서지주요정보
Sb 첨가를 통한 PZT박막의 electrical degradation mechanism에 관한 연구 = A study on the electrical degradation mechanism in PZT thin films by Sb addition
서명 / 저자 Sb 첨가를 통한 PZT박막의 electrical degradation mechanism에 관한 연구 = A study on the electrical degradation mechanism in PZT thin films by Sb addition / 최원열.
저자명 최원열 ; Choi, Won-Youl
발행사항 [대전 : 한국과학기술원, 1998].
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등록번호

8009217

소장위치/청구기호

학술문화관(문화관) 보존서고

DMS 98039

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초록정보

Lead zirconate titanate(PZT) is a ferroelectric materials which has perovskite structure. The PZT film is one of the promising materials applicable to capacitors in memory devices, such as dynamic random access memory(DRAM) and ferroelectric non-volatile memory(FRAM), because of its high dielectric constant, high remanent polarization and P-E hysteresis properties. There has been much research on integrated PZT thin film memories for the past several year. In particular the fatigue properties of PZT thin films, which is a critical problem in applications for FRAM devices, has been extensively studied. To date, many approaches to overcome the switching fatigue problem have been proposed. However, the detailed doping effects have not been firmly established and Sb doping effects in PZT thin films have never been reported. In this study, PZT thin films have been grown on platinized Si substrates at 550℃ by d.c. reactive sputtering using multi-target. The multi-target sputtering method leads to better control of the process in the case of multi-component films. Sb doped reactive sputtering-derived $Pb(Zr,Ti)O_3$ (Zr/Ti=48/52) thin films were investigated with the intention of improving ferroelectric properties. 5Ø Sb pellets were co-sputtered in order to add Sb in PZT film. Also, the atomic valence of Sb in PZT thin film was confirmed as trivalent cation $(Sb^{3+})$ by x-ray photoelectron spectroscopy(XPS). According to the electronegativity difference and tolerance factor t, $Sb^{3+}$ tends to occupy the B-site of $ABO_3$ perovskite structure and acts as an acceptor that generates oxygen vacancies and holes. Transmission Electron Microscope(TEM) was used to observe the structural changes of PZT thin films by Sb addition. The leakage current densities, Pr, Ec, Ei and polarization offset in lightly doped(< 1at%) PZT thin films increased as the Sb contents increased, but for heavily doped(> 1at%) PZT thin films, these parameters decreased. 0.7at% Sb doped PZT(PZST07) thin films exhibited improved fatigue properties (about 10% degradation of the remanent polarization after $10^9$ switching cycles). In order to observe the grain size effect, PZT and PZST thin films were annealed in oxygen atmosphere at 650℃, 30min. Annealed PZT and PZST thin films have a good fatigue behavior with larged grain size. Annealed PZST thin film is fatigue free to $10^{11}$ switching cycles and have a larger remanent polarization(33μC/㎠) than $SrBi_2Ta_2O_9$(SBT) thin films. Pt bottom electrodes with (111) and (200) preferred orientation were used in order to control the orientation of the PZT thin films. PZT thin film with (111) preferred orientation has a larger saturated polarization than that with (100) preferred orientation. Also this preferred orientation of PZT thin films did not affect the fatigue property. Pb concentration was controlled by the variation of Pb target current. This relation was expressed as y=0.89x-11.09. The pyrochlore phase was transformed to perovskite phase as Pb concentration was increased. This phase transformation improved the electrical properties of PZT thin films. In perovskite phase, fatigue properties were not improved with Pb concentration. Pb concentration(Pb vacancy) did not affect the fatigue properties of PZT thin films. Finally, main factor on fatigue properties was grain size. Microstructure(grain size) effect was predominant in fatigue behavior of PZT to ionic defects(oxygen vacancy and Pb vacancy).

서지기타정보

서지기타정보
청구기호 {DMS 98039
형태사항 iv, 135 p. : 삽도 ; 26 cm
언어 한국어
일반주기 저자명의 영문표기 : Won-Youl Choi
지도교수의 한글표기 : 김호기
지도교수의 영문표기 : Ho-Gi Kim
학위논문 학위논문(박사) - 한국과학기술원 : 재료공학과,
서지주기 참고문헌 : p. 132-135
주제 d.c. 반응성 스퍼터링
전기적 열화
피로
PZT박막
d.c. reactive sputtering
Electrical degradation
Fatigue
PZT thin film
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