Solid-phase crystallization of high growth rate amorphous silicon films deposited by gas-jet electron beam plasma CVD method

Abstract

Solid phase crystallization of amorphous silicon films (a-Si:H) deposited by gas-jet electron beam plasma chemical vapor deposition method and annealed at 700°C in vacuum has been investigated. This method provides high deposition rates (up to 2.3 nm/s) of a-Si:H thin films in a standard vacuum chamber. The effects of varying the substrate temperature from 190 to 415°C on the structural and optical properties of the as-deposited amorphous films and postannealed nanocrystalline films have been investigated. The crystallite size was determined by X-ray diffraction (about 5-8 nm) and agrees with that obtained from Raman scattering. The estimated degree of crystallinity was 45%-59%. Optical transmission spectra were recorded to investigate the optical properties and thickness of the silicon thin films. The refractive index and optical band gap data was obtained for both as-deposited amorphous and post-annealed nanocrystalline silicon. The behavior of the refractive index of nanocrystalline silicon depending on the substrate temperature is correlated with the crystalline volume fraction. a-Si:H films obtained at low temperatures have larger crystallite size and better crystallinity after annealing.Résumé : Nous étudions la cristallisation en phase solide de films de silicium amorphe (a-Si:H) fabriqués par dépôt chimique en phase vapeur avec faisceau de plasma et jet électronique, avant un recuit à 700°C, le tout dans le vide. Cette méthode donne un fort taux de déposition (jusqu'à 2.3 nm/s) de a-Si:H dans une chambre à vide standard. Nous étudions l'effet de varier la température du substrat de 190 à 415°C sur les propriétés structurelles et optiques des films tels que déposés avant recuit et des films nano-cristallisés après recuit. Nous déterminons la grosseur des cristallites par XRD (environ 5-8 nm) et elle correspond aux résultats par diffusion Raman. La cristallinité varie entre 45 % et 59 %. Nous enregistrons les spectres de transmission optique pour étudier les propriétés optiques et l'épaisseur des films de Si. Nous obtenons l'indice de réfraction et les données sur la bande interdite optique des films tels que déposés et après recuit. La dépendance sur la température du substrat de l'indice de réfraction est corrélée avec la fraction cristalline en volume. Les films de a-Si:H obtenus à basse température ont des cristallites plus grosses et une meilleure cristallinité après recuit. [Traduit par la Rédaction]

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Structural and optical properties of a‐SiOx:H thin films deposited by the GJ EBP CVD method

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