JP2010145315A - Vibration gyroscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance an S/N ratio of a vibration gyroscope by making excitations from being hardly leaked to a second axis, even when a weight is excited in directions in parallel with a first axis at its natural frequency, because displacements of the weight have different natural frequencies in directions in parallel with the first axis and in directions intersecting with the first axis at right angles. <P>SOLUTION: The vibration gyroscope includes a die 1A in which a support part; the weight M; flexible parts Fx and Fy which connect the support part to the weight and deform with the motion of the weight; a driving means for exciting the weight in directions in parallel with the first axis at a first frequency; and a detection means which correlates with displacements of the weight in directions intersecting with the first axis at right angles and in parallel with the second axis in parallel with a plane including the flexible parts for detecting physical quantities corresponding to angular velocity on a third axis intersecting with the first axis and the second axis at right angles are formed. The first frequency is a frequency different from a second frequency, the natural frequency of displacements of the weight in directions in parallel with the first axis and the natural frequency of displacements of the weight in directions in parallel with the second axis. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vibrating gyroscope configured as MEMS (Micro Electro Mechanical Systems).

Conventionally, a MEMS that functions as a vibrating gyroscope for detecting angular velocity is known. In Patent Document 1, a weight portion is coupled to a central region of a circular diaphragm, and the weight portion is rotated by a piezoelectric element provided on the diaphragm, and a Coriolis force acting on the weight portion is provided by another piezoelectric element provided on the diaphragm. A vibrating gyroscope to detect is described. In Patent Document 2, a weight portion is coupled to a central region of two beams coupled in a cross shape, and the weight portion is vibrated in a direction in which the beam extends by a piezoelectric element provided on one beam, and the other beam Describes a vibrating gyroscope that detects a Coriolis force acting on a weight portion by a piezoelectric element provided on the surface. When detecting an angular velocity around a certain axis, the weight portion is vibrated in a direction orthogonal to the rotation axis, and a Coriolis force acting in a direction orthogonal to the rotation axis and the vibration direction of the weight portion is detected. Therefore, as described in Patent Documents 1 and 2, the direction in which the set of piezoelectric elements that drive the weight portion is aligned and the direction in which the set of piezoelectric elements that detect the Coriolis force are aligned are orthogonal to each other.
JP 2004-294450 A Japanese Patent No. 3303379

  However, because there is a positional shift of the piezoelectric element that drives the weight portion, as described in Patent Document 1, a vibration gyroscope having the same natural frequency in an arbitrary direction parallel to the diaphragm is described in Patent Document 2, or in Patent Document 2 In the vibration gyroscope in which two beams having the same shape have the same natural frequency, even if an attempt is made to vibrate the weight part in a specific direction, the weight part vibrates in a direction perpendicular to the direction. End up. Such a phenomenon that the weight part vibrates in a direction different from the direction in which the weight part is excited is referred to as excitation leakage. When excitation leakage occurs, the piezoelectric element for detecting the Coriolis force detects the distortion caused by the Coriolis force and the distortion caused by the excitation leakage in a superimposed manner. Therefore, it is difficult to increase the S / N with the vibrating gyroscope described in Patent Documents 1 and 2.

  One object of the present invention is to increase the S / N ratio of a vibrating gyroscope.

  (1) A vibrating gyroscope for achieving the above object includes a support portion, a weight portion, a flexible portion that connects the support portion and the weight portion and deforms as the weight portion moves, Driving means for exciting the weight part at a first frequency in a direction parallel to one axis, and the weight part in a direction parallel to a second axis perpendicular to the first axis and parallel to a plane including the flexible part Detecting means for detecting a physical quantity corresponding to an angular velocity about a third axis that is correlated with the displacement of the first axis and orthogonal to the first axis and the second axis, and the first frequency is the first frequency The natural frequency of the displacement of the weight portion in a direction parallel to one axis, and a frequency different from the second frequency that is the natural frequency of the displacement of the weight portion in a direction parallel to the second axis. .

  According to the present invention, since the natural frequency of the displacement of the weight part is different between the direction parallel to the first axis and the direction perpendicular to the first axis, the weight part is excited at the natural frequency in the direction parallel to the first axis. Even so, the excitation hardly leaks to the second shaft. Therefore, according to the present invention, the S / N of the vibrating gyroscope can be increased.

(2) In the vibrating gyroscope for achieving the above object, the flexible portion is stretched over the support portion in a direction parallel to the first axis and in a direction parallel to the second axis, respectively. It consists of two beams that are mutually connected in the region and have different lengths, the weight part is connected to the central region of the two beams, and the driving means is stretched in a direction parallel to the first axis A set of piezoelectric elements arranged on the beam, wherein the detection means may be another set of piezoelectric elements arranged on the beam spanned in a direction parallel to the second axis. .
According to the present invention, since the lengths of the two beams constituting the flexible portion are different from each other, even if the weight portion is excited at the natural frequency in a direction parallel to the first axis in which one beam extends, It is difficult for the excitation to leak in a direction parallel to the second axis extending from.

(3) In the vibrating gyroscope for achieving the above object, the flexible portion has an elliptical end fixed to the support portion, a major axis is parallel to the first axis, and a minor axis is the minor axis. A pair of diaphragms parallel to a second axis, wherein the weight portion is coupled to a central region of the diaphragm, and the driving means is arranged on the diaphragm along one of a major axis and a minor axis of the diaphragm The detection means may be another set of piezoelectric elements arranged on the diaphragm along the other of the major axis and the minor axis of the diaphragm.
According to the present invention, since the end of the diaphragm constituting the flexible portion is elliptical, even if the weight portion is excited at the natural frequency in a direction parallel to the first axis parallel to the major axis of the diaphragm, Excitation is difficult to leak in the direction parallel to the second axis parallel to the short axis.

