High temperature superconductor Josephson junction element and manufacturing method for the same

Abstract

In a method of manufacturing a Josephson junction, a first superconductive layer is formed on a substrate. An insulating film is formed on the first superconductive layer. The insulating film is etched to have an inclination portion. The first superconductive layer is etched using the etched insulating film as a mask, to have an inclination portion. A barrier layer is formed on a surface of the inclination portion of the first superconductive layer. A second superconductive layer is formed on the barrier layer and the inclination portion of the insulating layer.

What is claimed is:  
     
         1 . A method of manufacturing a Josephson junction comprising: 
 forming a first superconductive layer on a substrate;    forming an insulating film on said first superconductive layer;    etching said insulating film to have an inclination portion;    etching said first superconductive layer using said etched insulating film as a mask, to have an inclination portion;    forming a barrier layer on a surface of said inclination portion of said first superconductive layer; and    forming a second superconductive layer on said barrier layer and said inclination portion of said insulating layer.    
     
     
         2 . A method according to  claim 1 , wherein said first superconductive layer and said second superconductive layer are a copper oxide system superconductive layer.  
     
     
         3 . A method according to  claim 2 , wherein said copper oxide system superconductive layer is YBaCuO superconductive layer.  
     
     
         4 . A method according to  claim 1 , wherein said second superconductive layer is formed in a same sample chamber without being exposed to an atmosphere, after said inclination portion of said first superconductive layer is formed.  
     
     
         5 . A method according to  claim 1 , wherein said barrier layer has a film thickness equal to or less than 2 nm.  
     
     
         6 . A method according to  claim 1 , wherein said barrier layer has a perovskite structure.  
     
     
         7 . A method according to  claim 6 , wherein a material of said barrier layer has a lattice constant from 0.41 nm to 0.43 nm.  
     
     
         8 . A method according to  claim 1 , wherein said insulating film contains at least one element selected from the group consisting of La, Sr, Al, Ca and Ta.  
     
     
         9 . A method according to  claim 1 , wherein a composition of said barrier layer is Y 1−x Ba 1 Cu x O y  (x being in a range of 0 to 1).  
     
     
         10 . A method according to  claim 9 , wherein said x is equal to or less than 0.5.  
     
     
         11 . A method according to  claim 10 , wherein said x is 0.  
     
     
         12 . A method according to  claim 1 , wherein said barrier layer includes at least one element selected from the group consisting of La, Sr, Al, Ca and Ta which are supplied from said insulating layer or said substrate.  
     
     
         13 . A method according to  claim 1 , wherein said first superconductive layer and said insulating layer are formed by a pulsed laser deposition method.  
     
     
         14 . A method according to  claim 1 , wherein said first superconductive layer is formed at a first substrate temperature, and said insulating layer is formed at a second substrate temperature lower than said first substrate temperature.  
     
     
         15 . A method according to  claim 1 , wherein said etching a first superconductive layer includes: 
 etching said first superconductive layer while inert gas ions are irradiated.    
     
     
         16 . A method according to  claim 15 , wherein said etching a first superconductive layer includes: 
 etching said first superconductive layer while inert gas ions are irradiated and said substrate is rotated.    
     
     
         17 . A method according to  claim 1 , wherein said insulating layer is etched while said first superconductive layer is etched such that at least one of the elements of said insulating layer is re-deposited on a surface of said inclination portion of said first superconductive layer.  
     
     
         18 . A method according to  claim 17 , wherein a surface portion of said inclination portion where said at least one element is re-deposited forms an amorphous layer.  
     
     
         19 . A method according to claims  18 , further comprising heating said substrate in an oxygen ambience and crystallizing said surface portion of said inclination portion where said at least one element is re-deposited.  
     
     
         20 . A method according to  claim 19 , wherein said crystallizing is a part of said forming a second superconductive layer.  
     
     
         21 . A method according to  claim 1 , further comprising: 
 changing a structure and composition of a surface portion of said inclination portion of said first superconductive layer through an ion irradiation damage.    
     
