Metal mask and manufacturing method

Abstract

The present invention relates to a metal mask in which a plurality of through holes are formed side by side in a thin-film metal base material, wherein a width x (μm) of a rib positioned between the through holes is 90-180 μm, and the width x and a longitudinal dimension y (μm) of the through hole satisfy the following formula. y ≤ 0.0321x3 - 14.814x2 + 2324.3x - 100503

Description

Metal mask and manufacturing method

[0001] The present invention relates to a metal mask, and more particularly to a metal mask suitable for forming components of a multilayer ceramic capacitor (MLCC). This application also describes a method for manufacturing such a metal mask. This application claims priority based on Japanese Patent Application No. 2024-101089 filed on June 24, 2024, and Japanese Patent Application No. 2025-057855 filed on March 31, 2025, the contents of which are incorporated herein by reference.

[0002] MLCCs are chip-type capacitors with multiple layers of internal electrodes and dielectric layers. While MLCCs are becoming smaller, they still require capacitance as a capacitor. In order to increase capacitance without increasing size, it is necessary to reduce the thickness of the internal electrodes and increase the number of layers. Screen printing has traditionally been used to form the internal electrodes, but by using the sputtering method, it is possible to form thinner internal electrodes and increase the number of layers compared to conventional methods.

[0003] One method for producing a metal mask used in sputtering or the like is to wet-etch a thin metal substrate (see, for example, Patent Document 1). Material flying from a target passes through through holes formed by etching, and is deposited at a predetermined position with predetermined dimensions and shape.

[0004] Japanese Patent No. 6168944

[0005] In normal film formation, many through holes are formed with shapes and dimensions corresponding to one product. By forming these through holes with shapes and dimensions corresponding to a plurality of products and cutting (singling) the formed plurality of films into shapes and dimensions corresponding to one product, it is possible to produce more products from a substrate of the same area, thereby improving production efficiency.

[0006] However, this method increases the area ratio of the through holes in the metal mask while decreasing the area ratio of the metal portion, which may reduce the stability of the structure. The inventors investigated this issue from various angles and completed the present invention.

[0007] In view of the above circumstances, an object of the present invention is to provide a metal mask that has a high through-hole ratio and is also excellent in stability as a structure.

[0008] A first aspect of the present invention is a metal mask having a plurality of through holes arranged in a thin film metal substrate, wherein the width x (μm) of a rib located between the through holes is 90 μm or more and 180 μm or less, and the width x and the longitudinal dimension y (μm) of the through hole satisfy the following formula: y≦0.0321x ３ -14.814x ２ +2324.3x-100503

[0009] A second aspect of the present invention is a metal mask having a plurality of through holes arranged in a thin-film metal substrate, wherein the width x (μm) of a rib located between the through holes is 180 μm or more and 300 μm or less, and the width x and the longitudinal dimension y (μm) of the through hole satisfy the following formula: y≦244.27x+22653.6

[0010] A third aspect of the present invention is a metal mask having a thin-film metal substrate with a plurality of through holes arranged in a row, wherein the width x (μm) of a rib located between the through holes is 300 μm or more, and x and the longitudinal dimension y (μm) of the through hole satisfy the following formula: y≦110.0071x−15867.8621

[0011] A fourth aspect of the present invention is a metal mask having a thin-film metal substrate with a plurality of through holes arranged in a row, wherein the width x (μm) of a rib located between the through holes is 90 μm or less, and the width x and the longitudinal dimension y (μm) of the through hole satisfy the following formula: y≦206.2354x−6668.0204

[0012] A fifth aspect of the present invention is the metal mask according to any one of the first to fourth aspects, wherein the thin film metal substrate is made of a magnetic metal material.

[0013] A sixth aspect of the present invention is the metal mask according to the fifth aspect, wherein the magnetic metal material is one of SUS430, Invar, and Super Invar.

[0014] A seventh aspect of the present invention is the metal mask according to any one of the first to fourth aspects, wherein the thin film metal substrate has a thickness of 50 μm or more.

