Laser processing apparatus and method for manufacturing electronic devices

Abstract

The present invention provides a laser processing apparatus that enables improved processing speed in hole drilling of glass substrates and the like, and a method for manufacturing electronic devices. [Solution] A laser processing apparatus that performs hole processing on a workpiece using pulsed laser light output from a laser device, comprising: a Z polarizer arranged in the optical path of the pulsed laser light and converting the polarization state of the pulsed laser light to azimuth polarization; a diffractive optical element that splits the azimuth-polarized pulsed laser light that has passed through the Z polarizer into a plurality of laser beams; and a focusing optical system that generates a plurality of focused spots on the workpiece by focusing the plurality of laser beams.

Description

Technical Field

[0001] The present disclosure relates to a laser processing apparatus and a method for manufacturing an electronic device.

Background Art

[0002] In recent years, in semiconductor exposure apparatuses, as semiconductor integrated circuits are miniaturized and highly integrated, improvement in resolution has been demanded. For this reason, shortening of the wavelength of light emitted from an exposure light source has been promoted. For example, as a gas laser device for exposure, a KrF excimer laser device that outputs laser light with a wavelength of about 248.4 nm and an ArF excimer laser device that outputs laser light with a wavelength of about 193.4 nm are used.

[0003] Further, since excimer laser light has a pulse width of about several 10 ns and a short wavelength, it may be used for direct processing of polymer materials, glass materials, and the like.

[0004] Chemical bonds in polymer materials can be broken by excimer laser light having photon energy higher than the bond energy. Therefore, non-thermal processing of polymer materials is possible with excimer laser light, and it is known that the processed shape becomes beautiful.

[0005] Further, since glass, ceramics, etc. have a high absorption rate for excimer laser light, it is known that even materials that are difficult to process with visible and infrared laser light can be processed with excimer laser light.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

[0007] A laser processing apparatus according to one aspect of the present disclosure is a laser processing apparatus that performs hole processing on a workpiece using pulsed laser light output from a laser device, comprising: a Z polarizer arranged in the optical path of the pulsed laser light and converting the polarization state of the pulsed laser light to azimuth polarization; a diffractive optical element that splits the azimuth-polarized pulsed laser light that has passed through the Z polarizer into a plurality of laser beams; and a focusing optical system that generates a plurality of focused spots on the workpiece by focusing the plurality of laser beams.

[0008] A method for manufacturing an electronic device according to one aspect of this disclosure is a laser processing apparatus that processes a workpiece using pulsed laser light output from a laser device, comprising: a Z polarizer arranged in the optical path of the pulsed laser light and converting the polarization state of the pulsed laser light to azimuth polarization; a diffractive optical element that splits the azimuth-polarized pulsed laser light that has passed through the Z polarizer into a plurality of laser beams; and a focusing optical system that generates a plurality of focused spots on the workpiece by focusing the plurality of laser beams; an interposer substrate being laser processed by the laser processing apparatus to produce an interposer; the interposer and an integrated circuit chip being coupled and electrically connected to each other; and the interposer and a circuit board being coupled and electrically connected to each other. [Brief explanation of the drawing]

[0009] Some embodiments of this disclosure are described below, merely as examples, with reference to the accompanying drawings. [Figure 1] Figure 1 is a schematic diagram showing the configuration of a laser processing system related to a comparative example. [Figure 2] Figure 2 is a schematic diagram showing the configuration of the laser device. [Figure 3] Figure 3 is a schematic diagram showing the configuration of the laser processing system according to the first embodiment. [Figure 4] Figure 4 shows an example of a Z polarizer configuration. [Figure 5] Figure 5 shows the action of a Z polarizer. [Figure 6] FIG. 6 is a diagram for explaining the position adjustment of the Z - polarizer. [Figure 7] FIG. 7 is a diagram showing an example of the laser light incident on the inner wall of the hole during hole machining. [Figure 8] FIG. 8 is a diagram showing an example of the laser light incident on the inner wall of the hole during hole machining. [Figure 9] FIG. 9 is a diagram for explaining the polarization state on the inner wall when linearly polarized laser light is incident on the hole. [Figure 10] FIG. 10 is a diagram for explaining the polarization state on the inner wall when azimuthally polarized laser light is incident on the hole. [Figure 11] FIG. 11 is a diagram showing the configuration of the Z - polarizer according to the modified example. [Figure 12] FIG. 12 is a diagram showing the operation of the Z - polarizer according to the modified example. [Figure 13] FIG. 13 is a diagram schematically showing the configuration of the laser processing system according to the second embodiment. [Figure 14] FIG. 14 is a diagram showing a configuration example of the multi - spot polarization converter. [Figure 15] FIG. 15 is a diagram showing the configuration of the multi - spot polarization converter according to the first modified example. [Figure 16] FIG. 16 is a diagram showing the configuration of the multi - spot polarization converter according to the second modified example. [Figure 17] FIG. 17 is a diagram schematically showing the configuration of the electronic device. [Figure 18] FIG. 18 is a flowchart showing the manufacturing method of the electronic device. Embodiment

[0010] <Content> 1. Comparative Example 1.1 Configuration 1.1.1 Laser Processing System 1.1.2 Diffractive Optical Element 1.1.3 Laser Device 1.2 Operation 1.3 Problems 2. First Embodiment 2.1 Configuration 2.2 Operation 2.3 Effect 2.4 Variation 3. Second Embodiment 3.1 Configuration 3.2 Operation 3.3 Effect 3.4 Variation 4. Method for Manufacturing an Electronic Device

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below show some examples of the present disclosure and do not limit the content of the present disclosure. Also, not all of the configurations and operations described in each embodiment are essential as the configurations and operations of the present disclosure. Note that the same reference numerals are assigned to the same components, and redundant descriptions are omitted.

