JP2008307661A - Structure manufacturing method and structure - Google Patents

Abstract

Disclosed is a method for manufacturing a structure that can form dots, lines, or holes made of a nanoscale inorganic material on a substrate without aggregation of the inorganic material.
A method of manufacturing a structure in which any one of dots, lines, or holes made of an inorganic material is formed on a substrate, wherein the block copolymer is coated on the substrate and the block copolymer segments are separated. Forming a microphase-separated structure, contacting the microphase-separated structure with a solution in which an inorganic component is dissolved, and infiltrating the phase-separated segment in the microphase-separated structure with the inorganic component; And removing the block copolymer to form any one of dots, lines or holes containing the inorganic component.
[Selection figure] None

Description

  The present invention relates to a method for manufacturing a structure in which any one of dots, lines, or holes made of an inorganic material is formed on a substrate, and a structure obtained by the manufacturing method.

  With the advancement of material technology and material processing technology, the size of materials handled is now on the order of nanometers (one billionth of a meter) as represented by the term nanotechnology. The establishment of new basic technology is an important issue when manufacturing, measuring, evaluating, processing and applying size materials. For example, when considering a particle as an example, the finer the particle size becomes, and the smaller the diameter, the higher the proportion of atoms existing on the particle surface among the atoms constituting the particle. Ultimately, all of the atoms constituting the particle are in a state of being atoms constituting the surface. In this way, as the miniaturization progresses, the ratio of the force applied to the particle surface with respect to the size of the particle increases. Even with the same material, the properties of micron-scale (parts per million) and nanoscale particles It is not uncommon for the to change significantly.

  In the fine area of nanometer scale, for example, the wavelength of visible light is several hundred nanometers, and the size of biomolecules such as proteins is several to several tens of nanometers. In the field of optical materials and biomaterials, However, it is expected that special characteristics that cannot be achieved by conventional micron-scale materials will be extracted. Also in semiconductor materials, it is possible to obtain quantum dots that exhibit a quantum size effect in which electron energy is quantized within one particle by making the particle size several to several tens of nanometers. It is expected that new characteristics can be brought out not only in optics but also in the field of electronic materials.

  Such a nano-scale material manufacturing method includes a top-down method in which a lump of the same composition is further refined by repeating or combining fine processing processes such as crushing, polishing, decomposition, and cutting, and an atomic method. There are two main methods: a bottom-up process in which the smallest unit of a material called a molecule is gradually assembled using a method such as self-assembly.

  However, the nanoscale material obtained using either of the above methods is the same from the viewpoint that the proportion of atoms present on the surface is increased, and the individual weight is reduced by miniaturization. As a result, the surface area increases, and as a result, the cohesive force due to the surface effect increases and spontaneous aggregation occurs. As a result, there was a problem that it was not possible to draw out new properties expected to be exhibited at nanometer size, which was a major obstacle to the development of nanotechnology technology, but nanometer size dots, There was no technique for releasing aggregation of lines (wires) and holes by a highly versatile method.

  The reason why the nanoscale material exhibits strong self-aggregation property is the size effect as described above. In particular, many of the materials that are promising as nanoscale materials easily change in valence state, and cause aggregation through more various processes. Nanoscale inorganic materials such as semiconductor materials and conductive materials are almost agglomerated unless they are subjected to special dispersion treatments, using particle size distribution measurement, electron microscope (SEM or TEM), atomic force microscope, etc. It can be easily confirmed.

  When a nanoscale material is actually used as an effective device, it is used on some kind of substrate (substrate). However, if individual nanoscale inorganic substances are not isolated on the substrate, the nanoscale material is used. There are many cases where the properties expected of scale inorganic materials cannot be expressed.

In order to prevent agglomeration of nanoscale inorganic substances, for example, a method of creating a very dilute dispersion state and drying the dispersion solution can be considered, but this method increases the concentration of the dispersion solution during the evaporation process of the solvent. However, it was impossible to completely prevent aggregation. Also, in the first place, the dispersion in the form of primary particles in the solution itself requires special means such as applying a large share to release the cohesive force or adding a dispersing agent. Operations required to release the force (shearing, addition of a dispersant, surface treatment, etc.) may have some influence on the properties of the original nanoscale inorganic substance.
JP 2004-097910 A JP 2004-35858 A

  The present invention has been made in view of such background art, and provides a method for producing a structure capable of forming dots, lines, or holes made of a nanoscale inorganic material on a substrate without aggregation of the inorganic material. It is to provide.

