Substrate protection and deprotection with salt films to prevent surface contamination and enable selective atomic layer deposition

Abstract Surface contamination can decrease surface reactivity, and removal of surface contaminants adds additional steps to a process. Here we demonstrate surface protection from contamination and one-sided atomic layer deposition (ALD) by means of protective, sacrificial, thermally evaporated NaCl layers. This approach allows clean silicon surfaces to be stored under ambient conditions for extended periods of time in a pristine state, and ALD to be performed selectively on one side of a planar material. For the ALD depositions, planar substrates are (i) selectively coated on one side with ca. 100 nm of NaCl by thermal evaporation, (ii) non-selectively coated using traditional ALD, and (c) rinsed with water to remove the NaCl layer. Water treatment removes the salt film and any ALD deposition on top of it. Salt film deposition, surface protection, and selective ALD are confirmed by X-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry (SE). Selective, thermal ALD of alumina and ZnO are demonstrated, and protective salt films of different thicknesses (10, 50, and 100 nm) are investigated.