Pyramid micro led ga n driving circuit and device preparation method thereof

Abstract

The application discloses a GaN driving 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 array-arranged micro-LED light-emitting units and one GaN HEMT driving circuit connected in correspondence with each micro-LED light-emitting unit; the GaN HEMT driving circuit comprises a plurality of GaN HEMT devices and a storage capacitor, and adopts a current mirror structure and a fast switching network to realize constant current driving and fast response. The GaN HEMT devices share a substrate and an epitaxial layer, are electrically isolated through ion implantation, and are cooperatively designed in source-drain electrodes, gate dielectric and the like to ensure high performance. The application realizes high switching frequency, low on-resistance and fast response, and significantly improves the driving performance and reliability of the micro-LED.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of integrated circuit device structure, and particularly relates to a GaN driving circuit of a pyramid Micro LED and a device preparation method thereof. BACKGROUND

[0002] With the continuous improvement of people's display requirements for intelligent electronic products, display technology is constantly updating and developing, from liquid crystal display (LCD), organic light-emitting diode (OLED) to mini-LED, and then to the current emerging micro-LED technology. Among them, micro-LED technology refers to a display technology composed of a high-density integrated micro light-emitting diode (LED) array. The size of each micro-LED pixel is usually less than 100 microns. As a new generation of display technology, it has the characteristics of high brightness, high contrast, high resolution, low power consumption, long service life, etc. It not only has the advantages of self-luminous, but also can be compatible with the current large-scale array production process, and is expected to obtain attention and wide application in the fields of AR / VR, vehicle-mounted, commercial display, large-size high-pixel display screen, etc. However, since each pixel of micro-LED needs a separate driving circuit, and since the pixel spacing is generally microns, there are higher requirements for the compactness of the driving circuit and the accurate control of the current. At present, silicon-based MOSFET is mainly used as a driving element to control the light-emitting of micro-LED, and its turn-off control ability is poor, which limits the light-emitting ability of micro-LED.

[0003] Since the gate charge and output capacitance of GaN-based HEMT (High Electron Mobility Transistor) devices are significantly lower than those of traditional MOSFET devices, higher switching frequencies are supported, and the band gap and electron mobility of GaN are larger (>2000 cm² / V·s), which is more suitable for the compact structure design of micro-LED. In addition, GaN HEMT devices have the advantages of low on-resistance, small switching loss, high device sensitivity, etc., which are crucial for the fast response and high refresh rate of micro-LED. SUMMARY

[0004] The purpose of the present application is to provide a GaN driving circuit of a pyramid Micro LED and a device preparation method thereof, which mainly solves the problem of poor turn-off control ability of the existing silicon-based MOSFET as a driving element.

[0005] To achieve the above-mentioned purpose, the technical solutions adopted by the present application are as follows:

[0006] A GaN driving circuit of a pyramid Micro LED, comprising an array of micro-LED light-emitting units and one GaN HEMT driving circuit corresponding to each micro-LED light-emitting unit. The GaN HEMT driving circuit 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 driving switch tube DT1 and the reference switch tube DT2 have a proportional relationship in channel width and length. The gate of the fast switch tube TS1 is connected to the gate of the fast switch tube TS2, one source-drain electrode of the fast switch tube TS1 is connected to the gate of the driving switch tube DT1, the other source-drain electrode of the fast switch tube TS1 is connected to one source-drain electrode of the fast switch tube TS4 and connected to a circuit port Vdrv, the gate of the fast switch tube TS4 is connected to a circuit port EN, the other source-drain electrode of the fast switch tube TS4 is connected to one source-drain electrode of the fast switch tube TS4 and connected to the n electrode of the micro-LED light-emitting unit, the gate of the fast switch tube TS3 is connected to a circuit port ELVDD, the other source-drain electrode of the fast switch tube TS3 is connected to one source-drain electrode of the reference switch tube DT2, the other source-drain electrode of the reference switch tube DT2 is connected to one source-drain electrode of the driving switch tube DT1 and grounded, the other source-drain electrode of the driving switch tube DT1 is connected to one source-drain electrode of the fast switch tube TS2, the other source-drain electrode of the fast switch tube TS2 is connected to a circuit port Idrv, one end of the storage capacitor Cst is connected to the gate of the driving switch tube DT1 and the other end is grounded, and the p electrode of the micro-LED light-emitting unit is connected to a circuit port ELVDD.

[0007] The driving switch tube DT1 controls the output current by adjusting the gate voltage Vg, and provides constant current driving to the micro-LED light-emitting unit, thereby controlling the stable light emission of the micro-LED light-emitting unit.

[0008] The fast switch tubes TS1 and TS2 are responsible for setting the gate voltage Vg to a target value in advance, and act as circuit switches.

