Self-limiting deposition of aluminum oxide thin films by pulsed plasma-enhanced chemical vapor deposition

Abstract

Self-limiting deposition of aluminum oxide (Al2O3) thin films was accomplished by pulsed plasma-enhanced chemical vapor deposition using a continuous delivery of trimethyl aluminum (TMA) and O2. Film characterization included spectroscopic ellipsometry and Fourier transform infrared (FTIR) spectroscopy. Deposition rates scaled with TMA exposure and could be controlled over a large range of 1–20Å∕pulse. For fixed conditions, digital control over film thickness is demonstrated. Deposition rates initially decreased with substrate temperature before becoming constant for Ts>100°C. Higher growth rates at low temperature are attributed to the thermal reaction between H2O, produced during the plasma on step, with TMA during the plasma off step. Gas-phase analysis confirms the coexistence of these species, and their degree of overlap is a strong function of the chamber wall temperature. With both the substrate and chamber wall temperature elevated, impurities related to carbon and hydroxyl groups are attenuated below the detection limit of FTIR.