Substrate manufacturing method

Abstract

To provide a method for manufacturing a substrate, capable of easily forming a laminated film into a predetermined shape, the laminated film having a bottom film and a top film formed on a substrate.SOLUTION: Provided is a method for manufacturing a substrate having thereon a bottom film and a top film formed on the bottom film. The method includes: a first resist film formation step of forming, on a substrate 1, a first resist film 2 having an opening 21; a first film formation step of forming, on the substrate 1 and the first resist film 2, a first film 30 serving as the bottom film; a second resist film formation step of forming, on the first film 30, a second resist film 4 having an opening 41 smaller than the opening 21 of the first resist film 2; a second film formation step of forming, on the first film 30 and the second resist film 4, a second film 50 serving as the top film; and a resist film removal step of removing, from the substrate 1, the first resist film 2 and the second resist film 4.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a substrate having a film formed on its surface. [Background technology]

[0002] As a method for forming a metal film on a substrate using photolithography technology, a substrate manufacturing method using a lift-off method is known in which a resist having openings is formed on the surface of the substrate, a metal film is formed on the surface of the substrate exposed through the openings in the resist and on the surface of the resist, and then the resist is peeled off from the substrate to form the metal film in a predetermined region of the substrate surface.

[0003] Resists used for such substrates on which metal films are formed can be in the form of film-like dry film resists or liquid resists. Dry film resists, in particular, have the advantage that the thickness of the resist layer can be selected as desired, a resist coating device is not required, and a uniform film thickness can be obtained, making them applicable to a variety of manufacturing processes. They are superior in workability and productivity to liquid resists, and are widely used in the manufacture of printed wiring boards and the like.

[0004] Patent Document 1 describes a method for forming a burr-free metal pattern on the surface of a substrate by forming a dry film resist consisting of two layers, a non-photosensitive layer and a photosensitive layer, on the surface of the substrate, patterning this dry film resist to form a resist having an opening with an eaves-shaped cross section in which the upper photosensitive layer in the dry film resist overhangs the lower non-photosensitive layer, and using this resist as a mask to form a metal film on the surface of the substrate, and it is shown that the metal film formed in this way has a trapezoidal cross section.

[0005] Patent Document 2 also describes a ceramic wiring board used as a mounting substrate for semiconductor elements. In this ceramic wiring board, a laminated metal film consisting of an undercoat metal film, a diffusion prevention film, a solder film, etc. is formed on the surface of the ceramic substrate using a resist, and a semiconductor element is mounted on the solder film, which is the outermost surface of the metal film. The metal film formed on the surface of the ceramic substrate can increase the bonding strength of the semiconductor element by forming a diffusion prevention film on the underside of the solder film, and can prevent an increase in resistance of the connection part and an increase in the operating current of the semiconductor element due to the resistance increase. Furthermore, the disclosure describes that the outer periphery of the diffusion prevention film is shaped to protrude from the end of the solder film over its entire circumference, thereby preventing poor melting of the solder film and poor positioning of the semiconductor element in the height direction. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2015-90380 A [Patent Document 2] JP 2013-16838 A Summary of the Invention [Problem to be solved by the invention]

[0007] When attempting to form a laminated film on a substrate in which the outline of the undercoat film located on the substrate side is larger than that of the film on the surface layer side, if a resist having an opening with an overhanging cross section as described in Patent Document 1 is used, the overhanging part of the resist becomes an obstacle, making it difficult to form the undercoat film up to the edge of the opening located on the substrate side of the resist (the opening located on the substrate side of the overhanging part in the opening of the resist with an overhanging cross section). Therefore, there is a problem that the undercoat film cannot be formed in a specified shape, and the outline is likely to vary.

[0008] To address this issue, there is a method for obtaining a film of a predetermined shape by applying a first resist film for forming an undercoat film on a substrate, patterning the film to form an undercoat film, and then peeling off the first resist film, and applying a second resist film for forming a film on the surface layer side on the undercoat film and the substrate, and patterning the film to form a film on the surface layer side. However, this method has the problem that the resist film needs to be formed and peeled off according to the number of layers of the film and the number of pattern shapes, and many steps and man-hours are required.

