Method for manufacturing substrate having micropores

Abstract

The present invention provides, as a TGV formation technology, a method for manufacturing a substrate having micropores, the method comprising: perforating a substrate by using time waveform modulated laser pulses; and performing chemical etching when the pore diameter of a through-via formed through the perforation is at least 1 μm.

Description

Method for manufacturing a substrate having micropores

[0001] The present disclosure relates to a method for manufacturing a substrate having micropores.

[0002] Conventionally, as a method for manufacturing a substrate having micropores in the field of semiconductor manufacturing technology, TGV (Through-Glass Via) technology is known. TGV is a technology in which a glass substrate is modified using a picosecond laser or a femtosecond laser, and then chemical etching is performed to form holes in the modified portion. Regarding this type of technology, for example, Non-Patent Document 1 describes an example in which a microchannel is formed by internal modification of glass using a femtosecond laser and subsequent selective etching.

[0003] Further, as a method for manufacturing a substrate having micropores, as shown in Patent Document 1, (1) a step of preparing a substrate having a first surface and a second surface facing each other, and (2) irradiating the first surface of the substrate with a first laser having a wavelength transparent to the substrate to form a light-absorbing region extending along the extension axis from the first surface of the substrate, wherein the first laser has a pulse width of 100 nanoseconds or less, and (3) irradiating the light-absorbing region with a second laser having a wavelength transparent to the substrate for at least a time overlapping with the irradiation time of the first laser to selectively remove the substrate in the light-absorbing region, wherein the second laser has a pulse width of 1 microsecond or more, and the second laser is incident on the first surface of the substrate at an incident angle of 5° or more and 50° or less with respect to the extension axis of the light-absorbing region. A manufacturing method having the above steps is disclosed.

[0004] The technique described in this Patent Document 1 can form holes in the substrate by using two lasers, a first laser composed of an ultrashort pulse laser and a second laser composed of a long pulse laser.

[0005] Japanese Unexamined Patent Application Publication No. 2024-89171

[0006] Andrius Marcinkevicius et al., Femtosecond laser-assisted-three-dimensional microfabrication in silica, "OPTICS LETTERS", U.S.A., Optical Society of America, March 1, 2001, Vol. 26, No. 5, pp. 277–279.

[0007] By the way, the above-mentioned techniques for forming micropores using laser processing and chemical etching have a problem: when performing the hole-making process using chemical etching, for example, it can take about 8 hours to form a hole with a diameter of 50 μm, resulting in a long working time.

[0008] Furthermore, in the technique of forming micro-holes using the first and second lasers described above, there was a problem in that there was a limit to the diameter of the holes that could be made because the two lasers were irradiated onto the substrate coaxially.

[0009] The problem that this disclosure aims to solve is to provide a method for manufacturing a substrate having micropores that can create large-diameter holes in a shorter time compared to conventional technologies.