     
         22 . A method according to  claim 21 , wherein said changing includes: 
 crystallizing said surface portion of said inclination portion of said first superconductive layer, while a heating is carried out to said first superconductive layer in an oxygen ambience.    
     
     
         23 . A method of manufacturing a Josephson junction comprising: 
 forming a first superconductive layer on a substrate;    forming an insulating film on said first superconductive layer;    etching said insulating film and said first superconductive layer to have an inclination portion;    forming a barrier layer on a surface of said inclination portion of said first superconductive layer; and    forming a second superconductive layer on said barrier layer and said inclination portion of said insulating layer.    
     
     
         24 . A method according to  claim 23 , wherein said first superconductive layer and said second superconductive layer are a copper oxide system superconductive layer.  
     
     
         25 . A method according to  claim 24 , wherein said copper oxide system superconductive layer is YBaCuO superconductive layer.  
     
     
         26 . A method according to  claim 23 , wherein said second superconductive layer is formed in a same sample chamber without being exposed to an atmosphere, after said inclination portion of said first superconductive layer is formed.  
     
     
         27 . A method according to  claim 23 , wherein said barrier layer has a perovskite structure.  
     
     
         28 . A method according to  claim 27 , wherein a material of said barrier layer has a lattice constant from 0.41 nm to 0.43 nm.  
     
     
         29 . A method according to  claim 23 , wherein said insulating film contains at least one element selected from the group consisting of La, Sr, Al, Ca and Ta.  
     
     
         30 . A method according to  claim 23 , wherein a composition of said barrier layer is Y 1−x Ba 1 Cu x O y  (x being in a range of 0 to 1).  
     
     
         31 . A method according to  claim 30 , wherein said x is equal to or less than 0.5.  
     
     
         32 . A method according to  claim 31 , wherein said x is 0.  
     
     
         33 . A method according to  claim 23 , wherein said barrier layer includes at least one element selected from the group consisting of La, Sr, Al, Ca and Ta which are supplied from said insulating layer or said substrate.  
     
     
         34 . A method according to  claim 23 , wherein said first superconductive layer and said insulating layer are formed by a pulsed laser deposition method.  
     
     
         35 . A method according to  claim 23 , wherein said first superconductive layer is formed at a first substrate temperature, and said insulating layer is formed at a second substrate temperature lower than said first substrate temperature.  
     
     
         36 . A method according to  claim 23 , wherein said etching a first superconductive layer and an insulating layer includes: 
 etching said first superconductive layer and said insulating layer while inert gas ions are irradiated.    
     
     
         37 . A method according to  claim 36 , wherein said etching a first superconductive layer and an insulating layer includes: 
 etching said insulating layer and said first superconductive layer while inert gas ions are irradiated and said substrate is rotated.    
     
     
         38 . A method according to  claim 23 , wherein said forming a barrier layer includes: 
 ion-etching a surface of said inclination portion of said insulating film and a surface of said inclination portion of said first superconductive layer, and    wherein said ion-etching includes: 
 ion-etching said surface of said inclination portion of said insulating film and said surface of said inclination portion of said first superconductive layer, such that at least one of elements of said insulating layer re-deposited on said surface of said inclination portion of said first superconductive layer.  
   
     
     
         39 . A method according to  claim 38 , wherein a surface portion of said inclination portion where said at least one element is re-deposited forms an amorphous layer.  
     
     
         40 . A method according to  claim 39 , further comprising heating said substrate in an oxygen ambience and crystallizing said surface portion of said inclination portion where said at least one element is re-deposited.  
     
     
         41 . A method according to  claim 23 , further comprising: 
 changing a structure and composition of a surface portion of said inclination portion of said first superconductive layer through an ion irradiation damage.    
     
     
         42 . A method according to  claim 41 , wherein said changing includes: 
 crystallizing said surface portion of said inclination portion of said first superconductive layer, while a heating is carried out to said first superconductive layer in an oxygen ambience.    
     
