Materials and Methods for Passivation of Metal-Plated Through Glass Vias

Abstract

A through-glass via (TGV) formed in a glass substrate may comprise a metal plating layer formed in the TGV. The TGV may have a three-dimensional (3D) topology through the glass substrate and the metal plating layer conformally covering the 3D topology. The TGV may further comprise a barrier layer disposed over the metal plating layer, and a metallization layer disposed over the barrier layer. The metallization layer may be electrically coupled to the metal plating layer through the barrier layer. The barrier layer may comprise a metal-nitride film disposed on the metal plating layer that is electrically coupled to the metallization layer. The barrier layer may comprise a metal film disposed over the metal plating layer and over a portion of glass surrounding the TGV, and an electrically-insulating film disposed upon the metal film, the electrically-insulating film completely overlapping the metal plating layer and partially overlapping the metal film.

Claims

1. A method of disposing a barrier film on a metallized through-glass via (TGV) formed in a glass substrate, comprising: using an atomic layer deposition (ALD) procedure to establish a metal-nitride film on a metal plating layer of the metallized TGV; and forming an electrically-conductive metallization layer upon the metal-nitride film, the electrically-conductive metallization layer being electrically coupled to the metal-nitride film.

2. The method of claim 1, further comprising formulating the conductive metal-nitride film to comprise titanium nitride (TiN).

3. The method of claim 1, further comprising electrically coupling the outer metallization layer to the conductive metal-nitride film.

4. The method of claim 1, further comprising depositing one or more conductive coatings on the conductive metal-nitride film.

5. The method of claim 4, wherein the one or more conductive coatings comprise one or both of TiW and Au.

6. A method of disposing a barrier film on a metallized through-glass via (TGV) formed in a glass substrate, comprising: using a physical vapor deposition (PVD) procedure to establish a metal film (i) over a metal plating layer of the metallized TGV and (ii) over at least portions of glass surrounding the TGV; using a chemical vapor deposition (CVD) procedure to establish an electrically-insulating film upon the metal film, the electrically-insulating film completely overlapping the metal plating layer and partially overlapping the metal film; and using a PVD procedure to form an electrically-conductive metallization layer over the insulating film and over the metal film, the electrically-conductive metallization layer being electrically coupled to the metal film.

7. The method of claim 6, further comprising preparing the conductive metal film to include titanium tungsten (TiW).

8. The method of claim 6, further comprising preparing the insulating film to include silicon dioxide (SiO.sub.2).

9. The method of claim 6, further comprising patterning the insulating film to form a diffusion barrier patch that covers at least a region of the conductive metal film that overlays the TGV.

10. The method of claim 9, further comprising extending the insulating film so that the diffusion barrier patch covers at least a portion of the glass surrounding the TGV.

11. The method of claim 6, further comprising electrically coupling the outer metallization layer to the conductive metal film.

12. The method of claim 6, further comprising depositing one or more conductive coatings on the conductive metal-nitride film.

13. The method of claim 12, wherein the one or more conductive coatings comprise one or both of TiW and Au.

14. A through-glass via (TGV) formed in a glass substrate, comprising: a metal plating layer formed in the TGV, the TGV having a three-dimensional (3D) topology through the glass substrate and the metal plating layer conformally covering the 3D topology; a barrier layer disposed over the metal plating layer; and an electrically-conductive metallization layer disposed over the barrier layer, the electrically-conductive metallization layer being electrically coupled to the metal plating layer through the barrier layer.

15. The TGV of claim 14, wherein the barrier layer further comprises a metal-nitride film disposed on the metal plating layer, the metal-nitride layer being electrically coupled to the electrically-conductive metallization layer.

16. The TGV of claim 15, wherein the metal-nitride film is titanium nitride (TiN).

17. The TGV of claim 14, wherein the barrier layer further comprises (i) a metal film disposed over the metal plating layer and over at least a portion of glass surrounding the TGV, and (ii) an electrically-insulating film disposed upon the metal film, the electrically-insulating film completely overlapping the metal plating layer and partially overlapping the metal film, and wherein the metal film being electrically coupled to the electrically-conductive metallization layer.

