WO2023071910A1 - Micro-led chip structure and manufacturing method therefor - Google Patents

Abstract

Disclosed are a Micro-LED chip structure and a manufacturing method therefor. The Micro-LED chip structure comprises a first substrate, and a plurality of LED units arranged in an array and provided on the first substrate; the LED units are electrically connected to the first substrate, each LED unit comprises a first reflector layer, an LED semiconductor layer, and a second reflector layer, and the LED semiconductor layer is provided between the first reflector layer and the second reflector layer; each LED unit has a step structure such that adjacent LED units can be driven independently, and the first reflector layer, the LED semiconductor layer, and the second reflector layer are configured to jointly provide a resonant cavity. According to the Micro-LED chip structure provided by the present application, the light emitting amount can be increased, the wavelength stability is enhanced, and the light emitting collimation and the light emitting efficiency are improved.

Description

Micro-LED chip structure and its manufacturing method

This application is based on and claims the priority of the Chinese patent application with the application number 202111285592.2 and the title of the invention "Micro-LED chip structure and its manufacturing method" submitted on November 1, 2021.

technical field

The present application relates to a Micro-LED chip structure and a manufacturing method thereof, more specifically to a Micro-LED chip structure with a resonant cavity and a manufacturing method thereof.

Background technique

Displays with tiny sized LEDs are called micro-LEDs. Micro LED displays have an array of tiny LEDs forming a single pixel element. A pixel is a tiny illuminated area on a display screen, and many pixels can make up an image. In other words, pixels can be the small discrete elements that together make up an image on a display. Pixels are usually arranged in a two-dimensional (2D) matrix and represented using dots, squares, rectangles, or other shapes. A pixel can be the basic unit of a display or a digital image and has geometric coordinates.

Conventional micro-LEDs have the physical property of large emission angles due to the random emission of photons from the luminescent material of the micro-LED. When micro-LEDs are used in various applications that require collimated light, such as virtual/augmented reality glasses or projectors, the low light output does not meet the requirements, and the collimation is poor, resulting in the contrast and brightness of the displayed image will also be affected. Influence.

Another disadvantage of conventional micro-LEDs is the so-called red shift and poor wavelength stability. Since LEDs are made of direct-gap semiconductors, the spectrum of emitted light is centered within and near specific wavelengths defined by the energy gap. By increasing the temperature caused by continuous use, the band gap energy decreases and the emitted wavelength increases. This is followed by a shift of the peak wavelength to longer wavelengths (ie, towards the wavelength of red light), so this phenomenon is often referred to as redshift. Therefore, thermal stability is one of the important issues for color displays using micro LEDs.

Another disadvantage of conventional micro LEDs is their low luminous efficiency. Micro LEDs have a relatively low external quantum efficiency compared to large LEDs. When micro-LEDs are applied to battery-powered consumer electronics, such as smart glasses, the luminous efficiency is not sufficient.

application content

The main purpose of the present application is to provide a Micro-LED chip structure and its manufacturing method, so as to overcome the deficiencies in the prior art.

In order to achieve the foregoing application purpose, the technical solutions adopted in this application include:

The embodiment of the present application provides a Micro-LED chip structure, including:

first substrate,

A plurality of LED units arranged in an array are arranged on the first substrate,

The LED unit is electrically connected to the first substrate, and the LED unit includes a first reflector layer, an LED semiconductor layer and a second reflector layer, and the LED semiconductor layer is disposed on the first reflector layer between the second reflector layer;

The LED units have a stepped structure such that adjacent LED units can be driven independently, and the first reflector layer, the LED semiconductor layer and the second reflector layer are configured to jointly provide a resonant cavity.

Further, the LED semiconductor layer includes:

a first doped semiconductor layer disposed on the first reflector layer;

an active layer disposed on the first doped semiconductor layer;

a second doped semiconductor layer disposed on the active layer;

The step structure is formed on the second doping type semiconductor layer, the height of the step structure is not less than the thickness of the second doping type semiconductor layer but less than or equal to the thickness of the LED semiconductor layer, the The stepped structure at least isolates the second doped semiconductor layers of adjacent LED units from each other.

It can be understood that the part of the step structure penetrates the second doped semiconductor layer at least along the thickness direction, for example, the part of the step structure penetrates the second doped semiconductor layer along the thickness direction, or, The part of the step structure penetrates the second doped semiconductor layer and the active layer along the thickness direction, or, the part of the step structure penetrates the second doped semiconductor layer and the active layer along the thickness direction. layer and extend into the first doped type semiconductor layer, or, part of the step structure penetrates the second doped type semiconductor layer, the active layer, and the first doped type semiconductor layer along the thickness direction.

Further, the first reflector layer forms an ohmic contact with the first doped semiconductor layer.

Further, the first doped semiconductor layer is a p-type semiconductor layer, and the second doped semiconductor layer is an n-type semiconductor layer.

Further, the LED semiconductor layer also includes:

a passivation layer disposed on the second doped semiconductor layer and having a first opening; and

An electrode layer is arranged on the passivation layer and covers the first opening, and the electrode layer is in electrical contact with the second doped semiconductor layer from the first opening.

Further, the first doped semiconductor layers of the plurality of LED units are a common first doped semiconductor layer and the first doped semiconductor layers of adjacent LED units are electrically connected.

Further, the stepped structure of each LED unit is formed on the second doped semiconductor layer, and the height of the stepped structure is equal to the thickness of the LED semiconductor layer, and the stepped structure at least makes adjacent LED units The active layer is electrically isolated from the first doped semiconductor layer.

