Light emitting diode structure and manufacturing method thereof

Abstract

To provide an LED structure comprising a plurality of individually-functionable LED units.SOLUTION: A light-emitting diode (LED) structure includes a substrate 102, and a plurality of LED units 116 that are formed on the substrate. Each of the LED units includes a coupling layer 104 that is formed on the substrate, a first doping-type semiconductor layer 106, a second doping-type semiconductor layer 108, a passivation layer 112, and an electrode layer 114 that is brought into contact with the second doping-type semiconductor layer. The plurality of LED units include the first LED unit 116-1, and the second LED unit 116-2 adjacent to the first LED unit. The first doping-type semiconductor layer of the first LED unit is horizontally extended to the first doping-type semiconductor layer of the second LED unit adjacent to the first LED unit. The first and second LED units are individually-functionable LED units.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] Cross-references related to the application This application claims priority to U.S. Provisional Application No. 63 / 007,829, entitled "Semiconductor Array and Method of Monolithic Integration," filed April 9, 2020, and non-provisional U.S. Application No. 17 / 162,515, entitled "Light Emitting Diode Structure and Method for Manufacturing the Same," filed January 29, 2021, the contents of which are incorporated herein by reference in their entireties.

[0002] The present disclosure relates to a light emitting diode (LED) structure and a method for fabricating the LED structure, and more particularly to an LED structure having multiple independently functioning LED units that share a doping layer and a method for fabricating the same. [Background technology]

[0003] In recent years, LEDs have become popular for lighting applications. As a light source, LEDs offer many advantages, including improved luminous efficacy, reduced energy consumption, longer lifespan, smaller size, and faster switching speed.

[0004] Displays with microscale LEDs are known as microLEDs. MicroLED displays have an array of microLEDs that form individual pixel elements. A pixel is one of many areas that make up an image and may be a tiny, illuminated area on a display screen. In other words, a pixel may be a small, individual element that makes up an image on a display. Pixels are typically arranged in a two-dimensional (2D) matrix and are represented using dots, squares, rectangles, or other shapes. Pixels are the basic building blocks of a display or digital image and may have geometric coordinates.

[0005] When manufacturing micro-LEDs, etching processes such as dry etching and wet etching processes are frequently used to electrically isolate individual micro-LEDs. To produce multiple, fully isolated, functional micro-LED mesas, conventional processes typically completely etch away the continuous, functional epitaxy layer. However, due to the poor adhesion of micro-LED mesas, the fully isolated, functional micro-LED mesas can easily peel off from the substrate during or after transfer onto a substrate such as a drive circuit board. This problem becomes even more severe as micro-LED mesas become smaller. Furthermore, during conventional etching processes to isolate the micro-LED mesas, the sidewalls of the micro-LED mesas can be damaged, potentially affecting the optical and electrical properties of the LED structure.

[0006] The embodiments of the present disclosure address the above problems by providing an LED structure with multiple individually operable LED units, along with doping or bonding layers and methods for fabricating the same. Summary of the Invention

[0007] SUMMARY OF THE INVENTION Embodiments of LED structures and methods for forming LED structures are disclosed herein.

[0008] In one example, an LED structure is disclosed. The LED structure includes a substrate and a plurality of LED units formed on the substrate. Each LED unit includes a bonding layer formed on the substrate, a first doping-type semiconductor layer formed on the bonding layer, a second doping-type semiconductor layer formed on the first doping-type semiconductor layer, a passivation layer formed on a portion of the first doping-type semiconductor layer and the second doping-type semiconductor layer, and an electrode layer formed on a portion of the passivation layer and in contact with the second doping-type semiconductor layer. The plurality of LED units includes a first LED unit and a second LED unit adjacent to the first LED unit. The first doping-type semiconductor layer of the first LED unit extends horizontally and is physically connected to the first doping-type semiconductor layer of the second LED unit adjacent to the first LED unit, and the first LED unit and the second LED unit are individually functioning LED units.

[0009] In another example, an LED structure is disclosed. The LED structure includes a substrate and a plurality of LED units formed on the substrate. Each LED unit includes a pn diode layer formed on the substrate, a passivation layer formed on the pn diode layer, and an electrode layer formed on the passivation layer and in contact with the pn diode layer. The plurality of LED units includes a first LED unit and a second LED unit adjacent to the first LED unit. The first LED unit and the second LED unit have a common anode, and the first LED unit and the second LED unit are individually functioning LED units.

[0010] In a further example, a method for fabricating an LED structure is disclosed. A semiconductor layer is formed on a first substrate. The semiconductor layer includes a first doping type semiconductor layer and a second doping type semiconductor layer. A first etching operation is performed to expose a portion of the first doping type semiconductor layer and remove a portion of the second doping type semiconductor layer. A second etching operation is performed to remove a portion of the first doping type semiconductor layer and expose a portion of the first substrate with contacts for the pixel circuit. A passivation layer is formed on the second doping type semiconductor layer and the exposed first doping type semiconductor layer. A third etching operation is performed to form a first opening in the passivation layer for the second doping type semiconductor layer and a second opening in the passivation layer for the first substrate in contact with the pixel circuit. An electrode layer covers the first opening formed on the passivation layer in contact with the second doping type semiconductor layer and the second opening in contact with the pixel circuit and the first substrate. [Brief explanation of the drawings]

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate implementations of the present disclosure and, together with the description, further explain and enable one skilled in the art to practice the present disclosure.

