HK1053295B - Etching pastes for inorganic surfaces - Google Patents

Description

Etching paste for inorganic surfaces

The invention relates to novel etching media in the form of printable, homogeneous, particle-free etching pastes having non-Newtonian flow behaviour for etching inorganic, glassy amorphous or crystalline surfaces, in particular glass or ceramics, preferably in SiO₂Etching on silicon nitride-based systems, and also to the use of these etching media.

The term "inorganic surface" refers to oxide or nitrogen-containing compounds of silicon, especially silicon dioxide and silicon nitride surfaces.

Definition of glass:

the term "glass" denotes per se homogeneous materials, such as quartz glass, window glass or borosilicate glass, but also thin layers of these materials produced by various methods known to the person skilled in the art, in particular CVD (chemical vapor deposition), PVD (physical vapor deposition), spin-on (spin-on), thermal oxidation, on other substrates, such as ceramics, metal foils or silicon wafers.

The term "glass" hereinafter refers to silicon dioxide-and silicon nitride-containing materials that exist in a solid amorphous state without crystallization of the glass component and are highly disordered in the microstructure due to the lack of long-range order.

Except for pure SiO₂All except glass (quartz glass) contain SiO₂And glasses of other composition (e.g. doped glasses such as borosilicate, phosphosilicate and borophosphosilicate glasses, coloured, opal and crystalline glasses, optical glasses), including in particular elements such as calcium, sodium, aluminium, lead, lithium, magnesium, barium, potassium, boron, beryllium, phosphorus, gallium, arsenic, antimony, lanthanum, zinc, thorium, copper, chromium, manganese, iron, cobalt, nickel, molybdenum, vanadium, titanium, gold, platinum, palladium, silver, cerium, caesium, niobium, tantalum, zirconium, neodymium and praseodymium, which are present in the glass in the form of oxides, carbonates, nitrates, phosphates, sulphates and/or halides or which act as doping elements. Doped glasses are, for example, borosilicate, phosphosilicate and borophosphosilicate glasses, colored, opalescent and crystalline glasses and optical glasses.

Silicon nitride may likewise contain other elements such as boron, aluminum, gallium, indium, phosphorus, arsenic or antimony.

Definition of silicon dioxide-and silicon nitride-based systems:

the term ` silica matrix system ` is used below for all amorphous SiO particles which do not fall under the abovementioned meaning₂A crystalline system under the definition of glass and based on silica; they may be, in particular, salts and esters of orthosilicic acid and condensation products thereof, which are generally known to the person skilled in the art as silicates, as well as quartz and glass ceramics.

This definition also covers other silicon dioxide-and silicon nitride-based systems, in particular salts and esters of orthosilicic acid and condensation products thereof. Except for pure SiO₂(Quartz, tridymite, and cristobalite), this definition covers all SiO₂Or 'discrete' and/or linked [ SiO₄]Tetrahedra such as nesosilicate, sorosilicate (sorosilicate), cyclosilicate, inosiliconAcid salts (inosilicates), phyllosilicates and tectosilicates and other components, in particular SiO consisting of elements/components such as calcium, sodium, aluminium, lithium, magnesium, barium, potassium, beryllium, scandium, manganese, iron, titanium, zirconium, zinc, cerium, yttrium, oxygen, hydroxyl and halides₂-a radical system.

The term ` silicon nitride based system ` is applied below to all crystalline and partially crystalline (commonly referred to as microcrystalline) systems which do not fall under the definition of amorphous silicon nitride glass/layer as described above. These include Si₃N₄(in the form of its alpha-Si₃N₄And beta-Si₃N₄Crystal modification) and all crystalline and partially crystalline SiN_xAnd SiN_x: and H layer. The crystalline silicon nitride may be doped with other elements such as boron, aluminum, gallium, indium, phosphorus, arsenic and antimony.

1. Etching of structures on glass

An etchant, i.e., a chemically aggressive compound, is used to dissolve the material attacked by the etchant. Not only is the first layer of the erosion surface eroded and removed, but also deeper layers-seen from the erosion surface-are eroded and removed.

