JP7109739B2 - Glass substrate for laser-assisted etching and method for manufacturing perforated glass substrate using the same - Google Patents

Description

The present invention relates to a glass substrate for laser-assisted etching and a method for manufacturing a perforated glass substrate using the glass substrate.

Conventionally, a glass substrate having a hole formed therein is used as an interposer by forming a through electrode in the hole. A glass interposer has advantages over a resin interposer in that it has excellent high-frequency dielectric properties and insulation properties, and has low dielectric loss. A glass substrate having holes is generally produced by altering glass using a laser beam such as an ultraviolet laser, and then performing an etching treatment to remove the altered portions (see, for example, Patent Document 1). Such a method is generally called laser assisted etching.

International Publication No. 2016/129254

In the glass substrate for interposer, as the circuit configuration becomes complicated according to the arrangement of the electrodes, it is necessary to form the holes with high accuracy. Here, if the etching selectivity (ratio of erosion depth due to etching) between the altered portion and the non-altered portion after laser irradiation is low, for example, not only the altered portion but also the non-altered portion are dissolved in the etchant in large amounts. It is difficult to form holes with desired accuracy.

In view of the above, an object of the present invention is to provide a laser-assisted etching glass substrate capable of forming holes with high precision, and a method for manufacturing a perforated glass substrate using the same.

As a result of intensive studies, the present inventors focused on the coordination number (bonded oxygen number) of element B in a glass substrate for laser-assisted etching made of borosilicate glass, and by regulating the ratio of the coordination number, , found that the above problems can be solved.

That is, the glass substrate for laser-assisted etching of the present invention is made of borosilicate glass, and the ratio of the coordination number of element B in the glass is 0.4 or more. characterized by being In addition, "as the ratio of the coordination number of the B element, 3 coordination / (3 coordination + 4 coordination) is 0.4 or more", more specifically, "the number of 3 coordination B element / ( It means that the value of the number of 3-coordinated B elements + the number of 4-coordinated B elements) is 0.4 or more.

In borosilicate glass, the coordination number of element B is generally 4, which is the same as that of Si, and chemical durability is high. On the other hand, the three-coordinated B element has a weak bonding force with the oxygen element, and thus has low chemical durability and is easily dissolved in an acid solution or an alkaline solution. Therefore, when the amount of 3-coordinated B element in the glass is large, the etching rate tends to increase. It is considered that when a certain amount of 3-coordinated B element is present in the glass before laser irradiation, it becomes a starting point, and the 4-coordinated B element is easily changed to 3-coordinated by laser irradiation. In particular, when a pulse wave femtosecond laser is irradiated onto a glass substrate, the irradiated area turns into plasma and the temperature rapidly rises and then falls continuously, so that the 4-coordinated B element becomes 3-coordinated. subject to change. As a result, the etching selectivity between the altered portion and the non-altered portion after laser irradiation is increased, and the hole can be formed with high accuracy by etching.

The glass substrate for laser-assisted etching of the present invention preferably contains more than 1 to 4.5% by mol of R ₂ O (R is at least one selected from Li, Na and K). In this way, the coordination number of B is easily changed from 4-coordinate to 3-coordinate.

The glass substrate for laser-assisted etching of the present invention contains, in mol%, SiO ₂ 50 to 85%, B ₂ O ₃ 5 to 30%, and R ₂ O (R is at least one selected from Li, Na and K). It preferably contains more than 1-4.5%, 0-5% Al ₂ O ₃ and 0-5% MgO. In this way, the coordination number of B is easily changed from 4-coordinate to 3-coordinate.

The glass substrate for laser-assisted etching of the present invention preferably has a thermal expansion coefficient of 20 to 50×10 ⁻⁷ /K. By doing so, it is possible to achieve thermal matching with the silicon semiconductor to be mounted when the glass substrate for interposer is formed, and it is possible to suppress the occurrence of cracks at the junction between the glass substrate and the silicon semiconductor.

The method for producing a perforated glass substrate of the present invention comprises the steps of: irradiating the glass substrate for laser-assisted etching with a laser beam to form an altered portion; and etching the glass substrate to dissolve the altered portion. A step of forming a hole by

In the method for producing a perforated glass substrate of the present invention, the laser light is preferably femtosecond pulse laser light with a wavelength of 700 to 1200 nm. This is preferable because the glass substrate can be altered in a short period of time to the extent that it can be dissolved by etching.

