Planar Bulk MOSFETs With Self-Aligned Pocket Well to Improve Short-Channel Effects and Enhance Device Performance

Abstract

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- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$k$ </tex-math></inline-formula> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{T}$ </tex-math></inline-formula> . Compared with halo doping with the same <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{{T,{\rm sat}}}$ </tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\rm DD} = 0.8$ </tex-math></inline-formula> V, despite no <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\mathrm{{\scriptscriptstyle ON}}}$ </tex-math></inline-formula> enhancement, the SPW reduces DIBL by 45% and enhances <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\rm EFF}$ </tex-math></inline-formula> by 18%. Compared with halo doping with the same <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\mathrm{{\scriptscriptstyle OFF}}} = 100$ </tex-math></inline-formula> nA/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\rm DD} = 0.8$ </tex-math></inline-formula> V, the SPW structure reduces DIBL by 16%, enhances <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\mathrm{{\scriptscriptstyle ON}}}$ </tex-math></inline-formula> by 5%, and improves <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$I_{\rm EFF}$ </tex-math></inline-formula> 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.