Method for manufacturing multilayer wiring board

Abstract

The present invention is a method for manufacturing a multilayer wiring board, the method comprising: a board preparation step for preparing a wiring board having an organic insulating film and a metal film on the organic insulating film; an opening formation step for providing an opening in the metal film; and an organic insulating film removal step for removing the organic insulating film from the opening by using the metal film provided with the opening as a mask. The thickness of the metal film is 100 nm or less. Thus, since the film thickness of the metal film is thin, peeling due to thermal expansion can be suppressed. In addition, the need for roughening of the base of the metal film is eliminated, or the time for the roughening step can be shortened. Furthermore, since the film thickness of the metal film is thin, the opening can be easily formed in the metal film. As a result, the present invention provides a method for manufacturing a multilayer wiring board with which it is possible to manufacture a multilayer wiring board with high productivity and low cost.

Description

Method for manufacturing multilayer wiring substrate

[0001] The present invention relates to a method for manufacturing a multilayer wiring substrate.

[0002] Multilayer wiring substrates, for example semiconductor package substrates, have been developed mainly for the purpose of improving packaging density. Furthermore, multilayer wiring substrates are trending toward larger sizes. In a multilayer wiring substrate, for example, trenches for in-layer connection and via holes for interlayer connection are formed. Various proposals have been made as techniques for forming via holes and trenches in multilayer wiring substrates. For example, Patent Documents 1 to 3 describe using a conductive layer or a metal foil as a mask when forming trenches or vias by laser irradiation. It is known to perform window processing by irradiating a conductive layer with laser, and also process an interlayer insulating film such as a resin layer.

[0003] Japanese Patent Application Laid-Open No. 2001-44642, Japanese Patent Application Laid-Open No. 11-121931, Japanese Patent Application Laid-Open No. 10-224040

[0004] Conventionally, as the thickness of a metal foil or conductive layer used as a mask during laser irradiation processing, for example, 7 to 50 μm (Patent Document 2) and 0.5 to 50 μm (Patent Document 3) have been adopted. When a metal foil or conductive layer of such a thickness becomes high temperature during laser irradiation processing or the like, there has been a problem that it peels off due to thermal expansion caused by heat conduction. Countermeasures such as roughening the base of the conductive layer or metal foil have been studied against this problem, but there have been problems such as a decrease in productivity and an increase in cost due to the addition of a roughening step and the like.

[0005] The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for manufacturing a multilayer wiring substrate that can manufacture a multilayer wiring substrate with high productivity and low cost.

[0006] The present invention has been made to achieve the above object, and is a method for manufacturing a multilayer wiring substrate comprising: a substrate preparation step of preparing a wiring substrate having an organic insulating film and a metal film on the organic insulating film; an opening forming step of providing an opening in the metal film; and an organic insulating film removing step of removing the organic insulating film from the opening using the metal film provided with the opening as a mask, wherein the thickness of the metal film is 100 nm or less.

[0007] This method for manufacturing multilayer wiring boards allows for a reduction in the time required to form the metal film and a decrease in the amount of material used, due to the thinness of the metal film. Furthermore, delamination due to thermal expansion can be suppressed. Additionally, roughening of the metal film substrate is either unnecessary or the time required for the roughening process can be reduced. Moreover, because the metal film is thin, openings can be easily formed in the metal film. As a result, it becomes possible to manufacture multilayer wiring boards with high productivity and low cost.

[0008] In this case, the manufacturing method for a multilayer wiring board can be made in which the metal film is a Cu film.

[0009] Generally, since copper (Cu) is widely used for conductivity between the upper and lower layers and for intralayer wiring in multilayer wiring boards, using a Cu film for the metal film eliminates or minimizes the need for new equipment. Furthermore, using a Cu film for the metal film allows for good absorption of ultraviolet laser light, which facilitates microfabrication. As the film thickness decreases, the processability improves (processing can be done with a lower energy density), and a larger area can be processed with the same power laser, resulting in higher productivity and lower costs.

