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Influences of Ni silicide phases on the effective work function (Φeff) modulation effect with Al incorporation has been investigated in the Ni silicide/HfSiON systems. We formed metal-insulator-semiconductor capacitors with Al incorporated Ni silicide (NiSi, Ni2Si, and Ni3Si) gates on HfSiON by Al solid-phase diffusion (Al-SPD) process or Al ion implantation (I/I) process. In the Al-SPD process, Al is deposited on Ni silicide gate. In the Al-I/I process, Al ions were doped in the upper part of Ni silicide layer. In both cases, we performed Al drive-in annealing under the condition of 450 °C for 30 min in N2 ambient. It is found that the flat-band voltage (Vfb) values of Al incorporated NiSi and Ni2Si gates shift negatively and identical independent of Al incorporation processes. A highly concentrated Al piled-up layer, which induces Φeff modulation to Al-Φeff value, seems to correspond to the Vfb modulation. On the other hand, Al incorporation has little influence on Φeff at the Ni3Si/HfSiON interface. We...

In order to elucidate influences of nitrogen on the change of effective work function (ΔΦeff) with impurity segregation, we systematically investigated the ΔΦeff at arsenic (As) and boron (B) segregated NiSi∕SiO2 and NiSi∕SiON interfaces. These impurities are introduced to NiSi∕SiON (SiO2) interfaces by using the conventional predoping process. It was found that increase in Φeff with B segregation is suppressed as low as ΔΦeff=+0.05eV at NiSi∕SiON interface compared to ΔΦeff=+0.14eV at NiSi∕SiO2 interface, though there is little change in decrease of Φeff with As segregation. Moreover, the opposite (negative) Φeff modulation occurred at NiSi∕SiON interface in the case of low B dose. We also performed the B postdoping process, in which B atoms were introduced after Ni silicide gate formation with lower thermal process (∼500°C) than conventional predoping process (∼1000°C). A large ΔΦeff of +0.2eV occurred even at NiSi∕SiON system in the postdoping process. Based on the results of backside x-ray photoelectr...

An effective work function (Φeff) modulation caused by impurity doping in Ni-FUSI/SiO2 systems has been systematically investigated. To clarify the physical origin, we reveal the relationship between changes of Φeff modulation factors at gate electrode interfaces and Φeff modulation ranges (ΔΦeff) in two different doping processes (predoping and post-doping). In the predoping process, in which impurities (As or B) are implanted into polycrystalline Si gate before Ni fully silicided gate formation, both the crystal structure of the Ni silicide layer and the impurity concentration at the Ni silicide/SiO2 interface change depending on the impurity species. On the other hand, the impurity post-doping process, in which impurities are implanted and introduced to the Ni silicide/SiO2 interface after Ni silicide formation, makes it possible to introduce the desired amount of impurities into the interface without any structural change of the Ni silicide. In both cases, dependence of ΔΦeff on interface impurity con...