Method for manufacturing redistribution stack, and carrier-attached metal foil

Abstract

Provided is a method for manufacturing a redistribution stack with which warpage can be reduced. This method for manufacturing a redistribution stack comprises: a step for obtaining a first stack by forming a first redistribution layer having a thickness of 100 μm or less on a first metal layer of a first-carrier-attached metal foil that has a first carrier, a first peeling layer, and the first metal layer in this order; a step for preparing a second stack having a second redistribution layer or a dummy insulating layer having a thickness of 100 μm or less on the second carrier; and a step for obtaining a third stack by bonding the first carrier of the first stack and the second carrier of the second stack via an adhesive layer containing an adhesive material.

Description

Manufacturing method of rewiring laminate and metal foil with carrier

[0001] The present disclosure relates to a method for manufacturing a rewiring laminate and a metal foil with a carrier.

[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 build-up method for manufacturing a multilayer printed wiring board has been adopted. The coreless build-up method is a method for forming a multilayer structure by alternately stacking (building up) insulating layers and wiring layers without using a so-called core substrate. In the coreless build-up 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 a semiconductor element, 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 build-up 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 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., a thickness of 300 nm) 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 predetermined 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 in image inspection (e.g., automatic image inspection (AOI)).

[0005] In particular, with the further miniaturization and power saving of electronic devices, there is an increasing need for higher integration and thinner semiconductor chips and printed wiring boards. As next-generation packaging technologies to meet such needs, the adoption of fan-out wafer level packaging (FO-WLP) and panel level packaging (PLP) has been considered in recent years. Furthermore, the adoption of a coreless build-up method is also being considered for FO-WLP and PLP. One such method is called the redistribution layer-first (RDL-First) method, in which a wiring layer and, if necessary, a build-up wiring layer are formed on the surface of a coreless support, and the support is further peeled off if necessary, and then the chip is mounted. For example, Patent Document 4 (JP 2015-35551 A) discloses a method for manufacturing a semiconductor device, which includes forming a metal release layer on the main surface of a support made of glass or a silicon wafer, forming an insulating resin layer thereon, forming a redistribution layer including a build-up layer thereon, mounting and sealing a semiconductor integrated circuit thereon, exposing the release layer by removing the support, exposing secondary mounting pads by removing the release layer, and forming solder bumps on the surfaces of the secondary mounting pads, and secondary mounting.

[0006] Recently, a method called a 2.1-dimensional (2.1D) packaging method has been proposed, in which a rewiring layer including fine wiring is formed on a conventional build-up substrate. For example, Patent Document 5 (Japanese Patent No. 6298722) discloses that a first wiring structure having wiring layers with low wiring density is formed on both the upper and lower surfaces of a core substrate by a build-up method, and then a second wiring structure having a wiring layer with high wiring density is formed on the upper surface of an insulating layer formed on the top layer of the first wiring structure.

[0007] Japanese Patent Application Laid-Open No. 2005-101137 International Publication No. 2017 / 150283 International Publication No. 2017 / 150284 Japanese Patent Application Laid-Open No. 2015-35551 Japanese Patent No. 6298722

[0008] However, when forming a rewiring layer including fine wiring on a build-up substrate as disclosed in Patent Document 5, there is a problem that it is difficult to form the desired wiring due to the surface roughness of the prepreg, etc. used in the build-up substrate. To address this problem, it is conceivable to form a rewiring layer on one side (on the metal layer) of a carrier-attached metal foil, and then further form a build-up layer on this rewiring layer to produce a laminate (sometimes referred to as a "rewiring laminate"). However, a laminate produced in this manner may suffer from significant warping, making subsequent mounting processes, etc. difficult to perform.

[0009] The inventors have now discovered that a rewiring laminate with reduced warping can be produced by forming a first rewiring layer having a thickness of 100 μm or less on the metal layer of a carrier-attached metal foil to obtain a first laminate, and then bonding a specified second laminate to this first laminate via an adhesive layer.

[0010] Therefore, an object of the present invention is to provide a method for manufacturing a rewiring laminate capable of reducing warpage. Another object of the present invention is to provide a metal foil with a carrier capable of manufacturing such a rewiring laminate.

[0011] The present disclosure provides the following aspects. [Aspect 1] A method for manufacturing a redistribution laminate, comprising: forming a first redistribution layer having a thickness of 100 μm or less on a first metal layer of a first carrier-attached metal foil, the first metal layer including a first carrier, a first release layer, and a first metal layer in this order, to obtain a first laminate; preparing a second laminate including a second redistribution layer or a dummy insulating layer having a thickness of 100 μm or less on a second carrier; and bonding the first carrier of the first laminate and the second carrier of the second laminate together via an adhesive layer containing an adhesive material to obtain a third laminate. [Aspect 2] A method for manufacturing a redistribution laminate according to Aspect 1, further comprising: forming a first buildup layer on the first redistribution layer of the third laminate, and forming a second buildup layer on the second redistribution layer or the dummy insulating layer of the third laminate, to obtain a fourth laminate. [Aspect 3] A method for manufacturing a redistribution laminate according to Aspect 2, further comprising the step of peeling the first carrier from the fourth laminate. [Aspect 4] A method for manufacturing a redistribution laminate according to any one of Aspects 1 to 3, wherein the second laminate comprises the second redistribution layer, and the step of preparing the second laminate comprises forming the second redistribution layer on the second metal layer of a metal foil with a second carrier, the metal foil comprising the second carrier, a second release layer, and a second metal layer in this order. [Aspect 5] A method for manufacturing a redistribution laminate according to any one of Aspects 1 to 4, wherein each of the first carrier and the second carrier has a linear expansion coefficient of 2.0 ppm / K or more and 30.0 ppm / K or less. [Aspect 6] A method for manufacturing a redistribution laminate according to any one of Aspects 1 to 4, wherein the thickness T of the first redistribution layer is 2.0 ppm / K or more and 30.0 ppm / K or less. Ｒ１ the thickness T of the second rewiring layer or the dummy insulating layer Ｒ２ The ratio T Ｒ２ / T Ｒ１is 0.1 or more and 30.0 or less. [Aspect 7] The method for manufacturing a redistribution laminate according to any one of Aspects 1 to 6, wherein the step of forming the first redistribution layer includes: a step of forming a first wiring layer on the surface of the first metal layer; and a step of alternately forming insulating layers and wiring layers on the surface of the first metal foil with a carrier on which the first wiring layer has been formed, to obtain a first redistribution layer in which the first wiring layer is embedded as a buried wiring layer. [Aspect 8] The method for manufacturing a redistribution laminate according to Aspect 7, wherein the insulating layer is made of an insulating resin containing at least one selected from the group consisting of a thermosetting epoxy resin, a thermosetting polyimide resin, and a thermosetting phenolic resin. [Aspect 9] The method for manufacturing a redistribution laminate according to any one of Aspects 1 to 8, wherein the adhesive material includes a solventless adhesive. [Aspect 10] The method for manufacturing a redistribution laminate according to any one of Aspects 1 to 9, wherein the adhesive material comprises at least one selected from the group consisting of a thermosetting epoxy resin, a thermosetting polyimide resin, a photosensitive polyimide resin, an acrylic resin, and a phenolic resin. [Aspect 11] The method for manufacturing a redistribution laminate according to any one of Aspects 1 to 10, wherein the adhesive layer has a thickness of 5 μm or more and 1000 μm or less. [Aspect 12] The method for manufacturing a redistribution laminate according to any one of Aspects 2 to 11, wherein each of the first buildup layer and the second buildup layer has a thickness of 20 μm or more. [Aspect 13] The method for manufacturing a redistribution laminate according to any one of Aspects 2 to 11, wherein the thickness T of the first buildup layer is 20 μm or more. Ｂ１ the thickness T of the second build-up layer Ｂ２ The ratio T Ｂ２ / T Ｂ１is 0.5 or more and 1.5 or less. [Aspect 14] A method for manufacturing a redistribution laminate according to any one of Aspects 2 to 13, wherein each of the first buildup layer and the second buildup layer includes a prepreg. [Aspect 15] A metal foil with a carrier comprising: a first carrier; a first release layer provided on the first carrier; a first metal layer provided on the first release layer; an adhesive layer containing an adhesive material provided on a surface of the first carrier opposite to the first release layer; and a second carrier provided on the first carrier via the adhesive layer. [Aspect 16] The metal foil with a carrier according to Aspect 15, further comprising: a second release layer provided on the second carrier; and a second metal layer provided on the second release layer. [Aspect 17] A laminate comprising: the metal foil with a carrier according to Aspect 16; a first rewiring layer provided on the first metal layer of the metal foil with a carrier; and a second rewiring layer or an insulating layer provided on the second metal layer of the metal foil with a carrier. [Aspect 18] The laminate according to Aspect 17, further comprising a first buildup layer provided on the first rewiring layer, and a second buildup layer provided on the second rewiring layer or the insulating layer.

