Quartz resonance type micro force sensor

Abstract

The invention relates to a quartz resonant micro-force sensor. The micro-force sensor comprises a mechanical sensing unit, a mechanical amplification structure, a frequency sensing unit and a fixing structure, the mechanical induction unit comprises a mechanical induction disc, and the mechanical induction disc is used for receiving external mechanical energy and transmitting the external mechanical energy to the mechanical amplification structure; the mechanical amplification structure is used for concentrating and amplifying the received mechanical energy, and the amplified mechanical energy is transmitted to the frequency induction unit; the frequency sensing unit converts mechanical energy into a frequency signal and outputs a frequency drift distance based on piezoelectric and inverse piezoelectric effects; the fixing structure is used for being connected with an external device. According to the invention, the AT-cut quartz crystal is used as the frequency sensing unit, when a micro force is transmitted to the mechanical sensing unit, the micro force is transmitted to the frequency sensing unit through the amplification structure, and the micro force sensing function is realized through the change of the vibration frequency of the resonator caused by stress.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of micro force sensing, in particular to a quartz crystal-based piezoelectricity developed ultra-high sensitivity, high resolution, high stability, low loss resonant micro force sensor. It belongs to the micron level probe structure, the overall size range is about millimeter, can be applied to the micro Newton (μN) to nanometer (nN) order static / dynamic force precision measurement, suitable for biomedical operation, semiconductor micro process, material characterization and MEMS device testing and other fields. BACKGROUND

[0002] The traditional mechanical sensor, such as strain gauge sensor, capacitive sensor, optical sensor, etc., has the problems of limited precision and sensitivity, easy to be affected by temperature drift, poor long-term stability, easy to be affected by electromagnetic interference, high cost, etc., which is difficult to meet the precision measurement demand of micro force range (such as micro Newton to nanometer order).

[0003] The quartz crystal is widely used in frequency control devices (such as oscillator) due to its natural piezoelectric effect, which has the characteristics of ultra-high sensitivity (resonant frequency is extremely sensitive to force, precision can reach hertz or even millihertz level, force resolution can reach nanometer or even picometer level), high resolution (frequency signal is easy to measure with high precision, strong anti-interference ability), high stability (low mechanical loss, small thermal expansion coefficient, small frequency drift, relatively insensitive to temperature change), wide dynamic range (suitable for micro force measurement, can cover from micro Newton to millinewton or even larger range), direct digital output (easy to digital processing, transmission and recording), high Q value (resonance peak is sharp, detection is sensitive, high signal-to-noise ratio), low power consumption (small excitation power required to maintain resonance), high reliability (solid-state device, no mechanical wear and tear parts, long service life), etc., which is very suitable as an ultra-high precision mechanical sensor. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a quartz resonant micro force sensor, which uses an AT-cut quartz crystal as a frequency sensitive unit. When a small force is transmitted to the mechanical sensing unit, it passes through the amplification structure to the frequency sensing unit, and the change of the resonator vibration frequency caused by stress is realized. Micro force sensing function.

[0005] The technical solution adopted by the present application to solve its technical problem is to provide a quartz resonant micro force sensor, which includes a mechanical sensing unit, a mechanical amplification structure, a frequency sensing unit and a fixing structure.

[0006] The mechanical sensing unit includes a mechanical sensing disc, which is used to receive external mechanical energy and transmit it to the mechanical amplification structure.

[0007] The mechanical amplification structure is used for concentrating and amplifying the received mechanical energy, and the amplified mechanical energy is transmitted to the frequency sensing unit.

[0008] The frequency sensing unit converts the mechanical energy into a frequency signal based on piezoelectric and inverse piezoelectric effects, and outputs a frequency drift amount.

[0009] The fixing structure is used for connecting external devices.

[0010] As a supplement to the technical solution of the application, the mechanical sensing disc is a micron-level conical or spherical probe, the contact curvature radius of the mechanical sensing disc is ≤5μm, and the surface roughness of the mechanical sensing disc is <50nm.

[0011] As a supplement to the technical solution of the application, the surface of the mechanical sensing disc is provided with a functional material plating layer, the functional material plating layer is a conductive material or a magnetic material, and is used for realizing non-contact mechanical sensing through electrostatic force or magnetic force, and the spacing control accuracy during non-contact sensing is ±100nm.