  The present invention also provides a method for producing a structure that can form dots, lines, or holes made of a nanoscale inorganic material on a curved substrate without aggregation of the inorganic material.

  The present invention also provides a structure in which any of dots, lines, or holes made of an inorganic material is formed on a substrate by the manufacturing method described above.

  A method of manufacturing a structure that solves the above problem is a method of manufacturing a structure in which either inorganic dots, lines, or holes are formed on a substrate, and a block copolymer is applied on the substrate. A step of forming a microphase separation structure of the block copolymer, and a solution in which the inorganic component is dissolved in contact with the microphase separation structure to bring the inorganic component into the phase separated segment in the microphase separation structure. A step of infiltrating, and a step of removing the block copolymer to form any of dots, lines or holes containing the inorganic component.

  A structure that solves the above-described problems is a structure that is manufactured by the above-described method and that has any of dots, lines, or holes made of an inorganic material formed on a substrate.

The present invention can provide a method of manufacturing a structure that can form dots, lines, or holes made of a nanoscale inorganic material on a substrate without aggregation of the inorganic material.
In addition, the present invention can provide a method for manufacturing a structure that can form dots, lines, or holes made of a nanoscale inorganic material on a curved substrate without aggregation of the inorganic material.

  In addition, the present invention can provide a structure in which any of dots, lines, or holes made of an inorganic material is formed on a substrate by the above manufacturing method.

Hereinafter, the present invention will be described in detail.
As a result of intensive studies, the inventors of the present invention formed a micro phase separation structure by a block copolymer on a substrate, and then converted the inorganic component of the raw material for forming the nanoscale inorganic material into one component of the micro phase separation structure. After obtaining a solution dissolved in a solvent that acts only on the liquid, the solution and the microphase separation structure are brought into contact with each other, and the dissolved inorganic component is caused to undergo microphase separation of the microphase separation structure. It was found that dots, lines or holes can be formed on the substrate by infiltrating into the existing domain and finally removing the block copolymer component.

  That is, the method for manufacturing a structure according to the present invention is a method for manufacturing a structure in which any of dots, lines, or holes made of an inorganic material is formed on a substrate, and a block copolymer is applied on the substrate. A step of forming a microphase separation structure of the block copolymer, and a solution in which the inorganic component is dissolved in contact with the microphase separation structure to bring the inorganic component into the phase separated segment in the microphase separation structure. A step of infiltrating, and a step of removing the block copolymer to form any of dots, lines or holes containing the inorganic component.

It is preferable that the microphase separation structure is brought into contact with a solution in which an inorganic component is dissolved in a solvent having affinity for the phase-separated segment of the microphase separation structure.
It is preferable that the inorganic component contained in the solution in which the inorganic component is dissolved is a metal chloride, and the solvent is water.

  It is preferable that after the step of removing the block copolymer, a step of oxidizing or reducing an inorganic component consisting of any of dots, lines, or holes obtained by removing the block copolymer is included.

The shape of the phase-separated segment in the microphase-separated structure is preferably composed of either a dot, a line, or a hole.
The surface on the substrate is preferably a curved surface.

In addition, the structure according to the present invention is a structure manufactured by the above method and having any of dots, lines, or holes made of an inorganic material formed on a substrate.
Next, the present invention will be described with reference to the drawings.

(1) Step of forming block copolymer microphase separation structure on substrate A block copolymer is applied on a substrate to form a microphase separation structure in which the block copolymer segments are separated. The block copolymer is a copolymer composed of two or more kinds of repeating units, and is polymerized by the same repeating units. For example, in the case of two kinds of repeating monomers A and B, it is called AAAAAAA-BBBBBB. Each of the repeating units such as the configuration and AAAAA-BBBBBBB-AAAAAAA is polymerized in one lump. In this block copolymer, A and B are compatible with each other depending on their chemical composition. However, when these molecular chains are gathered, the same segments of A and B will be assembled as much as possible due to the difference in compatibility. And As a result, even in the aggregate, the segments A and B exist in a separated state, and this state is called microphase separation. It is known that the form of microphase separation takes the form of a lamellar shape, a spherical shape, a cylindrical shape, etc., depending on the molecular weight, molecular weight distribution, and compatibility of each segment.

