METHOD FOR DEPOSITTING A PARTICLE MATERIAL AND OPTOELECTRONIC SEMICONDUCTOR DEVICE COMPLIMENTING WITH A PARTICLE MATERIAL

Abstract

The method for depositing a particle material onto a target substrate (1) comprises a step A) in which the particle material is provided on an auxiliary carrier (3) as a plurality of individual particles (2), wherein the particle material is free of a matrix material. In a step B) of the method, at least some of the particles (2) are detached by local heating of the auxiliary carrier (3). In a step C) of the method, detached particles (2) are deposited onto a main surface (10) of the target substrate (1), wherein the main surface (10) faces the auxiliary carrier (3). The target substrate (1) can be an optoelectronic semiconductor chip (100), in particular a micro-LED.

Description

[0001] A method for depositing a particle material onto a target substrate is described. An optoelectronic semiconductor device comprising a particle material is also described.

[0002] One task to be solved is to specify an improved method for depositing a particle material onto a target substrate. Another task is to specify an improved optoelectronic semiconductor device that can be manufactured using such a method.

[0003] These tasks are solved by the method with the features of independent claim 1 or by an object with the features of claim 17. Advantageous embodiments and further developments are the subject of the respective dependent claims.

[0004] According to at least one embodiment of the method for applying a particle material to a target substrate, in process step A) the particle material is provided on an auxiliary carrier. The particle material is provided as a plurality of individual particles. In particular, the particle material is free of a matrix material. That is to say, specifically, the particles are not embedded in a matrix material and connected to each other via the matrix material.

[0005] The particles exist, for example, as individual particles on the support structure without any direct connection to each other. The particles are, for example, only connected to each other via the support structure.

[0006] The particles can each have a maximum dimension of at most 30 µm, or for example at most 20 µm, or for example at most 10 µm, or for example at most 2 µm. The maximum dimension is the largest external dimension of the particles. If the particles are, for example, spherical or approximately spherical, then the maximum dimension corresponds in particular to the diameter of the particles.

[0007] The particles can be applied directly to the support carrier. Preferably, at least in certain areas, one or more intermediate layers are arranged between the particles and the support carrier, which, for example, increases the adhesion between the particles and the support carrier.

[0008] The particles can be coated alternatively or additionally to increase adhesion between the support carrier and the particles.

[0009] The support structure is, for example, a flexible element such as a film or a film strip. The film or film strip can have adhesive properties, allowing the particles to adhere to the flexible element. Alternatively or additionally, the support structure can include a rigid element such as a glass substrate or a semiconductor substrate.

[0010] According to at least one embodiment of the method for applying a particle material to a target substrate, in a process step B) at least some of the particles are detached by local heating of the support. Step B) is preferably carried out after step A).

[0011] Locally heating the support carrier can reduce the adhesion between the particle and the support carrier. For example, the support carrier can be heated in such a way that the adhesion of only some particles is reduced, allowing these particles to detach. Alternatively, the support carrier can be heated in such a way that the adhesion of a single particle is reduced, allowing that single particle to detach.

[0012] Heating can cause an intermediate layer between the support and the particles to at least partially evaporate. The resulting gas evolution can transfer momentum to the corresponding particles, directing them away from the support, thus pushing these particles away from the support and detaching them.

[0013] According to at least one embodiment of the method for applying a particle material to a target substrate, in process step C) detached particles are applied to a main surface of the target substrate facing the auxiliary carrier. Step C) is preferably carried out after step B).

[0014] To deposit the detached particles onto the target substrate, the main surface of the target substrate is brought close, for example to a distance of between 50 µm and 200 µm. After detachment, the particles overcome the distance between the support and the target substrate, primarily in free flight.

[0015] An adhesive layer can be arranged on the main surface of the target substrate so that the particles adhere to the target substrate after application.

[0016] The target substrate can comprise a semiconductor body. The target substrate can also be a support for an electrical component or an electrical component itself. In particular, the target substrate can be any element that is to be at least partially coated with the particle material.

[0017] In at least one embodiment, the method for applying a particle material to a target substrate comprises a step A) in which the particle material is provided on an auxiliary carrier as a plurality of individual particles, wherein the particle material is free of a matrix material. In a step B) of the method, at least some of the particles are detached by local heating of the auxiliary carrier. In a step C) of the method, detached particles are applied to a major surface of the target substrate, wherein the major surface faces the auxiliary carrier.

[0018] According to at least one embodiment, the target substrate is an optoelectronic semiconductor chip. The optoelectronic semiconductor chip may include an active region for generating or absorbing electromagnetic radiation.

[0019] The active region is located, for example, between a first semiconductor layer and a second semiconductor layer of the semiconductor body. For instance, the first semiconductor layer contains charge carriers of a first type, such as p-type or n-type charge carriers. The second semiconductor layer contains charge carriers of a second type, in particular a type opposite to the first.

