Study On Ds Rolling Process Of Ultrahigh Purity Copper Target For Sputtering

Nowadays,the requirements for the mechanical properties,grain size,and texture distribution of ultra high purity copper sputtering targets for chips are increasingly high.However,at present,the using method of forging,rolling,and annealing to product metal targets can not satisfied the developing demand.In this study,a new method of combining DS(Dynamic adjustment distribution angle and shear stress)rolling with vacuum annealing was proposed to prepare ultra-high purity copper sputtering targets.The synchronous rolling and DS rolling of ultra high purity 6N(99.9999%)copper were numerically simulated by using DEFORM-3D software,and compared with traditional rolling at our library.The finite element models of 6N copper targets base on synchronous rolling,serpentine rolling,and DS rolling based on actual production parameters were established and meshed.The effects of rolling processes with different rolling methods and reduction types on the stress field,strain field,and metal flow velocity were established.The simulation results showthat serpentine rolling can improve the strain permeability of the rolled piece,but the equivalent stress during the rolling process was small,and its impact on the deformation of the rolled piece was limited.DS rolling with a constant shear angle of 4°generate shear strain can effectively improve the non-uniformity of strain in the core of the target material.Compared to synchronous rolling,the rolled metal on the side of fast roller generated larger shear deformation and the effect of strain permeability was more obviously,at the condition of DS rolling.Compared with synchronous rolling,when the total reduction was 60%,70%,and 87.5%,the equivalent strain of the rolled piece after DS rolling increased by 40%,25%,and 32% respectively.At the same time,the influence of reverse bending force on shape correction by DS rolling was studied,and a shape correction process using cross rolling and DS rolling was proposed.Rolling experiments were carried out by using a revamped DS mill in the laboratory,and followed vacuum annealing.The results showe that after DS rolling combined with heat treatment compared to synchronous rolling(average grain size,36.3 μm)the 6N copper target has significantly finer grain sizes(average grain size,24.4 μm),and have a smaller proportion of twin boundaries,and a uniform and random texture,which was more beneficial for sputtering a film to obtain a more uniform thickness and increas the service life of the target.DS rolling gradually transformed the Cube texture during synchronous rolling into a recrystallization texture composed of copper type texture and brass texture,with the copper texture Copper {112}<111>accounting for the largest proportion,and the grain orientation distribution was uniform.Experimental and simulation results showed that using DS rolling can produce 6N copper sputtering targets with more uniform sputtering thickness and longer service life.