JP2016176104A - Method for manufacturing self-supporting copper thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a copper thin film, capable of efficiently manufacturing a self-supporting copper thin film having a lower resistance.SOLUTION: The method for manufacturing a copper thin film comprises: a step S1 of forming the copper thin film having a film thickness of 2-30 μm on the surface of a substrate having a surface consisting of a ceramic material constituted of a compound of aluminum and/or silicon and at least one kind of elements selected from a group consisting of oxygen, nitrogen and carbon or carbon by setting a temperature of a vapor deposition source to 1200°C or more and circulating inert gas so as to be a total pressure of 0.001-10 Pa; and a step S2 of peeling the formed copper thin film in a thin film state from the surface of the substrate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a self-supporting copper thin film, and a self-supporting copper thin film produced thereby.

  In general, a self-supporting copper thin film (copper foil) is manufactured by a method such as rolling or electrolysis.

  In the rolling process, for example, as described in Patent Document 1, a plurality of rolls having a certain width are rotated, a copper plate is passed between the rolls, and a copper foil is stretched thinly by applying pressure to the copper plate. To manufacture. On the other hand, in order to manufacture a copper foil by electrolysis, as described in Patent Document 2, for example, copper is electrodeposited on the surface of the metal drum while rotating the metal drum.

JP 2012-106283 A JP 2001-62955 A

  When using a copper thin film that can be self-supporting as described above for applications that require electrical conductivity, it is desirable to further reduce the resistivity and to reduce the weight per area by making the copper thin film thinner. It is. Therefore, an object of the present invention is to provide a method for producing a copper thin film, which can efficiently produce a self-supporting copper thin film having a lower resistance.

  Although methods for forming a copper thin film on a support such as a circuit board by vapor deposition are known, these methods are intended to adhere copper to the support, and the copper thin film is peeled off from the support to form a self-supporting film. Not intended to be. As a result of intensive studies, the present inventors have found that when copper is deposited on a specific material such as ceramics, the formed film can be easily peeled off as a self-supporting copper thin film, and the present invention has been achieved. .

According to a first aspect of the present invention, a method for producing a copper thin film comprising:
Depositing copper on the surface of the substrate having a surface made of a ceramic material or carbon to form a copper thin film;
There is provided a method of manufacturing a self-supporting copper thin film including a step of peeling the formed copper thin film as it is from the surface.

  In the method for producing a copper thin film, the ceramic material is composed of a compound of aluminum and / or silicon and at least one element selected from the group consisting of oxygen, nitrogen, and carbon, and has a surface made of the ceramic material. The copper may be deposited on the surface of the substrate. The ceramic material may be silicon oxide.

  You may form the said copper thin film which has a film thickness in the range of 2-30 micrometers in the process of forming the said copper thin film of the manufacturing method of the said copper thin film.

  In the step of forming the copper thin film in the method for producing the copper thin film, the temperature of the vapor deposition source is set to 1200 ° C. or more, and the vapor deposition source and the substrate are longer than the shortest side length in the projected shape of the substrate viewed from the vapor deposition source. The copper may be deposited by reducing the distance between them.

  In the step of forming the copper thin film in the method for producing the copper thin film, the copper may be deposited by setting the total pressure within a range of 0.001 to 10 Pa. At this time, an inert gas may be circulated to make the total pressure within a range of 0.001 to 10 Pa.

  In the step of forming the copper thin film in the method for producing the copper thin film, the temperature of the substrate may be maintained at 300 to 600 ° C.

  In the step of peeling the copper thin film in the method for producing the copper thin film, one end of the copper thin film is adhered to a support film, and the copper thin film is peeled from the substrate by applying tension to the copper thin film from the support film. It's okay.

  In the method for producing a copper thin film, the substrate may have a cylindrical shape, and in the step of peeling the copper thin film, the copper is deposited while rotating the substrate about the cylindrical axis, The copper thin film may be continuously peeled from the substrate by forming the copper thin film on the outer peripheral surface of the substrate having a cylindrical shape and applying tension to one end of the copper thin film. In the step of peeling the copper thin film, the copper thin film may be peeled off by lowering the temperature of the substrate by 100 ° C. or more than the temperature of the substrate in the step of depositing copper.

  According to the 2nd aspect of this invention, the self-supporting copper thin film manufactured by the manufacturing method of a 1st aspect is provided.

According to a third aspect of the present invention, a self-supporting copper thin film comprising:
The film thickness is in the range of 2 to 30 μm,
In the X-ray diffraction measurement pattern by the out-of-plane method using CuKα rays of the copper thin film, 111 diffraction lines of copper are detected, and diffraction lines from any other copper crystal plane are substantially detected. not,
A free-standing copper thin film having a resistivity in the range of 1.6 to 2.1 μΩcm is provided.

  In the self-supporting copper thin film, the resistivity may be in a range of 1.6 to 2.0 μΩcm.

  In the self-supporting copper thin film, the film thickness may be in a range of 2 to 9 μm.

