Glass substrate and method for manufacturing glass substrate

Abstract

This glass substrate has a glass layer and an opening that opens on the first main surface side of the glass layer, the thickness of the glass layer is 10-300 [mu] m, and there is no burr at the end of the opening on the first main surface side.

Description

Technical Field

[0001] The invention relates to a glass substrate and a method for manufacturing the glass substrate. Background Art

[0002] In the past, in circuit substrates, composite substrates in which epoxy resin is impregnated in glass fiber are sometimes used as base substrates. However, with the high integration of circuits, substrates are required to be thinner, have high dimensional stability and high insulation. Therefore, it is considered to apply glass substrates in which through holes are provided on a thin glass layer by laser processing to packaging substrates of glass interposers or ball grid arrays (BGA).

[0003] Patent document 1: Japanese Patent Application Publication No. 2018-24563. Summary of the invention

[0004] Technical problem to be solved by the invention

[0005] However, when a through hole is formed in a thin glass layer by laser processing, the end of the opening of the through hole does not have a smooth shape but has a burr shape. If there is a burr, stress will be concentrated on this part, thereby reducing the mechanical strength of the glass substrate.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to improve the mechanical strength of a glass substrate having a glass layer in which an opening is formed.

[0007] Technical solutions for solving technical problems

[0008] The glass substrate comprises: a glass layer; and an opening portion opened on a first main surface side of the glass layer, wherein the glass layer has a thickness of 10 μm to 300 μm, and an end portion of the opening portion on the first main surface side has no burrs.

[0009] Effects of the Invention

[0010] According to the disclosed technology, it is possible to improve the mechanical strength of a glass substrate having a glass layer having an opening formed therein. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a cross-sectional view illustrating a glass substrate according to the first embodiment.

[0012] Figure 2 yes Figure 1 The opening 11 and the opening 12 shown are partially enlarged cross-sectional views of the parts and their vicinities.

[0013] Figure 3 This is a cross-sectional view (part 1) illustrating the manufacturing process of the glass substrate according to the first embodiment.

[0014] Figure 4 This is a cross-sectional view (part 2) illustrating the manufacturing process of the glass substrate according to the first embodiment.

[0015] Figure 5 This is a cross-sectional view of a glass substrate illustrating Modification 1 of the first embodiment.

[0016] Figure 6 This is a cross-sectional view of a glass substrate illustrating Modification 2 of the first embodiment.

[0017] Figure 7 It is a graph showing the evaluation results of mechanical strength.

[0018] Figure 8 This is a diagram showing the distribution of aspect ratios of the formed through holes.

[0019] Fig. 9 yes Figure 8 The photographs are of the shapes of the openings and the shapes of the through-holes of the samples No. A to D.

[0020] Fig.10 yes Figure 8 The photographs of the shapes of the openings and the shapes of the through holes of sample numbers E to H are shown. DETAILED DESCRIPTION

[0021] Hereinafter, the mode for carrying out the present invention will be described with reference to the drawings. In each of the drawings, the same components are denoted by the same reference numerals, and duplicate descriptions may be omitted.

[0022] <First Embodiment>

[0023] Figure 1 2 is a cross-sectional view of a glass substrate according to the first embodiment. Figure 1 As shown in FIG. 1 , the glass substrate 1 has a glass layer 10, a through hole 10x, an opening 11, and an opening 12. However, the glass substrate of the present invention only needs to have at least one opening, and does not necessarily have to have a plurality of openings and through holes. For example, the glass substrate of the present invention may also have a groove with a bottom having an opening, instead of a through hole.

[0024] exist Figure 1 In the illustrated glass substrate 1, the glass layer 10 includes a first principal surface 10a and a second principal surface 10b which is the opposite surface of the first principal surface 10a. The first principal surface 10a and the second principal surface 10b may be parallel to each other or may not be parallel to each other.

[0025] The glass layer 10 is not particularly limited, and an appropriate glass layer can be used according to the purpose. The glass layer 10 can be classified according to the components, such as soda-lime glass, boric acid glass, aluminosilicate glass, quartz glass, etc. In addition, according to the alkali component classification, alkali-free glass and low-alkali glass can be cited. The content of the alkali metal component (for example, Na2O, K2O, Li2O) of the above-mentioned glass is preferably 15% by weight or less, and more preferably 10% by weight or less.

[0026] Considering the surface hardness, airtightness and corrosion resistance of glass, the thickness of the glass layer 10 is preferably 10 μm or more. In addition, since it is desirable that the glass layer 10 has flexibility like a thin film, the thickness of the glass layer 10 is preferably 300 μm or less. The thickness of the glass layer 10 is more preferably 20 μm or more and 200 μm or less, and particularly preferably 30 μm or more and 150 μm or less.