[0010] The present disclosure relates to a method for manufacturing a substrate having micropores, which is a TGV formation technology and includes the steps of: perforating a substrate with a time-wavelength modulated laser pulse; and performing chemical etching when the diameter of the through-vias becomes 1 μm or more as a result of the perforation. One embodiment of the present manufacturing method is a method for manufacturing a substrate having micropores in which perforation is performed on the substrate with a time-wavelength modulated laser pulse obtained by combining a first laser consisting of an ultrashort pulse laser and a second laser consisting of a long pulse laser. Another embodiment of the present manufacturing method is a method for manufacturing a substrate having micropores in which the diameter of the pores is in the range of 1 μm to 30 μm. Another embodiment of the present manufacturing method is a method for manufacturing a substrate having micropores in which the pulse width of the first laser is 100 femtoseconds to less than 100 picoseconds, and the pulse width of the second laser is 1 nanosecond to less than 1 millisecond. Another embodiment of the present manufacturing method is a method for manufacturing a substrate having micropores in which the wavelengths of the first laser and the second laser are in the 1-micron band. One embodiment of the present manufacturing method is a method for manufacturing a substrate having micropores, wherein the second laser is irradiated after the first laser. Another embodiment of the present manufacturing method is a method for manufacturing a substrate having micropores, wherein the second laser is irradiated within 5 picoseconds after the first laser is irradiated. Another embodiment of the present manufacturing method is a method for manufacturing a substrate having micropores, wherein the first laser is irradiated after the second laser is irradiated, provided that the irradiation time of the second laser after the irradiation time of the first laser is 1 nanosecond or more and less than 1 millisecond. Another embodiment of the present manufacturing method is a method for manufacturing a substrate having micropores, wherein a ytterbium-doped solid-state laser as the first laser and a ytterbium-doped fiber laser as the second laser are coupled by coupling means including polarization coupling and wavelength coupling, and the time-wavelength modulated laser pulse obtained by integrating the two laser pulses optically coaxially is used to form the holes.One embodiment of the present manufacturing method is a method for manufacturing a substrate having micropores, wherein the first laser is a laser that wavelength-converts a laser output in the 1-micron wavelength band and outputs at any wavelength including the second and third harmonics, and the second laser is a solid-state laser that outputs in the 1-micron or 2-micron wavelength band. Another embodiment of the present manufacturing method is a method for manufacturing a substrate having micropores, wherein the time-wavelength modulated laser pulse, consisting of the first laser and the second laser, is irradiated once per micropore. Another embodiment of the present manufacturing method is a method for manufacturing a substrate having micropores, wherein the chemical etching is performed using a solution mainly composed of a chemical substance including hydrofluoric acid or potassium hydroxide. Another embodiment of the present manufacturing method is a method for manufacturing a substrate having micropores, wherein drilling is performed with a single laser that emits the time-wavelength modulated laser pulse having an ultrashort pulse portion with high peak power and a long pulse portion with low power. One embodiment of this manufacturing method is a method for manufacturing a substrate having micropores, in which perforation is performed with a time-wavelength modulated laser pulse in which the ultrashort pulse portion has been shortened in wavelength by harmonic generation using a nonlinear optical crystal. Another embodiment of this manufacturing method is a method for manufacturing a substrate having micropores in which the thickness of the substrate is in the range of 50 μm to 1000 μm.

[0011] This is a schematic diagram showing the basic configuration of the laser device of the first embodiment. This is an explanatory diagram showing the relationship between the laser output and time of the laser device. This is a cross-sectional view showing the pore shape of the substrate after chemical etching. This is a cross-sectional view showing the pore shape of the substrate after chemical etching. This is a graph showing the relationship between pore diameter and chemical etching processing time. This is a schematic diagram showing the laser generating means of the laser device of the second embodiment. This is an explanatory diagram showing the relationship between the laser output and time of the laser device, where (a) is the output waveform of the LD and (b) is the output waveform of the power amplifier. This is a schematic diagram showing the basic configuration of the laser device. This is an explanatory diagram of wavelength conversion in the third embodiment. This is a graph showing the relationship between fundamental wave intensity and harmonic intensity.

[0012] (First Embodiment) The method for manufacturing a substrate having micropores according to the present disclosure is suitable for application to, for example, TGV formation technology used in semiconductor manufacturing technology, and the first embodiment will be described in detail below.

[0013] First, we will describe the laser apparatus used in the manufacturing method of the substrate having micropores according to this first embodiment.

[0014] Figure 1 is a schematic diagram showing the basic configuration of the laser device 1. As shown in Figure 1, the laser device 1 used in TGV formation technology includes a first laser light source 2, a first beam expander 3, a first axicon lens 4, a first lens 5, a mirror 6, a beam splitter 7, an objective lens 8, a second laser light source 9, a second beam expander 10, a second axicon lens 11, and a second lens 12.

[0015] By using this laser device 1, one or more fine holes (through vias) can be made in the substrate 21, which will be described later.

