Degradation of RuO2 thin films in hydrogen atmosphere at temperatures between 150 and 250 °C

Ruthenium dioxide films were sputtered on silicon dioxide/silicon in thin-film resistors and MOS capacitors structures. Such structures with RuO2 were exposed to H-2/N-2 ambient with 1% hydrogen content in the temperature range from 150 to 250 degreesC. Severe morphological degradation of RuO2 films was observed by scanning electron microscope. By X-ray diffraction analysis it was proved that RuO2 tends to reduce to Ru in the presence of hydrogen. The pattern of degradation is strongly influenced by the preparation condition: films deposited at room temperature show irregular degradation shape, and films deposited at 300 degreesC exhibit star-like shape. The shift in capacitance-voltage curves of MOS capacitors with RuO2 gate electrode after degradation also proves the presence of Ru in the electrode. The failure of the above structures when exposed to hydrogen ambient suggests the need of introduction of hydrogen barrier layers to exploit the good properties of RuO2. (C) Elsevier Science Ltd. All rights reserved.