Study On The Influence Of Silicon Doping And Magnetic Field On Metal-assisted Chemical Etching

Silicon has received much attention and widely studied in the 21st century and can be fabricated into the micro/nano-structures with specific pattern by using metal-assisted chemical etching（MACE）with the advantages of low cost,simple process and controllable etching scale.The doping concentration of silicon substrate,etchant ratio,catalyst and other factors all affect the fabrication of silicon nanostructures to some extent in MACE.Therefore,the thesis explored the effect of doping concentration of silicon substrate and etchant on the density of etched pores.Moreover,the effect of applying magnetic field and other factors on etching rate were also creative proposed by using Fe₃O₄@Au magnetic nanoparticles as catalyst in etching reaction and faster etching was realized.In the thesis,firstly,porous silicon structures were obtained after P（100）silicon substrates with resistivity of 0.01Ω·cm and 10.65Ω·cm in an etchant ratio（amount of substance concentration of HF/（amount of substance concentration of HF+amount of substance concentration of H₂O₂））of 0.7with Ag particles as catalyst after being etched for 1 hour.It was found that the density of etched pores increased as the silicon doping concentration increased.After that,the heavily doped P（100）silicon wafer with resistivity of 0.0013Ω·cm was etched for 1 hour in an etchant solution with different etchant ratio of 0.5 and 0.7.It can be seen that a water ripple-like pattern was observed on the surface of the silicon wafer and was visible to the naked eyes.It was later found out that the resistivity of this wafer was not uniformly doped in the microscopic scale by analyzing the density of porous silicon and this conclusion was verified by using the two-point probe measurement technique.Therefore,it is a simple and convenient method to detect the doping uniformity at the microscopic scale of highly doped P type silicon by using MACE.Then in the thesis,Fe₃O₄@Au magnetic nanoparticles were used as catalyst and the etching rate was obviously improved by applying an external magnetic field.Furthermore,the effects of resistivity,etching time,etchant ratio and the concentration of catalyst on the etching reaction were also investigated under an applied magnetic field.The result of the experiment showed that the average rate could reach 12.00μm/min and the etched structure was smoother and flatter after the silicon wafer with resistivity of 0.01～0.03Ω·cm was etched for 30 minutes.However,the average etching rate was only 5.17μm/min and the bottom of etched structure was relatively rough for the silicon wafer with resistivity of 20～30Ω·cm.At the same time,it was found that the average etching rate had a positive relationship with the etchant ratio and the concentration of the catalyst.