Search

Due to its high intrinsic mobility, germanium (Ge) is a promising candidate as a channel material (offering a mobility gain of approximately ×2 for electrons and ×4 for holes when compared to conventional Si channels). However, many issues still need to be addressed before Ge can be implemented in high-performance field-effect-transistor (FET) devices. One of the key issues is to provide a high-quality interfacial layer, which does not lead to substantial drive current degradation in both low equivalent oxide thickness and short channel regime. In recent years, a wide range of materials and processes have been investigated to obtain proper interfacial properties, including different methods for Ge surface passivation, various high-k dielectrics and metal gate materials and deposition methods, and different post-deposition annealing treatments. It is observed that each process step can significantly affect the overall metal-oxide-semiconductor (MOS)-FET device performance. In this review, we describe and compare combinations of the most commonly used Ge surface passivation methods (e.g. epi-Si passivation, surface oxidation and/or nitridation, and S-passivation) with various high-k dielectrics. In particular, plasma-based processes for surface passivation in combination with plasma-enhanced atomic layer deposition for high-k depositions are shown to result in high-quality MOS structures. To further improve properties, the gate stack can be annealed after deposition. The effects of annealing temperature and ambient on the electrical properties of the MOS structure are also discussed. [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]

Atomic layer deposition (ALD) with HfCl4 as a precursor is widely used for HfO2 fabrication. Due to the nature of the precursor under study, i.e., HfCl4 and H2O, the presence of chlorine residues in the film due to insufficient hydrolysis is eminent. Obviously, the chlorine residue in the HfO2 film is suspected to affect the quality of the HfO2 film. In this paper, we reduced the concentration of chlorine residues by increasing the H2O oxidant pulse time in between the deposition cycles from 0.3 to 10 and 90s. Time-of-flight secondary ion mass spectrometry analysis shows that this decreases the chlorine concentration in the HfO2 film by more than one order of magnitude. However, time-dependent dielectric breakdown analysis shows that the lifetime remains quasi unaffected (within identical error bars) for the different injection cycles. Charge pumping analysis was done by varying both pulse frequency and amplitude to investigate the creation of defects, but negligible differences were observed. Therefore, we conclude that the presence of chlorine residues has no significant impact on the trap generation and reliability of ALD HfO2 layers, and this result corresponded with the mobility result. The experimental picture is confirmed with first-principle calculations that show that the presence of chlorine residues does not induce defect levels in the bandgap of HfO2. [ABSTRACT FROM AUTHOR]

In this paper, an effective technique and methodology for the estimation of fixed charge components in high-k stacks was demonstrated by varying both the SiO2 and high-k dielectric thicknesses. The SiO2 thickness was scaled on a single wafer by uniformly changing the etch time of a thermally grown SiO2 layer across the wafer. This minimized wafer-to-wafer variations and enables acquisition of statistically significant datasets. Layers with different thickness of both the nitrided and non-nitrided hafnium-silicate layers were then grown on these wafers to estimate all the interfacial and bulk charge components. The reproducibility and validity of this technique were demonstrated, and this method was used to compare the fixed charge levels in Hf-silicates (HfSiO) and nitrided-Hf-silicate (HfSiON) layers. [ABSTRACT FROM AUTHOR]

We report on a novel Au-free CMOS process-compatible process for AlGaN/GaN metal–insulator–semiconductor high-electron-mobility transistors. The process starts from a 150-mm GaN-on-Si substrate with an embedded \Si3\N4\/ \Al2\O3 bilayer gate dielectric, encapsulated by a high-temperature low-pressure chemical vapor deposited nitride layer. Power devices with a 20-mm gate width reach a maximum output current of 8 A, a breakdown voltage of 750 V, and a specific on-resistance Ron, sp of 2.9 \m\Omega\cdot\cm^2. The off-state drain leakage at 600 V is 7 \mu\A. We show robust gate dielectrics with a large gate bias swing. [ABSTRACT FROM PUBLISHER]

Metal-oxide-semiconductor capacitor was fabricated using in situ O2 plasma passivation and subsequent deposition of a HfO2 high-k gate stack on Ge. By extracting flat band voltages from capacitors with different equivalent oxide thicknesses (EOT), the effect of forming gas annealing (FGA) and O2 ambient annealing on the fixed charge was systematically investigated. The O2 ambient annealing is more effective than FGA as it reduced fixed charge density to 8.3 × 1011 cm-2 compared to 4.5 × 1012 cm-2 for at the same thermal budget and showed no degradation of EOT. Further, the distribution of fixed charges in gate stack was discussed in detail. [ABSTRACT FROM AUTHOR]

