The mechanism of complex formation in solutions of tungstates and molybdates

Babad‐Zakhryapin, A. A.; Berezkina, Yu. F.

doi:10.1007/bf00745530

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“…In the case of basic baths, that are used for Co͑W, P͒ deposition, we propose that there is tungsten citrate complexing. 21,22 These complexes dissocia-tion results in the formation of a tungstile ion, WO 2 2ϩ . Gorbunova 17 proposed also that the reduction of these ions can be presented as…”

Section: Discussionmentioning

confidence: 99%

Electroless Deposition of Thin-Film Cobalt-Tungsten-Phosphorus Layers Using Tungsten Phosphoric Acid (H[sub 3][P(W[sub 3]O[sub 10])[sub 4]]) for ULSI and MEMS Applications

Shacham‐Diamand

Sverdlov

Petrov

2001

J. Electrochem. Soc.

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This paper describes an electroless deposition method for the formation of thin metallic films that contain mainly cobalt with significant amount of tungsten ͑up to ϳ11 atom % ͒ and phosphorus ͑in the range of 1-3 atom % ͒. The Co͑W, P͒ films can be applied for microelectronics multilevel metallization or for ultralarge-scale integrated ͑ULSI͒ and microelectromechanical systems ͑MEMS͒ applications. The film was deposited from an aqueous electrolyte that contained tungsten phosphoric acid, H 3 ͓P͑W 3 O 10 ͒ 4 ͔, as a source for tungsten. Cobalt sulfate was used as a source for the cobalt ions and sodium hypophosphite as the reducing agent and a source for phosphorus. The Co͑W, P͒ thin films from solutions with tungsten phosphoric acid were studied and compared to Co͑W, P͒ films that had been obtained from solutions wherein the tungsten was supplied by tungstate ions. The use of tungsten phosphoric acid allowed higher tungsten content and lower deposition rate when compared to solutions with Na 2 WO 4 and (NH 4 ͒ 2 WO 4 . The deposition with tungsten phosphoric acid was studied for 20-200 nm thick layers and was found to be reproducible. The deposited layers were bright colored and their specific resistance was in the range of 48-90 ⍀ cm. The process parameters of typical solutions are presented and discussed. The film sheet resistance, composition, and surface morphology are presented for various solutions and process conditions. The deposition process involves several reactions that occur simultaneously and are described in this work. Finally, various applications are proposed for copper metallization as a barrier layer, to confine the copper, or as a capping layer to prevent copper oxidation and improve adhesion of the inlaid copper to upper interlevel dielectric layers.

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Section: Discussionmentioning

confidence: 99%