Method for manufacturing wiring board, and wiring board

Abstract

To provide a method for manufacturing a wiring board and a wiring board which can achieve copper wiring having high adhesion strength, even if copper is directly sputtered on an insulation layer.SOLUTION: A method for manufacturing a wiring board includes the steps of: irradiating an insulation resin layer with vacuum ultraviolet rays; and directly forming a copper film on the insulation resin layer irradiated with the vacuum ultraviolet rays by sputtering.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a wiring board used in electronic devices and the like, and to a wiring board. [Background technology]

[0002] Conventionally, wiring boards on which semiconductor elements and the like are mounted are known. In the wiring board, a wiring layer made of a conductive material is formed on the surface of an insulating layer made of a resin material. As a method for providing a conductive material on the surface of the insulating layer, for example, electroless copper plating has been used. In electroless copper plating, by forming irregularities on the surface of the insulating layer, the copper plating can be adhered to the insulating layer by the anchor effect and intermolecular attraction.

[0003] On the other hand, if the surface of the insulating layer is uneven, it is thought that the quality of high-frequency signals will deteriorate due to the skin effect. For this reason, in order to perform high-speed communication or high-frequency communication, for example, a smoother surface is required as the interface between the resin material and the conductive material. In addition, in order to reduce the transmission loss of high-frequency signals, resin materials with low dielectric constants and dielectric tangents have been developed. Such resin materials have a small number of polar groups in the molecule, and it is thought that the intermolecular attractive force is small. For this reason, a method of using sputtering instead of electroless copper plating has attracted attention as a method of providing a conductive material on the surface of an insulating layer.

[0004] For example, Patent Document 1 describes a method for manufacturing a multilayer wiring board in which wiring layers and insulating layers are laminated. In this method, a via hole is formed in the insulating layer using a laser, and ultraviolet rays with a wavelength of 220 nm or less are irradiated to remove smears (residues) generated at this time. A titanium (Ti) sputtered film is formed on the surface of the insulating layer irradiated with ultraviolet rays to ensure adhesion strength, and a copper sputtered film is formed thereon to serve as a seed layer. A copper plating layer is formed by electrolytic plating using this seed layer as a power supply path. By using ultraviolet rays to remove smears, it is possible to improve the adhesion of the sputtered film made of titanium and copper while maintaining the surface of the insulating layer smooth (paragraphs

[0011] -

[0013] ,

[0018] Figure 1, etc. of the specification of Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-11010 A Summary of the Invention [Problem to be solved by the invention]

[0006] It is generally known that the adhesive strength of a sputtered film of titanium or nickel (Ni) is higher than that of a sputtered film of copper for the resin material constituting the insulating layer of a wiring board. Therefore, in order to sufficiently adhere the resin material to the conductive material, as in Patent Document 1, it was necessary to first form an adhesive layer using titanium or nickel on the surface of the insulating layer, and then form a copper seed layer or the like on top of that.

[0007] However, when such an adhesion layer is provided, the etching process after lithography requires two steps, one for etching copper and the other for etching titanium or nickel, making the process complicated. Furthermore, since the two steps are different etching processes, it is possible that, for example, the adhesion layer underlying the copper wiring may be etched, resulting in undercuts, or that the adhesion layer may remain on the insulating layer, reducing reliability.

[0008] In view of the above circumstances, an object of the present invention is to provide a method for manufacturing a wiring board, and a wiring board, which can realize copper wiring with high adhesion strength even when copper is directly sputtered onto an insulating layer. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, a manufacturing method for a wiring board according to one embodiment of the present invention includes a step of irradiating an insulating resin layer with vacuum ultraviolet light, and a step of directly forming a copper film by sputtering on the insulating resin layer that has been irradiated with the vacuum ultraviolet light.

[0010] In this method of manufacturing a wiring board, the insulating resin layer is irradiated with vacuum ultraviolet light to generate functional groups capable of bonding with copper atoms from the surface of the insulating resin layer to a certain depth from the surface. This makes it possible to form bonds between the insulating resin layer and the copper film not only on the surface of the insulating resin layer but also inside the insulating resin layer. As a result, it is possible to realize copper wiring with high adhesion strength even if copper is directly sputtered onto the insulating layer.

[0011] The pressure inside the chamber during the sputtering may be a medium vacuum.

[0012] The pressure inside the chamber during the sputtering may be 0.13 Pa or more and 13 Pa or less.

[0013] The method for manufacturing a wiring board may further include annealing a laminate in which the copper film is formed directly on the insulating resin layer.

[0014] The step of irradiating the insulating resin layer with vacuum ultraviolet light may be a step of irradiating the insulating resin layer with vacuum ultraviolet light in the atmosphere. In this case, the irradiation amount of the vacuum ultraviolet light is 0.1 J / cm 2 More than 5J / cm 2 It may be the following.

[0015] The step of forming the copper film by sputtering includes forming a copper seed layer as the copper film, Furthermore, a copper wiring layer may be formed on the copper seed layer by electrolytic plating.

[0016] The step of forming the copper film by sputtering may form a copper wiring layer as the copper film.

[0017] The surface of the insulating resin layer on which the copper film is formed may have a surface roughness, expressed as an arithmetic mean roughness Ra, of 40 nm or less.

[0018] The step of forming the copper film by sputtering may include performing a surface treatment with plasma on the surface of the insulating resin layer on which the copper film is to be formed, before the copper film is formed.

[0019] The pressure in the chamber during the surface treatment may be 10 Pa or more and 100 Pa or less.

[0020] The method for manufacturing a wiring board may further include heating and degassing the insulating resin layer before the step of forming the copper film by sputtering.

[0021] The step of heating the insulating resin layer to degas it may be performed before the irradiation with vacuum ultraviolet light.

[0022] The source of the vacuum ultraviolet light may be at least one of a xenon excimer lamp and a low-pressure mercury lamp.

[0023] A wiring board according to one embodiment of the present invention includes an insulating resin layer and a copper film. The insulating resin layer has a surface roughness, expressed as an arithmetic mean roughness Ra, of 40 nm or less. The copper film is formed directly on the insulating resin layer.

[0024] The copper film may have an adhesive strength to the insulating resin layer of 1 N / cm or more. Effect of the Invention

[0025] As described above, according to the present invention, it is possible to realize copper wiring with high adhesion strength even if copper is directly sputtered onto an insulating layer. Note that the effects described here are not necessarily limited to those described herein, and may be any of the effects described in the present disclosure. [Brief description of the drawings]

[0026] [Figure 1] 1 is a schematic cross-sectional view showing a configuration example of a wiring board according to an embodiment of the present invention; [Diagram 2] 5 is a flowchart showing an example of a method for manufacturing a wiring board according to the embodiment. [Diagram 3] This is a scanning electron microscope (SEM) image of an insulating layer used in a wiring board. [Figure 4] 1 is a graph showing VUV absorption characteristics in an insulating layer. [Diagram 5] FIG. 2 is a schematic diagram showing functional groups formed in an insulating layer irradiated with VUV. [Figure 6] 1 is a schematic diagram showing a bonding state between an insulating layer and a copper film irradiated with VUV. [Figure 7] 1 is a flowchart showing an embodiment of a method for manufacturing a wiring board. [Figure 8] 8A to 8C are schematic diagrams for explaining steps of a method for manufacturing the wiring board shown in FIG. 7. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0028] [Wiring board] Fig. 1 is a schematic cross-sectional view showing an example of the configuration of a wiring board according to an embodiment of the present invention. The wiring board 100 is a board on which a wiring pattern for mounting, for example, a semiconductor element is formed. Fig. 1 shows a schematic cross-sectional view of the wiring board 100 cut along the thickness direction. The wiring board 100 has a support substrate 10, an insulating layer 20, and a wiring layer 30.

