Method for manufacturing wiring board, and wiring board

Abstract

A method for manufacturing a wiring board according to one embodiment of the present invention comprises: a step for irradiating an insulating resin layer with vacuum ultraviolet rays; and a step for directly forming a copper film by sputtering on the insulating resin layer irradiated with the vacuum ultraviolet rays.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a wiring substrate for electronic devices and the like, and to a wiring substrate thereof. Background Art

[0002] Conventional wiring substrates for mounting semiconductor components are known. In these wiring substrates, a wiring layer made of a conductive material is formed on the surface of an insulating layer made of resin. One method for depositing a conductive material on the surface of the insulating layer is, for example, electroless copper plating. In electroless copper plating, by forming irregularities on the surface of the insulating layer, the copper plating can be tightly bonded to the insulating layer using anchoring effects and intermolecular attraction.

[0003] On the other hand, if there are irregularities on the surface of the insulating layer, the quality of high-frequency signals is considered to degrade due to the skin effect. Therefore, for high-speed and high-frequency communication, a smoother surface is required, such as for the interface between resin and conductive materials. Furthermore, to reduce transmission loss of high-frequency signals, resin materials with low dielectric constants and low dielectric loss tangents have been developed. It is believed that such resin materials have fewer polar groups within their molecules, resulting in weaker intermolecular attraction. Therefore, sputtering, as a method for depositing conductive materials on the surface of the insulating layer, is gaining attention as an alternative to electroless copper plating.

[0004] For example, Patent Document 1 describes a method for manufacturing a multilayer wiring substrate having a wiring layer and an insulating layer stacked on top of each other. In this method, a laser is used to form a via in the insulating layer, and ultraviolet light with a wavelength of 220 nm or less is irradiated to remove the adhesive residue generated at this time. A titanium (Ti) sputtered film is formed on the surface of the irradiated insulating layer to ensure adhesion strength, and a copper sputtered film is formed on it as a seed layer. This seed layer is used as a power supply path, and a copper plating layer is formed by electroplating. By utilizing ultraviolet light in the removal of adhesive residue, the adhesion of the sputtered film composed of titanium and copper can be improved while maintaining a smooth surface of the insulating layer (paragraphs

[0011] ~

[0013] ,

[0018] of the specification of Patent Document 1). Figure 1 wait).

[0005] Existing technical documents Patent Literature Patent Document 1: Japanese Patent Application Publication No. 2017-11010 Summary of the Invention

[0006] The problem that the invention aims to solve Generally, it is known that for resin materials constituting the insulating layer of a wiring substrate, sputtered films of titanium, nickel (Ni), etc., have higher adhesion strength than sputtered films of copper. Therefore, in order to ensure sufficient adhesion between the resin material and the conductive material, it is necessary to first form an adhesion layer using titanium, nickel, etc. on the surface of the insulating layer, as in Patent Document 1, and then form a copper seed layer thereon.

[0007] However, with such an adhesive layer, the etching process after photolithography requires two steps: etching of copper and etching of titanium and nickel, which complicates the process. Furthermore, since the two steps are different etching processes, it is believed that, for example, the adhesive layer, which serves as the substrate for copper wiring, will be etched to the point of undercut, leaving the adhesive layer on the insulating layer, thus reducing reliability.

[0008] In view of the above, the object of the present invention is to provide a method for manufacturing a copper wiring substrate that can achieve high bonding strength even when copper is directly sputtered on an insulating layer, and a wiring substrate thereof.

[0009] Means for solving problems To achieve the above objectives, one method of manufacturing a wiring substrate according to 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 on the insulating resin layer irradiated with the vacuum ultraviolet light by sputtering.

[0010] In this method for manufacturing the wiring substrate, functional groups capable of bonding with copper atoms are generated from the surface of the insulating resin layer to a certain depth by irradiating the insulating resin layer with vacuum ultraviolet light. This creates a bonding area between the insulating resin layer and the copper film not only on the surface of the insulating resin layer but also within the insulating resin layer. As a result, even when copper is directly sputtered onto the insulating layer, copper wiring with high bonding strength can be achieved.

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

[0012] The chamber pressure during sputtering can be above 0.13 Pa and below 13 Pa.

[0013] The method for manufacturing the wiring substrate may also anneal the laminate in which the copper film is directly formed on the insulating resin layer.

[0014] The step of irradiating the insulating resin layer with vacuum ultraviolet light can be a step of irradiating the insulating resin layer with vacuum ultraviolet light in the atmosphere. In this case, the irradiation dose of the vacuum ultraviolet light can be 0.1 J / cm². 2 Above and 5J / cm 2 the following.

[0015] The copper film is formed by sputtering, which forms a copper seed layer, and then a copper wiring layer is formed on the copper seed layer by electroplating.

[0016] The copper film can be formed by sputtering, which forms a copper wiring layer as the copper film.

[0017] The surface roughness of the insulating resin layer on which the copper film is formed can be less than 40 nm, expressed as arithmetic mean roughness Ra.

[0018] The process of forming the copper film by sputtering can involve surface treatment of the surface of the insulating resin layer on which the copper film is formed using plasma before forming the copper film.

[0019] The pressure inside the chamber during the surface treatment can be above 10 Pa and below 100 Pa.

[0020] The method for manufacturing the wiring substrate may also include heating the insulating resin layer to degas it before the step of forming the copper film by sputtering.

[0021] The process of heating and degassing the insulating resin layer can be performed before irradiation with the vacuum ultraviolet light.

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

[0023] One embodiment of the wiring substrate of the present invention has an insulating resin layer and a copper film.

[0024] The surface roughness of the insulating resin layer, expressed as an arithmetic mean roughness Ra, is less than 40 nm.

[0025] The copper film is formed directly on the insulating resin layer.

[0026] The adhesion strength between the copper film and the insulating resin layer can be above 1 N / cm.

[0027] Invention Effects As described above, according to the present invention, even when copper is directly sputtered onto an insulating layer, copper wiring with high bonding strength can be achieved. Furthermore, the effects described herein are not necessarily limiting and can be any effects described in this disclosure. Attached Figure Description

[0028] Figure 1 This is a schematic cross-sectional view showing an example of the configuration of a wiring substrate according to an embodiment of the present invention.

[0029] Figure 2 This is a flowchart illustrating an example of a method for manufacturing a wiring substrate according to this embodiment.

[0030] Figure 3 It is a scanning electron microscope (SEM) image of the insulating layer used in wiring substrates.

[0031] Figure 4 This is a graph representing the VUV absorption characteristics of the insulating layer.

[0032] Figure 5 This is a schematic diagram showing the functional groups formed on an insulating layer irradiated with VUV.

[0033] Figure 6 This is a schematic diagram showing the bonding state between the insulating layer and the copper film after being irradiated with VUV.

[0034] Figure 7 This is a flowchart illustrating an embodiment of a method for manufacturing a wiring substrate.

[0035] Figure 8 It is used for explanation Figure 7 The diagram shows a process flow of the wiring substrate manufacturing method. Detailed Implementation

[0036] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0037] [Wiring substrate] Figure 1 This is a schematic cross-sectional view illustrating a structural example of a wiring substrate according to one embodiment of the present invention. The wiring substrate 100 is, for example, a substrate having wiring patterns formed for mounting semiconductor elements, etc. Figure 1 The diagram schematically illustrates a cross-sectional view of a wiring substrate 100 cut along its thickness direction. The wiring substrate 100 includes a support substrate 10, an insulating layer 20, and a wiring layer 30.

