Given that the number of modern integrated devices is reducing, a deposition technique to produce high-quality films with atomic thickness controllability is necessary. One of the critical disadvantages of the existing methods (e.g., sputtering, chemical vapor deposition (CVD)) that cannot be applied to current fabrication of a sub-10 nm device fabrication is poor conformality. When the film is deposited on the high-aspect ratio substrate such as a trench or fin, the thickness on the top and bottom of the structure varies, resulting in the failure of the post-deposition process.
Unlike these deposition methods, ALD is one of the promising deposition technologies used in various fields that employ nanoscale fabrications including electronics, displays, energy applications, and functional coatings due to its unique deposition mechanism based on self-limiting surface-saturated reactions. When a precursor (or reactant) is exposed to the process chamber, the chemical species similarly react with the surface-adsorbed species. The residual species are purged out because no reaction sites are present on the surface.