Quartz MEMS angular velocity sensor chip and sensor device thereof

Abstract

The invention belongs to the field of sensors, and relates to a quartz MEMS angular velocity sensor chip and a sensor device thereof, the quartz MEMS angular velocity sensor chip comprises a substrate and an electrode, the substrate comprises driving shafts and a detection shaft, the driving shafts comprise a first driving shaft and a second driving shaft, and the detection shaft is located between the first driving shaft and the second driving shaft; the electrode is arranged on the surface of the substrate and is used for exciting the first driving shaft and the second driving shaft to simultaneously generate vibration; according to the quartz MEMS angular velocity sensor, two pairs of driving shafts are utilized, so that the sensitivity of the quartz MEMS angular velocity sensor is improved, and meanwhile, the process complexity is not increased too much; the sensor chip is fixedly connected with the supporting structure through the anchor point structure, so that driving vibration and detection vibration are not easily influenced by the outside; according to the invention, the isolation structure is designed on the sensor chip structure, so that the impact or vibration influence is not liable to affect the driving shaft and the detection shaft, and the influence of external interference on the vibration of the sensor chip is further reduced.

Description

Technical Field

[0001] The invention belongs to the field of sensors and relates to a quartz MEMS angular velocity sensor chip and a sensor device thereof. Background Art

[0002] Angular velocity sensors are devices that can sense angular velocity signals and convert them into usable electrical signals according to certain rules and output them. Quartz crystal materials have the characteristics of high quality factor, stable physical properties, good time and temperature stability, and piezoelectric effect. Quartz crystal is used as the sensor chip material. Angular velocity sensors manufactured by micromachining technology have the characteristics of good temperature performance, small size, high reliability, and suitability for low-cost mass production. They can be widely used in stability, control, guidance, navigation and other fields. Among them, the sensor chip is one of the key components of the quartz angular velocity sensor. The structure of the sensor chip and the electrode layout determine the accuracy level of the angular velocity sensor.

[0003] The working principle of the quartz MEMS angular velocity sensor is based on the Coriolis effect (also known as the Coriolis effect) in rotational dynamics and the piezoelectric and inverse piezoelectric effects of quartz crystals. The sensor chip is divided into a drive shaft and a detection shaft. When the sensor is working, the inverse piezoelectric effect of the quartz crystal is first used to make the drive shaft vibrate at a fixed frequency. When there is an angular velocity input from the outside, the detection shaft will vibrate under the action of the Coriolis force, and its vibration amplitude is proportional to the external angular velocity input. Finally, the piezoelectric effect of the quartz crystal is used to extract the electrical signal, and the angular velocity information can be obtained after conversion with the scale factor.

[0004] The signal-to-noise ratio of the angular velocity sensor directly determines the accuracy performance of the sensor. The mainstream quartz MEMS angular velocity sensors on the market are not sufficient to meet the needs of high-precision inertial navigation applications. Therefore, there is an urgent need to further improve the signal-to-noise ratio of quartz MEMS angular velocity sensor chips. One of the main methods to improve the signal-to-noise ratio of angular velocity sensors is to increase the sensitivity of the sensor chip. Under the premise that the volume of the sensor chip does not increase, a feasible measure is to increase the vibration amplitude of the detection axis. However, the conventional angular velocity sensor chip structure usually has only one pair of drive axes and one pair of detection axes. If the external input angular velocity remains unchanged, if you want to increase the vibration amplitude of the detection axis, it can only be achieved by increasing the drive voltage, but this will cause the circuit noise to increase synchronously, and will not improve the signal-to-noise ratio.

