Complementary metal oxide semiconductor (CMOS) ultrasonic transducers (CUTs) and methods for forming CUTs are described. The CUTs may include monolithically integrated ultrasonic transducers and integrated circuits for operating in connection with the transducers. The CUTs may be used in ultrasound devices such as ultrasound imaging devices and/or high intensity focused ultrasound (HIFU) devices.

Micromachined ultrasonic transducers formed in complementary metal oxide semiconductor (CMOS) wafers are described, as are methods of fabricating such devices. A metallization layer of a CMOS wafer may be removed by sacrificial release to create a cavity of an ultrasonic transducer. Remaining layers may form a membrane of the ultrasonic transducer.

Representative methods for sealing MEMS devices include depositing insulating material over a substrate, forming conductive vias in a first set of layers of the insulating material, and forming metal structures in a second set of layers of the insulating material. The first and second sets of layers are interleaved in alternation. A dummy insulating layer is provided as an upper-most layer of the first set of layers. Portions of the first and second set of layers are etched to form void regions in the insulating material. A conductive pad is formed on and in a top surface of the insulating material. The void regions are sealed with an encapsulating structure. At least a portion of the encapsulating structure is laterally adjacent the dummy insulating layer, and above a top surface of the conductive pad. An etch is performed to remove at least a portion of the dummy insulating layer.

Systems and methods that protect CMOS layers from exposure to a release chemical are provided. The release chemical is utilized to release a micro-electro-mechanical (MEMS) device integrated with the CMOS wafer. Sidewalls of passivation openings created in a complementary metal-oxide-semiconductor (CMOS) wafer expose a dielectric layer of the CMOS wafer that can be damaged on contact with the release chemical. In one aspect, to protect the CMOS wafer and prevent exposure of the dielectric layer, the sidewalls of the passivation openings can be covered with a metal barrier layer that is resistant to the release chemical. Additionally, or optionally, an insulating barrier layer can be deposited on the surface of the CMOS wafer to protect a passivation layer from exposure to the release chemical.

A multi-layer sealing film for high seal yield is provided. In some embodiments, a substrate comprises a vent opening extending through the substrate, from an upper side of the substrate to a lower side of the substrate. The upper side of the substrate has a first pressure, and the lower side of the substrate has a second pressure different than the first pressure. The multi-layer sealing film covers and seals the vent opening to prevent the first pressure from equalizing with the second pressure through the vent opening. Further, the multi-layer sealing film comprises a pair of metal layers and a barrier layer sandwiched between metal layers. Also provided is a microelectromechanical systems (MEMS) package comprising the multilayer sealing film, and a method for manufacturing the multi-layer sealing film.

Various embodiments may provide a device arrangement. The device arrangement may include a substrate including a conductive layer. The device arrangement may further include a microelectromechanical systems (MEMS) device monolithically integrated with the substrate, wherein the MEMS device may be electrically coupled to the conductive layer. A cavity may be defined through the conductive layer for acoustically isolating the MEMS device MEMS device from the substrate. At least one anchor structure may be defined by the conductive layer to support the MEMS device.

A method of forming an ultrasonic transducer device includes forming an insulating layer having topographic features over a lower transducer electrode layer of a substrate; forming a conformal, anti-stiction layer over the insulating layer such that the conformal layer also has the topographic features; defining a cavity in a support layer formed over the anti-stiction layer; and bonding a membrane to the support layer.

According to various embodiments, a PMUT device may include a wafer, an active layer including a piezoelectric stack, an intermediate layer having a cavity therein where the intermediate layer is disposed between the wafer and the active layer such that the cavity is adjoining the piezoelectric stack. A via may be formed through the active layer and the intermediate layer to the wafer. A metallic layer may be disposed over the active layer and over surfaces of the via. The intermediate layer may include an interposing material surrounding the cavity, and may further include a sacrificial material surrounding the via. The sacrificial material may be different from the interposing material. The metallic layer may include a first member at least substantially overlapping the piezoelectric stack, a second member extending from the first member to the cavity, and a third member extending into the active layer to contact an electrode therein.

The present disclosure relates to a microelectromechanical systems (MEMS) package featuring a flat plate having a raised edge around its perimeter serving as an anti-stiction device, and an associated method of formation. A CMOS IC is provided having a dielectric structure surrounding a plurality of conductive interconnect layers disposed over a CMOS substrate. A MEMS IC is bonded to the dielectric structure such that it forms a cavity with a lowered central portion the dielectric structure, and the MEMS IC includes a movable mass that is arranged within the cavity. The CMOS IC includes an anti-stiction plate disposed under the movable mass. The anti-stiction plate is made of a conductive material and has a raised edge surrounding at least a part of a perimeter of a substantially planar upper surface.

A method for fabricating a semiconductor device is disclosed. A semiconductor substrate comprising a MOS transistor is provided. A MEMS device is formed over the MOS transistor. The MEMS device includes a bottom electrode in a second topmost metal layer, a diaphragm in a pad metal layer, and a cavity between the bottom electrode and the diaphragm.