[0012] As a supplement to the technical solution of the application, the stress amplification coefficient of the mechanical amplification structure is 2-3 times.

[0013] As a supplement to the technical solution of the application, an arc-shaped notch is formed on the outer side of the connection between each auxiliary beam and the frequency sensing unit.

[0014] As a supplement to the technical solution of the application, the frequency sensing unit adopts an AT-cut quartz crystal wafer, the thickness of the quartz crystal wafer is 5-100μm, and the natural frequency of the frequency sensing unit is 1MHz to 100MHz.

[0015] As a supplement to the technical solution of the application, the middle part of the upper and lower ends of the frequency sensing unit is provided with an oscillation electrode, the oscillation electrode and the upper surface or the lower surface of the frequency sensing unit overlap to form a main vibration zone, and the main vibration zone can generate a vibration resonance frequency f.

[0016] As a supplement to the technical scheme of the application, the oscillation electrode is a double-layer electrode, the outer layer is an Au electrode layer, the inner layer is a Cr electrode layer, the Cr electrode layer is connected with the frequency sensing unit, the thickness of the oscillation electrode is 150 nm, and the electrode pattern is a ring shape to match the thickness shear vibration mode.

[0017] As a supplement to the technical scheme of the application, the force-frequency conversion coefficient of the sensor is 5500-6500 Hz / N (after amplification).

[0018] As a supplement to the technical scheme of the application, the mechanical energy concentration and amplification through hole is a circular through hole structure formed by deep reactive ion etching (DRIE).

[0019] As a supplement to the technical scheme of the application, the frequency sensing unit is provided with a mechanical isolation through hole two on both sides of the oscillation electrode, the mechanical isolation through hole two is a long strip-shaped through hole, and the two sides are provided with mechanical isolation through holes two to reduce the external force interference on the oscillation electrode.

[0020] As a supplement to the technical scheme of the application, the fixing structure includes a fixing seat, the fixing seat is provided with an electrode pad corresponding to the oscillation electrode, the electrode pad is used to provide power, read frequency signals, and control the movement of the sensor, and the oscillation electrode and the corresponding electrode pad are connected through electrode wires.

[0021] Beneficial effects: the present application relates to a quartz resonant micro force sensor, which has the following advantages:

[0022] 1. Ultra-high sensitivity and high resolution: the piezoelectric property of the quartz crystal is used, the resonant frequency is extremely sensitive to the change of force, the force-frequency conversion coefficient is 5500-6500 Hz / N (after amplification), the force measurement can be realized from micro-newton to nanonewton level, and the precision can reach hertz or even millihertz level;

[0023] 2. High stability: the AT-cut quartz crystal is adopted, the mechanical loss is low, the thermal expansion coefficient is small, the frequency drift is small, the temperature change is relatively insensitive, the temperature drift can be effectively inhibited through temperature compensation technology, and the repeatability and reliability of measurement are guaranteed;

[0024] 3. Strong anti-interference ability: the mechanical isolation through hole and other structure designs are adopted to reduce the interference of external force; the frequency signal is digital output, and the anti-electromagnetic interference ability is strong;

[0025] 4. Wide dynamic range: the measurement range can cover from 0.1 muN to 1mN, and is suitable for various micro force measurement scenes;

[0026] 5. Compact structure: the structure of the micro-probe is compact, the overall size is about millimeter, and the micro-probe is convenient to integrate into various precision measurement systems;

[0027] 6. Low power consumption and high reliability: only a small excitation power is needed to maintain resonance, and the sensor is a solid-state device without mechanical wear parts, and has a long service life. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a structural schematic diagram of the present application;

[0029] Figure 2 is a schematic diagram of the mechanical induction disc of the present application;

[0030] Figure 3 is a working area schematic diagram of the micro-force sensor of the present application;

[0031] Figure 4 is a base frequency diagram of the intermediate region of the frequency induction unit of the present application at 25MHz;

[0032] Figure 5 is a base frequency diagram of the micro-force sensor of the present application at 25MHz;

[0033] Figure 6 is a displacement nephogram of the micro-force sensor of the present application after being stressed.

