Patent Application
20140023827
The application claims the benefit of and priority to Korean Patent Application No. 10-2012-0077882, filed on Jul. 17, 2012, in the Korean Intellectual Property Office, and entitled: “ETCHING PASTE, METHOD OF PREPARING THE SAME, AND METHOD OF FORMING PATTERN USING THE SAME,” which is incorporated by reference herein in its entirety.
1. Field
Embodiments relate to an etching paste, a method of preparing the same, and a method of forming a pattern using the same.
2. Description of the Related Art
A pattern forming process may be used for semiconductor devices and flat panel displays such as LCDs, OLEDs, and PDPs. A typical pattern forming process is performed using a photosensitive material such as photoresist, in which a photoresist layer is formed by depositing the photoresist on a metal layer formed on a substrate of an insulating material, such as glass, or a semiconductor material, followed by exposure and development through a photo mask. Then, the metal layer it etched using an etching solution and the photoresist pattern is removed using a stripper, leaving a metal pattern on the substrate.
Such a metal pattern formation process using photoresist may involve a complicated manufacturing process since a pattern is formed via photoresist application, baking, exposure, and development. Particularly, a soft baking process at a particular temperature and a hard baking process at a higher temperature than the soft baking temperature may be needed to bake the photoresist, thereby making the process complicated. As a result, the typical pattern forming process may have undesirable characteristics such as increase in manufacturing costs, environmental contamination due to waste photoresist contaminates, and device defects caused by remaining photoresist.
Embodiments are directed to an etching paste, including an acid compound, an organic binder, a nitrogen-containing component, the nitrogen-containing component including one or more of an amine compound or an ammonium compound, a cobalt aluminum oxide, and a solvent.
The cobalt aluminum oxide may be present in an amount of about 1 wt % to about 20 wt % in the etching paste.
The cobalt aluminum oxide may have an average particle diameter (D50) of about 0.001 μm to about 5 μm
A mole ratio of the nitrogen-containing component to the acid compound may be about 1 to about 1.5.
The nitrogen-containing component may include the amine compound, and the amine compound may be represented by Formula 1:
(R)n—N—Hm [Formula 1]
wherein, in Formula 1, R may be a substituted or unsubstituted C1 to C12 alkyl group, a substituted or unsubstituted C6 to C 12 aryl group, or a substituted or unsubstituted C7 to C15 arylalkyl group, n may be an integer from 1 to 3, m may be an integer from 0 to 2, and n+m may be 3.
The nitrogen-containing component may include the ammonium compound, and the ammonium compound may be represented by Formula 2:
(NH4)kX [Formula 2]
wherein, in Formula 2, X may be CO3, OH, or CO2NH2, and k may be 1 or 2.
The acid compound may include one or more of phosphoric acid, hydrogen fluoride, ammonium fluoride, or ammonium hydrogen fluoride.
The organic binder may include one or more of methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, sodium carboxymethyl hydroxyethyl cellulose, nitrocellulose, xanthan gum, starch, gelatin, polyvinyl butyral, a polyamide resin, thixoton, polyvinylpyrrolidone, polyvinyl alcohol, an acrylic polymer obtained by copolymerization of acrylic monomers having a hydroxyl group or a carboxylic acid group, a water-soluble (meth)acrylic resin, a polyether-polyol, or a poly(ether urea)-polyurethane.
The etching paste may include about 15 wt % to about 50 wt % of the acid compound, about 3 wt % to about 20 wt % of the organic binder, about 0.1 wt % to about 10 wt % of the nitrogen-containing component, about 1 wt % to about 20 wt % of the cobalt aluminum oxide, and a balance of the solvent.
The etching paste may further include one or more of an organic acid, inorganic particles, a foaming agent, a leveling agent, an antifoaming agent, a thickener, a thixotropic agent, a plasticizer, a dispersant, a viscosity stabilizer, a UV stabilizer, an antioxidant, or a coupling agent.
The etching paste may further include inorganic particles. A weight ratio of the cobalt aluminum oxide to the inorganic particles may be about 0.1 to about 7.
