Deposition of non-stoichiometric metal compound layers

Abstract

A method of depositing a layer on a workpiece by sputter deposition, a coating machine and a processor for controlling the coating machine in accordance with the method are provided. The method comprises providing a sputter deposition of a metal and a reactive species simultaneously on a workpiece under predetermined sputter conditions to form a layer, thereby providing a deposited layer comprising a metal compound on the workpiece. The deposited layer is subsequently irradiated and the optical transmittance is measured. A measured parameter related to the measuring radiation is compared with a stored value of the parameter. As a result of the comparison, the sputter conditions are thereby adapted.

Description

Technical Field

[0001] This invention relates to the field of sputtering. More specifically, this invention relates to sputtering non-stoichiometric metal compound layers, particularly substoichiometric metal oxide and / or metal nitride and / or metal carbide layers. Background Technology

[0002] In the fabrication of compound layers, controlling the layer composition is an important but challenging issue. Providing layers containing compounds, such as oxide layers, requires careful conditioning of materials and environment, as well as good control of growth parameters. Many chemical and physical vapor deposition techniques can be used for this purpose. In particular, sputtering deposition can provide layers a few nanometers thick, which can be used as coatings for a number of applications.

[0003] Deposition via magnetron sputtering is a well-known technique that uses a powered target under the influence of a magnetic field, causing a gas in a controlled environment to form plasma orbits on the target. This results in the removal of material from its surface by bombardment with plasma ions and the deposition of sputtered atoms onto a substrate. When custom materials require specific properties, a specific composition needs to be provided in the deposited layers, such as in one or more stacked layers. Sputter deposition can be used to provide multiple layers of potentially different materials, allowing control over the composition and thickness of the material forming each individual layer of the stack. This can be done at different stages. However, controlling the composition of the coating is challenging because changing one deposition parameter often affects the remaining parameters in uncontrollable or unpredictable ways.

[0004] To form oxide or nitride layers by sputtering deposition, a metal target can be sputtered in a “reactive mode,” i.e., in an environment containing not only a discharge gas (typically argon) but also a reactive gas (e.g., oxygen or nitrogen). The metal is sputtered onto a substrate and reacts with the surrounding reactive gas to form a metal compound layer. Although metal targets are readily available, they suffer from the well-known target poisoning effect when sputtered in reactive mode. The metal compound film forms not only on the substrate as needed but also on the sputtering target itself. As a result, the sputtering yield and thus the sputtering deposition rate are significantly reduced. Furthermore, the reactive gas partial pressure exhibits hysteresis as a function of the reactive gas flow rate in the coating chamber. At low reactive gas flow rates, the method operates in a so-called “metal mode,” and the deposited layer is metallic in nature. At higher reactive gas flow rates, the compound layer forms on the substrate but also on the target surface. The method now operates in a “poisoning mode,” and the deposited metal compound layer is ceramic in nature. The transition point from metallic to poisoned mode can occur at a different threshold reactive gas flow rate than the reverse transition and depends on the current state of the target surface. Furthermore, the transition between the two modes is characterized by abrupt changes in sputtering process variables, where small changes in reactive gas flow rates lead to large changes in the properties of the deposited layer. Therefore, the operating point near the transition point is inherently unstable. This means that metallic targets readily provide the deposition of metallic layers or stoichiometric metallic compound layers. However, depositing low-valence oxide layers (MO) with specific non-stoichiometric compositions using metallic targets is challenging. x ) or a nitrous oxide layer (MN) with a specific non-stoichiometric composition X ) or a subcarbide layer with a specific non-stoichiometric composition (MC X It has become very difficult technically.

[0005] Compared to metal targets, ceramic targets (e.g., oxide targets) offer more stable operation at their operating points because target poisoning and the resulting hysteresis effects are reduced or largely absent. However, the manufacture and manipulation of ceramic targets are often difficult due to the high melting points of the raw materials and the poor mechanical properties of these ceramics, such as the relatively high brittleness and hardness of the ceramic coating. Furthermore, oxides are generally not good conductors, so sputtering from ceramic targets is typically more electrically limited than from metals and requires the use of power supplies with advanced arc management settings. In the case of fully insulated target materials, their use is often limited to being powered by RF AC during the process, which is expensive and inefficient and cannot be easily scaled up to larger targets and higher power levels. Summary of the Invention

[0006] The objective of embodiments of the present invention is to provide a reliable and sensitive method for depositing layers, particularly substoichiometric metal compound layers, such as substoichiometric metal oxides, that allows for control of at least radiation absorption, optionally layer composition, and optionally other layer parameters, such as thickness and / or density. A further objective is to provide a computer implementation of the method, a computer program configured to perform the algorithmic steps of the method, and a sputtering system including such a computer implementation for performing the method.

[0007] This invention provides a method for depositing a layer on a workpiece by sputtering. The method includes:

[0008] - Under predetermined sputtering conditions, a layer of metal and reactive material is sputtered and deposited on the workpiece to form a layer, thereby providing a deposited layer containing a metal compound on the workpiece.

[0009] -Then the deposited layer on the workpiece is irradiated and the optical transmittance through at least the deposited layer is measured.

[0010] - Compare the measured radiation parameters of the emitted radiation with at least one stored value of the radiation parameters.

[0011] - As a comparison response, it adapts to predetermined sputtering conditions.

[0012] The method of the present invention can provide reactive substances from the target material itself and / or from the added reactive gas flow rate.

[0013] The advantage of embodiments of the present invention is that accurate non-stoichiometric compositions can be deposited by measuring composition-dependent optical properties. The advantage of embodiments of the present invention is that measuring the transmittance of the deposited layer can provide a highly sensitive measurement of oxygen levels, which is at least better than existing online chemical or spectroscopic analyses.

[0014] This method can be automated, at least between the sputtering and irradiation steps, without human intervention. Parameter comparison and condition matching can also be automated.

[0015] In some embodiments of the invention, at least one stored value corresponds to a reference amount of the reactive substance in a non-stoichiometric compound of a metal having reactive substances (e.g., oxygen and / or nitrogen and / or carbon).

[0016] In some embodiments of the invention, at least one stored value corresponds to a reference density of a compound of a metal containing reactive substances.

[0017] In some embodiments of the present invention, at least one stored value includes a value corresponding to a reference density and / or a reference amount of oxygen in an oxygen-deficient metal oxide.

[0018] The advantage of this implementation scheme is that the composition of the layer can be accurately determined and controlled, and optionally, the density can also be accurately determined and controlled based on optical measurements. This can be accomplished for non-stoichiometric metallic compounds, such as the density and / or amount of oxygen in oxygen-deficient metal oxide layers.

[0019] In some embodiments of the invention, measuring optical transmittance includes measuring wavelength-resolved transmittance of radiation, wherein the radiation has wavelengths ranging from UV radiation to IR radiation.

[0020] The advantage of embodiments of the present invention is that the opacity level of the layer can be easily estimated as a function of its composition, particularly the oxygen content in the deposited layer. Another advantage is that information about other parameters of the deposited layer (such as thickness, density, etc.) can also be obtained from measurements.

[0021] In some embodiments of the invention, measuring optical transmittance involves measuring the transmittance of radiation generated by multiple sources having a predetermined wavelength range and / or by a broadband light source using an integrating sensor. An advantage of embodiments of the invention is that the measurement of radiative transmittance (such as the optical transmittance of visible light) can be accomplished using inexpensive integrating sensors (such as photodiodes).

[0022] In some embodiments of the invention, the method includes providing a ceramic target for sputtering, the ceramic target comprising at least one metal compound, such as a metal oxide and / or nitride and / or carbide, optionally a conductive ceramic target.

[0023] An advantage of embodiments of the present invention is that it reduces or even avoids metal target poisoning. Another advantage is that the dynamic deposition rate and voltage depend in a continuous relationship on the oxygen reaction. An advantage of embodiments of the present invention is that conductive targets (e.g., resistivity below 1000 ohms.cm, such as below 100 ohms.cm, or even less than 1 ohms.cm) can be used for medium-frequency or DC sputtering.

[0024] In some embodiments of the invention, providing a sputtered deposition of a metal includes providing a sputtered deposition of at least tungsten. In some embodiments, providing a sputtered deposition further includes providing a target comprising at least one tungsten oxide. In some embodiments, the method includes depositing a non-stoichiometric tungsten oxide layer wherein the oxygen-to-tungsten ratio is 2.3 or higher, for example 2.5 or higher, for example 2.7 or higher, and less than 3, for example 2.99 or lower, for example 2.95 or lower, for example 2.9 or lower. An advantage of embodiments of the invention is that the metal-containing layer (e.g., the tungsten oxide layer) can be configured with a custom oxygen content for deposition.

