HERMETICALLY SEALED MEMS DEVICE AND ITS FABRICATION

摘要

A hermetic package comprising a substrate (110) having a surface with a MEMS structure (101) of a first height (102), the substrate hermetically sealed to a cap (120) forming a cavity over the MEMS structure; the cap attached to the substrate surface by a vertical stack (130) of metal layers adhering to the substrate surface and to the cap, the stack having a continuous outline surrounding the MEMS structure while spaced from the MEMS structure by a distance (140); the stack having a bottom metal seed film (131) adhering to the substrate with a first width (131a), and further a top metal seed film (132) adhering to the cap with a second width (132a) smaller than the first width, the top metal seed film tied to a layer (135) including gold-indium intermetallic compounds, layer (135) having a height greater than the first height.

主权项

1. A method for fabricating a MEMS device, comprising:
providing a substrate including a MEMS structure having at least a portion raised to a height above a substrate surface; forming a first seed layer over the substrate surface; forming a first mask layer over the first seed layer to a thickness greater than the height; patterning the first mask layer with a first opening to expose an underlying portion of the first seed layer, the first opening having a contour continuously peripherally surrounding the MEMS structure and laterally spaced from the MEMS structure; forming a first vertical stack of one or more metal layers over the first seed layer within the first opening, the first stack including a top layer of a first metal; removing the patterned first mask layer and a part of the first seed layer not covered by the first vertical stack within the first opening; providing a cap material element; forming a second seed layer over a surface of the cap material element; forming a second mask layer over the second seed layer; patterning the second mask layer with a second opening to expose an underlying portion of the second seed layer, the second opening having a lateral continuous contour similar to but of lesser or greater lateral width than the contour of the first opening; forming a second vertical stack of one or more metal layers over the second seed layer within the second opening, the second stack including a top layer of a second metal; removing the patterned second mask layer and a part of the second seed layer not covered by the second vertical stack within the second opening; aligning the cap and the substrate to bring the top layer of the second metal into contact with the top layer of the first metal, with a greater lateral spacing of the first or second metal of the top layer of lesser lateral width than the lateral spacing of the second or first metal of the top layer of greater lateral width from the MEMS structure; and applying thermal energy to the one of the first and second metals having a lower melting temperature to liquefy and dissolve the one of the first and second metals into the other of the first and second metals by forming one or more intermetallic compounds of the first and second metals.