JP2010216837A - Sensor for detecting dynamic quantity - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor for detecting the dynamic quantity which is of high sensitivity, of which the other axis sensitivity ratio is small and which accurately detects the dynamic quantity. <P>SOLUTION: The sensor for detecting the dynamic quantity includes: a first semiconductor substrate wherein a frame, a displacement part positioned inside the frame and beams supporting the displacement part so that the displacement part can rock in relation to the frame, are formed, a second semiconductor substrate wherein a support having an opening and connected with the frame and a weight connected with the displacement part in the opening are formed and which is laid on the first semiconductor substrate by the medium of an insulating layer; and detecting elements which are provided on the first semiconductor substrate and output signals according to the dynamic quantity, based on the amount of deflection of the beams. Each of the beams is fixed, at one end, to the frame, while being fixed, at the other end, to the displacement part, and is provided in extension along the outer peripheral surface of the displacement part with a prescribed space left between the outer peripheral surface of the displacement part and it. The other end of the beam is thick relatively. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a mechanical quantity detection sensor capable of detecting acceleration in three axial directions of an X axis, a Y axis, and a Z axis that are orthogonal to each other.

  In the automobile industry and the machine industry, there is an increasing demand for small mechanical quantity detection sensors that can accurately detect acceleration. As such a mechanical quantity detection sensor, an acceleration sensor that can simultaneously detect accelerations in three axial directions orthogonal to each other is known (see, for example, Patent Document 1). This acceleration sensor is formed by etching a three-layer SOI substrate obtained by bonding a first semiconductor substrate made of silicon, an insulating layer made of silicon oxide, and a second semiconductor substrate made of silicon.

  The first semiconductor substrate is formed with a frame body by etching, a displacement portion located at the center of the frame body, and a beam portion continuous from the four sides of the frame body to the displacement portion, and the second semiconductor substrate by frame etching. A support part joined to the body and a weight part joined to the displacement part are formed. In addition, a detection element is disposed on the upper surface of each beam portion, and an inertial force acts on the weight portion to cause each beam portion to bend and deform, thereby detecting acceleration in three axes.

JP 2007-322300 A

  In such a mechanical quantity detection sensor having four beams, if the width of the beam is narrowed to increase the sensitivity, the other axis sensitivity ratio (other axis sensitivity / principal axis sensitivity) also increases, and the mechanical quantity is accurately determined. There is a problem that it becomes impossible to detect.

  The present invention has been made in view of such points, and an object thereof is to provide a mechanical quantity detection sensor that is highly sensitive and has a small other-axis sensitivity ratio and can accurately detect a mechanical quantity. .

  The mechanical quantity detection sensor of the present invention includes a first frame body, a displacement portion positioned inside the frame body, and a beam portion that supports the displacement portion so as to be swingable with respect to the frame body. A semiconductor substrate, a support portion having an opening and connected to the frame, and a weight portion connected to the displacement portion in the opening are formed, and an insulating layer is formed on the first semiconductor substrate. A second semiconductor substrate stacked via the first semiconductor substrate, and a detection element that is provided on the first semiconductor substrate and outputs a signal corresponding to a mechanical amount based on a deflection amount of the beam portion, One end of the beam is fixed to the frame, the other end is fixed to the displacement portion, and a predetermined distance is provided between the beam and the outer peripheral surface of the displacement portion, along the outer peripheral surface of the displacement portion. The other end of the beam is relatively thick.

  The mechanical quantity detection sensor of the present invention includes a first frame body, a displacement portion positioned inside the frame body, and a beam portion that supports the displacement portion so as to be swingable with respect to the frame body. A semiconductor substrate, a support portion having an opening and connected to the frame, and a weight portion connected to the displacement portion in the opening are formed, and an insulating layer is formed on the first semiconductor substrate. A second semiconductor substrate stacked via the first semiconductor substrate, and a detection element that is provided on the first semiconductor substrate and outputs a signal corresponding to a mechanical amount based on a deflection amount of the beam portion, The detection element includes a lower electrode formed on the beam and the displacement portion, a piezoelectric thin film formed on the lower electrode, and an upper electrode partially formed on the piezoelectric thin film. The beam has one end fixed to the frame and the other end fixed to the displacement portion. Serial and extends along the outer peripheral surface of the displacement portion taking a predetermined gap between the outer peripheral surface of the displacement portion, the other end of the beam is equal to or relatively thick.