[0029] The support substrate 10 is a member that supports the insulating layer 20 and the wiring layer 30. The support substrate 10 is made of an insulating material such as glass epoxy resin. A conductive material such as copper foil may be provided on the main surface of the support substrate 10. The type of the support substrate 10 is not limited, and a rigid substrate with high rigidity or a flexible substrate that can be bent may be used.

[0030] 1, an insulating layer 20 and a wiring layer 30 are laminated in this order on one main surface of a flat support substrate. Hereinafter, the side on which the insulating layer 20 and the wiring layer 30 are laminated (the upper side in the figure) may be referred to as the upper side of the wiring substrate 100, and the opposite side (the lower side in the figure) may be referred to as the lower side of the wiring substrate 100. Furthermore, in the support substrate 10, the insulating layer 20, and the wiring layer 30, the surface facing upward may be referred to as the upper surface, and the surface facing downward may be referred to as the lower surface.

[0031] The insulating layer 20 is a layer made of an insulating resin material, and is provided on the surface of the support substrate 10 (here, the upper surface of the support substrate 10). In this embodiment, the insulating layer 20 corresponds to an insulating resin layer. For example, a glass epoxy resin is used as the resin material constituting the insulating layer 20. For example, the insulating layer 20 is formed by attaching a glass epoxy film, which is made by processing glass epoxy resin into a film shape, to the support substrate 10.

[0032] The method for forming the insulating layer 20 is not limited, and for example, a method in which a composition that becomes an insulating resin material is applied to the support substrate 10 and then the resin material is cured may be used. The type of resin material constituting the insulating layer 20 is not limited, and for example, epoxy resin, bismaleimide triazine resin, polyimide resin, polyester resin, etc. may be used. The insulating layer 20 may also contain any material, such as a granular filler.

[0033] The wiring layer 30 is a layer in which copper is laminated on the insulating layer 20. That is, the wiring layer 30 is a layer in which copper is laminated directly on the surface of the insulating layer 20 (here, the upper surface of the insulating layer 20). Therefore, no metal layer other than copper is provided between the wiring layer 30 and the insulating layer 20. In this embodiment, the wiring layer 30 corresponds to a copper wiring layer. In the wiring layer 30, various wiring patterns (copper wiring) are formed according to the application of the wiring board 100, etc.

[0034] In the wiring board 100, at least a portion of the wiring layer 30 that is the interface between the insulating layer 20 and the wiring layer 30 is formed by sputtering. That is, the portion that adheres to the insulating layer 20 is a sputtered copper film. As described below, the wiring layer 30 may be formed by electrolytic plating using the sputtered copper film as a seed layer, or the wiring layer 30 may be formed only of the sputtered copper film.

[0035] The wiring board 100 shown in Fig. 1 is a board in which only one set of an insulating layer 20 and a wiring layer 30 is laminated, but the present invention can also be applied to a multi-layer board in which insulating layers 20 and wiring layers 30 are alternately laminated. For example, a second insulating layer 20 is formed on the surface (upper surface) of the wiring layer 30 shown in Fig. 1, and a copper sputtered film is laminated on the surface (upper surface) of the second insulating layer 20 to form the second wiring layer 30. When constructing a multi-layer board, the copper sputtered film may be directly laminated on all of the insulating layers 20, or the copper sputtered film may be directly laminated on some of the insulating layers 20.

[0036] In addition, in FIG. 1, the insulating layer 20 and the wiring layer 30 are laminated on one side of the support substrate 10, but the insulating layer 20 and the wiring layer 30 may be laminated on both sides of the support substrate 10, for example. Furthermore, it is not always necessary to provide the support substrate 10. For example, the insulating layer 20 may be configured as a structural member that supports the entire wiring substrate 100.

[0037] [Outline of manufacturing method for wiring boards] Fig. 2 is a flowchart showing an example of a method for manufacturing a wiring board according to this embodiment. Fig. 2 shows basic steps of the method for manufacturing a wiring board 100. These steps are necessarily performed to bond the insulating layer 20 and the wiring layer 30 (copper sputtered film) to each other. In the following, it is assumed that a substrate material having an insulating layer 20 provided on a supporting substrate 10 has been prepared in advance.

[0038] First, the insulating layer 20 is irradiated with vacuum ultraviolet light (VUV: Vacuum Ultra Violet) (step 101). Specifically, VUV is irradiated from the front side of the insulating layer 20 toward the insulating layer 20. Here, the front side of the insulating layer 20 is the surface on which the wiring layer 30 is laminated, and is the surface on which the insulating layer 20 is exposed in the substrate material. For example, the surface of the insulating layer 20 facing the side opposite the support substrate 10 (the top surface of the insulating layer 20 in FIG. 1) is the surface of the insulating layer 20 irradiated with VUV.

[0039] VUV is a wavelength band of ultraviolet light that is efficiently absorbed by atmospheric components. For example, a vacuum environment (reduced pressure atmosphere) is generally prepared to propagate VUV. The wavelength λ of VUV is, for example, 200 nm ≥ λ ≥ 10 nm. Therefore, part of VUV overlaps with the soft X-ray region.

[0040] For example, the insulating layer 20 is irradiated with VUV by an irradiation device equipped with a light source (such as an excimer lamp) that emits VUV. As described later, the present inventors have found that irradiating the insulating layer 20 with VUV makes it possible to change the properties of the insulating layer 20 from the surface to the inside of the insulating layer 20 so as to increase the adhesive strength (adhesion force) between the insulating layer 20 and the copper sputtered film. Therefore, the process of irradiating the insulating layer 20 with VUV is a process for modifying the insulating layer 20.

[0041] Next, a copper film is formed by sputtering on the insulating layer 20 irradiated with VUV (step 102). Sputtering (sputtering method) is a dry process carried out in a vacuum chamber. For example, a substrate material irradiated with VUV is introduced into the vacuum chamber of a sputtering device, and a copper sputtered film is formed in a state where the pressure is reduced to a predetermined pressure.

[0042] In the sputtering device, plasma of, for example, argon (Ar) or the like is collided with a copper sputtering target, and the copper particles (copper ions, etc.) that are ejected are laminated on the insulating layer 20. At this time, the resin material that constitutes the insulating layer 20 is modified by VUV irradiation, so that it is in a state in which it is easy to form bonds with the copper particles from the surface to the inside. This allows the resin material to bond with the copper particles in the surface region of the insulating layer 20. Here, the surface region of the insulating layer 20 is, for example, a region from the surface of the insulating layer 20 to a certain depth, and is the region where bonds with the copper particles are formed. In this way, VUV irradiation makes it possible to chemically bond with copper particles not only on the surface of the resin material but also inside the material, resulting in the formation of a copper film with high adhesion strength.

[0043] The copper film formed by sputtering on the insulating layer 20 is a seed layer for performing, for example, electrolytic copper plating. That is, in the process of forming the copper film by sputtering, a copper seed layer is formed as the copper film. The copper seed layer is a layer that becomes a power supply path (electrode) for growing a copper plating layer. This process can be said to be a direct copper seed formation process in which a copper seed layer is directly formed on the insulating layer 20. The copper seed layer is relatively thin, for example, 1 μm or less, but the copper seed layer (copper sputtered film) may be formed to any thickness as long as it functions as electrolytic copper plating.

[0044] In addition, when a copper seed layer is formed, a copper wiring layer is further formed on the copper seed layer by electrolytic plating. For example, the substrate material on which the copper seed layer is formed is immersed in an electrolytic copper plating solution to form a copper wiring layer, which is a copper plating layer, on the copper seed layer. The thickness of the copper wiring layer is not limited, but is, for example, about several tens of μm. In this case, the copper seed layer and the copper wiring layer constitute the wiring layer 30 shown in FIG. 1.

