Study of Etch Stop Layer on Characteristics of Amorphous Aluminum Oxide Thin Film

To protect the active layer, which are inter layer dielectrics (ILD) and metal lines, from being damaged by UV laser during the etching process, etch stop layers (ESL) are used in patterning process of the integrated circuits (ICs) fabrication in back end of line (BEOL). The ESL material should have a higher etch selectivity than the active layer. Therefore, it must have a low dielectric constant and high chemical resistance. Aluminum oxide compounds (AlOx, AlOC, AlON, etc.) are highly suitable for use as ESL due to the low dielectric constant between about 4 and 9, high etch selectivity, high density (2.5-3.8 g/cm3) and pattern transfer capability. We focused on lowering the dielectric permittivity and increasing the density by controlling the precursor/reactant pulsed time of atomic layer deposition (ALD).