  According to these configurations, the four beams that support the swinging portion of the displacement portion are fixed to the frame body at one end, fixed to the displacement portion at the other end, and between the outer peripheral surface of the displacement portion. Is extended along the outer peripheral surface of the displacement portion at a predetermined interval, and the other end of the beam is relatively thick, so that the sensitivity is high and the other-axis sensitivity ratio is small. A mechanical quantity can be detected.

  According to the present invention, a so-called beam neck portion is relatively thick, so that it is possible to provide a mechanical quantity detection sensor that is highly sensitive, has a small other-axis sensitivity ratio, and can accurately detect a mechanical quantity. it can.

It is a perspective view which shows the mechanical quantity detection sensor which concerns on embodiment of this invention. It is a disassembled perspective view of the mechanical quantity detection sensor shown in FIG. (A) is a top view which shows the mechanical quantity detection sensor which concerns on embodiment of this invention, (b) is a figure for demonstrating the detection element shown to (a). It is a figure which shows the relationship between the width | variety of a beam, an other-axis sensitivity ratio, and a sensitivity. It is a figure which shows the relationship between a beam neck width, an other-axis sensitivity ratio, and a sensitivity. (A)-(d) is a figure for demonstrating the manufacturing method of the mechanical quantity detection sensor which concerns on embodiment of this invention. (A)-(c) is a figure for demonstrating the manufacturing method of the mechanical quantity detection sensor which concerns on embodiment of this invention. It is a detection operation explanatory view of a mechanical quantity detection sensor, (a) is a detection operation explanatory view when the weight portion rotates around the X axis, (b) when the weight portion linearly moves in the Z axis direction FIG. It is a figure which shows an example of the circuit which shows the mechanical quantity sensor which concerns on embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a perspective view of a mechanical quantity detection sensor according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of the mechanical quantity detection sensor according to the embodiment of the present invention.

  As shown in FIGS. 1 and 2, the mechanical quantity detection sensor 1 is configured by joining a first semiconductor substrate 2 and a second semiconductor substrate 3 via an insulating layer 4. The mechanical quantity detection sensor 1 is, for example, an SOI (Silicon On Insulator) substrate having a three-layer structure in which a first semiconductor substrate 2 is a silicon layer, an insulating layer 4 is a silicon oxide layer, and a second semiconductor substrate 3 is a silicon layer. Can be manufactured.

  The first semiconductor substrate 2 includes a rectangular frame 11 having a relatively thin plate-like silicon layer as compared with the second semiconductor substrate 3 and having a storage space. The displacement part 12 arrange | positioned inside and the four beam parts 13 which connect the four sides of the frame 11 and the displacement part 12 are formed. The frame body 11, the displacement portion 12, and the beam portion 13 are formed by providing four openings that are L-shaped in top view around the displacement portion 12 by etching the first semiconductor substrate 2.

  The frame 11 is formed so as to surround the displacement portion 12 by four L-shaped openings. The displacement part 12 is formed in a substantially square shape, and is disposed in the center of the frame 11. Each of the four beam portions 13 includes a long portion 15 extending from one side of the frame 11 toward the opposite side, and a short portion 16 connected to the four corners of the displacement portion 12 connected to the long portion 15. Is done. Thus, since the four beam parts 13 have the elongate part 15, they become the structure which is easy to bend.

  A detection element 17 is provided on the upper surface of the long portion 15 of each beam portion 13, and the deflection amount of each beam portion 13 is detected by the detection element 17. The detection element 17 is a so-called piezoelectric element, and is formed by depositing the lower electrode 25, the piezoelectric thin film 26, and the upper electrode 27 in this order on the upper surface of a base film (not shown) by vapor deposition or the like. The detection element 17 is deformed by the bending generated in the beam portion 13, and the pressure generated by the deformation is converted into a voltage and output.

