JP2008010456A - Metal wiring forming method and firing furnace - Google Patents

Abstract

To provide a metal wiring forming method and a firing furnace for improving the flatness of a conductive layer.
A second droplet discharge step of applying a wiring forming ink X2 in which metal fine particles are dispersed on a manganese layer 25 formed on a substrate S; and heating the wiring forming ink X2 to form the metal. A second firing step of growing fine particles to form a silver layer 26, and in the second firing step, at least wiring forming ink X2 is applied to the substrate S with a space above and below the substrate S. The substrate S is heated up to the firing temperature in a state in which a pair of metal plates 18 that uniformly irradiate infrared rays to the region is disposed.
[Selection] Figure 5

Description

  The present invention relates to a metal wiring forming method and a firing furnace.

  With the spread of portable devices such as notebook personal computers and mobile phones, thin and light liquid crystal display devices are widely used. Such a liquid crystal display device has a structure in which a liquid crystal layer is sandwiched between a pair of substrates.

  As shown in FIG. 12, an active matrix substrate 150, which is one of the pair of substrates, includes a glass substrate 151, data lines 152 and scanning lines 153 formed on the glass substrate 151 so as to cross each other, Similarly, a drain electrode 154 formed on the glass substrate 151, a pixel electrode (ITO) 155 connected to the drain electrode 154, an insulating layer 156 formed between the data line 152 and the scanning line 153, and a thin film semiconductor A TFT (Thin Film Transistor) element 157.

  The data line 152, the scanning line 153, and the drain electrode 154 are formed by, for example, repeating a process combining a dry process and photolithography etching a plurality of times (see, for example, Patent Document 1). However, in such a forming method, since the dry process and the photolithographic etching are repeated a plurality of times, there are problems that the costs such as the material cost and the management cost become high and the yield is difficult to increase.

  By the way, in recent years, as a coating technique used in the manufacturing process of an electronic device, the use of a droplet discharge method tends to expand. In the coating technique using this droplet discharge method, generally, a functional liquid is discharged as a droplet from a plurality of nozzles provided in the droplet discharge head while relatively moving the substrate and the droplet discharge head. The coating film is formed by repeatedly adhering to the substrate, and there is an advantage that it is possible to directly apply a pattern of an arbitrary shape without using a means such as photolithography. is doing.

For example, a metal wiring that forms a fine metal wiring such as a semiconductor integrated circuit by applying (arranging) the material to the pattern forming surface by discharging a functional liquid containing a pattern forming material onto a substrate from a droplet discharge head A forming method has been proposed (see, for example, Patent Documents 2 and 3).
Japanese Patent No. 3261699 Japanese Patent Laid-Open No. 11-274671 JP 2000-216330 A

  However, the following problems remain in the conventional metal wiring forming method. That is, for example, when a functional liquid containing silver fine particles is applied to a glass substrate by a droplet discharge method to form a silver conductive layer, since the functional liquid has fluidity, In order to further stabilize the characteristics, it is desired to form the conductive layer more uniformly.

  The present invention has been made in view of the above-described conventional problems, and an object thereof is to provide a metal wiring forming method and a firing furnace that improve the flatness of a conductive layer.

  The present invention employs the following configuration in order to solve the above problems. That is, the metal wiring forming method according to the present invention includes a coating step of applying a functional liquid in which metal fine particles are dispersed on an underlayer formed on a substrate, and heating the functional liquid to granulate the metal fine particles. A metal wiring forming method including a firing step of growing and forming a conductive layer, wherein at least a region of the substrate to which the functional liquid is applied is uniformly irradiated with infrared rays in the firing step. The substrate is heated to a firing temperature in a state where covering members are arranged above and below the substrate with a space therebetween.

  The firing furnace of the present invention is a firing furnace for heating a substrate coated with a functional liquid in which metal fine particles are dispersed on the surface, and is disposed at intervals above and below the substrate. It is characterized by comprising a pair of covering members that uniformly irradiate infrared rays to the area where the functional liquid is applied.

  In this invention, in the baking process for forming the conductive layer, the region where the functional liquid is applied can be uniformly heated by uniformly irradiating at least the region where the functional liquid is applied to the substrate. . Therefore, the layer thickness of the conductive layer obtained by growing the metal fine particles can be made more uniform.

  That is, when the functional liquid is irradiated with infrared rays, a dispersion medium for dispersing metal fine particles in the functional liquid evaporates. Here, if the temperature distribution is uneven in the area where the functional liquid is applied, the functional liquid has fluidity, so that the functional liquid flows from the high temperature area toward the low temperature area. To flow. For this reason, the uniformity of the thickness of the conductive layer formed by evaporating the dispersion medium and growing the metal fine particles is reduced. Therefore, by arranging a pair of covering members on the upper and lower sides of the substrate, infrared rays are uniformly irradiated toward at least the region of the substrate to which the functional liquid has been applied, and unevenness occurs in the temperature distribution in this region. Can be suppressed. Thereby, the dispersion medium etc. in a functional liquid can evaporate uniformly, and the thickness of a conductive layer can be made more uniform.

  In the present invention, the fact that the temperature distribution is not uneven includes not only the case where there is no temperature difference in each part of the region where the functional liquid is applied, but also the case where the temperature difference between each part is as small as about 10%. .

  In the metal wiring forming method of the present invention, the metal fine particles may be Au, Ag, Cu, Ni, ITO, Pd, Bi, or Mn, or a mixture thereof.

  In this invention, the fine metal particles are Au (gold), Ag (silver), Cu (copper), Ni (nickel), ITO (Indium Tin Oxide), Pd (palladium), Bi (bismuth) or Mn ( By constituting with any of manganese) or a mixture thereof, a good anchor effect with the underlayer can be obtained.

  Moreover, the metal wiring formation method of this invention is good also as the said base layer being comprised by the oxide in any one of Mn, Ti, Cu, Ni, In, or Cr.

  In the present invention, the base layer is made of an oxide of any of Mn, Ti (titanium), Cu, Ni, In (indium), or Cr (chromium), thereby providing good adhesion between the substrate and the conductive layer. Sex can be obtained.

  In the metal wiring forming method of the present invention, the functional liquid is preferably applied using a droplet discharge method.

  In this invention, since the functional liquid is selectively formed by the droplet discharge method, the waste of the functional liquid can be suppressed and the cost can be reduced.

  Hereinafter, an embodiment of a metal wiring forming method and a firing furnace according to the present invention will be described with reference to the drawings.