  First, a block copolymer solution is applied on a substrate. As a coating method, a conventionally known method such as spin coating, dip coating, coating with a doctor blade, spray coating, or the like can be used. When the solvent evaporates, depending on the compatibility, molecular weight, and molecular weight distribution of each segment of the block copolymer, it may be possible to form microphase separation without any special treatment. If microphase separation cannot be formed simply by coating, the entire coated substrate is once raised above the glass transition temperature (Tg) of the block copolymer and then gradually cooled to form microphase separation. Often it becomes possible.

  The form of the microphase separation structure also depends on the affinity between the substrate and each segment of the block copolymer. If the interaction between the substrate and a certain segment in the copolymer is too strong, The segment may form a layer directly on the substrate, making it difficult to form a cylinder or spherical layer separation. In that case, it is necessary to change the properties of the substrate in advance so that the affinity between the substrate and each segment of the copolymer is not biased. As a method for dispersing this affinity, a random copolymer prepared by a surface treatment with a compound having an intermediate affinity of each segment of the block copolymer or a repeating unit contained in the block copolymer to be coated is used. Alternatively, it is also effective to apply a thin alternating copolymer.

Moreover, when performing heat processing, in order to prevent the oxidative deterioration of a copolymer, it is preferable to carry out in vacuum or inert gas, such as nitrogen and argon.
(2) Step of infiltrating inorganic component A solution in which the inorganic component is dissolved is brought into contact with the microphase separation structure to infiltrate the inorganic component into the phase-separated segment in the microphase separation structure. As the solution, a solution in which an inorganic component is dissolved in a solvent is used. At this time, the solvent is selected from among the block copolymers applied in the step (1), which has an affinity for only the segment in which the inorganic component is to be infiltrated in the microphase separation structure. Here, the solvent having affinity means that the homopolymer of the segment to be infiltrated with the inorganic component can be dissolved or swollen. For example, when the block copolymer is a polystyrene-polyethylene oxide system, when it is desired to infiltrate an inorganic component on the polyethylene oxide side, the polystyrene cannot be dissolved or swollen, that is, there is no affinity for polystyrene, and the polyethylene oxide It is preferable to select water that can dissolve the water.

  After preparing the solution in which the inorganic component is dissolved in the selected solvent, the substrate on which the microphase separation structure prepared in the step (1) is formed is allowed to act. As a method of action, a method of immersing the immersion substrate in a solution, a method of leaving it in the solution for a while after immersion, or a conventionally known method such as spin coating, spray coating, dip coating, doctor blade, etc. There is a method of drying after applying. When the amount of infiltration is small, these methods can be repeated or combined as appropriate.

  Also, prior to bringing the solution in which the inorganic component is dissolved into contact with the microphase separation structure on the substrate, the solvent in the segment infiltrating the inorganic component is completely removed by subjecting the substrate to vacuum or / and heat treatment. It is also possible to increase the efficiency of infiltration of the inorganic component by removing it.

It is possible to further increase the infiltration of the inorganic component by sufficiently infiltrating the inorganic component and rinsing the surface of the substrate lightly so that no excess inorganic component remains on the surface of the substrate.
(3) The step of removing the block copolymer to form any of dots, lines or holes containing the inorganic component In the step of removing the block copolymer, the following conversion of the inorganic component as necessary Processing may be performed before or after, or simultaneously.

  In removing the block copolymer, any conventional method for removing the organic thin film such as wet, dry, heat treatment, light treatment, and active gas treatment can be used.

(4) Inorganic component conversion treatment Here, after the step of removing the block copolymer, or simultaneously, the inorganic component consisting of any of dots, lines, or holes obtained by removing the block copolymer is oxidized or This is a step of reducing to an inorganic substance.

  For example, when the desired inorganic chemical composition is an oxide or metal and the inorganic raw material component is a chloride, some conversion process is required. By heating the inorganic component of chloride prepared in the step (3) in an oxygen atmosphere, an oxide nanostructure can be prepared, and reduced by heat treatment in a hydrogen atmosphere or vacuum. Thus, a metal nanostructure can also be created.

