JP2013077807A - Method for manufacturing substrate and method for manufacturing wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of reducing the time required to end filling of a through hole with metal by electrolytic plating as compared with conventional methods.SOLUTION: A method for manufacturing a substrate comprises: a step A of forming a plating ground layer 7 on a lower surface side a glass substrate 2 in which a through hole 3 is formed; a step B of blocking a lower opening of the through hole 3 by forming a first plated layer 4a on an upper surface side of the glass substrate 2 by electrolytic plating; and a step C of filling the through hole 3 with metal by depositing a second plated layer 4b made of metal in the through hole 3 by electrolytic plating from the upper surface side of the glass substrate 2. The step A forms the plating ground layer 7 from an edge of the lower opening of the through hole 3 to a part of a side wall surface of the through hole 3. The step B blocks the lower opening of the through hole 3 by causing a growth of the first plated layer 4a from a surface of the plating ground layer 7 inside the through hole 3. The step C fills the through hole 3 with plated metal by causing a growth of the second plated layer 4b from a surface of the first plated layer 4a toward the upper opening of the through hole 3 inside the through hole 3.

Description

  The present invention relates to a substrate manufacturing method using a glass substrate and a wiring substrate manufacturing method.

  In recent years, for example, it has been demanded to enable high-density mounting of electronic components and the like while ensuring high connection reliability on a wiring board on which electronic components such as MEMS (Micro Electro Mechanical System) are mounted. . To meet this demand, the wiring board is not a resin board, but a glass board with excellent smoothness, hardness, insulation, heat resistance, etc. is used as the core board, and metal is filled in the through holes formed in the glass board. Thus, a method for manufacturing a substrate that can be used as a double-sided wiring substrate has been proposed by the present inventors (see, for example, Patent Document 1).

  Patent Document 1 proposes a substrate manufacturing method having a step of forming a through hole in a glass substrate and a step of filling a metal into the through hole by a plating method (electrolytic plating). Among these, in the step of filling the through holes with metal, in the initial stage, one of the openings of the through holes on the front and back surfaces of the glass substrate is closed with metal, and then from one of the closed openings to the other A metal is deposited toward the opening of the metal and the through hole is filled with the metal. Specifically, the steps shown in FIGS. 7A to 7D are employed in a series of steps of the substrate manufacturing method.

  In the step shown in FIG. 7A, a chromium layer 53a, a chromium copper layer 53b, and a copper layer 53c are sequentially laminated on the lower surface side of the glass substrate 52 provided with the through holes 51, thereby forming a three-layer structure. A plating base layer 53 is formed. Next, in the step shown in FIG. 7B, the plating layer 54 is formed on the lower surface side of the glass substrate 52 by electrolytic plating, so that one (lower) opening of the through hole 51 is closed by the plating layer 54. ing. Thereafter, in the steps shown in FIGS. 7C and 7D, the through hole 51 is filled with the plating layer 54 by growing the plating layer 54 by electrolytic plating from the upper surface side of the glass substrate 52.

International Publication No. 2005/027605

  However, the conventional substrate manufacturing method has the following problems. That is, when one through-hole 51 is closed with metal (plating layer 54) and then the through-hole 51 is embedded by the growth of the plating layer 54, from one opening to the other through-hole 51. The metal needs to be grown by plating over almost the entire region, that is, the entire depth dimension of the through hole 51 (the thickness dimension T of the glass substrate 52). For this reason, there is a problem that it takes time to finish filling the through hole 51 with metal by electrolytic plating. In particular, in recent years, the hole diameter of the through hole 51 is reduced with the miniaturization of the wiring, and metal ions generated by electrolytic plating are difficult to enter the through hole 51. For this reason, it takes a long time to finish filling the through hole 51 with metal by electrolytic plating.

  The present invention has been made in view of the above problems, and its purpose is a technique capable of shortening the time required to finish filling the through hole with metal by electrolytic plating, as compared with the case where the conventional method is adopted. Is to provide.

The invention disclosed in this specification is a substrate manufacturing method. In this substrate manufacturing method, a plate-like glass base material having a first surface and a second surface that are in a front-back relationship, the first surface side is a first opening, and the second surface side is a second opening. A first step of preparing a glass substrate having a through-hole formed therein, a second step of forming a metal plating underlayer on the first surface side of the glass substrate, and the first surface side of the glass substrate Forming a metal first plating layer by electrolytic plating on the first opening of the through-hole by the first plating layer, and electrolytic plating from the second surface side of the glass substrate. And a fourth step of filling the through hole with metal by depositing a second plating layer of metal in the through hole.
The substrate manufacturing method is characterized in that, in the second step, the plating base layer is formed from the edge of the first opening of the through hole to a part of the side wall surface of the through hole, and in the third step, By growing the first plating layer from the surface of the plating base layer inside the through hole, the first opening of the through hole is closed by the first plating layer, and the through hole is formed in the fourth step. The through hole is filled with a metal by growing the second plated layer from the surface of the first plated layer inside to the second opening of the through hole.
According to this substrate manufacturing method, the first plating layer also grows from the plating base layer formed on the side wall of the through hole. If the first plating layer grows from the side wall, the first opening is closed with a thick metal layer. When the hole is viewed from the second opening, it becomes a bottomed hole, but the bottom becomes shallow because the first opening is closed with a metal having a thickness. Metal ions in the electrolytic solution easily enter the metal layer, and a decrease in metal ion concentration associated with metal plating growth is suppressed. As a result, the metal plating growth rate is maintained, and the metal filling of the through holes proceeds efficiently.

