ICMCTF2000 Session G8: Innovative Electrochemical Deposition ECD for Innovative Alternatives and Combined Layers
Monday, April 10, 2000 10:30 AM in Town & Country
G8-1 Fatigue Properties of a SAE 4340 Steel Coated with a Nimet HP Deposit
C. Guzmán, N. Díaz, A. Pertuz, J. Berríos, E.S. Puchi (Universidad Central de Venezuela)
The influence of a commercial electroless Ni-P (EN) deposit known as Nimet HP on the fatigue properties of a quenched and tempered SAE 4340 steel has been investigated. Standard tensile and fatigue samples of the substrate material were industrially coated with such a deposit of approximately 12% (wt) P and 10 ?m in thickness. Some of the coated samples were further post-heat treated at 450°C for 1 hour in an argon atmosphere. Such a treatment gave rise to a surface hardness of 1356±82 KHN @sub50@. The samples were subsequently tested under rotating bending conditions in order to determine both the fatigue strength and fatigue limit of the composite material. The fatigue fracture surfaces were analyzed by means of scanning electron microscopy (SEM) and EDS techniques in order to determine the crack initiation sites and to study the cracks propagation throughout the transverse section of the samples. It has been determined that the application of such a coating to the steel substrate gives rise to a reduction of its fatigue life. From the microscopic point of view it has been observed that the deposit applied remains well adhered to the substrate during fatigue testing. Interfacial cracks have been very rarely observed, possibly as a consequence of the good adhesion properties of the coating.
G8-2 Influence of a Commercial Electroless Ni-P Deposit on the Fatigue Properties of a notched and unnotched SAE 4340 Steel
E. Batoni, B. Lozada, A. Pertuz, E.S. Puchi (Universidad Central de Venezuela)
The present investigation has been conducted in order to study the fatigue properties of an AISI 4340 in the quenched and tempered condition, with and without the application of an electroless Ni-P (EN) deposit of approximately 12-14% (wt) P, when the substrate is in a notched and an unnotched condition. The fatigue properties were evaluated employing a number of 112 samples, according to the ASTM standard E-606. The EN coating was deposited at industrial scale and achieved about 25 ?m in thickness. The fatigue strength of the material has been evaluated under rotating bending conditions at stress levels of the order of 50, 54, 58 and 62% of the yield stress. The fatigue strength of the material is reported in terms of the Basquin equation for every condition, namely: the uncoated substrate, the uncoated and notched substrate, the coated substrate and the coated and notched substrate. The results obtained for the notched samples have allowed to determine the values of the constants involved both in Paris and Forman equations for the description of the fatigue crack growth rate as a function of the stress intensity factor. The theoretical value of the critical crack length and the K@sub Ic@ of the material have also been determined. Several fatigue fracture surfaces were analyzed by means of SEM techniques in order to determine the role of the EN deposit on the nucleation of fatigue cracks and to monitor the behavior of the deposit in relation to its adhesion to the substrate.
G8-3 Study on the Seed Layer Texture and Related Properties of TaNx Barriers for Copper Electrodeposition Technologies
Y.L. Wang (Taiwan Semiconductor Manufacturing Company Ltd., R.O.C.); T.C. Wang, T.E. Hsieh (National Chiao-Tung University, R.O.C.); S.Y. Chiu (National Chiao - Tung University, Taiwan, R.O.C.); M.S. Feng (National Chiao-Tung University, R.O.C.); Y.L. Wu (National Ch-Nan University, R.O.C.)
In ultra-large integrated circuit (ULSI) technology, copper replaced aluminum metallization is being developed. The use of copper metallization, which can further reduce RC delay and assure high-speed performance of ULSI, has in fact become an advanced technique to accommodate the next-generation microprocessor. In a significant departure from the trend towards dry processing, electroplating is emerging as the method of choice for the Cu deposition. This is based on a combination of factors including the ability to fill single or dual damascene architectures without voids, but with lower cost and better electromigration performance. In this study, a systematic investigation of copper electrodeposition technologies was carried out to evaluate the seed layer texture and related properties of TaNx barriers for copper electrodeposition technologies. Barrier characterization of TaN with different compositions was determined by X-ray diffraction, AFM image of morphological characterization, RBS for composition analysis and resistivity measurement. The adhesion between seed layer/barriers and the recrystallization texture of copper electrodeposits would have been also discussed.
