JP2008174811A - Method for forming metal conductive layer, method for forming conductive spring, and conductive spring - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a metal conductive layer capable of forming a metal conductive layer with a fine wire width by a simple method; to provide a method for forming a conductive spring; and to provide a conductive spring. <P>SOLUTION: In the surface of a substrate 10 formed by silicon or the like, a flow passage 12 into which a metal nanoparticle-dispersed liquid flows and a liquid pool 16 communicated with the flow passage 12 via a communication path 14 are formed. When the metal nanoparticle-dispersed liquid is poured into the liquid pool 16 in this state, the metal nanoparticle-dispersed liquid flows into the flow passage 12 via the communication path 14 by a capillary phenomenon. Next, the metal nanoparticle-dispersed liquid is heated via the substrate 10 or directly, and the metal nanoparticles are flocculated, so as to form a metal conductive layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a metal conductive layer forming method, a conductive spring forming method, and a conductive spring.

  In recent years, various pattern formations using metal nano-inks have been proposed as a method for forming a fine pattern by a simpler method than the lithography method. For example, Patent Document 1 below discloses a technique for controlling a surface property of a substrate, making a pattern forming unit more lyophilic than other portions, selectively depositing metal nano ink, and obtaining a desired pattern. It is disclosed.

Patent Document 2 below discloses a technique for forming a fine pattern by ejecting metal nano-ink by inkjet.
JP 2006-303199 A JP 2003-80694 A

  However, the conventional technique described in Patent Document 1 has a problem that the amount of metal nano ink used is increased and the control of the surface characteristics of the substrate is complicated. Further, the conventional technique described in Patent Document 2 has a problem that the line width can only be reduced to about 50 μm.

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a metal conductive layer forming method, a conductive spring forming method, and a method for forming a metal conductive layer having a fine line width by a simple method. It is to provide a conductive spring.

  In order to achieve the above object, the method of forming a metal conductive layer according to claim 1 includes a step of forming a flow channel into which the metal nanoparticle dispersion liquid flows in or on the surface of the insulating material, and And a step of pouring the metal nanoparticle dispersion liquid by capillary action and a step of heating the metal nanoparticle dispersion liquid to aggregate the metal nanoparticles to form a metal conductive layer.

  According to a second aspect of the present invention, in the metal conductive layer forming method according to the first aspect, the metal nanoparticle dispersion is poured into the flow path by a capillary phenomenon from a liquid reservoir formed in or on the surface of the insulating material. It is characterized by that.

  According to a third aspect of the present invention, in the metal conductive layer forming method according to the first or second aspect, the metal nanoparticles are silver nanoparticles.

  According to a fourth aspect of the present invention, there is provided a conductive spring forming method comprising: forming a spring-shaped groove in a mold material; and depositing an insulating material layer, which is an organic substance, on both walls and the bottom of the groove. A step of forming an insulating material structure having a flow path into which the metal nanoparticle dispersion flows, a step of flowing the metal nanoparticle dispersion into the flow path by capillary action, and heating the metal nanoparticle dispersion to form a metal The method includes a step of aggregating nanoparticles to form a metal conductive layer, and a step of removing the mold material.

  According to a fifth aspect of the present invention, in the conductive spring forming method according to the fourth aspect, the metal nanoparticle dispersion is poured into the flow path by a capillary phenomenon from a liquid reservoir formed in the mold material. .

  According to a sixth aspect of the present invention, in the conductive spring forming method according to the fourth or fifth aspect, the insulating material is polyparaxylylene.

  According to a seventh aspect of the present invention, there is provided the conductive spring according to claim 7, comprising: a spring portion formed of an insulating material that is an organic substance; and a metal conductive layer formed by aggregation or aggregation of metal nanoparticles formed inside or on the surface of the spring portion. It is characterized by.

  According to the first to third aspects of the invention, since the metal nanoparticle dispersion liquid is poured into the fine flow path by capillary action, a fine pattern can be easily manufactured.

