Patent Application
20200127177
The invention concerns a method for producing an optoelectronic component. Furthermore, the invention concerns an optoelectronic component.
Embodiments provide a method for producing an optoelectronic component, where the component has improved light extraction. Further embodiments provide an optoelectronic component with improved light extraction compared to conventional components.
In at least one embodiment, the method for producing an optoelectronic component comprises the steps:
A) providing a carrier,
B) applying an adhesive on the carrier,
C) applying a radiation-emitting semiconductor chip having a main radiation surface and side surfaces on the carrier so that the adhesive covers the main radiation surface and the side surfaces of the semiconductor chip at least predominantly and obliquely,
D) applying a reflector layer at least on an outer adhesive surface arranged obliquely to the side surfaces of the semiconductor chip, wherein the carrier is removed again after step C), if applicable.
The invention also concerns an optoelectronic component, which is obtainable from the method described here with the embodiments described here. In this case, all embodiments and definitions of the method for producing an optoelectronic component preferably also apply to the optoelectronic component and vice versa.
According to at least one embodiment, the method has a step A), providing a carrier. For example, the carrier can have one or more materials in the form of a layer, plate, foil or laminate selected from glass, quartz, plastic, metal, stainless steel, Printed Circuit Board (PCB), silicon wafer. In particular, the carrier comprises or consists of glass, a stainless steel plate or PCB.
The carrier is preferably formed temporary. In other words, the carrier is removed again in a later method step, preferably after step C), so that the carrier is not part of the finished optoelectronic component.
According to at least one embodiment, the method has a step B), application of an adhesive on the carrier.
The fact that a layer or element is arranged or applied “on” or “over” another layer or another element can mean here and in the following that the one layer or the one element is arranged or applied directly in mechanical and/or electrical contact with the other layer or the other element. Furthermore, it can also mean that the one layer or the one element is arranged indirectly or over the other layer or the other element. Further layers and/or elements can then be arranged between the one and the other layer or between the one and the other element.
According to at least one embodiment, the adhesive is an inorganic and/or organic adhesive. In particular, the adhesive is a silicone, such as dimethylsiloxane, arylalkylsiloxane or diarylsiloxane. Preferably the adhesive is silicone and does not have any scattering particles. In other words, the adhesive is free of scattering particles or filler materials. The scattering particles or filler materials can be, for example, aluminum oxide, aluminum nitride, titanium dioxide, silicon dioxide, zirconium dioxide, other ceramic as well as vitreous particles, metal oxides or other inorganic particles.
Alternatively, the adhesive can also be an epoxy resin.
According to at least one embodiment, the method comprises a step C), applying a radiation-emitting semiconductor chip having a main radiation surface and side surfaces on the carrier so that the adhesive covers the main radiation side. Alternatively or additionally, the adhesive covers the side surfaces of the semiconductor chip at least predominantly and/or obliquely.
“At least predominantly’ can mean here and in the following that in particular the side surfaces are covered to a proportion of at least 50%, 60%, 70%, 80%, 90%, 95% or 100% by the adhesive.
“Obliquely covered” can mean here that the adhesive seen in the side cross-section forms an outer adhesive surface, which is arranged with respect to the side surfaces obliquely, so there is an angle between the side surfaces and the outer adhesive surface, so that the adhesive has at least regionally an oblique configuration. Preferably, the adhesive, which is arranged on the side surfaces of the semiconductor chips as seen from the side cross-section, has an approximately triangular shape.
The semiconductor chip has at least one semiconductor layer sequence. The semiconductor layer sequence is preferably a III-V compound semiconductor material. The semiconductor material can preferably be based on a nitride compound semiconductor material. “Based on a nitride compound semiconductor material” in the present context means that the semiconductor layer sequence or at least one layer thereof comprises a III-nitride compound semiconductor material, preferably InxAlyGa1-x-yN, wherein 0≤x≤1, 0≤y≤1 and x+y≤1. This material does not necessarily have to have a mathematically exact composition according to the above formula. Rather, it can contain one or more dopants and additional components, which essentially do not alter the characteristic physical properties of the InxAlyGa1-x-yN material. For simplicity's sake, however, the above formula contains only the essential components of the crystal lattice (In, Al, Ga, N), even if these can be partially replaced by small amounts of other substances.