[0016] The first laser light source 2 has the role of emitting a first laser 2a (femtosecond laser), which consists of an ultrashort pulse laser, towards the first axicon lens 4 via the first beam expander 3.

[0017] The first beam expander 3 is used to expand or contract the diameter of the first laser 2a.

[0018] The first axicon lens 4 is a cone-shaped lens. Alternatively, a DOE (Diffractive Optical Element) or a spatial phase modulator can be used as a substitute optical element with equivalent functionality to the first axicon lens 4. The first axicon lens 4 focuses the laser beam toward the optical axis, forming a Bessel beam in the space immediately behind it.

[0019] The first laser 2a emitted from the first axicon lens 4 travels through the first lens 5 and propagates toward the mirror 6. The first lens 5 is composed of a single-element spherical plano-convex lens, an aspherical lens, or a lens in which multiple lenses are combined and fixed.

[0020] Mirror 6 reflects the first laser 2a and guides it to the beam splitter 7. The beam splitter 7 has the function of reflecting the first laser 2a and transmitting the second laser 9a, which will be described later. The beam splitter 7 also directs these two lasers toward the objective lens 8.

[0021] The objective lens 8 is the lens positioned closest to the substrate 21, which will be described later. The objective lens 8 is composed of a single-element spherical plano-convex lens, an aspherical lens, or a lens in which multiple lenses are combined and fixed.

[0022] On the other hand, the second laser light source 9 has the role of emitting a second laser 9a (microsecond laser), which consists of a long-pulse laser, towards the second axicon lens 11 via the second beam expander 10.

[0023] The second beam expander 10 is used to expand or contract the diameter of the second laser 9a.

[0024] The second axicon lens 11 is a cone-shaped lens. Alternatively, a DOE (Diffractive Optical Element) or a spatial phase modulator can be used as a substitute optical element with equivalent functionality to the second axicon lens 11. The second axicon lens 11 forms a Bessel beam by focusing the laser beam toward the optical axis.

[0025] The second laser 9a emitted from the second axicon lens 11 is guided to the beam splitter 7 via the second lens 12. The second lens 12 is composed of a single-element spherical plano-convex lens, an aspherical lens, or a lens in which multiple lenses are combined and fixed.

[0026] The first laser 2a and the second laser 9a then pass through the beam splitter 7 and the objective lens 8 before being irradiated onto the first surface 21a of the substrate 21, which will be described later.

[0027] It should be noted that embodiments without the axicon lens and DOE, which are characteristic of the above embodiments, are also possible. When the pulsed beams of the first laser 2a and the second laser 9a are not beam-shaped by an axicon lens, they are both Gaussian beams, and the depth of focus changes depending on the size of the focal point. The first beam is irradiated onto the first surface 21a of the substrate 21, which will be described later, at a focal point with a small beam waist on the order of 1 μm, and modifies the substrate 21 while maintaining a narrow, parallel beam of light while causing filamentation inside the substrate 21, which will be described later. The pulsed beam of the second laser 9a is beam-shaped to focus the beam waist on the order of 15 μm, and its depth of focus is approximately 1 mm, and it is irradiated so that its focal point is located inside the substrate 21, which will be described later.

[0028] The following describes the steps for carrying out the manufacturing method of the substrate having micropores according to this embodiment using the laser device 1 described above.

[0029] First, the operator prepares the substrate 21 to be processed (irradiated object). The material of the substrate 21 is transparent to the wavelengths of the first laser 2a and the second laser 9a, and is, for example, quartz glass.

[0030] The substrate 21 is formed in a plate shape and is a semiconductor material that is generally available on the market. The thickness of the substrate 21 is, for example, in the range of 50 μm to 1000 μm.

[0031] The substrate 21 has a first surface 21a and a second surface 21b that face each other. The operator operates the laser device 1 to perform laser processing on the substrate 21 from the first surface 21a toward the second surface 21b.