(4) In the vibrating gyroscope for achieving the above object, the flexible part has a rhombus at the end fixed to the support part, and one of the diagonal lines is parallel to the first axis and the other of the diagonal lines Is a diaphragm parallel to the second axis, wherein the weight portion is coupled to a central region of the diaphragm, and the driving means is a set of piezoelectric elements arranged on the diaphragm along one of the diagonal lines of the diaphragm. It is an element, Comprising: The said detection means may be another 1 set of piezoelectric elements arranged in the said diaphragm along the other diagonal of the said diaphragm.
According to the present invention, since the end of the diaphragm constituting the flexible portion is a rhombus, even if the weight portion is excited at the natural frequency in a direction parallel to the first axis parallel to one of the diagonal lines of the diaphragm, Excitation is unlikely to leak in a direction parallel to the second axis parallel to the other of the diagonal lines.

(5) In the vibrating gyroscope for achieving the above object, the flexible portion has a rectangular end fixed to the support portion, and one of the long side and the short side is parallel to the first axis. The other of the long side and the short side is a diaphragm parallel to the second axis, the weight portion is coupled to a central region of the diaphragm, and the driving means is parallel to one of the long side and the short side of the diaphragm. A pair of piezoelectric elements arranged on the diaphragm, wherein the detecting means is another set of piezoelectric elements arranged on the diaphragm in parallel with the other of the long side and the short side of the diaphragm. Good.
According to the present invention, since the end of the diaphragm constituting the flexible portion is rectangular, even if the weight portion is excited at the natural frequency in the direction parallel to the first axis parallel to the long side of the diaphragm, the diaphragm short Excitation is difficult to leak in a direction parallel to the second axis parallel to the side.

(6) In the vibrating gyroscope for achieving the above object, the weight portion may have a length in the direction of the first axis and a length in the direction of the second axis.
According to the present invention, since the length of the weight portion is different between the direction of the first axis and the direction of the second axis, even if the weight portion is excited at the natural frequency in the direction parallel to the first axis, The excitation is difficult to leak in the direction parallel to the.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the corresponding component in each figure, and the overlapping description is abbreviate | omitted.
1. First embodiment (Configuration)
A vibrating gyroscope according to a first embodiment of the present invention is shown in FIGS. 1A and 1B are sectional views showing a sensor die 1A of the vibrating gyroscope 1, and are sectional views taken along lines AA and BB shown in FIG. 1C, respectively. FIG. 1C is a top view of the sensor die 1A. FIG. 2 is a bottom view of the sensor die 1A. FIG. 3 is a cross-sectional view showing the vibrating gyroscope 1. In FIG. 1A, FIG. 1B, and FIG. 3, the interface of the layer which comprises the sensor die 1A is shown with the broken line, and the boundary of the mechanical component which comprises the sensor die 1A is shown with the continuous line. The xyz coordinate axes fixed to the vibrating gyroscope 1 used in the following description are determined as shown in FIG.

  The vibration gyroscope 1 is a MEMS sensor that detects angular velocity components around the x-axis, y-axis, and z-axis in a time-sharing manner. The vibration gyroscope 1 includes a package 1B shown in FIG. 3 and a sensor die 1A housed in the package 1B.

As shown in FIG. 1A, the sensor die 1A includes a base layer 11, an etching stopper layer 12 in contact with the base layer 11, a semiconductor layer 13 in contact with the etching stopper layer 12, a first insulating layer 20 in contact with the semiconductor layer 13, An electrode layer 31 in contact with the first insulating layer 20, a piezoelectric layer 32 in contact with the electrode layer 31, an electrode layer 33 in contact with the piezoelectric layer 32, a first layer in contact with the electrode layers 31, 33, the piezoelectric layer 32, and the first insulating layer 20. This is a laminated structure composed of two insulating layers 40 and a surface conductive layer 50 in contact with the second insulating layer 40. Both the base layer 11 and the semiconductor layer 13 are made of single crystal silicon (Si). The base layer 11 may be made of a bulk material such as glass. The thickness of the base layer 11 is 625 μm. The thickness of the semiconductor layer 13 is 10 μm. The etching stopper layer 12 and the first insulating layer 20 are made of a silicon oxide film (SiO ₂ ). The thickness of the etching stopper layer 12 is 1 μm. The thickness of the first insulating layer 20 is 0.5 μm. The electrode layers 31 and 33 are made of platinum (Pt). The electrode layers 31 and 33 may be made of a conductive material such as iridium (Ir), iridium oxide (IrO ₂ ), or gold (Au). The electrode layers 31 and 33 have a thickness of 0.1 μm. The piezoelectric layer 32 is made of PZT (lead zirconate titanate). The thickness of the piezoelectric layer 32 is 3 μm. The second insulating layer 40 is made of photosensitive polyimide. The second insulating layer 40 may be made of an inorganic insulating material such as a silicon oxide film, a silicon nitride film (Si _x N _y ), or alumina (Al ₂ O ₃ ). The thickness of the second insulating layer 40 is 5 μm. The surface conducting wire layer 50 is made of aluminum (Al). The surface conducting wire layer 50 may be made of a conductive material such as aluminum silicon (AlSi) or AlSiCu. The thickness of the surface conducting wire layer 50 is 0.5 μm.

The sensor die 1A of the vibrating gyroscope 1 includes a frame-shaped support portion S, two beams F _x and F _y coupled in a cross shape inside the support portion S, and two beams F _x and F _y coupled. to the weight portion M which is coupled to a central region and two beams F _x, the two beams F _x provided respectively on the F _y, driven to vibrate the weight portion M by deflecting the F _y Piezoelectric element 30c for detection and a piezoelectric element 30a for detection that detects distortion of the two beams F _x and F _y provided on the two beams F _x and F _y , respectively.

  The support portion S has a rectangular frame shape as shown in FIG. 1C. The support part S includes a base layer 11, an etching stopper layer 12, a semiconductor layer 13, and a first insulating layer 20. The support portion S includes a thick base layer 11 made of a bulk material, and is fixed to the package 1B via the base layer 11. Therefore, the support portion S behaves as a substantially rigid body that does not move in the coordinate system fixed to the vibrating gyroscope 1. The bottom surface of the support portion S is bonded to the bottom surface of the package 1B via an adhesive layer 92.