[0027] There is no particular limitation on the method for forming the glass layer 10, and an appropriate method can be adopted according to the purpose. Typically, the glass layer 10 can be made by melting a mixture containing a main raw material such as silicon dioxide or aluminum oxide, a defoaming agent such as sodium sulfate or antimony oxide, and a reducing agent such as carbon at a temperature of about 1400°C to 1600°C, forming it into a thin plate, and then cooling it. Examples of the forming method of the glass layer 10 include a slit down-draw method, a melting method, and a float method. The glass layer formed into a plate by these methods can be chemically polished with a solvent such as hydrofluoric acid as needed in order to thin the plate or improve the smoothness.

[0028] In the glass layer 10, a through hole 10x is formed in a direction substantially perpendicular to the first main surface 10a. For example, when viewed from the normal direction of the first main surface 10a, the through hole 10x can be arranged two-dimensionally vertically and horizontally, or can be arranged at any position. The through hole 10x includes an opening 11 and an opening 12. The opening 11 is located at one end of the through hole 10x and opens on the first main surface 10a side of the glass layer 10. The opening 12 is located at the other end of the through hole 10x and opens on the second main surface 10b side of the glass layer 10.

[0029] When viewed from the normal direction of the first main surface 10a, the shape of the through hole 10x is, for example, circular or elliptical. When viewed from the normal direction of the first main surface 10a, the shape of the through hole 10x may also be a special shape similar to a circular or elliptical shape. Alternatively, when viewed from the normal direction of the first main surface 10a, the shape of the through hole 10x may also be a rectangular, trapezoidal, or any other shape.

[0030] The opening width L of the through hole 10x viewed in the normal direction of the first main surface 10a is preferably 5 μm to 1000 μm, more preferably 10 μm to 500 μm. The pitch of the through holes 10x is preferably 5 μm to 5000 μm, more preferably 100 μm to 1000 μm.

[0031] Note that, when the shape of the through hole 10x observed from the normal direction of the first main surface 10a is circular, the opening width L of the through hole 10x is the diameter, when it is elliptical, it is the major diameter, and when it is rectangular or square, it is the length of the diagonal. In addition, when the shape of the through hole 10x observed from the normal direction of the first main surface 10a is a shape other than the above shapes, the length of the longest straight line that can be continuously drawn from the shape of the through hole 10x observed from the normal direction of the first main surface 10a is defined as the opening width L.

[0032] The depth D of the through hole 10x is the same as the thickness of the glass layer 10. In the through hole 10x, the aspect ratio is defined by depth D / opening width L. The aspect ratio of the through hole 10x may be, for example, approximately 3 or more and 9 or less. In consideration of the ease of forming the through hole 10x, the aspect ratio of the through hole 10x is preferably 3 or more and 6 or less.

[0033] Figure 2 yes Figure 1 The opening 11 and the opening 12 shown in FIG. Figure 2 As shown, there is no burr at the end 11e on the first main surface 10a side of the opening 11. Similarly, there is no burr at the end 12e on the second main surface 10b side of the opening 12. Here, burrs refer to tiny protrusions that appear on the processed surface and cause unnecessary unevenness.

[0034] like Figure 2 As shown, the end 11e of the opening 11 and the end 12e of the opening 12 are, for example, R-shaped (rounded) in the cross-sectional view. Here, the R-shape refers to a gentle shape without small and sharp parts. The R-shape can be, for example, an arc shape, or a curved shape close to an arc. The R-shape preferably has a radius of curvature of more than a few nm and less than tens of nm. Here, the radius of curvature can be obtained by image analysis based on cross-sectional observation using an electron microscope or the like.

[0035] Figure 3 and Figure 4 1 is a cross-sectional view illustrating the manufacturing process of the glass substrate according to the first embodiment. Figure 3In the process shown, the glass layer 10 is prepared and a predetermined position of the first principal surface 10 a of the glass layer 10 is irradiated with laser light P to form a seed hole 10 s having an opening 11 opened on the first principal surface 10 a side and an opening 12 opened on the second principal surface 10 b side.

[0036] For forming the seed hole 10s, a pulsed laser is preferably used, for example, a femtosecond laser or a picosecond laser can be used. The opening width La of the seed hole 10s is smaller than the opening width L of the through hole 10x of the finally formed glass substrate 1. In addition, in this process, burrs may also exist at the ends of the opening 11 and the opening 12.