  The second semiconductor substrate 3 is composed of a relatively thick silicon layer compared to the first semiconductor substrate 2, and has a support portion 21 having a rectangular opening 23 and an inner side of the opening 23. The weight part 22 arrange | positioned in this is formed. The support portion 21 and the weight portion 22 are formed by providing a rectangular frame-shaped opening around the weight portion 22 by etching the first semiconductor substrate 2.

  The support portion 21 has a shape corresponding to the frame body 11 in a top view, and is joined to the lower surface of the frame body 11 via the insulating layer 4. The weight portion 22 is formed in a substantially rectangular parallelepiped shape, and is joined to the lower surface of the displacement portion 12 via the insulating layer 4. Therefore, in this way, the weight portion 22 is supported by the four beam portions 13 via the displacement portion 12 in a swingable manner in the storage space of the frame 11 and the inside of the opening portion 23 of the support portion 21. Therefore, when an inertial force acts on the position of the center of gravity of the weight portion 22, rotation about the X axis, rotation about the Y axis, and linear movement in the Z axis direction are possible.

FIG. 3A is a plan view showing a mechanical quantity detection sensor according to the embodiment of the present invention. As shown in FIG. 3A, one end of the beam 13 is fixed to the frame body, and the other end is fixed to the displacement portion 12. In FIG. 3A, the frame is not shown. Each of the beams 13 extends along the outer peripheral surface of the displacement portion 12 with a predetermined interval between the beam 13 and the outer peripheral surface of the displacement portion 12. Moreover, the other end (beam neck 13e) of the beam 13 is relatively thick. Here, the fact that the beam neck 13e is thick means that the width W _n of the beam neck 13e is relatively thick with respect to the width W _b of the beam 13 in FIG.

  As shown in FIG. 3 (a), in the case of a bent four-beam structure, it is conceivable to reduce the width of the beam in order to increase the sensitivity. If the beam width is narrowed with the beam width uniform throughout, the sensitivity increases as shown in FIG. 4, but the sensitivity of the other axis includes the other axis sensitivity in the sensitivity of the detection axis (main axis). The other axis sensitivity / main axis sensitivity) also increases. However, if the thickness of the beam neck 13e is increased as shown in FIG. 3A, the influence of the sensitivity of other axes can be reduced without decreasing the sensitivity as shown in FIG. In this way, by making the beam neck relatively thick, it is possible to realize a mechanical quantity detection sensor that is highly sensitive and has a small other-axis sensitivity ratio and can accurately detect the mechanical quantity.

  As shown in FIG. 3B, the detection element 17 includes a lower electrode 25 formed on the beam 13 and the displacement portion 12, a piezoelectric thin film 26 formed on the lower electrode 25, and a piezoelectric thin film 26. The upper electrode 27 is partially formed. The upper electrode 27 is formed in a stress concentration portion where stress is concentrated when a mechanical quantity is applied in the laminate of the lower electrode 25 / piezoelectric thin film 26. According to such a configuration, the upper electrode 27 is formed in the stress concentration portion without misalignment as compared with the case where the three-layered structure of the lower electrode 25 / piezoelectric thin film 26 / upper electrode 27 is formed in the stress concentration portion. It becomes possible to do.

  Next, an example of the machining process of the mechanical quantity detection sensor will be described with reference to FIGS. 6 (a) to 6 (d) and FIGS. 7 (a) to 7 (c) are views for explaining a method of manufacturing a mechanical quantity detection sensor according to the embodiment of the present invention.

  As shown in FIG. 6A, an SOI substrate in which the first semiconductor substrate 2, the insulating layer 4, and the second semiconductor substrate 3 are stacked is prepared, and the support substrate 30 is disposed on the upper surface of the first semiconductor substrate 2. Is done. Next, as shown in FIG. 6B, the lower surface of the second semiconductor substrate 3 is polished and thinned, and the second semiconductor substrate 3 is processed and supported by photolithography and etching (deep RIE). A portion 21 and a weight portion 22 are formed.

  Next, as shown in FIG. 6C, the third substrate 31 is processed by photolithography and etching to form a recess 31 a and bonded to the lower surface of the second semiconductor substrate 3. Next, as shown in FIG. 6D, the support substrate 30 is peeled from the upper surface of the first semiconductor substrate 2, and the upper surface of the first semiconductor substrate 2 is polished and thinned to a desired thickness.

