Method for manufacturing a lithography mask with sub-micrometer resolution.

Abstract

"Method for manufacturing a lithography mask with sub-micrometer resolution." The present invention relates to a method for manufacturing a lithography mask comprising at least the steps of: a) having a substrate coated on at least one of its faces with a film of at least one polysaccharide, b) exposing one or more localized areas of said film to radiation from photons or electron beams to cause the breaking of glycosidic bonds of said polysaccharide, and c) bringing said film, having been exposed according to b), into contact with a solvent medium distinct from pure water and having a permittivity ranging from 15 to 81 to selectively dissolve said polysaccharide having been exposed to radiation from photons or electron beams.

Description

Title of the invention: Method for manufacturing a lithography mask with sub-micrometer resolution. Technical field

[0001] The present invention relates to the technical field of lithography and transfer processes using resin masks for the creation of patterns on different substrates and in particular in the field of semiconductors. Previous technique

[0002] Lithography processes are widely used techniques, particularly in the fabrication of microfluidic circuits and in the semiconductor industry. In particular, photolithography is a technique that uses light to create patterns on a thin film to protect silicon wafers during etching or deposition steps. Optical UV (UV / Deep-UV) or electron beam lithography is currently one of the most widely used techniques in the microelectronics industry. This technology uses photosensitive or electrosensitive resins that allow the transfer of a series of patterns onto a substrate.Thus, after spreading a photosensitive resin onto a substrate, patterns can be generated in the applied resin film by illuminating it with light, typically UV, through a physical mask opaque to the radiation and containing openings corresponding to the desired patterns. This selective illumination locally alters the properties of the resin layer. A development step is then performed to reveal the patterns in the resin.

[0003] However, conventional photosensitive resins are derived from petroleum-based polymers and also require the use of organic solvents for their formulation and spreading, as well as toxic alkaline solutions for their development or disposal. Given that the semiconductor ecosystem has committed to achieving carbon neutrality by 2050 to reduce greenhouse gases and conserve energy and water, alternatives to current petroleum-based resin systems are needed. Therefore, there is a drive to develop new, more eco-responsible processes and to offer transfer lithography techniques that are more respectful of the environment and natural resources.

[0004] In this approach, it has already been proposed to use bio-based materials as resins. In this respect, polysaccharides such as dextrin, cellulose and its derivatives, alginates, and in particular chitosan, have attracted considerable interest. Chitosan is a natural polysaccharide derived from chitin, which is the second Chitosan is the most abundant natural biopolymer on Earth after cellulose, primarily derived from fishing industry waste (crustacean shells). Chitosan films have already been shown to enable pattern creation processes without organic solvents or alkali-based developers, by replacing them with a green solvent (deionized water (DI)) [Olha Sysova et al ACS Applied Polymers Mater. JCA I JCA11.2.5208 2021 / 10 / 27; Olha Sysova et al J Appl Polym Sci. 2023;140:e54244.]. Exposure of chitosan to DUV induces its depolymerization by cleaving glycosidic bonds, which decreases the molar mass. The removal of the exposed resin during the development step reveals the patterns. Since chitosan is a cationic polyelectrolyte, its dissolution is currently mainly carried out in acidic aqueous media, where its amino groups are protonated and can thus interact with water molecules, thereby promoting its dissolution.During its development, the low molecular weight chitosan generated in the exposed areas can dissolve in a neutral aqueous medium (DI water, pH 7) due to its low molecular weight. However, uncontrolled deformation of these motifs has been observed, particularly for patterns with a resolution below 1 pm, indicating suboptimal conditions during this development stage.

[0005] Consequently, the present invention aims to propose a development method suitable for producing, from chitosan and more generally from a polysaccharide, transfer masks with sub-micrometer resolution.

[0006] The present invention also aims to propose a method for manufacturing a transfer mask for lithography whose impact on the environment is significantly reduced thanks to a choice of particular materials for this method of manufacture.

