Selective deposition of Ti: An interface study

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Abstract
If different substrates are bombarded by energetic (500–1000 eV) Ar ions during deposition of Ti, quite different film thicknesses may result on the substrates. In fact, on some of the substrates there will be no net deposition of Ti, while on others there will be formed a thin film of Ti. This is the bias sputtering selective deposition technique. The advantage with this technique is that the process is carried out in inert argon gas. Furthermore, almost any material may be selectively deposited. Since the substrate is bombarded by energetic argon ions during deposition its surface will be sputter etched. During the buildup of the Ti film a mixed interface may result. We have investigated the sharpness of these interfaces by Rutherford backscattering and by Auger depth profiling. We have found a critical processing interval where soft interfaces are formed by this technique. The experiments indicate that this ‘‘soft interface’’ interval appears when the deposition rate of sputtered Ti dominates only by a fraction over the bias sputter removal rate. However, if this processing interval is avoided, sharp interfaces may be obtained. In fact, the interfaces are as sharp as if Ti was sputtered onto the substrates without ion bombardment. However, the results found indicate that one has to compromise between interface sharpness and deposition selectivity. Results for Ti on Si, Pt, and Au will be presented.

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