EP2507184A1 - Method for structuring a surface by means of reactive ion-beam etching, structured surface and uses - Google Patents

Abstract

The invention relates to a method for structuring a surface, in other words, for forming at least one set of irregularities or patterns (2) having a submicronic height H and at least one characteristic lateral dimension W referred to as the micronic or submicronic width, on a surface of a material (1), in particular a glass, by means of reactive ion-beam etching, characterised in that said method includes the following steps: providing said material with a thickness of at least 100 nm, the material being hybrid and solid and including a single or mixed Si oxide, the molar percentage of oxide in the material being at least 40%, in particular 40% to 94%, and at least one species, separate from the Si of the oxide, in particular a metal, the molar percentage of species in the material ranging from 1% to 50% and being lower than the percentage of said oxide, at least the majority of the species having a largest characteristic dimension smaller than 50 nm, said hybrid material in particular being metastable prior to said etching; optionally heating said hybrid material prior to said etching; and structuring the surface of said hybrid material with an etching time of less than one hour on an etching surface of more than 1 cm² until said set of patterns is formed, the structuring step optionally including heating the hybrid material.

Description

 SURFACE STRUCTURING METHOD BY ION ETCHING

 REACTIVE

 The present invention relates to the field of surface structuring and is aimed in particular at a surface-structuring method by reactive ion etching, a structured surface product and its uses.

 The structuring of materials is of considerable interest because it finds applications in many technological fields.

 The creation of a network of geometric patterns makes it possible to give a material a new and original function without changing its composition and its volume properties.

 Characteristic techniques of small dimensions, in particular width or submicron period, the techniques of structuring are for the most part techniques using transfer masks for liquid or dry etching including lithographic techniques (optical lithography, electronic lithography ...) , used in microelectronics, or for (small) integrated optical components.

Reactive ion etching (RIE) is one of the techniques for structuring glass with reactive gases that are fluorinated or chlorinated derivatives sulfur hexafluoride (SF ₆ ) or carbon tetrafluoride (CF ₄ ) being the most common by often lithographic masking.

 However, they are unsuitable for mass production processes for glass products, for one or more of the following reasons:

 their high cost (manufacture of the mask, setting up, alignment ...);

 - their slowness (scanning) and their complexity (several stages);

 the limitation of the size of the patterns (by the wavelength);

 the small size of the structural surfaces.

 Thus, the present invention firstly relates to a high-performance method of manufacturing a structured product, especially glass, on a submicron scale and in line with industrial constraints: speed and simplicity of design (without the need for masking, in particular a step preferably), and / or adaptation to any size of surface, even the largest, and with flexibility and control over the type and / or size of patterns and their density.

This process also aims to expand the range of structured products available including glass, in particular aims to obtain new geometries of new features and / or applications. For this purpose, the invention firstly proposes a surface structuring method that is to say forming at least one set of irregularities called patterns (generally of the same shape on average) with a submicron height and at least one sub-micron or micron sub-millimetric lateral dimension (called width) by reactive ion etching which comprises the following steps:

 the supply of said material having a thickness of at least 100 nm, a hybrid solid material and comprising:

 a single or mixed oxide of silicon, the molar percentage of oxide in the material being at least 40%, especially between 40 and 99%, and at least one species of nature distinct from the silicon of the oxide, in particular more mobile than silicon oxide under reactive ion etching, which is preferably a metal, the molar percentage of species (s) in the material ranging from 1% to even 50%, especially ranging from 5% to 20% or even 40% and being less than the percentage of said oxide, species, with at least the majority of the species (or species), or even at least 80% or even at least 90%, having a larger characteristic dimension (called size) less than 50 nm , preferably less than or equal to 25 nm, or even less than or equal to 15 nm,

 - In particular said hybrid material being metastable before etching, that is to say kinetically stable under normal conditions of temperature and pressure and thermodynamically unstable under normal conditions of temperature and pressure, being in a local minimum of energy potential, separated from the global minimum by a given activation energy Ea,

 the (pre) heating possible before the etching the material, in particular so as to reduce (without canceling) the activation energy up to a value E1 which is then provided by the etching, (possible heating because if Ea is too much high, the kinetics of the aggregation of the metal-type mobile species is too slow with respect to the etching rate of the hybrid material), the (pre) heating and etching being able to be spaced out in time, the preheating being possible possibly be replaced by an IR radiative treatment,

the structuring of the surface of said hybrid material under said reactive ion etching, thus rendering said hybrid material (metastable) kinetically unstable by the energy input of the beam ions, thus structuring obtained by the formation of a self-contained mask composed of a set of droplet-shaped zones essentially of said species, of type metal, and / or a set of zones enriched in said species, of metal type of the material, mask formed by the aggregation of said metal type species on the surface of said hybrid material,

 with an etching time of less than 30 min, preferably less than or equal to 15 min or even less than or equal to 10 min, of said hybrid solid material (metastable), it is thus ensured that the material is not consumed in particular as a layer,

- by the reactive gas, typically fluorinated or chlorinated, SF ₆ CF ₄ ) or

with an etching surface greater than 1 cm ² , or even greater than or equal to 10 cm ² or even 1 m ² ,

 - with the possible application of an electric field to make the directional engraving,

 until forming said set of patterns.

 the possible heating during the etching of the hybrid material, in particular so as to reduce (without canceling) the activation energy.

 Until now, mask-free structuring under reactive ion etching of glass and more widely of fast silicon oxides has never been observed.

 However, the Applicant has identified the intrinsic properties of an oxide-based material that make it possible to perform reactive ion etching without masking and which control the morphology of the surfaces created during etching.

 Silicon oxide and mobile element will segregate if provided with the energy required by reactive ion etching

 The engraving and the creation of the mask are simultaneous. The intrinsic properties of the material control the surface morphology created during etching.

 It is thus possible to make a structured material, directly functional, in one step.