[0034] Fig. 1 is a schematic diagram of the micro-force sensor of the present application; Fig. 2 is a schematic diagram of the mechanical induction disc of the present application; Fig. 3 is a schematic diagram of the mechanical isolation through hole one of the present application; Fig. 4 is a schematic diagram of the auxiliary beam of the present application; Fig. 5 is a schematic diagram of the mechanical energy concentration and amplification through hole of the present application; Fig. 6 is a schematic diagram of the mechanical isolation through hole two of the present application; Fig. 7 is a schematic diagram of the oscillation electrode of the present application; Fig. 8 is a schematic diagram of the electrode pad of the present application; Fig. 9 is a schematic diagram of the electrode trace of the present application; Fig. 10 is a schematic diagram of the fixed seat of the present application; and Fig. 11 is a schematic diagram of the arc-shaped notch of the present application. DETAILED DESCRIPTION

[0035] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and are not used to limit the scope of the present application. In addition, it should be understood that after reading the content taught by the present application, those skilled in the art can make various modifications or changes to the present application, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

[0036] The embodiments of the present application relate to a quartz resonant micro-force sensor, as shown in Fig. 1, which comprises a mechanical induction unit, a mechanical amplification structure, a frequency induction unit and a fixed structure. Figures 1-6

[0037] Referring to Fig. 1, Figure 3 ​As shown, the mechanical induction unit corresponds to region I, the mechanical amplification structure corresponds to region II, the frequency induction unit corresponds to region III, and the fixing structure corresponds to region IV.

[0038] The mechanical induction unit includes a mechanical induction disc 101 for receiving external mechanical energy and transmitting to the mechanical amplification structure; the mechanical induction disc 101 can directly contact or non-contact to the external mechanical energy, and the mechanical induction disc 101 can concentrate the external mechanical energy at the top end for transmission; the mechanical induction disc 101 non-contact senses the external mechanical energy, and the surface of the mechanical induction disc 101 is provided with a functional material coating, which is a conductive material or a magnetic material. The functional material coating can non-contact sense the external mechanical energy, and the functional material coating is used for non-contact mechanical sensing through electrostatic force or magnetic force, and the spacing control accuracy of non-contact sensing is ±100 nm; the functional material coating is preferably a magneto-electric composite coating, which mainly uses the magneto-electric coupling effect (magnetic and electric performance mutual influence and conversion). The effect can be used in magnetic field sensors, energy collectors, memories, spin electronic devices, and the magneto-electric composite coating belongs to the existing coating on the market.

[0039] The mechanical amplification structure is used for concentrating and amplifying the received mechanical energy, and the amplified mechanical energy is transmitted to the frequency induction unit; the mechanical amplification structure includes a main beam structure 102 and two auxiliary beams 104 symmetrically arranged on both sides of the main beam structure 102, and the main beam structure 102 transmits the mechanical energy of the mechanical induction disc 101 to the frequency induction unit; a mechanical isolation through hole one 103 is arranged between each auxiliary beam 104 and the main beam structure 102, the mechanical isolation through hole one 103 is used for mechanically isolating the main beam structure 102 and the auxiliary beam 104, reducing the interference of other forces, and a mechanical energy concentrating and amplifying through hole 105 is arranged at the connection between the main beam structure 102 and the frequency induction unit, the mechanical energy concentrating and amplifying through hole 105 concentrates the mechanical energy, realizes 20-50 times stress amplification, and then transmits to the frequency induction unit;

[0040] The frequency induction unit converts the mechanical energy into a frequency signal based on the piezoelectric and inverse piezoelectric effect, and outputs the frequency drift amount; the middle part of the upper and lower ends of the frequency induction unit is provided with an oscillation electrode 107, the oscillation electrode 107 and the upper surface or the lower surface of the frequency induction unit overlap to form a main vibration zone, and the main vibration zone can generate a vibration resonance frequency f.

[0041] The fixing structure is used for connecting external devices, and comprises a fixing seat 110, which is provided with electrode pads 108 corresponding to the oscillation electrodes 107, the electrode pads 108 being used for providing power supply, reading frequency signals and controlling the movement of the sensor, and the oscillation electrodes 107 are connected with the corresponding electrode pads 108 through electrode wires 109, and the electrode pads 108 are used for providing power supply and reading frequency signals.

