Methods for reducing surface charges during the manufacture of microelectromechanical systems devices
Provided herein are methods for preventing the formation and accumulation of surface-associated charges, and deleterious effects associated therewith, during the manufacture of a MEMS device. In some embodiments, methods provided herein comprise etching a sacrificial material in the presence of an ionized gas, wherein the ionized gas neutralizes charged species produced during the etching process and allows for their removal along with other etching byproducts. Also disclosed are microelectromechanical devices formed by methods of the invention, and visual display devices incorporating such devices.
1. A method of manufacturing a MEMS device, the method comprising:
depositing a sacrificial material on a substrate;
depositing a structural material over the sacrificial material; and
etching the sacrificial material, the etching comprising exposing the sacrificial material to a gas phase chemical etchant in the presence of ionized gas, the ionized gas being substantially non-reactive with the sacrificial material, wherein the etching further comprises substantially removing the sacrificial material to form a structural layer suspended over the substrate, the structural layer comprising at least a portion of the structural material, and wherein the structural layer is movable between a first position spaced from the substrate by a first distance and a second position spaced from the substrate by a second distance.
2. The method of claim 1 , wherein the structural layer moves from the first position to the second position in response to a first voltage difference between the substrate and the structural layer, and from the second position to the first position in response to a second voltage difference between the substrate and the structural layer, the second voltage difference being lower than the first voltage difference.
3. The method of claim 2 , wherein exposing the sacrificial material to the gas phase chemical etchant in the presence of ionized gas reduces the difference between the first and second voltage.
4. The method of claim 1 , wherein the structural layer is at least partially reflective to incident light.
5. The method of claim 4 , wherein the substrate comprises a reflective layer, the reflective layer being at least partially transmissive and at least partially reflective to incident light.
6. The method of claim 5 , wherein at least a portion of the light reflected by the structural layer interferes with at least a portion of the light reflected by the reflective layer.
7. The method of claim 6 , wherein the MEMS device is an interferometric modulator, the movement of the structural layer between the first and second positions modulating the interference of light reflected from the structural layer with light reflected from the reflective layer.
8. A method of manufacturing a MEMS device, the method comprising:
depositing a sacrificial material on a substrate;
depositing a structural material over the sacrificial material; and
etching the sacrificial material, the etching comprising exposing the sacrificial material to a gas phase chemical etchant in the presence of ionized gas, the ionized gas being substantially non-reactive with the sacrificial material, wherein exposing the sacrificial material to the gas phase chemical etchant in the presence of the ionized gas comprises:
applying the ionized gas to the sacrificial material, and
applying the gas phase chemical etchant to the sacrificial material; and
wherein the gas phase chemical etchant and the ionized gas are applied to the sacrificial material sequentially.