[0045] The copper film formed by sputtering on the insulating layer 20 may be a copper wiring layer. That is, in the process of forming the copper film by sputtering, a copper wiring layer may be formed as the copper film. In this case, electrolytic plating or the like is not performed on the copper film, and the copper film is used as it is as wiring. This process can be said to be a direct copper wiring layer formation process in which a copper wiring layer is directly formed on the insulating layer 20. The thickness of the copper film that becomes the copper wiring layer is appropriately set within a range that allows the wiring of the wiring board 100 to be configured. For example, a copper film having a thickness of 1 μm or more may be formed by sputtering as the copper wiring layer, or a thinner copper film may be formed as the copper wiring layer. In this case, the wiring layer 30 shown in FIG. 1 is configured only by the sputtered copper film (copper film).

[0046] In this way, the copper film formed by sputtering on the insulating layer 20 may be a seed layer for electrolytic plating, or the copper film itself may be used as wiring. In either case, the conductive material (wiring layer 30) in contact with the interface of the resin material (insulating layer 20) is the copper film formed by sputtering on the insulating layer 20 irradiated with VUV, so that copper wiring with high adhesion strength can be realized.

[0047] [Effects of VUV irradiation] In order to examine the interface between the insulating layer 20 and the wiring layer 30 (copper film formed by sputtering), the inventor peeled off the wiring layer 30 formed on the insulating layer 20 from the insulating layer 20, and measured the interface of the wiring layer 30 by X-ray photoelectron spectroscopy (XPS). As a result, when the adhesion strength was high, the intensity of the spectroscopic peak indicating COCu became high. COCu has a structure (CO-Cu) in which a carbon atom (C) and a copper atom (Cu) are bonded by an oxygen atom (O) through a single bond (see FIG. 6).

[0048] That is, it was found that the formation of COCu was observed at the interface in the wiring board 100 in which the insulating layer 20 and the wiring layer 30 have high adhesion. This is thought to be because hydroxyl groups (COH) are formed in the insulating layer 20 by irradiating the insulating layer 20 with VUV as a pretreatment, and the Cu that is blown in by sputtering reacts with the COH to form COCu.

[0049] Furthermore, the present inventors investigated where COH is formed in the insulating layer 20 when VUV is irradiated. Fig. 3 is a scanning electron microscope (SEM) image of the insulating layer 20 used in the wiring board 100. Fig. 4 is a graph showing the VUV absorption characteristics of the insulating layer 20. First, the VUV absorption characteristics of the insulating layer 20 will be described with reference to Figs. 3 and 4.

[0050] Conventionally, it was believed that resin materials have extremely high VUV absorption, and that VUV hardly penetrates into the resin. In this case, VUV irradiated to the resin material is absorbed by the surface of the resin material and does not reach the inside of the resin material. In this regard, the inventor measured the transmittance of VUV through the resin material and investigated the VUV absorption characteristics.

[0051] Fig. 3 is an SEM image of a cross section of a measurement sample including an insulating layer 20 used in measuring the VUV transmittance. A film of glass epoxy resin 40 was used as the insulating layer 20. For the transmittance measurement, a measurement sample was used in which the glass epoxy resin 40 was laminated onto a synthetic quartz glass substrate 41 and the glass epoxy resin 40 was polished to a thickness of 1 μm. In Fig. 3, the thick gray layer on the right side is the glass substrate 41, and the thin layer on the glass substrate 41 is the glass epoxy resin 40 (insulating layer 20).

[0052] In the transmittance measurement, a spectrophotometer (McPherson, VUVAS-1000) was used to measure the wavelength region from 140 nm to 225 nm, and transmittance data was obtained at 172 nm, which is the central emission wavelength of the excimer lamp. Figure 4 is a graph showing the measurement results of the transmittance of VUV through the glass epoxy resin 40 (insulating layer 20). The horizontal axis of the graph is the depth (nm) of the glass epoxy resin 40, and the vertical axis is the transmittance (%). The depth of the glass epoxy resin 40 is the distance from the surface where VUV is irradiated.

[0053] The absorbance of the glass epoxy resin 40 calculated from the measurement results of the VUV transmittance was 3.0×10^3. This consideration of absorbance is related to the emission spectrum of the excimer lamp, and the absorbance can be calculated similarly for single wavelength light and synthetic wavelength light in an emission region with a half-width of 14 nm, for example. In this case, as shown in FIG. 4, a part of the VUV is absorbed by the resin up to a depth of about 1000 nm from the surface of the glass epoxy resin 40, and the rest of the VUV is transmitted through the resin. In the following, the region where VUV absorption occurs is referred to as the absorption region 45. The absorption region 45 is, for example, a region up to a depth of 1000 nm.

[0054] In particular, it was found that at a depth of about several tens of nm from the surface of the glass epoxy resin 40, the transmittance drops from 100% to 90%, and about 10% of the VUV is absorbed. This region becomes the surface region 46 where bonds with the sputtered copper particles are formed. The surface region 46 is, for example, a region from the surface to a depth of about 20 nm to 40 nm. In FIG. 4, the surface region 46 is diagrammatically illustrated by a gray region.

[0055] Incidentally, VUV hardly reaches regions deeper than the absorption region 45 in the glass epoxy resin 40. Therefore, glass epoxy resin 40 having a practical thickness (several μm or more) behaves as to not transmit VUV at all. In reality, even in such a comparatively thick glass epoxy resin 40, an absorption region 45 that absorbs and transmits VUV will be generated at a certain depth on the surface side where VUV is irradiated.

[0056] Based on the above results, the effects of VUV irradiation will be explained. Fig. 5 is a schematic diagram showing functional groups formed in insulating layer 20 irradiated with VUV. Fig. 5 shows functional groups formed in insulating layer 20 by VUV irradiation, and carbon chains and the like in insulating layer 20. In Fig. 5, it is assumed that insulating layer 20 is irradiated with VUV in the air.

[0057] The resin material constituting the insulating layer 20 includes a chain polymer consisting of carbon atoms (C), oxygen atoms (O), hydrogen atoms (H), etc. The polymer includes single bonds (e.g., CC, CO, CH, OH, etc.) between each atom, and double bonds (e.g., C=O).

[0058] When the insulating layer 20 is irradiated with VUV, the energy of the VUV is absorbed at the surface 21 and inside (such as the absorbing region 45 including the surface region 46) of the insulating layer 20. At this time, part of the energy of the VUV becomes excitation energy that excites the atoms that make up the polymer. As a result, the bonding state of the polymer changes and new functional groups are formed.

[0059] Specifically, when exposed to VUV, intramolecular recombination occurs in the polymer, forming hydroxyl groups (COH). COH is a primary oxidation functional group that is easily bonded with copper atoms (Cu). When Cu bonds with COH, COCu is formed.

[0060] As described above, absorption of VUV energy occurs not only on the surface 21 of the insulating layer 20 but also inside the insulating layer 20. Therefore, COH is formed on the surface 21 and inside the insulating layer 20. FIG. 5 shows a schematic diagram of COH formed on the surface 21 of the insulating layer 20 and COH formed inside the insulating layer 20 (particularly the surface region 46). Of these, the COH surrounded by a dotted line represents COH formed in the surface region 46. In this way, the surface region 46 of the insulating layer 20 is modified by irradiation with VUV, and COH functional groups are also formed inside the insulating layer 20.

[0061] In addition, as VUV propagates through the air, oxygen molecules (O2) are excited to form ozone (O3) and ground-state oxygen atoms (O( 1 D )), and excited state oxygen atom (O( 3 P These oxygen-derived products form, for example, COH, COOH, etc. on the surface 21 of the insulating layer 20.

[0062] In this way, a copper film is formed by sputtering on the insulating layer 20 on which COH is formed. At this time, it is considered that a tentative bond occurs between the copper atoms (Cu) that fly to the insulating layer 20 and COH. Here, the tentative bond is, for example, a state in which a complete bond (COCu) between COH and Cu has not yet been formed, but which can become COCu. For example, a state in which Cu exists in a range that can bond with COH can be a tentative bond.