  In each drawing used for the following description, the scale of each member is appropriately changed in order to make each member a recognizable size.

In the present embodiment, a wiring forming ink (functional liquid) containing conductive fine particles is discharged in droplets from a discharge nozzle of a droplet discharge head using a droplet discharge method, and formed on a substrate according to a metal wiring. An example in which a metal wiring composed of a plurality of conductive films is formed between the formed banks will be described.
[Ink for wiring formation]
This wiring forming ink is composed of a dispersion liquid in which conductive fine particles are dispersed in a dispersion medium, or a dispersion liquid in which organic silver compounds or silver oxide nanoparticles are dispersed in a dispersion medium.

  Examples of the conductive fine particles include metal fine particles, oxides thereof, conductive polymers, and superconductor fine particles. The surface of these conductive fine particles may be coated with a dispersion stabilizer composed of an organic substance or the like in order to improve the dispersibility in the dispersion.

  The particle diameter of the conductive fine particles is preferably 1 nm or more and 0.1 μm or less. If it is larger than 0.1 μm, there is a risk of clogging in the discharge nozzle of the droplet discharge head 1 described later. On the other hand, if it is smaller than 1 nm, the volume ratio of the dispersion stabilizer described later with respect to the conductive fine particles becomes large, and the ratio of organic substances in the resulting film becomes excessive.

  The dispersion medium is not particularly limited as long as it can disperse the conductive fine particles and does not cause aggregation. For example, in addition to water, alcohols such as methanol, ethanol, propanol, butanol, n-heptane, n-octane, decane, dodecane, tetradecane, toluene, xylene, cymene, durene, indene, dipentene, tetrahydronaphthalene, decahydro Hydrocarbon compounds such as naphthalene and cyclohexylbenzene, or ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, 1,2-dimethoxyethane, bis (2- Methoxyethyl) ether, ether compounds such as p-dioxane, propylene carbonate, γ Butyrolactone, N- methyl-2-pyrrolidone, dimethylformamide, dimethyl sulfoxide, polar compounds such as cyclohexanone. Of these, water, alcohols, hydrocarbon compounds, and ether compounds are preferable and more preferable dispersion media in terms of fine particle dispersibility, dispersion stability, and ease of application to the droplet discharge method. Examples thereof include water and hydrocarbon compounds.

  Further, in order to prevent the conductive fine particles from coming into contact and causing aggregation, the surface of the conductive fine particles may be coated with a dispersion stabilizer. As the dispersion stabilizer, for example, an amine compound such as an alkylamine is used. This dispersion stabilizer must be capable of evaporating together with the dispersion solution after leaving the surface of the conductive fine particles, and at least within a range where the boiling point does not exceed 300 ° C. What is in the range of 250 ° C. or lower is preferable. For example, as the alkylamine, those having an alkyl group selected in the range of C8 to C18 and having an amino group at the end of the alkyl chain are used. For example, the alkylamine in the range of C8 to C18 has thermal stability, and the vapor pressure near room temperature is not so high, and the content rate is maintained in a desired range when stored at room temperature or the like. It is preferably used in terms of handling properties, such as being easy to control.

  And it is preferable that the surface tension of a functional liquid exists in the range of 0.02 N / m or more and 0.07 N / m or less, for example. When the liquid is ejected by the droplet ejection method, if the surface tension is less than 0.02 N / m, the wetting of the ink composition with respect to the nozzle surface increases, and thus flight bending tends to occur, resulting in 0.07 N / m. If it exceeds the upper limit, the shape of the meniscus at the nozzle tip is unstable, and it becomes difficult to control the discharge amount and the discharge timing. In order to adjust the surface tension, a small amount of a surface tension regulator such as a fluorine-based, silicone-based, or nonionic-based material may be added to the dispersion within a range that does not significantly reduce the contact angle with the substrate. Nonionic surface tension modifiers improve the wettability of the liquid to the substrate, improve the leveling properties of the film, and help prevent the occurrence of fine irregularities in the film. The surface tension adjusting agent may contain an organic compound such as alcohol, ether, ester, or ketone, if necessary.

  Moreover, it is preferable that the viscosity of a functional liquid is 1 mPa * s or more and 50 mPa * s or less, for example. When the liquid material is ejected as droplets using the droplet ejection method, if the viscosity is less than 1 mPa · s, the nozzle periphery is easily contaminated by the outflow of ink, and if the viscosity is greater than 50 mPa · s, The frequency of clogging in the nozzle holes increases, and it becomes difficult to smoothly discharge droplets.

Various substrates such as glass, quartz glass, Si wafer, plastic film, and metal plate can be used as the substrate on which the metal wiring is formed. In addition, a substrate in which a semiconductor film, a metal film, a dielectric film, an organic film or the like is formed as a base layer on the surface of these various substrates is also included.
[Droplet discharge device]
Next, a droplet discharge device (inkjet device) used for forming metal wiring will be described with reference to FIG. Here, FIG. 1 is a schematic perspective view of the droplet discharge device.

  As shown in FIG. 1, the droplet discharge device IJ discharges (drops) droplets from a droplet discharge head onto a substrate S. The droplet discharge head 1 and first and second drives The motors 2 and 3, the drive shaft 4, the guide shaft 5, the stage 6, the cleaning mechanism 7, the base 8, the heater 9, and an external controller CONT for controlling them are provided. Here, let the X direction shown in FIG. 1 be the scanning direction and the Y direction be the non-scanning direction.

  The droplet discharge head 1 is a multi-nozzle type droplet discharge head including a plurality of discharge nozzles, and the longitudinal direction is made to coincide with the Y-axis direction. The droplet discharge head 1 is configured to discharge the functional liquid from the discharge nozzle to the substrate S supported and fixed to the stage 6. The plurality of ejection nozzles are provided on the lower surface of the droplet ejection head 1 side by side in the Y-axis direction, which is the non-scanning direction, at regular intervals.

  The first drive motor 2 is constituted by a stepping motor, for example, and is connected to the drive shaft 4. Then, the first drive motor 2 rotates the drive shaft 4 by the drive signal in the X-axis direction supplied from the external controller CONT, and moves the droplet discharge head 1 in the X-axis direction.

  Similar to the first drive motor 2, the second drive motor 3 is configured by a stepping motor, for example, and is connected to the guide shaft 5. Then, the second drive motor 3 rotates the guide shaft 5 by the drive signal in the X-axis direction supplied from the external controller CONT, and moves the stage 6 in the X-axis direction. The guide shaft 5 is fixed with respect to the base 8.