[0025] In some embodiments of the invention, the method further includes sputtering in the presence of a reactive gas (e.g., oxygen and / or nitrogen) and / or an environment containing carbon. For example, sputtering in the presence of a gas includes sputtering in the presence of a gas containing oxygen and / or nitrogen and / or carbon and an inert gas, wherein the amount of inert gas is greater than the amount of reactive gas; for example, the fraction of the reactive gas flow rate relative to the total gas flow rate injected into the sputtering process is less than 50% of the total gas flow rate, for example less than 40%, for example even less than 30%, such as less than 20%.

[0026] In some embodiments of the invention, controlling predetermined sputtering conditions includes controlling conditions such that the deposited layer has a controlled transmittance that differs from the transmittance of the stoichiometric counterpart of the material of that layer. An advantage of embodiments of the invention is that layers comprising non-stoichiometric metal compounds (such as carbides, nitrides, or oxides, e.g., non-stoichiometric tungsten oxide) can be reliably deposited.

[0027] In some embodiments of the invention, controlling sputtering parameters includes controlling sputtering power, gas partial pressure or flow rate, and / or magnetic field strength. An advantage of embodiments of the invention is that it allows for precise control of the content of non-metallic elements in the layer, such as the content of reactive substances, like oxygen, to impart metallic or ceramic properties to the layer.

[0028] In some embodiments of the invention, the method may include a preliminary step of measuring the optical transmittance of the workpiece before providing sputter deposition for forming a deposited layer on the workpiece, thereby providing an initial measurement. The method may also include controlling predetermined sputtering conditions before providing sputter deposition as a response to the initial measurement. The advantage is that the conditions of the workpiece can be obtained and accurately measured to establish a reference measurement that can be used to correct measurements after deposition.

[0029] In some embodiments of the invention, measuring optical transmittance involves using a sensor and a radiation source arranged on the same side of the workpiece in a reflection mode. An advantage of embodiments of the invention is that layer transmittance can be measured even in workpieces with low transmittance or opacity, and sputtering conditions can be controlled.

[0030] In another aspect, the invention provides a processor including inputs for introducing transmission measurement data and data outputs for actuator control of sputtering parameters (including sputtering power, gas flow rate, etc.). The processor is configured, adapted, or programmed to perform the methods of the first aspect. It may include any of a database, instructions with algorithms, etc. It may include electronic units for processing data, such as processing units, like microprocessors.

[0031] In another aspect, the present invention provides a sputtering deposition coating apparatus for depositing a layer. The apparatus includes an actuator for controlling sputtering parameters, a sensing system including a radiation source for transmitting radiation through a layer deposited on a substrate, and a sensor for detecting the radiation passing through the layer. It also includes a processor of the foregoing aspects, which can be connected to or coupled to the sensing system and the actuator for controlling the actuator in response to measurements obtained from the sensing system.

[0032] Specific and preferred aspects of the invention are set forth in the appended independent and dependent claims. Features of the dependent claims may be suitably combined with features of the independent claims and other dependent claims, and not only as expressly set forth in the claims.

[0033] These and other aspects of the invention will become apparent and will be elucidated with reference to the embodiments described below. Attached Figure Description

[0034] Figure 1 This is a flowchart of a method for depositing a layer by sputter deposition with sputtering parameter control according to an embodiment of the present invention.

[0035] Figure 2 It shows Figure 1 Details of the method.

[0036] Figure 3 A sputtering apparatus including a sensing system according to an embodiment of the present invention is shown.

[0037] Figure 4 It shows a graph of transmittance as a function of wavelength for different layers placed in different oxygen flow rates, with standard cubic centimeters per minute (seem) as the unit.

[0038] Figure 5 It is a graph showing the general response of transmittance as a function of wavelength, indicating the effect of changing layer thickness (t), layer composition (x), and layer porosity (p).

[0039] Figure 6 A multi-zone coating machine according to an embodiment of the present invention is shown.

[0040] Figure 7 This is a side view of a rotary disc coating machine according to an embodiment of the present invention, used to provide layers of different or identical composition to different workpieces or to the same workpiece in several stages.

[0041] Figure 8 This is a top view of a drum-type multi-zone coating machine according to an embodiment of the present invention, used to provide layers of different or identical composition to multiple workpieces in several stages.

[0042] Figure 9 It is similar to Figure 4 The graph shows the transmission spectra of several layers at different oxygen flow rates and total pressures.

[0043] The accompanying drawings are illustrative only and not restrictive. In the drawings, for illustrative purposes, some elements may be enlarged and not drawn to scale.

[0044] Any reference numerals in the claims should not be construed as limiting the scope.

[0045] In different accompanying drawings, the same reference numerals refer to the same or similar elements. Detailed Implementation

[0046] The invention will be described with respect to specific embodiments and with reference to certain accompanying drawings, but the invention is not limited thereto, but is defined only by the claims. Dimensions and relative dimensions do not correspond to actual reductions in the practice of the invention.

[0047] Furthermore, the terms "first," "second," etc., used in the specification and claims are used to distinguish similar elements and are not necessarily used to describe a temporal, spatial, hierarchical, or any other order. It should be understood that such terms are interchangeable where appropriate, and embodiments of the invention described herein can be operated in a different order than those described or illustrated herein.

[0048] Furthermore, terms such as top, bottom, etc., in the specification and claims are used for descriptive purposes and are not necessarily used to describe relative positions. It should be understood that such terms are interchangeable where appropriate, and embodiments of the invention described herein can operate in orientations different from those described or illustrated herein.

[0049] It should be noted that the term "comprising" as used in the claims should not be construed as limited to the devices listed thereafter; it does not exclude other elements or steps. Therefore, the term should be interpreted as specifying the presence of the stated features, integers, steps, or components as mentioned, but does not exclude the presence or addition of one or more other features, integers, steps, or components, or groups thereof. Thus, the term "comprising" covers both the presence of only the stated features and the presence of these features along with one or more other features. Therefore, the scope of the expression "device comprising devices A and B" should not be construed as limited to a device consisting only of components A and B. It means that, with respect to the invention, the only relevant components of the device are A and B.

[0050] Throughout this specification, the reference to "an embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. Therefore, the phrase "in an embodiment" or "in an embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, but may refer to the same embodiment. Furthermore, in one or more embodiments, as will be apparent to those skilled in the art from this disclosure, particular features, structures, or characteristics may be combined in any suitable manner.

[0051] Similarly, it should be understood that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, drawing, or description therein for the purpose of simplification and aiding in the understanding of one or more aspects of the various aspects of the invention. However, this method of disclosure should not be construed as reflecting an intention to claim more features than are expressly recited in each claim. Rather, as reflected in the following claims, aspects of the invention lie in fewer features than all the features of a single foregoing disclosed embodiment. Therefore, the claims following the detailed description are thus explicitly incorporated into this detailed description, wherein each claim itself represents a separate embodiment of the invention.

[0052] Furthermore, while some embodiments described herein include features found in other embodiments but not others, it will be understood by those skilled in the art that combinations of features from different embodiments are intended to fall within the scope of the invention and form different embodiments. For example, in the appended claims, any embodiment protected by the claims may be used in any combination.

[0053] Numerous specific details are set forth in the description provided herein. However, it should be understood that embodiments of the invention can be implemented without these specific details. In other instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this description.

[0054] In embodiments of the present invention, the term "ceramic target" refers to a target comprising a metal and one or more other non-metallic elements. In some embodiments of the present invention, the ceramic target comprises a metal oxide (MO). y The amount of oxygen "y" in the target material is closer to 0 than its stoichiometric index. For example, for NiO... y or ZnO y The oxygen content "y" can typically be between 0.7 and 0.99; for TiO2 y SnO y or ZrOy The oxygen content "y" can typically be between 1.6 and 1.97; for In₂O y or WO Y y can have values ​​between 2.3 and 2.99; for Ta2O Y and Nb2O y The y-value can be between 4 and 4.98. However, the invention is not limited to metal oxides and other metal compounds can be provided. For example, the ceramic target may include metal nitrides, oxynitrides, etc.

[0055] In embodiments of the invention, the term "workpiece" refers to the object to be sputtered. This can be a substrate, such as glass, or a coated substrate, such as a substrate with one or more layers of deposited material. The workpiece includes the surface that receives the sputtered material. For example, the workpiece can be an uncoated substrate or a substrate coated with layers or stacks.

[0056] The properties of a material can be customized by adding layers or stacking layers by sputtering onto the surface of a workpiece. For example, a metallic compound can be deposited as a thin layer on the surface. Some properties of a material (such as those of some metal oxides and nitrides) can vary significantly with small changes in its composition (e.g., with the presence of dopants or vacancy defects). Providing the desired small changes can be challenging because variations in the composition of the gas, or the target, or generally most process parameters often affect the remaining parameters. This often occurs in an uncontrollable or unpredictable manner. This invention provides feedback control by providing optical analysis. Specifically, parameters related to light passing through or at least absorbed by the deposited (thin) layer are measured and compared to expected values. This parameter is an optical transmittance parameter, such as, but not limited to, transmission. Based on the comparison, sputtering parameters can be changed so that subsequent deposition steps can produce a layer with optical properties closer to the desired characteristics, depending on the comparison results. Additionally, the measured data can be correlated with compositional values ​​of the deposited layer, such as the amount of non-metallic elements on a metallic compound layer.

