bluuebunny/crossref_metadata_2025 huggingface dataset:
Low Temperature Formation of C54 TiSi2 Bypassing the C49 Phase: Effect of Si Crystallinity, Metallic Impurities and Applications TO 0.10 μm CMOS
Authors: Kittl J. A. , Gribelyuk M. A , Samavedam S. B. , Hong Q. Z. , Yu N. , Rodder M.
Published: April 2011

The mechanism and evolution from the early stages of the Ti/Si reaction by rapid thermal processing (RTP) at 650°C in the presence of Mo doping was studied and compared to the case without Mo doping; for amorphous, polycrystalline and single crystal (100) Si substrates. It was found that for Mo doped polycrystalline Si or Mo doped amorphous Si, the low resitivity C54 TiSi2 phase nucleates at the Ti/Si interface and grows following diffusion limited kinetics, bypassing the nucleation of the high resistivity C49 TiSi2 phase. The conventional phase sequence, with C49 TiSi 2 nucleation and growth, was observed on Mo doped (100) Si and all samples without Mo. The mechanism of early C54 nucleation was identified by high resolution transmission electron microscopy (HRTEM): at early stages of the reaction, precursor silicide phases lattice matched to C54 TiSi2 nucleate at the Ti/Mo doped Si interface, and act as templates for epitaxial nucleation of C54 TiSi2. Two such phases were observed, MoSi2 and a phase with spacings of 2.26 Å and 4.2 Å. Image simulations suggest that the structure of the second template phase is based on Mo5Si3. Similar kinetics were observed on large structures and narrow lines for Mo doped Si (except for the case of (100) Si), indicating that this growth mechanism eliminates the linewidth dependence. Implementation on a 0.10 μm CMOS technology of a process combining Mo doping with pre-amorphization (PAI) achieves low source/drain (S/D) sheet resistance, and the first Ti salicide process with low gate sheet resistance down to 0.06 μm.
Mechanism of Narrow Line Effect in TiSi2 films on highly As-Doped Diffusion Layers
Authors: Ishida Koichi , Wakabayashi Hitoshi , Mogami Tohru
Published: April 2011

The mechanism of the narrow line effect in TiSi2, films on highly As-doped diffusion layers is studied by TEM observation of grains in the TiSi2. The narrow line effect is shown to be due to an enlargement of the TiSi2, grain size caused by regrowth of the pre-amorphized regions before the start of silicidation. Knocked-on oxygen from the SiO2 cover layers is found to delay the onset of the silicidation.
The Control and Impact of Processing Ambient During RTP
Authors: Maex Karen , Kondoh Eiichi , Lauwers Anne , DePotter Muriel , Prost Joris
Published: April 2011

The introduction of rapid thermal processing for silicide formation has triggered a lot of research to temperature uniformity and reproducibility in RTP systems. From the other side there has been the demand to make the process itself as robust as possible for temperature variations. Indeed the way the module is set up can open or close the thermal process window for silicidation. In addition to the temperature, the ambient control is to be taken into account. Although gasses are specified to a low level of contaminants, the RTP step needs to be optimized for optimal contaminant reduction. Besides, the process wafer itself can be a source of contamination. In this paper an overview will be given of the role of temperature and ambient during RTP on the silicidation processes. The effect of the wafer on ambient purity will be highlighted. It will be shown that the latter can also have an impact on other process steps in the interconnect technology.
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

As 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

Atomic 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

The 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

Recently 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

We 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

As 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

The 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

Pd/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

Epitaxial 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

Integration 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

Advanced 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.
Materials and Devices for Silicon On-Chip Optical Interconnect
Authors: Ballantyne J. M.
Published: April 2011

We review progress on growth of direct-bandgap GaInP/GaP and other materials for light emitters monolithic on silicon, and discuss design, fabrication, process compatibility, and performance issues for optical emitters and detectors made in these materials.
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