  Next, as shown in FIG. 7A, an insulating material is deposited on the upper surface of the first semiconductor substrate 2 by sputtering. Next, as shown in FIG. 7B, the detection element 17 is formed on the region including the beam portion 13 region of the insulating layer 18. The detection element 17 includes a lower electrode 25 formed on the beam 13 and the displacement portion 12, a piezoelectric thin film 26 formed on the lower electrode 25, and an upper electrode 27 partially formed on the piezoelectric thin film 26. It is configured. First, a metal material for a lower electrode, a piezoelectric material, and a metal material for an upper electrode are deposited in this order on the beam 13 and the displacement portion 12 by sputtering, and the metal material and the piezoelectric material are patterned by photolithography and etching. Then, the lower electrode 25, the piezoelectric thin film 26, and the metal layer for the upper electrode are formed. After that, the upper electrode 27 is formed by patterning the metal layer for the upper electrode again by photolithography and etching.

  Next, as shown in FIG. 7C, the beam portion 13 and the displacement portion 12 are provided by partially removing the first semiconductor substrate 2 together with the insulating layers 4 and 18. In this way, the mechanical quantity detection sensor shown in FIG. 3 can be obtained.

  Next, the operation of the mechanical quantity detection sensor will be briefly described with reference to FIG. 8A and 8B are explanatory diagrams of detection operation of the mechanical quantity detection sensor. FIG. 8A is an explanatory diagram of detection operation when the weight portion rotates around the X axis. FIG. 8B is an explanatory diagram of the weight portion in the Z-axis direction. It is detection operation explanatory drawing at the time of linear motion.

  As shown in FIG. 8A, when acceleration acts on the mechanical quantity detection sensor and an inertial force acts on the weight part 22 in the Y-axis direction, the weight part 22 rotates about the X-axis. At this time, the displacement portion 12 side of the beam portions 13a and 13b moves downward in the Z-axis direction, and a force acts upward in the Z direction on the frame body 11 side of the beam portions 13a and 13b. Further, the displacement portion 12 side of the beam portions 13c and 13d moves upward in the Z-axis direction, and a force acts downward in the Z-axis direction on the frame body 11 side of the beam portions 13c and 13d. The frame 11 side of the beam portions 13a and 13b is bent so as to swell upward in the Z-axis direction, and the frame 11 side of the beam portions 13c and 13d is bent so as to be recessed downward in the Z-axis direction.

  The detection elements 17a and 17b are deformed so as to swell upward in the Z-axis direction in accordance with the bending of the beam portions 13a and 13b on the frame body 11 side, and output a voltage corresponding to the deformation. The detection elements 17c and 17d are deformed so as to be recessed downward in the Z-axis direction in accordance with the bending of the beam portions 13c and 13d on the frame body 11 side, and output a voltage corresponding to the deformation. The voltages output from the detection elements 17a, 17b, 17c, and 17d are calculated by an arithmetic circuit (not shown) to calculate acceleration.

  When the weight portion 22 rotates about the Y axis, conversely, a force acts downward in the Z axis direction on the frame body 11 side of the beam portions 13a and 13b, and the frame body 11 of the beam portions 13c and 13d. A force acts upward in the Z-axis direction. Accordingly, the detection elements 17a and 17b are deformed so as to be recessed downward in the Z-axis direction in accordance with the bending of the beam portions 13a and 13b on the frame body 11 side, and the detection elements 17c and 17d are respectively formed on the beam portions 13c and 13d. It deforms so as to swell upward in the Z-axis direction in accordance with the bending on the frame body 11 side.

  As shown in FIG. 8B, when acceleration acts on the mechanical quantity detection sensor and an inertial force acts on the weight part 22 in the Z-axis direction downward, the weight part 22 moves linearly downward in the Z-direction. . At this time, the displacement portion 12 side of the beam portions 13a, 13b, 13c, and 13d moves downward in the Z-axis direction, and a force acts upward in the Z-axis direction on the frame body 11 side of the beam portions 13a, 13b, 13c, and 13d. . The frame 11 side of the beam portions 13a, 13b, 13c, and 13d is bent so as to swell upward in the Z-axis direction, and the detection elements 17a, 17b, 17c, and 17d are also deformed so as to swell upward in the Z-axis direction. And the voltage output from each detection element 17a, 17b, 17c, 17d is calculated in the arithmetic circuit which is not shown in figure, and an acceleration is calculated.

