Micromechanical device with gold alloy contacts and method of manufacture

Abstract

A MEMS switch device is made using a gold alloy as the switch contact material. The increased mechanical hardness of the alloy compared to the pure gold prevents the contacts of the switch from welding together. A scrubbing action which occurs when the switch closes may allow the contact surfaces to come to rest where their surfaces are complementary, thus resulting in higher contact area and low contact resistance, despite the higher sheet resistance of the gold alloy material relative to the pure gold material.

1 . A micromechanical device, comprising:
 a first moveable member formed over a substrate surface, the first moveable member having a first contact comprising gold and a first alloying material; and   a second contact comprising gold and a second alloying material, wherein the first member moves such that electrical contact is established between the first contact and the second contact, and the first and the second alloying materials are chosen from a group consisting of palladium (Pd), cobalt (Co), copper (Cu), iron (Fe), platinum (Pt), bismuth (Bi), iridium (Ir), silver (Ag), and tungsten (W), rhodium (Rh), ruthenium (Ru), nickel (Ni), cadmium (Cd) and zinc (Zn), at a weight percentage of at least 0.1%.   
   
   
       2 . The micromechanical device of  claim 1 , wherein the first moveable member moves such that surfaces of the first contact and second contact have a component of lateral movement against each other. 
   
   
       3 . The micromechanical device of  claim 1 , wherein the first moveable member is a first thermally actuated cantilevered beam. 
   
   
       4 . The micromechanical device of  claim 3 , wherein the second contact is disposed on a second thermally actuated cantilevered beam formed over the substrate surface. 
   
   
       5 . The micromechanical device of  claim 1 , wherein the first alloying material and the second alloying material comprise palladium with a weight percentage of at most about 10%. 
   
   
       6 . The micromechanical device of  claim 5 , wherein the first alloying material and the second alloying material comprise palladium at a weight percentage of about 2%. 
   
   
       7 . The micromechanical device of  claim 4 , wherein the first thermally actuated cantilevered beam is less stiff than the second thermally actuated cantilevered beam. 
   
   
       8 . The micromechanical device of  claim 1 , wherein the first contact and the second contact have angled adjacent faces which maintain engagement of the first and second contacts. 
   
   
       9 . The micromechanical device of  claim 4 , wherein the first thermally actuated cantilevered beam and the second thermally actuated cantilevered beam each comprises a current-carrying drive loop and a signal-carrying passive beam. 
   
   
       10 . The micromechanical device of  claim 9 , wherein the first thermally actuated cantilevered beam is designed to move about 8 μm when actuated, and the second thermally actuated cantilevered beam is designed to move about 5 μm when actuated. 
   
   
       11 . The micromechanical device of  claim 9 , wherein the first thermally actuated cantilevered beam and the second thermally actuated cantilevered beam comprise at least one of nickel and a nickel alloy. 
   
   
       12 . A method of making a micromechanical device, comprising:
 forming a first moveable member over a substrate surface;   forming a first contact on the first moveable member, the first contact comprising gold and a first alloying material; and   forming a second contact comprising gold and a second alloying material, wherein the first moveable member is configured to move such that electrical contact is established between the first contact and the second contact, and wherein the first and the second alloying materials are chosen from a group consisting of palladium (Pd), cobalt (Co), copper (Cu), iron (Fe), platinum (Pt), bismuth (Bi), iridium (Ir), silver (Ag), and tungsten (W), rhodium (Rh), ruthenium (Ru), nickel (Ni), cadmium (Cd) and zinc (Zn), at a weight percentage of at least 0.1%.   
   
   
       13 . The method of  claim 12 , wherein forming the first and second contacts comprises electroplating a gold/palladium alloy with the palladium at a weight percentage of about 2%. 
   
   
       14 . The method of  claim 12 , further comprising forming a second moveable member over the substrate surface, wherein the second contact is attached to the second moveable member. 
   
   
       15 . The method of  claim 14 , wherein forming the first moveable member and the second moveable member comprises electroplating a first and a second cantilevered beam of at least one of nickel and a nickel alloy. 
   
   
       16 . The method of  claim 12 , wherein forming the first moveable member comprises forming the first moveable member such that surfaces of the first contact and second contact have a component of lateral movement against each other when the first moveable member moves. 
   
   
       17 . The method of  claim 14 , further comprising forming the first moveable member such that it is less stiff than the second moveable member. 
   
   
       18 . The method of  claim 14 , wherein forming the first contact and the second contact further comprises forming a first and a second contact having angled adjacent faces which maintain engagement of the first and second contacts. 
   
   
       19 . A method of using the micromechanical device of  claim 7 , comprising:
 energizing the second thermally actuated cantilevered beam;   energizing the first thermally actuated cantilevered beam;   de-energizing the second thermally actuated cantilevered beam; and   allowing the second thermally actuated cantilevered beam to relax against the first thermally actuated cantilevered beam to close the device.   
   
   
       20 . A micromechanical device, comprising:
 a first moveable member formed over a substrate surface, the first moveable member having a first contact; and   a second contact formed over the substrate surface, wherein the first member moves such that electrical contact is established between the first contact and the second contact, and moves such that contact surfaces of the first and the second contacts are moved with a component in a lateral direction, parallel to the contact surfaces as electrical contact is established.