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AVS2001 Session SE-MoP: Poster Session

Monday, October 29, 2001 5:30 PM in Room 134/135

Monday Afternoon

Time Period MoP Sessions | Topic SE Sessions | Time Periods | Topics | AVS2001 Schedule

SE-MoP-1 Developments in Ammonium-based Solution with Inhibitors and Ionic Carboxylic Acids on Post Cu CMP Cleaning for Removal Colloidal Silica Abrasives S.-Y. Chiu, T.-C. Wang, Y.-L. Wang (National Chiao Tung University, Taiwan, R.O.C.); M.-S. Tasi (National Nano Device Laboratories, Taiwan, R.O.C.); M.-S. Feng (National Chiao Tung University, Taiwan, R.O.C.) During the Cu CMP process with colloidal silica based slurry, colloidal slica abrasives would be selectively adsorbed onto copper line. These particle defects will influence the yields of the folloing thin deposition and lithography process. In this study, an approache are proposed to overcome the corrosion problem of copper line and to remove chemisorbed colloidal silica from polished copper surface. The clean solution would be formulated by adding ionic carboxylic acids into ammonium-based solution with inhibitors. We also elucidated the influence of electrostatic interaction between colloidal silica abrasives, copper and silicon dioxide films. Electrochemical polarizatio, zeta potetial, contact angle, AFM, SEM, surface scan, KLA defect mapping, and electro-property analyses are being evaluated for monitoring silicon dioxide (the polish stop layer) and copper films during post Cu CMP cleaning process. By means of these analytical methods, an suitable post Cu CMP cleaning chemistry in alkaline ammonium-based solution with inhibitor and carboxylic acids was developed to effectively remove colloidal abrasives left on the wafer, meanwhile not to cause copper wires corrosion.
SE-MoP-2 Mechanical Properties of Polymer-carbon Nanotube Composite C. Wei, K. Cho (Stanford University); D. Srivastava (NASA Ames Research Center) Recently carbon nanotubes are considered as nanoscale fibers which can strengthen polymer composite materials. Nanotube-polymer composite materials can be used for micron scale devices with designed mechanical properties and smart polymer coating to protect materials under extreme physical conditions. To explore these possibilities it is important to develop a detailed atomic scale understanding of the mechanical coupling between polymer matrix and embedded nanotubes. In this work we study the mechanical properties of polymer-carbon nanotubes (CNT) composite using molecular dynamics (MD). We will discuss the contribution of Van der Waals potential to the load transfer from matrix to nanotube. Our MD simulations show that polymer can chemically bonded to CNT. We will discuss about the resulting mechanical coupling between the CNTs and polymer matrix to develop an efficient nano-composite materials.
SE-MoP-4 Effect of Pre and Post Surface Modification on Copper (II) Fluoride Formation in the Cu/PTFE System J. Torres, C.C. Perry, S.R. Carlo, D.H. Fairbrother (Johns Hopkins University) Fluoropolymers are attractive materials for devices in the microelectronics industry because of their desirable physical, chemical, and dielectric properties. Copper is best suited for interconnect wiring because of its low resistivity and electro-migration; unfortunately, its adhesion to fluoropolymers is generally poor. In this study we present results of the effect of Ar⁺ and X-ray pre and post treatment of PTFE surface in terms of CuF₂ formation. There seems to be correlation between adhesion and chemical reactivity with the surface, thus, any pre or post processes that initiate the formation of Cu-F bonds will enhance adhesion. Although there are studies in the literature that characterize the Cu/PTFE interface, few studies have concentrated specifically on pre- and post surface modification with respect to compound formation. Copper thermally evaporated on unmodified PTFE is chemically inert, forming a metallic overlayer; no Cu-F bond formation in either the F(1s) or C(2p) XPS regions was observed. Pretreatment of PTFE with either Ar⁺ or X-ray irradiation was found to be ineffective in activating the surface towards Cu-F bond formation during physical vapor deposition of Cu. In contrast, post-surface modification of the Cu/PTFE interface with either Ar⁺ or X-ray irradiation resulted in the production of CuF₂. The extent of CuF₂ production was found to be similar for both Ar⁺ and X-ray irradiation post-treatment strategies for comparable initial Cu coverages, suggesting a common reaction mechanism for the formation of CuF₂. AFM images of virgin PTFE show an amorphous surface, composed of globular features, while after Ar⁺ treatment the surface becomes fibrous. When Cu is deposited on PTFE the surfaces appearance is smooth as a result of the metallic overlayer.
