Fabrication of a floating rocker MEMS device for light modulation
The current disclosure shows how to make a fast switching array of mirrors for projection displays. Because the mirror does not have a via in the middle connecting to the underlying spring support, there is an improved contrast ratio that results from not having light scatter off the legs or vias like existing technologies. Because there are no supporting contacts, the mirror can be made smaller making smaller pixels that can be used to make higher density displays. In addition, because there is not restoring force from any supporting spring support, the mirror stays in place facing one or other direction due to adhesion. This means there is no need to use a voltage to hold the mirror in position. This means that less power is required to run the display.
1. A method, comprising:
depositing a conductive layer over a first sacrificial layer and a plurality of conductive electrodes;
patterning the conductive layer to form a first mirror element and a second mirror element;
depositing a second sacrificial layer over the first mirror element and the second mirror element;
enclosing the first sacrificial layer, first mirror element, the second mirror element and second sacrificial layer within adjacent cavities, wherein each element is housed in a separate cavity;
removing the second sacrificial layer and the first sacrificial layer to release the first mirror element and the second mirror element within the cavities such that the first mirror element is a discrete, floating first rocker that rests on a first fulcrum and pivots into and out of contact with a first conductive electrode of the plurality of conductive electrodes and the second mirror element is a discrete, floating second rocker that rests on a second fulcrum and pivots into and out of contact with a second conductive electrode of the plurality of conductive electrodes; and
sealing the cavities.
2. The method of claim 1 , further comprising:
depositing a first titanium nitride layer over a substrate;
patterning the first titanium nitride layer;
etching the first titanium nitride layer;
depositing a second titanium nitride layer over the etched, first titanium nitride layer;
patterning the second titanium nitride layer;
etching the second titanium nitride layer to form the plurality of conductive electrodes;
depositing the first sacrificial layer over the plurality of conductive electrodes;
patterning the first sacrificial layer;
etching the first sacrificial layer;
forming the first mirror element and the second mirror element;
depositing the second sacrificial layer over the first mirror element and the second mirror element;
depositing a transparent layer over the second sacrificial layer to encapsulate the second sacrificial layer, the first mirror element, the second mirror element, the first sacrificial layer, and the one or more electrodes;
etching a hole through the transparent layer;
plasma etching the second sacrificial layer and the first sacrificial layer to form the discrete, first floating rocker and the discrete, second floating rocker; and
filling the hole to seal the cavities.
3. The method of claim 1 , wherein the conductive layer comprises titanium nitride.
4. The method of claim 3 , further comprising an aluminum layer over the titanium nitride layer.
5. The method of claim 4 , wherein the plurality of conductive electrodes comprises titanium nitride.
6. The method of claim 1 , wherein the plurality of conductive electrodes comprise a transparent conductive material.
7. The method of claim 1 , wherein the cavity is bound by a transparent window.