[0007] More particularly, the present invention is based on the inventors' observation that the choice of a particular solvent medium for the development step makes it possible, contrary to expectations, to increase the resolution up to a scale of 400 nm. Summary of the invention

[0008] Thus, the present invention relates primarily to a method for manufacturing a lithography mask comprising at least the steps of:

[0009] a) have a substrate coated on at least one of its external faces with a film of at least one polysaccharide,

[0010] b) exposing one or more localized areas of said film to photon radiation, in particular to DUV radiation, or electron beams, in order to cause the breaking of glycosidic bonds of said polysaccharide,

[0011] c) bringing said film, having been exposed according to b), into contact with a solvent medium capable of selectively dissolving said polysaccharide, having been exposed to UV radiation, and

[0012] d) where appropriate, expose said substrate treated in c) to an annealing step, in particular at a temperature of 150°C and in particular for approximately 5 minutes, to remove said solvent medium,

[0013] with said solvent medium in c) being distinct from pure water and having a permittivity ranging from 15 to 81.

[0014] According to another aspect, the present invention also relates to a method for forming at least one localized area of ​​micro- and / or nano-electronic and / or optical components on the surface of a semiconductor substrate, comprising at least the steps of:

[0015] a) to form on the surface of said substrate, a deposit of at least one polysaccharide from an aqueous solution of said polysaccharide,

[0016] b) exposing one or more localized areas of said deposit formed in a) to photon radiation, in particular to DUV radiation, or electron beams to cause the breaking of glycosidic bonds of said polysaccharide,

[0017] c) bringing at least the areas exposed in b) into contact with a solvent medium, to selectively remove the exposed polysaccharide,

[0018] d) where appropriate, expose said substrate treated in c) to an annealing step, in particular at a temperature of 150°C and in particular for approximately 5 minutes, to remove said solvent medium,

[0019] e) form a micro- and / or nano-electronic and / or optical component on at least one of the areas treated in c), preferably by etching and

[0020] f) remove the deposit of unexposed polysaccharide on said substrate with said solvent medium in c) being distinct from pure water and having a permittivity ranging from 15 to 81.

[0021] For the purposes of the invention, the term "solvent medium" means a medium consisting of a single organic solvent, a mixture of several organic solvents or a mixture of water with one or more organic solvents.

[0022] As can be seen from the examples below and in contrast to the essentially aqueous formulations proposed in the prior art for carrying out a development, the choice of the particular solvent medium retained according to the invention makes it possible to effectively eliminate the polysaccharide components appearing in the areas exposed to electromagnetic radiation while obtaining a very minimal dissolution of the polysaccharide(s) constituting the unexposed areas.

[0023] Similarly, as illustrated by the examples below, obtaining this selectivity makes it possible to effectively enhance the contrast of the process and, consequently, to improve the degree of conformity of the resulting structure on the surface of the substrate with the exposed pattern.

[0024] Advantageously, the polysaccharides usable according to the present invention are bio-based polysaccharides, that is to say, of natural origin, also called biopolysaccharides. They can notably be obtained from biodegradable waste such as chitosan derived from marine waste (e.g., shrimp shells or squid feathers).

[0025] According to a particular embodiment, the polysaccharide is or comprises at least chitosan, one of its derivatives or salts.

[0026] Other characteristics of the objects according to the invention will become clearer from the description, examples and figures that follow.

[0027] In the following text, the expressions "between ... and ...", "ranging from ... to ..." and "varying from ... to ..." are equivalent and are meant to mean that the limits are included, unless otherwise stated. Brief description of the drawings

[0028] [Fig-1] It presents top-view CD-SEM images with patterns of dense chitosan half-step (HP) trenches (a) HP 5 qm (b) HP 2 qm (c) HP 1 qm (d) HP 0.7 pm after DUV exposures at 700 mJ / cm2.

[0029] [Fig.2] It presents top-view CD-SEM images of trench patterns dense chitosan of 400, 500 and 600 nm (half-steps) obtained using different exposure doses for DUV exposure (400 mJ / cm2 or 700 mJ / cm2) and different development times (60 or 120 s).

[0030] [Fig.3] It presents pattern profiles obtained with AFM-3D at a dose exposure of 400 mJ / cm2 for DUV exposure for a chitosan formulation developed using DMSO for 60 s (Figure 3a) or 120 s (Figure 3b).

[0031] [Fig.4] It presents pattern profiles obtained with AFM-3D for a Chitosan formulations developed in water for 120 s or in DMSO for 60 s with an exposure dose of 400 mJ / cm2 for DUV exposure, (Figure 4a) or a dose of 700 mJ / cm2 (Figure 4b) were used.

