JP2010165887A - Etchant for conductive films, and method of etching conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an etchant which has superior suppressing effects on foaming and superior wettability during etching, and can obtain highly accurate conductive patterns free from an unetched part, and to provide an etching method. <P>SOLUTION: The etchant for conductive films is characterized in that it contains at least ceric ammonium nitrate; an etching agent (a) for conductive film having at least one selected from the group consisting of perchloric acid, nitric acid and acetic acid; and a compound (b) represented by general formula (1): (Rf1SO<SB>2</SB>)(Rf2SO<SB>2</SB>)NX. The method of etching the conductive film using the etchant is provided. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an etching solution for a conductive film (hereinafter sometimes simply referred to as an “etching solution”) used for manufacturing a conductive pattern such as a gate wiring or a gate electrode made of a conductive film used in a liquid crystal display device. More specifically, the present invention relates to an etching solution and an etching method that are excellent in foaming suppression effect and wettability and that can obtain a highly accurate conductive pattern without etching residue.

  In recent years, with the increase in size, thickness, and weight of color liquid crystal televisions, plasma televisions, personal computers, etc., the gate wiring and electrodes used in these are conductive films that are patterned conductive films on substrates such as glass. Sex patterns are spreading rapidly. The etching solution used for manufacturing the conductive pattern is required to have higher performance. In particular, in order to maintain the stable electrical characteristics of the obtained conductive pattern in the performance enhancement, the etching solution can perform etching without etching residue of the conductive film during etching, and obtain a highly accurate conductive pattern. Performance is required.

  For the conductive pattern, a conductive film formed on a substrate is used to form an etching mask having a desired pattern by a photolithography method or a printing method, and the conductive pattern is not covered with an etching mask by an acidic etching solution. The film is obtained by etching and removing the film by a method such as spray etching or immersion etching, and after etching, the etching mask is removed by an alkaline aqueous solution or an organic solvent.

  In general, the above acidic etching solution is mixed with an etching agent for a certain type of conductive film and a surfactant for the purpose of improving wettability in order to perform uniform etching. However, conventional surfactants are inferior in oxidation resistance to strong oxidizing compounds in the above-mentioned etching agents, and therefore cannot exhibit sufficient wettability and liquid drainage effects. Further, the surfactant induces foaming during the preparation of the etching solution or during etching. In particular, the generation of bubbles in the etching solution is likely to occur in a circulation process in which the etching solution is used while being filtered and in an etching process using a spray method.

  The generation of the bubbles in the etching solution is caused by the bubbles adhering to the conductive film or etching mask surface formed on the substrate in the conductive pattern manufacturing process, and the adhering part is inhibited by etching. An etching residue of the film is generated. This is because an electrically conductive pattern with high accuracy cannot be obtained, and the electric characteristics (conductivity) of the obtained patterned gate wiring or electrode become unstable. Furthermore, in order to suppress the generation of the bubbles as much as possible, it is necessary to replenish with a new etching solution, and the etching apparatus equipment including the replenishing equipment for the etching liquid becomes considerably large, resulting in poor production efficiency.

  In addition, when the wettability and the running out of the etching solution are insufficient, when the conductive pattern is manufactured by the spray etching method, the substrate to be etched is moved in the horizontal direction by a roller conveyor or the like, and is publicly known. Using a computer-controlled spray device, etching from multiple spray nozzles while swinging the nozzles and adjusting the amount of discharged liquid causes overetching due to retention of the etching liquid in the center of the substrate to be etched Etching unevenness due to poor wetting occurs, and the line width and opening of the obtained gate wiring or electrode etc. are narrowed, and the size of the opening is increased, resulting in high-precision electrical conductivity. I can't get a pattern. This means that the above-described gate wiring or electrode is disconnected or a change occurs in electric resistance, and stable conductivity cannot be obtained.

  In addition, when a gate wiring or an electrode of a liquid crystal display device is manufactured using a conventional acidic etchant, a dissolved product of the conductive film dissolved by the etchant or a hydrolyzed product of the etchant composition, etc. Tends to adhere to the glass substrate surface as a residue. These residues hinder the transparency of the glass substrate having the above gate wiring and electrodes.

  A certain patent document 1 is disclosed as the conductive film etching solution. The etching solution disclosed in Patent Document 1 contains a mixture of a perfluoroalkyl sulfonate having a linear fluorocarbon group and a perfluoroalkyl sulfonate having a branched fluorocarbon group as a surfactant. Etching solution.

  The etching solution of Patent Document 1 disclosed above is superior in chemical stability of oxidation resistance compared to an etching solution containing a conventional hydrocarbon-based surfactant, and is suitable for an etching target material or a resist. Since the wettability and the liquid cutting property are improved, the etching can be performed with high accuracy and less consumption of the etching solution during the etching.

  However, the etching solution tends to foam gradually while being repeatedly circulated and used while circulating and filtering the etching solution. In addition, when manufacturing conductive patterns such as wiring and electrodes while etching using the spray method using the etching solution that has passed over time, a new etching solution is added as necessary to increase foaming. It is necessary to replenish, and the etching equipment facilities including the replenishing equipment for the etching solution become considerably large, resulting in poor production efficiency.

  In view of the above, there is a demand for an etching solution and an etching method capable of obtaining a highly accurate conductive pattern having stable electrical characteristics without causing etching residue due to generation of bubbles during etching.

JP 2008-294054 A

  Accordingly, an object of the present invention is to provide an etching solution and an etching method which are excellent in foaming suppression effect and wettability during etching and can obtain a highly accurate conductive pattern without etching residue.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that an etching solution containing the following conductive film etching agent (a) and the compound (b) represented by the general formula (1) is etched. In this case, the inventors found that the etching solution is excellent in foaming suppression effect and wettability, and can obtain a highly accurate conductive pattern with no etching residue.

The above object is achieved by the present invention described below. That is, the present invention is represented by the conductive film etching agent (a) having at least ceric ammonium nitrate and at least one selected from perchloric acid, nitric acid and acetic acid, and the following general formula (1). And an etching solution for a conductive film, characterized by containing the compound (b).
(Rf1SO ₂ ) (Rf2SO ₂ ) NX (1)
(Rf1 and Rf2 in the above formula are linear fluorocarbon groups having 1 to 6 carbon atoms in which all of the alkyl group hydrogens are replaced by fluorine, or fluorocarbons having 1 to 6 carbon atoms branched. And X is a potassium ion, a lithium ion, or a sodium ion.)

  Moreover, in preferable embodiment of this invention, the compounding quantity of the said ceric ammonium nitrate is the quantity which occupies 50 mass%-90 mass% in the said etching agent for electrically conductive films (a), and for the said electrically conductive film The concentration of the etching agent (a) is 10% by mass to 30% by mass, the concentration of the compound (b) is 0.01% by mass to 0.1% by mass, and the surface tension is 15 mN / m to It is preferably 30 mN / m and the defoaming time is 20 seconds or less.

  Moreover, this invention provides the etching method of the electrically conductive film characterized by etching the electrically conductive film formed on the board | substrate for electrically conductive films using the etching liquid of the said this invention.

  The etching solution of the present invention is effective for producing a highly accurate conductive pattern having more stable conductivity. In addition, the effect of suppressing foaming at the time of etching has an effect that the etching apparatus can be set more compactly because it is not necessary to frequently replenish a new etching solution in order to prevent generation of bubbles.

Next, the present invention will be described in more detail with reference to preferred embodiments for carrying out the invention. The compound (b) that mainly characterizes the present invention is a compound represented by the following general formula (1).
(Rf1SO ₂ ) (Rf2SO ₂ ) NX (1)
(Rf1 and Rf2 in the above formula are linear fluorocarbon groups having 1 to 6 carbon atoms in which all of the alkyl group hydrogens are replaced by fluorine, or fluorocarbons having 1 to 6 carbon atoms branched. And X is a potassium ion, a lithium ion, or a sodium ion.)
Said compound (b) can be used individually or in mixture of 2 or more types.

  The compound (b) is a compound having 1 to 6 carbon atoms in the fluorinated carbon group constituting them as shown in the general formula (1), preferably of the fluorinated carbon groups of Rf1 and Rf2. A compound in which the number of carbon atoms is at least one selected from 1, 2, 3, 4 and 6 compounds, and particularly preferably a compound in which the number of carbon atoms of the fluorocarbon groups of Rf1 and Rf2 is 4 Can be mentioned.

  Moreover, the metal X which comprises the said compound (b) is a potassium ion, a lithium ion, or a sodium ion, Preferably it is a potassium ion. Since the compound (b) composed of these metals X has good solubility in the obtained etching solution and does not cause white turbidity in the obtained etching solution, no white spots are generated in the obtained conductive pattern. . The above white spots impair the transparency of the glass substrate on which the thin film transistors of the liquid crystal panel of the liquid crystal display device are formed.

Examples of the compound (b) include potassium salts, lithium salts, and sodium salts of bisperfluoroalkylsulfonimide having a fluorocarbon group having the above-mentioned carbon number, preferably potassium salts of bisperfluorobutanesulfonimide. , Lithium salts, and sodium salts, and the potassium salt of bisperfluorobutanesulfonimide, which is particularly preferably (C ₄ F ₉ SO ₂ ) ₂ NK. Said compound (b) can be used individually or as a mixture which mixed 2 or more types.

  The concentration of the compound (b) is preferably 0.01% by mass to 0.1% by mass and more preferably 0.01% by mass to 0.05% by mass in the obtained etching solution. When the concentration of the compound (b) is too high, the defoaming time of the obtained etching solution becomes long and the foaming suppression effect is lowered. On the other hand, if the concentration is too low, the defoaming time of the resulting etching solution is shortened and the foam suppression effect is improved, but conversely, the wettability effect on the conductive film and resist is reduced, and uneven etching cannot be performed. A highly accurate conductive pattern cannot be obtained.

  The etching liquid of this invention contains the etching agent for electrically conductive films (a) other than the said compound (b) as an essential component. The conductive film etching agent (a) has at least ceric ammonium nitrate and at least one selected from perchloric acid, nitric acid and acetic acid. That is, ceric ammonium nitrate is an essential component, and any one component selected from perchloric acid, nitric acid and acetic acid is used alone, or two or more components are appropriately blended.

  The conductive film etching agent (a) is preferably, for example, ceric ammonium nitrate / perchloric acid / nitric acid; ceric ammonium nitrate / nitric acid; ceric ammonium nitrate / perchloric acid; Examples include ceric ammonium / acetic acid.

  In the etching agent for conductive film (a), the blending amount of ceric ammonium nitrate is preferably an amount occupying 50% by mass to 90% by mass in the total amount of the etching agent for conductive film (a). When the amount of ceric ammonium nitrate is too large, ceric ammonium nitrate is likely to be precipitated in the resulting etching solution, while when the amount is too small, the conductive film that forms a conductive pattern is formed. The etching rate with respect to is slow, and the stability of the etching rate is deteriorated.

  The concentration of the conductive film etching agent (a) is preferably 10% by mass to 30% by mass, and more preferably 20% by mass to 28% by mass in the obtained etching solution. When the concentration of the etching agent for conductive film (a) is within the above range, an excellent etching effect is exhibited as a stable conductive film etching solution due to a synergistic effect with the compound (b).

  In the etching solution of the present invention, the conductive film etching agent (a) and the compound (b) are appropriately mixed in water, preferably so as to be within the concentration range, and uniformly mixed and dissolved by a known method. To prepare. As said water, ion-exchange water, soft water, distilled water etc., Preferably ion-exchange water is mentioned.

The etching solution of the present invention preferably has a surface tension of 15 mN / m to 30 mN / m, more preferably 17 mN / m to 25 mN / m. If the surface tension exceeds the upper limit, the wet wettability with respect to the conductive film and the patterned etching mask formed on the conductive film is inferior, and sufficient etching cannot be performed. A conductive pattern cannot be obtained. The surface tension in the present invention is a value determined by the following [Surface Tension Measurement Method].
[Surface Tension Measurement Method]: Measured at 25 ° C. by an electro-equilibrium method (platinum plate suspension method).

  The etching solution of the present invention preferably has a defoaming time of 20 seconds or less that exhibits a foaming suppression effect. When the above-mentioned defoaming time exceeds the above range, the foaming suppression effect is reduced, and the etching liquid bubbles generated on the conductive film and etching mask formed on the substrate during the etching in the manufacturing process of the conductive pattern As a result, the portion where the bubbles are attached is inhibited by etching, resulting in an etching residue of the conductive film. This means that since a highly accurate conductive pattern cannot be obtained, the electrical resistance of the obtained gate wiring or electrode changes, and stable conductivity cannot be obtained. Furthermore, in order to suppress the generation of the bubbles as much as possible, it is necessary to replenish with a new etching solution, and the etching apparatus equipment including the replenishing equipment for the etching liquid becomes considerably large, resulting in poor production efficiency. The defoaming time in the present invention is a value determined by the following [Defoaming time measuring method].

[Defoaming time measurement method]
20 ml of the obtained etching solution is put into a 50 ml test bottle (screw vial), shaken 50 times to foam, and the time until the foam generated at the top of the test bottle is removed is measured.

  The etching solution of the present invention can be used to produce conductive patterns used as electronic components such as gate wirings and electrodes used in liquid crystal display devices and optical devices. In particular, it is effective for manufacturing conductive patterns of gate wirings and electrodes used in liquid crystal display devices.

  An etching method for producing a conductive pattern by etching a conductive film formed on a conductive film substrate using the etching solution of the present invention will be described. As an etching method using the etching solution of the present invention, for example, the following steps (1) to (5) are included. First, in the step (1), a known positive photosensitive resin composition is applied by a known coating method on a conductive chromium-based metal thin film formed on a conductive film substrate, and dried to a thickness of 0.5 μm to 1 μm. A coating film of photosensitive resin having a thickness of 2 μm (dry thickness) is formed. Examples of the conductive film substrate include glass substrates such as alkali glass, soda lime glass, and float glass for liquid crystal displays, silicone substrates, polycarbonate, triacetyl cellulose, polymethacryl, polyester, aromatic polyamide, polyimide, and the like. Plastic substrate and the like.

  As said chromium-type metal thin film which has electroconductivity, Preferably it is 150 nm-300 nm which consists of electroconductive chromium metal by methods, such as a well-known vapor deposition method, sputtering method, and plating method, on said electrically conductive film board | substrate. A conductive thin film is formed. The above chromium metal does not contain impurities that impair the conductivity such as chromium nitride, chromium oxide, chromium nitride oxide, chromium oxide carbide, etc., and these products are mixed in when forming the conductive thin film. Must be suppressed.

  In addition, as the positive photosensitive resin composition, any known positive photosensitive resin composition used for manufacturing a conductive pattern using the chromium metal thin film may be used. Examples thereof include positive type photosensitive resin compositions such as AZ-TFP-210K manufactured by AZ Electronic Materials, or Microposit SC-500 manufactured by Rohm and Haas.

  In the step (2), a conductive pattern for a desired gate wiring or the like is applied to a photosensitive resin coating formed on the conductive chromium-based metal thin film, and an active energy such as ultraviolet rays through a photomask. To draw exposure.

  In the step (3), after exposure drawing, development is performed by a known developing method such as a spray method or a dipping method using a known alkaline developing aqueous solution such as tetramethylammonium hydroxide, sodium carbonate, or sodium metasilicate. Then, an etching mask having the shape of the photomask pattern is formed. The obtained etching mask is baked and cured as necessary.

  In the step (4), using the etching solution of the present invention, while circulating and filtering the etching solution in a clean room temperature (20 to 30 ° C.) atmosphere, by a known etching method such as a spray method or a dipping method, The conductive chromium metal thin film not covered with the etching mask is etched, and the thin film is dissolved and removed to expose the conductive film substrate such as glass. As for the condition of spray etching by the above spray method, etching is performed for 30 seconds to 130 seconds under the condition of spray pressure of 0.1 to 0.2 MPa.

  In the step (5), after the etching, the etching mask is removed using a known alkaline stripping solution that can peel off the etching mask, and further washed with water to expose the conductive pattern on the conductive film substrate. It can be a gate wiring or electrode made of a conductive chromium metal thin film used in a display device.

  Next, the present invention will be described more specifically with reference to examples and comparative examples. Unless otherwise specified, “part” or “%” in the text is based on mass. In addition, this invention is not limited to the following Example.

[Examples 1 to 5] (Etching liquids J1 to J5)
As shown in Table 1, etching agent for conductive film (a), compound (b), and ion-exchanged water were blended, and stirred and mixed uniformly to prepare etching solutions J1 to J5 of the present invention. The compound (b) is as follows.
Compound (b)
(C ₄ F ₉ SO ₂ ) ₂ NK (Bisperfluorobutanesulfonimide potassium salt)

[Comparative Examples 1 to 3] (Etching liquids K1 to K3)
Surfactant Y was used in place of compound (b) in the Examples, and each component was blended as shown in Table 1, and stirred and mixed uniformly to prepare etching solutions K1 to K3. The surfactant Y is as follows.
・ Surfactant Y (perfluoroalkyl sulfonate)
Y1: A mixture of 70 parts of C ₈ F ₁₇ SO ₃ K having a linear fluorocarbon group and 30 parts of C ₈ F ₁₇ SO ₃ K having a branched fluorocarbon group.
Y2: A mixture of 70 parts of C ₈ F ₁₇ SO ₃ Na having a linear fluorocarbon group and 30 parts of C ₈ F ₁₇ SO ₃ Na having a branched fluorocarbon group.
Y3: C ₈ F ₁₇ SO ₃ K simple substance having a linear fluorocarbon group.

上記表中の数値は配合部数を表し、硝酸、過塩素酸および酢酸の配合部数は１００％成分に換算した値である。

The numerical value in the said table | surface represents a compounding part number, and the compounding part number of nitric acid, perchloric acid, and an acetic acid is the value converted into a 100% component.

  A conductive pattern for a gate wiring for a liquid crystal display is formed by etching the conductive film formed on the conductive film substrate by the following etching method using the etching solutions of the above-mentioned examples and comparative examples, The following measurement methods evaluated the foaming suppression state, wettability, etching residue of the conductive pattern, and etching accuracy of the etching solution. The evaluation results are shown in Table 2.

(Etching method)
A conductive chrome metal conductive film having a thickness of 170 nm is formed on the surface of a glass substrate for liquid crystal display (conductive film substrate) by a sputtering method. Pogitt SC-500) was applied to 1 μm (dry thickness), and after drying, the coating surface was exposed and drawn with an ultrahigh pressure mercury lamp through a photomask pattern for a gate wiring for a liquid crystal display device. Thereafter, spray development was performed with an alkali developing aqueous solution (2.38% tetramethylammonium hydroxide aqueous solution) to form an etching mask for gate wiring. Next, a spray etching apparatus (NE-7000 manufactured by Takizawa Sangyo Co., Ltd.) is used while circulating and filtering the etching solution using the etching solution of the above-described example or comparative example in which the etching mask is adjusted to 23 ° C. Used for etching for 90 seconds (just etching 80 seconds + overetching 10 seconds) under spray conditions of nozzle scan 80 times / min, substrate rotation speed 150 rpm, etchant flow rate 250 g / min, and covered with an etching mask. The conductive film for gate wiring was formed by etching and rinsing away the non-conductive film.

(Etching liquid foam suppression state)
The foaming suppression state of the etching solution generated during the etching of each etching solution was measured by [Method for measuring the defoaming time] of the etching solution. From the above measurement results, the shorter the defoaming time, the better the foam suppression effect. On the other hand, the longer the defoaming time, the poorer the foam suppression effect, indicating that more bubbles are generated in the etching solution.

(Wettability)
The wettability of the etching solution with respect to the conductive film and the etching mask was measured by the [Surface Tension Measurement Method] of the etching solution. From the above measurement results, the smaller the measured value, the better the wettability, while the larger the measured value, the lower the wettability.

(Etching residue of conductive pattern)
The obtained conductive pattern was visually observed with a 1000 × microscope, and unnecessary conductive chromium metal thin films remaining on the glass substrate for liquid crystal displays other than the conductive pattern were measured and evaluated by the following evaluation methods.
○: An unnecessary conductive chromium metal thin film does not exist, and no etching residue of the conductive pattern is observed.
(Triangle | delta): The unnecessary electroconductive chromium metal thin film exists partially, and the etching remainder of an electroconductive pattern is recognized partially.
X: An unnecessary electroconductive chromium metal thin film exists in the whole, and the etching residue of an electroconductive pattern is recognized by the whole surface.

(Etching accuracy)
The absolute value σ (μm) of the line width variation of the line having a design dimension of 8 μm of the conductive pattern for gate wiring obtained by the etching method was measured with a laser microscope (OLS1100, manufactured by Olympus Corporation).

  From the above evaluation results, it was demonstrated that the etching solution of the present invention is excellent in the foaming suppression effect and wettability of the etching solution, and a highly accurate conductive pattern with no etching residue of the conductive pattern can be obtained. On the other hand, since the conventional etching solution seen in the comparative example is inferior in the foaming suppression effect of the etching solution, there is a risk that the etching residue of the conductive pattern accompanying the generation of bubbles occurs.

  Since the etching solution of the present invention provides a conductive pattern having good conductivity and high accuracy, etching used for manufacturing a conductive pattern used for a gate wiring or a gate electrode used in a liquid crystal display device. It can be used effectively as a liquid.

Claims (7)

An etching agent for conductive film (a) having at least ceric ammonium nitrate and at least one selected from perchloric acid, nitric acid and acetic acid; and a compound (b) represented by the following general formula (1): An etching solution for a conductive film, comprising:
(Rf1SO ₂ ) (Rf2SO ₂ ) NX (1)
(Rf1 and Rf2 in the above formula are linear fluorocarbon groups having 1 to 6 carbon atoms in which all of the alkyl group hydrogens are replaced by fluorine, or fluorocarbons having 1 to 6 carbon atoms branched. And X is a potassium ion, a lithium ion, or a sodium ion.)   2. The etching solution according to claim 1, wherein the mixing amount of ceric ammonium nitrate is an amount that occupies 50 mass% to 90 mass% in the total amount of the etching agent for conductive film (a).   The etching solution according to claim 1 or 2, wherein the concentration of the conductive film etching agent (a) is 10% by mass to 30% by mass.   The etching liquid according to claim 1 whose concentration of said compound (b) is 0.01 mass%-0.1 mass%.   The etching liquid according to any one of claims 1 to 4, wherein the surface tension is 15 mN / m to 30 mN / m.   The etching solution according to any one of claims 1 to 5, wherein the defoaming time is 20 seconds or less.   A method for etching a conductive film, comprising etching the conductive film formed on the conductive film substrate using the etching solution according to claim 1.