Surface-treated copper foil, copper-clad layered sheet, and method for forming circuit

Abstract

This surface-treated copper foil comprises copper foil 10 and a metal layer 20 that is disposed on one surface of the copper foil 10 and that has a slower etching rate than the copper foil 10. The surface sharpness Sku on the metal layer 20 side is at least 5.0. Moreover, etching is performed from the metal layer 20 side.

Description

Surface-treated copper foil, copper-clad laminate, and circuit formation method

[0001] The present disclosure relates to a surface-treated copper foil, a copper-clad laminate, and a circuit formation method.

[0002] Circuit patterns on printed wiring boards are formed by lithographically processing a copper-clad laminate, which is a laminate of copper foil and a resin substrate. The most common method is the subtractive method, in which copper foil is etched using a photosensitive resist layer (e.g., a dry film) patterned by photolithography as a mask. This method forms a circuit pattern by etching the copper foil, resulting in a trapezoidal shape in which the bottom width of the circuit pattern is greater than the top width in the thickness direction cross section. Therefore, although this method is simple, it is not suitable for forming fine circuit patterns.

[0003] On the other hand, a semi-additive method is also known in which a photosensitive resist layer patterned by photolithography is provided on a resin substrate, and then copper plating is applied to form a circuit pattern. This method is easy to form fine circuit patterns because the shape of the circuit pattern is determined by the precision of the resist pattern. However, this method has the problem of being costly because the circuit pattern must be formed by plating.

[0004] Therefore, development of a method that can form fine circuit patterns like the semi-additive method even with a low-cost subtractive method is underway. For example, Patent Document 1 proposes a technology that suppresses sagging due to etching (i.e., etching that spreads from the surface of the copper foil toward the resin substrate) by providing a layer of a different metal, such as nickel, that has a slower etching rate than the copper foil on the etching surface of the copper foil.

[0005] JP 2011-216528 A

[0006] However, copper-clad laminates, which have a layer of a different metal such as nickel on the surface of copper foil, have a problem of poor adhesion to a photosensitive resist layer during the circuit pattern formation process of a printed wiring board. Poor adhesion to the photosensitive resist layer makes it difficult to form a fine resist pattern when the photosensitive resist layer is exposed and developed. As a result, even if etching sagging can be suppressed, it is difficult to form a fine wiring pattern.

[0007] The embodiments of the present invention have been made to solve the above-mentioned problems, and have an object to provide a surface-treated copper foil, a copper-clad laminate, and a circuit formation method that can suppress sagging due to etching and improve adhesion to a photosensitive resist layer.

[0008] The present inventors have conducted extensive research into surface-treated copper foils having a metal layer on one side of the copper foil that has a slower etching rate than the copper foil. As a result, they have found that the above problems can be solved by controlling the sharpness Sku of the surface on the metal layer side, and have completed an embodiment of the present invention.

[0009] That is, an embodiment of the present invention relates to a surface-treated copper foil comprising a copper foil and a metal layer provided on one side of the copper foil and having an etching rate slower than that of the copper foil, wherein the surface on the metal layer side has a sharpness Sku of 5.0 or more and is etched from the metal layer side.

[0010] Another embodiment of the present invention relates to a copper-clad laminate comprising the surface-treated copper foil and a resin substrate provided on the other surface of the surface-treated copper foil.

[0011] Furthermore, an embodiment of the present invention relates to a circuit forming method for forming a circuit pattern on a copper-clad laminate comprising copper foil, a metal layer provided on one side of the copper foil and having an etching rate slower than that of the copper foil, and a resin substrate adhered to the other side of the copper foil, wherein the surface of the copper foil on the metal layer side has a sharpness Sku of 5.0 or more, the circuit forming method including: a photosensitive resist layer forming step of providing a photosensitive resist layer on the surface on the metal layer side; an exposure step of exposing the photosensitive resist layer to light in a predetermined pattern; a development step of developing the photosensitive resist layer to form a resist pattern layer; an etching step of etching the metal layer and the copper foil on which the resist pattern layer has been formed to form a circuit pattern; and a resist pattern layer removal step of removing the resist pattern layer.

[0012] Furthermore, an embodiment of the present invention relates to a circuit forming method including: a metal layer forming step of forming a metal layer having an etching rate slower than that of the copper foil on the other side of the copper foil of a copper-clad laminate including a copper foil and a resin substrate adhered to one side of the copper foil; a photosensitive resist layer forming step of providing a photosensitive resist layer on the surface of the metal layer side; an exposure step of exposing the photosensitive resist layer to light in a predetermined pattern; a development step of developing the photosensitive resist layer to form a resist pattern layer; an etching step of etching the metal layer and the copper foil on which the resist pattern layer has been formed to form a circuit pattern; and a resist pattern layer removing step of removing the resist pattern layer, wherein the sharpness Sku of the surface of the copper foil on the metal layer side is adjusted to 5.0 or more before the photosensitive resist layer forming step.

[0013] According to the embodiments of the present invention, it is possible to provide a surface-treated copper foil, a copper-clad laminate, and a circuit formation method that can suppress sagging due to etching and improve adhesion to a photosensitive resist layer.

[0014] FIG. 1 is a schematic diagram of a cross section of a surface-treated copper foil according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a cross section of another surface-treated copper foil according to an embodiment of the present invention. FIG. 3 is a schematic diagram of a cross section of another surface-treated copper foil according to an embodiment of the present invention. FIG. 4 is a schematic diagram of a cross section of another surface-treated copper foil according to an embodiment of the present invention. FIG. 5 is a SEM photograph showing defects in a circuit pattern caused by scratches on the metal layer or adhesion of foreign matter. FIG. 6 is a graph showing the etching properties of Ni and Cu with a soft etching solution. FIG. 7 is a schematic diagram of a cross section of another surface-treated copper foil according to an embodiment of the present invention. FIG. 8 is a schematic diagram of a cross section of a copper-clad laminate according to an embodiment of the present invention. FIG. 9 is a flow diagram of a circuit formation method according to an embodiment of the present invention. FIG. 10 is a schematic cross-sectional view for explaining steps after the photosensitive resist layer formation step. FIG. 11 is an SEM photograph of a circuit pattern produced using a surface-treated copper foil with a Ni layer formed thereon and a copper foil without a Ni layer formed thereon.

[0015] Preferred embodiments of the present invention will be described in detail below, but the present invention should not be construed as being limited thereto, and various modifications and improvements can be made based on the knowledge of those skilled in the art without departing from the gist of the present invention. The multiple components disclosed in the following embodiments can be appropriately combined to form various inventions. For example, some components may be deleted from all the components shown in the following embodiments, or components from different embodiments may be appropriately combined.

[0016] 1A and 1B are schematic diagrams of a cross section (a cross section parallel to the thickness direction) of a surface-treated copper foil according to an embodiment of the present invention. As shown in FIGS. 1A and 1B, the surface-treated copper foil comprises a copper foil 10 and a metal layer 20 provided on one side of the copper foil 10 and having a slower etching rate than the copper foil 10. This surface-treated copper foil is etched from the metal layer 20 side. By providing the metal layer 20 on one side of the copper foil 10, sagging due to etching (i.e., the copper foil 10 being etched in a divergent manner) can be suppressed when etching the surface-treated copper foil from the metal layer 20 side. Here, in this specification, the phrase "metal layer 20 having a slower etching rate than the copper foil 10" means that the metal layer 20 has a slower etching rate than the copper foil 10 with respect to the etching solution used in the etching step described below (i.e., the etching solution for etching the metal layer 20 and the copper foil 10). The copper foil 10 is not particularly limited and may be either a rolled copper foil or an electrolytic copper foil.

