JP2010199498A - Switching element, switching element manufacturing method, electronic device, logic integrated circuit, and memory element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching element to which an oxide ion conductor being excellent in semiconductor process affinity and can be driven at a low voltage, to provide a switching element manufacturing method, to provide an electronic device, to provide a logic integrated circuit, and to provide a memory element. <P>SOLUTION: The switching element includes a first electrode 11, a second electrode 12, a third electrode 13, and an ion conductive layer containing an oxide. The first electrode 11 supplies electrons to the ion conductive layer, and at least one electrode of the first and third electrodes supply metal ions to the ion conductive layer. The metal ions receive electrons to form a metal in the ion conductive layer, and the metal connects between the first and second electrodes, and the third electrode 13 controls the formation and elimination of the metal which connects between the first and second electrodes. The ion conductive layer is prepared in contact with the first electrode 11, second electrode 12, and third electrode 13, and contains fine crystals smaller than crystals of crystalline oxide crystallized at a crystallization temperature of the oxide, and the fine crystals form a crystal grain boundary. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a switching element using metal deposition, a method for manufacturing the switching element, an electronic device, a logic integrated circuit, and a memory element.

  In order to diversify the functions of the programmable logic and to 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. A switch using metal deposition is attracting attention as a switch applied to programmable logic because of its small size and relatively low on-resistance.

  As a switching element utilizing the metal deposition, a technique of a two-terminal switch is disclosed (for example, Patent Document 1). FIG. 10 shows the structure of the two-terminal switch of Patent Document 1. As illustrated, the two-terminal switch described in Patent Document 1 has a structure in which an ion conductive layer 14 is sandwiched between a first electrode 11 that supplies metal ions and a second electrode 12 that does not supply ions. Switching between the two electrodes is performed by formation / disappearance of a metal bridge in the ion conductive layer 14. 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.

  However, with the two-terminal element as described above, there is a problem that when switching is performed so as to reduce the on-resistance when turning on, the off-current, which is the current when transitioning to off, increases to several mA or more. It was. When the off-state current increases, the peripheral circuit size increases when applied to programmable logic. Therefore, the small size that is an advantage of the switching element using metal deposition cannot be utilized.

  In order to solve the above problem, a technique of a three-terminal switch using metal deposition has been disclosed (for example, Patent Document 2). FIG. 11 shows the structure of the three-terminal switch element described in Patent Document 2. Since the three-terminal switch described in Patent Document 2 includes the first electrode 11 and the second electrode 12 described in Patent Document 1, the third electrode 13 that controls the formation and disappearance of metal bridges is provided. The influence of the off-current on the signal line can be reduced. Moreover, since the thickness of the metal bridge | crosslinking is controllable, the 3 terminal switch of the said patent document 2 is excellent also in electromigration tolerance.

  However, in order to mount a switch using metal deposition as a wiring switch for programmable logic, a switching voltage higher than a logic operating voltage (for example, 1 V) and heat resistance that can withstand the manufacturing process of a semiconductor integrated circuit are required. . Since the switching voltage greatly depends on the diffusion rate of metal ions in the ionic conductor, selection and optimization of the ionic conductor material is important. In order to solve the above problem, a technique is disclosed in which an oxide having a slow diffusion of metal ions is used for an ion conductive layer to increase a switching voltage and obtain high heat resistance (for example, Patent Document 3).

Special Table 2002-536840 Publication Re-specialized WO2006 / 070773 JP 2006-319028 A

IE Transactions on Electron Devices, 2008, 55, 11, 3283-3287 Thin Solid Films, 1995, 262, 168-176 Journal of Crystal Growth, 2000, 212, 459-468

  However, in the technique of Patent Document 3 in which an oxide is applied to the ion conductive layer, the diffusion of metal ions is suppressed, so that it is difficult to generate and extinguish a metal bridge between the first electrode and the second electrode by the third electrode. Thus, there is a problem that the three-terminal operation becomes difficult.

  In addition, in a three-terminal switch using an oxide in the ion conductive layer like the switch of Patent Document 3, a large voltage is applied to the third electrode in order to operate the metal bridge between the first electrode and the second electrode. It is necessary to apply. However, when a large voltage is applied to the third electrode, before the metal bridge between the first electrode and the second electrode is generated or extinguished, between the third electrode and the first electrode or between the third electrode and the second electrode, There was a problem that a short circuit occurred due to metal deposition or dielectric breakdown.