2. Etching of structures on silicon dioxide-and silicon nitride-based glasses and other silicon dioxide-and silicon nitride-based systems

According to the current state of the art, any desired structure can be selectively etched in silica-and silicon nitride-based glasses and other silica-and silicon nitride-based systems or their surfaces or layers of variable thickness, either directly by laser-supported etching methods or after masking by wet chemical methods [ d.j.monk, d.s.soane, r.t.howe, [ Solid Films (Thin Solid Films)232(1993) ], 1; J.B uhler, F. -P.Steiner, H.Baltes, journal of micro-mechanical micro-engineering (J.Micromech.Microeng.)7(1997), R1] or by dry etching methods [ M.K ö hler, "Microtech etching methods" (* tzverfahren fur dieMikrotechnik), Wiley VCH 1998 ].

In the laser-supported etching method, the laser beam scans the entire etching pattern point by point on the glass, which, in addition to being highly precise, also requires considerable adjustment work and is very time-consuming.

Wet-chemical and dry-etching methods comprise material-intensive, time-consuming and expensive process steps:

A. masking of the etched area is not required, for example, by:

● lithography: producing a negative or positive etched structure (depending on the resist), coating the substrate surface (e.g. by spin-coating a suitable photoresist), drying the photoresist, exposing the coated substrate surface to light, developing, rinsing, and drying if desired

B. Etching the structure by:

● dipping method (e.g. wet etching in a wet chemistry pot): immersing the substrate in an etching bath, etching, and etching₂Repeatedly rinsing and drying in O-cascade basin

● spin coating or spray coating method: the etching solution is applied to a rotating substrate, the etching operation can be carried out with/without input of energy, for example IR (infrared) or UV (ultraviolet) radiation, and is subsequently rinsed and dried

● Dry etching methods, e.g. plasma etching in expensive vacuum installations or etching with reactive gases in flow reactors

3. Full area etch of silicon dioxide-and silicon nitride-based glasses and other silicon dioxide-and silicon nitride-based systems

In order to etch silicon dioxide-and silicon nitride-based glasses and other silicon dioxide-and silicon nitride-based systems and their layers with variable thickness to a certain depth over the entire area, wet etching methods are mainly used. Silicon dioxide-and silicon nitride-based glasses and other silicon dioxide-and silicon nitride-based systems and layers thereof with variable thickness are immersed in an etching bath which usually contains as etching component hydrofluoric acid or other mineral acids which are toxic and highly corrosive.

The disadvantages of the described etching methods are that the process steps are time-consuming, material-demanding and expensive, which steps are in some cases complicated from a technical or safety point of view or are carried out batchwise.

The object of the present invention is therefore to provide an etching medium which can be used in a technically simple etching process with a high potential throughput (potential through put) for inorganic surfaces, in particular glass and other silicon dioxide-or silicon nitride-based systems and layers thereof with variable thickness, which is significantly less expensive than existing wet and dry etching processes in the liquid or gas phase.

The invention therefore relates to printable, homogeneous, particle-free etching pastes having advantageous non-Newtonian flow behaviour and to the use thereof for etching inorganic surfaces, in particular silicon dioxide-and silicon nitride-based glass surfaces and also other silicon dioxide-and silicon nitride-based systems and surfaces of layers thereof having variable thicknesses.

The invention also relates to the use of these homogeneous, particle-free etching pastes having non-Newtonian flow behaviour in a less expensive, technically simpler printing/etching process compared to existing wet and dry etching processes in the liquid or gas phase for glass and other silicon dioxide-and silicon nitride-based systems suitable for high throughput (throughput) and which can be carried out continuously.

SiO₂The production, shaping and post-treatment of the base system, such as grinding, polishing, lapping and heat treatment, are of no importance for the use according to the invention of printable, homogeneous, particle-free etching pastes having non-Newtonian flow behaviour, as is the case for glasses.

The invention relates to the SiO₂-or silicon nitride coated substratesFor example, homogeneous, intact (full), non-porous and porous solids obtained from glass melts (for example, glass particles and powders as well as flat, hollow, mirror or sintered glasses), and to the etching of non-porous and porous glass layers of variable thickness produced on other substrates (for example, ceramics, metal foils or silicon wafers) by various methods known to the person skilled in the art (for example, CVD, PVD, spin coating of Si-containing precursors, thermal oxidation).