  The stage 6 includes a fixing mechanism (not shown) that supports the substrate S on which the functional liquid is discharged from the droplet discharge head 1 and fixes the substrate S at a reference position.

  The cleaning mechanism 7 cleans the droplet discharge head 1 and moves in the Y-axis direction along the guide shaft 5 by driving a drive motor (not shown).

  The heater 9 heats the substrate S by lamp annealing, for example, and performs evaporation and drying of the dispersion medium contained in the functional liquid applied to the substrate S.

  The external controller CONT supplies drive signals to the first and second drive motors 2 and 3, and supplies a voltage for controlling droplet ejection by the droplet ejection head 1.

  Accordingly, the droplet discharge device IJ discharges droplets onto the substrate S while relatively scanning the droplet discharge head 1 and the stage 6 that supports the substrate S.

Here, examples of the discharge technique of the droplet discharge method include a charge control method, a pressure vibration method, an electromechanical conversion method, an electrothermal conversion method, and an electrostatic suction method. In the charge control method, a charge is applied to a material by a charging electrode, and the flight direction of the material is controlled by a deflection electrode and discharged from a nozzle. In addition, the pressure vibration method is a method in which an ultra-high pressure of, for example, about 30 kg / cm ² is applied to the material and the material is discharged to the nozzle tip side. When discharged and applied with a control voltage, electrostatic repulsion occurs between the materials, and the materials are scattered, so that they are not discharged from the nozzle. The electromechanical conversion method utilizes the property that a piezoelectric element (piezoelectric element) deforms in response to a pulse-like electric signal. The piezoelectric element is deformed through a flexible substance in a space where material is stored. Pressure is applied, and the material is extruded from this space and discharged from the nozzle. Furthermore, in the electrothermal conversion method, a material is rapidly vaporized by a heater provided in a space in which the material is stored to generate bubbles, and the material in the space is discharged by the pressure of the bubbles. The electrostatic attraction method is a method in which a minute pressure is applied to the space in which the material is stored, a meniscus of the material is formed on the nozzle, and the material is drawn out after applying an electrostatic attractive force in this state. In addition, various techniques such as a method using a change in the viscosity of a fluid due to an electric field, a method using a discharge spark, and the like can be applied. This droplet discharge method has an advantage that the use of the material is less wasteful and a desired amount of the material can be accurately disposed at a desired position. Note that the amount of one droplet of the functional liquid ejected by the droplet ejection method is, for example, 1 ng or more and 300 ng or less.
[Baking furnace]
Next, the firing furnace according to the present invention will be described with reference to the drawings. Here, FIG. 2 is a schematic diagram of a firing furnace in the present embodiment.

  As shown in FIG. 2, the atmosphere firing furnace (firing furnace) 15 in the present embodiment includes a box-shaped casing 16 having a front opening and a door (not shown) covering the opening. A support portion 17 that is provided on the inner wall of the body 16 and that supports a substrate S coated with a wiring forming ink (functional liquid) X2 to be described later so as to be horizontal, and is parallel to the substrate S supported by the support portion 17. And a plate-like metal plate (covering member) 18 arranged so as to be.

  The housing 16 can accommodate a plurality of substrates S therein so as to be horizontal.

  The support portion 17 is configured to support the back surface of the substrate S by point contact. Accordingly, the substrate S is supported in the housing 16 by the plurality of support portions 17.

  A plurality of metal plates 18 are provided in the housing 16, and are disposed so as to be horizontal with the substrate S between the substrates S disposed in the housing 16. Here, the metal plate 18 has a shape that covers the substrate S in a plan view while being accommodated together with the substrate S in the housing 16. Therefore, the metal plate 18 has a shape that covers at least a region of the substrate S to which a wiring forming ink X2 described later is applied.

  Here, the distance between the metal plate 18 and the surface of the adjacent substrate S is, for example, 1 cm. Note that a pair of covering members is configured by the metal plate 18 adjacent on the upper surface side of the substrate S and the metal plate 18 adjacent on the lower surface side of the substrate S. Note that, in the substrate S arranged at the uppermost stage among the plurality of substrates S accommodated, a pair of covering members are constituted by the upper inner wall of the housing 16 and the metal plate 18 adjacent on the lower surface side of the substrate S. Similarly, in the substrate S arranged at the lowermost stage, a pair of covering members are constituted by the metal plate 18 adjacent on the upper surface side of the substrate S and the lower inner wall of the housing 16.

  Further, there is a gap between the substrate S supported by the support portion 17 and the metal plate 18 adjacent on the upper surface side of the substrate S, and no other member is provided.

In addition, although a pair of coating | coated member is comprised with the metal plate 18, what is necessary is just to be able to irradiate infrared rays uniformly with respect to the area | region to which the wiring formation ink X2 was apply | coated at least among the board | substrates S. It may be a plate made of ceramics or another member.
[Metal wiring formation method]
Next, a metal wiring forming method according to the present invention will be described with reference to the drawings. Here, FIG. 3 to FIG. 5 are cross-sectional views showing the forming process of the metal wiring forming method in the present embodiment.

The metal wiring forming method in the present embodiment includes an HMDS (hexamethyldisilazane) film forming process, a bank forming process, an HMDS film patterning process, a residue processing process (lyophilic process), a lyophobic process, and a first droplet. It comprises a discharge process (application process), a drying process, a first baking process, a second droplet discharge process (application process), and a second baking process.
(HMDS film formation process)
First, the HMDS film 21 is formed on the substrate S as shown in FIG. The HMDS film 21 improves the adhesion between the substrate S and a bank 23 described later. Here, for example, the HMDS film 21 is formed by depositing HMDS in a vapor state on the substrate S (HMDS treatment).
(Bank formation process)
Next, the bank 23 (see FIG. 3C) is formed on the substrate S. The bank 23 functions as a partition member. Here, the bank 23 is formed using a lithography method. First, as shown in FIG. 3B, the organic photosensitive material 22 is applied on the substrate S according to the height of the bank by a method such as spin coating, spray coating, roll coating, die coating, dip coating, or the like. A resist layer (not shown) is applied thereon. Then, a mask is applied in accordance with the bank shape (metal wiring formation region), and the resist layer is exposed and developed to leave a resist layer substantially in a rectangular shape. Thereafter, etching is performed to remove the bank material other than the mask. As a result, as shown in FIG. 3C, the bank 23 and the inter-bank 24 are formed so as to surround the periphery of the region (for example, 10 μm wide) where the metal wiring is to be formed.

