In situ investigation of temperature and bias dependent effects on the oxide growth of Si and Ge in an electron cyclotron resonance

Abstract

The electron cyclotron resonance (ECR) plasma oxidation of Si and Ge was investigated using in situ spectroscopic ellipsometry at substrate temperatures of 80–400 °C and at bias voltages of −30 to +60 V. A study of the oxide growth kinetics by ECR plasma oxidation results in three distinct regions of growth with the first two being linear and the last parabolic. At the earliest linear stage the rate of oxide growth is the fastest, and corresponds to ∼3 nm film thickness which is not dependent on bias. Following this, the second linear region displays an oxide growth rate proportional to the bias with typical growth rates of 0.10, 0.32, and 0.60 nm/min for 0, +30, and +60 V, respectively, at 300 °C. The third region displays parabolic kinetics and corresponds to the Cabrera–Mott (CM) theory for the oxidation by charged species in the limit of a low electric field. Activation energies of 0.19 and 0.28 eV are obtained using the CM model for the ECR plasma oxidation of Si and Ge, respectively. Increasing the negative bias causes oxide sputter etching and surface damage, with no significant contribution to oxidation. A probable mechanism for the ECR plasma oxidation process is also discussed.