Switching element method of driving switching element rewritable logic integrated circuit and memory

Abstract

A switching element has an ion conductor capable of conducting metal ions for use in an electrochemical reaction therein, a first electrode and a second electrode which are disposed in contact with said ion conductor and spaced a predetermined distance from each other, and a third electrode disposed in contact with the ion conductor. When a voltage for causing the switching element to transit to an on state is applied to the third electrode, metal is precipitated between the first electrode and the second electrode by metal ions, electrically interconnecting the first electrode and the second electrode. When a voltage for causing the switching element to transit to an off state is applied to the third electrode, the precipitated metal is dissolved to electrically disconnect the first electrode and the second electrode from each other.

1. A switching element comprising:  an ion conductor capable of conducting metal ions therein; , a first electrode and a second electrode which are disposed in contact with said ion conductor; and a third electrode disposed in contact with said ion conductor and including said metal ions; wherein an interelectrode distance L 1  between said first electrode and said second electrode, an interelectrode distance L 2  between said first electrode and said third electrode, and an interelectrode distance L 3  between said second electrode and said third electrode satisfy the condition according to the expression:
   L1<L2×2 and L1<L3×2 
 
 
       
        
       
       , a second electrode, and a third electrode;
   wherein said first electrode is of a structure including a region made of a material that is not capable of supplying said metal ions to said ion conductor;        at least one or two electrodes from among said second electrode and said third electrode is/are held in contact with said ion conductor, and at least one or two electrodes held in contact with said ion conductor is/are of a structure including a material capable of supplying said metal ions to said ion conductor; and        wherein the first, second and third electrodes are arranged such that an electrical conductivity between said first electrode and said second electrode is controlled by applying a voltage to said third electrode.      
     
     
       2. The switching element according to  claim 1 , wherein the interelectrode distance between said first electrode and said second electrode is 0.5 μm or less. 
     
     
       3. A switching element disposed on a substrate covered with an insulating film or an insulating substrate,  comprising:  an ion conductor capable of conducting metal ions therein; , a first electrode and a second electrode which are disposed in contact with said ion conductor; and a third electrode disposed in contact with said ion conductor and including a metal dissolvable into said ion conductor based on an electrochemical reaction; wherein an interelectrode distance L 1  between said first electrode and said second electrode, an interelectrode distance L 2  between said first electrode and said third electrode, and an interelectrode distance L 3  between said second electrode and said third electrode satisfy the condition according to the expression:
   L1<L2×2 and L1<L3×2 
 
 
       
        
       
       , a second electrode, and a third electrode;
   wherein said first electrode, said second electrode, and said third electrode are held in contact with said ion conductor;        said first electrode is of a structure including a region made of a material that is not capable of supplying said metal ions to said ion conductor;        at least one or two electrodes from among said second electrode and said third electrode is/are of a structure including a material capable of supplying said metal ions to said ion conductor; and        wherein the first, second and third electrodes are arranged such that an electrical conductivity between said first electrode and said second electrode is controlled by applying a voltage to said third electrode.      
     
     
       4. The switching element according to  claim 3 , wherein:
 said first electrode and said second electrode are disposed on said substrate in spaced-apart relation to each other, and the interelectrode distance between said first electrode and said second electrode is 0.5 μm or less;    said ion conductor is disposed to cover said first electrode and said second electrode; and    said third electrode is disposed on said ion conductor.    
     
     
       5. The switching element according to  claim 3 , wherein:
 said third electrode is disposed on said substrate;    said ion conductor is disposed on said third electrode; and    said first electrode and said second electrode are disposed on said ion conductor in spaced-apart relation to each other, and the interelectrode distance between said first electrode and said second electrode is 0.5 μm or less.    
     
     
       6. The switching element according to  claim 3 , wherein:
 said first electrode and said third electrode are disposed on said substrate;    said ion conductor is disposed on said first electrode and said third electrode; and    said second electrode is disposed on said ion conductor, and the interelectrode distance between said first electrode and said second electrode is equal to or on the order of a film thickness of said ion conductor.    
     
     
       7. The switching element according to  claim 1 , wherein an electrical characteristic between said first electrode and said second electrode is controlled by applying a voltage to said third electrode. 
     
