A monolithic integrated microwave radiation system based on an optically triggered switch and its fabrication method

Abstract

This invention proposes a monolithically integrated microwave radiation system based on an optically triggered switch and its fabrication method, belonging to the field of high-power microwave technology. The system includes a driver wafer and a device wafer bonded together. The device wafer uses cubic boron nitride or hexagonal boron nitride as a substrate, on which a heterojunction optically triggered switch, a monolithic microwave integrated circuit, and a monitoring and protection module are integrated. The optically triggered switch is vertically integrated on the side of the monolithic microwave integrated circuit. Under the excitation of the optical pulse output from the driver wafer, it generates an electrical trigger signal, which is amplified by the monolithic microwave integrated circuit and outputs a microwave signal. This invention, through the synergistic design of an ultra-wide bandgap semiconductor substrate, a two-dimensional material heterojunction, three-dimensional integration technology, and full-dimensional on-chip monitoring, achieves chip integration from optical triggering, microwave amplification to intelligent protection on a nitride-based substrate, significantly improving power density, response speed, operating frequency, and reliability.

Description

Technical Field

[0001] This invention relates to the field of high-power microwave (HPM) technology, and in particular to a monolithic integrated microwave radiation system based on an optically triggered switch and its fabrication method. Background Technology

[0002] High-power microwave (HPM) systems have important applications in fields such as radar. Traditional high-power microwave sources are mainly assembled from vacuum electronic devices (such as magnetrons and klystrons) or discrete solid-state devices, but the above technical routes have many inherent defects, which seriously limit the improvement of system performance.

[0003] The disadvantages of existing technologies are as follows:

[0004] Parasitic parameters limit frequency improvement: Discrete devices are connected through bonding wires and packaging shells, which introduce significant parasitic inductance and capacitance in the high-frequency band (especially the millisecond wave and terahertz band), resulting in severe signal attenuation and making it difficult to break through 100GHz in operating frequency, thus failing to meet the broadband and high-frequency requirements of high-end applications.

[0005] Heat dissipation bottleneck limits power density: High-power microwave devices generate a lot of heat when they are working. The thermal conductivity of traditional Si or GaAs substrates is only 150 to 500 W / mK, which makes it difficult to dissipate heat quickly. This leads to a sharp increase in the junction temperature of the device, which not only reduces the device performance but also shortens its lifespan and may even cause thermal failure.

[0006] Poor trigger synchronization and weak anti-interference capability: Traditional electric trigger switches are susceptible to interference from strong electromagnetic environments. The trigger jitter is usually at the nanosecond level, which cannot achieve precise synchronous triggering of ultra-wideband pulses. In addition, there is a pre-pulse problem, which affects the microwave output quality.

[0007] Application expansion due to limitations in material performance: Existing wide-bandgap semiconductor materials such as SiC and GaN still have physical limits in terms of breakdown field strength (≤3MV / cm) and thermal conductivity (≤490 W / mK), making it difficult to meet the requirements in higher power (GW level) and higher frequency (THz level) application scenarios.

[0008] To address these issues, the industry has attempted to optimize system performance through hybrid integration technology. However, hybrid integration still cannot completely eliminate packaging parasitic effects, and poor interconnect compatibility between different material systems leads to reduced system reliability. Therefore, developing a monolithically integrated high-power microwave radiation system that combines high thermal conductivity, low parasitic effects, ultrafast triggering, and high power density has become the core research direction in this field. Summary of the Invention

[0009] The technical problem to be solved by this invention is how to overcome the limitations of existing monolithic integrated microwave systems that cannot simultaneously achieve ultrafast triggering, efficient heat dissipation and high-frequency operation. This invention proposes a monolithic integrated microwave radiation system based on an optical trigger switch and its fabrication method.

[0010] A monolithic integrated microwave radiation system based on an optically triggered switch, according to an embodiment of the present invention, includes:

[0011] A driving wafer, wherein the driving wafer integrates a driving control module for generating and outputting optical pulses;

[0012] A device wafer, bonded to the driving wafer, the device wafer comprising:

[0013] The substrate is made of single-crystal cubic boron nitride or hexagonal boron nitride.

[0014] A two-dimensional material functional layer is disposed on the substrate;

[0015] The optical trigger switch is composed of a heterojunction formed by the contact between the two-dimensional material functional layer and the substrate, and is used to generate an electrical trigger signal under the excitation of the optical pulse output by the drive control module.

[0016] A monolithic microwave integrated circuit is integrated on the substrate and electrically connected to the optical trigger switch, used to receive and amplify the electrical trigger signal to generate a microwave signal;

[0017] The optical trigger switch is vertically integrated on the side of the monolithic microwave integrated circuit and is electrically connected to the monolithic microwave integrated circuit through a three-dimensional interconnect structure.

[0018] According to some embodiments of the present invention, the device wafer is further provided with a monitoring and protection module, including:

[0019] An optical path status monitoring circuit is used to monitor at least one of the arrival time, pulse width, or optical power intensity of the optical pulse;

[0020] A microwave power monitoring circuit is used to monitor at least one of the output power or reflected power of the monolithic microwave integrated circuit.

[0021] An electrical operating point monitoring circuit is used to monitor at least one of the operating current or bias voltage of the monolithic microwave integrated circuit.

[0022] Thermal condition monitoring circuit, used to monitor the junction temperature of the device wafer;

[0023] The optical path status monitoring circuit, the microwave power monitoring circuit, the electrical operating point monitoring circuit, and the thermal status monitoring circuit are electrically connected to the drive control module or external protection circuit to form a closed-loop control or protection circuit.

