JP2008028248A - Resistance changing element, and resistance changing memory using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resistance changing element which contains first and second electrodes and a resistance changing layer clamped by the respective electrodes, and in which two or more states exist that electric resistance values are different between the respective electrodes, and a drive voltage or current is applied to the resistance changing layer through the respective electrodes, whereby one state selected from the two or more states changes to the other state, making it possible to mitigate a concentration of a partial current on the resistance changing layer upon application of the drive voltage or current, and to suppress a deterioration of the resistance changing layer. <P>SOLUTION: There is provided this element in which a shape of a joint face is rectangular with a first electrode in the resistance changing layer. When seeing from a direction perpendicular to the joint face, an application face which applies the drive voltage or current to the electrode is provided in a portion which is not overlapped with the joint face in the first electrode, and the joint face has a long side in a direction substantially perpendicular to a direction of a current flowing in the first electrode from the application face to the joint face, upon application of the drive voltage or current. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a resistance change element whose electric resistance value changes when a drive voltage or drive current is applied, and a resistance change memory using the resistance change element.

  Memory elements are used in a wide range of fields as important basic electronic components that support the information society. In recent years, with the widespread use of portable information terminals, there has been an increasing demand for miniaturization of memory elements, and nonvolatile memory elements are no exception. However, as device miniaturization reaches the nanometer range, conventional charge storage type memory devices (typically DRAM [Dynamic Random Access Memory] and ferroelectric memory, etc.) have information units (bits). The reduction of the perimeter charge capacity C is becoming a problem, and various improvements have been made to avoid this problem, but there are concerns about future technical limitations.

As a memory element that is not easily affected by miniaturization, not a charge capacity C but a nonvolatile memory element (resistance change type memory element) that records information by a change in electric resistance value R has been attracting attention. As a type memory element, development of a resistance change element in which an electric resistance value is changed by application of a driving voltage or current is underway (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2003-68983

  A charge storage type memory element generally has a multilayer structure in which a capacitor storage layer composed of a capacitor (DRAM), a ferroelectric layer (ferroelectric memory), etc. is held between an upper electrode and a lower electrode. In the charge storage type memory element having such a multilayer structure, even when a voltage is applied between the upper electrode and the lower electrode for recording and reading of information, the capacity storage layer disposed between the two electrodes No current flows from one electrode to the other through the electrode. At this time, a voltage is uniformly applied to the entire capacity storage layer.

  On the other hand, the resistance change element has a multilayer structure in which a resistance change layer having two or more states having different electric resistance values R is sandwiched between an upper electrode and a lower electrode. By applying a driving voltage or current between the upper electrode and the lower electrode, the electrical resistance value of the resistance change layer can be changed. At this time, from one electrode to the other electrode via the resistance change layer Current flows into the. Here, the resistance change layer is a conductor or a semiconductor, and the flow of the current is greatly influenced by the shape of the resistance change layer and the electrode, the positional relationship between the two, and the like.

  Depending on the configuration of the element, the current may concentrate on a part of the resistance change layer when the drive voltage or current is applied. In the portion where the current is concentrated, the electric resistance value changes faster than the portion where the current is not concentrated, so the resistance may be lower than that of the surroundings. May deteriorate.

  Therefore, the present invention provides a resistance change element that can alleviate partial current concentration on the resistance change layer when a drive voltage or current is applied, and has excellent durability in which deterioration of the resistance change layer during use is suppressed. For the purpose.

  The variable resistance element (first variable resistance element) of the present invention includes a first electrode, a second electrode, and a variable resistance layer sandwiched between the first and second electrodes. There are two or more states having different electrical resistance values between the first and second electrodes, and by applying a driving voltage or a driving current to the resistance change layer via the first and second electrodes, An element that changes from one state selected from two or more states to another state. In the first variable resistance element, the shape of the joint surface with the first electrode in the variable resistance layer is a rectangle. Further, when viewed from a direction perpendicular to the bonding surface, there is an application surface that applies the driving voltage or driving current to the first electrode in a portion that does not overlap with the bonding surface of the first electrode, The bonding surface has a long side in a direction substantially perpendicular to a direction of a current flowing through the first electrode from the application surface to the bonding surface when the driving voltage or driving current is applied.

