Factors Affecting Film Uniformity On Magnetron Sputtering Vacuum Coaters

The homogeneity of the thickness of the coated film on a magnetron sputtering vacuum coating machine is a very important indicator of the film-forming properties, so it is very necessary to study the homogeneity of the coated film on a magnetron sputtering vacuum coating machine. Here enijor gives you more details:

 In simple terms magnetron sputtering is a closed magnetic field in an orthogonal electromagnetic field that binds electrons in a spiral motion around the target surface, which in the course of the motion continuously strikes the working gas argon ionising a large number of argon ions, which are accelerated by the electric field and bombard the target, sputtering out neutral target atoms (or molecules) deposited on the substrate to form a film. So to achieve a uniform coating, a uniform sputtering of target atoms (or molecules) is required, which requires that the argon ions bombarding the target are homogeneous and uniformly bombarded. Since the argon ions are accelerated by the electric field, uniform bombardment relies heavily on the uniformity of the electric field. The argon ions, in turn, originate from the working gas argon which is continuously struck by electrons bound by a closed magnetic field in motion, which requires a uniform magnetic field and a uniform working gas argon. In actual magnetron sputtering devices, however, these factors are inhomogeneous, which makes it necessary to investigate the effect of their inhomogeneity on the uniformity of the film formation.

1. The effect of an inhomogeneous magnetic field

      Since the electric and magnetic fields in a real magnetron sputtering device are not uniform everywhere, nor orthogonal everywhere, they are functions of space. The expressions written for the three-dimensional equations of motion are not solvable, at least not for the primary functions. Therefore the effect of the inhomogeneity of the magnetic field on the ions, i.e. on the inhomogeneity of the film formation, is difficult to calculate and is best analysed in conjunction with experimental specifics.

2. The effect of gas inhomogeneity

      Generally speaking gas inhomogeneity can be produced by two situations, one is uneven gas delivery and the other is uneven pumping. The normal pumping situation refers to the symmetrical pumping at both ends of the twin targets inside the vacuum chamber, which can be considered as uniform pumping; while the front molecular pump off and the back molecular pump off are pumping at one end, which is uneven pumping. As both are uniformly fed uneven pumping, the gas in the vacuum chamber is not uniform. It is obvious that when the front molecular pump is switched off and only the rear molecular pump is switched on, the air pressure decreases gradually from front to back, while when the rear molecular pump is switched off and only the front molecular pump is switched on, the air pressure decreases gradually from back to front. The experimentally obtained film thickness also corresponds to the change in air pressure after taking into account the influence of the magnetic field.

3. Target base distance, the impact of air pressure

     Magnetron sputtering vacuum coating machine target base distance is also an important process parameter affecting the uniformity of magnetron sputtering film thickness, film thickness uniformity in a certain range with the increase in target base distance has a tendency to improve, sputtering work air pressure is also an important factor affecting the uniformity of film thickness . However, this uniformity is within a small range, because the uniformity produced by increasing the target base distance is generated by increasing the area on the substrate corresponding to a point on the target, while increasing the working air pressure is generated by increasing particle scattering, obviously, these factors can only play a role in a small area.