Miniaturized MEMS circulator with TSV capacitor

Abstract

The invention discloses a miniaturized MEMS circulator with a TSV capacitor. The miniaturized MEMS circulator comprises a kovar metal layer, a first metal layer, a first silicon adapter plate layer and ferrite, first metal columns are distributed on the bottom surface of the first silicon adapter plate layer; second metal columns are distributed on the top surface of the first silicon adapter plate layer; a second metal layer; bonding the interconnection layer; a third metal layer; a second silicon adapter plate layer; an insulating spacer and a permanent magnet. According to the invention, the size is reduced and the bandwidth is improved by forming a capacitor through staggered and parallel TSVs. Besides, matching at ports is carried out through a capacitance-inductance-capacitance matching network, and an inductor in the matching network is a serpentine inductor, so that the size required by the matching network is further reduced, and miniaturization and integration of the MEMS circulator are facilitated.

Description

Technical Field

[0001] This invention relates to the field of microwave integrated devices, and in particular to a miniaturized MEMS circulator structure with a TSV capacitor. Background Technology

[0002] The circulator is a crucial component in the radar front-end T / R assembly. It features unidirectional transmission, its core function being to ensure that electromagnetic signals can only be transmitted along a predetermined, fixed direction, while providing extremely high isolation in the reverse direction. It is commonly used in radar and communication systems to achieve "one-way signal flow." In the front-end of communication and millimeter-wave radar systems, the circulator is a key hub connecting the antenna, transmitting unit, and receiving unit. It primarily addresses two core issues: signal isolation and structural simplification in the radar front-end. The superior performance of the circulator significantly impacts the stability of the T / R assembly and its transmission power.

[0003] Ferrite circulators utilize the gyromagnetic effect of ferrite materials to achieve unidirectional transmission of microwave signals, enabling isolation between upper and lower stages in a microwave link. In transceiver systems, they can also achieve antenna-transmitter sharing, fulfilling a full-duplex function and greatly simplifying the structure of RF transceiver systems. Compared to traditional ceramic circulators, MEMS circulators leverage the high precision of MEMS technology, improving circuit structure accuracy and product consistency. Furthermore, they are compatible with other passive devices or components, effectively enhancing integration.

[0004] Currently, most MEMS circulators use high-resistivity silicon as the core dielectric, but silicon has a lower dielectric constant compared to high-dielectric ceramics. This is a key factor limiting further miniaturization, making it unable to meet the actual requirements of system miniaturization. Therefore, this paper proposes to increase the equivalent capacitance of MEMS circulators by forming approximately parallel planar capacitors through non-through-thrust TSVs, thereby significantly reducing the device size to meet the requirements of miniaturization and integration. Summary of the Invention

[0005] Given the disadvantages of traditional MEMS circulators, such as their large size, it is difficult to further miniaturize and integrate them without improving the circulator circuitry. To achieve the above objectives, this invention provides a miniaturized MEMS circulator with a TSV capacitor that is highly miniaturized and integrated.

[0006] A miniaturized MEMS circulator with TSV capacitor includes: a Kovar metal layer and a first metal layer, wherein a first silicon interposer layer is disposed on the first metal layer, and a ferrite is placed in the center of the first silicon interposer layer. A first metal pillar is distributed on the bottom surface of the first silicon interposer layer. The first metal pillar grows from the bottom surface of the first silicon interposer layer to the top surface of the first silicon interposer layer but does not penetrate the top surface of the first silicon interposer layer. A second metal pillar is distributed on the top surface of the first silicon interposer layer. The second metal pillar grows from the top surface of the first silicon interposer layer to the bottom surface of the first silicon interposer layer but does not penetrate the bottom surface of the first silicon interposer layer. A second metal layer is disposed on the first silicon interposer layer; A bonding interconnect layer is disposed on the second metal layer; A third metal layer is disposed on the bonding interconnect layer; A second silicon adapter layer is disposed on the third metal layer; The second silicon adapter plate layer is provided with insulating pads and permanent magnets.

[0007] A conductive adhesive layer is disposed between the Kovar metal layer and the first metal layer.

[0008] The bottom surface of the first silicon adapter layer is connected to the first metal layer, and the first metal pillar is connected to the first metal layer.

[0009] The top surface of the first silicon interposer layer is connected to the second metal layer, and the second metal pillar is connected to the second metal layer.

[0010] The bottom surface of the second silicon interposer layer is connected to the third metal layer.

[0011] The bonding interconnect layer is disposed between the second metal layer and the third metal layer.

[0012] The bottom surface of the ferrite is connected to the first metal layer, and the top surface of the ferrite is connected to the third metal layer.

[0013] Both the second and third metal layers include: a multi-channel reactive center junction circuit and a matching network circuit connected in sequence with TSV capacitors; The multi-channel reactive center junction circuit with TSV capacitors includes: a central disk junction and a microstrip line group connected to the central disk junction, wherein the microstrip line in the microstrip line group is connected to the second metal pillar; The matching network includes a first-stage capacitor, a second-stage inductor, and a third-stage capacitor connected in sequence, wherein the second-stage inductor is a serpentine inductor.