[0020] For example, the first semiconductor layer is p-doped and the second semiconductor layer is n-doped. The first and second semiconductor layers can each also comprise two or more sublayers and thus each be configured as a sequence of semiconductor layers.

[0021] For example, the semiconductor body is based on a nitride compound semiconductor material, such as Al n In 1-n-m Ga m N, or on a phosphide compound semiconductor material, such as Al n In 1-n-m Ga m P, or on an arsenide compound semiconductor material, such as Al n In 1-n-m Ga m As or Al n In 1-n-m Ga m AsP, where 0 ≤ n ≤ 1, 0 ≤ m ≤ 1, and m + n ≤ 1. The semiconductor may contain dopants and additional components. For simplicity, however, only the essential components of the semiconductor's crystal lattice—Al, As, Ga, In, N, and P—are listed, even though these may be partially replaced and / or supplemented by small amounts of other substances.

[0022] The active zone is configured, for example, to generate electromagnetic radiation from a wavelength range including the IR and UV ranges. Preferably, radiation in the visible wavelength range is generated in the active zone during intended operation.

[0023] The active zone includes, in particular, at least one quantum well structure, for example in the form of a quantum dot, a single quantum well (SQW), or a multi-quantum well (MQW), for radiation generation. Additionally, the active zone includes one, preferably several, secondary well structures.

[0024] For example, the main surface of the target substrate is an emission surface of the optoelectronic semiconductor chip. Preferably, a large proportion, for example at least 70%, at least 80%, or at least 90%, of the electromagnetic radiation generated during operation is emitted via this emission surface.

[0025] According to at least one embodiment, the particles comprise optically active particles. Such optically active particles can, for example, influence radiation generated by the optoelectronic semiconductor chip during operation. For example, the particles include converter particles and / or scattering particles.

[0026] The converter particles allow the primary radiation emitted by the optoelectronic semiconductor chip to be at least partially converted into secondary radiation with a longer wavelength. The optoelectronic semiconductor chip can thus emit mixed radiation consisting of primary and secondary radiation, with the proportions of primary and secondary radiation in the mixed radiation depending on the converter particles and, for example, their arrangement. The converter particles are, for example, phosphorus particles and can be based on a ceramic material. For instance, a semiconductor chip emitting in the blue spectral range can emit white light using suitable converter particles.

[0027] Scattering particles can particularly influence the radiation characteristics of the optoelectronic semiconductor chip. For example, the optoelectronic semiconductor chip can exhibit a diffuse radiation characteristic due to the scattering particles. These scattering particles can be titanium dioxide particles.

[0028] For example, an optoelectronic semiconductor device can be fabricated by depositing optically active particles onto the optoelectronic semiconductor chip. In particular, if the particle material is a converter material comprising a multitude of converter particles and the target substrate is an optoelectronic semiconductor chip, then the process for depositing a particle material onto a target substrate can also be described as a process for fabricating an optoelectronic device.

[0029] Alternatively, the particle material can comprise optically inactive particles. For example, the particle material can be a passivation material. In this case, the particle material can, for example, consist of silicon dioxide particles.

[0030] The following technical considerations underlie the process described here. Converting electromagnetic radiation requires the application of converter materials to an emission surface of the radiation-generating semiconductor chip. The total quantity and distribution of the converter material or converter particles significantly determine the optical properties of the optoelectronic semiconductor chip or the component that comprises the semiconductor chip. Therefore, the application of converter material with the highest possible resolution and accuracy is necessary. Optical properties can include, for example, the chromaticity, brightness, and color-over-angle properties of the semiconductor chip.

[0031] Especially when small optoelectronic semiconductor chips, such as micro-LEDs, are to be coated with a converter material, small quantities of converter particles are necessary, which places special demands on the application process.

[0032] Conventionally, the converter material for application to the semiconductor chip comprises a matrix material in which the converter particles are embedded. The distribution of the converter particles within the matrix material can be uneven, leading to inconsistent or difficult-to-control optical properties of the semiconductor chip or component. For example, the converter particles may form sedimentations, agglomerations, or flow lines within the matrix material. Typically, such converter materials are applied together with the matrix material using dispensing, inkjetting, spray coating, layer attach, doctor blading, or sheet lamination methods.

[0033] The method described here utilizes, among other things, the idea of ​​transferring particles, such as converter particles, onto the target substrate either individually or in groups. This allows even small quantities of particles, such as converter material, to be transferred to the target substrate, such as the optoelectronic semiconductor chip, thus achieving high resolution in the deposition of converter particles. Furthermore, very small quantities of particles can be transferred, which is particularly advantageous for the production of small semiconductor chips, such as micro-LEDs.

[0034] Disadvantages that arise with previously common methods, where the converter material is transferred together with matrix material and where the exact ratio of converter particles to matrix material is unknown, can be overcome simultaneously.

[0035] This advantageously enables the highly repeatable, high-resolution deposition of converter material for the production of optoelectronic semiconductor chips and semiconductor devices with relatively narrow and controllable optical properties. This allows for high production yields and thus low manufacturing costs.

