JP2008060091A - Variable resistance element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resistance change element which shows stable operation even at 200 ° C.
An upper electrode (14) and a lower electrode (12) electrically connected to a resistance change layer (13) made of an oxide containing praseodymium (Pr), calcium (Ca), and manganese (Mn) are provided. A resistance change element that changes the resistance of the resistance change layer (13) by applying an electric pulse between the upper electrode (14) and the lower electrode (13),
A variable resistance element having an oxygen deficient layer (25) between the variable resistance layer (13) and at least one of the upper electrode (14) and the lower electrode (12).
[Selection] Figure 2

Description

  The present invention relates to a resistance change element used in a nonvolatile memory or the like.

  The current non-volatile memory is represented by flash memory and is applied to many electronic devices. However, flash memory has problems such as a slow write / erase speed and a high write voltage.

  A conventional memory is not limited to a flash memory, and a memory that performs a switching operation by changing a charge capacity C is mainly used. However, there is an increasing demand for miniaturization of these functional elements because of the influence of the spread of portable information terminals and the deflation of electronic component prices.

  In the conventional charge storage type memory, the charge capacity C is reduced. In order to avoid this, various devices have been studied. However, there are concerns about future technical failures. . Therefore, it is urgently required to develop next-generation nonvolatile memory that solves these drawbacks.

Recently, a perovskite oxide material represented by a chemical formula of Pr _0.7 Ca _0.3 MnO ₃ is sandwiched between an upper electrode and a lower electrode, and a current or an electric current between the upper electrode 14 and the lower electrode 12 is used. There has been reported a phenomenon in which the resistance value of the Pr _0.7 Ca _0.3 MnO ₃ 13 sandwiched between these electrodes by applying a voltage shows a change of two digits at room temperature, and the nonvolatile resistance using this resistance change phenomenon A change memory has been proposed (Patent Document 1).

The memory using such resistance change can overcome the problems such as slow write / erase speed and high write voltage, which are problems in the flash memory, and also the change in the electric resistance R instead of the charge capacity C. Therefore, it is expected to be used as a next-generation non-volatile memory because there is no limit to miniaturization without being restricted by the charge capacity.
US Pat. No. 6,204,139 Ignatiev et al. In Proceedings of 15h International Symposium on Integrated Ferroelectronics (ISIF 2003) p. 5 84-585 (2003)

However, in a conventional configuration having a configuration in which a Pr _0.7 Ca _0.3 MnO ₃ layer 13 (hereinafter referred to as a resistance change layer) is sandwiched between a lower electrode 12 and an upper electrode 14 on a substrate 11 as shown in FIG. There is a problem that memory characteristics deteriorate from a temperature around 100 ° C. For example, in the report by Ignashev et al. In Cited Document 1, deterioration in memory characteristics such as a decrease in the rate of change in resistance from around 100 ° C. can be seen.

  In electronic components such as memories that have come to be adopted in all functional fields, the influence of instability of operation on products is significant. Since memory has a wide variety of uses, its operation is required to be stable even when the ambient temperature rises. The high temperature (heat resistance) test method by JIS (JIS C 0021) is also used. Is required. Therefore, in the conventional configuration in which the memory characteristics deteriorate from a temperature around 100 ° C., a serious problem remains in practical use as an electronic component.

  The variable resistance element according to the present invention that solves the above problems includes an upper electrode and a lower electrode that are electrically connected to a variable resistance layer made of an oxide containing praseodymium (Pr), calcium (Ca), and manganese (Mn). A resistance change element that changes the resistance of the variable resistance layer by applying an electric pulse between the upper electrode and the lower electrode, and includes the variable resistance layer, the upper electrode, and the lower electrode. An oxygen deficient layer is provided between at least one of them.

  Provided is a variable resistance element that exhibits stable operation even at 200 ° C. as compared with a conventional configuration, which has conventionally been unstable at 200 ° C. Therefore, a more practical resistance change element can be provided as compared with the resistance change element having the conventional configuration.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
As shown in FIG. 2, after the lower electrode 12 is first disposed on the substrate 11, the resistance change layer 13 is disposed on the lower electrode 12, and the oxygen deficient layer 25 is formed on the surface of the resistance change layer 13. . Next, the resistance change element of the present invention can be configured by disposing the upper electrode 14 on the oxygen deficient layer 25. As shown in FIG. 5, the oxygen deficient layer 25 may be formed at the interface between the resistance change layer 13 and the lower electrode 12.

