Nanopatterning materials using area selective atomic layer deposition in conjunction with thermochemical surface modification via heated AFM cantilever probe lithography

Thermal probe based lithography methods are a new family of maskless nanopatterning techniques that utilize heated cantilever probes to perform local thermochemical modification of surfaces and films to achieve pattern definition. Previously, the authors demonstrated that a heated cantilever probe can be used to quickly pattern polycarbonate polymer thin films by locally decomposing the polymer film into volatile by-products. The authors also recently reported the use of PMMA polymer thin films as lithographically definable masking layers to enable area selective atomic layer deposition techniques (ASALDT). In this paper, the use of a heated cantilever probe to pattern a PMMA thin film for use as a masking layer in an ASALDT process has been investigated in detail. It is shown that PMMA films can be patterned using a heated cantilever probe tip at high tip scanning speeds, but that a small amount of organic residue is left in the patterned features at reasonable writing speeds that must be removed before ALD is performed. It is shown that a brief O₂ plasma is capable of removing this organic residue without significant degradation of the patterned PMMA features, thus enabling the deposition of titania features through the PMMA mask using an ALD process based on titanium-isopropoxide and water precursors at an ALD process temperature of 140 °C.