Substrate integrated microwave guide circulator and method of manufacturing the same
By constructing a fully enclosed planar rectangular waveguide structure and embedding a gyromagnetic sheet within a semiconductor substrate, the problems of large size, high loss, and poor consistency of the circulator were solved, and high-power, high-reliability microwave circulator fabrication was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- UNIV OF ELECTRONICS SCI & TECH OF CHINA
- Filing Date
- 2026-04-28
- Publication Date
- 2026-06-09
AI Technical Summary
Existing circulators are bulky and incompatible with semiconductor processes, resulting in high electromagnetic radiation losses, low power capacity, and poor batch consistency.
A planar rectangular waveguide structure is adopted, and a closed space is constructed using a metal layer, metallized sidewalls and a metal ground layer. A gyratory magnetic sheet is embedded in the semiconductor substrate by combining laser ablation and magnetron sputtering processes to form a fully enclosed microwave circulator.
It significantly reduces electromagnetic radiation loss, improves device isolation and power capacity, enhances batch consistency and reliability at high temperatures and high frequencies, and simplifies system-level packaging.
Smart Images
Figure CN122178088A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of microwave device and integrated circuit manufacturing, and specifically relates to a substrate-integrated microwave circulator and its fabrication method. Background Technology
[0002] Circulators, as key non-reciprocal devices for signal duplexing and isolation in radio frequency (RF) front-ends, play an irreplaceable role in radar and mobile communication integrated systems. However, traditional bulk circulators rely on manual assembly within metal cavities, resulting in large sizes and incompatibility with modern semiconductor processes. While existing technologies attempt to reduce size using planar microstrip line structures, microstrip lines, as semi-open transmission lines, are prone to significant electromagnetic radiation losses at high frequencies. Furthermore, their power capacity is limited by the cross-sectional area of thin-film conductors, making it difficult to meet the dual requirements of low loss and high reliability in high-power integrated systems. In addition, existing integration schemes, when embedding ferrite cores in substrates, often suffer from problems such as unsealed electromagnetic boundaries, uneven field distribution, and complex sidewall metallization processes, leading to limited device isolation and poor batch-to-batch consistency. Therefore, developing an integrated circulator fabrication process that maintains the high power and high shielding characteristics of rectangular waveguides, enables fully planar micro / nano fabrication integration using semiconductor substrates, and possesses excellent non-reciprocal transmission performance has become a pressing technical challenge in the field of microwave integrated circuits. Summary of the Invention
[0003] To address the challenges of the existing technologies, this invention provides a substrate-integrated microwave circulator and its fabrication method, aiming to solve the technical problems of high loss, low power capacity, and poor integration with semiconductor processes in existing integrated circulators.
[0004] To solve the above problems, the technical solution adopted by the present invention is as follows:
[0005] A substrate-integrated microwave circulator, comprising:
[0006] The integrated substrate 1 includes a hexagonal functional area at the center and an input / output port area at the edge; three sets of parallel through slots 5 form three side length regions with sides of 120° to each other, presenting a "Y" shaped structure; the input / output port area includes three metallized wires extending along the direction of the three side length regions, serving as signal input or output ports;
[0007] A planar rectangular waveguide is formed by a metal layer on the surface of an integrated substrate, metal sidewalls that penetrate the slot, and a metal ground layer on the back of the integrated substrate.
[0008] The gyromagnetic plate 7 is embedded in a metallized blind hole at the center of the integrated substrate and is wrapped in a metal layer of a planar rectangular waveguide.
[0009] Furthermore, the rotating magnetic plate is located at the center of the "Y"-shaped structure.
[0010] A method for fabricating a substrate-integrated microwave circulator includes the following steps:
[0011] Step 1. Pre-treatment of the integrated substrate;
[0012] Semiconductor materials, microwave ceramics, or other functional materials that need to be integrated are selected as the integration substrate, and the integration substrate is polished on both sides to make the roughness Ra of the upper and lower surfaces ≤ 5 nm.
[0013] Step 2. Metallize the surface of the integrated substrate;
[0014] A metallization pattern is formed on the surface of the integrated substrate after step 1 using photolithography and magnetron sputtering processes.
[0015] The metallization pattern includes a hexagonal functional area 2, and each of the three side length regions of the hexagonal functional area, which are 120° apart, has a set of two parallel rectangular slots 3. The adjacent sets of rectangular slot patterns extend towards the center and intersect, forming a "Y"-shaped closed area 4 in the center of the integrated substrate.
[0016] Step 3. Three-dimensional structure fabrication;
[0017] Based on the metallization pattern of step 2, a laser is used to ablate and cut along the path of the rectangular slot pattern to form a through slot 5 that penetrates the integrated substrate; and a blind hole 6 is formed in the center of the central closed region 4.
[0018] Step 4. Integration of rotating magnetic sheets;
[0019] Place the ferrite magnetic plate 7 into the blind hole and fix it in place;
[0020] Step 5. Secondary metallization;
[0021] Metal deposition is performed again to form a uniform metal layer on the sidewalls of the through-hole 5, the sidewalls of the blind hole 6, and the upper surface of the ferrite magnetic sheet 7.
