Method for forming deep blind hole

Abstract

The invention discloses a method for forming a deep blind hole. The method comprises the following steps: providing a substrate comprising an outer conductive layer, a dielectric layer and a target conductive layer; forming a copper window on the outer conductive layer to define an opening on the surface of the substrate, and exposing the dielectric layer at the copper window; aligning a mechanical drill bit with the copper window, performing mechanical blind drilling in the dielectric layer to form a first hole wall section extending along the hole depth direction, and reserving a residual dielectric layer at the hole bottom of the dielectric layer; and performing laser sintering processing on the residual dielectric layer by using a laser beam through the first hole wall section so as to remove the residual dielectric layer and form a second hole wall section positioned below the first hole wall section along the hole depth direction, so that the target conductive layer is exposed at the hole bottom, wherein the first hole wall section and the second hole wall section jointly define the deep blind hole. Therefore, the machining efficiency of the large blind hole is improved, and the uncertainty of residual materials at the bottom of the hole can be reduced.

Description

Technical Field

[0001] This invention relates to a circuit board processing technology, and more particularly to a method for forming deep blind vias. Background Technology

[0002] With the development of high-density electronic devices and multilayer substrate structures, the design of blind vias in circuit boards is gradually evolving towards larger apertures and greater depths to meet the demands of high-density wiring, structural integration, and electrical connections. Under this trend, as the ratio of the depth to the aperture of a blind via increases, forming a via shape that meets design requirements in the dielectric layer and accurately aligning the bottom of the via with the target conductive layer becomes a crucial issue in process design and parameter configuration.

[0003] In practical applications, the formation of deep blind vias often involves multi-stage material removal and via shaping, especially in the via bottom region. The method, sequence, and configuration of material removal directly affect the consistency of the via shape and the overall processing time. When the processing configuration fails to effectively distribute the material removal load, the processing time can easily increase significantly with increasing via depth, or cause uneven structural differences in the via wall and via bottom morphology under repeated processing. In addition, the via shape structure of deep blind vias with large diameters is also an important consideration affecting the quality of subsequent electroplating operations. Summary of the Invention

[0004] This invention discloses a method for forming deep blind holes, which is mainly used to improve the technical problems existing in the prior art.

[0005] One embodiment of the present invention discloses a method for forming deep blind vias, comprising: providing a substrate including an outer conductive layer, a dielectric layer, and a target conductive layer, wherein the dielectric layer is disposed between the outer conductive layer and the target conductive layer; performing a copper window opening step, comprising: forming a copper window in the outer conductive layer to define an opening on the surface of the substrate, the opening having a copper window aperture Dcw, and exposing the dielectric layer at the copper window; and performing a mechanical drilling step, comprising: aligning a mechanical drill bit with a drilling diameter Dm with the copper window and performing mechanical blind drilling within the dielectric layer. The mechanical drill bit is controlled to descend along the hole depth direction at a predetermined drilling depth to form a first hole wall section extending along the hole depth direction, and a residual dielectric layer is retained at the bottom of the hole to cover the target conductive layer; and a laser burning step is performed, including: using a laser beam to perform laser burning processing on the residual dielectric layer through the first hole wall section to remove the residual dielectric layer and form a second hole wall section located below the first hole wall section along the hole depth direction, exposing the target conductive layer at the bottom of the hole; wherein the first hole wall section and the second hole wall section together define the deep blind hole.

[0006] Preferably, the borehole diameter Dm is not less than the copper window aperture Dcw.

[0007] Preferably, the mechanical drill bit in the mechanical drilling step is a flathead drill.

[0008] Preferably, the dielectric layer has a dielectric layer thickness Td at the copper window, and the predetermined drilling depth of the mechanical drilling step is 60% to 75% of the dielectric layer thickness Td.

[0009] Preferably, the residual dielectric layer has a residual thickness Tr, and the residual thickness Tr is 25% to 33.3% of the dielectric layer thickness Td.

[0010] Preferably, the aperture Dcw of the copper window is 300μm to 500μm.

[0011] Preferably, the laser burning process involves scanning the laser beam relative to the center of the opening using a spiral trajectory or a concentric circle trajectory.

[0012] Preferably, the ratio of the depth of the deep blind hole to the diameter of the copper window hole is greater than 1.0, and the ratio of the bottom diameter of the deep blind hole to its opening diameter is not less than 0.80.

[0013] Preferably, the first hole wall section forms a hole wall region that is basically straight along the hole depth direction, and the second hole wall section forms a hole wall region with a taper along the hole depth direction. The first hole wall section has a first hole diameter change rate, and the second hole wall section has a second hole diameter change rate that is greater than the first hole diameter change rate.

[0014] Preferably, the method includes electroplating the deep blind hole after the laser winding step to form a conductive plating layer on the hole wall of the deep blind hole.

[0015] In summary, this invention improves the processing efficiency of large blind holes by first forming a first hole wall section through mechanical drilling at the opening of the copper window, and then forming a second hole wall section through laser burning. This reduces the uncertainty of residual material at the bottom of the hole. By dividing and configuring the methods for removing dielectric materials, the hole wall morphology and subsequent electroplating controllability can still be maintained even under high aspect ratio conditions, while improving the overall processing efficiency.

[0016] To further understand the features and technical content of this invention, please refer to the following detailed description and accompanying drawings. However, these descriptions and drawings are only for illustrating the invention and are not intended to limit the scope of protection of the invention in any way. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the substrate according to an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of a copper window formed according to an embodiment of the present invention.

[0019] Figure 3 This is a schematic diagram of mechanical drilling to form the first hole wall section according to an embodiment of the present invention.

[0020] Figure 4 This is a schematic diagram of the laser-driven burning process used to form the second hole wall section according to an embodiment of the present invention.

[0021] Figure 5 This is a schematic diagram of the formation of a conductive plating layer on the wall of a deep blind hole according to an embodiment of the present invention.

