Silica-containing substrate with vias having axially variable sidewall taper

Abstract

A method for forming a via with an axially variable sidewall taper and a silica-containing substrate incorporating such a via are provided. The silica-containing substrate (100) includes 85 mole % or more silica, a first side (102), a second side (104) opposite the first side, and a via (110) extending through the silica-containing substrate from the first side toward the second side, the via (110) having a first diameter (D1) of 100 μm or less at the first side (102), a second diameter (D2) of 100 μm or less at the second side (104), and a via body between the first and second sides. The via body has a body diameter (Dw) that is smaller than the first diameter (D1) and the second diameter (D2) such that a ratio between the body diameter (Dw) and each of the first diameter (D1) and the second diameter (D2) is 75% or less.

Description

Priority

[0001] This application claims the benefit of priority under U.S.C. Title 35, Section 119 of U.S. Provisional Patent Application No. 62 / 510957, filed on 25 May 2017, and U.S. Provisional Patent Application No. 62 / 588615, filed on 20 November 2017. [Technical Field]

[0002] This disclosure broadly relates to silica-containing substrates with vias. More specifically, this disclosure relates to silica-containing substrates containing at least 75 mol% silica, having vias having axially variable sidewall taper; electronic devices incorporating the silica-containing substrate with vias; and methods for forming vias having axially variable sidewall taper within a silica-containing substrate. [Background technology]

[0003] Substrates such as silicon have been used as interposers, placed between electrical components (e.g., printed circuit boards, integrated circuits, etc.). Metallized through-vias provide pathways through the interposer for electrical signals to pass between the two sides of the interposer. Glass substrates are extremely attractive materials for electrical signal transmission due to their excellent thermal dimensional stability with a low coefficient of thermal expansion (CTE), as well as their very good low electrical loss at high-frequency electrical performance, and the possibility of forming them in thickness and large panel sizes. Specifically, high silica content substrates such as fused silica are even more attractive than general-purpose glass because the CTE of fused silica can be extremely low (about 0.5 ppm / °C), and the dielectric loss tangent can often be even lower than in glass containing a considerable proportion of non-silica material. However, the formation and metallization of through-vias in high silica content substrates present significant challenges.

[0004] Vias may be filled by an electroplating process in which a conductive material (e.g., copper) is deposited on the sidewalls of the via, continuously accumulating until the via is sealed. Electroplating a via requires an hourglass shape with a narrow body that provides a metal "bridge" for the initial deposition of the conductive material. The conductive material is then continuously deposited on both sides of this bridge until the via is filled.

[0005] Small vias, which lead to electrical connections within the glass interposers of electronic devices, can be formed by a laser damage-etching process. In this process, a damage trajectory is first formed on the glass substrate by using a laser to modify the glass material along the trajectory. Next, an etching solution is applied to the glass substrate. This glass substrate is thinned by the etching solution. Since the etching rate of the glass material is faster along the damage trajectory, the damage trajectory is preferentially etched so that a via can be created by penetrating the glass substrate. In most glass materials, the via shape is selectively hourglass-shaped to facilitate electroplating. However, in silica-containing substrates with a high silica content, such as fused silica, the resulting vias are cylindrical, lacking a narrow body to provide a metal bridge during the electroplating process. Such straight walls in fused silica cannot be electroplated. [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Therefore, there is a need for an alternative method for forming vias having axially variable sidewall taper (e.g., hourglass shape) in a silica-containing substrate, as well as a silica-containing substrate incorporating such vias. [Means for solving the problem]

[0007] A method for processing a substrate, including silica, a first surface and a second surface opposite to the first surface, comprises the step of using a laser beam to form a damage trajectory through the substrate from the first surface to the second surface, wherein the level of modification of the substrate along the damage trajectory decreases in a first direction starting from the first surface and toward the interior of the substrate, and the level of modification of the substrate decreases in a second direction starting from the second surface and toward the interior of the substrate. The damage trajectory includes a first modification segment adjacent to the first surface, a second modification segment adjacent to the second surface, and a third modification segment located between the first and second highly modified segments, wherein the level of modification of the third modification segment is less than the level of modification of the first and second modification segments. The method further comprises the step of using an etching solution to etch the substrate to form vias having via bodies having a first diameter on the first surface, a second diameter on the second surface, and a body diameter between the first and second surfaces, wherein the body diameter is less than the first diameter and less than the second diameter.

[0008] In another embodiment, the article comprises a silica-containing substrate comprising 85 mol% or more of silica, a first surface, a second surface opposite the first surface, and vias extending through the silica-containing substrate from the first surface toward the second surface. The vias have a first diameter on the first surface having a diameter of 100 μm or less, a second diameter on the second surface having a diameter of 100 μm or less, and a via body between the first surface and the second surface. The via body has a diameter smaller than the first and second diameters, such that the ratio of the diameter of the body to each of the first and second diameters is 75% or less.

[0009] In yet another embodiment, the electronic device comprises a silica-containing substrate comprising 85 mol% or more silica, a first surface, a second surface opposite the first surface, and vias extending through the silica-containing substrate from the first surface toward the second surface. The via has a first diameter on the first surface having a diameter of 100 μm or less, a second diameter on the second surface having a diameter of 100 μm or less, and a via body between the first surface and the second surface, wherein the via body has a diameter smaller than the first and second diameters, such that the ratio of the diameter of the body to each of the first and second diameters is 75% or less. The electronic device further comprises a semiconductor element coupled to the silica-containing substrate, the semiconductor element being electrically coupled to the via.

[0010] In yet another embodiment, the substrate includes 85 mol% or more silica, a first surface, a second surface opposite the first surface, and a damage trajectory that penetrates the substrate from the first surface to the second surface. The level of modification of the substrate along the damage trajectory decreases in a first direction starting from the first surface and toward the interior of the substrate, and the level of modification of the substrate decreases in a second direction starting from the second surface and toward the interior of the substrate. The damage trajectory includes a first modification segment adjacent to the first surface, a second modification segment adjacent to the second surface, and a third modification segment located between the first highly modified segment and the second highly modified segment.

[0011] In yet another embodiment, the article comprises a silica-containing substrate comprising 85 mol% or more of silica, a first surface, a second surface opposite the first surface, and vias extending through the silica-containing substrate from the first surface toward the second surface. The vias have a first diameter on the first surface having a diameter of 100 μm or less, a second diameter on the second surface having a diameter of 100 μm or less, and a via body between the first surface and the second surface. The via body has a diameter smaller than the first and second diameters such that the ratio of the difference between the first diameter and the diameter of the via relative to half the thickness of the silica-containing substrate is 1 / 15 or more.

[0012] Additional features and advantages of the embodiments described herein are set forth in the following detailed description, are in part readily apparent to those skilled in the art from the description, or will be recognized by practicing the embodiments described herein, which include the following detailed description, the claims, and the accompanying drawings.

[0013] Both the foregoing general description and the following detailed description are of various embodiments and are intended to provide an overview or framework for understanding the nature and characteristics of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments and are part of this specification. The drawings illustrate the various embodiments described herein and, together with the description, serve to explain the principles and operation of the claimed subject matter.

[0014] The embodiments shown in the drawings are, in fact, illustrative and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, in which like structures are indicated by like reference numerals.