  The above steps (1) to (4) are very simple and versatile. On the other hand, it is possible to obtain a nanostructured substrate by a top-down process such as photolithography, but in addition to the increase in size of the apparatus, the photolithographic process has a limitation on the shape of the substrate and has a shape that is greatly curved. In some cases, the processing may not be possible, and there is a point of low versatility. However, the steps (1) to (4) are not particularly limited by the substrate shape, and the surface on the substrate may be a curved surface.

  The substrate material that can be used in the present invention is not particularly limited, and metals, semiconductors, insulators, resin materials, optical materials such as glass and quartz, ceramics, and the like can be used. Further, the shape of the substrate is not particularly limited, and is not necessarily flat, as long as it can apply a block copolymer that causes microphase separation. Further, in the present invention, the substrate material is coated with a block copolymer, an operation for causing microphase separation of the block copolymer (heating), an action with a solution in which an inorganic precursor component is dissolved, a step of removing the block copolymer, Although it will be exposed to the process which converts an inorganic component into the target compound, it is necessary to satisfy | fill the conditions that it is the material which has the tolerance with respect to these processes.

  As a selection of the block copolymer, it is first required to be a material that causes microphase separation. Conventionally known materials can be used for the block copolymer that causes microphase separation. However, in order to cause layer separation, it is generally necessary that the block copolymer has poor phase solubility between the segments. . As for the form of microphase separation, for example, in a diblock copolymer, one segment is dispersed in a spherical shape, a state where it is dispersed in a cylindrical shape, or a state where both segments are folded in a lamellar shape. Are known. The shape of these phase separations is not only the chemical composition that constitutes the block copolymer, but also the solvent for dissolving the block copolymer, the heat treatment conditions after coating, and each segment of the coated surface and block copolymer. It can also be controlled by the difference in affinity. In addition, the size of the microphase separation structure can be adjusted by adjusting the molecular weight of each segment of the block copolymer.

  Examples of each segment of the block copolymer that can be used in the present invention are shown below, but the present invention is not limited to these compounds.

  A conventionally known solvent may be used as a solvent for applying the block copolymer. The solvent may be a single solvent or a mixed solvent, and can be appropriately selected according to the composition and molecular weight of the block copolymer. For example, tetrahydrofuran, toluene, benzene, ethyl acetate, ethanol, dimethylformamide, chloroform and the like can be mentioned.

The inorganic substance forming the structure is a metal or a metal oxide, but the inorganic component of the precursor needs to have a composition that is soluble in a solvent such as a salt, a complex, or an alkoxide. If platinum is selected as the nanostructure material, it is possible to use a salt of H ₂ PtCl ₆ as the precursor, and when forming a nanostructure with ruthenium oxide (RuO ₂ ), as the precursor It is possible to select a complex such as RuCl ₃ or Ru (III) acetylacetone. In order to form nanostructures with TiO ₂ , complexes such as chlorides such as TiCl ₄ , alkoxides such as Ti (OEt) ₄ and Ti (OiPr) ₄ , or titanium oxide bis (pentanedionate) Alternatively, TiOSO ₄ , Ti (NO ₃ ) _4, or the like can be selected.

  As a solvent for dissolving the inorganic component, a conventionally known solvent can be selected, but as a condition required for the solvent, it is first necessary to have solubility in the inorganic component. The concentration at which the inorganic component is dissolved is 1 to 80% by mass, preferably 3 to 60% by mass, and more preferably 5 to 40% by mass. If the solubility is too low, the amount of the inorganic component that infiltrates even if it acts on the block copolymer that has undergone microphase separation is small, resulting in a nanostructure reflecting the microphase separation of the block copolymer. It is difficult to form. On the contrary, even if a solution dissolved at an excessively high concentration is brought into contact with the block copolymer, a phenomenon that the microphase separation structure of the block copolymer is destroyed when infiltrated is observed.

  In removing the block copolymer, any conventional method for removing the organic thin film such as wet, dry, heat treatment, light treatment, and active gas treatment can be used. Thus, it is possible to select a process other than the step of disturbing the microphase separation structure or damaging the inorganic component. In particular, although the method of removing the block copolymer by heating is simple, it often disturbs the form of the microphase-separated structure. Therefore, when attempting removal by heating, it is necessary to pay attention to the heating rate and atmosphere. High energy light irradiation such as ultraviolet rays or dry process such as RIE (reactive ion etching) is preferable from the viewpoint of maintaining the shape of the block copolymer. In addition, by performing ultraviolet irradiation in a highly oxidizing atmosphere such as ozone, the block copolymer can be efficiently removed while maintaining the form of the phase separation structure.

