Study of side burr formation in steady-state nano-polishing of Si-wafer using molecular dynamics simulation

With advancements in the semiconductor industry, it is required to have angstrom level surface finish on silicon wafers which is achieved by nano-polishing. However, side burr is formed due to material pile-up from material removal due to abrasive which becomes detrimental to achieving the high surface finish. This study employs molecular dynamics simulations to explore the mechanism underlying side burr formation during nano-polishing of mono-crystalline silicon (Si)-wafer. The study utilizes a diamond nano-abrasive grit to scratch the surface of the Si-wafer and investigates the formation of pile-ups during the steady-state process. It was observed that increasing the depth of cut by four times led to a 6.3-fold increase in the number of amorphous atoms, indicating greater bond breakage in the direction of scratching. As a result, the cutting force exceeds the thrust force at larger depths of the cut. The correlation between the side burr height and the depth of cut is also studied. Results show that the side burr height ratio increases with the depth of cut, indicating a higher sensitivity of side burr height to the depth of cut. The study suggests that to achieve a ductile mode of material removal and minimize the height of the side burr during nano-polishing of Si-wafers, it is crucial to maintain the depth of cut at or below half (≤0.5) of the abrasive radius and ensure an average friction coefficient below 0.6. The outcome of this study can be useful for the actual manufacturing of miniaturized sensors, actuators, and microsystems for microelectromechanical system devices where a high surface finish is crucial.