ALD enables precise thickness control because it allows the deposition of atoms one layer at a time. Also, uniformity and conformity are good. ALD has good step coverage even in structures with a large aspect ratio. ALD is being used in DRAM capacitors, nanolaminates, spacers, etc.
ALD is a process that deposits atoms layer by layer using a surface reaction. ALD is a four-step process. ALD is a four-step process. In the first step, the reactive site on the surface and the precursor bind. When the surface is all saturated, it becomes self-limting by the ligand of the precursor. After that, the unreacted precursors are purged. After that, the ligand of the precursor is removed through the reactant. Unreacted reactants are removed during the purging process. By repeating this process, you can control the thickness by stacking atoms one by one.
ALD is divided into thermal ald and plasma ald depending on the type of reactant. Due to the high reactivity of the plasma, the growth per cycle of plasma ald is higher. It also has the advantage of being able to process at a lower temperature. However, since damage to the substrate by plasma occurs, additional research is needed to reduce the damage to the substrate.
