Surfactant-enhanced protection of micromechanical components from galvanic degradation
View Patent ↗A microelectromechanical structure is formed by depositing sacrificial and structural material over a substrate to form a structural layer on a component electrically attached with the substrate. The galvanic potential of the structural layer is greater than the galvanic potential of the component. At least a portion of the structural material is covered with a protective material that has a galvanic potential less than or equal to the galvanic potential of the component. The sacrificial material is removed with a release solution. At least one of the protective material and release solution is surfactanated, the surfactant functionalizing a surface of the component.
1. A method for forming a microelectromechanical structure, the method comprising:
depositing sacrificial and structural material over a substrate to form a structural layer on a component electrically attached with the substrate, wherein a galvanic potential of the structural layer is greater than a galvanic potential of the component;
passivating the compnent from galvanic degradation;
adding a surfactant to a release solution to produce a surfactanated release solution; and
removing the sacrificial material with the surfactanated release solution.
2. The method recited in claim 1 wherein the release solution comprises HF.
3. The method recited in claim 1 wherein the surfactant comprises a hydrophilic moiety and a hydrophobic moiety commonly linked to an aryl group.
4. The method recited in claim 1 wherein the sacrificial material comprises an oxide.
5. The method recited in claim 1 wherein the sacrificial material comprises a nitride.
6. The method recited in claim 1 wherein the sacrificial material comprises a metal.
7. The method recited in claim 1 wherein the sacrificial material comprises silicon or polysilicon.
8. The method recited in claim 1 wherein removing the sacrificial material comprises removing a first portion of the sacrificial material before passivating the component from galvanic degradation and removing a second portion of the sacrificial material after passivating the component from galvanic degradation.
9. The method recited in claim 1 wherein the surfactant comprises an alkyl group and a polyether-linked hydroxy group commonly linked to an aryl group.
10. The method recited in claim 9 wherein the surfactant is included in the release solution with a concentration approximately between 0.01 and 0.1 vol. %.
11. The method recited in claim 1 wherein the structural layer comprises a metal.
12. The method recited in claim 11 wherein the metal is selected from the group consisting of gold, aluminum, copper, and platinum.
13. The method recited in claim 1 wherein passivating the component from galvanic degradation comprises exposing the component to an organic alkene or organic alkyne.
14. The method recited in claim 13 wherein exposing the component to the organic alkene or organic alkyne is performed in the presence of ultraviolet radiation.
15. The method recited in claim 13 wherein exposing the component to the organic alkene or organic alkyne is performed at a temperature greater than room temperature.
16. The method recited in claim 15 wherein:
exposing the component to the organic alkene or organic alkyne is performed for a period of time between 30 and 90 minutes; and
the temperature is between 180 and 200° C.