CN107131819A - Single shaft micromechanics displacement transducer based on tunnel magneto-resistance effect - Google Patents

Abstract

A uniaxial micromechanical displacement sensor based on the tunnel magnetoresistance effect, including a bonded substrate, a displacement sensitive body, a ferromagnetic thin film, and a tunnel magnetoresistor. The displacement sensitive body is composed of a displacement sensitive body frame, a sensitive mass block, and a folded beam , the frame of the displacement sensitive body is fixed on the bonded substrate, the sensitive mass is placed in the frame of the displacement sensitive body, and connected to the frame of the displacement sensitive body through a folded beam, the upper surface of the sensitive mass is fixed with a ferromagnetic thin film, and the sensitive mass is fixed on the bonded substrate The surface is provided with a tunnel magnetoresistor corresponding to the position of the ferromagnetic film. The single-axis micro-mechanical displacement sensor of the present invention adopts an overall structural design, and the displacement sensor is integrated and manufactured on the same frame body, which can increase the sensitivity of the micro-mechanical displacement sensor by 1 to 2 orders of magnitude.

Description

Uniaxial Micromechanical Displacement Sensor Based on Tunneling Magnetoresistance Effect

technical field

The invention belongs to the technical field of micro-inertial navigation, and relates to a sensor for measuring displacement, in particular to a sensor device for measuring displacement by tunnel magnetoresistance effect.

Background technique

Commonly used detection methods for micromechanical displacement sensors include piezoresistive, capacitive, piezoelectric, and tunnel effect types.

The piezoresistive type is realized based on the piezoresistive effect principle of highly doped silicon. The piezoresistive device formed by highly doped silicon has a strong dependence on temperature. The bridge detection circuit composed of piezoresistive devices will change due to temperature. cause sensitivity drift. The improvement of capacitive precision depends on the increase of capacitance area, but due to the miniaturization of devices, its accuracy is difficult to improve due to the reduction of effective capacitance area. The sensitivity of the piezoelectric effect sensor is easy to drift, requires frequent calibration, and is slow to return to zero, so it is not suitable for continuous testing. The manufacturing process of the tunnel effect sensor is complicated, and the detection circuit is relatively difficult to realize, and the yield rate is low, which is not conducive to integration.

The measurement of the displacement by the micromechanical displacement sensor is completed by the force-electric conversion of the detection device, and its sensitivity and resolution are very important. Due to the miniaturization and integration of the displacement sensor, the detection sensitive area is reduced accordingly, so the detection sensitivity, resolution and other indicators have reached the detection limit state of the sensitive area, thus limiting the further improvement of the sensor detection accuracy, it is difficult Meet the needs of modern military and civilian equipment.

Based on the spin effect of electrons, there is a magnetic multilayer film structure with an insulator or a semiconductor non-magnetic layer between the magnetic pinned layer and the magnetic free layer. Since the current passing between the magnetic pinned layer and the magnetic free layer is based on electrons The tunneling effect, so this multilayer film structure is called Magnetic Tunnel Junction (MTJ, Magnetic Tunnel Junction). Under the action of a voltage across the insulating layer, the tunnel current and tunnel resistance of this magnetic tunnel junction depend on the relative orientation of the magnetization of the two ferromagnetic layers (magnetic pinned layer and magnetic free layer). When the magnetic free layer is under the action of an external field, its magnetization direction changes, while the magnetization direction of the pinned layer remains unchanged. At this time, the relative orientation of the magnetization of the two magnetic layers changes, and the magnetic tunnel across the insulating layer A large resistance change is observed across the junction. This physical effect is based on the tunneling effect of electrons in the insulating layer, which is called tunneling magnetoresistance (TMR, Tunneling Magnetoresistance). That is to say, the TMR sensor uses the change of the magnetic field to cause the change of the magnetoresistance.

At present, as the fourth generation of magnetoresistive sensors, TMR sensors have the characteristics of high sensitivity, good linearity, and wide dynamic range, which to some extent make up for the shortcomings of the previous generation of giant magnetoresistance (GMR, Giant Magnetoresistance). TMR has replaced GMR heads in the high-precision technical field of hard disk heads, which requires extremely high performance such as work stability. Therefore, the performance of TMR has withstood the strictest test. With the large-scale application of TMR magnetic sensors, its excellent performance will penetrate into the sensor industry and application fields with the development of its industrialization, providing new technical solutions for many sensor application fields.

