As the others have said, it's NEVER the turbo unit itself that's somehow the cause of your oil leak. It's a simple device yet obviously often misdiagnosed by those unfamiliar with turbochargers.
Besides the drain tube o-ring listed below, another common source of seapage seen from the bottom of the turbo itself is coming from the intake air tube as there's always some oil mist in all turbo air hoses. For that, simply tighten the large clamp on that hose at the turbo itself (hose between turbo and MAF meter).