G8-4 Growth of Metal Chalcogenides by Modifed Chemical Deposition Method
B. Sankapal, C. Lokhande (Shivaji University, India)
Conducting polymers have been known for several decades. Some of the new fields for application of conducting polymer includes gas separation membrane, photoelectrochemical cell, optical devices, ion gates, memory storage devices, non linear circuits elements etc. The most exciting prospect of conducting polymer has been envisaged in the development of molecular electronics in which individual conducting polymer molecules will act as wires, diodes, transistors and other electronic devices. @paragraph@ Recently, polyaniline (PANI) has been identified as an electrical conducting polymer. It shows interesting properties such as electrochemical redox behavior, electrochromic and catalytic activities etc. Among the family of polymer, polyaniline is only conducting polymer whose properties are dependent on the oxidation and protonation states. It is p-type semiconductor whose bandgap is about 2.4 eV. Recently, a variety of rectifying junctions based on organic semiconductors and metals and inorganic semiconductors have been reported. @paragraph@ In the present investigation, polyaniline films are formed onto stainless steel substrate using anodization method. To 500 ml of 10% H@sub 2@SO@sub 4@ (V/V) , 10 g of aniline was added and boiled for 15 min., treated with charcoal, filtered and cooled. Using this solution as a electrolyte and graphite a cathode, oxidation of aniline was carried out on stainless steel anode. A dark green deposit of polyaniline was obtained on the anode surface. The films are p-type semiconductor. On this n-type CdS film is deposited by using a simple, successive ionic layer adsorption and reaction (SILAR ) method. A sandwich type structure such as st. steel/PANI/CdS was formed. The current-voltage (I-V) characteristic was studied by making a silver contact to CdS film. The I-V plot shows ohmic behaviour of CdS film in contact with the polyaniline film.
G8-5 Magnetron Sputtered SiC Coatings as Corrosion Protection Barriers for Steels
A.P. Ordine, C.A. Achete, S.S. Camargo, O.R. Mattos (University of Rio de Janeiro, Brazil)
Silicon carbide films (2,0 µm) were deposited on AISI304 stainless steel (ss), carbon steel (cs) and crystalline silicon from a SiC target in a magnetron sputtering system. Good mechanical properties were obtained for the films by carefully controlling the deposition parameters. Results of scratch tests revealed that adhesion of the films is function of deposition parameters and substrate type. Additionally, an influence of substrates preparation prior to deposition was also observed. Critical loads of 20N, 8N and 5N were obtained in case of Si, ss and cs substrates, respectively. Vickers micro-hardness values were between 10 and 30 GPa, films on ss being harder than films on cs. The behavior of the films as a corrosion protection barrier in aggressive environments were evaluated by immersion tests and electrochemical impedance spectroscopy measurements. Films on ss were better barriers than those on cs. Their adhesion to the ss was outstanding, even after a long time of immersion in a NaCl 0.5M solution, showing that they are efficient protection barriers with large resistance values. The corrosion process of the substrates starts at micro-pores present on the films so that corrosion pits all over the surface of the samples can be observed.
G8-6 Corrosion Behavior of TiN-Coated 304 Stainless Steel
G.P. Yu, J.H. Huang, W.C. Chou (National Tsing Hua University, Republic of China)
Titanium nitride (TiN) was deposited on AISI 304 stainless steel using a hollow cathode discharge ion-plating (HCD-IP) technique. Corrosion behavior of the TiN-coated stainless steel was studied on the specimens with controlling TiN film thickness. The composition depth profiles of TiN films were determined using a secondary ion mass spectrometer (SIMS). The N/Ti ratios were measured using both X-ray photoelectron spectrometer (XPS) and Rutherford back scattering spectrometer (RBS). From the results of RBS, packing factors of the TiN films can also be obtained. The corrosion resistance was evaluated by standard salt spray test, and by potentiodynamic polarization scan in two kinds of solutions, 5% NaCl and 1N H@sub2@SO@sub4@ + 0.05M KSCN. The surface morphology of the specimens after corrosion tests was observed by both FEG-SEM and optical microscope. There is a good agreement between the results of salt spray tests and potentiodynamic polarization scans. The corrosion resistance was correlated to film thickness, packing factor, and thickness x packing factor. In the case of 5% NaCl solution, the critical thickness is about 0.7 micrometer, while in 1N H@sub2@SO@sub4@ + 0.05M KSCN, the critical thickness is about 0.3 micrometer. As the film thickness was larger than the critical thickness, the corrosion current decreased abruptly. It is also found that when the value of thickness x packing factor > 0.6, there is only minor increase in corrosion resistance for the TiN coated specimens tested in 5% NaCl solution. This index was found to be 0.3 for the specimens tested in 1N H@sub2@SO@sub4@ + 0.05M KSCN.