The acid compound may include phosphoric acid, the organic binder may include hydroxypropyl cellulose, the nitrogen-containing component may include one or more of ammonium hydroxide 35% or methylamine, the cobalt aluminum oxide may include CoAl2O4, and the solvent may include water and n-methylpyrrolidone, the etching paste may further include acetic acid and silica particles, a weight ratio of the CoAl2O4 to the silica particles may be about 0.4 to about 6.5, a mole ratio of the phosphoric acid to the nitrogen-containing component may be about 1:1.1 to about 1:1.3, and the etching paste may include: about 25 wt % to about 30 wt % of the phosphoric acid, about 5 wt % to about 10 wt % of the hydroxypropyl cellulose, about 0.1 wt % to about 0.5 wt % of the nitrogen-containing component, about 1 wt % to about 15 wt % of the CoAl2O4, about 1 wt % to about 5 wt % of the acetic acid, about 1 wt % to about 5 wt % of the silica particles, and a balance of the solvent.
Embodiments are also directed to a method of forming a pattern, the method including printing the etching paste according to an embodiment on a substrate on which an etching target is deposited, drying the etching paste, and washing the etching paste to form a pattern in the etching target.
The etching target may be aluminum or indium tin oxide.
Embodiments are also directed to a device including a pattern formed by the method according to an embodiment.
Features will become apparent to those of skill in the art by describing in detail example embodiments with reference to the attached drawings in which:
Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings; however, they may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey example implementations to those skilled in the art.
In the drawing figures, the dimensions of layers and regions may be exaggerated for clarity of illustration. It will also be understood that when a layer or element is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. Further, it will be understood that when a layer is referred to as being “under” another layer, it can be directly under, and one or more intervening layers may also be present. In addition, it will also be understood that when a layer is referred to as being “between” two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present. Like reference numerals refer to like elements throughout.
An embodiment provides an etching paste including: an acid compound; an organic binder; nitrogen-containing component including one or more of an amine compound or an ammonium compound; a cobalt aluminum oxide; and a solvent.
Acid Compound
The acid compound may include a suitable compound capable of etching an etching target (for example, metal, or indium tin oxide (ITO)) on which the etching paste acts. For example, the acid compound may include inorganic acid, for example one or more of phosphoric acid, hydrogen fluoride, ammonium fluoride, or ammonium hydrogen fluoride. In an implementation, phosphoric acid may be used.
The acid compound may be used as an acid solution having a concentration of about 80% or higher, e.g., about 85% to 90% (based on weight). In an implementation, a phosphoric acid aqueous solution may be used.
The acid compound or a solution containing the acid compound may be present in an amount of about 15 wt % to about 50 wt % in the etching paste. Within this range, the etching paste may exhibit excellent etching performance while reducing effects on equipment. The acid compound or the solution containing the acid compound may be present in an amount of, e.g., about 20 wt % to about 35 wt %, or about 25 wt % to about 30 wt %, in the etching paste.
Organic Binder
The organic binder may enhance viscosity and printability of the etching paste, so as to enable printing of the etching paste.
The organic binder may include, e.g., cellulose derivatives including methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, sodium carboxymethyl hydroxyethyl cellulose and nitrocellulose, xanthan gum, starch, gelatin, polyvinyl butyral, a polyamide resin, thixotron, polyvinylpyrrolidone, polyvinyl alcohol, water-soluble (meth)acrylic resins including acrylic polymers obtained by copolymerization of acrylic monomers having a hydrophilic group, such as a hydroxyl group and a carboxylic acid group, polyether-polyol, and poly(ether urea)-polyurethane, etc. The organic binder may be used alone or in combination of two or more thereof.
The organic binder may be present in an amount of about 3 wt % to about 20 wt % in the etching paste. Within this range, the etching paste may have a suitable viscosity and printability may be enhanced. The organic binder may be present in an amount of about 5 wt % to about 15 wt %, or about 5 wt % to about 10 wt %.
Nitrogen-containing component including one or more of an amine compound or an ammonium compound
The amine compound and/or the ammonium compound may react with the acid compound to form a complex, which is separated at about 100 to 250° C. to have an etching function.
The amine compound may be represented by Formula 1:
(R)n—N—Hm, [Formula 1]
where, in Formula 1, R may be a substituted or unsubstituted C1 to C12 alkyl group, a substituted or unsubstituted C6 to C12 aryl group, or a substituted or unsubstituted C7 to C 15 arylalkyl group, n may be an integer from 1 to 3, m may be an integer from 0 to 2, and n+m may equal 3. When R is substituted, a substituent may be, e.g., a C1 to C5 alkyl group or a C6 to 10 aryl group.
