Metal foil with carrier and method for manufacturing millimeter-wave antenna substrate using same

Abstract

Provided is a metal foil with a carrier that exhibits excellent carrier releasability and metal layer selective etching properties, and that can reduce transmission loss and resistance in a semiconductor package (e.g., a millimeter-wave antenna substrate) manufactured using the same. This metal foil with a carrier includes: (a) a carrier; (b) a release functional layer provided on the carrier, the release functional layer including (b1) an adhesion layer closer to the carrier and having a thickness of more than 10 nm and less than 200 nm, and (b2) a release auxiliary layer farther from the carrier and having a thickness of 50 nm to 500 nm; and (c) a composite metal layer provided on the release functional layer, the composite metal layer including (c1) a carbon layer closer to the release auxiliary layer, and (c2) a first metal layer farther from the release auxiliary layer, the composite metal layer comprising mainly Au or Pt.

Description

[Technical Field]

[0001] The present invention relates to a metal foil with a carrier and a method for manufacturing a millimeter-wave antenna substrate using the same. [Background technology]

[0002] In recent years, multilayer printed wiring boards have become widespread in order to increase the packaging density and reduce the size of printed wiring boards. Such multilayer printed wiring boards are used in many portable electronic devices for the purpose of reducing weight and size. However, there is a demand for further reductions in the thickness of interlayer insulating layers and further weight reductions as wiring boards.

[0003] To meet these demands, a coreless buildup method has been adopted for manufacturing multilayer printed wiring boards. The coreless buildup method is a method of alternately stacking (building up) insulating layers and wiring layers to form a multilayer structure without using a so-called core substrate. In the coreless buildup method, the use of a carrier-attached copper foil has been proposed to facilitate peeling of the support and the multilayer printed wiring board. For example, Patent Document 1 (JP 2005-101137 A) discloses a method for manufacturing a package substrate for mounting semiconductor elements, which includes: attaching an insulating resin layer to the carrier surface of a carrier-attached copper foil to form a support; forming a first wiring conductor on the ultrathin copper layer side of the carrier-attached copper foil through steps such as photoresist processing, patterned electrolytic copper plating, and resist removal; then forming a buildup wiring layer; peeling off the carrier-attached support substrate; and removing the ultrathin copper layer.

[0004] Furthermore, in order to miniaturize embedded circuits as shown in Patent Document 1, a carrier-attached copper foil with an ultrathin copper layer having a thickness of 1 μm or less is desired. Therefore, in order to achieve a reduced thickness of the ultrathin copper layer, it has been proposed to form the ultrathin copper layer by a vapor phase method such as sputtering. For example, Patent Document 2 (WO 2017 / 150283) discloses a carrier-attached copper foil in which a release layer, an anti-reflection layer, and an ultrathin copper layer are formed by sputtering on a carrier such as glass or ceramics. Furthermore, Patent Document 3 (WO 2017 / 150284) discloses a carrier-attached copper foil in which an intermediate layer (e.g., an adhesion metal layer and a release aid layer), a release layer, and an ultrathin copper layer (e.g., 300 nm thick) are formed by sputtering on a carrier such as glass or ceramics. Patent Documents 2 and 3 also teach that the inclusion of an intermediate layer made of a specific metal provides excellent stability in the mechanical peel strength of the carrier, and that the anti-reflection layer exhibits a desirable dark color, thereby improving visibility during image inspection (e.g., automated image inspection (AOI)). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-101137 [Patent Document 2] International Publication No. 2017 / 150283 [Patent Document 3] International Publication No. 2017 / 150284 Summary of the Invention

[0006] In recent years, safe driving support systems such as collision prevention functions have become increasingly common in the automotive field, and in-vehicle millimeter-wave radars are being utilized in these systems. Furthermore, in the field of information and communications technology, technological development is underway regarding millimeter-wave communications, which enable wideband and high-capacity transmission. Accordingly, demand for millimeter-wave semiconductor packages (hereinafter referred to as "millimeter-wave antenna substrates") suitable for these applications is also increasing. Here, a fine circuit formation method using Au plating is used to manufacture millimeter-wave antenna substrates and the like. However, when millimeter-wave antenna substrates and the like are manufactured using conventional carrier-attached copper foil, problems such as high resistance (e.g., connection resistance with Au plating) can occur due to the low chemical stability of Cu. Furthermore, in the manufacture of millimeter-wave antenna substrates and the like, a relatively thick resin (e.g., 200 μm or thicker) is laminated on the carrier-attached metal foil as an insulating layer to reduce interference. Therefore, the carrier-attached metal foil is susceptible to stress from the resin, which can result in unstable carrier peeling.

[0007] The present inventors have now discovered that by controlling the thickness of the layer that contributes to carrier peeling within a specific range and employing a metal layer that is primarily composed of Au or Pt, it is possible to provide a metal foil with a carrier that has excellent carrier peeling properties and selective etching properties for the metal layer, and that can achieve reduced transmission loss and resistance in semiconductor packages (e.g., millimeter-wave antenna substrates) manufactured using the same.

[0008] Therefore, an object of the present invention is to provide a metal foil with a carrier that has excellent carrier peelability and metal layer selective etching properties, and that can reduce transmission loss and resistance in semiconductor packages (e.g., millimeter-wave antenna substrates) manufactured using the same.

[0009] According to one aspect of the present invention, (a) career and (b) a release functional layer provided on the carrier, (b1) an adhesion layer closer to the carrier, the thickness of which is greater than 10 nm and less than 200 nm; and (b2) a release functional layer including a release auxiliary layer having a thickness of 50 nm or more and 500 nm or less on the side farther from the carrier; (c) a composite metal layer provided on the release functional layer, (c1) a carbon layer closer to the peeling aid layer, and (c2) a composite metal layer including a first metal layer mainly composed of Au or Pt on the side farther from the peeling auxiliary layer; A metal foil with a carrier is provided.

[0010] According to another aspect of the present invention, there is provided a method for manufacturing a millimeter-wave antenna substrate, the method including manufacturing a millimeter-wave antenna substrate using the metal foil with a carrier. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing an example of a carrier-attached metal foil of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing another example of the carrier-attached metal foil of the present invention. [Figure 3] FIG. 1 is a process flow diagram showing an example of a method for manufacturing a millimeter-wave antenna substrate according to the present invention, illustrating the first half of the process (processes (i) to (iii)). [Figure 4] 4 is a process flow diagram showing an example of a method for manufacturing a millimeter-wave antenna substrate according to the present invention, showing steps (steps (iv) to (vi)) subsequent to FIG. [Figure 5] FIG. 4 is a process flow diagram showing another example of the method for manufacturing a millimeter-wave antenna substrate of the present invention, illustrating the first half of the process (processes (i) to (iii)). [Figure 6] 5. FIG. 6 is a process flow diagram showing another example of the method for producing a millimeter-wave antenna substrate of the present invention, showing steps (steps (iv) to (vi)) subsequent to FIG. [Figure 7] FIG. 1 is a process flow diagram showing the procedure for producing a sample for measuring transmission loss in evaluation 2-1 of the example, showing the first half of the steps (steps (i) to (iii)). [Figure 8]8 is a process flow diagram showing the procedure for producing a sample for measuring transmission loss in evaluation 2-1 of the example, and is a process flow diagram showing the steps (steps (iv) to (vi)) following FIG. 7. [Figure 9] FIG. 8(vi) is a perspective view of the sample for measuring transmission loss shown in FIG. [Figure 10] FIG. 1 is a process flow diagram showing the procedure for producing a sample for measuring transmission loss in evaluation 2-2 of the example, showing the first half of the process (processes (i) to (iii)). [Figure 11] 11 is a process flow diagram showing the procedure for producing a sample for measuring transmission loss in evaluation 2-2 of the example, and is a process flow diagram showing the steps (steps (iv) to (vi)) following FIG. 10. [Figure 12] FIG. 10 is a cross-sectional view showing the angle θ of the edge portion of the wiring pattern in evaluations 3-1 and 3-2 of the examples. [Figure 13] FIG. 1 is a process flow diagram showing the procedure for producing a coreless support in evaluation 3-2 of the example, showing the first half of the steps (steps (i) to (iii)). [Figure 14] 14 is a process flow diagram showing the procedure for producing a coreless support in evaluation 3-2 of the example, and showing the steps (steps (iv) to (vi)) following FIG. 13. [Figure 15] 1 is a process flow diagram showing the procedure (steps (i) to (iv)) for producing a sample for measuring connection resistance in evaluation 4 of the example. [Figure 16] FIG. 10 is a schematic diagram showing an IV measurement using a sample for connection resistance measurement in Evaluation 4 of the Examples. DETAILED DESCRIPTION OF THE INVENTION