[0010] In this case, the method for manufacturing a multilayer wiring substrate can be used, in which the opening is formed by irradiating it with an excimer laser during the opening formation process.

[0011] Using an excimer laser allows for efficient and precise machining.

[0012] In this case, the method for manufacturing a multilayer wiring substrate can be obtained by removing the organic insulating film by irradiating it with an excimer laser in the organic insulating film removal step.

[0013] This allows for more efficient removal of the organic insulating film following the opening formation process.

[0014] In this case, the method for manufacturing a multilayer wiring substrate can be used, in which the organic insulating film removal step is performed by plasma etching to remove the organic insulating film.

[0015] This allows for the simultaneous formation of multiple openings. Furthermore, when forming via holes, it is advantageous in that it facilitates the removal of smear remaining at the bottom of the via holes and prevents the deterioration of further metal films exposed at the bottom of the via holes, for example.

[0016] In this case, the method for manufacturing a multilayer wiring substrate can be one in which trenches are formed during the organic insulating film removal step. Alternatively, the method for manufacturing a multilayer wiring substrate can be one in which via holes are formed during the organic insulating film removal step.

[0017] This allows for the efficient formation of trenches and / or via holes.

[0018] In this case, a method for manufacturing a multilayer wiring board can be used in which multiple openings are formed in the opening formation step, and the spacing between adjacent multiple openings is 5 μm or less.

[0019] This makes it possible to manufacture multilayer wiring boards in which recesses such as trenches and / or via holes are formed at high density.

[0020] As described above, the manufacturing method for multilayer wiring boards of the present invention allows for a reduction in the time required to form the metal film and a reduction in the amount of material used, due to the thin film thickness of the metal film. Furthermore, peeling due to thermal expansion can be suppressed. In addition, roughening of the metal film substrate is either unnecessary or the time required for the roughening process can be shortened. Moreover, because the metal film thickness is thin, openings can be easily formed in the metal film. As a result, it becomes possible to manufacture multilayer wiring boards with high productivity and low cost.

[0021] This document outlines the steps of the manufacturing method for a multilayer wiring substrate according to the present invention. It shows an example of a wiring substrate prepared in the substrate preparation step. It shows an example of a wiring substrate with openings formed in the opening formation step. It shows an example of a wiring substrate with a portion of the organic insulating film removed after openings are formed in the opening formation step. It shows an example of an intermediate substrate after the organic insulating film removal step. It shows a modified example of the intermediate substrate after the organic insulating film removal step. It shows a schematic cross-sectional perspective view of an example of an intermediate substrate after the organic insulating film removal step. It shows an example of a multilayer wiring substrate obtained by the manufacturing method of the multilayer wiring substrate according to the present invention.

[0022] The present invention will be described in detail below, but the present invention is not limited to these descriptions.

[0023] As mentioned above, there was a need for a method of manufacturing multilayer wiring boards that could produce them with high productivity and low cost.

[0024] As a result of diligent study on the above problems, the present inventors have found that a method for manufacturing a multilayer wiring substrate, comprising a substrate preparation step of preparing a wiring substrate having an organic insulating film and a metal film on the organic insulating film, an opening formation step of creating an opening in the metal film, and an organic insulating film removal step of removing the organic insulating film from the opening using the metal film with the opening as a mask, wherein the thickness of the metal film is 100 nm or less, provides the following effects. Specifically, with the method for manufacturing a multilayer wiring substrate according to the present invention, the time required to form the metal film can be shortened and the amount of material used can be reduced because the thickness of the metal film is thin. Furthermore, peeling due to thermal expansion can be suppressed. In addition, roughening of the metal film substrate can be eliminated or the time of the roughening step can be shortened. Furthermore, because the thickness of the metal film is thin, openings can be easily formed in the metal film. The present inventors have found that the method for manufacturing a multilayer wiring substrate according to the present invention makes it possible to manufacture multilayer wiring substrates with high productivity and low cost, and have completed the present invention.

