CN216485109U

CN216485109U - Omnibearing dynamic heat source pendulum type three-axis micromechanical accelerometer

Info

Publication number: CN216485109U
Application number: CN202122910667.3U
Authority: CN
Inventors: 朴林华; 李备; 王灯山; 佟嘉程
Original assignee: Beijing Information Science and Technology University
Current assignee: Beijing Information Science and Technology University
Priority date: 2021-11-25
Filing date: 2021-11-25
Publication date: 2022-05-10
Anticipated expiration: 2031-11-25

Abstract

The application discloses an omnidirectional dynamic heat source pendulum type three-axis micro mechanical accelerometer which comprises an upper sensitive layer, a lower sensitive layer and a cover plate, wherein a heater is arranged at the central position of the sensitive layer, six completely symmetrical semi-circular support beams are suspended at the central position of the sensitive layer, and a circular middle heating cavity is arranged below the sensitive layer; the lower sensitive layer contains four thermistors which are orthogonally distributed, and a rectangular middle detection cavity is arranged below the lower sensitive layer; the electrifying modes of the heater and the thermistor are constant 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 detection of the three-axis acceleration, and has wide measurement range, high sensitivity and high response speed. Meanwhile, the sensor has the advantages of simple processing technology, compact structure, small structural stress, high reliability, easy intellectualization and integration, and accords with the development direction of the sensor towards microminiature, synthesis and intelligence.

Description

Omnibearing dynamic heat source pendulum type three-axis micromechanical accelerometer

Technical Field

The utility model relates to the technical field of detecting acceleration attitude parameters of a motion carrier by utilizing the swinging of an omnidirectional moving heat source pendulum under the action of linear acceleration, in particular to an omnidirectional moving heat source pendulum type three-axis micro mechanical accelerometer, belonging to the field of inertial measurement.

Background

Due to the application requirements of the carrier attitude measurement in various fields of civil vehicles, railway construction, industrial production, bridge construction, seismic research, geodetic surveying, geological exploration, marine investigation, satellite communication, robot engineering and the like, in recent years, the organic combination between the sensor technology and the emerging scientific technology enables the attitude sensor to develop towards microminiature, comprehensive and intelligent. 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 accelerometer is a core inertial sensor for measuring and controlling the motion attitude of the carrier.

The most common among accelerometers is the pendulum acceleration sensor. The pendulum tilt sensor commonly used at present has three types, namely a liquid pendulum type sensor, a solid pendulum type sensor and a heat flow type sensor. The solid pendulum type tilt angle sensor has the advantages of complex structure, high cost, large motion amplitude of the solid pendulum and difficulty in bearing high overload or impact. The main problems of the liquid pendulum tilt angle sensor are that the number of structural components is large, the response time is long, and the performance changes greatly along with the temperature. The heat flow type accelerometer has the characteristics of small sensitive mass, simple structure, high overload bearing capacity, short response time, good temperature performance, low cost and the like, and can be applied to severe environments. At present, the requirement of the market on the capability of the micro accelerometer to adapt to the harsh environment is higher and higher, so that in the micro acceleration sensor, the micro mechanical system (MEMS) heat flow acceleration is unique in the MEMS sensor by the ultra-high impact resistance and ultra-low manufacturing cost, and is not comparable to other MEMS sensors.

The working principle of the micro-mechanical (MEMS) heat flow accelerometer is as follows: the resistance heater is arranged in the closed cavity, the parallel detection thermistors are symmetrically distributed around the resistance heater, the resistance heater is electrified and heated to form a heat source to emit heat flow to the periphery, and the temperature fields are symmetrically distributed, so that the influence on the thermistors is consistent. When the external wired acceleration is input, the flowing direction of hot air flow is the same as the acceleration direction, and the hot air flow changes towards the input acceleration direction, so that the temperature field of the air flow is asymmetrically distributed, the temperature changes of two adjacent detection thermistors in the same direction are opposite, and the two detection thermistors generate temperature difference. The acceleration can be detected by detecting the temperature difference through the Wheatstone bridge. Chinese patent: in a micro-mechanical heat flow accelerometer in a silicon bridge type thermal convection acceleration sensor (patent application No. 02116842.3), a heater generates heat flow, the heat flow moves under the action of the acceleration of an input line to generate an asymmetric temperature field, and the asymmetric distribution of the temperature field is detected by arranging symmetrical thermistors. 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 an omnidirectional dynamic heat source pendulum type three-axis micro mechanical accelerometer 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 an omnidirectional dynamic heat source pendulum type three-axis micro mechanical accelerometer which is characterized by comprising an upper sensitive layer, a lower sensitive layer and a cover plate, wherein,

an omnidirectional dynamic heat source swing heater is arranged at the central position of the upper sensitive layer, four thermistors are arranged on the upper surface of the lower sensitive layer, and the upper sensitive layer and the lower sensitive layer are bonded together to form a sensitive layer;

