Selected area growth of nickel micropillars on aluminum thin films by electroless plating for applications in microbolometers

Journal of Science: Advanced Materials and Devices (2017) 192e198 Contents lists available at ScienceDirect Journal of Science: Advanced Materials and Devices journal homepage: www.elsevier.com/locate/jsamd Original Article Selected-area growth of nickel micropillars on aluminum thin films by electroless plating for applications in microbolometers Do Ngoc Hieu a, b, Dang Nguyen Ha My b, c, Vu Thi Thu c, Nguyen Quoc Hung b, Do Ngoc Chung d, Nguyen-Tran Thuat b, * a Faculty of Engineering Physics and Nanotechnology, VNU University of Engineering and Technology, Vietnam National University, 144 Xuan Thuy, Hanoi, Viet Nam Nano and Energy Center, VNU University of Science, 334 Nguyen Trai Street, Hanoi, Viet Nam c Department of Advanced Materials Science and Nanotechnology, University of Science and Technology of Hanoi, 18 Hoang Quoc Viet, Hanoi, Viet Nam d Center for High Technology Development, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Hanoi, Viet Nam b a r t i c l e i n f o a b s t r a c t Article history: Received April 2017 Received in revised form 12 May 2017 Accepted 12 May 2017 Available online 18 May 2017 An optimization process of electroless plating of nickel was carried out with NiCl2 as the nickel ion source, NaH2PO2 as the reduction agent, CH3COONa and Na3C6H5O7 as complexing agents Electroless plated nickel layers on sputtered aluminum corning glass substrates with a resistivity of about 75.9 mU cm and a nickel concentration higher than 93% were obtained This optimum process was successfully applied in growing nickel micropillars at selected areas with a well-controlled height The microstructure of the masking layers was fabricated by means of optical photolithography for subsequent growth of nickel micropillars on selected areas Micropillars size was defined by the opening size and the height was controlled by adjusting the plating time at a growth rate of 0.41 mm/min This result shows that electroless nickel plating could be a good candidate for growing micropillars for applications in microbolometers © 2017 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) Keywords: Nickel electroless plating Micropillars MEMS Microbolometer Selected-area growth Introduction The integration between micro electro-mechanical systems (MEMS) and complementary metal oxide semiconductor (CMOS) circuits allows a huge range of smart applications starting from simple actuator functionalities to sophisticated sensing and fluidic system-on-a-chip devices [1] Microbolometers are typical MEMSbased devices whose performance had been enhanced by the monolithic integration of MEMS upon integrated circuit (IC) substrates using MEMS-last processing via layer deposition and surface micromachining Since then MEMS-based microbolometers have been used for the detection of long wavelength infrared (LWIR) [2e5] and terahertz electromagnetic radiation [6e8] * Corresponding author Nano and Energy Center, VNU University of Science, Room 503, 5th floor, T2 building 334 Nguyen Trai street, Thanh Xuan, Hanoi, Viet Nam Fax: þ84 435 406 137 E-mail address: thuatnt@vnu.edu.vn (N.-T Thuat) Peer review under responsibility of Vietnam National University, Hanoi Electroless or autocatalytic plating of metals is a well-developed coating technique which involves the presence of a chemical agent in a solution to reduce metallic ions into its bulk or thin metal film state [9] The autocatalytic plating is defined as the deposition of a metal layer by a controlled chemical reduction which is catalyzed by the metal or alloy being deposited This plating process has been used to yield metal deposits, such as Ni, Pd, Cu, Au, and Ag as well as some alloys containing these metals with impurities such as P, B or N [10] In semiconductor industry, electroless plating and electroplating have been used in making interconnection between metal layers [11] On the other hand, electroless plating and electroplating of nickel is one of the important fabrication steps in MEMS process, which is described by the term LIGA (lithography, galvanoforming and moulding) [12e14] Among other metals, nickel is one of the common elements to be electroless plated on a metal surface, such as aluminum, copper or alloys Electroless nickel (EN) plating has been widely used in MEMS fabrication process thank to its simplicity [15e17] EN plating was reported in Ref [4] for making pillars of microbolometer arrays with a good sensitivity and detectivity but the sacrificial planarization layer has not been intentionally http://dx.doi.org/10.1016/j.jsamd.2017.05.004 2468-2179/© 