[0022] Figure 6 This is a schematic diagram of the laser-wound hole configuration area according to an embodiment of the present invention. Detailed Implementation

[0023] In the following description, if a specific drawing is indicated or shown in a specific drawing, it is only to emphasize that most of the relevant content mentioned in the following description appears in that specific drawing, but does not limit the following description to refer only to that specific drawing.

[0024] [Methods for forming deep blind holes]

[0025] like Figures 1 to 5 As shown, an embodiment of the present invention provides a method for forming a deep blind hole, comprising steps S110, S120, S130, S140, and S150.

[0026] like Figure 1 As shown, in step S110, a substrate 100 is provided, wherein the substrate 100 includes an outer conductive layer 110, a dielectric layer 120 and a target conductive layer 130, and the dielectric layer 120 is disposed between the outer conductive layer 110 and the target conductive layer 130.

[0027] In some embodiments, the outer conductive layer 110 and the target conductive layer 130 may each include a copper layer. The dielectric layer 120 may include at least one prepreg and a resin material, which may include one or a combination of epoxy resin, bismaleimide triazine resin, or polyimide resin, but the invention is not limited thereto.

[0028] like Figure 2 As shown, in step S120, a copper window opening step is performed, which includes: forming a copper window 200 on the outer conductive layer 110 to define an opening 210 on the surface of the substrate 100, the opening 210 having a copper window aperture Dcw, and exposing the dielectric layer 120 at the copper window 200.

[0029] In some embodiments, the copper window 200 is formed on the outer conductive layer 110 by etching. For example, a predetermined area is first defined with a corrosion-resistant material, and then etching is performed to remove part of the outer conductive layer 110 of the predetermined area to form the copper window 200, so that the dielectric layer 120 is exposed at the location of the copper window 200. However, the present invention is not limited to this.

[0030] The copper window aperture Dcw characterizes the aperture size of opening 210. In some embodiments, the copper window aperture Dcw is 300 μm to 500 μm, and preferably 380 μm to 420 μm, to facilitate the subsequent formation of large-sized deep blind holes. In subsequent steps, opening 210 serves as the entry point for mechanical drilling and laser winding.

[0031] like Figure 3 As shown, in step S130, a mechanical drilling step is performed, which includes: aligning a mechanical drill bit with a drilling diameter of Dm with the copper window 200 and performing blind drilling in the dielectric layer 120, and controlling the mechanical drill bit to descend along the hole depth direction corresponding to a hole axis 350 at a predetermined drilling depth to form a first hole wall section 310 extending downward from the opening 210 along the hole depth direction, and leaving a residual dielectric layer 121 above the hole bottom 340 of the dielectric layer 120 to cover the target conductive layer 130.

[0032] In some embodiments, the mechanical drill bit may be a flathead drill, so that the formed first hole wall section 310 presents a substantially straight wall profile near the opening 210.

[0033] At this stage, the first hole wall section 310 can be regarded as the upper hole wall section of the deep blind hole 300, which defines a hole outline extending downward from the opening 210, while the residual dielectric layer 121 is retained above the target conductive layer 130 so that the subsequent laser burning process can remove the residual dielectric layer 121.

[0034] In the mechanical blind drilling in step S130, the drill hole diameter Dm is not less than the copper window aperture Dcw; and optionally, the drill hole diameter Dm is greater than the copper window aperture Dcw (e.g., Dm / Dcw is between 1 and 1.2), but the present invention is not limited thereto.

[0035] Since mechanical drilling proceeds downwards from the opening 210 along the depth direction, when the drilling diameter Dm is not less than (for example, greater than) the copper window hole diameter Dcw, the mechanical drill bit may also drill and remove the edge area of ​​the copper window 200 while drilling downwards into the medium layer 120, so that the finished product has a shape where the hole wall of the first hole wall section 310 is flush with the hole wall of the copper window 200 near the opening 210.

[0036] Furthermore, such as Figure 3As shown, in step S130, the dielectric layer 120 can define a dielectric layer thickness Td at the copper window 200. The dielectric layer thickness Td refers to the distance from the plane where the copper window 200 of the outer conductive layer 110 is located to the upper surface of the target conductive layer 130, so as to characterize the dielectric layer thickness at which a deep blind hole 300 needs to be formed at the opening 210.

[0037] The predetermined drilling depth in step S130 can be set relative to the dielectric layer thickness Td; in some embodiments, the predetermined drilling depth is 60% to 75% of the dielectric layer thickness Td, and preferably 66.7% to 75%, but the present invention is not limited thereto.

[0038] With the aforementioned depth setting, the residual dielectric layer 121 retained above the bottom of the hole 340 has a residual thickness Tr. In some embodiments, the residual thickness Tr is 25% to 33.3% of the dielectric layer thickness Td, but the present invention is not limited thereto.

[0039] In practice, the above-mentioned ratio range can be used to control the amount of residual medium covering the target conductive layer 130 above the bottom of the hole 340 during the mechanical blind drilling stage, and to enable the subsequent laser burning process to remove the residual medium layer 121 and form the bottom of the hole; at the same time, the ratio range can also serve as a parameter basis for adjusting the junction position of the first hole wall section 310 and the second hole wall section 320 and the hole shape profile, but the present invention is not limited thereto.

[0040] In order to enable the mechanical blind drill in step S130 to form the first hole wall section 310 at a predetermined position and a predetermined depth and retain the residual medium layer 121, in some embodiments, the descent depth of the mechanical drill bit can be controlled by a depth sensor or a depth control module, so that the predetermined drilling depth conforms to the aforementioned proportional range relative to the medium layer thickness Td.

[0041] For example, a depth sensor can be used to detect the actual downward displacement of the mechanical drill bit in the 350-degree direction of the hole axis, and the depth control module can adjust the drilling feed based on the feedback of the downward displacement so that the drilling termination depth falls within the predetermined drilling depth range, but the present invention is not limited thereto.