  The variable resistance element (second variable resistance element) of the present invention viewed from a different aspect from the above is sandwiched between the first electrode, the second electrode, and the first and second electrodes. A variable resistance layer, and there are two or more states having different electric resistance values between the first and second electrodes, and a drive voltage or a voltage is applied to the variable resistance layer via the first and second electrodes. It is an element that changes from one state selected from the two or more states to another state by applying a driving current. In the second resistance change element, the first electrode has an application surface for applying the drive voltage or drive current to the electrode, and the shape of the joint surface of the second electrode with the resistance change layer is rectangular. It is. Further, when viewed from a direction perpendicular to the bonding surface, the application surface of the first electrode and the bonding surface of the second electrode do not overlap, and the application surface and the bonding surface The junction surface has a resistance change layer, and the junction surface flows the first electrode and the resistance change layer from the application surface to the junction surface when the drive voltage or drive current is applied. It has a long side in a direction substantially perpendicular to the direction.

  The resistance change type memory according to the present invention includes the resistance change element according to the present invention as a memory element.

  In the variable resistance element of the present invention, the shape of the bonding surface between the electrode and the variable resistance layer is defined, and the arrangement of the bonding surface is a current flowing between the application surface and the bonding surface when a driving voltage or current is applied. With respect to the above, it is possible to alleviate partial current concentration on the resistance change layer when a drive voltage or drive current is applied to the element, and to suppress deterioration of the resistance change layer during use.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same reference numerals may be given to the same members, and overlapping descriptions may be omitted.

  1 and 2 show an example of the first variable resistance element. FIG. 2 is a plan view of the resistance change element 1 shown in FIG. 1 as seen from a direction perpendicular to the bonding surface 15 of the upper electrode 13 with the resistance change layer 12 (direction of arrow A shown in FIG. 1).

  The element 1 shown in FIG. 1 is sandwiched between a substrate 10, a pair of electrodes including a lower electrode (second electrode) 11 and an upper electrode (first electrode) 13, and the lower electrode 11 and the upper electrode 13. And a resistance change layer 12. The lower electrode 11, the resistance change layer 12, and the upper electrode 13 are arranged on the substrate 10 in the above order so as to be in contact with each other as a multilayer structure (laminated body) 14.

  In the element 1, there are two or more states in which the electric resistance value between the lower electrode 11 and the upper electrode 13 is different. By applying a driving voltage or current to the element 1, specifically, between the lower electrode 11 and the upper electrode 13, the element 1 changes from one state selected from the two or more states to another state. Change. When the element 1 has two states having different electrical resistance values (a state having a relatively high resistance is a state A and a state having a relatively low resistance is a state B), by applying a driving voltage or a current, Element 1 changes from state A to state B or from state B to state A.

  In the element 1, as shown in FIG. 2, there is an application surface 16 for applying a driving voltage or current to the upper electrode 13 in a portion that does not overlap with the bonding surface 15 in the upper electrode 13. A member 51 (for example, a contact plug) that supplies a driving voltage or current to the upper electrode 13 is normally connected to the application surface 16 (see FIGS. 1 and 2).

  When the variable resistance element is incorporated in an electronic device such as a memory device, it is sufficiently conceivable that an application surface is provided in a portion that does not overlap with the bonding surface in the upper electrode from the wiring of the bit line, the word line, and the like. In the element in which the application surface and the bonding surface are arranged in this way, when a driving voltage (positive bias voltage) or a driving current (positive bias current) in which the potential of the upper electrode is positive with respect to the lower electrode is applied. The current flowing through the upper electrode is concentrated on one side of the bonding surface (for example, the left side of the bonding surface 15 in FIG. 2), that is, the current is concentrated on a part of the resistance change layer.

  In the element 1 of the present invention, as shown in FIG. 2, the shape of the bonding surface 15 (the shape viewed from the direction perpendicular to the bonding surface 15) of the upper electrode 13 with the resistance change layer 12 is rectangular, and the bonding surface The long side of 15 is set to a direction substantially perpendicular to the direction of the current 17 flowing through the upper electrode 13 from the application surface 16 to the bonding surface 15 when a driving voltage or current is applied to the element 1. In the element 1, partial concentration of current on the resistance change layer 12 when a drive voltage or current is applied can be alleviated, and deterioration of the resistance change layer 12 during use can be suppressed.

  The term “substantially vertical” in the present specification means that a slight width is allowed within a range where the effect of the present invention can be obtained around 90 ° as an angle. The angle may be an angle of about 90 ° ± 10 °, which is a value reflecting an allowable range in design or an error range in the manufacturing method at the time of manufacturing the element.

  The direction of the current 17 flowing through the upper electrode 13 is the direction of a line segment connecting the application surface 16 and the bonding surface 15 of the upper electrode 13 with the shortest distance when the element 1 is viewed from a direction perpendicular to the bonding surface 15. That's fine.

