Ultraviolet irradiation device, ultraviolet irradiation method, and wiring substrate manufacturing method

Abstract

The invention provides an ultraviolet irradiation device, an ultraviolet irradiation method and a wiring substrate manufacturing method, which can realize electric connection with excellent reliability through slag removal based on a dry process. An ultraviolet irradiation apparatus according to one embodiment of the present invention is provided with a processing chamber, an ultraviolet light source, and a gas supply unit. The ultraviolet light source causes ultraviolet light to enter the processing chamber. The gas supply unit is capable of switching between a first state in which an oxidizing gas is supplied to the processing chamber and a second state in which a reducing gas is supplied to the processing chamber.

Description

Technical Field

[0001] This invention relates to an ultraviolet irradiation apparatus, an ultraviolet irradiation method, and a wiring board manufacturing method for irradiating objects with ultraviolet light. Background Technology

[0002] In recent years, the manufacturing methods for wiring boards incorporating electronic components such as semiconductors have been changing. Traditional wet processes involving chemical treatments are struggling to handle miniaturization and micro-scale manufacturing, necessitating dry processes that approximate semiconductor manufacturing methods. Here, the manufacturing process for wiring boards includes a descaling process. This descaling process removes adhesive residue (debris) generated when openings are made in the insulation layer using methods such as laser irradiation. Descaling processes based on dry processes utilize ultraviolet light (see, for example, Patent Documents 1 to 5).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2003-144913

[0006] Patent Document 2: International Publication No. 2002 / 036259

[0007] Patent Document 3: Japanese Patent Application Publication No. 2008-43925

[0008] Patent Document 4: Japanese Patent Application Publication No. 2014-127604

[0009] Patent Document 5: Japanese Patent Application Publication No. 2016-4802 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] After slag removal, a seed layer is stacked on the metal layer exposed from the aforementioned opening, and a wiring layer is formed on the seed layer by plating. At this point, fine etching can be performed in a wet process to clean the metal layer surface before forming the seed layer. However, in a dry process, fine etching is not possible, thus the surface condition of the metal layer becomes problematic. While slag removal generates metal oxides on the metal layer surface, if a seed layer is formed on such a surface, even if a wiring layer is formed on the seed layer, metal oxides remain at the interface between the metal layer and the seed layer, causing high resistance and delamination at this interface, thus compromising the reliability of the wiring substrate.

[0012] In view of the above, the object of the present invention is to provide an ultraviolet irradiation device, an ultraviolet irradiation method, and a wiring board manufacturing method, which can perform slag removal based on a dry process while forming an electrical connection with excellent reliability.

[0013] Technical solutions for solving the problem

[0014] To achieve the above objectives, one aspect of the ultraviolet irradiation apparatus of the present invention includes a processing chamber, an ultraviolet light source, and a gas supply unit.

[0015] The ultraviolet light source directs ultraviolet light into the processing chamber.

[0016] The gas supply unit can switch between a first state of supplying oxidizing gas to the processing chamber and a second state of supplying reducing gas to the processing chamber.

[0017] According to this structure, ultraviolet light can be incident into the processing chamber in an oxidizing gas atmosphere in the first state, and ultraviolet light can be incident into the processing chamber in a reducing gas atmosphere in the second state. The object to be processed, on which slag has formed on the metal layer, is contained in the processing chamber. Ultraviolet light is irradiated onto the object to be processed by setting the gas supply section to the first state, thereby removing the slag. Furthermore, by setting the gas supply section to the second state and irradiating the object to be processed with ultraviolet light, the metal oxides formed on the surface of the metal layer during slag removal can be reduced. Thus, slag removal can be performed by a dry process, and a metal layer surface with reduced metal oxides can be formed. Therefore, even if other conductive layers are stacked on the surface of the metal layer, the resistance and peeling at these layer interfaces can be suppressed, forming an electrical connection with excellent reliability.

[0018] Alternatively, the gas supply unit may include: a flow path switching mechanism; a first flow path connecting an oxidizing gas source (serving as the oxidizing gas) to the flow path switching mechanism; a second flow path connecting a reducing gas source (serving as the reducing gas) to the flow path switching mechanism; and a third flow path connecting the flow path switching mechanism to the processing chamber. In the first state, the flow path switching mechanism connects the first flow path and the third flow path, and disconnects the second flow path and the third flow path. In the second state, it connects the second flow path and the third flow path, and disconnects the first flow path and the third flow path.

[0019] Alternatively, the flow path switching mechanism may be a three-way valve connected to the first flow path, the second flow path, and the third flow path.

[0020] Alternatively, the ultraviolet irradiation device may also include a control unit that controls the gas supply unit and the ultraviolet light source, such that after setting the gas supply unit to the first state to allow ultraviolet light to enter the processing chamber from the ultraviolet light source, the gas supply unit is set to the second state to allow ultraviolet light to enter the processing chamber from the ultraviolet light source.

[0021] Alternatively, the ultraviolet irradiation device may also include a light source chamber, which is separated from the processing chamber by an ultraviolet transmission component and houses the ultraviolet light source.

[0022] Alternatively, the oxidizing gas may be air, oxygen, moist nitrogen, moist hydrogen, or a gas containing at least one of these.

[0023] Alternatively, the reducing gas may be hydrogen, an argon-hydrogen mixture, a nitrogen-hydrogen mixture, or a gas containing at least one of these.

