JP5052074B2 - Method for forming nano metal particles and nano-order wiring - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a method for forming nano metal particles and nano-order wiring, and in particular, a method for forming nano metal particles used for formation of fuel cell catalyst particles, wiring to semiconductors, and the like by vacuum deposition. The present invention relates to a method of forming nano-order wiring using nano-metal particles. The nano-order in the present invention means about 30 nm or less and about 1 nm or more.

  Conventionally, when nano metal particles are formed by a dry process, metal particles are deposited to a thickness of several nanometers on a substrate at room temperature by an electron beam vapor deposition method or a resistance vapor deposition method. The substrate is heated (annealed) until nano metal particles are formed on the substrate.

  When nano metal particles are formed by the method of the prior art, there is a problem that the particle size is different from the variation in aggregation of the metal particles during temperature control of the substrate and heating process. In addition, there is a problem that the particle size varies depending on the deposition amount even at the same substrate temperature.

  An object of the present invention is to solve the above-mentioned problems of the prior art, and there is little variation in the particle size of the nanometal particles, and the method of forming the nanometal particles and the formation of the nano-order wiring that can easily control the particle size It is to provide a method.

The method for forming nano metal particles of the present invention comprises a nano-order flatness and a vacuum deposition atmosphere when a metal material is vacuum-deposited on a graphite substrate made of a material having very few chemical bonds on the surface. In the state where the substrate is heated to a temperature in the range from 400 ° C. to less than the melting point of the metal material, the deposition amount of the metal material is controlled by a nano-order thickness to deposit the nanometal particles having a controlled diameter. It is characterized by forming.

  When the substrate and the metal material as described above are not used, and the substrate temperature is less than 400 ° C. in a vacuum deposition atmosphere, the diameter of the metal particles is increased, and the portion is agglomerated and localized to grow. As the substrate temperature further decreases, metal particles overlap on a very thin film, and the particle diameter is controlled to form an isolated particle monolayer on the substrate. Can no longer grow.

In the method for forming nano metal particles, the graphite substrate is a flat substrate having at least one step of 10 nm or less, and the nano metal particles are arranged along an intersection line between a plane of the step and a lower end of a rising surface of the step. It is characterized by arranging.

  By adopting such a configuration, the metal particle single layer can be arranged in a line along the intersection line between the step plane on the substrate surface and the lower end of the rising surface of the step. Convenient to.

The method of forming a nano-order wiring of the present invention is a flat graphite substrate having at least one step of 10 nm or less, and a metal material is vacuum-deposited on a substrate made of a material having very few chemical bonds on the surface. When the wiring is formed, the deposition amount of the metal material is controlled by the nano-order thickness in a state where the substrate is heated to a temperature ranging from 400 ° C. to less than the melting point of the metal material in the vacuum deposition atmosphere. The nano metal particles having a controlled diameter are arranged along the intersection line between the plane of the step and the lower end of the rising surface of the step to form a wiring.

  By adopting such a configuration, the metal particle single layer can be arranged in a line along the intersection line between the step plane on the substrate surface and the lower end of the rising surface of the step. convenient.

  According to the present invention, by controlling the deposition amount of the metal particles, the diameter of the nano metal particles, that is, the particle height can be controlled, and the step surface of the substrate surface and the lower end of the rising surface of the step can be controlled. Since vapor deposition is performed by arranging in a line along the intersecting line, there is an effect that a nano-order wiring can be formed.

  According to the embodiment of the method for forming nano metal particles according to the present invention, the surface is made of a material having nano-order flatness and extremely few chemical bonds on the surface, and has at least one step of about 10 nm or less. When vacuum depositing a metal material on a flat substrate, the vacuum deposition process conditions are appropriately set in a state where the substrate is heated to a temperature ranging from 400 ° C. to less than the melting point of the metal material in the vacuum deposition atmosphere. By evaporating a predetermined amount of the metal material, the deposition amount of the metal material is controlled by nano-order to form the nano-metal particles having a controlled particle diameter, that is, a particle height, It can be formed by arranging in a straight line along the intersection line between the step plane on the substrate surface and the lower end of the rising surface of the step. If the substrate temperature is equal to or higher than the melting point, the crystal state of the deposited metal particles changes, which is not preferable. The vapor deposition particles move on the surface of the substrate, and aggregate at the substrate temperature during the process to increase the particle diameter, thereby forming nano metal particles having a controlled diameter.

  An apparatus including an electron beam evaporation source will be described below as an example of an evaporation apparatus used for carrying out the method for forming nano metal particles. The vapor deposition source that can be used in the present invention is not particularly limited. For example, a sputtering, arc ion plating, or coaxial vacuum arc vapor deposition source may be used in addition to the electron beam vapor deposition source.