Texture 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

We 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

A 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

The 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

To 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

The 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

The 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

The 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.
Channel Cracking Technique for Toughness Measurement of Brittle Dielectric Thin Films on Silicon Substrates
Authors: Ma Qing , Xie Joseph , Chao Sam , El-Mansy Safaa , Mcfadden Robert , Fujimoto Harry
Published: April 2011

A technique for the measurement of brittle thin film toughness has been developed. It is based on the mechanics of channel cracking in thin films. Dielectric films including CVD silicon oxide and silicon nitride films were studied using this technique. To prevent channel cracks from propagating into silicon substrates, an aluminum layer was deposited prior to the deposition of the dielectric layer. By using a specially made bending fixture, the cracks were observed in situ when the samples were subject to well controlled stresses. It was observed that for each film, a well defined critical film stress level existed, beyond which the crack velocity accelerated very rapidly. The critical film stresses were obtained by superposition of the critical applied stresses and the residual stresses in the films due to deposition and thermal expansion mismatch. It was shown that this technique was highly consistent in critical stress measurement. A simple shear-lag model was used to obtain the film toughness values using the measured critical film stress data.
The Reliability Assessment of Flip Chip Type Solder Joints Based on the Damage Integral Approach
Authors: Su Peng , Zhou Chen , Rzepka Sven , Korhonen Matt , Li Che-Yu
Published: April 2011

Thermal fatigue of flip-chip solder joints between a chip and chip carrier is a serious reliability concern. Differences in the temperature and/or in the coefficients of thermal expansion between the chip and substrate lead to stresses which may result in fatigue damage and eventual failure of the interconnect. Conventionally, the solder lives have been estimated by a Coffin-Manson type relation. However, this largely empirical approach becomes inadequate when comparing thermal histories that are widely different, as in the cases of accelerated thermal cycling and power cycling. In this study, we use a damage integral approach where the fatigue damage rate is calculated based on the momentary stress and strain (estimated analytically) experienced by the solder joints. The momentary damage is then integrated over the entire loading history to yield total damage at any moment.
Tensile Testing of Ultra-Thin-Film Materials Deposited on Polyimide for Mems Applications
Authors: Tregilgas J.H. , Strumpell M.
Published: April 2011

A newly developed approach to thin-film tensile testing has been utilized for evaluating ultra-thin-films of about 60-100 nm in thickness. Thin sputtered metal films deposited on 3.5 gm thick polyimide film substrates were tested using a Mesotronix nanotensiometer. Modifications to sample handling and zero strain calibration helped to improve testing reproducibility. The response of a thin-film metal was determined by subtracting the response of the polyimide carrier film from that of the metal-on-polyimide composite. Stress-strain curves for two amorphous alloys sputtered from Al-25 at% Ti and Nb-25 at% Al targets exhibited well-defined elastic regions followed by brittle behavior. The ultimate tensile strengths (UTS) were about 1200 MPa for the Al-Ti and 1700 MPa for the Nb-Al, both of which occurred near the elastic strain limit of about 2%. After recrystallization at 280°C for an hour, the Al-Ti film showed what appears to be an upper and lower yield point, in addition to strain hardening. Initial yielding occurred at a strain of about 1.2% and a stress of about 800 MPa, while the UTS of about 1000-1060 MPa occurs at strains as high as 9%. Stress relaxation measurements performed on both the amorphous and the recrystallized films showed lower values of stress relaxation at 1% strain compared to low alloy polycrystalline Al films.
Measurement of Elastic Modulus and Poisson's Ratio of Diamond–Like Carbon Films
Authors: Cho Sung-Jin , Lee Kwang-Ryeol , Eun Kwang Yong , Ko Dae-Hong
Published: April 2011