Brief Description of the Drawings

[0015] [Figure 1] Partial perspective view of a silica-containing substrate as an interposer, according to one or more embodiments described and illustrated herein [Figure 2] Schematic diagram of an exemplary electronic device including a silica-containing substrate as an interposer disposed between electronic devices, according to one or more embodiments described and illustrated herein [Figure 3] Schematic diagram showing dimensional features of an exemplary via through a silica-containing substrate, according to one or more embodiments described and illustrated herein [Figure 4A] Schematic diagram showing the progress of formation of an exemplary via through a silica-containing substrate, according to one or more embodiments described and illustrated herein [Figure 4B] Schematic diagram following FIG. 4A [Figure 4C] Schematic diagram following FIG. 4B [Figure 4D] Schematic diagram following FIG. 4C [Figure 4E] Schematic diagram following FIG. 4D [Figure 5] Schematic diagram showing a method of forming a damage track in a silica-containing substrate by scanning a laser spot through the interior of the silica-containing substrate while adjusting the intensity of the laser spot, according to one or more embodiments described herein and illustrated [Figure 6] Schematic diagram showing a method of forming a damage track in a silica-containing substrate by using a pulsed laser beam focused on a laser beam focal line positioned within the silica-containing substrate, according to one or more embodiments described herein and illustrated [Figure 7] Schematic diagram showing sub-pulses of the pulsed laser beam shown in FIG. 6, according to one or more embodiments described herein and illustrated [Figure 8] Schematic diagram showing sub-pulses of the pulsed laser beam shown in FIG. 6, according to one or more embodiments described herein and illustrated [Figure 9A] Graph showing the intensity profile of the Gaussian Bessel laser beam focal line of FIG. 6, with maximum intensity positioned at various locations within the silica-containing substrate, according to one or more embodiments described herein and illustrated [Figure 9B] Graph showing the intensity profile of the Gaussian Bessel type laser beam focal line of FIG. 6, with maximum intensity positioned at various locations within the silica-containing substrate, according to one or more embodiments described herein and illustrated [Figure 9C] Graph showing the intensity profile of the Gaussian Bessel type laser beam focal line of FIG. 6, with maximum intensity positioned at various locations within the silica-containing substrate, according to one or more embodiments described herein and illustrated [Figure 10A] The graph showing the intensity profile of one on the laser beam focal line shown in FIG. 6, according to one or more embodiments described herein and illustrated [Figure 10B]A graph showing a different intensity profile on the laser beam focal line shown in Figure 6, according to one or more embodiments described and illustrated herein. [Figure 11A] Digital images of damage trajectories in a silica-containing substrate according to one or more embodiments described and illustrated herein. [Figure 11B] Digital images of damage trajectories in a silica-containing substrate according to one or more embodiments described and illustrated herein. [Figure 11C] Digital images of damage trajectories in a silica-containing substrate according to one or more embodiments described and illustrated herein. [Figure 12] Digital images of hourglass-shaped vias in a silica-containing substrate formed by a laser damage etching process, according to one or more embodiments described and illustrated herein. [Figure 13A] Histogram showing the distribution of the first diameter of vias in a silica-containing substrate formed by a laser damage etching process according to one or more embodiments described and illustrated herein. [Figure 13B] Histogram showing the distribution of the second diameter of vias in a silica-containing substrate formed by a laser damage etching process according to one or more embodiments described and illustrated herein. [Figure 13C] Histogram showing the distribution of via body diameters in a silica-containing substrate formed by a laser damage etching process according to one or more embodiments described and illustrated herein. [Figure 14A] Histogram showing the distribution of roundness with respect to the first diameter of vias in a silica-containing substrate formed by a laser damage etching process, according to one or more embodiments described and illustrated herein. [Figure 14B] Histogram showing the distribution of roundness with respect to the second diameter of vias in a silica-containing substrate formed by a laser damage etching process, according to one or more embodiments described and illustrated herein. [Figure 14C]Histogram showing the distribution of roundness with respect to the diameter of the via body in a silica-containing substrate formed by a laser damage etching process, according to one or more embodiments described and illustrated herein. [Figure 15A] Histogram showing body defects for samples laser-processed using a laser beam focal line at four different burst energies and three different focus settings, according to one or more embodiments described and illustrated herein. [Figure 15B] Histogram showing all defects for samples laser-processed using a laser beam focal line at four different burst energies and three different focus settings, according to one or more embodiments described and illustrated herein. [Figure 16A] Histograms showing via body variation across samples laser-processed using laser beam focals at four different burst energies and three different focus settings, according to one or more embodiments described and illustrated herein. [Figure 16B] Histograms showing via body variation across samples laser-processed using laser beam focals at four different burst energies and three different focus settings, according to one or more embodiments described and illustrated herein. [Figure 16C] Histograms showing via body variation across samples laser-processed using laser beam focals at four different burst energies and three different focus settings, according to one or more embodiments described and illustrated herein. [Modes for carrying out the invention]

[0016] By broad reference to the drawings, embodiments of the present disclosure generally relate to articles comprising silica-containing substrates having vias (e.g., pores) capable of successfully undergoing post-processing processes including via metallization / electroplating and application of redistribution layers (RDLs), but are not limited to the following. These articles can be used in semiconductor devices, radio frequency (RF) devices (e.g., antennas, electronic switches, etc.), interposer devices, microelectronic devices, optoelectronic devices, microelectromechanical systems (MEMS) devices, and other applications where vias can be utilized.

[0017] Embodiments of this disclosure also relate, in general, to methods for forming vias in a silica-containing substrate. In some embodiments, the vias have an external shape that facilitates electroplating of the vias. Silica-containing substrates include glass and glass ceramics. As used herein, the term “silica-containing substrate” means a silica-containing substrate having a silica (SiO2) content of 75 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, 91 mol% or more, 92 mol% or more, 93 mol% or more, 94 mol% or more, 95 mol% or more, 96 mol% or more, 97 mol% or more, 98 mol% or more, 99 mol% or more, or 99.9 mol% or more. In some embodiments, the silica-containing substrate may be fused silica. Exemplary silica-containing substrates include, but are not limited to, HPFS® fused silica, sold by Corning Incorporated, Corning, New York, under glass codes 7980, 7979, and 8655. In one example, a silica-containing substrate is a substrate containing unintentionally doped silica. The phrase "unintentionally doped" means that no additional components were intentionally added to the silica before it was melted.

[0018] Due to the properties of silica, it is a desirable substrate for use as an interposer in electronic devices. The term “interposer” generally refers to any structure that extends or completes an electrical connection between two or more electronic devices that penetrate the structure, for example, but are located on both sides of the interposer. These two or more electronic devices may be located in the same location within a single structure, or adjacent to each other within different structures, so that the interposer functions as part of an interconnection nodule, etc. Thus, the interposer may contain one or more active areas where vias and other interconnection conductors (e.g., power, ground, and signal conductors) are present and formed. The interposer may also contain one or more active areas where blind vias are present and formed. When the interposer is formed together with other components such as dies, underfill material, and encapsulant, the interposer may be referred to as an interposer assembly. The term “interposer” may also further include multiple interposers, such as an array of interposers.

[0019] Due to silica's low coefficient of thermal expansion (CTE), expansion and movement of the silica-containing substrate due to the application of heat flux, such as the heat flux generated by the semiconductor element bonded to the silica-containing substrate acting as an interposer, is minimized. Expansion of the interposer due to a mismatch in CTE between the interposer and the semiconductor element (or other electronic component) can break the bond between the interposer and the semiconductor element, leading to separation or other damage.

[0020] In addition, silica-containing substrates offer desirable RF characteristics that surpass those of other substrates such as silicon. These desirable RF characteristics are important for high-frequency applications such as high-speed data communication.

[0021] Therefore, silica-containing substrates containing 75 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, 95 mol% or more, or 99 mol% or more of silica (SiO2) would be desirable materials for interposers in certain electronic devices. However, the use of silica-containing substrates presents challenges when a specific via shape, including hourglass-shaped vias, is desired, although this is not limited to the following. Hourglass-shaped vias facilitate the metallization of vias by an electroplating process. During the electroplating process, a conductive material (e.g., copper, silver, aluminum, titanium, gold, platinum, nickel, tungsten, magnesium, or any other suitable material) is deposited within the via. Hourglass-shaped vias have a narrow body with a diameter smaller than the diameter of the opening on the interposer surface. During the electroplating process, the deposited metal first forms a metal bridge at the location of the body, and then more metal is deposited on the bridge to complete the via filling, enabling airtight, gap-free filling of the via.

[0022] Laser damage etching techniques are sometimes used to form vias in silica-containing materials. However, conventional laser damage etching techniques used to form vias in silica-containing substrates as defined herein result in substantially cylindrical vias (i.e., vias with substantially straight walls). Therefore, electroplating of vias formed in silica-containing substrates using conventional techniques would not be possible due to the lack of ability to form narrow bodies and metal bridges. The inability to produce vias with narrow bodies in silica-containing substrates is likely due to the slow etching rate of hydrofluoric acid and the absence of insoluble byproducts in the etching process that clog or inhibit etching in the central part of the substrate, resulting in differences in etching rates between the surface and deeper parts of the silica-containing substrate. It should be noted that the method disclosed herein is not limited to silica-containing substrates containing 75 mol% or more of silica (SiO2). The method disclosed herein may also be used for glass or glass-ceramic substrates containing less than 75 mol% silica. For example, the method described herein may also be used to form narrow vias in glass or glass-ceramic substrates having less than 75 mol% silica (SiO2), such as Eagle XG® glass and Gorilla® Glass, sold by Corning Incorporated.

[0023] The embodiments described herein relate to articles and methods comprising a silica-containing substrate having vias formed by a laser damage-etching process, including a specific inner wall shape such as an inner wall having multiple regions, each having a unique angle, thereby defining an hourglass shape. The embodiments provide high-quality hourglass-shaped vias in a silica-containing substrate that are practically and reliably formed. Various embodiments of articles, semiconductor packages, and methods for forming vias having a narrow body in a substrate are described in detail below.

[0024] Referring here to Figure 1, an exemplary article comprising a silica-containing substrate 100 is schematically shown in a partial perspective view. The silica-containing substrate 100 has a first surface 102 and a second surface 104 opposite to the first surface 102. Multiple vias 110 extend through the silica-containing substrate 100 from the first surface 102 to the second surface 104. It should be understood that any number of vias 110 may extend through the silica-containing substrate 100 in any arrangement. The thickness t of the silica-containing substrate 100 may be any appropriate thickness depending on the application. As a non-limiting example, the thickness t of the silica-containing substrate may be in the range of 50 μm to 1 mm including the endpoints, in the range of 100 μm to 700 μm including the endpoints, in the range of 100 μm to 500 μm including the endpoints, or in the range of 250 μm to 500 μm including the endpoints.

[0025] The pitch of the vias 110 is the center-to-center distance between adjacent vias 110, and the pitch may be any dimension according to the desired application, such as approximately 10 μm to approximately 2,000 μm, including approximately 10 μm, approximately 50 μm, approximately 100 μm, approximately 250 μm, approximately 1,000 μm, approximately 2,000 μm, or any value or range (including endpoints) between any two of these values. In some embodiments, the pitch may vary between vias 110 on the same silica-containing substrate 100 (i.e., the pitch between a first via and a second via may differ from the pitch between a first via and a third via). In some embodiments, the pitch may be in the range of approximately 10 μm to approximately 100 μm, approximately 25 μm to approximately 500 μm, approximately 10 μm to approximately 1,000 μm, or approximately 250 μm to approximately 2,000 μm.