2017 The Authors Publishing services by Elsevier B.V on behalf of Vietnam National University, Hanoi This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/) D.N Hieu et al / Journal of Science: Advanced Materials and Devices (2017) 192e198 193 Table 100 ml zincating solutions composition Volume (ml) Composition 1st beaker 2nd beaker 3rd beaker 20 NaOH 0.1 g 50 HNO3 10% 20 NaOH 0.1 g ZnO 0.05 g removed for enhancing the thermal isolation of microbolometers The growing of these pillars in EN plating process must be occurred only in selected aluminum areas, thus requiring a masking layer to protect un-wanted deposition of nickel on other areas [18] The drawback is that this masking layer could be damaged by a large range of pH level of the electroless plating bath and the pretreatment, activation and zincating solutions [15,16,19,20] In this paper, we present an experimental study on electroless nickel plating for applications in microbolometers The study starts from an optimization of the electroless plating bath for depositing nickel on aluminum surface and ends up at the controlled growth of nickel micropillars on selected areas with the masking layer patterned by a conventional optical lithography process Fig EDS spectrum of electroless nickel plating on bulk aluminum sample Inserted figures are bulk aluminum sample (a) before and (b) after electroless nickel plating with additives The morphology of all samples was characterized on a conventional optical microscope and by scanning electron microscopy (SEM), on a SEM Hitachi S-4800 system The chemical composition of nickel electroless plated was characterized by energy-dispersive X-ray spectroscopy (EDS) on the same SEM system The sheet resistance of electroless plated nickel was measured on a four-point RM3000 Jandel prober The thickness of nickel micropillars was characterized on an Alpha-Step DEKTAK150 profilometer Experimental procedures Nickel electroless plating processes were carried out as following: (i) aluminum samples preparation, (ii) zincating and rinsing, (iii) EN plating in a Ni-P containing a bath Bulk aluminum samples with a purity of 99.99% were used as a reference and the optimization of bath composition Thin aluminum films were used after obtaining the optimum bath composition These Al thin films, with thicknesses about 200 nm, were deposited on clean corning glass substrates by sputtering a two-inch aluminum target, 99.99% of purity, at 60 W for 60 min, on a 4-mangetron-gun sputtering system from SYSKEY Before the electroless plating step, aluminum samples were pretreated by a zincating procedure, with the composition of each solution described on Table For bulk Al samples the zincating time was 15 s for each dipping step, while it was s for thin Al film samples After the zincating step, all samples were rinsed in deionized water and the electroless plating step was taken place immediately afterward Compositions of nickel electroless plating baths are showed on Table The optimization of the bath composition was carried out only on bulk aluminum samples with the starting “plain bath” composition The optimum composition is denoted as “bath with additives”, after using CH3COONa and Na3C6H5O7 as additives The plating temperature was fixed at 90  C, and the pH level of the bath was kept around to For selected-area growth of nickel by electroless plating, only aluminum thin films samples were used The masking layer, with various opening size ranging from mm to mm, was patterned by using a conventional photolithography contact procedure The photoresist AZ5214E, from Microchemicals, was used as both the transferring layer and the masking layer Since the zincating and plating duration was quite short, the hard-baked photoresist layer was not damaged during all experiments After the pattering process by photolithography, nickel micropillars were grown on unmasked areas by the optimized electroless plating process showed above Results and discussion 3.1 Electroless plating of nickel The optimization of electroless nickel plating was performed on bulk aluminum samples with the starting “plain bath” composition showed on Table The morphology, the chemical composition of samples' surface and sheet resistance of the sample were used an optimizing parameter In order to obtain this “plain bath” composition, many trial experiments have been done by changing the bath temperature, the order of putting the substrate and the reduction agent (NaH2PO2) into the solution, and different combination of nickel source (NiCl2 and NiSO4) On the one hand, the concentration of Ni in the “plain bath”, about 7.5 g/L, was quite similar to the concentration of electroless plating of