[0014] The microstrip line group consists of three groups, which are symmetrically distributed at 120° intervals.

[0015] Specifically, the main structure is as follows; The bottom layer consists of a Kovar metal layer, a first metal layer, and a conductive adhesive layer connecting the Kovar metal layer and the first metal layer.

[0016] The middle layer is the first silicon interposer layer. The front and back of the first silicon interposer layer are metal layers. The front is the first metal layer mentioned above, and the back is the second metal layer. The first metal layer forms an electrical connection with the conductive adhesive layer.

[0017] The first metal layer has a first metal pillar structure that grows from the first metal layer to the first silicon interposer layer but does not penetrate the first silicon interposer layer.

[0018] The middle two layers are the second silicon interposer layer, and the back of the second silicon interposer layer is the third metal layer. The third metal layer and the aforementioned second metal layer form a bonding interconnect layer.

[0019] The top layer consists of a permanent magnet and an insulating pad. The insulating pad is located on the front side of the second silicon adapter layer, and the permanent magnet is placed on it.

[0020] The aforementioned second and third metal layers, along with the bonding interconnect layer connecting them, constitute the main structure of the circulator, namely the microstrip circuit section. This mainly includes: a multi-channel reactive structure, first, second, and third RF ports, and a matching network that matches the central disk junction with the first, second, and third RF ports. Furthermore, the CLC matching network that matches the aforementioned multi-channel reactive structure with the first, second, and third RF ports exhibits a 120° symmetrical relationship.

[0021] The microstrip line groups of the first, second, and third multi-channel reactance circuits mentioned above have second metal pillar structures distributed at their ends. These structures grow from the second metal layer toward the first silicon interposer layer but do not penetrate the first silicon interposer layer. The second metal pillar structures are arranged parallel to the first metal pillar structures mentioned above, which is used to increase the capacitance and thus reduce the size of the circulator.

[0022] As described above, the present invention provides a miniaturized MEMS circulator structure with a TSV capacitor, which has the following advantages: This invention increases capacitance by embedding TSVs (Transient Voltage Slabs) at the ends of the circulator's multi-path reactive structure and between the first metal layer and the first silicon interposer layer. Compared to traditional circulator multi-path reactive structures, this allows for further reduction in circulator size and increased integration. Simultaneously, the matching network and intermediate inductor at the three ports utilize serpentine bends instead of traditional microstrip lines, saving matching network area. Finally, since the capacitance formed by the TSVs does not create a lateral electric field near the second metal layer, this helps reduce performance deviations caused by assembly errors in the circulator, improving its consistency. Attached Figure Description

[0023] Figure 1 This is an exploded perspective view of the miniaturized MEMS circulator with TSV capacitor proposed in this invention.

[0024] Figure 2 This is a cross-sectional view of the miniaturized MEMS circulator with TSV capacitor proposed in this invention.

[0025] Figure 3 This is a top view of the miniaturized MEMS circulator with TSV capacitor proposed in this invention.

[0026] Figure 4 , 5 Figures 6 and 7 are the simulated S-parameter curves of the miniaturized MEMS circulator with TSV capacitor proposed in this invention.

[0027] The names corresponding to the numbers in the attached diagram are as follows: 1. Kovar metal layer; 2. Conductive adhesive layer; 3. First metal layer; 4. First silicon interposer layer; 5. First metal pillar; 6. Second metal pillar; 7. Second and third metal layers and the bonding interconnect layer connecting them; 8. Ferrite; 9. Second silicon interposer layer; 10. Insulating gasket; 11. Permanent magnet; 12. Central disk junction; 13. Microstrip line group; 14. First-stage capacitor; 15. Serpentine inductor; 16. Second-stage capacitor. Detailed Implementation

[0028] like Figure 1 and Figure 2 As shown, the structure of the miniaturized MEMS circulator with TSV capacitor proposed in this invention, from bottom to top, is as follows: The bottom layer is Kovar metal layer 1, and a conductive adhesive layer 2 with a thickness of about 20~40um is coated on Kovar metal layer 1. The conductive adhesive layer 2 is responsible for connecting Kovar metal layer 1 and the first metal layer 3.

[0029] The first silicon interposer layer 4 is located on the first metal layer 3. The first metal layer 3 has 1 to 3 first metal pillars 5 growing in the direction of the first silicon interposer layer 4 but not penetrating the first silicon interposer layer 4. In addition, a disk with a radius slightly larger than 25 μm than the ferrite 8 is cut off from the first metal layer 3 to hold the ferrite 8. The height of the ferrite 8 needs to be slightly higher than the first silicon interposer layer by about 10 to 20 μm to place the second metal layer.

[0030] The second metal layer, the third metal layer, and the bonding interconnect layer 7 connecting the two have second metal pillars 6 (1 to 3 pillars) growing in the direction of the first silicon interposer layer 4 but not penetrating the first silicon interposer layer 4. The function of the first metal pillars 5 and the second metal pillars 6 is to increase the capacitance.