  The mechanical quantity detection sensor of the present invention includes four beam portions 13 each having a detection element 17, and outputs the mechanical quantities in the respective sensitivity axis directions using the detection elements 17 of the four beam portions 13. . FIG. 9 is a diagram showing an example of a circuit showing the mechanical quantity sensor according to the embodiment of the present invention.

  In the circuit diagram shown in FIG. 9, the detection result (sensor output) of the mechanical quantity detection sensor 1 is output to the arithmetic circuit 5. The arithmetic circuit 5 mainly includes a differential circuit 53, an adder circuit 54, switches 51 and 52 for switching inputs from the mechanical quantity detection sensor 1, and a switch 55 for switching calculation results.

  In the arithmetic circuit 5, the detection element input to the differential circuit 53 includes a state in which the detection element A and the detection element B are input, and a state in which the detection element C and the detection element D are input. The switch 51, 52 is used for switching. On the other hand, the detection element A, the detection element B, the detection element C, and the detection element D are input to the addition circuit 54. Switching between the output of the differential circuit 53 and the output of the adder circuit 54 is performed by a switch 55. The switching timing of the switches 51, 52, and 55 is synchronized with the output timing of the calculation result (X-axis output timing, Y-axis output timing, Z-axis output timing).

  Note that the circuit configuration shown in FIG. 9 is an example, and is particularly limited as long as it is a configuration that obtains one output of the dynamic quantity detection result (calculation result) using the detection results of the detection elements provided in the four beam portions 13 respectively. There is no.

  For example, in the arithmetic circuit 5, when detecting the mechanical quantity in the X-axis direction, the difference between the sensor output of the detection element A of the mechanical quantity detection sensor 1 and the sensor output of the detection element B is obtained as a result of the mechanical quantity detection. Output as. Therefore, when detecting the mechanical quantity in the X-axis direction, the switches 51 and 52 are switched so that the detection element A and the detection element B are input to the differential circuit 53, and the output from the differential circuit 53 is detected as the dynamic quantity. The switch 55 is switched so that a result (calculation result) is obtained. In this manner, the mechanical quantity detection result in the X-axis direction is obtained from the difference (AB) between the output of the detection element A and the output of the detection element B, and this is the output.

  Further, in the arithmetic circuit 5, when detecting the mechanical quantity in the Y-axis direction, the difference between the sensor output of the detection element C of the mechanical quantity detection sensor 1 and the sensor output of the detection element D is obtained as a result of the mechanical quantity detection. Output as. Therefore, when detecting the mechanical quantity in the Y-axis direction, the switches 51 and 52 are switched so that the detection element C and the detection element D are input to the differential circuit 53, and the output from the differential circuit 53 is detected as the dynamic quantity. The switch 55 is switched so that a result (calculation result) is obtained. In this manner, a mechanical quantity detection result in the Y-axis direction is obtained from the difference (C−D) between the output of the detection element C and the output of the detection element D, and this is the output.

  Further, in the arithmetic circuit 5, when detecting the mechanical quantity in the Z-axis direction, the sensor output of the detection element A of the mechanical quantity detection sensor 1, the sensor output of the detection element B, the sensor output of the detection element C, and the detection element The sum of the sensor outputs of D is output as the mechanical quantity detection result. Therefore, when the mechanical quantity in the Z-axis direction is detected, the detection element A, the detection element B, the detection element C, and the detection element D are input to the addition circuit 54, and the output from the addition circuit 54 is the mechanical quantity detection result ( The switch 55 is switched so that the calculation result is obtained. In this way, the mechanical quantity detection result in the Z-axis direction is obtained from the sum (A + B + C + D) of the output of the detection element A, the output of the detection element B, the output of the detection element C, and the output of the detection element D. Become.

