Method for manufacturing metal member, and mold member

Abstract

A method for manufacturing a metal member according to the present disclosure includes: a step for making a laminate, in which a mask layer is formed on a conductive substrate, the mask layer having a groove with a desired shape for exposing the conductive substrate ; a step for plating to form a metal layer, which is made of a prescribed metal, on the laminate by electroplating; and a step for isolating the metal layer, which has been formed in the groove, from the laminate after the plating.

Description

METAL MEMBER MANUFACTURING METHOD AND MOLD MEMBER

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to Japanese Patent Application No. 2023-218561, filed on December 25, 2023, the entire disclosure of which is incorporated herein by reference.

[0002] The present disclosure relates to a method for manufacturing a metal member and a mold member.

[0003] In semiconductor devices, in order to dissipate the heat generated by the semiconductor element when it is energized to the outside of the system, the semiconductor element is mounted on a heat dissipation substrate, and the heat dissipation substrate is then thermally attached to a heat sink (heat dissipation fins), so that the heat generated by the semiconductor element when it is energized is transferred to the heat sink and dissipated to the outside.

[0004] FIG. 4 is a diagram showing an example of the configuration of a semiconductor device 1, taking an IGBT (Insulated Gate Bipolar Transistor) module power semiconductor device as an example. As shown in FIG. 4, a ceramic substrate 3 is bonded to one surface of a heat dissipation substrate 4 with a solder bonding material 7. Furthermore, a semiconductor element 2 (IGBT) is bonded to the ceramic substrate 3 with the solder bonding material 7. The semiconductor element 2 and ceramic substrate 3 are sealed in a package case 5. A heat sink 6 is attached to the other surface of the heat dissipation substrate 4. In the semiconductor device 1 shown in FIG. 4, heat generated by the semiconductor element 2 is dissipated via the ceramic substrate 3, the heat dissipation substrate 4, and the heat sink 6, as indicated by the white arrows in FIG. 4.

[0005] In recent years, miniaturized power semiconductor elements using compound semiconductors such as SiC or GaN, which operate stably even at high temperatures, have been used as semiconductor elements. As a result, heat generation has become more pronounced, causing problems such as melting of solder joint materials. Furthermore, in high-performance computing, the problem of heat generation has become more pronounced due to the need to perform complex arithmetic processing on massive amounts of data at high speeds. Thus, the importance of heat diffusion from the heat source has increased.

[0006] Furthermore, solder is used to join the wiring, but solder has a high resistance and generates heat. To solve this problem, methods such as wafer-to-wafer hybrid bonding, which directly bonds copper to copper, have been developed. However, this method has issues such as the need for large-scale equipment, the fact that wasted space is generated if the wafers being bonded are not the same size, and the fact that extremely high flatness is required on the wafer surface, making it less versatile.

[0007] There is a need for a method for producing metal materials having desired shapes of submicron size or smaller as bonding materials to ensure stable electrical and thermal conductivity at high temperatures. For example, Patent Document 1 describes a method for producing silver nanowires using silver precipitation in a solution. Also, Non-Patent Document 1 describes a method for producing nano-sized metal members using porous alumina as a mold.

[0008] Japanese Patent Application Laid-Open No. 2018-193613

[0009] Journal of Nanoparticle Research 5: 17-30, 2003. (c) 2003 Kluwer Academic Publishers. Printed in the Netherlands. Fabrication of nanomaterials using porous alumina templates

[0010] As described above, a method for producing a metal component having a desired shape is needed to ensure stable electrical and thermal conductivity at high temperatures. The method described in Patent Document 1 makes it possible to produce a wire-shaped component (silver nanowire), but it is not possible to produce a metal component having a desired shape other than a wire. Furthermore, the method described in Non-Patent Document 1 also makes it impossible to produce a metal component having a desired shape because the metal component is produced using the pores in porous alumina as a mold.

[0011] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a metal component manufacturing method that can manufacture a metal component having a desired shape, and the metal component.

[0012] A method for manufacturing a metal component according to one embodiment is a method for manufacturing a metal component having a desired shape and made of a predetermined metal, and includes the steps of: producing a laminate in which a mask layer having a groove portion of the desired shape exposing the conductive substrate is formed on a conductive substrate; performing a plating process to form a metal layer made of the predetermined metal on the laminate by electroplating; and isolating the metal layer formed in the groove portion from the laminate after the plating process.

[0013] In one embodiment of the method for manufacturing a metal member, the conductive substrate is a metal plate or a conductive film on which a conductive layer made of a conductive material is formed.

