COMBINING PATTERNED SELF-ASSEMBLED MONOLAYERS OF ALKANETHIOLATES ON GOLD WITH ANISOTROPIC ETCHING OF SILICON TO GENERATE CONTROLLED SURFACE MORPHOLOGIES

Self-assembled monolayers (SAMs) of hexadecanethiolate were patterned onto gold films supported on titanium-primed silicon wafers using microcontact printing (mu CP). Wet etching of the gold, and subsequently of the silicon, using three systems of resists based on these patterned SAMs, denoted by the shorthand labels Au/SAM, Ni/Au/SAM, and Au/SAM/polymer, produced features in silicon having dimensions in the 1 to 10 mu m scale. In the Au/SAM system, the SAM acted as a resist to protect gold from etching by CN-/O-2, and the resulting, patterned gold protected silicon from etching by KOH (4M)/i-PrOH (25% by volume) at 60 degrees C. In the Ni/Au/SAM system, the pattern In the gold layer was transferred to an underlying nickel layer by etching in a bath consisting of cone H2SO4, 30% H2O2, cone H3PO4, and 30% aqueous solution (w/v) of NiSO4, (5:5:1:4 by volume) at 35-40 degrees C; in turn, the nickel acted as a resist to protect the silicon from etching. In the Au/SAM/polymer, a prepolymer of.epoxy resin or polyurethane was self-assembled onto hydrophilic SAMs on the surface that was patterned into regions of different interfacial free-energy and wettability; after curing, the polymer served as the resist during etching gold by aqua regia, and etching silicon by KOH/i-PrOH. All three resists were compatible with etchants for silicon, and they masked the underlying silicon effectively.