[0012] [Figure 1] 1 illustrates a plan view of an exemplary LED structure, according to some embodiments of the present disclosure. [Figure 2] 1 shows a cross-sectional view of an exemplary LED structure according to some embodiments of the present disclosure. [Figure 3] 1 illustrates another cross-sectional view of an exemplary LED structure according to some embodiments of the present disclosure. [Figure 4] 1 illustrates another plan view of an exemplary LED structure, according to some embodiments of the present disclosure. [Figure 5] 1 shows a plan view of another exemplary LED structure, according to some embodiments of the present disclosure. [Figure 6A]1A-1C illustrate cross sections of an exemplary LED structure at different stages of a manufacturing process, according to some embodiments of the present disclosure. [Figure 6B] 1A-1C illustrate cross sections of an exemplary LED structure at different stages of a manufacturing process, according to some embodiments of the present disclosure. [Figure 6C] 1A-1C illustrate cross sections of an exemplary LED structure at different stages of a manufacturing process, according to some embodiments of the present disclosure. [Figure 6D] 1A-1C illustrate cross sections of an exemplary LED structure at different stages of a manufacturing process, according to some embodiments of the present disclosure. [Figure 6E] 1A-1C illustrate cross sections of an exemplary LED structure at different stages of a manufacturing process, according to some embodiments of the present disclosure. [Figure 6F] 1A-1C illustrate cross sections of an exemplary LED structure at different stages of a manufacturing process, according to some embodiments of the present disclosure. [Figure 6G] 1A-1C illustrate cross sections of an exemplary LED structure at different stages of a manufacturing process, according to some embodiments of the present disclosure. [Figure 6H] 1A-1C illustrate cross sections of an exemplary LED structure at different stages of a manufacturing process, according to some embodiments of the present disclosure. [Figure 7] 1 is a flowchart of an exemplary method for fabricating an LED structure, according to some embodiments of the present disclosure.

[0013] Embodiments of the present disclosure will now be described with reference to the accompanying drawings. DETAILED DESCRIPTION OF THE INVENTION

[0014] While specific configurations and arrangements are described, it should be understood that this is done for illustrative purposes only. Accordingly, other configurations and arrangements can be used without departing from the scope of the present disclosure. The present disclosure can also be used for a variety of other applications. The functional and structural features described in the present disclosure can be combined, adjusted, and modified with one another in ways not specifically shown in the drawings, such that these combinations, adjustments, and modifications are within the scope of the present disclosure.

[0015] Generally, terms can be understood, at least in part, from their usage in context. For example, as used herein, the term "one or more" may be used to describe any feature, structure, or characteristic in a singular sense, or may be used to describe a combination of features, structures, or characteristics in a plural sense, depending at least in part on the context. Similarly, terms such as "a," "an," or "the" may be understood to indicate either the singular use or the plural use, depending at least in part on the context. Furthermore, the term "based on" may be understood as not necessarily intended to indicate exclusive factors, but instead may allow for the presence of additional factors not necessarily explicitly described, depending at least in part on the context.

[0016] It should be readily understood that the meanings of "on," "above," and "over" in the present disclosure should be interpreted in the broadest manner, such that "on" not only means "directly on" something but also includes the meaning of "on" something with an intermediate feature or layer therebetween, and "above" or "over" not only means "above" or "over" something but also includes the meaning of "above" or "over" something with no intermediate feature or layer (i.e., directly on something).

[0017] Additionally, spatially relative terms such as "beneath," "below," "lower," "above," "upper," and the like may be used to describe the relationship of one element to another element and function as shown in the figures for ease of description. Spatially relative terms are intended to encompass various orientations of the device in use or operation in addition to the orientation shown in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptions used herein may likewise be interpreted accordingly.

[0018] As used herein, the term "layer" refers to a portion of material that includes a region of thickness. A layer can extend across an underlying or overlying structure, or it can have an extent that is smaller than the extent of the underlying or overlying structure. Furthermore, a layer can be a homogeneous or heterogeneous region of a continuous structure that has a thickness that is less than the thickness of the continuous structure. For example, a layer can be disposed between the top and bottom surfaces of a continuous structure, or between any pair of horizontal surfaces above it. A layer can extend along horizontal, vertical, and / or tapered surfaces. A substrate can be a layer and can include one or more layers therein and / or have one or more layers above and / or below it. A layer can include multiple layers. For example, a semiconductor layer can include one or more doped or undoped semiconductor layers, and can have the same or different materials.

[0019] As used herein, the term "substrate" refers to a material onto which subsequent layers of material are added. The substrate itself can be patterned. Materials added onto the substrate can be patterned or left unpatterned. Additionally, substrates can include a wide range of semiconductor materials, such as silicon, silicon carbide, gallium nitride, germanium, gallium arsenide, indium phosphide, etc. Alternatively, substrates can be made from non-conductive materials, such as glass, plastic, or sapphire wafers. Alternatively, substrates can have semiconductor devices or circuits formed therein.

[0020] As used herein, the terms "micro" LED, "micro" pn diode, or "micro" device refer to descriptive dimensions of a particular device or structure according to the practice of the present disclosure. As used herein, the term "micro" device or structure is meant to refer to a dimension of 0.1 to 100 μm. However, it should be understood that practice of the present disclosure is not necessarily so limited, and that certain aspects of the practice may be applicable to larger and, in some cases, smaller size scales.

