Formulation for preparing an optical layer containing a metal oxide

Abstract

The present invention relates to a formulation for preparing an optical or encapsulating layer containing a metal oxide. The formulation may exhibit at least one of properties as an advanced material or as a high performance material. The formulation may be used in the nanotechnology process to make semiconductor device / display device application, for example semiconductor chip, or a liquid crystal, quantum dot, OLED display fabricated on a substrate controlled by semiconductors.

Description

[0001] FORMULATION FOR PREPARING AN OPTICAL LAYER CONTAINING A METAL OXIDE

[0002] Field of the invention

[0003] The present invention relates to a formulation for preparing an optical layer containing a metal oxide, method for preparing a formulation, use of a formulation, method for preparing a composite, a composite, an optical device and a display device.

[0004] Background Art

[0005] BBC News, last updated on Thursday, 3 May 2007, 12:04 GMT 13:04 UK, http: / / news.bbc.co.Uk / 2 / hi / technology / 6618919.stm, reported that IBM has developed a method of controlling the interaction between self-assembling molecules, called deblock copolymers, to create the vacuum holes. IBM says that the chips will run 35% faster and consume 15% less energy.

[0006] Hsiao Kang Chang et al., TSMC, IITC (International Interconnect Technology Conference), Tuesday, May 23, 2023, Dresden, 3.1 Airgap Integration on Patterned Metal Lines for Advanced Interconnect Performance Scaling, reports 4 step process to introduce air gaps between metal lines for capacitance including deposition of sacrificial Materials and lithographic process as described in Fig. 1a to 1e.

[0007] Summary of the invention

[0008] The inventors newly have found that there are still one or more of considerable problems for which improvement is desired, as listed below: providing new simple method to create air / vaccum gaps; providing new cheaper & faster process method to create air / vacuum gaps; providing new material which fits to new simple, cheaper and / or faster process method; realizing improved geometric quality of air / vacuum gaps; providing a printable formulation for preparing an optical layer / composite containing a material which provides sufficiently high refractive indices after curing; providing a formulation which enables preparation of a dense, crack-less or crack-free optical layer; providing a formulation for preparing an optical layer containing a metal oxide precursor material of a high refractive index material, which is well dispersed in the formulation; realizing a more stable formulation, zero or reduced viscosity change of the formulation, providing suitable formulation for wet printing, namely for spin-coating or ink jetting, realizing continuous inkjet printing.

[0009] The inventors aimed to solve one or more of the above-mentioned problems.

[0010] Then, the present inventors have surprisingly found that one or more of the above-described technical problems can be solved by the features as defined in the claims.

[0011] Namely, it is found a novel formulation for preparing an optical layer containing a metal oxide, preferably to be used for preparing an encapsulation layer of a display device or a semiconductor device, comprising at least;

[0012] - a metal oxide precursor containing a group 4, group 5 and / or group 13 element of the periodic table; and

[0013] - a solvent, wherein the solvent is a secondary alcohol having no, one or two alkoxy groups or one or two alkyl groups where one or more non- adjacent groups of said alkyl group is replaced by oxygen atom, or a secondary linear or branched >C3 alcohol;

[0014] - wherein the total amount of the metal oxide precursor in the formulation is 0.5wt.% or more based on the total amount of the formulation.

[0015] In another aspect, the present invention further relates to a method for preparing a formulation of the present invention, containing at least the following step;

[0016] (X1) dissolving a metal oxide precursor in solvent 1 , preferably said solvent 1 is a dry or water-free solvent to form a metal oxide precursor solution; (X2) optionally dissolving an acid in solvent 2, preferably said solvent 2 is dry or water-free, wherein said acid is selected from one or more members of the group consisting of sulfonic acids, amine hydrochlorides and carboxylic acids to form an acid solution;

[0017] (X3) optionally adding said acid solution obtained in step (X2) to the metal oxide precursor solution obtained in step (X1 );

[0018] (X4) mixing water and solvent 3 to form an aqueous solvent; and

[0019] (X5) adding said aqueous solvent to the alkoxide solution obtained in step (X1 ) or the metal oxide precursor solution obtained in step (X3);

[0020] (X6) optionally dissolving an acid and water in solvent 4, preferably said solvent 4 is dry or water-free solvent, wherein said acid is selected from one or more members of the group consisting of sulfonic acids, amine hydrochlorides and carboxylic acids to form an acid solution to form an aqueous acid solution;

[0021] (X7) optionally adding said aqueous acid solution (X6) to the metal oxide precursor solution (X1 ), wherein said metal oxide precursor is a metal alkoxide, a metal halide or a metal carboxylate containing a group 4 and / or group 5 and / or group 13 element of the periodic table, more preferably said metal oxide precursor is a metal alkoxide containing a group 4, group 5 and / or group 13 element of the periodic table; wherein said solvents 1 to 4 are independent from each other, selected from a secondary linear or branched >C3 alcohols, preferably it is selected from 2-propanol, 2-butanol, 2-pentanol, 3-pentanol, more preferably it is a linear or branched secondary >C4 alcohol; preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers, more preferably said solvent is selected from one or more members of the group consisting of propylene glycol monoalkyl ethers, preferably it is propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether and / or propylene glycol monopropyl ether; glycerol 1 ,3-dialkyl ethers, 1 ,3-dimethoxy-2-propanol, even more preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers; and wherein the total amount of the metal oxide precursor in the formulation is 1wt.% or more based on the total amount of the formulation.

[0022] In another aspect, the present invention also relates to use of the formulation of the present invention for preparing an optical layer containing a metal oxide.

[0023] In another aspect, the present invention further relates to a method for preparing a composite containing a metal oxide; comprising the following steps (a) and (b):

[0024] (a) providing the formulation of the present invention onto a surface of a substrate or a surface of an underlayer; and

[0025] (b) applying a thermal treatment to the formulation provided on the surface of the substrate or on the surface of an underlayer to convert at least a part of the metal oxide precursor of the formulation to a metal oxide.

[0026] In another aspect, the present invention further relates to a composite, preferably being a layered composite, preferably said layered composite is an optical layer, obtained or obtainable by the method of the present invention.

[0027] In another aspect, the present invention further relates to a composite, preferably being an optical layer containing a metal oxide, more preferably an encapsulation layer of a display device or a semiconductor device, derived from the formulation of the present invention.

[0028] In another aspect, the present invention further relates to an optical device comprising the composite of the present invention, and a substrate comprising a patterned surface or an uneven surface. Preferably a gap or trench of said patterned surface or an uneven surface of the substrate is encapsulated by said composite, preferably said composite is an encapsulation layer encapsulating said patterned surface or an uneven surface of the substrate. Preferably said composite of claim 15 is directly attached onto the top part of the patterned layer or the top part of the uneven layer to form a void, and air or gas is in the void.

[0029] In another aspect, the present invention further relates to a display device comprising at least one functional medium configured to direct and modulate a light or configured to emit light; and the composite of the present invention or an optical device of the present invention.

[0030] In another aspect, the present invention further relates to a semiconductor device comprising at least a patterned layer or an uneven layer; and said patterned layer or an uneven layer is encapsulated by the composite of the present invention.

[0031] Technical effects of the invention

[0032] The present invention may provide one or more of following effects; providing new simple method to create air / vacuum gaps; providing new cheaper & faster process method to create air / vacuum gaps; providing new material which fits to new simple, cheaper and / or faster process method; realizing improved geometric quality of air / vacuum gaps; providing a printable formulation for preparing an optical layer / composite containing a material which provides sufficiently high refractive indices after curing; providing a formulation which enables preparation of a dense, crack-less or crack-free optical layer; providing a formulation for preparing an optical layer containing a metal oxide precursor material of a high refractive index material, which is well dispersed in the formulation; realizing a more stable formulation, zero or reduced viscosity change of the formulation, providing suitable formulation for wet printing, namely for spin-coating or ink jetting, realizing continuous inkjet printing. Preferred embodiments of the present invention are described hereinafter and in claims.

