JP2004218034A - Metal mask manufacturing method and metal mask - Google Patents

Abstract

An object of the present invention is to eliminate a frame used in the past, simplify a manufacturing process such as laminating, eliminate a dimensional error due to a non-uniformity of tension at the time of pasting, which has been a problem in the past, and furthermore, a method of manufacturing a mask. Provided are a method for manufacturing a metal mask which is unlikely to cause permanent deformation and a metal mask.
After applying a photoresist on the surface of a metal plate, exposing and developing it, and partially thinning only one surface of the metal plate by primary etching, removing the photoresist, and further applying the photoresist on both surfaces. Then, after exposing and developing using a desired photomask on the front and back surfaces of the metal portion thinned by the primary etching, through holes are formed by secondary etching.
[Selection diagram] FIG.

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a metal mask used for depositing a deposit only on a desired portion by closely adhering to a substrate in a method of forming a fine pattern by a vapor deposition method, and a method for manufacturing the same.
[0002]
[Prior art]
2. Description of the Related Art In recent years, organic electroluminescent elements (organic EL), which are display devices, have attracted attention because they have a faster response time than liquid crystal displays, have a wide viewing angle, and can be made thinner because a backlight is not required. In the production of an organic EL device, after forming an ITO transparent electrode or the like on a transparent substrate, a pattern of an organic electroluminescent layer is formed by a vapor deposition method via a metal mask tightly held on the substrate. In the photolithography method, which is a usual fine pattern formation method, the organic electroluminescent material which is unstable to air, heat, and moisture is damaged because of the steps of photoresist coating, exposure, development, etching, and photoresist stripping. This is because the above method is difficult. Since the dimensional accuracy of forming an organic electroluminescent material depends on the accuracy of a metal mask for vapor deposition, it is desired to stably produce a metal mask with good dimensional accuracy.
[0003]
Full-color organic EL elements are also being actively studied, including a method using a white light-emitting layer and a color filter, a method of converting light generated in a blue light-emitting layer into three colors of RGB by a fluorescent layer, and light emission having each of RGB fluorescent characteristics. There is a method of forming a layer (parallel method). Since a color filter and a fluorescent layer are not required, lightening can be expected, and since there is no reduction in luminance due to the color filter and the fluorescent layer, the parallel method is more advantageous. However, since the light emitting layers of the three colors RGB are sequentially deposited, the requirements for the dimensional accuracy of the metal mask are becoming more severe.
[0004]
In the conventional method of manufacturing a metal mask, a thin metal foil is used as a mask material to form a through-hole by a photo-etching method in order to form a fine vapor-deposited layer. Was pasted on a frame. With this method, there is no denying that there is a risk that the mask itself will be deformed by the operation up to pasting. Further, when attaching the metal foil to the frame, it is necessary to apply a uniform tension to the metal foil having the fine through holes. If the tension is not uniform, distortion occurs in the pattern shape and the entire mask, and it is difficult to satisfy the required dimensional accuracy. Further, when the mask pattern changes, it is necessary to optimize the way of applying the tension each time.
[0005]
Conventional metal masks that require a frame also have the problem of welding burrs during lamination. That is, the lamination is performed by applying a uniform tension to a metal mask having a through hole on the frame and then performing laser or spot welding from the metal foil. However, since the welding surface and the contact surface with the substrate at the time of vapor deposition are the same, when welding burrs occur, a gap between the vapor deposition substrate and the mask is generated, and the vapor deposition layer bleeds, and the light emitting layer with high accuracy is formed. There is a problem that the formation of the film becomes difficult.
[0006]
Patent Literature 1 discloses an attempt to eliminate a poor adhesion due to welding burrs by forming a groove in advance on a welding surface of a metal foil and performing welding with a frame inside the groove. However, in this method, a step of forming a groove in the metal foil by etching or performing a machining process is required separately. Also, the formation of grooves in the metal thin film causes a decrease in mask strength, and it is also difficult to apply uniform tension.
