Pyramid Micro LED GaN drive circuit and device preparation method thereof

Abstract

The invention discloses a GaN drive circuit of a pyramid Micro LED and a device preparation method thereof, and belongs to the technical field of integrated circuit devices. The structure comprises micro-LED light-emitting units which are arranged in an array and a GaN HEMT driving circuit which is correspondingly connected with each micro-LED light-emitting unit. The GaN HEMT driving circuit comprises a plurality of GaN HEMT devices and a storage capacitor, and a current mirror structure and a fast switching network are adopted to realize constant current driving and fast response. The GaN HEMT device shares a substrate and an epitaxial layer, electrical isolation is achieved through ion implantation, and high performance is ensured through collaborative design of a source electrode, a drain electrode, a gate medium and the like. According to the invention, high switching frequency, low on-resistance and quick response are realized, and the driving performance and reliability of the micro-LED are remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuit device structures, and specifically relates to a GaN driving circuit for a pyramid Micro LED and a device preparation method thereof. Background Art

[0002] As demand for displays in smart electronic products continues to rise, display technology is constantly evolving, from liquid crystal displays (LCDs) and organic light-emitting diodes (OLEDs) to mini-LEDs and the now-emerging micro-LED technology. Micro-LED technology refers to a display technology composed of densely integrated arrays of tiny light-emitting diodes (LEDs). Each micro-LED pixel is typically less than 100 microns in size. As a next-generation display technology, micro-LEDs offer high brightness, high contrast, high resolution, low power consumption, and a long lifespan. They not only achieve self-luminescence but are also compatible with current large-scale array production processes. They are expected to gain attention and widespread application in areas such as AR / VR, automotive, commercial displays, and large-size, high-pixel displays. However, since each micro-LED pixel requires a separate driver circuit, and the pixel spacing is typically at the micron level, high requirements are placed on the compactness of the driver circuit and precise current control. Currently, silicon-based MOSFETs are primarily used as driver elements to control micro-LED light emission, but their poor turn-off control capabilities limit the micro-LED's light emission capability.

[0003] Because GaN-based HEMTs (High Electron Mobility Transistors) have significantly lower gate charge and output capacitance than traditional MOSFETs, they support higher switching frequencies. Furthermore, GaN's wide bandgap and high electron mobility (>2000 cm² / V·s) make them more suitable for compact micro-LED designs. Furthermore, GaN HEMTs offer advantages such as low on-resistance, minimal switching losses, and high device sensitivity, all of which are crucial for the fast response and high refresh rates of micro-LEDs. Summary of the Invention

[0004] The purpose of the present invention is to provide a GaN driving circuit for pyramid Micro LEDs and a device preparation method thereof, mainly to solve the problem that the existing silicon-based MOSFET as a driving element has poor shutdown control capability.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows: A GaN driving circuit for a pyramid Micro LED includes arrayed micro-LED light-emitting units and a GaN HEMT driving circuit corresponding to each micro-LED light-emitting unit. The GaN HEMT driving circuit includes a driving switch tube DT1, a reference switch tube DT2, fast switching tubes TS1-TS4, and a storage capacitor Cst. The gate of the driving switch tube DT1 is connected to the gate of the reference switch tube DT2 to form a current mirror structure, and the channel widths and lengths of the driving switch tube DT1 and the reference switch tube DT2 are proportional. The gate of the fast switching tube TS1 is connected to the gate of the fast switching tube TS2, one source and drain of the fast switching tube TS1 is connected to the gate of the driving switch tube DT1, the other source and drain of the fast switching tube TS1 is connected to a source and drain of the fast switching tube TS4 and connected to a circuit port Vdrv, the gate of the fast switching tube TS4 is connected to the circuit port EN, and the other source and drain of the fast switching tube TS4 is connected to the fast switching tube TS2. One source and drain of the fast switching transistor TS4 is connected to the n-electrode of the micro-LED light-emitting unit, the gate of the fast switching transistor TS3 is connected to the circuit port ELVDD, the other source and drain of the fast switching transistor TS3 is connected to a source and drain of the reference switching transistor DT2, the other source and drain of the reference switching transistor DT2 is connected to a source and drain of the driving switching transistor DT1 and then grounded, the other source and drain of the driving switching transistor DT1 is connected to a source and drain of the fast switching transistor TS2, the other source and drain of the fast switching transistor TS2 is connected to the circuit port Idrv, one end of the storage capacitor Cst is connected to the gate of the driving switching transistor DT1 and the other end is grounded, and the p-electrode of the micro-LED light-emitting unit is connected to the circuit port ELVDD; The driving switch tube DT1 controls the output current by adjusting its gate voltage Vg, providing a constant current drive to the micro-LED light-emitting unit, thereby controlling the stable emission of the micro-LED light-emitting unit; The fast switching transistors TS1 and TS2 are responsible for setting the gate voltage Vg to the target value in advance, acting as circuit switches; The fast switch TS3 is the main control switch of the micro-LED light-emitting unit and is used to control the shutdown of the micro-LED light-emitting unit. When the fast switch TS3 is turned on, the driving switch DT1 adjusts the voltage Vg of the storage capacitor Cst to achieve constant current driving of the micro-LED light-emitting unit, and the micro-LED light-emitting unit is illuminated. When the fast switch TS3 is turned off, the current of the micro-LED light-emitting unit is cut off, and the voltage Vg of the storage capacitor Cst regulates the driving switch DT1 to quickly extinguish the micro-LED light-emitting unit. The fast switching tube TS4 acts as a switching tube for the fast discharge channel of the micro-LED light-emitting unit. When the fast switching tube TS3 is turned off, the fast switching tube TS4 is quickly turned on, providing a low-resistance discharge channel for the parasitic capacitance of the micro-LED light-emitting unit, and eliminating the afterimage of the micro-LED light-emitting unit by quickly discharging the charge.

