Study On Electrochemistry And Polishing Rate Of Chemical Mechanical Polishing Of Semiconductor Silicon Wafer

Integrated circuit (IC) is the basic of modern information industry and information society. And the technique of IC is the high and new technology of promoting the national economy and the development of information society. It is also the core technology of converting and promoting the traditional industry. The semiconductor material of IC is mainly of silicon wafer, germanium, and gallium arsenide and so on. More than 90ï¼…of IC products are made from silicon wafer in the world. The high quality silicon wafer is the basic of chip manufacturing and IC development. The silicon wafer of IC manufacturing is required not only high degree of the plane, minimum surface roughness but also without metamorphic layer and scratch on the surface. Chemical mechanical polishing (CMP), which is the last process to produce defect-free surface, become a key step of silicon processing in semiconductor technology.The process of CMP is actually an electrochemical process with abrasive wear, so the study on CMP with electrochemical method is great of significance. In this article, the film-forming behaviors ofn (100), n (111), p (100) andp (111) semiconductor silicon wafers in the slurry of nano-silica, the electrochemical behaviors during CMP, polishing rate and CMP process mechanism and so on were systematically investigated in instruction of principles of solution chemistry, corrosion electrochemistry, friction and wear, and fluid boundary layer of hydrodynamics by rotate disk electrode of electrochemical experimental methods.. The main contents researched and conclusions are as follows:The corrosion behavior of semiconductor silicon wafer in the nano-silica based slurry was investigated, and the influences of film-forming characteristic by pH values, silica solid content, filming time and hydrogen peroxide concentration were also studied by using electrochemical DC polarization and AC impedance techniques. The results revealed that pH values had a serious impact on the formation of the film. The passivation film was the thickest at pH 10.5, and the corresponding thickness was about 5.989 (?) tested by electrochemical impedance spectroscopy (EIS); The solid content of SiO₂ had little effect on the formation of the film.; The addition of H₂O₂ into the slurry accelerated the formation of the film and its presence caused the gradual increase of the corrosion potential and the continual decrease of the current density; We also found that the film formation rate of (100) was faster than that of (111 ). Formation processes of passivation film were proved to accord with Müller model according to variation of apex current with scan rate of potential by circle volt-ampere method of linear potential scan in the nano-silica based slurry.Relations of corrosion potential and corrosion current density varying with polishing pressure, rotation speed, silica solid content, pH values and H₂O₂ concentration were studied during CMP. The increase of polishing pressure, rotation speed and solid content contributed to the removal of surface film. We also discovered that corrosion current density varied with polishing pressure, rotating speed and silica solid content basically linearly to some extent; Corrosion potential and corrosion current density were strongly affected by pH values during CMP. The corrosion current density reached the maximum at pH 10.5; The addition of H₂O₂ into the slurry enhanced corrosion potential and corrosion current density during CMP.Polishing rate and its dependences in the slurry of nano-silica were investigated and the rules of dependence of polishing rate on polishing pressure, rotating speed, silica solid content, pH values, H₂O₂ concentration and polishing time were studied during CMP. The experimental results revealed that the removal rate increased sublinearly with applied pressure and rotating speed; Polishing rate increased with the increase of solid content, when the solid content was larger than a certain value, a phenomenon of material removal saturation would happen; There was a peak in the curves of polishing rate varying with pH and H₂O₂ concentration, where polishing rate was the maximum due to dynamic balance between chemical and mechanical action; We also found that the removal rate decreased gradually with the extension of time and the polishing rate of (100) was much higher than that of (111). We found that polishing was a process with continuous cycles of formation-removal-reformation, which was confirmed by testing the change of AC impedance spectra before and after CMP.The consistency of the results obtained from the study on the electrochemistry of CMP of silicon wafer with the polishing rate results, manifested that electrochemical technique could become a reliable method applied to the investigations on the CMP process and mechanism of silicon wafer, which provided a new idea of studing on the CMP of silicon wafer.By above researches the optimal technology parameters suitable for the CMP of semiconductor silicon wafers were finally obtained as follows:n (100): 40kPa, 100rpm, 20wt%SiO₂, pH10.5, 1vo1%H₂O₂n (111): 40kPa, 200rpm, 20wt%SiO₂, pH10.5, 1vo1%H₂O₂p (100): 40kPa, 200rpm, 20wt%SiO₂, pH10.5, 2vo1%H₂O₂p (111): 60kPa, 200rpm, 20wt%SiO₂, pH10.5, 2vo1%H₂O₂...