[0033] Brief description of the figures

[0034] Fig.1 : shows process flow (steps (a) to (e)) of direct metal line patterning scheme combined with an airgap formation technique disclosed in prior art Hsiao Kang Chang et al., TSMC, IITC (International Interconnect Technology Conference), Tuesday, May 23, 2023, Dresden, 3.1

[0035] Fig. 1 (a) shows Metal Line Patterning

[0036] Fig. 1 (b) shows deposition process of Sacrificial Materials

[0037] Fig. 1 (c) shows recession process of Sacrificial Materials

[0038] Fig. 1 (d) shows deposition process of Gap-Fill IMD

[0039] Fig. 1 (e) shows removal process of Sacrificial Materials

[0040] Fig.2 : shows process of our invention.

[0041] Fig.3 : stacked device image of our invention.

[0042] Fig.4 : SEM image of an encapsulation top layer (150 nm wide trenches)

[0043] List of reference signs

[0044] 100. Substrate

[0045] 110. Patterned metal line

[0046] 120. Sacrificial material

[0047] 130. Gap-Fill inter-metal dielectric (Gap-Fill IMD)

[0048] 130. Air gap: air / gas trapped within the area defined by the metal lines and the Gap-Fill inter-metal dielectric

[0049] 200. Substrate

[0050] 210. Patterned metal line

[0051] 230. Encapsulation layer made from the formulation of the present invention

[0052] 240. Air gap: air / gas trapped within the area defined by the metal lines and the Gap-Fill inter-metal dielectric Definition of the terms

[0053] In the context of the present invention, the term “formulation medium” or the plural term “formulation media” as used herein, denote one or more compounds serving as a solvent, suspending agent, carrier and / or matrix for the metal oxide precursor compound and any other component included in the formulation. Formulation media are generally inert compounds that do not react with said metal oxide precursor compounds and said other components. Formulation media may be liquid compounds, solid compounds or mixtures thereof. Typically, formulation media are organic compounds.

[0054] The term “surfactant” as used herein, refers to an additive that reduces the surface tension of a given formulation.

[0055] The term “wetting and dispersion agent” as used herein, refers to an additive that increases the spreading and filling properties of a given formulation. In this way, the tendency of the molecules to adhere to each other is reduced.

[0056] The term “adhesion promoter” as used herein, refers to an additive that increases the adhesion of a given formulation.

[0057] The term “polymer matrix” as used herein, refers to an additive that acts as a macromolecular matrix for one or more components of a given formulation.

[0058] The term “optical device” as used herein, relates to a device containing one or more optical components for forming a light beam including, but not limited to, gratings, lenses, prisms, mirrors, optical windows, filters, polarizing optics, UV and IR optics, and optical coatings. Preferred optical devices in the context of the present invention are augmented reality (AR) glasses, virtual reality (VR) glasses and / or mixed reality (MR) glasses. The term “display device” as used herein, is a kind of an optical device configured to output / present information in visual or tactile form. Examples are Liquid crystal display (LCD), Light emitting diode display (LED display), organic light emitting display (OLED), micro-LED display, quantum dot display (QLED), AR display, VR display, MR display, plasma (PDP) display, electroluminescent (ELD) display.

[0059] Detailed description of the invention

[0060] The present invention relates to a formulation for preparing an optical layer containing a metal oxide, preferably to be used for preparing an encapsulation layer of a display device or a semiconductor device, comprising at least, essentially consisting of or consisting of;

[0061] - a metal oxide precursor containing a group 4, group 5 and / or group 13 element of the periodic table, preferably said metal oxide precursor is a metal alkoxide, a metal halide or a metal carboxylate containing a group 4 and / or group 5 element of the periodic table, more preferably said metal oxide precursor is a metal alkoxide containing a group 4 and / or group 5 element of the periodic table; and

[0062] - a solvent, wherein the solvent is a secondary alcohol having no, one or two alkoxy groups or one or two alkyl groups where one or more non- adjacent groups of said alkyl group is replaced by oxygen atom, or a secondary linear or branched >C3 alcohol, preferably it is selected from 2-propanol, 2-butanol, 2-pentanol, 3-pentanol, more preferably it is a linear or branched secondary >C4 alcohol; preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers, more preferably said solvent is selected from one or more members of the group consisting of propylene glycol monoalkyl ethers, preferably it is propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether and / or propylene glycol monopropyl ether; glycerol 1 ,3-dialkyl ethers, 1 ,3- dimethoxy-2-propanol, even more preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers; wherein the total amount of the metal oxide precursor in the formulation is 0.5wt.% or more based on the total amount of the formulation, preferably it is in the range from 1 .0 to 40wt%, more preferably from 1 .3 to 30wt%, even more preferably from 3 to 28wt%.

[0063] - Metal oxide precursor

[0064] According to the present invention, said metal oxide precursor contains at least a group 4 and / or group 5 and / or group 13 element of the periodic table, preferably said metal oxide precursor is a metal alkoxide, a metal halide or a metal carboxylate containing a group 4, group 5 and / or group 13 element of the periodic table, more preferably said metal oxide precursor is a metal alkoxide containing a group 4 and / or group 5 element of the periodic table.

[0065] As the metal oxide precursor, any publicly known metal oxide precursors can be used.

[0066] - Metal alkoxides

[0067] According to the present invention, a metal alkoxide containing a group 4, group 5 and / or group 13 element of the periodic table is used. As said metal alkoxide, commercially available metal alkoxides containing a group 4, group 5 and / or group 13 element of the periodic table, can be used. Preferably, titanium tetra-n-butoxide, zirconium tetra-n-butoxide, niobium pentaethoxide can be used.

[0068] In a preferred embodiment of the present invention, said metal oxide precursor is represented by following chemical formula (IV), formula (V) or formula (VI):

[0069] Mb1O4(Rx1Rx2Rx3Rx4) - (IV)

[0070] Mb2Os(Rx1Rx2Rx3Rx4Rx5) - (V) Mb3O3(Rx1Rx2Rx3) - (VI) wherein Mb1is a tetravalent metal of a group 4 element of the periodic table, preferably it is Ti, Zr or Hf;

[0071] Mb2is a pentavalent metal of a group 5 element of the periodic table, preferably it is Nb or Ta;

[0072] Mb3is a three valent metal of a group 13 element of the periodic table, preferably it is Al or In;

[0073] Rb1, Rb2, Rb3, Rb4and Rb5are each independently selected from a straightchain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3-25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups and / or one or more adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, and where one or more H atoms may be replaced by D; where each of groups may be substituted by one or more groups Ra;

[0074] Rais at each occurrence, identically or differently, H, a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups two or more adjacent substituents Ramay optionally form a mono- or polycyclic, aliphatic ring system with one another.

[0075] According to the present invention, the total amount of the metal oxide precursor in the formulation is 0.5wt.% or more based on the total amount of the formulation, preferably it is in the range from 1 .0 to 40wt%, more preferably from 1 .3 to 30wt%, even more preferably from 3 to 28wt%.

[0076] It is believed that the above-mentioned total amount of the metal oxide precursor based on the total amount of formulation is very important to realize an improved encapsulation layer placed directly onto a patterned surface or directly onto an uneven surface of a substrate. Namely for forming air or gas filled gaps encapsulated by said encapsulation layer for AR / VR devices or for semiconductor devices. In case a thin layer is fabricated directly onto a patterned surface or an uneven surface of a substrate or a patterned surface or an uneven surface of an under layer, it is desirable that the bumps, trenches, grooves of the patterned surface and / or an uneven structure is filled with air and said thin layer is placed to cover said air filled patterned bumps, trenches, grooves. It is believed that by adjusting the total amount of the metal oxide precursor(s) of the formulation, an improved encapsulation layer can be made preferably to cover said air filled patterned bumps, trenches, grooves and to form air / gas filled gaps.

[0077] According to the present invention, said nominal relative weight content of metal oxide in the formulation is calculated by using the following formula: M(OR)x and MOx (w%) in the total amount of the formulation = generic formulae for metal alkoxides and metal oxides (MO2 and M2O5) and their nominal relative weight contents in the formulation (sol-gel mixture).

[0078] -Solvent

[0079] According to the present invention, the formulation of the present invention contains a solvent, wherein the solvent is a secondary alcohol having one or two alkoxy groups or one or two alkyl groups where one or more non- adjacent groups of said alkyl group is replaced by oxygen atom.