[0026] The silica-containing substrate 100 may be an interposer for an electronic device 200, as schematically shown in Figure 2. The non-limiting electronic device 200 schematic in Figure 2 comprises a first electrical component 201 coupled to a first surface 102 of the silica-containing substrate 100 and a second electrical component 203 coupled to a second surface 104 of the silica-containing substrate 100. The first electrical component 201 and the second electrical component 203 may be made as any type of electrical component, such as a semiconductor element, substrate, power supply, or antenna, without limitation. The silica-containing substrate 100 comprises a plurality of metallized vias 110 that electrically couple the first electrical component 201 to the second electrical component 203, allowing electrical signals and / or power to pass between them.

[0027] An exemplary conductive via 110 penetrating a silica-containing substrate 100 having an hourglass-shaped profile is schematically shown in Figure 3. The via 110 has a first diameter D1 on the first surface 102 and a second diameter D2 on the second surface 104. The exemplary via 110 has a longitudinal axis LA along the length of the via 110, an inner wall 111, and a body diameter D which is the minimum diameter of the via 110. w It further includes a body w having a diameter D of the body. w is smaller than both the first diameter D1 and the second diameter D2. As a non-limiting example, the profile of via 110 is such that the diameter of the body D wHowever, the first diameter D1 and the second diameter D2 are less than 75%, less than 65%, less than 60%, less than 55%, less than 50%, less than 50%, less than 45%, less than 40%, less than 35%, less than 30%, less than 25%, less than 20%, less than 15%, less than 10%, or less than 5%. Furthermore, as etching time decreases, the holes from the two surfaces fail to connect, resulting in "blind" vias. These blind vias are vias that terminate inside the substrate. As a non-limiting example, the first diameter D1 and the second diameter D2 after etching are within the range of 5 μm to 150 μm including the endpoint, 5 μm to 100 μm including the endpoint, 20 μm to 150 μm including the endpoint, 30 μm to 60 μm including the endpoint, or 40 μm to 50 μm including the endpoint. In some embodiments, the first diameter D1 and the second diameter D2 are 100 μm or less, 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. The first diameter D1 may or may not be equal to the second diameter D2.

[0028] The example via 110 in Figure 3 has four distinct tapered regions: a first tapered region 112, a second tapered region 113, a third tapered region 118, and a fourth tapered region 119. The example via 110 has four different taper angles: a first angle θ1, a second angle θ2, a third angle θ3, and a fourth angle θ4, corresponding to the first tapered region 112, the second tapered region 113, the third tapered region 118, and the fourth tapered region 119, respectively. The example via 110 is further characterized by four segment lengths: a first segment length L1 extending from the first surface 102 to the transition to the second tapered region 113; a second segment length L2 extending from the transition between the first tapered region 112 and the second tapered region 113 to the body w; a third segment length L3 extending from the body w to the transition between the third tapered region 118 and the fourth tapered region 119; and a fourth segment length L4 extending from the transition between the third tapered region 118 and the fourth tapered region 119 to the second surface 104.

[0029] The first to fourth segment lengths L1 to L4 may be any suitable length and are not limited by this disclosure. In the example in Figure 3, each of the four segment lengths is different from one another. However, embodiments are not limited thereto. For example, the first segment length L1 may be equal to the fourth segment length L4, and / or the second segment length L2 may be equal to the third segment length L3.

[0030] Note that the taper angles shown in Figure 3 are measured between each reference line parallel to the vertical axis LA and the inner wall 111 of the via 110. The first angle θ1 is measured from the inner wall 111 of the first tapered region 112 to the vertical axis LA. The second angle θ2 is measured from the inner wall 111 of the second tapered region 113 to the vertical axis LA. The third angle θ3 is measured from the inner wall 111 of the third tapered region 118 to the vertical axis LA. The fourth angle θ4 is measured from the inner wall 111 of the fourth tapered region 119 to the vertical axis LA.

[0031] The angle of the via 110 with respect to the vertical axis LA can be determined by forming a trace line TL that coincides with the contour of the inner wall 111 of a particular tapered region. The trace line can then be analyzed to determine the gradient of one or more portions of the inner wall 111 (including various tapered regions 112, 113, 118, 119). For example, as shown in Figure 3, the trace line TL is illustrated, and one or more linear regions of the trace line TL are determined using the computer software described herein. A linear region is defined as follows: (1) the length of the region is 5 μm or more, and generally may be greater than 10 μm; (2) the region can be fitted to a linear function (y = a + bx), where y is the radius of the hole and x is the depth of the substrate, and the absolute value of the fitting residual is less than 1 μm; and (3) the gradients of the fitting functions of any adjacent regions should differ by at least 0.01, which translates to a difference of 0.57 degrees with respect to the taper angle. A region that satisfies all the criteria described above is called a region with a constant gradient (i.e., a linear region). As shown in Figure 3, the trace line TL has four distinct linear regions: the region between points A and B, the region between points B and C, the region between points C and D, and the region between points D and E. Thus, the gradients of the regions between points A and B, between points B and C, between points C and D, and between points D and E are constant. However, there may be regions of the trace line TL surrounding each of points A, B, C, D, and E that have a non-constant gradient. These regions may be transitional regions between regions with a constant gradient, as will be described in more detail here. Such regions may occur when there is a stepwise transition between tapered regions.

[0032] Transition zones between each gradient of the tapered region will occur in any case where the constant-gradient region of the inner wall 111 ends. Briefly referring to Figure 12, a via 510 formed in a silica-containing substrate is illustrated, including a first tapered region 512 between points A and B, a second tapered region 513 between points C and D, a third tapered region 518 between points E and F, and a fourth tapered region 519 between points G and H. The exemplary via 510 has transition zones with non-constant gradients, which are the regions of the trace lines 1415 between points B and C, between points D and E, and between points F and G. In some embodiments, the gradient of the transition zone differs from the gradient of the constant-gradient region by only about 0.57 degrees or more, about 1 degree or more, about 2 degrees or more, about 3 degrees or more, about 4 degrees or more, or about 5 degrees or more.

[0033] As previously mentioned, the constant slope of each tapered region may be defined by the angle of the via with respect to the longitudinal axis LA. This longitudinal axis LA is approximately perpendicular to the first surface 102 and / or the second surface 104. Referring again to Figure 3, the first angle θ1 and the fourth angle θ4 are smaller than the second angle θ2 and the third angle θ3, respectively, due to the strongly modified material adjacent to the first surface 102 and the second surface 104 of the silica-containing substrate 100, and the less modified material in the internal regions of the silica-containing substrate 100. Not limited, but as an example, each of the first angle θ1 and the fourth angle θ4 may be less than 5 degrees, for example, within the range of greater than 0 to 5 degrees, greater than 0 to 4 degrees, greater than 0 to 3 degrees, greater than 0 to 2 degrees, 1 to 5 degrees, 1 to 4 degrees, 1 to 3 degrees, 1 to 2 degrees, 2 to 5 degrees, 2 to 4 degrees, 2 to 3 degrees, or 4 degrees, 3 degrees, 2 degrees, or 1 degree. In the example in Figure 3, each of the taper angles is different from one another. However, the embodiments are not limited thereto. For example, the first angle θ1 and the fourth angle θ4 may be equal to each other, and / or the second angle θ2 and the third angle θ3 may be equal to each other.

[0034] As mentioned earlier, the body w has a minimum diameter (D w This is the region of a via having ). The via 110 that penetrates the substrate as described herein is given by the following relationship:

[0035]

number

[0036] It may be characterized by the ratio of the difference between the first diameter (or second diameter) and the diameter of the body to half the thickness of the silica-containing substrate being 1 / 15 or greater, as given in the example.

[0037] The vias 110 may be filled with a conductive material by any known or undeveloped process, such as sputtering, electroplating, or paste filling. The conductive material may be any suitable material, without limitation, such as copper, silver, aluminum, titanium, gold, platinum, nickel, tungsten, or magnesium.

[0038] Referring here to Figures 4A-4E, the progress of the laser damage-etching process and the fabrication of vias 110 having axially variable sidewall tapers within a silica-containing substrate 100 having an initial thickness t1 is schematically shown. Referring to Figure 4A, a damage trajectory 120 is formed using a laser beam passing through the interior of the silica-containing substrate 100 from the first surface 102 to the second surface 104. Not limited to, but as an example, the damage trajectory 120 has a diameter of 1 μm or less. The laser beam modifies the material along the damage trajectory 120. As used herein, the terms “modify” or “alter” with respect to the silica-containing substrate mean a change in refractive index, a change in material density, melting, compression, ablation, or chemical alteration of the material. The modification may also include crack formation in the material to create microscopic cracks or voids that can facilitate the penetration of gaseous or liquid etchants. The laser beam forms the damage trajectory 120 such that the damage trajectory 120 has segments that give different etching properties. The level of modification in the silica-containing substrate 100 is strongest near the first surface 102 and the second surface 104, and decreases in the direction toward the interior of the silica-containing substrate 100 along the damage trajectory 120. The level of modification affects the etching rate of the silica-containing substrate 100. A higher level of modification results in a faster etching rate of the silica-containing substrate 100. In the embodiments described herein, the level of modification is determined by evaluating the damage trajectory 120 with a microscope in the presence of back illumination. In the presence of back illumination, the darker the material along the damage trajectory 120, the higher the level of modification. In the embodiments, the damage trajectory 120 appears darker near the surface of the silica-containing substrate 100 (i.e., the damage trajectory has a high level of modification in these segments) and brighter near the center of the silica-containing substrate 100 (i.e., the damage trajectory has a low level of modification in these segments compared to segments closer to the surface). Figure 11A, which will be described in more detail below, shows the various levels of material changes in the damage trajectory 120, 120', and 120'' of a silica-containing substrate 100 illuminated from the back, as observed by a microscope.

