ALL-SILICON ELECTRODE CAPACITIVE TRANSDUCER ON A GLASS SUBSTRATE

• US 20150115770A1
• Filed: 10/29/2013
• Published: 04/30/2015
• Est. Priority Date: 10/29/2013
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Johnson, Burgess R., Supino, Ryan
• Granted Patent: US 9,837,935 B2
• Time in Patent Office: Days
• US Class Current: 310/309
• CPC Class Codes: B32B 2307/202 Conductive
• CPC Class Codes: B32B 2310/0418 other than water
• CPC Class Codes: B32B 2457/16 Capacitors
• CPC Class Codes: B32B 37/02 characterised by a sequence of laminating steps, e.g. by adding new layers at consecutive laminating stations
• CPC Class Codes: B32B 38/10 Removing layers, or parts of layers, mechanically or chemically
• CPC Class Codes: B81B 3/0086 Electrical characteristics, e.g. reducing driving voltage, improving resistance to peak voltage
• CPC Class Codes: H02N 1/08 with conductive charge carrier, i.e. capacitor machines

Abstract

An all-silicon electrode capacitive transducer comprising: a movable silicon microstructure coupled to a glass substrate, the movable silicon microstructure having a movable silicon electrode, the glass substrate having a top surface and at least one recess, the movable silicon electrode having a first flat surface parallel to a plane of the top surface of the glass substrate, the movable silicon electrode having a first electronic work function; and a stationary silicon electrode coupled to a glass substrate, the stationary silicon electrode located adjacent to the movable silicon electrode, the stationary silicon electrode configured to sense or actuate displacement of the movable silicon microstructure, wherein the stationary silicon electrode has a second flat surface parallel to the first flat surface, the stationary silicon electrode having a second electronic work function equal to the first electronic work function.

Claims

1. An all-silicon electrode capacitive transducer comprising:

a movable silicon microstructure coupled to a glass substrate, the movable silicon microstructure having a movable silicon electrode, the glass substrate having a top surface and at least one recess, the movable silicon electrode having a first flat surface parallel to a plane of the top surface of the glass substrate, the movable silicon electrode having a first electronic work function; and

a stationary silicon electrode coupled to a glass substrate, the stationary silicon electrode adjacent to the movable silicon electrode, the stationary silicon electrode configured to sense or actuate displacement of the movable silicon microstructure, wherein the stationary silicon electrode has a second flat surface parallel to the first flat surface, the stationary silicon electrode having a second electronic work function equal to the first electronic work function, wherein the glass substrate has a first recess, wherein the stationary silicon electrode is bonded to the first recess.

2. The capacitive transducer of claim 1, wherein the movable silicon microstructure is coupled to the glass substrate through silicon anchors, wherein the silicon anchors are bonded to the top surface of the glass substrate, wherein the movable silicon microstructure is coupled to the silicon anchors by flexible silicon suspensions.

3. The capacitive transducer of claim 1, wherein the glass substrate has a first recess and a second recess, the first recess located below a top surface of the glass substrate, the second recess deeper than the first, wherein the stationary silicon electrode is coupled to the first recess, wherein the movable silicon microstructure is coupled to the top surface of the glass substrate.

4. The capacitive transducer of claim 3, wherein the stationary silicon electrode has an overhang, wherein the overhang is a part of the stationary silicon electrode that extends beyond the surface of the first recess, wherein the overhang extends over the second recess such that the overhang shields the movable silicon microstructure from electric field lines from a surface of the second recess.

5. The capacitive transducer of claim 1 wherein the stationary silicon electrode and movable silicon electrode are highly doped epitaxial silicon electrodes, wherein the electrical work function of the stationary silicon electrode and movable silicon electrode are matched to mitigate a contact potential difference between the stationary silicon electrode and movable silicon electrode.

6. The capacitive transducer of claim 1, wherein the capacitive transducer is a horizontal capacitive transducer configured to sense or to actuate horizontal motion of the movable silicon electrode, wherein the stationary silicon electrode is configured to perform at least one of:

electrically shielding the movable silicon electrode;

preventing vertical forces on the movable silicon microstructure; and

preventing induced charges from vertical motion of the movable silicon microstructure.

7. The capacitive transducer of claim 1, wherein the capacitive transducer is a vertical capacitive transducer configured to sense or to actuate vertical motion of the movable silicon electrode, wherein the stationary silicon electrode is further configured to electrically shield the movable silicon electrode.

8. The capacitive transducer of claim 1 having more than one stationary silicon electrode attached to glass substrates above and below the movable silicon microstructure, the more than one stationary silicon electrode configured to electrically shield the movable silicon electrode from above and below the movable silicon microstructure respectively.

