Full Symmetric Multi-Throw Switch Using Conformal Pinched Through Via

Abstract

A hermetically sealed component may comprise a glass substrate, a device with at least one electrical port associated with the glass substrate, and a glass cap. The glass cap may have at least one side wall. The glass cap may have a shaped void extending therethrough, from top surface of the glass cap to bottom surface of glass pillar. An electrically conductive plug may be disposed within the void, the plug configured to hermetically seal the void. The electrically conductive plug may be electrically coupled to the electrical port. The glass cap may be disposed on the glass substrate, with the at least one side wall disposed therebetween, to form a cavity encompassing the device. The side wall may contact the glass substrate and the glass cap to provide a hermetic seal, such that a first environment within the cavity is isolated from a second environment external to the cavity.

Claims

1. A method of fabricating a plurality of device packages, comprising: fabricating at least two devices directly on a glass substrate, each of the at least two devices having at least one electrical port; fabricating a glass cover that comprises at least two glass caps, one for each of the two devices, each of the at least two glass caps having: (i) at least one side wall; (ii) a void that extends through the glass cap and through a glass pillar from a top surface of the glass cap to a bottom surface of the glass pillar; and (iii) an electrically conductive plug disposed within the void, the electrically conductive plug configured to be electrically coupled to the at least one electrical port of a respective device and to hermetically seal the void; disposing the glass cover on the glass substrate, such that each of the at least two glass caps covers a corresponding device on the glass substrate to form a respective device package, and such that each of the at least two glass caps provides a cavity that encompasses the corresponding device; attaching the at least one side wall to the glass substrate to provide a hermetic seal, to isolate a first environment within the cavity from a second environment external to the device package; and electrically coupling each of the electrically conductive plugs to a respective electrical port at the top surface of the glass cap.

2. The method of claim 1, further comprising fabricating the glass cover as an array of four or more glass caps arranged in an n by m grid, n being a first integer greater than one, and m being a second integer greater than one.

3. The method of claim 1, further comprising disposing the glass cover on the glass substrate, such that each of the at least two glass caps covers at least two devices on the glass substrate to form a device package for the respective at least two devices.

4. The method of claim 1, further comprising cutting the glass substrate along one or more delineations between each pair of the two or more glass caps, such that the hermetic seal of each respective cavity is maintained.

5. The method of claim 1, further comprising disposing an electrical conductor on the glass substrate, a first end of the electrical conductor electrically coupled to an electrical port of at least one of the at least two devices, and a second end of electrical conductor electrically coupled to an electrical port on the glass substrate outside of the first environment within the cavity.

6. The method of claim 1, wherein fabricating at least two devices directly on a glass substrate further comprises integrating the at least two devices on the glass substrate using a series deposition-lithography-pattern etch process.

7. The method of claim 1, wherein attaching the at least one side wall to the glass substrate further comprises implementing a bond between the at least one side wall and the glass substrate by one of (i) metal compression, (ii) eutectic bonding, (iii) laser bonding, (iv) glass frit, and (v) anodic wafer bonding.

8. The method of claim 1, further comprising disposing a re-distribution layer on the top surface of the glass cap, and electrically coupling the redistribution layer to the electrically conductive plug.

9. The method of claim 1, further comprising forming the glass cover such that the glass cap and the at least one side wall comprise a single integrated component.

10. The method of claim 1, further comprising fabricating the at least one side wall and the glass substrate such that the at least one side wall and the glass substrate comprise a single integrated component.

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 drawings 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 an example embodiment of a hermetically sealed component according to the invention.

[0021] FIG. 1B illustrates an exploded view of the component shown in FIG. 1A.

[0022] FIG. 1C shows another example embodiment of a hermetically sealed component according to the invention.

[0023] FIG. 1D shows an exploded view of the example embodiment shown in FIG. 1C.

[0024] FIG. 1E shows another example embodiment of a hermetically sealed component according to the invention.

[0025] FIG. 1F shows yet another example embodiment of a hermetically sealed component according to the invention.

[0026] FIG. 2A shows a cross-sectional view of an hourglass-shaped void according to the invention.

[0027] FIG. 2B shows a cross-sectional view of an embodiment of the metallic plug of a conformal pinched via, according to the invention.

[0028] FIG. 2C illustrates a cross-sectional view of another embodiment of the metallic plug of a conformal pinched via, according to the invention.

[0029] FIG. 3A illustrates an example of a wafer-scale hermetically sealed package assembly according to the invention.

[0030] FIG. 3B shows an exploded view of the wafer-scale hermetically sealed package assembly of FIG. 3A.