  According to the fourth to sixth aspects of the present invention, there can be provided a conductive spring forming method in which a metal conductive layer is formed inside or on the surface of the spring.

  According to invention of Claim 7, the electroconductive spring in which the metal conductive layer was formed in the inside or surface of a spring can be provided.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described with reference to the drawings.

  FIGS. 1A and 1B are explanatory views of an embodiment of a metal conductive layer forming method according to the present invention. FIG. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along line bb in FIG.

  In FIGS. 1A and 1B, a channel 12 into which a metal nanoparticle dispersion liquid flows is formed on the surface of a substrate 10 made of silicon or the like. Further, a liquid reservoir 16 communicating with the flow path 12 through the communication path 14 is also formed on the surface of the substrate 10. When the metal nanoparticle dispersion liquid is injected into the liquid reservoir 16 in this state, the metal nanoparticle dispersion liquid flows into the flow path 12 through the communication path 14 by capillary action. Next, the metal nanoparticle dispersion is heated through the substrate 10 or directly, and the metal nanoparticles are aggregated to form a metal conductive layer.

  In the example of FIGS. 1A and 1B, an example in which the metal nanoparticle dispersion liquid is poured into the flow channel 12 from the liquid reservoir 16 is shown. However, at any one or a plurality of locations in the flow channel 12. The metal nanoparticle dispersion liquid may be dropped, and the metal nanoparticle dispersion liquid may be poured into the flow path 12 by capillary action.

  Further, in the example of FIGS. 1A and 1B, the flow path 12 is formed on the surface of the substrate 10, but may be formed inside the substrate 10.

  Here, the metal nanoparticle dispersion is obtained by dispersing metal nanoparticles (metal fine particles) in a solvent using a dispersant. As a material for the metal nanoparticles, for example, a metal having excellent conductivity such as gold, silver, copper, platinum, palladium, nickel, and alloys thereof is suitable. The average primary particle diameter is preferably fine in order to form a fine pattern, and is preferably 1 to 100 nm. Moreover, as a solvent, organic solvents, such as toluene, tetradecane, or alcohol, and water can be used. Moreover, as a dispersing agent, what prevents the aggregation of a metal nanoparticle in the said solvent and can maintain a dispersed state stably, for example, an alkylamine, a citric acid, etc. can be used. As such a metal nanoparticle dispersion, for example, silver nanometal ink manufactured by Asahi Glass Co., Ltd., copper nanometal ink, silver nanometal ink manufactured by ULVAC, or the like can be used.

  According to this embodiment, since the metal nanoparticle dispersion is poured into the flow channel 12 by capillary action, it can be easily poured even if the diameter of the flow channel 12 is fine, and a fine pattern with a line width of 50 μm or less can be formed. It can be manufactured easily.

  The material of the substrate 10 on which a fine pattern is formed by the metal conductive layer forming method of the present embodiment described above is not limited to the above silicon, but polyimide, glass epoxy, PDMS (polydimethylsiloxane), glass, acrylic resin. In addition to insulating materials such as those described above, the above insulating material or an insulating layer such as silicon dioxide or silicon nitride may be formed on a substrate.

  As another application example of the metal conductive layer forming method of the present embodiment, there is a conductive spring in which a fine metal conductive layer is provided on the surface or inside of a resin spring. Here, as a material of the spring that can be polymerized in the gas phase, as a polymer, there is polyparaxylylene, fluorinated polyparaxylylene, or a fluorinated derivative thereof. As monomers, olefin monomers such as ethylene, propylene, styrene, vinyl chloride, TFE (tetrafluoroethylene), CTFE (chlorotrifluoroethylene), VdF (vinylidene fluoride), perfluoroallyl vinyl ether, perfluorobutenyl There are fluorine-based olefin monomers such as vinyl ether, acrylic monomers such as methyl methacrylate, methyl acrylate, and fluoro acrylate.

  Hereinafter, specific examples of the present invention will be described as examples.