The optoelectronic component comprises an active layer with at least one pn-junction and/or with one or more quantum well structures. During operation of the optoelectronic component, electromagnetic radiation is generated in the active layer. A wavelength or wavelength maximum of the radiation is preferably in the ultraviolet and/or visible range, in particular at wavelengths between 420 nm and 680 nm inclusive, for example, between 440 nm and 480 nm inclusive.
According to at least one embodiment, the optoelectronic component is a light-emitting diode, LED for short. The component is then preferably configured to emit blue, red or green light or, in combination with a conversion layer, white light.
The semiconductor chip in each case has a main radiation surface. The main radiation surface is preferably arranged perpendicular to the growth direction of the semiconductor layer sequence. The main radiation surface is applied in particular on the carrier in step B). In other words, the main radiation surface of the respective semiconductor chip is arranged directly or indirectly downstream of the carrier. Indirect means here in particular that, for example, an adhesive is arranged between the carrier and the main radiation surface. Directly means here that no further layers or elements are arranged between the carrier and the main radiation surface.
According to at least one embodiment, a plurality of semiconductor chips is arranged on the carrier. In particular, the semiconductor chips are arranged in matrix, preferably as an array, on the carrier. The semiconductor chips are preferably arranged on the carrier in such a way that they are laterally spaced apart in cross-section. The semiconductor chips are in particular configured to preferably emit radiation from the visible range.
According to at least one embodiment, the semiconductor chip or the respective semiconductor chip has contact structures. In particular, the contact structures are a p-contact for contacting the at least one p-doped semiconductor layer and an n-contact for contacting the at least one n-doped semiconductor layer of the semiconductor chip. In particular, the contact structures are both arranged on the side opposite the main radiation surface, that is to say the mounting surface.
The side surfaces are preferably arranged perpendicular to the main radiation surface. If the semiconductor chip is formed as a cuboid, the semiconductor chip has at least four side surfaces, one main radiation surface and the mounting surface opposite the main radiation surface.
According to at least one embodiment, the method has a step D), application of a reflector layer at least on the outer adhesive side. The outer adhesive side is arranged at in particular obliquely to the side surfaces of the semiconductor chip.
According to at least one embodiment, the carrier is removed again after step C).
According to at least one embodiment, the adhesive completely covers the main radiation side and the side surfaces of the semiconductor chip.
According to at least one embodiment, the reflector layer is additionally arranged at least regionally on the mounting surface of the semiconductor chip. The reflector layer surrounds the semiconductor chip frame-like or bowl-like seen from in the side cross-section. In other words, the reflector layer covers both the side surfaces of the semiconductor chip and the mounting underside with the exception of the regions covered by the contact structures of the semiconductor chip. Preferably, the reflector layer is applied in such a way that a short circuit is avoided.
The reflector layer can be formed from an insulating material. The material can be inorganic. Alternatively or additionally, the material can also be formed reflective. The reflector layer can also be a dielectric mirror made of aluminum, for example. In principle, however, all other metals or materials, which are capable of reflecting the light emitted by the semiconductor chip and thus coupling it out of the component efficiently, are also suitable. For example, the reflector layer can be formed from silver.
According to at least one embodiment, in or after step C), the adhesive laterally projects beyond the side surfaces of the semiconductor chip as seen in the side cross-section by a maximum of wo nm to 1 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm as seen in the side cross section.
By providing a carrier and applying an adhesive, preferably in excess, on the carrier and subsequently applying the semiconductor chip on the adhesive, the adhesive can cover both the main radiation surface and the side surfaces of the semiconductor chip as a result of surface tension and/or volume displacement and thus surround the semiconductor chip frame-like at the side surfaces and at the main radiation surface. In the subsequent method step, a reflector layer can be applied, which reflects the light emitted by the semiconductor chip during operation and thus increases the light extraction via the main radiation surface.
According to at least one embodiment, the adhesive arranged on the main radiation surface is removed. The removal can be done, for example, by grinding. In particular, the grinding takes place after the production of a housing in order to expose contact pads again.
According to at least one embodiment, the adhesive arranged on the main radiation surface is not removed.
According to at least one embodiment, a housing is produced after step D), which surrounds the reflector layer frame-like.
According to at least one embodiment, the material of the housing is different from the material of the reflector layer.
The reflector layer is therefore preferably not produced with the material of the housing or component. The functionalities, i.e., the reflectivity and the housing material, are produced separately from one another and can thus be optimized for the respective purpose.