[0012] 1. Comparative Example 1.1 Configuration 1.1.1 Laser Processing System FIGS. 1 schematically shows the configuration of a laser processing system 1 according to a comparative example. Note that the comparative example is a form recognized by the applicant as being known only to the applicant and is not a known example recognized by the applicant.

[0013] The laser processing system 1 mainly includes a laser device ၂ and a laser processing device ၄. The laser processing system 1 is used for hole processing such as forming holes such as via holes in a glass substrate for an interposer.

[0014] The laser device၂ is a laser device that outputs ultraviolet pulsed laser light. For example, the laser device ၂ is a discharge-excited laser device that outputs ultraviolet pulsed laser light using F2, ArF, KrF, XeCl, XeF, etc. as a laser medium. In the present disclosure, the laser device ၂ is a KrF excimer laser device that outputs ultraviolet pulsed laser light having a center wavelength of 248.4 nm. Hereinafter, the ultraviolet pulsed laser light output by the laser device ၂ is simply referred to as laser light Lb.

[0015] The laser device 2 and the laser processing device 4 are connected by an optical path tube 5. The optical path tube 5 is positioned on the optical path of the laser beam Lb between the output port of the laser device 2 and the input port of the laser processing device 4.

[0016] The laser processing apparatus 4 includes a laser processing processor 40, an optical device 41, a frame 42, an XYZ stage 43, and a table 44. The optical device 41 and the XYZ stage 43 are fixed to the frame 42.

[0017] Table 44 supports the workpiece 45. The workpiece 45 is the object to be processed, specifically the part that will be drilled. The workpiece 45 is a glass substrate for an interposer, for example, an alkali-free glass substrate. The workpiece 45 may also be a substrate made of quartz glass, organic material, silicon single crystal, ceramics, metal, etc. Multiple holes H are formed in the workpiece 45 by so-called multi-point drilling.

[0018] The XYZ stage 43 supports the table 44. The workpiece 45 is fixed on the table 44. The XYZ stage 43 makes the table 44 movable in the X, Y, and Z directions, and by moving the table 44, the position of the workpiece 45 is changed. The X, Y, and Z directions are orthogonal to each other. The X and Y directions are parallel to the surface 45a of the workpiece 45. The Z direction is perpendicular to the surface 45a. The XYZ stage 43 is a moving stage that enables the workpiece 45 to be moved in a direction perpendicular to the optical axis of the focusing lens 60. The XYZ stage 43 is connected to the laser processing processor 40.

[0019] The optical device 41 comprises a housing 41a, high-reflection mirrors 47a, 47b, and 47c, an attenuator 49, a diffractive optical element (DOE) 50, a moving stage 51, and a focusing lens 60.

[0020] Each component within the optical device 41 is fixed to a holder (not shown) and is positioned in a predetermined location within the housing 41a.

[0021] The high-reflection mirror 47a is positioned to reflect the laser light Lb that has passed through the optical path tube 5, and the reflected laser light Lb passes through the attenuator 49 and enters the high-reflection mirror 47b. The optical path tube 5 and the housing 41a are purged with, for example, a purge gas. The purge gas is an inert gas such as N2 gas, which hardly absorbs the laser light Lb.

[0022] The attenuator 49 is located within the housing 41a on the optical path between the high-reflection mirror 47a and the high-reflection mirror 47b. The attenuator 49 includes, for example, two partial-reflection mirrors 49a and 49b, and rotation stages 49c and 49d for these partial-reflection mirrors. The partial-reflection mirrors 49a and 49b are optical elements whose transmittance changes depending on the incident angle of the laser light Lb. The incident angle of the laser light Lb is adjusted by the rotation stages 49c and 49d for the partial-reflection mirrors 49a and 49b.

[0023] The high-reflectivity mirrors 47b and 47c are positioned to reflect the laser light Lb that has passed through the attenuator 49, and the reflected laser light Lb is incident on the DOE 50.

[0024] The DOE50 is positioned on the optical path of the laser beam Lb reflected by the high-reflection mirror 47c such that its center coincides with the optical axis A of the laser beam Lb. The DOE50 diffracts the laser beam Lb incident from the high-reflection mirror 47c, thereby splitting it into multiple laser beams Lv with different emission angles. That is, the DOE50 splits the laser beam Lb in the X and Y directions. In this disclosure, the optical axis A of the laser beam Lb refers to the axis passing through the center of the light beam of the laser beam Lb.

[0025] The moving stage 51 holds the DOE 50 so that it can move in a direction perpendicular to the optical axis A of the laser beam Lb. Specifically, the moving stage 51 holds the DOE 50 so that it can move in the X and Y directions.