Elastic modulus and Poisson's ratio of diamond-like carbon (DLC) film was measured by a simple method using DLC bridges which are free from mechanical constraint of substrate. The DLC films were deposited on Si wafer by C6H6r.f. glow discharge at the deposition pressure 1.33 Pa. Because of the high residual compressive stress of the film, the bridge exhibited a sinusoidal displacement by removing the constraint of the substrate. By measuring the amplitude with known bridge length, we could determine the strain of the film required to adhere to the substrate. Combined with independent stress measurement by laser reflection method, this method allows calculation of the biaxial elastic modulus, E/(1–v), where E is the elastic modulus and v Poisson's ratio of the DLC film. By comparing the biaxial elastic modulus with plane-strain modulus, E/(1–v2), measured by nano-indentation, we could further determine the elastic modulus and Poisson's ratio, independently. The elastic modulus, E, increased from 87 to 133 GPa as the negative bias voltage increased from 400 to 550 V. Poisson's ratio was estimated to be about 0.20 in this bias voltage range. For the negative bias voltages less than 400 V, however, the present method resulted in negative Poisson's ratio which is physically impossible. The limitation of the present method was also discussed.
Residual Stress of Silicon Films Deposited by Lpcvd From Silane
Authors: Temple-Boyer P. , Imbernon E. , Rousset B. , Scheid E.
Published: April 2011

In this paper, amorphous, semi-crystalline and polycrystalline silicon films have been deposited by low pressure chemical vapour deposition (LPCVD) from silane SiH4 by ranging the deposition temperature from 555 to 635°C and the total pressure from 100 to 300 millitorrs. Films residual stresses have been determined thanks to the formula of Stoney by measurements of the wafer curvature before and after removal of the back side deposition. The influences of the different deposition parameters are reported and major stress variations are evidenced. By studying the effects of a 600°C crystallisation anneal and by comparing them to those observed for amorphous silicon films deposited from disilane Si2H6, compressive and tensile stresses are respectively related to “surface” and “volume” crystallisation phenomena. The different stress values of amorphous and polycrystalline silicon have been estimated and, according to these results, solutions are finally proposed in order to have a real control of residual stress into silicon depositions and to obtain low stress (σ ≈ 0) polysilicon films.
Silicon-Based Epitaxial Films for Mems
Authors: Fitzgerald E.A. , Wu K.C. , Currie M. , Gerrish N. , Bruce D. , Borenstein J.
Published: April 2011

The objective of this work was to develop an improved wet etch-stop technology for silicon micromachining. To establish a reference for process improvement, the diffusion process currently used to fabricate p++ Si:B etch stops was comprehensively investigated. Subsequently, a novel germanium- based epitaxial etch-stop technology was developed.

A range of techniques were used to study p++ silicon layers created by boron diffusion into (001) silicon wafers. The results revealed gradients in boron and lattice constant, as well as a graded three- dimensional dislocation array from lattice-mismatch stress. The gradients in boron concentration and dislocation density can lead to curl in micromachined structures. Although annealing steps can remove the boron gradient, a flat membrane will be a tenuous balance.

Epitaxial films of p++Si:B and strain-compensated p++Si1-xGex:B can remove composition gradients and improve process control. However, it is undesirable to depend on p-type layers doped at levels near the solubility limit to prevent etching. We have therefore developed a unique etch stop created from relaxed SiGe alloys. Etch-stop behavior quite similar to heavily boron-doped silicon has been demonstrated in undoped silicon-germanium. Neither strain nor defects are responsible for the etch-stop behavior. A model is proposed based on energy band structure and a SiOx passivation mechanism.
Curvature of A Cantilever Beam Subjected to An Equi-Biaxial Bending Moment
Authors: Krulevitch P. , Johnson G.C.
Published: April 2011

Results from a finite element analysis of a cantilever beam subjected to an equi-biaxial bending moment demonstrate that the biaxial modulus E/(1-v) must be used even for narrow beams.
Formation of Continuous Cubic Mesoporous Films by Spin Casting
Authors: Honma I. , Zhou H.S. , Kundu D.
Published: April 2011

