Angular velocity sensor having multiaxial detection capability

The present invention generally relates to a microelectromechanical system (MEMS) angular velocity sensor. More specifically, the present invention relates to a MEMS angular velocity sensor having multi-axis detection capability.

Microelectromechanical system (MEMS) technology provides a way to manufacture micromechanical structures and integrates these micromechanical structures with electrical devices on a single substrate using traditional batch semiconductor processing technology. Therefore, it has won a wide and high reputation in recent years. One common use of MEMS is the design and manufacture of sensor devices. MEMS sensor devices are widely used in applications such as automotive, inertial guidance systems, home appliances, gaming devices, protection systems for various devices, and many other industrial, scientific, and engineering systems. .. One example of a MEMS sensor is a MEMS angular velocity sensor. The angular velocity sensor detects an angular velocity or motion velocity centered on one or more axes.

<p><patcit num="1"><text>U.S. Pat. No. 7,649,563</text></patcit></p>

<p num="0004"> The present invention relates to a microelectromechanical system (MEMS) angular velocity sensor.</p>

<p num="0005"> According to the first aspect of the present invention, in the angular velocity sensor, A substrate with a surface and A drive mass flexibly coupled to the substrate, the drive mass is configured to move by vibrating and rotating motion about a first axis that is substantially perpendicular to the surface of the substrate. And the drive mass has a central opening defined by the inner circumference. A coupler element provided in the central opening and suspended above the surface of the substrate. A first detection mass provided in the central opening and interconnected between the inner circumference of the drive mass and the coupler element via a first spring element. A second detection mass located in the central opening and interconnected between the inner circumference of the drive mass and the coupler element via a second spring element. The detection mass and the second detection mass are arranged on opposite sides of the second axis by the coupler element located between the first detection mass and the second detection mass. The second axis comprises a second detection mass that is substantially parallel to the surface of the substrate, and the oscillating rotational motion of the drive mass is the first spring element and A linear drive motion is applied to the first detection mass and the second detection mass via the second spring element, and the linear drive motion is the first drive substantially parallel to the second axis. The gist is the angular velocity sensor in the direction.</p><p num="0006"> According to the second aspect, in the first aspect, the coupler element via the first spring element and the second spring element, and the first detection mass and the second detection mass, respectively. By the flexible interconnection between the first detection mass and the first detection mass, the first detection mass is substantially parallel to the second axis in response to the linear drive motion. The gist is that reverse phase motion in the driving direction is possible.</p><p num="0007"> In the third aspect, in the first aspect, the first spring element and the second spring element have angular movements of the first detection mass and the second detection mass about the input axis. It is possible to vibrate with respect to a detection axis that is substantially perpendicular to the second axis in response to velocity so that the input axis is perpendicular to each of the second axis and the detection axis. It is a summary.</p><p num="0008"> According to the fourth aspect, in the third aspect, the input shaft further includes electrodes arranged on the surface of the substrate under each of the first detection mass and the second detection mass. Is substantially parallel to the surface of the substrate, and the detection axis is substantially perpendicular to the surface of the substrate.</p><p num="0009"> According to the fifth aspect, in the third aspect, a fixed electrode fixed to the substrate and a movable electrode extending from the ends of the first detection mass and the second detection mass are further provided. The gist is that the movable electrode is provided close to the fixed electrode, and the fixed electrode and the movable electrode are position-aligned with the second axis in the longitudinal direction.</p><p num="0010"> According to the sixth aspect, in the fifth aspect, the second input axis is substantially perpendicular to the surface of the substrate and the second detection axis is substantially parallel to the surface of the substrate. The gist is that.</p><p num="0011"> According to the seventh aspect, in the first aspect, A third detection mass provided in the central opening and interconnected between the inner circumference of the drive mass and the coupler element via a third spring element. A fourth detection mass provided in the central opening and interconnected between the inner circumference of the drive mass and the coupler element via a fourth spring element, the third detection mass. The detection mass and the fourth detection mass are arranged on opposite sides of the third axis by the coupler element located between the third detection mass and the fourth detection mass. The third axis is further comprising a fourth detection mass that is substantially parallel to the surface of the substrate and perpendicular to the second axis, said to the drive mass. The oscillating rotary motion imparts the linear drive motion to the third drive mass and the fourth drive mass via the third spring element and the fourth spring element, and the linear drive motion is the third drive mass. The gist is that it is applied to the third drive mass and the fourth drive mass in a second drive direction substantially parallel to the axis.</p><p num="0012"> According to the eighth aspect, in the seventh aspect, the coupler element via the third spring element and the fourth spring element, and the third detection mass and the fourth detection mass, respectively. The second drive direction of the third detection mass and the fourth detection mass substantially parallel to the third axis in response to the linear drive motion by the flexible interconnection with. The gist is that the reverse phase movement is possible.</p><p num="0013"> According to the ninth aspect, in the seventh aspect, The third spring element causes the third detection mass to vibrate with respect to a detection axis that is substantially perpendicular to the third axis in response to an angular motion velocity centered on the input axis. The input axis is perpendicular to each of the third axis and the detection axis. The gist of the fourth spring element is to enable the fourth detection mass to vibrate with respect to the detection shaft in response to an angular motion velocity centered on the input shaft.</p><p num="0014"> According to the tenth aspect, in the ninth aspect, the input shaft further includes electrodes arranged on the surface of the substrate under each of the third detection mass and the fourth detection mass. Is substantially parallel to the surface of the substrate and the sense axis is substantially perpendicular to the surface of the substrate.