LOW SURFACE ROUGHNESS SUBSTRATE HAVING A VIA AND METHODS OF MAKING THE SAME

Abstract

Methods of forming a via in substrates include etching a damage region extending through a thickness of a stack of a plurality of substrates removably bonded together. Each of the substrates in the stack has at least one surface removably bonded to a surface of another substrate in the stack, wherein when the substrates in the stack are debonded, each substrate has at least one surface that has a surface roughness (Ra) of less than or equal to about 0.6 nm.

Claims

1. A method of forming substrates with a via, the method comprising: etching a damage region in a stack to form a via in the stack, wherein the stack comprises a plurality of substrates including a first substrate and at least one additional substrate, wherein each of the plurality of substrates has at least one surface removably bonded to a surface of another of the plurality of substrates, wherein the damage region extends through the entire thickness of the at least one additional substrate, and the etching forms a through via in the at least one additional substrate, wherein the etching forms a blind via in the first substrate, and the at least one surface of each of the plurality of substrates removably bonded to the surface of another of the plurality of substrates has a surface roughness (Ra) of less than or equal to about 0.6 nm upon debonding the plurality of substrates.

2. The method of claim 1, wherein the damage region of the first substrate extends through only a portion of the first substrate.

3. The method of claim 1, wherein the damage region of the first substrate extends through the first substrate and only a portion of the damage region is etched to form the blind via.

4. The method of claim 1, further comprising debonding the plurality of substrates from one another.

5. The method of claim 1, further comprising creating at least one damage region extending through the thickness of the stack prior to etching.

6. The method of claim 5, wherein creating at least one damage region within the stack comprises applying a laser pulse to the bonded wafer pair to create the at least one damage region.

7. The method of claim 1, wherein the plurality of substrates is bonded together using Van der Waals forces.

8. The method of claim 1, further comprising: creating at least one damage region extending through a portion of a thickness of the first substrate; and creating at least one damage region extending through the entire thickness of the at least one additional substrate disposed; wherein when the first substrate and the at least one additional substrate are removably bonded together, the at least one damage region in the first substrate is aligned with the at least one damage region in the at least one additional substrate.

9. The method of claim 1, wherein the plurality of substrates is selected from a group consisting of glass, glass-ceramic, ceramic, and combinations thereof.

10. The method of claim 1, wherein the damage region of the stack is etched with an etching solution comprising hydrofluoric acid.

11. The method of claim 1, wherein the stack comprises two or more substrates removably bonded together.

12. A stack, comprising: a plurality of substrates including a first substrate and at least one additional substrate; at least one blind via in the first substrate; and at least one through via in the at least one additional substrate, wherein each of the plurality of substrates has a surface removably bonded to a surface of another one of the plurality of substrates, and wherein the surface of each of the plurality of substrates removably bonded to a surface of another one of the plurality of substrates has a surface roughness (R.sub.a) of less than or equal to about 0.6 nm upon debonding the plurality of substrates.

13. The stack of claim 12, wherein the stacks comprises 2 or more substrates removably bonded together.

14. The stack of claim 12, wherein the plurality of substrates is bonded together using Van der Waals forces.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The embodiments set forth in the drawings are illustrative and exemplary in nature and are 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, where like structure is indicated with like reference numerals and in which:

[0042] FIG. 1 illustrates an exemplary cross-sectional view of an article achieved through the processes described herein;

[0043] FIG. 2 illustrates an exemplary flowchart outlining a process for making an article with at least one via;

[0044] FIGS. 3A-3D illustrates exemplary cross-sectional views of substrates at various stages of the process for forming at least one via in the substrates;

[0045] FIG. 4 illustrates an exemplary cross-sectional view of a stack of more three substrates removably bonded together; and

[0046] FIG. 5 illustrates an exemplary stack in an etchant bath.

