A diamond-aluminum nitride composite substrate high-frequency power load and a preparation method thereof

Abstract

The application provides a diamond and aluminum nitride composite substrate high-frequency power load and a preparation method thereof, which comprises a composite substrate layer, a high-frequency power absorption and conversion structure formed on the composite substrate layer and used for realizing power absorption and impedance matching of a high-frequency signal, and a back electrode formed on a lower surface of the composite substrate layer opposite to the high-frequency power absorption and conversion structure and used for providing a grounding path and a heat dissipation path, wherein the composite substrate layer comprises a diamond substrate and an aluminum nitride film epitaxially grown on a surface of the diamond substrate to form a diamond and aluminum nitride heterojunction structure. The application can effectively solve the problem of excessively high junction temperature of an existing aluminum oxide substrate load and meet the demand of high-frequency and high-power application.

Description

Technical Field

[0001] This invention relates to the field of semiconductor high-frequency device technology, and in particular to a high-frequency power load made of diamond and aluminum nitride composite substrate and its preparation method. Background Technology

[0002] High-frequency power loads are core terminal devices in radio frequency microwave systems. Their performance directly determines the system's power capacity, frequency coverage, and operational stability, playing an indispensable role in high-frequency, high-power applications such as 5G / 6G communication, radar, and satellite communication. As communication and radar technologies evolve towards higher power, wider bandwidth, and miniaturization, higher demands are placed on the heat dissipation efficiency, power carrying capacity, and integration adaptability of high-frequency power loads.

[0003] The mainstream substrate for existing high-frequency power loads is alumina ceramic. This type of substrate has a core defect of low thermal conductivity, which makes the junction temperature of the device prone to be too high under high power conditions. This not only limits the improvement of the device's power capacity, but also shortens its service life, and cannot meet the application requirements of high-end high-frequency systems. Summary of the Invention

[0004] To address the above problems, this invention provides a high-frequency power load based on a diamond-aluminum nitride composite substrate and its preparation method.

[0005] To solve the above problems, the technical solution adopted by the present invention is as follows: A high-frequency power load based on a diamond and aluminum nitride composite substrate includes: Composite substrate layer; A high-frequency power absorption and conversion structure is formed on the composite substrate layer to achieve power absorption and impedance matching of high-frequency signals; The back electrode, formed on the lower surface of the composite substrate layer opposite to the high-frequency power absorption and conversion structure, serves to provide a grounding path and a heat dissipation path.

[0006] Preferably, the composite substrate layer includes a diamond substrate and an aluminum nitride thin film epitaxially grown on the upper surface of the diamond substrate, forming a diamond-aluminum nitride heterojunction structure.

[0007] Preferably, the diamond substrate has a preferred crystal orientation, a thickness of 200–500 μm, and a surface roughness Ra ≤ 0.5 nm.

[0008] Preferably, the aluminum nitride thin film has a preferred crystal orientation, a thickness of 50–200 nm, a half-width at half-maximum (FWHM) of the XRD rocking curve of the crystal plane ≤ 1.5°, and a resistivity ≥ 10⁻⁶. 12 Ω·cm.

[0009] Preferably, the interfacial thermal resistance of the composite substrate layer is ≤15m.2 ·K / GW.

[0010] Preferably, the high-frequency power absorption and conversion structure includes: A transition metal layer is deposited on the upper surface of the aluminum nitride film; A resistive film layer, formed on the transition metal layer and patterned into a serpentine structure; and Matching electrodes are symmetrically disposed at both ends of the resistive film layer; The transition metal layer is made of titanium or a titanium-tungsten alloy and has a thickness of 5–15 nm.

[0011] Preferably, the resistive film layer is made of tantalum nitride or silicon carbide, with a thickness of 20-50 nm and a sheet resistance of 50-200 ohms per square.

[0012] Preferably, both the matching electrode and the back electrode are titanium / platinum / gold multilayer alloy structures with a total thickness of 200–500 nm.

[0013] A method for preparing a high-frequency power load based on a diamond-aluminum nitride composite substrate includes the following steps: Provide a diamond substrate and perform pretreatment; On the surface of the pretreated diamond substrate, an aluminum nitride thin film is epitaxially grown using radio frequency reactive magnetron sputtering to form a composite substrate layer, wherein the deposition process maintains the target material self-bias stability. The high-frequency power absorption and conversion structure is prepared on the composite substrate layer; The back electrode is fabricated on the lower surface of the composite substrate layer; and Post-process the load.

