EP3475739A1

EP3475739A1 - Method and device for locating the origin of a defect affecting a stack of thin layers deposited on a substrate

Info

Publication number: EP3475739A1
Application number: EP17740056.1A
Authority: EP
Inventors: Bernard Nghiem; Yohan FAUCILLON; Grégoire MATHEY; Thierry KAUFFMANN
Original assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Current assignee: Saint Gobain Glass France SAS
Priority date: 2016-06-27
Filing date: 2017-06-22
Publication date: 2019-05-01
Also published as: FR3053126B1; WO2018002482A1; FR3053126A1; JP2019518963A; KR102478575B1; KR20190020755A; US20190309409A1; CN109564299A; RU2019105190A3; BR112018075797A2; CN109564299B; JP7110121B2; US11352691B2; MX2018016116A; CA3026711A1; RU2742201C2; RU2019105190A

Abstract

This method for locating, in a deposition line comprising a succession of compartments, an origin of a defect affecting a stack of thin layers deposited on a substrate in the compartments, in which each thin layer of a material is deposited in one or more successive compartments of the deposition line and pieces of debris remaining on the surface of a thin layer deposited in a compartment act as masks for the subsequent depositions of thin layers and are the origin of defects, comprises: a step (E10) of obtaining at least one image showing said defect, said at least one image being acquired by at least one optical inspecting system placed at the end of the deposition line; a step (E20) of determining, from said at least one image, a signature of the defect, this signature containing at least one characteristic representative of the defect; and a step (E40) of identifying at least one compartment of the deposition line liable to be the origin of the defect from the signature of the defect and using reference signatures associated with the compartments of the deposition line.

Description

Method and device for locating the origin of a defect affecting a stack of thin layers deposited on a substrate

Background of the invention

The invention relates to the manufacture of substrates coated on at least one face of a stack of thin layers, in particular transparent substrates made of glass or polymeric organic material.

It is conventional to provide substrates, in particular made of glass or of polymeric organic material, with coatings which confer on them particular properties, in particular optical properties, for example reflection or absorption of radiation, of a wavelength range. data, electrical conduction properties, or properties related to ease of cleaning or the possibility for the substrate to self-clean. These coatings are generally stacks of thin layers based on inorganic compounds, especially metals, oxides, nitrides or carbides. For the purposes of the invention, the term "thin layer" refers to a layer whose thickness is less than one micrometer and generally ranges from a few nanometers to a few hundred nanometers, hence the term "thin".

A stack of thin layers is generally manufactured via a succession of thin film deposits made in a plurality of compartments of a deposition line (typically 20 to 30 compartments), these deposits being made in the different compartments using one or more methods. of deposition such as, in particular, magnetic field assisted sputtering (also known as magnetron sputtering), ion-assisted deposition (or IBAD for ion-assisted waste deposition), evaporation, chemical vapor deposition ( or CVD for Chemical Vapor Deposition), plasma enhanced chemical vapor deposition (PECVD for Plasma-Enhanced CVD), low pressure chemical vapor deposition (LPCVD for Low-Pressure CVD).

Unfortunately, the compartments of the deposit line are often dirty, and dust or debris present in some compartments can be caused to fall erratically on the substrate as it passes through these compartments. Some debris may remain on the surface of the substrate (specifically on the surface of the thin layer deposited in the compartment in question) and then act as masks for subsequent thin layer deposition. These debris are at the origin of defects affecting the quality of the stack of thin layers deposited on the substrate and which can be prohibitive depending on the intended application for the coated substrate thus produced.

In order to control the quality of the coated substrate produced, optical control systems are available in the state of the art intended to be placed at the output of the deposition line, and which are configured to provide different images of the stack of layers. thin deposited on the surface of the substrate. These optical control systems are generally equipped with a bench comprising a plurality of optical sensors (cameras) and several sources of radiation. at different wavelengths, allowing the acquisition of images in different configurations (eg images in reflection, in transmission, etc.) - The analysis of these images makes it possible to detect possible defects affecting the stacking of Thin layers made in the deposit line.

Although the control systems proposed today allow the detection of faults, they do not give any information on the origin of these faults. Knowledge of this origin can be invaluable to consider targeted and fast maintenance operations on the deposit line. Object and summary of the invention

The invention makes it possible in particular to overcome the drawbacks of the state of the art by proposing a method of locating, in a deposition line comprising a succession of compartments, an origin of a defect affecting a stack of thin layers deposited on a substrate in the compartments, where each thin layer of a material is deposited in one or more successive compartments of the deposition line and debris remaining on the surface of a thin layer deposited in a compartment act as masks for the deposits subsequent thin layers and are at the origin of defects, this method comprising:

A step of obtaining at least one image representing said defect acquired by at least one optical control system placed at the output of the deposition line;

A step of determining, from said at least one image, a signature of the defect, this signature comprising at least one representative characteristic of the defect;

A step of identifying at least one compartment of the deposit line likely to be at the origin of the defect from the signature of the defect and using reference signatures associated with the compartments of the deposit line.

Correlatively, the invention also provides a device for locating an origin of a defect affecting a stack of thin layers deposited on a substrate in a plurality of compartments succeeding one another in a deposition line, where each thin layer of a material is deposited in one or more successive compartments of the deposition line and debris remaining on the surface of a thin layer deposited in a compartment act as masks for subsequent thin layer deposits and are the cause of defects; device comprising:

A module for obtaining at least one image representing the defect acquired by at least one optical control system placed at the output of the deposition line;

A module for determining, from said at least one image, a signature of the defect, this signature comprising at least one characteristic representative of the defect;

A module for identifying at least one compartment of the deposit line that may be at the origin of the defect from the signature of the defect and using reference signatures associated with the compartments of the deposit line. The invention thus proposes a simple and effective solution for locating the origin in a deposition line of a defect affecting a stack of thin layers deposited on a substrate.

In the context of the invention, the deposition of the stack of thin layers on the substrate is achieved by scrolling the substrate successively in the different compartments of the deposit line, which are in a controlled environment. In particular, the deposition of the complete thin film stack on the substrate is done without venting or intermediate cleaning of the substrate between two compartments. Thus, debris fallen on the substrate in a deposition line compartment remains on the surface of the thin layer deposited in this compartment and acts as masks for subsequent thin film deposition, thereby creating defects. The invention then makes it possible to identify a reduced number of compartments of the deposit line, or even a single compartment, which may be at the origin of defects detected at the output of the deposit line.

For this, a reference signature associated with a given compartment of the deposit line is evaluated from a deposit of the thin film stack made by passing the substrate in all the compartments of the deposit line in the presence of at least one debris from said given compartment. In other words, in the context of the invention, a reference signature associated with a given compartment is obtained by placing itself under the conditions of generation of the complete thin-film stack and, because of the presence of the debris issuing from said compartment. given, some thin layers may be missing locally in the stack. Apart from the location of the debris, all the thin layers of the stack are present on the substrate for the determination of the reference signature.

In one embodiment of the invention, the deposition of thin layers is performed by the deposition line on the substrate by a magnetic field assisted sputtering method, called "magnetron cathode sputtering". Each compartment of the deposition line then comprises a sputtering target brought to a negative potential, called a "cathode", comprising the chemical elements to be deposited, in the vicinity of which a plasma is created under a high vacuum. The active species of the plasma, by bombarding the target, tear the chemical elements of the target, which are deposited on the substrate forming the desired thin layer. This process is said to be reactive when the thin layer consists of a material resulting from a chemical reaction between the elements torn from the target and a gas contained in the plasma. An advantage of this magnetron sputtering method lies in the possibility of depositing on the same deposition line a very complex stack of layers by moving the substrate successively under different targets.

In the context of the invention, several successive compartments of the deposition line may participate in the deposition of a thin layer of the same material, in predefined proportions. Advantageously, in the case of a defect present in a thin layer of the same material deposited in several successive compartments of the deposition line, the invention identify the compartment or compartments causing the defect among all the compartments participating in the deposition of this thin layer.

In the case of a magnetron sputtering deposition line, the parameterization of the different compartments in which the thin-film depositions take place comprises an adjustment of various parameters of the magnetron sputtering, and in particular, the pressure of the gas and its composition. , the power applied to the cathode, the angle of incidence of the bombardment particles, the thickness of the deposit, etc.

The substrate is preferably a mineral glass sheet or a polymeric organic material. It is preferably transparent, colorless or colored. The glass is preferably of the silico-soda-lime type, but it can also be, for example, a borosilicate or alumino-borosilicate type glass. Preferred polymeric organic materials are polycarbonate, polymethyl methacrylate, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or fluorinated polymers such as ethylene tetrafluoroethylene (ETFE). The substrate may be rigid or flexible. The substrate may be flat or curved.

The solution according to the invention is based on the exploitation of digital images resulting from an optical control conventionally performed at the output of the deposition line. According to the invention, these images are analyzed in order to extract a signature of the defect comprising one or more predetermined characteristics, representative of the defect, and the observation of which makes it possible to identify compartments of the deposit line capable of being the origin of the defect. For this purpose, the signature of the defect is approximated directly or indirectly (for example by means of one or more decision trees) of different reference signatures, generated for each of the compartments of the deposit line and containing the same characteristics as the signature of the defect. A reference signature associated with a compartment represents the predetermined characteristic values of a default originating in that compartment. It can be obtained for example experimentally from a noise made on the walls of the compartment so as to generate in each compartment debris resulting from noise, simulation or calculation. It is noted that several reference signatures can be associated with each of the compartments of the deposit line. Likewise, each reference signature does not necessarily correspond to a single point but may correspond to a range of values, a portion of a curve, a portion of a surface, and so on. following the number of components included in the reference signature.

The analysis of the signature of the defect taking into account the reference signatures associated with the different compartments of the deposit line makes it possible to identify a small number of compartments of the deposit line, or even a single compartment, likely to be at risk. origin of the defect.

Thus, for example, in a particular embodiment, the identification step comprises a step of comparing the signature of the defect with a plurality of reference signatures associated with each compartment of the deposit line, said at least one compartment identified as being likely to be at the origin of the defect being associated with a reference signature corresponding to the signature of the defect. In other words, the compartment or compartments identified as likely to be at the origin of the defect are in this case the compartments whose reference signatures are closest to the signature of the defect, in the sense for example of a predefined distance or equivalently, a predefined prediction error.

The invention is advantageously applied to different stacks of thin layers capable of being deposited on a substrate, in particular a transparent substrate, and in particular to a stack of thin layers forming an interference system. The choice of the characteristic or characteristics of the signature of the defect used in the context of the invention is adapted as a function of the optical properties of the thin film stack considered, in particular of its reflection or radiation transmission properties, as well as that of the type of images provided by the optical control system (images in reflection, in transmission, obtained with radiation sources capable of emitting in different wavelength ranges, etc.).

