Papers

ICMCTF2002 Session F5-2: Characterization of Thin Film Growth Mechanism and Evolving Film Properties

Thursday, April 25, 2002 1:30 PM in Room San Diego

Thursday Afternoon

Start	Invited?	Item
1:30 PM		F5-2-1 Deposition and Characterization of Freestanding NiTi Films D. Marton (University of Texas Health Science Center at San Antonio and Advanced Bio Prosthetic Surfaces Ltd.); C.T. Boyle, C.E. Banas (Advanced Bio Prosthetic Surfaces Ltd.); E. Sprague, S. Bailey, J.C. Palmaz (University of Texas Health Science Center at San Antonio) Thick (>2 μm) tubular metal films for medical device applications have been deposited using Ar plasma sputtering. The sputtering tool is essentially a high vacuum system equipped with a hollow cathode magnetron. The sputtering target is formed from a NiTi alloy sheet. The deposition rate is 0.2-1 μm/min. The NiTi films that were deposited using this equipment have been tested for chemical, structural, surface, thermal, and thermomechanical properties. The internal structure of the films is crystalline. The surface topography of the internal surface follows the shape of the substrate. The topography of the outside surface reflects the crystal growth. Both surfaces have been analyzed using SIMS and XPS and found to be covered by a titanium oxide layer. WDS and thermal analysis reveals that the film composition is quite uniform. The films exhibit strong shape memory effect. Thermomechanical analysis reveals that the film strength is similar to the strength of wrought NiTi materials. The conclusion of this work is that it is possible to manufacture tubular NiTi films that promise usefulness for the medical device industry.
1:50 PM		F5-2-2 Structure and Mechanical Properties of Co-deposited TiAl Thin Films J Hampshire, P.J. Kelly (University of Salford, United Kingdom); D.G. Teer (Teer Coatings Ltd., United Kingdom) Titanium-aluminium compounds are very attractive materials for aerospace and high performance engine applications owing to their low density, high temperature strength and high specific strength. Specific compositions may also be suitable as solar absorber surfaces. Consequently, a detailed investigation of the titanium-aluminium binary alloy coating system is being carried out. Coatings have been deposited from pure titanium and aluminium cathodes, via the closed field unbalanced magnetron sputter technique. Two different magnetron co-sputtering techniques were used: codeposition, giving a gradient in coating composition across the surface of the substrates; and multi-layer deposition, giving fine multi-layers of different thickness. A range of compositions from 0 to 100% titanium were deposited. The coatings were studied in the as-deposited condition and after successive annealing treatments in order to obtain stable inter-metallic phases. Changes in structure and phase composition were studied by SEM and XRD after each annealing process. Mechanical analysis was also conducted, consisting of hardness and friction and wear testing. This paper concentrates mainly on the multi-layer deposited films and the results obtained to date are presented here.
2:10 PM		F5-2-3 Characterization of Hot Wall Epitaxy Grown 1-(2-Methoxy Benzyloxy)-8-Hydroxy-9,10-Anthraquinone Films Aman Mahajan, R.K. Bedi (Guru Nanak Dev Unversity, India); Unknown Pramila (Nanak Dev University, India); Subodh Kumar (Guru Nanak Dev Unversity, India) 1-(2-methoxy benzyloxy)-8-hydroxy-9,10-anthraquinone compound have been synthesized and its films are grown by hot wall epitaxy technique onto the glass substrates kept at different temperatures in a vacuum of 10 ^-5 Torr. The experimental conditions are optimized to obtain better crystallinity of the films. These films are characterized by nuclear magnetic resonance (NMR), optical absorption (IR, visible, near-UV), X-ray diffraction and scanning electron microscopy. Besides these, the electrical properties of the films are determined in the temperature range 293-393 K. The IR and NMR studies identify the formation of 1-(2-methoxy benzyloxy)-8-hydroxy-9,10-anthraquinone deposits on the glass substrates. A platelet type of crystallites as large as 3 µm are observed in the case of films deposited at 348K. Observations reveal that the current-voltage characteristics of films show ohmic behaviour of conduction within the investigated field and temperature range. The conduction appears to take place by thermally activated hopping mechanism. The electrical conductivity and carrier concentration of the films increase with the increase in substrate temperature, whereas the drift mobility decreases. Analysis of optical absorption measurements indicate that the interband transition energies of films lie in the range 2.70 -3.15 eV.
2:30 PM		F5-2-4 The Intrinsic Characteristics of Low-k Dielectric MSZ for Interconnect Applications T.C. Chang (National Sun Yat-Sen University, Taiwan, ROC); S.T. Yan (National Chiao Tung University, Taiwan, ROC); P.T. Liu (National Nano Device Laboratory, Taiwan, ROC); T.M. Tsai, S.M. Sze (National Chiao Tung University, Taiwan, ROC) In order to reduce the RC time delay of the multiple interconnections of integrated circuits, we performed the Cu/low-k research. Low-k dielectric MSZ (Organo-Silsesquiazane), provided by Clariant Corp., whose dielectric constant is about 2.5~2.6, is a kind of organic polymer and it has excellent chemical compatibility and adhesive capability. In this study, we investigated the intrinsic characteristics of MSZ. From FTIR analysis, Si-C and C-H bonds are found which can determine the quality of MSZ. In our study of thermal stability, the results show that MSZ is excellent. Material analyses such as FTIR and TDS are used to confirm the material composition. In electrical study, we performed different types of sweeping methods for the I-V measurement. Experimental results exhibited that the leakage current decreased dramatically with increasing sweeping times for either Cu or Al electrodes. It can be inferred that the electrons are firmly captured by the traps within the MSZ films when the sweeping times increased and thereby repelled the other electrons. Also, some upward and downward saw-toothed peaks in the I-V curve measurement were observed and they finally disappeared when the sweeping times were gradually increased. It can be deduced that the upward peaks are micro-weak points. As the conductive electrons pass through, local short circuit and drastic Joule heating lead to self-annealing of the weak points. In other words, MSZ films can resist the attack of electrons when we operate the ICs.