[0015] In an eighth aspect of the present invention, there is provided a method for manufacturing a metal mask having a plurality of through holes arranged in a thin-film metal substrate, in which the longitudinal dimension y (μm) of the through holes to be formed and the set width x (μm) of the ribs located between the through holes are set to satisfy the following formula while the set width x is 90 μm or more and 180 μm or less, and the through holes are formed by etching based on the set x and y: y≦0.0321x ３ -14.814x ２ +2324.3x-100503

[0016] A ninth aspect of the present invention is a method for manufacturing a metal mask having a plurality of through holes arranged in a thin-film metal substrate, in which the longitudinal dimension y (μm) of the through holes to be formed and the set width x (μm) of the ribs located between the through holes are set to satisfy the following formula, with x being 180 μm or more and 300 μm or less, and the through holes are formed by etching based on the set x and y: y≦244.27x+22653.6

[0017] A tenth aspect of the present invention is a method for manufacturing a metal mask having a plurality of through holes arranged in a thin-film metal substrate, in which the longitudinal dimension y (μm) of the through holes to be formed and the set width x (μm) of ribs located between the through holes are set to satisfy the following formula, with x being 300 μm or greater, and the through holes are formed by etching based on the set x and y: y≦110.0071x−15867.8621

[0018] An eleventh aspect of the present invention is a method for manufacturing a metal mask having a plurality of through holes arranged in a thin-film metal substrate, in which the longitudinal dimension y (μm) of the through holes to be formed and the set width x (μm) of ribs located between the through holes are set to satisfy the following formula, with x being 90 μm or less, and the through holes are formed by etching based on the set x and y: y≦206.2354x−6668.0204

[0019] According to the present invention, it is possible to provide a metal mask that has a high through-hole ratio and is also excellent in stability as a structure.

[0020] 1 is a diagram for explaining through holes and ribs of a metal mask. FIG. 1 is a schematic diagram showing an evaluation area in the study. FIG. 1 is a schematic diagram showing rib twisting. FIG. 2 is a table showing the results of rib width measurements. FIG. 3 is a table showing the results of rib width measurements. FIG. 4 is a table showing the results of rib width measurements. FIG. 5 is a table showing the average twist range values ​​in the study. FIG. 6 is a graph showing the relationship between the average twist range values ​​and slit length for each rib width in the study. FIG. 7 is a graph showing the relationship between the average twist range values ​​and slit length for each rib width in the study. FIG. 8 is a graph showing the relationship between the average twist range values ​​and slit length for each rib width in the study. FIG. 9 is a graph showing the relationship between the average twist range values ​​and slit length for each rib width in the study. FIG. 10 is a diagram showing one step in a manufacturing procedure for an MLCC component using a thin film formed over a large area. FIG. 11 is a diagram showing one step in a manufacturing procedure for an MLCC component using a thin film formed over a large area. FIG. 12 is a graph showing an example of the relationship between rib width and maximum slit length in the study.

[0021] An embodiment of the present invention will be described with reference to Figures 1 to 16. It has already been explained that component manufacturing efficiency can be increased by simultaneously depositing thin films for multiple components using a metal mask. By laying out such through holes with as small an interval as possible, it becomes possible to further increase the number of components that can be manufactured using a single metal mask, further improving manufacturing efficiency.

[0022] On the other hand, when the spacing between the through holes becomes smaller, the ribs 2, which are metal portions that separate the through holes 10 in the metal mask 1, become elongated, as shown in Figure 1. Although the metal mask 1 is made of metal, its thickness is quite thin, at 100 µm or less. Therefore, the inventors' studies have revealed that if the ribs 2 become too thin, problems will arise during film formation.

[0023] Specifically, only the longitudinal ends of the rib 2 are supported by other metal parts. Therefore, the stability of the unsupported longitudinal middle portion of the rib 2 depends solely on its own rigidity. Therefore, even a slight external force applied when installing the metal mask 1 in a film-forming apparatus for film formation can easily cause the rib 2 to bend and displace in its width direction (hereinafter, this displacement may be referred to as "twist"). The rib 2 may be installed in the film-forming apparatus in a state where the twist is not fully restored. In other words, if the rib 2 becomes too thin in an attempt to further improve manufacturing efficiency, the shape of the thin film formed based on the through holes is likely to deviate from the designed shape in some parts, and the state of the thin film will also change with each film-forming process, making it unstable. As a result, defective products and other issues can occur, making it difficult to improve manufacturing efficiency.

