Controls of Crystallinity and Surface Roughness of Cu Film in Partially Ionized Beam Deposition
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ABSTRACT Changes of crystallinity and surface roughness are discussed in terms of the average energy per deposited atom in the partially ionized beam(PIB) deposition. The average energy per deposited atom can be controlled by adjusting the ionization potential, Vi and acceleration potential, Va. The ion beam consists of a Cu ion beam and residual gas ion beam and residual gases as well as Cu particles that were ionized and accelerated to provide the film with energy required for filmgrowth. The relative contribution of residual gas ions and Cu ions to total average energy per deposited atom was varied with the ionization potential. At fixed ionization potentials of Vi=400 V and Vi=450 V, the average energy per deposited atom was varied in the range of 0 to 120 eV with acceleration potential Va, of 0 to 4 kV. The relative intensity ratio, 1(111)/1(200), of the Cu films increased from 6 to 37 and the root mean square(R.) surface roughness decreased with an increase in acceleration potential at Vi=400 V. The relative intensity ratio, 1(111)/1(200), of Cu films increased up to Va=2 kV at Vi=2 kV, above which a decrease occurred, and the surface roughness of Cu films increased as a fintion of acceleration potential. The degree of preferred orientation was closely related with the average energy per deposited atomn The change of Rms roughness might be affected by ion flux, particle energy and preferred orientation.
INTRODUCTION In thin film formation, many sputtering techniques, ECR plasma deposition, ion plating have been used[l-3], but deposition parameters in these techniques are strongly correlated, which makes it difficult to understand effects of deposition parameters on resulting film properties. In spite of the great interest in this subject several correlations between the growth conditions and the structural properties of deposited films are not well understood[4]. In a partially ionized beam deposition system, the energy required for film growth is provided with acceleration of ionized particles, in which ionized particles consist of ionized deposition particles and ionized residual gas. These ions are accelerated to give energy to the substrate. Energy given to the substrate and the film is represented as an averge energy per depositing atom Ea, which varies with deposition conditions, such as ionization potential and acceleration potential[5]. In the case of thin film formation by adjusting the energy of depositing atoms or molecules themselves, it has been considered to solve many difficulties for interpreting relationships of deposition parameters and film properties in conventional thin film formation. The main purpose of this paper is to investigate the relation of structural properties (preferred orientation, surface roughness) with Ea which can be controlled by deposition parameter. In this article, Cu thin films on Si(100) substrates with various acceleration potentials and ionization potentials have been grown in order to try to find a relation between crystallinity, surface morphology, and average
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