nickel in industry At this range of nickel concentration, the deposition rate of electroless plating is not much affected by the fluctuation of nickel concentration in the bath [21,22] On the other hand, the pH value of the “plain bath” composition was smaller than the value yielding low value of phosphorus concentration of plated nickel film [21] This led to the introduction of additives into the bath for the subsequent optimization For the availability of chemicals in local, CH3COONa and Na3C6H5O7 were chosen As found in the literature, acetates and citrates are complexing agents They play three roles: (i) maintain stable pH level, (ii) prevent precipitation of nickel salts such as phosphites, (iii) reduce the concentration of free nickel ion [23e25] The optimizing “bath with additives” composition is showed in Table For this optimized bath, the inserted figures of Fig show (a) a bulk aluminum surface before and (b) after the electroless nickel plating process It can be seen that the aluminum Table 100 ml baths composition Bath description NiCl2$6H2O (g) NaH2PO2$H2O (g) CH3COOH 80% (ml) CH3COONa (g) Na3C6H5O7 (g) pH level Plain bath Bath with additives 3 2 0 2e3 6e7 194 D.N Hieu et al / Journal of Science: Advanced Materials and Devices (2017) 192e198 Fig Optical images of thin aluminum sample: (a) as deposited surface, (b) after zincating treatment, (c) after of electroless nickel plating and (d) after 10 of electroless nickel plating surface changes substantially; it is no longer shiny and is covered by an electroless plated nickel layer The graph of Fig exhibits the EDS spectrum taken from this electroless plated nickel deposition on bulk aluminum surface It is worth noting that all EDS spectra in this study are used for the purpose of chemical elements analysis only On Fig Ni and P peaks are found suggesting the abundance of nickel and the presence of phosphorus as an impurity Surprisingly, there is no aluminum peak observed even though this Fig Surface morphology on SEM images of electroless plating on aluminum thin film: (a) just after zingcating steps; (b) surface and (c) cross-section after min; (d) surface and (e) cross-section after 10 of plating D.N Hieu et al / Journal of Science: Advanced Materials and Devices (2017) 192e198 Fig EDS spectra of electroless nickel film on aluminum thin film after and 10 of plating spectrum was taken on a bulk aluminum sample It shows that the aluminum surface is coated completely by a P-containing Ni thick film and the nickel concentration was estimated roughly to be higher than 90% The residual phosphorus in the electroless plated nickel was unavoidable since the reducing agent was NaH2PO2 The optimum “bath with additives” composition was then applied to plate auto-catalytically nickel on 200 nm of thickness thin aluminum films Fig shows the surface of an aluminum thin film sample (a) as deposited by sputtering, (b) after the zincating treatment, (c) after and (d) after 10 of electroless plating 195 We can see that the aluminum surface is darken after the zincating treatment and the electroless plated nickel surface after is more homogenous than after 10 In order to shed some light on the morphology of the electroless plated nickel surface, Fig shows SEM micrographs of samples after each treatment step On Fig 3a, a nanostructured aluminum surface is observed after the zincating treatment This nanostructure surface favors the growth of nickel in the subsequent electroless plating step Fig 3b, and respectively Fig 3c, shows the morphology, and the cross-section respectively, of electroless plated nickel after Fig 3d, and respectively Fig 3e, are for the sample after 10 of nickel plating time From these micrographs, we can see that the morphology of nickel layers are likely an assembly of micro-sized spheres These spheres became larger as the plating time increased from to 10 From the cross-section micrographs, we can see that the underneath layer exhibits a submicron-sized structure By measuring the thickness, which is 2.88 mm for and 5.48 mm for 10 sample, it is deduced that the thickness increases rather linearly with the plating time For the sample after 10 of plating, a resistivity of about 75.9 mU cm was obtained from the sheet resistance measurement This is one order of magnitude higher than the resistivity of the bulk nickel material, which is about 6.93 mU cm In addition, Fig shows the EDS spectra of these two samples There are only peaks characterizing nickel and phosphorus, giving an estimated value of nickel concentration higher than 90% for both samples By comparing with the literature, the value of resistivity and the concentration of phosphorus obtained in this study