Laser machining method, substrate manufacturing method, and laser machining device

Abstract

A laser machining method according to the present invention is for forming a recess and / or a through-hole in a workpiece using a laser beam, and involves: irradiating the workpiece with a laser beam having an optical axis inclined with respect to a normal line of a workpiece surface of the workpiece; and performing laser machining while rotating the optical axis of the laser beam using the normal line of the workpiece surface as a rotation axis, to form a recess and / or a through-hole in the workpiece. Thus, even when a recess and / or a through-hole is formed at a high resolution, it is possible to prevent the formed recess and / or through-hole from having a tapered shape, and accordingly it becomes possible to form a complex and extremally-fine pattern.

Description

Laser processing method, substrate manufacturing method, and laser processing device

[0001] The present invention relates to a laser processing method, a substrate manufacturing method, and a laser processing apparatus.

[0002] Semiconductor package substrates have been actively developed in line with the trend of "More Than Moore" to SoC (System on a Chip), which integrates a system into a single chip.

[0003] Furthermore, the configuration of semiconductor package substrates is becoming more complex and denser, and devices using excimer lasers are being used to manufacture the base substrates.

[0004] For example, Patent Document 1 describes a laser processing method for performing shape processing on a workpiece to a predetermined depth position using laser light, characterized in that the laser power of the laser light and the relative movement speed between the workpiece and the laser light are increased so that the energy per unit length of the laser light, which is optimally set according to the workpiece, falls within an energy range that does not allow the laser light to penetrate the workpiece even when the laser power increases due to power fluctuations in a laser light oscillator, and the number of irradiations required for laser processing is reduced.

[0005] Patent Document 2 also describes a laser processing method for processing an excavation area of ​​a workpiece by sequentially irradiating the excavation area with laser light having a small beam cross-section relative to the excavation area, the method comprising: a first processing step in which the entire excavation area is sequentially irradiated with laser light having a beam cross-section of a first shape and forming a first irradiation area on the workpiece corresponding to the beam cross-section of the first shape; and a second processing step in which the excavation area is sequentially irradiated with laser light having a beam cross-section of a second shape smaller than the first shape and forming a second irradiation area on the workpiece corresponding to the beam cross-section of the second shape. In the first processing step, the laser light forming the first irradiation area is sequentially irradiated so as to form an overlapping area in which parts of the first irradiation area overlap each other, and in the second processing step, the laser light forming the second irradiation area is sequentially irradiated so that the second irradiation area is included in an area of ​​the excavation area other than the overlapping area.

[0006] Also, Non-Patent Document 1 introduces the formation of high-quality, high-aspect Si through-holes using a Bessel beam.

[0007] Patent Document 1: JP 2009-22978 A International Publication No. WO2013 / 094025

[0008] Koji Sugioka, "High-quality, high-aspect-ratio silicon through-hole formation using optimized ultrashort pulse Bessel beams," FORM TECH REVIEW 2016, VOL. 26

[0009] Conventionally, recesses formed by laser processing have had the problem that the higher the resolution, the smaller the width of the bottom of the recess is compared to the width of the opening of the recess on the initial processing surface, i.e., the tapered tip. Also, conventionally, the higher the resolution, the smaller the width of the opening at the bottom of the through hole is compared to the width at the top of the through hole, i.e., the tapered tip. Furthermore, the formation of such tapered recesses and / or through holes is inconvenient for forming high-definition, complex patterns (e.g., circuit patterns).

[0010] In particular, when used as a substrate for semiconductor packages, metal wiring may be embedded in the processed recesses, and high-resolution patterns can result in high wiring resistance, so to prevent this, processing that is deep and wide all the way to the bottom is required. By performing such processing, it is possible to produce high-quality substrates for semiconductor packages with low wiring resistance.

[0011] The present invention has been made to solve the above problems, and aims to provide a laser processing method that can prevent the recesses and / or through holes from becoming tapered even when forming recesses and / or through holes at high resolution, and thus can form high-definition, complex patterns; a substrate manufacturing method that can manufacture substrates having high-definition, complex patterns; and a laser processing apparatus that can prevent the recesses and / or through holes from becoming tapered even when forming recesses and / or through holes at high resolution, and can provide a high-quality semiconductor package substrate with low wiring resistance, and thus can form high-definition, complex patterns.

[0012] In order to solve the above problems, the present invention provides, as a first aspect of a laser processing method, a laser processing method for forming recesses and / or through holes in a workpiece using a laser, which includes irradiating the workpiece with a laser having an optical axis tilted with respect to a normal to the workpiece surface, and performing laser processing while rotating the optical axis of the laser around the normal to the workpiece surface as a rotation axis, thereby forming recesses and / or through holes in the workpiece.

[0013] With this laser processing method, even when recesses are formed with high resolution, the width of the bottom of the recess can be prevented from being smaller than the width of the opening of the recess on the surface of the workpiece. Furthermore, with this laser processing method, even when through holes are formed with high resolution, the width of the opening at the bottom of the through hole can be prevented from being smaller than the width at the top of the through hole. In other words, with the laser processing method of the present invention, even when recesses and / or through holes are formed with high resolution, the recesses and / or through holes formed can be prevented from having a tapered shape, and thus high-resolution, complex patterns can be formed.

[0014] It is preferable that the inclination angle of the optical axis with respect to the normal to the surface of the workpiece is 3° or more and 15° or less.

[0015] By performing processing while irradiating the workpiece with laser light at such an inclination angle, it is possible to more reliably prevent the recesses and / or through holes to be formed from having a tapered shape.

[0016] For example, laser processing can be performed while rotating the optical axis of the laser at a frequency of 10 Hz to 300 Hz.

[0017] The rotation frequency is not particularly limited, but can be, for example, 10 Hz or more and 300 Hz or less.

[0018] The present invention also provides, as a second aspect of the laser processing method, a laser processing method for forming recesses and / or through holes in a workpiece using a laser, in which laser processing is performed by irradiating a wobble laser using a wobble device to form recesses and / or through holes in the workpiece.

[0019] With this laser processing method, even when recesses are formed with high resolution, the width of the bottom of the recess can be prevented from being smaller than the width of the opening of the recess on the surface of the workpiece. Furthermore, with this laser processing method, even when through holes are formed with high resolution, the width of the opening at the bottom of the through hole can be prevented from being smaller than the width at the top of the through hole. In other words, with the laser processing method of the present invention, even when recesses and / or through holes are formed with high resolution, the recesses and / or through holes formed can be prevented from having a tapered shape, and thus high-resolution, complex patterns can be formed.