  As a method for converting from an inorganic component to a desired inorganic structure, for example, when the inorganic substance has a final target structure, conversion can be performed by heating in air or oxygen, RIE using oxygen gas, or the like. Further, when gold or platinum itself is used as the final target structure, it can be converted by a reductive treatment such as heating in a hydrogen atmosphere.

  In the present invention, examples of the structure include nanoparticles having nano-size characteristics, nanorods, nanocylinders, and nanoholes.

Embodiments of the present invention will be described below using specific examples, but the present invention is not limited to these examples.
Example 1
As a block copolymer, polystyrene (molecular weight 227000 g / mol) -polyethylene oxide (molecular weight 61000 g / mol) block copolymer (dispersion degree: 1.04, manufactured by Sowa Chemical Co., Ltd., trade name P2806-SEO) is 1% by mass. So that it was dissolved in toluene. Since white turbidity was observed in dissolution at room temperature, the white turbidity disappeared once the solution was heated to 60 ° C. Transparency was maintained even when the solution was returned to room temperature. This toluene solution was applied on a silicon wafer (3 mm × 3 mm, thickness: 0.5 mm) by spin coating at 3500 rpm for 1 minute. The surface of the substrate after coating was changed by the interference color, indicating that a thin film was coated.

  Further, when the surface of the substrate was observed with an atomic force microscope (AFM), a dot having a diameter of about 30 nm was observed, and from the composition of the block copolymer, a microsphere in which polyethylene oxide units existed in a spherical shape in the polystyrene matrix. The phase separation structure was confirmed. Subsequently, this substrate was vacuum-dried at 40 ° C. for 24 hours.

Platinum salt (H ₂ PtCl ₆ , manufactured by Aldrich) was dissolved in pure water as an inorganic component to prepare a 15% by mass solution. The vacuum-dried substrate is immersed in this H ₂ PtCl ₆ solution, taken out of the solution for 24 hours to infiltrate the platinum salt component into the polyethylene oxide unit having a high affinity with water, and the surface is rinsed with pure water. It is. Next, in order to remove the block copolymer component from the substrate, a structure was obtained by treatment with a UV / ozone decomposition apparatus for 4 hours. After the substrate surface after the treatment, the interference color due to the formation of the thin film seen before the treatment disappeared, and it was confirmed that the block copolymer was removed by the UV / ozone treatment. When the surface of the substrate was observed with AFM, a large number of nano-sized dot-like spots were observed. FIG. 1 shows an atomic force microscope (AFM) photograph of the substrate surface of the structure obtained in Example 1.

Example 2
In Example 1, a structure in which nanodots were formed on the substrate was obtained in the same manner except that the substrate material was changed from a silicon wafer to stainless steel (3 mm × 3 mm, thickness: 0.5 mm).

Example 3
In Example 2, a structure in which nanodots were formed on a substrate was similarly obtained except that the substrate material was changed from flat stainless steel to a stainless steel substrate (thickness: 0.5 mm) having a curved surface as shown in FIG. Obtained. AFM measurement was performed near the top of the curved surface, and it was confirmed that nano-sized dots were formed in the same manner.

Example 4
In Example 1, the block copolymer was changed to polystyrene (molecular weight 19000 g / mol) -polyethylene oxide (molecular weight 123000 g / mol) block copolymer (dispersion degree: 1.04, manufactured by Soka Chemical Co., Ltd., trade name P1920-SEO). A platinum nanostructure was prepared in the same manner except that it was changed. FIG. 3 shows an atomic force microscope (AFM) photograph of the substrate surface of the structure obtained in Example 4.

Example 5
In Example 1, a nanostructure was produced in the same manner except that the inorganic component was changed to RuCl ₃ . Note that the nanostructure finally formed on the substrate surface is RuO ₂ .

Application example 1
The nanostructure produced in Example 2 was used as a sample substrate for mass spectrometry.
The board | substrate created in Example 2 was adhere | attached and fixed to the stainless steel target board | substrate for MALDI-TOF MS measurement cut by 0.6 mm with the conductive double-sided tape.