  The present invention has been made in view of such a situation. The present invention solves the above-described problems, applies an oxide ion conductor excellent in semiconductor process affinity, and can be driven at a low voltage. An object of the present invention is to provide a manufacturing method, an electronic device to which the switching element is applied, a logic integrated circuit, and a memory element.

  The switching element of the present invention has a first electrode, a second electrode, a third electrode, and an ion conductive layer containing an oxide, and the first electrode has electrons in the ion conductive layer. At least one of the first electrode and the third electrode supplies a metal ion to the ion conductive layer, and the metal ion receives an electron to form a metal in the ion conductive layer. Connects between the first electrode and the second electrode, the third electrode controls formation and erasure of the metal connecting between the first electrode and the second electrode, and the ion conductive layer A microcrystal that is provided in contact with the first electrode, the second electrode, and the third electrode and that is smaller than an oxide crystal that is an oxide crystal that is crystallized at the crystallization temperature of the oxide The microcrystals can be characterized by forming grain boundaries.

  The switching element of the present invention can be characterized in that the microcrystal is formed by heating the ion conductive layer at a temperature lower than the crystallization temperature of the oxide.

  The switching element manufacturing method of the present invention includes a second electrode forming step for forming a second electrode, an ion conductive layer forming step for forming an ion conductive layer containing an oxide so as to be in contact with the second electrode, A heating step for heating the ion conductive layer at a temperature lower than the crystallization temperature of the oxide contained in the ion conductive layer, and a part of the surface of the ion conductive layer that faces the contact surface with the second electrode A first electrode forming step for forming a first electrode for supplying electrons to the ion conductive layer; and a third electrode on a surface that is a part of the surface of the ion conductive layer and faces the contact surface with the second electrode. A third electrode forming step for forming the first electrode, and at least one of the first electrode and the third electrode formed in the first electrode forming step and the third electrode forming step is ion-conductive. Supplying metal ions to the layer, Ions receive electrons can and forming a metal on the ion-conducting layer.

  In the method for manufacturing a switching element of the present invention, the heating step forms in the ion conductive layer a microcrystal that is an oxide crystal smaller than an oxide crystal that is an oxide crystal that crystallizes at the crystallization temperature of the oxide. In addition, a crystal grain boundary formed by microcrystals can be included in the ion conductive layer.

  The electronic device of the present invention may be characterized by having the above switching element.

  The logic integrated circuit according to the present invention can include the switching element.

  A memory element of the present invention can include the switching element and a transistor element that reads out whether the switching element is in an on state or an off state.

  According to the present invention, during the operation of a switching element to which an oxide is applied, it is possible to suppress the occurrence of a short circuit and easily manipulate the generation / extinction of a metal bridge between the first electrode and the second electrode. .

It is a cross-sectional schematic diagram which shows the schematic structural example of the switching element which concerns on this embodiment. It is a cross-sectional schematic diagram which shows the schematic structural example of the switching element which concerns on this embodiment. It is a cross-sectional schematic diagram which shows the movement path | route example of the metal ion within the microcrystal oxide ion conductive layer of the switching element concerning this embodiment. It is a cross-sectional schematic diagram which shows the schematic structural example of the switching element for demonstrating the effect of this embodiment. It is a graph which shows the electrical property example of the switching element for demonstrating the effect of this embodiment. It is a graph which shows the electrical property example of the switching element for demonstrating the effect of this embodiment. It is a cross-sectional schematic diagram which shows the manufacturing process of the switching element which concerns on this embodiment. It is a schematic diagram which shows the schematic structural example of the programmable logic to which the switching element which concerns on this embodiment is applied. It is a schematic diagram which shows the example of schematic structure of the memory element to which the switching element which concerns on this embodiment is applied. It is a cross-sectional schematic diagram which shows the structure of the 2 terminal switching element which concerns on patent document 1. FIG. It is a cross-sectional schematic diagram which shows the structure of the 3 terminal switching element concerning patent document 2. FIG.

  Hereinafter, examples of embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 shows a schematic configuration example of a switching element according to the present embodiment. The configuration of the three-terminal switching element according to this embodiment will be described below. In the present embodiment, the three-terminal switching element will be described by way of example, but the present invention is not limited to this.

