Research On CMP Slurrys For TSV Wafers

With the continuous development of integrated circuits with Moore's Law,the feature sizes of semiconductor devices continue to shrink.This brings more technical difficulties to the manufacturing process.Three-dimensional integration technology came into being,and realized the packaging method of chip stacking,which continued Moore's Law.TSV technology is the mainstream technology of 3D integrated chips,which greatly improves the performance of semiconductor devices.In TSV manufacturing process,chemical mechanical planarization of chips is one of the key technologies.Cu is a TSV filler metal due to its low resistivity and high reliability.Meanwhile,in order to prevent the diffusion of Cu,Ta is generally used as a barrier layer material.Therefore,in TSV CMP,Cu and Ta CMP are important.In TSV Cu rough polishing,a higher removal rate is required.The two systems of glycine-H₂O₂ and FA/O?-H₂O₂ were compared in the research:Cu removal rate was1267 nm/min and 5.8?m/min,respectively.The glycine-H₂O₂ system is more conducive to improving the electrochemical corrosion and removal rate of Cu.And the selectivity between Cu and Ta is adjustable within 20-50.Therefore,it is more suitable as a slurry for rough polishing of TSV Cu.In TSV Cu fine polishing,a higher quality of wafer is required.This project uses the glycine-H₂O₂ system.In order to improve the surface quality of the wafer,the corrosion inhibitor TAZ and the surfactant betaine were introduced,and the synergistic effect and mechanism of the two in the glycine-H₂O₂ system were studied.Studies have shown that TAZ can effectively inhibit Cu corrosion,reduce Cu removal rate to 424 nm/min,and improve wafer surface quality with a surface roughness of 1.06 nm.Betaine as an active agent can not only increase the ductility and wettability of the polishing solution on the Cu surface,clean the organic residue on the wafer surface,and it can help TAZ to form a denser passivation film because its structure.So it can further improve the wafer surface quality,reducing wafer surface roughness to 0.22 nm.Finally,the effects of guanidine hydrochloride-H₂O₂ system on the electrochemical and CMP of TSV Ta were investigated.During Ta CMP,a suitable selectivity between Cu and Ta is required.It shows that guanidine hydrochloride and hydrogen peroxide can effectively improve Ta removal rate and promote Ta corrosion.Moreover,at pH?10,tantalum will be oxidized to hexatantalate ions,which further improves the removal rate of Ta.Among them,5 wt%silica,1 wt%guanidine hydrochloride,0.15 vol.%H₂O₂,Ta removal rate reached a maximum of 1417(?)/min at pH 10,and the electrochemical corrosion was the strongest.The selectivity between Ta and Cu were also studied.The selectivity was controllable in the range of 1-15.On this basis,betaine was introduced to further improve the surface quality of Ta and Cu.The surface roughness of Cu was 0.3 nm,and the surface roughness of Ta was 0.4 nm.It is concluded in this paper that the effects of three different TSV CMP slurries(including Cu rough polishing slurry,Cu fine polishing slurry,and Ta polishing slurry)on the removal rate of Cu and Ta,the electrochemical characteristics of corrosion,and the local and global planarization of the wafer have been studied.