[0036] According to at least one embodiment of the method, the auxiliary carrier is locally heated in step B) using laser radiation. In this case, a detachment layer is preferably arranged between the auxiliary carrier and the particles. The detachment layer can be one of the intermediate layers mentioned above. The detachment layer is specifically designed to absorb the laser radiation. The detachment layer can at least partially vaporize. The resulting gas evolution can transfer a pulse to the corresponding particles, which are then detached from the auxiliary carrier.

[0037] Furthermore, the laser radiation can be partially absorbed by the particles that are to be detached, thus further heating the support.

[0038] The particles are preferably only partially embedded in the release layer. The release layer has a thickness of, for example, between 100 nm and 2 µm and is relatively thin.

[0039] The particles are preferably irradiated through the support structure. In other words, the support structure is irradiated from a rear side facing away from the particles. Preferably, the support structure is transparent to the laser radiation.

[0040] Laser radiation includes, for example, ultraviolet radiation or radiation in the blue spectral region of the electromagnetic spectrum. It is also possible that laser radiation includes radiation in the red spectral region of the electromagnetic spectrum or infrared radiation.

[0041] Preferably, the laser radiation is focused. The size of the laser beam's focal spot determines, in particular, which and how many particles are ejected. If the spot size is approximately the same as the particle size, individual particles can be ejected. Preferably, the spot size can be controlled and adjusted by suitable optics. For example, a diffracting optical element (DOE) and / or a beam expander can be used to adjust the spot size.

[0042] In an alternative embodiment to, or in addition to, the aforementioned embodiment, the auxiliary carrier can be locally heated by applying an electrical voltage. For example, a resistive layer is integrated into the auxiliary carrier or arranged on its rear side. The resistive layer comprises, in particular, a plurality of electrical resistors to which a controlled voltage can be applied, thereby heating the resistors.

[0043] According to at least one embodiment of the method, steps B) and C) are carried out in a field-free environment. This means, in particular, that there is no electric or electromagnetic field, for example, no homogeneous field, between the auxiliary carrier and the target substrate. Specifically, the detached particles are not guided along the field lines of an electric or electromagnetic field towards the target substrate.

[0044] If laser radiation is used to detach the particles, a portion of the radiation may be present between the support and the target substrate that is not absorbed by the particles or the detachment layer. However, this portion of the laser radiation is not necessary for particle transfer. In other words, this portion of the laser radiation has no effect on particle movement between the support and the target substrate.

[0045] Preferably, the space between the auxiliary carrier and the target substrate in step C) is filled with air. This means, in particular, that the particles move freely in the air during the transfer from the auxiliary carrier to the target substrate.

[0046] Advantageously, the method described here does not place any special demands on the environment. Unlike conventional, comparable methods in which particles are guided in an emulsion along electric field lines, this method can be carried out in a field-free environment and in air. Therefore, the particles and the target substrate advantageously do not need to possess any special properties regarding electrical conductivity and / or moisture resistance.

[0047] According to at least one embodiment, the particles are applied in a homogeneous distribution over the main surface of the target substrate. For example, the areal density of the particles on the main surface is constant or varies by less than 20% or less than 10% along the main surface.

[0048] A homogeneous distribution of the particles on the main surface can, for example, result in a homogeneous luminous pattern if the particles are optically active and the target substrate is an optoelectronic semiconductor chip.

[0049] It is also possible to apply the particles in a controlled, inhomogeneous manner to the main surface. This can be advantageous in some applications where an inhomogeneous luminescence pattern of an optoelectronic semiconductor chip or semiconductor component is beneficial or required.

[0050] According to at least one embodiment of the method, steps B) and C) are performed repeatedly in succession. In each execution of step B), preferably enough particles are detached such that in the corresponding step C) at most 10% of the main surface area of ​​the target substrate is covered by the particles.

[0051] According to at least one further development of the embodiment described above, exactly one particle is detached from the auxiliary carrier each time step B) is performed.

[0052] For example, a focal spot or focus area is adjusted to detach the particles from the support individually or in groups.

[0053] For example, the process is used to deposit a converter material onto a main area of ​​an optoelectronic semiconductor chip. The main area, for instance, has a surface area of ​​80 µm x 40 µm. The converter particles are detached from the substrate using laser radiation. The focal spot of the laser radiation has a size of, for example, 10 µm x 10 µm. This means that with each repetition of steps B) and C), 1 / 32 of the main area is deposited with converter particles. The transfer resolution is therefore 1 / 32. After each repetition of steps B) and C), the homogeneity of the deposited converter particles can be checked and adjusted if necessary.

[0054] By repeatedly partially filling the main surface, particle properties such as optical properties of the target substrate, which is for example an optoelectronic semiconductor chip, can be checked between individual or group transfers and the subsequent transfers of the particles can be adjusted.

[0055] According to at least one embodiment, in step B so many particles are detached that in step C essentially the entire main surface of the target substrate is covered by the particles. Advantageously, this allows for a fast and cost-effective application of the particle material to the main surface.