The (Pr, Ca) MnO ₃ to be the resistance change layer 13 can be formed using an RF magnetron sputtering method. Specifically, the growth temperature is 600 ° C. to 900 ° C., the sputtering input power is 60 W to 100 W, the atmospheric gas is a mixed gas of oxygen and argon, and the gas partial pressure ratio is O ₂ /Ar=0.2 to 0.5. The atmospheric gas pressure is 1 Pa to 5 Pa. In addition to the RF magnetron sputtering method, pulsed laser deposition (PLD), ion beam deposition (IBD), cluster ion beam or sputtering method such as DC, ECR, helicon, ICP or counter target, MBE, ion plating method It is possible to create by a PVD (Physical Vapor Deposition) method, a CVD (Chemical Vapor Deposition) method, a plating method, a metal organic compound deposition method (MOD: Metallic Deposition), a sol-gel method, or the like.

The lower electrode 12 may be a conductive material as long as the variable resistance layer 13 can be disposed on the lower electrode 12. Examples include platinum (Pt) and iridium (Ir), and examples of oxide materials include those in which Nb, Cr, and La are partly contained in SrTiO ₃ and conductive oxides such as SrRuO ₃ . These are preferable because they have a crystal structure similar to (Pr, Ca) MnO ₃ which is the resistance change layer 13.

  The material used for the upper electrode 14 may be any conductive material. Examples include silver (Ag), gold (Au), platinum (Pt), ruthenium (Ru), iridium (Ir), aluminum (Al), copper (Cu), tantalum (Ta), tin-doped indium oxide ( ITO) and the like are preferable.

  In addition to the RF magnetron sputtering method, the deposition method of the upper electrode 14 and the lower electrode 12 includes pulsed laser deposition (PLD), ion beam deposition (IBD), cluster ion beam or DC, ECR, helicon, ICP or facing. Sputtering methods such as targets, MBE, ion plating, and other PVD (Physical Vapor Deposition) methods, CVD (Chemical Vapor Deposition) methods, plating methods, metal organic compound deposition (MOD) and sol-gel methods. Can be created.

  Next, a method for creating the oxygen deficient layer 25 in the present invention will be described. For example, the following methods a) to c) can be used to create the oxygen deficient layer 25. (A) A method of reverse sputtering the surface of the resistance change layer 13, (b) a method of adjusting the oxygen partial pressure during deposition of the resistance change layer 13, and (c) under an inert gas atmosphere typified by a nitrogen atmosphere. For example, a method of annealing the surface of the resistance change layer 13 may be used.

  (A) In the case where the oxygen deficient layer 25 is formed on the surface of the resistance change layer 13 using the reverse sputtering method, the resistance change layer 13 is deposited on the lower electrode 12 disposed on the substrate 11 and then the resistance change layer. 13 Surface is reverse-sputtered at room temperature to 300 ° C. That is, the resistance change layer 13 deposited on the lower electrode 12 is used as a target, sputtering power is 40 W to 80, a reducing gas such as hydrogen is used as the sputtering gas, and the atmospheric gas pressure is 1 Pa to 10 Pa. . The surface of the resistance change layer 13 is physically etched with ions, and oxygen desorption is severe, so that an oxygen deficient layer 25 is generated on the surface of the resistance change layer 13. After the reverse sputtering, the upper electrode 14 is deposited.

  (B) Next, when the oxygen deficient layer 25 is formed by adjusting the oxygen atmosphere gas when depositing the variable resistance layer 13, it is created by temporarily reducing the oxygen partial pressure at the location where the oxygen deficient layer 25 is to be formed. I can do it. Specifically, after the lower electrode 12 is disposed on the substrate 11, the resistance change layer 13 is deposited. For deposition of the resistance change layer 13 using the RF magnetron sputtering method, the gas partial pressure ratio O2 / Ar of argon and oxygen is fixed to about 0.2 to 0.5. Deposition is performed by reducing the gas partial pressure ratio to 0.04 to 0.1. After the oxygen deficient layer 25 is deposited, the upper electrode 14 is disposed.

  (C) In the case where the surface of the resistance change layer 13 is annealed in a nitrogen atmosphere, first, the lower electrode 12 is disposed on the substrate 11, the resistance change layer 13 is deposited, and then 1 is used for rapid heat treatment. After heating to 500 ° C. to 600 ° C. for 3 minutes and maintaining for 3 minutes, the heater was turned off and rapidly cooled. As a result, the oxygen deficient layer 25 can be formed on the surface of the resistance change layer 13, and the upper electrode 14 is deposited after annealing.

  Next, an element for actually measuring memory characteristics is created by the following method.

  As shown in FIG. 3A, the lower electrode 12 is disposed on the substrate 11, and an insulating oxide film 36 such as SiO 2 is deposited on the lower electrode 12 (FIG. 3B). Next, a contact hole 38 for contact with the lower electrode 12 is created (FIG. 3C), and the resistance change layer 13 is deposited on the lower electrode 12 to fill the contact hole 38 (FIG. 3D). If necessary, the surface is planarized (CMP treatment or the like) (FIG. 3E), and the oxygen deficient layer 25 is formed on the surface of the resistance change layer 13 using such a method (FIG. 3). (F)) The upper electrode 14 is provided so as to constitute a desired memory element, thereby realizing the memory element (FIG. 3G).

