The preparation process of 4N chromium target mainly involves high-purity raw material processing, melting and shaping, and post-processing. The core methods include vacuum melting and powder metallurgy. The specific process is as follows:
1. Raw material preparation
Purity requirement: Select chromium raw materials with an initial purity of ≥ 99.9%, and remove surface oxides and impurities through chemical cleaning and vacuum drying.
Physical processing: Screening or ball milling of raw materials to ensure particle uniformity and avoid uneven density during subsequent melting or sintering.
2. Melting and forming
Vacuum arc melting: Melting chromium raw materials at high temperatures in a vacuum environment, heating them above the melting point through an arc, and forming dense chromium ingots after cooling. This method can effectively avoid the mixing of impurities such as oxygen and nitrogen, and is suitable for the production of industrial grade high-purity target materials.
Electron beam melting: higher purity, but expensive equipment cost, mostly used in high-end semiconductor fields.
3. Powder metallurgy method
Cold isostatic pressing: Place chromium powder into a mold, press it into a billet at a pressure of 100-180MPa, and hold for 15-20 minutes.
Hot isostatic pressing sintering: degassing and high-temperature sintering are carried out in stages, with a pressure of 300-450MPa, to ultimately obtain high-density target materials.
4. Post processing
Mechanical processing: Processing chromium ingots into target materials through forging, rolling, or extrusion, combined with cold/hot rolling to improve density and uniformity.
Surface treatment: Grind and polish to a surface roughness of ≤ 0.1 μ m to ensure the uniformity of the film during sputtering coating.
5. Quality control
Purity testing: Analyze impurity content using ICP-OES or XRF to ensure compliance with the 4N standard.
Density and Grain Size: The target density should be close to the theoretical value of 7.19 g/cm ³, and the grain size should be controlled at the micrometer level to optimize sputtering performance.
