bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanopatterning of Thin Cobaltdisilicide Layers by Local Oxidation
Authors: Klinkhammer F. , Kappius L. , Antons A. , Dolle M. , Trinkaus H. , Mesters St. , Bochem H.-P. , Mantl S. , Heinig K.-H. 
Published: April 2011

ABSTRACTLocal oxidation of thin cobaltdisilicide layers (10–30 nm) allows patterning with distances between silicide pads as small as 70 nm. The epitaxial silicide layers were grown by molecular beam allotaxy (MBA) on Si(100) substrates. They were characterized by TEM, RBS and sheet resistance measurements showing good crystal quality and excellent thermal stability up to 1200°C. Similar to the well established technology for local oxidation of silicon (LOCOS), the silicide layer was caped by 20 nm SiO2 followed by 300 nm of Si3N4. The nitride was patterned by optical lithography and dry etching. During dry oxidation at temperatures ranging from 900°C to 1000°C SiO2 is formed on the unprotected areas of the silicide. The Co atoms diffuse from the SiO2/CoSi2 interface to the CoSi2/Si interface to form CoSi2. Near the edges of the nitride mask the silicide layer thins and finally separates. Two metallic pads electrically separated by Si and SiO2 with a gap of 70 nm were produced this way. Monte Carlo simulations of the process revealed that the reason for the separation is stress dependent diffusion due to the stress induced by the nitride mask. The stress dependence of the separation process was experimentally verified using different nitride thicknesses. SEM and TEM studies showed perfect lateral patterning. This patterning process could be used in the fabrication of MOSFET's with ultrashort gatelengths.
IS Selective CVD an Improvement for the Titanium Silicide Process in Sub-Quarter Micron Technology? A Phase Formation Study Using X-ray Diffraction
Authors: Roy Ronnen , Cabral Cryil , Lavoie Christian , Jordan-Sweet Jean , Viswanathan R. , Ozturk Mehmet , Fang Hua , Swenberg Johanes , Achutharaman Raman 
Published: April 2011

ABSTRACTThe C54 phase formation process of titanium silicide was studied after selective chemical vapor despostion (CVD) onto very small silicon structures, to ascertain the efficacy of CVD to form low resistance contacts in sub-quarter micron technology. Because the selective CVD process forms silicide on any exposed silicon in a CMOS device, the process was studied on both polysilicon and Si (100) chips. The structures consisted of arrays of about 106 identical lines, 0.1 2.0 μm in width, depending on the chip. The CVD process employed TiCl4 and SiH4 for the most part as process gases and the depostion temperature ranged from 730–825°C. X-ray diffraction (XRD) was used to document the amount of C54 phase present after deposition. In some cases samples were annealed after deposition and the phase transformation behavior studied by in-situ XRD. The latter technique employed a synchrotron radiation source providng for rapid XRD spectra collection, so that the C49-C54 phase transformation could be examined with great precision in real time during rapid thermal annealing. The results of CVD depositions were compared to titanium silicide formed by sputter deposition of Ti on identical silicon chips, followed by a typical salicide protocol. Although the phase formation is affected by both film thickness and substrate temperature during CVD, the general result is that the C54 formation is more facile using the CVD process, especially for the smallest line dimensions. The findings are discussed with respect to nucleation processes occurring during growth and post-deposition thermal processing.
Formation of Tisi2 Thin Films from Chemical Vapor Deposition Using TiI4
Authors: Rhee HwaSung , Jang TaeWoong , Baek JongTae , Ahn ByungTae 
Published: April 2011

ABSTRACTThe formation of TiSi2 films by chemical vapor deposition was investigated for the application as a contact plug material because of its low resistivity, low contact resistance with n+ and p+ Si, and good chemical stability with Si. TiI4 and SiH4 were used as source gases. Since TiI4 is thermodynamically less stable than TiCl4, the deposition temperature of TiSi2 with TiI4 precursor could be lower than that of TiSi2 from TiCl4 precursor. TiSi2 thin films with C49 phase were formed at 650°C on Si (100) wafer, while a Ti5Si3 phase was formed at 650°C on SiO2 substrate. The resistivity of the C49 phase films was 210 μΩ-cm. The C49 phase was completely transformed into a C54 phase above 800°C annealing in an N2 atmosphere and the resistivity reduced to 34 μΩ-cm. We were able to deposit TiSi2 films at lower temperature using TiI4 precursor, compared to TiCl4 precursor. The Cl and HCI byproducts originated from TiCl4 can be excluded using TiI4 precursor.
Kelvin Test Structure Modeling of Metal-Silicide-Silicon Contacts
Authors: Reeves G. K. , Holland A. S. , Leech P. W. 
Published: April 2011

