JP4221660B2 - Pore structure and manufacturing method thereof, memory device and manufacturing method thereof, adsorption amount analyzing apparatus, and magnetic recording medium - Google Patents

Description

  The present invention relates to a structure having a large number of pores and a manufacturing method thereof, a memory device using the pore structure, a manufacturing method thereof, an adsorption amount analyzer, and a magnetic recording medium.

  Although the present invention relates to a structure having a plurality of pores, the pore diameter of the pores is not particularly limited. However, in recent years, interest in nano-sized structures has increased, and the present invention is suitable as a nano-sized pore structure and a method for producing the nano-sized structure. Give a brief background.

  In this specification, a size of about 1 nm or more and less than 1 μm is referred to as “nanosize”, and the prefix “nano” is used to refer to a size whose characteristic size is nanosize. To do. For example, a nanoparticle is a particle whose diameter is nanosize, a nanohole is a pore whose pore diameter or depth is nanosize, and a nanostructure is a feature of the structure. Is a structure having a nano size.

Now, with the speeding up of CPU (Central Processing Unit) and networks, the amount of data handled by information equipment is rapidly increasing, and accordingly, the capacity of storage devices for storing data is required to be increased. Specifically, a mass storage device of several hundred Gb / inch ^{2 to 1} Tb / inch ² is required between 2005 and 2010. In order to realize such a high-density memory, a nano-size processing technique is required that regularly forms high-density memory bits having a size of several nanometers to several tens of nanometers per bit.

  As a processing method for producing a structure having a nano-sized fine structure, semiconductor processing by a lithography method such as an electron beam lithography method or an X-ray lithography method, including a photolithography method conventionally used for semiconductor processing. There is technology. Such a top-down microfabrication technique has a problem in that as the pattern becomes finer, the yield decreases and the cost increases.

  On the other hand, recently, an attempt has been made to form a nano-sized fine structure by a so-called bottom-up method by self-organization utilizing a regular fine structure spontaneously formed by atoms and molecules. . The nanostructure formed by self-assembly may be used as it is, or another material may be nano-processed using the generated nanostructure as a template (formwork).

  One method for producing a nanostructure by such self-organization includes a method of producing a structure having nano-sized pores with good controllability by anodic oxidation. For example, when metallic aluminum is anodized in an acidic electrolyte aqueous solution, a porous oxide film having nano-sized pores can be formed. A method for producing alumina by this anodic oxidation has been known for a long time.

  The characteristic of the porous alumina film formed by anodization is that fine cylindrical pores (nanoholes) with a diameter of several tens to several hundreds of nanometers are arranged in parallel at intervals of several tens to several hundreds of nanometers. It has a unique geometric structure.

  In recent years, attempts have been made to control the periodicity of the generated pore array with a nano-sized size. For example, Masuda et al. Used a silicon carbide mold on the surface of an aluminum substrate as the starting point for nanohole generation when anodizing a bulk aluminum substrate (purity 99.99%) to form nanoholes. It has been reported that pores having good nano-periods can be formed by pre-forming by pressing (Appl. Phys. Lett., 71, p. 2770-2772 (1997)).

  As an example of filling anodized alumina nanoholes with metal, Kornelius Nielsh et al. Reported an example of filling alumina nanoholes formed using a bulk aluminum substrate with nickel by electrodeposition ( Mat.Res.Soc.Symp.Proc., Vol.705 (2002)).

  On the other hand, when a metal aluminum layer formed on a conductive underlayer, not a bulk aluminum substrate, is anodized, alumina is peeled off from the conductive underlayer.

  For example, a platinum layer (thickness: 200 nm) as a base conductive layer and a metal aluminum layer (thickness: 500 nm) are stacked by a sputtering method on a silicon substrate having a silicon oxide layer and a titanium oxide layer formed on the surface. When the sample formed in this way was anodized in an 0.25 M oxalic acid solution at an applied voltage (anodic oxidation voltage) of 50 V for 0.5 minutes, a phenomenon that the metal aluminum layer peeled off from the platinum layer was observed. FIG. 12 is an observation image of the peeled portion with an optical microscope. From this, it can be seen that it is difficult to produce a highly reliable device because the adhesion at the joint surface between the metal aluminum layer and the platinum layer is extremely low and peels off in the anodizing process.

  On the other hand, in Patent Document 1 to be described later, a laminate formed by laminating an intermediate layer and a metal aluminum layer on a conductive underlayer is anodized, and alumina is formed on the conductive underlayer. An example of producing a nanohole structure is disclosed by Tada et al.

  In Patent Document 1, noble metals such as copper and platinum, alloys thereof, or semiconductor materials such as graphite and silicon are used as the conductive underlayer, and Ti, Zr, Hf, Nb, Ta, Mo, and the like are used as the intermediate layer. A single element selected from the group consisting of W and Si, or an alloy containing two or more elements selected from the above group is used, and an intermediate oxide layer formed by anodizing the intermediate layer, It has been reported that there is a function of increasing the bonding strength between the conductive underlayer and the alumina layer. However, this method requires a step of forming an intermediate layer, and has a demerit that the number of steps increases.

  Among the combinations of the above materials, when Ti, Hf, and Ta are used as the intermediate layer, it is possible to improve the adhesion between the conductive underlayer made of copper, noble metal, or the like and the alumina layer. No peeling occurred between the conductive underlayer and the aluminum layer during the anodic oxidation process.

  However, the Ti, Zr, Hf, Nb, Ta, Mo, W, or Si materials used as the intermediate layer are oxidized during the anodizing process to become insulators, and the underlying electrode made of copper, noble metal, etc. There is a known problem that it is difficult to ensure a good electrical connection between them. These intermediate layer oxides are also difficult to dissolve and remove with an acid solution such as phosphoric acid after anodic oxidation. For this reason, the problem that subsequent processing steps, such as filling an alumina nanohole with a metal, for example by an electroplating method will become difficult will occur.

  Further, there are the following problems when aiming to use as a large-capacity recording medium by filling a nanohole of a porous oxide film of alumina with a ferroelectric material or a ferromagnetic material. That is, when an aluminum thin film is formed by sputtering or vapor deposition, irregularities are formed on the surface, so that corresponding irregularities are also formed on the surface of alumina obtained by anodizing the aluminum thin film. Therefore, an optical pickup equipped with an SPM (Scanning Probe Microscope), a near-field light, a magnetic head, a semiconductor laser, etc. in order to use an alumina pore structure filled with a recording medium material in the pores as a recording medium. Even when recording / reproduction is performed in combination with the above device, since unevenness becomes an obstacle and accurate surface tracing cannot be performed, it is difficult to exchange signals stably.

Japanese Patent Laying-Open No. 2003-25298 (page 2-5, FIG. 1-3)

  SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a pore structure excellent in adhesion to the underlying conductive layer and having improved surface flatness, a method for manufacturing the same, and a memory device using the pore structure. And a manufacturing method thereof, an adsorption amount analyzer, and a magnetic recording medium.

That is, the present invention is an aluminum - hafnium alloy layer is at least a portion of the plurality of pores formed by anodized is widened processed, that having a second pore formed by this first At least a part of a plurality of pores formed by anodizing a laminated body in which a metal aluminum layer is laminated on an aluminum-hafnium alloy layer is processed to widen and formed. that having a second pore, but according to a second pore structure.

  Further, in the first and second fine pore structure manufacturing methods, the anodic oxidation start point is formed in advance at a predetermined position on the surface of the aluminum-hafnium alloy layer or the surface of the laminated body, respectively. Then, the present invention relates to a method for manufacturing a pore structure that performs anodization, and a second method for manufacturing a pore structure, in which an anodizing voltage for anodizing the aluminum-hafnium alloy layer is: The present invention relates to a method for manufacturing a pore structure in which the metal aluminum layer is set to be higher than the anodizing voltage for anodizing.

  In addition, a memory element made of a laminate composed of a lower electrode, a memory layer made of a ferroelectric material or a resistance change material, and an upper electrode is provided in the pores of the first or second pore structure. In addition, a transfer gate element for selecting the memory element is formed on a base, and the pore structure is formed on the transfer gate element via an insulating layer, and the memory The present invention relates to a memory device in which the lower electrode of the element and the transfer gate are electrically connected by a conductive plug penetrating the insulating layer.

A method for manufacturing the memory device,
Forming an aluminum-hafnium alloy layer or a laminate of an aluminum-hafnium alloy layer and a metal aluminum layer on the surface of the insulating layer;
Forming an anodic oxidation starting point at a predetermined position on the surface of the aluminum-hafnium alloy layer or the surface of the laminate;
Performing the anodization ;
Performing the step of forming the second pores by widening processing at least a portion of the plurality of pores formed by the anodization, those related to the manufacturing method of the memory device.