SE-MoP-6 Adhesion Enhancement of Thin Film Metals onto Polyimide Substrates by Bias Sputtering S.Y. Kim, J.S. Kang, Y.H. Kim (Hanyang University, Korea) The adhesion of thin film metals deposited by bias sputtering has been studied. Al, Cr, Ta, and Ti thin films have been deposited onto polyimide substrates using DC magnetron sputter. RF bias of 0 ~ 400 watt was applied to the substrate during DC sputtering. The adhesion was evaluated using a 90 degree peel test. The peel adhesion strength was low when the RF bias was not applied during sputtering. However, it increased with RF bias power in all specimens. Scanning electron microscopy and Auger depth profile indicated that polyimide cohesive failure occurred during peeling and heavy deformation was observed in the metal films peeled from polyimide substrates when RF bias was applied during deposition. Cross-sectional transmission electron microscopy showed the thin implanted layer of metals in the polyimide interface. The implantation layer was likely formed due to the RF bias to the substrate. This implantation effect can explain the adhesion enhancement by bias sputtering.
SE-MoP-7 Oxidation Properties of Zn and Ni-Zn co-deposited with Nanometer Diamond Powder W.-H. Lee (National Taipei University of Technology, Taiwan, ROC) The co-deposition of nickel and zinc with or without reinforcement of nanometer diamond powder were successfully manufactured by the method of electro-plating process on the carbon steel substrate. The variables investigated within this research work include the additions of ZnCl2, anode current density (ACD) and cathode current density (CCD), PH value, plating temperature, and the concentration of nanodiamond powder in nickel sulphamate plating solution. It revealed that g (Zn21Ni5) phase could be plated on the specimen surface with the thickness of 30 ¢Ggm for 1 hour plating time. The diamond powder used in this research work had an average size of 25 nm and concentration of 2 g/l to 20 g/l in the solution. After experiments, the corrosion resistance of these co-deposited plating layers was tested by the salt spray (fog) testing procedure for 0.5 to 30 days. It was found that the pure Ni-Zn alloy without co-deposited with nanometer diamond powder exhibited three times of corrosion resistance than that of with reinforcement of nanodiamond powder. The structure, surface morphology and the cross section of plating layers were examined by the x-ray, SEM, and optical microscope. The distribution of chemical compositions of plating layers was analyzed by the energy despersive analyzer of x-ray (EDAX) as well.
SE-MoP-8 The Effect of Cooling Conditions on Plasma-Carbonitrided Iron Surfaces L.C. Gontijo, R. Machado, E.J. Miola (Universidade Federal de Sao Carlos, Brazil); L.C. Casteletti (Universidade de Sao Paulo, Brazil); P.A.P. Nascente (Universidade Federal de Sao Carlos, Brazil) Plasma- carbonitriding has been used to improve the tribological and mechanical properties of materials, specially iron-based alloys. In this work, the Pulsed Glow Discharge (PGD) technique was employed for carbonitriding pure iron. This method is more economical than others because it provides for faster nitrogen and carbon diffusion, which in turn allows for lower processing temperatures and shorter treatment times with satisfactory results. Three sample sets were carbonitrided in a gas mixture of 2 vol. % CH₄, 20 vol. % N₂, 78 vol. % H₂, under a pressure of 400 Pa, discharge frequency of 9 kHz, temperature of 580 °C, during 90 minutes. The first sample set was cooled under vacuum, the second set, under air, and the third set was quickly removed from the furnace and then quenched in oil. The three sample sets were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). For the samples cooled under vacuum, the diffusion zone comprised of enlongated needle-like precipitates and shorter ones, which were identified as γ'-Fe₄N and α"-Fe₁₆N₂, respectively. The same phases were also observed in the diffusion zone of the samples cooled under air. However, these phases were not detected in the samples quenched in oil. The compound layer for the three sample sets consisted of γ'-Fe₄N and ε-Fe_x(N,C). An austenite (γ) transformed zone was detected in between the compound layer and the diffusion zone.
