bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimization of Ti and Co Self-Aligned Silicide RTP for 0.10 μm CMOS
Authors: Kittl J. A. , Hong Q. Z. , Yang H. , Yu N. , Rodder M. , Apte P. P. , Shiau W. T. , Chao C. P. , Breedijk T. , Pas M. F. 
Published: April 2011

ABSTRACTAs CMOS technologies are scaled to 0.10 μm and beyond, self-aligned silicide (salicide) processes find difficult challenges. As junction depths and linewidths are scaled, achieving both low sheet resistance and low contact resistance maintaining low diode leakage becomes increasingly difficult. In this paper we present studies of Ti and Co salicide processes implemented into a 0.10 μm CMOS technology. We show that both for Ti and Co, the optimization of RTP parameters plays a crucial roll in achieving a successful implementation. For Co salicide, optimization of RTP conditions results in elimination of shallow junction leakage (its main scaling problem). Two-step RTP and one-step RTP Ti salicide processes are compared, showing the advantages of one-step RTP. The RTP process windows for low resistance narrow gates (the main scaling issue for Ti salicide) are analyzed. Processes with pre-amorphization, with Mo doping and with a combination of both are compared. An optimal process using Mo and preamorphization implants and one-step RTP is shown to result in excellent device characteristics and low resistance to 0.06 μm gates.
Atomic Layer Deposition of Tin Thin Films by Sequential Introduction of Ti Precursor and NH3
Authors: Min Jae-Sik , Son Young-Woong , Kang Won-Gu , Kang Sang-Won 
Published: April 2011

ABSTRACTAtomic layer deposition(ALD) of amorphous TiN films on SiO2 between 170°C and 210°C has been investigated by alternate supply of reactant sources, Ti[N(C2H5CH3)2]4 [tetrakis(ethylmethylamino)titanium : TEMAT] and NH3. Reactant sources were injected into the reactor in the order of TEMAT vapor pulse, Ar gas pulse, NH3 gas pulse and Ar gas pulse. Film thickness per cycle was saturated at around 0.5 nrm/cycle with sufficient pulse time of TEMAT at 200°C. The ideal linear relationship between number of cycles and film thickness is confirmed. As a result of surface limited reactions of ALD, step coverage was excellent. Particles caused by the gas phase reactions between TEMAT and NH3 were almost free because TEMAT was separated from NH3 by the Ar pulse. In spite of relatively low substrate temperature, carbon impurity was incorporated below 4at%.
Effect of lateral dimension scaling on thermal stability of thin CoSi2 layers on polysilicon implanted with Si
Authors: Via F. La , Alberti A. , Grimaldi M. G. , Ravesi S. 
Published: April 2011

ABSTRACTThe thermal stability of patterned cobalt silicide layers grown on amorphous silicon has been studied in the temperature range between 850 and 1000 °C. The degradation of patterned CoSi2, detected by resistance measurements, occurs via grain agglomeration at a temperature ∼100 °C lower than in blanket film. The reduction of the stability window in patterned samples is due to geometric constraints,. which results in a greater growth rate of the median grains with respect to lateral grains.
Copper Ulsi Interconnect Technology
Authors: Edelstein D. 
Published: April 2011

ABSTRACTRecently IBM announced the first implementation of full copper ULSI wiring in a CMOS technology, to be manufactured on its high-performance 0.22 um CMOS products this year. Features of this technology will be presented, as well as functional verification on CMOS chips. To reach this level, extensive yield, reliability, and stress testing had to be done on test and product-like chips, including those packaged into product modules. Data will be presented fom all aspects of this testing, ranging from experiments designed to promote Cu contamination of the MOS devices, to temperature/humidity/bias stressing of assembled functional modules. The results in all areas are shown to be equal to or better than standards set by our current AI(Cu)/Wstud technology. This demonstrates that the potential problems associated with copper wiring that have long been discussed can be overcome.
Theoretical Reactor Design from the Simple Tubular Reactor Analysis for Wsix CVD Process
Authors: Chae Y. K. , Egashira Y. , Shimogaki Y. , Sugawara K. , Komiyama H. 
Published: April 2011

