The deposition rate of target magnetron sputtering is also the deposition rate, which refers to the speed at which the deposit fills the accommodating space. The sputtering deposition rate is not only an important parameter of the film formation speed, but also has a great influence on the characteristics of the target film formation, such as strength, film stress, and surface finish. Let’s talk about the influence of magnetron sputtering on the target material. 5 factors of deposition rate.
Working gas pressure
With the change of the argon partial pressure, that is, the working pressure, the target voltage and vacuum will also change, correspondingly affecting the deposition rate of the target film. Some experimental results show that the deposition rate first increases and then decreases with the increase of working pressure. When the flow of argon gas is too large, the number of collisions between sputtered particles and argon gas is greatly increased, and the energy of the particles is greatly lost during the collision. As a result, the sputtered particles cannot reach the substrate or break through the gas adsorption layer, so the film cannot be formed. Or although it barely breaks through the gas adsorption layer, the adsorption energy with the substrate is very small, so the deposition rate is reduced.
The stronger and denser the plasma between the magnetic field control areas in front of the magnetron target, the higher the rate of atom detachment on the target. Among the factors that affect the sputtering coefficient, when the target material, sputtering gas, etc. have been selected, the more effective is the discharge voltage of the magnetron target. Generally speaking, within the normal process range of magnetron sputtering, the higher the discharge voltage, the greater the sputtering coefficient of the magnetron target; that is to say, the greater the energy of incident ions, the greater the sputtering coefficient. Within the range of energy required for sputtering deposition, its influence is gentle and gradual.
target base spacing
The target base distance refers to the distance between the target source and the substrate. When the target power is constant and the target base distance is small, the deposition rate will be distributed normally along the radial direction, which will seriously affect the deposition uniformity; when the target base distance is increased Larger, the uniformity is enhanced, but when the target base distance continues to increase, although the uniformity is stronger, the deposition rate decreases significantly. This is because when the distance between the target and the substrate is relatively close, the plasma density in the coating area is relatively high and the effect of gas scattering is small, and the film deposition rate is very high. With the increase of the target base distance, the number of collisions with gas molecules when the sputtered material hits the substrate increases. At the same time, the plasma density decreases and the kinetic energy decreases, so the film deposition rate decreases.
The sputtering current of the magnetron target is proportional to the ion current on the target surface, so the influence on the deposition rate is much greater than the voltage. There are two ways to increase the sputtering current: one is to increase the working voltage; the other is to appropriately increase the working gas pressure. The deposition rate corresponds to a gas pressure value. Under this gas pressure, its relative deposition rate is large. This phenomenon is a common law of magnetron sputtering. Under the premise of not affecting the quality of the film or meeting user requirements, it is more appropriate to consider the ideal value of gas pressure from the sputtering yield.
Generally speaking, when the sputtering power of the magnetron target increases, the deposition rate rate of the film also increases. There is a prerequisite here, that is, the sputtering voltage applied to the magnetron target is high enough so that the energy obtained by the working gas ions in the electric field between the cathode and anode is large enough to exceed the "sputtering energy threshold" of the target. Sometimes, the sputtering voltage of the magnetron target is very low, and the sputtering current is also relatively high. Although the average sputtering power is not low, the target ions cannot be sputtered out, and the sputtering deposition film cannot occur.