Preparation and sputtering properties of pure molybdenum target for TFT-LCD
In modern TFT-LCD manufacturing, molybdenum film is mainly used as the barrier layer of Al in conductive film, and part of molybdenum film is used as barrier layer of Al in conductive film. The barrier layer of Cu. The main requirements for conductive film in TFT-LCD are: low resistivity, good uniformity and appearance. Smooth, good adhesion, good step coverage, minimum stress, minimum abnormal protrusion, minimum electron mobility, etc. Molybdenum thin films are prepared by magnetron sputtering. At present, the requirement of molybdenum target material is grain size. When it is controlled within 100um or even less than 50um, the grain orientation is uniform and the sputtering rate is uniform. And to achieve these indicators are difficult. Therefore, how to prepare molybdenum target meeting the requirements of TFT-LCD conductive film becomes the field technical difficulties and hot spots. In this paper, high purity molybdenum powder (99.99%) was used as raw material. The technology of metallurgical preparation of molybdenum target and its magnetron sputtering performance. The research contents and results are as follows.
The results show that the particle size distribution is a single peak normal distribution, and the microstructure of molybdenum powder compacts with D (O.5) <10um is uniform, while that of bulk is uniform. When the isostatic pressure is greater than 200 MPa, there are less pores in the compact. The results show that the density of molybdenum powder is uniform and the shrinkage is uniform. The preparation technology of high-density fine-grained slab by high-pressure pressing was studied.
Through the analysis of the factors affecting the sintering process of molybdenum target and the study of sintering mechanism, the results show that the sintering pressure of 400MPa is higher than that of the former. In order to reduce the sintering temperature and obtain fine grains, high-pressure pressing and low-temperature sintering can be adopted; the sintering heating rate of 3K / min can be adopted for 100MPa slab, and 1K / min for 400MPa slab. In the initial stage of sintering from 1273K to 1673k, the surface diffusion is dominant; in the middle stage of sintering from 1773K to 1973k, the particles begin to bond and the grain boundary begins to move. The porosity has a quadratic relationship with the pore closure time, and the shrinkage rate is the largest and the densification speed is faster; In the later stage of sintering from 2073k to 2173k, the shape of pores is isolated and closed, the grains grow up obviously, and the shrinkage of green body reaches 90% ~ 100%, which is close to the theoretical density.
The effect of different blooming methods on the microstructure of molybdenum target was studied. The results show that the microstructure of Mo target prepared by forging + rolling is smaller than that by rolling.
The results show that the crystallizing degree and square resistance of the sputtering film of molybdenum target with 80% deformation are better than those of other target materials. When the deformation is 80%, the roughness of the sputtering film is less than 21nm and the thickness uniformity is better when the annealing temperature is 1373k and 1473k; The results show that the target grain size is less than 50um, the sputtering rate is fast and uniform, and the square resistance deviation of the sputtering film is less than 10%; the preferred orientation of the sputtering films is (110).
