Method for manufacturing multilayer wiring board

Abstract

The present invention provides 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, wherein the thickness of the metal film is 100 nm or less. As a result, because the metal film is thin, peeling caused by thermal expansion can be suppressed. In addition, the need for roughening the base of the metal film is eliminated, or the time for the roughening step can be shortened. Furthermore, because 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 capable of high-productivity and low-cost manufacture of multilayer wiring boards.

Description

Manufacturing method for multilayer wiring boards

[0001] This invention relates to a method for manufacturing a multilayer wiring board.

[0002] Multilayer wiring boards, such as semiconductor package substrates, have been developed primarily to improve mounting density. Furthermore, multilayer wiring boards are tending to become larger. Multilayer wiring boards have features such as trenches for intralayer connections and via holes for interlayer connections. Various techniques have been proposed for forming via holes and trenches in multilayer wiring boards. For example, Patent Documents 1-3 describe the use of conductive layers or metal foil as masks when forming trenches and vias by laser irradiation. It is known that a window is created by irradiating a conductive layer with a laser, and that interlayer insulating films such as resin layers are also processed in this way.

[0003] JP 2001-44642, JP 11-121931, JP 10-224040, JP 7-273458

[0004] Conventionally, metal foils and conductive layers used as masks during laser irradiation processing have been found to have thicknesses of, for example, 7 to 50 μm (Patent Document 2) and 0.5 to 50 μm (Patent Document 3). With metal foils and conductive layers of such thickness, there was a problem that they would peel off due to thermal expansion caused by heat conduction when they reached high temperatures during laser irradiation processing. In response to this, measures such as roughening the substrate of the conductive layer or metal foil have been considered, but these have resulted in problems such as decreased productivity due to an increase in the roughening process and increased costs.

[0005] This invention was made to solve the above problems and aims to provide a method for manufacturing multilayer wiring boards that can produce multilayer wiring boards with high productivity and low cost.

[0006] The present invention has been made to achieve the above objective, and provides 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 making 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.

[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 enables more efficient removal of the organic insulating film subsequent to the opening forming step.

[0014] In this case, the method for manufacturing a multilayer wiring board can be configured such that the organic insulating film is removed by plasma etching in the organic insulating film removing step.

[0015] This enables a plurality of openings to be formed simultaneously. Further, when forming a via hole, smear remaining at the bottom of the via hole can be easily removed, and this is also advantageous in that, for example, an additional metal film exposed at the bottom of the via hole is not degraded.

[0016] In this case, the method for manufacturing a multilayer wiring board can be configured such that a trench is formed in the organic insulating film removing step. Further, the method for manufacturing a multilayer wiring board can be configured such that a via hole is formed in the organic insulating film removing step.

[0017] This enables trenches and / or via holes to be formed efficiently.

[0018] In this case, the method for manufacturing a multilayer wiring board can be configured such that a plurality of openings are formed in the opening forming step, and an interval between adjacent ones of the plurality of openings is 5 µm or less.

[0019] This enables manufacturing of a multilayer wiring board in which recesses such as trenches and / or via holes are formed at a high density.

[0020] As described above, according to the method for manufacturing a multilayer wiring board of the present invention, since the thickness of the metal film is small, the time required for forming the metal film can be shortened and the usage amount of material can be reduced. Further, peeling due to thermal expansion can be suppressed. Further, roughening of the base of the metal film becomes unnecessary, or the time of the roughening step can be shortened. Furthermore, since the thickness of the metal film is small, openings can be easily formed in the metal film. As a result, it becomes possible to manufacture a multilayer wiring board with high productivity and low cost.

