Edge chipping minimisation strategy for milling of monocrystalline silicon: A molecular dynamics study

Abstract

Direct patterning of functional microstructures on monocrystalline silicon by mechanical micro-milling has drawn intense interests as an alternative to the conventional lithographybased technique in microelectronics fabrication. Despite the micro milling offers advantages such as versatility and low operating cost, machining induced defects such as edge chipping occur on the surface edges of a finished product and may affect its functionality. To address such challenge, a novel hybrid technique that combines mechanical machining and the deposition of a layered sacrificial structure on the silicon surface was proposed to minimise the machining induced edge chipping. In this paper, the cutting mechanism of silicon under the proposed hybrid technique has been studied by molecular dynamics simulation. Fundamental mechanisms such as material deformation, chip formation and stress behaviour are analysed.Reduction of stress intensity and machining forces has been observed when silicon was machined under the proposed hybrid conditions. The effect is believed to be contributed by thermal softening, resulted from the high cutting temperature and interfacial stress between the copper and silicon layers. In addition, machining silicon by the proposed hybrid technique also showed desirable properties which include low subsurface damages, large material removal rate and better surface finishing (Ra<0.1 nm). The results further enriched the machining theory and justified the feasibility for the proposal of such a hybrid technique.

Influence of the metal coating on nano-cutting process of cubic silicon carbide

“…11 The potential function used between the coated Cu atom and the Si atom in the workpiece in Model 1 and Model 3 is the Tersoff potential function improved by Zhang et al 37 The two-body potential Morse is used between all tool atoms, workpiece atoms, and coating atoms, and its parameters are taken from literature. 23,38,39 For Ni-Ti alloy coating and Ni coating, the MEAM potential function is used between metal atoms. 40 Finally, all models and data output are implemented using MDS software LAMMPS.…”

“…21,22 In addition to the method of surface modification by destroying the atomic structure of the workpiece surface, the effect of surface modification can also be achieved by adding a coating on the workpiece surface. Choong et al 23 achieved surface modification by covering the surface of monocrystalline silicon with an amorphous copper layer. It has been proposed that covering the workpiece surface with water film can greatly improve the processing quality.…”