Toshihide Nabatame

Structural Metastability and Size Scalability of Phase-Controlled HfO2 Formed through Cap-PDA

Introduction High-k gate dielectric film is indispensable for the suppression of gate leakage current in scaled MOSFETs. A HfO2-based high-k film recently has been introduced in the production. Today, material search for further higherk films is aggressively on-going for the next generation. A strong guideline for achieving higher-k is the phase control [1], which associates with molar volume change as well as molar polarizability one in the ClausiusMossotti relation sense. In fact, successful results have been reported in HfO2-based films by incorporation of rare earth dopants [2, 3] or forming ternary compounds [4] in terms of the phase control, but all of them reported so far are not pure HfO2. On the other hand, we have achieved the cubic phase formation of pure HfO2 through “Cap-PDA” process and demonstrated very high-k value (k~50) with keeping the insulating band gap [5-7]. This paper discusses metastable characteristics of phase-controlled HfO2 formed by the Cap-PDA process and applicability of cubic phase HfO2 to scaled devices.

Inversion Layer Mobility in High-k Dielectric MOSFETs - Intrinsic Mobility Degradation by Electric Dipoles at High-k/SiO2 Interface

Introduction The high dielectric constant (high-k) insulator is now indispensable in the advanced complementary metaloxide-semiconductor (CMOS) device to attain high drivability with low standby power consumption. However, it is well known that the inversion layer mobility at a low effective field in the high-k gate stack MOSFETs is generally lower than the universal mobility curve. Up to now, it is still unclear that the mobility degradation in MOSFETs with high-k dielectrics is due to their intrinsic properties or quality dependent factors such as a fixed charge. For example, the surface optical phonon scattering is widely concerned as an intrinsic origin of the mobility degradation inherent to high-k materials [1]. Besides, Yamamoto et al.[2], and we [3,4] have pointed out that the dipole layer which is formed intrinsically at high-k/SiO2 interface affects strongly the threshold voltage VTH in high-k gate stack CMOS. We are now concerned about the fact that such a dipole formed at high-k/SiO2 interface may degrade the carrier mobility. In this paper, we have examined contribution of the remote phonon scattering and the interface dipole scattering to the mobility degradation in the metal gate high-k MOSFETs.

Thermal Robustness of VFB and EOT in HfOx(N) p-MOS Devices with Partially Silicided Pt Gate Electrodes

We investigated the process window of partially silicided (PASI) Pt gate electrodes which can effectively suppress unintentional threshold voltage increases of Hf-based high-k p- MOSFETs, and the impact of application of the PASI Pt (PASI- PtSi) gate electrode on their electrical properties. The values of the EOT, flat-band voltage, and the gate leakage current density of the HfOx(N) p-MOS capacitors with the PASI- PtSi gate electrodes are almost identical when the Pt film is more than double the thickness of the poly-Si films at silicidation temperatures from 400 to 600oC. No degradation in the gate leakage current density of the HfOx(N) MOS capacitors with the PASI-PtSi gate electrodes was observed, compared with the FUSI-NiSi and FUSI-PtSi gate electrodes. Consequently, it is concluded that the PASI technology is useful in scaled CMOS devices with Hf-based high-k dielectrics.