New Plasma Source for Plasma Immersion Ion Implantation

Plasma immersion ion implantation (PIII) is a useful niche technology for the modification of surface properties of materials and industrial components that are large or have an irregular shape. The samples are immersed in an overlying plasma from which ions are extracted and implanted into the samples. A plasma source is typically needed to supply the ions. Traditionally, ions can be produced by thermionic discharge, pulsed high-voltage glow discharge, RF plasma source, microwave plasma source, cathodic arc metal plasma source, sputtering target, and so on. In spite of extensive research, there is still no single source that can provide ions of all elements. It is still inconvenient or difficult to ionize solid materials with poor electrical conductivity such as sulfur, phosphorus, boron, semiconducting materials such as silicon, germanium, and elements with low melt point and / or high chemical activity like the group IA and IIA elements. In this paper, we report a novel method to create ions from solid materials possessing low melting point and high vapor pressure using an evaporation-glow discharge hybrid technique. The elements investigated are sulfur, phosphorus, and sodium that are very important in biomaterials. Using this method, sulfur is vaporized first, and then the vapor is introduced into a small glass-shielded chamber to lessen contamination of the big vacuum chamber. Sulfur is then ionized and passed into the PIII chamber to carry out plasma implantation and deposition. The sulfur depth profiles are acquired from the implanted samples using XPS depth profiling and the implantation results are compared to theoretical ones simulated by TRIM. Using the results, the relationship between the vapor pressure/carrier gas pressure and the implantation results is evaluated.