JP2011165762A - Method of manufacturing wiring board - Google Patents

Abstract

Throughput is improved and electrical conductivity is ensured between a first electrode and a second electrode even with a small droplet amount.
A bottom electrode 3 serving as a bottom 2a of a fine hole 2 formed on a surface 10a of a base 10, and a top electrode disposed on the surface 10a of the base 10 near the upper end of an inner wall 2b of the fine hole 2. 5 is formed. In the formation of the conductive layer 12, first, the clear ink 8 for dispersing the metal nanoparticles 11 is filled in the fine holes 2. Next, droplets containing the metal nanoparticles 11 are supplied to the fine holes 2, and the metal nanoparticles 11 are dispersed with the clear ink 8 in the fine holes 2. Next, the conductive layer 12 having the metal nanoparticle film 11A deposited on the bottom 2a and the inner wall 2b of the fine hole 2 is formed by volatilizing the clear ink 8 in the fine hole 2.
[Selection] Figure 2

Description

  The present invention relates to a method of manufacturing a wiring board that forms a conductive layer that electrically connects a first electrode arranged on the back surface or inside of the wiring board and a second electrode arranged on the surface of the wiring board. .

  Usually, a wiring board is produced by forming a wiring or an electrode by patterning a conductive layer. In recent years, development of high definition has been actively performed in many devices. Accordingly, there is a demand for miniaturization and higher density of the wiring board. Therefore, photolithography using a photomask having a highly accurate opening is generally applied as a high-definition patterning method. However, this method requires a separate mask for each pattern. Furthermore, various processes such as a film forming process, a resist patterning process, an etching process, and a peeling process are necessary, which causes a problem in productivity. Along with this, there are also problems in terms of manufacturing costs such as low use efficiency of materials and the like.

  On the other hand, an ink jet method has attracted attention as a method for forming a wiring on a wiring board. Wiring formation by the ink jet method is performed by forming metal wiring by applying an ink containing a metal material to a target location on a substrate using an ink jet apparatus and then baking the ink. At this time, an ink prepared by dispersing and dissolving metal nanoparticles in a solvent is often used. In this way, wiring formation using an ink jet apparatus is very advantageous in terms of production efficiency because direct patterning can be performed without using a photomask or the like.

  Further, in a wiring board, a multilayer technology is generally used as a method for arranging wirings at high density. One of the multilayer wiring techniques is to electrically connect the layers on the front and back surfaces of the substrate. As a method of electrically connecting the front and back surfaces of the wiring board, the bottom of the fine hole (recess) formed in the wiring board is used as a lower surface electrode as the first electrode, and the conductive layer is formed by filling the fine hole with a conductive member. There is a method of forming. As a method for forming the conductive layer of the fine hole, when the aspect ratio of the fine hole is less than 1 and relatively small, it is possible to form the conductive layer in the fine hole by a dry process such as sputtering or vapor deposition. It is possible to establish electrical continuity between the upper and lower surfaces of the substrate. However, when the aspect ratio of the fine hole is 1 or more, it is extremely difficult to form a sufficient conductive layer for ensuring conductivity at the lower part of the inner wall of the fine hole by the dry process. Therefore, a method of growing a conductive portion by plating after a seed layer is formed on the inner surface of a fine hole by a dry process (see Patent Document 1). In particular, as a method for forming a seed layer on the inner wall of a fine hole by a directional film formation method such as sputtering, the film formation particles are incident at an incident angle corresponding to the shape of the fine hole. However, in order to form a conductive layer for a fine hole with a high aspect ratio by plating, it is necessary to suppress electrolytic concentration near the opening of the fine hole and non-uniform layer deposition resulting therefrom. To that end, measures such as adding an additive to suppress precipitation or lowering the input current during the plating process are taken. There was a problem.

  Therefore, for a wiring board having a fine hole with a high aspect ratio, a method of directly applying a conductive material to the fine hole by an ink jet method is employed (see Patent Document 2). In this method, the conductivity of the front and back surfaces of the substrate is ensured by filling the fine holes with a conductive material.

Japanese Patent Laid-Open No. 5-167062 JP 2003-243327 A

  However, in order to ensure conductivity when a conductive material is filled in the fine holes by the ink jet method, it is necessary to give a sufficient amount of droplets to the fine holes. For example, the shape of the microhole is Φ46 μm, the depth is 200 μm (aspect ratio is 4.35), the size of the inkjet droplet is Φ30 μm, and the concentration of the conductive material in the ink is 50%. In this case, in order to fill one minute hole with the conductive material, it is necessary to apply 30 or more droplets, and it is necessary to apply a large amount of droplets.