are in good agreement [23] Fig Simplified monolithic MEMS and IC integration using MEMS-last processing via layer deposition and surface micromachining: (a) starting CMOS wafer with aluminum pads, (b) masking for selected areas on aluminum pads, (c) electroless nickel plating on selected areas, (d) supporting layer deposition, (e) LWIR sensing layer deposition, (f) contact deposition, (g) encapsulation layer deposition and (h) masking layer removal 196 D.N Hieu et al / Journal of Science: Advanced Materials and Devices (2017) 192e198 Selected-area growth of nickel micropillars In order to show how electroless plating of nickel plays a central role in micromachining microbolometers for LWIR detection, Fig shows our simplified fabrication process of a monolithic MEMS and IC integration Starting from a CMOS wafer with aluminum pads for the connection with underneath circuits, on Fig 5a, a masking layer was coated, on Fig 5b The structure of the masking layer was patterned by a conventional photolithography by using AZ5214e photoresist This layer plays not only the role of defining the openings for subsequent electroless nickel plating, described by Fig 5c, but also a sacrificial layer, which will be stripped off at the final step, described by Fig 5h All other layers for supporting, sensing, contacting and encapsulating are deposited upon the sacrificial layer and nickel micropillars, described by Fig 5deg The height of the masking layer will define therefore the height of suspending microbolometers for absorbing LWIR radiation For the central absorption wavelength of 10 mm, the thickness of the sacrificial layer should be around 2.5 mm in order to have an effect of destructive reflection of incoming radiation It is true that the selected-area growth of micropillars by electroless nickel plating is a crucial step of our microbolometers fabrication process flow Since the openings height of the masking layer is about 2.5 mm, and thicknesses of other layers (such as supporting, sensing, contacting and encapsulating) are about 100 nm, without filling the openings it is quite difficult to micromachine the suspending structure of microbolometers Nickel micropillars not only fill the openings for preparing a planar surface, but also electrically conducting and mechanically supporting columns for the suspending structure The electroless plating technique gives a simple filling method and may not need a subsequent surface planarization step if the growth were well controlled Figs 6a and b shows optical images of different opening size of about 11 mm, and mm, respectively, after the photolithography patterning step Figs 6c and d show the corresponding micro-sized electroless plated nickel micropillars after removing the masking photoresist layer; Figs 6e and f are the corresponding zoomed SEM micrographs It can be seen easily that nickel micropillars were grown at intentionally selected areas on aluminum thin films The lateral sizes of nickel micropillars are similar to that of openings There will be little optimization for obtaining good shapes of micropillars On Fig 6c and d, the superposed features are images taken on our LWIR sensing multilayer, patterned by photolithography, for illustrating how microbolometers will be fabricated upon nickel micropillars Fig shows in addition the EDS spectrum taken on a selected nickel micropillar with a lateral size of 11 mm It is similar to the spectra taken on electroless plated nickel on bulk and aluminum surface showed on Figs and 4, respectively We can observe also that there are only Ni and P peaks, giving an estimated Ni concentration of 93% The value of P concentration in the plated Ni in our samples, about 7%, is ranged as middle impurity concentration In this paper, we focused on electrical properties of plated Ni layers, the structure of Ni-P was not fully characterized It was reported that Ni and P formed compounds such as Ni5P2, Ni3P in the plated Ni layer [26] In order to reduce the impurity to the low level of 2e5%, more complexing agents are needed such as the Fig Optical images of photoresist openings for selected-area electroless plating of nickel (a) 11 mm sized features (b) mm sized features SEM images of nickel micropillars with the size of (c) and (e) 11 mm, (d) and (f) mm The superposed images of (c) and (d) demonstrate how microbolometer are deposited upon nickel micropillars D.N Hieu et al / Journal of Science: Advanced Materials and Devices (2017) 192e198 197 ammonium bromide [28], will be considered with an optimized concentration in order to avoid the organic contamination in the plating bath Conclusion Fig EDS spectrum on an electroless plated nickel micropillar combination