[0042] Furthermore, in some embodiments, step S130 may use a drilling device with image scanning and recognition capabilities to identify the position of the copper window 200 in order to determine the drilling center of the mechanical drill bit. Specifically, the drilling device may obtain the relative coordinate position of the copper window 200 on the substrate 100 through image scanning, and thereby align the mechanical drill bit with the center of the opening 210 defined by the copper window 200 or the predetermined drilling center position, thereby forming a first hole wall section 310 within the processing area defined by the copper window 200.

[0043] In some embodiments, at least one pair of alignment holes (not shown) are formed on the substrate 100 to serve as a common coordinate reference for subsequent processing positioning.

[0044] Specifically, the alignment hole can be located in the peripheral area of ​​the substrate 100 or other suitable positions for establishing a coordinate reference, and can be in the form of a through hole or other reference hole form that can be recognized by the processing equipment, but the present invention is not limited thereto. In step S130 and subsequent step S140, a coordinate reference can be established using the alignment hole to position the mechanical drill bit and the laser beam. That is to say, the mechanical drilling equipment can first obtain the coordinates of the substrate 100 and complete the positioning of the drilling center based on the alignment hole, and the laser processing equipment can also obtain consistent coordinates based on the same alignment hole and complete the positioning of the laser beam, so that the mechanical blind drill and the laser beam are aligned with the opening 210 defined by the copper window 200 and its corresponding hole axis 350 under the same coordinate reference, which is beneficial to the control of the correspondence and hole shape consistency of the first hole wall section 310 and the second hole wall section 320 in the hole depth direction, but the present invention is not limited thereto.

[0045] like Figure 4 As shown, in step S140, a laser burning-around step is performed, which includes: using a laser beam to burn-around the residual dielectric layer 121 through the hole defined by the first hole wall section 310 formed in step S130, so as to remove the residual dielectric layer 121 and form a second hole wall section 320 located below the first hole wall section 310 along the hole depth direction, and expose the target conductive layer 130 at the bottom of the hole 340; wherein, the first hole wall section 310 and the second hole wall section 320 together define the deep blind hole 300.

[0046] In this step, the laser beam can act on the area where the residual dielectric layer 121 is located along the hole axis 350, so that the dielectric material that originally covered the target conductive layer 130 is removed, thereby forming an exposed surface at the bottom of the hole 340 that corresponds to the target conductive layer 130.

[0047] In some embodiments, the laser burning process can be performed by scanning the laser beam relative to the center of the opening 210, for example by using a spiral trajectory scan or a concentric circle trajectory scan, to burn away the residual dielectric layer 121 within the processing area defined by the opening 210; the scanning trajectory can be adjusted according to the aperture, residual thickness Tr or processing equipment settings, but the present invention is not limited thereto.

[0048] After laser burning, the deep blind hole 300 can present a segmented hole shape with a first hole wall section 310 and a second hole wall section 320 in the hole depth direction, and the two form a turning interface 330 at the junction.

[0049] like Figure 4As shown, in some embodiments, the laser burning in step S140 can be selected based on the residual thickness of the residual dielectric layer 121, so that the laser beam burns away the residual dielectric layer 121 and forms the second hole wall section 320.

[0050] The independent variables for laser processing may include one or a combination of energy, pulse width, repetition frequency, scanning speed, and number of pulses; wherein, energy can be used to characterize the energy output of a single pulse or per unit time, pulse width can be used to characterize the time width of a single pulse, repetition frequency can be used to characterize the frequency of repeated pulse emission, scanning speed can be used to characterize the scanning speed of the laser beam relative to the center of the opening 210, and number of pulses can be used to characterize the number of pulses emitted or the distribution setting within a predetermined scanning path or predetermined scanning area, but the present invention is not limited thereto. More detailed embodiments will be described below.

[0051] Furthermore, such as Figure 4 As shown, in the deep blind via 300 of this embodiment of the invention, the via depth H can be defined as the distance along the via axis 350 from the reference position on the substrate surface where the opening 210 is located to the bottom 340 of the via, where the bottom 340 corresponds to the position where the target conductive layer 130 is exposed at the bottom of the deep blind via 300. Based on the aforementioned use of the copper window aperture Dcw to characterize the aperture size of the opening 210, the geometric ratio of the deep blind via 300 can be further characterized by the ratio of the via depth H to the copper window aperture Dcw (H / Dcw). In some embodiments, the ratio (H / Dcw) is greater than 1.0; in more specific embodiments, the ratio (H / Dcw) is 1.2 to 1.3, but the invention is not limited thereto.

[0052] In practice, when (H / Dcw) is greater than 1.0, the deep blind hole 300 belongs to the type of blind hole with a large hole depth relative to the hole diameter. The removal of the medium material at the bottom 340 of the hole and the control of the hole shape may rely more on the combination setting of the residual thickness Tr and the laser processing independent variable.

[0053] By retaining the residual dielectric layer 121 in step S130 and removing the residual dielectric layer 121 by laser burning in step S140, the deep blind via 300 can form a stable hole bottom exposure surface at the target conductive layer 130, and make the position and outline of the hole segment (first hole wall segment 310 and second hole wall segment 320) obvious; the above-mentioned (H / Dcw) numerical range is only a setting of one embodiment, but the present invention is not limited thereto.

[0054] like Figure 4As shown, after steps S130 and S140 are completed, the deep blind hole 300 can present a segmented hole shape along the hole depth direction. The first hole wall segment 310 forms a hole wall region with a basically straight wall along the hole depth direction, while the second hole wall segment 320 forms a hole wall region with a taper relative to the first hole wall segment 310 along the hole depth direction. That is, the first hole wall segment 310 has a first hole diameter change rate, the second hole wall segment 320 has a second hole diameter change rate, and the second hole diameter change rate is greater than the first hole diameter change rate.

