WO2012069021A1

WO2012069021A1 - Microelectromechanical system switch, motion sensor, and motion sensing method

Info

Publication number: WO2012069021A1
Application number: PCT/CN2011/083065
Authority: WO
Inventors: 李秉纬
Original assignee: 苏州扩达微电子有限公司
Priority date: 2010-11-26
Filing date: 2011-11-28
Publication date: 2012-05-31
Also published as: CN102064039A

Abstract

Provided are a microelectromechanical system switch, a motion sensor using the switch, and a motion sensing method. The microelectromechanical system comprises a substrate, an anchor (10), and a cantilever beam (11). The anchor (10) is fixed on the substrate, one end of the cantilever beam (11) is a fixed end connected to the anchor (10), and the other end of the cantilever beam (11) is a free end. The free end of the cantilever beam is connected to a mass block. At lease one side around the mass block (12) is arranged with a contact wall (13), and a gap (15) is arranged between the mass block (12) and the contact wall (13). The mass block (12) and the free end of the cantilever beam have a degree of freedom to move in the direction towards the contact wall (13). When the mass block (12) and the contact wall (13) are in contact with each other, the microelectromechanical system switch is closed. An external voltage is not required to drive the microelectromechanical system switch, which can be used in motion sensing. The switch features ultra-low power consumption, and is especially suitable for use in waking-up a work module.

Description

徼Electro-mechanical system switch, motion sensor and motion sensing method

Technical field

The invention relates to a microelectromechanical system device and a sensor and a sensing method using the same, in particular to a sensor for oscillating an electromechanical system, a sensor and a sensing method using the microelectromechanical system switch.

Background technique

Meg Weng, there are a large number of electronic systems powered by batteries, which need to impose strict limits on the power consumption of the system. A common method is to put the system into a "sleep" state when the system is not being used, even if the system is dormant, Reduce power consumption. The system needs to determine what to enter the sleep state, and in the sleep state, it is necessary to determine what to cancel the sleep state, especially in order to release the sleep state, a low-power sensing module needs to maintain the work in the sleep state, waiting to be issued Wake up the command.

When the system is placed, it is often time to sleep, so a low-power motion sensor is urgently needed. Especially in some applications, most of the system is in a dormant state, and an ultra-low power motion sensor can greatly extend the system's standby time.

Microelectromechanical systems (MEMS) technology refers to the technology of designing, processing, manufacturing, measuring and controlling micro/nano materials. It can integrate mechanical components, optical systems, drive components and electronic control systems into one micro unit. system. Such an electronic mechanical system is capable of not only acquiring, processing and transmitting information or instructions, but also acting autonomously or according to external instructions in accordance with the acquired information. A manufacturing process that combines ffl microelectronics and micromachining technologies (including silicon body processing, silicon surface micromachining, LIGA, and wafer bonding) to produce a variety of sensors with excellent performance, low cost, and miniaturization. Actuators, drives, and microsystems.

At present, MEMS is mainly composed of two types: suspension arm contact type and parallel capacitance type. The suspension arm contact type switch is composed of a cantilever, a metal contact point and an electrostatically driven mechanical part, and the relatively rigid cantilever free end is made by electrostatic force. The inclination of the substrate material changes to cause a gap separation from the substrate to form an "on" or "off" state. This type of switch requires an external voltage drive and is not motion sensitive.

Summary of the invention

SUMMARY OF THE INVENTION It is an object of the present invention to provide a microelectromechanical system switch that can be used to sense motion or gravity orientation while providing motion sensors and motion sensing methods including the microelectromechanical system switches.

In order to achieve the above object, the technical solution adopted by the present invention is: a microelectromechanical system switch comprising a substrate anchor and a suspension beam, the anchor being fixed on the substrate, and one end of the suspension beam is a fixed end connected to the anchor, The other end of the cantilever beam is a free end, and the free end of the cantilever beam is connected with a mass, and at least one side is arranged around the mass The contact wall has a gap between the mass and the contact wall; the mass and the free end of the cantilever have a degree of freedom of movement toward the contact wall, and the microelectromechanical system switch is turned on when the mass and the contact wall are in contact with each other.

The invention designs a cantilever beam which can be bent by the action of gravity or other force. One end of the cantilever beam is connected with the anchor, and the other end is connected with a mass. The structure of the mass is used to increase the bending degree of the cantilever beam, and is placed on the two sides of the mass or one side of the mass. When the cantilever beam reaches a certain degree of bending, the mass can contact the contact wall to form a low-impedance path to achieve the effect of the switch conducting. Wherein, the anchor and the mass may be of any shape, and the cantilever beam may be provided with a curved structure according to the occasion of the occasion, and the shape and orientation of the contact wall may also be changed.

In a further technical solution, a contact wall is disposed on each of opposite sides of the mass, and a gap is formed between the mass and the contact walls on both sides. The contact walls on either side may be separate or may be joined together by other means as needed.

In the above technical solution, the width of the cantilever is smaller than the width of the mass.