of malic acid and succinic acid [27] In Ref [27], it was reported that the main source of P incorporation into the plated Ni was hypophosphorous acid H3PO2 and hydrogen radicals in the bath Thus reducing the concentration of H3PO2 and maintaining high pH level are the crucial elements for lowering the phosphorus concentration In our devices, the P concentration in Ni micropillars may lead to the diffusion of P into the CMOS substrates in future devices The fabrication of nickel micropillars are considered as a post-CMOS surface micromachining step Fortunately, transistors are protected by insulator layers deposited during the interconnection back end of line steps So phosphorus residual in micropillars would not have high impact on the device performance Nevertheless, more complexing agents such as malic acid and succinic acid will be used for the future optimization of the bath composition For controlling the height of nickel micropillars, a systematic series of electroless plating experiments with different plating time were carried out Fig presents the dependence between the micropillars height and the plating time For our optimum “bath with additives” composition, the deduced deposition rate is about 0.41 mm/min As a consequence, in order to grow micropillars of 2.5 mm of height, of plating time is enough The deposition rate could be decreased by diluting the nickel source, NiCl2, and the reducing agent, NaH2PO2, but longer time in plating bath would give some unwanted damage on the surface of device For future optimization of growing micropillars by electroless plating, surfactants for enhancing the wettability and for smoothing the plated Ni surface, such as sodium dodecyl sulphate or cetyltrimethyl Fig Dependence between the nickel micropillars height and the plating time, a deposition rate of about 0.41 mm/min is deduced We have presented an electroless nickel plating process for applying in surface micromachining of microbolometers upon an IC substrate The optimization of Ni-P containing bath composition was carried out on bulk aluminum samples The optimum plating bath was successfully applied on sputtered aluminum thin films by reducing the zincating time from 15 s to s A resistivity of 75.9 mU cm was obtained for electroless plated nickel film on a 200 nm of thickness aluminum thin film for 10 of plating time Selected-area growth of nickel micropillars was performed by using the optimum electroless plating process The lateral size of these micropillars was in a good agreement with the opening size, about mm and 11 mm The height of micropillars was well controlled by adjusting the plating time For our optimum bath composition, a growth rate of 0.41 mm/min was obtained, thus giving a way to control the height of micropillars for assuring the planarized surface before other subsequent surface micromachining steps This study thus opens a potential perspective in fabricating microbolometers for LWIR imaging Acknowledgments The authors greatly acknowledge the financial support of the National Foundation for Science and Technology Development e NAFOSTED under Project No 103.02-2015.79 “Fabrication of micro sized coolers based on thermoelectric effect” The authors would like to thank the Vietnam National University Hanoi for research equipment from the project named “Strengthening research and training capacity in fields of Nanoscience and Technology, and Application in Medical, Pharmaceutical, Food, Biology, Environmental protection and Climate Change adaptation in the direction of sustainable development” References [1] A.C Fischer, F Forsberg, M Lapisa, S.J Bleiker, G Stemme, N Roxhed, F Niklaus, Integrating MEMS and ICs, Microsystems Nanoeng (2015) 15005 [2] J.L Tissot, IR detection with uncooled focal plane arrays, state-of-the art and trends, Opto Electron Rev 12 (2004) 105e109 [3] F Niklaus, C Vieider, H Jakobsen, MEMS-based uncooled infrared bolometer arrays: a review, Proc SPIE 6836 (2007) 68360D [4] S Chen, H Ma, S Xiang, X Yi, Fabrication and performance of microbolometer arrays based on nanostructured vanadium oxide thin films, Smart Mater Struct 16 (2007) 696e700 [5] P Robert, J Tissot, D Pochic, V Gravot, F Bonnaire, H Clerambault, A Durand, S Tinnes, Easy to use uncooled ¼ VGA 17 mm FPA development for high performance compact and low-power systems, Proc SPIE 8353 (2012), 83531F1e83531F6 [6] J Grant, I Escorcia-Carranza, C Li, I.J.H Mccrindle, J Gough, D.R.S Cumming, A monolithic resonant terahertz sensor element comprising a metamaterial absorber and micro-bolometer, Laser Photonics Rev (2013) 1043e1048 [7] X.C Tu, L Kang, X.H Liu, Q.K Mao, C Wan, J Chen, B.B Jin, Z.M Ji, W.W Xu, P.H Wu, Antenna-coupled