Lithography with a Pattern of Block Copolymer Microdomains as a Positive or Negative Resist

Dense, periodic arrays of holes and troughs have been fabricated in silicon, silicon nitride, and germanium, at a length scale inaccessible by conventional lithographic techniques. The holes are approximately 20 nanometers (nm) wide, 20 nm deep, spaced 40 nm apart, and uniformly patterned with 3×10¹² holes on a three inch silicon wafer. To access this length scale, self-assembling resists were synthesized to produce either a layer of hexagonally ordered polyisoprene (PI) spheres or polybutadiene (PB) cylinders in a polystyrene (PS) matrix. The PI spheres or PB cylinders were then chemically modified by either degradation or stained with metal compounds to produce a useful mask for pattern transfer by fluorine-based reactive ion etching (RIE). A mask of spherical microdomains was used to fabricate a lattice of holes or posts and a mask of cylindrical voids was used to produce parallel troughs. This technique accesses a length scale difficult to produce by conventional lithography and opens a route for the patterning of surfaces via self-assembly.