  As shown in FIG. 1, the three-terminal switching element according to this embodiment includes a first electrode 11, a second electrode 12, a third electrode 13, and a microcrystalline oxide ion conductive layer 15. . In the three-terminal switching element according to this embodiment, the microcrystalline oxide ion conductive layer 15 is provided on the second electrode 12, and the second electrode 12 is formed on the surface of the microcrystalline oxide ion conductive layer 15. The first electrode 11 and the third electrode 13 are provided on the surface facing the surface with the microcrystalline oxide ion conductive layer 15 interposed therebetween. In this embodiment, it may be expressed as “up” or “down”, but this is merely a representation of the relative positional relationship for convenience. For example, the upper and lower sides are replaced or the upper and lower sides are replaced with left and right. Or you may.

  In the three-terminal switching element according to this embodiment, the first electrode 11 and the third electrode 13 are formed of a metal that supplies metal ions, and the second electrode 12 is formed of a metal that does not supply metal ions. The microcrystalline oxide ion conductive layer 15 serves as a medium for conducting metal ions supplied from the first electrode and the third electrode.

  In the present embodiment, the microcrystalline oxide ion conductive layer 15 is first formed by using a sputtering method or a laser ablation method, and then an annealing process is performed at a temperature lower than the crystallization temperature of the oxide. It is formed by doing. Thus, oxide microcrystals are formed in the microcrystalline oxide ion conductive layer 15 in the present embodiment. Here, the microcrystal refers to a fine oxide crystal which is smaller than the oxide crystal which is a crystal formed at the crystallization temperature of the oxide. In the above, an example in which microcrystals are formed and contained in the microcrystalline oxide ion conductive layer 15 is shown, but the present invention is not limited to this. For example, in addition to the microcrystal, a crystal having a size equal to or larger than that of the oxide crystal that is formed at the crystallization temperature of the oxide is formed and contained in the microcrystalline oxide ion conductive layer 15. It may be.

  FIG. 2 shows a schematic configuration example of the switching element according to the present embodiment. FIG. 3 shows an example of the movement path of metal ions in the microcrystalline oxide ion conductive layer 15 of the switching element according to this embodiment. Next, an example of a method for driving the three-terminal switch according to the present embodiment will be described with reference to FIGS.

  First, before the three-terminal switch operation, the two-terminal operation is performed between the first electrode 11 and the second electrode 12 to form and melt the metal bridge 17 bridge. Specifically, by grounding the second electrode 12 and applying a positive voltage to the first electrode 11, the metal of the first electrode 11 becomes a metal ion 16 and dissolves in the microcrystalline oxide ion conductive layer 15. . Then, metal ions 16 dissolved in the microcrystalline oxide ion conductive layer 15 are deposited on the surface of the second electrode 12, and the metal bridge 17 that connects the first electrode 11 and the second electrode 12 is formed by the deposited metal, Between the first electrode 11 and the second electrode 12 is turned on. Thereafter, by applying a negative voltage to the first electrode 11, a part of the metal bridge 17 is dissolved and the space between the first electrode 11 and the second electrode 12 is turned off.

  Next, when the first electrode 11 and the second electrode 12 are grounded and a positive voltage is applied to the third electrode 13, the metal of the third electrode 13 becomes a metal ion 16, and the microcrystalline oxide ion conductive layer 15 is formed. Dissolve. Then, the metal ions 16 dissolved in the microcrystalline oxide ion conductive layer 15 are deposited at the locations where the metal bridges 17 are dissolved in the above-described two-terminal operation. Thereby, the 1st electrode 11 and the 2nd electrode 12 connect again, and a 3 terminal switching element will be in an ON state.

  On the other hand, when the negative voltage is applied to the third electrode 13 when the three-terminal switching element is in the ON state as described above, the metal of the metal bridge 17 is dissolved in the microcrystalline oxide ion conductive layer 15 and the metal bridge A part of 47 is disconnected. At this time, the second electrode 12 collects the dissolved metal ions 16. Thereby, the electrical connection between the first electrode 11 and the second electrode 12 is cut off, and the three-terminal switch is turned off.

  The third electrode 13 is grounded and a negative voltage is applied to the first electrode 11 or the second electrode 12 to turn on the switching element, or a positive voltage is applied to the first electrode 11 or the second electrode 12. Thus, the switching element can be turned off. Further, the second electrode 12 does not have to be a material that does not supply metal ions, and any material that does not supply metal ions in at least a portion in contact with the microcrystalline oxide ion conductive layer 15 may be used.

  An oxide having excellent semiconductor process affinity can be applied to the microcrystalline oxide ion conductive layer 15. For example, tantalum oxide, silicon oxide, titanium oxide, nickel oxide, niobium oxide, tungsten oxide, molybdenum oxide, copper oxide, zirconium oxide, hafnium oxide, combinations thereof, and the like are preferable.