[0006] Furthermore, in the present invention, the driving switch transistor DT1, reference switch transistor DT2, and fast switching transistors TS1-TS4 of the GaN HEMT driving circuit all adopt GaN HEMT devices; multiple GaN HEMT devices share a substrate and epitaxial layer, and the epitaxial layer is located on the substrate; the epitaxial layer includes, from bottom to top, a nucleation layer, a buffer layer, a channel layer, a barrier layer, a cap layer, and a P-GaN layer; wherein, multiple GaN HEMT devices are formed by ion implantation of the epitaxial layer into the buffer layer to form multiple device isolation regions, wherein the device isolation region is defined as an inactive region, and the region outside the device isolation region is defined as an active region, and the inactive region surrounds the multiple active regions to achieve electrical isolation of the active regions perpendicular to the substrate and epitaxial layer; the P-GaN layer in the active region is etched to retain only the P-GaN layer in the gate region, so as to achieve the normally-off device requirement of the gate region; the region of the active region where the P-GaN layer is etched induces a two-dimensional electron gas on the side of the channel layer near the barrier layer interface due to a polarization effect.

[0007] Furthermore, in the present invention, the plurality of GaN HEMT devices further include source and drain electrodes, a first passivation layer, a gate dielectric, and a gate electrode formed in the active region; wherein the source and drain electrodes are formed by etching grooves to above the barrier layer and then depositing metal in the grooves; the first passivation layer is disposed above the side of the device away from the substrate; one of the regions in the passive region is defined as a capacitor region, wherein the first and second electrodes of the storage capacitor Cst are disposed on the first passivation layer in the capacitor region; the first passivation layer in the gate region is etched to above the P-GaN layer to form a gate groove, and then a gate dielectric is deposited on the side away from the substrate, and metal is deposited above the gate dielectric in the gate groove to form a gate; wherein the gate dielectrics in the capacitor region are respectively disposed between the first and second electrodes of the capacitor as a dielectric layer, together forming the storage capacitor Cst; an interconnect metal layer is formed by etching the first passivation layer above the source and drain electrodes and then depositing metal, and the corresponding electrodes of the plurality of GaN HEMT devices are interconnected via the interconnect metal layer to complete the electrical connection of the corresponding GaN HEMT devices in the GaN HEMT driving circuit.

[0008] Furthermore, in the present invention, a second passivation layer is also covered on the interconnect metal layer, and a protective layer is also covered on the second passivation layer. Electrode openings are formed by etching the protective layer above the electrode connected to the external drive circuit, and metal is evaporated to lead out the metal electrode of the GaN HEMT drive circuit.

[0009] Furthermore, in the present invention, the gate and interconnect metal layer are Schottky metal electrodes composed of one or more metal stacking structures of Ni / Au.

[0010] Furthermore, in the present invention, the micro-LED light-emitting unit includes an LED substrate and an LED epitaxial layer, the LED epitaxial layer is located on the LED substrate, and the LED epitaxial layer includes a dielectric layer and a vertical pyramid structure; the dielectric layer is deposited on the LED substrate, and a hole structure with a periodic array arrangement is opened to extend to the LED substrate; the vertical pyramid structure grows in the hole structure area of ​​the dielectric layer.

[0011] Furthermore, in the present invention, the vertical pyramid structure includes a pre-strained layer, a multi-quantum well light-emitting layer, a p-type AlGaN electron blocking layer, a p-type GaN layer, a transparent conductive layer, and a p-electrode layer stacked in sequence from bottom to top; after the vertical pyramid structure is grown, the LED substrate is thinned, and an n-electrode is formed on the side of the LED substrate away from the epitaxial layer using magnetron sputtering metal; the n-electrode is connected to the metal electrode of the GaN HEMT drive circuit.

[0012] Furthermore, in the present invention, the micro-LED light-emitting unit also includes a first bonding glue layer formed by wrapping the periphery of the vertical pyramid structure with bonding glue. After the first bonding glue layer is photolithographically opened, a p-electrode is drawn out on the p-electrode layer using magnetron sputtering metal. The p-electrode is connected to a power supply voltage ELVDD for providing the current required for the micro-LED light-emitting unit to emit light.

[0013] Furthermore, in the present invention, after the GaN HEMT driving circuit and the micro-LED light-emitting unit are metal-bonded, a second bonding adhesive layer is formed by filling the gap with bonding adhesive. The materials used for the second bonding adhesive layer and the first bonding adhesive layer are both one of organic silicone, epoxy resin, polycarbonate and polymethyl methacrylate.