[0012] 1 is a process flow diagram showing, in schematic cross-sectional views, an example of a method for producing a rewiring laminate of the present invention, which corresponds to early steps (steps (i) to (iii)). FIG. 2 is a process flow diagram showing, in schematic cross-sectional views, an example of a method for producing a rewiring laminate of the present invention, which corresponds to middle steps (steps (iv) to (vi)) subsequent to the steps shown in FIG. 1. FIG. 3 is a process flow diagram showing, in schematic cross-sectional views, an example of a method for producing a wiring board of the present invention, which corresponds to late steps (steps (vii) and (viii)) subsequent to the steps shown in FIG. 2. FIG. 4 is a photograph showing an observation of warpage of a first laminate produced in Example 1. FIG. 5 is a photograph showing an observation of warpage of a third laminate produced in Example 1. FIG. 6 is a process flow diagram showing, in schematic cross-sectional views, an example of a procedure for producing a metal foil with a carrier of the present invention.

[0013] The present invention relates to a method for manufacturing a rewiring laminate. The method of the present invention includes the steps of: (1) producing a first laminate; (2) preparing a second laminate; (3) bonding the first laminate and the second laminate; (4) optionally forming a first buildup layer and a second buildup layer; and (5) optionally peeling off the first carrier. Each of steps (1) to (5) will be described below with reference to the drawings.

[0014] (1) Fabrication of First Laminate An example of a method for manufacturing a rewiring laminate of the present invention is shown in FIGS. 1 to 3 . First, as shown in FIGS. 1( i ) to 2 ( iv ), a first rewiring layer 20 having a thickness of 100 μm or less is formed on the first metal layer 18 of a first carrier-attached metal foil 10 having a first carrier 12, a first release layer 16, and a first metal layer 18 in this order, to obtain a first laminate 22. In the present invention, the term "rewiring layer" refers to a layer including an insulating layer and a wiring layer formed inside and / or on the insulating layer. The first release layer 16 is a layer provided on the first carrier 12 and contributes to the delamination between the first carrier 12 and the first metal layer 18. The first metal layer 18 is a layer composed of metal provided on the first release layer 16. The first carrier-attached metal foil 10 may further include a first intermediate layer 14 between the first carrier 12 and the first release layer 16, which can contribute to improving adhesion. Preferred embodiments of the first carrier 12, first intermediate layer 14, first release layer 16, and first metal layer 18 will be described below.

[0015] As described above, when forming a rewiring layer including fine wiring on a build-up substrate such as that disclosed in Patent Document 5, there is a problem in that it is difficult to form the desired fine wiring due to the surface roughness (waviness) of the prepreg or the like used in the build-up substrate. In this regard, even when the surface of the prepreg is subjected to chemical mechanical polishing (CMP), it is generally difficult to flatten the prepreg to an extent that allows the desired fine wiring to be formed. In contrast, according to the method of the present invention, the first rewiring layer 20 is first formed on the flat surface of the first carrier-attached metal foil 10, which makes it easier to form the desired fine wiring. Furthermore, by forming the first rewiring layer 20 thin, at a thickness of 100 μm or less, the warpage of the first rewiring layer 20 itself can be reduced to a handleable range, making it possible to carry out the respective steps described below.

[0016] Therefore, the thickness T of the first redistribution layer 20 Ｒ１ is 100 μm or less, preferably 5 μm or more and 95 μm or less, more preferably 7 μm or more and 90 μm or less, even more preferably 9 μm or more and 80 μm or less, and particularly preferably 10 μm or more and 70 μm or less. The first redistribution layer 20 preferably includes a wiring pattern with a line / space (L / S) of 10 μm or less / 10 μm or less, more preferably 5 μm or less / 5 μm or less. The lower limit of the line / space (L / S) in the wiring pattern is not particularly limited, but is typically 1 μm or more / 1 μm or more.

[0017] The first rewiring layer 20 can be preferably formed, for example, as follows. First, as shown in FIG. 1(ii), a first wiring layer 20a is formed on the surface of the first metal layer 18 of the first carrier-attached metal foil 10. Typically, the first wiring layer 20a is formed according to a known method, through the formation of a photoresist layer, the formation of an electrolytic copper plating layer, the peeling off of the photoresist layer, and, if desired, copper flash etching. For example, the method is as follows: First, a photoresist layer is formed in a predetermined pattern on the surface of the first metal layer 18. The photoresist is preferably a photosensitive film, such as a photosensitive dry film. The photoresist layer may be imparted with a predetermined wiring pattern by exposure and development. An electrolytic copper plating layer is formed on the exposed surface of the first metal layer 18 (i.e., the portion not masked by the photoresist layer). The electrolytic copper plating may be performed by a known method and is not particularly limited. Next, the photoresist layer is peeled off. As a result, the electrolytic copper plating layer remains in a wiring pattern, forming the first wiring layer 20a.

[0018] Next, as shown in FIGS. 1(iii) and 2(iv), insulating layers 20b and wiring layers 20c are alternately formed on the surface of the first carrier-attached metal foil 10 on which the first wiring layer 20a is formed. In this manner, a first rewiring layer 20 is obtained in which the first wiring layer 20a is embedded as a buried wiring layer. The method for forming the insulating layer 20b and wiring layer 20c is not particularly limited, and known methods can be employed. For example, the insulating layer 20b can be preferably formed by laminating an insulating resin material and performing a thermosetting treatment. If desired, the insulating layer 20b and wiring layer 20c may be formed through known processes such as via drilling, desmearing, copper plating, and circuit formation. Preferred examples of the insulating resin constituting the insulating layer 20b include thermosetting epoxy resin, thermosetting polyimide resin, thermosetting phenolic resin, and combinations thereof, with thermosetting polyimide resin being more preferred. The insulating layer 20b may contain a curing agent, a filler, or the like. The thickness of each wiring layer constituting the first redistribution layer 20 is not particularly limited, but is typically 1 μm or more and 20 μm or less.

[0019] (2) Preparation of Second Laminate A second laminate 42 is prepared on the second carrier 32, which includes a second rewiring layer 40 or a dummy insulating layer (not shown) having a thickness of 100 μm or less (see FIG. 2(vi)). The dummy insulating layer means a layer composed of an insulating layer without a wiring layer, and functions as a dummy for the rewiring layer.

[0020] The second laminate 42 is laminated on the first laminate 22 described above and contributes to suppressing warpage of the first redistribution layer 20 (and further to the first buildup layer 46 described later). Here, warpage of the laminate typically occurs due to differences in the linear expansion coefficients of the materials constituting the carrier and the insulating layer during a heating process (e.g., thermal curing of the insulating layer). For this reason, for example, if the first redistribution layer 20 and the first buildup layer 46 described later are formed on only one side of the first carrier-attached metal foil 10, the manufactured redistribution laminate may exhibit significant warpage. In contrast, according to the method of the present invention, stresses in the opposite direction to the stresses (warping forces) of the first redistribution layer 20 and the first buildup layer 46 (if present) are applied to the laminate from the second redistribution layer 40 or dummy insulating layer, and the second buildup layer 48 described later (if present). In this way, the stresses cancel each other out, thereby suppressing warpage of the redistribution laminate.

[0021] As described above, the method of the present invention separately prepares the first laminate 22 including the first redistribution layer 20 and the second laminate 42 including the second redistribution layer 40 (or the dummy insulating layer). Therefore, compared to a method in which a metal foil with a carrier having a release layer and a metal layer on both sides of the carrier is used and redistribution layers including fine wiring are simultaneously formed from both sides of the metal foil with a carrier, the method has the advantages of being easier to handle and being less susceptible to problems such as quality issues due to the high difficulty of manufacturing.

[0022] The first carrier 12 and the second carrier 32 each preferably have a coefficient of linear expansion (CTE) of 2.0 ppm / K to 30.0 ppm / K, more preferably 2.5 ppm / K to 25.0 ppm / K, even more preferably 3.0 ppm / K to 20.0 ppm / K, and particularly preferably 3.2 ppm / K to 15.0 ppm / K. Within such a range, warping of the carrier itself in a process involving heat treatment can be suppressed, while warping of the laminate due to the difference in the coefficient of linear expansion between the carrier and the insulating layer can be more effectively suppressed.

[0023] The thickness T of the second rewiring layer 40 or the dummy insulating layer Ｒ is 100 μm or less, preferably 10 μm or more and 90 μm or less, more preferably 20 μm or more and 80 μm or less, further preferably 30 μm or more and 70 μm or less, and particularly preferably 40 μm or more and 60 μm or less. Ｒ１ The thickness T of the second rewiring layer 40 or the dummy insulating layer Ｒ２ The ratio T Ｒ２ / T Ｒ１ is preferably 0.1 or more and 30.0 or less, more preferably 0.2 or more and 10 or less, even more preferably 0.5 or more and 5.0 or less, particularly preferably 0.7 or more and 3.0 or less, and most preferably 0.8 or more and 2.0 or less. Within such a range, in a process involving heat treatment, a stress equivalent to the stress of the first redistribution layer 20 is applied to the laminate from the second redistribution layer 40 or the dummy insulating layer, and as a result, warping of the redistribution laminate can be more effectively suppressed.

