KR20230089375A - Method of manufacturing fine metal mask - Google Patents

Abstract

The present invention comprises a first step of laminating an Fe—Ni multilayer thin film on a conductive substrate by a pulse plating method; A second step of depositing a SiO ₂ or SiN _x thin film as an etch mask on the plating layer after plating the Fe—Ni multilayer thin film; A third step of forming a photoresist (PR) pattern by photolithography after depositing the SiO ₂ or SiN _x thin film; a fourth step of using the PR pattern as a mask to remove an etching mask of a region exposed by reactive ion etching (RIE); a fifth step of forming a cavity array having a curved surface by etching by wet isotropic etching after removing the etching mask of the exposed area; A sixth step of removing the residual etching mask by dry or wet etching; And a seventh step of peeling off the plating layer after heat treatment at 200 to 900 ° C. in a state where the plating layer is attached to the conductive substrate. There is an effect of providing a fine metal mask having high quality invar characteristics without deformation.

Description

Fine metal mask manufacturing method {METHOD OF MANUFACTURING FINE METAL MASK}

The present invention relates to a method for manufacturing a fine metal mask for manufacturing an OLED display.

Organic Light-Emitting Diode (OLED) displays emit self-luminescence by an electric field without using a backlight. It is attracting attention because it has the advantage of being applicable.

In the manufacturing process of small and medium-sized OLED displays such as smartphones, smart watches, tablets, notebooks, and AR/VR, it corresponds to each color of the three primary colors (R, G, and B) to form pixels on a substrate The organic light emitting layer to be deposited sequentially in vacuum on a substrate while aligning a shadow mask.

A fine metal mask (FMM) is a shadow mask used for the deposition of an organic light emitting layer and is a key component that determines the resolution of an OLED. To prevent the pixel size from changing due to thermal expansion during vacuum deposition, FMM uses Invar, an Fe-Ni alloy with a low thermal expansion coefficient, and is manufactured by forming through-hole arrays in an ultra-thin Invar plate. For high pixelation of the display, each hole of the through hole should be fine and uniform, and at the same time, it is desirable to have an appropriate taper or slope to minimize the shadow effect of the deposition material.

In the existing FMM manufacturing process, a rolling method and an electroforming method are used.

In the rolling method, an invar thin plate is obtained by rolling through a plurality of rolls, and a hole array is manufactured on the thin plate through photo and etching processes, or the thin plate is laser cut How to make a hole array.

The electroforming method is a method of plating an Fe-Ni alloy on a substrate having a predetermined pattern and then peeling it off.

However, the rolling method has a problem in that, although the alloy composition is uniform, it is difficult to obtain a thin plate having a thickness of 20 μm or less due to a limitation in reducing the thickness, and the cost increases as the thickness decreases. In addition, there is a problem in that it is difficult to form a uniform and fine hole array because the surface of the thin plate is rough. Furthermore, even in the etching process, there is a problem in that it is difficult to realize a uniform and accurate shape due to an undercut or overcut phenomenon.

Compared to the rolling method, the electroforming method can obtain a thin plate with a thin thickness, but it is not easy to implement a fine pattern, and due to the nature of alloy plating, it is difficult to control the composition and grain size in the thickness direction of the thin plate.

Registered Patent Publication No. 10-2119942 (Public date: 2020. 06. 06) Registered Patent Publication No. 10-1504543 (Public date: 2015. 03. 20)

An object of the present invention to improve the above problems is to provide a method for manufacturing a fine metal mask for implementing ultra-high resolution (1000 PPI or more, PPI: pixel per inch) OLED display for next-generation mobile and AR / VR.

In addition, an object of the present invention is to solve the problems of the FMM manufactured by the conventional rolling method and the electroforming method, have a constant thickness and a flat surface, minimize an overcut phenomenon, and easily control the composition of the invar alloy. It is to provide a method for manufacturing a fine metal mask with high resolution, high precision, and high quality.

