JP5023615B2 - Driving method of switching element - Google Patents

Description

  The present invention relates to a driving method of a switching element using an electrochemical reaction used in electronic devices such as programmable logic and memory.

  In recent years, development competition for electronic devices has intensified, and electronic devices have been downsized. Under such circumstances, programmable logic that can provide many functions with one chip by changing the circuit configuration by electronic signals even after manufacturing has been attracting attention. Typical examples of the programmable logic include a field-programmable gate array (FPGA) and a dynamically reconfigurable processor (DRP).

  In order to diversify the functions of the programmable logic and promote the mounting to electronic devices, it is necessary to reduce the size of the switch for connecting the logic cells to each other and to reduce the on-resistance. As a switch that can satisfy such requirements, a metal ion movement in an ion conductor (a solid in which ions can freely move inside) and a switching element utilizing an electrochemical reaction (hereinafter simply referred to as “switching element”). ) Has been proposed (see Patent Document 1). This switching element is known to be smaller in size and smaller in on-resistance than a semiconductor switch (such as a MOSFET) that has been often used in conventional programmable logic.

  The switching element includes a two-terminal switch disclosed in Patent Document 1 and a three-terminal switch disclosed in Patent Document 2. The two-terminal switch has a structure in which an ion conductive layer is sandwiched between an electrode that supplies ions and an electrode that does not supply ions. Switching between the two electrodes is caused by the formation and disappearance of metal bridges in the ion conductive layer. Since the two-terminal switch has a simple structure, the manufacturing process is simple, and the element size can be reduced to the nanometer order. The three-terminal switch is provided with a third electrode that controls the formation / disappearance of the metal bridge, thereby making it possible to control the thickness of the metal bridge and having excellent electromigration resistance. In addition, when applied to logic, the two-terminal switch has a low resistance for metal bridges, so that a large current flows through the element during connection and disconnection, and there is a risk of damage to the logic. With three terminals, there is a separate electrode for controlling the formation of metal bridges and a transfer machine for transmitting electrical signals, so that the current can be controlled. On the other hand, the three-terminal switch has a more complicated structure and a larger element size than the two-terminal switch.

  By using this switching element as a wiring changeover switch of a programmable device, the switch area can be reduced (1/30), the switch resistance can be reduced (1/50), and the switching element can be connected to the wiring layer compared to a conventional switch. Since it can be built in, it is expected to reduce the chip area and improve the wiring delay. Furthermore, since the unit logic cell of the programmable logic can be reduced, the circuit utilization efficiency is greatly improved. As a result, the chip area is reduced to 1/10, and the power efficiency is improved three times. Conventional programmable logic has a limited application range due to its large chip size and low power efficiency, but a new programmable logic using switching elements can cover a wide range of applications (Ref. 1). reference).

  In addition, as a time for maintaining the state of the switching element (a time for maintaining non-volatility), a longer period than a product life (generally 10 years) in which the programmable logic is used is necessary. When programming or debugging programmable logic during development, it is desirable that the wiring switch be rewritten many times, the circuit configuration is determined, and the ON state is permanently maintained when shipped as a product. Is desirable. In order to satisfy this method of use, a method of driving the switch that permanently switches the switch to the ON state is required.

  One drive example for permanently turning on is disclosed in Patent Document 3. In Patent Document 3, various writing methods are defined as follows. Soft writing is defined as a writing method that can keep the switch on for 2 hours to 10 days in an ionic conductor. A writing method capable of maintaining an on state for one month to several years (within 20 years) is defined as non-volatile lighting. The writing method that can keep the ON state permanently is defined as hard writing.

The hard lighting in Patent Document 3 is low resistance and strong by applying a pulse (voltage or current) having a large absolute value or application time so that metal dendrite (corresponding to metal bridge) is deposited in the ion conductive layer. It can be achieved by switching with a simple metal dendrite.
Special Table 2002-536840 Publication International Publication No. 2006/070773 Journal of Solid State Circuits, Vol. 40, No. 1, pp. 168-176, 2005 US2005 / 0120186 A1

  The switching element disclosed in Patent Document 3 may have the following problems.

  When the switch is turned on with a metal dendrite, the metal dendrite has a low resistance. For this reason, it is considered that all the current flowing between the connected electrodes flows in the metal dendrite, and no disconnection occurs due to the dissolution of the metal dendrite. However, in reality, since the resistance between the electrodes becomes a low resistance state of 100 ohms or less at the moment when the electrodes are connected with the metal dendrite, the thickness of the metal dendrite is difficult to grow to the order of several nanometers or more.