Further, the first substrate includes a driving circuit, the driving circuit has a plurality of contacts, and each contact corresponds to one LED unit, and a second opening is also provided on the passivation layer, and the second There is an etching hole exposing the contact in the opening, and the electrode layer electrically connects the second doped semiconductor layer and the contact through the first opening, the second opening and the etching hole.

Further, the stepped surface of the stepped structure forms the light emitting surface of the LED semiconductor layer, and the second reflector layer at least covers the stepped surface.

Further, the reflectivity of the first reflector layer is greater than the reflectivity of the second reflector layer, and the light emitted by the LED semiconductor layer exits the LED unit from the second reflector layer.

Further, the first reflector layer is a metal reflective layer or a distributed Bragg reflector.

Further, the second reflector layer is a metal reflective layer or a distributed Bragg reflector.

Further, the distributed Bragg reflector includes at least one TiO ₂ layer and at least one SiO ₂ layer stacked in sequence, or, the distributed Bragg reflector includes at least one SiO ₂ layer and at least one HfO layer stacked in sequence ₂ floors.

Further, a bonding layer is further disposed on the first substrate, and the first reflector layer is disposed on the bonding layer.

The embodiment of the present application also provides a method for fabricating a Micro-LED chip structure, which includes:

providing a second substrate, and sequentially forming an LED semiconductor layer and a first reflector layer on the second substrate,

providing a first substrate, bonding a first reflector layer to the first substrate, and removing the second substrate to expose the LED semiconductor layer;

A plurality of step structures are formed on the LED semiconductor layer, and the plurality of step structures separate the LED semiconductor layer to form a plurality of LED units arranged in an array, and the plurality of LED units can be driven independently;

A second reflector layer is formed on the LED semiconductor layer, the first reflector layer, the LED semiconductor layer and the second reflector layer being configured to collectively provide a resonant cavity.

Further, the LED semiconductor layer includes a first doped semiconductor layer, an active layer, and a second doped semiconductor layer sequentially stacked on the first reflector layer, and the LED semiconductor layer The manufacturing method for forming multiple stepped structures on the layer includes:

removing the second doped type semiconductor layer located in a plurality of selected regions, thereby forming a plurality of said step structures, wherein the height of said step structure is not less than the thickness of said second doped type semiconductor layer but less than or Equal to the thickness of the LED semiconductor layer, the step structure at least isolates the second doped semiconductor layers of adjacent LED units from each other.

Further, the LED semiconductor layer includes a first doped semiconductor layer, an active layer, and a second doped semiconductor layer sequentially arranged on the first reflector layer, and formed on the LED semiconductor layer The manufacturing method of multiple stepped structures includes:

The second doping type semiconductor layer, the active layer and part of the first doping type semiconductor layer located in a plurality of selected regions are removed, thereby forming a plurality of said step structures.

Further, the first substrate includes a driving circuit, the driving circuit has a plurality of contacts, and each contact corresponds to an LED unit, and the manufacturing method specifically includes:

forming a passivation layer on the second doped semiconductor layer, processing and forming a first opening exposing the second doped semiconductor layer at a position corresponding to the step structure on the passivation layer, and The position of the contact is processed to form a second opening, and the second opening has an etching hole exposing the contact, and then an electrode layer is formed on the passivation layer, and the electrode layer is separated from the first An opening is electrically connected to the second doped semiconductor layer, and is electrically connected to contacts on the first substrate from the second opening and the etching hole.

Further, the reflectivity of the first reflector layer is greater than the reflectivity of the second reflector layer, and the light emitted by the LED semiconductor layer exits the LED unit from the second reflector layer.

Further, the manufacturing method further includes: forming a bonding layer on the first reflector layer and/or the first substrate, and then bonding the first reflector layer to the first substrate.

Compared with the prior art, the Micro-LED chip structure provided by the present application can increase the light output, enhance the wavelength stability, and improve the light collimation and luminous efficiency.

Description of drawings

Figure 1a is a schematic top view of a Micro-LED chip structure provided in a typical implementation case of the present application;

Figure 1b is a schematic top view of another Micro-LED chip structure provided in a typical implementation case of the present application;

Fig. 1c is a schematic diagram of a cross-sectional structure formed along B-B' in Fig. 1b;

Figure 1d is a schematic diagram of a cross-sectional structure formed along A-A' in Figure 1b;

2a-2i are schematic structural diagrams of the fabrication process of a Micro-LED chip structure provided in a typical implementation case of the present application.

Detailed ways

In view of the deficiencies in the prior art, the applicant of this case was able to propose the technical solution of this application after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained in conjunction with the accompanying drawings and specific implementation cases as follows.

The term "layer" as used herein refers to a portion of material comprising a region having a certain thickness. A layer may extend across the entire underlying or superstructure, or may have an extent that is less than the extent of the underlying or superstructure. Furthermore, a layer may be a region of a homogeneous or heterogeneous continuous structure, the thickness of which is less than that of the continuous structure. For example, a layer may be located between the top and bottom surfaces of the continuous structure or between any pair of horizontal planes therebetween. Layers may extend horizontally, vertically and/or along the tapered surface. The second substrate can be one layer, can include one or more layers therein, and/or can have one or more layers thereon, above, and/or below. A layer can include multiple layers. For example, a semiconductor layer may comprise one or more doped or undoped semiconductor layers, and may be of the same or different materials.

