Research status and development trend of molybdenum and molybdenum alloy sputtering targets
Molybdenum belongs to refractory metal, body centered cubic structure, with good conductivity and thermal conductivity, low thermal expansion coefficient, good corrosion resistance and environmental friendly and other sub components and electronic products, such as thin film semiconductor tube liquid crystal display (TFT-LCD) plasma display, field emission display, touch screen, can also be used in solar cell back electrode, glass coating and other fields. In recent years, with the development of electronic industry and solar cells, the amount of molybdenum and molybdenum alloy targets as high value-added electronic materials is increasing year by year.
As a new high-end product in molybdenum industry, molybdenum and molybdenum alloy sputtering targets have high technical content, high purity, high relative density and fine and uniform grains.
Quality requirements of molybdenum sputtering target
Molybdenum target is mainly deposited on various substrates by magnetron sputtering. The quality of the target determines the sputtering efficiency and the properties of the films. In order to achieve high sputtering efficiency and obtain excellent sputtered films, the target material must meet the following requirements:
(1) High purity. In the sputtering process, molybdenum and molybdenum alloy targets are used as cathode sources. Impurities in the solid and Oz and HZO in the pores will pollute the films and affect the performance of the films. In the electronic industry, alkali metal ions (Na *, K *) are easy to be broken down under high temperature and high pressure and become bad points, affecting the use effect. Therefore, high purity is the most basic requirement of molybdenum target, and its purity requirement is generally ≥ 99.95% 19-10]. The purity of molybdenum target for TFT-LCD is higher than that of thin film solar cell.
(2) The relative density is high. The relative density of molybdenum and molybdenum alloy targets not only affects the deposition rate of the films, but also affects the electrical and optical properties of the films. The target with low relative density has more pores in the target. When magnetron sputtering, the sudden release of gas in the pores will cause the target particles or particles splashing, which will reduce the performance of the film. Therefore, high relative density of molybdenum and molybdenum alloy sputtering target is required. Thin film solar cells generally require the relative density of molybdenum target to be more than 98%. TFT-LCD field requires higher relative density, which should reach 99% or even more than 99.5%.
(3) The grains are fine and the size difference is small. The sputtering rate of the target with fine grain is faster than that of the coarse crystal. The thickness distribution of the deposited film is also uniform for the target with uniform distribution and small size difference. Generally, the grain size of molybdenum sputtering target should be less than 100μm, and some even require that the grain size should be controlled below 50μm.
