Dynamic heat source type z-axis micromechanical angular velocity sensor and processing method thereof

Abstract

The present application discloses a dynamic heat source Z-axis micromechanical angular velocity sensor and a processing method thereof, wherein the Z-axis angular velocity sensor comprises a base layer, a sensitive layer and a cover plate, wherein the sensitive layer comprises an intermediate heating cavity and an intermediate detection cavity, and an omnidirectional vibrator heater (dynamic heat source) and a pair of thermistors are arranged on the upper surface of the sensitive layer; the omnidirectional vibrator heater (dynamic heat source) is suspended at the center of the sensitive layer through six completely symmetrical semicircular support beams; the heater is powered by periodic alternating current; a groove is etched on the cover plate and is tightly connected to the upper surface of the sensitive layer. The present invention can realize the measurement of Z-axis angular velocity, has high sensitivity, fast response speed, and has the characteristics of compact structure, small size, light weight, easy intelligence and integration, and is in line with the development direction of sensors towards miniature, comprehensive and intelligent types.

Description

Technical Field

[0001] This invention relates to the technical field of detecting the angular velocity and attitude parameters of a moving body by deflecting an omnidirectional oscillator using Coriolis force, and particularly to a Z-axis micromechanical angular velocity sensor with a dynamic heat source pendulum and its processing method, belonging to the field of inertial measurement. Background Art

[0002] Miniature inertial sensors fabricated using Micro-Electro-Mechanical-System (MEMS) technology offer numerous advantages, including mass production, low cost, small size, and low power consumption, making them ideal products for future medium- and low-precision miniature inertial sensors. Gyroscopes and accelerometers are core inertial sensors for measuring and controlling the motion and attitude of a carrier, with gyroscopes being sensors sensitive to angular parameters such as angular velocity and angular acceleration. Currently, the market demands increasingly higher capabilities from miniature gyroscopes to withstand harsh and demanding environments. Miniature fluid inertial sensors (MEMS inertial sensors) stand out among MEMS sensors due to their ultra-high shock resistance and ultra-low manufacturing cost, unmatched by other MEMS inertial sensors.

[0003] Currently, microfluidic gyroscopes based on MEMS technology can be broadly classified into four categories: micro jet gyroscopes, ECF (elec+ro-conjuga+e fluid) fluid gyroscopes, micro thermal convection gyroscopes, and micro thermal flow gyroscopes. A Chinese patent, "A Micro Four-Channel Circulating Flow Triaxial Silicon Jet Gyroscope" (patent application number: 201510385582.4), belongs to the micro jet gyroscope category. The piezoelectric element within its sensing element increases manufacturing difficulty and cost, and its size is difficult to further reduce while maintaining flow velocity. ECF fluid gyroscopes are relatively large (40mm×60mm×7mm), and the formation of a jet stream requires voltages as high as thousands of volts, making large-scale, low-cost commercialization difficult. Micro thermal convection gyroscopes cannot operate without a gravity field and have low sensitivity. Due to their inherent drawbacks, these microfluidic gyroscopes are unlikely to be a viable option for low-cost commercialization. Miniature heat flow gyroscopes (also known as thermal expansion gyroscopes) are a relatively new type of miniature fluid gyroscope proposed in recent years. They lack piezoelectric elements in their sensing elements, do not require high voltage, and can be used in zero-gravity environments. Compared to the commercially available miniature heat flow accelerometers (MEMS heat flow accelerometers), MEMS heat flow gyroscopes are still in the research and development stage and are not yet mature. A major challenge to the practical application of MEMS heat flow gyroscopes lies in their lower sensitivity compared to micromechanical vibration gyroscopes. In Chinese patents 201410140298.6 and 201210130318.2, micromechanical heat flow gyroscopes almost all utilize the thermal expansion flow generated by a heater, which deflects under the influence of Coriolis force when the input angular velocity is low. The asymmetric distribution of the temperature field is detected by setting symmetrical thermistors. Because the hot air flow velocity is very small, the asymmetric temperature field gradient caused by the air flow deflection is very small. Therefore, the unbalanced voltage output by the Wheatstone bridge composed of thermistors is small, resulting in low sensor sensitivity. While existing solutions can improve sensitivity by increasing heater power, the sensitivity remains largely unchanged and unimproved due to power consumption limitations, making it difficult to overcome this bottleneck for practical application. Summary of the Invention