The simple spin casting technique has been successfully used for producing mesoporous thin films on glass substrate. The films are found to be homogeneous and continuous in a large size scale, however, the mesostructural phase of the film has been controlled systematically among amorphous (A), one-dimensional hexagonal (1-dH), cubic (C) and Lamellae (L) by increasing surfactant to TEOS concentration ratio in the casting solution. The 1-dH as well as cubic structure is thermally stable after the calcination so that a mesoporous thin film is obtained by surfactant removal. The solution additives of 1-propanol and 2-butanol might play a roll in the direct formation of the primitive cubic phase in the film form which has never been obtained.
Polyhedral Oligomeric Silsesquioxanes (Poss): Silicon Based Monomers and their Use in the Preparation of Hybrid Polyurethanes
Authors: Schwab Joseph J. , Lichtenhan Joseph D , Chaffee Kevin P. , Mather Patrick T , Romo-Uribe Angel
Published: April 2011

A series of Polyhedral Oligomeric Silsesquioxane (POSS) monomers bearing reactive hydroxyl functionalities, suitable for incorporation into step-growth polymers, is described. These monomers are difunctional in nature and are particularly well suited for use as chain extenders in the synthesis of polyurethanes. This work describes the synthesis of these POSS monomers and their incorporation into a series of polyurethanes. Preliminary thermal, mechanical and rheological data for the POSS containing polyurethanes will also be discussed.
Hybrid Organic-Inorganic Electrode-Membranes Based on Organo-Polysiloxane/Macrocycle Systems
Authors: Jiménez-Morales A. , Galvan J.C. , Aránda P. , Ruiz-Hitzky E.
Published: April 2011

Specific complexing agents for alkaline ions such as some crown-ethers of different intramolecular cavity size (12-crown-4, 15-crown-5 and 18-crown-6) are incorporated into a organo-polyorganosiloxane network generated via the sol-gel process. The resulting xerogels embody macrocycle compounds with different ion-selectivity. These xerogels are deposited onto porous supports (borosilicate, polyacrylonitrile,…) to obtain new composite electrode- membranes. The electrochemical characterization of the membranes and the electrode- membranes by electrochemical impedance spectroscopy (EIS) shows information about the reversible behavior and the ion resistance of the membranes, which are a function of both, nature and content of the entrapped macrocycle as well as the salt solution concentration. The electrochemical response of these systems acting as electrode-membranes shows their sensitivity towards different metal ions at variable concentrations.
New Inorganic-Organic Hybrid Polymers for Integrated Optics
Authors: Roscher Christof , Buestrich Ralf , Dannberg Peter , Rösch Oliver , Popall Michael
Published: April 2011

New fluorinated inorganic-organic hybrid polymers (ORMOCER*s) for integrated optics were synthesized via hydrolysis and condensation (sol-gel processing) of functionalized pentafluorophenylalkoxysi lanes followed by organic crosslinking reactions. Process parameters (catalyst, temperature and ratio of educts) were optimized to achieve low transmission losses at the most important wavelengths for telecommunication in the NIR range: 1310 nm and 1550 nm.

The result is a photopatternable transparent ORMOCER (negative resist behavior) with excellent low losses: 0.20 dB/cm at 1310 nm and 0.30 dB/cm at 1550 nm.

Besides their high transparency the fluorinated ORMOCERs show a variety of other properties enabling their use as waveguide materials within the production of optoelectronic devices and related thin film technology: good wetting and adhesion on various substrates (e.g. glass, silicon and several polymers), low processing temperatures (postbake below 160 °C), high thermal stability (decomposition > 250°C) and a tunable refractive index.
Aqueous Sol-Gel Derived Nanocomposite Coating Materials
Authors: Schmidt H.K. , Arpac E. , Schirra H. , Sepeur S. , Jonschker G. , Claflin B. , Lucovsky G. , Claflin B. , Lucovsky G. , Claflin B. , Lucovsky G.
Published: April 2011