1 μL of a tetrahydrofuran solution (10 μmol / L) of triacetyl-β-cyclodextrin (molecular formula = C ₈₄ H ₁₁₂ O ₅₆ , molecular weight = 2017.75, Tokyo Kasei: product code = T1844) was dropped onto this substrate with a micropipette. And dried.

  Next, this substrate was mounted on a MALDI-TOF MS apparatus (trade name: REFLEX-III, manufactured by Bruker Daltonics). The irradiation laser in the measurement of MALDI-TOF MS was a nitrogen laser (wavelength = 337 nm), which was a positive ion reflection mode (reflector mode). The irradiation laser intensity is measured at an intensity 2% stronger than the intensity at which the peak of the parent ion starts to appear, and the spectrum of 20 pulses is integrated at one location, integrated over 10 locations, and a total of 200 pulses. A spectrum was obtained by summing up signal intensities obtained from laser irradiation.

In addition, the acceleration voltage was set to 26.5 kV, and peaks with mass numbers from 0 to 2500 were captured.
Further, the cut-off value in the low molecular weight region in the measurement was 0 or more, that is, the cation species flying to the detector were taken in all regions without the cut-off.

  Evaluation of the obtained spectrum is based on a molecule to be measured (a peak appearing in the vicinity of 2018 to 2125 as a parent ion as a proton or an adduct of a monovalent metal cation such as Na, K, or Ag on a substrate) And the intensity of the peak and the number of types of decomposition products in the molecular weight range of 50 to 2000.

Comparative application example 1
For comparison, mass spectrometry was performed in the same manner as in Application Example 1 using a substrate on which no nanostructure was formed on the surface (a stainless steel substrate before treatment in Example 1).

  When the presence or absence of the nanostructure is compared, the molecular weight region: 2018 to 2125 as an adduct of a parent ion, that is, a monovalent metal cation such as Na, K, or Ag on the substrate from the substrate on which the nanostructure is formed. Whereas the peak appearing in the vicinity was the main peak group, the peak group derived from fragments with a mass number of 500 or less was the main even when the laser intensity was adjusted on the substrate without the formation of nanostructures. It was.

  In the production method of the present invention, an inorganic nanostructure can be formed on a substrate by a simple method. In addition, according to the manufacturing method of the present invention, an inorganic nanostructure can be formed on a curved substrate by a simple method. The structure thus created can be applied to electrode materials, optical materials, electronic materials, analytical elements, and the like.

The atomic force microscope (AFM) photograph of the substrate surface of the structure obtained in Example 1 of the present invention is shown. It is the schematic which shows the stainless steel substrate which has a curved surface used in Example 3 of this invention. The atomic force microscope (AFM) photograph of the substrate surface of the structure obtained in Example 4 of the present invention is shown.

Explanation of symbols

  1 Stainless steel substrate

Claims (7)

  A method of manufacturing a structure in which either inorganic dots, lines or holes are formed on a substrate, and the block copolymer is coated on the substrate to form a block copolymer microphase separation structure. A step of bringing a solution in which an inorganic component is dissolved into contact with the microphase-separated structure to infiltrate the inorganic component into a phase-separated segment in the microphase-separated structure, and removing the block copolymer And forming a dot, a line or a hole containing the inorganic component.   The structure according to claim 1, wherein the microphase separation structure is brought into contact with a solution in which an inorganic component is dissolved in a solvent having an affinity for the phase-separated segment of the microphase separation structure. Production method.   The method for producing a structure according to claim 1 or 2, wherein the inorganic component contained in the solution in which the inorganic component is dissolved is a metal chloride, and the solvent is water.   The step of removing the block copolymer includes a step of oxidizing or reducing an inorganic component composed of any one of dots, lines, and holes obtained by removing the block copolymer. The method for producing a structure according to any one of items 1 to 3.   The method of manufacturing a structure according to any one of claims 1 to 4, wherein the shape of the phase-separated segment in the microphase-separated structure consists of any one of dots, lines, and holes.   6. The method for manufacturing a structure according to claim 1, wherein the surface on the substrate is a curved surface.   A structure manufactured by the method according to any one of claims 1 to 6, wherein any of dots, lines, or holes made of an inorganic material is formed on a substrate.