High-quality remote plasma enhanced atomic layer deposition of aluminum oxide thin films for nanoelectronics applications

Here, we report comprehensive investigations of aluminum oxide (Al2O3) high-κ gate oxides deposited via remote plasma enhanced atomic layer deposition (Re-PEALD) with mesh configuration in a commercial 100 mm ALD reactor. Trimethylaluminum (Al(CH3)3), dioxygen (O2) plasma, and Argon (Ar) are used as the metal precursor, oxidant, and carrier/purge, respectively. The growth rate per cycle and non-uniformity of Al2O3 thin films is analyzed with the variation in duration of (Al(CH3)3) pulse, O2 plasma, post-precursor purge, post-oxidant purge, RF power, and substrate temperature. High-quality monolayer type Al2O3 thin films with a growth rate of ~ 1.1 Å/cycle are achieved for a wide temperature range from ~ 100 °C to ~ 300 °C suitable for various nanoelectronics applications ranging from flexible substrates to low thermal budget and high mobility alternate semiconductor substrates. Further, the Al/Re-PEALD-Al2O3/p-Si, metal-oxide-semiconductor (MOS) structures are investigated for capacitance-voltage, capacitance-frequency, and leakage current-voltage characteristics to demonstrate the quality of Re-PEALD-Al2O3 thin films. The Al/Re-PEALD-Al2O3/p-Si, MOS structures revealed excellent electrical characteristics with ultralow minimum interface trap density (Dit) ~ 9.9 × 109 eV−1cm−2, negative effective oxide charges (Neff) ~ 5.52 × 1012 cm−2, low leakage current density of ~ 4.1 nA/cm2 at −1 V, hysteresis-free, insignificant Vth shift, and trivial frequency dispersion. Moreover, the chemical analysis using XPS depth profiling disclosed that Re-PEALD deposited Al2O3 thin films results in a high-quality gradient Al2O3/SiOx/Si interface rather than an abrupt Al2O3/Si interface, and the oxygen rich thin films due to the oxygen (O2−) interstitials close to the interface are the sources of negative fixed oxide charges in Re-PEALD-Al2O3/Si, system. These results intend to boost the investigations of Re-PEALD Al2O3 ultrathin films for low thermal budget high mobility alternate semiconductor substrates for nanoelectronics applications.