EP2080019A1 - Method for producing at least one porous layer - Google Patents

Method for producing at least one porous layer

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Publication number
EP2080019A1
EP2080019A1 EP07821128A EP07821128A EP2080019A1 EP 2080019 A1 EP2080019 A1 EP 2080019A1 EP 07821128 A EP07821128 A EP 07821128A EP 07821128 A EP07821128 A EP 07821128A EP 2080019 A1 EP2080019 A1 EP 2080019A1
Authority
EP
European Patent Office
Prior art keywords
layer
suspension
particles
forming material
substrate
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP07821128A
Other languages
German (de)
French (fr)
Inventor
Richard Fix
Oliver Wolst
Markus Widenmeyer
Alexander Martin
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Publication of EP2080019A1 publication Critical patent/EP2080019A1/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/02—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/02—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition
    • C23C18/08—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of metallic material
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/02—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition
    • C23C18/12—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material
    • C23C18/1204—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material inorganic material, e.g. non-oxide and non-metallic such as sulfides, nitrides based compounds
    • C23C18/1208—Oxides, e.g. ceramics
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/02—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition
    • C23C18/12—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material
    • C23C18/1204—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material inorganic material, e.g. non-oxide and non-metallic such as sulfides, nitrides based compounds
    • C23C18/122—Inorganic polymers, e.g. silanes, polysilazanes, polysiloxanes
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/02—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition
    • C23C18/12—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by thermal decomposition characterised by the deposition of inorganic material other than metallic material
    • C23C18/125—Process of deposition of the inorganic material
    • C23C18/1262—Process of deposition of the inorganic material involving particles, e.g. carbon nanotubes [CNT], flakes
    • C23C18/127—Preformed particles
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
    • C23C18/14—Decomposition by irradiation, e.g. photolysis, particle radiation or by mixed irradiation sources
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C24/00—Coating starting from inorganic powder
    • C23C24/08—Coating starting from inorganic powder by application of heat or pressure and heat
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C26/00—Coating not provided for in groups C23C2/00 - C23C24/00
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/414—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS
    • G01N27/4141—Ion-sensitive or chemical field-effect transistors, i.e. ISFETS or CHEMFETS specially adapted for gases

Definitions

  • the invention relates to a method for producing at least one porous layer on a substrate.
  • Such porous layers are used, for example, for gate electrodes of differential effect transistors used as gas sensors.
  • the method according to the invention for producing at least one porous layer on a substrate comprises the following steps: (a) applying a suspension comprising particles of a layer-forming material or molecular precursors of the layer-forming material and at least one organic component to the substrate,
  • steps (a) to (d) can be repeated.
  • steps (a) to (c) are repeated until a sufficient layer thickness is obtained, then step (d) is performed.
  • Advantage of the method according to the invention is that a uniform porous structure is achieved by the organic component contained in the suspension, and the final removal of the organic component.
  • the organic component prevents particles of the layer-forming material from agglomerating, which would limit or prevent the formation of the desired layer.
  • the film-forming component is, for example, a metal, a ceramic or a mixture of metal and ceramic, a so-called cermet. Furthermore, it is also possible that the layer-forming component contains a mixture of several metals or more ceramics or a mixture of metal and ceramic. Suitable metals are, for example, elements of the 8th, 9th, 10th or 11th group of the periodic table. Particularly suitable metals are platinum, palladium, gold and iridium. Preferred ceramics are, for example, alumina, silica, zirconia or magnesia.
  • the porous layer produced according to the invention When the porous layers produced according to the invention are used, for example, for gate electrodes of field-effect transistors, it is necessary for the porous layer to be electrically conductive. If non-electrically conductive ceramics are contained in the porous layer, an electrically conductive material, preferably a metal, must additionally be contained. For an electrically conductive layer, the ratio of electrically conductive material to nonconductive ceramic applies:
  • V M is the volume fraction of the metal
  • V K the volume fraction of the ceramic
  • D ⁇ the mean diameter of the ceramic particles
  • D M the mean diameter of the electrically conductive particles.
  • the organic component contained in the suspension preferably comprises monomers, oligomers or polymers which can cure to a polymer matrix, at least one solvent or a mixture thereof.
  • Suitable polymers are, for example, polyethylene glycol and its derivatives or polyethylene lenimin.
  • Suitable monomers or oligomers are, for example, lactams, vinyl derivatives or styrene derivatives. If the monomers or oligomers are in liquid form, they may optionally be used as a solvent and a further organic solvent may be dispensed with. The organic solvent is generally used to adjust the viscosity of the suspension.
  • Suitable solvents are, for example, alcohols, ethers, glycol derivatives, N-containing solvents.
  • the suspension further contains organic particles as a structure-directing component.
  • the organic particles which act as a structure-directing component are also removed in step (d).
  • the organic particles acting as structure-directing component also affect the porosity of the porous layer.
  • the organic particles are preferably present in a size in the range of 10 to 1000 nm. Suitable organic particles are, for example, pyrolysis, latex, macromolecules or surfactants.
  • the suspension receives at least one stabilizer.
  • stabilizers are, for example, oxygen, nitrogen or phosphorus-containing, organic, usually gelating complexing agents, for example derivatives of polyethylene oxides, phenanthrolines or polyhydric alcohols.
  • a suitable stabilizer is, for example, diethylene glycol monobutyl ether.
  • the abovementioned organic substances can also be used as stabilizer.
  • the solvent contained in the suspension is at least partially removed by drying.
  • the solvent By removing the solvent creates a regular arrangement of the particles of layer-forming material. In the spaces between the particles are, for example, the monomers or oligomers, which can harden to the polymer matrix.
  • the monomers or oligomers contained in the suspension are optionally cured to form a polymer matrix.
  • the polymer matrix is located in the spaces between the particles of the layer-forming material. This avoids that the particles of the layer-forming material can agglomerate. The result is first a regular distribution of the particles of the layer-forming material in the cured polymer matrix.
  • sintering of the ceramic or metallic particles or the mixture of ceramic and metallic particles takes place.
  • the polymer which is in the interstices between the particles of the layer-forming material is removed. This creates a porous layer.
  • the removal of the organic polymer matrix takes place, for example, by burning.
  • the polymer matrix can also be triggered out of the layer, for example, with suitable solvents. Subsequently, however, it is necessary to subsequently remove the solvent.
  • the layer-forming particles contained in the suspension preferably have an average diameter in the range of 0.5 to 1000 nm. More preferably, the average diameter of the layer-forming particles is in the range of 0.5 to 100 nm, in particular in the range of 1 to 20 nm.
  • the layer-forming particles are present in a colloid.
  • the material used for the layer-forming particles is preferably at least one element of the 8th, 9th, 10th or 11th group of the Periodic Table, in particular platinum, palladium, gold, silver, rhodium and iridium.
  • the at least one metal is dissolved in a solvent, for example in the form of its salt or in the form of an organometallic compound, and reduced with stirring.
  • Suitable salts are nitrates, chlorides, bromides or carbonates.
  • Suitable organometallic compounds are acetates, alcoholates, acetylacetonates or corresponding organometallics in a suitable solvent, such as an alcohol, ether, glycol derivative or N-containing solvent.
  • a suitable solvent such as an alcohol, ether, glycol derivative or N-containing solvent.
  • the dissolved metal salts or organometallic compounds are then subjected to different reduction conditions.
  • a reducing agent for example, for the production of platinum colloids formaldehyde, formic acid, ethanol, a mixture of formic acid and ethanol, a mixture of citric acid and Ethanol, a mixture of ascorbic acid and ethanol, hydrazine, hydrogen, borane derivatives or a mixture of glyoxylic acid and ethanol.
  • the corresponding reducing agents are used in each case in excess, based on platinum.
  • the dissolved metal salts are reduced with stirring. The reduction takes place in a period of 5 minutes to several days.
  • the metal particle sizes in colloid which are achieved in this case, are in the range between 0.5 to 100 nm, preferably in the range between 1 to 20 nm.
  • the metal concentrations are in the range of 0.01 to 15% by weight, preferably in Range of 0.5 to 5 wt .-%.
  • the metal particles on the carrier, for example a gate of a semiconductor transistor.
  • the corresponding oxometallecolloids are reduced on the support.
  • the reduction can be carried out, for example, by gaseous hydrogen or by organic layer constituents.