[0024] The phenomenon that causes the deviation between the shape of the thin film assumed in the design of the through hole and the shape of the thin film after the actual film formation is not limited to the above-mentioned rib displacement, but also includes, for example, the deviation of the rib width from the set width of the rib due to the accuracy of etching when forming the through hole. However, because there is a technical limit to this accuracy, it is difficult to improve beyond the current state unless a new breakthrough occurs. Therefore, the inventors investigated the range of the width of the rib 2 (rib width) that allows for suitable film formation while improving manufacturing efficiency.

[0025] (Preparation of Thin Film Metal Substrate) A 50 μm thick metal substrate made of SUS430 was prepared. The ease of twisting of the rib also depends on the longitudinal dimension of the rib itself. Therefore, multiple sets of ribs with different longitudinal dimensions and width dimensions were formed on the metal substrate, and the degree of twisting of the rib during the standing operation was measured.

[0026] (Formation of Through Holes) Twelve through holes (slits) of the same width were formed in a metal substrate by wet etching in a line in the width direction, and eleven ribs of the same set width were created between the through holes. The slit lengths (Sl) were the following 12 types, and the rib widths (Rw) were the following 14 types. The units for all values ​​are μm. Slit lengths: 35,000, 30,000, 25,000, 21,502, 18,000, 16,000, 13,830, 9,994, 7,692, 5,062, 3,601, 1,363 Rib widths: 50, 65, 80, 90, 120, 150, 180, 210, 240, 270, 300, 400, 500, 1,000 The slit width (Sw) was fixed at 1,500 μm. As a result, a total of 168 evaluation regions, each consisting of a combination of slit length (Sl) and rib width (Rw), were formed on the metal substrate to prepare metal masks for measurement. Figure 2 shows the outline of one evaluation region.

[0027] (Measurement of Rib Width and Calculation of Rib Width Range) The completed metal mask was placed on the stage of a measuring device (Nikon Corporation NEXIV Series VMR-12072), and the actual width dimension of the rib in each measurement area (evaluation area) was measured. The measurement points were the rib widths (Rw1 to Rw5 shown in FIG. 2) of five ribs (R1 to R5 shown in FIG. 2) arranged continuously so as to include the width center of each evaluation area (the center of each evaluation area in the direction parallel to the width direction of the rib), and were taken to be the longitudinal center of the rib to match the measurement of the twist range average value described below. The difference (μm) between the maximum and minimum values ​​of the obtained actual width dimensions of the five ribs was taken as the "rib width range," which indicates the variation in rib width in each evaluation area.

[0028] (Measurement of Rib Twist Amount and Calculation of Average Twist Range Value) The metal mask was placed on the stage of the measuring instrument, and the actual widthwise dimensions (Sw1 to Sw5 shown in Figure 2) of five consecutive slits (Sw1 to Sw5 shown in Figure 2) were measured. Of the 12 slits in each evaluation area, five slits were measured, including the center of the widthwise direction of each evaluation area (the center of each evaluation area in the direction parallel to the rib width direction). Based on the assumption that the longitudinal center of the rib is the furthest from the support portion and thus most susceptible to displacement, the measurement point was the longitudinal center of the slit, which reflects the rib displacement. When twisting occurs in the rib, the widthwise dimension of the slit on one side of the twisted rib becomes smaller, for example, as shown by the distance between points P and Q in Figure 3, while the widthwise dimension on the other side becomes larger, as shown by the distance between points R and S. The difference (μm) between the maximum and minimum values ​​of the actual widthwise dimensions of the five slits obtained was used as the "twist range," which indicates the variation in the rib twist amount (rib twist amount) in each evaluation area. The twist state of each rib changes each time it is placed on the stage. Therefore, after the measurement, the metal mask was lifted up and moved away from the stage, and then placed back on the stage and the same measurement was performed five times in total. The arithmetic mean of the five twist range measurements obtained in each evaluation region was taken as the "average twist range value" for each evaluation region.

[0029] The measurement results of the rib width are shown in Figures 4 to 7. The rib width range was approximately 2 to 4 μm in all evaluation areas, regardless of the dimensions of the slits and ribs. This indicates the dimensional accuracy of etching at the current technological level, and means that even if twisting of the ribs could be completely eliminated, this variation in the dimensions of the deposited thin film would be unavoidable.

