An Analysis of the Deposition Mechanisms involved during Self‐Limiting Growth of Aluminum Oxide by Pulsed PECVD

Abstract

AbstractSelf‐limiting growth of Al2O3 is accomplished using both pulsed plasma‐enhanced (PE) CVD and plasma‐enhanced atomic layer deposition (PEALD). In pulsed PECVD the two reactants (Al(CH3)3/TMA and O2) are supplied continuously, while in PEALD the TMA is delivered in pulses separated by purge steps. For both processes the rate per cycle saturates with ∼200 L of TMA exposure. At 165 °C a rate of 1.37 Å per cycle is obtained using PEALD. For pulsed PECVD the rate scales linearly with the TMA partial pressure, and its extrapolation is in good agreement with PEALD. The results suggest that deposition in pulsed PECVD involves an ALD component which is supplemented by PECVD growth, and that the contribution of the latter may be tuned using the TMA partial pressure. Experiments using patterned wafers support this hypothesis. Conformal coatings are observed within 10:1 aspect ratio trenches using pulsed PECVD; however the deposition rate on the surface of these substrates is greater than within the trench. The ratio between the two corresponds well to the ratio of rates obtained from pulsed PECVD and PEALD on planar substrates. With cycle times <1 s, net rates up to 20 nm min−1 are obtained by pulsed PECVD while retaining high quality and digital control.