Atomic Understanding of the Formation Mechanism of Nanoscratches on the Surface of Indium Phosphide in Different Tool Directions

Nanoscratch is a key experimental method for evaluating material mechanical properties, studying material removal mechanisms, and revealing surface damage formation mechanisms at the nanoscale. In the semiconductor, microelectronics, and optoelectronics industries, nanoscratches on the surface of InP substrates are considered fatal defects that must be eliminated, as they can seriously affect the performance and reliability of devices. However, in the chemical mechanical polishing (CMP) process of InP, the formation of nanoscratches is difficult to avoid, and precise control is the core challenge to achieve atomic level smooth surfaces. To address this challenge, this study systematically investigated the effects of three typical scratch directions (Face-forward (FF); Edge-forward (EF); Side-face-forward (SFF)) of the Berkovich indenter on the single crystal InP(001) substrate during the nanofabrication process using molecular dynamics simulation (MD) and nanoscratch experiments. The research focuses on analyzing the evolution of surface morphology, scratch force response, and the material removal mechanism. The results indicate that the material removal mechanism of InP in the nanoscratch process is characterized by the coexistence of elastic and plastic deformation, and the damage is mainly manifested by the initiation and propagation of transverse microcracks and the accumulation of sheet-like chips. Compared with the EF direction, the FF direction can significantly reduce the lateral extension length of the groove by about 52%-55%; under the condition of small rake angle, the material removal rate is increased by about 8%-17% compared to the condition of large rake angle. The plastic transformation rate is highest in the EF direction with an average of 31%. The experimental results are highly consistent with the simulation results: the atomic displacement map simulated by MD and the SEM characterization of the experiment both show that the morphology and distribution characteristics of the chips are consistent under different scratch directions. The mechanism revealed in this study provides important theoretical basis and process guidance for effectively suppressing nanoscratch defects in the InP CMP process.