Anchoring structure for reducing temperature-based errors

Abstract

This invention relates to microelectromechanical systems (MEMS), and more particularly to anchoring structures for anchoring MEMS components within a MEMS device. The anchoring points of the rotor and stator components of the device are arranged such that the anchoring points are arranged along a common axis and overlap with the common axis.

Description

Technical Field

[0001] The present invention relates to microelectromechanical systems (MEMS), and more particularly to anchoring structures for anchoring MEMS components within a MEMS device. Background Technology

[0002] In MEMS devices, the motion of components within the device can be measured to facilitate the measurement of external quantities, such as acceleration or rotation. For example, in a MEMS accelerometer, a detection mass, relatively free to move along at least one axis, moves relative to a fixed component of the accelerometer under external acceleration. The motion of the mass is measured capacitively using one or more movable electrodes located on the mass and one or more fixed electrodes located on a fixed structure within the accelerometer. The fixed and movable electrodes form one or more capacitors, the capacitance of which changes as the detection mass moves relative to the fixed structure.

[0003] To accurately measure acceleration, the motion of the fixed structure due to external acceleration must be minimized. Therefore, the fixed structure is anchored to the MEMS device at one or more anchor points, such as to the device's substrate. However, as the MEMS device experiences temperature changes, the relative positions of the fixed and movable electrodes may change due to expansion or contraction within the device itself. Therefore, it is desirable to minimize the errors introduced into measurements by MEMS accelerometers and other devices due to temperature variations. Summary of the Invention

[0004] According to a first aspect of the present invention, a MEMS device is provided, the MEMS device comprising: a substrate defining a substrate plane; a rotor mounted to the substrate via rotor anchor points, wherein the rotor is rotatable relative to the substrate plane; and two stators, wherein each stator is positioned relative to the substrate plane and mounted to the substrate via stator anchor points. The rotor anchor points and stator anchor points are arranged such that all anchor points overlap with a common axis.

[0005] The rotor anchor point and the stator anchor point can have the same width, and the rotor anchor point and the stator anchor point can be aligned along a common axis.

[0006] The rotor anchor point and stator anchor point can be rectangular.

[0007] The stator anchor points can be L-shaped, and the L-shaped stator anchor points can be arranged such that the L-shaped dimensions of the stator anchor points are the same, and the L-shape of one stator anchor point is rotated 180 degrees relative to the other stator anchor points, and the first part of each L-shape is parallel to the common axis and the second part of each L-shape is perpendicular to the common axis; and the second part of the L-shaped stator anchor points is aligned along the common axis.

[0008] The first part of the L-shaped stator anchor point can overlap with the second axis, which is perpendicular to the common axis.

[0009] The width of the rotor anchor point, measured perpendicular to the common axis, can be the same as the width of the L-shaped stator anchor point.

[0010] The rotor anchor point can be rectangular in shape.

[0011] The length of the rotor anchor point and the stator anchor point can be less than the width of the individual rotor anchor point and stator anchor point.

[0012] The device can be an accelerometer, and acceleration can be measured by capacitively measuring the motion of the rotor relative to the stator.

[0013] The distance between adjacent anchor points in a direction parallel to the common axis can be less than twice the length of any anchor point in the direction parallel to the common axis. Attached Figure Description

[0014] Figure 1 An anchoring arrangement structure according to a first embodiment of the present invention is shown.

[0015] Figure 2 An anchoring arrangement structure according to a second embodiment of the present invention is shown.

[0016] Figure 3 An anchoring arrangement structure of a second embodiment used in a MEMS accelerometer is shown. Detailed Implementation

[0017] Figure 1 An anchoring arrangement structure for a MEMS device according to a first embodiment of the present invention is shown. Three anchoring points 101, 102 and 103 fix the micromechanical components of the MEMS device to a substrate on which the MEMS device is formed.

