JP2004296424A - Method for forming metal layer, metal layer, and display device using metal layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a metal layer, capable of achieving resource saving of a metal material. <P>SOLUTION: A hydrophobic layer 11 of a silane coupling agent is provided on a selected area on a substrate 10 with a hydrophilic surface to convert it to a hydrophobic surface. Particle dispersed liquid 5 containing metal particle 2 protected by an organic material 3 is affixed to at least the hydrophobic area, to selectively coagulate to the hydrophobic area, and to combine the same metal particles 2. This allows a metal layer 20 to be selectively formed on the substrate 10. The resulted metal surface 20 is used for wiring. Micro wiring, low resistance wiring, and long wiring are thus achieved. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention provides a method for forming a metal layer used for a wiring included in a semiconductor device such as a semiconductor integrated circuit device, a wiring included in a display device such as a liquid crystal display device, a terminal, an electrode, a part of a thin film transistor, or the like. , A metal layer, and a display device using the metal layer.

  2. Description of the Related Art In a semiconductor integrated circuit device, for example, LSI, ULSI, etc., the speed of signal transmission in a circuit is increased in order to realize a high degree of element integration and a high operation speed. Therefore, in such a semiconductor integrated circuit device, it is required to perform wiring using a material having a low specific resistance.

  On the other hand, in a display device such as a liquid crystal display device, an organic EL display device, or an inorganic EL display device, the wiring length is increased due to the enlargement of the screen, the miniaturization for high definition, and the peripheral circuit for multifunctionalization are performed. Addition, monolithicization for adding a memory function, and the like have been advanced. Therefore, such a display device is also required to be wired with a material having a lower specific resistance than conventional Al, Ta, Mo, or the like. Further, when a thin film transistor (TFT) or a complementary metal oxide semiconductor (CMOS) is directly formed on a silicon array on a substrate, it is necessary to form fine wiring at the same level as these.

  2. Description of the Related Art Conventionally, as a method for forming a wiring included in a semiconductor integrated circuit device or a display device, a method of forming a metal film over the entire surface of a substrate and etching a region other than a desired region after resist patterning, or a CMP (Chemical Mechanical Polishing). (See, for example, Patent Documents 1 and 2).

As another method for forming a wiring included in a semiconductor integrated circuit device or a display device, there is known a method of forming a wiring in a selected region using a hydrophobic treatment agent that can be made hydrophilic by exposure. Have been. In this formation method, first, the pattern forming surface of the substrate is made hydrophobic using a hydrophobic silane coupling agent, and the exposed portions are made hydrophilic. A hydrophilic or hydrophobic solution of a metal compound is applied to the pattern forming surface. Then, the metal compound is deposited by baking to form a metal layer in a desired wiring pattern (for example, see Patent Document 3).
JP-A-2002-353222 (paragraphs 0030 to 0032, FIG. 1) JP-A-2001-189295 (paragraphs 0004 to 0009, FIG. 1) JP-A-7-326235 (paragraphs 0025 to 0040, FIGS. 2 to 7)

  In a semiconductor integrated circuit device and a display device, the total area of the wiring is very small, about several percent of the area of the substrate. Therefore, in the technique described in Patent Literature 1 or 2, in which a metal film is formed on the entire surface of the substrate and then a region other than the selected wiring region is removed, most of the metal film is removed. . As a result, the utilization efficiency of the metal material for forming the metal film is extremely low, so that the production cost of the semiconductor integrated circuit device and the display device increases particularly when an expensive metal material is used as a raw material. There is a problem.

  Further, when the technology described in Patent Document 1 or 2 is applied to a manufacturing process of a display device using a large and thin glass substrate, a large warpage occurs in the glass substrate due to stress of a metal film formed on the entire surface of the glass substrate. There is also a problem.

  Patent Literature 3 describes that after forming a patterned hydrophobic region, a hydrophobic solution of a metal compound is applied in the form of droplets, and the deposited metal compound is metallized. There is no specific description of the size of the compound, the thickness of the film to be formed, and the like, and there is no technical disclosure of forming a fine long wiring with low resistance on a large area glass.

  The present invention has been made in view of such circumstances, and provides a metal layer forming method capable of achieving fine wiring, low resistance wiring, and long wiring, a metal layer, and a display device using the metal layer. The purpose is to do.

  In order to solve the above-described problems, the present invention has made it possible to form a wiring or a metal layer using metal particles, for example, metal nanoparticles.

  The method for forming a metal layer of the present invention based on the first aspect includes a step of preparing a substrate having at least a selected region having hydrophobicity, and a step of preparing a dispersion containing particles of a metal or metal oxide protected by an organic substance. At least a step of attaching the particles to the hydrophobic region on the substrate, and a step of binding the particles of the metal or metal oxide are provided.

  The “substrate in which at least the selected region has hydrophobicity” may be a substrate in which the entire area on the substrate is hydrophobic or a substrate in which a part of the substrate has hydrophobicity. Further, in the present invention, the “substrate” is a layer on which a metal layer is formed, and is formed so that at least a selected region has hydrophobicity. That is, when at least the selected region is the entire region on the substrate, a substrate having at least a surface having hydrophobicity can be used as it is. Further, the substrate includes one in which a film or layer of, for example, silicon oxide or the like is provided on a substrate, and a region corresponding to a selected region on the surface of the film or layer is formed hydrophobic.

  In order to solve the above problem, a method for forming a metal layer according to the second aspect of the present invention is a method for forming a metal layer on a selected region on a substrate, the method comprising: Hydrophobizing, attaching a dispersion containing metal or metal oxide particles protected by an organic substance to at least a hydrophobic region on the substrate, and bonding the metal or metal oxide particles. And a process.