SE-MoP-9 The Temperature Effects on Surface Energy of PVD Coatings S.M. Chiu, T.P. Cho, C.W. Chu (Metal Industries R&D Centre, Taiwan, ROC); Y.-C. Chen (Shu-Te University, Taiwan, ROC) There are serious sticking and wear problems in the molds surface during the IC packaging and die casting processes while the operation temperature ranges from 150°C to 800°C.Some surface treatment are performed on high speed steel for comparing the surface energy properties in different temperature and atmosphere condition.The surface energy properties was studied by the contact angle measurement.The surface treatments include electroplated hard Cr,PVD Cr-based and DLC coatings. The films microstructure is examinated by atomic force microscopy,SEM and X-ray defraction .The control of the surface morphology and phase structure of the coatings is most important to obtain low surface energy properties.
SE-MoP-10 Effect of Heat Treatment on the Oxidation and Properties of Ion-Plated ZrN Thin Film on 304 Stainless Steel W.-J. Chou, G.-P. Yu, J.-H. Huang (National Tsing Hua University, ROC) It is a common practice to apply heat treatment processes for improving the structure and properties of thin films. One of the problems during heat treatment process is the contamination and oxidation of the thin film by the atmosphere in the furnace. To solve the problem, using a controlling atmosphere in the furnace, especially lowering down the oxygen partial pressure, is considered to be the most effective method. In this study, an oxygen meter was used to monitor the furnace atmosphere during the heat treatment process, and the oxygen partially pressure was controlled down to 10-15 atm. Zirconium nitride (ZrN) films deposited on 304 stainless steel, by a hollow cathode discharge ion-plating (HCD-IP) technique, was used as the specimen in heat treatment. The thickness and composition of the coated specimen were controlled to be 0.6 mm and N/Zr=1, respectively. The residual stress and preferred orientations of the ZrN films were determined using X-ray diffraction (XRD). Hardness of the films was measured by nanoindentation. Atomic force microscopy (AFM) was used to study the surface roughness of thin film. The extent of surface oxidation and composition of the ZrN film were determined using X-ray photoelectron spectrometry (XPS). The (111) texture coefficient increases with increasing treatment temperature. The hardness of the ZrN film was rapidly increased after heat treatment. The oxidation of the thin film was incapable avoided even in the gas atmosphere with an oxygen partially pressure lower than 10-15 atm.
SE-MoP-11 Deposition of Ti(C,N) and Zr(C,N) Thin Films by Plasma Assisted MOCVD and In-situ Plasma Diagnostics with Optical Emission Spectroscopy Y.K. Cho, J.S. Yoon, C.-H. Heo, J.G. Han, S.W. Lee, J.-H. Boo (Sungkyunkwan University, Korea) Ti(C,N), Zr(C,N) films are synthesized by pulsed D.C. plasma assisted metalorganic chemical vapor deposition (PA-MOCVD) using metal-organic compounds of tetrakis diethylamido titanium and tetrakis diethylamido zirconium at 200 °C to 300 °C. H₂ and He+H₂ gases are used as carrier gases to compare plasma parameter. The effect of N₂ and NH₃ gases as reactive gas is also evaluated in reduction of C content of the films. Radical formation and ionization behaviors in plasma are analyzed by optical emission spectroscopy (OES) at various pulsed bias and gases conditions. He and H₂ mixture as carrier gas is very effective in enhancing ionization of radicals, especially N₂ resulting is high hardness. However, NH₃ as reactive gas highly reduces formation of CN radical, there by decreasing C content of Ti(C,N) and Zr(C,N) films in a great deal. The hardness of film is obtained to be 1400 HK to 1700 HK depending on gas species used and bias voltage. Higher hardness can be obtained for H₂ and N₂ gas atmosphere and bias voltage of 600 V. Plasma surface cleaning using N₂ gas prior to deposition appear to increases adhesion of films on cold forming steel. The changes of plasma including radicals and film properties are illustrated in terms of carrier and reactive gases as well as pulsed power variation.