ABSTRACTWe propose a methodology for systematic reactor design and optimization of operating conditions. The reactor can be designed systematically through the following steps: extraction of the chemistry from small-scale experiments, simulations for the virtual large-sized reactor configurations using the chemistry obtained from small-scale experiments, and final optimization by actual experiments on the real reactor manufactured according to the results of the simulation experiments. We call this technique ECONOMIX (Experiment, COmputer, kNOwledge MIXed CVD Process Design). The validity of this theoretical approach was confirmed for the WSix CVD process. The chemistry of the WSix CVD process was obtained from the tubular hot wall reactor. The rate constants of consecutive reaction were re-determined using two-dimensional simulation with consideration of temperature distribution. The growth rate and composition ratio were simulated for the cold wall reactor using reaction kinetics obtained by tubular hot wall reactor analysis. The predicted growth rates and composition ratios of Si/W showed good agreement with the experimental data. Therefore, the theoretical approach, ECONOMIX, is valid for the design of CVD reactor. We can design reactors and optimize operating conditions efficiently by this theoretical approach using computer simulation coupled with small-scale experiments.
Analysis of Copper and Low-K Dielectric Interconnect System for 0.18-μm Technology
Authors: Lin X. W. , Hui K. , Ghanderhari K. , Bothra S. , Pramanik D. , Findley P. 
Published: April 2011

ABSTRACTAs the interconnect RC delay plays an increasingly dominant role in the performance of deep submicron ULSI devices, Cu and low-k dielectric materials are deemed necessary to replace the traditional Al and SiO2 system to lower both the resistance and capacitance of metallization. This paper presents a systematic simulation method to assess the impact of Cu and low-k dielectric to the system speed and cross-talk noise for 0.18-μm design rules (0.6 μm pitch), and determine the practical process windows for metal line aspect ratio and the structural configuration of dielectrics. It was found that the high performance requirements for 0.18-μm devices (600 MHz and cross-talk <0.3 on a 2×2 cm2 chip) cannot be met by simply replacing Al with Cu or SiO2 with low-k dielectric (k=3), without any change in the interconnect architecture. By reverse scaling the metal pitch to 2× at upper levels, on the other hand, one can easily find a manufacturable process window, even with the Al and SiO2 system. Case studies on R and C of various structural configurations and boundary conditions have been performed, including Cu barrier layer thickness, metal gap fill and capping layer thickness of low-k dielectrics, as well as the influence of the lower and upper metal plates. The significance of the results on the strategy of implementing Cu/low-k interconnects versus extending Al/SiO2 will be discussed.
Effect of Boron on Diffusion Barrier Characteristics of Pecvd W-B-N Films
Authors: Kim Dong Joon , Kim Yong Tae , Park Jong-Wan 
Published: April 2011

ABSTRACTThe effects of B and N addition on the phase transition and barrier performance of the plasma deposited W-B-N films are investigated. The W-B-N films have chemical compositions in the range from W67N33 to W38B42N20 corresponding to the flow ratio of B10H14/NH3. Among the films of various compositions of B and N, W46B25N29 film shows excellent thermal stability against the Cu diffusion because the W46B25N29 film keeps the amorphous state even after the annealing at 800°C for 30 min. Resonance backscattering and x-ray photoemission spectra for B and N atoms before and after the annealing process indicate that the amorphous state is retained due to the formation of the B-N bonds.
The Stability to Ageing of Pd/Zn and Pt-Based Ohmic Contacts to p-InGaAs/InP
Authors: Leech P. W. , Reeves G. K. , Ressel P. 
Published: April 2011

ABSTRACTPd/Zn/Au contacts to p-In0.53Ga0.47As/InP with various barrier layers (Pd, Pt or LaB,) to the indiffusion of Au have been examined by Rutherford Backscattering Spectrometry (RBS). For the metallisations with a barrier layer of Pd, the ageing of the contacts at 400°C for 20 h produced a widespread indiffusion of Au. In comparison, the incorporation of a layer of Pt or amorphous LaB6 prevented an indiffusion of Au and significantly reduced any outdiffusion of the semiconductor elements. The presence of the barrier layer of Pt or LaB6 produced little or no detrimental increase in specific contact resistance, ρc, for this contact system. Values of ρc in the range 8–10 × 10−6 Ω cm2 were obtained for all of the contacts based on Pd/Zn/Au after annealing at 500°C. A comparison has been made with the characteristics of Pt/Ti/Pt/Au contacts to p-In0.53Ga0.47As/ InP which were shown as stable against the indiffusion of Au.
Epitaxial Growth of CoGa on (100)GaAs by Metal-Organic Molecular Beam Epitaxy
Authors: Viguier N. , Maury F. 
Published: April 2011