[0038] The support substrate 10 is a component that supports the insulating layer 20 and the wiring layer 30. The support substrate 10 is made of insulating materials such as glass epoxy resin. Alternatively, a conductive material such as copper foil may be provided on the main surface of the support substrate 10. Furthermore, the type of support substrate 10 is not limited; for example, a rigid substrate with high rigidity or a flexible substrate that can be bent may be used.

[0039] exist Figure 1 In the example shown, an insulating layer 20 and a wiring layer 30 are sequentially stacked on one main surface of a flat support substrate. Hereinafter, the side on which the insulating layer 20 and wiring layer 30 are stacked (the upper side in the figure) is sometimes referred to as the upper side of the wiring substrate 100, and the opposite side (the lower side in the figure) is sometimes referred to as the lower side of the wiring substrate 100. Furthermore, in the support substrate 10, insulating layer 20, and wiring layer 30, the surface facing upwards is sometimes referred to as the upper surface, and the surface facing downwards is sometimes referred to as the lower surface.

[0040] The insulating layer 20 is a layer made of an insulating resin material and is disposed on the surface of the support substrate 10 (here, the upper surface of the support substrate 10). In this embodiment, the insulating layer 20 is equivalent to an insulating resin layer. As the resin material constituting the insulating layer 20, glass epoxy resin is used for example. For example, the insulating layer 20 is formed by bonding a glass epoxy film, which is processed into a film shape, to the support substrate 10.

[0041] Furthermore, the method for forming the insulating layer 20 is not limited; for example, a method in which the resin material composition, which will become insulating, is applied to the support substrate 10 and then the resin material is cured can also be used. Additionally, the type of resin material constituting the insulating layer 20 is not limited; for example, epoxy resin, bismaleimide triazine resin, polyimide resin, polyester resin, etc., can be used. Furthermore, the insulating layer 20 may contain any material such as particulate fillers.

[0042] The wiring layer 30 is a copper layer stacked on top of the insulating layer 20. That is, the wiring layer 30 is a copper layer directly stacked on the surface of the insulating layer 20 (in this case, 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 is equivalent to a copper wiring layer. Various wiring patterns (copper wiring) corresponding to the purpose of the wiring substrate 100 are formed on the wiring layer 30.

[0043] In the wiring substrate 100, at least the portion of the wiring layer 30 that forms the interface between the insulating layer 20 and the wiring layer 30 is formed by sputtering. That is, the portion that is in close contact with the insulating layer 20 is a sputtered copper film. As will be described later, the wiring layer 30 can be formed by electroplating with a sputtered copper film as a seed layer, or the wiring layer 30 can be formed solely from a sputtered copper film.

[0044] Figure 1 The wiring substrate 100 shown is a substrate with only one set of insulating layer 20 and wiring layer 30 stacked together, but the present invention can also be applied to multilayer substrates with alternating layers of insulating layer 20 and wiring layer 30. For example, in Figure 1 A second insulating layer 20 is formed on the surface (upper surface) of the wiring layer 30 shown. A copper sputtered film is then deposited on the surface (upper surface) of the second insulating layer 20 to form the second wiring layer 30. In the case of constructing a multilayer substrate, the copper sputtered film can be directly deposited on all of the insulating layer 20, or a portion of the insulating layer 20 can be directly deposited with a copper sputtered film.

[0045] In addition, Figure 1 In this embodiment, an insulating layer 20 and a wiring layer 30 are stacked on one side of the support substrate 10, but for example, the insulating layer 20 and the wiring layer 30 may also be stacked on both sides of the support substrate 10.

[0046] Furthermore, it is not necessary to provide a support substrate 10. For example, the insulating layer 20 can be directly configured as a structural component supporting the entire wiring substrate 100.

[0047] [Overview of the manufacturing method of wiring substrate] Figure 2 This is a flowchart illustrating an example of a method for manufacturing a wiring substrate according to this embodiment. Figure 2 The basic steps of the manufacturing method of the wiring substrate 100 are shown. These steps are necessary to ensure that the insulating layer 20 and the wiring layer 30 (a sputtered copper film) are bonded together. Hereinafter, a substrate material on which the insulating layer 20 is provided is prepared in advance.

[0048] First, the insulating layer 20 is irradiated with vacuum ultraviolet (VUV) light (step 101). Specifically, VUV light is irradiated onto the insulating layer 20 from the surface side. Here, the surface of the insulating layer 20 refers to the surface of the stacked wiring layer 30, which is the surface of the insulating layer 20 exposed in the substrate material. For example, the surface of the insulating layer 20 facing the side opposite to the supporting substrate 10 (in... Figure 1 The upper surface of the insulating layer 20 (in the middle) becomes the surface of the insulating layer 20 that is irradiated by VUV.

[0049] VUV is a band of light in the ultraviolet spectrum that is efficiently absorbed by atmospheric components. For example, a vacuum environment (reduced pressure atmosphere) is typically prepared for VUV propagation. The wavelength λ of VUV is, for example, 200 nm ≥ λ ≥ 10 nm. Therefore, a portion of VUV overlaps with the region of soft X-rays.

[0050] For example, VUV is irradiated toward the insulating layer 20 by an irradiation device equipped with a light source (such as an excimer lamp) that emits VUV.

[0051] As described later, the inventors discovered that by irradiating the insulating layer 20 with VUV, the properties of the insulating layer 20 can be changed from the surface to the interior in a manner that increases the adhesion strength (adhesion force) between the insulating layer 20 and the sputtered copper film. Therefore, the process of irradiating the insulating layer 20 with VUV becomes a process for modifying the insulating layer 20.

[0052] Next, a copper film is formed on the VUV-irradiated insulating layer 20 by sputtering (step 102). Sputtering (sputtering method) is a dry process performed in a vacuum chamber. For example, a substrate material irradiated with VUV is introduced into the vacuum chamber of a sputtering apparatus, and a copper sputtered film is formed under reduced pressure to a specified pressure.

[0053] In a sputtering apparatus, for example, argon (Ar) plasma is collided with a copper sputtering target, causing ejected copper particles (copper ions, etc.) to be deposited onto the insulating layer 20. At this time, the resin material constituting the insulating layer 20 is modified by VUV irradiation, thus becoming a state where it easily bonds with the copper particles from the surface to the interior. Therefore, the bonding of the resin material and copper particles can occur in the surface region of the insulating layer 20. Here, the surface region of the insulating layer 20 refers to, for example, the region from the surface of the insulating layer 20 to a certain depth, which is the region where the bonding with copper particles occurs.

[0054] In this way, by irradiating with VUV, electrolytic bonding with copper particles can be achieved not only on the surface of the resin material but also inside it. As a result, a copper film with high adhesion strength can be formed.

[0055] The copper film formed by sputtering on the insulating layer 20 is, for example, a seed layer for electrolytic copper plating. That is, in the process of forming a copper film by sputtering, a copper seed layer is formed as the copper film. The copper seed layer is the layer that serves as the power supply path (electrode) for the growth of the copper plating layer. This process can be described as a direct copper seed formation process in which a copper seed layer is formed directly on the insulating layer 20.

[0056] The copper seed layer is relatively thin, for example, less than 1 μm. However, as long as it is the thickness that functions as a copper electroplating film, the copper seed layer (copper sputtering film) can be formed with any thickness.

[0057] Furthermore, in the case of forming a copper seed layer, a copper wiring layer is further formed on the copper seed layer by electroplating. For example, a substrate material with a copper seed layer is attached to an electrolytic copper plating solution, and a copper wiring layer, which serves as a copper plating layer, is formed on the copper seed layer. The thickness of the copper wiring layer is not limited, and is, for example, around tens of μm. In this case, the structure consists of a copper seed layer and a copper wiring layer. Figure 1 The wiring layer 30 is shown.