</p><p num="0015"> According to the eleventh aspect, in the tenth aspect, the angular velocity is the first angular velocity, the input shaft is the first input shaft, and the electrode is the first electrode. The angular velocity sensor further includes a second electrode arranged on the surface of the substrate under each of the first detection mass and the second detection mass, the first spring element and the first spring element. The spring element 2 is such that the first detection mass and the second detection mass vibrate with respect to the detection axis in response to the second angular velocity around the second input axis. The gist is that the second input axis is substantially parallel to the surface of the substrate and the second input axis is perpendicular to each of the first input axis and the sense axis. And.</p><p num="0016"> According to the twelfth aspect, in the eleventh aspect, the detection axis is the first detection axis, and the angular velocity sensor is the angular velocity sensor. The first movable electrode extending from the end of the first detection mass and the second detection mass, and the first fixed electrode fixed to the substrate, the first fixed electrode is The first movable electrode and the first movable electrode are provided close to the first movable electrode, and the first movable electrode and the first fixed electrode are positioned in the longitudinal direction with the second axis. Fixed electrode and A second movable electrode extending from the end of the third detection mass and the fourth detection mass, and a second fixed electrode fixed to the substrate, the second fixed electrode is The second movable electrode and the second fixed electrode are provided close to the second movable electrode, and the second movable electrode and the second fixed electrode are positioned in the longitudinal direction with the third axis. Further equipped with fixed electrodes, In the first spring element and the second spring element, the first detection mass and the second detection mass respond to a third angular motion velocity centered on a third input axis. It is possible to vibrate with respect to the detection axis of 2, the third input axis is substantially perpendicular to the surface of the substrate, and the second sense axis is substantially perpendicular to the surface of the substrate. Parallel and In the third spring element and the fourth spring element, the third detection mass and the fourth detection mass respond to the third angular motion velocity centered on the third input axis. The third sense axis is substantially parallel to the surface of the substrate and substantially perpendicular to the second detection axis. Is the gist.</p><p num="0017"> According to the thirteenth aspect, in the ninth aspect, a fixed electrode fixed to the substrate and a movable electrode extending from the ends of the third detection mass and the fourth detection mass are further provided. The movable electrode is located close to the fixed electrode, the fixed electrode and the movable electrode are positioned in the longitudinal direction with the third axis, and the input shaft is substantially aligned with the surface of the substrate. It is gist that the detection axis is vertical and substantially parallel to the surface of the substrate.</p><p num="0018"> According to a fourteenth aspect, in a method for manufacturing a microelectromechanical system (MEMS) angular velocity sensor. In the step of forming a drive mass that is flexibly coupled to the substrate and is capable of oscillating and rotating around a first axis that is substantially perpendicular to the surface of the substrate. The drive mass is a step of forming the drive mass, including a central opening defined by the inner circumference. A step of forming a coupler element suspended above the surface of the substrate in the central opening. A step of forming a first detection mass, a second detection mass, a third detection mass, and a fourth detection mass in the central opening. A step of forming a first spring element between the first detection mass and the inner circumference of the drive mass portion, and between the first detection mass and the coupler element. A step of forming a second spring element between the second detection mass and the inner circumference of the drive mass, and between the second detection mass and the coupler element. The first detection mass and the second detection mass are arranged on opposite sides of the second axis by the coupler element located between the first detection mass and the second detection mass. The second axis is substantially parallel to the surface of the substrate, and the first detection mass and the second detection mass respond to the vibration-rotational motion of the first detection mass. It is possible to receive a linear drive motion through the spring element and the second spring element, the linear drive motion being in a first drive direction substantially parallel to the second axis. The steps to form the second spring element, A step of forming a third spring element between the third detection mass and the inner circumference of the drive mass, and between the third detection mass and the coupler element. A step of forming a fourth spring element between the fourth detection mass and the inner circumference of the drive mass, and between the fourth detection mass and the coupler element. The third detection mass and the fourth detection mass are arranged on opposite sides of the third axis by the coupler element located between the third detection mass and the fourth detection mass. The third axis is substantially parallel to the surface of the substrate and is oriented perpendicular to the second axis, and the third detection mass and the fourth detection mass are the same. It is possible to receive the linear drive motion through the third spring element and the fourth spring element in response to the oscillating rotary motion, and the linear drive motion is substantially on the third axis. It is a gist to include a step of forming a fourth detection mass, which is given to the third drive mass and the fourth drive mass in a second drive direction parallel to each other.</p><p num="0019"> According to the fifteenth aspect, in the fourteenth aspect, A step of forming a first electrode on the surface of the substrate under each of the first detection mass and the second detection mass. A step of forming a second electrode on the surface of the substrate under each of the third detection mass and the fourth detection mass is further provided. The first spring element and the second spring element are centered on a first input axis in which the first detection mass and the second detection mass are substantially parallel to the third axis. It is possible to vibrate with respect to a detection axis perpendicular to the surface of the substrate in response to the angular motion velocity. The third spring element and the fourth spring element are centered on a second input axis in which the third detection mass and the fourth detection mass are substantially parallel to the second axis. The gist is to make it possible to vibrate with respect to the sense axis in response to the angular motion velocity.