Sol-gel reactions, in general, have to take place in organic solvents in order to control the hydrolysis and condensation reaction. This leads to drawbacks in applications, since the organic solvent vapor concentration has to be controlled for example in coating applications for environmental, health or security reasons. For this reason, a reaction route has been developed to produce coating precursors stable against water as solvent. To achieve this, conventional electrostatically stabilized sols obtained either by hydrolysis and condensation or commercially available sols (e.g. SiO2sols) have been surface-modified to reduce the particle-to-particle interaction and electrosterically stabilized precursors compatible to water have been obtained. By use of alkoxy silanes as surface modifiers, water-dispersable nanoparticulate liquid coating systems have been prepared, for example, with boehmite, SiO2 or TiO2 as nanoparticles to be crosslinked after coating thermally by inorganic condensation and organic condensation or polymerization reactions. Thus, aqueous sol-gel coating systems have been prepared with EtOH contents below 5 %. In the paper, the basic reaction as well as material properties will be discussed.
Sheet and Tube Organosilicon Polymers
Authors: Katsoulist D. E. , Chaot T. C.-S. , McQuistont E. A. , Chen Chenggang , Kenney Malcolm E. , Claflin B. , Lucovsky G. , Claflin B. , Lucovsky G.
Published: April 2011

Reaction of chlorosilanes with sheet silicates, such as the naturally occurring apophyllite, [Ca4Si8O2O(F, OH).8H2O] results in the formation of sheet organofunctional siloxane polymers. Similarly, reaction of chlorosilanes with the tube silicate K2CuSi4O10results in the formation of tube organofunctional siloxane polymers. Representative polymers have been characterized by XRD, KR, XPS and solid state 29Si NMR. The interlayer spacing of the sheet polymers varies with the type of the group pendent on the sheet. When the organofunctional pendent groups of the sheet polymers contain reactive sites, further reactivity can be demonstrated with heterogeneous reactions such as hydrosilation. The sheet polymers behave as very effective thickeners of siloxane fluids. Dispersions of them in siloxane fluids exhibit thixotropic properties. The organosilicon polymers have the potential to show useful chemical, thermal, rheological and mechanical properties
Synthesis and Structural Characterization of Organically-Modified Microporous Silicates
Authors: Babonneau F. , Leite L. , Fonlupt S. , Ribot F. , Bergogne L. , Roux C.
Published: April 2011

Organically-modified silicates have been synthesized from RSi(OEt)3 (R = CH3, C2H5, C8H17, CH2=CH, C6H5) and TEOS under acidic conditions, in the presence of cethyltrimethylammonium (CTAB). The introduction of RSiO1.5 units with R/Si =0.2, affects the ordering of the expected hexagonal silicate phase, except when R = C6H5. The sample containing phenyl functions was thus submitted to surfactant extraction; calcination at 350°C appears to be more efficient, and less disruptive for the network ordering than a washing procedure in ethanol. Nitrogen adsorption measurements on the hexagonally ordered calcined sample that still contains phenyl groups, yields a type I isotherm, typical of a microporous solid. BET method leads to a surface area of 1000 m2/g and a pore volume of 0.32 cm3/g.
Catalytic Materials by Design from Hybrid Organic-Inorganics
Authors: Joël  , Moreau J.E. , Man Michel Wong Chi
Published: April 2011

The sol-gel processing of appropriated molecular precursors easily leads to a variety of hybrid organic-inorganic materials with intrinsic properties. This approach is increasingly becoming an interesting way to prepare heterogeneous catalysts. The paper will focus on the use of hybrids for the preparation of selective catalytic materials. Two examples of the use of hybrid polysilsesquioxanes polymers will be given. i) The tailoring of the pore structure of silicas, under mild reaction conditions, based on the temporary introduction of different organic substructures in the hybrid network of polysilsesquioxane gels will be discussed. ii) Also the preparation of new chiral hybrid supports for enantioselective catalysis will be presented.
Characterization and Reactivity of Hybrid Organosilicate Mesoporous Sieves
Authors: Lim M. , Stein A.
Published: April 2011