  • the application of the suspension containing particles of the layer-forming material or molecular precursors of the layer-forming material to the substrate is effected, for example, by dropping by means of a microliter syringe, by spin coating in a higher-viscosity suspension or by means of a thick-layer printing technique, for example, if the suspension is present as a paste ,
  • the thickness and the porosity of the porous layer are adjusted by the concentration of the suspension, the thickness of the order of the suspension or by a possible multiple coating.
  • a multiple coating is particularly advantageous if larger amounts of coating-forming material are to be applied than the suspension contains for a given drop volume.
  • a multiple coating refers to a multiple application and drying of the particles of layer-forming material or molecular precursors of the layer-forming material containing suspension. Alternatively, thermolysis or combustion can also be carried out after application of the suspension before application of the next layer. An application in several layers is required, for example, if only a small concentration of layer-forming material in the suspension can be adjusted due to agglomeration of the particles of the layer-forming material.
  • a thermal treatment This includes pre-drying, thermolysis or pyrolysis and thermal sintering of the particles from the layer-forming material.
  • the predrying preferably takes place at a temperature in the range from 20 to 150 ° C.
  • the predrying removes solvent from the suspension. This will freeze the solution, a so-called Lack Struktur, causes which prevents unwanted agglomeration of the particles of the layer-forming material. As a result, an even distribution of the particles of the layer-forming material in the form of a porous film is realized on the substrate.
  • the predrying is followed by a thermolysis or pyrolysis step at a temperature in the range from 100 to 650 ° C. By thermolysis or pyrolysis, the organic components of the suspension are completely removed. Only the inorganic components remain. The achievement of the maximum temperature can be realized in one step or in several half steps with intermediate holding times.
  • thermolysis or pyrolysis it is also possible to use different atmospheres.
  • thermolysis or pyrolysis in the presence of air in the presence of an inert atmosphere, for example in the form of pure nitrogen, or in the presence of a reducing atmosphere, for example in the presence of a mixture of nitrogen and hydrogen, wherein the proportion of hydrogen in the mixture is 0.5 to 10 vol .-%, be carried out.
  • the porous layer produced by the method according to the invention is preferably used in semiconductor transistors having at least one gate electrode which has an electrically conductive porous coating.
  • Such transistors are used for example as gas sensors. This is possible because the gases interact with the gate electrode material of the field effect transistor.
  • a targeted adsorption of gases and / or a catalytic reaction takes place at the surface of the gate electrode produced according to the invention.
  • highly sensitive and selective material processes take place at the gate electrode surface.
  • Gas adsorption and selective material processes at the three-phase boundaries metal phase, oxide-ceramic phase and gas phase
  • the characteristic and fine calibration of the three-phase limit are decisive for the sensitivity and response time of the gas sensor.
  • the porosity of the surface of the gate electrode can be adjusted specifically.
  • the porous layers produced according to the invention are more resistant to thermal stress and therefore exhibit stable sensor signals over an extended temperature range and over a longer period of operation than the gate electrodes known from the prior art.
  • FIG. 1 shows a TEM image of solution-reduced platinum colloids
  • FIG. 2.1 shows a schematic representation of a suspension applied to a substrate which contains layer-forming particles
  • FIG. 2.2 shows the layer applied in FIG. 3.1 after predrying
  • FIG. 2.3 a schematic representation of a porous layer on a substrate
  • FIG. 3.1 a schematic representation of a first porous layer on a substrate
  • Figure 3.2 is a schematic representation of a two-layer structure.
  • FIG. 4 shows a SEM image of a porous layer of platinum produced according to the invention
  • FIG. 1 shows a transmission electron micrograph of a suspension containing platinum as a layer-forming material.
  • particles 3 are contained from a layer-forming material. As can be seen in FIG. 1, the particles 3 of the layer-forming material are distributed uniformly in the suspension 1.
  • the particles 3 are platinum colloids.
  • platinum is dissolved in the form of one of its salts, for example as nitrate, chloride, bromide or carbonate, or in the form of one of its organometallic compounds, for example as acetate, alkoxide, acetylacetonate or as appropriate metalorganyl in a suitable solvent.
  • Suitable solvents are, for example, alcohol, ethers, glycol derivatives or N-containing solvents.
  • the solution may be further added with a stabilizer.
  • a stabilizer for example, diethylene glycol monobutyl ether can be used.
  • the solution of the metal salt or organometallic compound is then subjected to different reduction conditions.
  • formaldehyde, formic acid, ethanol, hydrazine, hydrogen, borane derivatives or mixtures of ethanol are used for the reduction Citric acid, ascorbic acid, hydrazine or glyoxylic acid used.
  • the reducing agent is used in each case in excess, based on platinum.
  • platinum colloids As shown in Figure 1, and metal colloids of the other elements of the 8th, 9th, 10th and 11th Group of the Periodic Table are suitable.
  • platinum, palladium, gold, silver, rhodium and iridium are also particularly suitable.
  • ceramic particles may also be present in the suspension as a layer-forming material.
  • FIG. 2.1 schematically shows a substrate to which a suspension containing particles of a layer-forming material has been applied.
  • a substrate 11 to which the suspension 1 containing the layer-forming particles 3 is applied is, for example, a field-effect transistor to be provided with a gate electrode.
  • the suspension 1 is applied to the substrate 11, for example by means of a dispenser.
  • a substrate for example, a smooth, oxidic surface with low roughness is suitable.
  • a suitable suspension 1 contains, for example, 3% by weight of polyethylene glycol, 1.75% by weight of platinum colloids with a mean diameter d 50 of 50 nm, 0.25% by weight of Al 2 O 3 with an average diameter d 50 of 200 nm, and 95% by weight .-% ethanol. After application, this suspension is pre-dried at 30 0 C. By predrying ethanol is removed from the suspension. The volume of the applied layer on the substrate decreases. This is shown in FIG. 2.2. After volatilization of the ethanol, the polyethylene glycol forms a solid matrix containing platinum and alumina particles in a regular array.
  • the organic components After drying, the organic components are removed at a temperature of 400 0 C over a period of 4 h in the presence of air.
  • the layer-forming materials namely platinum and alumina, leave behind a porous, uniform layer. This is shown in FIG. 2.3.
  • FIGS. 3.1 and 3.2 schematically show a multilayer structure of the porous coating on the substrate.
  • a first porous layer 21 is first applied to the substrate 11.
  • the first porous layer 21 is predried in a first embodiment and then a second porous layer 23 is applied, as shown in FIG. 3.2 is shown. After the application of the second porous layer 23, this is also pre-dried. Subsequently, the organic component is removed from the first porous layer 21 and the second porous layer 23.
  • FIG. 4 shows a scanning electron micrograph of a porous layer produced according to the invention.
  • the individual particles 3 from the suspension 1 combine to form a sponge-like structure 33.
  • Voids 35 are formed in the sponge-like structure 33.
  • the cavities 35 are distributed uniformly in the porous layer 31. An agglomeration of layer-forming material and thus a massive area in the porous layer 31 can not be seen.
  • a suspension of 3 wt .-% polyethylene glycol, 1.75 wt .-% of platinum having an average particle diameter dso of 50 nm, 0.25 wt .-% Al 2 O 3 with an average diameter dso of 200 nm and 95 wt. -% ethanol is applied to a smooth, oxidic surface with low roughness by means of a dispenser so that 10 ⁇ l / cm 2 remain.
  • the suspension applied to the surface is predried at 30 ° C. and then at 150 ° C. for 2 hours
  • the organic components are finally removed at 400 ° C. in the course of 4 h in the presence of air.
  • the polyethylene glycol after volatilization of the ethanol, forms a matrix which regularly contains platinum and Al 2 O 3 particles. Upon burning off of the organic matrix, the layer-forming materials leave a porous, even layer.
  • a mean diameter d 50 of 100 nm is dispensed by means of a dispenser on a smooth, oxidic surface with low roughness, so that 5 .mu.l / cm "2 remain.
  • the suspension is first predried for 2 hours at 60 0 C and then dried for 4 hours at 120 0 C and cured by platinum is reduced After the removal of the ethanol, the latex beads form a regular array of balls in the interspaces of which the sintered platinum and zirconium dioxide and residues of the low-volatility solvent, 1,2-propanediol, are present.
  • the substrate with the applied layers is first subjected to a heat treatment at 100 ° C. for 8 hours. Subsequently, the organic or volatile components are removed at 300 ° C. for 8 h at nitrogen and subsequently at 480 ° C. for 4 h in air. After removal of the organic matrix, a mesoporous, uniform layer of a platinum-zirconium dioxide composite remains, which is covered with a mesoporous Al 2 O 3 layer.

