Patent Application
20240431027
The present invention relates to a glass substrate, a through electrode, a multi-layer wiring substrate, and a method for manufacturing a glass substrate.
In recent years, electronic devices have become more sophisticated and compact. Accordingly, there have been demands for sophisticating wiring substrates mounted on the electronic devices and increasing the density of the wiring substrates. In particular, glass substrates have more excellent electrical characteristics as wiring substrates than those of silicon or the like and are low in production cost, attracting much attention.
In a case where a glass substrate is used as a wiring substrate, it is necessary to provide the glass substrate with a through hole (TGV: Through Glass Via) and form a through electrode that conducts both sides of the glass substrate. Technology related to such a glass substrate with a through electrode includes the following.
PTL 1 describes a method for manufacturing a through electrode substrate including a substrate and a conductor. The substrate includes a through hole that penetrates the substrate from a first surface to a second surface. The diameter has a local minimum value inside the hole. The conductor is disposed inside the through hole. The through hole satisfies a condition that the value obtained by summing the inclination angles (an angle at which the first surface side is widened is assumed to be a positive inclination angle) of the inner surface of the through hole with respect to the center axis at positions at distances of 6.25%, 18.75%, 31.25%, 43.75%, 56.25%, 68.75%, 81.25%, and 93.75% from the first surface in the section from the first surface to the second surface is greater than or equal to 8.0°.
In addition, in PTL 2, one or more through holes are formed in a glass substrate. A first wiring line on a first surface side of the glass substrate and a second wiring line on a second surface side are conducted via the through holes. A method for manufacturing a glass device is described that includes forming a through hole by etching and thinning a glass substrate after forming a first wiring line, and then forming a wiring line into the through hole and a second wiring line. The thinned glass substrate has a thickness of 50 μm or more and 300 μm or less. The through hole has a frustoconical shape.
Citation List, Patent Literature: PTL 1: JP 2018-39678 A; PTL 2: WO 2019/235617.
In a case where wiring layers are formed on a glass substrate and a through electrode that connects them is formed, there is a concern about the influence of thermal stress because the CTE (COEFFICIENT OF THERMAL EXPANSION or thermal expansion coefficient) of the glass and the CTE of Cu or the like that serves as materials for the wiring lines and the through electrode are different. A TCT (Thermal Cycle Test) that is an acceleration test is therefore carried out as one of reliability tests for evaluating the reliability of a device.
The shape of a through hole for increasing the reliability of a through electrode for thermal stress has not been, however, studied sufficiently in the past.
Accordingly, an object of the present invention is to provide a glass substrate, a through electrode, a multi-layer wiring substrate, and a method for manufacturing a glass substrate that each make it possible to increase reliability.
To solve the problem described above, one of typical glass substrates according to the present invention includes a through hole that penetrates the glass substrate from a first surface to a second surface. The through hole has a minimum bore diameter in the through hole in a section which is 1% to 10% from the first surface in a section from the first surface to the second surface.
According to the present invention, it is possible to provide a glass substrate, a multi-layer wiring substrate, a through electrode, and a method for manufacturing a glass substrate that each make it possible to increase reliability.
A problem, a configuration, and an advantageous effect other than those described above will be clarified from Description of the Embodiments below.
With reference to the drawing, some embodiments of the present invention will be described below. It is to be noted that the present invention is not limited by these embodiments. In addition, the same portion is denoted by the same reference sign in the drawings.
It is to be noted that a “surface” sometimes refers to not only a surface of a plate-shaped member, but also an interface of a layer that is included in the plate-shaped member and is substantially parallel with the surface of the plate-shaped member in the present disclosure. In addition, an “upper surface” or a “lower surface” means a surface illustrated in the upper direction or the lower direction in each of the drawings in a case where a plate-shaped member or a layer included in the plate-shaped member is illustrated. It is to be noted that the “upper surface” and the “lower surface” are also sometimes referred to as a “first surface” and a “second surface”.
In addition, a “side surface” means a surface or layer thickness portion of a plate-shaped member or a layer included in the plate-shaped member. Further, a portion of the surface and the side surface are sometimes referred to together as an “end portion”.