  In the three-terminal switching operation according to this embodiment, as shown in FIG. 3, the metal ions 16 move through the crystal grain boundaries 19 of the oxide microcrystals 18 contained in the microcrystalline oxide ion conductive layer 15. As described in Non-Patent Document 1, the diffusion rate of metal ions is faster at the grain boundaries than in the bulk of the microcrystals.

  FIG. 4 is a diagram for explaining the effect of the three-terminal switching element according to the present embodiment. 5 and 6 are graphs showing examples of electrical characteristics of the switching element for explaining the effect of the three-terminal switching element according to the present embodiment. The effect of the microcrystalline oxide ion conductive layer of the three-terminal switch according to the present embodiment will be described with reference to FIGS. Hereinafter, for convenience of explanation, an example of a two-terminal switching element will be described, but it is needless to say that the present invention is not limited to this.

  5 and 6 show the results of fabricating a switch having an MIM (Metal Insulation Metal) structure and observing changes in switching characteristics accompanying annealing. As shown in FIG. 4, the switching element includes an upper electrode 20, an oxide ion conductive layer 21, a lower electrode 22, and a low resistance silicon substrate 23. Here, platinum 20 nm is provided as the lower electrode 22 on the low-resistance silicon substrate 23. Further, a tantalum oxide film having a thickness of 15 nm is formed as the oxide ion conductive layer 21 on the lower electrode 22. Furthermore, 100 nm of copper is deposited on the oxide ion conductive layer 21 as the upper electrode 20 by a vacuum deposition method through a mask made of silicon. A voltage is applied to the upper electrode 20, and the lower electrode 22 is installed via a low resistance silicon substrate 23. In the present embodiment, the case where the switching element having the above configuration is used will be described as an example. However, the present invention is not limited to this.

  FIG. 5 shows the transient response of the current when the oxide ion conductive layer 21 is annealed in oxygen before the upper electrode 20 is formed and when it is not annealed in the element shown in FIG. As shown in FIG. 5, when the upper electrode 20 is in contact with the oxide ion conductive layer 21 and a constant voltage is applied so that metal ions are supplied into the oxide ion conductive layer 21, the current value first decreases once. After that, there is a tendency to start to increase. The former decrease in current is an ionic current resulting from the exchange of electrons accompanying the ionization of the metal when the metal ion is supplied into the oxide ion conductive layer 21. On the other hand, the latter increase in current is an electron current in the oxide (for example, see Non-Patent Document 2).

  As shown in FIG. 5, the transient current of the switching element obtained by annealing the oxide ion conductive layer 21 in oxygen at 350 ° C. for 30 minutes before forming the upper electrode 20 is about 1 second when a constant voltage of 4 V is applied. During this period, the current decreases and then increases. That is, an ion current is observed for about 1 second when a constant voltage of 4 V is applied. On the other hand, as a transient current of the switching element not subjected to the annealing, an ionic current is observed for 500 seconds or more when a constant voltage of 5 V is applied. Since the time during which the ionic current is observed is related to the time until the metal ions are completely supplied, that is, the diffusion rate of the metal ions, the oxide ion conductive layer 21 is annealed to conduct oxide ion conduction. It can be seen that the diffusion rate of metal ions in the layer 21 is increased.

  FIG. 6 shows current-voltage characteristics measured using the device of FIG. When the voltage applied to the upper electrode 20 is moved to the positive side, the current suddenly approaches 8.9 V in the switching element in which the oxide ion conductive layer 21 is not annealed before the upper electrode 20 is formed. Increase to the ON state. On the other hand, the switching element in which the oxide ion conductive layer 21 is annealed in oxygen at 550 ° C. for 30 minutes before forming the upper electrode 20 transitions to the ON state at around 1.2V. That is, in the switching element in which the oxide ion conductive layer 21 is annealed before the upper electrode 20 is formed, the on-voltage can be significantly reduced as compared with the switching element that is not annealed. Here, as also shown in Non-Patent Document 1, the on-voltage decreases as the diffusion rate of metal ions increases. That is, it can be seen that annealing of the oxide ion conductive layer increases the diffusion rate of metal ions in the oxide ion conductive layer.

  In FIG. 5, the switching element annealed at 350 ° C. for 30 minutes has been described as an example. However, the present invention is not limited to this, and for example, even when annealed at 550 ° C. for 30 minutes as in FIG. The result as shown in can be obtained. Similarly, in FIG. 6, the results shown in FIG. 6 can be obtained not only when annealing is performed at 550 ° C. for 30 minutes but also when annealing is performed at 350 ° C. for 30 minutes. Of course, if the annealing temperature is 350 to 550 ° C., the results shown in FIGS. 5 and 6 can be obtained, but it may be 550 ° C. or higher.