 In the oxide, it is thus necessary to add at least one ad hoc species, in particular having the following properties that the skilled person will select:

 a higher mobility than that of Si oxide under reactive ionic etching, so that segregation and masking dominate the relaxation of the surface which smooths the surface, to thus select the species, one can for example help studies on the diffusion of ions in silicates or in other oxides)

 a cohesive energy high enough to allow segregation.

The species is in sufficient quantity on the large etching surface to feed the masking and obtain a sufficient density of patterns. The species is on a sufficient depth related to the desired depth of etching, to feed the masking during etching.

 The species is closely related to the oxide but is not miscible.

 The size of the species is limited for a homogeneous distribution of the species in the material and therefore a more homogeneous structure.

 The rate of the species in the Si oxide is measurable by microprobe or XPS Naturally after structuring, in the structured thickness, the rate of the species can vary, for example with a concentration profile depending on the height of the structuration profile, and even the state of the metal.

 The class of Si-metal oxide hybrid materials judiciously selected according to the invention spontaneously creates a mask that is sufficiently dense, homogeneous, and self-sustaining during reactive ion etching, giving access to one or more of the following characteristics (without a mask). :

 and to homogeneity of structuring, that is to say an average height H, a mean shape, a similar average density over the abraded surface,

 - 2D patterns in relief, relief generally rounded edges (circular), for example in the form of cones or bumps, lateral dimension or average W width submicron, possibly substantially symmetrical, so with a mean dimension "maximum" or length L sub-micron and close to or substantially equal to the width (width W = length L approximately or at least W greater than or equal to 0.7L,

- isotropic patterns, that is to say without direction (s) privileged (s) orientation, typically the case in normal incidence or close to normal,

a dense network of patterns, that is to say, with a ratio of the average spacing D over width W of less than 10 to less than or equal to 5, or even less than or equal to 2, on a scale of 1 cm ² even 100 cm ² or even 1 m ² ,

 - at a high H pattern height, and quickly.

 For each pattern, the height taken into account is the maximum height, the width is measured at the base. The spacing D is the average distance between the centers of 2 adjacent patterns.

 The distances H, W, D can be measured by AFM, and / or SEM scanning electron microscopy. The averages are for example obtained on at least 50 patterns.

The structured material has a set of patterns generally: - average height H greater than 5 nm, see greater than or equal to 30 or even 50 nm,

 of average width W, which may be less than 300 nm for applications in optics in particular, even more preferably less than 200 nm, of average spacing D, of less than 300 nm, and even more preferentially of less than 200 nm.

 The aspect ratio (H / W) may be greater than 3.

 The density, that is D / W, can depend on the height.

 Preferably the width W is less than or equal to 5D, in particular less than D.

 The average standard deviation of the height H, of the width W, may be less than 30% (for example at high temperature), or even less than or equal to 10%, even less than or equal to 5%.

 The average standard deviation of the spacing D may be less than 50% (for example at high temperature) or even less than 30%, even less than or equal to 10%.

 The hybrid material may be termed metastable. The known definition of metastability is the ability for a material to be kinetically stable but not thermodynamically stable. The transformation leading to the stable state is slow or even zero. If a physico-chemical system is represented by its potential energy, a metastable state will be characterized by a state that corresponds to a local minimum of potential energy. In order for the system to reach the state of the global energy minimum corresponding to the state of thermodynamic equilibrium, it must be supplied with a quantity of energy called activation energy Ea.

 For a given hybrid, the activation energy may depend on the manufacturing process.

 The structuring is induced by the intrinsic metastability of the material and the selective etching of the silica. This metastability is controlled by the selection of the mobile species.

 The hybrid material may consist essentially of mineral material. The hybrid material may comprise at least 70 mol% of the sum of the oxide and of said metal, or even 90 molar% or even 95%.

 The hybrid material may contain other "neutral" elements for reactive ion etching (especially less than 30%), preferably less than 10%, 5%.

The structuring method according to the invention can be easily automated and associated with other transformations of the product. The process also simplifies the production chain. The process is suitable for the manufacture of large volume and / or large scale products, especially glass products for electronics, building or automotive, including glazing. The structuring method according to the invention Furthermore, it makes it possible to achieve characteristic magnitudes of ever smaller patterns on larger and larger surfaces, with tolerance to acceptable texturing defects, that is to say, not detrimental to the desired performances.

 Plasma can instantly provide sufficient energy for structuring (exceeding activation energy.)

 The etching process further naturally creates a heating of the oxide which may be sufficient alone to provide the activation energy or alternatively requires additional heating as already indicated

 The temperature reached at the surface is variable depending on the hybrid material, the conditions of the structuring. The reference temperature is the temperature at the back of the material (opposite to the abraded surface)

 More broadly, the temperature can also play a role on the structuring of the hybrid material according to the invention.

 Moreover, to initiate or modify the structuring (modification of the pattern and / or acceleration), for example increasing the height of the reliefs (or pads) the aspect ratio or decrease the density, the material is heated to a temperature greater than 50 ° C or even greater than equal to 70 ° C, preferably greater than or equal to 100 or even 120 ° C, in particular ranging from 150 ° C to 300 ° C before etching and / or during (all or part of) etching .

 There is competition between segregation and relaxation during reactive ion etching. By heating during etching, preferably at a given controlled temperature, segregation rather than relaxation is surprisingly enhanced and thus promotes structuring.

 In a configuration with reliefs, by raising the temperature, the species forms larger aggregates (on the summits of the reliefs) which are more spaced so in particular one increases the height of reliefs and one increases the spacing between relief.

 It is also possible to limit the heating temperature / energy input (for reasons of energetic cost and / or resistance of the material or associated material (s), for example limited thermal resistance of an organic substrate carrying the hybrid material in a layer).

 Naturally one can combine heating, plasma power to obtain a wide variety of torque width / height / density.

