Patent Application
20180339936
The present application is based on and claims benefit of priority under 35 U.S.C. § 119 of Japanese Patent Application No. 2017-106007, filed May 29, 2017. The contents of the application are incorporated herein by reference in their entirety.
The disclosure herein generally relates to a manufacturing method of a glass substrate and a glass substrate, particularly relates to a glass substrate having a through hole and a manufacturing method thereof.
Conventionally, a glass substrate having fine through holes has been widely used. For example, a glass substrate having a plurality of fine through holes, in which a conductive material is filled, has been used as a glass interposer.
Typically, a glass substrate having through holes is formed by irradiating at a through hole forming target position on a surface of the glass substrate with laser, to form initial through holes, and performing a wet etching treatment on the glass substrate. The initial through holes were expanded according to the wet etching treatment, and thereby through holes having desired shapes can be formed.
Recently, finer through holes, i.e. through holes with smaller diameters, have been required. In order to satisfy the requirement, diameters of the initial through holes before performing wet etching treatment needs to be further smaller, and, as a result, diameters of apertures at both ends of each through hole need to be smaller.
However, when the diameters of the apertures of the initial through holes become smaller, when performing the wet etching treatment, it becomes difficult for an etchant to sufficiently penetrate inside the initial through holes. As a result, inside the through holes obtained after the etching, a part with small diameter (referred to as a “constriction part”) may be generated.
Such a constriction part may create an adverse effect when a conductive material is filled in the through holes after the etching treatment. That is, when a constriction part is present in a through hole, it may become difficult to uniformly fill the conductive material inside the through hole.
Moreover, even if the conductive material can be filled in the through holes, when a constriction part of a conductive material is present in a glass substrate having through electrodes (e.g. a glass interposer), an electric resistance of the constriction part, in which the conductive material is filled, increases, and an electric characteristic required for the glass substrate having through electrodes may not be obtained.
Note that U.S. Pat. No. 9,296,646 discloses applying ultrasonic vibrations to a glass substrate when performing a wet etching treatment. U.S. Pat. No. 9,296,646 describes that in this case, an etchant sufficiently penetrates inside initial through holes, and a constriction part can be controlled in a through hole obtained after the etching treatment.
However, the inventors of the present application have experimentally found that even if such a countermeasure is applied, constriction parts are not sufficiently controlled.
The present invention was made in view of the aforementioned problem, and aims at providing a manufacturing method of a glass substrate having through holes in which constriction parts are significantly controlled. Moreover, the present invention aims at providing a glass substrate having through holes in which constriction parts are significantly controlled.
An aspect of the present invention provides
a manufacturing method of a glass substrate having through holes, comprising
(i) irradiating at a through hole forming target position on a first surface of the glass substrate with a laser light; and
(ii) performing a wet etching treatment on the glass substrate.
In the step (ii), the glass substrate is subjected to the wet etching treatment in a state where an ultrasonic vibration with a frequency of less than 40 kHz is applied to an etchant over at least a part of a wet etching period referred to as an ultrasonic vibration application period.
Moreover, an aspect of the present invention provides a glass substrate including a first surface; a second surface and a through hole that penetrates from the first surface to the second surface.
The through hole has a first aperture with a first diameter ϕ1 on the first surface and a second aperture with a second diameter ϕ2 on the second surface, the first diameter ϕ1 being larger than or equal to the second diameter ϕ2.
The through hole has a constriction part inside the glass substrate, the constriction part has a third diameter ϕ3 in a cross-section orthogonal to an extending direction of the through hole, the third diameter ϕ3 being less than the second diameter ϕ2.
An aspect ratio of a thickness of the glass substrate (t) to the first diameter (ϕ1), t/ϕ1, is 25 or less, and a ratio of the third diameter (ϕ3) to the first diameter (ϕ1), ϕ3/ϕ1, is 0.50 or more.
Both an arithmetic average roughness Ra of the first surface near the first aperture and arithmetic average surface roughness Ra of the second surface near the second aperture are 0.05 μm or less.
