TWI392871B - Biaxial acceleration sensing element - Google Patents

Description

Biaxial acceleration sensing element

The invention relates to a biaxial acceleration sensing component, in particular to a capacitive biaxial acceleration sensing component.

The concept of Micro-electromechanical system (MEMS) technology is to manufacture and integrate various types of sensors, actuators, optical components, etc. by means of semiconductor processes and other micromachining methods, using MEMS technology. Component miniaturization has the advantages of low cost, low power loss, high response speed and high accuracy.

The principle of a general micro-sensor is to convert a physical quantity to be measured into an electrical signal by a sensing component, and indirectly to know the physical quantity to be sensed by analyzing the electronic signal. Therefore, the acceleration sensor senses the physical state change caused by the acceleration component through the sensing component, and generates corresponding electrical signals such as voltage, resistance, inductance, etc., which have been widely used in automobile safety perception, mobile phones, computers, and video games. Machine and other fields.

In 1972, Frobenius used a cantilever beam structure of different lengths and sizes as a sensing element. When the sensing element is disturbed by external force, the cantilever beam structure will be displaced by inertia, causing the corresponding conductor to generate a signal to detect acceleration; Roylance uses a combination of a cantilever beam and a mass to create a piezoresistive micro-accelerometer with the piezoresistive properties of the crucible; in 1983, Rudolf proposed a capacitive micro-acceleration sensor with a cantilever on both sides of the mass. The beam structure serves as a support. When the mass is swung by an external force, the cantilever beam is twisted by the interlocking, thereby generating a capacitance change to obtain a corresponding electrical signal.

Capacitive micro-acceleration sensors detect changes in capacitance to estimate the magnitude of the acceleration. Capacitive accelerometers have high sensitivity, low temperature effect, low power consumption, and structure compared to conventional piezoelectric (piezoelectric), piezoresistive, and tunneling current-type accelerometers. Simple and high-output characteristics, so its related research and application fields are particularly attracting attention. The "accelerometer" of the Republic of China Patent No. I284203 discloses a capacitive accelerometer comprising a fixed unit and a movable unit, the fixed unit and the movable unit each comprising a plurality of sensing electrodes, the sensing electrodes being indexed to each other The forks are arranged so that when the movable unit is displaced by an external force, the spacing between the sensing electrodes changes to cause a change in the capacitance, thereby detecting a change in acceleration.

According to the capacitance formula of the parallel electrode plate: C=εA/d (where ε is the dielectric constant, A is the overlap area of the two electrode plates, d is the distance between the two capacitor plates), and the capacitance change caused by the change of the detection pitch (symbol d) The capacitance change value and the variation of the pitch have a nonlinear relationship, so it is difficult to estimate and calculate the acceleration, and it is easy to generate an error. Therefore, the present invention proposes a biaxial acceleration sensor that obtains a linear relationship with a better acceleration relationship by detecting a change in capacitance caused by an area.

In summary, the object of the present invention is to provide a biaxial acceleration sensing element with high sensitivity and good linearity.

Another object of the present invention is to provide a biaxial acceleration sensing element that can detect a capacitance difference caused by a change in electrode area, thereby sensing the magnitude and direction of the acceleration.

In order to achieve the foregoing objective, the present invention provides a dual-axis acceleration sensing component including a first sensing component, a second sensing component, and a fixing unit. The first sensing member is movable relative to the second sensing member, and the second sensing member is movable relative to the fixed unit, and the axial directions of the relative movements are different from each other, thereby sensing the acceleration of the two mutually different axial directions. Further, a corresponding sensing electrode is disposed between the first sensing member and the second sensing member and between the second sensing member and the fixing unit, so when the first and second sensing members are When the fixed unit is in relative motion, the sensing electrodes may be changed by overlapping areas, so that the output capacitance generates a difference, and thereby sensing the change of the acceleration.

According to an embodiment of the invention, the sensing electrodes have a height difference from each other and comprise a stacking area, and further form a differential capacitive sensing electrode.

The biaxial acceleration sensing component proposed by the invention can be fabricated by using a micro-electromechanical process, so that the volume is small and the cost is low; further, the sensed acceleration has a good linear relationship, high sensitivity, and non-sensing axial sensing error. small. The detailed technical content and preferred embodiments of the present invention are described in conjunction with the drawings.