[0057] It is important to note that deposition is performed in a suitable coating machine, and optical analysis and feedback control are consistent with the coating machine in which the deposition occurs. No manual intervention is required during analysis or between the sputtering and analysis steps.

[0058] In a first aspect, the present invention relates to a method for providing at least one layer by sputter deposition under predetermined (e.g., known) process parameters. The method includes measuring and analyzing at least the radiation transmitted through the deposited layer and comparing it with a desired value of a parameter derived from the transmitted radiation. The value can be stored in a memory unit. The method also allows for the correction of sputtering conditions, for example by optimizing deposition based on a comparison to fit the deposition parameters, in order to provide a workpiece with a deposited layer having properties that make the transmitted radiation closer to the desired value. The method allows for control of the absorption of the deposited layer by optimizing the sputtering conditions. In particular, a precise amount of non-metallic elements is provided in the layer formed of a metallic compound. This alters the absorption properties of the layer.

[0059] In embodiments of the invention, where "radiative transmittance" or "optical transmittance" is mentioned in the specification and claims, it refers to the fraction of incident radiation power transmitted through the material. In this specification, the measurement of radiative transmittance refers to the measurement of at least one of these parameters of radiation transmitted through the deposited layer, such as the measurement of transmittance as a function of radiation wavelength, or the measurement of the total transmittance over the integral wavelength range provided by the source. It should be noted that reflectance, transmittance, and absorptivity follow the relationship R + T + A = 1. The effect of surface reflectance can be compensated for by calibration; theoretically, by measuring the surface reflectance of a given material (e.g., a thin film), the absorptivity can be obtained from the transmittance. Both parameters are related to and depend on the layer's thickness, porosity, and composition, and therefore these layer parameters can be inferred by measuring the transmittance.

[0060] In some implementations, at least one stored value is related to the composition of the layer, for example, to the amount of oxygen that is part of the oxide in the layer. In particular, the amount of oxygen can be oxygen present in oxygen-deficient, nonstoichiometric metal oxides, because transmittance is highly sensitive not only to thickness but also to composition, particularly to the oxygen content in the metal oxide. This is merely an example, and its stored value or range can be related to substoichiometric values ​​or ranges of nitrogen in nitrides, oxygen and nitrogen in oxynitrides, carbon in carbides, etc.

[0061] In some embodiments, the method includes providing variations in response to a measurement of radiation transmittance indicating that a previously deposited layer is too opaque or too transparent, for subsequent deposition, to adapt the sputtering power and / or the composition of gases in the deposition environment and / or the duration and / or magnetic field of the sputtering, to not only change the layer thickness but also additionally or alternatively change the composition, particularly its stoichiometry.

[0062] It should be noted that at least the steps of depositing and irradiating the workpiece can be performed sequentially without human intervention, for example, automatically using known automated processing equipment. In some embodiments, all steps of the method, including feedback loops and adaptation parameters, are performed automatically. In some embodiments, deposition is carried out in a coating machine at a pressure different from atmospheric pressure and with a customized composition, and the method steps are performed sequentially without requiring the coating machine to be changed to atmospheric pressure and with an atmospheric composition. In other words, it is not necessary to fully open the coating machine or for the user to manipulate the workpiece.

[0063] In some embodiments, the method of the present invention allows for uncoupled measurements of composition and, independently, at least the properties of individual additional layers; for example, the thickness of the layers or optical properties such as refractive index or extinction coefficient.

[0064] Figure 1 A flowchart of an embodiment of the method with optional steps is shown in a dashed box. The method includes providing 101 a workpiece to be coated, depositing 102 at least one layer of material, such as a single layer, thereon by sputtering deposition. Deposition 102 includes providing a metal and a reactive substance such as oxygen, for example, sputtering a metal or metal oxide in the presence of oxygen in the environment. The method includes subsequently measuring 103 radiative transmittance, such as the percentage of transmitted light as a function of wavelength, and comparing 104 this measurement with at least one reference value for transmittance. The method includes adapting 105 predetermined process parameters if the measurement is outside a predetermined range (e.g., if the measurement falls below a minimum value). Thus, the process parameters can be corrected for further deposition steps, such as for subsequent deposition in the workpiece. The composition of the layer on the workpiece to be coated, such as the oxygen content in the layer, can therefore be controlled.

[0065] Providing the 101 workpiece may include providing an uncoated substrate, or a previously coated substrate with a known transmittance, or a substrate comprising a coating or layer stack provided in-line with a known transmittance, such as a measured transmittance.

[0066] Some applications require the substrate to have accurate and known optical properties, such as transparency. This method allows for the measurement of radiative transmittance after layer deposition and comparison with a desired value or its range. The desired value or range can be stored in memory. If the transmittance does not fit the desired range (e.g., if it is greater than or less than the desired value), this method allows for the correction of deposition parameters. In some embodiments, if the transmittance is below or above the expected range, the parameters can be corrected for subsequent sputtering (e.g., on different workpieces or on the same workpiece).

[0067] For example, if the transmittance is lower than a predetermined value, or any value within a range near a preferred value, the sputtering parameters of the next workpiece to be sputtered are changed to provide higher transmittance. For example, a thinner layer can be provided by reducing the sputtering power during the deposition process. A higher oxide content can be provided in the layer, for example, by increasing the oxygen flow rate during the deposition process. Other parameters of the method can be changed, for example, by changing the magnetic field strength, or by changing the gas partial pressure, or by changing the residence time in front of the coated area, or by any other process parameter that can lead to higher transmittance. If the transmittance is higher than expected, any one or more parameters can preferably be adjusted in the opposite manner.

[0068] The difference between the expected value or range and the measured value can be used to determine how much of the deposition parameters should be adjusted. This can be based, for example, on a calibration reference stored in memory or on theoretical calculations. The invention is not limited to these. For example, learning algorithms can be applied to improve the adjustment of sputtering conditions, advantageously taking into account the interdependence of sputtering conditions experimentally. Additionally, some applications can benefit from the measurement of the chemical composition of the deposited layer. Chemical composition can affect many layer properties; for example, structural (e.g., layer morphology or crystallinity), mechanical (e.g., layer stress or hardness), electrical (e.g., carrier density and mobility), and optical (e.g., overall or spectral transmittance or absorptivity) properties. Transmittance is related at least to the composition and thickness of the layer. Since the sputtered elements are known, transmittance and thickness can be indicators of the amount of elements in the layer. The layer thickness can be measured by any suitable means after or during sputtering, or the layer thickness can be calculated (based on precise calibration such as deposition time), thus allowing the transmittance to be correlated with a specific amount of the deposited elements. Therefore, optionally, the method may include additionally correlating the measurement with at least one stored value corresponding to a specific composition. Optionally, the specific composition is a non-stoichiometric metallic compound, such as, but not limited to, oxygen-deficient oxides. In some embodiments of the invention, if the measured transparency is outside an acceptable threshold, the amount of oxygen incorporated into the deposited layer can be controlled and adjusted to provide a layer with more or less transmittance. An oxygen-deficient layer will typically exhibit some degree of absorptivity. Higher absorptivity reduces transmittance (because R + T + A = 1). Therefore, the reduced transmittance due to the substoichiometric oxide layer is directly related to the degree of substoichiometry and its layer thickness: for a given fixed composition, a thicker layer will produce greater absorptivity and lower transmittance.

[0069] In embodiments of the invention, the composition of one or more low-valence oxides of the metal oxide can be correlated with corresponding transmittance values ​​stored in a memory cell. The actual composition of the layer can be inferred by comparing the measured transmittance with the stored value associated with the specific composition. It has been found that very accurate measurements of the composition can be obtained, as the composition appears to have a significant effect on the transmittance of the oxide. Therefore, complex dedicated chemical spectroscopic apparatus such as Rutherford backscattered spectrometers or X-ray photoelectron spectrometers are not required to obtain the composition of the deposited layer; these instruments are expensive and difficult to integrate into sputtering deposition apparatuses. The invention allows for chemical composition analysis without the need for expensive apparatus, which can be provided online, by providing a sensing system capable of measuring radiation transmittance and a suitable processor configured to analyze the transmittance data.

[0070] The approach of the present invention allows for flexible and precise control of the transmittance of the layer, for example, without changing the thickness of the deposited layer, or even combining it with thickness variations for wide-ranging precise control. For example, a sputtering process that provides optimal thickness but suboptimal transmittance can be controlled and modified to alter the composition, thereby allowing control of transmittance without changing the layer thickness.