In order to achieve the above object, a method for manufacturing a fine metal mask according to an embodiment of the present invention includes a first step of stacking an Fe—Ni multilayer thin film on a conductive substrate by a pulse plating method; A second step of depositing a SiO ₂ or SiN _x thin film as an etch mask on the plating layer after plating the Fe—Ni multilayer thin film; A third step of forming a photoresist (PR) pattern by photolithography after depositing the SiO ₂ or SiN _x thin film; a fourth step of using the PR pattern as a mask to remove an etching mask of a region exposed by reactive ion etching (RIE); a fifth step of forming a cavity array having a curved surface by etching by wet isotropic etching after removing the etching mask of the exposed area; A sixth step of removing the residual etching mask by dry or wet etching; and a seventh step of peeling off the plating layer after heat treatment at 200 to 900° C. in a state where the plating layer is attached to the conductive substrate.

In the first step, the Fe-Ni multilayer thin film is formed by alternately stacking Fe _x Ni _{1 -x thin} films and Fe _y Ni _{1 -y} thin films using electroplating on the conductive substrate Fe _x Ni _{1 -x} / Fe _y Ni _{1 -y} is a multi-layer thin film, and the electroplating of each Fe _x Ni _{1 -x} thin film and Fe _y Ni _{1 -y} thin film is performed in the same electrolyte solution, but is characterized in that pulse plating is performed by applying a pulse current. .

The pulse train of the electroplating of the Fe _y Ni _{1 -y} thin film and the pulse train of the Fe _x Ni _{1 -x} thin film are delayed by a predetermined delay time ( t _d ).

The thickness of each of the Fe _x Ni _{1 -x thin} film and the Fe _y Ni _{1 -y} thin film is characterized in that it is controlled to have an Invar composition (Fe-36 wt% Ni) after heat treatment of the multilayer thin film.

In the fifth step, the wet isotropic etching is performed for a predetermined time until the upper surface of the conductive substrate is exposed.

It is characterized in that the weight ratio of Fe:Ni in the plating layer peeled off in the seventh step is 58-70:30-42.

It is characterized in that Co is additionally contained in a weight ratio of 3 to 7 in addition to Fe and Ni in the plating layer peeled off in the seventh step.

It is characterized in that the thickness of the Fe-Ni multilayer thin film laminated in the first step is 5 μm or more and 50 μm or less.

In the method for manufacturing a fine metal mask according to the present invention, Fe-Ni thin films having different compositions are alternately laminated on one surface of a conductive substrate by pulse plating to form a plating layer composed of multi-layer thin films, and a PR layer is spin-coated on the plating layer. A patterned PR layer is formed by photolithography, the exposed area is etched to remove an etch mask, the Fe-Ni multilayer thin film is wet-etched using the etch mask as a mask, and the plating layer attached to the substrate is By annealing and separation, it is possible to provide a fine metal mask having fine crystal grains, low residual stress, and a constant alloy ratio, and having high quality invar characteristics.

In addition, an embodiment of the present invention solves the problems of the FMM manufactured by the conventional rolling method and the electroforming method, has a constant thickness and a flat surface, can minimize an overcut phenomenon, and controls the composition of the invar alloy. It is possible to provide a high-resolution, high-precision, and high-quality fine metal mask that is easy to use.

In addition, according to the present invention, it is possible to provide an ultra-precise fine metal mask manufacturing method for implementing ultra-high resolution OLED displays for next-generation mobile and AR/VR.

1 is a diagram illustrating a method for manufacturing a fine metal mask according to an embodiment of the present invention.
FIG. 2 is a diagram showing a pulse application method and a laminated structure of the pulse plating method used in S10 of FIG. 1 .
3 is a diagram for explaining a plating method applied to a method for manufacturing a fine metal mask according to an embodiment of the present invention.

The present invention as described above will be described in detail through the accompanying drawings and embodiments.

It should be noted that technical terms used in the present invention are only used to describe specific embodiments and are not intended to limit the present invention. In addition, technical terms used in the present invention should be interpreted in terms commonly understood by those of ordinary skill in the art to which the present invention belongs, unless specifically defined otherwise in the present invention, and are excessively inclusive. It should not be interpreted in a positive sense or in an excessively reduced sense. In addition, when the technical terms used in the present invention are incorrect technical terms that do not accurately express the spirit of the present invention, they should be replaced with technical terms that those skilled in the art can correctly understand. In addition, general terms used in the present invention should be interpreted as defined in advance or according to context, and should not be interpreted in an excessively reduced sense.

