MEMS Process Compatibility of Multiwall Carbon Nanotubes
E.H. Cook, D.J.D. Carter
The Charles Stark Draper Laboratory, US
Keywords: nanotubes, MWNT, CNT, MEMS, fabrication, processing
Abstract:Because of their unique properties, carbon nanotubes have been proposed, and even used in limited demonstrations, as structural elements (e.g. cantilevers, bearings, nanofluidic channels, etc.) in microsystems. However, for nanotubes to be truly integrated into microsystems, it is crucial to know their compatibility with MEMS processing steps. In this work, we investigate the effect of several standard MEMS processing steps on PECVD-grown multiwall carbon nanotubes (MWNTs) in order to devise methods of integrating MWTNTs with microsystems. Specific individual nanotubes are observed using scanning-electron microscopy (SEM) and transmission-electron microscopy (TEM) before and after the application of each process. This allows detection of process-induced changes to the nanotube from the bulk to the several-nanometer scale (e.g. removal of material) and even at the atomic scale (e.g. introduction of atomic defects). Various thin-film deposition techniques (PECVD, sputtering, thermal CVD, polymer spinning, etc.) are used to deposit common MEMS materials (polysilicon, silicon dioxide, silicon nitride, metals, etc.) on MWNTs. A variety of wet and dry etching chemistries are used to subject both the tubes themselves and materials deposited on the tubes to etching. Most processes prove compatible with the MWNTs, which suggests their robustness for integration into MEMS devices.