[0005] From the perspective of structural design and mechanical simulation, since the amplitude of the Coriolis force is proportional to the effective mass of the moving object, increasing the effective mass of the drive shaft or directly increasing the number of drive shafts is an effective means to effectively increase the amplitude of the Coriolis force and thus improve the sensitivity of the sensor chip. At present, the patents or academic reports published on the market mainly focus on the technical solution of increasing the effective mass of the drive shaft. There is no mature quartz MEMS angular velocity sensor multi-drive shaft chip solution yet. The main difficulty is that the increase in the number of drive shafts is prone to the problem of parasitic mode coupling, that is, one or more parasitic modes appear between the drive mode and the detection mode (collectively referred to as the working mode) of the angular velocity sensor chip or in the adjacent frequency range. The coupling of the parasitic mode and the working mode will seriously affect the stability of the working mode, thereby reducing the working performance of the angular velocity sensor; at the same time, the increase in the number of drive shafts usually complicates the electrode layout on the surface of the sensor chip, increasing the design difficulty and process implementation difficulty of the electrode layout.

[0006] In addition, in the process of making an angular velocity sensor device, it is usually necessary to combine the sensor chip with the support structure. The area where the sensor chip and the support structure are combined is called the anchor point, and finally the electrical signal is led out from the anchor point through a metal wire. However, the traditional support method is a single-point fixation, so when vibration or impact is applied from the outside, the sensor chip structure is prone to tilt. Therefore, there is a problem of zero offset in a dynamic environment, which also restricts the environmental adaptability of the angular velocity sensor in actual engineering application scenarios.

[0007] In summary, the existing quartz MEMS angular velocity sensor chips have low sensitivity, resulting in the signal-to-noise ratio and accuracy performance of the angular velocity sensor not meeting the requirements of high-precision applications. At the same time, since the traditional sensor chip structure is prone to tilt under the influence of vibration and impact, the angular velocity sensor has a zero offset in a dynamic environment, which greatly limits the engineering application scope of the angular velocity sensor. It is urgent to achieve a breakthrough through the design of a new angular velocity sensor chip structure. Summary of the invention

[0008] In order to solve the above-mentioned problems of the prior art, the present invention adopts a quartz MEMS angular velocity sensor chip, including a substrate and an electrode, the substrate including: a driving shaft and a detection shaft 1-8, the driving shaft including a first driving shaft 1-1, 1-2 and a second driving shaft 1-3, 1-4, the detection shaft 1-8 is located between the first driving shaft 1-1, 1-2 and the second driving shaft 1-3, 1-4; the electrode is arranged on the surface of the substrate, for exciting the first driving shaft 1-1, 1-2 and the second driving shaft 1-3, 1-4 to vibrate simultaneously.

[0009] The substrate also includes: a connecting beam 1-9, both ends of which are respectively connected to the first driving shafts 1-1, 1-2 and the second driving shafts 1-3, 1-4, and the middle part of the connecting beam 1-9 is connected to the detection shaft 1-8.

[0010] The substrate also includes an isolation structure; the isolation structure includes: an outer frame structure 1-10 and four S-shaped flexible beams 1-7; two S-shaped flexible beams 1-7 are located between the first drive shaft 1-1, 1-2 and the detection shaft 1-8, and the other two S-shaped flexible beams 1-7 are located between the second drive shaft 1-1, 1-2 and the detection shaft 1-8, one end of the S-shaped flexible beam 1-7 is connected to the connecting beam 1-9, and the other end is connected to the outer frame structure 1-10; the outer frame structure 1-10 is located on the outside of the first drive shaft 1-1, 1-2, the second drive shaft 1-3, 1-4 and the detection shaft 1-8.

[0011] The quartz MEMS angular velocity sensor chip also includes: anchor point structures 1-5 and 1-6; the anchor point structures 1-5 and 1-6 are arranged at both ends of the substrate to fix the substrate.

[0012] The upper and lower surfaces of the first driving shafts 1-1, 1-2 and the second driving shafts 1-3, 1-4 are covered with driving electrodes, and the upper and lower surfaces of the detection shaft 1-8 are covered with detection electrodes and reference electrodes.

[0013] The material of the substrate is quartz crystal.

[0014] The width of the first driving axis 1-1, 1-2 and the second driving axis 1-3, 1-4 is 80um, and the inclination angle with the vertical direction is 1.75°. The width of the detection axis 1-8 is 75um, and the inclination angle with the vertical direction is 1.5°.

