CoWP 박막의 전착에 대한 연구

일반대학원 에너지시스템학부
The Graduate School, Ajou University
Publication Year
electrodepositionCoWP 박막barrier layercapping layer
CoWP박막은 구리 배선의 산화 및 확산을 방지하는 능력이 탁월하여 표면보호막/산화방지막으로 사용되고 있으며, 경도와 내부식성이 우수하여 탄소강의 부식을 막는 새로운 코팅물질로 주목 받고 있다. 본 연구에서는 CoWP 박막 전착을 수행하여, 전해질 내의 각 이온의 농도, 전해질의 pH, 전착 온도의 영향에 대하여 살펴보았다. 전기화학분석을 통하여 CoWP 박막 전착의 반응속도가 물질전달속도에 의해 결정됨을 알 수 있었으며, 박막의 결정핵 생성은 instantaneous 모델을 따름을 확인하였다. 전착된 CoWP 박막 내에는 원자상태의 Co, W, P와 더불어 hydroxide/oxide가 존재하였다. 하지만 hydroxide/oxide는 주로 박막의 표면에 존재하였음을 확인하였다. CoWP 박막의 두께는 Co2+와 PO23- 이온의 농도가 증가할수록, WO42- 이온의 농도가 감소할수록 증가하였다. 전해질 농도를 변화함으로써 CoWP박막 내의 조성을 변화할 수 있었는데 Co는 64~83, W은 0.5~24, P은 6~20 at.%로 조절할 수 있었다. 박막 내의 P의 함유량에 따라 박막의 미세구조와 표면조도가 변하였다. 한편, 전해질의 pH가 증가함에 따라 박막 내 hydroxide의 양이 증가하였다. 전류 효율은 전해질의 pH가 6, 7일 때, 박막의 두께는 pH가 5일 때 최대를 보였다. 산성 전해질에서 많은 양의 P가 전착되었으며, 이에 따라 박막의 미세구조가 무정형구조를 보였다. 전착 온도가 증가함에 따라 박막의 두께와 박막 내 코발트 함유량이 증가하였으며, 이에 따라 결정의 크기도 증가하였다. 전착된 CoWP 코팅은 고온에서도 경도가 감소하지 않고 오히려 증가하였다. 또한 CoWP 코팅은 Cr 코팅에 비해 더 낮은 부식전위를 가져 내부식성 역시 우수함을 확인하였다.
Alternative Abstract
It is well-known that CoWP thin films have superior capping/barrier properties to prevent copper from oxidation and diffusion. In addition, CoWP thin films show potential properties as a coating material such as corrosion protective, hardness, and wear resistance. In this work, CoWP thin films have been electrodeposited. It has been investigated that the effect of electrolyte concentration, electrolyte pH, deposition temperature on properties of CoWP thin films. The electrochemical analyses suggested that the electrodeposition of CoWP coatings occurred under mass transfer control and followed an instantaneous nucleation. Composition analyses showed that the film contained elemental Co, W and P as well as hydroxides, oxides. A Depth-profile, however, revealed that the bulk of the films predominantly consisted of cobalt, tungsten, and phosphorus. It was observed that the thickness of CoWP thin films increased with increasing cobalt and hypophosphite ion concentrations, and decreasing tungstate ion concentration in the electrolyte. Films with larger variations of cobalt (from 64 to 83 at.%), tungsten (from 0.5 to 24 at.%) and phosphorus(from 6 to 21 at.%) were electrodeposited by controlling the concentrations of the electrolytes. CoWP thin films containing high amount of phosphorus were amorphous and had smooth surface. More hydroxide species were formed on the surface with increasing pH of the electrolyte. The highest current efficiency was found when the CoWP films were deposited from neutral or slightly acidic electrolyte and the thickest film has been obtained when it was deposited from an electrolyte of pH 5. The films deposited from acidic solutions consisted of larger amounts of phosphorus and were amorphous. As the deposition temperature was increased, the thickness and the amount of cobalt in film, the size of crystallites increased. The hardness of CoWP coatings tended to increase with temperature. Potentiodynamic polarization experiments revealed that CoWP coating showed stronger resistance to corrosion, compared to Cr coatings.

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