By way of examples of stacks of thin layers that can be deposited on a substrate and analyzed according to the invention, mention may be made, without limitation:

Stacks of thin layers which modify the reflection properties of the substrate in the visible wavelength range, such as reflective metal layers, in particular based on metallic silver, which are used to form the mirrors, or antireflection coatings, which aim to reduce the radiation reflection at the interface between the air and the substrate. An antireflection coating may be formed, in particular, by a stack of thin layers having alternately lower and stronger refractive indices acting as an interference filter at the interface between the air and the substrate, or by a stack of thin layers having a gradient, continuous or staggered refractive indices between the refractive index of air and that of the substrate;

Stacks of thin layers which give the substrate infrared radiation reflection properties, such as transparent stacks, comprising at least one thin metal or electroconductive transparent oxide (TCO) layer, called the functional layer, in particular base of silver, niobium, chromium, nickel-chromium alloy (NiCr), mixed indium tin oxide (ITO), and coatings located on either side of each functional layer to form an interferential system. These transparent stacks with infrared radiation reflection properties are used to form solar control glazing, in particular sunscreen, aimed at reducing the amount of incoming solar energy, or low emissivity, aimed at reducing the amount of energy. dissipated to the outside of a building or vehicle;

Stacks of thin layers which give the substrate electrical conduction properties, such as transparent stacks, comprising at least one thin metallic layer, in particular based on silver, or a thin layer based on transparent oxides; Electro-conductors (TCO), for example based on mixed tin and indium oxide (ITO), based on mixed indium zinc oxide (IZO), based on doped zinc oxide with gallium or aluminum, based on niobium doped titanium oxide, based on cadmium stannate or zinc, based on tin oxide doped with fluorine and / or antimony. These coatings with electrical conduction properties are used, in particular, in heated glazings, where an electric current is circulated within the coating so as to generate heat by the Joule effect, or else as an electrode in layered electronic devices, in particular as a transparent electrode located on the front face of organic light-emitting diode (OLED) devices, photovoltaic devices, electrochromic devices;

Stacks of thin layers which give the substrate self-cleaning properties, such as transparent titanium oxide stacks, which facilitate the degradation of organic compounds under the action of ultraviolet radiation and the elimination of mineral soiling under the action of a runoff of water;

Stacks of thin layers which give the substrate anticondensation properties, hydrophobic properties, etc.

The characteristic (s) chosen to form the signature of the defect preferably has a value that changes as a function of the compartments participating in the deposition of the stack of thin layers, so as to easily allow the identification of a compartment to the origin of a defect in this stack. For example, a characteristic whose value is a strictly monotonic (ie increasing or decreasing) function of the deposition thickness on the substrate can be chosen, so that the value of this characteristic in the signature of the defect makes it possible to identify a deposit thickness at which it appeared. From the knowledge of this thickness and the compartment in charge of depositing a thin layer corresponding to this thickness, it is easy to deduce the compartment at the origin of the defect. This choice of a strictly monotonic characteristic as a function of the thickness of deposition on the substrate is particularly advantageous since it allows from a signature comprising a single well-chosen characteristic to identify a single compartment at the origin of the defect.

A unambiguous relationship between the value of each characteristic of the signature and a compartment of the deposit line, however, is not an essential condition of the invention, in other words, it is not necessary for each compartment to correspond to a distinct value. of each characteristic. An ambiguity, or degeneracy, between two or more compartments may indeed subsist when considering a given characteristic. In particular, the same value of a characteristic can correspond to two distinct compartments of the deposit line.

Indeed, it is noted first of all that, even in the case where there remains an ambiguity, the invention makes it possible to drastically reduce the number of compartments suspected of being at the origin of the defect. As mentioned earlier, a deposit line in the case of a depositing a stack of thin layers on a substrate can easily comprise 20 or even 30 compartments. The invention allows to be limited to a few compartments for which an ambiguity remains, that is to say, by choosing the characteristics, at most two or three compartments. It is also possible to further reduce this number by considering several characteristics in the signature of the defect, the multiplicity of characteristics to remove residual ambiguities.

It is noted that the characteristics considered to form the signature of a defect may depend on the nature of the images obtained and provided by the optical systems (eg images in reflection or in transmission, types of radiation sources used to generate the images, etc. .). The use of images of different natures can advantageously make it possible to remove the aforementioned ambiguities by extracting from each type of images different complementary characteristics to form the signature of the defect.

Said at least one image representing the defect can be, in particular, a grayscale-coded image, an RGB-encoded image, a hyperspectral image.

Thus, by way of illustration, in a particular embodiment, said at least one image may comprise a grayscale-coded reflection image and a grayscale-encoded transmission image.

This embodiment may have a preferred but nonlimiting application when the stack of thin layers comprises several layers having a low emissivity. The use of information extracted from a transmission image in addition to the information extracted from the image in reflection makes it possible to have a signature comprising more characteristics, and to be able to locate more precisely the origin of the fault affecting the stack. thin layers.

In another embodiment, said at least one image may comprise two grayscale-encoded images (in reflection and / or transmission) acquired by said at least one optical system using two radiation sources emitting in two different length domains. at least partially distinct wave, in particular a radiation source emitting in the visible wavelength range and a radiation source emitting in the infrared wavelength range. The combination of images obtained from two sources of radiation emitting at different wavelengths, which are cleverly chosen, can make it possible to remove an ambiguity.

Some stacks may indeed have strictly monotonic characteristics as a function of the deposition thickness in the infrared range that this embodiment advantageously allows to exploit.

The invention therefore makes it possible to carry out targeted maintenance on the deposit line, by concentrating maintenance operations (and especially cleaning operations) or, more generally, corrective actions on the few identified compartments, or even a single compartment. Such corrective actions may typically consist of knocking on the walls of each compartment identified to rid them of any debris and dust that may cover and which are likely to be deposited on the substrate during the deposition of the thin layer made in this compartment. These maintenance operations can take place indifferently during production, or at the end of production.

The invention thus makes it possible to intervene more quickly and more efficiently on the deposit line, while limiting the associated costs. The identification of the compartment or compartments causing defects is also very fast thanks to the invention. This results in a significant time saving in the resolution of crisis when detecting the appearance of defects on the coated substrates from the deposition line.

In a particular embodiment:

Said at least one image comprises a gray-scale coded reflection image, and the signature of the defect comprises a characteristic defined from a reflection coefficient of the defect determined from the reflection image; and or

Said at least one image comprises a grayscale-encoded transmission image, and the signature of the defect comprises a characteristic defined from a transmission coefficient of the defect determined from the transmission image.

These reflection and / or transmission coefficients can be determined for example by using a successive erosion method applied to the defect represented on the gray-scale coded image, and during which, at each step, a value of reflection coefficient and / or transmission is determined. Other methods may of course be envisaged alternatively.

The inventors have judiciously discovered that it is possible, from the reflection image or from the grayscale encoded transmission image of the defect and more particularly from a contrast level in reflection or transmission of the default determined from this image, to identify from which compartment (s) could be derived this defect. More particularly, the inventors have established a correlation between the level of contrast in reflection or in transmission of the defect and the thickness at which the stack was stopped following the fall of a dust or debris, ie the the thickness at which the defect appeared. This thickness can be easily associated with a compartment of the deposition line participating in the deposition of the stack of thin layers. Note that when the image is not hyperspectral, the invention is based on the assumption that the contrast value considered extracted from the images provided by the optical control system reflects the "true" integrated value of contrast (in reflection or in transmission) which would be calculated from the spectrum (of reflection or transmission). By "translated" is meant that the contrast value considered is representative of this true value, either absolutely or relative (i.e. it may be proportional to this true value or be a monotonic function thereof).

As an illustration, in the case of a transparent stack of thin films with infrared radiation reflection properties as described above, comprising a thin layer of silver framed by two coatings each comprising one or more thin layers to form an interference system, we can observe an evolution of the average light reflection coefficient observed on the reflection image (possibly normalized) as a function of the thickness of the stack having the shape of an inverted V (Λ ) and having a maximum at the thin layer of silver. This maximum at the level of the silver layer is explained by the low emissivity of the silver layer, which results in a maximum light reflection. In other words, the evolution of the light reflection coefficient as a function of the thickness is an increasing function before the silver layer and then decreasing after it. It is therefore easy to discriminate, from this representation and the knowledge of so-called reference light reflection coefficients characterizing each of the compartments of the deposit line, a compartment likely to be at the origin of the defect among the compartments of the deposit. a first series of compartments participating in depositing the first coating deposited before the silver layer, or a compartment likely to be at the origin of the defect among the compartments of a second series of compartments participating in the deposition of the deposited second coating after the silver layer.

Thus, in the example illustrated above, if the signature of the defect comprises a single characteristic defined from the average light reflection coefficient of the defect, at the end of the process according to the invention, two compartments are obtained which are capable of be at the origin of the defect found on the stack of thin layers.

In order to determine whether the compartment causing the defect observed belongs to the first or second series of compartments, the inventors advantageously propose to exploit a second characteristic of the defect, namely in the above example, the presence or absence of a clear ring (ie corresponding to a maximum reflection) surrounding the defect on the image in reflection.

In a particular embodiment of the invention, the locating method therefore also comprises a step of detecting a presence of a light ring around the defect represented on said at least one image, the signature of the defect comprising a characteristic reflecting this presence.

The inventors have in fact connected the presence of such a clear ring with the introduction of a defect before the deposit of the silver layer, ie in a compartment of the first series of compartments participating in the deposition of the first deposited coating before the silver layer, the absence of such a clear ring translating on the contrary the introduction of a defect after the deposition of the silver layer, ie in a compartment of the second series of compartments participating in the deposition of the second coating deposited after the silver layer. It is noted that the presence of such a clear ring can easily be detected by using the erosion method mentioned above, by observing the values of the light reflection coefficient obtained at the different iterations of the erosion method, and especially during the first iterations. This also applies when the optical system provides a transmission image of the defect and a characteristic of the signature of the defect is determined from a light transmission coefficient of the defect.

In a particular embodiment of the invention, the method further comprises: a step of determining a coefficient variation gradient (reflection or transmission); and

A step of detecting a form of the defect from the determined variation gradient.

This embodiment makes it possible to obtain additional information on the defect, especially if it is a flat defect or a three-dimensional defect. Such information may be useful for identifying, within a compartment, which elements of the compartment are responsible for the dust and / or debris deposited on the substrate.

The invention applies, as mentioned above, to gray-level coded images (eg reflection and / or transmission images acquired by means of a radiation source emitting in the range of lengths of visible wave and / or in the wavelength range of the infrared, etc.). However, this hypothesis is not limiting and the invention can also be implemented from other types of images. The signatures considered are then adapted to the information that can be extracted from these images.

Thus, in a particular embodiment, said at least one image comprises a reflection image or transmission coded in red, green and blue (RGB), and the method further comprises a step of converting the RGB image in a color space L * a * b *, the signature of the defect comprising components at a * and b * of a defect background surface determined from the converted image. The signature of the defect may also further comprise an L * component of the defect determined from the converted image.

In another embodiment, said at least one image comprises a hyperspectral image and the signature of the defect comprises a spectrum representing values of a reflection or transmission coefficient of a defect background surface as a function of a length. wave. Moreover, each reference signature associated with a compartment of the deposit line may comprise, in this embodiment, a plurality of spectra corresponding to different thicknesses of the layer deposited in the compartment.

These different types of images, encoded in RGB or hyperspectral, provide more information about the defect than grayscale-encoded images. However, they require the use of more complex optical control systems and often more expensive. The invention makes it possible to adapt to different optical control systems placed at the output of the deposition line.

In the aforementioned embodiments, a reduced number of characteristics representative of the defect has been extracted from the images of this defect and exploited. This reduced number of features limits the complexity of the identification step, since only a few characteristics are to be compared to the reference signatures of the compartments during this step.

