JP5717519B2 - Stripper for photoresist - Google Patents

Description

  The present invention relates to a photoresist stripping solution. In particular, the present invention relates to a photoresist stripping solution suitably used for manufacturing Cu or Cu alloy wiring boards for flat panel displays (FPD) such as liquid crystal displays and organic EL displays.

  In ICs, LSIs, etc., with the high integration of semiconductor elements and the reduction in chip size, the miniaturization and multilayering of wiring circuits have progressed, resulting from the resistance (wiring resistance) and wiring capacitance of metal films used in semiconductor elements. Wiring delay or the like becomes a problem, and copper (Cu) having a resistance lower than that of aluminum (Al) is used in order to improve wiring resistance.

  On the other hand, Al has been adopted as a wiring material in FPDs such as liquid crystal displays. However, in recent years, it has been necessary to lower the wiring resistance as in the case of semiconductor elements because of the increase in substrate size, higher definition, and organic EL compatibility. However, attempts have been made to use Cu, Cu alloy, or the like having a low resistance as a wiring material. Cu has a problem of being easily corroded in an aqueous solution because the protective film of the oxide film formed on the surface is weaker than Al, and semiconductors prevent corrosion by a dry process using plasma.

  However, since FPD has a larger substrate size than a semiconductor and it is difficult to apply a dry process using plasma, corrosion prevention of a substrate on which Cu wiring is formed or a substrate on which Cu wiring and an inorganic material layer are formed is possible. Development of a photoresist stripping solution for achieving a well-balanced stripping property of a photoresist film and a modified photoresist film has been performed.

  In Patent Document 1, (a) 10 to 65% by weight of a nitrogen-containing organic hydroxy compound, (b) 10 to 60% by weight of a water-soluble organic solvent, (c) 5 to 50% by weight of water, (d) ) A photoresist stripping solution containing 0.1 to 10% by weight of a benzotriazole-based compound is disclosed, and (a) the nitrogen-containing organic hydroxy compound has an acid dissociation constant (pKa) in an aqueous solution at 25 ° C. of 7. 5 to 13 amines are preferred.

However, in such a composition, the pH of the photoresist stripping solution is an alkaline solution of 11 or more, and the copper wiring is easily dissolved by generating HCuO ₂ ⁻ or CuO ₂ ⁻ ions by dissolved oxygen in the solution, that is, Corrosion. Further, the anticorrosive (d) benzotriazole-based compound cannot form a polymer film having a high degree of polymerization in a strong alkaline solution and has a low anticorrosion property. Therefore, the addition amount must be increased, and excessively added benzotriazole There is a possibility that the system compound remains on the Cu wiring and remains as a foreign substance.

  In Patent Document 2, (a) primary or secondary alkanolamine is 5-45 wt%, (b) polar organic solvent and water are 50-94.95 wt%, (c) maltol, uracil, 4-hydroxy- A photoresist stripping solution comprising 0.05 to 10% by weight of at least one heterocyclic compound selected from the group consisting of 6-methyl-2-pyrone and the like has been proposed. Even in such a composition, the pH of the photoresist stripping solution is a strong alkali of 11 or more, the copper wiring is easily corroded, and when the anticorrosive agent (c) is added excessively, the anticorrosive agent (c) becomes the Cu wiring. It may remain on top and remain as foreign matter.

Patent Document 3 proposes a method of manufacturing a semiconductor device in which a copper wiring pattern is formed on a substrate, and then the copper wiring pattern is cleaned with an aqueous solution containing 2 × 10 ⁻⁶ to 10 ⁻¹ mol · m ^{3 of} benzotriazole. ing.

Japanese Patent No. 3514435 JP 2008-216296 A Japanese Patent No. 3306598

  In Patent Document 1, the etching of Cu is evaluated by performing a dry etching process. It is known that the etchant of Cu and the etchant of Al are different. In particular, in an oxidant-based etchant that wet-etches Cu, the resist layer is altered and is difficult to peel off. In other words, the photoresist stripping solution disclosed in Patent Document 1 cannot be simply applied as a photoresist stripping solution used in the step of wet-etching Cu or Cu alloy.