[0056] For example, the process is used to deposit a converter material onto the main surface of an optoelectronic semiconductor chip. The main surface, for instance, has an area of ​​80 µm x 40 µm. The converter particles are detached from the substrate using laser radiation. The focal spot of the laser radiation has a size of, for example, 80 µm x 40 µm. Thus, the entire main surface can be covered with converter particles in a single execution of steps B) and C).

[0057] According to at least one embodiment of the method, the particles are applied to the main surface of the target substrate in a single layer. This means, in particular, that the particles form only one layer on the main surface. The particles are arranged side by side on the main surface and, in particular, are not stacked.

[0058] In the following, a mono-layer is understood to mean in particular a single layer in which the particles are arranged next to each other and not on top of each other.

[0059] According to at least one embodiment, the particles are arranged in at least two layers on the main surface of the target substrate. The layers are stacked on top of each other, particularly on the main surface. For example, a single layer of particles is first applied to the main surface. Subsequently, one or more further layers can be applied on top of the single layer.

[0060] For example, the strength of the wavelength conversion can be influenced by arranging the particles in multiple layers if the particles include converter particles and the target substrate is an optoelectronic semiconductor chip. Thus, for instance, the proportion of converted secondary radiation in the mixed radiation can be increased with multiple layers. This allows the color coordinate of the semiconductor chip or semiconductor device to be adjusted.

[0061] According to at least one embodiment, the particles on the target substrate are at least partially encapsulated with a capping material. The capping material allows the particles to be fixed to their main surface and protected against external influences.

[0062] The encapsulation material can completely surround the particles. The encapsulation material can essentially follow the shape of the particles, especially if it is applied in a relatively thin layer. For example, the thickness of the encapsulation material can range from 100 nm to 10 µm.

[0063] It is also possible that the encapsulation material only partially surrounds the particles.

[0064] The encapsulation material can be applied after the particles have been applied, for example, after a final execution of step C). The encapsulation material can be applied using atomic layer deposition (ALD).

[0065] Alternatively, the encapsulation material can be applied before step C). In this case, the particles are at least partially incorporated into the encapsulation material during step C). The encapsulation material can then be liquid or viscous and cured after the final execution of step C).

[0066] The encapsulation material comprises, for example, a siloxane or a silicone. Preferably, the encapsulation material is transparent to the primary and secondary radiation if the particles are converter particles and the target substrate is an optoelectronic semiconductor chip.

[0067] In the case that several layers of particles are applied, one, some or all layers can be at least partially encapsulated with the encapsulation material.

[0068] According to at least one embodiment, an adhesive layer is arranged on the main surface of the target substrate, and the particles are applied to the adhesive layer. Preferably, the adhesive layer is applied before step C). The adhesive layer is designed to fix the particles to the main surface.

[0069] The adhesive layer can have a thickness between 10 nm and 1 µm (inclusive). The adhesive layer may consist of materials such as silicone or siloxane.

[0070] Furthermore, the adhesive layer can dampen the impact of the particles on the main surface in step C). This reduces the risk of damage to the target substrate by the particles.

[0071] According to at least one embodiment of the method, the particle material is applied to the support in a single layer. For example, a single layer of particles of the particle material is applied to the support before step A).

[0072] To apply a single layer of particles to the substrate, an adhesive layer or similar is applied to one of the substrate's main faces. This main face can then be pressed into a loose bed of particles, thus adhering the single layer of particles to the main face. The adhesive layer can also serve as the release layer.

[0073] Alternatively, the monolayer of particles can be created using electrophoretic disposition (EPD). In this process, an emulsion of the particles is applied to the main surface, and the particles are guided to the main surface via an electric field. Once the monolayer has formed, the emulsion can be removed.

[0074] Alternatively, the particles can be coated with a hydrophobic coating and immersed in a suitable liquid, such as water. The hydrophobic coating allows the particles to float on the water surface in a single layer, which can then be picked up by the support carrier.

[0075] If the particles are arranged in a single layer on the support, it is advantageous that particles can be removed from the support particularly easily, either individually or in groups.

[0076] According to at least one embodiment of the method, the positions of the particles on the support carrier and / or the target substrate are optically detected before step B) and / or after step C). The positions are detected, for example, by means of imaging.

[0077] For example, before step B) is executed for the first time, a map of the particles on the support carrier is created. This map can then be used to precisely detach the particles in subsequent steps. If step B) is executed multiple times, the map can be used for each execution of step B). It is also possible to create a map of the particles on the support carrier before every, every second, every fifth, or every tenth execution of step B).

[0078] Similarly, after each execution of step C), a map of the particles on the target substrate can be created. This advantageously allows for a particularly homogeneous distribution of the particles on the target substrate.