[0063] The sputtered copper atoms (Cu) form temporary bonds with, for example, COH formed on the surface 21 of the insulating layer 20, and COH formed inside the insulating layer 20, particularly in the surface region 46. Therefore, in the insulating layer 20 on which a copper film is formed by sputtering, temporary bonds can be formed not only on the surface 21 but also in the internal surface region 46. It is also possible that the sputtered copper atoms (Cu) directly bond with COH to form COCu.

[0064] As described later, in this embodiment, a heat treatment (annealing treatment) is performed to bond the temporary bond. This forms a complete bond (COCu) over the surface region 46 of the insulating layer 20. For example, when a copper plating layer is formed after sputtering, an annealing treatment is performed to distribute stress in the copper plating layer. This annealing treatment can be used to make the temporary bond into a complete bond. The temporary bond may be formed by absorbing the kinetic energy of other Cu during sputtering, or by absorbing thermal energy applied during the manufacturing process of the wiring board 100. For this reason, it is not always necessary to perform annealing, for example, if sufficient adhesion strength can be obtained without annealing.

[0065] Fig. 6 is a schematic diagram showing a bonded state between an insulating layer 20 irradiated with VUV and a copper film 3. In Fig. 6, a copper film 3 is formed by sputtering directly on an insulating layer 20 irradiated with VUV, and a bonded portion (COCu) between the insulating layer 20 and the copper film 3 is formed over the entire substrate. For example, a copper seed layer is formed as the copper film 3, and electrolytic copper plating is performed. During this time, the temporary bond between COH and Cu is maintained. After the copper plating layer (wiring layer 30) is formed, an annealing process is performed to form COCu. In addition, when electrolytic copper plating is not performed, for example, an annealing process is performed at an appropriate timing after the copper film 3 is formed by sputtering.

[0066] Copper atoms (Cu) constituting the bonded portion (COCu) between the insulating layer 20 and the copper film 3 are bonded to oxygen atoms (O) and other copper atoms (not shown). In other words, it can be said that COCu bonds the insulating layer 20 (polymer) and the copper film 3. COCu is formed not only on the surface 21 of the insulating layer 20 but also in a surface region 46 inside the insulating layer 20. Therefore, the insulating layer 20 and the copper film 3 are bonded from the surface 21 to the surface region 46, which is several tens of nm deep. As a result, an adhesive interface is formed in the surface region 46, for example, where the bonded portion has a gradation in the depth direction. As a result, even if the copper film 3 is directly sputtered onto the insulating layer 20, it is possible to significantly improve the adhesive strength compared to, for example, a case in which COH is formed only on the surface.

[0067] It has been believed that VUV has the effect of modifying the surface of a resin material, forming functional groups such as COH and COOH on the surface of the resin material. However, measurements performed by the present inventors have revealed that VUV partially penetrates the resin material (insulating layer 20) and is absorbed inside the resin material (see FIG. 4). As a result, it has become clear that irradiation with VUV forms functional groups such as COH not only on the surface 21 of the insulating layer 20 but also inside (such as the surface region 46).

[0068] By the way, in sputtering equipment, a method is known in which surface treatment using plasma is performed before sputtering to clean the surface of the film formation target. It is thought that the plasma acting on the surface of the resin material may create functional groups on the surface of the resin material similar to those in the case of VUV irradiation, for example. However, unlike VUV, plasma does not penetrate into the interior of the resin material.

[0069] Thus, on the surface of a resin material, surface treatment with plasma has an effect that overlaps with the effect of VUV. If only functional groups on the surface were to form bonds, adhesion strength should improve even if surface treatment with plasma is performed without VUV irradiation. However, as described later, in reality, adhesion strength remains low without VUV irradiation.

[0070] In contrast, in the resin material (insulating layer 20) modified by VUV, the copper film formed by sputtering reacts with COH not only on the surface 21 but also in the inner surface region 46. As a result, it is believed that a bond exhibiting the adhesive strength shown in Fig. 6 is formed. Thus, in the present invention, strong adhesion is formed between the insulating layer 20 and the wiring layer 30 by bonding copper particles to functional groups formed in the surface region 46 of the insulating layer 20 by irradiating with VUV.

[0071] The above-mentioned method is a method for improving adhesion strength by a chemical bond (COCu) formed at the interface between the insulating layer 20 and the wiring layer 30. By using this method, for example, a wiring board 100 including a smooth insulating layer 20 is formed. Specifically, the wiring board 100 has an insulating layer 20 having a surface roughness of 40 nm or less expressed as an arithmetic mean roughness Ra, and a copper film 3 formed directly on the insulating layer 20.

[0072] Here, the arithmetic mean roughness Ra is, for example, the average value of the depth of the unevenness in a reference range. The reference range is, for example, a rectangular range in which the length of each side is 10 times or more the depth of the unevenness. For example, when the arithmetic mean roughness Ra is 150 nm or less, the adhesion effect dependent on the physical shape, such as the anchor effect, cannot be expected. Therefore, in an insulating layer 20 with Ra of 40 nm or less, it is difficult to increase the adhesion strength by the anchor effect. By applying the present invention to such a sufficiently smooth insulating layer 20, it is possible to exhibit sufficient adhesion strength.

[0073] In addition, in the wiring board 100 having the smooth insulating layer 20, the adhesion strength of the copper film 3 (wiring layer 30) to the insulating layer 20 is preferably 1 N / cm or more. For example, by using the manufacturing method according to this embodiment, an adhesion strength of 1 N / cm or more can be achieved, as shown in Tables 1 to 3 described later. This makes it possible to achieve smooth wiring and the like that has sufficiently high adhesion strength and is made of only copper.

[0074] [Method of manufacturing wiring board] Fig. 7 is a flow chart showing an embodiment of a method for manufacturing a wiring board. Fig. 8 is a schematic diagram for explaining the steps of the method for manufacturing a wiring board shown in Fig. 7. Fig. 7 and Fig. 8 show an example of a method for manufacturing a wiring board 100 according to the present invention. In the following, a copper seed layer is formed by sputtering, and then a wiring layer 30 is formed by electrolytic copper plating.

[0075] First, an insulating layer 20 is formed (step 201). This is a process for forming a substrate material having an insulating layer 20. Here, as shown in FIG. 8, the insulating layer 20 is provided on one main surface of a support substrate 10. Hereinafter, the substrate material in which the insulating layer 20 is laminated on the support substrate 10 will be referred to as substrate material 5a. A glass epoxy substrate or the like is used as the support substrate 10. A glass epoxy film or the like is used as the insulating layer 20.

[0076] When attaching an insulating layer 20 such as a glass epoxy film to a support substrate 10, a vacuum laminating device or the like is used, which sandwiches an object between carrier films and brings them into close contact. In this case, the substrate material 5a in which the insulating layer 20 and the support substrate 10 are attached is carried out while covered with the carrier film. Thereafter, a heating device such as an oven is used to carry out a heat treatment for hardening the glass epoxy film. This heat treatment is carried out while covered with the carrier film, for example. There are no other limitations on the method for forming the substrate material 5a having the insulating layer 20.

[0077] Next, heating for degassing is performed (step 202). This process is a process for removing gas components contained in the insulating layer 20 and the support substrate 10. For example, the substrate material 5a is heated to a predetermined temperature using a heating device such as an oven. The heating temperature for degassing is set within a range from the glass transition point (glass transition temperature) of the resin to a maximum of 200°C.

[0078] Thus, in this embodiment, a step of heating and degassing the insulating layer 20 is performed before the step of forming the copper film 3 by sputtering. For example, the copper film 3 formed by sputtering is a dense film, and may trap gas within the insulating layer 20. For this reason, if degassing is insufficient, an air layer called a void may occur during electrolytic copper plating. Therefore, by performing a heat treatment for degassing before sputtering, it is possible to avoid the occurrence of voids, etc. Incidentally, immediately after the curing process of the glass epoxy film, the amount of gas contained in the insulating layer 20 is sufficiently small. In such a case, it is not necessary to perform the heat treatment for degassing.

