Area-Selective Deposition: Background and Definition
Area Selective Deposition - ASD

For over 50 years, the fabrication and miniaturization of integrated circuits have relied on successive steps of deposition, lithography, and etching. Indeed, unlike building a house, one cannot directly create walls or pillars when stacking different layers on a silicon substrate. It is therefore necessary to uniformly coat the substrate’s surface with a layer of material before removing the unwanted portions through a lithography step—which defines the pattern to be retained—followed by an etching step, which removes the excess material. This approach is commonly referred to as the top-down approach.

The drastic reduction in the dimensions of microelectronic devices over the past twenty years—to the nanoscale—has significantly complicated these steps and increased their cost. For example, the wavelengths used to pattern the structures during the lithography step are now much greater than...