Diffusion experiments were performed using highly dislocated undoped and homogeneously doped material with B concentrations of 3.0 x 1019 and 1.7 x 1020/cm3. After Au diffusion at between 800 and 1100C, the Au profiles were measured by means of neutron-activation analysis and serial-sectioning. The diffusion of Au in dislocated material was accurately described by a kick-out mechanism, plus an additional reaction which took account of the capture of interstitial Au at dislocations. The profiles yielded data for the boundary concentration CAu0 and the Au diffusion coefficient, DAu; whose product equalled the transport capacity of interstitial Au. With increasing B doping, the Au diffusion increased (table 3); showing that interstitial Au was singly-positively charged. An enhanced boundary concentration and retarded Au diffusivity was observed below 1000C. This provided direct evidence of Au segregation at dislocations. A segregation enthalpy of 2.7eV was determined for the energy difference of Au atoms dissolved on substitutional lattice sites, and Au atoms trapped at dislocations.
Impact of High B Concentrations and High Dislocation Densities on Au Diffusion in Si. A.Rodriguez, H.Bracht, I.Yonenaga: Journal of Applied Physics, 2004, 95[12], 7841-9
Table 3
Boundary Concentrations and Diffusivities for Au in Dislocated Si
Temperature (C) | B (/cm3) | CAu0 | D (cm2/s) |
1100 | 0 | 4.2 x 1016 | 2.4 x 10-7 |
1100 | 3.0 x 1019 | 4.5 x 1016 | 4.0 x 10-7 |
1100 | 1.7 x 1020 | 6.9 x 1016 | 1.0 x 10-6 |
1000 | 0 | 1.8 x 1016 | 1.1 x 10-7 |
1000 | 3.0 x 1019 | 1.5 x 1016 | 2.5 x 10-7 |
1000 | 1.7 x 1020 | 4.1 x 1016 | 4.8 x 10-7 |
950 | 0 | 1.7 x 1016 | 3.4 x 10-8 |
950 | 3.0 x 1019 | 9.9 x 1015 | 1.5 x 10-7 |
900 | 0 | 2.9 x 1016 | 6.5 x 10-9 |
900 | 3.0 x 1019 | 2.1 x 1016 | 3.1 x 10-8 |
900 | 1.7 x 1020 | 3.6 x 1016 | 1.3 x 10-7 |
850 | 0 | 6.6 x 1016 | 7.7 x 10-10 |
850 | 3.0 x 1019 | 1.8 x 1016 | 1.3 x 10-8 |
800 | 0 | 3.5 x 1016 | 3.5 x 10-10 |
800 | 3.0 x 1019 | 3.7 x 1016 | 2.5 x 10-9 |