The etching paste is applied in a single process step to the surface of the substrate to be etched. The surface to be etched may be a surface or part-surface (e.g. the surface of a thin sheet of silica glass) on a homogeneous, dense, porous or non-porous element made of silica-or silicon nitride-based glass or other silica-or silicon nitride-based system and/or a surface or part-surface of a porous or non-porous layer of glass or other silica-or silicon nitride-based system on a carrier material.

A highly automated and high throughput method suitable for transferring etching pastes onto the surface of substrates to be etched uses printing techniques. In particular, printing methods known to the person skilled in the art are screen printing, pad printing, stamp printing and inkjet printing methods. Manual application is also possible.

Depending on the design of the screen, printing plate (klischee) or stamp (stamp) or cartridge selection, the printable, homogeneous, particle-free etching pastes having non-newtonian flow behavior according to the invention can be applied over the entire area or selectively masked depending on the etching structure only at the points to be etched. All masking and lithographic steps described under A) are unnecessary. The etching operation can be carried out with or without input of energy, for example in the form of thermal radiation (using an IR radiation source). After the etching is complete, the printable, homogeneous, particle-free etching paste with non-Newtonian flow behaviour is rinsed off the etched surface or burnt off using a suitable solvent.

The etch depth in silicon dioxide-and silicon nitride-based glasses or other silicon dioxide-and silicon nitride-based systems and layers thereof with variable thickness can be adjusted and, in the case of selective structure etching, the edge sharpness (edge sharpness) of the etched structure can also be adjusted by varying the following parameters:

● concentration and composition of etching components;

● concentration and composition of the solvent used;

● concentration and composition of the thickener system;

● concentration and composition of any added acid;

● concentration and composition of any added additives such as defoamers, thixotropic agents, flow control agents, air release agents, and adhesion promoters;

● viscosity of printable, homogeneous, particle-free etching pastes having non-Newtonian flow behaviour according to the invention

● duration of etching with or without input of energy to the inorganic surface and its layers printed with the respective etching pastes; and

● inputs energy to the system on which the etching paste is printed.

The etch duration may be a few seconds to a few minutes depending on the application of the etched structure, the desired etch depth and/or edge definition. The etching duration is usually set to 1 to 15 minutes.

With liquid, dissolved or gaseous etchants, e.g. selected from hydrofluoric acid, fluoride, HF gas and SF₆The printable, homogeneous, particle-free etching pastes having non-Newtonian flow behaviour which are described according to the invention are advantageously significantly simpler and safer to handle and the amount of etching agent is significantly more economical than the inorganic acids.

The printable, homogeneous, particle-free etching pastes having non-Newtonian flow behaviour according to the invention have the following composition:

a. for glass or other SiO₂-a system of substratesAnd etching composition of layer thereof

b. Solvent(s)

c. Thickening agent

d. If desired, organic and/or inorganic acids

e. If desired, additives such as defoamers, thixotropic agents, flow control agents, deaerators and adhesion promoters.

The etching action of the printable, homogeneous, particle-free etching pastes having non-Newtonian flow behaviour according to the invention on the surfaces of silicon dioxide-and silicon nitride-based glasses and other silicon dioxide-and silicon nitride-based systems is based on the use of solutions containing fluoride components (with or without addition of acids), in particular solutions of fluorides, bifluorides, tetrafluoroborates, for example solutions of ammonium fluoride, alkali metal fluorides, antimony fluoride, ammonium bifluoride, alkali metal bifluorides, calcium bifluoride, alkylated ammonium and potassium tetrafluoroborates and mixtures thereof. These etching components are effective in the etching paste even at temperatures of 15 to 50 ℃, especially at room temperature, and/or are activated by input of energy, such as thermal radiation by an IR radiation source (to about 300 ℃), UV or laser radiation.

The proportion of etching components used is in the range from 2 to 20% by weight, preferably from 5 to 15% by weight, based on the total weight of the etching paste.

The solvent may form the main component of the etching paste. The proportion thereof may be from 10 to 90% by weight, preferably from 15 to 85% by weight, based on the total weight of the etching paste.

