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
$V_{T}$
. Compared with halo doping with the same
$V_{{T,{\rm sat}}}$
at
$V_{\rm DD} = 0.8$
V, despite no
$I_{\mathrm{{\scriptscriptstyle ON}}}$
enhancement, the SPW reduces DIBL by 45% and enhances
$I_{\rm EFF}$
by 18%. Compared with halo doping with the same
$I_{\mathrm{{\scriptscriptstyle OFF}}} = 100$
nA/
$\mu \text{m}$
at
$V_{\rm DD} = 0.8$
V, the SPW structure reduces DIBL by 16%, enhances
$I_{\mathrm{{\scriptscriptstyle ON}}}$
by 5%, and improves
$I_{\rm EFF}$
by 30%. In addition, with the self-aligned feature, the SPW does not deteriorate junction band-to-band tunneling (BTBT) leakage in comparison with halo doping. Otherwise, 20 times larger BTBT leakage will emerge due to the profile overlap between retrograde doping and drain/extension doping.