  Instead of the method shown in FIG. 3, a lower electrode 12 is arranged on a substrate 11 as shown in FIG. 4A, and a resistance change layer 13 is deposited on the lower electrode 12 (FIG. 4B). . Next, the oxygen deficient layer 25 is formed on the surface of the resistance change layer 13 by the method described above (FIG. 4C). Further, the upper electrode 14 is formed on the oxygen deficient layer 25 (FIG. 4D), and a resist material 37 is disposed (FIG. 4E). The upper electrode 14, the oxygen deficient layer 25, the resistance change layer 13, and the lower electrode 12 that are not covered with the resist material 37 are removed by ion milling or the like. Thereafter, an insulating film 36 is deposited (FIG. 4G). Finally, the memory element can be realized by removing the insulating film 36 and the resist material 37 positioned thereon by a lift-off method or the like (FIG. 4H).

  Alternatively, as shown in FIG. 6, the lower electrode 12 is disposed on the substrate 11 (FIG. 6A), and an insulating film 36 such as SiO 2 is deposited on the lower electrode 12 (FIG. 6B). Next, a contact hole 38 for making contact with the lower electrode 12 is formed (FIG. 6C), an oxygen deficient layer 25 is first formed thereon, and a resistance change layer is formed on the oxygen deficient layer 25. 13 is deposited to fill the contact hole 38 (FIG. 6D), and if necessary, the surface is flattened (CMP treatment or the like) (FIG. 6E) to form a desired memory element. Is provided with an upper electrode 14 to realize a memory element (FIG. 6F).

Here, the insulating film 36 is preferably made of an insulating material such as SiO ₂ or Al ₂ O ₃ in order to separate the upper electrode 14 and the lower electrode 12 (lower wiring and upper wiring). It may be a laminated body. A resist material is also preferable because it can be easily formed by spinner coating or the like and can be formed flat on an uneven surface.

  For forming each layer of the lower electrode 12, the resistance change layer 13, the upper electrode 14, and the insulating layer 25, which are each layer, pulse laser deposition (PLD), ion beam deposition (IBD), cluster ion beam or RF, Sputtering methods such as DC, ECR, helicon, ICP or counter target, PVD (Physical Vapor Deposition) methods such as MBE, ion plating method, CVD (Chemical Vapor Deposition) method, MOCVD (Metal Organic ChemistryDepth) It can be manufactured by a method, a plating method, a metal organic compound deposition method (MOD: Metallographic Decomposition) or a sol-gel method.

  As microfabrication, physical processes such as semiconductor processes, ion milling used in magnetic device manufacturing processes such as GMR, TMR magnetic heads, and magnetic memories (MRAM), RIE (Reactive Ion Etching), FIB (Focused Ion Beam), etc. This can be achieved by combining a photolithography technique using a stepper, an EB (Electron Beam) method, or the like for forming a fine pattern. It is also effective to use CMP (Chemical Mechanical Polishing) or cluster ion beam etching for planarizing the surface of films such as interlayer insulating layers and conductive layers.

  Next, writing and reading of the variable resistance element of this configuration will be described. By applying a current or a voltage between the upper electrode 14 and the lower electrode 12, the resistance value of the resistance change layer 13 changes. The application of current or voltage is preferably performed by pulses. By applying a pulse to the lower electrode 12 with the upper electrode 14 having a positive bias, the resistance change layer 13 changes from a high resistance to a low resistance, and the change in resistance value is reversed by reversing the polarity of the pulse. It can be made.

  The resistance change of the resistance change element is measured by applying a pulse voltage between the lower electrode 12 and the upper electrode 14 using a pulse generator. The voltage used for reading the resistance change is a sufficiently small voltage of about 1/1000 to 1/4 with respect to the write voltage to the resistance change element. For example, a voltage having a pulse voltage of 5 V and a pulse width of 250 nsec is used. In order to read out the resistance value, a pulse voltage having a pulse voltage of 0.1 V and a pulse width of 250 nsec is used, and a change in the current value at that time is read out.

  The rate of change in resistance (%) is defined by (Rmax−Rmin) / Rmin × 100, and Rmax and Rmin are respectively obtained as applied voltage / applied current. In the present invention, this resistance change rate is preferably 600% or more.

  Further, the resistance change is read out from 75 ° C. to 200 ° C. in a thermostat, the temperature is changed every 25 ° C., and the resistance change is read out after holding the target temperature for 15 minutes.

(Example 1)
In Example 1, an element having the configuration shown in FIG. 2 was prepared by the method shown in FIG. 3, and the memory characteristics were measured. First, the lower electrode 12 was produced on the board | substrate 11 which consists of MgO using RF magnetron sputtering method. As a material, Pt was used to deposit 200 nm, forming conditions were room temperature, sputtering input power was 80 W, atmospheric gas was argon gas, and the gas pressure during growth was 1 Pa (FIG. 3A).