[0004] The purpose of this invention is to provide a dynamic heat source type Z-axis micromechanical angular velocity sensor to solve the technical problems existing in the prior art.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a dynamic heat source type Z-axis micromechanical angular velocity sensor, comprising a substrate layer, a sensitive layer, and a cover plate, wherein,

[0007] The sensitive layer contains an intermediate heating cavity and an intermediate detection cavity, and the upper surface of the sensitive layer is provided with an omnidirectional oscillator heater (dynamic heat source) and a pair of thermistors;

[0008] The length direction of the upper surface of the sensitive layer is defined as the X direction, the width direction as the Y direction, and the height direction as the Z direction; the omnidirectional oscillator heater is suspended at the center of the sensitive layer by six completely symmetrical semi-circular support beams; the thermistor is placed symmetrically on the left and right sides of the heater parallel to the Y direction to detect the angular velocity of the Z axis.

[0009] The omnidirectional oscillator heater (dynamic heat source) adopts a windmill-type sensitive structure, which contains a central wheel with a circular mass block at its center, and is suspended at the center of the sensitive layer by six completely symmetrical semi-circular support beams; below it is a circular central heating cavity.

[0010] The two ends of the omnidirectional oscillator heater (dynamic heat source) are covered with symmetrical electrodes along the Y direction to form a movable resistive heat source.

[0011] Below the thermistor is a rectangular intermediate detection cavity with the same depth as the intermediate heating cavity;

[0012] The heater is energized by periodic alternating current, generating an alternating excitation voltage; the thermistors are all energized by constant current.

[0013] The cover plate and base layer isolate the gas medium in the intermediate heating chamber and intermediate detection chamber from the outside world, forming a sealed working system; the height of the intermediate heating chamber and intermediate detection chamber and the depth of the groove in the upper sealing layer are the total cavity height z, 300μm≤z≤1000μm;

[0014] As a further technical solution, the depth of the groove is 2 / 3 of the height of the cover plate.

[0015] As a further technical solution, the height of the heater and thermistor on the upper surface of the sensitive layer is 100nm to 1000nm.

[0016] As a further technical solution, the two thermistors have the same length, which is 1 / 6 to 1 / 5 of the width of the entire sensitive layer.

[0017] As a further technical solution, both the heater and the thermistor are composed of metal layers consisting of a chromium adhesive layer and a platinum layer.

[0018] A method for fabricating a Z-axis micromechanical angular velocity sensor with a dynamic heat source, the specific process flow of which is as follows:

[0019] Step 1: Thermally oxidize a 0.5 μm thick silicon dioxide film on an N-type (100) single-crystal silicon wafer;

[0020] Step 2: Photolithography is used to form the omnidirectional dynamic heat source pendulum heater and thermistor structure pattern on the silicon dioxide film;

[0021] Step 3: Use magnetron sputtering to sequentially sputter a metal layer consisting of a chromium adhesion layer and a platinum layer onto the photoresist and silicon dioxide;

[0022] Step 4: Use ultrasonic peeling process to peel off the metal layer outside the omnidirectional dynamic heat source pendulum heater and thermistor structure pattern to form the omnidirectional dynamic heat source pendulum heater and thermistor structure.

[0023] Step 5: Use photolithography and wet etching processes to etch away a portion of the silicon dioxide;

[0024] Step 6: A 300μm deep groove is formed by etching using silicon etching technology, so that the omnidirectional dynamic heat source pendulum heater and thermistor are suspended and fixed on the sensitive layer through the silicon dioxide film, thus completing the processing of the gyroscope sensitive layer;

[0025] Step 7: The cover plate and the sensitive layer are bonded together using a bonding process, so that the upper surface of the sensitive layer is in a sealed cavity to complete the processing of the gyroscope sensitive element.

[0026] By adopting the above technical solution, the present invention has the following beneficial effects:

[0027] 1. This dynamic heat source type Z-axis micromechanical angular velocity sensor not only inherits the advantages of MEMS thermal flux gyroscope, but also has the advantages of simple structure, small size, light weight and low cost, which is in line with the development direction of sensors towards miniaturization, integration and intelligence.

[0028] 2. The sensitive structure of this angular velocity sensor is an omnidirectional oscillator heater. Besides vibrating along the Z-axis perpendicular to the plane of rotation, the omnidirectional oscillator heater sensor structure has a degree of freedom of inertial force at any azimuth angle within the plane of rotation. The omnidirectional oscillator heater is suspended at the center of the sensitive layer by six completely symmetrical semi-circular support beams, enabling it to sense the input angular velocity of the rotation axis along the Z-axis, exhibiting high sensitivity and fast response.