[0024] To achieve the above objectives, in one aspect of the ultraviolet irradiation method of the present invention, ultraviolet light is irradiated onto a workpiece exposed through an opening in an insulating layer in an oxidizing gas atmosphere to remove residues from the insulating layer on the metal layer, and ultraviolet light is irradiated onto the workpiece in a reducing gas atmosphere to reduce the metal oxides on the surface of the metal layer formed in the residue removal step.

[0025] Alternatively, the ultraviolet irradiation method may include, prior to the process of removing the residue, irradiating the object to be treated with a laser to form the opening in the insulating layer and expose the metal layer.

[0026] Alternatively, the ultraviolet irradiation method may include a step of stacking a conductive layer on the metal layer after the step of reducing the metal oxide.

[0027] Alternatively, in the process of stacking the conductive layer, a seed layer can be formed on the metal layer by sputtering, and then plating can be performed on the seed layer.

[0028] Alternatively, the process of removing the residue and the process of reducing the metal oxide can be performed while the object to be processed is housed in the same processing chamber. The ultraviolet irradiation method, after the step of removing the residue and before the step of reducing the metal oxide, further includes a step of replacing the supply path of the oxidizing gas and the reducing gas to the processing chamber and the processing chamber with an inactive gas.

[0029] Alternatively, after the process of removing the residue, a process may be included to remove residues that were not removed by ultraviolet irradiation by ultrasonic cleaning.

[0030] To achieve the above objectives, one aspect of the present invention is an ultraviolet irradiation method that irradiates the object to be treated with ultraviolet light in an oxidizing gas atmosphere and in a reducing gas atmosphere.

[0031] To achieve the above objectives, in one aspect of the wiring substrate manufacturing method of the present invention, ultraviolet light is irradiated onto a substrate to be processed in an oxidizing gas atmosphere, wherein an insulating layer is stacked on a metal layer and the metal layer is exposed through an opening provided in the insulating layer to remove residues from the insulating layer on the metal layer; ultraviolet light is then irradiated onto the substrate to be processed in a reducing gas atmosphere to reduce the metal oxides on the surface of the metal layer formed in the residue removal step; and a conductive layer is stacked on the metal layer to form wiring.

[0032] Invention Effects

[0033] According to the present invention, an ultraviolet irradiation device, an ultraviolet irradiation method, and a wiring board manufacturing method can be provided, which can perform slag removal based on a dry process while forming electrical connections with excellent reliability. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of an ultraviolet irradiation device according to an embodiment of the present invention.

[0035] Figure 2 This is a schematic diagram of the first state of the aforementioned ultraviolet irradiation device.

[0036] Figure 3 This is a schematic diagram of the second state of the aforementioned ultraviolet irradiation device.

[0037] Figure 4 This is a schematic diagram of other structures of the aforementioned ultraviolet irradiation device.

[0038] Figure 5 This is a schematic diagram of a wiring board manufactured using the aforementioned ultraviolet irradiation device.

[0039] Figure 6 This is a schematic diagram illustrating the manufacturing method of the aforementioned wiring board.

[0040] Figure 7 This is a schematic diagram illustrating the manufacturing method of the aforementioned wiring board.

[0041] Figure 8 This is a schematic diagram illustrating the manufacturing method of the aforementioned wiring board.

[0042] Figure 9 This is a schematic diagram illustrating the manufacturing method of the aforementioned wiring board.

[0043] Figure 10 This is a schematic diagram of slag removal treatment using the aforementioned ultraviolet irradiation device.

[0044] Figure 11 This is a schematic diagram of slag removal treatment using the aforementioned ultraviolet irradiation device.

[0045] Figure 12 This is a schematic diagram of a wiring board after oxidation treatment without reduction treatment.

[0046] Figure 13 This is a top view of the test substrate of the embodiments and comparative examples of the present invention.

[0047] Figure 14 This is a cross-sectional view of the substrate used in the above experiment.

[0048] Figure 15 This is a schematic diagram illustrating the manufacturing method of the aforementioned experimental substrate. Detailed Implementation

[0049] The light source device according to an embodiment of the present invention will be described.

[0050] [Structure of the ultraviolet irradiation device]

[0051] Figure 1 This is a schematic diagram showing the structure of the ultraviolet irradiation device 100 according to this embodiment. As shown in the figure, the ultraviolet irradiation device 100 includes a chamber 101, an ultraviolet transmission component 102, an ultraviolet light source 103, an oxidizing gas source 104, a reducing gas source 105, a gas supply unit 106, and an exhaust unit 107.

[0052] Chamber 101 seals off the internal space. The structure of chamber 101 is not particularly limited. The ultraviolet transmission component 102 is a component with ultraviolet transmission properties, made of synthetic quartz glass or the like. The ultraviolet transmission component 102 is disposed within the internal space of chamber 101, dividing the internal space into a processing chamber 111 and a light source chamber 112. A stage 113 is disposed within the processing chamber 111, and a processing object T is placed on the stage 113. The processing object T is, for example, a wiring board. A gas inlet 114 and an exhaust outlet 115 are provided in the processing chamber 111. The light source chamber 112 houses the ultraviolet light source 103 and is configured to be able to provide an atmosphere of inactive gases such as nitrogen.