[0058] Alternatively, the copper film formed by sputtering on the insulating layer 20 can also be a copper wiring layer. That is, during the process of forming the copper film by sputtering, a copper wiring layer can also be formed as the copper film. In this case, no electroplating or other processes are performed on the copper film, and the copper film is directly used as wiring. This process can be described as a direct copper wiring layer forming process that directly forms a copper wiring layer on the insulating layer 20.

[0059] The thickness of the copper film serving as the copper wiring layer is appropriately set within a range sufficient to form the wiring of the wiring substrate 100. For example, as the copper wiring layer, a copper film with a thickness of 1 μm or more can be formed by sputtering, or an even thinner copper film can be formed as the copper wiring layer. In this case, it consists only of a sputtered copper film (copper film). Figure 1 The wiring layer 30 is shown.

[0060] Thus, the copper film formed by sputtering on the insulating layer 20 can be an electroplated seed layer, or the copper film itself can 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 formed by sputtering on the copper film of the insulating layer 20 that has been irradiated with VUV, thus enabling copper wiring with high bonding strength.

[0061] [The effects of VUV irradiation] To investigate the interface between the insulating layer 20 and the wiring layer 30 (a copper film formed by sputtering), the inventors peeled the wiring layer 30, which was formed on the insulating layer 20, from the insulating layer 20 and measured the interface of the wiring layer 30 by X-ray electron spectroscopy (XPS). The results showed that a higher adhesion strength indicated a higher intensity of the spectroscopic peak of COCu. COCu is a structure in which carbon atoms (C) and copper atoms (Cu) are bonded to oxygen atoms (O) through single bonds (CO-Cu) (see [link to documentation]). Figure 6 ).

[0062] That is, in the wiring substrate 100 where the insulating layer 20 and the wiring layer 30 have high adhesion, the formation of COCu was observed at their interface. It is believed that this is because, by irradiating the insulating layer 20 with VUV as a pretreatment, hydroxyl groups (COH) are formed in the insulating layer 20, and COCu is formed by the reaction of sputtered Cu with the COH.

[0063] Furthermore, the inventors investigated where COH forms on the insulating layer 20 under VUV irradiation. Figure 3 It is a scanning electron microscope (SEM) image of the insulating layer 20 used in the wiring substrate 100. Figure 4 This is a graph representing the absorption characteristics of VUV in the insulating layer 20. First, refer to... Figure 3 and Figure 4 The absorption characteristics of VUV relative to insulating layer 20 are explained.

[0064] Previously, it was believed that resin materials had extremely high VUV absorption, meaning VUVs could hardly penetrate the resin. In this case, VUVs irradiating the resin material would be absorbed by the resin surface and would not reach the interior. To address this, the inventors measured the transmittance of VUVs relative to the resin material and investigated the absorption characteristics of VUVs.

[0065] Figure 3 This is a SEM image obtained by photographing a cross-section of the test sample containing the insulating layer 20 used in the VUV transmittance measurement. The insulating layer 20 is a film of glass epoxy resin 40. In the transmittance measurement, a test sample is used where glass epoxy resin 40 is laminated onto a synthetic quartz glass substrate 41, and the glass epoxy resin 40 is ground to a thickness of 1 μm. Figure 3In the middle, the thick gray layer on the right is the glass substrate 41, and the thin layer on the glass substrate 41 is glass epoxy resin 40 (insulating layer 20).

[0066] In the transmittance measurement, a spectrophotometer (MacPherson Corporation, VUVAS-1000 model) was used to measure the wavelength range from 140nm to 225nm, and the transmittance data of the excimer lamp's emission center wavelength of 172nm was obtained. Figure 4 This is a graph showing the measured transmittance of VUV relative to glass epoxy resin 40 (insulating layer 20). The horizontal axis of the graph represents the depth (nm) of glass epoxy resin 40, and the vertical axis represents the transmittance (%). Furthermore, the depth of glass epoxy resin 40 refers to the distance from the surface irradiated by the VUV.

[0067] The absorbance of glass epoxy resin 40, calculated from the VUV transmittance measurement results, is 3.0 × 10⁻⁶. 3 Furthermore, the examination of this absorbance involves the emission spectrum of the excimer lamp; for example, in a radiation region with a half-width of 14 nm, absorbance can be calculated similarly for single-wavelength light and combined-wavelength light. In this case, such as Figure 4 As shown, from the surface of the glass epoxy resin 40 to a depth of approximately 1000 nm, a portion of VUV is absorbed by the resin, while the remaining VUV passes through the resin. Hereinafter, the region where VUV absorption occurs will be referred to as absorption region 45. Absorption region 45 is, for example, a region with a depth up to 1000 nm.

[0068] Specifically, it was determined that at a depth of approximately tens of nm from the surface of the glass epoxy resin, the transmittance decreases from 100% to 90%, and VUV is absorbed by about 10%. This region becomes the surface layer region 46 that forms a bond with the sputtered copper particles. The surface layer region 46 is, for example, a region with a depth of approximately 20 nm to 40 nm from the surface. Figure 4 In the middle, the surface area 46 is schematically illustrated by gray areas.

[0069] Furthermore, VUV hardly reaches any region deeper than the absorption region 45 within the glass epoxy resin 40. Therefore, the glass epoxy resin 40, with a practical thickness (several μm or more), operates in a manner that completely blocks VUV transmission. In fact, even with such a relatively thick glass epoxy resin 40, an absorption region 45, which absorbs and transmits VUV, is formed at a certain depth on the surface side irradiated by VUV.

[0070] Based on the above results, the effects produced by VUV irradiation will be explained.

[0071] Figure 5 This is a schematic diagram showing the functional groups formed in the insulating layer 20 that has been irradiated with VUV. Figure 5 The diagram schematically illustrates functional groups formed in the insulating layer 20 by VUV irradiation, carbon chains located within the insulating layer 20, etc. Additionally, in Figure 5 In this case, the insulating layer 20 is irradiated with VUV in the air.

[0072] The resin material constituting the insulating layer 20 comprises a chain-like polymer composed of carbon atoms (C), oxygen atoms (O), hydrogen atoms (H), etc. The polymer contains single bonds (e.g., C=C, CO, CH, OH, etc.) and double bonds (e.g., C=O) between the atoms.

[0073] When the insulating layer 20 is irradiated with VUV, the energy of the VUV is absorbed on the surface 21 and inside the insulating layer 20 (including the absorption region 45 of the surface region 46, etc.). At this time, a portion of the energy of the VUV becomes the excitation energy for exciting the atoms constituting the polymer. As a result, the binding state of the polymer changes, and new functional groups are formed.

[0074] Specifically, during VUV irradiation, hydroxyl groups (COH) are formed in the polymer through intramolecular recombination. COH is a primary oxidation functional group that readily combines with copper atoms (Cu). When Cu combines with COH, COCu is formed.

[0075] As described above, the absorption of VUV energy occurs not only on the surface 21 of the insulating layer 20, but also inside it. Therefore, COH is formed on both the surface 21 and inside the insulating layer 20. Figure 5 The diagram schematically illustrates the COHs formed on the surface 21 of the insulating layer 20 and the COHs formed inside the insulating layer 20 (particularly in the surface region 46). The COHs enclosed by dashed lines represent those formed in the surface region 46. Thus, by VUV irradiation, the surface region 46 of the insulating layer 20 is modified, and COH functional groups are also formed inside the insulating layer 20.

[0076] In addition, during the propagation of VUVs in the air, oxygen molecules (O2) are excited, generating ozone (O3) and ground-state oxygen atoms (O2). 1 D), oxygen atoms in the excited state (O( 3 P)) etc. These oxygen-derived products, for example, form COH, COOH, etc. on the surface 21 of the insulating layer 20.