[0014] Preferably, the step of epitaxially growing the aluminum nitride thin film further includes: introducing a mixture of argon and nitrogen gas onto the surface of a hydrogen-terminated diamond substrate, adjusting the sputtering pressure to 0.3–0.6 Pa and the sputtering power to 300–500 W, and adjusting the process parameters every 10–30 min during the deposition process to maintain the target self-bias voltage stable at 240–260 V.

[0015] The beneficial effects of this invention are as follows: 1. Synergistic improvement in heat dissipation and power performance: This invention uses a composite substrate layer composed of diamond and aluminum nitride heterostructures, with an interfacial thermal resistance ≤15m. 2 • K / GW significantly improves heat dissipation efficiency and effectively solves the problem of excessively high junction temperature on existing alumina substrates; combined with the serpentine structure resistive film layer and low contact resistance electrode design, the device power capacity can be increased to over 150W, and the frequency coverage range can be extended to DC~40GHz to meet the needs of high-frequency and high-power applications.

[0016] 2. Excellent integration adaptability and process reliability: The composite substrate layer has high mechanical strength. Combined with the thin film preparation process, the device size can be reduced to less than 1 / 5 of the traditional product, which is suitable for miniaturization and chip integration requirements. The preparation process ensures the crystallization quality of aluminum nitride film and the strong interface bonding by stably controlling the self-bias voltage of the target material. The process is stable and controllable, and avoids the risk of using toxic substrates, which has good prospects for industrial application. Attached Figure Description

[0017] Figure 1 This is a diagram illustrating the method steps of the present invention.

[0018] Figure 2 This is a schematic diagram of the structural composition of the present invention. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0020] Reference Figure 1-2 A high-frequency power load based on a diamond and aluminum nitride composite substrate, comprising: The composite substrate layer serves as the core support and heat dissipation base for the device. A high-frequency power absorption and conversion structure is formed on the upper surface of the composite substrate layer to achieve power absorption, dissipation and impedance matching of high-frequency signals with external circuits. The back electrode, formed on the lower surface of the composite substrate layer opposite to the high-frequency power absorption and conversion structure, serves to provide a grounding path for the device and simultaneously construct a vertical heat dissipation path to accelerate the outward diffusion of heat conducted by the composite substrate layer.

[0021] The composite substrate layer includes a diamond substrate and an aluminum nitride thin film epitaxially grown on the upper surface of the diamond substrate, forming a heterojunction structure of diamond and aluminum nitride; the heterojunction structure achieves synergistic matching of the thermal and electrical properties of diamond and aluminum nitride through atomic-level bonding at the interface.

[0022] The diamond substrate has a preferred crystal orientation and is a diamond film grown on a self-supporting diamond or silicon substrate; the thickness is 200-500 μm and the surface roughness Ra≤0.5 nm; this parameter range ensures that the substrate has sufficient mechanical strength to support the subsequent film growth, while the low surface roughness ensures the quality of the interface bonding with the aluminum nitride film.

[0023] The aluminum nitride thin film has a preferred crystal orientation, a thickness of 50–200 nm, a half-width at half-maximum (FWHM) of the XRD rocking curve of the crystal plane ≤ 1.5°, and a resistivity ≥ 10⁻⁶. 12 Ω·cm, thermal conductivity ≥200W·m -1 ·K -1Preferred crystal orientation improves the crystallization quality of thin films, high resistivity ensures the insulation performance of devices, and high thermal conductivity enhances the heat dissipation capacity of composite substrate layers.

[0024] The interfacial thermal resistance of the composite substrate layer is ≤15m. 2 • K / GW; This interfacial thermal resistance is achieved through hydrogen terminal pretreatment on the diamond substrate surface and target self-bias voltage stabilization control during magnetron sputtering. Low interfacial thermal resistance ensures efficient thermal conduction between the diamond substrate and the aluminum nitride film.

[0025] The high-frequency power absorption and conversion structure includes: A transition metal layer, deposited on the upper surface of the aluminum nitride film, is used to enhance the interfacial adhesion between the aluminum nitride film and the subsequent resistive film layer and suppress interfacial peeling. A resistive film layer is formed on the transition metal layer and patterned into a serpentine structure. The serpentine structure achieves a specified resistance value by extending the current path, thereby completing the absorption and dissipation of high-frequency power. Matching electrodes, symmetrically arranged at both ends of the resistive film layer, are used to connect to external circuits to achieve impedance matching between the load and the external circuits and reduce signal reflection. The transition metal layer is made of titanium or a titanium-tungsten alloy and has a thickness of 5–15 nm. This material and thickness range ensure that the transition metal layer can achieve the effect of interface bonding enhancement without introducing additional electrical losses.

