Applications of plasma immersion ion implantation in microelectronics — a brief review

Recent advances in plasma immersion ion implantation (PIII) are progressing at a rapid pace. PIII was originally envisioned as a conformal ion implantation technology for the surface modification of materials. PIII also offers the advantages of high dose rates, even at low energy, and single wafer implants over large areas. Such advantages are becoming very important for semiconductor manufacturing, particularly for 300-mm wafers and flat panel displays. Applications of PIII in microelectronics introduce new considerations. Conformal implantation is not required, and is unwanted in most semiconductor processes, except for trench doping-type applications. In various implant applications, there are often radically different requirements of plasma physics and chemistry. For example, the formation of shallow junctions requires extremely low energy implantation, and a precise implant range may not be necessary or ideal. In this application, PIII becomes the concept of plasma doping, where a wafer under either a DC or pulse bias is directly exposed to the plasma. On the other hand, hydrogen PIII for layer transfer requires extremely precise implant ranges, straggles and sample temperature, but the exact dose may not be critical. In this paper, two important application areas that have attracted much attention and research in the past 2 years, hydrogen PIII and the fabrication of low-k materials, are reviewed.