In another embodiment of the invention, the identification step comprises an application of an automatic learning method on the signature of the defect, said learning method based on a model driven from the signatures. referred to the compartments of the deposit line.

The training of the model is preferably carried out on a large number of images representing defects of which we are able to identify the origin or of which we know the origin, these images having been obtained over several days of production. Such a model consists for example of one or more decision trees driven from reference signatures of the compartments extracted from the large number of images. The automatic learning method then used during the identification step may be for example a so-called decision tree forest algorithm also better known by the name of "random decision forest" in English adapted to use such decision trees. However, any other algorithm allowing to classify elements between them and based on a model driven from reference values can be used alternatively (eg nearest neighbors algorithm, support vector machines or Support Vector Machine ( SVM) in English, neural networks, etc.).

In this embodiment, outstanding features of the defect other than those mentioned above can be easily extracted from the digital images and exploited to identify the compartment causing the fault. Preferably, the signature of the fault determined from said at least one image comprises at least one light intensity characteristic of the defect and / or a characteristic relating to a form of the defect.

By way of example, said at least one light intensity characteristic of the defect can comprise:

Characteristics representative of a radial profile of light intensity of the defect; and or

Characteristics representative of a slope of a radial profile of light intensity of the defect; and or

A representative characteristic of a mean light intensity of the defect; and or

A representative characteristic of a luminous intensity at the center of the defect.

Similarly, said at least one characteristic relating to a form of the defect may comprise:

- a representative characteristic of an area of the defect; and or

A representative characteristic of a ratio of a perimeter of the defect on an area of the defect; and or

A characteristic representative of a form factor of the defect.

The aforementioned features have been identified by the inventors as allowing, when used in whole or in part, to very reliably identify the compartment with the origin of the defect. It should be noted that the use of an automatic learning method makes it easy to take into account a larger number of characteristics of the defect.

It should be noted that in all the previously described embodiments of the invention, the correspondences between the reference signatures and the compartments are likely to change, and depend in particular on the setting of the deposition line, during the deposition of the layers. thin on the substrate. Indeed the contribution of each cathode to the thickness of the stack can be made to be modified, in particular due to changes in the power applied to the cathode, the speed of travel of the substrate facing the cathode, the gas pressure used in the cathode compartment and its composition, etc. This dependence on the deposition parameters can be taken into account easily empirically or analytically, in particular by means of a calculation model connecting the parameters of the deposit to the thickness of the stack. corresponding to each compartment.

In a particular embodiment, the various steps of the localization method are determined by computer program instructions.

Consequently, the invention also relates to a computer program on a recording medium or information medium, this program being capable of being implemented in a localization device or more generally in a computer, this program comprising instructions adapted to the implementation of the steps of a locating method as described above.

This program can use any programming language, and be in the form of source code, object code, or intermediate code between source code and object code, such as in a partially compiled form, or in any other form desirable shape.

The invention also relates to a computer readable information or recording medium, and comprising instructions of a computer program as mentioned above.

The information or recording medium may be any entity or device capable of storing the program. For example, the medium may comprise storage means, such as a ROM, for example a CD ROM or a microelectronic circuit ROM, or a magnetic recording medium, for example a floppy disk or a disk. hard.

On the other hand, the information or recording medium may be a transmissible medium such as an electrical or optical signal, which may be conveyed via an electrical or optical cable, by radio or by other means. The program according to the invention can be downloaded in particular on an Internet type network.

Alternatively, the information or recording medium may be an integrated circuit in which the program is incorporated, the circuit being adapted to execute or to be used in the execution of the method in question.

The invention also relates to a system comprising: A deposition line comprising a succession of compartments able to deposit a stack of thin layers on a substrate, where each thin layer of a material is deposited in one or more successive compartments of the deposition line and debris remaining on the surface a thin layer deposited in a compartment act as masks for subsequent thin layer deposition and cause defects;

At least one optical control system placed at the output of the deposition line configured to provide at least one image representing a fault affecting the stack of thin layers deposited on the substrate; and

A locating device according to the invention, able to identify among the succession of compartments of the deposit line at least one compartment likely to be at the origin of the defect.

It can also be envisaged, in other embodiments, that the location method, the location device and the system according to the invention present in combination all or part of the aforementioned characteristics.

Brief description of the drawings

Other features and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate an embodiment having no limiting character. In the figures:

- Figure 1 shows schematically a system according to the invention, in a particular embodiment;

FIG. 2 represents a deposition line of a stack of thin layers included in the system of FIG. 1;

FIG. 3 represents an optical control system placed at the output of the deposition line in the system of FIG. 1;

FIG. 4 schematically represents the hardware architecture of a localization device according to the invention included in the system of FIG. 1, in a particular embodiment;

FIGS. 5, 11, 14 and 16 represent, in the form of flow charts, four embodiments of the localization method according to the invention;

FIG. 6 represents a successive erosion method that can be applied to an image of a defect affecting a stack of thin layers to determine the signature of this defect in a particular embodiment;

FIGS. 7, 9A-9C, 10, 12, 13, and 15 show various examples of reference signatures that can be used to identify the compartment causing a fault affecting a stack of thin layers in accordance with the invention; and

FIG. 8 illustrates a compartment comprising a cathode, as well as the various elements protecting this cathode. Detailed description of the invention

FIG. 1 represents, in its environment, a system 1 according to the invention, in a particular embodiment.

The system 1 comprises:

- A deposition line 2 for depositing a stack of thin layers on a transparent substrate 3;

An optical control system 4 placed at the output of the deposition line 2, and able to acquire various digital images of the transparent substrate coated with the stack of thin layers (referenced by 5), and to detect from these images the presence of defects affecting the coated substrate 5; and

A locating device 6 according to the invention capable of analyzing the digital images IM of the defects detected by the optical control system 4 in order to locate their origin in the deposition line 2.

In the examples envisaged hereinafter, the stack of thin layers is deposited on a glass substrate 3 and forms an interference system. In these examples, the thin film stack comprises one or more functional layers with infrared reflection properties (ie one or two silver layers in Examples 1 and 2, a mixed indium oxide layer). and tin (ITO) in Example 3), and coatings formed of one or more thin layers located on either side of each functional layer to form the interferential system. In the following, the term "module" (Ml, M2, M3) denotes each of the coatings which surround the functional layer (s) of silver or ITO, it being understood that a module may consist of a single thin layer or a plurality of thin layers.

Of course, the examples described hereinafter are not limiting in themselves and other stacks of thin layers as well as other substrates, in particular transparent substrates (eg substrates made of polymeric organic material, flexible or rigid), can be envisaged.

In the examples below, the coatings or "modules" which frame the functional layer or layers consist of thin layers based on dielectric materials (eg thin layers of oxide, nitride, oxynitride). As a variant, especially in the case of metallic thin layers as functional layers, each module which is disposed above, in the direction of deposition of the stack, with a thin metallic layer may comprise, as a layer above to the thin metal layer, a thin metal layer of over-blocker, oxidized or not, intended to protect the thin metal layer during the deposition of a subsequent layer, for example if the latter is deposited under an oxidizing or nitriding atmosphere, and during a possible subsequent heat treatment. Each thin metal layer can also be deposited on and in contact with a thin sub-blocker metal layer. The stack of thin layers may therefore comprise an over-blocking layer and / or a sub-blocker layer framing the or each metal thin layer. These layers of blocker, which are very thin layers, normally of a thickness less than 1 nm to not affect the light transmission of the stack, act as sacrificial layers, in particular capable of capturing oxygen.

In the embodiment illustrated in FIG. 1, the deposition of thin layers is carried out by the deposition line 2 on the glass substrate 3 by means of a magnetic field assisted sputtering technique also called magnetron sputtering.

In known manner, a sputtering technique relies on the condensation within a rarefied atmosphere of a vapor of a target material from a source of spray on a substrate. More precisely, the atoms of the source (also referred to as a target) are ejected into an ionized gas, such as, for example, argon, in a vacuum chamber maintained at a certain pressure. An electric field is created leading to the ionization of the gas thus forming a plasma. The target is brought to a negative potential (cathode) so that the ions present in the plasma are attracted to the target and eject atoms from it. The particles thus sprayed are diffused in the chamber and some of them are collected in particular on the substrate on which they form a thin layer. In the case of a magnetron cathode, a magnetic field oriented perpendicular to the electric field is also created by magnets placed near the cathode so as to confine the electrons in the vicinity of the cathode. This makes it possible to increase the ionization rate of the gas, and thus to significantly improve the deposition efficiency compared to a conventional sputtering technique. Since sputtering techniques are known to those skilled in the art, they are not described in more detail here.

FIG. 2 diagrammatically represents the deposition line 2 used for depositing thin films by cathode sputtering on the glass substrate 3. It comprises here an inlet chamber 7, a first buffer chamber 8, a magnetron sputtering chamber 10 comprising a first transfer section 9 and a second transfer section 11, a second buffer chamber 12 and an exit chamber 13.

The sputtering chamber 10 comprises, in addition to the two transfer sections 9 and 11, a succession of elements Ei, i = 1,..., N where N denotes an integer. Each element Ei comprises a compartment or deposition chamber 15-i containing a cathode used as a target during the magnetron sputtering, and one or two compartment (s) or chamber (s) pumping equipped (s) with a pump, and located (s) where appropriate on both sides of the deposition chamber to create the vacuum therein. The glass substrate 3 circulates in the different successive compartments of the sputtering chamber 10, driven by a conveyor or a conveyor belt 16.

The succession of the different elements Ei, i = 1,..., N makes it possible to deposit a stack of thin layers on the glass substrate 3. It should be noted that several successive compartments 15-i may participate in the deposition of a thin layer of the same material, in predefined proportions. The setting of the different compartments 15-i in which take place Thin film deposition consists in adjusting different parameters of the magnetron sputtering, and in particular, the gas pressure and its composition, the power applied on the cathode, the angle of incidence of the bombardment particles, the thickness of the deposit etc.

The optical control system 4 is placed at the output of the deposition line 2. As illustrated schematically in FIG. 3, it is equipped with one or more cameras 17 and with several radiation sources 18 making it possible to acquire and generate different types of digital images of the coated substrate 5 from the deposition line 2. In the example envisaged in FIG. 3, the optical control system 4 comprises three radiation sources 18, namely, a light source 18-1. of the RDF type (for Reflection Dark Field), an 18-2 light source of the RBF type (for Reflection Bright Field) and a light source 18-3 of the TBF type (for Transmission Bright Field or light field transmission). These light sources are turned on and off alternately in order to acquire different configurations of digital images in reflection (corresponding to the reflection of the light source on the coated substrate) and / or in transmission (corresponding to the light from the light source and transmitted through the coated substrate) representing the potential defects affecting the coated substrate having the thin film stack.

No limitation is attached to the nature of the cameras 17, the resulting digital images, and the configuration of the radiation sources. Thus, according to their nature and their capabilities, the cameras 17 may for example provide digital images coded in gray scale, trichromatic images encoded in RGB (Red Green Blue), or it may be still hyperspectral cameras capable of providing hyperspectral images, etc. Moreover, radiation sources operating in the visible domain or in other wavelength domains, for example in the infrared range, can be used by the optical control system 4. These sources of radiation can be oriented at different angles depending on the images that we want to acquire and use to locate the compartment or compartments at the origin of the defect.

