Transconductance bimodal effect of PDSOI submicron H-gate MOSFETs

A bimodal effect of transconductance was observed in narrow channel PDSOI sub-micron H-gate PMOSFETs, which was accompanied with the degeneration of device performance. This paper presents a study of the transconductance bimodal effect based on the manufacturing process and electrical properties of those devices. It is shown that this effect is caused by a diffusion of donor impurities from the N+ region of body contact to the P+ poly gate at the neck of the H-gate, which would change the work function differences of the polysilicon gate and substrate. This means that the threshold voltage of the device is different in the width direction, which means that there are parasitic transistors paralleled with the main transistor at the neck of the H-gate. The subsequent devices were fabricated with layout optimization, and it is demonstrated that the bimodal transconductance can be eliminated by mask modification with N+ implantation more than 0.2 μm away from a poly gate. (semiconductor devices)