Micro light emitting diode, micro light emitting diode device, display and method thereof

Abstract

The invention relates to various aspects of a [mu]-LED or a [mu]-LED arrangement for augmented reality or light applications, in particular in the automotive field. The [mu]-LEDs are characterized by particularly small dimensions in the range of several [mu] m.

Description

[0001] This invention is a divisional application of the parent application, which is filed on January 29, 2020, with application number 202080023800.9 and invention title "Miniature Light Emitting Diode, Miniature Light Emitting Diode Device, Display and Method Thereof" (PCT International Application PCT / EP2020 / 052191 entered the Chinese National Phase).

[0002] This patent application claims priority to the following German patent applications: DE 10 2019 201114.4, dated January 29, 2019; DE 10 2019 111 766.6, dated May 7, 2019; DE 10 2019 112 124.8, dated May 9, 2019; DE 10 2019 116 313.7, dated June 14, 2019; DE 10 2019 131 506.9, dated November 21, 2019; DE 10 2019 118 251.4, dated July 5, 2019; DE 10 2019 118 082.1, dated July 4, 2019; and DE 10 2019, dated March 29, 2019. 108 260.9, DE 10 2019 on September 20, 2019 125 349.7, DE 10 2019 on May 13, 2019 112 490.5, DE 10 2019 on May 14, 2019 112 604.5, DE 10 2019 on May 14, 2019 112 609.6, DE 10 2019 on January 31, 2019 102 509.5, DE 10 2019 on June 7, 2019 115 479.0, DE 10 2019 on May 14, 2019 112 616.9, DE 10 2019 on May 23, 2019 113791.8, DE 10 2019 110 499.8 on April 23, 2019, DE 10 2019 110523.4 on April 23, 2019, DE 10 2019 130 934.4 on November 15, 2019, DE 10 2019 114321.7 on May 28, 2019, DE 10 2019 127 425.7 on October 11, 2019, DE 10 2019 112639.8 on May 14, 2019, DE 10 2019 112 605.3 on May 22, 2019 113636.9, DE 10 2019 103 365.9 on February 11, 2019, DE 10 2019 116312.9 on June 14, 2019, DE 10 2019 115 991.1 on June 12, 2019, DE 10 2019 125875.8 on September 25, 2019, DE 10 2019 127 424.9 on October 11, 2019, DE 10 2019 118085.6 on July 4, 2019, DE 10 2019 125 336 on September 20, 2019.5. DE 10 2019 113793.4 on May 23, 2019; DE 10 2019 110 500.5 on April 23, 2019; DE 10 2019 111 767.4 on May 7, 2019; DE 10 2019 121 672.9 on August 12, 2019; DE 10 2019 118 084.8 on July 4, 2019; DE 10 2019 113 768.3 on May 23, 2019; DE 10 2019 113 792.6 on May 23, 2019; DE 10 2019 110 on April 23, 2019. 497.1, DE 10 2019 114 442.6 dated May 29, 2019, DE 10 2019 129 209.3 dated October 29, 2019, DE 10 2019 130 821.6 dated November 14, 2019, and DE10 2019 130 866.6 dated November 15, 2019, the disclosures of which are incorporated herein by reference, and also claim Danish patent applications DK PA201970059, DK PA201970060, and DK, dated January 29, 2019. The patent claims priority to PA201970061, the disclosure of which is incorporated herein by reference, and also to U.S. patent application US 62 / 937,552, dated November 19, 2019, the disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to miniature light-emitting diodes, miniature light-emitting diode devices, and displays. Background Technology

[0004] The ongoing developments in the Internet of Things (IoT) and communications fields have opened doors to a variety of new applications and designs. These designs and applications offer greater effectiveness and efficiency for development, service, and manufacturing purposes.

[0005] One aspect of the new design involves augmented reality, or virtual reality. The general definition of “augmented reality” is: “an interactive experience of a real environment in which objects in the real world are extended by computer-generated perceptible information.”

[0006] Information is primarily conveyed through visualization, but not limited to visual perception. Sometimes, tactile or other sensory perceptions can be used to augment reality. In the case of visualization, the overlaid sensory visual information can be constructive—that is, supplementing the natural environment—or non-constructive, such as by covering a portion of the natural environment. In some applications, interaction with the overlaid sensory information may also occur in one or another manner. Thus, augmented reality enhances the user's continuous perception of the real environment.

[0007] In contrast, "virtual reality" replaces the user's real environment with a completely simulated one. In other words, while users can perceive the real world at least partially in an augmented reality environment, the environment in virtual reality is completely simulated and may differ significantly from reality.

[0008] Augmented reality (AR) can be used to improve natural environmental conditions, thereby enriching the user experience or supporting them in performing certain tasks. For example, users can use displays with AR capabilities to assist them in performing certain tasks. By overlaying information about real objects to provide clues to the user, it provides additional information, enabling them to act faster, safer, and more efficiently during manufacturing, repair tasks, or other services. In the medical field, AR technology can be used to guide and support doctors in diagnosing and treating patients. In development, engineers can directly experience their test results, making it easier to evaluate the outcomes. In the tourism or events industry, AR can provide users with additional information about attractions, history, and more. AR can also support learning activities or tasks. Summary of the Invention

[0009] The following introduction illustrates various aspects of μ (micro) displays in automotive and augmented reality applications. These aspects include devices, displays, controls, process techniques, and other suitable features for augmented reality and automotive applications. This includes aspects designed to generate light through indicators, displays, etc. Additionally, aspects of control circuitry, power supplies, and optical coupling outputs, light guiding, and light focusing are listed, along with applications of such devices, explained using various examples.

[0010] Because of the various limitations and challenges posed by the small size of the light-generating components, combining various aspects is not only advantageous but often necessary. For ease of handling, this disclosure is divided into several parts with similar topics. However, it should not be explicitly understood that features of one topic cannot be combined with other topics. Rather, aspects from different subject areas must be combined to create displays for augmented reality or other applications or in the automotive field.

[0011] To consider the following solutions, some terms and expressions should be explained to define common and shared understanding. For clarity, the listed terms are generally used herein. However, in individual cases, they may deviate from the intended interpretation, where such deviation is identifiable.

[0012] "Active Matrix Display"

[0013] The term "active matrix display" originally referred to liquid crystal screens containing a matrix of thin-film transistors controlled by LCD (liquid crystal display) pixels. Each individual pixel has a circuit with active components (mainly transistors) and power connections. However, this technology should not be limited to liquid crystals at present, but should specifically refer to the control of μ-LEDs (micro-light-emitting diodes) or μ displays.

[0014] "Active Matrix Carrier Substrate"

[0015] An "active matrix carrier substrate" or "active matrix backplane" refers to the driving device for the light-emitting diodes (LEDs) of a display with thin-film transistor (TFT) circuitry. Here, these circuits can be integrated into or applied to the backplane. The "active matrix carrier substrate" has one or more interface contacts that form an electrical connection with the μ-LED display structure. Therefore, the "active matrix carrier substrate" can be part of or carry an active matrix display.

[0016] "Active layer"

[0017] An active layer is a layer in an optoelectronic device or light-emitting diode (LED) where charge carriers recombine. In its simplest form, an active layer is characterized by regions of two adjacent semiconductor layers with different conductivity types. More complex active layers include quantum wells (see related description), multiple quantum wells, or other structures with additional properties. Structural and material systems can also be used to define the band gap in the active layer (see related description), which defines the wavelength and thus the color of light.

[0018] "Alvarez Lens Device"

[0019] The optical path of the video glasses can be adjusted by using Alvarez lens pairs. The adjustment optics include Alvarez lens devices, particularly rotatable variants with moiré lens devices. Here, beam deflection is determined by the first derivative of the individual phase plate morphologies, approximately z = ax² + by² + cx + dy + e for the radiation direction z and the transverse directions x and y, and is determined by the offset of the two phase plates arranged in pairs in the transverse directions x and y. For alternative designs, pivotable prisms are provided in the adjustment optics.

[0020] Augmented Reality (AR)

[0021] This is an interactive experience of a real-world environment, where the filmed project is located in the real world and enhanced by computer-generated perceptible information. Augmented reality is understood as a computer-aided extension of the perception of reality through such computer-generated perceptible information. This information can appeal to all human senses. However, augmented reality often refers only to the visual representation of information, i.e., images or videos with computer-generated additional information or virtual objects added through fade-in / overlay. Applications and explanations of how augmented reality works can be found in the introduction to the examples and below.

[0022] "car"

[0023] "Automotive" generally refers to motor vehicles or the automotive industry. Therefore, the term is intended to include this branch, but also all other industry branches, including microdisplays or general luminous indicators with very high resolution and μ-LEDs.

[0024] "band gap"

[0025] The energy gap between the valence band and conduction band of a solid is called the band gap, also known as the band gap or band exclusion zone. Its electrical and optical properties depend largely on the size of the band gap. The size of the band gap is usually expressed in electron volts (eV). The band gap is used to distinguish metals, semiconductors, and insulators. The band gap can be tuned (i.e., changed) by various measures such as spatial doping to detune the crystal structure or by altering the material system. Material systems with a so-called direct band gap, where the maximum value of the valence band and the minimum value of the conduction band are superimposed in momentum space, allow electron-hole pairs to recombine with emitted light.

[0026] "Prague Grating"

[0027] A Bragg fiber grating is a special optical interference filter etched into an optical waveguide. Wavelengths within the filter bandwidth near λB are reflected. Various methods are used to generate periodic modulation of the refractive index within the fiber core of the waveguide. This creates regions with high and low refractive indices that reflect light of specific wavelengths (bandstop). The center wavelength of the filter bandwidth in a single-mode fiber is determined by the Bragg condition.

[0028] "Directionality"

[0029] Directivity, or directionality, is used to describe the radiation characteristics of μ-LEDs or other light-emitting components. High directionality corresponds to highly directional radiation or a low-radiation cone. Typically, the goal is to achieve a high level of directional radiation to minimize crosstalk between light and adjacent pixels. Consequently, the brightness of the light-emitting component varies depending on the viewing angle, thus differing from a Lambertian emitter.

[0030] Directionality can be altered, for example, by mechanical or other means on the side used for emission. Besides lenses, this includes photonic crystals or columnar structures (pillar structures) arranged on the emission surface of the pixelated array or, in particular, on an arrangement of μ-LEDs. These create a virtual bandgap that reduces or prevents the light vector from diffusing along the emission surface.

[0031] "Far field"

[0032] The terms near field and far field describe the spatial regions surrounding components that emit electromagnetic waves and have distinct characteristics. Typically, these spatial regions are divided into three areas: the reactive near field, the transition field, and the far field. In the far field, electromagnetic waves propagate as plane waves, independent of the radiating element.

[0033] "Screen window effect"

[0034] The screen-door effect (SDE) is a permanently visible image artifact in digital video projectors. The term describes an undesirable, technically relevant dark distance between individual pixels or their projected information, taking the form of a screen. This distance originates from the construction, as the conductive circuitry used for control runs between the individual LCD segments, where light is swallowed up and cannot reach the screen. If small photoelectric light-emitting devices are used, particularly μ-LEDs, or the distance between individual LEDs is too large, the low packing density produced when viewing a single LED can result in a visible difference in pixel areas between bright and dark spots. This so-called screen-door effect is particularly noticeable when viewed from a smaller distance, especially in applications such as VR (virtual reality) glasses. When the illumination differences within a pixel persist periodically across the entire matrix arrangement, the sub-pixel structure is often perceived and annoying. Therefore, the screen-door effect should be avoided as much as possible in automotive and augmented reality applications.

[0035] "Flip Chip"

[0036] Flip chip assembly is a method of fabrication and connection technology used to contact unpackaged semiconductor chips via contact bumps known as "bumps." With flip chip assembly, the chip can be directly mounted without additional interconnects, with its effective contact surface facing down (towards the substrate / circuit carrier) above the bumps. This results in a particularly small housing size and shorter conductor length. Therefore, flip chips are especially suitable for electronic semiconductor components that contact on their back side. Such components may also require special transfer techniques, such as using an auxiliary carrier. In the case of flip chips, the radiation direction is typically opposite to the side of the contact surface.

[0037] "trigger"

[0038] A flip-flop, also commonly known as a bistable switching stage or bistable switching element, is an electronic circuit with two stable output signal states. The current state depends not only on the currently available input signal but also on the state that existed prior to the point in time being considered. There is no time correlation, only event correlation. Due to its bistable nature, a flip-flop can store one bit of data indefinitely. However, unlike other types of memory, a voltage supply must always be guaranteed. Flip-flops are a fundamental component of sequential circuits and an essential part of digital technology, thus forming a basic element in many electronic circuits, from quartz clocks to microprocessors. In particular, as a basic one-bit memory, it is a fundamental element of the static memory module used in computers. Some embodiments may use different types of flip-flops or other buffer circuits to store state information. Their respective input and output signals are digital, meaning they alternate between logical "false" and logical "true". These values ​​are also referred to as "low" 0 and "high" 1.

[0039] Head-up display

[0040] A head-up display (HUD) is a display system or projection device in which a user maintains a certain head posture or gaze as information is projected into the user's field of view. HUDs are augmented reality systems. In some cases, HUDs incorporate sensors that determine the direction or orientation of the user's gaze in space.

[0041] Horizontal LED

[0042] In the case of horizontal LEDs, the electrical connection is located on the common side of the LED. This is typically the back side of the LED, away from the light-emitting surface. Therefore, horizontal LEDs have contacts formed only on the surface side.