  The “selected region on the substrate” may be the entire surface or a part of the surface. Further, since the present invention includes the step of making the selected area on the substrate hydrophobic, the substrate does not have to be formed so that the selected area has hydrophobicity. That is, the surface of the substrate may be hydrophobic or hydrophilic. Further, the substrate includes a substrate provided with a film or layer of, for example, silicon oxide on a base.

  In carrying out the invention based on the second aspect, the step of making the selected area on the substrate hydrophobic is a step of making at least the area around the selected area on the substrate hydrophilic. be able to.

  In this case, for example, a substrate having at least a surface having hydrophilicity is used as the substrate, and at least a region around the selected region on the substrate is made hydrophobic while making a selected region on the substrate hydrophobic. The step of making the surface hydrophilic includes forming a hydrophobic layer on the substrate having at least a hydrophilic surface, and removing the hydrophobic layer formed in at least a region around the selected region from the substrate. It can be realized by including the step of performing

  The hydrophobic layer may be formed on only one of the plurality of surfaces of the substrate, or may be formed on a plurality of surfaces. Further, it is not always necessary to form the metal layer on all surfaces where the hydrophobic layer is formed. "Removing the hydrophobic layer formed in at least a region around the selected region from the substrate" means removing the hydrophobic layer formed around the selected region from the substrate. The case where the hydrophobic layer formed in a region other than the selected region is removed from the substrate is also included.

  Further, the step of removing the hydrophobic layer formed at least in a region around the selected region from the substrate includes excimer laser light through a mask having a predetermined pattern, wavelength light in a vacuum ultraviolet region, Alternatively, a step of irradiating at least a region around the selected region with light having a wavelength in the ultraviolet region to decompose the hydrophobic layer may be performed.

  In that case, the step of bonding the metal or metal oxide particles may be a step of removing the hydrophobic layer formed in the selected region. This means that removing the hydrophobic layer formed in the selected region includes binding metal or metal oxide particles. That is, it means that in the step of removing the hydrophobic layer formed in the selected region, the metal or metal oxide particles are bonded together.

  The step of removing the hydrophobic layer formed in the selected region may include a step of binding the metal or metal oxide particles.

  In carrying out the invention based on the second aspect, a substrate having at least a surface having hydrophobicity is used as the substrate, and a selected region on the substrate is made hydrophobic and The step of making at least the surrounding area of the selected area hydrophilic may also be realized by including a step of forming a hydrophilic layer on the substrate having at least a surface having hydrophobicity. The method may include a step of leaving or removing the hydrophilic layer formed in the selected region on the substrate.

  According to these inventions, the bonding layer formed by bonding the particles of the metal or the metal oxide can be selectively formed, so that the metal layer having the bonding layer is formed while achieving the resource saving of the metal material. can do.

  By adjusting the particle size of the metal or metal oxide particles and the exposure mask, the metal layer can form a fine pattern such as a submicron and is excellent in mass productivity. Further, as described above, not only resource saving of the metal material can be achieved, but also the productivity is good because the apparatus is inexpensive as compared with the conventional vacuum film forming method.

  In addition, when forming a copper layer for wiring as a metal layer, a plating catalyst required when performing electroless plating on a normal barrier metal, for example, a colloid or an organic complex containing palladium ions. The step of applying and activating is not required. Furthermore, the increase in specific resistance due to the mixing of palladium ions as impurities does not occur.

  In practicing these inventions, the step of attaching the dispersion to at least the hydrophobic region on the substrate includes aggregating the metal or metal oxide particles protected by the organic substance in the hydrophobic region. And removing the dispersion medium in the dispersion.

  Here, the “dispersion medium in the dispersion” refers to a substantially uniform liquid that forms a medium of the dispersion. That is, even if the dispersion medium is a liquid composed of a single substance such as an organic solvent, a solution in which a solute other than particles of a metal or metal oxide protected by an organic substance as a dispersion phase is dissolved, for example, a pH is adjusted. An aqueous solution adjusted to a predetermined value may be used.

  Further, the step of bonding the metal or metal oxide particles may be a step of removing the organic substance protecting the metal or metal oxide particles.

  This means that the step of removing the organic substance protecting the metal or metal oxide particles includes the step of bonding the metal or metal oxide particles. That is, it means that in one step, the organic substance protecting the metal or metal oxide particles is removed, and together with this, the metal or metal oxide particles are combined.

  Note that the step of bonding the metal or metal oxide particles may include a step of removing the organic substance protecting the metal or metal oxide particles.

  Further, in the step of bonding the metal or metal oxide particles, it is preferable to perform a heat treatment in an atmosphere of an inert gas or a reducing gas. Alternatively, it is desirable to include a step of decomposing organic matter by performing ultraviolet irradiation. Needless to say, heat treatment may be performed after ultraviolet irradiation is performed to accelerate the decomposition of the organic substance, or ultraviolet light irradiation may be performed during the heat treatment to accelerate the decomposition of the organic substance.

  Further, the method may include a step of forming a metal plating layer by an electroless plating method or an electrolytic plating method on a bonding layer formed by bonding particles of a metal or a metal oxide.

  In carrying out these inventions, the particles are preferably particles having an average particle size of 1 nm to 100 nm, so-called nanoparticles. That is, as the particle size decreases, the surface energy of the particles increases exponentially. Due to this property, particles of the metal or metal oxide bind at a temperature much lower than the intrinsic melting point of the metal. Therefore, there is an advantage that this configuration contributes to lowering the temperature of the manufacturing process of a semiconductor device, a display device, or the like.

The particles are made of Au (gold), Ag (silver), Pd (palladium), Pt (platinum), Ni (nickel), Co (cobalt), Cu (copper), Sn (tin) and Ru (ruthenium). Particles composed of at least one metal of the above, an alloy containing at least one of these metals, or a metal oxide containing Cu ₂ O (copper (I) oxide) can be suitably used.

