COATING MATERIAL, CONVERSION MATERIAL, OPTOELECTRONIC COMPONENT AND METHOD FOR PRODUCING A COATING MATERIAL

Abstract

An enveloping material for an optoelectronic semiconductor chip is specified having —a starting material for forming a sol-gel material, and —a stabilizer material, configured for mechanical stabilization, wherein —the starting material comprises at least one alkoxy (alkyl)silane, and —the stabilizer material is selected from a group containing the following materials: salts, metal alkoxides, metal oxides. Furthermore, a conversion material and an optoelectronic component having such an enveloping material are specified. Additionally, a method for producing an enveloping material is specified.

Claims

1. A coating material for an optoelectronic semiconductor chip comprising a starting material for forming a sol-gel material, and a stabilizer material configured for mechanical stabilization, wherein the starting material comprises at least one alkoxysilane, and the stabilizer material is selected from a group including the following materials: Salts, metal alkoxides, metal oxides, in which an oxygen atom of the sol-gel material coordinates to the stabilizer material.

2. The coating material according to claim 1, in which the stabilizer material is selected from a group comprising phosphate salts, halide salts, carbonates, nitrates, sulfates and combinations thereof.

3. The coating material according to claim 1 in which the stabilizer material is selected exclusively from the group of metal alkoxides.

4. The coating material according to claim 1, in which the stabilizer material is selected from the group of metal oxides and is formed as nanoparticles.

5. The coating material according to claim 1, in which a surface of the stabilizer material is free of a modification.

6. The coating material according to claim 1, in which the alkoxysilane comprises a structural unit A of the following general formula: ##STR00003## wherein the substituents R.sup.1 to R.sup.4 are each independently selected from the group consisting of alkyls.

7. The coating material according to claim 1, in which the alkoxy(alkyl)silane comprises a structural unit B of the following general formula: ##STR00004## wherein substituents X.sup.1 to X.sup.4 are each independently selected from the group consisting of alkyls.

8. The coating material according to claim 6, in which the starting material comprises, in addition to the structural unit A, a further structural unit B different from the structural unit A.

9. A conversion material with a coating material according to claim 1, and a phosphor material, wherein the phosphor material is embedded in the coating material.

10. An optoelectronic component comprising a semiconductor chip which in operation emits electromagnetic primary radiation of a first wavelength range, and a conversion material according to claim 9 configured to emit secondary radiation of a second wavelength range, wherein the conversion material is arranged downstream of the semiconductor chip.

11. A method for producing a coating material comprising the steps: providing a solvent having a pH of at most 5, inserting a starting material to form a sol-gel material into the solvent, inserting a stabilizer material configured for mechanical stabilization into the solvent, wherein the starting material is selected from the group of alkoxysilanes, and the stabilizer material is selected from a group containing the following materials: Salts, metal alkoxides, metal oxides.

12. The method according to claim 11, wherein the solvent is selected from the group of protic solvents.

13. The method according to claim 11, wherein the pH of the solvent is between 1 and most 5.

14. The method according to claim 11, wherein the stabilizer material is inserted into the solvent or into the starting material prior to the insertion of the starting material.

15. The method according to claim 11, wherein the insertion of the starting material and/or the insertion of the stabilizer material is carried out under continuous mechanical mixing.

16. The method according to claim 11, in which a coating material according to claim 1 is produced.

17. A method for producing a coating material comprising the steps: providing a solvent having a pH of at most 5, inserting a starting material to form a sol-gel material into the solvent, inserting a stabilizer material configured for mechanical stabilization into the solvent, wherein the starting material is selected from the group of alkoxy(alkyl)silanes, and the stabilizer material is selected from a group containing the following materials: Salts, metal alkoxides, metal oxides, wherein an oxygen atom of the sol-gel material coordinates to the stabilizer material

Description

[0072] Further advantageous embodiments and further embodiments of the coating material, conversion material and optoelectronic component and of the method for producing a coating material are apparent from the exemplary embodiments described below in conjunction with the figures.