     
         43 . A method of manufacturing the Josephson junction comprising: 
 forming a first super conductive layer on a substrate;    forming an interlayer insulating layer as a barrier layer on said first superconductive layer;    forming a second superconductive layer on said barrier layer;    etching said second superconductive layer and said barrier layer to form 2 or more electrodes;    forming an insulating layer between said 2 or more electrodes.    
     
     
         44 . A method according to  claim 43 , wherein said first superconductive layer and said second superconductive layer are a copper oxide system superconductive layer.  
     
     
         45 . a method according to  claim 44 , wherein said copper oxide system superconductive layer is YBaCuO superconductive layer.  
     
     
         46 . A method according to  claim 43 , wherein said barrier layer has a film thickness equal to or less than 2 nm.  
     
     
         47 . A method according to  claim 43 , further comprising: 
 carrying out ion irradiation to a surface portion of said first superconductive layer to give a damage to said surface portion of said first superconductive layer before said barrier layer is formed on said first superconductive layer.    
     
     
         48 . A method according to  claim 47 , wherein said carrying out ion irradiation includes: 
 carrying out said ion irradiation at a temperature of said substrate in a range of room temperature to 700° C.    
     
     
         49 . A Josephson junction comprising: 
 a first superconductive layer formed on substrate and having an inclination portion;    an insulating film formed on said first superconductive layer and having an inclination portion following to said inclination portion of said first superconductive layer;    a barrier layer formed on said inclination portion of said first superconductive layer; and    a second superconductive layer formed on said inclination portion of said insulating film and said inclination portion of said barrier layer.    
     
     
         50 . A Josephson junction according to  claim 49 , wherein said barrier layer has a film thickness equal to or less than 2 nm.  
     
     
         51 . A Josephson junction according to  claim 49 , wherein said first superconductive layer and said second superconductive layer are a copper oxide system superconductive layer.  
     
     
         52 . A Josephson junction according to  claim 51 , wherein said copper oxide system superconductive layer is YBaCuO superconductive layer.  
     
     
         53 . A Josephson junction according to  claim 49 , wherein said barrier layer has a perovskite structure.  
     
     
         54 . A Josephson junction according to  claim 53 , wherein a material of said barrier layer has a lattice constant from 0.41 nm to 0.43 nm.  
     
     
         55 . A Josephson junction according to  claim 49 , wherein said insulating film contains at least one element selected from the group consisting of La, Sr, Al, Ca and Ta.  
     
     
         56 . A Josephson junction according to claims  49 , wherein a composition of said barrier layer is Y 1−x Ba 1 Cu x O y  (x being in a range of 0 to 1).  
     
     
         57 . A Josephson junction according to  claim 56 , wherein said x is equal to or less than 0.5.  
     
     
         58 . A Josephson junction according to  claim 57 , wherein said x is 0.  
     
     
         59 . A Josephson junction device comprising: 
 a first superconductive layer formed on a substrate;    2 or more interlayer insulating films provided on said first superconductive layer to be apart from each other; and    2 or more second superconductive layers respectively formed on said interlayer insulating layers.    
     
     
         60 . A Josephson junction device according to  claim 59 , wherein each of said interlayer insulating films has a film thickness equal to or less than 2 nm.  
     
     
         61 . A Josephson junction device according to  claim 59 , wherein said first superconductive layer and said second superconductive layer are a copper oxide system superconductive layer.  
     
     
         62 . A Josephson junction device according to  claim 61 , wherein said copper oxide system superconductive layer is YBaCuO superconductive layer.  
     
     
         63 . A method of manufacturing a Josephson junction, wherein a material of an insulating layer which is formed on a first superconductive layer is diffused into said first superconductive layer to form a barrier layer on a surface portion of said first superconductive layer, and a second superconductive layer is formed on said barrier layer to form a Josephson junction.