Improvement of Ta-based thin film barriers on copper by ion implantation of nitrogen and oxygen (original) (raw)
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Study of Ta–Si–N thin films for use as barrier layer in copper metallizations
Microelectronic Engineering, 2000
This work focuses on the deposition process, microanalytical characterization and barrier behaviour of 10-100-nm thick sputtered Ta-Si and Ta-Si-N films. Pure Ta-Si films were found to be already nanocrystalline. The addition of N leads to 2 a further grain fining resulting in amorphous films with excellent thermal stability. According to microanalytical investigations, Ta-Si barriers between Cu and Si with a thickness of only 10 nm are not stable at 6008C. Copper silicides are formed due to intensive Cu diffusion throughout the barrier. In contrast, 10-nm thick nitrogen-rich Ta-Si-N barriers remain thermally stable during annealing at 6008C and protect the Si wafer from Cu indiffusion.
Study of nanocrystalline Ta(N,O) diffusion barriers for use in Cu metallization
Microelectronic Engineering, 1997
In this study, the film properties and the barrier behaviour of 50 nm thin reactively sputtered Ta(N,O) diffusion barriers between Cu and Si were investigated. Auger electron microscopy, glancing-angle x-ray diffractometry and atomic force microscopy revealed that the Ta(N,O) films exhibit quasi-amorphous/nanocrystalline properties. Using sheet resistance measurements, scanning electron microscopy, Auger electron spectroscopy depth profiling and conventional x-ray diffractometry the 50 nm thin Ta(N,O) films were found to be effective diffusion barriers between Cu overlayers and Si substrates even after 1 h annealing at 600°C.
Journal of Materials Research, 1999
As-deposited and annealed tantalum films, grown by plasma-promoted chemical vapor deposition (PPCVD) using pentabromotantalum and hydrogen as coreactants, were evaluated as diffusion barriers in copper metallization. Stacks consisting of 500-nm-thick sputtered Cu/55-nm-thick untreated PPCVD Ta/Si were annealed in argon in the range 450 to 650 °C, in 50 °C intervals, along with sputtered Cu/preannealed PPCVD Ta/Si and sputtered Cu/sputtered Ta/Si stacks of identical thickness. Pre- and postannealed stacks were characterized by x-ray photoelectron spectroscopy, Auger electron spectroscopy, Rutherford backscattering spectrometry, hydrogen profiling, x-ray diffraction, atomic force microscopy, sheet resistance measurements, and Secco chemical treatment and etch-pit observation by scanning electron microscopy. The sputtered and preannealed PPCVD Ta films acted as viable diffusion barriers up to 550 °C, while the as-deposited PPCVD Ta films failed above 500 °C. In all cases, breakdown occurred through the migration of Cu into Si, rather than an interfacial reaction between Ta and Si, in agreement with previously reported results for sputtered Ta films. The accelerated barrier failure for as-deposited PPCVD Ta might have been caused by the presence of approximately 20 at.% hydrogen in the as-deposited PPCVD Ta, an observation which was supported by the enhanced performance of the same PPCVD Ta films after annealing-induced hydrogen removal.
A new method for deposition of cubic Ta diffusion barrier for Cu metallization
Thin Solid Films, 2003
We have deposited high-quality cubic a-Ta films by incorporating an AryN Plasma pre-treatment process prior to the deposition 2 of the Ta film. The a-Ta films have low resistivity of approximately 30.6 mV cm and near nanocrystalline texture. An ultrathin amorphous Ta(N) interlayer, generated during the AryN pre-treatment on the SiO surface, plays a critical role on the nucleation 2 2 in the initial stage and subsequent growth of a-Ta films. This method is reliable and could be easily applied to the ultralargescale integrated circuits. ᮊ
X-ray structure characterization of barriers for Cu metallization
Microelectronics Reliability, 2000
The possibilities and limitations of X-ray scattering techniques are discussed for the structure analysis of Ta-N barriers for Cu metallization. Diffraction measurements under grazing incident angle enable to analyze the phase composition and to determine structural parameters of 10 nm Ta-N films onto (100)-silicon wafers. Depending on the nitrogen flow nanocrystalline bcc Ta(N), fcc TaN, and amorphous Ta(N) phases were observed in the sputtered films. X-ray specular reflectivity measurements were explored to estimate film thickness and roughness as a function of preparation in a good agreement with transmission electron microscopy investigations.
