Integrating SCREAM micromachined devices with integrated circuits

We demonstrate the integration of SCREAM MEMS with a conventional, unmodified IC process. After fabricating the ICs, only two additional masks are needed to form the mechanical structure and the patterned metal interconnects. The mechanical structures are high-aspect-ratio beams formed from single-crystal silicon. SCREAM, which stands for single-crystal-silicon reactive etching and metallization, is a low temperature process requiring conventional IC fabrication tools including the following: RIE, PVD, CVD and optical lithography. None of the processing steps expose the wafer to temperatures above 300/spl deg/C. Also, the MEMS are independent of the substrate doping, and can be used with the substrate that is optimal for a particular IC process. We describe SCREAM as a "Portable" MEMS process. A portable process does not alter the ICs, can be run after the IC process, and does not require modification of commonly available IC processes. To support the claim that SCREAM is a portable process, we built structures on wafers containing industrially fabricated AD712 BiFET opamps. The ICs stayed within specification and the structures demonstrate successful fabrication adjacent to ICs.