In an implementation, R may be a C1 to C10 alkyl group or a C7 to C10 arylalkyl group.
In an implementation, n may be 1 or 2, and m may be 1 or 2.
Examples of the amine compound may include methyl amine, ethyl amine, propyl amine, butyl amine, dodecyl amine, benzyl amine, etc. The amine compound may be used alone or in combination of two or more thereof.
The ammonium compound may be represented by Formula 2:
(NH4)kX, [Formula 2]
where, in Formula 2, X may be OH, CO3, or CO2NH2, and k may be 1 or 2.
Examples of the ammonium compound may include an ammonia solution (ammonia water), ammonium carbonate, ammonium carbamate, etc. The ammonium compound may be used alone or in combination of two or more thereof.
In an implementation, the ammonium compound may be an ammonia solution (ammonia water).
The amine compound and the ammonium compound may be used as a combination thereof.
A mole ratio of the amine compound and/or the ammonium compound to the acid compound may range from about 1 to about 1.5. Within this range, the etching paste may be neutralized while reducing or avoiding decreases in printability. In an implementation, a mole ratio between the acid compound and the amine compound, the ammonium compound, or a mixture thereof may be about 1:1.1 to about 1:1.3.
The nitrogen-containing component may be present in an amount of about 0.1 wt % to about 10 wt % in the etching paste. Within this range, the etching paste may exhibit excellent etching performance while reducing effects on equipment. In an implementation, the amount may be about 0.1 wt % to about 1 wt %, or about 0.1 wt % to about 0.5 wt %, in the etching paste.
Cobalt Aluminum Oxide
The etching paste may form a metal pattern through screen printing. The etching paste may be printed on an etching target, dried through heat treatment or the like, and washed, thereby forming the metal pattern.
In forming the metal pattern, etching proceeds faster as heat treatment temperature rises. The color of the cobalt aluminum oxide changes from blue into black depending on the extent of etching. This color change may help make it possible to identify the extent of etching, an etched position on a substrate, and/or a substrate state before and after heat treatment with the naked eye.
Further, the cobalt aluminum oxide may allows etching at low temperature, for example, at a heat treatment temperature of about 100° C. to about 150° C., thereby securing a pattern in a predetermined range of line width, for example, a fine line width of about 50 μm to about 200 μm. The pattern may become finer with increasing heat treatment temperature.
In addition, the cobalt aluminum oxide may itself be etched to prevent expansion of etching at the distal end of the etched metal, thereby reducing or preventing resistance increase due to expansion of etching, which may otherwise occur.
In some embodiments, the cobalt aluminum oxide may include CoAl2O4.
The cobalt aluminum oxide may be a nano-scaling powder. The powder may have an average particle diameter (D50) of, e.g., about 0.001 μm to about 5 μm, or about 0.1 μm to about 2 μm, or about 0.1 μm to about 1.0 μm.
The cobalt aluminum oxide may be present in an amount of about 1 wt % to about 20 wt % in the etching paste. Within this range, the etching paste may have excellent printability, superior resolution after printing, and excellent visibility. The cobalt aluminum oxide may be present in an amount of about 1 wt % to about 15 wt %.
Solvent
As the solvent, a suitable solvent that does not significantly reduce water-solubility of the etching paste may be used. Examples of the solvent may include water (including distilled water), n-methylpyrrolidone (NMP), ethylene glycol butyl ether, propylene carbonate, ethylene glycol, N-methyl-2-pyridone, ethylene glycol monoacetate, diethylene glycol, diethylene glycol acetate, tetraethylene glycol, propylene glycol, propylene glycol monomethyl ether, trimethylene glycol, glyceryl diacetate, hexylene glycol, dipropyl glycol, oxylene glycol, 1,2,6-hexanetriol, glycerin, etc. These solvents may be used alone or in combination of two or more thereof.
The solvent may be added to the etching paste as a remaining amount (i.e., a balance)—excluding the acid compound, the organic binder, the nitrogen-containing component including one or more of the amine compound or the ammonium compound, the cobalt aluminum oxide, and additive(s) (if included). In an embodiment, the solvent may be present in an amount of about 25 wt % to about 60 wt %, or about 35 wt % to about 55 wt %, in the etching paste.