Each of the two beams F _x and F _y as the flexible portion has a beam shape in which both ends are fixed ends. The beams F _x and F _y include the semiconductor layer 13 and the first insulating layer 20. Since the beam F does not include the thick base layer 11 made of a bulk material, the beam F behaves as a flexible film. Both ends of the beams F _x and F _y are connected to the four sides inside the support portion S. Since the support portion S behaves as an immovable rigid body, both ends of the beams F _x and F _y are fixed ends in the coordinate system fixed to the vibrating gyroscope 1. The beams F _x and F _y are stretched over the four sides inside the support portion S. The beam F _x is stretched over the support portion S in a direction parallel to the x axis (x direction). The beam F _y is stretched over the support portion S in a direction (y direction) parallel to the y axis. The beams F _x and F _y are coupled to each other in the respective central regions. Central regions of the beams F _x and F _y are coupled to the weight portion M. That is, the central region of one cross-shaped beam constituted by the beams F _x and F _y is coupled to the weight portion M. Since the weight M is coupled only to the beams F _x and F _y and floats from the bottom surface 90a of the package 1B as shown in FIG. 3, the beams F _x and F _y are in a coordinate system fixed to the vibrating gyroscope 1. It behaves as a beam that deforms as the weight M moves.

Beam _F x, _{F y} of length (beam _F for _x in the x-direction length _{X f} (see FIG. 2), for the beam _{F y} be the length of the y-direction length _{Y f.)} Are different from each other. The length of the concrete to the beam F _x is longer than the length of the beam F _y. The lengths of the beams F _x and F _y are made different from each other in order to make the natural frequency in the displacement of the weight M in the x direction different from the natural frequency in the displacement in the y direction. The beams F _x and F _y having the same layer structure have the same thickness. The beam F _x, F _y width (beam F _x y direction length for, for the beam F _y. To width length in the x-direction) of the same. Note that the natural frequency in the displacement in the x direction and the natural frequency in the displacement in the y direction of the weight M may be made different by making the thicknesses or widths of the beams F _x and F _y different from each other. Further, the lengths, thicknesses and widths of the beams F _x and F _y may be different from each other. Of course, the natural frequency of the displacement of the weight M in the x direction and the natural frequency of the displacement in the y direction may be made different by changing part or all of the patterns of the beams F _x and F _y .

  As shown in FIG. 2, the bottom surface of the weight portion M has a pattern (a shape viewed from the z direction) in which one rectangle and four rectangles coupled to the four corners are combined. The weight portion M includes a base layer 11 and an etching stopper layer 12. Since the weight portion M includes the thick base layer 11 made of a bulk material, the weight portion M substantially behaves as a rigid body. Since the weight M is coupled only to the beam F and floats from the bottom surface 90a of the package 1B as shown in FIG. 2, the weight M moves in a coordinate system fixed to the vibrating gyroscope 1.

Length in the x direction of the weight portion M X _m is longer than the length Y _m of the y-direction. The length X _m in the x direction and the length Y _m in the y direction of the weight M are made different from each other in the natural frequency in the displacement in the x direction and the natural frequency in the displacement in the y direction. It is to make it. In order to make the natural frequency in the displacement in the x direction of the weight M different from the natural frequency in the displacement in the y direction depending on the shape of the weight M, the dispersion of the positions of the mass points constituting the weight M is essentially changed. What is necessary is just to make it differ by x direction and y direction. The mass points here mean those points when the weight M is regarded as a set of a finite number of points having a unit mass. Therefore, even when the length X _m in the x direction of the weight portion M is equal to the length Y _m in the y direction, the natural frequency and y in the displacement of the weight portion M in the x direction depend on the shape of the weight portion M. It is possible to vary the natural frequency in the direction displacement.

  Each of the driving piezoelectric element 30 c and the detecting piezoelectric element 30 a includes electrode layers 31 and 33 and a piezoelectric layer 32. The electrode layer 31 constituting the lower electrode of the driving piezoelectric element 30c and the detecting piezoelectric element 30a also constitutes an internal conductor 31b connecting the lower electrode of the piezoelectric elements 30a, 30c and the bonding pad 50a. The electrode layer 33 constituting the upper electrode of the driving piezoelectric element 30c and the detecting piezoelectric element 30a is connected to the surface conductor 50b through a contact hole 40h formed in the second insulating layer 40. The surface conducting wire 50 b connects the bonding pad 50 a and the electrode layer 33.

Each is two driving piezoelectric elements 30c and is arranged in the beam F _x is in a position straddling the boundary between the support portion S and the beam F _x, and is located at the center in the width direction of the beam F _x. The two driving piezoelectric element 30c are aligned in the x-direction beam F _x extends. The driving piezoelectric element 30c is a driving means for vibrating the weight portion M in the x direction and the z direction. A sine wave signal for vibrating the weight M in the x direction and a sine wave signal for vibrating in the z direction are applied to the two driving piezoelectric elements 30c in a time-sharing manner. When the weight M is vibrated in the x direction, the phases of the sine wave signals applied to the two driving piezoelectric elements 30c are shifted by a half cycle. When the weight M is vibrated in the z direction, the sine wave signals applied to the two driving piezoelectric elements 30c are synchronized.

Two detecting piezoelectric elements 30a which are arranged in the beam F _x is in a position straddling the boundary between the beam F _x and the weight portion M, and is located at the center in the width direction of the beam F _x. The two detecting piezoelectric elements 30a which are arranged in the beam F _x are aligned in the x direction. Two detecting piezoelectric elements arranged in the beam F _x 30a is detecting means for detecting the distortion of the beam F _x with the weight portion movement of M corresponding to the angular velocity around the y-axis. That the two detecting piezoelectric elements 30a which are arranged in the beam F _x for detecting the distortion of the beam F _x as a physical quantity corresponding to the angular velocity about the y-axis.

