JP2009065003A - Resistance change element and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable resistance element which includes a current path attainable in a simple and easy step and also can be miniaturized. <P>SOLUTION: A tunnel insulating film 204, a metal nano-particle 206, a variable resistance film 207, and a second electrode 208 are provided on a first electrode 203, thus forming a fine current path at a placement position of the metal nano-particle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a resistance change element using nanoparticles and a method for producing the element using a protein-inorganic nanoparticle composite.

  The resistance change type memory element is expected as one of new nonvolatile memories, but often requires a forming process (a process for initializing element characteristics by applying a high voltage after the element is manufactured). Or there is a problem that the characteristic variation between elements is large. The forming process is considered to be a process of forming a local current path inside the device, and the difference in the state of the formed current path is considered to be a cause of characteristic variation.

  In order to improve this problem, a technique has been reported so far in which a local current path is formed in the element in advance to narrow the current, or a fine structure that triggers the formation of the current path is arranged. .

  Patent Document 1 discloses a structure in which a concave portion or a convex portion is provided at the interface between the resistance change film and the electrode. Further, a structure (FIG. 2) in which metal fine particles are arranged at the upper end of the convex portion is disclosed. According to Patent Document 1, it is possible to reduce the voltage of an electric pulse necessary for resistance change, and it is possible to suppress variations in the width of the electric pulse.

  Patent Document 2 discloses a structure in which a resistance change film is provided between a first electrode and a second electrode provided with nanotips (ultrafine protrusions). Also disclosed is a structure (FIG. 3) in which a different material is provided between the nanotip and the resistance change film. According to Patent Document 2, the characteristics of bipolar switching are promoted, and a weak electric pulse can be used at a low voltage.

  Patent Document 3 discloses a structure in which a resistance change film is provided between two electrodes, and one electrode includes a protruding electrode object. According to Patent Document 3, it is possible to reduce power consumption during writing / erasing, and to form a memory element having a stable switching operation that does not cause writing failure due to low resistance with good reproducibility.

  Non-Patent Document 1 discloses a structure in which an insulating layer (mazelike nanogap insulator) partially having pores is formed on a lower electrode, and a resistance change film and an upper electrode are disposed thereon. According to Non-Patent Document 1, high-speed writing / erasing can be performed without a forming process.

  Although it is different from the current path control, a technology that increases the rate of resistance change and suppresses the variation by increasing the crystal interface region of the variable resistance material and making the crystal size uniform has already been reported. Has been.

  Patent Document 4 discloses a structure in which a variable resistance film and a multilayer film having an electric resistivity different from that of the variable resistance film are alternately stacked. Also disclosed is a structure (FIG. 4) in which crystals of a resistance change film grown using metal particles on an electrode as crystal nuclei are arranged. A structure (FIG. 5) is disclosed in which metal particles (island-like growth nuclei) are disposed on an electrode via a surface tension adjusting film having a tunnel effect. According to Patent Document 4, it is possible to increase the ratio (CER value) of the electrical resistivity between the high resistance state and the low resistance state by disposing a large number of bonding interfaces, and to make the crystal sizes uniform. , Variation in CER value can be suppressed.

  In addition, a technique for combining a resistance change material and a fine particle arrangement using protein has been reported.

Patent Document 5 discloses a structure in which fine particles are arranged on a columnar conductor embedded in a dielectric using ferritin. According to Patent Document 5, reliability related to insulation between the upper and lower electrodes is increased.
International Publication No. 2005/041303 Pamphlet JP 2006-203178 A JP 2007-180473 A JP 2007-180174 A (FIG. 4, FIG. 5, paragraph numbers 0052 to 0072, especially paragraph number 0065) JP 2006-210639 A Ogimoto et al., Appl. Phys. Lett. 90 (2007) 143515

  In order to obtain a large-capacity memory element, it is necessary to arrange a large number of miniaturized uniform variable resistance elements.