[0017] The surface on the metal layer 20 side has a sharpness Sku (hereinafter abbreviated as "Sku") of 5.0 or more. Sku is a parameter related to the tip shape of peaks or valleys, as defined in ISO 25178-2:2012. Specifically, Sku represents the sharpness (sharpness) of a height histogram created based on the average height. For example, Sku of 3.0 indicates that the height distribution is a normal distribution. When Sku is greater than 3.0, the larger this value, the more concentrated the height distribution (the more pointed the tip). Conversely, when Sku is less than 3.0, the smaller this value, the more dispersed the height distribution (the more flattened the tip). By controlling the Sku of the surface on the metal layer 20 side to 5.0 or more, when a photosensitive resist layer (e.g., dry film resist) is provided on the surface on the metal layer 20 side, the anchor effect and surface interaction can improve the adhesion between the metal layer 20 and the photosensitive resist layer. When the adhesion between the metal layer 20 and the photosensitive resist layer is improved, the L / S (line width and space width) of the resist pattern layer formed by the circuit formation method (particularly the exposure step and development step) described below can be made smaller, making it possible to form a fine circuit pattern by the etching step.

[0018] From the viewpoint of stably obtaining the above-mentioned effects, the Sku of the surface on the metal layer 20 side is preferably 5.5 or more, more preferably 6.0 or more, and particularly preferably 6.5 or more. On the other hand, the upper limit of the Sku of the surface on the metal layer 20 side is not particularly limited, but if the Sku is too large, when a photosensitive resist layer is provided on the surface on the metal layer 20 side, the sharp portions of the surface on the metal layer 20 side will break, which may actually reduce adhesion to the photosensitive resist layer. For this reason, the upper limit of the Sku of the surface on the metal layer 20 side is preferably 17.0 or less, more preferably 16.5 or less, even more preferably 16.0 or less, and particularly preferably 15.5 or less. The Sku of the surface on the metal layer 20 side can be measured by the method described below in accordance with ISO 25178-2:2012.

[0019] As shown in FIG. 1A , the Sku of the surface on the metal layer 20 side can be controlled by roughening one side of the copper foil 10 by soft etching. According to this method, the roughness of the surface on the metal layer 20 side reflects the roughness of the other side of the copper foil 10. Therefore, by roughening one side of the copper foil 10 to an Sku of 5.0 or more, the Sku of the surface on the metal layer 20 side formed thereon can be controlled to 5.0 or more. Furthermore, the Sku of the surface on the metal layer 20 side can be controlled by forming the metal layer 20 by a roughening plating process, as shown in FIG. 1B . Specifically, the roughening plating process can be performed on one side of the copper foil 10 under conditions such that the Sku of the surface on the metal layer 20 side is 5.0 or more. In this case, it is not necessary to roughen one side of the copper foil 10 by soft etching. Alternatively, the metal layer 20 may be formed by a roughening plating process after roughening one side of the copper foil 10 by soft etching.

[0020] When one side of the copper foil 10 is roughened by soft etching, the soft etching method is not particularly limited, and known methods such as spraying, immersion, and puddling can be used. The soft etching solution is not particularly limited as long as it is capable of roughening the surface of the copper foil 10. Examples of soft etching solutions that can be used include an aqueous solution containing sulfuric acid and hydrogen peroxide, an aqueous ammonium persulfate solution, and an aqueous sodium persulfate solution. Commercially available soft etching solutions may also be used. The temperature and treatment time of the soft etching solution are not particularly limited and can be adjusted appropriately depending on the type of soft etching solution used.

[0021] When the metal layer 20 is formed by roughening plating, the conditions for the roughening plating are not particularly limited and can be adjusted appropriately depending on the type of metal layer 20. For example, when an alloy layer of nickel and copper (Cu—Ni) is formed as the metal layer 20 by roughening plating, the following conditions can be used: Nickel sulfate: 60 to 150 g / L Copper sulfate: 50 to 70 g / L pH: 2 to 3 Bath temperature: 30 to 40° C. Current density: 25 to 35 A / dm 2Rotating electrode speed: 100 to 150 rpm As another example, when a Ni layer is formed as the metal layer 20 by roughening plating, the following conditions can be used: Plating solution: roughened nickel plating solution (manufactured by JX Metals Trading Co., Ltd.) Bath temperature: 57 to 63°C Current density: 9 to 11 A / dm 2

[0022] The metal layer 20 is not particularly limited as long as its etching rate is slower than that of the copper foil 10. For example, it can be a layer of a metal selected from nickel, cobalt, platinum group metals, gold, and silver, or a layer of an alloy containing these metals. By using such a metal or alloy for the metal layer 20, the effect of suppressing sagging due to etching (the effect of improving the etching factor) can be stably obtained. In this disclosure, "alloy" refers to a substance in which one or more metal elements or non-metal elements are added to a metal element. When the metal layer 20 is an alloy layer containing two or more of the above metals, it is preferable that the alloy contains the above metal as the main component. Here, "main component" in this specification means that the proportion of the metal in the total components exceeds 50% by mass. Examples of alloys that can be used for the metal layer 20 include Co—P, Ni—P, Co—Ni, Co—Zn, Ni—Zn, Cu—Ni, Pt—Zn, Pt—P, Pt—Mo, Pt—W, Pt—Fe, and Pt—Co.

[0023] Among the above-mentioned metals, it is preferable that the metal layer 20 contains nickel. By using the metal layer 20 containing nickel, it is possible to suppress costs and enhance the effect of suppressing sagging due to etching (the effect of improving the etching factor).

[0024] More specifically, the metal layer 20 is a nickel alloy layer, and the amount of nickel deposited in the nickel alloy layer is 1000 μg / dm 2 It is preferable that the concentration is 1500 μg / dm or more. 2 It is more preferable that the amount of nickel deposited is 1000 μg / dm or more. 2By setting the nickel content at or above 7000 μg / dm , it is possible to enhance the effect of suppressing sagging due to etching and improve adhesion to the photosensitive resist layer. The upper limit of the nickel deposition amount in the nickel alloy layer is not particularly limited, but if the nickel deposition amount is too high, a large amount of the nickel alloy layer is likely to remain on the surface of the copper foil 10. In this case, it becomes necessary to remove the nickel alloy layer using a nickel alloy stripping agent, and there is also a possibility that the underlying copper foil 10 will also dissolve. Therefore, the upper limit of the nickel deposition amount is set to 7000 μg / dm . 2 It is preferable that:

[0025] The nickel alloy layer preferably contains copper. That is, the nickel alloy layer can be an alloy of nickel and copper (Cu—Ni), an alloy of nickel, copper, and other metals, etc., but is preferably an alloy of nickel and copper. In addition to the above effects, such a nickel alloy layer has a high affinity with the underlying copper foil 10, thereby improving adhesion between the copper foil 10 and the nickel alloy layer. Whether the nickel alloy layer contains copper can be determined by performing EDX analysis simultaneously with TEM observation. Specifically, first, the surface of the copper foil 10 containing the nickel alloy layer is observed with a TEM to identify the roughened portion. Next, nickel and copper are mapped in the identified roughened portion by EDX analysis. Whether the nickel alloy layer contains copper can be determined by confirming whether nickel and copper are mixed in the roughened portion.

[0026] For TEM observation, a sample is prepared by applying a carbon protective film to a test piece of the surface-treated copper foil to be evaluated using an FIB, and the sample is fixed to a molybdenum sample support by microsampling and thinned to a thickness of 100 nm or less. Next, the sample is observed using a TEM and EDX analysis is performed. The various conditions for this may be as follows. <FIB> Instrument name: SMI3050SE manufactured by Hitachi High-Tech Corporation Acceleration voltage: 30 kV <TEM-EDX> Instrument name (TEM): JEM-ARM300F2 manufactured by JEOL Ltd. Instrument name (EDX): JED2300T manufactured by JEOL Ltd., two 150 mm SDD detectors STEM image observation + EDX analysis Mode: STEM mode Acceleration voltage: 300 kV Spot size: 0.15 nm Observation: BF image, HAADF image Magnification: 100,000, 500,000, 1,000,000 times Integration time (EDX): 0.1 msec / pixel Number of map pixels: 256 x 256

[0027] Alternatively, the metal layer 20 is a nickel layer, and the nickel coating weight in the nickel layer is 400 μg / dm 2 It is preferable that the concentration is 400 to 18,000 μg / dm or more. 2 More preferably, it is 600 to 15,000 μg / dm 2 It is more preferable that the amount of nickel deposited is 400 μg / dm 2 By setting the amount of nickel deposition at 18,000 μg / dm or more, the effect of suppressing sagging due to etching can be enhanced. 2 By making the following, it is possible to improve adhesion to the photosensitive resist layer. Here, in this specification, the "nickel layer" means one having a nickel content of 99.9 mass % or more in quantitative analysis by X-ray diffraction analysis (XRD).

[0028] The thickness of the metal layer 20 is not particularly limited, but is preferably 200 nm or less, and more preferably 100 nm or less. By controlling the thickness of the metal layer 20 within such a range, the metal layer 20 becomes easier to remove in the metal layer removal step described below. The thickness of the metal layer 20 can be measured by observing a cross section of the surface-treated copper foil in the thickness direction using a TEM.

[0029] The method for forming the metal layer 20 is not particularly limited, and may be a wet plating method, a dry plating method such as sputtering or vapor deposition, or the like.

[0030] Various other layers may be provided on the surface of the metal layer 20 as needed. For example, an anti-rust layer (e.g., a Cr layer) may be provided on the surface of the metal layer 20. This anti-rust layer is removed before forming the circuit. The Cr layer may be formed, for example, under the following conditions: Liquid composition: potassium dichromate 3.00 g / L, zinc sulfate 1.47 g / L Immersion time: 30 seconds Liquid temperature: room temperature

[0031] The surface-treated copper foil can further comprise a copper layer on the surface of the metal layer 20. A schematic diagram of a cross section (a cross section parallel to the thickness direction) of a surface-treated copper foil having such a configuration is shown in Fig. 2. Note that, although Fig. 2 shows an example in which a copper layer 30 is provided on the surface of the metal layer 20 of the surface-treated copper foil of Fig. 1A, it should be noted that a copper layer 30 may also be provided on the surface of the metal layer 20 of the surface-treated copper foil of Fig. 1B.

[0032] Because the metal layer 20 is a very thin layer, there is a risk of partial peeling of the metal layer 20 due to scratches, dents, and the like. Partial peeling of the metal layer 20 results in partial loss of the effects of the metal layer 20, and sagging due to etching cannot be suppressed. Furthermore, if foreign matter adheres to the metal layer 20, the foreign matter cannot be removed before the etching process described below, which may impede etching. For example, after the etching process described below, a circuit pattern defect occurs, as shown in the SEM photograph of FIG. 3 . In FIG. 3 , (a) shows a circuit pattern defect caused by a scratch on the metal layer 20, and (b) shows a circuit pattern defect caused by a foreign matter adhered to the metal layer 20. Therefore, by providing a copper layer 30 on the surface of the metal layer 20, these problems can be avoided.

[0033] In the circuit formation method described below, the copper layer 30 on the surface of the metal layer 20 is removed by pretreatment (specifically, soft etching) prior to the photosensitive resist layer formation process. This pretreatment soft etching can use the soft etching solution described above, eliminating the need to change chemical solutions and other hassles. For reference, FIG. 4 shows a graph showing the etching properties of Ni (metal layer 20) and Cu (copper layer 30) using a soft etching solution (Clean Etch EMR-2050 manufactured by Mitsubishi Gas Chemical Company, Inc.: an aqueous solution containing sulfuric acid and hydrogen peroxide). As shown in FIG. 4, Cu is more easily etched (the etching thickness is greater) than Ni, and the etching rates of the two are significantly different. Therefore, soft etching can selectively remove the copper layer 30, leaving only the metal layer 20, thereby suppressing sagging (improving the etching factor) in the etching process described below.

[0034] The thickness of the copper layer 30 is not particularly limited, but is preferably 0.3 to 2.0 μm. By making the thickness of the copper layer 30 0.3 μm or more, partial peeling of the metal layer 20 due to scratches, dents, etc. can be stably suppressed. Furthermore, by making the thickness of the copper layer 30 2.0 μm or less, it can be quickly removed by soft etching, thereby suppressing a decrease in productivity.

[0035] The method for forming the copper layer 30 is not particularly limited, and may be a wet plating method, a dry plating method such as sputtering or vapor deposition, or the like.

[0036] The surface-treated copper foil may further comprise a copper layer between the copper foil 10 and the metal layer 20. A schematic diagram of a cross section (a cross section parallel to the thickness direction) of a surface-treated copper foil having such a configuration is shown in Fig. 5. Fig. 5 shows an example in which a copper layer 40 is provided between the copper foil 10 and the metal layer 20 of the surface-treated copper foil of Fig. 1A, but it should be noted that a copper layer 40 may also be provided between the copper foil 10 and the metal layer 20 of the surface-treated copper foil of Fig. 1B or 2.

[0037] In a circuit formation method for a multilayer printed wiring board, through-holes such as via holes and through-holes may be provided to ensure electrical continuity between layers or to insert terminals of electronic devices. When the through-holes are through-holes, the through-holes are provided in a copper-clad laminate constituting the multilayer printed wiring board, and then a copper layer 40 (copper plating layer) is formed on the copper foil 10 located on the outer layer of the multilayer printed wiring board and on the surface of the through-hole. For the copper foil 10 located on the outer layer of such a multilayer printed wiring board, a metal layer 20 can be provided on the surface of the copper layer 40 to suppress sagging due to etching and improve adhesion with a photosensitive resist layer. In this case, the copper layer 40 is present between the copper foil 10 and the metal layer 20.

[0038] The surface-treated copper foil may further include a surface treatment layer provided on the other side of the copper foil 10. A schematic diagram of a cross section (a cross section parallel to the thickness direction) of a surface-treated copper foil having such a configuration is shown in FIG. 6. While FIG. 6 shows an example in which a surface treatment layer 50 is provided on the other side of the copper foil 10 of the surface-treated copper foil of FIG. 1A, it should be noted that a surface treatment layer 50 may also be provided on the other side of the copper foil 10 of the surface-treated copper foil of FIG. 1B, 2, or 5. The surface treatment layer 50 is not particularly limited, but may contain at least one selected from nickel, cobalt, and copper. By providing a surface treatment layer 50 containing these elements, various properties such as adhesion to a resin substrate and anti-rust effect can be imparted.

[0039] Examples of the surface treatment layer 50 include a roughening treatment layer, a chemical-resistant treatment layer, a heat-resistant treatment layer, a chromate treatment layer, and a silane coupling treatment layer. These layers can be used alone or in combination of two or more. Among these layers, the surface treatment layer 50 preferably includes a roughening treatment layer to improve adhesion to the resin substrate. Here, in this specification, the "roughening treatment layer" refers to a layer formed by roughening treatment and containing roughening particles. The surface treatment layer 50 can be formed in accordance with a method known in the art depending on the type of layer to be formed.

[0040] (2. Copper-Clad Laminate) Fig. 7 is a schematic diagram of a cross section (cross section parallel to the thickness direction) of a copper-clad laminate according to an embodiment of the present invention. While Fig. 7 shows an example of a copper-clad laminate having the surface-treated copper foil of Fig. 1A, it should be noted that the copper-clad laminate may have any of the surface-treated copper foils of Fig. 1B, Fig. 2, Fig. 5 and Fig. 6. As shown in Fig. 7, the copper-clad laminate comprises a surface-treated copper foil and a resin substrate 60 provided on the other side of the copper foil 10 of the surface-treated copper foil.

[0041] The resin substrate 60 is not particularly limited, and known substrates can be used. Examples of resin substrates include a paper-based phenolic resin, a paper-based epoxy resin, a synthetic fiber cloth-based epoxy resin, a glass cloth / paper composite substrate, a glass cloth / glass nonwoven fabric composite substrate, a glass cloth-based epoxy resin, a polyester film, a polyimide resin, a liquid crystal polymer, and a fluororesin. These can be used alone or in combination of two or more.

[0042] The method for manufacturing the copper-clad laminate is not particularly limited, and can be produced by known methods such as pressing, casting, laminating, and metallizing. For example, when using pressing, a resin substrate 60 may be placed on the other side of the surface-treated copper foil, and then bonded by thermocompression bonding. The timing for bonding the resin substrate 60 is also not particularly limited. For example, before forming the metal layer 20 or the like on the copper foil 10, the resin substrate 60 may be bonded to one side of the copper foil 10, and then the metal layer 20 or the like may be formed on the other side of the copper foil 10.

[0043] (3. Circuit Forming Method) The circuit forming method according to an embodiment of the present invention can be carried out by preparing a copper-clad laminate in which a resin substrate 60 is bonded to one side of a copper foil 10, forming a metal layer 20 on the other side of the copper foil 10, and then sequentially performing a photosensitive resist layer forming step, an exposure step, a development step, an etching step, and a resist pattern layer removing step. Furthermore, after the resist pattern layer removing step, a metal layer removing step for removing the metal layer may be further performed. In this method, copper layers 30, 40, etc. may be provided after the copper-clad laminate is prepared. If copper layer 30 is provided, it may be removed by soft etching at an appropriate stage, typically immediately before the photosensitive resist layer forming step described below. A typical example of the circuit forming method according to an embodiment of the present invention will now be described.

[0044] FIG. 8 is a flow diagram of a circuit formation method according to an embodiment of the present invention. As shown in FIG. 8, the circuit formation method according to an embodiment of the present invention includes a metal layer formation step, a photosensitive resist layer formation step, an exposure step, a development step, an etching step, and a resist pattern layer removal step. The metal layer removal step after the resist pattern layer removal step is performed as needed. FIG. 9 is a schematic cross-sectional view (schematic cross-sectional view parallel to the thickness direction) for explaining the steps after the photosensitive resist layer formation step. In FIG. 9, (a) represents the state after the photosensitive resist layer formation step, (b) the state after the exposure step, (c) the state after the development step, (d) the state after the etching step, (e) the state after the resist pattern layer removal step, and (f) the state after the metal layer removal step.

[0045] <Metal Layer Forming Step> The metal layer forming step is a step of forming a metal layer 20 having a slower etching rate than the copper foil 10 on the other side of the copper foil 10 of a copper-clad laminate including a copper foil 10 and a resin substrate 60 bonded to one side of the copper foil 10. The copper-clad laminate is not particularly limited, and one produced by the method described above can be used. The copper foil 10 and resin substrate 60 constituting the copper-clad laminate are also not particularly limited, and one described above can be used.

[0046] The sharpness Sku of the surface of the copper foil 10 on the metal layer 20 side is adjusted to 5.0 or more before the photosensitive resist layer formation process. Methods for achieving a sharpness Sku of 5.0 or more on the metal layer 20 side include soft etching of the other side of the copper foil 10 of the copper-clad laminate before the metal layer formation process (soft etching process), and / or forming the metal layer 20 by roughening plating in the metal layer formation process. These methods can be performed according to the method described above. By achieving a sharpness Sku of 5.0 or more on the metal layer 20 side surface, when a photosensitive resist layer 100 is disposed on the metal layer 20 side surface, as shown in FIG. 9( a), the anchor effect can be used to improve adhesion between the metal layer 20 side surface and the photosensitive resist layer 100. When the adhesion between the surface on the metal layer 20 side and the photosensitive resist layer 100 is improved, the L / S (line width and space width) of the resist pattern layer 120 formed by the exposure process and development process described below can be reduced, making it possible to form a fine circuit pattern 130 by the etching process described below.

[0047] Furthermore, if the metal layer 20 is provided on the surface of the copper foil 10 before the copper-clad laminate is produced, the heat (e.g., 300 to 400°C) generated when the copper foil 10 is bonded to the resin substrate 60 may cause the metal layer 20 and the copper foil 10 to diffuse together, promoting alloying, which may make it difficult to obtain the effect of improving the etching factor due to the metal layer 20. However, in the circuit formation method according to the embodiment of the present invention, the metal layer 20 is provided on the surface of the copper foil 10 after the copper-clad laminate is produced, so the above problem is unlikely to occur, and the effect of improving the etching factor due to the metal layer 20 can be stably obtained.

[0048] <Photosensitive Resist Layer Forming Step> As shown in FIG. 9( a), the photosensitive resist layer forming step is a step of providing a photosensitive resist layer 100 on the surface of the metal layer 20. The method for forming the photosensitive resist layer 100 is not particularly limited, and can be performed using a known method. For example, the photosensitive resist layer 100 can be formed by laminating a dry film (a film-like photosensitive resist) on the surface of the metal layer 20. Alternatively, the photosensitive resist layer 100 can be formed by applying a liquid photosensitive resist to the surface of the metal layer 20 and drying it. The application method is not particularly limited, and known methods such as dip coating, slide coating, curtain coating, bar coating, air knife coating, roll coating, gravure coating, slit die coating, and spray coating can be used.

[0049] Photosensitive resists can be either positive-type, in which the exposed (photoexposed) portions dissolve in a developer and the unexposed portions do not, or negative-type, in which the exposed portions do not dissolve in a developer and the unexposed portions dissolve in the developer; however, negative-type photosensitive resists are often used in the manufacturing process of printed wiring boards. In the example of FIG. 9 , a positive-type photosensitive resist layer 100 is used, but a negative-type photosensitive resist layer 100 may also be used. Known types of photosensitive resists, such as quinone diazide-based ones, can be used. Since photosensitive resists are commercially available, such commercially available products may also be used.

