Effect of internal gettering of iron on electrical characteristics of devices

Different types of gettering treatments were applied to a real device process to evaluate their ability to remove iron contamination from the device layer and improve the electrical characteristics of the devices. NMOS and PMOS transistors and other test structures were manufactured on boron doped, both iron contaminated and uncontaminated Cz silicon wafers with or without gettering treatment. Gettering treatments, which were designed to induce sufficient iron precipitate nucleation in the bulk to ensure iron precipitation, were inserted in the fabrication process after the last high temperature treatment in which the iron solubility was higher than the contamination level. The electrical characteristics of the devices, such as leakage currents, were measured. The applied gettering treatments were found to be inefficient to improve the device performance, possibly due to stronger gettering to heavily doped, ion implantation damaged device layer.