Study On Component Optimization And Mechanism Of Chemical Mechanical Polishing Liquid For Monocrystalline Silicon

Monocrystalline silicon is the core of the development of semiconductor industry,and is widely used in the IC manufacturing industry.Its surface quality has an important impact on the performance of semiconductor devices.Chemical mechanical polishing（CMP）can achieve global wafer flattening,which is widely used in the manufacturing process of IC.As the size and thickness of silicon wafers increase,silicon wafers are required to have better surface quality and greater material removal rate（MRR）during processing.Therefore,how to improve the efficiency of silicon wafer processing is one of the current research hotspots.In this paper,CMP is used to process the silicon wafer,the influence of polishing liquid composition and process parameters on the polishing effect is studied,and the material removal mechanism in the CMP process is studied.Firstly,the effects of p H value,Si O₂ concentration,H₂O₂ concentration,guanidine carbonate（GC）concentration and polyethylene glycol（PEG）concentration on CMP effect of silicon are studied.The results show that the material removal increases first and then decreases,and the surface roughness decreases with the increase of p H value.The increase of Si O₂concentration contributes to the improvement of MRR and surface quality.However,when the Si O₂ concentration exceeds 10 wt.%,the surface quality deteriorates.When H₂O₂ concentration is between 0 and 1.0 wt.%,the MRR increases with the increase of H₂O₂ concentration,while the Ra gradually decreases.However,when H₂O₂ concentration is higher than 1.0 wt.%,the polishing effect of the wafer will be worse.When GC is used as additive,it can promote the MRR of silicon wafer,but lead to a gradual increase of Ra.The PEG is introduced into the polishing liquid.The experimental results show that PEG has a weak inhibition on MRR,but can effectively reduce the Ra of silicon wafer.According to the above experimental results,five factors and four levels orthogonal experiment were designed to determine the best combination scheme:p H value（10）,Si O₂（10 wt.%）,H₂O₂（1.0 wt.%）,GC（1.2 wt.%）,PEG（0.003 wt.%）.Secondly,the effect of polishing process parameters on CMP effect of monocrystal silicon is studied by single factor experiment using the optimized polishing liquid.Then response surface experiment is designed to build mathematical prediction model of MRR and Ra,and the polishing process parameters are optimized.After variance analysis and experimental verification,the mathematical prediction model is significant and the prediction accuracy is high.According to the experimental results,the optimal combination scheme is determined as follows:polishing pressure（7.0 psi）,polishing speed（70 rpm）,polishing liquid flow（65m L/min）.At this time,the MRR of silicon wafer is 1058.2 nm/min,and the Ra is 0.771 nm.Finally,the mechanism of GC and PEG in CMP is investigated by electrochemical,friction and wear experiments and XPS experiment,and the effects of load and friction environment on the tribological behavior of abrasive-Si wafer contact are investigated by friction and wear experiments.The results show that GC can promote the chemical reaction on the surface of silicon wafers,and silicon atoms on the surface of silicon wafers form Si-N bonds under the action of GC.Thus,forming a chemical reaction layer that is easy to remove on the surface of silicon wafers,leading to an increase in the MRR of the silicon wafer.PEG can reduce the rate of chemical reaction on silicon wafer surface and hinder the reaction between GC and silicon wafer surface.At the same time,a lubricating film is formed on the surface of the silicon wafer,which reduces the damage of the grinding ball to the surface of the silicon wafer,resulting in the reduction of the MRR of the silicon wafer,and the surface quality is improved.According to the experimental results of ball disc friction and wear under different loads and different friction environments,the increase of wear rate is mainly caused by the synergistic effect of chemical and mechanical action.Combined with the above experiments,the material removal model of monocrystalline silicon is established,and the removal mechanism of wafer material is analyzed.