The term "second substrate" as used herein refers to a material onto which subsequent layers of material are added, the second substrate itself may be patterned, material added on top of the second substrate may be patterned or may remain unpatterned. In addition, the second substrate can include various semiconductor materials, such as silicon, silicon carbide, gallium nitride, germanium, gallium arsenide, indium phosphide, etc. Alternatively, the second substrate can be made of a non-conductive material components such as glass, plastic or sapphire wafers. The first substrate has a semiconductor device or a circuit formed therein, and the driving circuit or semiconductor device may be processed and formed according to specific requirements, which is not specifically limited here.

Please refer to FIG. 1a-FIG. 1d, which is a Micro-LED chip structure of a typical implementation case of the present application. The Micro-LED is intended to represent a scale of 0.1 to 100 μm. It should be understood, however, that embodiments of the present application are not necessarily so limited, and that certain aspects of the embodiments may be applicable to larger and possibly smaller scales.

In this embodiment, a Micro-LED chip structure includes a first substrate 102 and a plurality of LED units 100 arranged in an array formed on the first substrate 102, and the LED units 100 can be bonded The layer 104 is fixedly combined on the first substrate 102, and the LED unit 100 is also electrically connected to the contact 118 on the first substrate 102 through the electrode layer 122, and the LED unit also has a stepped structure 113, the step The structure 113 enables each LED unit 100 to be driven independently.

Taking one of the LED units 100 as an example, the LED unit 100 includes a first reflector layer 106, an LED semiconductor layer and a second reflector layer 110, the LED semiconductor layer is disposed on the first reflector layer 106, the The second reflector layer 110 is arranged on the LED semiconductor layer, and the second reflector layer 110 covers at least the light-emitting area of the LED semiconductor layer, and the light emitted by the LED semiconductor layer can be reflected by the first The reflector layer 106 is reflected to the second reflector layer 110 and is directional emitted from the second reflector layer 110, wherein the first reflector layer 106, the LED semiconductor layer and the second reflector layer 112 are configured to collectively provide a resonant cavity.

In this embodiment, the first substrate 102 can be made of semiconductor materials such as silicon, silicon carbide, gallium nitride, germanium, gallium arsenide, indium phosphide, etc. Of course, the first substrate 102 can also be Made of non-conductive materials such as glass, plastic, or sapphire wafers. In this embodiment, the first substrate 102 includes a driving circuit, and the first substrate 102 may be a CMOS backplane or a TFT glass substrate, etc., and the driving circuit is used to provide electrical signals to the LED unit 100 to control brightness.

In this embodiment, the drive circuit may include an active matrix drive circuit, wherein each individual LED unit 100 corresponds to an independent driver. In this embodiment, the drive circuit may include a passive matrix drive circuit, Wherein, a plurality of LED units 100 are distributed in an array and connected to data lines and scan lines driven by a driving circuit.

In this embodiment, the bonding layer 104 may be an adhesive material layer formed on the first substrate 102 to bond the first substrate 102 and the first reflector layer 106. In this embodiment, the bonding layer The material of 104 can be a conductive material, such as metal or metal alloy, for example, the material of the bonding layer can be Au, Sn, In, Cu or Ti, etc., and is not limited thereto.

In this embodiment, the material of the bonding layer 104 can also be a non-conductive material, such as polyimide (PI), polydimethylsiloxane (PDMS), etc., and is not limited thereto.

In this embodiment, the material of the bonding layer 104 may also be photoresist, such as SU-8 photoresist, etc., and is not limited thereto.

In this embodiment, the material of the bonding layer 104 can also be hydrogen silsesquioxane (HSQ) or divinylsiloxane-bis-benzocyclobutene (DVS-BCB), etc., and does not limited to this.

It should be understood that the description of the material of the bonding layer 104 is only exemplary rather than limiting, and those skilled in the art may make changes according to requirements, and all these changes are within the scope of the present application.

In this embodiment, the first reflector layer 106 is disposed on the bonding layer 104, the bonding layer 104 is disposed on the first substrate 102, and the LED semiconductor layer is connected to the first substrate via the electrode layer 122. Contacts 118 on 102 are electrically connected.

In this embodiment, the first reflector layer 106 is formed on the bonding layer 104, and the first reflector layer 106 may be a reflective p-type ohmic contact layer or a metal reflective layer or a distributed Bragg reflector, etc., The first reflector layer 106 can provide current conduction from the LED semiconductor layer to the bonding layer 104, and the first reflector layer 106 can also be used as a metal mirror to reflect light emitted by the LED semiconductor layer to the second reflector layer 110.

The first reflector layer 106 can also be a metal or metal alloy layer with high reflectivity, such as silver, aluminum, gold and alloys thereof, and is not limited thereto. It should be understood that the description of materials for the first reflector layer 106 is exemplary only and not limiting, and that other materials are also contemplated, all of which are within the scope of the present application.

In this embodiment, the LED semiconductor layer includes a first doped semiconductor layer 112, an active layer 114, and a second doped semiconductor layer 116 sequentially disposed on the first reflector layer 106, wherein the The first doping type semiconductor layer 112 is of the first doping type, and the second doping type semiconductor layer 116 is of the second doping type.

In this embodiment, the active layer 114 is disposed between the first doped semiconductor layer 112 and the second doped semiconductor layer 116 and provides light. The active layer 114 is a layer that recombines holes and electrons respectively supplied from the first doped type semiconductor layer 112 and the second doped type semiconductor layer 116 and outputs light of a specific wavelength, and may have a single A quantum well structure or a multiple quantum well (MQW) structure, and well layers and barrier layers are alternately stacked.