[0015] A sensor device using the above-mentioned quartz MEMS angular velocity sensor chip includes: a quartz MEMS angular velocity sensor chip 1, a supporting structure 2, an ASIC chip 3, a cover plate 4, and a ceramic shell 5, characterized in that the sensor chip 1 is connected to the supporting structure 2 by an adhesive, the supporting structure 2 is connected to the ceramic shell 5 by an adhesive, the ASIC chip 3 is fixed to the bottom of the ceramic shell 5 by an adhesive, and the cover plate 4 and the ceramic shell 5 are connected by welding; the ASIC chip 3 and the quartz MEMS angular velocity sensor chip 1 are connected to the ceramic shell 5 by metal wires.

[0016] The ceramic housing 5 is made of laminated ceramics.

[0017] Electrode wires are pre-buried inside the ceramic shell 5 , and a metal film is plated on the step of the ceramic shell 5 for connection with the metal wires.

[0018] Beneficial effects:

[0019] 1. The sensitivity of the traditional angular velocity sensor chip is low and it is difficult to meet the demand for higher precision. Therefore, the present invention proposes a sensor chip structure based on two pairs of driving shafts. The driving and signal detection functions of the sensor chip are realized through a reasonable electrode layout, which effectively improves the sensitivity of the quartz MEMS angular velocity sensor without increasing too much process complexity. 2. The sensor chip of the present invention is fixedly connected to the support structure through an anchor structure, so that the driving vibration and the detection vibration are not easily affected by the outside world, avoiding the problem of tilting caused by the traditional sensor chip being easily affected by vibration shock when it is directly bonded and fixed to the support structure. 3. The present invention designs an isolation structure on the sensor chip structure, which can make the impact of shock or vibration not easy to affect the driving shaft and the detection shaft, further reducing the impact of external interference on the vibration of the sensor chip, and making the angular velocity sensor zero position more stable under dynamic environment. 4. The driving mode, detection mode and parasitic mode of the sensor chip based on the two pairs of driving shafts will have modal coupling. The present invention effectively avoids the modal coupling problem by reasonably designing the width and the inclination angle of the first driving shaft, the second driving shaft and the detection shaft with respect to the vertical direction, making it feasible for engineering application. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A top view of the quartz MEMS angular velocity sensor chip structure of the present invention;

[0021] Figure 2 A top view of the front electrode of the quartz MEMS angular velocity sensor chip of the present invention;

[0022] Figure 3 A top view of the back electrode of the quartz MEMS angular velocity sensor chip of the present invention;

[0023] Figure 4 It is a schematic diagram of a typical driving mode, a typical detection mode and a typical parasitic mode of the quartz MEMS angular velocity sensor chip of the present invention;

[0024] Figure 5 It is a cross-sectional view of the quartz MEMS angular velocity sensor device of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] like Figure 1As shown, in this embodiment, the quartz MEMS angular velocity sensor chip 1 includes a substrate and a metal electrode, and the substrate includes a first driving axis 1-1, 1-2, a second driving axis 1-3, 1-4, a connecting beam 1-9, an isolation structure, an anchor structure 1-5, 1-6 and a detection axis 1-8; the detection axis 1-8 is located between the first driving axis 1-1, 1-2 and the second driving axis 1-3, 1-4; the two ends of the connecting beam 1-9 are respectively connected to the first driving axis 1-1, 1-2 and the second driving axis 1-3, 1-4, and the middle part of the connecting beam 1-9 is connected to the detection axis 1-8; the metal electrode is arranged on the surface of the substrate.