In addition, an “upper direction” means a vertically upper direction in a case where a plate-shaped member or a layer is horizontally placed. Further, the “upper direction” and a “lower direction” opposite thereto are sometimes referred to as a “Z axis plus direction” and a “Z axis minus direction”. The horizontal direction is sometimes referred to as an “X axis direction” or a “Y axis direction”.
Further, distance in the Z axis direction is referred to as “height” and distance in an XY plane defined by the X axis direction and the Y axis direction is referred to as “width”.
In addition, a “through electrode provided in a glass substrate” means a conductive path provided to electrically conduct the first surface and the second surface of the glass substrate in a case where the glass substrate is used as a portion of a multi-layer wiring substrate. The glass substrate does not necessarily have to be completely penetrated by a single conductive material. As long as a conductive path from the first surface and a conductive path from the second surface are connected, this is included in the through electrode. Further, the form of the through electrode includes any of a filled form in which the through hole (including any of the forms of a bottomed through hole and a completely penetrating through hole) is filled with a conductive material or a conformal form in which only the sidewall portion of the through hole is covered with a conductive material.
In addition, a “planar shape” and a “plan view” mean shapes obtained in a case where a surface or a layer is visually recognized from the upper direction. Further, a “cross-sectional shape” and a “cross-sectional view” mean shapes visually recognized from the horizontal direction in a case where a plate-shaped member or a layer is cut out in a specific direction.
Further, a “central portion” means a central portion that is not the peripheral portion of a surface or a layer. A “central direction” then means a direction from the peripheral portion of a surface or a layer to the center of the planar shape of the surface or the layer.
First, with reference to
In addition,
With reference to
As illustrated in
In addition, as illustrated in
Here, as illustrated in
In addition, the minimum point 105 is positioned in a section of 1% to 10% from the first surface in the section from the first surface 101 to the second surface 102. In other words, when the thickness of the glass substrate 100 is represented as Ts in the direction from the first surface 101 to the second surface 102 and the position of the minimum point is represented as Tm, the relationship of Ts/100<Tm<Ts/10 is satisfied. In other words, the through hole 103 has the minimum bore diameter in the through hole 103 in a section of 1% to 10% from the first surface 101 in the section from the first surface 101 to the second surface 102.
An example
An example
An example
As a result of the studies of the examples
Next, with reference to
In addition, the same applies to the region in the lower direction of the minimum point 105. A tangent line L2 that comes into contact with the inner wall surface is drawn and the intersection between the tangent line L2 and the virtual straight line Lm is represented as O2. The tangent line L2 is treated as a line segment originating from the intersection O2. It is possible to define an angle θ2 of the tangent line L2 of the inner wall surface of the through hole 103 as being within a range of 0° to −90° or a range of 270° to 360° in the lower direction of the minimum point 105. It is to be noted that
In such a case, as a method for setting a tangent line on the inner wall surface, for example, it is possible to obtain a regression line by using a least-squares method for any three points set on the inner wall surface and regard the regression line as a contact point. It is to be noted that a cross section including the center axis of the through hole 103 has been defined, but this method is not limitative. It is also possible to define a cross section in the up-down direction (z axis direction) including a plane in which the through hole has the minimum or maximum bore diameter. In addition, as a way to measure an angle, it is also possible to use, as a positive angle, an angle formed counterclockwise from the y axis plus direction of the virtual straight line Lm and use, as a negative angle, an angle formed clockwise.
It is to be noted that, as another method for indicating an inclination angle, it is also possible to divide the distance Tm from the first surface 101 to the virtual straight line Lm and use, as a tangent line, a line connecting the points on the inner wall surface corresponding to the points corresponding to the divided distances. A straight line L3 is a line that passes through the point at which the straight line apart from the first surface 101 in the lower direction by Tm/3 and parallel with the first surface 101 crosses the inner wall surface and the point at which the straight line apart from the first surface 101 in the lower direction by 2Tm/3 and parallel with first surface 101 crosses the inner wall surface. In this way, the distance between the first surface and a plane that is parallel with the first surface and passes through the minimum point may be divided and the line that passes through the point on the inner wall surface corresponding to the divided position may be considered a tangent line to evaluate the inclination angle of the inner wall surface.