  As described above, since the mechanical quantities in the respective axial directions can be detected from the detection elements 17 provided in each of the four beam portions 13, it is possible to detect the dynamic quantities in the multi-axial directions with a simple circuit configuration. Become.

  In the mechanical quantity detection sensor, the sensor sensitivity can be arbitrarily adjusted by appropriately changing the masses of the weight portion 22 and the displacement portion 12, the spring constant of each beam portion 13, and the like.

  As described above, according to the mechanical quantity detection sensor of the present invention, the four beams 13 that support the displacement portion 12 in a swingable manner are fixed at one end to the frame 11 and fixed at the other end to the displacement portion 12. And is extended along the outer peripheral surface of the displacement portion 12 with a predetermined interval between the outer peripheral surface of the displacement portion 12 and the other end of the beam 13 is relatively thick. It is highly sensitive and the other-axis sensitivity ratio is small, and the mechanical quantity can be accurately detected. Further, since the upper electrode 27 of the detection element 17 is formed in a stress concentration portion where stress is concentrated when a mechanical quantity is applied in the laminated body of the lower electrode 25 / piezoelectric thin film 26, the lower portion is placed in the stress concentration portion. Compared to the case of forming a three-layered structure of electrode 25 / piezoelectric thin film 26 / upper electrode 27, it is possible to form the upper electrode 27 in the stress concentration portion without misalignment.

  In the above-described embodiment, the piezoelectric element is exemplified as the detection element. However, the present invention is not limited to this configuration. Any structure that outputs a signal corresponding to the mechanical quantity based on the deflection of the beam portion may be used. For example, a piezoelectric element may be used instead of the piezoelectric element.

  The embodiment disclosed this time is illustrative in all respects and is not limited to this embodiment. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims for patent.

  INDUSTRIAL APPLICABILITY The present invention is useful for a mechanical quantity detection sensor that detects acceleration in three axial directions of the X axis, the Y axis, and the Z axis orthogonal to each other.

DESCRIPTION OF SYMBOLS 1 Mechanical quantity detection sensor 2 1st semiconductor substrate (1st board | substrate)
3 Second semiconductor substrate (second substrate)
4, 18 Insulating layer 5 Arithmetic circuit 11 Frame 12 Displacement part 13 Beam part 17 Detection element 21 Support part 22 Weight part 23 Opening part 25 Lower electrode 26 Piezoelectric thin film 27 Upper electrode 31 Third substrate 51, 52, 55 Switch 53 Differential circuit 54 Adder circuit

Claims (2)

A first semiconductor substrate formed with a frame, a displacement portion located inside the frame, and a beam portion that swingably supports the displacement portion with respect to the frame;
A support portion having an opening, connected to the frame, and a weight portion connected to the displacement portion in the opening is formed, and stacked on the first semiconductor substrate via an insulating layer A second semiconductor substrate,
A detection element that is provided on the first semiconductor substrate and outputs a signal corresponding to a mechanical quantity based on a deflection amount of the beam portion;
One end of the beam is fixed to the frame, the other end is fixed to the displacement portion, and a predetermined distance is provided between the beam and the outer peripheral surface of the displacement portion, along the outer peripheral surface of the displacement portion. A mechanical quantity detection sensor that is extended and has the other end of the beam relatively thick. A first semiconductor substrate formed with a frame, a displacement portion located inside the frame, and a beam portion that swingably supports the displacement portion with respect to the frame;
A support portion having an opening, connected to the frame, and a weight portion connected to the displacement portion in the opening is formed, and stacked on the first semiconductor substrate via an insulating layer A second semiconductor substrate,
A detection element that is provided on the first semiconductor substrate and outputs a signal corresponding to a mechanical amount based on a deflection amount of the beam portion;
The detection element includes a lower electrode formed on the beam and the displacement portion, a piezoelectric thin film formed on the lower electrode, and an upper electrode partially formed on the piezoelectric thin film. The beam has one end fixed to the frame, the other end fixed to the displacement portion, and a predetermined distance from the outer peripheral surface of the displacement portion along the outer peripheral surface of the displacement portion. A mechanical quantity detection sensor, wherein the other end of the beam is relatively thick.

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