Why are low-energy ions relevant to the surface processing of electronic materials? The answer lies in the overriding trend of miniaturization in microelectronics. The achievement of these feats in ultrasmall architecture has required surface processing capabilities that allow layer addition and removal with incredible precision. The resulting benefits of greater capacity and speed at a plummeting cost per function are near legendary.
The ability of low-energy ions to enhance the precision of surface etching, cleaning, and deposition/growth processes (Figure 1) provides one basis for the interest in ion-assisted processes. Low-energy ions are used, for example, to enhance the sharpness of side walls in plasma etching and to improve step coverage by metal layers in sputter deposition. Emerging optoelectronic applications such as forming ridges for wave-guides and ultrasmooth vertical surfaces for lasers further extend piesent requirements, and low-energy ions again provide one tool to help in this area of ultraprecise materials control. Trends associated with the decreased feature size include the movement from wet chemical processing to dry processing, the continuing need for reductions in defect densities, and the drive toward reduced temperatures and times in process steps.
How do the above trends focus interest on studies of low-energy ion-assisted processes? In current applications, these trends are driving the need for increased atomic-level understanding of the ion-enhancement mechanisms, for example, in reactive ion etching to minimize defect production and enhance surface chemical reactions.