Additionally, it is also possible to consider that the through hole 103 has a folded shape. As tangent lines are set for the respective points on the inner wall surface in the up-down direction (z direction), the positive and negative inclinations of the tangent lines change at the minimum point 105. In other words, the minimum point 105 is a point at which a tangent line of the inner wall surface of the through hole 103 is parallel with the Z axis direction, that is, vertical. Such a shape is referred to as a folded shape.
The reason why the three methods described above have been demonstrated is because the actual glass substrate sometimes has fine irregularities left behind on the inner wall surface. Although expressed with an ideally smooth boundary line in the diagram, a tangent line of the actual inner wall surface is difficult to evaluate. The use of any of the methods described above makes it possible to appropriately evaluate an inclination angle of the inner wall surface. It is to be noted that the methods for evaluating an inclination angle of the inner wall surface are not limited to the methods described above.
It is to be noted that the shape of the through electrode 106a is the same as the shape of the through hole 103 of the glass substrate 100 and it is thus possible to describe the shape in the same way. For example, it is possible to define the through electrode 106a as having the minimum point at which the through electrode 106a has the minimum diameter in a section of 1% to 10% from the first-surface-side electrode in the section from the first-surface-side electrode 1061a to the second-surface-side electrode 1062a.
In addition, it is also possible to use the expression of a folded shape. It is then possible to define the through hole 103 of the glass substrate 100 and the electrode outer wall portion 1064a of the through electrode 106a each as having a folded shape. In a case where the position is defined, the folded shape is positioned in a section of 1% to 10% from the first surface in the section from the first surface 101 to the second surface 102.
In addition, as illustrated in
It is possible to adopt a variety of shapes as the shape of a through electrode formed in a glass substrate. With reference to
As illustrated in
In addition, as illustrated in
As illustrated in
With reference to
As illustrated in
In addition, as illustrated in
Here, in the third embodiment, the through electrode 106c has a gap at the aperture 101a on the first surface 101 side of the glass substrate 100.
With reference to
As illustrated in
In addition, as illustrated in
As illustrated in
Additionally, it is possible to manufacture the glass substrate 100 according to the fourth embodiment by using a manufacturing method described below. It is possible to manufacture a glass substrate 300 and a multi-layer wiring substrate including the glass substrate 300 by selecting etching conditions in a step 9, for example, the concentration of a solvent to be used, the exposure time, a method such as spraying or dipping, and the like.
In each of the first embodiment to the fourth embodiment, the minimum point is provided on the inner wall portion of the through hole of the glass substrate. In the region 17 of the boundary between the glass substrate and the through hole, the shape of the glass substrate from the first surface 101 to the minimum point 105 is smoother than the shape of the conventional example. In other words, no ridge line is formed in the glass substrate 100 in the region 17. Even in a case where the glass substrate according to any of the first embodiment to the third embodiment is subjected to a thermal cycling test, such a shape releases the concentration of stress on the glass substrate. The reliability of the glass substrate is thus guaranteed in a case where a thermal cycling test is carried out.
It is to be noted that an angle θ3 in
In addition, in a case where a through electrode is filled with a conductive member like the through electrode 106a according to the second embodiment as illustrated in
In addition, the conventional through hole 103 does not have the chamfered shape 330. This causes risks that the glass substrate has a crack in a thermal cycling test and the through electrode is broken. As illustrated in
With reference to
First, ultrasonic cleaning or the like is carried out to remove a contaminant on a surface of the glass substrate. Subsequently, the glass substrate is irradiated with a laser beam from the first surface 101 side to form a laser modified portion 110 from which a through hole originates. The laser modified portion is formed to extend into the glass substrate 100 in the vertical direction from the first surface and have the lower end of the laser modified portion remain in the glass substrate.
First, a hydrofluoric acid resistant metal film (not illustrated) is formed on the first surface 101 of the glass substrate 100. The film thickness is, for example, greater than or equal to 10 nm and less than or equal to 500 nm. Subsequently, a copper coating is formed on the hydrofluoric acid resistant metal film. The film thickness is, for example, greater than or equal to 100 nm and less than or equal to 500 nm. A sputtering method or an electroless plating method is then applied. This forms the seed layer 111 on the first surface 101 of the glass substrate 100. It is possible to select a material for the hydrofluoric acid resistant metal film as appropriate from, for example, chromium, nickel, and nickel-chromium.
