Imec achieves record-low source/drain contact resistivity for PMOS transistors
The Belgium-based nano-electronics research and innovation hub imec has recently reported record breaking values below 10-9 Ohm.cm² for PMOS source/drain contact resistivity. These results were obtained through shallow Gallium implantation on p-SiliconGermanium (p-SiGe) source/drain contacts with subsequent pulsed nanosecond laser anneal.
In future N7/N5 nodes, the source/drain contact area of the transistors becomes so small that the contact resistance threatens to become the dominating parasitic factor, resulting in suboptimal transistor functioning. Researchers have therefore been working on techniques to reduce the contact resistance on highly doped n-Si and p-SiGe source/drain contacts, aiming for values below 10-9 Ohm.cm². Together with colleagues from the KU Leuven (Belgium), Fudan University (Shanghai, China), and Applied Materials (Sunnyvale, USA), imec’s specialists concentrated on p-SiGe contacts, comparing the effects of high-dose Boron and Gallium doping.
For the comparison, the researchers implanted SiGe separate wafers with a high dose of Gallium or Boron and applied various anneal processes. They then fabricated multi-ring circular transmission line model structures, which are highly sensitive to contact resistance. Subsequent measurements revealed the lowest contact resistance for the Gallium-implanted structures annealed with Applied Material’s nanosecond laser anneal. This process uniquely causes a Ge/Ga surface segregation, which is responsible for the ultralow sub-10-9 Ohm.cm² contact resistivity. This result shows a possible way to process next-generation technology nodes.
Naoto Horiguchi, distinguished member of the technical staff at imec, indicated: “This breakthrough achievement in our search to develop solutions for next generation deeply-scaled CMOS provides a possible path for further performance improvement using the current source/drain schemes in N7/N5 nodes.”
Imec’s research into advanced logic scaling is performed in cooperation with imec’s key partners in its core CMOS programs including GlobalFoundries, Huawei, Intel, Micron, Qualcomm, Samsung, SK Hynix, Sony Semiconductor Solutions and TSMC.
Caption: Imec and its partners have achieved record breaking values for PMOS source/drain contact resistivity (photo: imec)