microbolometer array for terahertz detection, in: Int Conf Infrared, Millimeter, Terahertz Waves, IRMMW-THz, 2012, p 5112 [8] N Oda, S Kurashina, M Miyoshi, K Doi, T Ishi, T Sudou, T Morimoto, H Goto, T Sasaki, Microbolometer terahertz focal plane array and camera with improved sensitivity in the sub-terahertz region, J Infrared, Millim Terahertz Waves 36 (2015) 947e960 [9] M Schlesinger, M Paunovic, Modern Electroplating, fifth ed., John Wiley & Sons, Inc., Hoboken, New Jesey, 2010 [10] G.O Mallory, J.B Hajdu, Electroless plating: Fundamentals and applications, Reprint Ed), Noyes Publications/William Andrew Publishing, LLC, Norwich, New York, 1990 [11] P.C Andricacos, Copper on-chip interconnections, a breakthrough in electrodeposition to make better chips, Electrochem Soc Interface (1999) 32e37 [12] M.-S Chen, Channel-constrained electroless metal deposition on ligating selfassembled film surfaces, J Electrochem Soc 146 (1999) 1421e1430 198 D.N Hieu et al / Journal of Science: Advanced Materials and Devices (2017) 192e198 [13] E.W Becker, W Ehrfeld, P Hagmann, A Maner, D Münchmeyer, Fabrication of microstructures with high aspect ratios and great structural heights by synchrotron radiation lithography, galvanoforming, and plastic moulding (LIGA process), Microelectron Eng (1986) 35e56 [14] C Müller, J Mohr, Microspectrometer fabricated by the liga process, Interdiscip Sci Rev 18 (1993) 273e279 [15] C Liu, D.A Hutt, D.C Whalley, P.P Conway, S.H Mannan, Under bump metallisation of fine pitch flip-chip using electroless nickel deposition, in: Int Symp Electron Mater Packag EMAP 2000, 2000, pp 64e71 [16] D.A Hutt, C Liu, P.P Conway, D.C Whalley, S.H Mannan, Electroless nickel bumping of aluminum bondpads - Part I: surface pretreatment and activation, IEEE Trans Components Packag Technol 25 (2002) 87e97 [17] K.-Y Lee, J.-T Huang, H.-J Hsu, C.-K Chen, T.-C Tsai, Fabrication technology of CMOS-MEMS probe chip compatible with electroless nickel plating process, in: 2010 5th Int Microsystems Packag Assem Circuits Technol Conf, IEEE, 2010, pp 1e4 [18] S.Z Chu, M Sakairi, H Takahashi, K Simamura, Y Abe, Laser-assisted electroless Ni-P deposition at selected areas on Al(-Mg, Si, Cu) alloys, J Electrochem Soc 147 (2000) 2181e2189 [19] S.G Robertson, I.M Ritchie, The role of iron(III) and tartrate in the zincate immersion process for plating aluminium, J Appl Electrochem 27 (1997) 799e804 [20] K Azumi, T Yugiri, M Seo, S Fujimoto, Double zincate pretreatment of sputter-deposited Al films, J Electrochem Soc 148 (2001) C433eC438 [21] G.O Mallory, J.B Hajdu, The electroless nickel plating bath: effect of variables on the process, in: G.O Mallory, J.B Hajdu (Eds.), Electroless Plat Fundam Appl., Reprint Ed, Noyes Publications/William Andrew Publishing, LLC, Norwich, New York, 1990, pp 57e99 [22] C Baldwin, T.E Such, The plating rates and physical properties of electroless nickel/phosphorus alloy deposits, Trans IMF 46 (1968) 73e80 [23] M Schlesinger, Electroless deposition of nickel, in: M Schlesinger, M Paunovic (Eds.), Morden Electroplat., fifth ed., John Wiley & Sons, Inc., Hoboken, New Jesey, 2010, pp 447e458 [24] T Zhai, X Lu, G Cui, G Wu, J Qu, Y Tong, Efficient electroless nickel plating from highly active NieB nanoparticles for electric circuit patterns on Al2O3 ceramics, J Mater Chem C (2013) 5149 [25] M.W Jung, S.K Kang, J.H Lee, Effects of sodium citrate concentration on electroless Ni-Fe bath stability and deposition, J Electron Mater 43 (2014) 290e298 [26] Y El Kaissi, M Allam, A Koulou, M Galai, M.E Touhami, Influence of sodium acetate on electroless Ni-P deposits and effect of heat treatment on corrosion behavior, Int J Chem Mol Nucl Mater Metall Eng 11 (2017) 139e144 [27] G Cui, N Li, D Li, M Chi, Study of optimized complexing agent for lowphosphorus electroless nickel plating bath, J Electrochem Soc 152 (2005) C669eC674 [28] V Kumar Bulasara, C.S.N Mahesh Babu, R Uppaluri, Effect of surfactants on performance of electroless plating baths for nickeleceramic composite membrane fabrication, Surf Eng 28 (2012) 44e48  ... concentration of electroless plating of nickel in industry At this range of nickel concentration, the deposition rate of electroless plating is not much affected by the fluctuation of nickel concentration... obtained for electroless plated nickel film on a 200 nm of thickness aluminum thin film for 10 of plating time Selected- area growth of nickel micropillars was performed by using the optimum electroless. .. electroless plating bath for depositing nickel on aluminum surface and ends up at the controlled growth of nickel micropillars on selected areas with the masking layer patterned by a conventional optical