</p><p num="0020"> According to the sixteenth aspect, in the fifteenth aspect, A step of forming a first movable electrode extending from the ends of the first detection mass and the second detection mass, and In the step of forming the first fixed electrode fixed to the substrate, the first fixed electrode is provided close to the first movable electrode, and the first movable electrode and the first movable electrode are provided. The fixed electrode of is aligned in the longitudinal direction with the second axis, and the step of forming, A step of forming a second movable electrode extending from the ends of the third detection mass and the fourth detection mass, and In the step of forming the second fixed electrode fixed to the substrate, the second fixed electrode is provided close to the second movable electrode, and the second movable electrode and the second movable electrode are provided. The fixed electrode of is further provided with a forming step that is longitudinally aligned with the third axis. The first spring element and the second spring element are centered on a third input axis in which the first detection mass and the second detection mass are substantially perpendicular to the surface of the substrate. It is possible to vibrate with respect to the second sense axis in response to the angular motion velocity, and the second sense axis is substantially parallel to the surface of the substrate. In the third spring element and the fourth spring element, the third detection mass and the fourth detection mass respond to the angular motion velocity centered on the third input axis by the third detection mass. It is a gist that the third sense axis is substantially perpendicular to the second sense axis.</p><p num="0021"> According to the seventeenth aspect, in the angular velocity sensor, A substrate with a surface and A drive mass flexibly coupled to the substrate, the drive mass is configured to move by vibrating and rotating motion about a first axis that is substantially perpendicular to the surface of the substrate. And the drive mass has a central opening defined by the inner circumference. With a coupler element located within the central opening and suspended above the surface of the substrate. A first detection mass located in the central opening and interconnected between the inner circumference of the drive mass and the coupler element via a first spring element. A second detection mass located in the central opening and interconnected between the inner circumference of the drive mass and the coupler element via a second spring element. The detection mass and the second detection mass are arranged on opposite sides of the second axis by the coupler element located between the first detection mass and the second detection mass. A second detection mass, wherein the second axis is substantially parallel to the surface of the substrate. A first electrode arranged on the surface of the substrate under each of the first detection mass and the second detection mass, and The first fixed electrode fixed to the substrate, and the first movable electrode extending from the ends of the first detection mass and the second detection mass, the first movable electrode is The first fixed electrode and the first movable electrode are provided close to the first fixed electrode, and the first fixed electrode and the first movable electrode are positioned in the longitudinal direction with the second axis. Equipped with movable electrodes The vibration-rotational motion of the drive mass imparts a linear drive motion to the first detection mass and the second detection mass via the first spring element and the second spring element, and the linear drive is performed. The motion is in the first drive direction substantially parallel to the second axis. In the first spring element and the second spring element, the first detection mass and the second detection mass are detected by the first detection mass in response to the angular motion velocity centered on the first input axis. The first detection axis is substantially perpendicular to the surface of the substrate and the first input axis is substantially parallel to the surface of the substrate, allowing it to vibrate with respect to the axis. , Substantially perpendicular to the second axis, In the first spring element and the second spring element, the first detection mass and the second detection mass have a second detection mass in response to the angular velocity around the second input axis. Allowing vibration with respect to the sense axis, the second sense axis is substantially parallel to the surface of the substrate and the second input axis is substantially perpendicular to the surface of the substrate. The gist is a certain angular velocity sensor.</p><p num="0022"> According to the eighteenth aspect, in the seventeenth aspect, A third detection mass located in the central opening and interconnected between the inner circumference of the drive mass and the coupler element via a third spring element. A fourth detection mass located in the central opening and interconnected between the inner circumference of the drive mass and the coupler element via a fourth spring element. The detection mass and the fourth detection mass are arranged on opposite sides of the third axis by the coupler element located between the third detection mass and the fourth detection mass. A fourth detection mass, the third axis of which is substantially parallel to the surface of the substrate and oriented perpendicular to the second axis. A second electrode disposed on the surface of the substrate under each of the third detection mass and the fourth detection mass is further provided. The vibration rotation motion of the drive mass imparts the linear drive motion to the third drive mass and the fourth drive mass via the third spring element and the fourth spring element, and the linear drive motion is applied. Is given to the third drive mass and the fourth drive mass in a second drive direction substantially parallel to the third axis. In the third spring element and the fourth spring element, the first detection mass and the fourth detection mass respond to the angular motion velocity centered on the third input axis. The gist is that the third input shaft is substantially parallel to the surface of the substrate and substantially perpendicular to the third axis. ..</p><p num="0023"> According to the nineteenth aspect, in the eighteenth aspect, The second fixed electrode fixed to the substrate, and the second movable electrode extending from the ends of the third detection mass and the fourth detection mass, the second movable electrode is The second fixed electrode and the second movable electrode are provided in close proximity to the second fixed electrode, and the second fixed electrode and the second movable electrode are positioned in the longitudinal direction with the third axis. With more movable electrodes In the third spring element and the fourth spring element, the third detection mass and the fourth detection mass respond to the angular motion velocity centered on the second input axis. It is possible to vibrate with respect to the two sense axes, the second sense axis is substantially parallel to the surface of the substrate, and the second input shaft is substantially parallel to the surface of the substrate. The gist is that it is vertical.</p><p num="0024"> According to the twentieth aspect, in the eighteenth aspect, The first by the flexible interconnection of the coupler element via the first spring element and the second spring element with each of the first detection mass and the second detection mass. It is possible to move the detection mass and the second detection mass in the first drive direction substantially parallel to the second axis in response to the linear drive motion. The third detection by the flexible interconnection of the coupler element via the third spring element and the fourth spring element with each of the third detection mass and the fourth detection mass. It is a gist that the reverse phase motion of the use mass and the fourth detection mass in the second drive direction substantially parallel to the third axis in response to the linear drive motion is possible.</p>