[0032] Therefore, the worker positions the substrate 21 such that the second surface 21b of the substrate 21 faces downwards towards the support base 13 of the laser device 1 that supports the substrate 21. In other words, the worker positions the substrate 21 such that the first surface 21a of the substrate 21 faces upwards towards the laser irradiation surface.

[0033] Next, the operator operates the laser device 1 to emit the first laser 2a from the first laser light source 2 toward the first axicon lens 4.

[0034] The first laser 2a, via the first beam expander 3, is refracted radially from the optical axis by the first axicon lens 4, forming a Bessel beam in the space immediately behind the first axicon lens 4.

[0035] The first laser 2a emitted from the first axicon lens 4 travels through the first lens 5 towards the mirror 6. The first laser 2a is reflected by the mirror 6 and travels towards the beam splitter 7. The first laser 2a is reflected by the beam splitter 7 and passes through the objective lens 8. The first laser 2a then irradiates the first surface 21a of the substrate 21.

[0036] The wavelength of the first laser 2a is, for example, within the 1-micron range. Specifically, the wavelengths of the first laser 2a are, for example, 1030 nm, 1040 nm to 1060 nm, and 1064 nm. Therefore, a ytterbium-doped solid-state laser can be used as the first laser 2a.

[0037] Furthermore, the pulse width of the first laser 2a is between 100 femtoseconds and less than 100 picoseconds. If the pulse width of the first laser 2a falls below 100 femtoseconds, the design difficulty of the laser device 1 increases, making it difficult to adopt this embodiment as a method for manufacturing the substrate 21 having micropores.

[0038] When the first laser 2a is irradiated onto the substrate 21, the irradiated area is modified to become a light-absorbing region.

[0039] Next, the second laser light source 9 emits the second laser 9a toward the second axicon lens 11.

[0040] The second laser 9a is refracted radially from the optical axis center by the second axicon lens 11 through the second beam expander 10 to form a Bessel beam in the space immediately after the second axicon lens 11.

[0041] The second laser 9a emitted from the second axicon lens 11 travels toward the beam splitter 7 via the second lens 12. The second laser 9a passes through the beam splitter 7 and the objective lens 8. Then, the second laser 9a irradiates the first surface 21a of the substrate 21.

[0042] The wavelength of the second laser 9a is, for example, in the range of 1 micron band or 2 micron band. Specifically, the wavelength of the second laser 9a is, for example, 1030 nm, 1040 nm to 1060 nm, 1064 nm, etc. Therefore, an ytterbium-doped fiber laser can be used as the second laser 9a. Note that the wavelength of the first laser 2a and the wavelength of the second laser 9a may be the same or different.

[0043] Also, the pulse width of the second laser 9a is from 1 nanosecond to less than 1 millisecond. Specifically, the pulse width of the second laser 9a is, for example, 2 microseconds, 20 microseconds, etc. Note that the pulse width of the second laser 9a is in the microsecond band rather than the nanosecond band in order to apply sufficient heat to the substrate 21 to perform drilling work on the order of 10 μm in diameter.

[0044] When the second laser 9a irradiates the substrate 21, the modified portion is removed and drilling is performed. In this case, since the optical axes of the first laser 2a and the second laser 9a coincide, the maximum value of the aperture diameter formed in the substrate 21 is limited, and about 30 μm is the limit.

[0045] Figure 2 illustrates the timing of emission of the first laser 2a and the second laser 9a. In this figure, time t indicates the emission interval between the first laser 2a and the second laser 9a. Note that time t includes 0 seconds and negative values. The timing of when the laser device 1 emits laser pulses can be adopted in several ways, as shown below. First, in Figure 2, an example can be given in which the first laser 2a is emitted from the first laser light source 2, and then the second laser 9a is emitted from the second laser light source 9. In this case, it is preferable that the time t from the emission of the first laser 2a to the emission of the second laser 9a be as short as possible. After irradiation (modification) by the first laser 2a, if heat is not applied quickly, holes cannot be made by the second laser 9a, so it is desirable that the time t until irradiation with the second laser 9a be within 5 picoseconds, for example.

