Mems resonator with high quality factor

Abstract

A symmetrical MEMS resonator is disclosed with a high quality factor. The MEMS resonator includes a silicon layer with a top surface and bottom surface opposite the top surface. A pair of first metal layers is provided above the top surface of the silicon layer and a corresponding pair of second metal layers is symmetrically provided below the second surface of the silicon layer relative to the pair of first metal layers. Furthermore, a first piezoelectric layer is disposed between the pair of first metal layers and a second piezoelectric layer is disposed between the pair of second metal layers.

1 . A MEMS resonator comprising:
 a silicon layer having a first surface and a second surface opposite the first surface;   at least one metal layer disposed above the first surface of the silicon layer and at least one corresponding metal layer disposed below the second surface of the silicon layer; and   a piezoelectric layer disposed above the first surface of the silicon layer and a corresponding piezoelectric layer disposed below the second surface of the silicon layer.   
     
     
         2 . The MEMS resonator according to  claim 1 , wherein the at least one metal layer and the at least one corresponding metal layer are symmetrically disposed with respect to each other about the silicon layer and the piezoelectric layer and the corresponding piezoelectric layer are symmetrically disposed with respect to each other about the silicon layer. 
     
     
         3 . The MEMS resonator according to  claim 1 , wherein the at least one metal layer comprises a pair of first metal layers with the piezoelectric layer disposed therebetween. 
     
     
         4 . The MEMS resonator according to  claim 3 , wherein the at least one corresponding metal layer comprises a pair of second metal layers with the corresponding piezoelectric layer disposed therebetween. 
     
     
         5 . The MEMS resonator according to  claim 4 , wherein the pair of first metal layers and the piezoelectric layer are symmetrically disposed about the silicon layer with respect to the pair of second metal layers and the corresponding piezoelectric layer. 
     
     
         6 . The MEMS resonator according to  claim 4 , wherein the pair of first metal layers is electrically coupled to a voltage source to actuate the MEMS resonator. 
     
     
         7 . The MEMS resonator according to  claim 6 , wherein the pair of second metal layers is electrically coupled to the voltage source. 
     
     
         8 . The MEMS resonator according to  claim 6 , wherein the pair of second metal layers is electrically insulated from the voltage source. 
     
     
         9 . The MEMS resonator according to  claim 4 , wherein the piezoelectric layer comprises a thickness substantially equal to a thickness of the corresponding piezoelectric layer. 
     
     
         10 . The MEMS resonator according to  claim 9 , wherein the pair of first metal layers each comprises a thickness substantially equal to respective thicknesses of the pair of second metal layers. 
     
     
         11 . The MEMS resonator according to  claim 1 , wherein the piezoelectric layer comprises a thickness substantially equal to a thickness of the corresponding piezoelectric layer. 
     
     
         12 . The MEMS resonator according to  claim 11 , wherein the at least one metal layer comprises a thickness substantially equal to a thickness of the at least one corresponding metal layer. 
     
     
         13 . The MEMS resonator according to  claim 1 , wherein the silicon layer comprises a thickness between 5 and 10 micrometers. 
     
     
         14 . A MEMS resonator comprising:
 a silicon layer having a first surface and a second surface opposite the first surface;   a pair of first metal layers disposed above the first surface of the silicon layer;   a first piezoelectric layer disposed between the pair of first metal layers;   a pair of second metal layers symmetrically disposed below the second surface of the silicon layer relative to the pair of first metal layers; and   a second piezoelectric layer disposed between the pair of second metal layers.   
     
     
         15 . The MEMS resonator according to  claim 14 , wherein the pair of first metal layers is electrically coupled to a voltage source to actuate the MEMS resonator. 
     
     
         16 . The MEMS resonator according to  claim 15 , wherein the pair of second metal layers is electrically insulated from the voltage source. 
     
     
         17 . The MEMS resonator according to  claim 14 , wherein the silicon layer comprises a thickness between 5 and 10 micrometers. 
     
     
         18 . A MEMS resonator comprising:
 a silicon layer having a first surface and a second surface opposite the first surface;   a pair of first metal layers disposed above the first surface of the silicon layer;   a first piezoelectric layer having a first thickness disposed between the pair of first metal layers; and   a second piezoelectric layer disposed below the second surface of the silicon layer,   wherein the second piezoelectric layer comprises a second thickness greater than the first thickness of the first piezoelectric layer to inhibit vibration in a thickness direction of the MEMS resonator when the pair of first metal layers are excited by a voltage source.   
     
     
         19 . The MEMS resonator according to  claim 18 , wherein the pair of first metal layers and the first piezoelectric layer have a combined mechanical stiffness that is substantially equal to a mechanical stiffness of the second piezoelectric layer. 
     
     
         20 . The MEMS resonator according to  claim 19 , wherein the combined mechanical stiffness of the pair of first metal layers and the first piezoelectric layer is within 10% MPa*m of the mechanical stiffness of the second piezoelectric layer.