Also, singular expressions used in the present invention include plural expressions unless the context clearly dictates otherwise. In the present invention, terms such as "consisting of" or "comprising" should not be construed as necessarily including all of the various elements or steps described in the invention, and some of the elements or steps are included. It should be construed that it may not be, or may further include additional components or steps.

In addition, terms including ordinal numbers such as first and second used in the present invention may be used to describe components, but components should not be limited by the terms. Terms are used only to distinguish one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention.

Hereinafter, a preferred embodiment according to the present invention will be described in detail with reference to the accompanying drawings, but the same or similar components are assigned the same reference numerals regardless of reference numerals, and redundant description thereof will be omitted.

In addition, in describing the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description will be omitted. In addition, it should be noted that the accompanying drawings are only for easily understanding the spirit of the present invention, and should not be construed as limiting the spirit of the present invention by the accompanying drawings.

1 is a view showing a method for manufacturing a fine metal mask according to an embodiment of the present invention, FIG. 2 is a view showing a pulse application method and a layered structure of the pulse plating method used in S10 of FIG. 1, and FIG. 3 is a view showing the present invention It is a view for explaining a plating method applied to a fine metal mask manufacturing method according to an embodiment of.

As shown in FIG. 1, a method for manufacturing a fine metal mask according to an embodiment of the present invention includes a first step of stacking an Fe—Ni multilayer thin film on a conductive substrate by a pulse plating method, and an Fe—Ni multilayer thin film. A second step of depositing a SiO ₂ or SiN _x thin film as an etch mask on the plating layer after plating, and forming a photoresist (PR) pattern by photolithography after depositing the SiO ₂ or SiN _x thin film A third step, a fourth step of removing the etching mask of the region exposed by reactive ion etching (RIE) using the PR pattern as a mask, and after removing the etching mask of the region exposed in the fourth step, wet isotropic etching ( A fifth step of forming a cavity array having a curved surface by etching by wet isotropic etching, a sixth step of removing the remaining etching mask by dry or wet etching, and a plating layer attached to the conductive substrate 200 A seventh step of peeling off the plating layer after heat treatment at ~900°C is included.

In the first step, the Fe-Ni multilayer thin film is formed by alternately stacking Fe _x Ni _{1 -x thin} films and Fe _y Ni _{1 -y} thin films using electroplating on a conductive substrate Fe _x Ni _{1 -x} / Fe _y Ni _{1 -y} multilayer thin film. At this time, x is 0≤x≤0.7, y is 0.7≤y≤1.0.

At this time, the electroplating of each of the Fe _x Ni _{1 -x} thin film and the Fe _y Ni _{1 -y} thin film is performed in the same electrolyte, but is performed by pulse plating by applying a pulse current.

Meanwhile, the pulse train of the electroplating of the Fe _y Ni _{1 -y} thin film and the pulse train of the Fe _x Ni _{1 -x} thin film are delayed by a preset delay time ( t _d ).

In addition, the thickness of each of the Fe _x Ni _{1 -x thin} film and the Fe _y Ni _{1 -y thin} film is controlled to have an Invar composition (Fe-36 wt% Ni) after heat treatment of the multilayer thin film.

In the present invention, Fe-Ni with different compositions Since an invar alloy can be obtained by alternately stacking thin films to form a multi-layered thin film and heat-treating it, an overall uniform composition is obtained by diffusion of atoms in a short distance in the thickness direction of the plating layer, and the control of the alloy composition is easy. In addition, by forming a multilayer thin film by pulse plating, fine and uniform crystal grains can be obtained and residual stress of the plating layer can be reduced.

Meanwhile, in the fifth step, wet isotropic etching is performed for a predetermined time until the upper surface of the conductive substrate is exposed.

Hereinafter, a pulse plating method and a wet etching method applied to a fine metal mask manufacturing method according to an embodiment of the present invention will be described.

[Function and action of pulse plating]

In general, when defects such as non-metallic inclusions or pores exist on the surface of a conductive substrate, the defects are transferred to the electroplating layer and pits occur. At this time, the pulse plating can prevent the occurrence of pits, obtain fine crystal grains, and minimize residual stress in the plating layer. Therefore, when the pulse plating is used, a flat plating layer having a uniform thickness can be obtained. In addition, if a pattern is formed on a flat plated thin plate having a uniform thickness and then etched, a fine and uniform cavity array can be obtained.