[0039] In the example in Figure 4A, the damage trajectory 120 includes four segments, each having a different level of modification and therefore different etching characteristics: the first modification segment 120A, the second modification segment 120B, the third modification segment 120C, and the fourth modification segment 120D. It should be understood that the levels of modification between the different segments do not have to be discontinuous. Rather, the levels of modification may change gradually along the damage trajectory 120. Therefore, the levels of modification may change within individual segments of the damage trajectory 120.

[0040] As previously stated, the damage trajectory 120 is constructed such that the highest level of modification occurs near the first surface 102 and the second surface 104 of the silica-containing substrate 100. Thus, the first modification segment 120A and the fourth modification segment 120D are the most modified segments. The second modification segment 120B and the third modification segment 120C are the least modified segments, in that they have a lower level of modification than the first modification segment 120A and the fourth modification segment 120D. Although the second modification segment 120B and the third modification segment 120C are shown as individual segments, in some embodiments, the second modification segment 120B and the third modification segment 120C are a single least modified segment having a lower level of modification than the first modification segment 120A and the fourth modification segment 120D.

[0041] Details regarding the laser beam characteristics used to form the damage trajectory are described below with respect to Figures 5-8.

[0042] After forming damage trajectories 120, the silica-containing substrate 100 is etched by applying an etching solution. In one example, the silica-containing substrate 100 is placed in a bath of etching solution. Alternatively, the etching solution may be sprayed onto the silica-containing substrate 100. The type of etching solution is not limited by this disclosure. Any known or undeveloped etching solution capable of etching a silica-containing substrate may be used. In one example, the etching solution contains hydrofluoric acid (HF) or sodium / potassium hydroxide. As a specific example, an etching solution for etching molten silica contains 20 vol% HF or 20 vol% HF and 20 vol% HCl at about 47°C, which gives an etching rate of about 0.005 μm / sec. The etching rate can be changed by adjusting the temperature (e.g., from 10°C to 50°C) and acid concentration. Other mineral acids, such as nitric acid (HNO3), may be used instead of HCl. Hydroxide etching agents such as sodium hydroxide (NaOH) and potassium hydroxide (KOH) may also be used.

[0043] As shown in Figure 4B, this etching solution removes material by etching from the first surface 102 and the second surface 104 of the silica-containing substrate 100 by an amount Δs. The damaged material within the strongly modified first segment 120A and fourth segment 120D of the damage trajectory 120 is etched at a faster rate than the undamaged area outside the damage trajectory 120. This faster etching rate by the damaged material causes a first pilot hole 115 to open on the first surface 102 and extend through the interior of the silica-containing substrate 100 along the first segment 120A of the damage trajectory, and a second pilot hole 117 to open on the second surface 104 and extend through the interior of the silica-containing substrate 100 along the fourth segment 120D of the damage trajectory. As shown in Figure 4C, the first pilot hole 115 and the second pilot hole 117 extend deeper into the interior of the silica-containing substrate 100, and the silica-containing substrate 100 becomes even thinner by an increase of Δs.

[0044] Referring to Figure 4D, as the silica-containing substrate 100 continues to etch, the diameter of the first pilot hole 115 increases, opening up to become the first tapered region 112, and the diameter of the second pilot hole 117 increases, opening up to become the fourth tapered region 119. The first surface 102 and the second surface 104 of the silica-containing substrate 100 are further thinned by an increase of Δs. By this time, the etching solution has reached the second segment 120B and the third segment 120C of the damage trajectory 120. The second segment 120B opens up to become the second tapered region 113, and the third segment 120C opens up to become the third tapered region 118. Since the level of material change is lower in the second segment 120B and the third segment 120C than in the first segment 120A and the fourth segment 120D, the etching rate is slower in the second segment 120B and the third segment 120C than in the first segment 120A and the fourth segment 120D. As shown in Figure 4D, due to the difference in the level of change along the damage trajectory 120, the angles of the second tapered region 113 and the third tapered region 118 with respect to the vertical axis LA are larger than those of the first tapered region 112 and the fourth tapered region 119.

[0045] The second tapered region 113 and the third tapered region 118 meet at the body w. The body w is the narrowest region of the via 110 and is where the metal bridge is formed during the electroplating process. Referring here to Figure 4E, the final thickness t F A completed example via 110 in a molten substrate is shown. As can be seen from the figure, the via 110 has an axially variable sidewall taper resulting in a separate segment, as well as a narrow body w that provides a position for a metal bridge to form during the electroplating process.

[0046] The damage trajectories 120 described herein, having varying levels of modification in the silica-containing substrate 100, can be formed by various laser processes. In the example shown in Figure 5, the damage trajectories 120 are formed within the silica-containing substrate 100 by scanning a focused laser spot LS of a laser beam 150 through the thickness t of the silica-containing substrate 100 in direction z, where the output of the laser beam is modulated during scanning, as shown in Graph 152, to produce different levels of material modification (i.e., damage) at different depths from the surface of the silica-containing substrate 100. The laser output is lower when the focused laser spot LS is located inside the silica-containing substrate 100 (i.e., near the center) than when the focused laser spot LS is located near the first surface 102 and the second surface 104 of the silica-containing substrate 100. However, this method would require many continuous laser exposures to form the damage trajectories 120 throughout the entire thickness of the silica-containing substrate 100, which would slow down the process.

[0047] Referring to Figure 6, in another example, the damage trajectory 120 is formed by a pulsed laser beam 302a focused on a laser beam focal line 302b positioned through the interior of a silica-containing substrate 100. This laser beam focal line causes multiphoton-induced absorption within the silica-containing substrate 100. This multiphoton-induced absorption causes material changes within the silica-containing substrate along the laser beam focal line 302b, thereby forming the damage trajectory 120. The laser beam focal line 302b is formed by an optical element 306, which, as a non-limiting example shown in Figure 6, is a conical lens (i.e., an axicon). Additional descriptions of methods for generating and using a laser beam focal line for drilling holes in a glass substrate are given in U.S. Patent No. 9,517,963, which is incorporated herein by reference.

[0048] The optical element 306 forms the laser beam into an extended-focus or quasi-nondiffractive beam, resulting in a Bessel-like beam or a Gauss-Bessel beam. Due to the quasi-nondiffractive nature of the beam, the light maintains a strongly focused intensity over a much longer range than is achieved with more commonly used Gaussian beams, allowing the entire thickness t of the glass substrate to be damaged by a single burst pulse or a precisely timed series of bursts of laser pulses.

[0049] To modify the silica-containing substrate and form a damage trajectory, the wavelength of the pulsed laser beam should be penetrating to the material of the silica-containing substrate. The pulse duration and intensity should be short enough to achieve the multiphoton absorption effect described above. Ultrashort pulsed lasers, such as picosecond or femtosecond laser sources, may be used. In some embodiments, pulsed lasers of about 10 picoseconds may be used. Not limited to, but as an example, a pulsed laser of about 10 picoseconds producing an output of more than about 50 W (250 μJ / pulse) with a line focus in the range of about 1 mm and about 3 mm and a repetition rate of 200 kHz, and consequently, the light intensity in the line region should be high enough to produce nonlinear absorption in the silica-containing substrate.

[0050] Note that such picosecond laser operation described herein generates subpulses 5a of “pulsed bursts” 5. Figure 7 shows three subpulses 5a, 5a', and 5a'' (collectively “5a”). Pulsed burst generation is a type of laser operation in which pulse emission is not a uniform steady flow, but rather a dense group of subpulses. Each pulsed burst contains a number of individual subpulses 5a with very short durations (without limitation, at least two subpulses, at least three subpulses, at least four subpulses, at least five subpulses, etc.). That is, pulsed bursts 5 are “pockets” of subpulses 5a, and pulsed bursts 5 are separated from each other by durations longer than the interval between individual adjacent pulses within each burst. Referring to Figure 8, which plots the laser emission against time for subpulse 5a in Figure 7, the subpulse has a pulse duration T up to 100 picoseconds (e.g., 0.1 picoseconds, 5 picoseconds, 10 picoseconds, 15 picoseconds, 18 picoseconds, 20 picoseconds, 22 picoseconds, 25 picoseconds, 30 picoseconds, 50 picoseconds, 75 picoseconds, or in between). d These may have. These individual subpulses within a single pulse burst 5 (e.g., subpulses 5a, 5a', and 5a") are referred to here as subpulses to indicate the fact that they occur within a single pulse burst. The energy or intensity of each individual subpulse 5a, 5a', 5a'' within the pulse burst 5 may not be equal to that of the other subpulses within that pulse burst, and the intensity distribution of multiple subpulses within a pulse burst often follows an exponential decay over time, which is determined by the laser design.

