Method for sputtering deposition of alloy films
In order to reduce the number of targets used in the sputtering system, the alloy thin films that meet the requirements of composition and performance can be prepared by sputtering deposition with one target as far as possible, such as alloy target, composite Mosaic target and multi-target sputtering.
Generally speaking, in the stable state of discharge, according to the composition of the target, all kinds of constituent atoms are subjected to the effect of sputtering, sputtering coating is superior to vacuum evaporation and ion plating in that: the composition of the film and target components are less different, and the coating components are stable.However, in some cases, due to the choice of sputtering phenomenon of different components, the film's anti-sputtering rate and adhesion are different, which will cause the film and target components have great differences.Using this alloy target, in order to make the film with certain components, in addition to preparing the target with specific proportion according to the experiment and reducing the temperature of the target as far as possible, the substrate temperature can also be reduced to reduce the difference in adhesion rate, and appropriate process conditions can be selected to reduce the anti-sputtering effect on the film layer as far as possible.
In some cases, it is not easy to prepare large areas of uniform alloy targets and compound targets. In this case, composite Mosaic targets composed of single elements can be adopted. The composition of the target surface is shown in figure 1.The fan-shaped Mosaic structure shown in FIG. D has the best effect, and it is easy to control the composition of the film and has good repeatability.In principle, not only binary alloys, but also ternary and quaternary alloys can be prepared by this method.
Figure 1 composite targets with different structures
(a) block Mosaic target; (b) round Mosaic target; (c) small square Mosaic target; (d) fan-shaped Mosaic target
To make the corresponding component distribution in the sputtering film, the Mosaic target as shown in figure 2 can be used. In the figure, a composite target of Al material was drilled into the etched area of a Ti matrix target to prepare Ti Al N alloy film or compound film. It can be seen from the figure that the film composition is different at different positions of the substrate. The inlaying position and quantity of Al material correspond to the determined alloy composition, so it is very convenient to make alloy or compound films of various components by this method.
Figure 2 Ti-Al Mosaic composite target
The structure of multi-target sputtering is shown in figure 3. Compound films can be prepared by rotating the substrate above two or more targets and controlling the deposition thickness of each film to be one or more atomic layers. For example, InSb and GaSb targets have been used to produce in1-xgax Sb single crystal films. Although this device is more complicated, the membrane of any component can be obtained by controlling the rotation speed of the substrate and changing the voltage applied on each target. By controlling these parameters, the composition of the film can be changed in the direction of the film thickness, and the superlattice structure can be obtained.
FIG. 3 schematic diagram of multi-target sputtering structure
When the composition of the alloy film varies greatly, the auxiliary cathode method is usually used. The main cathode target is made of the main component of the alloy, and the auxiliary cathode target is made of the added component of the alloy. Sputtering was performed on each target simultaneously to form alloy film. By adjusting the current of the auxiliary cathode target, the amount of added components in the alloy film can be changed at will.
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