A wideband adjustable integrated on-chip filter applied to seismic acquisition

Abstract

The application is suitable for the field of seismic exploration technology, and provides a wide-band adjustable integrated on-chip filter applied to seismic acquisition, which comprises a composite resonant unit, a gradually changing multilayer grounding shielding layer, an embedded MIM capacitor array, an input / output feed line and an adjustable dielectric layer. The composite resonant unit comprises an outer double-helix resonant part and an inner meander resonant part which are coaxially nested and electromagnetically coupled. The gradually changing multilayer grounding shielding layer is composed of seven metal layers with gradually changing thickness, and the shielding aperture gradually decreases from top to bottom. The embedded MIM capacitor array is embedded in the spiral gap and the interdigital gap of the resonant unit. The application realizes double-band coverage through the composite resonant structure, and realizes band-pass / band-stop mode switching through the adjustable dielectric layer, and has the advantages of wide-band, tunable, high integration, miniaturization, and is suitable for cable-free seismic instruments and millimeter wave communication equipment.

Description

Technical Field

[0001] This invention belongs to the field of seismic exploration technology, and in particular relates to a wideband adjustable integrated on-chip filter for seismic acquisition. Background Technology

[0002] Filters are key components in radio frequency (RF) front-end systems used to select useful components from RF signals and suppress interference signals. In the fields of seismic exploration and millimeter-wave communication, existing on-chip filters are mainly divided into the following two categories.

[0003] The first type of filter is used in cableless seismographs, operating in the 2.412-2.437 GHz frequency band. These filters are typically integrated on-chip using a metal spiral or zigzag structure. However, these filters suffer from limited functionality, low coupling coefficients, and large chip footprint, making it difficult to meet the dual requirements of miniaturization and high performance in cableless seismographs.

[0004] The second type of filter is used in the millimeter-wave band (60-80GHz) and employs a double-layer zigzag structure to achieve band-stop response. Although these filters are small in size, their operating frequency band is limited to the high-frequency range and cannot cover the low-frequency band (such as the 2.4GHz ISM band), severely limiting their application scope.

[0005] In addition, existing on-chip filter designs generally have the following shortcomings: First, the filtering mode is fixed and cannot be flexibly switched between bandpass and bandstop, making it difficult to adapt to the needs of multi-mode communication systems; Second, the ground shielding layer adopts a uniform multi-layer structure, resulting in inconsistent isolation at different frequency bands, leading to unbalanced anti-interference performance between high-frequency and low-frequency bands; Third, capacitor components are mostly arranged independently, which not only increases the total chip area but also introduces additional parasitic effects; Fourth, the tuning range is narrow, making it difficult to achieve wide-band coverage from low frequency (approximately 2.4 GHz) to millimeter-wave frequency band (60-80 GHz).

[0006] Therefore, there is an urgent need for an on-chip filter that combines multi-mode switching, wide-band tuning, high integration, and miniaturization to meet the application needs of various scenarios such as cableless seismographs and millimeter-wave communication equipment. Summary of the Invention

[0007] The purpose of this invention is to provide a wideband adjustable integrated on-chip filter for seismic acquisition, aiming to solve the problems mentioned in the background art.

[0008] The present invention is implemented as follows: a wideband adjustable integrated on-chip filter for seismic acquisition includes a composite resonant unit, a graded multilayer grounding shield, an embedded MIM capacitor array, input / output feed lines, an adjustable dielectric layer, and a high-resistivity silicon substrate.

[0009] The composite resonant unit includes an outer double-helix resonant section and an inner zigzag resonant section. The outer double-helix resonant section is etched by the top metal layer TM2 and has a Y-axis symmetrical structure. Its helical bends extend at right angles, forming parallel long lines and vertical short lines. The inner zigzag resonant section is etched by the metal layer TM1 and has a four-finger structure with its ends connected, including a first finger, a second finger, a third finger, and a fourth finger that are parallel to each other. The outer double-helix resonant section and the inner zigzag resonant section are coaxially nested and have no direct electrical connection. Energy is transmitted through electromagnetic coupling.