  When the switching element is set to either ON or OFF and the programmable logic is programmed, it is considered that the metal dendrite of the switching element set to ON is in a thin state. If programmable logic is used for a long time in this state, there is a risk that the metal dendrite will deteriorate due to high-speed operation of the logic, electromigration of the metal dendrite, or external stress such as heat, and the switch will transition from on to off. is there. As a result, the programmable logic may not operate as programmed, and the reliability of the programmable logic may be reduced.

  The present invention has been made to solve the above-described problems of the prior art, and provides a method for driving a switching element that prevents the occurrence of a change in the state of a switch to be fixed in an on state. Objective.

In order to achieve the above object, a method for driving a switching element of the present invention comprises
An ion conducting layer for conducting metal ions;
A first electrode provided in contact with the ion conductive layer, and a portion in contact with the ion conductive layer covered with a material that does not supply the metal ions;
A second electrode including a material that is provided in contact with the ion conductive layer and is capable of supplying the metal ions;
When repeatedly transitioning between ON and OFF, the second electrode is grounded and a negative voltage is applied to the first electrode, or the first electrode is grounded and a positive voltage is applied to the second electrode, Form metal deposits between the electrodes, turn on, ground the first electrode and apply a negative voltage to the second electrode, or ground the second electrode and apply a positive voltage to the first electrode Separate and turn off the metal deposits,
When fixing in the ON state, the second electrode is grounded from the OFF state and a predetermined positive voltage is applied to the first electrode, or the first electrode is grounded and a predetermined negative voltage is applied to the second electrode. Apply to connect these two electrodes ,
The predetermined positive voltage and the predetermined negative voltage applied when fixing in the ON state are values equal to or higher than a voltage causing dielectric breakdown in the ion conductive layer .

  In the present invention, it is possible to repeatedly turn the switch on and off by connecting two electrodes with metal deposits using an electrochemical reaction or by separating metal deposits between the two electrodes. To do. On the other hand, when fixing in the ON state, a voltage is applied in the voltage application direction for separating the metal deposit, and a current path is generated between the two electrodes. By forming a current path between the two electrodes, the ON state is maintained regardless of the subsequent voltage application conditions.

  According to the present invention, when driving the switching element in the programmable logic, it is possible to select one of a method that can repeatedly execute erasing and writing, and a method that cannot be erased after writing. Moreover, since the problem of the conventional instability of an ON state does not generate | occur | produce, a more reliable and flexible programmable logic can be provided than before.

The switching element driving method of the present invention is characterized in that a voltage is applied in the voltage application direction in the off state to fix it in the on state.
(Embodiment 1)
The configuration of the two-terminal switch of this embodiment will be described. FIG. 1 is a schematic cross-sectional view showing one configuration example of the two-terminal switch element of the present embodiment.

  The switching element includes a first electrode 11, an ion conductive layer 13, and a second electrode 12 provided via the first electrode 11 and the ion conductive layer 13. The ion conductive layer 13 becomes a medium for conducting metal ions. It is desirable that the material of the first electrode 11 does not supply metal ions into the ion conductive layer when a voltage is applied.

  A normal driving method of the two-terminal switch of the present embodiment will be described.

  When the second electrode 12 is grounded and a negative voltage is applied to the first electrode 11, the metal of the second electrode 12 becomes metal ions and dissolves in the ion conductive layer 13. Then, metal ions in the ion conductive layer 13 are deposited on the surface of the first electrode 12 as a metal, and a metal dendrite that connects the first electrode 11 and the second electrode 12 is formed by the deposited metal. The metal dendrite is a metal deposit in which metal ions in the ion conductive layer 13 are deposited. When the first electrode 11 and the second electrode 12 are electrically connected with a metal dendrite, the switch is turned on.

  On the other hand, when the second electrode 12 is grounded in the ON state and a positive voltage is applied to the first electrode 11, the metal dendrite is dissolved in the ion conductive layer 13 and a part of the metal dendrite is cut off. Thereby, the electrical connection between the first electrode 11 and the second electrode 12 is cut, and the switch is turned off. In order to switch from the off state to the on state, a negative voltage may be applied to the first electrode 11 again.