[0021] This shows an outline of the steps for manufacturing a multilayer wiring substrate according to the present invention. An example of a wiring substrate prepared in the substrate preparation step is shown. An example of a wiring substrate with openings formed in the opening formation step is shown. An example of a wiring substrate with a portion of the organic insulating film removed after openings are formed in the opening formation step is shown. An example of an intermediate substrate after the organic insulating film removal step is shown. A modified example of the intermediate substrate after the organic insulating film removal step is shown. A schematic cross-sectional perspective view of an example of an intermediate substrate after the organic insulating film removal step is shown. An example of a multilayer wiring substrate obtained by the manufacturing method of the multilayer wiring substrate of the present invention is shown. This is a schematic flow diagram showing a part of an example of the manufacturing method of the multilayer wiring substrate of the present invention. This is a schematic flow diagram following Figure 9. This is a schematic flow diagram following Figure 10. This is a schematic plan view showing an example of a mask that can be used in the laser processing step of an example of the manufacturing method of a multilayer wiring substrate of the present invention. This is a schematic plan view showing another example of a mask that can be used in the laser processing step of an example of the manufacturing method of a wiring substrate of 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] Conventionally, as described in Patent Document 4, pinholes can be observed in thin metal films of 0.1 to 1 μm thickness, and problems have been reported regarding unintended peeling of the metal film during subsequent etching processes. Therefore, in the present invention, it is preferable that there are no pinholes in the metal film that can remove the organic insulating film during organic insulating film removal processes such as plasma etching. Furthermore, if the removal of the organic insulating film is small enough that it does not pose a major problem, for example, if the diameter of the pinhole is extremely small, or if the depth of the pinhole is shallow and the organic insulating film is not exposed (also called a pit, where the metal film partially remains between the bottom of the pinhole and the organic insulating film), then pinholes can be allowed to exist in the metal film. The depth to which the organic insulating film is removed during the organic insulating film removal process by such pinholes remaining in the metal film is preferably small, for example, preferably 30% or less of the depth to which the organic insulating film is removed during the organic insulating film removal process at the opening, more preferably 10% or less, particularly preferably 5% or less, and very preferably 1% or less. The preferred lower limit is 0%.

[0030] On the other hand, by using such pinholes to remove the organic insulating film and create roughness on the surface of the organic insulating film, adhesion during subsequent pad formation or when forming further organic insulating films (further multilayering) may be improved.

[0031] Pinholes in these metal films can be controlled by varying the conditions of the plating and sputtering methods used to form the metal films, as well as the pretreatment conditions. Specifically, pinholes can be controlled by enhancing the cleanliness of the organic insulating film that forms the metal film, roughening the organic insulating film that forms the metal film, controlling the plating bath to suppress the adhesion of air bubbles to the organic insulating film, introducing a seed layer to improve metal adhesion, preheating the organic insulating film before sputtering to remove residual moisture, optimizing the sputtering power, pressure, and bias voltage, and optimizing the composition, concentration, and temperature of the plating solution.

[0032] 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.

[0033] 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).

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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 may be 1 μm or more, 5 μm or more, etc.

[0044] [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 can further improve productivity as it does not require the formation of a mask as in the case of etching.

[0045] The aforementioned laser is CO ２These include lasers, solid-state lasers, and excimer lasers. The wavelength of the laser can be appropriately selected depending on the type of metal in the metal film, and by using a laser with a wavelength that has high absorption efficiency in the metal, the processability of the metal film can be improved. For example, if the metal film contains copper, using a laser with wavelengths such as vacuum ultraviolet light or ultraviolet light (e.g., UV solid-state laser, excimer laser, etc.) makes it easy to process the metal film. In addition, depending on the type of metal used, lasers with other wavelengths such as visible light, near-infrared light, mid-infrared light, and far-infrared light (e.g., CO ２ A laser with a wavelength that has high absorption efficiency in metals can be appropriately selected from among lasers, visible light solid-state lasers, near-infrared light solid-state lasers, etc. In this way, even when processing with a widely used laser, the occurrence of delamination due to thermal expansion can be effectively suppressed by keeping the thickness of the metal film to 100 nm or less.

