All-inorganic sol-gel surface structuring process

Abstract

The field of the invention is that of all-inorganic surfaces, and more specifically that of the structuring of all-inorganic surfaces.

Description

Title of the invention: All-inorganic sol-gel surface structuring process technical field

[0001] The field of the invention is that of all-inorganic surfaces, and more specifically that of the structuring of all-inorganic surfaces.

[0002] In particular, the present invention relates to an all-inorganic sol-gel surface structuring process. Technological background

[0003] All-inorganic materials, in particular oxide materials, exhibit These materials possess properties not found in all-organic polymer materials or organic-inorganic hybrid materials. Examples include their high refractive index for optics, their electrical properties (semiconductive, dielectric, etc.) for microelectronics, and their mechanical strength (hardness, abrasion resistance) for applications under extreme conditions. These oxide materials can also undergo specific heat treatments, transforming them into all-inorganic, non-oxide materials, such as nitrided materials, which exhibit optical properties or electrical conductivity comparable to those of a metal. They can therefore be used in numerous application areas.

[0004] All-inorganic materials can, for example, be obtained by a sol-gel process. This process is based on an inorganic polymerization method (liquid-to-solid transformation) leading to oxide materials in extremely varied forms, particularly in the form of thin films.

[0005] It is possible to structure these thin films by photolithography. However, photolithography limits the size of the photoetched patterns to a micrometer dimensionality. Several technologies exist that allow for reducing this dimensionality for all-inorganic nanometer sol-gel patterns, but they generate costs that are not compatible with all applications. Furthermore, the need for structuring on large or complex surfaces is not compatible with electron beam technology (Saifullah et al., Nano Letters 2003, 3, 11, 1587-1591).

[0006] Nanoimprint lithography (NIL) without etching or nano-embossing can also be used to structure thin films of all-inorganic materials. However, a recurring problem with this technique is that it does not allow for complete exposure of the substrate between the printed patterns (total exposure of the substrate). substrate), i.e., there is always a residual resin layer between the patterns after embossing. This limitation is problematic for many applications where contrasts in surface chemical composition are required, for example, when nanostructured surfaces are intended for optical applications (diffraction gratings) or to serve as substrates for the selective epitaxy of nanostructured materials. Furthermore, alternative processes such as reactive ion etching (RIE) and ablation limit the size, nature, or shape of the substrate.

[0007] In this context, the present invention aims to remedy these problems.

[0008] In this context, the present invention aims to satisfy at least one of the objectives following.

[0009] One of the objectives of the present invention is the provision of an all-inorganic surface structuring process.

[0010] Another objective of the present invention is the provision of an all-inorganic surface structuring process, which can be used to produce substrates having patterns on the order of nanometers or micrometers.

[0011] Another objective of the present invention is the provision of an all-inorganic surface structuring process, which allows the substrate to be completely exposed between the printed patterns.

[0012] Another objective of the present invention is the provision of an all-inorganic surface structuring process that is simple, easy to implement and economical. Summary

[0013] The invention relates primarily to an all-inorganic sol-gel surface structuring process comprising the following steps: a. Deposition of a soil on a solid support and formation of a gel layer, the soil comprising (i) at least one inorganic precursor comprising at least one inorganic monomer and / or at least one inorganic polymer and / or at least one inorganic cluster based on at least one metal and / or at least one semiconductor, and (ii) at least one photosensitive compound, b. Structuring the gel layer using a structured buffer, or transferring the gel layer onto another support, c. Isolation of the gel layer with an irradiation source, preferably using a mask, steps b. and c. being able to be carried out simultaneously or successively: step b. before step c., or step c. before step b..

[0014] This process is easy to implement and makes it possible to obtain a layer of entirely inorganic material that can have patterns on the order of nanometers. Furthermore, this technique also makes it possible to completely expose the substrate between the printed patterns. Brief description of the drawings Fig. 1

[0015] [Fig. 1] shows a scanning electron microscopy image of the structured all-inorganic surface obtained in the example (scale 2 µm). Fig. 2

[0016] [fig-2] shows a photograph obtained by scanning electron microscopy of the structured all-inorganic surface obtained in the example (scale 1 pm). Fig. 3

[0017] [fig.3] shows a photograph obtained by scanning electron microscopy of the structured all-inorganic surface obtained in the example (scale 200 nm). Detailed description

[0018] By "structured all-inorganic surface," we mean, for example, a surface that includes a network of metal-oxygen-metal bonds. Preferably, the structured all-inorganic surface does not include an organic network having, for example, a succession of C-C bonds.

[0019] The invention relates primarily to an all-inorganic sol-gel surface structuring process comprising the following steps: a. Deposition of a soil on a solid support and formation of a gel layer, the soil comprising (i) at least one inorganic precursor comprising at least one inorganic monomer and / or at least one inorganic polymer and / or at least one inorganic cluster based on at least one metal and / or at least one semiconductor, and (ii) at least one photosensitive compound, b. Structuring the gel layer using a structured buffer, or transferring the gel layer onto another support, c. Isolation of the gel layer with an irradiation source, preferably using a mask, steps b. and c. being able to be carried out simultaneously or successively: step b. before step c., or step c. before step b..

[0020] The soil comprises (i) at least one inorganic precursor comprising at least one inorganic monomer and / or at least one inorganic polymer and / or at least one inorganic cluster based on at least one metal and / or at least one semiconductor, and (ii) at least one photosensitive compound. The concentration of the inorganic precursor in the soil may be between 0.01 mol / L and 5 mol / L, preferably between 0.1 mol / L and 2 mol / L.

[0021] Thus, the inorganic precursor (i) can be selected from: - inorganic monomers comprising at least one metal and / or at least one semiconductor, - inorganic polymers comprising at least one metal and / or at least one semiconductor, - inorganic clusters comprising at least one metal and / or at least one semiconductor, and - their combinations.

[0022] According to one embodiment, the inorganic precursor consists of at least one inorganic monomer and / or at least one inorganic polymer and / or at least one inorganic cluster based on at least one metal and / or at least one semiconductor.

[0023] According to one embodiment, the monomer and / or polymer and / or inorganic cluster comprises at least one metal, preferably chosen from: Zn, Ti, Pb, La, Nb, Zr, Ta, Fe, Al, W, Hf, and their combinations.

[0024] According to another embodiment, the monomer and / or polymer and / or inorganic cluster comprises at least one metal and one Si atom. Preferably, the metal is chosen from: Zn, Ti, Pb, La, Nb, Zr, Ta, Fe, Al, W, Hf, and their combinations.

[0025] Among the inorganic monomers that can be used, mention may be made of metal alkoxides and metal acetates. In particular, mention may be made of titanium alkoxide, such as tetraisopropylorthotitanate, and zinc acetate.

[0026] The photosensitive compound (ii) is a compound that reacts to light irradiation (UV or visible). This compound is preferably chosen from among the [3-diketones or aromatic ketones. The molar ratio between (ii) the photosensitive compound and (i) the inorganic precursor is between 0.1 and 5, preferably between 0.3 and 2.

[0027] Among the [3-diketones, examples include compounds of the formula R-(CO)-CH2-(CO)-R', where R and R' independently represent an alkyl group or an aryl group. In particular, acetylacetone and benzoylacetone are examples.

[0028] Among aromatic ketones, examples include compounds with the formula R”-(CO)-R”', where R” represents an aryl group, and R”' represents an alkyl or aryl group. In particular, benzophenone and acetophenone are examples.

[0029] Advantageously, the sol comprises an organic solvent. The solvent may, for example, be chosen from among alcohols, or butyl acetate, dimethyl formamide, and ethylene glycol. Preferably, the organic solvent is an alcohol. Among the alcohols, examples include C1-C6 alcohols, such as methanol, ethanol, propanol, and butanol. The solvent may also be chosen from among high-boiling-point solvents, for example, solvents with a boiling point above 100°C. The molar ratio between the organic solvent and the inorganic precursor may be between 2 and 1000, preferably between 5 and 100.

[0030] The soil may further comprise a chemical additive, preferably an amine. Among the amines, amino alcohols such as ethanolamine and diethanolamine may be mentioned. The molar ratio between the chemical additive and the inorganic precursor can be between 0.1 and 5, preferably between 0.5 and 3.

[0031] The process may include, prior to step a., a soil preparation step. The soil preparation step may be carried out by mixing the soil components.

[0032] The deposition of the soil on the solid support can be carried out by techniques well known to those skilled in the art, such as spin-coating, dip-coating, inkjet-coating or spray-coating.

[0033] The solid support can be any type of support. For example, it can be vitreous or ceramic materials, polymers, elastomers, metals, single crystals such as silicon, or micro- or nano-structured pads.

[0034] According to a first embodiment, step a. is a step of depositing a soil on a solid support and step b. is the structuring of the gel layer using a structured buffer.

[0035] According to a second embodiment, step a. is a step of depositing a soil onto a solid support which is a structured buffer, and step b. is the transfer of the gel layer onto another support. This transfer is carried out by pressing the structured buffer with the gel layer onto the other support, preferably under a certain pressure and temperature.

[0036] Step b. or step a. is carried out using a structured buffer. Advantageously, the structured buffer comprises motifs on the order of tens of nanometers and / or micrometers. The structured buffer may be a flexible buffer, such as an elastomeric buffer. Preferably, the buffer is made of PDMS.

[0037] The pad may include patterns having at least one dimension between 10 nm and a few mm, or between 10 nm and 1 mm, or between 20 nm and 500 pm, or between 50 nm and 100 pm.

[0038] According to one embodiment, step b. is carried out at a temperature between 15°C and 200°C, preferably for a duration between 0.5 seconds and 4 hours.

[0039] According to one embodiment, step b. is carried out at ambient pressure or under an imposed pressure, preferably between 0.01 bar and 16 bar.

[0040] Advantageously, in step c, the irradiation source is a light source, preferably a UV or visible light source. The light may, for example, have a wavelength between 100 and 450 nm.

[0041] Step c. of exposure reduces the thickness of the residual layer present between the engraved patterns. It is therefore possible to completely expose the substrate between the printed patterns.

[0042] A mask can be used during step c. This mask allows for selective exposure. tively certain areas of the all-inorganic surface. A silkscreen mask / stencil can be used during this step.

[0043] Steps b. and c. can be carried out simultaneously or successively: step b. before step c., or step c. before step b.

[0044] According to a first embodiment, steps b and c are performed simultaneously. According to a second embodiment, step b is performed before step c. According to a third embodiment, step c is performed before step b.

[0045] The process may further include a washing step d, preferably with an acidic solution or an organic solvent. The acidic solution may be based on an inorganic acid, such as nitric acid or hydrochloric acid. The washing may also be carried out using an organic solvent, preferably an alcohol. Examples of alcohols include C1-C6 alcohols, such as methanol, ethanol, propanol, and butanol.

[0046] The process may also include a heat treatment step e. at a temperature greater than or equal to 50°C, preferably a temperature between 250°C and 1000°C.

[0047] The process may also include a heat treatment step before and / or after step b. and / or step c, at a temperature between 30°C and 200°C, preferably for a duration between 0.5 seconds and 4 hours.

[0048] According to a particular embodiment, the process comprises the following steps: a. Deposition of a sol onto a solid support and formation of a gel layer, the sol comprising (i) at least one inorganic precursor comprising at least one inorganic monomer, and (ii) at least one photosensitive compound, b. Structuring or transfer of the gel layer onto another support using a structured buffer, c. Isolation of the gel layer with an irradiation source, preferably using a mask, d. Washing the structured surface, preferably with an acidic solution or an organic solvent, steps b. and c. can be carried out simultaneously or successively: step b. before step c., or step c. before step b.. Examples

[0049] Soil preparation: A sol is prepared comprising butanol in the range of 10–20 mL, tetraisopropyllotitanate in the range of 3–8 mL, methanol in the range of 10–20 mL, benzoylacetone in the range of 1–5 g, distilled water in the range of 0.01–0.1 mL, hydrochloric acid in the range of 0.05–0.15 mL, and diethanolamine in a range of 0.5-4 mL.

