the substrate (4, 5). It includes another sensor (1a) for receiving light, the other sensor (1a) being arranged such that a portion of the light beam from the at least one other beam splitter (8a) illuminates the other sensor (1a). Preferably, the beam splitter (8) for coupling out a portion of the light beam, the at least one other beam splitter (8a) for coupling out a portion of the light beam, the light guiding device (6) for guiding the transmitted light beam from the beam splitter (8) to the substrate (4, 5), and the at least one other light guiding device (6a) for guiding a plurality of transmitted light beams from the at least one other beam splitter (8a) to the substrate (4, 5) are all arranged outside the coating chamber for coating the first side and / or the second side of the substrate (4, 5).

13. The apparatus according to claim 11, characterized in that, The beam splitter (8b) is arranged such that a portion of the transmitted beam from which it couples is directed onto and through the substrates (4, 5), wherein the device is additionally The system includes at least one additional beam splitter (8c) for coupling out a portion of the beam, preferably one or two additional beam splitters (8c), wherein the at least one additional beam splitter (8c) is arranged such that a plurality of beams transmitted through the substrates (4, 5) are respectively irradiated onto the at least one additional beam splitter (8c), and is configured such that beams from which a portion of the beam is coupled are guided onto the substrates (4, 5) and at least partially transmitted through the substrates (4, 5), and Includes at least one additional sensor (1a) for receiving light, the at least one additional sensor (1a) being arranged such that a portion of the light beam from the at least one additional beam splitter (8c) illuminates the at least one additional sensor (1a). Preferably, the beam splitter (8b) for coupling out a portion of the beam and the at least one other beam splitter (8c) for coupling out a portion of the beam are arranged in a coating chamber for coating the first side and / or the second side of the substrate.

14. The apparatus according to claim 13, characterized in that, The device includes exactly two additional beam splitters (8c) for coupling out portions of the light beam, wherein the two additional beam splitters (8c) are arranged and configured such that a light beam transmitted through the substrate (4, 5) is reflected back and forth between the two additional beam splitters (8c) a number of times, wherein the light beam is transmitted through the substrate (4, 5) after each reflection by one of the two additional beam splitters (8c) and before the light beam illuminates the other of the two additional beam splitters (8c), and wherein the two additional beam splitters (8c) are configured such that they couple out portions of the light beam illuminating the at least one other sensor (1a) only when the light beam illuminates one of the two additional beam splitters (8c).

15. The apparatus according to any one of claims 11 to 14, characterized in that, The sensors (1, 1a, 1b) have a spectral slit width of up to 5 nm, preferably up to 1 nm, particularly preferably up to 0.5 nm, extremely preferably up to 0.2 nm, and / or Sensors (1, 1a, 1b) are broadband sensors, preferably having a measurement range of 190 to 2500 nm, and / or Sensors (1, 1a, 1b) are arranged outside the coating chamber for coating the first and / or second sides of the substrate (4, 5), and / or The light source (7) is broadband, preferably a broadband laser, halogen lamp, or laser-driven arc lamp, and preferably has a wavelength range from 190 nm to 2500 nm, and / or The light source (7) is arranged such that the light beam illuminates a first or second side of the substrate (4, 5) in a manner substantially perpendicular to the plane of the substrate, and is at least partially transmitted through the substrate, and / or The light source is disposed outside the coating chamber for coating the first and / or second sides of the substrate, and / or The light guiding device (6, 6a) is a mirror, and / or The light guiding device (6, 6a) is arranged such that a light beam guided onto the substrate (4, 5) illuminates a first or second side of the substrate in a manner substantially perpendicular to the plane of the substrate, and is at least partially transmitted through the substrate, and / or Beam splitters (8, 8a) for separating a portion of the transmitted beam are arranged outside or inside the coating chamber for coating the first and / or second sides of the substrate (4, 5).

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