(Ba,Sr)TiO3 (BST) films were deposited by electron cyclotron resonance (ECR) plasma sputtering with mirror confinement. DC bias voltage was applied to Pt/Ti/SiO2/Si substrates during deposition to vary the intensity of bombardment of energetic ions and to modify film properties. BST films deposited on the substrates at floating potential (approximately +20 V) were found to be amorphous, while films deposited on +40 V-biased substrates were crystalline in spite of a low substrate temperature below 648 K. In addition, atomic diffusion, which causes deterioration in the electrical properties of the films, was hardly observed in the crystallized films deposited with +40 V bias perhaps due to the low substrate temperature. Plasma diagnoses revealed that application of a positive bias to the substrate reduced the energy of ion bombardment and increased the density of excited neutral particles, which was assumed to result in the promotion of chemical reactions during deposition and the crystallization of BST films at a low temperature.
The energy distribution of ions (IED) incident onto a dc-biased substrate was measured in an electron cyclotron resonance (ECR) sputtering plasma with mirror magnetic confinement under thin film preparation conditions. It was confirmed that energy E i of ions incident onto the substrate was nearly proportional to the difference between plasma potential and substrate bias voltage. It was found that E i 30 eV was appropriate for the crystallization of SrTiO 3 thin films with high dielectric constant. Energy spread ÁE i , which was estimated from the full-width at half maximum in the IED, increased with positively increasing bias voltage V b for À60 V < V b < 0 V, while E i indicated a decrease away from the sputtering target in the axial direction in correspondence with the variation of the plasma potential.
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