[0043] "Interference filter"

[0044] An interference color filter is an optical component that uses the interference effect to filter light in a frequency-dependent manner (i.e., in a color-dependent manner for visible light).

[0045] "Collimation"

[0046] In optics, collimation refers to the parallel direction of diverging rays. The associated lens is called a collimator or condenser. A collimated beam contains mostly parallel rays and therefore has minimal scattering during propagation. Its use in this sense relates to the scattering of light emitted from a light source. A collimated beam emitted from a surface is highly dependent on the angle of radiation. In other words, the radiance (unit power per unit angle of a projected light source area) of a collimated light source varies with increasing angle. Light can be collimated in various ways, such as by using a special lens placed in front of the light source. Therefore, collimated light can also be considered as light with a high degree of directional dependence.

[0047] "Converter Materials"

[0048] Converter materials are materials suitable for converting light of a first wavelength into light of a second wavelength, shorter than the second. These include various permanent inorganic and organic dyes as well as quantum dots. Converter materials can be applied and constructed in a variety of processes.

[0049] "Lambert Launcher"

[0050] The so-called Lambertian radiation characteristic is required in many applications. This means that the luminescent surface ideally has a uniform radiation density on its surface, resulting in a vertically circular distribution of radiation intensity. Since humans can only assess brightness with their eyes (brightness is the luminous equivalent of illuminance), such Lambertian materials appear equally bright regardless of the viewing direction. This uniform, angle-independent brightness can be an important quality factor, especially for curved and flexible display surfaces, which is sometimes difficult to achieve with currently available displays due to their structure and LED technology.

[0051] LEDs and μ-LEDs are similar to Lambertian emitters and emit light at a large spatial angle. Depending on the application, further steps can be taken to improve radiation characteristics, or greater directionality can be attempted (see related notes).

[0052] "Conductivity type"

[0053] The term "conductivity type" refers to the majority (n- or p-type) charge carriers in a given semiconductor material. That is, a semiconductor material doped with n (negative) type is considered to be of n conductivity type. Similarly, if a semiconductor material is n-type, then it is n-type doped. The term "active" region in a semiconductor refers to the boundary region between an n-type doped layer and a p (positive)-type doped layer. Radiative recombination of p-type and n-type charge carriers occurs in this region. In some embodiments, the active region is further constructed and includes, for example, a quantum well or quantum dot structure.

[0054] "Light field display"

[0055] A display technology that projects raster images directly onto the retina of the eye is called a Virtual Retinal Display (VNA) or Light Field Display. The user gains the impression of a canvas floating in front of them. Light Field Displays can be provided as glasses, projecting raster images directly onto the user's retina. Using a Virtual Retinal Display, an image is created within the user's eye through direct projection of the retina. Light Field Displays are augmented reality systems.

[0056] "Plate printing" or "photolithography"

[0057] Photolithography is one of the core methods in semiconductor and microsystems technology, used to manufacture integrated circuits and other products. In this process, the image of a photomask is transferred onto a photosensitive photoresist through exposure. Subsequently, the exposed areas of the photoresist are dissolved (or the unexposed areas can also be dissolved when the photoresist cures under light). This forms a lithographic mask, which can be further processed through chemical and physical processes, such as applying material to the open areas or etching recesses in the open areas. The remaining photoresist can then be removed.

[0058] “μ-LED”

[0059] μ-LEDs are optoelectronic devices with edge lengths less than 70 μm, particularly less than 20 μm, and especially in the range of 1 μm to 10 μm. Another range is between 10 and 30 μm. This results in a range of several hundred μm. 2 Up to tens of μm 2 The area of ​​a μ-LED is approximately 60 μm², with an edge length of approximately 8 μm. In some cases, the edge length of a μ-LED is 5 μm or less, resulting in a size less than 30 μm². For example, the typical height of such a μ-LED is between 1.5 μm and 10 μm.

[0060] Besides classic lighting applications, μ-LEDs are primarily used in displays. Here, μ-LEDs form pixels or subpixels and emit light of a specified color. Due to their small pixel size and high density at close range, μ-LEDs are also suitable for small, monolithic displays used in AR applications.

[0061] Due to the extremely small size of μ-LEDs, their production and processing are significantly more difficult compared to previous large LEDs. This also applies to other components such as contact lenses, packaging, and lenses. Some aspects feasible in large optoelectronic components cannot be achieved in μ-LEDs, or must be achieved in different ways. In this respect, μ-LEDs are therefore significantly different from traditional LEDs, i.e., light-emitting elements with an edge length of 200 μm or more.

[0062] μ-LED array

[0063] See Microdisplay

[0064] "Miniature display"

[0065] A microdisplay, or μ-LED array, is a matrix with a large number of pixels arranged in prescribed rows and columns. Functionally, a μ-LED array typically forms a matrix primarily composed of μ-LEDs of the same type and color. Therefore, it provides a larger surface area for illumination. On the other hand, the purpose of a μ-display is to transmit information, which often also necessitates different colors or positional control for each individual pixel or subpixel. A microdisplay can consist of multiple μ-LED arrays, formed together on a backplane or other carrier. However, μ-LED arrays can also be used to form microdisplays.

[0066] Each pixel is on the order of a few μm, similar to a μ-LED. Therefore, a μ-display with 1920×1080 pixels, each with a 5μm μ-LED, and directly adjacent pixels has an overall size of 10 mm². In other words, a microdisplay or μ-LED array is a small-scale device implemented using μ-LEDs.

[0067] Microdisplays or μ-LED arrays can be formed from a single, identical component. The μ-LEDs in a μ-LED array can be formed monolithically. Such microdisplays or μ-LED arrays are called monolithic μ-LED arrays or microdisplays.

[0068] Alternatively, both components can be formed by growing μ-LEDs individually on a substrate and then arranging them individually or in groups on a carrier using a so-called pick-and-place process, maintaining a certain distance between them. Such a microdisplay or μ-LED array is referred to as non-monolithic. In a non-monolithic microdisplay or μ-LED array, other distances between individual μ-LEDs are also possible. These distances can be flexibly chosen depending on the application and implementation. Therefore, such a microdisplay or μ-LED array can also be referred to as a pitch-extended component. In a pitch-extended microdisplay or μ-LED array, the μ-LEDs are arranged at greater distances when delivered to the carrier than they are on the growth substrate. In a non-monolithic microdisplay or μ-LED array, each individual pixel may each include a blue-emitting μ-LED, a green-emitting μ-LED, and a red-emitting μ-LED.

[0069] To leverage the advantages of both monolithic and non-monolithic μ-LED arrays within a single module, monolithic μ-LED arrays can be combined with non-monolithic μ-LED arrays in a microdisplay. This allows the microdisplay to be used for different functions or applications. Such a display is called a hybrid display.

[0070] "μ-LED nanopillars"

[0071] μ-LED nanopillars are typically a stack of semiconductor layers with an active layer, thus forming a μ-LED. The edge length of a μ-LED nanopillar is less than its height. For example, the edge length of a μ-LED nanopillar is approximately 10 nm to 300 nm, while the height of the device may be 200 nm to 1 μm or higher.

[0072] "μ column"

[0073] μ-pillars or pillars specifically refer to a geometric structure, particularly a rod or bar, or generally a slender, cylindrical structure. The spatial dimensions of manufactured μ-pillars range from μm to nm. Therefore, nanopillars are also included herein.

[0074] "Nanopillars"

[0075] In nanotechnology, nanopillars are a design concept for nanoscale objects. Each of them ranges in size from approximately 10 nm to 500 nm. They can be synthesized from metallic or semiconducting materials. The aspect ratio (length divided by width) is 3 to 5. Nanopillars are made through direct chemical synthesis. A combination of ligands acts as a shape control agent and attaches to different faces of the nanopillar with varying strengths. This allows for different designs of nanopillars with different growth rates to produce an elongated object. μLED nanopillars are such nanopillars.

[0076] Miniature LED

[0077] Its size ranges from 100μm to 750μm, especially in the range greater than 150μm.

[0078] Moiré effect and Moiré lens array

[0079] The moiré effect refers to the noticeably coarser gratings produced by the superposition of regular, finer gratings. The resulting pattern, resembling a pattern from interference, is a special case of aliasing caused by undersampling. In signal analysis, aliasing occurs when the signal being sampled contains frequency components higher than half the sampling frequency. In image processing and computer graphics, aliasing occurs when an image is sampled, resulting in patterns not present in the original image. A moiré lens array is a special case of an Alvarez lens array.

[0080] "Single component"

[0081] A single-unit component refers to a component made from a single part. A typical example of such a component is a single-pixel array, where the array is made from a single part, and the array's μ-LEDs are fabricated together on a carrier.

[0082] "Optical mode"

[0083] A mode is a description of a wave's specific time-static properties. The wave is described as a sum of different modes. These modes differ in their spatial distribution of intensity. The shape of a mode is determined by the boundary conditions of wave propagation. Analysis based on vibration modes can be applied to both standing waves and continuous waves. For electromagnetic waves such as light, lasers, and radio waves, the following types of modes are distinguished: TEM (transverse electromagnetic) mode, TE (transverse electric) or H (magnetic) mode, TM (transverse magnetic) or E (electric) mode. TEM (transverse electromagnetic) mode: Both the electric and magnetic fields are always perpendicular to the direction of propagation. This mode can only propagate when there are two isolated conductors (equipotential surfaces) in a coaxial cable or when there are no electrical conductors in a gas laser or optical waveguide. TE or H mode: Only the electric field component is perpendicular to the direction of propagation, while the magnetic field component points in the direction of propagation. TM or E mode: Only the magnetic field component is perpendicular to the direction of propagation, while the electric field component points in the direction of propagation.

[0084] "Optoelectronic components"

[0085] An optoelectronic component is a semiconductor substrate that generates light through recombination of charge carriers during operation, and then emits light. The emitted light can range from infrared to ultraviolet, with the wavelength depending on various parameters, the material system used, and the doping. Optoelectronic components are also known as light-emitting diodes (LEDs).

[0086] For the purposes of this disclosure, the terms optoelectronic component and light-emitting component are used synonymously. Therefore, in terms of its geometry, a μ-LED (see related description) is a specific type of optoelectronic component. In displays, optoelectronic components are typically monolithic or single components placed on a matrix.

[0087] "Passive matrix backplane" or "passive matrix carrier substrate"

[0088] A passive matrix display is a matrix display in which individual pixels are passively controlled (without additional electronic components for each pixel). The light-emitting diodes (LEDs) of the display can be controlled by the circuitry of an integrated circuit (IC). In contrast, a screen with active pixels controlled by transistors is called an active matrix display. A passive matrix carrier substrate is part of and supports the passive matrix display.

[0089] "Photonic crystal" or "photonic structure"

[0090] A photonic structure can be a photonic crystal, a quasi-periodic, or a deterministic aperiodic photonic structure. A photonic structure generates a band structure for photons through periodic variations in the optical refractive index. This band structure can have a band gap within a specific frequency range. This means that photons cannot propagate through the photonic structure in all spatial directions. In particular, propagation parallel to the surface is generally blocked, but propagation perpendicular to the surface is possible. In this way, the photonic structure or photonic crystal determines propagation in a specific direction. It blocks or reduces the radiation along one direction and thus produces a radiation or a beam of radiation, directed as needed to a spatial region or emission region provided for this purpose.

[0091] Photonic crystals are photonic structures that appear or are generated in transparent solids. Photonic crystals are not necessarily crystals; their name comes from the diffraction and reflection effects of X-rays in crystals, due to their lattice constant. The structural size is equal to or greater than one-quarter of the photon's wavelength, meaning they range from 1 μm to several μm. They are generated using classical photolithography or through self-organizing processes.

[0092] Alternatively, similar or identical properties of photonic crystals can also be produced with aperiodic but still ordered structures. Such structures are in particular quasi-periodic or well-defined aperiodic structures. For example, this could be a helical arrangement of photons.

[0093] In particular, the so-called two-dimensional photonic crystal is mentioned here by way of example, which has a periodic variation of optical refractive index in two spatial directions that are perpendicular to each other, especially in two spatial directions that are parallel to the light emitting surface and perpendicular to each other.

[0094] However, one-dimensional photonic structures, particularly one-dimensional photonic crystals, also exist. One-dimensional photonic crystals exhibit a periodic change in refractive index along a single direction. This direction can extend parallel to the light exit surface. The one-dimensional structure allows beam shaping to occur in a first spatial direction. In a photonic structure, the photonic effect can be achieved in just a few cycles. The photonic structure can be designed, for example, to ensure that electromagnetic radiation is at least approximately collimated relative to the first spatial direction. Therefore, a collimated beam can be generated at least relative to the first spatial direction.

[0095] "Pixel"

[0096] The individual color values ​​of a digital photodiode pattern, and the surface elements required to record or display these color values ​​in an image sensor or screen with photodiode control, are called pixels, image points, image cells, or image dots. Therefore, a pixel is a positionable element in a display device and has at least one light-emitting device. Pixels have a definite size, and adjacent pixels are separated by a defined spacing or pixel space. In displays, especially μ displays, three (or several with added redundancy) sub-pixels of different colors are typically combined into one pixel.

[0097] "planar array"

[0098] A planar array is a substantially flat surface. It is typically smooth and has no protruding structures. Generally, surface roughness is undesirable and does not provide the desired functionality. A planar array is, for example, a monolithic planar array with multiple optoelectronic components.

[0099] Pulse Width Modulation

[0100] Pulse Width Modulation (PWM) is a type of modulation used to control components, particularly μ-LEDs. A PWM signal controls a switch configured to turn on and off the current flowing through the corresponding μ-LED, thus causing the μ-LED to light up or not. When using PWM, the output provides a square wave signal with a fixed frequency f. During each cycle T (= 1 / f), the relative amount of on-time compared to the off-time determines the brightness of the light emitted by the μ-LED. The longer the on-time, the brighter the light.

