Representative implementations of techniques and devices provide seals for sealing the joints of bonded microelectronic devices as well as bonded and sealed microelectronic assemblies. Seals are disposed at joined surfaces of stacked dies and wafers to seal the joined surfaces. The seals may be disposed at an exterior periphery of the bonded microelectronic devices or disposed within the periphery using the various techniques.

An optical electronics device includes first, second and third wafers. The first wafer has a semiconductor substrate with a dielectric layer on a side of the semiconductor substrate. The second wafer has a transparent substrate with an anti-reflective coating on a side of the transparent substrate. The first wafer is bonded to the second wafer at a silicon dioxide layer between the semiconductor substrate and the anti-reflective coating. The first and second wafers include a cavity extending from the dielectric layer through the semiconductor substrate and through the silicon dioxide layer to the anti-reflective coating. The third wafer includes micromechanical elements. The third wafer is bonded to the dielectric layer, and the micromechanical elements are contained within the cavity.

In one aspect, the disclosure is directed to a MEMS device. The MEMS device includes a silicon-based movable MEMS sensor element. The MEMS device also includes a plurality of wells formed into at least one surface of the movable MEMS sensor element. Each well is filled with at least one metal so as to increase the effective mass of the movable MEMS sensor element. The metal may be tungsten or tantalum, or an alloy with tungsten or tantalum.

Apparatus and Methods for fabricating apparatus having a hermetic seal to seal a portion of an apparatus, for example and without limitation, a portion having a MEMS sensor. One such method uses crimping devices to compress a seal in a cavity formed in a housing that includes a MEMS sensor attached to a stress isolator. Under such compression, the seal deforms to hermetically seal surfaces around the inside, outside and bottom of the stress isolator.

For an optical electronic device and method that forms cavities through an interposer wafer after bonding the interposer wafer to a window wafer, the cavities are etched into the bonded interposer/window wafer pair using the anti-reflective coating of the window wafer as an etch stop. After formation of the cavities, the bonded interposer/window wafer pair is bonded peripherally of die areas to the MEMS device wafer, with die area micromechanical elements sealed within respectively corresponding ones of the cavities.

A method and structure for a PLCSP (Package Level Chip Scale Package) MEMS package. The method includes providing a MEMS chip having a CMOS substrate and a MEMS cap housing at least a MEMS device disposed upon the CMOS substrate. The MEMS chip is flipped and oriented on a packaging substrate such that the MEMS cap is disposed above a thinner region of the packaging substrate and the CMOS substrate is bonding to the packaging substrate at a thicker region, wherein bonding regions on each of the substrates are coupled. The device is sawed to form a package-level chip scale MEMS package.

A method of applying a die attach material includes forming a wafer stencil by selectively removing on the back side of a wafer including a plurality of semiconductor die having an active top side a predetermined depth to form a recess having an inner circumference while not removing an outer most circumference of the wafer. The recess is filled with a B-stage adhesive material. The wafer is singulated to form a plurality singulated semiconductor die. The singulated semiconductor die is die attached back side down to a package substrate, and then the B-stage adhesive material is cured. The B-stage adhesive material across its full area generally has a minimum thickness of at least 20 m and a maximum thickness range of 6 m.

Aspects of the disclosure described herein related to packaging an ultrasound-on-a-chip. In some embodiments, an apparatus includes an ultrasound-on-a-chip that has through-silicon vias (TSVs) and an interposer coupled to the ultrasound-on-a-chip and including vias, where the ultrasound-on-a-chip is coupled to the interposer such that the TSVs in the ultrasound-on-a-chip are electrically connected to the vias in the interposer. In some embodiments, an apparatus includes an ultrasound-on-a-chip having bond pads, an interposer that has bond pads and that is coupled to the ultrasound-on-a-chip, and wirebonds extending from the bond pads on the ultrasound-on-a-chip to the bond pads on the interposer.

Exemplary microelectromechanical system (MEMS) devices, and methods for fabricating such are disclosed. An exemplary method includes providing a silicon-on-insulator (SOI) substrate, wherein the SOI substrate includes a first silicon layer separated from a second silicon layer by an insulator layer; processing the first silicon layer to form a first structure layer of a MEMS device; bonding the first structure layer to a substrate; and processing the second silicon layer to form a second structure layer of the MEMS device.

Miniaturized devices such as MEMS switches (10) have encapsulating enclosures (100). The enclosure (100) and the remainder of the switch (10) are fabricated on a concurrent basis by depositing layers of an electrically-conductive material, such as copper, on a substrate (26).