Removal of Cr and Zn impurities from the Si substrate using remote plasma H2

초록

Removal of Cr and Zn impurities on Si substrates using remote plasma H2 was investigated. Si substrates were contaminated intentionally by acetone. To determine the optimum process condition, remote plasma H2 cleaning was conducted for various rf-powers and plasma exposure time. After remote plasma H2 cleaning, Si surfaces were analyzed by TXRF(total x-ray reflection fluorescence), SPV(surface photo voltage) and AFM(atomic force microscope). The concentrations of Cr and Zn impurities were reduced by more than a factor of 10 or 100 and the minority carrier lifetime increased. Also RMS roughness decreased by more than 30%∼50% after remote plasma H2 cleaning. TXRF analysis results show that remote plasma H2 cleaning is effective in eliminating Cr and Zn impurities on Si surface if only it is performed under optimum process condition. AFM analysis results also show that remote plasma H2 cleaning makes no damage to the Si surface. Remote plasma H2 cleaning followed by HF cleaning has been found to be more effective than just remote plasma H2 cleaning. The Cr and Zn impurities on the Si substrate are considered to be contaminated as the forms of the hydroxides, silioxides and oxides on/into the chemical oxides which form during the chemical contamination. The removal mechanism of the Cr and Zn impurities using the remote plasma H2 treatments is proposed to be the combination of the volatile compounds formation and the lift-off phenomena during the removal of the underlying chemical oxides.