  When the switch is turned off, the electrical characteristics such as the resistance between the first electrode 11 and the second electrode 12 increasing and the capacitance between the electrodes change from the stage before the electrical connection is completely cut off. There is a change and eventually the electrical connection is broken.

  In addition, the first electrode 11 is grounded and a positive voltage is applied to the second electrode 12 to turn on the switch, or the first electrode 11 is grounded and a negative voltage is applied to the second electrode 12 to turn off the switch. Or may be in a state.

  The first electrode 11 does not need to be a material that does not supply metal ions as a whole, and at least a portion that contacts the ion conductive layer 13 may be a material that does not supply metal ions.

  The configuration of the two-terminal switch of this embodiment will be described. FIG. 2 is a schematic cross-sectional view showing a configuration example of the two-terminal switch of this embodiment.

  As shown in FIG. 2, the switching element is provided on the silicon substrate 35 covered with the silicon oxide film 36, and the switching element is provided via the first electrode 31, the ion conductive layer 33, and the ion conductive layer 33. The structure has two electrodes 32. The ion conductive layer 33 is made of tantalum oxide having a thickness of 15 nm, the first electrode 31 is made of platinum having a thickness of 100 nm, and the second electrode 32 is made of copper having a thickness of 100 nm. A part of the first electrode 31 is covered with an insulating layer 34 made of a silicon oxide film, and a part thereof is in contact with the ion conductive layer 33 through an opening of the insulating layer 34. In this configuration, a switch is formed in the opening of the insulating layer 34, and the junction area of the switch can be as large as the opening. That is, by determining the size of the opening and making the second electrode 32, the first electrode 31, and the ion conductive layer 33 larger than the opening, the junction area of the switch can be determined.

  Note that the two-terminal switch of this embodiment shown in FIG. 2 can be manufactured by using a conventional film formation technique and lithography technique, and thus detailed description of the manufacturing method is omitted here.

  Next, the operation of the switch of this embodiment will be described.

  When the two-terminal switch of this embodiment is used as a wiring switch for programmable logic, it is desirable that the wiring switch can be rewritten many times when the programmable logic is programmed or debugged during development. In this case, a “rewritable switching operation” described later may be applied to the driving method of the two-terminal switch. On the other hand, when the circuit configuration of the programmable logic is determined and shipped as a product, it is desirable that the ON state of the wiring switch is kept permanently. In this case, a “switching operation for fixing to the on state” described later may be applied to the driving method of the two-terminal switch.

  First, the “rewritable switching operation” will be described. FIG. 3 is a graph showing changes in electrical characteristics with respect to the operation of the switch.

  When the second electrode 32 is grounded and a negative voltage is applied to the first electrode 31, the switch transits from an off state (high resistance state) to an on state (low resistance state) at -4V (shown in FIG. 3). A). At this time, the current applied to the switching element was limited to 10 microamperes. Next, when a positive voltage was applied, the current decreased sharply at 0.4 V and transitioned to the off state (B shown in FIG. 3). At this time, the current flowing through the switching element was controlled so that the upper limit was 20 milliamperes. Furthermore, by applying a positive or negative voltage, the on state and the off state could be changed alternately. Further, the off state and the on state could be maintained when no voltage was applied.

  The electrical characteristics shown in FIG. 3 can be explained as follows. When a negative voltage is applied to the first electrode 31, the copper of the second electrode 32 becomes copper ions and dissolves in the ion conductive layer 33. Then, copper ions dissolved in the ion conductive layer 33 are deposited on the surface of the first electrode 31 as copper, and the deposited copper forms a metal dendrite that connects the first electrode 31 and the second electrode 32. When the first electrode 31 and the second electrode 32 are electrically connected with a metal dendrite, the switch is turned on. On the other hand, when a positive voltage is applied to the first electrode 31 in the ON state, copper of the metal dendrite is dissolved in the ion conductive layer 33 and a part of the metal dendrite is cut. Thereby, the electrical connection between the first electrode 31 and the second electrode 32 is cut off, and the device is turned off.

  Next, the “switching operation for fixing in the ON state” will be described. FIG. 4 is a graph showing changes in electrical characteristics with respect to the operation of the switch.