[0055] Specifically, the first hole wall section 310 can be regarded as the upper section of the hole wall adjacent to the opening 210 of the deep blind hole 300, and its hole wall profile is relatively close to the hole axis 350 and extends to the turning interface 330; the second hole wall section 320 is located between the turning interface 330 and the hole bottom 340, and its hole wall profile is an inwardly converging profile relative to the first hole wall section 310, exposing the target conductive layer 130 at the hole bottom 340.

[0056] A transition interface 330 is formed at the junction of the first hole wall section 310 and the second hole wall section 320, and a transition hole diameter Dj is defined, which can be used as a reference position for dimensional parameters such as transition height Δh or hole diameter change rate R1 / R2.

[0057] like Figure 5 As shown, in some embodiments, after the laser burning in step S140 is completed, copper electroplating can be performed on the deep blind hole 300 in step S150 to form a conductive plating layer 400 on the hole wall of the deep blind hole 300.

[0058] The conductive plating layer 400 can extend continuously along the first hole wall section 310 and the second hole wall section 320 to the bottom of the hole 340, and connect to and cover the target conductive layer 130. Please refer to the following: Figure 4 As shown, the opening diameter of the deep blind hole 300 at the opening 210 is defined as Dtop, and the bottom diameter of the deep blind hole 300 near the bottom 340 is defined as Dbottom.

[0059] In some embodiments, the ratio of the bottom diameter Dbottom to the opening diameter Dtop (Dbottom / Dtop) is not less than 0.80 (e.g., 0.8-1.0), but the present invention is not limited thereto.

[0060] Furthermore, in some embodiments, the maximum value of the hole wall roughness of the deep blind hole 300 is less than 35 μm, wherein the maximum value of the hole wall roughness refers to the maximum measured value obtained after roughness measurement of the hole wall of the deep blind hole 300 (e.g., including the first hole wall section 310 and the second hole wall section 320).

[0061] [Substrate with deep blind vias]

[0062] like Figure 4 and Figure 5 As shown, the present invention also discloses a substrate 100 having a deep blind via 300, which includes an outer conductive layer 110, a target conductive layer 130 and a dielectric layer 120, wherein the dielectric layer 120 is disposed between the outer conductive layer 110 and the target conductive layer 130.

[0063] The outer conductive layer 110 has a copper window 200 to define an opening 210 on the surface of the substrate 100. The opening 210 has a copper window aperture Dcw and exposes the dielectric layer 120 at the copper window 200.

[0064] The substrate 100 also has a deep blind via 300, which extends from the opening 210 along the hole depth direction corresponding to the hole axis 350 through the dielectric layer 120 to the target conductive layer 130, and exposes the target conductive layer 130 at the bottom 340 of the via.

[0065] In some embodiments of the present invention, the deep blind hole 300 includes a first hole wall section 310 and a second hole wall section 320 connected along the hole depth direction, wherein the first hole wall section 310 is adjacent to the opening 210 and has a generally straight wall profile, the second hole wall section 320 is adjacent to the hole bottom 340 and has a tapered profile that converges inward relative to the first hole wall section 310, and the first hole wall section 310 and the second hole wall section 320 form a turning interface 330 at the junction.

[0066] With the above structural configuration, the deep blind hole 300 can be regarded as a segmented hole with a straight wall hole type in the upper section and an inward-retracting hole type in the lower section.

[0067] In some embodiments, the outer conductive layer 110 and the target conductive layer 130 each include a copper layer.

[0068] In some embodiments, the medium layer 120 includes at least one layer of prepreg and a resin material, wherein the resin material comprises one or a combination of epoxy resin, bismaleimide triazine resin or polyimide resin.

[0069] In some embodiments of the present invention, the opening 210 defined by the copper window 200 has a copper window aperture Dcw, which is 300 μm to 500 μm, and preferably 380 μm to 420 μm.

[0070] Furthermore, the deep blind via 300 has a depth H, which is the distance along the via axis 350 from a reference position on the surface of the substrate 100 where the opening 210 is located to the bottom 340 of the via. Based on the definitions of the copper window aperture diameter Dcw and the depth H, the aspect ratio of the deep blind via 300 can be further characterized by the ratio (H / Dcw). In some embodiments, the ratio (H / Dcw) is greater than 1.0 and preferably 1.2 to 1.3, but the present invention is not limited thereto.

[0071] like Figure 4 As shown, in some embodiments of the present invention, the second hole wall section 320 has a taper angle α relative to the central axis (i.e., hole axis 350) of the first hole wall section 310. The taper angle α can be defined as the angle formed by the generatrix of the hole wall of the second hole wall section 320 relative to the hole axis 350. In some embodiments, the taper angle α is 1 degree to 8 degrees or 2 degrees to 6 degrees, but the present invention is not limited thereto.

[0072] Under the condition of the taper angle α, the second hole wall section 320 presents an inwardly converging taper profile relative to the first hole wall section 310, so that the deep blind hole 300 has an identifiable segmented hole type in the hole depth direction.

[0073] The numerical range of the taper angle α mentioned above is merely an exemplary parameter setting and is not intended to impose unnecessary restrictions on the hole type. This invention is not limited thereto.

[0074] In some embodiments of the present invention, the second hole wall section 320 has an inwardly tapering profile along the hole depth direction, and the second hole wall section 320 has a turning hole diameter Dj at the turning interface 330. The turning hole diameter Dj can be defined as the inner hole diameter measured at the cross-sectional position of the turning interface 330 in a direction perpendicular to the hole axis 350; the hole bottom diameter Dbottom can be defined as the inner hole diameter measured at the cross-sectional position near the hole bottom 340 in a direction perpendicular to the hole axis 350.

[0075] Under the aforementioned inward contour structure relationship, the bottom diameter Dbottom is smaller than the turning diameter Dj, so that the second hole wall section 320 presents an inwardly converging contour between the turning interface 330 and the bottom 340.

[0076] In some embodiments, the degree of inward taper of the second hole wall section 320 can be further characterized by a ratio (Dbottom / Dj), wherein the ratio (Dbottom / Dj) is 0.70 to 0.95. The definitions of Dj and Dbottom and their ratio range can be used together with parameters such as taper angle α, hole depth H, and turning height Δh to describe the segmented hole type of the deep blind hole 300; the above parameters are merely illustrative limitations and the present invention is not limited thereto.