[0080] It is believed that said secondary alcohol solvent chemically interacts with the metal oxide precursor in the formulation and allows controlling the rate of formation of a continuous metal oxide material during formulation deposition and final thermal curing process.

[0081] Preferably, said alkoxy group of the secondary alcohol is an alkoxy group having 1 -10 carbon atoms, more preferably it is an alkoxy group having 1 -5 carbon atoms, even more preferably an alkoxy group having 1 -3 carbon atoms.

[0082] Preferably, said alkyl groups where one or more non-adjacent groups of said alkyl group is replaced by oxygen atom, is an alkyl group having 1 -10 carbon atoms where one or more non-adjacent carbon groups of said alkyl group is replaced by oxygen atom, more preferably 2-5 carbon atoms, even more preferably 2 or 3 carbon atoms.

[0083] Furthermore preferably, said solvent is selected from one or more members of the group consisting of propylene glycol monoalkyl ethers, preferably it is propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether and / or propylene glycol monopropyl ether; glycerol 1 ,3-dialkyl ethers, 1 ,3-dimethoxy-2-propanol, more preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, a secondary linear or branched >C3 alcohol, preferably it is selected from 2-propanol, 2- butanol, 2-pentanol, 3-pentanol, more preferably it is a linear or branched secondary >C4 alcohol; preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers.

[0084] It is believed that the printing, especially ink jetting of structures is considered as a highly cost-efficient production step. Spin-coating is a convenient method and is preferable to form a uniform thin layer. Thus, suitable solvents of the formulation for spin-coating / inkjet printing the structures for forming an encapsulation layer for preferably forming an airgap / gas filled gaps, is described here.

[0085] It is believed that the selection between chemically closely related secondary alcohols as solvents for a reactive sol-gel mixture containing a group 4 and / or group 5 element of the periodic table in form of a metal alkoxide allows for a differentiated control of the rate of formation of a continuous metal oxide material during formulation deposition and final thermal curing.

[0086] After printing, to form an encapsulation layer, at least a part of the material as the metal oxide precursor needs to become converted into the respective metal oxides by any known means know to the persons skilled in the art (thermally, photochemically, etc.).

[0087] In a preferred embodiment, when the metal of said metal oxide precursor is Zr and said solvent is a propylene glycol monoalkyl ether, then the total amount of the metal oxide precursor in the formulation is in the range from 1wt.% to 3.4wt% based on the total amount of the formulation, preferably it is 1 .3 to 3.4wt%, preferably said propylene glycol monoalkyl ether is propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether, propylene glycol monopropyl ether or a mixture of any one of these. In a preferred embodiment, when the metal of said metal oxide precursor is Nb or Ti and said solvent is a glycerol 1 ,3-dialkyl ethers, preferably 1 ,3- dimethoxy-2-propanol, then the total amount of the metal oxide precursor in the formulation is in the range from 0.5 wt.% to 7.5wt% based on the total amount of the formulation, preferably it is 0.5 to 5wt%.

[0088] -Acid

[0089] According to the present invention, the formulation may optionally contain an acid selected from one or more members of the group consisting of sulfonic acids, amine hydrochlorides and carboxylic acids. It is believed that the acid can function as a reaction mediator.

[0090] In a preferred embodiment of the present invention, the formulation of the present invention contains an acid selected from one or more members of the group consisting of sulfonic acids, amine hydrochlorides and carboxylic acids.

[0091] It is believed that these acids are suitable as the reaction mediator according to the present invention.

[0092] In a more preferred embodiment of the invention, said sulfonic acid is represented by following chemical formula (I).

[0093] Ra1SO3H - (I) wherein

[0094] Ra1is selected from the group consisting of a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3- 25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, C=O, C=S, C=Se, C=NH, SiH2, SO, SO2, OS, or CONH and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2; where each of groups may be substituted by one or more groups Rax;

[0095] Raxis at each occurrence, identically or differently, H, D, a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups, one or more H atoms may be replaced by D, F, Cl, Br, I, and where two or more adjacent substituents Raxhere may optionally form a mono- or polycyclic, aliphatic ring system with one another; said amine hydrochloride is represented by following chemical formula (II)

[0096] HCI - Ra2- (II) wherein

[0097] Ra2is selected from the group consisting of N2H4, ammonia, hydroxylamine, imidazole and 1 ,4-diazabicyclo[2.2.2]octane; and / or said carboxylic acid is represented by following chemical formula (III) Ra3- COOH wherein

[0098] Ra3is selected from the group consisting of a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3- 25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, C=O, C=S, C=Se, C=NH, SiH2, SO, SO2, OS, or CONH and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2; where each of groups may be substituted by one or more groups Rax;

[0099] Raxis at each occurrence, identically or differently, H, D, a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups, one or more H atoms may be replaced by D, F, Cl, Br, I, and where two or more adjacent substituents Raxhere may optionally form a mono- or polycyclic, aliphatic ring system with one another.

[0100] In some preferred embodiments, the acid is an amine hydrochloride represented by following chemical formula (II)

[0101] HCI - Ra2- (II) wherein

[0102] Ra2is selected from the group consisting of N2H4, ammonia, hydroxylamine, imidazole and 1 ,4-diazabicyclo[2.2.2]octane.

[0103] In a preferred embodiment, said acid is a sulfonic acid represented by following chemical formula (I).

[0104] Ra1SO3H - (I) wherein

[0105] Ra1is selected from the group consisting of a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3- 25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, C=O, C=S, C=Se, C=NH, SiH2, SO, SO2, OS, or CONH and where one or more H atoms may be replaced by D, F, Cl, Br, I, CN or NO2; where each of groups may be substituted by one or more groups Rax;

[0106] Raxis at each occurrence, identically or differently, H, D, a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups, one or more H atoms may be replaced by D, F, Cl, Br, I, and where two or more adjacent substituents Raxhere may optionally form a mono- or polycyclic, aliphatic ring system with one another.

[0107] In a preferred embodiment of the present invention, the stoichiometric mole ratio of the acid and the metal oxide precursor, preferably the metal alkoxide, is in the range from 0.01 :100 to 120:100, preferably the mole ratio of the acid and metal oxide precursor is in the range from 0.1 to 50:100, more preferably 1 to 10:100.

[0108] It is believed that when the stoichiometric mole ratio of the acid and the metal oxide precursor is in the above-mentioned range, it provides improved refractive index value. - Water

[0109] According to the present invention, the formulation contains water, and the stoichiometric amount of water is in the range from 100 to 400 mol% based on the molar amount of metal oxide precursor and the ratio of metal and oxygen in the metal oxide sum formula, preferably the stoichiometric amount of water based on the total amount of the metal oxide precursor is in the range from 150 to 300 mol%, even more preferably from 180 to 270 mol%.

[0110] -Additives

[0111] In some embodiments of the present invention, the formulation may optionally comprise one or more additives selected from surfactants, wetting and dispersion agents, adhesion promoters, and polymer matrices. Or, in some embodiments, the formulation of the present invention does not contain any additives.

[0112] In some embodiments of the present invention, the formulation may further comprise additional one or more metal complexes, which may act as further metal oxide precursors.

[0113] In a preferred embodiment of the present invention, the formulation is an ink formulation being suitable for inkjet printing. Typical requirements for ink formulations are surface tensions in the range from 20 mN / m to 30 mN / m and viscosities in the range from 5 mPa s to 30 mPa s.