[0014] Based on the GaN HEMT driving circuit structure of the micro-LED array described above, the present invention further provides a device preparation method for a GaN driving circuit of a pyramid Micro LED, comprising the following steps: S1, epitaxially growing a nucleation layer, a buffer layer, a channel layer, a barrier layer, a cap layer and a P-GaN layer on a substrate in sequence; S2, defining the active area and the passive area by ion implantation from the epitaxial layer into the buffer layer. The ion implantation area is the passive area, i.e., the device isolation area, thereby achieving electrical isolation of the active area; S3, selectively etching the P-GaN layer by ion etching, leaving only the P-GaN layer below the gate region, to realize an enhancement-mode HEMT device; S4, etching an ohmic groove to the barrier layer by an ion etching method, evaporating an ohmic electrode to the groove to form an ohmic electrode, and forming an ohmic contact source and drain electrode after high temperature annealing; S5, forming a first passivation layer by plasma enhanced chemical vapor deposition; S6, selectively etching the first passivation layer to the P-GaN layer in the gate region by an ion etching method to form a gate groove; S7, preparing a first electrode and a second electrode of the storage capacitor Cst by metal evaporation or magnetron sputtering; S8, forming a gate dielectric on the first passivation layer and the P-GaN layer by chemical vapor deposition; S9, forming a gate on the gate dielectric in the gate groove region by using a metal evaporation method; S10, etching the gate dielectric and the first passivation layer in the required source and drain opening regions by plasma enhanced etching, and then evaporating metal lead electrodes in the etched regions to form an interconnect metal layer; S11, preparing a second passivation layer by plasma enhanced chemical vapor deposition; S12, etching the second passivation layer above the opening by RIE for the electrode of the required opening, and then evaporating the interconnect metal layer; S13, preparing a protective layer by plasma enhanced chemical vapor deposition; S14, etching the protective layer above the electrode using RIE to form an opening, and evaporating an interconnect metal layer and a metal electrode bonded to the micro-LED light-emitting unit in the opening; S15, arranging a plurality of metal bumps on the metal electrode of the GaN HEMT driving circuit by a metal wire heating method, transferring the micro-LED light-emitting unit onto the metal electrode, melting the metal into a ball shape by heating, and completing metal bonding with the n-electrode of the micro-LED light-emitting unit; S16: Fill the gap between the micro-LED light-emitting unit and the GaN HEMT driving circuit with transparent insulating die-bonding adhesive to complete device fabrication.

[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The embodiment of the present invention uses four enhancement-mode GaN HEMT devices (TS1-TS4) to form a fast switching network in the driving circuit, and uses two enhancement-mode GaN HEMT devices placed back-to-back to form a current mirror driving structure (DT1-DT2). This can better utilize the excellent luminous characteristics and fast response capabilities of micro-LEDs, and effectively improve the optical crosstalk and afterimage problems between micro-LED pixels.

[0016] (2) The vertical pyramid structure micro-LED used in the present invention has the advantages of smaller size and better luminous performance compared with the traditional vertical structure. It can be prepared by the MOCVD method for mass production without the need for additional etching steps. This array structure provides a technical route for mass transfer technology.

[0017] (3) The GaN micro-LED driving circuit preparation method of the present invention is compatible with the current mainstream mass-produced CMOS process, and the GaN HEMT device can adapt to the small size requirements of micro-LED, which is more conducive to the compactness of the device, providing a solution for the practical application of micro-LED. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the equivalent circuit of the vertical pyramid structure micro-LED / GaN HEMT driving circuit in an embodiment of the present invention.

[0019] Figure 2 Schematic diagram of the front view of the device structure of the vertical pyramid structure micro-LED / GaN HEMT driving circuit in an embodiment of the present invention.

[0020] Figure 3 Schematic diagram of the rear view of the device structure of the vertical pyramid structure micro-LED / GaN HEMT driving circuit in an embodiment of the present invention.

[0021] Figure 4 Schematic diagram of the device structure of a vertical pyramid structure micro-LED / GaN HEMT driving circuit in an embodiment of the present invention.

[0022] The names corresponding to the reference numerals are: 100-micro-LED / GaN driver circuit; 200-GaN HEMT driver circuit; 201-substrate; 202-nucleation layer; 203-buffer layer; 204-channel layer; 205-barrier layer; 206-cap layer; 207-P-GaN layer; 209-isolation device; 210-source and drain; 211-first passivation layer; 212-gate dielectric; 213-gate; 214-interconnect metal layer; 215-storage capacitor Cst; 216-first electrode; 217-second electrode; 218-dielectric layer; 219-second passivation layer; 220-protection Layer; 221-metal electrode; 222-metal bump; 300-micro-LED light-emitting unit; 301-LED substrate; 302-dielectric layer; 303-vertical pyramid structure; 304-pre-strained layer; 305-multi-quantum well light-emitting layer; 306-P-type AlGaN electron blocking layer; 307-P-type GaN layer; 308-transparent conductive layer; 309-P electrode layer; 310-first solid crystal glue layer; 311-P electrode; 312-n electrode; 313-second solid crystal glue layer. DETAILED DESCRIPTION

[0023] The present invention will be further described below with reference to the accompanying drawings and examples. The embodiments of the present invention include but are not limited to the following examples.

[0024] The present invention provides a GaN driving circuit for a pyramid Micro LED and a device preparation method thereof. Figure 1 To the attached Figure 4 The specific implementation is described in detail. In this embodiment, the micro-LED array includes multiple micro-LED light-emitting units 300, each of which is connected to a GaN HEMT driver circuit to control its stable emission. The GaN HEMT driver circuit 200 structure includes multiple GaN HEMT devices (driving switch DT1, reference switch DT2, fast switching transistors TS1-TS4) and a storage capacitor Cst. By sharing the same substrate and epitaxial layer, the monolithic integrated driver circuit is achieved, achieving high switching frequency, low on-resistance, and fast response driving performance.