[0009] The fast switch tube TS3 is the main control switch of the micro-LED light-emitting unit, used to control the turn-off of the micro-LED light-emitting unit. When the fast switch tube TS3 is turned on, the driving switch tube DT1 realizes constant current driving of the micro-LED light-emitting unit through voltage Vg adjustment of the storage capacitor Cst, and the micro-LED light-emitting unit is lit. When the fast switch tube TS3 is turned off, the micro-LED light-emitting unit current is cut off, and the micro-LED light-emitting unit is quickly extinguished due to the regulation of the driving switch tube DT1 by the voltage Vg of the storage capacitor Cst.

[0010] The fast switch tube TS4 acts as a switch tube of a micro-LED light-emitting unit fast discharge channel, and the fast switch tube TS4 is rapidly turned on after the fast switch tube TS3 is turned off, so as to provide a low-resistance discharge channel for the parasitic capacitance of the micro-LED light-emitting unit, and the residual image of the micro-LED light-emitting unit is eliminated by rapidly discharging the charge.

[0011] Further, in the application, the driving switch tube DT1, the reference switch tube DT2 and the fast switch tubes TS1-TS4 of the GaN HEMT driving circuit all adopt GaN HEMT devices; a plurality of GaN HEMT devices share a substrate and an epitaxial layer, and the epitaxial layer is located on the substrate; the epitaxial layer sequentially includes a nucleation layer, a buffer layer, a channel layer, a barrier layer, a cap layer and a P-GaN layer from bottom to top; wherein a plurality of device isolation regions are formed by ion implantation of the epitaxial layer to the buffer layer, the device isolation region is defined as a passive region, the region outside the device isolation region is defined as an active region, the passive region surrounds the plurality of active regions, so as to realize electrical isolation of the active region perpendicular to the substrate and the epitaxial layer; the P-GaN layer of the active region is etched to only reserve the P-GaN layer of the gate region, so as to realize the requirement of the normally-off device of the gate region; the region where the P-GaN layer is etched in the active region induces a two-dimensional electron gas on the side of the channel layer close to the barrier layer interface due to the polarization effect.

[0012] Further, in the application, the plurality of GaN HEMT devices further include a source-drain electrode, a first passivation layer, a gate dielectric and a gate electrode prepared in the active region; wherein the source-drain electrode is obtained by etching a groove to above the barrier layer and then depositing metal at the groove; the first passivation layer is arranged above the side of the device away from the substrate; one region of the passive region is defined as a capacitor region, the first electrode and the second electrode of the storage capacitor Cst are arranged on the first passivation layer of the capacitor region, the first passivation layer of the gate region is etched to above the P-GaN layer to form a gate recess, and then the gate dielectric is deposited on the side away from the substrate, and the metal is deposited on the gate dielectric in the gate recess to form the gate electrode; wherein the gate dielectric of the capacitor region is arranged between the capacitor first electrode and the second electrode as a dielectric layer, and together constitutes the storage capacitor Cst; the interconnection metal layer is formed by etching the first passivation layer above the source-drain electrode and then depositing metal, and the corresponding electrodes of a plurality of GaN HEMT devices are interconnected through the interconnection metal layer to complete the electrical connection of the corresponding GaN HEMT devices in the GaN HEMT driving circuit.

[0013] Further, in the application, the interconnection metal layer is further covered with a second passivation layer, and the second passivation layer is further covered with a protective layer, and an electrode opening is formed by etching the protective layer above the electrode connected to the external driving circuit, and a metal electrode of the GaN HEMT driving circuit is led out after metal evaporation.

[0014] Further, in the application, the gate and the interconnection metal layer are a Schottky metal electrode composed of one or more metal stack structures of Ni / Au.

[0015] Further, in the application, 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 extends to the LED substrate; the vertical pyramid structure is grown in the hole structure region of the dielectric layer.

[0016] Further, in the application, the vertical pyramid structure includes, from bottom to top, a pre-strain 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; 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 by using magnetron sputtering metal; the n-electrode is connected to the metal electrode of the GaN HEMT driving circuit.

[0017] Further, in the application, the micro-LED light emitting unit further includes a first die bonding adhesive layer formed by wrapping the vertical pyramid structure with die bonding adhesive; after the first die bonding adhesive layer is photoetched, a p-electrode is led out on the p-electrode layer by using magnetron sputtering metal; the p-electrode is connected to a power supply voltage ELVDD for providing a current required for the micro-LED light emitting unit to emit light.

[0018] Further, in the application, after the GaN HEMT driving circuit and the micro-LED light emitting unit are metal bonded, a second die bonding adhesive layer is formed by filling the gap with die bonding adhesive; the materials used in the second die bonding adhesive layer and the first die bonding adhesive layer are one of silicone adhesive, epoxy resin, polycarbonate, and polymethyl methacrylate.

