Microstructure Evolution And Regulation Of Co,Ta And CoTaZr Magnetron Sputtering Targets During Deformation

Co,Ta and Co Ta Zr are widely used as magnetron sputtering targets for coating electronic components in the storage and communications industries.Co undergoes an allotropic transformation,and the allotropes have completely different magnetic properties.Ta exhibits different texture evolution during deformation,which affects the sputtering performance.Therefore,how to control and optimize the microstructure of Co and Ta targets through deformation and heat treatment processes to meet the performance requirements of magnetron sputtering is one of the tasks of this paper.There are peritectic and eutectic reactions during the solidification of Co Ta Zr alloys.The single phase of Co undergoes a martensitic transformation with the change of temperature.The above factors lead to the complexity of the phase composition in the alloy.The microstructure of the alloy will directly affect the performance of the target.However,the current research on the composition,distribution and evolution of the microstructure of Co Ta Zr alloys is limited.Therefore,it is particularly important to study the microstructure of Co Ta Zr alloys.In this paper,by using modern physical analysis technology and performance testing,the evolution of the microstructure during the processing of Co,Ta,Co Ta Zr targets is studied.The details are as follows:1.Co:The microstructure evolution of the as-cast pure cobalt during the annealing process with different temperatures was studied,and the optimal annealing regime was determined.The effects of different rolling processes on the microstructure of Co were compared and studied,and a suitable rolling process was obtained（Accumulative roll-bonding,ARB）.The results show that:annealing at 800℃/1h could effectively improve the microstructure uniformity of the Co targets.Increasing the cold rolling deformation was beneficial to refine the cobalt grains and weaken the{0001}texture.Among the samples of different rolling processes（including cold rolling,room temperature ARB and cryogenic rolling）with the same deformation,the grain fragmentation and deformation uniformity of the room temperature ARB sample were the best.During the 500℃ARB process,the content of the FCC Co phase increased significantly with the increase of deformation,and the intensity of{0001}deformation texture was weakened,which reduced the coercivity of the cobalt target.2.Ta:The effect of different processes（including cold rolling,room temperature ARB and cryogenic rolling）on the microstructure（grain size,texture composition）of Ta targets was studied,and a suitable rolling process was obtained（Accumulative roll-bonding,ARB）.Under the same deformation（30%）,the ARB process could obtain lower texture content（includingα（<110>∥RD）,γ（<111>∥ND）andθ（<100>∥ND））,and was more conducive to the preparation of high performance magnetron sputtering pure tantalum target.Cryogenic rolling had better grain refinement effect.The sample had higher dislocation density(11.70(×10¹⁵/8)²))and stored energy（1.32（J/g））,resulting in earlier recrystallization behavior and larger grains after annealing at 900℃for30min.The increase of ARB deformation could increase the proportion ofαtexture from 36.27%in the first pass sample to 58.58%in the fourth pass sample.The total content of different textures could be reduced by annealing at proper temperature（900-950℃）.3.Co Ta Zr:The phase composition and distribution of the Co Ta Zr alloy with different states were studied.The Co Ta Zr alloy was mainly composed of the equiaxed pre-eutectic structure and the banded-like eutectic structure.The equiaxed pre-eutectic structure was mainly composed of the HCP Co phase and the HCP Zr phase.The banded eutectic structure was mainly composed of the HCP Co phase,Co₂Ta（HCP）and Co₂₃Zr₆（FCC）.The heat treatment at 900℃for 2h could effectively reduce the hardness of the Co Ta Zr alloy,and promoted the inverse martensitic transformation of Co from HCP structure to FCC structure,resulting in the residual of FCC Co.The 25%cold rolling had no effect on the phase composition of the heat-treated alloy.Fine equiaxed structures were found in the hot ARBed samples,which were mainly distributed around the equiaxed pre-eutectic structures and had the same phase composition as the equiaxed pre-eutectic structures.The banded eutectic structure in the hot ARBed sample was mainly composed of two different bands with different contrast.The bright band was mainly composed of the FCC Co phase with typical twinning characteristics.The dark band was mainly composed of smaller stripes with dark and light contrast.The contrast stripe was mainly composed of the Co₂₃Zr₆,in which the Ta was solidly dissolved.The light contras stripe was mainly composed of the HCP Co phase,in which the Co₃Ta（FCC）phase was precipitated.The hot ARB process could effectively increase the content of FCC Co phase,which was beneficial to improve the magnetron sputtering performance of Co Ta Zr alloy.