The substrate manufacturing method is also preferably applied to a configuration having a fifth step of flattening at least the first surface of the first and second surfaces of the glass substrate by machining after the fourth step. can do.
In this case, in the second step, even after the surface layer portion on the first surface side of the glass substrate is removed by the machining in the fifth step, the first opening portion of the through hole is formed by the plating base layer and the first layer. In order to be in a state of being blocked by one plating layer, the lower part of the plating is moved to a position deeper into the through hole than the planned removal area of the glass substrate scheduled to be removed by the machining in the fifth step. It is preferable to form a formation.

When the substrate manufacturing method includes the fifth step, the first plating layer and the plating base layer are removed from the first surface of the glass substrate after the fourth step and before the fifth step. It is preferable to have a step of exposing the first surface of the glass substrate.
When performing machining, it is preferable that the front and back surfaces of the glass substrate are made of the same material. By exposing the same material, the machining efficiency of both the front and back surfaces can be improved.

In this substrate manufacturing method, it is preferable to prepare a glass substrate in which the through hole having a cross-sectional shape (flared) in the first opening side of the through hole is formed in the first step.
According to this configuration, since the cross section of the first opening has a shape that widens toward the first surface side of the substrate on which the plating base layer is to be formed, a part of the side wall of the through hole is plated when the plating base layer is formed. It becomes easy to form an underlayer.

In the substrate manufacturing method, it is preferable that the plating base layer is formed by sputtering on the first surface side of the glass substrate in the second step.
When the sputtering method is used, the metal layer is formed on the glass substrate with good adhesion. The glass substrate and the plating layer are firmly bonded by the mediation of the plating base layer having excellent adhesion.

  The present specification also discloses a method for manufacturing a wiring board. According to the method for manufacturing the wiring substrate, after the glass substrate formed by filling the through hole with a metal is manufactured by the substrate manufacturing method described above, the wiring pattern is formed on at least one of the first surface and the second surface of the glass substrate. Is a method for manufacturing a wiring board.

  According to the present invention, it is possible to shorten the time required to finish filling the through hole with metal by electrolytic plating, as compared with the case where the conventional method is adopted. For this reason, the productivity of the board | substrate formed by filling the through-hole of a glass substrate with a metal can be improved.

It is sectional drawing which shows the structural example of the wiring board which concerns on embodiment of this invention. It is process drawing (the 1) explaining the manufacturing method of the wiring board which concerns on embodiment of this invention. It is process drawing (the 2) explaining the manufacturing method of the wiring board which concerns on embodiment of this invention. It is an enlarged view which shows the cross-sectional shape of a through-hole. It is process drawing (the 3) explaining the manufacturing method of the wiring board which concerns on embodiment of this invention. It is process drawing (the 4) explaining the manufacturing method of the wiring board which concerns on embodiment of this invention. It is process drawing explaining the conventional board | substrate manufacturing method.

The features of the embodiments described herein are listed first.
(Feature 1) The glass substrate is made of photosensitive glass. Since photosensitive glass can form a through-hole with high precision, it is suitable for a glass wiring board, especially a double-sided glass wiring board.
(Characteristic 2) The photosensitive glass substrate is prepared by performing a pretreatment for suppressing ion migration.
The photosensitive glass substrate contains alkali metal ions such as lithium ions and potassium ions. By performing ultraviolet irradiation or heat treatment, the alkali metal ions are fixed in the substrate. Since migration of alkali metal ions is suppressed, ion migration is also suppressed.
(Feature 3) The plating base layer has a double structure, and the first layer formed on the glass substrate is a chromium layer. A chromium film is formed on the glass surface with good adhesion. By interposing a layer having excellent adhesion, the bonding state between the glass and the filled metal can be improved.
(Feature 4) The plating current density in the through hole filling step is lower than that in the through hole closing step.
(Feature 5) It is preferable that the metal which comprises a 1st plating layer and the metal which comprises a 2nd plating layer are the same. By making it the same, the electrical interface resulting from the difference in the electrical characteristics of each metal does not appear.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In the embodiment of the present invention, description will be given in the following order.
1. 1. Schematic configuration of wiring board 2. Procedure of wiring board manufacturing method 2-1. Through-hole forming step 2-2. Plating underlayer forming process 2-3. Through-hole closing step 2-4. Through-hole filling step 2-5. Substrate surface exposure process 2-6. Substrate flattening step 2-7. 2. Wiring pattern formation process Effects of the present embodiment 4. Modifications etc.

<1. Schematic configuration of wiring board>
FIG. 1 is a cross-sectional view showing a configuration example of a wiring board according to an embodiment of the present invention. The illustrated wiring board 1 is configured using a glass substrate 2. The glass substrate 2 is used as a core substrate of the wiring substrate 1. The glass substrate 2 is provided with a plurality of through holes 3 (only one is shown in FIG. 1). The through hole 3 is filled with a metal 4. A wiring pattern 6 is formed on each of the first surface and the second surface of the glass substrate 2 via the adhesion layer 5. Therefore, the wiring board 1 constitutes a double-sided wiring board. The first surface and the second surface of the glass substrate 2 are in a front-back relationship. In FIG. 1, the lower surface of the glass substrate 2 is a first surface, and the upper surface of the glass substrate 2 is a second surface. The wiring pattern 6 is formed in a pattern shape corresponding to the wiring path.

  The glass substrate 2 is configured using a photosensitive glass substrate. The photosensitive glass substrate used for the glass substrate 2 is excellent as a core substrate of the wiring substrate 1 in terms of smoothness, hardness, insulation, workability, and the like. These properties are the same for chemically tempered glass such as soda lime glass, alkali-free glass, aluminosilicate glass, etc. in addition to photosensitive glass, and these glasses can also be used for the core substrate of wiring board 1. It is.