[0019] Based on the GaN HEMT driving circuit structure of the micro-LED array described above, the application further provides a device preparation method of a pyramid micro-LED GaN driving circuit, including the following steps:

[0020] S1, sequentially 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;

[0021] S2, defining active region and passive region by epitaxial layer ion implantation to buffer layer, ion implantation region is passive region, i.e. device isolation region, thereby realizing electrical isolation of active region;

[0022] S3, selectively etching P-GaN layer by ion etching method, only retaining P-GaN layer under gate region, thereby realizing enhancement mode HEMT device;

[0023] S4, etching ohmic recess to barrier layer by ion etching method, evaporating ohmic electrode to recess to form ohmic electrode, and forming ohmic contact source-drain electrode after high temperature annealing;

[0024] S5, forming first passivation layer by plasma enhanced chemical vapor deposition;

[0025] S6, selectively etching first passivation layer of gate region to P-GaN layer by ion etching method, thereby forming gate recess;

[0026] S7, preparing first electrode and second electrode of storage capacitor Cst by metal evaporation or magnetron sputtering method;

[0027] S8, preparing gate dielectric on first passivation layer and P-GaN layer by chemical vapor deposition;

[0028] S9, preparing gate on gate dielectric in gate recess region by metal evaporation method;

[0029] S10, etching gate dielectric and first passivation layer of required source-drain opening region by plasma enhanced etching, and then evaporating metal lead electrode in etched region to form interconnection metal layer;

[0030] S11, preparing second passivation layer by plasma enhanced chemical vapor deposition;

[0031] S12, etching second passivation layer above required opening electrode by RIE, and then evaporating interconnection metal layer;

[0032] S13, preparing protection layer by plasma enhanced chemical vapor deposition;

[0033] S14, etching protection layer above electrode by RIE to form opening, and evaporating interconnection metal layer and metal electrode bonded with micro-LED light emitting unit in the opening;

[0034] S15, a plurality of metal bumps are arranged on the metal electrode of the GaN HEMT driving circuit by the metal wire heating method, the micro-LED light emitting unit is transferred to the metal electrode, the metal is melted into a ball shape by the heating method, and the metal bonding with the n electrode of the micro-LED light emitting unit is completed;

[0035] S16, the gap after the bonding of the micro-LED light emitting unit and the GaN HEMT driving circuit is filled with transparent insulating die bonding glue, and the device manufacturing is completed.

[0036] Compared with the prior art, the present application has the following beneficial effects:

[0037] (1) The embodiment of the present application uses 4 enhanced GaN HEMT devices (TS1-TS4) to form a fast switching network in the driving circuit, and cooperates with 2 enhanced GaN HEMT devices placed back to back to form a current mirror driving structure (DT1-DT2), which can better play the excellent light emitting characteristics and fast response capability of micro-LED, and effectively improve the light crosstalk problem and residual image problem between micro-LED pixels.

[0038] (2) The vertical pyramid structure micro-LED adopted in the present application has the advantages of smaller size and better light emitting performance compared with the traditional vertical structure, can be prepared by the MOCVD method of quantitative production, and does not need additional etching steps, and such array structure provides a technical route for the mass transfer technology.

[0039] (3) The GaN micro-LED driving circuit preparation method of the present application is compatible with the current mainstream production CMOS process, and the GaN HEMT device can adapt to the requirement of small size of micro-LED, which is more conducive to the compactness of the device, and provides a solution for the practical application of micro-LED. DETAILED DESCRIPTION

[0040] Figure 1 It is an equivalent circuit schematic diagram of the vertical pyramid structure micro-LED / GaN HEMT driving circuit in the embodiment of the present application.

[0041] Figure 2 It is a front view schematic diagram of the device structure of the vertical pyramid structure micro-LED / GaN HEMT driving circuit in the embodiment of the present application.

[0042] Figure 3 It is a rear view schematic diagram of the device structure of the vertical pyramid structure micro-LED / GaN HEMT driving circuit in the embodiment of the present application.

[0043] Figure 4A device structure three-dimensional schematic view of a vertical pyramid structure micro-LED / GaN HEMT driving circuit in an embodiment of the present application.

[0044] Wherein, the name corresponding to the reference sign is:

[0045] 100-micro-LED / GaN driving circuit; 200-GaN HEMT driving circuit; 201-substrate; 202-nucleation layer; 203-buffer layer; 204-channel layer; 205-potential barrier layer; 206-capping layer; 207-P-GaN layer; 209-isolation device; 210-source-drain; 211-first passivation layer; 212-gate dielectric; 213-gate; 214-interconnected metal layer; 215-storage capacitor Cst; 216-first electrode; 217-second electrode; 218-dielectric layer; 219-second passivation layer; 220-protective 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-multiple 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 die-bonding adhesive layer; 311-P electrode; 312-n electrode; 313-second die-bonding adhesive layer. DETAILED DESCRIPTION

[0046] The present application will be further described in conjunction with the accompanying drawings and examples, and the modes of the present application include but are not limited to the following examples.

[0047] The present application provides a GaN driving circuit for pyramid micro LED and a device preparation method thereof, combined with the accompanying Figure 1 to the accompanying Figure 4 The specific embodiments are described in detail. In the present embodiment, the micro-LED array includes a plurality of micro-LED light-emitting units 300, and each micro-LED light-emitting unit 300 is connected to a GaN HEMT driving circuit to control its stable light emission. The GaN HEMT driving circuit 200 structure includes a plurality of GaN HEMT devices (driving switch tube DT1, reference switch tube DT2, fast switch tube TS1-TS4) and storage capacitor Cst, which completes a monolithic integrated driving circuit by sharing the same substrate and epitaxial layer, and has high switching frequency, low on-resistance and fast response driving performance.

