DEVICE FOR MEASURING FORCE COMPONENTS, AND METHOD FOR ITS PRODUCTION

• US 20140083210A1
• Filed: 09/24/2013
• Published: 03/27/2014
• Est. Priority Date: 09/25/2012
• Status: Active Grant

• Current Assignee: Acreo Swedish ICT AB
• Original Assignee: Acreo Swedish ICT AB
• Inventors: ANGUELOVA, Milena, ANDERSSON, Gert, HEDENSTIERNA, Nils, NAFARI, Alexandra, WESTBERG, David
• Granted Patent: US 9,366,585 B2
• Time in Patent Office: Days
• US Class Current: 73/862.639
• CPC Class Codes: G01L 1/04 by measuring elastic deformation of gauges, e.g. of springs
• CPC Class Codes: G01P 15/02 by making use of inertia forces using solid seismic massesG01P15/14 takes precedence
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/131 with electrostatic counterbalancing means
• CPC Class Codes: G01P 2015/0854 using a particular shape of the mass, e.g. annular
• CPC Class Codes: G01P 2015/0857 using a particular shape of the suspension spring

Abstract

A device for measuring force components formed from a single crystal material, wherein the device comprises at least one cantilever beam inclined to a wafer plane normal and formed in one piece with a mass body, which mass body provides a mass of inertia. The mass body has a first and a second major surface which are substantially parallel with a wafer plane. A mass body cross section presents a portion which is substantially symmetrical along a centrally (in the thickness direction) located plane parallel with the wafer plane. Disclosed is also a method for its production and an accelerometer comprising at least one such device. The device allow for a more compact 3-axis accelerometer.

Claims

1. A device for measuring force components formed from a single crystal material wafer, wherein said device comprises:

at least one cantilever beam inclined to a wafer plane normal and formed in one piece with a mass body, providing a mass of inertia,

wherein said mass body has a first and a second major surface which are substantially parallel with a wafer plane, and

wherein a mass body cross section presents a portion which is substantially symmetrical along a centrally (in a thickness direction) located plane parallel with said wafer plane.

2. Device according to claim 1, wherein said first and second major surfaces are substantially aligned along said wafer plane normal.

3. Device according to claim 1, wherein said mass body is substantially symmetrical along a plane perpendicular to said wafer plane.

4. Device according to claim 1, wherein said first and second major surfaces have substantially the same area.

5. Device according to claim 1, wherein a cross-sectional area of said mass body along said wafer plane normal, starting from one of said major surfaces, tapers towards a cross-section minimum and then increases towards the other major surface.

6. Device according to claim 5, wherein said tapering and said increase, respectively, substantially coincide with respective crystal planes of the wafer.

7. Device according to claim 1, wherein said device presents at least two respective connecting points for connection between at least two cantilever beams and said mass body, said connecting points being placed at substantially diametrically opposite portions of said mass body.

8. Device according to claim 7, wherein each cantilever beam has its principal length extension along an edge portion of said mass body.

9. Device according to claim 7, wherein said cantilever beams extend in different directions from the respective connecting point.

10. Device according to claim 9, wherein said different directions are substantially opposite.

11. Device according to claim 1, wherein said single crystal material may be chosen from a group consisting of silicon, silicon carbide, gallium arsenide, germanium, gallium nitride/silicon carbide, aluminum nitride, gallium nitride, aluminum/gallium nitride, or indium/gallium nitride.

12. An accelerometer comprising at least one device according to claim 1.

13. Accelerometer according to claim 12, wherein at least one electrode is provided on a device wafer surface.

14. A method for manufacturing a device for measuring force components in a single crystal material, said method comprising steps of:

dry etching a wafer of said single crystal material to provide a pattern extending substantially perpendicular to a wafer surface plane; and

subsequently anisotropically wet etching said wafer along at least one wafer crystal plane to provide a structure in said wafer, which is undercut, as seen from both major surfaces of said wafer.

15. Method according to claim 14, wherein said method further comprises steps of:

selectively covering said wafer surfaces in a wafer plane with a respective wet etch mask; and

selectively covering said wafer surfaces and/or said wet etch masks with a respective dry etch mask.

16. Method according to claim 14, further comprising a preceding step of creating a gap recess in said wafer surfaces along said wafer plane.