  The effect of alleviating partial current concentration on the resistance change layer 12 in the element 1 is that a driving voltage (negative bias voltage) or a driving current (negative bias current) in which the potential of the upper electrode 13 is negative with respect to the lower electrode 11. ) Can also be obtained in the same manner as described above.

  In the element 1 shown in FIGS. 1 and 2, the shape of the upper electrode 13 viewed from the direction perpendicular to the bonding surface 15 is rectangular, but the shape is particularly limited as long as the bonding surface 15 and the application surface 16 satisfy the above-described regulations. For example, it may be a square.

  In the element 1 shown in FIGS. 1 and 2, the shape and arrangement of the bonding surface 15 of the upper electrode 13 with the resistance change layer 12 are defined. Regardless of whether the element 1 has such a definition, The shape and arrangement of the joint surface (joint surface A) with the resistance change layer 12 in the lower electrode 11 may be defined similarly to the joint surface 15. That is, the shape of the bonding surface A with the resistance change layer 12 in the lower electrode 11 (second electrode) is a rectangle when viewed from the direction perpendicular to the bonding surface A, and when viewed from the direction, the lower electrode 11 There is an application surface (application surface A) for applying a driving voltage or current to the lower electrode 11 in a portion that does not overlap with the bonding surface A, and the bonding surface A is joined from the application surface A when the driving voltage or current is applied. You may have a long side in the direction substantially perpendicular | vertical to the direction of the electric current which flows into the surface A through the lower electrode 11. FIG. Even in such an element, the same effect as the element 1 can be obtained.

  It is preferable that the shape and the arrangement of both the bonding surface 15 of the upper electrode 13 with the resistance change layer 12 and the bonding surface A of the lower electrode 11 with the resistance change layer 12 satisfy the above-mentioned regulations.

  The effect of relieving partial current concentration on the resistance change layer 12 when a drive voltage or current is applied becomes more prominent in the element 1 shown in FIG.

  FIG. 3 is a plan view of another example of the first variable resistance element as viewed from a direction perpendicular to the bonding surface 15 of the upper electrode 13 with the variable resistance layer 12. The element 1 shown in FIG. 3 basically has the same configuration as the element 1 shown in FIGS. 1 and 2, but the shape of the upper electrode 13 viewed from the direction perpendicular to the bonding surface 15 is rectangular, When the electrode 13 is equally divided into two by a dividing line 18 parallel to the short side thereof, the equally divided portion 19 has the bonding surface 15 (the resistance change layer 12 is bonded), and the other portion. There is an application surface 16 at 20.

  In the element 1 shown in FIG. 3, it can be said that the rectangular upper electrode 13 has the bonding surface 15 at one end in the long side direction and the application surface 16 at the other end.

  In the element 1 shown in FIGS. 1 to 3, the ratio (aspect ratio) of the short side to the long side of the bonding surface 15 is, for example, short side: long side = 1: 1.5 to 1: 5.

  The substrate 10 may be, for example, a silicon (Si) substrate. In this case, the surface of the substrate 10 in contact with the lower electrode 11 may be oxidized (an oxide film may be formed on the surface of the substrate 10). ). When the substrate 10 is a Si substrate, the combination of the variable resistance element and the semiconductor element of the present invention becomes easy. Note that a processed substrate on which a transistor, a contact plug (hereinafter also simply referred to as “plug”), or the like is formed can be included in the substrate.

  The lower electrode 11 and the upper electrode 13 are basically required to have conductivity. For example, Au (gold), Pt (platinum), Ru (ruthenium), Ir (iridium), Ti (titanium), Al ( Aluminum), Cu (copper), Ta (tantalum), Fe (iron), Rh (rhodium), iridium-tantalum alloy (Ir-Ta), tin-added indium oxide (ITO), etc., or alloys thereof, oxidation It may be made of a material, nitride, fluoride, carbide, boride or the like.

The resistance change layer 12 may have a general configuration as a resistance change element. For example, as a resistance change material, a perovskite compound such as (Pr, Ca) MnO _z , Fe ₂ O ₃ , Fe ₃ O ₄ , Any variable resistance layer 12 including a transition metal oxide such as NiO may be used.

  The member 51 connected to the application surface 16 of the upper electrode 13 and supplying a driving voltage or current to the electrode is not particularly limited, and may be a contact plug, for example. The member 51 should just have electroconductivity fundamentally.

  4 and 5 show an example of the second variable resistance element. FIG. 5 is a plan view of the resistance change element 21 shown in FIG. 4 as seen from the direction (direction of arrow B shown in FIG. 4) perpendicular to the bonding surface 22 of the lower electrode 11 with the resistance change layer 12.