In this embodiment, the stepped structure 113 is formed on the second doped semiconductor layer 116, and the height of the stepped structure is not less than the thickness of the second doped semiconductor layer 116 and is less than or equal to the thickness of the second doped semiconductor layer 116. The thickness of the LED semiconductor layer, the step structure 113 at least isolates the second doped type semiconductor layer 116 of the adjacent LED unit from each other, that is, the part of the step structure penetrates and isolates the second doped type semiconductor layer along the thickness direction. semiconductor layer 116 .

In this embodiment, the material of the first doped semiconductor layer 112 and the second doped semiconductor layer 116 can be II-VI material (such as ZnSe or ZnO) or III-V nitride material (such as GaN, AlN, InN, InGaN, GaP, AlInGaP, AlGaAs and their alloys) form one or more layers.

In this embodiment, the first doped semiconductor layer 112 may be a p-type semiconductor layer extending across multiple LED units 100 and forming the common anode of these LED units 100, in this embodiment, extending across the LED units (that is, the part located between the two LED units) the first doped semiconductor layer 112 can be relatively thin; in this embodiment, the thickness of the first doped semiconductor layer 112 is 0.05 μm-1 μm, Preferably it is 0.05 μm-0.7 μm, especially preferably 0.05 μm-0.5 μm.

In this embodiment, by having a continuous first doped semiconductor layer on each LED unit, the bonding area between the first substrate 102 and the plurality of LED units 100 is not limited to the second doped semiconductor layer. The area below layer 116 also extends to the area between the individual LED units.

In this embodiment, the first doped semiconductor layer 112 may be p-type GaN, and in this embodiment, the first doped semiconductor layer 112 may be formed by doping magnesium (Mg) in GaN, In some other implementation cases, the first doped semiconductor layer 112 may also be p-type InGaN or p-type AlInGaP or the like.

In this embodiment, each LED unit 100 has an anode and a cathode connected to a driving circuit, for example, the driving circuit is formed in the first substrate 102 (the driving circuit is not explicitly shown in the figure), for example, each LED unit 100 each have an anode connected to a constant voltage source and a cathode connected to a source/drain of a driving circuit; in other words, by forming a continuous first doped semiconductor layer 112 across each LED unit 100, a plurality of LEDs The unit 100 may have a common anode formed of the first doped type semiconductor layer 112 .

In this embodiment, the second doped semiconductor layer 116 may be an n-type semiconductor layer and forms a cathode of the LED unit 110 .

In this embodiment, the second doped semiconductor layer 116 may be n-type GaN, n-type InGaN, n-type AlInGaP or the like.

In this embodiment, the second doped semiconductor layer 116 of different LED units 100 is electrically isolated, so that each LED unit 100 can have a cathode with a different voltage level from the other LED units, as disclosed in the embodiment As a result, a plurality of individually operable LED units 100 are formed, the first doped semiconductor layer 112 extending horizontally across adjacent LED units, and the second doped semiconductor layer 116 extending between adjacent LED units. electrical isolation between them.

In this embodiment, the active layer (that is, the MQW layer) 114 is the active region of the LED semiconductor layer. In this embodiment, the LED semiconductor layer (the first doped semiconductor layer 112, the MQW layer 114 and the second doped semiconductor layer 116) have a thickness of 0.4 μm-4 μm, preferably 0.5 μm-3 μm.

In this embodiment, a stepped structure 113 is formed on the second doped semiconductor layer 116, that is, a part of the stepped structure penetrates and isolates the second doped semiconductor layer 116 along the thickness direction, and the stepped structure The stepped surface of the LED semiconductor layer is used as the light-emitting area of the LED semiconductor layer.

In this embodiment, a passivation layer 120 is formed on at least a part of the second doped semiconductor layer 116 and the first doped semiconductor layer 112 , and the passivation layer 120 can be used to protect and isolate the LED unit 100 .

In this embodiment, the material of the passivation layer 120 can be SiO ₂ , Al ₂ O ₃ , SiN or other suitable materials, etc. In this embodiment, the material of the passivation layer 120 can also be poly imide, SU-8 photoresist or other photopatternable polymers, etc., the electrode layer 122 is formed on a part of the passivation layer 120, and the electrode layer 122 passes through the first opening on the passivation layer 120 121 is electrically connected to the second doped semiconductor layer 116 .

In this embodiment, the material of the electrode layer 122 can be a transparent conductive material, such as indium tin oxide (ITO) or zinc oxide (ZnO), or the material of the electrode layer 122 can be Cr, Ti, Conductive materials such as Pt, Au, Al, Cu, Ge or Ni.

In this embodiment, the first substrate 102 has a drive circuit formed therein for driving the LED units 100 , the contacts 118 of the drive circuit are exposed between adjacent LED units 100 , and the contacts 118 pass through the electrode layer 122 It is electrically connected to the second doped semiconductor layer 116 ; it can be understood that the electrical connection between the second doped semiconductor layer 116 and the contact 118 of the driving circuit is completed by the electrode layer 122 .

In this embodiment, the passivation layer 120 is also provided with a second opening, the second opening has an etching hole exposing the contact, the electrode layer 122 passes through the first opening, the second The opening and the etching hole electrically connect the second doped semiconductor layer 116 with the contact 118 .

In this embodiment, please refer to FIG. 1a and FIG. 1b, the first opening 121 is arranged in the central area of each LED unit 100 as far as possible, the shape of the first opening 121 can be circular or square, etc., of course, The first opening 121 can also be other regular or irregular patterns; the second opening is set at the gap between adjacent LED units 100, and the shape of the second opening can be set according to specific needs, which is not mentioned here. It is limited in this implementation case.