  The through hole 3 is formed in a circular shape in plan view. In carrying out the present invention, the arrangement of the through holes 3 is not particularly limited. For this reason, the through holes 3 may be randomly arranged according to the desired pattern shape of the wiring pattern 6, may be arranged in a matrix at predetermined intervals, or other than the matrix You may arrange with the arrangement of.

  The metal 4 electrically connects the wiring patterns 6 formed on both surfaces (first surface, second surface) of the glass substrate 2 as described above. For this reason, it is preferable that the metal 4 is a metal material (conductive material) with low electrical resistance. In the embodiment of the present invention, electrolytic plating is used as a method of filling the through hole 3 with the metal 4. For this reason, the metal 4 is preferably a metal material suitable for electrolytic plating. Specifically, the metal 4 is composed of one or more of copper, nickel, gold, silver, platinum, palladium, chromium, aluminum, and rhodium. In the present embodiment, the metal 4 is made of copper.

  The adhesion layer 5 is a layer that reinforces the adhesion of the wiring pattern 6 to the glass substrate 2. The adhesion layer 5 has the same pattern shape as the wiring pattern 6. In the present embodiment, the wiring pattern 6 is made of copper like the metal 4. If this copper is directly laminated on the glass substrate 2, sufficient adhesion cannot be obtained. For this reason, the adhesion layer 5 is interposed between the glass substrate 2 and the wiring pattern 6. The adhesion layer 5 may have a two-layer structure of a chromium layer and a copper layer, a three-layer structure in which a chromium copper layer is interposed between them, or a multilayer structure of four or more layers. In the present embodiment, as an example, the adhesion layer 5 has a three-layer structure. Specifically, the adhesion layer 5 has a three-layer structure in which a chromium layer 5a, a chromium copper layer 5b, and a copper layer 5c are sequentially laminated on the glass substrate 2.

  The wiring pattern 6 is formed in a state of being laminated on the adhesion layer 5. More specifically, the wiring pattern 6 is formed on the copper layer 5 c that is the uppermost layer of the adhesion layer 5. A part of the wiring pattern 6 formed on the first surface of the glass substrate 2 and a part of the wiring pattern 6 formed on the second surface of the glass substrate 2 pass through the metal 4 filled in the through hole 3. Are electrically connected (conductive).

<2. Procedure of wiring board manufacturing method>
Next, a method for manufacturing a wiring board according to an embodiment of the present invention will be described.
The series of manufacturing processes of the wiring board includes a through hole forming process, a plating underlayer forming process, a through hole closing process, a through hole filling process, a substrate surface exposing process, a substrate flattening process, and a wiring pattern forming process. Among these, a series of processes excluding the wiring pattern forming process is a process included in the substrate manufacturing method according to the embodiment of the present invention.

(2-1. Through-hole forming step)
The through hole forming step is a step of forming the through hole 3 in the glass substrate 2. In the through-hole forming step, a plate-like glass substrate having a first surface and a second surface that are in a front-back relationship, the first surface side is the first opening, and the second surface side is the second opening. This corresponds to a step of preparing a glass substrate formed with through holes to be formed. For this reason, as a method of obtaining the glass substrate 2 with the through-hole 3, in addition to performing the through-hole forming step, for example, the glass substrate 2 with the through-hole 3 may be purchased from another manufacturer. As a method for forming the through hole 3, for example, a laser processing method or a photolithography method can be used. In the present embodiment, a photolithography method that is more advantageous than a laser processing method is used to form the through-hole 3 with high accuracy. The photolithography method is performed through exposure and development processes. For this reason, photosensitive glass in which a photosensitive substance is dispersed in glass is used as the glass substrate to be formed with the through holes 3.

In that case, if the glass substrate 2 shows photosensitivity, there will be no restriction | limiting in particular. The glass substrate 2 preferably contains at least one of gold (Au), silver (Ag), cuprous oxide (Cu ₂ O), and cerium oxide (CeO ₂ ) as a photosensitive component. It is more preferable to include the above. Such glass substrate 2, for example by _{mass%, SiO 2: 55% ~85} %, aluminum oxide _{(Al 2 O 3): 2} % ~20%, lithium oxide _{(Li 2 O): 5%} ~15 %, SiO ₂ + Al ₂ O ₃ + Li ₂ O> 85% as a basic component, Au: 0.001% to 0.05%, Ag: 0.001% to 0.5%, Cu ₂ O: 0.001 It is possible to use a material containing 1% to 1% of a photosensitive metal component and further containing CeO ₂ : 0.001% to 0.2% as a photosensitizer.

  Hereinafter, a specific procedure when the through hole 3 is formed in the glass substrate 2 by photolithography will be described. First, the part (henceforth "a through-hole formation part") which forms the through-hole 3 of the glass substrate 2 is exposed. In this exposure process, a photomask (not shown) having a mask opening is used. For example, a photomask is formed by forming a light-shielding film (such as a chromium film) in a desired pattern shape on a transparent thin glass substrate, and blocking the passage of exposure light (ultraviolet rays in this embodiment). In the exposure process, the photomask is placed in close contact with the first surface or the second surface of the glass substrate 2. Next, the glass substrate 2 is irradiated with ultraviolet rays through a photomask. As a result, the glass substrate 2 is irradiated with ultraviolet rays through a mask opening formed in the photomask corresponding to the through hole forming portion of the glass substrate 2.