[0024] When the second laminate 42 includes the second rewiring layer 40, it is preferable to form the rewiring layer using a carrier-attached metal foil, as in the first laminate 22 described above. That is, as shown in FIG. 2( vi), it is preferable to form the second rewiring layer 40 on the second metal layer 38 of the second carrier-attached metal foil 30, which includes the second carrier 32, the second release layer 36, and the second metal layer 38 in this order. Furthermore, it is preferable to form the second rewiring layer 40 by forming a first wiring layer 40a on the surface of the second metal layer 38, and then alternately forming an insulating layer 40b and a wiring layer 40c on the surface of the second carrier-attached metal foil 30 on which the first wiring layer 40a has been formed. The second carrier-attached metal foil 30 may further include a second intermediate layer 34 that can contribute to improving adhesion between the second carrier 32 and the second release layer 36. The preferred aspects of the first carrier-attached metal foil 10 and the first laminate 22 also apply to the second carrier-attached metal foil 30 and the second laminate 42. That is, the second carrier 32, the second intermediate layer 34, the second release layer 36, the second metal layer 38, and the second rewiring layer 40 can be similar to the first carrier 12, the first intermediate layer 14, the first release layer 16, the first metal layer 18, and the first rewiring layer 20, respectively.

[0025] On the other hand, when the second laminate 42 includes a dummy insulating layer, the dummy insulating layer may be formed directly on the surface of the second carrier 32. However, as with the second rewiring layer 40 described above, it is permissible to form a dummy insulating layer on the second metal layer 38 of the second carrier-attached metal foil 30. The formation of the dummy insulating layer is not particularly limited, as long as it is similar to the formation of the insulating layer 20b constituting the first rewiring layer 20. Furthermore, the preferred aspects of the insulating layer 20b described above also apply to the dummy insulating layer. The constituent materials of the dummy insulating layer and the insulating layer 20b may be the same or different. For example, it is permissible to form the dummy insulating layer from an insulating resin material that is cheaper than the insulating layer 20b.

[0026] 2(v) and 2(vi), the first carrier 12 of the first laminate 22 and the second carrier 32 of the second laminate 42 are bonded together via an adhesive layer 24 containing an adhesive material to obtain a third laminate 44. By configuring the insulating layers symmetrically on both sides of the laminate in this manner, stresses in the insulating layers cancel each other out in a subsequent heating process, thereby suppressing warping of the redistribution laminate. Furthermore, even if the first laminate 22 and the second laminate 42 are warped to a degree that allows them to be handled, bonding them together via the adhesive layer 24 allows the adhesive layer 24 to absorb (flatten) any irregularities caused by the warping.

[0027] The adhesive layer 24 is preferably a layer capable of bonding the first laminate 22 and the second laminate 42 with the desired adhesion. The bonding mode between the first laminate 22 and the second laminate 42 via the adhesive layer 24 is not particularly limited and may be, for example, mechanical bonding (i.e., adhesion due to the anchor effect), physical interaction (i.e., adhesion due to van der Waals forces), chemical bonding, etc. Examples of adhesive materials contained in the adhesive layer 24 include phenolic resin, urea resin, melamine resin, epoxy resin, polyimide resin, ethylene-vinyl acetate copolymer resin (EVA), urethane resin, acrylic resin, synthetic rubber, starch, and silicone resin. Preferred examples include thermosetting epoxy resin, thermosetting polyimide resin, photosensitive polyimide resin, acrylic resin, phenolic resin, or a combination thereof. The bonding method for the first laminate 22 and the second laminate 42 is not particularly limited and may be, for example, roll lamination, vacuum lamination, or other suitable techniques.

[0028] The adhesive layer 24 preferably maintains its adhesiveness even after heat treatment at high temperatures (e.g., 190°C or higher). From this perspective, the adhesive material preferably contains a thermosetting resin. Preferred examples of thermosetting resins include thermosetting epoxy resins, thermosetting polyimide resins, thermosetting phenolic resins, thermosetting melamine resins, and combinations thereof, with thermosetting epoxy resins being more preferred. In particular, the adhesive material preferably contains a solventless adhesive. This suppresses gas generation during heat treatment, further improving adhesion between the first laminate 22 and the second laminate 42. An example of a solventless adhesive film containing a thermosetting epoxy resin is TSA-1602 manufactured by Toray Industries, Inc. When the adhesive layer 24 contains a thermosetting resin as the adhesive material, it is preferable to perform a heat curing treatment after bonding the first laminate 22 and the second laminate 42 together. The conditions for the heat curing treatment may be determined appropriately depending on the thermosetting resin used and are not particularly limited.

[0029] The adhesive layer 24 preferably has a thickness of 5 μm to 1000 μm, more preferably 7 μm to 800 μm, even more preferably 10 μm to 500 μm, and particularly preferably 20 μm to 300 μm. With such a thickness, it becomes easier to control the adhesion between the first laminate 22 and the second laminate 42 within a desired range, and it becomes even easier to absorb unevenness caused by warping of the first laminate 22 and the second laminate 42.

[0030] There are no particular limitations on the method for forming the adhesive layer 24, and any known method can be used. For example, the adhesive layer 24 can be formed by applying a coating liquid in which an adhesive material is dissolved in a solvent onto the first carrier 12 or the second carrier 32, and then drying to volatilize the solvent. Alternatively, a commercially available adhesive film may be placed on the first carrier 12 or the second carrier 32, and then the two may be bonded together by a method such as roll lamination or vacuum lamination.

[0031] 3(vii), a first buildup layer 46 is formed on the first redistribution layer 20 of the third laminate 44, and a second buildup layer 48 is formed on the second redistribution layer 40 or the dummy insulating layer of the third laminate 44, thereby obtaining a fourth laminate 50. By forming the buildup layers symmetrically on both sides of the laminate in this manner, stresses in the insulating layers included in the first buildup layer 46 and the second buildup layer 48 cancel each other out in a process involving heating, and as a result, warping of the redistribution laminate is suppressed.

[0032] The first buildup layer 46 can be fabricated by alternately stacking wiring layers 46a and insulating layers 46b using the known coreless buildup method described above. For example, the first buildup layer 46 is formed through various processes such as stacking and curing insulating layers, via processing, desmearing, copper plating, and circuit formation. The thickness T of the first buildup layer 46 is Ｂ１ is preferably 20 μm or more, more preferably 30 μm or more and 300 μm or less, even more preferably 40 μm or more and 250 μm or less, particularly preferably 50 μm or more and 200 μm or less, and most preferably 60 μm or more and 150 μm or less.

[0033] The second buildup layer 48 may have a configuration similar to that of the first buildup layer 46, and preferably includes, for example, a wiring layer 48a and an insulating layer 48b. However, in cases where the second laminate 42 includes a dummy insulating layer instead of the second rewiring layer 40, the second buildup layer 48 does not need to include the wiring layer 48a, and may instead be configured with the insulating layer 48b (i.e., a dummy layer).

[0034] The wiring layers 46a and 48a that may be included in the first buildup layer 46 and the second buildup layer 48, respectively, typically have larger line / space (L / S) than the wiring patterns included in the first redistribution layer 20 and the second redistribution layer 40. The line / space (L / S) of the wiring layers 46a and 48a is typically 5 μm or more / 5 μm or more to 30 μm or less / 30 μm or less, respectively, and more typically more than 10 μm / more than 10 μm to 30 μm or less / 30 μm or less.

[0035] The preferred thickness of the first buildup layer 46 described above also applies to the second buildup layer 48. In addition, the thickness T Ｂ１ The thickness T of the second buildup layer 48 Ｂ２ The ratio T Ｂ２ / T Ｂ１ is preferably 0.5 or more and 1.5 or less, more preferably 0.6 or more and 1.4 or less, even more preferably 0.7 or more and 1.3 or less, and particularly preferably 0.8 or more and 1.2 or less. Within such a range, the stress of the first buildup layer 46 and the stress of the second buildup layer 48 become approximately the same in a process involving heat treatment, and as a result, warpage of the redistribution layer stack can be more effectively suppressed.