  In addition, a single wiring board has a large number of fine holes for establishing conduction between the upper and lower sides of the board. Therefore, the method of filling each minute hole with a conductive material by the ink jet method is an obstacle to throughput. Metal nanoparticle inks are widely used as conductive materials used in the ink jet method. Since the metal nanoparticle ink generally has a high material cost, it is also desired to reduce the amount of ink used to reduce the cost of the wiring board.

  Accordingly, an object of the present invention is to provide a method of manufacturing a wiring board that can improve the throughput and ensure the electrical connection between the first electrode and the second electrode even with a small amount of droplets.

  The present invention provides a first electrode serving as a bottom portion of a recess formed on a surface of a base, a second electrode disposed on the surface of the base and in the vicinity of an upper end of an inner wall of the recess, and the first And a conductive layer for electrically connecting the second electrode to the second electrode, a dispersion solvent filling step of filling the recess with a dispersion solvent for dispersing metal fine particles, and a metal in the recess Supplying droplets containing fine particles and dispersing the fine metal particles with the dispersion solvent in the recesses, and volatilizing the dispersion solvent in the recesses and depositing on the bottom and inner wall portions of the recesses And a metal film forming step of forming the conductive layer with the metal film of the metal fine particles.

  According to the present invention, since the fine metal particles supplied to the concave portion are uniformly dispersed by the dispersion solvent filled in the concave portion, the metal fine particles are formed on the bottom and inner wall portions of the concave portion without supplying excessive metal fine particles. Unevenness of the thickness of the conductive layer can be suppressed. Thereby, the electrical continuity between the first electrode and the second electrode can be stabilized. Further, since the amount of metal fine particles supplied to the recesses can be reduced, the cost is reduced, and the number of droplets dropped can be reduced, so that the throughput in forming the conductive layer is improved, and thus the productivity of the wiring board is improved.

It is explanatory drawing which shows the outline of the wiring board which concerns on 1st Embodiment of this invention, (a) is a top view of a wiring board, (b) is a schematic diagram which shows the cross section of the fine hole of a wiring board. It is a schematic diagram for demonstrating the manufacturing process of a wiring board, (a) is a figure for demonstrating an insulating layer film-forming process, (b) is a figure for demonstrating a electrically conductive film formation process and a dispersion | distribution solvent filling process. (C) And (d) is a figure for demonstrating a metal microparticle supply process. (E) And (f) is a figure for demonstrating a metal film formation process. It is a schematic diagram which shows the cross section of the fine hole of the wiring board for demonstrating a dispersion | distribution solvent filling process. It is a schematic diagram for demonstrating the manufacturing process of the wiring board which concerns on 2nd Embodiment of this invention, (a) is a figure for demonstrating a metal microparticle supply process, (b) demonstrates a solvent component drying process. FIG. 4C is a diagram for explaining the dispersion solvent filling step. (D) is a figure for demonstrating a metal film formation process. It is a top view which shows the wiring board for demonstrating a dispersion | distribution solvent filling process. In Example 1, it is a schematic diagram which shows the cross section of the fine hole of the wiring board as a comparative sample. In Example 1, it is a figure which shows the table | surface which compared the electrical resistance value between the electrodes of the wiring board as an implementation sample, and the electrical resistance value between the electrodes of the wiring board as a comparative sample.

  Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is an explanatory diagram showing an outline of a wiring board according to the first embodiment of the present invention. As shown in FIGS. 1A and 1B, the wiring substrate 50 includes a base body 10 in which an insulating layer 4 of an electrical insulator is formed on a silicon substrate 1. That is, the base 10 is composed of the silicon substrate 1 and the insulating layer 4 formed on the silicon substrate 1. Although the case of the silicon substrate 1 will be described in the first embodiment, a substrate such as a glass substrate, a glass epoxy substrate, or a resin substrate may be used instead of the silicon substrate 1. Note that if the substrate is formed of an electrical insulator, the formation of the insulating layer can be omitted, and the substrate formed of the electrical insulator serves as a base.