[0026] The resistive film layer is made of tantalum nitride or silicon carbide, with a thickness of 20-50 nm and a sheet resistance of 50-200 ohms per square. This material has excellent high-frequency stability and power tolerance. The thickness and sheet resistance parameters are matched with a serpentine structure design to achieve the specified power absorption requirements.

[0027] Both the matching electrode and the back electrode are titanium / platinum / gold multilayer alloy structures with a total thickness of 200-500 nm. The titanium layer acts as an adhesion layer to enhance the bonding force with the substrate, the platinum layer acts as a barrier layer to prevent the gold layer from diffusing, and the gold layer acts as a conductive layer to reduce the electrode contact resistance. The multilayer structure works together to ensure the conductivity, stability, and bonding reliability of the electrode.

[0028] A method for preparing a high-frequency power load based on a diamond-aluminum nitride composite substrate includes the following steps: Step 1: Provide a diamond substrate and perform pretreatment; specifically, the diamond substrate is ultrasonically cleaned sequentially with acetone, ethanol, and deionized water, each cleaning time being 10-15 minutes, to remove surface oil and impurities; after cleaning, the diamond substrate is placed in a microwave plasma device, and hydrogen gas is introduced for hydrogen termination treatment; the hydrogen termination treatment conditions are: hydrogen flow rate 50-100 sccm, plasma power 300-500 W, treatment temperature 400-600℃, and treatment time 10-20 minutes; after treatment, a hydrogen-terminated diamond substrate is obtained. Hydrogen termination modification enhances the surface activity of the substrate and optimizes the interfacial bonding with the aluminum nitride film.

[0029] Step 2: On the pretreated diamond substrate, an aluminum nitride thin film is epitaxially grown using radio frequency reactive magnetron sputtering to form a composite substrate layer, wherein the deposition process maintains the target's self-bias voltage stability; specifically including: 2.1 Vacuum Pretreatment: The hydrogen-terminated diamond substrate obtained in step 1 was placed in the sample stage of the magnetron sputtering equipment, and the sputtering chamber was evacuated to 5 × 10⁻⁶. -5 Below Pa, the sample stage is then heated to 300-500℃ and held for 10-20 minutes to remove residual gas in the cavity and water vapor adsorbed on the substrate surface. 2.2 Substrate pretreatment: Argon gas with a purity of 99.999% is introduced into the sputtering cavity, the pulse bias power supply is turned on, the substrate negative bias voltage is adjusted to 800-1000V, the duty cycle is 20%-40%, and the substrate surface is bombarded with high-energy argon ions for 10-20 minutes to further remove residual impurities on the substrate surface and improve the surface flatness. 2.3 Target pre-sputtering: Introduce a mixture of argon and nitrogen into the sputtering chamber, with nitrogen comprising 20%–50% of the gas. Turn on the RF power supply and pulse bias power supply, adjust the sputtering pressure to 0.3–0.6 Pa, the sputtering power to 300–500 W, and the substrate negative bias voltage to 20–40 V, and pre-sputter the aluminum target for 10–15 min until the target self-bias voltage stabilizes at 240–260 V to remove the oxide layer and impurities on the aluminum target surface. 2.4 Thin Film Deposition: Turn on the sample stage and rotate at a speed of 20-40 r / min. Open the baffle to deposit aluminum nitride thin film. During the deposition process, adjust the ratio of argon to nitrogen gas mixture, sputtering pressure and sputtering power every 10-30 min to maintain the target self-bias voltage stable at 240-260 V. The deposition time is 1-3 h. After deposition, cool down to 200 °C at a rate of 5-10 °C / min, hold at that temperature for 1-2 h, and then allow to cool naturally to room temperature to obtain the composite substrate layer. Step 3: Fabricate the high-frequency power absorption and conversion structure on the composite substrate layer; specifically, this includes: sequentially depositing a transition metal layer and a resistive film layer on the surface of an aluminum nitride thin film using magnetron sputtering; coating the resistive film layer surface with photoresist using photolithography and performing pattern exposure and development to obtain a serpentine pattern mask; removing the resistive film layer and transition metal layer not covered by photoresist using ion etching, and after stripping the photoresist, obtaining a resistive film layer patterned into a serpentine structure; subsequently, depositing and patterning matching electrodes at both ends of the resistive film layer using magnetron sputtering combined with photolithography and etching processes. Step 4: Prepare the back electrode on the lower surface of the composite substrate layer; specifically, a titanium / platinum / gold multilayer alloy is deposited on the lower surface of the diamond substrate using a magnetron sputtering process, without the need for patterning, to form a complete back electrode layer; Step 5: Post-process the load; specifically, place the device in an annealing furnace and anneal it under a nitrogen atmosphere; the annealing temperature is 300-400℃, and the holding time is 30-60 minutes; after annealing, cool it to room temperature in the furnace to reduce the interfacial stress between layers, improve the bonding stability between the electrode and the film, and obtain the finished high-frequency power load.

