The Micro Structure Control And Application Of Pure Tantalum Magnetronsputtering Target

In this paper,the effects of cold deformation and heat treatment on the grain size and texture of pure Ta magnetron sputtering targets are studied.The pure tantalum target is a diffusion barrier for copper interconnects with silicon used in advanced semiconductor processes.Because it is key material in the copper interconnect process,As a barrier layer,the thickness and thickness uniformity of the film deposited by physical vapor deposition(PVD)directly affects the barrier effect.While the grain size and texture of the Ta target is the key factor which affect the deposition rate.At present,the material purity requirement of the pure Ta target used in semiconductor advanced technology is 99.995%.The ingots which meet the purity and density requirements are prepared by the electron beam melted(EBM)and the vacuum arc remelted(VAR),and then the ingot is plastically deformed and heat treated to control the grain size and texture.Then,bond the Ta material with backing plate with diffusion bonding.Due to the big and non-uniform grain size of the ingot after casting,the size has a large aspect ratio.Therefore,forging is required first,and the grain is preliminarily refined and homogenized.The forging process is side and uspset.The grain size and texture were analyzed by metallographic microscope and EBSD.The results show that after heat treatment at 950°C for one forging,the average grain size is 128.7 μm,the standard deviation is 125.67,and the average grain size is 90.3 μm after standard heat treatment 950°C after two times forging.The standard deviation is 64.34.After three times forging and 950°C heat treatment,the average grain size is 65.91μm and the standard deviation is 40.71.After four times of forging and 950°C heat treatment,the average grain size is 48.7μm,the standard deviation is 22.08,and the effect is obviouson grain refinement and uniformity of the four times forgings.The Ta material subjected to four times of forging and heat treatment at 950° C for 90 minutes was subjected to multi-angle rolling with a total deformation of 77%,and subjected to vacuum heat treatment after rolling.The heat treatment temperature was from 1000°C to1250° C,and the heat treatment time was 90 min.After 1000 ° C heat treatment,the average grain size is 45.71μm,the f(max)of <111> crystal orientation is 4.77,the average grain size after heat treatment at 1050°C is 58.79μm,the f(max)of <111> crystal orientation is 4.26,and the average grain size after heat treatment at 1100°C is 58.99μm.The <111> crystal orientation has a f(max)of 4.18,an average grain size of 65.12 μm after heat treatment at 1150°C,a f(max)of 4.10 in the <111> crystal orientation,and an average grain size of 107.07 μm after heat treatment at 1250°C.The f(max)of <111> crystal orientation is7.03,preferably 1150°C recrystallization heat treatment process,the grain meets the requirements of 50 ~ 80μm,and the texture density is the lowest,the best uniformity.The optimized target microstructure control process was applied to the Encore II sputtering machine made by Apply Materials,and the results showed that the depostion rate and the uniformity of the deposited Ta film were improved.