According to an aspect of the present invention, a manufacturing method of a glass substrate having through holes in which constriction parts are significantly reduced can be provided. Moreover, according to an aspect of the present invention, a glass substrate having through holes in which constriction parts are significantly reduced can be provided.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which:
In the following, with reference to drawings, embodiments of the present invention will be described.
(Glass Substrate According to Embodiment)
As illustrated in
Moreover, the glass substrate 100 may be a glass plate of any composition. For example, the glass substrate 100 may be a soda-lime glass, an alkali-free glass, or a quartz glass.
As illustrated in
As illustrated in
In the present application ϕ1, is assumed to be larger than or equal to ϕ2. That is, a surface having a larger diameter of an aperture of the through hole 120 will be referred to as a first surface 102, and a surface having a smaller diameter of an aperture of the through hole 120 will be referred to as a second surface 104. Note that in the case where both the diameters of the apertures ϕ1 and ϕ2 are substantially the same, either of the surfaces may be referred to as the first surface 102. The diameters (ϕ1 and ϕ2) may be obtained by specifying three points on an edge of an aperture to be measured (first aperture 130 and the second aperture 104) by using a reflection type optical microscope (e.g. Asahikogaku MS-200), and calculating from an approximate circle for the three points. Three points may be positions of 12 o'clock, 4 o'clock, and 8 o'clock of the edges of the aperture. When a plurality of through holes 120 are present, 10 through holes may be selected, of which their respective diameters may be obtained, and an average value of the diameters may be obtained.
Moreover, the through hole 120 has a constriction part 150 inside the through hole. The constriction part 150 is defined as a part having the smallest diameter in a cross section orthogonal to the axis of expansion of the through hole 120. Thus, a diameter ϕ3 of the constriction part 150 is less than or equal to ϕ2. The diameter ϕ3 of the constriction part is measured as follows. When the through hole 120 is irradiated with a transmitted illumination from the second surface 104 of the glass substrate side, a smallest outline of the through hole, observed using a length measuring device or the like, is approximated as a circle by a least-squares method. A diameter of the approximated circle is defined as the diameter ϕ3 of the constriction part of the through hole. When a plurality of through holes 120 are present, 10 through holes may be selected, of which their respective diameters ϕ3 may be obtained, and an average value of the diameters may be obtained.
Note that in the example of the cross section, illustrated in
Here the first glass substrate 100 has a feature that an aspect ratio t/ϕ1 of the first glass substrate 100 is 25 or less and a ratio ϕ3/ϕ2 is 0.50 or more. Note that t represents a thickness of the first glass substrate 100.
Moreover, the first glass substrate 100 has a feature that a surface roughness (arithmetic average roughness Ra) of the first surface 102 near the first aperture 130 and of the second surface 104 near the second aperture 140 is 0.05 μm or less.
Here, “near aperture” means an area between an outer periphery part of the aperture and a line separated from the outer periphery by 5 mm in a radial direction. For calculation, the surface roughness (arithmetic average roughness Ra) can be obtained by measuring using a confocal laser scanning microscope (e.g. confocal laser scanning microscope VK-X series by Keyence Corporation), and a surface irregularity in the area is measured at a measured length of 100 μm.
In this way, in the first substrate 100, the diameter ϕ3 of the constriction part 150 of the through hole 120 is sufficiently large. In other words, the through hole 120 does not have a noticeable constriction part 150.
Thus, in the first glass substrate 100, a conductive material can be filled inside the through hole 120 relatively easily. Moreover, in the first glass substrate 100, a possibility that an electric resistance of the filled part of the constriction part of the through hole 120 increases, and that a desired electric characteristic may not be obtained in a glass substrate having through through electrodes (e.g. glass interposer) can be reduced significantly.
The glass substrate 100 having such features can be applied to a high frequency device, for example.
(Manufacturing Method of Glass Substrate According to the Embodiment)
Next, with reference to
As illustrated in
(i) a step of irradiating at a through hole forming target position of a first surface of a glass substrate with a laser, to form an initial through hole (step S110); and
(ii) a step of performing a wet etching on the glass substrate, to form a through hole (step S120).
In the following, each step will be described in detail.
(Step S110)
First, a glass substrate to be processed is provided.
A glass substrate 200 has a first surface 202 and a second surface 204.
