Mems mass-spring-damper systems using an out-of-plane suspension scheme

Abstract

MEMS mass-spring-damper systems (including MEMS gyroscopes and accelerometers) using an out-of-plane (or vertical) suspension scheme, wherein the suspensions are normal to the proof mass, are disclosed. Such out-of-plane suspension scheme helps such MEMS mass-spring-damper systems achieve inertial grade performance. Methods of fabricating out-of-plane suspensions in MEMS mass-spring-damper systems (including MEMS gyroscopes and accelerometers) are also disclosed.

1 . A MEMS gyroscope, comprising:
 a. a shared proof mass;   b. one or more anchors;   c. one or more movable combs; and   d. a plurality of suspensions;   e. wherein said plurality of suspensions are out-of-plane with said shared proof mass.   
     
     
         2 . The MEMS gyroscope of  claim 1 , wherein said MEMS gyroscope is an inertial grade MEMS gyroscope. 
     
     
         3 . The MEMS gyroscope of  claim 1 , wherein said shared proof mass, together with said one or more movable combs, have a combined weight ranging from 30 μg to 3 mg. 
     
     
         4 . The MEMS gyroscope of  claim 1 , wherein said shared proof mass is positioned below said suspensions. 
     
     
         5 . The MEMS gyroscope of  claim 1 , wherein said suspensions have a cross-section ranging from 5×5 μm 2  to 100×100 μm 2 . 
     
     
         6 . The MEMS gyroscope of  claim 1 , wherein said suspensions have a length ranging from 150 μm to 600 μm. 
     
     
         7 . The MEMS gyroscope of  claim 1 , wherein said one or more movable combs rest on said suspensions. 
     
     
         8 . The MEMS gyroscope of  claim 1 , wherein said one or more movable combs are comprised of first and second sense combs and first and second drive combs. 
     
     
         9 . The MEMS gyroscope of  claim 1 , wherein said MEMS gyroscope is a three-fold symmetric gyroscope. 
     
     
         10 . The MEMS gyroscope of  claim 1 , wherein said shared proof mass, said one or more anchors, said one or more movable combs, and said suspensions are comprised of crystalline Silicon. 
     
     
         11 . The MEMS gyroscope of  claim 1 , wherein said MEMS gyroscope is bulk micromachined. 
     
     
         12 - 23 . (canceled) 
     
     
         24 . A quad-mass MEMS gyroscope, comprising:
 a. a plurality of proof masses;   b. one or more anchors;   c. one or more movable combs; and   d. a plurality of suspensions;   e. wherein said suspensions are out-of-plane with said proof masses.   
     
     
         25 . The quad-mass MEMS gyroscope of  claim 24 , wherein said one or more movable combs are comprised of a plurality of sense combs and a plurality of drive combs. 
     
     
         26 . The quad-mass MEMS gyroscope of  claim 25 , wherein each proof mass has its own respective drive comb, but said sense combs are shared by said proof masses. 
     
     
         27 . A MEMS mass-spring-damper system, comprising:
 a. at least one proof mass; and   b. a plurality of suspensions;   c. wherein said suspensions are out-of-plane with said at least one proof mass.   
     
     
         28 . The MEMS mass-spring-damper system of  claim 27 , wherein said MEMS mass-spring-damper system is an inertial grade range MEMS mass-spring-damper system. 
     
     
         29 . The MEMS mass-spring-damper system of  claim 27 , wherein said MEMS mass-spring-damper system is bulk micromachined. 
     
     
         30 . A method for fabricating a vertical suspension in a substrate in a MEMS mass-spring-damper system, said method comprising the steps of:
 a. realizing a first side and a second side of said vertical suspension by selectively etching through a top surface of said substrate; and   b. realizing a third side and a fourth side of said vertical suspension by selectively etching through a bottom surface of said substrate.   
     
     
         31 . The method of  claim 30 , wherein said etching in steps (a) and (b) is performed using DRIE. 
     
     
         32 . The method of  claim 30 , wherein said MEMS mass-spring-damper system is an inertial grade MEMS gyroscope. 
     
     
         33 . The method of  claim 30 , wherein said MEMS mass-spring damper system is an inertial grade MEMS accelerometer.