[0077] In some embodiments of the present invention, the first hole wall section 310 is flush with the hole wall of the copper window 200 near the opening 210.

[0078] In some embodiments of the present invention, the first hole wall segment 310 has a first segment depth L1 along the hole depth direction. The first segment depth L1 can be defined as the distance along the hole axis 350 from the reference position on the surface of the substrate 100 where the opening 210 is located to the position of the transition interface 330, that is, the extension depth of the first hole wall segment 310 in the hole depth direction; while the hole depth H is the distance from the reference position on the surface of the substrate 100 where the opening 210 is located to the bottom of the hole 340, but the present invention is not limited thereto. Based on the above definition, the depth ratio of the first hole wall segment 310 relative to the overall deep blind hole 300 can be further characterized by the ratio (L1 / H).

[0079] In some embodiments, the ratio (L1 / H) is 55% to 80%; in more specific embodiments, the ratio (L1 / H) is 65% to 75%, but the invention is not limited thereto. The above ratio range can be used to define the segmented configuration of the first borehole wall section 310 and the second borehole wall section 320 in the borehole depth direction.

[0080] like Figure 4 and Figure 5 As shown, in some embodiments of the present invention, the transition interface 330 formed at the junction of the first hole wall section 310 and the second hole wall section 320 has a transition height Δh along the hole depth direction. The transition height Δh can be defined as the hole profile transition height measured along the hole axis 350 with the transition interface 330 as a reference. That is, it characterizes the transition height scale in the hole depth direction when the basic straight wall profile of the first hole wall section 310 transitions to the inward profile of the second hole wall section 320, but the present invention is not limited thereto.

[0081] Based on the definition of hole depth H, the ratio (Δh / H) can be used to characterize the proportional relationship between the turning height Δh and the overall hole depth H. In some embodiments, the ratio (Δh / H) is 0.5% to 10% or 1% to 6%, but the present invention is not limited thereto.

[0082] In some embodiments of the present invention, the first hole wall section 310 has a first hole diameter variation rate R1, and the second hole wall section 320 has a second hole diameter variation rate R2; wherein the first hole diameter variation rate R1 is not greater than 3% (e.g., between 0% and 3%), and the second hole diameter variation rate R2 is not less than 4% (e.g., between 4% and 10%), but the present invention is not limited thereto. The first hole diameter variation rate R1 can be defined as: the difference between the maximum and minimum internal hole diameters measurable along the hole depth direction in the first hole wall section 310, divided by the maximum internal hole diameter; the second hole diameter variation rate R2 can be defined as: the difference between the maximum and minimum internal hole diameters measurable along the hole depth direction in the second hole wall section 320, divided by the maximum internal hole diameter. In some embodiments of the present invention, the hole wall of the first hole wall section 310 has a first average surface roughness (Ra1), and the hole wall of the second hole wall section 320 has a second average surface roughness (Ra2), wherein the first average surface roughness (Ra1) is less than the second average surface roughness (Ra2). The roughness of the hole wall of the second hole wall section 320 can provide a more favorable adhesion of the conductive plating layer 400 to the bottom section of the deep blind hole, thereby improving reliability.

[0083] like Figure 5 As shown, in some embodiments of the present invention, the wall of the deep blind via 300 is covered with a conductive plating layer 400. The conductive plating layer 400 extends continuously along the first wall section 310 and the second wall section 320 to the bottom 340 of the via and is connected to the target conductive layer 130. The conductive plating layer 400 may be a copper electroplated layer or other conductive plating layer, and its thickness, formation method and coverage range may be adjusted according to product design or process conditions. The opening diameter of the deep blind via 300 at the opening 210 is defined as Dtop, and the bottom diameter of the deep blind via 300 near the bottom 340 is defined as Dbottom. In some embodiments, the ratio of the bottom diameter Dbottom to the opening diameter Dtop (Dbottom / Dtop) is not less than 0.80, and preferably 0.80 to 0.92, but the present invention is not limited thereto.

[0084] [Laser winding processing method]

[0085] To improve the efficiency of laser winding processing, the following describes a laser winding processing method according to an embodiment of the present invention.

[0086] like Figure 6As shown, in some embodiments of the present invention, in addition to the aforementioned step S140 of using a laser beam to perform laser burning processing on the residual dielectric layer 121 through the first hole wall section 310 to form the second hole wall section 320 and expose the target conductive layer 130 at the bottom of the hole 340, the design of the striking point configuration and independent variable configuration method of the laser burning processing can be further extended to improve the processing efficiency of the laser burning section.

[0087] Specifically, the laser burning step includes setting a stacked hole configuration area 500 to describe the configuration of multiple stacked hole impact points 510 (which can also be regarded as small impact holes or small blind hole units) in the processing area corresponding to the opening 210. The multiple stacked hole impact points 510 included in the stacked hole configuration area 500 can be distributed in the outer ring layer 520, the middle ring layer 530 and the central ring layer 540 according to a predetermined ring layout, and together form the target hole outline 550 corresponding to the deep blind hole 300.

[0088] Under this architecture, the laser burning process in step S140 can sequentially burn the multiple stacked hole impact points 510, and configure the laser action position around the target hole contour 550 along the burning path 590.

[0089] In some embodiments, the laser burn-around process can be configured with two independent variables, that is, the first laser independent variable group and the second laser independent variable group are applied to the stacked hole impact point 510 in sequence. The first laser independent variable group can be used for the initial removal stage, and the second laser independent variable group can be used for the hole repair stage.

[0090] The above-mentioned stacked hole configuration area 500 and the two-stage independent variable configuration are used to specify the path design and strike configuration of laser burning, and do not change the basic structure of the substrate 100, copper window 200 and mechanical blind drilling to form the first hole wall section 310 and residual dielectric layer 121 described in steps S110 to S130.

