Etching of carbon–tungsten composite with oxygen plasma

The removal rate of carbon from amorphous graphite–tungsten composite during cleaning in oxygen plasma was studied. The composite was prepared by sputter deposition from C and WC-targets in Ar atmosphere. A total thickness of deposited layer was about 1 μm. The samples were treated in a weakly ionized highly dissociated oxygen plasma created in a microwave discharge at a power of 1 kW. The gas flow was 13 slh and the pressure was 200 Pa. The temperature of the samples during treatment was about 580 °C. After plasma treatment the samples were analyzed by AES (Auger electron spectroscopy) depth profiling, XPS (X-ray photoelectron spectroscopy), SEM (Scanning electron microscopy) and AFM (Atomic force microscopy). It was found that during the plasma treatment selective etching of the composite occurred. Carbon was preferentially removed from the composite. XPS results have shown that during the plasma treatment a layer of WO 3 was growing on the surface. After about 15 min, carbon was completely removed from the deposited composite layer.