[0010] The gradient multilayer grounding shielding layer surrounds the composite resonant unit and the input / output feed line. From top to bottom, it consists of metal layers TM2, TM1, M5, M4, M3, M2 and M1. The thickness of each metal layer is gradually distributed, and the shielding aperture of each metal layer gradually decreases from top to bottom. The interlayer is filled with a silicon dioxide dielectric layer.

[0011] The embedded MIM capacitor array is composed of a metal layer TM1, a metal layer M5 and an interlayer silicon dioxide dielectric layer, and is embedded in the helical gap of the outer double helix resonant part and the finger gap of the inner zigzag resonant part.

[0012] The input / output feed lines are etched by a metal layer TM2 and are respectively connected to the midpoint of the Y-axis symmetry of the outer double-helix resonant section. A dielectric adjustment window is provided in the middle of the input / output feed lines, and the dielectric adjustment window contains the feed line dielectric layer.

[0013] The adjustable dielectric layer is located between the composite resonant unit and the gradient multilayer grounding shield, and is made of electrostrictive material.

[0014] In a further technical solution, the spiral gap width of the outer double-helix resonant section near the input / output feed line is smaller than the outer gap width.

[0015] In a further technical solution, the width of the first and fourth fingers of the inner layer zigzag resonant part is 2-3 μm, the width of the second and third fingers is 16-26 μm, the length of each finger is 21-28 μm, and the spacing between the first and second fingers and between the third and fourth fingers is 14 μm.

[0016] In a further technical solution, the thickness of each metal layer of the gradient multilayer grounding shield is: 3μm for TM2 layer, 2μm for TM1 layer, 0.45μm for each of M5 to M2 layers, and 0.4μm for M1 layer; the shielding aperture gradually changes from 5μm in the upper layer to 1μm in the lower layer.

[0017] In a further technical solution, the embedded MIM capacitor array adjusts the capacitance by changing the number of parallel capacitors, or by adjusting the dielectric constant through a BST varactor tube.

[0018] In a further technical solution, the adjustable dielectric layer embedded in the dielectric adjustment window of the input / output feeder is made of aluminum nitride (AlN) electrostrictive material, with a thickness adjustment range of 1-3μm and an adjustment voltage of 0-5V.

[0019] In a further technical solution, the adjustable dielectric layer is made of lead zirconate titanate (PZT) electrostrictive material, with a thickness adjustment range of 2-5μm and an adjustment voltage of 0-10V.

[0020] The present invention provides a broadband tunable integrated on-chip filter for seismic acquisition, which has the following advantages:

[0021] (1) Wideband coverage: The composite resonant structure enables the operating frequency band to cover 2.412-2.437 GHz (ISM band of cableless seismograph) and 60-80 GHz (millimeter wave communication band) simultaneously, solving the problem of narrow frequency band coverage of existing filters.

[0022] (2) Switchable mode: By adjusting the adjustable dielectric layer thickness and MIM capacitance parameters, bandpass and bandstop modes can be switched. In bandpass mode, the insertion loss of the target frequency band is less than 2 dB; in bandstop mode, the suppression band attenuation is greater than 20 dB.

[0023] (3) High coupling and low interference: The coaxial nesting design of the inner zigzag line and the outer spiral line increases the coupling strength by about 30% compared with the traditional discrete structure. The gradient multilayer grounding shield attenuates external interference by more than 40 dB.

[0024] (4) Miniaturization: The embedded capacitor layout makes the total chip area less than 0.5 mm. 2 Compared to a discrete structure, it reduces the size by more than 25%.

[0025] (5) Process compatibility: It adopts the standard 0.13 μm Bi-CMOS process, which is easy to connect with existing integrated circuit production lines and has good industrialization prospects. Attached Figure Description

[0026] Figure 1 This invention provides a design principle for a wideband tunable integrated on-chip filter applied to seismic acquisition.

