Optoelectronic device with transparent connection between two bonding partners and method for producing the same

Abstract

The invention relates to an optoelectronic component (3, 10, 13, 22), comprising: a first bonding partner (1, 12, 17) having an LED chip (4, 12, 18) with a structured luminous surface (4c) and a compensation layer (4b, 19) applied to the luminous surface (4c), wherein the compensation layer (4b, 19) has a surface facing away from the luminous surface (4c) and spaced apart from the luminous surface (4c), which forms a first connection surface (4a, 12a, 18a, 19a); and a second bonding partner (2, 8, 11, 21a) having a second connection surface (2a, 8a, 11a, 21a). ), wherein two connection surfaces (4a, 12a, 18a, 19a; 2a, 8a, 11a, 21a) are arranged opposite to each other; and a connection layer (14, 20) made of a low-melting glass film with a layer thickness of up to 1 μm, which connects the two connection surfaces to each other, characterized in that the structure of the luminous surface (4c) is embedded in the compensation layer (4b), and the two connection surfaces (4a, 12a, 18a, 19a; 2a, 8a, 11a, 21a) are smoothed to the extent that the surface roughness of the two connection surfaces, expressed as an average roughness value Ra, is less than or equal to 50 nm, preferably less than or equal to 10 nm.

Description

[0001] This application claims the priority of German application DE 10 2019 105 831.7 filed on March 7, 2019, the disclosure of which is incorporated herein by reference. Technical Field

[0002] The present invention belongs to the technical field of connection for optoelectronic devices, and in particular relates to an optoelectronic device using an inorganic connection material such as low-melting-point glass and a method for manufacturing the same. Background Art

[0003] Optoelectronic components with a carrier are known from the prior art, wherein at least one optoelectronic component is arranged on the surface of the carrier. If the carrier is a lead frame and the optoelectronic component is an LED chip (LED stands for “light emitting diode”), this is an LED component. In such an LED component, the optical lens can be fixed to the LED chip by means of a transparent adhesive.

[0004] As such transparent adhesives, highly transparent organic materials such as epoxy resins or silicone resins are usually used, which have minimal light absorption. The problem in this case is that these organic adhesives are not suitable for special diode devices with high luminous brightness, such as high-power LEDs or laser packages. This is because these special devices generate a lot of heat due to the high power in use. Organic adhesives cannot withstand this heat for a long time. They will degrade, lose transparency, become brittle and crack. This will adversely affect the mode of action of the device.

[0005] In the case of high-power devices, optically transparent connections between components are therefore preferably made with the aid of heat-resistant inorganic materials such as glass, which also have a high refractive index in order to minimize reflection losses at the interfaces.

[0006] Furthermore, if the joined components of high-power devices cannot withstand the high temperatures of more than 600°C that are often used in glass joining, only low-melting-point glasses can be used. For example, low-melting-point glasses include so-called LARP light systems (Laser Activated Remote Phosphor), in which the luminescent ceramic converter must be transparently connected to the dichroic coating of the substrate. The connection technology for LARP components is described, for example, in WO 2017 / 214464 A1.

[0007] Another joining technique is known from the general document WO 2015 / 091374 A1. In this document, a light-transmitting, low-melting glass solder is used in the form of a powder or preform. In this document, the glass solder is applied to the surface of the component. The component is then heated to a temperature above the softening temperature T of the glass used. SOftand joined with the second component. Heated to a temperature above the softening temperature T of the glass soft The temperature ensures that the glass solder liquefies significantly and forms an adhesive layer that can compensate for shape deviations of the surfaces to be joined. In the process, when the components are joined, excess glass can overflow the mounting surface, thereby forming squeezed glass beads. This can be undesirable for certain applications.

[0008] Thus, WO 2015 / 091374 A1 shows a glass composition comprising at least one tellurium oxide and certain proportions of Mg, Ca, Sr, Ba, Zn, Mn and combinations thereof.

[0009] By using low-melting glass solder, it is possible to join components equipped with heat-sensitive LED chips. The semiconductor layers present in the LED chip can be easily damaged in the event of excessive heat. However, it has been found that even in the case of relatively low temperatures required to liquefy the low-melting glass, at least some damage to the LED chips involved in the joining cannot be ruled out.

[0010] In the case of high power devices, there are additional requirements on the adhesive layer used in manufacturing.

[0011] Since high-power components generate blue radiation with very high intensity, an optimal heat transfer through the glass bonding layer must also be ensured. To this end, the glass bonding layer must be applied very uniformly and as thinly as possible. This can be achieved, for example, by applying the glass bonding layer with the aid of vacuum-based coating methods (such as "physical vapor deposition" PVD) or thin-film technology. This is the subject of document US 2018 / 0258520 A1. Summary of the invention

[0012] The object of the present invention is to develop an optoelectronic component of the above-mentioned type so that it can be manufactured more carefully and better. In particular, possible damage to the semiconductor layer of the LED chip due to excessive heating and / or reaction with the glass adhesive layer should be excluded as much as possible during manufacturing.