[0037] Then, in Figure 4 In the process shown, Figure 3 In the process shown, the glass layer 10 having the openings 11, 12 and the seed holes 10s formed therein is entirely placed in an etching tank 100 provided with an etchant 110, and wet etching is performed. For wet etching, for example, an etchant 110 containing hydrofluoric acid may be used. Alternatively, other etchants capable of dissolving the glass layer 10 may be used.

[0038] exist Figure 4 In the figure, the upper side of the arrow indicates the state immediately after etching has started, and the lower side of the arrow indicates the state after etching has been completed. Figure 4 As shown in FIG. 1 , by wet etching the entire glass layer 10 , the entire glass layer 10 is dissolved over time. Figure 4 On the lower side of the arrow, the thickness and width of the glass layer 10 are smaller than those on the upper side of the arrow, and the seed hole 10s is enlarged to become a through hole 10x.

[0039] In addition, since the end of the opening 11 on the first main surface 10a side and the end of the opening 12 on the second main surface 10b side are also dissolved by wet etching, after wet etching, for example Figure 2 The R shape shown in the figure. Figure 3 In the process shown, even if there are burrs at the ends of the openings 11 and 12, the burrs are dissolved and disappear during wet etching, so that the openings 11 and 12 are formed without burrs in this process.

[0040] exist Figure 4 After the process shown in FIG. 1 , the glass layer 10 is taken out from the etching tank 100 and dried, thereby completing the process of Figure 1 The glass substrate 1 is shown.

[0041] In this way, when forming the opening in the glass layer, by using laser processing and wet etching together, a glass substrate having no burrs at the end of the opening can be formed.

[0042] If the opening is formed only by laser processing as in the past, the end of the opening will not be in an R shape, and burrs will be generated at the end of the opening. If burrs are generated at the end of the opening, stress will be concentrated in this part, thereby reducing the mechanical strength of the vicinity of the opening of the glass substrate. In addition, if burrs are generated at the end of the opening, if a wiring layer is formed in the portion including the end of the opening, the wiring layer may be disconnected.

[0043] In contrast, in the glass substrate having an opening without burrs shown in the first embodiment, since there is no portion where stress is concentrated, the mechanical strength of the glass substrate can be improved. In addition, when a wiring layer is formed in a portion including the end of the opening, the possibility of disconnection of the wiring layer can be reduced. Therefore, the glass substrate of the first embodiment is suitable for use in, for example, a glass interposer for mounting a semiconductor chip or a packaging substrate of a ball grid array (BGA).

[0044] Note that glass substrates have advantages over resin substrates such as glass epoxy substrates and polyimide substrates in terms of low thermal expansion coefficient and high electrical resistance. In addition, glass substrates have advantages over silicon substrates in terms of easy realization of large area and thinness.

[0045] <Modification of the First Embodiment>

[0046] In the modification of the first embodiment, an example of a glass substrate having a hole formed in a glass layer with a different shape is shown. Note that in the modification of the first embodiment, description of the same components as those in the embodiment already described may be omitted.

[0047] Figure 5 FIG. 2 is a cross-sectional view of a glass substrate according to a first modification example of the first embodiment. Figure 5 As shown in FIG. 1 , the glass substrate 1A has a constricted portion 13 communicating with the opening 11. That is, the through hole 10y formed on the glass substrate 1A becomes narrower near the center portion in the thickness direction of the glass layer 10. In the case of the through hole 10y, Figure 2 Similarly, the end of the opening 11 and the end of the opening 12 are, for example, R-shaped in a cross-sectional view.

[0048] A through hole 10x having a substantially constant thickness may be formed as in the glass substrate 1, or a through hole 10y that tapers near the center of the thickness direction of the glass layer 10 may be formed as in the glass substrate 1A. If the aspect ratio is relatively high, it tends to be easy to form a shape like the through hole 10y, and if the aspect ratio is relatively low, it tends to be easy to form a shape like the through hole 10x. If a contraction portion 13 such as the through hole 10y is formed, when a through wiring that fills the through hole 10y is formed, the through wiring can be prevented from coming out of the through hole 10y. In addition, when an easy-adhesion layer is formed on the surface of the glass layer 10 by vapor deposition or the like, vapor deposition on a vertical surface is difficult, but if it is a contraction shape, vapor deposition inside is relatively easy.

