Anisotropy of machined surfaces involved in the ultra-precision turning of single-crystal silicon—a simulation and experimental study

Abstract

A new method was proposed for simulating the anisotropic surface quality of machined single-crystal silicon. This represents the first time that not only the mechanical properties of silicon, but also the crystal orientation, which is closely linked to the turning process, have been given consideration. In this paper, the crystallographic relationship between machined crystal planes and slip planes involved in ultra-precision turning was analyzed. The elasticity, plasticity, and brittleness properties of silicon in different crystal orientations were calculated. Based on the brittle-ductile transition mechanism of ultraprecision turning of single-crystal silicon, the orientation dependence of the surface quality of (111), (110), and (100) crystal planes were investigated via computer simulation. According to the simulation results, the surface quality of all machined planes showed an obvious crystallographic orientation dependence while the (111) crystal plane displayed better machinability than the other planes. The anisotropic surface properties of the (111) plane resulted from the continuous change of the cutting direction, which causes a change of actual angle between the slip/cleavage plane and machined plane. Anisotropic surface properties of planes (100) and (110) result from anisotropy of mechanical properties and the continuous changes of the cutting direction, causing the actual angle between slip/ cleavage plane and machined plane to change simultaneously. A series of cutting experiments were carried out on the (111) and (100) crystal planes to verify the simulation results. The experimental results showed that cutting force fluctuation features and surface roughness are consistent with the anisotropy characteristics of the machined surface as revealed in simulation studies.

Influence of temperature on the anisotropic cutting behaviour of single crystal silicon: A molecular dynamics simulation investigation

“…Moreover, it has been experimentally demonstrated that the (111) silicon surface provides a finer quality of machined surface roughness [1] and requires low specific cutting energy. Overall, it can be inferred that the (111)<1 ̅ 10> and (010)<100> crystal setups are the easy cutting combinations of orientation and directions for cutting silicon which is in accord with the published experimental results [29].…”

“…leading to the variation of the force acting on the tool along the length of cut. Also, experiments [29] and simulations [30] have shown that silicon is an intrinsically-anisotropic material even during cutting at room temperature. Hence, calculation of machining force was necessary and to do this, the total force exerted by the carbon atoms of the cutting tool on the silicon workpiece was calculated.…”

An atomistic simulation investigation on chip related phenomena in nanometric cutting of single crystal silicon at elevated temperatures

“…On the contrary, larger shear plane angle is witnessed while cutting silicon on the (111) crystal plane, manifesting higher machinability which confirms that (111)< 0> crystal setup is the easy cutting direction, in agreement with the experimental results [21][22]. …”

Weakening of the anisotropy of surface roughness in ultra-precision turning of single-crystal silicon

“…16 ), it is found that in order to obtain a high-quality surface with less anisotropy of surface roughness, the spindle speed should be higher than 1000 r/min, the cutting depth should be less than 2 μm, the feed rate should be smaller than 2 μm/r, and the edge radius of the diamond tool should be less than 50 nm with a -40° rake angle.…”

“…16 These dislocations can prevent crack extension within the silicon, but some dislocations inevitably form an atomic step on the machined surface. The heights of these atomic steps left behind in the surface of the workpiece can be considered as the scale of surface roughness that can be achieved by ultra-precision cutting.…”