JP2008244397A - Resistance change element, its manufacturing method and resistance change type memory - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resistance change element wherein a change of properties of a resistance change layer exerting influences on characteristics of the element such as an initial resistance value is inhibited to reduce the fluctuation of the characteristics more than a conventional element. <P>SOLUTION: The resistance change element includes a substrate and a multi-layer structure arranged on the substrate. The multi-layer structure includes a lower electrode, an upper electrode and a resistance change layer arranged between the lower electrode and the upper electrode. In the resistance change element, two or more states which have different electric resistance values between the lower electrode and the upper electrode exist. By applying a driving voltage or a current between the lower electrode and the upper electrode, the resistance change element is changed from one state to the other state selected from the two or more states. The multi-layer structure further includes first and second conductive oxygen barrier films sandwiching the resistance change layer so as to contact with it. The resistance change layer has a property-changing part near the side surface thereof, and an area viewed from the lamination direction of the multi-layer structure is larger than the lower electrode, and the property-changing part is not overlaid with the lower electrode when viewed from the direction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a resistance change element whose electric resistance value changes by application of a drive voltage or a drive current, a manufacturing method thereof, and a resistance change type memory including the element as a memory 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 the miniaturization of the device reaches the nanometer region, the charge capacity C per information unit (bit) decreases in the conventional charge storage type memory device (typically DRAM: Dynamic Random Access Memory). Although various improvements have been made to avoid this problem, 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 the electric resistance value R is changed by application of a driving voltage or current is underway.

  The resistance change element is usually configured by a multilayer structure including a lower electrode and an upper electrode and a resistance change layer sandwiched between both electrodes (see, for example, Patent Documents 1 and 2). It functions by applying a driving voltage (current) to the resistance change layer via the electrodes and detecting the state of the resistance change layer via both electrodes. Further, in a general resistance change element, an insulating film is disposed so as to be in contact with the multilayer structure. Depending on the arrangement of the insulating film, for example, two or more resistance change elements are arranged to form a resistance change type memory. When constructing, electrical insulation between adjacent elements can be ensured.

As the insulating film, a film made of oxide such as TEOS (tetraethylorthosilicate) and SiO ₂ film (TEOS film formed by ozone TEOS growth) formed from ozone is widely used. The TEOS film is formed in a strong oxidizing atmosphere as apparent from the use of ozone, and the film forming atmosphere of other oxides is often an oxidizing atmosphere.
JP 2006-080259 A US Patent Application Publication No. 2004/0159828

  As shown in Patent Documents 1 and 2, the conventional resistance change element has a structure in which the electrode covers the resistance change layer as seen from the stacking direction of each layer constituting the element, that is, resistance change seen from the direction. A structure in which the area of the layer is equal to or less than the area of the electrode. This is because it is common to use the entire resistance change layer in order to maximize the miniaturization of the element and to maximize the characteristics of the element.

  Further, during the manufacture of the variable resistance element, the insulating film is generally formed so as to be in contact with the multilayer structure and possibly covering the multilayer structure after the multilayer structure is formed on the substrate. Is done.

  However, in the variable resistance element having the above-described conventional structure, when the insulating film is formed, oxygen contained in the film forming atmosphere diffuses to change the variable resistance layer, and the element characteristics such as the initial resistance value fluctuate. Sometimes. When the initial resistance value of the element fluctuates, for example, it becomes difficult to construct a resistance change type memory having characteristics as designed.

  Further, not only when the insulating film is formed, but also in the process of manufacturing the variable resistance element, the change of the variable resistance layer may be unavoidable.

  Therefore, the present invention provides a variable resistance element in which the change in the resistance change layer that affects the characteristics of the element, such as the initial resistance value, is suppressed, and the variation in the characteristics is less than that of the conventional one. One purpose.

  The present invention also relates to a method of manufacturing a variable resistance element in which an insulating film is disposed so as to be in contact with the variable resistance layer, and affects the characteristics of the element such as an initial resistance value when the insulating film is formed. The second object is to provide a production method capable of suppressing the alteration of the resistance change layer.

  The resistance change element of the present invention includes a substrate and a multilayer structure disposed on the substrate, and the multilayer structure is disposed between a lower electrode and an upper electrode, and the lower electrode and the upper electrode. And a variable resistance layer. In the element of the present invention, there are two or more states in which the electric resistance value between the lower electrode and the upper electrode is different, and a driving voltage or current is applied between the lower electrode and the upper electrode. , And changes from one state selected from the two or more states to another state. The multilayer structure further includes conductive first and second oxygen barrier films that sandwich the variable resistance layer so as to be in contact with the layer. The variable resistance layer has an altered portion in the vicinity of the side surface, and has an area larger than that of the lower electrode as viewed from the stacking direction of the multilayer structure. In the element of the present invention, the altered portion does not overlap with the lower electrode when viewed from 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.

  The variable resistance element manufacturing method of the present invention further includes an insulating film disposed so as to be in contact with the variable resistance layer, wherein the insulating film is a film formed in an oxidizing atmosphere. A manufacturing method comprising: (I) a step of forming a lower electrode on a substrate; (II) a first oxygen barrier film having conductivity on the lower electrode; a resistance change layer; and conductivity. A step of sequentially forming a second oxygen barrier film in contact with each other; (III) a step of forming an upper electrode on the second oxygen barrier film; and (IV) a step of contacting the resistance change layer. And a step of forming an insulating film in an oxidizing atmosphere. In the manufacturing method of the present invention, in the step (II), a portion in the vicinity of the side surface of the variable resistance layer that is altered by the oxidizing atmosphere in the step (IV) is the lower electrode, the first and second oxygen barriers. Forming the variable resistance layer having an area viewed from the direction larger than that of the lower electrode so as not to overlap with the lower electrode when viewed from the stacking direction of the multilayer structure including the film, the variable resistance layer, and the upper electrode; .

  In the element of the present invention, the first and second oxygen barrier films that sandwich the layer so as to be in contact with the variable resistance layer are disposed. By the first and second oxygen barrier films, alteration from the main surface of the resistance change layer at the time of element formation can be suppressed. That is, an element in which the alteration of the resistance change layer at the interface between both the electrodes is suppressed can be obtained. In the element of the present invention, the area of the resistance change layer viewed from the stacking direction of the multilayer structure is larger than the area of the lower electrode, and the altered portion located near the side surface of the resistance change layer is lower when viewed from the above direction. Does not overlap with electrodes. In the altered part, it is thought that the resistance change is unstable or the resistance value is increased compared to the other parts in the variable resistance layer. By avoiding overlapping with the electrodes, it is possible to obtain a variable resistance element in which fluctuations in characteristics such as the initial resistance value are smaller than in the conventional case, in combination with the arrangement of the first and second oxygen barrier films.

  According to the manufacturing method of the present invention, by arranging the first and second oxygen barrier films sandwiching the resistance change layer so as to be in contact with the resistance change layer, a typical effect caused by an oxidizing atmosphere when forming the insulating film is obtained. Therefore, alteration from the main surface of the resistance change layer due to oxygen contained in the atmosphere in which the insulating film is formed can be suppressed. That is, the arrangement of the first and second oxygen barrier films can suppress the alteration of the resistance change layer at the interface with both the electrodes. Further, when the insulating film is formed, the portion in the vicinity of the side surface of the variable resistance layer changes in quality due to the atmosphere in which the film is formed. According to the manufacturing method of the present invention, this changed portion (modified portion) is a multilayer structure. By forming a variable resistance layer having a larger area than the lower electrode so as not to overlap with the lower electrode when viewed from the stacking direction, the initial resistance is combined with the effect of disposing the first and second oxygen barrier films. It is possible to suppress the alteration of the resistance change layer that affects the element characteristics such as the value.