[0024] In some embodiments of the present invention, the optical path status monitoring circuit includes an on-chip photodiode integrated in the vicinity of the optical trigger switch for converting received optical pulses into current signals.

[0025] According to some embodiments of the present invention, the microwave power monitoring circuit includes:

[0026] A directional coupler, integrated at the output of the monolithic microwave integrated circuit, is used to couple out a portion of the microwave signal;

[0027] The detector, electrically connected to the output of the directional coupler, is used to convert the coupled microwave signal into a DC voltage signal.

[0028] In some embodiments of the present invention, the detector is a Schottky diode detector or a thermistor detector.

[0029] According to some embodiments of the present invention, the electrical operating point monitoring circuit includes a current mirror sampling circuit or a voltage divider sampling circuit, which is integrated on the drain path or source path of the monolithic microwave integrated circuit.

[0030] In some embodiments of the present invention, the thermal state monitoring circuit includes a thermistor diode, which is either a separately fabricated diode or formed using the PN structure of the active device in the monolithic microwave integrated circuit.

[0031] In some embodiments of the present invention, the drive control module, in response to the output signal of at least one of the optical path state monitoring circuit, the microwave power monitoring circuit, the electrical operating point monitoring circuit, or the thermal state monitoring circuit, performs at least one of the following operations:

[0032] Adjust the repetition frequency or power of the optical pulse;

[0033] Disconnect the bias voltage of the monolithic microwave integrated circuit;

[0034] The output of the microwave signal is disabled.

[0035] According to some embodiments of the present invention, the two-dimensional material functional layer comprises at least one of graphene, transition metal chalcogenides, or MXene materials.

[0036] In some embodiments of the present invention, the response time of the optically triggered switch is less than 10 picoseconds and the withstand electric field strength is >10 kV / cm.

[0037] According to some embodiments of the present invention, the monolithic microwave integrated circuit includes AlGaN / GaN high electron mobility transistors or InGaN / GaN heterojunction bipolar transistors as active amplification devices.

[0038] In some embodiments of the present invention, the monolithic microwave integrated circuit includes two or more cascaded power amplifier units, with the final power amplifier unit connected to an on-chip integrated radiating antenna.

[0039] According to some embodiments of the present invention, the optical trigger switch and the monolithic microwave integrated circuit are connected via an on-chip interconnect structure, wherein the parasitic inductance of the on-chip interconnect structure is less than 10 picohens.

[0040] In some embodiments of the present invention, the drive control module includes a laser diode array or a mode-locked laser, and the wavelength of the optical pulse output by the drive control module is 200 nanometers to 2000 nanometers.

[0041] According to some embodiments of the present invention, the substrate is selected as single-crystal cubic boron nitride, with a substrate size of 6 inches, a thickness of 500 μm, a thermal conductivity of 1200 W / mK, a bandgap of 6.2 eV, a breakdown field strength of 15 MV / cm, and an intrinsic leakage current of 8 × 10⁻⁶. -13 A / cm 2 ,

[0042] In some embodiments of the present invention, the dimensions of the monolithic integrated microwave radiation system are: 5 mm × 5 mm × 0.5 mm.

[0043] According to an embodiment of the present invention, a method for fabricating a monolithic integrated microwave radiation system is provided. The method is used to fabricate the optically triggered switch-based monolithic integrated microwave radiation system described above. The fabrication method includes:

[0044] S10, fabrication of the driving wafer;

[0045] S20, fabricating a device wafer, including forming the two-dimensional material functional layer and the active structure of the monolithic microwave integrated circuit on the substrate;

[0046] S30, the driving wafer is bonded to the device wafer by wafer bonding;

[0047] S40, forming vertical interconnect vias to achieve electrical connection between the drive control module on the drive wafer and the optical trigger switch and the monolithic microwave integrated circuit;

[0048] S50, the patterning process forms the optical trigger switch, the device electrodes and interconnects of the monolithic microwave integrated circuit.

[0049] The present invention has the following beneficial effects:

[0050] Excellent thermal management performance: It adopts c-BN / h-BN ultrawide bandgap semiconductor substrate, which has a thermal conductivity 2 to 8 times that of traditional GaAs substrate. It can quickly dissipate the heat generated by high-power devices during operation, effectively reduce junction temperature, improve device reliability and power density, and achieve GW-level power output.

[0051] Ultra-fast trigger response and strong anti-interference capability: The optical trigger switch is based on the ultra-fast photoelectric response characteristics of two-dimensional materials, with a response time of picosecond level (<10 ps), which is far superior to the nanosecond level response of traditional electrical trigger switches; the optical triggering method is not affected by strong electromagnetic environment interference, has no pre-pulse, and ensures the stability and accuracy of microwave output;

[0052] Extremely low parasitic parameters: The system adopts a monolithic integrated architecture, eliminating parasitic inductance / capacitance introduced by traditional packaging and bonding wires; the parasitic inductance of the on-chip interconnect structure is <10 pH, which enables the system to operate at frequencies up to the terahertz (THz) band and achieve ultra-wideband microwave radiation.

[0053] Excellent material synergy: High carrier mobility (≥2000 cm⁻¹) in two-dimensional materials 2 The high breakdown field strength (≥10 MV / cm) of ultra-wide bandgap semiconductors ( / V·s) creates a synergistic effect, which not only ensures the fast switching characteristics of the device, but also improves the withstand voltage capability, achieving a balance between high power density and high efficiency.