[0030] Next, the twist range average values ​​are shown in Figures 8 and 9. For all rib widths, there was a tendency for the twist range average value, i.e., the amount of twist, to increase as the slit length increased, and there were also regions where the twist range average value was 10 times or more the rib width range shown in Figure 7. Figures 10 to 13 are graphs showing the relationship between the twist range average value and slit length for each rib width in this study. As the rib width decreased, the twist range average value, i.e., the amount of twist, increased, and this increase tended to become more pronounced when the rib width was less than 100 μm.

[0031] In a metal mask, the upper limit of the twist range average value for performing appropriate film formation varies depending on the application of the formed structure, but in any application, the difference obtained by subtracting the rib width range from the maximum allowable variation (maximum allowable rib width) is the upper limit of the twist range average value. Below, we will explain the concept and the upper limit of the twist range average value using an example where the metal mask according to this embodiment is used to produce an internal electrode member for an MLCC.

[0032] For example, a thin film 50 formed over a large area as shown in FIG. 14A is divided into multiple components 60 of the same shape and size as shown in FIG. 14B. Each component 60 has a rectangular shape in plan view, with a metal thin film 62 (e.g., nickel alloy) formed on a substrate 61 (e.g., ceramic green sheet), and a margin 63 along one side in plan view where the metal thin film 62 is not formed. By stacking and integrating multiple components 60 so that the margins 63 are alternately positioned, an internal electrode structure of an MLCC can be formed. In an MLCC, external electrodes are disposed at both ends of the margins 63. The margins 63 must be electrically disconnected from the external electrodes. Therefore, if the thin film 50 excessively extends beyond the margins 63 due to variations in film formation, the component 60 cannot be reliably used.

[0033] The width of the margin 63 depends on the dimensions of the MLCC to be manufactured, but is at least about 10 μm. In this case, if the planar dimension of the thin film varies by 10 μm or more, at least a portion of the margin will disappear across the width, potentially resulting in electrical continuity with the external electrodes. Based on this, in this embodiment, the upper limit of the average twist range is set to 6 μm, which is 10 μm minus the rib width range of 4 μm.

[0034] Based on Figures 10 to 13, the slit lengths at which the twist range average value is 6 µm for each set width of the rib were determined as follows: Set width 50 µm: 4073 µm Set width 65 µm: 5996 µm Set width 80 µm: 9967 µm Set width 90 µm: 12069 µm Set width 120 µm: 20511 µm Set width 150 µm: 23072 µm Set width 180 µm: 24948 µm Set width 210 µm: 27343 µm Set width 240 µm: 30357 µm Set width 270 µm: 43896 µm Set width 300 µm: 53312 µm Set width 400 µm: 54922 µm Set width 500 µm: 70591 µm Set width 1000 µm: 126662 µm Of the set rib widths, four points between 90 μm and 180 μm were plotted as shown in Figure 15. However, since it was difficult to imagine a straight line passing through all four points, a curve passing through all four points was calculated, resulting in the result shown in Figure 15. It was found that the value of the rib width x at which the average twist range value is 6 μm for a certain slit length y can be expressed by the following formula (A): y = 0.0321x ３ -14.814x ２ +2324.3x-100503...(A)

[0035] Therefore, when the rib width x is 90 μm or more and 180 μm or less, if the rib width x and the slit length y satisfy the following formula (1) based on the above formula (A), the metal mask can be used without problems in applications for producing internal electrode members for MLCCs, and the inventors' studies have revealed that safety is further ensured if the relationship satisfies formula (1a) obtained by multiplying formula (1) below by a safety factor: y≦0.0321x ３ -14.814x ２ +2324.3x-100503...(1) y≦(0.0321x ３-14.814x ２ +2324.3x-100503) x 0.95...(1a)

[0036] 15 shows that when the rib width is in the range of 120 μm or more and 180 μm or less, increasing the rib width does not significantly increase the slit length. Furthermore, it also shows that when the rib width is less than 120 μm, twisting of the rib becomes more likely to occur. This finding was first discovered by the inventors.

