Industry Trends

Scaling

The semiconductor industry is constantly scaling, which refers to the reduction of size to make each element smaller and thereby pack more into each chip.  With each scaling step, essentially all fabrication steps must be modified to manage the resulting transistor performance.  For ion implant, the main result of scaling is a reduction of the energy, since the vertical dimension must scale.  There are also changes to the doses being implanted, usually increasing the dose.

As all implant processes have their energy reduced, the lowest energy processes have difficulty in providing the required capability.  Conventional ion implanters have significant problems at low energy, due to limitations in extracting and transporting low energy beams.  There is a limit to the amount of beam current achievable at any energy (E), due to space charge effects, and the magnitude of the current limit follows an E^3/2 function.  This problem is severe enough that current production equipment does not meet the historical measure of “production worthy” which is processing 50 wafers per hour, for the low energy processes. This trend is shown in the figure below for the PMOS Drain Extension Implant.

300mm Transition

In addition, the industry is now in transition from 200mm to 300mm wafer size.  The larger wafers take longer to process, and thus further challenge the implant system’s ability to be “production worthy”.  The fab managers expect each tool to maintain its wafer throughput, but the ion implanter cannot increase its low energy beam current.  Thus, today’s tools are not capable of processing 300mm wafers with “production worthy” throughput.