[0029] 3. This angular velocity sensor uses a windmill-type sensitive structure, which allows for the fabrication of relatively long elastic elements and relatively large mass blocks within a small area, resulting in high inertial force sensitivity.

[0030] 4. The sensing element of this angular velocity sensor is fabricated on a silicon wafer using MEMS technology, resulting in good consistency and making it easy to integrate into a microcomputer embedded system for temperature compensation and nonlinearity compensation.

[0031] 5. This type of angular velocity sensor has a simple manufacturing process, extremely low cost, and high reliability. It also has excellent vibration and shock resistance, giving it an advantage in the market competition for micro gyroscopes with medium to low precision and low price. Attached Figure Description

[0032] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0033] Figure 1 A three-dimensional structural schematic diagram of the angular velocity sensor provided in an embodiment of the present invention;

[0034] Figure 2 A three-dimensional structural schematic diagram of the cover plate provided in an embodiment of the present invention;

[0035] Figure 3 A top view of the sensitive layer provided in an embodiment of the present invention;

[0036] Figure 4 for Figure 3 Sectional view along axis AA;

[0037] Figure 5 A schematic diagram illustrating the working principle of an embodiment of the present invention;

[0038] Figure 6 The schematic diagram of the output circuit provided in the embodiment of the present invention;

[0039] Figure 7 This is a process flow diagram of the fabrication process of the dynamic heat source type Z-axis micromechanical angular velocity sensor provided in an embodiment of the present invention;

[0040] Icons: 1-Sensitive layer, 2-Base layer, 3-Intermediate detection cavity, 4-Intermediate heating cavity, 5-Cover plate, 6-Groove, 7-Omnidirectional oscillator heater, 8-Thermistor, 9-Thermistor, 10-Electrode. Detailed Implementation

[0041] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0043] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0044] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0045] Combination Figure 1-4 As shown, this embodiment provides a dynamic heat source type Z-axis micromechanical angular velocity sensor, including a sensitive layer 1, a substrate layer 2, and a cover plate 5, wherein,

[0046] The sensitive layer 1 contains an intermediate heating cavity 4 and an intermediate detection cavity 3, and the upper surface of the sensitive layer 1 is provided with an all-around oscillator heater 7, a thermistor 8 and a thermistor 9.

[0047] The length direction of the sensitive layer 1 is defined as the X direction, the width as the Y direction, and the height direction as the Z direction;

[0048] The omnidirectional oscillator heater 7 is suspended at the center of the sensitive layer 1 by six completely symmetrical semi-circular support beams.

[0049] The omnidirectional oscillator heater 7 adopts a windmill-type sensitive structure, which contains a central wheel with a circular mass block at its center. It is suspended at the center of the sensitive layer by six completely symmetrical semi-circular support beams. Below it is a circular central heating cavity 4. In addition to being able to swing along the z-axis perpendicular to the sensitive layer, the heater 7 can also swing along any azimuth angle in the XOY plane where the sensitive layer 1 is located.

[0050] The two ends of the omnidirectional oscillator heater 7 are covered with symmetrical electrodes 10 along the Y direction to form a movable resistive heat source.

[0051] Thermistors 8 and 9 are symmetrically placed on the left and right sides of the heater along the Y direction to detect the angular velocity of the Z axis.

[0052] Below the thermistor is a rectangular intermediate detection cavity 3 with the same depth as the intermediate heating cavity 4;

[0053] The heater 7 is energized by periodic alternating current to generate alternating excitation voltage; the thermistor is energized by constant current.

[0054] The cover plate 5 has grooves 6 etched on it and is sealed to the upper surface of the sensitive layer 1.

[0055] In this embodiment, as a further technical solution, the omnidirectional oscillator heater 7 has a degree of freedom of inertial force at any azimuth angle on the rotation plane, and can be sensitive to the input angular velocity of the rotation axis on the Z-axis, thereby realizing the measurement of the Z-axis angular velocity.

[0056] Combination Figure 5 As shown, in this embodiment, as a further technical solution, the omnidirectional oscillator heater 7 is driven by an alternating excitation voltage to generate an alternating temperature field. Simultaneously, the oscillator generates Joule heating when energized, releasing heat to the surrounding gas for thermal diffusion, forming a heat flow. When the frequency of the AC excitation signal matches the oscillator's vibration frequency along the Y-axis, the oscillator resonates in the Y-axis direction, generating displacement and driving the heat flow along the Y-axis. In the figure, Tz1 and Tz2 refer to thermistors 8 and 9, respectively.

