Study On Material And Process On Ru Barrier Layer CMP In The GLSI Multilayer Copper Line

As the integrated circuit technology node gradually develops to 14 nm and below,the traditional barrier material?Ta/TaN?cannot meet the requirements of the 14 nm barrier due to its poor adhesion to Cu,excessive barrier thickness,and poor reliability.Instead,it is replaced by a new type of Ru barrier material.Due to the high hardness of Ru,there are problems such as low Ru removal rate and difficult to control the Ru/Cu removal rate during the Ru CMP process.In this paper,firstly,the polishing process optimization parameters of Ru and Cu CMP were optimized.A set of suitable polishing process parameters for Ru and Cu removal rates is obtained.Then,the effects of the weak oxidant H₂O₂ on the removal rate of Ru and Cu were investigated experimentally.It was found that the removal rate of Cu was much higher than that of Ru,resulting in a lower Ru/Cu removal rate selectivity.In order to further increase the removal rate of Ru and increase the Ru/Cu removal rate selectivity,the effects of complexing agent guanidinium ion?Gnd⁺?and inhibitor BTA on Ru CMP were studied.The results showed that:in pH 9 weak alkaline environment,Gnd⁺could interact with Ru surface oxide to increase Ru removal rate,and also significantly increase Cu removal rate,making Cu removal rate much larger than Ru;while BTA addition had little effect on Ru removal rate,but the Cu removal rate suppressing effect was very obvious,which greatly reduced the removal rate of Cu,increased the Ru/Cu removal rate selectivity,and significantly reduced the galvanic corrosion between Ru and Cu.However,although the removal rate of Ru increases,it is still low,and the appropriate Ru/Cu removal rate selection ratio cannot be achieved.In order to further increase the Ru removal rate and adjust the Ru/Cu removal rate selectivity,the effects of SiO₂ abrasive,KIO₄,pH,and guanidine hydrochloride?GH?on Ru CMP in a strong oxidant KIO₄ system were studied.The experimental results showed that KIO₄ could significantly increase the Ru removal rate under alkaline conditions,while the higher the pH?9-12?,the lower the Ru removal rate.When the low oxidant was low,GH could greatly reduce the removal rate of Ru,and slightly reduce the removal rate of Cu,which adjust Ru/Cu removal rate selectivity to 1:1.