EP3714327A1

EP3714327A1 - Method for producing a planar polymer stack

Info

Publication number: EP3714327A1
Application number: EP18826414.7A
Authority: EP
Inventors: Xavier CHEVALIER; Ilias Iliopoulos
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2017-11-24
Filing date: 2018-11-23
Publication date: 2020-09-30
Also published as: CN111615665A; SG11202004855YA; FR3074180B1; TW202004335A; WO2019102158A1; JP2021504114A; CN111615665B; FR3074180A1; TWI794316B; KR20200088881A; US20200371437A1

Abstract

The invention relates to a method for producing a planar polymer stack, said stack comprising at least one first and one second (co)polymer layer (20, 30) which are stacked one on top of the other, the first subjacent (co)polymer layer (20) having not received any previous treatment allowing the cross-linking thereof, and at least one of the (co)polymer layers being initially in a liquid or viscous state. Said method is characterised in that the upper layer (30), called the top coat (TC), is deposited on the first layer (20) in the form of a prepolymer composition (pre-TC), comprising at least one monomer and/or dimer and/or oligomer and/or polymer in a solution, and in that the upper layer is then subjected to a stimulus that can cause a cross-linking reaction of the molecular chains within said layer (30, TC).

Description

METHOD FOR MANUFACTURING A PLANAR POLYMERIC STACK

[Field of the invention

The present invention relates to the field of polymeric stacks.

More particularly, the invention relates to a method of controlling the flatness of such stacks. The invention further relates to a method of manufacturing a nano-lithography mask from such a stack whose flatness is controlled, and a polymeric stack obtained by said flatness control method.

The polymer stacks are used in a multitude of industrial applications among which may be mentioned, by way of non-exhaustive example, the production of coatings for aerospace or aeronautics or automotive or wind power. , inks, paints, membranes, biocompatible implants, packaging materials, or optical components, such as optical filters for example, or microelectronic, optoelectronic or microfluidic components. The invention is intended for any application whatsoever, since the stack comprises at least two polymer materials stacked one on the other.

Among the various possible industrial applications, the invention is also interested in, and not limited to, applications dedicated to the field of organic electronics, and more particularly to directed self-assembly nano-lithography applications. , also known as Directed Self-Assembly (DSA), for which other requirements are to be met concomitantly.

The stability and the behavior of the thin polymer films on a solid substrate or on an underlying layer, itself solid or liquid, are technologically important in certain industrial applications such as, for example, the protection of surfaces for aerospace or aerospace or automotive or wind power, paints, inks, membrane manufacturing, or microelectronic, optoelectronic or microfluidic components.

Polymer-based materials have so-called low surface energy interfaces, where the molecular chains thus have a relatively low cohesion energy, compared with other solid interfaces such as oxide or metal surfaces having a much greater surface energy, so less likely to be deformable under the effect of any force.

In particular, the dewetting phenomenon of a polymer film deposited in the liquid or viscous state on the surface of an underlying layer, itself in the solid or liquid state, has been known for a long time. "Liquid or viscous polymer" means a polymer having, at a temperature above the glass transition temperature, due to its rubbery state, increased deformation capacity due to the possibility given to its molecular chains to move freely. The hydrodynamic phenomena at the origin of the dewetting appear as long as the material is not in a solid state, that is to say, indeformable because of the negligible mobility of its molecular chains. This dewetting phenomenon is characterized by the spontaneous withdrawal of the polymer film applied to the surface of the underlying layer, when the initial stacking system is left free to evolve over time. There is then a loss of continuity of the initial film and a variation of thickness. The film does not spread and forms one or more spherical caps / droplets revealing a non-zero contact angle with the underlying surface. This phenomenon is illustrated in FIGS. 1A to 1C. FIG. 1A more particularly represents a solid substrate 10 on which a layer of polymer 20 in the liquid or viscous state is deposited. In this first case, the stacking system is in a "liquid / solid" configuration. After the deposition of such a polymer layer 20, the dewetting phenomenon appears and the polymer 20 no longer spreads out correctly on the surface of the substrate 10, forming spherical caps and resulting in a stack whose surface is not flat. . FIG. 1B shows a solid substrate on which a first polymer layer 20 is deposited, this first layer being solidified at the time of deposition of a second upper polymer layer 30. In this case, the second polymer layer 30 at the upper surface, is deposited in a liquid or viscous state on the solid surface of the first polymer layer 20. The interface between the two polymer layers is said to be in a "liquid / solid" configuration. In this case also, after a certain time, a dewetting phenomenon occurs and the polymer does not spread correctly on the surface of the first polymer layer 20, forming spherical caps and resulting in a stack whose surface is not flat. Finally, FIG. 1C represents a solid substrate, on which is deposited a first layer of polymer 20 in the liquid or viscous state, itself covered with a second upper polymer layer 30 in the liquid or viscous state. . In this case, the interface between the two polymer layers is in a "liquid / liquid" configuration. In this case too, the second upper polymer layer 30 does not spread out correctly on the surface of the first polymer layer 20 and it can also, optionally, partially solubilize in the first polymer layer 20, causing a phenomenon of inter-diffusion at the interface between the two layers. This layer 30 then deforms, among other things under the combined effect of gravity, its specific density, its surface energy, the viscosity ratio between the materials of the polymer layers 30 and 20 in the presence, as well as under the effect of Van der Waals interactions leading to the amplification of the capillary waves of the system. This distortion leads to obtaining a discontinuous film, further comprising spherical caps, and also deforming the first underlying polymeric layer. This results in a stack whose surface is not flat and whose interface between the two polymer layers is not clear.

The coefficient of spreading of a liquid or viscous layer, noted S, is given by the following Young equation:

S = yc - (YCL + YL),

wherein Yc represents the surface energy of the underlying layer, solid or liquid, YL represents the surface energy of the liquid polymer top layer and ga represents the energy at the interface between the two layers. By surface energy (denoted gc) of a given material "x" is meant the excess energy at the surface of the material compared to that of the bulk material. When the material is in liquid form, its surface energy is equivalent to its surface tension. When the spreading coefficient S is positive, then the wetting is total and the liquid film spreads completely on the surface of the underlying layer. When the spread coefficient S is negative, then the wetting is partial, that is to say that the film does not spread completely on the surface of the underlying layer and the dewetting phenomenon is observed if the initial stacking system is left free to evolve.

In these stack systems of layer (s) of polymeric materials, in which the configurations may for example be "liquid / solid" or "liquid / liquid", the surface energies of the different layers may be very different, thus rendering the entire system metastable or even unstable due to the mathematical formulation of the S spreading parameter.

When a stacking system, deposited on any substrate, comprises different layers of polymeric material in the liquid / viscous state, stacked on top of each other, the stability of the entire system is governed by the stability of each layer at the interface with different materials.

[001 1] For this kind of metastable liquid or liquid system, even unstable, dewetting phenomena have been observed during the relaxation of the initial stresses and this, independently of the nature of the materials involved (small molecules, oligomers, polymers ). Various studies (F. Brochart-Wyart & al., Langmuir, 1993, 9, 3682-3690, C. Wang & al., Langmuir, 2001, 17, 6269-6274, M. Geoghegan & al., Prog Polym Sci. , 2003, 28, 261-302) demonstrated and explained theoretically and experimentally the behavior as well as the origin of the observed dewetting. Whatever the mechanisms (spinodal decomposition or nucleation / growth), this type of liquid / liquid system tends to be particularly unstable and leads to the introduction of severe defects in the form of discontinuity of the film of interest. that is to say in the example of Figure 1 C the first polymeric layer 20, whose initial flatness is disrupted, with the appearance, in the best case, holes in the film or the double layer of polymer films thus rendering it unusable for the intended applications.

Dewetting is a thermodynamically favorable phenomenon, the materials spontaneously seeking to minimize the contact surface with each other as much as possible. However, for all the applications mentioned above, it is precisely to avoid such a phenomenon, so as to have perfectly flat surfaces. We also try to avoid inter-diffusion phenomena between the layers in order to obtain clear interfaces.

A first problem that the applicant has sought to solve therefore consists in avoiding the appearance of dewetting phenomena in polymer stack systems, at least one of the polymers is in a liquid / viscous state and this, whatever the polymers of the system and whatever the intended applications.

A second problem that the applicant has sought to solve is to avoid inter-diffusion phenomena at the interfaces, in order to obtain clear interfaces.

In the particular context of the applications in the field of directed self-assembly nano-lithography, or DSA, block copolymers capable of nano-structuring at an assembly temperature are used as masks. nano-lithography. For this, stacking systems of liquid / viscous materials are also used. These stacks comprise a solid substrate, on which is deposited at least one block copolymer film, denoted BCP thereafter. This BCP block copolymer film, intended to form a nano-lithography mask, is necessarily in a liquid / viscous state at the assembly temperature, so that it can self-organize into nano-domains. due to phase segregation between the blocks. The block copolymer film thus deposited on the surface of the substrate is therefore subject to dewetting phenomena when it is brought to its assembly temperature.

In addition, for the intended application, such a block copolymer must also preferably have nano-domains oriented perpendicularly to the lower and upper interfaces of the block copolymer, in order then to be able to selectively remove one of the blocks of the copolymer. in blocks, create a porous film with the (or) block (s) residual (s) and transfer, by etching, the patterns thus created to the underlying substrate.

However, this condition of perpendicularity of the patterns is met only if each of the lower (substrate / block copolymer) and higher (bead copolymer / ambient atmosphere) interfaces is "neutral" with respect to each of the blocks of said BCP copolymer, that is to say that there is no predominant affinity of the interface considered for at least one of the blocks constituting the BCP block copolymer. In this regard, the possibilities for controlling the affinity of the so-called "lower" interface, located between the substrate and the block copolymer, are well known and controlled today. There are two main techniques for controlling and guiding the orientation of blocks of a block copolymer on a substrate: graphoepitaxy and / or chemistry-epitaxy. Graphoepitaxy uses a topological constraint to force the block copolymer to organize in a predefined space and commensurable with the periodicity of the block copolymer. For this, graphoepitaxy consists of forming primary patterns, called guides, on the surface of the substrate. These guides, of any chemical affinity with respect to blocks of the block copolymer, delimit zones within which a layer of block copolymer is deposited. The guides make it possible to control the organization of the blocks of the block copolymer to form secondary patterns of higher resolution, within these zones. Classically, the guides are formed by photolithography. By way of example, among the possible solutions, if the intrinsic chemistry of the monomers constituting the block copolymer allows it, a random copolymer comprising a ratio judiciously selected from the same monomers as those of the BCP block copolymer can be grafted onto the substrate, thus making it possible to balance the initial affinity of the substrate for the BCP block copolymer. This is for example the conventional method of choice used for a system comprising a block copolymer such as PS-6-PMMA and described in the article by Mansky et al., Science, 1997, 275, 1458). The chemistry-epitaxy uses, for its part, a contrast of chemical affinities between a pre-drawn pattern on the substrate and the different blocks of the block copolymer. Thus, a pattern with high affinity for only one block of the block copolymer is pre-drawn on the surface of the underlying substrate, to allow the block copolymer blocks to be oriented perpendicularly, while the rest of the block copolymer is The surface has no particular affinity for the blocks of the block copolymer. For this, a layer is deposited on the surface of the substrate comprising, on the one hand, neutral zones (constituted, for example, of grafted random copolymer), which do not show any particular affinity with the blocks of the block copolymer to be deposited and of on the other hand, affine zones (consisting, for example, of graft homopolymer of one of the blocks of the block copolymer to be deposited and serving as an anchor point for this block of the block copolymer). The anchoring homopolymer can be made with a width slightly greater than that of the block with which it has a preferential affinity and allows, in this case, a "pseudo-fair" distribution of the blocks of the block copolymer at the same time. surface of the substrate. Such a layer is called "pseudo-neutral" because it allows a fair distribution or "pseudo fair" blocks of the block copolymer on the surface of the substrate, so that the layer does not exhibit, in its entirety, preferential affinity with one of the blocks of the block copolymer. Therefore, such a chemically epitaxial layer on the surface of the substrate is considered to be neutral with respect to the block copolymer. In contrast, the control of the so-called "upper" interface of the system, that is to say the interface between the block copolymer and the surrounding atmosphere, remains today much less well controlled. Among the different approaches described in the prior art, a promising first solution, described by Bâtes et al in the publication entitled "Polarity-switching top coats enable orientation of sub-10nm block copolymer domains", Science 2012, Vol.338, p. 775-779 and in US2013 280497, consists in controlling the surface energy at the upper interface of a nano-structuring block copolymer, of the poly (trimethylsilystyrene-b-lactide) type, denoted PTMSS-6 -PLA, or poly (styrene-6-trimethylsilystyrene-6-styrene), denoted PS-6-PTMSS-6-PS, by the introduction of an upper layer, also called "top coat" and noted TC thereafter deposited on the surface of the block copolymer. In this document, the top coat, polar, is deposited by spin coating (or "spin coating" in English terminology) on the block copolymer film to be nanostructured. The top coat is soluble in an acidic or basic aqueous solution, which allows its application to the upper surface of the block copolymer, which is insoluble in water. In the example described, the top coat is soluble in an aqueous solution of ammonium hydroxide. The top coat is a random or alternating copolymer whose composition comprises maleic anhydride. In solution, the ring opening of maleic anhydride allows the top coat to lose ammonia. At the time of self-organization of the block copolymer at the annealing temperature, the cycle of the maleic anhydride of the top coat closes, the top coat undergoes a transformation in a less polar state and becomes neutral with respect to the copolymer. blocks, thus allowing a perpendicular orientation of the nano domains with respect to the two lower and upper interfaces. The top coat is then removed by washing in an acidic or basic solution.

In such systems, based on stacks noted TC / BCP / substrate, the top coat TC, applied by spin coating, has a liquid / viscous state. The BCP block copolymer is also necessarily in its liquid / viscous state, in order to self-organize at the assembly temperature and create the desired patterns. However, in the same way as for any polymeric stack, the application of such a top coat layer TC, in the liquid or viscous state, on a layer of BCP block copolymer itself in the liquid state or viscous, causes the appearance at the upper interface copolymer blocks / top coat (BCP / TC), the same dewetting phenomenon as that described above with respect to Figure 1 C. Indeed, because of phenomena hydrodynamics leading to the amplification of capillary waves of the top-coat layer TC and its interaction with the underlying layer of BCP block copolymer, this type of stack tends to be particularly unstable and leads to the introduction of severe defects in the form of discontinuity of the BCP block copolymer film, thus rendering it unsuitable for use, for example, as a nano-lithography mask for electronics. In addition, the finer the deposited polymer film, that is to say at least once the gyration radius of a molecular chain of the polymer in question, the more it will tend to be unstable or metastable, the more so. when the surface energy of the underlying layer is different from that of said polymer and the system is left free to evolve. Finally, the instability of the polymer film deposited on the underlying layer is generally all the more important that the torque "annealing temperature / annealing time" is high.

Regarding the first solution described by Bâtes et al, just after the step of depositing the top coat layer TC by spin-coating, there remains trapped solvent in the polymer chains, as well as an "open" form. maleate, less rigid, of the monomer. These two parameters imply, in fact, a plasticization of the material and therefore a significant decrease in the glass transition temperature (Tg) of the material before thermal annealing allowing the return of said material to the anhydride form. In addition, the difference between the assembly temperature of the BCP block copolymer (which is 210 ° C for the PS-b-PTMSS-b-PS block copolymer and 170 ° C for the PTMSS block copolymer) -b-PLA) with respect to the glass transition temperature of the top coat layer TC (which is respectively 214 ° C. for the top coat TC-PS deposited on the block copolymer of PS-b-PTMSS-b- PS and 180 ° C for the top coat TC-PLA deposited on the block copolymer of PTMSS-b-PLA) is too weak to be able to guarantee the absence of dewetting phenomenon. Finally, the assembly temperature also does not allow to guarantee correct assembly kinetics for the formation of patterns in the context of the DSA application aimed.

In addition, still concerning the solution described by Bâtes & al., To avoid the problem of inter-diffusion or solubilization of the top coat layer TC in the underlying BCP block copolymer, the transition temperature vitreous Tg of the top coat layer TC must be large and greater than the assembly temperature of the block copolymer. For this, the constituent molecules of the top coat layer TC, are chosen so as to have a high molecular weight.

