MEMS scanning mirror with trenched surface and I-beam like cross-section for reducing inertia and deformation
A micro-electro-mechanical system (MEMS) device includes a mirror having a top surface with trenches, a beam connected to the mirror, rotational comb teeth connected to the beam, and one or more springs connecting the beam to a bonding pad. The mirror can have a bottom surface for reflecting light. The mirror can include a top flange and a bottom flange joined by a web, wherein the top and the bottom flanges form the top and the bottom surfaces, respectively. The rotational comb teeth can have a tapered shape. Stationary comb teeth can be interdigitated with the rotational comb teeth either in-plane or out-of-plane. Steady or oscillating voltage difference between the rotational and the stationary comb teeth can be used to oscillate or tune the mirror.
1. A micro-electro-mechanical system (MEMS) mirror device, comprising:
a bottom layer, comprising:
a bottom mirror layer comprising a web atop a bottom flange, the bottom
flange having a reflective surface;
a first anchoring pad;
a top layer, comprising:
a top mirror layer comprising a top flange bonded atop the web of the bottom mirror layer to form a mirror;
a beam connected to the top mirror layer;
a first spring connecting the beam to a first bonding pad, the first bonding pad being bonded atop but electrically insulated from the first anchoring pad;
a plurality of rotational comb teeth connected to the beam;
a first plurality of stationary comb teeth connected to a second bonding pad, the second bonding pad being bonded atop but electrically insulated from the first anchoring pad;
wherein the first plurality of stationary comb teeth and the plurality of rotational comb teeth are interdigitated in-plane.
2. The device of claim 1 , wherein the top mirror layer has a surface comprising a plurality of trenches.
3. The device of claim 2 , wherein the trenches are located along an outer perimeter of the top mirror layer.
4. The device of claim 2 , wherein the trenches comprises etched trenches and laser trimmed trenches.
5. The device of claim 1 , wherein:
the bottom layer further comprises a second anchoring pad;
the top layer further comprises a second spring connecting the beam to a third bonding pad, the third bonding pad being bonded atop but electrically insulated from the second anchoring pad.
6. The device of claim 5 , wherein:
the top layer further comprises a third spring connecting the beam to the third bonding pad.
7. The device of claim 5 , wherein the third bonding pad is located within the beam.
8. The device of claim 1 , wherein the plurality of rotational comb teeth and the first plurality of stationary comb teeth each comprises a tapered shape.
9. The device of claim 1 , wherein the plurality of rotational comb teeth is coupled to a first steady or oscillating voltage and the first plurality of stationary comb teeth is coupled to a second steady or oscillating voltage.
10. The device of claim 9 , wherein the bottom layer further comprises a second plurality of stationary comb teeth, wherein the second plurality of stationary comb teeth and the plurality of rotational comb teeth are interdigitated out-of-plane.
11. The device of claim 10 , wherein the second plurality of stationary comb teeth is coupled to a third steady or oscillating voltage.
12. The device of claim 10 , wherein the rotational comb teeth and the second plurality of stationary comb teeth are coupled to sense a capacitance that indicates a rotational angle of the mirror.
13. The device of claim 10 , wherein a first gap around the second plurality of stationary comb teeth has greater width and depth than a second gap between adjacent teeth in the second plurality of stationary comb teeth, the first gap accommodating a rotation of the rotational comb teeth.
14. The device of claim 1 , wherein the beam further comprises a plurality of holes.
15. The device of claim 1 , wherein the bottom layer further comprises mirror alignment marks for aligning another device to the mirror.
16. The device of claim 1 , wherein a gap surrounding the top mirror layer has a width greater than gaps around other components in the top layer.
17. The device of claim 1 , wherein:
the bottom layer further comprises a first separation trench;
the top layer further comprises a second separation trench proximate to the first separation trench, wherein the device is singulated along the first and the second separation trenches.