[0114] -Method for preparing a formulation

[0115] In another aspect, the present invention also relates to a method for preparing a formulation of the present invention, containing at least, essentially consisting of or consisting of, the following steps;

[0116] (X1 ) dissolving a metal oxide precursor in solvent 1 , preferably said solvent 1 is dry or water-free solvent to form a metal oxide precursor solution; (X2) optionally dissolving an acid in solvent 2, preferably said solvent 2 is dry or water-free solvent, wherein said acid is selected from one or more members of the group consisting of sulfonic acids, hydrochlorides and carboxylic acids to form an acid solution;

[0117] (X3) optionally adding said acid solution obtained in step (X2) to the metal oxide precursor solution obtained in step (X1 );

[0118] (X4) optionally mixing water and solvent 3 to form an aqueous solvent; and (X5) optionally adding said aqueous solvent to the alkoxide solution obtained in step (X1 ) or the metal oxide precursor solution obtained in step (X3);

[0119] (X6) optionally dissolving an acid and water in solvent 4, preferably said solvent 4 is dry or water-free solvent, wherein said acid is selected from one or more members of the group consisting of sulfonic acids, hydrochlorides and carboxylic acids to form an acid solution to form an aqueous acid solution;

[0120] (X7) optionally adding said aqueous acid solution (X6) to the metal oxide precursor solution (X1 ), wherein said metal oxide precursor is a metal alkoxide, a metal halide or a metal carboxylate containing a group 4 and / or group 5 and / or group 13 element of the periodic table, more preferably said metal oxide precursor is a metal alkoxide containing a group 4, group 5 and / or group 13 element of the periodic table; wherein said solvents 1 to 4 are independent from each other, selected from a secondary linear or branched >C3 alcohols, preferably it is selected from 2-propanol, 2-butanol, 2-pentanol, 3-pentanol, more preferably it is a linear or branched secondary >C4 alcohol; preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers, more preferably said solvent is selected from one or more members of the group consisting of propylene glycol monoalkyl ethers, preferably it is propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether and / or propylene glycol monopropyl ether; glycerol 1 ,3-dialkyl ethers, 1 ,3-dimethoxy-2-propanol, even more preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers; and wherein the total amount of the metal oxide precursor in the formulation is 1wt.% or more based on the total amount of the formulation, preferably it is in the range from 1 .3 to 40wt%, more preferably from 3 to 30wt%, even more preferably from 3 to 28wt%.

[0121] -Use

[0122] In another aspect, the present invention also relates to use of the formulation of the present invention for preparing an optical layer containing a metal oxide, preferably said formulation is used for preparing an encapsulation layer of a display device or a semiconductor device.

[0123] -Method for preparing a composite containing a metal oxide

[0124] In another aspect, the present invention also relates to a method for preparing a composite containing a metal oxide, preferably said metal oxide is selected from metal monoxide, metal dioxide or metal pentoxide, or a combination of these; comprising at least the following steps (a) and (b):

[0125] (a) providing the formulation of any one of claims 1 to 6 onto a surface of a substrate or a surface of an underlayer, preferably by wet deposition process, more preferably by spin-coating or an area selective printing, preferably said area selective printing is an ink-jetting, even more preferably the formulation is provided by ink-jetting; and

[0126] (b) applying a thermal treatment to the formulation provided on the surface of the substrate or on the surface of an underlayer to convert at least a part of the metal oxide precursor of the formulation to a metal oxide.

[0127] Preferably said composite being a layered composite, more preferably said composite is an encapsulation layer for a display device or for a semiconductor device. -Step (a)

[0128] According to the present invention, said formulation may preferably be provided onto a surface of a substrate or a surface of an underlayer by wet deposition process. Said wet deposition process is drop casting, coating, or printing. A more preferred coating method is spin-coating, spray coating, slit coating, or slot-die coating. A more preferred printing method is flexo printing, gravure printing, inkjet printing, EHD printing, offset printing, or screen printing. Furthermore, preferred printing method is spray coating and inkjet printing and the most preferred one is inkjet printing.

[0129] Thus, in a preferred embodiment, the formulation is applied onto a surface of a substrate or a surface of an underlayer by spin-coating or ink-jetting in step (a). From a viewpoint of cost effective, ink-jetting can preferably be used.

[0130] In a preferred embodiment of the present invention, the formulation provided in step (a) of the method is an ink formulation being suitable for inkjet printing. Typical requirements for ink formulations are surface tensions in the range from 20 mN / m to 30 mN / m and viscosities in the range from 5 mPa s to 30 mPa s.

[0131] Depending on the specific problem to be solved, the formulation needs to be deposited either as a homogeneous and dense thin layer covering the entire surface of the substrate or the entire surface of an underlayer by a coating method or the formulation needs to be deposited locally in a structured manner, thus requiring for a printing method. Both coating and printing methods require formulations to be formulated in an adequate manner to comply with the physico-chemical needs of the respective coating and printing method as well as to comply with certain needs regarding the surface of the substrate to be coated or printed. In a preferred embodiment of the method of the present invention, the surface of the substrate is pre-treated by a surface cleaning process. Preferred surface cleaning processes are silicon wafer cleaning processes such as described in W. Kern, The Evolution of Silicon Wafer Cleaning Technology, J. Electrochem. Soc., Vol. 137, 6, 1990, 1887-1892 and in New Process Technologies for Microelectronics, RCA Review 1970, 31 , 2, 185-454. Such silicon wafer cleaning processes include wet cleaning process involving cleaning solvents (e.g., isopropanol (IPA)); wet etching processes involving hydrogen peroxide solutions (e.g., piranha solution, SC1 , and SC2), choline solutions, or HF solutions; dry etching processes involving chemical vapor etching, UV / ozone treatments or glow discharge techniques (e.g., O2 plasma etching); and mechanical processes involving brush scrubbing, fluid jet or ultrasonic techniques (sonification). The surface of the substrate can also be pre-treated by salinization or an atomic layer deposition (ALD) process. The pre-treatment of the surface of the substrate serves to modify the hydrophobicity / hydrophi licity of the surface. This can improve the adhesion and interaction characteristics of the optical metal oxide layer on the surface of the substrate.

[0132] In a more preferred embodiment, a wet cleaning process involving cleaning solvents (e.g., isopropanol (IPA)) is combined with one or more of a wet etching process involving hydrogen peroxide solutions (e.g., piranha solution, SC1 , and SC2), choline solutions, or HF solutions; dry etching process involving chemical vapor etching, UV / ozone treatments or glow discharge techniques (e.g., O2 plasma etching); and mechanical process involving brush scrubbing, fluid jet or ultrasonic techniques (sonification).

[0133] In a most preferred embodiment, a wet cleaning process involving cleaning solvents (e.g., isopropanol (IPA)) is combined with a mechanical process involving brush scrubbing, fluid jet or ultrasonic techniques (sonification) and with a wet etching process involving hydrogen peroxide solutions (e.g., piranha solution, SC1 , and SC2), choline solutions, or HF solutions; Thus, in a preferable embodiment, in step (a), the formulation is applied to a surface of a substrate or to a surface of an underlayer by spin-coating or ink-jetting.

[0134] In a preferable embodiment, the formulation is at least partly converted on the surface of the substrate or the surface of an underlayer to a composite, wherein said composite contains a metal oxide, preferably selected from metal monoxide, metal dioxide and / or metal pentoxide; and a metal oxide precursor.

[0135] In a preferable embodiment, the substrate is a patterned substrate comprising topographical features on the surface thereof. Said patterned structure of the substrate can be an underlayer placed over the substrate (e.g., an underlayer of a semiconducting device).

[0136] -Step (b)

[0137] It is believed that the formulation is at least partly converted in step (b) on the surface of the substrate or on the surface of the underlayer to a metal oxide to form a composite by exposure to thermal treatment. Said composite is preferably a layered composite. And said solvent is usually removed in step (b).

[0138] It is believed that applying a lower temperature such as in the range from 60 to 400°C, preferably it is from 80 to 300°C, more preferably from 90 to 250°C, even more preferably 90 to 150°C can realize an improved air gap.

[0139] Thus, in a preferred embodiment, in step (b) of the method, the formulation is at least partly converted on the surface of the substrate or on the surface of an underlayer to a composite, preferably it is being of a layered composite; preferably by baking it at a temperature in the range from 60 to 400°C, preferably it is from 80 to 300°C, more preferably from 90 to 250°C, even more preferably 90 to 150°C can realize an improved air gap.

[0140] It is preferred to use the formulation containing a lower amount of the metal oxide precursor based on the total amount of the formulation in step (a) to form an air gap in a good quality, for examples, 0.5wt.% or more based on the total amount of the formulation, preferably it is in the range from 1.0 to 40wt%, more preferably from 1 .3 to 30wt%, even more preferably from 3 to 28wt%; and applying a lower temperature in step (b) such as in the range from 60 to 400°C, preferably it is from 80 to 300°C, more preferably from 90 to 250°C, even more preferably 90 to 150°C, can realize an improved air gap to form an air gap in a good quality.