  As shown in FIG. 1B, the wiring substrate 50 is a lower electrode 3 that is a first electrode disposed on the back surface 10 b of the base 10 and a second electrode that is disposed on the front surface 10 a of the base 10. And an upper surface electrode 5. In the first embodiment, a plurality of through holes are formed in the silicon substrate 1 as shown in FIG. 1A and correspond to the through holes in the back surface of the silicon substrate 1 as shown in FIG. The lower surface electrode 3 is disposed at the position. As a result, on the surface 10a of the base body 10, the fine hole 2 is formed as a contact hole, which is a recess having the bottom electrode 3 as the bottom 2a. In the first embodiment, the fine holes 2 are formed in a straight line with a pitch L. Although not shown in the figure, the bottom of the recess formed in the silicon substrate may be formed by a lower surface electrode, or the surface of the silicon substrate and in the through hole of the insulating film formed on the surface of the silicon substrate. You may form the bottom part of a recessed part with the lower surface electrode arrange | positioned in the corresponding position.

  The shape of the fine hole 2 is substantially cylindrical. The aspect ratio between the inner diameter and the depth of the fine hole 2 is 1 or more. Further, depending on the processing process of the fine hole 2, it may be tapered toward the bottom. The inner diameter of the fine hole 2 is limited by the thickness of the silicon substrate 1 and the devices installed on the wiring substrate 50, and is about several tens of μm. The inner wall 2b of the micro hole 2 and a part of the surface 10a of the base body 10 are formed of the insulating layer 4. This is particularly necessary for maintaining insulation from other terminals when the substrate is conductive. The lower electrode 3 may be made of Au, Pt, Ag, Al, Cu or the like. Here, when using a material having a relatively large ionization tendency such as Al and Cu, it is necessary to remove the surface oxide layer generated in the process from the viewpoint of reducing the contact resistance of the joint surface. Irradiation with inert gas ions may be performed to remove the surface alteration layer.

  In the first embodiment, a conductive layer 12 that connects the lower surface electrode 3 and the upper surface electrode 5 is formed in the minute hole 2. Hereinafter, the manufacturing method of the wiring board 50 for forming the conductive layer 12 will be described in detail. FIG. 2 is a schematic diagram for explaining a manufacturing process of the wiring board 50, and FIGS. 2A to 2F show each process. 2A to 2F show a cross section of one typical fine hole 2.

  First, referring to FIG. 2A, the insulating layer 4 is formed on the silicon substrate 1. For the formation of the insulating layer 4, it is possible to form the insulating layer 4 uniformly even to the inside of the fine holes 2 by using a CVD method or the like. After the formation of the insulating layer 4, only the insulating layer 4 formed on the lower electrode 3 is selectively removed by dry etching or the like. As a result, the micro hole 2 having the bottom 2a as the lower surface electrode 3 and the inner wall 2b as the insulating layer 4 is formed (insulating layer forming step).

  Next, the upper surface electrode 5 is formed, and the conductive film 5A that is continuously connected to the upper surface electrode 5 and extends to the upper portion of the inner wall portion 2b of the fine hole 2 is formed (conductive film formation step). That is, the upper surface electrode 5 and the conductive film 5A are simultaneously formed in the same process. More specifically, the substrate 10 is arranged so as to have an inclination from an arrangement facing an evaporation source (not shown), and a film is formed under a high vacuum condition by a sputtering method or an evaporation method. In the vapor deposition method, an ion plating method that ionizes the evaporated particles may be employed in order to improve the straightness and adhesion of the evaporated particles. By setting the film forming conditions in this way, the upper surface electrode 5 is formed on the surface 10a of the substrate 10 in the vicinity of the upper end of the minute hole 2, and the upper surface electrode 5 is also formed above the inner wall 2b of the minute hole 2. A continuous conductive film 5A is formed.

  The top electrode 5 and the conductive film 5A are composed of a Ti layer 5a and an Au layer 5b. A Ti layer 5a is formed on the insulating layer 4, and an Au layer 5b is formed on the Ti layer 5a. The Ti layer 5a is disposed in order to ensure adhesion between the Au layer 5b and the insulating layer 4. When the lower surface electrode 3 is Al, the Ti layer 5a plays a role for preventing the Au layer 5b and the material constituting the lower surface electrode 3 from diffusing and mixing. The shape of the conductive film 5A varies depending on the film forming method and the conditions during film formation. The formed Ti layer 5a and Au layer 5b are tented with a dry film resist and then patterned by wet etching to form the upper surface electrode 5. In this conductive film forming step, an electrode layer 6 made of Ti and Au is deposited and formed on the lower surface electrode 3 of the bottom 2a of the fine hole 2.

  Here, for the formation of the conductive layer 12 in the first embodiment, two kinds of liquids, that is, a metal-containing liquid and a dispersion solvent are used. The metal-containing liquid is a liquid containing metal nanoparticles as metal fine particles, and is hereinafter referred to as metal nanoparticle ink. As the metal material, Ag, Au, Cu or an alloy thereof is mainly used. The dispersion solvent is a liquid composed of a solvent component that does not contain a solute component and can disperse metal nanoparticles, and is hereinafter referred to as a clear ink. In the first embodiment, the metal solvent component of the metal nanoparticle ink and the clear ink are the same component.