[0021] The present invention describes an LED or micro LED structure and a method for fabricating the structure. To fabricate a micro LED display, an epitaxy layer is bonded to a receiving substrate. The receiving substrate may be a display substrate, including, but not limited to, a CMOS backplane or a TFT glass substrate. The epitaxy layer is then formed on the receiving substrate with an array of micro LEDs. When forming micro LEDs on the receiving substrate, the adhesion of small functional mesas to the receiving substrate is weak and proportional to the mesa size, which can cause multiple small functional mesas to peel off from the receiving substrate and cause display failures (dead pixels) during the fabrication process. To address the aforementioned issue, the present disclosure introduces a solution in which the functional epitaxy layer is partially patterned / etched, leaving a thin, continuous functional layer and bonding layer to avoid potential peeling. Furthermore, the fabrication method described in the present disclosure can further reduce physical damage to the sidewalls of the functional mesas, reducing damage to the quantum well structure, which is the light-emitting region of the LED, and improving the optical and electrical properties of the functional mesas.

[0022] FIG. 1 illustrates a plan view of an exemplary LED structure 100 according to some embodiments of the present disclosure, and FIG. 2 illustrates a cross-sectional view of the exemplary LED structure 100 along line A-A′ according to some embodiments of the present disclosure. To better explain the present disclosure, the plan view of the LED structure 100 in FIG. 1 and the cross-sectional view of the LED structure 100 in FIG. 2 will be described together. The LED structure 100 includes a first substrate 102 and a plurality of LED units 116 (e.g., LED units 116-1, 116-2, 116-3, and 116-4 as shown in FIG. 2 ). The LED units 116 are bonded onto the first substrate 102 via a bonding layer 104. In some embodiments, the first substrate 102 may include a semiconductor material such as silicon, silicon carbide, gallium nitride, germanium, gallium arsenide, or indium phosphide. In some embodiments, the first substrate 102 may be made of a non-conductive material such as glass, plastic, or a sapphire wafer. In some embodiments, the first substrate 102 may have a drive circuit formed therein, and the first substrate 102 may be a CMOS backplane or a TFT glass substrate. The drive circuit provides electronic signals to the LED units 116 to control brightness. In some embodiments, the drive circuit may include an active matrix drive circuit in which each LED unit 116 corresponds to an independent driver. In some embodiments, the drive circuit may include a passive matrix drive circuit in which multiple LED units 116 are arranged in an array and connected to data lines and scan lines that are driven by the drive circuit.

[0023] The bonding layer 104 is a layer of adhesive formed on the first substrate 102 to bond the first substrate 102 and the LED units 116. In some embodiments, the bonding layer 104 may include a conductive material such as a metal or a metal alloy. In some examples, the bonding layer 104 may include gold, tin, indium, copper, or titanium. In some embodiments, the bonding layer 104 may include a non-conductive material such as polyimide (PI) or polydimethylsiloxane (PDMS). In some embodiments, the bonding layer 104 may include a photoresist such as SU-8 photoresist. In some embodiments, the bonding layer 104 may be hydrosilsesquioxane (HSQ) or divinylsiloxane-bis-benzocyclobutene (DVS-BCB). It is understood that the description of the material of the bonding layer 104 is merely exemplary and not limiting, and that those skilled in the art can make modifications as desired, all of which are within the scope of the present application.

[0024] 2 , each LED unit 116 includes a portion of bonding layer 104, a first doping type semiconductor layer 106, and a second doping type semiconductor layer 108. The first doping type semiconductor layer 106 is formed on bonding layer 104. In some embodiments, the first doping type semiconductor layer 106 and the second doping type semiconductor layer 108 may include one or more layers based on II-VI materials such as ZnSe or ZnO, or III-V nitride materials such as GaN, AlN, InN, InGaN, GaP, AlInGaP, AlGaAs, and alloys thereof.

[0025] In some embodiments, the first doping type semiconductor layer 106 may be a p-type semiconductor layer that spans multiple LED units 116 (e.g., four LED units 116 as shown in FIG. 2) and forms a common anode for these LED units 116. For example, the first doping type semiconductor layer 106 of LED unit 116-2 extends to adjacent LED units 116-1 and 116-3, and similarly, the first doping type semiconductor layer 106 of LED unit 116-3 extends to adjacent LED units 116-2 and 116-4. In some embodiments, the first doping type semiconductor layer 106 extending across the LED units may be relatively thin. In some embodiments, the thickness of the first doping type semiconductor layer 106 may be between about 0.05 μm and about 1 μm. In other embodiments, the thickness of the first doping type semiconductor layer 106 may be between about 0.05 μm and about 0.7 μm. In some alternative embodiments, the thickness of the first doping type semiconductor layer 106 may be between about 0.05 μm and about 0.5 μm. By having a continuous thin layer of the first doping type semiconductor throughout the individual LED units, the bonding area between the first substrate 102 and the multiple LED units 116 is not limited to the area under the second doping type semiconductor layer 108, but also extends to the area between the individual LED units. In other words, by having a continuous thin layer of the first doping type semiconductor, the area of ​​the bonding layer 104 is increased. Therefore, the bonding strength between the first substrate 102 and the multiple LED units 116 is enhanced, and the risk of delamination of the LED structure 100 can be reduced.