  Further, the present invention relates to an adsorption amount analyzer in which the first or second pore structure is formed on the surface of a crystal resonator, and an organic material layer that adsorbs specific molecules is formed in the pores. And a laminated structure in which an antiferromagnetic material layer, a soft magnetic material layer, and an aluminum-hafnium alloy layer are laminated in this order, and a pore structure is formed by anodic oxidation of the aluminum-hafnium alloy layer. Magnetic recording medium in which pores having a pore structure are filled with a ferromagnetic material, and a laminate in which an antiferromagnetic material layer, a soft magnetic material layer, an aluminum-hafnium alloy layer, and an aluminum layer are laminated in this order Related to a magnetic recording medium in which a pore structure is formed by anodic oxidation of the aluminum-hafnium alloy layer and the aluminum layer, and the pores of the pore structure are filled with a ferromagnetic material Is

  According to the present invention, the aluminum-hafnium alloy layer or the laminate of the aluminum-hafnium alloy layer and the metal aluminum layer is anodized to form the first and second pore structures. The aluminum-hafnium alloy layer or the laminate of the aluminum-hafnium alloy layer and the metal aluminum layer is selected from the group consisting of Pt, Ir, Pd, Rh, Au, Ag, Ru, Cu, and Ni. Since it is excellent in adhesiveness with a single metal element or an alloy containing two or more metal elements selected from the above group, if the single metal element or alloy is used as a base conductive layer, the first or second The problem of insufficient adhesion between the pore structure 2 and the underlying conductive layer is solved.

Moreover, since the said aluminum-hafnium alloy layer or the said laminated body of the said aluminum-hafnium alloy layer and the said aluminum layer is also excellent in the flatness of a surface compared with a metal aluminum single layer, this outstanding flatness is reflected. Thus, the surfaces of the first and second pore structures are also excellent in flatness. As a result, for example, various oxides such as oxides, ferroelectric materials, ferromagnetic materials, resistance change materials, phase change materials, phosphor materials, etc., having the perovskite structure of the pores of the first or second pore structure. When a functional structure such as an information recording medium is formed by filling a functional material, a highly reliable and high-performance functional structure is formed, such as enabling stable recording and playback operations for information recording. can do.
In addition, since it has a pore structure in which at least some of the plurality of pores are widened to form second pores, a material having a more complicated configuration that is difficult to form in the pores, For example, a multi-functional pore structure can be formed by embedding a laminate of an electrode and various functional materials in the second pore.

  In addition, since the main part of the memory device, the adsorption amount analysis device, and the magnetic recording medium of the present invention is constituted by the first or second pore structure, peeling from the underlying conductive layer or surface The problem of insufficient flatness does not occur, the reliability is remarkably improved, and the function is stably exhibited. Further, by utilizing the surface in the depth direction by utilizing the pore structure, a large effective area, surface flatness, and the like are realized.

  That is, according to the memory device of the present invention, the lower electrode, the memory layer made of the ferroelectric material or the resistance change material, and the upper electrode are disposed in the pores of the first or second pore structure. Since a memory element made of a laminated body is embedded and provided, a memory element made of a ferroelectric element or a resistance change element having a large effective area can be formed, and a semiconductor memory having a large surface density and a large capacity can be manufactured. It becomes possible. In addition, since the surface is flattened by embedding the memory element, wiring and the like are easily formed.

  Moreover, according to the adsorption amount analyzer of the present invention, the organic material layer that adsorbs specific molecules is formed on the inner wall surfaces of the pores of the first or second pore structure, so that the porous structure A high-sensitivity adsorption amount analyzer can be realized by utilizing the large surface area that is a feature of the above.

  Further, according to the magnetic recording medium of the present invention, a perpendicular magnetic recording medium can be obtained, and a large-capacity magnetic recording medium having a high surface density can be manufactured. In addition, since the magnetic material is embedded in the pore structure to form a flat surface, scanning with a magnetic head or the like is facilitated.

  According to the first and second pore structure manufacturing methods of the present invention, the starting point of the anodization is set in advance at a predetermined position on the surface of the aluminum-hafnium alloy or the surface of the laminate. Since the forming step is performed, the position where the pores are formed can be reliably controlled. This step is also an essential step in the method of manufacturing the memory device according to the present invention, and the pores are formed at positions above the conductive plugs already formed, and are electrically connected to the conductive plugs. It is possible to form the memory element while forming the substrate.

  Further, according to the second method for producing a pore structure, the anodizing voltage for anodizing the aluminum-hafnium alloy layer is set higher than the anodizing voltage for anodizing the aluminum layer. Oxidation can be performed at an optimum anodic oxidation voltage depending on the degree of easy oxidation, and a good pore structure can be formed in any layer.

Pore structure of the present invention, wherein at least a portion of the plurality of pores is the pore structure in which the second pores are formed by widening process, widening the processing of the pores, an aqueous solution of acid It is good to carry out by etching using.

  In addition, the pores are formed on a base conductive layer, and the base conductive layer is a single element of a metal element selected from the group consisting of Pt, Ir, Pd, Rh, Au, Ag, Ru, Cu, and Ni, or It is good to consist of an alloy containing 2 or more types of metal elements chosen from the group. Since the aluminum-hafnium alloy layer is excellent in adhesion to these simple substances or alloys, peeling or the like due to anodization does not occur. The base conductive layer is used as an electrode or the like for filling the pores with a material by electrodeposition or for writing / reading information to / from a memory layer formed in the pores. .

  Further, the content of hafnium in the aluminum-hafnium alloy layer is preferably 1 to 30 at% (atomic percentage), and more preferably 5 at% or more. The higher the hafnium content, the higher the flatness of the surface of the alloy layer, and this effect is remarkable when the hafnium content is 5 at% or more. However, even if the content of hafnium is increased from 30 at%, the cost is increased, but the effect of improving the flatness is small and inconvenience occurs in the formation of the pore structure.

  In addition, at least a part of the pores is filled with one of an oxide having a perovskite structure, a ferroelectric material, a ferromagnetic material, a resistance change material, a phase change material, and a fluorescent material. It is good. Thereby, a pore structure having various functions can be formed. For example, a ferroelectric material is used for manufacturing capacitors and memories, a ferromagnetic material is used for manufacturing magnetic memories, a resistance change material is used for manufacturing memories, and a phase change material is a writable DVD (Digital Versatile Disc). The fluorescent material can be used for manufacturing a light emitting device or the like.

  At this time, in order to improve the performance by improving the flatness of the surface, it is preferable that the surface of the filled material is polished by chemical mechanical polishing (CMP).

  In the method for producing a pore structure of the present invention, the means for forming the starting point of the anodic oxidation is not particularly limited, and it is possible to activate a predetermined position on the surface for the anodic oxidation reaction. Any method is possible. For example, a method of forming a small hole by lithography and etching, or a method of forming a small hole by strongly pressing a pressing means obtained by processing polycrystalline silicon carbide or single crystal sapphire formed on a silicon substrate on the surface Etc.

  The method for filling the pores with the functional material is not particularly limited, but the following examples can be given. According to the electrodeposition method, the metal material can be filled, which is suitable for filling the magnetic material. An organic metal solution can be filled into the pores by dipping or spin coating, and the organic metal solution can be heat-treated to form an oxide layer in the pores. Suitable for filling materials and phosphor materials. The pores can be filled with an oxide by MOCVD (Metal Organic Chemical Vapor Deposition), which is suitable for filling a ferroelectric material or a resistance change material. The pores are preferably filled with a phase change material by sputtering.

  In addition, nanoparticles of any one of oxides, ferroelectric materials, ferromagnetic materials, resistance change materials, phase change materials, and phosphor materials having a perovskite structure are formed in at least a part of the pores. It should be filled. Nanoparticles, for example, have the merit of being able to fill the pores in the state of a dispersion, for example, but can be introduced as a material that already has the necessary functions, eliminating the need for heat treatment after filling and the burden on the substrate, etc. There is also an advantage that becomes smaller. In addition, some nanoparticles exhibit special physical properties due to their size, and there is an advantage that such special physical properties can be used.

  In the memory device of the present invention, it is preferable that the pores formed by the anodic oxidation are widened to form second pores, and the storage element is provided in the second pores. Further, it is preferable that a conductor embedded in the pore formed at a position different from the second pore forms an extraction electrode of the transfer gate.

  Further, when the memory device of the present invention is manufactured, it is preferable to form the starting point of the anodic oxidation in advance by a lithography method and an etching method. Alternatively, the starting point of the anodic oxidation may be formed by pressing a pressing means obtained by processing polycrystalline silicon carbide or single crystal sapphire formed on a silicon substrate against the surface. The anodic oxidation start point is preferably formed only at a position where the storage element and the extraction electrode of the transfer gate are formed.

