Micro-electro-mechanical system (mems) variable capacitor apparatuses and related methods

Abstract

Systems, devices, and methods for micro-electro-mechanical system (MEMS) tunable capacitors can include a fixed actuation electrode attached to a substrate, a fixed capacitive electrode attached to the substrate, and a movable component positioned above the substrate and movable with respect to the fixed actuation electrode and the fixed capacitive electrode. The movable component can include a movable actuation electrode positioned above the fixed actuation electrode and a movable capacitive electrode positioned above the fixed capacitive electrode. At least a portion of the movable capacitive electrode can be spaced apart from the fixed capacitive electrode by a first gap, and the movable actuation electrode can be spaced apart from the fixed actuation electrode by a second gap that is larger than the first gap.

What is claimed is: 
     
         1 . A micro-electro-mechanical system (MEMS) variable capacitor, comprising:
 a fixed capacitive electrode attached to a substrate;   a fixed actuation electrode attached to the substrate;   a movable component positioned above the substrate and movable with respect to the fixed capacitive electrode and the fixed actuation electrode, the movable component comprising:
 a movable capacitive electrode positioned above the fixed capacitive electrode, wherein at least a portion of the movable capacitive electrode is spaced apart from the fixed capacitive electrode by a first gap; and 
 a movable actuation electrode positioned above the fixed actuation electrode, wherein the movable actuation electrode is spaced apart from the fixed actuation electrode by a second gap that is larger than the first gap; and 
   at least one standoff bump positioned between the fixed actuation electrode and the movable actuation electrode for maintaining a desired distance between the movable actuation electrode and the fixed actuation electrode.   
     
     
         2 . The micro-electro-mechanical system (MEMS) variable capacitor of  claim 1 , wherein the movable capacitive electrode comprises:
 one or more first capacitive portions spaced apart from the fixed capacitive electrode by the first gap; and   one or more second capacitive portions spaced apart from the fixed capacitive electrode by a distance greater than the first gap.   
     
     
         3 . The micro-electro-mechanical system (MEMS) variable capacitor of  claim 2 , wherein a size of each of the one or more first capacitive portions is substantially similar to a size of the at least one standoff bump. 
     
     
         4 . The micro-electro-mechanical system (MEMS) variable capacitor of  claim 1 , wherein the at least one standoff bump comprises one or more first standoff bumps having a first dimension by which the one or more first standoff bumps extends between the fixed actuation electrode and the movable actuation electrode, the first dimension being substantially equal to the difference between the dimensions of the first gap and the second gap. 
     
     
         5 . The micro-electro-mechanical system (MEMS) variable capacitor of  claim 4 , wherein the at least one standoff bump comprises one or more second standoff bumps having a second dimension by which the one or more second standoff bumps extends between the fixed actuation electrode and the movable actuation electrode, the second dimension being greater than the first dimension of the one or more first standoff bumps. 
     
     
         6 . The micro-electro-mechanical system (MEMS) variable capacitor of  claim 5 , wherein the one or more first standoff bumps are positioned relatively closer to the fixed capacitive electrode than the one or more second standoff bumps. 
     
     
         7 . The micro-electro-mechanical system (MEMS) variable capacitor of  claim 1 , wherein one or more of the at least one standoff bump is attached to the substrate at or near the fixed actuation electrode. 
     
     
         8 . The micro-electro-mechanical system (MEMS) variable capacitor of  claim 1 , wherein one or more of the at least one standoff bump is attached to the movable component at or near the movable actuation electrode. 
     
     
         9 . The micro-electro-mechanical system (MEMS) variable capacitor of  claim 1  wherein a difference between the dimensions of the first gap and the second gap measured in microns is greater than a value of a ratio between an actuation voltage V actuation  and a maximum electric field E max  generated between the movable actuation electrode and the fixed actuation electrode, wherein V actuation  is between 10 and 100V, and wherein E max  is between 100 and 1000 V/μm. 
     
     
         10 . The micro-electro-mechanical system (MEMS) variable capacitor of  claim 1 , wherein the difference between the dimensions of the first gap and the second gap is selected such that a self-actuation voltage between the movable actuation electrode and the fixed actuation electrode is above a predetermined threshold value. 
     
     
         11 . The micro-electro-mechanical system (MEMS) variable capacitor of  claim 10 , wherein the difference between the dimensions of the first gap and the second gap is less than or equal to one quarter of the dimension of the second gap. 
     
     
         12 . The micro-electro-mechanical system (MEMS) variable capacitor of  claim 1 , wherein the difference between the dimensions of the first gap and the second gap is between about 10 nm and 500 nm. 
     
     
         13 . A micro-electro-mechanical system (MEMS) variable capacitor, comprising:
 a fixed capacitive electrode attached to a substrate;   a first fixed actuation electrode and a second fixed actuation electrode attached to the substrate on opposing sides of the fixed capacitive electrode;   a movable component comprising a first end that is fixed with respect to the substrate and a second end opposite the first end that is fixed with respect to the substrate, a center portion of the movable component being positioned above the substrate and movable with respect to the fixed capacitive electrode, the first fixed actuation electrode, and the second fixed actuation electrode, the movable component comprising:
 a first movable actuation electrode positioned above the first fixed actuation electrode; 
 a second movable actuation electrode positioned above the second fixed actuation electrode; and 
 a movable capacitive electrode positioned above the fixed capacitive electrode; and 
   at least one standoff bump positioned between the fixed actuation electrode and the movable actuation electrode for preventing contact of the movable actuation electrode with the fixed actuation electrode;   wherein at least a portion of the movable capacitive electrode is spaced apart from the fixed capacitive electrode by a first gap;   wherein the first movable actuation electrode and the second movable actuation electrode are spaced apart from the first fixed actuation electrode and the second fixed actuation electrode, respectively, by a second gap that is larger than the first gap; and   wherein a first dimension by which one or more of the at least one standoff bump extends between the fixed actuation electrode and the movable actuation electrode is substantially equal to the difference between the dimensions of the first gap and the second gap.   
     
     
         14 . The micro-electro-mechanical system (MEMS) variable capacitor of  claim 13 , wherein the at least one standoff bump comprises one or more additional standoff bumps having a second dimension by which the one or more additional standoff bumps extends between the fixed actuation electrode and the movable actuation electrode, the second dimension being greater than the first dimension. 
     
     
         15 . The micro-electro-mechanical system (MEMS) variable capacitor of  claim 14 , wherein the one or more of the at lest one standoff bump are positioned relatively closer to the fixed capacitive electrode than the one or more additional standoff bumps.