Comparison of PVD, PECVD & PEALD Ru(-C) films as Cu diffusion barriers by means of bias temperature stress measurements (original) (raw)
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Electrical Evaluation of Ru–W(-N), Ru–Ta(-N) and Ru–Mn films as Cu diffusion barriers
Microelectronic Engineering, 2012
Co-sputtered Ru-Ta(N), Ru-W(N) and Ru-Mn composites are investigated in terms of their barrier properties against Cu diffusion. A wide range of stoichiometries is analyzed with regard to crystallization, barrier properties, resistivity, Cu adhesion and direct Cu plating behaviour. All films were annealed at 350°C and 600°C in forming gas for 1h and subsequently stressed at elevated temperatures and electrical fields (BTS, 250°C, 2 MV/cm, 30 min). The leakage current was monitored during BTS to observe increased leakage due to Cu diffusion. The Cu ions that eventually have passed the barrier and drifted into the dielectric of the MIS test structure were detected and quantified using the triangular voltage sweep method. The addition of 10% W or Ta into a Ru film already leads to a highly improved barrier performance against Cu diffusion, comparable to TaN, as long as the temperatures involved are kept below 350°C. Outstanding barriers were identified after 600°C annealing and subsequent BTS, among them Ru 50 W 50, Ru 50 Ta 50 and Ru 95 Mn 5 . However, only Ru 90 Ta 10 and Ru 95 Mn 5 offer an excellent Cu adhesion and the possibility of direct Cu plating.
A Bilayer Diffusion Barrier of ALD-Ru/ALD-TaCN for Direct Plating of Cu
Journal of The Electrochemical Society, 2008
Diffusion barrier performances of atomic layer deposited ͑ALD͒-Ru thin films between Cu and Si were improved with the use of an underlying 2 nm thick ALD-TaCN interlayer as diffusion barrier for the direct plating of Cu. Ru was deposited by a sequential supply of bis͑ethylcyclopentadienyl͒ruthenium ͓Ru͑EtCp͒ 2 ͔ and NH 3 plasma and TaCN by a sequential supply of ͑NEt 2 ͒ 3 Ta = Nbu t ͑tert-butylimido-trisdiethylamido-tantalum͒, and H 2 plasma. Sheet resistance measurements, X-ray diffractometry, and Auger electron spectroscopy analysis showed that the bilayer diffusion barriers of ALD-Ru ͑12 nm͒/ALD-TaCN ͑2 nm͒ and ALD-Ru ͑4 nm͒/ALD-TaCN ͑2 nm͒ prevented the Cu diffusion up to annealing temperatures of 600 and 550°C for 30 min, respectively. This is because of the excellent diffusion barrier performance of the ALD-TaCN film against the Cu, due to its amorphous structure. A 5 nm thick ALD-TaCN film was even stable up to annealing at 650°C between Cu and Si. Transmission electron microscopy investigation, combined with energy-dispersive spectroscopy analysis, revealed that the ALD-Ru/ALD-TaCN diffusion barrier failed by the Cu diffusion through the bilayer into the Si substrate. This is due to the ALD-TaCN interlayer preventing the interfacial reaction between the Ru and Si.
Time-to-failure analysis of 5 nm amorphous Ru(P) as a copper diffusion barrier
Thin Solid Films, 2009
Evaluation of chemical vapor deposited amorphous ruthenium-phosphorous alloy as a copper interconnect diffusion barrier is reported. Approximately 5 nm-thick Ru(P) and TaN films in Cu/Ru(P)/SiO 2 /p-Si and Cu/ TaN/SiO 2 /p-Si stacks are subjected to bias-temperature stress at electric fields from 2.0 MV/cm to 4.0 MV/cm and temperatures from 200°C to 300°C. Time-to-failure measurements suggest that chemical vapor deposited Ru(P) is comparable to physical vapor deposited TaN in preventing Cu diffusion. The activation energy of failure for stacks using Ru(P) as a liner is determined to be 1.83 eV in the absence of an electric field. Multiple models of dielectric failure, including the E and Schottky-type √E models indicate that Ru(P) is acceptable for use as a diffusion barrier at conditions likely in future technology generations.
Diffusion Barrier Performance of thin Cr Films in the Cu/Cr/Si Structure
Physica Scripta, 1999
The Cu/Cr/Si structure was studied for thermal stability using thin Cr layers as a barrier in the range of 10 to 40 nm, between 250 and 500°C for 30 min. Investigations using sheet resistance method, deep level transient spectroscopy (DLTS), X-ray diffraction (XRD) analysis, Rutherford backscattering spectroscopy (RBS), and adhesion tests were carried out, to reveal the behavior of Cu and Cr in the Cu/Cr/Si structures. It is shown that even a 10-nm thin Cr layer preserves the multilayer structure up to 400°C and that Cu silicide formation is observed only after annealing at 450°C. However, as found by DLTS, compared with the conventional characterization techniques, Cu migration into the structure reduces the effectiveness of the Cr layers as a diffusion barrier at 50°C.
