Characteristics of Plasma-Enhanced Atomic Layer Deposited RuSiN as a Diffusion Barrier against Cu

Abstract

Ruthenium (Ru)-based ternary thin films, RuSiN, were prepared by plasma enhanced atomic layer deposition (PEALD) by repeating the super-cycles consisting of Ru and SiNx PEALD sub-cycles at 270 degrees C and were evaluated as diffusion barriers for the direct plating of Cu interconnects. The intermixing ratios of Ru and SiNx in RuSiN films were controlled by changing the number of unit cycles in a SiNx sub-cycle from 1 to 9, whereas the number of unit cycles allocated for the Ru sub-cycle was fixed to 10 cycles. Secondary ion mass spectrometry showed that Si and N content in the film increased but the Ru content decreased with increasing number of SiNx unit cycles. The incorporated Si and N mostly formed Si3N4 according to X-ray photoelectron spectroscopy. The amount of SiNx in the RuSiN film had a considerable effect on the properties of RuSiN films. X-ray diffraction showed that the crystallinity of the Ru film was degraded and the grains sizes decreased by incorporating SiNx into Ru by adding cyclic SiNx cycles. From transmission electron microscopy, it was revealed that the RuSiN film consisted of a SiNx amorphous matrix with very fine grains of Ru, similar to 3 nm in diameter, embedded in it. The SiNx amorphous region increased with increasing number of SiNx unit cycles, even though its resistivity increased. The sheet resistance and X-ray diffraction showed that the structure of Cu (100 nm)/PEALD-RuSiN (8 nm)/Si was stable until after annealing at 650 degrees C for 30 minutes, whereas that of Cu/PEALD-Ru (8 nm)/Si was stable until only 500 degrees C. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.054111jes] All rights reserved.