Here, the bank (convex portion) may be formed of two or more layers made of a material that is organic and exhibits liquid repellency. The formation of the bank 23 is not limited to the lithography method, and can be performed by other methods such as a printing method.
(HMDS film patterning process)
Subsequently, the HMDS film 21 is removed using the bank 23 as a mask. Here, as shown in FIG. 3D, the bank 23 is used as a mask for the substrate S on which the bank 23 is formed, and etching is performed using, for example, a 2.5% hydrofluoric acid aqueous solution. The HMDS film 21 between the uncoated banks 24 is removed. As a result, the substrate S is exposed at the bottom between the banks 23.
(Residue treatment process (lyophilic treatment process))
Next, the resist layer (organic substance) remaining as a residue in the bank space 24 is removed in the bank forming process. Here, the resist layer residue is removed by O ₂ plasma treatment using oxygen as a treatment gas in an air atmosphere. That is, oxygen in a plasma state is irradiated to the substrate S from the plasma discharge electrode. Here, as the conditions for the O ₂ plasma treatment, for example, the plasma power is 50 to 1000 W, the oxygen gas flow rate is 50 to 100 ml / min, the plate transport speed of the substrate S to the plasma discharge electrode is 0.5 to 10 mm / sec, and the substrate The temperature of S is 70 to 90 ° C.

As the residue treatment, not limited to the O ₂ plasma treatment, an ultraviolet irradiation treatment, or other processing. Further, when the substrate S is a glass substrate, the surface thereof is lyophilic with respect to the wiring forming ink. However, by performing O ₂ plasma treatment or ultraviolet irradiation treatment for residue treatment, The lyophilicity of the substrate S exposed at the bottom of 24 can be enhanced.
(Liquid repellency treatment process)
Subsequently, a liquid repellency treatment is performed on the bank 23 to impart liquid repellency to the surface. Here, for example, a plasma processing method (CF ₄ plasma processing method) using tetrafluoromethane as a processing gas in an air atmosphere is used. Here, the conditions of the CF ₄ plasma treatment are, for example, that the plasma power is 50 to 1000 W, the tetrafluoromethane gas flow rate is 50 to 100 ml / min, the substrate transport speed to the plasma discharge electrode is 0.5 to 1020 mm / sec, and the substrate temperature is 70 to 90 ° C.

  The processing gas is not limited to tetrafluoromethane (carbon tetrafluoride), and other fluorocarbon gases can also be used.

  By performing such a liquid repellency treatment, fluorine groups are introduced into the resin constituting the bank 23 and high liquid repellency is imparted to the substrate S.

The O ₂ plasma treatment as the lyophilic treatment described above may be performed before the formation of the bank 23, but acrylic resin, polyimide resin, and the like are more fluorinated when pre-treated with O ₂ plasma ( Since it has a property of being easily made liquid repellent, it is preferable to perform O ₂ plasma treatment after the bank 23 is formed.

  Here, the lyophobic treatment for the bank 23 has a slight influence on the surface of the substrate S previously lyophilicized. In particular, when the substrate S is made of glass or the like, introduction of fluorine groups by the lyophobic treatment is difficult. Since it does not occur, the lyophilicity of the substrate S, that is, the wettability is not substantially impaired.

Further, the bank 23 may be formed of a material having liquid repellency (for example, a resin material having a fluorine group), so that the liquid repellency treatment may be omitted.
(First droplet discharge process (application process))
Next, using the above-described droplet discharge device IJ, the wiring forming ink X1 is discharged and arranged on the substrate S exposed between the banks 24. Here, as shown in FIG. 4A, the wiring forming ink X <b> 1 is ejected as droplets from the droplet ejection head 1, and the droplets are disposed on the substrate S exposed between the banks 24. Here, the wiring forming ink X1 using organic manganese (manganese complex compound) as the conductive fine particles is discharged.

  At this time, since the substrate S exposed between the banks 24 is surrounded by the banks 23, it is possible to prevent the wiring forming ink X1 from spreading outside the position where the banks 24 are formed. Further, since the liquid repellency is imparted to the surface of the bank 23, even if a part of the ejected wiring forming ink X1 is ejected onto the bank 23, it is repelled from the bank 23 and flows down between the banks 24. Become. Furthermore, since the substrate S exposed between the banks 24 is given lyophilicity, the wiring forming ink X1 ejected between the banks 24 tends to spread on the substrates S. Thereby, as shown in FIG. 4B, the wiring forming ink X <b> 1 can be uniformly arranged along the extending direction of the inter-bank 24.

Here, the droplet discharge conditions are, for example, an ink weight of 4 ng / dot, an ink speed (discharge speed) of 5 to 7 m / sec, an atmosphere for discharging the liquid droplets at a temperature of 60 ° C. or less, and a humidity of 80 % Or less. Thereby, it is possible to perform stable droplet discharge without clogging the discharge nozzle of the droplet discharge head 1.
(Drying process)
Subsequently, in order to remove a part of the dispersion medium in the discharged wiring forming ink X1 and make the film thickness of the wiring forming ink X1 uniform, a drying process is performed as necessary. Here, for example, the substrate S is heated using a normal hot plate, and the dispersion medium in the wiring forming ink X1 is removed. The drying process is not limited to a hot plate, and can be performed by an electric furnace or lamp annealing. Here, the light source used for the lamp annealing is not particularly limited, but excimers such as infrared lamps, xenon lamps, YAG lasers, argon lasers, carbon dioxide lasers, XeF, XeCl, XeBr, KrF, KrCl, ArF, ArCl, etc. A laser or the like can be used as a light source. In general, these light sources have an output in the range of 10 W to 5000 W, but in this embodiment, a range of 100 W to 1000 W is sufficient.
(First firing step)
Further, the wiring forming ink X1 subjected to the drying process is subjected to a baking process to form a manganese layer 25 (FIG. 4C). Here, the wiring forming ink X1 is heated at a temperature of 180 ° C. or higher and 220 ° C. or lower, more preferably 200 ° C. for 30 minutes or longer. Thereby, the dispersion medium is removed, and the manganese layer 25 which is the uncured (semi-cured) wiring forming ink X1 is formed to a thickness of about 0.01 to 0.5 μm.