 Because of its efficiency, the etching time can be less than equal to 15min, or even less than equal to 15 min.

The etching is carried out under vacuum. It may be for example a thin film deposition frame. Before its structuring according to the invention, the surface is not necessarily smooth and may already have a form of structuring.

 In the hybrid structural material (or in the thickness underlying the structured surface), the species may be in optionally ionic form (thus oxidized) or not, may be diluted (isolated in the material) and / or in the form Aggregate preferably of (substantially) spherical shape.

 This depends on the method of manufacture of the hybrid structural material, its type of incorporation in particular.

 The incorporation of the species may be ion implantation (by ion bombardment), ion exchange, or incorporation of particles or growth in situ (from metal salts, etc.), as detailed later.

 The species is preferably chosen from at least one of the following species, in particular:

 Ag silver, in particular for an optical function (absorption induced at the UV / visible boundary) and / or for catalysis, and / or antibacterial,

 copper Cu especially for an optical function,

 Au gold for a grafting of biological molecules, for sensors, for optics (non-linear), and / or antibacterial

 cobalt Co for a magnetic function,

 iron Fe for a magnetic function, and / or catalysis,

 platinum Pt for a catalysis function,

 nickel Ni for a magnetic function, and / or catalysis,

 - Tin Sn for electrical functions,

 - even gallium Ga for a function in imaging and its wide distribution as antimony Sb, indium In.

 Lead Pb, Mo molybdenum may be omitted for environmental reasons.

 One can have several metals capable of forming an aggregate for a given functionality, Co-Pt for a magnetic memory for example.

 Other transition metals such as Ti, Nb, Cr, Cd, Zr (especially in silica), Mn are conceivable.

 For more efficient structuring, the effective charge on the species is zero or less than 0.5 (known by EELS) to allow the species to aggregate.

 For silica in particular, aluminum Al or boron B is preferably preferred since it integrates with the silica network and will not be easily aggregated.

Transition metals or even some semi-metals are particularly preferred to earth alkalis or alkaline earths which have an etching rate too high. important. Thus, for glass, we can indicate Li and Na are not suitable because they eject and do not aggregate (fast enough).

 The oxides can be further (sufficiently) transparent in the visible and even in a wider range to near or far IR or near UV depending on the intended applications.

 The mobile species may not be aggregated (under normal conditions of temperature and pressure), but still has sufficient mobility under reactive ion etching to form the structures.

 The oxide added to the oxide of Si is preferably chosen from at least one of the following oxides: alumina, zirconia, titanium oxide, cerium oxide, magnesium oxide, in particular a mixed oxide of aluminum and silicon , zirconium and silicon, titanium and silicon and preferably a glass.

 There are several hybrid materials according to the invention.

 The hybrid material may be first a glass, in particular silicocalcic, ionically exchanged, preferably with at least one of said species, ionic at the time of exchange, the following: silver, copper.

 The exchange depth is typically of the order of one micron or up to several tens of micrometers in depth. The distribution of the metal exchanged is therefore almost homogeneous in the abraded part of the material (<1 μηι).

 Ion exchange is the ability of certain glass ions, particularly cations such as alkali ions, to be able to exchange with other ions with different properties.

 The ion exchange may be the exchange of certain ions of the glass by ions selected from, in combination or not, barium, cesium, thallium and preferably silver, copper.

 Silver is very mobile in the matrix and has a strong tendency to aggregate The ion exchange rate of the hybrid material is measurable by microprobe before and after structuring.

Ion exchange is obtained by known techniques. The surface of the glass substrate to be treated in a bath of molten salts of the exchange ions, for example silver nitrate (AgNO ₃ ), is placed at a high temperature between 200 and 550 ° C. and for a correspondingly long period of time. at the desired exchange depth.

Concurrently, the glass in contact with the bath can advantageously be subjected to an electric field which is mainly a function of the conductivity of the glass and its thickness, and preferably varies between 10 and 100 V. In this case, the glass can then undergo another heat treatment, advantageously at a temperature between the exchange temperature and the glass transition temperature of the glass, in order to diffuse the ions exchanged in a direction normal to the face of the glass provided with the electrode, so as to obtain a linear profile index gradient.

The glass chosen may be extraclear. Reference may be made to WO04 / 025334 for the composition of an extraclear glass. In particular, it is possible to choose a silicosodocalcic glass with less than 0.05% Fe III or Fe ₂ O ₃ . For example, Saint-Gobain's Diamant glass, Saint-Gobain's Albarino glass (textured or smooth), Pilkington's Optiwhite glass, and Schott's B270 glass can be chosen.

 Ion exchange thus makes it possible to easily treat large areas, to be reproducible industrially. It allows to act directly and in a simple manner on the glass without the need to proceed to intermediate and / or complementary steps such as deposition of layers, etching.

For example, money is used. The diffusion depth of the Ag ⁺ silver ions in the glass as a replacement for Na ⁺ sodium ions is a function of the time during which the substrate is left in the bath.

As a variant of the AgNO ₃ bath, a layer of metallic silver may be deposited.

It is deposited by magnetron, CVD, inkjet or silkscreen. An electrode layer is also deposited on the opposite side. The electric field is then applied between the silver layer and the metal layer. After the exchange, the electrode layer is removed by polishing or chemical bonding.

 The electric field applied between the metal layer or the bath, and the electrode, therefore generates the ion exchange. The ion exchange is carried out at a temperature between 250 and 350 ° C. The exchange depth is a function of the intensity of the field, the time during which the substrate is subjected to this field and the temperature at which the exchange is carried out. The field is between 10 and 100 V.

 For example, it is chosen to carry out such an ionic exchange with a glass preferably extraclear, of 2 mm, at a temperature of 300 ° C., with a duration of 10 h under a field of 10 V / mm.