[0012] Metal foil with carrier An example of a carrier-attached metal foil of the present invention is shown schematically in FIGS. 1 and 2. As shown in FIGS. 1 and 2, the carrier-attached metal foil 10 includes a carrier 12, a release functional layer 14, and a composite metal layer 20, in this order. The release functional layer 14 is provided on the carrier 12 and includes an adhesion layer 16 on the side closer to the carrier 12 and a release auxiliary layer 18 on the side farther from the carrier 12. The adhesion layer 16 is a layer with a thickness of more than 10 nm and less than 200 nm. The release auxiliary layer 18 is a layer with a thickness of 50 nm or more and 500 nm or less. The composite metal layer 20 is provided on the release functional layer 14 and includes a carbon layer 22 on the side closer to the release auxiliary layer 18 and a first metal layer 26 on the side farther from the release auxiliary layer 18. The first metal layer 26 is a layer primarily composed of Au or Pt. As shown in FIG. 2, the composite metal layer 20 may further include a second metal layer 24 between the carbon layer 22 and the first metal layer 26. The composite metal layer 20 may further include a barrier layer 28 on the surface of the first metal layer 26 farther from the carbon layer 22. The carrier 12 may also be configured to have the above-mentioned various layers arranged in order, symmetrically, on both sides of the carrier 12. In this way, by controlling the thickness of the layers that contribute to the peeling of the carrier 12 (i.e., the adhesion layer 16 and the peel aid layer 18) within a specific range and employing a metal layer (i.e., the first metal layer 26) primarily composed of Au or Pt, it is possible to provide a carrier-attached metal foil that is excellent in carrier peelability and metal layer selective etching properties. Furthermore, it is possible to achieve reduced transmission loss and resistance in semiconductor packages (e.g., millimeter-wave antenna substrates) manufactured using this carrier-attached metal foil 10.

[0013] The material of the carrier 12 may be any of glass, ceramics, silicon, resin, and metal. Preferably, the carrier 12 is made of glass, silicon, or ceramic. The carrier 12 may be in the form of a sheet, film, or plate. The carrier 12 may also be a laminate of these sheets, films, and plates. For example, the carrier 12 may be a rigid support such as a glass plate, ceramic plate, silicon wafer, or metal plate, or may be in a non-rigid form such as a metal foil or resin film. Preferred examples of metals constituting the carrier 12 include copper, titanium, nickel, stainless steel, and aluminum. Preferred examples of ceramics include alumina, zirconia, silicon nitride, aluminum nitride, and various other fine ceramics. Preferred examples of resins include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyamide, polyimide, nylon, liquid crystal polymer, polyether ether ketone (PEEK®), polyamideimide, polyethersulfone, polyphenylene sulfide, polytetrafluoroethylene (PTFE), and ethylene tetrafluoroethylene (ETFE). To prevent warping of the coreless support due to heating when mounting electronic elements, a material with a coefficient of thermal expansion (CTE) of less than 25 ppm / K (typically 1.0 ppm / K to 23 ppm / K) is more preferred. Examples of such materials include the various resins mentioned above (particularly low-thermal expansion resins such as polyimide and liquid crystal polymer), glass, silicon, and ceramics. Furthermore, to ensure ease of handling and flatness during chip mounting, the carrier 12 preferably has a Vickers hardness of 100 HV or more, more preferably 150 HV to 2500 HV. As a material that satisfies these properties, the carrier 12 is preferably made of glass, silicon, or ceramics, more preferably made of glass or ceramics, and particularly preferably made of glass. An example of the carrier 12 made of glass is a glass plate.Glass, when used as the carrier 12, offers advantages such as light weight, a low thermal expansion coefficient, high insulation, rigidity, and a flat surface, thereby enabling the surface of the first metal layer 26 to be extremely smooth. Glass carriers 12 also offer advantages such as surface flatness (coplanarity) that is advantageous for fine circuit formation, chemical resistance in desmearing and various plating processes in wiring manufacturing processes, and the ability to employ chemical separation methods when peeling the carrier 12 from the carrier-attached metal foil 10. Preferred examples of glass constituting the carrier 12 include quartz glass, borosilicate glass, alkali-free glass, soda-lime glass, aluminosilicate glass, and combinations thereof. Alkali-free glass, soda-lime glass, and combinations thereof are more preferred, and alkali-free glass is particularly preferred. Alkali-free glass refers to glass that is essentially free of alkali metals and primarily contains silicon dioxide, aluminum oxide, boron oxide, and alkaline earth metal oxides such as calcium oxide and barium oxide, and further contains boric acid. This alkali-free glass has a stable low coefficient of thermal expansion in the range of 3 ppm / K to 5 ppm / K over a wide temperature range from 0°C to 350°C, which has the advantage of minimizing warping of the glass during processes involving heating. The thickness of the carrier 12 is preferably 100 μm to 2000 μm, more preferably 300 μm to 1800 μm, and even more preferably 400 μm to 1100 μm. A thickness within this range ensures appropriate strength for easy handling, while enabling thinner wiring and reducing warping that occurs when electronic components are mounted.

[0014] The surface of the carrier 12 adjacent to the adhesion layer 16 preferably has an arithmetic mean roughness Ra of 0.1 nm to 70 nm, more preferably 0.5 nm to 60 nm, even more preferably 1.0 nm to 50 nm, particularly preferably 1.5 nm to 40 nm, and most preferably 2.0 nm to 30 nm, as measured using a laser microscope in accordance with JIS B 0601-2001. As described above, a smaller arithmetic mean roughness Ra of the surface of the first metal layer 26 opposite the carbon layer 22 (the outer surface of the first metal layer 26) can be desirably low, which makes it suitable for forming a highly fine wiring pattern in which the line / space (L / S) is 13 μm / 13 μm or less (e.g., 12 μm / 12 μm to 2 μm / 2 μm) in the wiring formed using the first metal layer 26.

[0015] The release functional layer 14 is interposed between the carrier 12 and the carbon layer 22 and contributes to stable release of the carrier 12. As described above, the release functional layer 14 includes an adhesion layer 16 on the side closer to the carrier 12 and a release auxiliary layer 18 on the side farther from the carrier 12. In this regard, by controlling the thicknesses of the adhesion layer 16 and the release auxiliary layer 18 within a predetermined range, it is possible to impart a desired peel strength to the carrier-attached metal foil 10. To further improve the release function of the carrier-attached metal foil 10, the release functional layer 14 preferably includes at least one layer, as the adhesion layer 16 and / or the release auxiliary layer 18, containing 80 atomic % or more (preferably 85 atomic % or more, more preferably 90 atomic % or more) of at least one element selected from the group consisting of Cu, Ti, Ta, Cr, Ni, Al, Mo, Zn, W, TiN, and TaN. The upper limit of the content of the above elements or components in the release functional layer 14 is not particularly limited; it may be 100 atomic %, but a realistic upper limit is 98 atomic % or less. The content of the above elements or components in the release functional layer 14 is a value measured by analysis using X-ray photoelectron spectroscopy (XPS).

[0016] In the carrier-attached metal foil 10, the ratio T2 / T1, which is the ratio of the thickness T2 of the peel aid layer 18 to the thickness T1 of the adhesion layer 16, is preferably greater than 1 and not greater than 20, more preferably 1.5 to 15, even more preferably 2 to 10, and particularly preferably 2.5 to 6. By setting T2 / T1 within the above range, it is possible to suppress a decrease in the peel function of the carbon layer 22, even when heat treatment is performed over a wide temperature range, for example, from 240°C to 340°C. The mechanism by which the thickness ratio of the adhesion layer 16 to the peel aid layer 18 affects peelability is not entirely clear, but it is thought that this is because changing this thickness ratio causes changes in the diffusion behavior of the elements constituting each layer of the carrier-attached metal foil 10 during heating.

[0017] The adhesion layer 16 is a layer interposed between the carrier 12 and the release aid layer 18 to ensure adhesion between the carrier 12 and the release aid layer 18. Therefore, it is preferable that the adhesion layer 16 be composed of a component that has relatively better adhesion to the carrier 12 than the release aid layer 18. From this perspective, the adhesion layer 16 is preferably a layer composed of at least one selected from the group consisting of Cu, Ti, Ta, Cr, Ni, Al, Mo, Zn, W, TiN, and TaN, more preferably at least one selected from the group consisting of Ti, Ta, TiN, and TaN, even more preferably at least one selected from the group consisting of Ti and TiN, and particularly preferably Ti. The adhesion layer 16 preferably has a content of the above metal or component of 80 atomic % or more, more preferably 85 atomic % or more, and even more preferably 90 atomic % or more, as measured by XPS. The upper limit of the content of the above metal or component in the adhesion layer 16 is not particularly limited and may be 100 atomic %, but 98 atomic % or less is more realistic. The adhesion layer 16 may contain inevitable impurities resulting from the raw material components, the film formation process, and the like. Furthermore, although not particularly limited, if the adhesion layer 16 is exposed to the atmosphere after formation, the presence of oxygen mixed in due to this is acceptable. The adhesion layer 16 typically has an oxygen content of 0 atomic % or more and 5 atomic % or less, more typically 0.05 atomic % or more and 4 atomic % or less, and even more typically 0.1 atomic % or more and 3 atomic % or less, as measured by XPS. The adhesion layer 16 may be manufactured by any method, but is particularly preferably a layer formed by magnetron sputtering using a target, as this can improve the uniformity of the film thickness distribution.