  In the magnetic storage medium of the present invention, it is preferable that the second pore formed by widening is filled with the ferromagnetic material.

  Next, a preferred embodiment of the present invention will be described in detail with reference to the drawings.

Embodiment 1
FIG. 1 is a schematic cross-sectional view showing a process of producing a nanohole structure as a pore structure based on Embodiment 1 of the present invention.

  First, as shown in FIG. 1A, a base conductive layer 2 and an aluminum-hafnium (Al—Hf) alloy layer 3 are laminated on a substrate 1 by sputtering or the like. The film thickness of the underlying conductive layer 2 is about 100 nm, and the film thickness of the Al—Hf alloy layer 3 is about 30 to 500 nm. The underlying conductive layer 2 is composed of a single metal element selected from the group consisting of Pt, Ir, Pd, Rh, Au, Ag, Ru, Cu, and Ni, or two or more metal elements selected from the above group. It is good to use an alloy. This is because the adhesion to the Al—Hf alloy layer 3 is good. Although the material of the board | substrate 1 is not specifically limited, For example, a silicon | silicone, hard glass, metal aluminum, sapphire, etc. are suitable.

  Next, as shown in FIG. 1B, the Al—Hf alloy layer 3 is applied to an applied voltage (anodic oxidation voltage) of 5 to 150 V in an acid aqueous solution having a liquid temperature of 1 to 30 ° C. and a concentration of 0.1 to 1.5 M. The Al—Hf alloy layer 3 is changed to the Al—Hf oxide layer 5 to form a nanohole structure having nanoholes 8 having a pore diameter of 1 to 300 nm. The acid aqueous solution used here is preferably an aqueous solution of oxalic acid, phosphoric acid, or sulfuric acid.

  Next, the nanohole 8 is widened by etching the nanohole structure in an acid solution of 3 to 30% by mass, and as shown in FIG. Penetrating nanoholes 9 having a pore diameter of 5 to 500 nm are formed. The acid aqueous solution used here is preferably an aqueous solution of oxalic acid, phosphoric acid, or sulfuric acid. The shape of the nanohole 9 is not limited, and may be a cylinder, a quadrangular prism, or a triangular prism.

  By this widening process, not only can a single material be filled in the nanohole 8, but also a structure having a more complicated configuration can be embedded in the nanohole 9 to form a more multifunctional nanohole structure. Become.

  Next, as shown in FIG. 1D, in the nanohole 9, an oxide having a perovskite structure, a ferroelectric material, a ferromagnetic material, a resistance change material, a phase change material, a phosphor material, etc. By filling the functional material 10, nanohole structures having various functions can be produced.

  FIG. 2 is a schematic cross-sectional view showing another manufacturing process of the nanohole structure according to the first embodiment of the present invention. The difference from the manufacturing process shown in FIG. 1 is that an anodic oxidation start point is formed in advance at a predetermined position on the surface of the Al—Hf alloy layer 3 and then anodic oxidation is performed.

  That is, as shown in FIG. 2A, after the base conductive layer 2 and the Al—Hf alloy layer 3 are formed on the substrate 1 by a sputtering method or the like, as shown in FIG. Then, an anodic oxidation start point 7 is formed at a predetermined position on the surface of the Al—Hf alloy layer 3. The formation method of the starting point 7 is not particularly limited, and any method can be used as long as the predetermined position on the surface of the Al—Hf alloy layer 3 can be activated against anodic oxidation, but the starting point 7 can be determined by a lithography method and an etching method. And a pressing method obtained by processing polycrystalline silicon carbide or single crystal sapphire formed on a silicon substrate is strongly pressed against the surface of the Al—Hf alloy layer 3.

  The subsequent steps are the same as those shown in FIGS. 1B to 1D, and as shown in FIG. 2C, a nanostructure having nanoholes 8 by anodizing the Al—Hf alloy layer 3. As shown in FIG. 2D, the nanoholes 8 are widened to form nanoholes 9, and the functional material 10 is filled into the nanoholes 9 as shown in FIG. Thus, nanohole structures having various functions are produced.

  FIG. 3 shows the flatness of the surfaces of an aluminum thin film and an aluminum-hafnium alloy thin film formed on a silicon substrate by sputtering to clarify one advantage of the aluminum-hafnium alloy layer 3 over the metal aluminum layer. Is a result of comparison by atomic force microscope (AFM) measurement.

  3A is a pure Al thin film, FIG. 3B is an Al—Hf alloy thin film containing 5.5 at% (a few percentage of atoms) of Hf, and FIG. This is a case of an Al—Hf alloy thin film containing 7 at% (a few hundred percent) of Hf. FIG. 3 shows the root mean square roughness RMS, which is the square root of the mean square of the deviation from the mean line, and the maximum height Rmax from the lowest valley to the highest peak in the reference section together with the AFM observation image.

  It can be seen from the AFM observation image, RMS, and Rmax that the flatness of the surface is improved as the amount of Hf added is increased. Also, from the experimental results not shown, it was found that the effect of improving the flatness of the surface was remarkable when the amount of Hf added was 5 at% or more. In addition, quantitative data on the adhesion with the underlying layer could not be obtained from this experiment, but when adhesion was tested by a method in which an adhesive tape was applied and mechanically removed, the film added with Hf was a substrate. From the fact that no peeling occurred, the improvement effect is presumed to be remarkable when the amount of Hf added is 5 at% or more in terms of adhesion.

The film formation conditions in the above experiment are the same for all samples, the ultimate vacuum is 5 × 10 ⁻⁷ Torr, the reaction gas (Ar) pressure is 5 mTorr, the RF (Radio Frequency) input power is 300 W, and the film thickness is 500 nm.

  As described above, since the Al—Hf alloy layer 3 has excellent surface flatness, the nanohole structure obtained by anodizing the Al—Hf alloy layer 3 also has excellent surface flatness. As a result, the information recording medium formed by filling the nanohole with an oxide having a perovskite structure, a ferroelectric material, a ferromagnetic material, a resistance change material, a phase change material, a phosphor material, etc. Such an information recording medium is excellent in flatness, and a stable recording / reproducing operation can be performed.

  Further, when the Al—Hf alloy layer 3 is used, a single metal element selected from the group consisting of Pt, Ir, Pd, Rh, Au, Ag, Ru, Cu, and Ni, or 2 selected from the above group. Adhesion with the underlying conductive layer 2 made of an alloy containing at least a seed metal element is improved. For this reason, when the Al—Hf alloy layer 3 is formed on the underlying conductive layer 2, the anodic oxidation occurs due to a volume change accompanying the change of the Al—Hf alloy layer 3 to the Al—Hf oxide layer 5. The film does not peel off due to stress, and the reliability of the device is remarkably improved.

  FIG. 4 is a schematic cross-sectional view of the nanohole 9 filled with nanoparticles. As will be described later in Examples 13 and 14, the nanoparticles are introduced into the nanoholes 9 in the form of a dispersion, and then the solvent is evaporated from the nanoholes 9 so that the nanoholes 9 are closely packed as shown in FIG. be able to.

Embodiment 2
FIG. 5 is a schematic cross-sectional view showing a process of producing a nanohole structure as a pore structure based on Embodiment 2 of the present invention. The difference from the first embodiment is that the aluminum-hafnium (Al-Hf) alloy layer 3 is used as a laminate (Al-Hf / Al) layer with a metal aluminum (Al) layer 4 instead of using the aluminum-hafnium (Al-Hf) alloy layer 3 alone. is there. Except for the above points, the process and its features are the same as those of the first embodiment, and therefore, description will be given with emphasis on the differences.

  First, as shown in FIG. 5A, a base conductive layer 2, an aluminum-hafnium (Al-Hf) alloy layer 3, and a metal aluminum (Al) layer 4 are laminated on a substrate 1 by sputtering or the like. Form. The underlying conductive layer 2 is composed of a single metal element selected from the group consisting of Pt, Ir, Pd, Rh, Au, Ag, Ru, Cu, and Ni, or two or more metal elements selected from the above group. It is good to use an alloy.

  Next, as shown in FIG. 5B, the Al—Hf alloy layer 3 and the Al layer 4 are applied with an applied voltage of 5 to 150 V in an acid aqueous solution having a liquid temperature of 1 to 30 ° C. and a concentration of 0.1 to 1.5 M. And an Al—Hf alloy layer 3 and an Al layer 4 are replaced with an Al—Hf oxide layer 5 and an alumina layer 6 to form nanostructures having nanoholes 8 having a pore diameter of 1 to 300 nm, respectively. To do. The aqueous acid solution used here may be an aqueous solution of oxalic acid, phosphoric acid, or sulfuric acid.

