Studies on ultra shallow junction 20nm P-MOS with 250°C microwave annealing for activation of boron dopants in silicon

In order to fabricate ultra-shallow junction (USJ) for 20nm IC node application, a low energy (400eV) ion implantation and a novel microwave annealing technique with two steps for the solid phase epitaxy regrowth and activation of boron dopants in silicon were used in this study. In the first step annealing, a 2.4 kWatt(~500°C) high power microwave annealing was used to regrowth the amorphous layer with PAI treatment of Ge (20keV @5e14 atoms/cm²) into crystal silicon. The activation energy (2.3 eV) to attain rapid lattice restoration for the solid phase epitaxy regrowth by microwave annealing is lower than that by the conventional RTP. In the second step annealing, since the crystalline silicon has high absorption efficiency to microwave, a 0.6 kWatt(~250°C) low power microwave annealing is able to activate implanted boron in silicon (400eV @1e15 atoms/cm²), and decrease the resistance to 436 ohm. / sq without diffusion. We have successfully demonstrated that the novel ultra low temperature microwave annealing technique is promising for improvement on P-MOS performance. The on/off current ratio (I_on/off) of the P-MOS is more than 2×10⁶ (V_DS = -0.05 V). The low resistance of 436 ohm./sq after activating by 250°C microwave annealing is reflected to the high performance of P-MOS with a lower S.S.(-92.59mV), and a high hole mobility 27.5cm²/V-S.