[0071] To measure radiation transmittance, a sensing system comprising at least one radiation source and at least one sensor can be used. Figure 3An example of such an apparatus is shown, comprising a coating machine having a sputtering chamber and a sputtering target. The coating machine chamber 308 may include a sputtering target system, such as a planar or tubular target 309, which may be metallic or, for example, ceramic. Behind the coating machine chamber 308 is a measurement area where, after sputtering, a workpiece may be placed, for example, automatically. In other words, after sputtering deposition, the workpiece reaches the sensor 304. In this measurement area, radiation 300 from a source 301 can pass through the workpiece, which includes a stack of deposited layers 302 (which may consist of only one layer or several layers of the same or different materials and compositions), after deposition in the coating machine chamber 308. The radiation can also pass through a substrate 303 of the workpiece, which in some embodiments may be transparent to the radiation 300. The sensor and the radiation source may be located on opposite sides of the workpiece for measurement in transmission mode. In some embodiments, the radiation source directly impinges on the deposited layers. In some embodiments, the radiation source may impinge radiation on a surface of the substrate opposite the surface in which the layers are deposited. The signal obtained in sensor 304 is sent to processor 305, which provides a transmittance value corresponding to the signal and compares it with at least one value stored in memory 306, such as a desired value or a set thereof. If the measured value is significantly different from the desired value, the processor may send a signal to controller 307 to change the sputtering conditions of coating chamber 308 used to provide layers from layer stack 302 based on the comparison result.

[0072] This invention provides control over deposition parameters for at least one layer of a stack. For example, adapting sputtering conditions 105 may include adapting power settings or power delivery, runway angle width and orientation, and magnetic field strength. Geometry within the coating machine can be adjusted, for example, by moving the workpiece, shield, or sputtering source within the coating machine. In embodiments of the invention, adapting conditions include the amount and / or type of gas in the atmosphere of the adapting chamber. For example, partial pressure can be varied. Partial pressure will be a result of gas inlets, pumping capacity, and their relative geometry within the processing chamber; for example, if pumping capacity is also reduced, gas flow rate can be reduced while maintaining the same pressure state. For example, the method may include adapting the amount of reactive material in the environment 115, for example, by adjusting the amount of oxygen or nitrogen delivered to it (e.g., via a valve or mass flow controller) or extracted from it (e.g., by pumping or by aspirating from the reaction process). For example, the method may include adapting the amount of target material reaching the workpiece 115, for example, by adjusting the power level delivered to the target (since reactive material can be provided by the target material, for example, from a ceramic target). For example, adapting sputtering parameters 105, and particularly adapting reactive materials 115, may include, for example, adapting the plasma density in front of the target by adjusting the magnetic field strength and the local collision density of electrons bombarded by gas particles. Each of the sputtering parameters mentioned above can be adjusted individually or in combination to adapt the content of reactive material in the workpiece to be subsequently coated or in a layer in a subsequent coating step of the same workpiece. Controller 307 or multiple controllers may be configured to control actuators such as those for powering actuating valves and / or electromagnets.

[0073] Turning more specifically to the sensing system, this depends on the different information that sensor 304 can obtain from the measurement. For measurements where the layer thickness is known or can be measured by a dedicated measurement system, the sensor system may include a simple integrating photoelectric sensor, and broadband (e.g., white light source) or small strip (e.g., specific color LED) radiation sources may be included.

[0074] Therefore, in some embodiments of the invention, measuring transmittance 103 may include measuring the integrated transmittance of one or more radiation sources 113 using an integrating sensor that measures transmittance over a wide range of wavelengths. In this case, the fraction of the total radiation transmitted through the workpiece is measured (as a single value). If the light source is broadband (e.g., a halogen lamp), information on the total transmittance is obtained over that wide wavelength range. If the source has a narrower band, such as a red LED, with a spectral output close to 630 nm and a spectral bandwidth of + / - 30 nm (i.e., a Gaussian curve starting at approximately 600 nm, maximizing at 630 nm, and ending at 660 nm), the integrated spectral response is measured only for that specific wavelength window. However, additional (e.g., different) sources may be integrated in parallel, such as another LED light source 301, for example, green (wavelength range around 560 nm) and / or blue (range around 480 nm). Several integrated transmittance values ​​corresponding to the wavelength content of the source can be obtained. This can be accomplished, for example, by providing sequential radiation, such as by triggering sources one after another, and synchronizing the measurement with sensor 304, so that the transmittance response can be correlated with a corresponding source having a known small wavelength band. A photodiode always fully integrates any light arriving at it; therefore, the source defines the spectral content.

[0075] The advantages of using integrating sensors (such as photodiodes) are their wide availability and the low cost of the required devices.

[0076] Because optical transmittance measurements can be spectrally selective and display transmittance values ​​at multiple individual wavelengths or a range thereof, spectral information of the transmitted radiation can be used. Therefore, measuring transmittance can include obtaining spectral information of the transmitted radiation. In other words, transmittance can be measured with wavelengths resolved to the radiation wavelength. The radiation can have wavelengths ranging from UV radiation to IR radiation. For example, this can be used to study the thickness of a deposited layer. As previously mentioned, thickness can be obtained through a dedicated measurement system such as an electrical system, or it can be inferred from, for example, the deposition time through theoretical calculations and calibration. However, in some embodiments, the method can include calculating the properties of the 106 layers, such as the properties of a single layer or multiple layers. Based on the measurement of the radiation transmission itself, these properties can include refractive index, extinction coefficient, porosity and density, thickness, etc. For a given and / or known thickness, integral measurements can still define the composition, such as the amount of oxygen in an oxygen-deficient metal oxide. In contrast, spectroscopic measurements allow for the inference of additional layer parameters; for example, layer thickness, and even optical properties such as spectral refractive index and extinction coefficient. For example, the thickness and related data of the layer can be extracted from the spectral analysis of the transmitted radiation. In other words, the spectral transmittance curve itself is sufficient to calculate the layer thickness. Having an interference pattern can be sufficient and is used to adjust process parameters in order to adjust the layer thickness (in addition to composition; specific amounts of elements are deposited). This will be referenced below. Figure 4 Let's have a discussion.

[0077] Optionally, the method may include an additional measurement of the transmittance 107 prior to layer deposition to establish a baseline or initial conditions. This step is optional because setting the baseline can be done theoretically. For example, if layer deposition is performed on a well-known workpiece, only the transmittance after deposition needs to be known. For example, for a bare substrate such as uncoated glass, where the transmittance is known or can be measured in advance, the known transmittance can be considered in stored values ​​or during data processing.

[0078] In some implementations, transmittance measurement is performed by striking the surface of a workpiece with radiation and observing the light exiting the opposing surface. This means the workpiece needs to be placed between the radiation source and the sensor after sputtering, as previously described. However, if the workpiece exhibits very low transmittance, transmittance measurement can be performed even in reflection mode.

[0079] For example, some applications include the fabrication of mirrors (such as active mirrors). In the fabrication of active mirrors, the workpiece to be coated can be a high-quality mirror (e.g., with a sufficiently thick Ag or Al layer on a substrate, such as a glass or metal plate). In this case, spectral reflectance is an important parameter, while transmittance may be too low to be accurately measured on the workpiece. However, the present invention still allows for the use of transmittance measurements to define and control MO. x The composition of the layers. In this case, a baseline can preferably be set by measuring the reflectivity of the workpiece (which can be very high), although this can be done theoretically or as a pre-measurement. The reflectivity is measured (or measured again) after the sputtered deposit layer (e.g., a non-stoichiometric oxide layer). The effect of dual transmittance can be extracted from the measurement of the layer to be controlled, as radiation enters the deposited layer and is reflected back. In this case, the method can include calculations, such as computational algorithms, that need to take into account the interference that occurs before coating due to reflection at the top surface of the coated workpiece and due to radiation reflected at the interface between the sputtered deposited layer and the workpiece. Again, this reflectivity pattern allows for the calculation of single-layer or multi-layer properties based on two or more lateral radiations passing through the deposited layer, while using baseline optical data, in this case, reflectivity. Thus, layer quality is still evaluated on transmittance data (radiation passing through the deposited layer, such as a non-stoichiometric oxide layer or a stack of layers including such a layer), while the actual measurement is a reflectivity measurement.