The glass substrate 200 may be a glass plate of any composition. For example, the glass substrate 200 may be a soda-lime glass, an alkali-free glass, or a quartz glass.
A thickness of the glass substrate 200 is not particularly limited, but falls within a range from 0.05 mm to 0.7 mm, for example.
Note that a shape of the glass substrate 200 is not limited to a rectangular shape illustrated in
Next, the through hole forming target position of the first surface 202 of the glass substrate 200 is irradiated with laser.
A type of laser is not particularly limited, but the laser may be a pulsed laser with a pulse width of 100 nsec or less. The laser may be a YVO4 laser, for example.
By the laser irradiation, an initial through hole that penetrates from the through hole forming target position on the first surface 202 to the second surface 204 is formed.
As illustrated in
The diameter D1 of the first aperture 225 is, for example, 20 μm or less, and may be 18 μm or less. As the diameter D1 of the first aperture 225 becomes smaller, a constriction part becomes more likely to be formed after wet etching. The embodiment of the present invention achieves a remarkable effect as the first aperture 225 becomes smaller.
(Step S120)
Next the glass substrate 200 having the initial through hole 215 is subjected to the wet etching treatment. This treatment is performed in order to extend the diameter of the initial through hole 215 to a predetermined dimension.
An etchant (hereinafter referred to as an etchant) is not particularly limited, but typically an aqueous solution including a hydrofluoric acid is used. A concentration of hydrofluoric acid is not particularly limited and determined based on a required etching speed.
An etching speed falls, for example, within a range from 0.05 μm/min to 2.0 μm/min. The etching speed may fall within a range from 0.1 μm/min to 1.0 μm/min, and is preferably 0.3 μm/min or less.
In the case where the glass substrate 200 is merely subjected to wet etching treatment, a through hole having a constriction part may be formed.
As illustrated in
A diameter ϕ1 of the first aperture 30 is larger than a diameter of ϕ2 of the second aperture 40, and the diameter ϕ2 of the second aperture is larger than a diameter ϕ3 of the construction part 50.
Such a through hole 20 having a constriction part 50 is considered to be formed because an etchant cannot sufficiently enter an inside of the through hole 20 when the wet etching treatment is performed or because a circulation of the etchant inside the through hole 20 is insufficient. That is, the etchant inside the through hole 20 is insufficient or degrades compared with the apertures 30, 40 and near the apertures. It is expected that the constriction part 50 is formed inside the through hole 20 as a result.
Particularly, in the initial through hole 215, illustrated in
When such a constriction part 50 is formed inside the through hole 20, it may become difficult to uniformly fill a conductive material inside the through hole 20. Moreover, when a conductive material is filled inside such a through hole 20, an electric resistance of a part where the conductive material is filled in the constriction part increases, and a desired electric characteristic of the glass substrate having through electrodes may not be obtained.
In contrast, in the first manufacturing method, the wet etching treatment is performed over at least a part of the entire period, in a state where an ultrasonic vibration with a frequency of less than 40 kHz is applied to the etchant. Note that, in the following, a process of applying an ultrasonic vibration to the etchant will be referred to as an “ultrasonic vibration application treatment”.
In the case of performing such an ultrasonic vibrations application treatment during the wet etching treatment, it becomes possible to cause the etchant to sufficiently enter the initial through hole 215 and to circulate inside the through hole 215. Thus, in the first manufacturing method, a conspicuous constriction part can be significantly prevented from occurring inside the through hole obtained after the etching treatment.
Note that in the ultrasonic vibration application treatment, an ultrasonic vibration with a frequency of less than 40 kHz is applied to the etchant. As a result, a great vibration energy is given to the glass substrate 200 to be subjected to the etching treatment, and there could be concern for damage to the glass substrate.
However, the inventors of the present application have confirmed experimentally that any damage such as a roughness, breakage and/or a crack on a surface did not occur in the glass substrate for which the “ultrasonic vibration application treatment” had been performed.
Thus, in the first manufacturing method, it is possible to significantly prevent a conspicuous constriction part from occurring in a through hole while preventing damages from occurring in the glass substrate 200.
