Multilayer getter structures and methods for making same

Abstract

Getter multilayer structures are disclosed, embodiments of which include at least a layer of a non-evaporable getter alloy having a low activation temperature over a layer of a different non-evaporable getter material having high specific surface area, both preferably obtained by cathodic deposition. The multilayer NEG structures exhibit better gas sorbing characteristics and lower activation temperature lower than those of deposits made up of a single material. A process for manufacturing such structures includes depositing a first, high surface area NEG film on a support, and then depositing a thin over layer of low activation NEG film.

1 . A multilayer non-evaporable getter structure comprising 
 a first layer of a non-evaporable getter material having a surface area equivalent to at least 20 times its geometrical area, and    directly contacting said first layer, a second layer, having a thickness not greater than 1 μm, of a non-evaporable getter alloy having a low activation temperature.    
     
     
         2 . The structure of  claim 1 , wherein said second layer fully covers said first layer.  
     
     
         3 . The structure of  claim 1 , wherein the getter material of said first layer is selected from the group consisting of zirconium, titanium, niobium, tantalum, vanadium, hafnium, and Zr—Co—A alloys, wherein A represents one or more elements selected from yttrium and rare earth elements.  
     
     
         4 . The structure of  claim 1 , wherein the thickness of said first layer is between about 0.2 and 50 μm.  
     
     
         5 . The structure of  claim 4 , wherein said thickness is between about 10 and 20  82  m.  
     
     
         6 . The structure of  claim 1 , wherein the surface area of said first layer is equivalent to at least about 50 times its geometrical area.  
     
     
         7 . The structure of  claim 1 , wherein the getter alloy of said second layer comprises Zr and V.  
     
     
         8 . The structure of  claim 7 , wherein said getter alloy further comprises smaller quantities of one or more elements selected from Fe, Ni, Mn, and Al.  
     
     
         9 . The structure of  claim 8 , wherein said getter alloy has a composition by weight of about Zr 70%-V 24.6%-Fe 5.4%.  
     
     
         10 . The structure of  claim 1 , wherein the getter alloy of said second layer has the composition of about 80%:15%:5% Zr:Co:A by weight, wherein A represents one or more elements selected from yttrium and rare earth elements, and the material of said first layer is different from that of said second layer.  
     
     
         11 . The structure of  claim 10 , wherein said first layer is not a Zr:Co:A alloy.  
     
     
         12 . The structure of  claim 7 , wherein the getter alloy of said second layer is a Zr—Ti—V alloy.  
     
     
         13 . The structure of  claim 12 , wherein the getter alloy of said second layer has the composition of about Zr 44%-Ti 23%-V 33%.  
     
     
         14 . The structure of  claim 7 , wherein the getter alloy of said second layer is ZrV2.  
     
     
         15 . The structure of  claim 1 , wherein the thickness of said second layer is between about 50 and about 500 nm.  
     
     
         16 . The structure of  claim 1 , further comprising a continuous or discontinuous layer of palladium or a compound thereof, deposited on the surface of said second layer opposed to the surface in contact with said first layer.  
     
     
         17 . The structure of  claim 16 , wherein said palladium compound is selected from palladium oxide, silver-palladium alloys comprising up to about 30 atom % of silver, and compounds of palladium with one or more metals forming the getter material of the second layer.  
     
     
         18 . The structure of  claim 16 , wherein said layer of palladium or a compound thereof is discontinuous and covers from about 10 to about 90% of the second layer surface.  
     
     
         19 . The structure of  claim 16 , wherein said layer of palladium or a compound thereof has a thickness between about 10 and about 100 nm.  
     
     
         20 . A process for manufacturing a multilayer structure comprising: 
 depositing by cathodic deposition on a support a first layer of a non-evaporable getter material having a surface area equivalent to at least 20 times its geometrical area, and 
 depositing by cathodic deposition over said first layer at least a second layer, having a thickness not greater than 1 μm, of a non-evaporable getter alloy having a low activation temperature;  
 such that, between the two deposition steps, the first layer is not exposed to gaseous species able to react therewith.  
   
     
     
         21 . A process according to  claim 20 , wherein the cathodic deposition of said first layer comprises (a) cooling the support, (b) operating at low current values, (c) operating with the target not directly placed in front of the support, (d) moving, rotating or vibrating the support during the deposition, or any combination thereof.  
     
     
         22 . A getter structure comprising: 
 a support;    a first layer of a first non-evaporable getter having a high surface area disposed over a surface of said support; and    a second layer a second non-evaporable getter having a low activation temperature disposed over said first layer.    
     
     
         23 . A getter structure as recited in  claim 22  wherein said first layer and said second layer are cathodically deposited films.  
     
     
         24 . A process for making a getter structure comprising: 
 depositing a first layer of a non-evaporable getter having a high surface area over a surface of a support; and    depositing a second layer of a second non-evaporable getter having a low activation temperature over said first layer.    
     
     
         25 . A process for making a getter structure as recited in  claim 24  wherein said first layer and said second layer are films deposited by cathodic deposition.