To obtain nanoparticles of silver after ion exchange in the glass, a usual soda-lime glass such as Planilux glass from Saint-Gobain can be used. The size and depth of penetration of silver can be modified by changing the experimental conditions: increasing the time and temperature of the exchange gives larger particles to a greater depth and thus a more pronounced yellow coloration. The addition of an electric field during the exchange makes it possible to increase the depth of penetration without increasing the size of the particles. Thus the depth of penetration can be adjusted to match the depth of the engraving so that the yellow color disappears at the end of the etching or be slightly higher a few μηι so that the yellow color is lower and therefore optically acceptable at the end of the etching.

 As an example of copper-exchanged glass, mention may be made of the publication by Dong et al. Titled "Ultrafast Dynamics of Copper Nanoparticles Embedded in Sodium Thyline Glass Fabricated by Thin Exchange" Thin Solid Films 517 (2009) 6046-6049.

 The structured exchanged glass can be monolithic, laminated, two-component. After structuring, the structured exchanged glass can also undergo various glass transformations: tempering, shaping, laminating, etc.

 The hybrid material may be in bulk or as an added layer on any substrate, thick or thin, planar or curved, opaque or transparent, mineral or organic. The layer of the hybrid structural material may be reported by gluing etc. or, preferably, be deposited on a particular glass substrate. This layer can be part of a stack of layers (thin) on the substrate, including glass.

 This layer of the hybrid structural material may preferably be transparent, have an optical index for example greater than that of a glass (typically around 1, 5).

 The layer of the structurable hybrid material can be deposited by any known deposition techniques directly on the substrate or on one or more functional layers (thin etc.) underlying.

In particular, it may be deposited on a functional (thin) layer, for example a functional oxide layer such as a transparent conductive oxide (TCO) such as ΓΙΤΟ (Indium Tin Oxide), ZnO, a mixed oxide or simple tin-based, indium or zinc or a photocatalytic layer (Ti0 ₂ anatase form for example).

This layer of the hybrid material may advantageously be deposited on an alkali barrier layer (typically Si ₃ N _4, SiO 2) to prevent the migration of the alkali ions from the glass to the layer during the various heat treatments (annealing or quenching ...).

 The substrate is not necessarily mineral and may be a plastic or a hybrid material, to obtain properties of flexibility and formatting inaccessible with glass substrates. In this case, the system used must have a low activation energy because no heat treatment above 300 ° C and most often 200 ° C is possible.

It is possible to provide a step of depositing said layer in the hybrid material produced on a structuring line. The hybrid material may be a gel sol, mass or layer especially on transparent substrate, glass (mineral or organic). Gels have the advantage of being able to withstand even high heat treatments (eg type of operation (bending) hardening) and to resist UV exposure.

 In particular, it is a silicon oxide obtained by the sol gel route and incorporating said metal or semi-metal in the form of (nano) particles, optionally precipitated, in particular Ag, Cu, Au.

 The nanoparticles are preferably evenly distributed in the bulk material and / or the layer. Preferably, the largest dimension of the particles (formed or inserted, individualized or in a cluster, precipitate) is less than 25 nm and even more preferably less than 15 nm, and a shape ratio of less than 3 and preferably of spherical shape.

 The level of nanoparticles in the sol gel material is measurable by microprobe, XPS or EDX.

 Silica has the distinct advantage of being a transparent oxide, titanium oxide and zirconia to be high index. As an indication, at 600 nm, a silica layer typically has a refractive index of the order of 1.45, a titanium oxide layer has a refractive index of the order of 2, a zirconia layer. a refractive index of the order of 2.2.

 The layer may be essentially silica based in particular for its adhesion and its compatibility with a glass substrate.

 The precursor sol of the material constituting the silica layer may be a silane or a silicate.

 As a (mainly) inorganic layer, it is possible to choose a layer based on tetraethoxysilane (TEOS), or lithium, sodium or potassium silicate, for example deposited by "flow" coating ".

The silica layer can thus be based on a sodium silicate in aqueous solution, transformed into a hard layer by exposure to a CO ₂ atmosphere.

 The manufacture of a hybrid mass material by sol-gel process comprises, for example, the following steps:

 the hydrolysis of the precursor of the material constituting said Si oxide, especially a hydrolysable compound such as a halide or an alkoxide, in a particularly aqueous and / or alcoholic solvent, and then, the ripening of the soil,

- Mixing a colloidal suspension of the particles of said metals in a particular aqueous and / or alcoholic solvent, and / or salt of said metal for the in situ growth of the particles of said metals, which addition can take place at the beginning of the hydrolysis , or after a sufficient ripening to avoid too much great kinetics,

 the condensation of the precursor and the possible elimination of the solvent to increase the viscosity and to obtain a solid gel.

 The manufacture of a layer of hybrid material by sol-gel process comprises for example the following steps:

 the hydrolysis of the precursor of the material constituting said Si oxide, especially a hydrolysable compound such as a halide or an alkoxide, in a particularly aqueous and / or alcoholic solvent, and then, the ripening of the soil,

- Mixing a colloidal suspension of the particles of said metals in a particular aqueous and / or alcoholic solvent, and / or salt of said metal for the in situ growth of the particles of said metals, which addition can take place at the beginning of the hydrolysis , or after sufficient ripening to avoid excessive kinetics,

 layer deposition with evaporation of the solvent, for example by spin-coating, flow coating,

 a heat treatment to induce the condensation of the precursor and the possible elimination of the solvent.

 The choice of the colloidal suspension makes it possible to adjust, if necessary, the size of the particles inserted. As it is redispersed in the soil, care is taken to check the compatibility of the suspension with the soil to prevent aggregation of the particles. The addition of the salt of the said metal is simpler and presented more often in the literature.

 As the solvent, water or low molecular weight alcohols having a low boiling point (typically less than 100 ° C.) are preferred to allow the good dissolution of the metal salt.

 The amount of nanoparticles present in the oxide / metal hybrids can be simply controlled by the synthesis conditions, and increases with the amount of metal introduced into the soil.

