Study On Polishing Characteristics Of Different Doped Silicon Wafers

Nowadays,with the rapid development of information technology,the manufacturing of large-scale integrated circuit(IC)has higher and higher requirements for the substrate silicon wafer.In order to improve the overall performance of IC,the requirements of silicon wafer processing technology in the surface state,micro flatness and other aspects have reached the nanometer level.The micro-flatness and surface state of silicon wafer surface are mainly determined by the polishing process,and the polishing results are affected by many factors,among which the influence of silicon wafer properties on the polishing results is rarely studied.Widely used in this paper,through selecting the different doping concentration of boron,heavy mineral arsenic,antimony doped three silicon wafer polishing processing,and the cleaning after polishing,explore different doping concentrations,different dopant silicon on polishing removal rate and the influence of micro surface roughness after polishing,and thus to explore silicon dopant concentration and different influence on polishing removing mechanism,proposed to improve the boron silicon micro roughness of the surface of the method.In the experiment,the polishing time was kept the same,and the state of polishing liquid and polishing pad was consistent,so that the difference of polishing results was independent of polishing process parameters such as polishing time,polishing pressure and rotational speed.The experimental results show that the higher the doping concentration of p-type silicon wafer is,the lower the polishing removal rate is,and the higher the surface micro-roughness is,and the worse the surface micro-flatness is.The polishing removal rate of p-type silicon wafer with the same doping concentration was lower than that of n-type silicon wafer,while the surface micro-roughness was higher than that of n-type silicon wafer.Due to the removal of principle of chemical mechanical polishing technology is mainly composed of silicon wafer surface react with the alkaline polishing liquid and polishing pads and polishing abrasive friction to remove the reaction products of two aspects,the polishing pressure and rotational speed under the condition of identical,mechanical action of the effects of different silicon,produce difference in micro surface roughness after polishing and polishing removal rate is the main reason of the different between wafer and polishing solution chemistry under the influence of dopant concentration and types.When different impurity atoms are introduced,the intrinsic defects of direct pull silicon single crystal will interact with impurity atoms to form micro-defects on the surface of silicon wafer before polishing,resulting in the agglomeration of impurity atoms.During polishing,these micro-defects cause the surface of the silicon wafer to form a local micro-battery for local electrochemical reaction,where the anode reaction is:Si+60H-?SiO32-+3H2O+4e-,cathode reaction is:2H++2e-?H2 T.P-type silicon mixed with a large number of B,B to participate in the electrochemical cathodic reaction,make its reaction rate decreased,which makes the chemical reaction rate drop,when polishing not only results in mixed B silicon wafer polishing removal rate is low,still can make the role of the mechanical polishing and chemical action of the matching degree is reduced,the wafer surface roughness after polishing;In contrast,the impurity atoms introduced into n-type silicon wafer play an opposite role,accelerating the chemical reaction of the silicon wafer during polishing and better matching with the mechanical action,so that the polishing result of the silicon wafer is better.Based on the above analysis,the pH value of p-type silicon wafer polishing solution was reduced,so that the electrochemical cathodic reaction and anode reaction were relatively balanced,and the chemical and mechanical effects during polishing were matched.As a result,the micro-roughness of the surface of p-type silicon wafer after polishing was reduced,and the micro-flatness of the surface was improved.