The rapid development of electronic information technology has created great demand for magnetic thin films and magnetic components. The preparation of magnetic thin films and magnetic components is inseparable from ferromagnetic metals and alloys such as Fe, Co and Ni. Since the film prepared by magnetron sputtering technology has high purity and precise structure control, magnetron sputtering is a widely used method for depositing high quality magnetic films to manufacture magnetic components. However, magnetron sputtering deposited magnetic thin films have problems such as the difficulty of normal sputtering of ferromagnetic targets, which hinders the production and application of high-performance magnetic thin films and devices.

Problems in magnetron sputtering ferromagnetic targets

For ferromagnetic materials such as Fe, Co, Ni, Fe2O3, and permalloy, the use of ordinary magnetron sputtering is greatly limited to achieve low-temperature, high-speed sputter deposition. This is because the magnetic reluctance of the target made of the above materials is very low, and most of the magnetic field passes through the inside of the ferromagnetic target almost as shown in Fig. 1, so that the residual magnetic field on the upper surface of the target is too small to form. Effectively electron-trapping regions, it is impossible to form a strong magnetic field parallel to the target surface that causes the secondary electrons to move in a circular wobble, so that magnetron sputtering cannot be performed. At this time, magnetron sputtering becomes a very low-efficiency two-pole sputtering, which causes the deposition speed of the film to be greatly lowered, and the substrate is heated rapidly.

In addition to the magnetic shielding effect, the plasma magnetization phenomenon becomes more serious when sputtering ferromagnetic materials than ordinary targets. As shown in Fig. 2, points 1 and 3 in Fig. 2(a) are points on both sides of the bobbin C in the magnetic flux path. At the time of sputtering, since the electric field and the magnetic field coexist, the electrons at the positions of the point 1 and the point 3 are moved by the Coulomb force and the Lorentz force to the center line axis C of the magnetic flux path, and the electron at the point 2 position is not affected. The role of lateral forces.

Therefore, the plasma at the centerline axis is the most at the time of sputtering, the sputtering at the corresponding position of the target is the most intense, and the sputtering rate is also the largest. This condition is present in all target sputtering. However, when sputtering a ferromagnetic target, the phenomenon of plasma magnetization is more serious.

Due to the phenomenon of plasma magnetization, a sputtering channel first appears at the center line of the magnetic flux path, and the magnetic lines of force originally passed from the inside of the ferromagnetic target will leak out from the channel, and the deeper the channel being sputtered, the leaking The more magnetic lines, the greater the strength of the magnetic field at the axis of the magnetic field lines, so that more electrons are magnetized at the axis of the magnetic field lines. More plasma is generated at the axis of the magnetic field lines, so the sputtering rate at the channel is higher. Large, eventually causing the target at the channel to be splashed faster. Since the magnetic flux lines passing through the ferromagnetic target are far more than ordinary targets, the magnetic lines of the magnetic flux are more diarrhea, the magnetic field strength at the central axis of the magnetic lines is greater, and the sputter etching rate at the channel is faster.