[0046] Next, an example can be given in which the first laser 2a and the second laser 9a are emitted simultaneously (in this case, time t is 0 seconds). Furthermore, an example can be given in which the first laser 2a is emitted after the second laser 9a has been emitted (in this case, time t is a negative value). However, after the irradiation of the first laser 2a is completed, the irradiation time of the second laser 9a should be sufficient for the substrate 21 to absorb and impart energy, for example, between 1 nanosecond and less than 1 millisecond, and specifically preferably 20 microseconds or more.

[0047] The irradiation of the first laser 2a mainly aims to create a modified region in the substrate 21 where the pulse energy of the second laser 9a can be efficiently absorbed. Therefore, the wavelength can be shortened using harmonic generation technology to facilitate modification. For example, the first laser 2a is a laser that converts the laser output in the 1-micron wavelength band and outputs at any wavelength including the second harmonic and the third harmonic, and the second laser 9a may be a solid laser that outputs in the 2-micron wavelength band. For example, the first laser 2a converted to 515 nm or 532 nm as the second harmonic and 355 nm or 343 nm as the third harmonic can also be used. Although the glass material of the substrate 21 is transparent at any wavelength, it can be modified by multi-photon absorption through focused irradiation. Since multi-photon absorption is induced at a smaller energy density as the wavelength is shorter, it is advantageous to use a short-wavelength laser.

[0048] The irradiation by these first laser 2a and second laser 9a is synthesized as a time waveform modulated laser pulse and the optical axes coincide, so it can be performed by a single laser device 1. When synthesizing the first laser 2a and the second laser 9a to generate a single time waveform modulated laser pulse, their respective wavelengths may be different.

[0049] As means for synchronizing the first laser 2a and the second laser 9a and making the optical axes coincide, coupling means including polarization coupling and wavelength coupling can be used. In the drilling operation, for example, an ytterbium-doped solid laser as the first laser 2a and an ytterbium-doped fiber laser as the second laser 9a are coupled by coupling means including polarization coupling and wavelength coupling, and the two laser pulses are integrated optically coaxially. Then, drilling can be performed using the time waveform modulated laser pulse obtained by modulating the time waveforms of the two laser pulses integrated optically coaxially.

[0050] In addition, the same time-wavelength modulated laser pulse obtained by combining the first laser 2a and the second laser 9a can be realized using semiconductor lasers, semiconductor optical amplifiers (SOAs), and interferometric optical modulators. For example, a time-wavelength modulated laser pulse is created by generating a long pulse through gain-switch spike generation followed by long-duration current injection, and the pulse energy is amplified while maintaining the time waveform using a single linear optical amplifier. In this way, a laser with a time waveform and pulse energy equivalent to the pulse obtained by combining the first laser 2a and the second laser 9a can be created.

[0051] In the method for manufacturing a substrate having micropores as described above, micropores are formed, and a time-wavelength modulated laser pulse consisting of a first laser 2a and a second laser 9a is irradiated once per micropore.

[0052] Next, the operator performs chemical etching on the perforated substrate 21. Chemical etching enlarges the diameter of the holes in the substrate 21. In order to perform chemical etching, it is necessary that the diameter of the holes drilled by the first laser 2a and the second laser 9a is above a certain diameter. That is, in order to perform chemical etching to obtain VIA holes of a certain diameter, the holes must be large enough for the chemical etching solution to flow smoothly into the interior of the substrate 21. The hole diameter that does not get blocked by laser processing debris or foreign dust is, for example, in the range of 1 μm to 30 μm, and preferably in the range of 10 μm to 20 μm.