<figref num="1">Top view of a microelectromechanical system (MEMS) angular velocity sensor having multi-axis detection capability according to one embodiment.</figref><figref num="2">FIG. 2 is a cross-sectional view of the angular velocity sensor along the cutting line 2-2 of FIG.</figref><figref num="3">FIG. 3 is a cross-sectional view of the angular velocity sensor along the cutting line 3-3 of FIG.</figref><figref num="4">Top view of the angular velocity sensor showing the operation of the sensor receiving the X-axis angular velocity and the Y-axis angular velocity.</figref><figref num="5">A cross-sectional view of a part of an angular velocity sensor showing a detection motion of a pair of detection masses of a sensor that has received an X-axis angular velocity.</figref><figref num="6">A cross-sectional view of a part of an angular velocity sensor showing a detection motion of another detection mass pair of a sensor that has received a Y-axis angular velocity.</figref><figref num="7">Top view of the angular velocity sensor showing the operation of the sensor receiving the Z-axis angular velocity.</figref>

The present invention can be understood more completely by referring to the detailed description and claims in combination with the accompanying drawings. In these drawings, similar reference numerals generally indicate similar items, and the drawings are not necessarily drawn in proportion to the actual size.

Detection of angular velocity can be performed using an angular velocity sensor. Angular velocity sensors generally function by driving the sensor to make a first motion and measuring the second motion of the sensor in response to both the first motion and the angular velocity to be detected. Capacitance sensing MEMS device designs for angular velocity sensors are in terms of operation in small devices due to their low temperature sensitivity, small size, and low cost mass production suitability. Suitable.

As the use of MEMS angular velocity sensors continues to grow and diversify, more and more emphasis is placed on the development of devices capable of detecting angular velocity around multiple axes of rotation. In addition, more and more emphasis is being placed on how to make MEMS angular velocity sensors that achieve multi-axis detection capability without increasing manufacturing cost and complexity and without sacrificing component performance. These efforts are driven primarily by existing and future high capacity applications in automotive, medical, commercial and consumer products.

An embodiment disclosed herein is, for example, a microelectromechanical system in the form of an angular velocity sensor having a single drive mass and a plurality of distributed detection masses provided within the central opening of the drive mass. Brings a MEMS) device. The drive mass may be connected to the underlying substrate via a spring-fixed structure, which allows the drive mass to rotate about the Z-axis under electrostatic stimulation, which is the drive motion. Is. By using a single drive mass, it is possible to implement a single drive frequency, which simplifies the drive circuit and reduces crosstalk. The detection mass may be coupled to the drive mass by a spring element, whereby the oscillating and rotational motion of the drive mass imparts a linear drive motion to the detection mass. In addition, the detection cells may be coupled to each other via a central coupler to ensure that the detection cells of each detection mass pair are moving 180 degrees out of phase with each other. .. The dispersed detection masses form two detection mass pairs, one pair detects the angular velocities of the X-axis and the Z-axis, and the other pair detects the angular velocities of the Y-axis and the Z-axis. These features can enable multi-axis detection capability, more efficient wafer area utilization, and low cost mass production.

FIG. 1 shows a top view of a microelectromechanical system (MEMS) angular velocity sensor 20 having a multi-axis detection capability according to one embodiment. The angular velocity sensor has a substrate 22 and a drive mass 24 that is flexibly coupled to the surface 26 of the substrate 22 by a plurality of spring fixing structures 28. In one embodiment, the drive mass 24 is a substantially circular or disk-shaped structure having a central opening 30 penetrating the drive mass 24, the opening being defined or surrounded by an inner circumference 32. The spring fixing structure 28 is provided in the central opening 30. In addition, the coupler element 34 is deployed within the central opening 30 and is approximately central within the central opening. In one embodiment, the coupler element 34 is suspended above the surface 26 of the substrate 22. Although the drive mass 24 is shown to be circular, the drive mass 24 may be any closed polygon in an alternative embodiment.

A plurality of dispersed detection masses 36, 38, 40, 42 are also provided in the central opening 34. In one embodiment, the detection mass 36, which is hereinafter referred to as the "first detection mass" 36 in the present specification, includes the inner circumference 32 of the drive mass 24 and the coupler element 34 via the first spring element 44. Are interconnected between. Similarly, the detection mass 38, which is hereinafter referred to as the "second detection mass" 38 in the present specification, is placed between the inner circumference 32 of the drive mass 24 and the coupler element 34 via the second spring element 46. It is interconnected. The detection mass 40, which is hereinafter referred to as the "third detection mass" 40 in the present specification, is interconnected between the inner circumference 32 of the drive mass 24 and the coupler element 34 via the third spring element 48. ing. Then, the detection mass 42, which is hereinafter referred to as the "fourth detection mass" 42 in the present specification, is mutually connected between the inner circumference 32 of the drive mass 24 and the coupler element 34 via the fourth spring element 50. It is connected.