The molecules constituting the TC top coat must therefore have a high glass transition temperature Tg, as well as long molecular chains, in order to limit the solubilization of the top coat layer TC in the BCP sub-block copolymer. and avoid the appearance of a dewetting phenomenon. These two parameters are particularly restrictive in terms of synthesis. Indeed, the top coat layer TC must have a degree of polymerization sufficient for its glass transition temperature Tg is much higher than the assembly temperature of the underlying block copolymer. In addition, the possible choice of comonomers, allowing to vary the intrinsic surface energy of the TC topcoat layer so that it has a neutral surface energy vis-à-vis the sub-block copolymer. lie, is limited. Finally, in their publication, Bâtes et al describe the introduction of comonomers to stiffen the chains. These comonomers added are rather carbonaceous monomers, norbornene type, which do not promote proper solubilization in polar / protic solvents.

On the other hand, for the proper functioning of such stacked polymer systems for applications in the field of nano-lithography directed self-assembly, not only the dewetting and inter-diffusion phenomena must be avoided in order to satisfy the conditions of flatness of surface and clean interface, but in addition, additional requirements must be met to allow in particular to obtain a perfect perpendicularity of the nano-domains of the block copolymer after assembly.

Among these additional requirements to be satisfied, the top coat layer TC must be soluble in a solvent, or solvent system, in which the BCP block copolymer itself is not soluble, otherwise it will dissolve the block copolymer at the time of deposition of the top coat layer, the deposition of such a layer being generally performed by the well known technique of spin coating. Such a solvent is also referred to as "orthogonal solvent for the block copolymer". It is also necessary that the top coat layer can be easily removed, for example by rinsing in a suitable solvent, preferably itself compatible with standard electronic equipment. In the publication of Bâtes et al cited above, the authors bypass this point by using, as the main base of the polymeric chain constituting the top coat TC, a monomer (maleic anhydride) whose polarity changes once in basic aqueous solution ( with introduction of charges in the chain by acid-base reaction), then returns to its original unfilled form once the material deposited and then annealed at high temperature.

A second requirement lies in the fact that the top coat layer TC must preferably be neutral with respect to the blocks of the BCP block copolymer, that is to say that it must have an interfacial tension. equivalent for each of the different blocks of the nano-structuring block copolymer, at the time of the heat treatment for structuring the BCP block copolymer, in order to guarantee the perpendicularity of the patterns with respect to the interfaces of the block copolymer film.

Given all the aforementioned difficulties, the chemical synthesis of the top-coat material may prove to be a challenge in itself. Despite the difficulties of synthesis of such a layer of top coat and the phenomena of dewetting and inter-diffusion to avoid, the use of such a layer appears as a priori indispensable to guide the nano-domains of a block copolymer perpendicular to the interfaces.

In a second solution described in the document by J. Zhang et al., Nano Lett., 2016, 16, 728-735, as well as in the documents WO16193581 and WO16193582, a second block copolymer, BCP No. 2, is used as a top-coat layer, "embedded" with the first BCP block copolymer in solution. BCP block copolymer No. 2 comprises a block having a different solubility, for example a fluorinated block, and a low surface energy, thus naturally allowing the segregation of the second block copolymer BCPn ° 2 on the surface of the first copolymer in block and rinsing in a suitable solvent, for example a fluorinated solvent, once assembly is complete. At least one of the blocks of the second block copolymer has, at the organization temperature, a neutral surface energy with respect to all the blocks of the first block copolymer film to be organized perpendicularly. Like the first solution, this solution is also conducive to the appearance of dewetting phenomena.

In a third solution, described by HS Suh et al., Nature Nanotech., 2017, 12, 575-581, the authors deposit the top coat layer TC by the iCVD method (the acronym "initiated Chemical"). Vapor Deposition "), which allows them to overcome the problem of the solvent of the top coat TC at the time of deposition, which must be" orthogonal "to the block copolymer BCP, that is to say non-solvent of the block copolymer PCO. However, in this case, the surfaces to be coated require special equipment (an iCVD chamber), and therefore involve a longer process time than with a simple deposit by spin-coating. In addition, the ratio of different monomers to be reacted, can vary from one iCVD chamber to another, so it appears necessary to make constant adjustments / corrections and quality control tests, in order to use a such a method in the field of electronics.

The various solutions described above for the production of a stack of polymer layers having a flat surface, with clear interfaces between the layers are not entirely satisfactory. In addition, when such a stack is intended for DSA applications, and includes a nano-structuring block copolymer film with nano-domains that must be oriented perfectly perpendicular to the interfaces, the existing solutions generally remain too tedious and complex to implement and do not significantly reduce the defectivity associated with dewetting and non-perfect perpendicularity of the block copolymer patterns. The solutions envisaged also seem to be too complex to be compatible with industrial applications.

Therefore, in the context of the use of stacks comprising BCP block copolymers in the form of thin films, intended to be used as nanolithography masks, for applications in organic electronics, it is imperative to to be able to control not only that the BCP block copolymer film covers the entire previously neutralized surface of the substrate without de-wetting it, and that the top coat layer covers the entire surface of the block copolymer without dewetting, but also that the top coat layer deposited at the upper interface does not have a preponderant affinity with any of the blocks of the block copolymer, in order to guarantee the perpendicularity of the patterns with respect to the interfaces.

The invention therefore aims to remedy at least one of the disadvantages of the prior art. The invention aims in particular to provide a method of controlling the flatness of a polymer stacking system, said method making it possible to avoid the occurrence of dewetting phenomena of the stacked polymer layers, while at least one of the lower layers of the stack keeps the possibility of being in a liquid-viscous state depending on the temperature, as well as solubilization phenomena between the different layers and inter-diffusion interfaces, so as to obtain stacks whose layers are perfectly flat and whose interfaces between two layers are clear. The method must also be simple to implement and allow industrial execution.

The invention also aims to remedy other problems specific to applications dedicated to nano-lithography by directed self-assembly (DSA). In particular, it aims to allow the deposition of a layer of top coat on the surface of a block copolymer, which avoids the appearance of the aforementioned dewetting and inter-diffusion phenomena and which has, in addition, a neutral surface energy vis-à-vis blocks of the underlying block copolymer, so that the nano-domains of the block copolymer can be oriented perpendicular to the interfaces, at the assembly temperature of said block copolymer. It also aims to allow the deposition of such a layer of top coat with a solvent which is orthogonal to the underlying block copolymer, that is to say, not likely to attack, solvate even partially or dissolve this -latest.

[Brief description of the invention

For this purpose, the subject of the invention is a method for manufacturing a planar polymeric stack, which consists in depositing on a substrate (10) a first layer (20) of (co) non-crosslinked polymer and then a second layer (30) of (co-) polymer, at least one of the (co-) polymer layers being initially in a liquid or viscous state, said method being characterized in that at the time of deposition of the top layer on the first layer, the upper layer is in the form of a pre-polymer composition, comprising one or more monomer (s) and / or dimer (s) and / or oligomer (s) and / or polymer (s) in solution, and in that an additional step consists in subjecting said upper layer to a stimulus, chosen from a plasma, an ion bombardment, an electrochemical process, a chemical species, a luminous radiation, capable of provoking a crosslinking reaction of the molecular chains within said pre-polymer layer and making it possible to obtain a so-called cross-linked top coat layer.

Thus, the top coat layer crosslinks quickly to form a rigid network, so that it does not have the time or the physical possibility to dewake. The top layer thus crosslinked makes it possible to solve several different technical problems described above. In the first place, this crosslinking makes it possible to eliminate the dewetting inherent in the top-coat layer, since the molecular motions of the top coat layer are very limited once it is fully crosslinked. In the second place, this crosslinking of the upper layer also makes it possible to eliminate the typical so-called liquid-liquid dewetting possibilities of the system, the top-coat layer being able to be considered as a solid, possibly deformable, and no longer as a fluid viscous after crosslinking and once the system is brought to a temperature of use, higher than the glass transition temperature of the underlying polymer layer. Thirdly, the crosslinked top coat layer also stabilizes the underlying polymeric layer so that it does not dewater its substrate. Another remarkable and significant point is that the step of the chemical synthesis of the material of the top coat layer is facilitated because it makes it possible to overcome the problems related to the need to synthesize a material of high molecular mass, thus offering a better control over the final architecture of the material (composition, mass, etc.) as well as considerably less stringent synthesis operating conditions (allowable impurity level, solvent, etc.) than in the case of materials of significant molecular weight . Finally, the use of small molecular weights for the top layer makes it possible to widen the range of possible orthogonal solvents for this material. It is well known that polymers of small masses are easier to solubilize than polymers of the same chemical composition having large masses.

According to other optional features of the method:

the stimulus applied to initiate the crosslinking reaction is an electrochemical process applied via an electron beam;

the stimulus for causing the crosslinking reaction within the pre-polymer layer is light radiation in ultraviolet to infra-red wavelength ranges of between 10 nm and 1500 nm, and preferably between 100 nm and 500 nm;

the step of photo-crosslinking the pre-polymer composition layer is carried out at a power dose of less than or equal to 200 mJ / cm ² , preferably less than or equal to 100 mJ / cm ² and more preferably, less than or equal to 50 mJ / cm ² ; the crosslinking reaction is propagated within the upper layer, carrying the stack at a temperature below 150 ° C. and preferably below 110 ° C., for a period of less than 5 minutes, and preferably less than 2 minutes ;

the pre-polymer composition is a composition formulated in a solvent, or used without a solvent, and which comprises at least: a monomeric, dimeric, oligomeric or polymeric chemical entity, or any mixture of these different entities, of a chemical nature in any or the same part, and each comprising at least one chemical function capable of ensuring the crosslinking reaction under the effect of a stimulus; and one or more chemical entities capable of initiating the crosslinking reaction under the effect of the stimulus, such as a radical generator, an acid and / or a base;

at least one of the chemical entities of the pre-polymer composition has at least one fluorine and / or silicon and / or germanium atom, and / or an aliphatic carbon chain of at least two carbon atoms in its chemical formula ;

said pre-polymer composition further comprises in its formulation: a chemical entity chosen from an antioxidant, a base or a weak acid, capable of trapping said chemical entity capable of initiating the crosslinking reaction, and / or one or a plurality of additives for improving wetting and / or adhesion, and / or uniformity of the top layer of top coat deposited on the underlying layer, and / or one or more additives for absorbing one or more ranges of different wavelengths of light radiation, or to modify the electrical conductivity properties of the prepolymer;

the pre-polymer composition comprises a crosslinking photoinitiator and is crosslinked by radical polymerization;

when the polymerization is radical, the monomer (s) and / or dimer (s) and / or oligomer (s) and / or polymer (s) constitutive (s) of the pre-polymer layer, are chosen from the non-exhaustive list of derivatives of acrylates or di- or tri-acrylates or multi-acrylates, methacrylate, or multi-methacrylates, or polyglycidyl or vinyl, fluoroacrylates or fluoromethacrylates, vinyl fluorides or fluorostyrene, acrylate or methacrylate hydroxyalkyl alkyl, acrylate or methacrylate, alkylsilyl acrylate or methacrylate, unsaturated esters / acids such as fumaric or maleic acids, vinyl carbamates and carbonates, allyl ethers, and thiol-ene systems;

when the polymerization is radical, the photoinitiator is chosen from acetophenone, benzophenone, peroxide, phosphine, xanthone, hydroxycetone or diazonaphthoquinone derivatives, thioxanthones, α-aminoketones, benzil benzoin; the prepolymer composition comprises an initiator and is crosslinked by cationic polymerization;

when the polymerization is cationic, the monomer (s) and / or dimer (s) and / or oligomer (s) and / or polymer (s) constitutive (s) of the pre-polymer layer, are derivatives having epoxy / oxirane type chemical functions, or vinyl ethers, cyclic ethers, thiirane, trioxane, vinyl, lactones, lactams, carbonates, thiocarbonates, maleic anhydride;

when the polymerization is cationic, the initiator is a photo-generated acid from a salt chosen from among onium salts, such as the iodonium, sulphonium, pyrridinium, alkoxypyrridinium and phosphonium salts; , oxonium, or diazonium;

the photo-generated acid may optionally be coupled to a photo-sensitizing compound chosen from acetophenone, benzophenone, peroxide, phosphine, xanthone, hydroxy-ketone or diazonaphthoquinone derivatives, thioxanthones, α- aminoketones, benzil, benzoin, as said sensitizer photo absorbs at the desired wavelength;

the pre-polymer composition comprises an initiator and is crosslinked by anionic polymerization reaction;

when the polymerization is anionic, the monomer (s) and / or dimer (s) and / or oligomer (s) and / or polymer (s) constitutive (s) of the pre-polymer layer, are derivatives alkyl cyanoacrylates, epoxides / oxiranes, acrylates, or derivatives of isocyanates or polyisocynanates;

when the polymerization is anionic, the initiator is a photo-generated base from derivatives chosen from carbamates, acyloximes, ammonium salts, sulphonamides, formamides, amineimides, α-aminoketones, amidines ;

the first polymer layer is in a solid state when the stack is brought to a temperature below its glass transition temperature or in a liquid-viscous state when the stack is raised to a temperature above its glass transition temperature or at its highest glass transition temperature;

the first polymer layer is a block copolymer capable of nanoconstructing at an assembly temperature, prior to the step of depositing the first layer of block copolymer, the process comprises a step of neutralizing the surface; of the underlying substrate and, subsequent to the step of crosslinking the top layer to form a crosslinked top coat layer, the method comprises a step of nano-structuring the block copolymer constituting the first layer by submitting the stack obtained at an assembly temperature, said an assembly temperature being less than a temperature at which the top coat material behaves like a viscoelastic fluid, said temperature being higher than the glass transition temperature of said topcoat material and preferably, said assembly temperature being lower than the glass transition temperature of the top coat layer in its crosslinked form;

the prior step of neutralizing the surface of the underlying substrate consists in pre-drawing patterns on the surface of the substrate, said patterns being pre-drawn by a step or a sequence of lithography steps of any kind prior to deposition step of the first layer of block copolymer, said units being intended to guide the organization of said block copolymer by a technique called chemistry-epitaxy or graphoepitaxy, or a combination of these two techniques, to obtain a neutralized or pseudo-neutralized surface;

the block copolymer comprises silicon in one of its blocks;

the first layer of block copolymer is deposited on a thickness at least equal to 1.5 times the minimum thickness of the block copolymer;

the solvent of the pre-polymer layer is chosen from solvents or solvent mixtures whose Hansen solubility parameters are such that d _r > 10 MPa ^1/2 and / or 5 _h ³ 10 MPa ^1/2 and with 5 _d <25 MPa ^1/2 ;

the solvent of the pre-polymer layer is chosen from alcohols such as methanol, ethanol, isopropanol, 1-methoxy-2-propanol and ethyl lactate; diols such as ethylene glycol or propylene glycol; or from dimethylsulfoxide (DMSO), dimethylformamide, dimethylacetamide, acetonitrile, gammabutyrolactone, water or a mixture thereof;

the composition of the pre-polymer layer comprises a multi-component mixture of monomers and / or dimers and / or oligomers and / or polymers each carrying crosslinking functions, as well as different monomer units whose surface energies vary from one monomeric pattern to another;

the composition of the pre-polymer layer further comprises plasticizers and / or wetting agents, added as additives;

the composition of the pre-polymer layer further comprises rigid comonomers chosen from derivatives comprising either one or more aromatic ring (s) in their structure, or mono or multicyclic aliphatic structures, and having a chemical function (s) adapted to the targeted crosslinking reaction; and more particularly norbornene derivatives, isobornyl acrylate or methacrylate, styrenic, anthracene derivatives, acrylate or adamantyl methacrylate. The invention further relates to a method for manufacturing a nano lithography mask by directed assembly of block copolymers, said method comprising the steps in accordance with the method which has just been described above and being characterized in that after the nanostructuring step of the constituent block copolymer of the first layer, an additional step is to remove the top coat layer to leave a nanostructured block copolymer film of minimum thickness, and then at least one of the blocks of said block copolymer, oriented perpendicular to the interfaces, is removed in order to form a porous film capable of serving as a nano-lithography mask.

According to other optional features of this method:

when the block copolymer is deposited over a thickness greater than the minimum thickness, an excess thickness of said block copolymer is removed simultaneously or successively with the removal of the top coat layer, in order to leave a nano-structured block copolymer film; minimum thickness, then at least one block of said block copolymer, oriented perpendicular to the interfaces, is removed to form a porous film capable of serving as a nano-lithography mask;

the top coat layer and / or the excess thickness of the block copolymer and / or the block copolymer block (s) is / are removed by dry etching;

the etching steps of the top coat layer and / or the excess thickness of the block copolymer and of one or more blocks of the block copolymer are successively carried out in the same etching frame, by plasma etching;

at the time of the step of crosslinking the top coat layer, the stack is subjected to a light radiation and / or an electron beam located on certain areas of the top coat layer, in order to create top cured zones; coat having a neutral affinity for the underlying block copolymer and uncrosslinked areas having a non-neutral affinity for the underlying block copolymer;

after the photo-localized cross-linking of the top coat layer, the stack is rinsed with the solvent that has allowed the deposition of the pre-polymer layer to remove the non-irradiated areas;

another prepolymer material, which is non-neutral with respect to the underlying block copolymer, is deposited in the zones previously non-irradiated and without a top coat layer, and then said non-neutral pre-polymer material is exposed a stimulus to cross-link it to predefined places;

at the time of the step of annealing the stack at the assembly temperature of the block copolymer, nano-domains perpendicular to the interfaces are formed in zones situated opposite the zones of the crosslinked neutral topcoat layer, and nano-domains parallel to the interfaces in areas of the block copolymer located opposite the zones devoid of neutral crosslinked top coat layer.