[0080] For example, in another large application area, sputtering coatings are applied to flexible substrates, such as PET or PI, or any type of foil, which can even include flexible glass. Such coating systems are called web coaters or roll-to-roll coaters, where the substrate is unwound from the rolls, conveyed through the coating zone, and eventually rewound onto another roll. In this typical coater, the flexible substrate is guided on the rolls and wound onto a cooling drum as it is brought to the coating zone. In practice, many polymer flexible substrates can begin to deform under limited temperature rise, such as stretching or wrinkling, thus affecting the quality of the deposited film. While sputtering deposition places a significant heat load on the substrate due to film condensation, impacting particles, and radiation from the plasma, special precautions are needed to control the temperature. Wrapping the substrate around a cooled drum allows sufficient heat energy to be extracted from the substrate to allow for stable sputtering deposition without significant substrate deformation. In many cases, the substrate and deposited coating exhibit significant portions of transmittance because they are used in numerous applications: for example, as window films (requiring lamination to windows to control visual and thermal transmittance), as laminates in touchscreens of mobile devices, as anti-reflective coatings for displays, as gas or moisture barriers in food packaging, and in many other cases. In these situations, controlling the layer properties of the sputtered non-stoichiometric metallic compound layer is also necessary. Measuring transmittance through at least the deposited layer cannot be easily accomplished near the sputtering chamber by placing the radiation source and sensor on opposite sides of the flexible substrate. The substrate spans a metal cooling drum. However, in most cases, the cooling drum has a highly reflective and polished (low roughness) outer surface to optimize heat transfer between the cooling system and the substrate heated by the deposition process. Although a workpiece (e.g., a foil) with at least one coating may exhibit transparency, reflectivity measurements can be performed simultaneously using the cooling drum as a reference and calibration reflective surface to define the (double) transmittance of radiation through the layer that needs to be measured and controlled. The same rationale applies to mirrors as described above; however, in this case, the reference reflective surface is not part of the workpiece to be coated.

[0081] Therefore, in this reflective configuration, the sensor and the radiation source are arranged on the same side of the component, for example, both facing the surface with the deposited layer.

[0082] This also allows for the measurement of opaque or very low-transparency workpieces, such as transparent layers deposited on opaque substrates.

[0083] As long as the stack 302 exhibits sufficient transmittance to radiation 300, reflection measurements can be used to evaluate the transmittance of the layer stack. In the case of reflection; the incident radiation will then typically form an angle with the normal relative to the surface (preferably as small as possible; e.g., less than 15 degrees, such as less than 10 degrees, like 7 degrees). The detector will then preferably be placed close to the mirror surface, thus having a similar angle symmetrical to the normal of the incident angle, in order to capture the optimal signal of the reflected radiation. The reason for non-directional positioning in reflection measurements is generally from a practical point of view, as the source and sensor are typically two physical units and need to be placed adjacent to each other. However, the invention is not limited to the angular configuration in reflection, and other angles can be used.

[0084] Optionally, the method may include depositing one or more layers in a stack, subsequently measuring transmittance before layer deposition, and then measuring transmittance after deposition. In the process of depositing MR... x Measuring the layer region beforehand can help understand and compensate for uncontrolled variations in the workpiece, such as in one or more layers deposited upstream of a coating machine, where M refers to the metal component and R refers to one or more reactive components of the compound (e.g., oxygen, nitrogen, carbon).

[0085] This method involves providing a metal via sputtering while simultaneously providing non-metallic elements onto the deposited layer. In some embodiments, such as Figure 2 As shown, depositing layer 102 by reactive sputtering deposition includes sputtering layer 112 metal using a metal target in an environment including, for example, oxygen. In some embodiments, the metal target comprises a high-purity metal, such as tungsten or nickel. Alternatively, the metal target may comprise an alloy metal target, such as a nickel-tungsten alloy (NiW) target.

[0086] Optionally, sputtering deposition includes deposition 122 using at least one ceramic target. Such a target can simultaneously provide metallic and non-metallic elements through sputtering. The ceramic target may have a single-material part for sputtering without grooves. In some embodiments, the material used for sputtering is conductive, thereby allowing sputtering at sub-RF frequencies. It may contain a large amount of oxygen-deficient metal oxides or compounds thereof.

[0087] In a specific example, the tungsten oxide layer was deposited in a controlled environment with a controlled amount of oxygen, the amount of which could be varied. The remaining sputtering conditions were known. The target was a ceramic target (metal oxide target). Transmittance was measured after the deposition step. For nine different amounts of oxygen, transmittance as a function of wavelength is shown as the percentage of radiation emitted by the coated workpiece. Figure 4 In addition, although the amount of oxygen flow rate is different in each case, the rest of the deposition conditions are essentially the same for all measurements (e.g., slight variations in pressure with flow rate can be ignored or calculated if necessary).

[0088] Intentionally, oxygen-deficient tungsten trioxide (WO3) can be generated during the sputtering process. x The values ​​of x are between 3 and 2, for example, 2.3 or higher, 2.5 or higher, 2.7 or higher, and below 3, for example, 2.95 or lower, 2.9 or lower. Sputtering in a pure Ar gas environment may tend to further reduce the layer composition (reduce its x value) relative to the target composition. Figure 4 In the example, WO Y The target was set with a y-value close to 2.8. Sputtering in pure Ar gas reduced the layers that would form on the workpiece. For example, substoichiometric oxides WO3 have been found to be deposited. x The value of x is close to 2.1, which means that oxygen is pumped out of the target during the sputtering deposition process. This results in the deposition of a metal-rich layer. Compared to the process in pure Ar, adding oxygen during sputtering can increase the oxygen content of the layer, and if excess oxygen is introduced during layer formation, it provides a layer with a composition similar to, closer to, or even exceeding the stoichiometry of the target (x > 3).

[0089] For corresponding to Figure 4 The radiation source for the layer shown in the diagram is a broadband source. Radiation is transmitted through one side of the deposited layer, for example, illuminating the surface of a substrate that was not deposited in this step, or vice versa, and the transmittance is measured. The graph shows the spectral transmittance as a percentage of the radiation reaching the detector on the other side of the workpiece, compared to the case where no workpiece is present. Reference measurements that allow for calibration of source intensity and detector (spectral) sensitivity are typically performed in the gap between the two workpieces passing through the sensing area.

[0090] It is clear that when the oxygen content in the sputtering environment is 50 sccm or higher, the deposited layers have approximately the same maximum transmittance, with interference peaks showing a maximum transmittance slightly above 90% and an intermediate range close to 80%. These maxima of the interference pattern correspond to the transmittance of the workpiece entering the coated area, in this case, a flat glass substrate. It can be safely assumed that layers deposited at concentrations of 50 sccm and above are substantially transparent to radiation with wavelengths exceeding 400 nm. It can also be inferred that the layer primarily comprises stoichiometric tungsten oxide (WO3).

[0091] However, for concentrations of 40 sccm and lower, the maximum transmittance decreases. At 40 sccm, transmittance also decreases to below 70% in the intermediate range for wavelengths above approximately 700 nm. At 35 sccm, the maximum transmittance seen at approximately 400 nm is below 70%, and transmittance at approximately 600 nm wavelength has decreased to below 50%. The lowest relative minimum transmittance occurs at less than 30% of the radiation at 1000 nm wavelength. In the optimal case, transmittance decreases by 10% at approximately 500 nm (maximum and intermediate values), and by approximately 35% for radiation at 800 nm, with a change in oxygen concentration of only 5 sccm.

[0092] This trend continues at 30 sccm, with absolute maximum transmittance below 50%. Deposits with oxygen contents of 25 sccm and 20 sccm show maximum transmittances below 30% and 15%, respectively. In summary, as the oxygen content decreases from 40 sccm to 20 sccm, transmittance decreases by 60% for a wavelength of approximately 400 nm, ranging between almost 80% and almost 15%.

[0093] The table below shows the oxygen content (x-value) and layer thickness of the deposited layer as measured by an electron microprobe analyzer for different oxygen flow rates (in SEM) in the sputtering environment.

[0094] Table - Atomic ratio of tungsten / oxygen, oxygen content and thickness, and oxygen flow rate.

[0095] 0 2.08 15 2.55 20 2.8 666 25 2.88 630 30 2.96 620 35 2.98 571 40 2.99 555 50 3 506 60 3 452 80 3 355 100 3 293

[0096] Therefore, transmittance can be precisely controlled by controlling the oxygen content in a layer of a given thickness, which can then be used as an accurate indicator of the layer composition.

[0097] It is also noteworthy that for oxygen content below 35% in the chamber, the resulting layers are more absorbent of radiation above 750 nm. In fact, for layers deposited in the chamber at 25 sccm or 20 sccm, the layers have 0% transmittance for radiation above approximately 750 nm, and are therefore completely opaque. When these samples are observed, they exhibit a bluish appearance that darkens as the oxygen flow rate decreases.

