One of the key processes in the fabrication of state-of-the-art CMOS devices is ion implantation. Ion implantation is the primary technology to introduce doping atoms into semiconductors to form devices and integrated circuits. Strained silicon/relaxed SiGe CMOS devices show significant performance improvements compared to pure silicon devices. The silicon-germanium (SiGe) material technology offers the possibility of bandgap engineering, enhanced carrier mobility, and a higher dopant solubility. The capability of accurately predicting doping profiles by Monte Carlo simulation tools can significantly reduce integrated process development and implementation time.

The Monte Carlo ion implantation simulator MCIMPL-II is an object-oriented, multi- dimensional simulator, embedded in a process simulation environment. The simulator is based on the binary collision approximation (BCA), and cells arranged on an ortho-grid are used to count the number of implanted ions and of generated point-defects. We have extended the simulator from silicon to SiGe targets in order to analyze the applicability for advanced CMOS devices.

The penetration depth of ion implanted dopants in relaxed SiGe is significantly reduced compared to pure silicon due to the larger nuclear and electronic stopping power. The heavier germanium atom leads to a higher backscattering probability, which can be derived from the scattering integral. This integral is evaluated by the simulator to determine the scattering angle of a nuclear collision event. The larger electronic stopping power of SiGe compared to silicon is caused by the higher electron density due to the electron-rich germanium atom. It turned out that the Lindhard correction parameter of the electronic stopping model can be adjusted by a linear function of the germanium content to adopt the strength of electronic stopping in SiGe alloys. The successful calibration for the simulation of arsenic and boron implantations was demonstrated by comparing the predicted doping profiles with SIMS measurements. Thereby, the shift toward shallower profiles with increasing germanium content was found in a non-linear manner. Relaxed SiGe considerably facilitates the forming of shallow junctions which are a prerequisite to further scale  the MOSFET structure into the sub-100nm regime.