  Patent Documents 1-3 and Non-Patent Document 1 show current path narrowing techniques. To obtain a homogeneous and fine structure by these techniques, the following special and high-precision process techniques are required. Is done. Patent Document 1 discloses a technique for providing a concave or convex portion with high accuracy at the interface, Patent Document 2 discloses a nanochip forming technique, Patent Document 3 discloses a protruding electrode object forming technique, and Non-Patent Document 1 includes an insulating layer partially having pores. Forming technology is required. If the accuracy of these process technologies is insufficient, it is difficult to manufacture a miniaturized element. Also, if the reproducibility of nanostructure fabrication is low, the variation between elements increases. For example, the size of the current path reported in Non-Patent Document 1 is about 50 to 100 nm and has an irregular shape, and therefore cannot be applied to a fine element of 100 nm or less.

  Here, Patent Document 1 shows the structure of FIG. According to Paragraph No. 0036 of Patent Document 1, there are convex portions 66 on the surface of the information storage layer 62 formed on the substrate 60 and the lower electrode 61, and the fine particles 64 are upper electrodes on the convex portions 66 of the information storage layer 62. Embedded in 63. The information storage layer 62 has neither a concave portion nor a convex portion on its lower surface 68, but has a convex portion 66 on its upper surface 69. In this example, convex portions 63 b are formed above the fine particles 64 on the surface of the upper electrode 63.

  FIG. 2 shows fine particles 64 used as an etching mask. However, the fine particles 64 are embedded in the upper electrode 63, and according to paragraph number 0037 of Patent Document 1, when the fine particles 64 are a conductive material such as a metal, the fine particles 64 function as a part of the electrode 63. Further, the presence of a tunnel barrier layer which is a constituent element of the present invention is not shown around the fine particles 64. Therefore, in the configuration of FIG. 2, the current confinement effect described in the present invention cannot be obtained.

  Patent Document 2 shows the structure shown in FIG. According to Patent Document 2, the first electrode 102 includes nanotips 104, and the memory cell material 106 exists between the nanotips 104. According to paragraph number 0029 of Patent Document 2, the material 500 is a memory resistor material different from the material 106 or a dielectric having no memory resistance characteristic. In one embodiment, material 500 is crystallized I r.

  Here, it is clear that the material 500 is not a tunnel barrier layer in the present invention, but even if it is assumed that the material 500 is a tunnel barrier layer, the material 500 is disposed between the memory resistance material 106 and the nanochip 104. Therefore, it is different from the structure of the present invention. Therefore, the configuration of FIG. 3 cannot obtain the current confinement effect described in the present invention.

  Patent Document 4 does not disclose a current path narrowing technique. Patent Document 4 also requires a crystal growth technique for a resistance change film from metal particles (island-like growth nuclei) as a highly accurate process technique.

  In the figure showing the process steps of Patent Document 4, the structures of FIGS. 4 and 5 are shown. 4 and 5, an electrode film 12 a is disposed on a semiconductor substrate 11, a metal island crystal nucleus 14, a seed 15 grown from a material constituting the resistance change memory film, a resistance change memory film 13, An electrode film 12b is disposed. In addition to the above, FIG. 5 shows a surface tension adjusting film 16a and an electrode film 12c through which a current can flow by the tunnel effect.

  However, according to paragraph number 0072 of Patent Document 4, island-like growth nuclei 14 and seeds 15 are explicitly depicted in the figure for explanation, but these island-like growth nuclei 14 and seeds 15 are formed by a vacuum film formation method. The same crystal is formed as a part of the resistance change type memory film 13 after being formed. Therefore, in the configurations of FIGS. 4 and 5, the current confinement effect described in the present invention cannot be obtained.

  Patent Document 5 does not disclose a current path narrowing technique. Patent Document 5 also requires a columnar conductor forming technique as a highly accurate process technique.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and aims to provide a variable resistance element having a current path that can be realized by a simple and easy process, and provides a manufacturing method thereof. For the purpose.

  The variable resistance element according to the present invention for solving the above-described problems includes a first electrode, a tunnel barrier layer formed on the first electrode, and a metal nanoparticle having a diameter of 2 nm to 10 nm disposed on the tunnel barrier layer. Particles, a resistance change layer whose resistance changes in accordance with an applied voltage, and a second electrode formed on the resistance change layer, formed on the tunnel barrier layer and the metal nanoparticles.