[0025] The equivalent circuit diagram of the micro-LED / GaN driving circuit 100 is shown in FIG. Figure 1As shown, the device comprises a GaN HEMT driver circuit 200 and a micro-LED light-emitting unit 300. The multiple GaN HEMT devices in the GaN HEMT driver circuit 200 are a driver switch DT1, a reference switch DT2, and four fast switches TS1-TS4. The driver switch DT1 and the reference switch DT2 together form a current mirror structure. The channel width-to-length ratio of the reference switch DT2 is proportional to that of the driver switch DT1. This design ensures precise control of the output current. Fast switching transistors TS1-TS4 form a fast switching network. These transistors have identical channel lengths and widths, and each has a distinct functional division of labor: Fast switching transistors TS1 and TS2 are responsible for setting the gate voltage Vg to the target value in advance, acting as circuit switches. Fast switching transistor TS3 serves as the master switch for the micro-LED light-emitting unit 300, controlling the lighting and extinguishing of the micro-LED. Fast switching transistor TS4 acts as the switch for the fast discharge channel, quickly turning on after fast switching transistor TS3 turns off, providing a low-resistance discharge path for the parasitic capacitance of the micro-LED light-emitting unit 300, thereby eliminating image sticking. One electrode of storage capacitor Cst is connected to the gate of driver switch DT1, and the other electrode is grounded. This serves to stabilize the voltage and adjust the gate voltage Vg to ensure stable illumination of the micro-LED light-emitting unit 300.

[0026] During operation, an external driver circuit applies voltage Vdrv to the TS1 switch, turning it on. The storage capacitor Cst stores charge and sets the DT1 gate voltage Vg. When Vg reaches the target value, the DT1 driver turns on. When a high level is applied to the circuit port EN, the fast switch TS3 turns on. At this point, the drive signal Rn turns off the fast switch TS4, allowing the micro-LED light-emitting unit 300 to conduct at a constant current and emit stable light. Because parasitic capacitance during LED shutdown can cause residual light, when the micro-LED light-emitting unit 300 needs to be turned off, the fast switch TS3 first cuts off the current. At this time, the TS4 switch turns on under the drive signal Rn, providing a low-impedance discharge path for the parasitic capacitance of the micro-LED light-emitting unit 300, quickly eliminating the residual light and causing it to extinguish quickly. Subsequently, the drive switch DT1 turns off, and the storage capacitor Cst stores charge, completing a single light-emitting task. The high switching frequency and low on-resistance characteristics of GaN HEMT devices significantly improve the stability and reliability of micro-LED light emission.

[0027] like Figures 2 to 4The figures show the front view, back view, and three-dimensional structure of the micro-LED / GaN driver circuit 100, respectively. It can be seen that the multiple GaN HEMT devices in the GaN HEMT driver circuit 200 share a common substrate 201 and epitaxial layers. The epitaxial layers, from bottom to top, include a nucleation layer 202, a buffer layer 203, a channel layer 204, a barrier layer 205, a cap layer 206, and a P-GaN layer 207. Ion implantation into the buffer layer 203 forms multiple device isolation regions 209, which are defined as inactive regions, while the areas outside the inactive regions are defined as active regions. The inactive regions surround the multiple active regions, achieving electrical isolation perpendicular to the substrate 201 and epitaxial layers. Within the active region, only the P-GaN layer 207 in the gate region remains, while other regions are removed by etching. Polarization effects are used to induce a two-dimensional electron gas 208 on the interface between the channel layer 204 and the barrier layer 205, thus achieving the normally-off device requirement. The source and drain electrodes 210 are formed into ohmic contacts by etching grooves above the barrier layer 205 and then depositing metal. Subsequently, a first passivation layer 211 is disposed on a side away from the substrate 201 .

[0028] The storage capacitor Cst 215 has a multi-finger cross structure, wherein a first electrode 216 and a second electrode 217 are disposed above the first passivation layer 211 in the passive region. The first electrode 216 and the second electrode 217 are disposed before the gate dielectric 212. After the gate dielectric is deposited, the gate dielectric 212 located between the first electrode 216 and the second electrode 217 serves as a dielectric layer 218, which together with the first electrode 216 and the second electrode 217 form the storage capacitor Cst 215. The first passivation layer 211 in the gate region is etched to form a gate recess above the P-GaN layer 207. A gate dielectric 212 is then deposited above the first passivation layer 211 and the P-GaN layer 207. A metal gate is then deposited above the gate dielectric 212 in the gate recess to form a gate 213. The source and drain electrodes 210 are formed by etching the first passivation layer 211 above them and then depositing metal to form an interconnect metal layer 214. This interconnect metal layer 214 electrically connects some of the GaN HEMT device electrodes in the GaN HEMT driver circuit 200. The first electrode 216 of the storage capacitor Cst is connected to the gate of the drive switch DT1, which provides constant current drive to the micro-LED. The second electrode 217 of the storage capacitor Cst is connected to the ground electrode of the GaN HEMT driver circuit 200.

[0029] To further protect the GaN HEMT driver circuit 200 and enhance its reliability, a second passivation layer 219 is placed over the interconnect metal layer 214. Etching and metal evaporation are performed on this second passivation layer 219 to form metal interconnects for the remaining electrodes of the GaN HEMT device. A protective layer 220 is also placed over the second passivation layer 219. After etching the protective layer 220 to form openings, metal is then deposited, leading to the metal electrodes 221 of the GaN HEMT driver circuit 200. The gate 213 and interconnect metal layer 214 utilize Schottky metal electrodes composed of a stacked structure of one or more metals, such as Ni / Au, to achieve good ohmic contact and electrical performance. The first passivation layer 211, the second passivation layer 219, and the protective layer 220 are preferably made of silicon nitride or silicon oxide, which exhibit excellent mechanical strength and chemical stability. This multi-layered protection design significantly enhances the long-term reliability of the device.

