The impact of Zr addition on microstructure of HfO2 after high temperature processing was investigated using Rutherford backscattering, x-ray diffraction (XRD), transmission electron microscopy, and atomic force microscopy (AFM). The ZrO2 content in the films was varied from ∼25% to 75%. XRD analysis shows that adding >50% ZrO2 leads to partial stabilization of tetragonal phase of the HfxZr1−xO2 alloy. AFM images revealed smaller grains with Zr addition. Conducting AFM showed more uniform and tighter tunneling current distribution in HfxZr1−xO2 compared to HfO2. Constant capacitance-voltage stressing performed on HfO2 and HfxZr1−xO2 metal-oxide-semiconductor capacitors indicated reduced charge trapping with Zr addition.

In this study, the authors investigated the addition of zirconium (Zr) into HfO2 to improve its dielectric properties. HfxZr1−xO2 films were deposited by atomic-layer deposition at 200–350°C and annealed in a nitrogen ambient environment at 1000°C. Extensive physical characterization of the impact of alloying Zr into HfO2 is studied using vacuum ultraviolet spectroscopy ellipsometry, attenuated total reflectance Fourier transform infrared spectroscopy, secondary-ion mass spectrometry, transmission electron microscopy, atomic force microscopy, x-ray diffraction, Rutherford backscattering spectrometry, and x-ray reflectometry. HfxZr1−xO2 transistors are fabricated to characterize the impact of Zr addition on electrical thickness, mobility, and reliability. Zr addition into HfO2 leads to changes in film microstructure and grain-size distribution. HfxZr1−xO2 films have smaller and more uniform grain size compared to HfO2 for all deposition temperatures explored here. As Zr content and deposition temperature are increased, stabilization of the tetragonal phase is observed. A monotonic decrease in band gap is observed as ZrO2 content is increased. The chlorine impurity in the films is strongly dependent on deposition temperature and independent of film composition. TEM images of transistors showed excellent thermal stability as revealed by a sharp HfxZr1−xO2∕Si interface and no Zr silicide formation. Significant improvement in device properties such as lower electrical thickness (higher permittivities), lower threshold voltage (Vt) shift after stress (improved reliability), and higher mobilities are observed with Zr addition into HfO2. All of these results show HfxZr1−xO2 to be a promising candidate for SiO2 replacement.

HfO 2 films deposited via tetrakis diethylamido hafnium ͑TDEAH͒ precursor using MOCVD ͑metal organic chemical vapor deposition͒ are presented. TDEAH is a promising precursor candidate for the deposition of high permittivity gate dielectrics. We report the impact of process and annealing conditions on the physical and electrical properties of the film. Deposition and annealing temperatures influence the microstructure, density, and impurity levels of TDEAH HfO 2 films. Spectroscopic ellipsometry shows that film microstructure manifests itself in the optical properties of the film, particularly in the presence of a band edge related feature at 5.8 eV. An impurity analysis using Auger electron spectroscopy, secondary ion mass spectroscopy, and Raman spectroscopy, indicates that carbon impurities from the precursor exist as clusters within the HfO 2 dielectric. The impact of deposition temperature and annealing temperature on the capacitance vs. voltage and current density vs. voltage characteristics of platinum gated capacitors is studied. Correlation of physical film properties with the capacitance and leakage behavior of the TDEAH HfO 2 films indicates that impurities, in the form of carbon clusters, and low HfO 2 film density are detrimental to the electrical performance of the gate dielectric.As the smallest feature size on a microprocessor approaches 50 nm, the primary dielectric layer in the field effect transistor, referred to as the gate dielectric or gate oxide, will thin to below 15 Å. Around this thickness, electrical leakage current through the dielectric becomes excessive and is expected to cause problems due to either high power dissipation or circuit reliability. 1 One solution to this problem is to replace SiO 2 dielectrics with higher permittivity dielectrics. A higher permittivity dielectric can be thicker and still achieve the same capacitance as a thinner SiO 2 dielectric. The starting point for identifying possible replacements for SiO 2 dielectrics is to evaluate their thermal stability in direct contact with silicon. Reactions between the high permittivity dielectric and the silicon substrate or electrode are undesirable. Extensive thermodynamic calculations have been performed by Hubbard and Schlom, 2 identifying numerous binary and ternary oxides that are candidate materials. Some of the binary oxides that are leading contenders for replacing SiO 2 include: ZrO 2 , HfO 2 , Y 2 O 3 , and Al 2 O 3 . In addition, there are numerous ternary ͑or mixed͒ oxides that have also been predicted, or experimentally determined, to be stable in contact with silicon.In general, the class IIIB and IVB oxides tend to be the most thermodynamically stable oxides for potential use in integrated circuit manufacturing. Doping the IIIB and IVB oxides with Al 2 O 3 or SiO 2 increases the crystallization temperature. Such amorphous dielectrics are desirable because grain boundaries enhance diffusion of dopants from the electrode to the substrate and possibly contribute to electrical leakage. On the other hand, doping...