[0027] The isolation structure; the isolation structure includes: an outer frame structure 1-10 and four S-shaped flexible beams 1-7; two S-shaped flexible beams 1-7 are located between the first drive shaft 1-1, 1-2 and the detection shaft 1-8, and the other two S-shaped flexible beams 1-7 are located between the second drive shaft 1-1, 1-2 and the detection shaft 1-8, one end of the S-shaped flexible beam 1-7 is connected to the connecting beam 1-9, and the other end is connected to the outer frame structure 1-10; the outer frame structure 1-10 is located on the outside of the first drive shaft 1-1, 1-2, the second drive shaft 1-3, 1-4 and the detection shaft 1-8.

[0028] The quartz MEMS angular velocity sensor chip 1 further comprises anchor structures 1-5 and 1-6. The anchor structures 1-5 and 1-6 are arranged at two ends of the substrate for fixing the substrate.

[0029] Figure 2 A top view showing the electrode pattern on the front side of the sensor chip. Figure 3 It represents a top view of the back electrode, wherein the front side refers to the side facing the positive direction of the Z axis when assembled with the support structure, and the back side refers to the side facing the negative direction of the Z axis when assembled with the support structure. The oblique parallel lines and the horizontal and vertical grids represent the two poles of the driving electrode, which are similar to the two ends of applied alternating current, and can be named as drive and drive feedback, respectively, or generally referred to as driving electrodes; the twill grid and the oblique brick pattern represent two reference electrodes, which are used to detect the electrical signal generated by the potential difference between themselves and the detection electrode, and can be named as reference electrode 1 and reference electrode 2, respectively; the horizontal and vertical stripes and the horizontal brick pattern represent the detection electrode 1 and the detection electrode 2, respectively, which are used to pick up the electrical signal generated by the piezoelectric effect on the two detection axes 1-8.

[0030] Depend on Figure 2 , Figure 3 As shown, the upper and lower surfaces of the first drive shaft 1-1, 1-2 and the second drive shaft 1-3, 1-4 are covered with drive electrodes for exciting the first drive shaft 1-1, 1-2 and the second drive shaft 1-3, 1-4 to vibrate simultaneously, and the upper and lower surfaces of the detection shaft 1-8 are covered with detection electrodes and reference electrodes.

[0031] The quartz MEMS angular velocity sensor chip 1 excites the first drive shaft 1-1, 1-2 and the second drive shaft 1-3, 1-4 to vibrate simultaneously according to the layout of the electrodes, thereby increasing the vibration amplitude of the detection axis. Compared with traditional devices, the sensitivity is increased by about 2 times.

[0032] In one embodiment, reference electrode 1 and reference electrode 2 are respectively grounded or connected to a stable DC level such as a fixed 2.5V;

[0033] In one embodiment, reference electrode 1 and reference electrode 2 may also be directly connected together and regarded as one electrode.

[0034] Electrode pads are generally arranged on the anchor structures 1-5, 1-6 and the isolation structure. In one embodiment, there are a total of 6 pad positions covering the drive electrode, drive feedback electrode, detection electrode 1, detection electrode 2, reference electrode 1, and reference electrode 2, which are used to transmit external drive signals to the inside of the sensor chip and at the same time lead out the electrical signals generated by the sensor chip.

[0035] The first driving shafts 1-1, 1-2, the second driving shafts 1-3, 1-4, the detection shaft 1-8, the anchor structures 1-5, 1-6 and the left and right side walls of the isolation structure are also covered with electrodes for connecting electrodes of the same type.

[0036] The width of the first drive axis 1-1, 1-2 and the second drive axis 1-3, 1-4 is 80um, and the inclination angle with the vertical direction is 1.75°. The width of the detection axis 1-8 is 75um, and the inclination angle with the vertical direction is 1.5°. The driving mode, detection mode and parasitic mode of the sensor chip based on the two pairs of driving axes will be modally coupled. Through the above reasonable structural design, the modal coupling problem is effectively avoided, making it feasible for engineering application. The suppression of modal coupling is mainly achieved by adjusting the average width and inclination angle of the driving axis and the detection axis to control the driving modal frequency and the detection modal frequency, so as to avoid the parasitic modes adjacent to the driving mode and the detection mode as much as possible in frequency, and at the same time ensure that the frequency design value difference falls within a suitable range (the recommended frequency difference range in this embodiment is 450Hz to 600Hz). The specific method for obtaining the optimal average width and inclination angle of the driving axis and the detection axis generally includes: simplifying the calculation of the sensor chip structure model through theoretical mechanics methods, or using finite element simulation software to perform parametric scanning and topological optimization on the sensor chip structure. The latter is used in this embodiment.

