Basic Research On Polishing Monocrystalline Germanium Slices With Ice-fixed Abrasive Tools

As an important semiconductor material,germanium has excellent physical and chemical properties.In addition to the semiconductor industry,the germanium has a wide range of applications in the field of infrared optics,solar cells,chemical catalysts,biomedical field and others.As a single crystal germanium wafer for solar cell substrate,its shape accuracy,surface roughness,surface uniformity and processing efficiency have a higher demand.At the same time,the germanium belongs to brittle material.It is very difficult in achieving high-quality processing of ultra-thin single crystal germanium wafer.In this thesis,combined with low temperature polishing,fixed abrasive polishing and chemical mechanical polishing technology,a new method of ice-fixed abrasive polishing was proposed to polish single crystal germanium wafer.The polishing temperature field,the relative velocity field,the stress field and the processing technology were studied.The main work and achievements are as follows:1.A finite element analysis(FEA)model was established by ABAQUS software.The temperature field and melting thickness of ice-fixed abrasive polishing tools were obtained at different polishing times.The results of the model were validated by temperature measurement device.The effects of polishing time,initial temperature of ice tray,ambient temperature,cylinder pressure and rotational speed of ice tray on the temperature field were analyzed by using the established finite element model.2.The force analysis of the precision polishing system was carried out,and the method to improve the speed of workpiece was discussed.The influences of speed ratio and eccentricity on relative velocity distribution were analyzed.The stress field distribution of the load mode,ambient temperature,cylinder pressure and thickness of the carrier were studied by finite element analysis.The variation of the workpiece surface after polishing was controlled.3.The study on the processing technology of polishing single crystal germanium wafer with icefixed abrasive polishing tool was carried out.The effect of H2O2 on the polishing process was analyzed.The influences of ambient temperature,rotational speed of ice tray,cylinder pressure and polishing time on material removal rate during rough polishing were analyzed and optimized and the influences of them on surface roughness during fine polishing were analyzed and optimized.The optimized process parameters were obtained.