The invention finally relates to a polymeric stack deposited on a substrate and comprising at least two layers of (co) polymer stacked one on the other, characterized in that the top layer, called top coat, deposited on the first (co) polymer layer is obtained by in situ crosslinking according to the method described above, said stack being intended to be used in applications chosen from aerospace or aerospace or automotive surface protection or automobile or wind, paint, ink, membrane manufacturing, microelectronic, optoelectronic or micro-fluidic components.

More particularly, this stack is intended for applications in the field of nano-lithography by self-assembly directed, the first layer (co) polymer is a block copolymer and the surfaces of the layer on which the copolymer to The blocks are deposited and the top coat layer preferably has a neutral surface energy with respect to the blocks of the block copolymer.

Other features and advantages of the invention will become apparent on reading the description given by way of illustrative and nonlimiting example, with reference to the appended figures which represent:

FIGS. 1A to 1C, already described, diagrams seen in section of different stacks of polymers and their evolution over time,

FIG. 2, already described, a diagram seen in section of a stack of polymers according to the invention, not undergoing any phenomenon of dewetting or inter-diffusion,

FIG. 3, a diagram seen in section of a stack according to the invention dedicated to an application by directed self-assembly nano-lithography (DSA) for the production of a nano-lithography mask,

FIG. 4, a diagram seen in section of another stack according to the invention dedicated to a directed self-assembly nano-lithography application (DSA), for the creation of different patterns in a substrate,

FIG. 5, the evolution of the residual thickness of an electron beam-crosslinked PGFH copolymer as a function of the dose of electron applied,

FIG. 6 shows the evolution of the residual thickness of a crosslinked PGFH copolymer by exposure to a luminous radiation at 172 nm, as a function of the dose of exposure to said radiation and according to whether the film has been annealed. post-exposure (PEB) or not, FIG. 7, the evolution of the residual thickness of a copolymer of crosslinked PGFH by exposure to a light radiation at 365 nm, as a function of the dose of exposure to said radiation,

FIG. 8, images obtained by scanning electron microscopy of different reference samples, the top coat layer of which is not cross-linked, and of a sample prepared according to the invention with a cross-linked top coat layer, demonstrating the impact of the crosslinking of the top coat layer on the different possible moorings,

FIG. 9, the evolution of the residual thickness of a previously crosslinked PGFH copolymer, when subjected to a plasma, as a function of plasma times,

FIG. 10, an image obtained by scanning electron microscopy of a sample of a No. 1 block copolymer, whose self-organization is perpendicular to the substrate and whose period is of the order of 18 nm, for different stimuli of exposure,

1 a, respectively under the letter a) an image taken by optical microscopy and under the letter b) an image taken by scanning electron microscopy of a sample having patterns drawn by exposing the film of top coat to a beam electron

12, respectively under the letter a) an image taken by optical microscopy and under the letter b) an image taken by scanning electron microscopy of a sample having patterns drawn by exposure of the top coat film to light radiation at 365nm,

FIG. 13, the images obtained by scanning electron microscopy of a sample whose top coat layer has exposed areas and areas not exposed to an electron beam,

FIG. 14, the images obtained by scanning electron microscopy of a sample whose top coat layer has exposed areas and areas not exposed to 365 nm radiation,

FIG. 15, an image of the assembly of a lamellar block copolymer (PCO) No. 2, seen in section through a FIB-STEM preparation, after crosslinking of the top coat layer,

FIG. 16 is an image of a stack of different block copolymer and top coat films, seen in section through a FIB-STEM preparation.

By "polymers" is meant either a copolymer (of statistical type, gradient, alternating blocks), or a homopolymer.

The term "monomer" as used refers to a molecule that can undergo polymerization.

The term "polymerization" as used refers to the process of converting a monomer or a mixture of monomers into a predefined architectural polymer (block, gradient, statistic ..).

By "copolymer" is meant a polymer comprising several different monomeric units.

The term "random copolymer" is understood to mean a copolymer in which the distribution of the monomer units along the chain follows a statistical law, for example of the Bernoullien type (Markov zero order) or the Markovian type of the first or second order. When the repeat units are randomly distributed along the chain, the polymers were formed by a Bernouilli process and are called random copolymers. The term random copolymer is often used, even when the statistical process that prevailed during the synthesis of the copolymer is not known.

The term "gradient copolymer" is understood to mean a copolymer in which the distribution of the monomer units varies progressively along the chains.

The term "alternating copolymer", a copolymer comprising at least two monomer entities which are distributed alternately along the chains.

The term "block copolymer" is understood to mean a polymer comprising one or more uninterrupted sequences of each of the different polymeric species, the polymer blocks being chemically different from one another or from one another and being linked together. by a chemical bond (covalent, ionic, hydrogen bonding, or coordination). These polymer blocks are still referred to as polymer blocks. These blocks have a phase segregation parameter (Flory-Huggins interaction parameter) such that, if the degree of polymerization of each block is greater than a critical value, they are not miscible with each other and separate into nanoparticles. areas.

The term "miscibility" above refers to the ability of two or more compounds to mix completely to form a homogeneous or "pseudo homogeneous" phase, that is to say without crystalline symmetry or substantially crystalline apparent at short or long distance. The miscibility of a mixture can be determined when the sum of the glass transition temperatures (Tg) of the mixture is less than the sum of the Tg of the compounds taken alone. In the description, we speak as well of "self-assembly" as "self organization" or "nano-structuring" to describe the well-known phenomenon of phase separation of block copolymers, a assembly temperature also called annealing temperature.

The minimum thickness "e" of a block copolymer is understood to mean the thickness of a block copolymer film serving as a nanolithography mask, below which it is no longer possible to transfer the patterns. of the block copolymer film in the underlying substrate with a satisfactory final form factor. In general, for high C phase segregation parameter block copolymers, this minimum thickness "e" is at least equal to half the period U of the block copolymer.

The term "porous film" refers to a block copolymer film in which one or more nano-domains have been removed, leaving holes whose shapes correspond to the shapes of the nano-domains having been removed and which may be spherical, cylindrical. , lamellar or helical.

The term "neutral" or "pseudo-neutral" surface means a surface which, as a whole, does not have a preferential affinity with one of the blocks of a block copolymer. It thus allows a fair or "pseudo-equitable" distribution of blocks of the block copolymer on the surface.

The neutralization of the surface of a substrate makes it possible to obtain such a "neutral" or "pseudo-neutral" surface.

The surface energy (denoted yx) of a given material "x" is defined as being the excess energy at the surface of the material compared to that of the material which is set in mass. When the material is in liquid form, its surface energy is equivalent to its surface tension.

When speaking of the surface energies or more precisely the interfacial tensions of a material and a block of a given block copolymer, these are compared at a given temperature, and more particularly at a given temperature. allowing the self-organization of the block copolymer.

The term "lower interface" of a (co) polymer, the interface in contact with an underlying layer or substrate on which said (co) polymer is deposited. It will be noted that throughout the remainder of the description, when the polymer in question is a block copolymer to be nanostructured, intended to serve as a nanolithography mask, this lower interface is neutralized by a conventional technique, that is to say that is, it does not exhibit, as a whole, preferential affinity with one of the blocks of the block copolymer.

The term "upper interface" or "upper surface" of a (co) polymer, the interface in contact with an upper layer, called top coat and noted TC, applied to the (co) polymer surface. It will be noted that throughout the remainder of the description, when the polymer in question is a block copolymer to be nanostructured, intended to serve as a nanolithography mask, the top layer of top coat TC, just like the underlying layer preferably does not exhibit any preferential affinity with one of the blocks of the block copolymer so that the nano-domains of the block copolymer can orient perpendicularly to the interfaces at the time of assembly annealing.

The term "solvent orthogonal to a (co) polymer", a solvent not likely to attack or dissolve said (co) polymer.

The term "liquid polymer" or "viscous polymer", a polymer having, at a temperature above the glass transition temperature, due to its rubbery state, increased deformation capacity due to the possibility given to its molecular chains to move freely. The hydrodynamic phenomena at the origin of the dewetting appear as long as the material is not in a solid state, that is to say, indeformable because of the negligible mobility of its molecular chains.

In the context of this invention, we consider any polymeric stack system, that is to say a system comprising at least two layers of (co-) polymers stacked one on the other. This stack may be deposited on a solid substrate of any kind (oxide, metal, semiconductor, polymer, etc.) depending on the applications for which it is intended. The different interfaces of such a system may have a "liquid / solid" or "liquid / liquid" configuration. Thus, an upper (co) polymer layer having a liquid or viscous state is deposited on an underlying (co) polymer layer which may be in a solid or liquid or viscous state, depending on the intended applications. More particularly, the underlying (co) polymer layer may be solid or liquid or viscous depending on the working temperature, with respect to its glass transition temperature Tg, during the process of controlling the flatness of the stack according to the invention.

Figure 2 illustrates such a polymeric stack. This stack is for example deposited on a substrate 10 and comprises for example two polymer layers 20 and 30 stacked one on the other. Depending on the intended applications, the first layer 20 may be without a solid or liquid / viscous state at the time of deposition of the second top layer 30, so-called top coat TC. More particularly, the first layer 20 is in a solid state when the stack is brought to a temperature below its glass transition temperature or in a liquid-viscous state when the stack is raised to a temperature above its transition temperature. glass. The top coat layer TC is applied to the surface of the underlying layer by a conventional deposition technique, for example by spin coating or "spin coating", and is in a liquid / viscous state. The term "flatness of a polymeric stack" within the meaning of the invention is intended for all interfaces of the stack. The method according to the invention makes it possible to control the flatness of the interface between the substrate 10 and the first layer 20, and / or the flatness of the interface between the first layer 20 and the top coat layer 30, and or the flatness of the interface between the top coat layer 30 and the air.

To avoid the appearance of a dewetting phenomenon of the top coat layer TC just after its deposition on the underlying layer 20, and to avoid a phenomenon of inter-diffusion at the interface especially in the case of a liquid / liquid configuration of the interface, corresponding to the case shown in FIG. 1C, the invention advantageously consists in depositing the upper layer 30 in the form of a pre-polymer composition, denoted pre-TC, comprising one or more monomer (s) and / or a dimer (s) and / or an oligomer (s) and / or a polymer (s) in solution. For the sake of simplification, these compounds are also referred to as "molecules" or "entities" in the remainder of the description. Through the application of a stimulus, a crosslinking reaction is set up in situ within the pre-deposited TC pre-polymer layer and generates the creation of a high molecular weight TC polymer by intermediate of the crosslinking reaction of the polymeric chains constituting the deposited prepolymer layer. During this reaction, the initial size of the chains increases as the reaction propagates in the layer, thus severely limiting the solubilization of the crosslinked topcoat layer TC in the underlying polymeric layer when the latter is in a liquid or viscous state, and further delaying the occurrence of a dewetting phenomenon.

Preferably, the pre-polymer composition is formulated in a solvent orthogonal to the first polymer layer 20 already present on the substrate, and comprises at least:

a monomeric, dimeric, oligomeric or polymeric chemical entity, or any combination of these different entities, of a chemical nature in whole or in part identical, and each comprising at least one chemical function capable of ensuring the propagation of the crosslinking reaction under effect of a stimulus; and

one or more chemical entities capable of initiating the crosslinking reaction under the effect of the stimulus, such as a radical generator, an acid and / or a base.

The pre-polymer composition may, in an alternative embodiment, be used without a solvent.

Preferably, in the context of the invention, at least one of the chemical entities of the pre-polymer composition has at least one fluorine and / or silicon and / or germanium atom, and / or a chain aliphatic carbon of at least two carbon atoms in its chemical formula. Such entities make it possible to improve the solubility of the prepolymer composition in a solvent orthogonal to the underlying polymer layer and / or effectively modulate the surface energy of the top coat layer TC if required, especially for DSA applications, and / or to facilitate the wetting the pre-polymer composition on the underlying (co) polymer layer, and / or reinforcing the resistance of the topcoat layer TC to a subsequent plasma etching step.

Optionally, this pre-polymer composition may further comprise in its formulation:

a chemical entity chosen from an antioxidant, a base or a weak acid capable of trapping said chemical entity capable of initiating the crosslinking reaction, and / or

one or more additives making it possible to improve the wetting and / or adhesion, and / or the uniformity of the top layer of top coat, and / or

one or more additives making it possible to absorb one or more ranges of light radiation of different wavelength, or to modify the electrical conductivity properties of the pre-polymer.

The crosslinking may be carried out by any known means such as chemical crosslinking / polymerization, by means of a nucleophilic or electrophilic chemical species or the like, by an electrochemical process (oxidation-reduction or by cleavage of monomers via a beam of electrons), by plasma, by ion bombardment or by exposure to light radiation. Preferably, the stimulus is of electrochemical nature and applied via an electron beam or a light radiation, and even more preferably, it is a light radiation.

In a particularly advantageous embodiment, the crosslinking reaction of the components of the pre-polymer pre-TC layer is activated by the exposure of the layer to light radiation, such as radiation in ranges of wavelength from ultraviolet to infrared. Preferably, the illumination wavelength is between 10 and 1500 nm and more preferably it is between 100 nm and 500 nm. In a particular embodiment, the light source for exposing the layer to the light radiation may be a laser device. In such a case, the wavelength of the laser will preferably be centered on one of the wavelengths 436nm, 405nm, 365nm, 248nm, 193nm, 172nm, 157nm or 126nm. Such a crosslinking reaction has the advantage of being carried out at ambient or moderate temperature, preferably less than or equal to 150 ° C. and more preferably less than or equal to 110 ° C. It is also very fast, of the order of a few seconds to a few minutes, preferably less than 2 minutes. Preferably, the constituent compounds of the pre-polymer layer, before crosslinking, are stable in solution as long as they are protected from exposure to the light source. They are stored in containers opaque. When such a pre-polymer layer is deposited on the underlying polymer layer, the components, stable in solution, are subjected to light radiation allowing the layer to be crosslinked in a very fast time (typically less than 2 minutes). . Thus, the layer of top coat does not have time to dewake. In addition, as the reaction propagates, the size of the chains increases which limits the problems of solubilization and inter-diffusion at the interface when the latter is in a "liquid / liquid" configuration.

As regards this photoinduced crosslinking, two large classes of compounds are distinguished for the composition of the pre-polymer pre-TC layer.

A first class concerns compounds that react via a species of radical type. It is therefore a free radical photopolymerization, of which a possible reaction mechanism is illustrated by the reaction (I) below.

In this reaction example, the photoinitiator, denoted PI, is a photo-cleavable aromatic ketone and the telechelic / di-functional oligomer is a diacrylate with R which can be chosen from polyesters, polyethers, polyurethanes or polysiloxanes. for example.

More generally, the monomer (s) and / or dimer (s) and / or oligomer (s) and / or polymer (s) constitutive (s) of the pre-polymer composition is ( are) selected from derivatives of acrylates or di- or tri-acrylates or multi-acrylates, methacrylate, or multi-methacrylates, or polyglycidyl or vinyl, fluoroacrylates or fluoromethacrylates, vinyl fluorides or fluorostyrene, alkyl acrylate or methacrylate, hydroxyalkyl acrylate or methacrylate, alkylsilyl acrylate or methacrylate, unsaturated esters / acids such as fumaric or maleic acids, vinyl carbamates and carbonates, allylic ethers, and thiol-ene systems . Preferably, but in a non-limiting manner for the invention, the constituents of the pre-polymer layer are multifunctional and have at least two chemical functions on the same molecule capable of providing the polymerization reaction.

The composition further comprises a carefully chosen photoinitiator according to the selected illumination wavelength. There are on the market very many radical photoinitiators with various chemistries such as acetophenone derivatives, benzophenone, peroxide, phosphines, xanthones, hydroxyketone or diazonaphthoquinone, thioxanthones, aminoketones, benzine, benzoin for example.