[0031] The second silicon interposer layer 9 is located above the second metal layer, the third metal layer, and the bonding interconnect layer 7 connecting the two. An insulating pad 10 is placed on it to hold the permanent magnet 11 and provide a stable static magnetic field.

[0032] like Figure 3As shown, the miniaturized MEMS circulator with TSV capacitor of the present invention includes a multi-path reactive structure and a matching network in the second metal layer, the third metal layer, and the bonding interconnect layer 7 connecting the two. The multi-path reactive structure mainly includes a central disk junction 12 and microstrip line groups 13, typically 9-15 lines, evenly distributed at 120° intervals along the central disk junction 12. The matching network mainly includes a first-stage capacitor 14, a first-stage inductor 15, and a second-stage capacitor 16. The second-stage inductor uses a serpentine inductor to reduce the size of the matching network.

[0033] like Figures 4 to 6 As shown, it displays the S-parameter simulation results obtained after performing a three-dimensional electromagnetic simulation of the capacitor-enhanced ring isolator structure of the present invention. Figure 4 It can be seen that within the 8.8~10.5GHz frequency band, the insertion loss is less than 0.7dB, the isolation is better than 30dB, and the return loss is better than 20dB. The circulator's planar dimensions are only 3mm*3mm. Compared with traditional MEMS circulators, this represents a significant size reduction.

[0034] As described above, the present invention provides a miniaturized MEMS circulator structure with a TSV capacitor, which has the following advantages: This invention increases the equivalent capacitance at the microstrip line end by using TSV capacitance at the end of the circulator multi-path reactive structure and at the first metal layer to the first silicon transition plate layer. Compared with the traditional circulator multi-path reactive structure, this further reduces the circulator size and increases its integration. Simultaneously, the inductor in the matching network uses a serpentine bend instead of a traditional microstrip line, saving matching network area. Finally, since the introduction of TSV does not introduce a lateral electric field near the second metal layer, this helps reduce assembly error requirements and improve consistency.

[0035] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A miniaturized MEMS circulator with a TSV capacitor, comprising: Kovar metal layer and first metal layer, characterized in that a first silicon transition plate layer is disposed on the first metal layer, and ferrite is placed in the center of the first silicon transition plate layer. A first metal pillar is distributed on the bottom surface of the first silicon interposer layer. The first metal pillar grows from the bottom surface of the first silicon interposer layer to the top surface of the first silicon interposer layer but does not penetrate the top surface of the first silicon interposer layer. A second metal pillar is distributed on the top surface of the first silicon interposer layer. The second metal pillar grows from the top surface of the first silicon interposer layer to the bottom surface of the first silicon interposer layer but does not penetrate the bottom surface of the first silicon interposer layer. A second metal layer is disposed on the first silicon interposer layer; A bonding interconnect layer is disposed on the second metal layer; A third metal layer is disposed on the bonding interconnect layer; A second silicon adapter layer is disposed on the third metal layer; The second silicon adapter plate layer is provided with insulating pads and permanent magnets.

2. The miniaturized MEMS circulator with TSV capacitor according to claim 1, characterized in that, A conductive adhesive layer is disposed between the Kovar metal layer and the first metal layer.

3. The miniaturized MEMS circulator with TSV capacitor according to claim 1, characterized in that, The bottom surface of the first silicon adapter layer is connected to the first metal layer, and the first metal pillar is connected to the first metal layer.

4. The miniaturized MEMS circulator with TSV capacitor according to claim 1, characterized in that, The top surface of the first silicon interposer layer is connected to the second metal layer, and the second metal pillar is connected to the second metal layer.

5. The miniaturized MEMS circulator with TSV capacitor according to claim 1, characterized in that, The bottom surface of the second silicon interposer layer is connected to the third metal layer.

6. The miniaturized MEMS circulator with TSV capacitor according to claim 1, characterized in that, The bonding interconnect layer is disposed between the second metal layer and the third metal layer.

7. The miniaturized MEMS circulator with TSV capacitor according to claim 1, characterized in that, The bottom surface of the ferrite is connected to the first metal layer, and the top surface of the ferrite is connected to the third metal layer.

8. The miniaturized MEMS circulator with TSV capacitor according to claim 1, characterized in that, Both the second and third metal layers include: a multi-channel reactive center junction circuit and a matching network circuit connected in sequence with TSV capacitors; The multi-channel reactive center junction circuit with TSV capacitors includes: a central disk junction and a microstrip line group connected to the central disk junction, wherein the microstrip line in the microstrip line group is connected to the second metal pillar; The matching network includes a first-stage capacitor, a second-stage inductor, and a third-stage capacitor connected in sequence, wherein the second-stage inductor is a serpentine inductor.

9. The miniaturized MEMS circulator with TSV capacitor according to claim 1, characterized in that, The microstrip line group consists of three groups, which are symmetrically distributed at 120° intervals.

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