Package for Damping Inertial Sensor
First Claim
Patent Images
1. An accelerometer having a Q-factor of less than 2.0, the accelerometer comprising:
- a substrate having a substrate surface;
a movable mass suspended from the substrate and configured to sense acceleration by moving parallel to the substrate, the movable mass having a first surface and a second surface opposite the first surface, the first surface facing the substrate surface and separated from the substrate surface by a first gap;
a cap having a cap surface, the cap coupled to the substrate and forming a hermetically sealed volume with the substrate and enclosing the movable mass, wherein the second surface is opposite the cap surface and is separated from the cap surface by a second gap;
a gas filling the volume at a pressure of less than 1 atmosphere, the gas having a viscosity of less than 25.0 μ
Pa·
s,each of the first gap and the second gap being less than 10 um, such that the accelerometer has a Q-factor of less than 2.0 for motion of the movable mass parallel to the substrate.
1 Assignment
0 Petitions
Accused Products
Abstract
A capped micromachined accelerometer with a Q-factor of less than 2.0 is fabricated without encapsulating a high-viscosity gas with the movable mass of the micromachined accelerometer by providing small gaps between the movable mass and the substrate, and between the movable mass and the cap. The cap may be an silicon cap, and may be an ASIC smart cap.
-
Citations
20 Claims
-
1. An accelerometer having a Q-factor of less than 2.0, the accelerometer comprising:
-
a substrate having a substrate surface; a movable mass suspended from the substrate and configured to sense acceleration by moving parallel to the substrate, the movable mass having a first surface and a second surface opposite the first surface, the first surface facing the substrate surface and separated from the substrate surface by a first gap; a cap having a cap surface, the cap coupled to the substrate and forming a hermetically sealed volume with the substrate and enclosing the movable mass, wherein the second surface is opposite the cap surface and is separated from the cap surface by a second gap; a gas filling the volume at a pressure of less than 1 atmosphere, the gas having a viscosity of less than 25.0 μ
Pa·
s,each of the first gap and the second gap being less than 10 um, such that the accelerometer has a Q-factor of less than 2.0 for motion of the movable mass parallel to the substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
-
11. A method of fabricating an accelerometer having a Q-factor of less than 2.0, the method comprising:
-
providing a substrate having a substrate surface; suspending a movable mass from the substrate and configured to sense acceleration by moving parallel to the substrate, the movable mass having a first surface and a second surface opposite the first surface, the first surface facing the substrate surface and separated from the substrate surface by a first gap; providing a gas around the substrate at a pressure of less than 1 atmosphere, the gas having a viscosity of less than 25.0 μ
Pa·
s;providing a cap, the cap having a cap surface; mounting the cap to the substrate such that the second surface is opposite the cap surface and is separated from the cap surface by a second gap, and such that the substrate and cap form a hermetically sealed volume and enclose the movable mass and trap some of the gas within the volume; each of the first gap and the second gap being less than 10 um, such that the accelerometer has a Q-factor of less than 2.0 for motion of the movable mass parallel to the substrate. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
-
Specification