[0018] The MEMS device can be an accelerometer, in which case anchor point 101 can be referred to as rotor anchor point 101, and anchor points 102 and 103 can be referred to as stator anchor points 102 and 103. (See also: ...) Figure 3As shown in more detail, rotor anchor point 101 anchors rotor structure 104 to the substrate, which rotor structure 104 is, for example, a rotor suspension to which the rotor is attached and allows a certain degree of movement. Stator anchor points 102, 103 anchor stators 105, 106, which are held in a fixed position relative to the substrate, to the substrate. It should be understood that... Figure 1 Only portions of the rotor structure 104 and stators 105 and 106 are shown. In operation, the acceleration of the MEMS device is detected by measuring the motion of the rotor relative to the stator using capacitive measurements.

[0019] like Figure 1 As shown, anchor points 101 to 103 are arranged such that all anchor points overlap with the common axis 110. In other words, anchor points 101 to 103 are arranged in a line. This contrasts with the conventional anchor point arrangement where stator anchor points 102 and 103 are typically "side by side" rather than one being "above" the other. The advantage of this arrangement is that when the MEMS device experiences temperature changes and anchor points 101 to 103 inevitably move due to stress caused by substrate expansion / contraction and temperature changes, the movement of all anchor points 101 to 103 is generally in the same direction. Conversely, when stator anchor points 102 and 103 are arranged side by side, these stator anchor points tend to move apart in the horizontal direction (i.e., perpendicular to axis 110) in addition to moving in the vertical direction (i.e., parallel to axis 110). Figure 1 The arrangement of the anchor points shown reduces the movement of anchor points 101 to 103 relative to each other, and thus also reduces the movement of components connected to anchor points 101 to 103 relative to each other. Since acceleration in a MEMS accelerometer is measured based on the varying distance between electrodes located on the stator and rotor, reducing movement caused by sources other than external acceleration improves the accuracy of acceleration measurement.

[0020] In this embodiment, anchor points 101 to 103 are preferably aligned along a common axis 110. In this context, "aligned" means that the center points of anchor points 101 to 103 are all in the same position relative to the common axis 110 as measured on an axis perpendicular to axis 110. Since the expansion / contraction or other deformation of the substrate along the common axis 110 has approximately equal effect on all anchor points, this arrangement minimizes the relative movement of anchor points 101 to 103.

[0021] Anchor points 101 to 103 may also all have the same width as measured perpendicular to axis 110. This arrangement also reduces the relative movement of anchor points 101 to 103.

[0022] Preferably, the length of each anchor point 101 to 103, i.e., the distance between the outermost edges of the anchor points measured parallel to the common axis 110, is less than the width of the anchor points 101 to 103 measured perpendicular to the common axis 110. In this way, the width of each individual anchor point 101 to 103 is sufficiently stable after the anchor point has been etched.

[0023] Figure 2 The second embodiment of the invention is shown in the figure. Anchor points 201 to 203 are again arranged such that all anchor points 201 to 203 overlap with the common axis 210; however, with... Figure 1 Compared to stator anchor points 102 to 103, stator anchor points 202 to 203 are L-shaped. One of the stator anchor points 202 to 203 is arranged such that it is a 180-degree rotation of the other stator anchor point. Furthermore, all three anchor points 201 to 203 are preferably aligned along a common axis 210.

[0024] The L-shape of the stator anchor points 202 and 203 allows for a greater maximum length and width for each anchor point, thereby providing increased stiffness in each direction while reducing the space occupied by anchor points 202 to 304 on the substrate. In fact, stator anchor points 202 to 203 can also overlap with the second axis 211—which is perpendicular to the common axis 210—to minimize the space occupied by stator anchor points 202 to 203 on the substrate.

[0025] The rotor anchor point 201 can have the same maximum width as the stator anchor points 202 and 203, but if Figure 2 As shown, the rotor anchor point 201 can be roughly rectangular in shape.

