Interconnect Challenges in Highly Integrated MEMS/ASIC Subsystems
  Micromechanical devices like accelerometers or rotation sensors form an increasing segment beneath the devices supplying the consumer market. A hybrid integration approach to build smart sensor clusters for the precise detection of movements in all spatial dimensions requires a large toolbox of interconnect technologies, each with its own constraints regarding the total process integration. Specific challenges described in this paper are post-CMOS feedthroughs, front-to-front die contact arrays, vacuum-compliant lateral interconnect and fine-pitch solder balling to finally form a Chip-Scale System-in-Package (CSSiP). 
N. Marenco, S. Warnat, W. Reinert