Substrate orientation, doping and plasma frequency dependencies of structural defect formation in hydrogen plasma treated silicon

The formation of structural defects in hydrogen plasma treated (100)- and (111)-oriented p-type Czochralski (Cz) Si and in [100]-oriented n-type Si was studied by Raman spectroscopy, scanning electron microscopy and transmission electron microscopy. The samples were treated either by a 110 MHz or 13.56 MHz hydrogen plasma at 250degreesC for 50 min. The distribution of hydrogen was studied by nuclear reaction analysis. It is found that. after the hydrogen plasma treatment, the surface of Cz Si is structured and the roughness of the surface depends on the orientation and doping level of the substrate. The defect density increases for (100)-oriented wafers for the higher plasma frequency but for (111)-oriented wafers it is lower, applying the same hydrogen plasma frequency. Different defect types were found: stacking faults on {111} planes, dislocations and circular shaped defects exhibiting a strong stress field. The formation of nearly free hydrogen molecules (Raman shift of about 4150 cm(-1)) was observed by Raman spectroscopy after the plasma hydrogenation. It was found that the H-2 molecule concentration depends on the concentration of structural defects. The hydrogen molecules can be formed in both n- and p-type Si, unlike the case of remote plasma hydrogenation.