Research On Inverse Segregation Of AlSi1Ingots Applicated In Targets

Sputtering targets of high-purity aluminum and its alloys are used commonly in integrated circuits and flat display field. Aluminum connection process has many advantages, such as mature technology, stable process, low price and so on. Adding alloy elements in pure aluminum can improve the properties(Such as stress migration, electricity migration)of the sputter film. But it also causes the concentration to distribute nonuniformly. In an ingot of AlSi1(Al-1%Si) alloy, the concentration of Si in the edge is much higher than that in the center, which makes it difficult to prepare qualified target materials. What’s more, the price of AlSi1ingots imported from foreign countries is very high, which increases the cost of AlSi1targets. Besides, the reasons affecting inverse segregation of AlSi1ingots are various. So it has very important meaning to study the inverse segregation of AlSi1ingots.Inverse segregation of AlSi1ingot was homogenizing annealed in order to eliminate the segregation. After530℃×8h heat treatment, ingot was quenched in water. Through analysising the compositions of Si, it could be found that the inverse segregation was reduced slightly, but still didn’t reach the requirement. Besides, the grain size became bigger, second phase distributed uniform.Graphite model and copper model were used in the casting experiment and casting temperature were680℃,700℃,720℃,740℃,760℃,780℃, then chose a better one to cast. After analysising the concentration of Si, we found that:no matter what kind of models,740℃was a better casting temperature, and graphite model ingot of740℃was better than the copper model’s.Base on the above casting experiments, when ingots were cooled in the Muffle furnace under natural conditions, the uniformity of ingot was improved, inverse segregation was eliminated. However, the grains became much bigger and the second phase got together, that were not good for the deformation of ingots. In addition, we tried to increase the solidification rate of ingot through using water-cooled copper model of Φ80mm(diameter),20mm(wall thickness) to cast. The uniformity was fine, second phase distributed dispersion, and reached the requirement of targets.Now that the ingots of Φ80mm using graphite mold and water-cooled copper mold could meet the requirement, we tried to expand the diameter size to Φ150mm, the same as actual production, to do the casting experiments. Before the experiments, used ANSYS to simulate of the temperature field of ingots, and then used the experimental results to verify the accuracy of the simulation results, expecting to get some guidance to the future production. The inverse segregation of six ingots could not meet the requirements, and the segregation of the ingots of water-cooled copper mold is more intense. Besides, the simulation results of the graphite mold are ideal, but the results of water-cooled copper mold had a larger deviation.