Deposition of Highly Ordered CF2-Rich Films Using Continuous Wave and Pulsed Hexafluoropropylene Oxide Plasmas

The structure and composition of fluorocarbon materials deposited in pulsed and continuous wave (CW) hexafluoropropylene oxide (HFPO) plasmas were investigated. Results indicate substantial dependence on substrate position relative to the rf coil. When the substrate was placed 8 cm downstream from the rf coil (25 W CW), highly amorphous, cross-linked films were obtained. In contrast, materials deposited 28 cm downstream from the rf coil contained less cross-linked moieties and a higher degree of order. Angle-resolved X-ray photoelectron spectroscopy (XPS) C1s analysis showed that the 28 cm materials contain up to ∼80% CF2 and CF3 surface-enriched layers. Static secondary ion mass spectroscopy (SIMS) data revealed that these fluorocarbon materials are composed of long CF2 chains. Near edge X-ray absorption fine structure (NEXAFS) analysis showed that the CF2 chains were oriented perpendicular to the substrate surface for the films deposited at 28 cm downstream, while the films obtained 8 cm downstream do not exhibit any particular orientation. The compositions of materials deposited in pulsed HFPO systems have rf power and distance dependencies similar to those observed in the CW plasmas.