Method of providing a hydrophobic layer and condenser microphone having such a layer

Abstract

A method of providing at least part of a diaphragm and at least a part of a back-plate of a condenser microphone with a hydrophobic layer so as to avoid stiction between said diaphragm and said back-plate. The layer is deposited via a number small of openings in the back-plate, the diaphragm and/or between the diaphragm and the back-plate. Provides a homogeneous and structured hydrophobic layer, even to small internal cavities of the microstructure. The layer may be deposited by a liquid phase or a vapor phase deposition method. The method may be applied naturally in continuation of the normal manufacturing process. Further, a MEMS condenser microphone is provided having such a hydrophobic layer. The static distance between the diaphragm and the back-plate of the microphone is smaller than 10 μm.

1. A condenser microphone comprising a diaphragm and a back-plate, wherein an inner surface of said diaphragm forms a capacitor in combination with an inner surface of said back-plate, said back-plate and/or said diaphragm is/are provided with a number of openings, and said inner surface of the back-plate and said inner surface of the diaphragm being provided with a hydrophobic layer, and wherein the static distance between said diaphragm and said back-plate is smaller than 10 μm. 
     
     
       2. A condenser microphone according to  claim 1 , wherein at least the inner surfaces of the diaphragm and the back-plate are made from a hydrophilic material. 
     
     
       3. A condenser microphone according to  claim 1 , wherein the smallest dimension of each of the openings does not exceed 10 μm. 
     
     
       4. A condenser microphone according to  claim 3 , wherein the smallest dimension of each of the openings does not exceed 5 μm. 
     
     
       5. A condenser microphone according to  claim 4 , wherein the smallest dimension of each of the openings does not exceed 1 μm. 
     
     
       6. A condenser microphone according to  claim 5 , wherein the smallest dimension of each of the openings does not exceed 0.5 μm. 
     
     
       7. A condenser microphone according to  claim 4 , wherein the smallest dimension of each of the openings is approximately 3 μm. 
     
     
       8. A condenser microphone according to  claim 1 , wherein the hydrophobic layer base material comprises an alkylsilane. 
     
     
       9. A condenser microphone according to  claim 1 , wherein the hydrophobic layer base material comprises a perhaloalkylsilane. 
     
     
       10. A condenser microphone according to  claim 1 , wherein the static distance between the diaphragm and the back-plate is smaller than 5 μm. 
     
     
       11. A condenser microphone according to  claim 10 , wherein the static distance between the diaphragm and the back-plate is smaller than 1 μm. 
     
     
       12. A condenser microphone according to  claim 11 , wherein the static distance between the diaphragm and the back-plate is smaller than 0.5 μm. 
     
     
       13. A condenser microphone according to  claim 12 , wherein the static distance between the diaphragm and the back-plate is smaller than 0.3 μm. 
     
     
       14. A condenser microphone according to  claim 11 , wherein the static distance between the diaphragm and the back-plate is approximately 0.9 μm. 
     
     
       15. A condenser microphone according to  claim 1 , wherein the hydrophobic layer has a contact angle for water being between 90° and 130°. 
     
     
       16. A condenser microphone according to  claim 15 , wherein the hydrophobic layer has a contact angle for water being between 100° and 110°. 
     
     
       17. A condenser microphone according to  claim 1 , wherein the hydrophobic layer is stable at temperatures between −40° C. and 130° C. 
     
     
       18. A condenser microphone according to  claim 17 , wherein the hydrophobic layer is stable at temperatures between −30° C. and 110° C. 
     
     
       19. A condenser microphone according to  claim 1 , wherein the hydrophobic layer is stable at temperatures up to at least 400° C. for at least 5 minutes. 
     
     
       20. A condenser microphone comprising a diaphragm and a back-plate, wherein an inner surface of said diaphragm forms a capacitor in combination with an inner surface of said back-plate, said back-plate and/or said diaphragm is/are provided with a number of openings, and said inner surface of the back-plate and/or said inner surface of the diaphragm being provided with a hydrophobic layer having a contact angle for water being larger than 90°, and wherein the static distance between said diaphragm and said back-plate is smaller than 10 μm. 
     
     
       21. A condenser microphone comprising:
 a diaphragm;  
 a back-plate, wherein an inner surface of said diaphragm forms a capacitor in combination with an inner surface of said back-plate, said back-plate and/or said diaphragm being provided with a number of openings, wherein the static distance between said diaphragm and said back-plate is smaller than 10 μm; and  
 a hydrophobic layer, provided on said inner surface of the back-plate and/or on said inner surface of the diaphragm.  
 
     
     
       22. A microelectromechanical microphone, comprising:
   a diaphragm and a back - plate with an air gap therebetween, the diaphragm and a back - plate including respective inner surfaces forming a capacitor, the respective inner surfaces being made of a hydrophobic or hydrophilic materials;        a number of openings leading to the air gap; and        a hydrophobic molecular monolayer coating on the inner surface of the diaphragm or the back - plate, wherein molecules of the molecular monolayer are cross - linked and multi - bounded to the inner surface of the diaphragm or the back - plate.     
     