[0054] High integration and reliability: The wafer-level heterogeneous integration technology enables seamless integration of Si-based driving circuits and ultra-wide bandgap semiconductor power devices, simplifying the system structure and improving integration. At the same time, it avoids compatibility issues caused by the integration of different material systems, significantly improving the long-term reliability of the system. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of the overall structure of a monolithic integrated microwave radiation system based on an optically triggered switch according to an embodiment of the present invention;

[0056] Figure 2 This is a front view of the monolithic integrated microwave radiation system structure based on an optically triggered switch according to an embodiment of the present invention;

[0057] Figure 3 This is a top view of the structure of a monolithic integrated microwave radiation system based on an optically triggered switch according to an embodiment of the present invention;

[0058] Figure 4This is a flowchart of a method for manufacturing a monolithic integrated microwave radiation system based on an optically triggered switch according to an embodiment of the present invention, wherein 4(a) is a schematic diagram of wafer bonding, 4(b) is a schematic diagram of thinning process, and 4(c) is a schematic diagram of vertical interconnect and back-end processes.

[0059] Figure 5 This is a diagram showing the response characteristics of an optically triggered switch according to an embodiment of the present invention.

[0060] Figure label:

[0061] Substrate 100, two-dimensional material functional layer 200, monolithic microwave integrated circuit 300, interconnect structure 400, drive control module 500, mode-locked laser array 600, low noise amplification unit 700, drive amplification unit 800, power amplification unit 900, optical trigger switch 101, radiation output port 102. Detailed Implementation

[0062] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments.

[0063] The steps described in the specification and the flowcharts in the accompanying drawings of this invention are not necessarily to be strictly followed according to the step numbers; the execution order of the steps can be changed. Furthermore, certain steps can be omitted, multiple steps can be combined into one step, and / or one step can be broken down into multiple steps.

[0064] According to an embodiment of the present invention, a monolithic integrated microwave radiation system based on an optically triggered switch includes: a driver wafer and a device wafer.

[0065] like Figure 1 As shown, the driving wafer integrates a driving control module 500 for generating and outputting optical pulses. The device wafer is bonded to the driving wafer. The device wafer includes: a substrate 100, a two-dimensional material functional layer 200, an optical trigger switch 101, and a monolithic microwave integrated circuit 300.

[0066] The substrate 100 is made of single-crystal cubic boron nitride or hexagonal boron nitride. A two-dimensional material functional layer 200 is disposed on the substrate 100. The optical trigger switch 101 is a heterostructure formed by the contact between the two-dimensional material functional layer 200 and the substrate 100. It is used to generate an electrical trigger signal under the excitation of the optical pulse output by the drive control module 500.

[0067] A monolithic microwave integrated circuit 300 is integrated on a substrate 100 and electrically connected to an optical trigger switch 101 for receiving and amplifying an electrical trigger signal to generate a microwave signal.

[0068] The optical trigger switch 101 is vertically integrated on the side of the monolithic microwave integrated circuit 300 and is electrically connected to the monolithic microwave integrated circuit 300 through a three-dimensional interconnection structure.

[0069] It should be noted that traditional microwave systems (whether vacuum tubes or discrete solid-state) suffer from system-level problems such as modularity, large parasitic parameters, slow triggering, and poor heat dissipation, making it impossible to simultaneously achieve high power, fast response, and high frequency.

[0070] According to an embodiment of the present invention, a monolithic integrated microwave radiation system based on a light-triggered switch innovatively combines materials and devices: a two-dimensional material heterojunction light-triggered switch 101 (OTS) is constructed on a boron nitride substrate 100, achieving light-controlled ultrafast conduction. Innovative integration of circuits and systems is achieved: a monolithic microwave integrated circuit 300 (MMIC) and the OTS are integrated on the same substrate 100, and fused with an independent driving wafer through wafer bonding, forming a monolithic, heterogeneous integrated system of "light control-amplification-radiation". This achieves the following technical effects:

[0071] Extremely low parasitics: Monolithic integration eliminates parasitic inductance and capacitance introduced by bonding wires and packaging, laying the foundation for high-frequency (THz) operation.

[0072] Ultra-fast triggering and anti-interference: The optical triggering method achieves picosecond-level response and is unaffected by electromagnetic interference.

[0073] High-efficiency heat dissipation: The boron nitride substrate 100 fundamentally solves the thermal management problem under high power density.

[0074] High integration and miniaturization: Integrating drive, control, switching, amplification, and radiation ports on the chip scale significantly improves system reliability and applicability.

[0075] According to some embodiments of the present invention, a monitoring and protection module is further provided on the device wafer, including: an optical path status monitoring circuit, a microwave power monitoring circuit, an electrical operating point monitoring circuit, and a thermal status monitoring circuit. The optical path status monitoring circuit, microwave power monitoring circuit, electrical operating point monitoring circuit, and thermal status monitoring circuit are electrically connected to the drive control module 500 or an external protection circuit to form a closed-loop control or protection circuit. This enables the monolithic integrated microwave radiation system to integrate self-testing functions in the optical domain, microwave domain, bias domain, and thermal domain.

[0076] The optical path status monitoring circuit monitors at least one of the arrival time, pulse width, or optical power intensity of the optical pulse. Since the optical trigger switch 101 relies on the laser pulse, laser jitter and power drift can cause unstable microwave output. The optical path status monitoring circuit monitors at least one of the arrival time, pulse width, or optical power intensity of the optical pulse to perform optical domain detection and achieve optical-electric synchronous monitoring. If insufficient optical power is detected, the monolithic integrated microwave radiation system can automatically adjust the laser or disable microwave output to prevent "false triggering."

[0077] In some embodiments of the present invention, the optical path status monitoring circuit includes a small-area photodiode (on-chip PD) integrated on a region adjacent to the optical trigger switch 101 for converting received optical pulses into current signals.