  Patent Document 2 considers this point, and exactly discloses a photoresist stripping solution used when wet-etching Cu or a Cu alloy on a large-area substrate. However, since the primary or secondary alkanolamine used as the main component of the stripping solution shows strong alkali, the action of the heterocyclic compound added as a corrosion inhibitor is weakened. Therefore, the heterocyclic compound has a considerably large composition of 0.05 to 10 wt%.

  Patent Document 2 does not consider that these heterocyclic compounds added as corrosion inhibitors form insoluble compounds with Cu to prevent corrosion, but at the same time, on the Cu layer. It is a point which reduces the adhesiveness between the layers processed into a film-forming process. That is, the amount of 0.05 to 10 wt% of the corrosion inhibitor has a problem that the adhesion with the layer formed on the Cu layer is lowered.

  Patent Document 3 describes that BTA forms an insoluble compound with Cu in order to prevent Cu from being corroded when it comes into contact with a cleaning agent in the cleaning process when peeling the photoresist on the Cu film. However, Cu is disclosed as a treatment in anisotropic dry etching, although it is disclosed that BTA is precipitated by addition of excess BTA. In addition, as in Patent Document 2, there is a problem of lowering the adhesion with the next layer on Cu, and this adhesion is not considered.

  A stripping solution composition in such a conventional Cu wiring substrate to which BTA is added forms an insoluble compound between BTA and Cu, and lowers the adhesion to the layer formed on the Cu layer. It had the problem that.

  The present invention solves the above-described conventional problems. When a wiring or the like is formed by wet-etching a Cu or Cu alloy layer on a large-area substrate, it is exposed to a Cu etchant and deteriorates and peels off. An object of the present invention is to provide a photoresist stripping solution that peels off a photoresist that has become difficult to damage without damaging the Cu layer, and that does not reduce the adhesion between the layer and the layer deposited on the Cu layer. To do.

  The photoresist stripping solution is a water-based stripping solution using tertiary amine as a main ingredient and water, and is a composition not containing a corrosion inhibitor typified by a benzotriazole-based compound. It is.

More specifically, the photoresist stripping solution of the present invention comprises:
Tertiary alkanolamine 1-9 wt%, of a polar solvent 10-70 wt%, water 10 to 40 wt% Tona is, the polar solvent is a diethylene glycol monobutyl ether, a mixed solvent of propylene glycol, corrosion It is characterized by not adding an inhibitor . Further, the stripping solution for photoresist of the present invention comprises tertiary alkanolamine in an amount of 1 to 9% by mass, polar solvent in an amount of 10 to 70% by mass, and water in an amount of 10 to 40% by mass. It is only a mixed solvent of butyl ether and propylene glycol.

In the photoresist stripping solution,
The tertiary alkanolamine is N-methyldiethanolamine (MDEA).

  The photoresist stripping solution of the present invention uses a tertiary amine as the amine used as the main agent. Tertiary amines have relatively low basicity compared to primary or secondary amines. Also, the amount used is small relative to the total amount of the stripping solution. Therefore, the degree to which copper is corroded when the resist is peeled is extremely small.

  Moreover, since the corrosion inhibitor is not contained, no impurities remain on the copper surface after the resist is peeled off. Therefore, even if another film is formed on the copper film, peeling between the film layers does not occur. On the other hand, the releasability of the resist is at a level that causes no problem in practical use. Moreover, since a trace amount additive is not contained, there exists an effect that it is easy to perform a regeneration process.

Photoresist stripping liquid of the present invention, tertiary alkanolamines are 1-9 wt%, of a polar solvent 10-70 wt%, water Ri Tona 10 to 40% by mass, the polar solvent is a diethylene glycol monobutyl ether , a mixed solvent of propylene glycol, Ru der those without added corrosion inhibitors. Further, the stripping solution for photoresist of the present invention comprises tertiary alkanolamine in an amount of 1 to 9% by mass, polar solvent in an amount of 10 to 70% by mass, and water in an amount of 10 to 40% by mass. Only a mixed solvent of butyl ether and propylene glycol.

