Effects of reactive ion etching induced damage on contact resistance

Highly selective SiO/sub 2/ over Si reactive ion etching has been achieved by utilizing carbon rich fluorocarbon plasma. The carbon rich plasma is very useful for deposition of a thick carbon rich fluorocarbon film that protects the Si surface from the etchant (Akimoto et al., 1993; Hayashi and Sekine, 1996; Goto and Hori, 1996). On the other hand, because the SiO/sub 2/ etching reactions occur under ion bombardment, implantation of a large amount of carbon to the Si substrate results from plasma exposure during the overetch period. This damage layer can degrade the contact resistance or increases the junction leakage current. Consequently, a great deal of research has been directed at removal or recovery of the damage layer. However, the damage formation has become a critical issue. As the projected ion implantation depth range for the MOS transistor source and drain may become shallower, contact hole etching demands low damage without removal of the damage layer. For further development of low damage SiO/sub 2/ etching, it is necessary to determine the cause of degradation of contact resistance in order to control the damage-inducing factor. In this study, damage layer properties were investigated by evaluation of implanted element profiles and carrier concentration profiles in the damage layer induced by reactive ion etching. Also, the relationship of the damage layer properties and contact resistance were investigated for various plasma sources or etching conditions.