  FIG. 1 schematically shows a configuration example of an electron beam evaporation apparatus provided with an electron beam evaporation source for carrying out the method for forming nano metal particles of the present invention.

  As shown in FIG. 1, the electron beam vapor deposition apparatus includes a cylindrical vacuum chamber 1, and an electron beam vapor deposition source 2 attached to a bottom flange is provided in the vacuum chamber 1. A metal material for vapor deposition 3 is accommodated in the crucible of the vapor deposition source 2, and a substrate stage 4 is provided facing the electron beam vapor deposition source 2. The substrate stage 4 is configured such that the deposition surface of the substrate S for depositing nano metal particles is attached to face the metal material 3. A substrate manipulator 5 is attached to the center of the back surface of the substrate stage 4 through the upper wall surface of the vacuum chamber 1 so that the substrate S can be rotated together with the substrate stage 4 by the substrate manipulator 5. A heating means 6 such as a heater is attached to the surface opposite to the surface of the substrate stage 4 to which the substrate S is attached, so that the substrate stage 4 and consequently the substrate S can be heated. A film thickness gauge 7 is attached in the vicinity of the vapor deposition surface of the substrate S so that the film thickness of the vapor deposition film can be measured.

A turbo molecular pump 8, a valve 9 and a rotary pump 10 are sequentially connected to the wall of the vacuum chamber 1, and the turbo molecular pump 8 to the rotary pump 10 are connected by a metal vacuum pipe 11. It is comprised so that evacuation of can be performed. In this case, the inside of the chamber is preferably evacuated to 10 ⁻⁵ Pa or less and can be held.

  The case where the method for forming nano metal particles of the present invention is carried out using the electron beam vapor deposition apparatus shown in FIG. 1 will be described below.

  According to the present invention, the particle size is controlled by depositing a predetermined metal material in a predetermined amount within a predetermined range on a substrate heated to 400 ° C. or higher and below the melting point of the metal material. Forming nano metal particles, and forming nano metal particles with controlled particle size by arranging them in a straight line along the intersection line between the step plane of the substrate surface and the lower end of the rising surface of the step can do.

  As described above, a preferable substrate that can be used in the present invention is a flat substrate having a nano-order flatness and a material having extremely few chemical bonds on the surface and having at least one step of about 10 nm or less. And a substrate made of graphite, for example, High Orientated Pyretic Graphite (abbreviation HOPG), silicon or the like.

When forming a deposited film of nano metal particles on a substrate, it is preferable to use a HOPG substrate. Since the HOPG substrate is sintered at a high temperature in the manufacturing process, its manufacturing cost is high. However, since it can be peeled off for each graphene sheet, the nanometal particles can be peeled off after vapor deposition, and the substrate can be used repeatedly. The problem is solved. In addition, when a nanometal particle powder is collected instead of forming a vapor deposition film of nanometal particles on a substrate, a substrate such as a silicon substrate is used instead of a HOPG substrate, as described below. It is also possible to deposit the nanometal particles on a metal particle desorption layer such as a SiO ₂ film provided on the substrate, and then perform a predetermined treatment to desorb and collect the powder.

  Examples of the metal material used in the present invention include platinum and cobalt.

  According to the present invention, the substrate S made of HOPG or the like is heated to the above-described predetermined temperature using the heating means 6 before the nano metal particles are formed. The crucible of the electron beam evaporation source 2 is filled with a metal material 3 such as platinum. The electron beam evaporation source 2 is operated, an electron beam is injected into the crucible, the evaporation material is melted and evaporated, and the metal material 3 is evaporated on the substrate S with a predetermined thickness. The thickness of the deposited film is a value calculated from the weight adhering to the film thickness gauge 7 by assuming that the same amount is uniformly adhering to the substrate S and calculating the weight from the substrate area and the specific gravity of the metal material 3. It is. The size (diameter) of the deposited metal particles is calculated by measuring the height of the particles using an AFM (Atomic Force Microscope). In this case, it is assumed that the particle height is approximately the same as the particle diameter.

  In this case, the height of the metal particles, that is, the particle diameter can be controlled by changing the metal deposition amount in nano order.

  Next, a case where nano metal particles are collected will be described. The substrate and the metal material are as described above. Hereinafter, a case where a silicon substrate is used will be described.