Figure 6 shows in its lower portion, for illustrative purposes, a digital image in reflection, coded in gray levels, acquired from a light source RBF operating in the visible range. The task appearing on this image reflects a defect detected by the optical control system 4. In this image, the contrast measured by the camera of the optical control system 4 is proportional to the light reflection of the defect. Note that when the image is not hyperspectral as is the case here, the invention is based on the assumption that the value of contrast considered extracted from the images provided by the optical control system reflects the true value of the integrated quantity (RL or TL) that would be extracted from a spectral response (relative or absolute).

Such an optical control system is known per se and conventionally used to detect defects affecting the deposits made in a deposition line such as the line of 2. It is not described in more detail here. Note that the invention is not limited to the use of a single optical control system and it is conceivable that the images processed by the localization device according to the invention come from a plurality of optical control systems placed at the exit of the deposit line.

As mentioned above, the defects affecting the coated substrate may be in particular due to dust or debris present in certain compartments 15-i of the sputtering chamber 10 which have fallen erratically onto the substrate when it has circulated in these compartments. Very advantageously, by exploiting the images of the defects detected on the coated substrates 5 coming from the deposition line 2, the locating device 6 according to the invention is capable of locating the compartment 15-i of the deposition line 2 to the origin of this defect.

In the embodiment described here, the location device 6 is a computer whose hardware architecture is shown schematically in FIG. 4. It comprises a processor 19, a random access memory 20, a read-only memory 21, a non-volatile memory 22 , a communication module 23, and various input / output modules 24.

The communication module 23 enables the location device 6 to obtain the images of faults acquired by the optical control system 4. It can notably comprise a digital data bus, and / or means of communication on a network (local or remote) such as for example a network card, etc., depending on how the optical control system 4 and the location device 6 are interconnected.

The input / output modules 24 of the location device 6 comprise in particular a keyboard, a mouse, a screen, and / or any other means (eg a graphical interface) making it possible to configure the location device 6 and to access the results. of the analysis he conducts on the images of defects that are provided to him.

The read-only memory 21 of the localization device 6 constitutes a recording medium in accordance with the invention, readable by the processor 19 and on which is recorded a computer program PROG according to the invention, comprising instructions for execution. steps of a localization method according to the invention.

This computer program PROG equivalently defines functional and software modules here configured to implement the steps of the localization method according to the invention. These functional modules support or control the hardware elements 19 to 24 mentioned above. They include in particular here:

A module 6A for obtaining at least one image representing a defect, acquired by the optical control system 4, this module 6A being able to communicate and to control the communication module 23;

A determination module 6B, from said at least one image, of a signature of the defect comprising at least one characteristic representative of the defect; and An identification module 6C of at least one compartment likely to be at the origin of the defect configured to use the signature of the defect and a plurality of reference signatures associated with the compartments of the deposit line.

The functions of these modules are described in more detail below with reference to FIGS. 5 to 16, in four distinct embodiments of the invention. The first three embodiments are distinguished by the nature of the digital images that are provided by the optical control system 4 and analyzed by the location device 6 to locate the origin of a fault. Thus, in the first embodiment, the images used by the locating device 6 are digital images coded in gray level; in the second embodiment, it is trichromatic digital images (or RGB for Red Green Blue), and in the third embodiment, the images provided by the optical control system are hyperspectral images. In the fourth embodiment, the locating device 6 implements an alternative treatment with respect to the first three modes for locating the defect in the deposition line 2. These four embodiments of the invention are, however, based on the same main steps to locate the defect, namely:

A step of obtaining one or more images representing said defect and acquired by the optical control system 4;

A step of determining, from these images, a signature of the defect comprising at least one representative characteristic of the defect; and

A step of identification of at least one compartment among the compartments 15-i, i = 1,..., N, of the deposit line likely to be at the origin of the defect from the signature of the defect and using the reference signatures associated with compartments 15-i, i = 1, ..., N.

We will now describe in more detail these steps in each of the embodiments. To illustrate these different modes, the following three examples of stacks of thin layers are alternately considered.

- Example 1: the stack is deposited on a soda-lime-silica glass substrate and comprises, in the depositing direction of the stack on the substrate:

a first coating or module M1 formed by a plurality of thin layers based on dielectric materials (eg oxide, nitride, oxynitride layers);

o a thin layer of silver; and

a second coating or module M2 formed by a plurality of thin layers based on dielectric materials (eg oxide, nitride, oxynitride layers);

each layer of the stack being able to be deposited by several different cathodes in order to obtain the required thickness, and the geometrical thicknesses of the thin layers of the stack being adapted so that the whole of the stack forms an interferential system . - Example 2: the stack is deposited on a soda-lime-silica glass substrate and comprises two thin layers of silver framed by thin layers of Si ₃ N ₄ , with the following thicknesses:

The geometrical thicknesses of the thin layers of the stack are adapted such that the entire stack forms an interference system. In this example 2, different thin layers of the same material (Si ₃ N ₄ or Ag) are deposited on the substrate at different thicknesses. The layer to which reference is made is indicated in parentheses, for example Ag (Ll) denotes the first deposited silver layer and Ag (L2) the second silver layer. For example 2, "module M1" is also referred to as the thin layer of S13N4 deposited on the substrate before the first silver layer Ag (L1), the "M2 module" being the thin layer of Si ₃ N ₄ deposited between the first layer of silver Ag (Ll) and the second layer of silver Ag (L2), and "module M3" the thin layer of Si ₃ N ₄ deposited after the second layer of silver Ag (L2).

- Example 3: the stack is deposited on a soda-lime-silica glass substrate and comprises a thin layer of indium mixed oxide tin (ITO) framed by coatings or modules M1, M2 based on dielectric materials, with the following thicknesses:

The geometrical thicknesses of the thin layers of the stack are adapted such that the entire stack forms an interference system. In this example 3, different thin layers of the same material are deposited on the substrate at different thicknesses. The layer to which reference is made in parentheses. For example 3, "module M1" is called the coating formed by the thin films of SiN and SiO 2 (Ll). deposited on the substrate before the ITO layer, and "M2 module" the coating formed by the thin layers of SiO 2 (L 2) and TiO 2 deposited on the substrate after the ITO layer.

Of course these examples are given for illustrative purposes only and are in no way limiting of the invention. As mentioned above, the invention applies to various stacks of thin layers capable of being deposited on a substrate, and in particular to the stacks forming an interference system.

It is assumed in the embodiments described below that a defect has been detected thanks to the images acquired by the optical control system 4. The manner in which this defect is detected is known per se and is not described here.

FIG. 5 represents the main steps of the locating method according to the invention as implemented by the locating device 6 in the first embodiment.

In this first embodiment of the invention, the optical control system 4 is equipped with digital cameras capable of providing gray-scale IM digital images of the detected defect, acquired by activating all or part of the different radiation sources of the 4. Such images consist of a plurality of pixels, each pixel being associated with a gray level reflecting its brightness.

We are interested here in IMR-designed defect-reflecting digital images, acquired by activating the RBF-type light source 18-2 and reflecting the reflection coefficient of the defect, as well as designated default transmission digital images. by IMT acquired by activating the light source 18-3 of type TBF and representing a transmission coefficient of the fault. For the sake of simplification, in the remainder of the description, the following is limited to an image in IMR reflection, and possibly to an image in IMT transmission.

Note that as further detailed below, depending on the thin film stack configurations considered, it is not necessary for the location device 6 to systematically arrange both types of images.

In the case of a stack similar to Example 1 comprising a single layer of silver (or other low-emissivity material), a single image in IMR reflection may indeed be sufficient for a precise location of the origin of the defect.

In Example 2 comprising several silver layers, the use of a single image in IMR reflection can isolate a small number of compartments likely to be at the origin of a defect but is not always sufficient to identify a single compartment among this reduced number of compartments. To eliminate this residual ambiguity, another image than a reflection image can be used, such as for example a transmission image acquired by means of a radiation source operating in the infrared wavelength range, or several images of the defect can be used, such as an image in IMR reflection and an image in IMT transmission both acquired by means of radiation sources operating in the visible wavelength range. Taking into account an image in reflection and / or a transmission image, acquired by means of a radiation source in the wavelength range of the visible and / or with other wavelengths such as wavelengths in the infrared range depends in particular on the absorption and reflection properties of the thin-film stack considered, and on the characteristics representative of the defect considered for implementing the invention. This is further illustrated with reference to the examples given.

It is assumed that the locating device 6 obtains from the optical control system 4 at least one greyscale-encoded IM image of the detected defect on the stack of thin layers deposited on the glass substrate 3 (step E10). This IM image or these images are received by the locating device 6 via its communication module 23 and its obtaining module 6A.

The locating device 6, via its determination module 6B, then determines from the IM image or images, a signature SIG (DEF) of the defect (step E20). By signature of the defect, the meaning of the invention means one or more characteristics representative of the defect and which will make it possible to locate its origin in the filing line 2 by bringing it closer to reference signatures associated with each of the compartments 15 of the line deposit. These characteristics may depend in particular on the nature of the IM images exploited by the localization device 6 and the information on the defect contained in these images, the reflection and absorption properties of the thin film stack deposited on the substrate, the shape of the defect, etc.

To better illustrate this step, we first consider the stack of thin layers of Example 1 described above and comprising a thin layer of silver framed by two modules Ml, M2 each formed by a plurality of thin layers based on dielectric materials (eg oxide, nitride, oxynitride layers). It is furthermore assumed that the optical control system 4 provides a single reflection image IM = IMR encoded in gray levels, acquired by means of the light source 18-2 operating in the visible wavelength range.

In the embodiment described here, the determination module 6B extracts from this image in IMR reflection various characteristics relating to the light reflection coefficient of the defect. For this purpose, it applies here, on the image in reflection IMR, a successive erosion method allowing it to extract during several iterations different values of the reflection coefficient of the defect.

FIG. 6 schematically illustrates the application of this method to a defect DEF represented by an IMR reflection image. This method consists, from the image in reflection IMR of the defect, to successively "erode" or "to eliminate" the defect on its contour (ie with each iteration iter one eliminates a small thickness of the contour of the defect, this thickness n not being uniform from one iteration to another) and to calculate average levels gray pixels on the surface of the defect eliminated, the gray level of a pixel translating the light reflection coefficient of the defect at the location represented by the pixel. The remaining area after each erosion is shown for illustrative purposes in FIG. 6 in the frames associated with each iteration (iter = 1, iter = 2, ..., iter = 7). The number of iterations and the erosion step applied to each iteration (for example 1 pixel) used to implement this successive erosion method are chosen in coherence with the shape of the defect in order to allow the extraction of relevant information. on this defect.

In the example shown in Figure 6, the defect is represented by a task surrounded by a clear ring. At the first iteration (iter = 1), the eroded surface considered to compute the average of the grayscale of the pixels voluntarily includes only a "black" part of the background of the image located outside the defect and surrounding it. this. This results in a relatively low gray level average (because only integrating very low gray levels representative of the black surface surrounding the defect).

At the second iteration (iter = 2), the eroded portion of the defect corresponds to the clear ring surrounding the defect. This clear ring corresponds to high gray levels, resulting in a maximum light reflection coefficient.

