MEMS device with differential vertical sense electrodes

Patent metadata

Field	Value
Publication number	US-9346670-B2
Application number	US-201514958966-A
Country	US
Kind code	B2
Filing date	Dec 4, 2015
Priority date	Aug 6, 2013
Publication date	May 24, 2016
Grant date	May 24, 2016

Abstract

A MEMS device includes a first sense electrode and a first portion of a sense mass formed in a first structural layer, where the first sense electrode is fixedly coupled with the substrate and the first portion of the sense mass is suspended over the substrate. The MEMS device further includes a second sense electrode and a second portion of the sense mass formed in a second structural layer. The second sense electrode is spaced apart from the first portion of the sense mass in a direction perpendicular to a surface of the substrate, and the second portion of the sense mass is spaced apart from the first sense electrode in the same direction. A junction is formed between the first and second portions of the sense mass so that they are coupled together and move concurrently in response to an imposed force.

First claim

What is claimed is:

1. A method for fabricating a microelectromechanical systems (MEMS) device comprising:
forming a first structural layer on a first sacrificial layer overlying a substrate to produce first and second elements separated from one another;
depositing a second sacrificial layer over said first structural layer;
forming a second structural layer over said second sacrificial layer to produce third and fourth elements separated from one another;
forming at least one junction between said second element and said fourth element; and
suspending said second, third, and fourth elements over said substrate by removing at least portions of said first and second sacrificial layers, wherein said third element is spaced apart from said second element in a direction perpendicular to a surface of said substrate, said fourth element is spaced apart from said first element in said direction, and said fourth element is coupled with said second element via said at least one junction.

2. The method of claim 1 further comprising:
forming an anchor on said substrate; and
forming a compliant member interconnected between said anchor and said second element, wherein following said suspending operation, said compliant member allows concurrent movement of said second and fourth elements.

3. The method of claim 2 wherein said compliant member is connected at an outer edge of said second element such that said second element is a cantilevered structure.

4. The method of claim 2 wherein following said suspending operation, said compliant member enables rotational movement of said second and fourth elements about an axis of rotation that is offset away from said second element.

5. The method of claim 1 wherein said forming said first structural layer comprises
forming an opening extending through a thickness of said second element; and
forming said first element such that said first element resides within said opening.

6. The method of claim 5 wherein said forming said at least one junction comprises:
forming a first junction element positioned at a first side of said opening; and
forming a second junction element positioned at a second side of said opening such that following said suspending operation, said first and second junction elements couple said forth element with said second element so that said fourth element spans across a width of said opening.

7. The method of claim 1 wherein said forming said first structural layer produces a shield in said first structural layer interposed between said first element and said second element, said shield being configured to electrically isolate said first element from said second element.

8. The method of claim 7 further comprising forming a shield anchor attached to said substrate and coupled to said shield, wherein following said suspending operation, said shield is suspended over said substrate.

9. The method of claim 1 wherein:
said forming said first structural layer produces a fifth element in said first structural layer that is fixedly coupled with said substrate; and
said forming at least one junction produces a second junction between said third element and said fifth element, said second junction coupling said third element with said fifth element.

10. The method of claim 9 wherein said fifth element is displaced away from said first and second elements in a lateral direction that is approximately parallel to a surface of said substrate, and said forming said first structure layer produces a shield interposed between said fifth element and said first and second elements, said shield being configured to electrically isolate said fifth element from said first and second elements.

11. The method of claim 1 wherein:
said forming said first structural layer produces said first and second elements separated from one another by a trench; and
said depositing said second sacrificial layer at least partially fills said trench.

12. The method of claim 1 wherein:
said method further comprises creating an aperture through said second sacrificial layer to expose a portion of said second element; and
said forming said second structural layer comprises filling said aperture with said second structural layer to form said at least one junction between said second element and said fourth element.

13. The method of claim 1 wherein said depositing said second sacrificial layer produces a first region of said second sacrificial layer having a first thickness and a second region of said second sacrificial layer having a second thickness, said first thickness being less than said second thickness, wherein said suspending operation comprises removing said second sacrificial layer between said first and fourth elements such that said fourth element is spaced apart from said first element by a gap having a width that is substantially equivalent to said first thickness.

14. The method of claim 1 wherein:
said substrate is a first substrate:
said method further comprises creating an aperture through said first sacrificial layer to expose a portion of said first substrate;
said forming said first structural layer comprises filling said aperture with said first structural layer to form said at least one junction;
said depositing said second sacrificial layer occurs following said filling operation; and
said forming said second structural layer comprises coupling said first substrate to a second substrate with said first sacrificial layer, said junction, and said sacrificial layer being interposed between said first and second substrates, and forming said third and fourth elements in said first substrate.

15. A method for fabricating a microelectromechanical systems (MEMS) device comprising:
forming a first structural layer on a first sacrificial layer overlying a substrate to produce a first electrode and a first portion of a movable sense mass separated from one another, said first electrode being fixedly coupled with said substrate;
depositing a second sacrificial layer over said first structural layer;
forming a second structural layer over said second sacrificial layer to produce a second electrode and a second portion of said movable sense mass separated from one another;
forming at least one junction between said first and second portions of said movable sense mass; and
suspending said first and second portions of said movable sense mass and said second electrode over said substrate by removing at least portions of said first and second sacrificial layers, wherein second electrode is spaced apart from said first portion of said movable sense mass in a direction perpendicular to a surface of said substrate, said second portion of said sense mass is spaced apart from said first electrode in said direction, and said second portion of said movable mass is coupled with said first portion of said movable sense mass via said at least one junction.

16. The method of claim 15 further comprising:
forming an anchor on said substrate; and
forming a compliant member interconnected between said anchor and said first portion of said movable sense mass, wherein following said suspending operation, said compliant member allows concurrent movement of said first and second portions of said movable sense mass relative to said substrate.

17. The method of claim 16 wherein said compliant member is connected at an outer edge of said first portion of said movable sense mass such that said first portion of said movable mass is a cantilevered structure, and following said suspending operation said compliant member enables rotational

Assignees

• Freescale Semiconductor Inc
• Freescale Semiconductor Inc

Inventors

• Geisberger Aaron A
• Kniffin Margaret L

Classifications

• H10W10/01

  Manufacture or treatment · CPC title

• H10W10/00

  Isolation regions in semiconductor bodies between components of integrated devices · CPC title

• H01L41/1136

  Electricity · mapped topic

• H01L21/76

  Electricity · mapped topic

• B81C1/00658 Primary

  Treatments for improving the stiffness of a vibrating element · CPC title