[0079] Next, the insulating layer 20 is irradiated with VUV (step 203). This step corresponds to step 101 described with reference to FIG. 2. For example, the substrate material 5a is introduced into a VUV irradiation device, and VUV is irradiated toward the surface 21 of the insulating layer 20. As a result, functional groups such as COH are formed on the surface 21 and inside (the absorbing region 45) of the insulating layer 20. In FIG. 8, the insulating layer 20 modified by irradiating with VUV is diagrammatically illustrated by gradation.

[0080] As a light source of VUV, for example, a xenon excimer lamp (peak wavelength 172 nm) containing xenon gas or a low pressure mercury lamp (185 nm emission line) can be used. These light sources may also be used in combination. The amount of VUV irradiated by the VUV irradiator is adjusted by, for example, the irradiation time, the brightness of the light source, the irradiation distance, etc. A sensor (illuminometer) that detects the amount of VUV irradiated to the insulating layer 20 may also be provided.

[0081] In this embodiment, VUV is irradiated in the atmosphere. That is, the step of irradiating VUV is a step of irradiating the insulating layer 20 with VUV in the atmosphere. Since VUV is irradiated in the atmosphere, there is no need to provide a vacuum chamber or the like in the VUV irradiation device, and steps such as introducing the substrate material 5a into the vacuum chamber and evacuating the vacuum chamber are not required. Therefore, it is possible to complete the step of irradiating VUV in a short time. In addition, surface modification using oxygen in the atmosphere is also possible.

[0082] Note that the configuration is not limited to irradiating VUV in the atmosphere, and VUV may be irradiated in, for example, a predetermined reduced pressure atmosphere or a low oxygen concentration atmosphere. In this case, since there is no absorption of VUV by the atmosphere, it is possible to reduce the amount of VUV light, for example, to reduce power consumption. In addition, for example, a VUV light source may be provided in the chamber of the sputtering device. This makes it possible to perform processes from VUV irradiation to sputtering in one device.

[0083] After the insulating layer 20 of the substrate material 5a is irradiated with VUV, the substrate material 5a is introduced into a vacuum chamber of a sputtering device. Steps 204 and 205 described below are steps performed by the sputtering device.

[0084] In the sputtering device, first, a surface treatment using plasma is performed (step 204). This step is a pre-treatment for sputtering, and is a step of cleaning the surface 21 of the insulating layer 20 using plasma. By the surface treatment using plasma, the surface 21 of the insulating layer 20 that has been contaminated during, for example, the period between the irradiation with VUV and the introduction into the sputtering device is cleaned. The atmospheric gas for generating plasma may be, for example, a mixed gas of argon and hydrogen (Ar / H2) or a mixed gas of argon and oxygen (Ar / O2), and is appropriately selected according to the material.

[0085] In this embodiment, hollow cathode plasma (HCD plasma) is used for the surface treatment. That is, before the copper film 3 is formed by sputtering, the surface 21 of the insulating layer 20 on which the copper film 3 is to be formed is subjected to surface treatment by hollow cathode plasma. The hollow cathode plasma is generated by using, for example, a cylindrical cathode (hollow cathode) and is emitted as a high-density plasma jet. For example, a hollow cathode plasma device built into a sputtering device generates a plasma jet (hollow cathode plasma) in a vacuum chamber. The surface 21 of the insulating layer 20 is cleaned by this plasma.

[0086] It should be noted that the hollow cathode plasma acts only on the surface 21 of the insulating layer 20, and does not act on the inside of the insulating layer 20. Therefore, functional groups such as COH formed inside the insulating layer 20 by, for example, VUV irradiation are maintained. Meanwhile, on the surface 21 of the insulating layer 20, in addition to cleaning contaminants, functional groups such as COH are formed. In this way, by modifying the surface 21 of the insulating layer 20 with the hollow cathode plasma, it is possible to further improve the adhesion strength between the insulating layer 20 and the copper film 3.

[0087] Furthermore, the pressure inside the chamber during surface treatment using hollow cathode plasma is 10 Pa or more and 100 Pa or less. By setting the pressure within this range, sufficient surface modification can be achieved using hollow cathode plasma. Also, since the pressure is relatively high, the time required for decompression is short. This makes it possible to shorten the time required for surface treatment.

[0088] Next, in a sputtering device, a copper film 3 is formed directly on the insulating resin layer irradiated with vacuum ultraviolet light by sputtering (step 204). This step corresponds to step 102 described with reference to FIG. 2. Here, a copper seed layer 31 is formed as the copper film 3, which serves as a power supply path for electrolytic copper plating. The thickness of the copper seed layer 31 is, for example, about 300 nm, but any thickness may be set. FIG. 8 shows a schematic diagram of the copper seed layer 31 formed on the insulating layer 20. Hereinafter, the member on which the copper seed layer 31 is formed on the insulating layer 20 will be referred to as a substrate material 5b.

[0089] For example, plasma is generated by a plasma device built into the sputtering device, and a copper sputtering target is sputtered by the plasma. Copper particles ejected from the sputtering target are layered on the surface 21 of the insulating layer 20 to form a copper seed layer 31. At this time, the thickness of the copper seed layer 31 is monitored, and sputtering is continued until a predetermined thickness is reached. The atmospheric gas for generating the plasma is, for example, argon. As the plasma device, the hollow cathode plasma device described above may be used, or a device dedicated to sputtering may be used.

[0090] In this embodiment, the pressure in the chamber during sputtering is a medium vacuum. That is, the sputtering apparatus performs medium vacuum sputtering. Here, the medium vacuum pressure is a pressure of 0.1 Pa or more and 100 Pa or less. When the pressure inside the chamber is a medium vacuum, for example, copper particles flying from the sputtering target to the insulating layer 20 are more likely to collide with the plasma atmosphere gas, etc., and the kinetic energy of the copper particles decreases. This makes it possible to suppress the temperature rise of the insulating layer 20 during sputtering. As a result, for example, it becomes possible to form the copper seed layer 31 without losing the temporary bonds between the copper atoms (Cu) and the functional groups (COH).

[0091] Generally, film formation by sputtering is performed at a pressure (e.g., 0.01 Pa) that is sufficiently lower than 0.1 Pa. In this case, it is considered that the target on which the film is formed is heated by target particles having a relatively high kinetic energy. In contrast, in this embodiment, sputtering is performed at a medium vacuum pressure to suppress the temperature rise of the insulating layer 20 and maintain a state in which the insulating layer 20 and the copper seed layer 31 can be well bonded to each other. This makes it possible to form a copper seed layer 31 with strong adhesion strength. In addition, the evacuation time required to reach the medium vacuum pressure is relatively short. This makes it possible to shorten the time required for sputtering.

[0092] Next, a copper wiring layer 32 is formed by electrolytic copper plating (step 206). Here, electrolytic copper plating is performed using the copper seed layer 31 formed by sputtering as a power supply path, and the copper wiring layer 32 is formed by a copper plating layer. The thickness of the copper wiring layer 32 is, for example, about several tens of μm, but any thickness may be set. FIG. 8 shows a schematic diagram of the copper wiring layer 32 formed on the copper seed layer 31. Hereinafter, the member on which the copper wiring layer 32 is formed on the copper seed layer 31 is referred to as a substrate material 5c.

[0093] For example, the substrate material 5b produced in step 205 and a copper electrode are immersed in an electrolytic copper plating bath containing a copper sulfate solution. A current is supplied at a predetermined current density to the copper electrode as the anode and the copper seed layer 31 as the cathode. As a result, a copper plating layer (copper wiring layer 32) is formed on the copper seed layer 31. The substrate material 5c on which copper plating has been completed is subjected to a drying process.

[0094] Next, an annealing process is performed (step 207). This process is a heating process for converting a temporary bond formed at the interface between the copper seed layer 31 and the insulating layer 20 into a complete bond (COCu, etc.). Here, the substrate material 5c in which the copper seed layer 31 and the copper wiring layer 32 are formed on the insulating layer 20 is annealed. Here, the substrate material 5c is an example of a laminate in which a copper film is formed directly on an insulating resin layer. The substrate sample 5c after the annealing process becomes the wiring substrate 100.