Subsequently, an SiO ₂ film was formed as the insulating film 36 by using an RF magnetron sputtering method (FIG. 3B). The substrate temperature was 100 ° C., the sputtering input power was 100 W, the atmosphere gas was argon, and the atmosphere gas pressure was 0.1 Pa.

  Next, for contact with the lower electrode 12 of the resistance change layer 13, a contact hole 38 having a diameter of 0.5 μm was formed using RIE (FIG. 3C).

On the contact hole 38, Pr _0.7 Ca _0.3 MnO _{3 serving} as the resistance change layer 13 was deposited by 300 nm by RF magnetron sputtering (FIG. 3D). The sputtered target was an oxide composed of praseodymium, calcium, and manganese and represented by the chemical formula Pr _0.7 Ca _0.3 MnO ₃ . The RF magnetron sputtering method is used for deposition, the sputtering input power is 80 W, the substrate temperature is 700 ° C., the growth gas pressure is 3 Pa, and the atmosphere gas is a mixture of oxygen and argon in a ratio of O ₂ / Ar to 0.25. Gas was used. Pr _0.7 Ca _0.3 MnO ₃ was a polycrystalline film as a result of X-ray diffraction.

  After filling the contact hole 38, CMP was performed (FIG. 3E), and the oxygen deficient layer 25 was formed on the surface of the resistance change layer 13 by reverse sputtering the surface (FIG. 3F). The reverse sputtering was performed using an RF magnetron sputtering method under the conditions that the sputtering input power was 40 W at 300 ° C., the atmosphere gas was hydrogen gas, and the atmosphere gas pressure was 5 Pa. In addition, by performing reverse sputtering with the applied voltage frequency set to 100 MHz, an element exhibiting extremely stable memory operation could be produced.

  On top of this, 50 nm of Ag was formed by the magnetron sputtering method as the upper electrode 14. The upper electrode 14 was at room temperature, the sputtering input power was 80 W, the atmosphere gas was argon, and the gas pressure during growth was 1 Pa (FIG. 3G). The memory characteristics of the variable resistance element configured by the above method were measured.

  As a comparative example, a variable resistance element having the same configuration as in FIG. Except for the oxygen deficient layer 25, it was formed under the same conditions as in Example 1, and the structure of the insulating film 36 and the like was also formed in the same manner.

  In order to investigate the difference in memory operation when the depth of the oxygen deficient layer 25 differs from the interface between the oxygen deficient layer 25 and the upper electrode 14 toward the substrate 11, the reverse sputtering time is adjusted to 100 to 200 seconds, Elements having different depths of the oxygen deficient layer 25 in the direction of the substrate 11 were also produced.

  Next, in order to confirm the memory characteristics of Example 1 and Comparative Example A, the resistance change was measured by the following procedure. First, the elements of Example 1 and Comparative Example A were placed in a thermostatic bath, the temperature was raised from 75 ° C. to 200 ° C., and the resistance change was measured every 25 ° C. The resistance change was measured according to the following procedure. The resistance change of the resistance change element was measured by applying a pulse voltage between the lower electrode 12 and the upper electrode 14 using a pulse generator. To change from high resistance to low resistance and from low resistance to high resistance, the resistance is switched using a voltage of 5V and a pulse width of 250nsec, and a resistance value is read out by a pulse having a pulse voltage of 0.1V and a pulse width of 250nsec. Using voltage, the change in current value at that time was read out. The rate of change in resistance (%) was defined by (Rmax−Rmin) / Rmin × 100, and Rmax and Rmin were respectively determined as applied voltage / applied current. The results are shown in Table 1 below.

本実施例に基づいて作成した素子のメモリ特性を測定した結果、逆スパッタリングを１００秒施した素子の抵抗変化率が最も大きく、２００℃まで安定したメモリ特性を示し、逆スパッタリング時間を２００秒と長くすると抵抗変化は小さくなるが２００℃まで安定した動作を示した。

As a result of measuring the memory characteristics of the element produced based on this example, the resistance change rate of the element subjected to reverse sputtering for 100 seconds was the largest, and showed stable memory characteristics up to 200 ° C., and the reverse sputtering time was 200 seconds. The longer the resistance, the smaller the change in resistance, but it showed stable operation up to 200 ° C.

  On the other hand, Comparative Example A having no oxygen deficient layer 25 showed a large resistance change at 25 ° C., but a remarkable deterioration in the resistance change rate was observed at temperatures of 100 ° C. and 200 ° C. From these results, it seems that it is preferable to form the oxygen deficient layer 25 as thin as possible on the surface of the resistance change layer 13. Further, in the present example, when the experiment was carried out by changing the reverse sputtering temperature, input power, atmospheric gas pressure, etc. as the formation conditions of the oxygen deficient layer 25, the same results could be obtained.