[0101] "Quantum trap"

[0102] A quantum well is understood as a potential line in a strip structure within one or more semiconductor materials, which restricts the degree of freedom of a particle to move in one spatial dimension (typically the z-direction). Thus, a charge carrier can only occupy a planar region (the xy-plane). The width of the quantum well determines the quantum mechanical states that the particle can adopt, resulting in the formation of energy levels (sub-bands), meaning the particle can only have discrete (potential) values.

[0103] "complex"

[0104] There is generally a distinction between radiative and nonradiative recombination. The latter produces a photon that can leave the component. Nonradiative recombination results in the generation of acoustic quanta, which heat the component. The ratio of radiative to nonradiative recombination is an important parameter that depends on the component size, among other factors. Typically, the smaller the component, the smaller the ratio, thus increasing nonradiative recombination relative to radiative recombination.

[0105] Refresh time

[0106] The refresh time is the time after which units such as displays must be rewritten to prevent information loss or premature refresh by external factors.

[0107] "Rohchip" or "light-emitting element"

[0108] A light emitter, or virgin chip, is a semiconductor structure fabricated on a wafer and then separated from it. This semiconductor structure is adapted to generate light after electrical contact during operation. Therefore, in this context, a virgin chip is a semiconductor structure containing active layers for generating light. Virgin chips are typically separated after contact, but can also be further processed in array form.

[0109] "Slot antenna"

[0110] A slot antenna is a special type of antenna in which, instead of surrounding the metallic structure with air (as a non-conductor) in space, an interruption is provided in the metallic structure (e.g., a metal plate, waveguide, etc.). This interruption causes the reflection of electromagnetic waves, the wavelength of which depends on the geometry of the interruption. Typically, the interruption follows the dipole principle, but theoretically it can have any other geometry. Therefore, a slot antenna comprises a metallic structure with a cavity resonator whose length is on the order of the visible light wavelength. The metallic structure can be arranged in or surrounded by an insulating material. The metallic structure is typically grounded to establish a certain potential.

[0111] Field of view

[0112] The field of view (FOV) refers to the area within the field of view of an optical device, solar sensor, camera's image surface (film or recording sensor), or perspective display where events or changes can be perceived and recorded. The field of view is specifically the area that a person can see without moving their eyes. Regarding augmented reality and prominent objects placed in front of the eyes, the field of view includes the area specified as multiple angles of view during stable eye fixation.

[0113] "Subpixel"

[0114] A subpixel describes the internal structure of a pixel. Generally, the term "subpixel" is associated with a higher resolution than that expected from a single pixel. A pixel can also contain several smaller subpixels, each emitting a different color. The overall color impression of a pixel is produced by the mixing of the individual subpixels. Therefore, a subpixel is the smallest locatable unit in a display device. Similarly, a subpixel has a specific size, smaller than the size of the pixel to which it belongs.

[0115] Vertical LED

[0116] Compared to horizontal LEDs, vertical LEDs have electrical connections on both the front and back sides. One of the two sides also forms a light-emitting surface. Therefore, a vertical LED has contacts formed on two opposing main surface sides. Consequently, a conductive yet transparent material must be deposited to ensure electrical contact while allowing light to pass through.

[0117] Virtual Reality

[0118] Virtual reality (VR) refers to the representation and simultaneous perception of reality and its physical properties in a real-time, computer-generated, interactive virtual environment. Virtual reality can replace the operator's real environment with a completely simulated environment.

[0119] In the following sections, aspects of the processing and manufacturing methods for μ-LEDs or μ displays or modules will be considered in more detail. However, as mentioned above, aspects related to processing also include aspects related to semiconductor structures or materials, and vice versa. In this regard, the following aspects can be readily combined with the preceding aspects.

[0120] The designs presented above for reducing defects or crosstalk improve the yield of functional elements during manufacturing. Several aspects involve measures to improve μ-LED transmission. For this purpose, μ-LEDs with edge lengths typically less than 100 μm, usually between 70 μm and 20 μm, are increasingly being developed. For specific applications in augmented reality, sizes are also less than 20 μm, for example, in the range of 1 μm to 10 μm or even 1 μm to 5 μm.

[0121] One of the technological challenges associated with μ-LEDs is particularly the manufacturing process, as not only must a large number of μ-LEDs be produced, but they must also be integrated into a matrix or module. To produce such a module or even a larger display, the generated μ-LEDs are either transferred as individual chips or, as presented here, incorporated into the module or display's carrier surface, where they are attached and electrically connected. Given the millions of LEDs to be transferred, speed and accuracy are paramount in this process.

[0122] Various methods are known for this purpose, such as transfer methods. Using flat punches, a large number of μ-LEDs can be received simultaneously from the wafer, transferred to the carrier surface of a subsequent display, and precisely assembled there into a large-area monolithic arrangement. For example, elastomeric punches can be used for this purpose, to which individual μ-LEDs are attached by suitable surface structures and material properties without mechanical or electrical damage. Depending on the processing technology, this can present problems because μ-LEDs can tilt, move, or twist when they detach. Therefore, it is desirable to be able to receive μ-LEDs with reduced holding forces or damage.

[0123] The aspects and concepts described below are based on the consideration that when using mass transfer methods, i.e., simultaneously repositioning a large number of semiconductor chips locally, suitable tools can be used to receive or lift μ-LEDs from the wafer. For this purpose, the chips must have precise and determinable positions on the wafer so that, for example, tools with elastic buffer structures (such as elastomeric punches) can be positioned as precisely as possible on each μ-LED. Simultaneously, the surface structure should always be spatially uniformly positioned in the same manner so that the transfer tool can attach itself to the chip surface as uniformly as possible with a high probability of success.

[0124] According to a first aspect, a method for providing a μ-LED is proposed, wherein a first conductive contact layer is disposed on a first main surface side of a functional stack facing away from the substrate. The stack is designed as an optically active stack and thus specifically forms the μ-LED. At least one retaining structure is then formed, which is fixed to the substrate and carries the μ-LED. Due to the retaining structure, the functional stack in contact with it can be disconnected when lifted. A sacrificial layer, particularly comprising AlGaAs or InGaAlP, is then at least partially removed between the second main surface side of the functional stack facing the substrate and the substrate. After partial removal, a second conductive contact layer can be applied to the second main surface side of the functional stack in the region of the removed sacrificial layer.

[0125] In the method presented here, the photolithography process, particularly for the functional stacks, is performed only on one side of the substrate, thereby avoiding additional re-bonding. This allows the structure to be adapted to requirements, stack dimensions, and other parameters in terms of photolithography. Simultaneously, the stacks contact on both sides, forming vertical μ-LEDs.

[0126] According to the second aspect, a μ-LED with a functional stack is proposed. A first conductive contact layer is applied to the first main surface side of the functional stack facing away from the substrate, and a second conductive contact layer is applied to the second main surface side of the functional stack facing the substrate. Here, the contacted functional stack is particularly freely supported by at least one retaining structure fixed to the substrate. Due to the retaining structure, the contacted functional stack can be broken in a further processing step when lifted. Therefore, the stack of layers or μ-LEDs has a breakage edge after being lifted and in all subsequent processing steps.

[0127] As a result of the measures proposed here, rebonding is unnecessary and the photolithographic mask can be easily aligned. The formation of vertical μ-LEDs can be the same as that of horizontal LEDs. Absorption is reduced, and light output through optical coupling at the horizontal surface is increased, where the epitaxially generated layer can be thinner. Without bonding, the epitaxial structure of the layer sequence experiences less mechanical stress. Furthermore, the sacrificial layer allows for a more precise etching process because the etching process of the sacrificial layer can be highly selective. Therefore, the contact layer can be thinner.

[0128] In some aspects, the retaining structure may specifically have InGaAlP or AlGaAs or BCB or oxides, such as SiO2, or nitrides or combinations of these materials, and is particularly non-conductive. In this case, it can also be passivated into a stack. The retaining structure can be at least partially epitaxially grown or generated by vaporization or electric current. Conversely, the sacrificial layer may have AlGaAs or InGaAlP and can be etched away by wet chemical methods. The first and / or second conductive contact layers can be achieved by sputtering, vapor deposition, electro- or epitaxial growth. The contact layers can be transparent and comprise ITO or ZnO or metals. To avoid oxidation or degradation, in some aspects it is proposed that one side of the contacted functional stack can be covered by a passivation layer. Alternatively, metals, particularly Zn, can be diffused from the side of the contacted functional stack to the outer edge region of the functional stack. This alters the band structure in the edge region, thereby keeping charge carriers away from the affected region where defect density increases.

[0129] To securely hold the structure in place, it can extend from its first main surface side into the substrate on a functional stack of layers.

[0130] According to another design, a first support layer, particularly comprising InGaAlP and / or AlGaAs, can be formed on the first main surface side of the functional stack, wherein a first conductive contact layer can be applied on the first support layer, wherein the first support layer and the first conductive contact layer are connected at least at one location on the substrate, and thus together can provide a retaining structure.

[0131] There are typically various methods for transferring chips from carrier wafers to corresponding target substrates.

[0132] In the prior art, known methods include laser transfer printing or transfer processes such as “assembling” individual micro LED raw chips from solution, or electrostatic activation or bimagnetic transfer processes.

[0133] Extensions to these designs will be detailed here through the electrostatic transfer disclosed herein. A method will be proposed that allows for the reception and placement of extremely small optoelectronic semiconductor chips, i.e., μ-LEDs, while simultaneously selecting those μ-LEDs with defined defects. Furthermore, corresponding devices for receiving and placing optoelectronic semiconductor chips will be created.

[0134] The proposed design is based on the generation of electron-hole pairs in μ-LEDs, and typically in optoelectronic semiconductor chips. Each μ-LED can have a semiconductor layer with a photosensitive region, also known as an optical active region. By appropriate excitation, particularly by incident light, charge carriers or electron-hole pairs can be generated in the optical active region. An electron-hole pair consists of a defect electron and an electron that has been transported from the ground state in the crystal to the excited state by absorbing energy.

[0135] Electron-hole pairs can be separated from each other by suitable properties of semiconductor materials, such as two regions with different concentrations of dopant, like a pn junction. This generates charge within the individual semiconductor chip, which in turn produces a dipole field outside the chip. This process is also known as the photoelectric effect. The degree of the dipole field generated by the corresponding semiconductor chip depends on its characteristics. Semiconductor chips may have defects such as short circuits, shunting, or reduced efficiency, which typically cause the excitation-generated charge to discharge more rapidly, resulting in a reduced dipole field.

[0136] Furthermore, according to the proposed method, a receiving tool is provided for receiving μ-LEDs or optoelectronic semiconductor chips and placing them in predetermined locations, such as on a circuit board on which the μ-LEDs are to be mounted. In English-language professional literature, this process is also referred to as "pick and place." It is further proposed that the receiving tool generates an electric field at at least some of these locations, for example, by charging these locations. The μ-LEDs are received by the receiving tool during or after the generation of electron-hole pairs.

[0137] The electric field generated by the receiving tool interacts with the dipole field of the photoelectric semiconductor chip, thereby generating an attractive or repulsive force between the receiving tool and the photoelectric semiconductor chip. Even without an electric dipole field caused by electron-hole pairs, electrostatic interactions or forces can superimpose on the interactions or forces that are prevalent between the receiving tool and the photoelectric semiconductor chip. For example, even without excitation-generated dipole charges, van der Waals attraction or electrostatic attraction may exist between the receiving tool and the individual photoelectric semiconductor chips. This additional electrostatic attraction can overcome a threshold above which the μ-LED separates from the carrier on which the μ-LED is disposed and is received by the receiving tool.

[0138] The force required to remove the photoelectric semiconductor chip from the carrier can be greater than the force required for the receiving tool to hold the removed chip. Therefore, in some cases, only electrostatic force is needed to remove it, without needing to hold the chip. Thus, the presence of an electric dipole field is only necessary for removing the photoelectric semiconductor chip, not for holding it.

[0139] The dipole field when excited by a μ-LED with defined defects (e.g., short circuits, shunting, low efficiency, or other defects) is lower than that of a μ-LED without such defects. Therefore, the electrostatic interaction between the receiving tool and the defective μ-LED is so small that they cannot be received by the receiving tool and remain on the carrier. In other words, the electrostatic interaction between the receiving tool and the μ-LED is chosen such that the effective force is only strong enough in functional μ-LEDs. In other words, the electric field generated by the receiving tool is chosen in such a way that the resulting electrostatic force is only sufficient to lift the μ-LED when interacting with it. In the case of defective μ-LEDs with lower dipole fields, the interaction is not large enough.

[0140] Therefore, the design presented here makes it possible to avoid accepting defective μ-LEDs and thus avoid installing defective μ-LEDs, thereby significantly reducing maintenance work caused by the installation of defective optoelectronic semiconductor chips. It should also be mentioned that the interaction also depends on the quality or size of the μ-LEDs and must be selected according to the nominal size so that the functional μ-LEDs adhere precisely.

[0141] With appropriate design, it may be possible to selectively allow μ-LEDs or optoelectronic semiconductor chips with certain defects (which reduce the dipole field) to be received by the receiving tool, while "good" μ-LEDs with higher dipole fields are rejected by the receiving tool and remain on the carrier. This design can also separate good and defective μ-LEDs from the optoelectronic semiconductor chip.

