A Chartered Semiconductor Manufacturing & National University of Singapore-Nanyang Technological University joint research programme is working on short channel devices, scaled down to 0.1μm regime, and the need for a steep retrograded channel profile (SRCP) is essential. This results in the use of indium to replace boron as a channel dopant. Using SIMS analysis, indium is shown to give an SRCP as-implanted, because of its large atomic weight of 115 and high segregation into the oxide. However, in the integration of the entire n-MOSFET, additional thermal cycles from subsequent process steps may result in severe diffusion of both the indium channel and boron pocket implants, hence degrading the SRCP.
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