[0141] Thermal treatment method in Step (b) is not limited to any specific thermal treatment methods or times. Depending on the type of substrate and formulation, a person skilled in the art is able to determine suitable thermal treatment methods.

[0142] Baking (hard baking, sintering, or annealing) serves the purpose to convert the metal oxide precursor or metal oxide precursor mixture layers on the substrate into a metal oxide layer. Moreover, the final properties of the metal oxide layer may be adjusted by the baking treatment. Baking is preferably carried out at the time in the range from 1 to 60m in, preferably 2 to 20 min, more preferably 3 to 10m in.

[0143] Said baking (step (b)) may be carried out under ambient atmosphere or atmospheres with increased oxygen content in order to decompose unwanted organic components, which can lead to a lower activation energy when the composite is formed and is believed to improve the physicalchemical properties of the resulting layered composite material. In a preferred embodiment of the method of present invention, the substrate or the underlayer is patterned.

[0144] In a preferred embodiment of the present invention, the substrate is a patterned substrate comprising topographical features on the surface or an uneven surface, more preferably said substrate is a patterned substrate for a semiconductor device or for an optical device.

[0145] Preferred topographical features include, for example, gaps, grooves, trenches and vias. Topographical features may be distributed uniformly or non-uniform ly over the surface of the substrate. Preferably, they are arranged as an array or grating on the surface of the substrate. It is preferred that the topographical features have different lengths, widths, diameters as well as different aspect ratios. It is preferred that said topographical features have an aspect ratio of 1 :20 to 20:1 , more preferably 1 :10 to 10:1 . The aspect ratio is defined as width of structure to its height (or depth). From the viewpoint of dimension, the depth of the topographical features is preferably in the range from 10 nm to 10 pm, more preferably 50 nm to 5 pm, and most preferably 100 nm to 1 pm.

[0146] It is also preferred that the topographical features are inclined at a certain angle, such as an angle from 10 to 80°, preferably from 20 to 60°, more preferably from 30 to 50°, most preferably about 40°. Such inclined topographical features are also referred to as slanted or blazed topographical features.

[0147] The substrate is preferably a substrate of an optical device. Preferred substrates are made of inorganic or organic base materials, preferably inorganic base materials. Preferred inorganic base materials contain materials selected from the list consisting of ceramics, glass, fused silica, sapphire, silicon, silicon nitride, quartz, and transparent polymers or resins. The geometry of the substrate is not specifically limited, however, preferred are sheets or wafers.

[0148] In step (a) of the method, the formulation is applied onto a surface of a substrate or a surface of an underlayer, wherein said surface may be either a surface of a base material of the substrate or a surface of a layer of a material being different from the base material of the substrate, wherein such layer has been formed prior to applying said formulation.

[0149] In this way, sequences of different layers (layer stacks) can be formed on top of one another. Such layer stacks may be also structured, wherein such structures typically have dimensions on the nanometer scale, at least with respect to diameter, width and / or aspect ratio.

[0150] Thus, in a preferable embodiment, in step (b), the formulation is at least partly converted on the surface of the substrate or on the surface of an underlayer to a composite, preferably it is being of a layered composite; preferably by baking it at a temperature in the range from 60 to 400°C, preferably it is from 80 to 300°C, more preferably from 90 to 250°C.

[0151] In a preferred embodiment of the present invention, said thermal treatment of step (b) is applied at the time in the range from 1 to 60m in, preferably 2 to 20 min, more preferably 3 to 10m in.

[0152] In some embodiments, the formulation is at least partly converted on the surface of the substrate to a composite during the thermal treatment process of step (b), the formulation is at least partly converted on the surface of the substrate to a composite, wherein said composite contains a metal oxide, preferably selected from metal monoxide, metal dioxide and / or metal pentoxide; and a metal alkoxide, metal halide, metal oxo halide or metal carboxylate. - Composite

[0153] In another aspect, the present invention relates to a composite, preferably being a functional layer containing a metal oxide, more preferably an encapsulation layer of a display device or a semiconductor device, obtained or obtainable by the method of the present invention.

[0154] In another aspect, the present invention relates to a composite, preferably being a functional layer containing a metal oxide, more preferably an encapsulation layer of a display device or a semiconductor device, derived from the formulation the present invention.

[0155] In a preferred embodiment of the present invention, the composite comprises at least a metal oxide derived from the metal oxide precursor of the formulation and metal oxide precursor as a non-converted part of the formulation used in step (a) of the method.

[0156] The details of the metal oxide precursor are indicated in the section of metal oxide precursor above.

[0157] - Optical device

[0158] The present invention relates to an optical device comprising the composite of the present invention, which is preferably obtainable or obtained by the method of the present invention as described above. It is preferred that the optical device is a waveguide for display device selected from an augmented reality (AR) device, virtual reality (VR) device and / or Mixed Reality (MR) device. Preferably said composite fills gap of said topographical features, more preferably said composite fills trench of the patterned substrate.

[0159] The present invention further relates to an optical device comprising the composite of the present invention, which is prepared by using the formulation according to the present invention as described above; and a substrate comprising a patterned surface or an uneven surface.

[0160] Preferably a gap or trench of said patterned surface or an uneven surface of the substrate is encapsulated by said composite, preferably said composite is an encapsulation layer encapsulating said patterned surface or an uneven surface of the substrate. Preferably said composite is directly attached onto the top part of the patterned layer or the top part of the uneven layer to form a void, and air or gas is in the void.

[0161] It is preferred that the optical device is an augmented reality (AR) and / or virtual reality (VR) device.

[0162] - Display device

[0163] The present invention further relates to a display device comprising at least one functional medium configured to modulate a light or configured to emit light; and the composite, or an optical device of the present invention.

[0164] Examples of said display device is selected from a liquid crystal display (LCD), light emitting diode display (LED display), organic light emitting display (OLED), micro-LED display, quantum dot display (QLED), Augmented Reality (AR) display, Virtual Reality (VR) display, Mixed Reality (MR) display, plasma (PDP) display and an electroluminescent (ELD) display.

[0165] - Semiconductor device

[0166] The present invention finally relates to a semiconductor device comprising at least a patterned layer or an uneven layer; and said patterned layer or an uneven layer is encapsulated by the composite the present invention. Preferably said composite is directly attached onto the top part of the patterned layer or the top part of the uneven layer to form a void, and air or gas is in the void. Semiconductor device according to this invention includes all types of semiconductor devices of WSTS (Worle semiconductor Trade Statistics) classification 2021 . It includes discretes, optoelectronics, sensors and actuators, Integrated Circuits (IC) and Total semiconductors of WSTS classification 2021 . Discretes include Diodes, small signal and switching transistors, power transistors, Power Diodes, thyristors, all other discretes. Optoelectoronics includes image sensors, light sensors, laser transmitters, laser pick-ups, couplers. Isolators & switches. IC includes analogs, MOS Micros, Total Logics (MOS & Bipolar), MOS Memories, Total application Specific ICs, Total ICs of the classification of WSTS 2021 .

[0167] The present invention is further illustrated by the examples following hereinafter which shall in no way be construed as limiting. The skilled person will acknowledge that various modifications, additions and alternations may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims.

[0168] Examples

[0169] - Analytics and measurement methods

[0170] Ellipsometry is used to determine layer thickness, refractive index (n) and absorption index (k) of a metal oxide layer. Measurements are performed using an ellipsometer M2000 from J. A. Woolam and three different angles of incidence (65°, 70 ° and 75°). The measurement data is analyzed with software CompleteEase from J. A. Woolam, assuming either full or almost nearly complete transparent behavior above a wavelength of 600 nm (at 560nm) and applying B-spline fitting for obtaining refractive indices (n) as well as absorption indices (k). The optical constants are averaged from three to four measured samples each of them providing a different layer thickness either after soft bake or after hard bake or after combined soft and subsequent hard bake. All chemicals for synthesis described are purchased from Sigma Aldrich and used without further purification, unless differently mentioned elsewhere.