[0007]
In order to further increase the strength of the metal foil, attempts have been made to increase the thickness of the metal foil mask opening outer peripheral portion. The methods described in Patent Documents 2 and 3 are methods in which after a mask is formed by an electroforming method, a new photoresist is applied and patterned, and the outer peripheral portion is further thickened by an electroforming method. In this method, there are two electroforming steps, and it is difficult to say that the productivity is good. Further, in the manufacturing method by the etching method described in the same document, a thick metal plate is formed with a through hole by an etching method, and then the mask opening portion is polished to a thin film by mechanical polishing, and a peripheral portion is left, or a primary etching is performed. After the through hole is formed, patterning is performed so as to expose the peripheral portion of the through hole, and half etching is performed by dry etching to increase the film thickness around the through hole. In the above-described method, there is a risk that the stress at the time of mechanical polishing may cause deformation of the mask pattern. Further, as the pitch becomes narrower, it becomes difficult to form a through hole by etching. In the method described later, it is necessary to carry out a dry process, and it is difficult to say that the method is suitable for mass production.
[0008]
[Patent Document 1]
JP-A-2001-69619
[Patent Document 2]
JP 2001-237071 A
[Patent Document 3]
JP 2001-237072 A
[0009]
[Problems to be solved by the invention]
The problem to be solved by the present invention is that, in a fine pattern forming method using an evaporation method, a metal mask used for the purpose of adhering to a substrate and depositing an evaporation material on a desired portion is manufactured with good yield and high dimensional accuracy. And a metal mask manufactured by the method. In other words, the present invention does not require a conventionally used frame, thereby simplifying a manufacturing process such as laminating, and eliminating a dimensional error due to non-uniformity of tension at the time of bonding, which has been a problem in the past. It is still another object of the present invention to provide a method of manufacturing a metal mask which is unlikely to cause permanent deformation during mask manufacturing, and a metal mask.
[0010]
[Means for Solving the Problems]
The present invention has been made in view of this problem. Claim 1 is to apply a photoresist on the surface of a metal plate, and then expose and develop the photoresist, and to partially thin only one surface of the metal plate by primary etching. The photoresist is peeled off, the photoresist is coated on both sides, and the front and back surfaces of the metal part thinned by the primary etching are exposed using a desired photomask, developed, and the through holes are formed by the secondary etching. A method of manufacturing a metal mask, characterized by performing the method.
[0011]
That is, in the metal mask according to the present invention, although depending on the size of the metal plate, a metal plate having a thickness sufficient to prevent permanent deformation during organic EL deposition during manufacturing is used. As a result of detailed research by the present inventors, it is desirable to use a metal plate having a thickness of 0.5 to 5 mm. The metal plate can be manufactured as long as it can be etched, but generally, iron, an iron-based alloy, nickel, a nickel-based alloy, stainless steel, or the like is used.
[0012]
In the first aspect, as exemplified below, a resist pattern having a thickness of about 10 μm is formed using a photomask on which a desired pattern is formed. As the resist used in the first etching step, a positive photoresist of a naphthoquinone azide type or a novolak resin type, or a negative type photoresist of a dichromic acid type, a polyvinyl cinnamate type, or a cyclized rubber azide type can be used. . Of course, the electrodeposition photoresist may be used from the first etching.
[0013]
For the coating of the liquid photoresist, a commonly used photoresist coating method such as a spin coater, a roll coater or a dip coater is used. When a dry film resist is used, a laminator is used. Further, the printing resist may be printed in a pattern.
[0014]
Further, in the step of exposing and developing the primary resist, only one surface to be thinned is patterned. The patterning portion may be the entire mask effective portion as shown in FIG. 1A, or may be only the peripheral portion where a through hole is formed by secondary etching as shown in FIG. 1B. Then, after etching to a desired thickness with an etching solution such as a ferric chloride solution, a nitric acid solution, or a chromic acid-sulfuric acid solution, the primary resist is further stripped.
[0015]
Subsequently, when coating a photoresist used for secondary etching on a surface obtained by thinning a flat metal surface by primary etching, when a liquid photoresist is used, a photoresist liquid is applied to the thinned (half-etched hole) portion. There is a problem that the photoresist is easily accumulated and a photoresist having a uniform film thickness cannot be formed. Further, there is a problem that the dry film resist cannot be stuck to the half-etched surface well.
