Capacitive micro-electro-mechanical force sensor and corresponding force sensing method
First Claim
1. A MEMS force sensor comprising:
- a substrate;
a fixed electrode coupled to the substrate;
a mobile electrode suspended above the substrate and facing the fixed electrode, the mobile electrode and the fixed electrode defining a sensing capacitor, the mobile electrode including a hole extending from a surface adjacent to the fixed electrode to a surface opposite the surface adjacent to the fixed electrode, the mobile electrode being configured to undergo deformation in response to a force;
a dielectric material located on the fixed electrode and spaced apart from the mobile electrode by an air gap when the mobile electrode is in a rest condition, wherein the hole in the mobile electrode places the air gap in fluid communication with an environment that is external to the MEMS force sensor when the force sensor is in operation,the mobile electrode including a contact surface that is configured to contact the dielectric material in response to the force, an area of the contact surface contacting the dielectric material increases as the force increases; and
a coating surrounding lateral edges of the mobile electrode, the coating having a surface that is coplanar with the surface of the mobile electrode opposite the surface adjacent to the fixed electrode.
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Accused Products
Abstract
A MEMS force sensor has: a substrate; a fixed electrode coupled to the substrate; and a mobile electrode suspended above the substrate at the fixed electrode to define a sensing capacitor, the mobile electrode being designed to undergo deformation due to application of a force to be detected. A dielectric material region is set on the fixed electrode and spaced apart by an air gap from the mobile electrode, in resting conditions. The mobile electrode comes to bear upon the dielectric material region upon application of a minimum detectable value of the force, so that a contact surface between the mobile electrode and the dielectric material region increases, in particular in a substantially linear way, as the force increases.
35 Citations
21 Claims
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1. A MEMS force sensor comprising:
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a substrate; a fixed electrode coupled to the substrate; a mobile electrode suspended above the substrate and facing the fixed electrode, the mobile electrode and the fixed electrode defining a sensing capacitor, the mobile electrode including a hole extending from a surface adjacent to the fixed electrode to a surface opposite the surface adjacent to the fixed electrode, the mobile electrode being configured to undergo deformation in response to a force; a dielectric material located on the fixed electrode and spaced apart from the mobile electrode by an air gap when the mobile electrode is in a rest condition, wherein the hole in the mobile electrode places the air gap in fluid communication with an environment that is external to the MEMS force sensor when the force sensor is in operation, the mobile electrode including a contact surface that is configured to contact the dielectric material in response to the force, an area of the contact surface contacting the dielectric material increases as the force increases; and a coating surrounding lateral edges of the mobile electrode, the coating having a surface that is coplanar with the surface of the mobile electrode opposite the surface adjacent to the fixed electrode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An electronic apparatus, comprising:
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a microprocessor unit; and a MEMS force sensor coupled to the microprocessor unit, the MEMS force senor including; a substrate; a fixed electrode coupled to the substrate; a spacer coupled to the substrate, the spacer having a first thickness; a mobile electrode coupled to the substrate and suspended above the fixed electrode, the mobile electrode being a semiconductor material and including a through hole, the mobile electrode and the fixed electrode defining a sensing capacitor, the mobile electrode having a second thickness, the first thickness less than the second thickness; and a dielectric material located between the fixed and mobile electrode and a distance from the mobile electrode such that an air gap is between the mobile electrode and the dielectric material, wherein when the MEMS force sensor is in operation, the through hole remains open and in fluid communication with the sir gap and an environment that is external to the MEMS force sensor, wherein when the MEMS force sensor is in operating, the mobile electrode is configured to abut the dielectric material at a contact surface in response to a force being applied to the mobile electrode, wherein an area of the contact surface increases as the force increases. - View Dependent Claims (12, 13, 14, 15, 16, 17)
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18. A method for sensing a force using a MEMS force sensor, the method comprising:
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through a hole in the mobile electrode, equalizing air between the mobile electrode and the fixed electrode with air external to the MEMS force sensor; while the hole in the mobile electrode remains open, applying forces to a mobile electrode of semiconductor material that is suspended above a fixed electrode and a dielectric material, the dielectric material being located above the fixed electrode; and in response to the forces, the mobile electrode deforming and contacting a portion of the dielectric material at a contact surface, wherein when the forces applied increase, the contact surface increases. - View Dependent Claims (19, 20, 21)
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Specification