[0050] A cleaning process for cleaning the metal layer 20 may be performed before the photosensitive resist layer formation process (i.e., between the metal layer formation process and the photosensitive resist layer formation process). In particular, the copper-clad laminate on which the metal layer 20 is formed may have subsequent processes performed at a different location. In this case, the copper-clad laminate on which the metal layer 20 is formed is packaged and transported, and then unpacked at a different location. This may result in oxides forming on the surface of the metal layer 20, or oils adhering to the surface of the metal layer 20. If the photosensitive resist layer 100 is formed on the metal layer 20 in this state, the adhesion between the metal layer 20 and the photosensitive resist layer 100 may be reduced. Therefore, by performing a cleaning process, oxides and oils on the surface of the metal layer 20 can be removed, thereby stably improving the adhesion between the metal layer 20 and the photosensitive resist layer 100. The metal layer 20 can be cleaned using an acid cleaning solution or cleaning solution capable of removing oxides and oils. For example, the metal layer 20 can be cleaned using a cleaning solution containing dilute sulfuric acid or a surfactant.

[0051] Furthermore, in order to prevent partial peeling of the metal layer 20 due to scratches, dents, etc., a copper layer 30 may be provided on the surface of the metal layer 20. In this case, the copper layer 30 may be removed by soft etching. The soft etching solution may be any of those described above.

[0052] <Exposure Process> As shown in Fig. 9(b), the exposure process is a process of exposing the photosensitive resist layer 100 to light in a predetermined pattern. Here, Fig. 9(b) shows an example in which a positive photosensitive resist layer 100 is provided, and exposure in a predetermined pattern can improve the solubility of the exposed portion 110 in a developer. Note that when a negative photosensitive resist layer 100 is provided, exposure in a predetermined pattern can reduce the solubility of the exposed portion 110 in a developer compared to when a positive photosensitive resist layer 100 is provided.

[0053] The exposure method is not particularly limited, and any known method can be used, such as a mask exposure method in which a light beam of a required size is irradiated onto the photosensitive resist layer 100 through a mask on which a predetermined pattern is drawn, or a laser direct writing method in which a predetermined pattern is irradiated with laser light using a polygon mirror or a digital mirror device (DMD).

[0054] 9(c), the development process is a process of developing the photosensitive resist layer 100 to form a resist pattern layer 120. In the method for treating a copper-clad laminate according to an embodiment of the present invention, the adhesion between the metal layer 20 and the photosensitive resist layer 100 is good, so that the photosensitive resist layer 100 can be developed to form a resist pattern layer 120 with fine L / S.

[0055] The developing method is not particularly limited, and any known method can be used. For example, when a positive photosensitive resist layer 100 is provided, the exposed portion 110 can be dissolved and removed by treating it with a developer capable of dissolving the exposed portion 110. The type of developer may be appropriately selected depending on the type of the formed photosensitive resist layer 100, and is not particularly limited.

[0056] 9(d), the etching process is a process of etching the metal layer 20 and the copper foil 10 on which the resist pattern layer 120 has been formed to form a circuit pattern 130. In the circuit forming method according to the embodiment of the present invention, the resist pattern layer 120 can be formed with a fine L / S, and therefore the L / S of the circuit pattern 130 formed by etching can also be made small. Furthermore, because the metal layer 20 is provided on the surface of the copper foil 10, it is possible to prevent etching from spreading out from the surface of the copper foil 10 toward the resin substrate 60, and it is possible to form a circuit pattern 130 with a high etching factor.

[0057] The etching method is not particularly limited, and known methods such as spraying, immersion, and puddling can be used. The etching solution used in the etching step is not particularly limited, and examples include iron chloride-based etching solutions such as ferric chloride and copper chloride-based etching solutions such as cupric chloride. Alternatively, the copper foil 10 may be etched after pre-etching the metal layer 20. In this case, it is preferable that the etching solution used for pre-etching the metal layer 20 is different from the etching solution used for etching the copper foil 10. For example, if the metal layer 20 is nickel, cobalt, or an alloy thereof, a sulfuric acid-hydrochloric acid-based etching solution can be used as the pre-etching solution. If the metal layer 20 is a platinum group metal, gold, silver, or an alloy thereof, an etching solution containing nitric acid blended with chloride ions, a cationic polymer, or the like can be used as the pre-etching solution. The etching conditions are not particularly limited and can be adjusted appropriately depending on the type of etching solution used.

[0058] 9( e), the resist pattern layer removal step is a step of removing the resist pattern layer 120. The resist pattern layer 120 remaining on the circuit pattern 130 is an unnecessary layer, and therefore the resist pattern layer 120 is removed in this step. The method for removing the resist pattern layer 120 is not particularly limited, and it is sufficient to dissolve the resist pattern layer 120 using a solution that can dissolve the resist pattern layer 120.

[0059] <Metal Layer Removal Process> The metal layer removal process is a process of removing the metal layer 20, as shown in FIG. 9( f). The resin substrate 60 on which the circuit pattern 130 is formed is used as an inner layer circuit of a multilayer printed wiring board. In a multilayer printed wiring board, through holes (via holes or through holes) are provided to allow electrical connection with other wiring layers, and a copper layer (copper plating layer) is formed in the through holes. If the metal layer 20 remains on the circuit pattern 130, the adhesion between the circuit pattern 130 and the copper layer may be reduced, and the circuit pattern 130 and the copper layer may be separated due to impact, bending, or the like. Furthermore, when fabricating a multilayer printed wiring board, a roughening process (e.g., CZ process, Brown process, etc.) may be performed on the surface of the circuit pattern 130 to improve adhesion between the circuit pattern 130 and the resin layer in contact with the circuit pattern 130. However, if the metal layer 20 remains, the roughening process may not be performed properly. Therefore, by removing the metal layer 20 on the circuit pattern 130 in the metal layer removal process, the above problem can be resolved.

[0060] The method for removing the metal layer 20 is not particularly limited, and it may be removed using a solution capable of dissolving the metal layer 20. For example, if the metal layer 20 is nickel, cobalt, or an alloy thereof, a sulfuric acid-hydrochloric acid based etching solution may be used, and if the metal layer 20 is a platinum group metal, gold, silver, or an alloy thereof, an etching solution containing nitric acid mixed with chloride ions, a cationic polymer, or the like may be used.

[0061] <Other Steps> The circuit forming method according to an embodiment of the present invention may further include a through-hole / copper layer forming step in which, prior to the metal layer forming step, through-holes are formed in a copper-clad laminate and a copper layer 40 is formed on the copper foil 10 and the surface of the through-holes of the copper-clad laminate. As described above, through-holes (via holes or through-holes) are provided in a multilayer printed wiring board to establish electrical connection with other wiring layers. In this case, by forming a copper layer 40 on the surface of the copper foil 10 located in the outer layer and then forming a metal layer 20 on the copper layer 40, it is possible to suppress sagging due to etching of the copper foil 10 located in the outer layer and improve adhesion with the photosensitive resist layer 100. When the photosensitive resist layer 100 is a positive type, the copper layer 40 formed on the surface of the copper foil 10 corresponding to the exposed portion 110 is removed in the etching step. That is, in the etching step, the metal layer 20, copper layer 40, and copper foil 10 corresponding to the exposed portion 110 are etched to form a circuit pattern 130.

[0062] In the above-described embodiment, the metal layer 20 is formed on the copper foil 10 of the copper-clad laminate. However, in other embodiments, a copper-clad laminate may be used in which the metal layer 20 is formed on the copper foil 10 and then bonded to a resin substrate 60. The surface sharpness Sku of the metal layer 20 side of the copper-clad laminate is 5.0 or more. A circuit can be formed on the copper-clad laminate by performing a photosensitive resist layer formation process, an exposure process, a development process, an etching process, and a resist pattern layer removal process. Furthermore, after the resist pattern layer removal process, a metal layer removal process for removing the metal layer may be further performed. In the above-described copper-clad laminate, the surface sharpness Sku of the metal layer 20 side of the surface-treated copper foil has already been adjusted to 5.0 or more, so it is not necessary to adjust the surface sharpness Sku of the copper foil 10 on the metal layer 20 side to 5.0 or more before the photosensitive resist layer formation process. In this circuit forming method, the photosensitive resist layer forming step, exposure step, development step, etching step, resist pattern layer removing step, and metal layer removing step can be carried out in the same manner as described above.

[0063] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples in any way.

[0064] Example 1 A copper-clad laminate was prepared, in which a resin substrate was bonded to one side of a copper foil having a thickness of 18 μm. The other side of the copper foil of this copper-clad laminate was soft-etched to roughen the surface. For the soft etching, Clean Etch EMR-2050 manufactured by Mitsubishi Gas Chemical Company, Inc. was used as the soft etching solution, and the copper-clad laminate was immersed in the soft etching solution at 30°C for 50 seconds. The amount of etching by the soft etching was approximately 0.5 μm. Next, the other side of the roughened copper foil was subjected to nickel (Ni) plating (static bath plating) under the following conditions to form a Ni layer. The thickness of the Ni layer calculated from the plating conditions was 10 nm. Composition of Ni plating solution: nickel sulfate 60 g / L, sodium citrate 8 g / L Plating temperature: 50°C Current density: 4 A / dm 2 Plating time: 1 second

[0065] Example 2 The procedure was the same as Example 1, except that the plating time for Ni plating was changed to 2 seconds. The thickness of the Ni layer calculated from the plating conditions was 20 nm.

[0066] Example 3 The procedure was the same as in Example 1, except that the plating time for Ni plating was changed to 4 seconds. The thickness of the Ni layer calculated from the plating conditions was 30 nm.

[0067] Example 4 The procedure was the same as in Example 1, except that the plating time for Ni plating was changed to 6 seconds. The thickness of the Ni layer calculated from the plating conditions was 70 nm.

[0068] Example 5 The procedure was the same as Example 1, except that the plating time for Ni plating was changed to 9 seconds. The thickness of the Ni layer calculated from the plating conditions was 100 nm.

[0069] Example 6 The procedure was the same as in Example 1, except that the plating time for Ni plating was changed to 13 seconds. The thickness of the Ni layer calculated from the plating conditions was 150 nm.

[0070] Example 7 The procedure was the same as in Example 1, except that the plating time for Ni plating was changed to 27 seconds. The thickness of the Ni layer calculated from the plating conditions was 300 nm.

[0071] Example 8 A copper foil having a thickness of 35 μm was subjected to roughening plating with Cu—Ni. The roughening plating was performed under the following conditions to form a Cu—Ni layer: nickel sulfate: 140.9 g / L, copper sulfate: 61.5 g / L, pH: 2.3 to 2.5, bath temperature: 35 to 37° C., current density: 29.7 A / dm 2 Rotating electrode speed: 120 rpm Plating time: 1.6 seconds

[0072] Next, the surface of the Cu-Ni layer was washed with water, and then immersion treatment was carried out under the following conditions to form a Cr layer on the surface of the Cu-Ni layer: potassium dichromate: 3.00 g / L, zinc sulfate: 1.47 g / L, immersion time: 30 seconds, liquid temperature: room temperature.

[0073] Example 9 The same procedure as in Example 8 was carried out except that the plating time was changed to 2.4 seconds and the concentration of nickel sulfate was changed to 70.5 g / L.

[0074] Example 10 The procedure was the same as in Example 8, except that the plating time was changed to 2.4 seconds.

[0075] Examples 11 and 12 The same procedures as in Example 8 were carried out except that the plating time and current density were changed as appropriate.

[0076] Comparative Example 1 For comparison, copper foil (original foil) without a metal layer (Ni layer or Cu--Ni layer) was used.

[0077] Comparative Example 2 The same procedure as in Example 8 was carried out except that the plating time was changed to 0.8 seconds.

[0078] The surface-treated copper foils obtained in the above examples and the copper foil of Comparative Example 1 were evaluated as follows.

[0079] (Sku of the surface on the metal layer side) The Sku of the surface on the metal layer side was measured using a laser microscope (LEXT OLS 4000) manufactured by Olympus Corporation. In Comparative Example 1, since no metal layer was formed, the Sku of the copper foil surface was measured. The Sku was measured by averaging the results of measurements at five arbitrary points. The temperature during measurement was 23 to 25°C. The main setting conditions of the laser microscope were as follows: Objective lens: MPLAPONLEXT50x (magnification: 50x, numerical aperture: 0.95, immersion: air (dry system), W.D.: 0.35 mm, objective field of view: 26.5) Optical zoom magnification: 1x Scanning mode: XYZ high precision + color Captured image size: 258 μm x 258 μm (1024 x 1024 pixels) DIC: Off Multilayer: Off Laser intensity: 100 Offset: 0 Confocal level: 0 Beam diameter aperture: Off Image averaging: 1 time Noise reduction: On Brightness uniformity correction: On Optical noise filter: On Cutoff: λc 200 μm, λs, λf none Filter: Gaussian filter Noise removal: None Tilt correction: None Minimum height discrimination value: 10% of the ratio to Rz

[0080] (Nickel deposition amount in metal layer) For the surface-treated copper foils of Examples 8 to 12 and Comparative Example 2, a sample of 0.5 dm x 0.5 dm was cut out from the surface-treated copper foil, the metal layer was dissolved in a nitric acid solution, and the nickel concentration in the sample solution was quantified using an ICP emission spectrometer to determine the nickel deposition amount per unit area (μg / dm 2) was calculated. Specifically, a PS3520UVDD2 (AN-063 ICP3520UV-DD2) manufactured by Hitachi High-Tech Corporation was used as the ICP optical emission spectrometer, and the measurement was performed under the following conditions. Wavelength: 231.675 nm Integration time: 1.0 second Number of integrations: 3 Quantitative method: Calibration curve method Blank subtraction: None Output: 1.2 kW Pre-spray time: 30 seconds Cleaning time: 30 seconds The standard solution used during measurement was a solution prepared by adding JCSS chemical analysis standard solution (nickel standard solution (Ni 1000), specifications: for atomic absorption spectrometry, for ICP analysis) manufactured by Kanto Chemical Co., Ltd. to a solution containing nitric acid and copper to adjust the Ni concentration to 2 ppm, and a solution with a Ni concentration of 0 ppm to which JCSS chemical analysis standard solution manufactured by Kanto Chemical Co., Ltd. had not been added. A calibration curve was created, and the Ni concentration in the sample solution was adjusted to be within the range of the calibration curve. A solution containing nitric acid and copper before adding the JCSS standard solution for chemical analysis manufactured by Kanto Chemical Co., Inc. was prepared as follows: (1) Copper foil without a nickel plating layer was cut out to 15.68 g. (2) The cut copper foil was added to 100 mL of pure water and 60 mL of 65% by mass nitric acid. (3) The solution was heated to dissolve all of the copper foil. (4) After cooling, pure water was added to make a final volume of 500 mL. The analysis was performed after masking the opposite side of the surface to be measured (the surface with the nickel plating layer) to prevent contamination with metal from the opposite side.

[0081] (Evaluation of Adhesion to Photosensitive Resist Layer) A dry film (RY5115 manufactured by Resonac Corporation) was placed on the metal layer side surface of the surface-treated copper foil in the above Examples and on the copper foil in the above Comparative Examples, and laminated at a lamination temperature of 100°C, a lamination linear speed of 1 m / min, and a lamination pressure of 0.3 MPa. The laminates thus obtained were subjected to a cross-cut test as specified in JIS K5600-5-6 (1999). In the cross-cut test, grid-like cuts (cross-cuts) were made in the laminate, extending from the dry film surface to the surface-treated copper foil or copper foil. The grid-like cuts were six in each direction, 1 mm wide, forming a total of 25 cross-cut portions. Next, Cellotape (registered trademark) was applied to the dry film with the grid-like cuts, and the Cellotape (registered trademark) was then peeled off at an angle of approximately 60°. Peeling of the dry film at this time was evaluated based on the following criteria. The peeling rate (%) was calculated by the following formula: Peeling rate (%) = area of ​​peeled part of dry film / total area of ​​cross-cut part × 100

[0082] <Evaluation criteria for adhesion evaluation> 0: The edges of the crosscuts are completely smooth, and there is no peeling of the dry film at any of the crosscuts. 1: There is small peeling of the dry film at the intersections of the crosscuts, but the peeling rate is 5% or less. 2: The dry film has peeled along the edges of the crosscuts and / or at the intersections. The peeling rate is more than 5% and 15% or less. 3: The dry film has peeled extensively, partially or entirely, along the edges of the crosscuts, and / or has peeled partially or entirely at various locations in the crosscuts. The peeling rate is more than 15% and 35% or less. 4: The dry film has peeled extensively, partially or entirely, along the edges of the crosscuts, and / or has peeled partially or entirely at several crosscuts. The peeling rate is 35% or less. 5: The degree of peeling cannot be classified into the above 0 to 4.

[0083] (Evaluation of Etching Factor (EF)) A polyimide substrate was laminated on the surface opposite to the surface on which the metal layer (Cu—Ni layer) of each of the surface-treated copper foils of Examples 8 to 12 was formed, and the substrate was heated at 360° C. for 1 hour under vacuum conditions and pressure-bonded to produce a copper-clad laminate. Next, a dry film (RY5115 manufactured by Resonac Corporation) was placed on the surface on the metal layer side of the copper-clad laminate, and lamination was performed at a lamination temperature of 110° C., a lamination linear speed of 1 m / min, and a lamination pressure of 0.3 MPa. Similarly, a polyimide substrate was laminated on one side of the copper foil of Comparative Examples 1 and 2, heated at 360°C for 1 hour under vacuum conditions, and pressure-bonded to produce a copper-clad laminate. A dry film (RY5115 manufactured by Resonac Co., Ltd.) was then placed on the other side of the copper foil, and laminated at a lamination temperature of 110°C, a lamination linear speed of 1 m / min, and a lamination pressure of 0.3 MPa. Next, a resist pattern with an L / S width of 40 μm / 40 μm was formed by exposing and developing the dry film. Then, the exposed portions (unnecessary portions) of the surface-treated copper foil were removed by etching to form a copper circuit pattern with an L / S width of 40 μm / 40 μm. The widths of L and S of the circuit pattern are the widths of the bottom surface of the circuit, i.e., the surface in contact with the polyimide substrate. Etching was performed using spray etching under the following conditions. Etching solution: Cupric chloride hydrochloric acid (35%) etching solution Specific gravity: 1.240 (±0.005) Hydrochloric acid: 3.28 mol (±0.5) Cu concentration: 110-120 g / L HCl concentration: 117-121 g / L Solution temperature: 50°C Next, the cross section of the formed circuit pattern was observed with an SEM, and the EF was calculated based on the following formula: EF = circuit height / {(circuit bottom width - circuit top width) / 2} A larger EF value means a larger inclination angle of the side surface of the circuit.

[0084] The results of the above evaluations are shown in Table 1. The Ni deposition amounts of the surface-treated copper foils of Examples 1 to 7 shown in Table 1 are values ​​calculated from the Ni thicknesses described above.

[0085]

[0086] As shown in Table 1, the surface-treated copper foils of Examples 1 to 12, in which the surface sharpness Sku of the metal layer side was 5.0 or more, had a better evaluation of adhesion to the photosensitive resist layer than the copper foil of Comparative Example 1. The surface-treated copper foils of Examples 8 to 12 also had a better EF than the copper foils of Comparative Examples 1 and 2. Although EF was not evaluated in Examples 1 to 7, as is clear from the SEM photograph shown in FIG. 10, a 5-nm-thick Ni layer (Ni deposition amount 445 μg / dm) was used as the metal layer. 2 Even in the case of surface-treated copper foil with a Ni layer formed, an improvement in EF (suppression of sagging) was confirmed compared to copper foil without a Ni layer. 2 ), the EF is further improved, so the Ni deposition amount is 800 μg / dm 2 It is presumed that the surface-treated copper foils of Examples 1 to 7 also have good EF.

[0087] As can be seen from the above results, according to the embodiments of the present invention, it is possible to provide a surface-treated copper foil, a copper-clad laminate, and a circuit formation method that can suppress sagging due to etching and improve adhesion to a photosensitive resist layer.

[0088] Therefore, according to the embodiments of the present invention, by adopting the following aspects [1] to

[18] , it is possible to provide a surface-treated copper foil, a copper-clad laminate, and a circuit formation method that can suppress sagging due to etching and improve adhesion to a photosensitive resist layer.

[0089] [1] A surface-treated copper foil comprising a copper foil and a metal layer provided on one side of the copper foil and having an etching rate slower than that of the copper foil, wherein the surface on the metal layer side has a sharpness Sku of 5.0 or more, and the copper foil is etched from the metal layer side. [2] The surface-treated copper foil according to [1], wherein the metal layer contains nickel. [3] The metal layer is a nickel alloy layer, and the nickel deposition amount in the nickel alloy layer is 1000 μg / dm 2[4] The surface-treated copper foil according to [2], wherein the nickel alloy layer contains copper. [5] The metal layer is a nickel layer, and the nickel coating amount in the nickel layer is 400 μg / dm 2[6] The surface-treated copper foil according to any one of [1] to [5], wherein the sharpness Sku is 17.0 or less. [7] The surface-treated copper foil according to any one of [1] to [6], wherein the thickness of the metal layer is 200 nm or less. [8] The surface-treated copper foil according to any one of [1] to [7], further comprising a copper layer provided on the surface of the metal layer. [9] The surface-treated copper foil according to any one of [1] to [8], further comprising a copper layer between the copper foil and the metal layer.

[10] The surface-treated copper foil according to any one of [1] to [9], further comprising a surface treatment layer provided on the other side of the copper foil and containing at least one selected from nickel, cobalt, and copper.

[11] A copper-clad laminate comprising the surface-treated copper foil according to any one of [1] to [8], and a resin substrate provided on the other side of the copper foil of the surface-treated copper foil.

[12] A copper-clad laminate comprising the surface-treated copper foil according to any one of [9] to

[11] and a resin substrate provided on the other side of the copper foil of the surface-treated copper foil.

[13] A circuit forming method for forming a circuit pattern on a copper-clad laminate comprising copper foil, a metal layer provided on one side of the copper foil and having a slower etching rate than the copper foil, and a resin substrate adhered to the other side of the copper foil, wherein the surface of the copper foil on the metal layer side has a sharpness Sku of 5.0 or more, the method comprising: a photosensitive resist layer forming step of providing a photosensitive resist layer on the surface on the metal layer side; an exposure step of exposing the photosensitive resist layer to light in a predetermined pattern; a development step of developing the photosensitive resist layer to form a resist pattern layer; an etching step of etching the metal layer and the copper foil on which the resist pattern layer has been formed to form a circuit pattern; and a resist pattern layer removing step of removing the resist pattern layer.

[14] A circuit forming method comprising: a metal layer forming step of forming a metal layer having an etching rate slower than that of the copper foil on the other side of the copper foil of a copper-clad laminate including copper foil and a resin substrate bonded to one side of the copper foil, a photosensitive resist layer forming step of providing a photosensitive resist layer on the surface of the metal layer side, an exposure step of exposing the photosensitive resist layer to light in a predetermined pattern, a development step of developing the photosensitive resist layer to form a resist pattern layer, an etching step of etching the metal layer and the copper foil on which the resist pattern layer has been formed to form a circuit pattern, and a resist pattern layer removing step of removing the resist pattern layer, wherein the sharpness Sku of the surface of the copper foil on the metal layer side is adjusted to 5.0 or more before the photosensitive resist layer forming step.

[15] The circuit forming method according to

[14] , further comprising a soft etching step of soft etching the other side of the copper foil before the metal layer forming step.

[16] The circuit forming method according to

[14] or

[15] , wherein in the metal layer forming step, the metal layer is formed by a roughening plating treatment.

[17] The circuit forming method according to any one of

[14] to

[16] , further comprising a through hole / copper layer forming step, before the metal layer forming step, of forming a through hole in the copper-clad laminate and forming a copper layer on the copper foil of the copper-clad laminate and on the surface of the through hole, and in the etching step, etching the metal layer, copper layer, and copper foil on which the resist pattern layer has been formed to form a circuit pattern.

[18] The circuit forming method according to any one of

[13] to

[17] , further comprising a metal layer removing step, after the resist pattern layer removing step, of removing the metal layer.

[0090] (Potential Contribution to SDGs) According to embodiments of the present invention, it is possible to provide a surface-treated copper foil, a copper-clad laminate, and a circuit formation method that can suppress sagging due to etching and improve adhesion to a photosensitive resist layer, which may improve product yield in the manufacture of electronic devices, etc. Improving product yield leads to a stable supply of products and reduced loss of metal raw materials, which are limited resources. Therefore, the above embodiments may contribute to Goal 9 "Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation" and Goal 12 "Ensure sustainable consumption and production patterns" of the United Nations-led Sustainable Development Goals (SDGs).

[0091] REFERENCE SIGNS LIST 10 Copper foil 20 Metal layer 30, 40 Copper layer 50 Surface treatment layer 60 Resin substrate 100 Photosensitive resist layer 110 Exposed portion 120 Resist pattern layer 130 Circuit pattern

Claims

1. A surface-treated copper foil comprising a copper foil and a metal layer provided on one side of the copper foil and having an etching rate slower than that of the copper foil, wherein the surface on the metal layer side has a sharpness Sku of 5.0 or more, and the copper foil is etched from the metal layer side.

2. The surface-treated copper foil of claim 1, wherein the metal layer comprises nickel.

3. The metal layer is a nickel alloy layer, and the amount of nickel deposited in the nickel alloy layer is 1000 μg / dm 2 The surface-treated copper foil according to claim 2, wherein 4. The surface-treated copper foil according to claim 3, wherein the nickel alloy layer contains copper.

5. The metal layer is a nickel layer, and the amount of nickel in the nickel layer is 400 μg / dm 2 The surface-treated copper foil according to claim 2, wherein 6. The surface-treated copper foil according to any one of claims 1 to 5, wherein the kurtosis Sku is 17.0 or less.

7. The surface-treated copper foil according to any one of claims 1 to 5, wherein the thickness of the metal layer is 200 nm or less.

8. The surface-treated copper foil according to any one of claims 1 to 5, further comprising a copper layer provided on the surface of the metal layer.

9. The surface-treated copper foil according to any one of claims 1 to 5, further comprising a copper layer between the copper foil and the metal layer.

10. The surface-treated copper foil according to any one of claims 1 to 5, further comprising a surface treatment layer provided on the other surface of the copper foil and containing at least one selected from nickel, cobalt, and copper.

11. A copper clad laminate comprising the surface-treated copper foil according to any one of claims 1 to 5 and a resin substrate provided on the other side of the surface-treated copper foil.

12. A copper clad laminate comprising the surface-treated copper foil according to claim 9 and a resin substrate provided on the other side of the surface-treated copper foil.

13. A circuit formation method for forming a circuit pattern on a copper clad laminate comprising copper foil, a metal layer provided on one side of the copper foil and having an etching rate slower than that of the copper foil, and a resin substrate adhered to the other side of the copper foil, wherein the surface of the copper foil on the metal layer side has a sharpness Sku of 5.0 or more, the circuit formation method comprising: a photosensitive resist layer formation step of providing a photosensitive resist layer on the surface on the metal layer side; an exposure step of exposing the photosensitive resist layer to light in a predetermined pattern; a development step of developing the photosensitive resist layer to form a resist pattern layer; an etching step of etching the metal layer and the copper foil on which the resist pattern layer has been formed to form a circuit pattern; and a resist pattern layer removal step of removing the resist pattern layer.

14. A circuit formation method comprising: a metal layer formation step of forming a metal layer having an etching rate slower than that of the copper foil on the other side of the copper foil of a copper-clad laminate comprising copper foil and a resin substrate adhered to one side of the copper foil; a photosensitive resist layer formation step of providing a photosensitive resist layer on the surface of the metal layer side; an exposure step of exposing the photosensitive resist layer to light in a predetermined pattern; a development step of developing the photosensitive resist layer to form a resist pattern layer; an etching step of etching the metal layer and the copper foil on which the resist pattern layer has been formed to form a circuit pattern; and a resist pattern layer removal step of removing the resist pattern layer, wherein the sharpness Sku of the surface of the copper foil on the metal layer side is adjusted to 5.0 or more before the photosensitive resist layer formation step.

15. The circuit forming method according to claim 14, further comprising a soft etching step of soft etching the other surface of the copper foil before the metal layer forming step.

16. The circuit forming method according to claim 14 or 15, wherein in the metal layer forming step, the metal layer is formed by a roughening plating treatment.

17. A circuit forming method according to claim 14 or 15, further comprising a through hole / copper layer forming step of forming through holes in the copper clad laminate before the metal layer forming step, and forming a copper layer on the surfaces of the copper foil of the copper clad laminate and the through holes, and in the etching step, etching the metal layer, copper layer and copper foil on which the resist pattern layer has been formed to form a circuit pattern.

18. The circuit forming method according to any one of claims 13 to 15, further comprising a metal layer removing step of removing the metal layer after the resist pattern layer removing step.

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