Two detecting piezoelectric elements 30a which are arranged in the beam F _y is in a position straddling the boundary between the beam F _y and the weight portion M, and is located at the center in the width direction of the beam F _y. The two detecting piezoelectric elements 30a which are arranged in the beam F _y are aligned in the y-direction. Detection means for the two detecting piezoelectric elements 30a which are arranged in the beam F _y is to detect the deformation of the beam F _y due to movement of the weight portion M corresponding to the angular velocity of the angular velocity and z axis around the x-axis is there. That the two detecting piezoelectric elements 30a which are arranged in the beam F _y to detect the distortion of the beam F _y as a physical quantity corresponding to the angular velocity of the angular velocity and z axis around the x axis.

  Stress and strain associated with the deformation of the beam F are concentrated at the boundary between the weight portion M that behaves substantially as a rigid body and the beam F having flexibility. For this reason, by providing the detecting piezoelectric element 30a across the boundary between the weight portion M and the beam F, it is possible to efficiently detect the strain accompanying the deformation of the beam F. The driving piezoelectric element 30c may be provided across the boundary between the weight part M and the beam F. Further, the detection piezoelectric element 30a may be provided across the boundary between the support portion S and the beam F. In any case, it is desirable to provide the driving piezoelectric element 30c and the detecting piezoelectric element 30a in the vicinity of the boundary (vibration end) between the beam F and a substantially rigid body coupled thereto.

  The package 1B shown in FIG. 2 includes a lidless box type package base 90 and a cover 94 that closes the internal space of the package base 90. The package base 90 and the cover 94 are joined via an adhesive layer 93. The package base 90 is provided with a plurality of through electrodes 91. One end of the wire 95 is bonded to the bonding pad 50a of the sensor die 1A, and the other end is bonded to the through electrode 91 of the package 1B. The bottom surface of the support portion S of the sensor die 1 </ b> A is bonded to the bottom surface 90 a inside the package base 90 with an adhesive layer 92. The height of the gap between the weight portion M of the sensor die 1A and the bottom surface 90a on the inner side of the package base 90 is set by the depth of the recess formed in the bottom surface 90a and the thickness of the adhesive layer 92. Note that an LSI die that generates a signal corresponding to a three-axis angular velocity component from a detection signal output from the detection piezoelectric element 30a by applying a drive signal to the drive piezoelectric element 30c is housed inside the package 1B. Good.

(Operation)
The operation of the vibrating gyroscope 1 will be described with reference to FIGS. Hereinafter, among the detecting piezoelectric elements 30a, the piezoelectric element S _y1 as using what is arranged in the beam F _x extending in the x direction as shown in FIG. 4 in order to detect the y-axis component of the angular _velocity, S _y2 The elements arranged on the beam F _y extending in the y direction are represented as piezoelectric elements S _xz1 and S _xz2 as those used for detecting the x-axis component and the z-axis component of the angular velocity. The driving piezoelectric element 30c is represented as piezoelectric elements D ₁ and D ₂ . FIG. 4 is a simplified view of the top surface of the sensor die 1A.

When detecting the component of the angular velocity around the z-axis, sinusoidal signals whose phases are shifted from each other by a half period as shown in FIG. 5 are applied to the piezoelectric elements D ₁ and D ₂ . Then, since one of the piezoelectric elements D ₁ and D ₂ extends when one contracts, the center of gravity of the weight portion M vibrates in the x direction as shown in FIG. The natural frequency of displacement of the weight portion M in the x direction is determined by the forms of the beams F _x and F _y and the weight portion M. By exciting the weight M at the natural frequency of the displacement of the weight M in the x direction, the amplitude of the weight M is increased. Therefore, the first frequency, which is the frequency of the sine wave signal applied to the piezoelectric elements D ₁ and D ₂ when the weight M is excited in the x direction, is set equal to the natural frequency of the displacement of the weight M in the x direction. To do.

When sinusoidal signals whose phases are shifted from each other by half a period are applied to the piezoelectric elements D ₁ and D ₂ to excite the weight M in the x direction, the beam F _y extending in the y direction is twisted. However, in the width direction of the center of the beam F _y to the piezoelectric element _{S xz1,} S xz2 are arranged offset compression stress due to the tensile stress is twisted, also nor bent as shown in Figure 6B. Therefore, when sine wave signals whose phases are shifted from each other by a half cycle are applied to the piezoelectric elements D ₁ and D ₂ to vibrate the center of gravity of the weight M in the x direction, the piezoelectric elements S _xz1 and S arranged on the beam F _y are _used . signals due to distortion of the beam F _y from _xz2 is not detected as shown in FIG.

Further, since the beam F _x is longer than the beam F _y and the weight portion M is longer in the x direction than the y direction, the second frequency that is the natural frequency of the displacement of the weight portion M in the y direction is x of the weight portion M. It becomes lower than the first frequency which is the natural frequency of the displacement in the direction. That is, the natural frequency of the displacement of the weight M in the y direction is different from the natural frequency of the displacement of the weight M in the x direction. Therefore, even if the piezoelectric elements D ₁ and D ₂ are formed at positions deviated from the design, if the sine wave signal having the first frequency is applied to the piezoelectric elements D ₁ and D ₂ , the excitation is in the y direction. Therefore, the amplitude of the weight portion M in the y direction is sufficiently smaller than the amplitude in the x direction.

In this way, when the weight M is excited in the x direction, if an angular velocity around the z axis is generated, a Coriolis force C acts in the y direction as shown in FIG. As a result, the beam F _y extending in the y direction bends symmetrically with respect to the center point in the length direction, and the piezoelectric elements S _xz1 and S _xz2 arranged on the beam F _y detect distortion. Since the magnitude of the Coriolis force C is proportional to the speed of the weight portion M, the center of gravity of the weight portion M vibrates at the first frequency even in the y direction. As a result, as shown in FIG. 9, sine wave signals corresponding to the magnitude of the angular velocity around the z-axis are output from the piezoelectric elements S _xz1 and S _xz2 . When the weight part M vibrates in the y direction, the beam deflection is reversed at the position where the piezoelectric elements S _xz1 and S _xz2 are provided, so the polarity of the signal output from the piezoelectric elements S _xz1 and S _xz2 is Reverse. Therefore, if synchronous detection taking the difference of the piezoelectric element S _xz1, signals output from the _S xz2, it is possible to obtain an angular velocity component about the z axis.