(Example 2)
In Example 2, an element having the configuration shown in FIG. 2 was prepared as shown in FIG. 4, and the memory characteristics were measured.

  First, a variable resistance element was formed on a substrate 11 made of Si as follows. The lower electrode 12 was disposed by magnetron sputtering. Pt was used as the material to deposit 200 nm, the production conditions were room temperature, sputtering input power was 80 W, the atmosphere gas was argon, and the gas pressure was 1 Pa (FIG. 4A).

Subsequently, Pr _0.7 Ca _0.3 MnO ₃ to be the resistance change layer 13 was deposited by 300 nm by RF magnetron sputtering (FIG. 4B). The target to be sputtered was an oxide composed of praseodymium, calcium, and manganese and represented by the chemical formula Pr _0.7 Ca _0.3 MnO ₃ . In the actual deposition, the substrate temperature was 700 ° C., the sputtering input power was 80 W, the atmospheric gas was a gas in which oxygen and argon were mixed at a ratio of O 2 / Ar to 0.25, and the atmospheric gas pressure was 3 Pa. Thereafter, the oxygen deficient layer 25 was formed by reducing the oxygen / argon mixing ratio O ₂ / Ar. Further, by changing the mixing ratio O ₂ / Ar from 0.08 to 0.1, elements having different oxygen amounts in the portion where oxygen was lost were prepared. Pr _0.7 Ca _0.3 MnO ₃ was a polycrystalline film as a result of X-ray diffraction.

  Further thereon, an upper electrode 14 was made of 50 nm Ag by magnetron sputtering (FIG. 4D). The upper electrode 14 was at room temperature, the sputtering input power was 80 W, the atmosphere gas was argon gas, and the gas pressure during growth was 1 Pa.

Next, a resist material 37 is disposed on the upper electrode 14, and the upper electrode 14, the oxygen deficient layer 25, the resistance change layer 13, and the upper electrode 12 that are not covered with the resist material 37 are removed by ion milling ( 4 (f)), an SiO ₂ film to be the insulating film 36 was deposited by magnetron sputtering (FIG. 4 (g)). Sputtering was performed at a substrate temperature of 100 ° C., argon was used as the atmospheric gas, and the atmospheric gas pressure was 0.1 Pa. Finally, the resist material 37 and the insulator 36 located thereon were removed using a lift-off method (FIG. 4 (h)). The memory characteristics of the variable resistance element of Example 2 were measured using the configuration created by the above procedure.

  As a comparative example, a variable resistance element having a conventional configuration was created and used as comparative example B. Except for the oxygen deficient layer 25, it was formed under the same conditions as in Example 1 above, and the configuration and preparation method of the insulating film 36 and the like were also prepared in the same manner. Further, in order to investigate the difference in memory operation when the amount of oxygen in the oxygen deficient layer 25 is different, an element was produced by reducing the oxygen gas partial pressure ratio when forming the oxygen deficient layer 25.

  Next, in order to confirm the memory characteristics of the example and the comparative example B, the resistance change was measured by the following procedure. First, the elements of Example 2 and Comparative Example B were put in a thermostatic bath, the temperature was raised from 75 ° C. to 200 ° C., and the resistance change was measured every 25 ° C. The resistance change was measured according to the following procedure. The resistance change of the resistance change element was measured by applying a pulse voltage between the lower electrode 12 and the upper electrode 14 using a pulse generator. To change from high resistance to low resistance and from low resistance to high resistance, the resistance is switched using a voltage of 5V and a pulse width of 250nsec, and a resistance value is read out by a pulse having a pulse voltage of 0.1V and a pulse width of 250nsec. Using voltage, the change in current value at that time was read out. The rate of change in resistance (%) was defined by (Rmax−Rmin) / Rmin × 100, and Rmax and Rmin were respectively determined as applied voltage / applied current. The results are shown in Table 2 below.

抵抗変化率の測定結果である表２について説明する。酸素欠損層２５の作成時に用いた酸素分圧比Ｏ２／Ａｒを変えた場合の抵抗変化率を２５℃、１００℃、２００℃とそれぞれの温度について測定した。比較例Ｂは比較例Ａと同様にして２５℃においては大きな抵抗変化率を示すものの１００℃、２００℃の温度では抵抗変化率に著しい劣化が見られた。一方、Ｏ２／Ａｒが０．０８及び０．１の実施例においては２５℃から２００℃に至るまで大きく安定した抵抗変化率が見られた。

Table 2 which is a measurement result of the resistance change rate will be described. The resistance change rate when the oxygen partial pressure ratio O2 / Ar used when the oxygen deficient layer 25 was formed was measured at each temperature of 25 ° C., 100 ° C., and 200 ° C. In the same manner as Comparative Example A, Comparative Example B showed a large rate of change in resistance at 25 ° C., but significant deterioration was observed in the rate of change in resistance at temperatures of 100 ° C. and 200 ° C. On the other hand, in the examples where O2 / Ar was 0.08 and 0.1, a large and stable resistance change rate was observed from 25 ° C to 200 ° C.