[0042] When the external mechanical energy is electrostatic force Fe or magnetic force Fm, the change amount Δf of the vibration resonance frequency f has a linear relationship with Fe or Fm, that is, Δf=C·ΔFe or Δf=C·ΔFm, wherein C is a proportional coefficient; and the force-frequency conversion coefficient of the frequency sensing unit is 5500-6500 Hz / N (amplified by the mechanical amplification structure).

[0043] The electrostatic force or magnetic force sensing mechanism is Fe=qvBsinθ, wherein Fe is the Lorentz force, q is the charge amount of the charged particle, v is the velocity of the charged particle, B is the magnetic induction intensity, and θ is the included angle between the velocity and the magnetic field direction. Fm is the external magnetic force, is the gradient operator, χ is the magnetic susceptibility, H is the external magnetic field intensity, V is the volume of the magnetized object, and B is the magnetic induction intensity.

[0044] As a preferred scheme of the mechanical sensing disc 101, the mechanical sensing disc 101 is a micron-level conical or spherical probe, the contact curvature radius of the mechanical sensing disc 101 is ≤5 μm, and laser processing or FIB (focused ion beam) technology can be used to ensure that the surface roughness of the mechanical sensing disc 101 is <50 nm.

[0045] As a preferred scheme of the frequency sensing unit, the frequency sensing unit adopts an AT-cut quartz wafer, the thickness of the quartz wafer is 5-100 μm, the natural frequency of the frequency sensing unit is 1 MHz to 100 MHz, the oscillation electrode 107 is a double-layer electrode, the outer layer is an Au electrode layer, and the inner layer is a Cr electrode layer, the Cr electrode layer is connected with the frequency sensing unit, the thickness of the oscillation electrode 107 is 150 nm, and the electrode pattern is ring-shaped to match the thickness shear vibration mode, and the sensitivity, such as the force-frequency conversion coefficient, is 5500-6500 Hz / N (amplified by 2-3 times).

[0046] The mechanical sensing disc 101, the main beam structure 102, the auxiliary beam 104 and the frequency sensing unit are integrally formed and are all made of a quartz wafer.

[0047] An arc-shaped notch 111 is arranged on the outer side of the connection between each auxiliary beam 104 and the frequency sensing unit, so as to avoid stress concentration and breakage.

[0048] As a structure of the mechanical energy concentration and amplification through hole 105, the mechanical energy concentration and amplification through hole 105 is a circular through hole structure formed by deep reactive ion etching (DRIE), and the mechanical isolation through hole 1 103 is also formed by deep reactive ion etching (DRIE).

[0049] As a preferred scheme of the frequency sensing unit, a mechanical isolation through hole 2 106 is arranged on both sides of the oscillation electrode 107 on the frequency sensing unit, and the mechanical isolation through hole 2 106 is a long strip-shaped through hole, so that the mechanical isolation through hole 2 106 arranged on both sides can reduce the external force interference on the oscillation electrode 107.

[0050] The sensor of the application can be applied to the fields of biomedical operation (such as cell force measurement), semiconductor micro-process (such as microstructure assembly force detection), material characterization (such as surface force test) and MEMS device test, and has a wide application prospect.

[0051] In the description of the application, it should be understood that the orientation words such as "front, rear, upper, lower, left, right", "transverse, vertical, perpendicular, horizontal" and "top, bottom" and the like indicate the orientation or position relationship shown in the drawings, and are only for the convenience of description of the application and simplification of description, and in the absence of contrary description, these orientation words do not indicate and imply that the indicated device or element must have a specific orientation or be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the protection scope of the application; the orientation words "inner, outer" refer to the inner and outer of the contour of each component itself.

[0052] For the convenience of description, spatial relative terms such as "on", "above", "upper surface", "upper" and the like can be used herein to describe the spatial positional relationship of one device or feature with other devices or features as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the device described in the drawings. For example, if the device in the drawing is inverted, the device described as "above" or "on" other devices or structures will be positioned "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0053] In addition, it should be noted that the use of the terms "first", "second" and the like is merely intended to distinguish the corresponding components, and the above terms have no special meaning unless otherwise stated, and therefore cannot be understood as a limitation on the scope of protection of the present application.