  As shown in FIGS. 5 and 6, annealing of the oxide ion conductive layer increases the diffusion rate of metal ions in the oxide ion conductive layer. The increase in the diffusion rate due to the annealing is caused by the microcrystallization of the oxide serving as the ion conductive layer. For example, the crystallization temperature of tantalum oxide suitable as an oxide is about 700 ° C., but it is also shown in Non-Patent Document 3 that microcrystallization proceeds even in the vicinity of 350 ° C. to 400 ° C. Specifically, Non-Patent Document 3 confirms that crystals are formed when tantalum oxide is deposited at 350 ° C. using an atomic layer deposition method. Thus, it has been suggested that microcrystallization of tantalum oxide proceeds even at a temperature below the crystallization temperature.

  FIG. 7 shows an example of a method for manufacturing the three-terminal switching element according to this embodiment. Next, an example of a method for manufacturing the three-terminal switching element according to this embodiment will be described with reference to FIG.

  As shown in FIG. 7A, a silicon oxide film 102 is formed on the surface of the low resistance silicon substrate 103. A second electrode 101 is formed on the silicon oxide film 102 using a vacuum deposition method, a sputtering method, or the like. Then, as shown in FIG. 7B, the oxide ion conductive layer 104 is formed on the second electrode. At this time, the composition of the deposited oxide is set as close as possible to the composition of the target.

  Next, as shown in FIG. 7C, the microcrystalline oxide ion conductive layer 105 is obtained by annealing the oxide ion conductive layer 104. Then, as shown in FIG. 7D, an insulating layer 106 is formed on a part of the microcrystalline oxide ion conductive layer 105 obtained in FIG. As shown in FIG. 7E, the first electrode is formed on the patterned insulating layer 106 and on the microcrystalline oxide ion conductive layer 105 not covered with the insulating layer 106 by vacuum deposition or sputtering. Deposit metal to be applied. A resist is spin-coated thereon, and the resist is patterned by a lithography technique. After the patterning, the first electrode 107 is formed by etching the metal.

  Finally, as shown in FIG. 7F, a vacuum deposition method or sputtering is performed on the patterned insulating layer 106, the microcrystalline oxide ion conductive layer 105 not covered with the insulating layer 106, and the first electrode 101. The metal applied to the third electrode is deposited by the method. A resist is spin-coated thereon, and the resist is patterned by a lithography technique. After the patterning, the metal is etched to form the third electrode 108.

  According to this embodiment, it is possible to improve the diffusion rate of metal ions supplied from the electrode by annealing the oxide ion conductive layer containing an oxide having excellent semiconductor process affinity, and to turn on the switching element. The voltage can be reduced. Thereby, the switching element which annealed to the oxide ion conductive layer can improve reliability, such as repetition resistance and holding | maintenance tolerance.

(Embodiment 2)
In the present embodiment, an example in which the three-terminal switching element of the first embodiment is applied to programmable logic will be described.

  FIG. 8 shows a schematic configuration example of a programmable logic using the three-terminal switching element of the first embodiment. As shown in FIG. 8, the programmable logic 114 is configured to switch a large number of logic cells 111 arranged in a two-dimensional array, wiring for connecting the logic cells 111, and connection / non-connection between the wirings. And a large number of switching elements 112. By changing the connection state of the switch to connected or disconnected, it is possible to set the wiring configuration between the logic cells 111, the function of the logic cell 111, and the like, and obtain a logic integrated circuit that meets the specifications.

  The switching element 112 is a transistor element including, for example, a drain electrode D, a source electrode S, and a gate electrode G. When the three-terminal switching element of the first embodiment is applied to the switch of the present embodiment, the first electrode of the first embodiment corresponds to the drain electrode D shown in FIG. 8, the second electrode corresponds to the source electrode S, The third electrode corresponds to the gate electrode G. As shown in FIG. 8, the source electrode S is connected to the logic cell 111, and the drain electrode D is connected to the signal line 113 in the programmable logic 114.

  The three-terminal switch set to the on state maintains a state where the source electrode S and the drain electrode D are electrically connected. When the logic signal reaches the drain electrode D via the signal line 113, it enters the logic cell 111 via the source electrode S. On the other hand, the three-terminal switch set to the off state maintains the state where the source electrode S and the drain electrode D are electrically disconnected. In this case, even if the logic signal reaches the drain electrode D via the signal line 113, it cannot enter the logic cell 111 connected to the source electrode S.