[0026] In some embodiments, the first doping type semiconductor layer 106 may be p-type GaN. In some embodiments, the first doping type semiconductor layer 106 may be formed by doping GaN with magnesium (Mg). In some embodiments, the first doping type semiconductor layer 106 may be p-type InGaN. In some embodiments, the first doping type semiconductor layer 106 may be p-type AlInGaP. Each of the LED units 116 has an anode and a cathode connected to a drive circuit, such as one formed on the first substrate 102 (the drive circuit is not explicitly shown). For example, each LED unit 116 has an anode connected to a constant voltage source and a cathode connected to the source / drain electrodes of the drive circuit. In other words, by forming a continuous first doping type semiconductor layer 106 across each individual LED unit 116, the multiple LED units 116 have a common anode formed by the first doping type semiconductor layer 106 and the bonding layer 104.

[0027] In some embodiments, the second doping type semiconductor layer 108 may be an n-type semiconductor layer and form the cathode of each LED unit 116. In some embodiments, the second doping type semiconductor layer 108 may be n-type GaN. In some embodiments, the second doping type semiconductor layer 108 may be n-type InGaN. In some embodiments, the second doping type semiconductor layer 108 may be n-type AlInGaP. The second doping type semiconductor layers 108 of different LED units 116 are electrically isolated, and thus each LED unit 116 has a cathode that can have a different voltage level from the other units. As a result of the disclosed implementations, multiple individually functional LED units 116 are formed with first doping type semiconductor layers 106 extending horizontally across adjacent LED units and second doping type semiconductor layers 108 that are electrically isolated between adjacent LED units.

[0028] Each LED unit 116 further includes a multiple quantum well (MQW) layer 110 formed between the first doping type semiconductor layer 106 and the second doping type semiconductor layer 108. The MQW layer 110 is the active region of the LED unit 116. In some embodiments, the thickness including the first doping type semiconductor layer 106, the MQW layer 110, and the second doping type semiconductor layer 108 may be between about 0.3 μm and about 5 μm. In other embodiments, the thickness including the first doping type semiconductor layer 106, the MQW layer 110, and the second doping type semiconductor layer 108 may be between about 0.4 μm and about 4 μm. In some alternative embodiments, the thickness including the first doping type semiconductor layer 106, the MQW layer 110, and the second doping type semiconductor layer 108 may be between about 0.5 μm and about 3 μm.

[0029] As shown in FIG. 2 , a passivation layer 112 is formed on the second doping type semiconductor layer 108 and a portion of the first doping type semiconductor layer 106. The passivation layer 112 may be used to protect and isolate the LED units 116. In some embodiments, the passivation layer 112 may comprise SiO 2 , Al 2 O 3 , SiN, or other suitable materials. In some embodiments, the passivation layer 112 may comprise polyimide, SU-8 photoresist, or other optically patternable polymers. An electrode layer 114 is formed on a portion of the passivation layer 112, and the electrode layer 114 is electrically connected to the second doping type semiconductor layer 108 through an opening in the passivation layer 112. In some embodiments, the electrode layer 114 may be a conductive material such as indium tin oxide (ITO), Cr, Ti, Pt, Au, Al, Cu, Ge, or Ni.

[0030] 3 shows another cross-sectional view of the exemplary LED structure 100 along line B-B' according to some embodiments of the present disclosure. The first substrate 102 has a driving circuit formed therein for driving the LED units 116. A contact 118 of the driving circuit is exposed between two LED units 116, and the contact 118 is electrically connected to the second doping type semiconductor layer 108 via the electrode layer 114. In other words, the electrical connection between the second doping type semiconductor layer 108 and the contact 118 of the driving circuit is achieved by the electrode layer 114. As described above, the second doping type semiconductor layer 108 forms the cathode of each LED unit 116, and therefore the contact 118 provides a driving voltage for the cathode of each LED unit 116 from the driving circuit to the second doping type semiconductor layer 108 via the electrode layer 114.

[0031] 4 shows another plan view of an LED structure 100 according to some embodiments of the present disclosure. For illustrative purposes, layers below the electrode layer 114 and the passivation layer 112 are shown with dashed lines in FIG. 4 . In FIG. 4 , the LED structure 100 includes 16 LED units 116. Each LED unit 116 includes a pn diode layer formed by a first doping type semiconductor layer 106, a second doping type semiconductor layer 108, and a multiple quantum well 110. The passivation layer 112 is formed on the pn diode layer, and the electrode layer 114 is formed on the passivation layer 112.

[0032] An opening 120 is formed on the passivation layer 112 exposing the second doping type semiconductor layer 108, and an opening 122 is formed on the passivation layer 112 exposing the contact portion 118. An electrode layer 114 is formed on a portion of the passivation layer 112 covering the opening 120 and the opening 122. Thus, the electrode layer 114 is electrically connected to the second doping type semiconductor layer 108 and the contact portion 118. In the example shown in FIG. 4 , the opening 120 is disposed at the center of each LED unit 116, and the opening 122 is disposed at the space between adjacent LED units 116. It is understood that the positions and designs (such as shape and size) of the opening 120, the opening 122, and the electrode layer 114 may deviate from the example shown in FIG. 4 based on requirements and are not limited thereto.