[0013] According to the invention, this object is achieved in that the structure of the luminous surface is embedded in the compensation layer and the two connecting surfaces are smoothed to such an extent that the surface roughness of the two connecting surfaces expressed as an average roughness value Ra is less than or equal to 50 nm, preferably less than or equal to 10 nm.

[0014] Due to the compensation layer and the particularly smooth connection surface, the glass connection layer no longer needs to compensate for any shape deviations. This means that when joining, it is sufficient to heat the glass at least to the transition temperature and at most to the softening temperature. In this temperature range, the glass becomes soft enough to perform its bonding function. There is no need to increase the temperature further in order to liquefy the glass, because there are no obvious grooves or scratches in the connection surface where the glass must flow. Therefore, both the joining temperature and the thickness of the connection layer can be reduced, which on the one hand minimizes possible thermal damage to the semiconductor components and on the other hand leads to reduced light absorption by the connection layer. In addition, the special smoothness leads to lower light scattering losses at the junction between the connection surface and the glass connection layer. Due to the limited heating of the glass, the glass has a relatively high viscosity in the softened state. The speed of chemical reactions that may cause damage to the joining partners in some cases is correspondingly reduced.

[0015] The efficiency of coupling out the light from the LED chip is improved by the structuring of the light-emitting surface.

[0016] In some embodiments of the optoelectronic device, the structured surface can be produced by roughening the surface.

[0017] LED chips with increased light output can be manufactured with the aid of roughening. For example, a plasma etching method can be used to roughen the surface of an LED chip or a light-emitting semiconductor layer. In some embodiments, the roughening or structuring of the semiconductor layer can also be performed by deposition onto a rough surface.

[0018] By applying the compensation layer, the structuring can be filled and thus leveled. In this case, the compensation layer then forms the connection surface of the joining partner.

[0019] The two connection surfaces of the joining partners can be smoothed by means of chemical mechanical polishing (CMP method).

[0020] Smoothing is generally understood to mean the leveling of ripples, grooves or scratches on the connection surfaces of the joining partners to be joined, which may have been produced during the production of the joining partners. Smoothing can be performed by grinding and / or polishing.

[0021] In some embodiments, the compensation layer of the first bonding partner may consist of a dielectric.

[0022] A dielectric is understood to be a substance that is a non-conductive insulating substance and that is in solid form after being applied to the structured surface. The function of the compensation layer is to compensate for shape deviations of the structured surface and to seal the structured surface. This allows the thickness of the connecting layer used to be significantly reduced.

[0023] For efficient light outcoupling, it is advantageous if the refractive indices n of the two materials (LED semiconductor layer and compensation layer) are d Different, preferably differ by at least 0.3, more preferably by 0.5.

[0024] The dielectric is preferably amorphous or single crystalline and may be, for example, a material selected from the group consisting of SiO2, Al2O3, ZrO2, TiO2, HfO2, MgO, Nb2O5, Ta2O5, Si3N4, ZnO, SiON (in the form of a mixture between SiO2 and Si3N4).

[0025] ITO (Indium Tin Oxide) can be used as a material for the compensation layer. ITO absorbs short-wave light, in particular blue light or short-wave light. ITO can provide a conductive compensation layer. This conductive compensation layer is particularly suitable for InGaAIP or InGaN thin-film chips. There are concepts for such chips.

[0026] Ideally, a material is used for the compensation layer whose refractive index lies between the refractive indices of the two adjacent materials, since this is particularly advantageous for the efficiency of the light outcoupling. Since the light-emitting semiconductor layer has a very high refractive index and usually has a refractive index of >2, aluminum oxide (Al2O3) is particularly suitable as a dielectric, since it has a refractive index n of approximately 1.8. d In addition, it has a high permeability to infrared to ultraviolet radiation and has a similar coefficient of thermal expansion as the semiconductor layer, thereby having good resistance to temperature changes. In addition, aluminum oxide has good thermal conductivity and a softening temperature that is higher than the softening temperature of low-melting glass. It can therefore be ensured that the compensation layer retains its strength when the two bonding partners are bonded to each other.

[0027] Other materials which are light-transmissive and have a softening temperature higher than that of the low-melting glass used as the connecting layer can also be used as compensation material.

[0028] In certain embodiments, the compensation layer may also consist of a plurality of layers.

[0029] In exemplary embodiments, the second bonding partner can be in the form of an optical component, for example a lens, a conversion element (eg a conversion ceramic, a luminescent substance in glass) or a transmissive ceramic or a transparent crystal such as sapphire.