[0049] Figure 6 FIG. 2 is a cross-sectional view of a glass substrate illustrating a second modification of the first embodiment. Figure 6 As shown in FIG. 1 , the glass substrate 1B has a hole 10z. The hole 10z is not a hole that penetrates the glass layer 10 in a direction substantially perpendicular to the first main surface 10a, but includes a vertical hole extending in a direction substantially perpendicular to the first main surface 10a and a horizontal hole extending in a direction substantially parallel to the first main surface 10a. The hole 10z may also include a hole extending in a direction inclined relative to the first main surface 10a. In the case of the hole 10z, Figure 2 Similarly, the end of the opening 11 and the end of the opening 12 are, for example, R-shaped in a cross-sectional view.

[0050] Holes of various shapes such as the hole 10z can be formed in the glass layer 10. That is, since the glass layer 10 has high transparency, the transmittance of the laser is very high. Therefore, by focusing the laser light at a desired position in the glass layer 10 to form a high energy density and performing three-dimensional scanning, a seed hole of a desired shape can be formed. Then, by performing the same Figure 4 By the same wet etching, the seed holes are enlarged to form holes 10z, thereby obtaining the glass substrate 1B.

[0051] [Evaluation of mechanical strength]

[0052] The Weibull distribution is calculated for a glass substrate having a through hole formed in a glass layer with a thickness of 100 μm and a glass substrate having no through hole formed in a glass layer with a thickness of 100 μm. Figure 7 shown.

[0053] exist Figure 7 In the above, “without through-holes” refers to the Weibull distribution of a glass substrate in which no through-holes are formed in a glass layer with a thickness of 100 μm. In addition, “with through-holes” refers to the Weibull distribution of a glass substrate in which through-holes are formed in a glass layer with a thickness of 100 μm by referring to Figure 3 and Figure 4The method described above forms circular through holes with a diameter of 20 μm at a pitch of 100 μm. In addition, "laser processing only" refers to an area where Weibull distribution appears on a glass substrate with through holes formed in the following manner: on a glass layer with a thickness of 100 μm, only laser processing is performed without wet etching to form through holes with the same diameter and the same pitch as "with through holes".

[0054] Note that the through-holes formed only by laser processing are Figure 1 The straight shape shown has no constriction. In addition, the end of the opening does not become Figure 2 The R shape shown in the figure is not formed into a shape with sharp corners and burrs. Figure 3 and Figure 4 No burrs are formed in the through-hole formed by the described method.

[0055] like Figure 7 As shown, it was confirmed that the mechanical strength of the glass substrate formed with through holes by laser processing combined with wet etching was higher than that of the glass substrate formed with through holes by laser processing alone, and was close to that of the glass substrate without through holes. This is considered to be because, in the glass substrate formed with through holes by laser processing combined with wet etching, burrs are not generated at the ends of the openings, so there is no stress concentration caused by the presence of burrs, which leads to a decrease in mechanical strength.

[0056] [Aspect Ratio]

[0057] On a glass layer with a thickness of 100 μm, by referring to Figure 3 and Figure 4 The method described above forms through holes with different aspect ratios, and the shapes of the openings and the cross-sectional shapes of the through holes are confirmed. Note that the aspect ratio can be adjusted by changing the etching rate when wet etching the glass layer.

[0058] Figure 8 : is a graph showing the distribution of aspect ratios of the formed through holes. Figure 8 As shown, in this experiment, an attempt was made to form through holes with an aspect ratio of about 3 to 9. Note that Figure 8 The aspect ratio shown is the value of the depth a of the through hole when the opening width of the through hole is normalized to 1. Figure 8 A to H shown on the horizontal axis are sample numbers.

[0059] Fig. 9 yes Figure 8 The shapes of the openings and through holes of sample numbers A to D are shown in the following figure. Fig. 9As shown, through holes are formed in each of the sample numbers A to D. However, it can be seen that the contraction portion of the sample number A is extremely thin, and when the aspect ratio is close to 9, it is difficult to form a through hole.

[0060] Fig.10 yes Figure 8 The shapes of the openings and through holes of sample numbers E to H are shown in the following figure. Fig.10 As shown, each of the sample numbers E to H has a through hole formed therein. Fig. 9 The constriction portion becomes extremely thin as shown in the sample number A. Fig. 9 and Fig.10 From the results, it can be considered that if the aspect ratio is 3 or more and 6 or less, the through-hole can be stably formed.

[0061] In addition, it is difficult to control the aspect ratio of the through-hole formed by laser processing alone. Figure 3 and Figure 4 In the method described above, the aspect ratio can be easily controlled by adjusting the etching rate, and a through hole having a relatively high aspect ratio of about 6 can be formed.