[0033] 4 , the LED structure 100 includes 16 LED units 116, each of which can function individually. The first doping type semiconductor layer 106 is located below the second doping type semiconductor layer 108 and the passivation layer 112, and the first doping type semiconductor layer 106 is a common anode for these 16 LED units 116. When the first doping type semiconductor layers 106 of these LED units (e.g., the 16 LED units 116) are electrically connected not only during the manufacturing process to form the LED structure 100 but also after the manufacturing process, throughout this disclosure, the multiple LED units are said to be “individually functionable,” and each LED unit 116 can be individually driven by a different driving circuit.

[0034] FIG. 5 shows a plan view of another LED structure 500 according to some embodiments of the present disclosure. The shape of the second doping type semiconductor layer 108 in the plan view of FIG. 5 is circular, which differs from the shape of the second doping type semiconductor layer 108 in the plan view of the LED structure 100 shown in FIG. 4. In some embodiments, the position and shape of the second doping type semiconductor layer 108 in the plan view can be changed according to various designs or applications, and it is understood that the shape of the second doping type semiconductor layer 108 or the LED unit 116 in the plan view is not limited thereto. In some embodiments, the position and shape of the opening 120, the opening 122, the electrode layer 114, or the contact 118 in the plan view can also be changed according to various designs and applications, including, but not limited to, the position and shape of the opening 120, the opening 122, the electrode layer 114, or the contact 118 in the plan view.

[0035] 6A-6H illustrate cross sections of an exemplary LED structure 100 during a manufacturing process according to some embodiments of the present disclosure. FIG. 7 is a flowchart of an exemplary manufacturing method 700 for manufacturing an LED structure 100 according to some embodiments of the present disclosure. To better explain the present disclosure, FIGS. 6A-6I and the flowchart of FIG. 7 are described together. In FIG. 6A, a driving circuit is formed on a first substrate 102, and the driving circuit includes contacts 118. For example, the driving circuit may include CMOS devices fabricated on a silicon wafer, and several wafer-level packaging layers or fan-out structures are stacked on the CMOS devices to form the contacts 118. As another example, the driving circuit may include TFTs fabricated on a glass substrate, and several wafer-level packaging layers or fan-out structures are stacked on the TFTs to form the contacts 118. Semiconductor layers are formed on a second substrate 124, and the semiconductor layers include a first doping type semiconductor layer 106, a second doping type semiconductor layer 108, and an MQW layer 110.

[0036] In some embodiments, the first substrate 102 or the second substrate 124 may comprise a semiconductor material such as silicon, silicon carbide, gallium nitride, germanium, gallium arsenide, or indium phosphide. In some embodiments, the first substrate 102 or the second substrate 124 may be made of a non-conductive material such as glass, plastic, or a sapphire wafer. In some embodiments, the first substrate 102 may have driving circuitry formed therein, and the first substrate 102 may comprise a CMOS backplane or a TFT glass substrate. In some embodiments, the first doping type semiconductor layer 106 and the second doping type semiconductor layer 108 may comprise one or more layers based on II-VI materials such as ZnSe or ZnO, or III-V nitride materials such as GaN, AlN, InN, InGaN, GaP, AlInGap, AlGaAs, and alloys thereof. In some embodiments, the first doping type semiconductor layer 106 may comprise a p-type semiconductor layer and the second doping type semiconductor layer 108 may comprise an n-type semiconductor layer.

[0037] In FIG. 6B , a bonding layer 104 is formed on the first substrate 102. In some embodiments, the bonding layer 104 may comprise a conductive material such as a metal or a metal alloy. In some embodiments, the bonding layer 104 may comprise Au, Sn, In, Cu, or Ti. In some embodiments, the bonding layer 104 may comprise a non-conductive material such as polyimide (PI) or polydimethylsiloxane (PDMS). In some embodiments, the bonding layer 104 may comprise a photoresist such as SU-8 photoresist. In some embodiments, the bonding layer 104 may comprise hydrosilsesquioxane (HSQ) or divinylsiloxane-bis-benzocyclobutene (DVS-BCB). In some embodiments, a conductive layer 126 may be formed on the first doped semiconductor layer 106. In some embodiments, the conductive layer 126 may form a common electrode over the first doped semiconductor layer 106. In some embodiments, the conductive layer 126 may form an ohmic contact on the first doped semiconductor layer 106. In some embodiments, the conductive layer 126 and the bonding layer 104 may be collectively referred to as one layer in subsequent operations.

[0038] 6C and operation 702 of FIG. 7 , the second substrate 124 and semiconductor layers, including the first doping type semiconductor layer 106, the second doping type semiconductor layer 108, and the MQW layer 110, are flipped over and bonded to the first substrate 102 via the bonding layer 104 and the conductive layer 126. The second substrate 124 is then removed from the semiconductor layers. FIG. 6C shows the bonding layer 104 between the first substrate 102 and the first doping type semiconductor layer 106. However, in some embodiments, the bonding layer 104 may include one or more layers for bonding the first substrate 102 and the first doping type semiconductor layer 106. For example, the bonding layer 104 may include a single conductive or non-conductive layer. As another example, the bonding layer 104 may include an adhesive and a conductive or non-conductive layer. In some embodiments, the bonding layer 104 and the conductive layer 126 may be collectively referred to as one layer after operation 702. It is understood that the description of the materials of the bonding layer 104 is merely exemplary and not limiting, and that those skilled in the art can make modifications as required, all of which are within the scope of the present application.