Suitable solvents may be inorganic and/or organic solvents, or mixtures thereof. Suitable solvents which can be used in pure form or in the form of corresponding mixtures can, depending on the application:

● Water

● mono-or polyhydric alcohols, such as diethylene glycol, dipropylene glycol, 1, 2-propanediol, 1, 4-butanediol, 1, 3-butanediol, glycerol, 1, 5-pentanediol, 2-ethyl-1-hexanol or mixtures thereof,

● ketones, such as acetophenone, methyl-2-hexanone, 2-octanone, 4-hydroxy-4-methyl-2-pentanone or 1-methyl-2-pyrrolidone

● ethers, such as ethylene glycol monobutyl ether, triethylene glycol monomethyl ether, diethylene glycol monobutyl ether or dipropylene glycol monomethyl ether

● Carboxylic acid esters, e.g. 2, 2-butoxy (ethoxy) ethyl acetate

● carbonates, e.g. propylene carbonate

● inorganic acids, such as hydrochloric acid, phosphoric acid, sulfuric acid or nitric acid, or organic acids with an alkyl chain length n-1-10, or mixtures thereof. The alkyl group may be straight-chain or branched. Specifically, organic carboxylic acids, hydroxycarboxylic acids, and dicarboxylic acids such as formic acid, acetic acid, lactic acid, oxalic acid, and the like are suitable.

These solvents or mixtures thereof are also suitable in particular for removing the etching medium again after the etching has been completed and for cleaning the etched surface if required.

The viscosity of the printable, homogeneous, particle-free etching pastes having non-Newtonian flow behaviour according to the invention is achieved by network-forming thickeners which swell in the liquid phase and can be varied according to the desired application area. The printable, homogeneous, particle-free etching pastes having non-Newtonian flow behaviour which are described according to the invention include all etching pastes whose viscosity is not independent of the shear rate, in particular etching pastes having a shear-thinning action. The network created by the thickener collapses under shear stress. The recovery of this network can take place without a time delay (non-newtonian etching pastes with plastic or pseudoplastic flow characteristics) or with a time delay (etching pastes with thixotropic flow characteristics).

Printable, homogeneous, particle-free etching pastes having non-Newtonian flow behaviour are completely homogeneous with the addition of thickeners. No particulate thickeners such as particulate silicones or acrylic resins are used.

Possible thickeners are polymers based on the following monomer units:

● glucose unit

Beta-glucoside-linked, i.e. cellulose and/or cellulose derivatives, such as cellulose ethers, in particular ethyl-cellulose (e.g. Aqualon ® EC), hydroxypropyl cellulose (e.g. Klucel ®) and hydroxyethyl cellulose (e.g. Natrosol ®), and also salts of glycolic acid ethers of cellulose, in particular sodium carboxymethylhydroxyethyl cellulose (e.g. Na-hecmc)

Alpha-glucoside-linked, i.e. starch and/or starch derivatives, such as oxidized starch, in particular sodium carboxymethyl starch (vivastar ® P0100 or vivastar ® P5000), and starch ethers, in particular anionic heteropolysaccharides (Deuteron ® VT819 or Deuteron ® XG)

● functionalized methacrylate units, especially cationic methacrylates/methacrylamides, such as Borchigel ® A PK

● functional vinyl units, i.e.

Polyvinyl alcohols of various degrees of hydrolysis, in particular Mowiol ® 47-88 (partially hydrolyzed, i.e. vinyl acetate and vinyl alcohol units) or Mowiol ® 56-98 (fully hydrolyzed)

Polyvinylpyrrolidone (PVP), in particular PVP K-90 or PVP K-120

The thickeners may be used alone or in combination with other thickeners.

The proportion of thickener necessary for the specific setting of the viscosity range and for the formation of the printable paste is from 0.5 to 25% by weight, preferably from 3 to 20% by weight, based on the total weight of the etching paste.