[0091] like Figure 6 As shown, in some embodiments of the present invention, the stacked aperture configuration region 500 can be characterized by a stacking aperture ratio Rol to describe the degree of overlap between two adjacent stacked aperture impact points 510. Hereinafter, the "stacking aperture ratio Rol" is the center-to-center distance between adjacent stacked aperture impact points 510, that is, the ratio of the center-to-center distance Scc (center-to-center distance) of adjacent impact points to the equivalent impact aperture diameter or equivalent impact scale, characterizing the degree of overlap between adjacent impact positions in a planar configuration. In other words, the stacking aperture ratio Rol is a representation of the overlap ratio corresponding to the center-to-center distance Scc between two adjacent stacked aperture impact points relative to the equivalent impact aperture diameter Dp of each stacked aperture impact point.

[0092] In some embodiments, the center distance Scc is smaller than the equivalent impact aperture Dp. The overlap ratio Rol is defined by the following formula: Rol = (Dp - Scc) / Dp × 100%. The overlap ratio Rol can be expressed as a percentage and can be set within a general range to describe the degree of overlap, for example, it can be set to a range of 30% to 60% to cover configurations with different overlap densities; in specific embodiments, the overlap ratio Rol can also be adjusted according to the size of the target aperture profile 550, the equivalent impact size of the impact point 510, the material properties of the dielectric layer 120, or the laser stage capability, but the present invention is not limited thereto.

[0093] By defining the stacked aperture configuration area 500 with the center distance Scc and the stacked aperture ratio Rol, the subsequent laser burning path 590, the layer configuration (outer ring layer 520, middle ring layer 530, and central ring layer 540), and the number of shots per point, etc., can have a consistent geometric reference.

[0094] like Figure 6 As shown, in some embodiments of the present invention, the stacked hole configuration area 500 may be arranged in a concentric circle so that the stacked hole striking points 510 are distributed on the plane according to a predetermined contour and together form the target hole contour 550 corresponding to the deep blind hole 300.

[0095] Specifically, the stacked hole configuration area 500 may include an outer ring layer 520, a middle ring layer 530, and a central ring layer 540. The outer ring layer 520 may have more stacked hole impact points 510 than the middle ring layer 530, while the central ring layer 540 may include a central stacked hole impact point 510 located at the center of the circle, so as to form a ring distribution from the outside to the inside.

[0096] In this architecture, the stacked hole striking points 510 of the outer ring layer 520 can be used to define the outer periphery of the target hole outline 550 (the range of the outer ring layer 520 extends beyond the opening 210 of the substrate 100), the stacked hole striking points 510 of the middle ring layer 530 can be used to supplement the striking coverage of the middle area, and the stacked hole striking points 510 of the center ring layer 540 can be used to strike the central area of ​​the hole; the distribution, arrangement, and number of stacked hole striking points 510 of each ring can be adjusted according to actual design requirements, and the present invention is not limited thereto. For example, the middle ring layer 530 can be more than just... Figure 6 The layer shown can also be multiple layers, such as 2 to 5 inner ring layers.

[0097] To facilitate the description of the layered hole stacking layout, the total number of multiple hole stacking impact points 510 in the hole stacking configuration area 500 can be defined as N, and N can be the sum of the number of hole stacking impact points 510 in each layer. In some embodiments, N can be on the order of tens, for example, less than 50 (preferably less than 40, more preferably less than 35), to define a hole stacking configuration area for a large blind hole or deep blind hole; in other embodiments, N can also be increased or decreased depending on the size of the target hole profile 550, the hole stacking rate Rol, and the center distance Scc, and can be adjusted in conjunction with the point distribution of the outer layer 520, the middle layer 530, and the central layer 540. By defining the hole stacking configuration area 500 in a layered layout, the laser burning path 590 can be configured with impact positions sequentially along the hole stacking impact points 510 of each layer, and the subsequent two-stage laser independent variable sets can perform segmented action on each hole stacking impact point 510 under the same hole stacking configuration area 500.

[0098] In some embodiments of the present invention, when the number of pulses for each stacked hole impact point 510 is set to n in a certain laser independent variable group, the "number of pulses n" refers to the number of pulses emitted by the laser beam at the position of the stacked hole impact point 510; therefore, if the stacked hole configuration area 500 contains a total of N stacked hole impact points 510, the total number of pulses under the same laser independent variable group can correspond to N×n, rather than completing the processing by firing only one pulse at the entire target hole outline 550.

[0099] For example, when the number of shots per point n is set to 1, it means that one shot is fired at each of the stacked hole impact points 510; if N is on the order of tens, the total number of shots will be tens, and each firing position is distributed on the stacked hole impact points 510 corresponding to the outer ring layer 520, the middle ring layer 530 and the center ring layer 540.

[0100] Conversely, when the number of shots per point n is set to multiple shots (e.g., more than ten to dozens of shots), it means that multiple pulses are repeatedly applied to each stacked hole strike point 510, and the total number of shots increases accordingly.

[0101] Furthermore, in some embodiments, the laser burning sequence can be configured along the burning path 590, which can be a sequence of striking the stacked holes 510 of the outer ring layer 520, and then striking the middle ring layer 530 and the central ring layer 540 as needed; or the central ring layer 540 can be struck first, and then extended outward to the middle ring layer 530 and the outer ring layer 520, forming a striking sequence from the inside out or from the outside in, but the present invention is not limited to this.

[0102] Based on the above definitions, "number of shots per point" and "total number of stacked hole impact points" can be used as basic quantitative units to describe the laser burning process behavior. This will facilitate further explanation in subsequent paragraphs of how the two-stage laser independent variable set applies different shot configurations to each stacked hole impact point 510 to form the second hole wall section 320 and define the transition interface 330.