  The element 21 shown in FIG. 4 is sandwiched between the substrate 10, a pair of electrodes including a lower electrode 11 (second electrode) and an upper electrode 13 (first electrode), and the lower electrode 11 and the upper electrode 13. And a resistance change layer 12. The lower electrode 11, the resistance change layer 12, and the upper electrode 13 are arranged on the substrate 10 in the above order so as to be in contact with each other as a multilayer structure (laminated body) 14.

  In the element 21, there are two or more states in which the electric resistance value between the lower electrode 11 and the upper electrode 13 is different. By applying a driving voltage or current to the element 1, specifically, between the lower electrode 11 and the upper electrode 13, the element 1 changes from one state selected from the two or more states to another state. Change. When the states A and B having different electric resistance values exist in the element 1, the element 1 changes from the state A to the state B or from the state B to the state A by applying a driving voltage or current.

  As shown in FIG. 4, in the element 21, the upper electrode 13 has an application surface 16 that applies a driving voltage or current to the electrode. A member 51 for supplying a driving voltage or current to the upper electrode 13 is normally connected to the application surface 16. In the element 21, the application surface 16 and the bonding surface 22 do not overlap when viewed from a direction perpendicular to the bonding surface 22 of the lower electrode 11 with the resistance change layer 12, and the application surface 16 and the bonding surface are not overlapped. There is a resistance change layer 12 between them (see FIG. 5).

  When the resistance change element is incorporated in an electronic device such as a memory device, it is fully possible that the application surface, the joint surface, and the layers constituting the element have such an arrangement. In such an element, a positive bias voltage or When a positive bias current is applied, the current flowing through the resistance change layer from the application surface of the upper electrode to the bonding surface of the lower electrode is concentrated on one side of the bonding surface (for example, the left side of the bonding surface 22 in FIG. 5). Current concentrates on a part of the resistance change layer.

  In the element 21 of the present invention, as shown in FIG. 5, the shape of the bonding surface 22 (the shape seen from the direction perpendicular to the bonding surface 22) of the lower electrode 11 and the resistance change layer 12 is rectangular, and the bonding surface When the driving voltage or current is applied to the element 1, the long side 22 flows through the upper electrode 13 and the resistance change layer 12 from the application surface 16 to the bonding surface 22, and the current 23 viewed from the direction perpendicular to the bonding surface 22. The direction is substantially perpendicular to the direction. In the element 21, partial concentration of current on the resistance change layer 12 when a drive voltage or current is applied can be alleviated, and deterioration of the resistance change layer 3 during use can be suppressed.

  The direction of the current 23 flowing through the upper electrode 13 and the resistance change layer 12 is such that when the element 1 is viewed from the direction perpendicular to the bonding surface 22, the application surface 16 of the upper electrode and the bonding surface 22 of the lower electrode are at the shortest distance. The direction of connecting line segments may be used.

  The effect of relieving partial current concentration on the resistance change layer 12 in the element 21 can be obtained in the same manner as described above even when a negative bias voltage or a negative bias current is applied to the element 21.

  In the element 21 shown in FIGS. 4 and 5, the shapes of the upper electrode 13 and the resistance change layer 12 viewed from the direction perpendicular to the bonding surface 22 are rectangular. However, the shapes are not particularly limited as long as the above-described regulations are satisfied. For example, it may be a square. Further, the shape of the lower electrode 11 viewed from the direction is not particularly limited as long as the bonding surface 22 satisfies the above-described regulations.

  In the element 21, the shapes of the upper electrode 13 and the resistance change layer 12 as viewed from the direction perpendicular to the bonding surface 22 are the same. (See FIG. 7).

  4 and 5, the shape and arrangement of the bonding surface 22 of the lower electrode 11 with the resistance change layer 12 are defined. Regardless of whether the element 21 has such a definition, The shape and arrangement of the joint surface (joint surface B) with the resistance change layer 12 in the upper electrode 13 may be defined similarly to the joint surface 22. That is, the lower electrode 11 (second electrode) has an application surface (application surface B) for applying a driving voltage or current to the electrode, and the upper electrode 13 (first electrode) is joined to the resistance change layer 12. The shape of the surface B is a rectangle when viewed from the direction perpendicular to the bonding surface B. When viewed from the direction, the application surface B and the bonding surface B do not overlap, and the application surface B and the bonding surface B are not overlapped. There is a resistance change layer 12 between them, and the junction surface B flows through the lower electrode 11 and the resistance change layer 12 from the application surface B to the junction surface B when a driving voltage or current is applied. You may have a long side in the direction substantially perpendicular | vertical to a direction. Even in such an element, the same effect as the element 21 can be obtained.