[0046] CO ２ Lasers often penetrate deep into organic insulating films, making it easy for the organic insulating film to be processed along with Cu films, etc. Therefore, care must be taken in irradiation control to prevent unintended processing of the organic insulating film. On the other hand, lasers with ultraviolet wavelengths are used for CO ２ Compared to lasers, the penetration depth into organic insulating films is shallower, making irradiation control relatively easier.

[0047] On the other hand, even when using a laser with a wavelength that is not optimal for absorption by metal, it is possible to process the metal film by forming a laser absorption layer on the surface of the metal film, roughening the surface shape of the metal film, or reducing the thickness of the metal film. For example, by blackening the surface of a copper film to form copper oxide, or by etching to roughen the surface shape, it is possible to process the metal film even when using a laser with a wavelength that is not optimal for absorption by the copper film. ２ Even with a laser, it is possible to process copper films.

[0048] Alternatively, an ultrashort pulse laser with a pulse width on the order of femtoseconds to picoseconds (e.g., a picosecond UV laser, a femtosecond UV laser, etc.) may also be used.

[0049] Furthermore, by using an excimer laser, preferably a KrF excimer laser, precise processing can be performed efficiently.

[0050] When removing the metal film 2 in the area that will become an opening by etching, etching can be performed by forming an etching mask. If the metal film 2 contains Cu, the components of the etching solution for Cu may 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.

[0051] In the opening formation process, multiple openings 5A and 5B can be provided in the metal film 2, as shown in Figure 3, for example, in the intermediate substrate 10A. In this case, for example, opening 5A can be an opening for forming a via hole, and opening 5B can be an opening for forming a trench.

[0052] Furthermore, as shown in Figure 3, when forming multiple openings 5A and 5B, the spacing D between adjacent openings can be set to 5 μm or less. In the manufacturing method of the multilayer wiring substrate according to the present invention, since the thickness of the metal film 2 is 100 nm or less, damage to the metal film 2 can be prevented as described above, and openings can be formed with high precision. As a result, it is possible to manufacture a multilayer wiring substrate in which recesses such as trenches and / or via holes are formed at a high density by setting the spacing between adjacent openings to 5 μm or less.

[0053] The adjacent openings may be a combination of openings for forming trenches, a combination of openings for forming via holes, or a combination of an opening for forming a trench and an opening for forming a via hole. The existence of a region where the shortest distance D between these adjacent openings is 5 μm or less makes it possible to increase the density of the recesses. On the other hand, because the contact area between the metal film and the organic insulating film between the openings becomes small, it becomes more susceptible to the effects of thermal expansion caused by the heat generated during the opening formation process, such as laser processing. In this invention, we succeeded in suppressing the effects of thermal expansion by making the thickness of the metal film 2 thin.

[0054] [Organic Insulating Film Removal Process] As shown in Figure 1, after forming the opening in the opening formation process, an organic insulating film removal process is performed in which the metal film 2 with the opening is used as a mask to remove the organic insulating film from the opening. This makes it possible to produce an intermediate substrate 10B having recesses that become via holes 7 and trenches 8, as illustrated in Figure 5. In this invention, the metal film with the opening may have other films laminated on it to enhance its mask function. Of course, the metal film may also be used as a mask in an exposed state (without other films laminated on it). Lamination of other films onto the metal film may be performed before the laser processing process, and openings may be created together with the metal film by laser processing. Alternatively, lamination of other films onto the metal film may be performed after the laser processing process, and openings may be created in locations corresponding to the openings in the metal film as needed.

[0055] The method for removing the organic insulating film in the organic insulating film removal process is not particularly limited. For example, methods of removing the organic insulating film by irradiation with a laser such as an excimer laser or by plasma etching are preferred. As the laser, for example, a laser that can be used in the aperture formation process can be used.