[0026] The moving stage 51 is connected to the laser processing processor 40. The laser processing processor 40 controls the moving stage 51 when adjusting so that the center of the DOE 50 coincides with the optical axis A of the laser beam Lb. Here, coincidence means that the amount of deviation between the center of the DOE 50 and the optical axis A is 1 / e of the laser beam Lb. 2 This refers to a beam diameter of 10% or less. 2 The beam diameter is 1 / e² of the peak intensity. 2 This is the radius of the beam at the point where it doubles.

[0027] The focusing lens 60 is positioned such that multiple laser beams Lv emitted from the DOE 50 are incident on it, and its focal plane is located on the surface 45a of the workpiece 45. The focusing lens 60 is, for example, an Fθ lens, which focuses each of the multiple laser beams Lv emitted from the DOE 50, generating a multi-point pattern in which multiple focused spots are arranged in a grid. The focusing lens 60 is an example of a "focusing optical system" according to the technology of this disclosure.

[0028] 1.1.2 Diffractive Optical Elements DOEs function by utilizing the phenomenon of light diffraction. By designing a fine structure through simulation, DOEs can output diffracted light in various patterns. Furthermore, the intensity of each diffracted light can be controlled. The DOE50 disclosed herein is fabricated by engraving a pattern onto a substrate such as quartz.

[0029] 1.1.3 Laser equipment Figure 2 schematically shows the configuration of the laser device 2. The laser device 2 includes an oscillator 20, a monitor module 30, a shutter 35, and a laser processor 38. The oscillator 20 includes a chamber 21, an optical resonator consisting of a rear mirror 25a and an output coupling mirror 25b, a charger 23, and a power supply unit (PPM: Pulsed Power Module) 22.

[0030] Chamber 21 is provided with windows 21a and 21b. A laser gas, which serves as the laser medium, is sealed inside Chamber 21.

[0031] Furthermore, an opening is formed in the chamber 21, and an electrical insulating plate 26 with multiple feedthroughs 26a embedded in it is provided to close this opening. A PPM 22 is placed on the electrical insulating plate 26. Inside the chamber 21 are a pair of discharge electrodes 27a and 27b as the main electrodes, and a ground plate 28. The discharge surfaces of the discharge electrodes 27a and 27b are rectangular in shape.

[0032] The discharge electrodes 27a and 27b are arranged so that their discharge surfaces face each other in order to excite the laser medium by discharge. The discharge electrode 27a is supported on the side opposite to the discharge surface by the electrical insulating plate 26. The discharge electrode 27a is connected to the feedthrough 26a. The discharge electrode 27b is supported on the side opposite to the discharge surface by the ground plate 28.

[0033] The PPM22 includes a switch 22a, a charging capacitor (not shown), a pulse transformer, a magnetic compression circuit, and a peaking capacitor. The peaking capacitor is connected to a feedthrough 26a via a connector (not shown). The charger 23 charges the charging capacitor based on control from the laser processor 38.

[0034] Switch 22a is controlled on / off by the laser processor 38. The laser processor 38 turns on switch 22a in response to the light emission trigger Tr transmitted from the laser processing processor 40.

[0035] When switch 22a is turned on, current flows from the charging capacitor to the primary side of the pulse transformer, and electromagnetic induction causes a reverse current to flow to the secondary side of the pulse transformer. The magnetic compression circuit is connected to the secondary side of the pulse transformer and compresses the pulse width of the current pulse. The peaking capacitor is charged by this current pulse. When the voltage of the peaking capacitor reaches the breakdown voltage of the laser gas, dielectric breakdown occurs in the laser gas between the discharge electrodes 27a and 27b, causing a discharge. This discharge generates one pulse of laser light Lb.

[0036] The rear mirror 25a is formed by coating a planar substrate with a highly reflective film. The output coupling mirror 25b is formed by coating a planar substrate with a partially reflective film. The chamber 21 is positioned between the rear mirror 25a and the output coupling mirror 25b. The laser light Lb generated in the chamber 21 is amplified by an optical resonator and output from the output coupling mirror 25b.

[0037] The monitor module 30 includes a beam splitter 31 and an optical sensor 32. The beam splitter 31 is positioned on the optical path of the laser beam Lb output from the output coupling mirror 25b and reflects a portion of the laser beam Lb. The optical sensor 32 is positioned where the laser beam Lb reflected by the beam splitter 31 enters. The optical sensor 32 measures the pulse energy of the laser beam Lb and transmits the measured value to the laser processor 38.

[0038] The laser processor 38 controls the pulse energy of the laser light Lb output from the laser device 2 to the target pulse energy Et by changing the charging voltage of the charger 23 based on the pulse energy measurement value from the optical sensor 32.

[0039] The shutter 35 is positioned on the optical path of the laser light Lb that passes through the beam splitter 31. The shutter 35 opens and closes in response to commands from the laser processor 38. The laser processor 38 controls the output of the laser light Lb from the laser device 2 by controlling the shutter 35. The laser light Lb output from the laser device 2 is linearly polarized.