Tantalum carbide and nitride diffusion barriers for Cu metallisation
Microelectronic Engineering, 2002
The reactions in the Si/TaC/Cu and Si/Ta 2 N/Cu metallisation systems were investigated by x-ray diffraction, Rutherford backscattering, scanning electron microscope and the transmission electron microscopy. The results were then combined with the assessed ternary Si-Ta-C, Ta-C-Cu, Si-Ta-N and Ta-N-Cu phase diagrams. It was found that both barriers ultimately failed due to diffusion of Cu through the barrier and accompanied formation of Cu 3 Si at temperatures higher than 725 °C. However, in the TaC barriers the formation of amorphous TaO x layer with significant amounts of C took place at the TaC/Cu interface already at 600 °C. Similar behaviour at "low" temperatures was also noted in the Ta 2 N barriers.
Journal of The Electrochemical Society, 1999
Nucleation and growth of Cu by chemical vapor deposition (CVD) using hexafluoracetylacetonato-Cu(I)-trimethylvinylsilane [hfac(Cu)tmvs] on different physical vapor deposition (PVD) diffusion barriers, namely, tantalum (Ta) and tantalum nitride (TaN x with x < 0.5), were studied by means of scanning and transmission electron microscopy to understand the dependence of morphology and microstructure on deposition parameters. X-ray diffraction measurements were carried out to study the orientation of the polycrystalline films. Atomic force microscopy was used to investigate the surface roughness. The results were compared to sheet resistance and reflectivity measurements. Nucleation on bare Ta and TaN x surfaces is significantly more difficult than on Ta with a 200 Å PVD Cu "flash" layer. The films directly deposited on Ta or TaN x show a random orientation and an amorphous interlayer between the CVD Cu film and the barrier. CVD Cu films grown on a PVD Cu "flash" layer expose a highly preferred <111> orientation of the grains and no amorphous interlayer.
MRS Proceedings, 1990
ABSTRACTThe effect of deposition pressure and controlled oxygen dosing on the diffusion barrier performance of thin film Ta to Cu penetration was investigated. In-situ resistivity, Auger compositional profiling, scanning electron microscopy and cross-sectional transmission electron microscopy were used to determine the electrical, chemical and structural changes that occur in Cu/Ta bilayers on Si upon heating. A 20 nm Ta barrier allowed the penetration of Cu at temperatures ranging from 320 to 630°C depending on processing conditions. Barrier failure temperature is dependent upon the deposition pressure and oxygen contamination at the Ta/Cu interface. This indicates the importance of understanding how deposition conditions affect diffusion barrier performance.
Microstructural comparisons of ultrathin Cu films deposited by ion-beam and dc-magnetron sputtering
Journal of Applied Physics, 2005
We report and contrast both the electrical resistance and the microstructure of copper thin films deposited in an oxygen containing atmosphere by ion-beam and dcmagnetron sputtering. For films with thicknesses 5 nm or less, the resistivity of the Cu films is minimized at oxygen concentrations ranging from 0.2% to 1% for dc-magnetron sputtering and 6% to 10% for ion beam sputtering. Films sputtered under both conditions show a similar decrease of interface roughness with increasing oxygen concentration, although the magnetron deposited films are smoother. The dc-magnetron produced films have higher resistivity, have smaller Cu grains, and contain a higher concentration of cuprous oxide particles. We discuss the mechanisms leading to the grain refinement and the consequent reduced resistivity in both types of films.
Electrochemical and Solid-State Letters, 2003
͑Ti,Zr͒N films were prepared by dc reactive magnetron sputtering from a Ti-5 atom % Zr alloy target in N 2 /Ar gas mixtures and then employed as diffusion barriers between Cu thin films and Si substrates. Material characteristics of the ͑Ti,Zr͒N film were investigated by X-ray photoelectron spectroscopy and cross-sectional transmission electron microscopy ͑XTEM͒. The ͑Ti,Zr͒N film microstructure was an assembly of very small columnar crystallites with a rock-salt ͑NaCl͒ structure. Metallurgical reactions of Cu/(Ti,Zr)N 0.95 /Si, Cu/(Ti,Zr)N 0.76 /Si, and Cu/TaN 0.71 /Si were studied by X-ray diffraction and sheet resistance measurements. The variation percentage of sheet resistance for all Cu/barrier/Si systems stayed at a constant value after annealing up to 500°C for 30 min. However, the sheet resistance increased dramatically after annealing above 750°C for Cu/(Ti,Zr)N 0.95 /Si, and 500°C for both Cu/(Ti,Zr)N 0.76 /Si and Cu/TaN 0.71 /Si. For these samples, the interface deteriorated seriously and formation of Cu 3 Si was observed by XTEM. Our results suggest that the refractory binary metal nitride film, ͑Ti,Zr͒N, can be used as a diffusion barrier for Cu metallization as compared to the well-known TaN film.