[0079] According to at least one embodiment of the method, in which the particles are optically active particles and the target substrate is an optoelectronic semiconductor chip, an actual value of at least one optical property of the semiconductor chip is determined after each execution of step C). The actual value is then compared with a target value for the at least one optical property. Steps B) and C) are then repeated until a predetermined maximum deviation between the target value and the actual value is reached.

[0080] Optical properties that can be determined include, for example, a color coordinate, a radiation pattern, a brightness and / or a color-over-angle behavior.

[0081] The specified maximum deviation indicates, for example, a tolerance for the optical property.

[0082] The method described here allows the optically active particles to be transferred individually or in groups, enabling a particularly fine adjustment of the optical properties of the semiconductor chip or semiconductor component. This allows the maximum deviation to be advantageously kept relatively small, resulting in tight tolerances.

[0083] According to at least one embodiment of the method, in which the particles are optically active and the target substrate is an optoelectronic semiconductor chip, optical properties, such as conversion rate or scattering characteristics, of the optically active particles are determined on the auxiliary carrier after step A). ​​In steps B) and C), only those optically active particles whose optical properties lie within a predetermined tolerance range can then be transferred to the semiconductor chip. This allows for an increase in the manufacturing yield of the semiconductor chip or semiconductor device.

[0084] For example, the determination of the optical properties of the particles is carried out in conjunction with the creation of a map of the particles' positions. In particular, the map can contain information regarding both the optical properties and the positions of the particles.

[0085] According to at least one embodiment of the method, in which the particles are optically active particles and the target substrate is an optoelectronic semiconductor chip, the electrical contact structures of the semiconductor chip are covered with a protective layer before step C). The protective layer is, for example, a photoresist. After the final execution of step C), the protective layer can be removed.

[0086] According to at least one embodiment of the method, the particles comprise at least particles of the first kind and at least particles of the second kind, which differ from each other in their optical properties.

[0087] For example, both type I and type II particles are converter particles that exhibit different conversion wavelengths or conversion rates. Type I converter particles are configured to convert primary radiation into type I secondary radiation, and type II converter particles are configured to convert primary radiation into type II secondary radiation. Type I and type II secondary radiations differ from each other. A mixed radiation then exhibits, in particular, primary radiation as well as type I and type II secondary radiations. Thus, the bandwidth of the mixed radiation can advantageously be relatively high.

[0088] Alternatively, it is possible that the particles of the first type are converter particles and the particles of the second type are scattering particles.

[0089] It is also possible that the particles of the first type are optically active particles and the particles of the second type are optically inactive particles.

[0090] In further training, it is also possible that the particles include particles of the third type and more.

[0091] According to at least one embodiment of the method, in which particles of the first type and particles of the second type are transferred, the particles of the first type are provided on a first auxiliary carrier and the particles of the second type are provided on a second auxiliary carrier. Preferably, the particles of the first type and the particles of the second type are transferred to the target substrate. In particular, a separate auxiliary carrier is used for each type of particle.

[0092] For example, particles of different types are arranged in separate layers on the target substrate. For instance, particles of the second type can be arranged in a second layer on top of a first layer of particles of the first type on the target substrate. In this case, the particles of the second type can be optically inactive and form a protective layer for the particles of the first type, which can be optically active.

[0093] Alternatively, the particles of different types can be arranged in a pattern, for example, alternating. A random distribution of the particles of different types on the target substrate is also conceivable.

[0094] Furthermore, an optoelectronic component is specified. This optoelectronic component can be manufactured using a method described herein. That is to say, all features disclosed for the method are also disclosed for the optoelectronic component, and vice versa.

[0095] In at least one embodiment, the optoelectronic component comprises a particle material and an optoelectronic semiconductor chip. The particle material is applied as a plurality of individual optically active particles to a main surface of the optoelectronic semiconductor chip. The main surface is, for example, an emission surface of the semiconductor chip. The particle material is preferably free of a matrix material. In particular, an adhesive layer is arranged between the particles and the main surface, wherein the particles are at most partially surrounded by the adhesive layer.

[0096] According to at least one embodiment of the optoelectronic semiconductor device, the maximum particle size is at most 30 µm or, for example, at most 10 µm. Preferably, the particles are arranged in a monolayer on the main surface.

[0097] According to at least one embodiment of the optoelectronic semiconductor device, the particles on the main surface are at least partially encapsulated with a coating material. The coating material allows the particles to be fixed to the main surface and protected against external influences.

[0098] The encapsulation material can completely surround the particles. The encapsulation material can essentially follow the shape of the particles, especially if it is applied in a relatively thin layer. For example, the thickness of the encapsulation material can range from 100 nm to 10 µm.

[0099] It is also possible that the encapsulation material only partially surrounds the particles.

[0100] According to at least one embodiment of the optoelectronic semiconductor device, the semiconductor chip and / or the semiconductor device is a micro-LED.

[0101] A micro-LED could be broadly defined as any light-emitting diode (LED) - not a laser - with a particularly small size.

[0102] As a rule - this is also a very important criterion besides size - a growth substrate is removed in micro-LEDs, so that typical heights of such micro-LEDs are, for example, in the range of 1.5 µm to 10 µm.

