High sensitivity microphone and manufacturing method thereof

Abstract

A high sensitivity microphone includes a substrate having a through portion provided in a central portion thereof, a vibration membrane disposed on the substrate and covering the through portion, a fixed membrane installed above the vibration membrane, spaced apart from the vibration membrane with an air layer interposed therebetween, and having a plurality of air inlets perforated in a direction toward the air layer, and a plurality of support posts provided as vertical elastic posts between the fixed membrane and the vibration membrane and mechanically fixing the vibration membrane by a frictional force, regardless of an applied voltage.

What is claimed is: 
     
         1 . A high sensitivity microphone comprising:
 a substrate having a through portion formed in a central portion of the substrate;   a vibration membrane disposed on the substrate and covering the through portion;   a fixed membrane disposed above the vibration membrane, spaced apart from the vibration membrane with an air layer interposed therebetween, and having a plurality of air inlets perforated in a direction toward the air layer; and   a plurality of support posts disposed between the fixed membrane and the vibration membrane, as elastic vertical posts, and mechanically fixing the vibration membrane by a frictional force regardless of an applied voltage.   
     
     
         2 . The high sensitivity microphone of  claim 1 , wherein:
 the support posts are formed of carbon nanotube (CNT) patterned between the fixed membrane and the vibration membrane and arranged at a predetermined interval in a circular shape from a central point of the fixed membrane.   
     
     
         3 . The high sensitivity microphone of  claim 1 , wherein:
 the support posts serve as springs with rigidity deformed by a sound pressure and are simultaneously deformed together with the vibration membrane by a sound pressure.   
     
     
         4 . The high sensitivity microphone of  claim 1 , wherein:
 the vibration membrane has a free-floating membrane structure whose contacts with respect to the support posts and the substrate are not attached.   
     
     
         5 . The high sensitivity microphone of  claim 1 , wherein:
 the vibration membrane has a depression and protrusion portion formed at edge on a bottom surface of the vibration membrane to prevent attachment of the vibration membrane to the substrate.   
     
     
         6 . The high sensitivity microphone of  claim 1 , wherein:
 the fixed membrane includes a support portion that vertically extends from an edge of the fixed membrane on the substrate.   
     
     
         7 . The high sensitivity microphone of  claim 1 , wherein:
 the fixed membrane has a fixed electrode disposed on a lower surface thereof and perforated in the same pattern as that of the air inlets.   
     
     
         8 . A method for manufacturing a high sensitivity microphone, the method comprising:
 a) forming a first sacrificial layer on a substrate and forming a vibration membrane thereon;   b) forming a second sacrificial layer on the vibration membrane and patterning carbon nanotube (CNT) seeds on opposing sides of the second sacrificial layer;   c) forming a fixed membrane on the substrate including the CNT seeds and the second sacrificial layer;   d) etching the fixed membrane to generate a plurality of perforated air inlets; and   e) removing the first sacrificial layer and the second sacrificial layer and growing the CNT seeds to form a plurality of CNT support posts as vertical elastic posts between the fixed membrane and the vibration membrane to mechanically fix the vibration membrane by a frictional force, regardless of an applied voltage.   
     
     
         9 . The method of  claim 8 , wherein operation a) comprises:
 etching a portion of the first sacrificial layer to pattern a plurality of recesses; and   forming a depression and protrusion portion by the plurality of recesses formed in the first sacrificial layer under the vibration membrane.   
     
     
         10 . The method of  claim 8 , wherein operation b) comprises:
 patterning a fixed electrode in a central portion of the second sacrificial layer.   
     
     
         11 . The method of  claim 10 , wherein in operation d),
 the fixed membrane and the fixed electrode are etched to generate a plurality of air inlets perforated in the same pattern.   
     
     
         12 . The high sensitivity microphone of  claim 8 , wherein operation d) comprises:
 etching a rear side of the substrate to form a through portion to which a sound pressure is input from the outside.   
     
     
         13 . The method of  claim 8 , wherein
 the vibration membrane includes a monolayer membrane formed of polysilicon or a silicon nitride or a multi-layer membrane formed by alternately stacking polysilicoin and a silicon nitride.   
     
     
         14 . The method of  claim 8 , wherein
 the first sacrificial layer and the second sacrificial layer are formed of any one of a photosensitive material, a silicon oxide, and a silicon nitride.   
     
     
         15 . The method of  claim 8 , wherein operation e) comprises:
 removing the first sacrificial layer to position the vibration membrane in a state of not being attached to the substrate; and   fixing the vibration membrane positioned in a non-attached manner on the substrate by a frictional force of the CNT support posts.