Article comprising improved noble metal-based alloys and method for making the same

Abstract

A device having electrical contacts formed from an alloy having improved wear resistance is provided, the alloy being particularly useful in microrelay devices formed by MEMS technology. In one embodiment, the alloys are chosen to allow sufficient precipitation hardening to improve wear resistance, but keep precipitation below a level that would unacceptably reduce electrical conductivity. This is achieved by using alloying materials that have very limited or no solid solubility in the noble metal matrix, e.g., less than 4 wt. % solid solubility. In a second embodiment, an alloy contains a noble metal matrix and insoluble, dispersoid particles having no solubility in the matrix, these dispersoid particles offering a similar strengthening mechanism.

What is claimed is:  
     
         1 . An article comprising at least one electrical contact formed from an electrically conductive alloy comprising: 
 one or more noble metal elements;    one or more alloying elements, wherein the solid solubility of each of the one or more alloying elements in each of the one or more noble metal elements is less than 4 weight percent and wherein the one or more alloying elements are present in the alloy in a total amount of 0.1 to 30 weight percent; and    precipitate particles comprising the one or more alloying elements, wherein the particles have an average diameter less than 500 nm, and are present in a volume fraction of 0.1 to 30%,    wherein the mechanical hardness of the alloy is at least 30% greater than the mechanical hardness of the one or more noble metal elements alone.    
     
     
         2 . The article of    claim 1   , wherein the solid solubility of each of the one or more alloying elements is less than 2 weight percent.  
     
     
         3 . The article of    claim 2   , wherein the solid solubility of each of the one or more alloying elements is less than 0.5 weight percent.  
     
     
         4 . The article of    claim 1   , wherein the mechanical hardness is at least 50% greater.  
     
     
         5 . The article of    claim 1   , wherein the one or more noble metal elements is rhodium and the one or more alloying elements are selected from the group consisting of C, Ce, Dy, Y, Si, Zr, Al, B, Bi, Er, Gd, Ge, Pb, Sm, and Yb.  
     
     
         6 . The article of    claim 1   , wherein the one or more noble metal elements is gold, and the one or more alloying elements are selected from the group consisting of C, Co, Ho, Lu, Th, Mn, Re, Rh, Ru, Sb, Yb, Y, B, Bi, Dy, Er, La, P, Pb, Si, Sr, and W.  
     
     
         7 . The article of    claim 1   , wherein the one or more noble metal elements is platinum, and the one or more alloying elements are selected from the group consisting of B, Bi, Er, Pb, La, Mo, and Ti.  
     
     
         8 . The article of    claim 1   , wherein the one or more noble metal elements is palladium, and the one or more alloying elements are selected from the group consisting of B, Bi, and Si.  
     
     
         9 . The article of    claim 1   , wherein the one or more noble metal elements is ruthenium, and the one or more alloying elements are selected from the group consisting of C, Ce, Hf, Lu, La, Si, Bi, and Gd.  
     
     
         10 . The article of    claim 1   , wherein the alloy exhibits an electrical conductivity that is at least 30% of the electrical conductivity of the one or more noble metal elements alone.  
     
     
         11 . The article of    claim 10   , wherein the alloy exhibits an electrical conductivity that is at least 50% of the electrical conductivity of the one or more noble metal elements alone.  
     
     
         12 . The article of    claim 1   , wherein the contact is formed on an adhesion promoting layer that is formed on a substrate  
     
     
         13 . The article of    claim 1   , wherein the alloy comprises Rh and Si, Rh and Al, Rh and Zr, Rh and Y, Rh and Sm, Au and Si, Au and Dy, Au and La, Pt and La, Pd and Si, Ru and Hf, Ru and Si, or Ru and La.  
     
     
         14 . The article of    claim 1   , wherein the article comprises a microrelay device comprising at least two contacts formed from the electrically conductive alloy.  
     
     
         15 . The article of    claim 14   , wherein the microrelay device further comprises a base structure having one of the contacts located thereon and a cantilever structure having another of the contacts located thereon.  
     
     
         16 . The article of    claim 1   , wherein the precipitates are present in a volume fraction of 0.5 to 5%.  
     
     
         17 . A process for fabricating an article, comprising the steps of: 
 providing a substrate; and    depositing on the substrate an alloy comprising one or more noble metal elements, and one or more alloying elements, wherein the solid solubility of each of the one or more alloying elements in each of the one or more noble metal elements is less than 4 weight percent and wherein the one or more alloying elements are present in the alloy in a total amount of 0.1 to 30 weight percent,    wherein the substrate is heated to at least 100° C. during the deposition such that, upon deposition, particles comprising the one or more alloying elements precipitate, the particles having an average diameter less than 500 nm and being present in the alloy in a volume fraction of 0.3 to 30%.    
     