[0039] 6D , a thinning operation may be performed on the second doping type semiconductor layer 108 to remove a portion of the second doping type semiconductor layer 108. In some embodiments, the thinning operation may include a dry etching or a wet etching operation. In some embodiments, the thinning operation may include a chemical mechanical polishing (CPM) operation. In some embodiments, the thickness including the first doping type semiconductor layer 106, the MQW layer 110, and the second doping type semiconductor layer 108 may be between about 0.3 μm and about 5 μm. In other embodiments, the thickness including the first doping type semiconductor layer 106, the MQW layer 110, and the second doping type semiconductor layer 108 may be between about 0.4 μm and about 4 μm. In other embodiments, the thickness including the first doping type semiconductor layer 106, the MQW layer 110, and the second doping type semiconductor layer 108 may be between about 0.5 μm and about 3 μm.

[0040] 6E and 7 , a first etching operation may be performed to remove a portion of the second doping type semiconductor layer 108 and expose a portion of the first doping type semiconductor layer 106. The portion of the first doping type semiconductor layer 106 is exposed until a predetermined thickness of the first doping type semiconductor layer 106 remains on the first substrate 102. In some embodiments, the remaining first doping type semiconductor layer 106 extends horizontally across multiple LED units 116 (such as the four LED units 116 shown in FIG. 6E ) of the LED structure 100. In some embodiments, the predetermined thickness of the first doping type semiconductor layer 106 may be between about 0.05 μm and about 1 μm. In other embodiments, the predetermined thickness of the first doping type semiconductor layer 106 may be between about 0.05 μm and about 0.7 μm. In some alternative embodiments, the predetermined thickness of the first doping type semiconductor layer 106 may be between about 0.05 μm and about 0.5 μm. After operation 704, the second doping type semiconductor layer 108 and the MQW layer 110 of each LED unit 116 may be electrically isolated, and the first doping type semiconductor layers 106 of adjacent LED units 116 (such as LED units 116-1, 116-2, 116-3, and 116-4) may be electrically connected.

[0041] In some embodiments, during operation 704, a first etching operation is performed to remove a portion of the second doping type semiconductor layer 108, exposing a portion of the MQW layer 110. The portion of the MQW layer 110 is exposed until a predetermined thickness of the first doping type semiconductor layer 106 and the MQW layer 110 remains on the first substrate 102. In some embodiments, the remaining first doping type semiconductor layer 106 and the MQW layer 110 extend horizontally across multiple LED units 116 of the LED structure 100 (such as the four LED units 116 shown in FIG. 6E). In some embodiments, the predetermined thickness of the first doping type semiconductor layer 106 and the MQW layer 110 may be between about 0.05 μm and about 1 μm. In other embodiments, the predetermined thickness of the first doping type semiconductor layer 106 and the MQW layer 110 may be between about 0.05 μm and about 0.7 μm. In some alternative embodiments, the predetermined thickness of the first doping type semiconductor layer 106 and the MQW layer 110 may be between about 0.05 μm and about 0.5 μm. After operation 704, the second doping type semiconductor layer 108 of each LED unit 116 may be electrically isolated, and the first doping type semiconductor layer 106 and the MQW layer 110 of adjacent LED units 116 (such as LED units 116-1, 116-2, 116-3, 116-4) may be electrically connected.

[0042] 6F, a second etching operation may be performed to remove a portion of the first doping type semiconductor layer 106 and expose the contact 118. The second etching operation may be a dry etching or a wet etching operation. In the dry etching or wet etching operation, a hard mask (e.g., photoresist) may be formed on the second doping type semiconductor layer 108 and a portion of the first doping type semiconductor layer 106 by a photolithography process. Then, the uncovered portion of the first doping type semiconductor layer 106 is removed by a dry etching plasma or a wet etching solution to expose the contact 118.

[0043] 6G and operation 706 in FIG. 7 , a passivation layer 112 is formed over the second doping type semiconductor layer 108, the exposed first doping type semiconductor layer 106, and the exposed contact 118. In some embodiments, the passivation layer 112 may comprise SiO 2 , Al 2 O 3 , SiN, or other suitable materials for isolation and protection. In some embodiments, the passivation layer 112 may comprise polyimide, SU-8 photoresist, or other photopatternable polymer. In operation 708 in FIG. 7 , openings 120 and 122 are formed, as shown in FIG. 6G . Opening 120 exposes a portion of the second doping type semiconductor layer 108, and opening 122 exposes the contact 118. In some embodiments, operation 708 may be performed by a third etching operation to remove a portion of the passivation layer 112 to form openings 120 and 122. In some further embodiments, when the provided passivation layer 112 is formed by a photosensitive material (e.g., polyimide, SU-8 photoresist, or other photopatternable polymer), the operation of 708 may be performed by a photolithography operation to pattern the passivation layer 112, exposing the openings 120 and 122.

[0044] 6H and operation 710 of FIG. 7 , an electrode layer 114 is formed on the passivation layer 112 to cover the openings 120 and 122. The electrode layer 114 thus electrically connects the second doping type semiconductor layer 108 and the contacts 118, forming an electrical path for connecting the LED unit with a driving circuit on the first substrate 102. The driving circuit may control the voltage and current levels of the second doping type semiconductor layer 108 via the contacts 118 and the electrode layer 114. In some embodiments, the electrode layer 114 may include a conductive material such as indium tin oxide (ITO), Cr, Ti, Pt, Au, Al, Cu, Ge, or Ni.