[0053] The ultraviolet light source 103 directs ultraviolet light into the processing chamber 111. The ultraviolet light source 103 only needs to emit ultraviolet light; for example, an excimer lamp or a low-pressure mercury lamp can be used. The ultraviolet light source 103 allows ultraviolet light to enter the processing chamber 111 from the light source chamber 112 via the ultraviolet transmission component 102. Furthermore, the ultraviolet light source 103, as long as it allows ultraviolet light to enter the processing chamber 111, can be disposed inside the processing chamber 111 or outside the chamber 101. The number and arrangement of the ultraviolet light sources 103 are not particularly limited.

[0054] Oxidizing gas source 104 supplies oxidizing gas to gas supply unit 106. The oxidizing gas can be any gas containing oxygen (oxygen molecules or oxygen atoms in a compound), such as air, oxygen, moist nitrogen, moist hydrogen, or a gas containing at least one of these. Alternatively, the oxidizing gas can be a variety of gases. Oxidizing gas source 104 can be a gas cylinder, a gas generating device, a gas supply mechanism installed in a building, etc.

[0055] The reducing gas source 105 supplies reducing gas to the gas supply unit 106. The reducing gas only needs to contain hydrogen (hydrogen molecules or hydrogen atoms in compounds), and can be hydrogen, an argon-hydrogen mixture, a nitrogen-hydrogen mixture, or a gas containing at least one of these. Alternatively, the reducing gas can be multiple gases. The reducing gas source 105 can be a gas storage cylinder, a gas generating device, a gas supply mechanism installed in a building, etc.

[0056] The gas supply unit 106 connects the oxidizing gas source 104 and the reducing gas source 105 to the processing chamber 111. The gas supply unit 106 can switch between a first state and a second state. Figure 2 This is a schematic diagram of the first state. As shown by the arrow in the diagram, the first state is the state in which oxidizing gas is supplied from the oxidizing gas source 104 to the processing chamber 111. Figure 3 This is a schematic diagram of the second state. As shown by the arrow in the diagram, the second state is the state in which reducing gas is supplied from the reducing gas source 105 to the processing chamber 111.

[0057] Specifically, such as Figure 1 As shown, the gas supply unit 106 includes a first flow path 121, a second flow path 122, a third flow path 123, and a flow path switching mechanism 124. The first flow path 121 connects the oxidizing gas source 104 to the flow path switching mechanism 124 and includes a pipe 131, a valve 132, and an MFC (mass flow controller) 133. The second flow path 122 connects the reducing gas source 105 to the flow path switching mechanism 124 and includes a pipe 134, a valve 135, and an MFC 136. The third flow path 123 connects the flow path switching mechanism 124 to the gas inlet 114 and includes a pipe 137. A humidifier such as an bubbler can also be installed in the third flow path 123.

[0058] The flow path switching mechanism 124 switches the flow paths connected between the first flow path 121, the second flow path 122, and the third flow path 123. The flow path switching mechanism 124 is, for example, a three-way valve. The flow path switching mechanism 124 forms a [structure / function] by connecting the first flow path 121 and the third flow path 123 and isolating the second flow path 122 and the third flow path 123. Figure 2The first state is shown. Furthermore, by connecting the second flow path 122 and the third flow path 123, and isolating the first flow path 121 and the third flow path 123, a [structure / condition] is formed. Figure 3 The second state is shown.

[0059] Furthermore, various oxidizing and reducing gases can be used. The flow path switching mechanism 124 can switch the flow path according to the amount of gas used; for example, a four-way valve or a five-way valve can be used. The structure of the gas supply unit 106 is not limited to the structure shown here; it can be used as long as it can switch between a first state of supplying oxidizing gas from the oxidizing gas source 104 to the processing chamber 111 and a second state of supplying reducing gas from the reducing gas source 105 to the processing chamber 111.

[0060] The exhaust section 107 is connected to the exhaust port 115 to exhaust air from the processing chamber 111. Figure 1 As shown, the exhaust section 107 includes a piping 141 and an MFM (mass flow meter) 142. Alternatively, the exhaust section 107 may have other structures.

[0061] The ultraviolet irradiation device 100 may also include a control unit (not shown). The control unit is connected to at least the ultraviolet light source 103 and the gas supply unit 106, and controls them.

[0062] Specifically, the control unit can activate the flow path switching mechanism 124 to switch the gas supply unit 106 between the first state and the second state, and in each of the first and second states, the ultraviolet light source 103 can irradiate ultraviolet light into the processing chamber 111.

[0063] The control unit may include hardware circuitry required by a computer, such as a CPU (Central Processing Unit) and storage devices (RAM, ROM). The CPU loads the control program stored in ROM into RAM and executes it, thereby performing various processes. As the control unit, devices such as PLDs (Programmable Logic Devices) such as FPGAs (Field Programmable Gate Arrays) or other ASICs (Application Specific Integrated Circuits) may also be used. Alternatively, the ultraviolet irradiation device 100 may not have a control unit; instead, the operator controls the ultraviolet light source 103 and the flow path switching mechanism 124.

[0064] The ultraviolet irradiation device 100 has the structure described above. However, the structure of the ultraviolet irradiation device 100 is not limited to the above-described structure; additional or alternative structures may also be included.

[0065] [Operation of the ultraviolet irradiation device]

[0066] The operation of the ultraviolet irradiation device 100 will be explained. In the ultraviolet irradiation device 100, the gas supply unit 106 is configured as... Figure 2 The first state shown is that, while an oxidizing gas is supplied from the oxidizing gas source 104 to the processing chamber 111, the ultraviolet light source 103 emits ultraviolet light. Thus, the object T to be processed is irradiated with ultraviolet light in an oxidizing gas atmosphere. Hereinafter, the process of irradiating ultraviolet light in this oxidizing gas atmosphere will be referred to as "oxidation treatment".