Example 1.
-Method for Forming Metal Conductive Layer on Substrate Surface FIGS. 2A to 2D are cross-sectional views of the substrate for explaining the steps of this embodiment. In FIG. 2A, a photoresist 104 is applied on an oxide film (thickness 2 microns) 102 on a silicon substrate 100 by spin coating, and an electrode shape is patterned by photolithography.

Next, as shown in FIG. 2B, the oxide film 102 is etched with buffered hydrofluoric acid to expose the silicon surface, and then SF ₆ gas and C ₄ F are etched with a silicon deep etching apparatus (DRIE). A groove 106 having a width of 20 to 40 microns is formed in the silicon substrate 100 in a high-density plasma of ₈ gases. At the same time, a liquid reservoir 108 for storing the metal nanoparticle dispersion is also formed in the same manner as the groove 106. In this silicon deep etching step, the photoresist 104 on the oxide film 102 is also removed.

  After that, as shown in FIG. 2C, a polyparaxylylene (common name: Parylene) layer having a thickness of 10 to 25 microns is deposited as an insulating material 110 using a paraxylylene dimer. This vapor deposition can be performed by, for example, CVD (chemical vapor deposition). After the vapor deposition is completed, a V-shaped valley substantially the same as the groove width is formed on the surface of the polyparaxylylene layer. This valley becomes the flow path 112 of the metal nanoparticle dispersion. Note that the liquid reservoir 108 formed in FIG. 2B and the flow path 112 are communicated with each other through a communication path (not shown).

  2A, 2B, and 2C is an example of a method of forming the metal nanoparticle dispersion liquid channel 112, and the substrate 100 is formed by a method such as imprinting or laser processing. The flow path 112 may be formed directly on the top.

  Next, as shown in FIG. 2 (d), silver particles are used in a tetradecane solvent as a metal nanoparticle dispersion liquid 114, which is a material for the metal conductive layer, in a liquid reservoir 108 previously formed on the silicon substrate 100. Dispersed silver nanometal ink L-Ag1TeH manufactured by ULVAC is injected. The metal nanoparticle dispersion liquid 114 injected into the liquid reservoir 108 flows from the liquid reservoir 108 into the flow path 112 through the communication path by capillary action.

  Next, in order to vaporize the solvent of the metal nanoparticle dispersion or release the dispersant on the surface of the silver particles, baking is performed in an oven at 150 ° C. for 1 hour, as shown in FIG. In addition, the silver particles aggregate to form the metal conductive layer 116 along the flow path 112. In order to flow the metal nanoparticle dispersion liquid 114 into the flow path 112, formation of the liquid reservoir 108 is not an essential condition. The metal nanoparticle dispersion liquid 114 can be poured into the flow path 112 by capillary action simply by dropping the metal nanoparticle dispersion liquid 114 at one or a plurality of locations in the flow path 112.

-Evaluation of the metal conductive layer formed on the surface of the insulating material The electric resistance of the metal conductive layer 116 manufactured in the above-described process was measured with a multimeter (AD-7451 manufactured by Advantest Corporation).

  In the case of the metal conductive layer 116 formed along the flow path 112 having a width of 40 microns, the resistance value was about 3 ohms per 1 mm length, and the volume resistivity was about 13 micro ohms · cm. This is almost equal to the catalog value of 10 micro ohm · cm of the nano metal ink (ULVAC L-Ag1TeH) used as a raw material, and the metal conductive layer 116 formed in this example can be used as a printed circuit board or other conductive part without any problem. It was confirmed that it was possible.

Example 2
-Conductive spring forming method provided with a metal conductive layer inside the spring FIGS. 3A to 3G are substrate cross-sectional views for explaining the steps of the present embodiment. In FIG. 3A, a photoresist 104 is applied onto an oxide film (thickness 2 microns) 102 on a silicon substrate 100 by spin coating, and a spring shape is patterned by photolithography.

