Mems tilt sensor

Abstract

An acoustic sensor includes a back plate; at least one back plate electrode coupled to the back plate; a proof of mass with the proof of mass elastically coupled to the back plate; and a proof of mass electrode coupled to the proof of mass. Movement of the sensor causes a capacitance between the proof of mass electrode and the at least one back plate electrode to vary and the capacitance represents a magnitude of the movement of the sensor.

What is claimed is: 
     
         1 . A microelectromechanical system (MEMS) microphone comprising:
 a substrate;   a MEMS microphone disposed on the substrate;   an integrated circuit coupled to the MEMS microphone;   a tilt sensor disposed on the substrate, the tilt sensor comprising:
 a back plate; 
 at least one back plate electrode disposed on the back plate; 
 a proof of mass coupled to the back plate; and 
 a sensing electrode coupled to the proof of mass that moves relative to the back plate, wherein movement of the MEMS microphone moves the sensing element relative to the back plate such that the distance between the sensing electrode and the at least one back plate electrode changes, wherein a capacitance between the sensing electrode and the at least one back plate electrode is communicated to the integrated circuit, wherein the integrated circuit determines an orientation of the MEMS microphone based upon the capacitance. 
   
     
     
         2 . The MEMS microphone of  claim 1 , wherein the back plate has a plurality of openings through the back plate. 
     
     
         3 . The MEMS microphone of  claim 1 , further comprising a housing, coupled to the substrate, which encloses the MEMS microphone and the tilt sensor. 
     
     
         4 . The MEMS microphone of  claim 1 , wherein at least one back plate electrode comprises two back plate electrodes. 
     
     
         5 . The MEMS microphone of  claim 1 , wherein at least one back plate electrode comprises four back plate electrodes. 
     
     
         6 . The MEMS microphone of  claim 1 , wherein the integrated circuit is configured to calculate a pitch of the back plate. 
     
     
         7 . The MEMS microphone of  claim 1 , wherein the proof of mass is coupled to the back plate via a spring. 
     
     
         8 . The MEMS microphone of  claim 1 , wherein the integrated circuit is configured to calculate an acceleration 
     
     
         9 . The MEMS microphone of  claim 1 , wherein the proof of mass weighs 0.2 milligrams. 
     
     
         10 . The MEMS microphone of  claim 1 , wherein the proof of mass is cylindrical. 
     
     
         11 . The MEMS microphone of  claim 10 , wherein the proof of mass has a diameter of 500 microns. 
     
     
         12 . The MEMS microphone of  claim 1 , wherein the proof of mass comprises silicon. 
     
     
         13 . The MEMS microphone of  claim 1 , further comprising a polysilicon layer that comprises the sensing electrode. 
     
     
         14 . The MEMS microphone of  claim 1 , wherein the back plate is charged.