Contents of the invention

The purpose of the present invention is to provide a micro-mechanical displacement sensor, which is based on the tunnel magnetoresistance effect to measure small changes in displacement, thereby improving the detection accuracy of the micro-mechanical displacement sensor.

The uniaxial micromechanical displacement sensor based on the tunnel magnetoresistance effect described in the present invention includes:

a bonding substrate;

At least one displacement sensitive body, the displacement sensitive body is composed of a displacement sensitive body frame, a sensitive mass block and a folding beam, the displacement sensitive body frame is fixed on the bonding substrate, and the sensitive mass block is placed on the displacement sensitive body In the frame, it is connected to the frame of the displacement sensitive body through a folded beam; the sensitive mass is supported by the folded beam and can vibrate along a direction (Z axis) perpendicular to the surface of the bonded substrate;

The ferromagnetic thin film is fixed on the upper surface of the sensitive mass, and vibrates with the sensitive mass in a direction (Z axis) perpendicular to the surface of the bonding substrate;

Tunnel magnetoresistor, the tunnel magnetoresistor is arranged on the upper surface of the bonded substrate, corresponding to the position of the ferromagnetic film on the sensitive mass, and the tunnel magnetoresistor connects with the tunnel set on the bonded substrate through the resistance lead-out wire The magneto-resistor electrodes are connected.

The above-mentioned single-axis micro-mechanical displacement sensor of the present invention is used to detect the displacement in the Z-axis.

Wherein, preferably, four folded beams of the same size are arranged symmetrically on the frame of the displacement sensitive body to connect with the sensitive mass.

In the present invention, the folded beam is used to support the sensitive mass which can only vibrate along the Z axis and has no displacement in the X and Y axes. Therefore, the thickness of the folded beam is much smaller than its width, ensuring that its stiffness in the Z-axis direction is much smaller than that in the other two directions.

Furthermore, the basic structure of the tunnel magnetoresistor in the present invention is composed of multi-layer ferromagnetic layers arranged on the substrate layer of semiconductor material and separated by insulating layers, and has a resistance layer with tunnel magnetoresistance effect.

More specifically, the tunnel magnetoresistor has a square structure.

As a preferred technical solution of the present invention, only one displacement sensitive body is fixed on the bonding substrate, the displacement sensitive body is placed at the center of the bonding substrate, and the area of the bonding substrate is larger than the area of the displacement sensitive body .

Based on the above structure, the present invention places the tunnel magnetoresistive electrode at the position where the displacement sensitive body is exposed on the bonding substrate.

Furthermore, the surface of the sensitive mass in the present invention is square, that is, the length in the X-axis is equal to the length in the Y-axis.

At the same time, the ferromagnetic thin film is placed at the center of the displacement sensitive body. The ferromagnetic thin film of the present invention is a multi-layer nano film structure arranged in sequence on the semiconductor material substrate layer.

The single-axis micro-mechanical displacement sensor of the present invention adopts an overall structural design, and the displacement sensor is integrated and manufactured on the same frame body. The structural design is reasonable and simple, convenient to use and good in reliability, and is suitable for miniaturization of devices.

The uniaxial micromechanical displacement sensor of the present invention arranges a ferromagnetic thin film on the sensitive mass, facing the tunnel magnetoresistor arranged in the corresponding area on the bonding substrate. A drastic change occurs, which can increase the sensitivity of the micromechanical displacement sensor by 1 to 2 orders of magnitude.

Description of drawings

Fig. 1 is a schematic diagram of the structure of the single-axis micro-mechanical displacement sensor of the present invention.

FIG. 2 is a schematic structural diagram of the displacement sensitive body 5 in FIG. 1 .

FIG. 3 is a schematic structural view of the bonded substrate portion in FIG. 1 .

FIG. 4 is a partially enlarged view of the folded beam 4 in FIG. 1 .