  It is preferable that the tunnel barrier layer is made of a silicon oxide film and has a thickness of 1 nm to 3 nm.

  A method of manufacturing a variable resistance element according to the present invention that solves the above problems includes a step of forming a tunnel barrier layer on a substrate having a first electrode on a surface thereof, and a metal compound core on the tunnel barrier layer. Arranging a ferritin to be removed, removing the ferritin protein to modify the metal compound core into metal nanoparticles, and applying resistance on the tunnel barrier layer and the metal nanoparticles according to an applied voltage. Forming a variable resistance layer in which the resistance changes, and forming a second electrode on the variable resistance layer.

  It is preferable that the tunnel barrier layer is made of a silicon oxide film and has a thickness of 1 nm to 3 nm.

  According to the variable resistance element of the present invention, it is possible to provide a variable resistance element that has a current path that can be realized by a simple and easy process and can be miniaturized.

  A silicon substrate can be used as the substrate.

  By thermally oxidizing the surface of the silicon substrate, a high-quality silicon oxide film serving as a tunnel barrier layer can be formed.

  Ferritin is a globular protein that contains a metal compound inside. In addition, when a metal compound is not included in the interior and the interior is hollow, it is called “apoferritin”. Apoferritin is composed of 24 protein subunits. As the apoferritin of the present invention, horse-derived apoferritin can be used.

(Embodiment)
First, a method for manufacturing a variable resistance element according to the present invention will be described.

  In this embodiment, as shown in FIGS. 6 and 7, after preparing the substrate 202 having the first electrode 203 on the surface in “Preparation of the substrate having the first electrode” (FIG. 7A). ), A tunnel barrier layer 204 is formed on the first electrode 203 in the “tunnel barrier layer forming step” (FIG. 7B), and a metal compound is formed on the tunnel barrier layer 204 in the “ferritin arrangement step”. Ferritin 205 composed of a core 205a and a protein 205b outside the core 205a is disposed (FIG. 7 (c)), and the protein 205b outside the ferritin 205 is removed in the “protein removal / core modification step” to thereby remove the metal compound. The core 205a is modified into the metal nanoparticles 206 (FIG. 7 (d)), and applied to the tunnel barrier layer 204 and the metal nanoparticles 206 in the “resistance change layer forming step”. Forming a resistance change layer 207 whose resistance changes in accordance with the pressure (FIG. 7E), and forming a second electrode 208 on the resistance change layer 207 in the “second electrode formation step”; Yes.

  In the present embodiment, metal nanoparticles are formed from a metal compound core inside ferritin. Since the size of the internal space of apoferritin is uniform, the size of the metal compound core is also uniform, and as a result, metal nanoparticles having a uniform particle size can be easily arranged. In addition, metal nanoparticles having a uniform density can be arranged even on a large-area substrate, and there is also an advantage that the adsorption density of metal nanoparticles can be easily controlled by changing the solution conditions during adsorption.

  Next, the structure of the variable resistance element of the present invention will be described.

  As shown in the cross-sectional structure diagram of FIG. 1, the variable resistance element 201 of the present invention includes a first electrode 203 on a substrate 202, a tunnel barrier layer 204 formed on the first electrode 203, and the tunnel barrier layer. A metal nanoparticle 206 having a diameter of 2 to 10 nm disposed on 204, a resistance change layer 207 formed on the tunnel barrier layer 204 and the metal nanoparticle 206, the resistance of which varies according to an applied voltage, A second electrode 208 formed on the variable resistance layer 207 is provided.

  Here, the density of the tunnel current flowing through the tunnel barrier layer 204 greatly depends on the density of states in the vicinity of the Fermi level of the material sandwiching the tunnel barrier layer 204. Since the density of states of electrons near the Fermi level of the metal is larger than the density of states of electrons near the Fermi level of the variable resistance material, when the same potential difference is applied, the metal nanoparticles 206 and the first electrode 203 The current density between them is higher than the current density between the resistance change film 207 and the first electrode 203 in the region where there are no metal nanoparticles. In other words, the tunnel resistance between the metal nanoparticle 206 and the first electrode 203 is lower than the tunnel resistance between the resistance change film 207 and the first electrode 203, and the virtual resistance is directly below the metal nanoparticle 206. It has the same effect as the current path is formed. As a result, the electric field strength in the resistance change film 207 above the metal nanoparticles 206 becomes larger than the electric field strength in the resistance change film 207 in the region where the metal nanoparticles 206 do not exist, and the electric field concentration on the surface of the metal nanoparticles 206 occurs. .