  In the method for producing a copper thin film of the present invention, a copper thin film is formed on the surface of a substrate having a surface made of a ceramic material or carbon having a weak interaction with copper. Can be peeled off. Moreover, since the copper thin film manufactured by the manufacturing method of this invention is low resistance and thin, it is used for the current collection foil of an electrical storage device, a heat radiating sheet, an electromagnetic wave shielding sheet, a flexible circuit board (FPC), a conductive tape, and a decoration sheet. Can be used. In addition, since the copper thin film produced by the production method of the present invention has a {111} crystal plane on the surface, it can be suitably used for various applications such as a catalyst for synthesizing graphene.

FIG. 1 is a flowchart showing a method for producing a self-supporting copper thin film. FIG. 2 is a schematic view of an apparatus for producing a free-standing copper thin film in a continuous process. FIG. 3A is a digital camera photograph of the Cu thin film of Example 1 and the substrate from which the Cu thin film was peeled off. FIG. 3B is a digital camera photograph of the Cu thin film of Example 2 and the substrate from which the Cu thin film was peeled off. FIG. 3C is a digital camera photograph of the Cu thin film of Example 3 and the substrate from which the Cu thin film was peeled off. FIG. 3D is a digital camera photograph of the Cu thin film of Example 4 and the substrate from which the Cu thin film was peeled off. FIG. 3E is a digital camera photograph of the Cu thin film of Example 5 and the substrate from which the Cu thin film was peeled off. FIG. 3F is a digital camera photograph of the Cu thin film of Example 6 and the substrate from which the Cu thin film was peeled off. FIG. 3G is a digital camera photograph of the Cu thin film of Example 7 and the substrate from which the Cu thin film was peeled off. FIG. 3H is a digital camera photograph of the Cu thin film of Example 8 and the substrate from which the Cu thin film was peeled off. FIG. 3I is a digital camera photograph of the Cu thin film of the reference example and the substrate from which the Cu thin film was peeled. FIG. 3J is a digital camera photograph of the Cu thin film of Example 9 and the substrate from which the Cu thin film was peeled off. FIG. 3K is a digital camera photograph of the Cu thin film of Example 10 and the substrate from which the Cu thin film was peeled off. 4 is a diagram showing XRD patterns of Cu thin films of Examples 9 and 10 and copper foils of Comparative Examples 1 to 3. FIG. FIG. 5 is a table showing the formation conditions, film thicknesses, resistivity, and results of peeling from the substrates of the Cu thin films of Examples 1 to 10 and Reference Example and the copper foils of Comparative Examples 1 to 3.

  Hereinafter, the manufacturing method of the copper thin film of this invention and embodiment of the copper thin film manufactured by it are described, referring drawings. In the present application, a self-supporting film (a self-supporting film) is a film that has no permanent contact with a support member such as a substrate and can maintain its entire structure (that is, does not collapse or decompose). Say. That is, the self-supporting membrane can maintain its shape as a membrane at least in a predetermined area even if no other support exists, and can be handled alone. The self-supporting film is different from a “coating” formed by, for example, vapor deposition on a support made of another material and held on the support.

[Manufacturing method of copper thin film]
As shown in FIG. 1, the method for producing a copper thin film mainly includes a step of forming a copper thin film on the substrate surface (copper thin film forming step) S1 and a step of peeling the copper thin film from the substrate (peeling step) S2. Have.

<Copper thin film formation process S1>
As the substrate for forming the copper thin film, a substrate having a surface made of a ceramic material or carbon is used. As for the board | substrate which has the surface which consists of ceramic material or carbon, the whole board | substrate may be comprised from ceramic material or carbon, and only the surface of a board | substrate may be comprised from ceramic material or carbon. That is, the substrate used in the manufacturing method of the present embodiment only needs to have a surface made of a ceramic material or carbon, and any material other than the surface can be used. Note that the substrate preferably has heat resistance to a high temperature of 400 ° C. or higher. The ceramic material may be composed of a compound of aluminum and / or silicon and at least one element selected from the group consisting of oxygen, nitrogen, and carbon. For example, SiO ₂ , Si ₃ N ₄ , SiC, Al ₂ O ₃ , AlN, Al ₄ C ₃ , and a mixture thereof. In particular the surface of the substrate is preferably constituted of SiO _2. Since the surface made of a ceramic material or carbon has a small interaction with copper, the copper thin film does not adhere firmly to such a surface (adhesion is weak). Therefore, the copper thin film can be easily peeled from the substrate surface in the peeling step described later. In addition, about the surface which consists of carbon, the state, for example, an amorphous state, a crystalline state, etc. are not ask | required.

  In order to form a copper thin film on the substrate, copper is deposited on the surface of the substrate. Copper is used as the evaporation source. The purity of copper (metal copper) used as a vapor deposition source is preferably high in order to obtain a low-resistance copper thin film, and particularly preferably 99.9 wt% or more. The temperature of the vapor deposition source at the time of vapor deposition may be 1200 ° C. or higher, which is sufficiently higher than the melting point of copper (1085 ° C.). Further, the distance between the vapor deposition source and the substrate is smaller than the length of the shortest side in the projected shape of the substrate viewed from the vapor deposition source (the length of the shortest side of the substrate when the substrate is flat and square). Then, vapor deposition may be performed. By doing in this way, copper can be laminated | stacked on a board | substrate with a high film-forming speed | rate and a high yield. Moreover, you may distribute | circulate an inert gas in a vapor deposition chamber during vapor deposition, and let the pressure in a chamber be 0.001Pa-10Pa, Preferably it is the range of 0.1Pa-10Pa, More preferably, it is the range of 1Pa-10Pa. Good. The inventors of the present invention have made it possible to perform deposition under a relatively high pressure condition of 10 Pa or less by sufficiently increasing the temperature of the deposition source as described above or by sufficiently reducing the distance between the deposition source and the substrate. It has been found that a low-resistance copper thin film can be formed even if this is performed. Vapor deposition under such a relatively high pressure condition can be performed using an inexpensive vacuum exhaust device such as a rotary pump. The substrate temperature during vapor deposition may be in the range of 300 ° C to 600 ° C.

