Experimental Study Of CMP Based On Fenton Reaction For Gallium Nitride Wafer

As integrated circuits and communication technologies in the electronic information industry have increasingly higher requirements on the quality and manufacturing standards of third-generation semiconductors,gallium nitride a a third-generation semiconductor material with superior performance,wide band gap and high critical breakdown field strength,high electron mobility,high thermal conductivity and other excellent characteristics have broad applications in blue light illumination,high temperature,high frequency and anti-irradiation devices.In order to achieve a low environmental load and energy-saving society,next-generation optoelectronic devices based on gallium nitride(Ga N)have received much attention.Therefore,it is very meaningful to study the process of surface planarization of Ga N crystals.In order to achieve the surface planarization of gallium nitride crystals,based on four different oxidation reactions of Fenton reaction,sodium persulfate,potassium permanganate,and potassium hydroxide,oxidation reaction experiments and chemical mechanical polishing methods were used for the sapphire-based substrate gallium nitride single crystal thin film to study the mechanism of chemical action,chemical influencing factors,mechanical influencing factors,process parameters and so on.First,the oxidation reaction experiment was carried out on the gallium nitride crystal based on sapphire substrate for Fenton reaction,sodium hydroxide solution,sodium persulfate solution,and permanganic acid.oxidation effects of four different oxidants on gallium nitride were studied,detecte the energy spectrum and morphology of the crystal surface before and after the corrosion reaction,observe the surface morphology of gallium nitride before and after the oxidation reaction,analysis of the mechanism of gallium nitride in different chemical reactions,and determine the chemical reaction with the rate of optimal oxidation reaction of gallium nitride.The study found that after the four oxidation reactions,oxide layers with different shapes,numbers,and sizes can appear on the surface of the gallium nitride crystal.The oxide layer on the surface of the gallium nitride crystal after the Fenton reaction is the most obvious,and the oxidation range is the largest.Using scanning electron microscopy to detect the four oxidation regions after reaction,it was found that the content of oxygen in the spectrum of the oxidation region of gallium nitride after Fenton reaction increased the most significantly.Then,a polishing solution containing four different oxidants was prepared to conduct chemical mechanical polishing experiments on the gallium nitride crystals,and the surface morphology after polishing was tested,combine with the chemical action mechanism and polishing results of gallium nitride under the four oxidants to choose the best oxidation reaction to have systematic research.The polishing experiment shows that the surface roughness of the gallium nitride crystal after polishing is Fenton reaction,potassium permanganate,sodium persulfate,and potassium hydroxide,the roughness after polishing is at least Ra3.2nm.The results of the polishing experiment are in good agreement with the results of the oxidation experiment.Therefore,determine the Fenton reaction as the preferred reaction principle of gallium nitride chemical mechanical polishing for subsequent systematic research.On this basis,Fenton reaction test solutions of different mass fractions were prepared for gallium nitride polishing experiments,combined with the effect of the type and particle size of the catalyst on the experimental polishing effect,the chemical mechanical polishing rules and principles of gallium nitride crystals were studied and optimized the best chemical reaction parameters.The study found that the gallium nitride crystals polished with different mass fractions has the best surface quality after polishing the gallium nitride crystals with 7.5%mass fraction of Fenton reaction solution and the lowest surface roughness is Ra3.21nm.Comparing the polishing effect of the solid-phase catalyst under the two particle sizes,the surface quality of the iron oxide powder catalyst with a small particle size after polishing is better,which is Ra2.4nm.The ferrous sulfate solution catalyst can accelerate the oxidation reaction more than the solid powder catalyst,and the surface quality after polishing is better(the surface roughness is lower at Ra1.2nm).Finally,the CMP process test was carried out on the single crystal gallium nitride film,and the single factor test method was used to study the influence of the parameters on the polishing effect of single crystal gallium nitride film which includes type of abrasive,abrasive concentration,abrasive particle size,polishing time,polishing pressure,polishing wheel speed,magnetorheological fluid flow,processing time,and then the orthogonal optimization experiment was carried out on the main process parameters such as abrasive particle size,abrasive concentration and polishing speed during the polishing process,and the analysis of different processing parameters on single crystal gallium nitride Thin film chemical mechanical polishing polishing quality affects the degree,and determine the optimized process parameters of gallium nitride single crystal thin film.Orthogonal experimental results show that the degree of influence of different factors on the surface roughness of CMP polishing of gallium nitride from large to small is as follows:polishing disc speed>abrasive concentration>polishing pressure>abrasive particle size.When the polishing disc rotation speed is 60r/min,the polishing pressure is 2.25kg/cm~2,the abrasive particle size is 60nm,and the abrasive concentration is 25wt%,the polishing effect is the best,and the surface roughness can reach Ra0.92nm.