[0020] In both the first and second aspects, for example, the workpiece may be a substrate for a semiconductor package, and recesses and / or through holes may be formed in the substrate for a semiconductor package.

[0021] As described above, in both the first and second embodiments, recesses and / or through holes can be formed in the semiconductor package substrate. In particular, when processing semiconductor package substrates, there are processing patterns that include a mixture of through holes and recesses, such as via processing and groove processing. In this case, the method of the present invention allows processing in the same process without separating the via processing and groove processing steps. Furthermore, as semiconductor package substrates become increasingly dense, the conventional laser drilling method for via processing increases the number of holes drilled as a result of higher density, which increases processing time. However, this method does not increase processing time due to the increased number of holes drilled or the increased pattern resolution.

[0022] For example, the laser may be generated by using an excimer laser oscillator.

[0023] The laser oscillation means is not particularly limited, but for example, an excimer laser oscillator can be used.

[0024] The laser can be irradiated onto the workpiece through a photomask.

[0025] The laser processing of the present invention can also be carried out using a photomask.

[0026] The processing may be performed while the laser is scanned relatively to the workpiece.

[0027] The laser processing of the present invention can also be scanning processing.

[0028] For example, ablation processing can be performed.

[0029] According to the laser processing method of the present invention, for example, ablation processing can be performed.

[0030] For example, the recesses and / or through holes can be formed to have a width of 20 μm or less.

[0031] According to the laser processing method of the present invention, it is possible to form a highly precise pattern including recesses and / or through holes having a width of, for example, 20 μm or less.

[0032] For example, the recess and / or through hole may have a ratio of the height of the processed portion to the width of the bottom of the recess or the width of the lower opening of the through hole of 1.0 or more.

[0033] According to the laser processing method of the present invention, recesses and / or through holes with such a high aspect ratio can be formed.

[0034] For example, the recess can be formed such that the width of the bottom of the recess is 70% or more of the opening width of the recess on the initial work surface of the workpiece, and / or the through hole can be formed such that the width of the lower opening of the through hole is 70% or more of the width of the upper opening of the through hole on the initial work surface.

[0035] According to the laser processing method of the present invention, for example, a recess can be formed in which the width of the bottom of the recess is 70% or more of the opening width of the recess on the initial processing surface of the workpiece, and / or a through hole in which the width of the lower opening of the through hole is 70% or more of the width of the upper opening of the through hole on the initial processing surface of the workpiece.

[0036] For example, a plurality of recesses may be formed, and the distance between the bottoms of adjacent recesses may be set to 110% or less of the width of the bottoms.

[0037] In this way, the laser processing method of the present invention allows for the formation of multiple recesses at a high density.Furthermore, since the contact area at the interface between the wiring and the substrate can be increased, problems such as peeling of the wiring are less likely to occur.

[0038] It is preferable that the processing be performed while the laser is being imaged on the surface of the workpiece.

[0039] By performing processing while focusing the laser in this way, the laser can be irradiated so that the rotational orbit of the laser becomes larger as the processing progresses and moves away from the imaged surface of the workpiece. Also, focusing the laser enables accurate positioning at the processing point.

[0040] It is preferable that the laser be irradiated onto the workpiece through a photomask, and that the laser be imaged on a film surface formed on the photomask.

[0041] By using a photomask and performing processing while focusing the laser in this way, the pattern transfer by the photomask can be made more reliable, and the desired processing can be performed with even greater precision.

[0042] The present invention also provides a method for manufacturing a substrate having the recesses and / or through holes, which includes forming the recesses and / or through holes in the substrate, which is the workpiece, by the laser processing method of the first or second aspect of the present invention.

[0043] With this substrate manufacturing method, even when recesses are formed with high resolution, the width of the bottom of the recess can be prevented from being smaller than the width of the opening of the recess on the surface of the workpiece. Furthermore, with this laser processing method, even when through holes are formed with high resolution, the width of the lower opening of the through hole can be prevented from being smaller than the width of the upper end of the through hole. In other words, with the substrate manufacturing method of the present invention, even when recesses and / or through holes are formed with high resolution, the recesses and / or through holes formed can be prevented from having a tapered shape, and thus substrates having high-resolution and complex patterns can be manufactured.

[0044] The present invention also provides, as a first aspect of the laser processing apparatus, a laser processing apparatus that uses a laser to form recesses and / or through holes in a workpiece, comprising: a laser light source that oscillates a laser; and a shaping optical system that is configured to irradiate the workpiece with the laser having an optical axis that is inclined with respect to a normal to the workpiece surface, and to rotate the optical axis of the laser around the normal to the workpiece surface as a rotation axis.

[0045] With such a laser processing device, even when processing a workpiece at high resolution, it is possible to prevent the pattern formed from having a tapered shape, and therefore it is possible to form a highly precise and complex pattern.

[0046] Furthermore, the present invention provides a second aspect of a laser processing apparatus that forms recesses and / or through holes in a workpiece using a laser, the laser processing apparatus comprising: a laser light source that oscillates a laser; and a wobble device configured to convert the laser into a wobble laser.

[0047] With such a laser processing device, even when processing a workpiece at high resolution, it is possible to prevent the pattern formed from having a tapered shape, and therefore it is possible to form a highly precise and complex pattern.

[0048] The laser processing apparatus of the second aspect further includes a shaping device that shapes the energy distribution of the laser emitted from the laser light source, and it is preferable that the wobbling device is arranged between the laser light source and the shaping device.

[0049] Such a laser processing device can form a desired pattern with higher precision.

[0050] The wobbling device may include, for example, a galvanometer scanner.

[0051] The wobble device may also include a rotation mechanism configured to rotate the prism.

[0052] The wobble device may, for example, include a galvanometer scanner, or may include a rotation mechanism configured to rotate the prism, or may include both.

[0053] In both the first and second aspects of the laser processing apparatus, the laser light source may be, for example, an excimer laser oscillator.

[0054] The laser light source is not particularly limited, but may be, for example, an excimer laser oscillator.

[0055] In both the first and second aspects, it is preferable to further include an optical system configured to focus the laser on the surface of the workpiece.