  In order to cause electric field concentration due to the shape effect disclosed in the prior art, it is necessary to form a sharp protrusion shape with a high aspect ratio, and the degree of electric field concentration is subtle in the shape of the protrusion tip (curvature radius). Since it fluctuates greatly depending on the sensitivity to changes, a process technology with high precision and high reproducibility is required to obtain uniform characteristics with a large number of elements.

  The electric field concentration in the present invention is not caused by the shape effect at the tip of the protrusion, but utilizes the difference in tunnel resistance due to the difference in the state density of electrons between the resistance change film and the metal nanoparticle, so that the sharp protrusion shape There is no need to make a high precision. In the present invention, an electric field concentrated on a minute region can be formed by a simple process, and as a result, a minute current path can be formed.

  As the metal nanoparticles, for example, nanoparticles composed of gold or platinum can be used.

  It is preferable that the diameter of the metal nanoparticles is 10 nm or less because a plurality of nanoparticles can be arranged even in a 25 nm fine resistance change cell required in the future. By arranging a plurality of nanoparticles in the cell, even if some of the current paths do not operate, other current paths can assume the function, and thus reliability can be ensured.

  The diameter of the metal nanoparticles is preferably 2 nm or more because uniform nanoparticles can be prepared using colloidal particles. Furthermore, since the diameter of the metal nanoparticle is 3 nm or more and 5 nm or less, it can be easily produced using a cage protein such as Listeria ferritin or ferritin, which is preferable.

  For example, a silicon oxide layer can be used as the tunnel barrier layer.

  It is preferable that the thickness of the tunnel barrier layer is 3 nm or less because the tunnel current can be efficiently transmitted.

  The thickness of the tunnel barrier layer is preferably 1 nm or more because leakage current in a region where no metal nanoparticles exist can be suppressed.

Example 1
Below, the manufacturing method of the resistance change element of the present Example 1 is demonstrated in detail.

(Introduction of gold sulfide core into apoferritin)
First, the operation for introducing the gold sulfide core into the cavity inside the apoferritin will be described below.

  First, 17 mg of thiourea was added to 1 mL of a 20 mM potassium chloroaurate (KAuCl4) solution and mixed.

  A few minutes later, the yellow solution of Au (III) ions changed to colorless and transparent Au (I) -thiourea complex, and this was used as a 20 mM gold thiourea complex solution.

  Next, the purified horse-derived apoferritin solution and the gold thiourea complex solution were mixed in a phosphate buffer (pH 8).

  Here, the phosphate buffer concentration of the final mixed solution was 50 mM, the thiourea concentration was 3 mM, and the equine-derived apoferritin concentration was 0.5 mg / mL.

  In order to complete the reaction of incorporating gold sulfide into apoferritin, the mixed solution was allowed to stand overnight.

  By this operation, gold sulfide was introduced into the apoferritin holding part, and gold sulfide ferritin (a complex of apoferritin and gold sulfide fine particles) was generated.

  Next, the mixed solution was put in a container and centrifuged using a centrifuge at 10,000 rpm for 15-30 minutes to remove precipitates. Subsequently, the supernatant after removing the precipitate was further centrifuged at 10,000 rpm for 30 minutes.

  At this time, soluble gold sulfide ferritin is dispersed in the supernatant, and the aggregated gold sulfide ferritin precipitates as an aggregate.

(Purification of gold core-introduced ferritin)
The solvent of the supernatant of the ferritin solution containing metal sulfide obtained as described above is concentrated using an ultrafiltration membrane [Amicon Ultra-15 (NMWL: 50,000)], and this concentrated ferritin fraction is further purified. Column chromatography by flowing through Sephacryl S-300 (gel filtration column) equilibrated with 50 mmol / L Tris (2-Amino-2- (hydroxymethyl) -1,3-propanediol) buffer (pH 8) at 25 ° C Was purified by performing

  Thereby, the eluate from which the aggregate of the ferritin particle was removed by the gel filtration column was obtained.