In addition, various pulse parameters of pulse plating and the thickness of the Fe _x Ni _{1 -x} thin film and the Fe _y Ni _{1 -y} thin film can be variably set using a programmable pulse rectifier, resulting in a heat treatment for the plating layer. It is easy to control the alloy composition, and the Invar composition (Fe-36 wt% Ni) showing the lowest thermal expansion coefficient can be obtained.

[Pulse plating method]

In the present invention, as shown in FIG. 3, plating is performed in an electrolyte solution using a conductive substrate as a cathode, Ni or an insoluble electrode (Ti, Ir, Ru, etc.) as an anode, and Fe _x Ni _{1 -x} (0≤x ≤0.7) layers and Fe _y Ni _{1 - y} (0.7≤y≤1.0) layers are alternately and continuously laminated to form a multilayer thin film.

The plating of the Fe _x Ni _{1 - x} layer and the Fe _y Ni _{1 - y} layer is performed in the same electrolyte, but is performed by pulse plating by applying a pulse current, and the pulse current density ( J _F ), pulse width ( t _p ), Pulse interval ( t _r ), reverse pulse current density ( J _R ), pulse repetition number ( n ), etc. can be set differently. As shown in (a) of FIG. 2, pulse train 2 for forming the Fe _y Ni _{1 - y} layer may be delayed by a delay time ( t _d ) than pulse train 1 for forming the Fe _x Ni _{1 - x} layer. there is. At this time, the parameters of the pulse plating included in FIG. 2 (c) can be variably set using a programmable pulse rectifier.

In addition, the thickness t ₁ , t ₂ of each layer of Fe _x Ni _{1 - x} layer and Fe _y Ni _{1 - y} layer is the Invar composition (Fe-36 wt% Ni) showing the lowest thermal expansion coefficient of the overall alloy composition after heat treatment The thickness of each layer can be precisely digitally controlled.

In addition, it is necessary to prevent aging of the electrolyte so that the composition of the Fe _x Ni _{1 - x} layer and the Fe _y Ni _{1 - y} layer is constant in the thickness direction of the plating thin film, and the metal ion concentration must be kept constant. Therefore, the components of the plating solution are periodically analyzed so that the metal ion concentration of the electrolyte solution does not fluctuate, and the plating solution of a certain composition and a certain flow rate is circulated and supplied by a metered supply pump. In addition, the electrolyte is circulated through regular filtration so that impurities are not mixed in the electrolyte.

In the plating method shown in FIG. 3, the plating solution includes various metal salts such as ferrous sulfate hydrate (FeSO ₄ 6H ₂ O) and nickel sulfate hydrate (NiSO ₄ 6H ₂ O), a pH buffer, a pit inhibitor, and a brightening agent. May contain additives.

More specifically, the metal salt includes 0.05 to 0.5 M of ferrous sulfate hydrate (FeSO ₄ 6H ₂ O) and 0.1 to 1.0 M of nickel sulfate hydrate (NiSO ₄ 6H ₂ O), and boric acid as an additive ) 0.1 ~ 1.0 M, Ascorbic Acid 0.1 ~ 5 g/L, Sodium lauryl sulfamate 0.1 ~ 3 g/L, Saccharin 0 ~ 2 g/L, At this time, the pH may be 2.5 to 5 and the temperature may be 30 to 80 °C.

However, it is not limited to the types and compositions of metal salts or additives shown above. In addition, as a metal salt in the plating solution, a metal salt containing Co such as cobalt sulfate hydrate (CoSO ₄ ·6H ₂ O) can be added.

At this time, Ni or an insoluble anode (Ti, Ir, Rh, etc.) can be used as the anode, and the plating solution can be circulated by stirring or by connecting a liquid circulation line to the outside of the plating bath. A plating solution having a certain composition may be supplied at a constant flow rate using a metering pump (not shown), and at this time, a filter (not shown) may be used to remove impurities in the plating solution.