The detailed description and technical content of the present invention will now be described as follows:

Please refer to FIG. 1 , which is a perspective view of an appearance of an embodiment of the present invention. The biaxial acceleration sensing component 1 of the present invention comprises a first sensing component 10, a second sensing component 20 and a fixing unit 30, and the three form a sensing platform. The second sensing member 10 is transported (rotated) relative to the second sensing member 20 and the second sensing member 20 is moved (rotated) relative to the fixed unit 30 to sense the magnitude and direction of the acceleration of the two-phase different axial directions. .

FIG. 2-1 and FIG. 2-2 respectively show an external perspective view and a top view of an embodiment of the first sensing member 10 of the present invention. The first sensing member 10 includes a mass body 11 including a first shaft 12 and a plurality of first sensing electrodes 13 that are parallel to each other. The first shaft 12 is connected to opposite sides of the mass body 11 so that the mass body 11 can be pivoted (twisted/turned) with the first shaft 12 when inertia is applied by an external force; A sensing electrode 13 is disposed in parallel with each other to form a comb structure. In this embodiment, the first sensing electrodes 13 are disposed on opposite sides of the mass body 11 and the directions thereof are different from the axial direction of the first axis 12, for example, the figures are perpendicular to each other.

FIG. 3-1 and FIG. 3-2 respectively show an external perspective view and a top view of an embodiment of the second sensing component 20 of the present invention. The second sensing component 20 includes a ring portion 21, and the ring portion The inner side of the inner portion of the inner portion of the inner portion of the inner portion of the inner portion of the inner portion of the inner portion of the second portion of the second sensing electrode 13 is disposed in parallel with each other to form a comb-like structure; The outer side of the ring portion 21 includes a plurality of third sensing electrodes 24, and the third sensing electrodes 24 are disposed in parallel with each other to form a comb structure; the ring portion 21 includes a second shaft 25, so that the ring portion 21 The second shaft 25 can be pivoted (twisted/rotated). In this embodiment, the third sensing electrodes 24 are disposed on opposite sides of the ring portion 21, and the direction thereof is The two axes 25 are axially different, for example, the figures are perpendicular to each other, and the first axis 12 is also perpendicular to the second axis 25 at this time.

The first sensing member 10 can be received in the accommodating space 22 and connected to the ring portion 21 by the first shaft 12, as shown in FIG. At this time, the first sensing electrodes 13 and the second sensing electrodes 23 overlap each other in parallel and staggered, and are arranged in the form of an interdigitated fork to form a corresponding capacitive sensing structure.

Please refer to FIG. 4-1 and FIG. 4-2, which are perspective views and top views of an embodiment of the fixing unit 30 of the present invention. The fixing unit 30 defines a second accommodating space 31 therein, and the inner side thereof includes a plurality of fourth sensing electrodes 32 disposed corresponding to the third sensing electrodes 24; the fourth sensing electrodes 32 are parallel to each other. Set to form a comb structure. As shown in FIG. 1 , the second sensing component 20 can be received in the second accommodating space 31 and connected to the fixing unit 30 by the second shaft 25 to cause the third sensing electrodes 24 . The fourth sensing electrodes 32 are overlapped with each other in parallel and staggered, and are arranged in the form of an interdigitated fork to form a corresponding capacitive sensing structure.

Referring to FIG. 1 again, in the above embodiment, the first sensing electrode 13 is disposed perpendicular to the first axis 12 (in the X-axis direction in the figure), and the third sensing electrode 24 is The second axis 25 is disposed perpendicularly (in the Y-axis direction as shown in the figure), but is not limited thereto. Further, the first sensing electrode 13, the second sensing electrode 23, the third sensing electrode 24, and/or the fourth sensing electrode 32 can be a high aspect ratio comb sensing electrode (HARM (high) -aspect-ratio-micromachined) vertical-combs), which may be formed by etching a substrate, electroforming, electrical discharge machining, trench backfilling, etc.; the first shaft 12 and the second shaft 25 may be a spring structure ( Gimbal spring). Please refer to FIG. 5-1 and FIG. 5-2 again, which are respectively shown from the AA' line segment and the BB' line segment of FIG. 1 : in another embodiment, the first sensing electrode 13 and the second sensing electrodes 23 overlap each other and are arranged in the Z-axis direction; the third sensing electrodes 24 and the fourth sensing electrodes 32 also overlap each other and are arranged in the Z-axis direction.

