Sputtering Targets
Introduction
The target is the basic consumable in the magnetron sputtering process. It is not only used in large quantities, but also the quality of the target plays a crucial role in determining the performance of the metal film. Therefore, the target is the key material in the magnetron sputtering process. At present, the most commonly used classification method of targets is based on their application fields, mainly including targets for semiconductor, recording media, display films, optical targets, superconducting targets, etc. Among them, the semiconductor target, recording medium target and display target are the three types of targets with the largest market demand.
Targets for semiconductor field
The electrode wiring conductive film, barrier film, adhesive film, ohmic contact film and resistance film of semiconductor devices are prepared by sputtering with corresponding targets. Generally, pure Al and Al alloy targets are used in integrated circuits and discrete devices with low power consumption; Au targets are mainly used in power transistors and microwave devices. The target materials for the barrier film are mainly refractory metals such as W, Mo and refractory metal silicides. The target materials for adhesive film mainly include Ti, W, etc. The target materials for resistance film include NiCr, MoSi2, WSi, etc.
Targets for recording medium
- Targets for magnetic recording medium
Most of the magnetic films in the field of high-density hard disk drives are deposited by sputtering. Magnetic recording media include longitudinal magnetized Co system, longitudinal magnetized Fe system and vertical magnetized Co system. The longitudinal magnetization of Co system is that Cr film is plated by sputtering method and then Co film is sputtered on it. There are many Co alloys targets used as longitudinally magnetized Co system recording medium, the most commonly used is CoCrTa. γ-Fe2O3 thin films deposited by sputtering are the most commonly used films of longitudinally magnetized Fe system.
- Targets for optical recording medium
Optical recording mainly includes two types of optical disk, magneto-optical disk and phase change optical disk. The typical structure of an optical disk includes a substrate, a lower protective layer, a recording layer, an upper protective layer and a reflective layer.
The reflective film is made of pure Al or AI alloy target by sputtering deposition; The recording film is made of rare-earth transition metal target sputtering deposition; The protective film was prepared by reactive sputtering deposition of Si target in N2 atmosphere. Rare-earth transition metal targets include GdCo, GdFe, DyFe, GdTbFe, FeTbCo, etc., among which FeTbCo is the most widely used. In order to overcome the oxidation problem of FeTbCo alloy films, superlattice targets consisting of rare-earth transition metals have been developed.
Targets for display device
At present, ITO (indium tin oxide) transparent film is most commonly used in display device industry. ITO films are usually prepared by sputtering, which includes two methods. One is reactive sputtering with In-Sn alloy target in O2 atmosphere. The other method is ITO target sputtering deposition, which is widely used today. It is the best method to prepare transparent conductive ITO films with high performance. In addition, the targets used for preparing display device films include: refractory metals for preparing electrode wiring films, Al and Al alloy targets for preparing electrode wiring films and light shielding films, ZnS-Mn targets for preparing electroluminescent film luminescent layers, Y2O3 and BaTiO3 targets for preparing electroluminescent film insulating layers, etc.
Reference
- Depla, Diederik; MAHIEU, Stijn; GREENE, J. E. Sputter deposition processes. In: Handbook of deposition technologies for films and coatings. William Andrew Publishing, 2010. p. 253-296.