Certain devices, such as switches, may not operate reliably and consistently when exposed to uncontrolled operational environmental conditions. For example, moisture and contamination could cause an increase in early device failures. Accordingly, it is common practice to contain such devices within a protective package, which, at least to some extent, separates an internal device environment from an external environment. Electrical connections, which electrically couple the device to components in the external environment, must pass from the external environment into the device environment and to the device. Device packages may use a through-package via, which is a shaped void in the package walls, to convey a conductor through the package from the external environment to the device environment. When the package is made of glass (e.g., fused SiO2), the via may be referred to as a through-glass via (TGV).
Such TGVs need to be metallized to implement a hermetic seal at the TGV, while facilitating an electrically conductive path through the package. Aluminum (Al) may be used to metalize a TGV, as disclosed in U.S. Pat. No. 8,242,382, in which molten aluminum is pressurized to flow into the via. A disadvantage of using Al to metalize a TGV, particularly when the package hosting the TGV is a material such as fused SiO2, is that the molten aluminum may interact with the fused SiO2 when the aluminum contacts the fused SiO2 at the TGV walls, causing the overall fused SiO2 package to become brittle and thus easily damaged. Certain operations, such a chemical-mechanical planarization (CMP), may fracture or otherwise damage altered package material.
A through-glass via (TGV) may be formed in a wall of a device package to allow access to components within the package from outside of the package. The TGV may be metallized to facilitate communication of electrical signals through the TGV, while maintaining a hermetic seal at the TGV. The described embodiments are directed to implementing a barrier between (i) a metal plug disposed within a TGV of a device package and (ii) the walls of the TGV. The barrier may be configured to prevent the metal plug from direct contact with the package material in which the TGV resides, thereby preventing an interaction between the aluminum and the device package material.
The described embodiments are directed to processes that introduce molten metal (such as aluminum) into via holes of device package materials. Such device package materials therefore should be survivable at the temperatures of the molten metals (e.g., up to 1,100° C.). Semiconductor materials (e.g., silicon wafers) would not survive such molten metal temperatures, so the molten metal barrier layers of the described embodiments are not used in typical semiconductor processing environments.
In one aspect, the invention may be a metallized via structure, comprising a via hole formed through a substrate. The via hole may be defined by at least one interior wall of the substrate. The metallized via structure may further comprise a barrier layer disposed upon the at least one interior wall to form a barrier layer lined via hole, and a metallic plug disposed within the barrier layer lined via hole by pressurized injection of molten metal. The barrier layer may be situated between the metallic plug and the at least one interior wall. The barrier layer configured to prevent the metallic plug from contacting the interior wall. The barrier layer and the plug together seal the via hole to prevent passage of substances through the substrate at the location of the via hole.
The barrier layer may comprise silicon nitride (SiXNYHZ). In other embodiments, the barrier layer may comprise a material selected from silicon nitride (SiXNYHZ), silicon carbide (SiC), titanium disilicide (TiSi2), tungsten disilicide (WSi2), tungsten (W), aluminum nitride (AlN), aluminum oxide (Al2O3), carbon (C), titanium nitride (TiN), titanium tungsten, zirconia (ZrO2), yttria (Y2O3), and combinations thereof.
The barrier layer may be disposed upon the at least one interior wall using a conformal film deposition procedure. The conformal film deposition procedure comprises one of low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD), metalorganic chemical vapor deposition (MOCVD), or atomic layer deposition (ALD).
The metallic plug may comprise a metal selected from aluminum (Al), gold (Au), silver (Ag), copper (Cu), tin (Sn), lead (Pb), magnesium (Mg), and alloys thereof. The metallic plug disposed within the barrier layer lined via hole may be formed by melting the metal to form molten metal, evacuating the barrier layer lined via hole, and injecting the molten metal into the barrier layer lined via hole. The molten metal may be injected into the barrier layer lined hole under pressure. The molten metal may have a melting point that is between 600° C. and 1,100° C.
In another aspect, the invention may be a method of fabricating a metalized via structure, comprising forming a via hole in a substrate. The via hole may be defined by at least one interior wall of the substrate. The method may further comprise disposing a barrier layer upon the at least one interior wall to form a barrier layer lined via hole, and disposing a metallic plug within the barrier layer lined via hole. The barrier layer may be situated between the metallic plug and the at least one interior wall. The barrier layer may be configured to prevent the metallic plug from contacting the interior wall.
The method may further comprise using silicon nitride to form the barrier layer. The method may further comprise using a material selected from silicon nitride (SiXNYHZ), silicon carbide (SiC), titanium disilicide (TiSi2), tungsten disilicide (WSi2), tungsten (W), aluminum nitride (AlN), aluminum oxide (Al2O3), carbon (C), titanium nitride (TiN), titanium tungsten, zirconia (ZrO2), yttria (Y2O3), and combinations thereof, to form the barrier layer. The method may further comprise disposing the barrier layer upon the at least one interior wall using a conformal film deposition procedure. The method may further comprise using a conformal film deposition procedure comprises one of low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD), metalorganic chemical vapor deposition (MOCVD), or atomic layer deposition (ALD).