  As the tertiary alkanolamine, specifically, the following can be suitably used. Triethanolamine, N, N-dimethylethanolamine, N, N-diethylethanolamine, N, N-dibutylethanolamine, N-methylethanolamine, N-ethylethanolamine, N-butylethanolamine, N-methyldiethanolamine Etc. These may be used in combination of a plurality of types.

  The polar solvent may be an organic solvent having an affinity for water. Moreover, it is more suitable if the mixing property with said tertiary alkanolamine and diethylene glycol monobutyl ether mentioned later is favorable.

  Examples of such water-soluble organic solvents include sulfoxides such as dimethyl sulfoxide; sulfones such as dimethyl sulfone, diethyl sulfone, bis (2-hydroxyethyl) sulfone, and tetramethylene sulfone; N, N-dimethylformamide, N-methyl Amides such as formamide, N, N-dimethylacetamide, N-methylacetamide, N, N-diethylacetamide; N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-propyl-2-pyrrolidone, N -Lactams such as hydroxymethyl-2-pyrrolidone and N-hydroxyethyl-2-pyrrolidone; 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-diisopropyl -2-imidazolidinones such as imidazolidinone; Glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, Examples thereof include polyhydric alcohols such as diethylene glycol monoalkyl ether such as diethylene glycol monobutyl ether (alkyl is a lower alkyl group having 1 to 6 carbon atoms), and derivatives thereof. Among these, at least one selected from dimethyl sulfoxide, N-methyl-2-pyrrolidone, and diethylene glycol monobutyl ether is preferably used from the viewpoints of further peelability and corrosion resistance to the substrate. These components may be used in combination of a plurality of types. Among these, a mixed solvent of diethylene glycol monobutyl ether and propylene glycol is particularly preferable. This is because the pH is in a neutral region, the Cu layer is not corroded, and the permeability to the photoresist to be peeled is excellent.

  The blending amount of the tertiary alkanolamine in the stripping solution for photoresist of the present invention is 1 to 9% by mass with respect to the total amount of the stripping solution. It is because corrosion will arise in Cu layer when 9 mass% or more is contained. Further, when the amount is 1% by mass or less, the photoresist cannot be peeled off. Thus, in the present invention, the amount of tertiary alkanolamine is relatively small.

  The ratio of the polar solvent is 10 to 70% by mass with respect to the total amount of the stripping solution. Moreover, water is 10-40 mass%. The polar solvent and water may be prepared so that the viscosity of the stripping solution, which is a mixed solution of a tertiary alkanolamine, is suitable at the temperature to be used.

  In the present invention, it is not particularly added as a corrosion inhibitor. This is to prevent the corrosion inhibitor added for preventing copper corrosion from remaining on the surface of copper and reducing the adhesive force with the layer laminated on the copper layer. That is, the resist is peeled off and the peeled copper surface is not corroded by the stripping solution and the temperature control so that there is no practical problem. Therefore, temperature control when using the stripping solution is strictly performed. In the following examples of the present invention, the stripping solution and the object to be treated are strictly managed so as to be 40 ° C.

  Examples of the present invention are shown below together with comparative examples, but the present invention is not limited to the following examples. First, sample preparation and evaluation methods will be described.

<Method for producing evaluation substrate>
In order to show the effect of the stripping solution for photoresist of the present invention, an evaluation substrate was prepared by the following procedure. This is usually a process using a 6-inch wafer and is called a spin processor. First, ITO (Indium Tin Oxide: transparent electrode) was formed on a 6-inch wafer-shaped glass substrate (thickness 1 mm) by sputtering. The thickness was 0.2 nm (2,000 angstroms).

  Next, a Cu film for gate lines was formed on the ITO film to a thickness of about 0.3 nm by vapor deposition. Next, a positive resist was applied to a thickness of 1 μm with a spinner. After the resist film was formed, prebaking was performed for 2 minutes in an environment of 100 ° C.

  Next, it exposed using the photomask. The photomask used was a linear pattern with a width of 5 μm. Then, development was performed using tetramethylammonium hydroxide (TMAH). This removed the exposed portion of the photoresist.