In the following, with reference to
As illustrated in
In contrast, a line segment indicating a period of the ultrasonic vibration application treatment (in the following, referred to as an “ultrasonic vibration application period”) B2 extends on the time axis (horizontal axis) from the start point tc0 to an end point tcf. In other words, the ultrasonic vibration application treatment is performed from a start time tc0 to a completion time tcf. An ultrasonic vibration application treatment B2 indicates a period from the start time tc0 to the completion time tcf.
Here, in the example illustrated in
However, the above example is merely an example, and the ultrasonic vibration application period B2 may be performed in any appropriate part of the etching treatment period B1.
For example, the ultrasonic vibration application period B2 may coincide with the etching treatment period B1. In this case, the time tc0 is zero, and the time tcf is tf. Alternatively, the ultrasonic vibration application period B2 may be a period from the time 0 to a time less than the time ½·tf. In this case the time tc0 is zero and the time tcf is less than ½·tf. Moreover, the ultrasonic vibration application period B2 may not necessarily start at the time 0. In this case, the start point tc0 is greater than the time zero.
However, typically, the start point tc0 of the ultrasonic vibration application period B2 is preferably 0 (zero) or near 0. Moreover, the end point tcf of the ultrasonic vibration application period B2 preferably satisfies the relation tcf>½·tf, as illustrated in
Note that in the ultrasonic vibration application treatment, an ultrasonic vibration with a frequency less than 40 kHz, preferably less than or equal to 35 kHz, more preferably less than or equal to 30 kHz is applied. Moreover, in the ultrasonic vibration application treatment, an ultrasonic vibration with a frequency greater than or equal to 20 kHz is applied.
Note that in the wet etching treatment, an oscillatory motion may be applied to the glass substrate 200. Particularly, in the ultrasonic vibration application treatment, an oscillatory motion is preferably applied to the glass substrate 200.
In this case, an etchant can be penetrated inside the initial through holes 215 more rapidly. Moreover, a product generated by the etching treatment can be discharged to the outside of the initial through hole 215 rapidly.
As illustrated in
Note that actually the first surface 202 of the glass substrate 200, illustrated in
As illustrated in
For example, in the through hole 220, a ratio ϕ3/φ1 is 0.50 or more. Moreover, an aspect ratio of the through hole 220, i.e. the thickness of the glass substrate 200 t divided by the diameter ϕ1, is 25 or less.
In this way, in the first manufacturing method, it is possible to form the through hole 220 without a conspicuous constriction part after the wet etching treatment.
(Another Manufacturing Method of Glass Substrate According to the Embodiment)
Next, with reference to
As illustrated in
(i) a step of irradiating at a through hole forming target position of a first surface of a glass substrate with a laser, to form a reforming part (step S210); and
(ii) a step of performing a wet etching on the glass substrate, to form a through hole (step S220).
In the following, each step will be described in detail.
(step S210)
First, a glass substrate to be processed is provided.
Note that a specification or the like of the glass substrate is the same as that of the aforementioned first manufacturing method. Thus, a detailed description of the glass substrate will be omitted here. Moreover, in the following, when indicating a glass substrate or the like, the reference numerals shown in
Next, a through hole forming target position of the first first surface 202 of the glass substrate 200 is irradiated with a laser.
A type of laser is not particularly limited, but the laser may be a pulsed laser with a pulse width of 100 nsec or less. The laser may be a YVO4 laser, for example.
By the laser irradiation, a laser reforming part that extends from the first surface 202 to the second surface 204 in the glass substrate is formed. Note that the laser reforming part is different from the initial through hole formed in the step S110 in the first manufacturing method, and at this stage does not have a shape of a “hole”.
However, because the shape of the laser reforming part in the glass substrate 200 is similar to the initial through hole 215, in the laser reforming part, a diameter on the first surface will be denoted as ϕ1 and a diameter on the second surface will be denoted as ϕ2.
(Step S220)
Next, the glass substrate 200 having the reforming part is subjected to the wet etching treatment. This treatment is performed in order to ablate the reforming part, and to form a through hole at the location of the reforming part
Also in the second manufacturing method, for at least a part of the entire period of performing the etching treatment, an ultrasonic vibration with a frequency of less than 40 kHz is applied to the etchant. Thus, also in the second manufacturing method, a conspicuous constriction part can be significantly prevented from occurring inside the through hole obtained after the etching treatment.
