Apparatus and method capable of a high fundamental acoustic resonance frequency and a wide resonance-free frequency range

Abstract

An embodiment of the present invention provides an apparatus capable of a high fundamental acoustic resonance frequency, comprising a substrate, a bottom electrode layer adjacent the substrate, a voltage tunable dielectric layer adjacent the bottom electrode layer, the voltage tunable dielectric layer including an active region, a top electrode adjacent the voltage tunable dielectric layer, a final interconnect layer connected to the top electrode via an interlayer, and wherein the top and bottom electrodes are at a predetermined thickness such that a desired high fundamental acoustic resonance is obtained. The active region of the voltage tunable dielectric layer may be approximately the length of the top electrode and the interlayer and the final interconnect layer may cover only a small fraction of the active region of the voltage tunable dielectric layer, thereby reducing the amplitude of resonances due to the interlayer or final interconnect layer.

1 . An apparatus capable of a high fundamental acoustic resonance frequency, comprising: 
 a substrate;    a bottom electrode layer adjacent said substrate;    a voltage tunable dielectric layer adjacent said bottom electrode layer, said voltage tunable dielectric layer including an active region;    a top electrode adjacent said voltage tunable dielectric layer;    a final interconnect layer connected to said top electrode via an interlayer; and    wherein said top and bottom electrodes are at a predetermined thickness such that a desired high fundamental acoustic resonance is obtained.    
   
   
       2 . The apparatus of  claim 1 , wherein said active region of said voltage tunable dielectric layer is approximately the length of said top electrode.  
   
   
       3 . The apparatus of  claim 1 , wherein said interlayer and said final interconnect layer cover only a small fraction of said active region of said voltage tunable dielectric layer, thereby reducing the amplitude of resonances due to the interlayer or final interconnect layer.  
   
   
       4 . The apparatus of  claim 1 , wherein said substrate is chosen to have a high acoustic loss factor thereby reducing the amplitude of resonances due to the substrate layer.  
   
   
       5 . The apparatus of  claim 1 , wherein said voltage tunable dielectric layer is 300 nm thick BST layer matched with a 150 nm gold top electrode and 200 nm platinum bottom electrode and said interlayer and final interconnect layers cover only a small percentage of said active region.  
   
   
       6 . An apparatus capable of a wide resonance-free frequency range comprising: 
 a substrate;    a bottom electrode layer adjacent said substrate;    a voltage tunable dielectric layer adjacent said bottom electrode layer, said voltage tunable dielectric layer including an active region;    a top electrode adjacent said voltage tunable dielectric layer;    a final interconnect layer connected to said top electrode via an interlayer; and    wherein said top electrode is made sufficiently thick such that the fundamental acoustic resonance lies below a desired frequency range and the bottom electrode thickness is selected to suppress the second overtone of the acoustic resonance thereby creating a wide resonance-free frequency range lying between the fundamental and third overtone of the acoustic resonance.    
   
   
       7 . The apparatus of  claim 6 , wherein said active region of said voltage tunable dielectric layer is approximately the length of said top electrode.  
   
   
       8 . The apparatus of  claim 6 , wherein said interlayer and said final interconnect layer cover only a small fraction of said active region, thereby reducing the amplitude of resonances due to the interlayer or final interconnect layer.  
   
   
       9 . The apparatus of  claim 6 , wherein said substrate has a high acoustic loss factor, thereby reducing the amplitude of resonances due to the substrate layer.  
   
   
       10 . The apparatus of  claim 6 , wherein said voltage tunable dielectric layer is an approximately 0.71 μm thick BST layer and is matched with a 0.49 μm gold top electrode and a 0.56 μm platinum bottom electrode.  
   
   
       11 . A method of modeling electrostrictive effects and acoustic resonances in a tunable capacitor, comprising: 
 adjusting empirically the characteristic impedances and complex propagation constants to account for actual process variations in manufacturing of said tunable capacitor;    adjusting empirically the characteristic impedances and complex propagation constants to account for end-effects in the directions transversal to the wave direction;    modeling the electrostrictive effect by dividing a BST layer of said tunable capacitor into thin layers or slices with each slice's thickness representing a small fraction of an acoustic wavelength and injecting at each junction between slices, an acoustic “current” proportional to the electrical current through said voltage tunable capacitor.    
   
   
       12 . The method of  claim 11 , wherein the real part of the vector sum of acoustic “voltages” at all slice junctions, divided by the electrical current vector, is taken to be representative of that part of the voltage tunable capacitor's effective series resistance contributed by the electrostrictive effect and acoustic resonances.  
   
   
       13 . The method of  claim 11 , wherein said electrostrictive effect is the transducer mechanism that links the electrical and acoustic domains.  
   
   
       14 . A method of producing a high fundamental acoustic resonance frequency, comprising: 
 placing a bottom electrode layer adjacent a substrate with a voltage tunable dielectric layer adjacent said bottom electrode layer, said voltage tunable dielectric layer including an active region;    placing a top electrode adjacent said voltage tunable dielectric layer with a final interconnect layer connected to said top electrode via an interlayer; and    using said top and bottom electrodes at a predetermined thickness such that a desired high fundamental acoustic resonance is obtained.    
   
   
       15 . The method of  claim 14 , further comprising requiring said active region of said voltage tunable dielectric layer to be approximately the length of said top electrode.  
   
   
       16 . The method of  claim 14 , wherein said interlayer and said final interconnect layer cover only a small fraction of said active region of said voltage tunable dielectric layer, thereby reducing the amplitude of resonances due to the interlayer or final interconnect layer.  
   
   
       17 . The method of  claim 14 , further comprising using a substrate chosen to have a high acoustic loss factor thereby reducing the amplitude of resonances due to the substrate layer.  
   
   
       18 . The method of  claim 14 , further comprising forming the thickness of said voltage tunable dielectric layer to a 300 nm thick BST layer and matching in with 150 nm gold top electrode and approximately 200 nm platinum bottom electrode and wherein said interlayer and final interconnect layers cover only a small percentage of said active region.  
   
   
       19 . The apparatus of  claim 1 , wherein said voltage tunable dielectric layer is a BST layer.  
   
   
       20 . (canceled)