[0095] For example, the substrate material 5c is heated to a predetermined temperature using a heating device such as an oven. The heating temperature of the annealing treatment is, for example, about 200° C., and the heating time is, for example, about 1 hour. The heating temperature and heating time of the annealing treatment may be appropriately set so as to achieve a desired adhesion strength. By performing the annealing treatment, a complete bond is formed from the surface 21 to the surface region 46 of the insulating layer 20. This makes it possible to form the wiring layer 30 (the copper seed layer 31 and the copper wiring layer 32) with high adhesion strength.

[0096] [Adhesion evaluation] The following describes an experiment for evaluating the adhesion between the insulating layer 20 and the wiring layer 30 in the wiring substrate 100. In this experiment, the adhesion strength was evaluated for samples manufactured by the manufacturing method described with reference to Figures 7 and 8. For comparison, the adhesion was also evaluated for a sample manufactured without irradiating VUV by omitting step 203.

[0097] The wiring board 100 used in the experiment used a copper-clad laminate called CCL (e.g., Hitachi Chemical's MCL-800) as the support substrate 10. Also, a glass epoxy film (e.g., Ajinomoto Fine-Techno Co., Ltd.'s ABF-GX-T31) was used as the insulating layer 20. In the experiment, a glass epoxy film was attached to one side of the copper-clad laminate using a vacuum laminating device (Meiki Seisakusho: Model MVLP-500 / 600-IIA), and after lamination, a heat treatment was performed using an oven to harden the glass epoxy resin components of the insulating layer 20 (step 201). In this treatment, a heat treatment was performed at 100°C for 30 minutes, followed by a heat treatment at 180°C for 30 minutes.

[0098] If the leaving time after step 201 is long, it is preferable to perform a heat treatment for degassing in an oven (step 202) before irradiating with VUV. In this treatment, a heat treatment was performed at 190°C for 1 hour. Note that, if moving to the next process immediately after hardening the glass epoxy resin, step 202 is omitted, and the carrier film used in the vacuum lamination device is peeled off and VUV irradiation is performed.

[0099] Next, the insulating layer 20 was irradiated with VUV (step 203). An excimer irradiation device (manufactured by Ushio Inc.: SVM-453S type) that emits light with a wavelength of 172 nm was used as the VUV irradiation device. The VUV irradiation was performed in an air atmosphere. The sample was moved using a stage transport mechanism, and the irradiation distance was set to 5 mm. The VUV irradiation amount was measured with an illuminance meter (manufactured by Ushio Inc.: UIT-250 type) that is compatible with light with a wavelength of 172 nm. In the experiment, the VUV irradiation amount was 0 to 5.4 J / cm. 2 The irradiation was performed at a level of .

[0100] After VUV irradiation, the surface roughness of the insulating layer 20 was measured by an atomic force microscope. The surface roughness measurement range was 1 μm × 1 μm. For Experiment No. 1 described later, the surface roughness was measured without VUV irradiation. This is the surface roughness of the insulating layer 20 with the carrier film removed. The surface roughness of the insulating layer 20 without VUV irradiation was Ra = 32 nm.

[0101] Next, the VUV-irradiated sample was introduced into a medium vacuum sputtering device, and surface treatment was performed using plasma (step 204). In the experiment, the surface 21 of the sample (insulating layer 20) was cleaned using a plasma jet generated by a hollow cathode plasma device built into the medium vacuum sputtering device. Next, a copper seed layer 31 was formed on the insulating layer 20 by sputtering under a medium vacuum pressure (step 205). The thickness of the copper seed layer 31 was set to 300 nm. In the experiment, samples were also created at a pressure outside the pressure range of the medium vacuum sputtering.

[0102] Next, the sample on which the copper seed layer 31 was formed was immersed in an electrolytic copper plating bath to perform electrolytic copper plating (step 206). The current density was set to 1 ASD (Ampere per Square Decimator), and the thickness of the copper plating layer was set to 25 μm. In addition, the sample after copper plating was subjected to a drying process. Next, the copper-plated sample was subjected to an annealing treatment (step 207). In the experiment, a heat treatment was performed at 200° C. for 1 hour using an oven to anneal the copper film.

[0103] The annealed samples were used as the measurement objects to evaluate the adhesion between the insulating layer 20 and the wiring layer 30. In the experiment, a 1 cm wide cut was made in the wiring layer 30, and the wiring layer 30 was peeled off using a peel tester (Shimadzu Corporation: EZ-TEST) to measure the adhesion strength. The maximum adhesion strength was recorded when the wiring layer 30 was peeled off at a speed of 50 mm / s.

[0104] [Relationship between VUV irradiation dose and adhesion strength] Below, the adhesion strength when the VUV irradiation amount is changed will be described with reference to Table 1.

[0105] [Table 1]

[0106] In Experiments Nos. 1 to 10 shown in Table 1, the sputtering pressure was set to 1.3 Pa, and the VUV irradiation dose was changed to form the wiring layer 30. For the samples, the surface roughness and adhesion strength of the insulating layer 20 were measured. In Experiment No. 1, VUV was not irradiated.

[0107] As shown in experiment number 1, the surface 21 of the insulating layer 20 after the carrier film is peeled off is smoother than a surface where, for example, an anchor effect occurs. Also, since VUV was not irradiated in experiment number 1, the copper sputtered film formed using a medium vacuum sputtering device is unstable. Therefore, the adhesion strength is very small at 0.9 N / cm.

[0108] In Experiments 2 to 10, the VUV irradiation dose was gradually increased. In this case, the surface roughness of the insulating layer 20 increases slightly due to VUV irradiation. For example, in Experiment 10, the VUV irradiation dose of 5.4 J / cm 2 Even with an irradiation dose of 100 nm, the Ra value increases by only 6 nm. With this surface roughness, no improvement in adhesion strength due to the anchor effect can be expected. On the other hand, in Experiments 2 to 9, the adhesion strength was greater than that in the case where VUV was not irradiated (Experiment 1). Of these, in Experiment 4, the adhesion strength was 0.54 J / cm 2 The adhesion strength reached a maximum of 4.5 N / cm at an irradiation dose of 100 nm. This maximum value is five times that of the case without VUV irradiation. This is believed to be because the COH formed in the surface region 46 of the insulating layer 20 is bonded to the sputtered copper particles by VUV irradiation, and bonds (COCu) are formed not only on the surface 21 of the insulating layer 20 but also inside the insulating layer 20. Thus, even though the surface roughness hardly changes, it is possible to sufficiently improve the adhesion strength by irradiating VUV.

[0109] Also, as shown in Experiment No. 2, 0.1 J / cm 2 At an exposure dose of 0.01 J / cm, the adhesion strength was 1.2 N / cm, which was greater than the case without VUV exposure (Experiment No. 1). 2 However, almost no improvement in adhesion strength was observed. In addition, looking at the tendency of adhesion strength, the VUV irradiation dose was 0.54 J / cm 2 The adhesion strength peaks around 5 J / cm and gradually decreases as the VUV irradiation dose increases. For example, as shown in experiment number 9, 2 At this dose, the adhesion strength was 1N / cm. Although this was lower than the peak, the adhesion strength was still higher than when no VUV was irradiated. On the other hand, in experiment number 10, the adhesion strength was smaller than when VUV was not irradiated (experiment number 1). This is because the VUV irradiation modified the insulating layer 20 too much, decreasing the structure (COH) that easily bonds with copper particles and increasing the structure that does not easily bond with copper particles. An example of a structure that does not easily bond with copper particles is a structure that has a double bond between a carbon atom and an oxygen atom (C=O), such as COOH.

