Preparation Of Fine Patterning Of Ferroelectric Films And Their Performances

PZT, PLZT and BST films have significant applications in the High-tech fields such as non-volatile ferroelectric random access memories, uncooled focal plane arrays infrared sensor and micro electrics mechanics system, etc. because of their ferroelectricity, piezoelectricity and pyroelectricity. With the development of the integrated ferroelectrics and the ongoing improvement in integrated density of ferroelectric devices, the preparation of fine patterning has became one of the key technologies in making ferroelectric devices with high performances apart from making fine quality ferroelectric films. For this reason, research on the preparation of fine patterning of ferroelectric film and their performances is of theoretical significance and practicable value in developing ferroelectric devices.This thesis systematically deals with the photosensitivity Sol synthetic mechanism by chemical modification method and the principle of preparation of fine patterning by direct patterning method of PZT, PLZT and BST series ferroelectric films, discusses the effects of different substrates and different crystal layers upon the temperature of phase transformation, crystal structure and performances, and suggests the photosensitivity Sol-gel process and new method for preparing fine patterning and micro arrays of series of PZT, PLZT and BST films.The chemical coordinating chelating reactions betweenβ-diketone (acetylacetone (AcAcH), benzyl acetone (BzAcH)) and precursors such as lead acetate, zirconium oxynitrate, zirconium t-butoxide, tetrabutoxy titanate, lanthanum nitrate, barium acetate and strontium chloride have been studied systematically. The results show: (1)β-diketone (AcAcH, BzAcH) can react with precursors such as lead acetate, zirconium oxynitrate, zirconium t-butoxide and tetrabutoxy titanate to form the stable corresponding coordinating chelates which can can stably exist in the subsequent sol or gel systems, but can not react with precursors such as lanthanum nitrate, barium acetate and strontium chloride. (2) The PZT, PLZT, BST series sols containing the chelates mentioned above can besynthesized. The band position and intensity of the feature peaks of UV spectrum of the series sols are the superposition of the feature peaks of all chelates, and vary with the different chelates and their relative contents. (3) The PZT, PLZT, BST sols and their corresponding gel films have good thermal and chemical stability in air and visible-light. The coordinating chelates of the sols or the gel films can be decomposed when irradiated by the UV-light with wavelength of the nearby feature peak, and the sols and the gel films exhibit good photosensitivity. (4) The fine patterning of ferroelectric films can be directly prepared by using direct patterning method, rinsing process with organic solvent and annealing treatment. (5) The chelates modified by BzAcH and their sol or gel films have better photosensitivity.The phase transformation temperature, crystal structures, ferroelectric and dielectric performance of the PZT, PLZT and BST films on various substrates such as low resistance silicon, ITO and Pt/TiO2/SiO2/Si are studied. The results show: (1) The fine patterning preparation process adopted in this research has no obvious effect upon the stoichiometry, crystal structure, ferroelectric and dielectric performance. (2) PZT, PLZT and BST films growth and their crystal phase transformation belong to the"nucleation-control"type. The nucleation and growth conditions, the dielectric and ferroelectric properties of PZT, PLZT and BST films can be improved by using suitable substrate or seeding layer as heterogeneous nucleation substrate. Fine perovskite patterning films of PZT, PLZT, and BST with good ferroelectric and dielectric properties have been prepared at 550oC~600oC.Based on the photosensitivity of the PZT, PLZT gel films, large area, micro and sub-micro size gratings, two-dimensional (2D) lattices and array of the PZT, PLZT films have been fabricated by using twice-exposure of double-beam interference method via He-Cd laser, adjusting exposure time and without mask. At present, the micro-arrays with pitch of 0.9μm and cell size with the size of 350nm×350nm×40nm have been obtained. The arrays have obvious hysteresis loops with alternating electric field, and exhibit fine ferroelectricity.The high density 2-D ZrO2 lattice template has been prepared, and the ferroelectric micro arrays have been obtained by Self-Assembly (the PZT assembly arrays with pitch of 1μm and cell size of about 500nm×500nm×30nm, the PLZT assembly arrays with pitch of 0.5μm and cell size of about 250nm×250nm×30nm). The results show that the ferroelectric films still have ferroelectricity in such size.In this research, the online-operation of TF Analyzer and AFM is used to study and discuss the hysteresis loops of direct in-situ measurement method of the single cell of ferroelectric micro-arrays. In comparison with the newly-developed PFM (Piezoresponse Force Microscope), this method without strict limitation of pizoelectricity, orientation and film thickness can be used to carry out the direct measurement of the hysteresis loops of ferroelectric arrays in sub- micron and nano-size, and enrich the evaluation method of ferroelectric features of ferroelectric micro-array.