[0048] The equivalent circuit schematic diagram of the micro-LED / GaN driving circuit 100 is as shown in FIG. 3. Figure 1As shown, the micro-LED light-emitting unit 300 is composed of a GaN HEMT driving circuit 200; wherein the plurality of GaN HEMT devices in the GaN HEMT driving circuit 200 are a driving switch tube DT1, a reference switch tube DT2, and four fast switch tubes TS1-TS4, wherein the driving switch tube DT1 and the reference switch tube DT2 jointly constitute a current mirror structure. The reference switch tube DT2 and the driving switch tube DT1 have a proportional relationship in terms of channel width-length ratio, which ensures accurate control of the output current. The fast switch tubes TS1-TS4 constitute a fast switch network, and the fast switch tubes TS1-TS4 have the same channel length and width, and each fast switch tube has a clear functional division: the fast switch tube TS1 and the fast switch tube TS2 are responsible for setting the gate voltage Vg to the target value in advance, and play the role of circuit switch; the fast switch tube TS3 serves as the main control switch of the micro-LED light-emitting unit 300, and controls the lighting and extinguishing of the micro-LED; and the fast switch tube TS4 acts as a switch tube of a fast discharge channel, and quickly turns on after the fast switch tube TS3 is turned off, thereby providing a low-impedance discharge path for the parasitic capacitance of the micro-LED light-emitting unit 300, and thus eliminating the residual image problem. One electrode of the storage capacitor Cst is connected to the gate of the driving switch tube DT1, and the other electrode is grounded, for stabilizing the voltage and adjusting the gate voltage Vg, thereby ensuring stable light emission of the micro-LED light-emitting unit 300.

[0049] In the specific operation process, the external driving circuit applies a voltage Vdrv to the TS1 switch tube, the TS1 switch tube is turned on, the storage capacitor Cst stores the electric charge and sets the DT1 gate voltage Vg, and when the Vg reaches the target value, the DT1 driving tube is turned on. When the circuit port EN applies a high level, the fast switch tube TS3 is turned on, at this time the driving signal Rn makes the fast switch tube TS4 closed, and the micro-LED light-emitting unit 300 is turned on under constant current and emits light stably; since the existence of parasitic capacitance during the LED closing process will cause the light-emitting residual image, when the micro-LED light-emitting unit 300 needs to be turned off, the fast switch tube TS3 first cuts off the current, at this time the TS4 switch tube is turned on under the driving signal Rn, thereby providing a low-impedance discharge path for the parasitic capacitance of the micro-LED light-emitting unit 300, and thus quickly eliminating the residual image and making it quickly extinguish; then, the driving switch tube DT1 is turned off, and the storage capacitor Cst stores the electric charge, thereby completing a light-emitting task. Due to the high switching frequency and low on-resistance characteristics of the GaN HEMT device, the light-emitting stability and reliability of the micro-LED are significantly improved.

[0050] As Figures 2 to 4As shown, the front view, rear view and perspective structural schematic diagram of the micro-LED / GaN driving circuit 100 are shown respectively; it can be seen that the plurality of GaN HEMT devices of the GaN HEMT driving circuit 200 share one substrate 201 and an epitaxial layer, and the epitaxial layer includes, 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 in sequence. A plurality of device isolation regions 209 are formed by ion implantation into the buffer layer 203, and these regions are defined as passive regions, while the regions outside the passive regions are defined as active regions. The passive regions surround the plurality of active regions, achieving electrical isolation perpendicular to the substrate 201 and the epitaxial layer. In the active region, only the P-GaN layer 207 of the gate region is reserved, and other regions are removed by etching, and a two-dimensional electron gas 208 is induced on the side of the channel layer 204 close to the barrier layer 205 interface by using the polarization effect, thereby achieving the requirements of the normally-off device. The source-drain electrode 210 is formed by etching a groove to the barrier layer 205 and then depositing metal to form an ohmic contact, and then the first passivation layer 211 is disposed away from the substrate 201.

[0051] The storage capacitor Cst 215 is a multi-finger cross structure, and the first electrode 216 and the second electrode 217 are disposed above the first passivation layer 211 of the passive region, and the first electrode 216 and the second electrode 217 are disposed before the gate dielectric 212, and the gate dielectric 212 between the first electrode 216 and the second electrode 217 after deposition as a dielectric layer 218, together with the first electrode 216 and the second electrode 217, to form the storage capacitor Cst 215;

[0052] The first passivation layer 211 of the gate region is etched to the P-GaN layer 207 to form a gate recess, and then the gate dielectric 212 is deposited above the first passivation layer 211 and the P-GaN layer 207, and the metal is deposited above the gate dielectric 212 in the gate recess to form the gate 213. The source-drain electrode 210 is formed by etching the first passivation layer 211 above and then depositing metal to form an interconnection metal layer 214, and the electrical connection of the electrodes of part of the GaN HEMT devices of the GaN HEMT driving circuit 200 is completed through the interconnection metal layer 214. The first electrode 216 of the storage capacitor Cst is connected to the gate of the driving switch tube DT1 responsible for providing constant current driving to the micro-LED, and the second electrode 217 of the storage capacitor Cst is connected to the ground electrode of the GaN HEMT driving circuit 200.