[0016]
To solve this problem, it is necessary to use at least an electrodeposited photoresist as the secondary photoresist. When an electrodeposited photoresist is used, there is an advantage that an electrodeposited photoresist having a uniform film thickness can be formed along irregularities on the metal surface.
[0017]
Here, the electrodeposition photoresist material used for the secondary etching is preferably a positive electrodeposition photoresist. Although negative electrodeposited photoresists cannot be used, they do cause problems. FIG. 2 is a partial explanatory view showing a cross section of an etching process when a negative electrodeposition photoresist is used for a metal material, and shows a state in which a surface portion of a half-etched hole has an inverse taper. . In the figure, a negative electrodeposition resist 221 is applied to a half-etched metal material 211 formed in a primary etching step. A negative photomask 231 is provided on the surface of the metal material 211, and light is emitted from above the negative photomask 231. Here, since the surface layer of the half-etched hole has a reverse taper, a negative electrodeposition resist portion 222 that cannot be exposed occurs. As shown in the figure, when the primary etching amount is large and the surface layer of the half-etched surface becomes reverse-tapered (resist portion 222), when a negative photoresist is used as the secondary photoresist, the half-etched surface is removed. Since the surface layer cannot be exposed, it is preferable to use a positive photoresist.
[0018]
According to a second aspect of the present invention, there is provided the method of manufacturing a metal mask according to the first aspect, wherein the photoresist used in the secondary etching is a positive electrodeposition resist.
[0019]
A metal surface is coated with an electrodeposited photoresist using an electrodeposition method in a uniform film thickness of about 8 μm. The thickness can be controlled by the dielectric constant of the material itself and the electrodeposition conditions. However, the thickness is preferably 2 μm or more because of the problem of mechanical strength of the eaves generated by side etching, and 10 μm to form a high-definition pattern. The following film thicknesses are preferred. Subsequently, a mask pattern is exposed to the electrodeposited photoresist applied to a desired film thickness and development is performed.
[0020]
The substrate coated with the electrodeposition resist has a gap between the bottom of the half-etched hole thinned by the primary etching and the metal surface as indicated by 331 in FIG. Therefore, the bottom of the half-etched hole cannot be brought into close contact with the photomask. If a pattern is exposed to the bottom of the half-etched hole coated with the electrodeposition resist using a scattered light source exposure apparatus, it becomes impossible to resolve a desired metal mask pattern.
[0021]
According to a third aspect of the present invention, there is provided the method of manufacturing a metal mask according to the first aspect, wherein a light source used for exposing a desired pattern on the front and back surfaces of the thinned metal portion is parallel light. It is what it was.
[0022]
According to a fourth aspect of the present invention, when a desired pattern is exposed on the front and back surfaces of the thinned metal portion, the half etching holes formed on the metal plate by primary etching and the photomasks on the front and back surfaces are provided. The method for manufacturing a metal mask according to any one of claims 1 to 3, wherein the metal plate and the front and back photomasks are aligned using the alignment marks thus formed, and are exposed and developed.
[0023]
The positive photoresist using an electrodeposition method on a metal surface thinned by half etching after the photoresist used in the primary etching step is dissolved and stripped with a hot alkaline solution, as exemplified below in claim 4. Is coated with a uniform film thickness of about 8 μm. Next, using a proximity exposure method, exposure is performed with parallel ultraviolet light in alignment with the half etching hole in the primary etching step, and development is performed. If the alignment is not performed, when the through-hole is formed by the secondary etching, the front and back positions are shifted, and not only can the organic EL material not be uniformly deposited, but also be deposited at a desired position on the deposition substrate. Is impossible.
[0024]
Subsequently, an alkaline aqueous solution is sprayed and developed on the metal plate on which the electrodeposition resist is applied to the bottom of the half-etching hole and exposed, and a second etching process is performed. As an etchant used in the secondary etching, a ferric chloride, nitric acid-based, or chromic acid-sulfuric acid-based etchant may be used. When the through holes are formed, spray etching may be performed from both sides, or etching may be performed on each side, and the through processing may be performed. Finally, the electrodeposited resist is stripped with a hot alkaline solution to complete a metal mask.
[0025]
A fifth aspect of the present invention is a metal mask manufactured by the metal mask manufacturing method according to the first, second, third or fourth aspect.