Here and in the following, reflection means that at least 80%, 90% and 95% of the light emitted by the semiconductor chip is reflected by the reflector layer and is thus coupled out of the component, in particular via the main radiation surface, towards the front.
In the method for producing optoelectronic components, for example, in the case of semiconductor chips that are formed as volume emitters, the inventor has recognized that the optoelectronic component described here can improve the light extraction at the side surfaces in the direction of the main radiation surface. So far, only semiconductor components are known that have oblique structures, so that the light is deflected accordingly. In this case, the conventional components have reflective layers of silicone, which are often filled with scattering particles such as titanium dioxide or silicon dioxide. These filled silicones also form the housing of the component. With this technique, however, the properties of the reflector layer are bound to the material properties of the filler material (silicone and filler material such as titanium dioxide) and are therefore limited. Such components can emit both monochrome (red, blue, green, et cetera) but also white light, so that an additional conversion layer is required.
The highly reflective and age-resistant material used so far, such as silicone and titanium dioxide and, if appropriate, silicon dioxide, is difficult to process and less resilient. Also the adhesion of the material is not very good. In conventional components, the reflector layer is made of the same material as the housing. A compromise must therefore be found between the processability of the material, such as silicone and titanium dioxide, the reflectivity and the other material properties, such as temperature resistance, ageing stability, thermal expansion coefficients, material strength and adhesion.
The inventor has now recognized that the separate configuration of the reflector element makes it possible to dispense with an additional housing. Alternatively, a housing can also be used, wherein the material of the housing is in particular different from the material of the reflector layer. Thus, the layers or the housing can be optimally adapted separately for the respective purpose.
According to at least one embodiment, a conversion layer is applied at least on the main radiation surface after step D). The conversion layer can have converter materials such as phosphors such as YAG, garnets, calcines, orthosilicates or alkaline earth nitrides. These phosphors can be embedded in a matrix material such as silicone. The embedding can be homogeneous or inhomogeneous, i.e., with a concentration gradient.
According to at least one embodiment, the outer adhesive surfaces and the respective side surface have an angle a of less than or equal to 45°, 30°, 25°, 20°, 10°. Alternatively or additionally, the mounting surface of the semiconductor chip and the outer adhesive side have an angle b of less than or equal to 45°, 40°, 35°, 30°, 25°, 20°, 15°, 10°, 5°. If necessary, the angle a and/or b can be generated by further processing steps.
According to at least one embodiment, contact structures are arranged on the mounting surface of the semiconductor chip. Before step D) a masking element is arranged over the contact structures, which is removed again after step D). The masking element is preferably a photoresist mask. Thus, the reflector layer can be applied in a structured manner on the mounting surface and, if necessary, on the outer adhesive surface.
According to at least one embodiment, radiation is generated in the semiconductor chip during operation and reaches the reflector layer via the side surfaces and is reflected there. Thus, a majority of the radiation of the component is coupled out via the main radiation surface. In other words, the radiation substantially leaves the component via the main radiation surface.
According to at least one embodiment, the component is free of a housing. Preferably, the reflector layer then forms the final layer of the component, i.e., surrounds the semiconductor chip frame-like, wherein there is no additional housing, in which the semiconductor chip is embedded.
According to at least one embodiment, the reflector layer is produced by vacuum deposition. As a deposition technique, for example, physical vapour deposition (PVD) or chemical vapour deposition (CVD) can be used. Also a chemical separation from a liquid is also an option.
According to at least one embodiment, the reflector layer is formed from silver. In other words, the reflector layer forms a silver mirror.
According to at least one embodiment, the reflector layer has a layer thickness of 100 nm to 10 μm. In particular, the layer thickness depends on the type of reflector layer. A silver mirror, for example, can have a layer thickness of several 10 μm. An inorganic reflector layer, for example, a sequence of AlN and Al2O3, can have a layer thickness of less than 1 μm, for example, 100 nm to 900 nm.
According to at least one embodiment, the adhesive is transparent to the radiation emitted by the semiconductor chip. The adhesive is preferably silicone or has silicone, wherein the adhesive is free of scattering particles.
According to at least one embodiment, a plurality of semiconductor chips is applied on the carrier in step C). The semiconductor chips are preferably formed as an array in form of a matrix.