A second class of compounds that can enter the composition of the pre-polymer layer relates to the compounds that react by cationic polymerization. This is for example the case of derivatives comprising epoxy / oxirane type chemical functions, or vinyl ethers, cyclic ethers, thiirane, trioxane, vinyl, lactones, lactams, carbonates, thiocarbonates, maleic anhydride which crosslink / polymerize then through a photo-generated acid, noted PAG. A mechanism of such a cationic photo-polymerization reaction of an epoxy is illustrated by the reaction

Here again, many PAG photo-generated acid precursor structures are available on the market, thus giving access to a wide choice of possible light wavelengths for generating the acid, HMtX _n , a catalyst of the invention. crosslinking reaction. Such a precursor may for example be selected from onium salts, such as iodonium, sulfonium, pyrridinium, alkoxypyrridinium, phosphonium, oxonium or diazonium salts. The onium salts form strong acids, HMtX _n , under irradiation. The acid thus formed then gives a proton to the polymerizable (s) / crosslinkable (s) chemical function (s) of the monomer. If the monomer is poorly basic / reactive, the acid should be strong enough to shift the equilibrium significantly towards propagation of the crosslinking reaction and chain growth, as shown in reaction (II) above. In a variant, it is also possible to couple the photo-generated acid PAG to a photosensitizer if the wavelength of illumination chosen does not quite correspond to a correct absorbance of the acid. PAG. Such a photosensitizer may for example be selected from acetophenone derivatives, benzophenone, peroxide, phosphines, xanthones, hydroxycetone or diazonaphthoquinone, thioxanthones, aminoketones, benzil, benzoin, both said photosensitizer absorbs at the desired wavelength.

Other ionic polymerizations with other types of derivatives are also possible. Thus, reactions for example by polymerization / anionic crosslinking can also be envisaged. In this reaction class, the reactive species is a photo-generated organic base (denoted PBG), which reacts on a polymerizable (s) / crosslinkable (s) function (s) carried by the (s) ) monomer (s) of the composition of the pre-polymer layer.

In this case, the photo-generated organic base PBG can be chosen from compounds such as carbamates, acyloximes, ammonium salts, sulphonamides, formamides, amineimides, α-aminoketones, amidines. .

The monomers, dimers, oligomers and / or polymers of the composition may in turn be selected from derivatives such as alkyl cyanoacrylates, epoxides / oxiranes, acrylates, or derivatives of isocyanates or polyisocynanates. In this case, the photo-generated organic base PBG can be inserted within the molecular structure of the chains constituting the polymer during the polymerization / crosslinking reaction.

The solvent of the pre-polymer layer is chosen so as to be entirely "orthogonal" to the polymeric system of the underlying layer in order to avoid a possible re-dissolution of this polymer in the solvent of the pre-layer. -polymer during the deposition step (by spin-coating for example). The solvents of each respective layer will therefore be very dependent on the chemical nature of the polymer material already deposited on the substrate. Thus, if the polymer already deposited is slightly polar / protic, its solvent being selected from the low polar and / or impractical solvents, the pre-polymer layer can be solubilized and deposited on the first polymer layer from rather polar solvents and / or practices. Conversely, if the already deposited polymer is rather polar / protic, the solvents of the pre-polymer layer may be chosen from low polar and / or impractical solvents. According to a preferred embodiment of the invention, but without being restrictive in view of what has been explained above, the pre-polymer layer is deposited from polar solvents / solvent mixtures / and / or practical. More precisely, the polarity / proticity properties of the various solvents are described according to the nomenclature of the solubility parameters of Hansen (Hansen, Charles M. (2007) Hansen solubility parameters: a user's handbook, CRC Press, ISBN 0-8493-7248-8), where the term "5 _d" represents the dispersion forces between molecules solvent / solute, "d _r" represents the energy of the dipolar forces between molecules, and "5 _h" represents the energy of the possible hydrogen bonding forces between molecules, the values of which are tabulated at 25 ° C. In the context of the invention, "polar and / or protic" is defined as a solvent / molecule or mixture of solvents having a polarity parameter such that d _r > 10 MPa ^1/2 and / or a hydrogen bond parameter such as that ô _h ³10 MPa ^1/2 . Similarly, a solvent / molecule or mixture of solvents is defined as "little polar and / or protic" when the solubility parameters of Hansen are such that d _r <10 MPa ^1/2 and / or 6 _h <10 MPa ^1/2 , and preferably d _r <8 MPa ^1/2 and / or a hydrogen bonding parameter such that o _h 9 MPa ^1/2 .

According to a preferred but not restrictive embodiment of the invention, the solvent of the pre-polymer layer is chosen from compounds having a hydroxyl function such as, for example, alcohols, such as methanol, ethanol and isopropanol. 1-methoxy-2-propanol, ethyl lactate; or diols such as ethylene glycol or propylene glycol; or else from dimethylsulfoxide (DMSO), dimethylformamide, dimethylacetamide, acetonitrile, gammabutyrolactone, water or a mixture thereof.

In a more general manner, in the context of one of the preferred but non-exhaustive embodiments of the invention, the various constituents of the pre-polymer layer are soluble and stable in solvents whose solubility parameters are as follows: Hansen are such that d _r > 10 MPa ^1/2 and / or δ _h ³ 10 MPa ^1/2 as defined above, and with the dispersion parameter δ _d <25 MPa ^1/2 .

The crosslinking reaction, by irradiation of the pre-polymer layer, can be carried out at a moderate temperature, well below the glass transition temperature of the underlying polymer layer, in order to promote the diffusion of the reactive species. and thus increase the rigidity of the crosslinked network. Typically, the activation of the photoinitiator or of the photo-generated acid PAG or of the photo-generated base can be initiated at a temperature below 50.degree. C. and preferably below 30.degree. typically less than 5 minutes and preferably less than 1 minute. Then, in a second step, the crosslinking reaction can be propagated by bringing the stack to a temperature preferably of less than 150 ° C., and more preferably of less than 110 ° C., so as to promote the diffusion of the species. reactive (protons, radicals) within the pre-polymer layer, for a period of less than 5 minutes, and preferably less than 2 minutes. According to a variant of the invention, the light irradiation of the pre-polymer layer is carried out directly on a stack brought to the desired temperature, preferably below 1 10 ° C, to optimize the total reaction time.

Before the crosslinking reaction, the top coat layer TC may be in the form of a block copolymer or statistic, random, gradient or alternating, which may have a linear or star structure when one comonomers is multifunctional for example.

The invention as described above applies to any type of polymeric stack. Among the various and varied applications of such stacks, the Applicant has also been interested in directed self-assembly nano-lithography, or DSA. However, the invention is not limited to this example which is given for illustrative and not limiting. Indeed, in the context of such an application, the upper topcoat TC must also meet other additional requirements, in particular to allow the nano-domains of the underlying block copolymer to be oriented perpendicular to the interfaces.

FIG. 3 illustrates such a polymeric stack dedicated to an application in the field of organic electronics. This stack is deposited on the surface of a substrate 10. The surface of the substrate is previously neutralized, or pseudo-neutralized, by a conventional technique. For this, the substrate 10 comprises or not patterns, said patterns being pre-drawn by a step or a sequence of lithography steps of any kind prior to the step of depositing the first layer (20) of block copolymer (BCP), said patterns being intended to guide the organization of said block copolymer (BCP) by a technique called chemistry-epitaxy or graphoépitaxie, or a combination of these two techniques, to obtain a neutralized surface. A particular example consists of grafting a layer 1 1 of a random copolymer having a ratio judiciously chosen from the same monomers as those of the BCP block copolymer deposited above. The layer 1 1 of the random copolymer makes it possible to balance the initial affinity of the substrate for the BCP block copolymer 20. The grafting reaction can be obtained by any thermal, photochemical or oxidation-reduction means, for example. Then, a top coat layer TC 30 is deposited on the layer of BCP block copolymer 20. This layer TC 30 must have no preferential affinity with respect to the blocks of the block copolymer 20 so that the nano-domains 21, 22 which are created at the time of annealing at the assembly temperature Tass, are oriented perpendicular to the interfaces, as shown in FIG. 3. The block copolymer is necessarily liquid / viscous at the assembly temperature, in order to to be able to nano-structure. The top coat layer TC is deposited on the block copolymer in a liquid / viscous state. The interface between two polymer layers is therefore in a liquid / liquid configuration conducive to inter-diffusion and dewetting phenomena.

Preferably, the assembly temperature Tass of the block copolymer 20 is lower than the glass transition temperature Tg of the top coat layer TC in its crosslinked form or at least less than a temperature at which the material TC top coat behaves like a viscoelastic fluid. This temperature is then in a temperature zone, corresponding to this viscoelastic behavior, located above the glass transition temperature Tg of the top coat material TC.

As regards the nano-structured copolymer block copolymer layer 20, again denoted BCP, it comprises "n" blocks, n being any integer greater than or equal to 2. The BCP block copolymer is more particularly defined by the following general formula:

AbBbCbDb -....- bZ where A, B, C, D, ..., Z, are all blocks "i" ... "j" representing either pure chemical entities, that is to say each block is a set of monomers of identical chemical natures, polymerized together, that is to say a set of co-monomers copolymerized together, in form, in whole or in part, of random or random or gradient or alternating block copolymer.

Each of the blocks "i" ... "j" of the BCP block copolymer to be nano-structured can therefore potentially be written in the form: i = ai-co-bi-co-...- co- Zi, with i¹ ... ¹j, in whole or in part.

The volume fraction of each entity a... Z 1 can range from 1 to 99%, in monomer units, in each of the blocks of the BCP block copolymer.

The volume fraction of each of the blocks can range from 5 to 95% of the BCP block copolymer.

The volume fraction is defined as the volume of an entity relative to that of a block, or the volume of a block relative to that of the block copolymer.

The volume fraction of each entity of a block of a copolymer, or of each block of a block copolymer, is measured in the manner described hereinafter. In a copolymer in which at least one of the entities, or one of the blocks in the case of a block copolymer, comprises several comonomers, it is possible to measure, by means of proton, the mole fraction of each monomer throughout the copolymer, and then back to the mass fraction using the molar mass of each monomer unit. To obtain the mass fractions of each entity of a block, or each block of a copolymer, it is then sufficient to add the mass fractions of the comonomers constituting the entity or the block. The volume fraction of each entity or block can then be determined from the fraction mass of each entity or block and the density of the polymer forming the entity or the block. However, it is not always possible to obtain the density of polymers whose monomers are co-polymerized. In this case, the volume fraction of an entity or a block is determined from its mass fraction and the density of the bulk majority of the entity or block.

The molecular weight of the BCP block copolymer may range from 1000 to 500000 g. mol ^-1 .

The BCP block copolymer may have any type of architecture: linear, star (tri- or multi-arm), grafted, dendritic, comb.

Each of the blocks i, ... j of a block copolymer, has a surface energy denoted Yi ... y _j , which is its own and which is a function of its chemical constituents, that is to say -describe the chemical nature of the monomers or comonomers that compose it. Similarly, each of the materials constituting a substrate have their own surface energy value.

Each block i, ... j of the block copolymer furthermore has a Flory-Huggins type interaction parameter, denoted by: c, _c , when it interacts with a given "x" material, which can be a gas, a liquid, a solid surface, or another phase polymer for example, and an interfacial energy denoted "g, _{c ',} with g _c = y _i - (Y _X COS Q, _c), Where Q, _C is the contact angle between materials i and x. The interaction parameter between two blocks i and j of the block copolymer is therefore denoted x, _j .

[0103] There is a binding relation g, and the solubility parameter of Hildebrand d, of a given material i, as described in the document Jia et al., Journal of Macromolecular Science, B, 2011, 50, 1042. In fact, the interaction parameter of Flory Huggins between two given materials i and x is indirectly related to the surface energies Y, and g _c specific to the materials, we can therefore either speak in terms of surface energies, or in interaction parameter terms to describe the physical phenomenon appearing at the interface of the materials.

When we speak of the surface energies of a material and those of a given BCP block copolymer, it is implied that the surface energies are compared at a given temperature, and this temperature is the one (or at least part of the temperature range) allowing PCO self-organization.

In the same manner as described above for any stack of polymers, the upper layer 30, which is deposited on the layer 20 of BCP block copolymer, is in the form of a pre-polymer composition, noted pre -TC, and comprises one or more monomer (s) and / or dimer (s) and / or oligomer (s) and / or polymer (s) in solution. Through the application of a stimulus, in this case a light radiation whose wavelength goes from ultraviolet to infrared, between 10nm to 1500nm, and preferably between 100nm and 500 nm, a reaction of crosslinking or polymerization of Molecular chains constituting the pre-polymer layer is set up in situ, within the pre-deposited pre-polymer pre-polymer layer, and generates the creation of a high molecular weight TC polymer. A single polymer chain is then created that is extremely immiscible with the underlying BCP block copolymer, thus severely limiting the solubilization of the top coat layer TC in the underlying and retarding BCP block copolymer layer 20. as much as the appearance of a dewetting phenomenon. Thus, the photo-crosslinking / top coat TC layer avoids not only the inter-diffusion and dewetting problems of the top coat layer TC over the underlying BCP block copolymer, but It is also possible to stabilize the layer of block copolymer 20 so that it does not depress its substrate 10. The crosslinking / of the top coat layer TC therefore makes it possible to obtain a stack, the surface of which is perfectly flat, with substrate / block copolymer (substrate / BCP) and block copolymer / top coat (BCP / TC) interfaces are perfectly sharp.

Such a crosslinked TC topcoat layer has a surface energy, at the temperature allowing self-assembly of the underlying BCP block copolymer, between 10 and 50 mN / m, preferably between 20 and 50 mN / m, preferably between 20 and 50 mN / m. and 45 mN / m and more preferably between 25 and 40 mN / m.

However, this crosslinking reaction involves chemical species, such as carbanions, carbocations or radicals, which are more reactive than a single non-crosslinkable top coat layer. It is therefore possible in some cases that these chemical species can diffuse and possibly degrade the BCP block copolymer 20. Such diffusion is a function of the reaction propagation temperature and the nature of the chemical species involved. However, it is very limited, to a thickness of a few nanometers maximum and in all cases less than 10 nm, because of the immiscibility of the TC 30 top coat and BCP 20 block copolymer layers. such diffusion, the effective thickness of the block copolymer layer may then be reduced. To compensate for this possible diffusion, the BCP block copolymer may be deposited over a greater thickness (e + E), for example at least equal to 1.5 times the minimum thickness e of the block copolymer. In this case, after the nano-structuring and at the time of the removal of the top coat layer TC, the extra thickness E of the block copolymer is also removed to retain only the lower part, of minimum thickness e, of the block copolymer .

Anyway, if it takes place, the diffusion being limited to a thickness of a few nanometers maximum, it forms an intermediate layer comprising an intimate mixture of the constituents of the BCP block copolymer and the top layer. TC 30. This intermediate layer then has an intermediate surface energy, between that of the pure TC 30 top coat and that of the average of the surface energies of the blocks of the BCP block copolymer 20, so that it does not have any particular affinity with one of the blocks of the BCP block copolymer and thus makes it possible to orient the nano-domains of the underlying BCP block copolymer perpendicular to the interfaces.

Advantageously, the deposition of a pre-polymer layer followed by its crosslinking makes it possible to overcome the problems related to the need to synthesize a high molecular weight top coat material. It suffices to synthesize monomers, dimers, oligomers or polymers, whose molecular weights are much more reasonable, typically of the order of an order of magnitude less, thus limiting the difficulties and the operating conditions specific to the step of chemical synthesis. The crosslinking of the pre-polymer composition then makes it possible to generate in situ these high molecular masses.

The fact of depositing a pre-polymer composition, comprising monomers, dimers, oligomers or polymers of much lower molecular weight than an uncrosslinked top coat material, also makes it possible to widen the possible range of solvents. for the top coat material TC, these solvents must be orthogonal to the BCP block copolymer.

[01 1 1] Advantageously, the pre-polymer pre-TC composition may comprise monomers, dimers, oligomers or fluorinated polymers, soluble in alcoholic solvents, such as, for example, methanol, ethanol or isopropanol, 1-methoxy-2-propanol, ethyl lactate; in diols such as ethylene glycol or propylene glycol or in dimethylsulfoxide (DMSO), dimethylformamide, dimethylacetamide, acetonitrile, gammabutyrolactone, water or a mixture thereof in which the copolymers with blocks are usually not soluble.

