Evaluation of Thin Film Residual Stress through the Analysis of Stress Relaxation Path and the Modeling of Contact Morphology

응력완화 경로분석과 압입자/시편간 접촉형상 모델링에 바탕한 박막재료의 국소 잔류응력 평가

Residual stress is a dominant obstacle to efficient production and safe usage of products by reducing the mechanical strength and failure properties. Especially, it causes interfacial failure and substrate deflection in the case of thin film. So, the exact evaluation and optimum control of thin film residual stress is indispensable. However, hole drilling or X-ray diffraction techniques have some limits in application to thin film. And, curvature technique for thin film materials cannot give the information about local stress variation. Therefore, we applied the nanoindentation technique in evaluating the thin film residual stress. In this study, we modeled the change of indentation loading curve for residually stressed and stress-free thin films during stress relaxation. The value of residual stress was directly related to the indentation depth change by relaxation. The residual stress from nanoindentation analysis was consistent with the result from curvature technique.