| With the rapid development of modern science and technology in the fields of microelectronics,precision optics and the rapid rise of industries such as cloud computing,big data,and the Internet of Things,the demand for monocrystalline silicon parts with special properties is increasing.Monocrystalline silicon substrates in integrated circuits require integrity,high quality,high precision and super-smooth surface.Monocrystalline silicon is also commonly used in high-intensity optical systems to make optical elements with high quality and mirror or Super-mirror appearance.Chemical mechanical polishing(CMP)is the most widely used technology for flattening monocrystalline silicon wafers.However,CMP still has many problems,such as low removal rate and high pollution.At present,it is urgent to develop a new polishing technologies which can be suitable for most brittle and hard materials with high precision,high efficiency,low cost,pollution-free or low pollution.In this paper,based on molecular dynamics simulation,combined with chemical mechanical polishing,ultrasonic vibration polishing and other theories,the external energy field of ultrasonic vibration is introduced into CMP technology to assist monocrystalline silicon polishing.The variation characteristics and processing mechanism of nanometer surface polished by monocrystalline silicon are analyzed and studied from the atomic point of view.The research work mainly focuses on the ultrasonic vibration assisted polishing of monocrystalline silicon molecular dynamics simulation and experimental research,which has the following aspects:(1)Summarize the research status of chemical mechanical polishing,ultrasonic vibration polishing and material removal mechanism at home and abroad,based on the abrasive wear model and the atom/molecular model material removal mechanism,the removal mechanism and intrusion theoretical model of ultrasonic vibration on single abrasive material are extracted.,to build a foundation for relevant research.(2)The flow chart of simulation was constructed based on the basic principle of molecular dynamics simulation;the ensemble and potential energy function of the simulated real environment system were selected,and the boundary conditions and integration step were set up;based on Materials Studio(MS)and LAMMPS software,the models of SiO2 abrasive particles and monocrystalline silicon matrix with different crystal surfaces were constructed and compiled.The program(in file)was compiled,Ultrasonic vibration-assisted polishing of monocrystalline silicon model was carried out,and the model energy was minimized.The potential energy of the system was analyzed.The temperature change was used to determine the equilibrium time.Finally,the system equilibrium conditions were established.(3)With the aid of molecular dynamics simulation,the mechanism of deformation in the process of ultrasonic vibration-assisted polishing of monocrystalline silicon was investigated from the atomic point of view.Comparing the surface generation,system potential energy and cutting force changes of CMP and UV-CMP under the condition of ultrasonic vibration,the influence of ultrasonic vibration process was analyzed and explained,and the influence of the change of amplitude,scratch speed and indentation depth on surface generation,material removal and system under the same condition was revealed.Under the same polishing conditions,the influence of ultrasonic vibration assistance on(100),(110)and(111)surface Nano processing was studied.(4)Through experimental research,the effect of ultrasonic vibration on polishing monocrystalline silicon was confirmed from a macroscopic point;the influence of amplitude,rotation speed and pressure on material removal rate and surface roughness was studied by means of single factor test method,the influence factors of polishing result were tested by seven factors and two levels by means of orthogonal test method,the optimal combination of parameters was obtained by range analysis and synthesis method. |
PDF Full Text Request