Next, as shown in FIG. 3 (b), the oxide film 102 is etched with buffered hydrofluoric acid to expose the silicon surface of the portion to be a spring, and then SF _{6 is} etched by a silicon deep etching apparatus (DRIE). gas and _C 4 _{F 8} the width 20, 30 or 40 microns into the silicon substrate 100 in a high density plasma gas to form a groove 106 having a depth of about 200 to 400 microns. At the same time, a liquid reservoir 108 for storing the metal nanoparticle dispersion is also formed in the same manner as the groove 106. Note that the grooves 106 may be formed by a method such as imprinting or laser processing, as in the case of forming the flow path 112 in FIGS. 2 (a), 2 (b), and 2 (c).

  Thereafter, as shown in FIG. 3C, a polyparaxylylene layer having a thickness of 10 to 25 microns is deposited as an insulating material 110 using a paraxylylene dimer. At the time of vapor deposition, a vapor deposition film is quickly formed at the upper corner of the groove 106. Therefore, after the vapor deposition is completed, an insulating material structure in which a gap 118 having a width of about 5 to 10 microns is formed inside the groove 106 is obtained. Note that the liquid reservoir 108 and the gap 118 formed in FIG. 3B are communicated with each other through a communication path (not shown).

  Next, as shown in FIG. 3 (d), silver particles are used in a tetradecane solvent as a metal nanoparticle dispersion liquid 114, which is a material of the metal conductive layer, in a liquid reservoir 108 previously formed on the silicon substrate 100. Dispersed silver nanometal ink L-Ag1TeH manufactured by ULVAC is injected. The metal nanoparticle dispersion liquid 114 injected into the liquid reservoir 108 flows from the liquid reservoir 108 into the gap 118 via the communication path by capillary action.

  Next, in order to vaporize the solvent of the metal nanoparticle dispersion or release the dispersant on the surface of the silver particles, baking is performed in an oven at 150 ° C. for 1 hour, as shown in FIG. In addition, the silver particles aggregate to form the metal conductive layer 116 along the gap 118. In order to flow the metal nanoparticle dispersion liquid 114 into the void 118, formation of the liquid reservoir 108 is not an essential condition. The metal nanoparticle dispersion liquid 114 can be poured into the gap 118 by capillary action simply by opening a hole in the insulating material 110 at an appropriate position of the gap 118 and dropping the metal nanoparticle dispersion liquid 114 onto the hole.

  Next, a copper thin film is formed on the entire surface of the silicon substrate 100 by vacuum deposition, and is patterned by photolithography to obtain a copper thin film 120 as shown in FIG. Using the copper thin film 120 as a mask, the insulating material 110 is etched by oxygen plasma, and the oxide film 102 is removed by buffered hydrofluoric acid. As shown in FIG. The substrate 100 is exposed.

Finally, after the copper thin film 120 is wet-etched, the silicon substrate 100 is etched using XeF ₂ gas to obtain a spring structure independent of the surrounding silicon substrate 100 as shown in FIG. As described above, the metal conductive layer 116 was formed inside the spring, and three types of conductive springs made of parylene having a width of 20, 30 and 40 microns were obtained. In this embodiment, the metal conductive layer 116 is formed inside the spring. However, as in the first embodiment, along the V-shaped valley formed on the surface of the polyparaxylylene layer, that is, the conductivity. A metal conductive layer 116 may be formed on the surface of the spring.

・ Evaluation of Parylene-made conductive spring The conductive spring manufactured in the above-described process is attached to a small speaker, and the speaker is minutely vibrated by a frequency generator (AFG-3022 manufactured by Tektronix) and a small amplifier (P2632 manufactured by Velleman). The device was vibrated from the outside. The amplitude of the vibrator was measured by observing the vibrator supported by a conductive spring made of parylene with a CCD camera (XC-75 made by SONY). The electrical resistance of the conductive spring was measured by attaching a lead wire to the end of the conductive spring and measuring the resistance at both ends with a multimeter (AD-7451 manufactured by Advantest).

