Plasma‐enhanced Chemical Vapor Deposition of Aluminum Oxide Using Ultrashort Precursor Injection Pulses

Abstract

AbstractAn alternative plasma‐enhanced chemical vapor deposition (PECVD) method is developed and applied for the deposition of high‐quality aluminum oxide (AlOx) films. The PECVD method combines a continuous plasma with ultrashort precursor injection pulses. We demonstrate that the modulation of the precursor flow in the reactor leads to enhanced control over plasma‐surface interactions. By variation of the time interval between the sequential Al(CH3)3 precursor injection pulses (10–50 ms) into the O2 plasma, the deposition rate (>30 nm · min−1) and material properties can be tailored. In situ diagnostics revealed that the deposition process is governed by fast precursor depletion and film growth directly after the precursor pulse. Subsequently, in the remainder of the interval between the precursor pulses, densification of the layer takes place under influence of the O2 plasma. The resulting AlOx films exhibit a low impurity content and refractive index >1.6 for optimized process settings. The films can be applied for effective surface passivation of Si as indicated by ultralow surface recombination velocities <1 cm · s−1. The structural properties and interface quality are quite similar as obtained for atomic layer deposited films. We anticipate that pulsed‐flow PECVD processes may also prove beneficial for the synthesis of other functional thin films.magnified image