[0018] The thickness T1 of the adhesion layer 16 is greater than 10 nm and less than 200 nm, preferably 15 nm to 180 nm, more preferably 20 nm to 150 nm, even more preferably 30 nm to 120 nm, particularly preferably 40 nm to 100 nm, and most preferably 40 nm to 80 nm. Within this range, it is possible to ensure adequate adhesion between the carrier 12 and the release aid layer 18 while effectively suppressing a decrease in release function (increase in peel strength) associated with heat treatments such as vacuum pressing during lamination of the insulating resin. The thickness of the adhesion layer 16 is a value measured by analyzing a cross section of the layer using a transmission electron microscope energy dispersive X-ray spectrometer (TEM-EDX).

[0019] In order to control the peel strength of the carrier 12 to a desired value, the peel auxiliary layer 18 is preferably a layer composed of at least one selected from the group consisting of Cu, Ti, Ta, Cr, Ni, Al, Mo, Zn, W, TiN, and TaN, more preferably at least one selected from the group consisting of Cu, Ni, AlZn, and W, even more preferably at least one selected from the group consisting of Cu, Ni, and Al, and particularly preferably a layer composed of Cu. The content of the above metals or components in the peel auxiliary layer 18, as measured by XPS, is preferably 80 atomic % or more, more preferably 85 atomic % or more, and even more preferably 90 atomic % or more. The upper limit of the content of the above metals or components in the peel auxiliary layer 18 is not particularly limited and may be 100 atomic %, but 98 atomic % or less is more realistic. The peel auxiliary layer 18 may contain inevitable impurities resulting from raw material components, the film formation process, etc. Furthermore, although not particularly limited, the presence of oxygen mixed in when the peel auxiliary layer 18 is exposed to the atmosphere after formation is acceptable. The oxygen content of the peeling auxiliary layer 18 measured by XPS is typically 0 atomic % to 5 atomic %, more typically 0.05 atomic % to 4 atomic %, and even more typically 0.1 atomic % to 3 atomic %. The peeling auxiliary layer 18 may be produced by any method, but is particularly preferably a layer formed by magnetron sputtering using a target, as this can improve the uniformity of the film thickness distribution.

[0020] The thickness T2 of the peeling auxiliary layer 18 is 50 nm to 500 nm, preferably 100 nm to 450 nm, more preferably 150 nm to 400 nm, even more preferably 200 nm to 350 nm, and particularly preferably 250 nm to 300 nm. Within this range, a decrease in peeling function (an increase in peel strength) can be effectively suppressed, and delamination (interlayer peeling of the substrate) during processes such as the manufacture of millimeter-wave antenna substrates can also be effectively suppressed. The thickness of the peeling auxiliary layer 18 is a value measured by analyzing a cross section of the layer using a transmission electron microscope with an energy dispersive X-ray spectrometer (TEM-EDX).

[0021] The composite metal layer 20 includes a carbon layer 22 closer to the release aid layer 18 and a first metal layer 26 farther from the release aid layer 18. The composite metal layer 20 may further include a second metal layer 24 between the carbon layer 22 and the first metal layer 26. The composite metal layer 20 may also include a barrier layer 28 on the surface of the first metal layer 26 farther from the carbon layer 22. The thickness of the composite metal layer 20 is preferably 51 nm or more and 3220 nm or less, more preferably 100 nm or more and 2000 nm or less, and even more preferably 300 nm or more and 1000 nm or less. The thickness of the composite metal layer 20 is a value measured by analyzing a cross section of the layer using a transmission electron microscope with an energy dispersive X-ray spectrometer (TEM-EDX).

[0022] The carbon layer 22 is a layer primarily containing carbon, preferably a layer primarily composed of carbon or hydrocarbon, and more preferably a hard carbon film made of amorphous carbon. Therefore, the carbon layer 22 preferably contains amorphous carbon. The carbon layer 22 preferably has a carbon concentration of 60 atomic % or more, more preferably 70 atomic % or more, even more preferably 80 atomic % or more, and particularly preferably 85 atomic % or more, as measured by XPS. The upper limit of the carbon concentration is not particularly limited and may be 100 atomic %, but 98 atomic % or less is more realistic. The carbon layer 22 may contain unavoidable impurities (e.g., oxygen, carbon, hydrogen, etc., derived from the ambient environment such as the atmosphere). Furthermore, the carbon layer 22 may contain metal atoms (e.g., Au, Pt, etc.) due to the deposition method of the first metal layer 26 or, if present, the second metal layer 24. Carbon has low interdiffusibility and reactivity with the release functional layer 14. Even when subjected to press processing or the like at temperatures exceeding 300°C, it prevents the formation of a metallic bond between the first metal layer 26 (or the second metal layer 24, if present) and the bonding interface due to high-temperature heating, maintaining a state in which the carrier can be easily peeled off and removed. This carbon layer 22 is also preferably formed by a vapor-phase method such as sputtering, in order to suppress excessive impurities in the amorphous carbon and to facilitate continuous production with the formation of the adhesion layer 16 and release auxiliary layer 18. The thickness of the carbon layer 22 is preferably 1 nm or more and 20 nm or less, more preferably 1 nm or more and 10 nm or less. This thickness is measured by analyzing the layer cross section using a transmission electron microscope with an energy-dispersive X-ray spectrometer (TEM-EDX).

[0023] The first metal layer 26 is a layer primarily composed of Au or Pt, preferably a layer primarily composed of Au. These elements have higher chemical stability than other metal elements such as Cu, and therefore can desirably achieve reduced transmission loss and connection resistance in a millimeter-wave antenna substrate manufactured using the carrier-attached metal foil 10. Furthermore, it is considered desirable for a millimeter-wave antenna substrate to maintain the edge shape of the wiring (i.e., an angle of the edge portion of the wiring close to 90°) to ensure antenna directivity. Because these metals have excellent selective etching properties, it is easy to achieve this edge shape during wiring formation (patterning) involving Au etching. The metal constituting the first metal layer 26 may be a pure metal or an alloy. The content of the metal (e.g., Au) in the first metal layer 26, as measured by XPS, is preferably 60 atomic % or more, more preferably 70 atomic % or more, even more preferably 80 atomic % or more, and particularly preferably 90 atomic % or more. Furthermore, the upper limit of the content of the metal (e.g., Au) in the first metal layer 26 is not particularly limited and may be 100 atomic %, but is typically 98 atomic % or less. The metal constituting the first metal layer 26 may contain inevitable impurities resulting from the raw material components, the film formation process, etc. The first metal layer 26 is preferably a layer formed by a vapor phase method such as sputtering. The first metal layer 26 preferably has a thickness of 50 nm to 2000 nm, more preferably 70 nm to 1500 nm, even more preferably 100 nm to 800 nm, and particularly preferably 200 nm to 500 nm. This thickness is measured by analyzing the layer cross section using a transmission electron microscope energy dispersive X-ray spectrometer (TEM-EDX).

[0024] The second metal layer 24 preferably provides the carrier-attached metal foil 10 with desired functions, such as an etching stopper function or an anti-reflection function. Preferred examples of metals constituting the second metal layer 24 include Ti, Ta, Ni, W, Cr, Pd, and combinations thereof. More preferred are Ti, Ta, Ni, W, Cr, and combinations thereof. Even more preferred are Ti, Ta, Ni, and combinations thereof. Particularly preferred are Ti, Ta, and combinations thereof. Most preferred is Ti. The metal constituting the second metal layer 24 may be a pure metal or an alloy. The second metal layer 24 preferably has a metal content of 50 atomic % or more, more preferably 60 atomic % or more, even more preferably 70 atomic % or more, and particularly preferably 80 atomic % or more, as measured by XPS. The upper limit of the metal content in the second metal layer 24 is not particularly limited and may be 100 atomic %, but is typically 98 atomic % or less. These elements are insoluble in flash etching solutions (e.g., Au flash etching solutions), resulting in excellent chemical resistance to flash etching solutions. Therefore, the second metal layer 24 is less susceptible to etching by a flash etching solution than the first metal layer 26 (described later), and therefore can function as an etching stopper layer. Furthermore, since the metals constituting the second metal layer 24 also function to prevent light reflection, the second metal layer 24 can also function as an anti-reflection layer to improve visibility during image inspection (e.g., automated image inspection (AOI)). The second metal layer 24 may contain nitrogen, and the nitrogen content measured by XPS is typically 0 atomic % or more and 50 atomic % or less, more typically 10 atomic % or more, even more typically 20 atomic % or more, and particularly typically 30 atomic % or more. The metal constituting the second metal layer 24 may contain inevitable impurities resulting from raw material components, the film formation process, etc. The second metal layer 24 is preferably formed by a vapor-phase method such as sputtering. The thickness of the second metal layer 24 is preferably 50 nm or more and 1000 nm or less, more preferably 100 nm or more and 800 nm or less, even more preferably 200 nm or more and 500 nm or less, and particularly preferably 300 nm or more and 400 nm or less.This thickness is a value measured by analyzing a cross section of the layer with a transmission electron microscope energy dispersive X-ray spectrometer (TEM-EDX).