[0022] Step 6. Constructing the metallic grounding layer;
[0023] A metal ground layer is deposited on the back side of the structure obtained in step 5. At this time, the metal layer on the front side of the integrated substrate, the metallized sidewall that penetrates the slot 5, and the metal ground layer on the back side enclose and form a closed planar rectangular waveguide structure.
[0024] Furthermore, in step 1, the integrated substrate is one of gallium nitride, silicon carbide, high-resistivity silicon, low-temperature co-fired ceramic (LTCC), or other functional materials.
[0025] Furthermore, in step 2, in the hexagonal functional area, except for the rectangular slots, the remaining areas are covered with a metal layer (the rectangular slot pattern does not contain metal).
[0026] Furthermore, in step 2, the three sides of the hexagonal functional area 2 with rectangular slot patterns extend three metallized wires to the edge of the integrated substrate, serving as signal input or output ports 8.
[0027] Furthermore, in step 4, a resistivity ≥10 is used. 6 The conductive silver paste with a strength of S / m bonds and fixes the ferrite magnetic sheet to the bottom of the blind hole.
[0028] Furthermore, the metallization pattern in step 2, the metal layer in step 5, and the grounding metal layer in step 6 are made of one or more of Ti / Au, Cr / Cu, or Au.
[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0030] This invention provides a substrate-integrated microwave waveguide and its fabrication method. It employs a planar rectangular waveguide structure constructed from a metal layer, metallized sidewalls, and a metal ground layer. This effectively confines electromagnetic field energy within a closed space formed by the metal layers on the upper and lower surfaces of the substrate and the sidewalls of the through-groove, fundamentally eliminating radiation loss and signal crosstalk inherent in traditional microstrip structures, and significantly improving the device's isolation and Q-value. Secondly, the fully enclosed metallized boundary greatly enhances the device's power capacity, enabling it to meet the application requirements of high-power radar and communication front-ends. Furthermore, by combining laser ablation and magnetron sputtering, precise embedding and electrical interconnection of gyromagnetic materials within the semiconductor substrate are achieved, solving the problems of miniaturization and low assembly precision of discrete magnetic components. Finally, this fabrication method is highly compatible with the processing flow of semiconductor substrates such as gallium nitride and silicon carbide, greatly simplifying the complexity of system-level packaging, reducing device size, and improving the reliability and batch consistency of the device under high-temperature and high-frequency operating environments. Attached Figure Description
[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.
[0032] Figure 1 A schematic diagram of a substrate-integrated microwave circulator provided by the present invention;
[0033] Figure 2This is a schematic diagram of the structure of an integrated substrate after laser processing;
[0034] Figure 3 The S-parameter simulation curves of the Q-band integrated microwave circulator used in this embodiment are shown. Detailed Implementation
[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.
[0036] Example
[0037] A method for fabricating an integrated circulator operating in the Q-band includes the following steps:
[0038] S1: Substrate Preparation and Material Selection
[0039] The embodiment uses a 0.42 mm thick single-crystal gallium nitride (GaN) substrate as the integration substrate. First, the substrate undergoes double-sided chemical mechanical polishing to achieve a surface roughness Ra of less than 5 nm. The choice of GaN substrate not only facilitates integration with power devices, but its high thermal conductivity also helps dissipate heat from the circulator under high-power operation.
[0040] S2: Photolithography and initial metallization
[0041] Photolithography was performed on the front side of the substrate to define three propagation axes radially distributed at 120° intervals. Parallel non-metallic rectangular slots (0.4 mm wide) were defined on both sides of each axis, and the distance between the slots determined the width of the rectangular waveguide, a = 1.72 mm. The three sets of slots extended towards the center, enclosing a closed window with a diameter of approximately 1.30 mm at the center of the substrate. Subsequently, a Ti / Au metal layer with a thickness of approximately 1 μm was deposited using magnetron sputtering. At this point, except for the rectangular slots, the entire front side of the substrate was covered with metal.
[0042] S3: Laser Precision Machining
[0043] Using the front-side metallized pattern as a mask, an ultrafast laser is used to ablate along a rectangular slit path, forming a groove that penetrates the entire thickness of the substrate (0.42 mm). Simultaneously, a circular blind hole with a depth of 0.24 mm and a diameter of 1.29 mm is machined at the central window location. Figure 2 As shown. The diameter of the blind hole is slightly larger than the core to be embedded (approximately 0.01 mm larger) to compensate for assembly tolerances and to allow space for conductive adhesive.
[0044] S4: Rotary magnetic sheet integration
[0045] M-type barium ferrite single crystal was selected as the gyromagnetic core, and its saturation magnetization M s=4500 Oe. The material was fabricated into a disc with a diameter of 1.28 mm and a height of 0.24 mm. After applying silver conductive paste to the bottom of the blind hole, the ferrite gyromagnetic sheet was precisely placed into the blind hole. Because the depth of the blind hole and the height of the gyromagnetic sheet were consistent, the upper surface of the gyromagnetic sheet was ensured to be flush with the front side of the substrate.