  After the switch is turned off by the above-described “rewritable switching operation”, the second electrode 32 is grounded and a positive voltage is applied to the first electrode 31. This means that a voltage having a polarity opposite to that when copper ions are supplied from the second electrode 32 to the ion conductive layer 33 is applied to the first electrode 31. Even if the first electrode 31 is grounded and a negative voltage is applied to the second electrode 32, the first electrode 31 becomes a positive voltage with reference to the second electrode 32, and thus the same manner as the above-described voltage application. become. When the voltage was applied in this manner, the tantalum oxide ion conductive layer breakdown at 4.5 V, and a current path was generated between the two electrodes. By forming a current path between the two electrodes, a low resistance state was achieved as in the on state (A in FIG. 4).

  The resistance value between the first electrode 31 and the second electrode 32 after the dielectric breakdown was 35Ω. The two electrodes are electrically connected via a 35Ω resistive element. After the dielectric breakdown, even if the second electrode 32 is grounded and a negative voltage is applied to the first electrode 31 as shown in the graph of FIG. As shown in the graph of FIG. 4, during the switching operation, the current flowing through the switching element is controlled so that the upper limit is 20 milliamperes.

  As described above, the two-terminal switch of this embodiment can select two types of switch driving methods, that is, a case where the on / off state is repeatedly changed and a case where the two-terminal switch is fixed in the on state. In the case of fixing in the on state, two electrodes are connected by dielectric breakdown by applying a positive voltage equal to or higher than the dielectric breakdown of the ion conductive layer to an electrode that does not supply metal ions.

After the dielectric breakdown, the ion conductive layer is physically changed to a low resistance state by a large current, and therefore does not return to the insulating state permanently. If the switch is fixed in the on state, the switch can be prevented from transitioning to the off state during use of the electronic device provided with the switch, and the operational reliability of the switch is improved.
(Embodiment 2)
The configuration of the three-terminal switch of this embodiment will be described. FIG. 5 is a schematic cross-sectional view showing a configuration example of the three-terminal switch of this embodiment.

  As shown in FIG. 5, the three-terminal switch has a configuration including a second electrode 22, a first electrode 21 and a third electrode 23 provided via the second electrode 22 and the ion conductive layer 24. The first electrode 21 and the second electrode 22 are made of platinum, and the third electrode 23 is made of copper. The ion conductive layer 24 becomes a medium for conducting metal ions.

  A normal driving method of the three-terminal switch of this embodiment will be described.

  When the second electrode 22 and the third electrode 23 are grounded and a negative voltage is applied to the first electrode 21, the copper of the third electrode 23 becomes copper ions and dissolves in the ion conductive layer 24. Then, the copper ions in the ion conductive layer 24 are deposited as copper on the surfaces of the first electrode 21 and the second electrode 22, and the deposited copper forms a metal dendrite that connects the first electrode 21 and the second electrode 22. Is done. The metal dendrite is a metal deposit in which metal ions in the ion conductive layer 24 are deposited. When the first electrode 21 and the second electrode 22 are electrically connected with a metal dendrite, the three-terminal switch is turned on.

  On the other hand, when the first electrode 21 or the second electrode 22 is grounded in the ON state and a negative voltage is applied to the third electrode 23, copper of the metal dendrite is dissolved in the ion conductive layer 24, and a part of the metal dendrite is Cut out. Thereby, the electrical connection between the first electrode 21 and the second electrode 22 is cut, and the three-terminal switch is turned off. Note that the electrical characteristics change from the stage before the electrical connection is completely cut off, such as the resistance between the first electrode 21 and the second electrode 22 is increased, the capacitance between the electrodes is changed, etc. The connection is lost.

  In order to change from the off state to the on state, a positive voltage may be applied to the third electrode 23. As a result, the copper of the third electrode 23 becomes copper ions and dissolves in the ion conductive layer 24. And the copper ion melt | dissolved in the ion conductive layer 24 turns into copper in the cutting | disconnection location of a metal dendrite, and a metal dendrite electrically connects the 1st electrode 21 and the 2nd electrode 22. FIG.

  The switch may be turned off by grounding the third electrode 23 and applying a positive voltage to the first electrode 21 or the second electrode 22. The first electrode 21 and the second electrode 22 do not need to be made of a material that does not supply metal ions as a whole, and at least a portion that contacts the ion conductive layer 24 may be a material that does not supply metal ions.

  The configuration of the three-terminal switch of this embodiment will be described. FIG. 6 is a schematic cross-sectional view showing a configuration example of the three-terminal switch of this embodiment.

  As shown in FIG. 6, the three-terminal switch includes a first electrode 61 and a second electrode 62 that are electrically connected and disconnected, and a third electrode that is provided via these two electrodes and the ion conductive layer 64. 63. An ion conductive layer 64 is also provided between the first electrode 61 and the second electrode 62.

