PCB processing apparatus and PCB processing method

Abstract

To form a uniform hole in a wide range of a substrate.SOLUTION: A substrate processing device 100 includes a laser light source 1, a reflection type spatial modulator 2, a rocking mirror 4, a condenser lens 5, an imaging optical system 3, and a moving mechanism 6. The laser light source 1 emits a laser beam L1. The reflection type spatial modulator 2 modulates the laser beam L1, and generates a plurality of processing laser beams L2. The rocking mirror 4 reflects the plurality of processing laser beams L2. The condenser lens 5 condenses each of the plurality of processing laser beams L2 to a substrate SU. The imaging optical system 3 constitutes a both side telecentric optical system having such a relation that a reflection surface 21 of the reflection type spatial modulator 2 and an incident surface 41 of the rocking mirror 4 are imaged. The moving mechanism 6 moves the substrate SU to the plurality of processing laser beams L2. The reflection type spatial modulator 2 corrects a phase hologram so as to irradiate the predetermined position of the substrate SU with the plurality of processing lase beams L2, and thereby form a plurality of holes having a uniform shape and size.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a substrate processing apparatus for forming a plurality of processing marks on a substrate by laser light, and a substrate processing method.

Background Art

[0002] Conventionally, there is known an apparatus for forming fine processing marks having a predetermined dimension in the thickness direction of a substrate, such as holes having a diameter of about 100 μm and grooves having a line width on the order of micrometers, on the substrate using laser light. This apparatus can form processing marks with an intended shape at an intended position with high accuracy. For example, there is known an apparatus including a diffractive optical component, a galvanometer mirror, and an fsinθ lens that condenses a number of branched beams (see, for example, Patent Document 1). However, in this apparatus, due to the quality of the diffractive optical component, distortion of the lens, etc., the processing position of the actual processing mark may deviate from the intended position, and / or the processing shape of the actual processing mark may deviate from the intended shape.

[0003] In order to solve the above problems, there is known an apparatus using a reflective spatial light modulator instead of a diffractive optical component (see, for example, Patent Document 2). In this apparatus, the reflective spatial light modulator simultaneously condenses laser light for forming processing marks at a plurality of positions on the substrate using a phase hologram.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, when using the above-described apparatus to form multiple uniform processing marks arranged one-dimensionally or two-dimensionally over a wide area of ​​a substrate (for example, an area on the order of several millimeters), the processing state of the processing marks formed on the substrate was not uniform depending on the position on the substrate.

[0006] The objective of the present invention is to form uniform processing marks over a wide area of ​​a substrate. [Means for solving the problem]

[0007] Several embodiments for solving the problem are described below. These embodiments can be combined as needed. The substrate processing apparatus according to the present invention is an apparatus for forming a plurality of processing marks having predetermined dimensions in the thickness direction of a substrate. The substrate processing apparatus comprises a laser light source, a reflective spatial modulator, a mirror, a focusing lens, an imaging optical system, and a moving mechanism. The laser light source emits laser light. The reflective spatial modulator modulates the laser light using a phase hologram to generate a plurality of processing laser beams for simultaneously forming a plurality of processing marks arranged one-dimensionally or two-dimensionally on the substrate. The mirror reflects the plurality of processing laser beams generated by the reflective spatial modulator. The focusing lens focuses each of the plurality of processing laser beams reflected by the mirror onto the substrate. The imaging optical system constitutes a double-sided telecentric optical system in which the reflective surface of the reflective spatial modulator and the incident surface of the mirror are in an imaging relationship. The moving mechanism moves the substrate relative to the plurality of processing laser beams.

[0008] In the above-described substrate processing apparatus, the reflective spatial modulator corrects the phase hologram to simultaneously form multiple processing marks of uniform shape and size at predetermined locations on the substrate by changing the reflection angle of the mirror and irradiating multiple processing laser beams at those predetermined locations.

[0009] The inventors of the present invention have found that the influence of optical systems, such as aberrations in the imaging optical system and focusing lens of the above-mentioned substrate processing apparatus, on the processing laser light is the reason why uniform processing marks cannot be formed over a wide area of ​​the substrate. In other words, it is believed that the difference in the height of the focal points of multiple processing laser beams depending on the position on the substrate due to the influence of optical aberrations in the imaging optical system and focusing lens is the reason why uniform processing marks cannot be formed over a wide area of ​​the substrate.

[0010] Therefore, in the above-described substrate processing apparatus, a correction is applied to the phase hologram that generates the processing laser light, thereby generating processing laser light that can form multiple processing marks with a uniform processing shape at any position on the substrate. In other words, the misalignment of the focal points of the multiple processing laser beams is eliminated by correcting the phase hologram. As a result, the focal point of the processing laser light becomes the same over a wide area of ​​the substrate, so that multiple processing marks with a uniform processing shape can be formed over a wide area of ​​the substrate.

[0011] The aberrations generated in the multiple processing laser beams focused by the imaging optical system and focusing lens should preferably be 20 μm or less for field curvature and 5 μm or less for astigmatism (lateral aberration). This reduces the change in the focal position of the processing laser beams depending on the position of the substrate, allowing for the formation of multiple processing marks with uniform processing conditions over a wide area of ​​the substrate.

[0012] The imaging optical system may consist of a lens combination formed by placing the convex surfaces of two plano-convex lenses opposite each other, a doublet lens, or an aspherical lens. This reduces the aberrations generated by the imaging optical system.