  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.

  1A to 1D show an example of the production method of the present invention.

  First, as shown in FIG. 1A, the lower electrode 2 is formed on the substrate 11 (step (I)). The shape of the lower electrode 2 to be formed is not particularly limited, but is typically a dot shape. In the example shown in FIG. 1A, an interlayer insulating film 21 is formed on the side surface of the lower electrode 2 on the substrate 11 so that a flat surface including the upper surface of the lower electrode 2 is formed. 2 and the interlayer insulating film 21 can be formed by using a thin film forming process and a microfabrication process described later.

  Next, as shown in FIG. 1B, the first oxygen barrier film 12a, the resistance change layer 3, and the second oxygen barrier film 12b are in contact with each other on the lower electrode 2 and the interlayer insulating film 21. It forms in order (process (II)). The first and second oxygen barrier films 12a and 12b have conductivity.

  In step (II), when the insulating film 13 is formed in the subsequent step (IV) (see FIG. 1D), the portion near the side surface of the resistance change layer 3 (the altered portion 14) is altered by the oxidizing atmosphere in which the insulating film 13 is formed. However, the variable resistance layer 3 having a larger area than the lower electrode 2 may be formed so as not to overlap with the lower electrode 2. In this specification, when describing the shape and area of each layer (film) constituting the variable resistance element, and the positional relationship between each layer (film), the lower portion formed on the substrate 11 unless otherwise specified. This refers to the shape, area, and positional relationship of the multilayer structure 15 including the electrode 2, the first oxygen barrier film 12 a, the resistance change layer 3, the second oxygen barrier film 12 b, and the upper electrode 4 as viewed from the stacking direction.

  Next, as shown in FIG. 1C, the upper electrode 4 is formed on the second oxygen barrier film 12b (step (III)). The multilayer structure 15 is formed on the substrate 11 by the step (III).

  Next, as illustrated in FIG. 1D, an insulating film (interlayer insulating film) 13 is formed in an oxidizing atmosphere so as to be in contact with the resistance change layer 3 (so as to be in contact with the multilayer structure 15), and is in contact with the resistance change layer. Thus, the resistance change element 1 of the present invention can be formed, which further includes an insulating film arranged as described above, and the insulating film is a film formed in an oxidizing atmosphere.

  FIG. 2 shows a plan view of only the lower electrode 2 and the resistance change layer 3 in the element 1 shown in FIG. 1D as viewed from the upper surface thereof, that is, the stacking direction of the multilayer structure 15. As shown in FIG. 2, in the element 1 obtained by the manufacturing method shown in FIGS. 1A to 1D, the resistance change layer 3 has an altered portion 14 that has been altered by an oxidizing atmosphere when the insulating film 13 is formed at its peripheral portion. The resistance change layer 3 has a larger area than the lower electrode 2, and the altered portion 14 does not overlap the lower electrode 2.

  In the altered portion 14, it is considered that the resistance change characteristics are deteriorated such that the resistance change becomes unstable and the resistance value increases compared to other portions in the resistance change layer 3. In the element 1, such altered portions 14 are in a positional relationship that does not overlap each other with respect to the lower electrode 2, and therefore, an element in which fluctuations in characteristics such as an initial resistance value are suppressed more than in the past can be obtained. In other words, in the manufacturing method of the present invention, it is possible to suppress the alteration of the resistance change layer 3 that affects the characteristics of the element 1 such as the initial resistance value when the insulating film 13 is formed.

  The shape of the resistance change layer 3 formed in the step (II) is not particularly limited as long as the above conditions are satisfied. For example, in the step (II), the resistance change layer 3 that is similar to the shape of the lower electrode 2 is formed. May be. For example, in the example shown in FIGS. 1A to 1D, the lower electrode 2 and the resistance change layer 3 having a square shape are formed. By forming the resistance change layer 3 in this way, the above condition can be satisfied without excessively increasing the area of the resistance change layer 3, and the resistance change layer 3 that affects the characteristics of the element 1 can be obtained. Can be further suppressed.

  In this case, the resistance change layer 3 may be formed so that the centers of the lower electrode 2 are substantially coincident with each other. The “center” of the lower electrode 2, the resistance change layer 3, and the upper electrode 4 may be a geometric center when considering the shape of each layer viewed from the stacking direction of the multilayer structure 15. .

  In the manufacturing method of the present invention, the shape of the lower electrode 2 formed in the step (I) and the resistance change layer 3 formed in the step (II) may be a circle or a regular polygon. In this case, the above condition can be satisfied without excessively increasing the area of the resistance change layer 3, and alteration of the resistance change layer 3 that affects the characteristics of the element 1 can be further suppressed.

  Specifically, for example, when the shape of the lower electrode 2 is a circle, in the step (II), the resistance change layer 3 that is a circle may be formed so that the centers thereof substantially coincide with each other.

  For example, when the shape of the lower electrode 2 is a regular polygon, in the step (II), the resistance change layer 3 that is a regular polygon similar to the polygon is connected to the straight line connecting the center and the apex of the lower electrode. The resistance change layer 3 may be formed so that its own apex is located on the top. At this time, the resistance change layer 3 may be formed so that the center thereof substantially coincides with the center of the lower electrode 2.

  The regular polygon may be, for example, a square, a regular pentagon, a regular hexagon, a regular octagon, or a regular twenty square from the viewpoint of the balance between the ease of forming each layer and the above effect.

  FIG. 3 is a plan view of both layers when the regular hexagonal lower electrode 2 and the resistance change layer 3 are formed as the element 1 of the present invention, as viewed from the upper surface of the element 1. Similarly, both layers when the regular octagonal lower electrode 2 and the resistance change layer 3 are formed are shown in FIG. 4, and both layers when the circular lower electrode 2 and the resistance change layer 3 are formed are shown in FIG. Each is shown. As shown in FIGS. 3 to 5, also in each element 1, the resistance change layer 3 has the altered portion 14 at the peripheral portion thereof, and the area of the resistance change layer 3 is larger than that of the lower electrode 2. It does not overlap with the lower electrode 2. In the examples shown in FIGS. 2 to 5, the dot-like lower electrode 2 and the resistance change layer 3 are all formed.

  Although different depending on the shapes of the lower electrode 2 and the resistance change layer 3 formed in the steps (I) and (II), the area of the lower electrode 2 is 2 in the step (II) as shown in the examples described later. The resistance change layer 3 that is 6 times or more may be formed. In this case, the alteration of the resistance change layer 3 that affects the characteristics of the element 1 can be further suppressed.

  In the step (II), when the dot-like lower electrode 2 and the strip-like resistance change layer 3 are formed as shown in FIG. 6, the width is the width direction of the lower electrode 2 as shown in Examples described later. You may form the resistance change layer 3 which is 1.6 times or more of this length. In this case, the alteration of the resistance change layer 3 that affects the characteristics of the element 1 can be further suppressed. At this time, it is preferable to form the resistance change layer 3 so that the center line in the extending direction of the resistance change layer 3 is located at the center of the lower electrode 2. If the lower electrode 2 is square as shown in FIG. 6, it is preferable to form the resistance change layer 3 so that the side surface of the resistance change layer 3 and one side of the lower electrode 2 are substantially parallel.

  In the manufacturing method of the present invention, as shown in FIG. 1B, in step (II), the first and second barrier films 12a and 12b and the resistance change layer 3 having substantially the same shape may be formed. In this case, alteration from the main surface of the resistance change layer 3 due to oxygen contained in the atmosphere in which the insulating film is formed can be further suppressed, and alteration of the resistance change layer 3 that affects the characteristics of the element 1 can be further suppressed.