[0077] In this way, a copper film is formed on the insulating layer 20 where COH is formed by sputtering. At this time, it is assumed that a temporary bond is formed between the copper atoms (Cu) flying towards the insulating layer 20 and the COH. Here, a temporary bond means, for example, a state in which a complete bond (COCu) between COH and Cu is not formed, but it can become COCu. For example, a state in which Cu exists within the range that can bond with COH can be considered a temporary bond.

[0078] Sputtered copper atoms (Cu) can form temporary bonds with COH atoms formed on the surface 21 of the insulating layer 20, and with COH atoms formed inside the insulating layer 20, particularly in the surface region 46. Therefore, in the insulating layer 20 to 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. Alternatively, it is also believed that sputtered copper atoms (Cu) can directly bond with COH to form COCu.

[0079] As described later, in this embodiment, a heat treatment (annealing) is performed to bond the temporary bond. This forms a complete bond (COCu) in the surface region 46 of the insulating layer 20. For example, in the case of forming a copper plating layer after sputtering, annealing is performed to achieve stress dispersion in the copper plating layer. This annealing process allows the aforementioned temporary bond to become a complete bond.

[0080] Furthermore, regarding temporary bonding, cases such as the bonding portion (COCu) absorbing the kinetic energy of other Cu during sputtering or absorbing the heat energy applied during the manufacturing process of the wiring substrate 100 are also considered. Therefore, if sufficient bonding strength can be obtained even without annealing, annealing is not necessarily required.

[0081] Figure 6 This is a schematic diagram showing the bonding state between the insulating layer 20 and the copper film 3 after being irradiated with VUV. Figure 6 In the process, a copper film 3 is directly formed on the insulating layer 20 that is irradiated by VUV by sputtering, and a junction (COCu) between the insulating layer 20 and the copper film 3 is formed on the entire substrate.

[0082] For example, a copper seed layer is formed as copper film 3, and electrolytic copper plating is performed. During this process, a temporary bond between CO and Cu is maintained. After forming the copper plating layer (wiring layer 30), an annealing process is performed to form COCu. Alternatively, without electrolytic copper plating, an annealing process is performed at an appropriate time, for example, after the copper film 3 is formed by sputtering.

[0083] The copper atoms (Cu) that form the bonding 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, COCu can be said to bond the insulating layer 20 (polymer) to the copper film 3. Furthermore, COCu is formed not only on the surface 21 of the insulating layer 20 but also within the insulating layer 20, i.e., the surface region 46. Therefore, the insulating layer 20 is bonded to the copper film 3 from the surface 21 to the surface region 46, which has a depth of tens of nm. This creates a gradually changing, tightly bonded interface in the surface region 46, for example, with a bonding portion in the depth direction.

[0084] As a result, even when copper film 3 is sputtered directly onto insulating layer 20, the bonding strength can be significantly improved compared to, for example, when COH is formed only on the surface.

[0085] To date, VUV is believed to modify the surface of resin materials, forming functional groups such as COOH and COOH on the surface. However, measurements conducted by the inventors show that VUV partially permeates the resin material (insulating layer 20) and is absorbed within the resin material (see reference). Figure 4 The results show that, through VUV irradiation, functional groups such as COH are formed not only on the surface 21 of the insulating layer 20, but also inside (surface region 46, etc.).

[0086] However, in sputtering apparatuses, methods are known to clean the surface of the film-forming object by performing a surface treatment using plasma prior to sputtering. It is also thought that plasma acting on the surface of a resin material can, for example, form functional groups on the surface of the resin material similar to those formed by VUV irradiation. However, unlike VUV, plasma does not penetrate into the interior of the resin material.

[0087] Thus, plasma-based surface treatment on the surface of the resin material produces an effect similar to that of VUV. Assuming that only surface functional groups form bonds, the adhesion strength should be improved even without VUV irradiation and only with plasma-based surface treatment. However, as will be discussed later, in the absence of actual VUV irradiation, the adhesion strength remains low.

[0088] In contrast, in the VUV-modified resin material (insulating layer 20), copper, formed by sputtering, reacts with COH not only on the surface 21 but also in the internal surface region 46. As a result, it is believed that a film exhibiting the characteristics shown is formed. Figure 6 The bonding strength shown is such that, in this invention, copper particles bond with functional groups formed on the surface region 46 of the insulating layer 20 by VUV irradiation, thereby forming a strong bond between the insulating layer 20 and the wiring layer 30.

[0089] The above-described method utilizes an electroless bonding portion (COCu) formed at the interface between the insulating layer 20 and the wiring layer 30 to improve the adhesion strength. Using this method, for example, a wiring substrate 100 having a smooth insulating layer 20 can be constructed. Specifically, the wiring substrate 100 has an insulating layer 20 with 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.

[0090] Here, the arithmetic mean roughness Ra is, for example, the average depth of the unevenness within a reference range. The reference range is, for example, a rectangular range where the length of each side is more than 10 times the depth of the unevenness. For example, when the arithmetic mean roughness Ra is less than 150 nm, adhesion effects dependent on the physical shape, such as anchoring effects, cannot be expected. Therefore, in the insulating layer 20 with Ra less than 40 nm, it is difficult to improve the adhesion strength through the anchoring effect. Even with such a sufficiently smooth insulating layer 20, sufficient adhesion strength can be achieved by applying the present invention.

[0091] Furthermore, in the wiring substrate 100 having a 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 of this embodiment, as shown in Tables 1 to 3 below, an adhesion strength of 1 N / cm or more can be achieved. Thus, it is possible to achieve smooth wiring with sufficiently high adhesion strength and consisting only of copper.

[0092] [Manufacturing method of wiring substrate] Figure 7 This is a flowchart illustrating an embodiment of a method for manufacturing a wiring substrate. Figure 8 It is used for explanation Figure 7 The diagram shows a process flow of the wiring substrate manufacturing method. Figure 7 and Figure 8 This is an example of a method for manufacturing the wiring substrate 100 of the present invention. Hereinafter, a copper seed layer is formed by sputtering, and then a wiring layer 30 is formed by electrolytic copper plating.

[0093] First, an insulating layer 20 is formed (step 201). This step is the process of forming a substrate material having the insulating layer 20. Here, as... Figure 8 As shown, an insulating layer 20 is provided on one main surface of the support substrate 10. Hereinafter, the substrate material on which the insulating layer 20 is laminated on the support substrate 10 will be referred to as substrate material 5a. As the support substrate 10, a glass epoxy board or the like is used. Furthermore, as the insulating layer 20, a glass epoxy film or the like is used.

[0094] When an insulating layer 20, such as a glass epoxy film, is bonded to a support substrate 10, a vacuum lamination apparatus that uses a carrier film to hold and seal the object is used, for example. In this case, the substrate material 5a, formed by bonding the insulating layer 20 to the support substrate 10, is removed while covered by the carrier film. Then, a heat treatment for curing the glass epoxy film is performed using a heating apparatus such as an oven. This heat treatment is performed, for example, while the substrate material 5a is covered by the carrier film. Furthermore, the method for forming the substrate material 5a having the insulating layer 20 is not limited.

[0095] Next, degassing heating is performed (step 202). This process removes gaseous components contained in the insulating layer 20 and the supporting substrate 10. For example, a heating device such as an oven is used to heat the substrate material 5a to a specified temperature. The degassing heating temperature is set, for example, in a range from the glass transition temperature of the resin to a maximum of 200°C.

[0096] Thus, in this embodiment, a process of heating and degassing the insulating layer 20 is performed before the process of forming the copper film 3 by sputtering. For example, the copper film 3 formed by sputtering is a dense film, which may sometimes trap gas within the insulating layer 20. Therefore, if degassing is insufficient, an air layer called voids may be generated during electrolytic copper plating. Therefore, by performing a degassing heating treatment before sputtering, the generation of voids and the like can be avoided.

