Spatial light modulators for phased-array applications
A capacitive micro-electromechanical system (MEMS) structure or device and methods of making and operating the same are described. Generally, the MEMS device provides a large stroke while maintaining good damping, enabling fast beam steering and large scan angles. In one embodiment, the capacitive MEMS device includes a bottom electrode formed over a substrate; an electrically permeable damping structure formed over the bottom electrode, the electrically permeable damping structure including a first air-gap and a dielectric layer suspended above and separated from the bottom electrode by the first air-gap; and a plurality of movable members suspended above the damping structure and separated therefrom by a second air-gap, each of the plurality of movable members including a top electrode and being configured to deflect towards the bottom electrode by electrostatic force. Other embodiments are also described.
1. A micro electro-mechanical systems (MEMS) device comprising:
a bottom electrode formed over a substrate;
an electrically permeable damping structure including a damper, formed over the bottom electrode, the electrically permeable damping structure including a first air-gap and a dielectric layer suspended above and separated from the bottom electrode by the first air-gap; and
a plurality of movable members suspended above the damping structure and separated therefrom by a second air-gap, each of the plurality of movable members including a top electrode and being configured to deflect towards the bottom electrode by electrostatic force.
2. The MEMS device of claim 1 wherein the plurality of movable members comprise a plurality of independently deflectable ribbons, each of ribbon comprising a reflective surface to modulate light incident on the MEMS device.
3. The MEMS device of claim 2 wherein the plurality of independently deflectable ribbons are configured to deflect towards the bottom electrode by a distance substantially equal to a thickness of the second air-gap.
4. The MEMS device of claim 3 wherein the thickness of the second air-gap is up to 2 μm.
5. The MEMS device of claim 2 wherein the dielectric layer substantially surrounds and overlies the first air-gap.
6. The MEMS device of claim 2 wherein each of the plurality of independently deflectable ribbons comprise width of from 2.5 μm to 0.5 μm.
7. The MEMS device of claim 1 wherein the dielectric layer is separated from the bottom electrode by a distance of 2G/3, where G is a distance between the bottom electrode and the plurality of movable members when undeflected.
8. The MEMS device of claim 7 wherein an undeflected movable member is separated from the dielectric layer of the electrically permeable damping structure by a distance of G/3.