Abstract

The invention relates to a method for producing at least one porous layer (21, 23; 31) on a substrate (11), in which a suspension (1) containing particles (3) of a layer-forming material or molecular precursors of the layer-forming material and also at least one organic component is applied to the substrate (11), the precursors of the layer-forming material subsequently react to form the layer-forming material after application to the substrate (11), in a next step the particles (3) of the layer-forming material are sintered and, finally, the at least one organic component is removed. The invention furthermore relates to a field effect transistor comprising at least one gate electrode, wherein the gate electrode has an electrically conductive porous coating (21, 23; 31) produced via the method according to the invention.

Description

Beschreibung description
Titeltitle
Verfahren zur Herstellung mindestens einer porösen SchichtProcess for the preparation of at least one porous layer
Stand der TechnikState of the art
Die Erfindung betrifft ein Verfahren zur Herstellung mindestens einer porösen Schicht auf einem Substrat.The invention relates to a method for producing at least one porous layer on a substrate.
Derartige poröse Schichten werden zum Beispiel eingesetzt für Gateelektroden von FeId- effekttransistoren, die als Gassensoren verwendet werden.Such porous layers are used, for example, for gate electrodes of differential effect transistors used as gas sensors.
Derzeit erfolgt die Herstellung der Gateelektroden von Halbleitertransistoren im Zuge der Prozessierung des Transistors durch Aufsputtern oder Aufdampfen von Metallen, zum Beispiel Aluminium, Platin, Nickel usw. Die bei Raumtemperatur abgeschiedenen Gateschich- ten sind nahezu geschlossene, unporöse und thermisch instabile metallische Filme, die insbesondere bei höheren Temperaturen, d. h. bei Temperaturen von mehr als 200 0C, ihre makroskopische Struktur verlieren. Dies hat zur Folge, dass sich die elektrochemischen Eigenschaften der Gateelektroden verändern und somit die Sensoreigenschaften über die Betriebsdauer instabil sind bzw. die Sensorfunktion des Feldeffekttransistors sogar vollstän- dig ausfällt. Auch sind aufgrund der wenig definierten Gateelektrodenstrukturen bei auf- gesputterten oder aufgedampften Gateschichten hochsensitive oder selektive Stoffprozesse, d. h. eine gezielte Adsorption von Gasen und/oder katalytische Reaktionen, nicht zu erwarten. Eine gezielte Einstellung der Porosität der aufgesputterten oder aufgedampften Gateschichten ist nicht möglich.Currently, the production of the gate electrodes of semiconductor transistors in the course of processing the transistor by sputtering or vapor deposition of metals, for example aluminum, platinum, nickel, etc. The gate layers deposited at room temperature are almost closed, non-porous and thermally unstable metallic films, in particular at higher temperatures, ie at temperatures above 200 ° C., lose their macroscopic structure. This has the consequence that the electrochemical properties of the gate electrodes change and thus the sensor properties are unstable over the operating time or the sensor function of the field effect transistor even fails completely. Also, due to the poorly defined gate electrode structures in the case of sputtered-on or vapor-deposited gate layers, highly sensitive or selective material processes, ie a targeted adsorption of gases and / or catalytic reactions, are not to be expected. A targeted adjustment of the porosity of the sputtered or vapor-deposited gate layers is not possible.
Offenbarung der ErfindungDisclosure of the invention
Vorteile der ErfindungAdvantages of the invention
Das erfindungsgemäße Verfahren zur Herstellung mindestens einer porösen Schicht auf einem Substrat umfasst folgende Schritte: (a) Auftragen einer Suspension, die Partikel aus einem schichtbildenden Material oder molekulare Vorstufen des schichtbildenden Materials sowie mindestens eine organische Komponente enthält, auf das Substrat,The method according to the invention for producing at least one porous layer on a substrate comprises the following steps: (a) applying a suspension comprising particles of a layer-forming material or molecular precursors of the layer-forming material and at least one organic component to the substrate,
(b) gegebenenfalls Reaktion der Vorstufen des schichtbildenden Materials zum schichtbildenden Material nach dem Auftragen auf das Substrat,(b) optionally, reacting the precursors of the layer-forming material to the layer-forming material after application to the substrate,
(c) Tempern der Partikel aus dem schichtbildenden Material,(c) annealing the particles of the layer-forming material,
d) Entfernen der mindestens einen organischen Komponente.d) removing the at least one organic component.
Zur Herstellung von dickeren porösen Schichten können die Schritte (a) bis (d) wiederholt werden. Vorzugsweise werden die Schritte (a) bis (c) wiederholt, bis eine ausreichende Schichtdicke vorliegt, danach wird Schritt (d) durchgeführt.To produce thicker porous layers, steps (a) to (d) can be repeated. Preferably, steps (a) to (c) are repeated until a sufficient layer thickness is obtained, then step (d) is performed.
Vorteil des erfindungsgemäßen Verfahrens ist es, dass durch die organische Komponente, die in der Suspension enthalten ist, und das abschließende Entfernen der organischen Komponente eine gleichmäßige poröse Struktur erzielt wird. Durch die organische Komponente wird vermieden, dass Partikel des schichtbildenden Materials agglomerieren, wodurch die Bildung der gewünschten Schicht eingeschränkt oder verhindert würde.Advantage of the method according to the invention is that a uniform porous structure is achieved by the organic component contained in the suspension, and the final removal of the organic component. The organic component prevents particles of the layer-forming material from agglomerating, which would limit or prevent the formation of the desired layer.
Die schichtbildende Komponente ist zum Beispiel ein Metall, eine Keramik oder eine Mischung aus Metall und Keramik, ein so genanntes Cermet. Weiterhin ist es auch möglich, dass die schichtbildende Komponente eine Mischung aus mehreren Metallen oder mehreren Keramiken oder eine Mischung aus Metall und Keramik enthält. Geeignete Metalle sind zum Beispiel Elemente der 8., 9., 10. oder 11. Gruppe des Periodensystems. Besonders geeignete Metalle sind Platin, Palladium, Gold und Iridium. Bevorzugte Keramiken sind zum Beispiel Aluminiumoxid, Siliziumoxid, Zirkonoxid oder Magnesiumoxid.The film-forming component is, for example, a metal, a ceramic or a mixture of metal and ceramic, a so-called cermet. Furthermore, it is also possible that the layer-forming component contains a mixture of several metals or more ceramics or a mixture of metal and ceramic. Suitable metals are, for example, elements of the 8th, 9th, 10th or 11th group of the periodic table. Particularly suitable metals are platinum, palladium, gold and iridium. Preferred ceramics are, for example, alumina, silica, zirconia or magnesia.
Wenn die erfindungsgemäß hergestellten porösen Schichten zum Beispiel für Gateelektroden von Feldeffekttransistoren verwendet werden, ist es erforderlich, dass die poröse Schicht elektrisch leitfähig ist. Wenn in der porösen Schicht nicht elektrisch leitfähige Keramiken enthalten sind, muss zusätzlich ein elektrisch leitfähiges Material, vorzugsweise ein Metall enthalten sein. Für eine elektrisch leitfähige Schicht gilt für das Verhältnis von elekt- risch leitfähigem Material zu nicht leitfähiger Keramik:When the porous layers produced according to the invention are used, for example, for gate electrodes of field-effect transistors, it is necessary for the porous layer to be electrically conductive. If non-electrically conductive ceramics are contained in the porous layer, an electrically conductive material, preferably a metal, must additionally be contained. For an electrically conductive layer, the ratio of electrically conductive material to nonconductive ceramic applies:
— = \,2. $L) . (ßlL) (I) In Gleichung (I) bedeuten VM der Volumenanteil des Metalls, VK der Volumenanteil der Keramik, Dκ den mittleren Durchmesser der keramischen Teilchen, DM den mittleren Durchmesser der elektrisch leitfähigen Teilchen.- = \, 2. $ L). (III) (I) In equation (I) V M is the volume fraction of the metal, V K, the volume fraction of the ceramic, D κ the mean diameter of the ceramic particles, D M the mean diameter of the electrically conductive particles.
Die organische Komponente, die in der Suspension enthalten ist, umfasst vorzugsweise Monomere, Oligomere oder Polymere, die zu einer Polymermatrix aushärten können, mindestens ein Lösungsmittel oder eine Mischung daraus.The organic component contained in the suspension preferably comprises monomers, oligomers or polymers which can cure to a polymer matrix, at least one solvent or a mixture thereof.