  The thickness of the copper thin film formed on the substrate is preferably 2 μm or more. When the thickness of the copper thin film is less than 2 μm, it is difficult to peel the copper thin film from the substrate as a free-standing film in a peeling step S2 described later. Further, from the viewpoint of reducing the consumption of raw materials (vapor deposition source) and reducing the manufacturing time and reducing the weight of the copper thin film, the thickness of the copper thin film is preferably 30 μm or less, and more preferably 9 μm or less. .

  By such a vapor deposition method, a low-resistance copper thin film having a resistivity in the range of 1.6 to 2.1 μΩcm, preferably 1.6 to 2.0 μΩcm, more preferably 1.6 to 1.95 μΩcm is formed. can do. Moreover, from the Example mentioned later, the copper thin film formed by the above vapor deposition methods is in the X-ray diffraction (XRD) pattern by the out-of-plane method which observes the diffraction by the lattice plane parallel to the film surface. It has been found that 111 diffraction lines of copper are detected and substantially no other diffraction lines from the copper crystal plane are detected. Therefore, the copper thin film formed by the above evaporation method is preferentially oriented in the {111} plane.

<Peeling step S2>
Next, the copper thin film formed on the substrate is peeled from the substrate. For example, a support sheet such as an adhesive tape is fixed to any part of the outer periphery of the copper thin film on the substrate, and the copper thin film is pulled up from the substrate by applying tension to the copper thin film through the support sheet. Can do. As described above, the surface of the substrate on which the copper thin film is formed is made of a ceramic material or carbon, and since the interaction with the copper thin film is small, the adhesion between the copper thin film and the substrate surface is small. Therefore, the copper thin film can be easily peeled off from the substrate surface as a thin film. Moreover, since a support sheet is adhere | attached only on the end of the outer peripheral part of a copper thin film, most other parts can be kept clean. As can be seen from the examples to be described later, according to the method of the present embodiment, the copper thin film deposited on the substrate is peeled off as a free-standing film without breaking the copper thin film at almost 90% area ratio as it is. And can be recovered.

  The free-standing copper thin film thus obtained has a resistivity in the range of 1.6 to 2.1 μΩcm, preferably 1.6 to 2.0 μΩcm, more preferably 1.6 to 1.95 μΩcm, and low Resistivity. In addition, the obtained self-supported copper thin film has a diffraction from a {111} plane of copper in an X-ray diffraction (XRD) pattern by an out-of-plane method for observing diffraction by a lattice plane parallel to the film surface. A line (111 diffraction lines) is detected, and no diffraction lines from any other copper crystal plane are detected. Therefore, the self-supporting copper thin film obtained by the manufacturing method of this embodiment is preferentially oriented in the {111} plane. In the present application, “the diffraction line from any other copper crystal plane is not substantially detected” means the diffraction of copper other than the 111 diffraction line having an intensity of 1/10 or more of the intensity of the 111 diffraction line of copper. This means that no line is detected.

  In the above, although the manufacturing method of the copper thin film was demonstrated taking the example of the batch type process, you may use the continuous process which considered production efficiency. For example, the steps S1 and S2 can be performed continuously using the copper thin film manufacturing apparatus 100 shown in FIG. The apparatus 100 shown in FIG. 2 mainly includes a drum 52 and a vapor deposition device 58 installed below the drum 52. The drum 52 is used as a substrate for depositing copper, has a cylindrical shape, and its surface is made of a ceramic material or carbon. The drum 52 is connected to a drive source (not shown) for rotating the drum. The vapor deposition device 58 includes a boat for accommodating a copper piece as a vapor deposition source, and deposits copper on the outer peripheral surface of the drum 52 to form a copper thin film. The distance between the vapor deposition source and the drum 52 is preferably smaller than the length of the shortest side in the projected shape of the drum 52 when the drum 52 is viewed from the vapor deposition source. For example, when the width of the drum 52 (the length in the depth direction in FIG. 2) is smaller than the diameter of the drum 52, the distance between the vapor deposition source and the drum 52 is preferably smaller than the width of the drum 52.

  A continuous manufacturing process using the apparatus 100 will be described. When the drum 52 rotates around the cylindrical axis in the rotation direction indicated by the arrow in FIG. 2, the metal from the vapor deposition source heated and melted by the vapor deposition device 58 faces the vapor deposition device 58 on the outer peripheral surface of the drum 52. Adhere to. Thereby, the copper thin film 10 is formed on the outer peripheral surface of the drum 52. The copper thin film 10 is conveyed by the drum 52 in the rotation direction of the drum 52. As the drum 52 rotates, the copper thin film 10 is continuously formed on the outer peripheral surface of the drum 52. When the rotation direction front end of the drum 52 of the copper thin film 10 is conveyed to a predetermined position, the copper thin film 10 is sequentially detached from the drum 52 by, for example, applying a tensile force in the tangential direction of the drum 52 to the front end ( Once stripped or separated), a long self-supporting copper thin film (continuous film) 10 is obtained. The long copper thin film 10 can be appropriately wound around a roller and collected and managed.