[0056] If the organic insulating film is removed by irradiation with an excimer laser or the same laser used in the aperture formation process, the removal of the organic insulating film can be performed immediately following the aperture formation process without interrupting laser irradiation, which is preferable from the viewpoint of improving productivity. Furthermore, precise processing can be performed efficiently. Note that the laser used for processing the metal film and the laser used for processing the organic insulating film may be the same or different. For example, a combination of lasers with different wavelengths, combinations of lasers with different pulse widths, or combinations of lasers with different media materials may be used. Using the same laser can increase productivity, but using different lasers can increase production margin and material selection margin for the workpiece.

[0057] Removing the organic insulating film by plasma etching, which is a type of dry etching, allows for simultaneous removal of the organic insulating film 1A in multiple openings 5A and 5B, which is preferable from the viewpoint of improving productivity. Furthermore, when forming via holes, it is advantageous in that it allows for easy removal of smear remaining at the bottom of the via holes and does not degrade the metal film 3 exposed at the bottom of the via holes, for example.

[0058] By performing excimer laser irradiation and plasma etching in this manner, an intermediate substrate 10B, as shown in Figure 5, and an intermediate substrate 10C, as shown in Figure 6, can be obtained by further removing the metal film 2.

[0059] Furthermore, when providing via holes and trenches in the intermediate substrate 10A shown in Figure 3, it is also effective to remove the organic insulating film by combining excimer laser irradiation and plasma etching. In this case, after forming the openings 5A in the metal film 2 in the opening formation process described above, the excimer laser irradiation is continued to remove a portion of the organic insulating film where via holes are to be formed, as shown in Figure 4, thereby forming recesses 6A. In addition, the organic insulating film is not removed in the areas where trenches are to be formed, or recesses 6B are formed in the organic insulating film in the areas where trenches are to be formed, with a depth smaller than the recesses 6A formed in the areas where via holes are to be formed. Subsequently, the organic insulating film 1 can be etched using the metal film 2 with the openings 5A and 5B as a mask on the intermediate substrate 10a in this manner to provide via holes 7 and trenches 8 as shown in Figure 5.

[0060] 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.

[0061] 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.

[0062] 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 removed 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. Furthermore, the metal film may be partially removed or completely removed by plasma etching in the organic insulating film removal process. If the metal film is partially removed by plasma etching, the conditions for removal with the etching solution can be relaxed. If the entire metal film is removed by plasma etching, removal with the etching solution can be omitted.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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 was 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. The timing of removing the metal film 2 can be varied depending on the process, and may be before or after pad formation, or before or after filling with conductive material. Since the thickness of the metal film 2 is thin, it can be removed by flash etching. Therefore, it is possible to suppress the effect of etching on the formed pads and the filled conductive material.

[0067] 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.

[0068] The following describes a modified method for manufacturing a multilayer wiring board, with reference to Figures 9 to 11.

[0069] <Preparatory Step> First, a wiring substrate 10 shown in FIG. 9(A) is prepared. The wiring substrate 10 includes two organic insulating films 1 １ and 1 ２ stack.

[0070] Two through electrodes 7 １ penetrate through the organic insulating film 1 １ . Pads 6 １ and 6 １ are respectively connected to the end portions of each through electrode 7 ２ . Such an organic insulating film 1 １ can be obtained by, but not limited to, the following method, for example. First, a via hole 20 is formed in the organic insulating film 1 １ by a procedure similar to the formation procedure of the via hole 20 in the example of the method for manufacturing a multilayer wiring substrate described with reference to FIGS. 2 to 6. Next, the metal film 2 is removed. Then, the through electrode 7 １ is formed in the via hole 20 by, for example, plating. Next, the pads 6 １ and 6 １ are formed on the end portions of the through electrodes 7 ２ by a conventional method. Thus, the organic insulating film 1 １ penetrated by the two through electrodes 7 １ is obtained.