Geeignete Polymere sind zum Beispiel Polyethylenglycol und seine Derivate oder Polyethy- lenimin. Geeignete Monomere oder Oligomere sind zum Beispiel Lactame, Vinylderivate oder Styrolderivate. Wenn die Monomere oder Oligomere in flüssiger Form vorliegen, können diese gegebenenfalls als Lösungsmittel verwendet werden und auf ein weiteres organi- sches Lösungsmittel kann verzichtet werden. Das organische Lösungsmittel wird im allgemeinen eingesetzt, um die Viskosität der Suspension einzustellen. Als Lösungsmittel eignen sich zum Beispiel Alkohole, Ether, Glykolderivate, N-haltige Lösungsmittel.Suitable polymers are, for example, polyethylene glycol and its derivatives or polyethylene lenimin. Suitable monomers or oligomers are, for example, lactams, vinyl derivatives or styrene derivatives. If the monomers or oligomers are in liquid form, they may optionally be used as a solvent and a further organic solvent may be dispensed with. The organic solvent is generally used to adjust the viscosity of the suspension. Suitable solvents are, for example, alcohols, ethers, glycol derivatives, N-containing solvents.
In einer Ausführunsform enthält die Suspension weiterhin organische Teilchen als struktur- dirigierende Komponente. Die organischen Teilchen, die als strukturdirigierende Komponente wirken, werden ebenfalls in Schritt (d) entfernt. Somit beeinflussen die als strukturdirigierende Komponente wirkenden organischen Teilchen ebenfalls die Porosität der porösen Schicht. Die organischen Teilchen liegen vorzugsweise in einer Größe im Bereich von 10 bis 1000 nm vor. Geeignete organische Teilchen sind zum Beispiel Pyrolyseruß, Latexkü- gelchen, Makromoleküle oder Tenside.In one embodiment, the suspension further contains organic particles as a structure-directing component. The organic particles which act as a structure-directing component are also removed in step (d). Thus, the organic particles acting as structure-directing component also affect the porosity of the porous layer. The organic particles are preferably present in a size in the range of 10 to 1000 nm. Suitable organic particles are, for example, pyrolysis, latex, macromolecules or surfactants.
Damit die Partikel des schichtbildenden Materials homogen in der Suspension verteilt bleiben, erhält die Suspension in einer bevorzugten Ausführungsform mindestens einen Stabilisator. Als Stabilisator eignen sich zum Beispiel Sauerstoff-, Stickstoff- oder phosphorhaltige, organische, meist gelatisierende Komplexbildner, zum Beispiel Derivate von Polyethylen- oxiden, Phenanthrolinen oder mehrwertige Alkohole. Ein geeigneter Stabilisator ist zum Beispiel Diethylenglykolmonobutylether. Alternativ können auch die oben genannten organischen Stoffe als Stabilisator eingesetzt werden.So that the particles of the layer-forming material remain homogeneously distributed in the suspension, in a preferred embodiment the suspension receives at least one stabilizer. Suitable stabilizers are, for example, oxygen, nitrogen or phosphorus-containing, organic, usually gelating complexing agents, for example derivatives of polyethylene oxides, phenanthrolines or polyhydric alcohols. A suitable stabilizer is, for example, diethylene glycol monobutyl ether. Alternatively, the abovementioned organic substances can also be used as stabilizer.
Nach dem Auftragen der Suspension ist es bevorzugt, dass zunächst das in der Suspension enthaltene Lösungsmittel zumindest teilweise durch Trocknung entfernt wird. Durch das Entfernen des Lösungsmittels entsteht eine regelmäßige Anordnung der Partikel des schichtbildenden Materials. In den Zwischenräumen zwischen den Partikeln befinden sich zum Beispiel die Monomere oder Oligomere, die zur Polymermatrix aushärten können.After application of the suspension, it is preferred that first the solvent contained in the suspension is at least partially removed by drying. By removing the solvent creates a regular arrangement of the particles of layer-forming material. In the spaces between the particles are, for example, the monomers or oligomers, which can harden to the polymer matrix.
Nach dem Auftragen der Suspension und der gegebenenfalls durchgeführten Trocknung, bei der in der Suspension enthaltenes Lösungsmittel entfernt wird, werden gegebenenfalls die in der Suspension enthaltenen Monomere oder Oligomere zu einer Polymermatrix ausgehärtet. Die Polymermatrix befindet sich dabei in den Zwischenräumen zwischen den Partikeln des schichtbildenden Materials. Hierdurch wird vermieden, dass die Partikel des schichtbildenden Materials agglomerieren können. Es entsteht zunächst eine regelmäßige Verteilung der Partikel des schichtbildenden Materials in der ausgehärteten Polymermatrix.After application of the suspension and any drying carried out, in which the solvent contained in the suspension is removed, the monomers or oligomers contained in the suspension are optionally cured to form a polymer matrix. The polymer matrix is located in the spaces between the particles of the layer-forming material. This avoids that the particles of the layer-forming material can agglomerate. The result is first a regular distribution of the particles of the layer-forming material in the cured polymer matrix.
Nach dem Aushärten der Monomere oder Oligomere zur Polymermatrix erfolgt das Sintern der keramischen oder metallischen Partikel oder der Mischung aus keramischen und metallischen Teilchen. Während des Sinterns oder nach dem Sintern wird das Polymer, welches sich in den Zwischenräumen zwischen den Partikeln des schichtbildenden Materials befindet, entfernt. Hierdurch entsteht eine poröse Schicht. Das Entfernen der organischen Polymermatrix erfolgt zum Beispiel durch Verbrennen. Alternativ kann die Polymermatrix aber zum Beispiel auch mit geeigneten Lösemitteln aus der Schicht ausgelöst werden. Daran anschließend ist es jedoch erforderlich, anschließend das Lösungsmittel zu entfernen.After curing of the monomers or oligomers to the polymer matrix sintering of the ceramic or metallic particles or the mixture of ceramic and metallic particles takes place. During sintering or after sintering, the polymer which is in the interstices between the particles of the layer-forming material is removed. This creates a porous layer. The removal of the organic polymer matrix takes place, for example, by burning. Alternatively, however, the polymer matrix can also be triggered out of the layer, for example, with suitable solvents. Subsequently, however, it is necessary to subsequently remove the solvent.
Die in der Suspension enthaltenen schichtbildenden Partikel weisen vorzugsweise einen mittleren Durchmesser im Bereich von 0,5 bis 1000 nm auf. Mehr bevorzugt liegt der mittlere Durchmesser der schichtbildenden Partikel im Bereich von 0,5 bis 100 nm, insbesondere im Bereich von 1 bis 20 nm.The layer-forming particles contained in the suspension preferably have an average diameter in the range of 0.5 to 1000 nm. More preferably, the average diameter of the layer-forming particles is in the range of 0.5 to 100 nm, in particular in the range of 1 to 20 nm.