  Here, in the apparatus 100, a portion of the outer peripheral surface of the drum 52 facing the vapor deposition device 58 is referred to as a vapor deposition region, and the outer peripheral surface of the drum 52 located at a predetermined position where the copper thin film 10 is peeled from the drum 52 is referred to as a separation region. In other words, the temperature of the peeling region may be lower than the temperature of the vapor deposition region, and is preferably lower by 100 ° C. or more. Thereby, in a predetermined position where the copper thin film 10 is peeled from the drum 52, the thermal stress of the copper thin film 10 becomes large, and the peeling of the copper thin film 10 from the drum 52 becomes easy.

  In the apparatus 100, a mechanism such as a peeling roller for peeling (separating) the copper thin film 10 from the drum 52 by applying a tensile force to the front end of the copper thin film 10 may be provided.

  Further, a belt having a surface made of a ceramic material or carbon may be wound around the drum 52. In this case, the belt functions as a substrate, and copper is deposited on the surface of the belt. Therefore, the outer peripheral surface of the drum 52 may be made of any material. Further, instead of winding the belt around the drum 52, the belt may be wound around a plurality of rollers.

  Hereinafter, although the manufacturing method of the copper thin film of this invention is demonstrated concretely by an Example and a comparative example, this invention is not limited to these Examples.

Example 1
The silicon substrate with the thermal oxide film was washed for 5 minutes with a solution in which hydrogen peroxide solution and concentrated sulfuric acid were mixed at a volume ratio of 1: 3. The substrate was then dried for 1 hour under reduced pressure. Cu was vapor-deposited on the dried substrate as follows. An 80 mm × 6 mm tungsten board was placed in the vapor deposition chamber, and a Cu piece (Nilaco Corp. Cu111487, purity 99.9 wt%) was placed thereon, which was used as a vapor deposition source. In addition, since the Cu piece is melted by heating and spreads on the board, the size of the vapor deposition source is about 30 × 6 mm. The substrate was placed so that the substrate was parallel to the tungsten board. At this time, the distance between the deposition source and the substrate was set to 35 mm. The substrate was placed on a stage made of a quartz glass plate having an 18 mm square opening in the center, and heated from the top to about 400 ° C. with a PG / PBN heater. The inside of the chamber was decompressed to 2 × 10 ⁻³ Pa or less with a turbo molecular pump. By energizing the tungsten board at 538 W and heating the tungsten board to about 1740 ° C., the Cu piece was melted and Cu was deposited for 70 seconds. The substrate temperature during deposition was about 400 ° C. By the above operation, a Cu thin film was formed on the substrate. The thickness (converted thickness) of the Cu thin film obtained by dividing the value of the weight change of the sample before and after vapor deposition by the area of the Cu thin film and the density of copper was 8.96 μm.

  When the cross section of the obtained Cu thin film was observed with a scanning electron microscope (SEM, S-4800 manufactured by Hitachi, Ltd.), the thickness of the Cu thin film was about 9.0 μm.

  The sheet resistance of the Cu thin film was measured by a four-terminal method, and the resistivity of the Cu thin film was calculated by multiplying the sheet resistance value by the converted thickness of the Cu thin film. The resistivity of the Cu thin film was 1.64 μΩcm.

  The Cu thin film on the substrate was peeled off from the substrate with tweezers. The peeled Cu thin film and the digital camera photograph of the substrate after peeling the Cu thin film are shown in FIG. 3A. Cu did not remain on the substrate surface, and the Cu thin film did not collapse in the thin film state, that is, the Cu thin film could be peeled from the substrate at an area ratio of 100%. Further, the peeled Cu thin film was self-supporting, and the shape as a film could be maintained even without another support.

Example 2
At the time of Cu deposition, the chamber was depressurized, then argon gas was introduced at a flow rate of 1.3 sccm, exhausted with a turbo molecular pump, the pressure in the chamber was set to 0.09 Pa, and the tungsten boat was heated to about 1750 ° C. at 550 W. In the same manner as in Example 1, a Cu thin film was formed on the substrate. The converted thickness of the Cu thin film was 8.67 μm.

  When the cross section of the obtained Cu thin film was observed by SEM, the thickness of the Cu thin film was about 8.4 μm.

  The sheet resistance of the Cu thin film was measured by the four probe method, and the resistivity of the Cu thin film was calculated. The resistivity of the Cu thin film was 1.68 μΩcm.