[0071] Two through electrodes 7 ２ penetrate through the organic insulating film 1 ２ . One end portion of each through electrode 7 ２ is connected to a pad 6 ２ , and the other end portion is connected to a pad 6 ３ . In addition, an in-layer wiring 8 ２ is formed on the surface of the organic insulating film 1 １ on the opposite side from the organic insulating film 1 １ . Such an organic insulating film 1 ２ can be obtained by, but not limited to, the following method, for example. First, an organic insulating material is applied onto the organic insulating film 1 １ formed with the through electrodes 7 １ to form the organic insulating film 1 ２Next, the organic insulating film 1 is formed using a procedure similar to the procedure for forming via holes 20 in the example of the manufacturing method of a multilayer wiring board described with reference to Figures 2 to 6. ２ A via hole 20 is formed. Simultaneously with or separately from the formation of the via hole 20, an organic insulating film 1 ２ A trench is formed on the surface. When the trench is formed at the same time as the via hole 20, the trench can be formed simultaneously with the via hole by the method described below in detail with reference to Figures 10(D) to 10(F), 11(G), and 11(H). Alternatively, when the trench is formed separately from the via hole 20, the trench may be formed by a conventional method. Next, the metal film 2 is removed. Then, through electrodes 7 are placed in the via hole 20 and trench, for example by a plating method. ２ and intralayer wiring 8 １ Forms each through electrode 7. ２ One end of pad 6 ２ Connect to the through electrode 7. ２ At the other end, by conventional means, pad 6 ３ This forms two through electrodes 7 ２ Organic insulating film 1 that penetrated ２ This results in the wiring board 10 shown in Figure 9(A).

[0072] <Preparation Steps> Next, as shown in Figure 9(B), an organic insulating film 1 is formed on the wiring board 10. Next, as shown in Figure 9(C), a metal film 2 is formed on the organic insulating film 1. Thus, a stack 3 of the organic insulating film 1 and the metal film 2 on the organic insulating film 1, as shown in Figure 9(C), is prepared. The organic insulating film 1 and the metal film 2 can be formed, for example, by conventional methods.

[0073] <Laser Processing Process> Next, as shown in Figure 10(D), an opening 4 is made in the metal film 2 of the stack 3, and a portion of the area 11 where via holes are to be formed in the organic insulating film 1 is removed to form a recess 12. This process is a laser processing process in which the above processing is performed by laser processing.

[0074] In this case, as shown in Figure 10(D), the opening 4 of the metal film 2 corresponds to the portion 4 of the via hole. １And section 4, which corresponds to the beer hall. １ The surrounding part 4 ２ It may also include. In this example, as shown in Figure 10(D), the surrounding portion 4 of the organic insulating film 1 ２ The portion directly below it will not be removed.

[0075] In addition, as shown in Figure 10(D), a plurality of other openings 5 ​​are formed in the metal film 2. The plurality of openings 5 ​​are formed to correspond to the locations 13 where trenches are to be formed, which will be described later. In this example, as shown in Figure 10(D), the locations 13 where trenches are to be formed in the organic insulating film 1 are not removed. Alternatively, recesses smaller in depth than the recesses 12 formed at the locations where via holes are to be formed may be formed in the organic insulating film 1 where trenches are to be formed.

[0076] Such a laser processing process can be carried out using, for example, two masks: one for forming via holes and another for forming trenches. Specifically, for example, via holes can first be formed by laser processing using the via hole formation mask, and then the process can be switched from the via hole formation mask to the trench formation mask, and trenches can be formed by laser processing using the trench formation mask.

[0077] Alternatively, the laser processing process can be carried out using the laser processing mask shown in Figures 12 and 13, which will be explained in detail later. This mask 40 has laser transparency in the parts corresponding to the openings 4 and 5, respectively, and blocks the laser in the other parts, and in the part corresponding to the via hole of the opening 4 4 １ The laser transmittance of the portion corresponding to the aperture 5 and the transmittance of the surrounding portion 4 ２ It has the characteristic of being larger than each of the corresponding parts.

[0078] As shown in Figure 10(D), an intermediate substrate 10A with a recess 12 formed thereon is obtained through the laser processing process described above.