[0053] When the substrate 21 is glass, the chemical etching solution is a solution mainly composed of either hydrofluoric acid (HF) or potassium hydroxide. Specifically, a solution mainly composed of hydrofluoric acid (HF) is, for example, a hydrofluoric acid-nitric acid mixture obtained by adding an appropriate amount of nitric acid to hydrofluoric acid.

[0054] Chemical etching can enlarge the pore diameter of the substrate 21 to approximately 50 μm. Furthermore, when performing the drilling operation by irradiating with the second laser 9a, molten material adheres to the surface of the substrate 21, but chemical etching can also remove this molten material.

[0055] Furthermore, the pore size of the substrate 21 can be adjusted by adjusting the chemical etching process time. For example, shortening the chemical etching process time will result in a pore size smaller than 50 μm, while lengthening the chemical etching process time will result in a pore size larger than 50 μm.

[0056] Figures 3 and 4 are cross-sectional views showing the pore shape of the substrate 21 after chemical etching. Figure 5 is a graph showing the relationship between pore diameter and chemical etching time. Figure 3 shows the conventional technique, i.e., when the substrate 21 is irradiated with an ultrashort pulse laser and then chemically etched to perform the perforation work. As shown in this figure, the shape of the pores is drum-shaped. Therefore, the pore diameter in region a near the surface of the substrate 21 is larger than the pore diameter in region b in the center of the substrate 21.

[0057] In this conventional technique, the modified portion of the substrate 21 is gradually dissolved by chemical etching, starting from the first surface 21a and the second surface 21b and moving towards the center of the substrate 21. As a result, the pores become drum-shaped.

[0058] Figure 4 shows the shape of the holes in the substrate 21 manufactured according to this embodiment, where the holes are opened almost perpendicularly (straight) from the first surface 21a to the second surface 21b. Therefore, the diameter of the holes in region A near the surface of the substrate 21 is equivalent to the diameter of the holes in region B in the center of the substrate 21.

[0059] In the manufacturing method of the substrate 21 having micropores according to this embodiment, holes are made in the substrate 21 by the first laser 2a and the second laser 9a before chemical etching, so that the chemical etching solution enters the holes uniformly from immediately after the start of chemical etching. Therefore, chemical etching can be performed on the entire interior of the holes early on. As a result, the holes become almost vertical.

[0060] Figure 5 is a graph showing the relationship between pore size and chemical etching time for the prior art and the method of manufacturing a substrate 21 having micropores according to this embodiment. In the graph shown in Figure 5, the vertical axis represents pore size (μm), the horizontal axis represents time (h), the dotted line a represents the pore size of region a in Figure 3, the dotted line b represents the pore size of region b in Figure 3, the solid line A represents the pore size of region A in Figure 4, and the solid line B, which overlaps with solid line A, represents the pore size of region B in Figure 4.

[0061] As shown by the dotted lines a and b in Figure 5, when the substrate 21 is modified using the conventional technique, if the substrate 21 has no pores, or if the pores in the substrate 21 are less than, for example, 1 μm in diameter, the time required for chemical etching will be approximately 8 hours or more. In this case, in the conventional technique, when chemical etching is performed, the substrate 21 is gradually dissolved from the first surface 21a and the second surface 21b toward the center of the substrate 21, so the time required to enlarge the pore diameter in region b is longer than the time required to enlarge the pore diameter in region a.

[0062] This is because, if the substrate 21 does not have holes, or if the substrate 21 has holes but the hole diameter is, for example, less than 1 μm, the chemical etching solution will not enter the holes immediately after the start of chemical etching, or even if the chemical etching solution does enter the holes, only a small amount will enter.

[0063] As shown by the solid lines A and B in Figure 5, when holes are made in the substrate 21 using the manufacturing method of the substrate 21 having micropores of this embodiment, the pore diameter is approximately 20 μm (1 μm to 30 μm) in both region A and region B. As a result, the chemical etching solution flows into the pores quickly, and the time required for chemical etching is approximately 1 hour. Thus, the time required for chemical etching can be shortened by the manufacturing method of the substrate 21 having micropores of this embodiment.