  For the eluate, ferritin in the solution is further concentrated using an ultrafiltration membrane and an ultracentrifugation device, and then 20 mM MES (2- (4-Morpholino) ethanesulfonic acid) and 6 mM Tris (2-Amino) are concentrated. Dilution was carried out with a pH 5.8 buffer solution containing -2- (hydroxymethyl) -1,3-propanediol). This concentration and dilution operation was repeated 3 to 7 times to finally obtain a ferritin solution in which 0.2 mg / mL ferritin as a protein concentration was dispersed in water.

(Preparation of substrate with first electrode and tunnel barrier layer forming step)
A low resistance n-type silicon substrate having a resistivity of 3 mΩcm or less is used as the substrate 202. Since the n-type silicon substrate has conductivity, the vicinity of the surface is used as the first electrode 203. (Fig. 7 (a))
The surface of the n-type silicon substrate was cleaned by washing with sulfuric acid / hydrogen peroxide solution and ammonia water / hydrogen peroxide solution, and the natural oxide film on the surface was removed by hydrofluoric acid etching. The cleaned substrate was oxidized at 800 ° C., and a 2 nm thick silicon oxide film was formed as a tunnel insulating film 204 on the substrate surface. (Fig. 7 (b))
(Ferritin placement process)
The surface of the tunnel insulating film 204 was hydrophilized by supplying oxygen and ozone gas while irradiating the substrate with UV light at a substrate temperature of 110 ° C. for 10 minutes using a UV light / ozone treatment apparatus manufactured by Samco.

The ferritin solution prepared by the above-described purification of ferritin was dropped onto the above substrate and allowed to stand at room temperature for 30 minutes. Thereby, ferritin 205 was adsorbed on the substrate surface. After the above, the substrate was washed in pure water for 5 minutes to remove excess ferritin that was not adsorbed. The washed substrate was dried and baked at 110 ° C. for 3 minutes to immobilize the adsorbed ferritin 205 on the substrate. (FIG. 7 (c)) The surface density of ferritin 205 was 4 × 10 ¹⁰ particles / cm ² .

(Protein removal / core modification process)
The substrate on which ferritin was placed was placed in a UV light / ozone treatment apparatus manufactured by Samco Co., and oxygen and ozone gas were supplied for 20 minutes while being irradiated with UV light at a substrate temperature of 110 ° C. This removed the outer protein 205a of ferritin. At the same time, the gold sulfide core 205b with a diameter of 6 nm inside ferritin was reduced to form gold nanoparticles 206 with a diameter of 5 nm. (Fig. 7 (d)
(Resistance change layer forming process)
The substrate was placed in an electron beam evaporation apparatus, the inside of the apparatus was evacuated, and a 1.8 nm-thick metal titanium film was formed on the substrate by an electron beam evaporation method. Thereafter, the atmosphere is introduced into the electron beam evaporation apparatus and the substrate is taken out, so that the deposited metal titanium film is oxidized by contact with the air, and the titanium oxide layer having a thickness of about 3.5 nm as the resistance change layer 207 is formed. Formed (FIG. 7 (e)).

(Second electrode forming step)
A metal mask having a pattern with a diameter of 100 μm was placed on the substrate surface, and again introduced into the electron beam evaporation apparatus. The inside of the apparatus was evacuated, and a metal titanium film having a thickness of 4 nm was formed as a first second electrode 208a on the substrate by electron beam evaporation. Subsequently, a gold film having a thickness of 100 nm was formed as the second second electrode 208b on the substrate by electron beam evaporation. (FIG. 7 (f)).

  The resistance change element described below could be formed by the above process.

  In the first embodiment, low resistance n-type silicon having a resistivity of 3 mΩcm or less is used as the substrate 202. The n-type silicon has conductivity, and the vicinity of the surface functions as the first electrode 203. That is, in Example 1, both the substrate 202 and the first electrode 203 are made of n-type silicon, and there is no boundary between them.