DETAILED DESCRIPTION

[0047] Referring generally to the figures, embodiments of articles with at least one via and methods of creating at least one via in substrates provided herein allow for the preservation of surface roughness (Ra) of substrates so that the substrates may be removably bonded to carriers for further processing. Reference will now be made in detail to various embodiments of articles with at least one via and methods of forming at least one via in substrates, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts. It is noted that the embodiments illustrated in the figures are not to scale and that relative sizes and widths were selected for illustrative purposes only.

[0048] The articles disclosed herein may be used, for example, as an interposer in a semiconductor package, the articles having etched holes (e.g., vias) and surface attributes which allow for successful downstream processing including, but not limited to, via metallization and application of redistribution layers (RDL) for semiconductor devices, radio-frequency (RF) devices (e.g., antennae, switches, and the like), interposer devices, microelectronic devices, optoelectronic devices, microelectronic mechanical system (MEMS) devices and other applications where vias may be leveraged. Typically, glass or glass ceramic interposers require vias (holes) to be filled with electrically conductive material to provide electrical interfacing. An exemplary method of creating vias in glass or glass ceramic substrates is by creating a damage region through the thickness of the glass or glass ceramic substrate and then submerging to substrate into an etchant. The etchant may then remove material from the damage region to enlarge the hole. However, the etching process is not selective and material may be removed from both faces of the interposer as well as enlarging the hole. This invariably creates an increase in surface roughness (Ra). The articles may be removably/temporarily bonded to a carrier for downstream processing and if the surface roughness (Ra) of the substrate is increased too much it will be outside of the range for which a removable bond, for example Van der Waals bonding, can be appropriately formed.

[0049] Embodiments preserve a pre-etch surface roughness of at least one surface of a substrate by removably bonding a surface of one substrate to a surface of another before etching the removably bonded substrates for via formation. By preserving the low surface roughness of the substrate during via formation, the substrate may be removably bonded to a carrier for further processing. After processing, the substrate may be removed from the carrier, such that the carrier may be reused for processing further substrates. Various embodiments of articles and methods for via formation are described in detail below.

[0050] FIG. 1 depicts an exemplary finished article 100. In some embodiments, finished article 100 may be a substrate having first and second opposing surfaces, 102, 104. Finished article 100 may have at least one via 106. While multiple vias 106 are shown in FIG. 1, this is merely exemplary and finished article 100 may have a single via 106. Via 106 in finished article 100 may be a through via extending through the entire thickness of the substrate 100, as shown in FIG. 1. In alternative embodiments, via 106 in finished article 100 may be blind via extending only a portion of the way through the substrate 100. In yet another embodiment, finished article 100 may have a combination of through via(s) and blind via(s). At least one surface 102, 104 of the finished article 100 has a surface roughness (Ra) of less than or equal to about 0.6 nm. In some embodiments, both first and second surfaces 102, 104 of the substrate 100 may have a surface roughness (Ra) of less than or equal to about 0.6 nm, less than or equal to about 0.5 nm, less than or equal to about 0.4 nm, less than or equal to about 0.3 nm, or less than or equal to about 0.2 nm. As used herein, the surface roughness (R.sub.a) is defined as the arithmetic average of the differences between the local surface heights and the average surface height and can be described by the following equation:

[00001]$R_a-\frac{1}{n}.Math.\underset{i=1}{\overset{n}{.Math.}}.Math..Math..Math.y_i.Math.,$

[0051] where y.sub.i is the local surface height relative to the average surface height. The surface roughness (R.sub.a) may be measured using a surface profilometer available from Zygo where the surface roughness (R.sub.a) in at least three sample areas of about 100 m by 100 m are measured and averaged.