[0053] In order to further protect the GaN HEMT driving circuit 200 and improve its reliability, a second passivation layer 219 is covered above the interconnection metal layer 214, and the metal interconnection of the other part of the electrode of the GaN HEMT device is completed by etching and metal evaporation of the second passivation layer 219. The second passivation layer 219 is also covered with a protective layer 220, and the metal electrode 221 of the GaN HEMT driving circuit 200 is led out after the protective layer 220 is etched to form an opening for evaporation of metal. The gate electrode 213 and the interconnection metal layer 214 adopt a Schottky metal electrode composed of one or more metal stack structures of Ni / Au to achieve good ohmic contact and electrical performance. The materials of the first passivation layer 211, the second passivation layer 219 and the protective layer 220 are preferably silicon nitride or silicon oxide, which have excellent mechanical strength and chemical stability. This multiple protection design significantly improves the long-term reliability of the device.

[0054] The design of the micro-LED light emitting unit 300 is also optimized, which includes an LED substrate 301 and an LED epitaxial layer. The LED epitaxial layer is located above the LED substrate 301 and includes a dielectric layer 302 and a vertical pyramid structure 303. The dielectric layer 302 is deposited on the LED substrate 301 and has a periodic array of hole structures extending to the LED substrate 301. The vertical pyramid structure 303 is grown in the hole structure region of the dielectric layer 302 and includes, 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 growth of the vertical pyramid structure micro-LED, the LED substrate 301 is thinned, and the n electrode 312 is formed on the side of the LED substrate away from the epitaxial layer by using magnetron sputtering metal, and the n electrode 312 is connected to the metal electrode 221 of the GaN HEMT driving circuit. The first die bonding glue layer 310 is formed by wrapping the vertical pyramid structure 303 with die bonding glue, and the P electrode 311 is led out on the P electrode layer 309 after the first die bonding glue layer 310 is photoetched, and the P electrode 311 is connected to the power voltage ELVDD for providing the current required for the micro-LED light emitting unit 300 to emit light. After the metal bonding of the GaN HEMT driving circuit 200 and the micro-LED light emitting unit 300, the second die bonding glue layer 313 is formed by filling the gap with die bonding glue, and the materials used in the first die bonding glue layer 310 and the second die bonding glue layer 313 are one of organic silicone glue, epoxy resin, polycarbonate or polymethyl methacrylate.

[0055] The embodiment of the present application also provides a device preparation method, which 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 of the two, mainly including the following steps:

[0056] 1. Preparation of GaN HEMT driving circuit 200:

[0057] 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 the substrate 201 in sequence. The epitaxial growth process adopts a metal organic chemical vapor deposition (PECVD) method, and by precisely controlling the growth temperature and gas flow, the quality and interface characteristics of each layer of material are ensured. Subsequently, the active area and the passive area are defined by an ion implantation device (IMP) method, and by adjusting the ion implantation energy and dose, a device isolation region 209 is formed in the buffer layer 203, which is a high resistance region, thereby achieving electrical isolation between the active area and the passive area.

[0058] Next, the P-GaN layer 207 is selectively etched by an inductively coupled plasma etching device (ICP), only retaining the P-GaN layer under the gate region, to realize an enhancement mode GaN HEMT device. By optimizing the ion etching process parameters, the etching precision and surface flatness are ensured. Then, the ICP is used to etch an ohmic recess to the barrier layer 205, and a metal is evaporated in the recess to form an ohmic electrode, and after high-temperature annealing, the source and drain 210 are obtained, which form ohmic contact with the barrier layer 205. The high-temperature annealing process is carried out in a nitrogen atmosphere, and the annealing temperature is set to between 800°C and 900°C, to ensure the low resistance characteristics of the ohmic contact.

[0059] Subsequently, the first passivation layer 211 is deposited by PECVD, and the first passivation layer 211 in the gate region is etched to the P-GaN layer 207 by a selective ion etching process. The ion etching process adopts a reactive ion etching technology (RIE), and by optimizing the etching parameters, the etching precision and surface flatness are ensured. Then, the first electrode 216 and the second electrode 217 of the storage capacitor Cst 215 are prepared by metal evaporation or magnetron sputtering method. The electrode material is preferably a titanium / aluminum / nickel / gold multilayer metal stack structure, to improve the conductivity and adhesion of the electrode.

[0060] The first passivation layer 211 in the gate region is etched to the P-GaN layer 207 to form a gate recess, and then the gate dielectric 212 is deposited on the device by PECVD. The gate dielectric 212 material is preferably aluminum oxide or hafnium oxide, and the deposition thickness is 10 nm to 50 nm, to provide good insulation performance and interface characteristics. Subsequently, the gate is prepared in the gate recess region by a metal evaporation method, and the gate material is preferably a nickel / gold multilayer metal stack structure, to improve the conductivity and stability of the gate.