Then the erosion is continued and the average of the light reflection coefficients decreases to stabilize in the example shown from the fourth iteration (iter = 4). The "stabilized" value of the average over the last iterations gives the value of the light reflection coefficient of the defect, denoted RL (DEF). The presence of a maximum, at the second iteration here, denoted RLmax (DEF) and the peak pace of the average of the gray levels illustrates the presence of a clear ring around the defect. The erosion method thus described makes it easy to identify the presence of a clear ring around the defect. Note that in the absence of a clear ring, the values RLmax (DEF) and RL (DEF) are substantially the same.

In the first embodiment described here, the value of the light reflection coefficient RL (DEF) is a characteristic of the fault used by the determination module 6B to determine its signature. The light reflection coefficient RL (DEF) considered in the signature is preferably standardized, for example with respect to the light reflection of the coated substrate 5 resulting from the deposition line 2 (final product) or with respect to the light reflection of the glass. naked (medium contrast). Such a standardization advantageously makes it possible to overcome the adjustment fluctuations of the different cameras of the optical control system. It is however optional. In the remainder of the description, it will thus be possible to consider indifferently normalized or non-standardized reflection and / or transmission coefficients, the invention applying equally in these two cases.

The determination module 6B also adds to the signature of the fault an indicator of the presence or absence of a clear ring around the fault detected as indicated above from the value RLmax (DEF). Alternatively, other techniques than a successive erosion method can be used by the determination module 6B to determine the signature of the defect and detect the presence or absence of a clear ring around it. For example, the determination module 6B can determine a light intensity profile of the defect by evaluating the light reflection coefficient at different points of a diagonal of the defect (eg the largest diagonal or the smallest diagonal). The analysis of the different values thus obtained from the light intensity profile of the defect enables the determination module 6B to detect the possible presence of a clear ring around the defect and to evaluate the average value of the light reflection coefficient of the defect. .

According to another variant, intensity profiles can be determined by the determination module 6B on a plurality of fault radii, and then averaged to extract the signature of the defect.

Then the signature of the defect thus obtained is compared by the identification module 6C of the localization device 6 with several reference signatures (step E30) to identify the compartment or compartments likely to be at the origin of the defect.

In the embodiment described here, the identification module 6C uses a reference signature SIGref (i) for each compartment 15-i, i = 1, ..., N distinct from the deposit line 2. This signature of reference includes the same characteristics (ie the same types of characteristics) as the signature of the defect. The reference signature may comprise a single value (i.e. unique point) for each characteristic or on the contrary comprise a range of values for each characteristic, or only the bounds or some significant values of such a range of values.

As a variant, several reference signatures may be associated with the same compartment.

In the first embodiment described here, the reference signatures are generated beforehand (step E00) and stored for example in the nonvolatile memory 22 of the localization device 6. In a variant, they can be stored on a remote storage space and be obtained on request for example via the communication module 23 of the localization device 6.

The reference signatures are generated for example experimentally, from a fuss made on each of the compartments 15-i, i = 1, ..., N of the deposit line 2. This procedure consists in typing the walls and the elements of each of the compartments and to recover the debris resulting from this fuss. The observation by means of the optical control system 4 of the defects thus obtained for a compartment and the analysis of the images resulting from this observation makes it possible to estimate an average reference signature associated with the compartment having the same characteristics as those extracted for the defect (light reflection coefficient, presence or absence of a clear ring in the example envisaged here). In other words, at the end of step E00, the location device 6 has in memory of reference signatures for each of the compartments 15-i of the deposit line, these reference signatures giving for each compartment 15-i a reference mean light reflection coefficient (if appropriate, normalized), averaged over several defects from the noise made on the compartment 15 -i, and an indicator reflecting on average, the presence or absence of a clear ring on the periphery of the defects originating from this compartment.

As a variant, the indicator of presence or absence of a light ring included in the reference signature of each compartment 15-i can be determined as a function of the position of the compartment 15-i with respect to the compartments involved in the deposition of the layer of money. Indeed, the inventors judiciously established a connection between this position and the presence or absence of a clear ring around the defect: due to the high emissivity of the silver layer, the presence of a clear ring around the defect on a reflection image of a defect affecting a stack of thin layers comprising a single silver layer indicates the probable appearance of this defect before the deposition of the silver layer (ie in a compartment participating in the deposition of the module Ml ). Conversely, the absence of such a ring reflects the probable appearance of this defect after the deposit of the silver layer (i.e. in a compartment participating in the deposit of the M2 module). During the determination of the reference signatures, it is thus possible to directly assign to the compartments participating in the deposition of the layers forming the module M1 an indicator reflecting the presence of a clear ring, and to the compartments participating in the deposition of the layers forming the module M2 an indicator reflecting the lack of a clear ring.

It is noted that the reference signatures thus generated depend on the parameterization of the deposition line 2 and in particular the cathode sputtering processes implemented by the cathodes of the different compartments 15-i. Thus, they depend in particular on the power applied to each cathode, the deposit thickness to be deposited by each cathode, the gas mixture in the compartment, etc. The reference signatures can be determined experimentally for each condition (each parameterization) deposition, conducting noisy experiments under these different conditions.

As a variant, it is possible to envisage the use of a calculation model allowing the passage from one parameterization to the other.

Such a calculation model is for example the following, when the reference signatures correspond to intervals of values. Its application to a single value is immediate for those skilled in the art and is not described here.

We denote by e (k, x, y) the contribution of a cathode k depositing a material x on the substrate in a module y. This contribution is assumed here proportional to the electrical power injected into this cathode, denoted P (k, x, y). We also note E (x, y) the total thickness of the layer of material x in the module y.

To calculate the range of signatures corresponding to cathode k, it is possible to calculate the limit cumulative thicknesses framing the contribution of cathode k (ie corresponding to the limits of the reference signature of cathode k), namely: - for the lower bound: e (fc - l, x, y) = E (x, y) γ _{Ν ρ} ^ _χ ^ + ^■ ( _Xl , y)

- for the upper limit: ού Σ ^ Ε (j,) represents the sum of the thicknesses of the layers deposited before the layer of material x.

If F denotes the function which makes it possible, from the cumulative thickness, to deduce the reference signature from a compartment (F is for example a vector function providing the limits of the curve portions defining the reference signatures, or a function calculating averages over the curve portions), then the reference signatures corresponding to the new parameterization are obtained by applying the function F on the lower bounds e (k- Ι, χ, ν) and higher e (k, x, y) given ci -above.

In an alternative embodiment, the reference signatures are generated by simulation or by calculation.

FIG. 7 illustrates an example of reference reflection coefficients Rref measured on the side of the stack and obtained by fussing, and corresponding to the deposition of a stack of thin layers according to example 1 in which a plurality of cathodes identified as abscissa participate; (cathodes K1, K3, K4, etc.), these cathodes being included in as many compartments (ie there is a univocal relationship between the cathode indicated on the abscissa and a compartment of the deposit line).

In this example, the reference reflection coefficients Rref were generated from images acquired by four separate cameras of the optical control system 4 placed so as to monitor different areas of the coated substrate. During the generation of the reference reflection coefficients Rref, one can either estimate a reference coefficient per camera or zone of the coated substrate, or estimate a hybrid reference coefficient from the reference coefficients obtained by camera, for example resulting from the average of the reference coefficients obtained by camera.

In the example illustrated in FIG. 7, a single reference reflection coefficient value Rref for each cathode is determined. As a variant, it is possible to determine for each cathode not only a single reference reflection coefficient value but an interval comprising several possible values of the reference reflection coefficient, or in another variant also the limits of a range of possible values of the reference reflection coefficient. reference reflection coefficient. Note that in Figure 7, the cathodes K9, K9B and K10A correspond to the cathodes involved in the deposition of the silver layer. These cathodes are known not to generate (or generate little) debris. In other words, it is unlikely that a defect affecting the stack of thin layers originates from a compartment comprising one of these cathodes. Note also in the example illustrated in Figure 7 that some cathodes (or equivalently some compartments) are associated with the same value of reflection coefficient (for example cathodes K4 and K23).

The reference reflection coefficients Rref may alternatively be represented not according to the compartments with which they are associated but of a deposit thickness in the stack. In this case, a correspondence between the thickness of the deposit and the compartment participating in the deposit corresponding to this thickness is established and stored at the location device 6 for example in its non-volatile memory 22. The same compartment can therefore be associated at one or more deposit thicknesses, that is, one or more reference signatures.

In the first embodiment described here, the comparison of the signature of the defect with the reference signatures associated with the different compartments of the deposition line 2 is carried out in two stages by the identification module 6C.

More specifically, in a first step, the identification module 6C determines from the signature SIG (DEF) of the defect if it has a clear ring on its periphery.

For the reasons mentioned above, it is assumed here that the reference signatures associated with the compartments of the deposition line 2 located before the compartments containing the deposition cathodes of the silver layer (ie deposition compartments of the thin layers forming the module Ml containing the cathodes K1, K3, K4, K5, K5B, K6, K7 and K8 in the example illustrated in FIG. 7) comprise among their characteristics an indicator reflecting the presence of a clear ring around the periphery of a defect. originating in these compartments.

If the identification module 6C detects from the signature SIG (DEF) of the fault the presence of a clear ring around the periphery of the fault, the identification module 6C thus associates the defect with one of the compartments participating in the formation of the module Ml (and corresponding to one of the cathodes K1, K3, K4, K5, K5B, K6, K7 and K8 in the example illustrated in FIG. 7).

If, on the other hand, the signature of the defect SIG (DEF) indicates the absence of a clear ring on the periphery of the defect, the identification module 6C associates the defect with one of the compartments of the deposit line which is after the compartments containing the cathodes participating in the deposition of the silver layer, that is to say to one of the compartments participating in the deposition of the module M2 and containing a cathode among the cathodes K11, K12, K13, K19, K21 , K27B, K28, K30.

Then, in a second step, the identification module 6C compares the reflection coefficient of the defect DEF contained in its signature SIG (DEF) with the reference reflection coefficients Rref reported in the reference signatures of the previously selected compartments (or the intervals values or the limits of the intervals defining the reference reflection coefficients). It then selects the compartment whose reference reflection coefficient Rref corresponds to the reflection coefficient (or interval or terminals) reported in the signature of the defect, that is to say the one whose reference signature corresponds to the signature of the defect. By "corresponds to" is meant here the compartment whose reference signature is closest to the signature of the defect, for example in the sense of a predefined distance.

For this purpose, in the example illustrated in FIG. 7, of a single value of the reference reflection coefficient included in each reference signature, the identification module 6C selects the compartment from among all the compartments 15-i, i = l, .., N of the deposition line 2 minimizing a predefined distance, such as a Euclidean distance (also called "L2 distance") or an absolute distance (also called "L1 distance"). This distance is calculated between the reflection coefficient contained in the signature of the defect SIG (DEF) and the reference reflection coefficient Rref contained in the signature of the reference SIGref associated with the compartment in question.

Note that when the reference signature comprises not a single values but a range of values or boundaries of such an interval, the identification module 6C may equivalently evaluate a distance from the signature of the defect at that interval or at these terminals and select the compartment that minimizes this distance.

