Plasma-Enhanced ALD of Platinum with O2, N2 and NH3 Plasmas

Platinum thin films were grown by plasma-enhanced atomic layer deposition (PEALD) using (methylcyclopentadienyl)-trimethylplatinum (MeCpPtMe3) as precursor and respectively an oxygen, nitrogen and ammonia plasma as reactant. For each process the film thickness was found to be linearly dependent on the number of reaction cycles. Saturation curves and temperature windows were defined and growth rates of 0.45 angstrom cycle(-1), 0.30 angstrom cycle(-1) and 0.40 angstrom cycle(-1) were obtained for the oxygen, nitrogen and ammonia process respectively. All the films were metallic platinum, crystalline, uniform and closed, with low surface roughness and low impurity levels. At a pressure of 1 x 10(-3) mbar, nucleation on SiO2 was remarkably faster with the NH3 and N-2 processes than with the O-2 process. In-situ OES and MS measurements showed a fundamental difference between the NH3 and N-2 processes and the O-2 process. Based on these measurements we propose a reaction mechanism for the N-2 and NH3 PEALD processes where nitrogen will unstably adsorb on the substrate during the plasma pulse and be used during the subsequent precursor pulse to remove part of the precursor ligands. (C) 2012 The Electrochemical Society. All rights reserved.