  A second electrode 62 and a third electrode 63 are provided on the silicon oxide film 100 formed on the surface of the silicon substrate. The second electrode 62 and the third electrode 63 are formed on the same plane on the silicon oxide film 100, and these two electrodes are separated from each other by about 10 nm to 100 nm. The ion conductive layer 64 is provided on the silicon oxide film 67 so as to cover the second electrode 62 and the third electrode 63. An insulating layer 65 is provided on the ion conductive layer 64, and the first electrode 61 is provided on the insulating layer 65. The first electrode 61 is in contact with the ion conductive layer 64 through an opening provided in the insulating layer 65. The first electrode 61 and the second electrode 62 are made of platinum, and the third electrode 63 is made of copper. The ion conductive layer 64 is made of tantalum oxide.

  Note that the three-terminal switch of this embodiment shown in FIG. 6 can be manufactured by using a conventional film forming technique and a lithography technique, and therefore, detailed description of the manufacturing method is omitted here.

  Next, a method for driving the switch of this embodiment will be described.

  When the three-terminal switch of this embodiment is used as a programmable logic wiring switch, it is desirable that the wiring switch can be rewritten many times when the programmable logic is programmed or debugged during development. In this case, a “rewritable switching operation” described later may be applied to the driving method of the three-terminal switch. On the other hand, when the circuit configuration of the programmable logic is determined and shipped as a product, it is desirable that the ON state of the wiring switch is kept permanently. In this case, a “switching operation for fixing in the on state” described later may be applied to the driving method of the three-terminal switch.

  First, the “rewritable switching operation” will be described.

  When the first electrode 61 and the second electrode 62 are grounded and a positive voltage is applied to the third electrode 63, the copper of the third electrode 63 becomes copper ions and dissolves in the ion conductive layer 64. And the copper ion melt | dissolved in the ion conductive layer 64 turns into copper on the surface of the 1st electrode 61 and the 2nd electrode 62, and the metal dendrite which connects the 1st electrode 61 and the 2nd electrode 62 with the deposited copper becomes It is formed. When the first electrode 61 and the second electrode 62 are electrically connected with a metal dendrite, the three-terminal switch is turned on.

  On the other hand, when a negative voltage of about −0.5 V is applied to the third electrode 63 in the ON state, copper of the metal dendrite is dissolved in the ion conductive layer 64 and a part of the metal dendrite is cut. Thereby, the electrical connection between the first electrode 61 and the second electrode 62 is cut off, and the three-terminal switch is turned off.

  In order to change from the off state to the on state, a positive voltage of about 0.5 V is applied to the third electrode 63. As a result, the copper of the third electrode 63 becomes copper ions and dissolves in the ion conductive layer 64. And the copper ion melt | dissolved in the ion conductive layer 64 turns into copper at the cutting | disconnection location of a metal dendrite, and a metal dendrite electrically connects the 1st electrode 61 and the 2nd electrode 62. FIG.

  Next, the “switching operation for fixing in the ON state” will be described. For fixing in the ON state in the three-terminal switch, a voltage is applied to the first electrode 61 or the second electrode 62 instead of the third electrode 63, and the following is performed between the first electrode 61 and the second electrode 62. This is done with two-terminal operation.

  First, the switch is turned off by the above-described “rewritable switching operation”, the second electrode 62 is grounded, a positive voltage or a negative voltage is applied to the first electrode 61, the ion conductive layer 64 is dielectrically broken down, and the first A current path is generated between the first electrode 61 and the second electrode 62. If the film thickness of the ion conductive layer 64 is equivalent to that of the ion conductive layer 33 of the first embodiment, the voltage applied to the first electrode 61 may be 4.5 V or more as in the first embodiment. After the dielectric breakdown, even if a negative voltage is applied to the first electrode 61, the high resistance state is not obtained. Alternatively, the first electrode 61 may be grounded, and a positive voltage or a negative voltage may be applied to the second electrode 62 to cause dielectric breakdown in the ion conductive layer 64.

  In the case where the third electrode 63 is grounded, as described above, when the third electrode 63 is grounded and a negative voltage is applied to the first electrode 61 or the second electrode 62, the copper of the third electrode 63 becomes the ion conductive layer. There is a possibility that a phenomenon of dissolution in 64 occurs. Therefore, it is desirable that the third electrode 63 is in a floating state.