[0064] As described above, the method for manufacturing the substrate 21 having micropores according to this embodiment allows for the creation of large-diameter holes in a shorter time compared to the conventional technique.

[0065] (Second Embodiment) Next, a second embodiment will be described with reference to Figures 6, 7, and 8. In the method for manufacturing a substrate having micropores described in this embodiment, the method for creating a time-wavelength modulated laser pulse differs from that of the first embodiment described above, and this time-wavelength modulated laser pulse is created by a single laser generating means 22.

[0066] In this method for manufacturing a substrate having micropores, as shown in Figure 6, the seeder 23 of the laser generating means 22 modulates the ultrashort pulses generated by the ultrashort pulse current source 24 with long pulses generated by the long pulse current source 25. The output then oscillates as laser light via the LD 26 (laser diode), and is amplified by the preamplifier 27 and power amplifier 28 to create a time-waveform modulated laser pulse.

[0067] In this case, the output waveform of LD26 is shown in Figure 7(a), and the output waveform of power amplifier 28 is shown in Figure 7(b). As shown in these figures, the output of LD26 is emitted as a seed pulse having a high peak power ultrashort pulse portion (gain switch spike portion) and a low power long pulse portion (long pulse tail portion). The total output energy of the seed pulse is, for example, on the order of 1 nJ, which is amplified by the preamplifier 27 to, for example, the order of 100 nJ, and then amplified by the power amplifier 28 to, for example, the order of 100 μJ.

[0068] The pulse width of the ultrashort pulse section is, for example, about 10 picoseconds, and the pulse width of the long pulse section is, for example, about 2 microseconds. The pulse energy of the ultrashort pulse section is, for example, about 10 μJ, and the pulse energy of the long pulse section is, for example, about 100 μJ.

[0069] Figure 8 shows the overall structure of the laser device 1. The time-wavelength modulated laser pulse generated by the laser generation means 22 is emitted towards the axicon lens 30 via the beam expander 29. The beam expander 29 is used to expand or contract the diameter of the time-wavelength modulated laser pulse.

[0070] The axicon lens 30 is a cone-shaped lens. Alternatively, a Diffractive Optical Element (DOE) or a spatial phase modulator can be used as a substitute optical element with equivalent functionality to the axicon lens 30. The axicon lens 30 focuses the laser beam toward the optical axis, forming a Bessel beam in the space immediately behind the axicon lens 30.

[0071] The time-wavelength modulated laser pulse emitted from the axicon lens 30 travels through lens 31 and towards the objective lens 8. Lens 31 and the objective lens 8 are composed of single-element spherical plano-convex lenses, aspherical lenses, or lenses in which multiple lenses are combined and fixed. The time-wavelength modulated laser pulse then passes through the objective lens 8 and is irradiated onto the first surface 21a of the substrate 21 as a single laser.

[0072] In this second embodiment, as in the first embodiment, the hole diameter can be enlarged by chemical etching after drilling holes in the substrate 21. In this second embodiment, the same effects and advantages as in the first embodiment can be obtained.

[0073] (Third Embodiment) Next, a third embodiment will be described with reference to Figures 9 and 10. In this embodiment, a time-wavelength modulated laser pulse is generated by wavelength conversion using a nonlinear optical crystal (a time-wavelength modulated laser pulse is obtained in which the ultrashort pulse portion has a shorter wavelength due to harmonic generation using a nonlinear optical crystal). That is, as shown in Figure 9, for example, a pulse having a pulse width of 1064 nm is wavelength-converted to a pulse of 532 nm to obtain a time-wavelength modulated laser pulse having an ultrashort pulse portion and a long pulse portion.

[0074] Figure 10 shows the relationship between fundamental wave intensity and harmonic intensity. For example, in the case of the second harmonic (SHG), the conversion efficiency is approximately 50% in terms of energy ratio. The process after obtaining the time-waveform modulated laser pulse is the same as in the first and second embodiments described above. In this embodiment as well, the same effects and advantages as in the first and second embodiments described above can be obtained.