Etching was performed for 1 minute using an oxidant-based etchant heated to 40 ° C. By this treatment, the Cu film other than the portion where the photoresist remained was removed. The substrate after the treatment was washed with flowing pure water for 1 minute. The cleaned substrate was dried and stored for 1 minute in a spin drying apparatus at 8,000 rpm. At this time, nitrogen gas having a flow rate of 0.5 m ³ / s passed through the filter was blown from the center of rotation.

<Cu corrosion resistance>
The following procedure was implemented about Cu anticorrosion property. First, the substrate was cut into 10 mm × 60 mm strips so that the gate lines (made of the Cu layer) were in the longitudinal direction. 20 ml of stripping solution prepared with the composition shown in Table 1 was dispensed into a vial (30 ml). Then, the peeling solution was heated to 40 ° C. with a water bath while still in the vial. And the prepared evaluation board | substrate was put in the peeling liquid which became 40 degreeC, and it was immersed for 30 minutes. In addition, since this evaluation is an experiment for investigating how much the stripping solution corrodes Cu, it was immersed for a long time of 30 minutes.

After immersion, the evaluation substrate was pulled up from the stripping solution and washed with flowing pure water for 1 minute. After washing, it was dried for 2 minutes with dry air at a flow rate of 0.8 m ³ / s. Dry air was passed through the filter, but the temperature was room temperature. The surface and cross section of the treated substrate were observed by SEM (Scanning Electron Microscope), and the Cu concentration of the stripping solution remaining in the vial was analyzed by atomic absorption spectrometry.

  For observation with SEM, evaluation was performed according to the following criteria. The case where no corrosion was observed in the planar observation at 6,000 times and the cross-sectional observation at 50,000 times by SEM was marked as “no corrosion”. In addition, although both the line width and the film thickness decreased, the wiring remaining was marked as “corrosion” with a triangle mark. Also, those with no wiring were marked as crosses with severe “corrosion”. The evaluation results of each sample are shown in Table 1.

<Peelability>
The peelability of the photoresist was evaluated by the same procedure as that of Cu. Specifically, it was performed as follows. First, the substrate was cut into 10 mm × 60 mm strips so that the gate lines (made of the Cu layer) were in the longitudinal direction. 20 ml of stripping solution prepared with the composition shown in Table 1 was dispensed into a vial (30 ml). Then, the peeling solution was heated to 40 ° C. with a water bath while still in the vial. And the prepared evaluation board | substrate was put in the peeling liquid which became 40 degreeC, and it was immersed for 30 minutes.

After immersion, the evaluation substrate was pulled up from the stripping solution and washed with flowing pure water for 1 minute. After washing, it was dried for 2 minutes with dry air at a flow rate of 0.8 m ³ / s. Dry air was passed through the filter, but the temperature was room temperature. The surface of the treated substrate was observed with an SEM.

  In the observation with SEM, the peelability was evaluated according to the following criteria. When there was no resist residue over the entire length of the evaluation substrate (60 mm) by planar observation at 6,000 times with SEM, the mark was marked as “no residue”. Further, when there is a residue or when there is no meaning to evaluate severe corrosion of Cu, a minus sign (“−”) is given as “not evaluated”.

<Resist solubility>
The resist solubility with respect to the stripping solution was evaluated as follows. In this embodiment, since the photoresist is exposed to an oxidant etchant, it is denatured and cannot be easily removed. First, the substrate was cut into strips of 20 mm × 60 mm so that the gate lines (made of the Cu layer) were in the longitudinal direction. 50 ml of the stripping solution prepared with the composition shown in Table 1 was dispensed into a vial (50 ml). Then, the peeling solution was heated to 40 ° C. with a water bath while still in the vial. Then, the prepared evaluation substrate was put in the stripping solution at 40 ° C., and the time until the resist was lifted was measured with a stopwatch.

  The resist solubility was evaluated according to the following criteria. When the resist was dissolved within 30 seconds after the evaluation substrate was immersed in the stripping solution, it was marked as “having sufficient dissolving power”. If it took 30 seconds or more, it was marked with a cross mark as “the solubility of the photoresist was not sufficient”.