  The Cu thin film on the substrate was peeled off from the substrate with tweezers. FIG. 3B shows a digital camera photograph of the peeled Cu thin film and the substrate after peeling the Cu thin film. Cu did not remain on the substrate surface, and the Cu thin film did not collapse in the thin film state, that is, the Cu thin film could be peeled from the substrate at an area ratio of 100%. Further, the peeled Cu thin film was self-supporting, and the shape as a film could be maintained even without another support. In this example and the examples described later, in order to easily peel the Cu thin film from the substrate, the end of the substrate was divided and the Cu thin film was peeled off from the end. It is also possible to peel off. For example, by fixing a support sheet such as an adhesive tape to any part of the outer periphery of the Cu thin film on the substrate, applying tension to the Cu thin film via the support sheet, and pulling the Cu thin film from the substrate, the Cu thin film Can be peeled from the substrate.

Example 3
At the time of Cu deposition, the chamber was depressurized, argon gas was introduced at a flow rate of 40 sccm, exhausted with a turbo molecular pump, the pressure in the chamber was set to 0.9 Pa, and the tungsten boat was heated to about 1750 ° C. at 552 W. In the same manner as in Example 1, a Cu thin film was formed on the substrate. The converted thickness of the Cu thin film was 5.13 μm.

  When the cross section of the obtained Cu thin film was observed by SEM, the thickness of the Cu thin film was about 5.1 μm.

  The sheet resistance of the Cu thin film was measured by the four probe method, and the resistivity of the Cu thin film was calculated. The resistivity of the Cu thin film was 1.70 μΩcm.

  The Cu thin film on the substrate was peeled off from the substrate with tweezers. FIG. 3C shows a peeled Cu thin film and a digital camera photograph of the substrate after peeling the Cu thin film. Cu did not remain on the substrate surface, and the Cu thin film did not collapse in the thin film state, that is, the Cu thin film could be peeled from the substrate at an area ratio of 100%. Further, the peeled Cu thin film was self-supporting, and the shape as a film could be maintained even without another support.

Example 4
At the time of Cu deposition, the chamber was depressurized, then introduced with argon gas at a flow rate of 100 sccm, evacuated with a turbo molecular pump, the pressure in the chamber was set to 2.7 Pa, and the tungsten boat was heated to about 1750 ° C. at 550 W. In the same manner as in Example 1, a Cu thin film was formed on the substrate. The converted thickness of the Cu thin film was 6.24 μm.

  When the cross section of the obtained Cu thin film was observed by SEM, the thickness of the Cu thin film was about 5.6 μm.

  The sheet resistance of the Cu thin film was measured by the four probe method, and the resistivity of the Cu thin film was calculated. The resistivity of the Cu thin film was 1.68 μΩcm.

  The Cu thin film on the substrate was peeled off from the substrate with tweezers. The peeled Cu thin film and the digital camera photograph of the substrate after peeling the Cu thin film are shown in FIG. 3D. Cu remained on the substrate surface except for the outer peripheral portion of the Cu thin film, and the Cu thin film could be peeled from the substrate at an area ratio of 90% or more. The Cu thin film peeled off from the substrate was self-supporting without collapsing in the thin film state, and the shape as a film could be maintained without any other support.

Example 5
During Cu deposition, the chamber was decompressed by a turbo pump, and then argon gas was introduced at a flow rate of 2.0 sccm, the turbo molecular pump was disconnected, the pressure in the chamber was 10 Pa only with the rotary pump, and the tungsten boat was 576 W at about 1777 ° C. A Cu thin film was formed on the substrate in the same manner as in Example 1 except that Cu was vapor-deposited for 180 seconds. The converted thickness of the Cu thin film was 8.1 μm.

  The sheet resistance of the Cu thin film was measured by the four probe method, and the resistivity of the Cu thin film was calculated. The resistivity of the Cu thin film was 2.06 μΩcm.

  A cellophane tape was applied to one end of the Cu thin film on the substrate, and tension was applied to peel it from the substrate. The peeled Cu thin film and the digital camera photograph of the substrate after peeling the Cu thin film are shown in FIG. 3E. Cu remained on the substrate surface except for the outer peripheral portion of the Cu thin film, and the Cu thin film could be peeled from the substrate at an area ratio of 90% or more. The Cu thin film peeled off from the substrate was self-supporting without collapsing in the thin film state, and the shape as a film could be maintained without any other support.

Example 6
As a substrate, a quartz glass substrate having a carbon film with a thickness of 100 nm formed on the surface by a sputtering method was used. During the deposition of Cu, a tungsten boat was heated to about 1642 ° C. at 462 W, and Cu was deposited for 80 seconds. In the same manner as in Example 1, a Cu thin film was formed on the substrate. The converted thickness of the Cu thin film was 2.2 μm.

  The sheet resistance of the Cu thin film was measured by the four probe method, and the resistivity of the Cu thin film was calculated. The resistivity of the Cu thin film was 1.73 μΩcm.

  A cellophane tape was applied to one end of the Cu thin film on the substrate, and tension was applied to peel it from the substrate. The peeled Cu thin film and a digital camera photograph of the substrate after peeling the Cu thin film are shown in FIG. 3F. Cu remained on the substrate surface except for the outer peripheral portion of the Cu thin film, and the Cu thin film could be peeled from the substrate at an area ratio of 90% or more. The Cu thin film peeled off from the substrate was self-supporting without collapsing in the thin film state, and the shape as a film could be maintained without any other support.