The etching paste may include one or more additives, e.g., to improve fluidity, processibility, stability, etc. The additive(s) may include, e.g., an organic acid, inorganic particles, a foaming agent, a leveling agent, an antifoaming agent, a thickener, a thixotropic agent, a plasticizer, a dispersant, a viscosity stabilizer, a UV stabilizer, an antioxidant, a coupling agent, etc. The additive may be used alone or in combination of two or more thereof.
The organic acid may include, e.g., acetic acid, lactic acid, malonic acid, citric acid, etc. The organic acid may be present in an amount of about 0.1 wt % to about 10 wt %, e.g., about 1 wt % to about 5 wt %, in the etching paste.
The inorganic particles may include silica, carbon black, iron pigments, titanium dioxide, etc. A weight ratio of the cobalt aluminum oxide to the inorganic particles may be about 0.1 to 7, e.g., about 0.4 to about 6.5. The inorganic particles may be present in an amount of about 1 wt % to about 15 wt %, e.g., about 1 wt % to about 5 wt %, in the etching paste.
A method of preparing the etching paste according to an embodiment may include preparing a binder solution by dissolving the organic binder in the solvent, adding the cobalt aluminum oxide to the binder solution, adding any additive(s) to the binder solution, and reacting the solution with the acid compound and the nitrogen-containing component that includes one or more of the amine compound represented by Formula 1 or the ammonium compound represented by Formula 2.
Another embodiment provides a method of forming a pattern using the paste according to an embodiment.
In the example embodiment shown in
Then, the etching paste 10 is printed on the etching target 20 (Operation b). The etching paste 10 may be printed by screen printing, offset printing, ink-jet printing, coating, etc.
Then, the printed etching paste 10 may be dried. Drying may be carried out in a belt type dry oven or a box type dry oven at a temperature of, e.g., about 100° C. to about 250° C. Within this temperature range, the paste may allow an etching function to be exhibited while an acid and a complex are separated. In an implementation, the drying temperature may range from about 160° C. to about 230° C. After drying, the paste 10 may be left at room temperature for about 5 to about 60 minutes.
Then, the dried paste may be washed so that the paste is removed from the substrate and an area where the paste has been placed is etched, thereby forming a pattern (Operation c). In an implementation, the paste may be removed by washing with water. In an implementation, the paste may be removed by a developer using a developing agent.
Another embodiment provides a patterned element which includes a pattern formed using the etching paste. The patterned element may include a solar cell, an LCD, an OLED, a PDP, etc.
The following Examples and Comparative Examples are provided in order to highlight characteristics of one or more embodiments, but it will be understood that the Examples and Comparative Examples are not to be construed as limiting the scope of the embodiments, nor are the Comparative Examples to be construed as being outside the scope of the embodiments. Further, it will be understood that the embodiments are not limited to the particular details described in the Examples and Comparative Examples.
Etching pastes were prepared using components according to compositions (unit: % by weight) listed in Table 1.
Hydroxypropyl cellulose (L-IND, Ashland, Inc.) was dissolved in distilled water at 0° C. to 5° C. for 2 hours while stirring at 2,000 rpm and heated to room temperature, and NMP (Aldrich Co.) was added thereto, thereby preparing an organic binder solution. Then, silica (A200, Degussa Co.), acetic acid (Aldrich Co.), and cobalt aluminum oxide (Grade: 5462, CoAl2O4, Average diameter (D50): 0.8 μm, TomaTech Ltd.) were added to the prepared solution, and a paste was prepared using a bead-mill or a 3-roll mill. Phosphoric acid (Phosphoric acid aqueous solution, Concentration: 85%, Aldrich Co.) was added dropwise to the paste while stirring the paste, followed by dropwise addition of an ammonia water solution (Concentration: 35%, Aldrich Co.) or methylamine (Aldrich Co.) and stirring for 3 hours, thereby producing an etching paste.
In Comparative Example 2, carbon black (Grade: L600, Ketjen Black, Mitsubishi Chemical Corp.) was used instead of the cobalt aluminum oxide.
Metal patterns were formed using the etching pastes obtained in the Examples and Comparative Examples as follows.
