습식표면처리 및 열 사이클에 따른 Cu/SiNx 계면접착에너지 평가 및 분석
Effects of Wet Chemical Treatment and Thermal Cycle Conditions on the Interfacial Adhesion Energy of Cu/SiNx thin Film Interfaces
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반도체 미세구리배선 적용을 위하여 구리배선의 습식 표면처리 및 열 사이클에 따른 구리 박막과 실리콘질화막도포층 사이의 계면접착에너지를 4점굽힘시험을 통해 정량적으로 평가하였다. 구리배선을 화학적·기계적 연마한 후 습식표면처리를 통하여 구리 박막과 실리콘질화막의 계면접착에너지는 10.57 J/m2에서 14.87 J/m2 로 증가하였다. -45~175oC범위에서 250사이클 후, 표면처리를 하지 않은 시편의 계면접착에너지는 5.64 J/m2으로, 표면처리를 한 시편은 7.34 J/m2으로감소하였으며, 모든 시편의 박리계면은 구리 박막과 실리콘질화막 계면으로 확인되었다. X-선 광전자 분광법으로 계면 결합상태를 분석한 결과, 화학적·기계적 연마 공정 후 구리배선의 표면 산화물이 습식표면처리에 의해 효과적으로 제거된 것을 확인하였다. 또한, 열 사이클 처리동안, 구리 박막과 실리콘질화막의 큰 열 팽창 계수 차이로 인한 열응력으로 인하여 구리 박막과 실리콘질화막 계면이 취약해지고, 계면을 통한 산소유입에 따른 구리 산화층이 증가하여 계면접착에너지가 저하된 것으로 판단된다.
Abstract
Effects of wet chemical treatment and thermal cycle conditions on the quantitative interfacial adhesion energyof Cu/SiNx thin film interfaces were evaluated by 4-point bending test method. The test samples were cleaned by chemicaltreatment after Cu chemical-mechanical polishing (CMP). The thermal cycle test between Cu and SiNx capping layer wasexperimented at the temperature, -45 to 175oC for 250 cycles. The measured interfacial adhesion energy increased from10.57 to 14.87 J/m2 after surface chemical treatment. After 250 thermal cycles, the interfacial adhesion energy decreasedto 5.64 J/m2 and 7.34 J/m2 for without chemical treatment and with chemical treatment, respectively. The delaminatedinterfaces were confirmed as Cu/SiNx interface by using the scanning electron microscope and energy dispersivespectroscopy. From X-ray photoelectron spectroscopy analysis results, the relative Cu oxide amounts between SiNx andCu decreased by chemical treatment and increased after thermal cycle. The thermal stress due to the mismatch of thermalexpansion coefficient during thermal cycle seemed to weaken the Cu/SiNx interface adhesion, which led to increased CuOamounts at Cu film surface.
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