Investigation of Processing Effects on the Surface Condition of Chemical Vapor Deposition Single-Crystal Diamond by Sequential Indentation Tests

CVD single-crystal diamond is an ideal semiconductor material. Due to its ultra-high hardness and brittleness, manufacturing process is a big challenge. General manufacturing processes are divided into the rough machining and finishing machining. The processing quality in the rough processing has a great influence on the final surface quality. In this study, the sequential indentation test method was proposed for the damage layer evaluation of CVD SCD substrate. The graphitization layer and micro-crack layer can be differentiated by the contact forces recorded during the loading period. Utilizing the contact force intervals during unloading and the contact forces recorded during dwell time, one can assess the residual indentation depth and residual stress conditions. It is found that laser cutting weakens the machined surface of the diamond greatly. A new micro-crack layer may be introduced while lapping removes most graphitization layers. Polishing can improve the quality of the machined surface, so the hardness of after-polish surface is even higher than that of crystal seed and crystal growth. The rapid detection method introduced in this research is crucial for the subsequent achievement of high-efficiency and high-precision manufacturing of diamond substrates.