Pneumatic MEMS switch and method of fabricating the same

Abstract

A pneumatic micro electro mechanical system switch includes a substrate, a pneumatic actuating unit disposed on the substrate; the pneumatic actuating unit having a plurality of variable air cavities communicating such that when one of the plurality of variable air cavities is compressed, the rest are expanded; a signal line having a plurality of switching lines, each of which passes through a corresponding one of the plurality of variable air cavities and has switching ends disposed in a spaced-apart relation with each other in the corresponding one of the plurality of variable air cavities; a movable switching unit to connect the first and the second switching ends of each of the plurality of switching lines if one of the plurality of variable air cavities is compressed; and a driving unit to drive the pneumatic actuating unit so as to selectively compress the plurality of variable air cavities.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects and features of the present invention will be more apparent from the description for exemplary embodiments of the present invention taken with reference to the accompanying drawings, in which:

FIGS. 1A and 1B are a perspective view and a cross-sectional view exemplifying a pneumatic RF MEMS switch in accordance with an exemplary embodiment of the present invention when a second switching line is in a ‘ON’ state;

FIG. 2 is a perspective view exemplifying the pneumatic RF MEMS switch of FIG. 1A when a first switching line is in a ‘ON’ state;

FIGS. 3A through 3F are perspective views exemplifying a process of fabricating the pneumatic RF MEMS switch of FIGS. 1A and 1B;

FIG. 4 is a partial cross-sectional view exemplifying another example of a connecting pad of a first and a second switching lines of the pneumatic RF MEMS switch of FIGS. 1A and 1B;

FIG. 5 is a magnified cross-sectional view exemplifying a seal which seals first etching holes of a membrane and second etching holes of a first and a second driving electrodes of the pneumatic RF MEMS switch of FIGS. 1A and 1B;

FIG. 6 is a cross-sectional view exemplifying etching passages which are formed at a substrate when the first and the second etching holes are not formed at the membrane and the first and the second driving electrodes of the pneumatic RF MEMS switch of FIGS. 1A and 1B;

FIG. 7 is a perspective view exemplifying a modified example of the pneumatic RF MEMS switch in accordance with the exemplary embodiment of the present invention;

FIG. 8 is a perspective view exemplifying another modified example of the pneumatic RF MEMS switch in accordance with the exemplary embodiment of the present invention; and

FIG. 9 is a perspective view exemplifying still another modified example of the pneumatic RF MEMS switch in accordance with the exemplary embodiment of the present invention.

Claims

1. A pneumatic micro electro mechanical system switch comprising: a substrate;a pneumatic actuating unit disposed on the substrate, comprising a plurality of variable air cavities communicating such that when at least one of the plurality of variable air cavities is compressed, the rest are expanded;a signal line having a plurality of switching lines, each of which passes through a corresponding one of the plurality of variable air cavities and has a first and a second switching ends disposed in a spaced-apart relation with each other in the corresponding one of the plurality of variable air cavities;a switching unit movable with the pneumatic actuating unit to connect the first and the second switching ends of each of the plurality of switching lines when each of the plurality of variable air cavities is compressed; anda driving unit to drive the pneumatic actuating unit so as to selectively compress at least one of the plurality of variable air cavities.

2. The switch as claimed in claim 1, wherein the substrate is formed of one selected from a high resistivity silicon and a quartz.

3. The switch as claimed in claim 1, wherein the pneumatic actuating unit further comprises a membrane to enclose a plurality of trenches formed at the substrate to form the plurality of variable air cavities.

4. The switch as claimed in claim 3, wherein the membrane is formed of one selected from a silicon oxide film, a silicon nitride film and a parylene.

5. The switch as claimed in claim 3, wherein the membrane has a plurality of first etching holes to remove a sacrificing layer pattern for forming the plurality of variable air cavities during a fabrication, andwherein the plurality of first etching holes are sealed with a seal.

6. The switch as claimed in claim 3, wherein the membrane has a plurality of first etching holes to remove a sacrificing layer pattern for forming the plurality of variable air cavities during a fabrication, andwherein at least one of the plurality of first etching holes is not sealed with a seal within a range where the membrane is operable such that when the at least one of the plurality of variable air cavities is compressed, the rest are expanded.

7. The switch as claimed in claim 3, wherein each of the plurality of switching lines comprises a coplanar wave guide spaced apart from a ground formed on the plurality of trenches, so as to transmit a signal with an electronic field.

8. The switch as claimed in claim 7, wherein the ground and the signal line are formed of one selected from Au and Pt, respectively.

9. The switch as claimed in claim 3, wherein the switching unit comprises a plurality switching contacts, each of which is formed opposite to the first and the second switching ends of each of the plurality of switching lines in each of the plurality of variable air cavities.