[0078] Microwave power monitoring circuits are used to monitor at least one of the output power, standing wave ratio, and reflected power of a single-chip microwave integrated circuit.

[0079] According to some embodiments of the present invention, the microwave power monitoring circuit includes a directional coupler and a detector.

[0080] The directional coupler is integrated into the output of the monolithic microwave integrated circuit 300 and is used to couple out a portion of the microwave signal, such as one-thousandth of the main signal (e.g., -30dB or -40dB). The detector is electrically connected to the output of the directional coupler and is used to convert the coupled microwave signal into a DC voltage signal.

[0081] In some embodiments of the present invention, the detector is a Schottky diode detector or a thermistor detector, used to convert the coupled microwave signal into a DC voltage. It should be noted that traditional systems require an external high-power sampling head, while the present invention integrates the sampling head into the chip, placing it only micrometers away from the monolithic microwave integrated circuit, thus providing the most accurate reflection of the internal state of the tube.

[0082] An electrical operating point monitoring circuit is used to monitor at least one of the operating current or bias voltage of a monolithic microwave integrated circuit.

[0083] According to some embodiments of the present invention, the electrical operating point monitoring circuit includes a current mirror sampling circuit or a voltage divider sampling circuit, integrated on the drain path or source path of the monolithic microwave integrated circuit 300. By monitoring minute current drift, it determines whether the device has experienced thermal degradation or gate breakdown. For example, when the current suddenly increases abnormally, the electrical operating point monitoring circuit can directly cut off the bias, achieving microsecond-level "protection".

[0084] The monolithic integrated microwave radiation system of this invention has high integration and power. High-power microwaves mean high heat, and increased junction temperature can lead to decreased gain or even burnout. A thermal state monitoring circuit is used to monitor the junction temperature of the device wafer.

[0085] In some embodiments of the present invention, the thermal state monitoring circuit includes a thermistor, which can be a separately fabricated diode or formed using the PN structure of an active device in a monolithic microwave integrated circuit. The thermistor utilizes the characteristic that the forward voltage drop of the diode changes with temperature to achieve real-time detection of the junction temperature of the device wafer. When an excessively high temperature is detected, the system can automatically reduce the repetition frequency of the light trigger or activate external cooling, eliminating the need for an external temperature controller and achieving closed-loop thermal control.

[0086] In some embodiments of the present invention, the drive control module, in response to the output signal of at least one of the optical path state monitoring circuit, microwave power monitoring circuit, electrical operating point monitoring circuit, or thermal state monitoring circuit, performs at least one of the following operations:

[0087] Adjust the repetition frequency or power of the optical pulse;

[0088] Disconnect the bias voltage of the monolithic microwave integrated circuit;

[0089] Microwave signal output is prohibited.

[0090] According to some embodiments of the present invention, the two-dimensional material functional layer 200 comprises at least one of graphene, transition metal chalcogenides, or MXene materials. It should be noted that graphene, TMDs (such as MoS2), and MXene (such as Ti3C2T) are included. x This invention combines two-dimensional materials with excellent optoelectronic properties with the ultra-wide bandgap semiconductor boron nitride to construct an ultrafast photoconductive switch in the microwave band. This combination utilizes the interfacial properties and high-speed carrier transport capability of two-dimensional materials, which is the key material basis for realizing the function of the optical trigger switch 101.

[0091] In some embodiments of the present invention, the response time of the optically triggered switch 101 is less than 10 picoseconds, and it withstands an electric field strength >10 kV / cm. It should be noted that the response time of conventional electrically triggered switches is typically in the nanosecond range (1 ns = 1000 ps). The present invention, through the design of a two-dimensional material / boron nitride heterojunction, improves the response speed by more than two orders of magnitude. This parameter is not obtained through simple optimization, but rather through a technological breakthrough brought about by the specific material combination and device structure described above.

[0092] According to some embodiments of the present invention, the monolithic microwave integrated circuit 300 includes AlGaN / GaN high electron mobility transistors or InGaN / GaN heterojunction bipolar transistors as active amplification devices. It should be noted that AlGaN / GaN HEMTs and InGaN / GaN HBTs are high-performance microwave devices, and growing or integrating them on a boron nitride substrate 100 faces significant process challenges such as lattice mismatch and interface control. The present invention successfully achieves this integration, utilizing the high thermal conductivity of boron nitride to fully leverage the high power potential of these devices.

[0093] In some embodiments of the present invention, the monolithic microwave integrated circuit 300 includes two or more cascaded power amplifier units, with the final power amplifier unit connected to an on-chip integrated radiating antenna. It should be noted that the present invention employs two or more cascaded power amplifier units connected to the on-chip integrated radiating antenna via a matching network, thereby forming a complete monolithic microwave signal generation and radiation chain. Integrating the radiating antenna onto the same chip further reduces system cascading losses and parasitic effects.

[0094] According to some embodiments of the present invention, the optical trigger switch 101 is connected to the monolithic microwave integrated circuit 300 via an on-chip interconnect structure 400, the parasitic inductance of the on-chip interconnect structure 400 being less than 10 picohens.

[0095] In some embodiments of the present invention, the drive control module 500 includes a laser diode array or a mode-locked laser, and the wavelength of the light pulse output by the drive control module 500 is 200 nanometers to 2000 nanometers.