[ of the plating layer wet etching method]

Etching of the Fe-Ni multilayer thin film plating layer may be performed in a wet manner using an aqueous solution of ferric chloride (FeCl ₃ ). For example, ferric chloride (FeCl ₃ ) 1-5 M/L, ferrous chloride (FeCl ₂ ) 0.5-1.5 M/L, nickel ferrous chloride (NiCl ₂ ) 0.2-1 M/L, hydrochloric acid (HCl) It can be etched at a temperature of 40 to 80 ° C in an etchant consisting of an aqueous solution of 0.3 to 1 M / L.

Hereinafter, a method for manufacturing a fine metal mask according to an embodiment of the present invention will be described in detail with reference to FIG. 1 .

First, in S10, an Fe—Ni multilayer thin film is laminated on a conductive substrate by pulse plating. Here, the conductive substrate is preferably a Si single crystal substrate doped with an impurity concentration of at least 10 ¹⁹ cm ^-3 or more. Also, in S10, the thickness of the laminated plating layer may be 5 μm or more and 50 μm or less.

More specifically, in S10, a Fe _x Ni _{1 -x thin} film and a Fe _y Ni _{1 -y} thin film are alternately laminated on a conductive substrate using electroplating to obtain a Fe _x Ni _{1 -x} / Fe _y Ni _{1 -y} multilayer form a thin film At this time, plating of the Fe _x Ni _{1 -x thin} film (hereinafter, Layer 1) and the Fe _y Ni _{1 -y} thin film (hereinafter, Layer 2) is performed in the same electrolyte, but is performed by pulse plating by applying a pulse current. In addition, pulse current density ( J _F ), pulse width ( t _p ), pulse interval ( t _r ), reverse current density ( J _R ), pulse repetition number ( n ), etc. can be set differently in Layer 1 and Layer 2, respectively. there is. In this case, pulse train 2 may be delayed by a delay time ( t _d ) than pulse train 1. In addition, the parameters of pulse plating as shown in FIG. 2 (c) can be variably set using a programmable pulse rectifier (not shown), and the thickness of each layer of Layer 1 and Layer 2 is precisely digital ( can be controlled digitally.

In addition, the thicknesses t ₁ , t ₂ of the Fe _x Ni _{1 -x thin} film and the Fe _y Ni _{1 -y} thin film, respectively, were adjusted so that the Invar composition (Fe-36 wt% Ni) exhibiting the lowest coefficient of thermal expansion after heat treatment of the multilayer thin film. The thickness of the layer can be controlled.

Then, in S20, after the plating of the multilayer thin film is completed, a SiO ₂ or SiN _x thin film is deposited on the plating layer as an etch mask by chemical vapor deposition (CVD) or a spin coating method.

Then, in S30, a photoresist (PR) pattern is formed by photolithography. At this time, processes such as PR spin coating, baking, photomask mounting, exposure, and development are performed. Here, in the case of positive PR, the PR pattern formation region corresponds to the bottom of the through hole in the FMM (ie, fine metal mask). However, a method of attaching a PR film on the substrate and performing photolithography instead of the PR spin coating, or omitting S30 and attaching a pre-patterned PR film on the substrate is also applicable.

Then, in S40 , an etch mask of an exposed area by reactive ion etching (RIE) is removed using the PR pattern as a mask. In addition, after removing the etch mask of the exposed region, residual PR may be removed with a sulfuric acid hydrogen peroxide (H ₂ SO ₄ -H ₂ O ₂ ) mixed solution or the like.

Then, in S50 , a cavity array is formed by wet etching the multilayer thin film plating layer using the patterned etch mask layer as an etch mask. That is, in S50, the substrate may be loaded into a bath and wet-etched in an aqueous solution based on the above-described ferric chloride (FeCl ₃ ). The wet etching proceeds for a predetermined time until the conductive substrate is sufficiently exposed or until a predetermined area is exposed. The downward etching process ends when it meets the substrate.

Then, after the wet etching is finished in S60 , the remaining etch mask is removed by dry or wet etching.

Finally, in S70, the plating layer is peeled off after heat treatment at 200 to 900° C. while the plating layer is attached to the substrate. That is, in S70, the plating layer is annealed at a temperature of 200 to 900° C. in an inert gas atmosphere and then separated from the conductive substrate.