  Since the natural frequency of the displacement of the weight part M in the y direction is different from the first frequency, the Coriolis force C is greater than when the natural frequency of the displacement of the weight part M in the y direction is equal to the first frequency. As a result, the amplitude of vibration in the y direction decreases. However, noise due to excitation leakage can be sufficiently reduced, and since the Coriolis force is generally sufficiently smaller than the driving force for excitation, the S / N is improved due to the suppression effect of excitation leakage.

Further, when the center of gravity of the weight M is vibrated in the x direction, if an angular velocity around the y axis occurs, a Coriolis force C acts in the z direction as shown in FIG. 10A. As a result, the beam F _y extending in the y direction bends symmetrically with the center point in the length direction as a target point, and the piezoelectric elements S _xz1 and S _xz2 arranged on the beam F _y detect distortion. At this time, since the beam _y bends in the same direction at the position where the piezoelectric elements S _xz1 and S _xz2 are provided, the polarities of the signals output from the piezoelectric elements S _xz1 and S _xz2 are as shown in FIGS. 10B and 10C. Matches. Therefore, if the difference between the signals output from the piezoelectric elements S _xz1 and S _xz2 is taken, the angular velocity component around the y axis is canceled. In other words, if the sum of signals output from the piezoelectric elements S _xz1 and S _xz2 is taken and synchronous detection is performed, an angular velocity component around the y axis can be obtained. However, in this embodiment, the angular velocity component around the y-axis is obtained as follows.

When detecting the component of the angular velocity around the y-axis, a synchronized sine wave signal is applied to the piezoelectric elements D ₁ and D ₂ as shown in FIG. Then, when one of the piezoelectric elements D ₁ and D ₂ extends, the other also extends and when the other contracts, the other contracts, and the center of gravity of the weight M vibrates in the z direction as shown in FIG. The third frequency, which is the frequency of the sine wave signal applied to the piezoelectric elements D ₁ and D ₂ to excite the weight M in the z direction, is determined by the beams F _x and F _y and the form of the weight M. It is set equal to the natural frequency of the displacement of the part M in the z direction.

While exciting the weight portion M in the z-direction, the beam F provided piezoelectric element S _xz1, from S _Xz2 for _y, sine wave signal synchronized with each other as shown in FIG. 13 with the deflection of the beam F _y Is detected. At this time, sine wave signals synchronized with each other are also detected from the piezoelectric elements S _y1 and S _y2 provided on the beam F _x . Incidentally, the natural frequency of the displacement of the weight M in the z direction generally differs greatly from the frequency of the displacement of the weight M in the x direction and the frequency of the displacement in the y direction. Therefore, when the weight M is excited in the z direction, the excitation hardly leaks in the x direction or the y direction. Thus, rather than exciting the weight M in the x direction and detecting the angular velocity component around the y axis, the weight M is excited in the z direction to detect the angular velocity component around the y axis.

When the weight M is excited in the z-direction in this way, if an angular velocity around the y-axis occurs, a Coriolis force C acts in the x-direction as shown in FIG. Since the magnitude of the Coriolis force C is proportional to the speed of the weight portion M, the center of gravity of the weight portion M vibrates at the third frequency even in the x direction. As a result, the piezoelectric elements S _y1 and S _y2 arranged in the beam F _x extending in the x direction output a detection signal in which the excitation component in the z direction and the angular velocity component around the y axis are superimposed as shown in FIG. . To become a point symmetry as the target point the center point of the length direction of the deflection beam F _x of the beam F _x due to vibration in the x direction of the center of gravity of the weight M, of signals piezoelectric element S _y1, S _y2 outputs The polarity of the angular velocity component around the y-axis is reversed. The polarities of the excitation components in the z direction output from the piezoelectric elements S _y1 and S _y2 are the same. Therefore, if synchronous detection is performed by taking a difference between signals output from the piezoelectric elements S _y1 and S _y2 , an angular velocity component around the y axis can be obtained.

  When detecting the component of the angular velocity around the x-axis, the weight M may be excited in the y direction or the z direction. When switching the excitation direction of the weight part M, it is necessary to wait for detection of the angular velocity until the vibration of the weight part M is stabilized in the direction in which the weight part M is to be excited. Therefore, in this embodiment, the weight M is excited in the z direction in order to detect the component of the angular velocity around the x axis.

When an angular velocity around the x-axis occurs when the weight M is excited in the z direction at the third frequency, a Coriolis force C acts in the y direction as shown in FIG. Since the magnitude of the Coriolis force C is proportional to the speed of the weight part M, the center of gravity of the weight part M vibrates at the third frequency even in the y direction. As a result, the piezoelectric elements S _xz1 and S _xz2 arranged in the beam F _y extending in the y direction output detection signals in which the excitation component in the z direction and the angular velocity component around the x axis are superimposed as shown in FIG. . To become a point symmetry as the target point the center point of the length direction of the deflection beam F _y of the beam F _y due to vibration in the y direction of the center of gravity of the weight M, of signals piezoelectric element _{S xz1,} S xz2 outputs The polarity of the angular velocity component around the x axis is reversed. The polarities of the excitation components in the z direction output from the piezoelectric elements S _xz1 and S _xz2 are the same. Therefore, the synchronous detection by taking the difference of the signals output from the piezoelectric element _{S xz1,} S _xz2, it is possible to obtain an angular velocity component about the x-axis.