At this time, the Al layer 4 and the Al—Hf alloy layer 3 have different optimum voltages at which nanoholes are formed by anodic oxidation. Therefore, the voltage applied in the anodic oxidation process is different between the Al layer 4 and the Al—Hf alloy layer 3. You may select a different value with. For example, when the anodic oxidation voltage V ₁ of the Al layer 4 is 5 to 100 V, it is desirable that the anodic oxidation voltage V ₂ of the Al—Hf alloy layer 3 is 30 to 150 V and the relationship of V ₁ ≦ V ₂ is satisfied.

  Next, this nanostructure is etched in a 3 to 30% by mass acid aqueous solution to widen the nanoholes 8 and, as shown in FIG. A nanohole 9 having a through hole diameter of 5 to 500 nm is formed. The aqueous acid solution used here may be an aqueous solution of oxalic acid, phosphoric acid, or sulfuric acid.

  Next, as shown in FIG. 5 (d), in the nanohole 9, an oxide having a perovskite structure, a ferroelectric material, a ferromagnetic material, a resistance change material, a phase change material, a phosphor material, etc. By filling the functional material 10, nanohole structures having various functions are produced.

  FIG. 6 is a schematic cross-sectional view showing another manufacturing process of the nanohole structure according to the second embodiment of the present invention. The difference from the manufacturing process shown in FIG. 5 is that an anodic oxidation start point is formed in advance at a predetermined position on the surface of the laminate of the Al—Hf alloy layer 3 and the Al layer 4 and then anodization is performed. .

  That is, as shown in FIG. 6A, after the base conductive layer 2, the Al—Hf alloy layer 3, and the Al layer 4 are formed on the substrate 1 by sputtering or the like, ), An anodic oxidation start point 7 is formed at a predetermined position on the surface of the Al layer 4. The formation method of the starting point 7 is not particularly limited, and any method can be used as long as the predetermined position on the surface of the Al layer 4 can be activated against anodization. A method of forming by a lithography method and an etching method, a silicon substrate, Examples thereof include a method in which pressing means obtained by processing polycrystalline silicon carbide or single crystal sapphire formed above is strongly pressed against the surface of the Al layer 4.

  Subsequent steps are the same as those shown in FIGS.

  In the present embodiment, the thickness (for example, 20 μm) of the Al—Hf alloy layer 3 is about 1/10 to 1/5 of the thickness (for example, 200 μm) of the entire laminate with the Al layer 4. Good. Even if it is thin like this, the same effect as in the case of the Al—Hf alloy layer 3 alone can be obtained.

  That is, in the laminate of Al—Hf alloy layer 3 / Al layer 4 obtained by forming the Al layer 4 on the Al—Hf alloy layer 3, the Al—Hf alloy layer 3 is on the surface (with the Al layer 4). Reflecting this, the Al layer 4 also has excellent surface flatness, and the nanohole structure obtained by anodizing the laminate also has excellent surface flatness. It will be a thing. As a result, the information recording medium formed by filling the nanohole with an oxide having a perovskite structure, a ferroelectric material, a ferromagnetic material, a resistance change material, a phase change material, a phosphor material, etc. In such an information recording medium, a stable recording / reproducing operation can be performed.

  Further, when a laminate of Al—Hf alloy layer 3 / Al layer 4 is used, a single element of a metal element selected from the group consisting of Pt, Ir, Pd, Rh, Au, Ag, Ru, Cu, and Ni, or the aforementioned Since the Al—Hf alloy layer 3 is in contact with the underlying conductive layer 2 made of an alloy containing two or more kinds of metal elements selected from the group, the underlying conductive layer is the same as in the case of the Al—Hf alloy layer 3 alone. Adhesion with 2 is improved. Therefore, when an Al—Hf alloy layer 3 / Al layer 4 laminate is formed on the underlying conductive layer 2, the Al—Hf alloy layer 3 changes to an Al—Hf oxide layer 5 during anodization. As a result, the film is not peeled off by the stress generated by the volume change accompanying the above, and the reliability of the device is remarkably improved.

  In addition, the amount of expensive Hf used can be reduced to 1/10 to 1/5, and the cost can be reduced.

Embodiment 3
7 and 8 illustrate a semiconductor memory device in which a ferroelectric element, a resistance change element, and the like are formed as a memory element 30 in a nanohole formed using an anodization process according to the third embodiment of the present invention. It is a schematic sectional drawing which shows the process to produce.

  As shown in FIG. 7A, a field effect transistor 20 that functions as a transfer gate element for selecting the memory element 30 is formed on a semiconductor substrate 11 in advance, and an interlayer insulating film 21 and A conductive plug 22 for drawing out the electrode of the field effect transistor 20 is formed. Then, an aluminum-hafnium (Al—Hf) alloy layer 3 is formed on the interlayer insulating film 21 by sputtering or the like. Here, instead of the Al—Hf alloy layer 3, a laminate of an aluminum-hafnium (Al—Hf) alloy layer 3 and a metal aluminum layer 4 may be formed.

  Next, as shown in FIG. 7B, an anodic oxidation start point 7 is formed at a predetermined position where the conductive plug 22 is formed below. For example, a small hole having a depth of 5 to 100 nm is formed by lithography and etching.

  Next, as shown in FIG. 7C, the Al—Hf alloy layer 3 is anodized at an applied voltage of 5 to 150 V in an acid aqueous solution having a liquid temperature of 1 to 30 ° C. and a concentration of 0.1 to 1.5 M. Then, the Al—Hf alloy layer 3 is changed to the Al—Hf oxide layer 5 to form a nanostructure having nanoholes 8 having a hole diameter of 1 to 300 nm that penetrates to the conductive plug 22. The aqueous acid solution used here may be an aqueous solution of oxalic acid, phosphoric acid, or sulfuric acid.

  Next, this nanostructure is selectively etched in a 3 to 30% by mass acid aqueous solution to widen the nanoholes 8a, and as shown in FIG. Hole nano 9 of 5 to 500 nm is formed. At this time, the nanohole 8b is masked and no widening process is performed. The aqueous acid solution used here may be an aqueous solution of oxalic acid, phosphoric acid, or sulfuric acid.

  Next, as shown in FIG. 8E, the lower electrode 31, a memory layer 32 made of a ferroelectric material or a resistance change material is formed in the nanohole 9 by selective sputtering or MOCVD using a mask. And the upper electrode 33 are laminated to form a memory element 30 such as a ferroelectric element or a resistance change element. At this time, simultaneously with the formation of the upper electrode 33, an electrode material is embedded in the nanohole 8 b, and the extraction electrode 34 of the source electrode of the field effect transistor 20 is formed.

  In this filling process, when a film is formed in a portion other than the nanohole, an unnecessary deposited film may be planarized by a CMP method. For example, the surface is polished for 10 minutes using an alkaline abrasive GLANZOX 3700 manufactured by Fujimi Corporation.

  Finally, as shown in FIG. 8 (f), a wiring or the like for connecting the field effect transistor 20 or the memory element 30 and an external circuit is formed.

  The drain electrode of the field effect transistor 20 is electrically connected to the lower electrode 31 of the memory element 30. Information is written to or read from the memory element 30 by applying a selection signal to the gate electrode 16 of the field effect transistor 20 to turn on the transistor 20 and via the extraction electrode 34 of the source electrode.

  According to this embodiment, since it becomes possible to easily form nanoholes with a high aspect ratio, a ferroelectric element or a resistance change element having a large effective area can be manufactured as shown in FIG. This makes it possible to manufacture a large-capacity semiconductor memory with a high surface density.

FIG. 9 is an explanatory diagram showing the memory action that the variable resistance material, which is one of the materials constituting the memory layer 32 of the present embodiment, develops. As shown in FIG. 9A, the variable resistance material is thinned and sandwiched between the electrodes. Here, SrZrO ₃ doped with Cr (hereinafter referred to as a sample) is shown as an example of the resistance change material.

  This sample has two states, a high resistance state and a low resistance state. When a large positive voltage is applied, the sample is in a high resistance state, and when a large negative voltage is applied, the sample is in a low resistance state. Between -0.5V and 0.5V, either the high resistance state or the low resistance state can be taken, and which one is actually taken depends on the history.

  FIG. 9B is a graph showing an example of the change. In the figure, the horizontal axis represents the voltage applied to the sample, and the vertical axis represents the current flowing through the sample. In the region between −0.5 V and 0.5 V, the high resistance state (A) and the current change with a small current change with respect to the applied voltage change corresponding to the two states of the high resistance state and the low resistance state. Two graphs in a low resistance state (B) with a large A are shown.