[0037] Figure 4 The typical driving mode, typical detection mode and typical parasitic mode of the angular velocity sensor chip in this embodiment are shown. The resonant frequencies of the three modes are f D 、f R 、fS According to the simulation analysis results, the driving modal frequency f D and the detection modal frequency f R The difference (referred to as "frequency difference", symbolized as △f) is about 500Hz. The frequency difference directly affects the transmission efficiency of the angular velocity sensor chip for the Coriolis force signal, and also determines the upper limit of the response frequency (bandwidth) of the angular velocity sensor in the open-loop control mode; the parasitic mode frequency f S and the driving modal frequency f D , detect the modal frequency f R The difference between the two modes is 2500 Hz and 2000 Hz respectively. It is generally believed that the probability of coupling between two adjacent resonant modes with a frequency interval of more than 1000 Hz is extremely low. This shows that the sensor chip in this embodiment effectively avoids the problem of modal coupling.

[0038] In one embodiment, the substrate for making the sensor chip is cut from a quartz crystal according to a certain cut shape, and then made through thinning, grinding, polishing and other steps. Multiple sensor chips can be formed on the substrate at the same time. The specific processing flow of the quartz MEMS angular velocity sensor chip is as follows:

[0039] S1. Forming a structural shape metal mask on both sides of a quartz substrate by coating and double-sided photolithography;

[0040] S2, chemically corroding the quartz substrate forming the metal mask of the structural shape to remove excess quartz crystals to obtain a sensor chip with a basic structure;

[0041] S3, peeling off the metal mask on the surface of the sensor chip having the basic structure, and re-plating the surface with a metal film;

[0042] S4. An electrode pattern is produced on the sensor chip coated with a metal film by photolithography, and the photoresist produced by the photolithography is peeled off to obtain a quartz MEMS angular velocity sensor chip.

[0043] Figure 5 The angular velocity sensor device of the present invention comprises five components: a sensor chip 1, a support structure 2, an ASIC chip 3, a cover plate 4, a ceramic housing 5, etc.; the sensor chip 1 and the support structure 2 are connected by an adhesive at anchor structures 1-5 and 1-6. In order to reduce the influence of temperature on the sensor, the sensor chip 1 and the support structure 2 are both processed with quartz crystal as the base material; the support structure 2 is connected to the ceramic housing 5 by an adhesive, and the ceramic housing 5 is made of laminated ceramics, and an electrode wire is pre-buried inside the ceramic housing, and a metal film is provided on the step thereof, which can be connected with the metal wire; the ASIC chip 3 is fixed to the bottom of the ceramic housing 5 by an adhesive, and the cover plate 4 is made of metal, and the cover plate 4 and the ceramic housing 5 are connected by welding;

[0044] The anchor structures 1-5 and 1-6 are electrically connected to the ASIC chip 3 and the device shell pins by means of gold wire bonding (spot welding), thereby transmitting the driving signal generated by the ASIC chip 3 to the inside of the sensor chip, and at the same time leading the electrical signal detected by the sensor chip to the ASIC chip 3 for signal processing, and finally leading the angular velocity signal output to the ceramic shell 5.

[0045] The material used for fixing the sensor chip of the present invention is an insulating material with a certain elasticity, generally epoxy optical fiber glue is used, which can effectively buffer the vibration and impact from the outside world, and can stably maintain the driving vibration and the detecting vibration. Moreover, the fixing material also has the function of reducing the leakage of the sensor chip vibration to each supporting structure 2, so it can further reduce the impact of fixing each supporting structure 2 on the driving vibration and the detecting vibration.