[0040] 1.2 Operation Next, the operation of the comparative example laser processing system 1 will be described. First, the laser processing processor 40 controls the XYZ stage 43 so that the focal plane of the focusing lens 60 coincides with the surface 45a of the workpiece 45. Next, the laser processing processor 40 transmits a target pulse energy Et to the laser processor 38 and controls the transmittance Ta of the attenuator 49 so that the fluence on the surface 45a becomes the target fluence Ft.

[0041] Here, fluence is the pulse energy density per pulse at a single focused spot on the surface 45a of the workpiece 45. When the transmittance of the attenuator 49 is 100%, the transmittance of the optical device 41 is T0, the number of focused spots is Q, and the area of ​​the focused spots is S. Then the target fluence Ft is expressed by the following equation (1). Ft=Et×Ta×T0 / (Q×S) ···(1)

[0042] When the laser processor 38 receives the target pulse energy Et, it controls the charger 23 so that the pulse energy of the laser light Lb becomes the target pulse energy Et. Next, the laser processor 38 inputs a trigger to the switch 22a, causing the oscillator 20 to oscillate spontaneously. At this time, the shutter 35 is closed.

[0043] The laser light Lb output from the chamber 21 via the output coupling mirror 25b is partially sampled by the monitor module 30, and its pulse energy is measured. The laser processor 38 controls the charger 23 so that the difference ΔE between the pulse energy and the target pulse energy Et approaches zero. When the difference ΔE is within an acceptable range, the laser processor 38 sends a permission signal to the laser processing processor 40 and opens the shutter 35.

[0044] When the laser processing processor 40 receives a permission signal, it transmits a light emission trigger Tr with a predetermined repetition frequency and a predetermined number of pulses to the laser device 2. As a result, linearly polarized laser light Lb is output from the laser device 2 in synchronization with the light emission trigger Tr and incident on the laser processing device 4 via the optical path tube 5. This laser light Lb is reflected by the high-reflection mirror 47a, attenuated by the attenuator 49, and then reflected by the high-reflection mirrors 47b and 47c. The laser light Lb reflected by the high-reflection mirror 47c is incident on the DOE 50.

[0045] The DOE50 splits the incident laser beam Lb into multiple laser beams Lv on the surface 45a of the workpiece 45. The focusing lens 60 focuses each of the multiple laser beams Lv onto the surface 45a of the workpiece 45 to form a multi-point pattern. When a predetermined number of pulses of laser beam Lv are irradiated onto each focused spot of the multi-point pattern and the fluence exceeds the processing threshold, laser ablation occurs and holes H are formed.

[0046] Next, the laser processing processor 40 controls the XYZ stage 43 and the laser device 2 to repeatedly change the irradiation position and irradiate in a step-and-repeat manner, thereby forming multiple holes H throughout the processing area where hole processing is required.

[0047] 1.3 Challenges In the comparative example laser processing system 1, when the workpiece 45 is a glass substrate for an interposer, the laser irradiation time during hole processing becomes long, and it takes a long time to complete the hole processing. Therefore, it is desirable to shorten the laser irradiation time and improve the processing speed.

[0048] This disclosure provides a laser processing apparatus that enables improved processing speed in hole drilling of glass substrates and the like, and a method for manufacturing electronic devices.

[0049] 2. First Embodiment A laser processing system 1a according to the first embodiment of this disclosure will now be described. Components similar to those described above will be denoted by the same reference numerals, and redundant descriptions will be omitted unless otherwise specified.

[0050] 2.1 Configuration Figure 3 schematically shows the configuration of the laser processing system 1a according to the first embodiment. The laser processing system 1a has the same configuration as the laser processing system 1 according to the comparative example, except for the optical device 41.

[0051] The optical apparatus 41 according to this embodiment differs from the optical apparatus 41 according to the comparative example only in that, in addition to the above-described configuration, it includes a Z polarizer 70, a rotating stage 71, and a moving stage 72.

[0052] The Z polarizer 70 is positioned on the optical path of the laser beam Lb between the high-reflectivity mirror 47c and the DOE 50. The Z polarizer 70 only needs to be positioned upstream of the DOE 50 in the path of the laser beam Lb. The Z polarizer 70 is a polarization conversion element that converts the polarization state of the laser beam Lb from linear polarization to azimuth polarization. Azimuth polarization refers to a polarization state where the polarization direction is concentric, aligned with the circumferential direction of the beam.

[0053] Furthermore, the Z polarizer 70 is positioned so that its center coincides with the optical axis A of the laser beam Lb. Here, coincidence means that the amount of deviation between the center of the Z polarizer 70 and the optical axis A is 1 / e of the laser beam Lb. 2This refers to a beam diameter that is 10% or less of the beam diameter.

[0054] The rotating stage 71 holds the Z polarizer 70 so that it can rotate around the optical axis A as the axis of rotation. The Z polarizer 70 is positioned so that its center coincides with the axis of rotation. In this embodiment, the axis of rotation is parallel to the Z direction.

[0055] The moving stage 72 holds the Z polarizer 70 so that it can move in a direction perpendicular to the optical axis A. Specifically, the moving stage 72 holds the Z polarizer 70 so that it can move in the X and Y directions. In this embodiment, the moving stage 72 supports the rotating stage 71, but the rotating stage 71 may support the moving stage 72.