SE-MoP-12 A Study of Nitrided Layers of SAE 303 Stainless Steel using a Magnetized Plasma Process G.A. Lacerda, C. Otani, H.S. Maciel (Instituto Tecnologico de Aeronautica - ITA - Brazil); C. Alves Jr. (Universidade Federal do Rio Grande do Norte, Brazil) Iron nitride is an important material in metallurgy, especially as constituent of the so-called compound layers generated on the surface of workpieces made of steel and hardened by nitriding and carbonitriding. More recently the iron nitrides reappeared in the literature but now as thin films and as potencial candidates for magnetic recording heads or eventually recording media. Dealing with an investigation of this subject, a series of plasma nitriding experiments has been conducted on SAE 303 austenitic stainless steel samples, using an experimental system based on an ordinary dc glow discharge which was located between the magnetic poles of an electromagnet. In this system the sample is placed on the cathode and the magnetic field (B), which is uniform and perpendicular to the sample surface, can be varied from zero to 1440 Gauss. The nitriding processes were carried out under constant substrate temperature of 430 °C and gas pressure of 5.0 Torr, whereas different N₂-H₂ gas mixtures were used. The nitrided layers were characterized by micro-hardness testings, X-ray diffraction, conversion electron Mössbauer spectroscopy and scanning electron microscopy. The results showed a strong influence of the applied magnetic field upon the mechanical properties of the samples surface as consequence of different nitride phase growing. A decrease in the surface hardness with the increase of the magnetic field strengh was observed for all the conditions tested. For certain gas mixtures, as for example 50%N₂-50%H₂, a noticeable effect occurred, i.e., at low and high B field, in the range provided by the electromagnet, the prevalent structure of the nitrided layer is dominated by the Fe₃N, but it changes to Fe₄N based structure for B field in the middle range of (260-770) Gauss.
SE-MoP-14 Microscopic Polishing of Cu Thin Films using Atomic Force Microscopy K.M. Fishbeck, M.D. Arthur, J.S. McDonald, K.L. Muessig, D.C. Koeck, H.C. Galloway (Southwest Texas State University); M.-S. Lim, S.S. Perry (University of Houston) Chemical Mechanical Planarization of microelectronic wafers in multiple stages of fabrication is an important process in creating efficient multilayer devices in the modern semiconductor industry. The CMP process uses a rotating pad to apply pressure to a wafer surface exposed to a polishing slurry composed of both a corrosive solution and suspended abrasive particles. In order to study the fundamental mechanisms of CMP, an Atomic Force Microscope is used in conjunction with a liquid cell to simulate the CMP process. Copper thin films grown on Si wafers are exposed to chemicals of variable composition in the liquid cell, with the force of the AFM tip itself providing the mechanical component of the CMP process. A sputtering process is used to coat the AFM cantilever tips with a thin film of alumina to more closely model a single abrasive particle in a CMP slurry. The solutions used in the liquid cell are of varied concentrations and consist of both a corrosive agent(HNO₃ or NH₄OH) and a suitable corrosion inhibitor. The materials used for both the samples and the tip coating were chosen for their relevance to current microelectronic fabrication applications, as were the solution components used in the liquid cell. In this way it is possible to study the localized effects of CMP on the exposed samples as a functions of force, solution chemistry, and exposure time. In situ AFM imaging at varying time intervals allows analysis of both material removal processes and surface topography changes.

Time Period MoP Sessions | Topic SE Sessions | Time Periods | Topics | AVS2001 Schedule