[0096] According to some embodiments of the present invention, the substrate 100 is selected as a single-crystal cubic boron nitride, the substrate 100 has a size of 6 inches, a thickness of 500 μm, a thermal conductivity of 1200 W / mK, a bandgap of 6.2 eV, a breakdown field strength of 15 MV / cm, and an intrinsic leakage current of 8 × 10⁻⁶. -13 A / cm 2 ,

[0097] In some embodiments of the present invention, the dimensions of the monolithic integrated microwave radiation system are: 5 mm × 5 mm × 0.5 mm.

[0098] According to an embodiment of the present invention, a method for fabricating a monolithic integrated microwave radiation system is used to fabricate the above-mentioned monolithic integrated microwave radiation system based on an optically triggered switch. The fabrication method includes:

[0099] S10, fabrication of the driving wafer;

[0100] S20, fabricating a device wafer, including forming a two-dimensional material functional layer 200 and an active structure of a monolithic microwave integrated circuit on a substrate; vertically integrating the optical trigger switch on the side of the monolithic microwave integrated circuit through a three-dimensional integration process, and forming a light incident window; integrating an optical path status monitoring circuit, a microwave power monitoring circuit, an electrical operating point monitoring circuit, and a thermal status monitoring circuit on the device wafer; S30, bonding the driver wafer to the device wafer through wafer bonding;

[0101] S40 forms a vertical interconnect via to enable electrical connection between the drive control module on the drive wafer and the optical trigger switch and monolithic microwave integrated circuit;

[0102] S50 uses a patterning process to form the device electrodes and interconnects of optically triggered switches and monolithic microwave integrated circuits.

[0103] It should be noted that, in order to accommodate both the optical triggering region and the microwave power combining network within a limited chip area, this invention employs multilayer wiring technology and three-dimensional integration process. The optical trigger switch 101 is vertically integrated on the side of the active layer of the monolithic microwave integrated circuit 300, and vertical incidence or side coupling of the optical path is achieved through microfabrication technology. This three-dimensional integration level far exceeds that of traditional two-dimensional planar monolithic microwave integrated circuits, significantly reducing the system's size, weight, and cost.

[0104] The fabrication method of this invention achieves highly reliable and high-performance integration of silicon-based driving circuits with unconventional power devices based on boron nitride and two-dimensional materials, proposing a core process route of "separate fabrication + wafer bonding + vertical interconnect (TSV)". In particular, the wafer bonding and TSV processes solve challenges such as thermal expansion coefficient mismatch and electrical interconnection between different material systems (Si and c-BN / h-BN). This method enables reliable integration and three-dimensional stacking of heterogeneous materials.

[0105] The present invention will now be described in detail with reference to the accompanying drawings and two specific embodiments. It is to be understood that the following description is merely exemplary and should not be construed as a specific limitation of the present invention.

[0106] Example 1:

[0107] This embodiment proposes a monolithically integrated high-power microwave radiation system based on an optically triggered switch. Through the synergistic design of ultra-wide bandgap semiconductors (h-BN / c-BN) and two-dimensional materials, and the monolithic integration of the entire system, it achieves high-frequency, wide-bandwidth, high-power-density, and low-jitter microwave radiation output, while improving system reliability and integration.

[0108] According to an embodiment of the present invention, a monolithically integrated high-power microwave radiation system based on an optically triggered switch 101 has a core architecture including an ultra-wide bandgap semiconductor substrate 100, a two-dimensional material functional layer 200, an optically triggered switch 101 (OTS), a monolithic microwave integrated circuit 300 (MMIC), an on-chip interconnect structure 400, and a drive control module 500. These components work together to achieve high-performance microwave radiation. The specific structure is as follows:

[0109] Ultra-wide bandgap semiconductor substrate 100: Single-crystal cubic boron nitride (c-BN) or hexagonal boron nitride (h-BN) is selected as the main substrate 100. Utilizing its ultra-high thermal conductivity (≥1000 W / mK), high breakdown field strength (≥10 MV / cm), and excellent insulation properties, it solves the heat dissipation bottleneck and withstand voltage problems under high power conditions. Among them, the thermal conductivity of the single-crystal c-BN substrate 100 can reach over 1300 W / mK, the bandgap is ≥6.2 eV, and the intrinsic leakage current is ≤ A / cm 2 ;

[0110] Two-dimensional material functional layer 200: A two-dimensional material functional layer 200 is prepared on the surface of substrate 100 by van der Waals force transfer, MBE or MOCVD process. The two-dimensional material includes two-dimensional transition metal dichalcogenides (TMDs) such as graphene, MoS2, WSe2 or Ti3C2T. x Two-dimensional transition metal carbides, nitrides, or carbonitride MXene materials with a single-layer thickness of up to 100 nm are used. The two-dimensional materials form a low-interface-state heterojunction with an ultrawide bandgap semiconductor, providing an ultrafast photoelectric response channel for the optical trigger switch 101.

[0111] Optical Triggered Switch 101 (OTS): Composed of a two-dimensional material / ultra-wide bandgap semiconductor heterostructure, it can be configured as a photoconductive switch or a photoexcited Schottky diode; Under the excitation of the optical pulse output by the drive control module 500, the two-dimensional material rapidly generates a high concentration of charge carriers, realizing a picosecond-level transition from a high-resistivity state to a conduction state, with a response time <10 ps, ​​withstand electric field strength >10 kV / cm, and no pre-pulse output;

[0112] Monolithic microwave integrated circuit 300 (MMIC): Integrated with optical trigger switch 101 on a common substrate 100, including active power amplifier devices and passive components; the active devices are AlGaN / GaN HEMT or InGaN / GaN HBT to achieve efficient amplification of microwave signals; the passive components include on-chip transmission lines (coplanar waveguides, microstrip lines) with a characteristic impedance of 50Ω, passive matching networks (resistors, capacitors, inductors) and filters to ensure low-loss signal transmission and impedance matching;

[0113] On-chip interconnect structure 400: Made of low resistivity metals such as copper, aluminum, silver or gold, embedded in a low dielectric constant dielectric layer (k≤3.0) to form a coplanar waveguide or microstrip line structure; the parasitic inductance of interconnect structure 400 is <10 pH, realizing low-loss electrical connection between optical trigger switch 101 and MMIC, and between internal devices of MMIC.