[0098] Figure 4 It shows the distinction between WO xExtremely high resolution was achieved for different compositions of the layers, with x-values ​​ranging from 2.8 to 3. For the plots shown, estimating x-values, for example, between 2.1 and 2.8, appears to become more difficult or impossible when the transmittance of the layer with an x-value of 2.55 is below 1%. However, additional testing shows that this is not necessarily the case. In the cases shown, the resolution loss at lower oxygen flux and lower x-values ​​is due to the high relative thickness of 600 nm (measured using analytical laboratory equipment, e.g., Dektak step measurements). Reducing the layer thickness to, for example, 200 nm or less (which is more common in multilayer optical stacks) will exponentially increase transmittance and will allow for the introduction of higher sensitivity in more substoichiometric compositions; for example, between 2.3 and 2.8, and in WO... x In the case of oxygen flow rates between 5 sccm and 20 sccm, the resolution and extreme sensitivity shown now for compositions between 2.96 (30 sccm O2 flow rate) and 3.00 (at least 50 sccm O2 flow rate) decrease at smaller layer thicknesses, while it approaches a transparent state.

[0099] Furthermore, the transmission pattern formed by transmitted radiation exhibits maximum and minimum values ​​for different wavelengths. Information related to the thickness of the deposited layer can be extracted from this pattern. This is a typical optical interference effect from a layer with a specific refractive index deposited on a workpiece with different refractive indices. After traveling through the layer, the radiation is reflected on the top and bottom surfaces of the workpiece. The total reflected radiation may exhibit constructive interference for some wavelengths and destructive interference for others because the optical paths traveling from the radiation are different. The path difference depends on the refractive index and thickness of the top layer and is combined with the angle of incidence. The reflectivity may exhibit color stripes similar to the colored stripes of oil droplets on a water surface. Because reflectivity becomes wavelength-dependent, and assuming a neutral or steadily decreasing absorptivity with wavelength, the transmittance will exhibit an anti-interference pattern (since A+R+T=1). The optical thickness of the top layer can be calculated from the wavelengths at which the maximum and / or minimum values ​​occur. The amplitude of the interference (the difference between the maximum and minimum transmittance or reflectivity) allows for the calculation of the refractive index. As can be inferred from Figure 4, layers deposited at 50 sccm or higher are actually transparent, have similar refractive indices, but have different layer thicknesses (variations in wavelength spacing between extrema).

[0100] The transmittance response of layers deposited with an oxygen flux of 40 sccm or lower indicates some absorption. This is typical metallic behavior and becomes more dominant at lower x values; where there is an excess of metal relative to the stoichiometric dielectric layer. A higher metal fraction will exhibit greater absorptivity and lower transmittance. In this case, transmittance is determined by the total amount of metallic regions or particles that radiation must pass through. Therefore, the transmittance level is defined by the absorptivity level of the material; this is determined by its composition (or the x value in MOx) and its thickness.

[0101] The following parameters can also be obtained from the measurements. As porosity increases, non-stoichiometric layers with known x-values ​​and thicknesses change in a specific way, which can be viewed as a decrease in density. For high oxygen content (transparent layers), the minimum intensity of the interference pattern increases, thus reducing its amplitude. Materials with very low density ultimately do not exhibit interference patterns, similar to the behavior of having no layers. This will be explained below with reference to aspects of the processor used to analyze the results.

[0102] Other properties, such as extinction coefficient and optical index, can also be obtained, for example, from spectral information and optimized from transmission measurements by adapting sputtering conditions in further deposition steps.

[0103] In some implementations, the deposited metal includes depositing tungsten and nickel, for example using a target containing said metal (e.g., an alloy thereof).

[0104] This method can be applied to multi-zone coating machines. A multi-zone coating machine is a sputtering system or apparatus with multiple stages or zones, including those previously referenced. Figure 3 Defined compartments are used to perform sputtering steps. Each compartment includes a target assembly for sputtering, such as one or two tubular targets. These stages can be maintained in a controlled environment, such as in multiple sputtering chambers. If necessary, they can be isolated so that the environment in each chamber can be controlled independently and / or to avoid cross-contamination of gases leaking from one compartment to another. Some targets require sputtering in pure Ar gas to deposit a layer with a composition similar to the target material. In some applications, the presence of certain reactive gases can have an adverse effect on poisoning or contaminating the target surface or the layer being deposited. A transport system allows the introduction of substrates into the apparatus and also transports workpieces (e.g., substrates or at least partially coated substrates) from one stage to the next until the coating process is complete and can be removed from the apparatus. Such transport can include moving platforms, chains, conveyors, etc.

[0105] In summary, the method includes providing a workpiece 101, depositing a layer 102 on the workpiece by bringing the workpiece to a sputtering zone, and measuring the transmittance of the layer 103 and any remaining workpiece in the workpiece on which that layer is deposited. The method includes, if the transmittance is outside an acceptable range, then, after comparing the measurement with a desired range 104, changing the parameters of the sputtering process in the sputtering zone 105 so that subsequent workpieces can be sputtered with parameters closer to the ideal. This establishes a feedback loop in the method for improving the sputtering parameters of the desired layer to achieve the desired transparency, and thus obtain the desired layer characteristics.

[0106] In some implementations, prior to deposition, the 107 workpiece can be measured to establish a baseline for the transmittance of the substrate and any existing coatings, as previously explained, before depositing a new layer. Specifically, measurements can be taken between stages in a multi-zone coating machine. For example, measurements can be taken between two sputtering steps, such as between two sputtering stages or compartments, or between each sputtering step.

[0107] In another aspect, the present invention relates to a processor 305 or processing unit including one or more data input ports for receiving radiation transmittance measurements. The processor includes a control data output port for sending control signals to a sputtering apparatus to control the sputtering process. The processor is programmed to process the data and at least perform a comparison step when receiving radiation transmittance measurements, and to send control data outputs to control sputtering process parameters (e.g., gas composition, such as oxygen content in the sputtering chamber, though the invention is not limited thereto). The processor may also control other steps, such as deposition and impact radiation.

[0108] Processor 305 can access memory, such as a data port for accessing lookup tables, like memory unit 306, having desired transmittance values ​​or a range thereof. It can include data that correlates transmittance values ​​with chemical composition. For example, a set of transmittance values ​​can be correlated with the corresponding oxygen content of a predetermined low-valence oxide composition. The processor can be programmed to output data and display the chemical composition in a user interface device, such as a screen.

[0109] Processor 305 can be equipped with software that allows the execution of simple or complex algorithms, based on analytical or self-learning models and incorporating machine learning from historical data. Several algorithms can be run sequentially or in parallel to capture the maximum possible information from the provided transmitted data. The specific methods for how these algorithms can function to extract deposited MR... x General methods for determining the properties of layers, such as Figure 5 As shown, x is lower than the stoichiometric index. Qualitative interpretation can be performed to accurately quantify layer properties, such as layer thickness t, layer composition x, or layer porosity p.

[0110] In this example, a single spectral transmittance measurement is fed to the algorithm without using reference data or baseline measurements. In this illustrated case, but not limited to such a model or concept, the algorithm can attempt to extract various properties and accurate values ​​of the deposited non-stoichiometric oxide layer. As part of the analysis, the algorithm can detect several maximum and minimum values ​​in the curve caused by interference. Any consecutive extrema can allow the calculation of layer thickness. If several extrema appear in the graph, a consistency check can be performed to improve accuracy. If adjacent maximum values ​​are closer to each other (as shown in the graph); that is, if the vertical solid line moves closer to the vertical dashed line, this indicates an increase in layer thickness t. The overall shape of the transmittance curve or the integrated transmittance value can indicate the non-stoichiometric level of the oxide layer. If MR x If the x-value is close to the stoichiometric index, a dielectric layer with high transmittance is observed. If the x-value further decreases below the stoichiometric index of the compound, indicating the presence of an increasing fraction of metal in the layer, the total transmittance will decrease exponentially with increasing layer thickness (defined by another curve characteristic).

[0111] The curved arrows in the graph illustrate the evolution of the graph as the x-value increases. Further analysis is needed to limit the porosity of the layer under study. It has been observed that non-stoichiometric layers with known x-values ​​and thicknesses will change in a specific way as porosity increases (density decreases). In this case, two distinct changes in the curve can be noted, stemming from increased porosity. Within more dielectric behavior (for higher x-values ​​in MRx), the minimum of the interference pattern creeps upwards, as indicated on the graph: the horizontal solid line shifts towards the dashed line. In the case of extremely low densities, the interference pattern may disappear and high transmittance may be reached, as if no layer were present, corresponding to the limit of no density. In more mixed compositions where metal absorption is observed (for MRx)... x The transmittance curve for a layer with a known x-value and thickness shifts to a higher value (where the x-value is lower in the layer). In fact, radiation is more easily transmitted because there are fewer absorbing particles in the lower-density layer. In this case, the upward arrow representing porosity in the curve will affect the entire curve, not just the minimum value.

[0112] In parallel, different algorithms can be run to translate observed changes in layer properties into choices of process parameters to adjust the layer in order to return it to the desired nominal layer properties. This may require tuning one or more parameters locally or globally within the sputtering chamber to achieve the desired adjustments.