[0056] The movement stage 72 corresponds to the "first movement stage" in the technology of this disclosure. The movement stage 51 described above corresponds to the "second movement stage" in the technology of this disclosure.

[0057] Figure 4 shows an example of the configuration of the Z polarizer 70. As shown in Figure 4, the Z polarizer 70 is constructed by combining four half-wave plates 70a to 70d with different optical axis directions. Specifically, the half-wave plates 70a to 70d are four fan-shaped plates obtained by dividing a circular plate into four equal parts by four straight lines passing through the center C. For example, each of the half-wave plates 70a to 70d is formed from a birefringent crystal having optical anisotropy. In this disclosure, the optical axis refers to the axis in the birefringent crystal where the propagation speed of light does not depend on the polarization direction.

[0058] The solid lines shown for each of the half-wave plates 70a to 70d indicate the direction of the optical axis. Each of the half-wave plates 70a to 70d has an optical axis direction that differs by 45° from the adjacent half-wave plate. Each of the half-wave plates 70a to 70d converts incident linearly polarized light into linearly polarized light that is symmetrical with respect to the optical axis.

[0059] The Z polarizer 70 may be constructed by combining four or more half-wave plates. A larger number of half-wave plates is preferable. This is because the more half-wave plates combined, the closer the polarization direction of the generated azimuth polarization becomes to the direction along the circumference. However, practically speaking, the number of half-wave plates combined is preferably between 4 and 12. For example, when combining eight half-wave plates, the optical axis direction should differ by 22.5° for each half-wave plate. When combining twelve half-wave plates, the optical axis direction should differ by 15° for each half-wave plate.

[0060] 2.2 Operation The operation of the laser processing system 1a according to the first embodiment is the same as that of the laser processing system 1 according to the comparative example, except for the action of the Z polarizer 70. The differences from the comparative example will be explained below.

[0061] Linearly polarized laser light Lb, incident from laser device 2 to laser processing device 4, passes through high-reflection mirror 47a, attenuator 49, and high-reflection mirrors 47b and 47c before being incident on Z polarizer 70. The polarization state of laser light Lb is converted to azimuth polarization by Z polarizer 70. The laser light Lb that has passed through Z polarizer 70 is split into multiple laser beams Lv by passing through DOE 50. The polarization state of each of the multiple laser beams Lv is azimuth polarization.

[0062] The focusing lens 60 forms a multi-point pattern by focusing each of the multiple laser beams Lv onto the surface 45a of the workpiece 45. As a result, when a predetermined number of pulses of azimuth-polarized laser beams Lv are irradiated onto each focused spot and the fluence exceeds the processing threshold, laser ablation occurs and holes H are formed.

[0063] Figure 5 shows the operation of the Z polarizer 70. For example, the Z polarizer 70 converts linearly polarized light with a polarization direction in the Y direction into concentric azimuth polarization with center C as the axis. In order to generate azimuth polarization with a uniform polarization direction with center C as the axis, as shown in Figure 5, the direction of the linearly polarized light incident on the Z polarizer 70 must be at a predetermined angle with respect to the direction of each optical axis of the half-wave plates 70a to 70d. For example, the direction of the linearly polarized light incident on the Z polarizer 70 should be parallel to the direction of the optical axis of the half-wave plate 70d. In this embodiment, the laser processing processor 40 controls the rotating stage 71 so that the angle of the polarization direction of the laser light Lb incident on the Z polarizer 70 with respect to the optical axis is at a predetermined angle.

[0064] Figure 6 illustrates the position adjustment of the Z polarizer 70. As shown in Figure 6, if the optical axis A of the laser beam Lb incident on the Z polarizer 70 is deviated from the center C of the Z polarizer 70, a bias in azimuth polarization occurs. In this embodiment, the laser processing processor 40 controls the moving stage 72 so that the optical axis A of the laser beam Lb incident on the Z polarizer 70 coincides with the center C of the Z polarizer 70.

[0065] 2.3 Effects As shown in Figures 7 and 8, laser ablation occurs in the workpiece 45 when the fluence exceeds the processing threshold near the focused spot of the laser beam Lv. Furthermore, laser ablation also occurs when the laser beam Lv undergoes Fresnel reflection off the inner wall of the processed hole H and the fluence exceeds the processing threshold at the point where it is focused again.

[0066] The reflectivity of laser light Lv at the inner wall of hole H generally increases with increasing incidence angle θ. In the case shown in Figure 7, the incidence angle θ is larger than in the case shown in Figure 8, so the reflectivity is higher. Also, in Fresnel reflection, S-polarized light has a higher reflectivity than P-polarized light, so the reflectivity of laser light Lv incident on the inner wall of hole H increases as the polarization state at the time of incidence approaches S-polarization.

[0067] In the comparative example, as shown in Figure 9, linearly polarized laser light Lv is incident on hole H. In this case, the polarization state of the laser light Lv is P-polarized at points P1 and P3 on the inner wall of hole H that are opposite the polarization direction, and S-polarized at points P2 and P4 that are opposite in a direction perpendicular to the polarization direction. Therefore, the reflectivity of the laser light Lv decreases as it approaches points P1 and P3. Thus, in the comparative example, the reflectivity of the laser light Lv decreases depending on the position on the inner wall, so the energy contributing to laser ablation at the point where it is refocused decreases.

