A failure mechanism and improved method for abnormal IDS leakage current of shield gate trench MOSFET

In this paper, a new failure mechanism of high drain-to-source leakage current was investigated for Shield Gate Trench(SGT) MOSFET in low voltage. The element content and sectional structure of the failed transistors and the functional transistors were compared by a variety of instruments. It was found that the fluorine accumulation was higher in areas where IDS leakage current exceeds the upper limit, and this is related to the combination of fluorine and dangling bonds during ion implantation. The results also show that there was a significant correlation between the density of fluorine bubbles and the residual amount of fluorine, which was not conducive to the combination of TiSi2 silicide and P+-Si. The experimentals monstrate that the increase of fluorine bubbles caused by the adsorption of fluorine on silicon surface and residual fluorine in silicon body after ion implantation, was responsible for the IDS leakage current of failed transistors of SGT-30V device. Failure mechanisms are proposed by energy band diagram. The contact holes implantation with B+ ion implantation instead of BF2+ ion implantation, was proved to be an effective method to reduce IDS leakage current for SGT-30V device by using TCAD simulations and experiments.