In the method for manufacturing a perforated glass substrate of the present invention, the etching treatment is preferably performed using an acid solution or an alkaline solution.

In the method for manufacturing a perforated glass substrate of the present invention, the perforated glass substrate is used as, for example, an interposer glass substrate.

ADVANTAGE OF THE INVENTION According to the method of this invention, the glass substrate for laser assist etching which can form a hole with high precision, and the manufacturing method of a perforated glass substrate using the same can be provided.

The glass substrate for laser-assisted etching of the present invention is a glass substrate for laser-assisted etching made of borosilicate glass. ) is 0.4 or more. If the ratio of the coordination numbers is too small, the etching rate of the altered portion after laser irradiation becomes small, and as a result, the etching selection ratio between the altered portion and the non-altered portion after laser irradiation becomes small, and holes can be formed with high accuracy. It becomes difficult to form a part. The coordination number ratio is preferably 0.5 or more, 0.6 or more, 0.65 or more, 0.68 or more, and particularly 0.7 or more. On the other hand, although the upper limit of the coordination number ratio is not particularly limited, it is practically 0.9 or less.

The composition of the borosilicate glass is, for example, SiO ₂ 50 to 85%, B ₂ O ₃ 5 to 30%, R ₂ O (R is at least one selected from Li, Na and K) in terms of mol%. 1-4.5%, Al ₂ O ₃ 0-5%, and MgO 0-5%. The reason for limiting the composition in this way will be explained below.

SiO ₂ is a component that forms a glass skeleton and is a component that enhances chemical durability. The content of SiO ₂ is preferably 50-85%, in particular 60-85%. If the content of SiO ₂ is too low, the chemical durability will be poor and the etching selectivity will be low, making it difficult to form holes with high precision. On the other hand, if the content of _SiO2 is too high, vitrification becomes difficult.

B ₂ O ₃ is a component that becomes a glass skeleton. It is also a component that enhances chemical durability. In addition, when the B element is three-coordinated, it has the effect of lowering the chemical durability of the glass and increasing the etching rate. The content of B is preferably 5-30%, particularly preferably 10-25%. If the content of B ₂ O ₃ is too low, the chemical durability will be poor and the etching selectivity will be low, making it difficult to form holes with high accuracy. On the other hand, if the B ₂ O ₃ content is too high, vitrification becomes difficult.

The alkali metal oxide (at least one selected from R ₂ O=Li ₂ O, Na ₂ O and K ₂ O) is a component that changes the coordination number of element B from 4 to 3. It is also a component for facilitating vitrification and controlling the coefficient of thermal expansion. The content of R ₂ O is preferably more than 1 to 4.5%, especially 1 to 4%. If the content of R ₂ O is too small, it becomes difficult to obtain the above effects. On the other hand, if the content of R ₂ O is too large, conversely, it becomes difficult for the coordination number of the B element to change from 4-coordinate to 3-coordinate. In addition, the ultraviolet transmittance is lowered, the chemical durability is deteriorated, and the etching selectivity is lowered, making it difficult to form holes with high precision.

Al ₂ O ₃ is a component that enhances chemical durability. The content of Al ₂ O ₃ is preferably 0-5%, especially 0.1-4%. If the content of Al ₂ O ₃ is too high, it becomes difficult to vitrify.

MgO is a component that changes the coordination number of the B element from 4-coordinate to 3-coordinate. The content of MgO is preferably 0-5%, particularly 0.1-4%. If the content of MgO is too large, conversely, the coordination number of the B element becomes difficult to change from 4-coordinate to 3-coordinate.

In addition, alkaline earth metal oxides (CaO, SrO, BaO), P ₂ O ₅ , TiO ₂ , ZnO, ZrO ₂ , Bi ₂ O ₃ , SnO ₂ , rare earth oxides, as long as they do not impair the effects of the present invention. In addition, up to 5% of each of common oxide components used in glass production can be contained. In the process of mounting a semiconductor on a glass substrate for an interposer manufactured using the glass substrate of the present invention, when using an ultraviolet curable resin, the ultraviolet curable resin may be irradiated with ultraviolet rays through the glass substrate. In this case, it is desirable that the glass substrate has a high ultraviolet transmittance. Thus, when the object is to increase the ultraviolet transmittance of the glass substrate, it is preferable that the glass substrate does not substantially contain ultraviolet absorbing components such as TiO ₂ and CuO (for example, less than 0.1%).