[0062] As mentioned above, although the preferred embodiments and the like have been described in detail, the present invention is not limited to the above-mentioned embodiments and the like, and various modifications and substitutions may be made to the above-mentioned embodiments and the like without departing from the scope described in the claims.

[0063] For example, the opening may not be a closed shape when viewed from the normal direction of the first main surface. Figure 3 When the glass layer 10 shown in FIG. 1 is cut into two regions, the ends of the cut surface on the first main surface side and the second main surface side are also the ends of the opening. Figure 4 The end portions of the opening (i.e., the end portions on the first main surface side and the second main surface side of the cut surface) are wet-etched in the process of Figure 2 As a result, the mechanical strength of the glass substrate can be improved.

[0064] In addition to the above embodiment, the following supplementary notes are disclosed.

[0065] (Note 1)

[0066] A glass substrate having:

[0067] Glass layer; and

[0068] The opening portion is opened on the first main surface side of the glass layer,

[0069] The glass layer has a thickness of 10 μm or more and 300 μm or less.

[0070] There is no burr at the end of the opening on the first main surface side.

[0071] (Note 2)

[0072] The glass substrate according to Note 1, wherein:

[0073] An end portion of the opening on the first main surface side has an R-shape in a cross-sectional view.

[0074] (Note 3)

[0075] The glass substrate according to Supplementary Note 1 or 2, wherein:

[0076] The glass substrate has a contraction portion, and the contraction portion communicates with the opening portion.

[0077] (Note 4)

[0078] The glass substrate according to any one of Notes 1 to 3, wherein

[0079] The glass substrate has a hole, and the hole has the opening.

[0080] The aspect ratio of the hole is 3 or more and 6 or less.

[0081] (Note 5)

[0082] The glass substrate according to Note 4, wherein:

[0083] The hole includes a second opening portion, the second opening portion opening on a second main surface side opposite to the first main surface,

[0084] There is no burr at the end of the second opening on the second main surface side.

[0085] (Note 6)

[0086] A method for manufacturing a glass substrate comprises the following steps:

[0087] irradiating a first main surface of the glass layer with a laser beam to form an opening portion opened on the first main surface side; and

[0088] etching the glass layer in which the opening is formed,

[0089] The glass layer has a thickness of 10 μm or more and 300 μm or less.

[0090] After the etching step, no burr exists at the end of the opening on the first main surface side.

[0091] (Note 7)

[0092] The method for manufacturing a glass substrate according to Supplementary Note 6, wherein:

[0093] In the step of forming the opening, a femtosecond laser is used.

[0094] In the etching step, an etchant containing hydrofluoric acid is used.

[0095] This international application claims priority based on Japanese invention patent application No. 2022-156539 filed on September 29, 2022, and all contents of Japanese invention patent application No. 2022-156539 are incorporated herein by reference.

[0096] Description of Reference Numerals

[0097] 1. 1A, 1B, glass substrate;

[0098] 10 glass layers;

[0099] 10a, a first main surface;

[0100] 10b, second main surface;

[0101] 10s, seed hole;

[0102] 10x, 10y, through hole;

[0103] 10z, hole;

[0104] 11, 12, opening;

[0105] 11e, 12e, ends of the opening;

[0106] 13. Contraction;

[0107] 100, etching groove;

[0108] 110. Etching agent.

Claims

1. A glass substrate comprising: Glass layer; and The opening portion is opened on the first main surface side of the glass layer, in, The glass layer has a thickness of 10 μm or more and 300 μm or less. There is no burr at the end of the opening on the first main surface side.

2. The glass substrate according to claim 1, wherein An end portion of the opening on the first main surface side has an R-shape in a cross-sectional view.

3. The glass substrate according to claim 1, wherein The glass substrate has a contraction portion, and the contraction portion communicates with the opening portion.

4. The glass substrate according to claim 1, wherein The glass substrate has a hole, and the hole has the opening. The aspect ratio of the hole is 3 or more and 6 or less.

5. The glass substrate according to claim 4, wherein: The hole includes a second opening portion, the second opening portion opening on a second main surface side opposite to the first main surface, There is no burr at the end of the second opening on the second main surface side.

6. A method for manufacturing a glass substrate, comprising the following steps: irradiating a first main surface of the glass layer with a laser beam to form an opening portion opened on the first main surface side; and etching the glass layer in which the opening is formed, in, The glass layer has a thickness of 10 μm or more and 300 μm or less. After the etching step, no burr exists at the end of the opening on the first main surface side.

7. The method for manufacturing a glass substrate according to claim 6, wherein: In the step of forming the opening, a femtosecond laser is used. In the etching step, an etchant containing hydrofluoric acid is used.

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