In this embodiment, as mentioned above, the second doped semiconductor layer 116 forms the cathode of each LED unit 100 , so the contact 118 connects from the driving circuit to the second doped semiconductor layer 116 through the electrode layer 122 A driving voltage is provided to the cathode of each LED unit 116 .

In this embodiment, each LED unit 100 includes a p-n diode formed by the first doped semiconductor layer 112, the second doped semiconductor layer 116 and the multiple quantum well 110, and the passivation layer 120 is formed on the p-n diode , and the electrode layer 122 is formed on the passivation layer 120 .

In this embodiment, the second reflector layer 110 is formed on the LED semiconductor layer. The second reflector layer 110 may be a distributed Bragg reflector (DBR). In this embodiment, the second reflector Layer 110 may include multiple pairs of TiO ₂ /SiO ₂ layers or multiple pairs of SiO ₂ /HfO ₂ layers, for example, the second reflector layer 110 may include 3-10 pairs of TiO ₂ /SiO ₂ layers or 3-10 pairs SiO ₂ /HfO ₂ layer, it should be noted that each LED unit 100 includes a second reflector layer 110, of course, in this embodiment, multiple LED units 100 include a second reflector layer 110, namely The second reflector layer 110 serves as a common second reflector layer and is correspondingly matched with a plurality of LED semiconductor layers.

In this embodiment, the reflectivity of the first reflector layer 106 is greater than the reflectivity of the second reflector layer 110, as a result of the disclosed embodiment, the first reflector layer 106, LED semiconductor layer and The second reflector layer 110 together provides a resonant cavity, and the light emitted by the LED semiconductor layer is directionally emitted from the second reflector layer 110 .

In this embodiment, the Micro-LED chip structure provided by this application can obtain a relatively small half-power angle of about 27° to 30°. Since the resonant cavity effect can increase the directivity of light waves of the LED unit 100, extraction efficiency is improved. Extraction efficiency may also be referred to as optical efficiency. When photons are generated within the LED unit 100, they must escape from the crystal in order to produce the luminous effect; the extraction efficiency is the fraction of photons that escape from the LED unit 100 generated in the active area. Since the directivity of light waves of the LED unit 100 is improved by using the resonant cavity, photons escaped from the second reflector layer 110 of the LED unit 100 are increased and light extraction efficiency is improved.

The optical characteristics of the Micro-LED chip structure provided by the present application can have a narrower resonance wavelength peak. In other words, the full width at half maximum (FWHM) of the LED unit 100 is significantly smaller than that of conventional LEDs. LEDs are characterized by pure and saturated emission colors with a narrow bandwidth, and a light source with a narrower FWHM will result in a wider color gamut, with a smaller FWHM, the spectral purity of the LED unit 100 with a resonant cavity is improved.

The Micro-LED chip structure provided by this application passes through the resonant cavity, and the light emitted downward or sideways by the LED semiconductor layer can be reflected by the first reflector layer 106, and the stepped structure can confine the current in the aperture area and provide excellent Optical limitations. As a result, the light emitted by the semiconductor layer of the LED exits directionally from the second reflector layer 110 . Thus, the disclosed embodiments have excellent directivity of emitted light, stable peak wavelength, spectral purity, and high external quantum efficiency. That is, the Micro-LED chip structure provided by the present application can increase the light output, enhance the wavelength stability, and improve the light output collimation and luminous efficiency.

Please refer to Figure 2a-Figure 2i, a method for fabricating a Micro-LED chip structure provided by the embodiment of the present application may include the following steps:

1) Referring to FIG. 2a, the second doped semiconductor layer 116, the active layer 114, and the first doped semiconductor layer 112 are sequentially formed on the second substrate 130. The second doped semiconductor layer 116 , the active layer 114, and the first doped semiconductor layer 112 form the LED semiconductor layer; and, providing the first substrate 102,

Wherein, the material of the second substrate 130 can be non-conductive material such as glass, plastic or sapphire wafer, and the first substrate 102 can be made of such as silicon, silicon carbide, gallium nitride, germanium, gallium arsenide, phosphide Indium and other semiconductor materials are made and formed. Of course, the first substrate 102 can also be made of non-conductive materials such as glass, plastic or sapphire wafer. The first substrate 102 includes a driving circuit, and the first substrate 102 A plurality of contacts 118 are also provided. In this embodiment, the first substrate 102 may be a CMOS backplane or a TFT glass substrate, and the driving circuit is used to provide electrical signals to the LED unit 100 to control brightness; In this embodiment, the drive circuit may include an active matrix drive circuit, wherein each individual LED unit 100 is equivalent to an independent driver, and in this embodiment, the drive circuit may include a passive matrix drive circuit, Wherein, a plurality of LED units 100 are distributed in an array and connected to data lines and scan lines driven by a driving circuit;