As already mentioned, the etching pastes according to the invention are also completely homogeneous with the addition of thickeners. They do not contain particulate thickeners such as particulate silicones or acrylic resins.

pK_aOrganic and inorganic acids having values of 0 to 5 may be added to the non-Newtonian flow characteristics of the inventionPrintable, homogeneous, particle-free etching pastes. Inorganic acids such as hydrochloric acid, phosphoric acid, sulfuric acid and nitric acid and organic acids having an alkyl chain length of n ═ 1 to 10 can improve the etching action of printable, homogeneous, particle-free etching pastes having non-Newtonian flow behaviour. The alkyl groups of the organic acids may be straight-chain or branched, with organic carboxylic, hydroxycarboxylic and dicarboxylic acids, such as formic, acetic, lactic and oxalic acids or other acids, being particularly preferred. The proportion of acid can be from 0 to 80% by weight, based on the total weight of the etching paste.

Additives having properties which are advantageous for the desired purpose are

Defoamers, such as those available under the trade name TEGO ® Foamex N,

thixotropic agents, such as BYK ® 410, Borchigel ® Thixo2,

flow control agents, such as TEGO ® Glide ZG 400,

degassing agents, such as TEGO ® Airex 985, and

adhesion promoters such as Bayowet ® FT 929.

These additives can have a positive effect on the printability of the printing paste. The proportion of additives is 0 to 5% by weight, based on the total weight of the etching paste.

The fields of application of the etching pastes according to the invention are, for example:

● solar cell industry (photovoltaic cell modules, such as solar cells and photodiodes)

● semiconductor industry

● glass industry

● high-performance electronic device

The novel printable, homogeneous, particle-free etching pastes having non-Newtonian properties according to the invention can be used in particular in all cases where a full-area and/or structured etching of the surface of silicon dioxide-and silicon nitride-based glasses and other silicon dioxide-and silicon nitride-based systems and layers thereof is required.

Thus, the entire surface, but also the individual structures, can be etched down selectively to the desired depth in homogeneous, dense, non-porous and porous glass and other homogeneous, dense, non-porous and porous silica-and silicon nitride-based systems, i.e. the etching operation can cover all ranges from microstructural roughening (glass with a light-scattering effect but still transparent) via a matting effect to etching deep-etched structures (e.g. markings, decorations/patterns). The fields of application are, for example:

● Observation windows for all types of valves and measuring devices

● production of glass supports (supports) for outdoor applications, such as for solar cells and collectors

● etched glass surfaces in the medical and health fields and for decorative purposes including artistic and architectural applications

● etched glass container for cosmetic products, food and beverage

● etching of special parts of glasses and other silica-based systems for marking and labelling purposes, e.g. for marking/labelling container and sheet glasses

● Special partial etching of glass and other silica-based systems for mineralogical, geological and microstructural studies

In particular, screen printing, pad printing, stamp printing and inkjet printing methods are techniques suitable for applying the etching paste as required. In general, besides the printing method described, manual application (for example brushing) is also possible.

In addition to industrial applications, etching pastes are also suitable for DIY (do it yourself) and hobby needs.

The printable, homogeneous, particle-free etching pastes having non-Newtonian flow behaviour which are described in accordance with the invention can be used in all cases in which layers of glass and other silicon dioxide-based and silicon nitride-based systems having variable thicknesses are to be etched over the entire area and/or in a structured manner. The fields of application are, for example:

● all etching steps on the layers of silicon dioxide-and silicon nitride-based glasses and other silicon dioxide-and silicon nitride-based systems, which lead to the production of photovoltaic modules, such as solar cells, photodiodes, etc., in particular

a) Removing silicon dioxide/doped silicon dioxide (e.g. n-doped phosphorous glass for solar cells) and silicon nitride layers

b) Selective opening of the passivation layers of silicon dioxide and silicon nitride, resulting in a two-stage selective emitter (after opening, re-doping to produce n)⁺⁺Layer) and/or local p⁺Back Surface Field (BSF)

c) Edge etching of silicon dioxide-and/or silicon nitride-coated solar panels

● all etching steps on the layers of silicon dioxide-and silicon nitride-based glasses and other silicon dioxide-and silicon nitride-based systems that result in the production of semiconductor components and circuits and require the opening of passivation layers of silicon dioxide and silicon nitride

● all etching steps on layers of silicon dioxide-and silicon nitride-based glasses and other silicon dioxide-and silicon nitride-based systems that result in the production of components in high performance electronic devices

In particular, screen printing, pad printing, stamp printing and inkjet printing methods are techniques suitable for applying the etching paste as required. In general, besides the printing method described, manual application is also possible.