ABSTRACTLow resistance ohmic contacts for silicon devices commonly incorporate silicide materials as part of the contact. The electrical characterisation of ohmic contacts requires the use of various test structures such as the Cross Kelvin Resistor in order to determine the specific contact resistance ρc. This paper describes the results of using a three-dimensional finite element model of a Kelvin Resistor test structure in order to determine the influence of the electrical and geometrical parameters of a silicide-well on the magnitude of ρc. The same model of the test structure is further used to model the current density in the contact region. The results indicate that the presence of a silicide-well leads to reduced values of both ρc and the current density.
The Influence of Capping Layer Type on Cobalt Salicide Formation in Films and Narrow Lines
Authors: Besser P. R. , Lauwers A. , Roelandts N. , Maex K. , Blum W. , Alvis R. , Stucchi M. , Potter M. De 
Published: April 2011

ABSTRACTThe effect of capping layer (Ti vs TiN) on CoSi formation and CoSi2 sheet resistance has been investigated. Resistance measurements and XTEM analysis have been used to show that the Ti cap lowers the activation energy for CoSi formation by gettering the O2 from the RTA (rapid thermal anneal) ambient and eliminating the formation of SiO2 between the growing CoSi and the Co. The sheet resistance of cobalt silicide formed from Co/Ti and Co/TiN bilayers on poly- Si lines was measured as a function of linewidth and RTA temperature. With a Ti cap, the sheet resistance is low and independent of temperature, and the RTA process window is large.
Doping Influence on TiSi2 C49-C54 Phase Conversion Kinetics by Micro-Raman Spectroscopy
Authors: Meinardi F. , Quilici S. , Moro L. , Queirolo G. , Sabbadini A. 
Published: April 2011

ABSTRACTMicroRaman measurements on titanium silicide films grown on single-crystal and polycrystalline silicon substrates doped with As, BF2 and P have been performed. The data collected on patterns of different areas and shapes, but comparable doping level show that the doping has negligible effects both on C54 nucleation center density and on activation energy for the C49/C54 phase transition. On the contrary, substrate strongly affects the C54 growth rate, ruling the ability of the C54 phase to propagate after the nucleation.
Diffusion Barrier Properties of the Tin Films Prepared by Ecr Pecvd Method
Authors: Park Hye-Lyun , Jang Seong-Soo , Lee Won-Jong 
Published: April 2011

ABSTRACTTiN film is used as a diffusion barrier layer in contact and via holes in the metallization process of the microelectronics. In most cases, TiN film has been prepared by sputtering which has limited conformality. With the shrinkage of the dimension of the device structure there has been an urgent request for new deposition methods which offer better conformality. Recently, modified PVD systems like highly ionized sputtering system and CVD systems like MOCVD and PECVD systems have been developed.We prepared TiN films with TIC4, N2, and H2 in an ECR PECVD system. TiN films prepared at the temperature of 450°C had resistiveity lower than 50 μm Ω cm and better step coverage than those prepared by PVD system. Barrier properties of the TiN films against Cu were investigated and related with the film properties like composition and microstructure.The Cu/TiN/Si structure were annealed in an H2/Ar atmosphere for 30 min at the temperature range from 500 to 600°C.Plasma treatment and thermal treatment during and/or after the deposition in various atmosphere were adopted to change the composition and the microstructure of the TiN films.The composition of the film was analyzed with AES, the microstructure of the film was observed with SEM and the crystallinity was analyzed with XRD. The electrical resistivity was measured with four-point probe method. Barrier properties of the films were studied again Cu metallization. The change in the resistivity and the structure of the Cu/TiN/Si were investigated after the heat-treatment.
Asymmetrical Heating Behavior at Ni/Doped-Si Junctions for Soi Structures
Authors: Liao C. N. , Tu K. N. 
Published: April 2011