  In this manner, in the programmable logic 114, the three-terminal switch set to the on state by the user functions as a signal line, and the logic cell 111 connected to the on-state switch maintains an operable state.

  According to the present embodiment, by applying the three-terminal switch of the first embodiment to a programmable logic switch, it is possible to reduce the leakage current in the OFF state of the switch and to reduce the current consumption of the entire programmable logic. Further, by applying the three-terminal switch of the first embodiment to a programmable logic switch, a booster circuit is not necessary, and the chip size can be reduced.

  In the present embodiment, the switching element of the first embodiment is used for switching between connection and non-connection to the logic cell. However, the present invention is not limited to this. It is also possible to apply to a switch for performing switching.

  Here, as a programmable logic that can apply a switching element, change a circuit configuration by an electronic signal, and provide many functions with one chip, an FPGA (Field-Programmable Gate Array), a DRP (Dynamically Reconfigurable Processor), etc. As an example.

(Embodiment 3)
In this embodiment, an example of a memory element to which the three-terminal switching element of Embodiment 1 is applied will be described.

  FIG. 9 shows a schematic configuration example of a memory element using the three-terminal switching element of the first embodiment. As shown in FIG. 9, the memory element according to the present embodiment includes a switching element 122 for holding information and a transistor element 121 for reading information of the switching element 122. In the present embodiment, the three-terminal switching element of the first embodiment is applied as the switching element 122. The switching element 122 has the same configuration as a transistor having a drain electrode, a source electrode, and a gate electrode, and each electrode corresponds to the first electrode, the second electrode, and the third electrode of the three-terminal switching element of the first embodiment. is doing.

  The transistor element 121 has a source electrode connected to the bit line 123 and a gate electrode connected to the word line 125. The switching element 122 has a second electrode connected to the bit line 124 and a third electrode connected to the word line 126. The first electrode of the switching element 122 is connected to the drain electrode of the transistor element 121.

  Next, an example of a method for writing information to the memory element will be described. Here, of the information “1” and “0” stored in the memory element, the ON state of the switching element 122 is “1” and the OFF state is “0”. The switching voltage of the switching element 122 is Vt, and the operating voltage of the transistor element 121 is VR. However, of course, it is not limited to this.

  When writing information “1” in the memory element, the voltage Vt is applied to the word line 126 connected to the third electrode of the switching element 122, and the voltage of the bit line 124 connected to the second electrode is set to 0V. Then, a voltage (Vt / 2) is applied to the bit line 123. As a result, the switching element 122 is turned on, and information “1” is written in the memory element.

  On the other hand, when information “0” is written in the memory element, the voltage of the word line 126 connected to the third electrode of the switching element 122 is set to 0 V, and the voltage Vt is applied to the bit line 124 connected to the second electrode. Apply. Then, a voltage (Vt / 2) is applied to the bit line 123. As a result, the switching element 122 is turned off and information “0” is written.

  Next, an example of a method for reading information stored in the memory element will be described.

  A voltage VR is applied to the word line 125 to turn on the transistor element 121, and a resistance value between the bit line 123 and the bit line 124 is obtained. This resistance value is a combined resistance value of the ON resistance of the transistor element 121 and the switching element 122. If this combined resistance value is so large that it cannot be measured, it can be determined that the switching element 122 is in the OFF state, and it can be seen that the information held in the memory element is “0”. On the other hand, when the combined resistance value is smaller than the predetermined value, it can be determined that the switching element 122 is in the ON state, and it can be seen that the information held in the memory element is “1”.

  According to the present embodiment, by using the three-terminal switch of the first embodiment as a switching element for holding information in the memory element, it is possible to reduce the leakage current in the off state of the switch. Therefore, if the memory element of this embodiment is used for a memory device in which a plurality of memory elements are arranged in an array, the current consumption of the entire memory device can be reduced.

  Hereinafter, specific examples will be described as examples of the method for manufacturing a switching element according to the present invention. However, it is not limited to this.

  A method for manufacturing the three-terminal switching element of this embodiment will be described with reference to FIG. As shown in FIG. 7A, a silicon oxide film 102 having a thickness of 300 nm was formed on the surface of the low resistance silicon substrate 103. Titanium nitride and platinum were deposited on the silicon oxide film 102 with a film thickness of 5 nm and 40 nm by vacuum deposition or sputtering to form the second electrode 101.