[0027] Figure 2 A top view schematic diagram of a wideband tunable integrated on-chip filter for seismic acquisition provided in an embodiment of the present invention;

[0028] Figure 3 A cross-sectional structural schematic diagram of a wideband tunable integrated on-chip filter for seismic acquisition provided in an embodiment of the present invention;

[0029] Figure 4 The present invention provides test performance results for a wideband adjustable integrated on-chip filter used in seismic acquisition, as provided in an embodiment of the present invention.

[0030] In the attached diagram: 1. Outer double-helix resonant section; 2. Inner zigzag resonant section; 3. Gradient multilayer grounding shield; 4. Embedded MIM capacitor array; 5. Input / output feed line; 6. Dielectric adjustment window; 7. Adjustable dielectric layer; 8. Silicon dioxide dielectric layer; 9. High-resistivity silicon substrate. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0033] like Figures 1-3 As shown, a broadband tunable integrated on-chip filter for seismic acquisition is provided in one embodiment of the present invention. It is implemented based on 0.13μm Bi-CMOS technology and includes a composite resonant unit, a gradient multilayer grounding shield layer 3, an embedded MIM capacitor array 4, an input / output feed line 5, a tunable dielectric layer 7, and a high-resistivity silicon substrate 9.

[0034] The composite resonant unit is the core resonant structure of this invention, comprising an outer double-helix resonant section 1 and an inner zigzag resonant section 2. These two sections are coaxially nested and have no direct electrical connection, transmitting energy through electromagnetic coupling. The outer double-helix resonant section 1 is etched from the top metal layer TM2, exhibiting a Y-axis symmetrical structure. The helix curves at right angles, forming parallel long lines and perpendicular short lines. The helical gap width near the input / output feed line 5 is smaller than the outer gap width to optimize impedance matching between the feed line and the resonant unit. The inner zigzag resonant section 2 is etched from the metal layer TM1, featuring a four-finger structure with four fingers connected end-to-end. These include a first finger, a second finger, a third finger, and a fourth finger that are parallel to each other. The first and fourth fingers have equal widths (2-3 μm) and are narrower than the second and third fingers (16-26 μm), with each finger having a length of 21-28 μm. The spacing between the first and second fingers, and between the third and fourth fingers, is fixed at 14 μm. The narrow linewidth design of the first and fourth fingers helps to improve the Q value of high-frequency resonance, while the wide linewidth design of the second and third fingers helps to reduce the conductor loss of low-frequency resonance.

[0035] The gradient multilayer grounding shield 3 surrounds the composite resonant unit and the input / output feed line 5, consisting of seven metal layers from top to bottom: TM2 (top layer), TM1, M5, M4, M3, M2, and M1. The thickness of each metal layer is gradually distributed: TM2 is 3 μm thick, TM1 is 2 μm thick, M5 to M2 are all 0.45 μm thick, and M1 is 0.4 μm thick. A silicon dioxide dielectric layer 8 fills the interlayer spaces, and the shielding aperture of each metal layer gradually decreases from top to bottom (5 μm for the top layer and 1 μm for the bottom layer), forming a gradient shielding structure. This gradient design maintains consistent isolation across different frequency bands and attenuates external electromagnetic interference by more than 40 dB.

[0036] The embedded MIM capacitor array 4 consists of an upper metal layer TM1, a lower metal layer M5, and a silicon dioxide dielectric layer 8 between them. The embedded MIM capacitor array 4 is embedded in the spiral gap of the outer double-helix resonant part 1 and the finger gap of the inner tortuous resonant part 2. The capacitance can be adjusted by changing the number of parallel capacitors or adjusting the dielectric constant of the BST varactor tube, without occupying additional chip area.