  It is preferable that both the shape and the arrangement of the joint surface 22 of the lower electrode 11 with the resistance change layer 12 and the joint surface B of the upper electrode 13 with the resistance change layer 12 satisfy the above-mentioned regulations.

  4 and 5, the ratio of the short side to the long side of the bonding surface 22 is, for example, short side: long side = 1: 1.5 to 1: 5.

  A driving voltage or current may be applied to the elements 1 and 21 via the lower electrode 11 and the upper electrode 13. When the driving voltage or current is applied, the above-described state in the elements 1 and 21 changes (for example, from the state A to the state B). It is held until the current is applied again, and changes again by applying the voltage or current (for example, from state B to state A).

  The driving voltage or current applied to the elements 1 and 21 does not necessarily have to be the same between when the element 1 is in the state A and when it is in the state B, and its size, polarity, flow direction, etc. May differ depending on the state of the elements 1 and 21. That is, the drive voltage and drive current in this specification may be any voltage and current that can change to another state different from the state when the elements 1 and 21 are in a certain state.

  Since the power consumption of the element can be further reduced, it is preferable to apply a voltage to the elements 1 and 21, and it is particularly preferable to apply a pulsed voltage.

  As described above, since the electrical resistance value of the elements 1 and 21 can be maintained until a drive voltage or current is applied to the elements 1 and 21, the above-described states of the elements 1 and 21 and the elements 1 and 21 are detected. Combining a mechanism (that is, a mechanism for detecting the electric resistance value of the elements 1 and 21) and assigning a bit to each of the above states (for example, state A is set to “0” and state B is set to “1”). Thus, a nonvolatile resistance change type memory (memory element or memory array in which two or more memory elements are arranged) can be constructed. Further, in the elements 1 and 21, such a change in state can be repeated at least twice, and a nonvolatile random access memory can be constructed. In addition, it is also possible to apply the elements 1 and 21 to switching elements by assigning ON or OFF to the above states.

  For detecting the electric resistance values of the elements 1 and 21, for example, a voltage (read voltage) that does not change the state of the elements is applied to the elements 1 and 21, and the current value flowing through the elements 1 and 21 at that time is detected. May be performed by detecting. As the read voltage, it is preferable to apply a pulse voltage because the power consumption of the element can be further reduced. The magnitude of the read voltage is usually about 1/4 to 1/1000 of the magnitude of the drive voltage.

  In order to construct a resistance change type memory using the resistance change element of the present invention, the element of the present invention may be combined with a semiconductor element, for example, a diode or a transistor such as a MOS field effect transistor.

  The resistance change element of the present invention can be formed by a general thin film forming process and a fine processing process by applying a semiconductor manufacturing process. For example, pulsed laser deposition (PLD), ion beam deposition (IBD), cluster ion beam, and various sputtering such as RF, DC, electron cycloton resonance (ECR), helicon, inductively coupled plasma (ICP), and counter target For example, a vapor deposition method such as molecular beam epitaxy (MBE) or an ion plating method may be used. In addition to these PVD (Physical Vapor Deposition) methods, CVD (Chemical Vapor Deposition) methods, MOCVD (Metal Organic Chemical Vapor Deposition) methods, plating methods, MOD (Metal Organic Decomposition) methods, or sol-gel methods may also be used. Good.

  For microfabrication of each layer, for example, physical processes such as ion milling, RIE (Reactive Ion Etching), and FIB (Focused Ion Beam) used in semiconductor manufacturing processes and magnetic device (magnetoresistive elements such as GMR and TMR) manufacturing processes. A combination of a photolithography technique using a chemical etching method, a stepper for forming a fine pattern, an EB (Electron Beam) method, or the like may be used. For planarizing the surface of each layer, for example, CMP (Chemical Mechanical Polishing), cluster-ion beam etching, or the like may be used.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the examples shown below.

(Example 1)
In Example 1, a plurality of variable resistance elements 21 as shown in FIGS. 4 and 5 are manufactured by changing the shape of the bonding surface 22, and the above state is repeatedly changed by applying a drive voltage to each of the manufactured elements. The variation of the resistance change characteristic of the element was evaluated.

  The specific shape of each evaluated element sample is shown in FIG.