(Example 3)
In Example 3, an element having the configuration shown in FIG. 5 was prepared by the method shown in FIG. 6, and the memory characteristics were measured. FIG. 5 is a diagram showing a configuration in which an oxygen deficient layer 25 is formed between the resistance change layer 13 and the lower electrode 12, and the upper electrode 14 is disposed on the resistance change layer 13. A method for producing the variable resistance element according to Example 3 will be described with reference to FIG.

  A resistance change element was formed on the substrate 11 made of MgO by using a magnetron sputtering method. The lower electrode 12 is made of Pt and deposited to a thickness of 200 nm, the production conditions are room temperature, the sputtering input power is 80 W, the atmosphere gas is argon gas, and the growth gas pressure is 1 Pa (FIG. 6). (A)).

Subsequently, a SiO ₂ film was formed as the insulating film 36 by using a magnetron sputtering method (FIG. 6B). The substrate temperature was 100 ° C., the sputtering input power was 100 W, the atmosphere gas was argon, and the atmosphere gas pressure was 0.1 Pa. Next, for contact with the lower electrode 12, a contact hole 38 having a diameter of 0.5 μm was formed using RIE (FIG. 6C). First, an oxygen deficient layer 25 is formed in this contact hole by using an RF magnetron sputtering method. As conditions, the substrate temperature was 700 ° C., the sputtering input power was 80 W, the atmosphere gas was a gas in which oxygen and argon were mixed at a ratio of O ₂ / Ar to 0.1, and the atmosphere gas pressure during growth was 3 Pa. Thereafter, oxygen and argon were returned to O ₂ / Ar to 0.25, and Pr _0.7 Ca _0.3 MnO _{3 serving} as the resistance change layer 13 was deposited to a thickness of 300 nm (FIG. 6D). The target to be sputtered was an oxide composed of praseodymium, calcium, and manganese and represented by the chemical formula Pr _0.7 Ca _0.3 MnO ₃ . The prepared Pr _0.7 Ca _0.3 MnO ₃ was a polycrystalline film as a result of X-ray diffraction. Then, after filling the contact hole 38, CMP processing was performed (FIG. 6- (e)), and 50 nm of Ag was formed thereon by magnetron sputtering. The upper electrode 14 was at room temperature, the sputtering input power was 80 W, the atmosphere gas was argon gas, and the gas pressure during growth was 1 Pa (FIG. 6G). With the above configuration, the memory characteristics of the variable resistance element of Example 3 were measured.

  In Example 3, Comparative Example C was prepared in the same manner as Example 1. The preparation conditions and configuration of Comparative Example C are the same as those of Comparative Example C in Example 3 except for the oxygen deficient layer 25.

  Next, in order to confirm the memory characteristics of Example 3 and Comparative Example C, resistance change was measured by the following procedure. First, the elements of Example 3 and Comparative Example C were placed in a thermostatic bath, the temperature was raised from 75 ° C. to 200 ° C., and the resistance change was measured every 25 ° C. The resistance change was measured according to the following procedure. The resistance change of the resistance change element was measured by applying a pulse voltage between the lower electrode 12 and the upper electrode 14 using a pulse generator. To change from high resistance to low resistance and from low resistance to high resistance, the resistance is switched using a voltage of 5V and a pulse width of 250nsec, and a resistance value is read out by a pulse having a pulse voltage of 0.1V and a pulse width of 250nsec. Using voltage, the change in current value at that time was read out. The rate of change in resistance (%) was defined by (Rmax−Rmin) / Rmin × 100, and Rmax and Rmin were respectively determined as applied voltage / applied current. The results are shown in Table 3 below.

実施例３における構成のメモリ特性を測定した結果、比較例Ｃの抵抗変化素子は２００℃の温度においてメモリ特性の明らかな劣化が見られた。一方、実施例３の構成を有する抵抗変化素子では２００℃においても抵抗変化率６００％以上であり、室温と同様の安定したメモリ特性が得られた。

As a result of measuring the memory characteristics of the configuration in Example 3, the resistance change element of Comparative Example C showed a clear deterioration in memory characteristics at a temperature of 200 ° C. On the other hand, the resistance change element having the configuration of Example 3 had a resistance change rate of 600% or more even at 200 ° C., and stable memory characteristics similar to those at room temperature were obtained.

Example 4
An element having the same configuration as in Example 2 was formed by the method shown in FIG. 4, and the memory characteristics were measured.

  First, a variable resistance element was formed on a substrate 11 made of Si as follows. The lower electrode 12 was disposed by magnetron sputtering. Pt was used as the material and deposited to 200 nm, the preparation conditions were room temperature, the sputtering input power was 80 W, the atmosphere gas was argon gas, and the growth gas pressure was 1 Pa (FIG. 4A).

