Study On CMP Rate Selectivity Of TSV Materials

Three dimensional integration technology can increase the integration of chips,however,the difficulty of 3D integrated circuits is also increased.Among them,whether the use of CMP technology to TSV copper film and barrier layer to achieve global planarization is a very critical part of the three-dimensional chip process,and becomes the hotspot research and the difficult point in the widly international study.Simultaneously,how to control the removal ratio of silicon substrate and copper pillars in TSV backside thinning process is also a big difficulty in TSV CMP.At present,the mainstream international TSV polishing solution is acidic and contains inhibitors,but the heavy metal ions generated in CMP will reduce the reliability of the device,and the inhibitor will remain on the surface of the barrier is difficult to remove.Therefore,it is necessary to study the new high-rate TSV polishing solution to explore the optimal polishing process and form the TSV flattening theory model to solve the shortcomings of the acidic slurry and further meet the development needs of the semiconductor manufacturing industry.In this paper,we study the new alkaline route to realize the global planarization of TSV and the rapid exposure of the back copper pillar.Experimental use of independent research and development of cost-effective TSV alkaline polishing solution,its composition is simple,no resists,easy to clean after CMP,as well as self-passivation function,can achieve high flattening efficiency.In this paper,the effects of the components and process parameters on the selectivity of Cu/Ti/SiO₂ removal rate were studied by means of a large number of single factor experiments in TSV barrier layer,and the planarization of TSV pattern wafer was studied;And then studyed the effect of chelating agent on the Cu/Ti rate selectivity,and the TSV copper film was planarized;finally the effect of combination and dilution of silicon substrate slurry on the removal rate selectivity of Si/Cu was studied.Optimization experiments for determining the polishing liquid ratio and process parameters are as follows:the volume fraction of silica sol,KOH,surfactant and chelating agent is 10%,2.8%,3%and 1.5%respectively,speed,flow and pressure were 93/87rpm,75%and 4psi,while the Cu/Ti/SiO₂ removal rate selectivity was best,and the volume fraction of the surfactant and chelating agent had no effect on the particle size and Zeta potential.The results obtained from the experiment of copper film flattening are as follows:the removal rate of copper film reaches the highest value of 2.1?m/min when the volume fraction of chelating agent is 5%,and the TTV of the copper film is reduced to about1.32176 nm after CMP.The barrier layer flattening results shows that:with the help of the active adsorption of the surfactant and the self passivation of the chelating agent,the extension of the dishing was successfully controlled,and the correction ability of the dishing were all above 1500?/min on the via pitches of 20?m?40?m?60?m and 80?m,the smaller the distance,the faster the correction.When the duration of the HP&MP&LP model three stages is 50%,30%and 20%of the total polishing time,the edge collapse phenomenon was solved.The experiment results showed that a higher removal rate of silicon substrate was gotten by using the slurry added silica sol,surfactant,KOH and chelating agent in turn and diluted 15-fold by deionized water,the removal rate was1.045?m/min,which is more than the removal rate by the imports of US slurry under the same conditions.The removal rate selectivity ratio of Si/Cu was controlled.