[0032] [Fig. 5] Figure 5a shows pattern profiles obtained by AFM-3D demonstrating Regular patterns at 600, 500, and 400 nm can be obtained using DMSO as a developer. The CD-SEM images shown in Figure 5b illustrate the patterns with good contrast.

[0033] [Fig.6] presents top-view CD-SEM images of trench patterns dense chitosan of 400 to 600 nm (half-steps) obtained using chitosan formulations containing a photoacid generator (PAG) and different exposure doses for DUV exposure - Development was carried out using DMSO (Figure 6a) or water (Figure 6b). Detailed description solvent medium

[0034] As can be seen from the above, the process of the invention is based in particular on the characterization by the inventors of a particular solvent medium for the development of polysaccharide(s) exposed to DUV radiation.

[0035] According to the invention, the term "solvent medium" is meant to designate a medium consisting of a single organic solvent, a mixture of several organic solvents or a mixture of water with one or more organic solvents.

[0036] Of course, one or more additional additives may be carried in the solvent medium. However, the mixture of this or these additives, particularly like those detailed below, with the solvent(s) forming the solvent medium is not covered by the term "solvent medium" according to the invention.

[0037] The solvent medium retained according to the invention is distinct from pure water, distilled or not, and comprises at least one organic solvent, or even consists of a single solvent, whose relative dielectric permittivity, also called permittivity or dielectric constant, varies from 15 to 81.

[0038] This permittivity can be evaluated via the theory described in the article: Dielectric constant of mixed solvents based on perturbation theory, Fluid Phase Equilibria, 555 (2022), 113346.

[0039] In particular, the solvent medium according to the invention is formed in whole or in part of at least one solvent selected from gamma-valerolactone, methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate (Rhodiasolv Polarclean), dimethyl sulfoxide, methanol, acetone, 1,2-propanediol, 1,5-pentanediol, 1,6-hexanediol, dimethyl isosorbide and mixtures thereof.

[0040] For example, the solvent medium can be chosen from a mixture of water and at least one solvent chosen from gamma-valerolactone, methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate (Rhodiasolv Polarclean), dimethyl sulfoxide, methanol, acetone, 1,2-propanediol, 1,5-pentanediol, 1,6-hexanediol, dimethyl isosorbide.

[0041] According to a particular embodiment, the solvent medium of the invention comprises at least dimethyl sulfoxide, DMSO, optionally mixed with water.

[0042] In particular, the solvent medium is an aqueous solution of DMSO in a volume proportion of 10 to 75%, and in particular 25% DMSO. Polysaccharide

[0043] The invention also relies on the choice of a polysaccharide as a resin.

[0044] Polysaccharides are polymers of the carbohydrate family consisting of several sugars linked together by glycosidic bonds.

[0045] In the context of the present invention, the polysaccharide compound may consist of sugars but also includes an amino derivative, a nitro derivative, a sulfo derivative, a halogenated derivative, a phosphoric acid derivative, an ether, an ester, or a salt thereof. Similarly, the polysaccharide compound may be a copolymer which, in addition to saccharide monomer units, also comprises non-saccharide monomer units.

[0046] By way of illustration and not limitation, examples of these polysaccharides may include dextrin, cellulose, pullulans, alginates, chitosan, their salts and derivatives.

[0047] As regards the salt, it may be a salt of a monobasic, dibasic, tribasic or tetrabasic acid. In particular, the salt may be a salt of a carboxylic acid, especially a salt of formic, acetic or propionic acid, or mixtures thereof.

[0048] Among these polysaccharides, chitosan, its salts and its derivatives are of particular interest.

[0049] In a more particular embodiment, the chitosan salt or derivative can be chosen from chitosan acetate, chitosan formate, chitosan lactate, chitosan glycolate, chitosan succinate, chitosan chloride, chitosan phthaloyl citrate, chitosan carboxymethyl and chitosan succinyl.

[0050] It is known that chitosan can be characterized by its degree of acetylation (DA i.e. the mole fraction of N-acetyl glucosamine units in the polymer chain) and by its mass average molar mass Mw.