In some specific embodiments, processes such as chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), plasma enhanced CVD (PECVD), plasma enhanced ALD (PEALD) can be used to form the first The second doped semiconductor layer 116, the active layer 114, and the first doped semiconductor layer 112; in this embodiment, the materials of the first doped semiconductor layer 112 and the second doped semiconductor layer 116 can be II-VI material (such as ZnSe or ZnO) or III-V nitride material (such as GaN, AlN, InN, InGaN, GaP, AlInGaP, AlGaAs and alloys thereof), the first doped semiconductor layer 112 can be used as The p-type semiconductor layer of the anode, in this embodiment, the thickness of the first doped semiconductor layer 112 is 0.05 μm-1 μm, preferably 0.05 μm-0.7 μm, especially preferably 0.05 μm-0.5 μm; In an embodiment, the first doped semiconductor layer 112 can be formed by doping magnesium (Mg) in GaN. In other embodiments, the first doped semiconductor layer 112 can also be p-type InGaN, p-type AlInGaP, etc.; in this embodiment, the second doped semiconductor layer 116 may be an n-type semiconductor layer, and the second doped semiconductor layer 116 serves as the cathode of each LED unit 110 . In this embodiment, the second doped semiconductor layer 116 can be n-type GaN, n-type InGaN, n-type AlInGaP, etc.; in this embodiment, the active layer (ie MQW layer) 114 is an LED The active region of the semiconductor layer. In this embodiment, the thickness of the LED semiconductor layer (the first doped semiconductor layer 112, the MQW layer 114 and the second doped semiconductor layer 116) is 0.4 μm-4 μm, preferably 0.5μm-3μm;

2) Please refer to Figure 2b, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), plasma enhanced CVD (PECVD), plasma enhanced ALD (PEALD) and other processes are used in the first doped The first reflector layer 106 is formed on the heterogeneous semiconductor layer 112; in this embodiment, the first reflector layer 106 can be a reflective p-type ohmic contact layer or a metal reflective layer or a distributed Bragg reflector, etc., the The first reflector layer 106 can provide current conduction from the LED semiconductor layer to the bonding layer 104, and the first reflector layer 106 can also be used as a metal mirror to reflect light emitted by the LED semiconductor layer to the second LED semiconductor layer. The second reflector layer 110, for example, the first reflector layer 106 can also be a metal or metal alloy layer with high reflectivity, such as silver, aluminum, gold and alloys thereof, and is not limited thereto. It should be understood that the description of the materials for the first reflector layer 106 is exemplary only and not limiting, and that other materials are also contemplated, all of which are within the scope of this application;

3) Referring to FIG. 2c, a bonding layer 104 is formed on the first doped semiconductor layer 112 and/or the first substrate 102, and the first substrate 102 is connected to the first doped semiconductor layer through the bonding layer 104. Layer 112 is bonded, wherein, the bonding layer 104 may be an adhesive material layer formed on the first substrate 102 to bond the first substrate 102 and the LED unit 100, in this embodiment, the bonding layer 104 The material can be a conductive material, such as metal or metal alloy, etc. For example, the material of the bonding layer can be Au, Sn, In, Cu or Ti, etc. In other embodiments, the material of the bonding layer 104 It can also be a non-conductive material, such as polyimide (PI), polydimethylsiloxane (PDMS), etc. In this embodiment, the material of the bonding layer 104 can also be photoresist, such as SU-8 photoresist, etc. In other implementation cases, the material of the bonding layer 104 can also be hydrogen silsesquioxane (HSQ) or divinylsiloxane-bis-benzocyclobutene (DVS-BCB), etc.; It should be understood that the description of the material of the bonding layer 104 is only exemplary, rather than limiting, and those skilled in the art can make changes according to requirements, and all these changes are within the scope of the present application ;

4) Referring to Fig. 2d, the second substrate 130 is removed, and the method of removing the second substrate 130 can be achieved by direct peeling or other methods known to those skilled in the art; of course, after removing the second substrate 130, it is also possible Perform a thinning operation on the second doped semiconductor layer 116 to remove a part of the second doped semiconductor layer 116; in some implementations, the thinning operation may include dry etching or wet etching, in some implementations In the mode, the thinning operation may include chemical mechanical polishing (CMP) operation, etc.;

5) Referring to FIG. 2e, the second doped semiconductor layer 116 and the active layer 114 located in the first region can be removed by means of etching, etc., and the first doped semiconductor layer 112 is exposed, thereby forming a stepped structure 113, the height of the step structure 113 is not less than the thickness of the second doped semiconductor layer 116 and less than or equal to the thickness of the LED semiconductor layer, and the step structure 113 at least makes the second doping of the adjacent LED unit Type semiconductor layers 116 are isolated from each other, wherein the step surface of the step structure 113 serves as the light emitting region of the LED semiconductor layer;

It can be understood that the part of the stepped structure 113 penetrates the second doped semiconductor layer 116 at least along the thickness direction, for example, the part of the stepped structure 113 penetrates the second doped semiconductor layer along the thickness direction 116, so as to realize the isolation of the second doped semiconductor layer 116; or, the part of the stepped structure 113 penetrates the second doped semiconductor layer 116 and the active layer 114 along the thickness direction, wherein the first The doped semiconductor layer 112 may span multiple epitaxial structure units along the horizontal direction.

In this embodiment, the thickness of the LED semiconductor layer including the first doped semiconductor layer 112, the active layer 114 and the second doped semiconductor layer 116 may be between about 0.3 μm and about 5 μm, and in some other implementations In this way, the thickness of the LED semiconductor layer including the first doped semiconductor layer 112, the active layer 114 and the second doped semiconductor layer 116 may be between about 0.4 μm and about 4 μm, and in some alternative embodiments , the thickness of the LED semiconductor layer including the first doped semiconductor layer 112, the active layer 114 and the second doped semiconductor layer 116 may be between about 0.5 μm and about 3 μm;

6) Please refer to FIG. 2f, the etching hole can be continuously formed by means of etching etc., the etching hole removes the first doped semiconductor layer 112 and the first reflector layer 106 located in the etching hole area, and exposes the first substrate located on the first substrate. Contact 118 on 102;