[0103] In some embodiments of the present invention, the laser burning process in step S140 can be carried out in a two-stage laser variable configuration, that is, the first laser variable group and the second laser variable group are applied sequentially to each stacked hole impact point 510 in the stacked hole configuration area 500 to remove the residual medium layer 121 under the same target hole contour 550 and form the second hole wall section 320.

[0104] The first laser independent variable set can be used in the initial removal stage, and may include the first stage energy E1, the first stage pulse width PW1, and the number of shots per point n1 in the first stage; wherein the first stage energy E1 and the first stage pulse width PW1 can be relatively large, while the number of shots per point n1 in the first stage can be relatively small, such as setting it to fire one shot (n1=1) or a few shots at each stacked hole impact point 510, so that the laser beam sequentially performs initial impact configuration on the stacked hole impact points 510 of the outer ring layer 520, the middle ring layer 530, and the central ring layer 540 along the burning path 590.

[0105] The second laser independent variable group is used in the hole-repairing stage. Its independent variables may include the second-stage energy E2, the second-stage pulse width PW2, and the number of shots per point n2 in the second stage. The second-stage pulse width PW2 may be shorter than the first-stage pulse width PW1, and the number of shots per point n2 in the second stage may be more than the number of shots per point n1 in the first stage. For example, it may be set to fire more than ten to dozens of shots at each stacked hole impact point 510, so that after the initial removal is completed, the area corresponding to each stacked hole impact point 510 can be further repaired.

[0106] In this two-stage configuration, the first and second laser independent variable groups can act sequentially on the same stacked hole configuration area 500. Alternatively, different action sequences can be used between the layers according to design requirements. For example, the first stage of impact can be performed on the central layer 540 and the middle layer 530, followed by the first stage of impact on the outer layer 520, and then the second stage of impact can be performed sequentially thereafter. The action sequence can be adjusted according to the actual equipment control and hole design, but the present invention is not limited thereto.

[0107] By using a two-stage laser independent variable component for separate configuration, laser burn-around processing can simultaneously achieve the controllability of initial removal and subsequent hole repair in the stacked hole configuration area 500, and also helps to define the formation of the second hole wall section 320.

[0108] The number of shots per point n2 in the second stage can be set to a relatively high value, and the pulse width PW2 in the second stage can be set to a relatively short value, so that the second stage of hole repair can apply more pulses to the area corresponding to the stacked hole strike point 510.

[0109] The number of shots per point n2 in the second stage can be reduced from a relatively high value to a relatively low value (e.g., from tens of shots to more than ten shots) to reduce the degree of repetitive action in the second stage of hole repair. At the same time, the energy E1 in the first stage can be relatively increased or adjusted to increase the removal load of the residual medium layer 121 in the initial removal stage, thereby reducing the load of the second stage of hole repair.

[0110] In some embodiments of the present invention, the second laser independent variable group in the two-stage laser independent variable configuration may adopt a shorter second-stage pulse width PW2 (e.g., a short pulse width on the order of microseconds) and be paired with a higher second-stage pulse count n2 to repair the area corresponding to the stacked hole impact point 510. Because the second-stage pulse width PW2 is significantly shortened, the equivalent energy acting on the surface of the substrate 100 may be attenuated relative to the first-stage energy E1 during actual processing.

[0111] Specifically, a relative energy ratio kE can be defined, let kE = E2 / E1, to characterize the proportional relationship between the second energy segment E2 and the first energy segment E1. In some embodiments, the relative energy ratio kE may fall in the range of 0.2 to 0.5; in more specific embodiments, the relative energy ratio kE may fall in the range of 0.3 to 0.4, but the present invention is not limited thereto.

[0112] like Figure 6 As shown, in some embodiments of the present invention, laser beam burning can use a laser shield 560 (also called a Mask) as a component in the optical path of the machine tool to define the opening range through which the laser beam passes. The laser shield 560 can be an annular component having a shielding hole 561 located in the central region of the laser shield 560, and the diameter of the shielding hole 561 can be defined as the shielding hole diameter Dms (i.e., Mask Size). The unit of the shielding hole diameter Dms can be millimeters (mm), used to characterize the geometric dimensions of the shielding hole 561; for example, in some embodiments, the shielding hole diameter Dms can be approximately 1 mm to 4 mm, but the present invention is not limited thereto.

[0113] In some embodiments, the laser beam may first pass through the shielding hole 561, then be guided by the reflected light path inside the machine, and finally projected onto the processing area corresponding to the opening 210 of the substrate 100 to burn the stacked hole impact point 510 in the stacked hole configuration area 500, but is not limited to this. The above-mentioned definitions of laser shielding 560 and shielding hole diameter Dms can be used as one of the common background parameters for subsequently describing the independent variables of laser burning (e.g., energy, pulse width, number of shots) and the stacked hole configuration area 500 (e.g., stacking ratio Rol, center distance Scc, ring layout).

[0114] In some embodiments of the present invention, the laser-spun hole configuration area 500 may include a hole overlap ratio Rol, a center distance Scc between adjacent hole impact points 510, a total number N of hole impact points 510, and a concentric ring layout (outer ring 520, middle ring 530, and central ring 540). The hole overlap ratio Rol can be represented by a percentage to indicate the degree of overlap and is set within a general range (e.g., 30% to 60%). The center distance Scc can be considered as a geometric distance parameter corresponding to the hole overlap ratio Rol. The total number of hole impact points N can be on the order of tens (e.g., less than 30) or other feasible ranges. The concentric ring layout can adopt a two-ring, three-ring, or more-ring configuration, and the point allocation of each ring can be adjusted according to the target hole profile 550 size and the hole overlap ratio Rol.

[0115] Regarding the configuration of two-stage laser independent variables, it may include the first stage energy E1, the first stage pulse width PW1, the number of shots per point in the first stage n1, and the second stage energy E2, the second stage pulse width PW2, and the number of shots per point in the second stage n2.

[0116] The number of shots per point in the first segment, n1, can be set to a relatively small number (1 shot or a few shots per point), and the number of shots per point in the second segment, n2, can be set to a relatively large number (e.g., more than ten to dozens of shots), and the pulse width PW2 of the second segment should be shorter than the pulse width PW1 of the first segment.