18. The TGV of claim 17, wherein the metal film is titanium tungsten (TiW), and the electrically-insulating film is silicon dioxide (SiO.sub.2).

19. The TGV of claim 14, further comprising one or more conductive coatings on the electrically-conductive metallization layer.

20. The TGV of claim 19, wherein the one or more conductive coatings comprise one or both of TiW and Au.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.

[0019] The foregoing will be apparent from the following more particular description of example embodiments, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating embodiments.

[0020] FIG. 1A shows a cross-sectional view of an example through-glass via (TGV), formed in a silicate glass substrate.

[0021] FIG. 1B shows the TGV of FIG. 1A with thin adhesion layer, a metal seed layer disposed on the adhesion layer, and a metal plating layer disposed upon the seed layer.

[0022] FIGS. 2A and 2B show scanning electron micrographs (SEMs) that depict micro-meter and nano-meter scale particles on the Au surface of a TGV.

[0023] FIG. 3 shows an example TGV with metal films deposited on the top and/or bottom surfaces of the glass substrate.

[0024] FIG. 4 shows one embodiment of passivation layer deployed on a TGV according to the invention.

[0025] FIG. 5 shows another embodiment of passivation layer deployed on a TGV according to the invention.

[0026] FIGS. 6A and 6B show examples of TGVs fabricated with a passivation layer according to the invention.

[0027] FIG. 7 shows an embodiment of the passivated TGV of FIG. 4 with additional metal coatings for use as conductive interconnect paths and/or seal rings for use in IC and MEMS packaging.

[0028] FIG. 8 shows an embodiment of the passivated TGV of FIG. 5 with additional metal coatings for use as conductive interconnect paths and/or seal rings for use in IC and MEMS packaging.

DETAILED DESCRIPTION

[0029] A description of example embodiments follows.

[0030] The teachings of all patents, published applications and references cited herein are incorporated by reference in their entirety.

[0031] The embodiments described herein are directed to a passivation (or barrier) layer associated with a metallized through-glass via (TGV). As described herein, FIG. 1B illustrates an example hourglass-shaped TGV lined with an adhesion layer 120, a metal seed layer 122, and a metal plating layer 124. This example TGV is shown in FIG. 3 with one or more metal films deposited on the top and/or bottom surfaces of the glass substrate, using, for example, a physical vapor deposition (PVD) technique. For the example illustrated in FIG. 3, a first metal layer 302 of titanium tungsten (TiW) is deposited on the metal plating layer 124, and a second metal layer 304 of gold (Au) is disposed on the first metal layer 302. The outer metallization layer 304 may serve not only as a conductive path for die-to-die interconnects, but also as bond pads or seal rings when joining device and lid substrates using a wafer bonding technique, e.g., through thermos-compressive bonding. For thermo-compressive bonding with the Au seal rings of a counter substrate, clean Au bond pads that are free of foreign particles are needed for strong Au-to-Au bonds to achieve a hermetic seal. Appropriate surface passivation for metal-filled TGVs may reduce or prevent metal diffusion and interaction with O.sub.2 and hence prevent unwanted metal-oxide particle formation.

[0032] The described embodiments allow for a significant reduction in parasitic metal-oxides created on the substrate. Specifically, the surface of a silicate glass wafer, which has metal-filled TGVs, is coated with a passivation layer. Further, the described embodiments facilitate disposing the passivation layer on the non-planar, 3-dimensional (3D) topographies of the types of TGVs described herein. In certain applications, the TGV is required to convey a significant amount of electrical power, and is necessarily physically larger than typical TGVs. The described embodiments facilitate complete coverage of the TGV, to prevent potential diffusion paths.