  Initially, a large negative voltage is applied, and starting from a sample in a low resistance state (B), the current changes as shown in (1) to (5) in the figure as the applied voltage is gradually increased. Thereafter, when the applied voltage is decreased again, the current changes as shown in (6) to (10) in the figure. The transition from the low resistance state (B) to the high resistance state (A) occurs when a voltage of 0.5 V or more is applied (for example, (4)), and the transition from the high resistance state (A) to the low resistance state (B ) Occurs when a voltage of −0.5 V or less is applied (for example, (9)). In the region between -0.5V and 0.5V, the previous state is maintained.

  Accordingly, the two states of the high resistance state and the low resistance state are made to correspond to 0 and 1, and writing is performed by applying a positive pulse exceeding 0.5 V and a negative pulse lower than −0.5 V, and a DC voltage ( If the two states are read by the strength of the current when a constant value between −0.5 V and 0.5 V is applied, the resistance change element of the sample can be used as a memory. FIG. 10 is a graph illustrating a write operation and a read operation of the resistance change element memory.

Embodiment 4
It has been proposed by Masuda et al. (Solid Physics 31, 493 (1996)) to be used as a chemical sensor by filling a nanohole obtained by anodizing with a chemical substance. As an application similar to this, it is possible to create an adsorption amount analyzer that adsorbs and quantifies a specific substance using the host-guest effect.

For example, in a crystal resonator having a fundamental frequency of 27 MHz, gold electrodes are vapor-deposited on both sides of a 160 nm-thick crystal plate, and when a material of 0.6 ng / cm ² is deposited on the gold electrode, the frequency is 1 Hz. I know it will change. Therefore, if the host molecule is fixed on the gold electrode, the mass of the guest molecule captured by the binding with the host molecule can be measured with high sensitivity (Y. Okhata, K. Niikura, Y. Sugiura, M. Sawada and T. Morii, Biochemistry, 37, 5666-5672 (1998)).

  In the present embodiment, the fact that the inner wall of the nanohole in the nanohole structure has a very large surface area as a characteristic of the porous structure is applied to the above-described quantitative detection method for guest molecules. That is, in the adsorption amount analyzer of the present embodiment, a titanium layer, a platinum layer, an aluminum-hafnium (Al—Hf) alloy layer, and a metal aluminum (Al) layer are stacked on the gold electrode of the crystal resonator. After the formation, a laminate of the Al—Hf alloy layer and the Al layer is anodized to form a nanohole structure, and a host molecule layer that adsorbs specific molecules on the inner wall surface of the nanohole is formed by vapor deposition or the like.

  If a guest molecule that selectively binds to the host molecule exists in the atmosphere surrounding the adsorption amount analyzer, a part of the guest molecule is captured by the host molecule, causing an increase in mass on the gold electrode. If this increase in mass is measured as a change in the frequency of the crystal resonator, the surface area on which the host molecule layer is formed is extremely large, so that guest molecules can be quantitatively analyzed with high sensitivity.

Embodiment 5
FIG. 11 shows a magnetic storage medium 46 that can be used as a perpendicular magnetic recording medium by forming a ferromagnetic alloy layer 45 in nanoholes formed using an anodization process based on Embodiment 5 of the present invention. It is a schematic sectional drawing which shows the process of producing.

  First, as shown in FIG. 11A, a thallium Ta layer 42, an antiferromagnetic material layer 43, a soft magnetic material layer 44, an Al—Hf layer (5 nm) 3 and an Al layer (250 nm) 4 are formed on a substrate 41. Are stacked by sputtering or the like.

  Next, as shown in FIG. 11B, after anodizing in a 1M sulfuric acid solution kept at 5 ° C. at an anodic oxidation voltage of 15 V for 3 minutes, as shown in FIG. A nanohole 9 penetrating to the surface of the soft magnetic layer 44 having a diameter of 20 nm and a depth of 30 nm was formed by performing a widening process by etching with a phosphoric acid solution having a concentration of 10% for 10 minutes. The anodic oxidation time is set so that the nanoholes 8 do not penetrate to the surface of the soft magnetic layer 44 so that the surface of the soft magnetic layer 44 is not oxidized, and the surface of the soft magnetic body 44 is subjected to widening treatment using phosphoric acid. It is desirable to select a condition in which is exposed in the nanohole 9.

  The soft magnetic layer 44 is necessary to efficiently transmit the magnetic field from the magnetic head to the uppermost ferromagnetic layer 45, and includes Co—Ta—Zr, Co—Nb—Zr, Co—Zr, Co An alloy such as -Ta, Fe-Al-Si, Ni-Fe, Fe-Ga-Si-Ru, or Fe-Ta-C is used. The film thickness of the soft magnetic layer 44 is in the range of 50 nm to 1 μm.

  Further, the antiferromagnetic material layer 43 formed under the soft magnetic material layer 44 is necessary for suppressing the generation of a domain wall in the soft magnetic material layer 44, and an alloy such as PtMn, IrMn, RhMn is used. Used. The film thickness is 5 nm to 500 nm. The substrate 41 is made of glass, Al, NiAl alloy, or the like. Ti or Ta is used as a layer 42 for assisting adhesion between the antiferromagnetic layer 43 and the substrate 41.

Next, as shown in FIG. 11 (d), Co—Ni—Fe, Co—Pt, Co—Pt—Cr, Co—Pt—Cr—B, Fe— A ferromagnetic alloy 45 such as Pt is filled. The electrodeposition conditions are a plating bath temperature of 30 to 70 ° C. and a current density of 1 to 20 A / dm ² for 1 to 10 minutes. At this time, it is necessary to strictly control the structure in consideration of the characteristics of the ferromagnetic material, and in order to prevent the composition shift due to the supply rate limiting in the solution in the vicinity of the substrate, it is necessary to use the pulse electrodeposition method. desirable. The plating bath is a sulfamic acid bath or a sulfuric acid bath.

  When the magnetic recording medium 46 of this embodiment is used in combination with the single-pole magnetic head 48, next, as shown in FIG. 11E, a 2 to 10 nm carbon film 47 on the surface of the ferromagnetic material. It is desirable to coat.

  Next, preferred embodiments of the present invention will be described in detail.

Example 1
First, SiO ₂ layer and the TiO ₂ layer and the Si substrate which is formed on the surface, Pt layer as an underlying conductive layer (thickness 100 nm), the Al-Hf alloy layer (thickness 200 nm) and sputtering The laminated sample was anodized in a 0.5 M oxalic acid solution kept at 5 ° C. for 5 minutes at an anodic oxidation voltage of 50 V, and then widened by etching with a phosphoric acid solution having a concentration of 5 mass% for 1 hour. By processing, nanoholes penetrating to the Pt surface having a diameter of 100 nm and a depth of 200 nm were formed.

  Next, an organometallic solution containing Pb, Zr, and Ti elements is poured into the nanoholes by dipping or spin coating. At this time, when the organic metal is poured after the substrate is immersed in a main solvent of the organic metal solution, such as ethanol, acetylacetone, xylene, for 30 minutes or more, the nanohole can be uniformly filled with the organic metal solution. .

  Then, after filling the nanoholes with an organometallic solution, heat treatment is performed at 400 ° C. for 5 minutes in oxygen, and then heat treatment is performed at 600 ° C. for 30 minutes in oxygen in a heat treatment furnace, thereby increasing the strength of the nano size. A dielectric PZT recording medium could be obtained.

The filling of the organometallic solution and the heat treatment process thereof may be repeated a plurality of times until the filling of the nanoholes cannot be completed in a single process until they can be completely filled. The ferroelectric material to be filled is not limited to PZT (Pb (Zr, Ti) O ₃ ), but may be Bi _3.75 La _0.25 Ti ₃ O ₁₂ , SrBi ₂ Ta ₂ O ₉ , or BaTiO ₃ .

Example 2
On a Si substrate having a SiO ₂ layer and a TiO ₂ layer formed on the surface, a Pt layer (thickness: 100 nm), an Al—Hf alloy layer (thickness: 20 nm), and an Al layer (thickness: 180 nm), which are underlying conductive layers. ) By anodization in a 0.5 M oxalic acid solution kept at 5 ° C. for 5 minutes at an anodic oxidation voltage of 50 V, and then a 5 mass% phosphoric acid solution. Then, a nanohole penetrating to the Pt surface having a diameter of 100 nm and a depth of 200 nm was formed by performing a widening process by etching for 50 minutes.

  Next, an organometallic solution containing Pr, Ca, and Mn elements is poured into the nanoholes by dipping or spin coating. At this time, when the organic metal is poured after the substrate is immersed in a main solvent of the organic metal solution, such as ethanol, acetylacetone, xylene, for 30 minutes or more, the nanohole can be uniformly filled with the organic metal solution. .