[0013] The focusing lens may also be an fsinθ lens. This allows multiple processing laser beams to be properly focused onto the substrate.

[0014] The reflective spatial modulator may correct the phase hologram to reduce the field curvature aberration that occurs in the multiple processing laser beams focused by the focusing lens. This reduces the field curvature aberration generated in the processing laser beam by the imaging optical system and focusing lens, thereby reducing the change in the irradiation state of the processing laser beam depending on the position of the substrate. As a result, multiple processing marks can be formed uniformly over a wide area of ​​the substrate.

[0015] The reflective spatial modulator may correct its phase hologram so that the intensity of the multiple processing laser beams focused by the focusing lens becomes uniform. This makes the intensity of the processing laser beams uniform over a wide area of ​​the substrate, allowing for the formation of multiple processing marks with uniform processing conditions over a wide area of ​​the substrate.

[0016] The reflective spatial modulator may correct the phase hologram so that the actual processing pitch of the multiple processing marks becomes the desired processing pitch. This suppresses the change in the irradiation pitch of the multiple processing laser beams depending on the position of the substrate, so that multiple processing marks with a uniform processing pitch can be formed over a wide area of ​​the substrate.

[0017] The reflective spatial modulator may correct its phase hologram so that the focusing positions of the multiple processing laser beams by the focusing lens differ from the focusing position of the zeroth-order beam. As a result, the zeroth-order beam, which has a higher intensity than the processing laser beam, is not used to form processing marks, allowing for the uniform formation of multiple processing marks over a wide area of ​​the substrate.

[0018] The moving mechanism may move the substrate in one or two dimensions to form a continuous group of processing marks on the substrate. This allows for the formation of multiple uniform processing marks over a wider area of ​​the substrate.

[0019] When a substrate is moved by a moving mechanism to form a group of processing marks, if there is a discrepancy between the position of the substrate after movement by the moving mechanism and the positions on the substrate where multiple processing laser beams should be irradiated, the reflective spatial modulator may correct the phase hologram to compensate for this discrepancy. This allows for highly accurate correction of positional discrepancies by correcting the phase hologram, even if the substrate cannot be moved to the appropriate position by the moving mechanism. As a result, multiple uniform processing marks can be formed over a wide area of ​​the substrate.

[0020] Another method for processing a substrate according to the present invention is a method for forming a plurality of processing marks on a substrate. The substrate processing method comprises the following steps. ◎The laser light is emitted from the laser light source and incident on the reflective spatial modulator. ◎To generate multiple processing laser beams for simultaneously forming multiple processing marks arranged one-dimensionally or two-dimensionally on a substrate by modulating laser light using a phase hologram of a reflective spatial modulator. ◎ Multiple processing laser beams generated by a reflective spatial modulator are imaged using a bilateral telecentric optical system. ◎Reflecting multiple processed laser beams that have been imaged using mirrors. ◎ Focusing each of the multiple processing laser beams reflected by the mirror onto the substrate.

[0021] In the above substrate processing method, the phase hologram is corrected by changing the reflection angle of the mirror and irradiating multiple processing laser beams onto predetermined positions on the substrate, thereby simultaneously forming multiple processing marks of uniform shape and size at predetermined positions.

[0022] In the above substrate processing method, a correction is applied to the phase hologram that generates the processing laser light, thereby generating processing laser light that can form multiple processing marks with a uniform processing shape at any position on the substrate. In other words, the misalignment of the focal points of the multiple processing laser beams is eliminated by correcting the phase hologram. As a result, the focal point of the processing laser light becomes the same over a wide area of ​​the substrate, so that multiple processing marks with a uniform processing shape can be formed over a wide area of ​​the substrate. [Effect of the Invention]

[0023] Uniform processing marks can be formed over a wide range of the substrate. [Brief Description of the Drawings]

[0024] [Figure 1] A diagram showing the configuration of a substrate processing apparatus. [Figure 2] A diagram showing an example of hole formation in a substrate. [Figure 3] A diagram showing an example of the cross-sectional shape of a hole formed in a substrate. [Figure 4] A diagram showing an example of the arrangement of processing laser light. [Figure 5] A diagram showing an example of the circumferential movement of a condensing point in tapered hole processing. [Figure 6] A diagram showing the irradiation state of a plurality of processing laser lights affected by field curvature aberration. [Figure 7] A diagram showing an example of the arrangement of the set condensing point and the condensing point of the processed laser light after correcting the reference phase hologram to correct field curvature aberration. [Figure 8] A diagram showing the optical intensity on the set reference phase hologram of the condensing point and the optical intensity after correction to make the intensity of the processing laser light uniform. [Figure 9] A diagram showing an example of a state where the processing pitch of through holes is shifted. [Figure 10] A diagram showing an example of the arrangement of the condensing point for correcting the shift of the processing pitch. [Figure 11] A diagram showing an example of the positional relationship between the condensing point of the zero-order light and the processing laser light L2. [Figure 12] A diagram showing an example of a state where the arrangement directions of the previously formed through hole and the currently formed through hole are different. [Figure 13] A diagram showing an example of the arrangement of the condensing point for correcting the shift of the formation position of the through hole caused by the movement of the moving mechanism. [Figure 14] A diagram showing another example of holes that can be formed in a substrate. [Embodiments for Carrying Out the Invention]