In the figure: 1—bonding substrate; 2—displacement sensitive body frame; 3—sensitive mass block; 4—folded beam; 5—displacement sensitive body; 6—ferromagnetic thin film; 7—tunnel magnetoresistor; 8—resistor Lead wire; 9—tunnel magnetoresistor electrode.

detailed description

The technical solutions of the present invention are described in detail below through specific examples. Examples of said embodiments are shown in the drawings, and it should be emphasized that the embodiments described by means of the drawings are examples and are used only for explaining the invention and are not to be construed as limiting the invention in any way.

In the description of the present invention, it should be understood that the orientations or positional relationships indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right" etc. are based on the attached The orientation or positional relationship shown in the figure is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be construed as a reference to this invention. Invention Limitations.

In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral Ground connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

As shown in FIG. 1 , FIG. 2 , and FIG. 3 , the constituent units of the uniaxial micromechanical displacement sensor of the embodiment of the present invention include a bonded substrate 1 , a displacement sensitive body 5 , a ferromagnetic thin film 6 and a tunnel magnetoresistor 7 .

Wherein, the bonding substrate 1 is used as a carrier, which can be made of semiconductor material, and is used to carry the displacement sensitive body 5 . The displacement sensitive body 5 is disposed above the bonding substrate 1 , and the center of the displacement sensitive body 5 is directly opposite to the center of the bonding substrate 1 .

The structure of the displacement sensitive body 5 is specifically shown in FIG. 2 , which further includes a sensitive mass 3 in the Z-axis direction, a folding beam 4 in the Z-axis direction, and a displacement-sensitive body frame 2 .

Specifically, the displacement sensitive body 5 is an integral structure, with the displacement sensitive body frame 2 as a carrier, on which is fabricated a sensitive mass 3 capable of sensing the Z-axis. The sensitive mass 3 in the Z-axis direction is connected to the displacement-sensitive body frame 2 through four folded beams 4 in the Z-axis direction. Wherein, the upper and lower surfaces of the sensitive mass 3 are square.

According to the sensitivity of the sensitive mass 3 to the Z-axis, the size of the folding beam 4 is set so that its thickness is much smaller than the width, so as to ensure that its stiffness in the Z-axis direction is much smaller than the other two directions, and on the sensitive mass 3, Both lower and lower sides are provided with z-axis direction folding beams 4 . It should be noted that the number of folded beams can be changed according to the performance requirements of the displacement sensor. For example, although there are two folded beams 4 in the Z-axis direction on the upper and lower sides of the sensitive mass 3 in this embodiment, according to As stated above, it is also possible to appropriately add the same number of folded beams on both sides, and the added folded beams are consistent with the properties described above.

The ferromagnetic thin film 6 is arranged at the center of the upper surface of the sensitive mass 3 , corresponding to the position of the tunnel magnetoresistor 7 fabricated on the bonded substrate 1 .

As shown in Figures 1 and 3, the bonded substrate 1 is square, and its area is larger than the displacement sensitive body 5. A tunnel magneto-sensitive resistor 7 is arranged at the center of its upper surface, and the tunnel magneto-sensitive resistor 7 adopts a square shape. 8 is connected to the tunnel magnetoresistor electrode 9 arranged on the edge of the bonded substrate 1 .

The tunnel magnetoresistor 7 includes a ferromagnetic layer, an insulating layer, and a ferromagnetic layer sequentially arranged on a semiconductor material substrate layer (for example, the upper surface of the bonding substrate 1 ). The above-mentioned tunnel magnetoresistor 7 can be designed and manufactured by molecular beam epitaxy. Molecular beam epitaxy is a method for growing high-quality crystal thin films on semiconductor wafers. Under vacuum conditions, they are grown layer by layer according to the crystal structure On the substrate layer, and form a nanoscale film layer, deposited layer by layer. During the deposition process, it is necessary to strictly control the quality and thickness of the film, so as to avoid the influence of the quality and thickness of the film on the detection accuracy and sensitivity of the micromechanical displacement sensor.