As described above, the three-terminal switch according to the present embodiment can select two types of switch driving methods, that is, a case of repeatedly changing between ON and OFF and a case of fixing to the ON state. In the case of fixing in the ON state, a voltage higher than a predetermined value is applied between the first electrode and the second electrode, whereby the two electrodes of the first electrode and the second electrode are connected by dielectric breakdown. As a result, as in the first embodiment, the switch is fixed in the ON state, and the effect of improving the operation reliability of the switch is obtained.
(Embodiment 3)
The configuration of the three-terminal switch of this embodiment will be described. The configuration of the three-terminal switch according to the present embodiment is described with reference to FIG. 5 because only the constituent members of the three-terminal switch described in FIG. 5 are different.

  As shown in FIG. 5, the three-terminal switch has a configuration including a second electrode 22, a first electrode 21 and a third electrode 23 provided via the second electrode 22 and the ion conductive layer 24. In the present embodiment, the first electrode 21 is made of platinum, and the second electrode 22 and the third electrode 23 are made of copper. The ion conductive layer 24 becomes a medium for conducting metal ions.

  A normal driving method of the three-terminal switch of this embodiment will be described.

  When the second electrode 22 and the third electrode 23 are grounded and a negative voltage is applied to the first electrode 21, the copper of the second electrode 22 and the third electrode 23 becomes copper ions and dissolves in the ion conductive layer 24. Then, the copper ions in the ion conductive layer 24 are deposited as copper on the surfaces of the first electrode 21 and the second electrode 22, and the deposited copper forms a metal dendrite that connects the first electrode 21 and the second electrode 22. Is done. The metal dendrite is a metal deposit in which metal ions in the ion conductive layer 24 are deposited. When the first electrode 21 and the second electrode 22 are electrically connected with a metal dendrite, the three-terminal switch is turned on.

  On the other hand, when the first electrode 21 or the second electrode 22 is grounded in the ON state and a negative voltage is applied to the third electrode 23, copper of the metal dendrite is dissolved in the ion conductive layer 24, and a part of the metal dendrite is Cut out. Thereby, the electrical connection between the first electrode 21 and the second electrode 22 is cut, and the three-terminal switch is turned off. Note that the electrical characteristics change from the stage before the electrical connection is completely cut off, such as the resistance between the first electrode 21 and the second electrode 22 is increased, the capacitance between the electrodes is changed, etc. The connection is lost.

  In order to change from the off state to the on state, a positive voltage may be applied to the third electrode 23. As a result, the copper of the third electrode 23 becomes copper ions and dissolves in the ion conductive layer 24. And the copper ion melt | dissolved in the ion conductive layer 24 turns into copper in the cutting | disconnection location of a metal dendrite, and a metal dendrite electrically connects the 1st electrode 21 and the 2nd electrode 22. FIG.

  The switch may be turned off by grounding the third electrode 23 and applying a positive voltage to the first electrode 21 or the second electrode 22. Further, the first electrode 21 does not need to be a material that does not supply metal ions as a whole, and at least a portion that is in contact with the ion conductive layer 24 may be a material that does not supply metal ions.

  The configuration of the three-terminal switch of this embodiment will be described. The configuration of the three-terminal switch according to the present embodiment will be described with reference to FIG. 6 because only the components differ in the three-terminal switch described in FIG.

  As shown in FIG. 6, the three-terminal switch includes a first electrode 61 and a second electrode 62 that are electrically connected and disconnected, and a third electrode that is provided via these two electrodes and the ion conductive layer 64. 63. An ion conductive layer 64 is also provided between the first electrode 61 and the second electrode 62.

  A second electrode 62 and a third electrode 63 are provided on the silicon oxide film 100 formed on the surface of the silicon substrate. The second electrode 62 and the third electrode 63 are formed on the same plane on the silicon oxide film 100, and these two electrodes are separated from each other by about 10 nm to 100 nm. The ion conductive layer 64 is provided on the silicon oxide film 67 so as to cover the second electrode 62 and the third electrode 63. An insulating layer 65 is provided on the ion conductive layer 64, and the first electrode 61 is provided on the insulating layer 65. The first electrode 61 is in contact with the ion conductive layer 64 through an opening provided in the insulating layer 65. In the present embodiment, the first electrode 61 is made of platinum, and the second electrode 62 and the third electrode 63 are made of copper. The ion conductive layer 64 is made of tantalum oxide.