[0117] In some embodiments of the present invention, laser burning can be performed in a layered stacked aperture configuration area 500 with a stacked aperture ratio Rol of approximately 35% for laser burning of deep blind apertures; or a stacked aperture ratio Rol of approximately 50% can be used. The laser beam can pass through a laser shield 560 shielding aperture 561, and the shielding aperture diameter Dms can be set to 1-4 mm, preferably 2-3 mm. Laser burning adopts a two-stage independent variable configuration, including a first stage laser independent variable group (E1, PW1, n1) and a second stage laser independent variable group (E2, PW2, n2), and is applied sequentially to each stacked aperture striking point 510 in the stacked aperture configuration area 500. The first stage laser independent variable group can be used for the initial removal stage, wherein the first stage energy E1 can be 2-6 mJ, preferably 3-5 mJ; the first stage pulse width PW1 can be 2-6 μs, preferably 3-5 μs; the number of shots per point in the first stage n1 can be 1-3 shots, and in the above embodiments it can be 1 shot. The second laser independent variable group can be used in the hole-repairing stage. The pulse width PW2 of the second segment can be 0.5 to 2 μs, and preferably 0.8 to 1.2 μs; the number of shots per point n2 of the second segment can be 10 to 40, and preferably 15 to 30. The relative energy ratio kE = E2 / E1 can be 0.2 to 0.5, and preferably 0.3 to 0.4, but the present invention is not limited thereto.

[0118] By introducing a stacked hole configuration region 500 (including a concentric layout of stacked hole impact points 510, and the geometric definitions of the stacked hole ratio Rol and center distance Scc) in the laser winding process in step S140, and in conjunction with a two-stage laser independent variable set (the first stage of independent variables is used for initial removal, and the second stage of independent variables is used for hole finishing), the impact position, impact density, and number of shots per point of the laser winding process can have a clear geometric reference and an adjustable set of parameters. Especially in the second stage of hole finishing, if the number of shots per point n2 in the second stage is set too high, the hole finishing action is likely to be concentrated near the bottom of the hole 340, which may cause the hole wall contour to be over-eaten or bent. In contrast, in the preferred embodiment, by reducing the number of shots per point n2 in the second stage and adjusting the energy E1 or its configuration in the first stage, the initial removal stage can bear a larger material removal load, thereby reducing the degree of over-finishing in the second stage of hole finishing.

[0119] [Beneficial Effects of the Examples]

[0120] The method of this invention improves the processing efficiency of large blind holes by mechanically drilling holes at the opening of copper windows to form a first hole wall section, and then using laser burning to form a second hole wall section. It can reduce the uncertainty of residual material at the bottom of the hole. By dividing and configuring the medium material removal methods, the hole wall morphology and subsequent electroplating controllability can still be maintained under the condition of high aspect ratio for deep and large blind holes, while improving the overall processing efficiency at the same time.

[0121] The above description is only a preferred embodiment of the present invention and is not intended to limit the patent scope of the present invention. All equivalent technical changes made based on the description and drawings of the present invention are included within the protection scope of the present invention.

Claims

1. A method for forming deep blind holes, characterized in that, The method includes: A substrate is provided, comprising an outer conductive layer, a dielectric layer and a target conductive layer, wherein the dielectric layer is disposed between the outer conductive layer and the target conductive layer; The step of opening a copper window includes: forming a copper window on the outer conductive layer to define an opening on the surface of the substrate, the opening having a copper window aperture Dcw, and exposing the dielectric layer at the copper window. A mechanical drilling step includes: aligning a mechanical drill bit with a drilling diameter of Dm with the copper window, performing blind drilling within the dielectric layer, and controlling the mechanical drill bit to descend along the hole depth direction at a predetermined drilling depth to form a first hole wall section extending along the hole depth direction, while leaving a residual dielectric layer at the bottom of the hole to cover the target conductive layer; and A laser burning-around step is performed, comprising: using a laser beam to burn-around the residual dielectric layer through the first hole wall section to remove the residual dielectric layer and form a second hole wall section located below the first hole wall section along the hole depth direction, thereby exposing the target conductive layer at the bottom of the hole; wherein the first hole wall section and the second hole wall section together define the deep blind hole.

2. The method according to claim 1, characterized in that, The borehole diameter Dm is not less than the copper window aperture Dcw.

3. The method according to claim 1, characterized in that, The mechanical drill bit used in the mechanical drilling step is a flathead drill.

4. The method according to claim 1, characterized in that, The dielectric layer has a dielectric layer thickness Td at the copper window, and the predetermined drilling depth of the mechanical drilling step is 60% to 75% of the dielectric layer thickness Td.

5. The method according to claim 4, characterized in that, The residual dielectric layer has a residual thickness Tr, and the residual thickness Tr is 25% to 33.3% of the dielectric layer thickness Td.

6. The method according to claim 1, characterized in that, The aperture Dcw of the copper window is 300μm to 500μm.

7. The method according to claim 1, characterized in that, The laser winding process involves scanning the laser beam relative to the center of the opening using a spiral trajectory or a concentric circle trajectory.

8. The method according to claim 6, characterized in that, The ratio of the depth of the deep blind hole to the diameter of the copper window hole is greater than 1.0, and the ratio of the bottom diameter of the deep blind hole to its opening diameter is not less than 0.

80.

9. The method according to claim 1, characterized in that, The first hole wall section forms a hole wall region that is basically straight along the hole depth direction, and the second hole wall section forms a hole wall region with a taper along the hole depth direction. The first hole wall section has a first hole diameter change rate, and the second hole wall section has a second hole diameter change rate that is greater than the first hole diameter change rate.

10. The method according to claim 1, characterized in that, The method includes electroplating the deep blind hole after the laser winding step to form a conductive plating layer on the hole wall of the deep blind hole.

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