[0113] Furthermore, the algorithm can take into account that most parameters may have interrelated responses. For example, the processor can include additional inputs from one or more sensing systems on the workpiece for detecting, for example, thickness. If the layer appears too thin at a particular location on the workpiece, the processor can take control and increase the sputtering power to increase the amount of particles leaving the target and ultimately result in an increased layer thickness. However, at the same time, the partial pressure of the reactive gas may decrease as more metal particles are carried into the plasma, balancing the reaction with the available reactive gas and reducing the amount of gas available for MR. x The available amount of reactant gas formed. As a result, the value of x can be influenced and reduced, while the layer thickness increases simultaneously. This can all be taken into account by the algorithm running in the processor.

[0114] In parallel, another artificial intelligence algorithm can be run based on machine learning to understand and control the sensitivity of each sputtering parameter in the sputtering parameters under given conditions and environments. If fine-tuning of specific parameters is required, the adjustment can be adapted in a way that executes critical and accurate control quantities. Adjustments that are too small will take too long and may result in sputtering several workpieces under suboptimal conditions before the desired conditions and layer performance are re-established. On the other hand, over-adjustment can cause the process to oscillate and become completely out of control. Self-learning algorithms can provide intelligence for fast and accurate process tuning.

[0115] In another aspect, the present invention relates to a coating machine, such as Figure 3 The coating machine shown, or, for example, a multi-zone coating machine, includes a sensing device for sensing transmittance, a control device for controlling process parameters based on measurements from the sensing device, and optionally a readout device for providing control values ​​of the layer within a certain tolerance level (e.g., the chemical composition of the deposited layer) based on transmittance measurements. The coating machine may include a processor 305 configured to perform the steps of the method of the first aspect of the invention, including but not limited to signal processing and comparison with stored values.

[0116] Figure 6 A coating machine 500 is shown, which includes a plurality of sputtering zones 501 having corresponding target assemblies. The sputtering zones may include, for example, a coating machine compartment 308, such as... Figure 3 As shown, the coating machine includes tubular targets, planar targets, etc. The coating machine includes a downstream measurement region 502, which includes a suitable sensing system, such as a radiation source 301 (e.g., an LED, multiple LEDs) and a sensor 304 (e.g., an integrating sensor, such as a spectrometer, photodiode, etc., which can be synchronized with the radiation source or multiple radiation sources, or a spectral analyzer). The sensor 304 generates a signal dependent on the received radiation transmitted through the coated layer or layer stack 302 and the substrate 303.

[0117] The coating machine may include a sensing system 311 that measures the intensity of reflection through the layer, thereby obtaining transmission data, as previously explained.

[0118] Electronic processor 305 receives signals 304 from sensors. The processor is adapted to process measurements. The processed signal can be compared with a transmittance value or a set of values ​​that can be stored in a memory unit 306, which can be integrated into or connected to the processor. Based on the comparison result, the processor can generate a signal and send it to controller 307 to control sputtering parameters. The sputtering parameters for the next workpiece are then adapted and optimized. Specific parameters and the amount of variation in sputtering parameters can be selected based on the difference between the measured transmittance parameter and the expected transmittance parameter. For example, the parameter could be a percentage of radiation transmission over a predetermined wavelength range. The difference between the measured parameter and the expected parameter can be correlated with the amount of variation in the sputtering parameters (e.g., gas flow rate) to be used in the next iteration. This can be obtained through experimentation or by using theoretical models, etc.

[0119] Optionally, the coating machine can be adapted to provide a first coating, then measure the transmittance, and if the transmittance differs from expectations, adapt the sputtering conditions for subsequent sputtering zones so that, if desired, additional coatings of the same or different materials can be applied under optimized conditions. Measurements can also be performed after multiple sputtering chambers of the same material to ensure the entire layer has the desired properties. In this case, one of the sputtering chambers can be equipped with an additional tuning mechanism (e.g., an in-line controllable magnetic system with an array of servo drives for very precise control of local plasma density) to allow compensation for other zones that introduce some drift or deviation.

[0120] At least one sputtering zone includes means for controlling deposition conditions (e.g., sputtering power, etc.). These means may include actuators 503, etc. In some embodiments, controller 307 and actuator 503 are adapted to control the amount and composition of the gas and the pressure of the environment, for example by controlling mechanical valves and pumps to introduce a predetermined gas, such as oxygen, in an accurate and predetermined amount. These zones may be isolated from the outside and / or isolated from each other in the presence of multiple zones (multi-coating machines) with valves, shields, doors, etc. The sputtering process is controlled in a feedback loop in response to measurements from a sensing system.

[0121] In some embodiments, any or each of processor 305, memory unit 306, and controller 307 may be part of computer system 504. Computer system 504 may include a user interface and output, such as screen 505, for displaying transmittance values ​​measured by the sensing system, and optionally the associated chemical composition of the deposited layer. Memory unit 306, or different memory units, such as external units, may also be used to store these measurements and optional chemical compositions.

[0122] The conveying system 506 (moving platform, chain, conveyor belt, etc.) allows workpieces to be introduced and transported into and between different zones or stages of the coating machine. This system can bring new workpieces into the chamber for deposition, or it can be a rotary configuration that allows for cyclic sputtering on the same workpiece; see [link to relevant documentation]. Figure 7 , Figure 8 .

[0123] A multi-zone coating machine may include a measurement area after at least one sputtering stage, for example, after multiple sputtering stages, such as after each sputtering stage. (At least one) measurement area or region may include a sensing system as previously explained. In some embodiments, sputtering conditions (including environmental conditions) at different stages may be controlled differently; for example, the environmental composition (such as the amount of oxygen) may differ and be controlled differently in one stage than in another.

[0124] If the baseline of the workpiece to be coated should be known, the multi-zone coating machine can have a first measurement area 507 before the first sputtering stage. This may occur in cases where the transmittance deviates from the theoretical value or where the workpiece or substrate is simply unknown.

[0125] Measurement area 507 allows for checking whether the workpiece meets expectations, and subsequent measurement area 502 allows for analysis of the effect of the final layer (MRx). Two sensing systems can be used, both located within the coating machine, for example, on the cover of one of the compartments of the coating machine, particularly on one or more compartments used for measurement. Thus, the coating machine may include one or more sputtering zones 501, and the sensing systems may be located within the coating machine at least behind the sputtering zone or compartment, optionally before the sputtering zone, optionally between coating chambers, or even after the coating machine (e.g., when the workpiece leaves or has already left the coating machine).

[0126] Figure 7 An alternative conveying system 603 for a coating machine according to an embodiment of the present invention is shown. Figure 7A side view of a rotary disk with an opening for mounting several workpieces is shown: a coating area 601 and a measurement area or zone 602 are shown; however, several coating and measurement zones may exist. At least one coating area 601 is activated to provide a layer of a single composition / material. For example, achieving a desired coating may require multiple rotations of the carrier plate to achieve the desired layer properties (e.g., thickness, composition, porosity, etc.). For each fraction of layers deposited per revolution, transmittance measurements can be performed to fine-tune the deposition process parameters in-situ. After deposition, the rotary disk, serving as a transport system 603, rotates to allow the workpiece to enter the measurement zone, which, as previously described, is isolated from the coating area 601. To fabricate multiple layers (with different compositions), various coating zones can be activated sequentially, and the same measurement system can be used between depositions on the same workpiece, thus forming a stack.

[0127] Figure 8 An alternative embodiment with a different conveying system 703 is shown, in which a drum is used instead of a disc or belt. The figure shows a top view of a rotating drum with an opening for mounting several workpieces (e.g., eight as shown in the figure): several coating zones 701 (e.g., three as shown in the figure) and a measuring zone 702 are shown. Including more measuring zones, and optionally more coating zones, can increase the speed of parallel processing and deposition. As previously mentioned, the measuring zones and coating areas can be enclosed so that sputtered material does not affect the sensors and / or radiation sources in the measuring zones.

[0128] To prepare a single composition / material layer, at least one coating area must be active, and the carrier drum may need to be rotated multiple times to achieve the desired layer properties (e.g., thickness, composition, porosity, etc.). For each fraction of layers deposited per revolution, the workpiece can be moved to the measurement area by rotating the drum, and transmittance measurements can be performed to fine-tune the deposition process parameters in-situ.

[0129] To create multilayers (with different compositions), various coating zones can be activated sequentially, and the same measurement system can be used.

[0130] This invention allows for the use of radiation transmittance to adapt and optimize sputtering conditions for metal compound layers, particularly for layers requiring a specific non-stoichiometric x-value, such as for substoichiometric metal oxides, for example, a stoichiometric index compound composition between 80% and 99%, preferably between 85% and 98%. In particular, this applies to materials whose radiation transmittance as a deposited layer varies with composition. These may include tungsten oxide, nickel-tungsten oxide, titanium oxide, zirconium oxide, indium oxide, tin oxide, tantalum oxide, niobium oxide, and most other oxides of transition metals. These may include silicon nitride, aluminum nitride, and some other nitrides of metallic elements. This is equally applicable to carbides or mixed compounds having a metal and multiple reactive compounds; for example, containing at least two of oxygen, nitrogen, carbon, and / or boron.