  Here, the phrase “the particles are at least one metal of Au, Ag, Pd, Pt, Ni, Co, Cu, Sn, and Ru” means that the particles are made of one of these metals. In addition to dispersing in a dispersion medium in a state of being protected by an organic substance to form a dispersion, a plurality of metals are selected from these metals, and particles of these metals are each protected by an organic substance in a dispersion medium. To form a dispersion, that is, a case where the dispersion is a dispersion containing a plurality of types of metal particles.

  The metal layer according to the present invention is a metal layer having a bonding layer formed by bonding particles of a metal or a metal oxide, wherein the bonding layer is provided in a selected region on a substrate. I do.

  In practicing the present invention, a metal plating layer may be provided on the bonding layer.

The display device according to the present invention includes a plurality of thin film transistors provided in a matrix, a plurality of scanning wirings and a plurality of signal wirings for driving the thin film transistors, a plurality of pixel electrodes, and a plurality of connection terminals. A display device comprising:
At least one of the electrode of the thin film transistor, the plurality of scanning wirings, the plurality of signal wirings, the pixel electrode, and the plurality of connection terminals is formed of a metal layer having a bonding layer of metal or metal oxide particles. It is characterized by having been done.

  The display device of the present invention can be applied to, for example, a liquid crystal display device having a liquid crystal layer provided between a pair of substrates, a display device having an organic EL layer or an inorganic EL layer, or the like.

  Further, in the display device of the present invention, at least one of the electrode of the thin film transistor, the plurality of scanning wirings, the plurality of signal wirings, the pixel electrode, and the plurality of connection terminals is formed of metal or metal oxide particles. What is necessary is just to be formed by the metal layer which has a bonding layer of these.

  Examples of the “electrode of the thin film transistor” include a gate electrode, a drain electrode, and a source electrode.

  According to this display device, at least one of the electrode of the thin film transistor, the plurality of scanning wirings, the plurality of signal wirings, the pixel electrode, and the plurality of connection terminals is made of metal or metal oxide particles. Since the metal layer is selectively formed of a metal layer having a bonding layer formed by bonding, resource saving of the metal material can be achieved and the metal material can be manufactured at low cost.

  In practicing the present invention, a metal plating layer may be provided on the bonding layer. The metal plating layer may be a laminate of a plurality of plating layers. In that case, at least the surface of the metal plating layer may be a metal diffusion prevention film.

  According to the present invention, a method for forming a metal layer, a metal layer, and a display device using the metal layer can achieve not only resource saving of a metal material but also fine wiring, low resistance wiring, and long wiring. Is obtained.

  Hereinafter, a first embodiment according to the present invention will be described.

  First, the protective particles 1 in which the metal particles 2 are protected by the organic substance 3 and a dispersion liquid (hereinafter referred to as a particle dispersion liquid) 5 containing the protective particles 1 will be described.

  It is preferable to use nanoparticles having an average particle size of 1 nm to 100 nm as the metal particles 2 for realizing low-resistance wiring with long-distance fine wiring. More preferably, nanoparticles having an average particle size of 2 nm to 30 nm are preferably used. In the present embodiment, for example, the protective particles 1 in which the surroundings of the gold nanoparticles as the metal particles 2 are protected by 11-mercaptoundecanoic acid (hereinafter, MUA) as the organic substance 3 are used. Hereinafter, the protective particles 1 are referred to as MUA-protected gold nanoparticles 1.

  The MUA-protected gold nanoparticles 1 are synthesized as follows. The chloroaurate (III) ion is transferred from the aqueous layer to the toluene layer by tetra-n-octyl ammonium bromide (hereinafter, referred to as TOAB). After the transfer, in the presence of MUA, chloroaurate (III) ions are reduced with an aqueous sodium hydroxide borate solution for about 1.5 hours. Thereby, the MUA-protected gold nanoparticles 1 are synthesized.

  After that, the toluene layer is washed with water, concentrated, and then reprecipitated with chloroform to purify the MUA-protected gold nanoparticles 1. In the MUA-protected gold nanoparticles 1 thus synthesized and purified, the thiol (SH) group of the MUA is adsorbed on the gold particles, and the terminal group is a carboxyl group.

  Next, a method of forming the metal layer 20 in a selected region on the substrate 10 will be described with reference to FIGS.

  First, in order to selectively form the metal layer 20 on the substrate 10, a selected region on the substrate 10 is made hydrophobic and at least a region around the selected region on the substrate 10 is made hydrophilic. . In this embodiment, a selected region on the upper surface of the substrate 10 on which the predetermined metal layer 20 is formed is made hydrophobic, and a region other than the selected region on the upper surface is made hydrophilic.

  As the substrate 10, a substrate on which the metal layer 20 is formed has a hydrophilic property, for example, a glass substrate having a hydroxyl group exposed on the surface can be used. By forming a hydrophobic layer to be modified with, for example, an alkyl group on the substrate 10, for example, on the upper surface of the substrate 10, the upper surface of the substrate 10 on which the metal layer 20 is formed is once made hydrophobic over the entire area. .

  That is, as shown in FIG. 1A, this hydrophobic treatment is performed to form a hydrophobic film on the substrate 10 by silane coupling such as n-octadecyltrimethoxysilane (hereinafter referred to as ODS). The agent is provided by, for example, a chemical vapor method, a vapor adsorption method, or a coating method. Thus, a hydrophobic film 11 made of a silane coupling agent is formed on the substrate 10 as the hydrophobic layer 11. Hereinafter, the hydrophobic layer 11 is referred to as a hydrophobic film.