  The variable resistance element 21 shown in FIG. 6 has a structure in which a stacked body 14 in which a lower electrode 11, a variable resistance layer 12, and an upper electrode 13 are stacked in this order is disposed on a Si substrate that is the substrate 10. Reference numeral 31 on the substrate 10 is a separation layer, reference numeral 32 is an impurity polycrystalline silicon layer used for extracting the upper electrode 13, and reference numeral 33 is an impurity diffusion layer used for extracting the lower electrode 11. Cobalt formed between the impurity polycrystalline silicon layer 32 and the impurity diffusion layer 33 and the contact plugs (hereinafter simply “plugs”) 34, 35 and 36 by depositing cobalt by sputtering and then further heat-treating. A silicide layer 37 was disposed. The impurity polycrystalline silicon layer 32 and the impurity diffusion layer 33 were formed by a known method.

  The plug 34 that electrically connects the impurity diffusion layer 33 and the lower electrode 11, the plug 35 that electrically connects the upper electrode 13 and the impurity polycrystalline silicon layer 32, and the resistance change between the impurity polycrystalline silicon layer 32 and Each of the plugs 36 for electrically connecting the metal wiring 38 corresponding to a bit line or a word line in the type memory is formed by depositing a barrier metal made of a titanium film and a titanium nitride film, and further adding a plug metal made of tungsten. Deposited and formed. The shape of each plug was controlled by a photolithography method and a CMP method. The metal wiring 38 was formed in the same manner as the above plugs except that aluminum or copper was deposited instead of the plug metal made of tungsten.

Between each plug, between the substrate 10 and the lower electrode 11, between the substrate 10 and the resistance change layer 12, and between the substrate 10 and the upper electrode 13, a TEOS film was disposed as an interlayer insulating layer 39. A member indicated by reference numeral 40 sandwiched between the pair of interlayer insulating layers 39 is a hydrogen barrier film 40 made of a Si ₃ N ₄ film. The TEOS film is a SiO ₂ film formed from TEOS (tetraethylorthosilicate) and O ₃ (ozone), and is formed together with the hydrogen barrier film 40 by a known method.

  The lower electrode 11 was formed by depositing titanium aluminum nitride and platinum by sputtering. The upper electrode 13 was formed by depositing platinum by a sputtering method. The sputtering conditions for forming the lower electrode 11 and the upper electrode 13 were general conditions for depositing titanium aluminum nitride and platinum.

The resistance change layer 12 was formed by depositing iron oxide (FeO _x ), which is a transition metal oxide, by a sputtering method. The composition of the iron oxide was changed in the range of x = 3/2 to 1 (typically x = 4/3) by changing the sputtering conditions (mainly the oxygen partial pressure ratio in the sputtering atmosphere). Specific sputtering conditions for forming the variable resistance layer 12 are as follows: a sputtering atmosphere is an argon-oxygen mixed atmosphere (typically, when x = 4/3, argon: oxygen (partial pressure ratio) = 8: 1), The Si substrate temperature was 150 ° C. and the applied power was RF 100 W.

  On the stacked body 14, a protective insulating layer 41 made of a TEOS film, a hydrogen barrier film 42, and a protective insulating layer 43 made of a BPSG (Boro-Phospho Silicate Glass) film were arranged. Each of these layers was formed by a known method, and the hydrogen barrier film 42 was formed so as to cover the entire laminate 14.

  FIG. 7 shows a plan view of the element 21 shown in FIG. 6 as seen from the direction perpendicular to the bonding surface 22 of the lower electrode 11 with the resistance change layer 12 (the direction of the arrow C shown in FIG. 6). In FIG. 7, members other than the lower electrode 11, the resistance change layer 12, the upper electrode 13, and the plug 35 (corresponding to the member 51 in FIG. 4) are omitted, and the upper electrode 13 is indicated by a solid line and the lower electrode 11. The resistance change layer 12 and the plug 35 are indicated by broken lines. As shown in FIG. 7, in the element 21 of FIG. 6, the application of the positive bias voltage causes the connection between the upper electrode 13 and the plug 35 (that is, the application surface 16) to the resistance change layer 12 in the lower electrode 11. It is considered that the current 23 flows through the upper electrode 13 and the resistance change layer 12 toward the bonding portion (that is, the bonding surface 22).

  In Example 1, 11 types (samples 1 to 11) of samples in which the shape of the joint surface viewed from the direction perpendicular to the joint surface 22 was changed were produced. In each sample except Sample 1, the shape of the bonding surface 22 is rectangular, and the direction substantially perpendicular to the direction of the current 23 shown in FIG. 7, that is, the direction of the straight line connecting the application surface 16 and the bonding surface 22 is the bonding surface. Each layer was formed to have 22 long sides.