In einer bevorzugten Ausführungsform liegen die schichtbildenden Partikel in einem Kolloid vor. Als Material für die schichtbildenden Partikel wird vorzugsweise mindestens ein Element der 8., 9., 10., oder 11. Gruppe des Periodensystems, insbesondere Platin, Palladium, Gold, Silber, Rhodium und Iridium eingesetzt. Zur Herstellung der Metallkolloide wird das mindestens eine Metall zum Beispiel in Form seines Salzes oder in Form einer metallorganischen Verbindung in einem Lösemittel gelöst und unter Rühren reduziert. Geeignete Salze sind dabei Nitrate, Chloride, Bromide oder Carbonate. Geeignete metallorganische Verbindungen sind Acetate, Alcoholate, Acetylacetonate oder entsprechende Metallorganyle in einem geeigneten Lösungsmittel, wie einem Alkohol, Ether, Glycolderivat oder N-haltigen Lösungsmittel. Die gelösten Metallsalze oder metallorganischen Verbindungen werden anschließend unterschiedlichen Reduktionsbedingungen unterworfen. Als Reduktionsmittel werden zum Beispiel zur Herstellung von Platinkolloiden Formaldehyd, Ameisensäure, E- thanol, eine Mischung aus Ameisensäure und Ethanol, eine Mischung aus Zitronensäure und Ethanol, eine Mischung aus Ascorbinsäure und Ethanol, Hydrazin, Wasserstoff, Boranderi- vate oder eine Mischung aus Glyoxylsäure und Ethanol eingesetzt. Die entsprechenden Reduktionsmittel werden dabei jeweils im Überschuss, bezogen auf Platin, eingesetzt. Die gelösten Metallsalze werden unter Rühren reduziert. Das Reduzieren erfolgt dabei in einem Zeitraum von 5 Minuten bis hin zu mehreren Tagen. Die Metallpartikelgrößen in Kolloid, die hierbei erzielt werden, liegen im Bereich zwischen 0,5 bis 100 nm, bevorzugt im Bereich zwischen 1 bis 20 nm. Die Metall-Konzentrationen liegen im Bereich von 0,01 bis 15 Gew.- %, bevorzugt im Bereich von 0,5 bis 5 Gew.-%.In a preferred embodiment, the layer-forming particles are present in a colloid. The material used for the layer-forming particles is preferably at least one element of the 8th, 9th, 10th or 11th group of the Periodic Table, in particular platinum, palladium, gold, silver, rhodium and iridium. To prepare the metal colloids, the at least one metal is dissolved in a solvent, for example in the form of its salt or in the form of an organometallic compound, and reduced with stirring. Suitable salts are nitrates, chlorides, bromides or carbonates. Suitable organometallic compounds are acetates, alcoholates, acetylacetonates or corresponding organometallics in a suitable solvent, such as an alcohol, ether, glycol derivative or N-containing solvent. The dissolved metal salts or organometallic compounds are then subjected to different reduction conditions. As a reducing agent, for example, for the production of platinum colloids formaldehyde, formic acid, ethanol, a mixture of formic acid and ethanol, a mixture of citric acid and Ethanol, a mixture of ascorbic acid and ethanol, hydrazine, hydrogen, borane derivatives or a mixture of glyoxylic acid and ethanol. The corresponding reducing agents are used in each case in excess, based on platinum. The dissolved metal salts are reduced with stirring. The reduction takes place in a period of 5 minutes to several days. The metal particle sizes in colloid, which are achieved in this case, are in the range between 0.5 to 100 nm, preferably in the range between 1 to 20 nm. The metal concentrations are in the range of 0.01 to 15% by weight, preferably in Range of 0.5 to 5 wt .-%.
Alternativ ist es auch möglich, die Metallpartikel auf dem Träger, zum Beispiel einem Gate eines Halbleitertransistors, zu erzeugen. Hierzu werden die entsprechenden Oxometallkol- loide auf dem Träger reduziert. Die Reduktion kann zum Beispiel durch gasförmigen Wasserstoffoder durch organische Schichtbestandteile erfolgen.Alternatively, it is also possible to produce the metal particles on the carrier, for example a gate of a semiconductor transistor. For this purpose, the corresponding oxometallecolloids are reduced on the support. The reduction can be carried out, for example, by gaseous hydrogen or by organic layer constituents.
Das Auftragen der Suspension, die Partikel aus dem schichtbildenden Material oder molekulare Vorstufen des schichtbildenden Materials enthält, auf das Substrat erfolgt zum Beispiel durch Auftropfen mittels einer Mikroliterspritze, durch Spincoating bei einer höherviskosen Suspension oder zum Beispiel mittels einer Dickschichtdrucktechnik, wenn die Suspension als Paste vorliegt.The application of the suspension containing particles of the layer-forming material or molecular precursors of the layer-forming material to the substrate is effected, for example, by dropping by means of a microliter syringe, by spin coating in a higher-viscosity suspension or by means of a thick-layer printing technique, for example, if the suspension is present as a paste ,
Die Dicke und die Porosität der porösen Schicht werden über die Konzentration der Suspension, die Dicke des Auftrages der Suspension oder auch durch eine mögliche Mehrfach- beschichtung eingestellt. Eine Mehrfachbeschichtung ist insbesondere dann vorteilhaft, wenn größere Mengen an schichtbildendem Material aufgetragen werden sollen, als die Suspension bei gegebenem Tropfenvolumen enthält. Unter einer Mehrfachbeschichtung wird ein mehrmaliges Auftragen und Trocknen der Partikel aus schichtbildendem Material oder molekulare Vorstufen des schichtbildenden Materials enthaltenden Suspension bezeichnet. Alternativ kann nach dem Auftragen der Suspension vor dem Auftrag der nächsten Schicht auch eine Thermolyse bzw. Verbrennung durchgeführt werden. Ein Auftrag in meh- reren Schichten ist zum Beispiel dann erforderlich, wenn aufgrund von Agglomeration der Partikel des schichtbildenden Materials nur eine geringe Konzentration an schichtbildendem Material in der Suspension eingestellt werden kann.The thickness and the porosity of the porous layer are adjusted by the concentration of the suspension, the thickness of the order of the suspension or by a possible multiple coating. A multiple coating is particularly advantageous if larger amounts of coating-forming material are to be applied than the suspension contains for a given drop volume. A multiple coating refers to a multiple application and drying of the particles of layer-forming material or molecular precursors of the layer-forming material containing suspension. Alternatively, thermolysis or combustion can also be carried out after application of the suspension before application of the next layer. An application in several layers is required, for example, if only a small concentration of layer-forming material in the suspension can be adjusted due to agglomeration of the particles of the layer-forming material.
Nach dem Auftragen der Suspension erfolgt vorzugsweise eine thermische Behandlung. Diese beinhaltet eine Vortrocknung, Thermolyse bzw. Pyrolyse und thermische Sinterung der Partikel aus dem schichtbildenden Material. Die Vortrocknung erfolgt vorzugsweise bei einer Temperatur im Bereich von 20 bis 150 0C. Durch die Vortrocknung wird Lösungsmittel aus der Suspension entfernt. Hierdurch wird ein Einfrieren der Lösung, eine so genannte Lackbildung, bewirkt, welche eine unerwünschte Agglomeratbildung der Partikel aus dem schichtbildenden Material verhindert. Hierdurch wird eine Gleichverteilung der Partikel aus dem schichtbildenden Material in Form eines porösen Filmes auf dem Substrat realisiert. An die Vortrocknung schließt sich ein Thermolyse- bzw. Pyrolyseschritt bei einer Temperatur im Bereich von 100 bis 650 0C an. Durch die Thermolyse bzw. Pyrolyse werden die organischen Komponenten der Suspension vollständig entfernt. Es bleiben lediglich die anorganischen Bestandteile zurück. Das Erreichen der Maximaltemperatur kann in einem Schritt oder auch in mehreren Halbschritten mit dazwischen liegenden Haltezeiten realisiert werden.After application of the suspension is preferably carried out a thermal treatment. This includes pre-drying, thermolysis or pyrolysis and thermal sintering of the particles from the layer-forming material. The predrying preferably takes place at a temperature in the range from 20 to 150 ° C. The predrying removes solvent from the suspension. This will freeze the solution, a so-called Lackbildung, causes which prevents unwanted agglomeration of the particles of the layer-forming material. As a result, an even distribution of the particles of the layer-forming material in the form of a porous film is realized on the substrate. The predrying is followed by a thermolysis or pyrolysis step at a temperature in the range from 100 to 650 ° C. By thermolysis or pyrolysis, the organic components of the suspension are completely removed. Only the inorganic components remain. The achievement of the maximum temperature can be realized in one step or in several half steps with intermediate holding times.
Während der Thermolyse bzw. der Pyrolyse ist es auch möglich, unterschiedliche Atmosphären anzuwenden. So kann zum Beispiel die Thermolyse oder Pyrolyse in Gegenwart von Luft, in Gegenwart einer inerten Atmosphäre, zum Beispiel in Form von reinem Stickstoff, oder in Gegenwart einer reduzierenden Atmosphäre, zum Beispiel in Gegenwart einer Mischung aus Stickstoff und Wasserstoff, wobei der Anteil an Wasserstoff in der Mischung 0,5 bis 10 Vol.-% beträgt, durchgeführt werden.During thermolysis or pyrolysis it is also possible to use different atmospheres. For example, thermolysis or pyrolysis in the presence of air, in the presence of an inert atmosphere, for example in the form of pure nitrogen, or in the presence of a reducing atmosphere, for example in the presence of a mixture of nitrogen and hydrogen, wherein the proportion of hydrogen in the mixture is 0.5 to 10 vol .-%, be carried out.
