Multi-layered, planar microshells having low stress for encapsulation of
devices such as MEMS and microelectronics. The microshells may include a
perforated pre-sealing layer, below which a sacrificial layer is
accessed, and a sealing layer to close the perforation in the pre-sealing
layer after the sacrificial material is removed. The sealing layer may
further include a nonhermetic layer to physically occlude the perforation
and a hermetic layer over the nonhermetic occluding layer to seal the
perforation. The various layers may be formed employing processes having
opposing stresses to tune the residual stress of the multi-layered
microshell. In an embodiment, the hermetic layer is a metal which is
deposited with a process tuned to impart a tensile stress to lower the
residual stress in the microshell below the magnitude of cumulative
stress present in sealing layer and pre-sealing layer.