High purity
tungsten and tungsten alloys (W-Ti, W-Si, etc.) are often used as sputtering targets for physical vapor deposition, and are used in making gate electrodes, wiring and diffusion barrier layers in semiconductor field.
With the development of microelectronics science and technology, the integration degree of ultra-large scale integrated circuit (ULSI) is getting higher and higher, and the number of devices in a chip is increasing at an alarming speed. In the manufacturing process of modern semiconductor devices, traditional Al, Cu and Ag are mainly used as metal interconnection materials. Because Al Cu and Ag will diffuse to Si or SiO2 in the dielectric layer to form metal silicides with high resistance, the current density in the wire decreases significantly, leading to the complete failure of the electrical performance of the whole wiring system. Therefore, it is necessary to add a diffusion barrier layer between the wiring and Si or SiO2. A large number of studies have shown that WTi barrier layer with 10%~30% Ti (mass fraction) has been successfully applied to Al, Cu and Ag wiring technology, where W is used to prevent diffusion (W has a low atomic diffusion in most metals), while Ti is used to prevent grain boundary diffusion and improve the corrosion resistance and bonding strength of the barrier layer.
Pure
tungsten targets are mainly used as fillers for through holes (Via) between metal layers and vertical Contact holes (W Plug). WSI is mainly used in the upper part of the gate polysilicon as the polysilicon silicide structure and local interconnection lines. As the size of semiconductor chip becomes smaller and smaller, the reduction of copper interconnection size leads to the increase of resistivity on the nanometer scale, which has become a technical bottleneck restricting the development of semiconductor industry. Some studies have shown that refractory metal tungsten is expected to replace copper as the next generation of semiconductor wiring metal material.
