Research On Surface Modification Of High-purity Ultrafine Sic Powder For Semiconductor Manufacturing

Due to strong oxidation resistance, high strength, good abrasion resistance and thermal stability, small coefficient of thermal expansion, large thermal conductivity, high hardness and elastic modulus, good thermal shock and chemical corrosion resistance, SiC has become one of preferred materials for high-tech fields in recent years.In semiconductor manufacturing, many projects are applying SiC ceramics. As raw powder of high-performance ceramic for semiconductor manufacturing, it must require a high-purity,ultrafine and good dispersion SiC powder. But it is easy for SiC powder to agglomerate and form secondary particles after mechanical grinding, due to the small particle size and high surface energy. So it is difficult to achieve dispersion of particles , the dispersed stability and suspension of slurry in casting molding process, thereby the performance of ceramic materials can not improve. Surface modification is one of the effective methods to improve the dispersion and fluidity of SiC powder as well as the mouding performance of ultrafine powder and the final performance of products.According to the three basic mechanism of dispersion and stability, we designed a double-coated model for SiC powder.The KH-550 coupling agent was used as bridge to connet the SiC powders and the organic polymer, sodium polyacrylate as a dispersion functional layer was formed on the surface of SiC powders by graft polymerization reaction.By coating the silicon carbide,the colloidal characteristics of powders in the water were changed greatly,the capacity of dispersion and stability were improved remarkably.During investigation,the technological parameters of surface modification were established.The surface characteristics of original and coated silicon carbide powders and the dispersed stability as well as fluidity of SiC slurry ware analyzed by Fourier Transform Iinfrared Spectrometer,XRD,SEM,Zeta potential instrument and viscometer,etal. During experiment, modified powders were made in ceramic and tested its performance.The results showed that KH-550, PAM, PAA-Na has existed on the surface of the modificated SiC powders. SiC powders treated by organics coating did not change the phase structure of original SiC powders,it just changed the colloidal properties in water; reunion reduced and dispersion property improved of SiC powders.Compared with the original SiC powder, Zeta potential of PAM-KH550SiC and PAA-Na-KH550SiC powders were increased.The latter increased more remarkable, its maximum positive potential was +57.08mV(pH=3), the maximum negative potential was -57.33mV(pH=10).The Zeta potential of graft copolymerization powder with AA-Na and AM was -76.61mV(pH=10), which higher than the first two. Higher Zeta potential values were effective to improve the dispersed stability in the water, so the dispersed stability of modified SiC powders was improved significantly at acidic or alkaline conditions. It can be inferred: the original SiC powder mainly relyed on electrostatic stabilization mechanism to achieve dispersion and stability in slurry, but modified SiC powders was based on electrostatic-steric stabilization mechanism.During experiment, uncoated and coated silicon carbide powders were made in ceramic and tested their performance.The results showed that the density of sintering samples using modified powders was increased. Microstructures were very dense and distributed evenly; there were no large aggregates and visible porosity, particle accumulation closely. All of those indicated the modified powders had excellent mouding and sintering performance.