Formation of Metal Pattern
Each etching paste was printed on an ITO-deposited glass substrate (PD200, Asahi Glass Co.) using a SUS 400 mesh screen mask having a pattern of 30 to 150 μm. The substrate was dried in a belt type dry oven or a box type dry oven while changing temperature to 100° C., 150° C., or 200° C. and then left at room temperature for 20 minutes. The applied etching paste was removed using a developer with a developing agent of 0.1% sodium carbonate, thereby forming a pattern.
The formed pattern was evaluated as to printing resolution, visibility of etching extent, and resistance after etching (including a picture of the pattern), and results thereof are shown in
(1) Printing resolution: Each etching paste was printed on an ITO-deposited glass substrate (PD200, Asahi Glass Co., Ltd.) through a screen mask having a line width of 30 μm to 200 μm. Then, disconnection of a pattern or a pattern not intruding into a non-etched region was expressed by a resolution limit.
(2) Visibility of etching extent: Each of the etching pastes was printed using an SUS 400 mesh screen mask having a 50 μm line-width pattern. The etching pastes were dried for the same duration in a belt type dry oven or a box type dry oven while changing temperature to 100° C., 150° C., or 200° C. The substrate was left at room temperature for 20 minutes, followed by photographing an image of the wiring pattern using a stereoscopic microscope (at a magnification of 1.5 times) and calculating a ratio of a black area to a blue area using an image analyzer (Image-Pro). A higher heated area ratio shows a higher degree of etching.
(3) Resistance after etching: Resistance of the etched wiring pattern was measured in a length of 50 mm using a 2-probe resistance tester (Keyence Co.)
As shown in Table 2, the etching pastes according to embodiments may etch with low-temperature heat treatment at 100° C. or 150° C., thereby realizing a fine line width of 100 μm or greater. On the other hand, the pastes not including the cobalt aluminum oxide or including the carbon black provided relatively poor etching properties in the same low-temperature heat treatment.
Further, as shown in Table 3, as the temperature of heat treatment increased, the etching pastes according embodiments had a gradually increasing ratio of the black area to the blue area, which was identified with the naked eye, and thus the extent of etching could be determined based on color change. On the other hand, the pastes not including the cobalt aluminum oxide or including the carbon black did not provide comparable effects. In addition, the etching pastes according to embodiments had a uniform cross section without etching expansion at a distal end of the pattern, as shown in
By way of summation and review, an etching paste may use an acid compound. In a pattern forming process using an etching paste that includes an acid compound, an etching target may be deposited on a substrate and then the etching paste may be printed thereon through a mask, dried by heat treatment, and washed, thereby forming a pattern. When the object is etched through heat treatment, the extent of etching may not be uniform and may vary depending on the thickness of the object. Further, a general etching paste may spread at a distal end of the target object during heat treatment, which may cause an increase in resistance of a final pattern. Further, it may be difficult to identify whether etching is finished by heat treatment. For example, a method of manufacturing an electrode may include forming a semiconductor unit having an opposite conductive type to a semiconductor substrate on the semiconductor substrate, forming a protective film on the semiconductor unit, printing an etching paste on the protective film, etching the semiconductor unit, and applying a conductive metal material. In this method, it may be difficult to recognize the extent of etching.
As described above, embodiments may provide an etching paste that enables an etching extent to be visually perceived. Further, the etching paste may allow etching at a low drying temperature, may prevent resistance increase by preventing expansion of etching at a distal end of a pattern during or after etching, an may increase etching selectivity (resolution). Further, the etching paste may help realize a fine line width, may exhibit good etching performance, and may reduce effects on equipment. Embodiments also provide a method of preparing the etching paste and a method of forming a pattern using the etching paste. According to embodiments, it may be possible to identify whether etching is finished by heat treatment, and thus pattern formation may be completed without excess heat treatment. Thus, embodiments may enable determination of the extent of etching based on temperature and duration of heat treatment.
Example embodiments have been disclosed herein, and although specific terms are employed, they are used and are to be interpreted in a generic and descriptive sense only and not for purpose of limitation. In some instances, as would be apparent to one of ordinary skill in the art as of the filing of the present application, features, characteristics, and/or elements described in connection with a particular embodiment may be used singly or in combination with features, characteristics, and/or elements described in connection with other embodiments unless otherwise specifically indicated. Accordingly, it will be understood by those of skill in the art that various changes in form and details may be made without departing from the spirit and scope of the present invention as set forth in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2012-0077882 | Jul 2012 | KR | national |