[0051] Each subpulse (e.g., subpulses 5a, 5a', and 5a) in the pulse burst 5 of the exemplary embodiments described herein has a duration t from 1 nanosecond to 50 nanoseconds (e.g., 10 to 50 nanoseconds, or 10 to 30 nanoseconds, the duration of which is usually determined by the design of the laser cavity). p However, there is a time interval between subsequent subpulses within that burst. For a given laser, the time interval t between each subpulse within pulse burst 5 is...p (The interval from sub-pulse to sub-pulse) is relatively uniform (±10%). For example, in some embodiments, each sub-pulse within a certain pulse burst may be separated from the next sub-pulse by about 20 nanoseconds (50 MHz). For example, the sub-pulse interval t p For a laser that produces p the interval t from sub-pulse to sub-pulse within a pulse burst is maintained within about ±10% or is about ±2 nanoseconds.

[0052] It has been observed that too many sub-pulses result in cylindrical vias. Specifically, cylindrical vias were produced by 15 sub-pulse bursts with 80 μJ of energy, while hourglass-shaped vias were produced by 5 sub-pulse bursts with 50 μJ of energy. The former has a small energy per sub-pulse but produces a very uniform damage track through the thickness of the silica-containing substrate, while the latter has a large energy per sub-pulse but produces a more non-uniform damage track through the thickness of the silica-containing substrate, with stronger damage observed near the glass surface and weaker damage observed near the center of the silica-containing substrate.

[0053] The laser beam focus 302b typically has a uniform intensity. However, in the embodiments described herein, the amount of energy and the number of laser beam bursts are controlled to give a non-uniform level of modification along the desired damage trajectory 120. In other words, the damage pattern as a function of depth within the silica-containing substrate 100 is not uniform. Observed is that the amount of material modification near the surface of the silica-containing substrate 100, particularly within 100 μm of each surface, is significantly different from and more intense than the damage in the center of the silica-containing substrate 100. As observed with a back-illuminated microscope, the areas near the surface of the silica-containing substrate 100 typically appear very dark and show greater light scattering and material modification, while the areas near the center of the silica-containing substrate 100 appear as bright-colored areas or divided dark areas and show less light scattering and therefore weaker or spatially inconsistent material modification. In addition, the areas near the surface of the silica-containing substrate 100 often show actual pores or areas where material has been released / removed from the substrate, which can provide pathways through which chemical etching agents can easily penetrate.

[0054] This effect of stronger damage near the substrate is particularly evident because the laser energy of the laser beam focus 302b is reduced to just above the threshold required to alter the silica-containing substrate 100, such as within 60% above the threshold, within 65% above the threshold, within 55% above the threshold, within 50% above the threshold, within 45% above the threshold, within 40% above the threshold, within 35% above the threshold, within 30% above the threshold, within 25% above the threshold, within 20% above the threshold, within 15% above the threshold, or within 10% above the threshold. As used here, the term "threshold" means the minimum energy required to cause surface damage on the substrate using the laser beam focus. In such a situation, the area closest to the surface still shows a dark damaged area, while the center of the silica-containing substrate, in some cases, shows no obvious damaged or altered area at all. As previously mentioned, by cleverly utilizing this difference in damage effect as a function of depth observed in non-diffractive beams, it may be possible to form such vias in a silica-containing substrate in locations where a tapered via shape would otherwise be impossible. As a non-limiting example, the operating range of the pulsed laser beam is in the range of 40 μJ to 55 μJ including the endpoints, or in the range of 45 μJ to 50 μJ including the endpoints, for five subpulses.

[0055] By changing the position of the maximum intensity of the laser beam focus, it is possible to shift the position of the via body w. Figure 9A plots the intensity 305 of the laser beam focus passing through the silica-containing substrate 100 and shows the resulting via 410 in an exemplary silica-containing substrate 400. As shown in Figure 9A, positioning the maximum intensity 305 at the center of the silica-containing substrate 100 results in a via 410 with a body at the center of the silica-containing substrate 400 after the etching process.

[0056] Figure 9B graphically shows the shift of the maximum intensity 305 of the laser beam focusing onto the first surface 102 of the silica-containing substrate 100. Figure 9B further shows an exemplary silica-containing substrate 400' having vias 410' with a body portion closer to the second surface 404 than to the first surface 402 after the etching process. Figure 9C graphically shows the shift of the maximum intensity 305 of the laser beam focusing onto the second surface 104 of the silica-containing substrate 100. Figure 9C further shows an exemplary silica-containing substrate 400' having vias 410'' with a body portion closer to the first surface 402 than to the second surface 404 after the etching process. Shifting the body portion w results in asymmetry around the plane passing through the center of the silica-containing substrate 100.

[0057] It should be noted that it is not necessary to increase the light intensity of the quasi-nondiffractive beam (e.g., laser beam focuser 302b) near the surface of the silica-containing substrate 100. However, it is possible to design optical elements such as waxicon-like elements, which create a customized light energy distribution along the beam propagation direction. In such cases, the light intensity of the laser beam focuser 302b may be enhanced near the surface of the molten substrate, while a region of lower intensity is created in the center of the silica-containing substrate. Exemplary optical elements for customizing the energy distribution of the laser beam focuser are described in U.S. Provisional Patent Application No. 62 / 381345.

[0058] Figures 10A and 10B graphically illustrate the manipulation of the intensity profiles of two laser beam focuses passing through a silica-containing substrate 100. In Figure 10A, the intensity profile 305' of the laser beam focus has a rectangular "top hat" shape. This intensity profile 305' may be formed, for example, by a waxicon optical element, and the changes closer to the surface of the silica-containing substrate may be stronger than those in the Gaussian profiles shown in Figures 9A-9C. The intensity profile 305'' shown in Figure 10B has two maximum peaks close to the first surface 102 and the second surface 104 of the silica-containing substrate 100, resulting in stronger changes closer to the first surface 102 and the second surface 104 than in the center of the silica-containing substrate. The laser beam focus in Figure 10B has greater intensity at the first and second ends of the laser beam focus than in the central region of the laser beam focus. The intensity profile 305'' shown in Figure 10B can be created using custom-made optical elements.

[0059] Other techniques to enhance laser damage / modification near the surface of a silica-containing substrate include heating or cooling the surface by applying a hot airflow, thereby creating a temperature gradient and thus differentiating the laser / glass interaction across the glass thickness. [Examples]

[0060] A 0.36 mm thick, 50 mm x 50 mm Corning code 7980 fused silica substrate was laser-damaged using a system equipped with a Coherent Hyper-Rapid-50 picosecond laser operating at a wavelength of 532 nm. The beam transmission optics were configured to create a Gauss-Bessel laser beam focus, and the optical intensity distribution along the laser propagation axis had a full width at half maximum of 0.74 mm. The spot size was 1.2 μm in diameter, measured at the diameter of the first null or minimum intensity in the Bessel-like cross-sectional profile of the beam. Each damage trajectory was formed by exposing the silica-containing substrate to a 50 μJ laser burst containing five laser pulses. Each pulse had a duration of 7.2 picoseconds, and the time interval between pulses within each burst was 20 nanoseconds. Next, the laser-processed silica-containing substrate was etched at 47°C in a static (no physical stirring, no ultrasonic) bath of 20% HF (vol%) and 12% HCl (vol%). The bulk etching rate ranged from 0.0046 μm / sec to 0.005 μm / sec.

[0061] Figure 11A shows low-magnification images of damage trajectories 120, 120', and 120'' made on a 0.36 mm thick fused silica substrate under back illumination before etching. The lateral spacing (i.e., pitch) of the damage trajectories in the images of Figure 11A is 150 μm. It is evident from the optical microscope images of Figure 11A that each damage trajectory has a more strongly modified portion (above and below the two horizontal dotted lines, darker linear features in the optical microscope image) near the first surface 102 (first modification) and the second surface 104 (second modification), as well as a weaker third modification in the center of the glass (between the two horizontal dotted lines, brighter linear features in the optical microscope image). Therefore, the level of modification in this third modification is smaller than that of the first and second modification portions. This difference is more clearly shown in the high-magnification images of Figure 11B (first surface 102) and Figure 11C (second surface 104).

[0062] Each of the damage trajectories 120, 120', and 120'' comprises at least a first segment 120A, 120A', and 120A'', a second segment 120B, 120B', and 120B'', and a third segment 120C, 120C', and 120C''.

[0063] It should be noted that the difference in intensity of the damage trajectory is not explained by the difference in light intensity created by the quasi-nondiffractive beam (Gauss-Bessel) forming optical element. Focal line intensity was measured using a CCD camera scanned along the optical axis and a high-NA microscope objective lens, and was shown to closely follow the Gauss-Bessel intensity profile. The focal line position was set to achieve nearly maximum intensity near the center of the silica-containing substrate, with a slight decrease in intensity near each surface. The predicted intensity variation for this focal line through a depth of 0.35 mm thick glass is approximately 6–8%.

