Experimental Study On The Effect Of Photoelectric Field On Photoelectrochemical Mechanical Polishing Of GaN Wafers

Gallium nitride has promising applications in optoelectronic,high-power,and high-frequency devices owing to its excellent properties of wide band gap,stable crystal structure,high thermal conductivity,high temperature resistance,and good chemical stability,which is one of a wide range of materials.However,due to the high hardness and high chemical stability of gallium nitride,the traditional polishing method,chemical mechanical polishing,is extremely inefficient and cannot meet the production capacity requirements,which limits the application of gallium nitride.Photoelectrochemical mechanical polishing is a processing method that can greatly improve the material removal rate under the assistance of multi-energy fields,and its feasibility has been proved.However,the influence of light field and electric field on the photoelectrochemical mechanical polishing efficiency of gallium nitride wafers is not clear.Therefore,this paper studies the influence of light field and electric field on the photoelectrochemical mechanical polishing efficiency of gallium nitride wafers.The main research content as follows:（1）The key issues of PECMP processing system were studied.Based on the energy band theory of semiconductor materials.It is determined the wavelength of the irradiated light is less than 365 nm.In order to ensure the conductivity and light transmittance of the slurry,the concentration and the particle size of Si O₂ are selected to be 5 wt%and 25 nm;For the stability of the slurry,the concentration of K₂SO₄ electrolyte is 0.1 M.（2）The effects of light field and electric field on the surface modification of GaN wafers were studied.The photoelectrochemical oxidation process in the photoelectrochemical mechanical polishing influenced by the optical field and electric field,but the oxide layer is removed immediately after formation,so the effect of the photoelectric field in PECMP cannot be reflected only through PECMP experiment.Therefore,photoelectrochemical oxidation experiments were carried out to study the effect of light field and electric field on the surface morphology,hardness and composition of the oxide layer formed on the surface of the GaN wafer.The experimental results show that:under the same light intensity and electric field intensity,it is easier to form an oxide layer under short-wavelength illumination;under the same light wavelength and electric field intensity,the stronger the light intensity,the easier it is to form an oxide layer on the wafer surface;Under the same light wavelength and light intensity,the stronger the electric field intensity,the easier it is to generate an oxide layer on the wafer surface.（3）PECMP experiments on GaN wafers with different photoelectric field parameters were studied.The experimental results show that the experimental results of the two polishing pads show that the material removal rate on the wafer surface is higher at 8 V and 10 V,but the surface quality becomes worse;the use of black damping cloth can obtain higher the material removal rate,which is about 1.7μm/h（electric field strength is 10 V）.