  As a result of the above measurement, the resonance frequencies of the vibrators supported by the conductive springs having a width of 20, 30, and 40 microns were 81, 155, and 270 Hz, respectively. This shows that the spring constant is increased by 50 to 80% with respect to the parylene spring in which the metal conductive layer 116 is not formed, but can be vibrated with an amplitude of 0.3 mm or more, It was found that a spring having no problem in practical use can be obtained.

  Further, the electric resistance was about 100Ω, and it was found that the value was practically usable.

Furthermore, it was found that even when the maximum amplitude was 0.3 mm and the vibration was repeated 10 ⁷ times or more, changes in the spring constant and electric resistance value were small and durability was provided.

Here, the outline of the etching conditions by SF ₆ and C ₄ F ₈ high-density plasma in Examples 1 and 2 is as follows.
Apparatus: AMS-100 manufactured by Alcatel
Plasma output: 1800W
_Gas: SF _6, C 4 _{F 8}
Bosch process cyclo time SF ₆ 5 seconds, C ₄ F ₈ 2 seconds

Moreover, the outline of the etching conditions by oxygen plasma is as follows.
Apparatus: RIE-10NR manufactured by Samco
Gas: Oxygen plasma output: 100W

  FIG. 4 shows an application example of the conductive spring manufactured in the second embodiment. In FIG. 4, the substrate 10 has a hollow structure, and an element 18 such as an electret power generator is formed therein. The element 18 is supported by the conductive spring 20 with respect to the substrate 10 so as to vibrate. The element 18 is configured to be driven to vibrate by being supplied with drive power from the appropriate drive circuit 22 via the conductive spring 20. Alternatively, a signal generated by the element 18 can be extracted to the outside through the conductive spring 20.

It is explanatory drawing of one Embodiment of the metal conductive layer formation method concerning this invention. FIG. 6 is a substrate cross-sectional view for explaining a process of the first embodiment. 10 is a substrate cross-sectional view for explaining a process of Example 2. FIG. 6 is a diagram illustrating an application example of a conductive spring manufactured in Example 2. FIG.

Explanation of symbols

  10 substrate, 12 flow path, 14 communication path, 16 liquid reservoir, 18 element, 20 conductive spring, 22 drive circuit, 100 silicon substrate, 102 oxide film, 104 photoresist, 106 groove, 108 liquid reservoir, 110 insulating material, 112 flow path, 114 metal nanoparticle dispersion, 116 metal conductive layer, 118 void, 120 copper thin film.

Claims (7)

Forming a flow path through which the metal nanoparticle dispersion flows in or on the surface of the insulating material;
Pouring the metal nanoparticle dispersion into the flow path by capillary action;
Heating the metal nanoparticle dispersion and aggregating the metal nanoparticles to form a metal conductive layer;
A method for forming a metal conductive layer, comprising:   2. The metal conductive layer forming method according to claim 1, wherein the metal nanoparticle dispersion liquid is poured into the flow path by a capillary phenomenon from a liquid reservoir formed inside or on the surface of the insulating material. Forming method.   3. The method for forming a metal conductive layer according to claim 1, wherein the metal nanoparticles are silver nanoparticles. Forming a spring-shaped groove in the mold material;
Vapor-depositing an insulating material layer which is an organic substance on both walls and the bottom of the groove, and forming an insulating material structure having a flow path through which the metal nanoparticle dispersion flows in or on the surface;
Pouring the metal nanoparticle dispersion into the flow path by capillary action;
Heating the metal nanoparticle dispersion and aggregating the metal nanoparticles to form a metal conductive layer;
Removing the mold material;
A method of forming a conductive spring, comprising:   5. The method for forming a conductive spring according to claim 4, wherein the metal nanoparticle dispersion liquid is poured into the flow path by a capillary phenomenon from a liquid reservoir formed in the mold material.   The method for forming a conductive spring according to claim 4 or 5, wherein the insulating material is polyparaxylylene. A spring portion formed of an insulating material that is organic,
A metal conductive layer in which metal nanoparticles are aggregated, formed inside or on the surface of the spring portion;
A conductive spring comprising:

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