[0026]
Although the present invention has been described with reference to the metal mask for organic EL deposition, the present invention is not limited to the metal mask for vapor deposition.
BEST MODE FOR CARRYING OUT THE INVENTION
[0027]
Example 1 shows an example of a method of forming a metal mask that does not require a frame according to the present invention. Comparative Example 1 shows an example of a conventional metal mask forming method of sticking to a frame.
[0028]
<Example 1>
FIG. 4 is a partial explanatory view showing the steps of the manufacturing method of the present invention in cross section.
A SUS304 material substrate having a width of 340 mm x 340 mm x 4 mm in width x length x thickness was degreased with an alkali, and both sides were coated with a positive photoresist PMER P-RH300PM (manufactured by Tokyo Ohka Kogyo) at a film thickness of 10 m (Fig. 4A). ). Next, a 60 mm × 70 mm aperture is exposed using 180 mJ / cm ² of parallel light via a photomask FIG. 5 having a total of 9 patterns, 3 × 3. At four corners of the mask, alignment marks used in secondary etching are arranged in advance. After exposure, a positive photoresist pattern (421) having the same dimensions as the photomask was formed by spray development with an aqueous alkali solution (FIG. 4B).
[0029]
As a primary etching step, a ferric chloride etchant is spray-etched at 50 ° C. and 0.3 MPa until the SUS material thickness after etching becomes 60 μm (73 μm in side-etch amount), and after washing with water, 60 ° C., 3 wt. Then, the positive photoresist pattern is stripped (FIG. 4C).
[0030]
Next, "Sonne EDUV P-500" (manufactured by Kansai Paint) of a positive electrodeposition photoresist (440) was coated with a film thickness of 8 [mu] m (FIG. 4 (D)). Next, through a photomask (451) in which a slit pattern of line / space = 40/140 μm is arranged on an effective portion of 50 mm × 60 mm, using parallel light of 150 mJ / cm ² from the front and back, alignment marks on the front and back of the mask, primary Exposure was performed after alignment using the alignment marks formed by etching (FIG. 4E). Then, after heat treatment at 140 ° C. for 15 minutes, spray development was performed with a 1% by weight aqueous sodium carbonate solution at 35 ° C. (FIG. 4F).
[0031]
Further, as a secondary etching step, a ferric chloride etching solution was spray-etched at 50 ° C. and 0.3 MPa, and then the resist was stripped off to form a metal mask 470 (FIG. 4G). The overall yield was 98%. The slit shape after the formation was good without any slack.
[0032]
When the dimensions of the metal mask 470 prepared as described above were measured with an automatic dimension measuring machine, the positional accuracy of the mask effective surface was within ± 3 μm in dimensional tolerance, and the dimensional accuracy of the slit width was as small as ± 2 μm. An accurate metal mask could be created. Further, there was no permanent deformation at the time of preparation.
[0033]
<Comparative Example 1>
FIG. 7 is a partial explanatory view showing steps of a manufacturing method of a comparative example in a cross section. A SUS304 material substrate having a width x length x thickness of 340 mm x 340 mm x 60 m was alkali-degreased, and a positive-type photoresist PMER P-RH300PM (manufactured by Tokyo Ohka Kogyo Co., Ltd.) was dried and coated on both sides with a film thickness of 10 m (Fig. A)). Next, exposure is performed using parallel light of 180 mJ / cm ² via a front and back photomask in which a slit pattern of line / space = 40/140 μm is arranged in an effective portion of 50 mm × 60 mm through FIG. At this time, the alignment of the front and back of the mask was performed after the alignment using the alignment marks arranged at the four corners of the mask. Thereafter, spray development was performed at 30 ° C. using a dedicated developer PMER-P-1S (25 vol%) (FIG. 4B).
[0034]
Next, a through-hole was formed by etching the ferric chloride etching solution at 50 ° C. and 0.3 MPa. After washing with water, it was immersed in a 3% by weight aqueous solution of caustic soda at 60 ° C. to remove the positive photoresist pattern, thereby obtaining a metal mask 730 (FIG. 7C).
