Modification of the Si amorphization process by in situ ultrasonic treatment during ion implantation
We report the first study of the effect of in situ ultrasound treatment (UST) during ion implantation on amorphization of crystalline silicon. Rutherford backscattering spectroscopy, ion channelling and cross-section transmission electron microscopy measurements show that amorphization of Si during Ar ion implantation is enhanced by UST, especially at ultrasound frequencies around 2 MHz. The influence on the amorphization process depends mainly on ion flux, ion masses and ultrasound frequency. For implantation conditions without amorphization, for example in the case of implantation with light atoms such as boron, defect concentrations are lower for wafers implanted with UST compared to reference wafers implanted without UST. The influence of ultrasound is discussed in terms of its interaction with point defects and ultrasound-stimulated enhanced diffusion of interstitials.