The compartment thus selected is identified by the identification module 6C as the compartment causing the fault DEF affecting the coated substrate 5 (step E40).

Following this identification, a maintenance operation can be undertaken on the compartment identified. This operation may include cleaning the compartment, for example by tapping on these walls to detach the debris that is deposited there.

It is noted that the analysis of the digital images of the defect provided by the optical control system 4 to the localization device 6 can make it possible to identify other useful information on the defect.

For example, during the step E20 of determining the signature of the defect, the determination module 6B can determine a gradient of variation of the reflection coefficient of the defect.

This gradient can be easily determined from the erosion curve obtained by implementing the successive erosion method or the values of reflection coefficients obtained, if necessary, on a diagonal or on the radii of the defect.

From the knowledge of this gradient and its variations, the determination module 6B can deduce information on the form of the defect. It can in particular identify whether the defect is flat (or relatively flat) when the gradient has a maximum on a small number of pixels (typically on a pixel), or if it has a three-dimensional protrusion when the gradient is maintained at almost constant value over a larger number of pixels. The knowledge of this information on the form of the defect facilitates the identification within a compartment of the element at the origin of the debris that created the defect, and optimizes the maintenance operation performed on the compartment . There are indeed in each compartment different protective shields arranged around the cathode, as illustrated in Figure 8 by means of the reference 25. Depending on whether the debris come from rough areas of these shields or flat areas, they do not have the same shape and generate different forms of defect on the substrate. As an illustration, a debris from a shield without a grid placed at the level of the ceiling of the compartment will cause a flat defect. On the contrary, debris from a horizontal shield on which is a metal grid with growths and located in the bottom of the compartment will generate a defect in three dimensions.

It is noted that although described from a grayscale reflection reflection image acquired from a radiation source emitting radiation in the visible wavelength domain, the first embodiment which comes to be presented can also be implemented using a grayscale reflection reflection image acquired from a radiation source operating in another wavelength domain (eg infrared) or an image in grayscale coded transmission, obtained from a radiation source emitting radiation in a wavelength range adapted to the reflection and absorption properties of the thin film stack considered.

In the example illustrated in FIG. 7, for a stack of thin layers according to example 1, it suffices for the location device 6 to analyze the IMR reflection image of the defect to identify which compartment is originally of this defect, the uncertainty as to the location of the compartment between the series of compartments participating in the formation of the module M1 and the series of compartments participating in the formation of the module M2 that can be easily removed as previously described by the detection of the presence or not a clear ring on the periphery of the defect.

Although described with reference to a stack according to example 1, this first embodiment applies to other thin-film stacks forming an interference system, and in particular to the stack of example 3 as well as to other stacks comprising a single functional layer.

It can also apply when the stack of thin layers comprises several functional layers, for example two thin layers of silver as in Example 2 introduced previously.

However, for such a stack, it may be necessary to take into account several images of the defect (eg a reflection image and a transmission image) if it is desired to identify more precisely the compartment at the origin of the fault affecting the stack of thin layers. FIG. 9A illustrates an example of reference reflection coefficients Rref of compartments participating in the deposition of a stack of thin layers according to example 2. The reference reflection coefficients Rref are measured on the stacking side and are normalized relative to the reflection coefficient of the coated glass substrate 5 obtained at the outlet of the deposition line 2. They are represented as a function of the deposition thickness on the glass substrate 3, expressed in nanometers (nm). As mentioned above, a correspondence between the thickness of the deposit and the compartment participating in the deposition of a thin layer associated with this thickness can be pre-established and stored in the non-volatile memory 22 of the location device 6 to enable it to identify the compartment causing the fault.

The reference reflection coefficients Rref of the compartments participating in deposition of the silver layers, which generate little debris, are identified in FIG. 9A by the references Agi (first silver layer corresponding to a thickness of deposition on the substrate varying between 41 nm and 48 nm) and Ag2 (second silver layer corresponding to a deposition thickness on the substrate varying between 123 nm and 143 nm) respectively.

As it appears in this figure, a value of reflection coefficient equal to 0.1 can correspond to different (ie three) different deposit thicknesses and therefore to different compartments of the deposit line 2. It follows that if the implementation of the invention for a stack according to example 2 is limited to considering a signature of the defect consisting of a single characteristic corresponding to the reflection coefficient of the defect, the identification step E40 can lead, depending on the value of this coefficient of reflection, at the identification of a plurality of compartments. In the example illustrated in FIG. 9A, the identification leads to three compartments. Note that this number, although not unitary, corresponds to a relatively small number of compartments with respect to all the compartments belonging to the deposit line, which makes it possible to simplify the maintenance implemented on the line. deposit 2.

Taking into account the presence of a clear ring around the defect as previously described in the signature of the defect can make it possible to distinguish a defect originating from a compartment which participated in the deposition of the thin layers of the module Ml of a compartment which participated the deposition of the thin layers of the module M2. However, this consideration may be insufficient to distinguish two compartments that participated in the deposition of thin layers within the same module (in this case M2 in the example shown in Figure 9A).

To overcome this insufficiency, it is possible to consider for example 2, in addition to the image in IMR reflection, an image in IMT transmission acquired by means of a radiation source emitting in the wavelength domain of infrared (for example at a wavelength of 850 nm). This radiation source can be placed in the optical control system 4 instead of for example the light source 18-3, or belong to another optical control system placed at the output of the deposition line 2. It can be indifferently a broadband source covering at least part of the length domain of the infrared wave, the optical control system then being preferably provided with a spectrally resolved camera making it possible to acquire an infrared image, or a spectrally resolved radiation source, the optical control system being able to be equipped with a broadband camera or a spectrally resolved camera in the infrared field.

The determination module 6B can therefore extract, from this IMT transmission image in the infrared domain, a transmission coefficient T (DEF) of the fault, in a manner similar to or identical to that described previously for extracting the reflection coefficient of the defect from the IMR reflection image. This transmission coefficient, possibly normalized, is used as a characteristic of the signature of the defect in addition to the normalized reflection coefficient extracted from the IMR image. The signature of the defect SIG (DEF) is thus constituted on the one hand, of the reflection coefficient of the defect determined from the IMR image and, on the other hand, of the transmission coefficient of the defect determined from the image. LMI. It is not envisaged here in the signature of the lack of indicator of presence of a clear ring.

FIG. 9B illustrates the reference transmission coefficients Tref of the compartments of FIG. 9A participating in the deposition of the thin-film stack according to example 2. These reference transmission coefficients Tref can be obtained as described previously for the coefficients reference reflection Rref by noise on each of the compartments of the deposition line 2. In the example illustrated in FIG. 9B, the reference transmission coefficients Tref are normalized with respect to the transmission coefficient of the coated glass substrate 5 obtained. at the outlet of the deposition line 2. They are represented as a function of the deposition thickness on the glass substrate 3, expressed in nanometers (nm). The reference transmission coefficients Tref of the compartments participating in the deposition of the silver layers are identified in FIG. 9B by the references Agi (first silver layer corresponding to a thickness of deposition on the substrate varying between 41 nm and 48 nm) and Ag2 (second silver layer corresponding to a deposition thickness on the substrate varying between 123 nm and 143 nm) respectively.

As it appears in this figure, a reference transmission coefficient Tref equal to 0.71 leads to two possible deposit thicknesses. In other words, taking into account only a transmission coefficient in the signature of the defect could lead, depending on the value of this coefficient, to identifying two compartments potentially at the origin of the defect.

In order to have a more precise estimate of the location of the compartment causing the fault, the identification module 6C takes into account in the signature of the fault both the reflection coefficient of the defect and the transmission coefficient of the defect determined by the determination module 6B. Each reference signature is then similarly composed of a reference reflection coefficient value Rref and a reference transmission coefficient value Tref. FIG. 9C illustrates, for different deposit thicknesses (the same as those considered in FIGS. 9A and 9B), the reference reflection coefficient Rref (as abscissa) as a function of the reference transmission coefficient Tref belonging to the same reference signature . It appears in this FIG. 9C that all the reference signatures corresponding to the different deposit thicknesses envisaged are distinct.

In other words, the comparison of the signature of the defect SIG (DEF), consisting of the reflection coefficient of the defect and the transmission coefficient of the defect, with the reference signatures associated with the compartments enables the identification module 6C to identify a unique compartment causing the fault. This compartment is associated with the reference signature closest to the signature of the defect, that is to say, minimizing a predefined distance, such as for example the Euclidean distance between the two vectors corresponding to the compared signatures, each vector having as its components a reflection coefficient and a transmission coefficient.

The taking into account of several characteristics in the signature of the defect and in the reference signatures is however not mandatory in the case of stacking such as the stack of example 2. In fact, the inventors have found that by using a transmission image acquired at a wavelength judiciously selected in the infrared range with respect to the absorption and reflection properties of the stack, it is possible from a signature comprising a single characteristic defined from a transmission coefficient of the defect extracted from this image, to identify precisely the compartment at the origin of the defect.

FIG. 10 illustrates an example of standardized reference transmission coefficients Tref of compartments participating in the deposition of a thin-film stack according to example 2 and extracted from images in transmission of defects resulting from a noise on the compartments. In the example of FIG. 10, the transmission images considered were acquired by means of a radiation source operating at a wavelength of 1050 nm, thus belonging to the infrared range.

It appears in this figure that these reference transmission coefficients Tref are all distinct as a function of the thickness of the deposit. In other words, the comparison of a signature of the defect consisting of a single transmission coefficient extracted from a transmission image acquired at the same wavelength of 1050 nm makes it possible to uniquely identify the compartment at the origin. of the defect.

In the first embodiment which has just been described, the optical control system 4 supplies the location device 6 with grayscale-coded digital images, and the localization device 6 uses various information contained in these images to determine the image. However, the invention applies to other types of images, as now described in the second and third embodiments. FIG. 11 represents the main steps of the locating method according to the invention as implemented by the locating device 6 in the second embodiment.

In this second embodiment of the invention, the optical control system 4 is equipped with color cameras and provides trichromatic digital images coded in green and blue red (RGB or RGB for Red Green Blue). By RGB images, it is preferentially to mean images coded according to the sRGB standard. In a manner known per se, according to the RGB coding, each point or pixel of the image is coded by means of three magnitudes respectively indicating the intensity of each of the primary colors red, green and blue for this point.

In the second embodiment, we are interested in RGB-encoded defect images acquired by the control system 4 by activating the light source 18-2 of the RBF type; these images translate a defect reflection coefficient detected on the coated substrate 5, taken from the side of the stack. For the sake of simplification, in the remainder of the description, the following is limited to a single IMR reflection image of the defect. However, a similar approach can be applied from a transmission image.

The locating device 6 obtains from the optical control system 4 the RGB-encoded IMR image of the detected defect on the stack of thin layers deposited on the glass substrate 3 (step F10). This IMR image is received by the locating device 6 via its communication module 23 and its obtaining module 6A.

In the second embodiment described here, before extracting the reference signature of the DEF defect of the received IMR image, the localization device 6 converts this image into a different color space than the RGB space. (step F20). More specifically, it performs a conversion of the IMR image in the color space a * b * L * known to those skilled in the art. In this color space, L * represents clarity, and the components a * and b * characterize the deviation of the color of the point considered from that of a gray surface of the same clarity. Note that in this color space, L * corresponds more or less to the level of light reflection of the defect.

