Sputtering ferromagnetic materials, for example, to interface magnetism with topological matter – which is one of MagTop’s goals – has proven challenging with commercially available sputtering sources. The problem is that the target shields the magnetic field and it is difficult to obtain a magnetic field of sufficient strength. Additionally, suboptimal field distribution above the target results in a non-uniform plasma distribution during the operation, resulting in turn in the need to frequently replace the target, which is not fully utilized and must additionally be thinner than 1.3 mm in case of iron (see Fig. 1 a.). Worse, it also leads to a flux that is not constant during the process.
The MagTop(MBE group)/PREVAC team proposed a solution to this problem through a special design of magnetic cores that not only provide a magnetic field that is parallel to the target’s surface and has sufficient strength, but is also obtained in a configuration that allows its safe cooling. Proof of concept was provided by an experimental demonstration carried out using a prototype source manufactured by PREVAC Ltd. that a much thicker magnetic target (up to 6 mm) can now be used and a much larger target volume can be utilized (see Fig.1 b.). Very important from a technological point of view is the achieved long-term stability of deposition rate of ferromagnets.
As a follow up of the “Agreement on joint rights to a patent and joint patent” signed on October 19, 2021, on June 08, 2022 Andreas Glenz (PREVAC), Krzysztof Fronc and Michał Chojnacki (MagTop(MBE group) filed an application to the European Patent Office to protect a declaration of priority for this invention entitled: “Device for magnetron sputtering from target” (application number EP22461556.7). In the mentioned agreement, MagTop granted PREVAC the right, against payment, to use the invention in a new line of two inch sputtering sources manufactured by this company.
|Fig. 1 a. 2” standard iron target with a thickness of 2 mm with a visible narrow and uneven erosion track, leading to flux that is not constant during deposition.
|Fig. 1 b. Modified target with a central ring of the original thickness of 3-mm-thick, after many sputtering processes. It is clearly seen that its surface is flat, which means that the material is consumed evenly.