Applications of plasma-based technology to microelectronics and biomedical engineering

Plasma-based ion implantation and deposition techniques are widely used in many applications. In addition to the ability to modify the materials surface, novel structures can be fabricated. Another advantage is that the surface characteristics such as mechanical properties and biocompatibility can be selectively enhanced with the favorable bulk attributes of the materials unchanged. In this invited paper, our recent research activities on microelectronics and biomedical engineering are reviewed. Silicon-on-insulator (SOI) is expected to replace conventional bulk silicon substrates in many high speed, low power microelectronic devices because it possesses advantages such as reduction of parasitic capacitance, excellent sub-threshold slope, elimination of latch up, and resistance to radiation. However, wider applications of SOI in microelectronics are hampered by the self-heating effects caused by the poor thermal conductivity of the buried silicon dioxide layer. We have produced alternative buried insulators such as diamond-like carbon that possesses better thermal conductivity compared to conventional silicon dioxide using plasma immersion ion implantation and deposition (PIII&D) and successfully fabricated SOI structures with improved thermal stability. The use of low-energy plasma hydrogenation to substitute for the costly beam-line hydrogen ion implantation in the ion-cutting layer transfer technology is also discussed. In biomedical engineering, plasma spraying is a versatile technique to produce relatively thick ceramic coatings on orthopedic implant surfaces. We have discovered that plasma-sprayed nano-structured TiO₂ coatings favor the growth of apatite. The surface bioactivity is enhanced by hydrogen plasma implantation and the mechanism is discussed. The antibacterial properties of polymers can also be improved by implanting elements such as Ag and Cu and recent work in our laboratory is described. © 2009 Elsevier B.V. All rights reserved.