Due to the high temperature stability, high electron migration resistance and high electron emission coefficient of refractory tungsten and tungsten alloys, high-purity tungsten and tungsten alloy targets are mainly used for manufacturing gate electrodes, connection wiring, diffusion barrier layers, etc. of semiconductor integrated circuits, and have high requirements for the purity, impurity element content, density, grain size and grain structure uniformity of materials. Now let’s take a look at the factors that affect the preparation of high-purity tungsten target.
1、 Effect of sintering temperature
The forming process of the tungsten target embryo is generally made by cold isostatic pressing. The tungsten grain will grow during the sintering process. The growth of the tungsten grain will fill the gap between the grain boundaries, thus improving the density of the tungsten target. With the increase of sintering times, the increase of tungsten target density gradually slows down. The main reason is that after multiple sintering, the quality of tungsten target has not changed much. Because most of the voids in the grain boundary are filled with tungsten crystals, after each sintering, the overall size change rate of tungsten target has been very small, resulting in limited space for the density of tungsten target to increase. With the sintering process, the grown tungsten grains are filled into the voids, resulting in a higher density of the target with smaller particle size.
2、 Effect of holding time
At the same sintering temperature, the compactness of the tungsten target will be improved with the prolongation of the sintering holding time. With the prolongation of the holding time, the tungsten grain size will increase, and with the prolongation of the holding time, the growth times of the grain size will gradually slow down, which means that increasing the holding time can also improve the performance of the tungsten target.
3、 Effect of rolling on target properties
In order to improve the density of tungsten target material and obtain the processing structure of tungsten target material, the medium temperature rolling of tungsten target material must be carried out below the recrystallization temperature. If the rolling temperature of the target billet is high, the fiber structure of the target billet will be coarse, and vice versa. When the warm rolling rate reaches more than 95%. Although the difference in fiber structure caused by different original grains or different rolling temperatures will be eliminated, the internal structure of the target will form a relatively uniform fiber structure, so the higher the processing rate of warm rolling, the better the performance of the target
Post time: Feb-15-2023