In the same manner as described above, two broad classes of compounds are distinguished for the composition of the pre-TC pre-polymer layer. A first class concerns compounds that react via a species of radical type. This is a free radical polymerization photo. The monomer (s) and / or dimer (s) and / or oligomer (s) and / or polymer (s) constitutive (s) of the pre-polymer composition is (are) selected from among derivatives of acrylates or di- or triacrylates or multi-acrylates, methacrylate or multi-methacrylates, or vinylic, fluoroacrylates or fluoromethacrylates, vinyl fluorides or fluorostyrene, alkyl acrylate or methacrylate, hydroxyalkyl acrylate or methacrylate, alkylsilyl acrylate or methacrylate, unsaturated esters / acids such as fumaric or maleic acids, vinyl carbamates and carbonates, allyl ethers, and thiol-ene systems. The composition further comprises a carefully chosen photoinitiator, according to the selected illumination wavelength, among acetophenone, benzophenone, peroxide, phosphine, xanthone, or hydroxycetone derivatives, thioxanthones, α-aminoketones, benzil, benzoin, for example. In another embodiment, the compounds of the pre-polymer composition react by cationic polymerization and are chosen from derivatives comprising chemical functions of epoxy / oxirane type, or vinyl ethers, cyclic ethers, thiirane, trioxane, vinyl, lactones, lactams, carbonates, thiocarbonates, maleic anhydride which then crosslink through a photo-generated acid PAG. In this case, the pre-polymer composition further comprises a photo-generated acid precursor PAG, making it possible to generate the catalyst acid of the crosslinking reaction under illumination, which can be chosen from onium salts, such as salts of iodinium, of sulphonium or of pyrridinium or of alkoxypyrridinium, of phosphonium, of oxonium, of diazonium.

[01 14] In order to further limit a possible phenomenon of dewetting of the top coat layer TC 30, the rigidity (measured for example through the estimation of the Young's modulus of the top-coat TC once cross-linked) and the glass transition temperature of the top coat layer can be reinforced by the introduction into the pre-polymer pre-polymer composition of rigid co-monomers chosen from derivatives comprising either one or more aromatic rings (s) ( s) in their structure, either mono or multi-cyclic aliphatic structures, and having a chemical function (s) adapted (s) to the targeted crosslinking reaction. More particularly, these rigid comonomers are chosen from norbornene derivatives, isobornyl acrylate or methacrylate, styrenic, anthracene derivatives, acrylate or adamantyl methacrylate. The rigidity and the glass transition temperature of the top coat layer can be further increased by multiplying the possible crosslinking points of the components, with oligomeric or multifunctional monomeric chains, such as, for example, polyglycidyl derivatives or di derivatives or tri-acrylates or multi-acrylates, derivatives having unsaturations, such as "sp2" or "sp" hybridized carbon atoms, in their chemical formula.

In all cases, care must be taken to ensure that the light wavelength used for the crosslinking of the top coat layer TC 30 does not interfere with or very little with the components of the BCP block copolymer. underlying, in order to avoid possible photo-induced degradation of the latter. The choice of the photoinitiator, the photo-generated acid or the photo-generated base, must therefore be done in such a way that the light radiation does not degrade the block copolymer. Nevertheless, in general photo-crosslinking is particularly effective, with a high quantum yield, even with a low dose of energy (typically ranging from a few milliJoules per square centimeter (mJ / cm ² ) to a few tens of mJ / cm ² , for example, for doses equivalent to the lithography processes commonly used for exposing photo-sensitive resins to 193 nm), unlike the degradation of the block copolymer at the same wavelength, which generally requires a larger dose (typically for example from 200 mJ / cm ² to 1000 mJ / cm ² at 193 nm for polymethyl methacrylate PMMA). Therefore, even with an overlap with a photo-crosslinked top coat TC layer at a wavelength of degradation of the underlying block copolymer, the energy dose remains low enough not to damage the BCP block copolymer. Preferably, the energy dose during the crosslinking photo is less than or equal to 200 mJ / cm ² , more preferably it is less than or equal to 100 mJ / cm ² and even more preferably, it is less than or equal to at 50 mJ / cm ² .

In order to obtain a crosslinked topcoat layer TC which is neutral with respect to the underlying block copolymer, that is to say which has no particular affinity for With respect to each of the blocks of the block copolymer, the pre-TC pre-polymer composition preferably comprises a multi-component mixture of derivatives all carrying crosslinking functions, but different chemical groups. Thus, for example, the composition may comprise a component with fluorinated groups, another with oxygenated groups, etc., in order to be able to finely modulate the surface energy specific to the topcoat layer TC once photo-crosslinked. Thus, among the molecules reacting by cationic photopolymerization with PAG photo-generated acids to form a crosslinked TC layer, there may be mentioned, for example, oligomers formed of a monomer of low surface energy, such as a fluorinated acrylate, for example, a monomer of medium to high surface energy, such as a hydroxylated acrylate for example, and a crosslinkable group, via an acid reaction through the use of a photo-generated acid, such as an epoxy, for example. In this case, the ratio of low surface energy monomer to high surface energy monomer, weighted by the proportion of crosslinkable monomer, determines the neutrality of the crosslinked topcoat layer TC relative to the underlying BCP block copolymer. The level of crosslinkable groups with respect to the nature of the molecules of the pre-polymer composition conditions the ultimate rigidity of the crosslinked top coat TC layer. Finally, the physico-chemical structure of the photo-generated acid PAG conditions its activation wavelength and its solubility.

However, in the context of directed self-assembly nano-lithography applications, it must be ensured that the TC top coat once formed does not correspond to a porous or multiphase network, in order to avoid possible problems of inhomogeneities / demixions of the top coat TC for the underlying BCP block copolymer. For this purpose, the pre-pre-TC pre-polymer composition may consist of a pre-polymer / photoinitiator binary mixture and possible plasticizers or wetting agents as additives if necessary. In the context of other applications, such as the manufacture of membranes or biocompatible implants, for example, it may be interesting to the contrary that the top coat TC once formed, corresponds to such a porous or multiphase network. In order to be able to manufacture a nano-lithography mask for example, once the topcoat layer TC is crosslinked, the stack obtained, having a clean BCP / TC interface and a perfectly flat surface, is subjected to annealing. preferably thermal, at an assembly temperature Tass, for a predetermined period, preferably less than 60 minutes and more preferably less than 5 minutes, in order to cause nano structuring of the block copolymer. The nano-domains 21, 22 which form then orient themselves perpendicular to the neutralized interfaces of the BCP block copolymer.

Then, once the block copolymer has been organized, the top coat layer TC can be removed.

One way of removing the crosslinked topcoat layer TC is to use dry etching, such as plasma for example with a suitable gas chemistry, such as a majority oxygen base in a mixture with a rather inert gas such as He, Ar, N ₂ for example. Such dry etching is all the more advantageous and easy to achieve if the underlying BCP block copolymer 20 contains, for example, silicon in one of its blocks, then acting as an etch stop layer.

Such a dry etching may also be advantageous in the case where the underlying BCP block copolymer has been deposited with an excess thickness E and where not only the top coat layer TC must be removed but also the extra thickness E of the copolymer to blocks. In this case, the plasma constituent gas chemistry will have to be adjusted according to the materials to be removed in order not to have a particular selectivity for a block of the BCP block copolymer. The top coat layer TC and the extra thickness E of the block copolymer BCP can then be removed simultaneously or successively, in the same etching frame, by plasma etching by adjusting the gas chemistry according to the constituents of each of the layers to be removed. .

In the same manner, at least one of the blocks 21, 22 of the BCP block copolymer 20 is removed so as to form a porous film capable of serving as a nano-lithography mask. This removal of the block (s) may also be carried out in the same dry etching frame, successively to the removal of the top coat layer TC and the possible extra thickness E of block copolymer.

It is also possible to create stacks comprising a succession of these two alternating layers of BCP block copolymer and top coat TC. An example of such a stack is illustrated in the diagram of Figure 4 which shows the first stack already described comprising a substrate 10 whose surface 1 1 is previously neutralized, a first layer of BCP1 block copolymer, then a first layer of top coat TC1. Then, once the TC1 top coat layer is crosslinked, a second BCP2 block copolymer is deposited on the first layer of top coat. This second BCP2 block copolymer can be of identical or different nature of the first and allows to create patterns, at its assembly temperature, different from those of the first BCP1 block copolymer.

In this case, it is also necessary that the first layer of TC1 top coat is neutral vis-à-vis the blocks of the second BCP2 block copolymer. If this is not the case, it is necessary to neutralize its surface, for example by grafting a random copolymer. Then, a second pre-polymer layer pre-TC2 is deposited on the second BCP2 block copolymer and illuminated in order to cause a crosslinking reaction and stiffen it. This second layer of crosslinked top coat TC2 must also be neutral vis-à-vis the second block copolymer BCP2. The assembly temperatures of the two block copolymers BCP1 and BCP2 may be identical or different. If they are identical, a single annealing is sufficient to cause structuring of the two block copolymers simultaneously. If they are not identical, two anneals are necessary to structure each one in turn. And so on, several alternating layers of block copolymers and top coat can thus be deposited on each other. Such polymer stacks can be used in microelectronics or optoelectronics applications such as Bragg mirrors, for example, or to create specific anti-reflective layers. Subsequently, optionally, several successive etching steps allow to transfer the different patterns of different block copolymers in the underlying substrate. These etching steps are then preferably performed by plasma by adjusting the gas chemistry at each layer according to the constituents of the layer.

A very large additional advantage of the present invention lies in the selectivity of the process through the photo-generated species. Thus, if a local light source, of the laser type for example, is used to carry out the irradiation of the pre-pre-polymer layer, then it becomes possible to define areas on the stack, where the pre-layer layer Pre-TC polymer may be cross-linked, by photo-irradiation, and other areas where the pre-polymer pre-polymer layer will remain in the molecular state because not irradiated. Such localized irradiation at the surface of the top coat TC may also be carried out by means of a lithography mask for example and overall irradiation of the surface covered with said mask.

In an alternative embodiment, such a selectivity for the creation of crosslinked areas and non-crosslinked areas can also be obtained by means of an electron beam.

In the context of the application of the method according to the invention to directed self-assembly nano-lithography, the crosslinked zones of top coat have a neutral affinity with respect to the underlying block copolymer, while non-irradiated top coat areas may have a preferential affinity with at least one of the blocks of the underlying block copolymer. It then becomes possible to define zones of interest on the same stack, where the patterns of the underlying BCP block copolymer will be perpendicular to the interfaces, in zones located opposite the irradiated and neutral zones of the top coat vis-à- screw blocks blocks copolymer, and other areas, facing the non-irradiated areas, where the units of the block copolymer will instead oriented parallel to the interfaces, they can not therefore be transferred into the substrate underlying in subsequent stages of engraving.

To do this, the following method can simply be carried out. The pre-TC pre-polymer layer is deposited, then areas of interest of this layer are irradiated, for example through a lithography mask. The layer obtained is then rinsed in the solvent used for its deposition for example, the solvent being itself orthogonal to the block copolymer. This rinsing can remove non-irradiated areas. Optionally, another pre-polymer material, which is non-neutral with respect to the underlying block copolymer, may be deposited in the previously non-irradiated zones and having been rinsed, thus deprived of a top coat layer, and then said non-neutral prepolymer material is exposed to a stimulus, which may be light radiation or another stimulus selected from electrochemical process, plasma, ion bombardment or chemical species, to crosslink at predefined locations. The stack is then annealed at the assembly temperature to form the block copolymer. In this case, the nano domains located opposite the irradiated and crosslinked zones of the top coat layer TC, and neutral with respect to the block copolymer, are oriented perpendicularly to the interfaces, whereas the nano domains facing the zones without cross-linked and neutral topcoats are oriented parallel to the interfaces.

The following examples illustrate in a non-limiting way the scope of the invention:

Example 1: block copolvers used

The block copolymers poly (1,1 dimethylsilacyclobutane) -b / oc-polystyrene ("PDMSB-b-PS") used were synthesized by sequential anionic polymerization, as already reported in the prior art (K. Aissou et al., Small, 2017, 13, 1603777). The block copolymer No. 1 more particularly used here has a number-average molecular mass (Mn) of 17,000 g / mol, with a polydispersity index of 1.09, measured by steric exclusion chromatography (SEC) with polystyrene standards. The characterization shows a composition of 51% PS (by mass) and 49% PDMSB (by mass). The block copolymer No. 2 more particularly used herein has a number-average molecular weight (Mn) of 14,000 g / mol, with a polydispersity index of 1.07. The block copolymer No. 3 more particularly used here has a number-average molecular weight (Mn) of 19,000 g / mol, with a polydispersity of 1.09. The characterization shows a composition of 52% PS (by mass) and 48% PDMSB. The period of the block copolymer No. 1 is measured at ~ 18 nm, that of the No. 2 is measured at ~ 14 nm, that of the BCP No. 3 at ~ 24 nm, via a fast Fourier transform (FFT) images taken by scanning electron microscopy (SEM), on self-organized films. As described in the cited literature, the block "PDMSB" contains silicon in its composition.

Example 2 Synthesis of the Surface Passivation Layers and Top Coat Layers

The copolymers or homopolymers used in the context of the invention were synthesized by standard methods such as NMP (nitroxide mediated polymerization, for example with an initiator such as the initiator of Arkema marketed under the name BlocBuilder® ) or conventional radical (with an initiator such as azobisisobutyronitrile), known to those skilled in the art. The molar masses in number obtained are typically of the order of Mn ~ 5000-10000 g / mol. The polymer used as a neutralization underlayer is a homopolymer of 2-ethylhexyl polymethacrylate. The copolymer used as a topcoat layer has a copolymer architecture of poly (methacrylate of lycidyl-co-methacrylate of trifluoroethyl-co-hydroxyethyl methacrylate), hereinafter abbreviated as "PGFH", of " GFH "variables, ranging from 25/3/72 to 25/47/28, in bulk compositions. Without other specifications explicitly mentioned, the results obtained being equivalent for the various compositions mentioned above, only those concerning the composition 25/37/38 are detailed below. A PGFH copolymer is also synthesized, with a mass composition of 25/0/75.

Example 3: Solvents i coats

The various copolymers synthesized according to Example 2 of the PGFHs type are all soluble entirely in alcoholic solvents at a level of 10% by mass or less, such as methanol, ethanol, isopropanol or PGME (methyl ether). propylene glycol), or ethyl lactate, as well as in mixtures of these same solvents in any proportions. The block copolymers described according to Example No. 1 are not soluble in these same solvents or their mixtures.

The solubility parameters of these various solvents are available in the literature (Hansen, Charles, 2007. Hansen Solubility Parameters: A User's Handbook, Second Edition, Boca Raton, Fia: CRC Press, ISBN 978-0-8493- 7248-3.), But they are grouped in Table 1 below for practical reasons:

Table 1

When these solvents are used to solubilize the PGFHs copolymers with their additives, the deposits made by spin-coating on the No. 1 or No. 2 block copolymers (PDMSB-b-PS) exhibit excellent uniformity.

Example 4 Example of crosslinking of the top-coat via different stimuli

- Electron beam cross-linking (e-beam)

The equipment used for the e-beam lithography is a JEOL 6300FS device operating at 100kV, the intensity of the electron beam is fixed at 5nA. A different exposure dose is tested for each sample, from 30pC / cm ² to 180pC / cm ² , in steps of 30pC / cm ² .

A 2% by weight PGFH copolymer solution is produced in absolute ethanol. A 2% by weight solution of triphenylsulfonium trifluoromethane sufonate (hereinafter abbreviated "TPST") is also prepared in absolute ethanol. A mixture solution PGFH and TPST is then prepared at a height of 90% PGFH for 10% of TPST, by mass. The solution thus obtained is filtered on a PTFE (polytetrafluoroethylene) filter with a porosity of 200 nm and then dispensed by spin-coating at 2000 revolutions / minute (rpm) on a silicon substrate of 3 cm side, so as to obtain a homogeneous film of ~ 60nm thick. Gentle annealing is then performed at 60 ° C for 1 minute to remove residual solvent traces from the copolymer film, and then the sample is exposed to an electron beam at a precise dose to draw rectangular patterns of 200pmx100pm. spaced at 400pm. After exposure, an annealing ("post-exposure bake" in English, or PEB) is carried out at 90 ° C for 2 minutes to allow the diffusion of the electro-generated acid in the PGFH film. The sample is then rinsed in an absolute ethanol bath for 1 minute to remove the unexposed areas of the substrate, and the residual solvent is removed under a stream of nitrogen. The sample thus prepared is then cleaved so that the fracture performed cuts the patterns drawn, then the residual thickness corresponding to the crosslinked copolymer PFGH is estimated by scanning electron microscopy via a sectional view on the patterns drawn. The thickness values thus determined are plotted on the graph of FIG. 5 which represents the evolution of the thickness of reticulated residual PGFH as a function of the electron dose applied. This graph thus makes it possible to demonstrate that the PGFH copolymer can be crosslinked via an electron beam, and that if a zone of the film is not exposed to the beam, this beam will be eliminated during the rinsing step. by the solvent. The example therefore shows that areas of the film can be specifically selected to undergo a crosslinking reaction. It is noted that the sensitivity of the material vis-à-vis the beam can be easily modified by varying various parameters well known to those skilled in the art, such as the ratio of constituents, the chemical nature of the sulfonium salt, etc. ..

