TABLE OF CONTENTS The need for ultra shallow junction formation in advanced devices makes the development of high productivity ion implantation solutions at very low energies increasingly more important. There are fundamental challenges associated with delivering these high productivity solutions. Nonetheless, progress in this area has been steady and significant.
The delivery of low energy p-type dopants (usually B + ions) has long been regarded as the most challenging task for an ion implanter to perform. Typical beam current specifications for B + implants, sampled across the entire industry over a 25-year period and spanning at least four generations of high current implant tools, are shown in Fig. 15.5. Each new generation of ion implanters exhibits basically the same characteristic dependence of usable beam current on implant energy. It is only the threshold, where a significant loss of usable beam current begins to occur, that has shifted to significantly lower energies over the years. The energies that are considered useful in high-volume manufacturing today are approximately two orders of magnitude lower than they were when ion implantation was in its infancy, decreasing from ?30 keV in the early 1980s to <0.5 keV today.
The challenges of overcoming space charge neutralization to increase low-energy beam transport are described in the following section. Novel approaches, such as...