[0030] The conversion element of the exemplary optoelectronic component may be designed to convert the primary radiation emitted by the LED chip into secondary radiation having one or more wavelengths different from the primary radiation.

[0031] In contrast, transmissive ceramics and transparent crystals such as sapphire can be used in the optics if a specific light transmittance of the second bonding partner is desired.

[0032] In particular, the lens or ceramic can be mounted on the LED chip by means of a transparent connecting layer made of low-melting glass. As a result, these bonding partners can be firmly connected to each other. The connecting layer serves as an adhesive layer.

[0033] In a further embodiment, the second joining partner can be a carrier material, preferably consisting of sapphire.

[0034] Furthermore, the epitaxial layers forming the LED chip can be mounted on a sapphire carrier. The epitaxial layer used as a bonding partner is a solid layer of a single crystal that has been epitaxially grown or produced by means of epitaxy. For example, the epitaxial layer can thus be connected to a substrate on which it cannot normally be epitaxially grown, such as an InGaAlP layer on a sapphire substrate.

[0035] The tie layer disclosed herein as a low melting point glass may be a transparent glass composition.

[0036] According to one embodiment, the low-melting glass is also highly refractive and has a refractive index n d >1.6, better >1.7, ideally ≥1.8, particularly preferably ≥1.9.

[0037] According to one embodiment, the glass composition can be colorless and absorb no electromagnetic radiation incident from the first joining partner or absorb at most 1% to 5% of the electromagnetic radiation. In other embodiments, the glass composition can be radiation-transmissive, i.e. more than 95% or more than 99% of the incident electromagnetic radiation can be transmitted in the direction of the second joining surface of the second joining partner. In this case, the glass composition can be free of any scattering.

[0038] The low melting point glass composition may include, for example, lead oxide (PbO) or bismuth oxide (Bi 2 O 3 ) or germanium oxide (GeO 2 ).

[0039] The low melting point glass composition may, for example, contain tellurium oxide (TeO 2 ).

[0040] For example, the glass composition may contain tellurium oxide in a proportion of at least 45 mol% and at most 90 mol%, better at least 50 mol% and at most 70 mol%, preferably at least 55 mol% and at most 70 mol%, ideally at least 59 mol% and at most 69 mol%. The glass composition may also contain oxides of at least one of the following elements: Mg, Ca, Sr, Ba, Zn, Mn, Li, Na, K, Ag, Al, Ga, In, Bi, Sc, Y, La, rare earth elements, Ti, Zr, Hf, Nb, Ta.

[0041] In one embodiment, the glass composition is free of boron trioxide, germanium oxide, lead oxide, phosphates, halides, P2O5, silicon dioxide, and silicates.

[0042] The low melting point glass may have a softening temperature T of at most 350°C, preferably at most 320°C or 300°C or 270°C or 250°C, but at least 200°C. SOft .

[0043] This has the advantage that the glass composition can already connect two joining partners to one another at these low temperatures. Temperature-sensitive joining partners of optoelectronic components can thus be joined in a particularly gentle manner.

[0044] Softening temperature of glass T SOft The temperature at which the viscosity η of the heated glass drops to logη = 7.6 dPa*s. Determination of the softening temperature T according to DIN ISO 7884-6 SOft According to the standard, the softening temperature is also called the Littleton temperature and is a guide value for the temperature above which the glass is suitable for many forming methods.

[0045] At the transition temperature T g When the glass viscosity η is about logη=13.3 dPa*s. Transition temperature T g It is determined in accordance with DIN ISO 7884-8 and characterizes a certain transition range from the brittle elastic state of the glass (at low temperatures) to the viscous state of the glass (at high temperatures).

[0046] The current low melting point glass composition may have at least n d = 1.8, preferably at least n d = 1.85, ideally at least n d = 1.90, especially at least n d = 1.93, particularly preferably at least n d =1.94, wherein the refractive index depends on the glass composition, for example on the tellurium oxide content.

[0047] For example, the glass composition may have a CTE of about 19.9*10 -6 K -1 The coefficient of thermal expansion.

[0048] Preferably, the connecting layer is applied to at least one connecting surface of the two joining partners by means of a PVD method. For example, a sputtering method, preferably an HF sputtering method, can be used for this purpose.

[0049] PVD method (English: physical vapour deposition) is physical vapor deposition.

[0050] In the PVD method disclosed here, a low-melting glass is used as a starting material in solid form. By bombardment, for example with a laser beam or magnetically deflected ions or electrons, glass atoms are released from this starting material and converted into a gas phase. The gaseous material is then conveyed to the joining surfaces of the joining partners to be coated, where it condenses and forms a very thin joining layer made of low-melting glass.