[0046] In one embodiment, the cover plate 4 is made of metal.

[0047] The above embodiments further illustrate the purpose, technical solutions and advantages of the present invention in detail. It should be understood that the above embodiments are only preferred implementation modes of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made to the present invention within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A quartz MEMS angular velocity sensor chip, comprising a substrate and an electrode, wherein the substrate comprises: A driving shaft and a detection shaft (1-8), characterized in that the driving shaft comprises a first driving shaft (1-1, 1-2) and a second driving shaft (1-3, 1-4), the detection shaft (1-8) is located between the first driving shaft (1-1, 1-2) and the second driving shaft (1-3, 1-4); the electrode is arranged on the surface of the substrate, and is used to excite the first driving shaft (1-1, 1-2) and the second driving shaft (1-3, 1-4) to generate vibration simultaneously.

2. A quartz MEMS angular velocity sensor chip according to claim 1, characterized in that: The substrate also includes a connecting beam (1-9), the two ends of the connecting beam (1-9) are respectively connected to the first driving shaft (1-1, 1-2) and the second driving shaft (1-3, 1-4), and the middle part of the connecting beam (1-9) is connected to the detection shaft (1-8).

3. A quartz MEMS angular velocity sensor chip according to claim 2, characterized in that: The substrate also includes an isolation structure; the isolation structure includes: an outer frame structure (1-10) and four S-shaped flexible beams (1-7); two S-shaped flexible beams (1-7) are located between the first drive shaft (1-1, 1-2) and the detection shaft (1-8), and the other two S-shaped flexible beams (1-7) are located between the second drive shaft (1-1, 1-2) and the detection shaft (1-8); one end of the S-shaped flexible beam (1-7) is connected to the connecting beam (1-9), and the other end is connected to the outer frame structure (1-10); the outer frame structure (1-10) is located outside the first drive shaft (1-1, 1-2), the second drive shaft (1-3, 1-4) and the detection shaft (1-8).

4. The quartz MEMS angular velocity sensor chip according to claim 1, characterized in that: Also includes: Anchor point structures (1-5, 1-6); the anchor point structures (1-5, 1-6) are arranged at two ends of the substrate and are used to fix the substrate.

5. The quartz MEMS angular velocity sensor chip according to claim 1, characterized in that: The upper and lower surfaces of the first driving shaft (1-1, 1-2) and the second driving shaft (1-3, 1-4) are both covered with driving electrodes, and the upper and lower surfaces of the detection shaft (1-8) are both covered with detection electrodes and reference electrodes.

6. The quartz MEMS angular velocity sensor chip according to claim 1, characterized in that: The material of the substrate is quartz crystal.

7. The quartz MEMS angular velocity sensor chip according to claim 1, characterized in that: The width of the first driving axis (1-1, 1-2) and the second driving axis (1-3, 1-4) is 80um, and the inclination angle with the vertical direction is 1.75°; the width of the detection axis (1-8) is 75um, and the inclination angle with the vertical direction is 1.5°.

8. A sensor device using the quartz MEMS angular velocity sensor chip according to claims 1 to 7, comprising: A quartz MEMS angular velocity sensor chip (1), a support structure (2), an ASIC chip (3), a cover plate (4), and a ceramic housing (5), wherein the sensor chip (1) and the support structure (2) are connected by an adhesive, the support structure (2) and the ceramic housing (5) are connected by an adhesive, the ASIC chip (3) is fixed to the bottom of the ceramic housing (5) by an adhesive, and the cover plate (4) and the ceramic housing (5) are connected by welding; and the ASIC chip (3) and the quartz MEMS angular velocity sensor chip (1) are connected to the ceramic housing (5) by metal wires.

9. A sensor device according to claim 8, characterized in that: The ceramic housing (5) is made of laminated ceramics.

10. A sensor device according to claim 8, characterized in that: An electrode wire is pre-buried inside the ceramic shell (5), and a metal film is plated on the step of the ceramic shell (5) for connection with the metal wire.

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