Study On Dynamic Pressure And Temperature Of Slurry In Chemical-Mechanical Polishing Of Silicon Wafer

Chemical mechanical polishing(CMP) as a critical technology in integrated circuit(IC) manufacturing is widely used to achieve a high degree of the local or global planarization of the substrate silicon wafer.The CMP process of silicon wafer usually affected by many factors is very complex.Both dynamic pressure and temperature of slurry in chemical-mechanical polishing of silicon wafer are two main factors influencing the nonuniformity and materials removal rate(MRR) of the silicon wafer during the CMP process. As the minimum resolvable feature size decreases and the silicon wafer size increases in IC manufacturing,the influence of dynamic pressure and temperature of slurry on the wafer surface quality becomes more and more prominent.However,the investigations on dynamic pressure and temperature of slurry in chemical-mechanical polishing of silicon wafer are still not clear at present.A further study on dynamic pressure and temperature of slurry in chemical-mechanical polishing of silicon wafer is important for finishing the silicon wafer with high quality,ultra-precision and damage-free surface.In term of the adequate analysis of the research background,dynamic pressure and temperature of slurry in chemical-mechanical polishing of silicon wafer during IC manufacturing are mainly studied in this paper.The main research content and results are listed as follows:Many vital factors such as size and concentration of suspending abrasives contained in the slurry,porous structure,thickness and surface roughness of polishing pad,size and curvature of silicon wafer,rotation speeds of both the silicon wafer and polishing pad,and so on,are taken into account.Flowing properties of the slurry in porous pad and pad roughness are analyzed and discussed in detail.Based on the lubrication theory and solid-liquid two-phase flow theory,a three-dimensional model of the large-sized silicon wafer under the light polishing pressure conditions is developed.The numerical analysis of the model under the quasi-steady states at the wafer scale is well done.The relationships between the important parameters and slurry flowing are discussed.According to the properties of CMP,the experiment platform for the CMP silicon wafer, which fully takes advantage of the existing experimental equipments in our experimental lab, is developed.In the design of the experiment platform,driving rotation function and floating universal function of silicon wafer carrier are utilized.At the same time,realization of exerting the constant pressure on the wafer and controlling slurry flowing during CMP process is considered.All these efforts are beneficial to providing a steady experiment platform on the measurement of the torque,positive pressure,friction force,dynamic pressure and temperature of slurry during CMP of silicon wafer.In light of the measurement theory of the hydrodynamic pressure,the measurement methods of dynamic pressure of slurry in the CMP of silicon wafer are studied,and a multiple-point in-situ and real-time measurement method of dynamic pressure of slurry in the CMP of silicon wafer is proposed.In accordance with the measurement method,the test system of dynamic pressure of slurry between the pad and silicon wafer during the CMP process of silicon wafer is addressed.Finally,a real-time test system of dynamic pressure of slurry is developed,which meets the real manufacturing process of the CMP of silicon wafer. The error of this test system is less than±0.25%.Some test experiments of the dynamic pressure of slurry are carried out to study the effects of the polishing pressure on the back of the silicon wafer,the pad speed and the pad type on the properties of the slurry flowing between the silicon wafer and pad,depending on the experiment platform and the test system that have been established.The results show that the dynamic pressure of slurry in chemical-mechanical polishing of silicon wafer increases with the polishing pressure increasing,and a lubrication film of slurry between the silicon wafer and the pad can be formed under the light polishing pressure condition.On the other hand,the dynamic pressure of slurry in chemical-mechanical polishing of silicon wafer increases with the relative speed between the silicon wafer and the pad increasing under the same conditions All above mentioned results can provide the experimental basis for the adjustment of the back pressure and the optimization of the operating parameters to obtain the uniform and high-quality silicon wafer.Considering the basic principle of the temperature measurement,the complicated factors that affect the temperature of slurry in the CMP of silicon wafer are fully analyzed,and a multiple-point in-situ and real-time measurement method of temperature of slurry in the CMP of silicon wafer,which is based on the contact method of temperature measurement,is presented.A measurement system of the temperature of slurry in chemical-mechanical polishing of silicon wafer is designed,and a equipment of the temperature of slurry in chemical-mechanical polishing of silicon wafer is developed on the basis of the experiment platform and the developed measurement method,and the error analysis of the temperature of slurry in chemical-mechanical polishing of silicon wafer is well done,at the same time,some measures that can reduce some errors and avoid the disturbances are taken,finally,the error of this test system that can be obtained is less than±0.47%. On the basis of the developed measurement system,some test experiments about the temperature of slurry in chemical-mechanical polishing of silicon wafer are completed on the experiment platform.The results show that the polising pressure,the relative speed and friction behavior between the pad and the silicon wafer have important influence on the temperature of slurry in chemical-mechanical polishing of silicon wafer.