[0037] Figure 16 shows a graph plotting the entire range of all set widths. It was inferred from each plot that the relationship between rib width x and slit length y changes depending on the value of rib width x, and it was thought that such relationships could roughly be classified into the following four types. This was a finding first revealed by the inventors. First range (Sec1 in Figure 16): x ≤ 90 μm Second range (Sec2 in Figure 16): 90 μm ≤ x ≤ 180 μm Third range (Sec3 in Figure 16): 180 μm ≤ x ≤ 300 μm Fourth range (Sec4 in Figure 16): 300 μm ≤ x Of the four ranges above, the second range has already been explained. For the other three ranges, it was inferred that linear approximation was possible from the plots belonging to each range, so linear approximation was attempted for each range. As a result, it was found that in the first range, if the rib width x and the slit length y satisfy the relationship shown in formula (2) below, twisting of the ribs can be suppressed and good film formation can be achieved, and it is more preferable that the relationship satisfy formula (2a) obtained by multiplying formula (2) below by a safety factor: y≦206.2354x−6668.0204 ... (2) y≦(206.2354x−6668.0204)×0.95 ... (2a) In the third range, if the rib width x and the slit length y satisfy the relationship shown in formula (3) below, twisting of the ribs can be suppressed and good film formation can be achieved, and it is more preferable that the relationship satisfy formula (3a) obtained by multiplying formula (3) below by a safety factor. y≦244.27x+22653.6 (3) y≦(244.27x+22653.6)×0.95 (3a) In the fourth range, if the rib width x and the slit length y satisfy the relationship in the following formula (4), twisting of the ribs can be suppressed and good film formation can be achieved, and it was considered more preferable if the relationship satisfied the following formula (4a) obtained by multiplying formula (4) by a safety factor: y≦110.0071x−15867.8621 (4) y≦(110.0071x−15867.8621)×0.95 (4a)

[0038] In accordance with the present embodiment, based on the above findings, the metal mask according to the present invention is configured such that the relationship between the width of the rib disposed between the plurality of through holes and the length of the through holes satisfies at least one of the above formulas (1) to (4a). Therefore, the metal mask has a high through hole ratio in a planar view while also exhibiting excellent structural stability. As a result, when formula (1) or (1a) is satisfied, the arrangement efficiency of large-area through holes corresponding to multiple components of an MLCC within the metal mask can be maximized, thereby contributing to the efficient manufacture of MLCC components. Note that when the value of the rib width x is within one of the range boundaries of 90 μm, 180 μm, or 300 μm, either formula (1) or (1a) may be applied.

[0039] Furthermore, in the method for manufacturing a metal mask according to this embodiment, which takes into account the above findings, a step of substituting the longitudinal dimension of the through hole to be formed into one of the above formulas (1) to (4) is performed, whereby the longitudinal dimension y (μm) of the through hole to be formed and the set width x (μm) of the rib located between the through holes are set so as to satisfy the used formula. Then, a step of forming the through hole by etching based on the set set width x of the rib and the longitudinal dimension y is performed, whereby an appropriate and minimum rib width can be easily achieved. As a result, the effort of fabricating multiple prototypes to verify the degree of rib twist, etc., can be significantly reduced, and a metal mask with high film formation efficiency and minimal rib twist can be produced in an extremely simple manner.

[0040] For example, by setting the slit width to 1000 μm, a thin film for an 0402-size MLCC can be formed on two sides. By setting the slit width to 2500 μm, a thin film for a 1005-size MLCC can be formed on two sides. By setting the slit width to 500 μm, a thin film for a 0201-size MLCC can be formed on two sides. When using a thin film 50 for an 0402-size MLCC, the slit width is set to 1500 μm, and the thin film 50 is singulated as described above to obtain a component 60 suitable for a 402-size MLCC, with a metal thin film 62 having a long side dimension of approximately 600 μm. The short side dimension of the component 60 is determined by the size of the MLCC, etc., but the longer the slit length, the more components 60 can be produced from a single substrate. As described above, the present invention makes it possible to determine the maximum slit length required for high-precision film formation on a metal mask, thereby contributing to maximizing the efficiency of two-side formation. Furthermore, the present invention can significantly contribute to maximizing manufacturing efficiency by optimizing the rib width and slit length in metal masks used for film formation to form elongated thin films with larger or smaller areas.