[0057] When an angular velocity Ωz is input in the Z-axis direction, due to the Coriolis force, the omnidirectional oscillator heater 7 will deflect towards the thermistor 8 or thermistor 9 in the XOY plane. The thermistor deflected by the heated oscillator heater is higher than the symmetrical parallel thermistor, thus generating a temperature difference between the two parallel thermistors 8 and 9 that is proportional to the input angular velocity. Figure 6 As shown, thermistors 8 and 9 are connected to form two arms of a Whistler bridge. The temperature difference generated by the input angular velocity is converted into an unbalanced voltage VZ output that is proportional to the angular velocity Ωz through the change in the resistance value of the Whistler bridge arm, thereby sensing the angular velocity in the Z direction.

[0058] In this embodiment, as a further technical solution, the cover plate 5 and the base layer 2 isolate the gas medium of the intermediate heating chamber 4 and the intermediate detection chamber 3 from the outside, forming a sealed working system; the height of the intermediate heating chamber 4 and the intermediate detection chamber 3 and the depth of the groove 6 in the upper sealing layer are the total cavity height z, 300μm≤z≤1000μm. In this embodiment, the total cavity height is on the order of hundreds of micrometers, which can effectively suppress the natural convection movement of gas flow in the cavity.

[0059] In this embodiment, as a further technical solution, the depth of the cover plate groove is increased to increase the space for gas flow, thereby increasing the sensitivity of the sensor. The depth of the groove 6 is 2 / 3 of the height of the cover plate 5.

[0060] In this embodiment, as a further technical solution, in order to form a thin-film resistor with a smaller resistance change with temperature and more stable and reliable, the height of the heater and thermistor on the upper surface of the sensitive layer is 100nm to 1000nm.

[0061] In this embodiment, as a further technical solution, to increase the stability and shock resistance of the sensor, the thermistor 8 and the thermistor 9 have the same length, which is 1 / 6 to 1 / 5 of the width of the entire sensitive layer.

[0062] In this embodiment, as a further technical solution, both the heater and the thermistor are composed of metal layers consisting of a chromium adhesive layer and a platinum layer.

[0063] Combination Figure 7 As shown, the specific process flow of the dynamic heat source type Z-axis micromechanical angular velocity sensor disclosed in this invention is as follows:

[0064] Step (a): Thermally oxidize a 0.5 μm thick silicon dioxide film on an N-type (100) single-crystal silicon wafer.

[0065] Step (b): Photolithography is used to form the omnidirectional dynamic heat source pendulum heater and thermistor structure pattern on the silicon dioxide film.

[0066] Step (c): A metal layer consisting of a chromium adhesion layer and a platinum layer is sequentially sputtered onto the photoresist and silicon dioxide using a magnetron sputtering process.

[0067] Step (d): Use ultrasonic stripping technology to remove the metal layer outside the omnidirectional dynamic heat source pendulum heater and thermistor structure pattern to form the omnidirectional dynamic heat source pendulum heater and thermistor structure.

[0068] Step (e): A portion of the silicon dioxide is etched away using photolithography and wet etching processes.

[0069] Step (f): A 300μm deep groove is formed by etching using silicon etching process, so that the omnidirectional dynamic heat source pendulum heater and thermistor are suspended and fixed on the sensitive layer through the silicon dioxide film, thus completing the processing of the gyroscope sensitive layer.

[0070] Step (g): The cover plate and the sensitive layer are bonded together by bonding process, so that the upper surface of the sensitive layer is in a sealed cavity to complete the processing of the gyroscope sensitive element.