Finally, the weight ratio of Fe:Ni in the peeled plating layer is preferably 58 to 70:30 to 42. Furthermore, Co may be additionally contained in a weight ratio of 3 to 7 in addition to Fe and Ni in the peeled plating layer.

According to the method for manufacturing a fine metal mask according to the present invention configured as described above, a multilayer thin film having a uniform thickness and surface flatness is manufactured by using pulse plating on a conductive substrate, and the plating layer is formed by photolithography and wet etching thereon. Since the through hole array is formed, a fine metal mask with high precision and high resolution can be provided.

In addition, according to an embodiment of the present invention, since a fine metal mask is manufactured by manufacturing a multilayer thin film by pulse plating, patterning, etching, and then heat-treating it, the plating layer has fine crystal grains and low residual stress, and further Since it can have a constant alloy ratio, it is possible to provide a fine metal mask having high quality invar characteristics.

In addition, according to one embodiment of the present invention, since the plating layer is patterned and etched in a state where the plating layer is attached to the conductive substrate during wet etching, the substrate acts as an etch stop layer, so that the control of the etching time is easy and the plating layer It is possible to prevent overcut in the vertical direction with respect to the cavity, so that a precise and uniform cavity shape can be obtained.

In addition, according to one embodiment of the present invention, since the plating layer in which the through hole array is formed by wet etching is heat-treated while attached to the substrate before being separated from the substrate, deformation of the fine metal mask and surface oxidation or contamination during the heat treatment process etc. can be minimized.

In the above, preferred embodiments according to the present invention have been shown and described. However, the present invention is not limited to the above-described embodiments, and various modifications can be made by anyone having ordinary knowledge in the technical field to which the present invention belongs without departing from the gist of the present invention appended within the scope of the claims. .

Claims (8)

A first step of laminating an Fe—Ni multilayer thin film on a conductive substrate by a pulse plating method;
A second step of depositing a SiO ₂ or SiN _x thin film as an etch mask on the plating layer after plating the Fe—Ni multilayer thin film;
A third step of forming a photoresist (PR) pattern by photolithography after depositing the SiO ₂ or SiN _x thin film;
a fourth step of using the PR pattern as a mask to remove an etching mask of a region exposed by reactive ion etching (RIE);
a fifth step of forming a cavity array having a curved surface by etching by wet isotropic etching after removing the etching mask of the exposed area;
A sixth step of removing the residual etching mask by dry or wet etching; and
A seventh step of peeling the plating layer after heat treatment at 200 to 900 ° C. in a state where the plating layer is attached to the conductive substrate.
According to claim 1,
In the first step, the Fe—Ni multilayer thin film,
_An Fe _x Ni ₁ -x / Fe y Ni 1 _-y multilayer thin film formed by alternately stacking _{Fe x Ni 1 -} x thin films and Fe _y Ni _{1 - y} thin films on the conductive substrate by electroplating;
Electroplating of each of the Fe _x Ni _{1 -x} thin film and the Fe _y Ni _{1 -y} thin film is performed in the same electrolyte, but a fine metal mask manufacturing method, characterized in that consisting of pulse plating by applying a pulse current.
According to claim 2,
A fine metal mask manufacturing method, characterized in that the pulse train of the electroplating of the Fe _y Ni _{1 -y} thin film and the pulse train of the Fe _x Ni _{1 -x} thin film are delayed by a preset delay time ( t _d ).
According to claim 2,
The thickness of each of the Fe _x Ni _{1 -x thin} film and the Fe _y Ni _{1 -y} thin film is controlled to have an Invar composition (Fe-36 wt% Ni) after heat treatment of the multilayer thin film.
According to claim 1,
In the fifth step, the wet isotropic etching is performed for a predetermined time until the upper surface of the conductive substrate is exposed.
According to claim 1,
A fine metal mask manufacturing method, characterized in that the weight ratio of Fe: Ni in the plating layer peeled off in the seventh step is 58 to 70: 30 to 42.
According to claim 6,
A method for manufacturing a fine metal mask, characterized in that the plating layer peeled off in the seventh step further contains Co in a weight ratio of 3 to 7 in addition to Fe and Ni.
According to claim 1,
A fine metal mask manufacturing method, characterized in that the thickness of the Fe—Ni multilayer thin film laminated in the first step is 5 μm or more and 50 μm or less.

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