Method and device for modulating light

1. A MEMS device, comprising:

a first wall and a second wall defining a cavity, the first and second walls movable relative to each other, wherein the first wall allows light to pass into the cavity, the second wall comprises a moveable membrane having

a first layer of a first metallic material;

a second layer of a second metallic material different from the first metallic material; and

a third layer sandwiched between the first and second layer, wherein the third layer separates the first and second layer so that the first and second layer are not in contact.

2. The device of claim 1 , wherein the moveable membrane is movable between a driven state and an undriven state.

3. The device of claim 1 , wherein the first layer comprises aluminum and the second layer comprises tungsten.

4. The device of claim 1 , wherein the third layer comprises at least one of a dielectric, silicon dioxide, or zirconium dioxide.

5. The device of claim 1 , wherein the third layer is about 50 nanometers thick.

6. The device of claim 1 , wherein the first layer of the movable membrane comprises a highly reflective surface disposed towards the cavity to reflect light into the cavity.

7. A method of manufacturing a MEMS device having a movable membrane, the method comprising:

depositing material on a substrate to form a partially transparent mirror;

depositing an insulator over the partially transparent mirror;

depositing sacrificial layer over the insulator;

forming a movable membrane by

depositing a first layer of a first metallic material over the sacrificial layer;

depositing a second layer over the first layer;

depositing a third layer of a second metallic material over the second layer such that the second layer is sandwiched between the first layer and the third layer, wherein the second layer preventing the third layer from contacting any portion of the second layer, and wherein the second metallic material is different from the first metallic material;

etching a pattern in the first layer, the second layer, and the third layer; and

removing the sacrificial layer to form a cavity defined by a first and second wall, the first wall comprising the partially transparent mirror and the second wall comprising the movable membrane.

8. The method of claim 7 , wherein the pattern etched in the first layer, the pattern etched in the second layer, and the pattern etched in the third layer are the same.

9. The method of claim 7 , wherein the first layer comprises aluminum.

10. The method of claim 7 , wherein the third layer comprises tungsten.

11. The method of claim 7 , wherein the second layer comprises at least one of a dielectric, zirconium dioxide, or silicon dioxide.

12. The method of claim 7 , wherein the second layer is about 50 nanometers thick.

13. The method of claim 7 , wherein the cavity is an interferometric cavity.

14. The method of claim 7 , wherein etching a pattern in the first layer, the second later, and the third layer is performed by a single etching process.

15. The method of claim 7 , wherein the etching is performed using a gas phase etchant.

16. The method of claim 7 , wherein the MEMS device is an interferometric modulator.