[0114] Drive control module 500: integrates laser source, beam shaping unit and modulation unit. The laser source is selected as laser diode array or mode-locked laser. The output light pulse wavelength is 200 nm to 2000 nm. The pulse width and repetition frequency are adjustable. Drive control module 500 is integrated with power chip through wafer bonding technology. The optical signal is transmitted to optical trigger switch 101 through spatial coupling or waveguide coupling.

[0115] Furthermore, the MMIC adopts a 2-5 stage cascaded power amplifier architecture. Each stage of the amplifier unit achieves impedance matching through a passive matching network. The last stage amplifier unit is directly connected to the on-chip integrated radiation output port 102 (microstrip antenna or slotted wire antenna) to achieve direct radiation of microwave signals.

[0116] Taking a monolithic integrated system based on a c-BN / graphene heterojunction as an example, a monolithic integrated high-power microwave radiation system based on a c-BN / graphene heterojunction optical trigger switch 101 focuses on achieving the synergistic integration of ultrafast triggering and high-power amplification, such as... Figure 1 As shown, the specific structure and performance of the system are as follows:

[0117] Ultra-wide bandgap semiconductor substrate 100: Single-crystal cubic boron nitride (c-BN) is used as the substrate. The substrate size is 6 inches, the thickness is 500 μm, the measured thermal conductivity is 1200 W / mK, the bandgap is 6.2 eV, the breakdown field strength is 15 MV / cm, and the intrinsic leakage current is 8 × 10⁻⁶. -13 A / cm 2 This can effectively solve the heat dissipation and pressure resistance problems under high power;

[0118] Two-dimensional material functional layer 200: Using van der Waals force transfer technology, monolayer graphene (0.34 nm thick) was precisely transferred onto the surface of c-BN substrate 100; characterization by atomic force microscopy (AFM) showed that the graphene and c-BN interfaces were tightly bonded, with an interface state density of 5 × 10⁻⁶. 11 cm -2 This forms a low-defect heterojunction, which serves as the core functional layer of the optical trigger switch 101.

[0119] Optically triggered switch 101: A photoconductive switch is formed from a graphene / c-BN heterostructure, with Au ohmic contact electrodes fabricated at both ends of the switch; the mode-locked laser array 600 in the drive control module 500 emits a light pulse with a wavelength of 1064 nm and a pulse width of 50 fs, which is then shaped and perpendicularly irradiated onto the graphene layer; under photoexcitation, the graphene rapidly generates a high concentration of hot electrons, with a carrier concentration reaching 1×10⁻⁶. 19 cm -3 The light-triggered switch 101 quickly transitions from a high-resistance state (resistance > 1 MΩ) to a conducting state (resistance < 10 Ω), with a measured response time of 5 ps, withstands an electric field strength of 15 kV / cm, and has no pre-pulse output.

[0120] MMIC: An AlGaN / GaN heterojunction (25 nm AlGaN layer thickness, 1 μm GaN layer thickness) is grown on the same c-BN substrate 100 using MOCVD. HEMT devices are fabricated using electron beam lithography and inductively coupled plasma etching (ICP). The HEMT device has a gate length of 0.15 μm, a gate width of 2 mm, a maximum saturation current of 800 mA / mm, and a peak transconductance of 250 mS / mm. The MMIC adopts a three-stage cascaded amplification architecture: the first stage is a low-noise amplifier unit 700 (gain 10 dB, noise figure 1.5 dB), the second stage is a drive amplifier unit 800 (gain 15 dB, output power 20 dBm), and the third stage is a power amplifier unit 900 (gain 8 dB, saturated output power 30 dBm).

[0121] On-chip interconnect structure 400: It is made of Au metal and embedded in a polyimide low-dielectric layer (k=2.8) to form a coplanar waveguide (CPW) structure; the CPW has a characteristic impedance of 50 Ω and an insertion loss of 0.3 dB / mm in the 30 GHz band. It transmits the turn-on signal of the optical trigger switch 101 to the input of the MMIC with low loss. The parasitic inductance was measured at 8 pH.

[0122] Radiation output: The third-stage power amplifier unit is directly connected to the on-chip integrated microstrip antenna (radiation output port 102). The antenna operates in the frequency band of 26–40 GHz (Ka band), with a gain of 8 dB and a beamwidth of 60°.

[0123] System performance: The entire chip measures 5 mm × 5 mm × 0.5 mm. Under 10 kV high-voltage pulse excitation, it can output a microwave signal with a peak power of 1 kW and a pulse width of 1 ns. The operating frequency is 35 GHz, and there is no performance degradation after 100 hours of continuous operation.

[0124] like Figure 5The diagram shows the response characteristics of the optical trigger switch 101 based on the present invention. It illustrates the ps-level response characteristics of the optical trigger switch 101 under the action of a square wave excitation signal from a microwave signal generator. The square wave excitation signal was acquired using a spectrum analyzer. In this waveform diagram, the response time of the optical trigger switch 101 is ≤5 ps, and the signal amplitude fluctuation during the response is small (maximum fluctuation ≤5 mV).