[0031] FIG. 3C shows a plurality of devices arranged in a two-dimensional grid array on a common substrate according to the invention.

[0032] FIG. 4A illustrates a top view of an example single pole, four-throw MEMS switch according to the invention.

[0033] FIG. 4B illustrates an isometric view of the MEMS switch depicted in FIG. 4A.

[0034] FIG. 5 illustrates an example embodiment of a method of fabricating a plurality of device packages.

DETAILED DESCRIPTION

[0035] A description of example embodiments follows.

[0036] The teachings of all patents, published applications and references cited herein are incorporated by reference in their entirety.

[0037] FIG. 1A illustrates an example embodiment of a hermetically sealed component 100 as described herein. FIG. 1B illustrates an exploded view of the component 100 shown in FIG. 1A. The hermetically sealed component 100 may comprise a glass substrate 102 and a glass cap 104. The glass cap 104 may comprise a cap side wall 106 and a cap upper wall 108. The glass cap 104 and the glass substrate 102 may be fabricated from any of a variety of glass materials, such as silicon dioxide (SiO.sub.2), fused silica, silica glass, quartz, sodium-doped glass, and borosilicate glass. In other embodiments, the substrate and cap may consist of non-glass materials, such as Silicon (Si), Silicon Carbide (SiC) and Galium Nitride (GaN), although other non-glass materials may also be used. Although the example embodiment shown in FIGS. 1A and 1B identify a glass cap 104 with a distinct cap side wall 106 and a distinct cap upper wall 108, the glass cap 104 may be fabricated with the side wall and the upper wall consolidated to form a single integrated glass cap 104. Similarly, the side wall and the glass substrate 102 may be consolidated to form a single glass substrate unit with an integrated side wall.

[0038] The coefficient of thermal expansion (CTE) of the glass cap material should be substantially the same as the CTE of the glass substrate material, to minimize stress at any bonding joints between the glass cap 104 and the glass substrate 102.

[0039] A void 110 may be implemented in the glass cap 104, for example through the entire thickness of the glass cap 104 cap, as shown in FIGS. 1A and 1B, thereby creating a passageway through the glass cap 104. In the example embodiment of FIGS. 1A and 1B, the void 110 is shown formed in the glass cap 104 and side wall 106 from the top surface 109 of the glass cap to the bottom surface 113 of the side wall 106. In other embodiments, the void may be formed in other locations, for example laterally through the side wall 106 or up through the glass substrate 102. The void may be configured to be cylindrical with a circular cross-section, although in other embodiments the void may have a non-cylindrical cross-section, for example an elliptical cross section or an irregular cross section. Alternatively, the void may be characterized by a non-constant cross-sectional diameter from the top surface 109 of the glass cap to the bottom of the glass cap. The void may be characterized by a diameter of less than or equal to 500 μm in a plane defined by the upper wall top surface.

[0040] In some embodiments, a cross-sectional view of the void 110 may exhibit an “hourglass” shape, as shown in FIGS. 2A and 2B. A shaped metallic plug 122 may be disposed within the hourglass void 110a, thereby implementing a conformal pinched via (CPV) 124 in the glass cap or substrate. The metallic plug 122 may be formed in the hourglass void 110a by filling the hourglass void 110a by conformal plating from the side wall of the hourglass void 110a, until the plated thickness closes off the center region. The resulting shape of the metallic plug 122 is such that the hourglass void 110a is not completely filled across the top of the glass cap (or substrate) to the bottom of the glass cap (or substrate). Glass may extend from the glass cap or glass substrate to form a glass pillar, as shown for example in FIG. 1C. In this case, the void extends through the outer (top) surface 330 of the glass cap (or substrate) and bottom surface 332 of the glass pillar, as depicted in the example embodiment shown in FIG. 3B. The CPV 124, along with the glass cap material surrounding it, is referred to herein as a CPV pillar 130.

[0041] Portions 123 of the metallic plug 122 may extend along the top surface 109 and/or the bottom surface 111 of the glass cap 104. The portions 123 may be a redistribution layer (RDL). The redistribution layer may be selected from a variety of metals, for example gold, aluminum, and copper. This incomplete filling of the void by the metallic plug may contribute to accommodating relative differences in expansion and contraction of the glass cap 104 and the metallic plug 122 across operating and storage temperature ranges of the hermetically sealed component 100, thereby maintaining a hermetic seal at the CPV. In other words, the described configuration of the metallic plug may mitigate a difference between a coefficient of thermal expansion (CTE) of the glass cap and a CTE of the electrically conductive plug, thereby maintaining a hermetic seal at the CPV across operating and storage temperature ranges of the hermetically sealed component 100. FIG. 2C shows an alternative embodiment of the hourglass-shaped CPV 124.