[0097] Furthermore, after the glass epoxy film has undergone curing treatment, the amount of gas contained in the insulating layer 20 is significantly reduced. In such cases, degassing heating treatment may not be necessary.

[0098] Next, the insulating layer 20 is irradiated with VUV (step 203). This process is similar to the reference process. Figure 2 This corresponds to step 101 of the process described. For example, substrate material 5a is introduced into a VUV irradiation apparatus, 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 (absorption region 45) of the insulating layer 20. Figure 8 The diagram illustrates the modified insulating layer 20 after VUV irradiation using a gradient method.

[0099] VUV light sources can be used, for example, xenon excimer lamps (peak wavelength 172nm) or low-pressure mercury lamps (185nm bright line) containing xenon gas. Alternatively, these light sources can be used in combination. Furthermore, the amount of VUV irradiation in the VUV irradiation device can be adjusted by factors such as irradiation time, light source brightness, and irradiation distance. Additionally, sensors (lux meters) can be installed to detect the amount of VUV irradiation directed onto the insulating layer 20.

[0100] In this embodiment, VUV irradiation is performed in the atmosphere. That is, the VUV irradiation process involves irradiating the insulating layer 20 with VUV in the atmosphere. Since VUV irradiation is performed in the atmosphere, there is no need to install a vacuum chamber in the VUV irradiation apparatus, nor is it necessary to introduce the substrate material 5a into the vacuum chamber or to perform a vacuum evacuation process. Therefore, the VUV irradiation process can be completed in a short time. Furthermore, surface modification can also be performed using oxygen in the atmosphere.

[0101] Furthermore, the structure is not limited to irradiating VUV in the atmosphere; for example, VUV can also be irradiated in a specified reduced-pressure atmosphere or a low-oxygen atmosphere. In this case, since there is no atmospheric absorption of VUV, the amount of VUV light can be reduced, thereby suppressing power consumption. Alternatively, for example, the VUV light source can be installed inside the chamber of the sputtering apparatus. Thus, the process from VUV irradiation to sputtering can be performed within a single apparatus.

[0102] When the insulating layer 20 of the substrate material 5a is irradiated with VUV, the substrate material 5a is introduced into the vacuum chamber of the sputtering apparatus. Steps 204 and 205 described below are processes performed by the sputtering apparatus.

[0103] In the sputtering apparatus, a surface treatment using plasma is first performed (step 204). This step is a pretreatment for sputtering, which involves cleaning the surface 21 of the insulating layer 20 using plasma. By using plasma for surface treatment, the surface 21 of the insulating layer 20 that has been contaminated during the period from VUV irradiation to introduction into the sputtering apparatus is cleaned.

[0104] As an atmospheric gas for generating plasma, for example, a mixture of argon and hydrogen (Ar / H2) or a mixture of argon and oxygen (Ar / O2) may be used, depending on the material.

[0105] In this embodiment, hollow cathode plasma (HCD plasma) is used for surface treatment. That is, before forming the copper film 3 by sputtering, the surface 21 of the insulating layer 20 on which the copper film 3 is formed is surface treated using hollow cathode plasma.

[0106] Hollow cathode plasma, for example, is plasma generated using a cylindrical cathode (hollow cathode) and emitted as a high-density plasma jet. For instance, a hollow cathode plasma device integrated into a sputtering apparatus generates a plasma jet (hollow cathode plasma) within a vacuum chamber. This plasma cleans the surface 21 of the insulating layer 20.

[0107] Furthermore, the hollow cathode plasma acts only on the surface 21 of the insulating layer 20, not on its interior. Therefore, functional groups such as COH formed inside the insulating layer 20, for example, by VUV irradiation, are maintained. On the other hand, functional groups such as COH are formed on the surface 21 of the insulating layer 20 in addition to the removal of contaminants. Thus, by modifying the surface 21 of the insulating layer 20 using hollow cathode plasma, the adhesion strength between the insulating layer 20 and the copper film 3 can be further improved.

[0108] Furthermore, the chamber pressure during surface treatment using hollow cathode plasma is between 10 Pa and 100 Pa. By setting this pressure range, sufficient surface modification can be achieved using hollow cathode plasma. Additionally, due to the relatively high pressure, the time required for decompression is short. This reduces the overall surface treatment time.

[0109] Next, in a sputtering apparatus, a copper film 3 is directly formed on the aforementioned insulating resin layer irradiated with vacuum ultraviolet light by sputtering (step 204). This process is similar to the reference... Figure 2 This corresponds to step 102 of the process described. Here, a copper seed layer 31 is formed as the copper film 3, which serves as the power supply path for electrolytic copper plating. The thickness of the copper seed layer 31 is, for example, about 300 nm, but any thickness can be set. Figure 8 The diagram schematically illustrates a copper seed layer 31 formed on the insulating layer 20. Hereinafter, the component on which the copper seed layer 31 is formed on the insulating layer 20 will be referred to as substrate material 5b.

[0110] For example, plasma is generated by a plasma device built into the sputtering apparatus, and a copper sputtering target is sputtered by the plasma. Copper particles ejected from the sputtering target are stacked 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 continues until the specified thickness is reached.

[0111] The atmospheric gas used to generate plasma is, for example, argon. Alternatively, the aforementioned hollow cathode plasma apparatus or a sputtering-specific apparatus can be used as the plasma device.

[0112] In this embodiment, the pressure inside the chamber during sputtering is a medium vacuum. That is, medium vacuum sputtering is performed in the sputtering apparatus. Here, the pressure of the medium vacuum is 0.1 Pa or more and 100 Pa or less.

[0113] When the chamber pressure is at a medium vacuum, for example, the probability of copper particles flying from the sputtering target insulating layer 20 colliding with the atmospheric gas of the plasma increases, and the kinetic energy of the copper particles decreases. Therefore, the temperature rise of the insulating layer 20 during sputtering can be suppressed. As a result, for example, a copper seed layer 31 can be formed without causing the temporary bonding between copper atoms (Cu) and functional groups (COH) to disappear.

[0114] Typically, film deposition is carried out using sputtering at pressures sufficiently below 0.1 Pa (e.g., 0.01 Pa). In this case, target particles with relatively high kinetic energy are assumed to fly towards the film deposition object, which is then heated.

[0115] In this embodiment, sputtering is performed under a deliberately low vacuum pressure to suppress the temperature rise of the insulating layer 20 and maintain a good bond between the insulating layer 20 and the copper seed layer 31. This results in the formation of a copper seed layer 31 with strong adhesion. Furthermore, the venting time until the low vacuum pressure is reached is relatively short. Therefore, the sputtering time required can be shortened.

[0116] Next, a copper wiring layer 32 is formed by electrolytic copper plating (step 206). Here, a copper seed layer 31 formed by sputtering is used as a power supply path for electrolytic copper plating, and the copper wiring layer 32 is formed by the copper plating. The film thickness of the copper wiring layer 32 is, for example, about tens of μm, but any film thickness can be set. Figure 8 The diagram schematically illustrates a copper wiring layer 32 formed on a copper seed layer 31. Hereinafter, the component on which the copper wiring layer 32 is formed on the copper seed layer 31 will be referred to as substrate material 5c.

[0117] For example, the substrate material 5b and the copper electrode generated in step 205 are immersed in an electrolytic copper plating bath containing a copper sulfate solution. Using the copper electrode as the anode and the copper seed layer 31 as the cathode, a current is supplied at a specified current density. This forms a copper plating layer (copper wiring layer 32) on the copper seed layer 31. The copper-plated substrate material 5c is then dried.