[0036] Typically, the first buildup layer 46 and the second buildup layer 48 each include a prepreg as an insulating layer. Prepreg is a general term for a composite material in which a synthetic resin is impregnated or laminated onto a substrate such as a synthetic resin sheet, a glass sheet, a woven glass fabric, a nonwoven glass fabric, or paper. Preferred examples of the insulating resin impregnated into the prepreg include epoxy resin, cyanate resin, bismaleimide triazine resin (BT resin), polyphenylene ether resin, phenolic resin, and polyamide resin. The insulating layer may contain a curing agent, a filler, or the like. However, the constituent materials of the insulating layer 46b of the first buildup layer 46 and the insulating layer 48b of the second buildup layer 48 may be the same or different. For example, when the second buildup layer 48 is used as the dummy layer described above, it is acceptable to form the second buildup layer 48 using a cheaper insulating resin material, etc.

[0037] 3(viii), the first carrier 12 is peeled off from the fourth stack 50. In this way, the first redistribution layer 20 and the first buildup layer 46 can be separated at the position of the first release layer 16. The first carrier 12 is preferably peeled off by a laser lift-off method in which the first carrier 12 is peeled off using a laser, or a mechanical method in which the first carrier 12 is peeled off by applying a physical force using a machine.

[0038] After the first carrier 12 is peeled off, the first release layer 16 and the first metal layer 18 remaining on the first redistribution layer 20 may be removed. The method for removing the first release layer 16 and the first metal layer 18 is not particularly limited, and a known method may be appropriately selected depending on the materials of the first release layer 16 and the first metal layer 18. For example, when the first release layer 16 is a carbon layer, the first release layer 16 can be preferably removed by performing oxygen plasma treatment on the laminate. Furthermore, the first metal layer 18 can be removed, for example, by contacting the laminate with an etching solution capable of dissolving the first metal layer 18.

[0039] After removing the first release layer 16 and the first metal layer 18, various electronic elements such as chips may be mounted on the first rewiring layer 20 by a known method, followed by resin sealing. Examples of electronic elements include semiconductor elements, chip capacitors, resistors, etc. Furthermore, solder resist, mounting bumps, etc. may be formed on the outer surface of the first buildup layer 46.

[0040] In cases where the second laminate 42 includes the second redistribution layer 40, the second carrier 32 may be further peeled from the fourth laminate 50, thereby separating the second redistribution layer 40 and the second build-up layer 48 at the position of the second release layer 36. The above-described preferred aspects regarding the peeling of the first carrier 12 and the subsequent steps also apply to the peeling of the second carrier 32 and the subsequent steps.

[0041] According to another preferred embodiment of the present invention, there is provided a metal foil with a carrier. The metal foil with a carrier comprises a first carrier 12, a first release layer 16, a first metal layer 18, an adhesive layer 24, and a second carrier 32. The first release layer 16 is provided on the first carrier 12. The first metal layer 18 is provided on the first release layer 16. The adhesive layer 24 includes an adhesive material and is provided on the surface of the first carrier 12 opposite the first release layer 16. The second carrier 32 is provided on the first carrier 12 via the adhesive layer 24. The metal foil with a carrier may further comprise a first intermediate layer 14 between the first carrier 12 and the first release layer 16. The metal foil with a carrier may further comprise a second release layer 36 provided on the second carrier 32 and a second metal layer 38 provided on the second release layer 36, or may further comprise a second intermediate layer 34 between the second carrier 32 and the second release layer 36. This metal foil with a carrier typically constitutes the third laminate 44 after the first laminate 22 and the second laminate 42 are bonded together in the above-mentioned method for manufacturing a rewiring laminate, and therefore it is possible to manufacture a rewiring laminate with reduced warping using this metal foil with a carrier.

[0042] Alternatively, the carrier-attached metal foil of the present invention may be formed by bonding a first carrier-attached metal foil 10 and a second carrier 32 via an adhesive layer 24, as shown in the examples described below. Specifically, as shown in FIG. 6 , a first carrier-attached metal foil 10 including a first carrier 12, an optional first intermediate layer 14 (optional layer), a first release layer 16, and a first metal layer 18 is prepared ( FIG. 6(i) ), an adhesive layer 24 is laminated on the first carrier 12 ( FIG. 6(ii) ), and a second carrier 32 is further laminated on the adhesive layer 24 ( FIG. 6(iii) ), thereby forming the carrier-attached metal foil of the present invention. This configuration effectively suppresses warpage of the laminate when a rewiring layer and / or build-up layer having a different thermal expansion coefficient is further laminated. The second carrier 32 may be provided in the form of a second carrier-attached metal foil 30, as shown in FIG. 6(iii) . The second carrier-attached metal foil 30 comprises, in this order, a second carrier 32, an optional second intermediate layer 34 (an optional layer), a second release layer 36, and a second metal layer 38. From the viewpoint of more effectively suppressing warpage of the laminate, it is particularly preferable that the first carrier-attached metal foil 10 and the second carrier-attached metal foil 30 have the same layer structure. That is, according to a preferred embodiment of the present invention, the carrier-attached metal foil has the first carrier-attached metal foil 10 and the second carrier-attached metal foil 30 provided symmetrically above and below with an adhesive layer 24 interposed therebetween. Specifically, in the carrier-attached metal foil, the first carrier 12 and the second carrier 32 are preferably made of the same material and thickness, the first intermediate layer 14 and the second intermediate layer 34 are preferably made of the same material and thickness, the first release layer 16 and the second release layer 36 are preferably made of the same material and thickness, and the first metal layer 18 and the second metal layer 38 are preferably made of the same material and thickness. The term "same" as used here does not necessarily mean that the materials and thicknesses of the layers in question are completely the same, but also means that they are approximately the same to the extent that they do not cause warping of the laminate.

[0043] Preferred aspects of the first carrier 12, first intermediate layer 14, first release layer 16, and first metal layer 18 are described below, but these preferred aspects also apply equally to the second carrier 32, second intermediate layer 34, second release layer 36, and second metal layer 38, respectively.

[0044] The first carrier 12 is preferably made of glass, silicon, ceramics, resin, metal, or a combination thereof, more preferably made of glass, silicon, or ceramics, and even more preferably made of glass or silicon. The first carrier 12 made of silicon may be any material containing Si as an element, and may be made of SiO ２ Substrates that can be used include SiN substrates, Si single crystal substrates, and Si polycrystalline substrates. According to a preferred embodiment of the present invention, the first carrier 12 is disc-shaped with a diameter of 100 mm or more, more preferably 200 mm to 450 mm. The first carrier 12 (e.g., a Si single crystal substrate) may have a notch or orientation flat (also called an orientation flat) to indicate a reference point for crystal orientation. Generally, an orientation flat is formed when the diameter of the first carrier 12 is 200 mm or less, and a notch is formed when the diameter of the first carrier 12 is 200 mm or more. According to another preferred embodiment of the present invention, the first carrier 12 is rectangular with a short side of 100 mm or more, more preferably 150 mm to 650 mm. The rectangular first carrier 12 may be in the form of a roll with a long side that is sufficiently longer than the short side, but preferably has a long side of 200 mm to 650 mm.

[0045] The first carrier 12 may be in the form of a sheet, film, or plate. The first carrier 12 may also be a laminate of these sheets, films, and plates. For example, the first carrier 12 may function as 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 first 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®), polyamide-imide, polyethersulfone, polyphenylene sulfide, polytetrafluoroethylene (PTFE), and ethylene tetrafluoroethylene (ETFE). From the viewpoint of ease of handling and ensuring flatness, the first carrier 12 preferably has a Vickers hardness of 100 HV or more, more preferably 150 HV to 2500 HV. As a material satisfying these properties, the first carrier 12 is preferably made of glass, silicon, or ceramics, more preferably glass or ceramics, and particularly preferably glass.

[0046] An example of the first carrier 12 made of glass is a glass plate. Glass, when used as the first carrier 12, offers advantages such as lightweight, a low thermal expansion coefficient, high insulation, rigidity, and a flat surface, allowing the surface of the first metal layer 18 to be extremely smooth. Furthermore, glass as the first carrier 12 offers advantages such as surface flatness (coplanarity) that is advantageous for forming fine circuits and chemical resistance in desmearing and various plating processes in the wiring manufacturing process. Preferred examples of the glass constituting the first carrier 12 include quartz glass, borosilicate glass, alkali-free glass, soda-lime glass, aluminosilicate glass, and combinations thereof. More preferred are alkali-free glass, soda-lime glass, and combinations thereof, with alkali-free glass being 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 thermal expansion coefficient 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 first 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. When the thickness of the first carrier 12 is within this range, it is possible to achieve thinner wiring and further reduce warping while maintaining appropriate strength that does not interfere with handling.

[0047] The surface of the first carrier 12 on the side of the first release layer 16 (or the side of the first intermediate layer 14, if present) 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 in accordance with JIS B 0601-2001. A smaller arithmetic mean roughness can result in a desirably low arithmetic mean roughness Ra on the outer surface of the first metal layer 18, making it suitable for forming a highly fine wiring pattern.

