The Role of Ru Passivation and Doping on the Barrier and Seed Layer Properties of Ru-Modified TaN for Copper Interconnects (original) (raw)
Related papers
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.
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.
MRS Proceedings, 2010
The scaling of BEOL interconnect technology in ULSI circuitry requires the integration of Cu wiring with ultra-low K (ULK) dielectrics. We present the results of a study of the interaction between different-stoichiometry Ta(N)/Cu barrier processes and porous ULK dielectrics (k=2.4) at 32nm groundrules Auger and diffraction analysis of blanket wafers was used to benchmark two different stoichiometries of TaN barrier deposited using commercially-available ionized PVD sources. Comparison TEM and EDX/EELS images indicates that barrier oxidation is occurring in the low nitrogen-content Ta(N) barrier, which is absent at the higher stoichiometry. These differences are further manifested in defect-density analysis of patterned wafers comparing the two processes. These results illustrate the critical importance the TaN barrier properties play in enabling the integration of Cu/ULK interconnects at 32nm at beyond.
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.
Development of sub-10-nm atomic layer deposition barriers for Cu/low-k interconnects
Microelectronic Engineering, 2002
The development of atomic layer deposition (ALD) barriers with a thickness below 10 nm for copper / low-k dielectric interconnects was reviewed. The CMOS 65-nm technology node, which is presumably the first node, at which ALD barriers will be employed, was taken as a reference. The ALD barrier process will most likely meet the geometrical requirements, i.e. the capability to deposit barrier films in narrow dimensions. In order to establish the compliance of ALD barriers with the thickness requirements, the growth of the ALD layer was investigated. It was shown that the growth of the ALD films proceeds via islands, which are formed in the nucleation step. The thickness, which is necessary to close the surface of the substrate, depends on process conditions and barrier material. It is argued that the minimum barrier thickness should be at least of the same order as the thickness to achieve closure. In the 65-nm technology node barriers have to be compatible with low-k dielectric materials. To achieve growth of ALD barriers on dense low-k materials, surface treatments of the dielectric films have to be implemented. The deposition of ALD films on dielectric materials with an interconnected pore structure results in penetration of the ALD precursors into the pore system and deposition of the barrier inside the dielectric material.
Thin Solid Films, 2002
Structural properties of thin Ta and Ta-N films acting as diffusion barriers were investigated. Blanket Ta-based films of 10 nm thickness were deposited by conventional sputtering techniques onto (100)-Si and covered with a Cu cap layer. X-ray diffraction, depth profile analysis and electron microscopy were used to correlate results of microstructure and phase characterization with diffusion phenomena. Different barrier failure mechanisms were observed after annealing at temperatures between 450 and 800 8C. Ta and Cu silicides were formed suddenly in layer stacks with pure Ta and Ta-20 at.% N barrier films at 550 8C. The application of the stoichiometric TaN as a diffusion barrier prevents the formation of Ta silicides and does not lead to significant Cu silicide formation up to 800 8C. However, trace Cu diffusion into the substrate was also detected at lower temperatures. The barrier stability against Cu diffusion is improving with increasing N content. ᮊ
Electrical Reliability Issues of Integrating Thin Ta and TaN Barriers with Cu and Low-K Dielectric
Journal of The Electrochemical Society, 1999
This work investigates the integration of very thin sputtered Ta and reactively sputtered TaN barriers with Cu and a low-dielectricconstant (low-K) layer of poly(arylene ether) (PAE-2). It is found that Cu readily penetrates into PAE-2 and degrades its dielectric strength in metal-insulator semiconductor capacitors of Cu/PAE-2/Si structure at temperatures as low as 200ЊC. Very thin Ta and TaN films of 25 nm thickness sandwiched between Cu and the low-K dielectric served as effective barriers during a 30 min thermal annealing at temperatures up to 400 and 450ЊC, respectively. We propose a failure mechanism of outgassing induced gaseous stress of PAE-2 under the Ta film to explain its premature barrier degradation. The TaN barrier did not suffer from this gaseous stress problem because of its stronger adhesion to PAE-2 than that of Ta to PAE-2, leading to a better long-term reliability.
physica status solidi (a), 2008
The objective of this work is to study the optical and electrical properties of tantalum nitride and tantalum barrier thin films used against copper diffusion in Si in integrated circuits using spectroscopic ellipsometry in the VUV and UV -visible range. Single layers of tantalum nitride and bilayer films o f Ta/TaN were produced by reactive magnetron sputtering on Si(100) substrates covered with a native oxide layer. Ellipsometric measurements were performed in the energy range from 0.73 -8.7 eV and the dielectric functions were simulated using Drude-Lorentz model and effectivem ediuma pproxi-mation (EMA) in order to obtain information regarding film thickness, film composition, free carrier plasma energy, mean relaxation time and electrical resistivity. The film thickness clearly affects the electrical resistivity and the electron mean free path. It was observed that for films of Ta on TaN even after maintaining the deposition condition suitable for the β -phase of Ta, it turned out to be a mixture of α -and β -phases with higher contribution of the α-phase. It is shown that even a very small intermixtur e of two different phases o f Ta can be determined accurately using ellipsometry.
Comparative study of novel barrier layers in ULSI copper interconnects
Microelectronic Engineering, 2007
As ULSI dimensions shrink, conventional Ta/TaN barriers will not meet the future demands for ULSI interconnects, i.e. thin conformal layer without overhangs. In this paper, we have compared the material properties of TaN/Ta barriers with Ta only and W based barriers by means of XRD, AFM, Stress and SEM imaging. We found that using a conformal CVD W based barriers has great potential for future ULSI interconnects. It grain size and tensile stress improve resistance to both electromigration and stress migration, extending conductor lifetime.
Electrochimica Acta, 2013
High aspect ratio through Si vias ( 2 m, depth 30 m) have been filled completely by Cu electroplating using an electroless deposited Cu seed layer. The electroless Cu deposition was carried out on ALD-Ru; the time transient of the mixed potential on Ru showed a catalyst type of behavior. The ELD-Cu, which was deposited inside TSVs along their sidewalls, was defect free and worked as a seed layer for electrodeposition of Cu to fill the structure. With a conventional method, such as PVD-Cu, it is challenging to deposit a seed in such structures. The adhesion strength of this ELD-Cu film on ALD-Ru was measured to be >100 MPa. These coupon-scale results show the feasibility of electroless deposition in TSV processing.