Evaluation of Stoney equation for determining the internal stress of DLC thin films using an optical profiler

Abstract

Excessive internal stresses in Diamond-like Carbon (DLC) films induced by the energetic ion bombardment during the deposition cause poor adhesion even delamination of the thin films from the substrate surfaces. As a result, determination of internal stresses in DLC films is essential for their applications. In this study, DLC thin films were prepared on thin silicon wafers with different shapes and sizes by end hall ion beam deposition. Optical profiler was used to measure the curvature of the samples before and after DLC deposition and then the Stoney equation was used to calculate the residual stress of DLC thin films in order to evaluate the feasibility of this method for measurement of DLC stress. For this purpose, the curvature radius in different directions of all the samples was measured before and after DLC deposition by the optical profiler. The calculated stress values using Stoney equation for all the samples are the same within reasonable errors. These results show that this simple method is appropriate and reliable for stress measurement of DLC films.