In a preferred technical solution, the width of the cantilever beam is between ium and 3 _l3 m, and the width of the cantilever beam is between 500 _μm and 3000 um. The gap width between the mass and the contact wall is between u _m and 3 _μm .

As a specific application of the above technical solution, a microelectromechanical system motion sensor includes at least

A further technical solution comprises a plurality of said microelectromechanical systems, wherein the suspension beams of the respective electromechanical system switches are arranged in an angular manner that is not zero. Generally, each switch can be arranged in an array of some form, and the angle between the switches is not zero, when a movement greater than a certain angle occurs, or a certain acceleration of the movement is performed, the switch array The status will change.

A preferred technical solution is to provide three said electro-mechanical systems, and the cantilever beams of the respective electromechanical system switches are arranged in a mutually perpendicular manner. At this time, no matter how it is placed, the angle between the cantilever beam of at least one switch and the horizontal plane is greater than or equal to 45 degrees, and the array of the gates is arranged in an appropriate manner, which can be proved that the system can be monitored under any circumstances. A certain angle of motion, or a certain angle of movement.

The above motion sensor can be fabricated as an integrated circuit.

The invention also provides a motion sensing method, which is configured to set one or more of the above-mentioned electronic mechanical system according to the moving direction or the direction of the force to be sensed, and monitor the conduction state of the electronic mechanical system. Change, to determine if there is movement. When not conducting, no current flows through the switch, and only a small amount of current is required to drive a small load capacitance to provide a signal when turned on, thus achieving ultra-low power motion sensing. In the present invention, the material of the anchor, the suspension beam, the mass, and the contact wall may be single crystal silicon or other materials. The anchor may be of any shape, the mass may be of any shape, the cantilever may be a straight line or a curve, and the contact wall may be of any shape. The anchor, the suspension beam, the mass, and the contact wall are each at least one, but not limited to one.

Due to the above technical solutions, the present invention has the following advantages over the prior art -

1. The invention realizes the conduction of the switch by providing the mass at the free end of the cantilever beam, and the movement of the mass block is in contact with the contact wall, so that no external voltage driving is required, and the motion sensing can be performed.

2. The invention detects whether there is motion through the switch state, and in the case of no motion, the switch remains unchanged, and no current flow is required; in the case of the motion trigger switch action, only a small amount is required on the switch. The battery flows through to drive a small load capacitor, which has ultra-low power consumption and is especially suitable for waking up the working module.

3. The chip area realized by the invention can be small. For different applications, depending on the angle at which the system may move, different numbers of gates can be placed to form an array to achieve a certain range of motion detection.

4. The microelectromechanical system switch output of the present invention is a digital signal, which is convenient for application.

i diagram description

1 is a top plan view of one embodiment of a MEMS switch in accordance with the present invention;

Figure 2 is a cross-sectional view of Figure 1;

3 is a top plan view showing an embodiment of the MEMS switch of the present invention in a conductive state by gravity;

Figure 4 is a plan view of another embodiment of the MEMS barrier of the present invention;

Figure 5 is a schematic view of the switch size measurement of Figure 4;

6 is a top plan view of one embodiment of a MEMS motion sensor constructed by the switches of FIG. 4 in an array manner; FIG. 7 is a schematic diagram of the output state change caused by the positional change of the MEMS motion sensor of FIG. 6 under the action of gravity.

Figure 8 is a clock circuit for generating the frequency of the output signal.

Figure 9 is a circuit for converting the results of the array of Figure 6 into a single level output.

detailed description

The invention is further described in the following with reference to the accompanying drawings, in which: FIG.

Example:

1 and 4 respectively illustrate top views of an embodiment of two MEMS switches in accordance with the present invention, including: anchor 10, cantilever 1 , mass 12, contact wall 13, gap between contact wall and mass 15 , cantilever beam deep quality The gap between the inside of the gauge block and the mass 14 (not required). The anchor 10 is fixed on the substrate, and one end of the cantilever beam 11 is fixed on the anchor 10, and the other end is connected to the mass block 12. The cantilever beam 11 and the mass block 12 are not connected to the substrate, and can be moved. The cantilever beam 11 is selected to penetrate the mass block 12. Internal, this way you can keep the cantilever! In the case of 1 length, the area is reduced. The contact wall 13 is fixed to the substrate J by somewhere, and in this embodiment, it is directly fixed to the underlying substrate, and the gap 15 between the contact wall 13 and the mass 12 is necessary.

2 is a cross-sectional view of the embodiment of FIG. 1, which is implemented on an SOI process, 20 is a substrate, 2 is a silicon dioxide between two layers of silicon, and 22 is a silicon dioxide 21 after being engraved The gap. In the fabrication of the MEMS switch embodiment, the upper layer of silicon is first etched to produce the anchor 10, the cantilever beam 11, the mass 12, the contact wall 13, the gap 14, the gap 15, and then the cantilever beam 11, the mass 2 Etching is performed below to create a void 22.