The image conversion is carried out here in two stages by the localization device 6: in a first step it proceeds to the conversion of the IMR image encoded in RGB in a color space in Χ, Υ, Ζ, for example as described in detail on the website http://wvvw.brucelindbloom.com/index.htmPEquations.html. Then it proceeds to a conversion of the image obtained from the color space (Χ, Υ, Ζ) to the color space (L * a * b *), as detailed in the aforementioned website or on the site. https://en.wikipedia.org/wiki/CIE L * a * b * CIE XYZ conversions to CIE L2Aa.2Ab.2A.

Following this conversion, the locating device 6, via its determination module 6B, determines from the converted image (denoted IMR ') the signature SIG (DEF) of the defect (step F30). For this purpose, it extracts from the converted image IMR 'the coordinates according to the components a * and b * of a bottom surface of the defect. He may use for this purpose a successive erosion method as previously described. We denote aDEF * and bDEF * these coordinates.

Then the signature of the defect thus obtained comprising the components aDEF * and bDEF * is compared by the identification module 6C of the localization device 6 with several reference signatures (step F40), each reference signature SIGref (i) being based on the same characteristics as the signature of the defect and being associated with a compartment 15-i, i = 1, ..., N of the deposit line 2, or at a deposit thickness which is itself connected to a compartment.

The reference signatures can be generated beforehand and stored for example in the nonvolatile memory 22 of the localization device 6. As a variant, they can be stored on a remote storage space and be obtained on request for example via the communication module 23. locating device 6.

As in the first embodiment, the reference signatures can be generated from a noisy experiment, performed beforehand on the compartments of the deposition line 2 (step F00). The observation by means of the optical control system 4 of the debris generated in each compartment and in particular the images in RGB reflection of these debris, makes it possible to obtain on average coordinates aref * (i) and brief * (i ) for each compartment 15-i, i = 1, ..., N, or for different deposit thicknesses associated with the different compartments. It will be noted, as mentioned previously for the first embodiment, that the correspondences between the reference signatures and the different compartments depend on the parameterization of the deposition line 2 and in particular the cathode sputtering parameters in the different compartments 15-i.

FIG. 12 illustrates an example of reference coordinates (aref *, brief *) obtained for different thicknesses of thin layers deposited in the different compartments 15-i, i = 1, ..., N of the deposition line 2 and leading to a stack of thin layers according to Example 3 described above. In this figure, the x-axis represents the component aref * and the y-axis the short component *. Each thickness corresponding to the deposit made by a cathode of one of the compartments is illustrated by a symbol, the shape of the symbol depending on the material deposited by this cathode (eg rhombus for the thicknesses corresponding to the deposition of the TiO 2 layer, square for the thicknesses corresponding to the deposition of the layer of SiO2 (L2), etc.). For the sake of readability, the deposit thicknesses corresponding to each point shown in the figure have been omitted.

In addition, for the sake of simplification, it is assumed here that each reference signature associated with a thickness is composed of a single value of the components aref * and brief *. However, as mentioned above, it is possible alternatively to consider that each thickness is associated with an interval of values aref * and a short interval of values *, or at the terminals defining such intervals.

The comparison of the signature of the defect SIG (DEF) with the reference signatures SIGref (i), i = 1,..., N is carried out very simply during step F40 while seeking the thickness stack whose reference signature is closest to the signature of the defect. This thickness is then connected as indicated above to the compartment or the cathode corresponding to a deposit at this thickness. In other words, the identification module 6C searches on the reference curve illustrated in FIG. 12 for the point (aref *, brief *) closest to the point (aDEF *, bDEF *) (illustrated by a cross in FIG. 12 ), and deduces the deposit thickness and the associated compartment.

Alternatively, when the reference signatures comprise a range of values for aref * and brief * or the boundaries of such intervals, the identification module 6C looks for the closest reference signature in the sense of a predefined distance from the point ( aDEF *, bDEF *) and deduces the deposit thickness and the associated compartment. No limitation is attached to the distance in question: it may be in particular the distance from the normal to the curve defined by the reference intervals considered for aref * and brief * passing through the point (aDEF *, bDEF *) .

The compartment thus determined is identified by the identification module 6C of the locating device 6 as the compartment likely to be at the origin of the defect DEF affecting the coated substrate 5 (step F50).

Following this identification, a maintenance operation can be undertaken on the compartment thus identified.

Note that this second embodiment can also be applied in other stacking configurations such as in a configuration similar to Example 2 and which comprises two layers of silver.

In such a configuration, in the event of ambiguity existing on the precise location of the compartment, the determination module 6B of the signature of the defect can add to the signature of the defect the component LDEF * of the bottom surface of the defect, and generate the equivalent component Lref * in the reference signatures of the compartments. A three-dimensional curve is thus obtained illustrating the reference signatures of compartments 15-i, i = 1,..., N (or deposit thicknesses corresponding to these compartments), as illustrated in FIG. another example of stacking thin layers with two layers of silver.

During the comparison step F40, the identification module 6C looks for the reference signature (point (Lref *, aref *, brief *)) on this curve closest to the signature of the defect (LDEF *, aDEF * , bDEF *) (represented by a cross in FIG. 13). The identification module 6C then identifies the compartment corresponding to the reference signature thus determined as the compartment causing the defect DEF.

FIG. 14 represents the main steps of the locating method according to the invention as implemented by the locating device 6 in a third embodiment.

In this third embodiment of the invention, the optical control system 4 is equipped with hyperspectral cameras and provides hyperspectral digital images of the defect detected on the coated substrate 5. These hyperspectral images are remarkable in that that they associate with each pixel of the image a spectrum over a given range of wavelengths (spectrum in reflection or in transmission according to the configuration of the radiation sources considered). Each spectrum is defined as a vector of K components Sp (k), k = l, ..., K where K denotes an integer greater than 1, each component Sp (k) denoting the value of the reflection (or reflectance) or from the transmission of the fault to the wavelength k.

The locating device 6 thus obtains from the optical control system 4 a hyperspectral image in IMR reflection of the detected defect on the stack of thin layers deposited on the glass substrate 3 (step G10). This IMR image is received by the locating device 6 via its communication module 23 and its obtaining module 6A.

The locating device 6, via its determination module 6B, then determines from the hyperspectral image IMR the signature SIG (DEF) of the defect (step G20). For this purpose, it extracts from the IMR image the spectrum in reflection of the background surface of the defect, for example by means of a successive erosion method as presented previously in the first embodiment of the invention. invention and applied to the reflection spectrum of each pixel (a reflection coefficient value is extracted for each wavelength of the reflection spectrum associated with each pixel instead of a single reflection coefficient value per pixel as in FIG. first embodiment).

The signature SIG (DEF) determined by the determination module 6B thus consists of K spectral components SpDEF (k), k = 1, ..., K thus extracted.

Then the signature of the defect SIG (DEF) thus obtained is compared by the identification module 6C of the localization device 6 with several reference signatures (step G30), each reference signature SIGref (i) being based on the same characteristics as the signature of the defect and being associated with a compartment 15-i, i = 1, ..., N of the deposit line 2.

As in the first two embodiments, the reference signatures can be generated beforehand and stored for example in the nonvolatile memory 22 of the localization device 6. In a variant, they can be stored on a remote storage space and can be obtained on request for example via the communication module 23 of the localization device 6.

As in the first and second embodiments described, the reference signatures can be generated from a noisy experiment, performed beforehand on the compartments of the deposition line 2 (step G00). The observation by means of the optical control system 4 of the debris generated by each compartment and in particular the hyperspectral images in reflection of these debris, makes it possible to obtain Spref reference spectra for each compartment 15-i, i = 1, ..., N, or for different deposit thicknesses themselves associated with compartments 15-i, i = 1, ..., N.

Moreover, as mentioned above for the first and second embodiments, it is noted that the correspondences between the reference signatures and the different The compartments depend on the parameterization of the deposition line 2 and in particular the sputtering processes in the different compartments 15-i.

FIG. 15 illustrates an example of reference spectra obtained for different thicknesses of thin layers deposited by the compartments 15-i, i = 1,..., N of the deposition line 2, for a stack of thin layers according to FIG. Example 3 previously described. In this figure, the different spectra are given as a function of the thickness of the deposit on the substrate. In other words, at the same compartment 15-i, corresponds a set of reference spectra Spref (j), j = Jl (i), ... J2 (i), where Jl (i) and J2 (i) denote two integers dependent on the index i, this set of spectra can be easily identified from the thickness of the deposit which is responsible for this compartment 15-i.

Each reference signature SIGref (i) associated with a compartment 15-i thus comprises a plurality of spectra (Spref (Jl (i)) ... Spref (J2 (i))), the number of spectra J2 (i) - Jl (i) +1 may vary from one compartment to another depending on the thickness of the thin layer deposited by the compartment) and the step of discretization envisaged, and each spectrum Spref (j), j = Jl ( i), ..., J2 (i) being defined by a vector of K components.

The comparison of the signature of the defect SIG (DEF) with the reference signatures SIGref (i), i = 1, ..., N is carried out during step G30 by the identification module 6C by calculating a distance (for example defined according to a type standard L2) between the signature of the defect SIG (DEF) and each reference signature SIGref (i). This distance is defined, in the third embodiment described here, by:

L2 (SpDEF - SprefiJ)) =

Where j = 1, ..., J1 (1), J1 (2), ..., J2 (N).

As a variant, each reference signature associated with a compartment 15-i may comprise only two limit spectra flanking on each side the surface portion defining the spectra associated with this compartment. In this case, the identification module 6C can proceed in two steps by first identifying a first limit spectrum among the reference signatures corresponding to the spectrum closest to the signature of the defect. Since two neighboring compartments share the same limit spectrum, it is then sufficient for the identification module 6C to identify among these two neighboring compartments which corresponds to the signature of the defect.

Alternatively, other distances can be used to compare the signature of the defect with the reference signatures, for example a distance based on an L2 standard such as that indicated above but which includes the application of a weighting factor. different for the wavelengths (indexed by k) belonging to the ultraviolet domain.

The identification module 6C identifies the compartment associated with the index j minimizing this distance (step G40) as the compartment of the deposition line 2 at the origin of the defect affecting the coated substrate 5. Following this identification, a maintenance operation can be undertaken on the compartment thus identified.

Note that this third embodiment can be applied identically in other stacking configurations such as in a configuration similar to Example 2 and which comprises two layers of silver.

In the first three embodiments described above, the location device 6 determines a signature of the fault from one or more characteristics representative of reflection and / or absorption properties of the defect, namely in particular a reflection coefficient. extracted from a reflection image, a transmission coefficient extracted from a transmission image, and compares this default signature with reference signatures associated with each compartment of the deposition line 2, obtained for example via a noise experiment . According to the absorption and / or reflection properties of the coated substrate 5 and the type of images provided by the optical control system (images in reflection, in transmission, acquired by means of radiation sources emitting in the range of lengths visible or infrared wave, etc.), a single characteristic may be sufficient in the signature to identify a single compartment likely to be at the origin of the defect or on the contrary several characteristics may be necessary to identify this unique compartment. However, in such a context, taking into account a single well-chosen characteristic of the defect already makes it possible to drastically reduce the number of compartments likely to be at fault, compared to the total number of compartments included. in the deposit line.