To distinguish the various elements manufactured within the structural layer of the angular velocity sensor 20, the drive mass 24 is shown using narrow shading in the upward-sloping direction, and the coupler element 34 uses a dark stippling pattern. The first detection cell 36 and the second detection cell 38 are shown using wide shading in the upward-sloping direction, and the third detection cell 40 and the fourth detection cell 38 are shown. 42 is shown using wide shading in the downward-sloping direction. These various elements can be generated using current and near future surface micromachining techniques such as deposition, patterning, and etching. Thus, although various shading and / or shading is utilized in the illustration, the various elements within the structural layer can generally be formed from the same material, such as polysilicon, single crystal silicon. In addition, the terms "first," "second," "third," "fourth," etc. used herein refer to the ordering of elements within a series of counted elements. Or it does not refer to prioritization. Instead, the terms "first," "second," "third," and "fourth" are used to distinguish specific elements for clarity of explanation. ..

The element of the angular velocity sensor 20 is "attached to", "attached to", "bonded to", "connected to", or "interconnected with" the other elements of the angular velocity sensor 20. It may be described in various ways as a thing. However, it is understood that these terms refer to the direct or indirect physical connections of certain elements of the angular velocity sensor 20 that occur during their formation through the patterning and etching steps of MEMS fabrication. I want to.

In one embodiment, the drive system 52 includes a plurality of driven arms 54 that extend outward in the radial direction from the drive mass 24 and are separated at equal angular distances. The drive system 52 further includes a plurality of drive arms 56, 58 fixed to the surface 26 of the substrate 22. The drive arms 56 and 58 are arranged on opposite sides of the respective driven arms 54. Each driven arm 54 holds several electrodes 60 that extend to either side of the driven arm 54 in a direction perpendicular to the driven arm 54. Similarly, each of the drive arms 56 and 58 points to the respective driven arm 54 and holds an electrode 62 that extends in an alternating arrangement with the electrode 60.

The drive system 52 further includes a drive circuit (not shown) that may be included in an application specific integrated circuit (ASIC) 63 that is configured to apply a voltage to the electrodes 62. The spring-fixed structure 28 allows the drive mass 24 to be electrostatically stimulated to rotate about a first shaft 64, commonly referred to as the drive shaft, at a given frequency. Therefore, the drive system 52 generates an oscillating rotational motion of the drive mass 24 about a first shaft 64, which is generally called a drive shaft, at a given frequency. In an alternative embodiment, the drive system may be located within the central opening 30 of the drive mass 24, and / or the drive system may have more or less arms and electrodes than shown. It may be included.

In an exemplary embodiment, the first axis, i.e. the drive axis, is the Z axis in the three-dimensional coordinate system. Therefore, the drive shaft is referred to as the Z-axis 64 in the present specification. In a three-dimensional coordinate system, the second axis is referred to herein as the Y-axis 66 and the third axis is referred to herein as the X-axis 68. Therefore, the angular velocity sensor 20 is shown to have a generally flat structure in the XY plane 70, with the X-axis 68 and the Y-axis 66 being substantially parallel to the surface 26 of the substrate 22 and the Z-axis. 64 extends out of the paper, perpendicular to the XY plane 70. It should be visible in the drawings that the terms "first", "second", and "third" are paired with the Z-axis 64, the Y-axis 66, and the X-axis 68, respectively. Again, the terms "first," "second," and "third" do not refer to axis ordering or prioritization. Instead, the terms "first," "second," and "third" are used to clarify and provide association with similar terms used in the claims, respectively. It is shown in the drawing as a pair with the axis of.

In one embodiment, the first detection mass 36 and the second detection mass 38 are on the Y-axis 66, i.e., the second, respectively, by means of a coupler element 34 provided between the detection masses 36 and 38, respectively. It is deployed on both sides of the axis facing each other. Similarly, the third detection mass 40 and the fourth detection mass 42 have their X-axis 68, that is, the third axis, respectively, due to the coupler element 34 provided between the detection mass 40 and 42, respectively. It is deployed on both sides of the opposite side. As will be described in more detail below, the first detection mass 36 and the second detection mass 38 pick up the angular motion velocity around the two input axes, namely the X-axis 68 and the Z-axis 64. That is, it is used for detection. In addition, the third detection mass 40 and the fourth detection mass 42 pick up, or detect, the angular motion velocity around the two input axes, namely the Y-axis 66 and the Z-axis 64. used. Therefore, the angular velocity sensor 20 may be regarded as a triaxial angular velocity sensor.

In order to detect the angular velocity around the Z-axis 64, the angular velocity sensor 20 comprises a fixed electrode 72 (shown using a thin stippling pattern) fixed to the surface 26 of the substrate 22. .. The angular velocity sensor 20 further includes a movable electrode 74 extending from each end 76 of each of the detection masses 36, 38, 40, 42, and the movable electrode 74 is arranged alternately with the fixed electrode 72. As shown, the fixed electrode 72 and the movable electrode 74 extending from each of the first detection mass 36 and the second detection mass 38 are the Y-axis 66 (that is, the three-dimensional coordinate system described herein). Aligned (ie, parallel) in the longitudinal direction with the second axis in. On the contrary, the fixed electrode 72 and the movable electrode 74 extending from each of the third detection mass 40 and the fourth detection mass 42, respectively, are in the X-axis 68 (that is, in the three-dimensional coordinate system described in the present specification). It is longitudinally aligned (ie, parallel) with the third axis). The detection of the angular motion velocity centered on the Z-axis 64 will be described in relation to FIG.