As described above, in order to detect the angular velocity component around the x, y, and z axes, that is, the xyz axis component of the angular velocity, the weight portion M is time-divisionally excited in the x direction and the z direction. That is, the drive signals applied to the piezoelectric elements D ₁ and D ₂ are switched in a time-sharing manner. The piezoelectric elements D _1, the piezoelectric element D ₁ to excite the vibration frequency in the y direction of the drive signal applied to the D _2, the drive signal applied to the D ₂ for specifically to excite weight portion M in the x-direction And the phase of the drive signal applied to the piezoelectric elements D ₁ and D ₂ are switched. The piezoelectric element S _xz1, when the S _Xz2 for detecting the x-axis component of the angular velocity is synchronously detects in a third frequency by taking the difference between their outputs, when detecting a z-axis component, takes the sum of their outputs And synchronous detection at the first frequency. In this way, a selector is required to drive the weight M in a time division manner and detect the xyz axis component of the angular velocity in a time division manner.

(Production method)
An example of a method for manufacturing the vibrating gyroscope 1 will be described with reference to FIGS. 18 to 26 are all cross-sectional views corresponding to the line AA shown in FIG. 1C except for FIG. 23A. FIG. 23A is a cross-sectional view corresponding to the line BB shown in FIG. 1C.

  First, as shown in FIG. 18, an SOI wafer 10 to be a base layer 11, an etching stopper layer 12, and a semiconductor layer 13 is prepared. The base layer 11 of the SOI wafer 10 is made of single crystal silicon having a thickness of 625 μm. The etching stopper layer 12 of the SOI wafer 10 is made of silicon oxide having a thickness of 1 μm. The semiconductor layer 13 of the SOI wafer 10 is made of single crystal silicon having a thickness of 10 μm. An etching stopper layer 12 made of silicon oxide is formed on the surface of the single crystal silicon wafer to be the base layer 11 by thermal oxidation, CVD (Chemical Vapor Deposition) or the like, and polycrystalline on the surface of the etching stopper layer 12 by CVD or the like. A semiconductor layer 13 made of silicon may be formed. Next, the first insulating layer 20 is formed on the surface of the semiconductor layer 13. As the first insulating layer 20, a silicon oxide film having a thickness of 0.5 μm is formed by thermal oxidation or CVD, for example.

Next, an electrode layer 31 serving as a lower electrode of the piezoelectric element is laminated on the entire surface of the first insulating layer 20, a piezoelectric layer 32 is laminated on the entire surface of the electrode layer 31, and an upper electrode and An electrode layer 33 is stacked. As the electrode layers 31 and 33, films made of platinum are formed by sputtering or the like. Titanium (Ti) with a thickness of 30 nm may be formed as an adhesion layer of platinum and silicon oxide. The material of the electrode layer 31 may be iridium oxide (IrO ₂ ). As a material of the electrode layer 33, iridium, iridium oxide, gold (Au), or the like may be used. As the piezoelectric layer 32, a film made of PZT is formed by sputtering, a sol-gel method, a hydrothermal synthesis method, or the like. Titanium having a thickness of 30 nm may be formed as an adhesion layer of platinum and PZT.

Next, as shown in FIG. 19, the electrode layer 33 and the piezoelectric layer 32 are patterned by etching the electrode layer 33 and the piezoelectric layer 32 using a protective film R1 made of a photoresist. Specifically, the electrode layer 33 made of platinum is patterned by ion milling using argon (Ar) ions. The piezoelectric layer 32 made of PZT is patterned by reactive ion etching using chlorine (Cl ₂ ) as an etching gas or wet etching using hydrofluoric acid.

  Next, as shown in FIG. 20, the electrode layer 31 is patterned by etching using the protective film R2 made of a photoresist. As a result, the internal conductor 31b and the piezoelectric elements 30a and 30c shown in FIG. 1 are formed.

  Next, as shown in FIG. 21, the second insulating layer 40 having a predetermined pattern having contact holes 40h on the surfaces of the piezoelectric elements 30a and 30b and the first insulating layer 20 is formed. For example, a photosensitive polyimide having a thickness of 5 μm is applied to the entire surface of the piezoelectric elements 30a and 30b and the first insulating layer 20, and patterned into a predetermined shape by exposure and development, thereby forming the contact hole 40h and the first insulating layer in a later process. 20 and the second insulating layer 40 having an opening 40b for partially etching the semiconductor layer 13 is formed.

Next, as shown in FIG. 22, the surface conductor layer 50 is laminated on the surface of the second insulating layer 40, and the surface conductor layer 50 is etched to form the surface conductor 50b and the bonding pad 50a. As the surface conductive layer 50, an aluminum (Al) film having a thickness of 0.5 μm is formed by sputtering, for example. An aluminum silicon (AlSi) film may be formed as the surface conducting wire layer 50. The pattern of the surface conductive layer 50 is formed by reactive ion etching using, for example, chlorine (Cl ₂ ) gas. A titanium film with a thickness of 30 nm may be formed as an aluminum adhesion layer. The surface conductive layer 50 may be patterned by, for example, reactive ion etching using Cl ₂ gas, ion milling, or wet etching using a mixed solution of phosphoric acid, nitric acid, and acetic acid.

Next, as shown in FIG. 23, the first insulating layer 20 and the semiconductor layer 13 are patterned into a predetermined shape using the second insulating layer 40 as a protective film. As a result, beams F _x and F _y are formed. The first insulating layer 20 is patterned by reactive ion etching using CHF ₃ gas or CF ₄ + H ₂ gas. The semiconductor layer 13 is patterned by reactive ion etching using CF ₄ + O ₂ gas. The patterns of the beams F _x and F _y may be formed by wet etching using tetramethylammonium hydroxide (TMAH) or potassium hydroxide (KOH).

  Next, the surface on which the piezoelectric elements 30a and 30c of the laminated structure W formed by the above-described steps are formed is bonded to the sacrificial substrate 99 as shown in FIG. As the adhesive layer 98, for example, a wax, a photoresist, a double-sided pressure-sensitive adhesive sheet, or the like is used.