[0037] The input / output feed line 5 is formed by a metal layer TM2 and is connected to the midpoint of the Y-axis symmetry of the outer double-helix resonant section 1. The input / output feed line 5 has a dielectric adjustment window 6 in the middle and a built-in feed line dielectric layer (aluminum nitride AlN electrostrictive material). The signal transmission characteristics can be adjusted by changing the thickness of the dielectric layer (1-3μm) by applying a voltage of 0-5V.

[0038] The adjustable dielectric layer 7 is located between the composite resonant unit and the gradient multilayer grounding shield 3. It is made of lead zirconate titanate (PZT) electrostrictive material, and its thickness can be adjusted (2-5μm) by external voltage (0-10V), thereby changing the ground capacitance and coupling strength of the composite resonant unit.

[0039] In this embodiment of the invention, the working principle of the filter consists of two parts: first, the structural parameters of the composite resonant unit determine the resonance points for low-frequency (predominantly spiral) and high-frequency (predominantly zigzag) frequencies; second, by adjusting the bias voltage of the adjustable dielectric layer and the feed line dielectric window, the equivalent capacitance and coupling coefficient of the resonant unit are changed, thereby achieving the switching of the operating frequency band and bandpass / bandstop modes. A gradient multilayer grounding shield is used to reduce the impact of external electromagnetic interference on the resonant unit.

[0040] In a preferred embodiment of the present invention, the specific structural dimensions of the relevant components in the filter are as follows:

[0041] Outer double-helix resonant section 1: linewidth 3μm, inner gap 8μm, outer gap 12μm, overall outer diameter of the helix 200μm.

[0042] Inner layer tortuous resonant section 2: The first and fourth fingers are 2.5 μm wide, the second and third fingers are 20 μm wide, and each finger is 25 μm long. This tortuous section is located in the central region of the double helix, and the distance between it and the inner wall of the helix is ​​5 μm.

[0043] The thickness of the interlayer silicon dioxide dielectric layer 8 of the gradient multilayer grounding shield 3 is as follows: 3 μm between TM2 and TM1, 2 μm between TM1 and M5, and 1 μm between M5 and M1. The total thickness of the shielding layer is 25 μm, and its outer edge extends 10 μm beyond the boundary of the composite resonant unit.

[0044] Embedded MIM capacitor array 4: Four capacitors are arranged in the spiral gap with a gap width of 3μm; two capacitors are arranged in the finger gap with a gap width of 2μm. The effective area of ​​each capacitor is 20μm×20μm.

[0045] Input / output feed 5: 5μm linewidth, 100μm length. Dielectric conditioning window 6 measures 50μm × 20μm, with an initial aluminum nitride dielectric thickness of 2μm and a conditioning voltage step of 1V.

[0046] Adjustable dielectric layer 7 (PZT): initial thickness 3μm, adjustable voltage step 2V, thickness control accuracy 0.5μm.

[0047] The relevant processes and tests are as follows:

[0048] The process employed a 0.13μm Bi-CMOS fabrication, with key steps including: oxidation of the high-resistivity silicon substrate 9, deposition and photolithography of each metal layer (M1 to TM2), PECVD deposition of the silicon dioxide dielectric layer 8, etching of the embedded MIM capacitor array 4, and sputtering and packaging of the tunable dielectric layer 7 and AlN thin film. Testing was performed using a Keysight E8361A vector network analyzer and a FormFactor GSG waveguide probe. Figure 4 As shown, the test results are as follows:

[0049] Bandpass mode (2.412-2.437GHz): Insertion loss 1.8dB, return loss <-15dB, out-of-band rejection >-30dB.

[0050] Band-stop mode (center 72GHz, stopband 65-78GHz): stopband attenuation > -22dB, passband insertion loss < 2dB.

[0051] Chip size: 0.45mm × 0.4mm (0.18mm) 2 ).

[0052] Temperature stability (-40℃ to 85℃): Center frequency deviation < ±0.5GHz, attenuation fluctuation < 0.3dB.

