Excimer Laser Induced Patterning of PSZT and PLZT Flms
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1052-DD06-03
Excimer Laser Induced Patterning of PSZT and PLZT Flms Patrick William Leech1, and Anthony S Holland2 1 CSIRO, Molecular and Health Technologies, Clayton, Victoria, 3168, Australia 2 School of Electrical and Computer Engineering, RMIT, Melbourne, Australia ABSTRACT The patterning of strontium-doped lead zirconium titanate (PSZT) and lanthanum-doped lead zirconium titanate (PLZT) films has been examined using excimer laser radiation. Both types of film were deposited by rf magnetron sputtering using in-situ heating and a controlled cooling rate in order to obtain the perovskite-oriented phase. The depth of laser ablation in both PSZT and PLZT films showed a logarithmic dependence on fluence. The threshold fluence required to initiate ablation was ~1.25 mJ/cm2 for PLZT and ~1.87 mJ/cm2 for PSZT films. The ablation rate of PLZT films was slightly higher than that of PSZT films over the range of fluence (10-150 J/cm2) and increased linearly with number of pulses. The higher ablation rate of PLZT films has been attributed to the finer grain size (160-200 nm) than in the PSZT films (1.0-1.2 µm).
INTRODUCTION Lead zirconium titanate (PZT) has become an important material in the fabrication of electromechanical devices such as bio-sensing cantilevers and sensors/ actuators. In these applications, the exceptional piezoelectric properties of PZT have been coupled with structural elements of silicon. A further significant enhancement in the piezoelectric properties of PZT has been reported by doping with strontium [1]. In particular, the growth of PSZT films in the perovskite orientation to obtain these enhanced piezoelectric properties has recently been demonstrated using magnetron sputter deposition on Si [2]. A similar sputter technique has also been used to deposit the perovskite phase in films of lanthanum doped PZT [3]. PLZT in a perovskite orientation has been characterized by a high electro-optic coefficient with the potential for application in a range of optoelectronic and optical devices [4]. The realization of device structures in PZT has required the development of techniques of lithographic patterning. The etching of PZT has been reported by several methods which have included wet chemical etching, reactive ion etching (RIE) and ion beam etching (IBE) as summarized in ref [5]. The wet chemical etching of PZT has been restricted to coarser patterns while the definition of fine structures using IBE and RIE has been characterised by a low etch rates. An alternative technique of micromachining bulk PZT by excimer laser radiation was initially reported by Eyett et.al. [6] and further demonstrated by Konishi [7] and Desbiens [8]. These studies of laser ablation were confined to the patterning of bulk PZT. However, the use of KrF laser applied to the direct patterning of PZT-based films offers a simple process compared with the multi-step methods associated with RIE and IBE. In this paper, we examine for the first time the patterning by excimer laser of Sr and La-doped PZT films comprising a perovskite st
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