[0073] It show:

[0074] FIGS. 1 and 2 each a chemical representation of a coating material according to a respective exemplary embodiment,

[0075] FIG. 3 schematic sectional view of a conversion material according to an exemplary embodiment,

[0076] FIG. 4 schematic sectional view of an optoelectronic component according to an exemplary embodiment,

[0077] FIGS. 5A, 5B, 5C, 5D, 5E and 5F schematic sectional views of various stages of a method for producing a coating material and applying a conversion material to an optoelectronic semiconductor chip according to an exemplary embodiment,

[0078] FIG. 6 scanning electron microscope image of a conversion material according to an exemplary embodiment.

[0079] Identical elements, elements of the same kind or elements having the same effect are given the same reference signs in the figures. The figures and the proportions of the elements shown in the figures with respect to one another are not to be regarded as to scale. Rather, individual elements, in particular layer thicknesses, may be shown exaggeratedly large for better representability and/or understanding.

[0080] The coating material 1 according to the exemplary embodiment of FIG. 1 comprises a starting material 3 for forming a sol-gel material 13. The starting material 3 used is an alkoxy(alkyl)silane, in this case tetraethyl orthosilicate 17. The starting material 3 is first hydrolyzed by the protons of the solvent 11. Ethanol is split off to form a hydrolyzed compound 4. The hydrolyzed compound 4 reacts with the starting material 3, alkoxy(alkyl)silane to form a dimer and ethanol. Similarly, a dimer can be formed by reacting two hydrolyzed compounds 4. In this case, water is formed as the second product instead of ethanol. Tetramers, oligomers and polymers can be formed from at least two dimers by an inorganic polycondensation reaction. In addition, tetramers, oligomers and polymers can be obtained from hydrolyzed compounds 4 and/or starting material 3, alkoxy(alkyl)silane. Silicon chains are formed, which are linked to each other via oxygen atoms 7. Part of the starting material is present polymerized as a gel in a 3D structure and another part is present as a sol which is free in the solvent.

[0081] The exemplary embodiment shown in FIG. 2 comprises a gel 5, in a 3D structure. Stabilizer material 6 is inserted into the gel 5. The stabilizer material 6 is configured for mechanical stabilization. The stabilizer material 6 can be formed as a metal oxide, metal alkoxide and as a salt. The stabilizer material 6 comprises, for example, monovalent cations 14, divalent cations 15 and/or trivalent cations 16. The stabilizer material 6 is formed as a cation and is coordinated by the oxygen atom 7 of the gel 5. The oxygen atom 7 is bonded by two silicon atoms 18 in each case. The insertion of the stabilizer material 6 into the gel 5 causes the ring tension in the 3D structure to be relaxed. That is, fewer cracks are formed in the gel 5.

[0082] The conversion material 8 according to the exemplary embodiment of FIG. 3 shows a coating material 1 described herein and a phosphor material 9. The phosphor material 9 is embedded in the coating material 1. The coating material 1 comprises a sol-gel material 13 in which stabilizer material 6 is inserted. The phosphor material 9 is formed as phosphor particles and comprises a ceramic host lattice, an organic conversion material 8, or quantum dots. The phosphor material 9 converts primary electromagnetic radiation of a first wavelength range into secondary electromagnetic radiation of a second wavelength range. For example, the phosphor material 9 comprises a garnet phosphor. The second wavelength range is, for example, in the green and/or yellow wavelength range. In particular, the garnet phosphor is a YAG phosphor having the chemical formula Y.sub.3Al.sub.5O.sub.12:Ce.sup.3+.

[0083] The exemplary embodiment shown in FIG. 4 comprises an optoelectronic component 10. The optoelectronic component 10 comprises a semiconductor chip 2 which, in operation, emits primary electromagnetic radiation of a first wavelength range. The conversion material 8 converts electromagnetic primary radiation of a first wavelength range into electromagnetic secondary radiation of a second wavelength range. The conversion material 8 is arranged downstream of the optoelectronic semiconductor chip 2. For example, the conversion material 8 is arranged in direct contact to the optoelectronic semiconductor chip 2. Depending on the phosphor material 9, the conversion material 8 can completely convert the electromagnetic primary radiation of a first wavelength range into electromagnetic secondary radiation of a second wavelength range or partially convert parts of the electromagnetic primary radiation of a first wavelength range into electromagnetic secondary radiation of a second wavelength range.