2:50 PM		F5-2-5 Grain Growth, Agglomeration and Interfacial Reaction of Copper Interconnects Ching-Yu Yang, J.S. Chen (National Cheng Kung University, Taiwan, ROC) Replacement of Al-based alloy with Cu for microelectronic interconnects is necessary to improve the operation speed of devices. However, the interconnects include not only Cu but also diffusion barriers to prevent the outdiffusion of Cu. In this work, Cu thin films (50nm and 200nm) are deposited on TaN (50nm) diffusion barrier, with or without a Ta (10nm) interlayer, by magnetron sputtering. Samples are subsequently annealed at various temperatures ranging from 400°C to 900°C in vacuum. X-ray diffraction, Auger electron spectroscopy, atomic force microscopy and scanning electron microscopy are employed to investigate the microstructural, morphological and compositional evolution of the samples during annealing. It is observed that as the annealing temperature increases, Cu films in the Cu/TaN structure exhibit grain growth, intergrain void formation, agglomeration and finally chemical reaction with the Si substrate (formation of Cu₃ Si). The grain size and degree of agglomeration depend on the initial thickness of Cu. Thin Cu films have smaller grains but agglomeration at lower temperature. However, the annealing temperature for forming Cu₃Si is 900°C, regardless the Cu film thickness . On the other hand, with the Ta interlayer, agglomeration of Cu is also observed but the matrix areas does not show intergrain voids. Although the Cu film is less agglomerated in the Cu/Ta/TaN structure, formation of Cu₃Si is observed after annealing at 800°C, which is 100°C lower than that of Cu/TaN structure. Correlations between the morphological/chemical changes and the configuration of the multiplayer stacks will be discussed.
3:10 PM		F5-2-6 Tribochemical Mechanisms of Copper CMP S.-Y. Chiu (National Chiao Tung University, Taiwan, ROC); Y.L. Wang (Taiwan Semiconductor Manufacturing Company, Taiwan, ROC); K.Y. Lo (National Chiyi University, Taiwan, ROC); Y.L. Wu (National Chi-Nan University, Taiwan, ROC) Chemical mechanical polishing (CMP) has been recognized as a viable technique for gobal planarization to delineate metal patterns for sub-micron integrated circuit processing. Under intensive investigation for ULSI, copper has emerged as an attrative, alternative choice for future interconnects applications. In the Cu CMP process, planarization is achieved by smoothing the uneven topography of nonplanar thin films by rotating and pressing its active surface against a rotating polymer-based pad filled with appropriate colloidal slurry. Abrasive particles in the slurry might be quite soft in a mechanical sense, so would offer relatively little material removal by themselves, but when mechanical effect of abrasive is combined with chemical effect of slurry chemistry, then the material removal can be quite substantial. In this study, we focus on the tribochemical mechanism results from the interaction of wear and corrosion of copper thin film in formulated slurries. The slurries used in the experiments are alumina, fumed silica and colloidal silica with various types of chemistry. The characteristics of these slurry chemistries have been inveastigated by electrochemical measurements and XPS to obtain a better fundamental understanding of the electrochemical reaction and the physical model of dynamic polished copper surface. The AFM morphology of polished Cu and the properties of the abrasive, such as phase, size, coagulation, physical shape, density and surface charge have also been carried out to build the tribochemical schemes of Cu CMP in various slurry chemistry, rspectively.
3:30 PM		F5-2-7 The Novel Pattern Method of Low-k Hybird-Organic-Siloxane-Polymer (HOSP) Film Using X-ray Exposure T.C. Chang (National Sun Yat-Sen University, Taiwan, ROC); T.M. Tsai (National Chiao Tung University, Taiwan, ROC); P.T. Liu (National Nano Device Laboratory, Taiwan, ROC); Y.S. Mor, C.W. Chen, T.Y. Tseng (National Chiao Tung University, Taiwan, ROC) The interconnect RC delay time increases and becomes a serious problem as device dimension shrinks under quarter micron. In order to suppress the increasing parasitic capacitance in interconnections, the low dielectric constant material is developed. An organic low-k material, Hybird-organic-siloxane-polymer (HOSP), with 2.6 dielectric constant is considered as one suitable IMD material for sub-quarter micron devices. In IC integration process, photoresist stripping with O₂ plasma and wet chemical stripper is inevitable step. Unfortunately, the PR stripping will degrade low-k dielectric properties. This makes low-k application limited. In order to avoid the integration issue, a novel pattern method with x-ray curing is provided. The dielectric regions illuminated by X-ray will be cross-linked and forms goal patterns. In contrast, the others without X-ray illumination will be dissolved by developer. There are several advantages for X-ray curing on low-k films as follows: 1.It does not need PR to define patterns; and thereby PR stripping can be eliminated. 2.It can avoid etching low-k dielectrics. 3.The process is simple. In this work, we will investigate the dielectric properties of X-ray cured HOSP film. Additionally, a single damascene structure will be fabricated to verify the process practicability.