Molybdenum and molybdenum alloy sputtering targets
Molybdenum and molybdenum alloy sputtering targets have been widely used in electronic components and electronic products, such as thin film semiconductor tube liquid crystal display (TFT-LCD), plasma display, field emission display, touch screen, and also can be used in solar cell back electrode, glass coating and other fields. In recent years, with the development of electronic industry and solar cell, the amount of molybdenum and molybdenum alloy target as high value-added electronic materials is increasing year by year. As a new high-end product of molybdenum industry, molybdenum and molybdenum alloy sputtering target material has high technical content, high purity, high relative density, fine and uniform grain size.
There are two methods to prepare molybdenum sputtering target. The first one is powder metallurgy. High purity molybdenum powder was selected as raw material, after cold isostatic pressing, sintered in medium frequency induction furnace or vacuum sintering furnace, after rolling and machining, the finished target material was obtained. Another method of preparing molybdenum sputtering target is high temperature melting. In this method, molybdenum plate or molybdenum bar billet is melted at high temperature in electron beam or arc melting furnace to form molybdenum ingot, and then processed by forging, extrusion or drawing forming process, and then the target material is obtained after heat treatment. The target material prepared by this method has high purity and good density, but compared with the powder metallurgy method, the equipment requirements of this method are higher, the process is complex, and the grain size is relatively coarse.
The thin films sputtered from pure molybdenum target have some problems in corrosion resistance (discoloration) and adhesion (film stripping), etc. Adding some alloying elements into molybdenum can make its performance of impedance, stress and corrosion resistance reach equilibrium. Therefore, the research of molybdenum alloy target has become a hot spot.
In order to prevent the diffusion of copper into silicon, the reverse diffusion barrier layer can be formed by pure tungsten target or tungsten titanium target. However, due to the heavy tungsten ratio, TFT-LCD active matrix LCD cannot meet the requirements of large size and light weight. Titanium can provide excellent adhesion and molybdenum can improve the stability of dense barrier layer. Therefore, molybdenum titanium film has excellent anti-diffusion blocking ability and has been widely used in TET-LCD.
Due to the advantages of low transportation cost and high material utilization rate, thin film solar cells have become a development trend of photovoltaic industry in recent years. In thin film solar cells, cu indium gallium Selenium (CIGS), as the absorption layer, is a kind of multicomponent semiconductor material with excellent performance and high photoelectric conversion rate, and the photoelectric conversion rate has reached 20.4%. The results show that doping a small amount of Na(0.1%, atom fraction) in CIGS can improve the photoelectric conversion efficiency significantly. By adding Mo - Na layer between the substrate and the back layer of molybdenum, Na can be doped into the CIGS absorption layer effectively. The process of preparing Mo - Na layer is the same as that of preparing Mo back electrode layer.
The specific impedance, film stress and corrosion resistance of molybdenum and niobium alloy can be improved by adding niobium into molybdenum. The thin films sputtered by Mo-Nb alloy target have better corrosion resistance. Molybdenum niobium alloy target material is mainly used for flat display and touch screen,TFT-LCD screen and photovoltaic field. Powder metallurgy is also used to prepare molybdenum-niobium alloy targets. Molybdenum niobium alloy target can be divided into plane target and rotating target according to shape.
