Alleviating Hydrogen Plasma Damage to Amorphous/Crystalline Silicon Interface Passivation

Hydrogen plasma treatment is used to enhance the interface passivation of amorphous/crystalline silicon (a-Si:H/cSi) heterojunctions, but prolonged hydrogen plasma treatment can cause adverse passivation damage. Although hydrogen plasma etching of the a-Si:H layer has been proposed as a plausible explanation, we find that hydrogen plasma damage to the c-Si substrate could be more important. We cap a-Si:H passivation layers with a ~2.5-nm-thick silicon oxide layer to preserve the a-Si:H/c-Si interface and find that severe hydrogen plasma damage is greatly alleviated (slowed down by a factor of 7-10) while the hydrogen still penetrates into the underlying aSi:H layer for interface passivation.