[0171] Preparation of formulations

[0172] Used precursors

[0173] Zirconium tetra-n-butoxide for working examples 1 to 5; Titanium tetra-n-butoxide for working examples 6-11 ; Niobium pentaethoxide for working examples 12-14

[0174] The stock solution and the organic cosolvents are weighed into a glass bottle and the formulations are stirred for 30 minutes prior to use.

[0175] Working example 1 : Preparation of formulation Zr-1 Formulation Zr-1 : Zirconium tetra-n-butoxide with 17 weight-% nominal solid content.

[0176] Zirconium tetra-n-butoxide is added to PGME (1-methoxy-2-propanol: dried over molecular sieves) in a two neck Schlenk flask connected to inert gas / vacuum line under argon atmosphere. The solution is stirred at room temperature and a solution of H2O and methane sulfonic acid (MSA) in PGME is added dropwise at room temperature, affording a clear solution that is stirred for another 60 mins. While the solvent and amounts of starting materials are varied, mass concentration of metal alkoxide starting material is not changed.

[0177] The wt% and mol% of each component used for fabricating formulation Zr-1 are indicated in table 1 of Zr-1 .

[0178] Working examples 2-5: Preparation of formulations Zr-2 to Zr-5a,b Formulations Zr-2 to Zr-5a,b are prepared in the same manner as described in Working example 1 except for that the materials described in Table 1 (Zr-2 to Zr-5) are used with the described amounts instead of the materials in Working example 1. Working examples 6-11 : Preparation of formulations Ti-1 to Ti-5 Formulations Ti-1 to Ti-5 are prepared in the same manner as described in Working example 1 except for that the materials described in Table 1 (Ti-1 to Ti-5) are used with the described amount instead of the materials in Working example 1 .

[0179] Working examples 12-14: Preparation of formulation Nb-1 to Nb-3 Formulations Nb-1 to Nb-3 are prepared in the same manner as described in Working example 1 except for that the materials described in Table 1 (Nb-1 to Nb-3) are used with the described amount instead of the materials used in Working example 1 .

[0180] Table 1 : MSA = methane sulfonic acid; PGME = 1-methoxy-2-propanol;

[0181] DM2P = 1 ,3-dimethoxy-2-propanol

[0182] *Encapsulation layer: A continuous layer of metal oxide material formed on across 50-150 nm wide trenches of the substate

[0183] Air gap: 50-150 nm wide trenches of the substrate are filled with air and encapsulated by the encapsulation layer Tit (°C / min): baking temperature / baking time

[0184] SC / IJP: Spin Coating / lnk Jet Printing

[0185] Working example 15: forming a layer

[0186] Sample Zr-1 is prepared by the following process.

[0187] Formulation Zr-1 from working example 1 (W.E.1 ) is spin coated onto an O2 plasma pretreated SisN4 / Si substrate having 150nm width trenches on the surface. Then the coated layer is baked at 200°C for 5m in. The obtained sample Zr-1 is observed by TEM analysis.

[0188] Samples Zr-2, Zr-3, Zr-4, Zr-5a, Zr-5b are prepared in the same manner as described in working example 15 above except for that the different conditions as described in Table 1 is applied. Namely, about Sample Zr-3, two samples (Sample Zr-3 (baking temperature 200°C / 5min) and Sample Zr-3 (baking temperature 300°C / 5min) are prepared. About sample Zr-4, three samples (Sample Zr-4 (baking temperature 100°C / 5min), Sample Zr-4 (baking temperature 200°C / 5min) and Sample Zr-4 (baking temperature 300°C / 5min)

[0189] For sol-gel derived ZrO2, selectivity for top layer formation vs. gap filling can be controlled through three different parameters. a) Curing temperature b) Solvent: PGME vs. DM2P c) Nominal ZrO2 solid content of formulation

[0190] In general, reactive building blocks contained in ZrO2 sol-gel formulations show a strong preference toward top encapsulation layer deposition on a O2 plasma pretreated SisN4 / Si substrate. This behavior is attributed to the high rate of condensation of reactive Zr-oxo clusters formed from the controlled hydrolysis of zirconium(IV) n-butoxide during formulation preparation. When kept in diluted form, gelling of acid stabilized sols containing nominal ZrO2 solid contents <8w% is a slow process (days to weeks) at ambient conditions. Spin-coating deposition on O2 plasma pretreated SisN4 / Si substrate causes rapid evaporation of solvent and condensation of reactive Zr-oxo clusters with surface Si-OH groups, which is believed to result in a high local concentration and therefore rapid condensation into a macroscopic network on the substrate surface.

[0191] In line with the mechanistic picture of a rapidly forming macroscopic ZrO2 domain, the impact of curing temperature on the selectivity for gap filling vs. top layer formation was observed only for ZrO2 sols with nominal solid contents <3.7w%. The viscoelasticity of a top layer formed initially from spin-coating a 1 ,3w% ZrO2 sol appears sufficient to induce material flow into gaps for curing at T> 200°C whereas a top layer persists at T = 100°C. Increasing the solid content to >~3w% ZrO2, results in initial top layers from spin-coating that are not prone to a temperature induced flow. This description is in line with the finding that no gap filling has been found for <100 nm gap widths.

[0192] Fig. 7a, b shows Temperature dependence of top layer formation vs. gap filling taken from examples Zr-2 and Zr-3, respectively, for 1 ,3w% ZrO2 solid content. Namely, Fig. 7a shows a TEM image of Sample Zr-2 and Fig. 7b shows a TEM image of Sample Zr-3.

[0193] The overall rate at which reactive Zr-oxo species condense forming a macroscopic ZrO2 network can be controlled through the choice of solvent. Indication from experimental data is that a lower rate of condensation correlates with improved gap filling, and it can be affected by solvents that i) act as terminal ligands to metal sites at the surface of reactive Zr-oxo clusters, and ii) are pH-responsive. In general, a secondary alcohol is preferred. More specifically for ZrO2, substituting 1 -methoxy-2-propanol (PGME) for 1 ,3-dimethoxy-2-propanol (DM2P) allows filling >100 nm gaps selectively at curing temperatures T = 100-300°C. However, this positive solvent effect on gap filling only holds for nominal ZrO2 solid contents <~3w%, otherwise top layer formation predominates.

[0194] Table 2 shows the result of TEM analysis. It also shows solvent dependence of top layer formation vs. gap filling taken from examples Zr-2 and Zr-4, respectively.

[0195] Table 2.

[0196] Table 3. shows Nominal ZrO2 solid content dependence of top layer formation vs. gap filling taken from examples Zr-5 and Zr-4, respectively.

[0197] Table 3.

[0198] Table 4 provides pertinent optical properties of <100 nm thick ZrO2 films. Table 4. Optical properties of sol-gel derived ZrO2 thin films; ft = film thickness deposited on plane Si wafer; Net abs. = net absorption determined at 460 nm, normalized to 100 nm film thickness. Working example 16: forming a layer

[0199] In working example 16, O2 plasma pretreated SisN4 / Si substrate having 50nm width trenches, O2 plasma pretreated SisN4 / Si substrate having 100nm width trenches and O2 plasma pretreated SisN4 / Si substrate having 150nm width trenches, are provided for each case.

[0200] Then, samples Ti-1 (50nm wide trenches), Ti-1 (100 nm wide trenches), Ti-1 (150 nm wide trenches), Ti-2 (50nm wide trenches), Ti-2 (100 nm wide trenches), Ti-2 (150 nm wide trenches), Ti-3 (50nm wide trenches), Ti-3 (100 nm wide trenches), Ti-3 (150 nm wide trenches), Ti-4a (50nm wide trenches), Ti-4a (100 nm wide trenches), Ti-4a (150 nm wide trenches), Ti- 4b (50nm wide trenches), Ti-4b (100 nm wide trenches), Ti-4b (150 nm wide trenches), Ti-5 (50nm wide trenches), Ti-5 (100 nm wide trenches), Ti- 5 (150 nm wide trenches) are prepared in the same manner as described in working example 15 above except for that different conditions as described in Table 1 (Ti-1 , 2, 3, 4a, 4b, and Ti-5) is applied.