[0056] If an optical system for focusing the laser is further provided, the laser beam can be processed with a non-rotating beam shape at the surface of the workpiece, while the laser beam rotates and expands as the processing proceeds from the surface of the workpiece. Furthermore, focusing the beam enables accurate positioning at the processing point.

[0057] It is also preferable that the apparatus further comprises a stage on which the workpiece is placed, and a photomask disposed between the shaping optical system and the stage.

[0058] If a photomask is further provided in this way, a desired pattern can be formed on the workpiece with high precision.

[0059] In this case, it is more preferable to further provide an optical system configured to focus the laser on the film surface formed on the photomask.

[0060] If such an optical system is further provided, the mask pattern can be transferred more reliably using a photomask, and a desired pattern can be formed on the workpiece with particularly high precision.

[0061] The apparatus may further include a controller configured to synchronously move the workpiece placed on the stage and the photomask.

[0062] The laser processing apparatus according to the first and second aspects of the present invention can further include such a controller.

[0063] As described above, with the laser processing method of the present invention, even when recesses and / or through holes are formed with high resolution, the recesses and / or through holes formed can be prevented from having a tapered shape, and thus high-resolution, complex patterns can be formed.

[0064] Furthermore, with the substrate manufacturing method of the present invention, even when recesses and / or through holes are formed with high resolution, the recesses and / or through holes formed can be prevented from having a tapered shape, and thus substrates having high-resolution and complex patterns can be manufactured.

[0065] Furthermore, with the laser processing device of the present invention, even when processing a workpiece at high resolution, it is possible to prevent the pattern formed from having a tapered shape, and therefore it is possible to form high-definition, complex patterns.

[0066] 7 is a schematic diagram showing an example of a laser processing apparatus of the present invention. FIG. 7 is a schematic diagram showing an example of rotation of a laser optical axis in the laser processing apparatus of the present invention. FIG. 7 is a schematic diagram showing an example of a galvanometer scanner that can be equipped in the laser processing apparatus of the present invention. FIG. 7 is a schematic diagram showing an example of a wobble device that can be equipped in the laser processing apparatus of the present invention. FIG. 7 is a schematic diagram showing an example of a change in the state of laser irradiation of a workpiece in the laser processing method of the present invention. FIG. 7 is a schematic diagram showing an example of a change in the beam profile of a laser in the laser processing apparatus of the present invention. FIG. 7 is a schematic diagram showing an example of a change in the beam profile of a laser in the laser processing method of the present invention. FIG. 7 is a schematic diagram showing a part of the beam profile change shown in FIG. 7 in more detail. FIG. 7 is a schematic partial cross-sectional view of a substrate having an example of a recess pattern that can be formed using the laser processing method of the present invention. FIG. 7 is a schematic perspective view of a substrate having another example of a recess pattern that can be formed using the laser processing method of the present invention. FIG. 7 is a schematic partial cross-sectional view of a substrate having an example of a through-hole pattern that can be formed using the laser processing method of the present invention.

[0067] As described above, there has been a demand for the development of a laser processing method that can prevent the recesses and / or through holes from becoming tapered even when forming recesses and / or through holes at high resolution, thereby enabling the formation of high-definition, complex patterns; a substrate manufacturing method that can manufacture substrates having high-definition, complex patterns; and a laser processing apparatus that can prevent the recesses and / or through holes from becoming tapered even when forming recesses and / or through holes at high resolution, and that can provide a high-quality semiconductor package substrate with low wiring resistance, thereby enabling the formation of high-definition, complex patterns.

[0068] As a result of extensive research into the above-mentioned problems, the inventors have discovered that by irradiating a workpiece with a laser having an optical axis tilted with respect to the normal to the workpiece surface, and performing laser processing while rotating the optical axis of the laser around the normal to the workpiece surface as the rotation axis, or by performing laser processing by irradiating a wobble laser using a wobble device, it is possible to prevent the recesses and / or through holes to be formed from having a tapered shape, and thereby to form high-resolution, complex patterns, and have completed the present invention.

[0069] That is, the present invention is a laser processing method for forming recesses and / or through holes in a workpiece using a laser, which includes irradiating the workpiece with a laser having an optical axis tilted with respect to a normal to the workpiece surface, and performing laser processing while rotating the optical axis of the laser around the normal to the workpiece surface as a rotation axis, thereby forming recesses and / or through holes in the workpiece.

[0070] The present invention also provides a laser processing method for forming recesses and / or through holes in a workpiece using a laser, the method comprising: performing laser processing by irradiating a wobble laser using a wobble device to form recesses and / or through holes in the workpiece.

[0071] The present invention also provides a method for manufacturing a substrate having the recesses and / or through holes, which includes forming the recesses and / or through holes in the substrate, which is the workpiece, by the laser processing method of the present invention.

[0072] The present invention also provides a laser processing device that uses a laser to form recesses and / or through holes in a workpiece, comprising: a laser light source that oscillates a laser; and a shaping optical system configured to irradiate the workpiece with the laser having an optical axis that is inclined with respect to a normal to the workpiece surface, and to rotate the optical axis of the laser around the normal to the workpiece surface as a rotation axis.

[0073] The present invention also provides a laser processing device that uses a laser to form recesses and / or through holes in a workpiece, the laser processing device comprising: a laser light source that oscillates a laser; and a wobble device configured to convert the laser into a wobble laser.

[0074] The present invention will be described in detail below with reference to the drawings, but the present invention is not limited thereto.

[0075] [Laser processing apparatus] Fig. 1 is a schematic diagram showing an example of a laser processing apparatus of the present invention. Note that the laser processing apparatus 100 shown in Fig. 1 is an example of the laser processing apparatus of the present invention, but the laser processing apparatus of the present invention is not limited to the apparatus shown in Fig. 1. Below, the laser processing apparatus shown in Fig. 1 will be described from the viewpoints of the first and second aspects.

[0076] <First Aspect> In terms of the first aspect, the laser processing apparatus 100 shown in FIG. 1 is a laser processing apparatus 100 that forms a recess and / or a through-hole in a workpiece 70 using a laser, and includes a laser light source 10 that oscillates a laser 1, and a shaping optical system 20.

[0077] The light source 10 that oscillates the laser 1 is, for example, a light source (laser oscillator) 10 that irradiates (emits) the pulsed laser 1. More specifically, the laser light source 10 shown in Fig. 1 includes an excimer laser oscillator.