[0014] In one embodiment of the method for manufacturing a metal member, the mask layer is formed by lithography or transfer printing.

[0015] The metal member according to one embodiment is manufactured by the above-described manufacturing method.

[0016] According to the present disclosure, a metal component having a desired shape and made of a predetermined metal can be manufactured.

[0017] 1 is a flowchart illustrating a method for manufacturing a metal member according to an embodiment of the present disclosure; FIG. 2 is a schematic diagram (part 1) illustrating a method for manufacturing a metal member according to an embodiment of the present disclosure; FIG. 3 is a schematic diagram (part 2) illustrating a method for manufacturing a metal member according to an embodiment of the present disclosure; FIG. 4 is a schematic diagram (part 4) illustrating a method for manufacturing a metal member according to an embodiment of the present disclosure; FIG. 5 is a SEM image of a metal member according to an example of the present disclosure; FIG. 6 is a SEM image of a metal member according to an example of the present disclosure; FIG. 7 is a diagram illustrating an example configuration of a semiconductor device;

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same reference numerals indicate the same or equivalent components.

[0019] A method for manufacturing a metal member according to an embodiment of the present disclosure will be described with reference to the flowchart shown in Fig. 1 and the schematic diagrams shown in Fig. 2A to 2D. The method for manufacturing a metal member according to this embodiment makes it possible to manufacture a metal member having a desired shape that can be drawn two-dimensionally, such as a triangle, a rectangle, a line, a circle, a cross, a star, an ellipse, a Y-shape, or a Z-shape.

[0020] First, a conductive substrate 10 is prepared (step S11). The conductive substrate 10 is, for example, a conductive film in which an inorganic film 12 is provided on a base film 11, as shown in FIG. 2A.

[0021] The substrate film 11 is, for example, a film formed of a resin containing a repeating unit having carbon atoms or silicone, such as PET (polyethylene terephthalate), PP (polypropylene), PVC (polyvinyl chloride), PEN (polyethylene naphthalate), PE (polyethylene), PS (polystyrene), acrylic film, a film formed by extrusion molding of TPU (polyurethane elastomer) resin, polycarbonate film, polyimide film, a film formed of an amide resin such as nylon, or a silicone film. Multiple types of repeating units may be used.

[0022] The inorganic film 12 is made of a conductive metal. For example, the inorganic film 12 is made of a metal such as copper, silver, gold, aluminum, zinc, or nickel. The inorganic film 12 may also be made of an alloy of these metals. Although the metal that makes up the inorganic film 12 is not limited to the above-mentioned examples, it is preferable to use copper or silver, which have particularly high conductivity.

[0023] The inorganic film 12 is formed on the substrate film 11 by, for example, sputtering, chemical vapor deposition, or atomic layer deposition. From the viewpoints of density, productivity, and the number of applicable metal species, it is preferable to use a sputtering method for producing the inorganic film 12.

[0024] The conductive substrate 10 is not limited to the conductive film having a conductive layer (inorganic film 12) made of a conductive material formed on a base film 11 as described with reference to Fig. 2A. The conductive substrate 10 may be a metal plate or metal foil. In the case of a metal plate, the inorganic film 12 may be provided on the surface.

[0025] 1 , a laminate 30 is fabricated in which a mask layer 20 is formed on a prepared conductive substrate 10 (step S12). As shown in FIG. 2B , the mask layer 20 has grooves 21 that expose the conductive substrate 10. The grooves 21 have the same shape as the metal member to be manufactured. That is, a laminate 30 is fabricated in which a mask layer 20 having grooves 21 of a desired shape that expose the conductive substrate 10 is formed on the conductive substrate 10.

[0026] The mask layer 20 may be an inorganic film made of an inorganic substance, an organic film made of an organic substance, or a hybrid film made of an inorganic substance and an organic substance. From the viewpoints of ease of handling, throughput, and shape control, the mask layer 20 is preferably an organic film or a hybrid film, and more preferably an organic film.

[0027] The grooves 21 having the desired shape can be formed in the mask layer 20 by a method such as lithography, ablation, transfer, or inkjet. From the viewpoints of productivity and resolution, the grooves 21 are preferably formed by lithography, ablation, or transfer, and more preferably by lithography or transfer.

[0028] When lithography is used to form the grooves 21, either negative or positive resists can be used. From the viewpoint of ease of demolding of the metal member, which will be described later, it is preferable to use a positive resist. Examples of positive resists that can be used include resists using naphthoquinone diazide and its derivatives, resists using phenolic resins such as novolak and resol, acetals using acid generators, chemically amplified resists using secondary and / or tertiary esters, sulfonate ester resists, and resists in which inter-polymer bonded resists are cleaved with acid.