  In forming the conductive layer 12, as shown in FIG. 2B, first, the clear ink 8 as a dispersion solvent is filled into the fine holes 2 (dispersion solvent filling step). At this time, the clear ink 8 is preferably filled up to a position in contact with the conductive film 5 </ b> A formed simultaneously with the upper surface electrode 5. The clear ink 8 is filled using the coating apparatus 100 shown in FIG. In the first embodiment, the clear ink 8 is sprayed onto the entire surface of the substrate by a spray coating method and then spin-dried. The coating apparatus 100 includes a plurality of nozzles 101 that eject the clear ink 8, and a rotation stage 102 that is disposed to face the nozzles 101 and that rotates while holding the substrate 10. The ejection pattern of the clear ink 8 by each nozzle 101 is conical, and each nozzle 101 is juxtaposed along the radial direction from the rotation center to the outer periphery of the rotary stage 102, and the clear ink is formed on the surface 10 a of the substrate 10. 8 can be applied uniformly. Further, after the application of the clear ink 8, the clear ink 8 on the surface 10 a of the substrate 10 can be dried by further rotating the rotary stage 102. However, drying is preferably performed in a short time and at a low speed so that all the clear ink 8 in the fine hole 2 does not volatilize. As a result, the clear ink 8 is filled into the fine holes 2. At this time, there may be a small amount of clear ink 8 residue on the substrate 10. Since the residue of the clear ink 8 does not contain a solute component, it can be volatilized and removed by a drying and baking process in a subsequent metal film forming step. In the first embodiment, since the clear ink 8 is filled in the fine holes 2 by spray coating, the permeability of the clear ink 8 into the fine holes 2 is good, and the throughput of the process of forming the conductive layer 12 is good. Will improve.

  Next, as shown in FIG. 2C, droplets of the metal nanoparticle ink 9 containing metal nanoparticles that are metal fine particles are supplied to the clear ink 8 filled in the fine holes 2 (metal fine particle supplying step). ). The metal solvent component contained in the droplets of the metal nanoparticle ink 9 and the clear ink 8 are composed of the same component. Therefore, the metal nanoparticles 11 contained in the metal nanoparticle ink 9 are easily dispersed in the clear ink 8, and the metal nanoparticles 11 are uniformly dispersed in the clear ink 8, as shown in FIG. . In the first embodiment, an inkjet method is used as a method for supplying the metal nanoparticle ink 9. This ink jet method is a method of ejecting droplets containing metal nanoparticles 11 from a nozzle, and various methods such as a bubble jet (registered trademark) method and a piezo method can be used.

  An inkjet head 200 is attached to an inkjet drawing apparatus (not shown), and the inkjet head 200 is relatively aligned with the substrate 10 by an alignment mark (not shown) of the substrate 10 (silicon substrate 1). . After the alignment, an ejection drive signal for forming a droplet is applied to the inkjet head 200 so that the droplet is positioned almost at the center of the microhole 2, and the droplet of the metal nanoparticle ink 9 is applied. Is discharged. The ejected droplets of the metal nanoparticle ink 9 land in the clear ink 8 filled in the fine holes 2. By the ink jet method using the ink jet head 200, it is possible to supply the droplets of the metal nanoparticle ink 9 only in the fine holes 2. The supply amount of the metal nanoparticle ink 9 to the clear ink 8 in the fine hole 2 is set by the number of drops of the liquid droplet. Discharged. The relative movement of the inkjet head 200 with respect to the substrate 10 may be performed by mounting the substrate 10 on a moving stage (not shown) and moving the inkjet head 200, or moving the inkjet head 200.

  Next, as shown in FIG. 2 (e), the clear ink 8 in the fine holes 2 (in the recesses) is volatilized in a state where the metal nanoparticles 11 are dispersed in the clear ink 8. Due to the volatilization of the clear ink 8, as shown in FIG. 2 (f), a metal nanoparticle film 11A as a metal film composed of the deposited metal nanoparticles 11 is formed on the bottom 2a and the inner wall 2b of the fine hole 2. (Metal film forming step). A part of the metal nanoparticle film 11A overlaps the conductive film 5A, and the conductive layer 12 is configured by the conductive film 5A and the metal nanoparticle film 11A. By forming the conductive film 5 </ b> A in this way, the reliability of conduction between the lower surface electrode 3 and the upper surface electrode 5 by the conductive layer 12 can be improved.