According to the present invention, a SiO ₂ film is formed on a silicon substrate according to a known process condition according to CVD or sputtering, and a metal is vapor-deposited on the film at the substrate temperature described above according to the evaporation method described above. When AFM observation is performed on the SiO ₂ surface before the metal is deposited, the height of the unevenness on the SiO ₂ film surface is about 0.2 to 0.3 nm, which is sufficiently flat. Also in this case, the height of the metal particles, that is, the particle size can be controlled by changing the metal deposition amount in nano order. The metal is sufficiently finely divided on the SiO ₂ film. In the case where metal particles are formed on the SiO ₂ film, for example, when nano-platinum particles are deposited and then treated with hydrofluoric acid or the like, the SiO ₂ film melts, and only platinum nanoparticles can be collected.

  In the above description, the electron beam evaporation apparatus is used. However, the evaporation source is not limited to the electron beam evaporation source, and similar results can be obtained by using sputtering or arc ion plating.

  Nano-platinum particles were formed on the HOPG substrate using the electron beam evaporation apparatus shown in FIG.

  Before forming the nanoplatinum particles, the HOPG substrate S was heated to a predetermined temperature (500 ° C.) using the heating means 6. The crucible of the electron beam evaporation source 2 was filled with platinum. The electron beam evaporation source 2 was operated, an electron beam was introduced into the crucible, and platinum was melted and evaporated to change the deposition amount to 1 nm, 2 nm, and 4 nm, and platinum particles were deposited on the HOPG substrate S. The surface of the obtained platinum vapor deposition film was observed with AFM.

  2 (a) and 2 (b) are photographs showing AFM observation images on the surface of a platinum vapor deposition film formed on a HOPG substrate with vapor deposition amounts of 1 nm and 2 nm, respectively. 2A and 2B, when the deposition amount is 1 nm, the height of the platinum particles, that is, the thickness of the platinum deposition film is about 8 nm, and when the deposition amount is 2 nm, the height of the platinum particles, that is, platinum deposition. The thickness of the film was 17 nm. In this case, it was assumed that the particle height was proportional to the particle diameter.

  The thickness of this platinum vapor deposition film is calculated from the weight adhering to the film thickness gauge 7 by assuming that the same amount is uniformly adhering to the HOPG substrate S and calculating the weight from the substrate area and the specific gravity of the vapor deposition material. It is the value.

  2A and 2B, it is observed from the AFM photographs on the left side of each of FIGS. 2A and 2B that the platinum particles are obliquely grown along the steps. It was found that the metal particles were linearly deposited and arranged along the intersecting line with the lower end of the surface. When the surface of the HOPG substrate before vapor deposition is observed by AFM, it can be seen that there are flat terraces and steps as shown in FIG. 3, and the higher step height is about 0.5 nm.

  In FIG. 4, the height (nm) of platinum particles is plotted against the amount of deposited platinum (nm), and the dependence of the height of the platinum particles on the deposited amount is shown. In FIG. 4, the particle height is plotted with respect to the deposition amount (1 nm, 2 nm, and 4 nm) when the above deposition process is repeated at a substrate temperature of 400 ° C. As is apparent from the graph of FIG. 4, it is understood that the grain height, that is, the particle diameter can be controlled by changing the deposition amount while the substrate temperature is heated to 400 ° C. and 500 ° C.

  A platinum material was deposited in the same manner as in Example 1 except that the substrate temperature was changed to room temperature (27 ° C.), 200 ° C., 300 ° C., 400 ° C., and 500 ° C. When the platinum vapor deposition film formed on the HOPG substrate is observed by AFM, in the case of vapor deposition at room temperature, as shown in FIG. 5, metal fine particles are formed in a dispersed manner, but the particle diameter is large (particle height). In the case of vapor deposition at 200 ° C., as shown in FIG. 6, the platinum particles are very large regardless of the terraces of the substrate, and have a portion that grows by aggregation and localization. In the case of vapor deposition at 300 ° C. as observed, platinum particles having a height of about 15 nm are formed to spread over the entire substrate as shown in FIG. It is observed that there is a part. Moreover, in the case of vapor deposition at 400 ° C., it can be seen that platinum particles are formed in a dot shape of about 30 nm as shown in FIG. Further, in the case of vapor deposition at 500 ° C., the same result as in the case of Example 1 shown in FIGS. 2 (a) and (b) was obtained.

  By changing the deposition amount in a state where the substrate temperature is heated to 400 ° C. or higher, the height of the grains, that is, the particle diameter can be changed. As described above, according to AFM observation, when the substrate temperature is less than 400 ° C., the particle size increases, and when the substrate temperature reaches 300 ° C. or 200 ° C., the particles overlap on a very thin film. It turns out that it becomes impossible to grow a particle monolayer on the substrate in isolation. In order to grow an isolated particle monolayer, the substrate temperature must be 400 ° C. or higher, preferably 500 to 600 ° C.