defining the length and width directions of the accelerometer as X and Y directions respectively, and the height direction of the accelerometer as Z direction; the thermistors are orthogonally distributed in the X and Y directions by taking the omnidirectional moving heat source pendulum heater as a center; the four thermistors are arranged in pairs in opposite mode and used for detecting the acceleration of the XYZ three axes;

the omnidirectional dynamic heat source swing heater adopts a wind-fire wheel type sensitive structure, the center of the omnidirectional dynamic heat source swing heater contains a central wheel hub with a circular mass block, and the omnidirectional dynamic heat source swing 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;

the electrifying modes of the heater and the thermistor are constant current;

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

the cover plate and the lower sensitive layer isolate the gas media of the middle heating cavity and the middle 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.

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

As a further technical solution, the height of the heater and thermistor is 100nm to 1000 nm.

As a further technical scheme, the length of the thermistor is 1/6-1/5 of the width of the whole sensitive layer.

As a further technical solution, the heater and the thermistor are formed of a metal layer composed of a chromium adhesion layer and a platinum layer.

A method for processing an omnidirectional dynamic heat source pendulum type three-axis micro mechanical accelerometer 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 and forming a thermistor structure pattern on the silicon dioxide film;

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 using a magnetron sputtering process;

step four: stripping off the metal layer outside the thermistor structure pattern by adopting an ultrasonic stripping process to form 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 thermistor is suspended and fixed on the lower sensitive layer through the silicon dioxide film to finish the processing of the lower sensitive layer;

step seven: thermally oxidizing a 0.5 μm thick silicon dioxide film on another N-type (100) single crystal silicon wafer;

step eight: photoetching the silicon dioxide film to form an omnidirectional oscillator heater structure pattern;

step nine: 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 ten: stripping off the metal layer outside the structure pattern of the omnidirectional oscillator heater by adopting an ultrasonic stripping process to form an omnidirectional oscillator heater structure;

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

step twelve: etching and etching through by adopting a silicon etching process to form an intermediate heating cavity, so that the omnibearing vibrator heater is suspended and fixed on the upper sensitive layer through the silicon dioxide film to complete the processing of the upper sensitive layer;

step thirteen: bonding the lower sensitive layer and the upper sensitive layer through a bonding process;

fourteen steps: and bonding the cover plate and the upper sensitive layer by a bonding process to enable the upper surface of the sensitive layer to be positioned in the closed cavity, thereby finishing the processing of the sensitive element.

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

1. the omnidirectional dynamic heat source pendulum type three-axis micro mechanical accelerometer inherits the advantages of an MEMS heat flow accelerometer, and is small in size, light in weight and easy to intelligentize and integrate.

2. The sensitive structure of the accelerometer is an omnidirectional moving heat source pendulum heater. The omnibearing movable heat source pendulum sensitive structure can swing up and down along a Z axis vertical to the plane of a sensitive layer, has the degree of freedom (swing) of inertia force at any azimuth angle on the XOY plane of the sensitive layer, and can sense the input acceleration on three axes. The omnidirectional moving heat source swinging heater is suspended at the center of the sensitive layer through six completely symmetrical semicircular supporting beams to realize three-axis measurement of acceleration, and has the advantages of wide measurement range, high sensitivity and high response speed.

3. The omnibearing movable heat source pendulum adopts a wind-fire wheel type sensitive structure, a central wheel is a mass block and is also a heater, the wind-fire wheel type sensitive structure adopts a sensitive structure center support, and the structural stress is small.

4. The accelerometer adopts a wind-fire wheel type sensitive structure, and the structure is flexible, so that a heat source with high temperature gradient can vibrate in all directions, a large temperature gradient is formed at the thermistor, and high-sensitivity output is realized. 5. The vibration-proof and impact-proof structure has the advantages of simple structure and processing technology, extremely low cost, high reliability and excellent vibration-proof and impact-proof characteristics.

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 accelerometer according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a three-dimensional double-layer structure of a sensitive layer provided in an embodiment of the present invention;

FIG. 3 is a schematic three-dimensional structure diagram of a cover plate according to an embodiment of the present invention;

FIG. 4 is a top view of an accelerometer according to an embodiment of the utility model;

FIG. 5 is a top view of a lower sensitive layer provided by an embodiment of the present invention;

FIG. 6 is a sectional view taken along line A-A of FIG. 4;

FIG. 7 is a schematic diagram of the operation of an embodiment of the present invention;

FIG. 8 is a schematic diagram of an output circuit provided by an embodiment of the utility model;

fig. 9 is a flow chart of a manufacturing process of the omnidirectional dynamic heat source pendulum type triaxial micro mechanical accelerometer according to the embodiment of the present invention;

icon: 1-upper sensitive layer, 2-lower sensitive layer, 3-electrode, 4-middle heating cavity, 5-middle detection cavity, 6-cover plate, 7-groove, 8-omnidirectional movable heat source swinging heater, 9-thermistor, 10-thermistor, 11-thermistor and 12-thermistor.