[0078] As shown in Fig. 2, the shaping optical system 20 is configured to irradiate the workpiece 70 with a laser 5 having an optical axis 5c inclined with respect to a normal 71n to a workpiece surface 71 of the workpiece 70. Furthermore, as shown in Fig. 2, for example, the shaping optical system 20 is configured to rotate the optical axis 5c of the laser 5 around the normal 71n to the workpiece surface 71 as the rotation axis. In the example shown in Fig. 1, the shaping optical system 20 includes a wobbling device 21 and a shaping device 22. However, the shaping optical system 20 in the laser processing apparatus 100 according to the first aspect is not limited to one including a wobbling device 21 and a shaping device 22.

[0079] The wobbling device 21 is configured to convert the laser beam 1 incident thereon into a wobble laser beam 2. The wobbling device 21 will be described in detail later.

[0080] The shaping device 22 is configured to shape the energy distribution of the laser 1 emitted from the laser light source 10, more precisely, the wobble laser 2 obtained by converting the laser 1 in the wobbling device 21. The shaping of the energy distribution by the shaping device 22 will be described later in the description of the laser processing method.

[0081] 1 further includes a photomask 30, a folding mirror 40, and an imaging lens (objective lens) 50, arranged in this order from the shaping optical system 20 to the workpiece 70 in the optical path of the laser processing apparatus 100. The laser processing apparatus 100 of this example employs a configuration in which a wobble device is disposed immediately before the workpiece, which is significantly different from conventional welding apparatuses that utilize a wobble device.

[0082] The laser 3, whose energy distribution has been shaped by the shaping device 22, is incident on the photomask 30. The photomask 30 has a mask pattern corresponding to the pattern of recesses and / or through holes to be machined in the workpiece 70. Thus, a laser beam 4 reflecting the mask pattern is emitted from the photomask 30. The direction of the optical axis of this laser beam 4 is changed by a folding mirror 40, and the laser beam 4 is incident on an imaging lens 50. The imaging lens 50 is an optical system configured to image the laser beam 4 on the workpiece surface 71 of the workpiece 70 (at a focal point F2). The laser beam 5 from the imaging lens 50 is irradiated onto the workpiece 70.

[0083] The laser processing apparatus 100 further includes a stage 60 on which the workpiece 70 is placed, and a controller 80 electrically connected to the photomask 30 and the stage 60. In another aspect, the laser processing apparatus 100 further includes the stage 60 on which the workpiece 70 is placed, and a photomask 30 disposed between the shaping optical system 20 and the stage 60.

[0084] In addition, as shown in Figure 1, the laser processing apparatus 100 may further include an optical system 90 between the molding device 22 and the photomask 30, which is configured to image the laser 3 at the film surface (focus F1) formed on the photomask 30.

[0085] The optical system 90, the photomask 30, the folding mirror 40, the imaging lens 50, the stage 60, and the controller 80 are optional components for the laser processing apparatus 100 of the present invention.

[0086] 1 also includes a mask alignment camera 31 as an imaging means for reading characteristic portions of the photomask 30, and a workpiece alignment camera 61 as an imaging means for reading characteristic portions of the workpiece 70. The mask alignment camera 31 is configured to send position information of the characteristic portions of the photomask 30 to the controller 80. The workpiece alignment camera 61 is configured to send position information of the characteristic portions of the workpiece 70 to the controller 80. The controller 80 is configured to adjust the relative positions of the workpiece 70 and the photomask 30 based on this position information. In another aspect, the controller 80 is configured to synchronously move the workpiece 70 and the photomask 30 placed on the stage 60.

[0087] <Second Aspect> In terms of the second aspect, the laser processing apparatus shown in FIG. 1 is a laser processing apparatus 100 that forms a recess and / or a through-hole in a workpiece 70 using a laser, and includes a laser light source 10 that oscillates a laser 1, and a wobbling device 21 configured to convert the laser 1 into a wobble laser 2.

[0088] 1 further includes a shaping device 22 configured to shape the energy distribution of the laser 1 emitted from the laser light source 10, more precisely, the wobble laser 2 obtained by converting the laser 1 in a wobbling device 21. The wobbling device 21 is disposed between the laser light source 10 and the shaping device 22. In the laser processing device 100 of the second embodiment, the shaping device 22 is an optional component.

[0089] For configurations other than those described above, please refer to the description in the first aspect.

[0090] Here, the wobble device 21 will be described in more detail.

[0091] The wobble device 21 is a device that rotates and / or oscillates a laser (converts it into a wobble laser) and irradiates the object to be irradiated. Examples of the application of wobble devices in laser welding and the like are disclosed, for example, in Japanese Patent Application Laid-Open No. 2022-001374, Japanese Patent Application Laid-Open No. 2022-127158, and Japanese Patent Application Laid-Open No. 2023-004207, but these examples are premised on welding, and there are no examples of using a wobble device in laser processing to form fine recesses or through holes.

[0092] The wobble device 21 may be, for example, a galvanometer scanner 21A as shown in FIG. 3 and / or a prism 21B as shown in FIG. １ The rotating mechanism 21B may be configured to rotate the

[0093] The galvanometer scanner 21A includes, for example, a galvanometer mirror 21A as shown in FIG. １ and 21A ２ The galvanometer mirror 21A may include: １ and 21A ２ can move in two axial directions (the direction of the arrow and the direction perpendicular to the paper surface) in unison, and as a result, the optical path of laser 1 passing through them can tilt and rotate the optical axis of laser 2.

[0094] The rotation mechanism 21B includes a pair of prisms (wedge prisms) 21B as shown in FIG. １ and a controller 21B configured to control the rotation thereof. ２ Prism (wedge prism) 21B １ Each of these has a generally trapezoidal cross-sectional shape.

[0095] As shown schematically in FIG. 4, the laser 1 rotates around a pair of prisms (wedge prisms) 21B. １ When the laser 1 is incident on the laser beam 1, the laser 1 becomes a wobble laser 2 whose optical axis tilts and rotates.

[0096] The laser processing apparatus of the present invention described above can be used to carry out the laser processing method of the present invention, which will be described in detail below. As will be described in detail below, the laser processing method of the present invention can prevent the recesses and / or through holes from tapering even when recesses and / or through holes are formed with high resolution, thereby enabling the formation of highly precise and complex patterns. Therefore, by using the laser processing apparatus of the present invention, even when recesses and / or through holes are formed with high resolution, the recesses and / or through holes can be prevented from tapering even when recesses and / or through holes are formed with high resolution, thereby enabling the formation of highly precise and complex patterns.