[0084] In the method for producing a coating material 1 and subsequently applying it to an optoelectronic semiconductor chip 2 according to the exemplary embodiment of FIG. 5, a solvent 11, having a pH value of at most 5, is provided in a first step, FIG. 5A. First, the stabilizer material 6, which is provided for mechanically stabilizing the sol-gel material 13, is inserted into the solvent 11. The stabilizer material 6 is selected from a group comprising salts, metal alkoxides and/or metal oxides. Subsequently, a starting material 3 provided to form a sol-gel material 13 is inserted into the solvent 11. The stabilizer material 6 may comprise, for example, an aluminum salt or a sodium salt. This is stirred in the solvent 11 until it is completely dissolved. A starting material 3, for example TEOS, is then added to the solution. The reaction mixture is stirred for several hours, FIG. 5B. After a certain time under constant stirring, heat develops and the reaction mixture becomes transparent, for example, which is a consequence of the hydrolysis and polycondensation reaction to form the sol-gel material 13, FIGS. 5B, 5C.

[0085] As shown in FIG. 5C, the sol-gel material 13 with stabilizer material 6 is contained in a solvent 11. A portion of the sol-gel material 13 is polymerized to form the 3D structure of the gel 5 and another portion is present, for example, as a hydrolyzed compound 4, dimer, tetramer and/or oligomer.

[0086] As shown in FIG. 5D, the phosphor material 9 is placed in a vessel and the previously synthesized sol-gel material 13 is added to the phosphor material 9. The reaction mixture is continuously mechanically mixed to ensure homogeneous distribution of the phosphor material 9 in the sol-gel material 13.

[0087] In a next step, an optoelectronic semiconductor chip 2 is provided onto which the phosphor sol-gel material 13 is deposited, FIG. 5E.

[0088] In a final step, the solvent 11 is removed from the sol-gel material 13 to obtain a coating material 1, FIG. 5F. The removal of the solvent 11 is done by initial drying on air. Then, the optoelectronic semiconductor chip 2 with the applied phosphor sol-gel material is placed in an 80° C. and 300° C. oven for a period of time. The complete solvent 11 is removed and the formation of a conversion material 8 is obtained.

[0089] For the method for producing a coating material 1 and then depositing a conversion material 8 on an optoelectronic semiconductor chip 2 according to the exemplary embodiment of FIG. 5, two specific examples are specified below.

EXAMPLE 1

[0090] Water, for example, is first provided as a solvent 11. The solvent 11 is adjusted to a pH value between 1 and 5, and an aluminum salt is added as a stabilizer material 6. The reaction mixture is mechanically mixed until the aluminum salt is dissolved. TEOS is added to the reaction mixture as the starting material and the reaction mixture is vigorously mechanically mixed for 0.5-3 hours. After about 0.5-2 hours of continuous mixing, heat develops in the reaction mixture and the reaction mixture becomes transparent, which is a result of the hydrolysis and polycondensation reaction starting to form the sol-gel material 13. Subsequently, mechanical mixing of the reaction mixture is stopped. Within in about one day, the sol-gel material 13 is further processed. A sol-gel material 13 with TEOS as the starting material 3 and without a stabilizer material 6 is further processed after a few hours compared to a sol-gel material 13 with a stabilizer material 6, because the polycondensation reaction to form a gel 5 is faster.

[0091] In a further step, for example, a YAG phosphor material 9 is placed in a glass vessel. The sol-gel material 13 with stabilizer material 6 is added. The reaction mixture is mechanically mixed until a homogeneous distribution of the phosphor material 9 in the sol-gel material 13 is achieved. Then, the sol-gel material 13 with stabilizer material 6 and phosphor material 9 is manually coated onto a microscopic glass slide or onto semiconductor chip wafer pieces. After coating the conversion material 8, the coated optoelectronic semiconductor chip 2 is dried in air and then placed in an oven. In the first annealing process, the coated optoelectronic semiconductor chip 2 is heated for a few minutes at an oven temperature between 70° C. and 100° C. and then cooled to room temperature in air. In the second annealing process, the coated optoelectronic semiconductor chip 2 is heated at an oven temperature of 300° C. and then cooled to room temperature in air.