  After filling nanoholes with an organometallic solution, heat treatment is performed in oxygen at 400 ° C. for 5 minutes, and then further heat treatment is performed in oxygen at 600 ° C. for 30 minutes in a heat treatment furnace, so that a nano-sized resistance is obtained. A change recording medium could be obtained.

The filling of the organometallic solution and the heat treatment process thereof may be repeated a plurality of times until the filling of the nanoholes cannot be completed in a single process until they can be completely filled. The ferroelectric material to be filled is not limited to Pr _0.7 Ca _0.3 MnO ₃ but may be Cr-doped SrTiO ₃ , Cr-doped SrZrO ₃ , Mn-doped SrTiO _3, or Mn-doped SrZrO ₃ .

Example 3
On a Si substrate having a SiO ₂ layer and a TiO ₂ layer formed on the surface, an Ir layer (thickness: 100 nm) as an underlying conductive layer, an Al—Hf alloy layer (thickness: 20 nm), and an Al layer (thickness: 80 nm) ) Was anodized in a 0.5 M oxalic acid solution maintained at 5 ° C. for 5 minutes at an anodic oxidation voltage of 50 V, and then a 5 mass% phosphoric acid solution was used. By performing the widening process by etching for 30 minutes, a nanohole penetrating to the Ir surface having a diameter of 50 nm and a depth of 100 nm was formed.

  Next, the nanohole was filled with an oxide of Pb, Zr, and Ti by MOCVD using an organic metal of Pb, Zr, and Ti as raw materials to obtain a nano-sized ferroelectric PZT recording medium. The substrate temperature is 400 ° C. to 650 ° C. In this filling process, when a film is formed in an unnecessary portion other than the nanohole, the deposited film may be planarized by a CMP method.

Further, the material to be filled is not limited to Pb (Zr, Ti) O ₃ , and may be Bi _3.75 La _0.25 Ti ₃ O ₁₂ , SrBi ₂ Ta ₂ O _9, or BaTiO ₃ by changing the organic metal raw material.

Example 4
A sample formed by stacking a Pt layer (thickness 100 nm), an Al—Hf alloy layer (thickness 10 nm), and an Al layer (thickness 40 nm) as a base conductive layer on a Ti substrate by a sputtering method is 5 After anodizing for 5 minutes at an anodic oxidation voltage of 20 V in a 1 M sulfuric acid solution kept at ° C., a widening treatment by etching for 15 minutes with a phosphoric acid solution having a concentration of 5% by mass has a diameter of 25 nm and a depth of 50 nm. A nanohole penetrating to the Pt surface was formed.

Next, this nanohole is filled with Ni, Co or Fe alone, an alloy containing two or more of these, or CoPt or FePt by electrodeposition. The electrodeposition conditions are a plating bath temperature of 50 ° C., a current density of 10 A / dm ² and an electrodeposition time of 3 minutes. At this time, when filling the alloy, it is necessary to strictly control the composition in consideration of the characteristics of the ferromagnetic material, and therefore it is desirable to use the pulse electrodeposition method.

Example 5
A semiconductor memory was fabricated by forming a dielectric capacitor, a ferroelectric capacitor, and a resistance change element on a silicon wafer on which a CMOS transistor was formed.

  First, a Ti layer (20 nm), a TiN layer (30 nm), an Ir—Hf alloy layer (20 nm), an Ir layer (100 nm), an Al—Hf alloy layer ( 20 nm thick) and an Al layer (thickness 180 nm) are stacked by sputtering, and then an anodic oxidation start point is formed at a predetermined position by forming a pore having a diameter of 20 nm and a depth of 50 nm by photolithography and etching. Formed as.

  Then, after anodizing in 1M sulfuric acid solution maintained at 5 ° C. for 5 minutes at an anodic oxidation voltage of 20V, a widening treatment by etching with a phosphoric acid solution having a concentration of 5% by mass for 30 minutes is performed, and the depth is 50 nm. Nanoholes penetrating to the Ir surface with a thickness of 200 nm were formed.

Next, the lower electrode layer Ir30 nm, an oxide material (dielectric material SrTiO ₃ or BaTiO ₃ , ferroelectric material Pb (Zr, Ti) O ₃ , Bi _3.75 La _0.25 Ti ₃ O is formed in the nanohole by MOCVD. ₁₂ or SrBi ₂ Ta ₂ O _9, the resistance change material Pr _0.7 Ca _0.3 MnO _3, Cr-doped SrTiO ₃ or SrZrO ₃ and Cr-doped) layer 50 nm, the semiconductor memory of a large capacity by forming an upper electrode material layer Ir30nm We were able to make it.

Example 6
A sample formed by laminating a Ti layer (20 nm), an Ir layer (100 nm), an Al—Hf alloy layer (thickness 20 nm) and an Al layer (thickness 80 nm) on a polycarbonate substrate at 5 ° C. Anodization was performed for 5 minutes at an anodic oxidation voltage of 40 V in a maintained 0.5 M oxalic acid solution, followed by widening treatment by etching with a phosphoric acid solution having a concentration of 5% by mass for 60 minutes, so that the diameter was 100 nm and the depth was 100 nm. Nanoholes penetrating to the Ir surface were formed.

  Next, a Ge—Te—Sb—S alloy is filled in the nanoholes as a phase change material by sputtering. The filling material is not limited to the Ge—Te—Sb—S alloy, but is Ag—In—Sb—Te, Te—Ge—Sn—Au, Ge—Te—Sn, Sn—Se—Te, Sb—Se—Te. Sb—Se, Ga—Se—Te, Ga—Se—Te—Ge, In—Se, Ge—Sb—Te, or In—Se—Te alloys may be used.

Example 7
SiO ₂ layer and the TiO ₂ layer and the Si substrate which is formed on the surface, Pt layer as an underlying conductive layer (thickness 100 nm), Al-Hf alloy layer (thickness 20 nm) and an Al layer (thickness 180nm ) Was anodized in a 0.5 M oxalic acid solution maintained at 5 ° C. for 5 minutes at an anodic oxidation voltage of 50 V, and then a 5 mass% phosphoric acid solution was used. By performing the widening process by etching for 60 minutes, a nanohole penetrating to the Pt surface having a diameter of 100 nm and a depth of 200 nm was formed.

  Next, an organometallic solution containing Sr, Al, and Eu elements is poured into the nanoholes by dipping or spin coating. At this time, when the organic metal is poured after the substrate is immersed in a main solvent of the organic metal solution, for example, ethanol, acetylacetone, xylene or the like for 30 minutes or more, the organic metal solution can be uniformly filled into the nanoholes.

After filling nanoholes with an organometallic solution, heat treatment is performed at 400 ° C. for 5 minutes in oxygen, and then heat treatment is performed at 1000 ° C. for 60 minutes in oxygen in a heat treatment furnace. It was possible to obtain a SrAl ₂ O ₄ recording medium doped with Eu. Eu-doped SrAl ₂ O ₄ emits light even when stress changes, and is a material that can emit light, for example, by contact or application of ultrasonic vibration.

  The filling of the organometallic solution and the heat treatment process thereof may be repeated a plurality of times until the filling of the nanoholes cannot be completed in a single process until they can be completely filled.

Example 8
On a Si substrate having a SiO ₂ layer and a TiO ₂ layer formed on the surface, a Pt layer (thickness: 100 nm), an Al—Hf alloy layer (thickness: 20 nm), and an Al layer (thickness: 180 nm) as a base conductive layer. ) Was anodized in a 0.5 M oxalic acid solution kept at 5 ° C. for 4 minutes at an anodizing voltage of 50 V, and further anodized at 75 V for 1 minute. A nanohole penetrating to a Pt surface having a diameter of 100 nm and a depth of 200 nm was formed by performing a widening process by etching with a 5 mass% phosphoric acid solution for 60 minutes.

Next, this nanohole is filled with Ni, Co or Fe alone, an alloy containing two or more of these, or CoPt or FePt by electrodeposition. The electrodeposition conditions are a plating bath temperature of 50 ° C., a current density of 10 A / dm ² and an electrodeposition time of 12 minutes. At this time, when filling the alloy, it is necessary to strictly control the composition in consideration of the characteristics of the ferromagnetic material, and therefore it is desirable to use the pulse electrodeposition method.

Example 9
On a Si substrate having a SiO ₂ layer and a TiO ₂ layer formed on the surface, an Ir layer (thickness: 100 nm), an Al—Hf alloy layer (thickness: 20 nm), and an Al layer (thickness: 180 nm) as a base conductive layer. ) Was anodized in a 0.5 M oxalic acid solution kept at 5 ° C. for 3 minutes at an anodic oxidation voltage of 50 V, and then a 5 mass% phosphoric acid solution was used. By performing the widening process by etching for 30 minutes, a nanohole having a diameter of 50 nm and a depth of 100 nm and penetrating to the Ir surface was formed.