  Next, the glass substrate 2 is heat-treated. The heat treatment is preferably performed at a temperature between the transition point and the yield point of the photosensitive glass substrate. This is because the heat treatment effect cannot be sufficiently obtained at a temperature lower than the transition point, and the photosensitive glass substrate may contract at a temperature higher than the yield point, which may reduce the exposure dimensional accuracy. The heat treatment time is preferably about 30 minutes to 5 hours.

  By performing such ultraviolet irradiation and heat treatment, the through hole forming portion irradiated with the ultraviolet light is crystallized. As a result, as shown in FIG. 2A, an exposure crystallization portion 3a is formed in the through hole forming portion of the glass substrate 2.

Thereafter, the glass substrate 2 on which the exposed crystallization portion 3a is formed as described above is developed. The development processing is performed by spraying an etching solution such as dilute hydrofluoric acid having an appropriate concentration on the glass substrate 2 as a developing solution. By this development processing, the exposed crystallization part 3a is selectively dissolved and removed. As a result, a through hole 3 is formed in the glass substrate 2 as shown in FIG.
The through-holes 3 are opened on the lower surface (first surface) and the upper surface (second surface) of the glass substrate 2, respectively. In the following description, the opening (first opening) of the through-hole 3 that opens to the lower surface side of the glass substrate 2 is defined as a lower opening, and the opening (second second) of the through-hole 3 that opens to the upper surface of the glass substrate 2. Opening) is defined as the upper opening.

  According to the method for forming the through holes 3 using the photolithography method, a desired number of through holes 3 having an aspect ratio of about 10 can be simultaneously formed on the glass substrate 2. For example, when the glass substrate 2 having a thickness of about 0.3 mm to 1.5 mm is used, a plurality of through holes 3 having a hole diameter (diameter) of about 30 μm to 150 μm can be simultaneously formed at a desired position. As a result, it is possible to reduce the size of the wiring pattern and increase the efficiency of the through hole forming process. Furthermore, when the land width is made extremely small or the land width is zero in order to increase the density of the wiring, the space between the through holes 3 can be secured sufficiently wide. Therefore, it is possible to form wiring between the through-holes 3 and to increase the degree of freedom in designing the wiring pattern and improve the wiring density. In addition, the wiring density can be improved by forming the plurality of through holes 3 at a narrow pitch.

  After forming the through-hole 3 using the photosensitive glass substrate 2 as described above, a glass substrate modification step may be performed as necessary. Hereinafter, the glass substrate modification step will be described.

Usually, the photosensitive glass substrate 2 contains alkali metal ions such as lithium ions (Li ⁺ ) and potassium ions (K ⁺ ). When these alkali metal ions leak to the wiring metal of the wiring substrate 1 and water is adsorbed thereto, the wiring metal is ionized between the circuits to which the voltage is applied, and this is ionized again by being reduced by the electric charge and deposited. Will occur. Due to this ion migration, in the worst case, a wiring from one circuit to the other circuit is formed by the deposited metal, and there is a possibility that the circuits are short-circuited. Such a short-circuit failure becomes prominent when the wiring interval is small. For this reason, in order to form fine wiring with high density, it is necessary to suppress ion migration.

In the glass substrate reforming step, the entire glass substrate 2 in which the through-holes 3 are formed is irradiated with, for example, ultraviolet rays at about 700 mJ / cm ² and then subjected to heat treatment at a temperature of about 850 ° C. for about 2 hours. The glass substrate 2 is crystallized. By crystallizing the entire photosensitive glass substrate 2 in this manner, alkali metal ions contained in the glass substrate 2 are less likely to move than before crystallization. For this reason, ion migration can be effectively suppressed.

(2-2. Plating underlayer forming step)
The plating base layer forming step is a step of forming a metal plating base layer 7 on the lower surface side of the glass substrate 2. In this step, the plating base layer 7 is not formed on the upper surface side of the glass substrate 2, but is formed only on the lower surface side of the glass substrate 2. Further, in the plating underlayer forming step, as shown in FIG. 3A, the side wall surface of the through hole 3 from the edge of the lower opening (first opening) of the through hole 3 together with the lower surface of the glass substrate 2. The plating underlayer 7 is also formed over a part of the substrate. Thereby, the side wall surface portion of the through hole 3 positioned on the lower surface side of the glass substrate 2 is covered with the plating base layer 7, whereas the side wall surface portion of the through hole 3 positioned on the upper surface side of the glass substrate 2 is plated. It is in an exposed state without being covered with the underlayer 7. Incidentally, the “part of the side wall surface of the through hole 3” described here is a side wall surface portion that occupies a part of the through hole 3 in the depth direction, and the edge of the lower opening of the through hole 3. The side wall surface part which continues toward the back side (upper opening part) of the through-hole 3 from.

  In the depth direction of the through hole 3, it is desirable to secure a range in which the plating base layer 7 is formed up to a position entering the deeper side of the through hole 3 than the planned removal region 8 of the glass substrate 2. The planned removal region 8 of the glass substrate 2 refers to a region where the glass substrate 2 is scheduled to be removed when the surface layer portion of the glass substrate 2 is removed by machining in a substrate flattening step described later. In FIG. 3A, the surface layer portion of the glass substrate 2 is scheduled to be removed by machining to the position indicated by two two-dot chain lines. For this reason, at the stage where the mechanical processing (planarization processing) of the glass substrate 2 is finished, the substrate portion 2 a inside the two two-dot chain lines finally becomes a portion remaining as the glass substrate 2.

