Research On Mechanism And Process Of Polishing Monocrystalline Germanium Wafers At Low Temperature

Because of the characteristics of radiation resistance,high temperature resistance,high conversion efficiency and high reliability,the germanium-based compound solar cells have been widely used in battery systems of aerospace field.Compound cells require the epitaxial GaAs and other materials on germanium substrate,so stringent requirements for surface quality and geometric accuracy of monocrystalline germanium polished wafers are put forward.In this paper,against the existing difficulties,an innovation process of ice-fixed abrasive polishing(IFAP)monocrystalline germanium thin wafer is proposed,which provides a new tool for ultra-precision machining of hard and brittle materials.Based on the analysis of the influence of processing ambient temperature on the surface and subsurface damage of monocrystalline germanium grinding wafer,the low-temperature polishing mechanism of monocrystalline germanium wafer was studied,and the ice-fixed abrasive polishing process was studied deeply.The main work and achievements are as follows:1.Influences of ambient temperature on the processing results of monocrystalline germanium wafer.The subsurface damage depthes of monocrystalline germanium wafer after grinding at different processing temperatures were measured by angle polishing method.In addition,the friction and wear experiments of monocrystalline germanium wafers were carried out by ball milling method,and the effects of ambient temperature on the friction coefficient,wear scar morphology,wear quantity and wear mechanism were analyzed.2.Mechanism of polishing monocrystalline germanium wafer by ice-fixed abrasive pad.From the perspective of friction and wear,the influence of ice particle couples on the friction and wear behavior of germanium wafer was investigated by the face to face friction at low temperature,and the material removal mechanism of low-temperature polishing was further analyzed.It is considered that the ice-fixed abrasive polishing belongs to chemical mechanical polishing.3.Technologic processes of polishing monocrystalline germanium thin wafer with ice-fixed abrasives.Taguchi method and overall balance method were applied for optimization of the polishing conditions.The monocrystalline germanium wafers were polished using self-made micron scale ice-fixed abrasive polishing pads,and the effects of polishing parameters on material removal rate and surface roughness were analyzed.Then,the optimum technological parameters of the semi-fine polishing were comprehensively evaluated.The germanium wafers were polished finely using nanometer scale ice-fixed abrasive polishing pads,and the effects of polishing parameters on material removal rate and surface roughness were analyzed.Finally,the optimization parameters of fine polishing were obtained.