[0030] The design of the micro-LED light-emitting unit 300 has also been optimized. It comprises an LED substrate 301 and an LED epitaxial layer. The LED epitaxial layer, located on the LED substrate 301, comprises a dielectric layer 302 and a vertical pyramid structure 303. The dielectric layer 302 is deposited on the LED substrate 301 and has a periodically arranged array of holes extending into the LED substrate 301. The vertical pyramid structure 303 is grown within the holes of the dielectric layer 302 and comprises, from bottom to top, a pre-strained layer 304, a multi-quantum well light-emitting layer 305, a p-type AlGaN electron blocking layer 306, a p-type GaN layer 307, a transparent conductive layer 308, and a p-electrode layer 309. After the vertical pyramid micro-LED is grown, the LED substrate 301 is thinned, and magnetron sputtering is used to form an n-electrode 312 on the side of the LED substrate away from the epitaxial layer. This n-electrode 312 is connected to the metal electrode 221 of the GaN HEMT driver circuit. A first bonding adhesive layer 310 is formed around the vertical pyramid structure 303 using bonding adhesive. After photolithography holes are formed in the first bonding adhesive layer 310, magnetron sputtering is used to create a P-electrode 311 on the P-electrode layer 309. The P-electrode 311 is connected to the power supply voltage ELVDD, which provides the current required for the micro-LED light-emitting unit 300 to emit light. After metal bonding between the GaN HEMT driver circuit 200 and the micro-LED light-emitting unit 300, bonding adhesive is used to fill the gap, forming a second bonding adhesive layer 313. Both the first bonding adhesive layer 310 and the second bonding adhesive layer 313 are made of a material selected from silicone, epoxy resin, polycarbonate, or polymethyl methacrylate.

[0031] The present invention also provides a device manufacturing method. The manufacturing method mainly includes the preparation of the GaN HEMT driving circuit 200, the preparation of the micro-LED light-emitting unit 300, and the metal bonding between the two. The method mainly includes the following steps: 1. Preparation of GaN HEMT driving circuit 200: First, a nucleation layer 202, a buffer layer 203, a channel layer 204, a barrier layer 205, a cap layer 206, and a P-GaN layer 207 are epitaxially grown on a substrate 201. The epitaxial growth process utilizes metal organic chemical vapor deposition (PECVD), precisely controlling the growth temperature and gas flow rate to ensure the quality and interface characteristics of each layer. Subsequently, an ion implantation tool (IMP) is used to define the active and passive regions. By adjusting the ion implantation energy and dose into the buffer layer 203, a device isolation region 209 is formed. This high-resistance region achieves electrical isolation between the active and passive regions.

[0032] Next, the P-GaN layer 207 is selectively etched using an inductively coupled plasma (ICP) etcher, retaining only the P-GaN layer below the gate region to achieve an enhancement-mode GaN HEMT device. Etching accuracy and surface flatness are ensured by optimizing the ion etching process parameters. ICP is then used to further etch an ohmic groove down to the barrier layer 205. Metal is evaporated in the groove to form an ohmic electrode. After high-temperature annealing, the source and drain electrodes 210 are formed to form an ohmic contact with the barrier layer 205. The high-temperature annealing process is performed in a nitrogen atmosphere at a temperature between 800°C and 900°C to ensure the low resistance characteristics of the ohmic contact.

[0033] Subsequently, a first passivation layer 211 is deposited by PECVD, and a selective ion etching process is used to etch the first passivation layer 211 in the gate region down to the P-GaN layer 207. The ion etching process uses reactive ion etching (RIE), optimizing etching parameters to ensure etching accuracy and surface flatness. Next, the first electrode 216 and second electrode 217 of the storage capacitor Cst 215 are formed by metal evaporation or magnetron sputtering. The electrode material is preferably a titanium / aluminum / nickel / gold multilayer metal stack structure to improve the electrode's conductivity and adhesion.

[0034] The first passivation layer 211 in the gate region is etched to form a gate recess above the P-GaN layer 207. A gate dielectric 212 is then deposited above the device using PECVD. The gate dielectric 212 is preferably made of aluminum oxide or hafnium oxide, with a thickness of 10 to 50 nm to provide good insulation and interface properties. A gate is then formed in the gate recess using metal evaporation. The gate material is preferably a nickel / gold multilayer metal stack to improve gate conductivity and stability.

[0035] The gate dielectric 212 and first passivation layer 211 in the desired source and drain opening areas are etched using RIE (Reactive Ion Etching). Metal extraction electrodes are then evaporated in the etched areas to form the interconnect metal layer 214. The interconnect metal layer 214 is preferably a nickel / gold multilayer metal stack to improve conductivity and adhesion. Next, a second passivation layer 219 is deposited using PECVD to provide good insulation and mechanical strength.

[0036] For the electrodes with the desired openings, RIE is used to etch the second passivation layer 219 above the openings, followed by evaporation of the interconnect metal layer. The interconnect metal layer material is preferably a nickel / gold multilayer metal stack structure to improve the conductivity and adhesion of the interconnect layer. Next, PECVD is used to deposit a protective layer 220 to provide good mechanical strength and chemical stability. For the electrodes with the desired openings, RIE is used to etch the protective layer 220 above the openings, followed by evaporation of the interconnect metal layer and the metal electrode 221 bonded to the micro-LED, completing the preparation of the GaN HEMT driver circuit 200. The metal electrode 221 material is preferably a nickel / gold multilayer metal stack structure to improve the conductivity and adhesion of the electrode.

