Effect of Relative Density and Gap of Sputtering Target on Large Area Coating
As a large raw material for coating, the characteristics of sputtering target
, including target shape, purity, density, porosity, grain size and binding quality, have a great influence on film quality and sputtering rate. Today, I will discuss the influence of the relative density and gap of sputtering target on large area coating.
Effect of target relative density on large area coating
The relative density of the target is the ratio of the actual density of the target to the theoretical density. The theoretical density of the single component target is the crystal density. The theoretical density of the alloy or mixture target is calculated by the theoretical density of each component and its proportion in the alloy or mixture. The target structure of thermal spraying is loose and porous, with high oxygen content (even in vacuum spraying, it is difficult to avoid the generation of oxides and nitrides in the alloy target). The surface is gray and lack of metallic luster. The adsorbed impurities and moisture are the main pollution sources, which hinder the rapid acquisition of high vacuum, and easily lead to discharge in the sputtering process, or even burn the target. Figure 1 shows the initial stage of installation and use The photos of spray target with low density are seriously discharged and burnt out.
At the same time, the high temperature on the sputtering surface of the target easily causes the loose particles to fall, contaminates the glass surface and affects the coating quality. The higher the relative density, the faster the film forming rate and the more stable the sputtering process. According to the difference of target preparation technology, the relative density of the casting target should be more than 98%, and the powder metallurgy target should be more than 97% to meet the production use. Therefore, the target density should be strictly controlled to reduce the occurrence of slag dropping. The density of spraying target is low, and the cost of preparation is also low. When the relative density can ensure more than 90%, it generally does not affect the use.
The effect of target gap on large area coating
In addition to densification, if the target is abnormal in the production process, such as large particles falling off or shrinkage holes due to heat, more pores (internal defects) will be formed, and larger or denser pores in the target will be discharged due to charge concentration, affecting the use.
The target with low density and air hole is easy to break when it is processed, transported or installed. The target with high relative density and few pores has good thermal conductivity, and the heat on the surface of sputtering target is easy to be transferred to the cooling water on the inner surface of target or liner quickly, which ensures the stability of film forming process.
AEM deposition, as a professional sputtering target manufacturer
, supplies all kinds of pure metal sputtering target, alloy sputtering target and ceramic compound sputtering target. The details are as follows:
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