Micro-electromechanical device for use in a flow control apparatus
Disclosed herein are embodiments of a sensor device, systems incorporating the same, and methods of fabricating the same. In one embodiment, a sensor device comprises a free-standing sensing element, such as a micro-electromechanical system (MEMS) device. The sensor device further comprises a metallic band to facilitate mounting the MEMS device to a mounting plate. The sensor device further comprises a conformal coating on a least a portion of a sensor region of the sensor device.
1. A sensor device comprising:
an elongated support structure comprising an interface region, a sensor region, and a coupling region located between the interface region and the sensor region, wherein the elongated support structure is composed of a material that is not brazable;
electrodes disposed on the interface region;
a free-standing sensing element suspended at the sensor region, wherein the free-standing sensing element is electrically coupled to the electrodes;
a conformal band-shaped metallic coating encompassing the coupling region, wherein the conformal band-shaped metallic coating is sealed against the coupling region of the elongated support structure, and wherein the conformal band-shaped metallic coating is brazable and enables brazing of the elongated support structure to a mounting plate to form a metal seal between the sensor device and the mounting plate; and
a non-conductive conformal coating on at least a portion of the sensor region, the non-conductive conformal coating comprising a plasma-resistant ceramic material.
2. The sensor device of claim 1 , wherein the sensor device comprises a silicon-based micro-electromechanical system (MEMS) device.
3. The sensor device of claim 1 , wherein the non-conductive conformal coating has a thickness of about 10 nanometers to about 300 nanometers.
4. The sensor device of claim 1 , wherein the free-standing sensing element comprises a nanowire, and wherein the sensor region defines a cavity across which the nanowire is suspended.
5. The sensor device of claim 4 , wherein the nanowire comprises platinum, and wherein the nanowire is at least partially coated by the non-conductive conformal coating.
6. The sensor device of claim 1 , wherein the electrodes are formed on or within the coupling region, and wherein the non-conductive conformal coating forms an insulating layer between the conformal band-shaped metallic coating and the electrodes.
7. The sensor device of claim 1 , wherein the mounting plate further comprises:
a gas-facing surface and a mounting surface opposite the gas-facing surface, the mounting plate having a slot formed therethrough, wherein:
the elongated support structure is disposed in the slot such that the sensor region extends from the gas-facing surface and the coupling region extends from the mounting surface, and
the elongated support structure is secured to the mounting plate at the coupling region by a metal seal formed between the conformal band-shaped metallic coating and the mounting surface of the mounting plate.
8. The sensor device of claim 1 , wherein the conformal band-shaped metallic coating has a thickness from 50 micrometers to 500 micrometers and a width from 0.5 millimeters to 2 millimeters.
9. A flow control apparatus comprising:
a gas flow channel defining a gas flow path;
a flow modulating valve configured to modulate gas flow in the gas flow channel;
a sensor device, comprising:
an elongated support structure, wherein the elongated support structure is composed of a material that is not brazable;
a sensing region on the elongated support structure, the sensing region comprising a non-conductive conformal plasma-resistant ceramic coating and a free-standing sensing element disposed within the gas flow path; and
a coupling region on the elongated support structure, the coupling region comprising a conformal band-shaped metallic coating that seals the sensor device to the gas flow channel, wherein the conformal band-shaped metallic coating is sealed against the coupling region, and wherein the conformal band-shaped metallic coating is brazable and enables brazing of the elongated support structure to a mounting plate or an exterior region of the gas flow channel to form a metal seal between the sensor device and the mounting plate or the exterior region of the gas flow channel; and
a processing device operatively coupled to the flow modulating valve and the sensor device, the processing device being configured to adjust the flow modulating valve based on signals received from the sensor device.
10. The flow control apparatus of claim 9 , wherein the sensor device is a silicon-based micro-electromechanical system (MEMS) device.
11. The flow control apparatus of claim 9 , wherein the free-standing sensing element comprises a nanowire.
12. The flow control apparatus of claim 9 , wherein the free-standing sensing element is at least partially coated by the non-conductive conformal plasma-resistant ceramic coating.
13. The flow control apparatus of claim 9 , wherein the elongated support structure is disposed within a slot formed in the gas flow path.
14. The flow control apparatus of claim 13 , wherein the coupling region corresponds to a portion of the elongated support structure that extends out of the slot of the gas flow path, wherein the sensor device is secured to the gas flow path by the mounting plate that is mechanically coupled to the gas flow path.
15. The flow control apparatus of claim 13 , wherein the coupling region corresponds to a portion of the elongated support structure that extends out of the slot of the gas flow channel, wherein the sensor device is secured to the gas flow path by the exterior region of the gas flow channel.
16. A method of adapting a sensor device for use in a flow control apparatus, the method comprising:
providing the sensor device comprising:
an elongated support structure comprising an interface region, a sensor region, and a coupling region located between the interface region and the sensor region, wherein the elongated support structure is composed of a material that is not brazable; and
a free-standing sensing element suspended at the sensor region;
depositing a conformal coating on the sensor device to at least partially coat the sensor region, the conformal coating comprising a plasma-resistant ceramic material; and
depositing a conformal band-shaped metallic coating on the sensor device to encompass the coupling region, wherein the conformal band-shaped metallic coating is sealed against the coupling region of an elongated support structure, and wherein the conformal band-shaped metallic coating is brazable and enables brazing of the elongated support structure to a mounting plate to form a metal seal between the sensor device and the mounting plate.
17. The method of claim 16 , wherein the conformal coating is deposited using an ion assisted deposition process, and wherein the plasma-resistant ceramic material is non-conductive.
18. The method of claim 16 , further comprising:
securing the sensor device to the mounting plate by forming the metal seal between the conformal band-shaped metallic coating and the mounting plate.
19. The method of claim 18 , wherein the metal seal is formed by brazing.
20. The method of claim 18 , further comprising:
inserting the sensor device into a gas flow channel; and
mechanically coupling the mounting plate to the gas flow channel.