Fig. 3 is a view showing the case where the embodiment of Fig. 1 is subjected to gravity and the MEMS switch is turned on. In Figure 3, the switch plane is perpendicular to the horizontal plane, and the cantilever beam 11 has a certain angle with the direction of gravity. Under the action of the gravity of the mass 12, the cantilever 11 is bent, and the mass 12 is displaced. When the displacement of the mass 12 reaches the size of the gap 15, the mass 12 contacts the gap 13 to form a low impedance path. The MEMS switch is in a conducting state. If the displacement of the mass 12 is less than the width of the gap 15 under the action of gravity, the mass 12 is not in contact with the contact wall 13, and the switch is in the off state.

Figure 5 is a detailed embodiment of the MEMS switch described above. The plane of the switch is perpendicular to the horizontal plane, the angle between the cantilever beam 11 and the direction of gravity is 9, and the mass of the mass is the Young's modulus of the cantilever beam is E, then the cantilever beam is bent by gravity, and the displacement of the mass block can be calculated by the following formula:

When the displacement v of the mass is greater than the width d ^ 间隙 of the gap 15, the switch will be turned on, and the switch will be turned off.

As a preferred solution, take the following data as the dimensions of the MEMS switch shown in Figure 5 - φ\ = 4°, = 2dQ, R2 - 400&r«3⁄4, i?3 = 210O m, H -\ 5am, CW - tm, = 2330Kgim ³ , E = l30GPa, d ^ 2 m, (the ratio of the physical part to the total area on the mass is 0.462), then:

When β > 5 ^ΰ , v > im = d, the switch is turned on.

When £f < 5 ^s 3 , ν <2 m - d , the 幵 is off.

6 is an embodiment of a MEMS motion sensor constructed from a plurality of embodiments of the MEMS switch of FIG. Whether the motion is judged by the state of the switch 1, the switch 2, the switch 3, and the switch N.

Fig. 7 is an output state diagram of the above-mentioned MEMS motion sensor at an angle of 90 degrees with respect to the horizontal plane, under the action of gravity, at different positions. In position A, due to the action of gravity G, the mass of the M+] mass is in contact with the contact wall, and the switch is in the conduction state, indicated by 1; and the displacement of the mass of the switch M is smaller than the width of the gap 15, and is not in contact with the contact wall. , Shaoguan is in the disconnected state, indicated by 0. The state of the switch array in position A is; i 1 1 0 1 1 1 1 . In position B, due to the action of gravity G, the mass of the switch M is in contact with the contact wall, and the switch is in an on state; the mass of the switch M+1 is not in contact with the contact wall, and the switch is in a broken state. The position of the switch in position B is: 1 1 1 1 0 1 1 1 . Therefore, it can be determined that the MEMS motion sensor has moved by the change of the switch state.

8 and 9 are an embodiment of a subsequent circuit of the above described MEMS motion sensor embodiment. Figure 8 shows the clock used to generate the output signal frequency. For an output clock of T < l kJ in general, the average power consumption of this circuit can be easily controlled at 0.5 Ω or even lower. Figure 9 is used to convert the result of the switch array into a single level output, such as output high level for motion and output low level for no motion. Therefore, the power consumption of the entire motion monitor can be easily controlled within the uA, or even smaller.

Claims

A microelectromechanical system switch comprising a substrate, an anchor (ί θ) and a cantilever beam (11), the anchor (10) being fixed on a substrate, and one end of the cantilever beam (11) is connected to the anchor ο) The fixed end is characterized in that - the other end of the cantilever (11) is a free end, and the free end of the cantilever (11) is connected with a mass (12), and at least one side is arranged around the mass (12) There is a contact wall (13) having a gap (IS) between the mass (12) and the contact wall (13); the mass (12) and the free end of the cantilever have a degree of freedom of movement toward the contact wall (13), When the mass (12) and the contact wall (13) are in contact with each other, the microelectromechanical system switch is turned on.

2. The microelectromechanical system switch according to claim 1, wherein: on the opposite sides of the mass, each of the contact walls is disposed, and between the mass and the contact walls on both sides, There are gaps respectively.

3. The microelectromechanical system switch of claim 1 wherein: the width of the cantilever beam is less than the width of the mass.

4. The microelectromechanical system switch according to claim 1, wherein: the width of the cantilever is between 1 m and 3 nm, and the length of the cantilever is between SOOiim and 3000 imi.

5. A microelectromechanical system switch according to claim 1 or 2, characterized in that the gap width between the mass and the contact wall is between ra and 3 TM.

A microelectromechanical system motion sensor, comprising: at least one microelectromechanical system switch according to claim 1.

7. The microelectromechanical system motion sensor according to claim 6, comprising: a plurality of said microelectromechanical system switches, wherein the suspension beams of the microelectromechanical system switches are arranged in an angular manner that is not zero. .

8. The motion sensor of the EM electromechanical system according to claim 6, wherein: three microelectromechanical system switches are provided, and the suspension beams of the switches of the microelectromechanical systems are arranged in a mutually perpendicular manner,

9. A motion sensing method, characterized in that: one or more of the electromechanical system switches according to claim 1 are arranged according to a direction of motion or a direction of force of the sensing, and the switches of the microelectromechanical system are monitored. The change in the conduction state determines whether there is motion.