[0097] [Laser Processing Method] The laser processing method of the present invention can be performed, for example, using the laser processing apparatus of the present invention described above. However, the laser processing method of the present invention can also be performed using an apparatus other than the laser processing apparatus of the present invention.

[0098] The laser processing method of the present invention will be described below from two perspectives, a first embodiment and a second embodiment, with reference again to FIGS. 1 to 4 and with new reference to FIGS.

[0099] <First Aspect> In a first aspect, the laser processing method of the present invention is a laser processing method for forming recesses and / or through-holes in a workpiece 70 using a laser 5, and as shown in FIG. 2 , this laser processing method involves irradiating the workpiece 70 with a laser 5 having an optical axis 5c inclined with respect to a normal 71n to a workpiece surface 71 of the workpiece 70, and performing laser processing while rotating the optical axis 5c of the laser 5 around the normal 71n to the workpiece surface 71 as a rotation axis, thereby forming recesses and / or through-holes in the workpiece 70.

[0100] By performing such processing, as shown in Fig. 5(b), even when the formation of the recesses and / or through holes proceeds, the laser 5 can exhibit a shape in which the beam expands and rotates as it proceeds in the depth direction of the workpiece 70. This allows processing to proceed on a processing surface 71c that is prevented from shrinking from the initial processing surface 71a shown in Fig. 5(a).

[0101] Therefore, for example, when forming a recess, even if the recess is formed at high resolution, the width of the bottom of the recess can be prevented from being smaller than the width of the opening of the recess on the surface of the workpiece. Or, when forming a through hole, even if the through hole is formed at high resolution, the width of the opening at the bottom of the through hole can be prevented from being smaller than the width at the top of the through hole. In other words, with the laser processing method of the first aspect of the present invention, even if the recess and / or through hole is formed at high resolution, the recess and / or through hole formed can be prevented from having a tapered shape, thereby enabling the formation of high-resolution, complex patterns. Furthermore, since a large contact area can be secured at the interface between the wiring and the substrate, defects such as peeling of the wiring are less likely to occur.

[0102] The inclination angle θ of the optical axis 5c with respect to the normal 71n of the workpiece surface 71 shown in FIG. 2 is preferably set to be 3° or more and 15° or less.

[0103] By performing processing while irradiating the workpiece 70 with the laser beam 5 at such an inclination angle θ, it is possible to more reliably prevent the recesses and / or through holes to be formed from having a tapered shape. １ The tilt angle θ can be controlled by controlling the mechanism 21B that rotates the imaging lens 50. It is preferable to control the tilt angle θ taking into consideration the numerical aperture NA of the imaging lens 50, for example.

[0104] For example, laser processing can be performed while rotating the optical axis of the laser at a frequency of 10 Hz to 300 Hz.

[0105] The frequency of rotation is preferably controlled, for example taking into account the pulse frequency of the laser.

[0106] <Second Aspect> In a second aspect, the laser processing method of the present invention is a laser processing method for forming recesses and / or through holes in a workpiece 70 using a laser 5, in which laser processing is performed by irradiating a wobble laser using a wobble device 21 to form recesses and / or through holes in the workpiece 70.

[0107] By performing such processing, for example, as shown in Fig. 5(b), even if the formation of the recesses and / or through holes proceeds, the laser 5 can exhibit a shape in which the beam expands and rotates as it proceeds in the depth direction of the workpiece 70. This allows processing to proceed on a processing surface 71c shown in Fig. 5(b), which prevents shrinkage from the initial processing surface 71a shown in Fig. 5(a).

[0108] Therefore, for example, when forming a recess, even if the recess is formed at high resolution, the width of the bottom of the recess can be prevented from being smaller than the width of the opening of the recess on the surface of the workpiece. Or, when forming a through hole, even if the through hole is formed at high resolution, the width of the opening at the bottom of the through hole can be prevented from being smaller than the width at the top of the through hole. In other words, with the laser processing method of the second aspect of the present invention, even if the recess and / or through hole is formed at high resolution, it is possible to prevent the recess and / or through hole from being tapered, and thus it is possible to form a high-resolution, complex pattern.

[0109] <Common Matters> The following describes common matters between the first and second aspects.

[0110] In the laser processing method of the present invention, for example, the workpiece 70 is a semiconductor package substrate, and recesses and / or through holes can be formed in the semiconductor package substrate.

[0111] The laser processing method of the present invention can form recesses and / or through holes in, for example, semiconductor package substrates. In particular, when processing semiconductor package substrates, there are processing patterns that combine through holes and recesses, such as via processing and groove processing. In this case, the laser processing method of the present invention can process the via processing and groove processing in the same process without separating them. Furthermore, as semiconductor package substrates become increasingly dense, the conventional laser drilling method for via processing increases the processing time due to the increased number of holes drilled as a result of higher density. However, this method does not increase the processing time due to the increased number of holes drilled or the increased pattern resolution.

[0112] For example, an excimer laser oscillator may be used to oscillate the laser 1. As described above, the oscillation means of the laser 1 is not particularly limited, but for example, an excimer laser oscillator can be used as the laser light source 10.

[0113] 1, the workpiece 70 can be irradiated with a laser. The photomask 30 has a mask pattern corresponding to the pattern of recesses and / or through holes to be formed in the workpiece 70. Therefore, by using the photomask 30, a desired pattern of recesses and / or through holes can be formed in the workpiece 70.

[0114] Processing may be performed while scanning the laser 5 relatively to the workpiece 70. For example, by using the stage 60 on which the workpiece 70 is placed and the controller 80 electrically connected to the photomask 30 and the stage 60, as described with reference to Fig. 1, processing can be performed while scanning the laser 5 relatively to the workpiece 70 (scan processing). However, in the laser processing of the present invention, scan processing may be performed by other means.

[0115] Furthermore, according to the laser processing method of the present invention, for example, ablation processing can be performed.

[0116] In the laser processing method of the present invention, it is preferable to perform processing while focusing the laser 5 on the workpiece surface 71 of the workpiece 70 .