[0025] 1. First Embodiment (1) Configuration of the circuit board processing equipment The configuration of the substrate processing apparatus 100 will be described below with reference to Figure 1. Figure 1 is a diagram showing the configuration of the substrate processing apparatus. The substrate processing apparatus 100 is a device that simultaneously forms multiple processing marks arranged in one or two dimensions on a substrate SU by simultaneously irradiating the substrate SU with multiple processing laser beams L2 arranged in one or two dimensions. This substrate processing apparatus 100 can form processing marks having predetermined dimensions in the thickness direction of the substrate SU. That is, the substrate processing apparatus 100 can form both processing marks that penetrate the substrate SU and processing marks that do not penetrate the substrate SU. Multiple processing laser beams L2 are generated by modulating laser beam L1 emitted from a laser light source with a reflective spatial modulator. The substrate processing apparatus 100 comprises a laser light source 1, a reflective spatial modulator 2, an imaging optical system 3, a oscillating mirror 4, a focusing lens 5, a moving mechanism 6, and a control unit 7.

[0026] The laser light source 1 emits laser light L1. The laser light L1 emitted from the laser light source 1 has a wavelength in the near-infrared region (for example, a wavelength of 1000 nm to 1200 nm). The laser light source 1 emits the laser light L1 as short pulse light. The pulse width of the laser light L1 can be, for example, picosecond to femtosecond. The wavelength and pulse width of the laser light L1 can be appropriately changed depending on the material of the substrate SU, etc.

[0027] The laser light L1 emitted from the laser light source 1 is reflected by the first mirror 11 and the second mirror 13, and then incident on the reflective spatial modulator 2. The second mirror 13 is, for example, a prism.

[0028] The reflective spatial modulator 2 receives the laser light L1 emitted from the laser light source 1 at the reflective surface 21, modulates the incident laser light L1 to generate processing laser light L2. The reflective spatial modulator 2 is, for example, a spatial light modulator (SLM) made of reflective liquid crystal on silicon (LCOS). The reflective spatial modulator 2 modulates the laser light L1 to generate processing laser light L2 and reflects the processing laser light L2 to the outside.

[0029] The reflective spatial modulator 2 includes pixel electrodes formed in an array on a reflective surface 21, counter electrodes provided opposite to the pixel electrodes, and liquid crystals disposed between the pixel electrodes and the counter electrodes. In this reflective spatial modulator 2, the refractive index can be adjusted for each pixel electrode by applying a voltage between each pixel electrode and the counter electrode to control the orientation state of the liquid crystal in the region corresponding to the pixel electrode.

[0030] The laser light L1 incident on the pixel electrode is reflected with a phase that depends on the refractive index of light at each pixel electrode on the reflective surface 21. In other words, the laser light L1 is phase-modulated depending on the refractive index of each pixel electrode. Therefore, by appropriately adjusting the refractive index for each of the multiple pixel electrodes on the reflective surface 21 and phase-modulating the laser light L1 incident on the reflective spatial modulator 2 on a pixel electrode-by-pixel basis, the reflective spatial modulator 2 can generate processing laser light L2 having any desired shape. The shape of the processing laser light L2 generated by the reflective spatial modulator 2 is determined by a "phase hologram" representing the refractive index of each pixel electrode. Furthermore, the voltage applied to each pixel electrode of the reflective spatial modulator 2 can be determined based on the phase hologram.

[0031] In this embodiment, the reflective spatial modulator 2 uses the above-mentioned phase hologram to phase-modulate the laser light L1 and generates a plurality of processing laser beams L2 arranged in a one-dimensional or two-dimensional sequence. One processing laser beam L2 forms one hole when irradiated onto the substrate SU. In other words, in the substrate processing apparatus 100 of this embodiment, multiple processing laser beams L2 can be irradiated onto the substrate SU simultaneously to form multiple holes in the substrate SU at the same time.

[0032] The imaging optical system 3 is positioned between the reflective spatial modulator 2 and the oscillating mirror 4 and is composed of a first lens 31 and a second lens 32. The first lens 31 is positioned on the optical path of the processing laser beam L2 at a distance equal to the focal length of the first lens 31 from the reflective surface 21 of the reflective spatial modulator 2. The second lens 32 is positioned on the optical path of the processing laser beam L2 at a distance equal to the focal length of the second lens 32 from the incident surface 41 of the oscillating mirror 4. Furthermore, the first lens 31 and the second lens 32 are positioned at a distance equal to the sum of the focal lengths of the first lens 31 and the second lens 32. The focal lengths of the first lens 31 and the second lens 32 can be, for example, 100 mm to 200 mm.

[0033] The imaging optical system 3, having two lenses (first lens 31, second lens 32) arranged as described above, constitutes a double-sided telecentric optical system in which the reflective surface 21 of the reflective spatial modulator 2 and the incident surface 41 of the oscillating mirror 4 form an image. As a result, the imaging optical system 3 can suppress the increase in aberrations caused by changes in the wavefront shape of the processing laser light L2 emitted from the reflective spatial modulator 2 due to spatial propagation.

