JP2010216840A - Method of manufacturing dynamic quantity detection sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a dynamic quantity detection sensor capable of exhibiting high sensitivity. <P>SOLUTION: The method of manufacturing the dynamic quantity detection sensor includes: a step of forming a frame, a weight positioned inside the frame, and a beam for swingably supporting the weight to the frame by working a base layer of an SOI (silicon on insulator) substrate constituted of an active layer, the base layer, and an insulation layer sandwiched between the active layer and the base layer; a step of reducing the thickness of the beam; and a step of forming a detecting element for output of signals according to the dynamic quantity based on the amount of deflection of the beam on the active layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a mechanical quantity detection sensor capable of detecting accelerations 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 has a three-layer structure SOI composed of a first semiconductor substrate (active layer) made of silicon, an insulating layer (sacrificial layer) made of silicon oxide, and a second semiconductor substrate (base layer) made of silicon. It is formed by etching the substrate.

  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, the beam portion is composed of two layers of a sacrificial layer and an active layer of an SOI substrate. In order to further improve the sensitivity of this mechanical quantity detection sensor, it is necessary to optimize the thicknesses of the sacrificial layer and the active layer in the beam portion.

  This invention is made | formed in view of this point, and it aims at providing the manufacturing method of the mechanical quantity detection sensor which can show high sensitivity.

  The method of manufacturing a mechanical quantity detection sensor according to the present invention includes processing a base layer of an SOI substrate including an active layer, a base layer, and an insulating layer sandwiched between the active layer and the base layer. Forming a body, a weight located inside the frame, and a beam portion that supports the weight so as to be swingable with respect to the frame, and a step of reducing the thickness of the beam portion; Forming a detection element that outputs a signal corresponding to a mechanical quantity on the active layer based on a deflection amount of the beam portion.

  According to this method, it is possible to form a beam portion in an optimum state in consideration of sensitivity and strength, and thus it is possible to manufacture a mechanical quantity detection sensor that can exhibit high sensitivity.

  In the manufacturing method of the mechanical quantity detection sensor of the present invention, it is preferable that the beam portion is thinned by processing from the active layer side of the beam portion. According to this method, it is possible to obtain a highly sensitive mechanical quantity detection sensor by reducing the spring constant of the beam portion while maintaining the strength of the active layer.

  In the manufacturing method of the mechanical quantity detection sensor of the present invention, it is preferable to process the beam portion from the insulating layer side to reduce the thickness of the beam portion. According to this method, since the Young's modulus of the insulating layer and the active layer can be matched by reducing the thickness of the insulating layer, a mechanical quantity detection sensor with high desired performance can be obtained.

  In the method for manufacturing a mechanical quantity detection sensor of the present invention, it is preferable to remove the insulating layer and further thin the active layer. According to this method, a highly sensitive mechanical quantity detection sensor can be obtained while maintaining the strength of the active layer.

  The method of manufacturing a mechanical quantity detection sensor according to the present invention includes processing a base layer of an SOI substrate including an active layer, a base layer, and an insulating layer sandwiched between the active layer and the base layer. Forming a body, a weight positioned inside the frame, and a beam portion that supports the weight so as to be able to swing with respect to the frame, and reducing the thickness of the beam portion on the active layer In addition, a detection element that outputs a signal corresponding to a mechanical quantity based on the deflection amount of the beam portion is formed. In this case, since the beam portion in an optimum state can be formed in consideration of sensitivity and strength, a mechanical quantity detection sensor that can exhibit high sensitivity can be manufactured.

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)-(c) is a figure for demonstrating the method to make a beam part thin. (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.

  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. In the mechanical quantity detection sensor 1, for example, the first semiconductor substrate 2 is a silicon layer (active layer), the insulating layer 4 is a silicon oxide layer (sacrificial layer), and the second semiconductor substrate 3 is a silicon layer (base layer). It can be manufactured using an SOI (Silicon On Insulator) substrate having a three-layer structure.

  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 (the weight portion 22 and the displacement portion 12 constitute a weight). Therefore, in this way, the weight part 22 forms a weight together with the displacement part 12 in the housing space of the frame 11 and the opening part 23 of the support part 21 and is supported by the four beam parts 13 so as to be swingable. . 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.

  The beam portion 13 includes a first semiconductor substrate 2 that is an active layer and an insulating layer 4 that is a sacrificial layer. The beam portion 13 is formed together with the frame body 11 and the weight by processing the base layer of the SOI substrate. Next, in order to cause the mechanical quantity detection sensor to exhibit desired performance, the thickness of the beam portion 13 is reduced (the beam portion 13 is corrected). In this case, as shown in FIG. 3A, the beam portion 13 is processed from the insulating layer 4 side to form a recess 4a in the insulating layer 4 to reduce the thickness of the beam portion 13. According to this method, since the Young's modulus of the insulating layer 4 and the first semiconductor substrate 2 (active layer) can be matched by reducing the thickness of the insulating layer, a mechanical quantity detection sensor with high desired performance can be obtained. Can do.

  Alternatively, as shown in FIG. 3B, the beam portion 13 is thinned by processing the beam portion 13 from the first semiconductor substrate 2 (active layer) side to form a recess 2a in the first semiconductor substrate 2. To do. According to this method, a highly sensitive mechanical quantity detection sensor can be obtained by reducing the spring constant of the beam portion 13 while maintaining the strength of the first semiconductor substrate 2.