The glass for laser-assisted etching of the present invention preferably has a coefficient of thermal expansion of 20 to 50×10 ⁻⁷ /K, particularly 25 to 45×10 ⁻⁷ /K. By doing so, it is possible to achieve thermal matching with the silicon semiconductor to be mounted when the interposer glass substrate is formed. As a result, it is possible to suppress the occurrence of cracks in the connecting portion between the glass substrate and the silicon semiconductor, and to ensure the electrical connection.

The thickness of the glass substrate is preferably 0.03 to 1 mm, 0.1 to 0.7 mm, particularly 0.2 to 0.5 mm. If the thickness of the glass substrate is too small, the mechanical strength tends to decrease. If the thickness of the glass substrate is too large, the deterioration due to laser light will be insufficient, making it difficult to form desired holes.

Hereinafter, a method for manufacturing a perforated glass substrate such as an interposer glass substrate using the glass substrate for laser-assisted etching of the present invention will be described.

The method for producing a perforated glass substrate of the present invention comprises the steps of: irradiating the above glass substrate for laser-assisted etching with a laser beam to form an altered portion; and etching the glass substrate to dissolve the altered portion. A step of forming a hole by

The wavelength of the laser light is preferably 700-1200 nm. For example, a Ti sapphire laser with a wavelength of 800 nm and a Yb fiber laser with a wavelength of 1030 nm can be used. By using such a laser beam, transparent glass can be altered in the ultraviolet region.

For example, pulsed laser light is used as the laser light. The pulse width of the pulsed laser light may be in the range of 10 to 10000 fs (femtoseconds), for example. In particular, it is preferable to use a so-called femtosecond laser with a pulse width of approximately 10 to 1000 fs, because the glass substrate can be altered in a short period of time to the extent that it can be etched and dissolved.

In addition, the glass may be partially melted by the energy of the laser beam to form holes (recesses) in the deteriorated portion of the glass substrate.

As the chemical solution used for the etching process, for example, acid solutions such as hydrofluoric acid, nitric acid, sulfuric acid, and mixed acids thereof, and alkaline solutions such as potassium hydroxide aqueous solution can be used.

The concentration of the chemical solution may be appropriately adjusted according to the desired etching ability. For example, in the case of hydrofluoric acid, it is preferably 0.5 to 5% by mass, particularly preferably 1 to 3% by mass. In the case of an aqueous potassium hydroxide solution, it is preferably 1 to 20 mol %, particularly preferably 5 to 15 mol %. If the concentration of the chemical solution is too low, the denatured portion is difficult to dissolve, making it difficult to form desired holes. On the other hand, if the concentration of the chemical solution is too high, there is a possibility that the portion of the glass substrate other than the altered portion may be dissolved.

The temperature of the chemical solution is preferably 0 to 50°C, particularly 20 to 40°C in the case of hydrofluoric acid. If the temperature of hydrofluoric acid is too low, the etching performance tends to decrease. On the other hand, if the temperature of hydrofluoric acid is too high, hydrogen fluoride volatilizes and the etching performance tends to decrease. Moreover, it is not preferable in terms of safety. In the case of an aqueous potassium hydroxide solution, the temperature is preferably 0° C. or higher, 20° C. or higher, 50° C. or higher, particularly 70° C. or higher. If the temperature of the aqueous potassium hydroxide solution is too low, the etching performance tends to decrease. On the other hand, if the temperature of the potassium hydroxide aqueous solution is too high, it boils, which is not preferable from the safety point of view. Therefore, it is preferably 95° C. or lower, particularly 90° C. or lower.

The etching time may be appropriately selected according to the type and concentration of the chemical used, and is preferably about 1 to 100 minutes, more preferably about 5 to 50 minutes.

The inner diameter of the hole to be formed may be appropriately selected according to the intended use. For example, when a perforated glass substrate is used as an interposer glass substrate, the inner diameter of the holes is preferably set within the range of 1 to 100 μm, 2 to 50 μm, and more preferably 5 to 20 μm. The hole may be a through hole or a non-through hole (bottomed hole).