[0118] Next, an annealing process is performed (step 207). This process is, for example, a heat treatment used to make the temporary bond formed at the interface between the copper seed layer 31 and the insulating layer 20 a complete bond (COCu, etc.). Here, the substrate material 5c on 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 directly formed on the insulating resin layer. The substrate sample 5c after the annealing process becomes the wiring substrate 100.

[0119] For example, a heating device such as an oven is used to heat the substrate material 5c to a specified temperature. The heating temperature for annealing is, for example, around 200°C, and the heating time is, for example, around 1 hour. In addition, the heating temperature and heating time for annealing can be appropriately set in a way that achieves the desired bonding strength.

[0120] By performing an annealing process, a complete bond is formed from the surface 21 of the insulating layer 20 to the surface region 46. As a result, a wiring layer 30 (copper seed layer 31 and copper wiring layer 32) with strong adhesion can be formed.

[0121] [Evaluation of fit] The following describes an experiment evaluating the adhesion between the insulating layer 20 and the wiring layer 30 in the wiring substrate 100. In this experiment, the adhesion was basically evaluated by referring to... Figure 7 and Figure 8 The bonding strength of the specimens manufactured using the described method was evaluated. Additionally, for comparison, the bonding performance of specimens manufactured without VUV irradiation and without step 203 was also evaluated.

[0122] The wiring substrate 100 used in the experiment uses a copper-clad laminate (CCL) as the support substrate 10 (e.g., Hitachi Chemical: MCL-800). Additionally, a glass epoxy film (e.g., Ajinomoto Fine Chemicals: ABF-GX-T31) is used as the insulating layer 20. In the experiment, the glass epoxy film was bonded to one side of the copper-clad laminate using a vacuum lamination apparatus (Meiki Manufacturing Co., Ltd.: Model MVLP-500 / 600-IIA). To harden the glass epoxy resin components of the insulating layer 20 after lamination, a heat treatment was performed using an oven (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.

[0123] If the placement time after step 201 is long, it is preferable to perform a degassing heat treatment in an oven (step 202) before VUV irradiation. In this treatment, the heat treatment is performed at 190°C for 1 hour. Alternatively, if the glass epoxy resin is transferred to the next process immediately after curing, step 202 is omitted, and the carrier film used in the vacuum lamination apparatus is peeled off before VUV irradiation.

[0124] Next, the insulating layer 20 was irradiated with VUV (step 203). An excimer irradiation device (USHIO Electric Machinery: SVM-453S type) emitting light at a wavelength of 172 nm was used as the VUV irradiation apparatus. VUV irradiation was performed in an atmospheric atmosphere. The sample was moved using a stage transport mechanism, and the irradiation distance was set to 5 mm. The VUV irradiation dose was measured using an illuminometer (USHIO Electric Machinery: UIT-250 type) corresponding to the 172 nm wavelength. In the experiment, the VUV irradiation dose ranged from 0 to 5.4 J / cm². 2 .

[0125] In addition, after VUV irradiation, the surface roughness of the insulating layer 20 was measured using atomic force microscopy. The surface roughness measurement range was 1 μm × 1 μm. Furthermore, regarding Experiment 1 described later, the surface roughness in the unirradiated state was measured. This is the surface roughness of the insulating layer 20 in the state after the carrier film has been peeled off. The surface roughness of the unirradiated insulating layer 20 is Ra = 32 nm.

[0126] Next, the VUV-irradiated sample was introduced into the medium vacuum sputtering apparatus for plasma-based surface treatment (step 204). In the experiment, the surface 21 of the sample (insulating layer 20) was cleaned by a plasma jet generated by a hollow cathode plasma device built into the medium vacuum sputtering apparatus.

[0127] Next, a copper seed layer 31 was formed on the insulating layer 20 by sputtering under medium vacuum pressure (step 205). The thickness of the copper seed layer 31 was 300 nm. In addition, samples were also prepared under pressures not included in the pressure range of medium vacuum sputtering in the experiment.

[0128] Next, the sample with the copper seed layer 31 was immersed in an electrolytic copper plating bath for electrolytic copper plating (step 206). The current density was set to 1 ASD (Ampere per Square Decimeter), and the thickness of the copper plating layer was 25 μm. In addition, the copper-plated sample was dried.

[0129] Next, the copper-plated samples were annealed (step 207). In the experiment, an oven was used to heat the copper film at 200°C for 1 hour.

[0130] Annealed samples were used as the test objects to evaluate the adhesion between the insulation 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 EZ-TEST) to measure the adhesion strength. Regarding the adhesion strength, the maximum value when peeling the wiring layer 30 at a speed of 50 mm / s was recorded.

[0131] [Relationship between VUV irradiation and sealing intensity] The following explanation, with reference to Table 1, illustrates the sealing strength when the VUV irradiation dose is changed.

[0132] Table 1 In Experiments 1-10 shown in Table 1, the surface roughness and adhesion strength of the insulating layer 20 were measured for samples in which the sputtering pressure was set to 1.3 Pa and the VUV irradiation dose was varied to form the wiring layer 30. Furthermore, in Experiment 1, VUV irradiation was not performed.

[0133] As shown in Experiment 1, the surface 21 of the insulating layer 20 after the carrier film has been peeled off is, for example, a smooth surface compared to the surface that produces the anchoring effect. Furthermore, since VUV irradiation was not performed in Experiment 1, the sputtered copper film from the vacuum sputtering apparatus used was unstable. Therefore, the adhesion strength was very low at 0.9 N / cm.

[0134] In experiments 2-10, the VUV irradiation dose was gradually increased. Under these conditions, the surface roughness of the insulating layer 20 increased slightly due to VUV irradiation, but, for example, as in experiment 10, even at 5.4 J / cm², the surface roughness remained relatively constant. 2 With the same irradiation dose, the Ra value only increases by 6 nm. At this surface roughness, an improvement in adhesion strength based on the anchoring effect cannot be expected.

[0135] On the other hand, in experiments 2-9, the sealing strength increased compared to the case without VUV irradiation (Experiment 1). Specifically, in Experiment 4, at 0.54 J / cm²... 2 Under VUV irradiation, the adhesion strength reaches a maximum of 4.5 N / cm. This maximum value is five times that without VUV irradiation. This is because, through VUV irradiation, the COH formed in the surface region 46 of the insulating layer 20 combines with the sputtered copper particles, forming a bond (COCu) not only on the surface 21 of the insulating layer 20 but also internally. Thus, although the surface roughness remains almost unchanged, VUV irradiation can significantly improve the adhesion strength.

[0136] Additionally, as shown in Experiment 2, at 0.1 J / cm 2 Under the irradiation dose of [missing value], the sealing strength was 1.2 N / cm, which is greater than that under the condition of no VUV irradiation (Experiment 1). Furthermore, at a dose 0.01 J / cm lower than that of Experiment 2... 2 Experiments were also conducted on the amount of irradiation, but almost no improvement in the sealing strength was observed.

[0137] Furthermore, if we observe the tendency of the seal intensity, the VUV exposure dose is 0.54 J / cm². 2The adhesion strength reaches its peak near the target area; if the VUV irradiation dose is further increased, the adhesion strength gradually decreases. For example, as shown in Experiment 9, at 5 J / cm²... 2 At the given exposure dose, the seal strength was 1 N / cm. As a result, although it decreased compared to the peak value, the seal strength was increased compared to the case without VUV irradiation.

[0138] On the other hand, in Experiment 10, the seal strength was weaker compared to the case without VUV irradiation (Experiment 1). This is because the modification of the insulating layer 20 was excessively carried out through VUV irradiation, reducing the structure (COH) that easily bonds with copper particles and increasing the structure that is difficult to bond with copper particles. The structure that is difficult to bond with copper particles refers to a structure with a double bond (C=O) between carbon and oxygen atoms, such as COOH.