[0034] The first lens 31 and the second lens 32 used in the imaging optical system 3 are a lens set formed by combining two plano-convex lenses with their convex surfaces facing each other. Alternatively, a doublet lens or an aspherical lens may be used instead of the plano-convex lens set. A doublet lens is formed by bonding a convex lens and a concave lens with different refractive indices. By using a plano-convex lens set, a doublet lens, or an aspherical lens as the first lens 31 and the second lens 32, the aberration of the processing laser light L2 generated by the imaging optical system 3 can be reduced.

[0035] The type and shape of the imaging optical system 3 are selected so as to suppress aberrations within a range that allows the focusing position of the processing laser beam L2 to be corrected to the desired position by the reflective spatial modulator 2 described later. Specifically, when a set of plano-convex lenses is used in the imaging optical system 3, it is desirable that the field curvature aberration, which affects the height of the focusing position that can be corrected by the reflective spatial modulator 2, be 20 μm or less. For example, the field curvature aberration of the imaging optical system 3, which is a set of plano-convex lenses, is 15 μm. Furthermore, it is desirable that the astigmatism, which is difficult to correct by the reflective spatial modulator 2, be 5 μm or less. On the other hand, when a tablet lens or an aspherical lens is used in the imaging optical system 3, it is desirable that the field curvature aberration of this imaging optical system 3 be 60 μm or less.

[0036] The oscillating mirror 4 is a mirror that reflects the processing laser light L2 that has passed through the imaging optical system 3 toward the focusing lens 5. The oscillating mirror 4 is rotatable around an axis A1 perpendicular to the propagation direction of the processing laser light L2, and the angle of the incident surface 41 of the oscillating mirror 4 with respect to the propagation direction of the processing laser light L2 can be changed. As a result, the oscillating mirror 4 can change the reflection angle of the processing laser light L2 at the incident surface 41, and irradiate a predetermined area of ​​the substrate SU placed on the moving mechanism 6 with the processing laser light L2.

[0037] The focusing lens 5 is positioned between the oscillating mirror 4 and the substrate SU, and focuses each of the multiple processing laser beams L2 reflected by the oscillating mirror 4 onto the substrate SU. The pupil position of the focusing lens 5 is aligned with the incident surface 41 of the oscillating mirror 4. As a result, the multiple processing laser beams L2 emitted from the focusing lens 5 become telecentric and incident perpendicular to the plane of the substrate SU. Each processing laser beam L2 focused onto the substrate SU forms a hole in the substrate SU. The distance between the focusing lens 5 and the substrate SU can be changed by a moving mechanism (not shown). The focusing lens 5 is, for example, an fsinθ lens with a focal length of 50 mm to 150 mm.

[0038] In the substrate processing apparatus 100, the imaging optical system 3 and the focusing lens 5 are selected such that the field curvature aberration generated with respect to the processing laser light L2 focused by the focusing lens 5 is 20 μm or less. As a result, the change in the irradiation state of the processing laser light L2 depending on the position of the substrate SU is reduced, so that multiple holes can be formed uniformly over a wide area of ​​the substrate SU.

[0039] The moving mechanism 6 moves the substrate SU in relation to multiple processing laser beams L2 focused by the focusing lens 5. Specifically, the moving mechanism 6 includes a stage 61 on which the substrate SU is placed, and a stage moving unit 62 that moves the stage 61 three-dimensionally (in the up, down, left, right, and normal directions of the paper in Figure 1). By moving the substrate SU one-dimensionally in relation to the multiple processing laser beams L2 (in the left, right, or normal directions of the paper in Figure 1) using the moving mechanism 6, a group of holes arranged in a one-dimensional sequence can be formed on the substrate SU. Furthermore, by moving the substrate SU two-dimensionally in relation to the multiple processing laser beams L2 (in the left, right, and normal directions of the paper in Figure 1), a group of holes arranged in a two-dimensional sequence can be formed on the substrate SU.

[0040] The control unit 7 is a computer system composed of a CPU, a memory device (e.g., RAM, ROM, etc.), and various interfaces, and controls each component of the substrate processing apparatus 100. The control unit 7 may be realized by a computer system in which the above configuration is made up of individual components, or by an SoC that integrates the above configuration onto a single chip. The control unit 7 implements the control of the substrate processing apparatus 100 described below using a program that can be executed by the computer system that constitutes the control unit 7. Alternatively, some of the control described below may be implemented in software, and the remaining control may be implemented in hardware.

[0041] Specifically, the control unit 7 controls the laser light source 1 to emit laser light L1 from the laser light source 1. The control unit 7 determines the voltage to be applied to each pixel electrode of the reflective spatial modulator 2 based on the phase hologram and controls the reflective spatial modulator 2 by outputting the said voltage to each pixel electrode. The control unit 7 rotates the oscillating mirror 4 to change the reflection angle of the processing laser light L2 at the incident surface 41. The control unit 7 moves the substrate SU placed on the stage 61 by controlling the stage moving unit 62 of the moving mechanism 6 to move the stage 61.