     
       8. The switching element according to  claim 3 , wherein an electrical characteristic between said first electrode and said second electrode is controlled by applying a voltage to said third electrode. 
     
     
       9. The switching element according to  claim 7 , wherein said electrical characteristic represents electric conductivity. 
     
     
       10. The switching element according to  claim 8 , wherein said electrical characteristic represents electric conductivity. 
     
     
       11. The switching element according to  claim 1 , wherein:
 said first electrode and said second electrode are electrically interconnected to bring the switching element into an on state by applying a voltage, which is positive with respect to at least one of said first electrode and said second electrode, to said third electrode; and    said first electrode and said second electrode are insulated from each other to bring the switching element into an off state by applying a voltage, which is negative with respect to at least one of said first electrode and said second electrode, to said third electrode.    
     
     
       12. The switching element according to  claim 3 , wherein:
 said first electrode and said second electrode are electrically interconnected to bring the switching element into an on state by applying a voltage, which is positive with respect to at least one of said first electrode and said second electrode, to said third electrode; and    said first electrode and said second electrode are insulated from each other to bring the switching element into an off state by applying a voltage, which is negative with respect to at least one of said first electrode and said second electrode, to said third electrode.    
     
     
       13. The switching element according to  claim 1 , wherein at least one or two electrodes from among said second electrode and said third electrode includes a metal dissolvable into said ion conductor based on an electrochemical reaction  include a portion held in contact with at least said ion conductor, said portion being of a composition capable of supplying said metal ions to said ion conductor. 
     
     
       14. The switching element according to  claim 3 , wherein said second electrode includes a metal dissolvable into said ion conductor based on an electrochemical reaction. 
     
     
       15. The switching element according to  claim 13 , wherein:
 said first electrode and said second electrode are electrically interconnected to bring the switching element into an on state by either applying a voltage, which is positive with respect to said first electrode, to said second electrode, or applying a voltage, which is positive with respect to at least one of said first electrode and said second electrode, to said third electrode; and    said first electrode and said second electrode are insulated from each other to bring the switching element into an off state by either applying a voltage, which is negative with respect to said first electrode, to said second electrode, or applying a voltage, which is negative with respect to at least one of said first electrode and said second electrode, to said third electrode.    
     
     
       16. The switching element according to  claim 14 , wherein:
 said first electrode and said second electrode are electrically interconnected to bring the switching element into an on state by either applying a voltage, which is positive with respect to said first electrode, to said second electrode, or applying a voltage, which is positive with respect to at least one of said first electrode and said second electrode, to said third electrode; and    said first electrode and said second electrode are insulated from each other to bring the switching element into an off state by either applying a voltage, which is negative with respect to said first electrode, to said second electrode, or applying a voltage, which is negative with respect to at least one of said first electrode and said second electrode, to said third electrode.    
     
     
       17. The switching element according to  claim 1 , wherein at least one of said first electrode, said second electrode, and said third electrode has  the electrodes held in contact with said ion conductor includes a pointed portion on a surface thereof held in contact with said ion conductor. 
     
     
       18. The switching element according to  claim 3 , wherein at least one of said first electrode, said second electrode, and said third electrode has a pointed portion on a surface thereof held in contact with said ion conductor. 
     
     
       19. The switching element according to  claim 1 , wherein said ion conductor comprises either a calcogenide material including an element belonging to the group 6B of the periodic table, or metal ionic glass, or metal ionic amorphous semiconductor. 
     
     
       20. The switching element according to  claim 3 , wherein said ion conductor comprises either a calcogenide material including an element belonging to the group 6B of the periodic table, or metal ionic glass, or metal ionic amorphous semiconductor. 
     
     
       21. The switching element according to  claim 1 , wherein:  said ion conductor and said third electrode are made of  includes either copper sulfide and copper, respectively,  or of silver sulfide and silver, respectively; and portions of said first electrode and said second electrode which are held in contact with said ion conductor are made of either a metal such as platinum, aluminum, gold, titanium, tungsten, vanadium, niobium, tantalum, chromium, or molybdenum, a nitride of the metal, or a silicide of the metal, or a combination thereof  silver sulfide. 
     
