Ultra-shallow 2D dopant profile simulation versus experimental measurement in the low thermal budget regime
The relationship between lateral and vertical impurity diffusion distances in silicon is mathematically well established for profiles that have been diffused at high temperature for a long time. And this relationship is experimentally verified. However, for small thermal budget diffusions of ion implanted dopants, there is a significant discrepancy between experiment and simulation regarding the lateral-to-vertical diffusion depths for (Dit)1/2<1×10-6 cm for B, P and As. We have compared available Monte Carlo models and analytical models contained in diffusion simulators with measurements from over 60 shallow 2D dopant profiles. The simulation of 2D implantation profiles as well as 2D dopant diffusion compares rather poorly with experimental data in the low thermal budget regime. This result has a serious impact on the wide-spread use of commercial simulators in the semiconductor industry for sub-0.35 micron technologies. Reasons for this poor comparison are presented along with a discussion of TED in two dimensions