EXAMPLE 2

[0092] First, water is provided as a solvent 11. The solvent 11 is adjusted to a pH between 1 and 5, and a sodium salt is added as a stabilizer material 6. The reaction mixture is mechanically mixed until the sodium salt is dissolved. TEOS is added to the reaction mixture as the starting material and the reaction mixture is vigorously mechanically mixed for 45 minutes. Subsequently, the mechanical mixing of the reaction mixture is stopped. Within usually two weeks, the sol-gel material 13 is further processed. A sol-gel material 13 with TEOS as a starting material 3 and without a stabilizer material 6 is further processed after a few hours compared to a sol-gel material 13 with a stabilizer material 6, because the polycondensation reaction to form a gel 5 is faster.

[0093] In a further step, for example, a YAG phosphor material 9 is placed in a glass vessel. The sol-gel material 13 with stabilizer material 6 is added. The reaction mixture is mechanically mixed until a homogeneous distribution of the phosphor material 9 occurs in the sol-gel material 13. Then, the sol-gel material 13 with stabilizer material 6 and phosphor material 9 is manually coated onto a microscopic glass slide or onto semiconductor chip wafer pieces. After coating the conversion material 8, the coated optoelectronic semiconductor chip 2 is dried in air and then placed in an oven. In the first annealing process, the coated optoelectronic semiconductor chip 2 is heated at an oven temperature between 70° C. and 100° C. and then cooled to room temperature in air. In the second annealing process, the coated optoelectronic semiconductor chip 2 is heated at an oven temperature of 300° C. and then cooled to room temperature in air.

[0094] The insertion of sodium salt or aluminum salt as stabilizer material 6 into the sol-gel material 13 results in a slower gelation and thus t an improved adhesion of the conversion material 8 to the optoelectronic semiconductor chip 2. In addition, the cracking in the conversion material 8 is reduced compared to a conversion material 8 without stabilizer material 6.

[0095] The product of the method for producing a coating material 1 and subsequently applying it to an optoelectronic semiconductor chip 2, FIG. 5F, corresponds, for example, to the exemplary embodiment shown in FIG. 4. In both examples, an optoelectronic semiconductor chip 2 is shown which comprises the conversion material 8 downstream. The conversion material 8 comprises the phosphor material 9 and the described coating material 1.

[0096] FIG. 6 shows a scanning electron microscope image of the conversion material 8. The right image shows an enlarged image of the left image. Here, the coating material 1 comprises TEOS as alkoxy(alkyl)silane of structural unit A with the sodium salt as stabilizer material 6. Phosphor material 9 is inserted into the coating material 1. The phosphor material 9 is preferably formed as phosphor particles and is embedded in the coating material 1.

[0097] The invention is not limited to the exemplary embodiments by the description thereof. Rather, the invention encompasses any new feature as well as any combination of features, which in particular includes any combination of features in the patent claims, even if that feature or combination itself is not explicitly specified in the patent claims or exemplary embodiments.

[0098] This patent application claims priority of the German patent application DE 10 2018 125 183.1, the disclosure content of which is hereby incorporated by reference.

LIST OF REFERENCE SIGNS

[0099] 1 coating material [0100] 2 optoelectronic semiconductor chip [0101] 3 starting material [0102] 4 hydrolyzed compound [0103] 5 gel [0104] 6 stabilizer material [0105] 7 oxygen atom [0106] 8 conversion material [0107] 9 phosphor material [0108] 10 optoelectronic component [0109] 11 solvent [0110] 13 sol-gel material [0111] 14 monovalent cations [0112] 15 divalent cations [0113] 16 trivalent cations [0114] 17 tetraethyl orthosilicate [0115] 18 silicon atom