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 obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to 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.

Referring to fig. 1-6, the present embodiment provides an omnidirectional moving heat source pendulum type three-axis micro mechanical accelerometer, which includes an upper sensitive layer 1, a lower sensitive layer 2 and a cover plate 6, wherein,

an omnidirectional dynamic heat source pendulum heater 8 is arranged at the central position of the upper sensitive layer 1, four thermistors are arranged on the upper surface of the lower sensitive layer 2, and the upper sensitive layer and the lower sensitive layer are bonded together to form a sensitive layer;

defining the length and width directions of the accelerometer as X and Y directions respectively, and the height direction of the sensitive layer as Z direction;

the omnidirectional moving heat source pendulum heater 8 is suspended at the central position of the upper sensitive layer 1 through six completely symmetrical semicircular spokes, and a circular middle heating cavity 4 is arranged below the omnidirectional moving heat source pendulum heater; the heater 8 can swing along any azimuth angle in an XOY plane of the upper sensitive layer 1 besides the Z axis vertical to the sensitive layer;

the four thermistors are oppositely arranged in pairs, the thermistors 9 and the thermistors 10 are symmetrically arranged in the left-right direction perpendicular to the X axis, and the thermistors 11 and the thermistors 12 are symmetrically arranged in the up-down direction perpendicular to the Y axis;

the electrifying modes of the heater and the thermistor are constant current;

and a groove 7 is etched in the cover plate 6 and is hermetically connected with the upper surface of the upper sensitive layer 1.

As a further technical solution in this embodiment, as shown in fig. 7 and fig. 8, the resistive omnidirectional moving heat source pendulum heater 8 is energized with a constant current, and the resistive heater is energized to generate joule heat, which releases heat to the surrounding air to perform heat diffusion, thereby forming heat flow around the omnidirectional moving heat source pendulum heater. Four thermistors T with same resistance_x1(thermistor 9) and T_x2(thermistor 10) or T_x3(thermistor 11) and T_x4(thermistor)12) The two arms forming the wheatstone bridge participate in the deflection of the sensitive airflow. When linear acceleration along an X axis or a Y axis is input, the moving heat source pendulum moves along the same direction with the acceleration direction under the action of the acceleration, and the asymmetrical distribution of hot air flow is caused. Two opposite thermistors T in the same direction_x1(thermistor 9) and T_x2(thermistor 10) or T_y1(thermistor 11) and T_y2(thermistor 12) the temperature change is opposite, the temperature of the thermistor with the dynamic heat source biased is higher than that of the thermistor parallel to the dynamic heat source, and the two opposite thermistors generate temperature difference. Two opposite bridge arm resistors T_x1And T_x2(thermistors 9 and 10) or T_y1And T_y2(thermistor 11 and thermistor 12) as the two arms of the Schneider bridge, the temperature difference caused by the acceleration of the input line is converted into the change of the resistance of the arms, thereby causing the unbalanced voltage V of the bridge proportional to the input acceleration_XOr V_Y. According to the output voltage V_XOr V_YThe linear acceleration of the X axis or the Y axis can be calculated, and the acceleration in the X direction or the Y direction is sensed.

When a linear acceleration is input in the direction vertical to the Z axis, the omnidirectional movable heat source pendulum moves along the same direction with the acceleration under the action of the acceleration. The heat flow emitted by the omnidirectional moving heat source swinging heater can deviate along the Z axis, when the acceleration points to the thermistor input along the Z axis, the moving heat source swinging heater is close to the four thermistors, and the resistance values of the four thermistors are increased. The sum V of the voltages across the four thermistors_ZAnd (4) increasing. When acceleration is input along the Z axis away from the thermistor. The heat source swing heater is far away from the four thermistors, the resistance values of the four thermistors are reduced, and the sum V of the voltages at the two ends of the four thermistors_ZAnd decreases. Thus can pass through V_ZThe magnitude of the acceleration is detected by V_ZDetects the direction of acceleration, and thus senses acceleration in the Z-axis direction.

In the embodiment, as a further technical scheme, the cover plate 6 and the lower sensitive layer 2 isolate the gas media of the intermediate heating cavity 4 and the intermediate detection cavity 5 from the outside to form a sealed working system; the height of the middle heating cavity 4 and the middle detection cavity 5 and the depth of the groove 7 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, the depth of the groove 7 is 2/3 of the height of the cover plate 6.

In this embodiment, as a further technical solution, in order to increase the depth of the cover plate groove, the gas flowing space is increased, and the height of the thermistor on the surface of the heater and the lower sensitive layer of the upper sensitive layer is 100nm to 1000 nm.