If the wiring forming ink X1 is not mixed with other types of wiring forming ink without removing the dispersion medium of the wiring forming ink X1, the intermediate drying step may be omitted.
(Second droplet discharge process)
Subsequently, a silver layer (conductive layer) 26 is formed on the manganese layer 25 (see FIG. 5C). Here, similarly to the wiring forming ink X1, the wiring forming ink X2 is arranged by using the droplet discharge device IJ described above. Here, the wiring forming ink X2 using metal fine particles made of silver as conductive fine particles is disposed. Further, the surface of the metal fine particles is coated with a dispersion stabilizer composed of an amino compound or the like.
(Second firing step)
Next, the wiring forming ink X2 is baked to form a silver layer 26 (FIG. 5C). Here, the dispersion medium and the dispersion stabilizer in the wiring forming ink X2 are removed by heating at 220 ° C. for 30 to 90 minutes (preferably 60 minutes) in the air atmosphere using the atmosphere firing furnace 15 described above. At the same time, the fine metal particles are fired.

  When the metal fine particles are fired, the dispersion stabilizer covering the metal fine particles is detached from the metal fine particles, and the metal fine particles are aggregated to start grain growth. And the disperse | distributed dispersion stabilizer melt | dissolves in a dispersion medium, and evaporates by heating with a dispersion medium. Thereafter, a silver layer 26 is formed on the manganese layer 25 by the metal fine particles grown.

  At this time, the substrate S accommodated in the atmosphere firing furnace 15 is heated, that is, the substrate S including the region where the wiring forming ink X2 is disposed is irradiated with infrared rays, whereby the wiring forming ink X2 is heated. Of this, the dispersion medium evaporates. Here, if the temperature distribution is uneven in the region where the wiring forming ink X2 is disposed, the wiring forming ink X2 has fluidity, so that the region from the high temperature region to the low temperature region. The wiring forming ink X2 flows toward the surface. Therefore, the uniformity of the layer thickness of the silver layer 26 formed by evaporating the dispersion medium or the like and growing metal fine particles is reduced.

  Therefore, at least until the temperature is raised to the firing temperature (220 ° C.) of the metal fine particles composed of silver, the metal is covered so as to cover at least the regions of the substrate S where the wiring forming ink X2 is disposed above and below the substrate S. By arranging the plate 18, infrared rays are uniformly irradiated from the metal plate 18 to the substrate S including the region where the wiring forming ink X <b> 2 is arranged. And it can suppress that the nonuniformity of the temperature distribution in this area | region generate | occur | produces by irradiating infrared rays uniformly to the area | region where the wiring formation ink X2 is arrange | positioned. For this reason, the dispersion medium in the wiring forming ink X2 is uniformly heated and evaporated uniformly. Therefore, the flatness of the layer thickness of the silver layer 26 is improved.

  In the present embodiment, the fact that there is no unevenness in the temperature distribution is not only when there is no temperature difference in each part of the area where the wiring forming ink X2 is applied, but also when the temperature difference between the parts is as small as about 10%. Cases are also included. And the metal plate 18 should just be arrange | positioned at the time of the temperature rise to a calcination temperature at least, and you may remove the metal plate 18 after the temperature rise to a calcination temperature.

  Here, it was confirmed that by arranging the metal plates 18 above and below the substrate S, the silver layer 26 with improved flatness can be obtained.

  In FIG. 5C, only one of the pair of metal plates 18 disposed above and below the substrate S is disposed only on the upper side.

  In addition, the firing treatment is not limited to the atmosphere firing furnace as long as it has a coating member that uniformly irradiates the region of the substrate S where the silver layer 26 is formed. Other firing means such as a furnace may be used.

  Further, after the second baking step, baking is performed at 300 ° C. for 30 minutes in a nitrogen atmosphere in order to improve resistance of the silver layer 26 and prevent generation of cracks and wrinkles due to shrinkage of the silver layer 26.

  As described above, the metal wiring composed of the manganese layer 25 and the silver layer 26 is formed.

A nickel layer made of nickel may be formed on the silver layer 26 as a protective layer. Thereby, deterioration of the silver layer 26 by plasma being irradiated by plasma processing with respect to the silver layer 26 can be suppressed.
Electro-optical device
The metal wiring formed by the metal wiring forming method described above is used as a metal wiring of a liquid crystal display device which is an electro-optical device as shown in FIGS. 6 is a plan view of the liquid crystal display device, FIG. 7 is a cross-sectional view taken along line AA of FIG. 6, FIG. 8 is a partially enlarged cross-sectional view of FIG. 6, and FIG.

  The liquid crystal display device 50 is a TFT active matrix liquid crystal display device using TFTs as pixel switching elements. As shown in FIGS. 6 and 7, the liquid crystal display device 50 includes a liquid crystal panel 51 and polarizing plates (not shown) disposed on the outer surface of the liquid crystal panel 51.

  As shown in FIGS. 6 and 7, the liquid crystal panel 51 includes a TFT substrate 52, a counter substrate 53 disposed opposite to the TFT substrate 52, a sealing material 54 for attaching the TFT substrate 52 and the counter substrate 53, and a TFT. And a liquid crystal layer 55 enclosed in a cell gap formed by the substrate 52 and the counter substrate 53. As shown in FIGS. 6 and 7, the liquid crystal panel 51 has a peripheral light shielding film 56 formed on the inner side of the sealing material 54 while the TFT substrate 52 and the counter substrate 53 overlap with each other. The inside of the seal area is an image display area 57 by the film 56. In FIG. 6, the counter substrate 53 is not shown.

  As shown in FIGS. 6 to 8, the TFT substrate 52 has a rectangular shape in plan view, and is made of a light-transmitting material such as glass, quartz, or plastic. In the region of the TFT substrate 52 that overlaps with the image display region 57, as shown in FIGS. 6 to 8, a pixel electrode 61, a TFT element 62, a plurality of data lines 63, and scanning lines 64 are formed. An alignment film 65 is formed on the inner surface of the TFT substrate 52.

  The pixel electrode 61 is made of, for example, a light-transmitting conductive material such as ITO, and is provided in each of a plurality of pixel regions arranged in a planar shape. As shown in FIGS. 6 and 7, the pixel electrode 61 is disposed to face a counter electrode 92 (described later) provided on the counter substrate 53 via a liquid crystal layer 55, and a liquid crystal is interposed between the pixel electrode 61 and the counter electrode 92. The layer 55 is sandwiched.