[0052] Substrate 100 may be a glass-based substrate. Example glass-based substrate materials include, but are not limited to glass (including fused silica) and glass-ceramic. When the substrate is a glass is may be formed from various glass compositions including, without limitation, fused silica (e.g., at least 99% silica), borosilicate glasses, aluminosilicate glasses, alkali-aluminosilicate glasses, aluminoborosilicate glasses, alkali-aluminoborosilicate glasses, and soda lime glasses. Furthermore, substrate 100 may be strengthened (e.g., by an ion exchange process) or non-strengthened. Exemplary substrates may include, but are not limited to, Corning EAGLE XG glass, Corning Gorilla glass, Corning Lotus NXT glass, and Corning Willow glass. In yet further embodiments, substrate 100 may be made from other materials such as ceramic. In some embodiments, substrate 100 may have a thickness in a range of from about 25 m to about 3,000 m, about 25 m to about 2,000 m, about 25 m to about 1,000 m, about 50 m to about 3,000 m, about 50 m to about 2,000 m, about 50 m to about 1,000 m, about 100 m to about 3,000 m, about 100 m to about 2,000 m, about 100 m to about 1,000 m, about 200 m to about 3,000 m, about 200 m to about 2,000 m, about 200 m to about 1,000 m, about 500 m to about 3,000 m, about 500 m to about 2,000 m, about 500 m to about 1,000 m, about 3,000 m or less, about 2,000 m or less, about 1,000 m or less, about 500 m or less, about 400 m or less, about 300 m or less, about 200 m or less, or about 100 m or less.

[0053] FIG. 2. depicts an exemplary flowchart 200 generally illustrating an exemplary process for forming at least one via in a substrate while maintaining the surface roughness (R.sub.a) of at least one surface of the substrate. The steps depicted in the flowchart will be described in greater detail throughout the description of the various figures, but generally include a step 202 of bonding substrates, a step 204 of creating a damage region in the substrates, a step 206 of etching the damage regions, and a step 208 of debonding the substrates. It is noted that though flowchart 200 is depicted as having a certain order, it should be understood that embodiments of the present disclosure are not limited to the order of steps shown in FIG. 2.

[0054] Referring now to FIG. 3A, at least a first substrate 310 having opposing first and second surfaces 312, 314 and a second substrate 320 having opposing first and second surfaces 322, 324 a provided. In some embodiments, first surface 312, 322 and/or second surface 314, 324 may have a surface roughness (Ra) of less than or equal to about 0.6 nm, less than or equal to about 0.5 nm, less than or equal to about 0.4 nm, less than or equal to about 0.3 nm, or less than or equal to about 0.2 nm.

[0055] In some embodiments, as shown in FIG. 2, an exemplary step 202 in the process may be removably bonding surface 314 of a substrate 310 to surface 322 of another substrate 320 to form a stack of substrates. FIG. 3B depicts a stack 300 of substrates 310, 320 removably bonded together. While FIG. 3B depicts a stack of two substrates, more than two substrates can be removably bonded together in a stack. As used herein, a bond is removable if the bonded substrates can be debonded upon application of sufficient separation force without causing catastrophic damage (e.g., breakage) of the substrates. One exemplary method of removably bonding substrates is by using Van der Waals bonding such as disclosed by U.S. Patent Publication No. 2014/0170378, which is hereby incorporated by reference in its entirety. Van der Waals bonding generally includes disposing a surface of a first article on a surface of a second article and raising the temperature of the first article followed by cooling it to room temperature. The result is the first and second substrates 310, 320 being removably bonded together in a stack, wherein the inner surfaces 314, 322 of the substrates in stack 300 bonded together have minimal exposure to an etching solution later on the process. As a result, a pre-etch surface roughness (Ra) of each of bonded surfaces 314, 322 is preserved after the etching process and/or minimally changed. In some embodiments, an adhesion energy of at least 200 mJ/m.sup.2 is needed for sufficient Van der Waals bonding. As noted above, a surface roughness (Ra) of bonded surfaces 314, 322 after debonding is less than or equal to about 0.6 nm, less than or equal to about 0.5 nm, less than or equal to about 0.4 nm, less than or equal to about 0.3 nm, or less than or equal to about 0.2 nm. A surface roughness (Ra) of less than or equal to about 0.6 nm will permit an adhesion energy of least 200 mJ/m.sup.2.

[0056] While FIG. 3B illustrates a stack with two substrates removably bonded together, this is merely exemplary. Thus, in some embodiments, the stack may have more than two substrates removably bonded together, as shown for example in FIG. 4 where the stack 400 may be made of three or more substrates 410, 420, 430 removably bonded together.