- Crosslinking by a photochemical process at A = 172 nm

The UV unit used was designed by the SCREEN SPE company. It comprises a chamber conditioned under an inert atmosphere (constant flow of nitrogen), irradiated by a UV lamp delivering a power of 30W.cm ² at the wavelength 172nm. The samples are first placed in the sealed chamber, then the atmosphere is conditioned for a few minutes to ensure the absence of oxygen, and the lamp is lit for a defined time corresponding to a given light dose.

A 2% by weight PGFH copolymer solution is produced in absolute ethanol. A 2% by weight solution of triphenylsulfonium trifluoromethane sufonate (abbreviated "TPST" thereafter) is prepared, also in absolute ethanol. A mixture solution PGFH and TPST is then prepared at a height of 90% PGFH for 10% of TPST, by mass. The solution thus obtained is filtered on a PTFE filter with a porosity of 200 nm and then dispensed by spin-coating at 2000 revolutions / minute (rpm) on a silicon substrate of 3 cm side, so as to obtain a homogeneous film of ~ 60 nm thick. A mild annealing ("softbake" in English) is then carried out at 60 ° C for 1 minute in order to remove residual traces of solvent from the copolymer film, then the sample is placed in the chamber of the UV unit and then subjected to a specific dose of light radiation. Subsequently, a post-exposure annealing (PEB) is performed or not at 90 ° C for 2 minutes on a single hot plate to allow the diffusion of photo-generated acids in the copolymer film, then the sample is rinsed in a absolute ethanol bath for 2 minutes to remove uncrosslinked copolymer chains and the residual solvent is removed under nitrogen flow. The residual thickness of the film corresponding to the photo-crosslinked PGFH copolymer is measured by ellipsometry. The thickness values thus obtained are collated in the graph of FIG. 6, and plotted as a function of the exposure dose to the luminous radiation at 172 nm and according to whether the film has been subjected to a post-exposure annealing (PEB) or no.

This graph thus makes it possible to demonstrate that the PGFH copolymer can be crosslinked via its exposure to a luminous radiation at 172 nm, and that if an area of the film is not exposed to the radiation, it will be eliminated during the step of rinsing with the solvent. So the example shows that areas of the film can be specifically selected to undergo a crosslinking reaction. It is also noted that the presence of the post-exposure annealing makes it possible to retain a greater proportion of the initial film because of the diffusion of the photo-generated acid in the copolymer film, thus demonstrating the interest of this optional step in the process. It is also important to note that the wavelength at 172nm is very close to the 193nm one commonly used in optical lithography, such a film of PGFH / TPST will therefore have a similar or better sensitivity to 193nm, as well as the 248nm wavelength also commonly used in optical lithography. Finally, it is noted that the sensitivity of the material vis-à-vis the light radiation can be easily modified by varying parameters well known to those skilled in the art, such as the ratio of constituents, the chemical nature of the sulfonium salt serving from PAG etc ....

- Crosslinking by a photochemical process at A = 365 nm

The UV unit used was designed by the company EVG. It comprises a closed chamber, irradiated by a UV lamp delivering a power of 3W.cnr ² at 365nm wavelength located a few centimeters from the sample. The samples are first placed in the closed enclosure and the lamp is lit for a definite time corresponding to a given light dose.

A PGFH copolymer solution at 2% by weight is produced in absolute ethanol. A 4 wt% solution of triarylsulfonium hexafluorophosphate (abbreviated "TAPS" thereafter) initially in 50% solution in propylene carbonate (CAS: 109037-77-6) is prepared in methanol. A PGFH and TAPS mixture solution is then prepared at 90% PGFH for 10% TAPS, by mass. The solution thus obtained is filtered on a PTFE filter with a porosity of 200 nm and then dispensed by spin-coating at 2000 revolutions / minute (rpm) on a silicon substrate of 3 cm side, so as to obtain a homogeneous film of ~ 60 nm thick. A mild annealing ("soft bake" in English) is then performed at 60 ° C for 1 minute to remove residual solvent traces of the copolymer film, then the sample is placed in the chamber of the UV unit and then subjected to a specific dose of light radiation. Subsequently, a post-exposure annealing (PEB) is carried out at 90 ° C for 2 minutes on a single hot plate to allow diffusion of the photo-generated acids in the copolymer film, then the sample is rinsed in a bath absolute ethanol for 2 minutes to remove uncrosslinked copolymer chains and the residual solvent is removed under nitrogen flow. The residual thickness of the film corresponding to the photo-crosslinked PGFH copolymer is measured by ellipsometry. The thickness values thus obtained are collated in the graph of FIG. 7 and plotted against the exposure dose to 365 nm light radiation.

This graph thus makes it possible to demonstrate that the PGFH copolymer can be crosslinked via its exposure to a light radiation at 365 nm, and that if a zone of the film is not exposed to radiation, this will be eliminated during the solvent rinsing step. The example therefore shows that areas of the film can be specifically selected to undergo a crosslinking reaction. It is also noted that the sensitivity of the material vis-à-vis the light radiation can be easily modified by varying various parameters well known to those skilled in the art, such as the ratio of constituents, the chemical nature of the salt of sulfonium serving as PAG etc ....

EXAMPLE 5 Effect of Crosslinking on the Possible Demolitions of the Block Copolymer / Topcoat Stack

The homopolymers used as undercoat are dissolved in a good solvent, such as propylene glycol acetate monomethyl ether (PGMEA), at 2% by weight. Block copolymer No. 1 is dissolved in a good solvent such as methyl isobutyl ketone (MIBK) at a level of 0.75% by weight. The topcoat copolymer PGFH is dissolved in absolute ethanol at a level of 1.8% by mass, to which 0.18% of photoacid generator (TPST for exposure at 172 nm and electron beam, TAPS for exposure at 365 nm) is added. ). Each solution is filtered on PTFE filters with a porosity of 200 nm to remove the particles and potential dust. The silicon substrates are cut into samples of 3cm x 3cm from 200mm wafers of crystallographic orientation silicon [100], and then used as such.

The following procedure is performed for the samples corresponding to a given predetermined experimental game:

- "solid / liquid" demolding: (demolding of the copolymer with blocks on its neutral underlayer): reference n ° 1

The neutral sub-layer solution is dispensed by spin-coating on the silicon substrate at a speed of 700 revolutions / minute (rpm), to obtain a film ~ 70 nm thick. The substrate is then annealed at 200 ° C. for 75 seconds in order to carry out the grafting of the molecules on said substrate, then the excess of ungrafted material is simply rinsed in a solvent bath (PGMEA), and the residual solvent is blown off. under nitrogen jet. The block copolymer solution is then dispensed by spin-coating at 2000 rpm, in order to obtain a homogeneous film of ~ 25 nm thick. The substrate is then annealed on a hot plate at 220 ° C for 5 minutes. The sample is then subjected to a plasma of chemistry and soft conditions such as Ar (80 sccm), O2 (40 sccm), 10mT, 100W _SOurce , 10W _bias , during 15 seconds in order to "freeze" the structure obtained and thus to prevent a creep of the polymer over time while improving the SEM imaging conditions. The resulting sample is then characterized by scanning electron microscopy (SEM), performing a statistic of ~ 10 images at a typical magnification of x5000 or x10000 in order to be able to determine the level of dewetting of the film. A typical SEM image corresponding to the reference sample 1 is shown in Figure 8, under the letter a).

- Demoulding "solid / liquid / liquid": (stripping of the copolymer system with blocks + Top coat, when the top-coat is not cross-linked): reference n ° 2

The top-coat copolymer PGFH is first dissolved in absolute ethanol at 2% by weight, then the solution obtained is filtered after dissolution, and will be used as it is thereafter. The neutral sub-layer solution is provided by spin-coating on the silicon substrate at a speed of 700 revolutions / minute (rpm), to obtain a film of ~ 70 nm thick. The substrate is then annealed at 200 ° C. for 75 seconds in order to carry out the grafting of the molecules on said substrate, then the excess of ungrafted material is simply rinsed in a solvent bath (PGMEA), and the residual solvent is blown off. under nitrogen jet. The block copolymer solution is subsequently dispensed by spin-coating at 2000 rpm, in order to obtain a homogeneous film of ~ 25 nm thick. The top-coat copolymer in ethanol is then dispensed onto the spin-coating block copolymer film at 2000 rpm so as to obtain a film of ~65 nm thick. The substrate is then annealed on a hot plate at 220 ° C for 5 minutes to organize the block copolymer. The samples are then subjected to a plasma of chemistry and mild conditions such as Ar (80 sccm), O2 (40 sccm), 10mT, 100W _source , 10W _bias , during 15 seconds in order to "freeze" the structure obtained and thus prevent a creep of polymer over time while improving SEM imaging conditions. The sample thus obtained is then characterized by scanning electron microscopy (SEM), performing a statistic of ~ 10 images at a typical magnification of x5000 or x10000 in order to be able to determine the level of dewetting of the film. A typical SEM image corresponding to the reference sample 2 is shown in Figure 8, under the letter b).

- Demoulding "solid / liquid / solid": (demobilized from the copolymer block system + top coat, when the topcoat is crosslinked): approach proposed by the invention

The neutral sub-layer solution is dispensed by spin-coating on the silicon substrate at a speed of 700 revolutions / minute (rpm), to obtain a film of ~ 70 nm thick. The substrate is then annealed at 200 ° C. for 75 seconds in order to carry out the grafting of the molecules on said substrate, then the excess of ungrafted material is simply rinsed in a solvent bath (PGMEA), and the residual solvent is blown off. under nitrogen jet. The block copolymer solution is subsequently dispensed by spin-coating at 2000 rpm, in order to obtain a homogeneous film of ~ 25 nm thick. The top-coat copolymer, in a 90/10 mixture with PAG, in ethanol is then dispensed onto the spin-coating block copolymer film at 2000 rpm to obtain a film ~ 65nm thick. The substrate is then subjected to a given stimulus (electron beam, light radiation) with a given dose (~ 1 OOmO / cm ² for exposure to an electron beam under conditions as set out in Example 4, 15 to 30 mJ / cm ² for exposure to radiation luminous wavelength 172 nm under conditions as set out in Example 4, 300 mJ / cm ² for exposure to light radiation of wavelength 365 nm under conditions as described in Example 4 ). A post-exposure annealing is then carried out at 90 ° C for 2 or 3 minutes on a hot plate to allow the diffusion of the electro or photo-generated acid in the top-coat film. A second annealing at 220 ° C for 5 minutes allows to organize the block copolymer. The samples are then subjected to a first plasma as described in Example 6 in order to remove the crosslinked topcoat, then to a second plasma of chemistry and mild conditions such as Ar (80 sccm), O 2 (40 sccm), 10 mT, 100W source, 10W _b ias, for 15 seconds to "freeze" the resulting structure of the block copolymer and thereby prevent creep of the polymer over time while improving the SEM imaging conditions. Each sample thus obtained is then characterized by scanning electron microscopy (SEM), performing a statistic of ~ 10 images at a typical magnification of x5000 or x10000 in order to be able to determine the level of dewetting of the films. A typical SEM image corresponding to the samples, the top coat of which has been crosslinked according to one embodiment of the invention, is shown in FIG. 8, under the letter c).

On the images a) and b) of Figure 8, the dark gray / black areas correspond to a cluster of copolymer film, so it is de-wet areas, while the light gray areas correspond to the substrate laid bare by the dewetting process. Image c) of Figure 8 shows a continuous film of uniform thickness.

According to this example, it is obvious that if the top-coat is not crosslinked (reference No. 2), it induces a deformation of the block copolymer layer rapidly leading to a complete dewetting of the block copolymer. the neutralized surface. The block copolymer itself (reference No. 1) wets on the corresponding neutralization layer at the self-organization temperature of the block copolymer, when no top coat is present. Finally, it can be seen that neither the block copolymer film nor the topcoat film have become dewaxed when the topcoat has undergone a crosslinking step, either by exposure to an electron beam or by exposure to an electron beam. light radiation, before being subjected to the self-organization temperature of the block copolymer ("solid / liquid / solid dewetting"). It is therefore undeniable that the cross-linked top-coat makes it possible to effectively control or even eliminate the possible dewetting phenomena of the stack. Moreover, it may be noted that this latter configuration makes it possible to obtain perpendicular oriented patterns, as described in Example 7. Example 6: Etching / removal of the top coat layer by plasma

The dry-etching / dry-etching experiments of the top-coat film were carried out in an induction-coupled plasma DPS reactor from Applied Materials, the walls of which consist of aluminum oxide. The samples are physically bonded to a silicon wafer 200mm in diameter before being introduced into the reactor chamber. The plasma is excited by induction via two radio frequency antennas at 13.56MHz with a power supply of up to 3kW to improve the uniformity of the ion flux.

A plasma of chemistry and conditions such as CF ₄ (50 sccm), O 2 (70 sccm), 10 mT, 100 W _source , 10 W _bias , is performed on PGFH copolymer films of initial thickness ~ 130 nm with varying times of plasma. . The PGFH films are prepared as described in Example 4. The concentration of the constituents is adjusted here to 4% by weight so as to obtain films a little thicker than in Example 4 and thus have a better accuracy on the burning speed of the PGFH film; the rest of the process is unchanged. Once the plasma is made, the residual thicknesses of the films are measured by ellipsometry. The results are reported in Table 2 below and illustrated in the graph of Figure 9.

Table 2: Residual thickness measured for a PGFH film having undergone different plasma times.

[0152] Following this example, the copolymer PGFH is etched at a rate of ~ 4,8nm.s ^_1 under the plasma conditions.

According to the samples prepared as in Example 7 below, as well as the data set out above, the top coat of initial thickness ~ 60nm is removed entirely with a plasma time of 13seconds. Subsequently, optionally, a soft plasma of chemistry and conditions Ar (80 sccm), O2 (40 sccm), 10 mT, 200 W _SO urce, 20 W _bias , carried out for 10seconds partially removes the phase corresponding to the PS of the block copolymer to improve contrast in SEM imaging.

It should be noted that in this example, the chemistries and plasma conditions for removing the PGFH film are very arbitrary and that, therefore, other conditions Equivalents easily established by those skilled in the art would just as easily achieve the same result.

EXAMPLE 7 Self-Organization of Block Copolymers According to the Invention Neutral Cross-Linked Top Coat

The homopolymers used as undercoat are dissolved in a good solvent, such as propylene glycol acetate monomethyl ether (PGMEA), at 2% by weight. The block copolymer is dissolved in a good solvent such as methyl isobutyl ketone (MIBK) at a level of 0.75% by weight. The top-coat copolymer PGFH is dissolved in absolute ethanol at a level of 1.8% by mass, to which 0.18% of photoacid generator (TPST for exposure at 172 nm and electron beam, TAPS for exposure at 365 nm) is added. ). Each solution is filtered on PTFE filters with a porosity of 200 nm to remove the particles and potential dust. The silicon substrates are cut into samples of 3cm x 3cm from 200mm wafers of crystallographic orientation silicon [100], and then used as such.

The neutral sub-layer solution is dispensed by spin-coating on the silicon substrate at a speed of 700 revolutions / minute (rpm), to obtain a film ~ 70 nm thick. The substrate is then annealed at 200 ° C. for 75 seconds in order to carry out the grafting of the molecules on said substrate, then the excess of ungrafted material is simply rinsed in a solvent bath (PGMEA), and the residual solvent is blown off. under nitrogen jet. The block copolymer solution is then dispensed by spin-coating at 2000 rpm, in order to obtain a homogeneous film of ~ 25 nm thick. The solution of topcoat / PAG copolymer in ethanol is then dispensed on the spin-coating block copolymer film at 2000 rpm so as to obtain a film of ~65 nm thick. The substrate is then subjected to a given stimulus (electron beam, light radiation) with a given dose (~ 100pC / cm ² for exposure to an electron beam under conditions as outlined in Example 4; 15 to 30 mJ / cm ² for exposure to light radiation of wavelength 172 nm under conditions as set forth in Example 4, 300 mJ / cm ² for exposure to light radiation of 365nm wave under conditions as set forth in Example 4). A post-exposure annealing is then carried out at 90 ° C for 2 or 3 minutes on a hot plate to allow the diffusion of the electro or photo-generated acid in the top-coat film. The samples are then subjected to a first plasma as described in Example 6 in order to remove the crosslinked topcoat, then to a second plasma of chemistry and mild conditions such as Ar (80 sccm), O 2 (40 sccm), 10 mT, 100W _source , 10W _bias , for 15 seconds to "freeze" the resulting structure of the block copolymer and thus prevent creep of the polymer over time while improving the SEM imaging conditions. The different samples are then analyzed by scanning electron microscopy (SEM) on a Hitachi CD-SEM H9300. The results obtained are reported in FIG. 10 which represents the SEM image of a sample of the # 1 block copolymer, the self-organization of which is perpendicular to the substrate and whose period is of the order of 18 nm, for the different stimuli of exposure. It is noted that the same type of results (lamellar block copolymer film PDMSB-b-PS whose patterns are oriented entirely perpendicularly with respect to the substrate) is observed for smaller thicknesses (from 0.5 to 1 times the period of the block copolymer used), or greater than that reported (more than 4 times the period of the block copolymer).