[0048] The first carrier 12 and the second carrier 32 each preferably have a coefficient of linear expansion (CTE) of 2.0 ppm / K or more and 30.0 ppm / K or less, more preferably 2.5 ppm / K or more and 25.0 ppm / K or less, even more preferably 3.0 ppm / K or more and 20.0 ppm / K or less, and particularly preferably 3.2 ppm / K or more and 15.0 ppm / K or less. Within such ranges, warping of the laminate due to the difference in the coefficient of linear expansion between the carrier and the insulating layer can be more effectively suppressed while suppressing warping of the carrier itself in a process involving heat treatment. Furthermore, from the viewpoint of more effectively suppressing warping of the laminate due to the difference in the coefficient of linear expansion between the first carrier 12 and the second carrier 32, the coefficient of linear expansion CTE of the first carrier 12 is １ The linear expansion coefficient C of the second carrier 32 with respect to ２ The ratio of (= (C ２ / C １ ) × 100) is preferably 70% or more and 130% or less, more preferably 80% or more and 120% or less, even more preferably 90% or more and 110% or less, and most preferably 100%. １ The thickness T of the second carrier 32 ２ The ratio of (= (T ２ / T １) × 100) is preferably 20% or more and 180% or less, more preferably 40% or more and 160% or less, even more preferably 60% or more and 140% or less, still more preferably 80% or more and 120% or less, particularly preferably 90% or more and 110% or less, and most preferably 100%. By doing so, the warpage of the first carrier 12 and the warpage of the second carrier 32 are effectively canceled out, and as a result, the warpage of the laminate can be suppressed even more effectively.

[0049] The optional first intermediate layer 14 is interposed between the first carrier 12 and the first release layer 16 and contributes to ensuring adhesion between the first carrier 12 and the first release layer 16. Examples of metals constituting the first intermediate layer 14 include Cu, Ti, Al, Nb, Zr, Cr, W, Ta, Co, Ag, Ni, In, Sn, Zn, Ga, Mo, and combinations thereof (hereinafter sometimes referred to as metal M). Preferred are Cu, Ti, Al, Nb, Zr, Cr, W, Ta, Co, Ag, Ni, Mo, and combinations thereof. More preferred are Cu, Ti, Zr, Al, Cr, W, Ni, Mo, and combinations thereof. Even more preferred are Cu, Ti, Al, Cr, Ni, Mo, and combinations thereof. Particularly preferred are Cu, Ti, Al, Ni, and combinations thereof. The first intermediate layer 14 may be a pure metal or an alloy. The metal constituting the first intermediate layer 14 may contain impurities resulting from the raw material components, the film formation process, etc. Furthermore, although not particularly limited, if the first intermediate layer 14 is exposed to the atmosphere after deposition, the presence of oxygen due to this is acceptable. The upper limit of the metal content is not particularly limited and may be 100 atomic %. The first intermediate layer 14 is preferably a layer formed by physical vapor deposition (PVD), more preferably a layer formed by sputtering. From the viewpoint of uniformity of film thickness distribution, it is particularly preferable that the first intermediate layer 14 be a layer formed by magnetron sputtering using a metal target. The thickness of the first intermediate layer 14 is preferably 10 nm to 1000 nm, more preferably 30 nm to 800 nm, even more preferably 60 nm to 600 nm, and particularly preferably 100 nm to 400 nm. By achieving such a thickness, it is possible to obtain an intermediate layer having a roughness equivalent to that of the carrier. 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).

[0050] The first intermediate layer 14 may have a single layer structure or a two or more layer structure. When the first intermediate layer 14 has a single layer structure, the first intermediate layer 14 is preferably a layer containing a metal such as Cu, Al, Ti, Ni, or a combination thereof (e.g., an alloy or an intermetallic compound), more preferably Al, Ti, or a combination thereof (e.g., an alloy or an intermetallic compound), and even more preferably a layer containing mainly Al or a layer containing mainly Ti. On the other hand, when a metal or alloy that does not have sufficiently high adhesion to the first carrier 12 is used for the first intermediate layer 14, it is preferable that the first intermediate layer 14 have a two-layer structure. That is, by providing a layer made of a metal (e.g., Ti) or alloy that has excellent adhesion to the first carrier 12 adjacent to the first carrier 12 and providing a layer made of a metal (e.g., Cu) or alloy that has poor adhesion to the first carrier 12 adjacent to the first release layer 16, adhesion to the first carrier 12 can be improved. Therefore, a preferred example of a two-layer structure for the first intermediate layer 14 is a laminated structure consisting of a Ti-containing layer adjacent to the first carrier 12 and a Cu-containing layer adjacent to the first release layer 16. Furthermore, changing the balance of the constituent elements and thicknesses of each layer in the two-layer structure will also change the peel strength, so it is preferable to appropriately adjust the constituent elements and thicknesses of each layer. In this specification, the category of "metal M-containing layer" also includes alloys containing elements other than metal M, as long as they do not impair the releasability of the carrier. Therefore, the first intermediate layer 14 can also be said to be a layer primarily containing metal M. From the above perspectives, the content of metal M in the first intermediate layer 14 is preferably 50 atomic % to 100 atomic %, more preferably 60 atomic % to 100 atomic %, even more preferably 70 atomic % to 100 atomic %, particularly preferably 80 atomic % to 100 atomic %, and most preferably 90 atomic % to 100 atomic %.

[0051] When the first intermediate layer 14 is made of an alloy, a preferred example of the alloy is a Ni alloy. The Ni alloy preferably has a Ni content of 45% by weight or more and 98% by weight or less, more preferably 55% by weight or more and 90% by weight or less, and even more preferably 65% ​​by weight or more and 85% by weight or less. A preferred Ni alloy is an alloy of Ni and at least one selected from the group consisting of Cr, W, Ta, Co, Cu, Ti, Zr, Si, C, Nd, Nb, and La, more preferably an alloy of Ni and at least one selected from the group consisting of Cr, W, Cu, and Si. When the first intermediate layer 14 is a Ni alloy layer, it is particularly preferred that the layer be formed by magnetron sputtering using a Ni alloy target in terms of uniformity of film thickness distribution.

[0052] The first release layer 16 is a layer that enables or facilitates the peeling of the first carrier 12 and, if present, the first intermediate layer 14. The first release layer 16 may be peelable by physical force application or by laser lift-off (LLO). When the first release layer 16 is made of a material that can be peeled by laser lift-off, it may be made of a resin whose interfacial adhesive strength decreases upon irradiation with a laser beam after curing, or it may be a layer of silicon, silicon carbide, metal oxide, or the like that is modified by laser beam irradiation. The first release layer 16 may be either an organic or inorganic release layer. Examples of organic components used in organic release layers include nitrogen-containing organic compounds, sulfur-containing organic compounds, carboxylic acids, etc. Examples of nitrogen-containing organic compounds include triazole compounds and imidazole compounds. On the other hand, examples of inorganic components used in the inorganic release layer include metal oxides or metal oxynitrides containing at least one of Ni, Mo, Co, Cr, Fe, Ti, W, P, Zn, Cu, Al, Nb, Zr, Ta, Ag, In, Sn, and Ga, or carbon layers. Among these, the first release layer 16 is preferably a carbon-containing layer, i.e., a layer primarily containing carbon, from the viewpoints of ease of release and film formability, more preferably a layer primarily composed of carbon or hydrocarbons, and even more preferably a layer composed of amorphous carbon, which is a hard carbon film. In this case, the carbon concentration of the first release layer 16 (i.e., the carbon-containing layer), 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 85 atomic % or more. The upper limit of the carbon concentration is not particularly limited and may be 100 atomic %, but 98 atomic % or less is practical. The first release layer 16 may contain impurities (e.g., oxygen, hydrogen, etc. derived from the ambient environment such as the atmosphere). Furthermore, the first release layer 16 may contain metal atoms of types other than the metal contained in the first release layer 16 due to the film formation method of the first metal layer 18, etc.When a carbon-containing layer is used as the first release layer 16, it has low interdiffusibility and reactivity with the carrier. Even when subjected to press processing or the like at temperatures exceeding 300°C, it is possible to prevent the formation of a metallic bond between the first metal layer and the bonding interface due to high-temperature heating, thereby maintaining a state in which the carrier can be easily peeled off and removed. This first release layer 16 is also preferably formed by a vapor phase method such as sputtering, in terms of suppressing excessive impurities in the first release layer 16 and facilitating continuous production with the deposition of the first intermediate layer 14, which is provided as desired. When a carbon-containing layer is used as the first release layer 16, its thickness is preferably 1 nm or more and 20 nm or less, more preferably 1 nm or more and 10 nm or less. By setting the thickness in this range, it is possible to obtain a release layer having the same roughness as the carrier and having peeling properties. This thickness is a value measured by analyzing the layer cross section using an energy dispersive X-ray spectrometer (TEM-EDX) of a transmission electron microscope.

