This Small Business Technology Transfer (STTR) Phase I project involves the synthesis of soluble, monodisperse copper nanocrystals as precursors in the formation of microelectronic copper seed layers and interconnects. The proposed synthetic component builds on existing nanoparticles syntheses to obtain soluble, monodisperse copper nanocrystals. Copper nanocrystals are to be applied by spin coating, thereby eliminating the current need for vacuum deposition. A passivating agent will be used to control average particle size and impart particle solubility in conventional spin coating solvents such as amyl acetate, cyclohexanone and ethyl lactate. Unlike conventional electrochemical and vapor deposition techniques, seed layer and interconnect formation occurs preferentially in wafer trenches and vias by taking advantage of the slower rates of nanocrystal solvent volatilization in these regions, as compared to substrate plateaus. Chemical mechanical polishing, associated with existing deposition techniques should be eliminated along with the undesired scouring of copper to form a nonlinear interface. Nanocrystals not adhering to a trenched substrate are readily redissolved, purified and reapplied to further lessen waste. The nanocrystals stranded in trenches are melted at a reduced, size-dependent melting temperature; to form bulk copper seed layer or interconnect structures. Nanocrystal melting temperatures will be tailored to remain below 350 degrees Celsius.
This project has immediate commercial application in the production of microelectronic seed layers and interconnects through the elimination of vacuum vapor deposition, chemical mechanical polishing and reduction of waste streams. Longer-term value is created through the formation of narrower and higher aspect ratio interconnects which are necessary for the continuing increases in computational speed demanded by the microelectronics industry.