In addition to industrial applications, etching pastes are also suitable for DIY and hobby needs.

Examples

For a better understanding and illustration, the following examples are given which fall within the scope of protection of the invention, but it is not appropriate to limit the invention to these examples.

Example 1

21g ethylene glycol monobutyl ether

39g 35％NH₄HF₂Solutions of

30g formic acid (98-100%)

10g PVP K-120

Ethylene glycol monobutyl ether and formic acid were introduced into a PE beaker. Then 35% NH was added₄HF₂An aqueous solution. PVP K-120 was then added continuously with stirring (at least 400 rpm). Vigorous stirring must be continued during and within about 30 minutes after addition. After a short standing time, transfer to a container. The standing time must be such that the bubbles formed in the etching paste can dissolve.

The etching pastes obtained from the mixtures can etch silicon dioxide-and silicon nitride-based glasses and other silicon dioxide-and silicon nitride-based systems and their layers down to the desired depth, either over the entire area or in the structure, specifically, with and/or without input of energy.

The etch rate (determined photometrically) on a thermally generated silicon dioxide layer was 120nm/min in the case of etching the entire area. The etching rate (determined photometrically) on a silicon nitride layer (refractive index n ═ 1.98) produced by PE-CVD (polyethylene-chemical vapor deposition) was 70nm/min with etching of the entire area.

The etching pastes obtained have a long shelf life, are easy to handle and are printable. He can be removed from the printed material or paste carrier (screen, knife, screen, stamp, plate, cartridge, etc.) using, for example, water or burnt off in an oven.

Example 2

22g triethylene glycol monomethyl ether

43g 35％NH₄HF₂Solutions of

20g of demineralized water

12g PVP K-120

Triethylene glycol monomethyl ether was first introduced and all liquid components were added with stirring as in example 1. Finally the thickener PVP K-120 was introduced continuously with stirring (at least 400 rpm). Vigorous stirring must be continued during and within about 30 minutes after addition. After a short standing time, transfer to a container. The standing time must be such that the bubbles formed in the etching paste can dissolve.

The etching paste obtained from the mixture can be used to etch silicon dioxide-and silicon nitride-based glasses and other SiO with and/or without input of energy₂And silicon nitride based systems and their layers are etched down specifically to the required depth over the whole area or in the structure.

The etch rate (determined photometrically) on a thermally generated silicon dioxide layer was 106nm/min in the case of etching the entire area.

The etching pastes obtained have a long shelf life, are easy to handle and are printable. It can be removed from the printed material or paste carrier (screen, knife, screen, stamp, plate, cartridge, etc.) for example using water or burnt off in an oven.

Example 3

12g of solid NH₄HF₂

142g lactic acid

10g of ethylcellulose

36g ethylene glycol monobutyl ether

The ethyl cellulose was continuously stirred into the initially introduced ethylene glycol monobutyl ether in a water bath at 40 ℃. NH in the solid state is likewise stirred₄HF₂Dissolved in lactic acid and subsequently added to the ethylcellulose stock paste. The two were then stirred together at 600rpm for 2 hours.

The etching pastes obtained from the mixtures can etch silicon dioxide-and silicon nitride-based glasses and other silicon dioxide-and silicon nitride-based systems and their layers down to the desired depth, either over the entire area or in the structure, specifically, with and/or without input of energy.

The etch rate (determined photometrically) on a thermally generated silicon dioxide layer was 23nm/min in the case of etching the entire area.

The etching pastes obtained have a long shelf life, are easy to handle and are printable. He can be removed from the printed material or paste carrier (screen, knife, screen, stamp, plate, cartridge, etc.) or burnt off in an oven, for example using acetone or butyl acetate.

