Stoichiometry for chalcogenide glasses useful for memory devices and method of formation

Abstract

A method of forming resistance changing elements with improved operational characteristics for use in memory devices and the resulting structures are disclosed. A chalcogenide glass having the formula (Ge x 1 Se 1−x1 ) 1−y1 Ag y1 , wherein 18 ≦x l ≦28 , or the formula (Ge x2 Se l−x2 ) 1−y2 Ag y2 wherein 39 ≦x 2 ≦42 , and wherein in both the silver is in a concentration which maintains the germanium selenide glass in the glass forming region is used in a memory cell. The glass may also have a glass transition temperature (Tg) near or higher than typical temperatures used for fabricating and packaging memory devices containing the memory cell.

What is claimed as new and desired to be protected by Letters Patent of the U.S. is:  
     
         1 . A memory cell comprising: 
 a chalcogenide glass doped with a metal, said chalcogenide glass having a stoichiometry and a maxium allowable amount of metal dopant which causes said chalcogenide glass to remain in a glass forming region;    a first electrode and a second electrode in contact with said chalcogenide glass; and    a dendrite formed between said first and second electrodes when voltage is applied to said first and second electrodes.    
     
     
         2 . The memory cell of  claim 1 , wherein said chalcogenide glass has a glass transition temperature which is about or higher than the highest temperature used in the formation and packaging of a memory device containing said memory cell.  
     
     
         3 . The memory cell of  claim 1 , wherein said chalcogenide glass comprises a material selected from the group consisting of oxygen, sulfur, tellurium and selenium.  
     
     
         4 . The memory cell of  claim 3 , wherein said chalcogenide glass comprises oxygen.  
     
     
         5 . The memory cell of  claim 3 , wherein said chalcogenide glass comprises sulfur.  
     
     
         6 . The memory cell of  claim 3 , wherein said chalcogenide glass comprises tellurium.  
     
     
         7 . The memory cell of  claim 3 , wherein said chalcogenide glass comprises selenium.  
     
     
         8 . The memory cell of  claim 1 , wherein said metal is selected from the group consisting of silver, copper, platinum, gold, cadmium, ruthenium, cobalt, zinc, chromium, maganese and nickel.  
     
     
         9 . The memory cell of  claim 1 , wherein said chalcogenide glass is a germanium selenide glass.  
     
     
         10 . The memory cell of  claim 9 , wherein said chalcogenide glass is a germanium selenide glass doped with silver.  
     
     
         11 . A non-volatile memory cell comprising: 
 a germanium selenide glass doped with silver, said silver doping being in a concentration which maintains said germanium selenide glass in the glass forming region;    a first electrode and a second electrode in contact with said doped germanium selenide glass; and    a dendrite formed between said first and second electrodes when voltage is applied to said first and second electrodes.    
     
     
         12 . The non-volatile memory cell of  claim 11 , wherein said germanium selenide glass has a glass transition temperature which is about or higher than the highest temperature used in the fabrication and packaging of a memory device containing said non-volatile memory cell.  
     
     
         13 . The non-volatile memory cell of  claim 11 , wherein said germanium selenide glass comprises a material having the formula (Ge x1 Se 1−x1 ) 1−y1 Ag y1 , wherein 18≦x 1 ≦28.  
     
     
         14 . The non-volatile memory cell of  claim 13 , wherein y 1  represents a silver atomic percentage which is less than or equal to that which approximately satisfies equation y 1 =19+15*sin [0.217*x 1 +3.23].  
     
     
         15 . The non-volatile memory cell of  claim 11 , wherein said germanium selenide glass comprises a material having the formula (Ge x2 Se 1−x2 ) 1−y2 Ag y2  , wherein 39≦x 2 ≦42.  
     
     
         16 . The non-volatile memory cell of  claim 15 , wherein y 2  represents a silver atomic percentage which is less than or equal to that which approximately satisfies equation y 2 =21−11.5 *exp[−(ln (x 2 /44.4)/(0.84) 2 )].  
     
     
         17 . A chalcogenide glass material having the formula (Ge x1 Se 1−x1 ) 1−y1 Ag y1 wherein 18≦x 1 ≦28 and wherein said silver is in a concentration which maintains said germanium selenide glass in the glass forming region.  
     
     
         18 . The chalcogenide glass material of  claim 17 , wherein x 1 =23.  
     
     
         19 . The chalcogenide glass material of  claim 17 , wherein x 1 =25.  
     
     
         20 . The chalcogenide glass material of  claim 17 , wherein x 1 =20.  
     
     
         21 . The chalcogenide glass material of  claim 17 , wherein y 1 represents a silver atomic percentage which is less than or equal to that which approximately satisfies equation y 1 =19+15*sin [0.217*x 1 +3.23].  
     
     
         22 . A chalcogenide glass material having the formula (Ge x2 Se 1−x2 ) 1−y2 Ag y2 , wherein 39≦x 2 ≦42 and wherein said silver is in a concentration which maintains said germanium selenide glass in the glass forming region.  
     
     
         23 . The chalcogenide glass material of  claim 22 , wherein y 2  represents a silver atomic percentage which is less than or equal to that which approximately satisfies equation y 2 =21−11.5*exp[−(ln (x 2 /44.4)/(0.84) 2 )].  
     