ABSTRACTWith an increasing component density and shrinking feature size in integrated circuit (IC) chips, the heat dissipation issue on the IC chips becomes increasingly important because of device performance and reliability concerns. The heating behavior at Ni/doped-Si junctions, which depends on Joule heating, Peltier effect and heat conduction, is explored in the study. A semiconductor-on-insulator (SOI) structure is used to obtain thermal isolation of the test specimen. The Si channel of 720 μm × 25 μm was lithographically defined and implanted with As+ and BF2+ dopants at a dose of 5×1015 ions/cm2, respectively. By applying a current through a Ni contact/doped-Si/Ni contact structure and measuring the resistance of the doped Si channel near the cathode and the anode ends, we found an obvious asymmetrical heating behavior at the two ends, depending on the dopant type and post-implanatation annealing condition. The Seebeck coefficients of doped Si were measured to be about 140 μV/K and 80 μV/K for BF2+ - doped Si and As+-doped Si, respectively.
Processing of Pure Ni Mocvd Films
Authors: Brissonneau Laurent , Reynes Alex , Vahlas Constantin 
Published: April 2011

ABSTRACTIn this study are reported results on the processing of nickel thin films by metal-organic chemical vapor deposition starting from nickelocene, at atmospheric and reduced pressures, and at temperatures varying between 150 °C and 300 °C. Films present a Volmer-Weber type nodular morphology. Nodules are composed of small crystallites, the mean size of which is about 50 nm. Carbon (up to 10 at. % depending on processing conditions) is incorporated at interstitial rather than intergranular position in the films. High operating pressure favors carbonfree films. An analysis of the gas phase reaction by mass spectrometry is presented in order to understand the mechanisms of the carbon contamination of the deposits.
The Best Way to Obtain Good Quality CVD-TiN Films from TiCl4 and NH3
Authors: Hamamura Hirotaka , Shimogaki Yukihiro , Akiyama Yasunobu , Egashira Yasuyuki , Komiyama Hiroshi 
Published: April 2011

ABSTRACTTiN films deposited by CVD utilizing TiCl4 and NH3 are widely used in ULSI processes. The residual chlorine in the film is one of the major issues of TiCl4 based chemistry [1–5]. We have examined the kinetics of TiN-CVD using TiCl4 and NH3 as precursors to determine method for controlling the residual chlorine concentration.We analyzed the deposition rate profiles obtained from a simple tubular isothermal reactor. Deposition was performed over the temperature range from 300°C to 500°C and with varying initial concentrations of TiCl4 and NH3. We found that the deposition rate was independent of the TiCl4 concentration at higher concentrations. The deposition rate was proportional to the TiCl4 concentration in the low concentration range. This phenomenon can be well explained by a Langmuir-Hinshelwood type mechanism. Examination of the deposition rate dependence on the concentration of NH3 showed that both the maximum deposition rate at high TiCl4 concentrations and the first order kinetic rate constant in the lower TiCl4 concentration range were proportional to the NH3 concentration. These results indicate that the deposition was controlled by the Eley-Rideal mechanism. The residual chlorine concentration was found to be proportional to the surface coverage factor of adsorbed TiCl4. We conclude that the best way to obtain good quality TiN films can be obtained theoretically through these kinetic studies.
Scaling and Integration of High Performance Interconnects
Authors: Yang Simon 
Published: April 2011

ABSTRACTInterconnect delay is believed to have a dominating impact on the speed of large logic circuits (such as micro-processors) when the Si technology is scaled into sub- 0.25um generations. In this paper, we analyzed interconnect scaling issues based on leading micro-processor trend data, simple RC delay model and the “Rents' rule”. It was concluded that, in order to not limit the speed of large logic circuits, “fat” metal wires need to be used for upper metal layers, which will lead to a rapid increase of required number of metal layers (>10) for sub-0.25um technology generations. Introducing Cu and low ε interconnect system can delay this rapid increase by ∼1 generation. Creating multiple clock frequencies in large logic chips and reducing the size of high frequency islands appears effective in containing the interconnection delay problem. Therefore, the proposed interconnection scaling/development strategy is to introduce Cu and low ε dielectric into manufacturing in next 1∼3 generation (0.25um∼0.13um), develop low cost and high yield interconnect system to enable ∼10 interconnect layers, and improve circuit design methodology to reduce high frequency island size.
Thermomechanical Behavior of Continuous and Patterned Al Thin Films
Authors: Kraft O. , Nix W.D. 
Published: April 2011