According to this example, it can be seen that the domains of the lamellar PDMSB-b-PS block copolymer are well oriented perpendicular to the substrate for the various studied top-coat compositions. On the other hand, when a copolymer containing no trifluoroethyl methacrylate (eg 25/0/75) is used as a top-coat under the same conditions, a parallel / perpendicular or entirely parallel orientation of the patterns is obtained, thus demonstrating the advantage of the presence of trifluoroethyl methacrylate as a co-monomer in the architecture of the top-coat to control the perpendicular orientation of the blocks of the block copolymer. Finally, as in Example 5 above (see FIG. 8c)), under these process conditions (in particular the self-organization annealing), no dewetting is observed on the films corresponding to FIG. 10.

Example 8 UV Patterninq and Electron Beam

- Patterninq by electron beam

The equipment used for electron beam lithography ("e-beam" in English) is a JEOL 6300FS operating at 100kV, the intensity of the electron beam is set at 5nA; an exposure dose of 150pC / cm ² is chosen arbitrarily for the proof of concept.

A 2% PGFH copolymer solution is produced in absolute ethanol. A 2% by weight solution of TPST is prepared, also in absolute ethanol. A mixture solution PGFH and TPST is then prepared at a height of 90% PGFH for 10% of TPST, by mass. The solution thus obtained is filtered on a PTFE filter with a porosity of 200 nm and then dispensed by spin-coating at 2000 revolutions / minute (rpm) on a silicon substrate of 3 cm side, so as to obtain a homogeneous film of ~ 60 nm. 'thickness. Soft bake is then performed at 60 ° C for 1 minute to remove residual solvent traces from the copolymer film, and the sample is exposed to an electron beam at a dose of 150pC / cm. ² to draw lines of 1 OOprn long for 1 pm wide, spaced 10pm apart. After exposure, a "post-exposure bake" (PEB) is carried out at 90 ° C for 2 minutes to allow the diffusion of the electro-generated acid into the PGFH movie. The sample is then rinsed in an absolute ethanol bath for 1 minute to remove the unexposed areas of the substrate, and the residual solvent is removed under a stream of nitrogen. The sample thus prepared is then observed under an optical microscope and SEM to characterize the patterns drawn. The characterizations are shown in FIG. 11, which represents, under the letter a), an image taken by optical microscopy and under the letter b) an image taken by scanning electron microscopy. In these figures, the gray / black areas that emerge from the background correspond to the patterns drawn by crosslinking of the PGFH copolymer.

The example thus clearly demonstrates that the PGFH copolymer, which will also be used as top coat in the context of the block copolymer-directed assembly, can be used as an electron-beam lithography resin in order to draw patterns of nanoscale dimensions of interest.

- Patterning by exposure to light radiation (l = 365nm)

The UV unit used is a MJB4 type mask aligner designed by Süss MicroTec. It includes a UV lamp delivering a power of ~ 12W.cnr ² at 365nm wavelength located a few centimeters above the sample. The sample is first placed on the dedicated sample holder, then the lithography mask is placed on the sample by contact, and the lamp is lit for a definite time corresponding to a given light dose of ~ 300mJ / cm. ² .

A 2% by weight PGFH copolymer solution is produced in absolute ethanol. A 4% by weight solution of PAG "TAPS" initially in a 50% solution in propylene carbonate is prepared in methanol. A PGFH and TAPS mixture solution is then prepared at 90% PGFH for 10% TAPS, by mass. The solution thus obtained is filtered on a PTFE filter with a porosity of 200 nm and then dispensed by spin-coating at 2000 revolutions / minute (rpm) on a silicon substrate of 3 cm side, so as to obtain a homogeneous film of ~ 60 nm. 'thickness. A soft bake is then performed at 60 ° C for 1 minute to remove residual solvent traces from the copolymer film, and then the sample is placed on the mask aligner sample holder. and then subjected to a specific dose of light radiation through the lithography mask (arbitrary patterns of lines of variable size up to 1 pm in width, for example). Subsequently, PEB annealing is carried out at 90 ° C for 2 minutes on a single hot plate to allow diffusion of the photo-generated acids in the copolymer film, then the sample is rinsed in an absolute ethanol bath during 2 minutes to remove uncrosslinked copolymer chains and the residual solvent is removed under nitrogen flow. The sample thus prepared is then observed under an optical microscope and SEM to characterize the patterns drawn. The characterizations are shown in Figure 12 which represents under the letter a) an image taken by optical microscopy and under the letter b) an image taken by scanning electron microscopy. In these figures, the gray / black areas that emerge from the background correspond to the patterns drawn by crosslinking of the PGFH copolymer.

The example thus clearly demonstrates that the PGFH copolymer, which will also be used as a top-coat in the context of the block copolymer-directed assembly, can be used as a resin for optical lithography via UV radiation in order to draw patterns of nanometric dimensions of interest.

Example 9: neutrality of patterns (or patterns) and selection of areas

- Electron beam exposure:

The equipment used for electron beam lithography (e-beam) is a JEOL 6300FS device operating at 10OkV, the intensity of the electron beam of which is set at 5nA; an exposure dose of 150pC / cm ² is chosen arbitrarily for the proof of concept.

The homopolymers used as an underlayer are dissolved in a good solvent, such as propylene glycol acetate monomethyl ether (PGMEA), at a level of 2% by weight. Block copolymer No. 1 is dissolved in a good solvent such as methyl isobutyl ketone (MIBK) at a level of 0.75% by weight. The top-coat copolymer PGFH is dissolved in absolute ethanol at a level of 1.8% by weight, to which 0.18% of photoacid generator (TPST) is added. Each solution is filtered on PTFE filters with a porosity of 200 nm to remove the particles and potential dust. The silicon substrates are cut into samples of 3cm x 3cm from 200mm wafers of crystallographic orientation silicon [100], and then used as such.

The neutral sub-layer solution is dispensed by spin-coating on the silicon substrate at a speed of 700 revolutions / minute (rpm), to obtain a film of ~ 70 nm thick. The substrate is then annealed at 200 ° C. for 75 seconds in order to carry out the grafting of the molecules on said substrate, then the excess of ungrafted material is simply rinsed in a solvent bath (PGMEA), and the residual solvent is blown off. under nitrogen jet. The block copolymer solution is then dispensed by spin-coating at 2000 rpm, in order to obtain a homogeneous film of ~ 25 nm thick. The top-coat copolymer in ethanol is then dispensed onto the spin-coating block copolymer film at 2000 rpm so as to obtain a film of ~65 nm thick. The substrate is then subjected to an electron beam with a dose of ~ 150pC / cm ² , in order to draw patterns of 100pmx100pm wide, thus defining neutral exposed areas for the block copolymer and unexposed areas [at the beam of electron] on the substrate. A post-exposure annealing is then carried out at 90 ° C for 2 or 3 minutes on a hot plate in order to allow the diffusion of the electro-generated acid in the top-coat film on the areas exposed to the beam electron. The sample is then rinsed in an absolute ethanol bath and the solvent is dried under a stream of nitrogen. Subsequently, a non-neutral topcoat copolymer PGFH (composition 25/0/75) at 1% in ethanol, to which 0.1% TPST is added, is dispensed at 2000 revolutions / minute (rpm). on the pre-patterned substrate. The sample is then subjected to a luminous radiation at 172 nm for a dose of 30 mJ / cm ^{2 in} order to crosslink this second topcoat, then a post-exposure annealing (PEB) is carried out at 90 ° C for 2 minutes in order to diffuse the photo-generated acid in the second top-coat. Annealing at 220 ° C for 5 minutes allows to organize the block copolymer. The sample is then subjected to a first plasma as described in Example 6 in order to remove the crosslinked topcoat, then to a second plasma of chemistry and mild conditions such as Ar (80 sccm), O2 (40 sccm), 10 mT , 100W _SOurce , 10W _bias , for 15 seconds to "freeze" the resulting structure of the block copolymer and thereby prevent creep of the polymer over time while improving the SEM imaging conditions. The sample thus produced is characterized on a Hitachi H9300 CDSEM. The result of the characterization is shown in FIG. 13 which represents SEM images of the exposed and unexposed areas of the electron beam. The area initially exposed to the electron beam has lamellar block copolymer patterns perpendicular to the substrate, while the unexposed area has patterns parallel to the substrate.

The example thus clearly demonstrates that neutral zones (perpendicular block copolymer units) for the block copolymer and non-neutral zones (parallel block copolymer units) can be defined on the substrate by lithography of the copolymer. PGFH via exposure of it to an electron beam.

- Exposure by light radiation at l = 365nm

The UV unit used is a MJB4 type mask aligner designed by the Süss MicroTec company. It includes a UV lamp delivering a power of ~ 12W.cnr ² at 365nm wavelength located a few centimeters above the sample. The sample is first placed on the dedicated sample holder, then the lithography mask is placed on the sample by contact, and the lamp is lit for a definite time corresponding to a given light dose of ~ 300mJ / cm. ² .

The homopolymers used as a sub-layer are dissolved in a good solvent, such as propylene glycol acetate monomethyl ether (PGMEA), at a level of 2% by weight. Block copolymer No. 1 is dissolved in a good solvent such as methyl isobutyl ketone (MIBK), at a level of 0.75% by weight. The top-coat copolymer PGFH is dissolved in absolute ethanol at a level of 2% by weight. The "TAPS" PAG is prepared by dissolving an initial 50% solution in propylene carbonate to a level of 4% in methanol. A PGFH and TAPS mixture solution is then prepared at 90% PGFH for 10% TAPS, by mass. Each solution is filtered through PTFE filters of porosity 200nm to eliminate the particles and potential dust. The silicon substrates are cut into samples of 3cm x 3cm from 200mm wafers of crystallographic orientation silicon [100], and then used as such.

The neutral sub-layer solution is dispensed by spin-coating on the silicon substrate at a speed of 700 revolutions / minute (rpm), to obtain a film ~ 70 nm thick. The substrate is then annealed at 200 ° C. for 75 seconds in order to carry out the grafting of the molecules on said substrate, then the excess of ungrafted material is simply rinsed in a solvent bath (PGMEA), and the residual solvent is blown off. under nitrogen jet. The block copolymer solution is subsequently dispensed by spin-coating at 2000 rpm in order to obtain a homogeneous film of ~ 25 nm thick. The top-coat copolymer in ethanol is then dispensed onto the BCP film by spin-coating at 2000 rpm so as to obtain a film of ~65 nm thick. The substrate is placed on the sample holder of the UV unit and then subjected to UV radiation through the selected lithography mask, in order to draw any patterns (for example lines of variable dimensions), thus defining neutral exposed areas. for the block copolymer and non-exposed areas [to UV radiation] on the substrate. A post-exposure annealing is then carried out at 90 ° C for 2 or 3 minutes on a hot plate to allow the diffusion of the photo-generated acid in the topcoat film on the areas exposed to light radiation. The sample is then rinsed in an absolute ethanol bath in order to dissolve the unexposed areas, then the solvent is dried under a stream of nitrogen. Subsequently, a non-neutral topcoat copolymer PGFH (composition 25/0/75) at 1% in ethanol, to which 0.1% TPST is added, is dispensed at 2000 rpm onto the substrate. pre-Patterne. The sample is then subjected to a luminous radiation at 172 nm for a dose of 30 mJ / cm ^{2 in} order to crosslink this second topcoat, then a post-exposure annealing (PEB) is carried out at 90 ° C for 2 minutes to make spread the photo-generated acid in the second top-coat. Annealing at 220 ° C for 5 minutes allows to organize the block copolymer. The sample is then subjected to a first plasma as described in Example 6 in order to remove the crosslinked topcoat, then to a second plasma of chemistry and mild conditions such as Ar (80 sccm), O2 (40 sccm), 10 mT , 100W _SOurce , 10W _bias , for 15 seconds to "freeze" the resulting structure of the block copolymer and thereby prevent creep of the polymer over time while improving the SEM imaging conditions. The sample thus produced is characterized on a Hitachi H9300 CDSEM. The result of the characterization is shown in FIG. 14 which represents the SEM images of the exposed and unexposed zones at 365 nm. The area initially exposed to 365 nm radiation has lamellar block copolymer patterns perpendicular to the substrate, while the unexposed area has patterns parallel to the substrate. The example thus clearly demonstrates that neutral zones (perpendicular BCP patterns) for the BCP and non-neutral zones (parallel BCP patterns) can be defined on the substrate by lithography of the PGFH copolymer of appropriate composition via exposure. from it to UV radiation.

Example 10: flatness of the interfaces

The homopolymers used as an underlayer are dissolved in a good solvent, such as propylene glycol acetate monomethyl ether (PGMEA), at a level of 2% by weight. Block copolymer No. 2 is dissolved in a good solvent such as methyl isobutyl ketone (MIBK), at a level of 3% by weight. The top-coat copolymer PGFH is dissolved in absolute ethanol at a level of 2% by weight. The "TAPS" PAG is prepared by dissolving an initial 50% solution in propylene carbonate to a level of 4% in methanol. A PGFH and TAPS mixture solution is then prepared at 90% PGFH for 10% TAPS, by mass. Each solution is filtered on PTFE filters with a porosity of 200 nm to remove the particles and potential dust. The silicon substrates are cut into samples of 3cm x 3cm from 200mm wafers of crystallographic orientation silicon [100], and then used as such.

The underlayer solution is dispensed by spin-coating on the silicon substrate at a speed of 700 revolutions / minute (rpm), to obtain a film ~ 70 nm thick. The substrate is then annealed at 200 ° C. for 75 seconds in order to carry out the grafting of the molecules on said substrate, then the excess of ungrafted material is simply rinsed in a solvent bath (PGMEA), and the residual solvent is blown off. under nitrogen jet. The block copolymer solution is subsequently dispensed by spin-coating at 1000 rpm, in order to obtain a film of ~ 130 nm in uniform thickness. Optionally, hot plate annealing at 90 ° C for 30 seconds is performed to evaporate the residual solvent. The top-coat solution is then dispensed on the block copolymer layer by spin-coating at 2000 rpm so as to obtain a thickness of ~ 60 nm of top coat. The stack of films is then exposed to light radiation of wavelength 365nm at a dose of ~ 300mJ / cm ² , then a post-exposure annealing (PEB) at 90 ° C for 3 minutes is carried out to promote the diffusion photo-generated acid in the top-coat film. The block copolymer is then self-organized at a temperature of 220 ° C for 10 minutes.

For the analysis of the sample in section via a preparation FIB-STEM (fast ion bombardment - scanning transmission electronic microscope), the following procedure is adopted: the preparation of the thin blade of the sample as well as STEM analysis is performed on a Helios 450S device. A platinum layer of 100 nm is first deposited on the sample by evaporation to avoid deterioration of the polymers. An additional layer of 1 μm is deposited on the sample in the STEM enclosure by a high energy ion beam. After careful alignment perpendicular to the sample (sectional view), a thin blade thereof is extracted via FIB, then refined gradually to a width of approximately 100 nm. In situ observation is then performed using the STEM detector. The result of the analysis is shown in Figure 15 which shows the assembly of the block copolymer (BCP) No. 2, lamellar, sectional view prepared FIB-STEM. Microscopy indicates that the lamellae are perpendicular to the substrate over the entire thickness of the film (in gray / black: lamellae of PDMSB, in gray / white: lamellae of PS).

FIG. 15 shows that the crosslinking of the top-coat material makes it possible to maintain a particularly sharp interface between the top-coat material and the block copolymer, as proposed in the context of the invention (no mixing observable between the two materials), as well as a flat film for both materials. Incidentally, Figure 15 also demonstrates that the invention is particularly effective both for generating perfectly oriented patterns (sipes) in the same direction throughout the thickness of the block copolymer film, as well as for generating copolymer patterns. block with a high form factor (lamella ~ 7nm wide ~ 25nm thick, so a form factor of ~ 18).