First, a copper coating or the like is formed on the dielectric film 113 in a sputtering method, an electroless plating method, and the like as an upper-electrode seed layer (not illustrated). A material for the copper coating is Cu or Ti/Cu (titanium copper alloy). The thickness of the copper coating ranges, for example, from 100 nm or more to 500 nm or less. Subsequently, a dry photoresist is laminated onto the first surface 101 side, a pattern is drawn, and the dry photoresist is developed. This exposes the upper-electrode seed layer. Finally, the upper-electrode seed layer is supplied with power and electrolytic copper plating of a thickness of 2 μm or more and 10 μm or less is carried out to form the upper electrode 114.
The carrier 117 is bonded onto the wiring layer formed on the first surface 101 via an adhesive (REVALPHA manufactured by Nitto Denko Corporation) for temporary adhesion. In the example of the first embodiment, the carrier 117 is a glass carrier. It is desirable that the thickness of the glass carrier range from 0.7 mm or more and 1.5 mm or less in view of the conveyance after thinning described below. It is possible to select the thickness of the carrier 117 as appropriate depending on the thickness of the glass substrate 100. In addition, the carrier 117 is a supporting body and a glass carrier is used as an example. The supporting body is not, however, limited to a glass supporting body. A metal or resin supporting body may be used.
In a case where the hydrogen fluoride solution comes into contact with the laser modified portion 110 of the glass substrate 100, etching proceeds more in the laser modified portion than in a portion on the second surface 102 that is not modified and a through hole 110a is formed. The portion on the glass substrate 100 at which the laser modified portion 110 is not formed is etched and thinned by the hydrogen fluoride solution in the direction parallel with the second surface 102. In this way, the glass substrate 100 decreases in thickness and is thinned as the through hole 110a is formed. That is, the glass substrate is thinned and the through hole is formed in a series of etching processes. The lower surface of the thinned glass substrate serves as a second surface on which a second-surface wiring layer is formed.
Additionally, it is possible to set an etching amount achieved by the hydrogen fluoride solution as appropriate depending on the thickness of the glass device. For example, in a case where the thickness of the glass substrate used in the step 1 is 500 μm, it is desirable that the etching amount thereof be greater than or equal to 100 μm and less than or equal to 450 μm. In addition, it is desirable that the thickness of the thinned glass substrate be greater than or equal to 50 μm and less than or equal to 300 μm.
Here, the control over the etching conditions makes it possible to obtain the shape at the minimum point illustrated in
In addition, for example, as the description of the control conditions, it is also possible to cause the seed layer 111 to function as an etching stopper layer, subject the second surface 102 to wet etching, and form a side-etching region having a tapered shape at the interface between the etching stopper layer and the glass substrate 100 by continuing etching for 20 minutes or more after the etching reaches the etching stopper layer.
A hydrogen fluoride aqueous solution to be used for the etching is a mixture etchant including at least one or more of hydrogen fluoride, hydrochloric acid, sulfuric acid, nitric acid, acetic acid, citric acid, and oxalic acid. It is desirable to set the composition of the etching hydrogen fluoride aqueous solution. In particular, it is desirable to set the hydrogen fluoride concentration. To achieve the ranges described above, it is desirable that the hydrogen fluoride concentration be greater than or equal to 1.0 wt % and less than or equal to 20.0 wt %. It is more desirable that the hydrogen fluoride concentration be greater than or equal to 1.0 wt % and less than or equal to 6.0 wt %.
It is desirable to set the hydrogen fluoride solution at the concentration described above and set an etching rate of 1.0 μm/min or less. It is desirable that the temperature of the etchant during the etching be greater than or equal to 10° C. and less than or equal to 40° C.
Here, as in the step 3, a pattern is formed by using a dry film resist, the seed layer is supplied with power, and electroplating of a thickness of 2 μm or more and 10 μm or less is carried out. After that, dry film resist that is no longer necessary is dissolved away. An electrode 119 formed in this way is conducted to the lower electrode 112. In this way, the seed layer 111, the lower electrode 112, and the seed layer 118 formed in the through hole 110a are formed as a through electrode 122 that penetrates the glass substrate 100. After that, the seed layer 118 that is no longer necessary is removed or an outer layer protective film 120 of an insulating resin, a solder resist, or the like is used for coating to form a second-surface wiring layer 121. In this way, the multi-layer wiring substrate according to the fifth embodiment is formed.