[0117] In the example shown in FIG. 5, machining is performed while focusing the laser beam 5 on the workpiece surface 71 of the workpiece 70. The imaging in this example can be performed using the imaging lens 50 shown in FIGS. 1 and 2. According to this method, the center of rotation of the optical axis of the laser beam 5 is formed at the initial machining surface 71a shown in FIG. 5(a). Therefore, the laser beam 5a does not rotate at the initial machining surface 71a shown in FIG. 5(a), as shown in FIG. 5(c). On the other hand, as shown in FIG. 5(c), the laser beam 5b expands and rotates as it moves away from the initial machining surface 71a, which is the image point (focus). This allows machining to proceed at the machining surface 71c shown in FIG. 5(b), which prevents shrinkage from the initial machining surface 71a shown in FIG. 5(a).

[0118] Furthermore, accurate positioning can be achieved by forming an image on the initial work surface 71a.

[0119] It is also preferable to use a shaping device 22 shown in FIG. 1 to shape the energy distribution of the laser 1 emitted from the laser light source 10, more precisely, the wobble laser 2 obtained by converting the laser 1 in a wobbling device 21.

[0120] The shaping device 22 can shape the energy distribution (beam profile) of the wobble laser 2 into a top-hat shape as shown in Fig. 6(a). The laser 3 (5a) having such a top-hat energy distribution changes to the laser 5b (5b) which approaches the energy distribution before shaping as it moves away from the image forming point, as shown in Figs. 6(b) and 6(c). １ and 5b ２ In the laser processing method of the present invention, the wobble laser 2, i.e., the beam profile of which the optical axis is tilted and rotated, can be made the beam profile before shaping. Therefore, as the laser 5b moves away from the initial processing surface 71a, which is the image formation point, １ and 5b ２ The beam profile shown in Fig. 1 becomes a beam shape that rotates while expanding.

[0121] Furthermore, it is preferable to irradiate the workpiece 70 with the laser 5 through the photomask 30 shown in FIG. 1, and it is more preferable to focus the laser 5 on the film surface formed on the photomask 30.

[0122] This imaging can be performed by the optical system 90 shown in Fig. 1. Specifically, the shaped laser 3 emitted from the shaping device 22 is imaged on the film surface of the photomask 30 at a focal point F1.

[0123] By using the photomask 30 and performing processing while focusing the laser in this manner, it is possible to perform desired pattern processing according to the pattern shape of the photomask 30 with even greater precision.

[0124] Next, with reference to FIGS. 7 and 8, a description will be given of changes in the energy distribution (beam profile) of the laser when a through-hole 300 is formed in a workpiece (substrate) 70 by an example of the laser processing method of the present invention.

[0125] In this example, a laser beam is focused on the film surface of the photomask 30 and on the surface 71 of the workpiece.

[0126] The laser 1 emitted from the laser light source 10 can have a Gaussian beam profile. In the wobbling device 21, this laser 1 becomes the wobble laser 2 whose optical axis tilts and rotates as described above. Naturally, the beam profile also has a shape in which the optical axis rotates. This is the original shape before shaping.

[0127] The wobble laser 2 becomes a top-hat laser 3 in the forming device 22. This laser 3 is imaged on the film surface of the photomask 30 by the optical system 90 shown in Fig. 1. The beam profile of the laser 3 at the focal point F1 has an optical axis that is not rotated, as shown in Fig. 7.

[0128] The beam 3 passes through a photomask 30 having a mask pattern, becoming a laser beam 4 having a beam profile corresponding to the mask pattern. Next, the laser beam 4 passes through an imaging lens 50, and an image of the laser beam 5 is formed on a workpiece surface 71 of a substrate 70, which is a workpiece. As a result, an image projection corresponding to the mask pattern shape of the photomask 30 is performed on the workpiece surface 71.

[0129] At the workpiece surface 71, which is the focal point, the laser beam 5a has a beam profile in which the optical axis does not rotate. On the other hand, when the laser beam deviates from the focal point, it is affected by the original profile before beam shaping. In other words, as shown in FIG. 7 and further shown in detail in FIG. 8, as processing progresses in the depth direction of the workpiece 70, it is affected by the original shape rotated by the wobbling device 21, and becomes laser beam 5d having a beam shape that rotates while expanding.

[0130] By performing such laser processing, it is possible to prevent a decrease in the laser energy density even when processing progresses in the depth direction of the workpiece 70. Thus, as shown in Figures 7 and 8, a through hole 300 that penetrates the substrate, which is the workpiece 70, can be formed while preventing tapering.

[0131] That is, with the laser processing method of the present invention, even when recesses are formed at high resolution, the width of the bottom of the recess can be prevented from being smaller than the width of the opening of the recess on the workpiece surface 71. Furthermore, with the laser processing method of the present invention, even when through holes are formed at high resolution, the width of the opening at the bottom of the through hole can be prevented from being smaller than the width at the top of the through hole. That is, with the laser processing method of the present invention, even when recesses and / or through holes are formed at high resolution, the recesses and / or through holes formed can be prevented from having a tapered shape, and therefore high-resolution, complex patterns can be formed.

[0132] Furthermore, the laser processing method of the present invention described above can be performed, for example, using the laser processing apparatus 100 of the present invention. Therefore, by using the laser processing apparatus 100 of the present invention, even when recesses are formed at high resolution, the width of the bottom of the recess can be prevented from being smaller than the width of the opening of the recess on the workpiece surface 71. Furthermore, by using the laser processing apparatus 100 of the present invention, even when through holes are formed at high resolution, the width of the lower opening of the through hole can be prevented from being smaller than the width of the upper end of the through hole. In other words, by using the laser processing apparatus of the present invention, even when recesses and / or through holes are formed at high resolution, the recesses and / or through holes formed can be prevented from having a tapered shape, and thus high-resolution, complex patterns can be formed.

[0133] Next, examples of a recess pattern, a through-hole pattern, and a recess and through-hole pattern that can be formed using the laser processing method of the present invention will be described.

[0134] <Recess Pattern> FIG. 9 shows a schematic partial cross-sectional view of a substrate having an example of a recess pattern that can be formed using the laser processing method of the present invention.