  In the manufacturing method of the present invention, the shape of the upper electrode 4 formed in the step (III) is not particularly limited. For example, the shape may be a dot shape or a belt shape, but in the step (III), the step (II) By forming the upper electrode 4 in consideration of the shape of the resistance change layer 3 formed in step), the alteration of the resistance change layer 3 that affects the characteristics of the element 1 can be further suppressed.

  For example, in the step (III), the upper electrode 4 may be formed so that a portion in the resistance change layer 3 near the side surface (the altered portion 14) does not overlap with the upper electrode 4.

  Further, for example, in the step (III), the upper electrode 4 similar to the lower electrode 2 may be formed. At this time, the upper electrode 4 having substantially the same shape as that of the lower electrode 2 may be formed, and it is preferable to form the upper electrode 4 so that the centers of the lower electrode 2 and the mutual center substantially coincide with each other.

  Further, for example, in the step (III), the upper electrode 4 having a circular shape or a regular polygon shape may be formed. At this time, the shape of the lower electrode 2 formed in the step (I) and the resistance change layer 3 formed in the step (II) are also preferably circular or regular polygon. More preferably, the upper electrode 4 is similar to each other.

  In the manufacturing method of the present invention, the shape of the insulating film 13 formed in the step (IV) is not particularly limited as long as the shape is in contact with the resistance change layer 3. For example, even if the shape covers the multilayer structure 15. Good.

  The atmosphere in which the insulating film 13 is formed is an oxidizing atmosphere. The atmosphere includes, for example, oxygen (“oxygen” in this specification includes each state such as an atom, a molecule, an ion, and a radical, and the molecule contains ozone. Atmosphere).

In step (IV), as the insulating film, for example, a SiO ₂ film may be formed by oxidizing TEOS (tetraethylorthosilicate). As a more specific example, a SiO ₂ film (TEOS) is formed by TEOS and ozone. Film) may be formed.

  In the manufacturing method of the present invention, an optional step may be included between the above steps, for example, between the lower electrode 2 and the first oxygen barrier film 12a or the second oxygen barrier film 12b. An arbitrary layer (film) may be formed between the upper electrode 4 and the upper electrode 4 by an arbitrary process.

  Each layer constituting the element 1 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, ion milling, RIE (Reactive Ion Etching), FIB (Focused Ion Beam), etc. used in a semiconductor manufacturing process or a magnetic device (for example, magnetoresistive element such as GMR or TMR) manufacturing process, etc. A physical or chemical etching method, a stepper for forming a fine pattern, and a photolithography technique using an EB (Electron Beam) method may be used in combination. Further, for example, CMP (Chemical Mechanical Polishing), cluster-ion beam etching, or the like may be used for planarizing the surface of each layer.

  The substrate 11 may be, for example, a silicon (Si) substrate. In this case, the surface of the substrate 11 in contact with the lower electrode 2 may be oxidized. That is, an oxide film may be formed on the surface of the substrate 11. Further, when the substrate 11 is a Si substrate, the combination of the variable resistance element 1 formed by the manufacturing method of the present invention and another semiconductor element becomes easy. Note that the “substrate” here includes a processed substrate on which a transistor, a contact plug (hereinafter also simply referred to as “plug”), and the like are formed.

  The lower electrode 2 and the upper electrode 4 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, It may be made of oxide, nitride, fluoride, carbide, boride and the like.

The material of the resistance change layer 3 has two or more states having different electric resistance values, typically a high resistance state and a low resistance state, and the driving voltage or the like via the lower electrode 2 and the upper electrode 4 or The material is not particularly limited as long as the material can be changed from one state selected from the two or more states to another state by applying a current. Examples of such a material (resistance change material) include perovskite compounds such as (Pr, Ca) MnO _x, and transition metal oxides such as Fe ₂ O ₃ , Fe ₃ O ₄ , and NiO.

  The altered portion 14 is a portion of the variable resistance layer 3 formed near the side surface of the variable resistance layer 3 when the insulating film 13 is formed. Usually, the altered portion 14 is in an oxidized state other than the altered portion 14. Are different (typically in a more oxidized state). When the resistance change layer 3 has a dot shape, the altered portion 14 is typically formed at the peripheral portion thereof.

  The material of the first and second oxygen barrier films 12a and 12b is conductive and has, for example, a dense crystal structure, or an active and easy oxide film can be formed with respect to oxygen. For reasons, there is no particular limitation as long as oxygen diffusion can be inhibited. Examples of such materials include nitride, and more specific examples include TiAlN, TiN, TaN, CoN, CuN, and GaN.

  The thickness of the first and second oxygen barrier films 12a and 12b formed in the step (II) may be in the range of about 50 nm to 100 nm, for example.

The insulating film 13 is not particularly limited as long as it is a film formed in an oxidizing atmosphere. For example, a SiO ₂ film formed by oxidizing TEOS (tetraethylorthosilicate), more specifically, a SiO ₂ film formed from TEOS and ozone (TEOS film formed by ozone TEOS growth) may be used. The atmosphere for forming the TEOS film is an oxidizing atmosphere containing ozone.

  The element of the present invention, which further includes an insulating film disposed so as to be in contact with the variable resistance layer and the film is formed in an oxidizing atmosphere, can be formed by, for example, the manufacturing method of the present invention described above. The altered portion is a portion of the variable resistance layer that has been altered by the oxidizing atmosphere during the formation of the insulating film. However, the altered portion does not necessarily have to be a portion that has been altered by the oxidizing atmosphere at the time of forming the insulating film. For example, when the altered portion is a portion that has changed in the variable resistance layer at any point in the device manufacturing process. In addition, it is possible to obtain the above-described effect that the variation in characteristics such as the initial resistance value is smaller than that in the prior art. That is, when attention is paid to the positional relationship between the altered portion and the lower electrode and the arrangement of the first and second oxygen barrier films, the variable resistance element of the present invention can be said as follows; It further includes conductive first and second oxygen barrier films that sandwich the layer so as to be in contact with the resistance change layer; the resistance change layer has an altered portion in the vicinity of a side surface thereof; a stacking direction of the multilayer structure The area of the resistance change layer viewed from the above is larger than the area of the lower electrode; as seen from the above direction, the altered portion does not overlap with the lower electrode.

  In the element of the present invention, the altered portion has a degradation in resistance change characteristics, such as the resistance change becomes unstable and the resistance value increases, compared to the portion other than the altered portion in the resistance change layer. In the resistance change layer, the oxidation state is different from the portion other than the altered portion.

  The material, area and shape of each layer constituting the element of the present invention, the positional relationship between the respective layers, and the like may be the same as those of each layer of the element 1 described in the manufacturing method of the present invention.

  For example, the element of the present invention may further include an insulating film disposed so as to be in contact with the resistance change layer, and the insulating film may be a film formed in an oxidizing atmosphere.

Examples of such a film include a SiO ₂ film formed by oxidation of TEOS, and a more specific example includes a SiO ₂ film formed from TEOS and ozone.

  Further, for example, in the element of the present invention, the shape of the lower electrode and the resistance change layer as viewed from the stacking direction of the multilayer structure including the lower electrode, the first and second oxygen barrier films, the resistance change layer, and the upper electrode. May be similar. The shape may be, for example, a circle or a regular polygon. In this case, the above condition can be satisfied without excessively increasing the area of the resistance change layer, and the characteristics are less changed. It can be.