AbstractIn this paper, we study the influence of the line width on the mechanical behavior of narrow unpassivated lines of pure Al and Al with 0.5 wt.-% Cu. The stress/temperature behavior during thermal cycling is investigated using x-ray diffractometry. Our results suggest that it is possible to distinguish between two temperature regimes in which different deformation mechanisms take place. At low temperatures, the narrowest lines sustain larger stresses than the continuous films, whereas at high temperatures the opposite behavior was found. Further, iso-thermal stress relaxation measurements on pure Al lines after various heat treatments were performed. These results indicate the existence of a threshold stress below which no deformation of the lines occurs.
The Stress Change in Passivated Al Lines Due to the Reaction Between Ti and Al
Authors: Marieb T. , Mack A. , Lee J. , Dibattista M. 
Published: April 2011

AbstractThe thin film reaction between Ti and Al-0.5%Cu to form TiAl3 is common in the microelectronics industry. In this paper the stress changes in Al-0.5%Cu films at elevated temperatures during the reaction are measured. The changes are measured in blanket films as well as in passivated interconnect lines. Results show that in blanket films the Al-0.5%Cu does not experience any stress change due to the reaction. However in passivated lines, where the layers are not allowed to relax in the normal direction, tensile stresses build up in the Al-0.5%Cu due to the volume shrinkage that happens when these films react.
FEM Analysis of Thermal Stresses in Advanced Electronic Packages
Authors: Rzepka Sven , Korhonen Matt A. , Li Che-Yu , Meusel Ekkehard 
Published: April 2011

AbstractFollowing the general tendency of downsizing in microelectronic packages, the interposing layer between silicon chip and organic board is constantly reduced while the differences in thermal expansion stay constant. Consequently, thermal stresses have become the most important reliability concern in advanced packages. Finite element analysis is known as an effective way of theoretically studying the mechanical situation in multi-component systems with complex material behavior. The paper presents results of finite element simulations that provide practical guidance for design, process and material developments of chip size packaging (CSP), flip chip (FC), and direct chip attach (DCA) modules. Using realistic and efficient models, a low-cost CSP concept is assessed, the effects of underfill, underfill imperfections, and underfill defects on the reliability of FC modules are studied, and an optimum set of mechanical properties for underfill materials is proposed. Finally, reliability risk factors in DCA modules are identified and preliminary design guidelines are given.
Novel Electromigration Failure Mechanism for Aluminium-Based Metallization on Titanium Substrate
Authors: Girardi G. , Caprile C. , Cazzaniga F. , Riva L. 
Published: April 2011

AbstractIn this paper a phenomenological characterisation of an anomalous grain growth, observed after classical electromigration lifetests, on Al-l%Si-0.5%Cu multigrain stripes, deposited at high temperature (460°C) on a Ti substrate, is reported. Failure analysis, carried out by Scanning Electron Microscopy (SEM) and Focus Ion Beam (FIB), has detected an abnormal single-grain growth in the vertical direction, starting from the Ti/Al interface. Medium Time to Failure (MTF) data are compared with those of stripes on Ti/TiN substrate, on which no grain growth was observed. The growth of the anomalous grains has been related to the Ti/Al interface properties. Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD) and Atomic Force Microscopy (AFM) analyses concurrently show a higher texture of the film on the Ti, compared with the film on the Ti/TiN substrate. The tight columnar orientation of grain boundaries strongly limits the mechanism of grain boundary diffusion during electromigration stress. The atomic flux is then forced to take place at the Ti/Al interface, where the epitaxial growth of the Al single grains is favoured.
Statistical Evaluation of Stressmigration Reliability in Al-Cu Interconnects
Authors: Jawarani D. , Gall M. , Capasso C. , Müller J. , Hernandez R. , Kawasaki H. 
Published: April 2011