  The planned removal regions 8 of the glass substrate 2 are set on both surfaces of the glass substrate 2, respectively. Among these, regarding the planned removal region 8 set on the lower surface side of the glass substrate 2, the lower opening portion of the through-hole 3 remains the plating base layer 7 and the first plating even after the surface layer portion of the glass substrate 2 is removed by machining. The plating base layer 7 is formed so as to be closed by a layer 4a (described later). Specifically, the plating base layer 7 is formed from the boundary position (the position indicated by the two-dot chain line) of the planned removal area 8 to the far side of the through hole 3.

  The plating base layer 7 is preferably formed by sputtering having good adhesion to the glass substrate 2. Specifically, for example, a chromium layer 7a having a thickness of about 0.05 μm and a copper layer 7b having a thickness of about 1.5 μm are sequentially laminated on the lower surface side of the glass substrate 2 by sputtering to form a two-layer structure. The plating base layer 7 is formed. At this time, some of the metal atoms (hereinafter also referred to as “sputtered atoms”) repelled from the target by sputtering enter the through hole 3 from the lower opening of the through hole 3 and enter the side wall surface of the through hole 3. Adhere to. For this reason, in order to efficiently attach sputtered atoms to the side wall surface of the through-hole 3, in the above-described through-hole forming step, the cross-sectional shape on the lower opening side of the through-hole 3 is flared (flared). It is desirable to form the through holes 3 in the glass substrate 2.

  Specifically, in the step of forming the through hole, when the exposed crystallization portion 3a is dissolved with the etching solution, the concentration of the etching solution is adjusted as appropriate, so that the bottom of the glass substrate 2 is formed in the depth direction of the through hole 3. The portion near the edge of the opening is melted more than the far portion. Thereby, the through-hole 3 is formed so that the hole diameter of the through-hole 3 gradually increases from the center in the depth direction toward the upper and lower openings. If the through hole 3 is formed in this way, the side wall surface on the lower opening side of the through hole 3 is the center of the through hole 3 as shown in FIG. It arrange | positions in the state inclined in flare shape with respect to the axis | shaft (alternate-dotted line). For this reason, sputtered atoms that have entered the through hole 3 from the lower opening of the through hole 3 by sputtering are likely to adhere to the side wall surface of the through hole 3. About the formation range of the plating base layer 7 in the depth direction of the through hole 3, for example, at least 1/20 or more of the depth dimension of the through hole 3 (thickness dimension of the glass substrate 2), more preferably 1/10 or more, More preferably, the range is about 1/5 to 1/2, and the side wall surface of the through hole 3 may be covered with the plating underlayer 7 within this range.

(2-3. Through-hole closing step)
The through hole closing step is a step of closing the lower opening of the through hole 3 with the first plating layer 4a by forming a metal first plating layer 4a on the lower surface side of the glass substrate 2 by electrolytic plating. In this step, as shown in FIG. 3B, the first plating layer 4 a is grown from the surface of the plating base layer 7 on the lower surface of the glass substrate 2, and also from the surface of the plating base layer 7 inside the through hole 3. By growing the first plating layer 4a, the lower opening of the through hole 3 is closed by the first plating layer 4a. In the present embodiment, the first plating layer 4a is formed by electrolytic plating of copper.

In the electrolytic plating in the through-hole closing step, for example, a copper plate is used as an anode and the plating base layer 7 of the glass substrate 2 is used as a cathode in a plating bath containing a copper sulfate aqueous solution as a plating solution. At that time, in order to perform electrolytic plating from the lower surface side (first surface side) of the glass substrate 2 on which the plating base layer 7 is formed, the lower surface side of the glass substrate 2 is made to face the anode (copper plate). In this state, copper is deposited on the surface of the plating base layer 7 by connecting a direct current power source to the anode and the cathode and applying a predetermined voltage. The formation of the first plating layer 4a depends on the diameter of the through-hole 3, but is performed under conditions of relatively higher current density than usual (for example, about 1 A / dm ^{2 to} 5 A / dm ² ). . Further, since this current density depends on the pH of the plating bath and the copper ion concentration, the value is appropriately set. Generally, when the plating solution concentration is high, the current density can be set higher than when the plating solution concentration is low. By performing electrolytic plating under such a current density condition, the lower opening of the through hole 3 can be closed by the first plating layer 4a. At this time, a part of the first plating layer 4a laminated on the plating base layer 7 by electrolytic plating crawls up the side wall surface of the through hole 3 so that the deeper side of the through hole 3 than the plating base layer 7 is. To grow up. Further, the surface of the first plating layer 4 a in the through hole 3 has a shape that is recessed in a substantially U-shaped cross section at the center of the through hole 3.

(2-4. Through hole filling step)
The through hole filling step is a step of filling the through hole 3 with metal by depositing a metal second plating layer 4 b in the through hole 3 by electrolytic plating from the upper surface side of the glass substrate 2. The “electrolytic plating from the upper surface side of the glass substrate 2” described here is electrolytic plating performed by arranging an anode on the upper surface side of the glass substrate 2 so as to face the upper surface and the lower surface of the glass substrate 2. Say. Further, “filling the through hole 3 with metal” means that the first plating layer is formed in the through hole 3 when the lower opening of the through hole 3 is closed with the first plating layer 4a in the above-described through hole closing step. Filling a portion not filled with 4a (unfilled portion) with metal.

  In the through hole filling step, as shown in FIG. 3C, the second plating layer 4 b is grown from the surface of the first plating layer 4 a toward the upper opening of the through hole 3 inside the through hole 3. The through hole 3 is filled with metal. In the present embodiment, similarly to the first plating layer 4a described above, the second plating layer 4b is formed in the through hole 3 by electrolytic plating of copper. In this case, chromium and copper constituting the plating base layer 7 (chrome layer 7a, copper layer 7b) are present inside the through hole 3 together with copper constituting the first plating layer 4a and the second plating layer 4b. The through holes 3 are buried by these metals.