Additionally, it is also possible to form a via 202 in the wiring layer immediately above the through electrode 122 as illustrated in
The manufacturing method according to the fifth embodiment has been described above. It is to be noted that an inductor (coil) may be formed in a step of forming a wiring line. It is possible to select the solenoid shape and the spiral shape as the shape of the inductor. In addition, the method for forming a through hole with a laser beam has been described, but the formation of a through hole may be achieved by using a variety of methods such as a mechanical processing method, plasma etching, and dry etching.
A sixth embodiment is different from the fifth embodiment in that the inside of a through electrode is filled with a conductive member. The case of a so-called conformal form has been described in each of the first embodiment to the fifth embodiment where the inside of the through electrode is not filled with a conductive member. The case of a so-called filled form will be described in the sixth embodiment where the inside of a through electrode is filled with a conductive member.
Cu has an elastic modulus of 130 Gpa and resin has an elastic modulus of about 5 Gpa to 20 Gpa. Cu has a greater elastic modulus than that of resin. The glass may thus have a greater load in a case where the inside of the through electrode is filled with Cu. The entire through electrode is then filled with Cu as illustrated in
Table 1 illustrates results of reliability tests. Example 1 to Example 8 are LC circuit substrates to which the structure of
The column “folding position” in Table 1 is Tm illustrated in
The conditions of the reliability tests are as follows.
When Example 1 and Comparative Example 1 are compared, the reliability of Example 1 is higher. It is indicated that a glass substrate according to the present invention has high reliability.
When Examples 2, 3, and 4 and Example 1 are compared, the reliability of each of Examples 2, 3, and 4 is higher. This indicates that the folding position, that is, the position of the minimum point of a glass substrate according to the present invention contributes to an increase in reliability.
Comparative Example 2 indicates that metallization is impossible. It is indicated that the folding position influences the formation of plating.
When Example 5, Example 6, and Example 2 are compared, the reliability of each of Examples 5 and 6 is higher. It is indicated that the angle of a folded shape contributes to an increase in reliability.
Comparative Example 3 indicates that metallization is impossible. It is indicated that the angle of the folding position influences the formation of plating.
When Example 7 and Example 5 are compared, the reliability of Example 7 is higher. An effect of the chamfered shape on the second surface 102 side is indicated.
When Example 5 and Comparative Example 4 are compared, the reliability of Example 5 is higher. It is indicated that the structure in
When Example 8 and Example 7 are compared, the reliability of Example 8 is higher. The reliability of the structure in which a through electrode is filled with Cu is indicated.
In this way, it is confirmed through the reliability tests that the multi-layer wiring substrate according to the invention of this application is secured reliability.
The embodiments of the present invention have been described above, but the present invention is not limited to the embodiments described above. It is possible to make a variety of changes with the scope that does not deviate from the gist of the present invention.
Reference Signs List 100: Glass substrate; 101: First surface; 102: Second surface; 103, 110a: Through hole; 105: Minimum point; 106, 106a, 106b, 106c, 106d: Through electrode; 110: Laser modified portion; 111: Seed layer; 112: Lower electrode; 113: Dielectric film; 114: Upper electrode; 115: Insulating resin; 116: First-surface wiring layer; 117: Carrier; 118: Seed layer; 119: Electrode; 120: Outer layer protective film; 121: Second-surface wiring layer; 122, 301: Through electrode; 300: Glass substrate; 330, 1065d: Chamfered shape; 1061a, 1061b, 1061c, 1061d: First-surface-side electrode; 1062a, 1062b, 1062c, 1062d: Second-surface-side electrode; 1063a, 1063b, 1063c, 1063d: Cavity portion; 1064a, 1064b, 1064c, 1064d: Electrode outer wall portion.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-037317 | Mar 2022 | JP | national |
This application is a continuation application filed under 35 U.S.C. § 111 (a) claiming the benefit under 35 U.S.C. §§ 120 and 365 (c) of International Patent Application No. PCT/JP2023/004603, filed on Feb. 10, 2023, which is based upon and claims the benefit to Japanese Patent Application No. 2022-037317, filed on Mar. 10, 2022, the disclosures of all which are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2023/004603 | Feb 2023 | WO |
| Child | 18824153 | US |