[0064] Figure 12 shows an optical microscope image of the side of the etched via 510 after the etching process in this embodiment. As can be seen from the figure, via 110 has an hourglass shape with a narrow body w. Via 510 has an inner wall profile similar to the exemplary via 110 schematically shown in Figure 5. Referring to Figures 5 and 12, via 510 has the following inner wall profile: θ1=θ4=1°, θ2=θ3=8°, L1=L4=62μm, L2=L3=88μm; first diameter D1=49.5μm; second diameter D2=51.2μm; and D w =25.7μm. In this case, the damage trajectory is nearly symmetrical around the central plane of the molten substrate thickness, and in contrast to the case shown in Figure 3, it becomes a via symmetrical arrangement around the horizontal centerline.

[0065] The silica-containing substrates manufactured using this process showed very low via-to-via variation at the component level. This indicates that the process is stable and not excessively affected by any small fluctuations in laser energy or system focus. As shown in Figures 13A–13C and 14A–14C, both diameter and roundness are very well controlled for the top, body, and bottom of 10,000 vias. For a number of holes as shown in each graph, Figure 13A is a histogram showing the first diameter, Figure 13B is a histogram showing the second diameter, and Figure 13C is a histogram showing the body diameter. Dimensional control is shown to be better than ±1% for the first diameter, better than ±2.5% for the second diameter, and better than ±6% for the body diameter.

[0066] Another criterion for via quality is roundness, which can be measured for the first diameter (Figure 14A), second diameter (Figure 14B), and body diameter (Figure 14C) of each via. As used here, roundness is determined by fitting a circle to a microscopic image of the via. H = {h1, h2, ..., h n} is a group of points h identified along the edge of the via at the first diameter, second diameter, or body diameter, as viewed from above (for example, from a microscopic image of the via at each diameter). i =(x i , y i ) we consider. These points can have a resolution of approximately 1 μm per pixel without any limitations. We can evaluate exactly one least-squares fit circle. The center point of this circle C = (x c , y c ) and its radius R, quantity TIFF0007837643000002.tif15114

[0067] The value is minimized. A series of distances (diameters) d i =dist(h i Considering C), the minimum value d min and maximum value d max We can find the difference d.max -d min This is called roundness. Therefore, all distances d i The theoretically perfect circles that are equal are d min and d max The values ​​become equal, and the roundness value becomes zero. A larger roundness value indicates a hole that is not very round.

[0068] Figure 15A is a histogram of body defects for the sample at four different burst energies. Vias with excessively high roundness are those that are too elliptical or imperfectly formed. Figure 15B is a histogram of all defects (blind vias, vias with an inlet or second diameter greater than 5 μm, or body roundness greater than 5 μm) for the sample at four different burst energies. Figures 16A (mean) and 16B (standard deviation) are histograms showing the variation in via body across parts for samples manufactured at different burst energies and focal conditions. Figure 16C is a histogram showing the ratio between the body diameter and the first diameter for different burst energies and focal conditions.

[0069] As shown in Figures 15A and 15B and 16A-16C, parts manufactured by this process, defined as the percentage of vias with roundness greater than 5 μm, have an extremely low defect rate, are within a reasonable process window (Figures 15A and 15B), and only the shell openings have small variations within the process window (Figures 16A-16C), both indicating the stability of the process. In addition, Figures 16A-16C show that a shell diameter / first diameter ratio of 35%-45% can be achieved using an energy of 5 μJ and a process window of 100 μm.

[0070] It should now be understood that the embodiments described herein provide methods and articles for providing hourglass-shaped vias in silica-containing substrates, such as high-purity silica-containing substrates. The hourglass-shaped vias can be metallized, for example, using an electroplating process. These hourglass-shaped vias are formed by a laser damage etching process that creates a custom-designed damage trajectory in the silica-containing substrate before the etching process. The damage trajectory has a stronger material transformation closer to the surface of the silica-containing substrate than the interior / center of the silica-containing substrate. The custom-designed damage trajectory results in an etched via having a tapered region defining a body. This body can function as a metal bridge for growing an internal metal layer within the via. Silica-containing substrates with hourglass-shaped vias can be used as interposers in electronic devices, such as high-frequency electronic devices.

[0071] It will be apparent to those skilled in the art that various modifications and alterations can be made to the embodiments described herein without departing from the spirit and scope of the subject matter of the claims. Therefore, this specification is intended to encompass such modifications and alterations to the various embodiments described herein, provided that such modifications and alterations fall within the scope of the accompanying claims and their equivalents.

[0072] Preferred embodiments of the present invention are described below in separate sections.

[0073] Embodiment 1 A method for processing a substrate including silica, a first surface, and a second surface opposite to the first surface, A step of forming a damage trajectory through the substrate from the first surface to the second surface using a laser beam, wherein the damage trajectory is A first segment with a modified height adjacent to the first surface, A second segment with altered height adjacent to the second surface, and The minimum modified segment, positioned between the first modified segment and the second modified segment, The process includes, and, the level of modification of the substrate along the damage trajectory decreases in a first direction starting from the first surface and toward the interior of the substrate, and the level of modification of the substrate decreases in a second direction starting from the second surface and toward the interior of the substrate, A step of etching the substrate using an etching solution to form vias having a via body having a first diameter on the first surface, a second diameter on the second surface, and a diameter of the body between the first surface and the second surface, wherein the diameter of the body is smaller than the first diameter and smaller than the second diameter, A method comprising [a certain characteristic].

[0074] Embodiment 2 The method according to Embodiment 1, wherein the smallest modified segment of the damage trajectory is modified by the laser beam.

[0075] Embodiment 3 The method according to Embodiment 1 or 2, wherein at least a portion of the substrate within the segment of the damage trajectory that has been minimally altered is not altered by the laser beam.

[0076] Embodiment 4 The method according to any one of Embodiments 1 to 3, wherein the substrate contains at least 75 mol% silica.

[0077] Embodiment 5 The method according to any one of Embodiments 1 to 3, wherein the substrate contains at least 90 mol% silica.

[0078] Embodiment 6 The method according to any one of Embodiments 1 to 3, wherein the substrate contains at least 99 mol% silica.

[0079] Embodiment 7 The method according to any one of Embodiments 1 to 3, wherein the substrate contains unintentionally doped silica.

[0080] Embodiment 8 The method according to any one of Embodiments 1 to 7, wherein the thickness of the substrate is 50 μm or more and 1 mm or less.

[0081] Embodiment 9 The method according to any one of embodiments 1 to 8, wherein the diameter of the body is at least 50% of the first diameter and the second diameter, respectively.

[0082] Embodiment 10 The method according to any one of embodiments 1 to 9, wherein the via has the shape of an hourglass.

[0083] Embodiment 11 The method according to any one of embodiments 1 to 10, wherein the via body is located closer to one of the first surface and the second surface than to the other of the first surface or the second surface.

[0084] Embodiment 12 The method according to any one of embodiments 1 to 11, wherein the first diameter and the second diameter are 5 μm or more.

[0085] Embodiment 13 The first surface of the substrate faces the laser source that emits the laser beam, The method according to any one of embodiments 1 to 12, wherein the ratio between the diameter of the body and the first diameter is 35% or more and 45% or less.

[0086] Embodiment 14 The via includes a vertical axis, an inner wall, a first tapered region located between the first surface and the via body, and a second tapered region located between the second surface and the via body. The first tapered region has a first angle measured between the inner wall within the first tapered region and the longitudinal axis, The method according to any one of embodiments 1 to 13, wherein the second tapered region has a second angle measured between the inner wall within the second tapered region and the longitudinal axis.

[0087] Embodiment 15 The method according to embodiment 14, wherein the first angle is equal to the second angle.

[0088] Embodiment 16 The method according to Embodiment 14, wherein the first angle is different from the second angle.

[0089] Embodiment 17 The aforementioned laser beam The damage trajectory includes an additional minimally modified segment located between the minimally modified segment and the second highly modified segment, The method according to any one of embodiments 1 to 16, wherein the level of change of the additional minimum changed segment is operated to be less than the level of change of the first highly changed segment and the second highly changed segment.

[0090] Embodiment 18 The aforementioned Via, Vertical axis, inner wall, A first tapered region located adjacent to the first surface, the first tapered region having a first angle measured between the inner wall of the first tapered region and the vertical axis, A second tapered region located between the first tapered region and the via body, the second tapered region having a second angle measured between the inner wall of the second tapered region and the longitudinal axis, A third tapered region adjacent to the via body, the third tapered region having a third angle measured between the inner wall of the third tapered region and the vertical axis, and A fourth tapered region located between the third tapered region and the second surface, the fourth tapered region having a fourth angle measured between the inner wall of the fourth tapered region and the vertical axis, Includes, The method according to any one of embodiments 1 to 17, wherein each of the second angle and the third angle is smaller than the first angle and the fourth angle.

[0091] Embodiment 19 The method according to embodiment 18, wherein the first angle and the fourth angle are different.

[0092] Embodiment 20 The method according to Embodiment 19, wherein each of the first angle and the fourth angle is 5 degrees or less.

[0093] Embodiment 21 The method according to embodiment 18, wherein the second angle and the third angle are different.

[0094] Embodiment 22 The method according to Embodiment 18, wherein each of the first angle, the second angle, the third angle, and the fourth angle is different from the other of the first angle, the second angle, the third angle, and the fourth angle.

[0095] Embodiment 23 The method according to any one of embodiments 18 to 22, wherein the via body is located closer to one of the first surface and the second surface than to the other of the first surface or the second surface.