  When the shapes of the lower electrode and the resistance change layer are circular, they may be arranged so that their centers substantially coincide.

  When the shape of the lower electrode and the resistance change layer is a regular polygon, the lower electrode and the resistance change layer are arranged so that the vertex of the resistance change layer is positioned on a straight line connecting the center and the vertex of the lower electrode. Also good.

  In the element of the present invention, although the area varies depending on the shapes of the lower electrode and the resistance change layer, the area of the resistance change layer may be 2.6 times or more the area of the lower electrode. It can be set as an element.

  In the element of the present invention, when the lower electrode has a dot shape and the resistance change layer has a strip shape, the width of the resistance change layer may be 1.6 times or more the length of the lower electrode in the width direction. . In this case, an element with less variation in characteristics can be obtained. When the lower electrode has a dot shape and the resistance change layer has a strip shape, it is preferable that the center line in the extending direction of the resistance change layer is located at the center of the lower electrode. For example, if the lower electrode is square as shown in FIG. 6, it is preferable that the side surface of the resistance change layer and one side of the lower electrode are substantially parallel.

  In the element of the present invention, the shape of the resistance change layer and the first and second oxygen barrier films may be substantially the same.

  In the element of the present invention, the altered portion may not overlap with the upper electrode when viewed from the stacking direction. In this case, it is possible to obtain an element with further less variation in characteristics.

  Hereinafter, as an example of the variable resistance element of the present invention including the example, the element 1 formed by the manufacturing method of the present invention will be used as an example.

  The driving voltage or current may be applied to the element 1 through the lower electrode 2 and the upper electrode 4. By applying the driving voltage or current, the state of the element 1 changes from, for example, a high resistance state to a low resistance state, but the state after the change is maintained until the driving voltage or current is applied to the element 1 again. Is done. The state of the element 1 can be changed again (for example, from the low resistance state to the high resistance state) by applying a driving voltage or current to the element 1.

  The driving voltage or current applied to the element 1 does not necessarily have to be the same between when the element 1 is in the high resistance state and when it is in the low resistance state. It may be different depending on the state of 1. In other words, the “drive voltage or current” in this specification may be a “voltage or current” that can change to another state different from the state when the element 1 is in a certain state.

  Thus, in the element 1, the state of the element exhibiting a specific electric resistance value can be maintained until a drive voltage or current is applied to the element 1. For this reason, a nonvolatile resistance change memory can be constructed by combining the element 1 and a mechanism for detecting the state of the element 1 (that is, a mechanism for detecting the electric resistance value of the element 1). Such a resistance change type memory is excellent in stability because fluctuations in characteristics in the element 1 are suppressed.

  Further, by using two or more elements 1, it is possible to construct a memory array in which two or more memory elements are arranged. In this memory, a bit, for example, “0” for the high resistance state and “1” for the low resistance state may be assigned to each state of the element 1. Since the change in the state of the element 1 can be repeated at least twice or more, a reliable nonvolatile random access memory can be obtained. Further, by assigning “ON” or “OFF” to each state of the element 1, the element 1 can be applied to a switching element.

  The driving voltage or current applied to the element 1 is preferably pulsed because it can reduce the power consumption of the element 1 and the power consumption of a device such as a memory including the element 1. In particular, a pulsed voltage is applied. It is preferable to do.

  The electric resistance value of the element 1 is detected by, for example, applying a voltage (read voltage) that does not change the state of the element to the element 1 and detecting the current value flowing through the element 1 at that time. Just do it. The read voltage is preferably a pulse voltage because the power consumption of the element 1 and the device including the element 1 can be further reduced. Although the magnitude of the read voltage varies depending on the configuration of the element 1, it is usually about 1/4 to 1/1000 of the magnitude of the drive voltage.

  A resistance change type memory can be constructed by combining the resistance change element of the present invention with a semiconductor element such as a diode or a transistor such as a MOS field effect transistor (MOS-FET).

  For example, as shown in FIG. 7, the resistance change element 1 of the present invention is connected in series with a selection element 31 having a non-linear current-voltage characteristic (a diode as an example in FIG. 7) to form a memory element 32. By arranging the memory elements 32 in a matrix, a nonvolatile and random access resistance change memory (memory array) 51 can be constructed.

In the memory 51, coordinates (B _n ) are selected by selecting one bit line (B _n ) selected from two or more bit lines 33 and one word line (W _n ) selected from two or more word lines 34. _n , W _n ), information can be recorded in the memory element 32a, and information can be read from the memory element 32a.

  The selection element 31 may be any element of a Schottky type, a double Schottky type, a PN junction type, a PIN junction type, or a varistor characteristic type. All of these elements have non-linear voltage-current characteristics, and the selectivity of the memory elements 32 in the memory array 51 can be improved by connecting them in series with the element 1 of the present invention.

Further, for example, as shown in FIG. 8, a non-volatile random access variable resistance memory (memory array) 52 can be constructed by using a pass transistor 41 and arranging two or more elements 1 in a matrix. . In the memory 52, the bit line 33 is connected to the upper electrode 4 of the element 1, and the word line 34 is connected to the lower electrode 2 of the element 1. In the memory 52, the pass transistor 41 a connected to one bit line (B _n ) selected from two or more bit lines 33 and one word line (W _n ) selected from two or more word lines 34 are connected. By selectively turning on the pass transistor 41b, information can be recorded on the variable resistance element 1a located at the coordinates (B _n , W _n ), and information can be read from the variable resistance element 1a. It becomes. In order to read the information of the element 1a, for example, the voltage V shown in FIG. 8 that is a voltage corresponding to the electric resistance value of the element 1a may be measured.

  In addition, when a memory element having nonlinear current-voltage characteristics such as the memory element 32 shown in FIG. 7 is used instead of the element 1, a nonvolatile and random access type memory array can be constructed with this configuration.

A reference element group 42 is arranged in the memory 52 shown in FIG. By selectively turning on the pass transistor 41c corresponding to the bit line (B ₀ ) connected to the reference element group 42 and measuring the voltage V _REF shown in FIG. 8, the output of the element 1a and the reference element group The difference from the output of 42 can be detected.

  Further, in the memory 52 shown in FIG. 8, the non-selected element 1 that is not selected by the pass transistor can be used as a reference element. In this method, since it is necessary to appropriately set the reference element while verifying the state of the element around the element 1a selected by the pass transistor, the operation as the memory array may be somewhat slow. The configuration can be simplified.

  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 cell plate type resistance change type memory including the element 1 was manufactured by the method shown in FIGS. 9 to 13 and the initial resistance value of the element was evaluated. A method for producing the evaluated samples is shown below.

  First, as shown in FIG. 9, a Si substrate is prepared as a substrate 11, and a MOS transistor (only a gate electrode is shown, and a source electrode and a drain electrode are not shown) is formed on the Si substrate using a known technique. And an isolation layer 61 for electrically isolating adjacent transistors. Specifically, an isolation layer 61 made of a silicon oxide film by HDP (high density plasma) growth, a gate oxide film 62 made of a silicon oxide film, and a gate electrode 63 made of polysilicon are used. Next, a cobalt silicide layer 64 is formed by self-alignment so as to cover the gate electrode 63 and the exposed portion of the substrate 11, and further BPSG (boric acid-added phosphoric acid silicate glass) by ozone TEOS growth so as to cover the whole. An interlayer insulating film 65 made of a film was formed. Next, the surface of the formed interlayer insulating film 65 was planarized by CMP, and then a silicon nitride layer 66 having a thickness of 150 nm was formed (up to this point in FIG. 9).