10. The switch as claimed in claim 9, wherein the plurality of switching contacts is formed of one selected from Au, Pt, Rh and Ir, respectively.

11. The switch as claimed in claim 9, wherein the driving unit comprises: a ground formed on the plurality of trenches in the plurality of variable air cavities; anda plurality of driving electrodes, each of which is formed opposite to the ground on the corresponding one of the plurality of trenches, to generate an electrostatic force with the ground therebetween when a voltage is applied and compress the corresponding one of the plurality of variable air cavities of the membrane.

12. The switch as claimed in claim 11, wherein the plurality of driving electrodes is formed of one selected from Al, Mo, and Ta, respectively.

13. The switch as claimed in claim 11, wherein each of the plurality of driving electrodes has a plurality of second etching holes to remove a sacrificing layer pattern for forming the plurality of variable air cavities during a fabrication, andwherein the plurality of second etching holes are sealed with a seal.

14. The switch as claimed in claim 11, wherein each of the plurality of driving electrodes has a plurality of second etching holes to remove a sacrificing layer pattern for forming the plurality of variable air cavities during a fabrication, andwherein at least one of the plurality of second etching holes is not sealed with a seal within a range where the membrane is operable in such a manner that when the at least one of the plurality of variable air cavities is compressed, the rest are expanded.

15. The switch as claimed in claim 11, wherein the plurality of trenches, the plurality of variable air cavities, the plurality of switching lines, the plurality of switching contacts, and the plurality of driving electrodes comprise two trenches, two variable air cavities, two switching lines, two switching contacts, and two driving electrodes, respectively.

16. The switch as claimed in claim 11, wherein the plurality of trenches, the plurality of variable air cavities, the plurality of switching lines, the plurality of switching contacts, and the plurality of driving electrodes comprise at least three trenches, at least three variable air cavities, at least three switching lines, at least three switching contacts, and at least three driving electrodes, respectively, and wherein the plurality of trenches and the plurality of variable air cavities are arranged in series and formed to communicate with one another, respectively.

17. The switch as claimed in claim 11, wherein the plurality of trenches, the plurality of variable air cavities, the plurality of switching lines, the plurality of switching contacts, and the plurality of driving electrodes comprise at least three trenches, at least three variable air cavities, at least three switching lines, at least three switching contacts, and at least three driving electrodes, respectively, and wherein the plurality of trenches and the plurality of variable air cavities are configured in such a manner that at least one of the plurality of trenches and the plurality of variable air cavities is disposed in a center of the rest and formed to communicate with one another, respectively.

18. The switch as claimed in claim 11, wherein the plurality of trenches, the plurality of variable air cavities, the plurality of switching contacts, and the plurality of driving electrodes constitute a plurality of switch units, each of which is formed of two trenches, two variable air cavities, two switching contacts, and two driving electrodes, and wherein the plurality of switch units are successively connected with one another in such a manner that one unit is disposed in parallel with another two units.

19. A method of fabricating a pneumatic micro electro mechanical system switch, the method comprising: forming a signal line and a ground on a substrate;forming a sacrificing layer pattern for forming a membrane over the substrate on which the signal line and the ground are formed, the membrane having a plurality of variable air cavities, which communicate with each other;forming a plurality of switching contacts for switching the signal line on the sacrificing layer pattern;forming a membrane to cover the sacrificing layer pattern on the sacrificing layer pattern on which the plurality of switching contacts is formed;forming a plurality of driving electrodes opposite to the ground at the membrane, the plurality of driving electrodes operating to selectively compress the plurality of variable air cavities; andremoving the sacrificing layer pattern.

20. The method as claimed in claim 19, wherein the forming a signal line and ground comprises: forming a groove part having a plurality of trenches communicating with each other on the substrate; andforming a signal line and a ground on the substrate on which the groove part is formed, the signal line having a plurality of switching lines, each of which is disposed across a corresponding one of the plurality of trenches and has a first and a second switching ends disposed in the corresponding one of the plurality of trenches, and the ground being spaced apart from the plurality of switching lines of the signal line.

21. The method as claimed in claim 20, wherein the forming a groove part comprises: forming a groove part etching mask pattern for forming the groove part on the substrate;etching the substrate by using the groove part etching mask pattern as an etching mask; andremoving the groove part etching mask pattern.

22. The method as claimed in claim 21, wherein the groove part etching mask pattern is formed of one selected from silicon oxide film, nitride film, a photo resist, an epoxy resin, and a metal.

23. The method as claimed in claim 21, wherein the groove part etching mask pattern further comprises an etching passage pattern for forming a plurality of etching passages, which etch and remove the sacrificing layer pattern, on the substrate.