Referring to FIG. 2 in relation to FIG. 1, FIG. 2 shows a side view of the angular velocity sensor 20 along the cutting line 2-2 of FIG. In order to detect the angular velocity around the X-axis 68, the angular velocity sensors 20 are arranged on the surface 26 of the substrate 22 under the first detection mass 36 and the second detection mass 38, respectively. Includes electrodes 78,80. As shown below, the angular motion velocity around the X-axis 68 is detected along the sense axis which is substantially perpendicular to the surface 26 of the substrate 22. This sense axis is the Z axis 64 (ie, the first axis in the three-dimensional coordinate system described herein). Only two electrodes 78, 80 are shown for simplicity of illustration. Those skilled in the art will appreciate that a plurality of electrodes may be arranged in various configurations under each of the first detection mass 36 and the second detection mass 38 on opposite sides of the X-axis 68. Let's do it.

Referring to FIG. 3 in relation to FIG. 1, FIG. 3 shows a side view of the angular velocity sensor 20 along the cutting line 3-3 of FIG. In order to detect the angular velocity around the Y-axis 66, the angular velocity sensor 20 is arranged on the surface 26 of the substrate 22 under the third detection mass 40 and the fourth detection mass 42, respectively. The electrodes 82 and 84 are included. As shown below, the angular motion velocity around the Y-axis 66 is detected along the sense axis that is substantially perpendicular to the surface 26 of the substrate 22. This sense axis is the Z axis 64 (ie, the first axis in the three-dimensional coordinate system described herein). Only two electrodes 82, 84 are shown for simplicity of illustration. Those skilled in the art will appreciate that a plurality of electrodes may be arranged in various configurations under each of the third detection mass 40 and the fourth detection mass 42 on opposite sides of the Y-axis 66. Let's do it.

The method of making the angular velocity sensor 20 is generally a first axis that is flexibly coupled to the surface 26 of the substrate 22 via a spring fixing structure 28 and is substantially perpendicular to the surface 26 of the substrate 22. That is, it includes a step of forming a drive mass 24 that can be moved by oscillating rotational motion about the Z axis 64, and the drive mass 24 includes a central opening 30 defined by an inner circumference 32. The method includes a step of forming a coupler element 34 suspended on the surface 26 of the substrate 22 in the central opening 30, a first detection mass 36 in the central opening 30, and a second detection. A step of forming a use mass 38, a third detection mass 40, and a fourth detection mass 42 is further provided. A further step of the fabrication method is for the first detection between the inner circumference 32 of the drive mass 24 and the coupler element 34 via the first spring element 44 at the positions relative to the Y-axis 66 and the X-axis 68 described above. The step of interconnecting the mass 36, the step of interconnecting the second detection mass 36 between the inner circumference 32 of the drive mass 24 and the coupler element 34 via the second spring element 46, and the first step. The step of interconnecting the third detection mass 40 between the inner circumference 32 of the drive mass 24 and the coupler element 34 via the spring element 48 of the drive mass 24, and the drive mass 24 via the fourth spring element 50. It includes a step of interconnecting a fourth detection mass 42 between the inner circumference 32 and the coupler element 34. In addition, electrodes 78, 80, 82, 84 and fixed electrodes 72 are formed on the surface 26 of the substrate 22, and movable electrodes 74 extending from the ends 76 of the detection masses 36, 38, 40, 42 are formed. ..

Fabrication of the angular velocity sensor 20 with its various components may be performed using any suitable known or future fabrication process. For example, the fabrication process implements a silicon micromachining fabrication process that results in structural and sacrificial layers that are properly deposited, patterned, and etched to produce the suspended structure of the angular velocity sensor.

FIG. 4 shows the X-axis angle motion velocity 86, Ω._XAnd Y-axis angle motion speed 88, Ω_YThe top view of the angular velocity sensor 20 which shows the operation of the received sensor 20 is shown. During operation, the oscillator circuit (not shown) of the drive system 52 locks into the drive resonance of the angular velocity sensor 20, whereby the angular velocity sensor 20 operates at its single drive frequency. That is, the drive mass 24 is subjected to the oscillating rotary motion represented by the double-headed curved arrow 90. The oscillating rotary motion 90 of the drive mass 24 is detected by the first detection in the Y-axis 66, that is, in the drive direction substantially parallel to the second axis, via the first spring element 44 and the second spring element 46, respectively. The linear driving motion represented by the straight arrow 92 is applied to the use mass 36 and the second detection mass 38. In addition, the oscillating rotary motion 90 of the drive mass 24 is located in the X-axis 68, i.e., in the drive direction substantially parallel to the third axis, via the third spring element 48 and the fourth spring element 50, respectively. The linear driving motion represented by the straight line arrow 94 is applied to the detection mass 40 and the fourth detection mass 42 of No. 3.

The spring fixing structure 28 is appropriately configured so that the drive mass 24 receives an electrostatic stimulus from the drive system 52 and rotates about the Z axis 64. In one embodiment, the spring elements 44, 46, 48, 50 are centered on the Z-axis 64 to have a strong coupling between the drive mass 24 and the respective detection masses 36, 38, 40, 42. It is rigid against in-plane rotation, that is, it withstands it. Due to the interconnection of the spring elements 44 and 46 via the coupler element 34, the first detection mass 36 and the second detection mass 38 are linearly out of phase with each other, that is, 180 degrees out of phase with each other. It becomes possible to receive the driving motion 92 (indicated by the opposite arrow). Similarly, by interconnecting the spring elements 48 and 50 via the coupler element 34, the third detection mass 40 and the fourth detection mass 42, respectively, have a linear drive motion 94 (opposite) in opposite phase to each other. It will be possible to receive (indicated by the pointing arrow).