[0067] Furthermore, in the ultraviolet irradiation device 100, the gas supply unit 106 is configured as... Figure 3 The second state shown is characterized by the ultraviolet light source 103 emitting ultraviolet light while a reducing gas is supplied from the reducing gas source 105 to the processing chamber 111. Thus, the object T to be processed is irradiated with ultraviolet light in a reducing gas atmosphere. Hereinafter, the process of irradiating ultraviolet light in this reducing gas atmosphere will be referred to as "reduction treatment".

[0068] Therefore, the object to be processed, T, undergoes a reduction treatment after oxidation. Specifically, after the object to be processed, T, is housed in the processing chamber 111, the first flow path 121 is connected to the third flow path 123 via the flow path switching mechanism 124, and the valve 132 is opened to put the gas supply unit 106 into a first state (see reference). Figure 2 Therefore, oxidizing gas is supplied from oxidizing gas source 104 to processing chamber 111.

[0069] At this time, the flow rate of the oxidizing gas is adjusted by MFC133. The oxidizing gas flows in the processing chamber 111 and is discharged from the exhaust section 107. Under these conditions, the ultraviolet light source 103 emits ultraviolet light for a specified time to perform oxidation treatment.

[0070] Then, valve 132 is closed, and the second flow path 122 is connected to the third flow path 123 via the flow path switching mechanism 124. Valve 135 is then opened to put the gas supply unit 106 into the second state (see reference). Figure 3 Therefore, reducing gas is supplied from reducing gas source 105 to processing chamber 111. At this time, the flow rate of reducing gas is adjusted by MFC 136. The reducing gas flows in processing chamber 111 and is discharged from exhaust section 107. In this state, ultraviolet light source 103 emits ultraviolet light for a specified time to perform reduction treatment. Afterward, the object T to be treated is removed from processing chamber 111.

[0071] The ultraviolet irradiation device 100 operates as described above. Furthermore, the operation of the ultraviolet irradiation device 100 is not limited to the operations described above, as long as a reduction treatment is performed after the oxidation treatment. For example, the oxidation treatment and the reduction treatment can be performed in different treatment chambers. The operation of the ultraviolet irradiation device 100 as described above can be achieved by controlling the ultraviolet light source 103 and the gas supply unit 106 through the control unit, or by the user operating the ultraviolet light source 103 and the gas supply unit 106.

[0072] [Other structures related to ultraviolet irradiation devices]

[0073] Other structures of the ultraviolet irradiation device 100 will be described. Figure 4 This is a schematic diagram showing other structures of the ultraviolet irradiation device 100. This ultraviolet irradiation device 100 differs from the structures described above in that the gas supply section 106 does not have a flow path switching mechanism 124. In this structure, by opening valve 132 and closing valve 135, it is possible to achieve a first state, i.e., supplying oxidizing gas from the oxidizing gas source 104 to the processing chamber 111. Furthermore, by opening valve 135 and closing valve 132, it is possible to achieve a second state, i.e., supplying reducing gas from the reducing gas source 105 to the processing chamber 111.

[0074] In this structure, it is preferable to replace the gas supply unit 106 with an inactive gas after oxidation treatment and before reduction treatment. Specifically, after oxidation treatment in the first state, valve 132 is closed, and the oxidizing gas source 104 is replaced with an inactive gas source (hereinafter, inactive gas source). Then, valve 132 is opened, and inactive gas is supplied from the inactive gas source to the first flow path 121 and the third flow path 123. By supplying inactive gas for a certain period of time, the first flow path 121, the third flow path 123, and the processing chamber 111 are replaced by inactive gas.

[0075] Then, valve 132 is closed and valve 135 is opened, thus entering the second state for reduction processing. By replacing the gas supply section 106 with an inert gas before the reduction processing, residual oxidizing gas in the first flow path 121 is removed. If oxidizing gas remains in the first flow path 121, it will leak from the first flow path 121 into the processing chamber 111 in the second state. This would cause a chemical reaction between the oxidizing and reducing gases, damaging the reducing gas atmosphere. In contrast, by performing replacement based on an inert gas, residual oxidizing gas in the first flow path 121 can be prevented, maintaining the reducing gas atmosphere in the second state.

[0076] Alternatively, after reduction treatment in the second state, the reducing gas source 105 can be replaced with an inactive gas source, and the second flow path 122 and the third flow path 123 can be replaced with an inactive gas. In this case, the residual reducing gas in the second flow path 122 can be prevented in the next oxidation treatment, and an oxidizing gas atmosphere can be maintained. Furthermore, the replacement of the gas supply unit 106 with an inactive gas can also be performed by other methods. For example, a pipe for supplying an inactive gas can be connected to the first flow path 121 and the second flow path 122, and an inactive gas can be supplied to the first flow path 121 and the second flow path 122 via this pipe, thereby performing replacement based on an inactive gas.

[0077] [Manufacturing of wiring boards using ultraviolet irradiation devices]

[0078] The ultraviolet irradiation device 100 can be used as part of the manufacturing process of the wiring board. Figure 5 This is a schematic diagram of the wiring substrate 300. As shown in the figure, the wiring substrate 300 includes an insulating layer 301, a metal layer 302, and a conductive layer 303.