The formation of hybrid metal / metal oxide material from the sol-gel process is very widely described in the literature. A large variety of metal / oxide pairs in the form of layers or massive materials has thus been synthesized. The metal particles are preferentially created in situ in the matrix by adding a salt of the corresponding metal and after reducing treatment (most often heat treatment or else a reducing agent: H ₂ , hydrazine, etc.).

In the publication titled "Recent trends on nanocomposites based on Cu, Ag, and Au clusters: A doser look" (L. Armelao et al., Coordination chemitry Reviews, 2006, 250, page 1294), is reported the introduction up to at 10% by weight of silver and copper salt in sol-gel-obtained silica layers and the controlled obtaining of metal particles of Ag or Cu / CuO _x particles of a few nm, after heat treatment (above 500 ° C). The author highlights the importance of heat treatment on the size and the oxidation state of the particles obtained. The production of other particles in metallic or oxide form in a silica matrix has been reported. Most often, a porous matrix is used as a host for the nanoparticles. However, it is possible to draw inspiration from this work to obtain a material without artificial porosity. Thus, in the publication "Insight into the properties of Fe oxide present in high concentrations on mesoporous silica" (Gervasini et al., Journal of Catalysis 2009, 262, 224), mesoporous silica (ie having a characteristic pore size of 3 -10 nm) containing up to 17% by mass of catalytic particles Fe ₂ 0 ₃ was obtained.

Nickel nanoparticles have been obtained for optical applications by thermal treatment of nickel nitrate impregnated in a silica matrix in the publication entitled "Optical properties of sol-gel fabricated Ni / SiO ₂ glass nanocomposites" (Yeshchenko OA et al. Journal of Physics and Chemistry of Solids, 2008, 69; 1615). Finally, in the publication "Synthesis and characterization of tin oxide nanoparticles dispersed in monolithic mesoporous silica" (YS Feng et al., Solid State Science, 2003 5, 729), Sn0 ₂ particles of 4-6 nm are obtained at 20 nm. % in mesoporous silica after heat treatment at 600 ° C.

In addition this sol gel method allows additional functionalization of the layer. The surface structured by said process can then be functionalized to obtain new wetting properties. In particular, the patent WO00 / 64829 reports creating a hydrophobic and oleophobic coating comprising at least one fluorinated alkoxysilane of the general formula CF3 (CF2) m- (CH ₂₎ n Si (X) 3-PrP (m = 0 to 15, n = 1 to 5, p = 0, 1, 2, where X is a hydrolyzable group and R is an alkyl group), an aqueous solvent system, preferably composed of an alcohol and approximately 10% of water and at least one catalyst selected from an acid and / or a Bronsted base. This compound can be deposited on large surfaces (greater than m ² ) of glass products or functional metal oxide layers, in particular textured products, and this after a possible deposition of a silica-based primer. The combination of this process and surface texturing gives superhydrophobic properties (lotus leaf type).

The preferred deposition methods for the organic layers are dip coating (dip coating), or the spraying of the soil and the spreading of the drops by scraping or brushing or by heating as described in particular in the article entitled "Thermowetting structuring of the organic-inorganic hybrid materials »WS. Kim, KS. Kim, YC. Kim, BS Bae, 2005, Thin Solid Films, 476 (1), 181-184. The chosen method can also be a coating by spin-coating.

 Naturally, annealing at at least 400 ° C., especially above 500 ° C., is preferred for at least 30 minutes or even 1 hour in order to obtain a sufficient condensation of the oxide and to reduce the activation energy with the forming aggregates of said metal-type material, and less than 800 ° C especially up to 750 ° C to have sufficient reaction kinetics and not to damage the glass substrate.

 This annealing may advantageously be coupled to the quenching step of the glass, which consists of heating the glass at high temperature (typically between 550 ° C. and 750 ° C.) and then cooling it rapidly.

 There are other hybrid materials that can be layered.

 Said hybrid material may be a layer of silica deposited by the physical vapor phase, typically by evaporation or by sputtering (especially magnetron) on a substrate, in particular transparent, glass, including by codépôt of the species (in the aforementioned list), especially copper, silver, or gold and silica oxide, with a target of the oxide element and under an oxygen atmosphere, or with a silica target.

 Spraying will generally be preferred to evaporation due to a much higher deposition rate to make 100 nm or even micron layers faster. Thus, if by evaporation a deposition rate is generally close to 1 A min, with a maximum of 1 A / s, the magnetron deposition rates are typically between 1A / s and several tens of nm / s.

 For example, for the deposition of mixed SiO 2 - copper layer, it would be possible either to use a codecode from silicon and copper target, with the introduction of oxygen, or to directly use a copper target and a silica target.

 The substrate can be glass. For the purposes of the invention, the term "glass substrate" means both an inorganic glass (silicosodocalcique, borosilicate, vitroceramic, etc.) and an organic glass (for example a thermoplastic polymer such as a polyurethane or a polycarbonate).

 For the purposes of the invention, a substrate which, under normal conditions of temperature and pressure, has a modulus of at least 60 GPa for a mineral element, and at least 4 GPa for an organic element, is described as rigid.

 The glass substrate is preferably transparent, in particular having a global light transmission of at least 70 to 75%.

In order to enter the composition of the glass substrate, a glass having a linear absorption of less than 0.01 mm ^-1 in the part of the spectrum useful for application, generally the spectrum ranging from 380 to 1200 nm, is preferably used. Even more preferably, an extra-clear glass is used, ie a glass having a linear absorption of less than 0.008 mm ^-1 in the wavelength spectrum from 380 to 1200 nm. example the glass brand Diamant marketed by Saint-Gobain Glass.

 The substrate may be monolithic, laminated, two-component. After structuring, the substrate can also undergo various glass transformations: quenching, shaping, laminating, etc.

