Study On The Characteristics Of CMP Hydrodynamics Considering The Surface Morphology

Chemical Mechanical Polishing(CMP)is one of the key technologies for VLSI manufacturing,and it is the only technology that can achieve global flatten.The improvement of IC integration and the decrease of feature line width have put forward higher requirements for CMP technology.The irregular rough structure on the surface of polishing pad has great influence on the polishing efficiency and quality in CMP.However,most of the current researches ignore the influence of the morphology on the fluidity of polishing liquid and nano particles.Therefore,considering the roughness characteristics of polishing pad,we analyzed the fluidity of polishing liquid and nano particles based on fractal geometry theory and computational fluid dynamics software Fluent.Firstly,the IC1000 polishing pad produced is taken as the research object.The SEM image is got and quantified with MATLAB image processing tools and statistical theory,and the grayscale map is got by smoothing,filtering and other processing methods.Based on the principle of box counting dimension,the MATLAB program is compiled to calculate the fractal dimension of the digital image.According to the box counting principle,different sizes of boxes is covered by fitting the data obtained,the fractal dimension of the image is 1.61.Secondly,the fractal dimension is imported into the Weierstrass-Mandelbrot function,and the appropriate parameters is selected to simulate the two-dimensional fractal curve and the three-dimensional fractal surface model.The 3D model point cloud data are extracted and the surface morphology of the polishing pad based on NURBS surface is generated in the Imageware software.Then the surface data is imported into Pro/E,and the 3D solid model of the polishing pad is established.The accuracy of the reconstruction model is verified by the comparison with the physical porosity.Finally,the obtained models CMP 2D and 3D computational domain is used in computational fluid dynamics software Fluent.Based on DPM model and VOF model,the different computational domains analyzed.The polishing fluid velocity distribution,pressure distribution,flow field the transient position of polishing particles,and trajectory are studied.The materials removal rate and non uniformity are discussed,which provides theoretical and technical support for the optimization of the CMP process.