[0061] The gate dielectric 212 and the first passivation layer 211 in the opening area of the source and drain electrode are etched by RIE (reactive ion etching), and then a metal lead electrode is evaporated in the etched area to form an interconnection metal layer 214. The material of the interconnection metal layer 214 is preferably a nickel / gold multilayer metal stack structure to improve the conductivity and adhesion of the interconnection layer. Then, a second passivation layer 219 is deposited by PECVD to provide good insulation performance and mechanical strength.

[0062] The second passivation layer 219 above the opening is etched by RIE for the electrode in the opening, and then an interconnection metal layer is evaporated. The material of the interconnection metal layer is preferably a nickel / gold multilayer metal stack structure to improve the conductivity and adhesion of the interconnection layer. Then, a protective layer 220 is deposited by PECVD to provide good mechanical strength and chemical stability. The protective layer 220 above the opening is etched by RIE for the electrode in the opening, and then an interconnection metal layer and a metal electrode 221 bonded with the micro-LED are evaporated to complete the preparation of the GaN HEMT driving circuit 200. The material of the metal electrode 221 is preferably a nickel / gold multilayer metal stack structure to improve the conductivity and adhesion of the electrode.

[0063] In this embodiment, the substrate 201 shared by the plurality of GaN HEMT devices of the GaN HEMT driving circuit 200 is one of a silicon substrate, a sapphire substrate or a GaN substrate. The distances of the source and drain electrodes and the gate of the plurality of GaN HEMT devices are the same, i.e., the switching tubes are all bidirectional conduction transistors.

[0064] In this embodiment, the source and drain electrodes are ohmic electrodes composed of a gold metal stack of Ti / Al / Ni / Au or an ohmic electrode composed of a non-gold metal stack of TiN / Ti / Al / W, with a total thickness of 200-500 nm.

[0065] In this embodiment, the first passivation layer, the second passivation layer and the protective layer are one or more materials of SiO2 and Si3N4, with thicknesses of 300-500 nm, 200-400 nm and 400-700 nm, respectively.

[0066] In this embodiment, the storage capacitor Cst is a multi-finger cross-structure capacitor, and the first and second electrode materials include copper (Cu), aluminum (Al), gold (Au) and titanium nitride (TiN) materials, with a thickness of 50-500 nm. The dielectric layer material is the gate dielectric layer, which includes one of SiO2 and Si3N4, with a thickness of 10-50 nm.

[0067] 2. Preparation of the micro-LED light-emitting unit 300:

[0068] First, epitaxially grow a medium layer 302 on the LED substrate 301, and etch the medium layer into a regular hexagon with a periodic array by ICP etching after using a photoetching mask, then continue to grow the medium layer to obtain an n-type GaN vertical pyramid structure 303 as the epitaxial layer of the micro-LED, and continue to grow a pre-strain 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 on the epitaxial layer. The epitaxial growth process adopts a metal organic chemical vapor deposition method.

[0069] Then, prepare a transparent P-electrode layer 309 on the top of the pyramid structure transparent conductive layer, use epoxy resin as a first die bonding adhesive layer 310 for encapsulation and curing, etch the epoxy resin layer above the top transparent P-electrode layer 309 to expose part of the P-electrode layer 309 as a P-electrode 311 for connecting an external driving power supply, and then use a patterning method to peel off part of the LED substrate 301 below the pyramid structure, thin the LED substrate to a certain thickness, and finally prepare an n-electrode 312 on one side of the LED substrate to complete the preparation of the vertical pyramid structure micro-LED light-emitting unit 300.

[0070] In this embodiment, the LED substrate 301 used by the micro-LED light-emitting unit 300 is a sapphire substrate or a β-Ga2O3 substrate. The material of the P-electrode layer 309 is a transparent conductive material, and the transparent conductive material is preferably ITO (indium tin oxide) with a thickness of 200-500 nm.

[0071] 3. Metal bonding of the GaN HEMT driving circuit 200 and the micro-LED light-emitting unit 300:

[0072] Arrange a plurality of metal bumps 222 on the metal electrode 221 of the GaN HEMT driving circuit 200 by a metal wire heating method, transfer the micro-LED light-emitting unit 300 to the metal electrode 221, and make the metal melt into a spherical shape by a heating method to complete the metal bonding with the n-electrode 312 of the micro-LED light-emitting unit. The material of the metal bump 222 is preferably gold or indium tin alloy to improve the bonding strength and conductivity. Finally, fill the gap after the bonding of the micro-LED light-emitting unit 300 and the GaN HEMT driving circuit 200 with transparent insulating die bonding adhesive to complete the device preparation. The die bonding adhesive material is preferably organic silicone or epoxy resin, which has good adhesion and transparency.