  9A is a cross-sectional view schematically showing a cross section in the direction in which the bit line extends in the manufactured sample, and FIG. 9B shows a cross section in the direction in which the word line in the manufactured sample extends. It is sectional drawing shown typically. The same applies to FIGS. 10 to 13 and FIGS. 15 to 19 in the second embodiment.

Next, as shown in FIG. 10, a plug 67 made of tungsten penetrating the silicon nitride layer 66 and the interlayer insulating film 65 was formed, and the surface thereof was flattened by CMP. Next, an adhesion layer 68 (thickness 20 nm) made of titanium nitride and a Pt film (thickness 100 nm) to be the lower electrode 2 are formed on the surfaces of the silicon nitride layer 66 and the plug 67, and then the adhesion layer 68 and the Pt film are formed. Was subjected to microfabrication so as to form a square having a side of 1.0 μm when viewed from the stacking direction of each layer to form the lower electrode 2. Next, an interlayer insulating film 21 made of SiO ₂ film (TEOS film) by ozone TEOS growth was laminated so as to cover the whole, and the surface of the lower electrode 2 was slightly covered with the interlayer insulating film 21. After flattening by CMP until it reached a state, the lower electrode 2 was exposed by dry etching (so far, FIG. 10). The surface of the lower electrode 2 could be exposed only by CMP. As shown in FIG. 10B, a drop electrode 69 that becomes a GND contact portion of the upper electrode 4 is formed separately from the formation of the lower electrode 2.

Next, as shown in FIG. 11, on the lower electrode 2, the interlayer insulating film 21, and the drop electrode 69, a first oxygen barrier film 12a (50 nm) made of TiAlN and a resistance change layer 3 made of Fe ₃ O ₄ ( 150 nm thick) and a second oxygen barrier film 12b (thickness 50 nm) made of TiAlN were formed in this order, and then portions of the formed layers immediately above the drop electrode 69 serving as the GND contact portion were removed by etching. Next, the upper electrode 4 (thickness 100 nm) made of Pt was formed so as to cover the whole (FIG. 11 so far). As shown in FIG. 11B, the formed upper electrode 4 is electrically connected to a predetermined region in the substrate 11 through the drop electrode 69 and the plug 67a in the GND contact portion 70 and grounded. .

Formation of the Fe ₃ O ₄ film as the resistance change layer 3 is performed by a magnetron sputtering method using Fe ₃ O ₄ as a target in an argon-oxygen mixed atmosphere at a pressure of 0.1 to 10 Pa (typically 2 Pa) ( Typically, argon / oxygen (partial pressure ratio) = 25/1), the temperature of the Si substrate was 20 to 400 ° C. (typically 300 ° C.), and the applied power was RF 100 W.

  The Pt film as the lower electrode 2 and the upper electrode 4 is formed by magnetron sputtering using Pt as a target in an argon atmosphere at a pressure of 0.7 Pa, the temperature of the Si substrate is 27 ° C., and the applied power is RF 100 W. Went as.

  Next, as shown in FIG. 12, the first oxygen barrier film 12a, the resistance change layer 3, the second oxygen barrier film 12b, and the upper electrode 4 are finely processed by a dry etching method to obtain a multilayer structure 15 (resistance A change element 1) was formed. The microfabrication is a strip shape in which the shape of the resistance change layer 3 and the first and second oxygen barrier films 12a and 12b extends in the word line direction as seen from the lamination method of each layer, and the center line is the lower electrode. The layers were formed so as to coincide with the center of the lower electrode 2 and to be parallel to one side of the lower electrode 2, and the shapes of the respective layers were the same. Further, the resistance change layer 3 is finely processed so that the width of the variable resistance layer 3 is larger than the width of the lower electrode in the width direction. At this time, the width of the variable resistance layer 3 is changed to thereby reduce the area of the lower electrode 2. Seven samples having different areas of the resistance change layer 3 were prepared. Specifically, the distance between the side surface of the lower electrode 2 and the side surface of the resistance change layer 3 as viewed from the stacking direction of each layer (distance in plan view: hereinafter referred to as “separation distance”) is 0.15 μm, 0 .2 μm, 0.3 μm, 0.4 μm, 0.43 μm, 0.5 μm, and 1.0 μm. This is because the width of the resistance change layer 3 is 1.3 times, 1.4 times, 1.6 times, 1.8 times, 1.86 times the length (1.0 μm) of the lower electrode 2 in the width direction. It corresponds to double, double and triple.

  Next, a TEOS film is formed as the insulating film 13 so as to cover the entire multilayer structure 15 including the interlayer insulating layer 21, the first and second oxygen barrier films 12 a and 12 b, the resistance change layer 3 and the upper electrode 4. After the formation, the surface of the insulating film was planarized by CMP (FIG. 12 so far).

  Next, as shown in FIG. 13, an opening reaching the predetermined region of the substrate 11 is provided in the insulating film 13, the interlayer insulating films 21 and 65, and the silicon nitride layer 66, and tungsten is deposited in the opening. The surface of the deposited tungsten was planarized by CMP to form a plug 71. Next, an Al film (thickness: 500 nm) was deposited on the entire surface, and then finely processed by a dry etching method to form the bit line 33 and the cell plate line 35 electrically connected to the plug 71 (as shown so far). 13).

  Next, when the initial resistance value between the lower electrode 2 and the upper electrode 4 was evaluated for the seven types of samples thus formed, the results shown in FIG. 14 were obtained. In FIG. 14, the initial resistance value of the sample with the magnification of 3 is almost the same as the value of each sample with the magnification of 1.6 or more, and thus illustration is omitted.

  The initial resistance value is evaluated by applying a current I of 1 to 10 μA to two of the four terminals using a Kelvin pattern, which is a general measurement pattern, and measuring the potential difference V between the remaining two terminals. went. In this method, the initial resistance value is a value indicated by (V / I).

  As shown in FIG. 14, the initial resistance value between the lower electrode 2 and the upper electrode 4 decreases as the width of the strip-shaped resistance change layer 3 increases with respect to the length of the lower electrode 2 in the width direction. The initial resistance value was almost stable when the width was 1.6 times the length of the lower electrode 2 or more. This is because the altered portion 14 formed by the diffusion of oxygen from the side surface of the resistance change layer 3 due to the formation of the insulating film in the oxidizing atmosphere after forming the element 1 and the lower electrode 2 are overlapped. It is considered that the overlap is eliminated when the width of the change layer 3 gradually increases as the width of the change layer 3 increases, and when the width becomes 1.6 times or more of the length of the lower electrode 2.

(Example 2)
In Example 1, a cross-point resistance change type memory including the element 1 was manufactured by the method shown in FIGS. 15 to 19 and the initial resistance value of the element was evaluated. A method for producing the evaluated samples is shown below.

  First, as shown in FIG. 15, a Si substrate is prepared as the substrate 11, and a MOS transistor (a gate electrode, a source electrode, and a drain electrode are not shown) is formed on the Si substrate using a known technique. An isolation layer 61 for electrically isolating adjacent transistors was formed. Specifically, the separation layer 61 is made of a silicon oxide film by HDP growth. Next, a cobalt silicide layer 64 was formed by self-alignment so as to cover the exposed portion of the substrate 11, and an interlayer insulating film 65 made of BPSG film by ozone TEOS growth was formed so as to cover the whole. Next, the surface of the formed interlayer insulating film 65 was planarized by CMP, and then a silicon nitride layer 66 having a thickness of 150 nm was formed (FIG. 15 so far).