  As described above, the metal nanoparticles 11 supplied to the fine holes 2 are uniformly dispersed by the clear ink 8 filled in the fine holes 2, so that the metal nanoparticles 11 are concentrated on the bottom 2 a of the fine holes 2. Can be suppressed. Thereby, even if it does not supply the metal nanoparticle 11 excessively, the deviation of the thickness of the conductive layer 12 formed in the bottom part 2a and the inner wall part 2b of the fine hole 2 can be suppressed. Therefore, the conductivity between the lower surface electrode 3 and the upper surface electrode 5 can be stabilized by the conductive layer 12 thus formed.

  In addition, the amount of the metal nanoparticles 11 supplied to the fine holes 2 can be reduced to the minimum amount necessary for conduction, thereby reducing the cost and reducing the number of droplets to be dropped. As a result, the productivity of the wiring board 50 is improved.

  Here, since the components of the clear ink 8 are saturated in the atmosphere in the fine holes 2, the drying speed of the clear ink 8 is very slow at room temperature. When the drying speed is low, the liquid level of the clear ink 8 is advanced without sufficiently depositing the metal nanoparticles 11 on the conductive film 5A and the inner wall 2b of the fine hole 2. As a result, there is a concern that the precipitation of the metal nanoparticles 11 is biased only to the bottom 2a of the fine hole 2 and its periphery. The metal nanoparticles 11 are coated with a polymer layer so as to be stably dispersed in the clear ink 8 (in the dispersion solvent). Therefore, it is necessary to improve the conductivity of the metal nanoparticle film 11A through a process such as heat treatment for removing the polymer layer.

  Therefore, in the first embodiment, volatilization of the clear ink 8 is promoted by the heat treatment of the substrate 10 in the metal film forming step. Thereby, the thickness deviation of the metal nanoparticle film 11A formed on the bottom 2a and the inner wall 2b of the fine hole 2 can be effectively suppressed. Furthermore, in the first embodiment, in the metal film forming step, after the volatilization of the clear ink 8, the heat treatment is continued for the time until the polymer layer of the metal nanoparticles 11 is removed. Specifically, after the clear ink 8 in which the metal nanoparticles 11 are dispersed is dried or simultaneously with the drying, a heat treatment at 120 to 350 ° C. is performed. As a result, the metal nanoparticle film 11A deposited in the fine hole 2 becomes a conductive film with good conductivity by removing the polymer layer. Therefore, the conductive layer 12 having good conductivity is formed by the metal nanoparticle film 11A and the conductive film 5A.

[Second Embodiment]
Next, the manufacturing method of the wiring board according to the second embodiment of the present invention will be described in detail. 4 and 5 are diagrams for explaining the manufacturing process of the wiring board. The same components as those of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and the description thereof is omitted. To do. Also in the second embodiment, the first electrode is the lower surface electrode 3, the second electrode is the upper surface electrode 5, the concave portion is the fine hole 2, the dispersion solvent is the clear ink 8, the metal fine particles are the metal nanoparticles 11, the metal The contained liquid will be described as the metal nanoparticle ink 9. The aspect ratio between the inner diameter and the depth of the fine hole 2 is 1 or more.

  First, as in the first embodiment, an insulating layer 4 is formed on a silicon substrate 1 to form a substrate 1. Next, similarly to the first embodiment, the upper surface electrode 5 and the conductive film 5A are formed (conductive film forming step). Next, as shown in FIG. 4A, a droplet of the metal nanoparticle ink 9 containing the metal nanoparticles 11 which are metal fine particles is supplied to the fine holes 2 (metal fine particle supplying step). In the second embodiment, as a method for supplying the metal nanoparticle ink 9, an ink jet method is used as in the first embodiment. The supply amount of the metal nanoparticle ink 9 into the fine hole 2 is set by the number of drops of the liquid droplet, and the liquid droplet is ejected until the amount of the metal nanoparticle ink 9 in the fine hole 2 reaches the required amount. The The relative movement of the inkjet head 200 with respect to the substrate 10 may be performed by mounting the substrate 10 on a moving stage (not shown) and moving the inkjet head 200, or moving the inkjet head 200.

  Next, as shown in FIG. 4B, after supplying the metal nanoparticle ink 9, the solvent component is naturally dried to form a deposited layer 11B of the metal nanoparticle 11 on the bottom 2a of the fine hole 2 (solvent component). Drying step). The reason why the deposited layer 11B is naturally dried in this manner is that before the clear ink 8 on the surface 10a side of the substrate 10 is volatilized by supplying the clear ink 8 onto the substrate 10 in the subsequent dispersion solvent filling step. This is to avoid the dispersion of the metal nanoparticles 11. Here, the metal nanoparticles 11 often do not bond and grow unless heat is applied. Therefore, it is possible to disperse the metal nanoparticles 11 again with the clear ink 8 filled in the fine holes 2.

  Next, as shown in FIG. 4C, the clear ink 8 which is a dispersion solvent for dispersing the metal nanoparticles 11 is filled into the micro holes 2 (dispersion solvent filling step). Specifically, the filling of the clear ink 8 into the fine holes 2 is performed by applying the clear ink 8 on the substrate by a dispensing method. More specifically, as shown in FIG. 4 (c), as shown in FIG. 5, with respect to the fine holes 2 arranged in a straight line on the substrate 10 from the dispenser 300 attached to the dispensing apparatus (not shown). The clear ink 8 is ejected linearly.

  After the application by the dispenser 300, the base 10 is allowed to stand at room temperature for 1 minute, whereby the clear ink 8 on the surface of the base 10 is volatilized and the clear ink 8 remains in the fine holes 2, thereby clear ink. 8 fillings are made. With the clear ink 8 filled in the fine holes 2, the metal nanoparticles 11 of the deposition layer 11B are uniformly dispersed.

  Next, as shown in FIG. 4D, the clear ink 8 is volatilized in a state where the metal nanoparticles 11 are dispersed in the clear ink 8 as in the first embodiment. By the volatilization of the clear ink 8, a metal nanoparticle film 11A as a metal film made of the deposited metal nanoparticles 11 is formed on the bottom 2a and the inner wall 2b of the fine hole 2 (metal film forming step). A part of the metal nanoparticle film 11A overlaps the conductive film 5A, as in the first embodiment, and the conductive layer 12 is configured by the conductive film 5A and the metal nanoparticle film 11A. By forming the conductive film 5 </ b> A in this way, the reliability of conduction between the lower surface electrode 3 and the upper surface electrode 5 by the conductive layer 12 can be improved.

  As described above, the metal nanoparticles 11 supplied to the fine holes 2 are uniformly dispersed by the clear ink 8 filled in the fine holes 2, so that the metal nanoparticles 11 are concentrated on the bottom 2 a of the fine holes 2. Can be suppressed. Thereby, even if it does not supply the metal nanoparticle 11 excessively, the deviation of the thickness of the conductive layer 12 formed in the bottom part 2a and the inner wall part 2b of the fine hole 2 can be suppressed. Therefore, the conductivity between the lower surface electrode 3 and the upper surface electrode 5 can be stabilized by the conductive layer 12 thus formed.

  In addition, the amount of the metal nanoparticles 11 supplied to the fine holes 2 can be reduced to the minimum amount necessary for conduction, thereby reducing the cost and reducing the number of droplets to be dropped. As a result, the productivity of the wiring board 50 is improved.

  In the metal film forming step, the volatilization of the clear ink 8 is promoted by the heat treatment of the substrate 10. Thereby, the thickness deviation of the metal nanoparticle film 11A formed on the bottom 2a and the inner wall 2b of the fine hole 2 can be effectively suppressed. Furthermore, in the second embodiment, in the metal film forming step, after the clear ink 8 is volatilized, the heat treatment is performed for the time until the polymer layer of the metal nanoparticles 11 is removed. Specifically, after the clear ink 8 in which the metal nanoparticles 11 are dispersed is dried or simultaneously with the drying, a heat treatment at 120 to 350 ° C. is performed. As for the heat treatment conditions, it is necessary to consider the grain growth of the metal nanoparticles 11 and the film shrinkage stress during the heat treatment, but are not particularly limited. As a result, the metal nanoparticle film 11A deposited in the fine hole 2 becomes a conductive film with good conductivity by removing the polymer layer. Therefore, the conductive layer 12 having good conductivity is formed by the metal nanoparticle film 11A and the conductive film 5A.