[0073] Figure 4A device structure perspective diagram of a vertical pyramid structure micro-LED / GaN HEMT driving circuit of the application is shown. The application significantly improves the response speed and refresh rate of the micro-LED by taking the GaN HEMT device as the core driving element and combining the high-efficiency integrated design of the micro-LED. The design of the shared substrate and the epitaxial layer realizes the high-density integration of multiple GaN HEMT devices, meeting the needs of the micro-LED array for compact driving circuits. The multiple protection of the passivation layer, the protective layer and the die bonding glue layer ensures the long-term stability and reliability of the device. The preparation method is highly compatible with the existing semiconductor process, easy to mass-produce, and has high industrialization prospects.

[0074] The above examples are only one of the preferred embodiments of the application and should not be used to limit the protection scope of the application, but any modification or embellishment made in the main design idea and spirit of the application without substantial meaning should be included in the protection scope of the application. The above examples are only one of the preferred embodiments of the application and should not be used to limit the protection scope of the application, but any modification or embellishment made in the main design idea and spirit of the application without substantial meaning should be included in the protection scope of the application.

Claims

1. A GaN driving circuit of a pyramid Micro LED, characterized in that, The application relates to a GaN HEMT driving circuit (200) and a micro-LED light-emitting unit (300) arranged in an array, wherein 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 driving switch tube DT1 and the reference switch tube DT2 are in proportional relationship in channel width and length; the gate of the fast switch tube TS1 is connected with the gate of the fast switch tube TS2; one source-drain electrode of the fast switch tube TS1 is connected with the gate of the driving switch tube DT1; the other source-drain electrode of the fast switch tube TS1 is connected with one source-drain electrode of the fast switch tube TS4 and connected with a circuit port Vdrv; the gate of the fast switch tube TS4 is connected with a circuit port EN; the other source-drain electrode of the fast switch tube TS4 is connected with one source-drain electrode of the fast switch tube TS3 and connected with the n electrode of the micro-LED light-emitting unit (300); the gate of the fast switch tube TS3 is connected with a circuit port ELVDD; the other source-drain electrode of the fast switch tube TS3 is connected with one source-drain electrode of the reference switch tube DT2; the other source-drain electrode of the reference switch tube DT2 is connected with one source-drain electrode of the driving switch tube DT1 and connected with the ground; the other source-drain electrode of the driving switch tube DT1 is connected with one source-drain electrode of the fast switch tube TS2; the other source-drain electrode of the fast switch tube TS2 is connected with a circuit port Idrv; one end of the storage capacitor Cst is connected with the gate of the driving switch tube DT1 and the other end is connected with the ground; and the p electrode of the micro-LED light-emitting unit (300) is connected with the circuit port ELVDD. The driving switch tube DT1 controls the output current by adjusting the gate voltage Vg, provides constant current driving for the micro-LED light-emitting unit (300), and controls the stable light emission of the micro-LED light-emitting unit (300). The fast switch tubes TS1 and TS2 are responsible for setting the gate voltage Vg to a target value in advance and play the role of circuit switch. The fast switch tube TS3 is the main control switch of the micro-LED light-emitting unit (300) and is used for controlling the turn-off of the micro-LED light-emitting unit (300); when the fast switch tube TS3 is turned on, the driving switch tube DT1 realizes the constant current driving of the micro-LED light-emitting unit (300) through the voltage Vg adjustment of the storage capacitor Cst, and the micro-LED light-emitting unit (300) is lighted up; 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 switch tube TS4 acts as a switch tube of a micro-LED light-emitting unit (300) fast discharge channel, and the fast switch tube TS4 is rapidly turned on after the fast switch tube TS3 is turned off, so as to provide a low-resistance discharge channel for the parasitic capacitor of the micro-LED light-emitting unit (300), and the residual image of the micro-LED light-emitting unit (300) is eliminated by rapidly discharging the charge. 2.The GaN driving circuit of a pyramid Micro LED of claim 1, wherein, The driving switch tube DT1, the reference switch tube DT2 and the fast switch tubes TS1-TS4 of the GaN HEMT driving circuit (200) are all GaN HEMT devices; a plurality of GaN HEMT devices share a substrate (201) and an epitaxial layer, and the epitaxial layer is located on the substrate (201); the epitaxial layer includes, 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 a plurality of device isolation regions (209) are formed by ion implantation of the epitaxial layer to the buffer layer (203), the device isolation region (209) is defined as a passive region, the region outside the device isolation region (209) is defined as an active region, the passive region surrounds the plurality of active regions, so as to realize electrical isolation of the active region perpendicular to the substrate (201) and the epitaxial layer; the P-GaN layer (207) of the active region is etched to retain only the P-GaN layer (207) of the gate region, so as to realize the requirement of the normally-off device of the gate region; the 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 barrier layer (205) interface due to the polarization effect. 3.The GaN driving circuit of a pyramid Micro LED of claim 2, wherein, The plurality of GaN HEMT devices further comprise 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 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 of the passive region is defined as a capacitor region, the first electrode (216) and the second electrode (217) of the capacitor are arranged on the first passivation layer (211) in the capacitor region, the first passivation layer (211) in the gate region is etched to above the P-GaN layer (207) to form a gate recess, and then the gate dielectric (212) is deposited on the side away from the substrate (201), and the gate electrode (213) is formed by depositing metal above the gate dielectric (212) in the gate recess; wherein the gate dielectric (212) in the capacitor region is arranged between the first electrode (216) and the second electrode (217) to act as a dielectric layer (218), and together constitutes a storage capacitor Cst (215); the interconnection metal layer (214) is formed by etching the first passivation layer (211) above the source-drain electrode (210) and then depositing metal, 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 of a pyramid Micro LED of claim 3, wherein, The interconnection metal layer (214) is further covered by a second passivation layer (219), and the second passivation layer (219) is further covered by a protective layer (220), the protective layer (220) above the electrode connected to the external driving circuit is etched to form an electrode opening, and a metal electrode of the GaN HEMT driving circuit (200) is led out after metal evaporation. 5.The GaN driving circuit of a pyramid Micro LED of claim 4, wherein, The gate electrode (213) and the interconnection metal layer (214) are Schottky metal electrodes composed of one or more metal stack structures of Ni / Au. 6.The GaN driving circuit of a pyramid Micro LED of claim 1, wherein, The micro-LED light-emitting unit (300) comprises an LED substrate (301) and an LED epitaxial layer, the LED epitaxial layer is located above 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 a hole structure with a periodic array arrangement extends to the LED substrate (301); the vertical pyramid structure (303) is grown in the hole structure region of the dielectric layer (302). 7.The GaN driving circuit of a pyramid Micro LED of claim 6, wherein, The vertical pyramid structure (303) comprises, from bottom to top, a pre-strain 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) arranged in sequence; after the vertical pyramid structure (303) is grown, the LED substrate (301) is thinned, and an n-electrode (312) formed by magnetron sputtering metal is used on the side of the LED substrate (301) away from the epitaxial layer; the n-electrode (312) is connected to the metal electrode (221) of the GaN HEMT driving circuit (200). 8.The GaN driving circuit of a pyramid Micro LED of claim 7, wherein, The micro-LED light-emitting unit (300) further comprises a first die-bonding adhesive layer (310) formed by wrapping the vertical pyramid structure (303) with die-bonding adhesive; after the first die-bonding adhesive layer (310) is photoetched to form an opening, a p-electrode (311) is introduced on the p-electrode layer (309) by 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 of a pyramid Micro LED of claim 8, wherein, After the GaN HEMT driving circuit and the micro-LED light-emitting unit are metal-bonded, a second die-bonding adhesive layer (313) is formed by filling the gap with die-bonding adhesive; the materials used in the first and second die-bonding adhesive layers (310) and (313) are one of silicone adhesive, epoxy resin, polycarbonate, and polymethyl methacrylate.