In this embodiment, as a further technical solution, in order to form a more stable and reliable thin film resistor with a resistance value that has a small variation with temperature, the length of the thermistor is 1/6 to 1/5 of the width of the whole sensing 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. 9, the specific process flow of the pendulum-type triaxial micro mechanical accelerometer of the dynamic heat source disclosed by the present invention 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 an omnidirectional oscillator heater and thermistor structure pattern.

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 layer except the omnibearing vibrator heater and the thermistor structure pattern by adopting an ultrasonic stripping process to form the omnibearing vibrator heater and thermistor structure.

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

A step (f): and a groove with the depth of 300 mu m is formed by corrosion processing by adopting a silicon etching process, so that the omnibearing vibrator heater and the thermistor are fixed on the sensitive layer in a suspended manner through the silicon dioxide film, and the processing of the sensitive layer is completed.

Step (g): a0.5 μm thick silicon dioxide film was thermally oxidized on another N-type (100) single crystal silicon wafer.

A step (h): and photoetching and forming an omnidirectional oscillator heater structure on the silicon dioxide film.

Step (i): 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 (j): and stripping off the metal layer outside the structure pattern of the omnidirectional oscillator heater by adopting an ultrasonic stripping process to form the omnidirectional oscillator heater structure.

Step (k): and etching off a part of silicon dioxide by adopting photoetching and wet etching processes.

Step (l): and etching through a silicon etching process to form an intermediate heating cavity, so that the omnibearing vibrator heater is suspended and fixed on the upper sensitive layer through the silicon dioxide film, and the processing of the upper sensitive layer is completed.

Step (m): and bonding the lower sensitive layer and the upper sensitive layer through a bonding process.

And (n): and bonding the cover plate and the upper sensitive layer by a bonding process to enable the upper surface of the sensitive layer to be positioned in the closed cavity, thereby finishing the processing of the sensitive element.

In summary, the utility model breaks through the inherent mode of the previous research on the heat flow accelerometer, and provides the omnidirectional moving heat source pendulum type triaxial micro mechanical accelerometer, so that the heater with a very high temperature gradient moves, the heater deflects under the action of the inertia force to form a large temperature gradient at the thermistor, and the output with high sensitivity is realized. The sensitive structure of the accelerometer is an omnidirectional moving heat source pendulum heater. The omnidirectional movable heat source pendulum sensitive structure can swing up and down along a Z axis vertical to the sensitive layer plane, has the freedom degree of inertia force on any azimuth angle on the sensitive layer XOY plane, and can sense the input acceleration on three axes. The omnidirectional moving heat source swinging heater is suspended at the center of the sensitive layer through six completely symmetrical semicircular supporting beams to realize three-axis measurement of acceleration, and has the advantages of wide measurement range, high sensitivity and high response speed. The utility model inherits the advantages of the MEMS sensor, 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 sensor towards microminiature, comprehensive type and intelligent type. Meanwhile, the method has the advantages of simple processing technology, extremely low cost, high reliability and excellent vibration and impact resistance.

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

1. An omnidirectional dynamic heat source pendulum type three-axis micro mechanical accelerometer is characterized by comprising an upper sensitive layer, a lower sensitive layer and a cover plate, wherein,

the center position of the upper sensitive layer is provided with an omnidirectional dynamic heat source swing heater, the upper surface of the lower sensitive layer is provided with four thermistors, and the upper sensitive layer and the lower sensitive layer are bonded together to form a sensitive layer;

defining the length and width directions of the accelerometer as X and Y directions respectively, and the height direction of the accelerometer as Z direction; the thermistors are orthogonally distributed in the X and Y directions by taking the omnidirectional moving heat source pendulum heater as a center; the four thermistors are arranged oppositely in pairs and used for detecting the acceleration of the three shafts;

the omnidirectional moving heat source swinging 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;

the electrifying modes of the heater and the thermistor are constant current;

2. The omnidirectional moving heat source pendulum-type triaxial micromachined accelerometer of claim 1, wherein the depth of the groove of said cover plate is 2/3 of the height of the cover plate.

3. The omnidirectional moving heat source pendulum-type triaxial micro-mechanical accelerometer of claim 1, wherein the height of the omnidirectional moving heat source pendulum heater and thermistor is 100nm to 1000 nm.

4. The omnidirectional moving heat source pendulum-type triaxial micro-mechanical accelerometer of claim 1, wherein the length of the thermistor is uniform and is 1/6 to 1/5 of the width of the entire lower sensitive layer.

5. The omnidirectional moving heat source pendulum-type triaxial micro-mechanical accelerometer according to claim 1, wherein the omnidirectional moving heat source pendulum heater and the thermistor are both formed of metal layers consisting of a chromium adhesion layer and a platinum layer.