A cyclic pre-cleaning technique may be used to clean the surfaces of a recess in which a deep trench isolation (DTI) structure is to be formed. The cyclic pre-cleaning technique may include performing one or more deposition and etch cycles to remove oxygen from the surfaces of the recess to reduce the oxygen concentration in the surfaces of the recess. A passivation layer may be formed in the recess after the cyclic pre-cleaning technique is used to clean the surfaces. The cyclic pre-cleaning technique may include the use of germanium (Ge) to bond with oxygen in the surfaces of the recess, which results in the formation of germanium oxide (GeO). The germanium oxide is removed, resulting in reduced oxygen concentration in the surfaces of the recess. The reduced oxygen concentration increases the quality of epitaxial growth of the passivation layer in the recess.