[0142] The receiving device can be made of a suitable material to generate an electric field. For example, the receiving device can have polydimethylsiloxane (PDMS) with embedded metal contacts. The metal contacts can be connected to a voltage source to charge the PDMS material accordingly to generate an electric field. Alternatively, the receiving device can be made of a suitable charged material that itself generates an electric field.

[0143] Another option for generating an electric field is to generate both the electric field and voltage, for example, through contacts within or on the surface of the receiving tool. The electric field can also extend between the receiving tool and the electrical contacts, with the μ-LED located between them. The electrical contacts can be, for example, a carrier on which the μ-LED or a photoelectric semiconductor chip is placed, or can be integrated therein.

[0144] μ-LEDs can be fabricated on semiconductor wafers and then separated, for example, by sawing. After separation, the μ-LEDs can be mounted on a circuit board or other carrier using the methods described herein. This method allows for the transfer of not only individual μ-LEDs but also smaller arrays of connected μ-LEDs. In such cases, reference should be made to the μ-LED modules or structures described in this application, which can be easily transferred with the aid of the proposed transfer method.

[0145] For μ-LEDs, due to their small size and potentially large number, it is not economical to use conventional methods to test the LEDs before mounting them on a circuit board. In contrast to conventional methods, the method described in this application allows defective μ-LEDs to be selected before assembly.

[0146] μ-LEDs can be excited to generate electron-hole pairs by irradiating them with light, particularly UV (ultraviolet) light. The spectrum must have wavelengths or wavelength ranges capable of excitation, particularly photoluminescence excitation. In particular, the excitation radiation must have higher energy than the radiation emitted by the optoelectronic semiconductor chip in order to directly generate electron-hole pairs. Therefore, the wavelength of the excitation radiation must be shorter than the wavelength of the radiation emitted by the optoelectronic semiconductor chip. For example, if a blue μ-LED emits light at approximately 460 nm, in this case, the excitation radiation should have a wavelength of 440 nm or shorter, such as approximately 420 nm.

[0147] The light used to generate electron-hole pairs can pass through a receiving tool and fall onto the μ-LED. To make this possible, the receiving tool can be made at least partially of a material that is at least partially transparent or light-permeable. Furthermore, an opening or light guide can be integrated into the receiving tool through which light reaches the μ-LED.

[0148] μ-LEDs or semiconductor chips can be arranged on a carrier or substrate before being received by a receiving tool. Light used to generate electron-hole pairs can pass through the carrier or substrate and fall onto the μ-LED. For this purpose, the carrier or substrate can be made at least partially of a material that is at least partially transparent or permeable to light, or an opening or light guide can be integrated into the carrier or substrate.

[0149] Alternatively, light can be directed to the side or at an angle onto the μ-LED or any optoelectronic semiconductor chip.

[0150] It can be proposed that electron-hole pairs are not generated in all μ-LEDs or optoelectronic semiconductor chips, but rather selectively generated only in some components. For example, multiple μ-LEDs generated on a wafer can be provided, and electron-hole pairs are generated only in selected μ-LEDs among the multiple optoelectronic semiconductor chips. Then, the receiving tool will only receive these μ-LEDs, excluding the selected defective ones. For example, μ-LEDs can be selectively excited by guiding light through a mask to generate electron-hole pairs.

[0151] Another possibility for receiving only selected μ-LEDs is that the receiving tool generates an electric field only within a predetermined area. This can be made possible, for example, because the metal contacts embedded in the receiving tool can be controlled individually, at least partially. This selection allows for the creation of suitable distances between the μ-LEDs to be received (e.g., only every third, fourth, tenth, etc.). The distances can be chosen so that the received μ-LEDs can be placed directly onto the target matrix.

[0152] According to one design, the receiving tool has multiple protrusions or protrusions on its surface facing the μ-LED. When the receiving tool is lowered, only the protrusions contact the photoelectric semiconductor chip, thus only the protrusions receive the μ-LED. The areas between the protrusions and the areas outside the protrusions do not receive any photoelectric semiconductor chip. Here, the protrusions can also be arranged at predetermined intervals, the predetermined intervals corresponding to their positions to occupy in the target matrix. Another design, which further develops this aspect, is disclosed in this application.

[0153] Alternatively, the receiving tool may have a continuous flat surface in at least one area for receiving μ-LEDs. This allows for greater flexibility, as μ-LEDs or optoelectronic semiconductor chips arranged in different patterns and / or at different distances can be received.

[0154] Furthermore, the receiving tool can be cylindrical in shape and roll over the μ-LED to receive it. For example, the receiving tool can be designed similarly to the photosensitive drum of a laser printer. To receive the μ-LED, the cylindrical receiving tool can be moved above the μ-LED. Alternatively, the axis of rotation of the cylindrical receiving tool can be fixed, and the carrier with the optoelectronic semiconductor chip can be pushed under the receiving tool.

[0155] To place the μ-LED, the charge of the receiving tool can be altered via metal contacts. For example, the polarity of the metal contacts can be reversed. This results in a repulsive electrical interaction between the receiving tool and the μ-LED, which is polarized by electron-hole pairs. This means the μ-LED will either fall onto or collide with the target matrix.

[0156] Furthermore, the charge can only be changed at certain locations or areas of the receiving tool, thus allowing for the selective placement of specific μ-LEDs.

[0157] Another feasible approach to releasing μ-LEDs is to ensure that the adhesive force generated by the carrier or substrate to which the μ-LEDs are applied is greater than the attractive force between the receiving tool and the μ-LEDs. For example, the surface of the carrier or substrate can be coated with adhesives, paints, solder materials, or other suitable materials. Furthermore, the μ-LEDs can be released from the receiving tool by mechanical force, such as shearing or accelerating forces.

[0158] According to one design, the receiving tool directly contacts the μ-LED or optoelectronic semiconductor chip to receive it. During the transmission of the optoelectronic semiconductor chip, the receiving tool holds it in place by van der Waals forces.

[0159] On the other hand, it relates to a device designed for receiving and placing optoelectronic semiconductor chips. This device can be, for example, an automated assembly machine, or can be integrated into an automated assembly machine.

[0160] The device includes: an excitation element for generating electron-hole pairs in a μ-LED or optoelectronic semiconductor chip, and a receiving tool for receiving and placing the μ-LED or optoelectronic semiconductor chip. The electron-hole pairs generate a dipole electric field near the μ-LED or optoelectronic semiconductor chip. The receiving tool is designed to generate an electric field that interacts with the electric dipole field of the μ-LED or optoelectronic semiconductor chip to receive them. The received μ-LED or optoelectronic semiconductor chip is transported to a predetermined location and placed there.

[0161] According to one design, the excitation element is configured to generate light with a predetermined wavelength or wavelength range to create electron-hole pairs in a μ-LED or optoelectronic semiconductor chip. The excitation element may include, for example, a light source and / or a light guide.

[0162] The excitation element can be arranged such that light used to generate electron-hole pairs falls onto the μ-LED through a receiving tool or a carrier on which the μ-LED is disposed. The receiving tool may have multiple protrusions on its surface facing the μ-LED or optoelectronic semiconductor chip. The μ-LED or optoelectronic semiconductor chip can be received through the protrusions of the receiving tool.

[0163] Alternatively, at least one region of the surface of the receiving tool facing the μ-LED or optoelectronic semiconductor chip may be continuously flat and designed to receive the μ-LED or optoelectronic semiconductor chip.

[0164] Furthermore, the device for receiving and placing μ-LEDs or optoelectronic semiconductor chips can have the design scheme described in the method for receiving and placing μ-LEDs or optoelectronic semiconductor chips. Attached Figure Description

[0165] The following sections use various design schemes and examples to illustrate some of the aspects mentioned above and summarized in more detail.

[0166] Figure 1 The diagram illustrates some requirements for a so-called μ display or microdisplay device in terms of various dimensions of field of view and pixel spacing in a μ display; Figure 2 A diagram showing the spatial distribution of rod and cone cells in the human eye; Figure 3 A diagram showing the perceptual abilities of the human eye with assigned projection areas; Figure 4 A graph showing the sensitivity of rod and cone cells at different wavelengths is presented; Figure 5 The diagram illustrates some requirements for microdisplays of various sizes in terms of the field of view and collimation of pixels in a μ display; Figure 6 An exemplary design of a pixel array is shown to illustrate... Figure 1 and Figure 5 The parameters represented in the text; Figure 7 A graph showing the required number of pixels depends on the number of fields of view for a given resolution; Figure 8 and Figure 9 Sections A through J illustrate a first embodiment of a method for manufacturing μ-LEDs with a retention structure, based on some aspects of the proposed design; Figure 10 and Figure 11 Sections A through J illustrate a second embodiment of a method for manufacturing μ-LEDs with a retention structure, based on some aspects of the proposed design; Figure 12 and Figure 13 Parts A through I illustrate a third embodiment of a method for manufacturing μ-LEDs with a retention structure, based on some aspects of the proposed design; Figure 14 and Figure 15 Sections A through J illustrate a fourth embodiment of a method for manufacturing μ-LEDs with a retention structure, based on some aspects of the proposed design; Figure 16 and Figure 17Two additional steps that can be used in the design scheme are shown; Figures 18 to 21 A schematic flow diagram of the mass transfer printing process for multiple μ-LEDs on a wafer is shown; Figures 22 to 25 Illustrations of methods and apparatus for receiving and placing μ-LEDs or optoelectronic semiconductor chips are shown to explain various aspects of the proposed design; Figure 26 An illustration shows another device for receiving and placing μ-LEDs or optoelectronic semiconductor chips; Figure 27 and Figure 28 An illustration shows an example of a method for receiving and placing a μ-LED or optoelectronic semiconductor chip using a cylindrical receiving tool; Figure 29 An illustration shows a receiving tool with protrusions for receiving μ-LEDs or optoelectronic semiconductor chips; Figure 30 A design for a receiving tool is shown, which is suitable for selectively irradiating μ-LEDs or optoelectronic semiconductor chips. Figure 31 An illustration shows a receiving tool with a flat surface for receiving μ-LEDs or optoelectronic semiconductor chips; Figures 32 to 34 An illustration shows a method for placing μ-LEDs; and Figures 35 to 37 Various illustrations are shown of some design schemes for generating an electric field through a receiving tool. Detailed Implementation

[0167] Augmented reality is largely created by a dedicated display that overlays images onto reality. This display can be placed directly in the user's line of sight, i.e., directly in front of them. Alternatively, beam deflection elements can be used to direct light from the display toward the user's eyes.

[0168] In both cases, a display can be implemented, and the user can wear glasses or other visual augmentation devices as part of the device. Google's™ Glasses is an example of such a visual augmentation device, allowing users to overlay certain information about objects in the real world. With Google™ Glasses, the information is displayed on a small screen in front of the glasses. In this respect, the appearance of this add-on device is a key feature of the glasses, combining technological functionality with the design aspects of wearing glasses. Simultaneously, users need glasses that don't have such bulky or easily damaged devices to provide augmented reality functionality. Therefore, one concept is that the glasses themselves become a display or at least one screen, with information projected onto or into a projector.

[0169] In this type of situation, the user's field of view is limited to the size of the glasses. Therefore, the area on which augmented reality can be projected is approximately the size of the glasses lenses. The same but different information can be projected onto or onto both lenses of a pair of glasses.

[0170] In other words, the image experienced by a user while wearing augmented reality glasses should have a resolution that creates a seamless impression, so that the user doesn't perceive augmented reality as a pixelated object or a low-resolution element. Straight bevels, arrows, or similar elements appear as staircase-like outlines at low resolutions, which is distracting for the user.

[0171] To achieve an ideal visual impression, two display parameters are considered important, as they influence the visual impression for a given or known human eye. One is the pixel size itself, the geometry and dimensions of a single pixel, or the area of ​​three subpixels representing that pixel. The second parameter is the pixel pitch, the distance between two adjacent pixels or subpixels, which varies depending on the context. Sometimes, pixel pitch is also referred to as the space between pixels. Larger pixel gaps can be detected by the user and perceived as gaps between pixels, potentially leading to what is known as the "flying screen effect." Therefore, the gap should not exceed a certain limit.

[0172] The maximum angular resolution of the human eye is typically between 0.02 and 0.03 arcminutes, roughly equivalent to 1.2 to 1.8 arcminutes per line. This results in a pixel pitch of 0.6-0.9 arcminutes. Some current mobile phone displays have approximately 400 pixels per inch, resulting in a viewing angle of approximately 2.9° at a distance of 25 cm from the user's eyes, or approximately 70 pixels per degree. Therefore, the distance between two pixels in such a display is within the range of maximum angular resolution. Furthermore, the pixel size itself is approximately 56 μm.

[0173] Figure 1 The pixel spacing is shown, that is, the distance between two adjacent pixels that depends on the field of view. In this respect, the field of view is the extension of the observable world seen at a given moment. This is because human vision is defined as the angle of view in degrees during a stable fixation of the eye.

[0174] In particular, the forward horizontal curvature of the binocular visual field is slightly higher than 210°, while the vertical curvature of the human visual field is approximately 135°. However, the range of visual ability is not uniform across the entire visual field and may vary from person to person.

[0175] Human binocular vision covers approximately 114° horizontally (peripheral vision) and approximately 90° vertically. The remaining degrees on both sides do not constitute binocular vision, but can be considered part of the field of view.

[0176] Furthermore, color vision and the ability to perceive shape and motion further limit the horizontal and vertical fields of vision. The rods and cones responsible for color vision are unevenly distributed.

