MEMS device with differential vertical sense electrodes
View Patent ↗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.
1. A microelectromechanical systems (MEMS) device comprising:
a substrate;
a first element and a second element formed in a first structural layer, said first element being fixedly coupled with said substrate, and said second element being suspended over said substrate;
a third element and a fourth element formed in a second structural layer, said third element being spaced apart from said second element in a direction perpendicular to a surface of said substrate, and said fourth element being spaced apart from said first element in said direction; and
a junction formed between said second element and said fourth element, said junction coupling said fourth element with said second element.
2. A MEMS device as claimed in claim 1 further comprising:
an anchor attached to said substrate; and
a compliant member interconnected between said second element and said anchor to allow concurrent movement of said second and fourth elements relative to said substrate.
3. A MEMS device as claimed in 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. A MEMS device as claimed in claim 2 wherein 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. A MEMS device as claimed in claim 1 wherein said second element includes an opening extending through a thickness of said second element, and said first element resides in said opening.
6. A MEMS device as claimed in claim 5 wherein said opening extends laterally from an outer edge of said second element such that said second element is a U-shaped member.
7. A MEMS device as claimed in claim 5 wherein said junction comprises:
a first junction element positioned at a first side of said opening; and
a second junction element positioned at a second side of said opening, said first and second junction elements coupling said fourth element with said second element so that said fourth element spans across a width of said opening.
8. A MEMS device as claimed in claim 1 further comprising a shield interposed between said first element and said second element, said shield being configured to electrically isolate said first element from said second element.
9. A MEMS device as claimed in claim 8 further comprising a shield anchor attached to said substrate and coupled to said shield so that said shield is suspended over said substrate.
10. A MEMS device as claimed in claim 1 wherein said junction is a first junction, and said MEMS device further comprises:
a fifth element formed in said first structural layer and fixedly coupled with said substrate; and
a second junction formed between said third element and said fifth element, said second junction coupling said third element with said fifth element.
11. A MEMS device as claimed in claim 10 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 MEMS device further comprises 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.
12. A MEMS device as claimed in claim 1 wherein:
said second and fourth elements form a movable sense mass;
said first element is a first fixed sense electrode, wherein a first sense signal is produced between said first fixed sense electrode and said fourth element in response to movement of said sense mass; and
said third element is a second fixed sense electrode, wherein a second sense signal is produced between said second fixed sense electrode and said second element in response to said movement of said sense mass, said second sense signal being opposite in polarity from said first sense signal.
13. A microelectromechanical systems (MEMS) device comprising:
a substrate;
a first element and a second element formed in a first structural layer, said first element being fixedly coupled with said substrate, and said second element being suspended over said substrate;
a third element and a fourth element formed in a second structural layer, said third element being spaced apart from said second element in a direction perpendicular to a surface of said substrate, and said fourth element being spaced apart said first element in said direction;
a first junction formed between said second element and said fourth element, said first junction coupling said fourth element with said second element;
an anchor attached to said substrate;
a compliant member interconnected between said second element and said anchor to allow concurrent movement of said second and fourth elements relative to said substrate;
a fifth element formed in said first structural layer and fixedly coupled with said substrate; and
a second junction formed between said third element and said fifth element, said second junction coupling said third element with said fifth element.
14. A MEMS device as claimed in claim 13 wherein said compliant member is connected at an outer edge of said second element such that said second element is a cantilevered structure, and 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.
15. A MEMS device as claimed in claim 13 further comprising a shield interposed between said first and second elements, said shield being configured to electrically isolate said first element from said second element.
16. A microelectromechanical systems (MEMS) accelerometer comprising:
a substrate;
a first electrode and a first portion of a movable sense mass formed in a first structural layer, said first electrode being fixedly coupled with said substrate, and said first portion of said movable sense mass being suspended over said substrate;
a second electrode and a second portion of said movable sense mass formed in a second structural layer, said second electrode being spaced apart from said first portion of said movable sense mass in a direction perpendicular to a surface of said substrate, and said second portion of said movable sense mass being spaced apart from said first electrode in said direction; and
a junction formed between said first and second portions of said movable sense mass, said junction coupling said second portion of said movable sense mass with said first portion of said movable sense mass.
17. A MEMS accelerometer as claimed in claim 16 further comprising:
an anchor attached to said substrate; and a compliant member interconnected between said first portion of said movable sense mass and said anchor to allow concurrent movement of said first and second portions of said movable sense mass relative to said substrate.
18. A MEMS accelerometer as claimed in claim 17 wherein said compliant member is connected to an outer edge of said first portion of said movable sense mass such that said second portion of said movable sense mass is a cantilevered structure, said compliant member enabling rotational movement of said first and second portions of said movable sense mass about an axis of rotation that is offset away from said first portion of said movable sense mass.
19. A MEMS accelerometer as claimed in claim 16 wherein:
said first portion of said movable sense mass includes an opening extending through a thickness of said first portion;
said first electrode resides in said opening; and
said junction comprises a first junction element positioned at a first side of said opening, and a second junction element positioned at a second side of said opening, said first and second junction elements coupling said second portion of said movable sense element with said first portion of said movable sense element so that said second portion of said movable sense element spans across a width of said opening and is suspended over said first electrode.
20. A MEMS accelerometer as claimed in claim 16 wherein said junction is a first junction, and said MEMS accelerometer further comprises:
a fixed element formed in said structural layer and fixedly coupled with said substrate, said fixed element being displaced away from said first portion of said movable sense mass and said first electrode in a lateral direction that is approximately parallel to a surface of said substrate; and
a second junction formed between said second electrode and said fixed element such that said second electrode is a cantilevered structure suspended over said first portion of said movable sense mass.