A silicon oxide film layer having a thickness of 2 nm is formed as a tunnel barrier layer 204 on the first electrode 203. On the tunnel barrier layer 204, gold nanoparticles having a diameter of 5 nm are arranged as metal nanoparticles 206 with an in-plane density of 4 × 10 ¹⁰ particles / cm ² . A titanium oxide layer having a thickness of 3.5 nm is formed on the tunnel barrier layer 204 and the metal nanoparticles 206 as a resistance change layer 207 whose resistance changes according to the applied voltage. Further, a second electrode 208 is formed on the resistance change layer 207. In this embodiment, the second electrode has a circular shape with a diameter of 100 μm. The second electrode 208 is composed of a first second electrode 208a and a second second electrode 208b. The first second electrode 208a is a metal titanium layer having a thickness of 4 nm, and the second second electrode 208b is a gold layer having a thickness of 100 nm.

  FIG. 8 shows electrical characteristics when the variable resistance element of Example 1 is swept in the voltage range of −4V to + 5V.

  As clearly shown in FIG. 8, the variable resistance element of Example 1 exhibited memory characteristics in which the resistance of the element varied with voltage application.

  In addition, the variable resistance element of Example 1 did not need to perform a forming operation for applying a high voltage initially.

(Example 2)
Below, the manufacturing method of the resistance change element of the present Example 2 is demonstrated in detail.

(Introduction of platinum sulfide core into apoferritin)
The operation for introducing the platinum sulfide core into apoferritin is described below.

  First, 0.85 mL of 100 mg / mL thiourea solution, 1 mL of 100 mM potassium platinum (II) chloride (K2 (PtCl4)) solution, and 0.15 mL of pure water were mixed, and this was mixed with 50 mM platinum thiourea complex solution. did.

  Next, the purified horse-derived apoferritin solution and the above platinum thiourea complex solution were mixed in a phosphate buffer (pH 8).

  Here, the phosphate buffer concentration of the final mixed solution was 50 mM, the thiourea concentration was 3 mM, and the equine-derived apoferritin concentration was 0.5 mg / mL.

  In order to complete the reaction of incorporating the platinum sulfide into apoferritin, the mixed solution was allowed to stand overnight.

  By this operation, platinum sulfide was introduced into the holding portion of apoferritin, and platinum sulfide ferritin (a complex of apoferritin and platinum sulfide fine particles) was generated.

  Next, the mixed solution was put in a container and centrifuged using a centrifuge at 10,000 rpm for 15-30 minutes to remove precipitates. Subsequently, the supernatant after removing the precipitate was further centrifuged at 10,000 rpm for 30 minutes.

  At this time, the dissolvable platinum sulfide ferritin is dispersed in the supernatant, and the aggregated platinum sulfide ferritin precipitates as an aggregate.

(Purification of platinum core ferritin)
The solvent of the supernatant of the ferritin solution containing platinum sulfide obtained as described above is concentrated using an ultrafiltration membrane [Amicon Ultra-15 (NMWL: 50,000)], and the concentrated ferritin fraction is further purified. Column chromatography by flowing through Sephacryl S-300 (gel filtration column) equilibrated with 50 mmol / L Tris (2-Amino-2- (hydroxymethyl) -1,3-propanediol) buffer (pH 8) at 25 ° C Was purified by performing

  Thereby, the eluate from which the aggregate of the ferritin particle was removed by the gel filtration column was obtained.

  For the eluate, ferritin in the solution is further concentrated using an ultrafiltration membrane and an ultracentrifugation device, and then 20 mM MES (2- (4-Morpholino) ethanesulfonic acid) and 6 mM Tris (2-Amino) are concentrated. Dilution was carried out with a pH 5.8 buffer solution containing -2- (hydroxymethyl) -1,3-propanediol). This concentration and dilution operation was repeated 3 to 7 times to finally obtain a ferritin solution in which 0.2 mg / mL ferritin as a protein concentration was dispersed in water.

After the above, preparation of the substrate provided with the first electrode, tunnel barrier layer forming step, ferritin placement step, protein removal / core reforming step, resistance change layer forming step, second electrode described in Example 1 Each step of the forming process was performed.
The surface density of ferritin in the ferritin arranging step was 1 × 10 ¹⁰ particles / cm ² . In the protein removal / core modification step, platinum nanoparticles having a diameter of 5 nm were formed.