Subsequently, Pr _0.7 Ca _0.3 MnO ₃ to be the resistance change layer 13 was deposited by 300 nm by RF magnetron sputtering (FIG. 4B). The target to be sputtered was an oxide composed of praseodymium, calcium, and manganese and represented by the chemical formula Pr0.7Ca0.3MnO3. When actually depositing, the substrate temperature is 700 ° C., the sputtering input power is 80 W, the atmospheric gas is a gas in which oxygen and argon are mixed at a ratio of O 2 / Ar to 0.25, and the atmospheric gas pressure during growth is 3 Pa. It was. Pr0.7Ca0.3MnO3 was a polycrystalline film as a result of X-ray diffraction.

  Thereafter, in order to form the oxygen deficient layer 25, the element having the resistance change layer 13 was subjected to rapid heat treatment in a nitrogen atmosphere. First, the element was heated to 500 ° C. in 1 minute and maintained for 3 minutes, and then the heater was turned off and rapidly cooled. As a result, the oxygen deficient layer 25 could be created on the surface (FIG. 4C).

  Further thereon, an upper electrode 14 was made of 50 nm Ag by magnetron sputtering (FIG. 4D). The upper electrode 14 was at room temperature, the sputtering input power was 80 W, the atmosphere gas was argon gas, and the gas pressure during growth was 1 Pa.

Next, a resist material 37 is disposed on the upper electrode 14, and after cutting the upper electrode 14, the oxygen deficient layer 25, the resistance change layer 13, and the lower electrode 12 that are not covered with the resist material 37 using ion milling, A SiO ₂ film to be the insulating film 36 was deposited by using a magnetron sputtering method (FIG. 4G). The substrate temperature was 100 ° C., the sputtering power was 100 W, the atmosphere gas was argon, and the atmosphere gas pressure was 0.1 Pa. Finally, the resist material 37 and the insulator 36 located thereon were removed using a lift-off method (FIG. 4 (h)). The memory characteristics of the variable resistance element of Example 4 were measured using the configuration created by the above procedure.

  As a comparative example, a variable resistance element having a conventional configuration was created and used as comparative example D. This Comparative Example D was prepared under the same conditions as in Example 1 except for the oxygen deficient layer 25, and the configuration and preparation method of the insulating film 36 and the like were also prepared in the same manner.

  Next, in order to confirm the memory characteristics of Example 4 and Comparative Example D, the resistance change was measured by the following procedure. First, the elements of Example 4 and Comparative Example D were placed in a thermostatic bath, the temperature was raised from 75 ° C. to 200 ° C., and the resistance change was measured every 25 ° C. The resistance change was measured according to the following procedure. The resistance change of the resistance change element was measured by applying a pulse voltage between the lower electrode 12 and the upper electrode 14 using a pulse generator. To change from high resistance to low resistance and from low resistance to high resistance, the resistance is switched using a voltage of 5V and a pulse width of 250nsec, and a resistance value is read out by a pulse having a pulse voltage of 0.1V and a pulse width of 250nsec. Using voltage, the change in current value at that time was read out. The rate of change in resistance (%) was defined by (Rmax−Rmin) / Rmin × 100, and Rmax and Rmin were respectively determined as applied voltage / applied current. The results are shown in Table 4 below.

抵抗変化率の測定結果である表４について説明する。酸素欠損層２５の作成した素子の抵抗変化率と作成しない素子の抵抗変化率を２５℃、１００℃、２００℃とそれぞれの温度について測定した。比較例Ｄは比較例Ａと同様に２５℃においては大きな抵抗変化率を示すものの１００℃、２００℃の温度では抵抗変化率に著しい劣化が見られた。熱処理した素子においては２５℃、１００℃、２００℃において大きく安定した抵抗変化率が見られた。

Table 4 which is a measurement result of the resistance change rate will be described. The resistance change rate of the element formed with the oxygen deficient layer 25 and the resistance change rate of the element not formed were measured at 25 ° C., 100 ° C., and 200 ° C., respectively. As in Comparative Example A, Comparative Example D showed a large resistance change rate at 25 ° C., but the resistance change rate was significantly deteriorated at temperatures of 100 ° C. and 200 ° C. In the heat-treated element, a large and stable resistance change rate was observed at 25 ° C., 100 ° C., and 200 ° C.

The variable resistance element according to the present invention includes a variable resistance layer 13 represented by a chemical formula (Pr _, Ca) MnO _3, and an upper electrode 14 and a lower electrode 12 sandwiching the variable resistance layer 13. The resistance value of the resistance change layer 13 is changed by applying a voltage or a current to the component, and the resistance value of the resistance change layer 13 is retained, so that the oxygen deficient layer 25 is formed at the interface of the resistance memory. Since a stable operation can be obtained even after passing through 200 ° C., it can be used as a practical nonvolatile memory.