[0103] In principle, a micro-LED does not necessarily have to have a rectangular main surface or radiation emission area. For example, an LED with a radiation emission area where, viewed from above, every lateral extent of the radiation emission area is less than or equal to 100 µm or less than or equal to 70 µm could generally be described as a micro-LED.

[0104] For example, for rectangular micro-LEDs, an edge length of less than or equal to 70 µm or less than or equal to 50 µm is often cited as a criterion, especially when looking at the layers of the layer stack from above.

[0105] Most of these micro-LEDs are provided on wafers with holding structures that can be removed without damaging the µLED.

[0106] Currently, the primary application for micro-LEDs is in displays. Micro-LEDs form pixels or subpixels and emit light of a defined color. Due to their small pixel size and high density with close spacing, micro-LEDs are suitable for small monolithic displays for AR applications, particularly smart glasses. Further applications are also being developed, especially in data communication and pixelated lighting applications.

[0107] In the literature you will find various spellings for micro-LED, e.g. µLED, µ-LED, uLED, u-LED or Micro Light Emitting Diode.

[0108] Further advantages and beneficial embodiments and developments of the method and the optoelectronic semiconductor device will become apparent from the exemplary embodiments presented below in conjunction with schematic drawings. Identical, similar, and functionally identical elements are designated with the same reference numerals in the figures. The figures and the relative sizes of the elements depicted in the figures are not necessarily to scale. Rather, individual elements may be exaggerated for clarity and / or better understanding.

[0109] They show: Fig. 1 a block diagram illustrating a method described herein according to a third embodiment, Fig. 2 a schematic view illustrating several process steps of the method according to the first embodiment, Fig. 3 a schematic view of an optoelectronic semiconductor device described herein according to a first embodiment, Fig. 4 a schematic view illustrating several process steps of the method according to a second embodiment.

[0110] In the method according to the first embodiment, which is described in Fig. As illustrated in section 101, a support material 3 is provided in a first step. The support material 3 is, for example, a foil or a foil strip.

[0111] A multitude of individual particles 2 are arranged on the support carrier 3, forming a particle material. The particles 2 are not directly connected to each other, but rather via the support carrier 3 (see Fig. 2) The particles 2 are arranged in a mono-layer on the auxiliary carrier 3.

[0112] A release layer 5 is arranged between the particles 2 and the support carrier 3. The release layer 5 has adhesive properties, so that the particles 2 adhere to the support carrier 3.

[0113] The particles 2 are specifically converter particles designed for wavelength conversion. These converter particles can partially absorb incident primary radiation and convert it into secondary radiation with a longer wavelength and / or wider bandwidth.

[0114] In a subsequent step 102, the particles 2 on the support carrier 3 are optically detected and measured. In particular, a map of the particles 2 on the support carrier 3 is created. The map can include information regarding the position of the particles 2 on the support carrier 3 as well as optical properties, such as the conversion rate of the particles 2. The map is stored, for example, in a memory.

[0115] In a further step 103, the particles 2 are detached from the auxiliary carrier 3 and applied to a target substrate 1.

[0116] The target substrate 1 is preferably an optoelectronic semiconductor chip 100. The optoelectronic semiconductor chip 100 is configured to emit primary radiation, for example in the blue spectral range. The optoelectronic semiconductor chip 100 is in particular a microLED. A main area 10 of the semiconductor chip 100 is in particular an emission surface through which the primary radiation leaves the semiconductor chip 100.

[0117] To detach the particles 2 from the support carrier 3, the support carrier 3 is irradiated with laser radiation 4 (see Fig. 2) The laser radiation 4 is incident on a rear side of the auxiliary carrier 3 facing away from the particles 2. The auxiliary carrier 3 is, in particular, transparent to the laser radiation 4. The laser radiation 4 is preferably UV radiation.

[0118] The laser radiation 4 locally heats the support carrier 3 or the detachable layer 5 by absorption of the laser radiation 4. In the present embodiment, the focal spot of the laser radiation is selected such that the support carrier 3 is heated only in the area surrounding a single particle 2. Due to the heating, the detachable layer 5 is at least partially vaporized locally. The associated gas formation transfers a pulse 20 to a particle 2 to be detached, thereby propelling it into free flight, for example in air, towards the target substrate 1. The distance between the support carrier 3 and the target substrate 1 is, for example, between 50 µm and 200 µm.

[0119] An adhesive layer 7 is applied to the main surface 10. The adhesive layer 7 comprises a silicone or a siloxane. The adhesive layer 7 is designed to fix the particles 2 to the target substrate 1. The adhesive layer 7 surrounds the particles 2 only partially, if at all. The adhesive layer 7 can also dampen the impact of the particles 2 on the main surface 100, thus reducing the risk of damage to the target substrate 1 by the particles 2.

[0120] The target substrate 1, or the optoelectronic semiconductor chip 100, can have contact structures 8. The contact structures 8 can be protected from the particles 2 during step 103 by a protective layer 9 comprising a photoresist.