[0037] In this embodiment, the substrate 201 shared by the multiple GaN HEMT devices of the GaN HEMT driving circuit 200 is a silicon substrate, a sapphire substrate, or a GaN substrate. The distances between the source, drain, and gate of the multiple GaN HEMT devices are the same, that is, the switching transistors are all bidirectional conducting transistors.

[0038] In this embodiment, the source and drain electrodes are ohmic electrodes composed of a gold-containing metal stack of Ti / Al / Ni / Au or an ohmic electrode composed of a gold-free metal stack of TiN / Ti / Al / W, with an overall thickness of 200 to 500 nm. In this embodiment, the first passivation layer, the second passivation layer and the protective layer are made of one or more materials selected from SiO2 and Si3N4, and their thicknesses are 300-500 nm, 200-400 nm and 400-700 nm respectively.

[0039] In this embodiment, the storage capacitor Cst is a multi-finger cross-structure capacitor. The first and second electrode materials include copper (Cu), aluminum (Al), gold (Au), and titanium nitride (TiN), with a thickness of 50 to 500 nm. The dielectric layer material is the gate dielectric layer, made of one of SiO2 and Si3N4, with a thickness of 10 to 50 nm.

[0040] 2. Preparation of micro-LED light-emitting unit 300: First, a dielectric layer 302 is epitaxially grown on an LED substrate 301. After being masked with a photolithography mask, the dielectric layer is etched using ICP into a periodically arranged regular hexagonal pattern. Further dielectric layer growth is then performed to obtain an n-type GaN vertical pyramid structure 303, which serves as the epitaxial layer of the micro-LED. A pre-strained layer 304, a multi-quantum well light-emitting layer 305, a p-type AlGaN electron blocking layer 306, a p-type GaN layer 307, and a transparent conductive layer 308 are then grown on the epitaxial layer. The epitaxial growth process utilizes metal organic chemical vapor deposition.

[0041] Then, a transparent P-electrode layer 309 is prepared on top of the pyramid-structured transparent conductive layer, and epoxy resin is used as the first die-bonding adhesive layer 310 for encapsulation and curing. The epoxy resin layer above the top transparent P-electrode layer 309 is etched to expose a portion of the P-electrode layer 309 as a P-electrode 311 for connecting to an external driving power supply. A graphical method is then used to peel off the portion of the LED substrate 301 located below the pyramid structure, and the LED substrate is thinned to a certain thickness. Finally, an n-electrode 312 is prepared on one side of the LED substrate, completing the preparation of the vertical pyramid-structured micro-LED light-emitting unit 300.

[0042] In this embodiment, the LED substrate 301 used in the micro-LED light-emitting unit 300 is a sapphire substrate or a β-Ga2O3 substrate. The P-electrode layer 309 is made of a transparent conductive material, preferably ITO (indium tin oxide), with a thickness of 200 to 500 nm.

[0043] 3. Metal bonding between the GaN HEMT driver circuit 200 and the micro-LED light-emitting unit 300: A plurality of metal bumps 222 are arranged above the metal electrode 221 of the GaN HEMT driver circuit 200 using a wire heating method. The micro-LED light-emitting unit 300 is transferred onto the metal electrode 221. The metal is then melted into a spherical shape by heating, and a metal bond is formed with the n-electrode 312 of the micro-LED light-emitting unit. The metal bumps 222 are preferably made of gold or indium tin alloy to improve bonding strength and conductivity. Finally, the gap between the micro-LED light-emitting unit 300 and the GaN HEMT driver circuit 200 is filled with a transparent insulating die-bonding adhesive to complete the device fabrication. The die-bonding adhesive is preferably made of silicone or epoxy resin, which has good adhesion and transparency.

[0044] Figure 4A schematic diagram of the device structure of the vertical pyramid-structured micro-LED / GaN HEMT driver circuit of the present invention is shown. By utilizing GaN HEMT devices as the core driver element and combining them with the efficient integrated design of micro-LEDs, the present invention significantly improves the response speed and refresh rate of micro-LEDs. The shared substrate and epitaxial layer design enables high-density integration of multiple GaN HEMT devices, meeting the requirements of micro-LED arrays for compact driver circuits. The multiple protections of the passivation layer, protective layer, and die-bonding adhesive layer ensure the long-term stability and reliability of the device. The preparation method is highly compatible with existing semiconductor processes, amenable to large-scale production, and has high industrialization prospects.

[0045] The above embodiment is only one of the preferred embodiments of the present invention and should not be used to limit the scope of protection of the present invention. Any changes or modifications made to the main design concept and spirit of the present invention that have no substantive significance, as long as the technical problems solved by them are still consistent with the present invention, should be included in the scope of protection of the present invention. The above embodiment is only one of the preferred embodiments of the present invention and should not be used to limit the scope of protection of the present invention. Any changes or modifications made to the main design concept and spirit of the present invention that have no substantive significance, as long as the technical problems solved by them are still consistent with the present invention, should be included in the scope of protection of the present invention.