[0026] Figure 3 An exemplary MEMS accelerometer is shown, in which the exemplary MEMS accelerometer uses Figure 2 The anchoring structure. From Figure 3 It is easy to understand how to use it. Figure 1 Anchoring structures are used as an alternative. Figure 3Rotor structures 304a and 304b are shown, each including a rotor suspension 304a and a rotor 304b itself. The rotor suspension 304a is a fixing element anchored to the substrate via a rotor anchor point 301. The rotor 304b is a movable element connected to the rotor suspension 304a via springs 321 and 322, which allow the rotor to rotate away from the plane of the page and relative to the substrate and stators 305 and 306, which are fixed to the substrate via stator anchor points 302 and 303. Specifically, the rotor is configured to rotate about a rotation axis 312 that is parallel to the substrate and perpendicular to a common axis 110. The rotor 304b and stators 305 and 306 each include capacitor electrodes, such as comb-shaped electrodes, such that movement of the rotor 304b toward or away from the stators 305 and 306 causes a change in capacitance between the electrodes. The degree of change in capacitance is proportional to the degree of motion of rotor 304b, and the degree of motion of rotor 304b is proportional to the force applied to the accelerometer in a direction perpendicular to the plane of the page (and therefore the acceleration applied to the accelerometer in the same direction). Therefore, the acceleration of the MEMS device can be determined by measuring the capacitance. Figure 3 As shown, stators 305 and 306 are electrically separated and symmetrical about a common axis 310, allowing stators 305 and 306 to be used for differential measurement of capacitance caused by the movement of rotor 304b. Arranging the stator anchor points and rotor anchor points to overlap with the common axis 310 reduces the movement of the stator anchor points relative to each other, and thus particularly improves the accuracy of differential detection through these anchor points.

Claims

1. A microelectromechanical system (MEMS) device, comprising: Substrate, the substrate defining a substrate plane; A rotor, the rotor being mounted to the substrate via a rotor anchor point, wherein the rotor is rotatable relative to the plane of the substrate; and Two stators, wherein the position of each stator is fixed relative to the plane of the substrate and is mounted to the substrate via stator anchor points; The rotor anchor point and the stator anchor point are arranged such that all anchor points in the rotor anchor point and the stator anchor point overlap with a common axis, wherein the length of each anchor point in the rotor anchor point and the stator anchor point in the direction parallel to the common axis is less than the width of the same anchor point in the direction perpendicular to the common axis.

2. The microelectromechanical system device according to claim 1, wherein, The rotor anchor point and the stator anchor point have the same width, and the rotor anchor point and the stator anchor point are aligned along the common axis.

3. The microelectromechanical system device according to claim 1 or 2, wherein, The rotor anchor point and the stator anchor point are rectangular.

4. The microelectromechanical system device according to claim 1 or 2, wherein, The stator anchor points are L-shaped, and the L-shaped stator anchor points are arranged such that: The L-shaped dimensions of the stator anchor points are the same, and one of the stator anchor points is rotated 180 degrees relative to the other stator anchor points; The first portion of each L-shape is parallel to the common axis, and the second portion of each L-shape is perpendicular to the common axis; and The second portion of the L-shaped stator anchor point is aligned along the common axis.

5. The microelectromechanical system device according to claim 4, wherein, The first portion of the L-shaped stator anchor point overlaps with the second axis, which is perpendicular to the common axis.

6. The microelectromechanical system device according to claim 4, wherein, The width of the rotor anchor point, measured perpendicular to the common axis, is the same as the width of the L-shaped stator anchor point.

7. The microelectromechanical system device according to claim 6, wherein, The rotor anchor point is rectangular in shape.

8. The microelectromechanical system device according to claim 1 or 2, wherein, The microelectromechanical system device is an accelerometer, wherein acceleration is measured by capacitively measuring the motion of the rotor relative to the stator.

9. The microelectromechanical system device according to claim 1 or 2, wherein, The distance between adjacent anchor points in the rotor anchor point and the stator anchor point in a direction parallel to the common axis is less than twice the length of any anchor point in the rotor anchor point and the stator anchor point in a direction parallel to the common axis.

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