[0121] In a further step 104, the particles 2 on the target substrate 1 are measured. For example, optical properties and / or positions of the particles 2 on the target substrate 1 are recorded. It is also possible to measure the optical properties of the semiconductor chip 100 after applying some particles 2 to the main surface 10.

[0122] In step 104, an actual value for at least one optical property, such as color coordinates, brightness, or the like, is determined. In a subsequent step 105, the actual value is compared with a corresponding target value. If the deviation between the actual value and the target value is greater than a predefined maximum deviation, steps 103 to 105 are repeated, as described in Fig. 1 is illustrated.

[0123] Steps 103 to 105 are performed repeatedly until the deviation between the actual value and the target value is less than the specified maximum deviation.

[0124] In step 106, an optoelectronic component 200 is completed.

[0125] Optionally, in step 106, an encapsulation material 6 can be applied to the main surface 10 so that the particles 2 are embedded in the encapsulation material 6 (see Fig. 3) The encapsulation material is, for example, silicone. The encapsulation material is applied using atomic layer deposition. The encapsulation material 6 allows the particles 2 to be fixed to the target substrate 1.

[0126] Fig. Figure 3 shows an optoelectronic semiconductor device 200, manufactured using the method of Fig. 1 and Fig. 2 can be produced. On the main surface 10 of the target substrate 1 or the optoelectronic semiconductor chip 100, the particles 2, which are in particular converter particles, are applied in a mono-layer 11. That is, the particles 2 are arranged next to each other on the main surface 10 and are not stacked on top of each other.

[0127] The adhesive layer 7 is arranged between the particles 2 and the main surface 10. The particles 2 are embedded in the encapsulation material 6.

[0128] During operation, primary radiation is generated in the optoelectronic semiconductor chip 100. This primary radiation has wavelengths in the blue spectral region of the electromagnetic spectrum, for example. The primary radiation is emitted via the main surface 10. The primary radiation is at least partially absorbed by the particles 2 and at least partially converted into secondary radiation. The secondary radiation has longer wavelengths and a wider bandwidth than the primary radiation. For example, the secondary radiation has a peak wavelength in the yellow spectral region.

[0129] The semiconductor device 200 emits mixed radiation comprising primary and secondary radiation. The mixed radiation is, for example, white light. Preferably, the adhesive layer 7 and the encapsulation material 6 are transparent to the primary radiation, secondary radiation, and mixed radiation.

[0130] Using the method described here, the particles 2 can be applied to the main surface 10 in groups or individually. Furthermore, optical properties of the optoelectronic semiconductor device 200 can be monitored during the application of the particles 2 (see step 105 of the Fig. 1) This allows the optical properties such as conversion rate, color coordinates, and brightness of the semiconductor device 200 to be precisely adjusted and small tolerance ranges to be achieved.

[0131] In contrast to the procedure according to the Fig. 1 and Fig. 4 are used in the method according to the second embodiment, which is described in Fig. Figure 4 illustrates that several layers 11, 12 are applied to the main surface 10 and the particles 2 comprise particles of the first kind 21 and particles of the second kind 22.

[0132] In the present embodiment, the particles of the first kind 21 and the particles of the second kind 22 are converter particles that differ in their conversion properties. The particles of the first kind 21 are configured to convert primary radiation into secondary radiation of the first kind, and the particles of the second kind 22 are configured to convert the primary radiation into secondary radiation of the second kind. The radiation emitted by the finished semiconductor device 200 in this case comprises the primary radiation as well as the secondary radiations of the first and second kind.

[0133] The particles of the first kind 21 are provided on a first auxiliary carrier 31, which has essentially the same features as the auxiliary carrier 3 of the Fig. 1 and Fig. 4. The particles of the second kind 22 are applied to a second auxiliary carrier 32, which has essentially the same features as the auxiliary carrier 3 of the Fig. 1 and Fig. 4.

[0134] The particles of the first and second kind 21, 22 are transferred from the first and second auxiliary carriers 31, 32 to the main surface 10 of the target substrate 1 or of the optoelectronic semiconductor chip 100, in particular using the same methods as in the method according to the first embodiment.

[0135] In the exemplary embodiment of the Fig. 4. First, a first layer 11 is applied to the main surface 10. The first layer 11 contains exclusively particles of the first kind 21.

[0136] Subsequently, a second layer 12 is applied to the first layer 11, positioned on the side of the first layer 11 facing away from the target substrate 1. The second layer 12 contains particles of the first type 21 and particles of the second type 22, arranged alternately.

[0137] In contrast to the one in Fig.In the arrangement of particles of the first kind 21 and particles of the second kind 22 shown in Figure 4, the particles of the first kind and of the second kind 21, 22 can also be arranged differently. For example, it is possible that the second layer 12 contains exclusively particles of the second kind 22, i.e., the particles of the first kind and of the second kind 21, 22 are separated according to layers 11, 12. A random arrangement of the particles of the first kind and of the second kind 21, 22 is also possible.

