DETACHABLE FINE BUMP CONNECTION USING MULTI-WALLED CARBON-NANOTUBE BUNDLES FOR 3D SEMICONDUCTOR MODULES

In the 3D chip stacking structure, fine TSV (Through Silicon Via) structures are used in the stacked chips and fine metallic bumps are jointed between the stacked chips for the 3D interconnection. It is not easy, however, to make perfect reliable joints of the huge number of fine bumps in micro scale due to the large bending deformation of each chip with different surface interconnection and dielectric structures and the height fluctuation among the bumps. It is, therefore, very important to establish the largely deformable bump joint system with easy detachability. In order to solve these problems of fine metallic bump joint structures, multi-walled carbon nanotube (MWCNT) bundle structures were applied to the bump joint structure. To investigate the possibility of detachable fine bumps, high quality MWCNTs were grown by thermal CVD method using acetylene gas. The area-arrayed MWCNTs bundle structures were grown on a silicon substrate and the deformation behavior by compression was measured. The MWCNTs bundles exhibited elastic deformation in the range of strain addition up to 3%. The electrical properties were measured by jointing the MWCNTs films. In the range of compressive strain up to about 30%, the connection between MWCNTs films shows stable ohmic contacts due to the point and side-wall contacts by each MWCNTs. The contact resistance did not change so much even after the 10 cyclic mounting and dismounting.