In another aspect, the invention may comprise a through-glass via (TGV) structure, comprising a via hole formed in a glass wall. The via hole may be defined by at least one interior surface of the glass wall. The TGV structure may further comprise a barrier layer disposed upon the at least one interior wall to form a barrier layer lined via hole, and a metallic plug disposed within the barrier layer lined via hole. The barrier layer may be situated between the metallic plug and the at least one interior wall.
The barrier layer may comprise silicon nitride (SiN). The barrier layer may comprise a material selected from silicon nitride (SiXNYHZ), silicon carbide (SiC), titanium disilicide (TISi2), tungsten disilicide (WSi2), tungsten (W), aluminum nitride (AlN), aluminum oxide (Al2O3), carbon (C), titanium nitride (TiN), titanium tungsten (TiW), zirconia (ZrO2), yttria (Y2O3), and combinations thereof. The barrier layer may be disposed upon the at least one interior wall using a conformal film deposition procedure. The conformal film deposition procedure may comprise one of low pressure chemical vapor deposition (LPCVD), plasma enhanced chemical vapor deposition (PECVD), metalorganic chemical vapor deposition (MOCVD), or atomic layer deposition (ALD). The metallic plug may comprise a metal selected from aluminum (Al), gold (Au), silver (Ag), copper (Cu), tin (Sn), lead (Pb), magnesium (Mg), and alloys thereof.
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.
A description of example embodiments follows.
The teachings of all patents, published applications and references cited herein are incorporated by reference in their entirety.
The described embodiments are directed to a barrier film, integrated with a through-glass via (TGV), to reduce or prevent temperature-driven material interactions between (i) the material in which the TGV is formed (e.g., TGV substrate material such as SiO2 or quartz), and (ii) a metal disposed into the TGV. It is desirable to prevent such temperature-driven material interactions because the interactions may cause local and global changes to the mechanical properties of the device package material. As a specific example, when molten aluminum is flowed into a TGV formed in a fused silica (SiO2) substrate, the molten aluminum may diffuse into and/or react with the SiO2 substrate structure, which may cause the substrate surface to become brittle. Subsequent process steps required for fabrication, such as chemical-mechanical planarization (CMP), may not be possible without causing damage due to the increased brittleness of the substrate.
A void or via 112 may be formed through the cap substrate 106 and its pillar 108, as shown in
A void 112 may be formed in the cap substrate 202, as shown in
As shown in
Using a subtractive procedure (e.g., wet etching, although other such techniques known in the art may alternatively be used), portions of the cap substrate 202 may be removed to form the cavities 110, as shown in
In general, the barrier layer 204 comprises a material that may prevent material of the metal fill 114 from propagating into the constituent material of the cap 106, and can do so at temperatures associated with the melting point of the constituent material of the metallic plug 114 (e.g., molten aluminum). The barrier layer 204, once formed on the walls 113 of the via hole 112, presents a barrier between the metal fill 114 and the cap substrate 202. In an example embodiment, the barrier layer 204 may comprise silicon nitride (SiXNYHZ, where X, Y, and Z are real numbers), although in alternative embodiments the barrier layer may comprise materials such as silicon carbide (SiC), titanium disilicide (TiSi2), tungsten disilicide (WSi2), tungsten (W), aluminum nitride (AlN), aluminum oxide (Al2O3), carbon (C), titanium nitride (TiN), titanium tungsten (TiW, although other ratios of Ti and W may alternatively be used), zirconia (ZrO2), and yttria (Y2O3), among others, and combinations thereof.
An example embodiment of a procedure 300 associated with the described embodiments is shown in
The procedure 300 may further comprise forming 304 a barrier film onto the interior walls of the TGV, using, for example, a conformal deposition process. The deposition process may also form a barrier film on the top, bottom, and edge surfaces of the TGV substrate, thereby establishing a barrier about the substrate to reduce or prevent undesirable interaction between the substrate and other materials (e.g., aluminum or other metals). In the example embodiment, the barrier film is silicon nitride (SiXNYHZ), although different barrier film materials as described herein may alternatively be used in other embodiments.
The procedure 300 may further comprise infusing 306 aluminum into the via holes lined with the barrier film, although other metals as described herein may alternatively be infused. In an example embodiment, the infusing 306 may be accomplished by placing the HPFS wafer into a carbon mold (e.g., a cavity form that is configured to accept the form factor of the wafer), closing carbon mold, evacuating the mold, pouring molten aluminum into the mold, then pressurizing the mold so that the molten aluminum flows completely into the via holes. The procedure 300 may further include opening the mold and removing 308, at a gross level, any aluminum material left over on the wafer (such left-over material may be referred to as “flash”). Once the flash is removed from the wafer at a gross level, the process 300 continues by subjecting 310 the wafer surface to a chemical-mechanical planarization (CMP) procedure to remove, at a fine level, any undesirable materials remaining on the wafer.
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.