Eutectic flow containment in a semiconductor fabrication process
View Patent ↗A disclosed semiconductor fabrication process includes forming a first bonding structure on a first surface of a cap wafer, forming a second bonding structure on a first surface of a device wafer, and forming a device structure on the device wafer. One or more eutectic flow containment structures are formed on the cap wafer, the device wafer, or both. The flow containment structures may include flow containment micro-cavities (FCMCs) and flow containment micro-levee (FCMLs). The FCMLs may be elongated ridges overlying the first surface of the device wafer and extending substantially parallel to the bonding structure. The FCMLs may include interior FCMLs lying within a perimeter of the bonding structure, exterior FCMLs lying outside of the bonding structure perimeter, or both. When the two wafers are bonded, the FCMLs and FCMCs confine flow of the eutectic material to the region of the bonding structure.
1. A semiconductor fabrication process, comprising:
forming a first bonding structure on a first surface of a cap wafer;
forming a device cavity in the first surface of the cap wafer;
forming a second bonding structure on a first surface of a device wafer;
forming a device structure on the device wafer;
forming a eutectic flow containment structure on at least one of the cap wafer and the device wafer, the eutectic flow containment structure comprising an exterior flow containment micro-levee (FCML), the exterior FCML comprising an elongated ridge overlying the first surface of the device wafer and extending substantially parallel to the second bonding structure, wherein a perimeter of the exterior FCML encloses a perimeter of the second bonding structure; and
bringing the first and second bonding structures into contact while maintaining at least one of the cap wafer and the device wafer at a predetermined temperature to create a eutectic bond from the first and second bonding structures.
2. The process of claim 1 , further comprising forming an interior FCML wherein a perimeter of the FCML lies within a perimeter of the second bonding structure.
3. The process of claim 1 , wherein the exterior FCML comprises an annular structure circumventing the device structure and wherein the FCML includes a silicon portion.
4. The process of claim 3 , wherein the silicon portion of the exterior FCML comprises polycrystalline silicon and wherein the exterior FCML further includes a metal portion overlying the silicon portion.
5. The process of claim 1 , wherein forming the at least one flow containment structure further comprises forming at least one flow containment micro-cavity on the cap wafer.
6. The process of claim 1 , wherein one of the first and second bonding structures comprises a first eutectic element and another of the first and second bonding structures comprises a second eutectic element, wherein the first eutectic element and the second eutectic element form the eutectic bond.
7. A semiconductor fabrication process, comprising:
forming a first bonding structure on a first surface of a cap wafer;
forming a device cavity in the first surface of the cap wafer;
forming a second bonding structure on a first surface of a device wafer;
forming a device structure on the device wafer;
forming a plurality of eutectic flow containment structures on at least one of the cap wafer and the device wafer, each eutectic flow containment structure being selected from a flow containment micro-cavity (FCMC) and a flow containment micro-levee (FCML); and
bringing the first and second bonding structures into contact while maintaining at least one of the cap wafer and the device wafer at a predetermined temperature to create a eutectic bond from the first and second bonding structures;
wherein forming the plurality of flow containment structures comprises forming an exterior flow containment micro-cavity (FCMC) on the cap wafer wherein a perimeter of the exterior FCMC encloses a perimeter of the first bonding structure.
8. The process of claim 7 , further comprising forming an interior FCMC wherein a perimeter of the interior FCMC lies within a perimeter of the first bonding structure.
9. The process of claim 7 , wherein forming the exterior FCMC comprises forming an annular void circumventing the device cavity.
10. A semiconductor fabrication process, comprising:
forming a first bonding structure on a first surface of a cap wafer;
forming a device cavity in the first surface of the cap wafer;
forming a second bonding structure on a first surface of a device wafer;
forming a device structure on the device wafer;
forming a eutectic flow containment structure on at least one of the cap wafer and the device wafer, the eutectic flow containment structure comprising an exterior flow containment structure, the exterior flow containment structure comprising an elongated ridge overlying the first surface of the device wafer and extending substantially parallel to the second bonding structure, wherein a perimeter of the exterior flow containment structure encloses a perimeter of the second bonding structure; and
creating a eutectic bond between the first and second bonding structures.
11. The process of claim 10 , wherein the exterior flow containment structure comprises an exterior flow containment micro-levee.