24. The method as claimed in claim 21, wherein the substrate is formed of one selected from a high resistivity silicon and a quartz; andwherein the etching the substrate is carried out by dry-etching if the substrate is formed of the high resistivity silicon, and by wet-etching if the substrate is formed of the quartz.

25. The method as claimed in claim 20, wherein the forming a signal line and a ground on the substrate on which the groove part is formed comprises: forming a first metal layer on the on the substrate on which the groove part is formed; andpatterning the first metal layer to form the signal line and the ground.

26. The method as claimed in claim 25, wherein the first metal layer is formed of one selected from Au and Pt.

27. The method as claimed in claim 19, wherein the forming a sacrificing layer pattern comprises: forming a first sacrificing layer over the substrate on which the signal line and the ground are formed;patterning the first sacrificing layer to form a first air cavity sacrificing layer pattern for forming at least one of the plurality of variable air cavities, which is in a compressed state;curing the substrate over which the first air cavity sacrificing layer pattern is formed;forming a second sacrificing layer on the cured substrate;patterning the second sacrificing layer to form a second air cavity sacrificing layer pattern for forming the remaining plurality of variable air cavities, which are in an expanded state; andcuring the substrate over which the second air cavity sacrificing layer pattern is formed.

28. The method as claimed in claim 27, wherein the first and the second sacrificing layers are formed of a photo resist.

29. The method as claimed in claim 20, wherein the forming a plurality of switching contacts comprises: forming a second metal layer over the substrate over which the sacrificing layer pattern is formed; andpatterning the second metal layer to form a plurality of switching contacts opposite to the first and the second switching ends of each of the plurality of switching lines or the signal line.

30. The method as claimed in claim 29, wherein the second metal layer is formed of one selected from Au, Pt, Rh and Ir.

31. The method as claimed in claim 19, wherein the forming a membrane comprises: forming a membrane layer over the substrate over which the plurality of switching contacts are formed; andpatterning the membrane layer to form a membrane, which covers the sacrificing layer pattern.

32. The method as claimed in claim 31, wherein the membrane layer is formed of one selected from a silicon oxide film, a silicon nitride film, and a parylene.

33. The method as claimed in claim 19, wherein the forming a plurality of driving electrodes comprises: forming a third metal layer over the substrate over which the membrane is formed; andpatterning the third metal layer to form a plurality of driving electrodes opposite to a plurality of variable air cavities in the membrane, respectively.

34. The method as claimed in claim 33, wherein the third metal layer is formed of one selected from Al, Mo, and Ta.

35. The method as claimed in claim 33, wherein the patterning the third metal layer further comprises pattering the third metal layer such that each of the plurality of driving electrodes further comprises a plurality of second etching holes for etching and removing the sacrificing layer pattern, andwherein the patterning the third metal layer to form a plurality of driving electrodes further comprises patterning the third metal layer such that the membrane further comprises a plurality of first etching holes for etching and removing the sacrificing layer pattern.

36. The method as claimed in claim 35, wherein the removing the sacrificing layer pattern comprises removing the sacrificing layer pattern through the plurality of first and second etching holes by using one of a wet-etching process and an ashing process.

37. The method as claimed in claim 36, further comprising sealing the plurality of first and second etching holes.

38. The method as claimed in claim 37, wherein the sealing the plurality of first and second etching holes comprises: forming a sealing layer over the substrate from which the sacrificing layer pattern is removed; andpatterning the sealing layer to form a seal, which seals the plurality of first and second etching holes.

39. The method as claimed in claim 38, wherein the sealing layer is formed of one selected from a silicon nitride film, a silicon oxide film, and a parylene.

40. The method as claimed in claim 38, wherein the patterning the sealing layer is carried out in such a manner that at least one of the plurality of first and at least one of the plurality of second etching holes is not sealed with the seal within a range where the membrane is so operable that when at least one of the plurality of variable air cavities is compressed, the rest of the plurality of variable air cavities are expanded.

41. The method as claimed in claim 23, wherein the removing the sacrificing layer pattern comprises removing the sacrificing layer pattern through the plurality of etching passages by using one of a wet-etching process and an ashing process.

42. The method as claimed in claim 41, further comprising sealing the plurality of etching passages.

43. The method as claimed in claim 42, wherein the sealing the plurality of etching passages comprises: inserting metal balls into the plurality of etching passages formed at the substrate from which the sacrificing layer pattern is removed; andheating the substrate to fuse the metal balls with heat and thus to seal the plurality of etching passages.

44. The method as claimed in claim 43, further comprising forming a protecting layer on the plurality of driving electrodes to protect the plurality of driving electrodes.