In order to produce the geometric form of the reflector layer, for example, silicone without filler materials is produced around the semiconductor chip with a transparent adhesive. This reflector layer is preferably produced due to the formation of the meniscus, due to the surface tension of the adhesive layer.
Subsequently, the reflector layer can be applied as an independent layer or element by means of CVD or PVD and, if necessary, with the aid of mask techniques. As a result, the reflector layer can be adapted to the given requirements. If the reflector layer is formed from a conductive material, additional masking of the component can be necessary, for example, to prevent short circuits between the contact structures by the conductive reflector layer. The mask technique can also be necessary with non-conductive reflectors, as these otherwise insulate the contact pads.
According to at least one embodiment, an adhesion promoter is applied. The adhesion promoter can improve the adhesion of the reflector layer to the housing material.
The method described here can be carried out both in the front-offline and in the end-offline process.
Since the reflector layer is applied as an independent layer, the housing material can also be applied separately and the material can be selected or adapted according to the requirements. However, there is also the possibility that the housing is completely omitted. In the case that additional housing material is applied, the adhesion between the reflector layer and the housing can be optimized by an adhesion promoter layer or further adhesion promoters.
The inventor has recognized that the method described here can be used to adapt and optimize the reflector layer to the respective requirements. In addition, the housing material can be adapted and optimized to the requirements and processability of the reflector layer independently of the requirements. It is also possible that the component does not have a housing.
Further advantages, advantageous embodiments and further modifications result from the exemplary embodiments described in the following in connection with the Figures. They show:
In the exemplary embodiments and in the Figures, identical, similar or similarly acting elements can each be provided with the same reference signs. The shown elements and their proportions are not to be regarded as true to scale. Rather, individual elements, such as layers, devices, components and regions, can be displayed exaggeratedly large for better representability and/or better understanding.
As shown in
An adhesive 2 is applied on the carrier (
At least one semiconductor chip 3 is applied on the adhesive 2 and/or carrier 1 (
Preferably the main radiation surface 31 and the side surfaces 32 are completely covered by the adhesive. A slant, i.e., an outer adhesive side 21, forms on the side surfaces 32. As shown in
Then, as shown in
The result is an optoelectronic component 100 with a semiconductor chip 3, which is covered by the adhesive 2 on its side surfaces 32 and on the main radiation surface 31. In addition, the component 100 has an obliquely shaped outer adhesive side 21, which is covered by the reflector layer 5 . The component 100 can additionally have contact structures 4, which are used to contact the semiconductor layer sequence of the semiconductor chip 3.
The adhesive 2 is preferably formed transparent. The outer adhesive side 21 and the respective side surface 32 have an angle a of less than or equal to 45°. Alternatively or additionally, the mounting surface 33 of the semiconductor chip 3 and the outer adhesive surface 21 have an angle b of less than or equal to 45° or greater than or equal to 45°. The angles a and b add up to 90°.
The masking element 8 can be removed again in a subsequent method step. The result is a component that has a reflector layer 5, which surrounds the semiconductor layer frame-like and additionally avoids short circuits in the case of a conductive reflector element.
The carrier 1 can be removed again in a final method step, so that a plurality of semiconductor chips can be produced with the embodiment described here.
The semiconductor chip 3 can be formed as a volume emitter in all embodiments.
As shown in
Subsequently, the carrier 1 can be removed from the front side of the LED arrays as shown in
Subsequently, as shown in
The step according to
The exemplary embodiments described in connection with the Figures and their features can also be combined with each other according to further exemplary embodiments, even if such combinations are not explicitly shown in the Figures. Furthermore, the exemplary embodiments described in connection with the Figures can have additional or alternative features as described in general part of the specification.
This patent application claims the priority of the German patent application 10 2017 113 388.7, the disclosure content of which is hereby incorporated by reference.
The invention is not limited by the description based on the exemplary embodiments of these. Rather, the invention includes any new feature and any combination of features, which in particular includes any combination of features in the claims, even if that feature or combination itself is not explicitly mentioned in the claims or exemplary embodiments.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2017 113 388.7 | Jun 2017 | DE | national |
This patent application is a national phase filing under section 371 of PCT/EP2018/065523, filed Jun. 12, 2018, which claims the priority of German patent application 102017113388.7, filed Jun. 19, 2017, each of which is incorporated herein by reference in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/065523 | 6/12/2018 | WO | 00 |