  Next, as shown in FIG. 7B, an oxide ion conductive layer 104 containing tantalum oxide was formed with a film thickness of 15 nm. At this time, the composition of the deposited oxide is set as close as possible to the composition of the target. Specifically, the amount of oxygen to be supplied is optimized when performing sputtering. In this example, a composite oxide layer was formed under film formation conditions of an oxygen flow rate of 1 sccm and a gas pressure of 0.5 Pa, and a stoichiometric oxide layer containing oxygen 2.5 times that of tantalum was obtained.

  As shown in FIG. 7C, the microcrystalline oxide ion conductive layer 105 was obtained by annealing the oxide ion conductive layer 104 in nitrogen at 550 ° C. for 30 minutes. Here, 550 ° C. is a temperature lower than the crystallization temperature of tantalum oxide.

  Next, as illustrated in FIG. 7E, an insulating layer 106 was formed using silicon oxide on part of the microcrystalline oxide ion conductive layer 105. Specifically, 100 nm of silicon oxide was formed on the microcrystalline oxide ion conductive layer 105 by a sputtering method, a resist was spin-coated thereon, and the resist was patterned by a lithography technique. After patterning, the silicon oxide was etched to form the insulating layer 106.

  Then, copper having a thickness of 100 nm was deposited on the patterned insulating layer 106 and on the microcrystalline oxide ion conductive layer 105 not covered with the insulating layer 106 by a vacuum evaporation method or a sputtering method. Then, a resist was spin-coated on the deposited copper, and the resist was patterned by a lithography technique. After the patterning, the copper was etched to form the first electrode 101.

  Next, as shown in FIG. 7F, vacuum evaporation or sputtering is performed on the patterned insulating layer 106, the microcrystalline oxide ion conductive layer 105 not covered with the insulating layer 106, and the first electrode 101. Copper having a film thickness of 100 nm was deposited by the method. Then, a resist was spin-coated on the deposited copper, and the resist was patterned by a lithography technique. After the patterning, the third electrode 103 was formed by etching copper.

  A switching element including the first electrode, the second electrode, the third electrode, and the microcrystalline oxide ion conductive layer was manufactured by the method as described above. In the switching element manufactured in this way, the third electrode and the first electrode or the third electrode and the second electrode are not short-circuited during operation, and the generation and disappearance of the metal bridge between the first electrode and the second electrode at a low voltage. Can be operated.

  In the present embodiment, an example in which copper is applied as the first electrode and the third electrode has been described. As described above, when copper is applied to the first electrode and the third electrode, high electromigration resistance can be obtained. However, the present invention is not limited to this, and any metal that can supply metal ions can be used as the first electrode and the third electrode.

  As described above, when the oxide ion conductive layer is included, and is a microcrystalline body and includes a crystal grain boundary, metal ions supplied from the electrode diffuse through the crystal grain boundary. The diffusion of metal ions at the grain boundary is faster than the diffusion between the bulk and the lattice. The faster the diffusion rate of the metal ions supplied from this electrode, the lower the switching voltage of the metal bridging switching element. Therefore, in the switching element according to this embodiment in which the oxide ion conductive layer is annealed at a temperature lower than the oxide crystallization temperature, it is possible to form and annihilate metal bridges at a low voltage during operation.

  In addition, since the switching element according to the present embodiment uses an oxide ion conductor excellent in semiconductor process affinity for the oxide ion conductive layer and can operate at a low voltage, reliability such as repeat resistance and retention resistance is also improved. It becomes possible to do.

  According to the present invention, when the switching element is a three-terminal switching element, the third electrode and the first electrode or the third electrode and the second electrode are not short-circuited during operation, and the first electrode and the second electrode are connected at a low voltage. It is possible to easily manipulate the generation and extinction of metal bridges. Thereby, it is possible to provide a three-terminal switching element having high reliability. Further, since the switching voltage is lowered, the programmable logic equipped with the three-terminal switching element does not require a booster circuit, and the chip size can be reduced.

  In the above embodiment, the switching element is applied to a logic integrated circuit or a memory element. However, the present invention is not limited to this and can be applied to various electronic devices.

  Although specifically described based on the above preferred embodiments, the present invention is not limited to the above-described switching element, switching element manufacturing method, electronic device, logic integrated circuit, and memory element, and departs from the gist thereof. It goes without saying that various changes can be made without departing from the scope.

