Comprehensive study of plasma pretreatment process for thin gate oxide (<10 nm) fabricated by electron cyclotron resonance plasma oxidation

Abstract

In this work, we comprehensively study the effect of ECR plasma pretreatment on ECR plasma grown SiO2 film. The ECR plasma grown gate oxide growth rate in the case of no plasma pretreatment is lower than that in the case of use of the plasma pretreatment step. Because the growth processes for these two methods (with and without pretreatment) differ only in terms of the initial surface conditions, the growth mechanisms are concluded to be determined by the initial Si surface conditions before plasma oxidation. The mid-gap interface states (Di(it-m)) of the ECR plasma grown SiO2 films in the case of plasma pretreatment are lower than those in the case of no plasma pretreatment. Through use of the plasma pretreatment process, the Si surface can be improved and cleaned before plasma oxidation. For SiO2 films pretreated with N-2 or Ar gas, the breakdown fields (E(bd)) are higher than those for SiO2 films not pretreated with N-2 or Ar gas. However, for NH3 gas pretreated films, the Ebd is lower than those for SiOz films pretreated with N-2 or Ar gas. This is because the NH3 gas contains H atoms which cause deterioration of F-N tunneling characteristics. Moreover, with the plasma pretreatment step, the stress-induced leakage currents (SILC) are lower than those without this step.