[0009] The present invention seeks to solve the above-mentioned problems, and aims to provide a method for manufacturing a substrate that can easily form a laminated film having a base film and an upper film on a substrate into a predetermined shape. [Means for solving the problem]

[0010] The method for manufacturing a substrate having an undercoat film on a substrate and an overcoat film formed on the undercoat film includes a first resist film forming step of forming a first resist film having an opening on the substrate, a first film forming step of forming a first film that will become the undercoat film on the substrate and the first resist film, a second resist film forming step of forming a second resist film on the first film, the second film forming step of forming a second film that will become the overcoat film on the first film and the second resist film, and a resist film removing step of removing the first resist film and the second resist film from the substrate. The outer shape of the upper film may be smaller than that of the lower film, and the cross section of the upper film may be substantially trapezoidal. Furthermore, the resist film removal process may include removing the first film formed on the first resist film and the second film formed on the second resist film from the substrate in conjunction with the removal of the first resist film and the second resist film. Effect of the Invention

[0011] According to the method for manufacturing a substrate of the present invention, it is possible to easily form a laminated film having an undercoat film and an overcoat film on a substrate in a predetermined shape. [Brief description of the drawings]

[0012] [Figure 1] 1A to 1C are schematic diagrams illustrating a method for manufacturing a wiring board according to an embodiment of the present invention. [Diagram 2] 1A to 1C are schematic diagrams illustrating a method for manufacturing a wiring board according to an embodiment of the present invention. [Diagram 3] 1 is a cross-sectional view of a substrate according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The substrate manufacturing method of the present invention will be described below with reference to the drawings. In the drawings, the scale and number of each structure may differ from the actual shape and structure in order to make each component easier to understand.

[0014] FIG. 3 is a cross-sectional view of a substrate according to an embodiment of the present invention. The wiring substrate 10 includes a substrate 1, which is a base material of the wiring substrate 10, a base metal film 3 formed on one surface of the substrate 1 and serving as an example of a base film, and a solder film 5 formed on the surface of the base metal film 3 and serving as an example of an upper film. The substrate 1 is a substantially square flat plate having an outer diameter of about 4 inches and a thickness of 0.5 mm, which is a silicon carbide substrate. The base metal film 3 is a laminated metal film in which a Ti film for obtaining adhesion with the substrate 1, a Pt film for preventing the Ti film from diffusing into the solder film 5, and an Au film for obtaining adhesion with the solder film 5 are laminated in this order from the surface side of the substrate 1. The base metal film 3 is a rectangular film having a thickness of 0.3 μm and an outer shape of 0.4 mm on one side when viewed from above, and is disposed in the center of the substrate 1. The solder film 5 is a film whose main component is an AuSn alloy, has a thickness of 0.5 μm, and its outline when viewed from above is a rectangle with each side measuring 0.3 mm, which is smaller than the outline of the underlying metal film 3. The solder film 5 is arranged so that its outline fits inside the outline of the underlying metal film 3, and its cross-sectional shape is approximately trapezoidal, the outline gradually becoming smaller from the surface side of the substrate 1.

[0015] Next, a method for manufacturing a substrate of the present invention will be described. Figures 1 and 2 are schematic diagrams showing a method for manufacturing a wiring substrate 10 according to one embodiment of the present invention. The wiring substrate 10 is manufactured by the following method.

[0016] [First resist film formation process 1: Figure 1(a)] First, a substrate 1 serving as the base material of the wiring board 10 is prepared, and a first resist film 2 is formed on one surface of the substrate 1. In this embodiment, the first resist film 2 is a dry film resist having a thickness of about 0.015 mm, and the first resist film 2 is formed on the substrate 1 by adhering an adhesive layer provided on one surface of the dry film resist to the substrate 1.

[0017] [First resist film formation process 2: Figure 1(b)] Next, the first resist film 2 is patterned using a known photolithography technique, and an opening 21 is formed in a portion of the first resist film 2 corresponding to the formation portion of the base metal film 3 on the wiring board 10 (hereinafter referred to as the base film formation region). The outer shape of the opening 21 is slightly larger than the base film formation region, and more specifically, it is set to be larger than the outer shape of the base film formation region by the thickness of the metal film 30 that is attached to the side surface of the opening 21 in the first film formation process described below.