 The glass substrate may be thin, for example of the order of 0.1 mm for mineral glasses or millimeter for organic glasses, or thicker for example with a thickness greater than or equal to a few mm or even cm.

 A step of depositing a conductive, semiconductive and / or hydrophobic layer, in particular an oxide-based layer, may succeed to the first structuring.

 This deposit is preferably carried out continuously.

 The layer is for example metallic, silver or aluminum.

 Advantageously, a step of selective deposition of a conductive layer (in particular metal, based on oxides) on the structured surface, on or between patterns, for example dielectric or less conductive, can be advantageously provided.

 The layer, for example metal, in particular silver or nickel, can be deposited electrolytically. In the latter case, to form an electrode for electrolysis, the structured layer may advantageously be a layer (semiconductor) or a sol-gel type dielectric layer loaded with metal particles or a multilayer with a top layer of germination (seed layer in English) conductive.

 The chemical potential of the electrolytic mixture is adapted to make the deposit preferential in areas of high curvature.

 After the structuring of the layer, it is possible to envisage a transfer of the pattern network to the glass substrate and / or to an underlying layer, in particular by etching.

 The structured layer may be a sacrificial layer optionally partially or completely eliminated.

 In one embodiment, it is possible to structure the surface by structuring domains, structuring domains having distinct patterns (by their shape, by one of their characteristic dimensions, especially the spacing) and / or orientations. distinct patterns.

 During the manufacture of the material one can differentiate the rate of the mobile species and the number of mobile species from one area to another.

Some areas of massive or thin layer oxide can be masked do not incorporate the mobile species or modify the incorporation conditions locally.

Naturally the structured layer can also be used as a mask for an underlayer or the adjacent substrate

 The invention also covers a product with surface structuring, that is to say with a set of irregularities or patterns with a submicron height and at least one (sub) micronic lateral characteristic dimension, a hybrid solid material comprising

 a single or mixed oxide of Si, the molar percentage of Si oxide in the material being at least 40%, especially between 40 and 99%, and at least one species of nature distinct from the element or elements of the oxide; and which is in particular a metal,

 the molar percentage of species (s) in the material ranging from 1 mol% up to 50% and below the percentage of said Si oxide with a larger maximum characteristic dimension of less than 50 nm obtainable by the method such as as previously described.

 The structured product can be for an application for electronics, building or automotive, or even for a microfluidic application

 There may be mentioned in particular different products, in particular glazing:

 - with modified chemical properties ("super" hydrophobicity, hydrophilicity),

 optics, in particular for LCD-type flat screen lighting or backlighting systems, in particular a light extraction means for an electroluminescent device, optical products for example intended for display screen, lighting, signage,

 - for building, in particular a solar and / or thermal control glazing, The function and the properties associated with the structuring depend on the characteristic dimensions H, W, D.

 The range of optical functionalities of nanostructured products is wide. The product may have at least one of the following characteristics:

 the pattern is a relief, in particular of maximum average lateral dimension, called length L, submicron, in particular with W greater than 0.3L under oblique incidence and 0.8L under normal incidence, the material being notably richer in mobile species in the summits of the reliefs, and on a thickness less than 10 nm, said superficial thickness,

it is a glass exchanged with silver or copper, a sol gel mass or layer with said species including silver or copper and / or gold on a particularly transparent substrate, the pattern is defined by a height H and a width W and a distance D between adjacent pattern,

 the distance D being chosen less than 5 μηι in microfluidic or for wetting properties, at 2 μηη for infrared applications, at 500 nm, preferably at 300 nm, even more preferably at 200 nm for optical applications or even extended to infrared (antireflection, light extraction, light collection for photovoltaic or photocatalysis ...),

the height H being preferably chosen to be greater than 20 nm, preferably greater than 50 nm, still more preferably greater than 100 nm for optical applications (visible and infrared), and greater than 70 nm, preferably 150 nm for the properties of wetting (superhydrophobic or superhydrophilic),

 the width W being chosen greater than D / 10, even more preferentially at D / 5 and even more preferentially at D / 2,

 the pattern is defined by a height H and a width W and a distance D between adjacent pattern,

 the distance D being chosen less than 5 μηη in microfluidic or for wetting properties, at 2 μηη for infrared applications,

the height H being preferably chosen to be greater than 70 nm, preferentially at 150 nm for the wetting properties (superhydrophobic or superhydrophilic),

 the width W being chosen greater than D / 10, even more preferentially at D / 5 and even more preferentially at D / 2.

 The etched surface may form a substrate for the growth of a thin layer deposited under vacuum, the pattern is defined by a height H and a width W and a distance D between adjacent pattern:

 the distance D being chosen less than 200 nm, preferably between 200 nm and 100 nm, even more preferably at 50 nm,

 the height H being chosen preferably greater than 20 nm, preferably greater than 50 nm,

 the width W being chosen greater than D / 10, even more preferentially at D / 5 and even more preferentially at D / 2.

 The relief can be particular punctual, cone-shaped.

For the relief patterns, it is possible to observe at the apices of the reliefs an enrichment in said metal over a thickness called superficial thickness typically of 2 to 10 nm. For the intaglio patterns, it is possible to observe at the bottoms of the recesses an enrichment in said metal over a thickness, typically from 2 to 10 nm.

 The presence of the reinforced metal zones can be made by known microscopic TEM, STEM techniques and / or by chemical mapping by known microscopic or spectrometric techniques STEM, EELS, EDX.

 The two main surfaces of said material may be structured with similar or distinct patterns, simultaneously or successively.

 FIG. 1 shows the AFM images of a planilux glass surface exchanged with silver after abrasion for 5 minutes by plasma of SF6. Fig. 2 shows an image of the SEM surface of the same sample as Fig. 1 taken at an angle of 45 °.

Figure 3 gives two images at several 45 ° SEM scales of the silver-doped silica sol-gel thin layers after RIE.