Die mit dem erfindungsgemäßen Verfahren hergestellte poröse Schicht wird vorzugsweise bei Halbleitertransistoren mit mindestens einer Gateelektrode, die eine elektrisch leitfähige poröse Beschichtung aufweist, eingesetzt. Derartige Transistoren werden zum Beispiel als Gassensoren eingesetzt. Dies ist möglich, da die Gase mit dem Gateelektrodenmaterial des Feldeffekttransistors in Wechselwirkung treten. An der erfindungsgemäß hergestellten O- berfläche der Gateelektrode erfolgt eine gezielte Adsorption von Gasen und/oder eine kata- lytische Reaktion. Hierbei laufen an der Gateelektrodenoberfläche hochsensitive und -selektive Stoffprozesse ab. Gasadsorption und selektive Stoffprozesse an den Dreiphasen- grenzen (Metallphase, oxidisch-keramische Phase und Gasphase) führen zur Ausbildung signalbildender polarer oder dipolarer Adsorbate. Die Ausprägung und Feinskaligkeit der Dreiphasengrenze ist ausschlaggebend für Empfindlichkeit und Ansprechzeit des Gassensors. Durch das erfindungsgemäße Verfahren lässt sich die Porosität der Oberfläche der Gateelektrode gezielt einstellen. Zudem sind die erfindungsgemäß erzeugten porösen Schichten gegenüber thermischer Belastung widerstandsfähiger und zeigen daher stabile Sensorsignale über einen erweiterten Temperaturbereich und über eine längere Betriebsdauer als die aus dem Stand der Technik bekannten Gateelektroden.The porous layer produced by the method according to the invention is preferably used in semiconductor transistors having at least one gate electrode which has an electrically conductive porous coating. Such transistors are used for example as gas sensors. This is possible because the gases interact with the gate electrode material of the field effect transistor. At the surface of the gate electrode produced according to the invention, a targeted adsorption of gases and / or a catalytic reaction takes place. Here, highly sensitive and selective material processes take place at the gate electrode surface. Gas adsorption and selective material processes at the three-phase boundaries (metal phase, oxide-ceramic phase and gas phase) lead to the formation of signal-forming polar or dipolar adsorbates. The characteristic and fine calibration of the three-phase limit are decisive for the sensitivity and response time of the gas sensor. By the method according to the invention, the porosity of the surface of the gate electrode can be adjusted specifically. In addition, the porous layers produced according to the invention are more resistant to thermal stress and therefore exhibit stable sensor signals over an extended temperature range and over a longer period of operation than the gate electrodes known from the prior art.
Kurze Beschreibung der ZeichnungenBrief description of the drawings
Ausführungsbeispiele der Erfindung sind in den Zeichnungen dargestellt und in der nachfolgenden Beschreibung näher erläutert. Es zeigenEmbodiments of the invention are illustrated in the drawings and explained in more detail in the following description. Show it
Figur 1 eine TEM- Aufnahme von in Lösung reduzierten Platinkolloiden,FIG. 1 shows a TEM image of solution-reduced platinum colloids,
Figur 2.1 eine schematische Darstellung einer auf einem Substrat aufgetragenen Suspension, die schichtbildende Partikel enthält,FIG. 2.1 shows a schematic representation of a suspension applied to a substrate which contains layer-forming particles,
Figur 2.2 die in Figur 3.1 aufgetragene Schicht nach Vortrocknung,FIG. 2.2 shows the layer applied in FIG. 3.1 after predrying,
Figur 2.3 eine schematische Darstellung einer porösen Schicht auf einem Substrat,FIG. 2.3 a schematic representation of a porous layer on a substrate,
Figur 3.1 eine schematische Darstellung einer ersten porösen Schicht auf einem Substrat,FIG. 3.1 a schematic representation of a first porous layer on a substrate,
Figur 3.2 eine schematische Darstellung eines Zweischichtaufbaus.Figure 3.2 is a schematic representation of a two-layer structure.
Figur 4 eine REM- Aufnahme einer erfindungsgemäß hergestellten porösen Schicht aus Platin,FIG. 4 shows a SEM image of a porous layer of platinum produced according to the invention,
Ausführungsformen der ErfindungEmbodiments of the invention
In Figur 1 ist eine transmissionselektronenmikroskopische Aufnahme einer Suspension, die Platin als schichtbildendes Material enthält, dargestellt.FIG. 1 shows a transmission electron micrograph of a suspension containing platinum as a layer-forming material.
In einer Suspension 1 , die zur Herstellung einer porösen Schicht eingesetzt wird, sind Partikel 3 aus einem schichtbildenden Material enthalten. Wie in Figur 1 zu sehen ist, sind die Partikel 3 aus dem schichtbildenden Material gleichmäßig in der Suspension 1 verteilt. In der in Figur 1 dargestellten transmissionselektronenmikroskopischen Aufnahme sind die Partikel 3 Platinkolloide. Zur Herstellung der Platinkolloide wird Platin in Form eines seiner Salze, zum Beispiel als Nitrat, Chlorid, Bromid oder Carbonat, oder in Form einer seiner metallorganischen Verbindungen, zum Beispiel als Acetat, Alkoholat, Acetylacetonat oder als entsprechendes Metallorganyl in einem geeigneten Lösungsmittel gelöst. Als Lösungsmittel eignen sich zum Beispiel Alkohol, Ether, Glykolderivate oder N-haltige Lösungsmittel. Die Lösung kann weiterhin mit einem Stabilisator versetzt sein. Als Stabilisator kann zum Beispiel Diethylenglykolmonobutylether verwendet werden. Die Lösung des Metallsalzes oder der metallorganischen Verbindung wird anschließend unterschiedlichen Reduktionsbedingungen unterworfen. Zur Reduktion werden zum Beispiel Formaldehyd, Ameisensäure, Ethanol, Hydrazin, Wasserstoff, Boranderivate oder Mischungen aus Ethanol mit Zitronensäure, Ascorbinsäure, Hydrazin oder Glyoxylsäure, eingesetzt. Das Reduktionsmittel wird dabei jeweils im Überschuss, bezogen auf Platin, eingesetzt.In a suspension 1, which is used for producing a porous layer, particles 3 are contained from a layer-forming material. As can be seen in FIG. 1, the particles 3 of the layer-forming material are distributed uniformly in the suspension 1. In the transmission electron micrograph shown in FIG. 1, the particles 3 are platinum colloids. To prepare the platinum colloids, platinum is dissolved in the form of one of its salts, for example as nitrate, chloride, bromide or carbonate, or in the form of one of its organometallic compounds, for example as acetate, alkoxide, acetylacetonate or as appropriate metalorganyl in a suitable solvent. Suitable solvents are, for example, alcohol, ethers, glycol derivatives or N-containing solvents. The solution may be further added with a stabilizer. As the stabilizer, for example, diethylene glycol monobutyl ether can be used. The solution of the metal salt or organometallic compound is then subjected to different reduction conditions. For example, formaldehyde, formic acid, ethanol, hydrazine, hydrogen, borane derivatives or mixtures of ethanol are used for the reduction Citric acid, ascorbic acid, hydrazine or glyoxylic acid used. The reducing agent is used in each case in excess, based on platinum.
Zur Herstellung von Gateelektroden, die in Halbleitertransistoren eingesetzt werden, eignen sich neben Platinkolloiden, wie sie in Figur 1 dargestellt sind, auch Metallkolloide der übrigen Elemente der 8., 9., 10. und 11. Gruppe des Periodensystems. Besonders geeignet sind neben Platin auch Palladium, Gold, Silber, Rhodium und Iridium. Weiterhin können in der Suspension als schichtbildendes Material auch keramische Partikel enthalten sein.For the preparation of gate electrodes which are used in semiconductor transistors, in addition to platinum colloids, as shown in Figure 1, and metal colloids of the other elements of the 8th, 9th, 10th and 11th Group of the Periodic Table are suitable. Besides platinum, palladium, gold, silver, rhodium and iridium are also particularly suitable. Furthermore, ceramic particles may also be present in the suspension as a layer-forming material.
Figur 2.1 zeigt schematisch ein Substrat, auf welches eine Suspension, die Partikel aus einem schichtbildenden Material enthält, aufgetragen wurde.FIG. 2.1 schematically shows a substrate to which a suspension containing particles of a layer-forming material has been applied.
