Dual substrate electrostatic MEMS switch with multiple hinges and method of manufacture
View Patent ↗Systems and methods for forming an electrostatic MEMS switch include forming a movable cantilevered beam on a first substrate, forming the electrical contacts on a second substrate, and coupling the two substrates using a hermetic seal. Electrical access to the electrostatic MEMS switch may be made by forming vias through the thickness of the second substrate. The cantilevered beam may be formed by etching the perimeter shape in the device layer of an SOI substrate. An additional void may be formed in the movable beam such that it bends about an additional hinge line as a result of the additional void. This may give the beam and switch advantageous kinematic characteristics.
1. An electrostatic MEMS switch, comprising:
a movable, cantilevered plate affixed on one side to a first substrate along a line of attachment at a proximal end, wherein the plate bends about a first hinge line along the line of attachment, wherein the cantilevered plate is movable as a result of a first void formed generally around a perimeter of the movable plate;
a second void formed in the movable plate, and wherein the plate also bends about a second hinge line as a result of the second void made in the movable plate, wherein the second hinge line is further away from the proximal end than the first hinge line.
2. The electrostatic MEMS switch of claim 1 , further comprising:
at least one electrical contact formed on a second substrate; and
a hermetic seal which couples the first substrate to the second substrate, and seals the MEMS switch.
3. The electrostatic MEMS switch of claim 1 , wherein the first substrate is a silicon-on-insulator substrate including a device layer, a handle wafer and an insulating oxide layer between the device layer and the handle wafer, and the second substrate is at least one of a silicon substrate and a silicon-on-insulator substrate.
4. The electrostatic MEMS switch of claim 1 , wherein the second void has a portion parallel to the first hinge line, and another portion perpendicular to the first hinge line.
5. The electrostatic MEMS switch of claim 1 , further comprising:
an electrostatic conductive plate formed on the second substrate.
6. The electrostatic MEMS switch of claim 1 , wherein the second void is in the shape of a straight line, C, U, I or H.
7. The electrostatic MEMS switch of claim 1 , wherein the at least on electrical contact comprises a layer of tungsten/gold alloy, a layer of gold, and a layer of ruthenium dioxide.
8. The electrostatic MEMS switch of claim 1 , wherein the hermetic seal comprises:
a gold/indium alloy which bonds the first substrate to the second substrate.
9. The electrostatic MEMS switch of claim 1 , wherein the cantilevered plate is formed from the device layer of the silicon-on-insulator substrate, and affixed to the handle wafer of the silicon-on-insulator substrate by the oxide layer.
10. The electrostatic MEMS switch of claim 1 , wherein the cantilevered plate further comprises a shunt bar which electrically connects two electrical contacts formed on the second substrate when the electrostatic MEMS switch is closed, wherein the shunt bar is electrically isolated from other portions of the cantilevered beam.
11. The electrostatic MEMS switch of claim 1 , wherein the first substrate is coupled to the second substrate with a gold-gold thermocompression bond.