     
       23. The microelectromechanical microphone according to  claim 22 , wherein the multi- bounded molecular monolayer forms hydrophobic chains pointing away from the inner surface of the diaphragm or the back - plate.   
     
     
       24. The microelectromechanical microphone according to  claim 23 , wherein the hydrophobic molecular monolayer has a contact angle for water greater than  90 °. 
     
     
       25. The microelectromechanical microphone according to  claim 24 , wherein the hydrophobic molecular monolayer includes a perfluoralkylsilane. 
     
     
       26. The microelectromechanical microphone according to  claim 24 , wherein the hydrophobic molecular monolayer includes an alkylsilane. 
     
     
       27. The microelectromechanical microphone according to  claim 24 , wherein the hydrophobic molecular monolayer includes a perhaloalkylsilane. 
     
     
       28. The microelectromechanical microphone according to  claim 23 , wherein the hydrophobic molecular monolayer has a contact angle for water greater than about  100 °. 
     
     
       29. The microelectromechanical microphone according to  claim 23 , wherein the hydrophobic molecule monolayer is stable at temperatures up to at least  400 ° C. for at least  5  minutes. 
     
     
       30. The microelectromechanical microphone according to  claim 22 , wherein the molecular monolayer comprises a structured molecule monolayer. 
     
     
       31. The microelectromechanical microphone according to  claim 22 , wherein the diaphragm or the back- plate comprises respective materials including at least one of silicon, poly - silicon, silicon - oxide, silicon nitride, or silicon - rich silicon nitride.   
     
     
       32. The microelectromechanical microphone according to  claim 22 , wherein the hydrophobic molecular monolayer includes a perfluoralkylsilane, an alkylsilane or a perhaloalkylsilane. 
     
     
       33. The microelectromechanical microphone according to  claim 22 , wherein the hydrophobic molecular monolayer has a contact angle for water between  90 ° and  130 °. 
     
     
       34. The microelectromechanical microphone according to  claim 22 , wherein the hydrophobic molecular monolayer is stable at temperatures up to at least  400 ° C. for at least  5  minutes. 
     
     
       35. The microelectromechanical microphone according to  claim 22 , wherein the number of openings is in the back- plate, the openings receiving the hydrophobic molecular monolayer during the coating process.   
     
     
       36. The microelectromechanical microphone according to  claim 35 , wherein the hydrophobic molecular monolayer is stable at temperatures up to at least  400 ° C. for at least  5  minutes and has a contact angle for water between  90 ° and  130 °. 
     
     
       37. The microelectromechanical microphone according to  claim 22 , wherein the number of openings is in the diaphragm, the openings receiving the hydrophobic molecular monolayer during the coating process. 
     
     
       38. The microelectromechanical microphone according to  claim 22 , wherein the number of openings is in the diaphragm and in the back- plate, the openings receiving the hydrophobic molecular monolayer during the coating process.   
     
     
       39. The microelectromechanical microphone according to  claim 22 , wherein the hydrophobic molecular monolayer has a contact angle for water between  100 ° and  110 °. 
     
     
       40. The microelectromechanical microphone according to  claim 22 , wherein the air gap has a static distance not exceeding  10  μm. 
     
     
       41. A microelectromechanical microphone, comprising:
   a diaphragm having an inner surface;        a back - plate having an inner surface that, together with the inner surface of the diaphragm, forms a capacitor, wherein the static distance between the back - plate and the diaphragm does not exceed  10  μm; and        a hydrophobic layer on the inner surface of the diaphragm and the inner surface of the back - plate, the hydrophobic layer being deposited through a number of openings provided in at least one of  ( i )  the back - plate,  ( ii )  the diaphragm, or  ( ii )  gaps at a periphery of the back - plate and the diaphragm.     
     
     
       42. The microelectromechanical microphone according to  claim 41 , wherein the hydrophobic layer is a hydrophobic molecular monolayer, wherein molecules of the molecule monolayer are cross- linked and multi - bounded to the respective inner surfaces of the diaphragm and the back - plate.   
     
     
       43. The microelectromechanical microphone according to  claim 37 , wherein the molecular monolayer comprises a structured molecular monolayer. 
     
     
       44. The microelectromechanical microphone according to  claim 37 , wherein the hydrophobic molecular monolayer has a contact angle for water greater than  90 °. 
     
     
       45. The microelectromechanical microphone according to  claim 39 , wherein the hydrophobic molecule monolayer is stable at temperatures up to at least  400 ° C. for at least  5  minutes. 
     
     
       46. The microelectromechanical microphone according to  claim 41 , wherein the hydrophobic coating has a contact angle for water greater than  90 °. 
     
     
       47. The microelectromechanical microphone according to  claim 41 , wherein the hydrophobic layer is stable at temperatures up to at least  400 ° C. for at least  5  minutes. 
     
     
       48. The microelectromechanical microphone according to  claim 41 , wherein the hydrophobic layer is deposited by gaseous- phase deposition onto the inner surfaces of the diaphragm and the back - plate through the number of openings.   
     
     
       49. The microelectromechanical microphone according to  claim 41 , wherein the hydrophobic layer is deposited by liquid- phase deposition onto the inner surfaces of the diaphragm and the back - plate through the number of openings.   
     
