Removal of Plasma-Induced Physical Damage Formed in Nanoscale Three-Dimensional FinFETs

During plasma etching for fin patterning in the three-dimensional (3D) FinFET structure, the exposure of the Si surface to plasma with reactive ions can induce physical damages, resulting in the degradation of electrical properties of the device. In this study, we evaluated the damage with a measurable value by simulation and surface damage analyses using HR-TEM and RBS. As a result, the degree of the damaged layer was strongly dependent on the energy of the ions bombarding the Si substrate during plasma etching. The damage was quantified with the interface defect density measured by the charge pumping method. Plasma etching with high ion energy showed approximately one order of magnitude higher defect density than that with low ion energy and/or wet etching with no ion bombardment. We introduced Si soft treatment (with very low ion energy) to remove the damaged layer. The Si soft treatment was very effective to remove the damage on a highly damaged silicon surface. However, the Si soft treatment itself increased the number of defects for a low damage silicon surface.