  Note that the manufacturing method of the three-terminal switch of the present embodiment can also be manufactured by using the conventional film forming technique and lithography technique as in the case of the second embodiment. Description is omitted.

  Next, a method for driving the switch of this embodiment will be described.

  When the three-terminal switch of this embodiment is used as a programmable logic wiring switch, it is desirable that the wiring switch can be rewritten many times when the programmable logic is programmed or debugged during development. In this case, a “rewritable switching operation” described later may be applied to the driving method of the three-terminal switch. On the other hand, when the circuit configuration of the programmable logic is determined and shipped as a product, it is desirable that the ON state of the wiring switch is kept permanently. In this case, a “switching operation for fixing in the on state” described later may be applied to the driving method of the three-terminal switch.

  First, the “rewritable switching operation” will be described.

  When the first electrode 61 and the second electrode 62 are grounded and a positive voltage is applied to the third electrode 63, the copper of the third electrode 63 becomes copper ions and dissolves in the ion conductive layer 64. And the copper ion melt | dissolved in the ion conductive layer 64 turns into copper on the surface of the 1st electrode 61 and the 2nd electrode 62, and the metal dendrite which connects the 1st electrode 61 and the 2nd electrode 62 with the deposited copper becomes It is formed. When the first electrode 61 and the second electrode 62 are electrically connected with a metal dendrite, the three-terminal switch is turned on.

  On the other hand, when a negative voltage of about −0.5 V is applied to the third electrode 63 in the ON state, copper of the metal dendrite is dissolved in the ion conductive layer 64 and a part of the metal dendrite is cut. Thereby, the electrical connection between the first electrode 61 and the second electrode 62 is cut off, and the three-terminal switch is turned off.

  In order to change from the off state to the on state, a positive voltage of about 0.5 V is applied to the third electrode 63. As a result, the copper of the third electrode 63 becomes copper ions and dissolves in the ion conductive layer 64. And the copper ion melt | dissolved in the ion conductive layer 64 turns into copper at the cutting | disconnection location of a metal dendrite, and a metal dendrite electrically connects the 1st electrode 61 and the 2nd electrode 62. FIG.

  Next, the “switching operation for fixing in the ON state” will be described. For fixing in the ON state in the three-terminal switch, a voltage is applied to the first electrode 61 or the second electrode 62 instead of the third electrode 63, and the following is performed between the first electrode 61 and the second electrode 62. This is done with two-terminal operation.

  First, the switch is turned off by the above-described “rewritable switching operation”, the second electrode 62 is grounded, a positive voltage is applied to the first electrode 61, the ion conductive layer 64 is dielectrically broken, and the first electrode 61 Current path is generated between the first electrode 62 and the second electrode 62. If the film thickness of the ion conductive layer 64 is equivalent to that of the ion conductive layer 33 of the first embodiment, the voltage applied to the first electrode 61 may be 4.5 V or more as in the first embodiment. After the dielectric breakdown, even if a negative voltage is applied to the first electrode 61, the high resistance state is not obtained. Note that the first electrode 61 may be grounded and a negative voltage may be applied to the second electrode 62 to cause dielectric breakdown in the ion conductive layer 64.

  When the third electrode 63 is grounded, as described above, when the third electrode 63 is grounded and a negative voltage is applied to the second electrode 62, the copper of the third electrode 63 is dissolved in the ion conductive layer 64. May occur. Therefore, it is desirable that the third electrode 63 is in a floating state.

  As described above, the three-terminal switch according to the present embodiment can select two types of switch driving methods, that is, a case of repeatedly changing between ON and OFF and a case of fixing to the ON state. In the case of fixing in the ON state, a voltage higher than a predetermined value is applied between the first electrode and the second electrode, whereby the two electrodes of the first electrode and the second electrode are connected by dielectric breakdown. As a result, as in the first embodiment, the switch is fixed in the ON state, and the effect of improving the operation reliability of the switch is obtained.

  As described in the above embodiments and examples, in the switching element driving method of the present invention, when driving the switching element in the programmable logic, a method that can repeatedly execute erasing and writing, and a method that cannot be erased after writing And can be selected. In addition, after programming the programmable logic, fixing the switch that does not change the writing, it is possible to operate the logic at high speed, metal migration electromigration, or metal bridge degradation due to external stress such as heat. There is no. Therefore, the problem of instability in the on state is solved, and a programmable logic that is more reliable and flexible than conventional ones can be provided.

