CN112886160A

CN112886160A - Compact substrate integrated waveguide filter based on silicon-based MEMS (micro-electromechanical systems) process

Info

Publication number: CN112886160A
Application number: CN202110047595.6A
Authority: CN
Inventors: 张皓; 蔡传涛; 张硕; 赵磊; 周潇潇
Original assignee: CETC 55 Research Institute
Current assignee: CETC 55 Research Institute
Priority date: 2021-01-14
Filing date: 2021-01-14
Publication date: 2021-06-01
Anticipated expiration: 2041-01-14
Also published as: CN112886160B

Abstract

The invention discloses a compact substrate integrated waveguide filter based on a silicon-based MEMS (micro electro mechanical system) process, which comprises a SIW (substrate integrated waveguide) cavity structure of a top substrate and a bottom substrate, and further comprises a top metal layer, a middle metal layer, a bottom metal layer, a silicon-based through hole arranged in the substrate, excitation of a first coplanar waveguide port on the upper surface of the top substrate, excitation of a second coplanar waveguide port on the lower surface of the bottom substrate and a cross-shaped groove line structure on the middle metal layer; the top substrate and the bottom substrate are bonded together by wafer level gold. The filter has the characteristics of small volume, light weight, high power capacity, good passband selectivity and high out-of-band rejection degree, and is widely applied to millimeter wave radio frequency front-end systems.

Description

Compact substrate integrated waveguide filter based on silicon-based MEMS (micro-electromechanical systems) process

Technical Field

The invention relates to a substrate integrated waveguide filter, in particular to a compact substrate integrated waveguide filter based on a silicon-based MEMS (micro-electromechanical systems) process.

Background

The filter is an essential important component of the radio frequency microwave system, and the filter module with excellent performance is a necessary premise for the normal work of the radio frequency microwave communication system. With the rapid development of Monolithic Microwave Integrated Circuit (MMIC) technology, higher requirements are also placed on the filter. Substrate Integrated Waveguide (SIW) filters are a significant effort. The structure has a high Q (power capacity) value and electromagnetic shielding capability while greatly reducing the volume. The MEMS technology is a high-precision multilayer three-dimensional micromachining technology, the SIW structure filter is manufactured by the MEMS technology, micron-scale machining precision can be achieved, the obtained filter has remarkable advantages in the aspects of volume, loss, selectivity, consistency and the like, and index requirements of millimeter wave frequency bands can be met. MEMS coplanar waveguide transmission lines have many advantages over other transmission lines: it can be integrated with other radio-frequency devices in a coplanar manner without opening holes on the substrate, and has high transmission bandwidth which can reach dozens or even hundreds of GHz. Secondly, the combination of the SIW technology and the silicon micro-mechanical technology is used for realizing the monolithic silicon-based MEMS filter, which is a technical approach for realizing the miniaturization and integration of an RF (radio frequency) system and has wide application prospect in the fields of wireless communication base stations, space satellite communication and the like.

The existing filter has overlarge area, so that a microwave communication system is larger, and meanwhile, the cost of a product is increased; secondly, most of the existing filters have a microstrip line transmission structure with a low Q value, and due to the parasitic effect of the microstrip line at a high-frequency end, the use of the microstrip line in the millimeter wave field is limited. Therefore, the existing filter cannot meet the engineering application of a future millimeter wave radio frequency front-end system from the aspect of area size or power capacity.

Disclosure of Invention

The purpose of the invention is as follows: the invention aims to provide a compact substrate integrated waveguide filter based on a silicon-based MEMS (micro-electromechanical systems) process, which has small area and large power capacity.

The technical scheme is as follows: the filter comprises a SIW cavity structure of a top substrate and a bottom substrate, and further comprises a top metal layer, a middle metal layer, a bottom metal layer, a TSV through hole arranged in the substrate, a first coplanar waveguide excitation port on the upper surface of the top substrate, a second coplanar waveguide excitation port on the lower surface of the bottom substrate and a cross-shaped groove line structure on the middle metal layer; the top substrate and the bottom substrate are bonded together by wafer level gold.

The distance from the first coplanar waveguide excitation port to the second side line of the TSV is one fourth of the total length of the first side line of the TSV, and the distance from the second coplanar waveguide excitation port to the third side line of the TSV is one fourth of the total length of the fourth side line of the TSV. Two sides of the first coplanar waveguide excitation port are respectively provided with a first rectangular groove, and two sides of the second coplanar waveguide excitation port are respectively provided with a second rectangular groove; the width sizes of the first rectangular groove and the second rectangular groove are both adjustable; the width dimensions of the first coplanar waveguide excitation port and the second coplanar waveguide excitation port are the same. The first coplanar waveguide excitation port is overlapped with the outer edge of the top substrate; the second coplanar waveguide excitation port coincides with an outer edge of the underlying substrate.