The first sensing member 10 is suspended by the support of the first shaft 12 and is stationary with respect to the second sensing member 20; in the same manner, the second sensing member 20 borrows the first The support of the two shafts 25 is suspended and is stationary relative to the fixed unit 30. When the biaxial acceleration sensing element 1 of the present invention receives an acceleration in a parallel XY plane, the mass body 11 can output an inertial force and generate torque through a pendulum type structure to transmit power to the first shaft 12 And the second shaft 25, causing the first shaft 12 and/or the second shaft 25 to be decoupled, so that the mass body 11 respectively outputs corresponding torque to the first shaft 12 and the second shaft 25 to drive the The sensing platform produces a wobble.

According to the aforementioned capacitance formula C = εA / d, when the area of the two parallel electrodes changes, the capacitance also changes. Therefore, when the first sensing component 10 is oscillated (twisted) with the first axis 12 as an axis, the first sensing electrodes 13 on the two sides of the first axis 12 are opposite to the second sensing electrodes 23 . The area change will be generated, and the capacitance values of +ΔC and -ΔC will be respectively generated at both ends, and the difference of the capacitances on both sides will be output to achieve the quantitative side of the differential capacitance to sense parallel to the second axis. Acceleration in the direction of the 25th direction (the X-axis direction). Similarly, when the second sensing member 20 is pivoted about the second axis 25, the acceleration parallel to the direction of the first axis 12 (the Y-axis direction) can be sensed. . It should be noted that different acceleration magnitudes may cause the first sensing component 10 or the second sensing component 20 to have a corresponding degree of oscillation, and different degrees of oscillation correspond to different capacitance differences detected last, which may be sensed. Measure the magnitude of the acceleration.

"Figure 6-1" and "Figure 6-2" respectively show the biaxial acceleration sensing results of the above embodiment, which can illustrate the advantages of the measurement of the present invention, which is to use the capacitance difference generated by the acceleration as a commercial capacitor. A voltage conversion circuit (commercial capacitive readout IC) is converted into a voltage output. From the results, the detected biaxial acceleration results have a linear relationship, and their sensitivity to the X-axis and the Y-axis are 2.44 mV/G and 51.99 mV/G, respectively. The cross-talk errors for the non-sensing axes are minimal.

It should be noted that the first sensing member 10, the second sensing member 20, and the fixing unit 30 are separately defined and described herein for convenience of description and understanding. In fact, the structures can be assembled separately from each other or directly fabricated by techniques known in the art, such as etching, lithography, backfilling, by microelectromechanical or semiconductor processes. For example, the biaxial acceleration sensing element 1 of the present invention can be fabricated by MOSBE's MEMS platform process, and the related platform technology can be found in "The Molded Surface-micromachining and Bulk Etching Release (MOSBE) Fabrication" published in 2005. Platform on (111) Si for MOEMS" (Journal of Micromechanics and Microengineering, vol. 15, pp. 260-265), which is not described herein. Thereby, the sensing electrodes and the first shaft 12 and the second shaft 25 can be achieved by a trench-refill technique, and the material can be polycrystalline germanium; the mass 11 can be etched by the underlying substrate. Formed by (backside etching), for example, the material is 矽. The acceleration sensing component manufactured by the micro-electromechanical process has the advantages of small size, low cost and high sensitivity.

The above is only the preferred embodiment of the present invention, and is not intended to limit the scope of the patent protection of the present invention. Therefore, the equivalent changes and modifications of the present invention and the contents of the drawings are equally included in The scope of protection of the present invention is combined with Chen Ming.

