MOCVD processed ni films from nickelocene. Part III: Gas phase study and deposition mechanisms

Presented in this paper is an online mass spectrometry study of the gas pha se during the CVD of nickel films from nickelocene under various conditions , The results are illustrated by means of calibrated molar ratios of C5H8/C 5H10 and CH4/(C5H8+C5H10) These ratios describe the relative advancement ol two types of reactions leading to deposition of pure nickel. and to the in corporation of carbon in the films. Their evolution with deposition time, t emperature, pressure, hydrogen flow rate, and nickelocene molar fraction in the input gas is investigated and compared with equilibrium calculations p erformed under similar conditions. The information obtained is combined wit h previously reported results on the morphology and growth rate, ([1]) the composition (especially the carbon content) of the deposits,([2]) the adsor ption mode, and the decomposition of nickelocene and of the cyclopentadieny l derivatives. It is proposed that, for low surface coverage by nickelocene molecules, a Langmuir-Hinshelwood mechanism prevails for the deposition. f ollowing which nickelocene competes with H-2 for the occupation of most of the adsorption sites. For high surface coverage, reaction between neighbori ng nickelocene molecules also occurs, and this reaction is responsible for the incorporation of carbon in the deposits.