Journal of the Korea Institute of Information and Communication Engineering (한국정보통신학회논문지)

The Korea Institute of Information and Commucation Engineering (한국정보통신학회)
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Fatigue and Retention Characteristics of PLZT(10/y/z) Thin films with Various Zr/Ti Concentrations Ratio

PLZT(10/y/z) 박막에서 Zr/Ti 농도에 따른 피로와 리텐션 특성

  • 정양희 (여수대학교 전기공학과) ;
  • 강성준 (여수대학교 반도체학과)
  • Published : 2005.06.01
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Abstract

The effects of Zr/Ti concentration ratio in PLZT (10/y/z) thin films prepared by sol-gel method are investigated for the NVFRAM application. As Ti amount of Zr/Ti concentration ratio increases, the dielectric constants at 10 kHz decrease from 550 to 400, while the loss tangents increase from 0.028 to 0.053 and the leakage current densities at 170 kV/cm decrease from $1.64\times10^{-6}$ to $1.26\times10^{-7}\;A/cm^2$. In the results of hysteresis loops measured at $\pm170kV/cm$, the remanent polarization and the coercive field increase from 6.62 to $12.86{\mu}C/cm^2$ and from 32.15 to 56.45 kV/cm, respectively, according to the change from 40/60 to 0/100 in Zr/Ti concentration ratio. Fatigue and retention properties also improve much as the Zr/Ti concentration ratio change from 40/60 to 0/100. After applying $10^9$ square pulses with $\pm5V$, the remanent polarization of the PLZT (10/40/60) thin film decreases $50\%$ from the initial state while that of the PLZT (10/0/100) thin film decreases $28\%$. In the results of retention measurements of 10s s, the remanent polarization of the PLZT (10/0/100) thin film dec.eases only $10\%$ from the initial state, while that of the PLZT (10/40/60) thin film decreases $40\%$.

Sol-gel 법을 이용하여 La를 $10mo1\%$로 고정시킨 PLZT(10/y/z) 박막을 제작하여 Zr/Ti 조성비에 따른 전기적 특성을 조사하였다. Zr/Ti 조성비에서 Ti 함유량이 증가함에 따라, 10kHz에서 비유전률은 550에서 400으로 감소된 반면, 유전손실은 0.028에서 0.053로 증가되었으며, 170kV/cm에서 누설전류밀도는 $1.64\times10^{-6}$에서 $1.26\times10^{-7}\;A/cm^2$으로 감소되었다. PLZT 박막의 이력곡선을 $\pm170kV/cm$에서 측정한 결과, Zr/Ti 조성비가 40/60에서 0/100로 변화함에 따라 PLZT 박막의 잔류분극과 항전계는 6.62에서 $12.86{\mu}C/cm^2$, 32.15에서 56.45kV/cm로 각각 증가되었다. $\pm5V$의 사각펄스를 $10^9$회 인가하여 피로특성을 측정한 결과, PLZT(10/40/60) 박막의 잔류분극은 초기분극 값으로부터 $50\%$ 감소된 반면, PLZT(10/0/100) 박막은 $28\%$ 감소되었다. 또, $10^5$초의 retention 측정 결과에서 PLZT(10/0/100) 박막은 초기분극 값에서 오직 $10\%$만이 감소된 반면, PLZT(10/40/60) 박막은 $40\%$ 감소되었다.

Keywords

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