Figure 4 shows SEM images taken at 45 ° from the surface.

EXAMPLE OF A FIRST GLASS EXCHANGE STRUCTURE

A first 2 mm thick silver glass was obtained after ion exchange from a Planilux ^® glass from SAINT GOBAIN soda-lime float glass. It involves the ion exchange between the sodium of the glass and the silver of a silver nitrate bath.

 At first, the glass is immersed in pure silver nitrate at 300 ° C for 2 hours.

 The glass obtained has a silver concentration profile of the surface up to several micrometers in depth.

It is noted that it has a weak yellow color. This color is characteristic of silver nanoparticles. Part of the silver that has penetrated the glass is reduced and aggregated to the state of nanoparticles of a few nanometers during the exchange reaction.

The silver penetrates to a depth of around 4 micrometers. The percentage of silica remaining constant, the surface has an almost linear profile of silver. Is good the

RECTIFIED SHEET (RULE 91) ISA / EP sodium that has been exchanged with silver and not calcium, potassium or any other cation of glass. The silver is probably present in the form of particles a few microns deep. The surface contains about 15% Ag in mol.

The reactive etching is carried out in a vacuum frame under a pressure of 0.1 mbar and a flow of 90 sccm SF ₆ gas. The reactive etching is done by the formation of a plasma by radio frequency on the surface of the 200W power sample. The surface is etched for 5 minutes.

FIG. 1 represents the AFM images of a Planilux glass surface exchanged with silver after abrasion for 5 minutes by plasma of SF6. The AFM images of the surface of the silver glass show the appearance of a texturing composed of pads after abrasion. These pads are dense (almost contiguous, W close to D) and 60 nanometers wide and 40 nm high appear after only 5 minutes of etching.

The highly selective plasma of SF ₆ will preferentially abrade silica. The remaining money will aggregate and protect the surface. It should be noted that glass is not only made of silver, but also of Al ₂ O ₃ , CaO, MgO and Na ₂ O. These compounds will not be as easily abraded as silica, which will cause a poorly homogeneous surface.

Figure 2 shows an SEM surface image of the same sample as Figure 1 taken at an angle of 45 °. It can be seen that the surface consists of a dense stud, with the presence of large protuberances of height of about 200 nm spaced several microns without nuisance, especially for optical applications. The fact that the glass is not made solely of silicon and copper is probably responsible for this inhomogeneity of the surface.

Such images have been made at several places on the surface of the sample. It was thus possible to verify that the texturing observed in AFM took place on the entire surface exposed to the SF ₆ beam. The structuring is not linked to an edge effect

In summary, Planilux ^® silver glass has been abraded. Plots formed during abrasion over the entire surface. The pads obtained have a diameter W of 60 nm and a average height H of 40 nm. At the end of the abrasion, the yellow color is almost no longer visible on the sample.

The abrasion was non-directional. A larger and more regular structuring can be achieved by applying an electric field perpendicular to the surface that will render the RIE directional. The masking will be more efficient, and one can thus obtain a structuring more important and / or faster.

EXAMPLES OF STRUCTURED SILICONE SILICONE GEL LAYER

A second type of hybrid prepared by sol-gel was prepared and abraded.

The sol-gel pathway consists of synthesizing an inorganic polymer, such as silica, at room temperature from organic precursors. In a first step, this precursor is placed in the presence of water to hydrolyze. The solution obtained (called sol) can be deposited on different substrates such as glass or silicon. During the deposition, the solvent of the solution evaporates until the hydrolysed precursor is condensed into an inorganic polymeric network. The oxide gel obtained can be shaped, in particular in a thin layer, until the polymer is completely condensed.

The deposition conditions (rotation speed) make it possible to control the thickness. We can play in a very wide range on the layer size (from ten nanometers to a few microns). Other compounds may be added during the hydrolysis such as dyes, dopants, surfactants that confer porosity to the layer or organic compounds that will not be altered by the synthesis because it is carried out at room temperature

Silica layers of a few hundred nanometers thick containing 10 mol%. of silver were synthesized by sol-gel

Preparation of the silica and silver sol: a sol of TEOS (2 g, 9.6 mmol) at 10% by weight in a pH 2 solution of HNO ₃ (18 g) was prepared and left stirring for three hours. These pH conditions allow a high rate of hydrolysis while slowing down the condensation. After evaporation under reduced pressure of the ethanol formed during the reaction, a solution of AgNO ₃ was added to the soil (1 mL, 1 mol.L ^"1 ) to have n _Ag = [Ag] / ([Ag ] + [Si]) such as 10% <n _Ag

The thickness of the sol-gel layer containing silver was measured by ellipsometry and is 250 ± 20 nm Deposition and post-treatments: The silver sols were deposited by spin-coating on the substrate (1000 rpm, 100 rpm for 2 min). The samples obtained were annealed overnight at 200 ° C. to remove the solvent remaining in the layer and initiate the condensation of the silica network. Heat treatment at higher temperature T _reC uit (700 ° C) was applied. For silver samples to finish the condensation and induce the formation of silver aggregates. Their heat treatment determines the oxidation state of silver. To obtain metallic silver, the annealing must take place between 500 ° C. and 750 ° C.

The silica layer with the agent was structured under the effect of etching. Plots of several tens of nanometers have been formed and are distributed over the entire surface of the material

 We have previously seen that the layers annealed at 700 ° C contained aggregated silver metal. These holes can therefore result from the protection of these nanoparticles. Nevertheless, the particles usually observed in silver-containing sol-gel layers have characteristic sizes smaller than the observed holes. There must be segregation and dissemination of money.

Figure 3 gives two images at several 45 ° SEM scales of the silver-doped silica sol-gel thin films after RIE.