7) Referring to FIG. 2g, a passivation layer 120 is formed on the surface of the formed device epitaxial structure unit, and a first opening 121 is formed on the passivation layer 120 corresponding to the position of the step structure, and the second doping type The semiconductor layer 116 is exposed from the first opening 121, and a second opening is formed on the passivation layer 120 at a position corresponding to the contact, and the contact is exposed at the second opening. 118 etching holes; of course, in some other specific implementation cases, a passivation layer can also be directly formed in a selected area of the device epitaxial structure, and no passivation layer is provided in the area corresponding to the step structure and the contact;

In this embodiment, the material of the passivation layer 120 can be SiO ₂ , Al ₂ O ₃ , SiN or other suitable materials, etc. The passivation layer 120 can also include polyimide, SU-8 photo Resists or other photopatternable polymers, etc.;

In other embodiments of the present application, after forming the second opening on the passivation layer 120, the etching process or other processes may be used to form the etching hole. The purpose of the etching hole is to etch the first doped semiconductor layer 112. and the first reflector layer 106 , and expose the contacts 118 on the first substrate 102 .

8) Referring to FIG. 2h, a transparent electrode layer 122 is formed on the passivation layer 120 on the surface of the epitaxial structural unit of the device, and the transparent electrode layer 122 is formed from the first opening, the first opening, the etching hole and the second doped hole respectively. The contact 118 on the heterogeneous semiconductor layer 116 and the first substrate 102 is electrically connected, and the driving circuit on the first substrate 102 can control the voltage and current of the second doped semiconductor layer 116 through the transparent electrode layer 122; Compared with the implementation mode in this embodiment, the transparent electrode layer 122 is electrically isolated from the structural layers except the second doped semiconductor layer 116 through a passivation layer;

In this embodiment, the electrode layer 122 is formed on a part of the passivation layer 120, and the electrode layer 122 is electrically connected to the second doped semiconductor layer 116 through the first opening 121 on the passivation layer 120. In an implementation case, the material of the electrode layer 122 may be conductive materials such as indium tin oxide (ITO), Cr, Ti, Pt, Au, Al, Cu, Ge or Ni;

9) Referring to FIG. 2i, a second reflector layer 110 is formed on the passivation layer 120 and the transparent electrode layer 122, and the second reflector layer 110 at least covers the light-emitting region of the LED semiconductor layer (ie, the steps of the stepped structure surface), the second reflector layer 110, the LED semiconductor layer and the first reflector layer 106 are configured to jointly provide a resonant cavity;

In this embodiment, the second reflector layer 110 is formed on the LED semiconductor layer, and the second reflector layer 110 may be a distributed Bragg reflector (DBR) or a metal reflective layer. In this embodiment, The second reflector layer 110 may include multiple pairs of TiO ₂ /SiO ₂ layers or multiple pairs of SiO ₂ /HfO ₂ layers, for example, the second reflector layer 110 may include 3-10 pairs of TiO ₂ /SiO ₂ layers or 3-10 pairs of SiO ₂ /HfO ₂ layers, it should be noted that each LED unit 100 includes a second reflector layer 110, of course, in some specific implementation cases, multiple LED units 100 include a second reflector layer 110 The reflector layer 110, that is, the second reflector layer 110 is used as a common second reflector layer, and is matched with multiple LED semiconductor layers. In this embodiment, the reflectivity of the first reflector layer 106 is greater than that of the second reflector layer. The reflectivity of the second reflector layer 110, as a result of the disclosed embodiment, the first reflector layer 106, the LED semiconductor layer and the second reflector layer 110 together provide a resonant cavity from which light emitted by the LED semiconductor layer The second reflector layer 110 exits the LED semiconductor layer.

By using the first reflector layer 106, the LED semiconductor layer and the second reflector layer 110 together to provide a resonant cavity, the light emitted by the LED unit downward or sideways can be absorbed by the first reflector layer 106 and the second reflector layer 110. reflection. As a result, the light emitted by the semiconductor layer of the LED is directed out from the second reflector layer 110 . Therefore, the disclosed embodiments have excellent luminescence directivity, stable peak wavelength, spectral purity, and high external quantum efficiency.

It should be understood that the above-mentioned embodiments are only to illustrate the technical concept and features of the present application. The purpose is to enable those familiar with this technology to understand the content of the present application and implement it accordingly, and not to limit the protection scope of the present application. All equivalent changes or modifications made according to the spirit of the present application shall fall within the protection scope of the present application.

Claims (20)

1. A Micro-LED chip structure, characterized by comprising:

   first substrate,

   A plurality of LED units arranged in an array are arranged on the first substrate,

   The LED unit is electrically connected to the first substrate, and the LED unit includes a first reflector layer, an LED semiconductor layer and a second reflector layer, and the LED semiconductor layer is disposed on the first reflector layer between the second reflector layer;

   The LED units have a stepped structure such that adjacent LED units can be driven independently, and the first reflector layer, the LED semiconductor layer and the second reflector layer are configured to jointly provide a resonant cavity.
2. The Micro-LED chip structure according to claim 1, wherein the LED semiconductor layer comprises:

   a first doped semiconductor layer disposed on the first reflector layer;

   an active layer disposed on the first doped semiconductor layer;

   a second doped semiconductor layer disposed on the active layer;

