Ultrathin gate oxide grown on nitrogen-implanted silicon for deepsubmicron CMOS transistors

Nitrogen implantation on the silicon substrate was performed before the gate oxidation at a fixed energy of 30 keV and with the split dose of 1.0×10¹⁴/cm² and 2.0×10¹⁴ /cm². Initial O₂ injection method was applied for gate oxidation. The method is composed of an O₂ injection/N₂ anneal/main oxidation, and the control process is composed of a N₂ anneal/main oxidation. CMOS transistors with gate oxide thickness of 2 nm and channel length of 0.13 μm have been fabricated by use of the method. Compared to the control process, the initial O₂ injection process increases the amount of nitrogen piled up at the Si/SiO₂ interface and suppresses the growth of gate oxide effectively. Using this method, the oxidation retarding effect of nitrogen was enhanced. Driving currents, hot carrier reliability, and time-zero dielectric breakdown (TZDB) characteristics were improved