Study On The Mechanism Of Temperature Generation At The Interface Of SiC Single Crystal Substrate Solidified Abrasive Grain Friction Chemical Mechanical Polishing

Single crystal SiC materials are widely used in aerospace and chips due to their high temperature resistance,good thermal conductivity and stable chemical properties.Therefore,this paper investigates the temperature generation mechanism in the frictional chemical mechanical polishing process of solidified abrasive grains,and explains the temperature generation mechanism in the frictional chemical mechanical polishing process through theoretical calculations and experiments,so as to investigate the influence of the frictional contact interface temperature on the polished surface quality during the polishing process.The main research of this thesis is as follows:(1)To establish the temperature model of the interface of frictional chemical mechanical polishing of solidified abrasives.Set the abrasive grains and polishing pad surface micro-convexes as a whole,analyze the form of solidified abrasive polishing contact,calculate the abrasive grains force,the number of polishing pad surface micro-convexes,and the distribution of abrasive grains on the microconvexes during solidified abrasive polishing.The motion trajectory of the polishing process is analyzed,the abrasive particle velocity is calculated,and the heat source is calculated for the surface friction contact using the moving heat source analysis method.A coefficient k characterizing the heat source distribution of the abrasive grain in contact with the workpiece is introduced in the model,and the heat source distribution is simulated and calculated for the two objects in surface contact using this coefficient.(2)Measurement of the polishing interface temperature of solidified abrasives.In this paper,the temperature of polished interface is measured by a method similar to thermal coating pyrometry,which is an ex-post measurement method.Considering the high flash point temperature of the polishing interface,the titanium metal pyrometer with a larger measurement range is used as the pyrometer for the reaction temperature,and the temperature of the polishing friction interface is measured according to the change law of different physical colors of the metal surface oxide film at different temperatures.By observing the residual metal particles on the surface of the polishing pad and observing their physical characteristics and their surface generated compounds,the polishing interface temperature is determined and the feasibility of the solidified abrasive frictional chemical mechanical polishing interface temperature model is verified through experiments.(3)To investigate the effect of process parameters on the interface temperature of chemical mechanical polishing.A single-factor test method controlling the process variables(polishing pressure,polishing disc speed,and polishing time)was used for the study.The maximum steady-state temperature occurring during the polishing process was determined by the physical color of the reflection of the oxide film on the surface of the metal particles on the surface of the polishing pad after the test and the change in its surface element content.From the experimental results,it is clear that the correlation between the factors influencing the interface temperature for different process parameters is:polishing time > polishing speed >polishing pressure.(4)To investigate the relationship between the process parameters of chemical mechanical polishing of solidified abrasive grains and the polishing effect.The effect of polishing process parameters on the polishing effect(material removal rate,surface roughness)of dry mechanical friction polishing was investigated by varying two process parameters,namely polishing pressure and polishing disc speed.Under the same polishing pressure,the polishing material removal rate increased with the increase of polishing disc speed,which was the same as the results obtained from the model.At the same time,the number of abrasive grains involved in polishing is small,which causes the surface to be scratched at larger intervals when contact scratching is performed,causing the peak fluctuation of the surface topography height.The difference of the surface topography height of the wafer after the three different polishing disc speed tests remains in the same range,and the scratching depth of abrasive grains is less significant with the polishing disc speed.At the same polishing disc speed and three different polishing pressure levels,the material removal rate tends to increase with the increase of polishing pressure,the surface roughness of the tested wafers tends to increase,and the scratch depth of the surface remains at approximately the same level.The reason is that increasing the polishing pressure will increase the wear of the polishing pad,resulting in uneven distribution of surface abrasives and poor surface quality of the SiC single crystal substrate.The research results of this paper can provide a theoretical basis and new research ideas for the optimization and development of frictional chemical mechanical polishing process for SiC single crystal substrates with solidified abrasive grains.