Codiffusion of phosphorus and carbon in preamorphized ultrashallow junctions

The diffusion of implanted carbon in preamorphized silicon was investigated with and without phosphorus coimplantation. Coupling effects were observed when carbon and phosphorus diffused simultaneously during junction formation. With an implantation dose of 1 10 ¹⁵ cm ^-2, phosphorus diffusion resulted in interstitial supersaturation, enhancing the tail diffusion of carbon. However, the diffusion of carbon was not enhanced when the implantation dose of carbon was increased to 5 10 ¹⁵ cm ^-2. This result indicates that high-dose carbon implantation inhibited the interstitial supersaturation that was caused by phosphorus diffusion. Accordingly, the tail diffusion of phosphorus was suppressed and box-shaped diffusion profiles were obtained in the region of high carbon concentration.