At the 2017 Symposia on VLSI Technology and Circuits in Kyoto, Japan (5-8 June), nanoelectronics and photovoltaics research centre Imec of Leuven, Belgium unveiled new process improvements for next-generation devices. For the first time it is claimed, scaled strained germanium p-channel gate-all-around (GAA) field-effect transistors (FETs) have been demonstrated with a sub-10nm diameter, integrated on a 300mm platform. In addition, Imec has achieved a significant improvement in device performance and electrostatic control with high-pressure anneal (HPA) for both strained germanium p-channel FinFET and GAA devices.
High-mobility materials such as germanium and III-Vs have been considered as potential solutions for deeply scaled devices, due to their higher intrinsic carrier mobility. However, these materials have a larger permittivity and a smaller bandgap than silicon, making it more difficult to apply the necessary electrostatic control at scaled gate lengths. To mitigate this issue, new device architectures with better electrostatics are necessary. Imec says that its results bring significant improvements for both strained germanium p-channel FinFET and GAA devices.
Nadine Collaert, Distinguished Member of Technical Staff at Imec, says that her team “adapted the process flow of our previously published 14/16nm-node strained germanium p-finFETs to study the benefit of strained germanium GAA p-FETs at short gate lengths and sub-10nm diameter.” The team managed to process GAA p-FETs with the shortest gate lengths (LG=40nm) and smallest nanowire diameter (d=9nm) reported to date. At these shortest gate lengths, the devices maintain excellent electrostatic control with a drain-induced barrier lowering of 30mV/V and a sub-threshold slope of 79mV/dec.
In a second paper, Imec reported on the use of high-pressure anneal as a new performance booster for both germanium FinFETs and GAA devices. In their test, the researchers measured an improved interface quality and hole mobility (~600cm2/Vs) as a result of a HPA at 450°C. The optimized HPA is also shown to significantly improve the electrostatics and overall performance of GAA devices, reaching a subthreshold swing (SSLIN) of 65mV/dec at LG=60nm and a Q factor of 15 with a low off-current (IOFF) of ~3×10-9A/μm.
Imec’s research into advanced logic scaling is performed in cooperation with key partners in its core CMOS programs including GlobalFoundries, Huawei, Intel, Micron, Qualcomm, Samsung, SK Hynix, Sony Semiconductor Solutions and TSMC.