  Thereafter, the hydrophobic film 11 is selectively removed as follows. That is, as shown by an arrow X in FIG. 1B, the hydrophobic film is formed via the metal photomask 12 in which the opening 12a is formed corresponding to the region other than the selected region (the region where the metal layer 20 is formed). An area other than the selected area 11 is irradiated with ArF laser light having a wavelength for removing the hydrophobic film 11, for example, a wavelength of 193 nm. In the region irradiated with the ArF laser beam, the hydrophobic film 11 is removed by photolysis. Therefore, in a region other than the selected region, the surface of the substrate 10 having a hydroxyl group which is a hydrophilic group is exposed. Thereby, the selected area becomes hydrophobic by the hydrophobic film 11, and the area other than the selected area becomes hydrophilic.

  As the substrate 10, a substrate made of silicon oxide may be used. In this case, the selected region may be made hydrophobic and the region other than the selected region may be made hydrophilic as described below.

  The surface of the silicon oxide substrate on which the metal layer is to be formed is previously irradiated with ultraviolet rays to clean the surface. The surface of the substrate is modified with an alkyl group by a chemical vapor method. That is, the silicon oxide substrate is placed in a sealed container adjusted to a humidity of 10% together with a silane coupling agent such as ODS and heated in an electric furnace at 170 ° C. for about 1.5 hours, so that the silane coupling agent is placed on the substrate. Adsorb the ring agent. As a result, a hydrophobic film as a hydrophobic layer is formed. Note that the hydrophobic film may be formed by a vapor adsorption method or a coating method.

  It was confirmed that the substrate formed in this way had an increased contact angle compared to a silicon oxide substrate whose surface was cleaned by irradiating ultraviolet rays. From this, it is considered that the ODS having an alkyl group modifies the surface of the substrate by the chemical vapor method.

  Then, ultraviolet rays are irradiated to regions other than the selected region of the hydrophobic film through a metal photomask having openings formed corresponding to regions other than the selected region. The ODS molecules are decomposed and the hydrophobic film is removed at the ultraviolet irradiation location. As a result, the silicon oxide portion is exposed in a region other than the selected region of the substrate, so that the selected region becomes hydrophobic and the region other than the selected region becomes hydrophilic.

  In addition, as the silane coupling agent, besides n-octadecyltrimethoxysilane, a coupling agent such as hexamethyldisilazane, vinyltrichlorosilane, and vinyltrimethoxysilane can be used. Further, a fluorine silane coupling agent can also be used.

  When forming the hydrophobic layer with a silane coupling agent, from the viewpoint of removing the region other than the selected region by photolysis with a wavelength light in the vacuum ultraviolet region, a wavelength light in the ultraviolet region, or excimer laser light, The thickness of the hydrophobic film 11 is desirably about the size of a molecule, and more desirably a monomolecular film.

  Thereafter, as shown in FIG. 1C, a particle dispersion 5 in which the MUA-protected gold nanoparticles 1 are dispersed in an alkaline aqueous solution having a pH of 13 as a dispersion medium 4 is provided on the substrate 10 by a dispenser (not shown). Various methods can be used to provide the particle dispersion liquid 5 on the substrate 10, but from the viewpoint of material efficiency, disperser coating, inkjet coating, or local spraying on a hydrophobic region such as spraying can be used. It is preferable to use a method that allows coating.

  By applying an acidic solution, for example, hydrochloric acid having a pH of 1 to the particle dispersion 5 provided on the substrate 10, the protective particles 1 are placed in the selected region (hydrophobic region) as shown in FIG. ) To selectively aggregate. By removing the dispersion medium 4 in the particle dispersion liquid 5 with water or the like in a state where the protective particles 1 are aggregated, the protective particles 1 are fixed only to selected regions of the substrate 10.

  The reason why the protective particles 1 selectively aggregate only in the hydrophobic region is that the pH of the particle dispersion is biased toward the acidic side by hydrochloric acid and the surface of the protective particles 1 is protonated, so that the protective particles 1 It is considered that the dispersibility was reduced and the particles were aggregated. Further, since the hydrophobic property of the aggregate as a whole increases, it is considered that the aggregate is selectively aggregated only in the hydrophobic region.

  Further, a step of forming a bonding layer 21 formed by bonding the metal particles 2 is performed. In this step, the heat treatment is performed in a non-oxidizing atmosphere, for example, an inert gas made of nitrogen or a reducing gas containing hydrogen in order to suppress the oxidation of the metal particles 2 and promote the decomposition of the organic matter. Alternatively, it is desirable to use a step of decomposing organic matter by performing ultraviolet irradiation. Needless to say, heat treatment may be performed after ultraviolet irradiation is performed to accelerate the decomposition of the organic substance, or ultraviolet light irradiation may be performed during the heat treatment to accelerate the decomposition of the organic substance.

  The temperature at which the metal particles 2 are bonded to each other is preferably set to a temperature at which the protected organic substance (MUA) 3 and the hydrophobic film (silane coupling agent) 11 are decomposed, for example, a temperature of 180 ° C. or higher.

  Thus, as shown in FIG. 1E, a bonding layer 21 formed by bonding the metal particles 2 is formed. At the same time, the protected organic substance 3 is decomposed and vaporized and removed, and the hydrophobic film 11 remaining in the selected region is decomposed and vaporized and removed.

  By the way, 180 ° C. is a temperature lower than the melting point of gold constituting the metal particles 2. However, since the surface energy of the nano-sized metal particles 2 is increased, the metal particles 2 are not separated from each other even at a temperature lower than the melting point. Can be achieved. As a result, low-resistance wiring is possible even if wiring is performed over a long distance with fine wires.

  The thickness of the bonding layer 21 can be adjusted within a range of about 2 nm to about 100 nm by adjusting the concentration of the protective particles 1 in the particle dispersion 5.

  Although the metal layer 20 may be formed only of the bonding layer 21, the thickness of the metal layer 20 may be made larger than that of the bonding layer 21 as necessary. In this embodiment, as shown in FIG. 1 (f), the bonding layer 21 is used as a seed layer, and a metal plating for increasing the layer thickness of 400 nm is formed on the bonding layer 21 by electroless plating or electrolytic plating. The layers 22 are stacked to form the metal layer 20. The metal plating layer 22 can be suitably formed of, for example, an alloy such as silver, gold-silver, or gold-copper having a lower specific resistance than gold.