  Hereinafter, it is Example 1 corresponding to the said 1st Embodiment, Comprising: The wiring board as an implementation sample is demonstrated in detail. As the substrate 10, a silicon substrate 1 having an insulating layer 4 formed thereon was used. And as the base | substrate 10, the inside diameter (diameter) of the fine hole 2 was 50 micrometers, the depth was 200 micrometers, and the aspect ratio was set to 4. Deep-Reactive Ion Etching method was used for forming the fine hole 2. The bottom electrode 3 was made of an alloy containing aluminum as a main component, and the film thickness was about 0.4 μm. Further, the inside of the fine hole 2 is formed of an insulating layer 4 which is an organic insulating film, and the insulating layer 4 in the portion of the lower surface electrode 3 is removed by dry etching. The insulating layer 4 on the inner wall 2b of the fine hole 2 was formed almost conformally, and the film thickness was about 2 μm. Therefore, in the process of ensuring the conductivity between the lower surface electrode 3 and the upper surface electrode 5, the substantial opening diameter of the fine hole 2 is about 46 μm.

  The Ti layer 5a and the Au layer 5b were formed by sputtering. At this time, the Ti layer 5a was 0.2 μm thick on the surface 10a of the base 10, and the Au layer 5b was 0.15 μm on the surface 10a of the base 10. In addition, regarding the electrode layer 6 formed on the lower surface electrode 3 at the bottom 2a of the fine hole 2, the Ti layer was 50 nm thick and the Au layer was 30 nm. The conductive film 5A was formed by the Ti layer 5a and the Au layer 5b and had a depth of 50 μm from the upper end of the micro hole 2. The top electrode 5 was formed by patterning by wet etching after the Ti layer 5a and the Au layer 5b were tented with a dry film resist.

  Next, the metal nanoparticles 11 that are metal fine particles used in the metal fine particle supply step are silver nanoparticles having a particle diameter of about 10 nm, and the metal nanoparticle ink 9 contains 50 wt% of silver nanoparticles. Using. Here, in order to ensure the dispersibility of the silver nanoparticles in the solvent, silver nanoparticles coated with an organic protective film were used. As the solvent, a mixture of n-undecane and terpineol 4 to 1 was used.

  Further, as the clear ink 8 which is a dispersion solvent used in the dispersion solvent filling step, similar to the solvent component of the metal nanoparticle ink 9, n-undecane and terpineol mixed 4 to 1 were used. However, the ratio may be changed or another liquid may be used in consideration of the drying speed and leveling property of the clear ink 8.

  In the dispersion solvent filling step, the clear ink 8 was applied to the entire surface 10a of the substrate 10 by spray coating. Then, the substrate 10 was rotated at 30 rpm for 3 seconds, then increased to 500 rpm over 10 seconds, held in that state for 20 seconds, and the silicon substrate 1 was dried. As a result, a trace amount of clear ink 8 was observed on the surface 10a of the substrate 10 immediately after the drying treatment, but the fine hole 2 was filled with the clear ink 8. In this state, droplets of the metal nanoparticle ink 9 were ejected by an ink jet method. The liquid volume of this droplet was 15 pl. In the first embodiment, the substrate 10 is scanned 1, 2, 4, 8, 16, 23 times with respect to the ink-jet head 200, whereby the droplets of the metal nanoparticle ink 9 are totaled 1, 2, 4, 8, 16 , 23 drops were discharged into the fine hole 2. The scan speed was 250 mm / sec. Thereafter, the substrate 10 was immediately moved onto a hot plate (not shown), dried at 100 ° C. for 15 minutes, and then placed in a clean oven (not shown) for heat treatment. Heat treatment was performed from 140 ° C. to 200 ° C. over 30 minutes, and was further performed for 1 hour in that state.

  Here, for comparison, as shown in FIG. 6, a wiring substrate as a comparative sample in which the conductive layer 112 was formed only by applying the metal nanoparticle ink was produced. Under this condition, the substrate 10 is scanned 1, 2, 4, 8, 16, 23 times with respect to the ink-jet head 200, whereby the droplets of the metal nanoparticle ink 9 are totaled 1, 2, 4, 8, 16, 23 in total. A droplet was discharged into the fine hole 2. The scan speed was 250 mm / sec.

  When the electrical contact resistance value between the upper surface electrode 5 and the lower surface electrode 3 of the wiring board manufactured as described above was measured, the result shown in FIG. 7 was obtained. As shown in FIG. 7, in the result of the comparative sample using only metal nanoparticles, about 32 droplets were required to achieve the target value of 3Ω or less. With 16 drops or less, it is determined that the electrical resistance value did not decrease because the contact surface between the conductive film 5A in the fine hole 2 and the conductive layer 112 formed by the metal nanoparticles 11 was not sufficient.

  On the other hand, in the result of the working sample of Example 1, when 1, 2, 4 droplets lower than 8 droplets were supplied, the electrical resistance value was larger than the target 3Ω. In the case of 8 drops or more, a target electric resistance value of 3Ω or less could be obtained. This is determined that the electrical contact resistance could be kept low because the conductive film 5A in the microhole 2 and the conductive film 5A formed of metal nanoparticles have a sufficient contact area. As described above, according to Example 1, it was confirmed that the conductive film 5A can be easily formed with a small amount of metal nanoparticle ink.