  Next, as shown in FIG. 16, a plug 67 made of tungsten penetrating the silicon nitride layer 66 and the interlayer insulating film 65 was formed, and the surface thereof was flattened by CMP. Next, an adhesion layer 68 (thickness 20 nm) made of titanium nitride and a Pt film (thickness 100 nm) to be the lower electrode 2 are formed on the surfaces of the silicon nitride layer 66 and the plug 67, and then the adhesion layer 68 and the Pt film are formed. Was subjected to microfabrication so as to form a square having a side of 1.0 μm when viewed from the stacking direction of each layer to form the lower electrode 2. Next, an interlayer insulating film 21 made of a TEOS film is laminated so as to cover the whole, and the surface thereof is flattened by CMP until the surface of the lower electrode 2 is slightly covered with the interlayer insulating film 21. Then, the lower electrode 2 was exposed by dry etching (FIG. 16 so far). The surface of the lower electrode 2 could be exposed only by CMP.

Next, as shown in FIG. 17, a first oxygen barrier film 12a (50 nm) made of TiAlN and a resistance change layer 3 made of Fe ₃ O ₄ (thickness 150 nm) are formed on the lower electrode 2 and the interlayer insulating film 21. Then, the second oxygen barrier film 12b (thickness 50 nm) made of TiAlN and the upper electrode 4 (thickness 100 nm) made of Pt were sequentially formed (FIG. 17 so far).

The Fe ₃ O ₄ film as the resistance change layer 3 and the Pt films as the lower electrode 2 and the upper electrode 4 were formed in the same manner as in Example 1.

  Next, as shown in FIG. 18, the first oxygen barrier film 12a, the resistance change layer 3, the second oxygen barrier film 12b, and the upper electrode 4 are finely processed by a dry etching method to obtain a multilayer structure 15 (resistance A change element 1) was formed. In the microfabrication, the shape of the resistance change layer 3 and the first and second oxygen barrier films 12a and 12b as seen from the laminating method of each layer is square, the center thereof coincides with the center of the lower electrode, The top of each layer was positioned on a straight line connecting the center and the top of the lower electrode 2 and the areas of the layers were the same. Further, in the microfabrication, the area of the resistance change layer 3 was made larger than the area of the lower electrode 2, and at this time, seven types of samples having different areas of the resistance change layer 3 were prepared. Specifically, the separation distance between one side of the lower electrode 2 and one side of the resistance change layer 3 adjacent to the side is set to 0.15 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.43 μm, 0 .5 μm and 1.0 μm. This corresponds to the area of the resistance change layer 3 being 1.69 times, 1.96 times, 2.56 times, 3.24 times, 3.46 times, 4 times and 9 times the area of the lower electrode 2.

  Next, a TEOS film was formed as the insulating film 13 so as to cover the multilayer structure 15 including the interlayer insulating layer 21, the first and second oxygen barrier films 12 a and 12 b, the resistance change layer 3, and the upper electrode 4. Later, the surface of the insulating film was planarized by CMP (FIG. 18 so far).

  Next, as shown in FIG. 19, an opening reaching a predetermined region of the substrate 11 is provided in the insulating film 13, the interlayer insulating films 21 and 65, and the silicon nitride layer 66, and tungsten is deposited in the opening, The deposited tungsten surface was flattened by CMP to form a plug 73. Next, an Al film (thickness 500 nm) was deposited on the entire surface, and then finely processed by a dry etching method to form a word line 34 electrically connected to the plug 73. Next, a TEOS film is formed as an interlayer insulating film 72 so as to cover the whole, and then reaches a predetermined region of the substrate 11 in the interlayer insulating film 72, the insulating film 13, the interlayer insulating films 21 and 65, and the silicon nitride layer 66. An opening was provided, tungsten was deposited in the opening, and the surface of the deposited tungsten was planarized by CMP to form the plug 71. Next, an Al film (thickness 500 nm) was deposited on the entire surface, and then finely processed by a dry etching method to form the bit line 33 electrically connected to the plug 71 (FIG. 19 so far).

  Next, for the seven types of samples thus formed, the initial resistance value between the lower electrode 2 and the upper electrode 4 was evaluated in the same manner as in Example 1, and the results shown in FIG. 20 were obtained. It was. In FIG. 14, the initial resistance value of the sample with the magnification of 9 times is substantially the same as the value of each sample with the magnification of 2.56 times or more, and thus illustration is omitted.

  As shown in FIG. 20, the initial resistance value between the lower electrode 2 and the upper electrode 4 tends to decrease as the area of the resistance change layer 3 increases with respect to the area of the lower electrode 2. The initial resistance value was almost stable at 2.56 times or more the area of the lower electrode 2. This is because the altered portion 14 formed by the diffusion of oxygen from the side surface of the resistance change layer 3 due to the formation of the insulating film in the oxidizing atmosphere after forming the element 1 and the lower electrode 2 are overlapped. This is considered to be because the overlap was eliminated when the area of the change layer 3 gradually increased and the area became 2.56 times or more the area of the lower electrode 2.

Next, the same initial resistance value is evaluated by changing the shape of the lower electrode 2, the first and second oxygen barrier films 2a and 2b, the resistance change layer 3 and the upper electrode 4 from a square to a regular pentagon. It was. The area of the lower electrode 2 was 1 μm ² . The first oxygen barrier film 12a, the resistance change layer 3, and the second oxygen barrier film 12b are finely processed by the resistance change layer 3 and the first and second oxygen barriers as viewed from the stacking method of each layer. The shapes of the films 12a and 12b are regular pentagons, the center of which coincides with the center of the lower electrode, and the vertices of each layer are positioned on a straight line connecting the centers and vertices of the lower electrode 2, and The area of each layer was the same. Further, in the microfabrication, the area of the resistance change layer 3 was made larger than the area of the lower electrode 2, and at this time, seven types of samples having different areas of the resistance change layer 3 were prepared. Specifically, the separation distance between one side of the lower electrode 2 and one side of the resistance change layer 3 adjacent to the side is set to 0.15 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.43 μm, 0 .5 μm and 1.0 μm. This is because the area of the resistance change layer 3 is 1.65 times, 1.91 times, 2.47 times, 3.11 times, 3.31 times, 3.81 times and 8.44 times the area of the lower electrode 2. It corresponds to.

  For the seven types of samples thus formed, the initial resistance value between the lower electrode 2 and the upper electrode 4 was evaluated in the same manner as in Example 1, and the results shown in FIG. 21 were obtained. In FIG. 21, the initial resistance value of the sample with the magnification of 8.44 times is substantially the same as the value of each sample with the magnification of 2.47 times or more, and thus illustration is omitted.

  As shown in FIG. 21, as the area of the resistance change layer 3 increases with respect to the area of the lower electrode 2, the initial resistance value between the lower electrode 2 and the upper electrode 4 tends to decrease, and the area is The initial resistance value was almost stable when the area of the lower electrode 2 was 2.47 times or more. This is because the altered portion 14 formed by the diffusion of oxygen from the side surface of the resistance change layer 3 due to the formation of the insulating film in the oxidizing atmosphere after forming the element 1 and the lower electrode 2 are overlapped. This is considered to be because the overlap disappeared when the area of the change layer 3 gradually increased and the area became 2.47 times or more the area of the lower electrode 2.

