Effects of pre-amorphization on junction characteristics and damage behavior in low energy boron implantation

One of the major challenges of meeting the source/drain extension requirements for high performance scaled devices is to achieve low series resistance with shallow junctions. Pre-amorphization has been used to suppress implant channeling and to enhance dopant activation during solid phase crystal re-growth. In this paper the effects of Ge premorphization on the activation of 1 keV boron implants under various thermal treatments have been investigated. The wafers were pre-amorphized with 5 keV 1×10¹⁵ cm^-2 Ge⁺ implant. Subsequent anneals on some samples were performed in a furnace at temperatures ranging from 500°C to 750°C for 30 min and some were processed by RTA at 800°C to 1050°C under various soak times. While the activation behavior above 700°C for the crystalline and preaamorphized samples was similar, distinctly different behavior was observed at lower temperatures in the two cases. Lower sheet resistance was obtained In pre-amorphized samples below 300°C but reverse annealing is observed when the temperature is increased. Spreading resistance and SIMS analysis were used to generate junction profiles. In addition, TEM analysis was done to understand the physics of the observed phenomenon and to investigate the merits and demerits of preamorphization from a process integration standpoint