| AVS 55th International Symposium & Exhibition | |
| Manufacturing Science and Technology | Monday Sessions |
| Session MS+NC-MoM |
| Session: | CMOS Extension and Metrology |
| Presenter: | Y.V. Kondratenko, University of Illinois, Urbana-Champaign |
| Authors: | Y.V. Kondratenko, University of Illinois, Urbana-Champaign C.T.M. Kwok, University of Illinois, Urbana-Champaign E.G. Seebauer, University of Illinois, Urbana-Champaign |
| Correspondent: | Click to Email |
Formation of pn junctions in advanced Si-based transistors employs rapid annealing techniques after ion-implantation in order to increase the electrical activation of dopants while minimizing their diffusion. Over the past decade, these techniques have evolved from rapid thermal processing, with time scales of about 1 s, to millisecond methods accomplished by flashlamps or lasers. Although the dopant behavior in terms of diffusion and electrical activation clearly improves as a result of the shortened time scale, the technology transition has taken place on a largely phenomenological basis with little understanding of the physical mechanism for the improvement. The present work provides the key elements of that understanding and explains nonthermal contribution of illumination on the diffusion of dopants. Continuum-based simulations were used to model experimental data in order to obtain mechanistic picture of improvement in dopant diffusion and activation during millisecond annealing. The same method was applied to explain photostimulated effects on dopant diffusion during soak annealing. The simulations solve the partial differential equations for diffusion and reaction of interstitial atoms, with activation energies for elementary diffusion and reaction steps computed by Maximum a Posteriori parameter estimation. The fundamental reason for improvements of diffusion and electrical activation in the millisecond regime is that the short time scale promotes exchange of dopant interstitial atoms with the lattice in preference to exchange with interstitial clusters. Photostimulated diffusion of dopants, however, exhibited more complicated features. Depending on annealing temperature and time, boron diffusion in silicon could be either enhanced or inhibited. Dopant activation was similarly affected. Simulations using continuum equations for the reaction and diffusion of defects were used to determine whether illumination affects cluster dynamics or steady state boron diffusion.