[0057] In some embodiments, as shown in FIG. 2, step 204 may include creating at least one damage region 306 in stack 300 using a laser, as shown in FIG. 3B. In other embodiments, the at least one damage region 306 may be formed in each substrate before it is removably bonded to another substrate having at least one damage region to form a stack. In this embodiment, when a surface of a substrate having at least one damage region is removably bonded to a surface of another substrate having at least one damage region, the substrates are bonded such that their damage region(s) align. As indicated in FIG. 3B, the at least one damage region 306 may extend through the thickness of each of the substrates 310, 320. In an alternative embodiment (not shown), the at least one damage region may not extend through the entire thickness of the stack. In this embodiment, the at least one damage region extends through only a portion of a thickness of a first substrate 410, but extends through the entire thickness of each of substrates 420, 430 disposed on first substrate 410.

[0058] The at least one damage region 306 may be formed in a variety of ways. In some embodiments, the at least one damage region 306 may be created by applying a high energy laser pulse to ablate a narrow hole through the stack, allowing etchant to flow therein during downstream etching processes. In other embodiments, the at least one damage region 306 may not be a hole through the thickness of the substrates 310, 320 but rather a line of laser-induced damage formed by a pulsed laser. The pulsed laser may form the damage line by non-linear mullet-photon absorption, for example. The rate of material removal within the line of laser-induced damage defining the at least one damage region 306 is faster than the rate of material removal outside of the at least one damage region 306 during a subsequent etching process. Exemplary ways for performing the laser damage creation and subsequent etching are disclosed in U.S. Pat. No. 9,278,886 and U.S. Pub. No. 2015/0166395, each of which is hereby incorporated by reference in its entirety.

[0059] Referring to block 206 of FIG. 2, the at least one damage region 306 in stack 300 may be etched to create a via 308 from damage region 306. As shown in FIG. 5, etching processes may include submerging stack 300 in an etchant 500 bath. Additionally or alternatively, etchant 500 may be sprayed onto the stack 300. Etchant 500 may remove material from substrates 310, 320 of stack 300 to enlarge a diameter of the at least one damage region 306 to create a via 308. Any suitable etchants may be utilized. Non-limiting examples of etchants include strong mineral acids such as nitric acid, hydrochloric acid, or phosphoric acid with a fluorine containing etchant such as hydrofluoric acid, ammonium bifluoride, sodium fluoride, and the like. Etchant may flow into damage regions 306 from first surface 312 of first substrate 310, second surface 324 of the second substrate 320, or both surfaces. In some embodiments, the etchant and/or stack may be agitated through, for example, but not limited to ultrasonic or megasonic vibration. As an example and not a limitation, via 308 may have a diameter in a range from about 5 m to about 150 m, about 20 m to about 150 m, or about 5 m to about 20 m. In some embodiments, a diameter of an opening of via 308 in surface 324 and a diameter of an opening of via 308 in surface 312 may be the same or may differ by 2 m or less, such that via 306 is substantially cylindrical. In other embodiments, via 308 may have a cone shape and be symmetric only in a vertical direction.

[0060] Referring to block 208 of FIG. 2, after via(s) 308 has been etched, substrates 310, 320 may be debonded, or separated. One exemplary method of debonding removably bonded substrates is by inserting a razor blade between the substrates as disclosed by U.S. Patent Publication No. 2014/0170378. After substrates 310, 320 have been debonded, at least the surfaces that were temporarily bonded together 314, 322 during the etching process will have a surface roughness (Ra) of less than or equal to about 0.6 nm because they were not exposed to the etchant. And in the embodiment shown in FIG. 3D, each substrate will have one or more through vias 308 that extend through the thickness of the substrate. In other embodiments, such as that shown in FIG. 4, at least one substrate may have at least one blind via (e.g., in substrate 410) that does not extend through the entire thickness of the substrate and at least one substrate may have at least one through via (e.g., substrates 420 and 430). As noted above, the blind via in first substrate 410 may be achieved by having the damage region corresponding to the blind via extends through only a portion of a thickness of first substrate 410, but extends through the entire thickness of each of substrates 420, 430 disposed on first substrate 410. Etching is performed such that the damage region in substrates 420, 430 turn into through vias and the damage region in first substrate 410 turns into a blind via. Alternatively, in some embodiments, when the damage region is a line of laser-induced damage, the damage region may extend through the entire thickness of first substrate 410, but the etching is controlled such that only a blind via is formed in first substrate 410. While not shown, in some embodiments, one or more substrates in a stack may have at least one blind via and at least one through via.