[0018] [First film formation process: Figure 1(c)] Next, a first film (hereinafter referred to as metal film 30) that will become the base metal film 3 in the wiring board 10 is formed on the substrate 1 on which the first resist film 2 has been formed. The metal film 30 is formed by successively forming a Ti film, a Pt film, and an Au film on the substrate 1 on which the first resist film 2 has been formed by a deposition method, a sputtering method, or the like. As a result, the metal film 30 is formed on the surface of the first resist film 2, the side surfaces of the openings 21 in the first resist film 2, and the surface of the substrate 1 exposed from the openings 21 in the first resist film 2.

[0019] [Second resist film formation process 1: Figure 1(d)] Next, a second resist film 4 is formed on the substrate 1 on which the metal film 30 has been formed. In this embodiment, the second resist film 4 is made of the same dry film resist as the first resist film 2. The second resist film 4 is formed by adhering the adhesive layer of the second resist film 4 to the metal film 30, more specifically, by adhering the adhesive layer of the second resist film 4 to the surface of the metal film 30 formed on the first resist film 2. The second resist film 4 thus formed on the substrate 1 is not adhered to the surface of the metal film 30 in the base film formation region formed directly on the surface of the substrate 1, and is opposed to the metal film 30 in the base film formation region with a gap therebetween.

[0020] [Second resist film formation process 2: Figure 2(e)] Next, the second resist film 4 is patterned using a known photolithography technique, and an opening 41 is formed in a portion of the second resist film 4 corresponding to the portion where the solder film 5 is to be formed on the wiring board 10 (hereinafter referred to as the solder film formation region). The outer shape of the opening 41 is set slightly smaller than the solder film formation region and smaller than the outer shape of the base film formation region. The second resist film 4 with the opening 41 formed therein is in a state where the end of the opening 41 protrudes (overhangs) into the base film formation region from the end of the metal film 30 formed on the surface of the first resist film 2 and the side of the opening 21, and the overhanging portion 42 of the second resist film 4 faces the metal film 30 formed in the base film formation region with a gap therebetween.

[0021] [Second film formation process: Figure 2(f)] Next, a second film (hereinafter referred to as solder film 50) is formed on the substrate 1 on which the second resist film 4 has been formed. The solder film 50 is a film that will become the solder film 5 in the wiring substrate 10, and is formed by a deposition method, a sputtering method, or the like. As a result, the solder film 50 is formed on the surface of the second resist film 4, the side of the opening 41 of the second resist film 4, and the surface of the metal film 30 exposed from the opening 41 of the second resist film 4. The solder film 50 formed on the surface of the metal film 30 is in a state in which the second resist film 4 overhangs, and the overhanging portion 42 of the second resist film 4 and the metal film 30 formed in the base film formation region face each other with a gap between them, so that the cross section has a substantially trapezoidal shape whose outer shape gradually becomes smaller from the surface side of the substrate 1 toward the top, and the outer shape of the solder film 50 at the portion in contact with the metal film 30 is larger than the opening 41. In this embodiment, the size and thickness of the outer shape of the opening 41 of the second resist film 40 are set so that the outer shape of the solder film 50 is smaller than the outer shape of the base film formation region. If the cross section of the solder film 50 does not need to be trapezoidal, the overhang portion 42 of the second resist film 4 may be in a state of hanging down toward the substrate 1.

[0022] [Resist film removal process: Figure 2(g)] Finally, the first resist film 2 and the second resist film 4 are removed from the substrate 1. At this time, the solder film 50 formed on the surface of the second resist film 4 and the metal film 30 formed on the surface and side of the first resist film 2 are also removed together with the first resist film 2 and the second resist film 4 by the lift-off process, and do not remain on the surface of the substrate 1. The second resist film 4 and the first resist film 2 are removed by irradiating the second resist film 4 and the first resist film 2 with ultraviolet light to harden the adhesive layer, thereby reducing the adhesive force, and the second resist film 4 and the first resist film 2 are peeled off from the substrate 1. In this way, the adhesive force of the adhesive layer of the second resist film 4 and the first resist film 2 is reduced, so that the second resist film 4 and the first resist film 2 can be easily removed from the substrate 1.