3 is a schematic cross-sectional view illustrating a configuration example of a two-terminal switching element according to Embodiment 1. FIG. 3 is a schematic cross-sectional view illustrating a configuration example of a switching element of Example 1. FIG. It is a graph which shows the switching characteristic of "rewritable switching operation". It is a graph which shows the switching characteristic of "the switching operation for fixing to an ON state". FIG. 5 is a schematic cross-sectional view illustrating a configuration example of a three-terminal switching element according to Embodiment 2. 6 is a schematic cross-sectional view illustrating a configuration example of a switching element of Example 2. FIG.

Explanation of symbols

11, 21, 31, 61 First electrode 12, 22, 32, 62 Second electrode 23, 63 Third electrode 13, 24, 33, 64 Ion conductive layer 34, 65 Insulating layer 36, 67 Silicon oxide film 35, 66 Silicon substrate

Claims (3)

An ion conducting layer for conducting metal ions;
A first electrode provided in contact with the ion conductive layer, and a portion in contact with the ion conductive layer covered with a material that does not supply the metal ions;
A second electrode including a material that is provided in contact with the ion conductive layer and is capable of supplying the metal ions;
When repeatedly transitioning between ON and OFF, the second electrode is grounded and a negative voltage is applied to the first electrode, or the first electrode is grounded and a positive voltage is applied to the second electrode, Form metal deposits between the electrodes, turn on, ground the first electrode and apply a negative voltage to the second electrode, or ground the second electrode and apply a positive voltage to the first electrode Separate and turn off the metal deposits,
When fixing in the ON state, the second electrode is grounded from the OFF state and a predetermined positive voltage is applied to the first electrode, or the first electrode is grounded and a predetermined negative voltage is applied to the second electrode. Apply to connect these two electrodes ,
The method of driving a switching element, wherein the predetermined positive voltage and the predetermined negative voltage applied when fixing in an ON state are equal to or higher than a voltage causing dielectric breakdown in the ion conductive layer . An ion conducting layer for conducting metal ions;
A first electrode and a second electrode, which are provided in contact with the ion conductive layer, and in which a portion in contact with the ion conductive layer is covered with a material that does not supply the metal ions;
A third electrode comprising a material provided in contact with the ion conductive layer and capable of supplying the metal ions;
When repeatedly transitioning between ON and OFF, the second electrode and the third electrode are grounded and a negative voltage is applied to the first electrode, or the first electrode and the second electrode are grounded and the third electrode A positive voltage is applied to form a metal precipitate between the first electrode and the second electrode to turn it on, the first electrode or the second electrode is grounded, and a negative voltage is applied to the third electrode. Or ground the third electrode and apply a positive voltage to the first electrode or the second electrode to cut off the metal deposit and turn it off,
When fixing in the on state, from the off state, one of the two electrodes, the first electrode and the second electrode, is grounded, and a predetermined positive voltage is applied to the other electrode. connect,
The method for driving a switching element, wherein the predetermined positive voltage applied when fixing in an ON state is a value equal to or higher than a voltage causing dielectric breakdown in the ion conductive layer . An ion conducting layer for conducting metal ions;
A first electrode provided in contact with the ion conductive layer, and a portion in contact with the ion conductive layer covered with a material that does not supply the metal ions;
A switching element driving method comprising: a second electrode and a third electrode provided in contact with the ion conductive layer and including a material capable of supplying the metal ions;
When repeatedly transitioning between ON and OFF, the second electrode and the third electrode are grounded and a negative voltage is applied to the first electrode, or the first electrode and the second electrode are grounded and the third electrode A positive voltage is applied to form a metal precipitate between the first electrode and the second electrode to turn it on, the first electrode or the second electrode is grounded, and a negative voltage is applied to the third electrode. Or ground the third electrode and apply a positive voltage to the first electrode or the second electrode to cut off the metal deposit and turn it off,
When fixing in the ON state, the second electrode is grounded from the OFF state and a predetermined positive voltage is applied to the first electrode, or the first electrode is grounded and a predetermined negative voltage is applied to the second electrode. Apply to connect these two electrodes ,
The method of driving a switching element, wherein the predetermined positive voltage and the predetermined negative voltage applied when fixing in an ON state are equal to or higher than a voltage causing dielectric breakdown in the ion conductive layer .

Images