Novel PEALD-Ru formation technique using H2 & H2/N2 plasma as a seed layer for direct CVD-Cu filling
2009
In this paper, novel Ru film formation technique by plasma enhanced atomic layer deposition (PEALD) is reported to be extremely promising as a seed layer for direct CVD-Cu full filling. PEALD-Ru film property can be controlled by H2 to N2 gas flow ratio in plasma step. PEALD-Ru film using H2/N2 mixed gas based plasma can provide low resistivity (20 muOmega-cm), sufficient Cu barrier property and 100% step-coverage. PEALD-Ru film using H2 gas based plasma can provide (002) oriented Ru film, which is confirmed as good nucleation layer for CVD-Cu formation. Stacked film of Ru(H2)/ Ru(H2/N2) is demonstrated to be attractive as an underneath for direct CVD-Cu full filling without void generation in 50 nm via pattern.
Physical, Electrical, and Reliability Characterization of Ru for Cu Interconnects
2006 International Interconnect Technology Conference, 2006
Thin film characterization, electrical performance, and preliminary reliability of physical vapor-deposited (PVD) TaN/ chemical vapor-deposited (CVD) Ru bilayer were carried out to evaluate its feasibility as a liner layer for Back-End of Line (BEOL) Cu-low k integration. Adhesion and barrier strength were studied using 4 -point bend, x -ray diffraction (XRD), and triangular voltage sweep (TVS) techniques. Electrical yields and line/via resistances were measured at both single and dual damascene levels, with PVD TaN/Ta liner layer as a baseline control. Reliability studies included electromigration (EM) and current-voltage (I-V) breakdown tests.
Microelectronic Engineering, 1997
The diffusion barrier behaviour of 20 to 200 nm thin Ta(N,O) films in the Cu/Si contact system was evaluated by materials and transient ion drift analysis. Using high resolution transmission electron microscopy, grazing incidence X-ray diffractometry, Auger electron spectroscopy and secondary ion mass spectrometry depth profiling it was revealed that the as-deposited amorphous-like Ta(N,O) diffusion barriers tend to partially recrystallize after annealing at 1 h/500°C without any detectable diffusion and/or reaction of Cu and Si up to at least 1 h/600°C. By making use of the newly developed transient ion drift technique for trace element analysis down to 5 × 10 j~ cm -3 of interstitially dissolved Cu in Si, an exponential decrease of the Cu concentration on the Ta(N,O) barrier thickness is observed.
Comparison of characteristics and integration of copper diffusion-barrier dielectrics
Thin Solid Films, 2006
The characteristics of various copper (Cu) barrier layers, including SiN, SiCN, and SiCO, were investigated in this work. Carbon-based barrier films (SiCN and SiCO) improved the dielectric constant and line-to-line capacitance, but led to sacrifice in film deposition rate, diffusion-barrier performance, and adhesion strength to Cu in comparison with SiN films. In addition, SiN and SiCO films showed the superior electromigration (EM) performance and stress-induced void migration (SM) performance, respectively. Furthermore, the reliability results of SM and EM are strongly related to the barrier film stress characteristics and the adhesion strength between Cu layers. Therefore, optimization of the barrier layer stress and the enhancement of the interfacial condition between Cu and barrier films are crucial to significantly improve reliability.
Influence of diffusion barriers on the nucleation and growth of CVD Cu for interconnect applications
Microelectronic Engineering, 2000
Nucleation and growth behavior of Cu influence strongly the macroscopic properties of the resultant films. In this work the nucleation of CVD Cu on different underlayer materials is studied. It is found that nucleation on bare diffusion barrier surfaces leads to island growth and, therefore, bad wetting and adhesion. An enrichment of F, O and carbon was found at the interface between the CVD Cu film and the diffusion barrier. However CVD Cu deposited on top of Ta with a 200-A PVD Cu layer on top results in good wetting. CVD Cu films grown on a PVD Cu layer expose a highly preferred k111l orientation. In this case SIMS analysis reveals a comparably low concentration of oxygen, carbon and flourine at the interface region between the CVD Cu and the barrier. These observations shed light on relevance of surface conditions for the CVD Cu deposition process. They significantly affect both film adhesion and crystal orientation, which are crucial for the use of CVD Cu as interconnect material.
Electrolessly deposited diffusion barriers for microelectronics
IBM Journal of Research and Development, 1998
Electrolessly deposited materials were investigated as possible diffusion barrier layers for multilayer microelectronic structures. Attention was focused on selective deposition of barrier layers on various surfaces, the barrier's capability to inhibit Cu diffusion, changes in Cu resistivity caused by barrier material diffusion into Cu, and adhesion between a polyimide film and the barrier layer. Electroless Co(P) was the most effective barrier to Cu diffusion at elevated temperature, even at Co(P) thicknesses as low as 500 A. Diffusion-barrier effectiveness of electrolessly deposited materials decreased in the following order: Co(P) > Ni-Co(P) = Ni{P) » pure metals Co, Ni). Although a polyimide film bonded strongly to electrolessly deposited Ni(P) layers and only weakly to as-deposited Co(P), electroless Ni(P) significantly increased the Cu resistivity through interdiffusion. Polyimide adhesion to Co(P) was improved by oxidizing a Co(P) surface immediately after deposition to grow a passive film 50-75 A thick, yielding a surface to which the polyimide adheres strongly and reproducibly. A low-energy-beam, scanning electron microscopy/energy-dispersive X-ray analysis technique (SEM/EDX) was developed to measure the nonoxidized thin Co(P) barrier layer thickness.