[0045] The present disclosure provides an LED structure and a method for manufacturing the LED structure, in which functional epitaxy layers, such as the first doping-type semiconductor layer 106 and the second doping-type semiconductor layer 108, are partially patterned / etched to leave a thin continuous functional layer (such as the first doping-type semiconductor layer 106) while avoiding potential delamination. Furthermore, the present disclosure also provides another option for leaving an MQW layer on the first doping-type semiconductor layer 106. The manufacturing method introduced in the present disclosure can further reduce physical damage to the sidewalls of the functional mesa (such as the LED unit 116), reduce damage to the quantum well structure, which is the light-emitting region of the LED, and improve the optical and electrical properties of the functional mesa.

[0046] According to one embodiment of the present disclosure, an LED structure is disclosed. The LED structure includes a substrate and a plurality of LED units formed on the substrate. Each LED unit includes a bonding layer formed on the substrate, a first doping-type semiconductor layer formed on the bonding layer, a second doping-type semiconductor layer formed on the first doping-type semiconductor layer, a passivation layer formed on the second doping-type semiconductor layer and a portion of the first doping-type semiconductor layer, and an electrode layer formed on a portion of the passivation layer and in contact with the second doping-type semiconductor layer. The plurality of LED units includes a first LED unit and a second LED unit adjacent to the first LED unit. The first doping-type semiconductor layer of the first LED unit extends horizontally to the first doping-type semiconductor layer of the second LED unit adjacent to the first LED unit, and the first LED unit and the second LED unit are individually functioning LED units.

[0047] In some embodiments, the second doping type semiconductor layer of the first LED unit is electrically insulated from the second doping type semiconductor layer of the second LED unit. In some embodiments, each LED unit further includes a multiple quantum well (MQW) layer formed between the first doping type semiconductor layer and the second doping type semiconductor layer.

[0048] In some embodiments, the first doping type semiconductor layer is a p-type semiconductor layer and is the common anode of the first LED unit and the second LED unit. In some embodiments, the second doping type semiconductor layer is an n-type semiconductor layer and is the cathode of the first LED unit and the second LED unit.

[0049] In some embodiments, the substrate includes a driving circuit for driving the plurality of LED units, and in some embodiments, the electrode layer of each LED unit is connected to the driving circuit through an opening in the first doping type semiconductor layer.

[0050] According to another aspect of the present disclosure, an LED structure is disclosed. The LED structure includes a substrate and a plurality of LED units formed on the substrate. Each LED unit includes a pn diode layer formed on the substrate, a passivation layer formed on the pn diode layer, and an electrode layer formed on the passivation layer and in contact with the pn diode layer. The plurality of LED units includes a first LED unit and a second LED unit adjacent to the first LED unit. The first LED unit and the second LED unit have a common anode, and the first LED unit and the second LED unit are individually functioning LED units.

[0051] In some embodiments, the pn diode layer includes a p-doped layer, an n-doped layer, and a multiple quantum well (MQW) layer formed between the p-doped layer and the n-doped layer. In some embodiments, the p-doped layer is a common anode of the first LED unit and the second LED unit. In some embodiments, the n-doped layers of the first LED unit and the second LED unit are electrically insulated.

[0052] In some embodiments, each LED unit further includes a bonding layer formed between the substrate and the pn diode layer. In some embodiments, the substrate includes a drive circuit for driving the plurality of LED units. In some embodiments, the electrode layer of each LED unit is connected to the drive circuit through an opening in the pn diode layer.

[0053] According to a further aspect of the present disclosure, a method for fabricating an LED structure is disclosed. A semiconductor layer is formed on a first substrate. The semiconductor layer includes a first doping type semiconductor layer and a second doping type semiconductor layer. A first etching operation is performed to remove a portion of the second doping type semiconductor layer and expose a portion of the first doping type semiconductor layer. A passivation layer is formed on the second doping type semiconductor layer and the exposed first doping type semiconductor layer. A first opening is formed on the passivation layer. An electrode layer is formed on the passivation layer to cover the first opening and contact the second doping type semiconductor layer.

[0054] In some embodiments, performing the first etching operation further comprises removing a portion of the second doping-type semiconductor layer and exposing a portion of the first doping-type semiconductor layer until a predetermined thickness of the first doping-type semiconductor layer remains on the first substrate, the remaining first doping-type semiconductor layer extending horizontally across the plurality of LED units of the LED structure.

[0055] In some embodiments, forming the semiconductor layer on the first substrate further comprises bonding the semiconductor layer onto the first substrate via a bonding layer. In some embodiments, forming the semiconductor layer on the first substrate further comprises forming a drive circuit on the first substrate, forming the semiconductor layer on a second substrate, bonding the semiconductor layer onto the first substrate via a bonding layer, and removing the second substrate.

[0056] In some embodiments, forming a first opening on the passivation layer further comprises forming a second opening on the passivation layer to expose a contact of the drive circuit, and in some embodiments, forming an electrode layer on the passivation layer covering the first opening and in contact with the second doped type semiconductor layer further comprises forming an electrode layer on the passivation layer covering the first opening and the second opening to electrically connect the second doped type semiconductor layer to the contact of the drive circuit.

[0057] The foregoing description of specific embodiments may be readily modified and / or adapted for various applications. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein.

[0058] The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.