[0029] For exposure of the resist, a projection exposure machine using g-line, h-line, i-line, KrF-line, ArF-line, or EUV (Extreme Ultra Violet) light as a light source, or proxy exposure or direct imaging using a high-pressure mercury lamp or UV light as a light source can be used. After exposure of the resist, heating may be performed as necessary.

[0030] For developing the resist after exposure, water, aqueous systems, organic solvents, organic alkaline systems, etc. can be used.

[0031] Negative resists that can be used include cation-curing resists such as epoxy or oxetane, radical-curing resists, acid and / or radical-curing styrene-based resists, and dehydration or photodimerization resists of methylol or hydroxyl groups and carboxyl groups. Also usable as negative resists are resists that harden or reduce alkali solubility in exposed areas for negative tone imaging.

[0032] When transfer is used to form the groove portion 21, in addition to the above-mentioned positive resist and negative resist, acrylic resin, phenolic resin, urethane resin, amide resin, imide resin, urea resin, styrene resin, or oligomers or monomers of the above-mentioned resins can be used.

[0033] As a transfer method, a nanoimprinting method is preferably used, in which the above-mentioned resin is applied to a substrate, and then a substrate on which a fine unevenness (desired shape) is formed is pressed against the substrate to transfer the shape. The resin to which the shape has been transferred can be cured by heat curing or photocuring. When a monomer is used, the shape can be transferred by promoting the polymerization reaction using at least one of a photopolymerization initiator and a thermal polymerization initiator. A film mold or a quartz substrate can be used as the substrate on which the fine shape (desired shape) has been formed. When a quartz substrate is used, a flat substrate, a hollow cylindrical substrate with an internal cavity, or a solid cylindrical substrate without an internal cavity can be used. In particular, when a cylindrical or columnar substrate is used, roll-to-roll transfer of the fine structure is possible, enabling more efficient shape transfer.

[0034] Referring back to FIG. 1 , after the laminate 30 is fabricated, a metal layer 40 made of a predetermined metal (the metal constituting the metal member to be manufactured) is formed on the laminate 30 by electroplating (step S13), as shown in FIG. 2C . Examples of metals that can be plated (the metal constituting the metal layer 40) include nickel, gold, silver, copper, tin, platinum, and indium. From the viewpoint of electrical conductivity and thermal conductivity, gold, silver, copper, or nickel is preferred as the metal constituting the metal layer 40. Alternatively, the metal layer 40 may be formed by sequentially plating different metals. In this case, a layer made of a different metal may be formed between two layers made of one metal.

[0035] Although various plating techniques are applicable, electrolytic plating is preferred for selectively forming a metal layer 40 in the grooves 21 of the mask layer 20 where the conductive substrate 10 is exposed. The plating bath used for electrolytic plating varies depending on the type of metal to be plated, but the chemistry of the plating bath must be selected according to the material used for the mask layer 20. If the mask layer 20 is formed by lithography using a positive resist, it is believed that dissolution of the mask layer 20 will proceed under acidic conditions. In this case, the chemistry of the plating bath must be made alkaline before electrolytic plating.

[0036] As shown in FIG. 2C , the height of the mask layer 20 is preferably higher than the metal layer 40 to be formed. That is, it is preferable to make the mask layer 20 higher than the height of the metal member to be manufactured and adjust the plating process time, etc., according to the height of the metal member. This prevents the metal layer 40 from being formed beyond the mask layer 20, making it easier to shape the metal member into a desired shape that conforms to the shape of the groove 21. However, the metal layer 40 may be formed to the same height as the mask layer 20, as shown in FIG. 2D . Alternatively, the metal layer 40 may be formed beyond the mask layer 20, as shown in FIG. 2E . That is, the metal layer 40 may be formed into a mushroom shape that has the same width as the groove 21 up to the height of the mask layer 20 and is wider than the groove 21 beyond the mask layer 20.

[0037] Referring back to FIG. 1 , after the plating process, the metal layer 40 formed in the grooves 21 is isolated from the plated laminate 30 as shown in FIG. 2F (step S14). Specifically, the metal layer 40 can be isolated by separating the metal layer 40 from the laminate 30 using a demolding process, cleaning, recovering, and drying. As described above, the grooves 21 of the mask layer 20 have the same shape as the metal component to be manufactured. Therefore, by isolating the metal layer 40 formed in the grooves 21 from the laminate 30, a metal component having a desired shape can be obtained. Note that FIG. 2F illustrates the isolation of the metal layer 40 when the metal layer 40 is formed without extending beyond the grooves 21, as shown in FIG. 2C or 2D.