  The graph (a) in FIG. 2 shows that the chloroaurate (III) ion is transferred from the aqueous layer to the toluene layer by TOAB, and the chloroaurate (III) ion is transferred with an aqueous sodium hydroxide borate solution in the presence of MUA. 4 shows the results of FT-IR analysis after reduction.

Since a band (stretching bands) showing a stretching vibration of a double bond of carbon and hydrogen belonging to a carboxyl group is observed at a wave number (wave number) of around 1700 cm ⁻¹ , the surface of the carboxyl is reduced by sodium borohydride reduction. It was confirmed that MUA-protected gold nanoparticles 1 having a group were generated.

  The graph (b) in FIG. 2 shows the result of FT-IR analysis after dispersing the MUA-protected gold nanoparticles 1 in an alkaline aqueous solution of pH 13 in an alkaline aqueous solution as a dispersion medium.

From this analysis, the wave number is 1550 cm ^-1 and 1450 cm ^-1 attributable to a carboxylate anion near COO ^- antisymmetric stretching vibrations the band for the (asymmetric stretching band) and COO ^- band representing the symmetric stretching vibration of (symmetric stretching band) was confirmed respectively.

  The graph (c) in FIG. 2 shows an FT-IR analysis result after the MUA-protected gold nanoparticles 1 are dispersed and hydrochloric acid is dropped into an alkaline aqueous solution to aggregate the MUA-protected gold nanoparticles 1.

From this analysis result, a band showing a stretching vibration of a double bond of carbon and hydrogen belonging to a carboxyl group was confirmed at a wave number of about 1700 cm ⁻¹ , similarly to the result shown by the graph (a) in FIG. .

  The analysis results shown in graphs (b) and (c) in FIG. 2 indicate that the MUA-protected gold nanoparticles 1 have a carboxyl group at the terminal.

  As described above, according to this embodiment, the metal layer 20 having the bonding layer 21 formed by bonding the metal particles 2 can be selectively formed. Accordingly, the metal layer 20 can be formed while saving resources of the metal material. Moreover, by applying the metal layer 20 formed as described above to the wiring, fine wiring, low resistance wiring, and long wiring can be achieved.

  Also, the step of making the selected area on the substrate 10 hydrophobic includes the step of making the area other than the selected area hydrophilic, so that the area other than the selected area is provided with a bonding layer. The metal layer 20 having the bonding layer 21 can be selectively formed only in a selected region on the substrate 10 without forming the metal layer 20 having the bonding layer 21.

  In addition, since the step of bonding the metal particles 2 includes the step of removing the hydrophobic layer (hydrophobic film made of a silane coupling agent) 11 provided in the selected region, the substance forming the hydrophobic layer Can be suppressed from remaining in the bonding layer 21.

  Further, since the step of bonding the metal particles 2 includes the step of removing the organic substance 3 (MUA) protecting the metal particles 2, the organic substance 3 can be suppressed from remaining in the bonding layer.

  Since so-called nanoparticles having an average particle diameter of 1 nm to 100 nm are used as the metal particles 2, the metal particles 2 can be bonded at a temperature much lower than the melting point of the metal.

  Further, this embodiment includes a step of forming a metal plating layer 22 on the bonding layer 21 using the bonding layer 21 as a seed layer. Therefore, the specific resistivity of the metal layer 20 can be reduced by forming the metal plating layer 22 made of an alloy such as silver, gold-silver, or gold-copper having a lower specific resistance than gold.

  In addition, the length of the carbon chain from the thiol group to the polar functional group (the carboxyl group in the present embodiment) can be freely selected for the organic substance 3 that protects the metal particles 2. From the viewpoint of lowering the bonding temperature, a shorter carbon chain is preferred. Mercaptoacetic acid or mercaptoethanol having the shortest carbon chain may be used. By using the organic substance 3 having the shortest carbon chain, the bonding temperature can be set to about 150 ° C. Of course, from the viewpoint of lowering the bonding temperature, it is also effective to use organic matter decomposition by ultraviolet irradiation.

In this embodiment, gold is used as the metal particles 2. However, at least one of Au, Ag, Pd, Pt, Ni, Co, Cu, Sn, and Ru, and at least one of these metals. Particles composed of an alloy containing two metals or a metal oxide containing Cu ₂ O can also be used.

By the way, since nano-sized fine particles have a very active surface and are easily oxidized, when the protective particles are made using, for example, benzothiazole and polyethylene glycol, they are oxidized into fine particles of a metal oxide such as Cu ₂ O. Sometimes. In such a case, it is preferable to use protective particles of metal oxide particles. In this case, by performing a heat treatment in a reducing atmosphere containing hydrogen to reduce Cu ₂ O, a wiring metal layer made of Cu can be formed.

Further, in this embodiment, an ArF laser beam is used as a light source for making a region other than the selected region hydrophilic, but an excimer laser such as F ₂ , KrF, or XeCl may be used. Further, a light source that emits light having a wavelength in the ultraviolet region or a light source that emits light having a wavelength in the vacuum ultraviolet region may be used.

  In the case where the thickness of the metal layer 20 is larger than that of the bonding layer 21, in this embodiment, the metal plating layer 22 is formed by an electroless plating method or an electrolytic plating method using the bonding layer 21 as a seed layer. Although it is realized, the thickness of the metal layer 20 may be increased by repeating the steps of FIGS. 1A to 1E.