DESCRIPTION OF SYMBOLS 11 1st electrode 12 2nd electrode 13 3rd electrode 14 Ion conduction layer 15 Microcrystal oxide ion conduction layer 16 Metal ion 17 Metal bridge | crosslinking 18 Microcrystal 19 Grain boundary 20 Upper electrode 21 Oxide ion conduction layer 22 Lower electrode 23 Low resistance silicon substrate 101 Second electrode 102 Silicon oxide film 103 Low resistance silicon substrate 104 Oxide ion conductive layer 105 Microcrystalline oxide ion conductive layer 106 Insulating layer 107 First electrode 108 Third electrode 111 Logic cell 112 Switching element 113 Signal Line 114 Programmable logic 121 Transistor element 122 Switching element 123, 124 Bit line 125, 126 Word line

Claims (16)

A first electrode, a second electrode, a third electrode, and an ion conductive layer containing an oxide;
The first electrode supplies electrons to the ion conductive layer,
At least one of the first electrode and the third electrode supplies metal ions to the ion conductive layer;
The metal ions receive the electrons to form a metal in the ion conducting layer;
The metal connects between the first electrode and the second electrode;
The third electrode controls the formation and erasure of the metal connecting the first electrode and the second electrode;
The ion conductive layer is provided in contact with the first electrode, the second electrode, and the third electrode, and is an oxide that is a crystal of the oxide crystallized at a crystallization temperature of the electrode Containing microcrystals that are crystals of the oxide smaller than physical crystals,
The switching element, wherein the microcrystal forms a grain boundary.   The switching element according to claim 1, wherein the microcrystal is formed by heating the ion conductive layer at a temperature lower than a crystallization temperature of the oxide.   The switching element according to claim 1, wherein the ion conductive layer contains the oxide crystal and the microcrystal.   The oxide is any one of tantalum oxide, silicon oxide, titanium oxide, nickel oxide, niobium oxide, tungsten oxide, molybdenum oxide, copper oxide, zirconium oxide, hafnium oxide, and combinations thereof. 4. The switching element according to any one of items 1 to 3.   5. The switching element according to claim 1, wherein at least one of the first electrode and the third electrode is made of copper. 6.   6. The switching element according to claim 1, wherein at least a contact surface with the ion conductive layer of the second electrode is formed of a material that does not supply the metal ions. 7. A second electrode forming step of forming a second electrode;
An ion conductive layer forming step of forming an ion conductive layer containing an oxide so as to be in contact with the second electrode;
Heating the ion conductive layer at a temperature lower than the crystallization temperature of the oxide contained in the ion conductive layer;
A first electrode forming step of forming a first electrode for supplying electrons to the ion conductive layer on a part of the surface of the ion conductive layer opposite to a contact surface with the second electrode;
A third electrode forming step of forming a third electrode on a part of the surface of the ion conductive layer that faces the contact surface with the second electrode;
At least one of the first electrode and the third electrode formed in the first electrode forming step and the third electrode forming step supplies metal ions to the ion conductive layer, and the metal ions are A method of manufacturing a switching element, comprising receiving an electron and forming a metal in the ion conductive layer.   In the heating step, a microcrystal that is a crystal of the oxide smaller than an oxide crystal that is a crystal of the oxide that is crystallized at a crystallization temperature of the oxide is formed in the ion conductive layer, and the microcrystal The method for manufacturing a switching element according to claim 7, wherein a crystal grain boundary formed by the step is contained in the ion conductive layer.   9. The method of manufacturing a switching element according to claim 8, wherein the heating step forms the oxide crystal and the microcrystal in the ion conductive layer.   The oxide is any one of tantalum oxide, silicon oxide, titanium oxide, nickel oxide, niobium oxide, tungsten oxide, molybdenum oxide, copper oxide, zirconium oxide, hafnium oxide, and combinations thereof. The manufacturing method of the switching element of any one of 1-9.   11. The method of manufacturing a switching element according to claim 7, wherein in the first electrode forming step, the first electrode is formed of copper.   The method for manufacturing a switching element according to any one of claims 7 to 11, wherein in the third electrode forming step, the third electrode is formed of copper.   The said 2nd electrode formation step forms at least the contact surface with the said ion conductive layer among the said 2nd electrodes with the material which does not supply the said metal ion, The any one of Claim 7 to 12 characterized by the above-mentioned. The manufacturing method of the switching element of description.   An electronic device comprising the switching element according to claim 1.   A logic integrated circuit comprising the switching element according to claim 1. The switching element according to any one of claims 1 to 6,
A memory element, comprising: a transistor element that reads out whether the switching element is in an on state or an off state.

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