[0068] In contrast, in this embodiment, as shown in Figure 10, azimuth-polarized laser light Lv is incident on the hole H. In this case, the polarization state of the laser light Lv is S-polarized at all points P1 to P4. In this embodiment, since a higher proportion of the laser light Lv incident on the inner wall of the hole H is S-polarized, the reflectivity is higher compared to the comparative example, and the energy contributing to laser ablation at the refocused position is greater. Therefore, according to this embodiment, the laser irradiation time can be shortened and the processing speed can be improved. Furthermore, the number of laser light Lb pulses required for hole processing can be reduced.

[0069] 2.4 Variations Figure 11 shows the configuration of a modified Z polarizer 70. In the above embodiment, the Z polarizer 70 is constructed by combining multiple half-wave plates, but the Z polarizer 70 shown in Figure 11 is constructed using a polarization converter. The solid line shown in the Z polarizer 70 in Figure 11 indicates the direction of the optical axis. The direction of the optical axis changes continuously.

[0070] Figure 12 shows the operation of the Z polarizer 70 in the modified version. In this modified version, the polarization direction of the azimuth polarization after conversion by the Z polarizer 70 is along the circumference. As a result, the proportion of the laser light Lv incident on the inner wall of the hole H as S polarization increases, further improving the processing speed.

[0071] Furthermore, when the Z polarizer 70 is constructed by combining multiple half-wave plates as in the above embodiment, energy loss of laser light Lv occurs at the junction of two half-wave plates. In contrast, since there is no junction in the modified Z polarizer 70, energy loss of laser light Lv is reduced. This further improves the processing speed.

[0072] 3. Second Embodiment A laser processing system 1b according to a second embodiment of this disclosure will now be described. Components similar to those described above will be denoted by the same reference numerals, and redundant descriptions will be omitted unless otherwise specified.

[0073] 3.1 Configuration Figure 13 schematically shows the configuration of the laser processing system 1b according to the second embodiment. The laser processing system 1b has the same configuration as the laser processing system 1a according to the first embodiment, except for the optical device 41.

[0074] The optical device 41 according to this embodiment differs from the optical device 41 according to the first embodiment in that a multi-spot polarization converter 80 is provided instead of the Z polarizer 70 and DOE 50. Furthermore, the optical device 41 according to this embodiment includes a rotating stage 81 and a moving stage 82.

[0075] The multi-spot polarization converter 80 is positioned in the optical path of the laser beam Lb between the high-reflection mirror 47c and the focusing lens 60. The multi-spot polarization converter 80 only needs to be positioned upstream of the focusing lens 60 from the laser beam Lb. The multi-spot polarization converter 80 is an optical element that integrates the Z polarizer 70 and the DOE 50. The multi-spot polarization converter 80 converts the polarization state of the laser beam Lb from linear polarization to azimuth polarization and splits the laser beam Lb into multiple laser beams Lv with different emission angles.

[0076] Furthermore, the multi-spot polarization converter 80 is positioned so that its center coincides with the optical axis A of the laser beam Lb. Here, coincidence means that the amount of deviation between the center of the multi-spot polarization converter 80 and the optical axis A is 1 / e of the laser beam Lb. 2 This refers to a beam diameter that is 10% or less of the beam diameter.

[0077] The rotating stage 81 holds the multi-spot polarization converter 80 so that it can rotate around the optical axis A as the axis of rotation. In this embodiment, the axis of rotation is parallel to the Z direction.

[0078] The moving stage 82 holds the multi-spot polarization converter 80 so that it can move in a direction perpendicular to the optical axis A. Specifically, the moving stage 82 holds the multi-spot polarization converter 80 so that it can move in the X and Y directions. In this embodiment, the moving stage 82 supports the rotating stage 81, but the rotating stage 81 may support the moving stage 82.

[0079] Figure 14 shows an example configuration of a multi-spot polarization converter 80. The multi-spot polarization converter 80 has a light-transmitting substrate 83. The Z polarizer 70 and DOE 50 described above are formed within the substrate 83. The Z polarizer 70 is formed along the incident surface 83a of the substrate 83 to which the laser light Lb is incident. The DOE 50 is formed along the exit surface 83b of the substrate 83 to which the laser light Lv is emitted. The Z polarizer 70 and DOE 50 are positioned opposite each other and their centers coincide.

[0080] 3.2 Operation The operation of the laser processing system 1b according to the second embodiment is the same as that of the laser processing system 1a according to the first embodiment, except for the adjustment control of the multi-spot polarization converter 80. The differences from the first embodiment will be described below.

[0081] In this embodiment, the laser processing processor 40 controls the rotating stage 81 so that the angle of the polarization direction of the laser light Lb incident on the Z polarizer 70 of the multi-spot polarization converter 80 with respect to the optical axis becomes a predetermined angle.

[0082] In this embodiment, the laser processing processor 40 controls the moving stage 82 so that the optical axis A of the laser beam Lb incident on the Z polarizer 70 and DOE 50 of the multi-spot polarization converter 80 coincides with the center C of the Z polarizer 70.

