A Novel Defect Passivation Method for Multicrystalline Si Wafer by H2S Reaction

The passivation of multicrystalline silicon (mc-Si) wafers by reaction in H2S is discussed where the effective minority carrier lifetime (τ
_eff
) was measured to evaluate the improvements of the bulk quality. Mc-Si τ
_eff
improved to >200 μsec due to bulk and surface passivation by H
₂
S reaction, compared to 40~60 μsec with only surface passivation by quinhydrone-methanol (QHY/ME) or hydrogenated amorphous Si (a-Si:H), two well-developed surface passivation methods for monocrystalline Si. Injection level dependent τ
_eff
showed the reduction of both trap and recombination states for mc-Si passivation in H
₂
S. τ
_eff
> 250 μsec was yielded through surface repassivation in QHY/ME after removal of H
₂
S reaction-formed surface layer by wet chemical etching. This indicates the passivated bulk quality by H
₂
S reaction was not affected even after a series of wet chemistry treatments.