Interstitial oxygen (Oi) related defect and reverse current leakage were investigated on test trench metal-oxide-semiconductor field-effect transistors fabricated on epilayers over heavily As-doped wafers (As++). The devices on the wafers sealed with polysilicon at backside exhibited an increased yield loss in reverse current leakage with increasing Oi concentration. The Oi concentration depth profiles indicated that Oi did precipitate out at the interface between the polysilicon layer and bulk silicon. This precipitation may consume the polylayer and reduce its gettering efficiency, which leads to an Oi-dependent current leakage. Similar experiments carried out with damaged backside As++ wafers showed an overall low and Oi-independent current leakage yield loss. This reduced leakage yield loss was due to the intrinsic gettering effect of the Oi precipitates in these wafers close to the back surface. Transmission electron microscopy study revealed, in the junction region, the existence of intrinsic stacking faults and punch-out dislocation loop, characteristic of oxygen precipitation. The reverse current-voltage curves related to these defects were quantitatively analyzed using the Shockley-Read-Hall model. The effective generation lifetimes of intrinsic stacking fault and punch-out dislocation loop were about 4.3ps and 50ns, respectively, and were significantly shorter than 2.5µs in defect-free area.

Interstitial Oxygen-Related Defects and Current Leakage in Trench Metal-Oxide-Semiconductor Field-Effect Transistor on epi/As++ Structure. Q.Wang, M.Daggubati, H.Paravi, R.Yu, X.F.Zhang: Journal of Vacuum Science & Technology A, 2006, 24[4], 1238-42