The following summarizes the present invention:
1.
An upper electrode (14) and a lower electrode (12) electrically connected to a resistance change layer (13) made of an oxide containing praseodymium (Pr), calcium (Ca), and manganese (Mn), A resistance change element that applies an electric pulse between an electrode (14) and the lower electrode (13) to change the resistance of the resistance change layer (13);
A variable resistance element having an oxygen deficient layer (25) between the variable resistance layer (13) and at least one of the upper electrode (14) and the lower electrode (12).

2.
Item 2. The variable resistance element according to Item 1, wherein an oxygen deficient layer (25) is provided between the variable resistance layer (13) and the upper electrode (14). (Figure 2)
3.
Item 2. The variable resistance element according to Item 1, wherein an oxygen deficient layer (25) is provided between the variable resistance layer (13) and the lower electrode (12). (Fig. 5)
4).
The variable resistance element according to Item 1, wherein an oxygen deficient layer (25) is provided between the variable resistance layer (13) and both the upper electrode (14) and the lower electrode (12).

5.
A lower electrode forming step for forming the lower electrode (12);
A variable resistance layer forming step of forming a variable resistance layer (13) made of an oxide containing praseodymium (Pr), calcium (Ca), and manganese (Mn) on the surface of the lower electrode (12);
Resistance change, comprising a reverse sputtering step of reverse sputtering the surface of the variable resistance layer (13) and an upper electrode formation step of forming an upper electrode (14) on the surface of the reverse-sputtered variable resistance layer (13). Device manufacturing method.

6).
Item 6. The method for manufacturing a resistance change element according to Item 5, wherein the oxygen deficient layer (25) is formed by the reverse sputtering.

7).
A lower electrode forming step for forming the lower electrode (12);
A resistance change layer forming step of forming a resistance change layer (13) made of an oxide containing praseodymium (Pr), calcium (Ca), and manganese (Mn) on the surface of the lower electrode (12) in an oxygen atmosphere;
An upper electrode forming step of sequentially forming an upper electrode (14) on the surface of the variable resistance layer (13);
A method of manufacturing a resistance change element, wherein, in the resistance change layer forming step, the oxygen concentration is reduced when forming a portion to be a surface of the resistance change layer (13).

8).
Item 8. The method for manufacturing a resistance change element according to Item 7, wherein the surface of the variable resistance layer (13) formed when the oxygen concentration is reduced becomes an oxygen deficient layer (25).

9.
A lower electrode forming step for forming the lower electrode (12);
A resistance change layer forming step of forming a resistance change layer (13) made of an oxide containing praseodymium (Pr), calcium (Ca), and manganese (Mn) on the surface of the lower electrode (12) in an oxygen atmosphere;
An upper electrode forming step of sequentially forming an upper electrode (14) on the surface of the variable resistance layer (13);
A method of manufacturing a resistance change element, wherein the oxygen concentration is reduced immediately after the start of the resistance change layer forming step.

10.
Item 10. The method for manufacturing a resistance change element according to Item 9, wherein the portion of the resistance change layer (13) formed when the oxygen concentration is reduced becomes an oxygen deficient layer (25).

11.
A lower electrode forming step for forming the lower electrode (12);
A variable resistance layer forming step of forming a variable resistance layer (13) made of an oxide containing praseodymium (Pr), calcium (Ca), and manganese (Mn) on the surface of the lower electrode (12);
An annealing process for annealing the surface of the variable resistance layer (13) in an inert gas atmosphere, and an upper electrode forming process for forming an upper electrode (14) on the surface of the reverse-sputtered variable resistance layer (13) are sequentially performed. A method of manufacturing a resistance change element.

12
Item 12. The method for manufacturing a resistance change element according to Item 11, wherein the oxygen deficient layer (25) is formed by annealing in the inert gas atmosphere.

Schematic configuration diagram of variable resistance element in conventional configuration Configuration schematic diagram of variable resistance element according to an embodiment of the present invention Diagram of a method for creating a memory component of the present invention Diagram of a method for creating a memory component of the present invention Configuration schematic diagram of variable resistance element in Example 2 of the present invention Diagram of a method for creating a memory component of the present invention

Explanation of symbols

11 Substrate 12 Lower electrode 13 Variable resistance layer 14 Upper electrode 25 Oxygen deficient layer 36 Insulating film 37 Resist material 38 Contact hole

Claims (1)

An upper electrode and a lower electrode electrically connected to a resistance change layer made of an oxide containing praseodymium (Pr), calcium (Ca), and manganese (Mn) are provided, and between the upper electrode and the lower electrode A variable resistance element that changes the resistance of the variable resistance layer by applying an electric pulse,
A variable resistance element having an oxygen deficient layer between the variable resistance layer and at least one of the upper electrode and the lower electrode.

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