[0138] Furthermore, the method according to the second embodiment has the same features, effects and technical advantages as the method according to the first embodiment.

[0139] The invention is not limited to the description provided by the exemplary embodiments. Rather, the invention encompasses every new feature as well as any combination of features, which in particular includes every combination of features in the claims, even if that feature or combination itself is not explicitly stated in the claims or exemplary embodiments. Reference symbol list 1 Target substrate 2 particles 3 auxiliary carriers 4 Laser radiation 5. Delamination layer 6 Encapsulation material 7 adhesive layer 8 Contact structure 9 Protective layer 10 Main area of ​​the target substrate 11 first layer 12 second layer 21 particles of the first kind 22 particles of the second kind 31 first aid carrier 32 second aid carrier 100 optoelectronic semiconductor chips 101...106 Procedural steps 200 optoelectronic semiconductor device

Claims

Method for applying a particle material to a target substrate (1) comprising the following steps: A) Providing the particle material on an auxiliary support (3), wherein the particle material is provided as a plurality of individual particles (2) and is free of a matrix material, B) Detaching at least some of the particles (2) by locally heating the auxiliary support (3), C) Applying the detached particles (2) to a major surface (10) of the target substrate (1) facing the auxiliary support (3). Method according to claim 1, wherein the particles (2) comprise converter particles or scattering particles and the target substrate (1) is an optoelectronic semiconductor chip (100). Method according to claim 1 or 2, wherein the auxiliary carrier (3) is locally heated by means of laser radiation (4) and a delamination layer (5) is arranged between the particles (2) and the auxiliary carrier (3). Method according to one of the preceding claims, wherein at least steps B) and C) are carried out in an environment that is free from an electromagnetic field. Method according to one of the preceding claims, wherein the particles (2) are applied homogeneously distributed on the main surface (10) of the target substrate (1). Method according to one of the preceding claims, wherein at least steps B) and C) are repeated several times alternately in succession, wherein in each execution of step B) so many particles (2) are detached that in step C) at most 10% of the main surface (10) of the target substrate (1) is covered by the particles (2). Method according to claim 6, wherein in each execution of step B) exactly one particle (2) is detached from the auxiliary carrier (3). Method according to any one of claims 1 to 5, wherein in step B) so many particles (2) are detached that in step C) substantially the entire main surface (10) of the target substrate (1) is covered by the particles (2). Method according to one of the preceding claims, wherein the particles are arranged in a mono-layer (11) on the main surface (10) of the target substrate (1). Method according to any one of claims 1 to 8, wherein the particles (2) are arranged in at least two layers (11, 12) on the main surface (10) of the target substrate (1). Method according to one of the preceding claims, wherein the particles (2) on the target substrate (1) are at least partially encapsulated with an encapsulation material (6). Method according to one of the preceding claims, wherein an adhesive layer (7) is arranged on the main surface (10) of the target substrate (1) and the particles (1) are applied to the adhesive layer (7). Method according to one of the preceding claims, wherein the particle material is applied to the auxiliary carrier (3) in a mono-layer to provide the auxiliary carrier (3). Method according to one of the preceding claims in conjunction with claim 2, wherein after each step C) at least one actual value for optical properties of the semiconductor chip (100) is determined, the actual value is compared with a target value, steps B) and C) are repeated until a predetermined maximum deviation between target value and actual value is reached. Method according to one of the preceding claims in conjunction with claim 2, wherein optical properties of the particles (2) are determined on the auxiliary carrier according to step A), and in steps B) and C) particles (2) are transferred to the semiconductor chip (100) whose optical properties are within a predetermined tolerance range. Method according to one of the preceding claims, wherein the particles (2) comprise at least particles of the first kind (21) and at least particles of the second kind (22) which differ from each other in optical properties, the particles of the first kind (21) being provided on a first auxiliary carrier (31) and the particles of the second kind (22) being provided on a second auxiliary carrier (32), and the particles of the first kind (21) and the particles of the second kind (22) being transferred to the target substrate (1). Optoelectronic semiconductor device (200) comprising a particle material and an optoelectronic semiconductor chip (100), wherein: - the particle material is applied as a plurality of individual optically active particles (2) on a main surface (10), - the particle material is free of a matrix material, - an adhesive layer (7) is arranged between the particles (2) and the main surface (10), and - the particles (2) are at most partially surrounded by the adhesive layer (10). Optoelectronic semiconductor device (200) according to claim 17, wherein a maximum dimension of the particles (2) is at most 30 µm, and the particles (2) are arranged in a mono-layer (11) on the main surface (10). Optoelectronic semiconductor device (200) according to claim 17 or 18, wherein the particles (2) on the main surface (10) are at least partially encapsulated with an encapsulation material (6). Optoelectronic semiconductor device (200) according to one of claims 17 to 19, wherein the semiconductor chip (100) is a micro-LED.

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