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It has recently been reported that nitrogen oxide species (e.g., N2O5, NO2, NO3, and/or N2O) can have an impact on ozone based atomic layer deposition (ALD) of metal oxides when ozone is generated by dielectric barrier discharge (DBD) in O2/N2 mixtures. In this work, we further investigate the effect of the O2/N2 ratio in the DBD for HfO2 ALD using HfCl4 as metal precursor. Using O3 in the absence of nitrogen oxides, uniform HfO2 layers are obtained between 200 and 250°C in a hot wall cross flow reactor. The self-limiting nature of the O3 and HfCl4 reaction is demonstrated at 225°C and the growth-per-cycle is 0.12 nm. At higher temperature, O3 decomposes at the HfO2 coated reactor walls, resulting in a decreasing HfO2 thickness over Si substrates in the direction of the gas flow. Using O3 in combination with nitrogen oxides by DBD in N2/O2 mixtures, we obtained uniform HfO2 layers in the 200-300°C temperature range. At 300°C, the GPC is 0.14 nm and the HfO2 films show a low impurity content. Both processes produce high quality dielectric layers in Pt gated capacitors. [ABSTRACT FROM AUTHOR]

The role of moisture (H[sub2]O) in atomic-layer-deposited (ALD) HfO[sub2∙] and HfSiO[sub2∙] dielectrics on equivalent oxide thickness (EOT) scaling is investigated in gate-first devices with physical-vapor-deposited TaN gates. By reducing the amount of H[sub2]O present in the gate stack, the EOT increase during high-temperature (1030°C) spike annealing is reduced from 0.5 to0.25 nm. This was achieved by a premetallization degas at 350-550°C for 3 mm. The origin of this improvement lies in the elimination of H[sub2]O-related reoxidation of the interfacial SiO[sub2]. By means of temperature-programmed desorption measurements, it is found that the majority of the H[sub2]O is desorbed between 200 and 600°C with activation energies between ∼0.3 and -0.5 eV. Furthermore, the H[sub2]O concentration is dependent on the Hf concentration and nitridation. Non-nitrided HfSiO[sub2∙] with [Hf] = 40% adsorbs twice as much H[sub2]O as HfO[sub2∙]. Correspondingly, a significantly larger FOT increase is observed for HfSiO[sub2∙] with [Hf] 40% as compared to HfO[sub2∙]. In HfSiON, the desorbed H[sub2]O concentration is independent of [Hf]. Finally, a strong metal dependency on the EOT regrowth is observed. With ALD TiN, the EOT increase after thermal treatment is found to be independent of the degas condition at ∼0.2 nm. [ABSTRACT FROM AUTHOR]

The authors demonstrate high-performing n-channel transistors with a HfO2/TaN gate stack and a low thermal-budget process using solid-phase epitaxial regrowth of the source and drain junctions. The thinnest devices have an equivalent oxide thickness (EOT) of 8 Å, a leakage current of 1.5 A/cm² at VG = 1 V, a peak mobility of 190 cm²/V · s, and a drive-current of 815 μA/μm at an OFF-state current of 0.1 μA/μm for VDD = 1.2 V. Identical gate stacks processed with a 1000-°C spike anneal have a higher peak mobility at 275 cm²/V · s, but a 5-Å higher EOT and a reduced drive current at 610 μA/μm. The observed performance improvement for the low thermal-budget devices is shown to be mostly related to the lower EOT. The time-to-breakdown measurements indicate a maximum operating voltage of 1.6 V (1.2 V at 125 °C) for a ten-year lifetime, whereas positive-bias temperature-instability :measurements indicate a sufficient lifetime for operating voltages below 0.75 V. [ABSTRACT FROM AUTHOR]

Conduction band-edge effective work functions (ϕm,eff) are demonstrated with TaCx and TiN by means of La2O3 capping of HfSiOx in a gate-first process flow with CMOS- compatible thermal budget. With TaCx, a 10-Å-thick La2O3 cap results in a ϕm,eff of 3.9 eV with a low equivalent oxide thickness (EOT) increase (1-2 Å) and unaffected electron mobility. With TiN, non-nitrided La2O3 capping results in a smaller ϕm,eff reduction at a larger EOT increase, while with post-cap nitridation, the TiN ϕm,eff is lower at a smaller EOT increase. Results show that the choice of metal and nitridation conditions have significant effects on La2O3 capped stacks. [ABSTRACT FROM AUTHOR]

The density of hafnium oxide films grown by atomic layer deposition for high-κ gate dielectric applications was investigated for films with thickness in the nanometer range. The density, measured by combining the film thickness from transmission electron microscopy with the amount of hafnium deposited from Rutherford backscattering, decreased with decreasing film thickness. The dielectric constant of hafnium oxide remained constant with decreasing film thickness, however. The main reason for the decrease in the measured density seemed not to be a decrease in the inherent material density. Instead, the relative importance of interface roughness in the density measurement increased with decreasing film thickness. [ABSTRACT FROM AUTHOR]