Characterization of PbTiO 3 thin films deposited on Pt/Ti/SiO 2 /Si substrates by ECR PECVD
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Kwangsoo No Department of Ceramic Science and Engineering, Korea Advanced Institute of Science and Technology, Taejon, 305-701, South Korea
Sung-Soon Chun and Won-Jong Lee Department of Electronic Materials Engineering, Korea Advanced Institute of Science and Technology, Taejon, 305-701, South Korea (Received 28 April 1994; accepted 21 October 1994)
The electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR PECVD) method is used to prepare ferroelectric PbTiO3 films. Single-phase perovskite PbTiO3 films with smooth surfaces and fine grain size were successfully fabricated on Pt/Ti/SiO 2 /Si substrates at low temperatures of 400-500 °C using metal-organic (MO) sources. The chemical compositions, structural phases, surface morphologies, and depth profiles of the PbTiO3 thin films were investigated using EDS, XRD, SEM, RBS, and AES. Variations of those properties with process temperature and gas supply ratio are discussed. When the process temperature was above 450 °C, the stoichiometric perovskite PbTiO3 films could be obtained even though the MO source supply ratio was varied in a wide range if the oxygen supply was sufficient. I. INTRODUCTION Lead titanate (PbTiO3) ferroelectric thin films with perovskite structure have been extensively studied for application to pyroelectric infrared sensor, SAW device, and DRAM charge storage capacitor because they have excellent pyroelectric, piezoelectric, and dielectric properties.1"3 Sol-gel4"6 or sputtering methods7'8 have been largely used for the fabrication of PbTiO3 films because of their simplicity in processing. Recently attention has been paid to the chemical vapor deposition (CVD) method which provides good step coverage, large area uniformity, and good film quality. The thermal CVD method where the films are grown in thermal equilibrium state requires a high process temperature. This makes the control of the chemical composition of the multi-component film difficult and causes unwanted thermal strain or diffusion problems in device fabrication. The glow discharge can decompose the precursors and lower the film deposition temperature. Especially, the electron cyclotron resonance (ECR) plasma, which has an ionization efficiency greater than conventional RF plasma by several orders of magnitude, decomposes the precursors so efficiently that high quality films can be fabricated at a low temperature. The vapor-phase homogeneous reactions are also significantly inhibited in ECR plasma enhanced CVD (ECR PECVD) because the processing pressure can be lowered to 0.1 mTorr. The low ion energies (2/Si substrates
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FIG. 1. Schematic diagram of the ECR PECVD system.
of O 2 and Ar (carrier gas of MO sources) were controlled by mass flow controllers. The flow rates of MO sources were calculated from the equilibrium vapor pressures Peq of the sources and the conductances of the fine metering valves. Pb(DPM) 2 and TilP were independently introduced into the reaction chamber by passing Ar g
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