  The TFT element 62 is composed of, for example, an n-type transistor, and is provided at each intersection of the data line 63 and the scanning line 64. Further, an amorphous polysilicon film or a polysilicon film obtained by crystallizing the amorphous polysilicon film is partially formed on the upper surface of the TFT substrate 52, and partial impurity introduction and activation are performed on the polysilicon film. It is formed by doing. The TFT element 62 has a source electrode connected to the data line 63, a gate electrode connected to the scanning line 64, and a drain electrode connected to the pixel electrode 61. In addition, a storage capacitor 67 is connected between the pixel electrode 61 and the capacitor line 66 in order to prevent leakage of an image signal written to the pixel electrode 61.

  Here, a partially enlarged cross-sectional view of the bottom gate type TFT element 62 is shown in FIG. On the TFT substrate 52, as shown in FIG. 9, a gate wiring 71 formed by laminating a plurality of different materials formed by the above-described metal wiring forming method is formed. The gate wiring 71 is formed by laminating a manganese layer 25 and a silver layer 26. When forming the gate wiring 71, a bank material made of an inorganic material is used for heating to about 350 ° C. in the step of forming an amorphous silicon layer described later.

A gate insulating layer 72 made of SiN _x (silicon nitride) is formed on the gate wiring 71, and a semiconductor layer 73 made of amorphous silicon (a-Si) through the gate insulating layer 72. Are stacked.

On the semiconductor layer 73, bonding layers 74 and 75 made of, for example, an n ⁺ type α-Si layer are stacked in order to obtain an ohmic junction. An insulating etch stop layer 76 made of SiN _x for protecting the channel is formed on the semiconductor layer 73 at the center of the channel region.

  Note that the gate insulating layer 72, the semiconductor layer 73, and the etch stop layer 76 are patterned by, for example, resist coating, exposure development, and photoetching after the CVD method (Chemical Vapor Deposition). Has been.

  Further, the bonding layers 74 and 75 and the pixel electrode 61 are similarly formed and patterned by performing a photoetching process.

  A bank 77 is formed on each of the pixel electrode 61, the gate insulating layer 72, and the etch stop layer 76, and a source wiring and a drain wiring can be formed between these banks 77 using the above-described droplet discharge device IJ. . Note that these source wiring and drain wiring can also be formed by using the metal wiring forming method in this embodiment.

  As shown in FIG. 9, the data line 63 is a wiring formed so as to be electrically connected to the gate wiring 71 described above, and is formed so as to extend in the Y direction shown in FIG. Further, the scanning line 64 is a wiring formed so as to be conductive with the above-described source wiring, and is formed so as to extend in the X direction shown in FIG. Pixels are defined by the data lines 63 and the scanning lines 64.

  Further, as shown in FIG. 6, the TFT substrate 52 is formed with an overhanging region that projects outward from the counter substrate 53 at one side end (lower side shown in FIG. 1).

  On the TFT substrate 52, a data line driving circuit 81 is provided along the one side, and scanning line driving circuits 82 and 83 are provided along two sides adjacent to the one side. A terminal portion 84 that is a terminal group of the data line driving circuit 81 and the scanning line driving circuits 82 and 83 is provided in the overhanging region of the TFT substrate 52. The data line driving circuit 81, the scanning line driving circuits 82 and 83, and the terminal portion 84 are appropriately connected by a wiring 85.

  The data line driving circuit 81 is configured to supply image signals S1, S2,... As shown in FIG. 9 to the plurality of data lines 63 based on the supplied signals. Here, the image signal written to the data line 63 by the data line driving circuit 81 may be supplied line-sequentially or may be supplied for each of a plurality of adjacent data lines 63 for each group.

  Further, the scanning line driving circuits 82 and 83 supply the scanning signals G1, G2,... As shown in FIG. 9 in a pulsed manner at a predetermined timing to the plurality of scanning lines 64 based on the supplied signals. It has become. Here, the scanning signals sent to the scanning lines 64 by the scanning line driving circuits 82 and 83 are supplied line-sequentially.

  As shown in FIG. 3, the counter substrate 53 has a rectangular shape in plan view like the TFT substrate 52, and is made of a translucent material such as glass, quartz, or plastic. A light shielding film 91 and a counter electrode 92 are formed on the surface of the counter substrate 53 on the liquid crystal layer 55 side. An alignment film (not shown) is formed on the surface of the counter substrate 53.

  The counter electrode 92 is made of a light-transmitting conductive material such as ITO similarly to the pixel electrode 61.

  The alignment film formed on the TFT substrate 52 is provided on the surface of the pixel electrode 61. For example, a predetermined alignment process such as a rubbing process is performed on a film made of a light-transmitting organic material such as a polyimide film. It is formed with.

  In addition, the alignment film formed on the counter substrate 53 is subjected to a predetermined alignment process such as a rubbing process on a light-transmitting organic film such as a polyimide film, similarly to the alignment film formed on the TFT substrate 52. Is formed. Here, the rubbing direction of the alignment film is substantially the same as the rubbing direction of the alignment film formed on the TFT substrate 52. In addition, an inter-substrate conductive material 93 is provided at the corner of the counter substrate 53 to ensure electrical continuity between the TFT substrate 52 and the counter substrate 53.

  As shown in FIGS. 6 and 7, the liquid crystal layer 55 is in a predetermined alignment state between alignment films respectively formed on both the TFT substrate 52 and the counter substrate 53. As a liquid crystal mode of the liquid crystal layer 55, in addition to a TN (Twisted Nematic) mode, a VAN (Vertical Aligned Nematic) mode, an STN (Super Twisted Nematic) mode, an ECB (Electrically Controlled Birefringence) mode, an OCB (Optical Compensated Bend) mode Etc. can be adopted.

  As described above, according to the metal wiring forming method and the atmosphere firing furnace 15 in the present embodiment, the metal plate 18 is disposed above and below the substrate S so as to cover at least the region where the wiring forming ink X2 is disposed. Thus, the infrared rays are uniformly irradiated from the metal plate 18 to the substrate S including the region where the wiring forming ink X2 is disposed. In this way, by uniformly irradiating the region where the wiring forming ink X2 is disposed with infrared rays, the dispersion medium in the wiring forming ink X2 is uniformly heated and uniformly evaporated. Therefore, the flatness of the layer thickness of the silver layer 26 is improved.

