MEMS processes grew from traditional semiconductor technology. Over
the last decade, the processing methodology for MEMS devices has evolved
independently. While on the surface, both semiconductor and MEMS batch-process
wafers patterned by photolithography, MEMS-specific manufacturing
creates moving parts on wafers by removing sacrificial layers beneath
desired mechanical structures. This fundamental difference has several
processing implications.
MEMS processing typically involves deeper, more specialized etches,
and may fuse wafers into a stack to create a large multilayer device.
MEMS devices may often have features on both sides of a wafer. Finally,
while semiconductor foundries typically have process lines that are
optimized for commodity production, MEMS foundries have become highly
specialized and flexible to accommodate newly developed MEMS processes.