[0025] The steps of the method for manufacturing a multilayer wiring substrate according to the present invention will be described in detail below. Figure 1 shows an overview of the steps of the method for manufacturing a multilayer wiring substrate according to the present invention. As shown in Figure 1, the method for manufacturing a multilayer wiring substrate according to the present invention generally includes a substrate preparation step, an opening formation step, and an organic insulating film removal step.

[0026] [Substrate Preparation Process] In the substrate preparation process shown in Figure 1, a wiring substrate 10 having an organic insulating film 1A and a metal film 2 on the organic insulating film 1A is prepared, for example, as shown in Figure 2. The wiring substrate 10 may further include other combinations of organic insulating films and other metal films, for example, as shown in Figure 2, it may include an organic insulating film 1B and a metal film 3. However, the wiring substrate 10 is not limited to the structure shown in Figure 2, and the number of combinations of organic insulating film 1B and metal film 3 is not limited.

[0027] Furthermore, the wiring board 10 may also include a further metal film 4, as shown in Figure 2. The metal film 4 may be positioned below a pair of organic insulating film 1B and metal film 3, as shown in Figure 2. As shown in Figure 2, the metal film 3 and metal film 4 can be used to sandwich the organic insulating film 1B.

[0028] The metal film 2 is used as a mask (contact mask) in the organic insulating film removal process described later. The thickness of the metal film 2 is 100 nm or less. By making the thickness of the metal film 2 used as a mask in the organic insulating film removal process 100 nm or less, peeling due to thermal expansion can be suppressed. In addition, roughening of the substrate of the metal film 2 becomes unnecessary or the time of the roughening process can be shortened. Furthermore, because the thickness of the metal film 2 is thin, openings can be easily formed in the metal film 2. As a result, it becomes possible to manufacture multilayer wiring boards with high productivity and low cost. The upper limit of the thickness of the metal film 2 can be 50 nm or less or 30 nm or less. The lower limit of the thickness of the metal film 2 is not particularly limited, but for example, it can be 0.1 nm or more, 1 nm or more, or 5 nm or more.

[0029] The thickness of the metal films 3 and 4 is not particularly limited, but for example, it can be 3 μm or more and 35 μm or less, and preferably 5 μm or more and 30 μm or less.

[0030] The materials of metal films 2, 3, and 4 are not particularly limited as long as they are conductive metallic materials or metal-containing materials. For example, the materials of metal films 2, 3, and 4 may contain one or more metals selected from the group consisting of gold, platinum, palladium, silver, copper, aluminum, cobalt, chromium, zinc, nickel, titanium, tungsten, iron, tin, and indium. Furthermore, the materials of metal films 2, 3, and 4 may be single metals or alloys. Examples of alloys include layers formed from alloys of two or more metals selected from the above group (e.g., nickel-chromium alloys, copper-nickel alloys, and copper-titanium alloys).

[0031] The metal films 2, 3, and 4 may have a single-layer structure, or they may have a multi-layer structure comprising two or more single-metal films or alloy films made of different types of metals or alloys.

[0032] In particular, it is preferable that the metal film 2 is a Cu film. When the metal film 2 is a Cu film, Cu is generally widely used for conductivity between the upper and lower layers of multilayer wiring boards and for intralayer wiring. Therefore, by using a Cu film for the metal film, the introduction of new equipment can be eliminated or minimized. Furthermore, by using a Cu film for the metal film, it absorbs laser light in the ultraviolet region, which is easy to microfabricate, well, and the thinner the film thickness, the better the processability (it can be processed with a low energy density). This allows for processing of larger areas with the same power laser, resulting in higher productivity and lower costs.

[0033] The method for forming the metal films 2, 3, and 4 is not particularly limited, but examples include plating, sputtering, and methods combining these. When sheets formed on metal foil are used as the organic insulating films 1A and 1B, the metal foil may be used as the metal films 3 and 4.