  Here, by using fine metal particles made of Ag for the wiring forming ink X2 constituting the silver layer 26, a good anchor effect with the manganese layer 25 can be obtained. And since the manganese layer 25 is comprised with manganese oxide, favorable adhesiveness can be obtained with respect to the board | substrate S and the silver layer 26, respectively.

  Further, the wiring forming inks X1 and X2 constituting the manganese layer 25 and the silver layer 26 are applied by the droplet discharging method using the droplet discharging device IJ, and the wiring forming inks X1 and X2 are respectively selected. Therefore, waste of material can be suppressed and cost can be reduced.

  In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention.

  For example, in the above embodiment, the metal wiring is formed by discharging the wiring forming ink into the bank having the opening, but the following metal wiring forming method may be used.

  This metal wiring forming method includes a surface treatment process, a first droplet discharge process, a drying process, a first firing process, a second droplet discharge process (application process), and a second firing process.

  First, the lyophilic part H1 and the liquid repellent part H2 are formed on the surface of the substrate S (see FIG. 10B). Here, the surface of the substrate S on which the metal wiring is formed is subjected to a liquid repellency treatment so as to exhibit liquid repellency with respect to the wiring forming inks X1 and X2. That is, the surface of the substrate S is subjected to surface treatment so that a difference between a predetermined contact angle with respect to the wiring forming inks X1 and X2 and a contact angle in the lyophilic portion H1 described later is preferably 50 ° or more.

  Examples of a method for making the surface of the substrate S liquid repellent include a method of forming a self-assembled film on the surface of the substrate S and a method of performing plasma treatment.

  In the method for forming a self-assembled film, a self-assembled film composed of an organic molecular film or the like is formed in a region where a metal wiring is formed.

  Here, the organic molecular film used for the self-assembled film modifies the surface properties of the substrate such as a functional group capable of binding to the substrate S and a lyophilic group or a liquid repellent group on the opposite side (controls the surface energy). ) Functional group and a carbon straight chain or a partially branched carbon chain connecting these functional groups. The organic molecular film is bonded to the substrate S and self-assembles to form a molecular film, for example, a monomolecular film.

  Here, the self-assembled film is composed of a binding functional group capable of reacting with the constituent atoms of the substrate and other linear molecules, and aligns a compound having extremely high orientation by the interaction of the linear molecules. It shows the film formed in such a manner. Since the self-assembled film is formed by orienting single molecules, the film thickness can be extremely reduced and the film can be uniform at the molecular level. Therefore, since the same molecule is located on the surface of the film, uniform and excellent liquid repellency and lyophilicity can be imparted to the surface of the film.

  An example of such a highly oriented compound is fluoroalkylsilane. By using this fluoroalkylsilane, each compound is oriented so that the fluoroalkyl group is located on the surface of the film to form a self-assembled film, and uniform liquid repellency is imparted to the surface of the film.

  Examples of compounds that form a self-assembled film include heptadecafluoro-1,1,2,2 tetrahydrodecyltriethoxysilane, heptadecafluoro-1,1,2,2 tetrahydrodecyltrimethoxysilane, heptadecafluoro-1 , 1,2,2 tetrahydrodecyltrichlorosilane, tridecafluoro-1,1,2,2 tetrahydrooctyltriethoxysilane, tridecafluoro-1,1,2,2 tetrahydrooctyltrimethoxysilane, tridecafluoro-1 , 1,2,2 tetrahydrooctyltrichlorosilane, trifluoropropyltrimethoxysilane, and other fluoroalkylsilanes (hereinafter referred to as “FAS”). These compounds may be used alone or in combination of two or more. By using FAS, adhesion to the substrate S and good liquid repellency can be obtained.

FAS is generally represented by the structural formula RnSiX _(4-n) . Here, n represents an integer of 1 to 3, and X is a hydrolyzable group such as a methoxy group, an ethoxy group, or a halogen atom. R is a fluoroalkyl group, and has a structure of (CF ₃ ) (CF ₂ ) _x (CH ₂ ) _y (where x represents an integer of 0 to 10 and y represents an integer of 0 to 4). And when a plurality of R or X are bonded to Si, each R or X may be the same or different. The hydrolyzable group represented by X forms silanol by hydrolysis and reacts with the hydroxyl group on the base of the substrate S (glass, silicon) to bond to the substrate S through a siloxane bond. On the other hand, since R has a fluoro group such as (CF ₂ ) on the surface, the base surface of the substrate S is modified to a surface having no swell (low surface energy).

A self-assembled film made of an organic molecular film or the like is formed on the substrate S by placing the raw material compound and the substrate S in the same sealed container and leaving them at room temperature for about 2 to 3 days. The
Further, by holding the entire sealed container at 100 ° C., it is formed on the substrate S in about 3 hours. These are formation methods from the gas phase, but a self-assembled film can also be formed from the liquid phase. For example, the self-assembled film is formed on the substrate S by immersing the substrate S in a solution containing the raw material compound, washing and drying.

  Note that before the self-assembled film is formed, it is desirable to perform pretreatment of the surface of the substrate S by irradiating the surface of the substrate S with ultraviolet light or washing with a solvent.

  On the other hand, in the plasma processing method, plasma irradiation is performed on the substrate S under normal pressure or vacuum. The gas type used for the plasma treatment can be selected in consideration of the surface material of the substrate S on which the metal wiring is to be formed. Examples of the processing gas include tetrafluoromethane, perfluorohexane, and perfluorodecane.

  In addition, the process which processes the surface of the board | substrate S to liquid repellency is also performed by sticking to the surface of the board | substrate S the film which has desired liquid repellency, for example, the polyimide film processed by the tetrafluoroethylene, etc. Also good. Further, a polyimide film having high liquid repellency may be used as the substrate S as it is.

  As described above, by performing the self-organized film forming method or the plasma processing method, the liquid repellent film 101 is formed on the surface of the substrate S as shown in FIG.

  Next, as shown in FIG. 10 (b), a wiring forming ink is applied to reduce the liquid repellency of the region where the metal wiring is to be formed and to impart lyophilicity. The lyophilic part H1 is formed.

  Here, a method of irradiating ultraviolet light having a wavelength of 170 to 400 nm can be mentioned. At this time, by irradiating with ultraviolet light using a mask corresponding to the shape of the metal wiring, only the region where the metal wiring is to be formed in the liquid-repellent film 101 once formed is partially altered to make the liquid repellency. Can be relaxed and lyophilic. As a result, a lyophilic portion H1 having lyophilicity is formed in the region where the metal wiring is formed on the substrate S, and the lyophobic portion H2 is surrounded by the lyophobic film 101 so as to surround the lyophilic portion H1. It is formed.