1‧‧‧Biaxial acceleration sensing element

10‧‧‧First sensing parts

11‧‧‧Quality

12‧‧‧ first axis

13‧‧‧First sensing electrode

20‧‧‧Second sensing parts

21‧‧‧ Ring Department

22‧‧‧ accommodating space

23‧‧‧Second sensing electrode

24‧‧‧ Third sensing electrode

25‧‧‧second axis

30‧‧‧Fixed unit

31‧‧‧Second accommodation space

32‧‧‧fourth sensing electrode

Embodiments of the invention are described in conjunction with the drawings:

FIG. 1 is a perspective view showing the appearance of an embodiment of the present invention;

Figure 2-1 is a perspective view showing the appearance of an embodiment of the first sensing member of the present invention;

2-2 is a top view of an embodiment of a first sensing member of the present invention;

Figure 3-1 is a perspective view showing the appearance of an embodiment of the second sensing member of the present invention;

Figure 3-2 is a top view of an embodiment of a second sensing member of the present invention;

Figure 4-1 is a perspective view showing the appearance of an embodiment of the fixing unit of the present invention;

Figure 4-2 is a top view of an embodiment of the fixing unit of the present invention;

FIG. 5-1 shows an embodiment in which the first sensing electrode and the second sensing electrode overlap each other;

FIG. 5-2 shows an embodiment in which the third sensing electrode and the fourth sensing electrode overlap each other;

"Fig. 6-1" shows the acceleration sensing result of the first embodiment of the above embodiment;

Fig. 6-2 shows the acceleration sensing result of the other axis of the above embodiment.

1‧‧‧Biaxial acceleration sensing element

10‧‧‧First sensing parts

11‧‧‧Quality

12‧‧‧ first axis

13‧‧‧First sensing electrode

20‧‧‧Second sensing parts

21‧‧‧ Ring Department

22‧‧‧ accommodating space

23‧‧‧Second sensing electrode

24‧‧‧ Third sensing electrode

25‧‧‧second axis

30‧‧‧Fixed unit

31‧‧‧Second accommodation space

32‧‧‧fourth sensing electrode

Claims (13)

A biaxial acceleration sensing element comprising:
a first sensing member includes a mass body including a first axis and a plurality of first sensing electrodes that are parallel to each other;
a second sensing component includes a ring portion, the inner side of the ring portion includes a plurality of second sensing electrodes that are parallel to each other, and defines an accommodating space; the outer side of the ring portion includes a plurality of third sensing electrodes that are parallel to each other and a second axis; and a fixing unit comprising a plurality of fourth sensing electrodes;
The first sensing component is connected to the ring portion by the first axis, so that the first sensing electrodes and the second sensing electrodes are mutually staggered and arranged in a staggered manner; the second sensing component is borrowed from the second sensing component The shaft is connected to the fixing unit, so that the third sensing electrodes and the fourth sensing electrodes are arranged in a staggered manner with each other. The biaxial acceleration sensing element of claim 1, wherein the first sensing electrodes are located on opposite sides of the mass body. The biaxial acceleration sensing element of claim 1, wherein the third sensing electrodes are located on opposite sides of the ring portion. The biaxial acceleration sensing element of claim 1, wherein the first sensing electrodes are parallel to the second sensing electrodes; and the third sensing electrodes are parallel to the fourth sensing electrodes. The biaxial acceleration sensing element of claim 4, wherein the first sensing electrodes are perpendicular to the first axis, the third sensing electrodes are perpendicular to the second axis, and the first axis is The second axis is perpendicular to each other. The biaxial acceleration sensing element of claim 1, wherein the first sensing electrode and the second sensing electrode overlap each other and are set at a height. The biaxial acceleration sensing element of claim 1, wherein the third sensing electrode and the fourth sensing electrode overlap each other and are set at a height. The biaxial acceleration sensing element of claim 1, wherein the first axis is a spring structure. The biaxial acceleration sensing element of claim 1, wherein the second axis is a spring structure. The biaxial acceleration sensing element according to claim 1 is a capacitive acceleration sensing element. The biaxial acceleration sensing element of claim 1, wherein the first sensing electrode, the second sensing electrode, the third sensing electrode, and the fourth sensing electrode are made of polysilicon. The biaxial acceleration sensing element of claim 1, wherein the first axis and the second axis are made of polysilicon. The biaxial acceleration sensing element according to claim 1, wherein the mass is made of 矽.