Example 7
A Cu thin film was formed on the substrate in the same manner as in Example 1 except that during the deposition of Cu, the tungsten boat was heated to about 1720 ° C. at 525 W and Cu was deposited for 20 seconds. The converted thickness of the Cu thin film was 4.13 μm.

  The sheet resistance of the Cu thin film was measured by the four probe method, and the resistivity of the Cu thin film was calculated. The resistivity of the Cu thin film was 1.87 μΩcm.

  The Cu thin film on the substrate was peeled off from the substrate with tweezers. FIG. 3G shows a peeled Cu thin film and a digital camera photograph of the substrate after peeling the Cu thin film. Cu did not remain on the substrate surface, and the Cu thin film did not collapse in the thin film state, that is, the Cu thin film could be peeled from the substrate at an area ratio of 100%. Further, the peeled Cu thin film was self-supporting, and the shape as a film could be maintained even without another support.

Example 8
A Cu thin film was formed on the substrate in the same manner as in Example 1 except that during the deposition of Cu, the tungsten boat was heated to about 1700 ° C. at 508 W and Cu was deposited for 30 seconds. The converted thickness of the Cu thin film was 6.80 μm.

  The sheet resistance of the Cu thin film was measured by the four probe method, and the resistivity of the Cu thin film was calculated. The resistivity of the Cu thin film was 1.70 μΩcm.

  The Cu thin film on the substrate was peeled off from the substrate with tweezers. The peeled Cu thin film and the digital camera photograph of the substrate after peeling the Cu thin film are shown in FIG. 3H. Cu did not remain on the substrate surface, and the Cu thin film did not collapse in the thin film state, that is, the Cu thin film could be peeled from the substrate at an area ratio of 100%. Further, the peeled Cu thin film was self-supporting, and the shape as a film could be maintained even without another support.

Reference Example A Cu thin film was formed on a substrate in the same manner as in Example 1 except that a tungsten boat was heated to about 1640 ° C. at 461 W during Cu deposition and Cu was deposited for 15 seconds. The converted thickness of the Cu thin film was 1.33 μm.

  The sheet resistance of the Cu thin film was measured by the four probe method, and the resistivity of the Cu thin film was calculated. The resistivity of the Cu thin film was 1.99 μΩcm.

  When the Cu thin film on the substrate was peeled from the substrate with tweezers, the Cu thin film was broken and the Cu thin film remained on the substrate surface (see FIG. 3I). That is, the Cu thin film formed in this comparative example could not be peeled from the substrate without collapsing, and did not become a self-supporting film.

Example 9
At the time of Cu deposition, a Cu thin film was formed on the substrate in the same manner as in Example 1 except that the tungsten boat was heated to about 1600 ° C. at 507 W and Cu was deposited for 60 seconds. The converted thickness of the Cu thin film was 7.5 μm.

  The sheet resistance of the Cu thin film was measured by the four probe method, and the resistivity of the Cu thin film was calculated. The resistivity of the Cu thin film was 1.92 μΩcm.

  X-ray diffraction (XRD) of Cu thin film by an out-of-plane method (OP method) for observing diffraction by a lattice plane parallel to the substrate using an X-ray diffraction apparatus (RINT Ultimate III manufactured by Rigaku Corporation) Got a pattern. The obtained XRD pattern is shown in FIG. 4 together with a copper powder pattern (powder diffraction pattern, random orientation pattern). In this example, diffraction lines from the {111} plane of Cu (111 diffraction lines) were detected, but diffraction lines from the other planes of Cu were not substantially detected. Therefore, it was found that the Cu thin film of this example was preferentially oriented in the {111} plane.

  The Cu thin film on the substrate was peeled off from the substrate with tweezers. The peeled Cu thin film and the digital camera photograph of the substrate after peeling the Cu thin film are shown in FIG. 3J. Cu remained on the substrate surface except for the outer peripheral portion of the Cu thin film, and the Cu thin film could be peeled from the substrate at an area ratio of 90% or more. The Cu thin film peeled off from the substrate was self-supporting without collapsing in the thin film state, and the shape as a film could be maintained without any other support.

Example 10
A Cu thin film was formed on the substrate in the same manner as in Example 1 except that during the deposition of Cu, the tungsten boat was heated to about 1640 ° C. at 460 W and Cu was deposited for 80 seconds. The converted thickness of the Cu thin film was 13.3 μm.

  The sheet resistance of the Cu thin film was measured by the four probe method, and the resistivity of the Cu thin film was calculated. The resistivity of the Cu thin film was 1.84 μΩcm.

  An XRD pattern of a Cu thin film was obtained by an OP method using an X-ray diffractometer. The obtained XRD pattern is shown in FIG. The intensity of the 111 diffraction line of Cu was greater than the intensity of the diffraction line from the other surface of Cu. In this example, 111 diffraction lines of Cu were detected, and diffraction lines from other surfaces of Cu were not substantially detected. Therefore, it was found that the Cu thin film of this example was preferentially oriented in the {111} plane.

  The Cu thin film on the substrate was peeled off from the substrate with tweezers. FIG. 3K shows a peeled Cu thin film and a digital camera photograph of the substrate after peeling the Cu thin film. Cu did not remain on the substrate surface, and the Cu thin film did not collapse in the thin film state, that is, the Cu thin film could be peeled from the substrate at an area ratio of 100%. Further, the peeled Cu thin film was self-supporting, and the shape as a film could be maintained even without another support.