 The studs are similar in size to those found after abrasion of the silver-exchanged glass. By cons, the surface is much more homogeneous, this is due to the presence of silica and silver only (purity of the hybrid oxide). Therefore, gel sample making is a particularly promising avenue for transparent surface texturing by RIE. EXAMPLES OF STRUCTURED COPPER SILICA GEL SOLUBLE LAYER

 Like silver we have made sol-silica gel layers containing 10% copper.

Preparation of the silica and copper sol: a sol of TEOS (3 g, 9.6 mmol) at 15% by mass in ethanol (17 g) was prepared. Copper acetate (320 mg, 1, 6.10 ^-3 mol) and then the stoichiometric amount of water (1 g, 57.7.10 ^-3 mol) necessary for the hydrolysis of TEOS and acetate were added. After adjusting the pH to 3, the solution was left at reflux for two hours at 70 ° C. The molar ratio in the soil is n _Cu = [Cu] / ([Cu] + [Si]) = 10%. We looked at the structure after 5 minutes of abrasion at room temperature.

 Figure 4 shows SEM images taken at 45 ° from the surface. We observe the appearance of a very strong relief. There is a formation of reliefs of several hundreds of nm of height H and width W, dense (, but of morphology and size not very homogeneous.The surface is always more homogeneous than in the case of glass, because one has a constituted surface only silica and copper The inhomogeneity of the structures is likely caused by non-directive abrasion.

 The copper incorporated in the silica makes it possible to quickly obtain highly structured surfaces after abrasion with pads of more than 100 nm in height. Making the abrasion directive can make it possible to obtain more homogeneous studs, of more regular shape, and of higher aspect ratio.

 Three hybrid metal / silica materials have been developed. Two paths have been followed for the synthesis of these systems: the sol-gel pathway and the ion exchange. We always observe the formation of studs

The sol gel route makes it possible to avoid the formation of parasitic protuberance, unlike the ion exchange on the glass. Homogeneity can be improved by making abrasion directive.

Claims

A method of surface structuring, that is to say formation of at least one set of irregularities or patterns (2) with a submicron height H and at least one lateral characteristic dimension W, called width, micron or submicron, on a surface of a material (1), in particular a glass, by reactive ion etching, characterized in that it comprises the following steps:

 the supply of said material having a thickness of at least 100 nm, a hybrid solid material and comprising:

 a single or mixed oxide of silicon, the silicon oxide being predominant or even at least 80% to 90% of the oxides in the case of mixed oxide, the molar percentage of oxide in the material being at least 40%, especially between 40 and 99%,

and at least one species, of a nature distinct from the silicon of the oxide, and which is in particular a metal,

 the molar percentage of species (s) in the material ranging from 1 mol% up to 50% and lower than the percentage of said silicon oxide, with at least the majority of the species having a greater characteristic dimension smaller than 50 nm , in particular said hybrid material being metastable before said etching,

 the possible heating of said hybrid material before said etching,

- Structuring the surface of said hybrid material without masking necessary with an etching time of less than 30 minutes on an etching surface greater than 1 cm ² , until forming said set of patterns, the structuring being optionally accompanied by heating hybrid material.

 Surface structuring method according to claim 1 characterized in that the material is heated to a temperature greater than equal to 70 ° C especially from 120 to 300 ° C before etching and / or during etching.

 Surface structuring method according to one of the preceding claims, characterized in that the said species is in ionic form, in particular copper in silica and / or in the form of an aggregate, in particular silver in glass and / or species is preferably chosen from at least one of the following species, in particular metal: silver, copper, cobalt, platinum, nickel, tin, gold and preferably the effective charge on the species is zero or less than 0.5.

Surface structuring method according to claim 1 characterized in that the hybrid material is a glass, in particular silicocalcic, ionically exchanged with preferably at least one of the following species: silver, copper.

5. A method of surface structuring according to claim 1 characterized in that the hybrid material, mass or layer on a substrate, is a gel sol, incorporating said metal in particulate form, optionally aggregate, including Ag, Cu, Au .

6. surface structuring method according to one of claims 1 to 2 characterized in that said hybrid material is a layer deposited by the physical vapor phase on a substrate by codépôt, of the species, in particular metal, such as the copper, silver or gold, and Si oxide, especially with metal targets and under oxygen atmosphere.

7. Product with surface structuring, that is to say with a set of irregularities or patterns with a submicron height and at least one submicron lateral characteristic dimension, a hybrid solid material comprising

 an oxide of Si, the molar percentage of oxide in the material being at least 40%, especially between 40 and 99%,

 and at least one species of nature distinct from the Si of the oxide and which is in particular a metal,

 the molar percentage of species (s) in the material ranging from 1 mol% up to 50% and below the percentage of said Si oxide with a larger maximum characteristic dimension of less than 50 nm obtainable by the process according to the invention; one of the preceding method claims.

 8. structured product according to one of the preceding claims of a product characterized in that it is a glass exchanged with silver or copper, sol gel mass or layer with said species including silver or copper and or or on a particularly transparent substrate.

9. Structured product according to one of the preceding product claims, characterized in that the pattern is defined by a height H and a width W and a distance D between adjacent pattern,

 - The distance D being chosen less than 500 nm, preferably 300 nm, even more preferably 200 nm for optical applications even widened to infrared (antireflection, light extraction, light collection for photovoltaic or photocatalysis ...) ,

 the height H being chosen preferably greater than 20 nm, preferably greater than 50 nm, still more preferably greater than 100 nm for optical applications (visible and infrared),

the width W being chosen greater than D / 10, even more preferentially at D / 5 and even more preferentially at D / 2.

10. Structured product according to one of the preceding product claims, characterized in that the pattern is defined by a height H and a width W and a distance D between adjacent pattern,

 the distance D being chosen to be less than 5 μηη for wetting properties, the height H being preferably chosen to be greater than 70 nm, preferably to

150 nm for the wetting properties (superhydrophobic or superhydrophilic).

 the width W being chosen greater than D / 10, even more preferentially at D / 5 and even more preferentially at D / 2.