Dry etch damage in n-type crystalline silicon wafers assessed by deep-level transient spectroscopy and minority carrier lifetime

This paper compares the electrically active damage in dry-etched n-type float-zone silicon, using NF₃/Ar or H₂-plasma exposure and assessed by deep-level transient spectroscopy (DLTS) and recombination lifetime analysis. It is shown that the NF₃/Ar-plasma damage consists of at least four different types of electron traps in the upper half of the band gap, which can be associated with vacancy- and vacancy-impurity-related complexes. In the case of H₂-plasma damage, it is believed that the accumulation of point defects results in a gradual disordering of the near-surface layer. These defect levels also act as recombination centers, judged by the fact that they degrade the minority carrier lifetime. It is finally shown that lifetime measurements are more sensitive to the etching-induced damage than DLTS.