[0083] 3.3 Effects According to this embodiment, the same effects as in the first embodiment can be obtained.

[0084] Furthermore, in the first embodiment, since the Z polarizer 70 and DOE 50 are individually provided, the laser light Lb is Fresnel reflected by a total of four surfaces: the incident and exit surfaces of the Z polarizer 70 and the incident and exit surfaces of the DOE 50. In contrast, in this embodiment, the laser light Lb is Fresnel reflected by a total of two surfaces: the incident and exit surfaces of the multi-spot polarization converter 80. Thus, in this embodiment, the number of surfaces on which the laser light Lb is Fresnel reflected is reduced, and therefore the energy loss due to Fresnel reflection is reduced. For example, the energy loss due to Fresnel reflection is reduced from 15.5% to 8.1%.

[0085] Furthermore, in this embodiment, since the Z polarizer 70 and the DOE 50 are integrated, the positional adjustment of the Z polarizer 70 and the DOE 50 with respect to the optical axis A of the laser beam Lb can be performed with a single moving stage 82.

[0086] 3.4 Variations Next, a modified example of the multi-spot polarization converter 80 will be described. Figure 15 shows the configuration of the multi-spot polarization converter 80 according to the first modified example. In this modified example, the Z polarizer 70 is provided inside the substrate 83. The DOE 50 is formed along the exit surface 83b of the substrate 83, similar to the second embodiment. The Z polarizer 70 and the DOE 50 are positioned opposite each other and their centers coincide.

[0087] Figure 16 shows the configuration of a multi-spot polarization converter 80 according to a second modified example. In this modified example, the Z polarizer 70 and the DOE 50 are composed of a single optical element 84. For example, the optical element 84 is a DOE configured to convert the polarization state of the laser light Lb from linear polarization to azimuth polarization and to divide the laser light Lb into multiple laser beams Lv with different emission angles. The optical element 84 is formed along the emission surface 83b of the substrate 83. In other words, both the Z polarizer 70 and the DOE 50 are formed along the emission surface 83b. The optical element 84 may also be formed along the incident surface 83a of the substrate 83. In other words, both the Z polarizer 70 and the DOE 50 may be formed along the incident surface 83a.

[0088] 4. Methods for manufacturing electronic devices The laser processing methods according to each of the above embodiments can be applied to the formation of through-holes in the substrate of the interposer IP in the manufacturing of the following electronic device 100.

[0089] Figure 17 schematically shows the configuration of the electronic device 100. The electronic device 100 shown in Figure 17 includes an integrated circuit chip IC, an interposer IP, and a circuit board CS. The integrated circuit chip IC is, for example, a chip in which an integrated circuit (not shown) is formed on a silicon substrate. The integrated circuit chip IC is provided with a plurality of bump ICBs that are electrically connected to the integrated circuit.

[0090] The interposer IP comprises an insulating substrate with a plurality of through-holes (not shown) formed therein, and a conductor (not shown) is provided in each through-hole to electrically connect the front and back surfaces of the substrate. A plurality of lands (not shown) are formed on one side of the interposer IP, each connected to a bump ICB, and each land is electrically connected to one of the conductors in the through-holes. A plurality of bump IPBs are provided on the other side of the interposer IP, and each bump IPB is electrically connected to one of the conductors in the through-holes.

[0091] On one side of the circuit board CS, there are several lands (not shown) which are connected to bumps IPB. The circuit board CS is equipped with several terminals which are electrically connected to these lands.

[0092] Figure 18 shows the manufacturing method of the electronic device 100. First, in the first step SP1, laser processing and wiring formation are performed on the interposer substrate constituting the interposer IP. The laser processing of the interposer substrate includes the formation of through holes by irradiating the interposer substrate with pulsed laser light. The wiring formation includes the formation of a conductive film on the inner wall surface of the through holes formed in the interposer substrate. The interposer IP is manufactured by the first step SP1.

[0093] Next, in the second step SP2, the interposer IP and the integrated circuit chip IC are coupled. The second step SP2 includes, for example, placing the bump ICB of the integrated circuit chip IC on the land of the interposer IP and electrically connecting the bump ICB and the land.

[0094] Then, in the third step SP3, the interposer IP and the circuit board CS are coupled. The third step SP3 includes, for example, placing the bump IPB of the interposer IP on the land of the circuit board CS and electrically connecting the bump IPB and the land.

[0095] The laser processing processor 40 and the laser processor 38 may be physically configured in hardware form to perform the various processes included in this disclosure. For example, the laser processing processor 40 and the laser processor 38 may be a computer including a memory storing a control program that defines the various processes, and a processing unit that executes the control program. The control program may be stored in a single memory, or it may be stored in multiple physically separate memories, and the various processes may be defined by the control program as a collection of these memories. The processing unit may be a general-purpose processing unit such as a CPU (Central Processing Unit), or a purpose-specific processing unit such as a GPU (Graphics Processing Unit).