[0038] The demolding treatment may be a chemical treatment such as wet etching or dry etching, or a physical treatment such as using a scraper. From the viewpoints of maintaining the shape, releasability from the laminate 30, and treatment after demolding, it is preferable to use wet etching for the demolding treatment. Furthermore, it is preferable to use a selective etching agent in order to dissolve the laminate 30 without dissolving the metal layer 40.

[0039] After dissolution of the laminate 30, the dispersion of the metal layer 40 can be filtered and / or centrifuged to recover the metal layer 40. For filtering, in addition to dead-end filtration using a membrane filter or the like, dynamic loss-flow filtration using a ceramic porous disk filter can be used. When the size of the metal component to be manufactured is 1 μm or less, it is preferable to recover the metal layer 40 by solid-liquid separation using a centrifuge.

[0040] For drying the recovered metal layer 40, a method suited to the material constituting the metal member to be manufactured may be used. For example, drying under reduced pressure with heating in an electric oven, which allows for simple processing, or freeze drying, which can reduce the effects of oxidation and thermal deformation, may be used.

[0041] As described above, the method for manufacturing a metal component according to this embodiment includes the steps of: preparing a laminate 30 on a conductive substrate 10, the laminate 30 including a mask layer 20 having a groove 21 of a desired shape that exposes the conductive substrate 10; performing a plating process to form a metal layer 40 made of a predetermined metal on the laminate 30 by electroplating; and isolating the metal layer 40 formed in the groove 21 from the laminate 30 after the plating process.

[0042] By forming a metal layer 40 made of a specified metal in a groove portion 21 having a desired shape and isolating the metal layer 40 formed in the groove portion 21, a metal component made of a specified metal and having a desired shape can be manufactured.

[0043] Next, the present disclosure will be described more specifically with reference to examples, but the present disclosure is not limited to the following examples.

[0044] A conductive substrate was prepared by sputtering an inorganic film made of silver on a silicon wafer. The silicon wafer had a thickness of 500 μm. The inorganic film had a thickness of 200 nm. Next, a mask layer having grooves with curved portions having different curvature R and groove widths of 1, 2, 5, 10, 20, 50, and 100 μm was formed on the prepared conductive substrate. The mask layer was composed of a novolac resin positive resist, and the film thickness of the mask layer was approximately 200 nm. After the mask layer was formed, a metal layer made of copper was formed in the grooves by electrolytic plating.

[0045] After the metal layer was formed, the surface of the metal layer was observed using a scanning electron microscope (SEM). Figure 3A is an SEM image of the vicinity of a curved portion of a pattern with a groove width of 20 μm. Figure 3B is an SEM image of one groove portion taken at a higher magnification.

[0046] As shown in Figure 3A, it was confirmed that a metal layer was formed not only on the straight line portions but also on the curved portions having a curvature R. Furthermore, as shown in Figure 3B, it was confirmed that a metal layer having a width equivalent to the width of the groove formed in the mask layer was formed. This confirmed that a metal component having a desired shape can be manufactured by forming grooves in the mask layer according to the shape of the metal component to be manufactured, forming a metal layer in the groove by plating, and isolating the formed metal layer.

[0047] The present disclosure is not limited to the configurations specified in the above-described embodiments, and various modifications are possible within the scope of the invention as set forth in the claims. For example, the functions included in each component can be rearranged so as not to cause logical contradictions, and multiple components can be combined into one or divided.

[0048] REFERENCE SIGNS LIST 1 semiconductor device 2 semiconductor element 3 ceramic substrate 4 heat dissipation substrate 5 package case 6 heat sink 7 solder bonding material 10 conductive substrate 11 base film 12 inorganic film (conductive layer) 20 mask layer 21 groove 30 laminate 40 metal layer

Claims

1. A method for manufacturing a metal member made of a predetermined metal having a desired shape, the method comprising: producing a laminate in which a mask layer having groove portions of the desired shape for exposing the conductive substrate is formed on the conductive substrate; performing a plating process of forming a metal layer made of the predetermined metal on the laminate by an electrolytic plating method; and isolating the metal layer formed in the groove portions from the laminate after the plating process.

2. The manufacturing method according to claim 1, wherein the conductive substrate is a metal plate or a conductive film having a conductive layer formed of a conductive material.

3. The manufacturing method according to claim 1, wherein the mask layer is formed by lithography or transfer.

4. A metal member manufactured by the manufacturing method according to any one of claims 1 to 3.

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