Example 4

15g ethylene glycol monobutyl ether

15g triethylene glycol monomethyl ether

29g of propylene carbonate

72g of formic acid

46g 35％NH₄HF₂Solutions of

24g PVP K-90

The solvent mixture and formic acid were introduced into a PE beaker. Then 35% NH was added₄HF₂An aqueous solution. PVP K-90 was then added continuously with stirring (at least 400 rpm). Vigorous stirring must be continued during and within about 30 minutes after addition. After a short standing time, transfer to a container. The standing time must be such that the bubbles formed in the etching paste can dissolve.

The etching pastes obtained from the mixtures can etch silicon dioxide-and silicon nitride-based glasses and other silicon dioxide-and silicon nitride-based systems and their layers down to the desired depth, either over the entire area or in the structure, specifically, with and/or without input of energy.

The etch rate (determined photometrically) on a thermally produced silicon dioxide layer was 67nm/min in the case of selective etching of structures with a width of about 80 μm. The etch rate (determined photometrically) on a silicon nitride layer produced by PE-CVD was 35nm/min at a selective etch of structures with a width of about 100 μm and an etch temperature of 40 ℃.

The etching pastes obtained have a long shelf life, are easy to handle and are printable. He can be removed from the printed material or paste carrier (screen, knife, screen, stamp, plate, cartridge, etc.) using, for example, water or burnt off in an oven.

Claims (27)

1. A printable, homogeneous, particle-free etching medium with non-newtonian flow behaviour for etching glass surfaces, the glass being selected from the group consisting of silicon dioxide-based glass and silicon nitride-based glass, wherein the etching medium is an etching paste with non-newtonian flow behaviour, the paste comprising:

a) at least one etching component for the glass surface, selected from the group consisting of fluorides, bifluorides and tetrafluoroborates, wherein the etching component is present in a concentration of 5 to 15 wt. -%, based on the total amount of the medium,

b) a solvent, and

c) 0.5 to 25 wt.%, based on the total amount of the etching medium, of a thickener selected from the group consisting of cellulose/cellulose derivatives, starch/starch derivatives and/or polymers based on acrylate or functionalized vinyl units, wherein the thickener is not xanthan gum,

even at temperatures of 15-50 c.

2. Etching medium according to claim 1, characterized in that the etching paste further comprises d) an organic and/or inorganic acid.

3. Etching medium according to claim 1 or 2, characterized in that the etching paste further comprises e) additives selected from the group consisting of defoamers, thixotropic agents, flow control agents, degassing agents and adhesion promoters.

4. Etching medium according to claim 1 or 2, characterized in that the etching paste is activated by input of energy.

5. An etching medium according to claim 1 or 2 for use on a glass surface, said glass comprising an element selected from the group consisting of calcium, sodium, aluminium, lead, lithium, magnesium, barium, potassium, boron, beryllium, phosphorus, gallium, arsenic, antimony, lanthanum, scandium, zinc, thorium, copper, chromium, manganese, iron, cobalt, nickel, molybdenum, vanadium, titanium, gold, platinum, palladium, silver, cerium, cesium, niobium, tantalum, zirconium, yttrium, neodymium and praseodymium.

6. Etching medium according to claim 1 or 2, characterized in that it comprises as etching component at least one fluorine compound selected from the group consisting of ammonium fluoride, alkali metal fluorides, antimony fluoride, ammonium bifluoride, alkali metal bifluorides, calcium difluoride, alkylated ammonium tetrafluoroborates and potassium tetrafluoroborates.

7. Etching medium according to claim 6, characterized in that it comprises at least one mineral acid selected from the group consisting of hydrochloric acid, phosphoric acid, sulfuric acid and nitric acid.

8. Etching medium according to claim 6, characterized in that it comprises at least one organic acid which contains a linear or branched alkyl group having 1 to 10 carbon atoms and is selected from the group consisting of alkyl carboxylic acids, hydroxycarboxylic acids and dicarboxylic acids.

9. Etching medium according to claim 7, characterized in that it comprises at least one organic acid which contains a linear or branched alkyl group having 1 to 10 carbon atoms and is selected from the group consisting of alkyl carboxylic acids, hydroxycarboxylic acids and dicarboxylic acids.