[0025] The barrier layer 28 is a layer for suppressing the formation of an intermetallic compound between the metal (i.e., Au or Pt) constituting the first metal layer 26 and the metal (e.g., Cu) constituting a wiring layer that may be formed on the first metal layer 26 (i.e., the surface of the carrier-attached metal foil 10 opposite the carrier 12). To more effectively suppress the formation of intermetallic compounds, preferred examples of the metal constituting the barrier layer 28 include Ti, Ta, Ni, W, Cr, Pd, and combinations thereof, more preferably Ta, Ni, W, Cr, and combinations thereof. The metal constituting the barrier layer 28 may be a pure metal or an alloy. The content of the metal in the barrier layer 28, as measured by XPS, is preferably 50 atomic % or more, more preferably 60 atomic % or more, even more preferably 70 atomic % or more, and particularly preferably 80 atomic % or more. The upper limit of the content of the metal in the barrier layer 28 is not particularly limited; it may be 100 atomic %, but is typically 98 atomic % or less. The metal constituting the barrier layer 28 may contain inevitable impurities resulting from the raw material components, the film formation process, and the like. The barrier layer 28 is preferably a layer formed by a vapor phase method such as sputtering. The thickness of the barrier layer 28 is preferably 1 nm to 200 nm, more preferably 2 nm to 100 nm, even more preferably 3 nm to 70 nm, and particularly preferably 5 nm to 50 nm. This thickness is measured by analyzing the layer cross section with a transmission electron microscope energy dispersive X-ray spectrometer (TEM-EDX).

[0026] The adhesion layer 16, the peeling aid layer 18, the carbon layer 22, the second metal layer 24, the first metal layer 26 and the barrier layer 28 are preferably physical vapor deposition (PVD) films, i.e., films formed by the physical vapor deposition (PVD) method, and more preferably sputtered films, i.e., films formed by sputtering.

[0027] The overall thickness of the carrier-attached metal foil 10 is not particularly limited, but is preferably 500 μm to 3000 μm, more preferably 700 μm to 2500 μm, even more preferably 900 μm to 2000 μm, and particularly preferably 1000 μm to 1700 μm. The size of the carrier-attached metal foil 10 is not particularly limited, but is preferably 10 cm square or larger, more preferably 20 cm square or larger, and even more preferably 25 cm square or larger. The upper limit of the size of the carrier-attached metal foil 10 is not particularly limited, but 1000 cm square is cited as one guideline for the upper limit. Furthermore, the carrier-attached metal foil 10 is in a form that can be handled independently before and after the formation of wiring.

[0028] Manufacturing method of metal foil with carrier The carrier-attached metal foil 10 of the present invention can be produced by preparing a carrier 12 and forming an adhesion layer 16, a release aid layer 18, a carbon layer 22, an optional second metal layer 24, a first metal layer 26, and an optional barrier layer 28 on the carrier 12. The adhesion layer 16, the release aid layer 18, the carbon layer 22, the second metal layer 24 (if present), the first metal layer 26, and the barrier layer 28 (if present) are preferably formed by physical vapor deposition (PVD) in order to facilitate fine pitch by ultra-thinning. Examples of physical vapor deposition (PVD) methods include sputtering, vacuum evaporation, and ion plating. However, sputtering is most preferred because it allows for thickness control over a wide range, such as from 0.05 nm to 5000 nm, and ensures uniformity of film thickness over a wide width or area. In particular, forming all layers, including the adhesion layer 16, the release aid layer 18, the carbon layer 22, the second metal layer 24 (if present), the first metal layer 26, and the barrier layer 28 (if present), by sputtering significantly improves manufacturing efficiency. Physical vapor deposition (PVD) deposition can be performed using a known vapor deposition apparatus under known conditions, and is not particularly limited. For example, when sputtering is used, the sputtering method may be any of various known methods, such as magnetron sputtering, bipolar sputtering, and facing target sputtering. However, magnetron sputtering is preferred because of its high film formation rate and high productivity. Sputtering may be performed using either a DC (direct current) or RF (radio frequency) power source. Furthermore, while the widely known plate-shaped target can be used, a cylindrical target is preferable in terms of target utilization efficiency. Below, we will explain how to form each of the adhesion layer 16, peeling aid layer 18, carbon layer 22, second metal layer 24 (if present), first metal layer 26, and barrier layer 28 (if present) by physical vapor deposition (PVD) (preferably sputtering).

[0029] The adhesion layer 16 and the release auxiliary layer 18 are preferably formed by physical vapor deposition (PVD) (preferably sputtering) using a target composed of at least one metal selected from the group consisting of Cu, Ti, Ta, Cr, Ni, Al, Mo, Zn, and W, and magnetron sputtering in a non-oxidizing atmosphere, which can improve the uniformity of the film thickness distribution. The target purity is preferably 99.9 wt% or higher. An inert gas such as argon gas is preferably used as the gas used for sputtering. In this case, the adhesion layer 16 and / or the release auxiliary layer 18 composed of TiN or TaN can be formed by sputtering using a TiN target, TaN target, titanium target, or tantalum target in argon gas (and optionally nitrogen gas). The flow rate of the argon gas, etc., can be determined appropriately depending on the size of the sputtering chamber and the film formation conditions, and is not particularly limited. Furthermore, in order to achieve continuous film formation without operational problems such as abnormal discharge or poor plasma irradiation, the pressure during film formation is preferably in the range of 0.1 Pa to 20 Pa. This pressure range can be set by adjusting the film formation power and the flow rate of argon gas, etc., depending on the structure and capacity of the device, the exhaust capacity of the vacuum pump, the rated capacity of the film formation power supply, etc. Also, the sputtering power is set to 0.05 W / cm per unit area of ​​the target, taking into account the uniformity of the film thickness, productivity, etc. 2 More than 10.0W / cm 2 It may be set appropriately within the following range.

[0030] The carbon layer 22 is preferably formed by physical vapor deposition (PVD) (preferably sputtering) in an inert atmosphere such as argon using a carbon target. The carbon target is preferably composed of graphite, but may contain unavoidable impurities (e.g., oxygen and carbon derived from the ambient environment). The purity of the carbon target is preferably 99.99 wt% or higher, more preferably 99.999 wt% or higher. Furthermore, in order to achieve continuous film formation without operational problems such as abnormal discharge or plasma irradiation failure, the pressure during film formation is preferably in the range of 0.1 Pa to 20 Pa. This pressure range can be set by adjusting the film formation power and argon gas flow rate depending on the device structure, capacity, exhaust capacity of the vacuum pump, rated capacity of the film formation power supply, etc. Furthermore, the sputtering power is preferably 0.05 W / cm per unit area of ​​the target, taking into account factors such as film thickness uniformity and productivity. 2 More than 10.0W / cm 2 It may be set appropriately within the following range.

[0031] The second metal layer 24 and the barrier layer 28 are preferably formed by physical vapor deposition (PVD) (preferably sputtering) using a magnetron sputtering method with a target composed of at least one metal selected from the group consisting of Ti, Ta, Ni, W, Cr, and Pd. The purity of the target is preferably 99.9% or higher. In particular, the second metal layer 24 and the barrier layer 28 are preferably formed by magnetron sputtering in an inert gas atmosphere such as argon at a pressure of 0.1 Pa to 20 Pa. The sputtering pressure is more preferably 0.2 Pa to 15 Pa, and even more preferably 0.3 Pa to 10 Pa. The pressure range can be controlled by adjusting the film-forming power and the flow rate of argon gas according to the structure and capacity of the apparatus, the exhaust capacity of the vacuum pump, the rated capacity of the film-forming power supply, and the like. The flow rate of argon gas is not particularly limited and can be determined appropriately depending on the size of the sputtering chamber and the film-forming conditions. In addition, the sputtering power was set at 1.0 W / cm per unit area of ​​the target, taking into consideration the uniformity of the film thickness and productivity. 2 More than 15.0W / cm 2The temperature may be appropriately set within the following range. It is also preferable to maintain the carrier temperature constant during film formation, as this facilitates obtaining stable film properties (e.g., film resistance and crystal size). The carrier temperature during film formation is preferably adjusted within the range of 25°C or higher and 300°C or lower, more preferably 40°C or higher and 200°C or lower, and even more preferably 50°C or higher and 150°C or lower.

[0032] The physical vapor deposition (PVD) method (preferably sputtering) for forming the first metal layer 26 is preferably performed in an inert atmosphere such as argon using a target composed of at least one metal selected from the group consisting of Au and Pt. The target is preferably composed of a metal or alloy, but may contain unavoidable impurities. The purity of the target is preferably 99.9% or higher, more preferably 99.99%, and even more preferably 99.999% or higher. To prevent temperature increases during vapor deposition of the first metal layer 26, a stage cooling mechanism may be installed during sputtering. Furthermore, to ensure stable film formation without operational problems such as abnormal discharge or plasma irradiation failure, the pressure during film formation is preferably in the range of 0.1 Pa to 20 Pa. This pressure range can be set by adjusting the film formation power and argon gas flow rate depending on the device structure, capacity, exhaust capacity of the vacuum pump, rated capacity of the film formation power supply, etc. Furthermore, the sputtering power is preferably 0.05 W / cm per unit area of ​​the target, taking into account factors such as film thickness uniformity and productivity. 2 More than 10.0W / cm 2 It may be set appropriately within the following range.

[0033] Millimeter-wave antenna substrate manufacturing method The carrier-attached metal foil 10 of the present invention is preferably used for producing a millimeter-wave antenna substrate. That is, according to a preferred embodiment of the present invention, a method for producing a millimeter-wave antenna substrate is provided, which includes producing a millimeter-wave antenna substrate using the carrier-attached metal foil 10 described above, or a millimeter-wave antenna substrate obtained using the carrier-attached metal foil 10 described above. By using the carrier-attached metal foil 10 of the present invention, it is possible to provide a millimeter-wave antenna substrate with desirable reduced transmission loss and resistance, as described above. Hereinafter, an example of a preferred method for producing a millimeter-wave antenna substrate using the carrier-attached metal foil 10 of the present invention will be described. This method includes (1) laminating an insulating layer and a wiring layer on the carrier-attached metal foil to form a circuit, (2) mounting an IC chip, (3) peeling off the carrier, (4) etching away the second metal layer (if present), and then (5) patterning to form an antenna.

[0034] (1)Circuit formation A metal foil with a carrier 10 is prepared (FIG. 3(i)), and an insulating layer and a wiring layer are laminated on the surface of the metal foil with a carrier 10 on the side of the first metal layer 26 (or the side of the barrier layer 28, if present) to obtain a laminate 32 having a circuit board 30 (FIG. 3(ii)). The method for forming the circuit board 30 is not particularly limited; for example, the desired insulating layer and wiring layer can be formed by a known coreless build-up method such as that described in Patent Document 1. To reduce interference in the millimeter-wave antenna substrate, the thickness of the insulating resin (insulating layer) in the circuit board 30 is preferably 100 μm or more, more preferably 200 μm to 500 μm. Preferred examples of insulating resins include epoxy resin, cyanate resin, bismaleimide triazine resin (BT resin), polyphenylene ether resin, and phenolic resin. For example, ABF-GXT31 manufactured by Ajinomoto Fine-Techno Co., Inc. is preferably used as the insulating resin. The insulating layer may contain filler particles made of various inorganic particles such as silica and alumina to improve insulation properties. The insulating layer may be made up of multiple layers.

[0035] (2) IC chip implementation A millimeter-wave IC chip 34 is mounted on the outer surface of the circuit board 30 (i.e., the surface opposite to the carrier-attached metal foil 10) (FIG. 3(iii)). In this specification, "millimeter waves" refers to radio waves with frequencies of 24 GHz or more and 300 GHz or less. In this specification, "IC (integrated circuit)" broadly encompasses various ICs such as CPUs (central processing units), DSPs (digital signal processors), memories, PMICs (power management ICs), and RFICs (radio frequency integrated circuits (e.g., GPS (global positioning system))). Examples of chip mounting methods include flip-chip mounting and die bonding. The flip-chip mounting method is a method in which mounting pads of the IC chip 34 are bonded to the wiring layer of the circuit board 30. Columnar electrodes (pillars), solder bumps, etc. may be formed on these mounting pads, and a sealing resin film, NCF (non-conductive conductive film), is applied to the surface of the circuit board 30 before mounting. Alternatively, a bonding material such as a conductive film may be attached. The bonding is preferably performed using a low-melting-point metal such as solder, but an anisotropic conductive film may also be used. The die-bonding method is a method in which the surface of the IC chip 34 opposite the mounting pad surface is bonded to the wiring layer. For this bonding, a paste or film, which is a resin composition containing a thermosetting resin and a thermally conductive inorganic filler, is preferably used. The IC chip 34 is preferably resin-sealed using a known sealing material such as epoxy resin.

[0036] (3) Carrier peeling The carrier 12 is peeled off from the laminate 32 on which the IC chip 34 is mounted, together with the release functional layer 14, at the position of the carbon layer 22 (FIG. 4(iv)). By doing so, the second metal layer 24 (if present) is exposed on the outer surface of the laminate 32. If a thick insulating resin (e.g., a thickness of 200 μm or more) is used when forming the circuit board 30 described above, the metal foil with a carrier is easily affected by stress from the insulating resin, and the peel strength may become unstable. In this regard, as described above, the thicknesses of the adhesion layer 16 and the release auxiliary layer 18 of the metal foil with a carrier 10 of the present invention are controlled within a predetermined range, so that the carrier 12 can be stably peeled off.

[0037] (4) Etching and removing the second metal layer If the second metal layer 24 is present, the second metal layer 24 is etched away from the laminate 32 using a commercially available etching solution or the like to expose the first metal layer 26 on the outer surface of the laminate 32 (FIG. 4(v)). Etching of the second metal layer 24 may be performed based on a known method, and is not particularly limited.

[0038] (5) Antenna formation The surface of the laminate 32 facing the first metal layer 26 (the surface opposite the IC chip 34) is patterned to obtain a millimeter-wave antenna substrate 40 on which an antenna 38 is formed ( FIG. 4( vi) ). One example of a method for forming the antenna 38 involves first attaching a photosensitive dry film to the surface of the laminate 32 facing the first metal layer 26, exposing it to light, and developing it to form a photoresist layer (not shown) with a predetermined pattern. Electroless plating (e.g., electroless Au plating) is performed on the exposed surface of the first metal layer 26 (i.e., the portion not masked by the photoresist layer) to form the electroless plating layer 36, and then peeling off the photoresist layer. This leaves the first metal layer 26, the barrier layer 28, if present, and the electroless plating layer 36 in a wiring pattern to form the antenna 38, while exposing the first metal layer 26 in the portion where the wiring pattern is not to be formed. The exposed unnecessary portions of the first metal layer 26 and the unnecessary portions of the barrier layer 28, if present, are then removed with an etching solution to obtain a millimeter-wave antenna substrate 40 on which the antenna 38 is formed. When a millimeter-wave antenna substrate is produced using a conventional copper foil with a carrier, electroless Ni plating or the like must be performed before forming the electroless plated layer in order to ensure adhesion between the copper layer and the electroless plated layer (e.g., an Au layer), which can increase the resistance. In contrast, with the metal foil 10 with a carrier of the present invention, the first metal layer 26 is made of Au or the like, making electroless Ni plating unnecessary, and as a result, even lower resistance can be achieved in the millimeter-wave antenna substrate.

[0039] The antenna 38 may be partially or entirely in the form of an embedded circuit. That is, before the resin lamination in the above step (1), the first metal layer 26 and, if present, the barrier layer 28 may be patterned, thereby obtaining a laminate 32 in which a portion of the wiring layer is embedded in the surface in the form of an embedded circuit (FIG. 5(ii)). If the barrier layer 28 is not present, it is preferable to form a Ni thin film or the like on the surface of the first metal layer 26 by sputtering or the like before the above patterning. Thereafter, by performing the various steps (2) to (5) above on the laminate 32, a millimeter-wave antenna substrate 40 in which the antenna 38 is partially or entirely in the form of an embedded circuit can be obtained (see FIGS. 5 and 6). When the millimeter-wave antenna substrate 40 is produced using this procedure, it is preferable to form a seed layer by performing electroless plating (e.g., electroless Au plating) before forming the photoresist layer in the antenna formation step (5) above. [Example]

[0040] The present invention is further illustrated by the following examples.

[0041] Example 1 An adhesive layer 16, a release aid layer 18, a carbon layer 22, a second metal layer 24, and a first metal layer 26 were formed in this order on a carrier 12 to produce a carrier-attached metal foil 10. The specific procedure is as follows.

[0042] (1) Career preparation A glass sheet (material: soda lime glass, arithmetic mean roughness Ra: 0.6 nm) having a thickness of 1.1 mm was prepared as the carrier 12.

[0043] (2) Formation of an adhesive layer A titanium layer having a thickness of 50 nm was formed as an adhesive layer 16 by sputtering on the carrier 12. This sputtering was carried out using the following apparatus under the following conditions. Equipment: Single-wafer magnetron sputtering equipment (Canon Tokki Corporation, MLS464) Target: 8-inch (203.2 mm) diameter titanium target (99.999% purity) ·Achieved vacuum level: 1×10 -4 Less than Pa Sputtering pressure: 0.35Pa Sputtering power: 1000W (3.1W / cm 2 ) ·Temperature during film formation: 40℃

[0044] (3) Formation of a peeling aid layer A copper layer having a thickness of 200 nm was formed by sputtering as a peeling aid layer 18 on the surface of the adhesive layer 16 opposite to the carrier 12. This sputtering was carried out using the following apparatus under the following conditions. Equipment: Single-wafer DC sputtering equipment (Canon Tokki Corporation, MLS464) Target: 8-inch (203.2 mm) diameter copper target (99.98% purity) ·Achieved vacuum level: 1×10 -4 Less than Pa Gas: Argon gas (flow rate: 100sccm) Sputtering pressure: 0.35Pa Sputtering power: 1000W (6.2W / cm 2 ) ·Temperature during film formation: 40℃

[0045] (4) Formation of carbon layer An amorphous carbon layer having a thickness of 6 nm was formed as the carbon layer 22 by sputtering on the surface of the release assisting layer 18 opposite to the adhesive layer 16. This sputtering was carried out using the following apparatus under the following conditions. Equipment: Single-wafer DC sputtering equipment (Canon Tokki Corporation, MLS464) Target: 8-inch (203.2 mm) diameter carbon target (99.999% purity) ·Achieved vacuum level: 1×10 -4 Less than Pa Gas: Argon gas (flow rate: 100sccm) Sputtering pressure: 0.35Pa Sputtering power: 250W (0.7W / cm 2 ) ·Temperature during film formation: 40℃

[0046] (5) Formation of the second metal layer On the surface of the carbon layer 22 opposite to the peeling auxiliary layer 18, a titanium layer having a thickness of 100 nm was formed as the second metal layer 24 by sputtering using the following apparatus and conditions. Equipment: Single-wafer DC sputtering equipment (Canon Tokki Corporation, MLS464) Target: 8-inch (203.2 mm) diameter titanium target (99.999% purity) Carrier gas: Argon gas (flow rate: 100 sccm) ·Achieved vacuum level: 1×10 -4 Less than Pa Sputtering pressure: 0.35Pa Sputtering power: 1000W (3.1W / cm 2 )

[0047] (6) Formation of the first metal layer A 300 nm thick Au layer was formed as a first metal layer 26 by sputtering on the surface of the second metal layer 24 opposite to the peeling auxiliary layer 18. This sputtering was carried out using the following apparatus under the following conditions. Equipment: Single-wafer DC sputtering equipment (Canon Tokki Corporation, MLS464) Target: 8-inch (203.2 mm) diameter gold target (99.99% purity) ·Achieved vacuum level: 1×10 -4 Less than Pa Gas: Argon gas (flow rate: 100sccm) Sputtering pressure: 0.35Pa Sputtering power: 1000W (3.1W / cm 2 ) ·Temperature during film formation: 40℃

[0048] Example 2 A metal foil with a carrier was produced in the same manner as in Example 1, except that after the formation of the first metal layer 26 in (6) above, the barrier layer 28 was formed as follows.

[0049] (7) Formation of a barrier layer A nickel layer having a thickness of 30 nm was formed as a barrier layer by sputtering on the surface of first metal layer 26 opposite second metal layer 24. This sputtering was carried out using the following apparatus under the following conditions. Equipment: Single-wafer DC sputtering equipment (Canon Tokki Corporation, MLS464) Target: 8-inch (203.2 mm) diameter nickel target (99.9% purity) Carrier gas: Argon gas (flow rate: 100 sccm) ·Achieved vacuum level: 1×10 -4 Less than Pa Sputtering pressure: 0.35Pa Sputtering power: 1000W (3.1W / cm 2 )

[0050] Example 3 (comparison) A metal foil with a carrier was produced in the same manner as in Example 1, except that a copper target (purity 99.98%) was used as the sputtering target in order to form a copper layer instead of an Au layer as the first metal layer 26.

[0051] Example 4 A carrier-attached metal foil was prepared in the same manner as in Example 2, except that a tantalum target (purity 99.9%) was used as the sputtering target in order to form a tantalum layer instead of a titanium layer or nickel layer as the second metal layer 24 and the barrier layer 28.

[0052] Example 5 A metal foil with a carrier was produced in the same manner as in Example 2, except that a nickel target (purity 99.9%) was used as the sputtering target in order to form a nickel layer instead of a titanium layer as the second metal layer 24.

[0053] Example 6 A carrier-attached metal foil was prepared in the same manner as in Example 2, except that a tungsten target (purity 99.9%) was used as the sputtering target in order to form a tungsten layer instead of a titanium layer or nickel layer as the second metal layer 24 and the barrier layer 28.

[0054] Example 7 A carrier-attached metal foil was prepared in the same manner as in Example 2, except that a chromium target (purity 99.9%) was used as the sputtering target in order to form a chromium layer instead of a titanium layer or nickel layer as the second metal layer 24 and the barrier layer 28.

[0055] Example 8 A carrier-attached metal foil was prepared in the same manner as in Example 2, except that a palladium target (purity 99.9%) was used as the sputtering target in order to form a palladium layer instead of a titanium layer or nickel layer as the second metal layer 24 and the barrier layer 28.

[0056] Example 9 A metal foil with a carrier was produced in the same manner as in Example 2, except that the thickness of the peel auxiliary layer 18 was set to 300 nm.

[0057] Example 10 A metal foil with a carrier was produced in the same manner as in Example 2, except that the thickness of the peeling auxiliary layer 18 was set to 100 nm.

[0058] Example 11 A metal foil with a carrier was produced in the same manner as in Example 2, except that the thickness of the adhesive layer 16 was set to 100 nm and the thickness of the peeling auxiliary layer 18 was set to 50 nm.

[0059] Example 12 A metal foil with a carrier was produced in the same manner as in Example 2, except that the thickness of the adhesive layer 16 was set to 150 nm and the thickness of the peeling auxiliary layer 18 was set to 500 nm.

[0060] Example 13 (comparison) A metal foil with a carrier was produced in the same manner as in Example 2, except that the thickness of the adhesive layer 16 was set to 10 nm and the thickness of the release aid layer 18 was set to 30 nm.

[0061] Example 14 (comparison) A metal foil with a carrier was produced in the same manner as in Example 2, except that the thickness of the adhesive layer 16 was set to 200 nm and the thickness of the peeling auxiliary layer 18 was set to 600 nm.

[0062] evaluation Various evaluations were carried out on the carrier-attached metal foils 10 of Examples 1 to 14 as shown below. The evaluation results are shown in Table 1. Note that the items marked with "-" in Table 1 indicate that the corresponding evaluation was not carried out.

[0063] <Evaluation 1: Peelability> The peel strength of the carrier-attached metal foil 10 was measured as follows. First, panel electrolytic copper plating of 18 μm was applied to the surface of the carrier-attached metal foil 10 on the side of the first metal layer 26 (or barrier layer 28, if present) to form a plating-up layer. In Example 1, electroless Ni plating was applied before panel electrolytic copper plating to ensure adhesion between Au and Cu. The carrier-attached metal foil 10 on which the plating-up layer was formed was subjected to a heat treatment by solder reflow (held at 260°C or higher for 2 minutes) intended for mounting electronic components, and then naturally cooled to room temperature to obtain a copper-clad laminate. The peel strength (gf / cm) of the resulting copper-clad laminate was measured when the composite metal layer 20 integrated with the plating-up layer was peeled off in accordance with JIS C 6481-1996. The measurement width was 50 mm and the measurement length was 20 mm. The peel strength (average value) thus obtained was rated and evaluated according to the following criteria. - Rating A: Peel strength is 3 gf / cm or more and 10 gf / cm or less - Rating B: Peel strength is 1 gf / cm or more and 30 gf / cm or less (excluding those that fall under Rating A) - Rating C: Peel strength is less than 1 gf / cm or more than 30 gf / cm and less than 50 gf / cm - Rating D: Peel strength is 50 gf / cm or more

[0064] <Evaluation 2-1: Transmission loss (patterning after resin lamination)> For the carrier-attached metal foils 10 of Examples 1 to 8, samples 110 for measuring transmission loss were prepared according to the procedures shown in FIGS. 7 and 8, and the transmission loss was measured and evaluated.

[0065] First, six 35 μm thick insulating resin films (ABF-GXT31, manufactured by Ajinomoto Fine-Techno Co., Inc., relative dielectric constant 3.4) were laminated to form an insulating resin substrate 102 (FIG. 7(i)). The first metal layer 26 side (or the barrier layer 28 side, if present) of the carrier-attached metal foil 10 was bonded to one side of this insulating resin substrate 102, and lamination was performed using a vacuum press under conditions of a temperature of 100°C, a pressure of 0.7 MPa, and a pressing time of 90 seconds, to obtain a metal-clad laminate 104 in which the thickness h of the insulating resin substrate 102 was approximately 200 μm (FIG. 7(ii)).

[0066] Next, an 18 μm thick Cu foil was bonded as a ground layer 106 to the surface of the metal-clad laminate 104 on the insulating resin substrate 102 side (the side opposite the carrier-attached metal foil 10) by vacuum pressing (FIG. 7(iii)). The vacuum pressing was performed under conditions of a temperature of 100°C, a pressure of 0.7 MPa, and a time of 120 seconds. The insulating resin substrate 102 was then cured. The curing was performed by provisionally curing at 170°C for 30 minutes, followed by full curing at 200°C for 60 minutes.

[0067] Thereafter, the carrier 12 was peeled off from the metal-clad laminate 104 together with the release functional layer 14 at the position of the carbon layer 22 (FIG. 8(iv)). The second metal layer 24 exposed on one side of the metal-clad laminate 104 was removed by etching to expose the first metal layer 26. In this way, a double-sided metal-clad laminate 107 was obtained in which the first metal layer 26, insulating resin substrate 102, and ground layer 106 were laminated in this order (FIG. 8(v)). The surface of the obtained double-sided metal-clad laminate 107 on the side of the first metal layer 26 was washed with water and dried.

[0068] A photosensitive dry film (not shown) was attached to the surface of the double-sided metal-clad laminate 107 facing the first metal layer 26, followed by exposure, development, and electroless Au plating. Development was performed using a 1.0 wt % sodium carbonate aqueous solution as the developer at 25°C for 2 minutes by showering. After peeling off the dry film (photoresist layer), unnecessary portions of the first metal layer 26 (and the barrier layer 28, if present) were removed by etching. This patterning resulted in the formation of a signal line 108, a microstrip line with a characteristic impedance of 50 Ω and a differential impedance of 100 Ω ( FIG. 8(vi) ). More specifically, the signal line 108 was patterned to have a circuit width W of 0.47 mm and a thickness t of 20 μm. Further patterning was performed as needed to achieve the above characteristic impedance and differential impedance ( FIG. 9 ). In Example 3, electroless Ni plating was performed before electroless Au plating to ensure adhesion between Au (electroless Au plating) and Cu (first metal layer 26). On the other hand, etching was not performed on the ground layer 106. In this way, a transmission loss measurement sample 110 having a microstrip line was obtained (FIGS. 8(vi) and 9).

[0069] The transmission loss of the obtained microstrip line of the transmission loss measurement sample 110 was measured at frequencies from 1 GHz to 50 GHz using a vector network analyzer. The transmission loss ratio S 21 (=(S2 / S1) x 100(%)) was calculated and rated according to the following criteria. - Rating A: Transmission loss ratio S 21 is less than 330%. - Rating B: Transmission loss ratio S 21 is greater than 330% and less than or equal to 450%. - Rating C: Transmission loss ratio S 21 is greater than 450%.

[0070] <Evaluation 2-2: Transmission loss (patterning before resin lamination)> For the carrier-attached metal foils 10 of Examples 1 to 3 and 9 to 14, samples 110' for measuring transmission loss were prepared according to the procedures shown in Figs. 10 and 11, and the transmission loss was measured and evaluated.

[0071] First, the surface of the carrier-attached metal foil 10 on the first metal layer 26 side (or on the barrier layer 28 side, if present) was washed with water and dried. A photosensitive dry film was attached to the surface of the carrier-attached metal foil 10 on the first metal layer 26 side (or on the barrier layer 28 side, if present), and a photoresist layer (not shown) was formed by exposure and development. Unnecessary portions of the first metal layer 26 (and the barrier layer 28, if present) were removed by etching to form a circuit 103 for a signal line, and then the photoresist layer was peeled off (FIG. 10(i)).

[0072] Next, an insulating resin substrate 102 was prepared by laminating six 35 μm thick insulating resin films (ABF-GXT31, manufactured by Ajinomoto Fine-Techno Co., Inc., relative dielectric constant 3.4). One side of this insulating resin substrate 102 was bonded to the side opposite the carrier 12 (the side on which the circuit 103 was formed) of the carrier-attached metal foil 10 on which the circuit 103 was formed, and the layers were laminated using a vacuum press under conditions of a temperature of 100°C, a pressure of 0.7 MPa, and a pressing time of 90 seconds. In this way, a metal-clad laminate 104′ was obtained in which the thickness h of the insulating resin substrate 102 was approximately 200 μm (FIG. 10(ii)).

[0073] Next, an 18 μm thick Cu foil was bonded as a ground layer 106 to the surface of the metal-clad laminate 104′ on the insulating resin substrate 102 side (the side opposite the carrier-attached metal foil 10) by vacuum pressing (FIG. 10(iii)). The vacuum pressing was performed under conditions of a temperature of 100°C, a pressure of 0.7 MPa, and a time of 120 seconds. The insulating resin substrate 102 was then cured. The curing was performed by provisionally curing at 170°C for 30 minutes, followed by full curing at 200°C for 60 minutes.

[0074] Thereafter, the carrier 12 was peeled off from the metal-clad laminate 104′ together with the release functional layer 14 at the position of the carbon layer 22 (FIG. 11(iv)). The second metal layer 24 exposed on one side of the metal-clad laminate 104′ was removed by etching to expose the circuit 103 (FIG. 11(v)).

[0075] A photosensitive dry film (not shown) was attached to the surface of the metal-clad laminate 104′ on the circuit 103 side (opposite the ground layer 106), and then exposed and developed so that the area other than the circuit 103 was covered with resist. Electroless Au plating was performed on the circuit 103 not covered with resist, and then the dry film (photoresist layer) was peeled off. This patterning process formed a signal line 108′, which became a microstrip line with a characteristic impedance of 50 Ω and a differential impedance of 100 Ω ( FIG. 11(vi) ). More specifically, the signal line 108′ was patterned to have a circuit width W of 0.47 mm and a thickness t of 20 μm. Further patterning was performed as necessary to fine-tune the characteristic impedance and differential impedance. In Example 3, electroless Ni plating was performed before the electroless Au plating to ensure adhesion between the Au (electroless Au plating) and Cu (circuit 103). In this way, a transmission loss measurement sample 110' was obtained, which had a microstrip line in which part of the signal line 108' (ie, the circuit 103) was embedded in the surface of the insulating resin substrate 102 (FIG. 11(vi)).

[0076] The transmission loss of the obtained microstrip line of the transmission loss measurement sample 110' was measured from 1 GHz to 50 GHz using a vector network analyzer (Agilent, VNA E5071C). The transmission loss ratio S 21 (=(S2 / S1) x 100(%)) was calculated and rated according to the following criteria. - Rating A: Transmission loss ratio S 21 is less than 330%. - Rating B: Transmission loss ratio S 21 is greater than 330% and less than or equal to 450%. - Rating C: Transmission loss ratio S 21 is greater than 450%.

[0077] <Evaluation 3-1: Selective etching (patterning after resin lamination)> For the carrier-attached metal foils 10 of Examples 1 to 8, coreless supports with wiring patterns were produced, and the selective etching properties were measured and evaluated.

[0078] First, a double-sided metal-clad laminate 107 was obtained, consisting of a first metal layer 26, an insulating resin substrate 102, and a ground layer 106 laminated in this order, using the same procedure as in Evaluation 2-1. The surface of the double-sided metal-clad laminate 107 facing the first metal layer 26 was washed with water and dried. A photosensitive dry film was attached to the surface of the double-sided metal-clad laminate 107 facing the first metal layer 26, and a photoresist layer was formed by exposure and development to provide a line / space (L / S) pattern of 5 μm / 5 μm. Development was performed using a shower method at 25°C for 2 minutes using a 1.0 wt% sodium carbonate aqueous solution as the developer. Electroless Au plating was then performed on the exposed surface of the first metal layer 26 (i.e., the portion not masked by the photoresist layer), and the photoresist layer was then peeled off. This left the first metal layer 26, the barrier layer 28, if present, and the electroless Au plating layer in the form of a wiring pattern, while exposing the first metal layer 26 in the portion where the wiring pattern was not to be formed.

[0079] Thereafter, the exposed unnecessary portions of the first metal layer 26 and, if present, the unnecessary portions of the barrier layer 28 were removed by etching to form a coreless support body with a wiring pattern. The cross-sectional shape of the obtained wiring pattern was observed using an SEM, and the angle θ of the edge portion of the wiring pattern 112 with respect to the insulating resin substrate 102 was measured, as shown in Fig. 12. The obtained angle θ of the edge portion was ranked and evaluated according to the following criteria. - Evaluation A: Edge angle θ is between 87° and 93° - Grade B: The angle θ of the edge portion is equal to or greater than 80° and less than 87°, or is greater than 93° and less than 100°. - Rating C: The angle θ of the edge portion is equal to or greater than 60° and less than 80°, or is greater than 100° and less than 120°. - Grade D: The angle θ of the edge portion is less than 60° or greater than 120°.

[0080] <Evaluation 3-2: Selective etching (patterning before resin lamination)> For the carrier-attached metal foils 10 of Examples 1 to 3 and 9 to 14, coreless supports 116 with wiring patterns were produced according to the procedures shown in FIGS. 13 and 14, and the selective etching properties were measured and evaluated.

[0081] First, the surface of the carrier-attached metal foil 10 on the first metal layer 26 side (or on the barrier layer 28 side, if present) was washed with water and dried. A photosensitive dry film was attached to the surface of the carrier-attached metal foil 10 on the first metal layer 26 side (or on the barrier layer 28 side, if present), and a photoresist layer (not shown) was formed by exposure and development. Unnecessary portions of the first metal layer 26 (and the barrier layer 28, if present) were removed by etching to form a circuit 105 with a line / space (L / S) of 5 μm / 5 μm, and then the photoresist layer was peeled off (FIG. 13(i)).

[0082] Next, an insulating resin substrate 102 was prepared by laminating six 35 μm thick insulating resin films (ABF-GXT31, manufactured by Ajinomoto Fine-Techno Co., Inc., relative dielectric constant 3.4). One side of this insulating resin substrate 102 was bonded to the side opposite the carrier 12 (the side on which the circuit 105 was formed) of the carrier-attached metal foil 10 on which the circuit 105 was formed, and the layers were laminated using a vacuum press under conditions of a temperature of 100°C, a pressure of 0.7 MPa, and a pressing time of 90 seconds. In this way, a metal-clad laminate 114 was obtained in which the thickness h of the insulating resin substrate 102 was approximately 200 μm (FIG. 13(ii)).

[0083] Thereafter, using the same procedure as in Evaluation 2-2, an 18 μm thick Cu foil was vacuum-pressed to bond as a ground layer 106 to the surface of the insulating resin substrate 102 side (opposite the carrier-attached metal foil 10) of the metal-clad laminate 114 (FIG. 13(iii)). The carrier 12 was peeled off from the metal-clad laminate 114 together with the release functional layer 14 at the position of the carbon layer 22 (FIG. 14(iv)). The second metal layer 24 exposed on one side of the metal-clad laminate 114 was removed by etching to expose the circuit 105 (FIG. 14(v)). The surface of the metal-clad laminate 114 on the circuit 105 side was washed with water and dried.

[0084] A photosensitive dry film (not shown) was then attached to the surface of the metal-clad laminate 114 on the circuit 105 side (the side opposite the ground layer 106), and exposure and development were performed so that the area other than the circuit 105 was covered with resist. The development was performed under the same conditions as in Evaluation 3-1. Electroless Au plating was performed on the circuit 105 not covered with resist, and then the dry film (photoresist layer) was peeled off. In this way, a coreless support 116 having a wiring pattern 112 with a line / space (L / S) of 5 μm / 5 μm was formed ( FIG. 14(vi) ). The cross-sectional shape of the obtained wiring pattern was observed using an SEM, and the angle θ of the edge portion of the wiring pattern 112 relative to the insulating resin substrate 102 was measured, as shown in FIG. 12 . The obtained angle θ of the edge portion was ranked and evaluated using the same criteria as in Evaluation 3-1.

[0085] <Evaluation 4: Cu-plated connection resistance> For the carrier-attached metal foils 10 of Examples 1, 2, and 4 to 14, samples 124 for measuring connection resistance were prepared according to the procedure shown in FIG. 15, and the Cu plating connection resistance was evaluated.

[0086] First, the first metal layer 26 side (or the barrier layer 28 side, if present) of the carrier-attached metal foil 10 was bonded to a 35 μm-thick insulating resin film 101 (ABF-GXT31, manufactured by Ajinomoto Fine-Techno Co., Inc., dielectric constant 3.4), followed by vacuum pressing and curing of the insulating resin film to obtain a metal-clad laminate 118 ( FIG. 15(i) ). The vacuum pressing and curing of the insulating resin film 101 were performed under the same conditions as those for bonding the metal-clad laminate 104 and ground layer 106 in Evaluation 2-1. Furthermore, as shown in FIG. 15(i) , a region R was provided in the metal-clad laminate 118 where the first metal layer 26 (or the barrier layer 28, if present) was exposed (i.e., the insulating resin film 101 was not bonded) to perform the IV measurement described below.

[0087] Next, a via V with a diameter of 30 μm was formed in the metal-clad laminate 118 using a CO laser, penetrating the insulating resin film 101 and reaching the first metal layer 26 (or the barrier layer 28, if present) (FIG. 15(ii)). Then, Cu plating 120 was applied from the bottom of the via V to cover the surface of the insulating resin film 101 (FIG. 15(iii)). The Cu plating 120 was formed by electroless Cu plating to a thickness of approximately 1 μm on the surface of the insulating resin film 101, the sidewalls of the via V, and the bottom of the via V, followed by via filling with electrolytic Cu plating. The thickness of the Cu plating 120 was 55 μm (approximately 35 μm for the via V portion and approximately 20 μm for the portion covering the surface of the insulating resin film 101). A photosensitive dry film was attached to the surface of the Cu plating 120 in the metal-clad laminate 118, and a 300 μm × 300 μm photoresist layer (not shown) was formed by exposure and development to cover the via V portion. The unnecessary parts of the Cu plating 120 (i.e., the parts not covered with the photoresist layer) were removed by etching, and then the photoresist layer was peeled off to obtain a connection resistance measurement sample 124 on which a Cu electrode 122 was formed (Figure 15(iv)).

[0088] For the resulting connection resistance measurement sample 124, IV measurements were performed on the first metal layer 26 (or barrier layer 28, if present) and Cu electrode 122, and the connection resistance of the Cu plating (resistance before the HAST test, R1) was calculated (see FIG. 16 ). The measurements were performed using a four-terminal method. After the connection resistance measurement sample 124 was subjected to an HAST test (85°C, 85% RH, 200 hours), IV measurements were performed again on the first metal layer 26 (or barrier layer 28, if present) and Cu electrode 122, and the connection resistance of the Cu plating after the HAST test (resistance after the HAST test, R2) was calculated. The resistance increase rate before and after the HAST test (=((R2-R1) / R1)×100(%)) was calculated and ranked according to the following criteria. Four connection resistance measurement samples 124 were prepared, and the average of the results was used for evaluation. - Rating A: The resistance increase rate before and after the HAST test is 10% or less. - Rating B: The resistance increase rate before and after the HAST test is greater than 10% and less than 20%. - Grade C: The resistance increase rate before and after the HAST test is greater than 20% and less than 50%. - Rating D: The resistance increase rate before and after the HAST test is more than 50%.

[0089] [Table 1]

Claims

1. (a) a carrier; (b) a release functional layer provided on the carrier, (b1) an adhesion layer located closer to the carrier, having a thickness of more than 10 nm and less than 200 nm, and containing 80 atomic % or more of at least one selected from the group consisting of Ti, Ta, Cr, Ni, Al, Mo, Zn, W, TiN, and TaN; and (b2) a release functional layer including a release auxiliary layer having a thickness of 50 nm or more and 500 nm or less on the side farther from the carrier and containing 80 atomic % or more of Cu; (c) a composite metal layer provided on the release functional layer, (c1) a carbon layer closer to the peeling aid layer; (c2) a first metal layer, which is located farther from the peeling auxiliary layer and is mainly composed of Au or Pt; and (c3) a composite metal layer provided between the carbon layer and the first metal layer, the composite metal layer including a second metal layer containing 50 atomic % or more of at least one selected from the group consisting of Ti, Ta, Ni, W, Cr, and Pd; A metal foil with a carrier.

2. The metal foil with a carrier according to claim 1 , wherein the carrier is made of glass, silicon, or ceramics.

3. The thickness T of the adhesive layer １ The thickness T of the peeling aid layer ２ T is the ratio of ２ / T １ The metal foil with a carrier according to claim 1 or 2, wherein the value of the ρ is more than 1 and 20 or less.

4. The metal foil with a carrier according to any one of claims 1 to 3, wherein the carbon layer contains amorphous carbon.

5. The metal foil with a carrier according to any one of claims 1 to 4, wherein the first metal layer has a thickness of 50 nm or more and 2000 nm or less.

6. The metal foil with a carrier according to any one of claims 1 to 5, wherein the second metal layer has a thickness of 50 nm or more and 1000 nm or less.

7. The composite metal layer is (c4) The carrier-attached metal foil according to any one of claims 1 to 6, further comprising a barrier layer provided on a surface of the first metal layer farther from the carbon layer and containing at least one selected from the group consisting of Ti, Ta, Ni, W, Cr, and Pd in ​​a total amount of 50 atomic % or more.

8. The metal foil with a carrier according to any one of claims 1 to 7, which is used for producing a millimeter wave antenna substrate.

9. A method for producing a millimeter-wave antenna substrate, comprising producing a millimeter-wave antenna substrate using the metal foil with a carrier according to any one of claims 1 to 7.

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