[0061] In some embodiments, as a result of the processes described herein, a glass-based article 100 is produced having a thickness of about 300 m or less, 200 m or less, or 100 m or less with at least one via 106 extending from a surface having a surface roughness (Ra) of less than or equal to about 0.6 nm. In some embodiments, the at least one via 106 is a through via as shown in FIG. 1 and in other embodiments, the at least one via is a blind via. It is believed that a glass-based substrate with a thickness of 300 m or less, 200 m or less, or 100 m or less with a surface having a surface roughness (Ra) of less than or equal to about 0.6 nm and a via extending from the surface would not be able to be achieved through traditional processes. For example, polishing or etching a surface of a glass-based substrate to a thickness of 300 m or less, 200 m or less, or 100 m or less and a surface roughness (Ra) of less than or equal to about 0.6 nm would crack and/or break the glass-based substrate.

[0062] After via 308 has been etched and the substrates 310, 320 have been debonded, the substrates 310, 320 may be subjected to additional processing steps for acquiring additional properties. As discussed above, glass-based substrates may be very thin (e.g., anywhere from less than 200 m up to 700 m). Such thin material may be difficult to handle during fabrication procedures because of the fragility and lack of stiffness of the substrate 310. To counteract the fragility and lack of stiffness, the substrate 310 may be removably bonded to a carrier by disposing the second surface 314 of the substrate 310 on a bonding surface of a carrier. One exemplary method of removably bonding a substrate 310 to a carrier is by using Van der Waals bonding such as disclosed by U.S. Patent Publication No. 2014/0170378, as discussed above. Van der Waals bonding is beneficial to downstream processing because of its ability to form bonds that are capable of withstanding processing (e.g., high temperature processing), while allowing the entire area of the substrate to be removed (either all at once, or in sections) from the carrier. After the substrate 310 has been removed, the carrier may be reused for processing additional substrates.

[0063] The carrier may be of any suitable material, such as glass, for example. The carrier need not be glass, but instead may be ceramic, glass-ceramic, silicon or metal, for example. If made of glass, the carrier may be of any suitable composition including, but not limited to, aluminosilicate, borosilicate, aluminoborosilicate, soda lime silicate, and may be either alkali containing or alkali-free depending upon its ultimate application. The carrier may have any suitable thickness. Additionally, the carrier may be made of one layer or multiple layers (including multiple thin sheets) that are bonded together (e.g., by lamination). Furthermore, the coefficient of thermal expansion of the carrier may be substantially matched with that of substrate 310 to prevent warping of substrate 310 or decoupling of substrate 310 from the carrier during processing at elevated temperatures. The surface roughness (Ra) of substrate 310 is additive to the surface roughness of carrier. Therefore, in some embodiments, the carrier may have a surface roughness (Ra) less than or equal to 0.6 nm so that an adhesion energy of at least 200 mJ/m.sup.2 may be achieved.

[0064] Once the substrate 310 is sufficiently bonded to the carrier such that the carrier and the substrate 310 will not separate during processing, the substrate 310 may be subjected to further processing. Processing the substrate 310 may include steps such as applying alkaline cleaning solutions to the substrate 310, wet etching the substrate 310, polishing the substrate 310, metal plating the substrate 310, metal patterning the substrate 310 by wet etching, depositing material onto the substrate 310 by deposition, filling vias 108 with an electrically conductive material, and annealing the substrate 310.

[0065] It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents.