Maskless and electroless fabrication of patterned metal nanostructures on silicon wafers by controlling local surface activities

Attempt was made to develop novel maskless and electroless fabrication process of metal nanostructures by controlling local surface activity for the deposition reaction at silicon wafer surfaces. P-Si(100) wafers were cleaned to obtain hydrogen-terminated surface and nanoscopic patterns were formed on the surface by nanoindentation technique using a scanning probe microscope (SPM) with a diamond probe. By controlling the parameters such as the indentation force (within the order of 1-10 μN), nanoscopic patterns with different degrees of defects were formed. The scanning surface potential microscopy (SPoM) analysis clarified that these sites locally possessed negative shift in potential, i.e., higher activity for the reductive deposition of metal ions, which increased with an increase in the degree of defect. In order to achieve spontaneous (electroless) and selective deposition at those patterns, conditions of the solution were optimized and the formation of metal nanostructures, such as Cu nanodot arrays and wires, has been achieved. Capability of the present process to form nanostructures whose feature size is as small as 50 nm was demonstrated.