[0139] Based on these results, the preferred VUV irradiation dose for atmospheric VUV exposure is 0.1 J / cm². 2 Above and 5J / cm 2 The following applies. By setting the irradiation dose within this range, high sealing strength can be achieved. Furthermore, it is considered that the VUV irradiation dose is less than 0.1 J / cm². 2 In cases where the irradiation dose is too low to form sufficient functional groups, the adhesion strength will not increase. Additionally, for example, in VUV irradiation doses greater than 5 J / cm², the adhesion strength will not increase. 2 In the case described above, the amount of COH, which is a primary oxidation functional group, decreases. Conversely, the structure that is difficult to combine with copper particles such as COOH increases, which may result in insufficient bonding strength.

[0140] In addition, the resin material used in this experiment was glass epoxy resin (absorbance of 3×10⁻⁶). 3 However, as long as the resin material is used as a wiring substrate, the bonding strength can be improved within the aforementioned irradiation range. For example, in the case of liquid crystal polymer substrates (LCP substrates), which are expected to be next-generation insulating materials, the absorbance is 5 × 10⁻⁶. 2 The optimal VUV irradiation dose obtained through experiments was 1.4 J / cm². 2 .

[0141] Furthermore, the amount of VUV irradiation is not limited. For example, it is believed that the depth of the surface region 46, which represents the tight adhesion with the copper film 3, depends on the absorbance of the resin material. Additionally, the absorbance also varies depending on the resin material, having a value of 10. 2 to 10 4 The degree of intensity. To cope with various resin materials, the VUV irradiation dose can be appropriately set according to the light absorbance and other characteristics of the resin material to achieve the desired bonding strength.

[0142] [Relationship between sputtering pressure and adhesion strength] The following explanation of the sealing strength when the sputtering pressure is changed is based on Table 2.

[0143] [Table 2] In experiments 11-15 shown in Table 2, wiring layers 30 were formed by varying sputtering pressures without VUV irradiation, and the adhesion strength was measured. As shown in Table 2, the adhesion strength did not differ significantly even when the sputtering pressure was varied without VUV irradiation. However, in experiment 15, with a sputtering pressure of 133 Pa, the adhesion strength decreased slightly. Furthermore, attempts were made to reduce the sputtering pressure to below 0.013 Pa as shown in experiment 11, but achieving this required 5 hours; therefore, it was not evaluated from a productivity perspective.

[0144] In experiments 16-20 shown in Table 2, the VUV irradiation dose was set to 0.54 J / cm². 2 The sputtering pressure was varied to form the wiring layer 30. In experiments 17, 18, and 19, the sputtering pressure was set to a medium vacuum range. For example, when the sputtering pressure was 0.13 Pa (Experiment 17), the adhesion strength was 3.6 N / cm; when the sputtering pressure was 1.3 Pa (Experiment 18), the adhesion strength was 4.5 N / cm; and when the sputtering pressure was 13 Pa (Experiment 19), the adhesion strength was 2.4 N / cm.

[0145] Furthermore, in Experiment 16, the sputtering pressure was set to 0.013 Pa, but the adhesion strength decreased compared to the case where VUV irradiation was not performed at the same pressure (Experiment 11). For example, in a high vacuum environment, the sputtered particles (copper particles) flying towards the insulating layer 20 have high kinetic energy. Upon reaching the resin, this kinetic energy is converted into heat, potentially causing overheating of the sample (insulating layer 20). In Experiment 16, it is believed that due to the overheating of the sample, the temporary bond within the resin formed by VUV irradiation disappears, resulting in a decrease in adhesion strength.

[0146] Furthermore, in Experiment 20, the sputtering pressure was set to 133 Pa, but the adhesion strength was so low that it could not be measured. Thus, under high sputtering pressure, the kinetic energy of the copper particles became too low, potentially preventing them from penetrating the interior of the insulating layer 20 (resin material). As a result, in Experiment 20, it was considered that the copper particles only accumulated on the surface and were easily peeled off.

[0147] Based on these results, the sputtering pressure is preferably 0.13 Pa or higher and 13 Pa or lower. By setting the sputtering pressure within this range, for example, compared to the case without VUV irradiation, a bonding strength of more than 2.5 times can be achieved. Furthermore, it is considered that when the sputtering pressure is below 0.13 Pa, vacuuming takes time, and the sample is heated without increasing the bonding strength. Additionally, for example, when the sputtering pressure is greater than 13 Pa, it is considered that the kinetic energy of the copper particles decreases, and the bonding within the insulating layer 20 is suppressed.

[0148] [Relationship between degassing process and sealing strength] The following explanation, with reference to Table 3, details the sequence of the degassing process and the sealing strength when the heating temperature is changed.

[0149] Table 3 Substrates using insulating resins generally have a tendency to absorb moisture. For example, consider the possibility of moisture getting into the gaps between the fibers of the core material (the substrate that serves as the insulating resin), or the resin itself absorbing moisture from the air and thus drawing in gases. These gases can sometimes adversely affect the wiring process.

[0150] For example, when copper is directly sputtered onto a substrate with insufficient degassing, the internal gas is difficult to escape due to the sealing effect of the sputtered film. If electroplating of copper is then performed on this substrate, an air layer known as voids is created, which sometimes results in defects after plating. Furthermore, during annealing after plating, the expansion of gas within the substrate can cause stress that breaks the temporary bond between the copper wiring and the resin, potentially preventing the formation of a proper bond and resulting in poor adhesion.

[0151] To avoid such situations, it is preferable to immediately move the substrate material laminated with insulating resin to the next process. On the other hand, in terms of manufacturing process management, it is also necessary to be able to store substrate materials midway. Therefore, proper degassing treatment becomes important.

[0152] In experiments 21-27 shown in Table 3, samples stored prior to VUV irradiation were used. Specifically, after laminating the insulating layer 20 (glass epoxy film) onto the support substrate 10 (CCL), the samples were exposed for one week in a post-curing chamber after a curing treatment of epoxy resin (heat treatment at 100°C for 30 minutes followed by a heat treatment at 180°C for 30 minutes). For these samples, the degassing process sequence and heating temperature were changed to form the wiring layer 30. Furthermore, in experiments 21-27, the VUV irradiation dose was set to 0.54 J / cm². 2 The sputtering pressure was set to 1.3 Pa.

[0153] In Experiment 21, degassing was performed at a sufficiently high temperature (190°C) before VUV irradiation. Under these conditions, the insulating layer 20 was not modified by VUV at the time of degassing. After degassing, the insulating layer 20 was irradiated with VUV, and a 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.

[0154] Furthermore, the heating temperature for the degassing treatment performed 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. However, if the heating temperature is lower than 100°C, moisture and other substances may remain, preventing sufficient gas release. On the other hand, when the heating temperature is higher than 200°C, the properties of the resin may deteriorate.

[0155] In experiments 22, 23, 24, and 25, degassing was performed after VUV irradiation, with heating temperatures set at 90℃, 110℃, 130℃, and 150℃, respectively. As shown in Table 3, it can be seen that within this temperature range, increasing the temperature increases the sealing strength. Furthermore, at a heating temperature of 90℃ (Experiment 22), the sealing strength decreased significantly, because the heating temperature was insufficient to evaporate the moisture.

[0156] In experiments 26 and 27, degassing was performed after VUV irradiation, with heating temperatures set at 170°C and 190°C, respectively. Under these conditions, the bonding strength decreased sharply, reaching the level of the resin without VUV irradiation. This is because the bonding components (COH) formed within the resin during the heating process of degassing are deactivated. Especially when the temperature reaches above the resin's glass transition temperature, the activity of molecules within the resin becomes more active, and the active components disappear due to intramolecular recombination.

[0157] Therefore, the process of heating and degassing the insulating layer 20 is preferably performed before VUV irradiation. This ensures that even with degassing, the functional groups formed by VUV irradiation are not damaged, and sufficient degassing can be performed at a relatively high temperature. As a result, gas release from the resin can be effectively suppressed, preventing issues such as interface expansion (voids) and poor adhesion after electrolytic copper plating.

[0158] In the above-described method for manufacturing the wiring substrate 100 according to this embodiment, functional groups capable of bonding with copper atoms are generated from the surface 21 of the insulating layer 20 to a surface region 46 at a certain depth by irradiating the insulating layer 20 with VUV. As a result, a bonding portion between the insulating layer 20 and the copper film 3 can be formed not only on the surface 21 of the insulating layer 20 but also inside the insulating layer 20 (surface region 46). Consequently, even when copper is directly sputtered onto the insulating layer 20, copper wiring with high bonding strength can be achieved.

[0159] In recent years, with the increasing speed of semiconductor devices and the expansion of communication capacity, the demand for wiring substrates corresponding to high-speed and high-frequency communication has increased. To achieve high-speed communication, it is crucial to suppress the skin effect at the interface between the wiring and the insulating resin, requiring a smooth interface. Furthermore, the material of the insulating resin has been improved, with materials containing fewer polar groups developed to reduce signal loss. In electroless copper plating, where bonding is achieved through anchoring effects and intermolecular attraction, it is difficult to form wiring on such a smooth resin with few polar groups.

[0160] On the other hand, sputtering can be used to form wiring, but sufficient adhesion strength cannot be obtained if copper is sputtered directly onto the resin surface. Therefore, when using sputtering, an adhesion layer of titanium, nickel, etc., is usually formed on the resin surface first, and then copper is sputtered. However, the etching process is complicated by the presence of an adhesion layer. In addition, there is the possibility that the adhesion layer cannot be removed and that the adhesion layer is over-etched, making it difficult to manage the reliability of the wiring substrate.

[0161] In this embodiment, by irradiating the insulating layer 20 with VUV, functional groups (COH) that bond with copper are formed from the surface 21 to the interior of the insulating layer 20. Sputtered copper particles bond with these functional groups, thereby forming a bonding portion (COCu) with the copper film 3 on the surface 21 and inside (surface region 46) of the insulating layer 20. Thus, even when copper is directly sputtered onto the insulating layer 20, high adhesion strength can be achieved.

[0162] Thus, in this embodiment, a wiring layer 30 consisting solely of copper can be formed. Therefore, in the etching process used to form wiring patterns, only copper needs to be etched. Consequently, compared to the case where an adhesive layer such as titanium or nickel is provided, the etching process becomes simpler, and the number of processes can be reduced. Furthermore, wiring defects caused by metal residues other than copper, and undercuts caused by different types of etching processes, are avoided. As a result, a wiring substrate 100 with high reliability can be achieved.

[0163] Furthermore, even when using resin materials with few polar groups, COH, which readily bonds with copper, can be generated by VUV irradiation. Moreover, regardless of the shape of the surface 21 of the insulating layer 20, a bonding portion (COCu) with the wiring layer 30 is formed from the surface 21 of the insulating layer 20 into its interior. Therefore, even with resins that are smooth and have few polar groups, direct sputtering of copper by VUV irradiation can result in wiring with high bonding strength. This enables the wiring substrate 100 to achieve signal degradation due to the skin effect, minimal signal loss during transmission, and the ability to handle high-speed communication.

[0164] Furthermore, in this embodiment, the copper film 3 is formed by medium vacuum sputtering. While medium vacuum sputtering can suppress the temperature rise of the substrate, it is difficult to achieve a copper film 3 with high adhesion simply by suppressing the temperature rise (e.g., Experiment 1 in Table 1). In this invention, by combining VUV irradiation and medium vacuum sputtering, the functional groups generated by VUV can be fully utilized. Therefore, the adhesion strength of the copper wiring can be significantly improved.

[0165] In this disclosure, expressions using "compared to" such as "greater than A" and "smaller than A" encompass both concepts that include those equal to A and concepts that may include those equal to A. For example, "greater than A" is not limited to not including those equal to A, but also includes "above A". In addition, "smaller than A" is not limited to "less than A", but also includes "below A".

[0166] In implementing this technology, in order to achieve the effects described above, specific settings can be appropriately adopted based on the concepts contained in "larger than A" and "smaller than A".

[0167] In the feature portions of the present technology described above, at least two feature portions can be combined. That is, the various feature portions described in each embodiment can also be arbitrarily combined without distinguishing between each embodiment. In addition, the various effects described above are merely illustrative and are not limited thereto; other effects can also be achieved.

[0168] Explanation of reference numerals in the attached figures 3 Copper Film 20 insulation layers 21 surface 30 wiring layers 31 Copper Seed Layer 32 copper wiring layers 45 absorption region 46 Surface Areas 100 wiring board

Claims

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

2. The method for manufacturing a wiring substrate according to claim 1, wherein, The chamber pressure during the sputtering process is a medium vacuum.

3. The method for manufacturing a wiring substrate according to claim 2, wherein, The chamber pressure during the sputtering process is above 0.13 Pa and below 13 Pa.

4. The method for manufacturing a wiring substrate according to claim 1, wherein, The laminate in which the copper film is formed directly on the insulating resin layer is also annealed.

5. The method for manufacturing a wiring substrate according to claim 1, wherein, The process of irradiating the insulating resin layer with the vacuum ultraviolet light is a process of irradiating the insulating resin layer with the vacuum ultraviolet light in the atmosphere. The irradiation dose of the vacuum ultraviolet light is 0.1 J / cm. 2 Above and 5J / cm 2 the following.

6. The method for manufacturing a wiring substrate according to any one of claims 1-5, wherein, In the process of forming the copper film by sputtering, a copper seed layer is formed as the copper film, and a copper wiring layer is formed on the copper seed layer by electrolytic plating.

7. The method for manufacturing a wiring substrate according to any one of claims 1-5, wherein, In the process of forming the copper film by sputtering, a copper wiring layer is formed as the copper film.

8. The method for manufacturing a wiring substrate according to any one of claims 1-5, wherein, The surface roughness of the insulating resin layer forming the copper film is expressed as an arithmetic mean roughness Ra of less than 40 nm.

9. The method for manufacturing a wiring substrate according to any one of claims 1-5, wherein, In the process of forming the copper film by sputtering, before forming the copper film, the surface of the insulating resin layer for forming the copper film is surface treated with plasma.

10. The method for manufacturing a wiring substrate according to claim 9, wherein, The pressure inside the chamber during the surface treatment is above 10 Pa and below 100 Pa.

11. The method for manufacturing a wiring substrate according to any one of claims 1-5, wherein, Prior to the process of forming the copper film by sputtering, the insulating resin layer is heated to degas it.

12. The method for manufacturing a wiring substrate according to claim 11, wherein, The process of heating the insulating resin layer to degas it is performed before irradiating it with vacuum ultraviolet light.

13. The method for manufacturing a wiring substrate according to any one of claims 1-5, wherein, The source of the vacuum ultraviolet light is at least one of a xenon excimer lamp or a low-pressure mercury lamp.

14. A wiring substrate comprising an insulating resin layer having a surface roughness of less than 40 nm as expressed by an arithmetic mean roughness Ra, and a copper film formed directly on the insulating resin layer.

15. The wiring substrate according to claim 14, wherein, The adhesion strength between the copper film and the insulating resin layer is greater than 1 N / cm.

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