Cyclic Wet Etch Method to Improve Nanoconfined Wet Etching

The ongoing miniaturization and scaling of semiconductor devices have led to the creation of intricate, dense nanoscale structures. This has resulted in the formation of nanoconfined spaces that present significant challenges for selective and uniform wet etching. Typically, in nanoconfined spaces, etch rates are lower for smaller features or critical dimensions (CD) compared to the larger CDs. In the present study, we report the successful attainment of a uniform etch rate for TiN and a-Si nanoconfined test structure of various thicknesses, utilizing an enhanced wet cleaning technique that we refer to as the “Cycling Wet Etch Method”. This is a two-step method that first involves oxidizing the target film with a specific oxidizer that does not etch the film, followed by wet etching the oxidized portion of the film using an etchant that is selective for the target film. Multiple cycles of oxidation and etching are needed to obtain the desired etch amount.