  The degree of relaxation of liquid repellency can be adjusted by the irradiation time of ultraviolet light, but can also be adjusted by a combination with the intensity and wavelength of ultraviolet light, heat treatment (heating), and the like.

As another method of lyophilic treatment, plasma treatment using oxygen as a reaction gas can be given. Here, the substrate S is irradiated with oxygen in a plasma state from a plasma discharge electrode. At this time, the conditions for the O ₂ plasma treatment include, for example, a plasma power of 50 to 1000 W, an oxygen gas flow rate of 50 to 100 ml / min, a plate transport speed of the substrate S with respect to the plasma discharge electrode of 0.5 to 10 mm / sec, The temperature is 70-90 ° C.

  Further, the contact angle of the lyophilic portion H1 with respect to the wiring forming inks X1 and X2 containing conductive fine particles is adjusted by adjusting the plasma processing conditions, for example, by lowering the transport speed of the substrate S and increasing the plasma processing time. Is preferably set to 10 ° or less. Further, as another lyophilic process, a process of exposing the substrate to an ozone atmosphere can be employed.

  Next, similarly to the above-described embodiment, the wiring forming ink X1 is ejected and disposed on the lyophilic portion H1 using the droplet ejection device IJ. Here, as shown in FIG. 10C, the wiring forming ink X1 is ejected as droplets from the droplet ejection head 1, and the droplets are disposed on the lyophilic portion H1. At this time, by imparting liquid repellency to the liquid repellent part H2, even if a part of the ejected wiring forming ink X1 gets on the liquid repellent part H2, it is repelled from the liquid repellent part H2, and FIG. As shown in FIG. 3, the liquid stays on the lyophilic part H1 formed between the liquid repellent parts H2. Further, by imparting lyophilicity to the lyophilic portion H1, the discharged wiring forming ink X1 is more likely to spread in the lyophilic portion H1, thereby preventing the wiring forming ink X1 from being divided. The lyophilic part H1 can be embedded more uniformly within the predetermined position.

  Thereafter, similarly to the above-described embodiment, the manganese layer 25 is formed on the lyophilic portion H1 as shown in FIG. 11B by performing the drying step and the first firing step.

  Further, as in the above-described embodiment, by performing the second droplet discharge step (see FIG. 11C) and the second firing step, silver is formed on the manganese layer 25 as shown in FIG. 11D. Layer 26 is formed.

  In addition, the conductive layer is formed using fine metal particles made of Ag. However, the conductive layer is not limited to Ag, and any one of Au, Cu, Ni, ITO, Pd, Bi, and Mn, or a combination of Ag added thereto may be used. Metal fine particles made of a mixture selected from the above may be used.

  The underlayer is formed of an oxide of Mn, but is not limited to an oxide of Mn, and may be formed of any oxide of Ti, Cu, Ni, In, or Cr.

  Furthermore, each wiring forming ink constituting the manganese layer (underlying layer) and the silver layer (conductive layer) is applied by a droplet discharge method using an ink jet apparatus, but not limited to the droplet discharge method, spin coating Other wet methods such as a method may be applied. Here, it is sufficient that the wiring forming ink constituting at least the silver layer (conductive layer) is applied using a wet method such as a droplet discharge method, and the manganese layer (underlayer) is a method other than the wet method. May be formed.

  Moreover, although the TFT element is used as a switching element for driving the liquid crystal display device, the TFT element may be used for an organic EL (electroluminescence) display device in addition to the liquid crystal display device. This organic EL display device has a structure in which a thin film containing a fluorescent orientation or organic compound is sandwiched between a cathode and an anode, and is excited by injecting electrons and holes into the thin film and exciting them. A child (excitron) is generated, and light is emitted by utilizing light emission (fluorescence, phosphorescence) when the excitron is recombined. Then, on the substrate having the TFT element described above, among the fluorescent materials used in the organic EL display device, materials having red, green and blue emission colors, that is, a light emitting layer forming material and a hole injection / electron transport layer. A self-luminous full-color EL device can be manufactured by using ink as the material for forming and forming a pattern.

It is a schematic block diagram which shows the droplet discharge apparatus used for the metal wiring formation method of this invention. It is a schematic diagram which shows the atmosphere baking furnace in one Embodiment of this invention. It is process drawing which shows the metal wiring formation method in one Embodiment of this invention. Similarly, it is process drawing which shows a metal wiring formation method. Similarly, it is process drawing which shows a metal wiring formation method. It is a top view which shows a liquid crystal display device. It is AA arrow sectional drawing of FIG. It is a partial expanded sectional view of FIG. FIG. 7 is an equivalent circuit diagram of FIG. 6. It is process drawing which shows the other metal wiring formation method which can apply this invention. Similarly, it is process drawing which shows another metal wiring formation method. It is a schematic perspective view which shows the conventional active matrix substrate.

Explanation of symbols

15 atmosphere firing furnace (firing furnace), 18 metal plate (covering member), 25 manganese layer (underlayer), 26 silver layer (conductive layer), S substrate, X2 wiring forming ink (functional liquid)

Claims (5)

An application step of applying a functional liquid in which metal fine particles are dispersed on an underlayer formed on a substrate;
A method of forming a metal wiring by heating the functional liquid to grow the metal fine particles and forming a conductive layer,
In the baking step, the substrate is baked in a state where a pair of covering members that uniformly irradiate infrared rays to at least a region of the substrate to which the functional liquid is applied are arranged at intervals above and below the substrate. A metal wiring forming method, wherein the temperature is raised to a temperature.   2. The metal wiring forming method according to claim 1, wherein the metal fine particles are any one of Au, Ag, Cu, Ni, ITO, Pd, Bi, and Mn, or a mixture thereof.   3. The metal wiring forming method according to claim 1, wherein the underlayer is made of an oxide of any of Mn, Ti, Cu, Ni, In, or Cr.   The metal wiring formation method according to claim 1, wherein the functional liquid is applied using a droplet discharge method. A firing furnace for heating a substrate coated with a functional liquid in which metal fine particles are dispersed;
A firing furnace comprising a pair of covering members that are arranged at intervals above and below the substrate and uniformly irradiate infrared rays to at least a region of the substrate to which the functional liquid is applied.

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