Ein Substrat 11, auf welches die Suspension 1, die die schichtbildenden Partikel 3 enthält, aufgetragen wird, ist zum Beispiel ein Feldeffektransistor, der mit einer Gateelektrode ver- sehen werden soll. Die Suspension 1 wird auf das Substrat 11 zum Beispiel mit Hilfe eines Dispensers aufgebracht. Als Substrat eignet sich zum Beispiel eine glatte, oxidische Oberfläche mit geringer Rauigkeit. Eine geeignete Suspension 1 enthält beispielsweise 3 Gew.-% Polyethylenglycol, 1,75 Gew.-% Platinkolloide mit einem mittleren Durchmesser dso von 50 nm, 0,25 Gew.-% AI2O3 mit einem mittleren Durchmesser dso von 200 nm, und 95 Gew.-% Ethanol. Nach dem Auftragen wird diese Suspension bei 30 0C vorgetrocknet. Durch das Vortrocknen wird Ethanol aus der Suspension entfernt. Das Volumen der aufgetragenen Schicht auf das Substrat nimmt ab. Dies ist in Figur 2.2 dargestellt. Nach der Verflüchtigung des Ethanols bildet das Polyethylenglycol eine feste Matrix, die in regelmäßiger Anordnung Platin und Aluminiumoxid-Partikel enthält.A substrate 11 to which the suspension 1 containing the layer-forming particles 3 is applied is, for example, a field-effect transistor to be provided with a gate electrode. The suspension 1 is applied to the substrate 11, for example by means of a dispenser. As a substrate, for example, a smooth, oxidic surface with low roughness is suitable. A suitable suspension 1 contains, for example, 3% by weight of polyethylene glycol, 1.75% by weight of platinum colloids with a mean diameter d 50 of 50 nm, 0.25% by weight of Al 2 O 3 with an average diameter d 50 of 200 nm, and 95% by weight .-% ethanol. After application, this suspension is pre-dried at 30 0 C. By predrying ethanol is removed from the suspension. The volume of the applied layer on the substrate decreases. This is shown in FIG. 2.2. After volatilization of the ethanol, the polyethylene glycol forms a solid matrix containing platinum and alumina particles in a regular array.
Nach dem Trocknen werden die organischen Komponenten bei einer Temperatur von 400 0C über einen Zeitraum von 4 h in Gegenwart von Luft entfernt. Beim Abbrennen der organischen Matrix aus Polyethylenglycol hinterlassen die schichtbildenden Materialien, nämlich das Platin und das Aluminiumoxid, eine poröse, gleichmäßige Schicht. Dies ist in Figur 2.3 dargestellt.After drying, the organic components are removed at a temperature of 400 0 C over a period of 4 h in the presence of air. Upon burning off of the organic matrix of polyethylene glycol, the layer-forming materials, namely platinum and alumina, leave behind a porous, uniform layer. This is shown in FIG. 2.3.
In den Figuren 3.1 und 3.2 ist schematisch ein Mehrschichtaufbau der porösen Beschichtung auf dem Substrat dargestellt.FIGS. 3.1 and 3.2 schematically show a multilayer structure of the porous coating on the substrate.
Zur Herstellung eines Mehrschichtaufbaus wird zunächst eine erste poröse Schicht 21 auf das Substrat 11 aufgetragen. Zur Herstellung des Zweischichtaufbaus, wie er in Figur 3.2 dargestellt ist, wird in einer ersten Ausführungsform die erste poröse Schicht 21 vorgetrocknet und anschließend eine zweite poröse Schicht 23 aufgetragen, wie es in Figur 3.2 dargestellt ist. Nach dem Auftragen der zweiten porösen Schicht 23 wird diese ebenfalls vorgetrocknet. Anschließend erfolgt das Entfernen der organischen Komponente aus der ersten porösen Schicht 21 und der zweiten porösen Schicht 23. Alternativ ist es in einer weiteren Ausführungsform auch möglich, zuerst die erste poröse Schicht 21 aufzutragen und zu tempern und auf die ausgehärtete erste poröse Schicht 21 die zweite poröse Schicht 23 aufzutragen.To produce a multi-layer structure, a first porous layer 21 is first applied to the substrate 11. In order to produce the two-layer structure, as shown in FIG. 3.2, the first porous layer 21 is predried in a first embodiment and then a second porous layer 23 is applied, as shown in FIG. 3.2 is shown. After the application of the second porous layer 23, this is also pre-dried. Subsequently, the organic component is removed from the first porous layer 21 and the second porous layer 23. Alternatively, in another embodiment, it is also possible first to apply and temper the first porous layer 21 and second to the cured first porous layer 21 apply porous layer 23.
In Figur 4 ist eine rasterelektronenmikroskopische Aufnahme einer erfindungsgemäß hergestellten porösen Schicht dargestellt.FIG. 4 shows a scanning electron micrograph of a porous layer produced according to the invention.
Eine poröse Schicht 31, wie sie in Figur 4 dargestellt ist, wurde aus der in Figur 1 dargestellten Suspension 1 hergestellt. Die einzelnen Partikel 3 aus der Suspension 1 verbinden sich zu einer schwammartigen Struktur 33. In der schwammartigen Struktur 33 sind Hohlräume 35 ausgebildet. Wie in Figur 4 zu erkennen ist, sind die Hohlräume 35 gleichmäßig in der porösen Schicht 31 verteilt. Eine Agglomeration von schichtbildendem Material und damit ein massiver Bereich in der porösen Schicht 31 ist nicht zu erkennen.A porous layer 31, as shown in Figure 4, was prepared from the suspension 1 shown in Figure 1. The individual particles 3 from the suspension 1 combine to form a sponge-like structure 33. Voids 35 are formed in the sponge-like structure 33. As can be seen in FIG. 4, the cavities 35 are distributed uniformly in the porous layer 31. An agglomeration of layer-forming material and thus a massive area in the porous layer 31 can not be seen.
BeispieleExamples
Beispiel 1example 1
Eine Suspension aus 3 Gew.-% Polyethylenglycol, 1,75 Gew.-% Platin mit einem mittleren Partikeldurchmesser dso von 50 nm, 0,25 Gew.-% AI2O3 mit einem mittleren Durchmesser dso von 200 nm und 95 Gew.-% Ethanol wird auf eine glatte, oxidische Oberfläche mit ge- ringer Rauigkeit mittels eines Dispensers aufgebracht, so dass 10 μl/cm"2 verbleiben. Die auf die Oberfläche aufgebrachte Suspension wird bei 30 0C vorgetrocknet und anschließend bei 150 0C 2 h lang ausgehärtet. Abschließend werden die organischen Komponenten bei 400 0C in 4 h in Gegenwart von Luft entfernt.A suspension of 3 wt .-% polyethylene glycol, 1.75 wt .-% of platinum having an average particle diameter dso of 50 nm, 0.25 wt .-% Al 2 O 3 with an average diameter dso of 200 nm and 95 wt. -% ethanol is applied to a smooth, oxidic surface with low roughness by means of a dispenser so that 10 μl / cm 2 remain.The suspension applied to the surface is predried at 30 ° C. and then at 150 ° C. for 2 hours The organic components are finally removed at 400 ° C. in the course of 4 h in the presence of air.
Das Polyethylenglycol bildet nach Verflüchtigung des Ethanols eine Matrix, die in regelmäßiger Anordnung Platin und Al2θ3-Teilchen enthält. Beim Abbrennen der organischen Matrix hinterlassen die schichtbildenden Materialien eine poröse, gleichmäßige Schicht.The polyethylene glycol, after volatilization of the ethanol, forms a matrix which regularly contains platinum and Al 2 O 3 particles. Upon burning off of the organic matrix, the layer-forming materials leave a porous, even layer.