     
         24 . A memory cell comprising: 
 a germanium selenide glass having the formula (Ge x1 Se 1−x1 ) 1−y1 Ag y1 , wherein 18≦x 1 ≦28 and wherein said silver is in a concentration which maintains said germanium selenide glass in the glass forming region; and,    at least two electrodes in contact with said germanium selenide glass, said germanium selenide glass forming a dendrite between at least two electrodes in response to a voltage applied across said at least two electrodes.    
     
     
         25 . A memory cell comprising: 
 a germanium selenide glass having the formula (Ge x2 Se 1−x2 ) 1−y2 Ag y2 , wherein 39≦x 2 ≦42 and wherein said silver is in a concentration which maintains said germanium selenide glass in the glass forming region ; and    at least two electrodes in contact with said germanium selenide glass, said germanium selenide glass forming a dendrite between at least two electrodes in response to a voltage applied across said at least two electrodes.    
     
     
         26 . A method of forming a memory cell comprising the steps of: 
 providing a chalcogenide glass over a substrate;    doping said chalcogenide glass with a metal to form a doped chalcogenide glass, said doped chalcogenide glass having a stoichiometry which causes said doped chalcogenide glass to be in a glass forming region, said doped chalcogenide glass having a glass transition temperature which is about or higher than the highest temperature used in the formation and packaging of a memory device containing said memory cell; and,    forming a plurality of electrodes in contact with said doped chalcogenide glass.    
     
     
         27 . A method of forming a memory cell comprising the steps of: 
 providing a germanium selenide glass having the formula (Ge x1 Se 1−x1 ) 1−y1 Ag y1 ) wherein 18≦x 1 ≦28 over a substrate, and wherein said silver is in a concentration which maintains said germanium selenide glass in the glass forming region; and,    forming at least two electrodes in contact with said germanium selenide glass at locations which permit said glass to transition between high and low resistance states in response to signals applied to said electrodes.    
     
     
         28 . The method of  claim 27 , wherein x 1 =23.  
     
     
         29 . The method of  claim 27 , wherein x 1 =25.  
     
     
         30 . The method of  claim 27 , wherein x 1 =20.  
     
     
         31 . A method of forming a memory cell comprising the steps of: 
 providing a germanium selenide glass having the formula (Ge x2 Se 1−x2 ) 1−y2 Ag y2 , wherein 39≦x 2 ≦42 and wherein said silver is in a concentration which maintains said germanium selenide glass in the glass forming region; and,    forming at least two electrodes in contact with said germanium selenide glass at locations which permit said glass to transition between high and low resistance states in response to signals applied to said electrodes.    
     
     
         32 . A method of operating a memory cell comprising the steps of: 
 applying a voltage across a germanium selenide glass having the formula (Ge x1 Se 1−x1 ) 1−y1 Ag y1 , wherein 18≦x 1 ≦28 and wherein said silver is in a concentration which maintains said germanium selenide glass in the glass forming region, to change the resistance state of said glass.    
     
     
         33 . The method of  claim 32 , wherein x 1 =23.  
     
     
         34 . The method of  claim 32 , wherein x 1 =25.  
     
     
         35 . The method of  claim 32 , wherein x 1 =20.  
     
     
         36 . A method of operating a memory cell comprising the steps of: 
 applying a voltage across a germanium selenide glass having the formula (Ge x2 Se 1−x2 ) 1−y2 Ag y2 , wherein 39≦x 2 ≦42 and wherein said silver is in a concentration which maintains said germanium selenide glass in the glass forming region, to change the resistance state of said glass.    
     
     
         37 . A processor system comprising: 
 a processor; and    an integrated circuit coupled to said processor, at least one of said processor and integrated circuit including a memory cell, said memory cell comprising:    a germanium selenide glass having the formula(Ge x1 Se 1−x1 ) 1−y1 Ag y1 , wherein 18≦x 1 ≦28 and wherein said silver is in a concentration which maintains said germanium selenide glass in the glass forming region; and    at least two electrodes in contact with said doped germanium selenide glass, said germanium selenide glass changing a resistance state in response to application of a voltage across said at least two electrodes.    
     
     
         38 . The processor system of  claim 37 , wherein said processor and said integrated circuit are integrated on same chip.  
     
     
         39 . The processor system of  claim 37 , wherein x 1 =23.  
     
     
         40 . The processor system of  claim 37 , wherein x 1 =25.  
     
     
         41 . The processor system of  claim 37 , wherein x 1 =20.  
     
     
         42 . A processor system comprising: 
 a processor; and    an integrated circuit coupled to said processor, at least one of said processor and integrated circuit including a memory cell, said memory cell comprising:    a germanium selenide glass having the formula (Ge x2 Se 1−x2)   1−y2 Ag y2 wherein 39≦x 2 ≦42 and wherein said silver is in a concentration which maintains said germanium selenide glass in the glass forming region; and    at least two electrodes in contact with said doped germanium selenide glass, said germanium selenide glass changing a resistance state in response to application of a voltage across said at least two electrodes.    
     
     
         43 . The processor-based system of  claim 42 , wherein said processor and said integrated circuit are integrated on same chip.