Spatial atomic layer deposition: Performance of low temperature H₂O and O₃ oxidant chemistry for flexible electronics encapsulation

Water and oxygen were compared as oxidizing agents for the Al₂O₃ atomic layer deposition process using spatial atomic layer deposition reactor. The influence of the precursor dose on the deposition rate and refractive index, which was used as a proxy for film density, was measured as a function of residence time, defined as the time which the moving substrate spent within one precursor gas zone. The effect of temperature on the growth characteristics was also measured. The water-based process gave faster deposition rates and higher refractive indices but the ozone process allowed deposition to take place at lower temperatures while still maintaining good film quality. In general, processes based on both oxidation chemistries were able to produce excellent moisture barrier films with water vapor transmission rate levels of 10^-4 g/m² day measured at 38 °C and 90% of relative humidity on polyethylene naphthalate substrates. However, the best result of <5 × 10^-5 was obtained at 100 °C process temperature with water as precursor.