The porous glass substrate obtained as described above may be used as it is for a desired application such as an interposer, or may be used after being cut into a predetermined size as necessary.

EXAMPLES The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

Table 1 shows Examples (No. 1 to 4) and Comparative Example (No. 5).

(1) Preparation of Glass Substrate for Laser-Assisted Etching First, a glass batch prepared by mixing glass raw materials so as to have the glass composition shown in Table 1 was placed in a platinum crucible and then melted at 1400 to 1650° C. for 24 hours. When the glass batch was melted, it was homogenized by stirring using a platinum stirrer. Then, the molten glass was poured onto a carbon plate, shaped into a plate, and then slowly cooled at a temperature near the annealing point for 30 minutes. Thus, a glass substrate for laser-assisted etching was obtained.

For the obtained glass substrate, the coordination number of element B and the coefficient of thermal expansion were measured as follows.

The coordination number of the B element is obtained by measuring the ¹¹ B NMR spectrum under the conditions of a frequency of 500 MHz and a magnetic field of 5.7 T using an NMR (nuclear magnetic resonance) apparatus manufactured by Bruker, and analyzing the obtained spectrum. asked.

As the coefficient of thermal expansion, the average coefficient of thermal expansion measured with a dilatometer in the temperature range of 30 to 380° C. was adopted.

(2) Measurement of Etching Selectivity Both sides of the glass substrate obtained above were mirror-polished to a thickness of 0.5 mm. By irradiating the glass substrate with a femtosecond laser (pulse width of 450 fs) having a wavelength of 1035 nm, a substantially cylindrical altered portion having a diameter of 10 μm and a thickness of approximately 0.5 mm was formed in the glass substrate.

Then, the glass substrate after formation of the altered portion was etched by immersing it in a 2% by mass hydrofluoric acid solution at 25° C. or a 10 mol % potassium hydroxide solution at 80° C. for 30 minutes. After the etching treatment, the glass substrate was washed with an ultrasonic cleaner using pure water and dried at 120° C. for 3 hours. As a result, holes with bottoms were formed on both surfaces of the glass substrate to produce a perforated glass substrate. The etching selectivity of the obtained perforated glass substrate was measured according to the following formula. The depth of the hole was measured using a laser microscope (manufactured by Keyence Corporation).

Etching selectivity =
(depth of hole on one side in altered portion after etching-depth of hole on one side in altered portion before etching)/{(thickness of non-altered portion before etching-non-altered after etching) part thickness) ÷ 2)}

As shown in Table 1, no. The glass substrates of Nos. 1 to 4 had a large etching selectivity of 18 or more. On the other hand, no. The glass substrate No. 5 had a small etching selectivity of 1.

The perforated glass substrate produced from the glass substrate for laser-assisted etching of the present invention has microholes for aligning and holding optical components such as microfluidic device substrates and optical fibers with high precision in addition to interposer substrates. It can also be used as an array.

Claims (7)

It consists of borosilicate glass and contains 1 to 4.5% Na ₂ O, 0.5 to 4.5% K ₂ O, 0 to 0.5% ZnO, and 1.5 to 5% MgO in mol %. and a glass substrate for laser-assisted etching, wherein the ratio of the coordination number of element B in the glass is 3-coordination/(3-coordination+4-coordination) is 0.4 or more. 2. The glass substrate for laser-assisted etching according to claim 1, containing 50 to 85% SiO ₂ , 5 to 30% B ₂ O ₃ , and 0 to 5% Al ₂ O ₃ in terms of mol %. . 3. The glass substrate for laser-assisted etching according to claim 1, which has a thermal expansion coefficient of 20 to 50×10 ⁻⁷ /K. A step of forming an altered portion by irradiating the glass substrate for laser-assisted etching according to any one of claims 1 to 3 with a laser beam, and
forming a hole by etching the glass substrate to dissolve the altered portion;
A method for manufacturing a perforated glass substrate, comprising: 5. The method for producing a perforated glass substrate according to claim 4, wherein the laser light is femtosecond pulsed laser light with a wavelength of 700 to 1200 nm. 6. The method for producing a perforated glass substrate according to claim 4, wherein the etching treatment is performed using an acid solution or an alkaline solution. 7. The method for producing a perforated glass substrate according to claim 4, wherein the perforated glass substrate is used as an interposer glass substrate.