[0131] Furthermore, regarding transmittance control, the composition can be controlled due to the accurate transmittance exhibited by slight compositional variations. This invention also allows for the use of the same measurements to obtain the layer thickness or density described above, for example, through the use of broadband radiometric and spectral measurements.

[0132] Figure 9 The transmission spectra of several layers at different oxygen flow rates from 18 sccm to 30 sccm and much higher total pressures are shown. These layers are WO3 layers with a thickness approaching 900 nm. x Layer, compared to Figure 4 The layer shown is much thicker and has more pores. In particular, more interference peaks in the spectrum indicate a thicker layer, as the spacing within the peaks allows for thickness calculations. (Compared to...) Figure 4 Compared to the layers in the middle layer, the increased porosity leads to higher transmittance and reduced interference amplitude in these substoichiometric layers; absorption is reduced at lower oxygen fluxes due to the presence of less absorbed mass. The expected x-values ​​fall between 2.7 and 2.95.

[0133] Corresponding to Figure 4 30 sccm and Figure 9 At a gas flow rate of 24 sccm, the curves with a transmittance close to 40% exhibit different interference amplitudes. This confirms the smaller amplitude effect of more porous layers.

[0134] We can assume that the oxygen flow rate determines the composition or x-value of the metallic compounds in the layer. Let's compare again. Figure 9 and Figure 4 For the same oxygen flow rate (and therefore a similar x value), in Figure 9 Higher transmittance was found in [the sample]. For each curve, Figure 9 The stripes shown are more... Figure 4 Many, therefore Figure 9 The layers in the middle are thicker. Therefore, it can be deduced that the given... Figure 9 The resulting layer exhibits a higher degree of detail than the corresponding layer. Figure 4The layer has higher porosity.

[0135] In short, Figure 4 and Figure 9 The graphs show that the total transmittance or spectral-resolved transmittance varies greatly with oxygen flow rate, thus allowing for accurate control of the composition.

[0136] This invention takes advantage of the fact that the substoichiometric layer of most oxide materials exhibits spectral absorption (lower transmittance relative to its stoichiometric reference), while having excess oxygen (superstoichiometry) generally does not make the layer more transparent, thus preventing x from being controlled above its stoichiometric index value.

[0137] Most of the examples discussed above relate to methods and apparatus for providing metal oxide layers with controllable transmittance by controlling not only the thickness but also the composition of the layer, particularly the amount of oxygen in the deposited layer. However, the same methods can be used with other reactive gases, for example, during the deposition of other metal compounds (e.g., nitrides, carbides, etc.). Although many metal nitride layers exhibit metallic properties in UV, VIS, and NIR wavelengths, some nitrides are known to produce transparent coatings. For example, the present invention can be used to provide layers comprising wide-bandgap subnitrides: such as SiN... x AlN x BN x For example, sputtering a Si or Al layer in Ar gas produces an absorbing layer, while sputtering Si3N4 or AlN from a target containing Si or Al metals in a nitrogen-containing gas environment produces a transparent coating, or a coating with non-zero transparency for at least visible radiation, which may interfere with other layers of the workpiece. Therefore, the present invention can be used to provide, for example, non-stoichiometric SiN. x Layers. Similar analyses can be performed by measuring transmittance, and mixtures of non-stoichiometric compounds, stoichiometric compounds, and metallic compounds can be quantified and controlled through such optical measurements. This invention allows for the deposition of MO. x N y (Metal oxynitride), where M can be, for example, Ti, Si, Al, B, and many other metallic materials. By adding metal nitrides, most practical sputtered layers can be covered. This technique can be used to deposit any other metallic compound whose thin layers exhibit at least partial transparency. For example, some metal carbides can also exhibit transparency; similarly, the methods and apparatus of this invention can also be used to define layer composition, thickness, and density. Among the carbides exhibiting some transparency as thin films are silicon carbide and titanium carbide. Therefore, non-stoichiometric carbides can also be obtained through this invention.

Claims

1. An online method for depositing a layer on a workpiece by sputtering, the method comprising: -Providing a workpiece as a substrate to be coated and providing a metal compound layer by simultaneously depositing (102) a metal and a reactive substance on a first workpiece under predetermined sputtering conditions to form a layer, thereby providing a deposited layer on the workpiece containing the metal compound. - Subsequently, the deposited layer on the workpiece is irradiated and the optical transmittance (103) through at least the deposited layer is measured, thereby providing a measurement signal and sending the measurement signal to a processor. - Perform spectral analysis of the measured signal and compare the measured radiation parameters of the emitted radiation with at least one stored value of the radiation parameters (104), thereby obtaining an indication of the layer thickness and at least one of the following deposition layer characteristics: composition, Optical constants consisting of refractive index and / or extinction coefficient, and Density / Porosity - In response to the comparison, the predetermined sputtering conditions are adapted (105) for subsequent workpieces on different substrates, wherein adapted sputtering conditions are provided to change one or more properties of the deposited layer on the subsequent workpiece relative to the deposited layer on the first workpiece on which measurements are taken. - Subsequent workpieces are provided sequentially and automatically, and subsequent workpieces are sputtered with adapted parameters to provide a deposition layer on the subsequent workpieces.

2. The method of claim 1, wherein depositing (102) the metal material comprises providing a ceramic target containing a substoichiometric metal compound for sputtering.

3. The method of claim 2, wherein providing the ceramic target comprises providing a metal oxide and / or nitride and / or carbide for sputtering.

4. The method according to claim 1, wherein the reactive substance is oxygen and / or nitrogen and / or carbon.

5. The method according to claim 1, wherein the at least one stored value corresponds to the reference density of the compound of the metal having reactive substances.

6. The method of claim 1, wherein the at least one stored value includes a value corresponding to a reference density and / or a reference amount of oxygen in an oxygen-deficient metal oxide.

7. The method of claim 1, wherein measuring optical transmittance includes measuring wavelength-resolved transmittance of radiation, wherein the impact radiation includes impact radiation having wavelengths ranging from UV radiation to IR radiation.

8. The method of claim 1, wherein measuring optical transmittance comprises measuring (113) the transmittance of radiation generated by a plurality of sources having a predetermined wavelength range and / or by a broadband light source using an integrating sensor.

9. The method of claim 1, wherein providing the sputtering deposition of the metal comprises providing the sputtering deposition of at least tungsten.

10. The method of claim 9, further comprising providing a target comprising at least one tungsten oxide.

11. The method of claim 9, wherein the deposited layer comprises a deposited tungsten oxide layer, wherein the oxygen to tungsten ratio is 2.3 or higher.

12. The method of claim 1, further comprising sputtering in the presence of a gaseous environment containing reactive substances and / or gases.

13. The method of claim 12, wherein sputtering in the presence of a gas comprises sputtering in the presence of a gas containing oxygen and / or nitrogen and / or carbon and an inert gas, wherein the amount of the inert gas is greater than the amount of the reactant gas.

14. The method of claim 1, wherein controlling the predetermined sputtering conditions includes controlling the conditions such that the deposited layer has a controlled transmittance that differs from the transmittance of a stoichiometric counterpart of the material of the layer.

15. The method of claim 1, wherein controlling the sputtering parameters includes controlling the sputtering power, gas partial pressure or flow rate and / or magnetic field strength.

16. The method of claim 1, further comprising measuring the optical transmittance of the workpiece prior to providing sputtering deposition for forming a deposited layer on the workpiece, thereby providing a preliminary measurement.

17. The method of claim 16, further comprising controlling the predetermined sputtering conditions prior to providing sputtering deposition as a response to the preliminary measurement.

18. The method of claim 17, wherein measuring optical transmittance comprises measuring in reflection mode using a sensor and a radiation source arranged on the same side of the workpiece.

19. A processor (305) comprising input for introducing transmission measurement data and actuator-controlled data output for controlling sputtering parameters, the processor being configured to perform at least the steps of comparison (104) and adaptation (105) of the method according to claim 1.

20. A sputtering deposition coating machine, the sputtering deposition coating machine comprising: -Actuators for controlling sputtering parameters and a coating machine in which deposition occurs. - A sensing system comprising a radiation source for transmitting radiation through a layer deposited on a first single substrate and a sensor for detecting the radiation passing through the layer. - The processor of claim 19, wherein the processor is connectable to the sensing system and the actuator for controlling the actuator in response to measurements obtained from the sensing system, thereby providing feedback control for controlling sputtering parameters of a separate substrate from the first single substrate. in, The sensing system and feedback control are consistent with the coating machine, so that no manual operation is required during the analysis step or between the sputtering and analysis steps, wherein the sensing system and the coating machine are isolated from the outside and isolated from each other.

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