The electrical properties of plasma-enhanced atomic-layer-deposited (PE-ALD) TiO2 as gate dielectric were investigated for germanium-channel complementary metal-oxide-semiconductor capacitors by using ultrathin in situ HfO2/GeO2 interlayers. TiO2 grown by PE-ALD exhibited a k value of 50±5. An equivalent oxide thickness of 0.9 nm was obtained for the TiO2(3 nm)/HfO2(1.2 nm)/GeO2(0.7 nm)/Ge capacitor with very low leakage current density of 2×10-7 A/cm2 at VFB±1 V. Capacitance-voltage hysteresis was below 30 mV for the TiO2/HfO2/GeO2/Ge capacitors. Relatively low minimum density of interface states, Dit ∼5×1011 eV-1 cm-2 was obtained, suggesting the potential of HfO2/GeO2 passivation layer for the application of TiO2 as gate dielectric for both p- and n-type Ge channels. [ABSTRACT FROM AUTHOR]

Area‐selective deposition (ASD) receives increasing attention as a bottom‐up approach for nanoelectronic device fabrication. Uptake of ASD is however limited by defects, which manifest as undesired particle growth on the nongrowth surface. A defect mitigation solution is demonstrated for Ru ASD on TiN/SiO2 nanopatterns by making use of the size‐dependent Ru nanoparticle reactivity. During the initial stages of 1‐(ethylbenzyl)‐1,4‐(ethylcyclohexadienyl)ruthenium and oxygen (EBECHRu/O2) atomic layer deposition (ALD) on dielectrics, Ru particles are too small to catalytically dissociate oxygen, and their growth is suppressed. This phenomenon creates an ASD process window in which particles can be completely etched while retaining the integrity of the ASD pattern on a TiN growth surface. Decreasing the ALD temperature strongly suppresses defect growth, which can be used to expand the process window for ASD. The ASD process window is confirmed by self‐focusing secondary ion mass spectrometry (SF‐SIMS) with its low limit of detection while analyzing 104 structures simultaneously. No defects are detected for Ru ASD on 36 nm TiN/SiO2 patterns by SF‐SIMS. The Ru ASD process is applied for bottom‐up block patterning and functional hardmask patterns are obtained on 300 mm wafers. The approach followed in this work can produce defect‐free ASD processes for a wide variety of applications. [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]

A route is presented for activation of hydrogen-terminated Si(100) prior to atomic layer deposition. It is based on our discovery from in situ infrared spectroscopy that organometallic precursors can effectively initiate oxide growth. Narrow nuclear resonance profiling and Rutherford backscattering spectrometry show that surface functionalization by pre-exposure to 10[sup;8] Langmuir trimethylaluminum at 300 ?C leads to enhanced nucleation and to nearly linear growth kinetics of the high-permittivity gate dielectrics aluminum oxide and hafnium oxide. [ABSTRACT FROM AUTHOR]

Understanding the growth mechanisms during the early stages of atomic layer deposition (ALD) is of interest for several applications including thin film deposition, catalysis, and area‐selective deposition. The surface dependence and growth mechanism of (ethylbenzyl)(1‐ethyl‐1,4‐cyclohexadienyl)ruthenium and O2 ALD at 325 °C on HfO2, Al2O3, OH, and SiOSi terminated SiO2, and organosilicate glass (OSG) are investigated. The experimental results show that precursor adsorption is strongly affected by the surface termination of the dielectric, and proceeds most rapidly on OH terminated dielectrics, followed by SiOSi and finally SiCH3 terminated dielectrics. The initial stages of growth are characterized by the formation and growth of Ru nanoparticles, which is mediated by the diffusion of Ru species. Mean‐field and kinetic Monte Carlo modeling show that ALD on OSG is best described when accounting for (1) cyclic generation of new nanoparticles at the surface, (2) surface diffusion of both atomic species and nanoparticles, and (3) size‐dependent nanoparticle reactivity. In particular, the models indicate that precursor adsorption initially occurs only on the dielectric substrate, and occurs on the Ru nanoparticles only when these reach a critical size of about 0.85 nm. This phenomenon is attributed to the catalytic decomposition of oxygen requiring a minimum Ru nanoparticle size. Atomic layer deposition of ruthenium on dielectrics is governed by cyclic nanoparticle generation, surface diffusion, and aggregation of nanoparticles. The nanoparticle reactivity is strongly size‐dependent. This insight in the growth mechanism can help tune the morphology of the deposited material for several applications including thin film deposition, catalytic nanoparticles, and area‐selective deposition. [ABSTRACT FROM AUTHOR]

Abstract: A deeper understanding of Hf-based high-K materials in terms of their structural and electrical defects is important for device implementation. We have studied the occurrence of such defects using wet-etch defect delineation, electron microscopy, depth-profiling and conventional electrical measurements. It is evident that defects are present in HfO2 films that are related to the microstructure and stoichiometry of the film, which in turn depend on the deposition temperature, starting surface and post-deposition treatments. These results appear to be independent of the deposition technique. Two types of defects were observed, those that are physically visible and cause immediate failures especially on large-area structures, and those that cause high leakage but not immediate failures. The existence of defects affects not only leakage or performance but will also affect the reliability through trapping of charge at the defect sites. As films continue to be scaled thinner, the requirements on defect reduction to minimize electrical impact may become more stringent. [Copyright &y& Elsevier]