[0034] The materials of the organic insulating films 1A and 1B are not particularly limited as long as they are insulating organic materials, but typically examples include build-up materials, solder resists, molding materials, and other process materials. The organic insulating films 1A and 1B are generally preferably cured products of a curable resin composition, but may also be molded products of a thermoplastic resin composition.

[0035] A curable resin composition typically contains a curable resin. Examples of curable resins include thermosetting resins, photocurable resins, and resins that exhibit curability by heat and light. A curable resin composition may use one of these types alone or a combination of several types.

[0036] Examples of thermosetting resins include epoxy resins, bismaleimide resins, phenolic resins, activated ester resins, cyanate resins, carbodiimide resins, acid anhydride resins, amine resins, benzoxazine resins, thiol resins, and radical polymerizable resins. The thermosetting resin may, if necessary, contain a curing agent that reacts with the thermosetting resin to cure the resin composition.

[0037] Examples of photocurable resins include radical polymerizable resins and cationic polymerizable resins. Furthermore, the photocurable resin may contain photoinitiators such as photoradical generators and photoacid generators, as needed.

[0038] Curable resin compositions preferably contain a curable resin from the viewpoint of the mechanical properties of the cured product, but depending on the desired properties, they may also contain a combination of a thermoplastic resin and a radical polymerizable monomer, or a combination of a thermoplastic resin and a cationic polymerizable monomer. Furthermore, these resin compositions may contain fillers and additives, such as inorganic fillers.

[0039] Furthermore, these resin compositions can be provided, for example, in the form of a solution or in the form of a sheet in which a layer of the resin composition is formed on a support.

[0040] The thickness of the organic insulating films 1A and 1B is not particularly limited, but can be, for example, 100 μm or less, preferably 50 μm or less, and more preferably 40 μm or less. The lower limit of this thickness is not particularly limited, but can be 1 μm or more, 5 μm or more, etc.

[0041] [Opening Formation Process] Next, as shown in Figure 1, an opening formation process is performed to form an opening in the metal film 2. The method of forming the opening is not particularly limited. Removal of the metal film 2 in the area to be formed as an opening can be performed as appropriate depending on the material of the metal film 2. In addition to processing by laser irradiation, the opening may also be formed by forming a mask and performing etching. In particular, it is preferable to form the opening by irradiating with an excimer laser. This eliminates the need to form a mask as in the case of etching, thus further improving productivity. Furthermore, using an excimer laser allows for efficient and precise processing.

[0042] When removing the metal film 2 in the region to be the opening by etching, an etching mask can be formed before performing the etching. When the metal film 2 contains Cu, examples of components of the etching solution for Cu include, but are not limited to: chlorides such as ferric chloride and cupric chloride; acids such as hydrochloric acid and ammonium oxalate; oxidizing agents such as hydrogen peroxide and ammonia water; and additives such as water and surfactants.

[0043] In the opening forming step, a plurality of openings 5A and 5B can be provided in the metal film 2 as in the intermediate substrate 10A shown in FIG. 3. In this case, for example, the opening 5A can be an opening for forming a via hole, and the opening 5B can be an opening for forming a trench.

[0044] Furthermore, when forming a plurality of adjacent openings 5A and 5B as shown in FIG. 3, the distance D between the plurality of adjacent openings can be set to 5 μm or less. In the method for manufacturing a multilayer wiring board according to the present invention, the thickness of the metal film 2 is set to 100 nm or less, so damage to the metal film 2 can be prevented as described above, and openings can be formed with high precision. Thereby, a multilayer wiring board in which recesses such as trenches and / or via holes are formed at high density can be manufactured by setting the distance between a plurality of adjacent openings to 5 μm or less.

[0045] [Organic insulating film removing step] As shown in FIG. 1, after forming the opening in the opening forming step, an organic insulating film removing step is performed, in which the organic insulating film is removed from the opening using the metal film 2 provided with the opening as a mask. Thereby, an intermediate substrate 10B having recesses that become via holes 7 and trenches 8 as exemplified in FIG. 5 can be manufactured.

