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Control of reactive DC magnetron sputtering of SnO2 by means of optical emission

: Kirchhoff, V.; Heisig, U.

Oechsner, H. ; European Joint Committee on Plasma and Ion Surface Engineering:
Third International Conference on Plasma Surface Engineering 1992. Papers. Pt.1
Lausanne: Elsevier Sequoia, 1993 (Surface and coatings technology 59.1993,Nr.1/3)
International Conference on Plasma Surface Engineering <5, 1996, Garmisch-Partenkirchen>
Conference Paper
Fraunhofer FEP ()
chemical variables control; closed loop system; flow control; process control; semiconductor growth; semiconductor thin film; spectrochemical analysis; sputter deposition; tin compound

One procedure to stabilize reactive DC magnetron discharges is the so-called plasma emission monitoring (PEM). The intensity of the plasma emission of a characteristic target line is used as measuring signal for a closed loop to control the reactive gas flow. In an attempt to use PEM control for the reactive deposition of SnO2, a non-monotonic relation between film composition and line intensity was measured. The relation between line intensity and film deposition rate is obtained. In either case the line intensity approached a maximum. The behaviour is explained by a strong increase in the excitation of the sputtered metal particles in the oxygen-containing plasma. In this way, the decrease in the metal rate, and consequently the intensity of the metal line, are overcompensated. A concept and an instrumental solution are described which ensured the control of the reactive sputter process of SnO2 under the conditions mentioned. The method can be transferred to other materials that exhibit a similar behaviour.