Referring to FIG. 5 in connection with FIG. 4, FIG. 5 shows the detection motion 96 of the first detection mass 36 and the second detection mass 38 of the sensor 20 that received the X-axis angular velocity 86. , A side view of a part of the angular velocity sensor 20 (viewed from line 5-5 in FIG. 4) is shown. The coupler elements 34 and the spring elements 44, 46 are configured such that they withstand translations in and out of the XY plane 70, but follow rotational motion about the X-axis 68. In one embodiment of the angular velocity sensor 20, Kz may be defined as the out-of-plane stiffness of the spring elements 44,46 and Krx may be defined as the torsional spring constant about the X-axis 68. The spring elements 44 and 46 may be appropriately configured so that the out-of-plane rigidity Kz is larger than the torsional spring constant Krx. Therefore, the coupler element 34 tends to rotate about the X-axis 68 instead of translating in and out of the plane 70 in response to the X-axis angular velocity 86. When the coupler element 34 rotates about the X-axis 68, the coupler element 34 forces the first detection mass 36 and the second detection mass 38 to each other in response to the X-axis angular velocity 86. On the other hand, it swings in the opposite phase, that is, in a state where the phase is 180 degrees out of phase.

In this way, the spring elements 44 and 46, together with the coupler element 34, are driven by the first detection mass 36 and the second detection mass 38 in response to the X-axis angular motion velocity 86 centered on the input axis. It is possible to vibrate with respect to the axis, i.e. the detection axis perpendicular to the Y axis 66, i.e. the Z axis 64, where the input axis is the X axis 68. That is, the input X-axis velocity 86 produces Coriolis forces on the first detection mass 36 and the second detection mass 38, whereby they are in opposite phase in and out of the plane. It turns, that is, it swings around the X-axis 68. Therefore, in a known manner for determining the X-axis angular velocity 86, between the first detection mass 36 and the electrodes (s) 78 below it, and the second detection mass. The X-axis angular velocity information can be acquired and output by the ASIC 63 (FIG. 1) by detecting the differential capacitance change between the 38 and the electrodes (s) 80 below it.

Referring to FIG. 6 in connection with FIG. 4, FIG. 6 shows the detection motion 98 of the third detection mass 40 and the fourth detection mass 42 of the sensor 20 that received the Y-axis angular velocity 88. , A side view of a part of the angular velocity sensor 20 (visible from line 6-6 in FIG. 4) is shown. The coupler elements 34 and the spring elements 48 and 50 are configured such that they withstand translations in and out of the XY plane 70, but follow rotational motion about the Y axis 66. In one embodiment of the angular velocity sensor 20, the spring elements 48, 50 may be appropriately configured such that their out-of-plane stiffness Kz is greater than their torsional spring constant Kry about the Y-axis 66. Therefore, the coupler element 34 additionally tends to receive the Y-axis angular velocity 88 and rotate about the Y-axis 66 instead of translating in and out of the plane 70. When the coupler element 34 rotates about the Y-axis 66, the coupler element 34 forces the third detection mass 40 and the fourth detection mass 42 to each other in response to the Y-axis angle motion velocity 88. On the other hand, the motion is made to move in the opposite phase, that is, in a state of being 180 degrees out of phase.

In this way, the spring elements 48 and 50, together with the coupler element 34, are driven by the third detection mass 40 and the fourth detection mass 42 in response to the Y-axis angle motion speed 88 centered on the input axis. It is possible to vibrate with respect to the axis, i.e. the sense axis perpendicular to the X axis 68, i.e. the Z axis 64, where the input axis is the Y axis 66. That is, the input Y-axis angular velocity 88 produces Coriolis forces on the third detection mass 40 and the fourth detection mass 42, whereby they are in opposite phase in and out of the plane. It turns, that is, it swings around the Y-axis 66. Therefore, in a known manner for determining the Y-axis angular velocity 88, between the third detection mass 40 and the electrodes below it (s) and the fourth detection mass 42. The Y-axis angular velocity information can be acquired and output by the ASIC 63 (FIG. 1) by detecting the difference capacitance change between and the electrodes (s) 84 below it. In an alternative embodiment, the displacement of the detection masses 36, 38, 40, 42 may be detected using a technique different from the differential capacitance, such as detecting magnetic force.

FIG. 7 shows a top view of the angular velocity sensor 20 showing the operation of the sensor 20 that has received the Z-axis angular velocity 100. The spring elements 44, 46, 48, 50 are further configured so that they are flexible in the radial direction. That is, the spring elements 44 and 46 are flexible in a direction substantially parallel to the X-axis 68, and the spring elements 48 and 50 are flexible in a direction substantially parallel to the Y-axis 66. That is, the input Z-axis angle motion velocity 100 generates a Coriolis force with respect to the first detection mass 36 and the second detection mass 38, and the Coriolis force is substantially parallel to the X-axis 68. The detection motions represented by the arrows 102 are applied to the detection masses 36 and 38 in the direction of. However, the first detection mass 36 and the second detection mass 38 vibrate in opposite phases, that is, in opposite directions (indicated by arrows pointing in opposite directions of the detection motion 102). Similarly, the input Z-axis angle motion velocity 100 generates a Coriolis force on the third detection mass 40 and the fourth detection mass 42, and the Coriolis force is substantially on the Y-axis 66. The detection motion represented by the arrow 104 is applied in the direction parallel to each other. However, the third detection mass 40 and the fourth detection mass 42 vibrate in opposite phases, that is, in opposite directions (indicated by arrows pointing in opposite directions of the detection motion 104).