  Further, the substrate 10 can be formed using not only glass and silicon oxide but also an organic material capable of forming a hydrophilic surface by irradiating vacuum ultraviolet light or ultraviolet light, such as a polyimide resin or a fluorine resin. . By using the substrate 10 made of such an organic material, the process of forming the hydrophobic film 11 made of a silane coupling agent can be omitted. Alternatively, an opening corresponding to a desired wiring pattern may be formed by forming a hydrophilic insulating film or the like on a hydrophobic organic material.

  Hereinafter, a second embodiment according to the present invention will be described. In this embodiment, an example in which a metal layer is applied to a multilayer wiring will be described.

  First, a hydrophilic first metal layer 32 is formed in a predetermined pattern on a substrate 31, for example, a glass substrate. The first metal layer 32 can be formed, for example, by forming a layer made of aluminum with a thickness of 300 nm to 400 nm on the entire surface of the base 31 and patterning the layer.

  Note that the first metal layer 32 can be formed in the same manner as in the first embodiment. That is, a first metal layer 32 having a total thickness of 300 nm to 400 nm is formed by forming a bonding layer made of gold in a predetermined region on the base 31 and forming a copper metal plating layer thereon. May be.

  Next, an interlayer insulating film 33 made of, for example, hydrophilic silicon oxide is formed on the base 31. This interlayer insulating film 33 is provided so as to cover the first metal layer 32 formed on the base 31. Then, a contact hole 34 for forming an electrical contact between a second metal layer 40 and a first metal layer 32 described later is formed in the interlayer insulating film 33.

  That is, in this embodiment, the substrate 30 has the base 31, the hydrophilic first metal layer 32, the hydrophilic interlayer insulating film 33, and the contact hole.

  Thereafter, the steps of FIGS. 3A to 3F, which are the same steps as those of FIGS. 1A to 1F, are performed. That is, the hydrophobic film 11 is formed around the contact hole 34 that exposes the first metal layer 32 to form a hydrophobic region. Then, a particle dispersion liquid 5 is provided in the hydrophobic region, and the protective particles 1 are fixed by applying an acidic solution, and the dispersion medium 4 is removed by evaporation. Further, a heat treatment is performed to vaporize and remove the organic substance 3 and the hydrophobic film 11 that bind the metal particles 2 and protect the metal particles 2. Thus, a coupling layer 41 that is electrically connected to the first metal layer 32 via the contact hole 34 is formed. In order to improve the contact between the first metal layer 32 and the bonding layer 41, the heat treatment is preferably performed in a nitrogen atmosphere to which about 5% of hydrogen is added. Further, the thickness of the bonding layer 41 is increased by the metal plating layer 42. Thus, a second metal layer 40 having the bonding layer 41 and the metal plating layer 42 is formed.

  As described above, according to this embodiment, the metal layer 40 can be applied to a multilayer wiring.

  The metal layer of the present invention described in the above embodiment includes, for example, a part of a thin film transistor included in a display device, a plurality of scanning wirings, a plurality of signal wirings, a plurality of scanning wiring terminals, a plurality of signal wiring terminals, and a plurality of pixels. It can be applied as an electrode.

  4 and 5 show a display device, for example, an active matrix type liquid crystal display device. 4 and 5, the auxiliary capacitance is omitted.

  As shown in FIGS. 4 and 5, the liquid crystal display device 50 includes a pair of front and rear transparent substrates 51 and 52, a liquid crystal layer 53, a pixel electrode 54, a thin film transistor (hereinafter referred to as TFT) 55, a scanning wiring 56, a signal wiring 57, A scanning wiring terminal 58 as a connection terminal, a signal wiring terminal 59 as a connection terminal, a counter electrode 60 and the like are provided.

  As the pair of transparent substrates 51 and 52, for example, a pair of glass substrates can be used. Hereinafter, the transparent substrates 51 and 52 are referred to as glass substrates. These glass substrates 51 and 52 are joined via a frame-shaped sealing material (not shown). The liquid crystal layer 53 is provided in a region surrounded by a sealing material between the pair of glass substrates 51 and 52.

  As shown in FIG. 5, on one of the pair of glass substrates 51 and 52, for example, on the inner surface of the rear glass substrate (array substrate) 51, a matrix is provided in a row direction and a column direction. A plurality of transparent pixel electrodes 54, a plurality of TFTs 55 electrically connected to the plurality of pixel electrodes 54, scanning wirings 56 and signal wirings 57 electrically connected to the plurality of TFTs 55, and a glass substrate (substrate). ) 51 are provided with a plurality of scanning wiring terminals 58 and a plurality of signal wiring terminals 59 respectively formed on one end edge and one side edge.

  The scanning lines 56 are provided along the rows of the pixel electrodes 54, respectively. One end of each of the scanning wirings 56 is connected to a plurality of scanning wiring terminals 58 provided on one side edge of a rear glass substrate (rear base) 51. The plurality of scanning wiring terminals 58 are each connected to a scanning circuit (not shown).

  On the other hand, the signal lines 57 are provided along the columns of the pixel electrodes 54, respectively. One end of each of the signal wirings 57 is connected to a plurality of signal wiring terminals 59 provided on one edge of a rear glass substrate (rear base) 51. The plurality of signal wiring terminals 59 are each connected to a sample and hold circuit (not shown).

  On the inner surface of the front glass substrate (opposite substrate) 52 which is the other glass substrate, a single film-shaped transparent opposing electrode 60 facing the plurality of pixel electrodes 54 is provided. In addition, a color filter is provided on the inner surface of the front glass substrate 52 so as to correspond to a plurality of pixel portions in which the plurality of pixel electrodes 54 and the counter electrode 60 face each other, and to correspond to a region between the pixel portions. A light shielding film may be provided.

  A polarizing plate (not shown) is provided outside the pair of glass substrates 51 and 52. In the transmissive liquid crystal display device 50, a surface light source (not shown) is provided behind the rear glass substrate 51. The liquid crystal display device 50 may be of a reflective type or a transflective type.

  FIG. 5 shows, for example, a bottom gate type TFT 55. The TFT 55 is not limited to the bottom gate type, but may be a top gate type, for example.

  As shown in FIG. 5, in the TFT 55 included in the display device 50 of the present embodiment, the metal layer described in the first embodiment is applied to the gate electrode 62.

  As shown in the figure, the TFT 55 has a gate electrode 62 on a glass substrate 51 having a base insulating film 61 made of a silicon nitride film. That is, in this embodiment, the glass substrate (base) 51 having the base insulating film 61 made of the silicon nitride film corresponds to the substrates 10 and 30 in the first and second embodiments. As described in the first embodiment, after forming the bonding layer 62a serving as a seed, the gate electrode 62 is formed by forming a metal plating layer 62b by electroless plating to increase the thickness.

On this gate electrode 62, a gate insulating film 63 is formed. An amorphous silicon film (a-Si film) 64 of a channel portion is formed on the gate insulating film 63 above the gate electrode 62, and a contact is formed on the a-Si film 64. An n ⁺ type a-Si film 65 is formed as a layer. The a-Si film 64 and the n ⁺ -type a-Si film 65 form a semiconductor film. Further, a source electrode 66 and a drain electrode 67 made of Al are formed so as to cover the a-Si film 64 and the n ⁺ -type a-Si film 65. Then, a pixel electrode 54 made of ITO is formed on the gate insulating film 63, and the pixel electrode 54 is connected to a drain electrode 67. Further, an insulating protective film 68 made of silicon nitride is provided so as to cover the source electrode 66 and the drain electrode 67.

  The scanning wiring 56 is formed integrally with the gate electrode 62 of the corresponding TFT 55. The signal wiring 57 is electrically connected to the source electrode 66 of the corresponding TFT 55.

  When the metal layer serving as the gate electrode 62 is formed of a metal layer containing copper (Cu), for example, as shown in FIG. 6, a barrier such as Co-WB is used to prevent impurity diffusion of copper. It is desirable that the metal (metal diffusion preventing film) 62c be selectively plated only on the surface of the metal layer by an electroless plating method using dimethylamine borane as a reducing agent. Note that the base insulating film 61 made of silicon nitride is also effective for preventing diffusion of copper impurities.

  As described above, according to the liquid crystal display device 50, as described above, the gate electrode 62 and the scanning wiring 56 formed integrally with the gate electrode 62 are selectively provided on the inner surface of the glass substrate 51. Can be. Therefore, a liquid crystal display device can be manufactured at low cost.

  In the above embodiment, the method of forming the metal layer of the present invention and the case where the metal layer is applied to the gate electrode 62 and the scanning wiring 56 are described. Further, in the case of a reflective liquid crystal, a reflective electrode is required instead of a transparent electrode such as ITO, so that it may be used for the pixel electrode 54. Further, the auxiliary capacitance line may be used for the auxiliary capacitance line because it is formed simultaneously with the scanning line 56.

  In the above embodiment, an example of application to the TFT 55 using an a-Si film has been described. However, it is needless to say that the embodiment may be applied to a TFT using a polycrystalline silicon film (p-Si film). Further, the present invention can be applied to not only the above-described pixel TFT 55 but also a TFT for a driving circuit and a power supply wiring for a driving circuit for minimizing a potential drop.

  In the first and second embodiments, the hydrophilic region is formed by photolyzing the silane coupling agent. However, the hydrophobic terminal group is modified into a hydrophilic group by irradiation with ultraviolet light. A suitable coupling agent may be used. In this case, the terminal group may be made hydrophilic by generating a polar group such as a hydroxyl group, a carboxyl group, an amino group, or an aminocarbonyl group.

  In the first and second embodiments, the hydrophobic film 11 is formed on the substrates 10 and 30, and the hydrophobic film 11 in a region other than the hydrophobic region is excluded to realize the selective formation of the hydrophobic region. However, the method for selectively forming the hydrophobic region is not limited to this.

  Hereinafter, a third embodiment according to the present invention will be described with reference to FIGS. In this embodiment, instead of forming a film 11 of a silane coupling agent on a substrate 10 as shown in FIGS. 7A and 7B, the surface becomes hydrophobic as means for forming a hydrophobic region. An organic resin layer 13 is formed. The organic resin layer 13 can be formed of, for example, a polyimide layer or the like. Further, as a means for forming a hydrophilic region, a hydrophilic inorganic insulating film 14 is formed on the organic resin layer 13 instead of selectively removing the film 11. The inorganic insulating film 14 can be formed by, for example, a silicon nitride film or the like. Then, a hole 14a is formed so that the organic resin layer 13 is exposed in a selected region by using a normal thin film manufacturing process (for example, a photoetching process).

  FIGS. 7C to 7F show a step of providing the particle dispersion 5 on the substrate 10, a step of aggregating the protective particles 1 and a step of removing the dispersion medium 4, a step of bonding the metal particles 2 to each other, and an electroless plating. The step of increasing the thickness of the metal layer 20 is shown. These steps are performed in the same manner as in the first and second embodiments.

  That is, in this embodiment, the metal layer 20 is formed in the hole 14a of the inorganic insulating film 14. Therefore, as shown in FIG. 7F, there is an advantage that the pattern width in the electroless plating step (the pattern width of the metal plating layer 22) can be defined by the holes 14a. Needless to say, this embodiment may be applied to a multilayer wiring.

Alternatively, for example, by forming an inorganic layer or an organic layer capable of forming a hydrophilic surface by irradiating vacuum ultraviolet light or ultraviolet light on the substrates 10 and 30, selective hydrophobicity can be obtained. The formation of the region may be realized. As the inorganic layer as described above, for example, a metal oxide layer which is made hydrophilic by irradiation with light such as titanium oxide (TiO ₂ ) can be used. Examples of the organic layer as described above include a polyimide resin and a fluororesin.

  Alternatively, hydrophilic regions (regions around at least the selected region on the substrate) may be formed on the substrates 10 and 30 by another surface treatment method such as corona discharge.

FIG. 4 is a cross-sectional view illustrating a step for forming a metal layer according to the first embodiment of the present invention. FT-IR analysis results of MUA-protected gold nanoparticles, MUA-protected gold nanoparticle-dispersed alkaline aqueous solution, and MUA-protected gold nanoparticles dispersed and aggregated by adding hydrochloric acid to the MUA-protected gold nanoparticle-dispersed alkaline aqueous solution forming the metal layer FIG. FIG. 9 is a cross-sectional view illustrating a step for forming a metal layer according to the second embodiment of the present invention. FIG. 3 is a plan view showing a part of the liquid crystal display device. FIG. 2 is a cross-sectional view showing the vicinity of a thin film transistor of the liquid crystal display device. FIG. 6 is a cross-sectional view illustrating another embodiment of the thin film transistor of FIG. 5. FIG. 11 is a sectional view illustrating a step for forming a metal layer according to a third embodiment of the present invention.

Explanation of reference numerals

  DESCRIPTION OF SYMBOLS 1 ... MUA protection gold nanoparticle (protection particle), 2 ... metal particle, 3 ... organic substance, 4 ... dispersion medium, 5 ... particle dispersion liquid (dispersion liquid), 10, 30 ... substrate, 11 ... film (hydrophobic layer) ), 12: metal photomask (mask), 20, 40: metal layer, 21, 41: bonding layer, 22, 42: metal plating layer, 50: liquid crystal display device (display device), 51, 52: glass substrate ( 54) Pixel electrode, 55 ... Thin film transistor, 56 ... Scan wiring, 57 ... Signal wiring, 58 ... Scan wiring terminal (connection terminal), 59 ... Signal wiring terminal (connection terminal), 62a ... Coupling layer, 62b ... Metal Plating layer 62c ... Barrier metal (metal diffusion prevention film)

Claims (17)

Providing a substrate having at least a selected region having hydrophobicity,
Attaching a dispersion containing particles of a metal or metal oxide protected by an organic substance to at least a hydrophobic region on the substrate;
Bonding the metal or metal oxide particles. A method for forming a metal layer on a selected region on the substrate. A method of forming a metal layer on a selected area on a substrate, comprising:
Making selected areas on the substrate hydrophobic,
Attaching a dispersion containing particles of a metal or metal oxide protected by an organic substance to at least a hydrophobic region on the substrate;
Bonding the metal or metal oxide particles.   The metal layer according to claim 2, wherein the step of making the selected area on the substrate hydrophobic is a step of making at least a region around the selected area on the substrate hydrophilic. Formation method.   Using a substrate having at least a hydrophilic surface as the substrate, and making a selected region on the substrate hydrophobic and making at least a region around the selected region on the substrate hydrophilic Forming a hydrophobic layer on the substrate having at least a hydrophilic surface, and removing the hydrophobic layer formed in at least a region around the selected region from the substrate. The method for forming a metal layer according to claim 3, wherein:   The step of removing the hydrophobic layer formed in at least a region around the selected region from the substrate includes excimer laser light, wavelength light in a vacuum ultraviolet region, or ultraviolet light through a mask having a predetermined pattern. 5. The method according to claim 4, wherein the step of irradiating at least a region around the selected region with wavelength light of the region to decompose the hydrophobic layer.   The metal layer according to claim 4 or 5, wherein the step of bonding the metal or metal oxide particles is a step of removing the hydrophobic layer formed in the selected region. Forming method.   The step of adhering the dispersion to at least a hydrophobic region on the substrate includes aggregating the metal or metal oxide particles protected by the organic substance in the hydrophobic region, and dispersing the dispersion medium in the dispersion. The method for forming a metal layer according to any one of claims 1 to 6, wherein the method is a step of removing a metal layer.   The method according to claim 1, wherein the step of bonding the metal or metal oxide particles is a step of removing the organic substance protecting the metal or metal oxide particles. 2. The method for forming a metal layer according to claim 1.   The formation of a metal layer according to any one of claims 1 to 8, wherein the step of bonding the metal or metal oxide particles is performed in an atmosphere of an inert gas or a reducing gas. Method.   9. The method according to claim 1, further comprising a step of forming a metal plating layer on the bonding layer formed by bonding metal or metal oxide particles by electroless plating or electrolytic plating. 10. The method for forming a metal layer according to any one of claims 9 and 9.   The method according to any one of claims 1, 6, 7, 8, 9, and 10, wherein the particles are particles having an average particle diameter of 1 nm to 100 nm. The particles are at least one metal of Au, Ag, Pd, Pt, Ni, Co, Cu, Sn, and Ru, an alloy containing at least one of these metals, or a metal containing Cu ₂ O. The method for forming a metal layer according to any one of claims 1, 6, 7, 8, 9, and 10, comprising an oxide.   A metal layer having a bonding layer formed by bonding particles of a metal or a metal oxide, wherein the bonding layer is provided in a selected region on a substrate.   The metal layer according to claim 13, wherein a metal plating layer is provided on the bonding layer. A display device comprising: a plurality of thin film transistors provided in a matrix, a plurality of scanning wirings and a plurality of signal wirings for driving the thin film transistors, a plurality of pixel electrodes, and a plurality of connection terminals,
At least one of the electrode of the thin film transistor, the plurality of scanning wirings, the plurality of signal wirings, the pixel electrode, and the plurality of connection terminals is formed of a metal layer having a bonding layer of metal or metal oxide particles. A display device characterized by being performed.   The display device according to claim 15, wherein a metal plating layer is provided on the bonding layer.   17. The display device according to claim 16, wherein at least a surface of the metal plating layer is formed of a metal diffusion preventing film.

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