[0110] From these results, when irradiating VUV in the atmosphere, the VUV irradiation dose is 0.1 J / cm 2 More than 5J / cm 2 By setting the dose in this range, it is possible to achieve high adhesion strength. Note that the dose of VUV is preferably 0.1 J / cm or less. 2 If the exposure dose is less than 5 J / cm, sufficient functional groups will not be formed and the adhesion strength will not increase. 2 If it is larger, as mentioned above, the amount of COH, which is the primary oxidized functional group, will decrease, and conversely, structures such as COOH that are difficult to bond with copper particles will increase, which may make it difficult to obtain sufficient adhesion strength.

[0111] The resin material used in this experiment was glass epoxy resin (absorbance 3x10^3), but if the resin material is used as a wiring board, it is possible to improve the adhesion strength within the above-mentioned range of irradiation amount. For example, in the case of a liquid crystal polymer board (LCP board), which is expected to be a next-generation insulating material, the absorbance is 5x10^2, and the optimal VUV irradiation amount obtained through the experiment is 1.4 J / cm. 2 It was. Besides, the VUV irradiation amount is not limited. For example, the depth of the surface region 46 showing adhesion with the copper film 3 is considered to depend on the absorbance of the resin material. The absorbance also varies from about 10^2 to 10^4 depending on the resin material. In order to deal with such various resin materials, the VUV irradiation amount may be appropriately set so that the desired adhesion strength can be achieved according to the characteristics such as the absorbance of the resin material.

[0112] [Relationship between sputtering pressure and adhesion strength] Below, the adhesion strength when the sputtering pressure is changed will be explained with reference to Table 2.

[0113] [Table 2]

[0114] In the experiments Nos. 11 to 15 shown in Table 2, the wiring layer 30 was formed without VUV irradiation, while changing the sputtering pressure, and the adhesion strength was measured. As shown in Table 2, when VUV irradiation was not performed, there was no significant difference in adhesion strength even when the sputtering pressure was changed. In the experiment No. 15, in which the sputtering pressure was set to 133 Pa, the adhesion strength was slightly reduced. In the experiment, the sputtering pressure was reduced to a pressure of 0.013 Pa or less as shown in the experiment No. 11, but since it took 5 hours to reach a pressure of 0.01 Pa or less, it was not evaluated from the viewpoint of productivity.

[0115] In experiments 16 to 20 shown in Table 2, the VUV irradiation dose was 0.54 J / cm 2 The sputtering pressure was set to a value of 0.13 Pa (experiment number 17), and the sputtering pressure was changed to form the wiring layer 30. Among these, the sputtering pressure was set in the medium vacuum range in experiment numbers 17, 18, and 19. For example, when the sputtering pressure was 0.13 Pa (experiment number 17), the adhesion strength was 3.6 N / cm, when it was 1.3 Pa (experiment number 18), the adhesion strength was 4.5 N / cm, and when it was 13 Pa (experiment number 19), the adhesion strength was 2.4 N / cm.

[0116] In experiment number 16, the sputtering pressure was set to 0.013 Pa, but the adhesion strength was lower than in the case of not irradiating VUV at the same pressure (experiment number 11). For example, in a high vacuum environment, the kinetic energy of the sputtered particles (copper particles) flying toward the insulating layer 20 is high, and when they reach the resin, the kinetic energy is converted into heat, which may cause the sample (insulating layer 20) to be overheated. In experiment number 16, it is believed that the temporary bonds inside the resin formed by VUV irradiation were lost due to the sample being overheated, which instead resulted in a decrease in adhesion strength.

[0117] In addition, in experiment number 20, the sputtering pressure was set to 133 Pa, but the adhesion strength was so low that it could not be measured. In this way, when the sputtering pressure is high, the kinetic energy of the copper particles becomes excessively low, and there is a possibility that the copper particles cannot penetrate into the interior of the insulating layer 20 (resin material). As a result, in experiment number 20, it is believed that the copper particles simply accumulate on the surface and peel off easily.

[0118] From these results, it is preferable that the sputtering pressure is 0.13 Pa or more and 13 Pa or less. By setting the sputtering pressure in this range, it is possible to achieve an adhesion strength that is 2.5 times or more greater than that when VUV is not irradiated. If the sputtering pressure is 0.13 Pa or less, it may take a long time to evacuate and the sample may be heated, preventing an increase in adhesion strength. Also, if the sputtering pressure is greater than 13 Pa, for example, the kinetic energy of the copper particles may be reduced, suppressing bonding inside the insulating layer 20.

[0119] [Relationship between degassing process and adhesion strength] Below, with reference to Table 3, the adhesion strength when the order of the degassing steps and the heating temperature are changed will be described. [Table 3]

[0120] Generally, boards that use insulating resins have the property of absorbing moisture easily. For example, moisture can get into the gaps between the fibers that form the base material (core material) of the insulating resin, or the resin itself can absorb moisture from the air and take in gases. These gases can have a negative effect on the process of forming the wiring.

[0121] For example, if copper is directly sputtered onto a substrate that has not been degassed sufficiently, the gas inside will not escape easily due to the trapping effect of the sputtered film. If electrolytic copper plating is performed on top of that, air spaces called voids will be generated, which may result in defects after plating. In addition, when annealing after plating, the gas inside the substrate will expand, creating stress that breaks the temporary bond between the copper wiring and the resin, which may result in an insufficient bond being formed and poor adhesion.

[0122] To avoid such a situation, it is desirable to immediately move on to the next process for the board material laminated with insulating resin, for example. On the other hand, from the viewpoint of managing the manufacturing process, it is also necessary to be able to stock board materials midway through. For this reason, it is important to carry out an appropriate degassing process.

[0123] In Experiments Nos. 21 to 27 shown in Table 3, samples that were stocked at the stage before VUV irradiation were used. Specifically, after laminating the insulating layer 20 (glass epoxy film) onto the support substrate 10 (CCL), the epoxy resin was cured (heated at 100°C for 30 minutes, followed by heat treatment at 180°C for 30 minutes), and then the samples were exposed indoors for one week. The order of the degassing process and the heating temperature were changed for these samples to form the wiring layer 30. In Experiments Nos. 21 to 27, the VUV irradiation dose was 0.54 J / cm 2 and the sputtering pressure was set to 1.3 Pa.

[0124] In experiment number 21, a degassing process was performed at a sufficiently high temperature (190°C) before VUV irradiation. In this case, the insulating layer 20 had not been modified by VUV at the time the degassing process was performed. After the degassing process, the insulating layer 20 was irradiated with VUV, and the wiring layer 30 was formed by sputtering and electrolytic copper plating. As a result, a sufficiently high adhesion strength (4.6 N / cm) was achieved.

[0125] The heating temperature for the degassing process carried out before VUV irradiation is preferably 100°C or higher and 200°C or lower. By setting the heating temperature within this range, a sufficient degassing effect can be obtained. If the heating temperature is below 100°C, moisture and other substances remain and gas cannot be released sufficiently. On the other hand, if the heating temperature is above 200°C, the properties of the resin may deteriorate.

[0126] In experiments No. 22, 23, 24, and 25, a degassing process was performed after VUV irradiation, and the heating temperatures were set to 90°C, 110°C, 130°C, and 150°C, respectively. As shown in Table 3, within this temperature range, the adhesion strength increases as the temperature is increased. Note that when the heating temperature is 90°C (experiment No. 22), the adhesion strength is significantly reduced, but this is thought to be because the heating temperature is not high enough to evaporate moisture.

[0127] In experiments 26 and 27, a degassing process was performed after VUV irradiation, and the heating temperatures were set to 170°C and 190°C, respectively. In these cases, the adhesion strength dropped sharply to the level without VUV irradiation. This is thought to be because the moieties (COH) involved in the bonds formed inside the resin were deactivated by the heating in the degassing process. In particular, when the temperature exceeds the glass transition point of the resin, the movement of molecules inside the resin becomes active, and the active moieties are lost through intramolecular recombination.