Articles you may be interested inElectrical behavior of atomic layer deposited high quality SiO2 gate dielectric Atomic layer deposition grown metal-insulator-metal capacitors with RuO 2 electrodes and Al-doped rutile TiO 2 dielectric layer J. Vac. Sci. Technol. B 29, 01AC09 (2011); 10.1116/1.3534023 Lanthanum aluminate by atomic layer deposition and molecular beam epitaxyIn this article, we evaluated physical and electrical characteristics of La-based gate dielectrics ͑La 2 O 3 and LaAl x O y ͒ deposited by atomic layer deposition ͑ALD͒. The precursors used for La 2 O 3 and LaAl x O y are lanthanum tris͓bis͑trimethylsilyl͒amide͔ La͓N͑SiMe 3 ͒ 2 ͔ 3 , trimethyl aluminum ͓Al͑CH 3 ͒ 3 ͔, and water. Physical properties of these dielectric films were studied using ellipsometry, x-ray photoelectron spectroscopy ͑XPS͒, and transmission electron microscopy ͑TEM͒. To investigate electrical properties of these La-based dielectrics, metal oxide semiconductor capacitors ͑MOSCAPs͒ were fabricated using metal gates ͑Ta-Si-N, TiN and Pt͒. Linear growth rate characteristics were observed for ALD ͑La 2 O 3 and LaAl x O y films deposited at temperatures of 225 to 275°C. XPS and XTEM analysis of La-based films grown on a chemical oxide starting surface revealed a rough La-based dielectric/Si interface and chemical interaction with the Si substrate. In general, adding Al into La 2 O 3 improved electrical properties of the films. Devices with La based dielectric deposited on a ϳ10 Å Al 2 O 3 underlayer had better capacitance-voltage characteristics compared to those deposited directly on a chemical oxide surface. Adding Al to the dielectric also resulted in lower leakage current and smaller hysteresis. For devices with Ta-Si-N gates, a significant decrease in maximum capacitances was observed after forming gas annealing, probably due to interaction between the gate electrode and the dielectric. XTEM images for these devices indicated an indistinct interface between the Ta-Si-N gate and the La-based dielectrics. The XTEM images also showed microcrystals in Ta-Si-N that may be formed in Si deficient regions of the metal gate. No interaction between TiN or Pt with La gate dielectrics was observed by XTEM up to 800°C annealing temperature. After 900°C annealing, some interaction between LaAl x O y and Pt gate was observed. Our results indicated that silicon substrate interactions may limit the utilization of ALD La based dielectrics in future complementary metal-oxide semiconductor processing.

The impact of ultrathin metal underlayer on physical and electrical properties of Hf x Zr 1−x O 2 (x =∼0.4) after high-temperature processing was investigated. An ∼5-Å Zr, ∼5-Å Hf, or ∼10-Å Hf metal layer was sputter deposited prior to Hf x Zr 1−x O 2 growth. Cross-sectional transmission electron microscopy and secondary ions mass spectrometry analysis confirmed no Zr or Hf silicide formation between the high-k film and Si substrate even after 1000 • C processing. No significant increase in equivalent oxide thickness or gate leakage current is observed on devices with metal underlayer. Furthermore, devices with a 5-Å-thick Zr underlayer exhibited lower threshold voltage, higher mobility, and improved charge trapping characteristics.