[0096] Embodiment 24 The laser beam includes a pulsed laser beam that is focused onto a laser beam focal line positioned within the substrate, The method according to any one of embodiments 1 to 23, wherein the laser beam focusing causes multiphoton-induced absorption within the substrate, and the multiphoton-induced absorption causes a material change within the substrate along the laser beam focusing, thereby forming the damage trajectory.

[0097] Embodiment 25 The method according to Embodiment 24, wherein the pulsed laser beam includes a plurality of laser beam subpulses, and each of the plurality of laser beam subpulses is separated by a certain time interval.

[0098] Embodiment 26 The method according to Embodiment 25, wherein the plurality of laser beam bursts include fewer than 10 individual laser beam subpulses.

[0099] Embodiment 27 The method according to Embodiment 25, wherein the plurality of laser beam bursts include five or fewer individual laser beam subpulses.

[0100] Embodiment 28 The method according to any one of embodiments 24 to 27, wherein the laser beam focusing of the laser beam causes the area of ​​the substrate closer to the first and second surfaces to be more strongly focused than the area further away from the first and second surfaces of the substrate.

[0101] Embodiment 29 The method according to any one of embodiments 24 to 28, wherein the maximum intensity of the laser beam convergence is located at the midpoint between the first surface and the second surface along a desired line of the damage trajectory.

[0102] Embodiment 30 The method according to any one of embodiments 24 to 28, wherein the maximum intensity of the laser beam focusing is located closer to one of the first surface and the second surface than to the other of the first surface or the second surface.

[0103] Embodiment 31 The method according to any one of embodiments 1 to 30, further comprising the step of adjusting the temperature of one or more of the first and second surfaces while forming the damage trajectory using the laser beam.

[0104] Embodiment 32 The method according to any one of Embodiments 1 to 31, wherein the laser beam is a quasi-nondiffractive beam.

[0105] Embodiment 33 The method according to any one of embodiments 1 to 32, wherein the energy of the laser beam is higher than a threshold for changing the substrate.

[0106] Embodiment 34 The method according to embodiment 33, wherein the energy of the laser beam is less than 75 percent greater than the threshold for modifying the substrate.

[0107] Embodiment 35 The method according to embodiment 34, wherein the energy of the laser beam is less than 10 percent greater than the threshold for modifying the substrate.

[0108] Embodiment 36 The method according to any one of embodiments 24 to 28, further comprising the step of operating the laser beam such that the laser beam focus has a greater intensity at the first end and the second end of the laser beam focus than in the central region of the laser beam focus.

[0109] Embodiment 37 The method according to any one of Embodiments 1 to 36, wherein the etching solution contains hydrofluoric acid.

[0110] Embodiment 38 The method according to Embodiment 37, wherein the etching solution contains 20% by volume of hydrofluoric acid and 12% by volume of hydrochloric acid.

[0111] Embodiment 39 The method according to any one of embodiments 1 to 38, further comprising the step of electroplating the vias after the etching step of the substrate.

[0112] Embodiment 40 In articles, A silica-containing substrate comprising 75 mol% or more silica, a first surface, a second surface opposite to the first surface, and vias extending through the silica-containing substrate from the first surface toward the second surface, wherein the vias are The first diameter of the first surface, The second diameter of the second surface, and In the via body between the first surface and the second surface, the diameter of the via body is smaller than the diameter of the first diameter and the diameter of the second diameter, such that the ratio between the diameter of the via body and each of the first diameter and the second diameter is 75% or less. A silica-containing substrate having, An article equipped with.

[0113] Embodiment 41 The article according to Embodiment 40, wherein the silica-containing substrate contains at least 90 mol% silica.

[0114] Embodiment 42 The article according to Embodiment 40, wherein the silica-containing substrate contains at least 99 mol% silica.

[0115] Embodiment 43 The article according to Embodiment 40, wherein the silica-containing substrate contains doped silica unintentionally.

[0116] Embodiment 44 The article according to any one of embodiments 40 to 43, wherein the thickness of the silica-containing substrate is 50 μm or more and 1 mm or less.

[0117] Embodiment 45 The article according to any one of embodiments 40 to 44, wherein the diameter of the body is at least 50% of the first diameter and the second diameter, respectively.

[0118] Embodiment 46 The article according to any one of embodiments 40 to 45, wherein the via has the shape of an hourglass.

[0119] Embodiment 47 The article according to any one of embodiments 40 to 46, wherein the via body is located closer to one of the first surface and the second surface than to the other of the first surface or the second surface.

[0120] Embodiment 48 The article according to any one of embodiments 40 to 47, wherein each of the first diameter and the second diameter is 5 μm or more and 100 μm or less.

[0121] Embodiment 49 The article according to any one of embodiments 40 to 48, wherein the ratio between the diameter of the body and the first diameter is 35% or more and 45% or less.

[0122] Embodiment 50 The via includes a vertical axis, an inner wall, a first tapered region located between the first surface and the via body, and a second tapered region located between the second surface and the via body. The first tapered region has a first angle measured between the inner wall within the first tapered region and the longitudinal axis, The article according to any one of embodiments 40 to 49, wherein the second tapered region has a second angle measured between the inner wall within the second tapered region and the longitudinal axis.

[0123] Embodiment 51 The article according to embodiment 50, wherein the first angle is equal to the second angle.

[0124] Embodiment 52 The article according to embodiment 50, wherein the first angle is different from the second angle.

[0125] Embodiment 53 The aforementioned Via, Vertical axis, inner wall, A first tapered region located adjacent to the first surface, the first tapered region having a first angle measured between the inner wall of the first tapered region and the vertical axis, A second tapered region located between the first tapered region and the via body, the second tapered region having a second angle measured between the inner wall of the second tapered region and the longitudinal axis, A third tapered region adjacent to the via body, the third tapered region having a third angle measured between the inner wall of the third tapered region and the vertical axis, and A fourth tapered region located between the third tapered region and the second surface, the fourth tapered region having a fourth angle measured between the inner wall of the fourth tapered region and the vertical axis, Includes, The article according to any one of embodiments 40 to 49, wherein each of the second angle and the third angle is smaller than the first angle and the fourth angle.

[0126] Embodiment 54 The article according to embodiment 53, wherein the first angle and the fourth angle are different.

[0127] Embodiment 55 The article according to embodiment 54, wherein each of the first angle and the fourth angle is 5 degrees or less.

[0128] Embodiment 56 The article according to embodiment 53, wherein the second angle and the third angle are different.

[0129] Embodiment 57 The article according to any one of embodiments 53 to 56, wherein the via portion is located closer to one of the first surface and the second surface than to the other of the first surface or the second surface.

[0130] Embodiment 58 The article according to any one of embodiments 40 to 57, wherein the vias are electroplated with a conductive material.

[0131] Embodiment 59 The article according to any one of embodiments 40 to 58, further comprising a plurality of vias penetrating the silica-containing substrate.

[0132] Embodiment 60 In electronic devices, A silica-containing substrate comprising 75 mol% or more silica, a first surface, a second surface opposite to the first surface, and vias extending through the silica-containing substrate from the first surface toward the second surface, wherein the vias are The first diameter of the first surface, The second diameter of the second surface, and In the via body between the first surface and the second surface, the diameter of the via body is smaller than the first diameter and the second diameter, such that the ratio of the diameter of the via body to each of the first diameter and the second diameter is 75% or less. A silica-containing substrate having, A semiconductor element bonded to the silica-containing substrate, wherein the semiconductor element is electrically coupled to the via, An electronic device equipped with [a specific feature / feature].

[0133] Embodiment 61 The electronic device according to Embodiment 60, wherein the silica-containing substrate contains at least 90 mol% silica.

[0134] Embodiment 62 The electronic device according to Embodiment 60, wherein the silica-containing substrate contains at least 99 mol% silica.

[0135] Embodiment 63 The electronic device according to Embodiment 60, wherein the silica-containing substrate contains doped silica, not intentionally.

[0136] Embodiment 64 The electronic device according to any one of embodiments 60 to 63, wherein the thickness of the silica-containing substrate is 50 μm or more and 1 mm or less.

[0137] Embodiment 65 The electronic device according to any one of embodiments 60 to 64, wherein the diameter of the body is at least 50% of the first diameter and the second diameter, respectively.

[0138] Embodiment 66 The electronic device according to any one of embodiments 60 to 65, wherein the via has the shape of an hourglass.

[0139] Embodiment 67 The electronic device according to any one of embodiments 60 to 66, wherein the via body is located closer to one of the first surface and the second surface than to the other of the first surface or the second surface.

[0140] Embodiment 68 The electronic device according to any one of embodiments 60 to 67, wherein each of the first diameter and the second diameter is 5 μm or more and 100 μm or less.

[0141] Embodiment 69 The electronic device according to any one of embodiments 60 to 68, wherein the ratio between the diameter of the body and the first diameter is 35% or more and 45% or less.

[0142] Embodiment 70 The via includes a vertical axis, an inner wall, a first tapered region located between the first surface and the via body, and a second tapered region located between the second surface and the via body. The first tapered region has a first angle measured between the inner wall within the first tapered region and the longitudinal axis, The electronic device according to any one of embodiments 60 to 69, wherein the second tapered region has a second angle measured between the inner wall within the second tapered region and the longitudinal axis.