Therefore, in order to obtain the Z-axis angular velocity 100, between the fixed electrode 72 and the movable electrode 74 along the end 76 of the detection masses 36 and 38, the end of the fixed electrode 72 and the detection masses 40 and 42 By detecting the difference capacitance change between the movable electrode 74 and the movable electrode 74 along the 76, the Z-axis angular velocity information can be acquired and output by the ASIC 63 (FIG. 1). For example, by subtracting the capacitive signals detected between the electrodes 72 and 74 of the detection masses 36 and 38 from each other, the Coriolis contribution and therefore the angular velocity around the input axis, i.e. the Z axis 64, is measured. It is possible to do. Similarly, by subtracting the capacitive signals detected between the electrodes 72 and 74 of the detection masses 40 and 42 from each other, the Coriolis contribution, and therefore the angular velocity around the input axis, i.e. the Z axis 64, is determined. It is possible to measure. After that, the Z-axis angular velocity information can be acquired by appropriately combining the respective capacitance signals. The measured values from the four detection masses 36, 38, 40, 42 are used here to acquire the Z-axis angular velocity information. However, in an alternative embodiment, the Z-axis angular velocity information may be obtained using two detection masses facing each other, for example, detection masses 36, 38, or detection masses 40, 42.

Each of the detection masses 36, 38, 40, 42 can receive a driving motion, that is, a centripetal force caused by the oscillating rotary motion 90. This centripetal force can be expressed by the following equation.

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The Coriolis force is expressed by the following equation.

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In the formula, Φ_dIs the drive amplitude, ω_dIs the drive frequency, R is the radius of the drive mass 24, and Ω_dIs the angular velocity. Therefore, the centripetal force F_cenHas two components. These two components are the DC component and the drive frequency ω._dContains ingredients that are twice as much as. That is, the centripetal force appears at DC (zero frequency) and at twice the drive frequency. This centripetal force can be filtered out, or suppressed, by a low-pass filter without affecting the Coriolis force.

However, if the centripetal force is too great, this can saturate the ASIC front end. The ratio between the centripetal force and the Coriolis force is as follows.

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In an example where the drive amplitude is 5 micrometers (microns), the radius of the drive disk is 1 millimeter, the drive frequency is 10 kHz, and the angular velocity is the maximum measurement limit of 1600 dps, this has the following ratio: Generate.

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This ratio can be managed by the ASIC 63 by properly designing the dynamic range of the ASIC 63. The effect of centripetal force can be further suppressed by the dynamics of the sense oscillator. When the angular velocity sensor 20 is operated in mode matching, i.e., when the two resonance modes (drive and detection) have the same resonance frequency, the response from the Coriolis force is further amplified by the Q value of the sense oscillator. Q can be 200 or more. This means that the ratio of centripetal force to Coriolis force can be further reduced. Therefore, the centripetal force (acceleration) can be efficiently suppressed by the dynamics of the sense oscillator and the circuit trimming (filtering), if necessary.

In summary, embodiments disclosed herein are microscopic in the form of an angular velocity sensor that includes, for example, a single drive mass and four dispersed detection masses located within the central opening of the drive mass. Brings electromechanical system (MEMS) devices. The drive mass is connected to the underlying substrate via a spring-fixed structure, which allows the drive mass to rotate about the Z-axis under electrostatic stimulation, which is the drive motion. By using a single drive mass, it is possible to implement a single drive frequency, which simplifies the drive circuit and reduces crosstalk. The detection mass is coupled to the drive mass by a spring element, which causes the detection mass to linearly drive as a result of the oscillating and rotational motion of the drive mass. The dispersed detection masses form two detection mass pairs, one pair detects the angular velocities of the X-axis and the Z-axis, and the other pair detects the angular velocities of the Y-axis and the Z-axis. In addition, the detection cells are coupled to each other via a central coupler to ensure that each pair of detection cells is moving 180 degrees out of phase with each other. These features can enable multi-axis detection capability, more efficient use of die area, and suitability for low cost mass production.

Although preferred embodiments of the present invention have been exemplified and described in detail, those skilled in the art will be able to make various modifications thereof without departing from the spirit of the present invention or the appended claims. Will be easily apparent. That is, it should be understood that the exemplary embodiments are merely examples and are not intended to limit the scope, applicability or configuration of the invention. For example, the features presented above may be adapted for biaxial detection of X-axis and Y-axis, X-axis and Z-axis, or angular motion velocity centered on Y-axis and Z-axis. In addition, the features presented above may be adapted to include five or more dispersion detection cells.

20 ... angular velocity sensor, 22 ... substrate, 24 ... drive mass, 28 ... spring element 30 ... center opening, 34 ... coupler element, 36 ... first detection mass, 38 ... second detection mass.