Claims

1. A GaN driving circuit for a pyramid Micro LED, characterized in that: The invention comprises micro-LED light-emitting units (300) arranged in an array and a GaN HEMT driving circuit (200) correspondingly connected to each micro-LED light-emitting unit (300); the GaN HEMT driving circuit (200) comprises a driving switch tube DT1, a reference switch tube DT2, fast switch tubes TS1-TS4, and a storage capacitor Cst; the gate of the driving switch tube DT1 and the gate of the reference switch tube DT2 are connected to form a current mirror structure, and the channel width and length of the driving switch tube DT1 and the reference switch tube DT2 are proportional; the gate of the fast switch tube TS1 is connected to the gate of the fast switch tube TS2, one source and drain of the fast switch tube TS1 is connected to the gate of the driving switch tube DT1, the other source and drain of the fast switch tube TS1 is connected to a source and drain of the fast switch tube TS4 and connected to a circuit port Vdrv, the gate of the fast switch tube TS4 is connected to the circuit port EN, and the other source and drain of the fast switch tube TS4 is connected to the fast switch A source and drain of the transistor TS4 is connected and connected to the n-electrode of the micro-LED light-emitting unit (300); the gate of the fast switch transistor TS3 is connected to the circuit port ELVDD; the other source and drain of the fast switch transistor TS3 is connected to a source and drain of the reference switch transistor DT2; the other source and drain of the reference switch transistor DT2 is connected to a source and drain of the driving switch transistor DT1 and then grounded; the other source and drain of the driving switch transistor DT1 is connected to a source and drain of the fast switch transistor TS2; the other source and drain of the fast switch transistor TS2 is connected to the circuit port Idrv; one end of the storage capacitor Cst is connected to the gate of the driving switch transistor DT1 and the other end is grounded; the p-electrode of the micro-LED light-emitting unit (300) is connected to the circuit port ELVDD; The driving switch tube DT1 controls the output current by adjusting its gate voltage Vg, providing a constant current drive to the micro-LED light-emitting unit (300), thereby controlling the stable light emission of the micro-LED light-emitting unit (300); The fast switching transistors TS1 and TS2 are responsible for setting the gate voltage Vg to the target value in advance, acting as circuit switches; The fast switch tube TS3 is a main control switch of the micro-LED light-emitting unit (300), and is used to control the switching off of the micro-LED light-emitting unit (300); when the fast switch tube TS3 is turned on, the driving switch tube DT1 adjusts the voltage Vg of the storage capacitor Cst to achieve constant current driving of the micro-LED light-emitting unit (300), and the micro-LED light-emitting unit (300) is lit; when the fast switch tube TS3 is turned off, the current of the micro-LED light-emitting unit (300) is cut off, and the micro-LED light-emitting unit (300) is quickly extinguished due to the regulation of the voltage Vg of the storage capacitor Cst on the driving switch tube DT1; The fast switching tube TS4 acts as a switching tube for a fast discharge channel of the micro-LED light-emitting unit (300); when the fast switching tube TS3 is turned off, the fast switching tube TS4 is quickly turned on, providing a low-resistance discharge channel for the parasitic capacitance of the micro-LED light-emitting unit (300), thereby eliminating the residual image of the micro-LED light-emitting unit (300) by quickly discharging the charge.

2. The GaN driving circuit for a pyramid Micro LED according to claim 1, characterized in that: The driving switch tube DT1, the reference switch tube DT2, and the fast switch tubes TS1-TS4 of the GaN HEMT driving circuit (200) all adopt GaN HEMT devices; a plurality of the GaN HEMT devices share a substrate (201) and an epitaxial layer, and the epitaxial layer is located on the substrate (201); the epitaxial layer comprises, from bottom to top, a nucleation layer (202), a buffer layer (203), a channel layer (204), a barrier layer (205), a cap layer (206), and a P-GaN layer (207); wherein, the plurality of the GaN The HEMT device forms a plurality of device isolation regions (209) by ion implantation of an epitaxial layer into a buffer layer (203), wherein the device isolation region (209) is defined as a passive region, and the region outside the device isolation region (209) is defined as an active region, wherein the passive region surrounds the plurality of active regions to achieve electrical isolation of the active regions perpendicular to the substrate (201) and the epitaxial layer; the P-GaN layer (207) in the active region is etched to retain only the P-GaN layer (207) in the gate region to achieve the normally-off device requirement of the gate region; and a region in the active region where the P-GaN layer (207) is etched induces a two-dimensional electron gas (208) on the side of the channel layer (204) close to the interface of the barrier layer (205) due to a polarization effect.

3. The GaN driving circuit for a pyramid Micro LED according to claim 2, wherein: The plurality of GaN HEMT devices further include a source / drain electrode (210), a first passivation layer (211), a gate dielectric (212), and a gate electrode (213) prepared in the active region; wherein the source / drain electrode (210) is obtained by etching a groove to above the barrier layer (205) and then depositing metal at the groove; the first passivation layer (211) is arranged above the side of the device away from the substrate (201); one of the regions in the passive region is defined as a capacitor region, and a first electrode (216) and a second electrode (217) of the capacitor are arranged on the first passivation layer (211) in the capacitor region, and the first passivation layer (211) in the gate region is etched to the P- A gate groove is formed above the GaN layer (207), and then a gate dielectric (212) is deposited on a side away from the substrate (201), and a metal is deposited above the gate dielectric (212) in the gate groove to form a gate (213); wherein the gate dielectric (212) in the capacitor region is respectively arranged between a first capacitor electrode (216) and a second capacitor electrode (217) to serve as a dielectric layer (218), and together form a storage capacitor Cst (215); an interconnection metal layer (214) is formed by etching the first passivation layer (211) above the source and drain electrodes (210), and then metal is deposited to form the interconnection metal layer (214), and the corresponding electrodes of the plurality of GaN HEMT devices are interconnected through the interconnection metal layer (214) to complete the electrical connection of the corresponding GaN HEMT devices in the GaN HEMT driving circuit (200).