[0143] Embodiment 71 The electronic device according to embodiment 70, wherein the first angle is equal to the second angle.

[0144] Embodiment 72 The electronic device according to embodiment 70, wherein the first angle is different from the second angle.

[0145] Embodiment 73 The aforementioned Via, Vertical axis, inner wall, A first tapered region located adjacent to the first surface, the first tapered region having a first angle measured between the inner wall of the first tapered region and the vertical axis, A second tapered region located between the first tapered region and the via body, the second tapered region having a second angle measured between the inner wall of the second tapered region and the longitudinal axis, A third tapered region adjacent to the via body, the third tapered region having a third angle measured between the inner wall of the third tapered region and the vertical axis, and A fourth tapered region located between the third tapered region and the second surface, the fourth tapered region having a fourth angle measured between the inner wall of the fourth tapered region and the vertical axis, Includes, The electronic device according to any one of embodiments 60 to 69, wherein each of the second angle and the third angle is smaller than the first angle and the fourth angle.

[0146] Embodiment 74 The electronic device according to embodiment 73, wherein the first angle and the fourth angle are different.

[0147] Embodiment 75 The electronic device according to embodiment 74, wherein each of the first angle and the fourth angle is 5 degrees or less.

[0148] Embodiment 76 The electronic device according to embodiment 73, wherein the second angle and the third angle are different.

[0149] Embodiment 77 The electronic device according to embodiment 73, wherein the via body is located closer to one of the first surface and the second surface than to the other of the first surface or the second surface.

[0150] Embodiment 78 The electronic device according to any one of embodiments 60 to 77, wherein the vias are electroplated with a conductive material.

[0151] Embodiment 79 The electronic device according to any one of embodiments 60 to 78, further comprising a plurality of vias penetrating the silica-containing substrate.

[0152] Embodiment 80 A silica-containing substrate comprising 75 mol% or more silica, a first surface, a second surface opposite to the first surface, and a damage trajectory penetrating the silica-containing substrate from the first surface to the second surface, wherein the damage trajectory is A first segment with a modified height adjacent to the first surface, A second segment with altered height adjacent to the second surface, and The minimum modified segment, positioned between the first modified segment and the second modified segment, A silica-containing substrate in which the level of modification along the damage trajectory decreases in a first direction starting from the first surface and toward the interior of the silica-containing substrate, and the level of modification of the silica-containing substrate decreases in a second direction starting from the second surface and toward the interior of the silica-containing substrate.

[0153] Embodiment 81 The silica-containing substrate according to Embodiment 80, wherein the silica-containing substrate contains at least 75 mol% silica.

[0154] Embodiment 82 The silica-containing substrate according to Embodiment 80, wherein the silica-containing substrate contains at least 90 mol% silica.

[0155] Embodiment 83 The silica-containing substrate according to Embodiment 80, wherein the silica-containing substrate contains doped silica unintentionally.

[0156] Embodiment 84 The silica-containing substrate according to any one of embodiments 80 to 83, wherein the thickness of the silica-containing substrate is 50 μm or more and 1 mm or less.

[0157] Embodiment 85 In articles, A silica-containing substrate comprising 75 mol% or more silica, a first surface, a second surface opposite to the first surface, and vias extending through the silica-containing substrate from the first surface toward the second surface, wherein the vias are The first diameter of the first surface, The second diameter of the second surface, and In the via body between the first surface and the second surface, the diameter of the via body is such that the ratio of the diameter of the via body to the difference between the first diameter and the diameter of the via body relative to half the thickness of the silica-containing substrate is 1 / 15 or more, the diameter of the via body being smaller than the first diameter and the second diameter. A silica-containing substrate having, An article equipped with.

[0158] Embodiment 86 The article according to Embodiment 85, wherein the silica-containing substrate contains at least 90 mol% silica.

[0159] Embodiment 87 The article according to Embodiment 85, wherein the silica-containing substrate contains at least 99 mol% silica.

[0160] Embodiment 88 The article according to Embodiment 85, wherein the silica-containing substrate contains doped silica unintentionally.

[0161] Embodiment 89 The article according to any one of embodiments 85 to 88, wherein the thickness of the silica-containing substrate is 50 μm or more and 1 mm or less.

[0162] Embodiment 90 The article according to any one of embodiments 85 to 89, wherein the diameter of the body is at least 50% of the first diameter and the second diameter, respectively.

[0163] Embodiment 91 The article according to any one of embodiments 85 to 90, wherein the via has the shape of an hourglass.

[0164] Embodiment 92 The article according to any one of embodiments 85 to 91, wherein the via portion is located closer to one of the first surface and the second surface than to the other of the first surface or the second surface.

[0165] Embodiment 93 The article according to any one of embodiments 85 to 92, wherein each of the first diameter and the second diameter is 5 μm or more and 100 μm or less.

[0166] Embodiment 94 The article according to any one of embodiments 85 to 93, wherein the ratio between the diameter of the body and the first diameter is 35% or more and 45% or less.

[0167] Embodiment 95 The via includes a vertical axis, an inner wall, a first tapered region located between the first surface and the via body, and a second tapered region located between the second surface and the via body. The first tapered region has a first angle measured between the inner wall within the first tapered region and the longitudinal axis, The article according to any one of embodiments 85 to 94, wherein the second tapered region has a second angle measured between the inner wall within the second tapered region and the longitudinal axis.

[0168] Embodiment 96 The article according to embodiment 95, wherein the first angle is equal to the second angle.

[0169] Embodiment 97 The article according to embodiment 95, wherein the first angle is different from the second angle.

[0170] Embodiment 98 The aforementioned Via, Vertical axis, inner wall, A first tapered region located adjacent to the first surface, the first tapered region having a first angle measured between the inner wall of the first tapered region and the vertical axis, A second tapered region located between the first tapered region and the via body, the second tapered region having a second angle measured between the inner wall of the second tapered region and the longitudinal axis, A third tapered region adjacent to the via body, the third tapered region having a third angle measured between the inner wall of the third tapered region and the vertical axis, and A fourth tapered region located between the third tapered region and the second surface, the fourth tapered region having a fourth angle measured between the inner wall of the fourth tapered region and the vertical axis, Includes, The article according to embodiment 85, wherein each of the second angle and the third angle is smaller than the first angle and the fourth angle.

[0171] Embodiment 99 The article according to embodiment 98, wherein the first angle and the fourth angle are different.

[0172] Embodiment 100 The article according to embodiment 99, wherein each of the first angle and the fourth angle is 5 degrees or less.

[0173] Embodiment 101 The article according to embodiment 100, wherein the second angle and the third angle are different.

[0174] Embodiment 102 The article according to any one of embodiments 98 to 101, wherein the via portion is located closer to one of the first surface and the second surface than to the other of the first surface or the second surface.

[0175] Embodiment 103 The article according to any one of embodiments 98 to 102, wherein the vias are electroplated with a conductive material.

[0176] Embodiment 104 The article according to any one of embodiments 98 to 103, further comprising a plurality of vias penetrating the silica-containing substrate. [Explanation of Symbols]

[0177] 100, 400, 400', 400” silica-containing substrates 102, 402 Front page 104, 404 second side 110, 410, 410', 410”, 510 Beer 111 Interior wall 112, 512 First tapered region 113, 513 Second taper region 115 First pilot hole 117 Second pilot hole 118, 518 Third taper region 119, 519 Fourth taper region 120, 120', 120” damage trajectory 120A First change segment 120B Second Change Segment 120C Third Change Segment 120D Fourth Change Segment 150 laser beams 200 Electronic Devices 201 First Electrical Component 203 Second electrical component 302a Pulsed laser beam 302b Laser beam focusing 306 Optical elements D1 First diameter D2, the second diameter D w Body diameter

Claims

1. An article comprising a silica-containing substrate having 75 mol% or more of silica, a first surface, a second surface opposite to the first surface, and vias extending through the silica-containing substrate from the first surface toward the second surface, The via, The first diameter of the first surface, The second diameter of the second surface, and A via body between the first surface and the second surface, wherein the diameter of the via body is smaller than the first diameter and the second diameter, such that the ratio of the diameter of the via body to the first diameter and the second diameter is 35% or more and 60% or less. Equipped with, The aforementioned Via, Vertical axis, inner wall, A first tapered region with a constant gradient located adjacent to the first surface, the first tapered region having a first angle measured between the inner wall of the first tapered region and the vertical axis, A second tapered region with a constant gradient located between the first tapered region and the via body, the second tapered region having a second angle measured between the inner wall of the second tapered region and the vertical axis, A third tapered region with a constant slope adjacent to the via body, the third tapered region having a third angle measured between the inner wall of the third tapered region and the vertical axis, and A fourth tapered region with a constant gradient located between the third tapered region and the second surface, the fourth tapered region having a fourth angle measured between the inner wall of the fourth tapered region and the vertical axis, Includes, An article in which each of the first angle and the fourth angle is smaller than each of the second angle and the third angle.

2. The article according to claim 1, wherein the via portion is located closer to one of the first surface and the second surface than to the other of the first surface or the second surface.

3. The article according to claim 1 or 2, wherein the ratio between the diameter of the body and the first diameter is 35% or more and 45% or less.

4. The article according to claim 1, wherein the first angle is equal to the fourth angle.

5. The article according to claim 1, wherein the first angle is different from the second angle.

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