     
       50. The microelectromechanical microphone according to  claim 41 , wherein the hydrophobic layer is stable at temperatures between at least − 30 ° C. and at least  110 ° C. 
     
     
       51. The microelectromechanical microphone according to  claim 41 , wherein the hydrophobic layer has a contact angle for water greater than about  100 °. 
     
     
       52. A microelectromechanical microphone, comprising:
   a diaphragm and a back - plate defining an air gap between respective inner surfaces thereof, the respective inner surfaces forming a capacitor, the static distance between the diaphragm and the back - plate not exceeding  10  μm;        a number of openings leading to the air gap; and        a hydrophobic layer deposited through the number of openings into the air gap to form a structured monolayer on at least one of the inner surface of the diaphragm or the inner surface of the back - plate.     
     
     
       53. The microelectromechanical microphone of  claim 52 , wherein the diaphragm includes the number of openings. 
     
     
       54. The microelectromechanical microphone of  claim 52 , wherein the back- plate includes the number of openings.   
     
     
       55. The microelectromechanical microphone of  claim 52 , wherein the back- plate and the diaphragm includes the number of openings.   
     
     
       56. The microelectromechanical microphone according to  claim 55 , wherein the hydrophobic layer is deposited by gaseous- phase or liquid - phase deposition onto the inner surfaces of the diaphragm and the back - plate through the number of openings.   
     
     
       57. The microelectromechanical microphone of  claim 52 , wherein the number of openings correspond to gaps at the periphery of the back- plate and the diaphragm.   
     
     
       58. The microelectromechanical microphone of  claim 52 , wherein the number of openings are positioned between the diaphragm and the back- plate.   
     
     
       59. The microelectromechanical microphone according to  claim 58 , wherein the hydrophobic layer has a contact angle for water greater than about  100 °. 
     
     
       60. The microelectromechanical microphone of  claim 52 , wherein the hydrophobic layer is a hydrophobic molecular monolayer, wherein molecules of the molecular monolayer are cross- linked and multi - bounded to the respective inner surfaces of the diaphragm and the back - plate.   
     
     
       61. The microelectromechanical microphone according to  claim 60 , wherein the molecule monolayer comprises a structured molecule monolayer. 
     
     
       62. The microelectromechanical microphone according to  claim 61 , wherein the hydrophobic molecular monolayer has a contact angle for water greater than  90 °. 
     
     
       63. The microelectromechanical microphone according to  claim 62 , wherein the hydrophobic molecular monolayer is stable at temperatures between at least − 30 ° C. and at least  110 ° C. 
     
     
       64. The microelectromechanical microphone according to  claim 52 , wherein the hydrophobic layer is stable at temperatures up to at least  400 ° C. for at least  5  minutes. 
     
     
       65. The microelectromechanical microphone according to  claim 52 , wherein the hydrophobic layer is deposited by gaseous- phase deposition onto the inner surfaces of the diaphragm and the back - plate through the number of openings.   
     
     
       66. The microelectromechanical microphone according to  claim 52 , wherein the hydrophobic layer is deposited by liquid- phase deposition onto the inner surfaces of the diaphragm and the back - plate through the number of openings.   
     
     
       67. The microelectromechanical microphone according to  claim 52 , wherein the hydrophobic layer is stable at temperatures between at least − 30 ° C. and at least  110 ° C. 
     
     
       68. A condenser microphone comprising a diaphragm and a back- plate, wherein an inner surface of said diaphragm forms a capacitor in combination with an inner surface of said back - plate, a number of openings being provided in at least one of  ( i )  said back - plate,  ( ii )  said diaphragm, or  ( ii )  gaps at a periphery of said back - plate and said diaphragm, and said inner surface of the back - plate and/or said inner surface of the diaphragm being provided with a hydrophobic layer having a contact angle for water being larger than  90 °, and wherein the static distance between said diaphragm and said back - plate is smaller than  10  μm.   
     
     
       69. The condenser microphone according to  claim 1 , wherein said inner surface of the back- plate and said inner surface of the diaphragm is provided with said hydrophobic layer by depositing said hydrophobic layer through the number of openings.   
     
     
       70. The condenser microphone according to  claim 1 , wherein said hydrophobic layer is a hydrophobic molecular monolayer, and wherein molecules of said molecular monolayer are cross- linked and multi - bounded to the inner surface of at least one of said diaphragm or said back - plate.   
     
     
       71. The condenser microphone according to  claim 70 , wherein the multi- bounded molecular monolayer forms hydrophobic chains pointing away from the inner surface of the diaphragm or the back - plate.   
     
     
       72. The condenser microphone according to  claim 20 , wherein said hydrophobic layer is a hydrophobic molecular monolayer, and wherein molecules of said molecular monolayer are cross- linked and multi - bounded to the inner surface of at least one of said diaphragm or said back - plate.   
     
     
       73. The condenser microphone according to  claim 21 , wherein said hydrophobic layer is a hydrophobic molecular monolayer, and wherein molecules of said molecular monolayer are cross- linked and multi - bounded to the inner surface of at least one of said diaphragm or said back - plate.