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Development Of SiO2 ILD Chemical Mechanical Polishing Slurry And Its Performance Analysis

Posted on:2010-08-25Degree:DoctorType:Dissertation
Country:ChinaCandidate:R H LiuFull Text:PDF
GTID:1118360275958050Subject:Mechanical Manufacturing and Automation
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Intergrated Circuit is the core of the electronic information industry and one of the most important high-tech to promote national economic and social development.From the IC manufacturing process,we can see that chemical mechanical polishing(CMP) is used in the oxide layer,barrier and metal wiring.CMP is currently widely used in IC manufacturing,and has become one of the mainstream technologies to achieve chip global planarization in semiconductor processing industry.CMP is the combination technology of chemical and mechanical effects.In fact the micro process is complicated.There are many factors which affect polishing results.Both the chemical process and mechanical effect in CMP process are impacted by CMP slurry,which is one of the critical factors affecting the quality of CMP.Although CMP is considered to be one of the most effective way to acquire smooth surface of wafer,and have been widely used in SiO2 Inter level dielectric,the effects of CMP process,the mechanism of material removal. the effects of the composition of slurry in micro mechanism,and the formation mechanism of material non-uniformity have not yet entirely clear.Therefore,how to adjust the slurry recipe to control the material removal rate,acquire the higher quality surface,establish a more perfect model of material removal rate,achieve stable production and meet the requirements of next generation ultra-thin dielectric film,etc.,continue to be hot spots and cutting-edge issues for scholars.In this paper,the current research situation and problems of slurry characteristics and its mechanism in SiO2 CMP dielectric film are present.Tribology,contact mechanics,physical chemistry,colloid chemistry,surface and interface physics and other aspects of the theory are used to investgate.The physical and chemical properties of the slurry in CMP silicon dioxide. the choice and optimization of slurry ingredients,the form of abrasive in slurry contacting with the wafer,the material removal rate of the chip surface,the measurement and calculation of chemical activation energy are analyzed in a detailed study.First of all,the size and morphology of particles in slurry are investgated with laser particle size analyzer and TEM.The formations of the nano-abrasive in slurry and during CMP are analysed.The results show that the nano-abrasive particles are soft conglomeration in slurry.The surface topography,section microstructure and other characters of pads are observed with SEM and the surface profiler and microscopic,which provide reference for revealing the material removal mechanism and building relevant model.At the same time,the evaluation of slurry performance is determined by polishing results and the stabilization of slurry,which is prepared for slurry ingredients.Second,the main character and role of the essential components in the slurry are analysed.And then based on the polishing process parameters optimization,series basic components,from which the most obvious effect or fine polishing results are obtained,are proposed from the candidate of the chemical reagents through tests.The final orthogonal test is conducted to optimize the composition and the ratio.The slurry are made of silica 30g (6.0%wt),KOH 1.0g(0.2%wt),40%silica sol 280ml(22.4%wt),organic alkali 20ml(4.0%wt) and additive 5g(1.0%wt).Although the material removal rate of selfmade slurry is only 80% of the similar products,the metal ion content of slurry is greatly reduced with organic alkali. At the same time surface roughness of polishing wafer is almost as same as similar products.Then,surfactant features,adsorption model and its various roles in the slurry are analysed.According to the theory of EDLVO,a suitable dispersant to improve the stability of the slurry is chosed by contrasting different dispersant effect with ultraviolet spectrophotometer,Zeta Potential Analyzer and laser particle size analyzer.That is multi-polymer dispersant D.When its concentration is 0.3wt%,the stabilization of the slurry is the best,with which the slurry can be stabilized at around six months.Then,according to the equations of chemical kinetics,a chemical reaction rate equation for the process of polishing silicon dioxide ILD is provided.Based on the basic principles of chemical reaction activation energy,the static chemical reaction activation energy of SS25 slurry and the wafers is measured(67.406 kJ/mol) through immersion test.Furthermore the static chemical reaction activation energy of the different alkali and silicon dioxide ILD are compared,from which we can see that static chemical reaction in the entire share of removal is not large.Other forms energy can play a vital role in CMP.Furthermore,considering friction chemical reaction dynamics and the Arrhenius formula amended,the chemical reaction rate equation including the friction effect is established.The total material removal rate model of CMP silicon dioxide ILD is obtained.At the same time the material removal model is confirmed through immersion tests,polishing in different temperature and single-factor tests of pressure and talbe speed.The results showed that mechanical energy generated by the friction is not in the form of thermal energy through the play,but directly into chemical energy in the CMP process,which directly reduces the activation energy of chemical reaction to produce a certain amount of energy to reduce, significantly improved the reaction rate.Purely chemical and purely mechanical roles are in a very small share in the entire amount of CMP,which can be negligible.The different concentrations affect the friction force and the reduction of activation energy,which affect the the relevance of temperature and polishing results.Moreover the reduction of activation energy is basic linear with friction force.Finally,based on the nano effects of SiO2 particles in the CMP process,an adhesion removal model is proposed,which is identified through immersion tests,cycle polishing of SS25 and different particle size slurry.The cation of the contact forms between the nano-abrasive in slurry and the wafers in the CMP process is completed.The results show that:①The activation energy is reduced by the adhesion and abrasive role of nano-silica abrasive particles in slurry and the friction role of the pad,as a result of which the chemical bonds in the surface of SiO2 ILD are broken.And SiO2 come out from inside,which is the removal action.②When abrasive particle size is less than about 65nm,the reduction of adhesion generated by particle size increase is less than the increase of friction generated by particle size increase,which means the increase of particle size contribute to improve the total effects of adhesion and friction and help to improve the material removal rate.③Abrasive particle size in the range of 65~80nm should be a transition state.④The friction force generated by abrasive adhesion along with particle size increase in the range of 80nm~143nm is reduced. Moreover friction force generated by abrasive scratch is enhanced.Although the overall friction increases,the significant reduction of adhesion plays a decisive role in the total removal rate.The overall removal rate declines.⑤The state in the range of 143~60nm should be a transition.The friction force generated by abrasive adhesion is further reduced. The friction force increase generated by abrasive scratch is not enough to make up for the friction force reduction generated by abrasive adhesion.So the total friction force and removal rate decline.⑥When particle size is more than 160nm,abrasive scratch plays a leading role not only in the frciton force but also on the removal rate.That means abrasive scratch plays a decisive role in the whole process of CMP.Since then the abrasive adhesion can be ignored along with the particle size and the removal rate increase.
Keywords/Search Tags:Chemical Mechanical Polishing, Slurry, Adhesion removal mechanism, Material removal rate, Chemical reaction rate equation
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