     
       22. The switching element according to  claim 3 , wherein:
 said ion conductor and said third electrode are made of either copper sulfide and copper, respectively, or of silver sulfide and silver, respectively; and    portions of said first electrode and said second electrode which are held in contact with said ion conductor are made of either a metal such as platinum, aluminum, gold, titanium, tungsten, vanadium, niobium, tantalum, chromium, or molybdenum, a nitride of the metal, or a silicide of the metal, or a combination thereof.    
     
     
       23. The switching element according to  claim 13 , wherein:
 said ion conductor and said third and second electrodes are made of either copper sulfide and copper, respectively, or of silver sulfide and silver, respectively; and    a portion of said first electrode which is held in contact with said ion conductor is made of either a metal such as platinum, aluminum, gold, titanium, tungsten, vanadium, niobium, tantalum, chromium, or molybdenum, a nitride of the metal, or a silicide of the metal, or a combination thereof.    
     
     
       24. The switching element according to  claim 14 , wherein:
 said ion conductor and said third and second electrodes are made of either copper sulfide and copper, respectively, or of silver sulfide and silver, respectively; and    a portion of said first electrode which is held in contact with said ion conductor is made of either a metal such as platinum, aluminum, gold, titanium, tungsten, vanadium, niobium, tantalum, chromium, or molybdenum, a nitride of the metal, or a silicide of the metal, or a combination thereof.    
     
     
       25. The switching element according to  claim 1 , wherein said ion conductor comprises an electrolytic solution. 
     
     
       26. The switching element according to  claim 3 , wherein said ion conductor comprises an electrolytic solution. 
     
     
       27. The method of driving a switching element according to claim  7    43 , comprising the step of:
 controlling said  an electrical characteristic between said first electrode and said second electrode, based on the voltage applied to said third electrode and/or a period of time for which the voltage is applied to said third electrode.  
 
     
     
       28. The method of driving a switching element according to  claim 8 , comprising the step of:
 controlling said electrical characteristic based on the voltage applied to said third electrode and/or a period of time for which the voltage is applied to said third electrode.    
     
     
       29. The method of driving a switching element according to claim  11    43 , comprising the steps of: selectively bringing said switching element into said on state and said off state depending on the polarity of the voltage applied to said third electrode; and  step of:
 holding said switching element in either said on state or said off state even if no  by stopping application of the voltage is applied  to said third electrode.  
 
     
     
       30. The method of driving a switching element according to  claim 12 , comprising the steps of:
 selectively bringing said switching element into said on state and said off state depending on the polarity of the voltage applied to said third electrode; and    holding said switching element in either said on state or said off state even if no voltage is applied to said third electrode.    
     
     
       31. The method of driving a switching element according to  claim 15 , comprising the steps of:
 selectively bringing said switching element into said on state and said off state depending on the polarity of the voltage applied to said third electrode; and    holding said switching element in either said on state or said off state even if no voltage is applied to said third electrode.    
     
     
       32. The method of driving a switching element according to  claim 16 , comprising the steps of:
 selectively bringing said switching element into said on state and said off state depending on the polarity of the voltage applied to said third electrode; and    holding said switching element in either said on state or said off state even if no voltage is applied to said third electrode.    
     
     
       33. The method of driving a switching element according to claim  11 , comprising the steps of: when said switching element is caused to transit between said on state and said off state, measuring   43 , wherein the conductivity between said first electrode  and said  second electrode; and controlling  electrodes is measured, and the voltage applied to said  the third electrode is controlled based on a change in the conductivity. 
     
     
       34. The method of driving a switching element according to  claim 12 , comprising the steps of:
 when said switching element is caused to transit between said on state and said off state, measuring the conductivity between said first electrode and said second electrode; and    controlling the voltage applied to said third electrode based on a change in the conductivity.    
     
     
       35. The method of driving a switching element according to  claim 15 , comprising the steps of:
 when said switching element is caused to transit between said on state and said off state, measuring the conductivity between said first electrode and said second electrode; and    controlling the voltage applied to said third electrode based on a change in the conductivity.    
     