[0023] In the method for manufacturing a substrate in this embodiment, a first resist film 2 is formed on a substrate 1, and then a metal film 30 is formed. Then, a second resist film 4 and a solder film 50 are formed on the metal film 30 without peeling off the first resist film 2. Finally, the first resist film 2 and the second resist film 4 are removed to remove unnecessary portions of the metal film 30 and the solder film 50 by a lift-off process. In addition, the second resist film 4 is made to overhang the first resist film 2, and the cross section of the resist film is made to have an eaves shape. When the cross section of the resist film is made to have an eaves shape, it is usually difficult to form the base film with high accuracy in a predetermined shape. However, as in this embodiment, the metal film 30 is formed after the first resist film 2 is formed, and in that state, the second resist film 4 is formed to form the solder film 50, so that the metal film 30 can be reliably formed on the entire surface of the substrate 1 surface exposed from the opening 21 of the first resist 2, and the base film can be formed with high accuracy. In this embodiment, the second resist film 4 is formed on the metal film 30 without removing the first resist film 2, and finally the first resist film 2 and the second resist film 4 are removed. Therefore, it is possible to reduce the number of steps compared to the case where the first resist film 2 and the second resist film 4 are removed immediately after the formation of the metal film 30 and the solder film 50, respectively.

[0024] The method for manufacturing a substrate according to the present invention has been described above based on the embodiments, but the scope of the present invention is not limited to the above-mentioned embodiments and can be changed as desired within the scope of the technical concept of the present invention. For example, the base material of the substrate 1 is silicon carbide, but is not limited to silicon carbide and may be other materials such as aluminum nitride. Furthermore, the substrate 1 is not limited to a rectangular substrate and may be a circular substrate.

[0025] Although a dry film resist is used for the first resist film 2 and the second resist film 4, a liquid resist may be used for the first resist film 2 and the second resist film 4. However, when it is desired to form the second film into a trapezoidal cross section, it is preferable to use a film-like dry film resist for the second resist film 4 in order to provide the second resist film 4 with an overhang portion 42. In the resist film removal step, the second resist film 4 and the first resist film 2 are removed by irradiating the second resist film 4 and the first resist film 2 with ultraviolet light to harden the adhesive layer, thereby reducing the adhesive force, and the second resist film 4 and the first resist film 2 are peeled off from the substrate 1. However, for example, the substrate 1 may be immersed in a solvent, and the adhesive layer of the second resist film 4 and the first resist film 2 may be dissolved by the solvent to reduce the adhesive force, and the second resist film 4 and the first resist film 2 may be peeled off from the substrate 1. Furthermore, although the undercoat film is the undercoat metal film 3 in which a Ti film, a Pt film, and a Au film are laminated, the undercoat film is not limited to a laminated film and may be a single layer film, and the material is not limited either. Also, although the upper layer is the solder film 5 mainly composed of an AuSn alloy, the material of the upper layer is not limited to solder, and may be a laminated film composed of multiple films. [Explanation of symbols]

[0026] 1 Board 2 First resist film 21 Opening 3. Metallic undercoat 30 Metal Film 4 Second resist film 41 Opening 42 Overhang 5 Solder film 50 Solder film 10 Wiring board

Claims

1. A method for manufacturing a substrate comprising an underlying film on a substrate and an upper film formed on the underlying film, comprising: a first resist film forming step of forming a first resist film having an opening on the substrate; a first film forming step of forming a first film serving as the underlying film on the substrate and the first resist film; a second resist film forming step of forming a second resist film having an opening smaller than the opening of the first resist film on the first film; a second film forming step of forming a second film serving as the upper film on the first film and the second resist film; a resist film removing step of removing the first resist film and the second resist film from the substrate; A method for manufacturing a substrate, characterized by comprising the above steps.

2. The method for manufacturing a substrate according to claim 1, wherein an outer shape of the upper film is smaller than an outer shape of the underlying film.

3. The method for manufacturing a substrate according to claim 1 or 2, wherein a cross section of the upper film has a substantially trapezoidal shape.

4. The method for manufacturing a substrate according to any one of claims 1 to 3, wherein in the resist film removing step, the first film formed on the first resist film and the second film formed on the second resist film are removed from the substrate along with the removal of the first resist film and the second resist film.

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