[0033] In one embodiment, shown in FIG. 4, the passivation layer comprises a conductive metal-nitride film 402, deposited using an atomic layer deposition (ALD) method known in the art. In the example embodiment, the metal-nitride film 402 comprises titanium nitride (TiN), although in other embodiments other metal-nitride materials, e.g, tantalum nitride (TaN) may alternatively be used. The ALD processing facilitates complete conformal deposition of the metal-nitride film 402 within the 3D topography of the TGV.

[0034] In another embodiment, the passivation layer may comprise two parallel layers comprising an insulating oxide-based film 504, deposited by chemical vapor deposition (CVD) on the surface of a metal film 502, e.g., titanium tungsten (TiW), which is deposited by PVD on the metal plating layer 124, as shown in FIG. 5. In the example embodiment described herein, the insulating oxide-based film 504 comprises silicon dioxide (SiO.sub.2), although other insulating oxide-based materials known in the art, e.g., amorphous aluminum oxide (Al.sub.2O.sub.3) may alternatively be used. In the example embodiment described herein, the metal film 502 comprises titanium tungsten (TiW), although in alternative embodiments the metal film 502 may comprise other transition metals such as titanium (Ti) and chromium (Cr) deposited by PVD, or transition metal alloys such as TiN and TaN deposited by PVD.

[0035] The insulating oxide-based film 504 may be patterned to form a diffusion barrier patch 506 over a metal-filled TGV (i.e., the metal plating layer 124), thereby exposing the underlying metal film 502 outside of the diffusion barrier patch, as shown in FIG. 5. This oxide patch can effectively serve as a barrier that hampers metal-O.sub.2 diffusion and reaction.

[0036] Optical micrographs shown in FIGS. 6A and 6B demonstrate that metal-oxide particles are substantially obsolete in the presence of a SiO.sub.2/TiW diffusion barrier patch 506, whereas those in FIGS. 2A and 2B show that cupric oxide particles are prevalent on the Au surface in the absence of a passivation layer.

[0037] One or more extra metal coatings, e.g., Au and TiW, can be applied atop the passivation layer implemented by either of the techniques described with respect to FIGS. 4 and 5. The additional metal coatings may be deposited by PVD and then patterned by standard photolithography and etching techniques together with the passivation layer. In the example embodiment shown in FIG. 7, which corresponds to the embodiment depicted in FIG. 4, the additional metal coatings over the underlying TiN film 402 comprise a TiW film 702 and an Au film 704. In the example embodiment shown in FIG. 8, which corresponds to the embodiment depicted in FIG. 5, the additional metal coatings over the underlying TiW film 502 outside of the SiO.sub.2/TiW diffusion barrier patch 506 likewise comprise a TiW film 802 and an Au film 804. The additional metal coatings 702, 704, 802, 804 may be used to define conductive paths for die-to-die interconnects and bond pads, and/or seal rings for use in IC and MEMS packaging.

[0038] In the described embodiments, metal-nitride and oxide-based thin films, such as TiN and SiO.sub.2, have been proposed to passivate the surface of metal-filled TGVs. The metal-nitride and oxide-based thin films may function as an effective diffusion barrier, and may inhibit non-inert metal atoms within a metal plating layer from diffusing through a metallization layer and hence encountering and reacting with O.sub.2, enabling the fabrication of clean silicate glass substrate surfaces free of undesirable metal-oxide micro- and nano-particles. The metal-nitride and oxide-based thin films can be deposited easily with conventional deposition methods such as CVD, PVD, and ALD onto the surface of metallized TGV wafers and patterned easily with standard photolithography and etching techniques.

[0039] The described embodiments demonstrate great potential for applications in 3, 2.5, and 2-dimensional (3D, 2.5D, and 2D, respectively) ICs and MEMS that require silicate glass packaging for excellent electrical isolation, RF performance, optical transparency, and structural flexibility.

[0040] While example embodiments have been particularly shown and described, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the embodiments encompassed by the appended claims.