CN216248023U - Dynamic heat source type z-axis micro-mechanical angular velocity sensor - Google Patents

Abstract

The application discloses a dynamic heat source type z-axis micro-mechanical angular velocity sensor, which comprises a substrate layer, a sensitive layer and a cover plate, wherein the sensitive layer comprises a middle heating cavity and a middle detection cavity, and the upper surface of the sensitive layer is provided with an omnibearing vibrator heater (dynamic heat source) and a pair of thermistors; the omnibearing vibrator heater (dynamic heat source) is suspended in the central position of the sensitive layer through six completely symmetrical semicircular supporting beams; the electrifying mode of the heater is periodic alternating current; the cover plate is etched with a groove and is hermetically connected with the upper surface of the sensitive layer. The utility model can realize the measurement of the Z-axis angular velocity, has the characteristics of high sensitivity, high response speed, compact structure, small volume, light weight, easy intellectualization and integration and the like, and conforms to the development direction of the sensor towards microminiature, synthesis and intelligence.

Description

Dynamic heat source type z-axis micro-mechanical angular velocity sensor

Technical Field

The utility model relates to the technical field of detecting angular velocity attitude parameters of a moving body by utilizing a Coriolis force deflection omnibearing vibrator, in particular to a micro-mechanical angular velocity sensor of a moving heat source pendulum Z axis, and belongs to the field of inertia measurement.

Background

The Micro inertial sensor manufactured by using Micro-Electro-Mechanical-System (MEMS) technology has the advantages of mass production, low cost, small volume, low power consumption and the like, and is an ideal product of the future medium and low precision Micro inertial sensors. The gyroscope and the accelerometer are core inertial sensors for measuring and controlling the motion attitude of the carrier, and the gyroscope is a sensor sensitive to angular velocity, angular acceleration and other angular parameters. At present, the market has higher and higher requirements on the capability of a micro gyroscope to adapt to severe and harsh environments, and a micro fluid inertial sensor (MEMS inertial sensor) is unique in the MEMS sensor due to the ultra-high impact resistance and ultra-low manufacturing cost, and cannot be compared with other MEMS inertial sensors.

The current micro fluid gyroscopes based on MEMS technology can be roughly classified into four major categories, micro fluidic gyroscopes, ECF (elec ten-conjuga ten e fluid) fluid gyroscopes, micro thermal convection gyroscopes and micro thermal flow gyroscopes. Chinese patent: a miniature four-channel circulating flow type three-axis silicon jet gyro (patent application number: 201510385582.4) belongs to a miniature jet gyro, a piezoelectric plate in a sensitive element of the miniature jet gyro increases processing difficulty and cost, and the volume of the miniature jet gyro is difficult to further reduce on the premise of keeping flow rate. ECF fluid gyroscopes are relatively large (40mm x 60mm x 7mm) and are difficult to commercialize in large volumes and at low cost because of the high kilovoltage required to form the liquid jet. The miniature thermal convection gyro cannot work without a gravity field, and the sensitivity is low. The above-described microfluidic gyros have their own inherent disadvantages that make them difficult to be the low-cost choice for commercial microfluidic gyros. The micro heat flow gyro (also called thermal expansion gyro) is a new micro fluid gyro which is proposed in recent years, a voltage-free electric sheet is not arranged in a sensitive element, high voltage is not required, and the micro heat flow gyro can be used in a gravity-free environment. Compared with the micro heat flow accelerometer (MEMS heat flow accelerometer) which is commercialized, the MEMS heat flow gyroscope is not mature yet and is still in a development stage. The difficulty of the MEMS heat flow gyroscope in practical application is that the sensitivity is lower than that of a micromechanical vibration gyroscope. In chinese patents 201410140298.6 and 201210130318.2, micromechanical heat-flow gyroscopes almost all use a heater to generate a thermal expansion flow that is deflected by coriolis force when an angular velocity is input, and a symmetrical thermistor is provided to detect an asymmetric distribution of a temperature field. Because the velocity of hot air flow is very small, the gradient of asymmetric temperature field caused by deflection of air flow is very small, so that the unbalanced voltage output by the Wheatstone bridge formed by the thermistor is small, and the sensitivity of the sensor is low. In the conventional solution, although the sensitivity can be improved by increasing the heater power, the sensitivity is not substantially changed or improved due to the limitation of power consumption, and the bottleneck of practical use is difficult to break through.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a dynamic heat source type z-axis micro-mechanical angular velocity sensor, which aims to solve the technical problems in the prior art.

In order to achieve the purpose, the utility model adopts the following technical scheme:

the utility model provides a dynamic heat source type z-axis micro-mechanical angular velocity sensor, which comprises a substrate layer, a sensitive layer and a cover plate, wherein,

the sensing layer comprises a middle heating cavity and a middle detection cavity, and the upper surface of the sensing layer is provided with an omnibearing vibrator heater (a dynamic heat source) and a pair of thermistors;

defining the length direction of the upper surface of the sensitive layer as an X direction, the width direction as a Y direction and the height direction as a Z direction; the omnidirectional vibrator heater is suspended at the center of the sensitive layer through six completely symmetrical semicircular supporting beams; the thermistors are symmetrically arranged on the left side and the right side of the heater in parallel with the Y direction and are used for detecting the angular speed of a Z axis;

the omnibearing vibrator heater (dynamic heat source) adopts a wind-fire wheel type sensitive structure, the center of the omnibearing vibrator heater comprises a central wheel hub with a circular mass block, and the omnibearing vibrator heater is suspended at the central position of a sensitive layer through six completely symmetrical semicircular supporting beams; a circular middle heating cavity is arranged below the heating cavity;

two ends of the omnibearing vibrator heater (dynamic heat source) are covered with symmetrical electrodes along the Y direction to form a movable resistance type heat source;

a rectangular middle detection cavity with the same depth as the middle heating cavity is arranged below the thermistor;

the energization mode of the heater is periodic alternating current to generate alternating excitation voltage; the electrifying mode of the thermistor is constant current;

the cover plate and the basal layer isolate the gas media of the intermediate heating cavity and the intermediate detection cavity from the outside to form a sealed working system; the heights of the middle heating cavity and the middle detection cavity and the depth of the groove in the upper sealing layer are the total cavity height z, and z is more than or equal to 300 mu m and less than or equal to 1000 mu m;

as a further technical solution, the depth of the groove is 2/3 of the cover plate height.

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

As a further technical scheme, the lengths of the two thermistors are consistent and are 1/6-1/5 of the width of the whole sensitive layer.

As a further technical scheme, the heater and the thermistor are both composed of metal layers consisting of a chromium adhesion layer and a platinum layer.

A method for processing a dynamic heat source Z-axis micro-mechanical angular velocity sensor comprises the following specific process flows:

the method comprises the following steps: thermally oxidizing a 0.5 μm thick silicon dioxide film on an N-type (100) single crystal silicon wafer;

step two: photoetching the silicon dioxide film to form structural patterns of an omnidirectional dynamic heat source pendulum heater and a thermistor;

step three: sputtering a metal layer consisting of a chromium adhesion layer and a platinum layer on the photoresist and the silicon dioxide in sequence by a magnetron sputtering process;

step four: stripping off the metal layer outside the all-directional movable heat source pendulum heater and the thermistor structure pattern by adopting an ultrasonic stripping process to form an all-directional movable heat source pendulum heater and a thermistor structure;

step five: etching off a part of silicon dioxide by adopting photoetching and wet etching processes;

step six: a groove with the depth of 300 mu m is formed by corrosion processing by adopting a silicon etching process, so that the omnidirectional dynamic heat source pendulum heater and the thermistor are suspended and fixed on the sensitive layer through a silicon dioxide film to complete the processing of the gyroscope sensitive layer;

step seven: and bonding the cover plate and the sensitive layer by a bonding process to enable the upper surface of the sensitive layer to be positioned in the closed cavity to complete the processing of the gyroscope sensitive element.

By adopting the technical scheme, the utility model has the following beneficial effects:

1. the dynamic heat source type z-axis micro-mechanical angular velocity sensor not only inherits the advantages of an MEMS heat flow gyroscope, but also has the advantages of simple structure, small volume, light weight and low cost, and accords with the development direction of the sensor towards microminiature, comprehensive type and intelligent type.

2. The sensitive structure of the angular velocity sensor is an omnidirectional oscillator heater. The omnibearing vibrator heater sensitive structure can vibrate along the Z axis perpendicular to the rotating plane and has freedom of inertial force in any azimuth angle of the rotating plane. The omnibearing vibrator heater is suspended in the center of the sensitive layer through six completely symmetrical semi-circular support beams, can sense the input angular speed of the rotating shaft on the Z axis, and has high sensitivity and high response speed.

3. The angular velocity sensor adopts a wind-fire wheel type sensitive structure, can manufacture a relatively long elastic element and a relatively large mass block in a small area, and has high inertia force sensitivity.

4. The sensitive element of the angular velocity sensor is manufactured on a silicon chip by an MEMS process, has good consistency, and is convenient for introducing a microcomputer embedded system to carry out temperature compensation and nonlinear degree compensation.

5. The angular velocity sensor has the advantages of simple processing technology, extremely low cost, high reliability and excellent vibration and impact resistance, and has advantages in market competition of micro gyros with medium and low precision and low price.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is a schematic three-dimensional structure diagram of an angular velocity sensor according to an embodiment of the present invention;

fig. 2 is a schematic three-dimensional structure diagram of a cover plate according to an embodiment of the present invention;

FIG. 3 is a top view of a sensitive layer provided by an embodiment of the present invention;

FIG. 4 is a sectional view taken along line A-A of FIG. 3;

FIG. 5 is a schematic diagram of the operation of the present invention;

FIG. 6 is a schematic diagram of an output circuit provided by an embodiment of the utility model;

fig. 7 is a flowchart of a manufacturing process of a dynamic heat source type Z-axis micro-mechanical angular velocity sensor according to an embodiment of the present invention;

icon: 1-sensitive layer, 2-basal layer, 3-middle detection cavity, 4-middle heating cavity, 5-cover plate, 6-groove, 7-omnibearing vibrator heater, 8-thermistor, 9-thermistor and 10-electrode.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

The following detailed description of embodiments of the utility model refers to the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation.

As shown in fig. 1 to 4, the present embodiment provides a dynamic heat source type Z-axis micro-mechanical sensor of angular velocity, which includes a sensitive layer 1, a substrate layer 2 and a cover plate 5, wherein,

the sensitive layer 1 comprises an intermediate heating cavity 4 and an intermediate detection cavity 3, and the upper surface of the sensitive layer 1 is provided with an omnidirectional vibrator heater 7, a thermistor 8 and a thermistor 9;

defining the length direction of the sensitive layer 1 as an X direction, the width direction as a Y direction and the height direction as a Z direction;

the omnidirectional vibrator heater 7 is suspended at the central position of the sensitive layer 1 through six completely symmetrical semicircular supporting beams;

the omnibearing vibrator heater 7 adopts a wind-fire wheel type sensitive structure, the center of the omnibearing vibrator heater comprises a central wheel hub with a circular mass block, and the omnibearing vibrator heater is suspended at the central position of a sensitive layer through six completely symmetrical semicircular supporting beams; a circular middle heating cavity 4 is arranged below the heating cavity; the heater 7 can swing along any azimuth angle in an XOY plane of the sensitive layer 1 besides the z-axis vertical to the sensitive layer;

two ends of the omnidirectional vibrator heater 7 are covered with symmetrical electrodes 10 along the Y direction to form a movable resistance type heat source;

the thermistor 8 and the thermistor 9 are symmetrically arranged on the left side and the right side of the heater along the Y direction and used for detecting the angular speed of the Z axis;

a rectangular middle detection cavity 3 with the same depth as the middle heating cavity 4 is arranged below the thermistor;

the heater 7 is powered by periodic alternating current to generate alternating excitation voltage; the power-on mode of the thermistor is constant current;

a groove 6 is etched in the cover plate 5 and is hermetically connected with the upper surface of the sensitive layer 1;

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 sense the input angular velocity of the rotation axis on the Z axis, thereby realizing the measurement of the Z axis angular velocity.

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, as shown in fig. 5. Meanwhile, the vibrator is electrified to generate Joule heat, releases heat to surrounding gas, and conducts heat diffusion to form heat flow. When the frequency of the alternating current excitation signal is consistent with the vibration frequency of the vibrator along the Y direction, the vibrator resonates in the Y axis direction to generate displacement, and the heat flow is driven to flow along the Y direction. Tz1 and Tz2 in the figure indicate the thermistor 8 and the thermistor 9, respectively.

When an angular velocity Ω Z is input in the Z-axis direction, the omnidirectional oscillator heater 7 will deflect towards the thermistor 8 or 9 in the X-axis direction in the XOY plane due to the Coriolis force principle (Coriolis force), and the thermistor that the thermal oscillator heater deflects is higher than the one that is symmetrically parallel to it, so that the two parallel thermistors 8 and 9 generate a temperature difference proportional to the input angular velocity. As shown in fig. 6, the thermistor 8 and the thermistor 9 are connected to form two arms of an schrader bridge, and the temperature difference generated by the input angular velocity is converted into an unbalanced voltage VZ output proportional to the angular velocity Ω Z by the resistance change of the arms of the schrader bridge, thereby sensing the angular velocity in the Z direction.

In this embodiment, as a further technical solution, the cover plate 5 and the substrate layer 2 isolate the gas media of the intermediate heating chamber 4 and the intermediate detection chamber 3 from the outside, so as to form a sealed working system; the height of the middle heating cavity 4, the height of the middle detection cavity 3 and the depth of the groove 6 in the upper sealing layer are the total cavity height z, z is more than or equal to 300 microns and less than or equal to 1000 microns, and the total cavity height in the embodiment is hundreds of microns, so that natural convection motion of gas flow in the cavity can be effectively inhibited.

In this embodiment, as a further technical solution, in order to increase the depth of the cover plate groove, 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.

In this embodiment, as a further technical solution, in order to form a more stable and reliable thin film resistor having a resistance value with a small change with temperature, the heights of the heater and the thermistor on the upper surface of the sensitive layer are 100nm to 1000 nm.

In this embodiment, as a further technical solution, in order to increase the stability and shock resistance of the sensor, the length of the thermistor 8 and the length of the thermistor 9 are consistent, and are 1/6 to 1/5 of the width of the whole sensitive layer.

In this embodiment, as a further technical solution, the heater and the thermistor are each formed by a metal layer composed of a chromium adhesion layer and a platinum layer.

Referring to fig. 7, the specific process flow of the dynamic heat source type Z-axis micro-mechanical angular velocity sensor disclosed by the utility model is as follows:

step (a): a0.5 μm thick silicon dioxide film was thermally oxidized on an N-type (100) single crystal silicon wafer.

Step (b): and photoetching the silicon dioxide film to form structural patterns of the omnidirectional movable heat source pendulum heater and the thermistor.

Step (c): and sputtering a metal layer consisting of a chromium adhesion layer and a platinum layer on the photoresist and the silicon dioxide in sequence by using a magnetron sputtering process.

Step (d): and stripping off the metal layers outside the structure patterns of the omnidirectional moving heat source pendulum heater and the thermistor by adopting an ultrasonic stripping process to form the omnidirectional moving heat source pendulum heater and the thermistor structure.

A step (e): and etching off a part of silicon dioxide by adopting photoetching and wet etching processes.

Step (f): and etching and processing the groove with the depth of 300 mu m by adopting a silicon etching process, so that the omnidirectional dynamic heat source pendulum heater and the thermistor are suspended and fixed on the sensitive layer through the silicon dioxide film, and the processing of the gyroscope sensitive layer is finished.

Step (g): and bonding the cover plate and the sensitive layer by a bonding process to enable the upper surface of the sensitive layer to be positioned in the closed cavity to complete the processing of the gyroscope sensitive element.

In summary, the utility model breaks through the inherent mode of the previous research on the heat flow gyroscope, and provides a moving heat source type z-axis micro-mechanical angular velocity sensor, so that a heater with a very high temperature gradient moves, the heater deflects under the action of inertia force to form a large temperature gradient at a thermistor, and the output with high sensitivity is realized. The omnibearing vibrator heater sensitive structure provided by the utility model can vibrate along a Z axis vertical to a rotating plane, and has the freedom degree of inertia force at any azimuth angle of the rotating plane. The omnibearing vibrator heater is suspended in the center of the sensitive layer through six completely symmetrical semi-circular support beams, can sense the input angular speed of the rotating shaft on the Z axis, and has high sensitivity and high response speed. The central heater adopts a wind-fire wheel type sensitive structure, can realize the manufacture of a relatively long elastic element and a relatively large mass block in a small area, thereby obtaining large inertia force sensitivity, has the characteristics of compact structure, small volume, light weight, low cost, easy intellectualization and integration and the like, and accords with the development direction of the micro-mechanical vibration gyro towards microminiature, synthesis and intelligence. Meanwhile, the micro-accelerometer has the advantages of simple structure and processing technology, extremely low cost, high reliability and excellent vibration and impact resistance, so that the micro-accelerometer can compete with a capacitive micro-mechanical vibration gyroscope in the micro-accelerometer market with medium, low precision and low price.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the utility model has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (5)

1. A dynamic heat source type z-axis micro mechanical angular velocity sensor is characterized by comprising a substrate layer, a sensitive layer and a cover plate, wherein,

the sensing layer comprises a middle heating cavity and a middle detection cavity, and the upper surface of the sensing layer is provided with an omnibearing vibrator heater and a pair of thermistors;

defining the length direction of the upper surface of the sensitive layer as an X direction, the width direction as a Y direction and the height direction as a Z direction; the omnidirectional vibrator heater is suspended at the center of the sensitive layer through six completely symmetrical semicircular supporting beams; the thermistors are symmetrically arranged on the left side and the right side of the heater in parallel with the Y direction and are used for detecting the angular speed of a Z axis;

the omnibearing vibrator heater adopts a wind-fire wheel type sensitive structure, the center of the omnibearing vibrator heater comprises a central wheel hub with a circular mass block, and the omnibearing vibrator heater is suspended at the central position of a sensitive layer through six completely symmetrical semicircular supporting beams; the middle heating cavity is circular below the middle heating cavity;

the omnidirectional oscillator heater can swing along a Z axis vertical to the sensitive layer and also can swing along any azimuth angle in an XOY plane where the sensitive layer is located;

two ends of the omnidirectional vibrator heater are covered with symmetrical electrodes along the Y direction to form a movable resistance type heat source;

the rectangular middle detection cavity with the same depth as the middle heating cavity is arranged below the thermistor;

the omnibearing vibrator heater is electrified by periodic alternating current to generate alternating excitation voltage; the power-on mode of the thermistor is constant current;

the cover plate and the basal layer isolate the gas media of the intermediate heating cavity and the intermediate detection cavity from the outside to form a sealed working system; the height of the middle heating cavity and the middle detection cavity and the depth of the groove in the cover plate are the total cavity height z, and z is more than or equal to 300 mu m and less than or equal to 1000 mu m.

2. The moving heat source z-axis micromachined angular velocity sensor of claim 1, wherein the groove depth is 2/3 the cover plate height.

3. The dynamic heat source z-axis micromachined angular velocity sensor of claim 1, wherein the height of the omnidirectional vibrator heater and thermistor is 100nm to 1000 nm.

4. The sensor of claim 1, wherein the two thermistors are of uniform length, each 1/6-1/5 of the width of the entire sensing layer.

5. The sensor of claim 1, wherein the omnidirectional oscillator heater and the thermistor are each formed of a metal layer comprising a chromium adhesion layer and a platinum layer.

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