[0042] The device 112 may be fabricated directly on the glass substrate 102. In an embodiment, the device is fabricated on the glass substrate 102 using a series deposition-lithography-pattern etch process. The device 112 may comprise at least one electrical port 116, through which electrical signals may enter and/or leave the device 112.

[0043] Although not shown, the glass substrate 102 and the glass cap 104 may be laterally extended beyond the device 112. At the laterally-outer portions of the device 112, the glass cap side walls may extend down to contact the glass substrate 102. In these extended regions, the glass cap 104 may be fixedly attached to the glass substrate 102 by, for example, metal thermo-compression bonding (also referred to herein as metal bonding), eutectic bonding, laser bonding, glass frit bonding, and anodic wafer bonding, although other bonding techniques known in the art may also be used.

[0044] Arranging the glass cap 104 and the glass substrate 102 with the side walls 106 therebetween, as shown in FIG. 1A, forms a cavity 118 that defines a device environment, isolated from an external environment 120. The CPV 124 may be electrically coupled to the device port 116 through, for example, metal thermo-compression bonding.

[0045] In some embodiments, the hermetically sealed component 100 may be configured with the side wall 106 being part of the glass substrate 102, rather than part of the glass cap 104, such that the glass cap 104 comprises only the cap upper wall 108. In such a configuration, the cavity 118 is formed by fixedly attaching the glass cap 104 (comprising only the cap upper wall 108) to the side walls of the glass substrate 102.

[0046] Although FIGS. 1A and 1B depict a hermetically sealed component 100 with CPV pillars on the periphery of the device 112, a CPV pillar may contact the device 112 in a middle portion of the device, instead of, or in addition to, the peripheral CPV pillars. FIG. 1C shows an example embodiment with a mid-region pillar 130a, and FIG. 1D shows an exploded view of the example embodiment of FIG. 1C. FIG. 1E illustrates an example embodiment with a mid-region pillar 130a and periphery pillars 130b, 130c.

[0047] Further, as shown in FIG. 1F, a CPV 124 may be implemented through the glass substrate 102, as described for the glass cap. A CPV pillar through the glass substrate 102 may facilitate electrical signals to be coupled to a device port 116 on the underside of the device 112, and electrical communication through the glass substrate side of the hermetically sealed component 100. An embodiment with CPV pillars both in the glass cap and in the glass substrate may be used, for example, to interface to a component, such as a controller, mounted on the glass cap, while other external components may interface to the device 112 through the glass substrate.

[0048] In some embodiments, the device 112 may be a microelectromechanical system (MEMS)-based device. In other embodiments, the device 112 may be a nanoelectromechanical system (NEMS) device. In other embodiments, the device 112 may be an ohmic switch. The ohmic switch may be a single throw ohmic switch, or a multi-throw ohmic switch. The device may be fabricated of metal, polysilicon, or both.

[0049] The embodiments described herein may be configured to provide a hermetic seal, between the device environment within the cavity 118 and the external environment 120, capable of providing a measured helium leak rate that is less than 1.0×10.sup.−6 (atm-cm).sup.3/second.

[0050] In some embodiments, the device 112 may comprise two or more electrical ports 116, with corresponding CPVs 124 configured to convey electrical signals to and from the device 112 outside of the device environment defined by the cavity 118. In other embodiments, the device 112 may comprise two or more devices fabricated on the glass substrate 102, each having device port(s) and corresponding CPV(s).

[0051] The described embodiments may be directed to two or more hermetically sealed components fabricated together in what is referred to as wafer-scale fabrication. Referring to FIG. 3A, two or more devices may be fabricated on a common glass substrate 302. FIG. 3B depicts an exploded view of the assembly shown in FIG. 3A. In the example embodiment depicted in FIGS. 3A and 3B, three devices, device 322a, 322b, 322c, are shown fabricated on glass substrate 302. Although only three devices are shown in this example embodiment for descriptive simplicity, more devices may be implemented in other embodiments. For example, FIG. 3C shows another example embodiment with 100 devices, from device D01 through device D100, each of which is attached to the common glass substrate 302 in a 10×10 grid pattern. FIG. 3C is a top-down view of the devices on the common glass substrate 302, contrasted with the sectional side-views of FIGS. 1A, 1B, 1C, 2, 3A and 3B.