[0051] Within the framework of the invention, the mass average molar masses Mw or number averages Mn (also called molecular weights) of chitosan are determined by size exclusion chromatography coupled with light scattering, the experimental conditions of which are described in the publication "A. HONTEHAULT, C. VFFON, A. DO AD Biomaterials, 25(8), 933-943 2005".

[0052] As for the degree of acetylation (DA), it can be determined using the proton NMR technique, following the methodology of Hirai (Asako Hirai, Hisashi Odani, Akio Nakajima, Polymer Bulletin (1991) Volume 26, Issue: 11th Publisher: Springer, Pages: 87-94).

[0053] In the context of the invention, advantageously, a chitosan is used which preferably has a mass average molar mass M ranging from 200 to 700 kDa, preferably belonging to the range of 550 to 650 kDa and / or a degree of acetylation ranging from 2 to 50% and preferably from 25 to 40%.

[0054] Such chitosan has notably been used in the examples that will follow and has made it possible to obtain patterns with excellent resolution.

[0055] Of course, it is possible to implement a mixture of at least two polysaccharides, including at least chitosan.

[0056] According to one embodiment, for step a) of deposition, an aqueous solution of chitosan DMSO, optionally containing an acid, preferably in an equimolar quantity to the amino functions of glucosamine units. Such an acid is notably acetic acid, citric acid, lactic acid or tartaric acid.

[0057] The concentration of chitosan in the solution used for the deposition can vary from 0.1 to 9% preferably from 0.5 to 5% by mass relative to the total weight of the solution.

[0058] In order to stimulate the localized degradation of the polysaccharide during the development step following the exposure step, the aqueous deposition solution may further contain one or more additives, in particular as detailed below. Additives

[0059] By way of illustration and not limitation, the following additives may be considered in the process of the invention:

[0060] - photoinitiators, preferably water-soluble, such as, for example, the riboflavin, from the commercial product Irgacure 2959®, among others

[0061] - photoacid generators, also called "PAGs", preferably water-soluble, for example, triphenylsulfonium and diphenylsulfonium salts, and O-nitrobenzyl esters,

[0062] - plasticizers, preferably water-soluble, such as glycerol and sorbitol

[0063] - dissolution inhibitors, preferably water-soluble, such as for example the 1 -piperidinethanol

[0064] - crosslinking agents, preferably water-soluble, such as glutaraldehyde, glyoxal, formaldehyde, epichlorohydrin and isocyanates.

[0065] The implementation of these additives falls within the skills of a person skilled in the art who knows how to adjust their quantities.

[0066] If present, these additives are introduced via the polysaccharide formulation.

[0067] Thus; according to an advantageous embodiment, said polysaccharide of step a) is associated with at least one additive selected from surfactants, photoinitiators, preferably water-soluble, and in particular riboflavin and / or at least one generator of a photoacid “PAG”, preferably water-soluble, in particular at least one triphenylsulfonium and diphenylsulfonium salt, and O-nitrobenzyl esters. Method according to the invention Step a) of filing

[0068] As stated above, the process includes a first step of depositing the aforementioned polysaccharide solution onto a substrate.

[0069] This substrate can be of a very diverse nature, metallic, semiconductor, dielectric, glass, or plastic, particularly like those used in the field of manufacturing electronic components and circuits and transistors.

[0070] For obvious reasons, this substrate used is resistant to the conditions implemented in the process according to the invention, particularly during steps c) of development and e) of final elimination of the biopolymer.

[0071] It is possible to use a single-layer substrate or one comprising one or more surface layers, the surface layer being able to be partially eliminated, during the step of using the mask obtained according to the invention, to form a component on the surface of the substrate in particular by etching.

[0072] By way of illustration of suitable substrate materials, metals, semiconductors (particularly silicon), titanium oxide, silicon oxides (native oxides and sub-oxides), and silica (SiO2) may be specifically mentioned. Polysaccharide films may also be deposited on nitride and carbide substrates, particularly those of silicon or titanium.

[0073] For example, the substrate may consist of a semiconductor support, in particular silicon or a metal III, IV, or V, or an alloy of these metals, coated with a layer of a dielectric material, this layer being removed during the etching step in the areas not coated with polysaccharide. Crystalline silicon, possibly doped with N or P, is a widely used example of a semiconductor support. Such a substrate is particularly advantageous for forming a micro- and / or nano-electronic and / or optical component by etching.

[0074] The step of forming the polysaccharide film, preferably of chitosan or one of its salts or derivatives, on the substrate is carried out by depositing an aqueous solution of this polysaccharide, followed by a dehydration step, such as drying, to obtain a polysaccharide film on the surface. In order to promote localized degradation of the polysaccharide during the subsequent exposure step (b), the deposition solution may also contain an additive, for example, a photocatalyst in the case of exposure under UV electromagnetic radiation.

[0075] The polysaccharide film is generally formed by spin coating, but any other method may be suitable. Preferably, the polysaccharide film is produced by depositing an aqueous solution of said polysaccharide, in particular by spin coating, followed by a dehydration step.

[0076] The drying step, which can be carried out between the deposition and exposure steps, most often consists of a heat treatment, also called annealing, particularly at a temperature in the range of 70 to 160°C. According to one embodiment, this step is carried out at a temperature of 150°C for approximately 5 minutes.

[0077] Step a) of deposition on the substrate leads to the formation of a film that adheres to the substrate. In a particular embodiment, the polysaccharide film deposited on the substrate has a thickness of 20 to 190 nm, preferably 50 to 160 nm. Step b) of exposure

[0078] Step b) of exposure can be carried out by any optical radiation technique using UV or electron beams employed in the field of lithography. For example, it can be performed by exposure through a mask placed on the polysaccharide film or directly by electron beams without a mask.

[0079] This insolation is advantageously achieved through irradiation under UV radiation.

[0080] More specifically, the optical radiation is UV or deep UV radiation, DUV. This exposure mode can notably be carried out in the presence of a photocatalyst integrated into the polysaccharide film via the polysaccharide solution considered to form this film.

[0081] The conditions retained for this step are adjusted to allow the breaking of bonds in the polysaccharide structure undergoing exposure and the generation of polysaccharide fragments.

[0082] In particular, the energy deposited can vary from 10 to 1000 mJ / cm2, in particular from 50 to 700 mJ / cm2, in particular for a duration varying from a few seconds to a few minutes. Step c) of development

[0083] As can be seen from the above, step c) of development, following step b) of exposure, is carried out with a solvent medium according to the invention and as detailed above and capable of dissolving the polysaccharide present on the areas exposed to electromagnetic radiation and in particular DUV, in a selective manner with respect to the unexposed areas.

[0084] The choice of the solvent(s) constituting the solvent medium according to the invention and the contact time of this solvent medium with the areas having been exposed are adjusted to allow the selective removal of this exposed polysaccharide.

[0085] For carrying out the development step, the substrate coated with said exposed polysaccharide can be treated, for example by static immersion of said substrate in the solvent medium, in particular in the form of a puddle dispensed in static mode, or by dynamic dispensing, in particular by vaporization, of the solvent medium onto said substrate by vaporization.

[0086] According to one embodiment, the solvent medium consists of one or more solvents and is free of any additional reagents. In particular, this solvent medium is free of any transition elements such as zinc, nickel, copper, cobalt, and iron.

[0087] By removing the polysaccharide from the exposed areas, one or more areas of substrate not covered with polysaccharide are thus formed, corresponding to the openings of the mask that have been exposed to electromagnetic radiation.

[0088] According to a particular embodiment, the exposed polysaccharide film is only brought into contact with a single solvent medium according to the invention. This contact may be repeated if necessary. However, the exposed film is not brought into contact with an aqueous solution other than a solvent medium according to the invention.

[0089] The development step does not eliminate the polysaccharide present on the unexposed support areas. The polysaccharide remaining there then constitutes a mask, called a transfer mask, around the developed area(s).

[0090] The process according to the invention may include a step of removing this solvent medium or even drying it after the development step. Such treatment has, in particular, the advantage of improving the resolution of the lithography operation and of fixing the polysaccharide layer, so that the patterns defined by the lithography step do not become distorted.

[0091] As described above, the process of the invention may include a subsequent step of treating at least one area not covered with polysaccharide, to form at least one component generally micro- and / or nano-electronic and / or optical, preferably by etching.

[0092] Any dry or wet etching technique used in the semiconductor industry can be employed. Wet etching is performed by chemical attack in aqueous solution. For example, silica can be etched by a partially dilute solution of hydrofluoric acid buffered with ammonium fluoride. Dry etching combines chemical attack and beam etching and can be carried out by various methods: ion beam etching (IBE), reactive ion etching (RIE), or gaseous chemical etching.

