National project on 45 to 32 nm metal oxide semiconductor field effect transistors for next century IC fabrications

It is well known that the Taiwan Semiconductor industries play the very key roles for the worldwide IC foundry, and the advanced research of nanoelectronics is the lifeline for its long term developments. Professor Huey-liang Hwang effectively integrated the most outstanding research team and resource in Taiwan on the National Project on Nanometer CMOS Transistors for the 21 century, which is sponsored by the Ministry of Economic Affairs of ROC. A dozen of Professors from NTHU( National Tsing Hua University) with expertise at the novel materials and analysis and NCTU( National Chiao Tung University) with expertise at devices and reliability are devoted to the studies and are in collaboration with the world-wide-known company such as TSMC, and breakthrough of the key technologies of 45-32 nm technologies are achieved. The objective of this project is focused on the development of advanced metal gate/high-k MOSFET for 45 nm node generation and beyond, the efforts include the world first successful suppression the oxide/Si interfacial layer formation by using a bi-layer composite of HfO₂ 3.2 nm (ALD)/HfO₂ 1.5 nm (MBE), the results show a dielectric constant of 16 and an EOT of 1.15 nm, a Dit was estimated to be 4.6times10¹¹ cm^-2eV^-1 with the leakage at Vfb-1V being 8.5times10^-6 A/cm². Also, the thermal stability of HfO₂, HfAlO_x alloy and Al₂O₃/HfO₂ stack, prepared by ALD were compared, the incorporation of Al in alloy form gave superior characteristics by retaining an amorphous structure up to 1000 C, which suppress the leakage current and retards growth of the interfacial layer giving the least increment of EOT and interface traps. Besides, by incorporating Al into TiO₂ gave an EOT value of the Al₂O₃/TiAlO_x/Al₂O₃ film down to 0.8 nm. Furthermore, high selectivity was obtain- - ed via etching the HfAlO and silicon wafer with pattern using the ICP Plasma. In this project, YbSi metal gate for n-MOSFET and IrSi metal gate p-MOSFET were successfully fabricated for the HfAlON MESFET. The results showed the good effective workfunction of 4.15 and 4.9 eV and no degradation of gate dielectric current and mobility in the Yb_xSi/ HfAlON and Ir_xSi/ HfAlON FUSI-gates by reducing the metal diffusion at lower temperatures.