9. A method of manufacturing an all-silicon electrode capacitive transducer comprising:

etching at least one recess into a glass substrate;

patterning metal electrical leads onto the glass substrate;

etching recesses into a first silicon wafer having a doped epitaxial layer;

bonding epitaxial silicon of the first silicon wafer to a first recess of the at least one recess of the glass substrate;

removing an un-doped portion of the first silicon wafer, wherein a remaining portion of the first silicon wafer comprising a stationary silicon electrode;

etching recesses in a second silicon wafer having a doped epitaxial layer;

bonding epitaxial silicon of the second silicon wafer to a top surface of the glass substrate;

removing an un-doped portion of the second silicon wafer, wherein a remaining portion of the second silicon wafer comprises a movable silicon microstructure, the movable silicon microstructure having a movable silicon electrode.

10. The method of claim 9, wherein a first recess and a second recess are etched into the glass substrate, the first recess located below a top surface of the glass substrate, the second recess deeper than the first recess, wherein the stationary silicon electrode is coupled to the first recess.

11. The method of claim 10, wherein the stationary silicon electrode has an overhang, wherein the overhang is a part of the stationary silicon electrode that extends beyond a surface of the first recess, wherein the overhang extends over the second recess such that the overhang shields the movable silicon microstructure from charges on a surface of the second recess.

12. The method of claim 10 comprising:

etching at least one recess into a second glass substrate;

patterning metal electrical leads onto the second glass substrate;

etching recesses into a third silicon wafer having a doped epitaxial layer;

bonding epitaxial silicon of the third silicon wafer to a third recess of the at least one recess of the second glass substrate;

removing an un-doped portion of the third silicon wafer, wherein a remaining portion of the third silicon wafer comprises a second stationary silicon electrode;

bonding epitaxial silicon of the second silicon wafer to a top surface of a second glass substrate.

13. The method of claim 12, wherein a first recess and a second recess are etched into the glass substrate, the first recess located below a top surface of the glass substrate, the second recess deeper than the first recess, wherein the stationary silicon electrode is coupled to the first recess, wherein a third recess and a fourth recess are etched into the second glass substrate, the third recess located below a top surface of the second glass substrate, the fourth recess deeper than the third recess, wherein the second stationary silicon electrode is coupled to the third recess.

14. The method of claim 12, wherein:

the stationary silicon electrode has an overhang, wherein the overhang is a part of the stationary silicon electrode that extends beyond a surface of the first recess, wherein the overhang extends over the second recess such that the overhang shields the movable silicon microstructure from charges on a surface of the second recess;

the second stationary silicon electrode has an overhang, wherein the overhang is a part of the second stationary silicon electrode that extends beyond a surface of the third recess, wherein the overhang extends over the fourth recess such that the overhang shields the movable silicon microstructure from charges on a surface of the fourth recess.

15. A system for an all-silicon electrode capacitive transducer comprising:

an all-silicon electrode capacitive transducer comprising;

a movable silicon microstructure coupled to a glass substrate, the movable silicon microstructure having a movable silicon electrode, the glass substrate having a top surface and at least one recess, the movable silicon electrode having a first flat surface parallel to a plane of the top surface of the glass substrate, the movable silicon electrode having a first electronic work function; and

a stationary silicon electrode coupled to a glass substrate, the stationary silicon electrode adjacent to the movable silicon electrode, the stationary silicon electrode configured to sense or actuate displacement of the movable silicon microstructure, wherein the stationary silicon electrode has a second flat surface parallel to the first flat surface, the stationary silicon electrode having a second electronic work function equal to the first electronic work function, wherein the glass substrate has a first recess, wherein the stationary silicon electrode is bonded to the first recess;

a measurement unit coupled to the all-silicon electrode capacitive transducer, the measurement unit configured to read a signal from the all-silicon electrode capacitive transducer; and

an interface device coupled to the measurement unit configured to indicate a result indicative of the signal from the all-silicon electrode capacitive transducer.

16. The system of claim 15, wherein the glass substrate has a first recess and a second recess, the first recess located below a top surface of the glass substrate, the second recess deeper than the first, wherein the stationary silicon electrode is coupled to the first recess, wherein the movable silicon microstructure is coupled to the top surface of the glass substrate.

17. The system of claim 16 wherein the stationary silicon electrode has an overhang, wherein the overhang is a part of the stationary silicon electrode that extends beyond the surface of the first recess, wherein the overhang extends over the second recess such that the overhang shields the movable silicon microstructure from electric field lines from a surface of the second recess

18. The system of claim 15 wherein the stationary silicon electrode and movable silicon electrode are highly doped epitaxial silicon electrodes, wherein the electrical work function of the stationary silicon electrode and movable silicon electrode are matched to mitigate a contact potential difference between the stationary silicon electrode and movable silicon electrode

19. The system of claim 15, wherein the all-silicon electrode capacitive transducer has more than one stationary silicon electrode attached to glass substrates above and below the movable silicon microstructure, the more than one stationary silicon electrode configured to electrically shield the movable silicon electrode from above and below

20. The system of claim 19, wherein the more than one stationary silicon electrodes have respective overhangs, wherein each overhang is a part of a respective stationary silicon electrode that extends beyond a surface of the respective glass substrate to which the stationary silicon electrode is attached, wherein the overhang extends over a recess in the respective glass substrate such that the overhang shields the movable silicon microstructure from charges on a respective surface of the recess of each substrate.