ABSTRACTEpitaxial layers of the intermetallic β-CoGa cubic phase were grown at low temperature on (100)GaAs by metal-organic molecular beam epitaxy (MOMBE) using GaEt3 and CpCo(CO)2 as vapor sources. The film composition and the lattice mismatch on (100)GaAs may be adjusted by controlling the molecular beam pressure ratio. The growth on a Co-saturated GaAs surface leads to the formation of bi-phased CoGa-CoAs films whereas epitaxial single-phased β-CoGa layers are grown on a Ga-terminated GaAs surface with the simple cube on cube orientation [100](001 )CoGa//[100](001)GaAs. Annealing experiments under inert atmosphere have shown that MOMBE CoGa films are thermally stable on GaAs until ca. 823 K. Ohmic and Schottky CoGa/GaAs contacts have been made depending on the doping of the substrate by this process.
Effect of NH3 Plasma Treatment on Etching of Ti During Ticl4-Based Tin CVD Processes
Authors: Gross M. E. , Coleman E. , Ohto K. 
Published: April 2011

ABSTRACTIntegration of a TiCl4-based chemical vapor deposition (CVD) process for TiN barrier films with Ti underlayers for sub-micron integrated circuit metallization stacks exposes the Ti film to TiCl4 and NH3 adducts of TiCl4 that may etch the Ti in addition to depositing TiN. In this paper we report results of studies on the interactions of TiCl4 with ex situ PVD Ti films during the CVD TiN process. Deposition of TiN on Ti/SiO2/Si using a onestep 650°C process shows evidence of significant etching of the underlying Ti. A two-step process using a reduced TiCl4 flow for the initial deposition reduced the amount of etching but for Ti films over 200Å thick there was significant non-uniformity and peeling at the Ti/SiO2 interface. Pre-treatment of the Ti surface in situ with a 500W, 450 kHz NH3 plasma for 20–60 sec. leads to formation of TiN0.3, which shows a slight protective effect against etching. The same series of experiments with Ti deposited on Si reveals no etching, owing to reaction of the Ti with the Si substrate to form etch-resistant silicides. These results suggest that integration of a TiCl4-based CVD TiN process with an underlying Ti layer may be undesirable unless the surface of the Ti is protected against etching.
Optimizing Sputtered Tin ARC Film Properties for Lithography of Sub-0.25μm Interconnect
Authors: Sengupta S. S. , Baker D. , Sethi S. , Bothra S. 
Published: April 2011

ABSTRACTAdvanced interconnect fabrication may require alternative TiITiN processes, such as an ionized metal plasma (IMP) sputtering technique to deposit Ti/TiN liner for sufficient step coverage in high aspect ratio contacts/vias. Since TiN is also widely used as an anti-reflective coating on top of multilayer metal films, the optical properties of the TiN film are extremely important.In this paper, both IMP and standard PVD TiN films deposited on an aluminum layer are compared with respect to their lithography performance at exposure wavelengths of 365 nm (i-line) and 248 un (deep ultraviolet, or DUV). The measured optical constants of the two films were found to be very similar. The linewidth response of these two films at 365 nm was comparable; however, with DUV patterning, resist footing was observed on both films; but was especially severe with standard TiN. Differences in resist profile are explained in terms of the surface structure and density of the TiN film. By varying the conditions for deposition of IMP TiN (such as, RF bias, chamber pressure, etc.), the optical properties of the films may be varied. The impact of these varying film properties on DUV lithography is evaluated. Experimentally obtained linewidth response is compared with optical lithography simulations.
Texture Control and Electromigration Performance in Al-Based and Cu-Based Layered Interconnects
Authors: Kageyama Makiko , Abe Kazuhide , Harada Yusuke , Onoda Hiroshi 
Published: April 2011

