Characterization and reduction of a new particle defect mode in sub-0.25 μm semiconductor process flows

A new particle defect mode has manifested itself with the introduction of sub-0.25 μm process flows. Device structures can now be damaged as a result of collision of high velocity wafers with lower velocity “ambient” particles in the process chamber. This effect has been found in batch implanters where wafers are scanned on a spinning disk or wheel. As feature geometries shrink, yield losses from the ballistic particle collisions increase. The particles may be sourced within the process tool, or brought in on the incoming wafers. It is primarily the motion of the wafer which provides the damaging energy of collision, not the motion of the particle. High scan velocities were thought necessary to achieve implant process uniformity. Avoiding yield loss from these new defect modes requires careful attention to the conceptual and detailed design of the implanter to minimize the likelihood and energy of these collisions.