[0079] <Etching Process> Next, an etching process is performed on the intermediate substrate 10A. In the etching process, the organic insulating film 1 is plasma-etched using the metal film 2, which has openings 4, as a mask to create via holes 20 and trenches 30 in the stack 3. In other words, the metal film 2 functions as a mask in the etching process.

[0080] In this example, the opening 4 of the metal film 2 corresponds to the portion 4 of the via hole. １ In addition to this part 4 １ The surrounding part 4 ２ The metal film 2 further includes the opening 5. Therefore, in the etching process, not only the location 11 where via holes are to be formed in the organic insulating film 1, but also the portion 4 of the opening 4 in the metal film 2, as shown in Figure 10(D). １ The surrounding part 4 ２ The portion 14 of the organic insulating film 1 directly below and the portion 13 where the trench is to be formed are also removed. As a result, as shown in Figure 10(E), via holes 20 are formed at the portion 11 (where the recess 12 is formed) where via holes of the organic insulating film 1 are to be formed, trenches 30 are formed at the portion 13 (the portion directly below the opening 5 of the metal film 2) where trenches of the organic insulating film 1 are to be formed, and portion 4 of the opening 4 of the metal film 2 are removed. １ The surrounding part 4 ２ A recess 15 is formed in the portion 14 of the organic insulating film 1 directly beneath it. In other words, according to the manufacturing method of the wiring board in this example, via holes 20, trenches 30, and recesses 15 can be formed simultaneously.

[0081] Plasma etching can be anisotropic etching. Therefore, in this etching process, the portions of the organic insulating film 1 directly below the openings 4 and 5 of the metal film 2 are removed to the same depth. In the laser processing process, as explained earlier, the area 11 where the via hole 20 is to be formed is removed, but the portion of the opening 4 of the metal film 2 is removed. １ The surrounding part 4 ２ The portion 14 of the organic insulating film 1 directly beneath it, and the area 13 where a trench is to be formed, have not been removed. Therefore, after the etching process, the via hole 20 is on the pad 6 ３The organic insulating film 1 is penetrated to reach the depth of the via hole 20, and the depths of the trench 30 and recess 15 are smaller than the depth of the via hole 20. The ability to simultaneously form via holes 20 and trenches 30 with different depths has the advantage of making the manufacturing method of multilayer wiring boards more efficient.

[0082] Furthermore, by performing plasma etching, which is a type of dry etching, in this etching process, it is possible to reliably achieve the simultaneous creation of via holes 20, trenches 30, and recesses 15.

[0083] <Removal of Metal Film> Next, the metal film 2 can be removed. The removal of the metal film 2 can be carried out as appropriate depending on the material of the metal film 2. For example, a metal film 2 containing Cu can be easily dissolved and removed 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 ammonia water, and additives such as water and surfactants.

[0084] By removing the metal film 2, an intermediate substrate 10B can be obtained in which the main surface 1A of the organic insulating film 1 is exposed, as shown in Figure 10(F).

[0085] <Fabrication of through electrodes, pads and in-layer wiring> Next, as shown in Figure 11(G), the main surface 1A side of the organic insulating film 1 of the intermediate substrate 10B is subjected to a plating process, and conductive material is poured into the via holes 20, trenches 30 and recesses 15, thereby forming through electrodes 7 in the via holes 20, in-layer wiring 8 in the trenches 30, and pads 6 in the recesses 15. The through electrodes 7 consist of pads 6 and pads 6 of the wiring substrate 10. ３ It is adjacent to.

[0086] <Finishing> As shown in Figure 11(G), the pads 6 and in-layer wiring 8 are covered by the plating layer 9. By polishing the plating layer 9, a multilayer wiring board 100 with exposed pads 6 and in-layer wiring 8 can be obtained, as shown in Figure 11(H).

[0087] [Regarding the mask] Next, we will explain the mask 40 that can be used in the laser processing process described above, with reference to Figures 12 and 13.