[0125] Example 2:

[0126] like Figure 4 As shown, this embodiment provides a method for manufacturing a monolithically integrated high-power microwave radiation system based on an optically triggered switch 101, wherein 4(a) is a schematic diagram of wafer bonding, 4(b) is a schematic diagram of thinning process, and 4(c) is a schematic diagram of vertical interconnect and back-end processes. The core lies in the wafer-level heterogeneous integration of Si-based driving circuits and ultra-wide bandgap semiconductor power devices. Specific steps include:

[0127] Wafer fabrication: Si-based driving circuit wafers (integrated laser driver and logic control unit) and ultra-wide bandgap semiconductor power wafers (100 c-BN / h-BN substrate + 200 two-dimensional material functional layers + 300 MMIC active layer prototype of monolithic microwave integrated circuit) were fabricated respectively.

[0128] Wafer bonding: Using Cu-Cu hot-press bonding (bonding temperature 300~400℃, pressure 3~5 MPa, N2 atmosphere) or Au-Si eutectic bonding technology, Si-based wafers and power wafers are precisely aligned and bonded to achieve mechanical fixation and preliminary electrical interconnection.

[0129] Thinning process: The power wafer is thinned by chemical mechanical polishing (CMP) process. After thinning, the substrate thickness is controlled at 200-500μm to ensure the heat dissipation performance of the device and the chip is thinner.

[0130] Vertical interconnect via (TSV) fabrication: Through-holes are fabricated on the power wafer using deep hole etching (DRIE) process, and vertical interconnect vias (TSVs) are formed by metal filling (Cu or W), realizing efficient electrical interconnection between Si-based driving circuits and optically triggered switches (OTS) and monolithic microwave integrated circuits (MMICs) on the power wafer;

[0131] Back-end processes: Defining OTS patterns, MMIC device structures, and interconnects through photolithography and etching, and depositing SiN. x A passivation layer is applied, and finally, the wafers are diced to obtain individual chips.

[0132] Taking the seamless integration of Si-based driving circuits and ultra-wide bandgap semiconductor power devices as an example, based on the whole-system heterogeneous integration manufacturing process of Cu-Cu hot-press bonding, the specific steps are as follows:

[0133] Wafer preparation: ① Si-based driver circuit wafer: 8-inch Si wafers are selected, and laser driver circuits, logic control units, and Cu bonding pads (pad size 10μm×10μm, spacing 20μm) are integrated through CMOS process; ② Ultra-wide bandgap semiconductor power wafer: 6-inch c-BN epitaxial wafers are selected, and graphene transfer, AlGaN / GaN heterojunction growth, and MMIC active layer prototype preparation are completed sequentially. Cu bonding pads are prepared on the back side and precisely aligned with the Si-based wafer pads;

[0134] Cu-Cu hot-press bonding: Two wafers are aligned face to face and placed in a bonding machine. Under a N2 protective atmosphere, the bonding temperature is set to 300℃, the pressure to 4 MPa, and the holding time to 30 min. After bonding, the interfacial shear strength is >50 MPa and the resistance is <10 mΩ.

[0135] Power wafer thinning: The front side of the c-BN power wafer is thinned using CMP process from the initial thickness of 500μm to 200μm. After thinning, the wafer flatness is <5μm. No cracks or defects are observed by optical microscope.

[0136] TSV fabrication: Through-holes (5 μm in diameter and 200 μm in depth) were etched on a c-BN wafer using the DRIE process. A Ti adhesion layer (10 nm) and a Cu seed layer (50 nm) were deposited by physical vapor deposition (PVD). Cu was then filled by electroplating to form the TSV. The TSV resistance was <50 mΩ, enabling electrical interconnection between the Si-based driving circuit and the top OTS and MMIC.

[0137] Back-end processes: ① Photolithography definition: Define the graphene pattern of the OTS, the HEMT gate, source / drain electrodes, and interconnects of the MMIC using deep ultraviolet lithography (DUV); ② Metallization: Evaporate Au metal (200 nm thickness) to form device electrodes and interconnects; ③ Passivation: Deposit SiN x Passivation layer (100 nm thick) to protect the device surface; ④ Dicing: Dicing with a diamond dicing blade to obtain a single 5 mm × 5 mm chip;

[0138] Performance verification: The fabricated chip exhibits a 90% reduction in parasitic inductance and an increased operating frequency to the Ka band (26-40 GHz). After 100 hours of continuous operation under a 10 kV high-voltage pulse, the output power fluctuation is less than 5%, indicating excellent system integration reliability.

[0139] The present invention has the following beneficial effects:

[0140] Excellent thermal management performance: It adopts c-BN / h-BN ultra-wide bandgap semiconductor substrate 100, which has a thermal conductivity of 2 to 8 times that of traditional GaAs substrate 100. It can quickly dissipate the heat generated by high-power devices during operation, effectively reduce junction temperature, improve device reliability and power density, and achieve GW-level power output.

[0141] Ultra-fast trigger response and strong anti-interference capability: The optical trigger switch 101 is based on the ultra-fast photoelectric response characteristics of two-dimensional materials, with a response time of picosecond level (<10 ps), which is far superior to the nanosecond level response of traditional electrical trigger switches; the optical triggering method is not affected by strong electromagnetic environment interference, has no pre-pulse, and ensures the stability and accuracy of microwave output;

[0142] Extremely low parasitic parameters: The system adopts a monolithic integrated architecture, eliminating parasitic inductance / capacitance introduced by traditional packaging and bonding wires; the on-chip interconnect structure has a parasitic inductance of 400 < 10 pH, which enables the system to operate at frequencies up to the terahertz (THz) band and achieve ultra-wideband microwave radiation.