[0079] The insulating layer 301 is a layer made of insulating materials such as glass epoxy resin. An opening 301a is provided in the insulating layer 301. The opening 301a is an opening that penetrates the insulating layer 301, such as a through hole. The metal layer 302 is a layer made of a metallic material such as copper (Cu) and faces the opening 301a.

[0080] The conductive layer 303 is a layer made of conductive material and is stacked on the metal layer 302. The conductive layer 303 includes a seed layer 304 and a plating layer 305. The seed layer 304 is disposed on the insulating layer 301, the metal layer 302, and the inner peripheral surface of the opening 301a, and functions as a seed layer when the plating layer 305 is formed. The seed layer 304 has two layers: a lower layer 311 made of a metal material such as titanium (Ti) and an upper layer 312 made of a metal material such as copper (Cu). The thickness of the lower layer 311 is, for example, 30 nm, and the thickness of the upper layer 312 is, for example, 300 to 500 nm. In addition, the seed layer 304 may have one or more layers. The plating layer 305 is formed on the seed layer 304 by plating and is made of a metal material such as copper (Cu). The metal layer 302 and the conductive layer 303 constitute the wiring of the wiring substrate 300.

[0081] Figures 6 to 9 This is a schematic diagram illustrating the manufacturing method of the wiring board 300. First, as... Figure 6 As shown, a substrate 310 having a metal layer 302 and an insulating layer 301 is prepared, and a laser L is irradiated onto the insulating layer 301 on the metal layer 302. As a result, the insulating layer 301 is partially removed, as shown... Figure 7An opening 301a is formed as shown. At this time, as shown in the figure, adhesive residue (debris) S of the insulating layer 301 is generated on the metal layer 302. By removing this adhesive residue S, as shown in the figure, Figure 8 As shown, the surface 302a of the metal layer 302 is exposed at the opening 301a.

[0082] Next, as Figure 9 As shown, a seed layer 304 is formed on the insulating layer 301, the surface 302a, and the inner peripheral surface of the opening 301a. Next, a plating layer 305 is formed on the seed layer 304 by electroplating, thus fabricating... Figure 5 The wiring board 300 shown.

[0083] In the conventional manufacturing method of the wiring substrate 300, after irradiation by laser L, the adhesive residue S is removed using a solution such as permanganate. Then, the surface 302a is finely etched using sulfuric acid and hydrogen peroxide solution, and a seed layer 304 is formed on the clean surface 302a by electroless plating. Next, a conductive layer 303 is formed by stacking a plating layer 305 on the seed layer 304.

[0084] In this manufacturing method, although the electrical connection between the metal layer 302 and the conductive layer 303 is not problematic, it is difficult to handle further miniaturization and micro-scale reduction due to the use of a wet process. In contrast, by using the ultraviolet irradiation device 100, a good electrical connection between the metal layer 302 and the conductive layer 303 can be achieved through a dry process, as shown below.

[0085] Furthermore, the structure of the wiring substrate 300 described above is an example, and other structures are also possible. For instance, the conductive layer 303 may be formed by sputtering or the like without plating. In this case, the conductive layer 303 does not include the seed layer 304 and the plating layer 305, but is directly deposited on the metal layer 302 by sputtering.

[0086] [Regarding slag removal using ultraviolet irradiation devices]

[0087] In the above-described method for manufacturing the wiring board 300, the ultraviolet irradiation device 100 can be used to remove adhesive residue S (removal) generated by laser L irradiation. Figure 10 and Figure 11 This is a schematic diagram of a slag removal process using an ultraviolet irradiation device 100. In the slag removal process, such as... Figure 10 As shown, a substrate 310 containing adhesive residue S after laser L irradiation is placed in a processing chamber 111 as the irradiation target. Furthermore, the gas supply unit 106 is set to a first state (see reference). Figure 2 In this state, the substrate 310 is irradiated with ultraviolet light U to perform oxidation treatment.

[0088] The treatment chamber 111 is in an oxidizing gas atmosphere. Ultraviolet light (U) is irradiated in this atmosphere to remove the sludge S. Specifically, irradiation with U breaks the bonds in the organic compounds constituting the sludge S. Furthermore, irradiation with U generates oxygen free radicals from the oxygen contained in the oxidizing gas. These oxygen free radicals then bond with the broken sites on the sludge S, causing an oxidation reaction. Thus, the sludge S is decomposed into simple molecules such as CO2, H2O, and O2, which volatilize, thereby removing the sludge S.

[0089] At this point, the metal layer 302 is also oxidized, such as... Figure 11 As shown, a metal oxide M is formed on surface 302a. When the metal layer 302 is made of copper, the metal oxide M is mainly copper(II)(CuO).

[0090] Next, the gas supply unit 106 is set to the second state (see reference). Figure 3 In this state, the substrate 310 is irradiated with ultraviolet light U to perform a reduction treatment. The processing chamber 111 is a reducing gas atmosphere, and the metal oxide M is reduced by irradiating it with ultraviolet light U. Thus, as Figure 8 As shown, a clean surface 302a is formed. Then, as described above, a wiring substrate 300 is fabricated by forming a conductive layer 303 on surface 302a (see reference). Figure 5 The conductive layer 303 can be formed by sputtering to form a seed layer 304, and then electroplating a layer 305 on top of it. Alternatively, the conductive layer 303 can also be formed by sputtering.