Comparative Example 1
A 10 μm thick copper foil (Niraco Cu113173, purity 99.9 wt%) manufactured by a rolling method was prepared. The sheet resistance of this copper foil was measured by the four-terminal method, and the resistivity of the copper foil was calculated by multiplying the sheet resistance value by the converted thickness of the copper foil. The resistivity of the copper foil was 2.33 μΩcm.

  An XRD pattern of copper foil was obtained by the OP method using an X-ray diffractometer. The obtained XRD pattern is shown in FIG. Cu 111 diffraction line, 200 diffraction line, 220 diffraction line, and 311 diffraction line were detected, and the intensity of 220 diffraction line was particularly high. Therefore, it was found that the copper foil of this comparative example is preferentially oriented in the {220} plane.

Comparative Example 2
A 12 μm-thick copper foil manufactured by the electrodeposition method (manufactured by JX Nippon Mining & Metals, purity 99.5 wt% or more) was prepared. The sheet resistance of this copper foil was measured by the four-terminal method, and the resistivity of the copper foil was calculated by multiplying the sheet resistance value by the converted thickness of the copper foil. The resistivity of the copper foil was 2.25 μΩcm.

  An XRD pattern of copper foil was obtained by the OP method using an X-ray diffractometer. The obtained XRD pattern is shown in FIG. The 111 diffraction line, the 200 diffraction line, the 220 diffraction line, and the 311 diffraction line of Cu were detected, and the intensity ratio thereof was the same as that of the powder diffraction pattern of Cu. Therefore, it was found that the copper foil of this comparative example was non-oriented (random orientation).

Comparative Example 3
A 20 μm-thick copper foil (obtained from: Sunk Metal Co., Ltd., purity 99.9 wt%) produced by the electrodeposition method was prepared. The sheet resistance of this copper foil was measured by the four-terminal method, and the resistivity of the copper foil was calculated by multiplying the sheet resistance value by the converted thickness of the copper foil. The resistivity of the copper foil was 1.96 μΩcm.

  An XRD pattern of copper foil was obtained by the OP method using an X-ray diffractometer. The obtained XRD pattern is shown in FIG. The 111 diffraction line, the 200 diffraction line, the 220 diffraction line, and the 311 diffraction line of Cu were detected, and the intensity ratio thereof was the same as that of the powder diffraction pattern of Cu. Therefore, it was found that the copper foil of this comparative example was non-oriented (random orientation).

  In the table | surface of FIG. 5, the Cu thin film of said Examples 1-10 and a reference example, and the formation conditions of the copper foil of Comparative Examples 1-3, the thickness of Cu thin film (or copper foil), Cu thin film (or copper foil) The resistivity and the result of peeling from the substrate are shown. In FIG. 5, the Cu thin film can be peeled from the substrate at an area ratio of 90% or more and a self-supporting Cu thin film is obtained as “◯”, and the Cu thin film remains on the substrate to obtain a self-supporting Cu thin film. Those that were not indicated were indicated as “x”.

  From Examples 1 to 10, a Cu thin film formed with a thickness of 2 μm or more on a substrate having a surface made of silicon oxide or carbon can be separated from the substrate without breaking its structure and can be made independent. I understood.

  From Examples 1-5, it turned out that the self-supporting copper thin film is formed by forming the Cu thin film by making the pressure at the time of vapor deposition into the range of 10 Pa or less.

  From Examples 1 and 6 to 8, it was found that a Cu thin film having a thickness of 2 μm or more can be separated from the substrate and free-standing without breaking the structure. On the other hand, the 1.33 μm-thick Cu thin film of the reference example was not able to stand by itself because the film was broken when it was peeled off from the substrate. Moreover, the thickness of Cu thin film of Examples 1-9 was 9 micrometers or less, and the self-supporting Cu thin film smaller than the copper foil of Comparative Examples 1-3 was able to be formed.

  The Cu thin films of Examples 1 to 10 had a resistivity of 2.1 μΩcm or less, which was lower than the copper foils of Comparative Examples 1 and 2 having a relatively small thickness. In particular, the Cu thin films of Examples 1 to 4 and 6 to 10 had a resistivity of 1.95 μΩcm or less, which was lower than that of any of the copper foils of Comparative Examples 1 to 3. From this, it was found that a Cu thin film having a resistivity lower than that of a copper foil formed by a rolling method or an electrodeposition method can be formed by a vapor deposition method. This is presumably because a high-purity Cu thin film having higher crystallinity than a copper foil formed by a rolling method or an electrodeposition method could be formed by a vapor deposition method. In the case of the electrodeposition method, the temperature when forming the copper foil is as low as room temperature, and Cu atoms cannot be sufficiently diffused when deposited on the substrate and the copper foil surface, so that a copper foil with insufficient crystallinity is formed. It is thought. Furthermore, it is conceivable that the electrolytic solution used in the electrodeposition method and the substance dissolved therein are mixed as impurities into the copper foil. Further, in the rolling method, since the Cu thick plate once formed is stretched by applying pressure, the crystal of the copper foil is greatly distorted and the resistance is increased. On the other hand, the Cu thin films of Examples 1 to 10 have a high substrate temperature at the time of vapor deposition of about 400 ° C., and Cu atoms adhering to the substrate and the Cu thin film can be sufficiently diffused, so that a highly crystalline Cu thin film is formed. It is thought. Furthermore, since the Cu thin films of Examples 1 to 10 are formed by a method in which a solvent does not coexist, it is considered that the Cu thin films were high in purity with little contamination of impurities.

