Microelectromechanical element and a method for manufacturing it
A microelectromechanical element is provided with patterned regions of wafer material and glass material. The regions of glass material include at least a first glass region and a second glass region formed of a first glass material and a second glass material, respectively. The first glass material enables anodic bonding with the wafer material. An alkali metal content of the second glass material is less than an alkali metal content of the first glass material.
1 . A microelectromechanical element comprising:
a plurality of microstructures of wafers bonded to each other, such that a gap is closed by bonding of the microstructures;
mobile structure parts suspended to move within the closed gap;
at least one internal electrode arranged in the gap and configured to detect or actuate movement of the mobile structure parts; and
patterned regions of silicon wafer material and glass material, the regions of glass material including at least a first glass region comprising a first glass material and a second glass region comprising a second glass material,
wherein at least one microstructure in the plurality of microstructures includes a plurality of silicon through vias, electrically isolated from each other by regions of second glass material,
wherein the first glass material enables anodic bonding with the silicon wafer material, and
wherein the second glass material has an alkali metal content that is less than an alkali metal content of the first glass material.
2 . The microelectromechanical element according to claim 1 ,
wherein the first glass region and the second glass region are in one of the plurality of microstructures, and
wherein a glass transition temperature of the first glass region is lower than a glass transition temperature of the second glass region.
3 . The microelectromechanical element according to claim 1 , wherein the first glass region and the second glass region are in different microstructures.
4 . The microelectromechanical element according to claim 1 , wherein:
the plurality of microstructures include a first microstructure and a second microstructure,
the mobile structure parts are in the first microstructure,
the gap is closed by bonding the first microstructure to the second microstructure, and
the second glass region is in the second microstructure.
5 . The microelectromechanical element according to claim 4 , wherein the at least one internal electrode is on a first side of the second microstructure.
6 . The microelectromechanical element according to claim 5 , wherein:
the second microstructure includes at least one external electrode on a second side of the second microstructure,
a through via formed of the silicon wafer material connects the at least one internal electrode to the at least one external electrode, and
the second glass region surrounds the through via.
7 . The microelectromechanical element according to claim 6 , wherein the second microstructure is a cap microstructure that includes the plurality of through vias that are electrically isolated from each other by regions of second glass material.
8 . The microelectromechanical element according to claim 1 , wherein the alkali metal content of the first glass material in form of oxides is 1 wt % or more.
9 . The microelectromechanical element according to claim 1 , wherein the alkali metal content of the second glass material in form of oxides is less than 0.5 wt %.