In the electrolytic plating in the through hole filling step, for example, a copper plate is used as an anode and the first plating layer 4a of the glass substrate 2 is used as a cathode in a plating bath containing a copper sulfate aqueous solution as a plating solution. At that time, in order to perform electrolytic plating from the upper surface side (second surface side) of the glass substrate 2 on which the first plating layer 4a is not formed, the upper surface side of the glass substrate 2 is made to face the anode (copper plate). In this state, copper is deposited on the surface of the first plating layer 4a by connecting a direct current power source to the anode and the cathode and applying a predetermined voltage. Thus, the through hole 3 is embedded by the plating base layer 7 and the first plating layer 4a previously formed in the through hole 3 and the second plating layer 4b laminated on the first plating layer 4a. . This electrolytic plating is performed under a relatively low current density condition (for example, about 0.2 A / dm ^{2 to} 0.8 A / dm ² ). This step is performed under a condition (for example, 0.5 A / dm ² ) lower than the current density applied in the electroplating in the through hole closing step. Further, in this electrolytic plating, a so-called pulse plating method can be used. The pulse plating method is effective in that variation in the deposition rate of the plating metal in the through hole 3 is suppressed. In addition, it is important to set the applied voltage to be equal to or lower than the hydrogen overvoltage. This is because it is very difficult to remove the generated hydrogen gas bubbles when the through holes 3 have a high aspect ratio.

  By performing electrolytic plating under such conditions, copper ions in the plating bath advance into the through hole 3 from the upper opening of the through hole 3 and are deposited on the surface of the first plating layer 4a. For this reason, in the through-hole 3, the 2nd plating layer 4b grows from the surface of the 1st plating layer 4a formed previously toward an upper opening part, and the through-hole 3 is gradually embedded. When the surface of the second plating layer 4b reaches the upper opening of the through hole 3, the through hole 3 is completely embedded. Here, in order to ensure filling of the through holes 3 by the growth of the second plating layer 4b, the surface of the second plating layer 4b is placed on the upper surface side of the glass substrate 2 as shown in FIG. Electrolytic plating shall be performed until protruding.

(2-5. Substrate surface exposure process)
The substrate surface exposure step is a step of removing the first plating layer 4 a and the plating base layer 7 from the lower surface of the glass substrate 2 to expose the lower surface of the glass substrate 2. In this step, as can be seen by comparing FIG. 5A and FIG. 5B, the first plating layer 4a and the plating base layer 7 covering the lower surface of the glass substrate 2 are removed, and the glass substrate 2 The second plating layer 4b protruding to the upper surface side is recessed.

  In the substrate surface exposure process, an etching process is performed using a chemical suitable for the constituent material of the film to be removed. In this embodiment mode, the etching process is performed twice by changing the chemical solution. First, in the first etching process, for example, a copper solution constituting the first plating layer 4a or a copper layer 7b of the plating base layer 7 is formed using a chemical solution mainly composed of ferric chloride. Copper is removed (dissolved) by etching. In the first etching process, the copper constituting the second plating layer 4b is removed by etching. Next, in the second etching process, for example, using a chemical solution containing potassium ferricyanide as a main component, chromium constituting the chromium layer 7a of the plating base layer 7 is removed by etching.

  Incidentally, in the first etching process, copper is removed by etching until the chromium film 7b is exposed on the lower surface side of the glass substrate 2, but in the through hole 3, the receding surface F1 of the first plating layer 4a by the etching is formed. Etching time etc. are adjusted so that it may remain in the removal plan area | region 8 (refer FIG. 3 (A)) of the glass substrate 2. FIG. On the upper surface side of the glass substrate 2, the surface of the second plating layer 4 b is retracted into the through hole 3 by the first etching process so that the surface of the second plating layer 4 b does not protrude from the upper surface of the glass substrate 2. Let Also in this case, the etching time and the like are adjusted so that the receding surface F2 of the second plating layer 4b by the etching stays within the removal planned region 8 (see FIG. 3A) of the glass substrate 2.

(2-6. Substrate flattening step)
The substrate flattening step is a step of flattening at least the lower surface of the upper and lower surfaces of the glass substrate 2 by machining. In the present embodiment, both surfaces (upper surface and lower surface) of the glass substrate 2 are flattened by machining. Specifically, the upper and lower surfaces of the glass substrate 2 are flattened by double-sided lapping, and then both surfaces of the glass substrate 2 are finish-polished as necessary. By such machining, the surface layer portions on the upper surface side and the lower surface side of the glass substrate 2 are removed in accordance with the boundary positions of the regions to be removed 8 (positions indicated by two-dot chain lines in FIG. 3A). . As a result, as shown in FIG. 5C, both surfaces of the glass substrate 2 are flattened, and both end surfaces of the metal 4 filled in the through holes 3 are flush with the upper surface and the lower surface of the glass substrate 2, respectively. It is finished in the state. Further, the lower opening of the through hole 3 of the glass substrate 2 is closed by the plating base layer 7 and the first plating layer 4a. In this case, the copper and chromium constituting the plating base layer 7 and the copper constituting the plating layers 4a and 4b remain in the through hole 3. And these metals will be in the state with which the through-hole 3 was filled. Thereby, as shown in the said FIG. 1, the glass substrate 2 of the structure where the through-hole 3 was filled with the metal 4 is obtained.

(2-7. Wiring pattern forming step)
The wiring pattern forming step is a step of forming the wiring pattern 6 on at least one of the upper surface and the lower surface of the glass substrate 2. The wiring pattern forming process includes an adhesion layer forming process, a wiring layer forming process, and a patterning process. Hereinafter, each step will be described.