[0093] This etching step is then followed by a step of removing the unexposed polysaccharide film remaining on the surface of the substrate, in order to obtain a structure on the surface of the substrate conforming to a predefined pattern.

[0094] With the process according to the invention, it is possible, thanks to the solvent medium retained for the development step, to form patterns which exhibit very good resolution, and in particular patterns advantageously of a sub-micrometer size.

[0095] The process according to the invention can be implemented in all known applications of lithography and transfer processes, and in particular, in the semiconductor industry, for example, for the manufacture of transistors, printed circuits, memory cards...

[0096] Other characteristics, variants and advantages of the composite materials according to the invention, their preparation and implementation, will become clearer from reading the examples and figures that follow, given by way of illustration and not limitation of the invention. Materials and Methods Material

[0097] Chitosan obtained from squid feathers was supplied by Mahtani Chitosan from lot type 114 with a degree of acetylation (DA) of 2% determined by 'H NMR, an average molar mass (Mw) of 670kg / mol and a dispersity (D) of 1.8 determined by size exclusion chromatography. Characterization methods

[0098] The degree of acetylation (DA) of chitosan was determined by 1H NMR spectroscopy.

[0099] The thickness of the chitosan films on the bare silicon wafers was measured using a Nanometrics ellipsometer from KLA-Tencor using a Cauchy model.

[0100] Post-lithographic imaging and CD of patterns were measured with a HITACHI CG4000 top-view CD-SEM, with an accelerating voltage of 300 V. Profiles were made with a Bruker InSight 3D AFM (Atomic Force Microscopy), an ultrasonic camera and a handheld camera. Lithography protocol and equipment

[0101] The chitosan solution is deposited by centrifugation onto a SCREEN SOKUDO DUO spreading and developing track in a dedicated aqueous-type spreading unit.

[0102] DUV exposures were performed using a NIKON NSR370E 193 nm sec scanner to expose chitosan films approximately 100 nm thick. Irradiation doses of 50 to 900 mJ / cm2 through a binary mask with multiple characteristics were applied to the deposited chitosan films, acting as a positive resistance under DUV irradiation by chain depolymerization. Example 1

[0103] Synthesis of 0.5% (w / v) acetylated chitosan and its formulation

[0104] Chitosan was acetylated to 0.5% (w / v) in a hydroalcoholic mixture of 1,2- propanediol and AcOH (50 / 50 v / v). A quantity of acetic anhydride was stoichiometrically added to the D-glucosamine (GlcN) unit of chitosan and mixed for 18 h under vigorous mechanical stirring to achieve the target D-acetic anhydride concentration. The chitosan solution was then filtered through cellulose membranes. Acetylated chitosan was finally precipitated with NH4OH and washed with water. Deionized and lyophilized, acetylated chitosan with a DA of 35%, a Mw of 670 kDa, and a dispersity of 1.8 was obtained. This chitosan was solubilized with an aqueous solution of AcOH (stoichiometry to the unit GlcN) for 18 h. The solution was then filtered through 0.45 µm cellulose membranes before use.

[0105] In one embodiment, an aqueous solution of dimethyl-2,4-dihydroxyphenylsulfonium triflate was prepared by dissolving the powder (0.1% w / w) in deionized water. This was then added to the chitosan solution and stirred until homogenized.

[0106] In another embodiment, the chitosan solution is supplemented with riboflavin via an aqueous riboflavin solution which was prepared by dissolving the powder (0.008% w / w) in deionized water. Example 2 Transfer mask training

[0107] The substrate used is composed of an H-doped silicon support with an orientation <001> bearing on its surface a layer of silicon oxide with a thickness of 90 nm (Siltronix).

[0108] The chitosan solution selected from Example 1 (DA 35%, Mw 693 kDa) is spread by spin coating at speeds between 200 and 2500 rpm for 30 seconds. Films with thicknesses between 70 and 150 nm are obtained depending on the spin speed and concentration. The films were annealed for 5 minutes at 150°C to remove residual water.

[0109] For the DUV exposure, the substrates were irradiated using a binary mask with trench patterns with a given critical dimension (CD).