[0051] In the sputtering method, also known as cathode atomization, atoms of a low-melting glass are liberated from a solid by bombarding the solid with high-energy ions, primarily ions of a noble gas such as argon.

[0052] Radio frequency sputtering (HF sputtering) is particularly suitable for coating the joining partners disclosed here, wherein a high-frequency alternating field is applied instead of a direct current field. This results in a pressure reduction of 1-20*10 at the same sputtering rate. -3 mbar. The pressure reduction enables the deposition of thin connecting layers with a special microstructure without excessively heating the joining partners to be coated. HF sputtering is therefore particularly suitable for the coating of heat-sensitive components.

[0053] The connecting layer applied to the connecting surfaces of the joining partners by means of a PVD method can be in the form of a glass film with a layer thickness of at most 5 μm, preferably at most 3 μm, if it is not deposited as a dense layer, for example.

[0054] After the joining partners have been connected, i.e. on the finished component, the layer thickness of the glass composition can be between 10 and 1000 nm, in particular between 100 and 800 nm, particularly preferably between 200 and 500 nm (in each case inclusive of the limit values) according to at least one embodiment. The layer thickness is particularly preferably between 10 and 100 nm. The use of ultrathin transparent glass films as adhesives for joining components of optoelectronic components ensures a better thermal connection and reduced light absorption of the connecting layer. This in turn leads to an increase in the efficiency and light output of the optoelectronic component.

[0055] The present invention also relates to a method for producing an optoelectronic component disclosed here with two bonding partners. The method comprises the following steps:

[0056] a) coating a compensation layer on the structured light-emitting surface and smoothing the compensation layer to a desired waviness and surface roughness to produce a first connection surface;

[0057] b) smoothing the second connecting surface to a desired waviness and surface roughness;

[0058] c) coating at least one smoothed connection surface of the joining partners with a low-melting glass, preferably by means of a PVD method;

[0059] d) The two joining partners are connected to each other by:

[0060] i) heating the two bonding partners to a temperature T, wherein Tg≤T≤Tsoft, Tg is the transition temperature of the low melting point glass, Tsoft is the softening temperature of the low melting point glass, and

[0061] ii) placing the joining partners in succession so that a composite body between the two connecting surfaces and the low-melting glass is formed, wherein the successive placement is preferably carried out by applying a weight,

[0062] Steps i) and ii) may be performed in any order.

[0063] The method for producing an optoelectronic component comprises in principle two subprocesses, namely the preparation of the two joining partners described in steps a) to c) and the subsequent bonding of the two joining partners, the so-called bonding.

[0064] The joining partners can be joined, for example, under vacuum. This results in a strong connection of the connecting layer to the joining partners.

[0065] The joining can also be carried out by applying a weight or a pressure of, for example, about 5-10 MPa. Possible first-order shape deviations, such as unevenness of the connection surface, can thus be compensated during the joining process.

[0066] The mounted optoelectronic device can then be cooled under the applied weight.

[0067] It is also possible to first place the two joining partners in succession, then heat them, and then connect them to one another. The connection can also be carried out dynamically.

[0068] The technical terms used in this application to characterize the surface profile, such as waviness, surface roughness, unevenness, etc., correspond to the DIN 4760 standard, which classifies the surface shape deviation into six orders. As for the definition of terms and the relevant measurement techniques used to quantify surface characteristics, reference is made to this standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0070] Figure 1 A method for manufacturing a first optoelectronic device according to the present invention is shown;

[0071] Figure 2 A method for manufacturing a second optoelectronic device according to the present invention is shown;

[0072] Figure 3 A method for manufacturing a third optoelectronic device according to the present invention is shown; and

[0073] Figure 4 Three variants of methods for producing a fourth optoelectronic component according to the present invention are shown. DETAILED DESCRIPTION

[0074] In the following description, exemplary embodiments of the present invention are described with reference to the accompanying drawings, wherein the drawings are not necessarily drawn to scale but are intended to merely schematically illustrate the corresponding features.

[0075] It should be noted that the features and components described below can be combined with each other, regardless of whether they have been described in conjunction with a single embodiment. The combination of features in the respective embodiments is only used to illustrate the basic structure and function of the device claimed.

[0076] Figure 1-4 The production methods schematically illustrated in each case involve bonding two exemplary bonding partners of an optoelectronic component to one another.

[0077] Figure 1 An exemplary method for producing an optoelectronic component 3 is shown, wherein an optical bonding partner 2 is mounted on an optoelectronic bonding partner 1. The component 3 is a typical LED package including a focusing lens.