[0177] This viewpoint Figures 2 to 4 This was explained in more detail. In the central visual domain, that is, directly in front of the eyes, as required by augmented reality applications, and partly in the automotive field, the eye's sensitivity is very high in terms of spatial resolution and color perception.

[0178] Figure 2 The spatial density of cones and rods per square millimeter is shown, which is related to the angle of the central concave region. Figure 3 The wavelength-dependent color sensitivity of cones and rods is described. In the central region of the fovea, increased cone density (L, S, and M) leads to better color perception. Sensitivity begins to decrease at a distance of approximately 25° around the fovea, as the density of visual cells decreases. Near the edges, color perception decreases further, but contrast vision through rods remains over a wider angular range. Overall, this creates a radially symmetrical visual pattern for the eye, rather than a Cartesian one. Therefore, high resolution of all primary colors is necessary, especially at the center. At the edges, working with an emitter adapted to the spectral sensitivity of rods may suffice (maximum sensitivity 498 nm, see...). Figure 4 And the sensitivity of the eyes).

[0179] Figure 3 The graph of angular resolution A relative to the angular deviation α from the optical axis of the eye illustrates the different perceptual abilities of the human eye. It can be seen that the highest angular resolution A exists within the interval of + / - 2.5° angular deviation α, where the fovea 7 is arranged on the retina 19 with a diameter of 1.5 mm. Furthermore, the location of the blind spot 22 on the retina 19 is plotted, which appears in the region of the optic disc 23, with an angular deviation α of approximately 15°.

[0180] The eye can compensate for this non-constant density, and it can also compensate for so-called blind spots through minute eye movements. This change in the direction or focus of the gaze can be counteracted through appropriate optical systems and eye tracking.

[0181] In addition, even when wearing glasses, the field of vision is further limited; for example, the field of vision of each lens can be within approximately 80°.

[0182] Figure 1The pixel pitch on the Y-axis, measured in μm, defines the distance between two adjacent pixels. Different curves, C1 to C7, define the diagonal dimensions of the corresponding displays, ranging from 5mm to approximately 35mm. For example, curve C1 corresponds to a display with a diagonal dimension of 5mm, meaning a side length of approximately 2.25mm. For a field of view of approximately 80°, the pixel pitch of a display with a 5mm diagonal dimension is within the range of 1μm. For larger displays, such as those using curve C7 and a 35mm diagonal dimension, the same field of view can be achieved with a pixel pitch of approximately 5μm.

[0183] However, Figure 1 The curves in the diagram illustrate that a larger field of view is preferred for augmented reality applications, while very high pixel density and small pixel pitch are required to avoid the well-known screen-flying effect. We can now calculate the pixel size for a given number of pixels, a given field of view, and a given diagonal size for a μ display.

[0184] Equation 1 shows the relationship between pixel size D, pixel pitch pp, number of pixels N, and display edge length d. The distance r between two adjacent pixels, calculated from their respective centers, is given by the following equation.

[0185] r = d / 2 + pp + d / 2.

[0186] D = d / N-pp (1)

[0187] N = d / (D + pp)

[0188] Assuming the distance between the monitor (e.g., glasses) and the eye is 2.54 cm (1 inch), then for the roughly estimated 1 arcminute angular resolution above, the distance r between two adjacent pixels is...

[0189] r = tan(1 / 60°) × 30mm

[0190] r = 8.7μm

[0191] Therefore, pixel size is less than 10 μm, especially when a certain space is required between two different pixels. Using the distance r between two pixels and a display with a size of 15 mm × 10 mm, 1720 × 1150 pixels can be arranged on the surface.

[0192] Figure 6An arrangement with a carrier 21 is shown, on which a plurality of pixels 20 and 20a to 20c are arranged. Pixels 20 arranged adjacent to each other have a pixel pitch pp, while pixels 20a to 20c are placed on the carrier 21 with a larger pixel pitch pp. The distance between two pixels is given by the sum of the pixel pitch and half the size of each adjacent pixel. Each pixel 20 is configured such that its illumination characteristics, or emission vector 22, are substantially perpendicular to the emission surface of the corresponding LED.

[0193] The angle between the vertical axis on the emitting surface of the LED and the beam vector is defined as the collimation angle. In the example of emission vector 22, the collimation angle of LED 20 is approximately zero. LED 20 emits collinear light and does not expand significantly.

[0194] Conversely, the collimation angle of the emission vector 23 of LED pixels 20a to 20c is very large, and is in the range of approximately 45°. As a result, a portion of the light emitted by LED 20a overlaps with the emission of the adjacent LED 20b.

[0195] The emission of LEDs 20a to 20c partially overlaps, resulting in the superposition of their respective light emissions. If the LEDs emit different colors of light, the result will be a mixture or combination of colors. A similar effect occurs between high-contrast areas, i.e., when LED 20a is dark while LED 20b emits some kind of light. Due to the overlap, the contrast is reduced, and the information at each individual location corresponding to the pixel position is also reduced.

[0196] For displays with a small distance from the user's eyes, such as those mentioned above, a large collimation angle can be quite annoying due to the aforementioned effects and other drawbacks. Users can perceive a large collimation angle and may experience a slight difference in the color of depicted objects, a blurriness, or reduced contrast.

[0197] in this regard, Figure 5 This illustrates the collimation angle in degrees relative to the field of view in degrees, which is independent of a specific display size. For smaller display sizes, such as those in curve C1 (approximately 5 mm diagonally), the collimation angle increases significantly depending on the field of view.

[0198] As monitor sizes increase, the requirements for collimation change dramatically. Therefore, even with large monitor geometries, as shown by curve C7, the collimation angle reaches approximately 10° within a 100° field of view. In other words, the collimation requirements increase for larger monitors and larger fields of view. In such monitors, the light emitted from the pixels must be highly collimated to avoid or reduce the aforementioned effects. Therefore, when providing users with monitors that offer large fields of view, even if the monitor's geometry is relatively large, robust collimation capabilities are necessary.

[0199] Based on the above charts and equations, it can be deduced that as the geometry and field of view of a display increase, the requirements regarding pixel pitch and collimation become increasingly challenging. As Equation 1 shows, the size of a display increases dramatically with the number of pixels. Conversely, a large field of view requires a large number of pixels to achieve sufficient resolution and avoid screen flickering or other interference effects.

[0200] Figure 7 The diagram illustrates the number of pixels required to achieve an angular resolution of 1.3 armes. For a field of view of approximately 80°, the number of pixels exceeds 5 million. It can be quickly estimated that the pixel size for QHD resolution is far less than 10μm, even with a display size of 15mm × 10mm. In total, an augmented reality display with resolutions in the HD range (i.e., 1080p) requires a total of 2,073,600 pixels. This would cover a field of view of approximately 50°. The number of pixels arranged in a 10 × 10mm display with a pixel spacing of 1μm would result in a pixel size of approximately 4μm.

[0201] The above considerations make it clear that the challenges in terms of resolution, collimation, and field of view suitable for augmented reality applications are considerable. Therefore, the technical implementation of such displays also places very high demands on them.

[0202] Traditionally used technologies were designed for manufacturing displays with LED edge lengths in the range of 100 μm or even longer. However, they cannot automatically scale to the 70 μm and below dimensions required here. Pixel sizes of a few μm and distances of a few μm or even smaller, closer to the order of magnitude of the generated light wavelength, require new processing technologies.

[0203] Furthermore, new challenges have emerged in light collimation and guidance. For example, optical lenses that can be easily structured into larger LEDs and calculated using classical optics cannot be directly scaled down to such small sizes without using Maxwell's equations. In addition, it is nearly impossible to manufacture small lenses without large errors or deviations. In some variants, quantum effects affect the behavior of pixels of these sizes and must be taken into account. Tolerance requirements in the production or transmission techniques of pixels on auxiliary carriers or matrix structures are becoming increasingly stringent. Pixels must also be contactable and individually controllable. Conventional circuitry has space requirements that, in some cases, exceed the pixel area, creating placement and space issues.

[0204] Therefore, new designs for controlling and accessing pixels of this size may be entirely different from traditional technologies. Finally, a key focus is on the power consumption of such displays and controls. Low power consumption is particularly desirable for mobile applications.

[0205] In summary, many designs suitable for larger pixel sizes require extensive modifications before successful scaling down. While a design suitable for producing 200 μm LEDs can be easily scaled up to 2000 μm LEDs, scaling down to 20 μm is much more difficult. Many documents and literature disclosing such designs do not account for the various effects and increased requirements of extremely small sizes, and therefore are not directly applicable to or limited to pixel sizes significantly larger than 70 μm.

[0206] The following sections present various aspects of the structure and fabrication of μ-LED semiconductors, including processing, optical coupling output and light guidance, display, and control. These are suitable for designing displays with pixel sizes of 70 μm and below. Some designs are specifically designed for the production, optical coupling output, and control of μ-LEDs with edge lengths less than 20 μm, particularly less than 10 μm. It goes without saying that the designs presented here regarding these aspects can and should be combined with each other. For example, this relates to the design of μ-LEDs with designs for producing coupled output light. Specifically, μ-LEDs implemented, for example, by methods to avoid edge defects or by current conduction or current contraction, can provide optical coupling output structures based on photonic crystal structures. Special control can also be implemented for displays with variable pixel sizes. Light guidance with piezoelectric mirrors can be implemented in μ-LED displays based on slot antennas or conventional monolithic pixel matrices.

[0207] In some of the design options and aspects described below, additional examples of various design options or combinations of their aspects are indicated. These are intended to clearly show that those skilled in the art can combine the aspects, design options, or parts thereof with each other. Some applications require specially modified designs, while others have lower technical requirements. Automotive applications and displays, for example, typically have larger pixel edge lengths due to the greater distance from the user. In particular, there are classic pixel applications or virtual reality applications, in addition to augmented reality applications. In the context of this disclosure, this is also clearly desirable for realizing μ-LED displays with pixel edge lengths below 70 μm.

[0208] The following sections illustrate some designs for a method of transfer in the form of an improved transfer printing process. The background of this method is the transfer of μ-LEDs from a wafer to a carrier surface of a display. There, the individual μ-LEDs are fixed and electrically connected. On the one hand, the size of each μ-LED is only in the range of a few μm; on the other hand, a large number of such μ-LEDs must be transferred locally simultaneously. In this case, it is typically necessary to transfer millions of such microstructures from a large number of wafers to a common carrier surface.

[0209] exist Figure 18 In the example shown here, a wafer 12 is first provided on which an epitaxial layer has been formed using various semiconductor manufacturing processes, and then individual μ-LEDs 16 are formed therefrom. In some respects, the μ-LEDs emit different colors and wavelengths during operation. This is represented here by different shades. The μ-LEDs are flat at least on their underside and / or top side, for example, to facilitate simple mounting and transport. As part of the manufacturing process, the μ-LEDs 16 can be mechanically separated from the wafer 12. This is done by removing the so-called sacrificial layer (see, for example, see...). Figure 12 Parts A to D and Figure 9 The J part Figure 11 The J part and Figure 15 This is implemented in the J part, and optionally, the sacrifice layer is supplemented by one or more release layers.

[0210] Figure 19 The diagram illustrates how the elastomeric punch 18 moves vertically from above onto the wafer 12 and how it adheres to the surface of the μ-LED 16 via a suitable surface structure. For example, the maximum tensile force can be proportional to the surface dimensions of the μ-LED 16. Adhesive force can be generated, for example, by a silicone material, particularly by a so-called PDMS elastomer. Due to the separation of the μ-LED 16 from the wafer 12, a large number of μ-LEDs can be lifted from the wafer 12, thereby adhering them to the elastomeric punch 18. The elastomeric punch 18 is then moved from the wafer 12 to, for example, a carrier surface 14 adjacent to it on the display during a transport motion. This can be accomplished, for example, by means of a transfer tool, in which the elastomeric punch 18 is considered part.

[0211] exist Figure 20 In this configuration, the elastomer punch 18 is initially positioned above the carrier surface 14 and descends onto the surface of the carrier surface 14 with a downward movement. Here, the underside of the μ-LED 16 is in mechanical contact with the carrier surface 14. Figure 21 In the subsequent steps shown, the μ-LED 16 separates from the elastomer punch 18. The elastomer punch 18 then moves upward, for example, to begin a new transmission cycle. The μ-LED 16 can be permanently fixed to the carrier surface 14, for example, by an adhesive process.

[0212] Figures 18 to 21The steps shown indicate that, due to the large number of μ-LEDs 16, reliable and precise placement is desired in the shortest possible time. Specifically, when the μ-LEDs 16 are received by the punch 18, it is desirable to maintain low forces on the one hand, and to achieve reliable positioning and retention of the μ-LEDs 16 on the wafer 12 on the other. In particular, the avoidance of fluctuations or excessive adhesion forces on the wafer and / or on the punch can bring significant improvements here.

[0213] Figure 8 and Figure 9 Sections A to J illustrate a first embodiment of a method for manufacturing a μ-LED having a holding structure carrying a μ-LED. The manufacturing process of the μ-LED is shown in a simplified manner. In this context, it should be noted that the method can be supplemented and extended by the measures disclosed herein.

[0214] Figure 8 Part A illustrates a step in which a sacrificial layer made of AlGaAs is first applied to a substrate 3, which herein comprises GaAs. A functional stack 1 is then epitaxially grown on it, meaning that the optically active stack has at least one quantum well or another optically active structure 13. Additionally, the stack includes two differently doped layers 15 and 17. Here, an n-type doped semiconductor layer 15 is attached to the sacrificial layer 11. A first conductive contact layer 5 is then deposited on the side of the functional stack 1 facing away from the substrate 3. For example, it may comprise ITO (indium tin oxide).

