Molecular Dynamics Simulation And Experimental Research On Precision Lapping/Polishing Of Single-Crystal Silicon

The hard and brittle materials, generally present many incomparable advantagescompared with the general metals, such as high strength, high hardness, highbrittleness, fine wear resistance, good heat insulation property and chemical stability,have been widely applied in many areas. As the yield strength of the hard and brittlematerials approach their ultimate strength, the material would occur rupture failurewhen the external stress is slightly greater than the yield strength, and the surfacedefect, micro crack and concave pit would develop, and these phenomenon indicatethe weak machinability of the material. The vast majority of semiconductor materialsare hard and brittle materials, such as monocrystalline silicon, whose surface qualityaffects the performance, integration level, reliability and rate of finished products ofsemiconductor apparatus, therefore, the relevant techniques are required to improve.From the preparation to fabrication of monocrystalline silicon, many technologicalprocesses are required including mechanical and chemical processes, such as cutting,grinding and polishing, these processes would inevitably lead to the surface defects ofsilicon chip, such as surface residual stress, micro crack, micro scratches and latticedistortion, which are not expected as machining damage, and the tiny changes ofphysicochemical properties of the machining surface would lead to the invalidation ofsemiconductor apparatus. Although the CMP (chemico-mechanical polishing) isconsidered as the best global planarization technology currently, and is widely used inthe fabricating of IC (integrated circuit), deeply the investigating of high surfacequality and processing efficiency of the hard and brittle material become the perpetualtopic in the mechanical manufacturing area.This paper firstly introduces and discusses the theories of grinding and polishingas well as classical model of material removal, and the development tendency ofultra-precise grinding and polishing technology and CMP technology were alsosummarized. Based on the molecular dynamic simulation and experimental research,the deep research foundation of ultra-precise grinding and polishing technology ofmonocrystal silicon chip was established.The experiments of the article depended on changing the technological parameterduring the process of grinding and polishing, such as polishing pressure, rotationalspeed, polishing time, diameter of abrasive grain, concentration of abrasive grain, etc.Via the quantitative research and simulation analysis material on the removal rate andsurface roughness of monocrystal silicon piece, a series of optimized technologicalparameters were obtained. The relatively appropriate polishing speed of20r/min andupper limit of50r/min and concentration of abrasive grain of12%were obtained asthe main experimental conclusions.With the aid of molecular dynamics simulation, a series of simulations wascarried out to explore the deformation mechanism of nanometer grinding process onmonocrystal silicon. With the variation of grinding particle geometry parameters andconditions of different grinding process, the grinding force, atomic energy, subsurfacedamage depth were analyzed. In addition, the simulation results also revealed theinfluence of the rotational velocity process on the aspects of the evolution of the energy, grinding force, stress change. Research shows that when the rotationalvelocity increases, the material chips ahead of the abrasive reduce. The materialremoval mechanism by pushing extrusion mode changed for adhesion wear mode.Abrasive particle rotational velocity would influence the finishing surface quality andthe wear of abrasive particles.