Characteristics of atomic-layer-deposited thin HfxZr1−xO2 gate dielectrics

Abstract

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.

Physical and Electrical Properties of MOCVD and ALD Deposited HfZrO4 Gate Dielectrics for 32nm CMOS High Performance Logic SOI Technologies

“…Addition of ZrO 2 to HfO 2 forming HfZrO 4 helps to partially stabilize tetragonal phase being associated with higher k-and lower CET values [7]. Additionally a more uniform film quality, smaller and more uniform grains, a tighter leakage distribution, lower CV hysteresis, less charge trapping, lower D it values, higher transconductance and drive currents, reduced SILC and longer product reliability lifetimes have been reported among other things for HfZrO 4 compared with HfO 2 [7][8][9][10][11]. But on the other hand disadvantages like smaller band gap (~0.4 eV) and lower conduction band offsets resulting in increased leakage have been presented as well [7].…”

“…However, compared to SiO 2 , HfO 2 dielectrics suffer from mobility degradation and charge trapping as well as reliability degradation [5,6]. Recently HfZrO 4 gate dielectrics have been demonstrated to be beneficial compared to HfO 2 [7][8][9][10][11]. Addition of ZrO 2 to HfO 2 forming HfZrO 4 helps to partially stabilize tetragonal phase being associated with higher k-and lower CET values [7].…”

“…But on the other hand disadvantages like smaller band gap (~0.4 eV) and lower conduction band offsets resulting in increased leakage have been presented as well [7]. In the scientific literature up to now atomic layer deposition (ALD) [7][8][9][10] as well as physical vapor deposition (PVD) [11] have been explored to form the HfZrO 4 layers. As metal-organic chemical vapor deposition (MOCVD) stands out due to excellent manufacturability and high throughputs, we have recently shown first electrical 32 nm SOI high performance logic CMOS device data of HfZrO 4 gate dielectrics deposited with MOCVD and ALD [12].…”

Work Function and Effective Oxide Thickness Engineering via Alloying of Metal Gate Electrodes

“…The gate dielectric for the metal oxide semiconductor (MOS) transistors characterized in this work were fabricated with atomic layer deposited HfO 2 (3) or Hf x Zr 1-x O 2 (4,5). The Al 2 O 3 capping layers were deposited via atomic layer deposition and the MgO capping layers were deposited by cycling thin layers of sputtered Mg with low pressure, room temperature oxidation.…”

Laser annealed HfxZr1−xO2 high-k dielectric: Impact on morphology, microstructure, and electrical properties

“…Rutherford backscattering spectroscopy analysis was performed to determine the composition of Hf x Zr 1−x O 2 alloy and to confirm that film composition does not change significantly after annealing. 9,14,15 Film roughness was measured by atomic force microscopy ͑AFM͒ operated in tapping mode. The root mean square roughness values were calculated on 1 ϫ 1 m 2 images.…”