AbstractHigh-resolution resistance measurements of metal stripes have been performed to study void growth duringin situannealing at 180°C. Void growth has been characterized by resistance monitoring over 14,000 hours. During the annealing of Al-lwt%Cu stripes, Cu atoms from solution migrate to grain boundaries to form Al2Cu precipitates leading to a drop in resistance. At the same time, relaxation of tensile stresses in metal stripes takes place in the form of void nucleation and growth, leading to an increase in resistance. The resistance drop due to precipitation was shown to obey Avrami's precipitation kinetics while void growth over this time period obeyed a diffusion-type equation. The resulting equation to describe this physical model was fitted to the measured resistance data. Extrapolation to failure condition (ΔR/R=10%) could therefore be obtained for all the devices under test and plotted on a cumulative probability plot. Using the measured value of activation energy for void growth, stressmigration reliability was then assessed by extrapolation to an operating temperature. Post-mortem microscopy was performed to correlate resistance increase with void density and size in these interconnects. Finite element simulations were performed to calculate resistance increases due to voiding in metal stripes and correlate these with the experimentally obtained data.
A Quantitative Study of Void Nucleation Times in Passivated Aluminum Interconnects
Authors: Doan Jonathan C. , Bravman John C. , Flinn Paul A. , Marieb Thomas N. 
Published: April 2011

AbstractAccelerated electromigration tests were performed in a High Voltage SEM (HVSEM). These experiments were conducted on 10 identical, passivated Al interconnect test structures at a temperature of 237°C and a current density of 30mA/µm2. Simultaneous testing and observation of the entire structure allowed the void nucleation times to be measured. Two normal distributions fit the nucleation times. The second of these distributions coincides roughly with the distribution of failure times of the test structures. Fracture of the passivation is hypothesized as the mechanism that causes the concurrent late nucleation and failure processes.
Electromigration-Induced Drift in Damascene vs. Conventional Interconnects: An Intrinsic Difference
Authors: Proost J. , Samajdar I. , Witvrouw A. , Maexo K. 
Published: April 2011

AbstractThe electromigration (EM) behaviour of damascene Al(Cu)-interconnects has been studied for the first time by drift experiments and results directly compared to plasma-etched lines. For the latter EM is known to occur through sequential stages : an incubation period, needed for Cu-depletion, and an Al-drift stage. It is shown that using a damascene implementation, the incubation time significantly increases but the Al-drift velocity does as well. This is demonstrated to be an intrinsic effect, directly related to the technological nature of both metallization schemes. Implications on lifetime prediction at operating conditions are discussed.
Evolution of the Electrical Properties of Interconnects Under Electromigration Stress
Authors: Jones B.K. , Guo Jianping , Xu Yanzhong , Trefan G. 
Published: April 2011

AbstractWe report experimental results of measurements of the changes in the resistance and thermal non-linearity of a variety of samples during accelerated electromigration stress to failure. The value of the extra measurement of the second harmonic of the AC bridge signal is illustrated by observations of changes in the thermal conductance to the substrate and the temperature coefficient of resistivity which are not detected by the resistance measurement. These quantities are also larger than the resistance measurement.
Test Methods for Characterizing Piezoelectric Thin Films
Authors: von Preissig F. J. , Zeng H. , Kim E. S. 
Published: April 2011

AbstractTwo experimental techniques for quantifying MEMS-relevant material constants of piezoelectric thin films are presented. The first is an improved version of our recently developed ‘plank method.’ This technique is used to determine the product of the biaxial elastic modulus and the piezoelectric constant d31. The updated method is easier and more precise, and it utilizes the results of dynamic as well as improved static finite-element analyses. The second method is the bulge test, here emphasizing the special requirements of piezoelectric and fragile films. Results from both techniques applied to zinc oxide are presented.
The Fracture Toughness of Polysilicon Microdevices
Authors: Ballarini R. , Mullen R.L. , Kahn H. , Heuer A.H. 
Published: April 2011

AbstractThe development of polysilicon fracture mechanics specimens with characteristic dimensions comparable to those of typical microelectromechanical systems (MEMS) devices is presented. The notched cantilever specimens are fully integrated with a simultaneously microfabricated electrostatic actuator, which allows on-chip testing of the specimens without the need of an external loading device, and without any possible influences from external sources. Under monotonic loading, the average maximum tensile stress (strength) and average nominal fracture toughness were measured as 4.2 GPa and 3.5 MPa-m½ for boron-doped specimens, and 5.0 GPa and 4.0 MPa-m½ for undoped specimens. An average modulus of rupture of 3.3 GPa and average nominal toughness of 2.7 MPa-m½ were measured for specimens cracked under cyclic resonance loading. The differences between the monotonic loading and cyclic loading data are attributed to fatigue initiation of a sharp crack from the 1 ýtm radius notch. The experimental data is consistent with a critical flaw size in the fabricated devices, a, that is related to the fracture toughness Klc by Klc/a1/2=4600 MPa.