[0201] For sol-gel derived TiO2, selectivity for top layer formation vs. gap filling can be controlled mainly by two parameters. a) Solvent: PGME vs. DM2P b) Nominal TiO2 solid content of formulation

[0202] In general, reactive building blocks in TiO2 sol-gel formulations show variable reactivity allowing TiO2 deposition either in the form of a top layer forming or as a gap filling material. Addressing these complementary modes of deposition is possible through solvent choice, which controls the rate of condensation of reactive Ti-oxo clusters formed from initial controlled hydrolysis of titanium(IV) n-butoxide. In addition to the solvent, the nominal TiO2 solid content is the second parameter that impacts the rate of gelation of acid stabilized sols. While 1-methoxy-2-propanol (PGME) allows stabilizing reactive TiO2 sols with <8w% nominal solid content for days to weeks at ambient conditions, substitution for 1 ,3-dimethoxy-2- propanol reduces sol shelf-live and requires a reduction of the nominal solid content to < 2.3w%.

[0203] Table 5. shows solvent dependence of top layer formation vs. gap filling taken from examples Ti-4 and Ti-1 , respectively.

[0204] Table 5.

[0205] Spin-coating deposition on O2 plasma pretreated SisN4 / Si substrate causes rapid evaporation of solvent and condensation of reactive Ti-oxo clusters with surface Si-OH groups, presumably leading to a high local concentration favoring facile condensation into a macroscopic network on the substrate surface. The impact of solvent on condensation rate, which reflects in sol shelf life and selectivity of TiO2 deposition as a top layer or gap filler, presumably relates to the acid-base properties of Ti-oxo species. In contrast to PGME, DM2P binding to surface Ti(IV) sites of Ti-oxo clusters results in a two-fold increase of methoxy groups acting as potential yet spatially more remote proton acceptors. The net solvent impact is a reduced stabilizing effect of the acid component in reactive TiO2 sols, which further reflects in the lack of DM2P derived sols to gap fill of 50 nm wide trenches.

[0206] Table 6 highlights the impact of nominal solid content on top layer vs. gap fill selectivity for 8 and ~1w% TiO2 sol formulations. While selective gap filling was achieved from the 1w% TiO2 sol for all gap widths, selective top layer formation from the 8w% sol was achieved only for the narrowest gap, whereas partial filling in addition to top layer deposition was found for >100 nm wide trenches.

[0207] Table 6. shows nominal TiO2 solid content dependence of top layer formation vs. gap filling taken from examples Ti-3 and Ti-1 , respectively.

[0208] Table 6.

[0209] The formulation Ti-6 is prepared in the same manner as described in the same manner as described in Working example 1 except for that 4.2wt%, 96wt% PGME, 200mol% water and 4mol% of MSA are used instead of the used materials in Working example 1 .

[0210] The intrinsically high refractive index of crystalline TiO2 in rutile and other morphologies also reflects in the optical properties of thin films deposited from reactive TiO2 sol formulations, pertinent data are collected in table 7 along with processing conditions. Table 7. Representative optical properties of sol-gel derived TiO2 thin films; ft = film thickness deposited on plane Si wafer; Net abs. = net absorption determined at 460 nm, normalized to 100 nm film thickness.

[0211] Working example 17: forming a layer

[0212] In working example 17, O2 plasma pretreated SisN4 / Si substrate having 50nm wide trenches, O2 plasma pretreated SisN4 / Si substrate having 100nm wide trenches and O2 plasma pretreated SisN4 / Si substrate having 150nm wide trenches, are provided for all cases.

[0213] Then, samples Nb-1 (50nm wide trenches), Nb-1 (100 nm wide trenches), Nb-1 (150 nm wide trenches), Nb-2 (50nm wide trenches), Nb-2 (100 nm wide trenches), Nb-2 (150 nm wide trenches), Nb-3 (50nm wide trenches), Nb-3 (100 nm wide trenches), Nb-3 (150 nm wide trenches), are prepared in the same manner as described in working example 15 above except for that different conditions as described in Table 1 (Nb-1 , 2, and 3) is applied for each cases.

[0214] For sol-gel derived Nb2Os, selectivity for top layer formation vs. gap filling can be controlled by two parameters. a) Solvent: PGME vs. DM2P when nominal Nb2Os solid content is lower b) Nominal Nb2Os solid content of formulation

[0215] The chemical and deposition properties of Nb2Os derived sol formulations are largely congruent to those of TiO2, except for a more pronounced solvent impact on sol shelf life and top layer vs. gap fill selectivity, in line with the similar ionic radii of 6-coordinate Ti(IV) and Nb(V). In keeping the amount of acid at 5 mol-%, DM2P derived sols allow for only half the nominal Nb20s solid content that can be handled in PGME (~3w%).

[0216] Table 8. shows solvent dependence of top layer formation vs. gap filling taken from examples Nb-3 and Nb-1 , respectively.

[0217] Table 8.

[0218] Table 9. shows nominal Nb2Os solid content dependence of gap fill performance taken from examples Nb-2 and Nb-1.

[0219] Table 9.

[0220] Table 10 provides pertinent optical data of Nb20s sol derived thin films. Table 10. Optical properties of sol-gel derived Nb2Os thin films on quartz wafer; ft = film thickness; Net abs. = net absorption determined at 460 nm and normalized to 100 nm film thickness

[0221] For Nb-4 of the table, a formulation containing nominal solid content of

[0222] Nb2Os at 12.6wt% (28.8wt% Niobium pentaethoxide as metal alkoxide) is prepared based on the total amount of the formulation and used.

Claims

Claims1 . Formulation for preparing an optical layer containing a metal oxide, preferably to be used for preparing an encapsulation layer of a display device or of a semiconductor device, comprising at least;- a metal oxide precursor containing a group 4, group 5 and / or group 13 element of the periodic table, preferably said metal oxide precursor is a metal alkoxide, a metal halide or a metal carboxylate containing a group 4, group 5 and / or group 13 element of the periodic table, more preferably said metal oxide precursor is a metal alkoxide containing a group 4 and / or group 5 element of the periodic table; and- a solvent, wherein the solvent is a secondary alcohol having no, one or two alkoxy groups or one or two alkyl groups where one or more non- adjacent groups of said alkyl group is replaced by oxygen atom, or a secondary linear or branched >C3 alcohol, preferably it is selected from 2-propanol, 2-butanol, 2-pentanol, 3-pentanol, more preferably it is a linear or branched secondary >C4 alcohol; preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers, more preferably said solvent is selected from one or more members of the group consisting of propylene glycol monoalkyl ethers, preferably it is propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether and / or propylene glycol monopropyl ether; glycerol 1 ,3-dialkyl ethers, 1 ,3- dimethoxy-2-propanol, even more preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers;- wherein the total amount of the metal oxide precursor in the formulation is 0.5wt.% or more based on the total amount of the formulation, preferably it is in the range from 1 .0 to 40wt%, more preferably from 1 .3 to 30wt%, even more preferably from 3 to 28wt%.

2. Formulation of claim 1 , wherein said metal oxide precursor is represented by following chemical formula (IV), formula (V) or formula (VI):Mb1O4(Rx1Rx2Rx3Rx4) - (IV)Mb2Os(Rx1Rx2Rx3Rx4Rx5) - (V) Mb3O3(Rx1Rx2Rx3) - (VI) wherein Mb1is a tetravalent metal of a group 4 element of the periodic table, preferably it is Ti, Zr or Hf;Mb2is a pentavalent metal of a group 5 element of the periodic table, preferably it is Nb or Ta;Mb3is a three valent metal of a group 13 element of the periodic table, preferably it is Al or In;Rx1, Rx2, Rx3, Rx4and Rx5are each independently selected from H or a straight-chain alkyl group having 1 to 25 carbon atoms, preferably 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms; a branched or cyclic alkyl group having 3 to25 carbon atoms, preferably 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; an aryl group having 3 to 25 carbon atoms, preferably from 3 to 15 carbon atoms, more preferably 3 to 10 carbon atoms; a straight chain alkyl-cycloalkyl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-cycloalkyl group having carbon atoms 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; a straight chain alkyl-aryl group having 4 to 25 carbon atoms, preferably 4 to 15 carbon atoms; branched chain alkyl-aryl group having 6 to 25 carbon atoms, preferably 6 to 15 carbon atoms; where one or more non-adjacent CH2 groups and / or one or more adjacent CH2 groups of the above-mentioned groups may be replaced by oxygen atom, and where one or more H atoms may be replaced by D; where each of groups may be substituted by one or more groups Ra;Rais at each occurrence, identically or differently, H or a straight chain alkyl or alkoxy group having 1 to 15 carbon atoms, preferably 1 to 10 carbonatoms, more preferably 1 to 5 carbon atoms; a branched or cyclic alkyl or alkoxy group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; a straight-chain alkenyl or alkynyl group having 2 to 15 carbon atoms, preferably 2 to 10 carbon atoms, more preferably 2 to 5 carbon atoms; a branched alkenyl group or alkynyl group having 3 to 15 carbon atoms, preferably 3 to 10 carbon atoms, more preferably 3 to 5 carbon atoms; an aromatic or heteroaromatic ring system having 5 to 15 aromatic ring atoms, preferably 5 to 10 aromatic ring atoms; where in each of the above-mentioned groups, one or more H atoms may be replaced by D and where two or more adjacent substituents Rahere may optionally form a mono- or polycyclic, aliphatic ring system with one another.