Next, the base layer 11 is patterned into a predetermined shape by etching the base layer 11 using the protective film R3 made of a photoresist. Specifically, for example, the base layer 11 is anisotropically processed by Deep-RIE (so-called Bosch process) in which a passivation step using SF ₆ plasma gas and an etching step using C ₄ F ₈ plasma gas are alternately repeated at short time intervals. Etch. Note that the patterning of the base layer 11 may be performed first, or may be performed during the process of processing the surface side of the semiconductor layer 13.

  Next, as shown in FIG. 25, the exposed portion of the etching stopper layer 12 is removed by etching. As a result, the beam F and the weight part M are released. Specifically, the exposed portion of the etching stopper layer 12 is removed by wet etching using buffered hydrofluoric acid. Thereafter, post-processes such as dicing and packaging are performed to complete the vibrating gyroscope 1 shown in FIG.

2. Other Embodiments The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. For example, if the xy axis is parallel to a plane parallel to the film-like flexible part, the form of the flexible part and the form of the weight part are the natural frequency of the displacement of the weight part in the x-axis direction and the y axis. Any design may be used as long as the natural frequency of the displacement of the weight portion in the direction is different. FIG. 26 to FIG. 28 are simplified views of the upper surface of a modified example of the sensor die 1A.

Specifically, as shown in FIG. 26, the end of the diaphragm F as the flexible portion (that is, the boundary line between the support portion S and the diaphragm F indicated by a broken line) may be elliptical. In this case, even if the weight portion M coupled to the central region (region near the center) of the diaphragm F is cylindrical, the short axis of the diaphragm F compared to the x direction parallel to the long axis Ax of the diaphragm F. In the y direction parallel to Ay, the natural frequency of the displacement of the weight portion M increases. When the diaphragm F has such an elliptical shape, the piezoelectric elements D ₁ , D ₂ , S _y1 , S _y2 are arranged along the long axis (or short axis) of the diaphragm F, and the piezoelectric elements S _xz1 , S _xz2 What is necessary is just to arrange along the short axis (or long axis) of the diaphragm F. With this configuration, the weight portion can be excited at the natural frequency in the x direction parallel to the long axis A _x (or the short axis) of the diaphragm F as in the first embodiment, and the short axis of the diaphragm F can be excited. The excitation is less likely to leak in a direction parallel to A _y (or the long axis).

Further, as shown in FIG. 27, the end of the diaphragm F as the flexible portion may be formed in a diamond shape. Further, the weight part M coupled to the center region (region near the center of gravity) of the diaphragm F may be formed in a columnar shape having a rhombus bottom. When the pattern of the diaphragm F and the weight part M (the shape seen from the z direction) is such a rhombus, the diagonal line A _{y on} the shorter side of the diaphragm F compared to the x direction parallel to the longer diagonal line A _x on the diaphragm F , The natural frequency of the displacement of the weight portion M increases. In this case, the piezoelectric elements D ₁ and D ₂ may be arranged along one of the diagonal lines of the diaphragm F, and the piezoelectric elements S _xz1 and S _xz2 may be arranged along the other diagonal line of the diaphragm F. According to this structure, the weight portion diagonally A _x parallel x-direction of the longer of similarly diaphragm F in the first embodiment (or longer) can be excited at the natural frequency, the diaphragm F The excitation is less likely to leak in a direction parallel to the shorter (or shorter) diagonal _Ay .

Further, as shown in FIG. 28, the end of the diaphragm F as the flexible portion may be rectangular. In this case, compared to the x direction parallel to the long side of the diaphragm F, the natural frequency of the displacement of the weight portion M is higher in the y direction parallel to the short side of the diaphragm F. When the diaphragm F is such a rectangle, the piezoelectric elements D ₁ , D ₂ , S _y1 , S _y2 are arranged in parallel with the long side of the diaphragm F, and the piezoelectric elements S _xz1 , S _xz2 are the short side of the diaphragm F. What is necessary is just to arrange in parallel. With this configuration, the weight portion can be excited at the natural frequency in the x direction parallel to the long side (or short side) of the diaphragm F as in the first embodiment, and the short side (or the short side of the diaphragm F (or The excitation is less likely to leak in the direction parallel to the long side.

  As described above, even if the flexible part is an elliptical, rhombus or rectangular diaphragm, or the weight M is a columnar shape or a rhombus-shaped columnar shape, other configurations, functions, and manufacturing methods are as follows. This is substantially the same as the first embodiment.

  Further, as shown in FIG. 29, a piezoelectric layer 32 may be used as an interlayer insulating film between the internal conductor 31b and the surface conductor 50b shown in FIG. That is, the pattern of the piezoelectric layer 32 may not be divided for each of the piezoelectric elements 30a and 30c but may be a continuous pattern over all the piezoelectric elements 30a and 30c. In this case, since the second insulating layer 40 can be omitted, the beam F can be prevented from being bent by the thermal stress generated between the second insulating layer 40 and the beam F.

  The present invention can also be applied to other MEMS sensors such as a motion sensor that detects angular velocity and acceleration in addition to a vibrating gyroscope. Further, for example, the materials, dimensions, film formation methods, and pattern transfer methods shown in the above embodiment are merely examples, and descriptions of addition and deletion of processes and replacement of process orders that are obvious to those skilled in the art are omitted. Has been. Also, for example, in the above-described manufacturing process, the film composition, film forming method, film contour forming method, process sequence, etc. are appropriately selected according to the combination of film materials, film thickness, required contour shape accuracy, etc. There is no particular limitation.