In this embodiment, instead of depositing platinum on the HOPG substrate, a SiO ₂ film is formed on a silicon substrate under known sputtering process conditions, and platinum is formed on the SiO ₂ film in the same manner as in the first embodiment. Was deposited at a substrate temperature of 500 ° C., and nano platinum particle powder was collected.

Surface state before depositing platinum on SiO ₂ film, according to the AFM observation image shown in FIG. 9, the height of the unevenness of the SiO ₂ film surface is about 0.2 to 0.3 nm, a sufficient flat It was. Moreover, according to the AFM observation image with respect to the obtained platinum vapor deposition film | membrane, when a film thickness is 2 nm, as shown in FIG. 10, the height of a platinum particle is about 2-3 nm, and a film thickness is 1 nm. As shown in FIG. 11, the height of the platinum particles was about 1-2 nm. Also in this case, it is understood that the height of the platinum particles, that is, the particle size can be controlled by changing the platinum deposition amount. The metal is sufficiently finely divided on the SiO ₂ film.

Next, hydrofluoric acid treatment was performed on the substrate on which the platinum vapor deposition particles were formed to melt the SiO ₂ film, and nano platinum particles were collected.

  According to the present invention, the diameter of the nano metal particles can be controlled by controlling the deposition amount of the metal, and the metal is deposited on the step of the substrate surface, so that the nano-order wiring can be formed. it can. Therefore, the present invention can be used in the wiring formation field in the semiconductor field, the catalyst particle formation field in the fuel cell, and the like.

The schematic diagram of the example of 1 structure of the electron beam vapor deposition apparatus used in order to implement the formation method of this invention. It is a photograph which shows the AFM observation image of the platinum vapor deposition film (substrate temperature: 500 degreeC) obtained in Example 1, (a) is a case where the amount of vapor deposition is 1 nm, (b) is a case where the amount of vapor deposition is 2 nm. 2 is a photograph showing an AFM observation image of the surface of a HOPG substrate before vapor deposition used in Example 1. FIG. The graph which shows the platinum vapor deposition amount dependence with respect to the height of the platinum particle obtained in Example 1. FIG. The photograph which shows the AFM observation image of the platinum vapor deposition film | membrane (substrate temperature: room temperature) obtained in Example 2. FIG. The photograph which shows the AFM observation image of the platinum vapor deposition film | membrane (substrate temperature: 200 degreeC) obtained in Example 2. FIG. The photograph which shows the AFM observation image of the platinum vapor deposition film | membrane (substrate temperature: 300 degreeC) obtained in Example 2. FIG. The photograph which shows the AFM observation image of the platinum vapor deposition film | membrane (substrate temperature: 400 degreeC) obtained in Example 2. FIG. Photograph showing an AFM observation image of the surface of the SiO ₂ film before the platinum deposition used in Example 3. The photograph which shows the AFM observation image of the platinum vapor deposition film (film thickness: 2 nm) obtained in Example 3. The photograph which shows the AFM observation image of the platinum vapor deposition film | membrane (film thickness: 1 nm) obtained in Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum chamber 2 Electron beam vapor deposition source 3 Metal material for vapor deposition 4 Substrate stage 5 Substrate manipulator 6 Heating means 7 Film thickness measuring element 8 Turbo molecular pump 9 Valve 10 Rotary pump 11 Vacuum piping S Substrate

Claims (3)

When a metal material is vacuum-deposited on a graphite substrate made of a material having a nano-order flatness and extremely few chemical bonds on the surface, the melting point of the metal material from 400 ° C. in the vacuum deposition atmosphere. In a state where the metal material is heated to a temperature in a range up to less than the temperature, the deposition amount of the metal material is controlled by the nano-order thickness to form a nanometal particle having a controlled diameter. Forming method. The graphite substrate is a flat substrate having at least one step of 10 nm or less, and the nano metal particles are arranged along an intersection line between a plane of the step and a lower end of a rising surface of the step. Item 2. A method for forming nanometal particles according to Item 1. When a wiring is formed by vacuum deposition of a metal material on a flat graphite substrate having at least one step of 10 nm or less and made of a material having very few chemical bonds on the surface, the vacuum deposition is performed. In a state where the substrate is heated to a temperature in the range from 400 ° C. to less than the melting point of the metal material in an atmosphere, the deposition amount of the metal material is controlled by a nano-order thickness to deposit the nanometal with a controlled diameter A method of forming a nano-order wiring, wherein the wiring is formed by arranging particles along an intersection line between a plane of the step and a lower end of the rising surface of the step.