Journal of the Korean Vacuum Society (한국진공학회지)

The Korean Vacuum Society (한국진공학회)
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Self-Limiting Growth of ZnO Thin Films and Substrate-Temperature Effects on Film Properties

자기제한적 표면반응에 의한 ZnO 박막성장 및 기판온도에 따른 박막특성

  • Lee, D.H. (Department of Applied Physics, Dankook University) ;
  • Kwon, S.R. (Department of Applied Physics, Dankook University) ;
  • Lee, S.K. (Department of Applied Physics, Dankook University) ;
  • Noh, S.J. (Department of Applied Physics, Dankook University)
  • 이두형 (단국대학교 응용물리학과) ;
  • 권새롬 (단국대학교 응용물리학과) ;
  • 이석관 (단국대학교 응용물리학과) ;
  • 노승정 (단국대학교 응용물리학과)
  • Published : 2009.07.30
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Abstract

An inductively coupled plasma assisted atomic layer deposition(ICP-ALD) system has been constructed for the deposition of ZnO thin films, and various experiments of ZnO thin films on p-type Si(100) substrates have been carried out to find the self-limiting reaction conditions for the ICP-ALD system under non-plasma circumstances. Diethyl zinc[$Zn(C_2H_5)_2$, DEZn] was used as the zinc precursor, $H_2O$ as the oxidant, and Ar as the carrier and purge gas. At the substrate temperature of $150^{\circ}C$, atomic layer deposition conditions based on self-limiting surface reaction were successfully obtained by series of experiments through the variation of exposure times for DEZn, $H_2O$, and Ar. ZnO deposition was repeated at different substrate temperatures of $90{\sim}210^{\circ}C$. As a result, the thermal process window(ALD window) for ZnO thin films was observed to be $110{\sim}190^{\circ}C$ and the average growth rate was measured to be constant of 0.29 nm/cycle. Properties of the film's microstructure and composition(Zn, O, etc.) were also studied. As the substrate temperature increases, the crystallinity was improved and ZnO(002) peak became dominant. The films deposited at all temperatures were high purity, and the films deposited at high temperatures had the composition ratio between Zn and O closer to one of a stable hexagonal wurtzite structure.

ZnO에 대한 박막증착 연구를 위하여 유도결합 플라즈마 원자층박막증착(inductively coupled plasma assisted atomic layer deposition: ICP-ALD) 장치를 제작하고, 장치에 대한 기본 공정조건을 설정하기 위하여 플라즈마를 유도하지 않은 상태에서 p-type Si(100) 기판 위에 ZnO 박막을 증착하는 다양한 실험을 수행하였다. Zn 전구체(precursor)로는 Diethyl zinc [$Zn(C_2H_5)_2$, DEZn]를, 반응가스(reaction gas)로는 $H_2O$를, 캐리어(carrier) 및 퍼지가스(purge gas)로는 Ar을 사용하였다. 기판온도 $150^{\circ}C$에서 DEZn, $H_2O$, Ar의 공급시간을 변화시켜가면서 자기제한적 표면반응(self-limiting surface reaction)에 의한 박막성장조건을 성공적으로 유도하였다. 기판온도를 변화시켜가면서($90{\sim}210^{\circ}C$) 증착실험을 반복하여, 본 장치에 대한 ALD 공정온도(thermal ALD process window)를 확립하고 성장된 ZnO박막에 대한 증착특성, 결정성, 불순물 및 내부조성비등을 조사하였다. ALD 공정온도는 기판온도 $110{\sim}190^{\circ}C$로써 이 구간에서의 박막 평균증착률은 0.29 nm/cycle로 일정하게 나타났다. 기판온도가 높아질수록 결정성이 향상되어 ZnO(002) 피크가 우세하였다. 모든 ALD 공정온도에서 Zn와 O로만 구성된 고순도의 ZnO 박막을 실현하였는데, 온도가 높아질수록 Zn와 O의 비가 1에 근접하며 안정된 hexagonal wurtzite ZnO 구조의 박막이 성장되었다.

Keywords

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  1. Self-Limiting Growth of ZnO Thin Films and Substrate-Temperature Effects on Film Properties vol.18, pp.4, 2009, https://doi.org/10.5757/JKVS.2009.18.4.296