[0053] The first release layer 16 may include a metal oxide layer and a carbon-containing layer, or may include both a metal oxide and carbon. In particular, when the carrier-attached metal foil includes the first intermediate layer 14, the carbon-containing layer contributes to stable release of the first carrier 12, while the metal oxide layer can suppress the diffusion of metal elements derived from the first intermediate layer 14 and the first metal layer 18 that occurs during heating. As a result, stable release properties can be maintained even after heating at high temperatures, such as 350°C or higher. The metal oxide layer is preferably a layer containing a metal oxide composed of Cu, Ti, Al, Nb, Zr, Cr, W, Ta, Co, Ag, Ni, In, Sn, Zn, Ga, Mo, or a combination thereof. The metal oxide layer is preferably formed by reactive sputtering, which involves sputtering using a metal target under an oxidizing atmosphere, because the film thickness can be easily controlled by adjusting the film formation time. The thickness of the metal oxide layer is preferably 0.1 nm or more and 100 nm or less. The upper limit of the thickness of the metal oxide layer is more preferably 60 nm or less, even more preferably 30 nm or less, and particularly preferably 10 nm or less. This thickness is a value measured by analyzing the layer cross section with a transmission electron microscope energy dispersive X-ray spectrometer (TEM-EDX). In this case, the order in which the metal oxide layer and the carbon layer are stacked as the first release layer 16 is not particularly limited. Furthermore, the first release layer 16 may exist in a mixed phase state (i.e., a layer containing both metal oxide and carbon) in which the boundary between the metal oxide layer and the carbon-containing layer is not clearly defined.

[0054] Similarly, from the viewpoint of maintaining stable peelability even after heat treatment at high temperatures, the first peel layer 16 may be a metal-containing layer whose surface adjacent to the first metal layer 18 is a fluoride-treated surface and / or a nitride-treated surface. The metal-containing layer preferably has a region (hereinafter referred to as "(F+N) region") in which the sum of the fluorine content and the nitrogen content is 1.0 atomic % or more, present over a thickness of 10 nm or more, and the (F+N) region preferably exists on the first metal layer 18 side of the metal-containing layer. The thickness of the (F+N) region (SiO ２The "electron density" (density converted) is a value determined by performing depth direction elemental analysis of the carrier-attached metal foil using XPS. The fluoride-treated surface or nitride-treated surface can be preferably formed by reactive ion etching (RIE) or reactive sputtering. On the other hand, the metal element contained in the metal-containing layer preferably has a negative standard electrode potential. Preferred examples of the metal element contained in the metal-containing layer include Cu, Ag, Sn, Zn, Ti, Al, Nb, Zr, W, Ta, Mo, and combinations thereof (e.g., alloys and intermetallic compounds). The content of the metal element in the metal-containing layer is preferably 50 atomic % or more and 100 atomic % or less. The metal-containing layer may be a single layer composed of one layer, or a multilayer composed of two or more layers. The thickness of the entire metal-containing layer is preferably 10 nm to 1000 nm, more preferably 30 nm to 500 nm, even more preferably 50 nm to 400 nm, and particularly preferably 100 nm to 300 nm. The thickness of the metal-containing layer itself is a value measured by analyzing a cross section of the layer with a transmission electron microscope energy dispersive X-ray spectrometer (TEM-EDX).

[0055] Alternatively, the first release layer 16 may be a metal oxynitride-containing layer instead of a carbon layer or the like. The surface of the metal oxynitride-containing layer opposite the first carrier 12 (i.e., the first metal layer 18 side) preferably contains at least one metal oxynitride selected from the group consisting of TaON, NiON, TiON, NiWON, and MoON. Furthermore, in order to ensure adhesion between the first carrier 12 and the first metal layer 18, the surface of the metal oxynitride-containing layer facing the first carrier 12 preferably contains at least one metal oxynitride selected from the group consisting of Cu, Ti, Ta, Cr, Ni, Al, Mo, Zn, W, TiN, and TaN. This reduces the number of foreign particles on the surface of the first metal layer 18, improving circuit formability and enabling stable peel strength to be maintained even after heating at high temperatures for a long period of time. The thickness of the metal oxynitride-containing layer is preferably 5 nm to 500 nm, more preferably 10 nm to 400 nm, even more preferably 20 nm to 200 nm, and particularly preferably 30 nm to 100 nm, as measured by analyzing a cross section of the layer with a transmission electron microscope energy dispersive X-ray spectrometer (TEM-EDX).

[0056] The first metal layer 18 is a layer composed of metal. The first metal layer 18 may be composed of a single layer or two or more layers. When the first metal layer 18 is composed of two or more layers, the first metal layer 18 can be composed of metal layers from the first layer to the mth layer (m is an integer of 2 or greater) stacked in order on the side of the first release layer 16 opposite the first carrier 12. The total thickness of the first metal layer 18 is preferably 1 nm to 2000 nm, more preferably 100 nm to 1500 nm, more preferably 200 nm to 1000 nm, even more preferably 300 nm to 800 nm, and particularly preferably 350 nm to 500 nm. The thickness of the first metal layer 18 is measured by analyzing the layer cross section using an energy dispersive X-ray spectrometer (TEM-EDX) of a transmission electron microscope. Below, an example in which the first metal layer 18 is composed of a first layer and a second layer will be described.

[0057] The first layer of the first metal layer 18 preferably provides the carrier-attached metal foil with desired functions, such as an etching stopper function or an anti-reflection function. Preferred examples of metals constituting the first layer include Ti, Al, Nb, Zr, Cr, W, Ta, Co, Ag, Ni, Mo, and combinations thereof. More preferred are Ti, Zr, Al, Cr, W, Ni, Mo, and combinations thereof. Even more preferred are Ti, Al, Cr, Ni, Mo, and combinations thereof. Ti and Mo are particularly preferred. These elements are less soluble in flash etching solutions (e.g., copper flash etching solutions), thereby providing excellent chemical resistance to the flash etching solutions. Therefore, the first layer is less susceptible to etching by flash etching solutions than the second layer described below, and therefore can function as an etching stopper layer capable of slowing the progression of etching. Furthermore, since the above-mentioned metal constituting the first layer also has the function of preventing light reflection, the first layer can also function as an anti-reflection layer to improve visibility in image inspection (e.g., automated image inspection (AOI)). The first layer may be a pure metal or an alloy. The metal constituting the first layer may contain impurities resulting from raw material components, the film formation process, etc. The upper limit of the content of the above metal is not particularly limited and may be 100 atomic %. The first layer is preferably a layer formed by a physical vapor deposition (PVD) method, more preferably a layer formed by sputtering. The thickness of the first layer is preferably 1 nm or more and 500 nm or less, more preferably 10 nm or more and 400 nm or less, even more preferably 30 nm or more and 300 nm or less, and particularly preferably 50 nm or more and 200 nm or less.

[0058] Preferred examples of metals constituting the second layer of the first metal layer 18 include transition elements of Groups 4, 5, 6, 9, 10, and 11, Al, and combinations thereof (e.g., alloys and intermetallic compounds), more preferably transition elements of Groups 4 and 11, Al, Nb, Co, Ni, Mo, and combinations thereof, even more preferably transition elements of Group 11, Ti, Al, Mo, and combinations thereof, particularly preferably Cu, Ti, Mo, and combinations thereof, and most preferably Cu. The second layer may be manufactured by any method, and may be a metal foil formed by, for example, a wet film formation method such as electroless metal plating and electrolytic metal plating, a physical vapor deposition (PVD) method such as sputtering and vacuum evaporation, a chemical vapor deposition method, or a combination thereof. A particularly preferred second layer is a metal layer formed by a physical vapor deposition (PVD) method such as sputtering or vacuum deposition, most preferably a metal layer manufactured by sputtering, from the viewpoint of easily adapting to fine pitches through ultra-thinning. Furthermore, the second layer is preferably a metal layer that has not been roughened, but may be subjected to secondary roughening treatment such as preliminary roughening treatment, soft etching treatment, cleaning treatment, or oxidation-reduction treatment, as long as it does not interfere with wiring pattern formation. From the viewpoint of adapting to fine pitches, the thickness of the second layer is preferably 10 nm to 1000 nm, more preferably 20 nm to 900 nm, even more preferably 30 nm to 700 nm, even more preferably 50 nm to 600 nm, particularly preferably 70 nm to 500 nm, and most preferably 100 nm to 400 nm. A metal layer having a thickness within this range is preferably manufactured by sputtering from the viewpoint of in-plane uniformity of the deposited film thickness and productivity in sheet or roll form.

[0059] When the first metal layer 18 has a single-layer configuration, it is preferable to directly employ the second layer described above as the first metal layer 18. On the other hand, when the first metal layer 18 has an n-layer configuration (n is an integer of 3 or greater), it is preferable that the first to (n-1)th layers of the first metal layer 18 have the first layer configuration described above, and it is preferable that the outermost layer of the first metal layer 18, i.e., the nth metal layer, have the second layer configuration described above.

