Measured and calculated retained dose with different process parameters in plasma based ion implantation

This paper reports the research that systematically studied the effect of the adjustable process parameters on the retained dose in plasma based ion implantation with an aim to provide a method for optimizing the implantation process. Nitrogen was implanted in a silicon wafer clamped on a cylindrical sample holder while varying parameters such as implantation voltage, radio frequency (RF) power, pulse width and target size. Auger electron spectroscopy was used to execute sputter depth profiling and to obtain the retained dose at the middle of the silicon wafer. The retained dose on the wafer was also predicted using fluid dynamic model, which simulates the sheath dynamic mode with consideration of the sputtering effect of the implanted ions. The measured results were compared with theoretical calculations, and the agreement for all the samples was good. The implantation dose for the cylinder will increase with increasing implantation voltage, pulse width or the RF power. A larger sample will result in a decreased dose, although the large ion reception area will push the sheath edge to a further position from the substrate.