Example 11: Block Copolymer Film Stacking

Homopolymers used as an undercoat are dissolved in a good solvent, such as propylene glycol acetate monomethyl ether (PGMEA), at a level of 2% by weight. Block copolymer No. 1 and block copolymer No. 3 are dissolved in a good solvent such as methyl isobutyl ketone (MIBK), each of 0.75% by weight. The top-coat copolymer PGFH is dissolved in absolute ethanol at a level of 2% by weight. The "TAPS" PAG is prepared by dissolving an initial 50% solution in propylene carbonate to a level of 4% in methanol. A PGFH and TAPS mixture solution is then prepared at 90% PGFH for 10% TAPS, by mass. Each solution is filtered on PTFE filters with a porosity of 200 nm to remove the particles and potential dust. The silicon substrates are cut into samples of 3cm x 3cm from 200mm wafers of crystallographic orientation silicon [100], and then used as such.

The underlayer solution is dispensed by spin-coating on the silicon substrate at a speed of 700 revolutions / minute (rpm), to obtain a film of ~ 70 nm thick. The substrate is then annealed at 200 ° C. for 75 seconds in order to carry out the grafting of the molecules on said substrate, then the excess of ungrafted material is simply rinsed in a solvent bath (PGMEA), and the residual solvent is blown off. under nitrogen jet. The No. 3 block copolymer solution is subsequently dispensed by spin-coating at 2000 rpm, so that to obtain a film of ~ 27nm of homogeneous thickness. Optionally, hot plate annealing at 90 ° C for 30 seconds is performed to evaporate the residual solvent. The top-coat solution is then dispensed on the spin-coating block copolymer layer at 2000 rpm so as to obtain a thickness of ~ 60 nm of top coat. The stack of films is then exposed to light radiation of wavelength 365nm at a dose of ~ 300mJ / cm ² , then an annealing exposure (PEB) at 90 ° C for 3 minutes is carried out to promote the diffusion photo-generated acid in the top-coat film. The undercoat solution is provided by spin-coating on the stack of films at a speed of 700 revolutions / minute, to obtain a film ~ 70 nm thick. The substrate is then annealed at 200 ° C. for 75 seconds in order to carry out the grafting of the undercoat on the first topcoat film, then the excess of ungrafted material is simply rinsed by pure MIBK spin-coating. 'to evaporation. The No. 1 block copolymer solution is subsequently dispensed by spin-coating at 2000 rpm, in order to obtain a film of ~ 27 nm in uniform thickness. Optionally, hot plate annealing at 90 ° C for 30 seconds is performed to evaporate the residual solvent. The top-coat solution is then dispensed on the spin-coating block copolymer layer at 2000 revolutions / min so as to obtain a thickness of ~ 60 nm of top coat. The stack of films is then exposed to light radiation of wavelength 365nm at a dose of ~ 300mJ / cm ² , then a PEB annealing at 90 ° C for 3 minutes is carried out to promote the diffusion of photo acid -generated in the top-coat film. The stack thus produced of the various films is then annealed at a temperature of 220 ° C. for 5 minutes in order to promote the self-organization of the various BCP block copolymers (BCP No. 1 and BCP No. 3) of the stack. .

For the analysis of the sample in section via a preparation FIB-STEM (fast ion bombardment - scanning transmission electronic microscope), the following procedure is adopted: the preparation of the thin section of the sample as well as STEM analysis is performed on a Helios 450S device. A platinum layer of 100 nm is first deposited on the sample by evaporation to avoid deterioration of the polymers. An additional 1 μm layer is deposited on the sample in the STEM enclosure by a high energy ion beam. After careful alignment perpendicular to the sample (sectional view), a thin blade thereof is extracted via FIB, then refined gradually to a width of approximately 100 nm. In situ observation is then performed using the STEM detector. The result of the analysis is shown in FIG. 16 which represents the stacking of the various films seen in section by FIB-STEM.

[0179] FIG. 16 shows successive block copolymer (BCP) films of different periods (~ 24nm for BCPn ° 3, ~ 18nm for BCP # 1), each of which is organized perpendicularly with respect to the substrate, without observing any miscibility between different films put in the presence. The example thus demonstrates that the invention makes it possible to stack block copolymer films at will thanks to the crosslinking of the top-coat films, without the stack deicing the substrate.

Claims

A method of manufacturing a planar polymeric stack, said method comprising depositing on a substrate (10) a first layer (20) of non-crosslinked (co) polymer and then a second layer (30) of (co-) polymer, at least one of the (co-) polymer layers being initially in a liquid or viscous state, said method being characterized in that at the time of deposition of the top layer (30) on the first layer (20), the upper layer is in the form of a pre-polymer composition (pre-TC) comprising at least one monomer (s) and / or dimer (s) and / or oligomer (s) and / or polymer (s) in solution, and in that an additional step consists in subjecting said upper layer (30) to a stimulus, selected from a plasma, an ion bombardment, an electrochemical process, a chemical species, a light radiation, capable of causing a reaction crosslinking the molecular chains within said neck pre-polymer (30, pre-TC) and allow to obtain a cross-linked top coat (TC) layer.

2. Method according to claim 1, characterized in that the stimulus applied to initiate the crosslinking reaction is an electrochemical process applied via an electron beam.

3. Method according to claim 1, characterized in that the stimulus for causing the crosslinking reaction within the pre-polymer layer is light radiation in wavelength ranges from ultraviolet to ultraviolet light. infra-red, between 10nm and 1500nm, and preferably between 100nm and 500nm.

4. Method according to claim 3, characterized in that the step of photo-crosslinking of the pre-polymer composition layer is performed at a power dose of less than or equal to 200 mJ / cm ² , preferably less than or equal to 100mJ / cm ² and more preferably less than or equal to 50 mJ / cm ² .

5. Method according to one of claims 3 to 4, characterized in that the crosslinking reaction propagates within the upper layer (30) carrying the stack (20, 30) at a temperature below 150 ° C and preferably below 10 ° C, for less than 5 minutes, and preferably less than 2 minutes.

6. Method according to one of claims 1 to 5, characterized in that the pre-polymer composition (pre-TC) is a composition formulated in a solvent, or used without solvent, and which comprises at least: a monomeric, dimeric, oligomeric or polymeric chemical entity, or any combination of these different entities, of a chemical nature in whole or in part identical, and each comprising at least one chemical function capable of ensuring the crosslinking reaction under the effect a stimulus,

7. Method according to one of claims 1 to 6, characterized in that at least one of the chemical entities of the pre-polymer composition has at least one fluorine atom and / or silicon and / or germanium, and or an aliphatic carbon chain of at least two carbon atoms in its chemical formula.

8. Method according to claim 6 or 7, characterized in that said pre-polymer composition (pre-TC) further comprises in its formulation:

a chemical entity chosen from an antioxidant, a base or a weak acid, capable of trapping said chemical entity capable of initiating the crosslinking reaction, and / or

one or more additives for improving wetting and / or adhesion, and / or uniformity of the upper layer (30) of top coat (TC) deposited on the underlying layer (20), and or

one or more additives making it possible to absorb one or more ranges of light radiation of different wavelength, or to modify the electrical conductivity properties of the pre-polymer (pre-TC).

9. Method according to one of claims 1 to 8, characterized in that the pre-polymer composition (pre-TC) comprises a photoinitiator crosslinking and is crosslinked by radical polymerization.

10. Process according to claim 9, characterized in that the monomer (s) and / or dimer (s) and / or oligomer (s) and / or polymer (s) constitutive (s) of the pre-coated layer. polymer (pre-TC), are derivatives of acrylates or di- or tri-acrylates or multi-acrylates, methacrylate, or multi-methacrylates, or polyglycidyl or vinyl, fluoroacrylates or fluoromethacrylates, vinyl fluorides or fluorostyrene alkyl acrylate or methacrylate, hydroxyalkyl acrylate or methacrylate, alkylsilyl acrylate or methacrylate, unsaturated esters / acids such as fumaric or maleic acids, vinyl carbamates and carbonates, allylic ethers, and thiolated systems. enes.

11. Process according to claims 8 and 10, characterized in that the photoinitiator is chosen from acetophenone, benzophenone, peroxide, phosphine derivatives, xanthones, hydroxycetone or diazonaphthoquinone, thioxanthones, α-aminoketones, benzil, benzoin.

12. Method according to one of claims 1 to 7, characterized in that the pre-polymer composition (pre-TC) comprises an initiator and is crosslinked by cationic polymerization.

13. The method of claim 12, characterized in that the (s) monomer (s) and / or dimer (s) and / or oligomer (s) and / or polymer (s) constitutive (s) of the layer pre- polymer (pre-TC), are derivatives comprising epoxy / oxirane type chemical functions, or vinyl ethers, cyclic ethers, thiirane, trioxane, vinyl, lactones, lactams, carbonates, thiocarbonates, maleic anhydride.

14. Process according to claims 12 and 13, characterized in that the initiator is a photo-generated acid (PAG) from a salt chosen from among onium salts, such as iodonium or sulphonium salts. , pyrridinium, alkoxypyrridinium, phosphonium, oxonium, or diazonium.

15. Process according to claim 14, characterized in that the photo-generated acid (PAG) is coupled to a photosensitizer compound chosen from acetophenone, benzophenone, peroxide, phosphine, xanthone derivatives, hydroxycetone or diazonaphthoquinone, thioxanthones, α-aminoketones, benzil, benzoin, as long as said photosensitizer absorbs at the desired wavelength.

16. Method according to one of claims 1 to 7, characterized in that the pre-polymer composition (pre-TC) comprises an initiator and is crosslinked by anionic polymerization reaction.

17. The method of claim 16, characterized in that the (s) monomer (s) and / or dimer (s) and / or oligomer (s) and / or polymer (s) constitutive (s) of the layer pre- polymer (pre-TC), are derivatives of alkyl cyanoacrylate type, epoxides / oxiranes, acrylates, or derivatives of isocyanates or polyisocynanates.

18. Process according to claims 16 and 17, characterized in that the initiator is a photo-generated base (PBG) from derivatives chosen from carbamates, acyloximes, ammonium salts, sulphonamides, formamides, amineimides, α-aminoketones, amidines.

19. Method according to one of claims 1 to 18, characterized in that the first polymer layer (20) is in a solid state when the stack is brought to a temperature below its glass transition temperature or in a state liquid-viscous when the stack is raised to a temperature above its glass transition temperature.

20. The method of claim 19, characterized in that the first polymer layer (20) is a block copolymer (BCP) capable of nano-structuring at an assembly temperature, in that prior to the step of depositing the first layer (20) of block copolymer, the method comprises a step of neutralizing the surface of the underlying substrate (10), and that, subsequent to the step of crosslinking the top layer (30); ) to form a crosslinked top coat (TC) layer, the method comprises a step of nano-structuring the first layer building block copolymer (20) by subjecting the resulting stack to an assembly temperature, said an assembly temperature being less than a temperature at which the top coat material (TC) behaves like a viscoelastic fluid, said temperature being greater than the glass transition temperature of said material top coat and preferably, said assembly temperature being lower than the glass transition temperature of the layer (30) of top coat (TC) in its crosslinked form.

21. The method according to claim 20, characterized in that the preliminary step of neutralizing the surface of the underlying substrate (10) consists in pre-drawing patterns on the surface of the substrate (10), said patterns being pre-defined. drawn by a step or a sequence of lithography steps of any nature prior to the step of depositing the first layer (20) of block copolymer (BCP), said patterns being intended to guide the organization of said block copolymer (BCP) by a technique called chemistry-epitaxy or graphoepitaxy, or a combination of these two techniques, to obtain a neutralized or pseudo-neutralized surface.

22. Method according to one of claims 20 to 21, characterized in that the block copolymer comprises silicon in one of its blocks.

23. Method according to one of claims 210 to 22, characterized in that the first layer (20) of block copolymer (BCP) is deposited on a thickness (e + E) at least equal to 1, 5 times the minimum thickness (e) of the block copolymer.

24. Method according to one of claims 1 to 23, characterized in that the solvent of the pre-polymer layer (pre-TC) is selected from solvents or solvent mixtures of which the solubility parameters of Hansen are such that d _r > 10 MPa ^1/2 and / or 5h³10 MPa ^1/2 , and with 5 _d <25 MPa ^1/2 .

25. The process as claimed in claim 24, characterized in that the solvent of the pre-polymer layer (pre-TC) is chosen from alcohols such as methanol, ethanol, isopropanol and 1-methoxy-2- propanol, ethyl lactate, diols such as ethylene glycol or propylene glycol, or dimethylsulfoxide (DMSO), dimethylformamide, dimethylacetamide, acetonitrile, gammabutyrolactone, water or a mixture of those -this.

26. The method of claim 20, characterized in that the composition of the pre-polymer layer (pre-TC) comprises a multi-component mixture of monomers and / or dimers and / or oligomers and / or polymers each carrying functions ensuring crosslinking, as well as different monomer units whose surface energies vary from one monomer unit to another.

27. Method according to one of claims 20 to 26, characterized in that the composition of the pre-polymer layer (pre-TC) further comprises plasticizers and / or wetting agents, added as additives.

28. Method according to one of claims 1 to 27, characterized in that the composition of the pre-polymer layer (pre-TC) further comprises rigid comonomers selected from derivatives having either a cycle (s) ) aromatic (s) in their structure, either mono or multicyclic aliphatic structures, and having a chemical function (s) adapted (s) to the targeted crosslinking reaction; and more particularly norbornene derivatives, isobornyl acrylate or methacrylate, styrenic, anthracene derivatives, acrylate or adamantyl methacrylate.

29. A process for manufacturing a block copolymer nano-lithography mask, said method comprising the steps according to claims 20 to 28 and being characterized in that after the step of nano-structuring of the block copolymer constituting the first layer (20), an additional step consists in removing the top coat layer (TC) in order to leave a nanostructured block copolymer film of minimum thickness (e), then at least one of the blocks (21, 22) of said block copolymer, oriented perpendicular to the interfaces, is removed to form a porous film suitable for use as a nano-lithography mask.

30. Process according to claims 23 and 29, characterized in that when the block copolymer is deposited over a thickness greater than the minimum thickness (e), an excess thickness (E) of said block copolymer is removed simultaneously or successively with removal of the top coat layer (30, TC), to leave a nano-structured block copolymer film of minimum thickness (e), and then at least one of blocks of said block copolymer, oriented perpendicular to the interfaces, is removed to form a porous film capable of serving as a nano-lithography mask.

31. Method according to one of claims 29 to 30, characterized in that the top coat layer (30, TC) and / or the extra thickness (E) of the block copolymer and / or the block (s) (21, 22 ) of the block copolymer is / are removed by dry etching.

32. The method of claim 31, characterized in that the etching steps of the top coat layer (30, TC) and / or the excess thickness (E) of the block copolymer (20, BCP) and one or more blocks (21, 22) of the block copolymer are successively produced in the same etching frame, by plasma etching.

33. Method according to one of claims 29 to 32, characterized in that at the time of the step of crosslinking the top coat layer (30, TC), the stack is subjected to light radiation and / or a electron beam located in certain areas of the top coat layer, in order to create crosslinked areas of top coat (TC) having a neutral affinity for the underlying block copolymer and non-crosslinked areas (pre- TC) having a non-neutral affinity for the underlying block copolymer.

34. Method according to claim 33, characterized in that after the photo-localized crosslinking of the top coat layer (30, TC), the stack is rinsed with the solvent which has allowed the deposition of the pre-polymer layer (pre- TC) to remove non-irradiated areas.

35. Process according to claims 33 and 34, characterized in that another pre-polymer material, which is non-neutral with respect to the underlying block copolymer, is deposited in the previously non-irradiated zones and devoid of a coating layer. top coat, then said non-neutral prepolymer material is exposed to a stimulus in order to crosslink it to the predefined locations.

36. Process according to claims 20 and 33 to 35, characterized in that at the time of the step of annealing the stack at the assembly temperature (Tass) of the block copolymer (BCP), forms are formed. nano-domains (20, 21; 41, 42) perpendicular to the interfaces in areas located opposite the areas of the crosslinked neutral topcoat layer (TC), and nano-domains parallel to the interfaces in areas of the block copolymer located next to areas without cross-linked neutral topcoat layer.

37. A polymeric stack comprising at least two layers of (co) polymer (20, 30) stacked one on the other, characterized in that the upper layer (30), called top coat (TC), deposited on the first (co) polymer layer (20) is obtained by crosslinking in situ according to the method according to one of claims 1 to 36, said stack being intended to be used in applications selected from aerospace surface protection or aeronautics or automotive or wind power, paints, inks, membrane manufacturing, the production of microelectronic, optoelectronic or microfluidic components.