[0088] The mask 40 shown in Figure 12 has a transparent pattern 40A corresponding to the openings 4 and 5 to be formed in the metal film 2, and the remaining portion 40B.

[0089] The transparent pattern 40A corresponds to the via holes of the openings 4 in the metal film 2. １ The corresponding portion 41 and the portion 4 of the opening 4 of the metal film 2 １ The surrounding part 4 ２ It includes a portion 42 corresponding to the opening 5 and a portion 43 corresponding to the opening 5.

[0090] The portion 41 of the mask 40 is formed such that the energy of the laser passing through this portion 41 is greater than the energy of the laser passing through portions 42 and 43 of the mask 40, respectively. For example, portions 42 and 43 of the mask 40 may include portions 40s that do not allow the laser to pass through, as shown in Figure 13. This makes it possible to make the area of ​​the portion of portion 41 that allows the laser to pass through larger than the area of ​​the portions of portions 42 and 43 of the mask 40 that allow the laser to pass through. Alternatively, in the mask 40 shown in Figure 13, the laser transmittance of the materials constituting portions 42 and 43 of the mask 40 may be lower than the laser transmittance of the material constituting portion 41 of the mask, or the transmittance may be lowered by applying a thin film. Furthermore, portions 42 and 43 of the mask 40 may be provided with a component that lowers the transmittance in the polarization direction according to the polarization state of the laser.

[0091] The remaining portion 40B of the mask 40 is, for example, chrome-plated and acts as a shielding portion to prevent the transmission of laser light.

[0092] By using the mask 40 shown in Figures 12 and 13, the laser processing step in the modified method for manufacturing a multilayer wiring board described above can be carried out, for example, while referring to Figures 9 to 11.

[0093] In the above example, the area 13 where the trench 30 of the organic insulating film 1 is to be formed is not removed during the laser processing step. However, if the depth of removal is less than the depth of the portion to be removed in the area 11 where the via hole 20 is to be formed, a portion of the area 13 where the trench 30 of the organic insulating film 1 is to be formed may be removed during the laser processing step. Similarly, if the depth of removal is less than the depth of the portion to be removed in the area 11 where the via hole 20 is to be formed, a portion of the area 14 where the recess 15 of the organic insulating film 1 is to be formed may be removed during the laser processing step.

[0094] Furthermore, the intermediate substrate (for example, intermediate substrate 10A or 10B) obtained during the process of the example of manufacturing a multilayer wiring board described above can also be called an intermediate structure of the wiring board. This intermediate structure of the wiring board may be, for example, a build-up layer of the multilayer wiring board or a core layer of the multilayer wiring board.

[0095] [Experimental Example] A commercially available build-up material was laminated onto a commercially available copper-clad laminate, and metal films of predetermined thicknesses (9 μm, 1 μm, 500 nm, 200 nm, 100 nm) were formed on the build-up material by electroless copper plating. Next, a group of rectangular openings spaced at predetermined distances (2 μm, 5 μm, 10 μm, 30 μm) were processed using a KrF excimer laser. After processing, the adhesion of the metal film to the build-up material between the openings was observed and evaluated according to the following criteria A to C. The results are shown in Table 1. A: No peeling of the metal film from the build-up material was observed. B: Peeling of the metal film from the build-up material was observed in limited areas. C: Peeling of the metal film from the build-up material was observed in many areas.

[0096]

[0097] When the distance D between the apertures is large (10 μm, 30 μm), the contact area between the metal film and the build-up material is large, so it is presumed that the effect of thermal expansion is not significant even if the aperture group is formed by laser processing. On the other hand, when the distance D between the apertures is small (2 μm, 5 μm), the contact area between the metal film and the build-up material is relatively small, so it is more susceptible to the effects of thermal expansion, and it is presumed that delamination of the metal film occurred. This delamination occurred in the relatively thick regions, which are the metal film thicknesses commonly used in the past (9 μm, 1 μm). When the metal film thickness was 100 nm, good adhesion of the metal film between the apertures was obtained even when the distance D between the apertures was reduced to 2 μm. When the metal film thickness was 200 nm, delamination of the metal film was observed when the distance D between the apertures was reduced to 2 μm, but when the distance D between the apertures was 5 μm, it was limited to partial delamination. This means that even if the metal film thickness is 200 nm, it can be put into practical use by reducing the laser pulse width, adjusting the aperture pattern, forming a seed film to improve the adhesion between the metal film and the build-up material, or applying a roughening treatment.