The cross-shaped groove line structure is etched in the center of the middle metal layer through a corrosion process.

The TSV through holes are arranged on the periphery of the rectangular cavity and are uniformly distributed to form the rectangular SIW cavity. And the top metal layer, the middle metal layer and the bottom metal layer respectively grow a gold layer with standard thickness on the surface of the substrate through an electroplating process.

Compared with the prior art, the invention has the following remarkable effects: 1. the silicon-based substrate processed based on the semiconductor process can provide higher wiring precision; 2. the port is excited by adopting the coplanar waveguide technology, so that the transition of the electromagnetic signal from a microstrip transmission mode to an SIW cavity transmission mode is facilitated, the loss is low, and the transmission bandwidth is high; 3. by using the structure of the substrate integrated waveguide, the volume is greatly reduced, and simultaneously, the power capacity value and the electromagnetic shielding capability are high; 4. the etched cross-shaped groove line structure enables electromagnetic signals to be well coupled from the top layer cavity to the bottom layer cavity, and the integrity of the signals is guaranteed; 5. the positions of the input and output ports are reasonably selected, so that the SIW cavity simultaneously excites the TE201 mode and the TE102 mode, four transmission poles and a plurality of transmission zeros are obtained, and the passband bandwidth and the out-of-band rejection degree are increased.

Drawings

FIG. 1 is a schematic diagram of a filter structure according to the present invention;

fig. 2(a) is a schematic diagram of a top metal layer structure of a filter of the present invention, (b) is a schematic diagram of a middle metal layer structure of a filter of the present invention, and (c) is a schematic diagram of a bottom metal layer structure of a filter of the present invention;

fig. 3(a) is a TE101 mode magnetic field diagram of the present invention, (b) is a TE102 mode magnetic field diagram of the present invention, (c) is a TE201 mode magnetic field diagram of the present invention;

fig. 4 is a frequency response curve of an embodiment of the present invention.

Detailed Description

The invention is described in further detail below with reference to the drawings and the detailed description.

The filter of the present invention includes a top metal layer 1, a middle metal layer 2, a bottom metal layer 3, TSV (Through Silicon Via) Through holes 6 disposed inside the substrate, a first coplanar waveguide excitation port 4 on the upper surface of the top substrate 10, a second coplanar waveguide excitation port 5 on the lower surface of the bottom substrate 20, and a cross-shaped slot line structure 7 etched on the middle metal layer 2, as shown in fig. 1.

The distance from the first coplanar waveguide excitation port 4 on the upper surface of the top substrate 10 to the second side line 42 of the TSV via is one fourth of the total length of the first side line 41 of the TSV via, and the distance from the second coplanar waveguide excitation port 5 on the lower surface of the bottom substrate 20 to the third side line 43 of the TSV via is one fourth of the total length of the fourth side line 44 of the TSV via, so as to excite the degenerate modes (TE102 and TE201) in the top SIW cavity and the bottom SIW cavity.

A cross-shaped slot line structure 7 is etched in the center of the middle metal layer 2. The transmission signal is coupled from the top metal layer 1 to the bottom metal layer 3 through the cross-shaped slot line structure 7, and the cross-shaped slot line 7 does not influence the magnetic field distribution of the degenerate mode.

The top substrate 10 and the bottom substrate 20 are interconnected by wafer-level gold bonding. By utilizing the wafer-level gold bonding process, the bonding firmness is strong, and the bonding surface is attached, thereby being beneficial to the transition transmission of signals.

The TSV through holes 6 arranged in the substrate are arranged on the periphery of the rectangular cavity, the rectangular SIW cavity is constructed, the size of the cavity determines the main mode resonance frequency of the SIW cavity, and the larger the area is, the smaller the main mode resonance frequency is.

The top substrate 10 and the bottom substrate 20 are both TSV through hole 6 adapter plates (substrates with the depth of 400 microns and the diameter of 120 microns) with the depth-to-width ratio of 400:120, the top metal layer 1, the middle metal layer 2, the bottom metal layer 3 and the TSV through holes 6 arranged in the substrates are processed based on semiconductor process processing, and the top substrate 10 and the bottom substrate 20 are connected together through wafer-level gold bonding.

In the invention, the excitation port adopts the coplanar waveguide technology to excite the port, electromagnetic signals are transited from the microstrip transmission mode of the top substrate 10 to the SIW cavity transmission mode and then are output through the microstrip transmission mode of the bottom substrate 20, the loss is low, the transmission bandwidth is high, and the specific parameters shown in figure 2 are as follows: W1-W3-0.2 mm, W2-0.2 mm, W4-0.55 mm, L1-1.7 mm, L2-0.6 mm, L3-0.3 mm, L4-0.3 mm, and S-0.05 mm. The electromagnetic signal transmission process is as follows:

microstrip transmission mode of the top substrate 10: the electromagnetic wave signal enters the SIW cavity through the first rectangular slots 31 on both sides of the first coplanar waveguide excitation port 4.