     
       36. The method of driving a switching element according to  claim 16 , comprising the steps of:
 when said switching element is caused to transit between said on state and said off state, measuring the conductivity between said first electrode and said second electrode; and    controlling the voltage applied to said third electrode based on a change in the conductivity.    
     
     
       37. The rewritable  A logic integrated circuit incorporating a switching element, according to claim  7    1 , as a programming  programmable switch. 
     
     
       38. The rewritable logic integrated circuit incorporating a switching element according to  claim 8  as a programming switch. 
     
     
       39. The  A memory device having  element including a memory cells each  cell as a basic unit comprising a switching element according to claim  7    1  and either a MOS  a transistor or a diode. 
     
     
       40. The memory device having memory cells each comprising a switching element according to  claim 8  and either a MOS transistor or a diode. 
     
     
       41. The memory device according to  claim 39 , wherein:
 said memory cell comprises a MOS transistor;    said switching element has said second electrode connected to the drain electrode of said MOS transistor, said first electrode connected to a first bit line, and said third electrode connected to a first word line; and    said MOS transistor has a source electrode connected to a second bit line different from said first bit line and a gate electrode connected to a second word line different from said first word line.    
     
     
       42. A memory device according to  claim 40 , wherein:
 said memory cell comprises a MOS transistor;    said switching element has said second electrode connected to the drain electrode of said MOS transistor, said first electrode connected to a first bit line, and said third electrode connected to a first word line; and    said MOS transistor has a source electrode connected to a second bit line different from said first bit line and a gate electrode connected to a second word line different from said first word line.    
     
     
       43. A method of driving a switching element comprising an ion conductor capable of conducting metal ions therein, a first electrode, a second electrode, and a third electrode;
   wherein said first electrode is of a structure including a region made of a material that is not capable of supplying said metal ions to said ion conductor;        said third electrode is held in contact with said ion conductor and is of a structure including a material capable of supplying said metal ions to said ion conductor; and        wherein the first, second and third electrodes are arranged such that an electrical conductivity between said first electrode and said second electrode is controlled by applying a voltage to said third electrode;        said method comprising the steps of:      applying a positive voltage to said third electrode to form an on state in which said first electrode and said second electrode are electrically connected to each other; and        applying a negative voltage to said third electrode to form an off state in which said first electrode and said second electrode are insulated from each other.       
     
     
       44. A method of driving a switching element comprising an ion conductor capable of conducting metal ions therein, a first electrode, a second electrode, and a third electrode;
   wherein said first electrode is of a structure including a region made of a material that is not capable of supplying said metal ions to said ion conductor;        said second electrode is held in contact with said ion conductor and is of a structure including a material capable of supplying said metal ions to said ion conductor; and        wherein the first, second and third electrodes are arranged such that an electrical conductivity between said first electrode and said second electrode is controlled by applying a voltage to said third electrode;        said method comprising the steps of:      applying a positive voltage to said second electrode to form an on state in which said first electrode and said second electrode are electrically connected to each other, thereafter applying a voltage, which is positive with respect to said first electrode, to said third electrode to increase the amount of current between said first electrode and said second electrode, or applying a voltage, which is negative with respect to said first electrode, to said third electrode to reduce the amount of current between said first electrode and said second electrode; and        applying a voltage, whose polarity is opposite to the polarity thereof for forming the on state, to said second electrode to form an off state in which said first electrode and said second electrode are insulated from each other.       
     
     
       45. The switching element according to  claim 3 , wherein said first electrode includes a portion held in contact with at least said ion conductor, said portion being of a composition that is not capable of supplying said metal ions to said ion conductor. 
     
     
       46. The switching element according to  claim 1 , wherein one or two electrodes from among said first electrode, said second electrode, and said third electrode is/are disposed on a substrate. 
     
     
       47. The switching element according to  claim 46 , wherein another electrode is disposed above said electrode or electrodes on said substrate, with at least either said ion conductor or an insulating layer being interposed therebetween. 
     
     
       48. The switching element according to  claim 1 , wherein said region made of a material that is not capable of supplying said metal ions to said ion conductor, is made of either a metal such as platinum, aluminum, gold, titanium, tungsten, vanadium, niobium, tantalum, chromium, or molybdenum, a nitride of the metal, or a silicide of the metal, or a combination thereof.