Etch release residue removal using anhydrous solution
View Patent ↗A method of making a microelectromechanical systems (MEMS) device includes etching away a sacrificial material layer to release a mechanical element of the MEMS device. The MEMS device is formed at least partially on the sacrificial material layer, and the etching leaves a residue in proximity to the mechanical element. The residue is exposed to an anhydrous solution to remove the residue. The residue may be an ammonium fluorosilicate-based residue, and the anhydrous solution may include acetic acid, isopropyl alcohol, acetone, or any anhydrous solution that can effectively dissolve the ammonium fluorosilicate-based residue.
1. A method of making a microelectromechanical systems (MEMS) device comprising:
etching away a sacrificial material layer to release a mechanical element of said MEMS device, said mechanical element being formed at least partially on said sacrificial material layer, wherein said etching comprises performing a vapor phase etch (VPE) process and said etching leaves a residue in proximity to said mechanical element;
performing an oxygen plasma exposure process to remove a volatile portion of said residue from said MEMS device; and
following said etching and said performing, exposing said residue to an anhydrous solution to remove said residue.
2. The method of claim 1 wherein said mechanical element comprises a movable part, said residue underlies said movable part and said exposing comprises exposing said MEMS device to said anhydrous solution to remove said residue underlying said movable part.
3. The method of claim 1 wherein said anhydrous solution comprises acetic acid.
4. The method of claim 3 wherein said anhydrous solution further comprises acetic anhydride blended with said acetic acid.
5. The method of claim 1 wherein said anhydrous solution comprises isopropyl alcohol.
6. The method of claim 1 wherein said anhydrous solution comprises acetone.
7. The method of claim 1 further comprising rinsing said MEMS device in hydrogen peroxide following said exposing.
8. The method of claim 1 wherein said MEMS device further comprises metallization features, wherein following said etching, said residue is contaminated with aluminum from said metallization features, and wherein said exposing comprises exposing said metallization features to said anhydrous solution to remove said aluminum contaminated residue from said metallization features.
9. The method of claim 1 wherein said residue comprises a hygroscopic chemical compound that undergoes volumetric expansion when exposed to an aqueous solution, and said method further comprises abstaining from exposing said residue to said aqueous solution prior to said exposing.
10. The method of claim 1 wherein said residue comprises a chemical compound containing nitrogen, hydrogen, silicon, and fluorine.
11. The method of claim 1 wherein said residue comprises ammonium fluorosilicate, (NH 4 ) 2 SiF 6 .
12. The method of claim 11 wherein said MEMS device comprises metallization features, said metallization features comprising aluminum, and wherein said ammonium fluorosilicate residue is contaminated with said aluminum.
13. A method of making a microelectromechanical systems (MEMS) device comprising:
etching away a sacrificial material layer to release a mechanical element of said MEMS device by performing a vapor phase etch (VPE) process, said mechanical element being formed at least partially on said sacrificial material layer, wherein said etching leaves a residue in proximity to said mechanical element;
performing an oxygen plasma exposure process to remove a volatile portion of said residue from said MEMS device;
following said etching and said performing, exposing said residue to an anhydrous solution to remove said residue; and
rinsing said MEMS device in hydrogen peroxide following said exposing.
14. The method of claim 13 wherein said residue comprises a hygroscopic chemical compound that undergoes volumetric expansion when exposed to an aqueous solution, and said method further comprises abstaining from exposing said residue to said aqueous solution prior to said exposing.
15. A method of making a microelectromechanical systems (MEMS) device comprising:
etching away a sacrificial material layer to release a mechanical element of said MEMS device by performing a vapor phase etch (VPE) process, said mechanical element being formed at least partially on said sacrificial material layer, wherein said etching leaves an ammonium fluorosilicate, (NH 4 ) 2 SiF 6 , residue in proximity to said mechanical element;
performing an oxygen plasma exposure process to remove a volatile portion of said residue from said MEMS device; and
following said etching and said performing, exposing said ammonium fluorosilicate residue to an anhydrous solution to remove said ammonium fluorosilicate residue, said anhydrous solution comprising a blend of acetic acid and acetic anhydride.
16. The method of claim 15 wherein said mechanical element comprises a movable part, said ammonium fluorosilicate residue underlies said movable part and said exposing comprises exposing said MEMS device to said anhydrous solution to remove said ammonium fluorosilicate underlying said movable part.
17. The method of claim 15 wherein said MEMS device further comprises metallization features, wherein following said etching, said ammonium fluorosilicate residue is contaminated with aluminum from said metallization features, and wherein said exposing comprises exposing said metallization features to said anhydrous solution to remove said aluminum contaminated ammonium fluorosilicate residue from said metallization features.