A Method to Fabricate a Template With a Long Range Ordered Dense Array of True Nanometer Scale Pits

We present a method to form a patterned template having a dense array of subnanometer scale pits that is useful for numerous applications that require significant size reduction. The polystyrene-polymethylmethacrylate diblock copolymer nanopatterned sample has been used in order to form a hexagonal symmetry as a starting scaffold. The ordered copolymer pattern is then transferred to the oxide layer to form a hard mask for subsequent anisotropic silicon wet-etching process. With a controlled wet etching, we obtained inverted pyramidal pits on a silicon substrate of which the tips can be a few or even a single nanometer in its lateral dimension. The most common phase change material Ge₂Sb₂ Te₅ (GST225) was deposited on this substrate and isolated within the pits using chemical mechanical polishing approach, followed by X-ray photoelectron spectroscopy elemental analysis.