[0078] exist Figure 1 The first bonding partner 1 of the optoelectronic device 3 is shown in the upper part of FIG. The first bonding partner 1 comprises a carrier 6, which can be, for example, a ceramic substrate. The carrier 6 can also be referred to as a base of the first bonding partner 1. The carrier 6 is preferably made of a material with good thermal conductivity, such as Al2O3 or AlN.

[0079] An optoelectronic component 4, such as an LED chip (light emitting diode chip), is arranged on a carrier 6. The LED chip 4 comprises a plurality of semiconductor layers (epitaxial layers), wherein light in a specific wavelength range is generated in the active layer during operation of the LED chip 4. For example, the LED chip 4 can generate red light.

[0080] The LED chip 4 has a structured luminous surface 4c and a compensation layer 4b applied to the luminous surface 4c. Figure 1 The lower region is shown in an enlarged view. The surface 4a of the compensation layer 4b facing away from the luminous surface 4c and spaced apart from the luminous surface 4c forms the first connection surface of the first bonding partner 1. Light can be emitted from the LED chip 4 to the outside through the connection surface 4a. For example, amorphous silicon dioxide or aluminum oxide can be used as the material of the compensation layer 4b. Figure 1As can be seen from the enlarged view of FIG, the structure S of the light-emitting surface 4c is embedded in the compensation layer 4b. This means that the texture of the structure S is flattened by the compensation layer 4b. The compensation layer 4b is used to encapsulate the structure S so that the structure S no longer has any influence on the connection quality between the LED chip 4 and other components.

[0081] The LED chip 4 can be supplied with electrical current via electrical lines 5 in the form of bonding wires, which extend from corresponding bonding pads beside the first connection face 4 a of the LED chip 4 to corresponding electrical contact locations on the carrier 6 .

[0082] In order to produce the optoelectronic component 3, the second bonding partner 2, which is present in the form of a prefabricated hemispherical lens, is permanently connected to the LED chip 4 by means of a thin bonding layer 14 made of low-melting glass. For this purpose, the lens 2 has a second bonding surface 2a. The second bonding surface 2a of the lens 2 is arranged to face the first bonding surface 4a of the first bonding partner 1, so that the two bonding surfaces 2a, 4a can be bonded to each other.

[0083] According to the invention, the two connecting surfaces 4a, 2a are smoothed so that their waviness (expressed as average waviness Wa) is less than or equal to 500 nm and their surface roughness (expressed as average roughness value Ra) is less than or equal to 500 nm and preferably less than or equal to 10 nm.

[0084] In some embodiments, the lens 2 can be selected to have a coefficient of thermal expansion that corresponds to the coefficient of thermal expansion of the LED chip 4. It can thus be ensured that the two bonding partners 1, 2 will have similar tensile behavior during heating and cooling during bonding. This prevents the composite from bending due to cooling after bonding or the connection from breaking again.

[0085] The connection layer 14 made of low-melting glass is applied by means of a PVD method (e.g. by HF sputtering) as an ultra-thin film, preferably with a layer thickness of a maximum of 5 μm, particularly preferably a maximum of 3 μm, particularly preferably a maximum of 1 μm, to at least one of the two connection surfaces 2a, 4a of the joining partners 1, 2. The two joining partners 1, 2 are then heated to the softening temperature of the low-melting glass, which is preferably below 350°C, and placed in succession, so that a permanent connection can be produced.

[0086] The heating of the two joining partners 1, 2 is intentionally limited to the softening temperature of the low-melting glass layer 14. This protects the heat-sensitive semiconductor layer of the LED chip 4. Since the two connection surfaces 4a, 2a are very smooth according to the invention, a softening of the glass layer 14 is sufficient for bonding. The glass layer does not have to be liquefied, since there are no significant shape deviations at the two connection surfaces 4a, 2a that would have to be compensated by the glass layer 14 serving as an adhesive layer.

[0087] This does not rule out that the applied glass layer has also been heated to a higher temperature, for example to the flow temperature of the glass, before bonding, in order to produce a pore-free layer. In this case, the glass layer will be located on a heat-resistant bonding partner such as a glass lens.

[0088] In Figure 1 The completed optoelectronic device 3 is shown in the lower part of , in which two lenses 2, 7 are provided. Here, the lens 2 is configured as the inner lens of the device 3, which completely covers the connection surface 4a of the LED chip 4. For example, the inner lens 2 can be made of glass. Such a glass lens 2 can preferably have a refractive index nL1 lower than the refractive index nG of the low-melting glass. Thereby, the light output coupling rate of the optoelectronic device can be significantly improved.

[0089] The second lens 7 is an outer lens, which, similar to the lens 2 on the LED chip 4, completely surrounds the entire upper side of the carrier 6 and the components located on this upper side. The outer lens 7 can be made of silicone resin, for example, and has a refractive index nL2 lower than that of the inner lens 2. Therefore, the outer lens 7 can be used as a focusing lens.

[0090] Advantageously, the refractive index nG of the glass layer 14 should be located between the refractive index nC of the semiconductor material of the LED chip 4 and the refractive index nLl of the glass lens 2. In a particularly preferred variant, the following relationship applies to the refractive indices: nLuft < nL2 < nLl < nG < nC, where nLuft is the refractive index of the air surrounding the component 3, nL2 is the refractive index of the outer lens 7, nLl is the refractive index of the inner lens 2, nG is the refractive index of the glass bonding layer 14, and nC is the refractive index of the semiconductor material of the LED chip 4. If this relationship is maintained, the light output coupling efficiency of the device 3 is particularly high. It is particularly advantageous here that the refractive index jump from one material to another is substantially the same for all material transitions.

[0091] Figure 2 An exemplary manufacturing method of a second optoelectronic device 10 according to the invention is shown, which second optoelectronic device also includes an optoelectronic bonding partner 1 and other optical bonding partners 8. This is an LED package 10 including a converter and a lens for generating white light.

[0092] Only the differences from the embodiment according to Figure 1 will be described below. For the same parts, refer to the above.

[0093] The bonding partner 1 is an LED chip 4 including a carrier 6, and the carrier 6 has a first smooth connection surface 4a. The LED chip 4 can emit blue light, for example.

[0094] Figure 2The second joining partner 8 shown in FIG. 8 is a conversion ceramic which has a second connecting surface 8 a which is likewise smooth.

[0095] The method for producing the optoelectronic component 10 corresponds to the method for producing the first component 3 according to the invention. Here too, the two joining partners 1 , 8 are arranged such that their smooth connection surfaces 4a , 8a can be connected along the entire contact surface by means of a film 14 made of low-melting glass.

[0096] The conversion element 8 may include a conversion material, such as a luminescent substance, by means of which the light emitted by the LED chip 4 and transmitted through the connecting layer 14 can be converted into light of another wavelength. The optoelectronic component 10 may also include an outer lens 9. The lens 9 may be composed of silicone, for example, and have a lower light refractive index than the conversion element 8 and the LED chip 4.

[0097] In an alternative embodiment of the optoelectronic component 10, the LED chip 4 can be a so-called flip chip. In this case, the active contact side of the chip is mounted directly, i.e. without any connecting wires 5, on a substrate 6, which is preferably made of sapphire. As a result, the entire surface of a piece (die) of the semiconductor wafer can be used for contacting. In the case of flip chip bonding technology, all contacts are connected simultaneously. This saves time.

[0098] Figure 3 An exemplary method for manufacturing a third optoelectronic device 13 according to the invention is shown, the third optoelectronic device comprising a first bonding partner 12 and a second bonding partner 11. This example is a combination of an LED chip and a crystal to improve light outcoupling.

[0099] The second bonding partner 11 is a substrate, preferably made of sapphire (Al2O3). The sapphire substrate 11 comprises a smooth surface forming a second connection face 11a.

[0100] The first bonding partner 12 is an LED chip. The LED chip 12 is in the form of a crystalline layer, for example made of AlInGaP, which is grown by epitaxy on a carrier 15, preferably a substrate made of gallium arsenide (GaAs) or gallium phosphide (GaP). This produces an intermediate product 16.

[0101] The carrier 15 serves as a supporting element for the AlInGaP epitaxial layer 12 , which significantly simplifies the transfer of the AlInGaP epitaxial layer 12 to another substrate on which the AlInGaP epitaxial layer 12 cannot be grown.

[0102] Like all first bonding partners disclosed here, the LED chip 12 also has a structured surface and a compensation layer (not shown) applied on the structured surface. The compensation layer can consist of amorphous Al2O3.

[0103] The optoelectronic component 13 is produced by connecting the epitaxially produced AlInGaP layer 12 of the intermediate product 16 to the substrate 11 by means of a connecting layer 14 made of low-melting glass.

[0104] For this purpose, the substrate 11 has a second smooth connection surface 11a, wherein the epitaxial layer 12 has a first connection surface 12a which is also smooth. In order to establish a connection between the two bonding partners 11, 12, a connection layer 14 is applied to at least one of the two connection surfaces 11a, 12a in the form of a low-melting glass such as tellurite glass.

[0105] exist Figure 3 In an embodiment of the present invention, a glass connecting layer 14 is applied to the connecting surface 11a of the substrate 11 by means of a PVD method. Then, both the intermediate product 16 and the substrate 11 are heated to the softening temperature of the low-melting glass 14. Thereafter, the intermediate product 16 is arranged on the connecting layer 14 so that the connecting surface 12a can be completely wetted by the low-melting glass and a uniform and bubble-free connection with a layer thickness of at most 1 μm can be produced under the action of force.

[0106] It may be particularly advantageous to use a glass connecting layer 14 having a higher optical refractive index than the sapphire substrate 11 .

[0107] In a further step, the optoelectronic component 13 is cooled and the substrate 15 is removed from the epitaxial layer 12. The light is coupled out via the sapphire substrate 11.

[0108] Figure 4 An exemplary method of manufacturing a fourth optoelectronic device 22 according to the invention is shown. This also involves connecting the LED chip with a transparent crystal to maximize the light coupling out from the LED chip. The device 22 is here implemented in three different variants 22a, 22b and 22c.

[0109] The production method comprises three steps identified with a) to c). The optoelectronic component 22 comprises a second bonding partner 21 in the form of a sapphire substrate and a first bonding partner 17 in the form of a sapphire layer 19 having an LED chip 18 .

[0110] Each of the two bonding partners 17, 21 has a smooth connection surface 19a and 21a. In variants 22a and 22b, the sapphire layer 19 forms a compensation layer in which the structure of the light-emitting surface of the LED chip 18 is embedded. In the case of variant 22c, on the other hand, the first bonding partner 17 has an additional compensation layer (not shown) on the LED chip 18, which is located on the side opposite to the sapphire layer 19 when viewed from the LED chip 18.

[0111] The optoelectronic component 22 is produced by connecting a sapphire substrate 21 to a first bonding partner 17. For this purpose, a thin connecting layer 20 made of a low-melting glass can be applied, for example by sputtering, to the connecting surface 19a of the sapphire layer 19 or to the connecting surface 18a of a compensation layer (not shown) on the LED chip 18. Alternatively, the glass connecting layer 20 can be applied to the second connecting surface 21a of the substrate 21 or to both connecting surfaces 19a, 21a or 18a, 21a.

[0112] Step a) shows the sapphire layer 19 before the glass connecting layer 20 is sputtered. Step b) shows the joining of the two joining partners 17 and 21. Step c) shows the finished end product.

[0113] By means of this bonding method, an ultra-thin transparent connection is produced between the sapphire layer 19 and the sapphire substrate 21. This results in an LED component 22 with an enlarged light outcoupling surface. The increased volume of the sapphire leads to an increased light extraction efficiency. In addition, heat dissipation can be improved thereby.

[0114] Figure 4 The illustrations i) and ii) in FIG. 2 show the second and third variants. In the variant 22 b according to the illustration i), the sapphire layer 19 and the sapphire substrate 21 have substantially the same width compared to the optoelectronic component 22 a.

[0115] In the variant 22c according to the illustration ii), the LED chip 18 is surrounded by sapphire on two opposite sides. This increases the light coupling-out in both directions.

[0116] Reference numerals list

[0117] 1 First bonding partner

[0118] 2 Inner lens

[0119] 2a Connection surface

[0120] 3 Optoelectronic devices

[0121] 4 LED chips

[0122] 4a Connection surface

[0123] 5 Electric lines

[0124] 6 Carrier

[0125] 7 External lens

[0126] 8 Conversion elements

[0127] 8a Connection surface

[0128] 9 External lens

[0129] 10 Optoelectronic devices

[0130] 11 Substrate

[0131] 11a Connection surface

[0132] 12 LED chips

[0133] 12a Connection surface

[0134] 13 Optoelectronic devices

[0135] 14 Connection Layer

[0136] 15 Substrate

[0137] 16 Intermediate products

[0138] 17 First Engagement Partner

[0139] 18 LED chips

[0140] 18a Connection surface

[0141] 19 Sapphire Layer

[0142] 19a Connection surface

[0143] 20 Connection layer

[0144] 21 Sapphire substrate

[0145] 21a Connection surface

[0146] 22 Optoelectronic devices.

Claims

1. An optoelectronic device (3, 10, 13, 22), comprising: a first joining partner (1, 12, 17) having an LED chip (4, 12, 18) with a structured luminous surface (4c) and a compensation layer (4b, 19) applied to the luminous surface (4c), wherein the compensation layer (4b, 19) has a surface facing away from the luminous surface (4c) and spaced apart from the luminous surface (4c), which surface forms a first connection surface (4a, 12a, 18a, 19a); a second joining partner (2, 8, 11, 21) having a second connecting surface (2a, 8a, 11a, 21a), wherein the two connecting surfaces (4a, 12a, 18a, 19a; 2a, 8a, 11a, 21a) are arranged opposite one another; and a connecting layer (14, 20) made of a low-melting glass film with a layer thickness of at most 1 μm, which connects the two connecting surfaces to one another, It is characterized in that - the structure of the light emitting surface (4c) is encapsulated in the compensation layer (4b) so that the structure no longer has any influence on the quality of the connection of the LED chip (4, 12, 18) to other components, and The two connecting surfaces (4a, 12a, 18a, 19a; 2a, 8a, 11a, 21a) are smoothed to such an extent that the surface roughness of the two connecting surfaces, expressed as an average roughness value Ra, is less than or equal to 50 nm.