  Next, the nanohole was filled with an oxide of Pb, Zr, and Ti by MOCVD using an organic metal of Pb, Zr, and Ti as raw materials to obtain a nano-sized ferroelectric PZT recording medium. The substrate temperature is 400 ° C. to 650 ° C.

  In the filling process, when a film is formed in a portion other than the nanohole, an unnecessary deposited film may be planarized by a CMP method. For example, the surface is polished for 10 minutes using an alkaline abrasive GLANZOX 3700 manufactured by Fujimi Corporation. In this case, in order to improve the characteristics of PZT, it is desirable to perform a heat treatment for 30 minutes at 400 to 650 ° C. in an oxygen atmosphere after the CMP process.

Further, the material to be filled is not limited to Pb (Zr, Ti) O ₃ , and may be Bi _3.75 La _0.25 Ti ₃ O ₁₂ , SrBi ₂ Ta ₂ O _9, or BaTiO ₃ by changing the organic metal raw material.

Example 10
A sample formed by laminating a Ta layer, an antiferromagnetic layer, a soft magnetic layer, an Al—Hf layer (5 nm), and an Al layer (250 nm) on a substrate by a sputtering method was maintained at 5 ° C. After anodizing in a sulfuric acid solution for 3 minutes at an anodic oxidation voltage of 15 V, the surface of the soft magnetic layer having a diameter of 20 nm and a depth of 30 nm is obtained by performing a widening process by etching with a 10% by weight phosphoric acid solution for 10 minutes. A penetrating nanohole was formed. The anodizing time is set so that the nanoholes do not penetrate to the surface of the soft magnetic layer so that the surface of the soft magnetic layer is not oxidized, and the condition that the surface of the soft magnetic layer is exposed by the widening process using phosphoric acid. It is desirable to choose.

  The soft magnetic material layer is necessary for efficiently transmitting the magnetic field from the magnetic head to the uppermost ferromagnetic material layer, and includes Co—Ta—Zr, Co—Nb—Zr, Co—Zr, and Co—Ta. An alloy such as Fe—Al—Si, Ni—Fe, Fe—Ga—Si—Ru, or Fe—Ta—C is used. The film thickness of the soft magnetic layer is in the range of 50 nm to 1 μm.

  Moreover, the antiferromagnetic material layer formed under the soft magnetic material layer is necessary for suppressing the generation of the domain wall in the soft magnetic material layer, and an alloy such as PtMn, IrMn, RhMn or the like was used. The film thickness is 5 nm to 500 nm. As the substrate, glass, Al, NiAl alloy or the like was used. A Ti layer or a Ta layer was used as a layer for assisting adhesion between the antiferromagnetic material layer and the substrate.

This nanohole was filled with an alloy layer of Co—Ni—Fe, Co—Pt, Co—Pt—Cr, Co—Pt—Cr—B, Fe—Pt, or the like as a ferromagnetic layer by electrodeposition. The electrodeposition conditions were a plating bath temperature of 30 to 70 ° C. and a current density of 1 to 20 A / dm ² for 1 to 10 minutes. When the alloy is filled, it is necessary to strictly control the structure in consideration of the characteristics of the ferromagnetic material. Therefore, it is desirable to use a pulse electrodeposition method in order to prevent compositional deviation due to supply rate limiting in the solution in the vicinity of the substrate. The plating bath used was a sulfamic acid bath or a sulfuric acid bath.

  When the recording medium of the present invention is used in combination with a single-pole magnetic head, it is desirable to coat the surface of the ferromagnetic layer with a 2 to 10 nm carbon film.

Example 11
A Ti layer (20 nm), a Pt layer (thickness: 100 nm) as an underlying conductive layer, an Al—Hf alloy layer (thickness: 20 nm), and an Al layer (thickness: 480 nm) are formed on the quartz resonator by sputtering. The laminated sample was anodized in a 0.5 M oxalic acid solution maintained at 5 ° C. at an anodizing voltage of 50 V for 25 minutes. Thereafter, widening was performed by etching with a phosphoric acid solution having a concentration of 5% by mass for 60 minutes to form nanoholes penetrating to the Pt surface having a diameter of 100 nm and a depth of 500 nm.

  Next, a D-phenylalanine layer was formed on the inner wall surface of the nanohole by vapor deposition. By using this crystal resonator, the amount of adsorption of α-pinene, which is the main raw material of perfume, can be measured with high accuracy.

  The organic material formed on the inner wall surface of the nanohole is not limited to D-phenylalanine, but may be D-tyrosine, D, L-histidine, D-glucose, adenine, polyethylene, polychlorotrifluoroethylene, or the like.

Example 12
Polycrystalline silicon carbide was deposited on a silicon substrate to a thickness of 1 μm by MOCVD, and then planarized by CMP to a film thickness of 500 nm so that the surface irregularities were 5 nm or less in Ra. Thereafter, chlorine gas Cl ₂ at an RIE (Reactive Ion Etching) method is patterned by photolithography and electron beam lithography system, it is processed using an oxygen gas O _2, the diameter 50 nm, a height of 100nm cylindrical projections A polycrystalline silicon carbide template was prepared on the lattice points at a pitch of 100 nm.

A Pt layer (thickness: 100 nm) as a base conductive layer and an Al—Hf alloy layer (thickness: 200 nm) were stacked by a sputtering method on a Si substrate having a TiO ₂ layer (30 nm) formed on the surface. The mold was placed on the sample and held for 30 seconds in a state where a pressure of 500 kg / cm ² was applied by a press. Nanoholes having a depth of 100 nm and a diameter of 50 nm are formed in the Al—Hf layer.

  This sample was anodized in a 0.5 M oxalic acid solution maintained at 5 ° C. for 7 minutes at an anodic oxidation voltage of 50 V, and then subjected to a widening treatment by etching with a 5 mass% phosphoric acid solution for 1 hour. A periodic hole in which rectangular parallelepiped nanoholes each having a side length of 100 nm and a depth of 200 nm were arranged was obtained. By filling the nanohole with a strong derivative, a ferromagnetic material, a resistance change material, a phase change material, and a phosphor, a recording medium in which each material is regularly arranged can be obtained.

Example 13
A surfactant that has a hydrophilic portion and a hydrophobic portion, and the hydrophilic portion is oriented to the surface of the ultrafine particles, so that the ultrafine particles can be dispersed in an organic solvent without agglomerating, an organic solvent, and barium titanium A mixed solution of double alkoxide or lead titanium double alkoxide was set at 100 ° C.

  By adding hydrogen peroxide water to the above mixed solution and keeping it at 100 to 300 ° C. for 1 to 100 hours, the surface is covered with a surfactant, and the average particle diameter is excellent in dispersibility in an organic solvent. 1 to 50 nm barium titanate ultrafine particles or PT ultrafine particles were obtained. Treatment for exchanging the solvent was performed, and barium titanate particles or PT ultrafine particles were dispersed in a hexane solution.

  After spin-coating this solution on anodized alumina, the process of evaporating the solvent at 100 ° C. was repeated to obtain a nanohole structure in which nanoholes of anodized alumina were filled with barium titanate nanoparticles or PT nanoparticles. It was. This nanohole structure is improved in ferroelectric characteristics by heat treatment at 400 to 800 ° C. in oxygen.

The ultrafine particles are not limited to BaTiO ₃ and PbTiO ₃ , but by selecting an organic metal material, a dielectric material SrTiO ₃ , a ferroelectric material Pb (Zr, Ti) O ₃ , Bi _3.75 La _0.25 TiO ₃ O ₁₂ , SrBi Nanostructures such as ₂ Ta ₂ O ₉ , resistance change material Pr _0.7 Ga _0.3 MnO ₃ , Cr-doped SrTiO _3, or Cr-doped SrZrO ₃ can also be obtained.

Example 14
An organic compound that has a hydrophilic part and a hydrophobic part and can be dispersed in an organic solvent without agglomerating the ultrafine particles by causing the hydrophilic part to be oriented on the surface of the ultrafine particles is used as a reaction solvent, 30 to 350 ° C. The temperature is raised in advance.

  By implanting a raw material containing elements (here, Cd and Se) constituting the ultrafine particles to be synthesized into this reaction solvent, the raw materials are decomposed and reacted to form nuclei. By maintaining this at 100 to 350 ° C. for 1 to 100 hours, nanoparticles having an average particle diameter of 1 to 50 nm having a surface covered with a surfactant and excellent dispersibility in an organic solvent were obtained. A treatment for exchanging the solvent was performed, and CdSe ultrafine particles were dispersed in the hexane solution.

  After spin-coating this solution on anodized alumina, the step of evaporating the solvent at 100 ° C. was repeated to obtain a nanohole structure in which nanoholes of anodic alumina were filled with cadmium selenide nanoparticles. The ultrafine particles in the structure function as a highly efficient phosphor, and the emission color depends on the particle system of the ultrafine particles.