Vinyl-MCM-41 has been synthesized by a direct synthesis from the corresponding organosiloxane precursors. The location of vinyl groups on the internal channel surfaces of the mesoporous silicate sieves was confirmed by small angle neutron scattering (SANS) experiments using contrast matching techniques. To investigate further modification of the vinyl groups, bromination reactions were carried out on vinyl-MCM-41 samples in dichloromethane, carbon tetrachloride, and in a gas-phase reaction. With dichloromethane as a solvent, the bromination rate increased with increasing pore diameter. A strong dependence of the reaction rate on the presence and type of solvent molecules was observed. While gas-phase bromination was complete within 40 minutes, the reaction required several days for completion in dichloromethane and was even slower in the nonpolar solvent, carbon tetrachloride.
New Techniques for the Nanostructural Characterization of Semiconductor Materials and Devices Using Combined Focused Ion Beam and Transmission Electron Microscopy Techniques
Authors: Hull R. , Dunn D.
Published: April 2011

We describe novel techniques which extend the range of available nanostructural characterization capability for semiconductor materials and devices. These techniques combine high spatial resolution imaging and spectroscopy using transmission electron microscopy (TEM) and focused ion beam (FIB) microscopy. Specific capabilities described include nanoscale imaging of dopant distributions, ultra-high resolution secondary ion mass spectroscopy (SIMS) and tomographic image reconstruction.
The Challenge and Methods of TEM Cross-Sectioning of < 0.25 Micron Plugs
Authors: Hunt C. Amy , Zhang Yuhong , Su David
Published: April 2011

Transmission electron microscopy (TEM) is a useful tool in process evaluation and failure analysis for semiconductor industries. A common focus of semiconductor TEM analyses is metalization vias (plugs) and it is often desirable to cross-section through a particular one. If the cross-sectional plane deviates away from the center of the plug, then the thin adhesion layer around the plug will be blurred by surrounding materials such as the inter-layer dielectric and the plug material. The importance of these constraints, along with the difficulty of precision sample preparation, has risen sharply as feature sizes have fallen to 0.25 μm and below. The suitability of common sample preparation techniques for these samples is evaluated.
Probing Stress State and Phase Content in Ultra-Thin Ta Films
Authors: Whitacre J. F. , Rek Z. U. , Yalisove S. M. , Bilello J. C.
Published: April 2011

Ta films 25Å to 200Å in thickness were sputter-deposited using different sputter gas (Ar) pressures and cathode power settings. The average in-plane stresses were determined using double crystal diffraction topography (DCDT). X-ray analysis (using the grazing incidence x-ray scattering (GIXS) geometry) was performed using a synchrotron light source. To study microstructure and phase content, transmission electron microscopy (TEM) and transmission electron diffraction (TED) were used. Well resolved x-ray patterns were collected for all of the films. The DCDT stress data was found to be consistent with stress effects evident in the GIXS data. In general, residual stress state was not strongly dependent upon Ar pressure. The strongest evidence of amorphous content was found in both x-ray and TED data taken from 25Å thick films deposited using 2mTorr Ar pressure and 460 W cathode power. These results show that it is possible to create and study ultra-thin Ta films which posses a range of residual stresses and phase compositions.
Application of Synchrotron X-Ray Fluorescence Microscopy to the Study of Multi-Metal Oxide Ceramics
Authors: Perry Dale L. , McHugo Scott , Thompson Albert C. , Farmer Joseph C. , Ebbinghaus Bart B. , Konynenburg Richard Van , Brummond William A. , Armentrout Guy , Gould Thomas H. , Yang Nancy
Published: April 2011

Synchrotron x-ray fluorescence microscopy has been used to study multi-metal oxide ceramics that have been designed to sequester radioactive actinide elements for long-term storage and disposal. X-ray fluorescent lines for the various elements have been used for lateral elemental mapping of the materials, and the heterogeneity of the samples is discussed with respect to the elements in the crystallographic phases that have previously been documented by other means of structural and chemical analyses.