[0110] The development step was carried out in a standard development unit with

[0111] either DI water for 60 s, or pure DMSO for 60 or 120 seconds. Example 3

[0112] Formation of transfer masks not in accordance with the invention

[0113] The chitosan solution selected is that of example 1.

[0114] The irradiation protocol of Example 2 is applied with an irradiation dose of 700 mJ / cm2.

[0115] Dense chitosan half-step trench patterns (a) HP 5 pm (b) HP 2 pm (c) HP 1 pm (d) HP 0.7 pm are produced.

[0116] The development is carried out with DI water (pH7) for 24 s.

[0117] Fig. 1 presents top-view CD-SEM images of the dense chitosan trench patterns thus obtained.

[0118] It is observed that below 1 sqm, there is an uncontrolled deformation of the patterns, which limits the resolution of the chitosan resin. Example 4 Transfer mask training

[0119] The chitosan solution selected is that of Example 1 containing riboflavin.

[0120] The irradiation protocol of Example 2 is applied with irradiation doses of 400 or 700 mJ / cm2.

[0121] Dense chitosan trench patterns with half-steps of 400, 500 and 600 nm are produced.

[0122] The development is carried out according to the process of the invention with DMSO for 60 or 120 s.

[0123] [Fig.2] presents top-view CD-SEM images of dense trench patterns thus obtained.

[0124] Fig. 3 presents pattern profiles obtained with AFM-3D at an exposure dose of 400 mJ / cm2 for DUV exposure for the chitosan formulation developed using DMSO for 60 s (Figure 3a) or 120 s (Figure 3b).

[0125] It can be seen in the 3D patterns of 700 nm trenches obtained from AFM images that the very pronounced erosion of the upper part of the patterns, typical of samples developed with aqueous solutions, does not occur during development with DMSO. Furthermore, the patterns are very regular when DMSO is used.

[0126] On the other hand, the trenches obtained after development with the aqueous solution are not regular but reach a greater depth.

[0127] It is further noted that by increasing the exposure dose, from 400 to 700 mJ / cm2, deeper trenches can be obtained (Figure 4b), while maintaining the regularity of the patterns. Example 5

[0128] The chitosan solution selected is that of example 1 containing riboflavin.

[0129] The irradiation protocol of Example 2 is applied with irradiation doses of 400 or 700 mJ / cm2

[0130] Dense chitosan half-stepping 700 nm trench patterns are produced.

[0131] The development is carried out according to the process of the invention with DMSO for 60 s or water for 120 s.

[0132] Figures 4a and 4b show the pattern profiles obtained with the AFM-3D with an exposure dose of 400 mJ / cm2 for DUV exposure, (Figure 4a) and a dose of 700 mJ / cm2 (Figure 4b).

[0133] As shown in [Fig. 2], DMSO, used for development, allows the resolution of much smaller motifs (down to 400 nm). Although it is not possible to observe the top view of chitosan motifs developed using aqueous solutions by CD-SEM due to the lack of contrast in the unresolved structures, it is again confirmed using AFM-3D that the motif profiles are definitively different when using aqueous solutions or DMSO. Example 6

[0134] The chitosan solution selected is that of example 1 containing riboflavin.

[0135] The irradiation protocol of Example 2 is applied with an irradiation dose of 700 mJ / cm2.

[0136] Dense chitosan trench patterns with half-steps of 400, 500 and 600 nm are produced.

[0137] The development is carried out according to the process of the invention with DMSO or water for 60 s.

[0138] Figure 5a shows the pattern profiles obtained by AFM-3D and demonstrates that regular patterns of 600, 500, and 400 nm can be obtained using DMSO as the developer. The CD-SEM images shown in Figure 5b illustrate the patterns with good contrast. Example 7

[0139] The chitosan solution selected is that of example 1 containing PAG.

[0140] The irradiation protocol of Example 2 is applied with an irradiation dose of 100, 200, 300 and 700 mJ / cm2

[0141] Dense chitosan half-step trench patterns of 400 nm are produced.

[0142] The development is carried out according to the process of the invention with DMSO for 120 s or water for 60 s.

[0143] Figures 6a and 6b show top-view CD-SEM images of trench patterns thus obtained.

