Bulk FinFET junction isolation by heavy species and thermal implants

One of the challenges for bulk-Si FinFET is forming the junction isolation at the 14nm node and beyond. As the fins are scaled, source-drain punch-through can occur, which causes large leakage currents. A punch-through stop (PTS) layer/structure at the bottom of the fin is introduced to suppress this sub-fin leakage current. However, the introduction of PTS may result in dopant back diffusion into the active fin region from the PTS implant(s). This may result in device shift and variability. In this paper, we investigated novel approaches to reduce dopant back diffusion into the active fin region. Specifically, we studied the impact of (1) Carbon co-implants to block the dopant up-diffusion into the active fin region, (2) implants with heavy species at room temperature, and (3) thermal implants with heavy species. Results show that a lower channel concentration is achieved with antimony. These approaches can be extended to develop junction isolation for bulk FinFETs for 10nm and beyond.