[0046] S5: Secondary Metallization and Waveguide Shaping
[0047] The device is then metallized again using magnetron sputtering. In this step, metal is not only deposited on the upper surface of the gyromagnetic plate, but also deposited through laser-cut through-holes and blind via sidewalls to form a complete metallized sidewall with a thickness of approximately 1 μm. Finally, a metal layer with a thickness of approximately 1 μm is deposited on the back side of the substrate as a ground plane. At this point, the GaN dielectric within the substrate is completely encapsulated by the upper and lower metal layers and the sidewall metal, forming a substrate-integrated rectangular waveguide with a cross-sectional dimension of 1.72 mm × 0.42 mm.
[0048] S6: Performance Testing and Simulation
[0049] A static magnetic field of approximately 2150 Oe is applied externally to the device to cause the ferrite to operate in a biased state. For example... Figure 3 The figure shows the S-parameter simulation curves of the circulator fabricated in this embodiment in the Q-band. The results show that the device exhibits good non-reciprocal characteristics near the center frequency, with extremely low insertion loss of approximately 0.59 dB. The bandwidth is approximately 5.41 GHz with an isolation greater than -18 dB, demonstrating ultra-high isolation and ultra-large bandwidth, verifying the efficient transmission capability of the substrate-integrated microwave conductor structure in the millimeter-wave band.
Claims
1. A substrate-integrated microwave circulator, characterized in that, include: An integrated substrate (1) includes a hexagonal functional area at the center and an input / output port area at the edge; Three sets of parallel through slots (5) make the hexagonal functional area form three side length regions with a side length of 120° to each other, presenting a "Y" shaped structure; the input and output port area includes three metallized wires extending along the direction of the three side length regions, serving as signal input or output ports; A planar rectangular waveguide is formed by a metal layer on the surface of an integrated substrate, metal sidewalls that penetrate the slot, and a metal ground layer on the back of the integrated substrate. The gyromagnetic sheet (7) is embedded in a metallized blind hole at the center of the integrated substrate and is wrapped in a metal layer of a planar rectangular waveguide.
2. The substrate-integrated microwave circulator according to claim 1, characterized in that, The rotating magnetic plate is located at the center of the "Y"-shaped structure.
3. A method for fabricating a substrate-integrated microwave circulator, characterized in that, Includes the following steps: Step 1. Pre-treatment of the integrated substrate; The integrated substrate is polished on both sides to make the roughness Ra of the upper and lower surfaces ≤ 5 nm; Step 2. Metallize the surface of the integrated substrate; A metallization pattern is formed on the surface of the integrated substrate after step 1 using photolithography and magnetron sputtering processes; The metallization pattern includes a hexagonal functional area (2), and each of the three side length regions of the hexagonal functional area that are 120° apart has a set of two parallel rectangular slots (3). The adjacent sets of rectangular slot patterns extend towards the center and intersect, forming a "Y"-shaped closed area in the center of the integrated substrate (4). Step 3. Three-dimensional structure fabrication; Based on the metallization pattern of step 2, a laser is used to ablate and cut along the path of the rectangular slit pattern to form a through slot (5) that penetrates the integrated substrate; and a blind hole (6) is formed in the center of the central closed area (4). Step 4. Integration of rotating magnetic sheets; The ferrite magnetic disc (7) is placed into the blind hole and fixed. Step 5. Secondary metallization; Metal deposition is performed again to form a uniform metal layer on the sidewalls of the through-slot (5), the sidewalls of the blind hole (6), and the upper surface of the ferrite magnetic sheet (7). Step 6. Constructing the metallic grounding layer; A metal ground layer is deposited on the back side of the structure obtained in step 5. At this time, the metal layer on the front side of the integrated substrate, the metallized sidewall that penetrates the slot 5, and the metal ground layer on the back side enclose and form a closed planar rectangular waveguide structure.
4. The method for fabricating a substrate-integrated microwave circulator according to claim 3, characterized in that, In step 1, the integrated substrate is one of gallium nitride, silicon carbide, high-resistivity silicon, low-temperature co-fired ceramic or other functional materials.
5. The method for fabricating a substrate-integrated microwave circulator according to claim 3, characterized in that, In step 2, the hexagonal functional area is covered with a metal layer, except for the rectangular gaps.
6. The method for fabricating a substrate-integrated microwave circulator according to claim 3, characterized in that, In step 2, the three sides of the hexagonal functional area (2) with rectangular slot patterns extend three metallized wires to the edge of the integrated substrate, which serve as signal input or output ports (8).
7. The method for fabricating a substrate-integrated microwave circulator according to claim 3, characterized in that, In step 4, a resistivity ≥10 is used. 6 The conductive silver paste with a strength of S / m bonds and fixes the ferrite magnetic sheet to the bottom of the blind hole.
8. The method for fabricating a substrate-integrated microwave circulator according to claim 3, characterized in that, The metal material used in the metallization pattern in step 2, the metal layer in step 5, and the grounding metal layer in step 6 is one or more of Ti / Au, Cr / Cu, or Au.