[0046] The method for removing the organic insulating film in the organic insulating film removing step is not particularly limited. For example, a method of removing the organic insulating film by irradiating an excimer laser, and a method of removing the organic insulating film by plasma etching are preferable.

[0047] If the organic insulating film is removed by excimer laser irradiation, the organic insulating film can be removed without interrupting laser irradiation subsequent to the above-described opening forming step, which is preferable from the perspective of improving productivity. In addition, precise processing can be performed efficiently.

[0048] If the organic insulating film is removed by plasma etching, which is a type of dry etching, the organic insulating film 1A can be removed simultaneously in the plurality of openings 5A and 5B, which is preferable from the perspective of improving productivity. Furthermore, when forming a via hole, smear remaining at the bottom of the via hole can be easily removed, and this approach is also advantageous in that, for example, it does not degrade the metal film 3 exposed at the bottom of the via hole.

[0049] By performing excimer laser irradiation or plasma etching in this manner, for example, an intermediate substrate 10B as shown in FIG. 5, or an intermediate substrate 10C as shown in FIG. 6 obtained by further removing the metal film 2 can be obtained.

[0050] In addition, when providing via holes and trenches in the intermediate substrate 10A shown in FIG. 3, it is also effective to remove the organic insulating film by using a combination of excimer laser irradiation and plasma etching. In this case, after forming the opening 5A in the metal film 2 in the above-described opening forming step, excimer laser irradiation is continued to remove a part of the region where the via hole is to be formed in the organic insulating film to form the recess 6A in advance, as shown in FIG. 4. Furthermore, the organic insulating film is either not removed at the region where a trench is to be formed, or a recess 6B having a smaller dimension in the depth direction than the recess 6A formed at the region where a via hole is to be formed is formed in the organic insulating film at the region where a trench is to be formed. Thereafter, the organic insulating film 1 is etched using the metal film 2 provided with the openings 5A and 5B as a mask for such an intermediate substrate 10a, and an etching process for forming the via hole 7 and the trench 8 as shown in FIG. 5 can be performed.

[0051] In this etching process, the areas in the organic insulating film 1 where via holes 7 are to be formed (recesses 6A) and areas where trenches 8 are to be formed (recesses 6B if recesses are already formed) are simultaneously etched in the depth direction. As described above, in the organic insulating film 1A, before the etching process, the lower part of the opening 5A is etched further than the lower part of the opening 5B. Therefore, by performing the etching process through the metal film 2 with openings 5A and 5B on the entire surface of the intermediate substrate 10a, the trenches will not penetrate the organic insulating film 1A when the via hole formation is complete. Thus, via holes and trenches can be formed simultaneously by such a simple etching process.

[0052] By using excimer laser irradiation and plasma etching in combination in this way, for example, an intermediate substrate 10B as shown in Figure 5, and further intermediate substrate 10C as shown in Figures 6 and 7, can be obtained by removing the metal film 2 with openings 5A and 5B.

[0053] The removal of the metal film 2 can be carried out as appropriate depending on the material of the metal film 2. For example, in the case of a metal film 2 containing Cu, the metal film 2 can be easily dissolved and peeled off with an etching solution. Examples of components of the etching solution for Cu include, but are not limited to, chlorides such as ferric chloride and cupric chloride, acids such as hydrochloric acid and ammonium oxalate, oxidizing agents such as hydrogen peroxide and aqueous ammonia, and additives such as water and surfactants.

[0054] If the wiring board 10 has two or more organic insulating films, such as the organic insulating films 1A and 1B shown in Figure 2, a via hole 7 can be provided that penetrates one of the organic insulating films 1A.

[0055] Alternatively, if the wiring board 10 includes a further metal film 4 located below one organic insulating film 1B, the metal film 3 and the organic insulating film 1B can be removed following the removal of the organic insulating film 1A to create via holes that expose the metal film 4.