  The resistance change element described below could be formed by the above process.

The resistance change element of Example 2 also has almost the same structure as the resistance change element of Example 1, but platinum nanoparticles instead of gold nanoparticles were disposed as the metal nanoparticles 206. The diameter of the platinum nanoparticles is 5 nm, and the in-plane density is 1 × 10 ¹⁰ particles / cm ² .

  FIG. 9 shows electrical characteristics when the variable resistance element of Example 2 is swept in the voltage range of −4.4V to + 5.5V.

  As clearly shown in FIG. 9, the resistance change element of Example 1 exhibited memory characteristics in which the resistance of the element changed with voltage application.

  In addition, the variable resistance element of Example 2 did not need to perform a forming operation for applying a high voltage initially.

(Comparative Example 1)
The resistance change element of Comparative Example 1 also has substantially the same structure as the resistance change element of Example 1, but the metal nanoparticles 206 are not arranged.

  FIG. 10 shows electrical characteristics when the resistance change element of Comparative Example 1 is swept in the voltage range of −4V to + 5V.

  As clearly shown in FIG. 10, in the resistance change element of Comparative Example 1 in which the metal nanoparticles 206 are not arranged, the memory characteristics cannot be obtained.

  The resistance change element and the manufacturing method thereof according to the present invention are useful as a memory element, and particularly useful for a miniaturized large-capacity nonvolatile memory.

Sectional drawing of the resistance change element concerning Embodiment 1. FIG. Sectional drawing of the resistance change element by the prior art which concerns on patent document 1 Sectional drawing of the resistance change element by the prior art concerning patent document 2 First sectional view of a resistance change element according to the prior art related to Patent Document 4 Second sectional view of a variable resistance element according to the prior art related to Patent Document 4 The figure which shows the process flow of the resistance change element in connection with Embodiment 2. The figure which shows the manufacturing process of the resistance change element in connection with Embodiment 2. The figure which shows the electrical property of the resistance change element in Example 1 The figure which shows the electrical property of the resistance change element in Example 2 The figure which shows the electrical property of the resistance change element in the comparative example 1

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Semiconductor substrate 12a Electrode film | membrane 12b Electrode film | membrane 13 Resistance-change memory film 14 Island-like growth nucleus 15 Seed 16a Surface tension adjustment film | membrane 60 Substrate 61 Lower electrode 62 Information storage layer 63 Upper electrode 63b Convex part 64 on the surface of an upper electrode Fine particle 66 Projection 68 on the surface of the information storage layer Lower surface 69 of the information storage layer Upper surface 102 of the information storage layer First electrode 104 Nanochip 106 Memory cell material 201 Resistance change element 202 Substrate 203 First electrode 204 Tunnel barrier layer 205 Ferritin 205a Outside of ferritin Protein 205b Metal sulfide 206 in ferritin 206 Metal nanoparticle 207 Resistance change layer 208 Second electrode 208a First second electrode 208b Second second electrode 500 Material

Claims (4)

  A first electrode, a tunnel barrier layer formed on the first electrode, metal nanoparticles having a diameter of 2 nm to 10 nm disposed on the tunnel barrier layer, the tunnel barrier layer, and the metal nanoparticles A resistance change element comprising: a resistance change layer whose resistance changes in accordance with an applied voltage; and a second electrode formed on the resistance change layer.   The resistance change element according to claim 1, wherein the tunnel barrier layer is made of a silicon oxide film and has a thickness of 1 nm to 3 nm. Forming a tunnel barrier layer on a substrate having a first electrode on its surface;
Disposing ferritin containing a metal compound core on the tunnel barrier layer;
Removing the ferritin protein to modify the metal compound core into metal nanoparticles;
Forming a resistance change layer whose resistance changes according to an applied voltage on the tunnel barrier layer and the metal nanoparticles;
Forming a second electrode on the variable resistance layer;   The method of manufacturing a resistance change element according to claim 3, wherein the tunnel barrier layer is made of a silicon oxide film and has a thickness of 1 nm to 3 nm.

Images