[0098] 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] above, 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] above, 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] above, 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. [9]: A method for manufacturing a multilayer wiring substrate according to [1], [2], [3], [4], [5], [6], [7], or [8] above, wherein the metal film is exposed and used as a mask in the organic insulating film removal step.

[10] : A method for manufacturing a multilayer wiring substrate according to [1], [2], [3], [4], [5], [6], [7], [8], or [9], wherein in the opening formation step, the opening is formed by irradiating with a laser, and in the organic insulating film removal step, the organic insulating film is removed by plasma etching.

[0099] 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.

[0100] Up to this point, the description has focused on the process of forming via holes and trenches in the build-up layer and the process of removing the organic insulating film in the multilayering process of a multilayer wiring substrate. However, the invention is not limited to this form and can also be applied to, for example, the process of forming via holes and trenches in the core layer of a multilayer wiring substrate and the process of removing the organic insulating film (see [A] below), or the process of forming via holes and trenches in a single-layer wiring substrate and the process of removing the organic insulating film (see [B] below). Furthermore, the present invention also has an aspect of simply being a method for processing an organic insulating film (see [C] below). [A] A method for manufacturing a multilayer wiring substrate comprising: a preparation step of preparing a core layer 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. [B] A method for manufacturing a wiring substrate, comprising: a preparation step of preparing a 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. [C] A method for processing an organic insulating film, comprising: a preparation step of preparing a structure 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.

[0101] Furthermore, the various materials and process conditions used in the methods exemplified in [A], [B], and [C] above can preferably be those described in [1] above. In addition, the organic insulating film in [A], [B], and [C] may be composited with inorganic fiber materials such as glass nonwoven fabric. Also, the surface of the organic insulating film in [A], [B], and [C] opposite to the surface with the metal film may or may not have a metal film. If there is a metal film on the opposite side, that metal film may be patterned in advance, patterned in a process simultaneous with [A], [B], and [C], or patterned after the processes of [A], [B], and [C]. If there is no metal film on the opposite side, a plating process may be provided to provide a metal film in the necessary locations.

[0102] By the way, in cases where some degree of delamination due to thermal expansion is tolerable, or when the adhesion between the metal film and the organic insulating film is high, it is not necessarily required that the thickness of the metal film be 100 nm or less. In this case, the thickness of the metal film may be 300 nm or less, 250 nm or less, 200 nm or less, or 150 nm or less.

[0103] Furthermore, by using an ultrashort pulse laser with a pulse width on the order of femtoseconds to picoseconds (for example, a picosecond UV laser, a femtosecond UV laser, etc.) and suppressing thermal expansion, peeling due to thermal expansion can be reduced even if the thickness of the metal film is greater than 100 nm. In this case, the thickness of the metal film may be 300 nm or less, 250 nm or less, 200 nm or less, or 150 nm or less. Of course, the thickness of the metal film may be 100 nm or less, and in combination with an ultrashort pulse laser, more precise processing and omission of the metal film underlay become possible.

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.

9. The method for manufacturing a multilayer wiring substrate according to any one of claims 1 to 7, wherein in the organic insulating film removal step, the metal film is used as a mask in an exposed state.

10. A method for manufacturing a multilayer wiring substrate according to claim 1 or 2, wherein in the aperture forming step, the aperture is formed by irradiation with a laser, and in the organic insulating film removal step, the organic insulating film is removed by plasma etching.

11. The method for manufacturing a multilayer wiring board according to claim 10, 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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