[0091] Figure 12 This is a schematic diagram illustrating the wiring board 300 assuming that slag removal is performed using ultraviolet irradiation in an oxidizing gas atmosphere, but not ultraviolet irradiation in a reducing gas atmosphere. As shown in the figure, a metal oxide M is present on the surface 302a of the metal layer 302, resulting in high resistance at the interface between the metal layer 302 and the conductive layer 303, which easily leads to delamination. Even if the resistance at this interface is not very high initially during manufacturing, it will generate heat due to resistance during continued use of the wiring board 300, promoting oxidation of the metal layer 302, thus significantly impacting product lifespan. Therefore, the reliability of the wiring board 300 is compromised due to the presence of the metal oxide M.

[0092] In contrast, in the ultraviolet irradiation apparatus 100, after slag removal by ultraviolet irradiation in an oxidizing gas atmosphere, the metal oxide M is reduced by ultraviolet irradiation in a reducing gas atmosphere. Therefore, the interface between the metal layer 302 and the conductive layer 303 has low resistance and is less prone to peeling. Thus, a wiring substrate 300 with high reliability can be formed (see embodiment).

[0093] As described above, the ultraviolet irradiation device 100 can be used for slag removal during the manufacturing of the wiring board. Both the oxidation and reduction processes are dry processes, which can form a reliable electrical connection between the metal layer 302 and the conductive layer 303.

[0094] Alternatively, ultrasonic cleaning of the substrate 310 can be performed after oxidation treatment and before reduction treatment. When the insulating layer 301 is composed of a material containing both organic and inorganic substances, such as glass epoxy resin, the organic substances, including epoxy resin, are removed by oxidation treatment, but the inorganic substances, such as silica filler, are not removed. Ultrasonic cleaning can remove these inorganic substances. It should be noted that ultrasonic cleaning can be performed after oxidation treatment and before the formation of the conductive layer 303, or it can be performed after reduction treatment.

[0095] [About this announcement]

[0096] In this disclosure, the use of terms like "approximately" is merely for ease of understanding, and the use / absence of such terms has no particular significance. That is, in this disclosure, the concepts of "center," "central," "uniform," "equal," "identical," "orthogonal," "parallel," "symmetrical," "extended," "axial," "circular shape," "arc shape," "rectangular shape," "cubic shape," "polygonal shape," "ring shape," "cubic cube shape," "cylindrical shape," "disc shape," and "cone shape," which define shapes, sizes, positional relationships, and states, include concepts such as "substantially center," "substantially central," "substantially uniform," "substantially equal," "substantially identical," "substantially orthogonal," "substantially parallel," "substantially symmetrical," "substantially extended," "substantially axial," "substantially circular," "substantially arc shape," "substantially rectangular," "substantially rectangular," "substantially polygonal," "substantially ring shape," "substantially cubic," "substantially cuboid," "substantially cylindrical," "substantially disc shape," and "substantially conical." For example, it also includes states within a specified range (e.g., ±10%) based on terms such as "perfectly centered," "perfectly central," "perfectly uniform," "perfectly equal," "identically identical," "perfectly orthogonal," "perfectly parallel," "perfectly symmetrical," "perfectly extended," "perfectly axial," "perfectly circular," "perfectly arc-shaped," "perfectly rectangular," "perfectly cuboid," "perfectly polygonal," "perfectly toroidal," "perfectly cubic," "perfectly cuboid," "perfectly cylindrical," "perfectly disk-shaped," and "perfectly conical." Therefore, even without the addition of the phrase "approximately," it is possible to include concepts expressed with the addition of "approximately." Conversely, states expressed with the addition of "approximately" do not exclude perfect states.

[0097] In this disclosure, the use of terms like "greater than A" and "smaller than A" broadly encompasses both concepts that include those equal to A and those that do not. For example, "greater than A" is not limited to excluding those equal to A, but also includes "above A". Similarly, "smaller than A" is not limited to "less than A", but also includes "below A". When implementing this technology, to achieve the effects described above, specific settings can be appropriately adopted from the concepts included in "greater than A" and "smaller than A".

[0098] At least two of the feature portions described above can also be combined. That is, the various feature portions described in each embodiment can be arbitrarily combined without distinguishing between embodiments. In addition, the various effects described above are merely illustrative and not limiting; other effects may also be achieved.

[0099] Example

[0100] Test substrates for the examples and comparative examples were fabricated, and HAST (High Accelerated Stress Test) was performed. Figure 13 This is a top view of the experimental substrate 500. Figure 14 This is a cross-sectional view of the test substrate 500. As shown in these figures, the test substrate 500 includes a first insulating layer 501, wiring 502, a second insulating layer 503, a first terminal 504, a second terminal 505, and a protective layer 506.

[0101] The first insulating layer 501 is made of glass epoxy resin and has a surface 501a and a back surface 501b. A through hole 501c is provided in the first insulating layer 501, which penetrates the first insulating layer 501 between the surface 501a and the back surface 501b.

[0102] The seed layer of wiring 502 (not shown) is made of a metal material described later, except for copper (Cu), and includes a surface wiring portion 511, a back wiring portion 512, and a through-hole wiring portion 513. The surface wiring portion 511 is provided on the surface 501a, and the back wiring portion 512 is provided on the back surface 501b.

[0103] The through-hole wiring section 513 is disposed in the through-hole 501c and connects the surface wiring section 511 and the back wiring section 512.