  Further, the copper foil of Comparative Example 1 was preferentially oriented to the {220} plane of Cu, and the copper foils of Comparative Examples 2 and 3 were non-oriented (random orientation), whereas the Cu thin films of Examples 9 and 10 were used. Was preferentially oriented in the {111} plane of Cu. Since Cu has an fcc structure and the {111} plane is the most stable surface, it is easy to maintain the structure as it is without changing the crystal orientation, for example, even if it is used in applications where a thermal history or the like is required. In particular, when used as a catalyst for synthesizing graphene, graphene grows epitaxially on the {111} plane of Cu, so that high-quality graphene can be formed.

  As mentioned above, although this invention was demonstrated by embodiment, the copper thin film and its manufacturing method of this invention are not limited to the said embodiment, It can modify suitably within the range of the technical idea described in the claim. it can.

  The method for producing a copper thin film of the present invention makes it possible to efficiently produce a thin copper thin film with higher purity, lower resistance, and efficiency. Such a thin, lightweight copper thin film with low resistance can be used for a current collector foil, a heat radiating sheet, an electromagnetic wave shielding sheet, a flexible circuit board (FPC), a conductive tape, and a decorative sheet of an electricity storage device. Further, since the surface of the copper thin film of the present invention is aligned with the {111} crystal plane, it can be used as a catalyst for synthesizing graphene. Moreover, with the manufacturing method of the present invention, a high-purity copper thin film can be industrially manufactured while using a vapor deposition process. Therefore, the present invention provides a significant development in the industry using copper foil.

  10 Copper thin film, 58 Evaporator, 100 Production equipment

Claims (15)

A method for producing a copper thin film comprising:
Depositing copper on the surface of the substrate having a surface made of a ceramic material or carbon to form a copper thin film;
A method for producing a self-supporting copper thin film including a step of peeling the formed copper thin film from the surface as a thin film.   The ceramic material is composed of a compound of aluminum and / or silicon and at least one element selected from the group consisting of oxygen, nitrogen, and carbon, and the copper is formed on the surface of the substrate having a surface made of the ceramic material. The method of manufacturing the copper thin film of Claim 1 which vapor-deposits.   The method for producing a copper thin film according to claim 2, wherein the ceramic material is silicon oxide.   The method for producing a copper thin film according to any one of claims 1 to 3, wherein in the step of forming the copper thin film, the copper thin film having a film thickness within a range of 2 to 30 µm is formed.   In the step of forming the copper thin film, the temperature of the vapor deposition source is set to 1200 ° C. or more, and the distance between the vapor deposition source and the substrate is made smaller than the length of the shortest side in the projected shape of the substrate viewed from the vapor deposition source. The method for producing a copper thin film according to claim 1, wherein the copper is vapor-deposited.   The method for producing a copper thin film according to any one of claims 1 to 5, wherein, in the step of forming the copper thin film, the copper is vapor-deposited at a total pressure in a range of 0.001 to 10 Pa.   The method for producing a copper thin film according to claim 6, wherein, in the step of forming the copper thin film, the copper is vapor-deposited by passing an inert gas and setting the total pressure within a range of 0.001 to 10 Pa.   The method for producing a copper thin film according to claim 1, wherein the temperature of the substrate is maintained at 300 to 600 ° C. in the step of forming the copper thin film.   The process of peeling the said copper thin film WHEREIN: One end of the said copper thin film is adhere | attached on a support film, The said copper thin film is peeled from the said board | substrate by applying tension | tensile_strength to the said copper thin film from the said support film. The method to manufacture the copper thin film as described in any one. The substrate has a cylindrical shape;
In the step of peeling the copper thin film, the copper is deposited while rotating the substrate around the cylindrical axis, and the copper thin film is formed on the outer peripheral surface of the substrate having the cylindrical shape, The method for producing a copper thin film according to any one of claims 1 to 9, wherein the copper thin film is continuously peeled from the substrate by applying tension to one end of the copper thin film.   11. The copper thin film is peeled off in the step of peeling the copper thin film by lowering the temperature of the substrate by 100 ° C. or more than the temperature of the substrate in the step of depositing copper. A method for producing a copper thin film.   The self-supporting copper thin film manufactured by the manufacturing method as described in any one of Claims 1-11. A self-supporting copper film,
The film thickness is in the range of 2 to 30 μm,
In the X-ray diffraction pattern by the out-of-plane method using CuKα rays of the copper thin film, 111 diffraction lines of copper are detected, and diffraction lines from any other copper crystal plane are substantially detected. Without
A free-standing copper thin film having a resistivity in the range of 1.6 to 2.1 μΩcm.   The self-supporting copper thin film according to claim 12 or 13, wherein the resistivity is in a range of 1.6 to 2.0 µΩcm.   The self-supporting copper thin film according to any one of claims 12 to 14, wherein the film thickness is in a range of 2 to 9 µm.

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