[0060] The first intermediate layer 14 (if present), the first release layer 16, and the first metal layer 18 are preferably physical vapor deposition (PVD) films, i.e., films formed by a physical vapor deposition (PVD) method, and more preferably sputtered films, i.e., films formed by a sputtering method.

[0061] It is preferable that the first metal layer 18, optionally the first intermediate layer 14, and optionally the first release layer 16 (i.e., at least the first metal layer 18, e.g., the first metal layer 18 and the first intermediate layer 14) extend to the end face of the first carrier 12, thereby covering the end face. That is, it is preferable that not only the surface but also the end face of the first carrier 12 are covered with at least the first metal layer 18. Covering the end face not only prevents infiltration of chemicals into the first carrier 12 during the wiring board manufacturing process, but also firmly prevents chipping due to peeling at the side edge when handling the carrier-attached metal foil, i.e., chipping of the coating on the first release layer 16 (i.e., the first metal layer 18). The coated area on the end face of the first carrier 12 is preferably 0.1 mm or more, more preferably 0.2 mm or more, from the surface of the first carrier 12 in the thickness direction (i.e., the direction perpendicular to the carrier surface), and even more preferably extends over the entire end face of the first carrier 12.

[0062] The overall thickness of the carrier-attached metal foil is not particularly limited, but is preferably 500 μm or more and 3000 μm or less, more preferably 700 μm or more and 2500 μm or less, even more preferably 900 μm or more and 2000 μm or less, and particularly preferably 1000 μm or more and 1700 μm or less. The size of the carrier-attached metal foil is not particularly limited, but is preferably 10 cm or more in diameter or 10 cm square or more, more preferably 20 cm or more in diameter or 20 cm square or more, and even more preferably 25 cm or more in diameter or 25 cm square or more. The upper limit of the size of the carrier-attached metal foil is not particularly limited, but a diameter of 1000 cm or 1000 cm square is cited as one guideline for the upper limit. Furthermore, the carrier-attached metal foil is in a form that can be handled by itself.

[0063] Laminate According to a preferred aspect of the present invention, a laminate including the carrier-attached metal foil is provided. This laminate includes a carrier-attached metal foil, a first rewiring layer 20 provided on the first metal layer 18 of the carrier-attached metal foil, and a second rewiring layer 40 or an insulating layer provided on the second metal layer 38 (or on the second carrier 32 if the second release layer 36 and the second metal layer 38 are not present). The laminate preferably further includes a first buildup layer 46 provided on the first rewiring layer 20 and a second buildup layer 48 provided on the second rewiring layer 40 or the insulating layer. The laminate according to this aspect corresponds to the third laminate 44 or the fourth laminate 50 in the above-described method for manufacturing a rewiring laminate. Therefore, this laminate can be used to manufacture a rewiring laminate with reduced warpage. Preferred aspects of the first rewiring layer 20, the second rewiring layer 40, the first buildup layer 46, and the second buildup layer 48 are as described above.

[0064] The present invention will be explained in more detail by the following examples, but the present invention is not limited to the following examples.

[0065] Example A1: An insulating layer was formed on the metal layer of a metal foil with a carrier to prepare a first laminate and a second laminate, respectively, and then these were bonded together to obtain a third laminate. The degree of warping of the obtained first laminate and third laminate was observed. Specifically, the results are as follows.

[0066] (1) Preparation of the First Laminate A 236.4 mm x 241.0 mm, 1.1 mm thick glass substrate (material: soda lime glass, linear expansion coefficient: 8.5 ppm / K) was prepared as the first carrier 12. On this first carrier 12, a titanium layer (50 nm thick) and a copper layer (200 nm thick) were deposited by sputtering as the two-layer first intermediate layer 14, an amorphous carbon layer (6 nm thick) was deposited as the first release layer 16, and a titanium layer (100 nm thick) and a copper layer (300 nm thick) were deposited as the two-layer first metal layer 18 in this order to obtain a first carrier-attached metal foil 10. The first metal layer 18 was deposited so as to extend to the end face of the first carrier 12, thereby covering the end of the first release layer 16.

[0067] An interlayer insulating material (GX-T31, manufactured by Ajinomoto Fine-Techno Co., Ltd., thickness 20 μm) was laminated on the first metal layer 18 of the first carrier-attached metal foil 10, and a lamination process was performed for 60 seconds using a vacuum laminator (MVLP-500 / 600, manufactured by Meiki Seisakusho Co., Ltd.) at a temperature of 100°C and a pressure of 0.55 MPa. This was then subjected to a heat curing process at 100°C for 30 minutes, followed by a heat curing process at 190°C for 30 minutes to form an insulating layer. The above process was repeated five times to form an insulating layer 20b with a thickness of 100 μm, thereby obtaining a first laminate 22. In this example, a wiring layer was not formed because the purpose was to confirm the degree of warping in the laminate. However, a first laminate 22 equipped with a first rewiring layer 20 can be obtained by forming a wiring layer before laminating each insulating layer.

[0068] The obtained first laminate 22 was placed on a flat surface on a stage, and the warpage at the end of the first laminate 22 (the height from the flat surface to the bottom surface of the first carrier 12) was measured with a ruler (see FIG. 4). The results are shown in Table 1.

[0069] (2) Preparation of second laminate In the same manner as in (1) above, an insulating layer 40b was formed on the second metal layer 38 of the second carrier-attached metal foil 30 having the second carrier 32, the second intermediate layer 34, the second release layer 36 and the second metal layer 38 in this order, to obtain a second laminate 42.

[0070] (3) Bonding of the First Laminate and the Second Laminate Using a roll laminator (MP-600, manufactured by MCK Corporation), a thermosetting epoxy resin adhesive film (TSA-1602, manufactured by Toray Industries, Inc., thickness 20 μm) was laminated as the adhesive layer 24 on the surface of the first laminate 22 facing the first carrier 12 at a roll temperature of 100°C. Next, under the same roll conditions, the first carrier 12 of the first laminate 22 and the second carrier 32 of the second laminate 42 were bonded together via the adhesive layer 24. Thereafter, a heat curing treatment was performed at a temperature of 100°C for 60 minutes, and then a heat curing treatment was performed at a temperature of 170°C for 120 minutes to harden the adhesive layer 24, thereby obtaining a third laminate 44. When the edge of the third laminate 44 obtained using the same method as the first laminate 22 was observed (see FIG. 5), no warping was observed.

[0071] Example A2 The first laminate 22, the second laminate 42, and the third laminate 44 were produced in the same manner as in Example A1, except that borosilicate glass (linear expansion coefficient: 3.2 ppm / K) was used instead of soda lime glass for the first carrier 12 and the second carrier 32. The observation results for warpage at the ends of the first laminate 22 and the third laminate 44 were as shown in Table 1.

[0072] Example A3: The first laminate 22, the second laminate 42, and the third laminate 44 were produced in the same manner as in Example A1, except that the number of repetitions of the lamination of the interlayer insulating material and the heat curing treatment was changed to three, thereby forming insulating layers 20b, 40b with a thickness of 60 μm. The observation results for warpage at the ends of the first laminate 22 and the third laminate 44 are shown in Table 1.

[0073] Example A4 The first laminate 22, the second laminate 42, and the third laminate 44 were produced in the same manner as in Example A2, except that the number of repetitions of the lamination of the interlayer insulating material and the heat curing treatment was changed to three, thereby forming insulating layers 20b, 40b with a thickness of 60 μm. The observation results of warpage at the ends of the first laminate 22 and the third laminate 44 are shown in Table 1.

[0074] Example A5 A first laminate 22, a second laminate 42, and a third laminate 44 were produced in the same manner as in Example A1, except that the production process for the first laminate and the production process for the second laminate were changed as shown in a) and b) below, respectively. The results of observation of warpage at the ends of the first laminate 22 and the third laminate 44 were as shown in Table 1. a) A first laminate 22 including a 100 μm-thick first rewiring layer 20 was produced by alternately forming five layers of wiring layers made of copper and five layers of insulating layers made of the interlayer insulating material on the first metal layer 18 of the first carrier-attached metal foil 10 by a coreless build-up method. b) A second laminate 42 including a 100 μm-thick second rewiring layer 40 was produced in the same manner as in a) above.

[0075] Example A6 A first laminate 22, a second laminate 42, and a third laminate 44 were produced in the same manner as in Example A5, except that borosilicate glass (linear expansion coefficient: 3.2 ppm / K) was used instead of soda lime glass for the first carrier 12 and the second carrier 32. The observation results of warpage at the ends of the first laminate 22 and the third laminate 44 are shown in Table 1.

[0076]

[0077] Example B1 The metal foil with a carrier of the present invention was produced according to the procedure shown in Figure 6. Then, an insulating layer was formed on both sides of this metal foil with a carrier to obtain a laminate. In addition, the obtained laminate was observed for the occurrence of warpage. Specifically, the following procedure was followed.