ABSTRACTTexture control of Al and Cu by underlying refractory metal is discussed. Al texture can be controlled with underlayer metals like as Ti and TiN which have the same atomic arrangement within 3% misfits to Al. Cu texture can be also controlled by underlayer TiN in spite of a large difference in inter-atomic distance of Cu and TiN. Since the epitaxial growth of TiN on Cu is observed, it is suggested that epitaxial growth may occur at the early stage of Cu deposition on TiN.The electromigration performance was evaluated in double level interconnects with W-stud via. It is confirmed that highly <111> textured Al and Cu have high electromigration resistance. Both the diffusion of Cu in Al-Cu and Al drift are suppressed in <111> textured Al-alloy interconnects, and Cu drift is also suppressed in Cu damascene lines formed on <111> textured TiN. Grain boundary diffusion and the interfacial diffusion would be suppressed in highly textured metals with underlayer and it is speculated that interfacial diffusion is more important in Cu damascene lines.
Grain Structure Statistics in As-Patterned and Annealed Interconnects
Authors: Fayad W. , Andleigh V. , Thompson C. V. , Frost H.J. 
Published: April 2011

AbstractWe have simulated the development of grain structures in polycrystalline films with lognormally distributed grain sizes, and carried out extensive characterization of grain cluster and bamboo cluster statistics. These statistics were characterized as a function of line-width to initial-grain-size ratios in as-patterned strips, and in strips in which we have simulated post-patterning grain structure evolution resulting from annealing. Among the important findings is that polygranular and bamboo cluster-length distributions for as-patterned lines are best fit by Weibull distribution functions instead of lognormal or exponential functions, as is often assumed. We report analytic formulae describing grain structure statistics that can be used in reliability calculations and simulations. We have carried out structure-sensitive electromigration simulations to show that the predicted failure statistics are essentially the same for grain structures generated using grain growth simulations and grain structures generated using analytic models. Analytic models provide computationally efficient means of determining the lifetime variations associated with grain-structure variations.
Analysis of Failure in Metallic Thin-Film Interconnects Due to Stress and Electromigration-Induced Void Propagation
Authors: Rauf Gungor M. , Gray Leonard J. , Maroudas Dimitrios 
Published: April 2011

AbstractA theoretical analysis is presented of the morphological evolution of transgranular voids in metallic thin films driven by capillarity, stress, and electromigration. This highly nonlinear and complex dynamics is analyzed through self-consistent numerical simulations based on a two-dimensional phenomenological model of a passivated interconnect. The analysis follows a systematic exploration of a six-dimensional parameter space determined by the strengths of the electric and stress fields, surface diffusion anisotropy, and the size of the void. Our simulation results reveal a very rich nonlinear dynamical picture of void morphological evolution mechanism, including faceting, wedge void and faceted slit formation through a facet selection process, and soliton-like surface wave propagation. These results are in very good agreement with experimental observations and have important implications for interconnect failure.
Electric Field Direct Force in Electromigration Mechanism
Authors: Karpushin A.A. , Sorokin A.N. , Baklanov M.R. , Maex K. 
Published: April 2011

AbstractThe direct influence of the applied electric field on ions of lattice, as a whole, was considered. This influence induces the strains and stresses and its gradients. In turn, this additional stresses may induce the vacancy (ion) diffusion flux. It is shown that this flux coincides in the direction and is comparable in magnitude with the electromigration flux induced by the electron wind.
Electromigration and Diffusion in Short Al-Ni-Cr Lines
Authors: Jacobs L.C. , Verbruggen A.H. , Kalkman A.J. , Radelaar S. 
Published: April 2011

