He+ Ion Beam Implantation studied by In-situ X-ray Diffraction

Ion beam techniques are widely used in semiconductor industry for introducing dopant atoms into materials. Ion implantation is characterized by fast dynamic processes associated with the evolution of collision cascades resulting in formation of different types of defects such as vacancies, interstitials, etc. At large fluencies a strained layer that expands in the direction normal to the substrate surface is formed. This is due to the point that the bulk material prevents any lateral macroscopic expansion and as a result a thin irradiated layer is subjected to an in-plane biaxial compressive stress.

The penetration of an Ion into a solid is a very fast process of picoseconds and it is almost impossible to monitor it in-situ with present x-ray sources. However, the accumulation of damage and the diffusion of defects or the implanted species are much slower processes and can be studied in-situ already today.
An in-situ ion beam implantation experiment was set up at ROBL/MRH at ESRF using an ion gas source resulting in a maximal ion energy of 20keV. Si(001) samples were irradiated at room temperature using He+ with an ion flux of max. 1013ions/cm2s. In-situ/in-operando reciprocal space maps were measured to study the strain evolution. The time resolution for one high resolution reciprocal space maps as shown in figure 1 was 100ms resulting an acquisition time for one map of below 1min.