Study On Grinding Characteristics Of Single Crystal Gallium Nitride And Its Molecular Dynamics Simulation

Single-crystal gallium nitride is a third-generation semiconductor material with excellent physical and chemical properties.It has been widely used in many emerging fields such as 5G communication,energy vehicles,and so on.However,in practical applications,in addition to the good performance of Ga N itself,there are also strict requirements for shape accuracy and surface/subsurface damage of the wafer.Ga N is a typical hard-brittle hard-machining material with stable properties and excellent performance.At the same time,its high hardness,high brittleness,and,low fracture toughness make it easy to produce mechanical damage in nano-machining.Therefore,this paper aims to propose a high-efficiency and low-damage nano-machining process for Ga N.First of all,through molecular dynamics simulation and nano-scratch test,this paper explores the formation mechanism and influence factors of surface and sub-surface damage of gallium nitride in nano-scratch and obtains the best processing crystal plane and crystal orientation of gallium nitride.At the same time,a large number of studies have shown that using ultrasonic vibration-assisted grinding technology to process hard and brittle materials can effectively improve the processing efficiency and surface quality,but there are few studies on the grinding of single crystal gallium nitride materials,and its processing characteristics still need to be further studied.Therefore,this paper takes single-crystal gallium nitride material as the research object,compares the influence of various parameters on the processing effect of single-crystal gallium nitride material before and after ultrasonic vibration is applied,and explores its ultrasonic-assisted grinding characteristics.Finally,the sub-surface damage depth under different processing parameters is obtained through the section micro-corrosion test,which provides a reference for the subsequent grinding and polishing removal depth.The main contents of this article include:(1)Through nano-creating experiment and molecular dynamics simulation on different crystal planes and directions of Ga N crystal,and combining with fracture mechanics theory.Firstly,the loaddisplacement curve is analyzed to obtain the critical depth and critical load of the elastic-plastic and brittle plastic transformation of gallium nitride,and the crystal plane and direction of the first transformation.At the same time,the crack distribution and propagation direction under different conditions before and after reaching the critical depth of brittle plastic transition were observed by scanning electron microscope,and the results were verified with molecular dynamics simulation.Thus,the material removal rule and anisotropic deformation mechanism of Ga N crystal can be obtained,and the best processing crystal plane and crystal orientation of Ga N can be determined.(2)Gallium nitride was tested by ordinary grinding and ultrasonic vibration-assisted grinding.Firstly,the ultrasonic-assisted grinding system is established,and the formula of the ultrasonic-assisted motion path for single grinding is deduced.At the same time,the differences in anisotropy between Ga and N planes were analyzed by the XPS test.Then compare the grinding force,specific grinding energy,and surface roughness of gallium nitride under different grinding conditions such as the presence or absence of ultrasound,the application of ultrasound in different vibration directions,and the change of grinding depth,and comprehensively analyze the best ultrasonic vibration assisted grinding parameters of gallium nitride.At the same time,it guides the ultra-precision processing of gallium nitride and also prepares for obtaining the processing technology of high efficiency and low damage processing of gallium nitride.(3)Firstly,the formation mechanism of subsurface damage is studied,and the common detection methods of subsurface damage are introduced.In this paper,the sub-surface damage depth and defects of Ga N wafers after grinding with various processing parameters are obtained by Section microscopy and corrosion test.The influence of different vibration directions and the anisotropy of gallium nitride on the sub-surface damage defects produced by machining is analyzed to guide the removal depth of the subsequent grinding and polishing process.