[0078] (1) Preparation of Carrier-Attached Metal Foil First, a 300 mm x 300 mm, 1.1 mm thick glass substrate (material: soda lime glass, linear expansion coefficient: 8.5 ppm / K) was prepared as the first carrier 12. On this first carrier 12, a titanium layer (50 nm thick) and a copper layer (200 nm thick) were deposited by sputtering as the two-layer first intermediate layer 14, an amorphous carbon layer (6 nm thick) was deposited as the first release layer 16, and a titanium layer (100 nm thick) and a copper layer (300 nm thick) were deposited as the two-layer first metal layer 18 in this order (see FIG. 6(i)). The first metal layer 18 was deposited so as to extend to the end face of the first carrier 12, thereby covering the end of the first release layer 16.

[0079] Using a roll laminator (MP-600 manufactured by MCK Corporation), an adhesive film made of a thermosetting epoxy resin (TSA-1602 manufactured by Toray Industries, Inc., thickness 20 μm) was laminated as the adhesive layer 24 on the surface of the first carrier-attached metal foil 10 on the first carrier 12 side under the condition of a roll temperature of 100° C., and then the polyethylene terephthalate (PET) film as the substrate supporting the adhesive layer 24 was peeled off (see FIG. 6(ii)).

[0080] The second carrier-equipped metal foil 30 was produced by the same procedure as the above-mentioned first carrier-equipped metal foil 10. That is, the second carrier-equipped metal foil 30 comprises a second carrier 32, a second intermediate layer 34, a second release layer 36, and a second metal layer 38, in this order (see FIG. 6(iii)). The first carrier-equipped metal foil 10 and the second carrier-equipped metal foil 30 were bonded together via the adhesive layer 24 so that the second carrier 32 of the second carrier-equipped metal foil 30 was in contact with the surface of the adhesive layer 24 from which the PET film had been peeled. Thereafter, a heat curing treatment was performed at a temperature of 100°C for 60 minutes, and further at a temperature of 170°C for 120 minutes, thereby curing the adhesive layer 24. In this way, a carrier-equipped metal foil was obtained in which the first carrier-equipped metal foil 10 and the second carrier-equipped metal foil 30 were stacked symmetrically above and below (see FIG. 6(iv)).

[0081] (2) Preparation of Laminate Interlayer insulating material (Ajinomoto Fine-Techno Co., Ltd., GX-T31, thickness 35 μm) was laminated on both sides of the obtained carrier-attached metal foil, and a vacuum laminator (Meiki Seisakusho Co., Ltd., MVLP-500 / 600) was used to perform a vacuum lamination process for 60 seconds at a temperature of 100 ° C. and a pressure of 0.7 Pa. Then, a first heat curing treatment was performed at a temperature of 100 ° C. for 30 minutes, a second heat curing treatment at a temperature of 170 ° C. for 30 minutes, and a third heat curing treatment at a temperature of 190 ° C. for 60 minutes to form an insulating layer with a thickness of approximately 35 μm. In this example, the purpose was to confirm whether or not warping occurred in the laminate, so a wiring layer was not formed. However, a laminate with a rewiring layer can be obtained by forming a wiring layer before or after laminating the insulating layer.

[0082] The obtained laminate was placed on a flat surface on a stage, and an attempt was made to measure the warpage at the end of the laminate (the height from the flat surface to the bottom surface of the insulating layer) using a ruler, but no warpage of the laminate was observed (i.e., the warpage was 0 mm).

[0083] Example B2 A laminate was produced in the same manner as in Example B1, except that in (2) above, an insulating layer with a thickness of about 70 μm was formed on both sides of the metal foil with a carrier. The obtained laminate was placed on a flat surface on a stage, and an attempt was made to measure the warpage at the edge of the laminate (the height from the flat surface to the bottom surface of the insulating layer) with a ruler. However, no warpage of the laminate was observed (i.e., the warpage was 0 mm).

[0084] Example B3: A laminate was produced in the same manner as in Example B1, except that in (2) above, an insulating layer having a thickness of about 100 μm was formed on both sides of the metal foil with a carrier. The obtained laminate was placed on a flat surface on a stage, and an attempt was made to measure the warpage at the edge of the laminate (the height from the flat surface to the bottom surface of the insulating layer) with a ruler. However, no warpage of the laminate was observed (i.e., the warpage was 0 mm).

Claims

1. A method for manufacturing a redistribution laminate, comprising the steps of: forming a first redistribution layer having a thickness of 100 μm or less on a first metal layer of a metal foil with a first carrier, the first metal layer being provided in that order, to obtain a first laminate; preparing a second laminate having a second redistribution layer or a dummy insulating layer having a thickness of 100 μm or less on a second carrier; and bonding the first carrier of the first laminate and the second carrier of the second laminate together via an adhesive layer containing an adhesive material to obtain a third laminate.

2. A method for manufacturing a redistribution layer stack as described in claim 1, further comprising the steps of forming a first build-up layer on the first redistribution layer of the third stack, and forming a second build-up layer on the second redistribution layer or the dummy insulating layer of the third stack, to obtain a fourth stack.

3. The method for manufacturing a redistribution layer stack according to claim 2, further comprising the step of peeling off the first carrier from the fourth layer stack.

4. A method for manufacturing a rewiring laminate described in any one of claims 1 to 3, wherein the second laminate comprises the second rewiring layer, and the process of preparing the second laminate includes forming the second rewiring layer on the second metal layer of a metal foil with a second carrier comprising the second carrier, a second release layer, and a second metal layer in this order.

5. A method for manufacturing a redistribution layer stack according to any one of claims 1 to 3, wherein each of the first carrier and the second carrier has a linear expansion coefficient of 2.0 ppm / K or more and 30.0 ppm / K or less.

6. The thickness T of the first rewiring layer Ｒ１ The thickness T of the second rewiring layer or the dummy insulating layer Ｒ２ The ratio T Ｒ２ / T Ｒ１ The method for producing a redistribution layered body according to any one of claims 1 to 3, wherein the ratio of the thickness of the redistribution layered body to the thickness of the redistribution layered body is 0.1 or more and 30.0 or less.

7. A method for manufacturing a redistribution layer stack according to any one of claims 1 to 3, wherein the step of forming the first redistribution layer comprises the steps of: forming a first wiring layer on a surface of the first metal layer; and alternately forming insulating layers and wiring layers on the surface of the first metal foil with carrier on which the first wiring layer is formed, to obtain a first redistribution layer in which the first wiring layer is embedded in the form of an embedded wiring layer.

8. The method for producing a redistribution layer stack according to claim 7, wherein the insulating layer is made of an insulating resin containing at least one selected from the group consisting of a thermosetting epoxy resin, a thermosetting polyimide resin, and a thermosetting phenolic resin.

9. The method for producing a redistribution layer stack according to any one of claims 1 to 3, wherein the adhesive material includes a solventless adhesive.

10. A method for producing a redistribution layer stack according to any one of claims 1 to 3, wherein the adhesive material comprises at least one selected from the group consisting of thermosetting epoxy resin, thermosetting polyimide resin, photosensitive polyimide resin, acrylic resin, and phenolic resin.

11. The method for producing a redistribution layer stack according to any one of claims 1 to 3, wherein the adhesive layer has a thickness of 5 μm or more and 1000 μm or less.

12. The method for manufacturing a redistribution layer stack according to claim 2 or 3, wherein each of the first buildup layer and the second buildup layer has a thickness of 20 μm or more.

13. Thickness T of the first build-up layer Ｂ１ The thickness T of the second build-up layer Ｂ２ The ratio T Ｂ２ / T Ｂ１ The method for producing a redistribution layered body according to claim 2 , wherein the ratio of the redistribution layered body to the redistribution layered body is 0.5 or more and 1.5 or less.

14. The method for manufacturing a redistribution layer stack according to claim 2 or 3, wherein each of the first buildup layer and the second buildup layer includes a prepreg.

15. A metal foil with a carrier comprising: a first carrier; a first release layer provided on the first carrier; a first metal layer provided on the first release layer; an adhesive layer containing an adhesive material provided on the surface of the first carrier opposite the first release layer; and a second carrier provided on the first carrier via the adhesive layer.

16. The metal foil with a carrier according to claim 15, further comprising a second release layer provided on the second carrier, and a second metal layer provided on the second release layer.

17. A laminate comprising: a metal foil with a carrier according to claim 16; a first redistribution layer provided on the first metal layer of the metal foil with a carrier; and a second redistribution layer or an insulating layer provided on the second metal layer of the metal foil with a carrier.

18. The laminate according to claim 17, further comprising a first buildup layer provided on the first redistribution layer, and a second buildup layer provided on the second redistribution layer or the insulating layer.

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