[0042] (2) Hole formation operation by substrate processing equipment The following describes the hole formation operation in a substrate SU using the substrate processing apparatus 100 having the above configuration. In the following description, we will use as an example the operation of forming a total of 32 tapered through holes H on the substrate SU, with 2 holes vertically and 16 holes horizontally, as shown in Figures 2 and 3, where the hole diameter decreases from the front to the back surface. The substrate processing apparatus 100 modulates the laser beam L1 with a reflective spatial modulator 2 to form a total of 16 focal points P of processing laser beam L2 on the substrate SU, with 2 holes vertically and 8 holes horizontally, as shown in Figure 4. In other words, the substrate processing apparatus 100 can simultaneously form a total of 16 through holes H, with 2 holes vertically and 8 holes horizontally. Figure 2 is a diagram showing an example of hole formation as seen from the substrate surface, and Figure 3 is a diagram showing the cross-sectional shape of each hole. Figure 4 is a diagram showing an example of the arrangement of processing laser beams.

[0043] Therefore, when forming through holes H arranged as shown in Figure 2, the substrate processing apparatus 100 moves the substrate SU upward while rotating the focal point P of the processing laser beam L2, arranged as shown in Figure 4, along the outer shape of the through hole H to be formed, by changing the angle of the incident surface 41 of the oscillating mirror 4, as shown in Figure 5. At this time, as shown in Figure 5, as the substrate SU is moved upward (i.e., as the depth of the through hole H increases), the shape of the rotation of the focal point P is reduced to form a tapered hole. After forming 16 through holes H with the processing laser beam L2 arranged as shown in Figure 4, the substrate SU is moved laterally relative to the processing laser beam L2, and through holes H arranged as shown in Figure 4 are formed again at a position adjacent to the specific position, thereby forming 32 through holes H arranged as shown in Figure 2.

[0044] The hole-forming operation will now be described in detail. First, the control unit 7 generates a phase hologram model for generating the processing laser beam L2. Specifically, a phase hologram model is generated that allows for the simultaneous irradiation of the processing laser beam L2, arranged as shown in Figure 4, onto the substrate SU. This phase hologram model is generated assuming that no aberrations occur in the processing laser beam L2 focused by the focusing lens 5. Hereafter, this phase hologram model will be referred to as the "reference phase hologram".

[0045] Next, the control unit 7 corrects the reference phase hologram so that the irradiation state of the processing laser light L2 does not change depending on the position of the substrate SU due to optical factors of the substrate processing apparatus 100. Specifically, the following corrections are made to the reference phase hologram. Note that all or some of the corrections described below may be applied to the reference phase hologram, or only one of the corrections may be applied.

[0046] Firstly, the reference phase hologram is corrected to reduce the field curvature aberration generated in the processing laser beam L2 by the imaging optical system 3 and the focusing lens 5. The focal points P (P1~P8) of the processing laser beam L2 affected by field curvature aberration are positioned away from the substrate SU, as shown in Figure 6. Specifically, the focal points P are shifted upward (hereinafter referred to as the Z direction) from the surface of the substrate SU. This shift increases as it moves further away from the irradiation centers of the multiple processing laser beams L2. For example, focal points P1~P3 and P6~P8, which are located far from the irradiation centers of the multiple processing laser beams L2, are positioned above the surface of the substrate SU. As a result, if no correction is applied to the reference phase hologram, the irradiation position of the processing laser beam L2 differs depending on the position of the substrate SU, and therefore multiple through holes H with different shapes and / or dimensions are formed depending on the position of the substrate SU. Figure 6 is a schematic diagram that emphasizes the effect of the aberration on the irradiation state of the processing laser beam affected by field curvature aberration.

[0047] Therefore, if the focal point P shifts from the target position (i.e., the surface of the substrate SU) due to image field curvature aberration, the reference phase hologram is corrected to generate a processing laser beam L2 in which the position of the focal point P is shifted in the direction of the target position by the distance the focal point P has shifted from the target position.

[0048] For example, when a reference phase hologram is set so that a focal point is formed on the surface of the substrate SU without considering the effect of field curvature, if, as shown in Figure 7, some of the focal points P1 to P8 formed by irradiation with the processing laser light L2 are actually positioned above the substrate SU due to field curvature, then, as shown in Figure 7, the reference phase hologram is corrected so that the set focal points Q1 to Q8 of the processing laser light L2 are positioned below the target irradiation position (surface of the substrate SU). As a result, the focal points R1 to R8 of the processing laser light L2 are located on the surface of the substrate SU. Figure 7 shows an example of the arrangement of the focal points (P1 to P8) before correcting for field curvature, the set focal points (Q1 to Q8) after correcting the reference phase hologram to correct for field curvature, and the focal points (R1 to R8) of the processing laser light after correction.

[0049] By correcting the reference phase hologram settings to generate a focal point for the processing laser beam L2 that is offset from the target irradiation position, the effect of image field curvature aberration on the processing laser beam L2 can be reduced. As a result, all focal points P of multiple processing laser beams L2 can be positioned at the target irradiation position (the surface of the substrate SU). In other words, on the surface of the substrate SU, the focal points P of the processing laser beam L2 can be made the same depending on the position of the substrate SU, and multiple through-holes H with a uniform processing shape can be formed over a wide area of ​​the substrate SU.

[0050] Secondly, the reference phase hologram is corrected so that the intensity of the multiple processing laser beams L2 focused by the focusing lens 5 becomes uniform. Specifically, for example, as shown in Figure 8(a), the focusing point P (focusing point P3 in Figure 8(a)) of a processing laser beam L2 whose intensity is greater than that of the other processing laser beams L2 is corrected so that the intensity of the processing laser beam in the reference phase hologram settings becomes weaker than that of the other processing laser beams, as shown in Figure 8(b). The amount by which the intensity of the laser beam is reduced is changed according to the intensity of the corresponding processing laser beam L2. Specifically, the greater the difference in intensity between a processing laser beam L2 and the other processing laser beams L2, the greater the amount by which the laser beam intensity is reduced. As a result, as shown in Figure 8(c), the intensity of all focusing points P of the processing laser beam L2 becomes uniform. Figure 8 shows the optical intensity in the reference phase hologram settings for the focusing point and the corrected optical intensity to make the intensity of the processing laser beam uniform.

