Planar Bulk MOSFETs With Self-Aligned Pocket Well to Improve Short-Channel Effects and Enhance Device Performance
We present and demonstrate a self-aligned pocket well (SPW) structure used in planar bulk MOSFETs with a metal gate length of 25 nm and an effective channel length less than 20 nm. The SPW features a retrograde doping profile in vertical direction and a doping profile self-aligned with drain/extension in lateral direction. A novel process, called replacement spacer gate (RSG), is designed to avoid challenges in gate patterning and high-k metal gate filling. Planar bulk pMOSFETs, with SPW and halo doping, respectively, were simulated and fabricated adopting the RSG process. Due to its retrograde feature, the SPW can achieve low drain-induced barrier lowering (DIBL) along with low VT. Compared with halo doping with the same VT,sat at VDD = 0.8 V, despite no ION enhancement, the SPW reduces DIBL by 45% and enhances IEFF by 18%. Compared with halo doping with the same IOFF = 100 nA/μm at VDD = 0.8 V, the SPW structure reduces DIBL by 16%, enhances ION by 5%, and improves IEFF by 30%. In addition, with the self-aligned feature, the SPW does not deteriorate junction band-to-band tunneling (BTBT)