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 SiN x PEALD sub-cycles at 270 • C and were evaluated as diffusion barriers for the direct plating of Cu interconnects. The intermixing ratios of Ru and SiN x in RuSiN films were controlled by changing the number of unit cycles in a SiN x 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 SiN x unit cycles. The incorporated Si and N mostly formed Si 3 N 4 according to X-ray photoelectron spectroscopy. The amount of SiN x 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 SiN x into Ru by adding cyclic SiN x cycles. From transmission electron microscopy, it was revealed that the RuSiN film consisted of a SiN x amorphous matrix with very fine grains of Ru, ∼3 nm in diameter, embedded in it. The SiN x amorphous region increased with increasing number of SiN x 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 • C for 30 minutes, whereas that of Cu/PEALD-Ru (8 nm)/Si was stable until only 500 • C.

Review—Silicon Nitride and Silicon Nitride-Rich Thin Film Technologies: Trends in Deposition Techniques and Related Applications

“…88 Other applications include host matrix for ruthenium nanocrystals as seed/barrier layer for copper metallization in IC structures; 97,98 and hydrofluoric acid etch stop layer and electrically insulating spacer in MEMS and medical devices. 80,81 One common attribute in all these applications is the inherent ability of ALD to provide stringent atomic level control and excellent conformality 55 for SiN x coatings in challenging geometries where CVD begins to show its deficiencies and shortcomings.…”

“…Another report 97,98 of note developed a PE-ALD SiN x process as part of forming RuSiN x films as diffusion barriers for copper (Cu) interconnects for IC applications. The process employed tris(isopropylamino)silane (TIPAS) and NH 3 for SiN x .…”

Atomic layer deposition of ternary ruthenates by combining metalorganic precursors with RuO4 as the co-reactant

“…Next to ternary ruthenium oxides, ternary ruthenium nitrides have been deposited by ALD, also by using the supercycle approach. 13,14 The supercycle approach in principle offers excellent composition control by tuning the fraction of each binary process within the supercycle, but several challenges are encountered. 10 As ALD processes for different materials are alternated, overlapping ALD temperature windows are required to achieve saturated conditions and nucleation effects of one material on the other might occur, which can be difficult to control.…”

Atomic Layer Deposition of Silicon Nitride Thin Films: A Review of Recent Progress, Challenges, and Outlooks

“…Recently, PEALD SiN–AlN composite films with excellent etch resistance in HF acid were also developed by Kim et al [ 52 ]. In addition, researchers also studied ALD–TiSiN for use as a gate electrode and diffusion barrier, and ALD–RuSiN composite films for use as a Cu diffusion barrier [ 58 , 59 , 62 , 115 , 116 , 117 , 118 ].…”