[0035]
A 340 mm × 340 mm × 5 mm SUS304 material is cut to obtain a frame similar to the mask shape in FIG. 5 (the light transmitting portion 510 in FIG. 5 is cut) (FIG. 7E). The uniform frame was welded to the periphery of the effective portion by laser welding with a spot diameter of 0.5 mm at a welding interval of 1 mm while applying uniform tension to the metal mask and the metal mask was attached (FIG. 7F). Some of the prepared metal masks had undergone permanent deformation, some had a slack in the slit after the frame was attached, and others had burrs formed by laser welding at a height of 10 to 20 μm. The overall yield was as poor as 30% (after attaching the frame).
[0036]
Further, when the metal mask 770 (FIG. 7 (G)) prepared as described above was measured with an automatic size measuring machine, the dimensional tolerance of the mask effective surface was within ± 15 μm, and the dimensional accuracy of the slit width was ± 43 μm. It was big.
【The invention's effect】
As described above, the method for manufacturing a metal mask according to the present invention has made it possible to simplify the steps of manufacturing and attaching a frame. Further, by this method, there is no dimensional error due to non-uniformity of tension at the time of sticking, and a metal mask for vapor deposition having high dimensional accuracy can be manufactured with high yield.
[Brief description of the drawings]
FIG. 1A is an explanatory diagram showing a primary etching patterning shape when thinning the entire mask effective portion, and FIG. 1B is an explanatory diagram showing a primary etching patterning shape when thinning a portion around a through hole.
FIG. 2 is a partial explanatory view showing a cross section of an etching step when a negative electrodeposition photoresist made of a metal material is used.
FIG. 3 is an explanatory view showing an exposure process of an electrodeposition resist using a parallel light source.
FIGS. 4A to 4G are partial explanatory views showing a cross section of the manufacturing process of the first embodiment of the present invention.
FIG. 5 is an explanatory view showing a conventional photomask for primary resist exposure and its frame shape.
FIG. 6 is an explanatory view showing a photomask for electrodeposition resist exposure.
FIGS. 7A to 7G are explanatory views sequentially showing the steps of manufacturing a metal mask according to a conventional technique.
[Explanation of symbols]
111: photoresist 112 after primary etching patterning 112: metal material 114: processed sectional shape of primary etching 115: through-hole sectional shape 211 of secondary etching: half-etched metal material 221 formed in the primary etching step Negative electrodeposition resist 222: Negative electrodeposition resist portion 231 that cannot be exposed Negative photomask 311: Transmitted light (parallel light)
321, photomask for positive electrodeposition resist 322, electrodeposition resist 331, gap 410 between the photomask for secondary etching and the bottom of the half-etching hole 410, metal material 411, positive photoresist 421, for primary etching after development Positive resist 422… Exposed metal surface 430… Cross-sectional shape 440 after primary etching… Positive electrodeposition resist 451… Photomask 461 for secondary etching… Electrodeposited resist cross-section 462 after development… Electrodeposited resist opening 470 ... Created metal mask 510... Light transmitting part 511... Light shielding part 610... Mask effective part (slit pattern).
710 metal material 711 positive photoresist 721 resist opening 722 photoresist shape after development 730 metal mask 731 through hole 740 frame material 750 mask frame 761 laser welding part 770 created by conventional technology Metal mask

Claims (5)

After applying a photoresist on the surface of the metal plate, exposing and developing, and partially thinning only one side of the metal plate by the primary etching, the photoresist is peeled off, and the photoresist is further applied on both surfaces, and the primary A method for manufacturing a metal mask, comprising: exposing and developing a front and back surface of a metal portion thinned by etching using a desired photomask; developing the exposed portion; and forming a through hole by secondary etching. 2. The method according to claim 1, wherein the photoresist used in the secondary etching is a positive electrodeposition resist. 2. The method according to claim 1, wherein a light source used for exposing a desired pattern on the front and back surfaces of the thinned metal portion is a parallel light. When exposing a desired pattern on the front and back surfaces of the thinned metal portion, the metal is formed using the half etching holes formed on the metal plate by the primary etching and the alignment marks arranged on the front and back photomasks. 4. The method for manufacturing a metal mask according to claim 1, wherein the plate and the front and back photomasks are aligned and exposed and developed. A metal mask manufactured by the method for manufacturing a metal mask according to claim 1.

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