Table 1 shows the lengths of the short side and the long side of the bonding surface 22 in each sample. Table 1 also shows a ratio (aspect ratio) of the length of the long side to the length of the short side in the joint surface 22. In sample 1, the length of the short side is the same as the length of the long side, that is, the shape of the bonding surface 22 is a square. The area (bonding area) of the bonding surface 22 in each sample was all 0.36 μm ² .

For each of the above samples 1 to 11, a pulse generator is used as a drive voltage between the metal wiring 38 and the substrate 10, that is, between the upper electrode 13 and the lower electrode 11, and a pulsed positive bias voltage and Applying a negative bias voltage (each magnitude is 3V) and a pulsed positive bias voltage (size 0.05V) as a read voltage, the electrical resistance value in each state is detected while changing the above-mentioned state of the element. The resistance change characteristics of the element were evaluated. The resistance change ratio of the element was obtained from an equation represented by (R _MAX −R _MIN ) / R _MIN where R _{MAX is} the maximum value of the electric resistance value of the element and R _MIN is the minimum value. The evaluation method of the resistance change ratio of the element is the same in the second embodiment.

  The resistance change ratio (initial resistance change ratio) of each sample immediately after applying the positive bias voltage and the negative bias voltage alternately several times as the drive voltage was about 220 for all the samples. Thereafter, application of a positive bias voltage and a negative bias voltage as the drive voltage was repeated 100 times alternately, and the resistance change ratio of each sample was as shown in Table 1.

  As shown in Table 1, in samples 4 to 10 in which the aspect ratio is in the range of 1.5 to 5, the resistance change ratio of the element 21 can be maintained at 20 or more, but the shape of the bonding surface 22 is a square. 1 and sample 2 with an aspect ratio of 1.18 and sample 11 with an aspect ratio of 10, the resistance change ratio of the element 21 almost disappeared. In these samples, it is considered that partial application of current to the variable resistance layer 12 caused by repeated application of the drive voltage resulted in deterioration of the variable resistance layer 12.

(Example 2)
In Example 2, a plurality of variable resistance elements 1 as shown in FIGS. 1 and 2 were manufactured by changing the shape of the bonding surface 15, and the above state was repeatedly changed by applying a drive voltage to each of the manufactured elements. The variation of the resistance change characteristic of the element in each case was evaluated.

  The specific shape of each element sample evaluated is the area of the resistance change layer 12 (area seen from the direction of arrow C) in the element 21 shown in FIG. 6 as the area of the lower electrode 12 (area seen from the direction of arrow C). ).

  FIG. 8 shows a plan view of the element 1 evaluated in Example 2 as seen from the direction perpendicular to the bonding surface 15 of the upper electrode 13 with the resistance change layer 12. In FIG. 8, illustration of each member other than the lower electrode 11, the resistance change layer 12, the upper electrode 13, and the plug 35 (corresponding to the member 51 in FIG. 1) is omitted, and the upper electrode 13 is indicated by a solid line and the lower electrode 11. The resistance change layer 12 and the plug 35 are indicated by broken lines. As shown in FIG. 8, in the element 1 evaluated in Example 2, it is considered that a current 17 flows through the upper electrode 13 from the application surface 16 toward the bonding surface 15 by applying a positive bias voltage.

  In Example 2, 11 types (samples 12 to 22) of samples in which the shape of the joint surface viewed from the direction perpendicular to the joint surface 15 was changed were produced. In each sample except the sample 12, the shape of the bonding surface 15 is rectangular, and the direction substantially perpendicular to the direction of the current 17 shown in FIG. 8, that is, the direction of the straight line connecting the application surface 16 and the bonding surface 15 is the bonding surface. Each layer was formed to have 15 long sides.

Table 2 shows the lengths of the short side and the long side of the bonding surface 15 in each sample. Table 2 also shows the ratio of the length of the long side to the length of the short side of the joint surface 15 (aspect ratio). In the sample 12, the length of the short side is the same as the length of the long side, that is, the shape of the bonding surface 15 is a square. The area (bonding area) of the bonding surface 15 in each sample was all 0.36 μm ² .

  The resistance change ratio (initial resistance change ratio) of each sample immediately after applying a positive bias voltage and a negative bias voltage several times alternately as a drive voltage was about 160 for all the samples. Thereafter, application of a positive bias voltage and a negative bias voltage as the drive voltage was repeated 100 times alternately, and the resistance change ratio of each sample was as shown in Table 2.