     
         18 . The process of    claim 17   , wherein the alloy comprises Rh and Si, Rh and Al, Rh and Zr, Rh and Y, Rh and Sm, Au and Si, Au and Dy, Au and La, Pt and La, Pd and Si, Ru and Hf, Ru and Si, or Ru and La.  
     
     
         19 . A process for fabricating an article, comprising the steps of: 
 providing a substrate;    depositing on a substrate an alloy comprising one or more noble metal elements, and one or more alloying elements, wherein the solid solubility of each of the one or more alloying elements in each of the one or more noble metal elements is less than 4 weight percent and wherein the one or more alloying elements are present in the alloy in a total amount of 0.1 to 30 weight percent; and    heat treating the deposited alloy at a temperature of at least 100° C. subsequent to deposition, such that particles comprising the one or more alloying elements precipitate, the particles having an average diameter less than 500 nm and being present in the alloy in a volume fraction of 0.3 to 30%.    
     
     
         20 . The process of    claim 20    wherein the alloy comprises Rh and Si, Rh and Al, Rh and Zr, Rh and Y, Rh and Sm, Au and Si, Au and Dy, Au and La, Pt and La, Pd and Si, Ru and Hf, Ru and Si, or Ru and La.  
     
     
         21 . The process of    claim 19   , wherein the heat treatment increases the electrical conductivity, compared to the electrical conductivity of the deposited alloy, by at least 30%.  
     
     
         22 . An article comprising at least one electrical contact formed from an electrically conductive alloy comprising: 
 one or more noble metal elements; and    one or more types of insoluble dispersoid particles, wherein the insoluble dispersoid particles are present in the alloy in a total amount of 0.1 to 30 weight percent, and wherein the mechanical hardness of the alloy is at least 30% greater than the mechanical hardness of the one or more noble metal elements alone.    
     
     
         23 . The article of    claim 22   , wherein the dispersoid particles range in size from 2 to 500 nm.  
     
     
         24 . The article of    claim 23   , wherein the dispersoid particles range in size from 2 to 50 nm.  
     
     
         25 . The article of    claim 22   , wherein the noble metal elements are selected from the group consisting of gold, rhodium, platinum, palladium, ruthenium, and silver, and the dispersoid particles are selected from the group consisting of oxides, nitrides, carbides, and fluorides.  
     
     
         26 . The article of    claim 22   , wherein the alloy exhibits an electrical conductivity that is at least 50% of the electrical conductivity of the one or more noble metal elements alone.  
     
     
         27 . The article of    claim 26   , wherein the alloy exhibits an electrical conductivity that is at least 80% of the electrical conductivity of the one or more noble metal elements alone.  
     
     
         28 . The article of    claim 22   , wherein the article comprises a microrelay device comprising at least two contacts formed from the electrically conductive alloy.  
     
     
         29 . The article of    claim 28   , wherein the microrelay device further comprises a base structure having one of the contacts located thereon and a cantilever structure having another of the contacts located thereon.  
     
     
         30 . The article of    claim 22   , wherein the contact is formed on an adhesion promoting layer that is formed on a substrate.  
     
     
         31 . A process for forming an article, comprising the step of forming at least one electrical contact from an electrically conductive alloy that comprises one or more noble metal elements and one or more types of insoluble dispersoid particles, the insoluble dispersoid particles being present in the alloy in a total amount of 0.1 to 30 weight percent, and the mechanical hardness of the resultant alloy being at least 30% greater than the mechanical hardness of the one or more noble metal elements alone.  
     
     
         32 . The process of    claim 31   , wherein the step of forming the at least one contact comprises: 
 providing a substrate; and    forming a film on the substrate by co-sputtering from a first target comprising the one or more noble metal elements and from a second target comprising a dispersoid material insoluble in the one or more noble metal elements.    
     
     
         33 . The process of    claim 31   , wherein the step of forming the at least one contact comprises: 
 providing a substrate; and    forming a film onto the substrate by sputtering from a target that comprises the one or more noble metal elements and a dispersoid-forming material, wherein the sputtering is performed in an atmosphere comprising one or more gases reactive with the dispersoid-forming elements, such that the insoluble dispersoid particles are formed in the deposited film.    
     
     
         34 . The process of    claim 33   , wherein the atmosphere comprises at least one gas selected from the group consisting of oxygen-containing gases, nitrogen-containing gases, and fluorine-containing gases.  
     
     
         35 . The process of    claim 31   , wherein the step of forming the at least one contact comprises: 
 providing a substrate;    forming on the substrate a film comprising the one or more noble metal elements and one or more dispersoid-forming elements selected from the group consisting of Al, Ti, Si, Zr, and rare earth elements; and    heat treating the film in an oxidizing atmosphere to induce formation of oxide dispersoid particles from the dispersoid-forming elements.