Low cost fabrication and assembly of lid for semiconductor devices

A method is disclosed for encapsulating micromechanical elements or features on a substrate. In accordance with the method, a first substrate ( 111 ) is provided which has a patterned surface ( 113 ). A seed metallization ( 121 ) is then deposited onto the patterned surface, and a structural material layer ( 123 ), which preferably comprises copper, is electroplated onto the seed metallization. A solder ( 125 ), such as SnCu, is electroplated onto the metal layer, and the seed metallization, the structural material layer and the solder are removed from the first substrate as a cohesive structure ( 127 ), through the application of heat or by other suitable means, such that a negative replica of the patterned surface is imparted to the structure. The structure may then be placed on a second substrate ( 129 ) such that the solder is in contact with the second substrate, after which the solder is reflowed. Prior to reflow, the solder may be exposed to a fluorinated plasma, which forms a dry flux on the solder surface in the form of fluorinated metal oxides.