[0050] Deposition of the soil by spin coating (3000rpm for 5s) on a silicon wafer.

[0051] Embossing with a PDMS pad having structured cylindrical patterns with a period of 600nm and a diameter of 120nm. Embossing is carried out at a temperature of 100°C under 6 bars of pressure.

[0052] Insolation with a lamp (50mW) for 10 minutes at 365 nm.

[0053] Washing the structured all-inorganic surface obtained for 8 seconds with ethanol.

[0054] Heat treatment in air at 500°C for 15 minutes leading to an all-inorganic surface made of crystallized TiO2.

[0055] Figures 1, 2, and 3 show scanning electron microscopy photographs of the structured surface obtained at different scales.

[0056] These figures clearly show that the process according to the invention makes it possible to structure an all-inorganic surface with submicrometer patterns. Furthermore, the dots are not deformed and there is no residual layer. The process according to the invention therefore makes it possible to completely expose the substrate between the printed patterns.

Claims

Demands

1. An all-inorganic sol-gel surface structuring process comprising the following steps: a. Deposition of a sol onto a solid support and formation of a gel layer, the sol comprising (i) at least one inorganic precursor comprising at least one inorganic monomer and / or at least one inorganic polymer and / or at least one inorganic cluster based on at least one metal and / or at least one semiconductor, and (ii) at least one photosensitive compound, b. Structuring of the gel layer using a structured buffer, or transfer of the gel layer onto another support, c. Isolation of the gel layer with an irradiation source, preferably using a mask, steps b. and c. being able to be carried out simultaneously or successively: step b. before step c., or step c. before step b.

2. A process according to claim 1 characterized in that the monomer and / or polymer and / or inorganic cluster comprises at least one metal, preferably selected from: Zn, Ti, Pb, La, Nb, Zr, Ta, Fe, Al, W, Hf, and their combinations.

3. A process according to any one of the preceding claims characterized in that the monomer and / or polymer and / or inorganic cluster comprises at least one metal and one Si atom.

4. A method according to any one of the preceding claims characterized in that the photosensitive compound (ii) is selected from [3-diketones or aromatic ketones.

5. A process according to any one of the preceding claims characterized in that the soil comprises an organic solvent, preferably an alcohol.

6. A process according to any one of the preceding claims characterized in that the soil comprises a chemical additive, preferably an amine.

7. A method according to any one of the preceding claims characterized in that the structured buffer comprises patterns on the order of tens of nanometers and / or micrometers.

8. A method according to any one of the preceding claims, characterized in that step b. is carried out at a temperature between 15°C and 200°C, preferably for a duration between 0.5 seconds and 4 hours.

9. A method according to any one of the preceding claims characterized in that step b. is carried out at ambient pressure or under an imposed pressure, preferably between 0.01 bar and 16 bar.

10. A method according to any one of the preceding claims characterized in that the irradiation source is a light source, preferably a UV or visible light source.

11. A process according to any one of the preceding claims characterized in that the process comprises a washing step d., preferably with an acidic solution or an organic solvent.

12. A process according to any one of the preceding claims characterized in that the process comprises a heat treatment step e. at a temperature greater than or equal to 50°C, preferably a temperature between 250°C and 1000°C.

13. A method according to any one of the preceding claims characterized in that it comprises, before step a., a soil preparation step.

14. A process according to any one of the preceding claims characterized in that it comprises a heat treatment step before and / or after step b. and / or step c, at a temperature between 30°C and 200°C, preferably for a duration between 0.5 seconds and 4 hours.

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