(Adhesion layer forming process)
In the adhesion layer forming step, as shown in FIG. 6A, the adhesion layer 5 is formed on each surface of the glass substrate 2 by a sputtering method. In the present embodiment, the adhesion layer 5 is formed in a three-layer structure in which a chromium layer 5a, a chromium copper layer 5b, and a copper layer 5c are sequentially laminated. Each metal layer constituting the adhesion layer 5 is desirably formed as thin as possible in consideration of the amount of side etching that occurs when the wiring pattern 6 is formed by etching, which will be described later. However, if the thickness of each metal layer of the adhesion layer 5 is too thin, the adhesion layer 5 may be removed by a process performed for patterning the wiring layer. Therefore, for example, when the adhesion layer 5 is formed in a three-layer structure as described above, the thickness of the chromium layer 5a is about 0.04 μm to 0.1 μm, and the thickness of the chromium copper layer 5b is 0.04 μm to 0 μm. It is desirable that the thickness of the copper layer 5c be about 0.5 μm to 1.5 μm. Thereby, the thickness of the adhesion layer 5 is suppressed to 2 μm or less in total.

(Wiring layer formation process)
In the wiring layer forming step, as shown in FIG. 6B, the wiring layer 6a is formed on each surface of the glass substrate 2 so as to cover the adhesion layer 5 formed earlier. The wiring layer 6a is formed by electrolytic plating. The wiring layer 6a is desirably formed as thin as possible in consideration of the amount of side etching, like the adhesion layer 5 described above. However, if the wiring layer 6a is too thin, when the temperature change of the glass substrate 2 is repeated depending on the use environment, the wiring pattern 6 may be made of metal due to the difference between the thermal expansion coefficient of the wiring layer 6a and the thermal expansion coefficient of the glass substrate 2. Fatigue may occur. For this reason, in order to ensure the reliability of the connection of the wiring pattern with respect to metal fatigue, the wiring layer 6a needs to have an appropriate thickness. Specifically, the thickness of the wiring layer 6a is preferably about 1 μm to 20 μm, and more preferably about 4 μm to 7 μm. When the thickness of the wiring layer 6a is less than 1 μm, the risk of disconnection of the wiring due to the metal fatigue increases. Further, when the thickness of the wiring layer 6a exceeds 20 μm, it becomes difficult to meet the demand for miniaturization of the wiring pattern.

(Patterning process)
In the patterning step, as shown in FIG. 6C, the wiring pattern 6 is formed by patterning the adhesion layer 5 and the wiring layer 6a on each surface of the glass substrate 2 by photolithography and etching. Specifically, after covering the wiring layer 6a of the glass substrate 2 with a resist layer (not shown), the resist layer is exposed and developed to form a resist pattern. Thereby, a part of wiring layer 6a of glass substrate 2 (part left as a wiring pattern) will be in the state covered with the resist pattern. Next, the exposed portions of the wiring layer 6a and the adhesion layer 5 are removed by etching using the resist pattern as a mask. Thereby, the wiring pattern 6 having the same pattern shape as the resist pattern is obtained. The resist used here may be a liquid resist, a dry film resist, or an electrodeposition resist. The resist type may be either a positive type or a negative type. In general, a positive resist has higher resolution than a negative resist. Therefore, a positive resist is more suitable for forming a fine wiring pattern.

<3. Effects of this embodiment>
According to the substrate manufacturing method and the wiring substrate manufacturing method according to the embodiment of the present invention, the following effects can be obtained.

(First effect)
In forming the plating base layer 7 on the lower surface side of the glass substrate 2, the plating base layer 7 is formed from the edge of the lower opening of the through hole 3 to a part of the side wall surface of the through hole 3. Therefore, after that, when the first plating layer 4 a is formed on the lower surface side of the glass substrate 2 by electrolytic plating, the first plating layer 4 a grows from the surface of the plating base layer 7 inside the through hole 3. . As a result, the first plating layer 4a starts to grow from a position that enters the deeper side of the through hole 3 than the lower opening of the through hole 3, and the first plating layer 4a opens to the lower opening of the through hole 3 during this growth process. Blocks the part. Then, when the lower opening of the through hole 3 is closed with the first plating layer 4a, a part of the through hole 3 is already embedded with the first plating layer 4a. Therefore, after that, when the second plating layer 4b is formed in the through hole 3 by electrolytic plating from the upper surface side of the glass substrate 2, the depth dimension of the through hole 3 to be embedded by the growth of the second plating layer 4b is: It becomes smaller than the entire depth dimension of the through hole 3. For this reason, compared with the case where the plating layer is grown over the entire depth dimension of the through hole as in the prior art, the time required to finish filling the metal into the through hole can be shortened.

(Second effect)
In the plating base layer forming step, the plating base layer 7 is formed up to a position that enters the deeper side of the through hole 3 than the planned removal region 8 of the glass substrate 2. For this reason, in the substrate flattening step, the lower opening of the through hole 3 is blocked by the plating base layer 7 and the first plating layer 4a even after the surface layer portion on the lower surface side of the glass substrate 2 is removed by machining. Become. Under such a state, the first plating layer 4 a is in close contact with the side wall surface of the through-hole 3 through the plating base layer 7 due to the adhesion strengthening effect provided by the plating base layer 7. For this reason, the adhesiveness between the through hole 3 and the metal 4 in which the through hole 3 is embedded becomes higher than in the case where a manufacturing condition in which the plating base layer 7 does not remain in the through hole 3 after the substrate flattening step is applied. Therefore, the airtightness (gas barrier property etc.) in the through-hole 3 part filled with the metal 4 can be improved.

