Investigation on spatially separated atomic layer deposition by gas flow simulation and depositing Al2O3 films

Al2O3 thin films were deposited using tri-methyl aluminum and ozone by spatially separated atomic layer deposition (SALD). A large gap was kept between the reactor and substrates in an attempt to enhance the process gas flow. According to simulation data and deposition results, strong edge pumping for the dominantly lateral flow improved the gas isolation and deposition was very effective, with a resulting gap height of 5 mm. To compare this SALD process with conventional atomic layer deposition (ALD), the authors examined how the amount of source supplied, the deposition temperature, and the number of rotations affected the growth rate. The growth rate per rotation was saturated at ∼0.12 nm/rotation at a deposition temperature of 250 °C, which is comparable to the saturated growth rate of the same film using conventional ALD. The dielectric constant of the films was ∼8 and the film with a capacitance equivalent thickness of 3.2 nm had a leakage level of 9.8 × 10^-8 A/cm² (at -1 V). X-ray photoelectron spectroscopy peak area analysis indicates that the films deposited by SALD consist of Al2O3. This indicates that SALD is a viable option for several mass-production applications that require high throughput.