3. Formulation of claim 1 or 2, said solvent is selected from a secondary linear or branched >C3 alcohols, preferably it is selected from 2-propanol, 2-butanol, 2-pentanol, 3-pentanol, more preferably it is a linear or branched secondary >C4 alcohol; preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers, more preferably said solvent is selected from one or more members of the group consisting of propylene glycol monoalkyl ethers, preferably it is propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether and / or propylene glycol monopropyl ether; glycerol 1 ,3-dialkyl ethers,1 .3-dimethoxy-2-propanol, even more preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol1 .3-dialkyl ethers.

4. Formulation of any one of preceding claims, wherein the metal of said metal oxide precursor is Zr and said solvent is a propylene glycol monoalkyl ether, and the total amount of the metal oxide precursor in the formulation is in the range from 1wt.% to 3.4wt% based on the total amount of the formulation, preferably it is 1.3 to 3.4wt%, preferably said propylene glycol monoalkyl ether is propylene glycol monomethyl ether (PGME), propyleneglycol monoethyl ether, propylene glycol monopropyl ether or a mixture of any one of these.

5. Formulation of any one of preceding claims, wherein the metal of said metal oxide precursor is Nb or Ti and said solvent is a glycerol 1 ,3-dialkyl ethers, preferably 1 ,3-dimethoxy-2-propanol, and the total amount of the metal oxide precursor in the formulation is in the range from 0.5 wt.% to 7.5wt% based on the total amount of the formulation, preferably it is 0.5 to 5wt%.

6. Formulation of any one of preceding claims, wherein the formulation contains water, and the stoichiometric amount of water is in the range from 100 to 400 mol% based on the total amount of metal oxide precursor, preferably the stoichiometric amount of water based on the total amount of the metal oxide precursor is in the range from 150 to 300 mol%, even more preferably from 180 to 270 mol%.

7. Method for preparing a formulation of any one of the preceding claims, containing at least the following steps;(X1 ) dissolving a metal oxide precursor in solvent 1 , preferably said solvent 1 is dry or water-free solvent to form a metal oxide precursor solution;(X2) optionally dissolving an acid in solvent 2, preferably said solvent 2 is dry or water-free solvent, wherein said acid is selected from one or more members of the group consisting of sulfonic acids, hydrochlorides and carboxylic acids to form an acid solution;(X3) optionally adding said acid solution obtained in step (X2) to the metal oxide precursor solution obtained in step (X1 );(X4) optionally mixing water and solvent 3 to form an aqueous solvent; and (X5) optionally adding said aqueous solvent to the alkoxide solution obtained in step (X1 ) or the metal oxide precursor solution obtained in step(X6) optionally dissolving an acid and water in solvent 4, preferably said solvent 4 is dry or water-free solvent, wherein said acid is selected from one or more members of the group consisting of sulfonic acids, hydrochlorides and carboxylic acids to form an acid solution to form an aqueous acid solution;(X7) optionally adding said aqueous acid solution (X6) to the metal oxide precursor solution (X1 ), wherein said metal oxide precursor is a metal alkoxide, a metal halide or a metal carboxylate containing a group 4 and / or group 5 and / or group 13 element of the periodic table, more preferably said metal oxide precursor is a metal alkoxide containing a group 4, group 5 and / or group 13 element of the periodic table; wherein said solvents 1 to 4 are independent from each other, selected from a secondary linear or branched >C3 alcohols, preferably it is selected from 2-propanol, 2-butanol, 2-pentanol, 3-pentanol, more preferably it is a linear or branched secondary >C4 alcohol; preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers, more preferably said solvent is selected from one or more members of the group consisting of propylene glycol monoalkyl ethers, preferably it is propylene glycol monomethyl ether (PGME), propylene glycol monoethyl ether and / or propylene glycol monopropyl ether; glycerol 1 ,3-dialkyl ethers, 1 ,3-dimethoxy-2-propanol, even more preferably said solvent is selected from propylene glycol monoalkyl ethers, glycerol 1 ,3-dialkyl ethers, glycerol 1 ,3-dialkyl ethers; and wherein the total amount of the metal oxide precursor in the formulation is 1wt.% or more based on the total amount of the formulation, preferably it is in the range from 1 .3 to 40wt%, more preferably from 3 to 30wt%, even more preferably from 3 to 28wt%.

8. Use of the formulation of any one of claims 1 to 6 for preparing an optical layer containing a metal oxide, preferably said formulation is used forpreparing an encapsulation layer of a display device or a semiconductor device9. Method for preparing a composite containing a metal oxide, preferably said metal oxide is selected from metal monoxide, metal dioxide or metal pentoxide, or a combination of these; comprising the following steps (a) and (b):(a) providing the formulation of any one of claims 1 to 6 onto a surface of a substrate or a surface of an underlayer, preferably by wet deposition process, more preferably by spin-coating or an area selective printing, preferably said area selective printing is an ink-jetting, even more preferably the formulation is provided by ink-jetting; and(b) applying a thermal treatment to the formulation provided on the surface of the substrate or on the surface of an underlayer to convert at least a part of the metal oxide precursor of the formulation to a metal oxide.Preferably said composite being a layered composite, more preferably said composite is an encapsulation layer for a display device or for a semiconductor device.

10. Method according to claim 9, wherein in step (b), the formulation is at least partly converted on the surface of the substrate or on the surface of an underlayer to a composite, preferably it is being of a layered composite; preferably by baking it at a temperature in the range from 60 to 400°C, preferably it is from 80 to 300°C, more preferably from 90 to 250°C.Preferably said composite contains a metal oxide, preferably selected from metal monoxide, metal dioxide and / or metal pentoxide; and a metal alkoxide, metal halide, metal oxo halide or metal carboxylate.11 . Method according to claim 9 or 10, said thermal treatment of step (b) is applied at the time 1 min or more, preferably it is in the range from 1 to 60m in, preferably 2 to 20 min, more preferably 3 to 10m in.

12. Method according to any one of claims 9 to 11 , wherein the substrate is a patterned substrate comprising topographical features on the surface or an uneven surface, more preferably said substrate is a patterned substrate for a semiconductor device or for an optical device.

13. A composite, preferably being an optical layer containing a metal oxide, more preferably an encapsulation layer of a display device or a semiconductor device, derived from the formulation of any one of claims 1 to 6.

14. An optical device comprising the composite of claim 13, and a substrate comprising a patterned surface or an uneven surface. Preferably a gap or trench of said patterned surface or an uneven surface of the substrate is encapsulated by said composite, preferably said composite is an encapsulation layer encapsulating said patterned surface or an uneven surface of the substrate. Preferably said composite of claim 13 is directly attached onto the top part of the patterned layer or the top part of the uneven layer to form a void, and air or gas is in the void.

15. A display device comprising at least one functional medium configured to direct and modulate a light or configured to emit light; and the composite of claim 13, or an optical device of claim 14.

16. A semiconductor device comprising at least a patterned layer or an uneven layer; and said patterned layer or an uneven layer is encapsulated by the composite of claim 13. Preferably said composite of claim 13 is directly attached onto the top part of the patterned layer or the top part of the uneven layer to form a void, and air or gas is in the void.

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