Kenji Yoneda

The drain current asymmetry of 130 nm MOSFETs due to extension implant shadowing originated by mechanical angle error in high current implanter

The drain current asymmetry of 130 nm n-MOSFETs due to extension and source/drain ion implantation shadowing at the edge of gate electrode has been investigated. The ion implantation angle error is occurred even the tilt and twist angles are mechanically set as 0 degree. This ion implantation angle error is remarkable at periphery area of 200 mm wafer. This angle error originated in wheel design and scanning method of a high current ion implanter. Those are structural limitation of a high current batch type ion implanter. The drain current asymmetry can be dramatically reduced by using 4-step (Tilt/Twist=0/0, 0/90, 0/180, 0/270 deg.) ion implantation for extension implant similar to pocket implant. Therefore, even the low energy, high current ion implantation such as extension and source/drain implant, 4-step ion implantation is indispensable to reduce the drain current asymmetry.