[0075] Although methods for manufacturing the substrate 21 having micropores in these embodiments have been described, these are merely illustrative examples and do not limit the scope of the technology relating to this disclosure. The method for manufacturing the substrate 21 having micropores is a TGV formation technique that includes perforating the substrate with a time-wavelength modulated laser pulse, and performing chemical etching when the pore diameter of the through-vias becomes 1 μm or more as a result of the perforation. It can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the technology relating to this disclosure.

[0076] 1 Laser device 2 First laser light source 2a First laser 3 First beam expander 4 First axicon lens 5 First lens 6 Mirror 7 Beam splitter 8 Objective lens 9 Second laser light source 9a Second laser 10 Second beam expander 11 Second axicon lens 12 Second lens 13 Support base 21 Substrate 21a First surface 21b Second surface 22 Laser generating means 23 Seeder 24 Ultrashort pulse current source 25 Long pulse current source 26 LD 27 Preamplifier 28 Power amplifier 29 Beam expander 30 Axicon lens 31 Lens

Claims

1. A TGV formation technique comprising: perforating a substrate with time-wavelength modulated laser pulses; and performing chemical etching when the pore diameter of the through-vias becomes 1 μm or more as a result of the perforation; a method for manufacturing a substrate having micropores.

2. The method for manufacturing a substrate according to claim 1, wherein the drilling is performed on the substrate using a time-waveform modulated laser pulse obtained by combining a first laser consisting of an ultrashort pulse laser and a second laser consisting of a long pulse laser.

3. The method for producing a substrate according to claim 1, wherein the pore size is in the range of 1 μm to 30 μm.

4. The method for manufacturing a substrate according to claim 2, wherein the pulse width of the first laser is 100 femtoseconds to less than 100 picoseconds, and the pulse width of the second laser is 1 nanosecond to less than 1 millisecond.

5. The method for manufacturing a substrate according to claim 2, wherein the wavelengths of the first laser and the second laser are in the 1-micron range.

6. The method for manufacturing a substrate according to claim 2, wherein the substrate is irradiated with the second laser after being irradiated with the first laser.

7. The method for manufacturing a substrate according to claim 6, wherein the second laser is irradiated within 5 picoseconds after the first laser is irradiated.

8. The method for manufacturing a substrate according to claim 2, wherein the first laser is irradiated after the second laser has been irradiated.

9. A method for manufacturing a substrate according to claim 2, wherein a ytterbium-doped solid-state laser as the first laser and a ytterbium-doped fiber laser as the second laser are coupled by coupling means including polarization coupling and wavelength coupling, and the time-wavelength modulated laser pulse obtained by integrating the two laser pulses optically coaxially is used to perform the perforation.

10. The method for manufacturing a substrate according to claim 2, wherein the first laser is a laser that wavelength-converts a laser output in the 1-micron wavelength band and outputs at any wavelength including the second harmonic and the third harmonic, and the second laser is a solid-state laser that outputs in the 1-micron or 2-micron wavelength band.

11. A method for manufacturing a substrate having micropores, wherein the time-wavelength modulated laser pulse, consisting of the first laser and the second laser, is irradiated once per micropore, according to claim 2.

12. The method for producing a substrate according to claim 1, wherein the chemical etching is carried out using a solution mainly composed of a chemical substance containing hydrofluoric acid or potassium hydroxide.

13. The method for manufacturing a substrate according to claim 1, wherein the drilling is performed using a single laser that emits a time-waveform modulated laser pulse having an ultrashort pulse portion having high peak power and a long pulse portion having low power.

14. A method for manufacturing a substrate according to claim 1, wherein the drilling is performed with a time-wavelength modulated laser pulse in which the ultrashort pulse portion has been shortened by harmonic generation using a nonlinear optical crystal.

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