Electrochemical Study of the Electroless Deposition of Co(W, B) Alloys

Abstract

This paper presents the results of a study of the electroless deposition process and the film properties of cobalt-tungsten-boron ͓Co͑W, B͔͒ thin layers on thin copper films. Two solutions based on cobalt citric complexes and dimethylaminoborane reducing agent were developed. Tungsten was introduced into the solutions by using either sodium tungstate or tungsten acid. The deposited thin-film composition was characterized as a function of the bath formulation by X-ray photoemission spectroscopy. Electroless deposition was studied through electrochemical approach via linear sweep voltammetry analysis of the following two partial reactions: a. metal reduction and b. the oxidation of the reducing agent at the Co͑W, B͒ plated electrodes. In situ mixed potentials of the process for different electrolytes were measured. The deposition rate of cobalt alloys was gravimetrically measured as well. Comparison between direct experimental values of the mixed potential and deposition rate with those derived theoretically from the current-potential curves for partial reactions shows the electrochemical nature of the deposition reaction with current yield value of about 0.7-0.8 and 0.98 for solution with sodium tungstate and alkali metals free bath, respectively. The optimal conditions ͑i.e., temperature, pH͒ and composition of aqueous solution for the deposition of Co͑W, B͒ films were defined. Those films can be applied as both barrier and capping layers for ultra-large-scale-integration metallization for integrated circuits and microsystemtechnology applications.Metal and metal alloy coatings have a wide application range in numerous technologies featuring the increased functionality and reliability of different industry products. Metallic layers act as thermal and electricity conductors, protective shields, and magnetic media; they provide necessary chemical, mechanical, electrical, magnetic, and optical properties. They are also used for decorative and corrosion protection purposes.Electroless metal deposition remains one of the most attractive technologies for thin metallic coating formation due to few wellknown process advantages such as selective and conformal deposition, self-aligning, low processing temperature, high quality of the films, and the ability to deposit alloys. Increased attention to electroless and electroplating processing in microelectronics was raised in the last decade due to the introduction of copper interconnects to VLSI integrated circuits ͑ICs͒ and the forthcoming transition to sub-100 nm technology. The electroless method is under intensive study for future ͑i.e., with critical dimensions of 45 nm and below͒ ultralarge-scale integration ͑ULSI͒.Cobalt and cobalt alloys find their application in the production of hard materials, magnets, tire adhesives, catalysts, colorants, chemicals, and batteries. 1 Cobalt alloy coatings are distinguished by their unique magnetic and mechanical properties, high oxidation stability, and wear resistance. The magnetic properties of electrodeposited cobalt alloys are ...

Electroless Deposition of Silver on Multiwalled Carbon Nanotubes Using Iodide Bath

“…SEM images (data not shown) of the MWCNTs after electroless silver deposition at pH ¼ 10 indicated that the amount of deposit increased compared to that for deposition at pH ¼ 7.5. Sverdlov et al reported that the anodic reaction of the DMAB reducing agent on the catalytic surface in alkaline solution could be described as follows 33 …”

Development of an alkali-metal-free bath for electroless deposition of Co-W-P capping layers for copper interconnections

“…Tel. : +82 31 219 2389; fax: +82 31 219 1612. cap copper interconnections with cobalt-containing films such as Co-P, Co-W-P, Co-W-B and Co-Mo-P [1,[9][10][11][12] and nickelcontaining films such as Ni-P, Ni-W-P and Ni-Re-P [13,14]. Among the above-mentioned metallic capping/barrier layers, it was reported that the Co-W-P films had better performance as an effective capping/barrier layer for copper metallization up to 550 • C [3,16].…”

“…Co-W-P thin films can be deposited by both electroless [10][11][12] and electrochemical [17][18][19][20] deposition methods. The electroless plating, however, is widely used to deposit the metallic capping/barrier layers because it is a very simple and inexpensive method, does not require much instrumentations and offers highly selective and conformal deposition [5,12,15].…”

“…The electroless plating, however, is widely used to deposit the metallic capping/barrier layers because it is a very simple and inexpensive method, does not require much instrumentations and offers highly selective and conformal deposition [5,12,15]. In electroless deposition the reduction of ionic species in the presence of reducing agents such as dimethylamine borane (DMAB) and hypophosphite occurs through the mechanisms illustrated below [12,16,21]. In basic solution, DMAB and hypophosphite are oxidised according to the following equations, respectively.…”

Characterisation of electrodeposited Co–W–P amorphous coatings on carbon steel

“…Co-W-P thin films can be fabricated by both electroless [8][9][10][11] and electrochemical deposition methods [12][13][14][15]. Recently, it has been reported that electrodeposition method has some advantages over electroless deposition such as lower processing temperature, better control over the deposition technique and thus, a wide range of compositions [12][13][14][15].…”