[0051] Alternatively, the reference phase hologram may be corrected to increase the intensity of a processing laser beam L2 among multiple processing laser beams L2 whose intensity is lower than that of the other processing laser beams L2.

[0052] As described above, by correcting the reference phase hologram so that the intensity of the multiple processing laser beams L2 focused by the focusing lens 5 becomes uniform, the intensity of the processing laser beams L2 becomes uniform over a wide area of ​​the substrate SU, so that multiple through holes H can be uniformly formed over a wide area of ​​the substrate SU.

[0053] Thirdly, the reference phase hologram is corrected so that the actual processing pitch of the plurality of through-holes H becomes the desired processing pitch. For example, when a plurality of processing laser beams L2 are simultaneously irradiated onto the substrate SU, as shown in FIG. 9, consider the case where the processing pitch of the through-holes H increases at the side portions of the region irradiated with the processing laser beam L2 (d1 < d2, d1: pitch of the inner through-hole H, d2: pitch of the outer through-hole H). Note that the desired pitch of the through-hole H is d1. FIG. 9 is a schematic diagram highlighting an example of a state where the processing pitch of the through-holes is shifted.

[0054] In this case, as shown in FIG. 10, the reference phase hologram is corrected so that the irradiation pitch D2 of the processing laser beam L2 at the side portions becomes smaller than the irradiation pitch D1 of the processing laser beam L2 inside (that is, D2 < D1). Note that the irradiation pitch D1 of the processing laser beam L2 is the irradiation pitch determined by the reference phase hologram. FIG. 10 is a diagram showing an example of the arrangement of the setting focus points for correcting the shift of the processing pitch.

[0055] Thus, for example, when the processing pitch of the through-hole H becomes larger than the desired processing pitch, by correcting the phase hologram so as to decrease the irradiation pitch of the processing laser beam L2 irradiated to the location where the processing pitch of the through-hole H has increased, when the processing laser beam L2 is actually irradiated onto the substrate SU, the irradiation pitch of the processing laser beam L2 at the above location becomes the same as the desired processing pitch of the through-hole H. As a result, it is possible to suppress the change in the irradiation pitch of the plurality of processing laser beams L2 depending on the position of the substrate SU, so that a plurality of through-holes H with a uniform processing pitch can be formed over a wide range of the substrate SU.

[0056] Fourth, the reference phase hologram is corrected so that the focusing positions of the multiple processing laser beams L2 by the focusing lens 5 are different from the focusing position of the zero-order light. Here, the zero-order light refers to laser light that is not phase-modulated by the reflective spatial modulator 2. Such zero-order light has a greater intensity than the processing laser beam L2 generated by phase modulation. As a result, if the substrate SU is processed with the zero-order light, the desired processing will not be achieved. Therefore, the reference phase hologram is corrected so that the zero-order light is not used to process the substrate SU. Specifically, as shown in Figure 11, the reference phase hologram is corrected so that the focusing point of the zero-order light is located away from the substrate SU, while the focusing point P of the processing laser beam L2 is located at the target irradiation position on the substrate SU. Figure 11 shows an example of the positional relationship between the focusing points of the zero-order light and the processing laser beam L2.

[0057] In this way, by correcting the reference phase hologram so that the height position of the focusing point of the processing laser beam L2 is shifted from the focal position of the zero-order light, the zero-order light, which has a higher intensity than the processing laser beam L2, is not used to form the through-holes H, and therefore multiple through-holes H can be uniformly formed over a wide area of ​​the substrate SU.

[0058] After the reference phase hologram is corrected as described above, the control unit 7 determines the voltage to be applied to each pixel electrode of the reflective spatial modulator 2 based on the corrected reference phase hologram, and outputs the determined voltage to the corresponding pixel electrode. As a result, the reflective spatial modulator 2 can form a refractive index distribution (phase hologram) on the reflective surface 21 that corresponds to the corrected reference phase hologram.

[0059] After forming a phase hologram on the reflective surface 21, the control unit 7 emits laser light L1 from the laser light source 1. As a result, the laser light L1 is incident on the reflective surface 21 of the reflective spatial modulator 2. The laser light L1 incident on the reflective surface 21 is phase-modulated to generate processing laser light L2. The processing laser light L2 generated in the reflective spatial modulator 2 is focused by the focusing lens 5 and irradiated onto the substrate SU.

[0060] After simultaneously forming multiple through-holes H by irradiating multiple processing laser beams L2 at specific locations on the substrate SU, the control unit 7 moves the substrate SU laterally using the moving mechanism 6 and irradiates multiple processing laser beams L2 at positions different from the previous ones. For example, by irradiating a specific area of ​​the substrate SU with processing laser beams L2 arranged as shown in Figure 4, and then irradiating an area of ​​the substrate SU laterally adjacent to that specific location with processing laser beams L2 arranged as shown in Figure 4, a group of 32 through-holes H arranged laterally, as shown in Figure 2, can be formed.