The size, shape and thickness of the ferromagnetic thin film 6 can also be determined according to the strength and distribution requirements of the tunnel magnetoresistor 7 of the micromechanical displacement sensor to the magnetic field intensity.

In addition, the ferromagnetic thin film 6 can also be a multi-layer structure, so as to better cooperate with the tunnel magnetoresistor 7 . The ferromagnetic thin film 6 can be made of multi-layer ferromagnetic material nano-films sequentially arranged on the upper surface of the sensitive mass 3 . It should be noted that the above-mentioned ferromagnetic thin film 6 can also be fabricated and grown on the sensitive mass 3 by molecular beam epitaxy.

When the micromechanical displacement sensor is displaced in the direction of the Z axis, the sensitive mass 3 will deviate from the equilibrium position under the action of inertia and vibrate along the direction of the Z axis. Due to the change of the relative distance, the intensity of the magnetic field generated by the ferromagnetic thin film 6 on the upper surface of the sensitive mass 3 at the position corresponding to the tunnel magnetoresistor 7 on the bonding substrate 1 will increase or decrease. The change of the magnetic field intensity causes the tunnel magnetoresistance effect, which causes the resistance value of the tunnel magnetoresistor to change drastically. In this way, a weak displacement signal can be converted into a strong electrical signal, and the magnitude of the Z-axis input displacement can be detected by processing the signal.

The single-axis micro-mechanical displacement sensor of this embodiment adopts an overall structural design, which is suitable for device miniaturization, and can increase the sensitivity of the micro-mechanical displacement sensor by 1 to 2 orders of magnitude.

Although the specific embodiments of the present invention have been described above, those of ordinary skill in the art can understand that without departing from the principle and purpose of the present invention, various changes, modifications, replacements and modifications can be made to these embodiments. The scope of the invention is defined by the claims and their equivalents.

Claims (8)

1. a kind of single shaft micromechanics displacement transducer, it is characterised in that including：

One bonding substrate；

At least one displacement sensitive body, the displacement sensitive body is by displacement sensitive body framework, sensitive-mass block and inflection beam structure Into the displacement sensitive body framework is fixed on bonding substrate, and the sensitive-mass block is placed in displacement sensitive body framework, is passed through Inflection beam is connected with displacement sensitive body framework；The sensitive-mass block is supported by inflection beam, can be along perpendicular to bonding substrate surface Direction vibration；

Ferromagnetic thin film, is fixed on the upper surface of the sensitive-mass block, with sensitive-mass block along perpendicular to bonding substrate surface Direction vibration；

Tunnel mistor, the tunnel mistor is located at the upper surface of bonding substrate, with the ferromagnetism on sensitive-mass block Film position correspondence, the tunnel mistor electrode that the tunnel mistor is set by resistance lead-out wire with being bonded on substrate It is connected.

2. single shaft micromechanics displacement transducer according to claim 1, it is characterized in that in the displacement sensitive body framework The inflection beam for being symmetrically arranged with four identical sizes is connected with the sensitive-mass block.

3. single shaft micromechanics displacement transducer according to claim 1, it is characterized in that described tunnel mistor is row Cloth on semiconductive material substrate layer, the multilayer ferromagnetic layer that is separated with insulating barrier constituted, the electricity with tunnel magneto-resistance effect Resistance layer.

4. the single shaft micromechanics displacement transducer according to claim 1,2 or 3, it is characterized in that described tunnel mistor For square structure.

5. the single shaft micromechanics displacement transducer according to claim 1,2 or 3, it is characterized in that solid on the bonding substrate Surely there is a displacement sensitive body, the displacement sensitive body is placed in the center of the bonding substrate, and the area of bonding substrate More than the sensitive bulk area of displacement.

6. single shaft micromechanics displacement transducer according to claim 5, it is characterized in that described tunnel mistor electrode It is placed on bonding substrate at the position for exposing displacement sensitive body.

7. the single shaft micromechanics displacement transducer according to claim 1,2 or 3, it is characterized in that the table of the sensitive-mass block Face is square.

8. single shaft micromechanics displacement transducer according to claim 7, it is characterized in that the ferromagnetic thin film is placed in displacement The center of sensitive body.