Leakage increase of narrow and short BCPMOS

The leakage performance of BCPMOS (buried channel PMOS) is investigated by experimentally varying the LDD implant conditions. An anomalous leakage increase with a boron LDD implant is observed for a small geometry (narrow and short) PMOS. Experimental results indicate that the increase of leakage current for narrow and short channel PMOS can be explained by boron piling up at the edge of the STI and from the source/drain towards the middle of the channel. Further confirmation of boron piling up is proven by the surface channel NMOS threshold voltage. Based on the leakage sensitivity, the BC PMOS LDD is optimized to reduce the leakage current for small geometry transistors.