Next, the same initial resistance value was evaluated by changing the shapes of the lower electrode 2, the first and second oxygen barrier films 2a and 2b, the resistance change layer 3 and the upper electrode 4 from a regular pentagon to a regular octagon. went. The area of the lower electrode 2 was 1 μm ² . The microfabrication of the first oxygen barrier film 12a, the resistance change layer 3, and the second oxygen barrier film 12b is performed by the resistance change layer 3 and the first and second oxygen barrier films as viewed from the lamination method of each layer. The shape of 12a, 12b is a regular octagon, the center of which coincides with the center of the lower electrode, the vertex of each layer is positioned on a straight line connecting the center and the vertex of the lower electrode 2, and The area of each layer was the same as each other. Further, in the microfabrication, the area of the resistance change layer 3 was made larger than the area of the lower electrode 2, and at this time, seven types of samples having different areas of the resistance change layer 3 were prepared. Specifically, the separation distance between one side of the lower electrode 2 and one side of the resistance change layer 3 adjacent to the side is set to 0.15 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.43 μm, 0 .5 μm and 1.0 μm. This is because the area of the resistance change layer 3 is 1.62 times, 1.86 times, 2.39 times, 2.99 times, 3.18 times, 3.65 times and 7.95 times the area of the lower electrode 2. It corresponds to.

  For the seven types of samples thus formed, the initial resistance value between the lower electrode 2 and the upper electrode 4 was evaluated in the same manner as in Example 1, and the results shown in FIG. 22 were obtained. In FIG. 22, the initial resistance value of the sample with the magnification of 7.95 times is substantially the same as the value of each sample with the magnification of 2.39 times or more, and thus illustration is omitted.

  As shown in FIG. 22, as the area of the resistance change layer 3 increases with respect to the area of the lower electrode 2, the initial resistance value between the lower electrode 2 and the upper electrode 4 tends to decrease. The initial resistance value was almost stable when the area of the lower electrode 2 was 2.39 times or more. This is because the altered portion 14 formed by the diffusion of oxygen from the side surface of the resistance change layer 3 due to the formation of the insulating film in the oxidizing atmosphere after forming the element 1 and the lower electrode 2 are overlapped. This is considered to be because the overlap was eliminated when the area of the change layer 3 gradually increased and the area became 2.39 times or more the area of the lower electrode 2.

Next, the same initial resistance value is evaluated, and the shapes of the lower electrode 2, the first and second oxygen barrier films 2a and 2b, the resistance change layer 3 and the upper electrode 4 are changed from a regular octagon to a regular twenty square. Changed to. The area of the lower electrode 2 was 1 μm ² . The first oxygen barrier film 12a, the resistance change layer 3, and the second oxygen barrier film 12b are finely processed by the resistance change layer 3 and the first and second oxygen barriers as viewed from the stacking method of each layer. The shapes of the films 12a and 12b are regular tetragons, the center of which coincides with the center of the lower electrode, and the vertices of each layer are located on the straight line connecting the centers and vertices of the lower electrode 2. In addition, the area of each layer was the same. Further, in the microfabrication, the area of the resistance change layer 3 was made larger than the area of the lower electrode 2, and at this time, seven types of samples having different areas of the resistance change layer 3 were prepared. Specifically, the separation distance between one side of the lower electrode 2 and one side of the resistance change layer 3 adjacent to the side is set to 0.15 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.43 μm, 0 .5 μm and 1.0 μm. This is because the area of the resistance change layer 3 is 1.60 times, 1.84 times, 2.35 times, 2.93 times, 3.11 times, 3.57 times and 7.71 times the area of the lower electrode 2. It corresponds to.

  For the seven types of samples thus formed, the initial resistance value between the lower electrode 2 and the upper electrode 4 was evaluated in the same manner as in Example 1, and the results shown in FIG. 23 were obtained. In FIG. 23, the initial resistance value of the sample with the magnification of 7.71 times is substantially the same as the value of each sample with the magnification of 2.35 times or more, and thus illustration is omitted.

  As shown in FIG. 23, the initial resistance value between the lower electrode 2 and the upper electrode 4 tends to decrease as the area of the resistance change layer 3 increases with respect to the area of the lower electrode 2. The initial resistance value was almost stable when the area of the lower electrode 2 was 2.35 times or more. This is because the altered portion 14 formed by the diffusion of oxygen from the side surface of the resistance change layer 3 due to the formation of the insulating film in the oxidizing atmosphere after forming the element 1 and the lower electrode 2 are overlapped. This is considered to be because the overlap was eliminated when the area of the change layer 3 gradually increased and the area became 2.35 times or more the area of the lower electrode 2.

Next, the same initial resistance value was evaluated by changing the shape of the lower electrode 2, the first and second oxygen barrier films 2a and 2b, the resistance change layer 3 and the upper electrode 4 from a regular twenty square to a circle. Changed and went. The area of the lower electrode 2 was 1 μm ² . The microfabrication of the first oxygen barrier film 12a, the resistance change layer 3, and the second oxygen barrier film 12b is performed by the resistance change layer 3 and the first and second oxygen barrier films as viewed from the lamination method of each layer. The shape of 12a, 12b was circular, the center thereof coincided with the center of the lower electrode, and the areas of the layers were the same. Further, in the microfabrication, the area of the resistance change layer 3 was made larger than the area of the lower electrode 2, and at this time, seven types of samples having different areas of the resistance change layer 3 were prepared. Specifically, the separation distance between the circumference of the lower electrode 2 and the circumference of the resistance change layer 3 (that is, the difference between the radius of the lower electrode 2 and the radius of the resistance change layer 3) is 0.15 μm,. They were 2 μm, 0.3 μm, 0.4 μm, 0.43 μm, 0.5 μm, and 1.0 μm. This is because the area of the resistance change layer 3 is 1.60 times, 1.83 times, 2.35 times, 2.92 times, 3.10 times, 3.56 times and 7.68 times the area of the lower electrode 2. It corresponds to.

  For the seven types of samples thus formed, the initial resistance value between the lower electrode 2 and the upper electrode 4 was evaluated in the same manner as in Example 1, and the results shown in FIG. 24 were obtained. In FIG. 24, the initial resistance value of the sample with the magnification of 7.68 times is substantially the same as the value of each sample with the magnification of 2.35 times or more, and thus illustration is omitted.

  As shown in FIG. 24, as the area of the resistance change layer 3 increases with respect to the area of the lower electrode 2, the initial resistance value between the lower electrode 2 and the upper electrode 4 tends to decrease. The initial resistance value was almost stable when the area of the lower electrode 2 was 2.35 times or more. This is because the altered portion 14 formed by the diffusion of oxygen from the side surface of the resistance change layer 3 due to the formation of the insulating film in the oxidizing atmosphere after forming the element 1 and the lower electrode 2 are overlapped. This is considered to be because the overlap was eliminated when the area of the change layer 3 gradually increased and the area became 2.35 times or more the area of the lower electrode 2.

  As described above, according to the present invention, it is possible to provide a method of manufacturing a resistance change element that can suppress the alteration of the resistance change layer that affects the characteristics of the element such as the initial resistance value.

  The resistance change element of the present invention can be applied to various electronic devices including a resistance change type memory. As the device, 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 is conceivable.