   The step structure is formed on the second doped semiconductor layer, the height of the stepped structure is not less than the thickness of the second doped semiconductor layer and less than or equal to the thickness of the LED semiconductor layer, the The stepped structure at least isolates the second doped semiconductor layers of adjacent LED units from each other.
3. The Micro-LED chip structure according to claim 2, wherein the first reflector layer forms an ohmic contact with the first doped semiconductor layer.
4. The Micro-LED chip structure according to claim 2, wherein the first doped semiconductor layer is a p-type semiconductor layer, and the second doped semiconductor layer is an n-type semiconductor layer.
5. The Micro-LED chip structure according to claim 2, wherein the LED semiconductor layer further comprises:

   a passivation layer disposed on the second doped semiconductor layer and having a first opening; and

   An electrode layer is arranged on the passivation layer and covers the first opening, and the electrode layer is in electrical contact with the second doped semiconductor layer from the first opening.
6. The Micro-LED chip structure according to claim 2, wherein the first doped semiconductor layers of multiple LED units are a common first doped semiconductor layer and the first doped semiconductor layers of adjacent LED units layer electrical connection.
7. The Micro-LED chip structure according to claim 2, wherein the step structure of each LED unit is formed on the second doped semiconductor layer, and the height of the step structure is equal to the LED semiconductor layer The step structure at least electrically isolates the active layer of the adjacent LED unit from the first doped semiconductor layer.
8. The Micro-LED chip structure according to claim 5, wherein the first substrate includes a driving circuit, the driving circuit has a plurality of contacts, and each contact corresponds to one LED unit, and the blunt The electrode layer is also provided with a second opening, and the second opening has an etching hole exposing the contact, and the electrode layer injects the second doping through the first opening, the second opening, and the etching hole. type semiconductor layer and the contacts are electrically connected.
9. The Micro-LED chip structure according to claim 2, wherein the stepped surface of the stepped structure forms the light emitting surface of the LED semiconductor layer, and the second reflector layer at least covers the stepped surface.
10. The Micro-LED chip structure according to claim 1, characterized in that: the reflectivity of the first reflector layer is greater than the reflectivity of the second reflector layer, and the light emitted by the LED semiconductor layer is emitted from the The second reflector layer exits the LED unit.
11. The Micro-LED chip structure according to claim 1, wherein the first reflector layer is a metal reflective layer or a distributed Bragg reflector.
12. The Micro-LED chip structure according to claim 1, wherein the second reflector layer is a metal reflective layer or a distributed Bragg reflector.
13. The Micro-LED chip structure according to claim 12, wherein the distributed Bragg reflector comprises at least one _TiO2 layer and at least one _SiO2 layer stacked in sequence, or the distributed Bragg reflector It includes at least one SiO ₂ layer and at least one HfO ₂ layer stacked in sequence.
14. The Micro-LED chip structure according to claim 1, wherein a bonding layer is further disposed on the first substrate, and the first reflector layer is disposed on the bonding layer.
15. A method for manufacturing a Micro-LED chip structure, characterized by comprising:

    providing a second substrate, and sequentially forming an LED semiconductor layer and a first reflector layer on the second substrate,

    providing a first substrate, bonding a first reflector layer to the first substrate, and removing the second substrate to expose the LED semiconductor layer;

    A plurality of step structures are formed on the LED semiconductor layer, and the plurality of step structures separate the LED semiconductor layer to form a plurality of LED units arranged in an array, and the plurality of LED units can be driven independently;

    A second reflector layer is formed on the LED semiconductor layer, the first reflector layer, the LED semiconductor layer and the second reflector layer being configured to collectively provide a resonant cavity.
16. The manufacturing method according to claim 15, wherein the LED semiconductor layer comprises a first doped semiconductor layer, an active layer, and a second doped semiconductor layer sequentially stacked on the first reflector layer. type semiconductor layer, and the manufacturing method of forming a plurality of stepped structures on the LED semiconductor layer includes:

    removing the second doped type semiconductor layer located in a plurality of selected regions, thereby forming a plurality of said step structures, wherein the height of said step structure is not less than the thickness of said second doped type semiconductor layer but less than or Equal to the thickness of the LED semiconductor layer, the step structure at least isolates the second doped semiconductor layers of adjacent LED units from each other.
17. The manufacturing method according to claim 15, wherein the LED semiconductor layer comprises a first doped semiconductor layer, an active layer, and a second doped semiconductor layer sequentially arranged on the first reflector layer. layer, and the manufacturing method of forming multiple stepped structures on the LED semiconductor layer includes:

    The second doping type semiconductor layer, the active layer and part of the first doping type semiconductor layer located in a plurality of selected regions are removed, thereby forming a plurality of said step structures.
18. The manufacturing method according to claim 16 or 17, wherein the first substrate includes a driving circuit, the driving circuit has a plurality of contacts, and each contact corresponds to an LED unit, and the manufacturing method is specifically include:

    forming a passivation layer on the second doped semiconductor layer, processing and forming a first opening exposing the second doped semiconductor layer at a position corresponding to the step structure on the passivation layer, and The position of the contact is processed to form a second opening, and the second opening has an etching hole exposing the contact, and then an electrode layer is formed on the passivation layer, and the electrode layer is separated from the first An opening is electrically connected to the second doped semiconductor layer, and is electrically connected to contacts on the first substrate from the second opening and the etching hole.
19. The manufacturing method according to claim 15, characterized in that: the reflectivity of the first reflector layer is greater than the reflectivity of the second reflector layer, and the light emitted by the LED semiconductor layer is reflected from the second reflector layer. layer out of the LED unit.
20. The manufacturing method according to claim 15, further comprising: forming a bonding layer on the first reflector layer and/or the first substrate, and then combining the first reflector layer with the first Substrate bonding.

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