2. The optoelectronic device according to claim 1, characterized in that The LED chip (4, 12, 18) comprises a semiconductor layer having a light emitting surface (4c), wherein the refractive index (nG) of the connecting layer (14, 20) is: - less than the refractive index (nC) of the semiconductor layer, and - is greater than the refractive index (nL1) of the material forming the second bonding partner (2, 8, 11, 21).

3. The optoelectronic component according to claim 1, characterized in that The structure of the light-emitting surface (4c) is produced by roughening the surface.

4. The optoelectronic device according to any one of claims 1 to 2, characterized in that: The two connecting surfaces ( 4 a , 12 a , 18 a , 19 a ; 2 a , 8 a , 11 a , 21 a ) are smoothed by means of a CMP method.

5. The optoelectronic device according to any one of claims 1 to 2, characterized in that: The compensation layer consists of a dielectric.

6. The optoelectronic device according to claim 5, characterized in that The dielectric is selected from the following group of materials: SiO2, Al2O3, ZrO2, TiO2, HfO2, MgO, Nb2O5, Ta2O5, Si3N4, ZnO, SiON.

7. The optoelectronic device according to any one of claims 1 to 2, characterized in that: The second bonding partner is a lens (2), a conversion element (8) or a transmissive ceramic or a transparent single crystal.

8. The optoelectronic device according to any one of claims 1 to 2, characterized in that: The second bonding partner is a transparent substrate (11, 21).

9. The optoelectronic device according to any one of claims 1 to 2, characterized in that The low melting point glass is present in the form of a transparent glass composition and has a refractive index greater than 1.

7.

10. The optoelectronic device according to claim 9, characterized in that: The glass composition includes tellurium oxide TeO2.

11. The optoelectronic device according to claim 9, characterized in that: The softening temperature of the low melting point glass is at most 350°C.

12. The optoelectronic device according to any one of claims 1 to 2, characterized in that: The connecting layer is applied to at least one of the two connecting surfaces (4a, 12a, 18a, 19a; 2a, 8a, 11a, 21a) of the joining partners (1, 12, 17; 2, 8, 11, 21) by means of a PVD method and then heated to the softening temperature of the connecting layer to produce the connection.

13. The optoelectronic device according to claim 12, characterized in that: The PVD method is a sputtering method.

14. The optoelectronic device according to any one of claims 1 to 2, characterized in that: The connecting layer (14, 20) is in the form of a glass film.

15. The optoelectronic device according to claim 1, characterized in that: The surface roughness is less than or equal to 10 nm.

16. The optoelectronic device according to claim 8, characterized in that The second bonding partner is made of sapphire.

17. The optoelectronic device according to claim 13, characterized in that: The PVD method is an HF sputtering method.

18. A method for producing an optoelectronic component having two bonding partners (1, 12, 17; 2, 8, 11, 21) according to any one of claims 1 to 17, wherein the method comprises the following steps: a) coating the structured light-emitting surface with a compensation layer and smoothing the compensation layer to a desired waviness and surface roughness to produce a first connection surface (4a, 12a, 18a, 19a); b) smoothing the second connecting surface (2a, 8a, 11a, 21a) to a desired waviness and surface roughness; c) coating at least one of the smooth connection surfaces (4a, 12a, 18a, 19a; 2a, 8a, 11a, 21a) of the joining partners (1, 12, 17; 2, 8, 11, 21) with a low-melting-point glass; d) The two joining partners (1, 12, 17; 2, 8, 11, 21) are connected to one another by: i) heating the two joining partners (1, 12, 17; 2, 8, 11, 21) to a temperature T, wherein T g ≤T≤T soft , T g is the transition temperature of the low melting glass, T soft is the softening temperature of the low-melting glass, and ii) placing the joining partners (1, 12, 17; 2, 8, 11, 21) in succession so as to form a composite body between the two connecting surfaces (4a, 12a, 18a, 19a; 2a, 8a, 11a, 21a) and the low-melting glass, Steps i) and ii) may be performed in any order.

19. The method according to claim 18, characterized in that The continuous placement is performed by applying weight.

20. The method according to claim 18, characterized in that At least one smooth connection surface (4a, 12a, 18a, 19a; 2a, 8a, 11a, 21a) of the joining partners (1, 12, 17; 2, 8, 11, 21) is coated with a low-melting glass by means of a PVD method.

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