[0061] Alternatively, instead of moving the substrate SU laterally using the movement mechanism 6, the processing area may be moved by changing the angle of the incident surface 42 of the oscillating mirror 4. When the processing laser beam L2 is irradiated to a different position on the substrate SU by changing the reflection angle of the incident surface 41 of the processing laser beam L2, the incident position of the processing laser beam L2 to the focusing lens 5 will be different from the previous incident position. In this case, the aberrations etc. generated in the processing laser beam L2 this time may be different from those of the previous irradiation. In such cases, the correction of the reference phase hologram described above can be further applied to irradiate the substrate SU with the processing laser beam L2 under the same irradiation conditions as the previous time.

[0062] Furthermore, when the substrate SU is moved by the moving mechanism 6 and the processing laser light L2 is irradiated to different positions on the substrate SU, the direction of the through-holes H formed in the substrate SU may be misaligned due to a mismatch between the direction of movement by the moving mechanism 6 and the direction of the arrangement of the focusing point P shown in Figure 4. In this case, for example, as shown in Figure 12, the arrangement of the through-holes H formed in the previous time and the through-holes H formed in the current time may be misaligned with the arrangement of other through-holes H. Figure 12 is a diagram showing an example of a state in which the processing position differs at the boundary between the previously formed through-holes and the currently formed through-holes.

[0063] Therefore, if there is a discrepancy between the direction in which the substrate SU moves due to the movement mechanism 6 and the direction in which the processing laser beam L2 is positioned on the substrate SU, the reference phase hologram is corrected to compensate for this discrepancy. For example, as shown in Figure 12, if the position of the formed through-hole H is tilted with respect to the direction of movement by the movement mechanism 6, the reference phase hologram is corrected to tilt the direction of each focal point P of the processing laser beam L2 in the opposite direction to the positional discrepancy shown in Figure 12, as shown in Figure 13. Figure 13 shows an example of the arrangement of focal points in the setting after the reference phase hologram has been corrected to compensate for the discrepancy in the formation position of the through-hole caused by the movement of the movement mechanism.

[0064] Furthermore, if aberrations occur in the processed laser beam L2 due to the tilting of the direction of the arrangement of the focal point P, the above-described corrections to eliminate the aberrations may be applied to the phase hologram that has been corrected to tilt the direction of the arrangement of the focal point P.

[0065] (3) Features of the Embodiment The above embodiment can also be described as follows. A substrate processing apparatus (e.g., substrate processing apparatus 100) comprises a laser light source (e.g., laser light source 1), a reflective spatial modulator (e.g., reflective spatial modulator 2), a mirror (e.g., oscillating mirror 4), a focusing lens (e.g., focusing lens 5), an imaging optical system (e.g., imaging optical system 3), and a moving mechanism (e.g., moving mechanism 6). The laser light source emits laser light (e.g., laser light L1). The reflective spatial modulator modulates the laser light using a phase hologram to generate multiple processing laser beams (e.g., processing laser beams L2) for simultaneously forming multiple holes (e.g., through holes H) in a substrate (e.g., substrate SU). The mirror reflects the multiple processing laser beams generated by the reflective spatial modulator. The focusing lens focuses each of the multiple processing laser beams reflected by the mirror onto the substrate. The imaging optical system constitutes a bilateral telecentric optical system in which the reflective surface of a reflective spatial modulator (e.g., reflective surface 21) and the incident surface of a mirror (e.g., incident surface 41) are in an imaging relationship. The movement mechanism moves the substrate in relation to multiple processing laser beams.

[0066] In the above-described substrate processing apparatus, the reflective spatial modulator corrects the phase hologram to simultaneously form multiple holes of uniform shape and size at predetermined locations on the substrate by moving the substrate or changing the reflection angle of the mirror and irradiating multiple processing laser beams at those predetermined locations.

[0067] The inventors of the present invention have found that the inability to form holes with a uniform processing shape over a wide area of ​​the substrate is due to aberrations in the imaging optical system and focusing lens of the above-mentioned substrate processing apparatus. Specifically, it is believed that the difference in the height of the focal points of multiple processing laser beams depending on the position on the substrate due to the influence of optical aberrations in the imaging optical system and focusing lens is the reason why holes with a uniform processing shape over a wide area of ​​the substrate cannot be formed.

[0068] Therefore, in the above-described substrate processing apparatus, a correction is applied to the phase hologram that generates the processing laser light to produce processing laser light that can form multiple holes with a uniform processing shape at any position on the substrate. In other words, the shift in the focal points of the multiple processing laser beams caused by optical aberrations due to the imaging optical system and focusing lens is eliminated by correcting the phase hologram. As a result, the focal point of the processing laser light becomes the same over a wide area of ​​the substrate, so that multiple holes with a uniform processing shape can be formed over a wide area of ​​the substrate.

[0069] 2. Other Embodiments Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the invention. (A) The through-holes H that can be formed in the substrate SU by the substrate processing apparatus 100 are not limited to the tapered shape described above, but can be any shape depending on the application of the substrate SU, such as stepped holes where the hole diameter decreases in stages, or holes with an elliptical or square cross-section.

[0070] (B) The substrate processing apparatus 100 can form not only through holes H that penetrate the substrate SU, but also holes that do not penetrate the substrate SU (for example, grooves).