[0135] 9 has a recess 200 on its surface 71. The recess 200 may be one or more. Each recess 200 has an opening 200A and a bottom 200B on the surface 71 of the substrate 70. The substrate 70 has a protrusion 74 between adjacent recesses 200. The recesses 200 may have the same shape or different shapes. That is, the opening width W, which is the width of the opening 200A of the recess 200, ａ and the width W of the bottom 200B ｂ may be the same or may be all different. ２００ (For example, the depth of the recess 200 in the thickness direction of the substrate 70) may be different for each recess 200, or may be different for each recess 200 within the same processed portion height D ２００ There may also be some.

[0136] The distance W between the bottoms 200B of the adjacent recesses 200 in the cross section 73 of the substrate 70 ｃ is, for example, the width W of the bottom 200B of the recess 200 ｂ The distance W between the bottoms 200B of the recesses 200 can be 110% or less. ｃ The width W of the bottom 200B of the recess 200 may be set to 100% or more and 110% or less. ｂ is the width W of the bottom 200B of the adjacent recess 200 ｂ The distance W between the bottoms 200B of the recesses 200 is ｃ is the shortest distance between the bottoms 200B of the recesses 200.

[0137] Furthermore, according to the laser processing method of the present invention, the width W of the bottom 200B of the recess 200 in the cross section 73 of the substrate 70 ｂ The depth (height of the processed portion) D of the recess 200 ２００ The ratio (D ２００ / Wｂ ) can be 1.0 or more.

[0138] In this way, according to the laser processing method of the present invention, it is possible to form recesses with a high aspect ratio. ２００ / W ｂ The upper limit of the ratio D ２００ / W ｂ can be set to 10 or less, for example.

[0139] Furthermore, according to the laser processing method of the present invention, for example, the width W ｂ is the opening width W of the recess 200 on the surface (initial work surface) 71. ａ The ratio can be 70% or more, preferably 80% or more, and more preferably 90% or more.

[0140] In such a substrate 70, the recess 200 does not have a tapered shape but is close to a cylindrical shape, so that when wiring is incorporated into the recess 200, the wiring can exhibit low resistance. Therefore, such a substrate 70 can realize a wiring pattern with low wiring resistance.

[0141] Width W of the bottom 200B of the recess 200 ｂ is the opening width W ａ Ideally, it should be equal to (100%).

[0142] Furthermore, according to the laser processing method of the present invention, for example, the opening width W of the recess 200 on the surface 71 ａ and the width W of the bottom 200B ｂ That is, the width of the recess 200 can be set to 20 μm or less.

[0143] A finer wiring pattern can be realized with such a substrate 70. Although there is no particular lower limit, for example, the width of the recess 200 can be set to 1 μm or more and 20 μm or less.

[0144] The recess 200 may include, for example, a trench 200T as shown in the perspective view of Fig. 10. The trench 200T extends in a direction parallel to the surface 71 of the substrate 70. The multiple trenches 200T may extend in different directions from each other, as shown in Fig. 10 as an example.

[0145] The recess 200 is not limited to the trench 200T. For example, as shown in the example of Fig. 10, the recess 200 may include a fastening hole 200S having a rectangular surface shape or a fastening hole 200U having a circular surface shape. The recess 200 may also include a recess 200 having another surface shape.

[0146] When the recess 200 is a trench 200T, the width W ｂ and opening width W ａ is the width of the trench 200T in a direction perpendicular to the direction in which the trench extends. When the recess 200 is a fastening hole 200S having a rectangular surface shape, the smallest width in the surface shape is the width W ｂ and opening width W ａ When the recess 200 is a fastening hole 200U having a circular surface shape, the diameter of the circle is defined as the width W ｂ and opening width W ａ If the surface shape is an ellipse, the minor axis is the width W ｂ and opening width W ａ Let's say.

[0147] Height D of the recess 200 in the cross section 73 ２００ (For example, the depth of the recess 200 in the thickness direction of the substrate 70) may be different for each recess 200, or may be different for each recess 200 within the same processed portion height D ２００ The recess 200 may have a processed portion height D ２００ can be set to, for example, 5 μm or more and 20 μm or less.

[0148] <Through-Hole Pattern> FIG. 11 shows a schematic partial cross-sectional view of a substrate having an example of a through-hole pattern that can be formed using the laser processing method of the present invention.

[0149] The substrate 70 shown in FIG. 11 has a through-hole 300 that penetrates from the front surface 71 to the back surface 71B opposite to the front surface 71.

[0150] According to the laser processing method of the present invention, the width W of the lower end opening 300B of the through hole 300 on the back surface 71B ｅ is the width W of the upper end opening 300A of the through hole 300 on the surface (initial work surface) 71. ｄ It can be 70% or more of the above.

[0151] In this type of substrate 70, the through holes 300 are not tapered but are closer to a cylindrical shape, so when VIA processing is performed on these through holes 300, deep VIA electrode processing can be performed even with high precision without tapering during processing. Therefore, the substrate 70 of this type can realize a VIA electrode pattern with a high aspect ratio.

[0152] Furthermore, since the through-hole 300 is not tapered, the width W of the lower end opening 300B of the through-hole 300 is ｅ In order to ensure the size of the upper end opening 300A of the through hole 300, the width W ｄ Therefore, the substrate 70 can realize a highly precise and complicated via pattern.

[0153] Width W of the lower end opening 300B of the through hole 300 ｅ The width W of the upper end opening 300A ｄ The width W of the lower end opening 300B of the through-hole 300 is ideally equal to (100%). ｅ is the width W of the upper end opening 300A ｄ It can be 70% or more, preferably 80% or more, and more preferably 90% or more.

[0154] The number of through holes 300 may be one or more. When a plurality of through holes 300 are included, the width W of the plurality of through holes 300 is ｄ and width W ｅ may be the same or different.

[0155] The planar shape of the through-hole 300 is not particularly limited. When the through-hole 300 has a rectangular surface shape, the smallest width of the surface shape is defined as the width W ｄ and width W ｅ When the through-hole 300 has a circular surface shape, the diameter of the circle is defined as the width W ｄ and width W ｅ If the surface shape is an ellipse, the minor axis is the width W ｄ and width W ｅ Let's say.

[0156] According to the laser processing method of the present invention, the width W of the upper end opening 300A of the through hole 300 on the surface 71 ｄand the width W of the lower opening ｅ That is, according to the laser processing method of the present invention, a through hole having a width of 20 μm or less can be formed.

[0157] Such a substrate 70 makes it possible to realize a semiconductor package having a higher-definition VIA electrode pattern.

