Analytic model for ion channeling in successive implantations in crystalline silicon

Successive ion implantations are frequently used in the fabrication of silicon devices. Each ion implantation increases the crystal damage in the region near the surface. For successive implantations, the ion channeling in perfect crystal channels is reduced and the channeling tail is lowered. In the process simulation, the impurity distribution after ion implantation is often calculated as the sum of two Pearson functions, of which the second covers the channeling ions. In this work, we present a general model for the reduction of channeling in successive implantations. The crystal damage from the implantations is monitored and used for the calculation of a differential channel dose. The model allows a fast analytic calculation of impurity profiles in 1D, 2D, and 3D process simulators. It provides a similar accuracy as Monte Carlo simulations and gives excellent agreement with SIMS data of successive ion implantations.