[0104] The second insulating layer 503 is made of glass epoxy resin and covers the back surface 501b and the back wiring portion 512. The first terminal 504 is made of copper (Cu) and is disposed on the surface 501a, connecting to one end of the wiring 502. The second terminal 505 is also made of copper (Cu) and is disposed on the surface 501a, connecting to the other end of the wiring 502. The protective layer 506 covers the surface 501a and the surface wiring portion 511, protecting the wiring 502. Additionally, in... Figure 13 The illustration of protective layer 506 is omitted. Protective layer 506 is composed of solder resist.

[0105] The test substrate 500 has the configuration described above. The first terminal 504 and the second terminal 505 are connected via a wiring 502, which is configured to pass through all the through-hole wiring portions 513. The number of through-hole wiring portions 513 is 200. Figure 13Only a portion of it is shown in the diagram. Such experimental substrates are called "daisy chains".

[0106] Figure 15 This is a schematic diagram illustrating the manufacturing method of the test substrate 500. As shown in the figure, a substrate 530 having an insulating layer 501 and a back wiring portion 512 is prepared, and a through hole 501c is formed by irradiating the insulating layer 501 with a laser. Adhesive residue S is formed on the back wiring portion 512 exposed in the through hole 501c.

[0107] In the embodiment, the substrate 530 with the formed adhesive residue S is subjected to the oxidation treatment described in the above embodiment, i.e., ultraviolet irradiation in an oxidizing gas atmosphere, to remove the adhesive residue S. Then, a reduction treatment is performed, i.e., ultraviolet irradiation in a reducing atmosphere, to reduce the metal oxide. On the other hand, in the comparative example, the substrate 530 with the formed adhesive residue S is subjected to oxidation treatment to remove the adhesive residue S, without reduction treatment. Alternatively, adhesive residue S is removed using a wet process.

[0108] Subsequently, a seed layer is formed on surface 501a, the inner peripheral surface of through-hole 501c, and the back wiring portion 512. The seed layer is formed by sputtering or electroless plating. Next, a resist pattern is formed on the seed layer by photolithography, and Cu is deposited by electroplating at the openings of the pattern to form through-hole wiring portion 513, surface wiring portion 511, first terminal 504, and second terminal 505. After removing the resist pattern, a second insulating layer 503 and a protective layer 506 are formed to fabricate a test substrate 500.

[0109] HAST was performed on the test substrate 500. Specifically, the test substrate 500 was housed in a thermostatic bath set at 85°C / RH (relative humidity) of 85%, and a certain voltage was applied between the first terminal 504 and the second terminal 505 to energize it. A milliohm meter was used to measure the voltage. Digital Multimeter (manufactured by Iwasaki Telecommunications Co., Ltd.) measures resistance at the start and after 170 hours.

[0110] Table 1 below shows the composition and measurement results of the test substrate 500 for the comparative example.

[0111] [Table 1]

[0112] In Comparative Examples 1 to 5, only oxidation treatment was performed, i.e., slag removal was carried out using a dry process. The oxidizing gas in the oxidation treatment was set to 100% oxygen (O2). Regarding the processing time of the oxidation treatment, it was set to 10 seconds for Comparative Example 1, 100 seconds for Comparative Example 2, 300 seconds for Comparative Example 3, and 1000 seconds for Comparative Example 4. In Comparative Example 6, a cleaning treatment using permanganate was performed, i.e., slag removal was carried out using a wet process.

[0113] Regarding the seed layer, in Comparative Examples 1 to 4, a seed layer composed of titanium (Ti) / copper (Cu) was formed by sputtering. In Comparative Examples 5 and 6, a seed layer composed of nickel (Ni) was formed by electroless plating.

[0114] Table 2 below shows the configuration and measurement results of the test substrate 500 of the embodiment.

[0115] [Table 2]

[0116] In Examples 1 to 3, a reduction treatment was performed after the oxidation treatment, i.e., slag removal was carried out by a dry process. The oxidizing gas in the oxidation treatment was set to 100% oxygen (O2). The processing time for the oxidation treatment was 100 seconds in Examples 1 to 3. The reducing gas in the reduction treatment was 100% hydrogen (H2) in Example 1, an argon-hydrogen (5%) mixture (Ar / H2) in Example 2, and a nitrogen-hydrogen (5%) mixture (N2 / H2) in Example 3. The processing time for the reduction treatment was 100 seconds in Examples 1 to 3. Regarding the seed layer, in Examples 1 to 3, a seed layer composed of titanium (Ti) / copper (Cu) was formed by sputtering.

[0117] Tables 1 and 2 show the resistance values ​​before HAST (at the start of the thermostatic bath) and after HAST (after 170 hours of immersion in the thermostatic bath), as well as the rate of change of resistance as their rate of change. Furthermore, in Comparative Example 5, a seed layer was not formed through electroless plating, so the resistance value could not be measured.

[0118] In Table 1, if we compare Comparative Examples 1 to 4 as dry processes and Comparative Example 6 as wet processes, the resistance values ​​before and after HAST are larger in Comparative Examples 1 to 4.

[0119] This means that copper oxide (II) (CuO) is formed on the surface of the back wiring portion 512 through oxidation treatment, and the resistance between the back wiring portion 512 and the through-hole wiring portion 513 increases.

[0120] In particular, in Comparative Examples 1 and 4, the resistance value and resistance change rate were large, but in Comparative Example 1, this was due to insufficient slag removal caused by the short oxidation treatment time of only 10 seconds. In addition, in Comparative Example 4, a large amount of copper(II) oxide was generated due to the long oxidation treatment time of 1000 seconds.