  The ultrafine particles are not limited to CdSe, and nanostructures of CdS, CdTe, ZnSe, and ZnS can be obtained by selecting raw materials.

  As described above, according to the embodiments and examples of the present invention, a material in which an aluminum-hafnium alloy layer or a laminated film of an aluminum-hafnium alloy layer and a metal aluminum layer is formed on a base conductive layer. By anodizing, a novel structure having pores penetrating to the underlying conductive layer and a method for producing the same can be provided.

  This structure is characterized in that it can provide a recording medium that can perform stable recording and reproduction because of its high surface flatness even when it is used as a large-capacity recording medium by filling the pores with a ferroelectric material or a ferromagnetic material. To do. For devices other than large-capacity recording media, the use of a nanostructure obtained by anodizing an Al—Hf alloy or an Al / Al—Hf laminated film makes it possible to provide excellent reliability with respect to the substrate. High device can be manufactured.

  The present invention has been described based on the embodiment and the examples. However, the present invention is not limited to these examples, and it is needless to say that the present invention can be appropriately changed without departing from the gist of the invention. Yes.

  The conditions for anodization and the conditions for the hole diameter widening treatment by an etching method using an acid aqueous solution are not limited to the contents described in the above examples, and the film thickness of the material to be anodized or It is preferable to select an optimum condition depending on the diameter of the nanohole to be manufactured. For example, the anodic oxidation voltage applied for anodic oxidation is desirably in the range of 5 to 150V. Moreover, you may anodize with a constant current instead of a constant voltage, and the current value of the electrolysis current in this case has the desirable range of 0.01-10A. Moreover, the solution used for the hole diameter widening process by etching is not limited to a phosphoric acid aqueous solution, but may be an aqueous solution of other acids such as a sulfuric acid aqueous solution.

  It can be used in a wide range of functional materials such as electronic devices, memory media, memory elements, and structural materials. In particular, the structure can be used for a perpendicular magnetic recording medium, a solid magnetic memory, a magnetic sensor, a photonic device, and the like.

It is a schematic sectional drawing which shows the process of producing a nanohole structure as a pore structure based on Embodiment 1 of this invention. It is a schematic sectional drawing which shows the other manufacturing processes of a nanohole structure equally. The results are a comparison of the flatness between the surface of the Al thin film formed on the silicon substrate and the surface of the Al—Hf alloy thin film by AFM measurement. FIG. 2 is a schematic cross-sectional view of a nanohole filled with nanoparticle. It is a schematic sectional drawing which shows the manufacturing process of a nanohole structure based on Embodiment 2 of this invention. It is a schematic sectional drawing which shows the other manufacturing processes of a nanohole structure equally. It is a schematic sectional drawing which shows the manufacturing process of the memory device using the nanohole structure based on Embodiment 3 of this invention. It is a schematic sectional drawing which shows the manufacturing process of the memory device using a nanohole structure similarly. It is explanatory drawing which shows the memory effect | action of resistance change material similarly. 4 is a graph illustrating a write operation and a read operation of the resistance change element memory. It is a schematic sectional drawing which shows the manufacturing process of the magnetic-recording medium using a nanohole structure based on Embodiment 4 of this invention. It is an observation image by the optical microscope of the Al peeling part by the anodic oxidation which arose in the conventional Al-Pt junction part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Base conductive layer, 3 ... Aluminum-hafnium (Al-Hf) alloy layer,
4 ... Metal aluminum (Al) layer, 5 ... Al-Hf oxide layer, 6 ... Alumina layer,
7 ... starting point of anodization, 8, 8a, 8b ... nanoholes formed by anodization,
9 ... Nanohole widened by etching process, 10 ... Functional material,
DESCRIPTION OF SYMBOLS 11 ... Semiconductor substrate, 12 ... Well region, 13 ... Drain region, 14 ... Source region,
15 ... Gate oxide film, 16 ... Gate electrode, 20 ... Field effect transistor,
21 ... Interlayer insulating film, 22 ... Conductive plug, 30 ... Memory element, 31 ... Lower electrode,
32 ... Memory layer, 33 ... Upper electrode, 34 ... Lead electrode for source electrode, 41 ... Substrate,
42 ... Ta layer, 43 ... antiferromagnetic layer, 44 ... soft magnetic layer, 45 ... ferromagnetic layer,
46 ... magnetic recording medium, 47 ... carbon film, 48 ... single pole magnetic head

Claims (19)

Aluminum - at least some of the plurality of pores hafnium alloy layer is formed by anodic oxidation is widened processed, that having a second pores formed thereby, the pore structure. Aluminum - at least some of the plurality of pores laminate metallic aluminum layer are stacked is formed by anodic oxidation in a hafnium alloy layer is widened processed, that having a second pore formed by this , Pore structure. The pores are formed on a base conductive layer, and the base conductive layer is a single element of a metal element selected from the group consisting of Pt, Ir, Pd, Rh, Au, Ag, Ru, Cu, and Ni, or from the group The pore structure according to claim 1 or 2 , comprising an alloy containing two or more selected metal elements. At least a part of the pores is filled with any one of an oxide having a perovskite structure, a ferroelectric material, a ferromagnetic material, a resistance change material, a phase change material, and a fluorescent material. The pore structure described in 1 or 2 . The pore structure according to claim 4 , wherein the surface of the filled material is polished by a chemical mechanical polishing method.   The method for producing a pore structure according to claim 1 or 2, wherein the anodization is performed after the start point of the anodization is previously formed at a predetermined position on the surface of the aluminum-hafnium alloy layer or the laminate. A method for producing a pore structure.   3. The method for producing a pore structure according to claim 2, wherein an anodizing voltage for anodizing the aluminum-hafnium alloy layer is set higher than an anodizing voltage for anodizing the metal aluminum layer. A method for producing a pore structure. 3. The method for producing a pore structure according to claim 1 , wherein the pores are widened by etching using an acid aqueous solution. The pores of claim 1 or 2, (1) collecting metal filling by deposition method, to fill the organic metal solution by (2) a dipping method or a spin coating method, by heat-treating the organic metal solution An oxide layer is formed in the pores, (3) filled with oxide by MOCVD (Metal Organic Chemical Vapor Deposition) method, or (4) filled with phase change material by sputtering method. Production method. A memory element comprising a laminate composed of a lower electrode, a memory layer made of a ferroelectric material or a resistance change material, and an upper electrode is provided in the pores of the pore structure according to claim 1 or 2. A memory device. A transfer gate element for selecting the memory element is formed on a base, and the pore structure is formed on the transfer gate element via an insulating layer. The lower electrode of the memory element, the transfer gate, The memory device according to claim 10 , wherein the memory devices are electrically connected by a conductive plug that penetrates the insulating layer. The memory device according to claim 10 , wherein the storage element is formed in the second pore. The memory device according to claim 10 , wherein a conductor embedded in the pore formed at a position different from the second pore forms an extraction electrode of the transfer gate. A method for manufacturing a memory device according to claim 11 , comprising:
Forming an aluminum-hafnium alloy layer or a laminate in which an aluminum-hafnium alloy layer and a metal aluminum layer are laminated in this order on the surface of the insulating layer;
Forming an anodic oxidation starting point at a predetermined position on the surface of the aluminum-hafnium alloy layer or the laminated body;
Performing the anodization ;
Performing <br/> and forming a second pore by widening processing at least a portion of the plurality of pores formed by the anodic oxidation, a method of manufacturing the memory device. The method for manufacturing a memory device according to claim 14 , wherein the memory element is provided in the second pore. 15. The method of manufacturing a memory device according to claim 14 , wherein the anodization start point is formed only at a position where the storage element and the extraction electrode of the transfer gate are formed. An adsorption amount analysis apparatus, wherein the pore structure according to claim 1 or 2 is formed on a surface of a crystal resonator, and an organic material layer that adsorbs specific molecules is formed in the pores. It has a laminated body in which a hafnium alloy layer are laminated in this order, wherein the aluminum - - antiferromagnetic layer and the soft magnetic layer and the aluminum plurality of pores by anodic oxidation of the hafnium alloy layer is formed and this at least partially ferromagnetic material is filled in the second pores formed by widening process, the magnetic recording medium of al the pores, or these pores. An antiferromagnetic layer, a soft magnetic layer, an aluminum-hafnium alloy layer, and a metal aluminum layer are laminated in this order, and anodization of the aluminum-hafnium alloy layer and the metal aluminum layer is performed. a plurality of pores are formed, these pores, or at least part of these pores ferromagnetic material in the second pores formed by widening processing becomes filled, the magnetic recording Medium.