Effect of High Temperature Annealing on the Characteristics of SiC Schottky Diodes

고온 열처리 공정이 탄화규소 쇼트키 다이오드 특성에 미치는 영향

  • 정희종 (동의대학교 전자정보통신공학부) ;
  • 방욱 (한국전기연구원 전력반도체그룹) ;
  • 강인호 (한국전기연구원 전력반도체그룹) ;
  • 김상철 (한국전기연구원 전력반도체그룹) ;
  • 한현숙 (경남대학교 전자전기공학부) ;
  • 김형우 (한국전기연구원 전력반도체그룹) ;
  • 김남균 (한국전기연구원 전력반도체그룹) ;
  • 이용재 (동의대학교 전자정보통신공학부)
  • Published : 2006.09.01


The effects of high-temperature process required to fabricate the SiC devices on the surface morphology and the electrical characteristics were investigated for 4H-SiC Schottky diodes. The 4H-SiC diodes without a graphite cap layer as a protection layer showed catastrophic increase in an excess current at a forward bias and a leakage current at a reverse bias after high-temperature annealing process. Moreover it seemed to deviate from the conventional Schottky characteristics and to operate as an ohmic contact at the low bias regime. However, the 4H-SiC diodes with the graphite cap still exhibited their good electrical characteristics in spite of a slight increase in the leakage current. Therefore, we found that the graphite cap layer serves well as the protection layer of silicon carbide surface during high-temperature annealing. Based on a closer analysis on electric characteristics, a conductive surface transfiguration layer was suspected to form on the surface of diodes without the graphite cap layer during high-temperature annealing. After removing the surface transfiguration layer using ICP-RIE, Schottky diode without the graphite cap layer and having poor electrical characteristics showed a dramatic improvement in its characteristics including the ideality factor[${\eta}$] of 1.23, the schottky barrier height[${\Phi}$] of 1.39 eV, and the leakage current of $7.75\{times}10^{-8}\;A/cm^{2}$ at the reverse bias of -10 V.


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