[0121] On the other hand, in Examples 1 to 3 shown in Table 2, the resistance values ​​and resistance change rates are smaller than those of Comparative Examples 1 to 4, indicating that the copper oxide (II) generated by the oxidation treatment is reduced by the reduction treatment. Furthermore, it can be seen that in Examples 1 to 3, the resistance values ​​and resistance change rates are also smaller than those of Comparative Example 6, which uses a wet process, indicating that the resistance can be suppressed to the same level as or better than that of the wet process using a dry process.

[0122] As described above, in this technology, it can be said that by performing a reduction treatment after oxidation treatment, a highly reliable electrical connection can be achieved while removing adhesive residue.

[0123] Explanation of icon numbers

[0124] 100… Ultraviolet irradiation device; 101… chamber; 102…Ultraviolet transmission component; 103… Ultraviolet light source; 104…Oxidizing gas source; 105…reducing gas source; 106…Gas Supply Department; 107…exhaust section; 111…processing room; 112…light source chamber; 113…stage; 114…Gas inlet; 115…exhaust port; 121…First flow path; 122…Second flow path; 123… Third flow path; 124… Flow path switching mechanism.

Claims

1. An ultraviolet irradiation device, comprising: Processing room; An ultraviolet light source is used to direct ultraviolet light into the processing chamber; and The gas supply unit is capable of switching between a first state of supplying oxidizing gas to the processing chamber and a second state of supplying reducing gas to the processing chamber.

2. The ultraviolet irradiation device according to claim 1, wherein, The gas supply unit includes: a flow path switching mechanism; a first flow path connecting an oxidizing gas source (serving as the oxidizing gas) to the flow path switching mechanism; a second flow path connecting a reducing gas source (serving as the reducing gas) to the flow path switching mechanism; and a third flow path connecting the flow path switching mechanism to the processing chamber. In the first state, the flow path switching mechanism connects the first flow path and the third flow path, and disconnects the second flow path and the third flow path. In the second state, it connects the second flow path and the third flow path, and disconnects the first flow path and the third flow path.

3. The ultraviolet irradiation device according to claim 1, wherein, The flow path switching mechanism is a three-way valve connected to the first flow path, the second flow path, and the third flow path.

4. The ultraviolet irradiation device according to claim 1, wherein, The ultraviolet irradiation device further includes a control unit that controls the gas supply unit and the ultraviolet light source, such that after setting the gas supply unit to the first state to allow ultraviolet light to enter the processing chamber from the ultraviolet light source, the gas supply unit is set to the second state to allow ultraviolet light to enter the processing chamber from the ultraviolet light source.

5. The ultraviolet irradiation device according to claim 1, wherein, The ultraviolet irradiation device also includes a light source chamber, which is separated from the processing chamber by an ultraviolet transmission component and houses the ultraviolet light source.

6. The ultraviolet irradiation device according to claim 1, wherein, The oxidizing gas is air, oxygen, moist nitrogen, moist hydrogen, or a gas containing at least one of these.

7. The ultraviolet irradiation device according to claim 1, wherein, The reducing gas is hydrogen, an argon-hydrogen mixture, a nitrogen-hydrogen mixture, or a gas containing at least one of these.

8. A method for ultraviolet treatment, wherein, Ultraviolet light is used to irradiate the object to be processed, through an opening in the insulating layer, onto the metal layer to remove residue from the insulating layer. The metal oxides on the surface of the metal layer formed in the residue removal process are reduced by irradiating the object to be treated with ultraviolet light in a reducing gas atmosphere.

9. The ultraviolet treatment method according to claim 8, wherein, Prior to the process of removing the residue, the process includes irradiating the object to be processed with a laser to form the opening in the insulating layer and expose the metal layer.

10. The ultraviolet treatment method according to claim 8, wherein, The process includes a step of stacking a conductive layer on the metal layer after the step of reducing the metal oxide.

11. The ultraviolet treatment method according to claim 10, wherein, In the process of stacking the conductive layer, a seed layer is formed on the metal layer by sputtering, and a plating is performed on the seed layer.

12. The ultraviolet treatment method according to claim 8, wherein, The process of removing the residue and the process of reducing the metal oxide are performed while the object to be processed is housed in the same processing chamber. After the process of removing the residue and before the process of reducing the metal oxide, the process further includes a step of replacing the supply path of the oxidizing gas and the reducing gas to the processing chamber and the processing chamber with an inactive gas.

13. The ultraviolet treatment method according to claim 8, wherein, The process after removing the residue includes a step of removing residue that was not removed by ultraviolet irradiation by ultrasonic cleaning.

14. A method for ultraviolet treatment, wherein, Irradiating the object to be treated with ultraviolet light in an oxidizing gas atmosphere. The object to be treated is irradiated with ultraviolet light in a reducing gas atmosphere.

15. A method for manufacturing a wiring board, wherein, In an oxidizing gas atmosphere, a substrate with an insulating layer stacked on a metal layer, exposing the metal layer through an opening in the insulating layer, is irradiated with ultraviolet light to remove residue from the insulating layer on the metal layer. The substrate to be processed is irradiated with ultraviolet light in a reducing gas atmosphere to reduce the metal oxides on the surface of the metal layer formed in the residue removal process. A conductive layer is stacked on the metal layer to form a wiring.

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