AbstractTo investigate why the formation of electromigration damage in Al lines alloyed with both 0.1 at.% Ni and 0.1 at.% Cr is so effectively suppressed we studied electromigration induced changes in the electrical resistance of short lines. The length of the lines is 4, 6, 8, or 12 µm, the width is 4 µm and the film thickness is 0.3 µm. As previously reported for pure Al lines, depending on current density and sample length, the induced resistance changes fully recover or do not recover after DC stressing for a few hours. The recoverable resistance changes correspond to the build-up or relaxation of mechanical stress and the permanent resistance changes to the formation of a void or hillock. Electron microprobe analysis and resistance measurements after prolonged current stressing provided no evidence for changes in local solute concentration. Therefore diffusion of Al along grain boundaries is regarded as the dominating diffusion process. The activation energy and the pre-exponential factor of this process are determined from the temperature dependence of the relaxation time of the recoverable resistance changes. The activation energy of this process is 0.84±0.03 eV and the pre-exponential factor δD0 = (1.8±0.8)×10−8 cm3/s. At 175 °C the resulting diffusion coefficient is about a factor 70 smaller than that of pure Al. The transition from recoverable to permanent resistance changes is characterized by a constant critical current density -sample length product. It is found that the value of this product for the Al-Ni-Cr lines is two times larger than the value found for pure Al lines. This means that the threshold current density at given sample length for the formation of hillocks or voids is two times larger. Both the slower solvent diffusion and the higher threshold current density contribute positively to a long electromigration lifetime.
The Electromigration of CVD-Copper and PVD-Copper Polycrystalline Lines
Authors: Kim Seok , Choi Doo-Jin 
Published: April 2011

AbstractThe electromigration characteristics of CVD-Cu films were compared to those of PVDCu films. The CVD-Cu films were deposited using metal-organic precursor of (hfac)Cu(VTMS) and the PVD-Cu films were deposited by evaporation of a 99.995 % Cu metal on TiN and SiO2 substrates. To test EM-resistance, Cu film was patterned into the test structure of multi-lines with 20∼30 µm width and 2500 µm length per one line by a photolithography technique. These test lines had polycrystalline structures composed of much smaller grains than line width and thickness. An accelerated EM test was carried out in the vacuum of 10−6 Torr because the test in N2 ambient had lead to a resistance increase mainly due to oxidation of Cu.The CVD-Cu lines had shorter lifetime than PVD-Cu and the activation energy of electromigration was 0.754 eV for the CVD-Cu on SiO2, which means the grain boundary diffusion as the EM failure mechanism. The CVD-Cu films had larger grains and poorer continuity between grains than the PVD-Cu films so the resistivity of CVD-Cu films (3.20±0.21 µΩcm) was higher than that of PVD-Cu films (2.00±0.06 µΩcm) having a value of near bulk resistivity. The higher resistivity induces the higher driving force of EM. Moreover the PVD-Cu films had a huge domain structure, which might act as a larger grain than CVD-Cu grain to result in the longer life-time and the surface diffusion mechanism with the activation energy of 0.244 eV.
Deformation Mechanisms in Thin Cu Films
Authors: Baker Shefford P. , Keller Rose-Marie , Kretschmann André , Arzt Eduard 
Published: April 2011

AbstractThe deformation characteristics of continuous thin Cu films 0.3-1.0 μm thick on Si substrates with Si3N4 diffusion barriers and passivations have been investigated using substrate curvature and x-ray diffraction methods at room temperature and at temperatures up to 600°C. The stress levels at all temperatures were modelled on the basis of deformation mechanisms used to describe bulk Cu and using mechanisms and model modifications specific to thin films. The Cu films were found to support high stresses at room temperature which depended strongly on the film thickness and presence of a passivation. These stress levels could be adequately modelled by considering both dimensional and microstructural constraints on the glide motion of dislocations. At higher temperatures, the presence of a passivation was seen to change the stress levels reached in a film by one to two orders of magnitude. For unpassivated Cu films, a model based on power law creep could accurately describe stress-temperature data. For passivated films, the addition of a threshold stress to the power law model provides substantial agreement between model and measured data. Exposure of Cu films to small amounts of air or oxygen has a significant effect on thermomechanical behavior. The deformation behavior of differently oriented grains in the films were observed to be quite different from one another. Cu films behave neither like bulk Cu nor like Al thin films. A priori prediction of stress levels in Cu films or patterned structures for use in reliability calculations is not possible at this time.
Evaluation of the Electromigration Performance of New Aluminium Via Plug-Fill Techniques for 0.25μm and 0.18μm Technologies
Authors: Foley S. , Chan Tung N. , Gounelle C. , Wyborn G. , Louwers S. , Mathewson A. 
Published: April 2011

AbstractThe electromigration performance of samples fabricated with new Al via-filling techniques are studied and compared. The new techniques are (1) Hot Al mono-chamber and (2) CVD/PVD Al. Their electromigration performances are assessed over a range of stress conditions and compared with that of a standard W- etchback technique.