We investigated the impact of sputtering power of source/drain metal on the characteristics of a-IGZO TFTs fabricated using back-channel-etch (BCE) process. With the increase of sputtering power, the subthreshold swing of TFTs tends to deteriorate. From the analysis of atomic force microscope (AFM), it is shown that the surface roughness of the back-channel interface increases with the sputtering power. Therefore, a relatively low sputtering power during the deposition of source/drain metal is preferred for the fabrication of back-channel-etched a-IGZO TFTs.