  Hereinafter, Example 2 corresponding to the second embodiment will be described in detail. In Example 2, the number of droplets was 8 in the metal fine particle supply step. In the dispersion solvent filling step, in the dispenser 300, a needle having an inner diameter of 0.1 mm was used and the pressure was set to 50 kPa. At this time, the substrate 10 was scanned at 1000 mm / sec. After application by the dispenser 300, the silicon substrate 1 was left at room temperature for 1 minute, and then dried for 15 minutes on a hot plate (not shown) heated to 100 ° C. Thereafter, heat treatment at 200 ° C. was further performed.

  When the electrical contact resistance value between the upper surface electrode 5 and the lower surface electrode 3 of the silicon substrate 1 processed as described above was measured, the target value of 3Ω or less was obtained in Example 2. It was judged that this was because the metal nanoparticles 11 were redispersed in the liquid by filling with the clear ink 8 and then dried and fired to form the conductive film 5A having a sufficient contact area with the conductive film 5A. . As described above, also in Example 2, it was confirmed that the conductive film 5A can be easily formed with a small amount of metal nanoparticle ink. Furthermore, in Example 2, it was confirmed that the present invention is applicable even when a time interval is provided between the metal fine particle supply step and the dispersion solvent filling step.

2 Fine holes (recesses)
2a Bottom portion 2b Inner wall portion 3 Lower surface electrode (first electrode)
5 Top electrode (second electrode)
5A conductive film 8 clear ink (dispersion solvent)
10 Substrate 11 Metal nanoparticle (metal fine particle)
11A Metal nanoparticle film (metal film)
12 Conductive layer 50 Wiring board

Claims (9)

A first electrode serving as a bottom of a recess formed on the surface of the substrate; a second electrode disposed on the surface of the substrate near the upper end of the inner wall of the recess; the first electrode; In a method of manufacturing a wiring board having a conductive layer that conducts with a second electrode,
A dispersion solvent filling step of filling the recess with a dispersion solvent for dispersing the metal fine particles;
Supplying fine particles containing fine metal particles to the recess, and dispersing the fine metal particles with the dispersion solvent in the recess; and
And a metal film forming step of forming the conductive layer with a metal film of the metal fine particles deposited on the bottom and inner wall of the recess by volatilizing the dispersion solvent in the recess. Manufacturing method. A first electrode serving as a bottom of a recess formed on the surface of the substrate; a second electrode disposed on the surface of the substrate near the upper end of the inner wall of the recess; the first electrode; In a method of manufacturing a wiring board having a conductive layer that conducts with the second electrode,
A metal fine particle supplying step of supplying a droplet containing metal fine particles to the recess;
A dispersion solvent filling step of filling the recess with a dispersion solvent for dispersing the metal fine particles;
And a metal film forming step of forming the conductive layer with a metal film of the metal fine particles deposited on the bottom and inner wall of the recess by volatilizing the dispersion solvent in the recess. Manufacturing method.   The method for manufacturing a wiring board according to claim 1, wherein in the metal film forming step, the dispersion solvent is volatilized by heat treatment. The metal fine particles are coated with a polymer layer for dispersing the metal fine particles in the dispersion solvent,
4. The method of manufacturing a wiring board according to claim 1, wherein in the metal film forming step, after the dispersion solvent is volatilized, a heat treatment is performed to remove the polymer layer. 5. A conductive film forming step of forming a conductive film continuously connected to the second electrode and extending to the inner wall portion of the recess,
In the dispersion solvent filling step, the dispersion solvent is filled to a position in contact with the conductive film,
5. The method of manufacturing a wiring substrate according to claim 1, wherein, in the metal film forming step, the conductive layer is formed by overlapping a part of the metal film on the conductive film.   6. The method of manufacturing a wiring board according to claim 5, wherein the conductive film forming step is performed simultaneously with the formation of the second electrode.   The method for manufacturing a wiring board according to claim 1, wherein the dispersion solvent and the metal solvent component of the droplet are composed of the same component.   8. The method for manufacturing a wiring board according to claim 1, wherein in the dispersion solvent filling step, the dispersion solvent is applied onto the substrate by a spray coating method.   8. The method for manufacturing a wiring board according to claim 1, wherein in the dispersion solvent filling step, the dispersion solvent is applied onto the substrate by a dispensing method.

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