SIW cavity transmission mode: electromagnetic wave signals are coupled from the top SIW cavity to the bottom SIW cavity through the middle layer crosshatch structure 7. The excitation port is placed at the place where the TE201 mode magnetic field is strongest, such as the positions of (r) and (r) in fig. 3(c), the TE101 mode, the TE102 mode and the TE201 mode are successfully excited, wherein the degenerate modes TE102 and TE201 are used as two transmission poles in a passband, the TE101 mode is taken as a harmonic, and by using the coupling among the TE101 mode, the TE102 mode and the TE201 mode, the degenerate modes (TE102 and TE201) of the top SIW cavity and the degenerate modes (TE102 and TE201) of the bottom SIW cavity together construct four transmission zeros in a filter passband, so that the out-of-band rejection degree is effectively improved.

Microstrip transmission mode of the base substrate 20: after being transmitted through the SIW cavity, the electromagnetic wave signal is output through the second rectangular grooves 32 on both sides of the second coplanar waveguide excitation port 5.

In summary, the cross-shaped slot line structure 7 is etched on the middle metal layer, so that the signal is coupled from the top substrate 10 to the bottom substrate 20 through the cross-shaped slot line structure 7, as can be seen from fig. 3, the cross-shaped structure does not affect the transmission of the TE102 and TE201 modes in the pass band, but only affects the electromagnetic distribution of the TE101 mode, and by using this characteristic, the position of the transmission zero point can be flexibly changed, and a good suppression degree can be obtained at the designed frequency point according to the requirement.

As shown in fig. 4, which is a diagram of S parameters and frequency relationship according to the present invention, the present solution provides an example of a filter operating in the U-band, the simulated passband center frequency is 43.9GHz, the 3dB bandwidth is 2GHz, and the minimum in-band insertion loss is 0.8 dB.

Claims

1. A compact substrate integrated waveguide filter based on a silicon-based MEMS (micro-electromechanical systems) process comprises an SIW (substrate integrated waveguide) cavity structure of a top substrate (10) and a bottom substrate (20), and is characterized in that: the device comprises a top metal layer (1), a middle metal layer (2), a bottom metal layer (3), a TSV through hole (6) arranged in a substrate, a first coplanar waveguide excitation port (4) on the upper surface of the top substrate (10), a second coplanar waveguide excitation port (5) on the lower surface of the bottom substrate (20) and a cross-shaped groove line structure (7) on the middle metal layer (2); the top substrate (10) and the bottom substrate (20) are bonded together by wafer level gold.

2. The compact substrate integrated waveguide filter based on silicon-based MEMS process of claim 1, wherein the distance from the first coplanar waveguide excitation port (4) to the second side line (42) of the TSV is a quarter of the total length of the first side line (41) of the TSV, and the distance from the second coplanar waveguide excitation port (5) to the third side line (43) of the TSV is a quarter of the total length of the fourth side line (44) of the TSV.

3. The compact substrate integrated waveguide filter based on the silicon-based MEMS process as recited in claim 2, wherein two sides of the first coplanar waveguide excitation port (4) are respectively provided with a first rectangular groove (31), and two sides of the second coplanar waveguide excitation port (5) are respectively provided with a second rectangular groove (32); the width sizes of the first rectangular groove (31) and the second rectangular groove (32) are the same; the width dimensions of the first coplanar waveguide excitation port (4) and the second coplanar waveguide excitation port (5) are the same.

4. The compact substrate integrated waveguide filter based on silicon-based MEMS process according to claim 2, characterized in that the first coplanar waveguide excitation port (4) coincides with the outer edge of the top substrate (10); the second coplanar waveguide excitation port (5) coincides with an outer edge of the underlying substrate (20).

5. The compact substrate integrated waveguide filter based on silicon-based MEMS process as claimed in claim 1, characterized in that the cross-shaped slot line structure (7) is etched at the central position of the middle metal layer (2) by etching process.

6. The compact substrate integrated waveguide filter based on the silicon-based MEMS process as claimed in claim 1, wherein the TSV through holes (6) are placed around the rectangular cavity and uniformly distributed to construct a rectangular SIW cavity.

7. The compact substrate integrated waveguide filter based on the silicon-based MEMS process as claimed in claim 1, wherein the top metal layer (1), the middle metal layer (2) and the bottom metal layer (3) are respectively formed by electroplating to grow a gold layer with standard thickness on the surface of the substrate.