FIG. 1A is a cross-sectional view according to the first embodiment of the present invention. FIG. 1B is a cross-sectional view according to the first embodiment of the present invention. FIG. 1C is a top view according to the first embodiment of the present invention. The bottom view concerning a first embodiment of the present invention. Sectional drawing concerning 1st embodiment of this invention. The simplified top view concerning a first embodiment of the present invention. FIG. 5A is a waveform diagram according to the first embodiment of the present invention. FIG. 5B is a waveform diagram according to the first embodiment of the present invention. FIG. 6A is a schematic diagram according to the first embodiment of the present invention. FIG. 6B is a schematic diagram according to the first embodiment of the present invention. FIG. 7A is a waveform diagram according to the first embodiment of the present invention. FIG. 7B is a waveform diagram according to the first embodiment of the present invention. The schematic diagram concerning 1st embodiment of this invention. FIG. 9A is a waveform diagram according to the first embodiment of the present invention. FIG. 9B is a waveform diagram according to the first embodiment of the present invention. FIG. 10A is a schematic diagram according to the first embodiment of the present invention. FIG. 10B is a waveform diagram according to the first embodiment of the present invention. FIG. 10C is a waveform diagram according to the first embodiment of the present invention. FIG. 11A is a waveform diagram according to the first embodiment of the present invention. FIG. 11B is a waveform diagram according to the first embodiment of the present invention. FIG. 12A is a schematic diagram according to the first embodiment of the present invention. FIG. 12B is a schematic diagram according to the first embodiment of the present invention. FIG. 13A is a waveform diagram according to the first embodiment of the present invention. FIG. 13B is a waveform diagram according to the first embodiment of the present invention. The schematic diagram concerning 1st embodiment of this invention. FIG. 15A is a waveform diagram according to the first embodiment of the present invention. FIG. 15B is a waveform diagram according to the first embodiment of the present invention. The schematic diagram concerning 1st embodiment of this invention. FIG. 17A is a waveform diagram according to the first embodiment of the present invention. FIG. 17B is a waveform diagram according to the first embodiment of the present invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. FIG. 21A is a sectional view according to the first embodiment of the present invention. FIG. 21B is a top view according to the first embodiment of the present invention. Sectional drawing concerning 1st embodiment of this invention. FIG. 23A is a sectional view according to the first embodiment of the present invention. FIG. 23B is a plan view according to the first embodiment of the present invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. The simplified top view concerning other embodiments of the present invention. The simplified top view concerning other embodiments of the present invention. The simplified top view concerning other embodiments of the present invention. Sectional drawing concerning other embodiment of this invention.

Explanation of symbols

1: vibrating gyroscope, 1A: sensor die, 1B: package, 10: wafer, 11: base layer, 12: etching stopper layer, 13: semiconductor layer, 20: first insulating layer, 30a: piezoelectric element for detection, 30c: Piezoelectric element for driving, 31: electrode layer, 31b: internal conductor, 32: piezoelectric layer, 33: electrode layer, 40: second insulating layer, 40b: opening, 40h: contact hole, 50: surface conductor layer, 50a: Bonding pad, 50b: surface conducting wire, 90: package base, 90a: bottom surface, 91: through electrode, 92: adhesive layer, 93: adhesive layer, 94: cover, 95: wire, 98: adhesive layer, 99: sacrificial substrate, D _1: the piezoelectric element, F: diaphragm, F: Liang, M: weight part, R1: protective film, R2: protective film, R3: protective film, S: supporting _{portion, S xz:} a piezoelectric element, _{S y:} piezoelectric element , W: laminated structure

Claims (6)

A support part;
A weight part;
A flexible part that connects the support part and the weight part and deforms as the weight part moves;
Drive means for exciting the weight at a first frequency in a direction parallel to the first axis;
Around the third axis that is orthogonal to the first axis and the second axis in relation to the displacement of the weight portion in a direction parallel to the second axis that is orthogonal to the first axis and parallel to the plane including the flexible portion Detecting means for detecting a physical quantity corresponding to the angular velocity;
With a formed die,
The first frequency is a natural frequency of displacement of the weight portion in a direction parallel to the first axis, and is a natural frequency of displacement of the weight portion in a direction parallel to the second axis. A frequency different from the frequency,
Vibrating gyroscope. The flexible portion is stretched over the support portion in a direction parallel to the first axis and in a direction parallel to the second axis, and is coupled to each other in each central region, and from two beams having different lengths. Become
The weight portion is coupled to the central region of the two beams,
The drive means is a set of piezoelectric elements arranged on the beam spanned in a direction parallel to the first axis,
The detection means is another set of piezoelectric elements arranged on the beam spanned in a direction parallel to the second axis.
The vibrating gyroscope according to claim 1. The flexible part is a diaphragm whose end fixed to the support part is elliptical, whose major axis is parallel to the first axis, and whose minor axis is parallel to the second axis,
The weight portion is coupled to a central region of the diaphragm,
The driving means is a set of piezoelectric elements arranged on the diaphragm along one of a major axis and a minor axis of the diaphragm,
The detection means is another set of piezoelectric elements arranged in the diaphragm along the other of the major axis and the minor axis of the diaphragm.
The vibrating gyroscope according to claim 1. The flexible part is a diaphragm whose end fixed to the support part is rhombus, one of the diagonal lines is parallel to the first axis, and the other of the diagonal lines is parallel to the second axis,
The weight portion is coupled to the central region of the diaphragm,
The driving means is a set of piezoelectric elements arranged on the diaphragm along one of the diagonal lines of the diaphragm,
The detection means is another set of piezoelectric elements arranged in the diaphragm along the other diagonal of the diaphragm.
The vibrating gyroscope according to claim 1. The flexible part has a rectangular end fixed to the support part, one of the long side and the short side is parallel to the first axis, and the other of the long side and the short side is parallel to the second axis. A diaphragm,
The weight portion is coupled to the central region of the diaphragm,
The driving means is a set of piezoelectric elements arranged in the diaphragm in parallel with one of the long side and the short side of the diaphragm,
The detection means is another set of piezoelectric elements arranged in the diaphragm in parallel with the other of the long side and the short side of the diaphragm.
The vibrating gyroscope according to claim 1. The weight portion has a different length in the direction of the first axis and a length in the direction of the second axis.
The vibrating gyroscope according to any one of claims 1 to 5.

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