Claims

1. A high-frequency power load based on a diamond and aluminum nitride composite substrate, characterized in that, include: Composite substrate layer; A high-frequency power absorption and conversion structure is formed on the composite substrate layer to achieve power absorption and impedance matching of high-frequency signals; The back electrode, formed on the lower surface of the composite substrate layer opposite to the high-frequency power absorption and conversion structure, serves to provide a grounding path and a heat dissipation path.

2. The high-frequency power load based on a diamond and aluminum nitride composite substrate according to claim 1, characterized in that, The composite substrate layer includes a diamond substrate and an aluminum nitride thin film epitaxially grown on the upper surface of the diamond substrate, forming a diamond-aluminum nitride heterojunction structure.

3. The high-frequency power load based on a diamond and aluminum nitride composite substrate according to claim 2, characterized in that, The diamond substrate has a preferred crystal orientation, a thickness of 200–500 μm, and a surface roughness Ra ≤ 0.5 nm.

4. The high-frequency power load based on a diamond and aluminum nitride composite substrate according to claim 3, characterized in that, The aluminum nitride thin film has a preferred crystal orientation, a thickness of 50–200 nm, a half-width at half-maximum (FWHM) of the XRD rocking curve of the crystal plane ≤ 1.5°, and a resistivity ≥ 10⁻⁶. 12 Ω·cm.

5. The high-frequency power load based on a diamond and aluminum nitride composite substrate according to claim 4, characterized in that, The interfacial thermal resistance of the composite substrate layer is ≤15m. 2 ·K / GW.

6. The high-frequency power load based on a diamond and aluminum nitride composite substrate according to claim 5, characterized in that, The high-frequency power absorption and conversion structure includes: A transition metal layer is deposited on the upper surface of the aluminum nitride film; A resistive film layer, formed on the transition metal layer and patterned into a serpentine structure; and Matching electrodes are symmetrically disposed at both ends of the resistive film layer; The transition metal layer is made of titanium or a titanium-tungsten alloy and has a thickness of 5–15 nm.

7. The high-frequency power load based on a diamond and aluminum nitride composite substrate according to claim 6, characterized in that, The resistive film is made of tantalum nitride or silicon carbide, with a thickness of 20–50 nm and a sheet resistance of 50–200 ohms per square.

8. The high-frequency power load based on a diamond and aluminum nitride composite substrate according to claim 7, characterized in that, Both the matching electrode and the back electrode are titanium / platinum / gold multilayer alloy structures with a total thickness of 200-500 nm.

9. A method for preparing a high-frequency power load based on a diamond and aluminum nitride composite substrate according to any one of claims 1-8, characterized in that, Includes the following steps: Provide a diamond substrate and perform pretreatment; On the surface of the pretreated diamond substrate, an aluminum nitride thin film is epitaxially grown using radio frequency reactive magnetron sputtering to form a composite substrate layer, wherein the deposition process maintains the target material self-bias stability. The high-frequency power absorption and conversion structure is prepared on the composite substrate layer; The back electrode is fabricated on the lower surface of the composite substrate layer; and Post-process the load.

10. The preparation method according to claim 9, characterized in that, The step of epitaxially growing the aluminum nitride thin film further includes: introducing a mixture of argon and nitrogen gas onto the surface of a hydrogen-terminated diamond substrate, adjusting the sputtering pressure to 0.3–0.6 Pa and the sputtering power to 300–500 W, and adjusting the process parameters every 10–30 min during the deposition process to maintain the target self-bias voltage stable at 240–260 V.

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