Wafer level hermetic seal process for microelectromechanical systems (mems) devices

A microelectromechanical systems (MEMS) structure comprising:

• a MEMS substrate having a movable element;
• an integrated circuit (IC) arranged under and bonded to a lower side of the MEMS substrate, wherein the IC includes an IC cavity opening to the movable element;
• a capping substrate arranged over and bonded to an upper side of the MEMS substrate, wherein the capping substrate includes a capping cavity opening to the movable element, wherein the capping substrate includes a seal opening in fluid communication with the capping cavity, and wherein the seal opening has a ratio of height to top width that is at least about 30 to 1;
• a mask layer arranged over the capping substrate, wherein the mask layer overhangs the seal opening and laterally surrounds a mask opening arranged over the seal opening;
• and
• a seal layer arranged over the mask layer and the mask opening, wherein the seal layer partially fills the mask opening and is configured to hermetically seal the capping cavity.

A microelectromechanical systems (MEMS) structure comprising:

• a first substrate arranged over a second substrate and arranged under a third substrate, wherein the first substrate comprises a movable element arranged in a cavity defined between the second and third substrates, and wherein the third substrate comprises a first opening in fluid communication with the cavity;
• a mask layer arranged over the third substrate and comprising a second opening arranged over the first opening, such that the mask layer overhangs the first opening;
• and
• a seal layer arranged over the mask layer, wherein a lower surface of the seal layer is arranged in the first opening and spaced over a bottom surface of the mask layer.