[0056] Furthermore, in the manufacturing method of the multilayer wiring board of the present invention, pads can be further formed. In this case, the method of forming the pads is not particularly limited. For example, the metal film 2 can be removed by wet etching or the like before forming the pads. Also, for example, when vias and trenches are formed in the metal film 2 as a contact mask layer in different processes, the pad diameter is processed so that the area around the via processing location is processed in the same way as the trench processing area. When vias and trenches are formed in the metal film 2 as a contact mask layer in the same process, a halftone photomask is used to lower the photomask transmittance of the pad and trench areas surrounding the via area compared to the via area, thereby making the processing depth shallower.

[0057] Figure 8 shows an example of a multilayer wiring board 100 after wiring is completed by filling a multilayer wiring board having recesses such as via holes and trenches, which is manufactured by the manufacturing method of the multilayer wiring board of the present invention, with conductive material. The multilayer wiring board 100 according to the present invention comprises vias 7A filled with conductive material, trenches 8B filled with conductive material, and pads 40, as shown in Figure 8.

[0058] The method for manufacturing a multilayer wiring board according to the present invention makes it possible to obtain a multilayer wiring board having recesses such as via holes and trenches with high production efficiency and low cost.

[0059] This specification includes the following embodiments: [1] A method for manufacturing a multilayer wiring substrate, comprising: a substrate preparation step of preparing a wiring substrate having an organic insulating film and a metal film on the organic insulating film; an opening formation step of providing an opening in the metal film; and an organic insulating film removal step of removing the organic insulating film from the opening using the metal film with the opening as a mask, wherein the thickness of the metal film is 100 nm or less. [2] The method for manufacturing a multilayer wiring substrate according to [1], wherein the metal film is a Cu film. [3] The method for manufacturing a multilayer wiring substrate according to [1] or [2], wherein the opening is formed by irradiating with an excimer laser in the opening formation step. [4] The method for manufacturing a multilayer wiring substrate according to [1], [2] or [3], wherein the organic insulating film is removed by irradiating with an excimer laser in the organic insulating film removal step. [5] The method for manufacturing a multilayer wiring substrate according to [1], [2], [3] or [4], wherein the organic insulating film is removed by plasma etching in the organic insulating film removal step. [6]: A method for manufacturing a multilayer wiring substrate according to [1], [2], [3], [4], or [5], wherein a trench is formed in the organic insulating film removal step. [7]: A method for manufacturing a multilayer wiring substrate according to [1], [2], [3], [4], or [5], wherein via holes are formed in the organic insulating film removal step. [8]: A method for manufacturing a multilayer wiring substrate according to [1], [2], [3], [4], [5], [6], or [7], wherein a plurality of openings are formed in the opening formation step, and the spacing between adjacent plurality of openings is 5 μm or less.

[0060] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention.

Claims

1. A method for manufacturing a multilayer wiring substrate, comprising: a substrate preparation step of preparing a wiring substrate having an organic insulating film and a metal film on the organic insulating film; an opening formation step of providing an opening in the metal film; and an organic insulating film removal step of removing the organic insulating film from the opening using the metal film with the opening as a mask, wherein the thickness of the metal film is 100 nm or less.

2. The method for manufacturing a multilayer wiring substrate according to claim 1, wherein the metal film is a Cu film.

3. The method for manufacturing a multilayer wiring substrate according to claim 1, wherein the opening is formed by irradiating it with an excimer laser in the opening formation step.

4. The method for manufacturing a multilayer wiring substrate according to claim 1, wherein the organic insulating film is removed by irradiating it with an excimer laser in the organic insulating film removal step.

5. The method for manufacturing a multilayer wiring substrate according to claim 1, wherein the organic insulating film is removed by plasma etching in the organic insulating film removal step.

6. The method for manufacturing a multilayer wiring substrate according to claim 1, wherein a trench is formed in the organic insulating film removal step.

7. The method for manufacturing a multilayer wiring substrate according to claim 1, wherein via holes are formed in the organic insulating film removal step.

8. A method for manufacturing a multilayer wiring board according to any one of claims 1 to 7, wherein a plurality of openings are formed in the opening formation step, and the spacing between adjacent plurality of openings is 5 μm or less.

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