[0158] Width W of the upper end opening 300A ｄ The lower limit of the thickness is not particularly limited, but it can be set to, for example, 1 μm or more.

[0159] According to the laser processing method of the present invention, the width W of the lower end opening 300B of the through hole 300 on the back surface 71B ｅ The processed portion height D of the through hole 300 ３００ The ratio of the width W of the lower end opening 300B of the through hole 300 can be set to, for example, 1.0 or more. ｅ Height D of processed part ３００ The ratio is not particularly limited, but can be, for example, 1.0 or more and 10.0 or less.

[0160] <Recess and Through-Hole Pattern> According to the laser processing method of the present invention, it is also possible to form a pattern including both recesses 200 and through-holes 300, for example, as shown in Fig. 12. For details of the recesses 200 and through-holes 300, please refer to the above.

[0161] In particular, according to the laser processing method of the present invention, it is possible to form a fine pattern, for example, by forming a plurality of recesses 200 between through holes 300 as shown in Fig. 12. As described above, the recesses 200 and through holes 300 can be formed while preventing them from becoming tapered.

[0162] [Method for Manufacturing Substrate] As described above, according to the laser processing method of the present invention, recesses and through holes can be formed in a substrate, which is a workpiece.

[0163] That is, the present invention provides a method for manufacturing a substrate having the recesses and / or through holes, which includes forming the recesses and / or through holes in the substrate, which is the workpiece, by the laser processing method of the first or second aspect of the present invention.

[0164] As described above, this substrate manufacturing method can prevent the width of the bottom of the recess from being smaller than the width of the opening of the recess on the surface of the workpiece, even when the recess is formed with high resolution. Furthermore, this laser processing method can prevent the width of the lower opening of the through hole from being smaller than the width of the upper end of the through hole, even when the through hole is formed with high resolution. In other words, the substrate manufacturing method of the present invention can prevent the recess and / or through hole from being tapered, even when the recess and / or through hole is formed with high resolution, and thus can manufacture a substrate having a high-resolution, complex pattern.

[0165] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. A laser processing method for forming recesses and / or through holes in a workpiece using a laser, comprising: irradiating the workpiece with a laser having an optical axis tilted with respect to the normal to the workpiece surface; and performing laser processing while rotating the optical axis of the laser around the normal to the workpiece surface as a rotation axis, thereby forming recesses and / or through holes in the workpiece.

2. A laser processing method according to claim 1, wherein the inclination angle of said optical axis with respect to the normal to the surface of said workpiece is set to be 3° or more and 15° or less.

3. A laser processing method according to claim 1 or 2, wherein laser processing is performed while rotating the optical axis of the laser at a frequency of 10 Hz to 300 Hz.

4. A laser processing method for forming recesses and / or through holes in a workpiece using a laser, wherein the laser processing is performed by irradiating a wobble laser using a wobble device to form recesses and / or through holes in the workpiece.

5. A laser processing method according to any one of claims 1 to 4, wherein the workpiece is a substrate for a semiconductor package, and a recess and / or a through hole is formed in the substrate for a semiconductor package.

6. A laser processing method according to any one of claims 1 to 5, wherein the laser is oscillated using an excimer laser oscillator.

7. A laser processing method according to any one of claims 1 to 6, wherein the laser is irradiated onto the workpiece through a photomask.

8. A laser processing method according to any one of claims 1 to 7, wherein processing is performed while the laser is scanned relatively over the workpiece.

9. The laser processing method according to any one of claims 1 to 8, wherein ablation processing is performed.

10. A laser processing method according to any one of claims 1 to 9, wherein the recesses and / or through holes have a width of 20 μm or less.

11. A laser processing method according to any one of claims 1 to 10, wherein the recesses and / or through holes are formed such that the ratio of the height of the processed portion to the width of the bottom of the recess or the width of the lower opening of the through hole is 1.0 or greater.

12. A laser processing method according to any one of claims 1 to 11, wherein the recess is formed so that the width of the bottom of the recess is 70% or more of the opening width of the recess on the initial processing surface of the workpiece, and / or the through hole is formed so that the width of the lower opening of the through hole is 70% or more of the width of the upper opening of the through hole on the initial processing surface.

13. A laser processing method according to any one of claims 1 to 12, wherein a plurality of recesses are formed, and the distance between the bottoms of adjacent recesses is 110% or less of the width of the bottoms.

14. A laser processing method according to any one of claims 1 to 13, wherein processing is carried out while the laser is focused on the surface of the workpiece.

15. A laser processing method according to any one of claims 1 to 13, wherein the laser is irradiated onto the workpiece through a photomask, and the laser is imaged on a film surface formed on the photomask.

16. A method for manufacturing a substrate having recesses and / or through holes, comprising forming the recesses and / or through holes in the substrate, which is the workpiece, by the laser processing method according to any one of claims 1 to 15.

17. A laser processing device for forming recesses and / or through holes in a workpiece using a laser, comprising: a laser light source for oscillating a laser; and a shaping optical system configured to irradiate the workpiece with the laser having an optical axis tilted with respect to the normal to the workpiece surface, and to rotate the optical axis of the laser around the normal to the workpiece surface as a rotation axis.

18. A laser processing device for forming recesses and / or through holes in a workpiece using a laser, comprising: a laser light source that oscillates a laser; and a wobbling device configured to convert the laser into a wobble laser.

19. The laser processing device according to claim 18, further comprising a shaping device for shaping the energy distribution of the laser emitted from the laser light source, the wobbling device being disposed between the laser light source and the shaping device.

20. The laser processing device according to claim 18 or 19, wherein the wobbling device includes a galvanometer scanner.

21. The laser processing device according to any one of claims 18 to 20, wherein the wobbling device includes a rotation mechanism configured to rotate the prism.

22. The laser processing device according to any one of claims 17 to 21, wherein the laser light source is an excimer laser oscillator.

23. The laser processing apparatus according to any one of claims 17 to 22, further comprising an optical system configured to image the laser onto the workpiece surface of the workpiece.

24. The laser processing device according to any one of claims 17 to 22, further comprising: a stage on which the workpiece is placed; and a photomask disposed between the shaping optical system and the stage.

25. The laser processing device according to claim 24, further comprising an optical system configured to focus the laser on a film surface formed on the photomask.

26. The laser processing device according to claim 24 or 25, further comprising a controller configured to synchronously move the workpiece placed on the stage and the photomask.

Images