Highly (200)-oriented Pt films on SiO 2 /Si substrates by seed selection through amorphization and controlled grain grow
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Highly (200)-oriented Pt films on SiO2ySi substrates by seed selection through amorphization and controlled grain growth Min Hong Kim, Tae-Soon Park, Dong-Su Lee,a),b) and Euijoon Yoonc) School of Materials Science and Engineering, Seoul National University, Seoul 151-742, Korea
Dong-Yeon Park,b) Hyun-Jung Woo,b) Dong-Il Chun, and Jowoong Hab) Advanced Materials Area, Tong Yang Central Laboratories, Yongin, Kyungki 449-910, Korea (Received 26 June 1998; accepted 15 October 1998)
Highly (200)-oriented Pt films on SiO2ySi substrates were successfully prepared by a combination of a dc magnetron sputtering using AryO2 gas mixtures and subsequent controlled annealing. The intensity ratio of (200) to (111) planes sI200yI111 d was over 200. The (200)-oriented Pt microcrystallites were less susceptible to amorphization due to their lower strain energy with oxygen incorporation than (111)-oriented ones. The controlled grain growth from the selected (200)-oriented seed microcrystallites during subsequent annealing provided a kinetic pathway where grain growth of the seed microcrystallites was predominant, while suppressing the nucleation of surface energy-driven, (111)-oriented seed microcrystallites and subsequent (111) preferred orientation. Oxide films with high dielectric constant are essential for the fabrication of next-generation, high-density dynamic random access memory (DRAM) devices.1 In particular, ferroelectric oxide films are indispensable for the realization of nonvolatile ferroelectric random access memory (FRAM), infrared (IR) sensors, and other functional devices.2,3 The ferroelectric oxide films, prepared by various physical or chemical methods, are normally polycrystalline. Many physical properties of the films are sensitive to the preferred orientation of the films. However, the preferred orientation of the films is affected by the preferred orientation of the bottom electrode films on which they are grown. It was reported that the quality of electrode materials for the oxide films significantly affected the device performance.4,5 It was also reported that the c-axis oriented ferroelectric oxide films on a (200)-oriented Pt electrode gave better ferroelectric properties for FRAM, IR sensors, and other optoelectronic devices.6,7 Pt is one of the most commonly used materials for the bottom electrode since it is stable during subsequent oxide deposition processes. Moreover, the Pt electrode is less leaky than RuO2 ,8 and provides better nucleation sites for ferroelectric oxide films.8,9 However, Pt films are usually (111)-oriented since (111) planes are ones with lowest surface energy. When MgO (100) single-crystal substrate was used, the formation of (200)-oriented Pt bottom electrode on the substrate could lead to the deposition of highly c-axis oriented oxide
a)
Also with Tong Yang Central Laboratories. Present address: Inostek, Inc., Rm. 37-205, Seoul National University, Seoul 151-742, Korea. c) E-mail: [email protected] b)
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