[0071] In summary, this invention breaks away from the conventional research model of heat flow gyroscopes, proposing a dynamic heat source type Z-axis micromechanical angular velocity sensor. This sensor activates a heater with a high temperature gradient, causing it to deflect under inertial force, creating a large temperature gradient at the thermistor and thus achieving high sensitivity output. This omnidirectional oscillator heater sensing structure, proposed in this invention, not only vibrates along the Z-axis perpendicular to the plane of rotation but also possesses inertial force freedom at any azimuth angle within the plane of rotation. The omnidirectional oscillator heater is suspended at the center of the sensing layer by six completely symmetrical semi-circular support beams, enabling it to sense the input angular velocity of the rotation axis along the Z-axis with high sensitivity and fast response. The central heater employs a windmill-like sensing structure, allowing for the fabrication of relatively long elastic elements and a relatively large mass within a small area, thereby achieving high inertial force sensitivity. It features a compact structure, small size, light weight, low cost, and ease of intelligent integration, aligning with the development trend of micromechanical vibrating gyroscopes towards miniaturization, comprehensiveness, and intelligence. At the same time, it has a very simple structure and processing technology, extremely low cost, high reliability, and excellent vibration and shock resistance, which makes it possible for it to compete with capacitive micromechanical vibratory gyroscopes in the low-precision and low-price micro accelerometer market.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dynamic heat source type z-axis micromechanical angular velocity sensor, characterized in that: It includes a base layer, a sensitive layer and a cover plate, wherein: The sensitive layer comprises a middle heating cavity and a middle detection cavity, and an omnidirectional vibrator heater and a pair of thermistors are arranged on the upper surface of the sensitive layer; The length direction of the upper surface of the sensitive layer is defined as the X direction, the width direction is defined as the Y direction, and the height direction is defined as the Z direction; the omnidirectional vibrator heater is suspended at the center of the sensitive layer through six completely symmetrical semicircular support beams; the thermistors are symmetrically placed on the left and right sides of the heater parallel to the Y direction, and are used to detect the angular velocity of the Z axis; The omnidirectional vibrator heater adopts a Hot Wheels sensitive structure, the center of which contains a central wheel hub with a circular mass block, which is suspended at the center of the sensitive layer through six completely symmetrical semicircular support beams; below it is the circular intermediate heating cavity; The omnidirectional vibrator heater can not only swing along the Z axis perpendicular to the sensitive layer, but also swing along any azimuth angle in the XOY plane where the sensitive layer is located; Both ends of the omnidirectional vibrator heater are covered with symmetrical electrodes along the Y direction to form a movable resistive heat source; Below the thermistor is the rectangular middle detection cavity having the same depth as the middle heating cavity; The omnidirectional vibrator heater is powered by periodic alternating current, which generates an alternating excitation voltage; the thermistor is powered by constant current. The cover plate and the base layer isolate the gas medium of the intermediate heating cavity and the intermediate detection cavity from the outside world to form a sealed working system; the height of the intermediate heating cavity and the intermediate detection cavity and the depth of the groove in the cover plate are the total cavity height z, 300μm≤z≤1000μm; The depth of the groove is 2 / 3 of the height of the cover plate; The height of the omnidirectional oscillator heater and the thermistor is 100nm to 1000nm.

2. The dynamic heat source type z-axis micromechanical angular velocity sensor according to claim 1, characterized in that: The lengths of the two thermistors are consistent, both being 1 / 6 to 1 / 5 of the width of the entire sensitive layer.

3. The dynamic heat source type z-axis micromechanical angular velocity sensor according to claim 1, characterized in that: The omnidirectional oscillator heater and the thermistor are both composed of a metal layer consisting of a chromium adhesion layer and a platinum layer.

4. A method for processing the dynamic heat source type z-axis micromechanical angular velocity sensor according to any one of claims 1 to 3, characterized in that: The specific process is as follows: Step 1: thermally oxidize a 0.5 μm thick silicon dioxide film on an N-type (100) single crystal silicon wafer; Step 2: Photolithography forms a full-range dynamic heat source swing heater and a thermistor structure pattern on the silicon dioxide film; Step 3: sputtering a metal layer consisting of a chromium adhesion layer and a platinum layer on the photoresist and silicon dioxide in sequence by using a magnetron sputtering process; Step 4: Use ultrasonic stripping process to strip off the metal layer outside the omnidirectional dynamic heat source pendulum heater and thermistor structure pattern to form the omnidirectional dynamic heat source pendulum heater and thermistor structure; Step 5: Use photolithography and wet etching process to etch away a portion of silicon dioxide; Step 6: Use silicon etching process to form a groove with a depth of 300 μm, so that the omnidirectional dynamic heat source pendulum heater and thermistor are suspended and fixed on the sensitive layer through the silicon dioxide film, and the processing of the gyroscope sensitive layer is completed; Step 7: Bond the cover plate and the sensitive layer through a bonding process so that the upper surface of the sensitive layer is in a closed cavity to complete the processing of the gyro sensitive element.

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