[0128] In this way, the step of heating and degassing the insulating layer 20 is preferably performed before VUV irradiation. This allows sufficient degassing at a relatively high temperature without damaging the functional groups formed by VUV irradiation. As a result, it is possible to sufficiently suppress gas emission from the resin, and it is possible to avoid, for example, bulging (voids) at the interface after electrolytic copper plating and poor adhesion.

[0129] As described above, in the manufacturing method of the wiring board 100 according to the present embodiment, functional groups capable of bonding with copper atoms are generated from the surface 21 of the insulating layer 20 to a certain depth of the surface region 46 by irradiating the insulating layer 20 with VUV. This makes it possible to form bonding portions between the insulating layer 20 and the copper film 3 not only on the surface 21 of the insulating layer 20 but also inside the insulating layer 20 (surface region 46). As a result, even if copper is directly sputtered onto the insulating layer 20, it is possible to realize copper wiring with high adhesion strength.

[0130] In recent years, with the increasing speed of semiconductor elements and the increasing capacity of communication, there is an increasing demand for wiring boards that support high-speed and high-frequency communication. To achieve high-speed communication, it is important to suppress the influence of the skin effect at the interface between the wiring and the insulating resin, and a smooth interface is required. Insulating resin materials have also been improved, and materials with fewer polar groups have been developed to reduce signal loss. With electroless copper plating, which adheres by the anchor effect and intermolecular attraction, it is difficult to form wiring on such smooth resin with fewer polar groups.

[0131] On the other hand, a method of forming wiring by sputtering is considered, but simply sputtering copper directly onto the surface of the resin does not provide sufficient adhesion strength. For this reason, when using sputtering, it has been common to first form an adhesion layer of titanium, nickel, or the like on the surface of the resin, and then sputter copper. However, providing an adhesion layer complicates the etching process. In addition, there is a possibility that the adhesion layer cannot be removed, or that it may be over-etched, making it difficult to manage the reliability of the wiring board.

[0132] In this embodiment, by irradiating the insulating layer 20 with VUV, functional groups (COH) that form bonds with copper are formed from the surface 21 to the inside of the insulating layer 20. Sputtered copper particles bind to these functional groups, forming bonds (COCu) with the copper film 3 on the surface 21 and inside (surface region 46) of the insulating layer 20. This makes it possible to achieve high adhesion strength even when copper is directly sputtered onto the insulating layer 20.

[0133] In this manner, in this embodiment, it is possible to form the wiring layer 30 made only of copper. Therefore, in the etching process for forming the wiring pattern, etc., only etching of copper is required. This simplifies the etching process compared to the case where an adhesive layer of titanium, nickel, etc. is provided, and the number of steps can be reduced. In addition, there is no wiring defect caused by remaining metals other than copper, and no undercut caused by different types of etching processes. As a result, it is possible to realize a highly reliable wiring board 100.

[0134] Furthermore, even when a resin material with few polar groups is used, it is possible to generate COH that easily bonds with copper by irradiating VUV. Furthermore, regardless of the shape of the surface 21 of the insulating layer 20, a bond (COCu) with the wiring layer 30 is formed from the surface 21 of the insulating layer 20 to the inside. Therefore, even for a smooth resin with few polar groups, it is possible to form wiring with high adhesion strength by irradiating VUV and directly sputtering copper. This makes it possible to realize a wiring board 100 that is compatible with high-speed communication with little signal deterioration due to the skin effect and little signal loss during transmission.

[0135] In this embodiment, the copper film 3 is formed by medium vacuum sputtering. Medium vacuum sputtering can suppress the temperature rise of the film-forming target, but it is difficult to realize a copper film 3 with high adhesion by only suppressing the temperature rise (for example, Experiment No. 1 in Table 1). In the present invention, by combining VUV irradiation and medium vacuum sputtering, it becomes possible to fully utilize the functional groups generated by VUV. This makes it possible to sufficiently increase the adhesion strength of the copper wiring.

[0136] In this disclosure, expressions using "more than", such as "greater than A" and "smaller than A", are expressions that comprehensively include both concepts that include equivalent to A and concepts that do not include equivalent to A. For example, "greater than A" is not limited to cases that do not include equivalent to A, but also includes "A or greater." Furthermore, "smaller than A" is not limited to "less than A" but also includes "A or less." When implementing the present technology, specific settings and the like may be appropriately adopted from the concepts included in "greater than A" and "smaller than A" so as to achieve the effects described above.

[0137] It is also possible to combine at least two of the characteristic parts of the present technology described above. That is, the various characteristic parts described in each embodiment may be arbitrarily combined without distinction between the embodiments. In addition, the various effects described above are merely examples and are not limited thereto, and other effects may be exhibited. [Explanation of symbols]

[0138] 3…Copper film 20…Insulating layer 21…Surface 30...Wiring layer 31…Copper seed layer 32...Copper wiring layer 45…Absorption area 46...Surface area 100...Wiring board

Claims

1. The insulating resin layer is irradiated with vacuum ultraviolet light, A copper film is formed directly on the insulating resin layer irradiated with the vacuum ultraviolet light by sputtering. A method for manufacturing a wiring board.

2. 2. The method for manufacturing a wiring board according to claim 1, The pressure inside the chamber during the sputtering is medium vacuum. A method for manufacturing a wiring board.

3. 3. The method for manufacturing a wiring board according to claim 2, The pressure in the chamber during the sputtering is 0.13 Pa or more and 13 Pa or less. A method for manufacturing a wiring board.

4. 2. The method for manufacturing a wiring board according to claim 1, further comprising: Annealing the laminate in which the copper film is formed directly on the insulating resin layer. A method for manufacturing a wiring board.

5. 2. The method for manufacturing a wiring board according to claim 1, the step of irradiating with vacuum ultraviolet rays is a step of irradiating the insulating resin layer with vacuum ultraviolet rays in the atmosphere, The irradiation dose of the vacuum ultraviolet light is 0.1 J / cm 2 5J / cm or more 2 is A method for manufacturing a wiring board.

6. 6. A method for manufacturing a wiring substrate according to claim 1, The step of forming the copper film by sputtering includes forming a copper seed layer as the copper film, Furthermore, a copper wiring layer is formed on the copper seed layer by electrolytic plating. A method for manufacturing a wiring board.

7. 6. A method for manufacturing a wiring substrate according to claim 1, The step of forming the copper film by sputtering forms a copper wiring layer as the copper film. A method for manufacturing a wiring board.

8. 6. A method for manufacturing a wiring substrate according to claim 1, The surface roughness of the insulating resin layer on which the copper film is formed is 40 nm or less in terms of arithmetic mean roughness Ra. A method for manufacturing a wiring board.

9. 6. A method for manufacturing a wiring substrate according to claim 1, In the step of forming the copper film by sputtering, before forming the copper film, a surface of the insulating resin layer on which the copper film is to be formed is subjected to a surface treatment using plasma. A method for manufacturing a wiring board.

10. 10. The method for manufacturing a wiring board according to claim 9, The pressure in the chamber during the surface treatment is 10 Pa or more and 100 Pa or less. A method for manufacturing a wiring board.

11. 6. The method for manufacturing a wiring substrate according to claim 1, further comprising: Before the step of forming the copper film by sputtering, the insulating resin layer is heated to degas. A method for manufacturing a wiring board.

12. The method for manufacturing a wiring board according to claim 11, The step of heating and degassing the insulating resin layer is performed before the irradiation of the vacuum ultraviolet light. A method for manufacturing a wiring board.

13. 6. A method for manufacturing a wiring substrate according to claim 1, The source of the vacuum ultraviolet light is at least one of a xenon excimer lamp and a low-pressure mercury lamp. A method for manufacturing a wiring board.

14. an insulating resin layer having a surface roughness expressed as an arithmetic mean roughness Ra of 40 nm or less; a copper film formed directly on the insulating resin layer; A wiring board comprising:

15. 15. The wiring board according to claim 14, The adhesive strength of the copper film to the insulating resin layer is 1 N / cm or more. Wiring board.

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