[0143] Excellent material synergy: High carrier mobility (≥2000 cm⁻¹) in two-dimensional materials 2 The high breakdown field strength (≥10 MV / cm) of ultra-wide bandgap semiconductors ( / V·s) creates a synergistic effect, which not only ensures the fast switching characteristics of the device, but also improves the withstand voltage capability, achieving a balance between high power density and high efficiency.

[0144] High integration and reliability: The wafer-level heterogeneous integration technology enables seamless integration of Si-based driving circuits and ultra-wide bandgap semiconductor power devices, simplifying the system structure and improving integration. At the same time, it avoids compatibility issues caused by the integration of different material systems, significantly improving the long-term reliability of the system.

[0145] Through the description of specific embodiments, a more in-depth and specific understanding should be gained of the technical means and effects adopted by the present invention to achieve the intended purpose. However, the accompanying drawings are only provided for reference and illustration and are not intended to limit the present invention.

Claims

1. A monolithically integrated microwave radiation system based on an optically triggered switch, characterized in that, include: A driving wafer, wherein the driving wafer integrates a driving control module for generating and outputting optical pulses; A device wafer, bonded to the driving wafer, the device wafer comprising: The substrate is made of single-crystal cubic boron nitride or hexagonal boron nitride. A two-dimensional material functional layer is disposed on the substrate; The optical trigger switch is composed of a heterojunction formed by the contact between the two-dimensional material functional layer and the substrate, and is used to generate an electrical trigger signal under the excitation of the optical pulse output by the drive control module. A monolithic microwave integrated circuit is integrated on the substrate and electrically connected to the optical trigger switch, used to receive and amplify the electrical trigger signal to generate a microwave signal; The optical trigger switch is vertically integrated on the side of the monolithic microwave integrated circuit and is electrically connected to the monolithic microwave integrated circuit through a three-dimensional interconnect structure.

2. The monolithically integrated microwave radiation system based on an optically triggered switch according to claim 1, characterized in that, The device wafer is also equipped with a monitoring and protection module, including: An optical path status monitoring circuit is used to monitor at least one of the arrival time, pulse width, or optical power intensity of the optical pulse; A microwave power monitoring circuit is used to monitor at least one of the output power or reflected power of the monolithic microwave integrated circuit. An electrical operating point monitoring circuit is used to monitor at least one of the operating current or bias voltage of the monolithic microwave integrated circuit. Thermal condition monitoring circuit, used to monitor the junction temperature of the device wafer; The optical path status monitoring circuit, the microwave power monitoring circuit, the electrical operating point monitoring circuit, and the thermal status monitoring circuit are electrically connected to the drive control module or external protection circuit to form a closed-loop control or protection circuit.

3. The monolithic integrated microwave radiation system based on an optically triggered switch according to claim 2, characterized in that, The drive control module, in response to the output signal of at least one of the optical path state monitoring circuit, the microwave power monitoring circuit, the electrical operating point monitoring circuit, or the thermal state monitoring circuit, performs at least one of the following operations: Adjust the repetition frequency or power of the optical pulse; Disconnect the bias voltage of the monolithic microwave integrated circuit; The output of the microwave signal is prohibited.

4. The monolithic integrated microwave radiation system based on an optically triggered switch according to claim 1, characterized in that, The optical trigger switch has a response time of less than 10 picoseconds and can withstand an electric field strength of >10 kV / cm.

5. The monolithic integrated microwave radiation system based on an optically triggered switch according to claim 1, characterized in that, The monolithic microwave integrated circuit includes AlGaN / GaN high electron mobility transistors or InGaN / GaN heterojunction bipolar transistors as active amplification devices.

6. The monolithic integrated microwave radiation system based on an optically triggered switch according to claim 1, characterized in that, A monolithic microwave integrated circuit contains two or more cascaded power amplifier units, with the final power amplifier unit connected to an on-chip integrated radiating antenna.

7. The monolithic integrated microwave radiation system based on an optically triggered switch according to claim 1, characterized in that, The optical trigger switch is connected to the monolithic microwave integrated circuit via an on-chip interconnect structure, the parasitic inductance of which is less than 10 picohens.

8. The monolithic integrated microwave radiation system based on an optically triggered switch according to claim 1, characterized in that, The drive control module includes a laser diode array or a mode-locked laser, and the optical pulse wavelength output by the drive control module is 200 nanometers to 2000 nanometers.

9. The monolithically integrated microwave radiation system based on an optically triggered switch according to any one of claims 1-8, characterized in that, The dimensions of the monolithic integrated microwave radiation system are: 5 mm × 5 mm × 0.5 mm.

10. A method for fabricating a monolithic integrated microwave radiation system, characterized in that, The fabrication method is used to fabricate a monolithic integrated microwave radiation system based on an optically triggered switch as described in any one of claims 1-9, and the fabrication method includes: S10, fabrication of the driving wafer; S20, fabricating a device wafer, including forming the two-dimensional material functional layer and the active structure of the monolithic microwave integrated circuit on the substrate; vertically integrating the optical trigger switch on the side of the monolithic microwave integrated circuit through a three-dimensional integration process, and forming a light incident window; integrating an optical path status monitoring circuit, a microwave power monitoring circuit, an electrical operating point monitoring circuit, and a thermal status monitoring circuit on the device wafer; S30, the driving wafer is bonded to the device wafer by wafer bonding; S40, forming vertical interconnect vias to achieve electrical connection between the drive control module on the drive wafer and the optical trigger switch and the monolithic microwave integrated circuit; S50, the patterning process forms the optical trigger switch, the device electrodes and interconnects of the monolithic microwave integrated circuit.

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