Acid-Sensitive Molecular Glasses as Removable Thin-Film Protective Layers

A common problem encountered in semiconductor processing is the oxidation of metals, for example, copper interconnects, that constitute a significant portion of integrated circuits. Undesired oxidation may be mitigated by the application of a protective coating at various stages of processing, the removal of which is ultimately necessary but often nontrivial. To address this challenge, here, we demonstrate that acid-labile molecular glasses are both efficient at protecting copper surfaces from oxidation and readily removed after use. As evidenced by X-ray photoelectron spectroscopy, thin films of molecular glasses deposited on copper prevent underlying surface oxidation for at least 120 h. Molecular glasses that incorporate imine groups were found to be the most acid sensitive, with a hydrophobic-to-hydrophilic solubility switch reminiscent of photoresists that is readily tunable by changing the number of imines per molecule. The exquisite acid sensitivity of these imine-based molecular glasses provides a mechanism to fully remove the protecting layer in a solution of dilute sulfuric acid as low as 1 vol %. In summary, these results highlight the potential utility of readily accessible and tunable molecular glasses in the design of processes for fabricating advanced semiconductor devices.