[0054] The quartz resonant micro force sensor provided by the present application is described in detail above, and the principles and implementation modes of the present application are described by using specific examples. The above example is only used to help understand the method and core idea of the present application. Meanwhile, for those skilled in the art, the specific implementation modes and application ranges will be changed according to the idea of the present application. In summary, the content of the present description should not be understood as a limitation on the present application.

Claims

1. A quartz resonator micro-force sensor, characterized by: The micro force sensor (100) comprises a mechanical sensing unit, a mechanical amplification structure, a frequency sensing unit and a fixing structure; The mechanical sensing unit comprises a mechanical sensing disc (101) for receiving external mechanical energy and transmitting to the mechanical amplification structure; The mechanical amplification structure is used for concentrating and amplifying the received mechanical energy, and the amplified mechanical energy is transmitted to the frequency sensing unit. The mechanical amplification structure comprises a main beam structure (102) and two auxiliary beams (104) symmetrically arranged on both sides of the main beam structure (102), the main beam structure (102) transmits the mechanical energy of the mechanical sensing disc (101) to the frequency sensing unit, and a mechanical isolation through hole (103) is arranged between each auxiliary beam (104) and the main beam structure (102) to mechanically isolate the main beam structure (102) from the auxiliary beam (104). The main beam structure (102) is provided with a mechanical energy concentrating and amplifying through hole (105) at the connection with the frequency sensing unit.

2. A quartz resonator micro-force sensor according to claim 1, characterized in that: The frequency sensing unit converts the mechanical energy into a frequency signal based on piezoelectric and inverse piezoelectric effects, and outputs a frequency drift.

3. A quartz resonator micro-force sensor according to claim 1 or 2, characterized in that: The fixing structure is used for connecting external devices.

4. The quartz resonant micro-force sensor according to claim 1, wherein: The mechanical sensing disc (101) is a micron-level conical or spherical probe, the contact curvature radius of the mechanical sensing disc (101) is ≤5μm, and the surface roughness of the mechanical sensing disc (101) is <50nm.

5. The quartz resonant micro-force sensor according to claim 1, wherein: The surface of the mechanical sensing disc (101) is provided with a functional material plating layer which is a conductive material or a magnetic material, and is used for realizing non-contact mechanical sensing through electrostatic force or magnetic force, and the spacing control accuracy during non-contact sensing is ±100nm.

6. The quartz resonant micro-force sensor according to claim 1, wherein: An arc-shaped notch (111) is formed on the outer side of the connection between each auxiliary beam (104) and the frequency sensing unit.

7. A quartz resonator micro-force sensor according to claim 6, characterized in that: The frequency sensing unit adopts an AT-cut quartz wafer, the thickness of the quartz wafer is 5-100μm, and the natural frequency of the frequency sensing unit is 1MHz to 100MHz.

8. The quartz resonant micro-force sensor according to claim 1, wherein: The middle part of the upper and lower ends of the frequency sensing unit is provided with an oscillation electrode (107), the oscillation electrode (107) and the upper surface or the lower surface of the frequency sensing unit overlap to form a main vibration zone, and the main vibration zone can generate a vibration resonance frequency f.

9. The quartz resonant micro-force sensor according to claim 1, wherein: The oscillation electrode (107) is a double-layer electrode, the outer layer is an Au electrode layer, and the inner layer is a Cr electrode layer, the Cr electrode layer is connected with the frequency sensing unit, the thickness of the oscillation electrode (107) is 150nm, and the electrode pattern is ring-shaped to match the thickness shear vibration mode. The mechanical energy concentrating and amplifying through hole (105) is a circular through hole structure formed by deep reactive ion etching. Mechanical isolation through holes (106) are formed on both sides of the oscillation electrode (107) of the frequency sensing unit, the mechanical isolation through holes (106) are long strip-shaped through holes, and the mechanical isolation through holes (106) arranged on both sides can reduce the external force interference on the oscillation electrode (107).

10. The quartz resonant micro-force sensor according to claim 1, wherein: The fixing structure comprises a fixing seat (110), and electrode pads (108) corresponding to the oscillation electrodes (107) are arranged on the fixing seat (110), the electrode pads (108) are used for providing power, reading frequency signals and controlling movement of the sensor, and the oscillation electrodes (107) and the corresponding electrode pads (108) are connected through electrode traces (109).

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