4. The GaN driving circuit for a pyramid Micro LED according to claim 3, wherein: The interconnected metal layer (214) is further covered with a second passivation layer (219), and the second passivation layer (219) is further covered with a protective layer (220). Electrode openings are formed by etching the protective layer (220) above the electrode connected to the external drive circuit, and metal is evaporated to lead out the metal electrode of the GaN HEMT drive circuit (200).

5. The GaN driving circuit for a pyramid Micro LED according to claim 4, characterized in that: The gate (213) and the interconnected metal layer (214) are Schottky metal electrodes composed of one or more metal stacking structures of Ni / Au.

6. The GaN driving circuit for pyramid Micro LED according to claim 1, characterized in that: The micro-LED light-emitting unit (300) comprises an LED substrate (301) and an LED epitaxial layer, wherein the LED epitaxial layer is located on the LED substrate (301), and the LED epitaxial layer comprises a dielectric layer (302) and a vertical pyramid structure (303); the dielectric layer (302) is deposited on the LED substrate (301), and has a hole structure with a periodic array arrangement extending to the LED substrate (301); and the vertical pyramid structure (303) is grown in the hole structure region of the dielectric layer (302).

7. The GaN driving circuit for a pyramid Micro LED according to claim 6, wherein: The vertical pyramid structure (303) comprises a pre-strained layer (304), a multi-quantum well light-emitting layer (305), a P-type AlGaN electron blocking layer (306), a P-type GaN layer (307), a transparent conductive layer (308), and a p-electrode layer (309) stacked in sequence from bottom to top; after the vertical pyramid structure (303) is grown, the LED substrate (301) is thinned, and an n-electrode (312) is formed on the side of the LED substrate (301) away from the epitaxial layer by magnetron sputtering metal; the n-electrode (312) is connected to the metal electrode (221) of the GaN HEMT driving circuit (200).

8. The GaN driving circuit for a pyramid Micro LED according to claim 7, wherein: The micro-LED light-emitting unit (300) further includes a first solid crystal adhesive layer (310) formed by wrapping the periphery of the vertical pyramid structure (303) with solid crystal adhesive. After the first solid crystal adhesive layer (310) is photolithographically opened, a p-electrode (311) is drawn out on the p-electrode layer (309) using magnetron sputtering metal. The p-electrode (311) is connected to a power supply voltage ELVDD for providing a current required for the micro-LED light-emitting unit (300) to emit light.

9. The GaN driving circuit for pyramid Micro LEDs according to claim 8, wherein: After the GaN HEMT driving circuit and the micro-LED light-emitting unit are metal-bonded, a gap is filled with a solid crystal glue to form a second solid crystal glue layer (313), and the materials used for the second solid crystal glue layer (313) and the first solid crystal glue layer (310) are both one of organic silicone, epoxy resin, polycarbonate and polymethyl methacrylate.

10. A device method for a GaN driving circuit of a pyramid Micro LED, characterized in that: The following steps are involved: S1, epitaxially growing a nucleation layer (202), a buffer layer (203), a channel layer (204), a barrier layer (205), a cap layer (206), and a P-GaN layer (207) on a substrate (201) in sequence; S2, defining an active region and a passive region by implanting ions from an epitaxial layer into a buffer layer (203), wherein the ion implanted region is the passive region, i.e., the device isolation region (209), thereby achieving electrical isolation of the active region; S3, selectively etching the P-GaN layer (207) by an ion etching method, leaving only the P-GaN layer below the gate region, to realize an enhanced HEMT device; S4, etching an ohmic groove to the barrier layer (205) by an ion etching method, vapor-depositing an ohmic electrode to the groove to form an ohmic electrode, and forming an ohmic contact source-drain electrode after high-temperature annealing; S5, forming a first passivation layer (211) by plasma enhanced chemical vapor deposition; S6, selectively etching the first passivation layer (211) to the P-GaN layer (207) in the gate region by an ion etching method to form a gate groove; S7, preparing a first electrode (216) and a second electrode (217) of the storage capacitor Cst (215) by metal evaporation or magnetron sputtering; S8, preparing a gate dielectric (212) by chemical vapor deposition on the first passivation layer (211) and the P-GaN layer (207); S9, using a metal evaporation method to prepare a gate (213) above the gate dielectric (212) in the gate groove region; S10, etching the gate dielectric (212) and the first passivation layer (211) in the required source and drain opening regions by plasma enhanced etching, and then evaporating a metal lead-out electrode in the etched region to form an interconnect metal layer (214); S11, preparing a second passivation layer (219) by plasma enhanced chemical vapor deposition; S12, etching the second passivation layer (219) above the opening using RIE for the electrode of the desired opening, and then evaporating the interconnect metal layer; S13, preparing a protective layer (220) by plasma enhanced chemical vapor deposition; S14, etching the protective layer (220) above the electrode using RIE to form an opening, and evaporating an interconnecting metal layer and a metal electrode (221) bonded to the micro-LED light-emitting unit (300) in the opening; S15, arranging a plurality of metal bumps (222) above the metal electrode (221) of the GaN HEMT driving circuit (200) by a metal wire heating method, transferring the micro-LED light-emitting unit (300) onto the metal electrode (221), melting the metal into a spherical shape by a heating method, and completing metal bonding with the n-electrode (312) of the micro-LED light-emitting unit (300); S16, filling the gap between the micro-LED light-emitting unit (300) and the GaN HEMT driving circuit (200) with a transparent insulating solid crystal adhesive to complete device fabrication.

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