[0096] Furthermore, the laser processing processor 40 and the laser processor 38 may be programmed in software form to perform the various processes included in this disclosure. For example, the laser processing processor 40 and the laser processor 38 may have the functions for performing the various processes implemented in a dedicated device such as an ASIC (Application Specific Integrated Circuit) or a programmable device such as an FPGA (Field Programmable Gate Array).

[0097] The various processes included in this disclosure may be performed by one computer, one dedicated device, or one programmable device, or by the cooperation of multiple computers, multiple dedicated devices, or multiple programmable devices located physically separately. The various processes may be performed by at least two combinations of one or more computers, one or more dedicated devices, and one or more programmable devices.

[0098] The above description is intended to be illustrative, not restrictive. It will be apparent to those skilled in the art that modifications can be made to the embodiments of this disclosure without departing from the claims. It will also be apparent to those skilled in the art that the embodiments of this disclosure can be used in combination. Terms used herein and throughout the claims should be construed as "non-restrictive" unless otherwise specified. For example, terms such as "includes," "has," "equips," and "possesses" should be construed as "not excluding the existence of components other than those described." The modifier "one" should be construed as meaning "at least one" or "one or more." The term "at least one of A, B, and C" should be construed as "A," "B," "C," "A+B," "A+C," "B+C," or "A+B+C," and further construed as including combinations of these with anything other than "A," "B," and "C."

Claims

1. A laser processing apparatus that uses pulsed laser light output from a laser device to drill holes in a workpiece, A Z polarizer is placed on the optical path of the pulsed laser light and converts the polarization state of the pulsed laser light into azimuth polarization, A diffractive optical element that splits the pulsed laser light with azimuth polarization that has passed through the Z polarizer into a plurality of laser beams, A focusing optical system that generates multiple focused spots on the workpiece by focusing the multiple laser beams, A laser processing device equipped with the following features.

2. A laser processing apparatus according to claim 1, The Z polarizer is positioned such that its center coincides with the optical axis of the pulsed laser light.

3. A laser processing apparatus according to claim 1, The diffractive optical element is positioned so that its center coincides with the optical axis of the pulsed laser light.

4. A laser processing apparatus according to claim 1, The Z polarizer is constructed by combining multiple half-wave plates with different optical axis directions.

5. A laser processing apparatus according to claim 4, The number of the aforementioned half-wave plates is between 4 and 12.

6. A laser processing apparatus according to claim 1, The pulsed laser light output from the laser device is linearly polarized. Linearly polarized pulsed laser light is incident on the Z polarizer.

7. A laser processing apparatus according to claim 1, The system includes a rotating stage that holds the Z polarizer so as to be rotatable with respect to the optical axis of the pulsed laser beam.

8. A laser processing apparatus according to claim 7, The Z polarizer is positioned such that its center coincides with the axis of rotation.

9. A laser processing apparatus according to claim 1, The system includes a first moving stage that holds the Z polarizer so that it can move in a direction perpendicular to the optical axis of the pulsed laser light.

10. A laser processing apparatus according to claim 1, The system includes a second moving stage that holds the diffractive optical element so that it can move in a direction perpendicular to the optical axis of the pulsed laser light.

11. A laser processing apparatus according to claim 1, The Z polarizer is a polarization converter that directs the polarization direction of the azimuth polarization along the circumference.

12. A laser processing apparatus according to claim 1, The Z polarizer and the diffractive optical element are integrated as a multi-spot polarization converter.

13. A laser processing apparatus according to claim 12, The multi-spot polarizing converter has a substrate, The Z polarizer and the diffractive optical element are formed within the substrate.

14. A laser processing apparatus according to claim 13, The Z polarizer is formed along the incident surface of the substrate, The diffractive optical element is formed along the emission surface of the substrate.

15. A laser processing apparatus according to claim 13, The Z polarizer is formed inside the substrate, The diffractive optical element is formed along the emission surface of the substrate.

16. A laser processing apparatus according to claim 13, The Z polarizer is formed along the exit surface of the substrate, The diffractive optical element is formed along the emission surface of the substrate.

17. A laser processing apparatus according to claim 13, The Z polarizer is formed along the incident surface of the substrate, The diffractive optical element is formed along the incident surface of the substrate.

18. A laser processing apparatus according to claim 12, The multi-spot polarization converter is provided with a rotating stage that holds it so as to be rotatable with the optical axis of the pulsed laser beam as the axis of rotation.

19. A laser processing apparatus according to claim 12, The system includes a moving stage that holds the multi-spot polarization converter so that it can move in a direction perpendicular to the optical axis of the pulsed laser light.

20. A method for manufacturing electronic devices, A laser processing apparatus that uses pulsed laser light output from a laser device to drill holes in a workpiece, A Z polarizer is placed on the optical path of the pulsed laser light and converts the polarization state of the pulsed laser light into azimuth polarization, A diffractive optical element that splits the pulsed laser light with azimuth polarization that has passed through the Z polarizer into a plurality of laser beams, A focusing optical system that generates multiple focused spots on the workpiece by focusing the multiple laser beams, An interposer is manufactured by laser processing an interposer substrate using a laser processing device equipped with the following: The interposer and the integrated circuit chip are coupled together and electrically connected to each other. The interposer and the circuit board are coupled together and electrically connected to each other. A method for manufacturing electronic devices, including the following.

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