It is process drawing which shows typically an example of the manufacturing method of the resistance change element of this invention. It is process drawing which shows typically an example of the manufacturing method of the resistance change element of this invention. It is process drawing which shows typically an example of the manufacturing method of the resistance change element of this invention. It is process drawing which shows typically an example of the manufacturing method of the resistance change element of this invention. It is the top view which looked at the lower electrode and resistance change layer in the resistance change element formed by the process shown to FIG. 1A-FIG. 1D from the upper surface of the element. It is the top view which looked at the lower electrode (regular hexagon) and resistance variable layer (regular hexagon) in an example of the resistance change element formed with the manufacturing method of this invention from the upper surface of the element. It is the top view which looked at the lower electrode (regular octagon) and resistance variable layer (regular octagon) in an example of the variable resistance element formed by the manufacturing method of this invention from the upper surface of the element. It is the top view which looked at the lower electrode (circle) and resistance change layer (circle) in an example of the resistance change element formed with the manufacturing method of this invention from the upper surface of the element. It is the top view which looked at the lower electrode (square) and resistance change layer (band shape) in an example of the resistance change element formed with the manufacturing method of this invention from the upper surface of the element. It is a schematic diagram which shows an example of the structure as a memory array of the resistance change memory of this invention. It is a schematic diagram which shows an example of the structure as a memory array of the resistance change memory of this invention. FIG. 3 is a process diagram schematically showing a manufacturing method of the resistance change type memory sample of the present invention produced in Example 1. FIG. 3 is a process diagram schematically showing a manufacturing method of the resistance change type memory sample of the present invention produced in Example 1. FIG. 3 is a process diagram schematically showing a manufacturing method of the resistance change type memory sample of the present invention produced in Example 1. FIG. 3 is a process diagram schematically showing a manufacturing method of the resistance change type memory sample of the present invention produced in Example 1. FIG. 3 is a process diagram schematically showing a manufacturing method of the resistance change type memory sample of the present invention produced in Example 1. It is a figure which shows the change of the initial stage resistance value of the element evaluated in Example 1. FIG. FIG. 10 is a process diagram schematically showing a method of manufacturing a resistance change memory sample of the present invention produced in Example 2. FIG. 10 is a process diagram schematically showing a method of manufacturing a resistance change memory sample of the present invention produced in Example 2. FIG. 10 is a process diagram schematically showing a method of manufacturing a resistance change memory sample of the present invention produced in Example 2. FIG. 10 is a process diagram schematically showing a method of manufacturing a resistance change memory sample of the present invention produced in Example 2. FIG. 10 is a process diagram schematically showing a method of manufacturing a resistance change memory sample of the present invention produced in Example 2. It is a figure which shows the change of the initial resistance value of the element (The shape of a lower electrode and a resistance change layer is square) evaluated in Example 2. FIG. It is a figure which shows the change of the initial resistance value of the element (The shape of a lower electrode and a resistance change layer is a regular pentagon) evaluated in Example 2. FIG. It is a figure which shows the change of the initial resistance value of the element (The shape of a lower electrode and a resistance change layer is a regular octagon) evaluated in Example 2. FIG. It is a figure which shows the change of the initial resistance value of the element (The shape of a lower electrode and a resistance change layer is a regular 20 square) evaluated in Example 2. FIG. It is a figure which shows the change of the initial resistance value of the element (The shape of a lower electrode and a resistance change layer is circular) evaluated in Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a Resistance change element 2 Lower electrode 3 Resistance change layer 4 Upper electrode 11 Substrate 12a 1st oxygen barrier film 12b 2nd oxygen barrier film 13 Insulation film (interlayer insulation film)
14 Altered part 21 Interlayer insulating film 31 Select element 32, 32a Memory element 33 Bit line 34 Word line 35 Cell plate line 41, 41a, 41b, 41c Pass transistor 42 Reference element group 51 Resistance change type memory (array)
52 Resistance change memory (array)
61 Separation layer 62 Gate oxide film 63 Gate electrode 64 Cobalt silicide layer 65 Interlayer insulation film 66 Silicon nitride layer 67, 67a Plug 68 Adhesion layer 69 Drop electrode 70 GND contact portion 71 Plug 72 Interlayer insulation film

Claims (21)

A substrate and a multilayer structure disposed on the substrate,
The multilayer structure includes a lower electrode and an upper electrode, and a resistance change layer disposed between the lower electrode and the upper electrode,
There are two or more states with different electrical resistance values between the lower electrode and the upper electrode,
A resistance change element that changes from one state selected from the two or more states to another state by applying a driving voltage or current between the lower electrode and the upper electrode,
The multilayer structure further includes conductive first and second oxygen barrier films that sandwich the layer so as to be in contact with the variable resistance layer,
The resistance change layer has an altered portion in the vicinity of a side surface, and an area viewed from the stacking direction of the multilayer structure is larger than the lower electrode,
A variable resistance element in which the altered portion does not overlap the lower electrode when viewed from the direction.   The variable resistance element according to claim 1, wherein the altered portion has a different oxidation state from a portion other than the altered portion in the variable resistance layer. And further including an insulating film disposed in contact with the variable resistance layer,
The resistance change element according to claim 1, wherein the insulating film is a film formed in an oxidizing atmosphere. 4. The variable resistance element according to claim 3, wherein the insulating film is a SiO ₂ film formed by oxidation of TEOS (tetraethylorthosilicate).   The variable resistance element according to claim 1, wherein the lower electrode and the variable resistance layer are similar in shape when viewed from the direction.   The variable resistance element according to claim 5, wherein the shape is a circle or a regular polygon. The shape is a regular polygon;
The resistance change element according to claim 5, wherein the top of the resistance change layer is positioned on a straight line connecting the center and the top of the lower electrode when viewed from the direction.   The variable resistance element according to claim 1, wherein the variable resistance layer and the first and second oxygen barrier films have substantially the same shape as viewed from the direction.   The variable resistance element according to claim 1, wherein the altered portion does not overlap the upper electrode when viewed from the direction.   The method for manufacturing a resistance change element according to claim 1, wherein the first and second oxygen barrier films are made of nitride.   The resistance change element according to claim 10, wherein the nitride is TiAlN.   A resistance change type memory comprising the resistance change element according to claim 1 as a memory element. It is a manufacturing method of the resistance change element according to claim 3,
(I) forming a lower electrode on the substrate;
(II) forming a conductive first oxygen barrier film, a resistance change layer, and a conductive second oxygen barrier film on the lower electrode in order so as to be in contact with each other;
(III) forming an upper electrode on the second oxygen barrier film;
(IV) forming an insulating film in an oxidizing atmosphere so as to be in contact with the variable resistance layer,
In the step (II),
In the variable resistance layer, a portion in the vicinity of the side surface that is altered by the oxidizing atmosphere in the step (IV) includes the lower electrode, the first and second oxygen barrier films, the variable resistance layer, and the upper electrode. A method of manufacturing a resistance change element, wherein the resistance change layer having an area viewed from the direction larger than that of the lower electrode is formed so as not to overlap with the lower electrode when viewed from a body stacking direction. In the step (IV),
Wherein as the insulating film, the manufacturing method of the variable resistance element according to claim 13, by oxidizing the TEOS (tetraethylorthosilicate) to form a SiO ₂ film.   The method of manufacturing a resistance change element according to claim 13, wherein, in the step (II), the resistance change layer having a shape viewed from the direction similar to the lower electrode is formed.   The method of manufacturing a resistance change element according to claim 15, wherein the shape is a circle or a regular polygon. The shape is a regular polygon;
The method of manufacturing a resistance change element according to claim 15, wherein the resistance change layer is formed so that an apex of the resistance change layer is positioned on a straight line connecting a center and an apex of the lower electrode when viewed from the direction. .   14. The method of manufacturing a resistance change element according to claim 13, wherein, in the step (II), the first and second oxygen barrier films having substantially the same shape as viewed from the direction and the resistance change layer are formed. In the step (III),
The method of manufacturing a resistance change element according to claim 13, wherein the upper electrode is formed such that a portion in the vicinity of the side surface of the resistance change layer does not overlap the upper electrode when viewed from the direction.   The method of manufacturing a resistance change element according to claim 13, wherein in the step (II), the first and second oxygen barrier films made of nitride are formed.   The method for manufacturing a resistance change element according to claim 20, wherein the nitride is TiAlN.

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