10. Etching medium according to claim 1 or 2, characterized in that it comprises an organic acid selected from the group consisting of formic acid, acetic acid, lactic acid and oxalic acid.

11. Etching medium according to claim 1 or 2, characterized in that the proportion of organic and/or inorganic acids is in the concentration range of 0 to 80% by weight, based on the total amount of the medium, the acids added each having a pK_aThe value is 0 to 5.

12. Etching medium according to claim 1 or 2, characterized in that it comprises water as solvent; mono-or polyhydric alcohols selected from glycerol, 1, 2-propanediol, 1, 4-butanediol, 1, 3-butanediol, 1, 5-pentanediol, 2-ethyl-1-hexenol, ethylene glycol, diethylene glycol and dipropylene glycol, and ethers thereof selected from ethylene glycol monobutyl ether, triethylene glycol monomethyl ether, diethylene glycol monobutyl ether and dipropylene glycol monomethyl ether; esters selected from [2, 2-butoxy (ethoxy) ] ethyl acetate, carbonates; ketones selected from the group consisting of acetophenone, methyl-2-hexanone, 2-octanone, 4-hydroxy-4-methyl-2-pentanone and 1-methyl-2-pyrrolidone, which are used directly or in a mixture and in an amount of 10 to 90% by weight, based on the total amount of the medium.

13. Etching medium according to claim 12, characterized in that the amount of solvent is 15 to 85% by weight, based on the total amount of the medium.

14. Etching medium according to claim 1 or 2, characterized in that it contains 0 to 5% by weight, based on the total amount, of additives selected from the group consisting of defoamers, thixotropic agents, flow control agents, deaerators and adhesion promoters.

15. Etching medium according to claim 1 or 2, characterized in that the thickener is 3 to 20 wt.%, based on the total amount of the etching medium.

16. Use of an etching medium according to any of claims 1 to 15 in an etching process in which it is applied to the surface to be etched and removed again after an exposure time of 1 to 15 minutes.

17. Use of an etching medium according to any of claims 1 to 15 in the photovoltaic, semiconductor technology, high-performance electronics, mineralogy or glass industry and in the production of photodiodes, observation windows for valves or measuring devices, glass supports for outdoor applications, etched glass surfaces in the medical, decorative and hygiene field, etched glass containers for cosmetic articles, food and beverages, markings or labels on containers and flat glass.

18. Use of an etching medium according to any one of claims 1 to 15 in screen printing, screen printing pad printing, stamp printing, ink jet printing and manual printing processes.

19. Use of an etching medium according to any of claims 1 to 15 for the production of glass supports for solar cells or heat collectors.

20. Etching medium according to any of claims 1 to 15 for etching SiO-containing materials in the form of homogeneous, intact, non-porous or porous solids₂Or silicon nitride glass or corresponding non-porous or porous glass layers of variable thickness which have been produced on other substrates.

21. Use of an etching medium according to any one of claims 1 to 15 for etching uniform, dense, non-porous or porous glasses based on silicon dioxide or silicon nitride systems and variable thickness layers of such systems.

22. Etching medium according to any of claims 1 to 15 in the removal of silicon dioxide/doped silicon dioxide and silicon nitride layers, selective opening of passivation layers of silicon dioxide and silicon nitride to produce two-stage selective emitters and/or local p⁺Back surface field and edge etched silicon dioxide-and silicon nitride coated solar cells.

23. Use of an etching medium according to any one of claims 1 to 15 for opening passivation layers of silicon dioxide and silicon nitride in a process for producing semiconductor components and circuits thereof.

24. Use of an etching medium according to any one of claims 1 to 15 for opening passivation layers of silicon dioxide and silicon nitride in a process for producing components for high-performance electronic devices.

25. Use of an etching medium according to any of claims 1 to 15 in mineralogical, geological and microstructural studies.

26. A method for etching inorganic, glassy, crystalline surfaces, characterized in that an etching medium according to any of claims 1 to 15 is applied to the entire area or, in particular, to the etching structure-specific mask only to the points where etching is required, and is rinsed with a solvent or solvent mixture or burnt off in an oven after the etching has been completed.

27. The method according to claim 26, characterized in that the etching medium is rinsed with water after the etching has been completed.