[0052] In an embodiment, a single, composite glass cap structure 304 may comprise individual glass caps for each of the devices D01 through D100 attached to the glass substrate 302. Each individual glass cap may include at least one CPV 324 for conveying electrical signals to/from its respective device. As described herein, the CPV 324 is formed by a metallic plug disposed within an hourglass-shaped void 310 in the glass cap structure 304. Although the CPVs 324 shown in FIGS. 3A and 3B are CPV pillars arranged in the center of the device cavity, the CPV pillars may be disposed within the side walls instead of or in addition to the center positioned CPV pillars.

[0053] As described herein with respect to FIGS. 1A, 1B, 1C, 2, each individual glass cap of the composite cap structure 304 may have side walls associated with an upper cap wall to implement a device cavity, or the side walls may be associated with the common glass substrate 302 to facilitate the device cavity.

[0054] The composite glass cap structure 304 may be fixedly attached to the common glass substrate 302, which hosts the devices 322a, 322b, 322c with device ports 316a, 316b, 316c, as shown in FIG. 3A, thereby forming an assembly of two or more individual device packages. Three individual device packages are formed in the example of FIG. 3A. Each individual device 322n (where ‘n’ is an index from 1 to N, where N denotes the total number of devices being packaged), and its respective individual glass cap and individual glass substrate, may be separated from its neighbors in the combined assembly (i.e., composite glass cap, glass substrate and device) by cutting at the delineations 330 shown in FIG. 3A. Such cutting may be performed by any of various methods of accomplishing integrated circuit wafer die as is known in the art. In a grid array of packages, as depicted in FIG. 3C, orthogonal cuts (e.g., in the ‘x’ direction and ‘y’ direction, where the x-y plane is parallel to the surface of the common glass substrate 302) are made across the assembly, to separate individual Dn package elements.

[0055] Although the example embodiments described herein depict a single device packaged within a hermetically sealed device environment, the techniques described herein may alternatively be used to hermetically seal two or more devices within a common device environment.

[0056] A device packaged as described herein may include a MEMS-based or a NEMS-based device, although other types of devices may also be packaged according to the described embodiments. Specific types of MEMS or NEMS based devices may include a single-pole-single-throw switch, a single-pole-multi-throw switch, a multi-pole-single throw switch, or a multi-pole-multi-pole switch. An advantage to the described embodiments is that electrical signal paths to switch poles and switch throw ports do not need to follow a purely two-dimensional path, e.g., along the surface of the glass substrate.

[0057] An example symmetrical single-pole, four-throw (SP4T) MEMS switch is shown in a top view in FIG. 4A, and in an isometric view in FIG. 4B. The pole of the switch is situated centrally, with the four throws distributed symmetrically about the pole (to the top of the pole, to the bottom of the pole, to the left of the pole, and to the right of the pole). A pole CPV 402 is situated in the package glass cap directly above the pole port of the SP4T switch. Throw poles 404a, 404b, 404c, 404d are situated at each of the respective throw ports. Compared to signal distribution architectures that are restricted to two-dimensional routing, the required physical substrate space of this example embodiment is substantially reduced, because the center signal connection at CPV 402 is used for single pole port. Accordingly, no space needs to be reserved on the MEMS wafer for the single pole port signal trace routing. This direct access to the switch pole port may result in improved switch performance because of a shorter distance from the pole port to throw ports. All electrical paths are identical from the pole port to each throw port, which facilitates identical behavior for each throw channel.

[0058] The examples described herein depict device ports connected to CPV pillar electrical ports situated in the package top cap, which facilitates direct “three-dimensional” access to the device ports. It should be understood, however, that the CPV pillar ports can be situated in other package locations, for example on the side walls. Further, one or more package electrical ports may be non-CPV ports, providing traditional two-dimensional access to device ports at the periphery of the device, in addition to the CPV pillar ports.

[0059] FIG. 5 illustrates an example embodiment of a method 500 of fabricating a plurality of device packages, which may comprise attaching 502 at least two devices to a glass substrate. Each of the at least two devices may comprise at least one electrical port. The method 500 may further comprise fabricating 504 a glass cover that comprises at least two glass caps, one for each of the two devices. Each of the at least two glass caps may have an upper wall and at least one side wall. The upper wall may have a void extending through the upper wall from an upper wall top surface to an upper wall bottom surface. Each of the glass caps may further have an electrically conductive plug disposed within the void, the electrically conductive plug hermetically sealing the void. Each of the glass caps may further have a conductor configured to electrically couple the electrically conductive plug to the electrical port. The method may further comprise disposing 506 the glass cover on the glass substrate. Each of the glass caps may cover a corresponding device on the glass substrate, thereby forming a cavity that encompasses the corresponding device. The method may further comprise attaching 508 the at least one side wall to the glass substrate to provide a hermetic seal, thereby isolating a first environment within the cavity from a second environment external to the device package.

[0060] 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.