<Film peeling>
Even if the photoresist modified by exposure to an oxidant-based etchant is sufficiently dissolved and the Cu film is not corroded, the corrosion inhibitor remains on the Cu film surface, and the adhesion to the layer deposited thereon If it is bad, it is not practical. Therefore, the following evaluation was performed on the assumption that the amount of the corrosion inhibitor on the surface of the Cu film is so small that there is no practical problem, in other words, that the film can be deposited on the Cu layer without any practical problem.

First, the substrate was cut into 10 mm × 60 mm strips so that the gate lines (made of the Cu layer) were in the longitudinal direction. 20 ml of stripping solution prepared with the composition shown in Table 1 was dispensed into a vial (30 ml). Then, the peeling solution was heated to 40 ° C. with a water bath while still in the vial. And the evaluation board | substrate prepared in the peeling liquid which became 40 degreeC was immersed for 30 second. Next, it was taken out from the stripping solution and washed with running pure water for 1 minute. After washing, it was dried for 2 minutes with dry air at a flow rate of 0.8 m ³ / s at room temperature.

Then, an insulating film (SiO ₂ ) was formed to a thickness of 0.1 μm on the surface of the substrate on which the Cu film was formed by sputtering. Then, gold was further formed on the insulating film by about 0.01 μm by sputtering, and SEM observation was performed at a magnification of 1,000 times. Film peeling was evaluated according to the following criteria. When the film was formed integrally on the Cu film, it was marked as “No film peeling”. In addition, when there was a part of the edge portion or flat portion of the Cu film that was recognized as a SiO ₂ peeling or a hole, it was marked as “film peeling”. If the insulating film on the Cu film is not completely insulated, it causes a short circuit and immediately leads to a defect. Therefore, it is necessary to evaluate it strictly.

  In addition to the above evaluation, the composition and pH of the stripping solution are shown in Table 1. In the composition shown in Table 1, the corrosion inhibitor is described as “corrosion inhibitor”. For comparison, monoethanolamine (MEA) which is a primary alkanolamine and N-methyldiethanolamine (MDEA) which is a tertiary alkanolamine were used for comparison. As a comparative example, benzotriazole (BTA), pyrocatechol, and sorbitol were added as corrosion inhibitors. The composition and evaluation results of Examples and Comparative Examples are described below.

Example 1
The composition of the stripping solution was prepared as follows. MDEA (N-methyldiethanolamine) was 5% by mass as amines, BDG (diethylene glycol monobutyl ether) was 40% by mass, PG (propylene glycol) was 24% by mass, and water was 31% by mass as a polar solvent. The pH was 10.5. This example does not contain an anticorrosive.

  The anticorrosion property of copper was triangular as an evaluation, but the evaluation was round for both the resist peelability, the resist solubility, and the peeling of the insulating film laminated on the copper layer. Although the elution amount of copper in the stripping solution was 0.79 ppm, there was no practical problem at all.

(Comparative Example 1)
The composition of the stripping solution was prepared as follows. MDEA was 5% by mass as amines, BDG was 40% by mass as a polar solvent, PG was 24% by mass, BTA was 1% by mass as a corrosion inhibitor, 1% by mass of sorbitol, and water was 29% by mass. The pH was 9.1.

  The corrosion resistance of copper and the peelability of the resist were evaluated as round. However, both the solubility of the resist and the peeling of the insulating film laminated on the copper layer were evaluated as bad. The elution amount of copper in the stripping solution was 0.05 ppm. This is because the resist solution was poor and the stripping solution did not erode the surface of the copper layer. Although the corrosion resistance of copper was improved, the resist could not be peeled off, and the insulating film laminated on the upper part of the copper layer was peeled off.

(Comparative Example 2)
The composition of the stripping solution was prepared as follows. MDEA was added 5 mass% as amines, BDG 40 mass% as a polar solvent, PG 24 mass%, BTA 0.5 mass% as a corrosion inhibitor, and water was 30.5 mass%. The pH was 9.3.