(Third effect)
In the through-hole forming step, the through-hole 3 is formed in the glass substrate 2 so that the cross-sectional shape on the lower opening side of the through-hole 3 becomes a flared shape (flared). For this reason, after that, when the plating base layer 7 is formed on the lower surface side of the glass substrate 2 by sputtering, the sputter atoms are efficiently attached over a wide range from the edge of the lower opening of the through hole 3 to the side wall surface of the through hole 3. be able to.

(Fourth effect)
Prior to performing the substrate flattening step, the first plating layer 4a and the plating base layer 7 are removed from the lower surface of the glass substrate 2 to expose the lower surface of the glass substrate 2. Thereby, both the upper surface and the lower surface of the glass substrate 2 become surfaces exposed with the same (common) material called glass. For this reason, in the subsequent substrate flattening step, the flattening processing of the glass substrate 2 by machining can be performed by double-sided lapping. Thereby, it becomes possible to planarize both surfaces of the glass substrate 2 simultaneously. Therefore, the substrate manufacturing cost can be reduced compared to the case where the glass substrate 2 is planarized one side at a time. Incidentally, when the upper surface and the lower surface of the glass substrate 2 are exposed with different materials, it is difficult to apply double-sided lapping, and thus it is necessary to planarize the glass substrate 2 one side at a time.

(Fifth effect)
As a method for manufacturing a wiring board, a series of processes (through hole forming process, plating base layer forming process, through hole closing process, through hole filling process, substrate surface exposing process, substrate flattening process) belonging to the above substrate manufacturing method, The wiring pattern forming process is combined. For this reason, the wiring board 1 which used the glass substrate 2 for the core board | substrate can be efficiently manufactured by shortening the filling required time of the through-hole 3 mentioned above. Further, when the double-sided wiring board is configured, the front and back surfaces of the wiring board 1 can be metallized by inexpensive plating. Furthermore, all the wiring paths of the wiring board 1 can be made of copper (low resistance material) by performing the first plating layer 4a, the second plating layer 4b, and the wiring layer 6a by electrolytic plating of copper. .

<4. Modified example>
The technical scope of the present invention is not limited to the above-described embodiments, and various modifications and improvements may be added within the scope of deriving specific effects obtained by the structural requirements of the invention and combinations thereof. Including.

  For example, in the above-described embodiment, the method for manufacturing a wiring board has been described. However, the present invention is not limited to this, and can also be implemented as a board manufacturing method used for purposes other than the wiring board. is there.

  Moreover, in the said embodiment, although the glass substrate which has photosensitivity was used as the glass substrate 2, you may use the other glass substrate which does not have photosensitivity. In that case, in the through hole forming step, the through hole 3 can be formed in the glass substrate 2 by a method other than the photolithography method, for example, a laser processing method.

DESCRIPTION OF SYMBOLS 1 ... Wiring board 2 ... Glass board 3 ... Through-hole 4 ... Metal 4a ... 1st plating layer 4b ... 2nd plating layer 5 ... Adhesion layer 6 ... Wiring pattern 6a ... Wiring layer 7 ... Plating base layer 8 ... Plane removal area

Claims (6)

A plate-like glass substrate having a first surface and a second surface in a front-back relationship has a through hole having the first surface side as a first opening and the second surface side as a second opening. A first step of preparing a formed glass substrate;
A second step of forming a metal plating underlayer on the first surface side of the glass substrate;
A third step of closing the first opening of the through hole with the first plating layer by forming a metal first plating layer on the first surface side of the glass substrate by electrolytic plating;
A fourth step of filling the through hole with metal by depositing a second plating layer of metal in the through hole by electrolytic plating from the second surface side of the glass substrate;
In the second step, the plating base layer is formed from the edge of the first opening of the through hole to a part of the side wall surface of the through hole,
In the third step, by growing the first plating layer from the surface of the plating base layer inside the through hole, the first opening of the through hole is closed by the first plating layer,
In the fourth step, the through hole is filled with metal by growing the second plated layer from the surface of the first plated layer toward the second opening of the through hole inside the through hole. A substrate manufacturing method characterized by: After the fourth step, there is a fifth step of flattening at least the first surface of the first surface and the second surface of the glass substrate by machining,
In the second step, even after the surface layer portion on the first surface side of the glass substrate is removed by the machining in the fifth step, the first opening portion of the through hole is formed by the plating base layer and the first plating. In order to be in a state of being blocked by the layer, the plating base layer is moved to a position that is located deeper into the through hole than the planned removal region of the glass substrate that is scheduled to be removed by the machining in the fifth step. It forms, The board | substrate manufacturing method of Claim 1 characterized by the above-mentioned. After the fourth step and before the fifth step, a step of removing the first plating layer and the plating base layer from the first surface of the glass substrate to expose the first surface of the glass substrate. The substrate manufacturing method according to claim 2, further comprising: In the first step, a glass substrate is prepared in which the through hole having a cross-sectional shape on the side of the first opening of the through hole is formed in a flared shape. The manufacturing method of a board | substrate of description. 5. The substrate manufacturing method according to claim 1, wherein, in the second step, the plating base layer is formed by sputtering on the first surface side of the glass substrate. After manufacturing the board | substrate formed by filling the through-hole of the said glass substrate with the metal by the board | substrate manufacturing method in any one of Claims 1-5, at least one among the 1st surface and the 2nd surface of the said glass substrate. A method of manufacturing a wiring board, comprising forming a wiring pattern on the substrate.

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