Claims

1. 1. A light emitting diode (LED) structure comprising: a substrate; and a plurality of LED units formed on the substrate, a bonding layer formed on the substrate, a first doped semiconductor layer formed on the bonding layer, the first doped semiconductor layer constituting a common electrode for the plurality of LED units; Each LED unit further includes: a second doping type semiconductor layer formed on the first doping type semiconductor layer; a multiple quantum well (MQW) layer formed between the first doping type semiconductor layer and the second doping type semiconductor layer; a contact portion formed on the substrate; an electrode layer in contact with the contact portion and the second doping type semiconductor layer; the first doping type semiconductor layer is located entirely on a side of the MQW layer closest to the substrate, the second doping type semiconductor layer constitutes the other electrode of the LED unit and is located entirely on a side of the MQW layer remote from the substrate, and the contact is configured to provide a driving voltage to the LED units via the electrode layer so that the LED units can function individually; a plurality of openings are provided in the first doping type semiconductor layer, each of the plurality of openings corresponding to one of the LED units and positioned between the LED unit and an LED unit adjacent to the LED unit to expose the contact portion, the electrode layer is connected to the contact portion through the opening, and the substrate includes a drive circuit configured to drive the LED unit corresponding to the contact portion through the contact portion, thereby driving each of the plurality of LED units to function individually.

2. 2. The light-emitting diode structure according to claim 1, wherein the second doping type semiconductor layer of any one of the plurality of LED units is electrically insulated from the second doping type semiconductor layer of an adjacent LED unit.

3. 2. The light emitting diode structure of claim 1, wherein the first doping type semiconductor layer is a p-type semiconductor layer and the second doping type semiconductor layer is an n-type semiconductor layer.

4. Each LED unit further includes a passivation layer formed on a portion of the first doping type semiconductor layer and the second doping type semiconductor layer; 2. The light-emitting diode structure of claim 1, wherein the electrode layer is formed on a portion of the passivation layer.

5. the bonding layer is made of a conductive material; and / or 2. The light emitting diode structure of claim 1, further comprising a conductive layer between the bonding layer and the first doped semiconductor layer, the conductive layer being in ohmic contact with the first doped semiconductor layer.

6. bonding a semiconductor layer onto a first substrate by a bonding layer, the semiconductor layer including a first doping type semiconductor layer and a second doping type semiconductor layer sequentially provided in a direction away from the bonding layer, and an MQW layer formed between the first doping type semiconductor layer and the second doping type semiconductor layer, the first doping type semiconductor layer being entirely located on a side of the MQW layer that is closer to the first substrate, and the second doping type semiconductor layer being entirely located on a side of the MQW layer that is remote from the first substrate; performing a first etching operation to remove a portion of the second doping type semiconductor layer to form a plurality of second doping type semiconductor mesas electrically isolated from one another and to expose a portion of the first doping type semiconductor layer between adjacent second doping type semiconductor mesas, wherein the first doping type semiconductor layer constitutes a common electrode of a plurality of LED units and each second doping type semiconductor mesa constitutes the other electrode of one LED unit; performing a second etching operation to form a plurality of openings in the exposed portion of the first doping type semiconductor layer to expose a plurality of contact portions in the first substrate, the plurality of openings corresponding to the plurality of contact portions one-to-one, the plurality of contact portions corresponding to the plurality of second doping type semiconductor mesas one-to-one, each opening of the plurality of openings being located between a corresponding second doping type semiconductor mesa and a second doping type semiconductor mesa adjacent to the corresponding second doping type semiconductor mesa, and the contact portion corresponding to the opening is configured to provide a voltage to an LED unit constituted by the corresponding second doping type semiconductor mesa; forming an electrode layer for each LED unit, the electrode layer simultaneously contacting a second doping type semiconductor mesa and a corresponding contact portion of the LED unit, thereby connecting the second doping type semiconductor mesa and the contact portion to enable the LED unit to function individually.

7. Before forming the electrode layer of each LED unit, the manufacturing method includes: forming a passivation layer over the semiconductor layer; 7. The method for fabricating a light-emitting diode structure of claim 6, further comprising: forming a first opening in the passivation layer overlying each second doping type semiconductor mesa to expose a portion of the second doping type semiconductor mesa; and forming a second opening in the passivation layer overlying each contact to expose the contact.

8. The first etching operation is performed by: thinning the exposed portion of the first doping type semiconductor layer to a predetermined thickness; The method of claim 6 , wherein the first doping type semiconductor layer of the predetermined thickness extends horizontally between the plurality of LED units.

9. Before bonding the semiconductor layer onto the first substrate by the bonding layer, the manufacturing method further comprises: forming a drive circuit comprising the plurality of contacts on the first substrate; forming the semiconductor layer on a second substrate; After bonding the semiconductor layer onto the first substrate by the bonding layer, the manufacturing method further comprises: The method of claim 6 further comprising removing the second substrate.

10. After forming the semiconductor layer on the second substrate, the manufacturing method further comprises: further comprising forming a conductive layer on the semiconductor layer, the conductive layer covering the first doping type semiconductor layer and making ohmic contact with the first doping type semiconductor layer; The bonding of the semiconductor layer onto the first substrate by the bonding layer may include: The method of claim 9 , further comprising bonding the semiconductor layer onto the first substrate via the bonding layer and the conductive layer.

11. The method according to claim 6 or 9, wherein the bonding layer is made of a conductive material.

12. 7. The method of claim 6, wherein the first doping type semiconductor layer is a p-type semiconductor layer and the second doping type semiconductor layer is an n-type semiconductor layer.

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