  As shown in Table 2, in Samples 15 to 21 in which the aspect ratio is in the range of 1.5 to 5, the resistance change ratio of the element 1 was 6 or more, and in some cases, 20 or more could be maintained. In the sample 1 having a square shape, the sample 13 having an aspect ratio of 1.18, and the sample 22 having an aspect ratio of 10, the resistance change ratio of the element 1 almost disappeared. In these samples, it is considered that partial application of current to the variable resistance layer 12 caused by repeated application of the drive voltage resulted in deterioration of the variable resistance layer 12.

  As described above, the variable resistance element of the present invention can alleviate partial current concentration on the variable resistance layer when a driving voltage or current is applied to the element, and suppresses deterioration of the variable resistance layer during use. it can.

  The resistance change element of the present invention can be applied to various electronic devices including a next-generation high-density nonvolatile memory, for example, a nonvolatile memory, a switching element, and a sensor used for information communication terminals and the like. Application to an image display device or the like can be considered.

It is sectional drawing which shows typically an example of the resistance change element of this invention. It is the top view which looked at the variable resistance element shown in FIG. 1 from the direction perpendicular | vertical to the joint surface with the variable resistance layer in the upper electrode. It is a top view which shows typically another example of the variable resistance element of this invention. It is a top view which shows typically another example of the resistance change element of this invention. It is the top view which looked at the resistance change element shown in FIG. 4 from the direction perpendicular | vertical to the joint surface with the resistance change layer in the lower electrode. 2 is a cross-sectional view schematically showing a resistance change element sample evaluated in Example 1. FIG. It is the top view which looked at the resistance change element shown in FIG. 6 from the direction perpendicular | vertical to the joint surface with the resistance change layer in the lower electrode. It is the model top view which looked at the resistance change element sample evaluated in Example 2 from the direction perpendicular | vertical to the joint surface with the resistance change layer in the upper electrode.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Resistance change element 10 Board | substrate 11 Lower electrode 12 Resistance change layer 13 Upper electrode 14 Multilayer structure (laminated body)
DESCRIPTION OF SYMBOLS 15 Junction surface 16 Application surface 17 Current 18 Dividing line 19, 20 Portion 21 Resistance change element 22 Junction surface 23 Current 31 Separation layer 32 Impurity polycrystalline silicon layer 33 Impurity diffusion layer 34, 35, 36 Contact plug 37 Cobalt silicide layer 38 Metal Wiring 39 Interlayer insulating layer 40 Hydrogen barrier film 41 Protective insulating layer 42 Hydrogen barrier film 43 Protective insulating layer 51 Member

Claims (6)

A first electrode; a second electrode; and a resistance change layer sandwiched between the first and second electrodes;
There are two or more states with different electrical resistance values between the first and second electrodes,
A resistance change element that changes from one state selected from the two or more states to another state by applying a drive voltage or a drive current to the resistance change layer via the first and second electrodes. Because
The shape of the joint surface with the resistance change layer in the first electrode is a rectangle,
When viewed from a direction perpendicular to the joint surface,
There is an application surface for applying the drive voltage or drive current to the first electrode at a portion of the first electrode that does not overlap the junction surface, and the junction surface is applied with the drive voltage or drive current. A variable resistance element that sometimes has a long side in a direction substantially perpendicular to the direction of current flowing through the first electrode from the application surface to the bonding surface. The first electrode has a rectangular shape;
2. When the first electrode is equally divided into two by a dividing line parallel to the short side thereof, the joint surface is in one of the equally divided portions, and the application surface is in the other portion. The resistance change element according to 1.   2. The variable resistance element according to claim 1, wherein a ratio of a length of a short side to a long side of the joint surface is short side: long side = 1: 1.5 to 1: 5. A first electrode; a second electrode; and a resistance change layer sandwiched between the first and second electrodes;
There are two or more states with different electrical resistance values between the first and second electrodes,
A resistance change element that changes from one state selected from the two or more states to another state by applying a drive voltage or a drive current to the resistance change layer via the first and second electrodes. Because
The first electrode has an application surface for applying the driving voltage or driving current to the electrode,
The shape of the joint surface with the resistance change layer in the second electrode is a rectangle,
When viewed from a direction perpendicular to the joint surface,
The application surface and the bonding surface do not overlap, the resistance change layer is between the application surface and the bonding surface, and the bonding surface is the application surface when the driving voltage or driving current is applied. A variable resistance element having a long side in a direction substantially perpendicular to a direction of current viewed from the direction flowing through the first electrode and the variable resistance layer from the first to the junction surface.   5. The variable resistance element according to claim 4, wherein a ratio of a length between a short side and a long side of the joint surface is short side: long side = 1: 1.5 to 1: 5.   A resistance change type memory comprising the resistance change element according to claim 1 as a memory element.

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