Single-side microelectromechanical capacitive acclerometer and method of making same
First Claim
1. A single-side, microelectromechanical capacitive accelerometer having an input axis, the accelerometer comprising:
- first and second spaced conductive electrodes, each of the conductive electrodes including a planar layer which is relatively thin along the input axis, but is stiff to resist bending movement along the input axis;
a proof mass which is thicker than either of the planar layers by at least one order of magnitude along the input axis;
a first support structure for supporting the proof mass in spaced relationship from the first conductive electrode; and
a second support structure for supporting the second conductive electrode on the proof mass wherein the second conductive electrode moves with but is electrically isolated from the proof mass, and the second conductive electrode and the proof mass move together in opposite directions relative to the first conductive electrode, and wherein the conductive electrodes and the proof mass form a pair of substantially uniform, narrow air gaps on opposite sides of the first conductive electrode, and wherein the conductive electrodes and the proof mass form a pair of acceleration-sensitive capacitors.
2 Assignments
0 Petitions
Accused Products
Abstract
A high sensitivity, Z-axis, capacitive microaccelerometer having stiff sense/feedback electrodes and a method of its manufacture on a single-side of a semiconductor wafer are provided. The microaccelerometer is manufactured out of a single silicon wafer and has a silicon-wafer-thick proof mass, small and controllable damping, large capacitance variation and can be operated in a force-rebalanced control loop. One of the electrodes moves with the proof mass relative to the other electrode which is fixed. The multiple, stiffened electrodes have embedded therein damping holes to facilitate force-rebalanced operation of the device and to control the damping factor. Using the whole silicon wafer to form the thick large proof mass and using thin sacrificial layers to form narrow uniform capacitor air gaps over large areas provide large capacitance sensitivity. The manufacturing process is simple and thus results in low cost and high yield manufacturing. In one preferred embodiment, the fixed electrode includes a plurality of co-planar, electrically-isolated, conductive electrodes formed by thin polysilicon deposition with embedded vertical stiffeners. The vertical stiffeners are formed by refilling vertical trenches in the proof mass and are used to make the fixed electrode stiff in the sense direction (i.e. Z or input axis). The moving electrode is dimensioned and supported for movement on the proof mass so as to be stiff in the sense direction. In another embodiment both of the electrodes are electroplated. In yet another embodiment four support beams support the proof mass at an upper portion thereof and four support beams support the proof mass at a lower portion thereof.
-
Citations
14 Claims
-
1. A single-side, microelectromechanical capacitive accelerometer having an input axis, the accelerometer comprising:
-
first and second spaced conductive electrodes, each of the conductive electrodes including a planar layer which is relatively thin along the input axis, but is stiff to resist bending movement along the input axis;
a proof mass which is thicker than either of the planar layers by at least one order of magnitude along the input axis;
a first support structure for supporting the proof mass in spaced relationship from the first conductive electrode; and
a second support structure for supporting the second conductive electrode on the proof mass wherein the second conductive electrode moves with but is electrically isolated from the proof mass, and the second conductive electrode and the proof mass move together in opposite directions relative to the first conductive electrode, and wherein the conductive electrodes and the proof mass form a pair of substantially uniform, narrow air gaps on opposite sides of the first conductive electrode, and wherein the conductive electrodes and the proof mass form a pair of acceleration-sensitive capacitors. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
-
Specification
-
- Resources
-
Current AssigneeBoard of Regents of the University of Michigan (University of Michigan)
-
Original AssigneeBoard of Regents of the University of Michigan (University of Michigan)
-
InventorsYazdi, Navid, Najafi, Khalil
-
Primary Examiner(s)MOLLER, RICHARD ALAN
-
Application NumberUS09/679,849Time in Patent Office341 DaysField of Search735/243.2, 735/141.8, 735/141.7, 735/141.6US Class Current73/514.32CPC Class CodesG01P 15/0802 DetailsG01P 15/125 by capacitive pick-upG01P 15/131 with electrostatic counterb...G01P 2015/0882 for providing damping of vi...