  Alternatively, as shown in FIG. 3C, the beam portion 13 is processed from the insulating layer 4 side, the insulating layer 4 is removed, and a recess 2b is formed in the first semiconductor substrate 2 to form the first semiconductor substrate. Thin 2 According to this method, a more sensitive mechanical quantity detection sensor can be obtained while maintaining the strength of the first semiconductor substrate 2.

  The methods shown in FIGS. 3A to 3C are not alternative, and can be used in appropriate combination in consideration of desired characteristics to be exhibited by the mechanical quantity detection sensor. There is no restriction | limiting in particular about the order of a process in that case.

  The depths of the recesses 2a, 2b, 4a, that is, the amount of processing to the first semiconductor substrate 2 and the insulating layer 4 are determined in advance so that the relationship between the processing amount and the sensitivity is obtained in advance to meet the desired characteristics. From the above relationship, it is determined appropriately. Further, as processing for the first semiconductor substrate 2 and the insulating layer 4, etching, ion milling, or the like can be used. When etching is used for processing, it is preferable to set the processing amount in consideration of over-etching.

  Next, an example of the machining process of the mechanical quantity detection sensor will be described with reference to FIGS. 4 (a) to 4 (d) and FIGS. 5 (a) to 5 (c) are diagrams for explaining a method of manufacturing the mechanical quantity detection sensor according to the embodiment of the present invention.

  As shown in FIG. 4A, 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. 4B, 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. 4C, 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. 4D, 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, the thickness of the beam portion 13 is reduced. In this case, as shown in FIG. 3A, the beam portion 13 is processed from the insulating layer 4 side to form a recess 4a in the insulating layer 4 to reduce the thickness of the beam portion 13, or FIG. 3), the beam portion 13 is processed from the first semiconductor substrate 2 (active layer) side to form a recess 2a in the first semiconductor substrate 2 to reduce the thickness of the beam portion 13, or FIG. As shown in c), the beam portion 13 is processed from the insulating layer 4 side, the insulating layer 4 is removed, and the concave portion 2b is formed in the first semiconductor substrate 2 to make the first semiconductor substrate 2 thinner. In the case shown in FIG. 3 (a), it is necessary to process the structure shown in FIG. 4 (c), and in the case shown in FIG. 3 (b), the process shown in FIG. It needs to be processed after the structure shown.

  Next, as shown in FIG. 5A, an insulating material is deposited on the upper surface of the first semiconductor substrate 2 by sputtering. Next, as shown in FIG. 5B, 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 is deposited on the beam 13 and the displacement portion 12 by sputtering, and the lower electrode 25 is formed by patterning the metal material by photolithography and etching. Next, a piezoelectric material is deposited by sputtering, and the piezoelectric material is patterned by photolithography and etching to form the piezoelectric thin film 26. Next, a metal material is deposited by sputtering, and the metal material is patterned by photolithography and etching, so that the upper electrode 27 is partially formed on the piezoelectric thin film 26.

  Next, as shown in FIG. 5C, 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, a mechanical quantity detection sensor can be obtained.

  Next, the operation of the mechanical quantity detection sensor will be briefly described with reference to FIG. 6A and 6B are explanatory diagrams of detection operation of the mechanical quantity detection sensor. FIG. 6A is an explanatory diagram of detection operation when the weight portion rotates around the X axis. FIG. 6B 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. 6A, 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. 6B, when acceleration acts on the mechanical quantity detection sensor and an inertial force acts on the weight portion 22 downward in the Z-axis direction, the weight portion 22 moves linearly downward in the Z-axis direction. To do. 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.

  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.

  Thus, in the present embodiment, the second semiconductor substrate 4 of the SOI substrate is processed, and the frame body 11 and the weights (displacement portion 12 and weight portion 22) located inside the frame body 11, A beam portion 13 that supports the weight so as to be able to swing with respect to the frame body 11, the thickness of the beam portion 13 is reduced, and the bending amount of the beam portion 13 is formed on the active layer. Based on this, the detection element 17 that outputs a signal corresponding to the mechanical quantity is formed. In this case, since the beam portion 13 in an optimal state can be formed in consideration of sensitivity and strength, a mechanical quantity detection sensor that can exhibit high sensitivity can be manufactured.

  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)
2a, 2b, 4a Recess 3 Second semiconductor substrate (second substrate)
4,18 Insulating layer 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

Claims (4)

  Processing the base layer of the SOI substrate including an active layer, a base layer, and an insulating layer sandwiched between the active layer and the base layer, and a frame body and a weight located inside the frame body And a beam portion for swingably supporting the weight with respect to the frame body; a step of reducing the thickness of the beam portion; and a deflection amount of the beam portion on the active layer. And a step of forming a detection element that outputs a signal corresponding to the mechanical quantity based on the method.   The method of manufacturing a mechanical quantity detection sensor according to claim 1, wherein the beam portion is thinned by processing from the active layer side of the beam portion.   The method for manufacturing a mechanical quantity detection sensor according to claim 1, wherein the beam portion is thinned by processing from the insulating layer side of the beam portion.   4. The method of manufacturing a mechanical quantity detection sensor according to claim 3, wherein the insulating layer is removed and the active layer is further thinned.

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