  The corrosion resistance of copper and the peelability of the resist were evaluated as round. However, both the solubility of the resist and the peeling of the insulating film laminated on the copper layer were evaluated as bad. The elution amount of copper in the stripping solution was 0.05 ppm. This is because the resist solution was poor and the stripping solution did not erode the surface of the copper layer. Although the corrosion resistance of copper was improved, the resist could not be peeled off, and the insulating film laminated on the upper part of the copper layer was peeled off.

(Comparative Example 3)
The composition of the stripping solution was prepared as follows. MDEA was added 5 mass% as amines, BDG 40 mass% as a polar solvent, PG 24 mass%, BTA 0.1 mass% as a corrosion inhibitor, and water 30.9 mass%. The pH was 10.0.

  The corrosion resistance of copper and the peelability of the resist were evaluated as round. However, both the solubility of the resist and the peeling of the insulating film laminated on the copper layer were evaluated as bad. The elution amount of copper in the stripping solution was 0.05 ppm. This is because the resist solution was poor and the stripping solution did not erode the surface of the copper layer. Although the corrosion resistance of copper was improved, the resist could not be peeled off, and the insulating film laminated on the upper part of the copper layer was peeled off.

(Comparative Example 4)
The composition of the stripping solution was prepared as follows. MEA (monoethanolamine) 5 mass% as amines, BDG 42 mass% as a polar solvent, PG 18 mass%, pyrocatechol 5 mass% as a corrosion inhibitor were added, and water was 30 mass%. The pH was 10.3.

  The anticorrosion properties of copper were evaluated. The copper surface was severely corroded and the copper layer disappeared, and the peelability could not be evaluated. The resist peelability was evaluated as a circle. Of course, since the copper layer itself has disappeared, the evaluation of the peelability of the insulating film was not worthy of evaluation.

(Comparative Example 5)
The composition of the stripping solution was prepared as follows. 5% by mass of MEA (monoethanolamine) as amines, 42% by mass of BDG as polar solvent, 18% by mass of PG, 0.05% by mass of BTA as corrosion inhibitor, and 34.95% by mass of water did. The pH was 11.5.

  The anticorrosion properties of copper were evaluated. The copper surface was severely corroded and the copper layer disappeared, and the peelability could not be evaluated. The resist peelability was evaluated as a circle. Of course, since the copper layer itself has disappeared, the evaluation of the peelability of the insulating film was not worthy of evaluation.

(Comparative Example 6)
The composition of the stripping solution was prepared as follows. MEA (monoethanolamine) was 20% by mass as amines, BDG was only 60% by mass as a polar solvent, 5% by mass of pyrocatechol was added as a corrosion inhibitor, and water was 15% by mass. The pH was 11.2.

  The anticorrosion properties of copper were evaluated. The copper surface was severely corroded and the copper layer disappeared, and the peelability could not be evaluated. The resist peelability was evaluated as a circle. Of course, since the copper layer itself has disappeared, the evaluation of the peelability of the insulating film was not worthy of evaluation.

  As described above, since the photoresist stripping solution of the present invention does not contain a corrosive agent, although the copper layer is somewhat corroded, it has good adhesion to the insulating layer laminated on the copper layer, and is practically used. There was no problem.

  The photoresist stripping solution of the present invention is suitable for use in general FPDs such as liquid crystal displays, solar cells, organic ELs, etc., which are manufactured by wet etching using Cu as a conductive wire, particularly large areas and require fine processing. be able to.

Claims (3)

Tertiary alkanolamine 1-9 wt%, of a polar solvent 10-70 wt%, water 10 to 40 wt% Tona is, the polar solvent is a diethylene glycol monobutyl ether, a mixed solvent of propylene glycol, corrosion Stripping solution for photoresist without adding an inhibitor . Photo that consists of tertiary alkanolamine 1-9% by mass, polar solvent 10-70% by mass, water 10-40% by mass, and the polar solvent is only a mixed solvent of diethylene glycol monobutyl ether and propylene glycol Stripping solution for resist. The stripping solution for photoresist according to claim 1 or 2 , wherein the tertiary alkanolamine is N-methyldiethanolamine (MDEA).