Beispiel 2Example 2
Eine Suspension aus 8 Gew.-% Pt(NOs)2, 2 Gew.-% ZrO2 mit einem mittleren Durchmesser d50 von 30 nm, 10 Gew.-% 1 ,2-Propandiol, 80 Gew.-% Ethanol und 2 Gew.-% Latex- Kügelchen mit einem mittleren Durchmesser dso von 100 nm wird mittels eines Dispensers auf eine glatte, oxidische Oberfläche mit geringer Rauigkeit aufgebracht, so dass 5 μl/cm"2 verbleiben. Die Suspension wird zunächst 2 h lang bei 60 0C vorgetrocknet und dann 4 h lang bei 120 0C getrocknet und ausgehärtet, indem Platin reduziert wird. Die Latex- Kügelchen bilden nach dem Entfernen des Ethanols eine regelmäßige Anordnung von Ku- gelchen, in deren Zwischenräumen sich das gesinterte Platin und Zirkondioxid und Reste des schwerflüchtigen Lösungsmittels, 1 ,2-Propandiol, befinden. In einem nächsten Schritt werden 10 μl/cm"2 einer Suspension aus 5 Gew.-% A1(NC>3)3, 2 Gew.-% Harnstoff, 81 Gew.-% Wasser und 10 Gew.-% Latex-Kügelchen mit einem mittleren Durchmesser dso von 100 nm aufgetragen. Das Substrat mit den aufgetragenen Schichten wird zunächst für 8 h einer Wärmebehandlung bei 100 0C unterworfen. Anschließend werden die organischen bzw. flüchtigen Komponenten 8 h bei 300 0C an Stickstoff und daran anschließend bei 480 0C für 4 h an Luft entfernt. Nach dem Entfernen der organischen Matrix verbleibt eine me- soporöse, gleichmäßige Schicht eines Platin-Zirkondioxid-Komposits, welche mit einer me- soporösen Al2θ3-Schicht überdeckt ist. A suspension of 8 wt .-% Pt (NOs) 2 , 2 wt .-% ZrO 2 with a mean diameter d 50 of 30 nm, 10 wt .-% 1, 2-propanediol, 80 wt .-% ethanol and 2 % By weight of latex beads having a mean diameter d 50 of 100 nm is dispensed by means of a dispenser on a smooth, oxidic surface with low roughness, so that 5 .mu.l / cm "2 remain.The suspension is first predried for 2 hours at 60 0 C and then dried for 4 hours at 120 0 C and cured by platinum is reduced After the removal of the ethanol, the latex beads form a regular array of balls in the interspaces of which the sintered platinum and zirconium dioxide and residues of the low-volatility solvent, 1,2-propanediol, are present. cm "2 of a suspension of 5 wt .-% A1 (NC> 3) 3, 2 wt .-% urea, 81 wt .-% water and 10 wt .-% latex beads having a mean diameter dso of 100 nm applied , The substrate with the applied layers is first subjected to a heat treatment at 100 ° C. for 8 hours. Subsequently, the organic or volatile components are removed at 300 ° C. for 8 h at nitrogen and subsequently at 480 ° C. for 4 h in air. After removal of the organic matrix, a mesoporous, uniform layer of a platinum-zirconium dioxide composite remains, which is covered with a mesoporous Al 2 O 3 layer.

Claims

Patentansprüche claims
1. Verfahren zur Herstellung mindestens einer porösen Schicht (21, 23; 31) auf einem Substrat (11), welches folgende Schritte umfasst:Method for producing at least one porous layer (21, 23, 31) on a substrate (11), comprising the following steps:
(a) Auftragen einer Suspension (1), die Partikel (3) aus einem schichtbildenden Material oder molekulare Vorstufen des schichtbildenden Materials sowie mindestens eine organische Komponente enthält, auf das Substrat (11),(a) applying a suspension (1) containing particles (3) of a layer-forming material or molecular precursors of the layer-forming material and at least one organic component to the substrate (11),
(b) gegebenenfalls Reaktion der Vorstufen des schichtbildenden Materials zum schichtbildenden Material nach dem Auftragen auf das Substrat (11),(b) optionally, reacting the precursors of the layer-forming material to the layer-forming material after application to the substrate (11),
(c) Tempern der Partikel (3) aus dem schichtbildenden Material,(c) annealing the particles (3) of the layer-forming material,
(d) Entfernen der mindestens einen organischen Komponente.(d) removing the at least one organic component.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die schichtbildende Komponente mindestens ein Metall oder mindestens eine Keramik oder eine Mischung aus mindestens einem Metall und mindestens einer Keramik enthält.2. The method according to claim 1, characterized in that the layer-forming component contains at least one metal or at least one ceramic or a mixture of at least one metal and at least one ceramic.
3. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die organische Komponente Monomere, Oligomere oder Polymere, die zu einer Polymermatrix aushärten können, mindestens ein Lösungsmittel oder eine Mischung daraus umfasst.3. The method according to claim 1, characterized in that the organic component comprises monomers, oligomers or polymers which can cure to form a polymer matrix, at least one solvent or a mixture thereof.
4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass die Suspension (1) weiterhin organische Partikel als strukturdirigierende Komponente enthält.4. The method according to any one of claims 1 to 3, characterized in that the suspension (1) further contains organic particles as structure-directing component.
5. Verfahren nach einem der Ansprüche 1 bis 4, dadurch gekennzeichnet, dass die Suspension (1) mindestens einen Stabilisator enthält.5. The method according to any one of claims 1 to 4, characterized in that the suspension (1) contains at least one stabilizer.
6. Verfahren nach einem der Ansprüche 3 bis 5, dadurch gekennzeichnet, dass nach dem Auftragen der Suspension (1) in der Suspension (1) enthaltenes Lösungsmittel durch Trocknung entfernt wird.6. The method according to any one of claims 3 to 5, characterized in that after the application of the suspension (1) in the suspension (1) contained solvent is removed by drying.
7. Verfahren nach einem der Ansprüche 3 bis 6, dadurch gekennzeichnet, dass nach dem Auftragen der Suspension (1) und einer gegebenenfalls durchgeführten Trocknung die in der Suspension enthaltenen Monomere oder Oligomere zu einer Polymermatrix aushärten. 7. The method according to any one of claims 3 to 6, characterized in that after the application of the suspension (1) and an optionally carried out drying, the monomers or oligomers contained in the suspension cure to a polymer matrix.
8. Verfahren nach einem der Ansprüche 1 bis 7, dadurch gekennzeichnet, dass die in der Suspension (1) enthaltenen schichtbildenden Partikel (3) einen mittleren Durchmesser von 0,5 bis 1000 nm aufweisen.8. The method according to any one of claims 1 to 7, characterized in that in the suspension (1) contained layer-forming particles (3) have a mean diameter of 0.5 to 1000 nm.
9. Verfahren nach einem der Ansprüche 1 bis 8, dadurch gekennzeichnet, dass die schichtbildenden Partikel (3) Metallpartikel mindestens eines Elementes der 8., 9., 10. oder 11. Nebengruppe sind.9. The method according to any one of claims 1 to 8, characterized in that the layer-forming particles (3) are metal particles of at least one element of the 8th, 9th, 10th or 11th subgroup.
10. Verfahren nach Anspruch 9, dadurch gekennzeichnet, dass die schichtbildenden Partikel als Kolloide vorliegen, wobei zur Herstellung der Kolloide das mindestens eine Metall in Form seines Salzes oder in Form einer metallorganischen Verbindung in einem Lösemittel gelöst und unter Rühren reduziert wird.10. The method according to claim 9, characterized in that the layer-forming particles are present as colloids, wherein for the preparation of the colloids, the at least one metal in the form of its salt or in the form of an organometallic compound is dissolved in a solvent and reduced with stirring.
11. Verfahren nach Anspruch 10, dadurch gekennzeichnet, dass die Lösung weiterhin mindestens einen Stabilisator enthält.11. The method according to claim 10, characterized in that the solution further contains at least one stabilizer.
12. Verfahren nach einem der Ansprüche 1 bis 11, dadurch gekennzeichnet, dass das Entfernen der organischen Komponente in Schritt (d) durch Thermolyse, Pyrolyse, Be- Strahlung oder chemische Behandlung erfolgt.12. The method according to any one of claims 1 to 11, characterized in that the removal of the organic component in step (d) by thermolysis, pyrolysis, radiation or chemical treatment takes place.
13. Verfahren nach einem der Ansprüche 1 bis 12, dadurch gekennzeichnet, dass zur Herstellung einer dicken porösen Schicht die Schritte (a) bis (c) vor der Durchführung von Schritt (d) oder die Schritte (a) bis (d) wiederholt werden.13. The method according to any one of claims 1 to 12, characterized in that for producing a thick porous layer, the steps (a) to (c) before the implementation of step (d) or the steps (a) to (d) are repeated ,
14. Feldeffekttransistor mit mindestens einer Gateelektrode, wobei die Gateelektrode eine elektrisch leitfähige poröse Beschichtung (21, 23; 31) aufweist, die durch das Verfahren nach einem der Ansprüche 1 bis 13 aufgetragen wurde. 14. Field effect transistor having at least one gate electrode, wherein the gate electrode has an electrically conductive porous coating (21, 23, 31), which was applied by the method according to one of claims 1 to 13.
EP07821128A 2006-10-10 2007-10-10 Method for producing at least one porous layer Withdrawn EP2080019A1 (en)

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