[0071] (C) The substrate processing apparatus 100 can also form holes H' evenly spaced vertically and horizontally on the substrate SU, as shown in Figure 14, by moving the substrate SU in two dimensions using the moving mechanism 6. Figure 14 shows another example of holes that can be formed on the substrate.

[0072] (D) The substrate processing apparatus 100 can also form processing marks of any shape, such as linear grooves, on the substrate SU by appropriately forming a phase hologram with the reflective spatial modulator 2, for example. [Industrial applicability]

[0073] This invention can be widely applied to devices that form multiple processing marks on a substrate using laser light. [Explanation of symbols]

[0074] 100 Substrate processing equipment 1. Laser light source 2. Reflective spatial modulator 21 Reflective surface 3. Imaging optical system 31. First lens 32. Second lens 4. Oscillating mirror 41 Entrance plane 5. Focusing lens 6 Moving mechanism 61 stages 62 Stage Movement Section 7 Control Unit 11 First Mirror 13. Second Mirror L1 laser light L2 processing laser light P Focus point SU board H through hole H' hole

Claims

1. A substrate processing apparatus for forming a plurality of processing marks having predetermined dimensions in the thickness direction of the substrate, A laser light source that emits laser light, A reflective spatial modulator that modulates the laser light using a phase hologram to generate multiple processing laser beams for simultaneously forming the multiple processing marks arranged one-dimensionally or two-dimensionally on the substrate, A mirror that reflects the multiple processing laser beams generated by the reflective spatial modulator, A focusing lens that focuses each of the plurality of processing laser beams reflected by the mirror onto the substrate, An imaging optical system constituting a double-sided telecentric optical system in which the reflective surface of the reflective spatial modulator and the incident surface of the mirror are in an image-forming relationship, A moving mechanism for moving the substrate with respect to the plurality of processing laser beams, A control unit generates a reference phase hologram capable of simultaneously irradiating the substrate with the plurality of processing laser beams, assuming that no aberration occurs with respect to the plurality of processing laser beams focused by the focusing lens, corrects the reference phase hologram, and changes the reflection angle of the mirror to irradiate the plurality of processing laser beams at predetermined positions on the substrate, thereby generating a phase hologram that simultaneously forms a plurality of processing marks of uniform shape and size at the predetermined positions; A circuit board processing apparatus equipped with the following features.

2. The substrate processing apparatus according to claim 1, characterized in that the aberration generated in the plurality of processing laser beams focused by the imaging optical system and the focusing lens is 20 μm or less, and the astigmatism difference is 5 μm.

3. The substrate processing apparatus according to claim 1 or 2, wherein the imaging optical system is composed of a lens assembly formed by combining the convex surfaces of two plano-convex lenses facing each other, a doublet lens, or an aspherical lens.

4. The substrate processing apparatus according to any one of claims 1 to 3, wherein the focusing lens is an fsinθ lens.

5. The substrate processing apparatus according to any one of claims 1 to 4, wherein the control unit corrects the reference phase hologram to reduce the field curvature aberration that occurs with respect to the plurality of processing laser beams focused by the focusing lens.

6. The substrate processing apparatus according to any one of claims 1 to 5, wherein the control unit corrects the reference phase hologram so that the intensity of the plurality of processing laser beams focused by the focusing lens becomes uniform.

7. The substrate processing apparatus according to any one of claims 1 to 6, wherein the control unit corrects the reference phase hologram so that the actual processing pitch of the plurality of processing marks becomes a desired processing pitch.

8. The substrate processing apparatus according to any one of claims 1 to 7, wherein the control unit corrects the reference phase hologram so that the focusing position of the plurality of processing laser beams by the focusing lens is different from the focusing position of the zeroth-order beam.

9. The substrate processing apparatus according to any one of claims 1 to 8, wherein the moving mechanism moves the substrate in one or two dimensions to form a continuous group of processing marks on the substrate.

10. The substrate processing apparatus according to claim 9, wherein when the substrate is moved by the moving mechanism to form the group of processing marks, if a discrepancy occurs between the position of the substrate after movement by the moving mechanism and the positions on the substrate to be irradiated with the plurality of processing laser beams, the control unit corrects the reference phase hologram to correct the discrepancy.

11. A substrate processing method for forming multiple processing marks on a substrate, The process involves emitting laser light from a laser light source and directing it into a reflective spatial modulator, The laser light is modulated using a phase hologram of a reflective spatial modulator to generate multiple processing laser beams for simultaneously forming the multiple processing marks arranged one-dimensionally or two-dimensionally on the substrate, The plurality of processing laser beams generated by the reflective spatial modulator are imaged using a double-sided telecentric optical system, The imaged plurality of processing laser beams are reflected by a mirror, The process involves focusing each of the multiple processing laser beams reflected by the mirror onto the substrate, A reference phase hologram capable of simultaneously irradiating the substrate with the plurality of processing laser beams is generated assuming that no aberration occurs with respect to the plurality of processing laser beams focused by the focusing lens, The process involves correcting the reference phase hologram, changing the reflection angle of the mirror, and irradiating the substrate with the multiple processing laser beams at predetermined locations to generate a phase hologram that simultaneously forms multiple processing marks of uniform shape and size at those predetermined locations. A substrate processing method comprising the following:

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