10. A device method of GaN driving circuit of pyramid Micro LED, characterized in that, The method comprises the following steps: S1, sequentially 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); S2, defining an active region and a passive region by ion implantation into the buffer layer (203) through an epitaxial layer, the ion implantation region being the passive region, i.e., a device isolation region (209), thereby achieving electrical isolation of the active region; S3, selectively etching the P-GaN layer (207) by ion etching, only leaving the P-GaN layer under the gate region, to form an enhancement-mode HEMT device; S4, etching an ohmic recess to the barrier layer (205) by ion etching, and evaporating an ohmic electrode to the recess 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 ion etching to form a gate recess; S7, preparing a first electrode (216) and a second electrode (217) of a storage capacitor Cst (215) by metal evaporation or magnetron sputtering; S8, preparing a gate dielectric (212) on the first passivation layer (211) and the P-GaN layer (207) by chemical vapor deposition; S9, preparing a gate (213) on the gate dielectric (212) in the gate recess region by metal evaporation; S10, etching the gate dielectric (212) and the first passivation layer (211) of the desired source-drain opening area by plasma-enhanced etching, and then evaporating a metal lead electrode on the etched area to form an interconnection metal layer (214); S11, preparing a second passivation layer (219) by using plasma-enhanced chemical vapor deposition; S12, etching the second passivation layer (219) above the opening by RIE, and then evaporating an interconnection metal layer on the opening; S13, preparing a protective layer (220) by using plasma-enhanced chemical vapor deposition; S14, etching the protective layer (220) above the electrode by RIE to form an opening, and then evaporating an interconnection metal layer and a metal electrode (221) bonded with the micro-LED light-emitting unit (300) in the opening; S15, arranging a plurality of metal bumps (222) on the metal electrode (221) of the GaN HEMT driving circuit (200) by a wire heating method, transferring the micro-LED light-emitting unit (300) to the metal electrode (221), and making the metal melt into a spherical shape by a heating method to complete metal bonding with the n-electrode (312) of the micro-LED light-emitting unit (300); S16, filling the gap after bonding the micro-LED light-emitting unit (300) and the GaN HEMT driving circuit (200) with transparent insulating die bonding adhesive to complete the device fabrication.

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