Note that substantially step S120 in the aforementioned first manufacturing method can be referred for step step S220. Therefore, further explanation will be omitted here.
After step S220, the glass substrate 220 having the through hole 220, illustrated in
Next, examples of the present invention will be described.
Using the aforementioned first manufacturing method, a glass substrate having a through hole was manufactured as follows.
First, a first surface of a glass substrate was irradiated with laser, and an initial through hole was formed. For the glass substrate, an alkali-free glass with a thickness of 0.5 mm was used. For a laser light, a third-harmonic of a YVO4 laser (wavelength of 355 nm) was used.
A diameter ϕ1 of a first aperture of the initial through hole obtained as above was 14.5 μm, and a diameter ϕ2 of a second aperture was 3.1 μm.
Next, the glass substrate was subjected to a wet etching treatment at a room temperature.
For an etchant, a mixed acid aqueous solution of hydrofluoric acid (0.5 vol %) and hydrochloric acid (1.0 vol %) was used. An etching period was 137 minutes.
Moreover, over an entire period for the wet etching treatment, ultrasonic vibrations were applied to the etchant. Thus, in the timing chart illustrated in
The ultrasonic ultrasonic vibration was applied to the etchant by using an ultrasonic cleaning machine (VS-100III: by AS ONE Corporation). The frequency of the ultrasonic vibration was 28 kHz.
After the wet etching treatment, a glass substrate having through holes (referred to as a “sample 1”) was obtained. In the sample 1, a damage such as a crack was not found by visual inspection.
A glass substrate having a through hole was manufactured as follows.
First, with the same method as Example 1, the first surface of the glass substrate was irradiated with laser, to form an initial through hole.
Next, the glass substrate was subjected to the wet etching treatment at room temperature. However, in Example 2, ultrasonic vibration was not applied to the etchant, and only the wet etching treatment was performed. For the etchant, the aforementioned mixed acid aqueous solution was used. An etching period was 195 minutes.
After the wet etching treatment, a glass substrate having through holes (referred to as a “sample 2”) was obtained.
A glass substrate having a through hole was manufactured with the same method as Example 1.
However, in Example 3, the frequency of the ultrasonic vibration applied to the etchant during the wet etching treatment was 45 kHz. Moreover, the etching period was 175 minutes.
After the wet etching treatment, a glass substrate having through holes (referred to as a “sample 3”) was obtained.
A glass substrate having a through hole was manufactured with the same method as Example 1.
However, in Example 4, the frequency of the ultrasonic vibration applied to the etchant during the wet etching treatment was 100 kHz. Moreover, the etching period was 195 minutes.
After the wet etching treatment, a glass substrate having through holes (referred to as a “sample 4”) was obtained.
(Evaluation)
In each of the samples 1 to 4, surface roughnesses (arithmetic average roughness Ra) near the first aperture and the second aperture were measured. Moreover, dimensions of parts of the through hole were measured.
TABLE 1, in the following, shows results obtained for the respective samples as a whole.
Note that the surface roughness (arithmetic average roughness Ra) indicates only a result obtained near the first aperture. This is because the results obtained near the first aperture and near the second aperture were found to be almost the same.
From TABLE 1, it is found that a noticeable roughness on a surface of the glass substrate was not generated in any of the samples.
It is found that, in sample 2, in which the ultrasonic vibration was not applied and the wet etching treatment was performed, a conspicuous constriction part was generated, as shown in
In contrast, it is found that, in sample 3, in which the wet etching treatment was performed in the state where the ultrasonic vibration was applied, the generation of the constriction part was somewhat controlled, compared with sample 2, as shown in
However, it is found that, in sample 1, the formation of the constriction part was significantly controlled, as shown in
In this way, it was confirmed that a formation of a constriction part could be significantly controlled by applying an ultrasonic vibration with a prescribed frequency when a wet etching treatment was performed.
As described above, the preferred embodiments and the like have been described in detail. However, the present invention is not limited to the above-described specific embodiments, and various variations and modifications may be made without deviating from the scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-106007 | May 2017 | JP | national |