[0053] This invention achieves wide-band compatibility and multi-mode tunability through innovative design of composite resonant structure, gradient shielding layer and embedded capacitor. It solves the problems of single function and large size of existing filters. It can be widely used in various scenarios such as cableless seismographs, millimeter-wave communication equipment, and radio frequency sensors, and has significant practical value and industrialization prospects.

[0054] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A broadband tunable integrated on-chip filter for seismic acquisition, characterized in that, It includes a composite resonant unit, a graded multilayer grounding shield, an embedded MIM capacitor array, input / output feed lines, an adjustable dielectric layer, and a high-resistivity silicon substrate. The composite resonant unit includes an outer double-helix resonant section and an inner zigzag resonant section. The outer double-helix resonant section is etched by the top metal layer TM2 and has a Y-axis symmetrical structure. Its helical bends extend at right angles, forming parallel long lines and vertical short lines. The inner zigzag resonant section is etched by the metal layer TM1 and has a four-finger structure with its ends connected, including a first finger, a second finger, a third finger, and a fourth finger that are parallel to each other. The outer double-helix resonant section and the inner zigzag resonant section are coaxially nested and have no direct electrical connection. Energy is transmitted through electromagnetic coupling. The gradient multilayer grounding shielding layer surrounds the composite resonant unit and the input / output feed line. From top to bottom, it consists of metal layers TM2, TM1, M5, M4, M3, M2 and M1. The thickness of each metal layer is gradually distributed, and the shielding aperture of each metal layer gradually decreases from top to bottom. The interlayer is filled with a silicon dioxide dielectric layer. The embedded MIM capacitor array is composed of a metal layer TM1, a metal layer M5 and an interlayer silicon dioxide dielectric layer, and is embedded in the helical gap of the outer double helix resonant part and the finger gap of the inner zigzag resonant part. The input / output feed lines are etched by a metal layer TM2 and are respectively connected to the midpoint of the Y-axis symmetry of the outer double-helix resonant section. A dielectric adjustment window is provided in the middle of the input / output feed lines, and the dielectric adjustment window contains the feed line dielectric layer. The adjustable dielectric layer is located between the composite resonant unit and the gradient multilayer grounding shield, and is made of electrostrictive material.

2. The wideband tunable integrated on-chip filter for seismic acquisition according to claim 1, characterized in that, The spiral gap width of the outer double-helix resonant section near the input / output feed line is smaller than the outer gap width.

3. The wideband tunable integrated on-chip filter for seismic acquisition according to claim 1, characterized in that, The width of the first and fourth fingers of the inner layer zigzag resonant section is 2-3 μm, the width of the second and third fingers is 16-26 μm, the length of each finger is 21-28 μm, and the distance between the first and second fingers and the distance between the third and fourth fingers are both 14 μm.

4. The wideband tunable integrated on-chip filter for seismic acquisition according to claim 1, characterized in that, The thickness of each metal layer in the gradient multilayer grounding shield is as follows: TM2 layer 3μm, TM1 layer 2μm, M5 to M2 layers 0.45μm each, and M1 layer 0.4μm; the shielding aperture gradually changes from 5μm in the upper layer to 1μm in the lower layer.

5. The broadband tunable integrated on-chip filter for seismic acquisition according to claim 1, characterized in that, The embedded MIM capacitor array adjusts the capacitance by changing the number of parallel capacitors or by adjusting the dielectric constant through a BST varactor tube.

6. The broadband tunable integrated on-chip filter for seismic acquisition according to claim 1, characterized in that, The adjustable dielectric layer embedded in the dielectric conditioning window of the input / output feeder is made of aluminum nitride electrostrictive material, with a thickness adjustment range of 1-3μm and an adjustment voltage of 0-5V.

7. The wideband tunable integrated on-chip filter for seismic acquisition according to claim 1, characterized in that, The adjustable dielectric layer is made of lead zirconate titanate electrostrictive material, with a thickness adjustment range of 2-5μm and an adjustment voltage of 0-10V.

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