[0041] Although the present invention has been described above, the specific configuration is not limited to this embodiment, and modifications and combinations of the configuration within the scope of the gist of the present invention are also included.

[0042] For example, the thin-film metal substrate according to the present invention is not limited to stainless steel such as SUS430 used in the above-mentioned study. Therefore, the manufacturing method according to the present invention can be suitably applied to the case where a metal mask is produced using a thin-film metal substrate made of Invar, Super Invar, or the like. If the thin-film metal substrate is made of a magnetic metal material such as those described above, there is an advantage in that it can be fixed to the film-forming apparatus using magnetic force.

[0043] Furthermore, the thickness of the thin-film metal substrate is not limited to 50 μm as in the above study. As the thin-film metal substrate becomes thicker, the rigidity of the rib increases. Therefore, thicknesses of 50 μm or more can also be used without any problems.

[0044] The use of the metal mask according to the present invention is not limited to the internal electrodes of the MLCC described in the embodiment, but can be widely applied to various uses that require the deposition of a thin and long film.

[0045] According to the present invention, it is possible to provide a metal mask that has a high through-hole ratio and is also excellent in stability as a structure.

[0046] 1 Metal mask 2 Rib 10 Through hole

Claims

1. A metal mask having a plurality of through holes arranged in a thin film metal substrate, wherein the width x (μm) of a rib located between the through holes is 90 μm or more and 180 μm or less, and the width x and the longitudinal dimension y (μm) of the through hole satisfy the following formula: y≦0.0321x ３ -14.814x ２ +2324.3x-100503 2. A metal mask having a plurality of through holes arranged in a thin-film metal substrate, wherein the width x (μm) of a rib located between the through holes is 180 μm or more and 300 μm or less, and the width x and the longitudinal dimension y (μm) of the through hole satisfy the following formula: y≦244.27x+22653.6 3. A metal mask having a thin-film metal substrate with a plurality of through holes arranged in a row, wherein the width x (μm) of a rib located between the through holes is 300 μm or more, and the x and the longitudinal dimension y (μm) of the through hole satisfy the following formula: y≦110.0071x-15867.8621.

4. A metal mask having a plurality of through holes arranged in a thin-film metal substrate, wherein the width x (μm) of a rib located between the through holes is 90 μm or less, and the width x and the longitudinal dimension y (μm) of the through hole satisfy the following formula: y≦206.2354x-6668.0204 5. The metal mask according to any one of claims 1 to 4, wherein the thin film metal substrate is made of a magnetic metal material.

6. The metal mask according to claim 5, wherein the magnetic metal material is one of SUS430, Invar, and Super Invar.

7. The metal mask according to any one of claims 1 to 4, wherein the thin film metal substrate has a thickness of 50 µm or more.

8. A method for manufacturing a metal mask in which a plurality of through holes are formed in a line in a thin-film metal substrate, wherein the longitudinal dimension y (μm) of the through holes to be formed and the set width x (μm) of the ribs located between the through holes are set to satisfy the following formula, with x being 90 μm or more and 180 μm or less, and the through holes are formed by etching based on the set x and y: y≦0.0321x ３ -14.814x ２ +2324.3x-100503 9. A method for manufacturing a metal mask in which a plurality of through holes are formed in a line in a thin-film metal substrate, wherein the longitudinal dimension y (μm) of the through holes to be formed and the set width x (μm) of the ribs located between the through holes are set to satisfy the following formula, with x being 180 μm or more and 300 μm or less, and the through holes are formed by etching based on the set x and y: y≦244.27x+22653.6 10. A method for manufacturing a metal mask in which a plurality of through holes are formed in a line in a thin-film metal substrate, wherein the longitudinal dimension y (μm) of the through holes to be formed and the set width x (μm) of the ribs located between the through holes are set to satisfy the following formula, with x being 300 μm or more, and the through holes are formed by etching based on the set x and y: y≦110.0071x-15867.8621 11. A method for manufacturing a metal mask in which a plurality of through holes are formed in a line in a thin-film metal substrate, wherein the longitudinal dimension y (μm) of the through holes to be formed and the set width x (μm) of the ribs located between the through holes are set to satisfy the following formula with x being 90 μm or less, and the through holes are formed by etching based on the set x and y: y≦206.2354x-6668.0204

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