[0215] Figure 8 Part B illustrates the steps of performing a first photolithography process on the main surface side of the substrate 3 opposite to the first conductive contact layer 5 of the functional layer stack 1. Specifically, a first mask layer 19 is applied to the first conductive contact layer 5, wherein a region of the first conductive contact layer remains uncovered by the first mask layer 19 to create a retaining structure 9. Then, from this side of the layer sequence, the first conductive contact layer 5, the functional layer stack 1, the sacrificial layer 11, and a portion of the substrate 3 are etched out in the uncovered region, thereby forming a recess shown in cross-section. The sidewalls descend very steeply or substantially vertically.

[0216] Figure 8 Section C illustrates the steps of forming the retaining structure 9 in the etched area of ​​the layer sequence. For this purpose, a vapor-deposited material extends onto the mask 19 and fills the trenches until small recesses in the material of the sheet 9 are held at the level of the mask layer. These recesses are process-dependent and can optionally be omitted, for example, by applying material until the recesses are completely filled. Excessively thick material layers on the mask 9 can be appropriately thinned again using CMP or other methods.

[0217] Figure 8Part D shows the other side after the material on mask layer 19 and layer 9 itself have been removed. A second photomask 21 is then applied to the second region and structured to gain access to the sacrificial layer. The region between the structure and the structuring forms a μ-LED. After structuring, etching is performed again through layers 5 and 1 until it reaches the sacrificial layer 11. This results in… Figure 9 The structure shown in section J. In this case, the etching process can form trenches, etc., to define the size of the μ-LED.

[0218] Figure 8 Part E illustrates the structure after the etching process, where the sacrificial layer 11 is removed from the layer sequence, specifically etched away using a wet chemical method. The functional layer stack 1 is then supported by a retaining structure 9, which is fixed to the substrate 3. In this final step, a second conductive contact layer 7 is applied to the functional layer stack 1 on the substrate 3-facing side in the area where the sacrificial layer 11 has been removed. The material of the second conductive contact layer 7 may include ITO (indium tin oxide). In the areas where the sacrificial material has been etched away, the second conductive contact layer 7 can be applied by sputtering, see [reference needed]. Figure 8 The F portion. In this way, the space between the substrate 3 and the functional stack 1 can be reached. When the second conductive contact layer 7 is applied, the sides of the functional stack 1 and the exposed areas of the substrate 3 can also be covered. Vapor phase deposition, electroplating, or other techniques can also be considered.

[0219] After contact 7 on the lower side of the structure is completed, the conductive material on the sides, especially in the trench area, is removed again. The structure thus created... Figure 9 It is shown in section G. Figure 9 Section H illustrates a step in which the sides of the functional stack 1 without conductive material are covered by a passivation layer 23. This is optional. Additionally, the second mask layer 21 is removed. Another passivation layer 25 may also be formed on the substrate 3 of the conductive material covered with the second conductive contact layer 7.

[0220] The structure shown in this manner can now be broken off from the retaining structure using the aforementioned punch or another transfer tool. The sides of the stack 1 are also covered by the passivation layer 23. Figure 9 Section J again shows the steps of disconnecting the μ-LED produced in this way in a top view. The large arrow should indicate the break in carrier structure 9 and the serrated dots should indicate the break location 29.

[0221] exist Figure 10 and Figure 11 Another embodiment is shown in sections A through J. Figure 10 Sections A to F show the relationship with Figure 8The same steps as parts A through F. (And) Figure 9 The steps shown in section G are the reverse of those in section G. Figure 11 In section G, the conductive material deposited on the sides of the functional stack 1 is removed. Then, before or instead of passivation, metal is deposited on the sides and diffuses in. This material can be, in particular, Zn. It diffuses into the edge regions of the stack and forms changes in the band structure therein, thereby keeping charge carriers away from this region of high defect density. In this way, nonradiative recombination of charge carriers in the functional stack is correspondingly reduced. This is followed by... Figure 11 The H to J parts Figure 9 The same steps apply to sections H through J.

[0222] Figure 12 and Figure 13 Sections A through I illustrate a third embodiment of the proposed method for manufacturing μ-LEDs with a retention structure.

[0223] Figure 12 Part A illustrates the steps of epitaxially applying a functional stack 1 to a GaAs substrate 3 on a sacrificial layer 11 made of AlGaAs. Between the functional stack 1 and the sacrificial layer 11, a second support layer 24, having, for example, InGaAlP, and thinner than the sacrificial layer 11, is also epitaxially formed. Similar to previous designs, the doped semiconductor layers of the stack 1 adjacent to layer 24 and the sacrificial layer are n-type doped. The second semiconductor layer 17 is p-type doped. A first conductive contact layer 5 is then applied to the side of the functional stack 1 facing away from the substrate 3, particularly on the main surface side, which is not shown here. It may then have, for example, ITO (indium tin oxide).

[0224] Figure 12 Part B illustrates the steps of performing a first photolithography process on the main surface side of the functional stack 1 facing away from the substrate 3. For this purpose, a first mask layer 19 is applied to the second semiconductor layer 17 of the functional stack 1, wherein the outer edge region of the functional stack 1 is not covered by the first mask layer 19 in order to form the retaining structure 9. From this side of the layer sequence, in the uncovered edge region, the functional stack 1, the second support layer 24, and the sacrificial layer 11 can be etched away until the substrate 3, specifically by ICP (Inductively Coupled Plasma Etching). Finally, the first mask layer 19 is removed again. The trenches formed in this way can extend around all sides of the body, thereby forming one or more μ-LED structures separated by trenches.

[0225] Figure 12Section C illustrates another step of the method, wherein a first support layer 20 is formed to provide a retention structure 9 on the substrate 3, on the exposed edge regions of the layer sequence, and on the main surface of the μ-LED 1 facing away from the substrate 3. The support layer 20 is made of InGaAlP, which is vapor-deposited and epitaxially grown. The support layer 20 surrounds the layer sequence on at least one side, extending to the substrate 3, thus extending from the second main surface side to the substrate on at least one side. Finally, a second mask layer 21 is applied to the main surface of the first support layer 20 facing away from the substrate 3. The outer edge regions of the layer sequence remain uncovered by the second mask layer 21.

[0226] Figure 12 Part D illustrates this step, in which the outer edge regions of the layer stack 1, the first support layer 24, and the sacrificial layer 11, not covered by the first mask layer, are removed up to the substrate 3, specifically by etching. In this way, a pathway to the sacrificial layer 11 is formed from this side of the layer sequence. Even... Figure 12 After the second mask layer 21 is removed again in part D, the area covered by the second mask layer 21 is still retained.

[0227] Figure 12 Section E illustrates the steps of removing the sacrificial layer 11 from the layer sequence, specifically by etching it away using a wet chemical method. This removal is achieved from the outer edge region of the layer sequence exposed in step 150D. The functional layer stack 1 is then supported by a first support layer 20 and a second support layer 24, with the first support layer 20 fixed to the substrate 3. In this way, a retaining structure 9 is provided that carries the functional layer stack 1 without the sacrificial layer 11.

[0228] Figure 13 Part F illustrates a structure according to which a first conductive contact layer 5 and a second conductive contact layer 7 are formed. Here, a conductive layer is formed, which is attached to the first support layer 20 on the side facing away from the substrate 3 and is attached to the functional stack 1 in a carrier- and conductive manner. The conductive layer is also attached to the side of the functional stack 1 facing the substrate 3 in the region of the removed sacrificial layer 11 on the second support layer 24. The material of the conductive layer may include ITO (indium tin oxide). Particularly in the regions where the sacrificial layer 11 is etched away, the conductive layer can be applied by sputtering. In this way, the space between the substrate 3 and the functional stack 1 can be easily reached. When the conductive layer is applied, at least a portion of the sides of the functional stack 1 and the exposed areas of the substrate 3 can also be covered.

[0229] Figure 13Section G illustrates this step, in which the conductive material deposited on the sides of the functional stack 1 is at least partially removed, and in particular etched away, such that the first conductive contact layer 5 on the side facing away from the substrate 3 is electrically separated from the second conductive contact layer 7 on the side of the functional stack 1 facing the substrate 3. In this way, the functional stack 1 with contacts is formed.

[0230] To this end, a third mask layer 31 is first applied to the first support layer 20. This third mask layer 31 leaves the edge regions on the sides of the functional stack uncovered. The third mask layer 31 covers the edge regions of the first support layer 20, which is fixed to the substrate 3. By removal, particularly by etching, the first contact layer 5 and the second contact layer 7 are electrically separated from each other, and the support layer 20 is mechanically reinforced by means of the first contact layer 5. The retaining structure 9 is additionally mechanically reinforced.

[0231] Figure 13 The H section illustrates the step in which the third mask layer 31 has been removed. The functional stack 1 is secured to the substrate 3 by the retaining structure 9. For this securing, a first support layer 20, reinforced by a first conductive contact layer 5, interacts with the functional stack 1, which is stabilized and protected by a second support layer 24. The contacted functional stack 1 (i.e., the stack indirectly covered by contact layers 5 and 7) can be lifted or broken from the retaining structure 9 by means of the extraction head 27. Reference numeral 29 indicates a predetermined breakage location at which the electronic component or the contacted functional stack 1 can be separated from the substrate 3.

[0232] Figure 13 Part I again illustrates the step of disconnecting the stack 1, which has electrical contacts and provides at least one function, and is related to... Figure 12 and Figure 13 The cross-sections in sections A through H differ from those in this top view. Large arrows should indicate the breakage of carrier structure 9, and serrated edges should indicate the breakage location 29. Liftable electronic components, particularly liftable miniature LEDs, can be secured to multiple retaining structures 9, for example, to the rounded corners of the components in the top view.

[0233] Figure 14 and Figure 15 Sections A through J illustrate a fourth embodiment of the proposed method. Figure 14 Parts A to D show the relationship with the source Figure 12 and Figure 13 The steps are similar to those in the previous example.

[0234] and Figure 12 The opposite of part E, Figure 14Section E illustrates the steps of removing only a portion of the sacrificial layer 11 using a wet chemical method. As a result, a sub-region of layer 24 is exposed, upon which a contact layer 7 is subsequently applied. Removal is performed from the outer edge regions of the layer sequence exposed in step 4d. The functional stack 1 is then supported by a first support layer 20 and a second support layer 24, with the first support layer 20 attached to the substrate 3. In this way, a retaining structure 9 is provided that precisely supports the functional stack 1 without the complete sacrificial layer 11.

[0235] Figure 14 Part F illustrates the step in which a sacrificial layer 11 is formed in the first conductive contact layer 5 and the second conductive contact layer 7, the sacrificial layer being in Figure 14 In this case, only part of the E portion is removed. A conductive layer 5 is formed, attached to the first support layer 20 on the side facing away from the substrate 3, and attached to the functional stack 1 in a supporting and conductive manner. The conductive layer also extends into the area of ​​the removed sacrificial layer 11 to the side of the functional stack 1 facing the substrate 3. Particularly in the area where the sacrificial layer 11 is etched away, the conductive layer can be applied by sputtering. In this way, the space between the substrate 3 and the functional stack 1 can be easily reached. When the conductive layer is applied, the sides of the functional stack 1 and the exposed areas of the substrate 3 can also be covered with the conductive material.

[0236] Figure 15 Section G illustrates the step of at least partially removing the conductive material deposited on the side surface of the functional stack 1. Thus, the first conductive contact layer 5 on the side electrically opposite to the substrate 3 separates from the second conductive contact layer 7 on the side of the functional stack 1 facing the substrate 3.

[0237] For this purpose, a third mask layer 31 is applied to the first support layer 20. This third mask layer 31 leaves the edge regions on the sides of the functional stack uncovered. The third mask layer 31 covers the edge regions of the first support layer 20, which is fixed to the substrate 3. On one hand, the first contact layer 5 and the second contact layer 7 are electrically separated from each other by an etching process. Independently, the first contact layer 5 further mechanically reinforces the support layer 20. During this step, the remaining sacrificial layer 11 is retained.

[0238] Figure 13 The H section illustrates the structure after the removal of the third mask layer 31 and the remaining sacrificial layer 11, both of which can be removed by various etching processes. The functional layer stack 1 is secured to the substrate 3 by a retaining structure 9. For this fixation, a first support layer 20, reinforced by a first conductive contact layer 5, interacts with the functional layer stack 1, which is stabilized and protected by a second support layer 24. Figure 15 In section I, the predetermined fracture location 29 is shown again. Figure 15Section J again shows a top view of the steps for disconnecting the μ-LED 1 with electrical contacts. By design, the retaining structure can hold multiple such μ-LEDs so that they can be extracted together or one by one using a transfer tool.

[0239] In the final design shown here, an interruption edge is formed. Although it is very narrow, it can still lead to a non-radiative recombination center, thus reducing the efficiency of the μ-LED. Furthermore, it places higher demands on the transfer punch or transfer technology.

[0240] exist Figure 16 and Figure 17 The diagram illustrates aspects that lead to a further reduction in the effect of nonradiative recombination centers. As already mentioned, fracture edges often generate recombination centers, leading to an increase in nonradiative recombination in that region, thus reducing efficiency. After processing the semiconductor layer sequence, photomask 23 is now applied and structured in such a way that the surface adjacent to the subsequent edge region is exposed. Conversely, photoresist remains on the later active layer or active region. A dopant, such as Zn, is then applied to the surface. Figure 17 In the next step shown, a diffusion step is performed. Zn diffuses through layer 17 and reaches the active region. If the active region is formed by one or more quantum wells, appropriate process parameters will result in quantum well mixing. As described in this application, quantum well mixing exhibits a strong change in the mask edge region, thus the bandgap process is very steep, similar to a bandgap transition. Therefore, the increased bandgap occurs primarily in the edge region and region 25a, where a break edge will subsequently form. Thus, a break edge is formed in the increased bandgap region, thereby keeping the charge carrier away from defects generated by the edges during operation. After quantum well mixing is achieved, the assembly can be further processed as already described.

