Ultra-shallow, abrupt, and highly-activated junctions by low-energy ion implantation and laser annealing

With the recent advances in low-energy ion implantation, the challenges for device manufacturers become how to anneal the implant damage and how to electrically activate implanted dopants. Current rapid thermal processes cause undesired dopant diffusion and have a low electrical activation limited by solid solubility. We report on a process that utilizes a pulsed, ultraviolet laser beam to anneal and activate low-energy implanted junctions. Junctions with depths shallower than 35 nm and sheet resistance smaller than 100 Ω/sq are demonstrated. The results indicate an activated dopant concentration higher than 10²¹ cm^-3. The de-activation of the highly-activated dopants in a subsequent thermal process is also studied. The results suggest that boron junctions will not suffer from de-activation and severe dopant diffusion, and phosphorus may be the choice of n-type dopant because it de-activates less than arsenic. Finally, we will discuss advantages of this process to device performance, present the integration issues, and forecast challenges to the ion implantation community if this process is adopted by device manufacturers