[0144] When water is used for development ([Fig. 6], bottom), it can be observed that low exposure doses do not produce regular patterns (100, 200 mJ / cm²), and that increasing doses (300, 700 mJ / cm²) significantly distort the pattern. When DMSO is used for development, this effect is eliminated, and more contrasting patterns can be obtained by increasing the exposure dose.

Claims

Demands

1. A method for manufacturing a lithography mask comprising at least the steps of: a) having a substrate coated on at least one of its faces with a film of at least one polysaccharide, b) exposing one or more localized areas of said film to radiation from photons or electron beams to cause the breaking of glycosidic bonds of said polysaccharide, c) contacting said film having been exposed according to b) with a solvent medium capable of selectively dissolving said polysaccharide having been exposed to radiation from photons or electron beams and, d) where appropriate, exposing said substrate treated in c) to an annealing step to remove said solvent medium, with said solvent medium in c) being distinct from pure water and having a permittivity ranging from 15 to 81.

2. A method for forming at least one localized area of ​​a micro- and / or nano-electronic and / or optical component on a semiconductor substrate comprising at least the steps of: a) forming on the surface of said substrate a film of at least one polysaccharide from an aqueous solution of said polysaccharide, b) exposing one or more localized areas of said film formed in a) to radiation from photons or electron beams to cause the breaking of glycosidic bonds of said polysaccharide, c) contacting at least the areas exposed in b) with a solvent medium to selectively remove the exposed polysaccharide, d) where appropriate exposing said substrate treated in c) to an annealing step, e) forming a micro- and / or nano-electronic and / or optical component on at least one of the areas treated in c), and f) removing the deposit of unexposed polysaccharide from said substrate.with said solvent medium in c) being distinct from pure water and having a permittivity ranging from 15 to 81.

3. A method according to any one of the preceding claims, wherein said solvent medium comprises at least one organic solvent, or even consists of a single solvent, the dielectric permittivity of which varies from 15 to 81.

4. A method according to any one of the preceding claims, wherein said solvent medium comprises at least one solvent having a permittivity ranging from 15 to 81.

5. A process according to any one of the preceding claims wherein said solvent medium is formed in whole or in part of at least one solvent selected from gamma-valerolactone, methyl-5-(dimethylamino)-2-methyl-5-oxopentanoate (Rhodiasolv Polarclean), dimethyl sulfoxide, methanol, acetone, 1,2-propanediol, 1,5-pentanediol, 1,6-hexanediol, dimethyl isosorbide and mixtures thereof.

6. A process according to any one of the preceding claims, wherein said solvent medium comprises at least dimethyl sulfoxide, DMSO.

7. A process according to any one of the preceding claims, wherein said polysaccharide is or comprises at least chitosan, one of its derivatives or salts, and in particular chitosan having a mass average molar mass M ranging from 200 to 700 kDa, preferably from 550 to 650 kDa, and / or a degree of acetylation ranging from 2 to 50%, and preferably from 25 to 40%.

8. A method according to any one of the preceding claims, wherein said substrate is selected from metals, semiconductors in particular silicon, titanium oxide, silicon oxides (native oxides and sub-oxides) and silica (SiO2).

9. A method according to any one of the preceding claims, wherein said photon or electron beam radiation is UV or deep UV radiation, DUV, in particular from 10 to 1000 mJ / cm2, in particular from 50 to 700 mJ / cm2.

10. A process according to any one of the preceding claims, wherein said polysaccharide is associated with at least one additive selected from surfactants, photoinitiators, preferably water-soluble, and in particular riboflavin and / or at least one generator of a photoacid "PAG", preferably water-soluble, in particular at least one triphenylsulfonium and diphenylsulfonium salt, and O-nitrobenzyl esters.

11. A method according to any one of the preceding claims, wherein said film of at least one polysaccharide is produced by deposition of an aqueous solution of said polysaccharide, in particular by centrifugal coating, followed by a dehydration step.

12. A method according to any one of the preceding claims, wherein said step c), is carried out by static immersion of said substrate in the solvent medium, in particular in the form of a pool dispensed in static mode, or by dynamic dispensing, in particular by vaporization, of the solvent medium onto said substrate.

13. A method according to any one of claims 2 to 12, wherein said component generally micro- and / or nano-electronic and / or optical is formed by etching.

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