These three embodiments are similar to sort of consider a decision tree to identify one or more compartments that may be at the origin of the defect.

We will now describe a fourth embodiment in which the identification of the compartment causing the defect is implemented using a learning method. In the fourth embodiment described here, this learning method makes it easy to take into account a plurality of decision trees.

FIG. 16 represents the main steps of the localization method implemented by the localization device 6, in this fourth embodiment.

It is assumed here, as in the first embodiment, that the optical control system 4 generates, for each defect detected at the output of the deposition line 2, digital images in reflection and / or transmission encoded in gray levels. For the sake of simplification, the following description is limited to a gray-scale IMR reflection image provided by the optical control system 4 for each detected fault. Note that this fourth embodiment also applies in the case where the optical control system 4 generates and provides RGB-encoded digital images or hyperspectral images.

The locating device 6 thus obtains from the optical control system 4 a gray scale encoded IMR image of the detected defect on the stack of thin layers deposited on the glass substrate 3 (step H 10). This IMR image is received by the locating device 6 via its communication module 23 and its obtaining module 6A.

The locating device 6, via its determination module 6B, then determines from the IMR image a signature SIG (DEF) of the defect (step H20). Preferentially the signature of the defect SIG (DEF) comprises one or more characteristics of the light intensity of the defect and / or one or more characteristics relating to a form of the defect.

More specifically, in the fourth embodiment described here, the signature of the defect SIG (DEF) comprises:

Characteristics representative of a radial profile of light intensity in reflection (or in transmission if the image received is a transmission image) of the defect. Such a profile may comprise a plurality of intensity values taken on the largest diagonal of the defect (for example 8 values, in other words 8 characteristics);

Characteristics representative of a gradient (slope) of a radial profile of light intensity in reflection (or in transmission if the received image is a transmission image) of the defect. Such characteristics are to be compared with the detection of the presence of a clear ring described in the first embodiment of the invention;

- a representative characteristic of an area of the defect;

A representative characteristic of a ratio of a perimeter of the defect on an area of the defect; A representative characteristic of a form factor of the defect;

A characteristic representative of a mean light intensity in reflection (or in transmission if the received image is a transmission image) of the defect; and

A representative characteristic of a light intensity in reflection (or in transmission if the received image is a transmission image) at the center of the defect.

The extraction of these characteristics does not pose any difficulty in itself to those skilled in the art and is not described in detail here.

Of course, this list is not exhaustive and other characteristics can be easily extracted from the IMR image to represent the default DEF.

Then the signature of the defect SIG (DEF) thus obtained is compared by the identification module 6C of the localization device 6 to reference signatures (step H30), each reference signature SIGref (i) being based on the same characteristics as the signature of the defect and being associated with a compartment 15-i, i = 1, ..., N distinct from the deposit line 2.

In the fourth embodiment described here, the reference signatures were generated beforehand from a so-called learning set consisting of a plurality of defect images detected at the output of the filing line 2 acquired by the system. 4 optical control over several days of production. For each of these images, the signature of the defect is determined on the basis of the same characteristics chosen in step H20, and this signature (referred to as reference) is associated with the compartment at the origin of the defect or the thickness of the deposit. corresponding. This compartment or this deposit thickness is determined experimentally, for example by making a fuss on the compartments of the deposition line 2 for each detected defect, or by using a localization method according to the invention according to the first embodiment of the invention. embodiment described above.

These reference signatures are then used, in the fourth embodiment described here, to generate decision trees or decision trees (step H00). In known manner, such trees can be used as a predictive model for evaluating the value of a characteristic of a system since the observation of other characteristics of the same system. In other words, in the case envisaged here, it is to use these decision trees driven using the reference signatures of the compartments of the deposit line 2 to predict the compartment of origin of the defect from its signature . The decision trees are therefore created here from the reference signatures extracted from the training set images and the compartment information associated with those signatures. These decision trees thus in themselves model the reference signatures of each of the compartments 15-i.

By using these decision trees and a learning algorithm based on such trees as for example a so-called decision tree forest algorithm also called "random decision forest" in English, the identification module 6C can "classify" automatically the signature of the defect SIG (DEF), that is to say to associate him a reference signature or even a compartment of the deposit line 2 whose reference signature corresponds to the signature of the defect. Such a learning algorithm is known per se and is not described in more detail here. It is for example described in the document by T. Hastie et al. Entitled "The elements of statistical learning - Data Mining, Inference and Prediction", ^2nd edition, Springer.

Alternatively, other algorithms for classifying elements between them (the elements here being signatures associated with compartments) can be considered, such as for example nearest neighbor algorithms, SVM (Support Vector Machine) or algorithms. 'relying on neural networks.

The identification module 6C identifies the compartment thus determined by the learning algorithm and corresponding to the signature of the defect as being the compartment causing the fault (step H40).

The four previously described embodiments allow a fast and efficient identification of a compartment of a deposition line causing a defect affecting a stack of thin layers made by the deposition line. It should be noted that these embodiments have been described with reference to a deposition line implementing magnetron sputtering deposition. However, the invention applies to other methods of deposition, likely to be affected by similar problems (regardless of the type of debris and defects generated), such as other spraying methods such as Ion Beam Sputtering (IBS) or Ion Beam Assisted Deposition (IBAD), or vapor deposition (CVD) Chemical Vapor Deposition), plasma enhanced chemical vapor deposition (PECVD for Plasma-Enhanced CVD), low pressure chemical vapor deposition (LPCVD for Low-Pressure CVD), etc.

Claims

1. A method of locating, in a deposition line (2) comprising a succession of compartments (15-i), an origin of a defect affecting a stack of thin layers deposited on a substrate (3) in said compartments, where each thin layer of a material is deposited in one or more successive compartments (15-i) of the deposition line and debris remaining on the surface of a thin layer deposited in a compartment act as masks for the deposits of subsequent thin layers and are at the origin of defects, this method comprising:

A step of obtaining (E10, F10, G10, H10) at least one image representing said defect acquired by at least one optical control system placed at the output of the deposition line;

A determination step (E20, F30, G20, H20), from said at least one image, of a signature of the defect, this signature comprising at least one representative characteristic of the defect;

An identification step (E40, F50, G40, H40) of at least one compartment of the deposit line likely to be at the origin of the defect from the signature of the defect and by using reference signatures associated with the compartments of the deposit line.

2. The method of claim 1 wherein the deposition of thin layers is achieved by the deposition line (2) on the substrate (3) by magnetic field assisted sputtering.

3. Method according to claim 1 or 2 wherein the substrate (3) is a transparent substrate made of mineral glass or a polymeric organic material.

4. Method according to any one of claims 1 to 3 wherein the identification step comprises a step of comparing the signature of the defect with a plurality of reference signatures each associated with the compartments of the deposit line, said unless a compartment identified as being likely to be at the origin of the defect is associated with a signature corresponding to the signature of the defect.

5. Process according to any one of claims 1 to 4, in which:

Said at least one image comprises a reflection image (IMR) coded in gray levels, and the signature of the defect comprises a characteristic defined from a reflection coefficient of the defect determined from the image in reflection; and or

Said at least one image comprises a transmission image (IMT) coded in grayscale, and the signature of the defect comprises a characteristic defined from a transmission coefficient of the fault determined from the transmission image.

The method of claim 5 wherein said coefficient is determined using a successive erosion method applied to the defect represented on the gray scale coded image.

The method of claim 5 or 6 further comprising:

A step of determining a gradient of variation of the coefficient; and

8. Method according to any one of claims 5 to 7 comprising a step of detecting a presence of a light ring on the periphery of the defect represented on said at least one image, the signature of the defect comprising a characteristic reflecting this presence. .

The method according to any one of claims 1 to 8 wherein said at least one image comprises two grayscale-coded images acquired by said at least one optical system using two radiation sources emitting in two different length domains. at least partially distinct wave.

The method of any of claims 1 to 4 wherein:

Said at least one image comprises an image in reflection or transmission coded in red, green and blue (RGB),

The method further comprises a conversion step (F10) of the RGB image in a color space L * a * b *; and

The signature of the defect comprises components at a * and b * of a defect background surface determined from the converted image.

11. The method of claim 10 wherein the signature of the defect further comprises an L * component of the defect determined from the converted image.

The method of any one of claims 1 to 4 wherein said at least one image comprises a hyperspectral image and the signature of the defect comprises a spectrum representing values of a reflection coefficient or a transmission coefficient of a bottom surface of the defect according to a wavelength.

13. The method of claim 12 wherein each reference signature associated with a compartment of the deposition line comprises a plurality of spectra corresponding to different thicknesses of the layer deposited in said compartment.

14. Method according to any one of claims 1 to 13 wherein the reference signatures associated with the compartments of the deposit line are determined experimentally (E00, F00, G00) from a fuss made on each of the compartments. to generate in each compartment debris resulting from the noise.

15. Method according to any one of claims 1 to 3 wherein the identification step (H40) comprises an application (H30) of an automatic learning method on the signature of the defect, said learning method s relying on a driven model (H00) from the reference signatures associated with the deposit line compartments.

16. The method of claim 1 or 15 wherein the signature of the fault determined from said at least one image comprises at least one light intensity characteristic of the defect and / or a characteristic relating to a form of the defect.

The method of claim 16 wherein said at least one light intensity characteristic of the defect comprises:

A representative characteristic of a mean light intensity of the defect; and or

The method of claim 16 or 17 wherein said at least one feature relating to a form of the defect comprises:

- a representative characteristic of an area of the defect; and or

A characteristic representative of a form factor of the defect.

19. A method according to any one of claims 1 to 18 wherein the stack of thin layers forms an interference system.

20. The method as claimed in claim 1, in which the reference signatures associated with the compartments of the deposition line depend on a parameterization of the deposition line during the deposition of the thin layers on the substrate.

21. A computer program comprising instructions for executing the steps of the locating method according to any one of claims 1 to 20 when said program is executed by a computer.

A computer readable recording medium on which a computer program according to claim 21 is stored including instructions for performing the steps of the locating method according to any one of claims 1 to 20.

23. Device for locating (6) an origin of a defect affecting a stack of thin layers deposited on a substrate (3) in a plurality of compartments succeeding each other in a deposition line (2), where each thin layer of a material is deposited in one or more successive compartments (15-i) of the deposition line and debris remaining on the surface of a thin layer deposited in a compartment act as masks for the subsequent thin layer deposits and are causing defects, this device comprising:

A module for obtaining (6A) at least one image representing the defect acquired by at least one optical control system placed at the output of the deposition line;

A determination module (6B), from said at least one image, of a signature of the defect, this signature comprising at least one representative characteristic of the defect;

An identification module (6C) of at least one compartment of the deposit line likely to be at the origin of the defect from the signature of the defect and using reference signatures associated with the compartments of the line deposit.

24. System (1) comprising:

A deposition line (2) comprising a succession of compartments (15-i) able to deposit a stack of thin layers on a substrate (3), where each thin layer of a material is deposited in one or more compartments (15); i) successive deposition lines and debris remaining on the surface of a thin layer deposited in a compartment act as masks for subsequent thin film deposits and are the cause of defects;

- A locating device (6) according to claim 21, adapted to identify among the succession of compartments of the deposit line at least one compartment likely to be at the origin of the defect.