[0241] Conventionally, there are various possibilities for transporting chips from carrier wafers to corresponding target substrates.

[0242] In the prior art, solutions involving electrostatic activation or antimagnetic transfer processes are known as laser transfer printing or "self-assembly" transfer methods, such as for individual micro-LED chips.

[0243] Extensions to these designs will be detailed here through the electrostatic transfer disclosed herein. A method will be proposed for receiving and placing optoelectronic semiconductor chips, i.e., μ-LEDs, with particularly small dimensions, while simultaneously selecting defective optoelectronic semiconductor chips.

[0244] Figure 22An apparatus 10 for receiving and placing optoelectronic semiconductor chips according to an embodiment of the present invention is schematically shown. In this embodiment, the optoelectronic semiconductor chips are designed as μ-LEDs 11 and arranged spaced apart from each other on a carrier 12. The apparatus 10 includes a receiving tool 13, an excitation element 14, and a voltage source 15.

[0245] Excitation element 14 emits light 16, which illuminates μ-LED 11. The light 16 emitted by excitation element 14 includes a wavelength that, upon excitation, generates electron-hole pairs in the optically active region of μ-LED 11. The electron-hole pairs induce electrostatic polarization within μ-LED 11, resulting in an electric dipole field near each μ-LED 11. In this embodiment, receiving tool 13 is arranged between excitation element 14 and μ-LED 11. Receiving tool 13 is at least partially permeable to the light 16 emitted by excitation element 14, allowing the light 16 to reach μ-LED 11.

[0246] The receiving tool 13 has metal contacts, which are embedded, for example, in polydimethylsiloxane (PDMS) or another suitable material. The metal contacts are connected to a voltage source 15. An electrostatic field can be generated by applying a voltage to the metal contacts. In addition, the receiving tool 13 has a protrusion 17 that extends from the underside surface of the receiving tool 13 in the direction of the μ-LED 11.

[0247] The following reference Figures 22 to 25 A method for receiving and placing a μ-LED 11 by means of a device 10 according to an embodiment of the present invention is described. Light 16 emitted by an excitation element 14 induces excitation in the μ-LED 11 and generates electrostatic polarization. Simultaneously, a receiving tool 13 is charged by a voltage source 15, causing a mutual attraction between the receiving tool 13 and the μ-LED 11.

[0248] The receiving tool 13 moves downward toward the μ-LED 11 until the protrusion 17 contacts the μ-LED 11 located below it. In this embodiment, each second μ-LED 11 contacts one of the protrusions 17. Figure 23 As shown, the receiving tool 13 is then raised together with the LED 11 attached to the protrusion 17. Figure 24 It shows Figure 23 Zoomed-in details. Figure 24 The electrostatic charge of the receiving tool 13 and the polarization of the μ-LED 11 are shown. For simplicity, in Figure 23 Excitation element 14 and voltage source 15 are not shown in all subsequent figures.

[0249] The μ-LEDs 11 located between the protrusions 13 are not raised by the receiving tool 13. Furthermore, without raising the μ-LEDs 11, the light 16 emitted by the excitation element 14 experiences very little polarization or no polarization due to defects in the μ-LEDs 11. These μ-LEDs 11 in Figures 22 to 24 The image has a dark background. The lower polarization compared to a complete μ-LED 11 allows for the selection of μ-LED 11s with corresponding defects without prior testing. Then, as... Figure 25 As shown, the μ-LED 11 is delivered to the desired location and placed there by receiving tool 13.

[0250] Figure 26 An apparatus 20 for receiving and placing an optoelectronic semiconductor chip is schematically shown according to another embodiment of the present invention. Figure 26 The device 20 shown is largely related to Figure 22 The equipment is the same as device 10. The difference is that... Figure 26 The excitation element 14 is arranged below the carrier 12 where the μ-LED 11 is located. In this case, the carrier 14 must be at least partially permeable to the light 16 emitted by the excitation element 14 so that photoluminescence excitation can be performed in the μ-LED 11.

[0251] Figure 27 A cylindrical receiving tool 13 is schematically shown, which can be constructed like the drum of a laser printer. The receiving tool 13 is electrostatically loaded so that a mutual attraction occurs between the surface of the receiving tool 13 and the μ-LED 11 located beneath it due to polarization induced by photoluminescence excitation. Figure 28 As shown, a cylindrical receiving tool 13 rolls on a carrier 12 and receives a μ-LED 11, where the incident light 16 has been sufficiently polarized.

[0252] Figure 29 A receiving tool 13 is schematically shown, having a protrusion 17 on its underside extending in the direction of a μ-LED 11 disposed below the receiving tool 13. The excitation element 14 (in...) Figure 29 The light 16 emitted (not shown) falls onto the μ-LED 11 through the receiving tool 13. To allow the light 16 to pass through, the receiving tool 13 is made of a material that allows at least partial penetration by the light 16. Alternatively, a corresponding through-hole or light guide can be integrated into the receiving tool 13.

[0253] Figure 30 Showing from Figure 29 The receiving tool 13, but in Figure 30In this process, only certain μ-LEDs 11 are selectively illuminated by light 16, for example, every second μ-LED 11. To make this possible, corresponding vias or light guides can be integrated into the receiving tool 13, or a corresponding shadow mask can be provided, which ensures that the light 16 falls only on the predetermined μ-LEDs 11. Thus, only the μ-LEDs 11 illuminated by light 16 are excited to photoluminescence, and only these μ-LEDs 11 can be received by the receiving tool 13, provided that they form sufficient polarization due to the excitation of photoluminescence.

[0254] Figure 31 A receiving tool 13 is schematically shown, having a continuous flat surface 21 on its underside. The flat surface 21 allows for the reception of μ-LEDs 11 arranged in different patterns and / or at different distances. Furthermore, light-shielding elements, such as masks, can be provided to selectively excite only certain μ-LEDs 11 for photoluminescence.

[0255] Figures 32 to 34 The device 10 is shown during the placement of the μ-LED 11. (As shown) Figures 22 to 25 As shown, after receiving μ-LED 11, the receiving tool 13 is transferred to... Figure 32 On the circuit board shown, some μ-LEDs 11 should be mounted.

[0256] With the help of Figure 33 The voltage source 15 shown alters the electrostatic charge of the receiving tool 13, reducing the attractive interaction between the receiving tool 13 and the μ-LED 11 or converting it into a repulsive interaction. By means of individually controllable metal contacts in the receiving tool, the charge in certain areas of the receiving tool can be changed in a desired manner, thereby placing only a predetermined number of μ-LEDs 11 on the circuit board 22. Then, as... Figure 34 As shown, remove the receiving tool 13 from the circuit board 22. The μ-LED 11 remaining on the receiving tool 13 can be removed or placed elsewhere, such as on an adhesive cleaning tape.

[0257] exist Figures 35 to 37 The diagram schematically illustrates various options for generating an electric field via the receiving tool 13. Figures 35 to 37 The magnetic field lines 23 shown indicate the direction and intensity of the electric field at various locations.

[0258] exist Figure 35 In the design shown, the charge is located in the protrusion 17 of the receiving tool 13. The opposite charge is arranged near the receiving tool 13. This results in an electric field near each protrusion 17 that is similar to that of a point charge. Figure 36In the receiving tool 13, there is a dipole charge, which is arranged such that the electric field strength at the tip of the protrusion 17 is particularly large. Figure 37 In this configuration, the protrusion 17 of the receiving tool 13 is charged, and a countercharge is arranged below the carrier 12, such that the μ-LED 11 to be received is located between the receiving tool 13 and the light-emitting diode 13. The countercharge is thus within the electric field.

[0259] The electric field generated by the receiving tool 13 should not be uniform so that an effective force can be applied to the dipoles of the μ-LEDs 11, allowing them to be received by the carrier 12. Additionally, Figures 35 to 37 The electric field line 24 of the μ-LED 11 generated by excitation is shown. For simplicity, the interaction between the field line 24 of the μ-LED 11 and the field line 23 of the receiving tool 13 is not shown.

[0260] The following design is provided.

[0261] 412. A method for manufacturing μ-LEDs, comprising the following steps: - Provide a base; - Apply a sacrificial layer, particularly one with AlGaAs or InGaAlP, onto the substrate; - Creates a stack of layers with the functionality of an active layer between relatively doped semiconductor layers; - Apply a first conductive contact layer to the first main surface side of the functional stack; - Form at least one retaining structure that is fixed to the substrate and carries the functional stack of layers, and the functional stack of layers in contact with it can be disconnected during the peeling process; - At least partially remove the sacrificial layer disposed between the second main surface side of the functional stack and the substrate; - In the area where the sacrificial layer has been removed, a second conductive contact layer is applied to the second main surface side of the functional stack.

[0262] 413. The method according to item 412, wherein the step of generating a functional layer stack includes the step of forming one or more quantum wells in an active layer.

[0263] 414. The method according to any one of the preceding items, wherein the step of generating a functional stack of layers comprises the following steps: forming a quantum well mix in the edge region of the active layer and / or at least in the region adjacent to the retaining structure or adjacent to a possible break-off edge.

[0264] 415. The method according to item 414, wherein the step of forming quantum well mixing comprises: - Provide structured photomasks on functional stacks; - Apply a dopant with the first process parameters; - Diffusion and / or formation of quantum well mixtures with second process parameters.

[0265] 416. The method according to any one of the preceding items, wherein the step of generating a functional stack comprises the step of forming a quantum well mixture having the features described in any one of the preceding items.

[0266] 417. The method according to any one of the preceding items further includes: lifting the contacted functional stack by peeling it off the retaining structure and placing it on an auxiliary substrate.

[0267] 418. The method according to any one of the preceding items, wherein the step of forming the retaining structure comprises: forming, in particular, a conical retaining structure on the functional stack from the first main surface side of the functional stack to the substrate.

[0268] 419. The method according to any one of the preceding items, wherein the step of applying the first conductive contact layer comprises: A first support layer is applied to the functional stack on the first main surface side of the functional stack; A first conductive contact layer is applied to a first support layer, wherein the first support layer and the first conductive contact layer are attached to at least one location on the substrate and thus at least partially form a retaining structure.

[0269] 420. The method according to any one of the preceding items, wherein the step of applying the second conductive contact layer comprises: A second support layer is attached directly to the functional stack on the second main surface side facing the substrate; The second conductive contact layer is attached to the second support layer.

[0270] 421. The method according to any one of the preceding items, wherein the structure is maintained at least partially epitaxially or formed by vaporization or electroplating.

[0271] 422. The method according to any one of the foregoing items, wherein

[0272] A portion of the functional stack is kept passivated by a retention structure, which can be transparent in particular.

[0273] 423. The method according to any one of the preceding items, characterized in that the sacrificial layer is removed by wet chemical etching.

[0274] 424. The method according to any one of the preceding items, characterized in that the sacrificial layer is removed in two steps, namely before and after the application of the second conductive contact layer.

[0275] 425. The method according to any one of the preceding items further includes: covering the side of the functional layer with a passivation layer.

[0276] 426. The method according to any one of the preceding items, characterized in that the metal, in particular Zn, diffuses from the side of the functional stack to the outer edge region of the functional stack.

[0277] 427. The method according to any one of the preceding items, characterized in that the first and / or second conductive contact layer is applied by sputtering, vapor deposition or electroplating.

[0278] 428. μ-LED or μ-LED module or μ-LED array, having

[0279] - Functional layered stack; in which

[0280] - A first conductive contact layer is applied to the first main surface side of the functional stack facing away from the substrate, and a second conductive contact layer is applied to the second main surface side of the functional stack facing the substrate; wherein

[0281] - The contacted functional stack is supported by at least one retaining structure that is fixed to the base row, and the contacted functional stack can be broken off while being peeled off.

[0282] 429. The μ-LED or μ-LED module or μ-LED array according to item 428, characterized in that the functional stack has an optically active layer between oppositely doped layers, particularly an active layer formed of one or more quantum wells.

[0283] 430. The μ-LED or μ-LED module or μ-LED array according to any one of the preceding items, wherein the active layer in the edge region of the μ-LED and / or at least in the region adjacent to the retaining structure or in the region adjacent to a possible break-off edge has an increased bandgap.

[0284] 431. The μ-LED or μ-LED module or μ-LED array according to any one of the preceding items, having quantum well mixing in the edge region of the active layer or in the region of the active layer adjacent to the holding structure or adjacent to a possible break edge.

[0285] 432. The μ-LED or μ-LED module or μ-LED array according to any one of the preceding items, characterized in that it is transferred to an auxiliary substrate by lifting and placing the functionally stacked contacts.

[0286] 433. The μ-LED or μ-LED module or μ-LED array according to any one of the preceding items, characterized in that the substrate has GaAs.

[0287] 434. The μ-LED or μ-LED module or μ-LED array according to any one of the preceding items, characterized in that the retaining structure is in particular InGaAlP or AlGaAs or BCB or oxide, such as SiO2, or nitride or combination of these materials, and / or particularly non-conductive.

[0288] 435. The μ-LED or μ-LED module or μ-LED array according to any one of the preceding items, characterized in that the first support layer attached to the first main surface side of the functional stack has, in particular, InGaAlP and / or AlGaAs.

[0289] 436. The μ-LED or μ-LED module or μ-LED array according to any one of the preceding items, characterized in that the second support layer attached to the second main surface side of the functional stack has, in particular, InGaAlP and / or AlGaAs.

[0290] 437. The μ-LED or μ-LED module or μ-LED array according to any one of the preceding items, characterized in that the first and / or second conductive contact layers have ITO or ZnO or metal and / or are particularly attached to the first and second support layers.

[0291] 438. The μ-LED or μ-LED module or μ-LED array according to any one of the preceding items, characterized in that the μ-LED is less than 70 μm, particularly less than 50 μm, less than 20 μm, or less than 10 μm.

[0292] 439. A method for receiving and placing an optoelectronic semiconductor chip, wherein

[0293] Electron-hole pairs are generated in optoelectronic semiconductor chips, thereby creating an electric dipole field near the corresponding optoelectronic semiconductor chip. The receiving tool generates an electric field, and During or after the generation of electron-hole pairs, a receiving tool is used to receive the optoelectronic semiconductor chip and place it at a predetermined location.

[0294] 440. The method according to item 439, wherein the optoelectronic semiconductor chip is a μ-LED or an LED.

[0295] 441. The method according to item 439 or 440, wherein the optoelectronic semiconductor chip for generating electron-hole pairs is irradiated with light having a predetermined wavelength or a predetermined wavelength range.

[0296] 442. The method according to item 441, wherein light for generating electron-hole pairs is incident on a photoelectric semiconductor chip via a receiving tool.

[0297] 443. The method according to item 442, wherein an optoelectronic semiconductor chip is arranged on a carrier, and light for generating electron-hole pairs is incident on the optoelectronic semiconductor chip through the carrier.

[0298] 444. The method according to any one of the preceding items, wherein a plurality of optoelectronic semiconductor chips are provided, and an electric dipole field is generated only in selected optoelectronic semiconductor chips among the plurality of optoelectronic semiconductor chips.

[0299] 445. The method according to any one of the preceding items, wherein the receiving tool generates an electric field only in a predetermined area.

[0300] 446. The method according to any one of the preceding items, wherein the receiving tool has a plurality of protrusions on a surface facing the optoelectronic semiconductor chip, and the optoelectronic semiconductor chip is received by the protrusions of the receiving tool.

[0301] 447. The method according to any one of the preceding items, wherein at least one region of the surface of the receiving tool facing the optoelectronic semiconductor chip is flat, and the optoelectronic semiconductor chip is received with the flat region of the receiving tool.

[0302] 448. The method according to any one of the preceding items, wherein the receiving tool has a cylindrical shape, the cylinder rolling on the photoelectric semiconductor chip to receive the photoelectric semiconductor chip.

[0303] 449. The method according to any one of the preceding items, wherein the electric field generated by the receiving tool is changed in order to place the photoelectric semiconductor chip.

[0304] 450. The method according to any one of the preceding items, wherein the receiving tool for receiving the optoelectronic semiconductor chip directly contacts the optoelectronic semiconductor chip and holds it by means of van der Waals forces.

[0305] 451. An apparatus for receiving and placing an optoelectronic semiconductor chip, a μ-LED device, or a means of placing a μ-LED according to any one of the foregoing or following items, comprising: Excitation elements are used to generate electron-hole pairs in optoelectronic semiconductor chips to create an electric dipole field in the vicinity of the corresponding optoelectronic semiconductor chip. A receiving tool for receiving and placing optoelectronic semiconductor chips is designed to generate an electric field, and then uses electron-hole pairs generated by an excitation element to receive and deposit the optoelectronic semiconductor chips at a predetermined location.

[0306] 452. The apparatus according to item 451, wherein the excitation element is designed to generate light having a predetermined wavelength or a predetermined wavelength range to generate electron-hole pairs in an optoelectronic semiconductor chip.

[0307] 453. The apparatus according to item 452, wherein the excitation element is arranged such that light for generating electron-hole pairs is incident on the photoelectric semiconductor chip via a receiving tool or via a carrier on which a photoelectric semiconductor chip is disposed.

[0308] 454. The apparatus according to any one of items 451 to 453, wherein the receiving tool has a plurality of protrusions on a surface facing the photoelectric semiconductor chip, and the photoelectric semiconductor chip is received by the protrusions of the receiving tool.

[0309] 455. The apparatus according to any one of items 451 to 453, wherein at least one region of the surface of the receiving tool facing the photoelectric semiconductor chip is flat, and the photoelectric semiconductor chip is received with the flat region of the receiving tool.

[0310] 456. The apparatus according to any one of items 451 to 453, wherein the receiving tool has a cylindrical shape, the cylinder rolling on the photoelectric semiconductor chip to receive the photoelectric semiconductor chip.

Claims

1. A method for manufacturing μ-LEDs, comprising the following steps: - Provide a base; - Apply a sacrificial layer, particularly one with AlGaAs or InGaAlP, onto the substrate; - A stack of layers with the functionality of an active layer is generated between relatively doped semiconductor layers; - Apply a first conductive contact layer to the first main surface side of the functional stack; - Form at least one retaining structure that is fixed to the substrate and carries the functional stack of layers, and the functional stack of layers in contact with it can be disconnected during the peeling process; - At least partially remove the sacrificial layer disposed between the second main surface side of the functional stack and the substrate; - In the area where the sacrificial layer has been removed, a second conductive contact layer is applied to the second main surface side of the functional stack.

2. The method according to claim 1, wherein, The steps to produce a functional layer stack include the following: forming one or more quantum wells in an active layer.

3. The method according to claim 1, wherein, The steps for generating a functional layer stack include the following: forming quantum well mixing in the edge region of the active layer and / or at least in the region adjacent to the retaining structure or adjacent to the possible break-off edge.

4. The method according to claim 3, wherein, The steps to form quantum well mixing include: - Provide structured photomasks on functional stacks; - Apply a dopant with the first process parameters; - Diffusion and / or formation of quantum well mixtures with second process parameters.

5. The method according to claim 1, further comprising: By peeling it from the retaining structure and placing it on an auxiliary substrate, the already contacted functional stack is lifted.

6. The method according to claim 1, wherein, The steps for forming the retaining structure include: forming a retaining structure, particularly a conical shape, on the functional stack from the first main surface side of the functional stack to the substrate.

7. The method according to claim 1, wherein, The steps of applying the first conductive contact layer include: A first support layer is applied to the functional stack on the first main surface side of the functional stack; A first conductive contact layer is applied to a first support layer, wherein the first support layer and the first conductive contact layer are attached to at least one location on the substrate and thus at least partially form a retaining structure.

8. The method according to claim 1, wherein, The steps of applying the second conductive contact layer include: A second support layer is attached directly to the functional stack on the second main surface side facing the substrate; The second conductive contact layer is attached to the second support layer.

9. The method according to claim 1, wherein, The structure is formed at least partially epitaxially or by vaporization or electroplating.

10. The method of claim 1, wherein A portion of the functional layer stack is kept structurally passivated, in which, The structure can be transparent, in particular.

11. The method according to claim 1, characterized in that, The sacrificial layer is removed by wet chemical etching.

12. The method according to claim 1, characterized in that, The sacrificial layer is removed in two steps, before and after the application of the second conductive contact layer.

13. The method of claim 1, further comprising: The sides of the functional layer are covered by a passivation layer.

14. The method according to claim 1, characterized in that, Metals, especially Zn, diffuse from the sides of the functional stack to the outer edge region of the functional stack.

15. The method according to claim 1, characterized in that, The first and / or second conductive contact layers are applied by sputtering, vapor deposition, or electroplating.

16. μ-LEDs, μ-LED modules, or μ-LED arrays, having - Functional layered stack; in - Apply a first conductive contact layer to the first main surface side of the functional stack facing away from the substrate, and apply a second conductive contact layer to the second main surface side of the functional stack facing the substrate; in - The contacted functional stack is supported by at least one retaining structure that is fixed to the base row, and the contacted functional stack can be broken off while being peeled off.

17. The μ-LED, μ-LED module, or μ-LED array according to claim 16, characterized in that, Functional stacks have optically active layers between oppositely doped layers, particularly active layers formed by one or more quantum wells.

18. The μ-LED, μ-LED module, or μ-LED array according to claim 16, wherein, The active layer in the edge region of the μ-LED and / or at least in the region adjacent to the retaining structure or in the region adjacent to a possible break-off edge has an increased bandgap.

19. The μ-LED, μ-LED module, or μ-LED array according to claim 16, wherein a quantum well is mixed in the edge region of the active layer or in a region of the active layer adjacent to the holding structure or adjacent to a possible break edge.

20. The μ-LED, μ-LED module, or μ-LED array according to claim 16, characterized in that, The functional layers of the contact are lifted and placed, and then transferred to the auxiliary substrate.

21. The μ-LED, μ-LED module, or μ-LED array according to claim 16, characterized in that, The substrate contains GaAs.

22. The μ-LED, μ-LED module, or μ-LED array according to claim 16, characterized in that, The structure should ideally contain InGaAlP or AlGaAs or BCB or oxides, such as SiO2, or nitrides or combinations of these materials, and / or be particularly non-conductive.

23. The μ-LED, μ-LED module, or μ-LED array according to claim 16, characterized in that, The first support layer attached to the first main surface side of the functional stack is in particular InGaAlP and / or AlGaAs.

24. The μ-LED, μ-LED module, or μ-LED array according to claim 16, characterized in that, The second support layer attached to the second main surface side of the functional stack is in particular InGaAlP and / or AlGaAs.

25. The μ-LED, μ-LED module, or μ-LED array according to claim 16, characterized in that, The first and / or second conductive contact layers have ITO or ZnO or metal and / or are particularly attached to the first and second support layers.

26. The μ-LED, μ-LED module, or μ-LED array according to claim 16, characterized in that, μ-LEDs are less than 70 μm, especially less than 50 μm, less than 20 μm, or less than 10 μm.

27. A method for receiving and placing an optoelectronic semiconductor chip, wherein Electron-hole pairs are generated in optoelectronic semiconductor chips, thereby creating an electric dipole field near the corresponding optoelectronic semiconductor chip. The receiving tool generates an electric field, and During or after the generation of electron-hole pairs, a receiving tool is used to receive the optoelectronic semiconductor chip and place it at a predetermined location.

28. The method according to claim 27, wherein, The optoelectronic semiconductor chip is a μ-LED or an LED.

29. The method according to claim 27, wherein, A photoelectric semiconductor chip used to generate electron-hole pairs is irradiated with light having a predetermined wavelength or a predetermined wavelength range.

30. The method according to claim 29, wherein, The light used to generate electron-hole pairs is incident on the optoelectronic semiconductor chip through a receiving tool.

31. The method according to claim 30, wherein, Optoelectronic semiconductor chips are arranged on a carrier, and light used to generate electron-hole pairs is incident on the optoelectronic semiconductor chips through the carrier.

32. The method according to claim 27, wherein, Multiple optoelectronic semiconductor chips are provided, and an electric dipole field is generated only in a selected optoelectronic semiconductor chip among the multiple optoelectronic semiconductor chips.

33. The method according to claim 27, wherein, The receiving tool generates an electric field only within a predetermined area.

34. The method according to claim 27, wherein, The receiving tool has multiple protrusions on its surface facing the optoelectronic semiconductor chip, and the optoelectronic semiconductor chip is received by the protrusions of the receiving tool.

35. The method according to claim 27, wherein, At least one region of the surface of the receiving tool facing the optoelectronic semiconductor chip is flat, and the optoelectronic semiconductor chip is received with the flat region of the receiving tool.

36. The method according to claim 27, wherein, The receiving tool has a cylindrical shape and rolls on the photoelectric semiconductor chip to receive the photoelectric semiconductor chip.

37. The method of claim 27, wherein, The electric field generated by the receiving tool is changed in order to place the optoelectronic semiconductor chip.

38. The method according to claim 27, wherein, The receiving tool used to receive the optoelectronic semiconductor chip directly contacts the optoelectronic semiconductor chip and holds it by means of van der Waals forces.

39. An apparatus for receiving and placing a photoelectric semiconductor chip, a μ-LED device, or a means of placing a μ-LED according to any one of the preceding or following claims, comprising: Excitation elements are used to generate electron-hole pairs in optoelectronic semiconductor chips to create an electric dipole field in the vicinity of the corresponding optoelectronic semiconductor chip. A receiving tool for receiving and placing optoelectronic semiconductor chips is designed to generate an electric field, and then uses electron-hole pairs generated by an excitation element to receive and deposit the optoelectronic semiconductor chips at a predetermined location.

40. The device according to claim 39, wherein, The excitation element is designed to generate light with a predetermined wavelength or a predetermined wavelength range to generate electron-hole pairs in an optoelectronic semiconductor chip.

41. The device according to claim 40, wherein, The excitation element is arranged such that light used to generate electron-hole pairs is incident on the photoelectric semiconductor chip through a receiving tool or through a carrier on which the photoelectric semiconductor chip is disposed.

42. The device according to claim 39, wherein, The receiving tool has multiple protrusions on its surface facing the optoelectronic semiconductor chip, and the optoelectronic semiconductor chip is received by the protrusions of the receiving tool.

43. The device according to claim 39, wherein, At least one region of the surface of the receiving tool facing the optoelectronic semiconductor chip is flat, and the optoelectronic semiconductor chip is received in the flat region of the receiving tool.

44. The device according to claim 39, wherein, The receiving tool has a cylindrical shape and rolls on the photoelectric semiconductor chip to receive the photoelectric semiconductor chip.

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